Evaluation of antidiarrhoeal and toxicological properties of Hermannia Incana cav.: a South African medicinal plant
- Authors: Appidi, Jaipal Reddy
- Date: 2010
- Subjects: Sterculiaceae , Medicinal plants -- South Africa -- Eastern Cape , Diarrhea , Botany, Medical
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11304 , http://hdl.handle.net/10353/259 , Sterculiaceae , Medicinal plants -- South Africa -- Eastern Cape , Diarrhea , Botany, Medical
- Description: Hermannia incana Cav. (Sterculiaceae), known as sweet yellow bells, is a medicinal plant used by the people of the Eastern Cape for the treatment of stomach-ache and diarrhoea. It has purgative and diaphoretic effects. It is a prostrate herb with yellow flowers and sparsely hairy and slightly glandular leaves, occurring in grassland and marshes in the Eastern Cape Province of South Africa. Based on the ethnomedical uses of this plant, the research project was designed to evaluate its antidiarrhoeal and toxicological properties. An ethnobotanical study of plants used for the treatment of diarrhoea in the Eastern Cape Province was carried out, using a questionnaire which was administered to herbalists, traditional healers and rural dwellers. This survey indicated a total of 17 plant species from 14 families. Elephantorrhiza elephantine (Burch.) Skeels, Hermannia incana Cav., Pelargonium reniforme Curt., Alepidea amatymbica Eckl. & Zeyh. and Bulbine latifolia (L.f.) Roem. et Schult. were the most frequently mentioned and highly recommended plants for the treatment of diarrhoea by both the traditional healers and rural dwellers. The root, bark and leaves are the common parts of plants used, while decoctions and infusions are the main methods of preparation. The agar dilution method was used to study the antimicrobial activity. The methanol extracts of the plant showed appreciable activity against Gram-positive and Gram-negative bacteria at concentrations ranging from 0.5 to 7.0 mg/ml. The acetone and water extracts of both the leaves and the roots showed moderate activity against Gram positive bacteria and less activity against Gram negative bacteria. All the extracts inhibited the growth of the fungi Aspergillus flavus, Aspergillus niger, and Mucor hiemalis with growth inhibition ranging from 54.31 percent to 96.67 percent at 0.1-10 mg/ml. None of the extracts suppressed the growth of Candida albicans at the maximum concentration (10 mg/ml) tested. iii In the in vivo antidiarrhoeal evaluation using Wistar rats, the aqueous extract at all the doses tested, significantly prolonged the time of induction of diarrhoea and also reduced the frequency of diarrhoeal episodes and fecal parameters (total number, number of wet, fresh and dry weight and water content of the faeces). The percentage inhibition of defecation and intestinal content (enteropooling) were increased in dose dependent manner. The doses also reduced the intestinal transit time of charcoal, masses and volumes of intestinal fluid (gastrointestinal motility). These results are indications of antidiarrhoeal property of H. incana leaf extract with the 600 mg/kg body weight of the extract being the most effective. In the toxicological evaluation using Wistar rats, the oral administration of the extract did not produce any significant effect on the liver and kidney body weight ratios, RBC, HB, PCV, MCV MCH, MCHC, RCDW, WBC, neutrophils, monocytes and basophils cholesterol, triacylglycerol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and atherogenic index. The extract also did not affect the levels of sodium, potassium, chloride, inorganic phosphorus, urea, creatinine, total protein, globulin, albumin, total and conjugated bilirubin. The activities of alkaline phosphatase, gamma glutamyl transferase and alanine aminotransaminase in the serum were increased by the extract whereas aspartate aminotransaminase was decreased. The levels of LUC, platelets, lymphocytes and eosinophils were significantly affected at 600 mg/kg body weight. The available evidence in this study suggests that the extract of H. incana leaf is mild, parameter and dose specific. The structure and distribution of foliar appendages on the leaves of this plant were investigated with the JEOL (JSM-6390LV) scanning electron microscope (SEM). Both glandular and non-glandular trichomes were observed. Long stalked glandular trichomes were present on both the abaxial and adaxial surfaces while short stalked glandular trichomes were present only on the adaxial surface. Glandular trichomes were capitate while nonglandular trichomes were stellate with many arms. Energy dispersive X-ray spectroscopyiv SEM showed that Al, Ca, K, Na, Ti and Si were the major constituents of the crystals analyzed from the leaf surfaces. The phytochemical screening of H. incana revealed the presence of bioactive antidiarrhoeal agents such as alkaloids, tannins, saponins, phenolics, triterpenes, cardiac glycosides, flavonoids, cardenolides and dienolides. Two flavonoids, epicatechin and 3, 5, 7, 2’ tetra-hydroxy flavone-3- O--D-glucopyranoside were isolated from the leaves of the plant through bio-active guided fractionation. Both these compounds were screened against diarrhoea causative organisms (Echerichia coli, Shigella flexneri, Bacillus cereus and Staphylococcus aureus) and exhibiting minimum inhibitory concentrations ranging from 12.5 to 100 μg/ml. The findings from this research have generally justified the traditional use of this plant for the treatment of diarrhoea in this province.
- Full Text:
- Date Issued: 2010
- Authors: Appidi, Jaipal Reddy
- Date: 2010
- Subjects: Sterculiaceae , Medicinal plants -- South Africa -- Eastern Cape , Diarrhea , Botany, Medical
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11304 , http://hdl.handle.net/10353/259 , Sterculiaceae , Medicinal plants -- South Africa -- Eastern Cape , Diarrhea , Botany, Medical
- Description: Hermannia incana Cav. (Sterculiaceae), known as sweet yellow bells, is a medicinal plant used by the people of the Eastern Cape for the treatment of stomach-ache and diarrhoea. It has purgative and diaphoretic effects. It is a prostrate herb with yellow flowers and sparsely hairy and slightly glandular leaves, occurring in grassland and marshes in the Eastern Cape Province of South Africa. Based on the ethnomedical uses of this plant, the research project was designed to evaluate its antidiarrhoeal and toxicological properties. An ethnobotanical study of plants used for the treatment of diarrhoea in the Eastern Cape Province was carried out, using a questionnaire which was administered to herbalists, traditional healers and rural dwellers. This survey indicated a total of 17 plant species from 14 families. Elephantorrhiza elephantine (Burch.) Skeels, Hermannia incana Cav., Pelargonium reniforme Curt., Alepidea amatymbica Eckl. & Zeyh. and Bulbine latifolia (L.f.) Roem. et Schult. were the most frequently mentioned and highly recommended plants for the treatment of diarrhoea by both the traditional healers and rural dwellers. The root, bark and leaves are the common parts of plants used, while decoctions and infusions are the main methods of preparation. The agar dilution method was used to study the antimicrobial activity. The methanol extracts of the plant showed appreciable activity against Gram-positive and Gram-negative bacteria at concentrations ranging from 0.5 to 7.0 mg/ml. The acetone and water extracts of both the leaves and the roots showed moderate activity against Gram positive bacteria and less activity against Gram negative bacteria. All the extracts inhibited the growth of the fungi Aspergillus flavus, Aspergillus niger, and Mucor hiemalis with growth inhibition ranging from 54.31 percent to 96.67 percent at 0.1-10 mg/ml. None of the extracts suppressed the growth of Candida albicans at the maximum concentration (10 mg/ml) tested. iii In the in vivo antidiarrhoeal evaluation using Wistar rats, the aqueous extract at all the doses tested, significantly prolonged the time of induction of diarrhoea and also reduced the frequency of diarrhoeal episodes and fecal parameters (total number, number of wet, fresh and dry weight and water content of the faeces). The percentage inhibition of defecation and intestinal content (enteropooling) were increased in dose dependent manner. The doses also reduced the intestinal transit time of charcoal, masses and volumes of intestinal fluid (gastrointestinal motility). These results are indications of antidiarrhoeal property of H. incana leaf extract with the 600 mg/kg body weight of the extract being the most effective. In the toxicological evaluation using Wistar rats, the oral administration of the extract did not produce any significant effect on the liver and kidney body weight ratios, RBC, HB, PCV, MCV MCH, MCHC, RCDW, WBC, neutrophils, monocytes and basophils cholesterol, triacylglycerol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and atherogenic index. The extract also did not affect the levels of sodium, potassium, chloride, inorganic phosphorus, urea, creatinine, total protein, globulin, albumin, total and conjugated bilirubin. The activities of alkaline phosphatase, gamma glutamyl transferase and alanine aminotransaminase in the serum were increased by the extract whereas aspartate aminotransaminase was decreased. The levels of LUC, platelets, lymphocytes and eosinophils were significantly affected at 600 mg/kg body weight. The available evidence in this study suggests that the extract of H. incana leaf is mild, parameter and dose specific. The structure and distribution of foliar appendages on the leaves of this plant were investigated with the JEOL (JSM-6390LV) scanning electron microscope (SEM). Both glandular and non-glandular trichomes were observed. Long stalked glandular trichomes were present on both the abaxial and adaxial surfaces while short stalked glandular trichomes were present only on the adaxial surface. Glandular trichomes were capitate while nonglandular trichomes were stellate with many arms. Energy dispersive X-ray spectroscopyiv SEM showed that Al, Ca, K, Na, Ti and Si were the major constituents of the crystals analyzed from the leaf surfaces. The phytochemical screening of H. incana revealed the presence of bioactive antidiarrhoeal agents such as alkaloids, tannins, saponins, phenolics, triterpenes, cardiac glycosides, flavonoids, cardenolides and dienolides. Two flavonoids, epicatechin and 3, 5, 7, 2’ tetra-hydroxy flavone-3- O--D-glucopyranoside were isolated from the leaves of the plant through bio-active guided fractionation. Both these compounds were screened against diarrhoea causative organisms (Echerichia coli, Shigella flexneri, Bacillus cereus and Staphylococcus aureus) and exhibiting minimum inhibitory concentrations ranging from 12.5 to 100 μg/ml. The findings from this research have generally justified the traditional use of this plant for the treatment of diarrhoea in this province.
- Full Text:
- Date Issued: 2010
Investigations of the bioavailability/bioequivalence of topical corticosteroid formulations containing clobetasol propionate using the human skin blanching assay, tape stripping and microdialysis
- Authors: Au, Wai Ling
- Date: 2010
- Subjects: Adrenocortical hormones -- Bioavailability , Drugs -- Therapeutic equivalency , Adrenocortical hormones -- Effectiveness , Adrenocortical hormones -- Testing , Adrenocortical hormones -- Side effects , Transdermal medication
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3743 , http://hdl.handle.net/10962/d1003221 , Adrenocortical hormones -- Bioavailability , Drugs -- Therapeutic equivalency , Adrenocortical hormones -- Effectiveness , Adrenocortical hormones -- Testing , Adrenocortical hormones -- Side effects , Transdermal medication
- Description: Currently, clinical trials in patients are required by most regulatory authorities for the assessment of bioequivalence of topical products where the drug is not intended for systemic absorption. Hence there is a dire need for suitable methods for the assessment of bioavailability and bioequivalence of such products since clinical safety and efficacy studies are expensive, time-consuming and require very large numbers of patients. Except for topical corticosteroid products where the human skin blanching assay/vasoconstrictor assay has been approved by the US FDA for bioequivalence assessment of those products, no other method has been “officially” approved for use in those investigations. However, a few alternative methods such as tape stripping and microdialysis have been pursued and considered to have the potential for use in ioequivalence/bioavailability studies. The human skin blanching assay was used to assess the bioequivalence of commercially available topical products containing 0.05% clobetasol propionate. Both visual and chromameter data were obtained and a commercially available topical corticosteroid product, Dermovate® cream was used as both the “Test” and the “Reference” product. The results indicated that both visual and chromametric assessments were comparable to each other and that either could be used for the assessment of the bioequivalence of topical products containing clobetasol propionate. The screening procedure was optimized to identify potential “detectors” for inclusion in the bioequivalence studies. This resulted in fewer subjects being required in a bioequivalence pivotal study, still having the necessary power to confirm bioequivalence using the human skin blanching assay. Another objective of this research was to re-visit tape stripping and other possible alternative methods such as dermal microdialysis and to optimize these procedures for bioequivalence assessment of topical formulations where the drug is not intended for systemic absorption. In the past few decades, tape stripping has been used to investigate bioavailability/bioequivalence of various topical formulations. This technique involves the removal of the stratum corneum to assess drug penetration through the skin. A draft FDA guidance for tape stripping was initially published but was subsequently withdrawn due to high variability and poor reproducibility. This research project used an optimized tape stripping procedure to determine bioavailability and establish bioequivalence between three commercially available formulations containing 0.05 % m/m clobetasol propionate. Furthermore, tape stripping was validated by undertaking a study to assess the bioequivalence of a 0.05% topical cream formulation (Dermovate® cream) using the same cream as both the “Test” and “Reference” product, in which bioequivalence was confirmed. The findings highlight the potential of tape stripping as an alternative method for the assessment of bioequivalence of clobetasol propionate formulations and may possibly be extended for use in other topical products. Microdialysis is another useful technique that can assess the penetration of topically applied substances which diffuses through the stratum corneum and into the dermis. Microdialysis has previously been successfully used for in vivo bioavailability and bioequivalence assessments of topical formulations. However, the drugs which were under investigation were all hydrophilic in nature. A major problem with the use of microdialysis for the assessment of lipophilic substances is the binding/adherence of the substance to the membrane and other components of the microdialysis system. As a result, this necessitates the development of a microdialysis system which can be used to assess lipophilic drugs. Intralipid® 20% was investigated and successfully utilized as a perfusate to recover a lipophilic topical corticosteroid, clobetasol propionate, in microdialysis studies. Hence, the bioavailability of clobetasol propionate from an extemporaneous preparation was determined in healthy human volunteers using microdialysis. These findings indicate that in vivo microdialysis can be used to assess lipophilic drug penetration through the skin. A novel approach to investigate drug release from topical formulations containing 0.05% clobetasol propionate using in vitro microdialysis was also undertaken. The in vitro findings were found to be in agreement with the results obtained using tape stripping to assess bioequivalence of the same commercially available products, namely Dermovate® cream, Dovate® Cream and Dermovate® ointment. These results indicate the potential to correlate in vitro with in vivo data for bioequivalence assessment of such topical dosage forms.
- Full Text:
- Date Issued: 2010
- Authors: Au, Wai Ling
- Date: 2010
- Subjects: Adrenocortical hormones -- Bioavailability , Drugs -- Therapeutic equivalency , Adrenocortical hormones -- Effectiveness , Adrenocortical hormones -- Testing , Adrenocortical hormones -- Side effects , Transdermal medication
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3743 , http://hdl.handle.net/10962/d1003221 , Adrenocortical hormones -- Bioavailability , Drugs -- Therapeutic equivalency , Adrenocortical hormones -- Effectiveness , Adrenocortical hormones -- Testing , Adrenocortical hormones -- Side effects , Transdermal medication
- Description: Currently, clinical trials in patients are required by most regulatory authorities for the assessment of bioequivalence of topical products where the drug is not intended for systemic absorption. Hence there is a dire need for suitable methods for the assessment of bioavailability and bioequivalence of such products since clinical safety and efficacy studies are expensive, time-consuming and require very large numbers of patients. Except for topical corticosteroid products where the human skin blanching assay/vasoconstrictor assay has been approved by the US FDA for bioequivalence assessment of those products, no other method has been “officially” approved for use in those investigations. However, a few alternative methods such as tape stripping and microdialysis have been pursued and considered to have the potential for use in ioequivalence/bioavailability studies. The human skin blanching assay was used to assess the bioequivalence of commercially available topical products containing 0.05% clobetasol propionate. Both visual and chromameter data were obtained and a commercially available topical corticosteroid product, Dermovate® cream was used as both the “Test” and the “Reference” product. The results indicated that both visual and chromametric assessments were comparable to each other and that either could be used for the assessment of the bioequivalence of topical products containing clobetasol propionate. The screening procedure was optimized to identify potential “detectors” for inclusion in the bioequivalence studies. This resulted in fewer subjects being required in a bioequivalence pivotal study, still having the necessary power to confirm bioequivalence using the human skin blanching assay. Another objective of this research was to re-visit tape stripping and other possible alternative methods such as dermal microdialysis and to optimize these procedures for bioequivalence assessment of topical formulations where the drug is not intended for systemic absorption. In the past few decades, tape stripping has been used to investigate bioavailability/bioequivalence of various topical formulations. This technique involves the removal of the stratum corneum to assess drug penetration through the skin. A draft FDA guidance for tape stripping was initially published but was subsequently withdrawn due to high variability and poor reproducibility. This research project used an optimized tape stripping procedure to determine bioavailability and establish bioequivalence between three commercially available formulations containing 0.05 % m/m clobetasol propionate. Furthermore, tape stripping was validated by undertaking a study to assess the bioequivalence of a 0.05% topical cream formulation (Dermovate® cream) using the same cream as both the “Test” and “Reference” product, in which bioequivalence was confirmed. The findings highlight the potential of tape stripping as an alternative method for the assessment of bioequivalence of clobetasol propionate formulations and may possibly be extended for use in other topical products. Microdialysis is another useful technique that can assess the penetration of topically applied substances which diffuses through the stratum corneum and into the dermis. Microdialysis has previously been successfully used for in vivo bioavailability and bioequivalence assessments of topical formulations. However, the drugs which were under investigation were all hydrophilic in nature. A major problem with the use of microdialysis for the assessment of lipophilic substances is the binding/adherence of the substance to the membrane and other components of the microdialysis system. As a result, this necessitates the development of a microdialysis system which can be used to assess lipophilic drugs. Intralipid® 20% was investigated and successfully utilized as a perfusate to recover a lipophilic topical corticosteroid, clobetasol propionate, in microdialysis studies. Hence, the bioavailability of clobetasol propionate from an extemporaneous preparation was determined in healthy human volunteers using microdialysis. These findings indicate that in vivo microdialysis can be used to assess lipophilic drug penetration through the skin. A novel approach to investigate drug release from topical formulations containing 0.05% clobetasol propionate using in vitro microdialysis was also undertaken. The in vitro findings were found to be in agreement with the results obtained using tape stripping to assess bioequivalence of the same commercially available products, namely Dermovate® cream, Dovate® Cream and Dermovate® ointment. These results indicate the potential to correlate in vitro with in vivo data for bioequivalence assessment of such topical dosage forms.
- Full Text:
- Date Issued: 2010
An empirical phenomenological investigation of procrastinating behaviour
- Authors: Barratt, Neal Anthony
- Date: 2010
- Subjects: Procrastination Self-actualization (Psychology) Cognitive psychology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2929 , http://hdl.handle.net/10962/d1002438
- Description: A qualitative empirical phenomenological study was undertaken to determine the self-experience of procrastinating behaviour. Five students each gave an account of an occasion when they procrastinated. The resultant protocols were analysed and the Situated Structure of each individual’s experience was reported. From these, the General Structure of procrastinating behaviour was determined. A further, novel step was added to the standard methodology, whereby ‘themes’ were extracted from participant protocols and a ‘Composite Reality’ of everyday-life procrastination was rendered. Participants’ accounts suggest they are concerned the results of intellectual tasks they undertake will be seen as equivalent to their quality of being-as-an-individual: poor work results will be interpreted by important-others as evidence of participants’ poor quality of self – which is to be avoided. This study suggests that procrastination is a ploy used by individuals to avoid criticism, by deflecting assessment of their capacity to complete a task well, to instead, what they are capable of when only a limited time is available. Conclusions drawn by the important-others of participants’ true ability are thereby confounded. The results achieved in the phenomenological study were compared with others originating from various quantitative studies, and considerable overlap was found. The experiential richness of the phenomenological results point to a worthwhile methodological strategy for future procrastination research.
- Full Text:
- Date Issued: 2010
- Authors: Barratt, Neal Anthony
- Date: 2010
- Subjects: Procrastination Self-actualization (Psychology) Cognitive psychology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2929 , http://hdl.handle.net/10962/d1002438
- Description: A qualitative empirical phenomenological study was undertaken to determine the self-experience of procrastinating behaviour. Five students each gave an account of an occasion when they procrastinated. The resultant protocols were analysed and the Situated Structure of each individual’s experience was reported. From these, the General Structure of procrastinating behaviour was determined. A further, novel step was added to the standard methodology, whereby ‘themes’ were extracted from participant protocols and a ‘Composite Reality’ of everyday-life procrastination was rendered. Participants’ accounts suggest they are concerned the results of intellectual tasks they undertake will be seen as equivalent to their quality of being-as-an-individual: poor work results will be interpreted by important-others as evidence of participants’ poor quality of self – which is to be avoided. This study suggests that procrastination is a ploy used by individuals to avoid criticism, by deflecting assessment of their capacity to complete a task well, to instead, what they are capable of when only a limited time is available. Conclusions drawn by the important-others of participants’ true ability are thereby confounded. The results achieved in the phenomenological study were compared with others originating from various quantitative studies, and considerable overlap was found. The experiential richness of the phenomenological results point to a worthwhile methodological strategy for future procrastination research.
- Full Text:
- Date Issued: 2010
Messages from the deep : water divinities, dreams and diviners in Southern Africa
- Authors: Bernard, Penelope Susan
- Date: 2010
- Subjects: Dreams -- Religious aspects , Zulu (African people) -- Religion , Xhosa (African people) -- Religion , Shamanism -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2112 , http://hdl.handle.net/10962/d1007644 , Dreams -- Religious aspects , Zulu (African people) -- Religion , Xhosa (African people) -- Religion , Shamanism -- South Africa
- Description: This thesis is a comparative regional study of a complex of beliefs and practices regarding the water divinities in southern Africa. These snake and mermaid-like divinities, which are said to work in conjunction with one's ancestors, are believed to be responsible for the calling and training of certain diviner-healers by taking them underwater for periods of time. In addition to granting healing knowledge, these divinities are associated with fertility, water and rain, and the origins of humanity. The research combines comparative ethnography with the anthropology of extraordinary experience (AEE), and focuses particularly on the Zulu, Cape Nguni, Shona and Khoisan groups. The use of the 'radical participation' method, as recommended by AEE, was facilitated by the author being identified as having a ' calling' from these water divinities, which subsequently resulted in her initiation under the guidance of a Zulu isangoma (diviner-healer) who had reputedly been taken underwater. The research details the rituals that were performed and how dreams are used to guide the training process of izangoma. This resulted in the research process being largely dream-directed, in that the author traces how the izangoma responded to various dreams she had and how these responses opened new avenues for understanding the phenomenon of the water divinities. The comparative study thus combines literature sources, field research and dream-directed experiences, and reveals a complex of recurring themes, symbols and norms pertaining to the water divinities across the selected groups. In seeking to explain both the commonalities and differences between these groups, the author argues for a four-level explanatory model that combines both conventional anthropological theory and extraordinary experience. Responses to the author's dream-led experiences are used to throw light on the conflicting discourses of morality regarding traditional healers and the water divinities in the context of political-economic transformations relating to capitalism and the moral economy; to illuminate the blending of ideas and practices between Zulu Zionists and diviner-healer traditions; and to link up with certain issues relating to San rock art, rain-making and healing rituals, which contribute to the debates regarding trance-induced rock art in southern Africa.
- Full Text:
- Date Issued: 2010
- Authors: Bernard, Penelope Susan
- Date: 2010
- Subjects: Dreams -- Religious aspects , Zulu (African people) -- Religion , Xhosa (African people) -- Religion , Shamanism -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2112 , http://hdl.handle.net/10962/d1007644 , Dreams -- Religious aspects , Zulu (African people) -- Religion , Xhosa (African people) -- Religion , Shamanism -- South Africa
- Description: This thesis is a comparative regional study of a complex of beliefs and practices regarding the water divinities in southern Africa. These snake and mermaid-like divinities, which are said to work in conjunction with one's ancestors, are believed to be responsible for the calling and training of certain diviner-healers by taking them underwater for periods of time. In addition to granting healing knowledge, these divinities are associated with fertility, water and rain, and the origins of humanity. The research combines comparative ethnography with the anthropology of extraordinary experience (AEE), and focuses particularly on the Zulu, Cape Nguni, Shona and Khoisan groups. The use of the 'radical participation' method, as recommended by AEE, was facilitated by the author being identified as having a ' calling' from these water divinities, which subsequently resulted in her initiation under the guidance of a Zulu isangoma (diviner-healer) who had reputedly been taken underwater. The research details the rituals that were performed and how dreams are used to guide the training process of izangoma. This resulted in the research process being largely dream-directed, in that the author traces how the izangoma responded to various dreams she had and how these responses opened new avenues for understanding the phenomenon of the water divinities. The comparative study thus combines literature sources, field research and dream-directed experiences, and reveals a complex of recurring themes, symbols and norms pertaining to the water divinities across the selected groups. In seeking to explain both the commonalities and differences between these groups, the author argues for a four-level explanatory model that combines both conventional anthropological theory and extraordinary experience. Responses to the author's dream-led experiences are used to throw light on the conflicting discourses of morality regarding traditional healers and the water divinities in the context of political-economic transformations relating to capitalism and the moral economy; to illuminate the blending of ideas and practices between Zulu Zionists and diviner-healer traditions; and to link up with certain issues relating to San rock art, rain-making and healing rituals, which contribute to the debates regarding trance-induced rock art in southern Africa.
- Full Text:
- Date Issued: 2010
Audit of community pharmacy activities
- Authors: Blignault, Suzette Martha
- Date: 2010
- Subjects: Pharmacy , Community health services
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10130 , http://hdl.handle.net/10948/1533 , Pharmacy , Community health services
- Description: In South Africa the pharmacy profession has experienced a number of changes around the turn of the century such as the introduction of the National Drug Policy (NDP), pharmacy ownership and price regulation. With this the role and earnings of the pharmacy profession, as well as to what extent the pharmacist adds value to the profession and society, are being questioned. Community pharmacists are thus faced with the challenge to prove that the value that they add to society is meaningful. Therefore, the aim of the study was to document community pharmacy availability and activities in South Africa and based on this to quantify the perceived value that the community pharmacist adds to society through the delivery of pharmaceutical services and pharmaceutical care. In order to determine the pharmacist’s true value added two surveys were conducted in 2006; an original pharmacist survey and a general public survey. The results obtained were verified by a follow–up pharmacist survey in 2009 to confirm or reject the results obtained in the original survey. The study was representative of both the community pharmacies and the general public in South Africa and was primarily quantitative in design and analysis. More than half of the responding pharmacies (63.16%) were open seven days a week. The average hours of service per day ranged from 10 hours (Monday to Friday) through to 6.45 hours on Saturdays and 3 hours on Sundays. Pharmacists continuously upgraded their professional knowledge. More than three quarters of pharmacies had the necessary equipment available to perform the services investigated in the study. The general public was not aware of all the services provided by pharmacists and as a result, depending on the service, many people did not make use of these services. The general public that made use of services delivered by community pharmacies mainly perceived the services delivered to be of good quality. The main barrier to practicing pharmaceutical care was indicated by pharmacists as not receiving payment for the advice given followed by pharmaceutical care being time consuming, and that there was not enough time to talk to patients. The general public indicated that they found it difficult to ask questions in pharmacies because other patients could hear what was discussed, or other patients had to wait longer if they asked something, and pharmacy staff being too busy. The results of the original pharmacist and the general public survey were confirmed by the results of the follow-up survey with the exception of dispensing prescription medicine (8 minutes 28 seconds), OTC medicine (7 minutes 23 seconds), counselling of prescription medicine (8 minutes 51 seconds) and OTC medicine (8 minutes) which on average took longer to conduct than in the previous analysis. The study highlighted the value added to the wellness and quality of life of the community of South Africa through the delivery of pharmaceutical care and pharmaceutical services by community pharmacy staff, and proved that pharmacists are committed to the provision of pharmaceutical care and pharmaceutical services.
- Full Text:
- Date Issued: 2010
- Authors: Blignault, Suzette Martha
- Date: 2010
- Subjects: Pharmacy , Community health services
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10130 , http://hdl.handle.net/10948/1533 , Pharmacy , Community health services
- Description: In South Africa the pharmacy profession has experienced a number of changes around the turn of the century such as the introduction of the National Drug Policy (NDP), pharmacy ownership and price regulation. With this the role and earnings of the pharmacy profession, as well as to what extent the pharmacist adds value to the profession and society, are being questioned. Community pharmacists are thus faced with the challenge to prove that the value that they add to society is meaningful. Therefore, the aim of the study was to document community pharmacy availability and activities in South Africa and based on this to quantify the perceived value that the community pharmacist adds to society through the delivery of pharmaceutical services and pharmaceutical care. In order to determine the pharmacist’s true value added two surveys were conducted in 2006; an original pharmacist survey and a general public survey. The results obtained were verified by a follow–up pharmacist survey in 2009 to confirm or reject the results obtained in the original survey. The study was representative of both the community pharmacies and the general public in South Africa and was primarily quantitative in design and analysis. More than half of the responding pharmacies (63.16%) were open seven days a week. The average hours of service per day ranged from 10 hours (Monday to Friday) through to 6.45 hours on Saturdays and 3 hours on Sundays. Pharmacists continuously upgraded their professional knowledge. More than three quarters of pharmacies had the necessary equipment available to perform the services investigated in the study. The general public was not aware of all the services provided by pharmacists and as a result, depending on the service, many people did not make use of these services. The general public that made use of services delivered by community pharmacies mainly perceived the services delivered to be of good quality. The main barrier to practicing pharmaceutical care was indicated by pharmacists as not receiving payment for the advice given followed by pharmaceutical care being time consuming, and that there was not enough time to talk to patients. The general public indicated that they found it difficult to ask questions in pharmacies because other patients could hear what was discussed, or other patients had to wait longer if they asked something, and pharmacy staff being too busy. The results of the original pharmacist and the general public survey were confirmed by the results of the follow-up survey with the exception of dispensing prescription medicine (8 minutes 28 seconds), OTC medicine (7 minutes 23 seconds), counselling of prescription medicine (8 minutes 51 seconds) and OTC medicine (8 minutes) which on average took longer to conduct than in the previous analysis. The study highlighted the value added to the wellness and quality of life of the community of South Africa through the delivery of pharmaceutical care and pharmaceutical services by community pharmacy staff, and proved that pharmacists are committed to the provision of pharmaceutical care and pharmaceutical services.
- Full Text:
- Date Issued: 2010
The in vitro biological activities of three Hypoxis species and their active compounds
- Authors: Boukes, Gerhardt Johannes
- Date: 2010
- Subjects: Potatoes -- Africa , Potatoes -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10322 , http://hdl.handle.net/10948/1228 , Potatoes -- Africa , Potatoes -- Therapeutic use , Medicinal plants
- Description: The African potato is used as an African traditional medicine for its nutritional and medicinal properties. Most research has been carried out on H. hemerocallidea, with very little or nothing on other Hypoxis spp. The main aim of this project was to provide scientific data on the anticancer, anti-inflammatory and antioxidant properties of H. hemerocallidea, H. stellipilis and H. sobolifera chloroform extracts and their active compounds. The hypoxoside and phytosterol contents of the three Hypoxis spp. were determined using TLC, HPLC and GC. H. hemerocallidea and H. sobolifera chloroform extracts contained the highest amounts of hypoxoside and β-sitosterol, respectively. For the anticancer properties, cytotoxicity of the Hypoxis extracts and its purified compounds were determined against the HeLa, HT-29 and MCF-7 cancer cell lines (using MTT), and PBMCs (using CellTiter-Blue®). H. sobolifera had the best cytotoxicity against the three cancer cell lines, whereas H. stellipilis stimulated HeLa and HT-29 cancer cell growth. IC50 values of hypoxoside and rooperol were determined. DNA cell cycle arrest (using PI staining) occurred in the late G1/early S (confirmed by increased p21Waf1/Cip1 expression) and G2/M phases after 15 and 48 hrs, respectively, when treated with Hypoxis extracts and rooperol. H. sobolifera and rooperol activated caspase-3 and -7 (using fluorescently labelled antibodies) in HeLa and HT-29 cancer cells, and caspase-7 in MCF-7 cancer cells after 48 hrs. Annexin V binding to phosphatidylserines in rooperol treated U937 cells confirmed early apoptosis after 15 hrs. The TUNEL assay showed DNA fragmentation in the three cancer cell lines when treated with H. sobolifera and rooperol for 48 hrs. A shift pass the G2/M phase has led to the investigation of endoreduplication, which was confirmed by cell/nucleus size, and anti-apoptotic proteins (Akt, phospho-Akt, phospho-Bcl-2 and p21Waf1/Cip1). U937 cell differentiation to monocyte-macrophages was optimized using PMA and 1,25(OH)2D3, which was confirmed by morphological and biochemical changes. For the anti-inflammatory properties, Hypoxis extracts and rooperol significantly increased NO production in monocyte-macrophages (pre-loaded with DAF-2 DA) and phagocytosis of pHrodoTM E. coli BioParticles®. The treatments had no effect on COX-2 expression in monocyte-macrophages. The phytosterols significantly increased IL-1β and IL-6 secretion xv (using the FlowCytomix Multiplex human Th1/Th2 10plex Kit I) in the PBMCs of one donor. For the antioxidant properties, Hypoxis extracts and rooperol significantly increased ROS production in undifferentiated and differentiated U937 cells, which were pre-loaded with DCFH-DA. Hypoxis extracts and purified compounds had ferric reducing activities, but only rooperol had ferric reducing activities significantly greater than ascorbic acid. β-sitosterol, campesterol and cholesterol significantly increased SOD activity in Chang liver cells, while H. stellipilis, H. sobolifera and rooperol decreased SOD activity. Anticancer, anti-inflammatory and antioxidant properties of the Hypoxis extracts may be attributed to the β-sitosterol content, because Hypoxis chloroform extracts contained very little or no hypoxoside. Unidentified compounds, and synergistic and additive effects of the compounds may have contributed to the biological effects. This study confirms previous reports that rooperol is the active compound. Results provide scientific data on the medicinal properties of one of the most frequently used medicinal plants in South Africa.
- Full Text:
- Date Issued: 2010
- Authors: Boukes, Gerhardt Johannes
- Date: 2010
- Subjects: Potatoes -- Africa , Potatoes -- Therapeutic use , Medicinal plants
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10322 , http://hdl.handle.net/10948/1228 , Potatoes -- Africa , Potatoes -- Therapeutic use , Medicinal plants
- Description: The African potato is used as an African traditional medicine for its nutritional and medicinal properties. Most research has been carried out on H. hemerocallidea, with very little or nothing on other Hypoxis spp. The main aim of this project was to provide scientific data on the anticancer, anti-inflammatory and antioxidant properties of H. hemerocallidea, H. stellipilis and H. sobolifera chloroform extracts and their active compounds. The hypoxoside and phytosterol contents of the three Hypoxis spp. were determined using TLC, HPLC and GC. H. hemerocallidea and H. sobolifera chloroform extracts contained the highest amounts of hypoxoside and β-sitosterol, respectively. For the anticancer properties, cytotoxicity of the Hypoxis extracts and its purified compounds were determined against the HeLa, HT-29 and MCF-7 cancer cell lines (using MTT), and PBMCs (using CellTiter-Blue®). H. sobolifera had the best cytotoxicity against the three cancer cell lines, whereas H. stellipilis stimulated HeLa and HT-29 cancer cell growth. IC50 values of hypoxoside and rooperol were determined. DNA cell cycle arrest (using PI staining) occurred in the late G1/early S (confirmed by increased p21Waf1/Cip1 expression) and G2/M phases after 15 and 48 hrs, respectively, when treated with Hypoxis extracts and rooperol. H. sobolifera and rooperol activated caspase-3 and -7 (using fluorescently labelled antibodies) in HeLa and HT-29 cancer cells, and caspase-7 in MCF-7 cancer cells after 48 hrs. Annexin V binding to phosphatidylserines in rooperol treated U937 cells confirmed early apoptosis after 15 hrs. The TUNEL assay showed DNA fragmentation in the three cancer cell lines when treated with H. sobolifera and rooperol for 48 hrs. A shift pass the G2/M phase has led to the investigation of endoreduplication, which was confirmed by cell/nucleus size, and anti-apoptotic proteins (Akt, phospho-Akt, phospho-Bcl-2 and p21Waf1/Cip1). U937 cell differentiation to monocyte-macrophages was optimized using PMA and 1,25(OH)2D3, which was confirmed by morphological and biochemical changes. For the anti-inflammatory properties, Hypoxis extracts and rooperol significantly increased NO production in monocyte-macrophages (pre-loaded with DAF-2 DA) and phagocytosis of pHrodoTM E. coli BioParticles®. The treatments had no effect on COX-2 expression in monocyte-macrophages. The phytosterols significantly increased IL-1β and IL-6 secretion xv (using the FlowCytomix Multiplex human Th1/Th2 10plex Kit I) in the PBMCs of one donor. For the antioxidant properties, Hypoxis extracts and rooperol significantly increased ROS production in undifferentiated and differentiated U937 cells, which were pre-loaded with DCFH-DA. Hypoxis extracts and purified compounds had ferric reducing activities, but only rooperol had ferric reducing activities significantly greater than ascorbic acid. β-sitosterol, campesterol and cholesterol significantly increased SOD activity in Chang liver cells, while H. stellipilis, H. sobolifera and rooperol decreased SOD activity. Anticancer, anti-inflammatory and antioxidant properties of the Hypoxis extracts may be attributed to the β-sitosterol content, because Hypoxis chloroform extracts contained very little or no hypoxoside. Unidentified compounds, and synergistic and additive effects of the compounds may have contributed to the biological effects. This study confirms previous reports that rooperol is the active compound. Results provide scientific data on the medicinal properties of one of the most frequently used medicinal plants in South Africa.
- Full Text:
- Date Issued: 2010
An investigation of IgE regulation by recombinant soluble IgE receptors and co-receptors in human cell culture models
- Authors: Bowles, Sandra Lyn
- Date: 2010
- Subjects: Immunoglobulin E , Allergy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10321 , http://hdl.handle.net/10948/1231 , Immunoglobulin E , Allergy
- Description: Type I hypersensitivities are mediated by the IgE antibody. The effector functions and synthesis of IgE result from interactions with a network of proteins that include a high affinity (FcRIα) and a low affinity (CD23, FcRII) Fc receptor in conjunction with the B lymphocyte receptor, CD21. CD23 is a multifunctional type II transmembrane protein that binds its known ligands through its ectodomain either as a membrane-bound or soluble receptor generated in vivo by specific proteolytic cleavages. IgE production is primarily regulated by interactions between IgE, CD23 and CD21. Despite its importance for development of strategies to limit hypersensitivity, precise information about the molecular interactions remains limited. During this study, I engineered, expressed and purified from bacteria three soluble human CD23 fragments that are normally formed in vivo and shed from the cell surface (1) derCD23, amino acids 156-298 (2) sCD23, amino acids 150-321 and (3) the entire ectodomain, exCD23, amino acids 48-321 to examine the comparative binding of recombinant human CD21 SCR 1-2 and native human IgE to these fragments. Gel filtration HPLC revealed that derCD23 and sCD23 were monomeric whereas exCD23 assembled as a heterogeneous mixture that included trimers and monomers. At the concentrations utilized, CD23 fragments sCD23 and exCD23 bound CD21 with similar affinity, whereas interaction between derCD23 and CD21 was minimal when analyzed by surface plasmon resonance (SPR) spectroscopy. These findings suggest that penultimate “tail” amino acids between 298 and 321 stabilize CD21 attachment, although it cannot be ruled out, the region between Met 150 and Ser 156 may also play a role in binding CD21 SCR 1-2. In contrast, there is a progressive increment in the affinity of soluble fragments (exCD23>sCD23>derCD23) for IgE, upon increasing length of the proximal CD23 “stalk” domain. These findings highlight the differences in both the structural basis and affinity of the three physiological fragments of human CD23 for the ligands CD21 and IgE and underscore the complexity of CD23-mediated regulatory networks. It was found that B-cells only make up ~5% of the PBMC population, and that these cells were able to be activated, via STAT-6 phosphorylation, to enter class switch recombination (CSR) by the addition of switch factors (IL-4 and anti-CD40). Titration experiments dictated that 25 ng/mL of CD23 was the most efficient concentration to up-regulate IgE synthesis in PBMCs; furthermore, soluble CD23 proteins were incubated with PBMCs in the presence and absence of CD21 SCR 1-2 to investigate the effect that these recombinant proteins have on IgE synthesis. Results showed that the influence of recombinant proteins (both CD23 and CD21) on IgE synthesis was slight. It was shown that while derCD23 had no significant effect, monomeric sCD23 down-regulated, and the mixture of monomeric and oligomeric exCD23 up-regulated IgE synthesis. On addition of CD21 SCR 1-2 to the cells switched and treated with soluble CD23, it was found that in both cases for sCD23 and exCD23, IgE synthesis was increased, while for derCD23, there was no noticeable difference in IgE synthesis. This confirmed previous data showing the lack of binding between derCD23 and CD21 SCR 1-2. The exact binding site for CD21 on the CD23 molecule is unknown, and incompletely represented in the NMR and crystal structures. It is thought that CD21 binds to the C-terminal tail section, not present in derCD23. It is therefore likely that only a negative-feedback mechanism operates with derCD23 to regulate IgE synthesis. Further investigation of the binding of CD23 fragments to SCR 5-8 of CD21 and the effect of this on IgE synthesis may lead to a potential therapeutic role for derCD23 in the treatment of allergic disease. Data accumulated in this study suggests that investigating the modulation of oligomeric state and thus the activity of soluble CD23 fragments may be important in the construction of new regulators of IgE synthesis.
- Full Text:
- Date Issued: 2010
- Authors: Bowles, Sandra Lyn
- Date: 2010
- Subjects: Immunoglobulin E , Allergy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10321 , http://hdl.handle.net/10948/1231 , Immunoglobulin E , Allergy
- Description: Type I hypersensitivities are mediated by the IgE antibody. The effector functions and synthesis of IgE result from interactions with a network of proteins that include a high affinity (FcRIα) and a low affinity (CD23, FcRII) Fc receptor in conjunction with the B lymphocyte receptor, CD21. CD23 is a multifunctional type II transmembrane protein that binds its known ligands through its ectodomain either as a membrane-bound or soluble receptor generated in vivo by specific proteolytic cleavages. IgE production is primarily regulated by interactions between IgE, CD23 and CD21. Despite its importance for development of strategies to limit hypersensitivity, precise information about the molecular interactions remains limited. During this study, I engineered, expressed and purified from bacteria three soluble human CD23 fragments that are normally formed in vivo and shed from the cell surface (1) derCD23, amino acids 156-298 (2) sCD23, amino acids 150-321 and (3) the entire ectodomain, exCD23, amino acids 48-321 to examine the comparative binding of recombinant human CD21 SCR 1-2 and native human IgE to these fragments. Gel filtration HPLC revealed that derCD23 and sCD23 were monomeric whereas exCD23 assembled as a heterogeneous mixture that included trimers and monomers. At the concentrations utilized, CD23 fragments sCD23 and exCD23 bound CD21 with similar affinity, whereas interaction between derCD23 and CD21 was minimal when analyzed by surface plasmon resonance (SPR) spectroscopy. These findings suggest that penultimate “tail” amino acids between 298 and 321 stabilize CD21 attachment, although it cannot be ruled out, the region between Met 150 and Ser 156 may also play a role in binding CD21 SCR 1-2. In contrast, there is a progressive increment in the affinity of soluble fragments (exCD23>sCD23>derCD23) for IgE, upon increasing length of the proximal CD23 “stalk” domain. These findings highlight the differences in both the structural basis and affinity of the three physiological fragments of human CD23 for the ligands CD21 and IgE and underscore the complexity of CD23-mediated regulatory networks. It was found that B-cells only make up ~5% of the PBMC population, and that these cells were able to be activated, via STAT-6 phosphorylation, to enter class switch recombination (CSR) by the addition of switch factors (IL-4 and anti-CD40). Titration experiments dictated that 25 ng/mL of CD23 was the most efficient concentration to up-regulate IgE synthesis in PBMCs; furthermore, soluble CD23 proteins were incubated with PBMCs in the presence and absence of CD21 SCR 1-2 to investigate the effect that these recombinant proteins have on IgE synthesis. Results showed that the influence of recombinant proteins (both CD23 and CD21) on IgE synthesis was slight. It was shown that while derCD23 had no significant effect, monomeric sCD23 down-regulated, and the mixture of monomeric and oligomeric exCD23 up-regulated IgE synthesis. On addition of CD21 SCR 1-2 to the cells switched and treated with soluble CD23, it was found that in both cases for sCD23 and exCD23, IgE synthesis was increased, while for derCD23, there was no noticeable difference in IgE synthesis. This confirmed previous data showing the lack of binding between derCD23 and CD21 SCR 1-2. The exact binding site for CD21 on the CD23 molecule is unknown, and incompletely represented in the NMR and crystal structures. It is thought that CD21 binds to the C-terminal tail section, not present in derCD23. It is therefore likely that only a negative-feedback mechanism operates with derCD23 to regulate IgE synthesis. Further investigation of the binding of CD23 fragments to SCR 5-8 of CD21 and the effect of this on IgE synthesis may lead to a potential therapeutic role for derCD23 in the treatment of allergic disease. Data accumulated in this study suggests that investigating the modulation of oligomeric state and thus the activity of soluble CD23 fragments may be important in the construction of new regulators of IgE synthesis.
- Full Text:
- Date Issued: 2010
The use of response surface methodology and artificial neural networks for the establishment of a design space for a sustained release salbutamol sulphate formulation
- Authors: Chaibva, Faith Anesu
- Date: 2010
- Subjects: Salbutamol sulphate Artificial intelligence -- Medical applications Neural networks (Computer science) Response surfaces (Statistics) Pharmaceutical biotechnology -- Quality contro Drugs -- Design Pharmacokinetics Drugs -- Dosage forms Drugs -- Controlled release
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3845 , http://hdl.handle.net/10962/d1010432
- Description: Quality by Design (QbD) is a systematic approach that has been recommended as suitable for the development of quality pharmaceutical products. The QbD approach commences with the definition of a quality target drug profile and predetermined objectives that are then used to direct the formulation development process with an emphasis on understanding the pharmaceutical science and manufacturing principles that apply to a product. The design space is directly linked to the use of QbD for formulation development and is a multidimensional combination and interaction of input variables and process parameters that have been demonstrated to provide an assurance of quality. The objective of these studies was to apply the principles of QbD as a framework for the optimisation of a sustained release (SR) formulation of salbutamol sulphate (SBS), and for the establishment of a design space using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). SBS is a short-acting ♭₂ agonist that is used for the management of asthma and chronic obstructive pulmonary disease (COPD). The use of a SR formulation of SBS may provide clinical benefits in the management of these respiratory disorders. Ashtalin®8 ER (Cipla Ltd., Mumbai, Maharashtra, India) was selected as a reference formulation for use in these studies. An Ishikawa or Cause and Effect diagram was used to determine the impact of formulation and process factors that have the potential to affect product quality. Key areas of concern that must be monitored include the raw materials, the manufacturing equipment and processes, and the analytical and assessment methods employed. The conditions in the laboratory and manufacturing processes were carefully monitored and recorded for any deviation from protocol, and equipment for assessment of dosage form performance, including dissolution equipment, balances and hardness testers, underwent regular maintenance. Preliminary studies to assess the potential utility of Methocel® Kl OOM, alone and in combination with other matrix forming polymers, revealed that the combination of this polymer with xanthan gum and Carbopol® has the potential to modulate the release of SBS at a specific rate, for a period of 12 hr. A central composite design using Methocel® KlOOM, xanthan gum, Carbopol® 974P and Surelease® as the granulating fluid was constructed to fully evaluate the impact of these formulation variables on the rate and extent of SBS release from manufactured formulations. The results revealed that although Methocel® KlOOM and xanthan gum had the greatest retardant effect on drug release, interactions between the polymers used in the study were also important determinants of the measureable responses. An ANN model was trained for optimisation using the data generated from a central composite study. The efficiency of the network was optimised by assessing the impact of the number of nodes in the hidden layer using a three layer Multi Layer Perceptron (MLP). The results revealed that a network with nine nodes in the hidden layer had the best predictive ability, suitable for application to formulation optimisation studies. Pharmaceutical optimisation was conducted using both the RSM and the trained ANN models. The results from the two optimisation procedures yielded two different formulation compositions that were subjected to in vitro dissolution testing using USP Apparatus 3. The results revealed that, although the formulation compositions that were derived from the optimisation procedures were different, both solutions gave reproducible results for which the dissolution profiles were indeed similar to that of the reference formulation. RSM and ANN were further investigated as possible means of establishing a design space for formulation compositions that would result in dosage forms that have similar in vitro release test profiles comparable to the reference product. Constraint plots were used to determine the bounds of the formulation variables that would result in the manufacture of dosage forms with the desired release profile. ANN simulations with hypothetical formulations that were generated within a small region of the experimental domain were investigated as a means of understanding the impact of varying the composition of the formulation on resultant dissolution profiles. Although both methods were suitable for the establishment of a design space, the use of ANN may be better suited for this purpose because of the manner in which ANN handles data. As more information about the behaviour of a formulation and its processes is generated during the product Iifecycle, ANN may be used to evaluate the impact of formulation and process variables on measureable responses. It is recommended that ANN may be suitable for the optimisation of pharmaceutical formulations and establishment of a design space in line with ICH Pharmaceutical Development [1], Quality Risk Management [2] and Pharmaceutical Quality Systems [3]
- Full Text:
- Date Issued: 2010
- Authors: Chaibva, Faith Anesu
- Date: 2010
- Subjects: Salbutamol sulphate Artificial intelligence -- Medical applications Neural networks (Computer science) Response surfaces (Statistics) Pharmaceutical biotechnology -- Quality contro Drugs -- Design Pharmacokinetics Drugs -- Dosage forms Drugs -- Controlled release
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3845 , http://hdl.handle.net/10962/d1010432
- Description: Quality by Design (QbD) is a systematic approach that has been recommended as suitable for the development of quality pharmaceutical products. The QbD approach commences with the definition of a quality target drug profile and predetermined objectives that are then used to direct the formulation development process with an emphasis on understanding the pharmaceutical science and manufacturing principles that apply to a product. The design space is directly linked to the use of QbD for formulation development and is a multidimensional combination and interaction of input variables and process parameters that have been demonstrated to provide an assurance of quality. The objective of these studies was to apply the principles of QbD as a framework for the optimisation of a sustained release (SR) formulation of salbutamol sulphate (SBS), and for the establishment of a design space using Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). SBS is a short-acting ♭₂ agonist that is used for the management of asthma and chronic obstructive pulmonary disease (COPD). The use of a SR formulation of SBS may provide clinical benefits in the management of these respiratory disorders. Ashtalin®8 ER (Cipla Ltd., Mumbai, Maharashtra, India) was selected as a reference formulation for use in these studies. An Ishikawa or Cause and Effect diagram was used to determine the impact of formulation and process factors that have the potential to affect product quality. Key areas of concern that must be monitored include the raw materials, the manufacturing equipment and processes, and the analytical and assessment methods employed. The conditions in the laboratory and manufacturing processes were carefully monitored and recorded for any deviation from protocol, and equipment for assessment of dosage form performance, including dissolution equipment, balances and hardness testers, underwent regular maintenance. Preliminary studies to assess the potential utility of Methocel® Kl OOM, alone and in combination with other matrix forming polymers, revealed that the combination of this polymer with xanthan gum and Carbopol® has the potential to modulate the release of SBS at a specific rate, for a period of 12 hr. A central composite design using Methocel® KlOOM, xanthan gum, Carbopol® 974P and Surelease® as the granulating fluid was constructed to fully evaluate the impact of these formulation variables on the rate and extent of SBS release from manufactured formulations. The results revealed that although Methocel® KlOOM and xanthan gum had the greatest retardant effect on drug release, interactions between the polymers used in the study were also important determinants of the measureable responses. An ANN model was trained for optimisation using the data generated from a central composite study. The efficiency of the network was optimised by assessing the impact of the number of nodes in the hidden layer using a three layer Multi Layer Perceptron (MLP). The results revealed that a network with nine nodes in the hidden layer had the best predictive ability, suitable for application to formulation optimisation studies. Pharmaceutical optimisation was conducted using both the RSM and the trained ANN models. The results from the two optimisation procedures yielded two different formulation compositions that were subjected to in vitro dissolution testing using USP Apparatus 3. The results revealed that, although the formulation compositions that were derived from the optimisation procedures were different, both solutions gave reproducible results for which the dissolution profiles were indeed similar to that of the reference formulation. RSM and ANN were further investigated as possible means of establishing a design space for formulation compositions that would result in dosage forms that have similar in vitro release test profiles comparable to the reference product. Constraint plots were used to determine the bounds of the formulation variables that would result in the manufacture of dosage forms with the desired release profile. ANN simulations with hypothetical formulations that were generated within a small region of the experimental domain were investigated as a means of understanding the impact of varying the composition of the formulation on resultant dissolution profiles. Although both methods were suitable for the establishment of a design space, the use of ANN may be better suited for this purpose because of the manner in which ANN handles data. As more information about the behaviour of a formulation and its processes is generated during the product Iifecycle, ANN may be used to evaluate the impact of formulation and process variables on measureable responses. It is recommended that ANN may be suitable for the optimisation of pharmaceutical formulations and establishment of a design space in line with ICH Pharmaceutical Development [1], Quality Risk Management [2] and Pharmaceutical Quality Systems [3]
- Full Text:
- Date Issued: 2010
Photophysiochemical studies of d¹⁰ metallophthalocyanines and their interaction with nanoparticles
- Chidawanyika, Wadzanai Janet Upenyu
- Authors: Chidawanyika, Wadzanai Janet Upenyu
- Date: 2010
- Subjects: Nanoparticles Phthalocyanines Photochemistry Electrochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4335 , http://hdl.handle.net/10962/d1004996
- Description: The syntheses, extensive spectroscopic characterization, photophysical and photochemical studies have been conducted for a variation of d10 metallophthaloycanines (MPcs). Comparisons have been made taking into consideration the nfluence of the central metal ion, solvent properties, substituent type and position. Coordination to heavy central metals i.e. Hg gives enhanced triplet state properties. Low symmetry metallophthalocyanine complexes were similarly haracterized and the influence of nteractions with nanoparticles on their photophysical and photochemical properties determined. The MPcs have been linked and adsorbed or mixed with nanoparticles i.e. hemically functionalized single-walled carbon nanotubes SWCNT) and mercaptocarboxylic acid capped CdTe quantum dots (QDs) and changes in the spectra accounted for with respect to the proposed conjugate structures. Distinct differences ccur for linked and adsorbed or mixed conjugates in the bsorption, infrared (IR) and Raman spectra and for thermal ravimetric decay profiles, suggesting successful formation f covalent bonds (linked) and point to structurally ifferent materials. SWCNT quench MPc fluorescence by a photoinduced electron transfer mediated process to give low fluorescence quantum yields. The QDs were used as energy transfer donors and facilitate energy transfer, through Förster resonance energy transfer (FRET) from the QDs to the MPcs. Improved FRET efficiencies were found for linked MPc-QD conjugates relative to the mixed species. Photophysicochemical properties of MPcs were, in general, improved as a result of interactions with nanoparticles.
- Full Text:
- Date Issued: 2010
- Authors: Chidawanyika, Wadzanai Janet Upenyu
- Date: 2010
- Subjects: Nanoparticles Phthalocyanines Photochemistry Electrochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4335 , http://hdl.handle.net/10962/d1004996
- Description: The syntheses, extensive spectroscopic characterization, photophysical and photochemical studies have been conducted for a variation of d10 metallophthaloycanines (MPcs). Comparisons have been made taking into consideration the nfluence of the central metal ion, solvent properties, substituent type and position. Coordination to heavy central metals i.e. Hg gives enhanced triplet state properties. Low symmetry metallophthalocyanine complexes were similarly haracterized and the influence of nteractions with nanoparticles on their photophysical and photochemical properties determined. The MPcs have been linked and adsorbed or mixed with nanoparticles i.e. hemically functionalized single-walled carbon nanotubes SWCNT) and mercaptocarboxylic acid capped CdTe quantum dots (QDs) and changes in the spectra accounted for with respect to the proposed conjugate structures. Distinct differences ccur for linked and adsorbed or mixed conjugates in the bsorption, infrared (IR) and Raman spectra and for thermal ravimetric decay profiles, suggesting successful formation f covalent bonds (linked) and point to structurally ifferent materials. SWCNT quench MPc fluorescence by a photoinduced electron transfer mediated process to give low fluorescence quantum yields. The QDs were used as energy transfer donors and facilitate energy transfer, through Förster resonance energy transfer (FRET) from the QDs to the MPcs. Improved FRET efficiencies were found for linked MPc-QD conjugates relative to the mixed species. Photophysicochemical properties of MPcs were, in general, improved as a result of interactions with nanoparticles.
- Full Text:
- Date Issued: 2010
Neurocognitive and symptom profiles of concussed and nonconcussed provincial rugby players over one season
- Authors: Clark, Susan Beverley
- Date: 2010
- Subjects: Rugby football injuries Brain -- Concussion -- Complications Head -- Wounds and injuries -- Complications Sports injuries -- Psychological aspects Brain damage Neuropsychological tests Rugby Union football players
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2950 , http://hdl.handle.net/10962/d1002459
- Description: Neurocognitive and symptom profiles of concussed and nonconcussed adult provincial rugby union players were investigated over one rugby season, including early season (baseline), intermittent postconcussion, and end of season testing. In a non-equivalent quasi-experimental design, nonconcussed (n = 54) and concussed (n = 17) rugby groups were compared with demographically equivalent noncontact sport controls (n = 37, and n = 17, respectively). Measures included the ImPACT cognitive and symptom composites, and the WMS-III Visual Reproduction and Verbal Paired Associates subtests. The independent and dependent comparative analyses in respect of both nonconcussed and concussed groups, provided cross-validation of poorer acute and/or chronic neuropsychological outcomes for the rugby groups on the ImPACT Reaction Time, Visual Motor Speed, Impulse Control and Symptom composites, and the WMS-III Verbal Paired Associates. The finding of significantly poorer scores on Verbal Paired Associates up to 24 days post concussion for the rugby players versus controls, was longer than the 7 – 10 day recovery period frequently cited in the literature. The overall implication of the study is that even in a group with high cognitive reserve such as these provincial level athletes, there may be prolonged acute recovery, as well as permanent deleterious neuropsychological consequences of cumulative concussive injury in association with a sport such as rugby. Accordingly, the move towards careful individualised postconcussion monitoring of neurocognitive functioning is endorsed, including early identification of any significant permanent reductions in cognitive reserve. Sensitivity of the ImPACT test might be enhanced via inclusion of a verbal associate learning task.
- Full Text:
- Date Issued: 2010
- Authors: Clark, Susan Beverley
- Date: 2010
- Subjects: Rugby football injuries Brain -- Concussion -- Complications Head -- Wounds and injuries -- Complications Sports injuries -- Psychological aspects Brain damage Neuropsychological tests Rugby Union football players
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2950 , http://hdl.handle.net/10962/d1002459
- Description: Neurocognitive and symptom profiles of concussed and nonconcussed adult provincial rugby union players were investigated over one rugby season, including early season (baseline), intermittent postconcussion, and end of season testing. In a non-equivalent quasi-experimental design, nonconcussed (n = 54) and concussed (n = 17) rugby groups were compared with demographically equivalent noncontact sport controls (n = 37, and n = 17, respectively). Measures included the ImPACT cognitive and symptom composites, and the WMS-III Visual Reproduction and Verbal Paired Associates subtests. The independent and dependent comparative analyses in respect of both nonconcussed and concussed groups, provided cross-validation of poorer acute and/or chronic neuropsychological outcomes for the rugby groups on the ImPACT Reaction Time, Visual Motor Speed, Impulse Control and Symptom composites, and the WMS-III Verbal Paired Associates. The finding of significantly poorer scores on Verbal Paired Associates up to 24 days post concussion for the rugby players versus controls, was longer than the 7 – 10 day recovery period frequently cited in the literature. The overall implication of the study is that even in a group with high cognitive reserve such as these provincial level athletes, there may be prolonged acute recovery, as well as permanent deleterious neuropsychological consequences of cumulative concussive injury in association with a sport such as rugby. Accordingly, the move towards careful individualised postconcussion monitoring of neurocognitive functioning is endorsed, including early identification of any significant permanent reductions in cognitive reserve. Sensitivity of the ImPACT test might be enhanced via inclusion of a verbal associate learning task.
- Full Text:
- Date Issued: 2010
The phytogeography of the Sneeuberg, Nuweveldberge and Roggeveldberge (Great Escarpment): assessing migration routes and endemism
- Authors: Clark, Vincent Ralph
- Date: 2010
- Subjects: Phytogeography -- South Africa Endemic plants -- South Africa Plants -- Migration -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4187 , http://hdl.handle.net/10962/d1003756
- Description: The Great Escarpment forms a semi-continuous mountain system 5 000 km long, stretching from Angola in the north-west, south through Namibia, and into western, southern and eastern South Africa, including Lesotho and Swaziland. It is composed of a wide variety of geological suites but is unified in representing the edge of the African plateau and the passive Gondwanan continental margin. The Great Escarpment falls into all major climatic zones on the subcontinent, is a repository of palaeo- and neo-endemics, hosts more than half of southern Africa‟s centres of plant endemism, and has a rich suite of endemic fauna. In addition, the Great Escarpment is believed to be both a refugium and corridor for biological diversity. Despite the biological richness of the Great Escarpment, research to date has been fragmented and many sections of the Great Escarpment have not been studied. The aim of this study is to contribute to research on the Great Escarpment by undertaking a detailed floristic study of the southern Great Escarpment (the Sneeuberg, Nuweveldberge and Roggeveldberge). Together these mountains comprise approximately 1 000 km (one fifth) of the Great Escarpment, and occupy a transition zone between the summer rainfall zone in the east and the winter rainfall zone in the west. They are also the sections of Great Escarpment most closely situated to the Cape Floristic Region (CFR) and would thus be involved in hypothesised migration routes for lineages that also occur further north through the Drakensberg Alpine Centre (DAC) to the East African mountain chain. Detailed fieldwork of the southern Great Escarpment was undertaken over a period of four years in all seasons. Approximately 8 000 specimens were collected. Particular emphasis was placed on areas that may represent refugia, i.e. the highest plateaux and peaks, mesic areas and cliff-lines. An overview of each mountain range, together with their endemic plant species and phytogeography, is provided. Approximately ten new species have been discovered during this study, two of which have been described to date. Numerous endemics only known from their types have also been rediscovered. The Sneeuberg is defined as a new centre of plant endemism on the Great Escarpment (endemism of 2.3%), and the role of the Boschberg and Groot-Bruintjieshoogde (part of the Sneeuberg) as a nexus for floristic migration routes is discussed. The Nuweveldberge is shown to have low endemism despite a floristic tally similar to the Sneeuberg, while the Roggeveldberge are confirmed to be the most endemic-rich section of the southern Great Escarpment. The field data collected was augmented by available data in taxonomic revisions, and floras for the Sneeuberg, Nuweveldberge and Roggeveldberge were compiled. In order to floristically compare the southern Great Escarpment with other sections of the Great Escarpment and the CFR, a database of some 12 000 taxa was created using available floristic data for the CFR, DAC and Great WinterbergAmatolas, together with the data collated for the Sneeuberg, Nuweveldberge and Roggeveldberge. These data were analysed using phenetic methods and Parsimony Analysis of Endemicity (PAE). The results indicate stronger linkages in the east, particularly between the Sneeuberg and Nuweveldberge, and between the Sneeuberg and the Great WinterbergAmatolas. The relationship of the Roggeveldberge with the rest of the southern Great Escarpment remains ambiguous. In order to refine notions of connectivity and migration routes, 19 well-sampled phylogenies were assessed for sister-taxon disjunctions to explore CFRGreat Escarpment connections. Palaeo-connectivity between the CFR and southern Great Escarpment is most strongly supported for the south-eastern (SE) connection, and less so for the north-western (NW) and Matjiesfontein connections. There is support for the current (or recent) use of these three connections from numerous species that occur on both sides of the connections. Results of these analyses indicate that the southern Great Escarpment is a palaeo-corridor, the functioning of which has been broken by the aridification of the Nuweveldberge since the Last Glacial Maximum (LGM). Floristic connectivity is strongest in the east, from the Nuweveldberge to the DAC, and is less so in the west between the Nuweveldberge and the Roggeveldberge a finding attributed to the transition from a reliable winter rainfall regime on the Roggeveldberge to an unpredictable moisture regime on the Nuweveldberge. The mountains of the southern Great Escarpment are thus a series of refugia from a previous moister, cooler climate and are a corridor between the eastern and western components of the Great Escarpment. The SE connection is the primary link between the CFR and the eastern Great Escarpment Afromontane region in southern Africa. The implications of this research are that accurate conservation assessments and Red Data listings for many of the previously poorly-known endemics can now be made, and appropriate conservation measures implemented. Climate change remains the primary threat to these endemics and montane taxa in general, while degradation of wetlands is the primary threat to the water catchment service provided by the southern Great Escarpment. Future detailed research on the Great WinterbergAmatolas and Stormberg and a comprehensive flora of the HantamRoggeveldberge will further enhance our understanding of the floristics of the southern Great Escarpment, and provide the necessary data for comprehensive GIS-based models of proposed climate change scenarios for local, regional and national conservation planning.
- Full Text:
- Date Issued: 2010
- Authors: Clark, Vincent Ralph
- Date: 2010
- Subjects: Phytogeography -- South Africa Endemic plants -- South Africa Plants -- Migration -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4187 , http://hdl.handle.net/10962/d1003756
- Description: The Great Escarpment forms a semi-continuous mountain system 5 000 km long, stretching from Angola in the north-west, south through Namibia, and into western, southern and eastern South Africa, including Lesotho and Swaziland. It is composed of a wide variety of geological suites but is unified in representing the edge of the African plateau and the passive Gondwanan continental margin. The Great Escarpment falls into all major climatic zones on the subcontinent, is a repository of palaeo- and neo-endemics, hosts more than half of southern Africa‟s centres of plant endemism, and has a rich suite of endemic fauna. In addition, the Great Escarpment is believed to be both a refugium and corridor for biological diversity. Despite the biological richness of the Great Escarpment, research to date has been fragmented and many sections of the Great Escarpment have not been studied. The aim of this study is to contribute to research on the Great Escarpment by undertaking a detailed floristic study of the southern Great Escarpment (the Sneeuberg, Nuweveldberge and Roggeveldberge). Together these mountains comprise approximately 1 000 km (one fifth) of the Great Escarpment, and occupy a transition zone between the summer rainfall zone in the east and the winter rainfall zone in the west. They are also the sections of Great Escarpment most closely situated to the Cape Floristic Region (CFR) and would thus be involved in hypothesised migration routes for lineages that also occur further north through the Drakensberg Alpine Centre (DAC) to the East African mountain chain. Detailed fieldwork of the southern Great Escarpment was undertaken over a period of four years in all seasons. Approximately 8 000 specimens were collected. Particular emphasis was placed on areas that may represent refugia, i.e. the highest plateaux and peaks, mesic areas and cliff-lines. An overview of each mountain range, together with their endemic plant species and phytogeography, is provided. Approximately ten new species have been discovered during this study, two of which have been described to date. Numerous endemics only known from their types have also been rediscovered. The Sneeuberg is defined as a new centre of plant endemism on the Great Escarpment (endemism of 2.3%), and the role of the Boschberg and Groot-Bruintjieshoogde (part of the Sneeuberg) as a nexus for floristic migration routes is discussed. The Nuweveldberge is shown to have low endemism despite a floristic tally similar to the Sneeuberg, while the Roggeveldberge are confirmed to be the most endemic-rich section of the southern Great Escarpment. The field data collected was augmented by available data in taxonomic revisions, and floras for the Sneeuberg, Nuweveldberge and Roggeveldberge were compiled. In order to floristically compare the southern Great Escarpment with other sections of the Great Escarpment and the CFR, a database of some 12 000 taxa was created using available floristic data for the CFR, DAC and Great WinterbergAmatolas, together with the data collated for the Sneeuberg, Nuweveldberge and Roggeveldberge. These data were analysed using phenetic methods and Parsimony Analysis of Endemicity (PAE). The results indicate stronger linkages in the east, particularly between the Sneeuberg and Nuweveldberge, and between the Sneeuberg and the Great WinterbergAmatolas. The relationship of the Roggeveldberge with the rest of the southern Great Escarpment remains ambiguous. In order to refine notions of connectivity and migration routes, 19 well-sampled phylogenies were assessed for sister-taxon disjunctions to explore CFRGreat Escarpment connections. Palaeo-connectivity between the CFR and southern Great Escarpment is most strongly supported for the south-eastern (SE) connection, and less so for the north-western (NW) and Matjiesfontein connections. There is support for the current (or recent) use of these three connections from numerous species that occur on both sides of the connections. Results of these analyses indicate that the southern Great Escarpment is a palaeo-corridor, the functioning of which has been broken by the aridification of the Nuweveldberge since the Last Glacial Maximum (LGM). Floristic connectivity is strongest in the east, from the Nuweveldberge to the DAC, and is less so in the west between the Nuweveldberge and the Roggeveldberge a finding attributed to the transition from a reliable winter rainfall regime on the Roggeveldberge to an unpredictable moisture regime on the Nuweveldberge. The mountains of the southern Great Escarpment are thus a series of refugia from a previous moister, cooler climate and are a corridor between the eastern and western components of the Great Escarpment. The SE connection is the primary link between the CFR and the eastern Great Escarpment Afromontane region in southern Africa. The implications of this research are that accurate conservation assessments and Red Data listings for many of the previously poorly-known endemics can now be made, and appropriate conservation measures implemented. Climate change remains the primary threat to these endemics and montane taxa in general, while degradation of wetlands is the primary threat to the water catchment service provided by the southern Great Escarpment. Future detailed research on the Great WinterbergAmatolas and Stormberg and a comprehensive flora of the HantamRoggeveldberge will further enhance our understanding of the floristics of the southern Great Escarpment, and provide the necessary data for comprehensive GIS-based models of proposed climate change scenarios for local, regional and national conservation planning.
- Full Text:
- Date Issued: 2010
Ecology and degree of specialization of South African milkweeds with diverse pollination systems
- Authors: Coombs, Gareth
- Date: 2010
- Subjects: Milkweeds -- South Africa Milkweeds -- South Africa -- Ecology Milkweeds -- South Africa -- Pollination Allee effect Self-pollination Pollination by insects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4189 , http://hdl.handle.net/10962/d1003758
- Description: Like orchids, the complexity of flowers found in asclepiads (Asclepiadoideae, Apocynaceae) and the fact that pollen is presented as pollinaria, offers excellent opportunities to study various aspects of plant-pollinator interactions. In this thesis I investigated two broad themes: ecological aspects of the pollination biology of hymenopteran and fly-pollinated asclepiads as well as the degree of specialization to certain pollinators in these species. Colonizing plants often reproduce through self-pollination, or have highly generalized pollination systems, or both. These characteristics facilitate establishment in small founding populations and generates the prediction that reproductive success should be independent of population size in these species. Chapter one examines the pollination biology of Gomphocarpus physocarpus, an indigenous, weedy species and investigates the relationship between reproductive success and population size. In this species, there is no evidence of an Allee effect and reproductive success is not correlated with population size. In addition G. physocarpus is not capable of self-pollination, suggesting it is completely reliant on pollinators for seed set. The lack of a relationship between pollination success and population size is therefore likely explained by the generalized wasp pollination system of this species. Several milkweeds are invasive outside of their native ranges. Invasive species either need to co-opt native pollinators in order to reproduce or reduce their reliance on pollinators through having the ability to self-pollinate. Co-opting native pollinators is expected to be easier in species that have generalized pollination systems, alternatively species with specialized flower morphologies need to rely on similar functional groups of pollinators to be present within the invaded range. Chapter two investigates the pollination biology and pollination success of the invasive milkweed, Araujia sericifera, and finds that in South Africa, this species is visited mainly by native honeybees and nocturnal moths. Moths however contribute little to pollen removal, and deposition. Based on the apparent morphological mismatch between the flower of A. sericifera and native honeybees, I propose that the native pollinators of this species are likely to be larger Hymenoptera (e.g. Bumblebees). Data from a breeding system study, indicated that this species is not capable of automatic self-pollination, but could set fruit from geitonogamous self-pollinations pointing to the importance of native pollinators for successful reproduction. The pollinaria of milkweeds can accumulate on pollinators to form pollen masses large enough to physically interfere with the foraging behaviour of pollinating insects. In chapter three I describe the pollination biology of Cynanchum ellipticum and find that this species is mainly pollinated by honeybees although this species is visited by several other members of Hymenoptera, Lepidoptera and Diptera. Due to the structure of the pollinaria, these chain together relatively efficiently and frequently form large pollinarium loads on the mouthparts of honeybees. However there is little evidence that these pollinarium loads influence the foraging times of pollinators and only a few individual honeybees exhibited longer foraging times and most honeybees were unaffected by the presence of large pollinarium loads. Within the genus Cynanchum there is large variation in the gynostegium structure that may influence the pattern of pollinarium loading on pollinators as well as pollen reception as shown in chapter three. In Chapter four, the pollination biology of Cynanchum obtusifolium is examined, and like that of C. ellipticum, this species is visited by a wide diversity of pollinators but honeybees appear to be the primary pollinators. More importantly this species is shown to be andromonoecious and produces two morphologically different flower types, that may be distinguished based on differences in the gynostegium structure. These two types of flower could mainly be distinguished by the length of the anther wings. I found that flowers with short anther wings function as male flowers by only exporting- and rarely receiving pollinia. Flowers with longer anther wings function as hermaphrodite flowers and can both export and receive pollinia. The ratio of male to hermaphrodite flowers varied at different times during the flowering season, but preliminary data suggested that this was not related to levels of pollination success. The genera Stapelia and Ceropegia are well known for their intricate floral adaptations that mimic the brood and feeding substrates of pollinating flies. Despite several studies that have documented the various adaptations to fly pollination in different species, there is a lack of natural history studies documenting different flower visitors, pollen loads and long term levels of pollination success in these species. In Chapter six I document the pollination biology of Ceropegia ampliata by documenting different pollinators and quantifying average levels of pollination success and the nectar reward. I also experimentally manipulated the trapping hairs of this species to determine whether trapping hairs influence average levels of pollen export and receipt. I show that Ceropegia ampliata is pollinated by a generalist guild of flies (mainly Tachinidae, Sarcophagidae, Muscidae and Lauxaniidae) and produces minute quantities of relatively dilute nectar as a reward. Pollination success was generally low in this species and increases periodically suggesting that the abundance of pollinators is patchy. I found that flowers with trapping hairs that had already wilted had higher levels of pollinarium removal than flowers with erect hairs, however experimentally removing the hairs had no significant effect on pollen export and receipt. In Chapter seven, I document the pollinators, pollen loads and long term levels of pollination success in Stapelia hirsuta var. bayllissi, a rare sapromyiophilous stapeliad. I find that, in contrast to C. ampliata, this species was specialized to pollination by small flies of the family Anthomyiidae. Similar to the results from Chapter seven, I find that long term levels of pollination success were typically low but could increase periodically, although such increases were generally unpredictable. There are currently very few records documenting pollinator interactions in the Periplocoideae. Many species within this subfamily exhibit open-access flowers suggestive of pollination by short-tongued insects. I investigated the pollination biology of Chlorocyathus lobulata, a rare species with a highly localized distribution. I aimed to determine the pollinators, average levels of pollination success and demography of this species in order to determine whether this rare species is suffering from the collapse of a highly specialized pollinator mutualism. I also quantified the high incidence of flower herbivory caused by larvae of the moth, Bocchoris onychinalis. I find that C. lobulata has a highly generalized fly pollination system and average levels of pollination success suggested that a large proportion of flowers had pollen removed and deposited suggesting that this species is not experiencing pollination failure. The large numbers of juveniles present also indicated that recruitment is taking place.
- Full Text:
- Date Issued: 2010
- Authors: Coombs, Gareth
- Date: 2010
- Subjects: Milkweeds -- South Africa Milkweeds -- South Africa -- Ecology Milkweeds -- South Africa -- Pollination Allee effect Self-pollination Pollination by insects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4189 , http://hdl.handle.net/10962/d1003758
- Description: Like orchids, the complexity of flowers found in asclepiads (Asclepiadoideae, Apocynaceae) and the fact that pollen is presented as pollinaria, offers excellent opportunities to study various aspects of plant-pollinator interactions. In this thesis I investigated two broad themes: ecological aspects of the pollination biology of hymenopteran and fly-pollinated asclepiads as well as the degree of specialization to certain pollinators in these species. Colonizing plants often reproduce through self-pollination, or have highly generalized pollination systems, or both. These characteristics facilitate establishment in small founding populations and generates the prediction that reproductive success should be independent of population size in these species. Chapter one examines the pollination biology of Gomphocarpus physocarpus, an indigenous, weedy species and investigates the relationship between reproductive success and population size. In this species, there is no evidence of an Allee effect and reproductive success is not correlated with population size. In addition G. physocarpus is not capable of self-pollination, suggesting it is completely reliant on pollinators for seed set. The lack of a relationship between pollination success and population size is therefore likely explained by the generalized wasp pollination system of this species. Several milkweeds are invasive outside of their native ranges. Invasive species either need to co-opt native pollinators in order to reproduce or reduce their reliance on pollinators through having the ability to self-pollinate. Co-opting native pollinators is expected to be easier in species that have generalized pollination systems, alternatively species with specialized flower morphologies need to rely on similar functional groups of pollinators to be present within the invaded range. Chapter two investigates the pollination biology and pollination success of the invasive milkweed, Araujia sericifera, and finds that in South Africa, this species is visited mainly by native honeybees and nocturnal moths. Moths however contribute little to pollen removal, and deposition. Based on the apparent morphological mismatch between the flower of A. sericifera and native honeybees, I propose that the native pollinators of this species are likely to be larger Hymenoptera (e.g. Bumblebees). Data from a breeding system study, indicated that this species is not capable of automatic self-pollination, but could set fruit from geitonogamous self-pollinations pointing to the importance of native pollinators for successful reproduction. The pollinaria of milkweeds can accumulate on pollinators to form pollen masses large enough to physically interfere with the foraging behaviour of pollinating insects. In chapter three I describe the pollination biology of Cynanchum ellipticum and find that this species is mainly pollinated by honeybees although this species is visited by several other members of Hymenoptera, Lepidoptera and Diptera. Due to the structure of the pollinaria, these chain together relatively efficiently and frequently form large pollinarium loads on the mouthparts of honeybees. However there is little evidence that these pollinarium loads influence the foraging times of pollinators and only a few individual honeybees exhibited longer foraging times and most honeybees were unaffected by the presence of large pollinarium loads. Within the genus Cynanchum there is large variation in the gynostegium structure that may influence the pattern of pollinarium loading on pollinators as well as pollen reception as shown in chapter three. In Chapter four, the pollination biology of Cynanchum obtusifolium is examined, and like that of C. ellipticum, this species is visited by a wide diversity of pollinators but honeybees appear to be the primary pollinators. More importantly this species is shown to be andromonoecious and produces two morphologically different flower types, that may be distinguished based on differences in the gynostegium structure. These two types of flower could mainly be distinguished by the length of the anther wings. I found that flowers with short anther wings function as male flowers by only exporting- and rarely receiving pollinia. Flowers with longer anther wings function as hermaphrodite flowers and can both export and receive pollinia. The ratio of male to hermaphrodite flowers varied at different times during the flowering season, but preliminary data suggested that this was not related to levels of pollination success. The genera Stapelia and Ceropegia are well known for their intricate floral adaptations that mimic the brood and feeding substrates of pollinating flies. Despite several studies that have documented the various adaptations to fly pollination in different species, there is a lack of natural history studies documenting different flower visitors, pollen loads and long term levels of pollination success in these species. In Chapter six I document the pollination biology of Ceropegia ampliata by documenting different pollinators and quantifying average levels of pollination success and the nectar reward. I also experimentally manipulated the trapping hairs of this species to determine whether trapping hairs influence average levels of pollen export and receipt. I show that Ceropegia ampliata is pollinated by a generalist guild of flies (mainly Tachinidae, Sarcophagidae, Muscidae and Lauxaniidae) and produces minute quantities of relatively dilute nectar as a reward. Pollination success was generally low in this species and increases periodically suggesting that the abundance of pollinators is patchy. I found that flowers with trapping hairs that had already wilted had higher levels of pollinarium removal than flowers with erect hairs, however experimentally removing the hairs had no significant effect on pollen export and receipt. In Chapter seven, I document the pollinators, pollen loads and long term levels of pollination success in Stapelia hirsuta var. bayllissi, a rare sapromyiophilous stapeliad. I find that, in contrast to C. ampliata, this species was specialized to pollination by small flies of the family Anthomyiidae. Similar to the results from Chapter seven, I find that long term levels of pollination success were typically low but could increase periodically, although such increases were generally unpredictable. There are currently very few records documenting pollinator interactions in the Periplocoideae. Many species within this subfamily exhibit open-access flowers suggestive of pollination by short-tongued insects. I investigated the pollination biology of Chlorocyathus lobulata, a rare species with a highly localized distribution. I aimed to determine the pollinators, average levels of pollination success and demography of this species in order to determine whether this rare species is suffering from the collapse of a highly specialized pollinator mutualism. I also quantified the high incidence of flower herbivory caused by larvae of the moth, Bocchoris onychinalis. I find that C. lobulata has a highly generalized fly pollination system and average levels of pollination success suggested that a large proportion of flowers had pollen removed and deposited suggesting that this species is not experiencing pollination failure. The large numbers of juveniles present also indicated that recruitment is taking place.
- Full Text:
- Date Issued: 2010
Multilingualism and ICT education at Rhodes University: an exploratory study
- Authors: Dalvit, Lorenzo
- Date: 2010
- Subjects: Educational technology -- South Africa Educational equalization -- South Africa Digital divide -- South Africa Information technology -- Social aspects -- South Africa Educational innovations Information technology -- Study and teaching Language and education -- South Africa Native language and education -- South Africa Rhodes University -- Students -- Attitudes Computer science -- Study and teaching (Higher)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1673 , http://hdl.handle.net/10962/d1003556
- Description: In South Africa, the linguistic hegemony of English over the African languages in the academic field reproduces unequal power relationships between their speakers. The present study shows that an intervention shaped by a counterhegemonic ideology can change the attitudes of Black university students, key players in spearheading social change. Usign statistical analysis and survey methodologies, this research explored the hegemonic role of English as the only language of learning and teaching (LoLT) in the discipline of Computer Science (CS) at Rhodes University. The study found that those speakers of an African language who are the most disadvantaged by the use of English as LoLT are also the most likely to resist a more extensive use of their mother tongue as an alternative. A group of such students were involved in the development and use of an online glossary of CS terms translated, explained and exemplified in an African language (isiXhosa). This experience increased the support for the use of African languages as additional LoLT, even in the Englishdominated field of study of Computer Science. This is an initial step towards promoting linguistic equality between English and African languages and social equality between their speakers.
- Full Text:
- Date Issued: 2010
- Authors: Dalvit, Lorenzo
- Date: 2010
- Subjects: Educational technology -- South Africa Educational equalization -- South Africa Digital divide -- South Africa Information technology -- Social aspects -- South Africa Educational innovations Information technology -- Study and teaching Language and education -- South Africa Native language and education -- South Africa Rhodes University -- Students -- Attitudes Computer science -- Study and teaching (Higher)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1673 , http://hdl.handle.net/10962/d1003556
- Description: In South Africa, the linguistic hegemony of English over the African languages in the academic field reproduces unequal power relationships between their speakers. The present study shows that an intervention shaped by a counterhegemonic ideology can change the attitudes of Black university students, key players in spearheading social change. Usign statistical analysis and survey methodologies, this research explored the hegemonic role of English as the only language of learning and teaching (LoLT) in the discipline of Computer Science (CS) at Rhodes University. The study found that those speakers of an African language who are the most disadvantaged by the use of English as LoLT are also the most likely to resist a more extensive use of their mother tongue as an alternative. A group of such students were involved in the development and use of an online glossary of CS terms translated, explained and exemplified in an African language (isiXhosa). This experience increased the support for the use of African languages as additional LoLT, even in the Englishdominated field of study of Computer Science. This is an initial step towards promoting linguistic equality between English and African languages and social equality between their speakers.
- Full Text:
- Date Issued: 2010
Photoluminescence study of ZnO doped with nitrogen and arsenic
- Authors: Dangbegnon, Julien Kouadio
- Date: 2010
- Subjects: Photoluminescence , Zinc oxide , Nitrogen , Arsenic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10518 , http://hdl.handle.net/10948/1216 , Photoluminescence , Zinc oxide , Nitrogen , Arsenic
- Description: In this work, the optical properties of ZnO doped with arsenic and nitrogen were studied. The ZnO samples were grown by Metalorganic Chemical Vapor Deposition (MOCVD). The solubility of nitrogen in the ZnO films, as well as its activation upon annealing, was also investigated. Hydrogen is known as a major source for passivation of the acceptors in ZnO:N. Therefore, it is crucial to dissociate the complex(es) formed by nitrogen and hydrogen and diffuse out the hydrogen in order to prevent the reformation of such complexes. High temperatures (≥ 600 C) are required for these purposes. In order to effectively remove the hydrogen impurities from the sample, it is important to know the optical fingerprints of hydrogen and its thermal stability. Therefore, the effects of annealing and hydrogen plasma treatment on bulk ZnO (hydrothermally grown) were first studied. The use of bulk material for this purpose was motivated by the well-resolved photoluminescence (PL) lines observed for bulk ZnO, which allow the identification of the different lines related to hydrogen after plasma treatment. Annealing at 850 C was effective for the removal of most of the hydrogen related transitions in the near-band-edge emission. Also, additional transitions at ~3.364 eV and ~3.361 eV were observed after hydrogen plasma treatment, which were ascribed to hydrogen-Zn vacancy complexes. In this work, a comparative study of the annealing ambient and temperature on ZnO films grown on GaAs substrate, using diethyl zinc (DEZn) and tertiary butanol (TBOH), showed that arsenic diffuses in the ZnO films and gives a shallow level in the band gap, which is involved in an acceptor-bound exciton line at 3.35 eV. This shallow level is visible when annealing is performed in oxygen, but not when annealing is performed in nitrogen, and indeed only for annealing temperatures around 550 C. However, annealing in either ambient also causes zinc to diffuse from the ZnO films into the GaAs substrate, rendering the electrical properties deduced from Hall measurements ambiguous. For ZnO:N, NO was used as both oxygen and nitrogen sources. Monitoring the concentration of nitrogen, carbon and hydrogen in the ZnO films, the formation of different complexes from these impurities were deduced. Furthermore, an investigation of the effect of annealing on the concentrations of impurities showed that their out- diffusion was strongly dependent on the crystalline quality of the ZnO films. For porous ZnO films, obtained at low growth temperatures (≤310 C), the out-diffusion of impurities was efficient, whereas for films grown at higher temperatures, which have improved crystalline quality, the out-diffusion was practically nonexistent. The out-diffusion of unwanted impurities may activate the nitrogen dopant in the ZnO films, as was confirmed by the PL measurements on the different samples grown at different temperatures. PL transitions at ~3.24 eV and ~3.17 eV were related to substitutional NO. These transitions were more dominant in the spectra of samples grown at low temperatures. An additional transition at ~3.1 eV was assigned to a donor-acceptor pair transition involving VZn, instead of NO, as previously reported.
- Full Text:
- Date Issued: 2010
- Authors: Dangbegnon, Julien Kouadio
- Date: 2010
- Subjects: Photoluminescence , Zinc oxide , Nitrogen , Arsenic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10518 , http://hdl.handle.net/10948/1216 , Photoluminescence , Zinc oxide , Nitrogen , Arsenic
- Description: In this work, the optical properties of ZnO doped with arsenic and nitrogen were studied. The ZnO samples were grown by Metalorganic Chemical Vapor Deposition (MOCVD). The solubility of nitrogen in the ZnO films, as well as its activation upon annealing, was also investigated. Hydrogen is known as a major source for passivation of the acceptors in ZnO:N. Therefore, it is crucial to dissociate the complex(es) formed by nitrogen and hydrogen and diffuse out the hydrogen in order to prevent the reformation of such complexes. High temperatures (≥ 600 C) are required for these purposes. In order to effectively remove the hydrogen impurities from the sample, it is important to know the optical fingerprints of hydrogen and its thermal stability. Therefore, the effects of annealing and hydrogen plasma treatment on bulk ZnO (hydrothermally grown) were first studied. The use of bulk material for this purpose was motivated by the well-resolved photoluminescence (PL) lines observed for bulk ZnO, which allow the identification of the different lines related to hydrogen after plasma treatment. Annealing at 850 C was effective for the removal of most of the hydrogen related transitions in the near-band-edge emission. Also, additional transitions at ~3.364 eV and ~3.361 eV were observed after hydrogen plasma treatment, which were ascribed to hydrogen-Zn vacancy complexes. In this work, a comparative study of the annealing ambient and temperature on ZnO films grown on GaAs substrate, using diethyl zinc (DEZn) and tertiary butanol (TBOH), showed that arsenic diffuses in the ZnO films and gives a shallow level in the band gap, which is involved in an acceptor-bound exciton line at 3.35 eV. This shallow level is visible when annealing is performed in oxygen, but not when annealing is performed in nitrogen, and indeed only for annealing temperatures around 550 C. However, annealing in either ambient also causes zinc to diffuse from the ZnO films into the GaAs substrate, rendering the electrical properties deduced from Hall measurements ambiguous. For ZnO:N, NO was used as both oxygen and nitrogen sources. Monitoring the concentration of nitrogen, carbon and hydrogen in the ZnO films, the formation of different complexes from these impurities were deduced. Furthermore, an investigation of the effect of annealing on the concentrations of impurities showed that their out- diffusion was strongly dependent on the crystalline quality of the ZnO films. For porous ZnO films, obtained at low growth temperatures (≤310 C), the out-diffusion of impurities was efficient, whereas for films grown at higher temperatures, which have improved crystalline quality, the out-diffusion was practically nonexistent. The out-diffusion of unwanted impurities may activate the nitrogen dopant in the ZnO films, as was confirmed by the PL measurements on the different samples grown at different temperatures. PL transitions at ~3.24 eV and ~3.17 eV were related to substitutional NO. These transitions were more dominant in the spectra of samples grown at low temperatures. An additional transition at ~3.1 eV was assigned to a donor-acceptor pair transition involving VZn, instead of NO, as previously reported.
- Full Text:
- Date Issued: 2010
Molecular and cellular analysis of the interaction between soluble CD23 and CD11/CD18 integrins
- Authors: Daniels, Brodie Belinda
- Date: 2010
- Subjects: CD23 antigen , Immune response -- Regulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10303 , http://hdl.handle.net/10948/1217 , CD23 antigen , Immune response -- Regulation
- Description: The low affinity IgE receptor, CD23, is expressed by a wide variety of cells and cleaved from its original 45 kDa size to several smaller soluble CD23 proteins. Soluble CD23 function depends on the form of the protein and its interaction with various ligands. CD23 is believed to play an important role in regulating allergic responses and in inflammation, amongst others. β2 integrins are important in a variety of cell-adhesion reactions during immune-inflammatory mechanisms and the binding of their natural ligands generates outside-in cellular signalling, leading to cell activation. Although the binding of CD23 to β2 integrins contributes to this signalling in monocytes, the interaction site for CD23 is unknown. This study focused on the interaction of three soluble CD23 proteins with the β2 integrins CD11b/CD18 and CD11c/CD18. Differentiated HL60, THP1 and U937 monocytic cells were used to demonstrate the binding of three recombinant CD23 constructs (corresponding to 16, 25 and 33 kDa human soluble CD23) to upregulated CD11b/CD18 and CD11c/CD18. This binding was partially blocked by an antibody specific for the CD11b/CD18 αI domain, demonstrating that αI domains are involved in binding to CD23. Recombinant αI domain proteins of CD11b and CD11c were demonstrated to bind CD23 using ELISA and in surface plasmon resonance spectroscopy. The dissociation constants for CD23-CD11b/CD18 and CD23-CD11c/CD18 are comparable to other integrin ligands. This study has shown that CD23 interacts directly with the αI domains of β2 integrins and that the interaction surface likely spans the lectin domain as well as either the stalk and/or C-terminal tail of CD23. This study also looked at the effect that soluble CD23 proteins had on monocyte biology. It appears that iv sCD23 proteins have little effect on the phagocytic or chemotactic ability of monocytes, while an increase in oxidative burst was shown with the 16 kDa and 25 kDa CD23 proteins. Signalling pathways for the production of reactive oxygen species were investigated and it appears that the CD23 proteins signal mainly through the phosphoinositide-3 kinase pathway, although the mitogen activated protein kinase and Src kinase pathways may also play a role. These data suggest that sCD23 proteins induce outside-in signalling of β2 integrins and are able to change the activation state of CD11b/CD11c by stimulating oxidative burst. This needs to be further investigated by determining how the three sCD23 proteins are binding the CD11 proteins and investigating further leukocyte function and inflammatory responses by the cells.
- Full Text:
- Date Issued: 2010
- Authors: Daniels, Brodie Belinda
- Date: 2010
- Subjects: CD23 antigen , Immune response -- Regulation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10303 , http://hdl.handle.net/10948/1217 , CD23 antigen , Immune response -- Regulation
- Description: The low affinity IgE receptor, CD23, is expressed by a wide variety of cells and cleaved from its original 45 kDa size to several smaller soluble CD23 proteins. Soluble CD23 function depends on the form of the protein and its interaction with various ligands. CD23 is believed to play an important role in regulating allergic responses and in inflammation, amongst others. β2 integrins are important in a variety of cell-adhesion reactions during immune-inflammatory mechanisms and the binding of their natural ligands generates outside-in cellular signalling, leading to cell activation. Although the binding of CD23 to β2 integrins contributes to this signalling in monocytes, the interaction site for CD23 is unknown. This study focused on the interaction of three soluble CD23 proteins with the β2 integrins CD11b/CD18 and CD11c/CD18. Differentiated HL60, THP1 and U937 monocytic cells were used to demonstrate the binding of three recombinant CD23 constructs (corresponding to 16, 25 and 33 kDa human soluble CD23) to upregulated CD11b/CD18 and CD11c/CD18. This binding was partially blocked by an antibody specific for the CD11b/CD18 αI domain, demonstrating that αI domains are involved in binding to CD23. Recombinant αI domain proteins of CD11b and CD11c were demonstrated to bind CD23 using ELISA and in surface plasmon resonance spectroscopy. The dissociation constants for CD23-CD11b/CD18 and CD23-CD11c/CD18 are comparable to other integrin ligands. This study has shown that CD23 interacts directly with the αI domains of β2 integrins and that the interaction surface likely spans the lectin domain as well as either the stalk and/or C-terminal tail of CD23. This study also looked at the effect that soluble CD23 proteins had on monocyte biology. It appears that iv sCD23 proteins have little effect on the phagocytic or chemotactic ability of monocytes, while an increase in oxidative burst was shown with the 16 kDa and 25 kDa CD23 proteins. Signalling pathways for the production of reactive oxygen species were investigated and it appears that the CD23 proteins signal mainly through the phosphoinositide-3 kinase pathway, although the mitogen activated protein kinase and Src kinase pathways may also play a role. These data suggest that sCD23 proteins induce outside-in signalling of β2 integrins and are able to change the activation state of CD11b/CD11c by stimulating oxidative burst. This needs to be further investigated by determining how the three sCD23 proteins are binding the CD11 proteins and investigating further leukocyte function and inflammatory responses by the cells.
- Full Text:
- Date Issued: 2010
The introduction of cyberhunts as a teaching and learning strategy to guide teachers towards the integration of computer technology in schools
- Authors: Du Plessis, André
- Date: 2010
- Subjects: Educational technology , Computers -- Study and teaching , Computer-assisted instruction , Competency-based education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9555 , http://hdl.handle.net/10948/1210 , Educational technology , Computers -- Study and teaching , Computer-assisted instruction , Competency-based education
- Description: This study, which is based on a computer literacy teacher development programme that included introducing the teacher participants to the Internet, investigated whether the development of teacher ICT skills through the design of cyberhunts in a learning-as-design context, has the potential to promote the critical and developmental outcomes which form the basis of the South African National Curriculum Statement (NCS) and Draft White Paper on e-Education. The research was conducted within the post-positivist paradigm underpinned by a critical realist position and made use of qualitative and quantitative data1 gathering methods (mixed research) within an interpretative case study. Several different quantitative and qualitative data collection tools were used. Quantitative data gathering tools that had been used comprised of Likert scale questionnaires, a computer skills questionnaire, as well as certain sections within semi-closed-openended questionnaires. The qualitative data gathering tools that had been used were semi-closed-openended questionnaires, journal reflection sheets, observation and interviews. Ontologically the research was informed by a critical-realist perspective, epistemologically by a socio-cultural perspective; including situated learning within communities of practice; recognising the cognitive, social and situated learning dimension of teacher learning. Methodologically an interpretive case study approach was used, as the aim was to explore and investigate what the participants experienced, perceived and to understand the participants: what they felt, how they felt and why they felt and responded in certain ways. Initially the study focused on identifying how ready the participating schools and their participating teachers were in terms of the implementation and integration of Information and Communications Technology (ICT) with reference to first- and second order barriers. The findings suggest that addressing the first- and second order barriers is a vital aspect when assisting schools to move towards ICT integration. The next phase of the research focused on whether the cyberhunt design approach is capable of developing the critical outcomes of the NCS, whether it promotes motivation and interest, and whether it promotes collaboration. Both the quantitative and qualitative data portrayed positive results regarding the perceptions of the participating teachers in the cyberhunt design approach related to the critical and 1PLEASE NOTE: All the data referred to as in the appendix and all appendices are attached to this thesis on a CD containing the portable document format (PDF) files. This can be found at the back. iv developmental outcomes with reference to search and research, reading attitude, decision making, planning skills - which include time management and goal setting, knowledge and skills related to composing questions on different cognitive levels, computer skills, reflection and design skills. Positive results were also found related to audience, confidence, mental effort, motivation, interest and collaboration. The probabilities (p values) and practical statistical significance in the form of Cohen's d, were highly significant. The teachers’ final cyberhunt products suggest that the majority of the participants had obtained basic cyberhunt design skills. However, in spite of the positive results, it was found that not all teachers are yet ready to implement this approach exactly as it is intended. When interpreted within an activity theory perspective; the positive results might be attributed to the unmediated functioning of the rules, division of labour and community aspects of the theory, while the conditions required by complexity theory for the development of a complex learning community appear to have been met by the implementation of cyberhunts as a strategy. The conditions for enabling the development of a complex learning community; namely internal diversity, redundancy, decentralised control, organised randomness and neighbour interaction; also appear to have interacted with the unmediated aspects of activity theory in developing consensual rules and through the negotiation of the division of labour located within the community. In a like manner, positive results related to search and research, decision making, questioning, computer skills, reflection, design skills and audience reported can most likely be attributed to the functioning of the mediational tools as described by activity theory such as the computer technology, the Internet, the software that had been used and language. The data thus suggest that the interaction between both the unmediated elements and higher order mediated elements of activity theory, have most likely been the defining factors which created high levels of motivation, interest, collaboration and a positive classroom culture through which the critical and developmental outcomes of the South Africa curriculum can possibly be achieved within a complex learning community. The study also investigated how the teacher development process regarding ICT implementation should be managed. This study found that the acronym CRAR3FS2 holds the key to teacher development and classroom implementation. This acronym represents the verbs or actions that the participating teachers highly valued during implementation and what they have indicated as being important, namely: Care, Relate, Assess, Reflect, Read, Re-Plan, Feedback, Share and Support.
- Full Text:
- Date Issued: 2010
- Authors: Du Plessis, André
- Date: 2010
- Subjects: Educational technology , Computers -- Study and teaching , Computer-assisted instruction , Competency-based education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9555 , http://hdl.handle.net/10948/1210 , Educational technology , Computers -- Study and teaching , Computer-assisted instruction , Competency-based education
- Description: This study, which is based on a computer literacy teacher development programme that included introducing the teacher participants to the Internet, investigated whether the development of teacher ICT skills through the design of cyberhunts in a learning-as-design context, has the potential to promote the critical and developmental outcomes which form the basis of the South African National Curriculum Statement (NCS) and Draft White Paper on e-Education. The research was conducted within the post-positivist paradigm underpinned by a critical realist position and made use of qualitative and quantitative data1 gathering methods (mixed research) within an interpretative case study. Several different quantitative and qualitative data collection tools were used. Quantitative data gathering tools that had been used comprised of Likert scale questionnaires, a computer skills questionnaire, as well as certain sections within semi-closed-openended questionnaires. The qualitative data gathering tools that had been used were semi-closed-openended questionnaires, journal reflection sheets, observation and interviews. Ontologically the research was informed by a critical-realist perspective, epistemologically by a socio-cultural perspective; including situated learning within communities of practice; recognising the cognitive, social and situated learning dimension of teacher learning. Methodologically an interpretive case study approach was used, as the aim was to explore and investigate what the participants experienced, perceived and to understand the participants: what they felt, how they felt and why they felt and responded in certain ways. Initially the study focused on identifying how ready the participating schools and their participating teachers were in terms of the implementation and integration of Information and Communications Technology (ICT) with reference to first- and second order barriers. The findings suggest that addressing the first- and second order barriers is a vital aspect when assisting schools to move towards ICT integration. The next phase of the research focused on whether the cyberhunt design approach is capable of developing the critical outcomes of the NCS, whether it promotes motivation and interest, and whether it promotes collaboration. Both the quantitative and qualitative data portrayed positive results regarding the perceptions of the participating teachers in the cyberhunt design approach related to the critical and 1PLEASE NOTE: All the data referred to as in the appendix and all appendices are attached to this thesis on a CD containing the portable document format (PDF) files. This can be found at the back. iv developmental outcomes with reference to search and research, reading attitude, decision making, planning skills - which include time management and goal setting, knowledge and skills related to composing questions on different cognitive levels, computer skills, reflection and design skills. Positive results were also found related to audience, confidence, mental effort, motivation, interest and collaboration. The probabilities (p values) and practical statistical significance in the form of Cohen's d, were highly significant. The teachers’ final cyberhunt products suggest that the majority of the participants had obtained basic cyberhunt design skills. However, in spite of the positive results, it was found that not all teachers are yet ready to implement this approach exactly as it is intended. When interpreted within an activity theory perspective; the positive results might be attributed to the unmediated functioning of the rules, division of labour and community aspects of the theory, while the conditions required by complexity theory for the development of a complex learning community appear to have been met by the implementation of cyberhunts as a strategy. The conditions for enabling the development of a complex learning community; namely internal diversity, redundancy, decentralised control, organised randomness and neighbour interaction; also appear to have interacted with the unmediated aspects of activity theory in developing consensual rules and through the negotiation of the division of labour located within the community. In a like manner, positive results related to search and research, decision making, questioning, computer skills, reflection, design skills and audience reported can most likely be attributed to the functioning of the mediational tools as described by activity theory such as the computer technology, the Internet, the software that had been used and language. The data thus suggest that the interaction between both the unmediated elements and higher order mediated elements of activity theory, have most likely been the defining factors which created high levels of motivation, interest, collaboration and a positive classroom culture through which the critical and developmental outcomes of the South Africa curriculum can possibly be achieved within a complex learning community. The study also investigated how the teacher development process regarding ICT implementation should be managed. This study found that the acronym CRAR3FS2 holds the key to teacher development and classroom implementation. This acronym represents the verbs or actions that the participating teachers highly valued during implementation and what they have indicated as being important, namely: Care, Relate, Assess, Reflect, Read, Re-Plan, Feedback, Share and Support.
- Full Text:
- Date Issued: 2010
A combination of platinum anticancer drugs and mangiferin causes increased efficacy in cancer cell lines
- Authors: Du Plessis-Stoman, Debbie
- Date: 2010
- Subjects: Cancer -- Chemotherapy , Antineoplastic agents , Platinum compounds -- Therapeutic use , Cancer cells
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10338 , http://hdl.handle.net/10948/d1016160
- Description: This thesis mainly deals with some biochemical aspects regarding the efficacy of novel platinum anticancer compounds alone and in combination with mangiferin, as part of a broader study in which both chemistry and biochemistry are involved. Various novel diamine and N-S donor chelate compounds of platinum II and IV have been developed in which factors such as stereochemistry, ligand exchange rate and biocompatibility were considered as additional parameters. In the first order testing, each of these compounds was tested with reference to their “killing” potential by comparing their rate of killing, over a period of 48 hours with those of cisplatin and oxaliplatin. Numerous novel compounds were tested in this way, using the MTT cell viability assay and the three cancer cell lines MCF7, HT29 and HeLa. Although only a few could be regarded as equal to or even better than cisplatin, CPA7 and oxaliplatin, the testing of these compounds on cancer cells provided useful knowledge for the further development of novel compounds. Three of the better compounds, namely Yol 25, Yol 29.1 and Mar 4.1.4 were selected for further studies, together with oxaliplatin and CPA7 as positive controls, to obtain more detailed knowledge of their anticancer action, both alone and when applied in combination with mangiferin. In addition to the above, resistant cells were produced for each of the three different cell lines tested and all the selected compounds, both in the presence and absence of mangiferin. The effects of these treatments on the activation of NFĸB when applied to normal and resistant cell lines were also investigated. All the compounds induced apoptosis in the cell lines tested as well as alter the DNA cycle at one or more phase. Additionally, combination of these compounds with mangiferin enhanced the above-mentioned effects. Mangiferin decreases the IC50 values of the platinum drugs by up to 3.4 times and, although mangiferin alone did not induce cell cycle arrest, the presence of mangiferin in combination with oxaliplatin and Yol 25 shows an earlier and greatly enhanced delay in the S-phase, while cells treated with CPA7, Yol 29.1 and Mar 4.1.4 in combination with mangiferin showed a later, but greatly enhanced delay in the S-phase. It was also found that mangiferin acts as an NFĸB inhibitor when applied in combination with these drugs, which, in turn, reduces the occurrence of resistance in the cell lines. Resistance to oxaliplatin was counteracted by the combination with mangiferin in HeLa and HT29, but not in MCF7 cells, while resistance to CPA7 was only counteracted in the MCF7 cell line. Yol 25 and Mar 4.1.4 did not seem to induce resistance in HeLa and MCF7 cells, but did in HT29 cells, whereas Yol 29.1 caused resistance in HeLa and HT29 cells, but not in MCF7 cells. Finally, an effort was made to evaluate the different compounds by comparing them with respect to their properties relating to anticancer action with and without the addition of mangiferin.
- Full Text:
- Date Issued: 2010
- Authors: Du Plessis-Stoman, Debbie
- Date: 2010
- Subjects: Cancer -- Chemotherapy , Antineoplastic agents , Platinum compounds -- Therapeutic use , Cancer cells
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10338 , http://hdl.handle.net/10948/d1016160
- Description: This thesis mainly deals with some biochemical aspects regarding the efficacy of novel platinum anticancer compounds alone and in combination with mangiferin, as part of a broader study in which both chemistry and biochemistry are involved. Various novel diamine and N-S donor chelate compounds of platinum II and IV have been developed in which factors such as stereochemistry, ligand exchange rate and biocompatibility were considered as additional parameters. In the first order testing, each of these compounds was tested with reference to their “killing” potential by comparing their rate of killing, over a period of 48 hours with those of cisplatin and oxaliplatin. Numerous novel compounds were tested in this way, using the MTT cell viability assay and the three cancer cell lines MCF7, HT29 and HeLa. Although only a few could be regarded as equal to or even better than cisplatin, CPA7 and oxaliplatin, the testing of these compounds on cancer cells provided useful knowledge for the further development of novel compounds. Three of the better compounds, namely Yol 25, Yol 29.1 and Mar 4.1.4 were selected for further studies, together with oxaliplatin and CPA7 as positive controls, to obtain more detailed knowledge of their anticancer action, both alone and when applied in combination with mangiferin. In addition to the above, resistant cells were produced for each of the three different cell lines tested and all the selected compounds, both in the presence and absence of mangiferin. The effects of these treatments on the activation of NFĸB when applied to normal and resistant cell lines were also investigated. All the compounds induced apoptosis in the cell lines tested as well as alter the DNA cycle at one or more phase. Additionally, combination of these compounds with mangiferin enhanced the above-mentioned effects. Mangiferin decreases the IC50 values of the platinum drugs by up to 3.4 times and, although mangiferin alone did not induce cell cycle arrest, the presence of mangiferin in combination with oxaliplatin and Yol 25 shows an earlier and greatly enhanced delay in the S-phase, while cells treated with CPA7, Yol 29.1 and Mar 4.1.4 in combination with mangiferin showed a later, but greatly enhanced delay in the S-phase. It was also found that mangiferin acts as an NFĸB inhibitor when applied in combination with these drugs, which, in turn, reduces the occurrence of resistance in the cell lines. Resistance to oxaliplatin was counteracted by the combination with mangiferin in HeLa and HT29, but not in MCF7 cells, while resistance to CPA7 was only counteracted in the MCF7 cell line. Yol 25 and Mar 4.1.4 did not seem to induce resistance in HeLa and MCF7 cells, but did in HT29 cells, whereas Yol 29.1 caused resistance in HeLa and HT29 cells, but not in MCF7 cells. Finally, an effort was made to evaluate the different compounds by comparing them with respect to their properties relating to anticancer action with and without the addition of mangiferin.
- Full Text:
- Date Issued: 2010
Implementation of novel flow cytometric methods to assess the in vitro antidiabetic mechanism of a Sutherlandia Frutescens extract
- Authors: Elliot, Gayle Pamela
- Date: 2010
- Subjects: Insulin resistance -- South Africa , Insulin -- Therapeutic use -- South Africa , Medicinal plants -- South Africa , Non-insulin-dependent diabetes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10304 , http://hdl.handle.net/10948/1439 , Insulin resistance -- South Africa , Insulin -- Therapeutic use -- South Africa , Medicinal plants -- South Africa , Non-insulin-dependent diabetes -- South Africa
- Description: The ability of insulin to stimulate glucose uptake into muscle and adipose tissue is central to the maintenance of whole-body glucose homeostasis. Deregulation of insulin action manifests itself as insulin resistance, a key component of type 2 diabetes. Insulin resistance is also observed in HIV patients receiving protease inhibitors. An agent that can reversibly induce an insulin-resistant state would be a very useful tool in developing model systems that mimic the pathogenesis of type 2 diabetes. Insulin resistance can arise from defects in insulin signal transduction, changes in the expression of proteins or genes that are targets of insulin action, cross talk from other hormonal systems or metabolic abnormalities. Deterioration of the insulin-receptor-signalling pathway at different levels leading to decreased levels of signalling pathway intermediates and/or decreased activation through phosphorylation accounts for the evolution from an insulin-resistant state to type 2 diabetes. In addition, defects in GLUT4 glucose transporter translocation are observed, further fuelling impairments in skeletal muscle glucose uptake. Levels of insulin-induced GLUT4 translocation in the skeletal muscle of type 2 diabetic patients are typically reduced by 90%. Many cellular pathways & their intermediates are in some way or another linked to insulin signalling. This study focused on three of these namely the PI3-kinase/Akt pathway, the Mitogen Activated Protein Kinase (MAPK) cascade and the AMP Kinase pathway, with successful monitoring of the PI3-K pathway. Investigations involved observing and evaluating the effects of various compounds as well as an indigenous medicinal plant, Sutherlandia frutescens on the activities of key insulin signalling pathway intermediates within the three fore mentioned pathways including Akt, AMPK and MEK1/2 as well as membrane surface GLUT4 levels. Scientific research has in the past leant heavily on Western blotting as the method of choice for gaining vital information relating to signal transduction pathways, however for research into cellular mechanisms the negatives of this method outweigh the positives. The drawbacks include a need for large amount of cells, multiple washing steps which may be disadvantageous to any weak and transient interactions as well as lysing of cells which may interfere with the maintenance of the subcellular localisation of a specific signalling event. Based on these, the need for a better method in terms of speed & reliability to monitor phosphorylation states of signal transduction pathway intermediates & GLUT4 translocation was evident and was one VII of the main aims & successes of this study. The method created used the mouse muscle cell line C2C12 in conjunction with the quick, sensitive method of flow cytometry which allowed us to monitor these processes in these cells through immune-labelling. Adherent cell cultures such as the C2C12 cell line pose the problem of possible damage to plasma membrane receptors (including insulin receptors) during harvesting to obtain a cell suspension for flow cytometry. We however used C2C12 mouse myocytes to optimize a method yielding insulin responsive cells in suspension that were successfully used for flow cytometry after immunelabelling of insulin signalling intermediates. Insulin (0.1μM) significantly raised the levels of both P-Akt and GLUT4 above basal levels. This effect was shown to be dose dependent. At a concentration of 50μg/ml, Sutherlandia frutescens was able to act as an insulin-mimetic in terms of its ability to increase P-Akt levels, GLUT4 translocation and glucose utilisation in an acute manner. These increases could be reduced with the addition of wortmannin, a PI3-K inhibitor. Therefore, these results suggest the mechanism of the plant extract’s insulin-like activity may be in part due to the activation of the insulin signalling pathway leading to GLUT4 translocation, which involves the phosphorylation of insulin receptor- and subsequent PI3-K activity, leading to P-Akt activity. These results provide further evidence of this plant extract’s anti-diabetic potential. The effect of Sutherlandia frutescens on insulin secretion, calcium signalling and proliferation in INS-1 rat pancreatic cells was also investigated and it was found to increase the activities of all of these processes. However no change in the levels of GLUT2 glucose transporter was seen. Ritonavir is prescribed by the South African Department of Health in co-formulation with other protease inhibitors within its second regime in the treatment of HIV and AIDS. Using C2C12 cells, ritonavir decreased glucose uptake acutely and had no effect on GLUT4 translocation however surprisingly increased P-Akt levels. In conclusion, it was found that Sutherlandia frutescens has antidiabetic benefits, diverse in nature depending on tissue type as well as length of time administered. The establishment of novel flow cytometry techniques to assess antidiabetic properties using in vitro cell culture was achieved. These methods will be useful in the future for the assessment of insulin sensitivity and in the identification of novel compounds that stimulate the insulin signalling pathways.
- Full Text:
- Date Issued: 2010
- Authors: Elliot, Gayle Pamela
- Date: 2010
- Subjects: Insulin resistance -- South Africa , Insulin -- Therapeutic use -- South Africa , Medicinal plants -- South Africa , Non-insulin-dependent diabetes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10304 , http://hdl.handle.net/10948/1439 , Insulin resistance -- South Africa , Insulin -- Therapeutic use -- South Africa , Medicinal plants -- South Africa , Non-insulin-dependent diabetes -- South Africa
- Description: The ability of insulin to stimulate glucose uptake into muscle and adipose tissue is central to the maintenance of whole-body glucose homeostasis. Deregulation of insulin action manifests itself as insulin resistance, a key component of type 2 diabetes. Insulin resistance is also observed in HIV patients receiving protease inhibitors. An agent that can reversibly induce an insulin-resistant state would be a very useful tool in developing model systems that mimic the pathogenesis of type 2 diabetes. Insulin resistance can arise from defects in insulin signal transduction, changes in the expression of proteins or genes that are targets of insulin action, cross talk from other hormonal systems or metabolic abnormalities. Deterioration of the insulin-receptor-signalling pathway at different levels leading to decreased levels of signalling pathway intermediates and/or decreased activation through phosphorylation accounts for the evolution from an insulin-resistant state to type 2 diabetes. In addition, defects in GLUT4 glucose transporter translocation are observed, further fuelling impairments in skeletal muscle glucose uptake. Levels of insulin-induced GLUT4 translocation in the skeletal muscle of type 2 diabetic patients are typically reduced by 90%. Many cellular pathways & their intermediates are in some way or another linked to insulin signalling. This study focused on three of these namely the PI3-kinase/Akt pathway, the Mitogen Activated Protein Kinase (MAPK) cascade and the AMP Kinase pathway, with successful monitoring of the PI3-K pathway. Investigations involved observing and evaluating the effects of various compounds as well as an indigenous medicinal plant, Sutherlandia frutescens on the activities of key insulin signalling pathway intermediates within the three fore mentioned pathways including Akt, AMPK and MEK1/2 as well as membrane surface GLUT4 levels. Scientific research has in the past leant heavily on Western blotting as the method of choice for gaining vital information relating to signal transduction pathways, however for research into cellular mechanisms the negatives of this method outweigh the positives. The drawbacks include a need for large amount of cells, multiple washing steps which may be disadvantageous to any weak and transient interactions as well as lysing of cells which may interfere with the maintenance of the subcellular localisation of a specific signalling event. Based on these, the need for a better method in terms of speed & reliability to monitor phosphorylation states of signal transduction pathway intermediates & GLUT4 translocation was evident and was one VII of the main aims & successes of this study. The method created used the mouse muscle cell line C2C12 in conjunction with the quick, sensitive method of flow cytometry which allowed us to monitor these processes in these cells through immune-labelling. Adherent cell cultures such as the C2C12 cell line pose the problem of possible damage to plasma membrane receptors (including insulin receptors) during harvesting to obtain a cell suspension for flow cytometry. We however used C2C12 mouse myocytes to optimize a method yielding insulin responsive cells in suspension that were successfully used for flow cytometry after immunelabelling of insulin signalling intermediates. Insulin (0.1μM) significantly raised the levels of both P-Akt and GLUT4 above basal levels. This effect was shown to be dose dependent. At a concentration of 50μg/ml, Sutherlandia frutescens was able to act as an insulin-mimetic in terms of its ability to increase P-Akt levels, GLUT4 translocation and glucose utilisation in an acute manner. These increases could be reduced with the addition of wortmannin, a PI3-K inhibitor. Therefore, these results suggest the mechanism of the plant extract’s insulin-like activity may be in part due to the activation of the insulin signalling pathway leading to GLUT4 translocation, which involves the phosphorylation of insulin receptor- and subsequent PI3-K activity, leading to P-Akt activity. These results provide further evidence of this plant extract’s anti-diabetic potential. The effect of Sutherlandia frutescens on insulin secretion, calcium signalling and proliferation in INS-1 rat pancreatic cells was also investigated and it was found to increase the activities of all of these processes. However no change in the levels of GLUT2 glucose transporter was seen. Ritonavir is prescribed by the South African Department of Health in co-formulation with other protease inhibitors within its second regime in the treatment of HIV and AIDS. Using C2C12 cells, ritonavir decreased glucose uptake acutely and had no effect on GLUT4 translocation however surprisingly increased P-Akt levels. In conclusion, it was found that Sutherlandia frutescens has antidiabetic benefits, diverse in nature depending on tissue type as well as length of time administered. The establishment of novel flow cytometry techniques to assess antidiabetic properties using in vitro cell culture was achieved. These methods will be useful in the future for the assessment of insulin sensitivity and in the identification of novel compounds that stimulate the insulin signalling pathways.
- Full Text:
- Date Issued: 2010
Beta-N-methylamino-L-alanine in South African fresh water cyanobacteria : incidence, prevalence, ecotoxicological considerations and human exposure risk
- Authors: Esterhuizen-Londt, Maranda
- Date: 2010
- Subjects: Cyanobacteria , Bioaccumulation , Chromatographic analysis , Neurotoxic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10306 , http://hdl.handle.net/10948/1473 , Cyanobacteria , Bioaccumulation , Chromatographic analysis , Neurotoxic agents
- Description: β-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid associated with human neurodegenerative disease. Due to the cosmopolitan nature of cyanobacteria, detection of BMAA in cyanobacteria has caused concerns about human exposure risk. This study was therefore based on the hypothesis that BMAA poses a health risk to humans either by direct ingestion or by indirect exposure to BMAA from a cyanobacterial source via a freshwater food chain. A validated gas chromatography-mass spectrometry (GC-MS) BMAA analysis method and a confirmatory liquid chromatography-mass spectrometry (LC-MS) method, with improved sensitivity, were developed in addition to a LC-MS/MS method for analyte confirmation. These methods were used to quantify BMAA in South African cyanobacteria, isolated from various potable water reservoirs. The majority of the isolates tested, contained BMAA. Possible human exposure by direct consumption of BMAA released from cyanobacterial blooms was investigated by the development of a robust solid phase extraction (SPE) method used for BMAA concentration and quantification in raw and treated tap water. Despite the use of the SPE method that facilitated the concentration of BMAA from large quantities of water, no free dissolved BMAA was detected in raw or processed fresh water. The fate of exogenous BMAA was therefore investigated firstly by evaluating the efficacy of standard water treatment processes employed in South Africa and secondly by investigating the possibility of BMAA bioaccumulation and biomagnification in aquatic food chains. Standard water treatment processes proved highly efficient at removing free dissolved BMAA, explaining the absence of BMAA in treated tap water. However, the cause of the BMAA absence in raw potable water remained unknown. Uptake of BMAA by model aquatic organisms was investigated in controlled experiments. BMAA uptake was documented in both Ceratophyllum demersum and Daphnia magna, however, BMAA-protein association and biomagnification were not observed in D. magna. BMAA had an inhibitory effect on the oxidative stress enzyme acitivties of both organisms tested (as well as human S9 extracts), resulting in accumulation of detrimental reactive oxygen species (ROS) in the cells. Exposure of crop plants to BMAA in controlled experiments resulted in BMAA uptake, protein association, and subsequent inhibition of the antioxidative enzyme activities. However, BMAA was detected in neither free nor protein-associated form in natural crop plants irrigated with known BMAA-containing bloom water. Post-mortem liver samples of Clarias gariepinus (Catfish) and Crocodylus niloticus (Crocodile), from a natural fresh water ecosystem that experienced frequent cyanobacterial blooms, contained both free and protein-associated BMAA. Higher BMAA concentrations were found in crocodile liver samples compared to fish liver samples, strongly suggesting biomagnification from one trophic level to the next. BMAA concentrations corresponded to crocodile age. This is the first report of bioaccumulation and biomagnification in two trophic levels in a fresh water ecosystem. These findings strongly suggest possible human exposure via aquatic food chains of cyanobacterial origin. Direct BMAA exposure via drinking water is not plausible due to the efficiency of standard water treatment processes to remove BMAA. The use of raw water for agricultural and recreational use, however, remains a problem. The development of management strategies as well as daily tolerable levels for BMAA is urgently required.
- Full Text:
- Date Issued: 2010
- Authors: Esterhuizen-Londt, Maranda
- Date: 2010
- Subjects: Cyanobacteria , Bioaccumulation , Chromatographic analysis , Neurotoxic agents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10306 , http://hdl.handle.net/10948/1473 , Cyanobacteria , Bioaccumulation , Chromatographic analysis , Neurotoxic agents
- Description: β-N-methylamino-L-alanine (BMAA) is a non-proteinogenic amino acid associated with human neurodegenerative disease. Due to the cosmopolitan nature of cyanobacteria, detection of BMAA in cyanobacteria has caused concerns about human exposure risk. This study was therefore based on the hypothesis that BMAA poses a health risk to humans either by direct ingestion or by indirect exposure to BMAA from a cyanobacterial source via a freshwater food chain. A validated gas chromatography-mass spectrometry (GC-MS) BMAA analysis method and a confirmatory liquid chromatography-mass spectrometry (LC-MS) method, with improved sensitivity, were developed in addition to a LC-MS/MS method for analyte confirmation. These methods were used to quantify BMAA in South African cyanobacteria, isolated from various potable water reservoirs. The majority of the isolates tested, contained BMAA. Possible human exposure by direct consumption of BMAA released from cyanobacterial blooms was investigated by the development of a robust solid phase extraction (SPE) method used for BMAA concentration and quantification in raw and treated tap water. Despite the use of the SPE method that facilitated the concentration of BMAA from large quantities of water, no free dissolved BMAA was detected in raw or processed fresh water. The fate of exogenous BMAA was therefore investigated firstly by evaluating the efficacy of standard water treatment processes employed in South Africa and secondly by investigating the possibility of BMAA bioaccumulation and biomagnification in aquatic food chains. Standard water treatment processes proved highly efficient at removing free dissolved BMAA, explaining the absence of BMAA in treated tap water. However, the cause of the BMAA absence in raw potable water remained unknown. Uptake of BMAA by model aquatic organisms was investigated in controlled experiments. BMAA uptake was documented in both Ceratophyllum demersum and Daphnia magna, however, BMAA-protein association and biomagnification were not observed in D. magna. BMAA had an inhibitory effect on the oxidative stress enzyme acitivties of both organisms tested (as well as human S9 extracts), resulting in accumulation of detrimental reactive oxygen species (ROS) in the cells. Exposure of crop plants to BMAA in controlled experiments resulted in BMAA uptake, protein association, and subsequent inhibition of the antioxidative enzyme activities. However, BMAA was detected in neither free nor protein-associated form in natural crop plants irrigated with known BMAA-containing bloom water. Post-mortem liver samples of Clarias gariepinus (Catfish) and Crocodylus niloticus (Crocodile), from a natural fresh water ecosystem that experienced frequent cyanobacterial blooms, contained both free and protein-associated BMAA. Higher BMAA concentrations were found in crocodile liver samples compared to fish liver samples, strongly suggesting biomagnification from one trophic level to the next. BMAA concentrations corresponded to crocodile age. This is the first report of bioaccumulation and biomagnification in two trophic levels in a fresh water ecosystem. These findings strongly suggest possible human exposure via aquatic food chains of cyanobacterial origin. Direct BMAA exposure via drinking water is not plausible due to the efficiency of standard water treatment processes to remove BMAA. The use of raw water for agricultural and recreational use, however, remains a problem. The development of management strategies as well as daily tolerable levels for BMAA is urgently required.
- Full Text:
- Date Issued: 2010
Improving Productivity of Maize-based Smallholder Irrigated Cropping Systems: A Case Study of Zanyokwe Irrigation Scheme, Eastern Cape, South Africa
- Authors: Fanadzo, Morris
- Date: 2010
- Subjects: Farms, Small -- South Africa -- Eastern Cape Crop yields -- South Africa -- Eastern Cape Agricultural productivity -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/11009 , vital:36450
- Description: Smallholder irrigation schemes (SIS) in South Africa have performed poorly and failed to achieve the development objectives of sustaining rural livelihoods by increasing crop production and income. Limited knowledge of crop production among farmers is one constraint to improved crop productivity and, yet little research has been carried out to relate agronomic practices to productivity. This study was aimed at identifying strategies to improve the productivity of maize-based smallholder irrigated cropping systems in South Africa, using Zanyokwe irrigation scheme (ZIS) in the Eastern Cape Province as a case study. The research design was emergent, developed progressively as influenced by the progressive analyses that were made. The research work involved two main phases: exploratory studies and refinement on-farm experiments for testing technologies as informed by the exploratory studies. Exploratory studies were aimed at describing farmer crop production practices in major crop enterprises and identifying and prioritizing major agronomic yield constraints. Findings indicated that the overall performance of the cropping systems was poor as evidenced by low overall yields of < 25% of the potential in maize and butternut. Poor management of weeds, soil fertility, plant populations and water, late planting and poor cultivar choice were the most important yield constraints. The average cropping intensity achieved by farmers was only 48%. New hybrids yielded 50 - 65% higher grain than the cultivars commonly grown by farmers. However, farmers favoured their traditional cultivars, as they preferred green maize production as opposed to dry grains. As a result of these findings, focused research was designed on options for iii improving green maize production, soil fertility, crop stand and weed management in crop production. On-farm trials were, therefore, designed to (1) compare the response to nitrogen (N) rate of direct seeded and transplanted maize; (2) evaluate comparative performance of direct seeded and transplanted green maize under farmer management, and to work out the economics of transplanting; (3) investigate the effects of row spacing and atrazine dosage on weed dynamics maize yield; (4) determine the effects of inter-row spacing and plant population on weed dynamics and maize yield; and (5) investigate the effects of pre-plant weed control, N rate and plant population on weed dynamics and butternut yield. Maize transplanting improved crop stand, had earlier maturity and yielded higher at lower N rates compared to direct seeding for both green and grain maize. Total costs that varied were higher by R3 565 ha-1 for transplanted maize compared to direct-seeded maize, but the net benefits from transplanting were also much higher by R8 773 ha-1. Farmers favoured transplanting, citing bigger cobs, early maturity and the absence of seedling damage by birds, when maize was transplanted. However, a follow-up survey conducted during the subsequent year indicated that five of the six farmers abandoned transplanting, citing shortage of labour and high cost of commercially produced seedlings. It was concluded that transplanting is unlikely to be adopted unless the labour intensiveness of manual transplanting can be solved. Increasing atrazine dosage from a third of the label recommended dosage (LRD) and reducing row spacing from 90 to 45 cm resulted in an increase in weed mortality. A 100% kill of annual broadleaf weeds was possible while iv perennial grasses and the annual broadleaf weed, Oxalis latifolia, could not be controlled even at the LRD. However, improved weed mortality with increase in atrazine dosage and/or narrow rows did not translate into improved maize productivity. In butternut, pre-plant weed control resulted in a six-fold decrease in weed biomass and a 100% increase in fruit yield. These findings demonstrated the possibility of incorporation of reduced herbicide dosages and narrow rows to achieve adequate weed control and optimise on maize yields in smallholder farming systems. The results also suggested that pre-plant weed control is one of the pre-requisite to successful butternut production in SIS in South Africa. Increasing maize population from 40 000 to 60 000 plants ha-1 resulted in a 30% grain yield increase, but decreased length of cobs. Row spacing had no effect on maize yield at 40 000 plants ha-1, but at 60 000 plants ha-1 45 cm rows resulted in 11% higher grain yield (12 547 kg ha-1) than 90 cm rows (11 288 kg ha-1). Butternut yield increased significantly (p < 0.01) with increase in plant population and N rate. The optimum butternut population and N rate were estimated at 25 000 plants ha-1 and 120 kg N ha-1, respectively. Pre-plant weed control in butternut resulted in a six-fold decrease in weed biomass. Increasing butternut planting density from 10 000 to 30 000 plants ha-1 decreased weed biomass by 47%. No marketable fruits were obtained when planting was done without prior weed control. This result suggest that application of non-selective herbicide before planting is one technique that can be used by farmers as part of integrated weed management to give the crop a competitive advantage in the early growth stages before the plants start to produce vines. Yield increased significantly (p < 0.01) with increase in plant density and N rate. The optimum plant density and N rate were estimated at 25 000 plants ha-1 and 120 kg N ha-1, respectively. These findings emphasise the need to take into consideration production practices by farmers as a basis to build up skills in the management of crop enterprises and the farm as a viable business in any efforts to improve on the performance of SIS in South Africa. Future research should concentrate on labour-saving sustainable production technologies for SIS in South Africa.
- Full Text:
- Date Issued: 2010
- Authors: Fanadzo, Morris
- Date: 2010
- Subjects: Farms, Small -- South Africa -- Eastern Cape Crop yields -- South Africa -- Eastern Cape Agricultural productivity -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/11009 , vital:36450
- Description: Smallholder irrigation schemes (SIS) in South Africa have performed poorly and failed to achieve the development objectives of sustaining rural livelihoods by increasing crop production and income. Limited knowledge of crop production among farmers is one constraint to improved crop productivity and, yet little research has been carried out to relate agronomic practices to productivity. This study was aimed at identifying strategies to improve the productivity of maize-based smallholder irrigated cropping systems in South Africa, using Zanyokwe irrigation scheme (ZIS) in the Eastern Cape Province as a case study. The research design was emergent, developed progressively as influenced by the progressive analyses that were made. The research work involved two main phases: exploratory studies and refinement on-farm experiments for testing technologies as informed by the exploratory studies. Exploratory studies were aimed at describing farmer crop production practices in major crop enterprises and identifying and prioritizing major agronomic yield constraints. Findings indicated that the overall performance of the cropping systems was poor as evidenced by low overall yields of < 25% of the potential in maize and butternut. Poor management of weeds, soil fertility, plant populations and water, late planting and poor cultivar choice were the most important yield constraints. The average cropping intensity achieved by farmers was only 48%. New hybrids yielded 50 - 65% higher grain than the cultivars commonly grown by farmers. However, farmers favoured their traditional cultivars, as they preferred green maize production as opposed to dry grains. As a result of these findings, focused research was designed on options for iii improving green maize production, soil fertility, crop stand and weed management in crop production. On-farm trials were, therefore, designed to (1) compare the response to nitrogen (N) rate of direct seeded and transplanted maize; (2) evaluate comparative performance of direct seeded and transplanted green maize under farmer management, and to work out the economics of transplanting; (3) investigate the effects of row spacing and atrazine dosage on weed dynamics maize yield; (4) determine the effects of inter-row spacing and plant population on weed dynamics and maize yield; and (5) investigate the effects of pre-plant weed control, N rate and plant population on weed dynamics and butternut yield. Maize transplanting improved crop stand, had earlier maturity and yielded higher at lower N rates compared to direct seeding for both green and grain maize. Total costs that varied were higher by R3 565 ha-1 for transplanted maize compared to direct-seeded maize, but the net benefits from transplanting were also much higher by R8 773 ha-1. Farmers favoured transplanting, citing bigger cobs, early maturity and the absence of seedling damage by birds, when maize was transplanted. However, a follow-up survey conducted during the subsequent year indicated that five of the six farmers abandoned transplanting, citing shortage of labour and high cost of commercially produced seedlings. It was concluded that transplanting is unlikely to be adopted unless the labour intensiveness of manual transplanting can be solved. Increasing atrazine dosage from a third of the label recommended dosage (LRD) and reducing row spacing from 90 to 45 cm resulted in an increase in weed mortality. A 100% kill of annual broadleaf weeds was possible while iv perennial grasses and the annual broadleaf weed, Oxalis latifolia, could not be controlled even at the LRD. However, improved weed mortality with increase in atrazine dosage and/or narrow rows did not translate into improved maize productivity. In butternut, pre-plant weed control resulted in a six-fold decrease in weed biomass and a 100% increase in fruit yield. These findings demonstrated the possibility of incorporation of reduced herbicide dosages and narrow rows to achieve adequate weed control and optimise on maize yields in smallholder farming systems. The results also suggested that pre-plant weed control is one of the pre-requisite to successful butternut production in SIS in South Africa. Increasing maize population from 40 000 to 60 000 plants ha-1 resulted in a 30% grain yield increase, but decreased length of cobs. Row spacing had no effect on maize yield at 40 000 plants ha-1, but at 60 000 plants ha-1 45 cm rows resulted in 11% higher grain yield (12 547 kg ha-1) than 90 cm rows (11 288 kg ha-1). Butternut yield increased significantly (p < 0.01) with increase in plant population and N rate. The optimum butternut population and N rate were estimated at 25 000 plants ha-1 and 120 kg N ha-1, respectively. Pre-plant weed control in butternut resulted in a six-fold decrease in weed biomass. Increasing butternut planting density from 10 000 to 30 000 plants ha-1 decreased weed biomass by 47%. No marketable fruits were obtained when planting was done without prior weed control. This result suggest that application of non-selective herbicide before planting is one technique that can be used by farmers as part of integrated weed management to give the crop a competitive advantage in the early growth stages before the plants start to produce vines. Yield increased significantly (p < 0.01) with increase in plant density and N rate. The optimum plant density and N rate were estimated at 25 000 plants ha-1 and 120 kg N ha-1, respectively. These findings emphasise the need to take into consideration production practices by farmers as a basis to build up skills in the management of crop enterprises and the farm as a viable business in any efforts to improve on the performance of SIS in South Africa. Future research should concentrate on labour-saving sustainable production technologies for SIS in South Africa.
- Full Text:
- Date Issued: 2010