Application of high-performance liquid chromatography to the analysis, stability and pharmacokinetics of erythromycin
- Authors: Stubbs, Christopher
- Date: 1988
- Subjects: Erythromycin High performance liquid chromatography
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3809 , http://hdl.handle.net/10962/d1004372
- Description: Erythromycin is a macrolide antibiotic used mainly in the treatment of infections caused by gram-positive organisms. Erythromycin base is rap idly degraded in acidic media necessitating the use of structurally modified erythromycin derivatives or acid resistant dosage forms in order to decrease gastric inactivation of the drug. The majority of pharmacokinetic studies to-date have utilized relatively non-specific microbiological assay procedures which are unable to differentiate between concentrations of active erythromycin base and the inactive pro-drug derivatives. A high-performance liquid chromatographic (HPLC) technique is described for the simultaneous determination of erythromycin base and propionate (inactive pro-drug form) in human serum and urine following the oral administration of erythromycin estolate, an acid stable derivative of erythromycin. The method involves a solid-phase extraction step prior to chromatography on a C18 reversed-phase column with coulometric electrochemical detection. Sample handling and storage techniques are presented which minimize hydrolysis of the inactive ester moiety between sample collection and analysis, thereby more accurately reflecting the in vivo situation than in previously published studies. Results from single dose pharmacokinetic studies indicate that only 10-15% of the total erythromycin concentration in vivo is present as the active base component following oral administration of erythromycin estolate. This percentage increases to approximately 25% during multiple dose administration. Novel urinary excretion data are presented which reveal that approximately 40% and 55% of the total erythromycin excreted in urine is excreted as erythromycin base following single and multiple dosages respectively. Computer fitting of mean serum concentration-time data revealed that an open one compartment model with linear first order absorption and elimination best described the absorption and disposition of erythromycin, although poor computer fits for individual data sets were observed. Some evidence of non-linear elimination is presented utilizing both compartmental and non-compartmental pharmacokinetic techniques. Large intra-and inter-personal variability in erythromycin absorption and disposition was experienced which was evaluated in five subjects who each received one 500 mg erythromycin estolate tablet from the same batch, on three separate occasions. In addition. an HPLC method is described for the analysis of "total erythromycin" concentrations following erythromycin estolate administration which involves hydrolysis of the ester component prior to chromatography. as well as an HPLC method utilizing amperometric electrochemical detection capable of monitoring the stability of erythromycin base in stored biological fluids. These methods were uti I ized in various stability studies involving erythromycin base and propionate as well as for the analysis of erythromycin estolate dosage forms.
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- Date Issued: 1988
Assessing the role of social transfers in curbing household food insecurity in Harare rural district, Zimbabwe
- Authors: Nyabvudzi, Tatenda Gaudencia
- Date: 2015
- Subjects: Poverty -- Zimbabwe Food security -- Zimbabwe Households -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/12205 , vital:39197
- Description: Purpose – Empirical work on the career development processes of vulnerable groups such as refugees is beginning to receive currency within the academic literature. However, little is known about the intersection of factors such as gender and structural constraints on such processes especially within developing countries such as South Africa. The purpose of this study was to explore the career development processes of women refugees in South Africa. Design/methodology/ approach – A qualitative research approach through narrative inquiry was used. Snowball sampling was employed to select the 20 women refugees who took part in this research. The study location was the city of Port Elizabeth located in the Eastern Cape Province. The three levels of meaning-making incorporated in previous narrative research was utilised to analyse the data. Findings Results show that women refugees are more concerned with a short-term desire to survive and acquire basic commodities than a long-term focus to advance and develop their careers. This is mainly compounded by constraints personal to the individual and those in the environment. Finally, the results illustrate that career development processes of women refugees are affected by the inextricably intertwined factors associated with their gender, immigration status as well as person-environmental factors. Practical implications – The research suggests strategies that policy makers in South Africa and other developing nations that are hosting refugees can use to assist women not just their career development but also their lived experiences. Originality/value – This study extends and advances literature on the career development issues of vulnerable groups such as women refugees especially in developing nations such as South Africa.
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- Date Issued: 2015
Environmental conflict resolution: a critical analysis of the role of interests and value
- Authors: Mweshi, John
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/55842 , vital:26740
- Description: This thesis intends to contribute to an enhanced understanding of environmental conflicts and their resolution. To accomplish this task the thesis will ascertain the role that value and interests play in environmental conflicts in order to establish an adequate basis upon which they can be resolved. In the process, the thesis will also examine three different approaches, namely, the Standard Approach; the Environmental Impact Assessment (EIA) framework; and the Structured Decision Making (SDM) approach. First, the standard approach is informed by the understanding that focusing on interests instead of human values makes the resolution of conflicts more tractable. In contrast, this thesis argues that an exclusive focus on interests, in the context of environmental conflict resolution, is inadequate in some important respects because there are other factors to be considered such as the environmental impacts at the root of the conflict. Second, the thesis examines the focus on impacts that characterises EIAs. It argues that this approach remedies the limitations of the standard approach insofar as impacts are understood in terms of object value. However, the EIA approach does not provide much guidance on how to deal with conflicting human values. Third, taking into account the fact that the standard approach does not address the question of object value, while the EIA addresses object value but does not deal directly with human values, the thesis examines the SDM approach to environmental risk decisions. The thesis argues that while the SDM approach claims to deal with conflicts involving human values head-on, it does not provide a viable alternative in terms of environmental conflict resolution. This is because it fails to recognise the key distinction between human values and object value despite acknowledging the presence of multiple value dimensions as a major obstacle to value trade-offs and therefore to the resolution of value conflicts. Finally, the thesis recommends an adequate basis upon which environmental conflicts can be resolved.
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- Date Issued: 2015
Processes of transformation in a group psychotherapy intervention for single mothers
- Authors: Spiro, Monica
- Date: 2002
- Subjects: Single mothers -- Psychological aspects Group psychotherapy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3100 , http://hdl.handle.net/10962/d1004375
- Description: South African and international statistics indicate that single mother families account for a large and growing proportion of the population. The economic, practical, and emotional stresses of single mothering have been documented and the experience of isolation that often accompanies their circumstances is noted in the literature. Group therapy has been utilised as a treatment plan with single mothers to provide social support and to help the women cope with stress. This thesis examines the experience of single mothers who attended a slow, open group therapy intervention for single mothers at the Child Guidance Clinic, University of Cape Town. The study is located in a feminist social constructionist tradition that recognises the multiplicity of social realities. It places the women's experiences at the foreground of the investigation so as to allow for insight into the socially constructed and first-order reality of the respondents. The research investigates the women's subjective experiences of single parenting; their experiences in the group and its impact on them; and their perceptions of group processes that may have facilitated transformation in their lives. Ten members of the single mother groups were selected for in-depth interviews. Five of the most recent graduates were interviewed and five more participants were selected as the five longest standing members currently participating in the groups. The participants' length of stay in the group at the time of interview varied between eight months and five years. The women were drawn from a range of race, class, cultural and educational backgrounds. The data was collected using individual semi-structured in -depth interviews. A constructivist grounded theory approach was employed to analyse the data. Results revealed the value of the group therapy intervention as a transformative experience for these women who face the challenges of being single parents. The participants highlighted the interpersonal factor of the group intervention as central to their experience and identified this relational aspect as the unique site of their emotional growth. The five interpersonal factors that were identified are: non-judgemental acceptance; support; commonality of experience; reciprocity; and challenge and confrontation between group members. Their accounts of personal changes brought about by participation in the group reflect internal intrapsychic transformations, which are understood in terms of increased se lf-acceptance, enhanced self-esteem, and improved self-confidence. Furthermore, their accounts of personal transformations include a reorganisation of their relational patterns from their immediate to their larger social context. The centrality of relational processes in this research reinforces contemporary theory of women's psychology, particularly theory emerging from the Stone Center, which offers a view of women's psychological growth as occurring in and through participation and engagement with others to achieve more mature and satisfying forms of relating. The accounts of personal and collective transformation provide further insight in to the concept of relational empowerment as it occurs in these groups and offer an understanding of the potentially restorative value of group therapy for single mothers. Future therapeutic interventions are considered and the need for further research in the field is discussed.
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- Date Issued: 2002
Spatio-temporal variation in the phytobenthos and phytoplankton community structure and composition of particulate matter along a river-estuary continuum assessed using microscopic and stable isotope analyses
- Authors: Dalu, Tatenda
- Date: 2015
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54416 , vital:26563
- Description: Phytoplankton and phytobenthos communities play an important role in lotic systems as primary producers providing essential biomolecules to higher trophic oganisms and are important indicators for environmental or ecological change. In this thesis, field studies (observational and experimental) along a river–estuary continuum were conducted to assess the spatio-temporal variation and development of phytobenthos and phytoplankton communities using a combination of stable isotope and community analyses in a temperate southern African system across four study periods: September (early spring) and November/December (late spring) 2012, and February (summer) and May/June (winter) 2013. Additionally, the sources and composition of the particulate organic matter were also analysed using stable isotope (δ15N and δ13C) analysis. The effects of substrate type and flood occurrence were assessed through experimental studies at an up- and downstream site of the river after a major flood event that occurred between October and November 2012. Common household tiles were used as artificial substrates to study the development/succession of phytobenthos communities after the flood disturbance. Distinct diatom communities were observed between upstream and downstream sites and at each site, community structure changed with time indicating succession. In addition to recording diatom characteristics on three natural substrates, namely; macrophytes, rocks and sediment, artificial substrates observations were also made on three different types of artificial substrates, namely; brick, brown clay and grey clay tiles. The natural (species richness 78) and artificial substrates (sp. richness 93) had different communities with the latter having greater species richness. Common phytobenthos taxa were not restricted to a single substrate but preference was generally high for the artificial substrates, especially brown tiles (mean sp. richness 47). Results of the redundancy analysis (RDA) analysis indicated that ammonium, conductivity, total dissolved solids, salinity, pH, oxygen reduction potential, phosphate and water depth were the major determinants of the phytobenthos composition at the two sites. The spatio–temporal variation of phytoplankton and phytobenthos communities and allochthonous organic matter along the river–estuary continuum was assessed at 8 sites using a combination of community and stable isotope analyses. A total of 178 species belonging to 78 genera were recorded with diatoms being predominant, accounting for 81.9 % of the total abundance. The total chl-a concentration along the river-estuary continuum increased from spring to a high in summer before decreasing to a low in winter. Periphyton communities were observed to be significantly different across sites (p < 0.05) in terms of species richness, abundances and isotopically The high periphytic δ15N values (range 7.9–15.2 ‰) recorded at the downstream sites compared to the pristine upstream sites (δ15N values range 4–7 ‰) suggest nutrient enrichment most likely derived from anthropogenic sources. Overall, our results reveal general patterns of periphyton communities and stable isotopes and provide improved information in the use of periphyton δ15N as an excellent indicator of anthropogenic nitrogen pollution. Ecologists are interested in the factors that control, and the variability in, the contributions of different sources to mixed organic materials traveling through lotic systems. We hypothesized that the source matter fuelling mixed organic pools in a river-estuary continuum varies over space and time, with the upper reaches of a system characterized by allochthonous-dominated material and autochthonous contributions becoming more important in the lower reaches. Samples of the mixed organic pools and allochthonous and autochthonous source materials were collected during the four study periods. The C:N ratios of suspended particulate matter (SPM) collected during summer and winter indicated that the lower reaches of the system had similar organic matter contributions from the freshwater and terrestrial sources. Stable isotope analysis in R revealed that the contributions of autochthonous organic matter were high in SPM along the entire continuum, and aquatic macrophytes were significant contributors to SPM specifically in the upper reaches. The terrestrial leaves made major contributions to the SPM in the middle regions of the system (i.e. downstream sites of the river, particularly in early and late spring). Bulk detritus had large allochthonous matter components in the lower reaches (estuary), and the contributions of aquatic macrophytes and benthic algae to bulk detritus were high (> 50 %) in the upper to middle reaches (river), but low (< 20 %) in the lower reaches (estuary). The current investigation represents the first attempt to assess the validity of the River Continuum Concept (RCC) in a southern African temperate river. The phytoplankton and phytobenthos communities, and chl-a concentration followed a trend similar to that proposed for the river continuum concept (RCC). The middle reaches based on the phytobenthos or phytoplankton communities and chl-a concentrations which were employed as proxies for primary production, were the most productive, while the upper reaches were the least primary productive. The evaluation of organic matter contributions to the SPM and detritus along the river–estuary continuum provided a baseline assessment of the nature and sources of potential food for consumers inhabiting different locations during different times of the year. Incorporating such spatio-temporal variations in SPM and detritus into food web studies will improve our understanding of the flow of carbon through aquatic systems.
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- Date Issued: 2015
The ecology and control of Opuntia Aurantiaca in South Africa in relation to the cochineal insect, Dactylopius Austrinus
- Authors: Zimmermann, Helmuth G
- Date: 1982
- Subjects: Cochineal insect -- South Africa Cactus -- South Africa Weeds -- Control -- South Africa Insect-plant relationships
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5612 , http://hdl.handle.net/10962/d1003061
- Description: The cochineal insect Dactylopius austrinus De Lotto, which was released on jointed cactus, Opuntia aurantiaca Lindley, in South Africa in 1932, failed to bring the weed under an acceptable level of control in spite of the encouraging results during the first few years after release. The reasons for this apparent failure were never clearly understood. In 1957 the State embarked on an intensive herbicidal control programme which is still in force today. This sustained and expensive programme has undoubtedly reduced the density of the weed in most areas but has failed to solve the problem and the plant continues to expand its range. The biological control of o. aurantiaca in South Africa has been fundamentally influenced by this chemical control campaign. The relationship between chemical and biological control methods is reported in this study.
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- Date Issued: 1982