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
Psigobiografiese persoonlikheidsbeskrywing van Generaal Christiaan de Wet
- Authors: Henning, Riana
- Date: 2010
- Subjects: De Wet, Christiaan Rudolf, 1854-1922 Psychology -- Biographical methods Psychoanalysis Big Five model Politicians -- Psychology South Africa -- Politics and government -- 1836-1909 South Africa -- Politics and government -- 1909-1948
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2990 , http://hdl.handle.net/10962/d1002499
- Description: Hierdie is 'n psigobiografiese studie van Generaal Christiaan Rudolph de Wet. 'n Psigobiografiese studie is die bestudering van 'n persoon se volledige lewe met die doel om die persoon beter te verstaan. Psigobiografiese navorsing maak gebruik van psigologiese teorieë wat aangewend word om die biografiese data van 'n persoon se lewe te beskryf en moontlik ook te verklaar. Die individu wat bestudeer word, is gewoonlik 'n bekende, invloedryke, navolgenswaardige, interessante of modelfiguur. Daar is tans 'n oplewing in die veld van psigobiografiese studies, maar daar word nog steeds nie genoeg in die akademiese veld gedoen om psigobiografiese studies te bevorder nie. De Wet (1854-1922) is vir hierdie studie gekies omdat hy 'n interessante, dog komplekse figuur was. Hy het veral tydens die Anglo-Boereoorlog in 1899-1902 bekendheid verwerf. As 45-jarige man het De Wet in die Anglo-Boereoorlog geveg en vinnig opgang as 'n militêre leier gemaak. Sy vindingryke ontsnappingspogings het die Britse magte hoofbrekens besorg. Wat De Wet verder uniek maak, is dat hy met net drie maande skoolopleiding in die parlement gedien het, as president verkies is, die hoogste gesag in die Verdedigingsmag gehad het en 'n boek oor sy oorlogsherinneringe geskryf het. Alhoewel daar akademiese werke oor De Wet bestaan, is daar tot op hede nog geen psigobiografiese studie oor hom gedoen nie. Die doel van die studie was om die mens agter die legende na vore te bring. Daar is ook gepoog om moontlike antwoorde en verklarings op onbeantwoorde vrae te gee. Die studie het van beide kwalitatiewe en kwantitatiewe data gebruik gemaak en kan as 'n psigobiografiese gevalstudie beskryf word. Die Vyf-faktor model van Costa en McCrae (1992) is op die biografiese data van De Wet toegepas om sodoende sy persoonlikheidseienskappe te beskryf. Die bevindinge het interessante persoonlikheidseienskappe van De Wet deur middel van die Vyf-faktor model aan die lig gebring. Volgens die kwalitatiewe navorsingsbevindinge was De Wet 'n vyandige, aksie-gedrewe, bevoegde, prestasie-strewende, selfgedissiplineerde, warm, openhartige, saggeaarde en beskeie persoon. Die kwalitatiewe en kwantitatiewe data-ontledings het uiteenlopende persoonlikheidskenmerke by De Wet geïdentifiseer. Die grootste verskille het by die fasette warmte, openhartigheid en altruïsme voorgekom. Die waarde van die studie is dat 'n wetenskaplike persoonlikheidsontleding van De Wet gedoen is. Dit is ook die eerste studie waar 'n teoretiese model op De Wet se persoonlikheid toegepas is. Alhoewel die studie sekere tekortkominge toon, beklemtoon dit terselfdertyd die wenslikheid daarvan om alternatiewe modelle te gebruik tydens die ontleding van persoonlikheidskenmerke. Die studie dui ook op die behoefte aan verdere navorsing, byvoorbeeld soortgelyke ontledings en vergelykings van die persoonlikhede van ander militêre bevelvoerders (De la Rey, Smuts, Beyers, Hertzog).
- Full Text:
- Date Issued: 2010
- Authors: Henning, Riana
- Date: 2010
- Subjects: De Wet, Christiaan Rudolf, 1854-1922 Psychology -- Biographical methods Psychoanalysis Big Five model Politicians -- Psychology South Africa -- Politics and government -- 1836-1909 South Africa -- Politics and government -- 1909-1948
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2990 , http://hdl.handle.net/10962/d1002499
- Description: Hierdie is 'n psigobiografiese studie van Generaal Christiaan Rudolph de Wet. 'n Psigobiografiese studie is die bestudering van 'n persoon se volledige lewe met die doel om die persoon beter te verstaan. Psigobiografiese navorsing maak gebruik van psigologiese teorieë wat aangewend word om die biografiese data van 'n persoon se lewe te beskryf en moontlik ook te verklaar. Die individu wat bestudeer word, is gewoonlik 'n bekende, invloedryke, navolgenswaardige, interessante of modelfiguur. Daar is tans 'n oplewing in die veld van psigobiografiese studies, maar daar word nog steeds nie genoeg in die akademiese veld gedoen om psigobiografiese studies te bevorder nie. De Wet (1854-1922) is vir hierdie studie gekies omdat hy 'n interessante, dog komplekse figuur was. Hy het veral tydens die Anglo-Boereoorlog in 1899-1902 bekendheid verwerf. As 45-jarige man het De Wet in die Anglo-Boereoorlog geveg en vinnig opgang as 'n militêre leier gemaak. Sy vindingryke ontsnappingspogings het die Britse magte hoofbrekens besorg. Wat De Wet verder uniek maak, is dat hy met net drie maande skoolopleiding in die parlement gedien het, as president verkies is, die hoogste gesag in die Verdedigingsmag gehad het en 'n boek oor sy oorlogsherinneringe geskryf het. Alhoewel daar akademiese werke oor De Wet bestaan, is daar tot op hede nog geen psigobiografiese studie oor hom gedoen nie. Die doel van die studie was om die mens agter die legende na vore te bring. Daar is ook gepoog om moontlike antwoorde en verklarings op onbeantwoorde vrae te gee. Die studie het van beide kwalitatiewe en kwantitatiewe data gebruik gemaak en kan as 'n psigobiografiese gevalstudie beskryf word. Die Vyf-faktor model van Costa en McCrae (1992) is op die biografiese data van De Wet toegepas om sodoende sy persoonlikheidseienskappe te beskryf. Die bevindinge het interessante persoonlikheidseienskappe van De Wet deur middel van die Vyf-faktor model aan die lig gebring. Volgens die kwalitatiewe navorsingsbevindinge was De Wet 'n vyandige, aksie-gedrewe, bevoegde, prestasie-strewende, selfgedissiplineerde, warm, openhartige, saggeaarde en beskeie persoon. Die kwalitatiewe en kwantitatiewe data-ontledings het uiteenlopende persoonlikheidskenmerke by De Wet geïdentifiseer. Die grootste verskille het by die fasette warmte, openhartigheid en altruïsme voorgekom. Die waarde van die studie is dat 'n wetenskaplike persoonlikheidsontleding van De Wet gedoen is. Dit is ook die eerste studie waar 'n teoretiese model op De Wet se persoonlikheid toegepas is. Alhoewel die studie sekere tekortkominge toon, beklemtoon dit terselfdertyd die wenslikheid daarvan om alternatiewe modelle te gebruik tydens die ontleding van persoonlikheidskenmerke. Die studie dui ook op die behoefte aan verdere navorsing, byvoorbeeld soortgelyke ontledings en vergelykings van die persoonlikhede van ander militêre bevelvoerders (De la Rey, Smuts, Beyers, Hertzog).
- Full Text:
- Date Issued: 2010
Sample preparation for pesticide analysis in water and sediments a case study of the Okavango Delta, Botswana
- Authors: Mmualefe, Lesego Cecilia
- Date: 2010
- Subjects: Water quality -- Botswana -- Okavango Delta Water -- Analysis Pesticides -- Environmental aspects -- Botswana -- Okavango Delta Water -- Pollution -- Botswana -- Okavango Delta DDT (Insecticide) -- Environmental aspects -- Botswana -- Okavango Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4344 , http://hdl.handle.net/10962/d1005006
- Description: This thesis presents a first ever extensive analysis of pesticides in water and sediments from the Okavango Delta, Botswana, employing green sample preparation techniques that require small volumes of organic solvents hence generating negligible volumes of organic solvent waste. Pesticides were extracted and pre-concentrated from water by solid phase extraction (SPE) and headspace solid phase microextraction (HS-SPME) while supercritical fluid extraction (SFE) and pressurized fluid extraction (PFE) were employed for sediments. Subsequent analysis was carried out on a gas chromatograph with electron capture detection and analytes were unequivocally confirmed by high resolution mass spectrometric detection. Hexachlorobenzene (HCB), trans-chlordane, 4,4′-DDD and 4,4′-DDE were detected after optimized HS-SPME in several water samples from the lower Delta at concentrations ranging from 2.4 to 61.4 μg L-1 that are much higher than the 0.1 μg L-1 maximum limit of individual organochlorine pesticides in drinking water set by the European Community Directive. The same samples were cleaned with ISOLUTE C18 SPE sorbent with an optimal acetone/n-hexane (1:1 v/v) mixture for the elution of analytes. No pesticides were detected after SPE clean-up and pre-concentration. HCB, aldrin and 4, 4‟-DDT were identified in sediments after SFE at concentration ranges of 1.1 - 30.3, 0.5 – 15.2 and 1.4 – 55.4 μg/g, respectively. There was an increase of pesticides concentrations in the direction of water flow from the Panhandle (point of entry) to the lower delta. DDE, fatty acids and phthalates were detected after PFE with optimized extraction solvent and temperature. The presence of DDT metabolites in the water and sediments from the Okavango Delta confirm historical exposure to the pesticide. However their cumulative concentration increase in the water-flow direction calls for further investigation of point sources for the long-term preservation of the Delta. The green sample preparation techniques and low toxicity solvents employed in this thesis are thus recommended for routine environmental monitoring exercises.
- Full Text:
- Date Issued: 2010
- Authors: Mmualefe, Lesego Cecilia
- Date: 2010
- Subjects: Water quality -- Botswana -- Okavango Delta Water -- Analysis Pesticides -- Environmental aspects -- Botswana -- Okavango Delta Water -- Pollution -- Botswana -- Okavango Delta DDT (Insecticide) -- Environmental aspects -- Botswana -- Okavango Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4344 , http://hdl.handle.net/10962/d1005006
- Description: This thesis presents a first ever extensive analysis of pesticides in water and sediments from the Okavango Delta, Botswana, employing green sample preparation techniques that require small volumes of organic solvents hence generating negligible volumes of organic solvent waste. Pesticides were extracted and pre-concentrated from water by solid phase extraction (SPE) and headspace solid phase microextraction (HS-SPME) while supercritical fluid extraction (SFE) and pressurized fluid extraction (PFE) were employed for sediments. Subsequent analysis was carried out on a gas chromatograph with electron capture detection and analytes were unequivocally confirmed by high resolution mass spectrometric detection. Hexachlorobenzene (HCB), trans-chlordane, 4,4′-DDD and 4,4′-DDE were detected after optimized HS-SPME in several water samples from the lower Delta at concentrations ranging from 2.4 to 61.4 μg L-1 that are much higher than the 0.1 μg L-1 maximum limit of individual organochlorine pesticides in drinking water set by the European Community Directive. The same samples were cleaned with ISOLUTE C18 SPE sorbent with an optimal acetone/n-hexane (1:1 v/v) mixture for the elution of analytes. No pesticides were detected after SPE clean-up and pre-concentration. HCB, aldrin and 4, 4‟-DDT were identified in sediments after SFE at concentration ranges of 1.1 - 30.3, 0.5 – 15.2 and 1.4 – 55.4 μg/g, respectively. There was an increase of pesticides concentrations in the direction of water flow from the Panhandle (point of entry) to the lower delta. DDE, fatty acids and phthalates were detected after PFE with optimized extraction solvent and temperature. The presence of DDT metabolites in the water and sediments from the Okavango Delta confirm historical exposure to the pesticide. However their cumulative concentration increase in the water-flow direction calls for further investigation of point sources for the long-term preservation of the Delta. The green sample preparation techniques and low toxicity solvents employed in this thesis are thus recommended for routine environmental monitoring exercises.
- Full Text:
- Date Issued: 2010
Studies on the nutritional value of seven accessions of cocoyam growing in South Africa
- Authors: Lewu, Muinat Nike
- Date: 2010
- Subjects: Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11305 , http://hdl.handle.net/10353/d1001054 , Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
- Description: Cocoyam [Colocasia esculenta (L.) Schott] is widely cultivated as a staple food in the tropical and subtropical regions of the world. The crop, however, remains unpopular and not well known outside KwaZulu-Natal Province of South Africa where it is cultivated mainly for subsistence. The aims of the study were to collect local landraces (accessions) of the crop from where it is found growing within the country for various studies and also to document its nutritional values as well as the safety/toxicity of the crop. The study was carried out using various methods. These included a comparative assessment of the proximate, mineral and antinutrient compositions of cooked and uncooked tubers of a typical commercially available cocoyam and potato found in South African markets. These investigations were repeated for the tubers and leaves of available landraces (seven accessions) of C. esculenta found growing in the farmers’ fields in KwaZulu-Natal Province. Also, an in vivo toxicological study on cooked accessions of the local landraces was conducted to determine possible toxicity effects after consumption using albino rats as a model. The results revealed that commercially available cocoyam and potato tubers have very close nutritional components. Analysis of the proximate composition of seven accessions (UFCe1- UFCe7) of cooked and uncooked tubers of cocoyam indicated that UFCe7 was better in ash, crude protein, crude fibre and crude lipid contents but with higher moisture which could make it more vulnerable to microbial attack. No tubers of the seven accessions appeared to be ii outstandingly better than the others based on their mineral compositions. However, in terms of antinutritional factors, UFCe1, UFCe3 and UFCe7 had the least amounts of oxalate, tannins and phytate in their cooked states. It was discovered however, that the leaves of the accessions of this vegetable contain substantial amount of minerals, and therefore, can contribute significantly to the nutrient requirements of humans and could be recommended as a cheap source of nutrients in South Africa. None of the accessions was outstandingly better than the others in terms of their mineral contents and anti-nutritional factors. Moreover, the current study has shown that boiling the leaves of cocoyam prior to consumption is an effective way of reducing the antinutrient contents of the leaves of the plant thereby making it safe for consumption. The findings also revealed that cooking C. esculenta leaves may increase the levels of protein, fibre and lipid contents while cooking may also decrease the mineral, carbohydrate and caloric contents of the leaves of the accessions. The leafy vegetable may, therefore, be recommended as a cheap source of plant protein. Cooking improved the nutritive value as a result of the reduction in antinutrient levels, thereby improving the food quality in all the tuber and leaf samples used for this study. At the same time, cooked samples also suffered loss of some nutrients with respect to the proximate and mineral compositions. However, supplementation from other food sources that are rich in these nutrients is necessary when these crops are cooked for consumption. Any of the cocoyam accessions may be recommended for consumption for improved protein and mineral nutrients while tubers of accession UFCe7 have also shown good promise in terms of protein and fibre content availability. The results of the in vivo study, using the liver and kidney functional endpoints of weanling albino rats (Rattus norvegicus) maintained on different accessions of cooked cocoyam-based iii diets (UFCe1-UFCe7) for 28 days, revealed that all the accessions produced selective alterations on the hepatorenal indices of weanling rats. The highest alterations were produced by UFCe4 while the least was from UFCe2. These alterations may have consequential effects on the normal functioning of the liver and kidney of the animals. The UFCe2 exhibited the least toxicity risk among the accessions of C. esculenta growing in KwaZulu-Natal Province of South Africa.
- Full Text:
- Date Issued: 2010
- Authors: Lewu, Muinat Nike
- Date: 2010
- Subjects: Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:11305 , http://hdl.handle.net/10353/d1001054 , Taro , Nutrition , Field crops -- Nutrition , Taro -- Nutritional aspects
- Description: Cocoyam [Colocasia esculenta (L.) Schott] is widely cultivated as a staple food in the tropical and subtropical regions of the world. The crop, however, remains unpopular and not well known outside KwaZulu-Natal Province of South Africa where it is cultivated mainly for subsistence. The aims of the study were to collect local landraces (accessions) of the crop from where it is found growing within the country for various studies and also to document its nutritional values as well as the safety/toxicity of the crop. The study was carried out using various methods. These included a comparative assessment of the proximate, mineral and antinutrient compositions of cooked and uncooked tubers of a typical commercially available cocoyam and potato found in South African markets. These investigations were repeated for the tubers and leaves of available landraces (seven accessions) of C. esculenta found growing in the farmers’ fields in KwaZulu-Natal Province. Also, an in vivo toxicological study on cooked accessions of the local landraces was conducted to determine possible toxicity effects after consumption using albino rats as a model. The results revealed that commercially available cocoyam and potato tubers have very close nutritional components. Analysis of the proximate composition of seven accessions (UFCe1- UFCe7) of cooked and uncooked tubers of cocoyam indicated that UFCe7 was better in ash, crude protein, crude fibre and crude lipid contents but with higher moisture which could make it more vulnerable to microbial attack. No tubers of the seven accessions appeared to be ii outstandingly better than the others based on their mineral compositions. However, in terms of antinutritional factors, UFCe1, UFCe3 and UFCe7 had the least amounts of oxalate, tannins and phytate in their cooked states. It was discovered however, that the leaves of the accessions of this vegetable contain substantial amount of minerals, and therefore, can contribute significantly to the nutrient requirements of humans and could be recommended as a cheap source of nutrients in South Africa. None of the accessions was outstandingly better than the others in terms of their mineral contents and anti-nutritional factors. Moreover, the current study has shown that boiling the leaves of cocoyam prior to consumption is an effective way of reducing the antinutrient contents of the leaves of the plant thereby making it safe for consumption. The findings also revealed that cooking C. esculenta leaves may increase the levels of protein, fibre and lipid contents while cooking may also decrease the mineral, carbohydrate and caloric contents of the leaves of the accessions. The leafy vegetable may, therefore, be recommended as a cheap source of plant protein. Cooking improved the nutritive value as a result of the reduction in antinutrient levels, thereby improving the food quality in all the tuber and leaf samples used for this study. At the same time, cooked samples also suffered loss of some nutrients with respect to the proximate and mineral compositions. However, supplementation from other food sources that are rich in these nutrients is necessary when these crops are cooked for consumption. Any of the cocoyam accessions may be recommended for consumption for improved protein and mineral nutrients while tubers of accession UFCe7 have also shown good promise in terms of protein and fibre content availability. The results of the in vivo study, using the liver and kidney functional endpoints of weanling albino rats (Rattus norvegicus) maintained on different accessions of cooked cocoyam-based iii diets (UFCe1-UFCe7) for 28 days, revealed that all the accessions produced selective alterations on the hepatorenal indices of weanling rats. The highest alterations were produced by UFCe4 while the least was from UFCe2. These alterations may have consequential effects on the normal functioning of the liver and kidney of the animals. The UFCe2 exhibited the least toxicity risk among the accessions of C. esculenta growing in KwaZulu-Natal Province of South Africa.
- Full Text:
- Date Issued: 2010
Intertidal patterns and processes : tracking the effects of coastline topography and settlement choice across life stages of the mussels perna perna and mytilus galloprovincialis
- Von Der Meden, Charles Eric Otto
- Authors: Von Der Meden, Charles Eric Otto
- Date: 2010
- Subjects: Mexilhao mussel -- Behavior -- South Africa Mytilus galloprovincialis -- Behavior -- South Africa Perna -- Behavior -- South Africa Mussels -- Ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5721 , http://hdl.handle.net/10962/d1005407
- Description: Within landscapes, spatial heterogeneity is common and specific landscape features can influence propagule dispersal by wind or water, affecting population connectivity and dynamics. Coastline topographic features, such as bays and headlands, have a variety of biophysical effects on nearshore oceanography, larval transport, retention and supply, and the processes of larval settlement and recruitment. Although this has been demonstrated in several parts of the world, engendering a perception of a general ‘bay effect’, few studies have investigated this generality in a single experiment or region, by replicating at the level of ‘bay’. The Agulhas biogeographic region of the south coast of South Africa is a useful system within which to test for such generality. Using the intertidal mussels Mytilus galloprovincialis and Perna perna as model organisms, patterns of adult distribution were surveyed across four large ‘halfheart’ bays and intervening stretches of open coast, providing replication at the level of ‘bay’ and duplication of ecologically similar species. In support of a general, pervasive influence of bays on intertidal populations, mussel cover was found to be greater in bays than on the open coast for both species, although the effect was strongest for M. galloprovincialis. To explain this adult distribution, settlement, post-settlement mortality and recruitment were examined over 12mo at the same sites, with the prediction that rates of each would favour larger bay populations. Contrary to this, an interaction between month and bay-status was found, with greater settlement and recruitment on the open coast than in bays reflecting extreme settlement and recruitment events at 3 westerly open coast sites during summer. Re-analysis excluding these outliers, revealed the expected effect, of greater settlement and recruitment in bays. While this indicates the broad generality of the bay effect, it highlights exceptions and the need for replication in time and space when examining landscape effects. Measuring post-settlement mortality required testing small-scale settlement behaviour on established and newly deployed settler collectors. It was found that all settlers preferred collectors with biofilm, but that primary settlers avoided conspecific settlers, while secondary settlers were attracted to them. With discrepancies in settler attraction to new and established collectors accounted for, initial (over 2d) and longer-term (over 7d) post-settlement mortality rates were found to be substantial (ca 60 %) for both species. No topographic effect on p-s mortality was evident. Finally, recruit-settler, adult-recruit and interspecies correlations were examined at regional and local scales. Synergistic (or neutral) effects maintained the initial settlement pattern in recruit and adult populations regionally, but not at local scales; striking interspecies correlations suggested the influence of common regional transport processes. Ultimately, the results emphasize the importance of the direction of effects in different life stages and at different spatial scales, and the possibility that antagonistic effects may mask even strong patterns.
- Full Text:
- Date Issued: 2010
- Authors: Von Der Meden, Charles Eric Otto
- Date: 2010
- Subjects: Mexilhao mussel -- Behavior -- South Africa Mytilus galloprovincialis -- Behavior -- South Africa Perna -- Behavior -- South Africa Mussels -- Ecology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5721 , http://hdl.handle.net/10962/d1005407
- Description: Within landscapes, spatial heterogeneity is common and specific landscape features can influence propagule dispersal by wind or water, affecting population connectivity and dynamics. Coastline topographic features, such as bays and headlands, have a variety of biophysical effects on nearshore oceanography, larval transport, retention and supply, and the processes of larval settlement and recruitment. Although this has been demonstrated in several parts of the world, engendering a perception of a general ‘bay effect’, few studies have investigated this generality in a single experiment or region, by replicating at the level of ‘bay’. The Agulhas biogeographic region of the south coast of South Africa is a useful system within which to test for such generality. Using the intertidal mussels Mytilus galloprovincialis and Perna perna as model organisms, patterns of adult distribution were surveyed across four large ‘halfheart’ bays and intervening stretches of open coast, providing replication at the level of ‘bay’ and duplication of ecologically similar species. In support of a general, pervasive influence of bays on intertidal populations, mussel cover was found to be greater in bays than on the open coast for both species, although the effect was strongest for M. galloprovincialis. To explain this adult distribution, settlement, post-settlement mortality and recruitment were examined over 12mo at the same sites, with the prediction that rates of each would favour larger bay populations. Contrary to this, an interaction between month and bay-status was found, with greater settlement and recruitment on the open coast than in bays reflecting extreme settlement and recruitment events at 3 westerly open coast sites during summer. Re-analysis excluding these outliers, revealed the expected effect, of greater settlement and recruitment in bays. While this indicates the broad generality of the bay effect, it highlights exceptions and the need for replication in time and space when examining landscape effects. Measuring post-settlement mortality required testing small-scale settlement behaviour on established and newly deployed settler collectors. It was found that all settlers preferred collectors with biofilm, but that primary settlers avoided conspecific settlers, while secondary settlers were attracted to them. With discrepancies in settler attraction to new and established collectors accounted for, initial (over 2d) and longer-term (over 7d) post-settlement mortality rates were found to be substantial (ca 60 %) for both species. No topographic effect on p-s mortality was evident. Finally, recruit-settler, adult-recruit and interspecies correlations were examined at regional and local scales. Synergistic (or neutral) effects maintained the initial settlement pattern in recruit and adult populations regionally, but not at local scales; striking interspecies correlations suggested the influence of common regional transport processes. Ultimately, the results emphasize the importance of the direction of effects in different life stages and at different spatial scales, and the possibility that antagonistic effects may mask even strong patterns.
- 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
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
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
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
The adoption of quality assurance in e-Health acquisition for rural hospitals in the Eastern Cape Province
- Authors: Ruxwana, Nkqubela
- Date: 2010
- Subjects: Quality assurance -- Management , Hospital care -- Quality control , Health facilities -- Quality control , Health -- Computer network resources , Public health -- Information services
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9731 , http://hdl.handle.net/10948/1514 , Quality assurance -- Management , Hospital care -- Quality control , Health facilities -- Quality control , Health -- Computer network resources , Public health -- Information services
- Description: The evolution of e-health has the potential to assist in the management of scarce resources and the shortage of skills, enhance efficiencies, improve quality and increase work productivity within the healthcare sector. As a result, an increase is seen in e-health solutions developments with the aim to improve healthcare services, hospital information systems, health decision support, telemedicine and other technical systems that have the potential to reduce cost, improve quality, and enhance the accessibility and delivery of healthcare. However, unfortunately their implementation contiues to fail. Although there are several reasons for this, in this study a lack of project quality management is viewed as a key contributor to the failure of e-health solutions implementation projects in rural hospitals. This results in neglected aspects of quality assurance (QA), which forms an integral part of project quality management. The purpose of this study is to develop a Genertic Quality Assurance Model (GQAM) for the successful acquisition (i.e. development and implementation) of e-health solutions in rural hospitals in the Eastern Cape Province to enable improved quality of care and service delivery. In order to develop and test this model it was necessary to identify the QA methodologies that are currently used in rural hospitals and to evaluate their strengths and weaknesses, as well as their impact on project success. The study is divided into four phases; in each phase different study designs were followed. The study used triangulation of qualitative and some elements of quantitative research approaches, in terms of which a case study approach was adpoted to answer the research questions. This study did indeed develop a GQAM that can be used to ensure e-health solution success in rural hospitals. Furthermore, to aid in the implementation of this model, a set of QA value chain implementation guidelines were developed, as a framework, to inject the nodel into typical (SDLC) phases.
- Full Text:
- Date Issued: 2010
- Authors: Ruxwana, Nkqubela
- Date: 2010
- Subjects: Quality assurance -- Management , Hospital care -- Quality control , Health facilities -- Quality control , Health -- Computer network resources , Public health -- Information services
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9731 , http://hdl.handle.net/10948/1514 , Quality assurance -- Management , Hospital care -- Quality control , Health facilities -- Quality control , Health -- Computer network resources , Public health -- Information services
- Description: The evolution of e-health has the potential to assist in the management of scarce resources and the shortage of skills, enhance efficiencies, improve quality and increase work productivity within the healthcare sector. As a result, an increase is seen in e-health solutions developments with the aim to improve healthcare services, hospital information systems, health decision support, telemedicine and other technical systems that have the potential to reduce cost, improve quality, and enhance the accessibility and delivery of healthcare. However, unfortunately their implementation contiues to fail. Although there are several reasons for this, in this study a lack of project quality management is viewed as a key contributor to the failure of e-health solutions implementation projects in rural hospitals. This results in neglected aspects of quality assurance (QA), which forms an integral part of project quality management. The purpose of this study is to develop a Genertic Quality Assurance Model (GQAM) for the successful acquisition (i.e. development and implementation) of e-health solutions in rural hospitals in the Eastern Cape Province to enable improved quality of care and service delivery. In order to develop and test this model it was necessary to identify the QA methodologies that are currently used in rural hospitals and to evaluate their strengths and weaknesses, as well as their impact on project success. The study is divided into four phases; in each phase different study designs were followed. The study used triangulation of qualitative and some elements of quantitative research approaches, in terms of which a case study approach was adpoted to answer the research questions. This study did indeed develop a GQAM that can be used to ensure e-health solution success in rural hospitals. Furthermore, to aid in the implementation of this model, a set of QA value chain implementation guidelines were developed, as a framework, to inject the nodel into typical (SDLC) phases.
- Full Text:
- Date Issued: 2010
Leonotis leonurus: the anticoagulant and antidiabetic activity of Leonotis leonurus
- Authors: Mnonopi, Nandipha
- Date: 2010
- Subjects: Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , Diabetes -- Alternative treatment -- South Africa , Plant bioactive compounds , Leonotis leonurus -- Physiological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10323 , http://hdl.handle.net/10948/1194 , Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , Diabetes -- Alternative treatment -- South Africa , Plant bioactive compounds , Leonotis leonurus -- Physiological aspects
- Description: Commercial marrubiin, aqueous and organic extracts of Leonotis leonurus were tested in vitro for their anticoagulant and antiplatelet activities. The aqueous extract inhibited platelet aggregation by 69.5 percent (100 μg/mL), while the organic extract (100 μg/mL) and marrubiin (5 μg/mL) showed 92.5 percent and 91.6 percent inhibition, respectively, by inhibiting the binding of fibrinogen to glycoprotein IIb/IIIa receptor in a concentration dependent manner. The extracts significantly prolonged activated partial thromboplastin time compared to untreated plasma controls. Fibrin and D-Dimer formation were drastically decreased. The extracts and marrubiin concentration-dependently inhibited calcium mobilization induced by collagen and thrombin. The formation of thromboxane A2 was also significantly reduced by both the extracts and marrubiin. Protein secretion and platelet adhesion were significantly reduced by both the extracts and marrubiin. The organic extract and marrubiin showed a more pronounced effect than the aqueous extracts in all the in vitro assays. The ex-vivo animal model confirmed the results obtained in vitro. Similar to the in vitro studies, activated partial thromboplastin time clotting time was prolonged by marrubiin and the number of aggregated platelets were significantly reduced relative to aspirin. The findings reflect that marrubiin largely contributes to the organic extract's anticoagulant and antiplatelet effect in vitro. INS-1 cells were cultured under normo- and hyperglycaemic conditions. Marrubiin and the two Leonotis leonurus extracts were screened for anti-diabetic activity in vitro. The stimulatory index of INS-1 cells cultured under hyperglycaemic conditions was significantly increased by 60 percent and 61 percent (p<0.01; n=5) in cells exposed to the organic extract (10 μg/mL) and marrubiin (500 ng/mL), respectively, relative to the normoglycaemic conditions. The gene expression of insulin was significantly increased by 76.5 and 71 percent, and of glucose transporter-2 by 93 and 92.5 percent for marrubiin and the organic extract, respectively, under the same conditions stipulated above (p<0.01; n=4). The extract and marrubiin similarly showed an increase in respiratory rate under hyperglycaemic conditions. Marrubiin increased insulin secretion, HDL-cholesterol, while it decreased total cholesterol, LDL-cholesterol and the atherogenic index in the in vivo rat model.
- Full Text:
- Date Issued: 2010
- Authors: Mnonopi, Nandipha
- Date: 2010
- Subjects: Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , Diabetes -- Alternative treatment -- South Africa , Plant bioactive compounds , Leonotis leonurus -- Physiological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10323 , http://hdl.handle.net/10948/1194 , Medicinal plants -- South Africa , Materia medica, Vegetable -- South Africa , Diabetes -- Alternative treatment -- South Africa , Plant bioactive compounds , Leonotis leonurus -- Physiological aspects
- Description: Commercial marrubiin, aqueous and organic extracts of Leonotis leonurus were tested in vitro for their anticoagulant and antiplatelet activities. The aqueous extract inhibited platelet aggregation by 69.5 percent (100 μg/mL), while the organic extract (100 μg/mL) and marrubiin (5 μg/mL) showed 92.5 percent and 91.6 percent inhibition, respectively, by inhibiting the binding of fibrinogen to glycoprotein IIb/IIIa receptor in a concentration dependent manner. The extracts significantly prolonged activated partial thromboplastin time compared to untreated plasma controls. Fibrin and D-Dimer formation were drastically decreased. The extracts and marrubiin concentration-dependently inhibited calcium mobilization induced by collagen and thrombin. The formation of thromboxane A2 was also significantly reduced by both the extracts and marrubiin. Protein secretion and platelet adhesion were significantly reduced by both the extracts and marrubiin. The organic extract and marrubiin showed a more pronounced effect than the aqueous extracts in all the in vitro assays. The ex-vivo animal model confirmed the results obtained in vitro. Similar to the in vitro studies, activated partial thromboplastin time clotting time was prolonged by marrubiin and the number of aggregated platelets were significantly reduced relative to aspirin. The findings reflect that marrubiin largely contributes to the organic extract's anticoagulant and antiplatelet effect in vitro. INS-1 cells were cultured under normo- and hyperglycaemic conditions. Marrubiin and the two Leonotis leonurus extracts were screened for anti-diabetic activity in vitro. The stimulatory index of INS-1 cells cultured under hyperglycaemic conditions was significantly increased by 60 percent and 61 percent (p<0.01; n=5) in cells exposed to the organic extract (10 μg/mL) and marrubiin (500 ng/mL), respectively, relative to the normoglycaemic conditions. The gene expression of insulin was significantly increased by 76.5 and 71 percent, and of glucose transporter-2 by 93 and 92.5 percent for marrubiin and the organic extract, respectively, under the same conditions stipulated above (p<0.01; n=4). The extract and marrubiin similarly showed an increase in respiratory rate under hyperglycaemic conditions. Marrubiin increased insulin secretion, HDL-cholesterol, while it decreased total cholesterol, LDL-cholesterol and the atherogenic index in the in vivo rat model.
- Full Text:
- Date Issued: 2010
Metabolic energy relations in the Eastern Cape Angulate Tortoise (Chersina Anguluta)
- Authors: Setlalekgomo, Mpho Rinah
- Date: 2010
- Subjects: Eastern Cape angulate Tortoise , Oxygen consumption (Physiology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10690 , http://hdl.handle.net/10948/1400 , Eastern Cape angulate Tortoise , Oxygen consumption (Physiology)
- Description: The daily oxygen consumption (VO2) pattern, the effects of varying ambient temperatures, season and mass on the resting oxygen consumption (RVO2) of Chersina angulata of the Eastern Cape were investigated. The RVO2 was measured using flow-through respirometry and specific resting oxygen consumption (sRVO2) calculated. To determine the daily pattern in the VO2 of C. angulata, the tortoises were acclimated in an environmentally controlled room (ECR) to an ambient temperature of 26 ± 1°C and a light regime of 14 hours of light and 10 hours of darkness (14L:10D) for at least a week prior to the RVO2 measurements. The RVO2 was measured at a constant temperature of 26 ± 1°C, and at three different light regimes, namely: 14L:10D, constant darkness (DD) and constant light (LL). There were no significant effects of mass or gender on the sRVO2 of the tortoises used. Rhythms in the sRVO2 were detected under all three light regimes. The amplitudes of the rhythm were largest at 14L:10D, followed by DD and smallest at LL regime. The persistence of the rhythmic pattern under constant conditions suggests the existence of an endogenous circadian rhythm in the sRVO2 for adult C. angulata. To test for the effect of ambient temperature on the sRVO2 of adult C. angulata, the tortoises were acclimated to 22 ± 1°C and a 14L:10D light regime prior to the RVO2 measurements. RVO2 was measured at eight experimental temperatures; 14°C, 18°C, 22°C, 26°C, 30°C, 35°C, 38°C and 40°C. The sRVO2 was not influenced by gender and increased with experimental temperatures, but this did not happen consistently over the whole range of temperatures tested. A plateau, possibly a thermal preferendum zone, was detected within the temperature range of 26 - 38°C. Determination of seasonal effect on the sRVO2 of adult C. angulata was accomplished by acclimating tortoises to standard summer and winter conditions. Seasonal effects were tested in the appropriate seasons. Winter experiments were conducted in winter and summer experiments conducted in summer. The RVO2 was measured at experimental temperature 14°C, 18°C and 22°C. In addition RVO2 of iv winter-acclimated tortoises was also measured at 10°C. The sRVO2 increased significantly with increasing temperature within the temperature range tested. No distinct pattern was observed in the seasonal acclimation of adult C. angulata. The metabolic rate-temperature curves of the summer and the winter-acclimated tortoises cross each other. Season and temperature had no significant effects on the mass-scaling exponent of the sRVO2. The exponent ranged from 0.48 to 0.73 within the temperature range of 22 - 38°C. Below and above this temperature range, the exponent ranged from 1.47 to 1.67. An inverse relationship was observed between sRVO2 and body mass over the temperature range of 22 - 38°C. At 14°C and 18°C, sRVO2 increased with body mass, while at 10°C and at 40°C the slope was 1.01.
- Full Text:
- Date Issued: 2010
- Authors: Setlalekgomo, Mpho Rinah
- Date: 2010
- Subjects: Eastern Cape angulate Tortoise , Oxygen consumption (Physiology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10690 , http://hdl.handle.net/10948/1400 , Eastern Cape angulate Tortoise , Oxygen consumption (Physiology)
- Description: The daily oxygen consumption (VO2) pattern, the effects of varying ambient temperatures, season and mass on the resting oxygen consumption (RVO2) of Chersina angulata of the Eastern Cape were investigated. The RVO2 was measured using flow-through respirometry and specific resting oxygen consumption (sRVO2) calculated. To determine the daily pattern in the VO2 of C. angulata, the tortoises were acclimated in an environmentally controlled room (ECR) to an ambient temperature of 26 ± 1°C and a light regime of 14 hours of light and 10 hours of darkness (14L:10D) for at least a week prior to the RVO2 measurements. The RVO2 was measured at a constant temperature of 26 ± 1°C, and at three different light regimes, namely: 14L:10D, constant darkness (DD) and constant light (LL). There were no significant effects of mass or gender on the sRVO2 of the tortoises used. Rhythms in the sRVO2 were detected under all three light regimes. The amplitudes of the rhythm were largest at 14L:10D, followed by DD and smallest at LL regime. The persistence of the rhythmic pattern under constant conditions suggests the existence of an endogenous circadian rhythm in the sRVO2 for adult C. angulata. To test for the effect of ambient temperature on the sRVO2 of adult C. angulata, the tortoises were acclimated to 22 ± 1°C and a 14L:10D light regime prior to the RVO2 measurements. RVO2 was measured at eight experimental temperatures; 14°C, 18°C, 22°C, 26°C, 30°C, 35°C, 38°C and 40°C. The sRVO2 was not influenced by gender and increased with experimental temperatures, but this did not happen consistently over the whole range of temperatures tested. A plateau, possibly a thermal preferendum zone, was detected within the temperature range of 26 - 38°C. Determination of seasonal effect on the sRVO2 of adult C. angulata was accomplished by acclimating tortoises to standard summer and winter conditions. Seasonal effects were tested in the appropriate seasons. Winter experiments were conducted in winter and summer experiments conducted in summer. The RVO2 was measured at experimental temperature 14°C, 18°C and 22°C. In addition RVO2 of iv winter-acclimated tortoises was also measured at 10°C. The sRVO2 increased significantly with increasing temperature within the temperature range tested. No distinct pattern was observed in the seasonal acclimation of adult C. angulata. The metabolic rate-temperature curves of the summer and the winter-acclimated tortoises cross each other. Season and temperature had no significant effects on the mass-scaling exponent of the sRVO2. The exponent ranged from 0.48 to 0.73 within the temperature range of 22 - 38°C. Below and above this temperature range, the exponent ranged from 1.47 to 1.67. An inverse relationship was observed between sRVO2 and body mass over the temperature range of 22 - 38°C. At 14°C and 18°C, sRVO2 increased with body mass, while at 10°C and at 40°C the slope was 1.01.
- Full Text:
- Date Issued: 2010
Lag length selection for vector error correction models
- Authors: Sharp, Gary David
- Date: 2010
- Subjects: Akaike Information Criterion Mathematical models -- Evaluation Autoregression (Statistics) Error analysis (Mathematics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5568 , http://hdl.handle.net/10962/d1002808
- Description: This thesis investigates the problem of model identification in a Vector Autoregressive framework. The study reviews the existing research, conducts an extensive simulation based analysis of thirteen information theoretic criterion (IC), one of which is a novel derivation. The simulation exercise considers the evaluation of seven alternative error restricted vector autoregressive models with four different lag lengths. Alternative sample sizes and parameterisations are also evaluated and compared to results in the existing literature. The results of the comparative analysis provide strong support for the efficiency based criterion of Akaike and in particular the selection capability of the novel criterion, referred to as a modified corrected Akaike information criterion, demonstrates useful finite sample properties.
- Full Text:
- Date Issued: 2010
- Authors: Sharp, Gary David
- Date: 2010
- Subjects: Akaike Information Criterion Mathematical models -- Evaluation Autoregression (Statistics) Error analysis (Mathematics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5568 , http://hdl.handle.net/10962/d1002808
- Description: This thesis investigates the problem of model identification in a Vector Autoregressive framework. The study reviews the existing research, conducts an extensive simulation based analysis of thirteen information theoretic criterion (IC), one of which is a novel derivation. The simulation exercise considers the evaluation of seven alternative error restricted vector autoregressive models with four different lag lengths. Alternative sample sizes and parameterisations are also evaluated and compared to results in the existing literature. The results of the comparative analysis provide strong support for the efficiency based criterion of Akaike and in particular the selection capability of the novel criterion, referred to as a modified corrected Akaike information criterion, demonstrates useful finite sample properties.
- Full Text:
- Date Issued: 2010
Fostering information security culture through intergrating theory and technology
- Van Niekerk, Johannes Frederick
- Authors: Van Niekerk, Johannes Frederick
- Date: 2010
- Subjects: Information technology -- Security measures , Data protection , Corporate culture -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9754 , http://hdl.handle.net/10948/1404 , Information technology -- Security measures , Data protection , Corporate culture -- South Africa
- Description: Today information can be seen as a basic commodity that is crucial to the continuous well-being of modern organizations. Many modern organizations will be unable to do business without access to their information resources. It is therefor of vital importance for organizations to ensure that their infor- mation resources are adequately protected against both internal and external threats. This protection of information resources is known as information security and is, to a large extent, dependent on the behavior of humans in the organization. Humans, at various levels in the organization, play vital roles in the pro- cesses that secure organizational information resources. Many of the prob- lems experienced in information security can be directly contributed to the humans involved in the process. Employees, either intentionally or through negligence, often due to a lack of knowledge, can be seen as the greatest threat to information security. Addressing this human factor in information security is the primary focus of this thesis. The majority of current approaches to dealing with the human factors in information security acknowledge the need to foster an information security culture in the organization. However, very few current approaches attempt to adjust the "generic" model(s) used to define organizational culture to be specific to the needs of information security. This thesis firstly proposes, and argues, such an adapted conceptual model which aims to improve the understanding of what an information security culture is. The thesis secondly focuses on the underlying role that information security educational programs play in the fostering of an organizational information security culture. It is argued that many current information security edu- cational programs are not based on sound pedagogical theory. The use of learning taxonomies during the design of information security educational programs is proposed as a possible way to improve the pedagogical rigor of such programs. The thesis also argues in favor of the use of blended and/or e-learning approaches for the delivery of information security educational content. Finally, this thesis provides a detailed overview demonstrating how the various elements contributed by the thesis integrates into existing trans- formative change management processes for the fostering of an organizational information security culture.
- Full Text:
- Date Issued: 2010
- Authors: Van Niekerk, Johannes Frederick
- Date: 2010
- Subjects: Information technology -- Security measures , Data protection , Corporate culture -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9754 , http://hdl.handle.net/10948/1404 , Information technology -- Security measures , Data protection , Corporate culture -- South Africa
- Description: Today information can be seen as a basic commodity that is crucial to the continuous well-being of modern organizations. Many modern organizations will be unable to do business without access to their information resources. It is therefor of vital importance for organizations to ensure that their infor- mation resources are adequately protected against both internal and external threats. This protection of information resources is known as information security and is, to a large extent, dependent on the behavior of humans in the organization. Humans, at various levels in the organization, play vital roles in the pro- cesses that secure organizational information resources. Many of the prob- lems experienced in information security can be directly contributed to the humans involved in the process. Employees, either intentionally or through negligence, often due to a lack of knowledge, can be seen as the greatest threat to information security. Addressing this human factor in information security is the primary focus of this thesis. The majority of current approaches to dealing with the human factors in information security acknowledge the need to foster an information security culture in the organization. However, very few current approaches attempt to adjust the "generic" model(s) used to define organizational culture to be specific to the needs of information security. This thesis firstly proposes, and argues, such an adapted conceptual model which aims to improve the understanding of what an information security culture is. The thesis secondly focuses on the underlying role that information security educational programs play in the fostering of an organizational information security culture. It is argued that many current information security edu- cational programs are not based on sound pedagogical theory. The use of learning taxonomies during the design of information security educational programs is proposed as a possible way to improve the pedagogical rigor of such programs. The thesis also argues in favor of the use of blended and/or e-learning approaches for the delivery of information security educational content. Finally, this thesis provides a detailed overview demonstrating how the various elements contributed by the thesis integrates into existing trans- formative change management processes for the fostering of an organizational information security culture.
- Full Text:
- Date Issued: 2010
An investigation into the feasibility of incorporating didanosine into innovative solid lipid nanocarriers
- Authors: Wa Kasongo, Kasongo
- Date: 2010
- Subjects: Antiretroviral agents HIV infections -- Drug testing Didanosine Nanoparticles Drug delivery systems Nanostructured materials Lipids -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3800 , http://hdl.handle.net/10962/d1003278
- Description: The research undertaken in these studies aimed to investigate the feasibility of developing and manufacturing innovative solid lipid carriers, such as solid lipid nanoparticles (SLN) and/or nanostructured lipid carriers (NLC) using a hot high pressure homogenization method, for didanosine(DDI). In addition, studies using in vitro differential protein adsorption were undertaken to establish whether the SLN and/or NLC have the potential to deliver DDI to the central nervous system (CNS). Prior to initiating pre-formulation, formulation development and optimization studies of DDI-Ioaded SLN and/or NLC, it was necessary to develop and validate an analytical method for the in vitro quantitation and analysis of DDI. An accurate, precise and sensitive RP-HPLC method with UV detection set at 248 nm was developed, optimized and validated for the quantitative in vitro analysis of DDI in formulations. Pre-formulation studies were designed to evaluate the thermal stability of DDI and to select and characterize lipid excipients that may be used for the manufacture of the nanocarriers. It was established that DDI is thermostable at temperatures not exceeding 163°C and therefore a hot high pressure homogenization technique could be used to manufacture DDI-loaded SLN and/or NLC. Lipid screening studies revealed that DDI is poorly soluble in both solid and liquid lipids. A combination of Precirol® ATO 5 and Transcutol® HP was found to have the best solubilizing-potential for DDI of all lipids investigated. The inclusion of Transcutol® HP into Precirol® ATO 5 changed the polymorphic form of the solid lipid from the stable 13-modification to a material that exhibited the co-existence between α- and β-polymorphic forms. The relatively high solubility of DDI in Transcutol® HP compared to Precirol® ATO 5 was an indication that a solid lipid matrix prepared from a binary mixture of Precirol® ATO 5 and Transcutol® HP was likely to have a higher loading capacity and encapsulation efficiency for DDI than a matrix consisting of Precirol® ATO 5 alone. Furthermore, the potential for the solid lipid matrix to exist in the α- and/or β-modifications when Transcutol® HP was added to Precirol® ATO 5 suggested that expulsion of DDI from a solid lipid matrix during prolonged storage periods was likely to be minimal. Therefore it was considered logical to investigate the feasibility of incorporating DDI into NLC and not in SLN. However, due to the limited solubility of DDI in lipids, formulation development of DDI-loaded NLC commenced using small quantities of DDI. Formulation development and optimization studies of DDI-loaded NLC were initially aimed at selecting a surfactant system that was capable of stabilizing NLC in an aqueous environment. Solutol® HS alone or a ternary mixture consisting of Solutol® HS, Tween® 80 and Lutrol® F68 was found to stabilize the nanoparticles in terms of particle size and the polydispersity index. The use of the ternary mixture as the surfactant system was preferred to using Solutol® HS alone as Lutrol® F68 and especially Tween® 80 have been successfully used to target the delivery of API to the brain. Aqueous DDI-free and DDI-Ioaded NLC containing increasing amounts of DDI were manufactured using hot high pressure homogenization at 800 bar for three cycles. The NLC formulations were characterized in terms of particle size, polydispersity index, zeta potential, and polymorphism, degree of crystallinity, encapsulation efficiency (EE), shape and surface morphology. The mean particle size for all formulations was below 250 nm with narrow polydispersity indices, indicating that narrow particle size distribution had been achieved. The d99% values for all formulations tested, were generated using laser diffractometry, and were below 400 nm, with span values ranging from 0.84 - 1.19 also suggesting that a narrow particle size distribution had been achieved. The zeta potential values measured in double distilled water with the conductivity adjusted to 50 μS/cm ranged from -18.4 to -11.4 mV. In addition, all the formulations showed a decrease in the degree of crystallinity as compared to the bulk lipid material and WAXS shows that the formulations existed in a single β-modification form. Furthermore DDI that had been incorporated into the NLC appeared to be molecularly dispersed in the lipid matrices. These parameters remained unaffected for most formulations following storage for two months at 25°C. In addition these formulations contained a mixture of spherical and non-spherical particles irrespective of the amount of DDI that was added during the manufacture of the formulations. These studies showed that it was feasible to develop and incorporate small amounts of DDI into NLC. However in order to use these delivery systems for oral administration of DDI to paediatric patients, strategies to improve the amount of DDI that could be loaded into the particles and to achieve high encapsulation efficiencies had to be developed. The limited solubility of DDI in lipid media was identified as a major factor that affected the loading capacity and encapsulation efficiency of DDI in the NLC. Therefore, a novel strategy aimed at increasing the saturation solubility of DDI in the lipid by attempting to increase the dissolution velocity of the drug in the lipid using a particle size reduction approach, was designed and investigated. DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid medium was reduced gradually using hot high pressure homogenization and the product obtained from these studies was used to manufacture DDI-loaded NLC using a cold high pressure homogenization procedure. Although the encapsulation efficiency and drug loading following use of this approach was relatively high, the particles were large and showed a tendency to grow in size leading to the formation of microparticles after storage for two months at 25°C. In addition, the degree of crystallinity of the nanoparticles increased rapidly over the same storage period which led to expulsion of DDI nanoparticles for the NLC, despite the DDI loading in NLC being unaffected. It was clearly evident that this new approach of manufacturing solid lipid nanocarriers could be used as a platform not only for enhancing the loading capacity of DDI in solid lipid nanocarriers but also for other hydrophilic drugs. Differential protein adsorption patterns of DDI-loaded NLC were generated in vitro using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) in order to establish the potential for these systems to deliver DDI to the CNS. NLC formulations containing small amounts of DDI were used as these formulations showed a better stability profile than the formulation with a higher encapsulation efficiency and drug loading capacity. Furthermore, the encapsulation efficiency and drug loading of DDI were considered sufficient for use in 2-D PAGE studies. Data obtained from 2-D PAGE analysis reveal that DDI-loaded NLC preferentially adsorb proteins in vitro that are responsible for specific brain targeting in vivo. More importantly, these studies reveal that in addition to Tween® 80 that has already been shown to have the potential to target CDDS to the brain, Solutol® HS 15 has the potential to achieve a similar objective. Consequently, DDI-loaded NLC have the potential to deliver DDI to the brain and these results may be used as a platform for conducting in vivo studies to establish whether DDI can cross the blood brain barrier and enter the CNS when administered in NLC which may in turn lead to a major breakthrough in the management of HIV/AIDS and Aids Dementia Complex (ADC).
- Full Text:
- Date Issued: 2010
- Authors: Wa Kasongo, Kasongo
- Date: 2010
- Subjects: Antiretroviral agents HIV infections -- Drug testing Didanosine Nanoparticles Drug delivery systems Nanostructured materials Lipids -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3800 , http://hdl.handle.net/10962/d1003278
- Description: The research undertaken in these studies aimed to investigate the feasibility of developing and manufacturing innovative solid lipid carriers, such as solid lipid nanoparticles (SLN) and/or nanostructured lipid carriers (NLC) using a hot high pressure homogenization method, for didanosine(DDI). In addition, studies using in vitro differential protein adsorption were undertaken to establish whether the SLN and/or NLC have the potential to deliver DDI to the central nervous system (CNS). Prior to initiating pre-formulation, formulation development and optimization studies of DDI-Ioaded SLN and/or NLC, it was necessary to develop and validate an analytical method for the in vitro quantitation and analysis of DDI. An accurate, precise and sensitive RP-HPLC method with UV detection set at 248 nm was developed, optimized and validated for the quantitative in vitro analysis of DDI in formulations. Pre-formulation studies were designed to evaluate the thermal stability of DDI and to select and characterize lipid excipients that may be used for the manufacture of the nanocarriers. It was established that DDI is thermostable at temperatures not exceeding 163°C and therefore a hot high pressure homogenization technique could be used to manufacture DDI-loaded SLN and/or NLC. Lipid screening studies revealed that DDI is poorly soluble in both solid and liquid lipids. A combination of Precirol® ATO 5 and Transcutol® HP was found to have the best solubilizing-potential for DDI of all lipids investigated. The inclusion of Transcutol® HP into Precirol® ATO 5 changed the polymorphic form of the solid lipid from the stable 13-modification to a material that exhibited the co-existence between α- and β-polymorphic forms. The relatively high solubility of DDI in Transcutol® HP compared to Precirol® ATO 5 was an indication that a solid lipid matrix prepared from a binary mixture of Precirol® ATO 5 and Transcutol® HP was likely to have a higher loading capacity and encapsulation efficiency for DDI than a matrix consisting of Precirol® ATO 5 alone. Furthermore, the potential for the solid lipid matrix to exist in the α- and/or β-modifications when Transcutol® HP was added to Precirol® ATO 5 suggested that expulsion of DDI from a solid lipid matrix during prolonged storage periods was likely to be minimal. Therefore it was considered logical to investigate the feasibility of incorporating DDI into NLC and not in SLN. However, due to the limited solubility of DDI in lipids, formulation development of DDI-loaded NLC commenced using small quantities of DDI. Formulation development and optimization studies of DDI-loaded NLC were initially aimed at selecting a surfactant system that was capable of stabilizing NLC in an aqueous environment. Solutol® HS alone or a ternary mixture consisting of Solutol® HS, Tween® 80 and Lutrol® F68 was found to stabilize the nanoparticles in terms of particle size and the polydispersity index. The use of the ternary mixture as the surfactant system was preferred to using Solutol® HS alone as Lutrol® F68 and especially Tween® 80 have been successfully used to target the delivery of API to the brain. Aqueous DDI-free and DDI-Ioaded NLC containing increasing amounts of DDI were manufactured using hot high pressure homogenization at 800 bar for three cycles. The NLC formulations were characterized in terms of particle size, polydispersity index, zeta potential, and polymorphism, degree of crystallinity, encapsulation efficiency (EE), shape and surface morphology. The mean particle size for all formulations was below 250 nm with narrow polydispersity indices, indicating that narrow particle size distribution had been achieved. The d99% values for all formulations tested, were generated using laser diffractometry, and were below 400 nm, with span values ranging from 0.84 - 1.19 also suggesting that a narrow particle size distribution had been achieved. The zeta potential values measured in double distilled water with the conductivity adjusted to 50 μS/cm ranged from -18.4 to -11.4 mV. In addition, all the formulations showed a decrease in the degree of crystallinity as compared to the bulk lipid material and WAXS shows that the formulations existed in a single β-modification form. Furthermore DDI that had been incorporated into the NLC appeared to be molecularly dispersed in the lipid matrices. These parameters remained unaffected for most formulations following storage for two months at 25°C. In addition these formulations contained a mixture of spherical and non-spherical particles irrespective of the amount of DDI that was added during the manufacture of the formulations. These studies showed that it was feasible to develop and incorporate small amounts of DDI into NLC. However in order to use these delivery systems for oral administration of DDI to paediatric patients, strategies to improve the amount of DDI that could be loaded into the particles and to achieve high encapsulation efficiencies had to be developed. The limited solubility of DDI in lipid media was identified as a major factor that affected the loading capacity and encapsulation efficiency of DDI in the NLC. Therefore, a novel strategy aimed at increasing the saturation solubility of DDI in the lipid by attempting to increase the dissolution velocity of the drug in the lipid using a particle size reduction approach, was designed and investigated. DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid medium was reduced gradually using hot high pressure homogenization and the product obtained from these studies was used to manufacture DDI-loaded NLC using a cold high pressure homogenization procedure. Although the encapsulation efficiency and drug loading following use of this approach was relatively high, the particles were large and showed a tendency to grow in size leading to the formation of microparticles after storage for two months at 25°C. In addition, the degree of crystallinity of the nanoparticles increased rapidly over the same storage period which led to expulsion of DDI nanoparticles for the NLC, despite the DDI loading in NLC being unaffected. It was clearly evident that this new approach of manufacturing solid lipid nanocarriers could be used as a platform not only for enhancing the loading capacity of DDI in solid lipid nanocarriers but also for other hydrophilic drugs. Differential protein adsorption patterns of DDI-loaded NLC were generated in vitro using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) in order to establish the potential for these systems to deliver DDI to the CNS. NLC formulations containing small amounts of DDI were used as these formulations showed a better stability profile than the formulation with a higher encapsulation efficiency and drug loading capacity. Furthermore, the encapsulation efficiency and drug loading of DDI were considered sufficient for use in 2-D PAGE studies. Data obtained from 2-D PAGE analysis reveal that DDI-loaded NLC preferentially adsorb proteins in vitro that are responsible for specific brain targeting in vivo. More importantly, these studies reveal that in addition to Tween® 80 that has already been shown to have the potential to target CDDS to the brain, Solutol® HS 15 has the potential to achieve a similar objective. Consequently, DDI-loaded NLC have the potential to deliver DDI to the brain and these results may be used as a platform for conducting in vivo studies to establish whether DDI can cross the blood brain barrier and enter the CNS when administered in NLC which may in turn lead to a major breakthrough in the management of HIV/AIDS and Aids Dementia Complex (ADC).
- Full Text:
- Date Issued: 2010
Exploring and expanding learning processes in sustainable agriculture workplace contexts
- Authors: Mukute, Mutizwa
- Date: 2010
- Subjects: Sustainable agriculture -- Africa, Southern Sustainable development -- Study and teaching -- Africa, Southern Permaculture -- Zimbabwe Organic farming -- South Africa Farmers -- Social conditions -- Africa, Southern Farmers -- Economic conditions -- Africa, Southern Farmers -- Training of -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1539 , http://hdl.handle.net/10962/d1003421
- Description: The focus of this study is to explore and expand farmer learning processes in sustainable agriculture workplace contexts. It examines change oriented learning processes in the context of three sustainable agriculture practices. The study begins by discussing the history and emergence of environmental discourses and approaches; sustainable agriculture; and the histories of three kinds of sustainable agriculture practices: Permaculture, Organic Farming and Machobane Farming System. It also traces the evolution of agricultural extension approaches within the wider context of education for sustainable development. The main focus of the study is an exploration of how farmer learning can be mediated through an expansive learning process. The study methodology surfaces some of the contradictions in sustainable agriculture and learning activity systems that farmers encounter in learning and practising sustainable agriculture. It uses these contradictions as sources of expansive learning in and between the respective activity systems of farmers, sustainable agriculture facilitators, agricultural extension workers (conventional) and organic entrepreneurs. As shown in the study, the expansive learning processes result in the modelling, implementation and reviewing of solutions to contradictions being faced in the learning and practice of sustainable agriculture. The study also proposes a number of tools that can be adapted and used by development farmers and agricultural trainers to examine and expand learning as well as build farmer agency. The study was conducted in three case study sites in Lesotho, South Africa and Zimbabwe. In Zimbabwe the study is located in Hwedza district in the St Margaret Primary School and community that learn, practise and facilitate the learning of Permaculture within the Schools and Colleges Permaculture Programme (SCOPE). The second study site is in South Africa: Durban urban and peri-urban areas where a community of organic farmers, facilitators and entrepreneurs coordinate the marketing of their produce through Isidore Farm and Earth Mother Organic and support each other to learn and practise organic farming. The third study site is based in the Mafeteng and Mohale‟s Hoek districts of Lesotho where the focus was on farmers who learn and practise the Machobane Farming System (MFS) and are supported in this by the Rural Self Development Association (RSDA) and the Machobane Agricultural Development Foundation (MADF). Drawing on three sensitising concepts of dialectics, reflexivity and agency, the study worked with Cultural Historical Activity Theory (CHAT) underpinned by critical realism to reveal how farmer learning is mediated and expanded. The theory of practice/habitus also provided a useful theoretical lens with which to examine data generated. Using a two-phased, multiple embedded case study approach, the study worked within the broad framework of social learning. It used semi-structured individual and group interviews, observations and document analysis to explore learning processes and generate „mirror‟ data. This data was then used in Change Laboratory Workshops, within the Developmental Work Research methodology, where double stimulation and focus group discussions contributed to expanding learning processes. Drawing on critical realism the study used inductive, abductive and retroductive modes of inference to analyse data in each case study as well as across case studies. The findings of the study reveal that farmer learning is influenced by both intrinsic motives, such as identity, and extrinsic motives which are primarily associated with economic, ecological and health benefits. Farmers learn through scaffolding and mediating tools that link everyday and scientific knowledge. They also learn from fellow farmers through observation, practising and experimentation. Some of the issues that were raised in connection with farmer learning processes are: language; time to learn, practice and appropriate concepts; time to improve the natural resource base while at the same time improving income generation; and responses to climate change. The study also found that farmer learning and practice of sustainable agriculture in the case studies investigated, is influenced by past and current agricultural and educational policies; societal values and attitudes; social and cultural backgrounds; work affordances and gender relations; quality of training offered; poverty; and, HIV and AIDS. In the second phase of the study, which built on the problematic situations being encountered by research participants (sustainable agriculture farmers, sustainable agriculture facilitators, extension workers, and organic marketers) to surface contradictions, the main finding was that the expansive learning process has potential to enhance farmer learning and practice of sustainable agriculture. It does this by mobilising distributed cognition among participants as well as their preparedness to act. Through the expansive learning processes in each case study, research participants were able to question their practices, surface contradictions, model solutions and implement them, and thus build individual, collective and relational agency reflexively. Observation of this required micro-analysis of agentive talk and reflective talk. The study contributes in-depth insight into participatory research and learning processes, especially within the context of people-centred learning and innovation in the agricultural development arena. It provides empirical and explanatory insight into how change oriented social learning can emerge and be expanded in Education for Sustainable Development, explaining learning and change relationships in three sustainable agricultural practices. It also provides learning and extension tools to work with contradictions that arise from intentionality, experience, context and history in farming and training activity systems. Its key contribution lies in providing in-depth insight into mobilisation of human agency and reflexivity in change oriented sustainable agriculture learning and development, processes that are critical for responding to contemporary socio-ecological issues and risks.
- Full Text:
- Date Issued: 2010
- Authors: Mukute, Mutizwa
- Date: 2010
- Subjects: Sustainable agriculture -- Africa, Southern Sustainable development -- Study and teaching -- Africa, Southern Permaculture -- Zimbabwe Organic farming -- South Africa Farmers -- Social conditions -- Africa, Southern Farmers -- Economic conditions -- Africa, Southern Farmers -- Training of -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1539 , http://hdl.handle.net/10962/d1003421
- Description: The focus of this study is to explore and expand farmer learning processes in sustainable agriculture workplace contexts. It examines change oriented learning processes in the context of three sustainable agriculture practices. The study begins by discussing the history and emergence of environmental discourses and approaches; sustainable agriculture; and the histories of three kinds of sustainable agriculture practices: Permaculture, Organic Farming and Machobane Farming System. It also traces the evolution of agricultural extension approaches within the wider context of education for sustainable development. The main focus of the study is an exploration of how farmer learning can be mediated through an expansive learning process. The study methodology surfaces some of the contradictions in sustainable agriculture and learning activity systems that farmers encounter in learning and practising sustainable agriculture. It uses these contradictions as sources of expansive learning in and between the respective activity systems of farmers, sustainable agriculture facilitators, agricultural extension workers (conventional) and organic entrepreneurs. As shown in the study, the expansive learning processes result in the modelling, implementation and reviewing of solutions to contradictions being faced in the learning and practice of sustainable agriculture. The study also proposes a number of tools that can be adapted and used by development farmers and agricultural trainers to examine and expand learning as well as build farmer agency. The study was conducted in three case study sites in Lesotho, South Africa and Zimbabwe. In Zimbabwe the study is located in Hwedza district in the St Margaret Primary School and community that learn, practise and facilitate the learning of Permaculture within the Schools and Colleges Permaculture Programme (SCOPE). The second study site is in South Africa: Durban urban and peri-urban areas where a community of organic farmers, facilitators and entrepreneurs coordinate the marketing of their produce through Isidore Farm and Earth Mother Organic and support each other to learn and practise organic farming. The third study site is based in the Mafeteng and Mohale‟s Hoek districts of Lesotho where the focus was on farmers who learn and practise the Machobane Farming System (MFS) and are supported in this by the Rural Self Development Association (RSDA) and the Machobane Agricultural Development Foundation (MADF). Drawing on three sensitising concepts of dialectics, reflexivity and agency, the study worked with Cultural Historical Activity Theory (CHAT) underpinned by critical realism to reveal how farmer learning is mediated and expanded. The theory of practice/habitus also provided a useful theoretical lens with which to examine data generated. Using a two-phased, multiple embedded case study approach, the study worked within the broad framework of social learning. It used semi-structured individual and group interviews, observations and document analysis to explore learning processes and generate „mirror‟ data. This data was then used in Change Laboratory Workshops, within the Developmental Work Research methodology, where double stimulation and focus group discussions contributed to expanding learning processes. Drawing on critical realism the study used inductive, abductive and retroductive modes of inference to analyse data in each case study as well as across case studies. The findings of the study reveal that farmer learning is influenced by both intrinsic motives, such as identity, and extrinsic motives which are primarily associated with economic, ecological and health benefits. Farmers learn through scaffolding and mediating tools that link everyday and scientific knowledge. They also learn from fellow farmers through observation, practising and experimentation. Some of the issues that were raised in connection with farmer learning processes are: language; time to learn, practice and appropriate concepts; time to improve the natural resource base while at the same time improving income generation; and responses to climate change. The study also found that farmer learning and practice of sustainable agriculture in the case studies investigated, is influenced by past and current agricultural and educational policies; societal values and attitudes; social and cultural backgrounds; work affordances and gender relations; quality of training offered; poverty; and, HIV and AIDS. In the second phase of the study, which built on the problematic situations being encountered by research participants (sustainable agriculture farmers, sustainable agriculture facilitators, extension workers, and organic marketers) to surface contradictions, the main finding was that the expansive learning process has potential to enhance farmer learning and practice of sustainable agriculture. It does this by mobilising distributed cognition among participants as well as their preparedness to act. Through the expansive learning processes in each case study, research participants were able to question their practices, surface contradictions, model solutions and implement them, and thus build individual, collective and relational agency reflexively. Observation of this required micro-analysis of agentive talk and reflective talk. The study contributes in-depth insight into participatory research and learning processes, especially within the context of people-centred learning and innovation in the agricultural development arena. It provides empirical and explanatory insight into how change oriented social learning can emerge and be expanded in Education for Sustainable Development, explaining learning and change relationships in three sustainable agricultural practices. It also provides learning and extension tools to work with contradictions that arise from intentionality, experience, context and history in farming and training activity systems. Its key contribution lies in providing in-depth insight into mobilisation of human agency and reflexivity in change oriented sustainable agriculture learning and development, processes that are critical for responding to contemporary socio-ecological issues and risks.
- 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
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
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
A social realist analysis of collaborative curriculum development processes in an academic department at a South African university
- Authors: Vorster, Jo-Anne
- Date: 2010
- Subjects: Rhodes University -- Curricula Journalism -- Study and teaching -- South Africa -- Grahamstown Curriculum planning -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3339 , http://hdl.handle.net/10962/d1004314
- Description: This study reports on a social-realist analysis of collaborative curriculum development in a journalism and media studies (JMS) department at a South African university. Archer's social-realist meta-theoretical framework is used to theorise about mechanisms that influence collaborative curriculum development within the context of the JMS Department. The thesis examines the cultural, structural and agential conditions that influenced the process of developing a JMS curriculum that aimed to integrate theory and practice. Bernstein's theories of knowledge recontextualisation and disciplinary knowledge structures are used in the analysis. Bernstein argues that knowledge recontextualisation constitutes a site of struggle. This thesis is an examination of the "struggles" for the epistemic-pedagogic device (Maton's elaboration of Bernstein's epistemic device) during the recontextualisation process that aimed to integrate media studies (MS) and media production (MP) in the JMS curriculum. Traditionally academic work has been an individual endeavour. However, given the growing need to work in disciplinary and inter-disciplinary teams, it is imperative to develop knowledge of the mechanisms that influence such practices. This thesis is a contribution to knowledge of collaborative processes at the level of an academic department in a university. It contributes to knowledge of cultural, structural and agential mechanisms that enable or constrain collaborative curriculum development within a particular kind of context. In addition it contributes to knowledge of the nature of leadership that may be necessary to facilitate productive collaborative relationships and practices in such a context. The curriculum development project reported on in this thesis was initiated in 2003; however, data collection for the study was conducted in 2006 when the curriculum for the fourth year (JMS 4) of the Bachelor of Journalism degree was developed. Since the JMS course prepares students to work as journalists or media workers it is necessary for the curriculum and pedagogy to be oriented both towards the academy and towards the media industries. The aim of the JMS degree is to develop students who will be critically reflexive journalists or media workers. As such the course is both theoretical (MS) and practical (MP). One of the findings of this research project is that the integration of MS and MP is a complex project given that the knowledge of the two disciplines is structured differently. MS is concept-dependent and some aspects of it can be applied to journalism and media practice, while MP is practical and thus context-dependent, though underpinned by theory. A further finding is that both the collaborative work and the integration project required different identity shifts from the lecturers in the JMS Department. Some were more able to make the shifts than others. The thesis shows that the knowledge recontextualisation struggles in the curriculum development processes of the Department of JMS centred around, inter alia, the setting of boundaries between the department and the media and journalism industries, between MS and MP and between MS theory and journalism theory. In addition, existing boundaries between MS and MP lecturers had to be traversed. These boundaries were circumscribed by, amongst other things, unequal power relations emanating from the higher status traditionally accorded to theoretical knowledge by universities, the tensions around the nature of journalism education and training and the differential properties and powers of the various lecturers within the department. The existence of a strong regulative discourse was found to be an important unifying mechanism in a tension-ridden context.
- Full Text:
- Date Issued: 2010
- Authors: Vorster, Jo-Anne
- Date: 2010
- Subjects: Rhodes University -- Curricula Journalism -- Study and teaching -- South Africa -- Grahamstown Curriculum planning -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3339 , http://hdl.handle.net/10962/d1004314
- Description: This study reports on a social-realist analysis of collaborative curriculum development in a journalism and media studies (JMS) department at a South African university. Archer's social-realist meta-theoretical framework is used to theorise about mechanisms that influence collaborative curriculum development within the context of the JMS Department. The thesis examines the cultural, structural and agential conditions that influenced the process of developing a JMS curriculum that aimed to integrate theory and practice. Bernstein's theories of knowledge recontextualisation and disciplinary knowledge structures are used in the analysis. Bernstein argues that knowledge recontextualisation constitutes a site of struggle. This thesis is an examination of the "struggles" for the epistemic-pedagogic device (Maton's elaboration of Bernstein's epistemic device) during the recontextualisation process that aimed to integrate media studies (MS) and media production (MP) in the JMS curriculum. Traditionally academic work has been an individual endeavour. However, given the growing need to work in disciplinary and inter-disciplinary teams, it is imperative to develop knowledge of the mechanisms that influence such practices. This thesis is a contribution to knowledge of collaborative processes at the level of an academic department in a university. It contributes to knowledge of cultural, structural and agential mechanisms that enable or constrain collaborative curriculum development within a particular kind of context. In addition it contributes to knowledge of the nature of leadership that may be necessary to facilitate productive collaborative relationships and practices in such a context. The curriculum development project reported on in this thesis was initiated in 2003; however, data collection for the study was conducted in 2006 when the curriculum for the fourth year (JMS 4) of the Bachelor of Journalism degree was developed. Since the JMS course prepares students to work as journalists or media workers it is necessary for the curriculum and pedagogy to be oriented both towards the academy and towards the media industries. The aim of the JMS degree is to develop students who will be critically reflexive journalists or media workers. As such the course is both theoretical (MS) and practical (MP). One of the findings of this research project is that the integration of MS and MP is a complex project given that the knowledge of the two disciplines is structured differently. MS is concept-dependent and some aspects of it can be applied to journalism and media practice, while MP is practical and thus context-dependent, though underpinned by theory. A further finding is that both the collaborative work and the integration project required different identity shifts from the lecturers in the JMS Department. Some were more able to make the shifts than others. The thesis shows that the knowledge recontextualisation struggles in the curriculum development processes of the Department of JMS centred around, inter alia, the setting of boundaries between the department and the media and journalism industries, between MS and MP and between MS theory and journalism theory. In addition, existing boundaries between MS and MP lecturers had to be traversed. These boundaries were circumscribed by, amongst other things, unequal power relations emanating from the higher status traditionally accorded to theoretical knowledge by universities, the tensions around the nature of journalism education and training and the differential properties and powers of the various lecturers within the department. The existence of a strong regulative discourse was found to be an important unifying mechanism in a tension-ridden context.
- Full Text:
- Date Issued: 2010