The ecophysiology of selected coastal dune pioneer plants of the Eastern Cape
- Authors: Ripley, B S
- Date: 2002
- Subjects: Sand dune plants -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Sand dune plants -- Ecophysiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4222 , http://hdl.handle.net/10962/d1003791
- Description: Understanding the mechanisms and adaptations that allow only certain species to thrive in the potentially stressful foredune environment requires a knowledge of the basic ecophysiology of foredune species. Ecophysiological measurements were conducted on the foredune pioneer species Arctotheca populifolia (Berg.) Norl., Ipomoea pes-caprae(L.) R. Br. and Scaevola plumieri (L.) Vahl. and showed significant differences among species with respect to the physiology associated with biomass production, water and nutrient relations. Differences related to CO₂ assimilation included differences in photosynthetic and respiratory rates, susceptibility to light stress and leaf and stem non-structural carbohydrate concentrations. These resulted in differences in primary production rates of shoots. Mechanisms leading to the differences in CO₂ assimilation among species included differences in stomatal behaviour, carboxylation efficiencies, efficiencies of utilisation of incident photosynthetic photon flux density (PPFD) and rates of ribulose-1,6-bisphosphate (RuBP) regeneration. Correlated with differences in photosynthetic capacity were differences in chlorophyll contents but not differences in leaf nitrogen content. Differences in interspecific stomatal behaviour resulted in significantly different transpiration rates which in combination with differences in assimilation rates resulted in differences in water-use efficiency. The absolute amounts of water transpired, although significantly different among species, were moderate to high in comparison with species from other ecosystems and were typical of mesophytes. Transpiration rates in combination with plant hydraulic conductances and soil water availability resulted in leaf water potentials that were not very negative and none of the investigated species showed evidence of osmotic adjustment. The volume of water transpired by each of the species per unit land surface area was estimated from the relationship between abiotic factors and plant water loss. These relationships varied among species and had varying degrees of predictability as a result of differences in stomatal behaviour between the three species. The water requirements of A. populifolia and S. plumieri were adequately met by the water supplied by rainfall and the water stored in the dune sands. It was therefore not necessary to invoke the utilisation of ground water or the process of internal dew formation to supply sufficient water to meet the requirements. However, I. pes-caprae despite its lower transpiration rates and due to its higher biomass, lost greater volumes of water per unit dune surface area than either A. populifolia or S. plumieri. This resulted in periods of potential water limitation for I. pes-caprae. Incident light was the most important determinant of leaf photosynthetic CO₂ assimilation and transpiration, particularly as a linear relationship between incident PPFD and atmospheric vapour pressure deficit (VPD) could be demonstrated. Whole plant photosynthetic production by S. plumieri was shown to be light limited as a result of mutual shading despite high incident and reflected PPFD occurring in the foredune environment. The leaf hair-layer of A. populifolia was shown to be important in reducing transmitted UV and hence reducing photoinhibition but it also caused reduced transpiration rates because of the thicker boundary layer and thus increased leaf temperatures. The nutrient content of above-ground plant parts of the investigated species were typical of higher plants despite the low nutrient content measured for the dune soils. With the possible exception of nitrogen the nutrient demand created by above-ground production was adequately met by the supply of nutrients either from sand-water or from aquifer-water transpired by the plants. Differences in the volumes of water transpired, and hence the quantity of nutrients potentially taken up via the transpiration stream, resulted in interspecific differences in above-ground plant macronutrient content. The reallocation patterns of nutrients differed both between the various nutrients measured and interspecifically. Standing biomass and the density of plants per unit land area was low in comparison to that of other ecosystems and was different among investigated species. This may be important in maintaining the adequate supply of resources (water, nutrients and light). As a result of the interspecific differences in biomass when production was expressed per unit land surface area the resultant productivity was not dissimilar among species. Productivity was high when comparisons were made with species from other ecosystems. No single resource (water, nutrients or light) could be identified as the controlling factor in the foredune environment and a combination of both resource stress and environmental disturbance are likely to be involved. Physiology, production, growth and growth characteristics conveyed certain adaptive advantages to these species in respect to both resource stress and environmental disturbance. Interspecific differences in these adaptations can be used to offer explanations for the observed microhabitat preferences of the three investigated species. Furthermore features common to all three species offer some explanations as to why these species and not others are able to inhabit the foredunes.
- Full Text:
- Date Issued: 2002
- Authors: Ripley, B S
- Date: 2002
- Subjects: Sand dune plants -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Sand dune plants -- Ecophysiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4222 , http://hdl.handle.net/10962/d1003791
- Description: Understanding the mechanisms and adaptations that allow only certain species to thrive in the potentially stressful foredune environment requires a knowledge of the basic ecophysiology of foredune species. Ecophysiological measurements were conducted on the foredune pioneer species Arctotheca populifolia (Berg.) Norl., Ipomoea pes-caprae(L.) R. Br. and Scaevola plumieri (L.) Vahl. and showed significant differences among species with respect to the physiology associated with biomass production, water and nutrient relations. Differences related to CO₂ assimilation included differences in photosynthetic and respiratory rates, susceptibility to light stress and leaf and stem non-structural carbohydrate concentrations. These resulted in differences in primary production rates of shoots. Mechanisms leading to the differences in CO₂ assimilation among species included differences in stomatal behaviour, carboxylation efficiencies, efficiencies of utilisation of incident photosynthetic photon flux density (PPFD) and rates of ribulose-1,6-bisphosphate (RuBP) regeneration. Correlated with differences in photosynthetic capacity were differences in chlorophyll contents but not differences in leaf nitrogen content. Differences in interspecific stomatal behaviour resulted in significantly different transpiration rates which in combination with differences in assimilation rates resulted in differences in water-use efficiency. The absolute amounts of water transpired, although significantly different among species, were moderate to high in comparison with species from other ecosystems and were typical of mesophytes. Transpiration rates in combination with plant hydraulic conductances and soil water availability resulted in leaf water potentials that were not very negative and none of the investigated species showed evidence of osmotic adjustment. The volume of water transpired by each of the species per unit land surface area was estimated from the relationship between abiotic factors and plant water loss. These relationships varied among species and had varying degrees of predictability as a result of differences in stomatal behaviour between the three species. The water requirements of A. populifolia and S. plumieri were adequately met by the water supplied by rainfall and the water stored in the dune sands. It was therefore not necessary to invoke the utilisation of ground water or the process of internal dew formation to supply sufficient water to meet the requirements. However, I. pes-caprae despite its lower transpiration rates and due to its higher biomass, lost greater volumes of water per unit dune surface area than either A. populifolia or S. plumieri. This resulted in periods of potential water limitation for I. pes-caprae. Incident light was the most important determinant of leaf photosynthetic CO₂ assimilation and transpiration, particularly as a linear relationship between incident PPFD and atmospheric vapour pressure deficit (VPD) could be demonstrated. Whole plant photosynthetic production by S. plumieri was shown to be light limited as a result of mutual shading despite high incident and reflected PPFD occurring in the foredune environment. The leaf hair-layer of A. populifolia was shown to be important in reducing transmitted UV and hence reducing photoinhibition but it also caused reduced transpiration rates because of the thicker boundary layer and thus increased leaf temperatures. The nutrient content of above-ground plant parts of the investigated species were typical of higher plants despite the low nutrient content measured for the dune soils. With the possible exception of nitrogen the nutrient demand created by above-ground production was adequately met by the supply of nutrients either from sand-water or from aquifer-water transpired by the plants. Differences in the volumes of water transpired, and hence the quantity of nutrients potentially taken up via the transpiration stream, resulted in interspecific differences in above-ground plant macronutrient content. The reallocation patterns of nutrients differed both between the various nutrients measured and interspecifically. Standing biomass and the density of plants per unit land area was low in comparison to that of other ecosystems and was different among investigated species. This may be important in maintaining the adequate supply of resources (water, nutrients and light). As a result of the interspecific differences in biomass when production was expressed per unit land surface area the resultant productivity was not dissimilar among species. Productivity was high when comparisons were made with species from other ecosystems. No single resource (water, nutrients or light) could be identified as the controlling factor in the foredune environment and a combination of both resource stress and environmental disturbance are likely to be involved. Physiology, production, growth and growth characteristics conveyed certain adaptive advantages to these species in respect to both resource stress and environmental disturbance. Interspecific differences in these adaptations can be used to offer explanations for the observed microhabitat preferences of the three investigated species. Furthermore features common to all three species offer some explanations as to why these species and not others are able to inhabit the foredunes.
- Full Text:
- Date Issued: 2002
Biocatalytic and biomimetic studies of polyphenol oxidase
- Authors: Burton, Stephanie Gail
- Date: 1994
- Subjects: Phenol oxidase Polyphenols Oxidases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4028 , http://hdl.handle.net/10962/d1004088
- Description: Mushroom polyphenol oxidase (EC 1.14.18.1) was investigated to determine its potential for application as a biocatalyst in the synthesis of o-quinones, in organic medium. In order to determine the kinetic properties of the biocatalyst, a system was devised which comprised an immobilised polyphenol oxidase extract, functioning in chloroform. The system was hydrated by the addition of buffer. A simple method for the consistent measurement of reaction rates in this heterogenous system was designed and used to obtain detailed enzyme kinetic data relating to optimisation of reaction conditions and substrate specificity. The aqueous content of the system was optimised using p-cresol as a substrate. A crude, immobilised extract of Agaricus bisporus was used to hydroxylate and oxidise a range of selected p-substituted phenolic substrates, yielding, as the sale products, o-quinones. These products were efficiently reduced to catechols by extracting the reaction mixtures with aqueous ascorbic acid solution. The biocatalytic system was also successfully utilised to produce L-DOPA, the drug used to treat Parkinson's disease, from L-acetyl tyrosine ethyl ester (ATEE). Michaelis-Menten kinetics were used to obtain apparent Km and V values with respect to the selected phenolic substrates, and the kinetic parameters obtained were found to correlate well with the steric requirements of the substrates and with their hydrophobicity. In the course of the investigation, a novel ¹H NMR method was used to facilitate measurement of the UV molar absorption coefficients of the o-quinones in reaction mixtures, thus avoiding the necessity to isolate these unstable, water-sensitive products. The biocatalytic system was extended to a continuous process, in which the immobilised enzyme was shown to function successfully in the chloroform medium for several hours, with high conversion rates. Modifications, involving partial purification and the addition of a surfactant, were investigated to determine their effect on the kinetic parameters. The results obtained using partially purified enzyme indicated that the removal of extraneous protein and/or melanoid material lead to a reduced capacity for conversion of sterically demanding substrates. The addition of the anionic detergent, sodium dodecyl sulphate (SOS), enhanced the ability of the biocatalyst to bind and oxidise sterically demanding substrates. These effects are attributed to changes in the polar state of groups within the protein binding pocket, which result in altered flexibility and hydrophobicity. Computer modelling of several biomimetic dinuclear copper complexes also indicated the importance of flexibility for effective biocatalysis. Novel binuclear copper (II complexes, containing a flexible biphenyl spacer and imidazole or benzimidazole donors, were prepared and analysed using NMR, UV, AA and cyclic voltammetric techniques. The complexes were also shown, in a detailed kinetic study, to mimic the catecholase activity of polyphenol oxidase by oxidising 3,5-di-tertbutylcatechol, and to catalyse the coupling of the phenolic substrate 2,4-di-tert-butylphenol. However, the complexes were apparently too flexible to react with smaller substrates. These biomimetic complexes provided valuable insights into the nature of the dinuclear copper binding site.
- Full Text:
- Date Issued: 1994
- Authors: Burton, Stephanie Gail
- Date: 1994
- Subjects: Phenol oxidase Polyphenols Oxidases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4028 , http://hdl.handle.net/10962/d1004088
- Description: Mushroom polyphenol oxidase (EC 1.14.18.1) was investigated to determine its potential for application as a biocatalyst in the synthesis of o-quinones, in organic medium. In order to determine the kinetic properties of the biocatalyst, a system was devised which comprised an immobilised polyphenol oxidase extract, functioning in chloroform. The system was hydrated by the addition of buffer. A simple method for the consistent measurement of reaction rates in this heterogenous system was designed and used to obtain detailed enzyme kinetic data relating to optimisation of reaction conditions and substrate specificity. The aqueous content of the system was optimised using p-cresol as a substrate. A crude, immobilised extract of Agaricus bisporus was used to hydroxylate and oxidise a range of selected p-substituted phenolic substrates, yielding, as the sale products, o-quinones. These products were efficiently reduced to catechols by extracting the reaction mixtures with aqueous ascorbic acid solution. The biocatalytic system was also successfully utilised to produce L-DOPA, the drug used to treat Parkinson's disease, from L-acetyl tyrosine ethyl ester (ATEE). Michaelis-Menten kinetics were used to obtain apparent Km and V values with respect to the selected phenolic substrates, and the kinetic parameters obtained were found to correlate well with the steric requirements of the substrates and with their hydrophobicity. In the course of the investigation, a novel ¹H NMR method was used to facilitate measurement of the UV molar absorption coefficients of the o-quinones in reaction mixtures, thus avoiding the necessity to isolate these unstable, water-sensitive products. The biocatalytic system was extended to a continuous process, in which the immobilised enzyme was shown to function successfully in the chloroform medium for several hours, with high conversion rates. Modifications, involving partial purification and the addition of a surfactant, were investigated to determine their effect on the kinetic parameters. The results obtained using partially purified enzyme indicated that the removal of extraneous protein and/or melanoid material lead to a reduced capacity for conversion of sterically demanding substrates. The addition of the anionic detergent, sodium dodecyl sulphate (SOS), enhanced the ability of the biocatalyst to bind and oxidise sterically demanding substrates. These effects are attributed to changes in the polar state of groups within the protein binding pocket, which result in altered flexibility and hydrophobicity. Computer modelling of several biomimetic dinuclear copper complexes also indicated the importance of flexibility for effective biocatalysis. Novel binuclear copper (II complexes, containing a flexible biphenyl spacer and imidazole or benzimidazole donors, were prepared and analysed using NMR, UV, AA and cyclic voltammetric techniques. The complexes were also shown, in a detailed kinetic study, to mimic the catecholase activity of polyphenol oxidase by oxidising 3,5-di-tertbutylcatechol, and to catalyse the coupling of the phenolic substrate 2,4-di-tert-butylphenol. However, the complexes were apparently too flexible to react with smaller substrates. These biomimetic complexes provided valuable insights into the nature of the dinuclear copper binding site.
- Full Text:
- Date Issued: 1994
Social structure and rural economic development
- Authors: Berger, Guy
- Date: 1989
- Subjects: Social structure -- Developing countries , Rural development-- Developing countries
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2864 , http://hdl.handle.net/10962/d1007643
- Description: New concepts and a synthesis of existing theories may assist in studying the relationship between social structure, development and rural development. The concept of social structure encompasses the concept of economic structure which may be analysed in terms of three "Moments" of production. On this basis, one can distinguish between heterogeneous and homogeneous relations of production structures. "Homogeneous relations" together with "system dynamics" and ''reproduction", define the concept of a mode of production. "Development" refers to the expansion of total productive capacity, premissed on advanced means of production, and corresponding to the particular relations and forces of production in an economic system. The capitalist mode of production has both tendencies and countertendencies to development. The latter prevail in the Third World due to the admixture and heterogeneity of production relations there, and to their subordinate articulation within an international capitalist economic system. In this context, underdevelopment is the result of the specific factors of monopoly competition, dependence-extraversion, disarticulation-unevenness, the three-tier structure of the peripheral economy, surplus transfer, and class structures and struggles. Rural development can be understood in terms of the specific contribution of agriculture to development, theorized as the "Agrarian Question". Agrarian capitalism has been slow to develop in the Third World, and the state of agriculture remains a problem there. "Rural development" has emerged as a deliberate and interventionist state strategy designed to restructure agrarian relations for development. This has contributed to the formation of particular heterogeneous relations of production articulated to the capitalist mode. In this context, the character of the associated classes has left the Agrarian Question unresolved. "Rural development" continues because it has an important~ and even primary, political significance - although this is not without contradictions.
- Full Text:
- Date Issued: 1989
- Authors: Berger, Guy
- Date: 1989
- Subjects: Social structure -- Developing countries , Rural development-- Developing countries
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2864 , http://hdl.handle.net/10962/d1007643
- Description: New concepts and a synthesis of existing theories may assist in studying the relationship between social structure, development and rural development. The concept of social structure encompasses the concept of economic structure which may be analysed in terms of three "Moments" of production. On this basis, one can distinguish between heterogeneous and homogeneous relations of production structures. "Homogeneous relations" together with "system dynamics" and ''reproduction", define the concept of a mode of production. "Development" refers to the expansion of total productive capacity, premissed on advanced means of production, and corresponding to the particular relations and forces of production in an economic system. The capitalist mode of production has both tendencies and countertendencies to development. The latter prevail in the Third World due to the admixture and heterogeneity of production relations there, and to their subordinate articulation within an international capitalist economic system. In this context, underdevelopment is the result of the specific factors of monopoly competition, dependence-extraversion, disarticulation-unevenness, the three-tier structure of the peripheral economy, surplus transfer, and class structures and struggles. Rural development can be understood in terms of the specific contribution of agriculture to development, theorized as the "Agrarian Question". Agrarian capitalism has been slow to develop in the Third World, and the state of agriculture remains a problem there. "Rural development" has emerged as a deliberate and interventionist state strategy designed to restructure agrarian relations for development. This has contributed to the formation of particular heterogeneous relations of production articulated to the capitalist mode. In this context, the character of the associated classes has left the Agrarian Question unresolved. "Rural development" continues because it has an important~ and even primary, political significance - although this is not without contradictions.
- Full Text:
- Date Issued: 1989
Colonisation and succession of fishes in Lake Liambezi, a shallow ephemeral floodplain lake in Southern Africa
- Authors: Peel, Richard Anthony
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/65211 , vital:28707
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
- Authors: Peel, Richard Anthony
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/65211 , vital:28707
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2017
An investigation into the neuroprotective properties of melatonin
- Authors: Southgate, Garrick Steven
- Date: 1999
- Subjects: Melatonin
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3900 , http://hdl.handle.net/10962/d1003959
- Description: Until the beginning of this decade the neurohormone, melatonin, had been considered as little more than a tranquillising hormone, responsible for regulating certain circadian and circannual rhythms. In the last eight years, a whole new dimension to melatonin’s role in biological organisms has emerged. In 1991 it was discovered [1,2] that melatonin exhibited antioxidant properties. Since then, many researchers [3,4] have found melatonin to be a powerful free radical scavenger and antioxidant. In the present study, the ability of melatonin to offer neuroprotection against glutamate, N-methyl-D-aspartate (NMDA), quinolinic acid (QA) and kainic acid (KA) (collectively referred to as the glutamate receptor agonists) was investigated. It was first shown that stress causes an increase in circulating glucocorticoid concentrations, which resulted in an increase the number of glutamate receptors on synaptic membranes in rat brain homogenate. Melatonin acted to reduce the number of glutamate receptors present on the synaptic membranes, implying that melatonin has neuroprotective properties, as overstimulation of the glutamate receptors leads to excitotoxicity and neurodegeneration. Further investigations showed that the glutamate receptor agonists induce neurodegeneration in primary neuronal cell cultures. Both co-treatment and posttreatment with melatonin against the glutamate receptor agonists, increased neuronal cell viability in a dose dependent manner. Melatonin also appeared to offer protection against quinolinic acid-induced neurodegeneration following intrahippocampal injections of quinolinic acid. The mechanism whereby melatonin offered this protection was investigated. The glutamate receptor agonists caused an increase in intracellular calcium concentrations, which is known [5] to be responsible for initiating the excitotoxic response. Melatonin had no effect on regulating intracellular calcium concentrations Additional studies indicated that melatonin was effective at scavenging superoxide radicals. Production of superoxide radicals was induced by the glutamate receptor agonists in primary neuronal cultures. Superoxide radicals induce lipid peroxidation, which involves the destruction of lipid membranes by chain reactions. By acting as an antioxidant, melatonin was able to reduce quinolinic acid-induced lipid peroxidation in rat brain homogenate, in a dose dependent manner. Melatonin was also effective at reducing lipid peroxidation induced by the glutamate receptor agonists in primary neuronal cultures. Melatonin therefore appeared to be offering neuroprotection by removing superoxide radicals and inhibiting lipid peroxidation. It had been reported [6] that melatonin inhibits nitric oxide synthase activity. This enzyme produces the free radical, nitric oxide, and can also produce superoxide radicals. Melatonin was able to reduce nitric oxide synthase activity in a dose dependent manner. This is a novel method of neuroprotection, as melatonin was now acting as an enzyme regulator. The results obtained demonstrate that melatonin offers neuroprotection against glutamate induced excitotoxicity, by removing free radicals and preventing lipid peroxidation. The neurohormone offers further protection by decreasing the activity of enzymes that aid in the neurotoxic cascade. Melatonin is the most potent naturally occurring free radical scavenger in the body [3]. During aging, the serum concentrations of melatonin decrease [7]. During the senescence of life, free radical damage to the body is at its highest [8], while at the same time melatonin concentrations are at their lowest. Melatonin therefore shows potential for the treatment of diseases and disorders that exhibit an excitotoxic pathology.
- Full Text:
- Date Issued: 1999
- Authors: Southgate, Garrick Steven
- Date: 1999
- Subjects: Melatonin
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3900 , http://hdl.handle.net/10962/d1003959
- Description: Until the beginning of this decade the neurohormone, melatonin, had been considered as little more than a tranquillising hormone, responsible for regulating certain circadian and circannual rhythms. In the last eight years, a whole new dimension to melatonin’s role in biological organisms has emerged. In 1991 it was discovered [1,2] that melatonin exhibited antioxidant properties. Since then, many researchers [3,4] have found melatonin to be a powerful free radical scavenger and antioxidant. In the present study, the ability of melatonin to offer neuroprotection against glutamate, N-methyl-D-aspartate (NMDA), quinolinic acid (QA) and kainic acid (KA) (collectively referred to as the glutamate receptor agonists) was investigated. It was first shown that stress causes an increase in circulating glucocorticoid concentrations, which resulted in an increase the number of glutamate receptors on synaptic membranes in rat brain homogenate. Melatonin acted to reduce the number of glutamate receptors present on the synaptic membranes, implying that melatonin has neuroprotective properties, as overstimulation of the glutamate receptors leads to excitotoxicity and neurodegeneration. Further investigations showed that the glutamate receptor agonists induce neurodegeneration in primary neuronal cell cultures. Both co-treatment and posttreatment with melatonin against the glutamate receptor agonists, increased neuronal cell viability in a dose dependent manner. Melatonin also appeared to offer protection against quinolinic acid-induced neurodegeneration following intrahippocampal injections of quinolinic acid. The mechanism whereby melatonin offered this protection was investigated. The glutamate receptor agonists caused an increase in intracellular calcium concentrations, which is known [5] to be responsible for initiating the excitotoxic response. Melatonin had no effect on regulating intracellular calcium concentrations Additional studies indicated that melatonin was effective at scavenging superoxide radicals. Production of superoxide radicals was induced by the glutamate receptor agonists in primary neuronal cultures. Superoxide radicals induce lipid peroxidation, which involves the destruction of lipid membranes by chain reactions. By acting as an antioxidant, melatonin was able to reduce quinolinic acid-induced lipid peroxidation in rat brain homogenate, in a dose dependent manner. Melatonin was also effective at reducing lipid peroxidation induced by the glutamate receptor agonists in primary neuronal cultures. Melatonin therefore appeared to be offering neuroprotection by removing superoxide radicals and inhibiting lipid peroxidation. It had been reported [6] that melatonin inhibits nitric oxide synthase activity. This enzyme produces the free radical, nitric oxide, and can also produce superoxide radicals. Melatonin was able to reduce nitric oxide synthase activity in a dose dependent manner. This is a novel method of neuroprotection, as melatonin was now acting as an enzyme regulator. The results obtained demonstrate that melatonin offers neuroprotection against glutamate induced excitotoxicity, by removing free radicals and preventing lipid peroxidation. The neurohormone offers further protection by decreasing the activity of enzymes that aid in the neurotoxic cascade. Melatonin is the most potent naturally occurring free radical scavenger in the body [3]. During aging, the serum concentrations of melatonin decrease [7]. During the senescence of life, free radical damage to the body is at its highest [8], while at the same time melatonin concentrations are at their lowest. Melatonin therefore shows potential for the treatment of diseases and disorders that exhibit an excitotoxic pathology.
- Full Text:
- Date Issued: 1999
Studies directed towards the synthesis of chromone carbaldehyde-derived HIV-1 protease inhibitors
- Authors: Molefe, Duduzile Mabel
- Date: 2008
- Subjects: Protease Inhibitors , HIV infections , HIV (Viruses) , AIDS (Disease) , Proteolytic enzymes , Heterocyclic compounds -- Derivatives , Chemical kinetics , Nuclear magnetic resonance spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4526 , http://hdl.handle.net/10962/d1015542
- Description: A series of chromone-3-carbaldehydes have been prepared using Vilsmeier-Haack methodology while a corresponding series of chromone-2-carbaldeydes have been synthesized via the Kostanecki-Robinson reaction. Baylis-Hillman reactions have been conducted on both series of chromone carbaldehydes using three different catalysts, viz., 1,4-diazabicyclo(2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec- 7-ene (DBU) and 3-hydroxyquinuclidine (3HQ), and acrylonitrile, methyl acrylate and methyl vinyl ketone as the activated alkenes. These reactions have typically (but not always!) afforded both normal Baylis-Hillman and dimeric products. Attention has also been given to the use of 1-methyl-2-pyrrolidine (1-NMP), an ionic liquid, to replace normal organic solvents, and it has been found that, in the presence of DABCO, chromone-3-carbaldehydes afford the dimeric products alone. Reactions of chromone-3-carbaldehydes with methyl vinyl ketone have yielded unexpected, novel adducts, which appear to arise from preferential attack at C(2) in the chromone nucleus. Research on chromone-2-carbaldeydes under Baylis-Hillman conditions has also resulted in the formation of some interesting products instead of the expected Baylis-Hillman adducts. The Baylis-Hillman products have been explored as substrates for aza-Michael reactions using various amino derivatives including protected amino acids in the presence of the tetrabutylammonium bromide (TBAB) and the ionic liquid, 3-butyl-1- methylimidazoleboranetetrafluoride (BmimBF₄), as catalysts. The aza-Michael products have been targeted as truncated ritonavir analogues for investigation as potential HIV -1 protease inhibitors, and representative compounds have been subjected to enzyme inhibition assays to explore the extent and type of inhibition. Lineweaver-Burk and Dixon plots have indicated competitive inhibition in one case as well as non-competitive inhibition in another, and the inhibition constants (Ki) have been compared with that of the ritonavir. Computer modelling studies have also been conducted on selected chromonecontaining derivatives, using the ACCELRYS Cerius² platform. Interactive docking of the chromone-containing ligands into the HIV -1 protease receptor site, using the Ligandfit module, has indicated the importance of hydrogen-bonding interactions mediated by bridging water molecules situated in the receptor cavity. NMR spectroscopy has been used to elucidate complex and competing mechanistic pathways involved in the Baylis-Hillman reactions of selected 2-nitrobenzaldehydes with MVK in the presence of DABCO - reactions which afford the normal BaylisHillman product, the MVK dimer and syn- and anti-Baylis-Hillman type diadducts. The kinetic data confirm the concomitant operation of two pathways and reveal that, in the initial stage of the reaction, the product distribution is kinetically controlled, whereas in the latter stage, thermodynamic control results in the consumption of the normal Baylis-Hillman product and predominance of the anti-diadduct.
- Full Text:
- Date Issued: 2008
- Authors: Molefe, Duduzile Mabel
- Date: 2008
- Subjects: Protease Inhibitors , HIV infections , HIV (Viruses) , AIDS (Disease) , Proteolytic enzymes , Heterocyclic compounds -- Derivatives , Chemical kinetics , Nuclear magnetic resonance spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4526 , http://hdl.handle.net/10962/d1015542
- Description: A series of chromone-3-carbaldehydes have been prepared using Vilsmeier-Haack methodology while a corresponding series of chromone-2-carbaldeydes have been synthesized via the Kostanecki-Robinson reaction. Baylis-Hillman reactions have been conducted on both series of chromone carbaldehydes using three different catalysts, viz., 1,4-diazabicyclo(2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec- 7-ene (DBU) and 3-hydroxyquinuclidine (3HQ), and acrylonitrile, methyl acrylate and methyl vinyl ketone as the activated alkenes. These reactions have typically (but not always!) afforded both normal Baylis-Hillman and dimeric products. Attention has also been given to the use of 1-methyl-2-pyrrolidine (1-NMP), an ionic liquid, to replace normal organic solvents, and it has been found that, in the presence of DABCO, chromone-3-carbaldehydes afford the dimeric products alone. Reactions of chromone-3-carbaldehydes with methyl vinyl ketone have yielded unexpected, novel adducts, which appear to arise from preferential attack at C(2) in the chromone nucleus. Research on chromone-2-carbaldeydes under Baylis-Hillman conditions has also resulted in the formation of some interesting products instead of the expected Baylis-Hillman adducts. The Baylis-Hillman products have been explored as substrates for aza-Michael reactions using various amino derivatives including protected amino acids in the presence of the tetrabutylammonium bromide (TBAB) and the ionic liquid, 3-butyl-1- methylimidazoleboranetetrafluoride (BmimBF₄), as catalysts. The aza-Michael products have been targeted as truncated ritonavir analogues for investigation as potential HIV -1 protease inhibitors, and representative compounds have been subjected to enzyme inhibition assays to explore the extent and type of inhibition. Lineweaver-Burk and Dixon plots have indicated competitive inhibition in one case as well as non-competitive inhibition in another, and the inhibition constants (Ki) have been compared with that of the ritonavir. Computer modelling studies have also been conducted on selected chromonecontaining derivatives, using the ACCELRYS Cerius² platform. Interactive docking of the chromone-containing ligands into the HIV -1 protease receptor site, using the Ligandfit module, has indicated the importance of hydrogen-bonding interactions mediated by bridging water molecules situated in the receptor cavity. NMR spectroscopy has been used to elucidate complex and competing mechanistic pathways involved in the Baylis-Hillman reactions of selected 2-nitrobenzaldehydes with MVK in the presence of DABCO - reactions which afford the normal BaylisHillman product, the MVK dimer and syn- and anti-Baylis-Hillman type diadducts. The kinetic data confirm the concomitant operation of two pathways and reveal that, in the initial stage of the reaction, the product distribution is kinetically controlled, whereas in the latter stage, thermodynamic control results in the consumption of the normal Baylis-Hillman product and predominance of the anti-diadduct.
- Full Text:
- Date Issued: 2008
The screening and characterisation of compounds for modulators of heat shock protein (Hsp90) in a breast cancer cell model
- Authors: Moyo, Buhle
- Date: 2013 , 2013-07-18
- Subjects: Heat shock proteins Breast -- Cancer Breast -- Cancer -- Chemotherapy Breast -- Cancer -- Treatment Cancer cells Naphthoquinone PQQ (Biochemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4060 , http://hdl.handle.net/10962/d1004129
- Description: Breast cancer is a leading cause of cancer death in Africa. Hsp90 has been identified as a target for anti-cancer treatments as its inhibition results in the disruption and ubiquitin–proteasome degradation of activated oncoproteins. Currently, there are no US Food and Drug Administration approved Hsp90 inhibitor drugs and existing Hsp90 inhibitors such as geldanamycin and novobiocin are hepatotoxic and display a low affinity for Hsp90, respectively. Therefore, there is a need for the development of Hsp90 inhibitors with improved inhibitory properties. In this study twelve natural compounds bearing a quinone nucleus were screened and characterised for the modulation of Hsp90. The compounds analysed formed three series; the sargaquinoic acid (SQA), naphthoquinone, and pyrroloiminoquinone alkaloid series. Certain compounds exhibited half maximal inhibitory concentrations of between 3.32 μM and 12.4 μM, while others showed no antiproliferative activity at concentrations of up to 500 μM in the MDA-MB-231 breast adenocarcinoma cell line. Immunofluorescence and Western analyses indicated that the modulation of Hsp90 and partner proteins by SQA was more similar to that of novobiocin. Isothermal titration calorimetry analyses suggested that SQA interacted with Hsp90β with a low affinity, and saturation-transfer difference nuclear magnetic resonance confirmed that this interaction with Hsp90β occurred through the methyl moiety bound to 1, 4 benzoquinone of SQA. Pulldown assays indicated SQA disrupted the association between Hsp90 and Hop dose-dependently, more similarly to novobiocin. Immunofluorescence and Western analyses performed on naphthoquinone and pyrroloiminoquinone alkaloid compounds indicated modulation of Hsp90 and Hsp90 partner proteins by the compounds. Naphthoquinone compounds were prioritised for analysis for binding to Hsp90β over the pyrroloiminoquinone alkaloid compounds. Lapachol interacted with Hsp90β with a low affinity however; this interaction was thought to be too weak to disrupt the association of Hsp90 and Hop. The remaining naphthoquinone compounds showed no interaction with Hsp90β, thus allowing the determination of a preliminary structure-activity relationship for these compounds. To the best of our knowledge, this is the first study to describe a systematic subcellular analysis of the effects of geldanamycin and novobiocin in comparison to sargaquinoic acid and compounds of the naphthoquinone and pyrroloquinoline scaffold on Hsp90 and its partner proteins. , Microsoft� Word 2010 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
- Authors: Moyo, Buhle
- Date: 2013 , 2013-07-18
- Subjects: Heat shock proteins Breast -- Cancer Breast -- Cancer -- Chemotherapy Breast -- Cancer -- Treatment Cancer cells Naphthoquinone PQQ (Biochemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4060 , http://hdl.handle.net/10962/d1004129
- Description: Breast cancer is a leading cause of cancer death in Africa. Hsp90 has been identified as a target for anti-cancer treatments as its inhibition results in the disruption and ubiquitin–proteasome degradation of activated oncoproteins. Currently, there are no US Food and Drug Administration approved Hsp90 inhibitor drugs and existing Hsp90 inhibitors such as geldanamycin and novobiocin are hepatotoxic and display a low affinity for Hsp90, respectively. Therefore, there is a need for the development of Hsp90 inhibitors with improved inhibitory properties. In this study twelve natural compounds bearing a quinone nucleus were screened and characterised for the modulation of Hsp90. The compounds analysed formed three series; the sargaquinoic acid (SQA), naphthoquinone, and pyrroloiminoquinone alkaloid series. Certain compounds exhibited half maximal inhibitory concentrations of between 3.32 μM and 12.4 μM, while others showed no antiproliferative activity at concentrations of up to 500 μM in the MDA-MB-231 breast adenocarcinoma cell line. Immunofluorescence and Western analyses indicated that the modulation of Hsp90 and partner proteins by SQA was more similar to that of novobiocin. Isothermal titration calorimetry analyses suggested that SQA interacted with Hsp90β with a low affinity, and saturation-transfer difference nuclear magnetic resonance confirmed that this interaction with Hsp90β occurred through the methyl moiety bound to 1, 4 benzoquinone of SQA. Pulldown assays indicated SQA disrupted the association between Hsp90 and Hop dose-dependently, more similarly to novobiocin. Immunofluorescence and Western analyses performed on naphthoquinone and pyrroloiminoquinone alkaloid compounds indicated modulation of Hsp90 and Hsp90 partner proteins by the compounds. Naphthoquinone compounds were prioritised for analysis for binding to Hsp90β over the pyrroloiminoquinone alkaloid compounds. Lapachol interacted with Hsp90β with a low affinity however; this interaction was thought to be too weak to disrupt the association of Hsp90 and Hop. The remaining naphthoquinone compounds showed no interaction with Hsp90β, thus allowing the determination of a preliminary structure-activity relationship for these compounds. To the best of our knowledge, this is the first study to describe a systematic subcellular analysis of the effects of geldanamycin and novobiocin in comparison to sargaquinoic acid and compounds of the naphthoquinone and pyrroloquinoline scaffold on Hsp90 and its partner proteins. , Microsoft� Word 2010 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2013
The doctrine of duress in the law of contract and unjustified enrichment in South Africa
- Authors: Glover, Graham Brian
- Date: 2004
- Subjects: Contracts -- South Africa , Duress (Law) -- South Africa , Remedies (Law) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3672 , http://hdl.handle.net/10962/d1003187 , Contracts -- South Africa , Duress (Law) -- South Africa , Remedies (Law) -- South Africa
- Description: This thesis analyses the doctrine of duress and its application in the law of contract and unjustified enrichment in South Africa. Following an initial examination of the historical development of the doctrine from its roots in Roman and Roman-Dutch law, the study focuses on the current legal position in the two areas of law under review, identifies the substantive and formal deficiencies in the current approach, and suggests, using comparative authorities, how the law might be developed. As far as the law of contract is concerned, after exposing the difficulties inherent in the current approach, and placing the doctrine in its proper context in the South African law of contract generally, it is argued that the duress doctrine finds its juridical basis in the principle of good faith. A more modern and coherent test for duress is then proposed: one that concentrates on the question whether an illegitimate threat was made, which induced a contract in that it left the other person no reasonable choice but to succumb to the proposal. Additionally, the need for South African contract law to recognise and deal with cases of economic duress is emphasised. The study then shifts to an examination of the position in situations where non-contractual performances have occurred under duress: cases that are decided in terms of the principles of the law of unjustified enrichment. The current position is reviewed, and it is shown that the approach to duress cases is substantially different to the approach that applies in contract. An attempt is made to reconcile this problem. From a structural perspective, the nature and application of the relevant enrichment action where a non-contractual performance is made under duress (the condictio indebiti) is also investigated, in the light of approaches to enrichment adopted in both Germany and England, in an attempt to make better sense of this enrichment action in the South African context. The study closes with an analysis of the various contractual, delictual and enrichment remedies that are available once a case of duress has been proved.
- Full Text:
- Date Issued: 2004
- Authors: Glover, Graham Brian
- Date: 2004
- Subjects: Contracts -- South Africa , Duress (Law) -- South Africa , Remedies (Law) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3672 , http://hdl.handle.net/10962/d1003187 , Contracts -- South Africa , Duress (Law) -- South Africa , Remedies (Law) -- South Africa
- Description: This thesis analyses the doctrine of duress and its application in the law of contract and unjustified enrichment in South Africa. Following an initial examination of the historical development of the doctrine from its roots in Roman and Roman-Dutch law, the study focuses on the current legal position in the two areas of law under review, identifies the substantive and formal deficiencies in the current approach, and suggests, using comparative authorities, how the law might be developed. As far as the law of contract is concerned, after exposing the difficulties inherent in the current approach, and placing the doctrine in its proper context in the South African law of contract generally, it is argued that the duress doctrine finds its juridical basis in the principle of good faith. A more modern and coherent test for duress is then proposed: one that concentrates on the question whether an illegitimate threat was made, which induced a contract in that it left the other person no reasonable choice but to succumb to the proposal. Additionally, the need for South African contract law to recognise and deal with cases of economic duress is emphasised. The study then shifts to an examination of the position in situations where non-contractual performances have occurred under duress: cases that are decided in terms of the principles of the law of unjustified enrichment. The current position is reviewed, and it is shown that the approach to duress cases is substantially different to the approach that applies in contract. An attempt is made to reconcile this problem. From a structural perspective, the nature and application of the relevant enrichment action where a non-contractual performance is made under duress (the condictio indebiti) is also investigated, in the light of approaches to enrichment adopted in both Germany and England, in an attempt to make better sense of this enrichment action in the South African context. The study closes with an analysis of the various contractual, delictual and enrichment remedies that are available once a case of duress has been proved.
- Full Text:
- Date Issued: 2004
Synthesis of pH responsive carriers for pulmonary drug delivery of anti-tuberculosis therapeutics: mesoporous silica nanoparticles and gelatin nanoparticles
- Authors: Ngoepe, Mpho Phehello
- Date: 2019
- Subjects: Drug delivery systems , Pulmonary pharmacology , Nanosilicon , Nanomedicine , Nanoparticles , Mesoporous materials , Silica , Tuberculosis -- Treatment
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/76519 , vital:30590
- Description: Pulmonary drug delivery has historically been used as a route for delivery of therapeutics for respiratory disease management. However, while there are many advantages, there are also some serious limitations, arising mostly from the physical aspects of the inhaler devices. This is more profound when the devices are the driving force for controlling particle size generation, which results in non-uniform particles that end up being swallowed/wasted/expelled. One promising solution to overcome this limitation is to pre-formulate nano/microscale particles with a high degree of manufacturing control. Nanomedicine has advanced such that there are already several nanoparticle formulations commercially available. In the case of tuberculosis treatment, there is an opportunity not only to examine the use of nanoparticles for inhalation therapy, but to take advantage of the fact that the physiochemical environment of diseased tissue is significantly different to health lung tissue (lower pH and increased enzyme concentrations). We formulated two series of nanoparticles, whose design included moieties that could respond to pH and enzymes. To address variability, a Box-Behnken statistical approach was followed to construct mesoporous silica nanoparticles. These “hard nanoparticles” can entrap both lipophilic and hydrophilic drugs and were coated with a pH-sensitive hydrazone linker. It was observed that pH, calcination temperature and ratio of water to silica source played the greatest role, not only in controlling the physicochemical properties of the nanoparticles but also the drug release rate. A second series of nanoparticles were synthesized based on gelatin. This was done partly to add support the comparison of hard (inorganic silica) versus soft, organic particles, but also to enable enzymatic degradation and drug release. Again, diseased lung tissue expresses increased concentrations of gelatinase enzymes that could be used to stimulate drug release at the site of the disease. In addition, it was observed that the non-ionic surfactant C12E10 could interact with the protein via hydrophobic interactions thus affecting the gelatin folding. The folding states affected crosslinking with the pH responsive linker, which in turn affected the rate of drug release. To support the synthetic work, we sought to develop a unique 3D lung model directly from MRI data of tuberculosis infected lungs. This would not only permit the evaluation of our nanoparticles but could be used as a proxy for in-vivo studies in future to predict lung deposition in diseased lung. Thus, this study shows that it is possible to synthesize pH and enzyme sensitive nanoparticles for pulmonary drug delivery in the treatment and management of pulmonary tuberculosis. These particles could be loaded with either hydrophobic or hydrophilic drugs and their distribution in the airway modelled using an in-silico 3D model based on real data. Further development and verification of these results should improve treatment for pulmonary diseases and conditions such as tuberculosis. This is especially urgent in the face of multi-drug resistance and poor side effects profiles for current treatment.
- Full Text:
- Date Issued: 2019
- Authors: Ngoepe, Mpho Phehello
- Date: 2019
- Subjects: Drug delivery systems , Pulmonary pharmacology , Nanosilicon , Nanomedicine , Nanoparticles , Mesoporous materials , Silica , Tuberculosis -- Treatment
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/76519 , vital:30590
- Description: Pulmonary drug delivery has historically been used as a route for delivery of therapeutics for respiratory disease management. However, while there are many advantages, there are also some serious limitations, arising mostly from the physical aspects of the inhaler devices. This is more profound when the devices are the driving force for controlling particle size generation, which results in non-uniform particles that end up being swallowed/wasted/expelled. One promising solution to overcome this limitation is to pre-formulate nano/microscale particles with a high degree of manufacturing control. Nanomedicine has advanced such that there are already several nanoparticle formulations commercially available. In the case of tuberculosis treatment, there is an opportunity not only to examine the use of nanoparticles for inhalation therapy, but to take advantage of the fact that the physiochemical environment of diseased tissue is significantly different to health lung tissue (lower pH and increased enzyme concentrations). We formulated two series of nanoparticles, whose design included moieties that could respond to pH and enzymes. To address variability, a Box-Behnken statistical approach was followed to construct mesoporous silica nanoparticles. These “hard nanoparticles” can entrap both lipophilic and hydrophilic drugs and were coated with a pH-sensitive hydrazone linker. It was observed that pH, calcination temperature and ratio of water to silica source played the greatest role, not only in controlling the physicochemical properties of the nanoparticles but also the drug release rate. A second series of nanoparticles were synthesized based on gelatin. This was done partly to add support the comparison of hard (inorganic silica) versus soft, organic particles, but also to enable enzymatic degradation and drug release. Again, diseased lung tissue expresses increased concentrations of gelatinase enzymes that could be used to stimulate drug release at the site of the disease. In addition, it was observed that the non-ionic surfactant C12E10 could interact with the protein via hydrophobic interactions thus affecting the gelatin folding. The folding states affected crosslinking with the pH responsive linker, which in turn affected the rate of drug release. To support the synthetic work, we sought to develop a unique 3D lung model directly from MRI data of tuberculosis infected lungs. This would not only permit the evaluation of our nanoparticles but could be used as a proxy for in-vivo studies in future to predict lung deposition in diseased lung. Thus, this study shows that it is possible to synthesize pH and enzyme sensitive nanoparticles for pulmonary drug delivery in the treatment and management of pulmonary tuberculosis. These particles could be loaded with either hydrophobic or hydrophilic drugs and their distribution in the airway modelled using an in-silico 3D model based on real data. Further development and verification of these results should improve treatment for pulmonary diseases and conditions such as tuberculosis. This is especially urgent in the face of multi-drug resistance and poor side effects profiles for current treatment.
- Full Text:
- Date Issued: 2019
Structural analysis of some Escherichia coli capsular antigens
- Authors: Hackland, Peter Linton
- Date: 1992
- Subjects: Antigens , Enterobacteriaceae , Escherichia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3758 , http://hdl.handle.net/10962/d1003236 , Antigens , Enterobacteriaceae , Escherichia
- Description: The work presented in this thesis forms part of a collaborative effort to determine the chemical structures of the surface antigens of bacteria which belong to the Enterobacteriaceae. These antigens are largely polysaccharides and occur as lipopolysaccharides and capsular polysaccharides which give rise to the somatic or 0 antigens and the capsular or K antigens, respectively. In recent years interest has mostly been focused on the extracellular polysaccharide antigens expressed by the genus Escherichia coli because of the effect they exert on normal immunological processes and their structural relatedness to the surface antigens of other more pathogenic bacteria. Therefore the molecular structures of the capsular polysaccharides (Kantigens)produced by E. coli 09:K35(AI04a) and 09:K38(A262a) have been determined by novel enzymic, chemical and spectroscopic procedures. These investigations show that the structures of these polysaccharides can be determined by a combination of chemical and spectroscopic procedures , or almost entirely by n.m.r. spectroscopy alone. The in vitro bacteriophage mediated depolymerisation of the native E. coli K35 polysaccharide demonstrates the value of this method for the isolation of oligosaccharides representing the repeating- unit and multiples thereof. Finally E. coli K37 and K38 capsular polysaccharides were used as model compounds for the evaluation of partial and selective reductive cleavage as methods of generating oligosaccharide for further structural analysis. The products of these reactions were analysed largely by a combination of mass spectrometric procedures.
- Full Text:
- Date Issued: 1992
- Authors: Hackland, Peter Linton
- Date: 1992
- Subjects: Antigens , Enterobacteriaceae , Escherichia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3758 , http://hdl.handle.net/10962/d1003236 , Antigens , Enterobacteriaceae , Escherichia
- Description: The work presented in this thesis forms part of a collaborative effort to determine the chemical structures of the surface antigens of bacteria which belong to the Enterobacteriaceae. These antigens are largely polysaccharides and occur as lipopolysaccharides and capsular polysaccharides which give rise to the somatic or 0 antigens and the capsular or K antigens, respectively. In recent years interest has mostly been focused on the extracellular polysaccharide antigens expressed by the genus Escherichia coli because of the effect they exert on normal immunological processes and their structural relatedness to the surface antigens of other more pathogenic bacteria. Therefore the molecular structures of the capsular polysaccharides (Kantigens)produced by E. coli 09:K35(AI04a) and 09:K38(A262a) have been determined by novel enzymic, chemical and spectroscopic procedures. These investigations show that the structures of these polysaccharides can be determined by a combination of chemical and spectroscopic procedures , or almost entirely by n.m.r. spectroscopy alone. The in vitro bacteriophage mediated depolymerisation of the native E. coli K35 polysaccharide demonstrates the value of this method for the isolation of oligosaccharides representing the repeating- unit and multiples thereof. Finally E. coli K37 and K38 capsular polysaccharides were used as model compounds for the evaluation of partial and selective reductive cleavage as methods of generating oligosaccharide for further structural analysis. The products of these reactions were analysed largely by a combination of mass spectrometric procedures.
- Full Text:
- Date Issued: 1992
Combined in silico approaches towards the identification of novel malarial cysteine protease inhibitors
- Authors: Musyoka, Thommas Mutemi
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/4488 , vital:20679
- Description: Malaria an infectious disease caused by a group of parasitic organisms of the Plasmodium genus remains a severe public health problem in Africa, South America and parts of Asia. The leading causes for the persistence of malaria are the emergence of drug resistance to common antimalarial drugs, lack of effective vaccines and the inadequate control of mosquito vectors. Worryingly, accumulating evidence shows that the parasite has developed resistant to the current first-line treatment based on artemisinin. Hence, the identification and characterization of novel drug targets and drugs with unique mode of action remains an urgent priority. The successful sequencing and assembly of genomes from several Plasmodium species has opened an opportune window for the identification of new drug targets. Cysteine proteases are one of the major drug targets to be identified so far. The use of cysteine protease inhibitors coupled with gene manipulation studies has defined specific and putative roles of cysteine proteases which include hemoglobin degradation, erythrocyte rupture, immune evasion and erythrocyte invasion, steps which are central for the completion of the Plasmodium parasite life cycle. In an aim to discover potential novel antimalarials, this thesis focussed on falcipains (FPs), a group of four papain-like cysteine proteases from Plasmodium falciparum. Two of these enzymes, FP-2 and FP-3 are the major hemoglobinases and have been validated as drug targets. For the successful elimination of malaria, drugs must be safe and target both human and wild Plasmodium infective forms. Thus, an incipient aim was to identify protein homologs of these two proteases from other Plasmodium species and the host (human). From BLASTP analysis, up to 16 FP-2 and FP-3 homologs were identified (13 plasmodial proteases and 3 human cathepsins). Using in silico characterization approaches, the intra and inter group sequence, structural, phylogenetic and physicochemical differences were determined. To extend previous work (MSc student) involving docking studies on the identified proteins using known FP-2 and FP-3 inhibitors, a South African natural compound and its ZINC analogs, molecular dynamics and binding free energy studies were performed to determine the stabilities and quantification of the strength of interactions between the different protein-ligand complexes. From the results, key structural elements that regulate the binding and selectivity of non-peptidic compounds onto the different proteins were deciphered. Interaction fingerprints and energy decomposition analysis identified key residues and energetic terms that are central for effective ligand binding. This research presents novel insight essential for the structure-based molecular drug design of more potent antimalarial drugs.
- Full Text:
- Date Issued: 2017
- Authors: Musyoka, Thommas Mutemi
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/4488 , vital:20679
- Description: Malaria an infectious disease caused by a group of parasitic organisms of the Plasmodium genus remains a severe public health problem in Africa, South America and parts of Asia. The leading causes for the persistence of malaria are the emergence of drug resistance to common antimalarial drugs, lack of effective vaccines and the inadequate control of mosquito vectors. Worryingly, accumulating evidence shows that the parasite has developed resistant to the current first-line treatment based on artemisinin. Hence, the identification and characterization of novel drug targets and drugs with unique mode of action remains an urgent priority. The successful sequencing and assembly of genomes from several Plasmodium species has opened an opportune window for the identification of new drug targets. Cysteine proteases are one of the major drug targets to be identified so far. The use of cysteine protease inhibitors coupled with gene manipulation studies has defined specific and putative roles of cysteine proteases which include hemoglobin degradation, erythrocyte rupture, immune evasion and erythrocyte invasion, steps which are central for the completion of the Plasmodium parasite life cycle. In an aim to discover potential novel antimalarials, this thesis focussed on falcipains (FPs), a group of four papain-like cysteine proteases from Plasmodium falciparum. Two of these enzymes, FP-2 and FP-3 are the major hemoglobinases and have been validated as drug targets. For the successful elimination of malaria, drugs must be safe and target both human and wild Plasmodium infective forms. Thus, an incipient aim was to identify protein homologs of these two proteases from other Plasmodium species and the host (human). From BLASTP analysis, up to 16 FP-2 and FP-3 homologs were identified (13 plasmodial proteases and 3 human cathepsins). Using in silico characterization approaches, the intra and inter group sequence, structural, phylogenetic and physicochemical differences were determined. To extend previous work (MSc student) involving docking studies on the identified proteins using known FP-2 and FP-3 inhibitors, a South African natural compound and its ZINC analogs, molecular dynamics and binding free energy studies were performed to determine the stabilities and quantification of the strength of interactions between the different protein-ligand complexes. From the results, key structural elements that regulate the binding and selectivity of non-peptidic compounds onto the different proteins were deciphered. Interaction fingerprints and energy decomposition analysis identified key residues and energetic terms that are central for effective ligand binding. This research presents novel insight essential for the structure-based molecular drug design of more potent antimalarial drugs.
- Full Text:
- Date Issued: 2017
Breaking the karmic complex: the role of transpersonal phenomena in psychotherapy with an adult survivor of child abuse : a clinical case study
- Authors: Oberholzer, Sofia Adriana
- Date: 1997
- Subjects: Transpersonal psychology Reincarnation Adult child abuse victims -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3034 , http://hdl.handle.net/10962/d1002543
- Description: This longitudinal study addresses the interface between the emerging paradigm of Transpersonal Psychology, which recognizes the transbiographical domain of consciousness, and the clinical area of child abuse. By using the transpersonal concept of the karmic complex, which was developed in the discourse of Roger Woolger, it explores the clinical value of past-life regressions and other transpersonal phenomena in the therapeutic process. The study provides an in-depth phenomenological description and a theoreticalheuristic explication of the experience of a single subject who was an adult survivor of physical and sexual abuse as well as early emotional deprivation in childhood, and who, over a four-year period of intensive psychotherapy, experienced a wide spectrum of transpersonal phenomena which included 123 past-life regressions. The therapeutic process could be clearly delineated into a biographical phase, which was dominated by biographical traumas, and a subsequ~nt transpersonal phase, during which the focus was almost exclusively on transpersonal material. This provided the opportunity to explore the therapeutic impact of trans personal mechanisms" of healing on an interlocking constellation of complexes in terms of achieving an integration of archetypal opposites in the psyche. The study provides strong support for transpersonal concepts about the nature of consciousness, as developed by Grof and Woolger. It affirms spirituality as an intrinsic property of the psyche, and verifies that the healing of psychological trauma is on a continuum with the process of spiritual purification and growth. The ,study establishes support for the clinical value of the karmic complex as a conceptual tool and provides a systematic, extended analysis of the multi levelled processes involved in the breaking of the complex.
- Full Text:
- Date Issued: 1997
- Authors: Oberholzer, Sofia Adriana
- Date: 1997
- Subjects: Transpersonal psychology Reincarnation Adult child abuse victims -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3034 , http://hdl.handle.net/10962/d1002543
- Description: This longitudinal study addresses the interface between the emerging paradigm of Transpersonal Psychology, which recognizes the transbiographical domain of consciousness, and the clinical area of child abuse. By using the transpersonal concept of the karmic complex, which was developed in the discourse of Roger Woolger, it explores the clinical value of past-life regressions and other transpersonal phenomena in the therapeutic process. The study provides an in-depth phenomenological description and a theoreticalheuristic explication of the experience of a single subject who was an adult survivor of physical and sexual abuse as well as early emotional deprivation in childhood, and who, over a four-year period of intensive psychotherapy, experienced a wide spectrum of transpersonal phenomena which included 123 past-life regressions. The therapeutic process could be clearly delineated into a biographical phase, which was dominated by biographical traumas, and a subsequ~nt transpersonal phase, during which the focus was almost exclusively on transpersonal material. This provided the opportunity to explore the therapeutic impact of trans personal mechanisms" of healing on an interlocking constellation of complexes in terms of achieving an integration of archetypal opposites in the psyche. The study provides strong support for transpersonal concepts about the nature of consciousness, as developed by Grof and Woolger. It affirms spirituality as an intrinsic property of the psyche, and verifies that the healing of psychological trauma is on a continuum with the process of spiritual purification and growth. The ,study establishes support for the clinical value of the karmic complex as a conceptual tool and provides a systematic, extended analysis of the multi levelled processes involved in the breaking of the complex.
- Full Text:
- Date Issued: 1997
The Integration of Personally-owned Information and Communication Technologies (PICTs) for Teaching and Learning in Resource-Constrained Higher Education Environments – The Case of a Nigerian University
- Authors: Lewis, Oláñrewájú Olúrotimi
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163582 , vital:41050 , doi:10.21504/10962/163582
- Description: Thesis (PhD)--Rhodes University, Faculty of Commerce, Information Systems, 2020
- Full Text:
- Date Issued: 2020
- Authors: Lewis, Oláñrewájú Olúrotimi
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/163582 , vital:41050 , doi:10.21504/10962/163582
- Description: Thesis (PhD)--Rhodes University, Faculty of Commerce, Information Systems, 2020
- Full Text:
- Date Issued: 2020
A study of the reading interests and reading habits of English (first language) secondary-school pupils in South Africa: with particular reference to the Province of Natal
- Authors: Gardner, John Murray
- Date: 1990
- Subjects: Reading interests English language -- Study and teaching (Secondary) -- South Africa -- KwaZulu-Natal Books and reading -- South Africa -- KwaZulu-Natal Readership surveys -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1781 , http://hdl.handle.net/10962/d1003666
- Description: The study derives from a belief, based on many researchers' writings, that wide and frequent book-reading aids the development of knowledge, emotional maturity and human sympathy, which are all essential attributes in a fragmented culture such as South Africa's. It is not accepted that conventional secondary-school literature-teaching in this country promotes a lifelong reading habit among the majority of pupils and a plea is made for the recognition of Reading as a curricular entity in its own right. The study suggests that, owing to a paucity of local research in this field, South African teachers and educational authorities are severely disadvantaged. If they are unable to offer advice based on a proper study of their pupils as readers, they run the risk of guiding many pupils' reading along paths that cannot promise satisfaction and fulfilment. Such stultifying of reading habits would contradict the aims of the present National Core Syllabuses for English (First Language). The thesis sets little store by the investigation of specific bookchoices, pointing out that the validity of such incidental findings, if gleaned from a latitudinal survey, is questionable. Instead, using the findings of questionnaires administered to nearly 2 800 pupils and their teachers, the thesis investigates the relationships between voluntary leisure-time reading and such factors as age, gender, intelligence, academic achievement and standard of living. It also looks at the influences of parents, teachers, peers, contemporary literature-teaching practices, school and public libraries, and leisure- time pursuits other than reading. Many suggestions are offered for further research into finer aspects of those considerations. Many of the findings serve merely to corroborate research from abroad, particularly in respect of age, gender and intelligence. That is none the less alarming when a striking decline in reading is found to occur in the early years of the secondary school. A number of other interesting findings emerge. Standard of living is shown to be inversely correlated with amount of reading, and television-viewing is not found to displace reading. Nor are other leisure-time pursuits found to affect amount of reading: avid readers are by and large extremely active and committed pupils. Reading emerges from the study as providing its own peculiar satisfaction, as does each of the other leisure activities investigated. The challenge is to ensure that infrequent readers become aware of what reading has to offer, and strategies for attempting to achieve that are posited, particularly with regard to the roles of public and school libraries. The roles of teachers and parents are found to be crucial to the development of an appetite for books, and it is suggested that schools and parents liaise formally and closely in this matter. The study groups pupils by a number of personal variables, and investigates their reactions to common forms and genres as well as to certain specifics of style, thereby discussing the relationship between reading, social maturity and academic achievement It argues strongly for recognition of the fact that educating secondary-school pupils in the development of keen and sensitive lifelong reading habits is a process which cannot be systematically taught as a set of skills.
- Full Text:
- Date Issued: 1990
- Authors: Gardner, John Murray
- Date: 1990
- Subjects: Reading interests English language -- Study and teaching (Secondary) -- South Africa -- KwaZulu-Natal Books and reading -- South Africa -- KwaZulu-Natal Readership surveys -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1781 , http://hdl.handle.net/10962/d1003666
- Description: The study derives from a belief, based on many researchers' writings, that wide and frequent book-reading aids the development of knowledge, emotional maturity and human sympathy, which are all essential attributes in a fragmented culture such as South Africa's. It is not accepted that conventional secondary-school literature-teaching in this country promotes a lifelong reading habit among the majority of pupils and a plea is made for the recognition of Reading as a curricular entity in its own right. The study suggests that, owing to a paucity of local research in this field, South African teachers and educational authorities are severely disadvantaged. If they are unable to offer advice based on a proper study of their pupils as readers, they run the risk of guiding many pupils' reading along paths that cannot promise satisfaction and fulfilment. Such stultifying of reading habits would contradict the aims of the present National Core Syllabuses for English (First Language). The thesis sets little store by the investigation of specific bookchoices, pointing out that the validity of such incidental findings, if gleaned from a latitudinal survey, is questionable. Instead, using the findings of questionnaires administered to nearly 2 800 pupils and their teachers, the thesis investigates the relationships between voluntary leisure-time reading and such factors as age, gender, intelligence, academic achievement and standard of living. It also looks at the influences of parents, teachers, peers, contemporary literature-teaching practices, school and public libraries, and leisure- time pursuits other than reading. Many suggestions are offered for further research into finer aspects of those considerations. Many of the findings serve merely to corroborate research from abroad, particularly in respect of age, gender and intelligence. That is none the less alarming when a striking decline in reading is found to occur in the early years of the secondary school. A number of other interesting findings emerge. Standard of living is shown to be inversely correlated with amount of reading, and television-viewing is not found to displace reading. Nor are other leisure-time pursuits found to affect amount of reading: avid readers are by and large extremely active and committed pupils. Reading emerges from the study as providing its own peculiar satisfaction, as does each of the other leisure activities investigated. The challenge is to ensure that infrequent readers become aware of what reading has to offer, and strategies for attempting to achieve that are posited, particularly with regard to the roles of public and school libraries. The roles of teachers and parents are found to be crucial to the development of an appetite for books, and it is suggested that schools and parents liaise formally and closely in this matter. The study groups pupils by a number of personal variables, and investigates their reactions to common forms and genres as well as to certain specifics of style, thereby discussing the relationship between reading, social maturity and academic achievement It argues strongly for recognition of the fact that educating secondary-school pupils in the development of keen and sensitive lifelong reading habits is a process which cannot be systematically taught as a set of skills.
- Full Text:
- Date Issued: 1990
The rupture in the Rainbow: an exploration of Joburg Pride’s fragmentation, 1990 to 2013
- Authors: McLean, Nyx Nicolene Cindy
- Date: 2018
- Subjects: Gay pride celebrations -- South Africa -- Johannesburg , Sexual minorities -- South Africa , Sexual minorities -- Crimes against -- South Africa , Hate crimes -- South Africa , Group identity -- South Africa -- Johannesburg , Identity politics -- South Africa -- Johannesburg , Racism -- South Africa , One in Nine Campaign
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63822 , vital:28492
- Description: In 2012 Joburg Pride was disrupted by the One in Nine Campaign who asked for a moment of silence to honour the lives of victims of hate crimes1 and violence. This interruption of the parade was met with violence from Joburg Pride organisers, marshals and participants, who explicitly told the campaign’s activists that they “had no right to be at the parade.” The activists were predominantly black lesbians and gender non-conforming people. This response suggested that there was no place within Joburg Pride for honouring and mourning the lives of LGBTIAQ people of colour that had been lost to hate crimes. In addition to the call for one minute of silence, the One in Nine Campaign argued that Joburg Pride had become depoliticised as a result of its increased commercialisation. This study is motivated by a need to understand this rupture that occurred in 2012, and to situate it within the history of the LGBTIAQ movement in South Africa. In particular, it investigates the argument made by the One in Nine Campaign that Joburg Pride had become depoliticised and commercialised. The tensions that were facilitated by the 2012 clash and the subsequent formation of alternative Pride events in 2013 are interesting in light of current conversations circulating in broader South African discourse around what it means to be a South African citizen. The study applies a poststructuralist, anti-racist queer feminist lens informed by queer theory, critical theory, critical race theory, and whiteness studies to the historical and current fractures within Joburg Pride. The study analyses Exit newspaper articles from 1990 to 2013, alongside interviews with key stakeholders involved in the 2012 clash. The analysis, informed by both thematic and discursive approaches, interrogates the following themes: depoliticisation, commercialisation, “community”, assimilation, whiteness, racism, rainbowism and rainbow-washing. In this thesis I argue that the commercial interests and apolitical stance of predominantly white Joburg Pride organisers came to exclude LGBTIAQ people of colour’s experiences, at a time when political organising around hate crimes was most necessary. The analysis further highlights a politics of assimilation rooted in rights-based discourse informed by the Rainbow Nation rhetoric of post-apartheid South Africa. Further, this study problematises the notion of “community”, and discusses its strategic use in assimilationist politics within the LGBTIAQ “community”. This study shows that the rupture in the rainbow that occurred at Joburg Pride 2012 was constituted by multiple ruptures that exist in South African society. The issues explored in this thesis are therefore not only useful for constructing more inclusive spaces for LGBTIAQ people, but also for the nation building project of South Africa.
- Full Text:
- Date Issued: 2018
- Authors: McLean, Nyx Nicolene Cindy
- Date: 2018
- Subjects: Gay pride celebrations -- South Africa -- Johannesburg , Sexual minorities -- South Africa , Sexual minorities -- Crimes against -- South Africa , Hate crimes -- South Africa , Group identity -- South Africa -- Johannesburg , Identity politics -- South Africa -- Johannesburg , Racism -- South Africa , One in Nine Campaign
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63822 , vital:28492
- Description: In 2012 Joburg Pride was disrupted by the One in Nine Campaign who asked for a moment of silence to honour the lives of victims of hate crimes1 and violence. This interruption of the parade was met with violence from Joburg Pride organisers, marshals and participants, who explicitly told the campaign’s activists that they “had no right to be at the parade.” The activists were predominantly black lesbians and gender non-conforming people. This response suggested that there was no place within Joburg Pride for honouring and mourning the lives of LGBTIAQ people of colour that had been lost to hate crimes. In addition to the call for one minute of silence, the One in Nine Campaign argued that Joburg Pride had become depoliticised as a result of its increased commercialisation. This study is motivated by a need to understand this rupture that occurred in 2012, and to situate it within the history of the LGBTIAQ movement in South Africa. In particular, it investigates the argument made by the One in Nine Campaign that Joburg Pride had become depoliticised and commercialised. The tensions that were facilitated by the 2012 clash and the subsequent formation of alternative Pride events in 2013 are interesting in light of current conversations circulating in broader South African discourse around what it means to be a South African citizen. The study applies a poststructuralist, anti-racist queer feminist lens informed by queer theory, critical theory, critical race theory, and whiteness studies to the historical and current fractures within Joburg Pride. The study analyses Exit newspaper articles from 1990 to 2013, alongside interviews with key stakeholders involved in the 2012 clash. The analysis, informed by both thematic and discursive approaches, interrogates the following themes: depoliticisation, commercialisation, “community”, assimilation, whiteness, racism, rainbowism and rainbow-washing. In this thesis I argue that the commercial interests and apolitical stance of predominantly white Joburg Pride organisers came to exclude LGBTIAQ people of colour’s experiences, at a time when political organising around hate crimes was most necessary. The analysis further highlights a politics of assimilation rooted in rights-based discourse informed by the Rainbow Nation rhetoric of post-apartheid South Africa. Further, this study problematises the notion of “community”, and discusses its strategic use in assimilationist politics within the LGBTIAQ “community”. This study shows that the rupture in the rainbow that occurred at Joburg Pride 2012 was constituted by multiple ruptures that exist in South African society. The issues explored in this thesis are therefore not only useful for constructing more inclusive spaces for LGBTIAQ people, but also for the nation building project of South Africa.
- Full Text:
- Date Issued: 2018
The development of East London through four decades of municipal control, 1873-1914
- Tankard, Keith Peter Tempest
- Authors: Tankard, Keith Peter Tempest
- Date: 1991
- Subjects: East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2560 , http://hdl.handle.net/10962/d1002413 , East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Description: This thesis is a study in Urban History which explores the development of East London, a port in the Border region of the Eastern Cape, South Africa, through four decades of municipal control from 1873 to 1914. The town had been established in 1847 as a supply route for the British forces during the War of the Axe (7th Frontier War) but the frontier nature of the port led to economic and physical stagnation during its initial 25 years of existence. Indeed, by the time that the municipality was established in 1873, there were still no streets beyond cart tracks, no established water supply, and sanitary conditions were medieval. The Town Council therefore had much to occupy its attention but lack of positive leadership resulted in failure to capitalise on prosperous economic conditions, while a depression in the 1880's led to a further truncation of growth. It was only in the 1890's that a combination of economic growth and vibrant leadership brought about rapid civic advance, with large-scale expenditure on street construction, as well as the establishment of electricity and a tramway system. The outbreak of the Anglo-Boer War in 1899 slowed progress, however, and a post-war depression placed renewed stress on the municipality. The thesis examines the progress of the town on a broad front, dealing with the issues of economic fluctuations, the growth of the harbour as the heart of the trading sector, the physical advance of the municipality, the search for a viable water supply, the evolution of public health and sanitation, and the establishment of the port as a coastal resort. In addition, it studies the conflict of social attitudes among the townspeople, the evolution of racial segregation, and the effects of the Anglo-Boer War on the town, with the influx of some 5 000 Uitlander refugees and the establishment of a Boer concentration camp. A final chapter attempts an analysis of the reasons behind the Town Council's inability to make the best use of its opportunities to foster the development of East London.
- Full Text:
- Date Issued: 1991
- Authors: Tankard, Keith Peter Tempest
- Date: 1991
- Subjects: East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2560 , http://hdl.handle.net/10962/d1002413 , East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Description: This thesis is a study in Urban History which explores the development of East London, a port in the Border region of the Eastern Cape, South Africa, through four decades of municipal control from 1873 to 1914. The town had been established in 1847 as a supply route for the British forces during the War of the Axe (7th Frontier War) but the frontier nature of the port led to economic and physical stagnation during its initial 25 years of existence. Indeed, by the time that the municipality was established in 1873, there were still no streets beyond cart tracks, no established water supply, and sanitary conditions were medieval. The Town Council therefore had much to occupy its attention but lack of positive leadership resulted in failure to capitalise on prosperous economic conditions, while a depression in the 1880's led to a further truncation of growth. It was only in the 1890's that a combination of economic growth and vibrant leadership brought about rapid civic advance, with large-scale expenditure on street construction, as well as the establishment of electricity and a tramway system. The outbreak of the Anglo-Boer War in 1899 slowed progress, however, and a post-war depression placed renewed stress on the municipality. The thesis examines the progress of the town on a broad front, dealing with the issues of economic fluctuations, the growth of the harbour as the heart of the trading sector, the physical advance of the municipality, the search for a viable water supply, the evolution of public health and sanitation, and the establishment of the port as a coastal resort. In addition, it studies the conflict of social attitudes among the townspeople, the evolution of racial segregation, and the effects of the Anglo-Boer War on the town, with the influx of some 5 000 Uitlander refugees and the establishment of a Boer concentration camp. A final chapter attempts an analysis of the reasons behind the Town Council's inability to make the best use of its opportunities to foster the development of East London.
- Full Text:
- Date Issued: 1991
Intellectualisation of African languages with particular reference to isiXhosa
- Authors: Maseko, Pamela
- Date: 2011
- Subjects: Xhosa language -- Study and teaching -- South Africa , Language and education -- South Africa , African languages
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/58035 , vital:27035
- Description: The research explores the relationship between language and education, and motivates for the intellectualisation of African languages, isiXhosa in particular, and for their use in education. The main rationale behind this is that access to, and success in education can largely be realised if that education is mediated in one’s first language. The thesis discusses works of prominent scholars who have written on the subject - relating cognitive abilities and achievement in education to language in which that education is offered. The lack of terminology in new domains in African languages as barrier to mother tongue education is laid bare by looking specifically at the history of intellectualisation of isiXhosa, from the missionaries in the 1820s up to the new endeavours as recently as 2008. Terminologies that were developed during the Bantu Education era, where development of isiXhosa and other indigenous African languages was accelerated in order to respond to the demands of moedertaal-onderwys (mother tongue education) are surveyed, and the process of their development analysed. Three main terminology lists developed during this period are analysed against terminology development principles, approaches and methods that are seen as a measure to ensure quality terminology development. The efforts of the development of isiXhosa during the post-apartheid South Africa, especially the government-driven initiatives, are also critiqued even though these are not as effective and as extensive, especially in education. The result of this analysis is that African languages and isiXhosa in particular, can be used in scientific disciplines and at the highest levels of education. Its grammar is advanced, and its lexicon is extensive such that new concepts that need to be named can be named, using appropriate term creation strategies. There are also technological tools such as WordSmith tools that can be used that can advance its development, ensuring that the concept represented in the newly-created term is precise, concise and appropriate in terms of its discipline. Therefore it is argued that, in the interim, terminologies should be developed, in various subjects, to support learning, which at this stage is mediated in English, for those students who have other languages as mother tongue. Those terminologies that have been developed in the various historical periods should be collated, revised and brought into the classrooms. The thesis argues that real intellectualisation of isiXhosa and other African languages rests on the use of these languages in classrooms and lecture halls, and in the value that all role players place on these languages.
- Full Text:
- Date Issued: 2011
- Authors: Maseko, Pamela
- Date: 2011
- Subjects: Xhosa language -- Study and teaching -- South Africa , Language and education -- South Africa , African languages
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/58035 , vital:27035
- Description: The research explores the relationship between language and education, and motivates for the intellectualisation of African languages, isiXhosa in particular, and for their use in education. The main rationale behind this is that access to, and success in education can largely be realised if that education is mediated in one’s first language. The thesis discusses works of prominent scholars who have written on the subject - relating cognitive abilities and achievement in education to language in which that education is offered. The lack of terminology in new domains in African languages as barrier to mother tongue education is laid bare by looking specifically at the history of intellectualisation of isiXhosa, from the missionaries in the 1820s up to the new endeavours as recently as 2008. Terminologies that were developed during the Bantu Education era, where development of isiXhosa and other indigenous African languages was accelerated in order to respond to the demands of moedertaal-onderwys (mother tongue education) are surveyed, and the process of their development analysed. Three main terminology lists developed during this period are analysed against terminology development principles, approaches and methods that are seen as a measure to ensure quality terminology development. The efforts of the development of isiXhosa during the post-apartheid South Africa, especially the government-driven initiatives, are also critiqued even though these are not as effective and as extensive, especially in education. The result of this analysis is that African languages and isiXhosa in particular, can be used in scientific disciplines and at the highest levels of education. Its grammar is advanced, and its lexicon is extensive such that new concepts that need to be named can be named, using appropriate term creation strategies. There are also technological tools such as WordSmith tools that can be used that can advance its development, ensuring that the concept represented in the newly-created term is precise, concise and appropriate in terms of its discipline. Therefore it is argued that, in the interim, terminologies should be developed, in various subjects, to support learning, which at this stage is mediated in English, for those students who have other languages as mother tongue. Those terminologies that have been developed in the various historical periods should be collated, revised and brought into the classrooms. The thesis argues that real intellectualisation of isiXhosa and other African languages rests on the use of these languages in classrooms and lecture halls, and in the value that all role players place on these languages.
- Full Text:
- Date Issued: 2011
A conductimetric investigation of phenomena in extremely dilute aqueous solutions
- Authors: Faure, Pierre Knobel
- Date: 1957
- Subjects: Adsorption , Solution (Chemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4524 , http://hdl.handle.net/10962/d1014891
- Description: 1. The apparatus used in this investigation is fully described, and a new method is outlined for the calibration of bridge resistances "in situ". 2. A chart is given for the accurate correction of weights in air to weights in vacuum for a range of temperatures extending from 10° to 28°C, and for pressures from 690 to 730 mm. 3. An automatic recycling still has been designed for the continuous production of "ultra-pure" water. This still is capable of delivering daily, in routine operation, 16 l. of water of conductivity less than 100 nm/cm after aeration with "C0₂- and NH₃-free" air. 4. A very soluble layer appears to form on the surface of' glass when it is dried; this layer is readily removed on contact with water. 5. The removal of carbon dioxide and of ammonia from aqueous solution by aeration with an indifferent gas has been fully investigated, and it has been shown that these gases can be completely eliminated by such a process. Whereas the carbon dioxide is removed fairly rapidly, however, the ammonia, whether present alone or together with carbon dioxide, only goes out of solution rather slowly. 6. It has been shown that ammonia is adsorbed from aqueous solution on the glass walls of the cell. 7. There does not appear to be any ammonium bicarbonate in the residual impurity left in the "ultra-pure" water obtained from the still; the impurity can, in fact, be regarded as neutral salt with sufficient accuracy for most purposes. 8. The resistance change which accompanies any variation in the rate of bubbling of the stirring gas through the water has been investigated, but no solution has been found as to the cause of this change. 9. A comparison has been made of the efficiency of different gases for stirring purposes, and it seems that, for general work, nitrogen is by far the most suitable of the common gases. 10. The extrapolation to be used for converting resistances to their values at infinite frequency appears ...
- Full Text:
- Date Issued: 1957
- Authors: Faure, Pierre Knobel
- Date: 1957
- Subjects: Adsorption , Solution (Chemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4524 , http://hdl.handle.net/10962/d1014891
- Description: 1. The apparatus used in this investigation is fully described, and a new method is outlined for the calibration of bridge resistances "in situ". 2. A chart is given for the accurate correction of weights in air to weights in vacuum for a range of temperatures extending from 10° to 28°C, and for pressures from 690 to 730 mm. 3. An automatic recycling still has been designed for the continuous production of "ultra-pure" water. This still is capable of delivering daily, in routine operation, 16 l. of water of conductivity less than 100 nm/cm after aeration with "C0₂- and NH₃-free" air. 4. A very soluble layer appears to form on the surface of' glass when it is dried; this layer is readily removed on contact with water. 5. The removal of carbon dioxide and of ammonia from aqueous solution by aeration with an indifferent gas has been fully investigated, and it has been shown that these gases can be completely eliminated by such a process. Whereas the carbon dioxide is removed fairly rapidly, however, the ammonia, whether present alone or together with carbon dioxide, only goes out of solution rather slowly. 6. It has been shown that ammonia is adsorbed from aqueous solution on the glass walls of the cell. 7. There does not appear to be any ammonium bicarbonate in the residual impurity left in the "ultra-pure" water obtained from the still; the impurity can, in fact, be regarded as neutral salt with sufficient accuracy for most purposes. 8. The resistance change which accompanies any variation in the rate of bubbling of the stirring gas through the water has been investigated, but no solution has been found as to the cause of this change. 9. A comparison has been made of the efficiency of different gases for stirring purposes, and it seems that, for general work, nitrogen is by far the most suitable of the common gases. 10. The extrapolation to be used for converting resistances to their values at infinite frequency appears ...
- Full Text:
- Date Issued: 1957
Reading to learn for secondary schooling: an interventionist action research study within a South African under-privileged setting
- Authors: Mataka, Tawanda Wallace
- Date: 2019
- Subjects: Rose, David, 1955-. Reading to learn , Reading (Secondary) , English language -- Study and teaching (Secondary) -- Foreign speakers -- South Africa , English language -- Study and teaching (Secondary) -- Foreign speakers -- South Africa -- Case studies , Literacy -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/92191 , vital:30706
- Description: The study examined the contribution that Rose’s (2005) Reading to Learn (RtL) methodology made in development of advanced literacy abilities recommended in the schooling system. RtL was influenced by Bernstein’s theory of pedagogic discourse, Bruner, Vygotsky’s social learning theory and Halliday’s systemic functional linguistics theory. The study used the same cohort of learners during Grades 11 and 12 in a black township secondary school in Grahamstown, Eastern Cape, South Africa. RtL was birthed in Australia with the intention of accelerating literacy development of learners in disadvantaged communities. Based on its success in Australia, I implemented the methodology against a backdrop of continuously declining literacy standards in South African primary and secondary schools. Researchers on literacy acknowledge that socioeconomic and geosocial circumstances cannot be divorced from poor literacy performances in South African schools. Although these two factors play a role in regressing literacy, pedagogical approaches play a role. RtL was employed as an intervention strategy with learners whose literacy abilities were found lacking in comparison to curriculum demands. Despite the focus being on learners whose performance was below expected academic levels, the able learners were motivated to further their advanced abilities. The learners whose performance was previously compromised performed to par with their able counterparts. RtL provided all learners an opportunity to apply, with less difficulty, the language approved by the schooling system. The two research questions sought to illuminate the role RtL played in developing learners’ ability to read, so that they could converse with text and put into writing practice what they had read. In this regard, creative and transactional assignments were written, and performance assessed to evaluate the RtL intervention. Secondly, the research allowed me to get an insight through interviews with learners as to how they were positively or negatively influenced through RtL in learning English as a First Additional Language. The study was a longitudinal action research study which had a life span of 22 months. It was dominantly qualitative with a thin quantitative strand. Data to evaluate effectiveness was generated from learners’ written work and interviews. The learners’ work was analysed using an RtL assessment tool adopted from Rose (2018), for the purposes of uniformity and reliability. Findings from interviews highlighted various views regarding the positive impact of RtL. What emerged from the findings is a reflection of the positive impact RtL had on literacy development. Significantly, learners’ work improved across the board, true to Rose’s assertion that learners exposed to teaching using RtL principles experience accelerated literacy development. Based on these findings, RtL implemented in a township setting in South Africa yields results similar to those in Australia and other countries.
- Full Text:
- Date Issued: 2019
- Authors: Mataka, Tawanda Wallace
- Date: 2019
- Subjects: Rose, David, 1955-. Reading to learn , Reading (Secondary) , English language -- Study and teaching (Secondary) -- Foreign speakers -- South Africa , English language -- Study and teaching (Secondary) -- Foreign speakers -- South Africa -- Case studies , Literacy -- South Africa -- Makhanda
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/92191 , vital:30706
- Description: The study examined the contribution that Rose’s (2005) Reading to Learn (RtL) methodology made in development of advanced literacy abilities recommended in the schooling system. RtL was influenced by Bernstein’s theory of pedagogic discourse, Bruner, Vygotsky’s social learning theory and Halliday’s systemic functional linguistics theory. The study used the same cohort of learners during Grades 11 and 12 in a black township secondary school in Grahamstown, Eastern Cape, South Africa. RtL was birthed in Australia with the intention of accelerating literacy development of learners in disadvantaged communities. Based on its success in Australia, I implemented the methodology against a backdrop of continuously declining literacy standards in South African primary and secondary schools. Researchers on literacy acknowledge that socioeconomic and geosocial circumstances cannot be divorced from poor literacy performances in South African schools. Although these two factors play a role in regressing literacy, pedagogical approaches play a role. RtL was employed as an intervention strategy with learners whose literacy abilities were found lacking in comparison to curriculum demands. Despite the focus being on learners whose performance was below expected academic levels, the able learners were motivated to further their advanced abilities. The learners whose performance was previously compromised performed to par with their able counterparts. RtL provided all learners an opportunity to apply, with less difficulty, the language approved by the schooling system. The two research questions sought to illuminate the role RtL played in developing learners’ ability to read, so that they could converse with text and put into writing practice what they had read. In this regard, creative and transactional assignments were written, and performance assessed to evaluate the RtL intervention. Secondly, the research allowed me to get an insight through interviews with learners as to how they were positively or negatively influenced through RtL in learning English as a First Additional Language. The study was a longitudinal action research study which had a life span of 22 months. It was dominantly qualitative with a thin quantitative strand. Data to evaluate effectiveness was generated from learners’ written work and interviews. The learners’ work was analysed using an RtL assessment tool adopted from Rose (2018), for the purposes of uniformity and reliability. Findings from interviews highlighted various views regarding the positive impact of RtL. What emerged from the findings is a reflection of the positive impact RtL had on literacy development. Significantly, learners’ work improved across the board, true to Rose’s assertion that learners exposed to teaching using RtL principles experience accelerated literacy development. Based on these findings, RtL implemented in a township setting in South Africa yields results similar to those in Australia and other countries.
- Full Text:
- Date Issued: 2019