A taxonomic revision of the genera of the subtribe Dracophilinae (Aizoaceae: Ruschioideae)
- Authors: Mannheimer, Coleen Anne
- Date: 2006
- Subjects: Aizoaceae , Plants -- Classification , Cladistic analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4247 , http://hdl.handle.net/10962/d1007461 , Aizoaceae , Plants -- Classification , Cladistic analysis
- Description: Namibia, Juttadinteria and Dracophilus, the three genera belonging to the subtribe Dracophilinae Schwantes (Aizoaceae: Ruschioideae) were revised. Macro-morphology, leaf anatomy and micromorphology of leaf epidermides, pollen, tapetal orbicules and seed were studied in order to test taxon limits, to determine relationships between taxa, and to improve knowledge of their characteristics as well as the taxonomy of the subtribe. The investigation was based on herbarium specimens, field observations and cultivated, living plants. Phenetic cluster analyses were used to confirm species while intergeneric and interspecific relationships of the taxa so indicated were later tested by means of a phylogenetic analysis. The existence of the three genera was provisionally upheld by this study although phylogenetic analysis showed Namibia nested as a strongly supported monophyletic group within a poorly supported luttadinteria. Further work is needed to clarify whether Namibia should be sunk into Juttadinteria. The latest treatments of Juttadinteria and Dracophilus by Hartmann (2001) were supprted. However, in contrast to her latest treatment of Namibia, N. pomonae was sunk into N. cinerea and N. ponderosa was reinstated and typified. Juttadinteria was found to be a poorly resolved genus with many intergrading and overlapping characters, possible due to recent speciation. Possible subspecific groups within J. deserticola and J. simpsonii were indicated by the phenetic study but further work is needed before any formal infraspecific taxonomic rank can be assigned to them. Detailed descriptions of the nine elucidated species and the three genera as well as new keys for their identification are provided in order to facilitate further work in this group. Distribution maps are provided for the genera and species, and the subtribe. Variation of character states within the subtribe, distribution area, ecology and biology are discussed.
- Full Text:
- Date Issued: 2006
- Authors: Mannheimer, Coleen Anne
- Date: 2006
- Subjects: Aizoaceae , Plants -- Classification , Cladistic analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4247 , http://hdl.handle.net/10962/d1007461 , Aizoaceae , Plants -- Classification , Cladistic analysis
- Description: Namibia, Juttadinteria and Dracophilus, the three genera belonging to the subtribe Dracophilinae Schwantes (Aizoaceae: Ruschioideae) were revised. Macro-morphology, leaf anatomy and micromorphology of leaf epidermides, pollen, tapetal orbicules and seed were studied in order to test taxon limits, to determine relationships between taxa, and to improve knowledge of their characteristics as well as the taxonomy of the subtribe. The investigation was based on herbarium specimens, field observations and cultivated, living plants. Phenetic cluster analyses were used to confirm species while intergeneric and interspecific relationships of the taxa so indicated were later tested by means of a phylogenetic analysis. The existence of the three genera was provisionally upheld by this study although phylogenetic analysis showed Namibia nested as a strongly supported monophyletic group within a poorly supported luttadinteria. Further work is needed to clarify whether Namibia should be sunk into Juttadinteria. The latest treatments of Juttadinteria and Dracophilus by Hartmann (2001) were supprted. However, in contrast to her latest treatment of Namibia, N. pomonae was sunk into N. cinerea and N. ponderosa was reinstated and typified. Juttadinteria was found to be a poorly resolved genus with many intergrading and overlapping characters, possible due to recent speciation. Possible subspecific groups within J. deserticola and J. simpsonii were indicated by the phenetic study but further work is needed before any formal infraspecific taxonomic rank can be assigned to them. Detailed descriptions of the nine elucidated species and the three genera as well as new keys for their identification are provided in order to facilitate further work in this group. Distribution maps are provided for the genera and species, and the subtribe. Variation of character states within the subtribe, distribution area, ecology and biology are discussed.
- Full Text:
- Date Issued: 2006
A VLBI polarisation study of 43 GHZ SiO masers towards VY CMA
- Authors: Richter, Laura
- Date: 2006
- Subjects: Very long baseline interferometry , Polarization (Light) , Masers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5498 , http://hdl.handle.net/10962/d1005284
- Description: This thesis reports the calibration, imaging and analysis of one epoch of VLBI observations of the v (italics) = J (italics) = 1-0 transition of SiO towards VY CMa. Full polarisation information was recorded, allowing high resolution synthesis maps of each of the four Stokes parameters to be produced. A total of 81 maser components were extracted from the total intensity map, each approximately 1 mas in size. The emission spans approximately 100 x 80 mas in right ascension and declination and is concentrated to the east. The maser component positions were fitted to a ring of radius ~ 3.2R₊ (italics), or 7.2 x 1O¹⁴ cm for a stellar distance of 1.5 kpc. If the stellar position is assumed to be the centre of this ring then almost all of the maser components fall within the inner dust shell radius, which is at ~ 5R (italics)ϰ All of the maser components fall between 1.5R (italics)ϰ and 6R (italics)ϰ. A velocity gradient with position angle was observed in the sparsely filled western region of the maser ring. If interpreted as evidence of shell rotation, this gradient implies a rotational velocity of v (italics) rot (subscirpt) sin i (italics) = 18 km.s⁻¹. The fractional circular and linear polarisations of the maser spots were derived from the Stokes parameter maps. The mean fractional circular polarisation of the masers components was ~ 2 percent and the median fractional linear polarisation was ~ 6 percent, with many spots displaying over ~ 30 percent linear polarisation. The mean circular polarisation implies a magnetic field of ~ 4 G in the SiO maser region if the polarisation is due to Zeeman splitting. Two maser components display a rotation of linear polarisation position angle with velocity, possibly implying a connection between the magnetic field and the velocity field variations in the region of these components.
- Full Text:
- Date Issued: 2006
- Authors: Richter, Laura
- Date: 2006
- Subjects: Very long baseline interferometry , Polarization (Light) , Masers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5498 , http://hdl.handle.net/10962/d1005284
- Description: This thesis reports the calibration, imaging and analysis of one epoch of VLBI observations of the v (italics) = J (italics) = 1-0 transition of SiO towards VY CMa. Full polarisation information was recorded, allowing high resolution synthesis maps of each of the four Stokes parameters to be produced. A total of 81 maser components were extracted from the total intensity map, each approximately 1 mas in size. The emission spans approximately 100 x 80 mas in right ascension and declination and is concentrated to the east. The maser component positions were fitted to a ring of radius ~ 3.2R₊ (italics), or 7.2 x 1O¹⁴ cm for a stellar distance of 1.5 kpc. If the stellar position is assumed to be the centre of this ring then almost all of the maser components fall within the inner dust shell radius, which is at ~ 5R (italics)ϰ All of the maser components fall between 1.5R (italics)ϰ and 6R (italics)ϰ. A velocity gradient with position angle was observed in the sparsely filled western region of the maser ring. If interpreted as evidence of shell rotation, this gradient implies a rotational velocity of v (italics) rot (subscirpt) sin i (italics) = 18 km.s⁻¹. The fractional circular and linear polarisations of the maser spots were derived from the Stokes parameter maps. The mean fractional circular polarisation of the masers components was ~ 2 percent and the median fractional linear polarisation was ~ 6 percent, with many spots displaying over ~ 30 percent linear polarisation. The mean circular polarisation implies a magnetic field of ~ 4 G in the SiO maser region if the polarisation is due to Zeeman splitting. Two maser components display a rotation of linear polarisation position angle with velocity, possibly implying a connection between the magnetic field and the velocity field variations in the region of these components.
- Full Text:
- Date Issued: 2006
An appraisal of the impact of the Fast Track Land Reform Programme on land use practices, livelihoods and the natural environment at three study areas in Kadoma District, Zimbabwe
- Authors: Chigumira, Easther C
- Date: 2006
- Subjects: Land reform -- Zimbabwe , Land tenure -- Zimbabwe , Land settlement -- Government policy -- Zimbabwe , Land use -- Government policy -- Zimbabwe , Agriculture -- Zimbabwe , Sustainable development -- Zimbabwe , Rural development -- Zimbabwe , Zimbabwe -- Economic conditions , Natural resources -- Zimbabwe , Environmental policy -- Zimbabwe , Farms, Large -- Zimbabwe , Farms, Small -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4815 , http://hdl.handle.net/10962/d1005489 , Land reform -- Zimbabwe , Land tenure -- Zimbabwe , Land settlement -- Government policy -- Zimbabwe , Land use -- Government policy -- Zimbabwe , Agriculture -- Zimbabwe , Sustainable development -- Zimbabwe , Rural development -- Zimbabwe , Zimbabwe -- Economic conditions , Natural resources -- Zimbabwe , Environmental policy -- Zimbabwe , Farms, Large -- Zimbabwe , Farms, Small -- Zimbabwe
- Description: This research appraises the impact of the Fast Track Land Reform Programme at three resettled communities in Kadoma District, Zimbabwe. In particular it assesses the livelihood practices of land recipients and their effects on the natural environment. Two of the communities, Lanteglos and CC Molina were resettled under the A1 villagised and self-contained settlement scheme and are found in the Natural Farming Region III. Pamene, the third community, was resettled under the A2 small-scale commercial settlement scheme and is found in the Natural Farming Region IIb. Multiple research methods including household surveys, interviews, observations, reviews of literature and map construction through the use of Geographic Information Systems, allowed for the collection of empirical, descriptive, and spatial data to provide for the appraisal. The land use practices included dry land crop production, livestock rearing, vegetable gardening and exploitation of the natural environment for a variety of purposes. Farming was mostly subsistence with the use of traditional equipment by all three communities. Tenure was perceived to be insecure by beneficiaries and although a variety of papers to show ownership were held, none provided for leasing or freehold tenure. Despite acquiring natural capital from the resettlement process, the findings of this research show low levels of financial, physical and social capital amongst beneficiaries. Moreover climatic variability, the declining macro-economic and unstable political environment and little support from government have adversely affected the livelihoods of beneficiaries. The implication of all this has been a reduction in livelihoods that are based solely on agricultural production, leading to off-farm practices primarily exploiting the natural environment. The long term effect would be increased degradation of the environment, leading to reduced arable and grazing land, and thereby hindering sustainable livelihoods from farming. Recommendations are proposed based on this research’s findings being typical in Zimbabwe. Central to this is the need for government to revise its present land policy and, provide for a comprehensive and holistic land policy that should be based on the vision of how agriculture should evolve in Zimbabwe
- Full Text:
- Date Issued: 2006
- Authors: Chigumira, Easther C
- Date: 2006
- Subjects: Land reform -- Zimbabwe , Land tenure -- Zimbabwe , Land settlement -- Government policy -- Zimbabwe , Land use -- Government policy -- Zimbabwe , Agriculture -- Zimbabwe , Sustainable development -- Zimbabwe , Rural development -- Zimbabwe , Zimbabwe -- Economic conditions , Natural resources -- Zimbabwe , Environmental policy -- Zimbabwe , Farms, Large -- Zimbabwe , Farms, Small -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4815 , http://hdl.handle.net/10962/d1005489 , Land reform -- Zimbabwe , Land tenure -- Zimbabwe , Land settlement -- Government policy -- Zimbabwe , Land use -- Government policy -- Zimbabwe , Agriculture -- Zimbabwe , Sustainable development -- Zimbabwe , Rural development -- Zimbabwe , Zimbabwe -- Economic conditions , Natural resources -- Zimbabwe , Environmental policy -- Zimbabwe , Farms, Large -- Zimbabwe , Farms, Small -- Zimbabwe
- Description: This research appraises the impact of the Fast Track Land Reform Programme at three resettled communities in Kadoma District, Zimbabwe. In particular it assesses the livelihood practices of land recipients and their effects on the natural environment. Two of the communities, Lanteglos and CC Molina were resettled under the A1 villagised and self-contained settlement scheme and are found in the Natural Farming Region III. Pamene, the third community, was resettled under the A2 small-scale commercial settlement scheme and is found in the Natural Farming Region IIb. Multiple research methods including household surveys, interviews, observations, reviews of literature and map construction through the use of Geographic Information Systems, allowed for the collection of empirical, descriptive, and spatial data to provide for the appraisal. The land use practices included dry land crop production, livestock rearing, vegetable gardening and exploitation of the natural environment for a variety of purposes. Farming was mostly subsistence with the use of traditional equipment by all three communities. Tenure was perceived to be insecure by beneficiaries and although a variety of papers to show ownership were held, none provided for leasing or freehold tenure. Despite acquiring natural capital from the resettlement process, the findings of this research show low levels of financial, physical and social capital amongst beneficiaries. Moreover climatic variability, the declining macro-economic and unstable political environment and little support from government have adversely affected the livelihoods of beneficiaries. The implication of all this has been a reduction in livelihoods that are based solely on agricultural production, leading to off-farm practices primarily exploiting the natural environment. The long term effect would be increased degradation of the environment, leading to reduced arable and grazing land, and thereby hindering sustainable livelihoods from farming. Recommendations are proposed based on this research’s findings being typical in Zimbabwe. Central to this is the need for government to revise its present land policy and, provide for a comprehensive and holistic land policy that should be based on the vision of how agriculture should evolve in Zimbabwe
- Full Text:
- Date Issued: 2006
An insight into magma supply to the Karoo Igneous Province a geochemical investigation of Karoo dykes adjacent to the Northwestern sector of the Lesotho volcanic remnant
- Authors: Mitha, Vindina Ramesh
- Date: 2006
- Subjects: Flood basalts -- Lesotho , Volcanism -- Lesotho , Magmatism -- Lesotho , Dikes (Geology) -- Lesotho , Geochemistry -- Lesotho , Lava -- Lesotho
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4973 , http://hdl.handle.net/10962/d1005585 , Flood basalts -- Lesotho , Volcanism -- Lesotho , Magmatism -- Lesotho , Dikes (Geology) -- Lesotho , Geochemistry -- Lesotho , Lava -- Lesotho
- Description: The emplacement of continental flood basalt provinces is often ascribed to fissure eruption. However, in many provinces the locations of actual vent complexes remains illusive. In southern Africa, the Karoo continental flood basalt province was erupted during the Jurassic between 183 and 179 Ma. The southernmost outcrop of the Karoo continental flood basalt lavas is the Lesotho remnant; and is comprised of the Drakensberg Group which forms the uppermost portion of the Karoo Supergroup. The geochemical stratigraphy for the Drakensberg Group is well established. At the base, there are a number of small volume compositionally diverse units, which form the Barkly East Formation, overlying which, there are larger volume, compositionally less variable units of the Lesotho Formation, which form the bulk of the volcanic sequence. The Lesotho remnant is associated with an abundance of dykes in the adjacent vicinity. This suggests that the lavas were fed from local rather than distal eruption sites. This study presents whole rock major and trace element data for 94 dykes and three sills from the northern Lesotho - northeastern Free State region and demonstrates that on the basis of geochemistry, all 97 intrusions can be correlated with various units of the northern Barkly East and Lesotho Formations. In addition, the petrographical; characteristics, orientation and distribution of the dykes do not correlate with geochemistry. Geochemical discrimination diagrams have been used to identify five compositionally diverse dykes, which are similar to the northern Barkly East Formation units. Three dykes are characteristic of the Letele unit and two are compositionally similar to the Wonderkop unit. Although the geochemical characteristics of the Lesotho Formation units are rather well constrained, the composition of these units is typified by considerable overlap in composition. Therefore, since unambiguous classification of dykes with geochemical similarities to the various units of the Lesotho Formation is unachievable using an empirical approach, the multivariate forward-stepwise discriminant function analysis (DFA) technique was used to facilitate the classification of the remaining 89 dykes and three sills. Forward-stepwise DFA classified 23 dykes as having compositional similarities to the Mafika Lisiu unit, 29 as having compositions of the Maloti or Senqu types; and 32 as having the composition of the Mothae type. In addition, eight dykes are compositionally similar to the Oxbow dykes, which intrude the Senqu unit in northern Lesotho. These results suggest that that the Lesotho remnant was fed from local eruption sites and that long distance magma transport for the bulk of the Lesotho remnant basalt lavas is unlikely.
- Full Text:
- Date Issued: 2006
- Authors: Mitha, Vindina Ramesh
- Date: 2006
- Subjects: Flood basalts -- Lesotho , Volcanism -- Lesotho , Magmatism -- Lesotho , Dikes (Geology) -- Lesotho , Geochemistry -- Lesotho , Lava -- Lesotho
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4973 , http://hdl.handle.net/10962/d1005585 , Flood basalts -- Lesotho , Volcanism -- Lesotho , Magmatism -- Lesotho , Dikes (Geology) -- Lesotho , Geochemistry -- Lesotho , Lava -- Lesotho
- Description: The emplacement of continental flood basalt provinces is often ascribed to fissure eruption. However, in many provinces the locations of actual vent complexes remains illusive. In southern Africa, the Karoo continental flood basalt province was erupted during the Jurassic between 183 and 179 Ma. The southernmost outcrop of the Karoo continental flood basalt lavas is the Lesotho remnant; and is comprised of the Drakensberg Group which forms the uppermost portion of the Karoo Supergroup. The geochemical stratigraphy for the Drakensberg Group is well established. At the base, there are a number of small volume compositionally diverse units, which form the Barkly East Formation, overlying which, there are larger volume, compositionally less variable units of the Lesotho Formation, which form the bulk of the volcanic sequence. The Lesotho remnant is associated with an abundance of dykes in the adjacent vicinity. This suggests that the lavas were fed from local rather than distal eruption sites. This study presents whole rock major and trace element data for 94 dykes and three sills from the northern Lesotho - northeastern Free State region and demonstrates that on the basis of geochemistry, all 97 intrusions can be correlated with various units of the northern Barkly East and Lesotho Formations. In addition, the petrographical; characteristics, orientation and distribution of the dykes do not correlate with geochemistry. Geochemical discrimination diagrams have been used to identify five compositionally diverse dykes, which are similar to the northern Barkly East Formation units. Three dykes are characteristic of the Letele unit and two are compositionally similar to the Wonderkop unit. Although the geochemical characteristics of the Lesotho Formation units are rather well constrained, the composition of these units is typified by considerable overlap in composition. Therefore, since unambiguous classification of dykes with geochemical similarities to the various units of the Lesotho Formation is unachievable using an empirical approach, the multivariate forward-stepwise discriminant function analysis (DFA) technique was used to facilitate the classification of the remaining 89 dykes and three sills. Forward-stepwise DFA classified 23 dykes as having compositional similarities to the Mafika Lisiu unit, 29 as having compositions of the Maloti or Senqu types; and 32 as having the composition of the Mothae type. In addition, eight dykes are compositionally similar to the Oxbow dykes, which intrude the Senqu unit in northern Lesotho. These results suggest that that the Lesotho remnant was fed from local eruption sites and that long distance magma transport for the bulk of the Lesotho remnant basalt lavas is unlikely.
- Full Text:
- Date Issued: 2006
An investigation into the neuroprotective effects of dehydroepiandrosterone
- Authors: Palvie, Stefanie Michelle
- Date: 2006
- Subjects: Aging -- Physiological aspects , Nervous system -- Degeneration -- Treatment , Steroid hormones , Dehydroepiandrosterone , Dehydroepiandrosterone -- Therapeutic use , Neurosciences , Neuroanatomy , Apoptosis , Pineal gland -- Physiology , Neurotoxic agents , Free radicals (Chemistry) -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3782 , http://hdl.handle.net/10962/d1003260 , Aging -- Physiological aspects , Nervous system -- Degeneration -- Treatment , Steroid hormones , Dehydroepiandrosterone , Dehydroepiandrosterone -- Therapeutic use , Neurosciences , Neuroanatomy , Apoptosis , Pineal gland -- Physiology , Neurotoxic agents , Free radicals (Chemistry) -- Physiological effect
- Description: Dehydroepiandrosterone, a C-19 steroid, is found endogenously with the highest circulating serum levels. It is converted to important steroids such as the sex hormones oestrogen and testosterone. DHEA has come under the spotlight as a purported “fountain of youth” due to its well-characterised age-related decline. The supplementation of DHEA in both the elderly and those with a pathophysiological deficiency has been shown to be of benefit, particularly with regard to wellbeing and depression. The role of DHEA in the periphery has not been elucidated beyond its role as a precursor hormone in sex steroid biosynthesis, though it has been established as a neuroactive neurosteroid, capable of exerting neuroprotective effects in the brain. Since the importance of free radicals in aging and neurodegeneration is well established, investigations were conducted on the ability of DHEA to inhibit free radical generation or scavenge existing free radicals. DHEA was able to significantly inhibit quinolinic acid-induced lipid peroxidation, a measure of membrane damage, over a range of concentrations, although the reduction did not appear to be dose-dependent. This was observed in both in vitro and in vivo studies. Thus, the ability of a compound to reduce the degree of lipid peroxidation may indicate its value as a neuroprotectant. However, DHEA did not significantly reduce cyanide induced generation of the superoxide free radical, suggesting that DHEA is not an effective free radical scavenger of the superoxide anion and that the reduction in lipid peroxidation does not occur through a scavenging mechanism. Apoptosis is a physiological process which is necessary for development and homeostasis. However, this form of programmed cell death can be initiated through various mechanisms and too much apoptotic cell death results in deleterious effects in the body. DHEA was shown not to induce apoptosis. Even the lowest concentration of DHEA investigated in this thesis shows a remarkable decrease in the degree of apoptosis caused by intrahippocampal chemical insult by the neurotoxin quinolinic acid. Cresyl violet was used to visualise tissue for histological examination which revealed that DHEA is able to preserve the normal healthy morphology of hippocampal cells which have been exposed to quinolinic acid. Cells maintained their integrity and showed little evidence of swelling associated with necrosis. Organ culture studies were performed by assessing the impact of DHEA on several pineal metabolites. The study revealed that DHEA exerted an effect on the metabolism of indoleamines in the pineal gland. Melatonin, the chief pineal hormone, did not appear to be affected while the concentrations of N-acetylserotonin, serotonin and methoxytryptamine showed significant alterations. Thus, the neuroprotective mechanism of DHEA does not appear to be mediated by an increase in the presence of melatonin. The biological importance of metal ions in neurodegeneration is also well established and thus the potential interaction between DHEA and metal ions was considered as a mechanism of action. Spectroscopic and electrochemical analyses were performed to determine whether DHEA is able to interact with metal ions as a ligand. These reveal that DHEA does not form a strong bond with the metals investigated, namely copper (II) and iron (III), but that a weak interaction is evident. These investigations were conducted in a rodent model, which has neither large amounts of endogenous DHEA, nor the enzymatic infrastructure present in humans. Thus, the theory that DHEA exerts its effects through downstream metabolic products is unlikely. However, these investigations reveal that there is merit in the statement that DHEA itself is a neuroprotective molecule, and confirm that the further investigation of DHEA is an advisable strategy in the war against neurodegeneration and aging.
- Full Text:
- Date Issued: 2006
- Authors: Palvie, Stefanie Michelle
- Date: 2006
- Subjects: Aging -- Physiological aspects , Nervous system -- Degeneration -- Treatment , Steroid hormones , Dehydroepiandrosterone , Dehydroepiandrosterone -- Therapeutic use , Neurosciences , Neuroanatomy , Apoptosis , Pineal gland -- Physiology , Neurotoxic agents , Free radicals (Chemistry) -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3782 , http://hdl.handle.net/10962/d1003260 , Aging -- Physiological aspects , Nervous system -- Degeneration -- Treatment , Steroid hormones , Dehydroepiandrosterone , Dehydroepiandrosterone -- Therapeutic use , Neurosciences , Neuroanatomy , Apoptosis , Pineal gland -- Physiology , Neurotoxic agents , Free radicals (Chemistry) -- Physiological effect
- Description: Dehydroepiandrosterone, a C-19 steroid, is found endogenously with the highest circulating serum levels. It is converted to important steroids such as the sex hormones oestrogen and testosterone. DHEA has come under the spotlight as a purported “fountain of youth” due to its well-characterised age-related decline. The supplementation of DHEA in both the elderly and those with a pathophysiological deficiency has been shown to be of benefit, particularly with regard to wellbeing and depression. The role of DHEA in the periphery has not been elucidated beyond its role as a precursor hormone in sex steroid biosynthesis, though it has been established as a neuroactive neurosteroid, capable of exerting neuroprotective effects in the brain. Since the importance of free radicals in aging and neurodegeneration is well established, investigations were conducted on the ability of DHEA to inhibit free radical generation or scavenge existing free radicals. DHEA was able to significantly inhibit quinolinic acid-induced lipid peroxidation, a measure of membrane damage, over a range of concentrations, although the reduction did not appear to be dose-dependent. This was observed in both in vitro and in vivo studies. Thus, the ability of a compound to reduce the degree of lipid peroxidation may indicate its value as a neuroprotectant. However, DHEA did not significantly reduce cyanide induced generation of the superoxide free radical, suggesting that DHEA is not an effective free radical scavenger of the superoxide anion and that the reduction in lipid peroxidation does not occur through a scavenging mechanism. Apoptosis is a physiological process which is necessary for development and homeostasis. However, this form of programmed cell death can be initiated through various mechanisms and too much apoptotic cell death results in deleterious effects in the body. DHEA was shown not to induce apoptosis. Even the lowest concentration of DHEA investigated in this thesis shows a remarkable decrease in the degree of apoptosis caused by intrahippocampal chemical insult by the neurotoxin quinolinic acid. Cresyl violet was used to visualise tissue for histological examination which revealed that DHEA is able to preserve the normal healthy morphology of hippocampal cells which have been exposed to quinolinic acid. Cells maintained their integrity and showed little evidence of swelling associated with necrosis. Organ culture studies were performed by assessing the impact of DHEA on several pineal metabolites. The study revealed that DHEA exerted an effect on the metabolism of indoleamines in the pineal gland. Melatonin, the chief pineal hormone, did not appear to be affected while the concentrations of N-acetylserotonin, serotonin and methoxytryptamine showed significant alterations. Thus, the neuroprotective mechanism of DHEA does not appear to be mediated by an increase in the presence of melatonin. The biological importance of metal ions in neurodegeneration is also well established and thus the potential interaction between DHEA and metal ions was considered as a mechanism of action. Spectroscopic and electrochemical analyses were performed to determine whether DHEA is able to interact with metal ions as a ligand. These reveal that DHEA does not form a strong bond with the metals investigated, namely copper (II) and iron (III), but that a weak interaction is evident. These investigations were conducted in a rodent model, which has neither large amounts of endogenous DHEA, nor the enzymatic infrastructure present in humans. Thus, the theory that DHEA exerts its effects through downstream metabolic products is unlikely. However, these investigations reveal that there is merit in the statement that DHEA itself is a neuroprotective molecule, and confirm that the further investigation of DHEA is an advisable strategy in the war against neurodegeneration and aging.
- Full Text:
- Date Issued: 2006
An investigation into the neuroprotective effects of estrogen and progesterone in a model of homocysteine-induced neurodegeration
- Authors: Wu, Wing Man
- Date: 2006
- Subjects: Homocysteine , Estrogen , Estrogen -- Therapeutic use , Progesterone , Hormone receptors , Methyl aspartate , Oxidative stress , Alzheimer's disease -- Treatment , Nervous system -- Degeneration -- Prevention
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3806 , http://hdl.handle.net/10962/d1003284 , Homocysteine , Estrogen , Estrogen -- Therapeutic use , Progesterone , Hormone receptors , Methyl aspartate , Oxidative stress , Alzheimer's disease -- Treatment , Nervous system -- Degeneration -- Prevention
- Description: Homocysteine (Hcy) is a sulfur containing amino acid and is a potent neurotoxin. It has been shown that elevated levels of Hcy, termed hyperhomocysteinemia, plays a role in the pathologies of Alzheimer’s disease (AD) and age-related cognitive decline. Hcy is a glutamate agonist, which causes in increase in Ca[superscript (2+)] influx via the activation of NMDA class of excitatory amino acid receptors, which results in neuronal cell death and apoptosis. Estrogen and progesterone are female hormones that are responsible for reproduction and maternal behaviour. However, in the last decade, it is evident that both female hormones have neuroprotective properties in many animal models of neurodegeneration. Collectively, both estrogen and progesterone reduce the consequences of the oxidative stress by enhancing the antioxidant defence mechanisms, reducing excitotoxicity by altering glutamate receptor activity and reducing the damage caused by lipid peroxidation. However, the mechanisms by which estrogen and progesterone provide such neuroprotection probably depend on the type and concentration of hormone present. Moreover, numerous studies have shown that hormone replacement therapy (HRT, estrogen and progestins) or estrogen-only replacement therapy (ERT) may prevent or delay the onset of AD and improve cognition for women with AD. Clinical trials have also shown that women taking HRT may modify the effects of Hcy levels on cognitive functioning. Oxidative stress increases in the aging brain and thus has a powerful effect on enhanced susceptibility to neurodegenerative disease. The detection and measurement of lipid peroxidation and superoxide anion radicals in the brain tissue supports the involvement of free radical reactions in neurotoxicity and in neurodegenerative disorders. The hippocampus is an important region of the brain responsible for the formation of memory. However, agents that induce stress in this area have harmful effects and could lead to dementia. This study aims to investigate and clarify the neuroprotective effects of estrogen and progesterone, using Hcy-induced neurodegenerative models. The initial studies demonstrate that estrogen and progesterone have the ability to scavenge potent free radicals. Histological studies undertaken reveal that both estrogen and progesterone protect against Hcy-induced neuronal cell death. In addition, immunohistochemical investigations show that Hcy-induced apoptosis in the hippocampus can be inhibited by both estrogen and progesterone. However, estrogen also acts at the NMDA receptor as an agonist, while progesterone blocks at the NMDA receptor. These mechanisms reduce the ability of Hcy to cause damage to neurons, since Hcy-induced neurotoxicity is dependent on the overstimulation of the NMDA receptor. SOD and GPx are important enzymatic antioxidants which can react with ROS and neutralize them before these inflict damage in the brain. Hcy can increase oxidative stress by inhibiting expression and function of these antioxidants. However, it has been shown that the antioxidant abilities of both estrogen and progesterone can up-regulate the activities of SOD and GPx. These results provide further evidence that estrogen and progesterone act as antioxidants and are free radical scavengers. The discovery of neuroprotective agents is becoming important as accumulating evidence indicates the protective role of both estrogen and progesterone in Hcy-induced neurodegeneration. Thus further work in clinical trials is needed to examine whether reducing Hcy levels with HRT can become the treatment of neurodegenerative disorders, such as Alzheimer’s disease.
- Full Text:
- Date Issued: 2006
- Authors: Wu, Wing Man
- Date: 2006
- Subjects: Homocysteine , Estrogen , Estrogen -- Therapeutic use , Progesterone , Hormone receptors , Methyl aspartate , Oxidative stress , Alzheimer's disease -- Treatment , Nervous system -- Degeneration -- Prevention
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3806 , http://hdl.handle.net/10962/d1003284 , Homocysteine , Estrogen , Estrogen -- Therapeutic use , Progesterone , Hormone receptors , Methyl aspartate , Oxidative stress , Alzheimer's disease -- Treatment , Nervous system -- Degeneration -- Prevention
- Description: Homocysteine (Hcy) is a sulfur containing amino acid and is a potent neurotoxin. It has been shown that elevated levels of Hcy, termed hyperhomocysteinemia, plays a role in the pathologies of Alzheimer’s disease (AD) and age-related cognitive decline. Hcy is a glutamate agonist, which causes in increase in Ca[superscript (2+)] influx via the activation of NMDA class of excitatory amino acid receptors, which results in neuronal cell death and apoptosis. Estrogen and progesterone are female hormones that are responsible for reproduction and maternal behaviour. However, in the last decade, it is evident that both female hormones have neuroprotective properties in many animal models of neurodegeneration. Collectively, both estrogen and progesterone reduce the consequences of the oxidative stress by enhancing the antioxidant defence mechanisms, reducing excitotoxicity by altering glutamate receptor activity and reducing the damage caused by lipid peroxidation. However, the mechanisms by which estrogen and progesterone provide such neuroprotection probably depend on the type and concentration of hormone present. Moreover, numerous studies have shown that hormone replacement therapy (HRT, estrogen and progestins) or estrogen-only replacement therapy (ERT) may prevent or delay the onset of AD and improve cognition for women with AD. Clinical trials have also shown that women taking HRT may modify the effects of Hcy levels on cognitive functioning. Oxidative stress increases in the aging brain and thus has a powerful effect on enhanced susceptibility to neurodegenerative disease. The detection and measurement of lipid peroxidation and superoxide anion radicals in the brain tissue supports the involvement of free radical reactions in neurotoxicity and in neurodegenerative disorders. The hippocampus is an important region of the brain responsible for the formation of memory. However, agents that induce stress in this area have harmful effects and could lead to dementia. This study aims to investigate and clarify the neuroprotective effects of estrogen and progesterone, using Hcy-induced neurodegenerative models. The initial studies demonstrate that estrogen and progesterone have the ability to scavenge potent free radicals. Histological studies undertaken reveal that both estrogen and progesterone protect against Hcy-induced neuronal cell death. In addition, immunohistochemical investigations show that Hcy-induced apoptosis in the hippocampus can be inhibited by both estrogen and progesterone. However, estrogen also acts at the NMDA receptor as an agonist, while progesterone blocks at the NMDA receptor. These mechanisms reduce the ability of Hcy to cause damage to neurons, since Hcy-induced neurotoxicity is dependent on the overstimulation of the NMDA receptor. SOD and GPx are important enzymatic antioxidants which can react with ROS and neutralize them before these inflict damage in the brain. Hcy can increase oxidative stress by inhibiting expression and function of these antioxidants. However, it has been shown that the antioxidant abilities of both estrogen and progesterone can up-regulate the activities of SOD and GPx. These results provide further evidence that estrogen and progesterone act as antioxidants and are free radical scavengers. The discovery of neuroprotective agents is becoming important as accumulating evidence indicates the protective role of both estrogen and progesterone in Hcy-induced neurodegeneration. Thus further work in clinical trials is needed to examine whether reducing Hcy levels with HRT can become the treatment of neurodegenerative disorders, such as Alzheimer’s disease.
- Full Text:
- Date Issued: 2006
An investigation into the neuroprotective properties of acyclovir
- Authors: Müller, Adrienne Carmel
- Date: 2006
- Subjects: Acyclovir -- Therapeutic use , Acyclovir -- Physiological effect , Nervous system -- Degeneration -- Treatment , Memory disorders -- Treatment , Quinolinic acid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3776 , http://hdl.handle.net/10962/d1003254 , Acyclovir -- Therapeutic use , Acyclovir -- Physiological effect , Nervous system -- Degeneration -- Treatment , Memory disorders -- Treatment , Quinolinic acid
- Description: Accumulating evidence suggests that quinolinic acid has a role to play in disorders involving impairment of learning and memory. In the present study, the effect of the guanosine analogue antiherpetic, acyclovir, on quinolinic acid-induced spatial memory deficits was investigated, as well as some of the mechanisms which underlie this effect. Behavioural studies using a Morris water maze show that post-treatment of rats with acyclovir significantly improves spatial memory deficits induced by intrahippocampal injections of quinolinic acid. Histological analysis of the hippocampi show that the effect of acyclovir is related to its ability to alleviate quinolinic acid-induced necrotic cell death, through interference with some of the mechanisms of neurodegeneration. However, acyclovir is unable to alter a quinolinic acid-induced increase in glutamate release in the rat hippocampus, even though it alleviates quinolinic acid induced oxidative stress by scavenging the superoxide anion in vitro and in vivo in whole rat brain and hippocampus respectively. Due to the inverse relationship which exists between superoxide anion and glutathione levels, acyclovir also curtails the quinolinic acid-induced decrease in hippocampal glutathione levels. Acyclovir suppresses quinolinic acid-induced lipid peroxidation in vitro and in vivo, in whole rat brain and hippocampus respectively, through its alleviation of oxidative stress and possibly through the binding of iron (II) and / or iron (III), preventing the participation and redox recycling of iron (II) in the Fenton reaction, which quinolinic acid is thought to enhance by weak binding of ferrous ions. This argument is further strengthened by the ability of the drug to suppress iron (II)-induced lipid peroxidation in vitro directly. Inorganic studies including ultraviolet and visible spectroscopy, electrochemistry and the ferrozine assay show that acyclovir binds to iron (II) and iron (III) and that quinolinic acid forms an easily oxidisable association with iron (II). Acyclovir inhibits the endogenous biosynthesis of quinolinic acid by inhibiting the activity of liver tryptophan-2,3-dioxygenase, intestinal indoleamine-2,3-dioxygenase and rat liver 3-hydroxyanthranillic acid oxygenase in vitro and in vivo, possibly through competitive inhibition of haeme, scavenging of superoxide anion and binding of iron (II) respectively. An inverse relationship exists between tryptophan-2,3-dioxygenase activity and brain serotonin levels. Acyclovir administration in rats induces a rise in forebrain serotonin and 5-hydroxyindole acetic acid and reduces the turnover of forebrain serotonin to 5-hydroxyindole acetic acid. Furthermore, it shows that acyclovir does not alter forebrain norepinephrine levels. The results of the pineal indole metabolism study show that acyclovir increases 5-hydroxytryptophol, N-acetylserotonin and the neurohormone melatonin, but decreases 5-hydroxyindole acetic acid. The results of this study show that acyclovir has some neuroprotective properties which may make it useful in the alleviation of the anomalous neurobiology in neurodegenerative disorders.
- Full Text:
- Date Issued: 2006
- Authors: Müller, Adrienne Carmel
- Date: 2006
- Subjects: Acyclovir -- Therapeutic use , Acyclovir -- Physiological effect , Nervous system -- Degeneration -- Treatment , Memory disorders -- Treatment , Quinolinic acid
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3776 , http://hdl.handle.net/10962/d1003254 , Acyclovir -- Therapeutic use , Acyclovir -- Physiological effect , Nervous system -- Degeneration -- Treatment , Memory disorders -- Treatment , Quinolinic acid
- Description: Accumulating evidence suggests that quinolinic acid has a role to play in disorders involving impairment of learning and memory. In the present study, the effect of the guanosine analogue antiherpetic, acyclovir, on quinolinic acid-induced spatial memory deficits was investigated, as well as some of the mechanisms which underlie this effect. Behavioural studies using a Morris water maze show that post-treatment of rats with acyclovir significantly improves spatial memory deficits induced by intrahippocampal injections of quinolinic acid. Histological analysis of the hippocampi show that the effect of acyclovir is related to its ability to alleviate quinolinic acid-induced necrotic cell death, through interference with some of the mechanisms of neurodegeneration. However, acyclovir is unable to alter a quinolinic acid-induced increase in glutamate release in the rat hippocampus, even though it alleviates quinolinic acid induced oxidative stress by scavenging the superoxide anion in vitro and in vivo in whole rat brain and hippocampus respectively. Due to the inverse relationship which exists between superoxide anion and glutathione levels, acyclovir also curtails the quinolinic acid-induced decrease in hippocampal glutathione levels. Acyclovir suppresses quinolinic acid-induced lipid peroxidation in vitro and in vivo, in whole rat brain and hippocampus respectively, through its alleviation of oxidative stress and possibly through the binding of iron (II) and / or iron (III), preventing the participation and redox recycling of iron (II) in the Fenton reaction, which quinolinic acid is thought to enhance by weak binding of ferrous ions. This argument is further strengthened by the ability of the drug to suppress iron (II)-induced lipid peroxidation in vitro directly. Inorganic studies including ultraviolet and visible spectroscopy, electrochemistry and the ferrozine assay show that acyclovir binds to iron (II) and iron (III) and that quinolinic acid forms an easily oxidisable association with iron (II). Acyclovir inhibits the endogenous biosynthesis of quinolinic acid by inhibiting the activity of liver tryptophan-2,3-dioxygenase, intestinal indoleamine-2,3-dioxygenase and rat liver 3-hydroxyanthranillic acid oxygenase in vitro and in vivo, possibly through competitive inhibition of haeme, scavenging of superoxide anion and binding of iron (II) respectively. An inverse relationship exists between tryptophan-2,3-dioxygenase activity and brain serotonin levels. Acyclovir administration in rats induces a rise in forebrain serotonin and 5-hydroxyindole acetic acid and reduces the turnover of forebrain serotonin to 5-hydroxyindole acetic acid. Furthermore, it shows that acyclovir does not alter forebrain norepinephrine levels. The results of the pineal indole metabolism study show that acyclovir increases 5-hydroxytryptophol, N-acetylserotonin and the neurohormone melatonin, but decreases 5-hydroxyindole acetic acid. The results of this study show that acyclovir has some neuroprotective properties which may make it useful in the alleviation of the anomalous neurobiology in neurodegenerative disorders.
- Full Text:
- Date Issued: 2006
An investigation of integrated development planning (IDP) as a mechanism for poverty alleviation in Grahamstown in the Makana Municipality, Eastern Cape, South Africa
- Authors: Alebiosu, Olumide Ademola
- Date: 2006
- Subjects: Makana Municipality , Local government -- South Africa -- Eastern Cape , Poor -- South Africa -- Eastern Cape , Poverty -- South Africa -- Eastern Cape , Poverty -- Government policy -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4841 , http://hdl.handle.net/10962/d1005517 , Makana Municipality , Local government -- South Africa -- Eastern Cape , Poor -- South Africa -- Eastern Cape , Poverty -- South Africa -- Eastern Cape , Poverty -- Government policy -- South Africa -- Eastern Cape
- Description: Poverty among individuals, households or communities is not a static condition. There are many factors which contribute to its causes and depth. In South Africa the economic gaps imposed by the previous apartheid government aggravated economic inequalities and caused considerable disparities, which has resulted in high unemployment rates. Inequalities were also manifest in the neglect of infrastructural and service provision as well in the effective absence of independent governance among some race group. This led to a call for pro-active initiatives by the post-1994 democratic government to remedy the living condition of the previously disadvantaged people. As part of its poverty relief drive the South African government has embarked on a series of developmental initiatives in bringing infrastructure related services to the poor and to reduce the enormous prevailing backlog, with the aim of increasing community participation, improving service delivery and promoting the upliftment of the lives of poor people through the medium of local governance. This study investigated the Integrated Development Planning, which has been undertaken in Grahamstown in the Makana Municipality in the Eastern Cape to respond to the prevailing poverty and underdevelopment among the poor communities. Relying on their developmental mandate to initiate and co-ordinate all development activities within their area of jurisdiction through the IDP, the Makana Municipality has drawn up a development strategic plan in conjunction with the local communities and with other stakeholders and organisations to identify and assess development backlogs within the communities with the aim of addressing such backlogs. This study revealed from the interviews conducted with some municipal personnel and questionnaires administered to sampled residents of Grahamstown that some faces of poverty, such as unemployment and lack of access to some of the most basic of infrastructure such as, sanitation facilities, water, electricity, formal house, education, security and recreation facilities are apparent in Grahamstown. However, the Makana Municipality through, the IDP has achieved some notable feats in the provision of providing some of the basic amenities such as water, housing, electricity and sanitation albeit at a slow rate. The mechanism of delivery is hampered by bureaucratic settings within government and the ambiguity attached to some of the projects. The service and infrastructural developments targeted towards the poor and the involvement of communities in the affairs of the local government might be seen as a partially panacea for poverty alleviation in South Africa. However the capacity of the local governments to effectively carry out this developmental challenge assignment might be a new twist in the developmental challenge facing local governments in South Africa. The thesis provides an overview of the Makana Municipality IDP and the degree to which is serving as one mechanism to address poverty in the Grahamstown urban area
- Full Text:
- Date Issued: 2006
- Authors: Alebiosu, Olumide Ademola
- Date: 2006
- Subjects: Makana Municipality , Local government -- South Africa -- Eastern Cape , Poor -- South Africa -- Eastern Cape , Poverty -- South Africa -- Eastern Cape , Poverty -- Government policy -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4841 , http://hdl.handle.net/10962/d1005517 , Makana Municipality , Local government -- South Africa -- Eastern Cape , Poor -- South Africa -- Eastern Cape , Poverty -- South Africa -- Eastern Cape , Poverty -- Government policy -- South Africa -- Eastern Cape
- Description: Poverty among individuals, households or communities is not a static condition. There are many factors which contribute to its causes and depth. In South Africa the economic gaps imposed by the previous apartheid government aggravated economic inequalities and caused considerable disparities, which has resulted in high unemployment rates. Inequalities were also manifest in the neglect of infrastructural and service provision as well in the effective absence of independent governance among some race group. This led to a call for pro-active initiatives by the post-1994 democratic government to remedy the living condition of the previously disadvantaged people. As part of its poverty relief drive the South African government has embarked on a series of developmental initiatives in bringing infrastructure related services to the poor and to reduce the enormous prevailing backlog, with the aim of increasing community participation, improving service delivery and promoting the upliftment of the lives of poor people through the medium of local governance. This study investigated the Integrated Development Planning, which has been undertaken in Grahamstown in the Makana Municipality in the Eastern Cape to respond to the prevailing poverty and underdevelopment among the poor communities. Relying on their developmental mandate to initiate and co-ordinate all development activities within their area of jurisdiction through the IDP, the Makana Municipality has drawn up a development strategic plan in conjunction with the local communities and with other stakeholders and organisations to identify and assess development backlogs within the communities with the aim of addressing such backlogs. This study revealed from the interviews conducted with some municipal personnel and questionnaires administered to sampled residents of Grahamstown that some faces of poverty, such as unemployment and lack of access to some of the most basic of infrastructure such as, sanitation facilities, water, electricity, formal house, education, security and recreation facilities are apparent in Grahamstown. However, the Makana Municipality through, the IDP has achieved some notable feats in the provision of providing some of the basic amenities such as water, housing, electricity and sanitation albeit at a slow rate. The mechanism of delivery is hampered by bureaucratic settings within government and the ambiguity attached to some of the projects. The service and infrastructural developments targeted towards the poor and the involvement of communities in the affairs of the local government might be seen as a partially panacea for poverty alleviation in South Africa. However the capacity of the local governments to effectively carry out this developmental challenge assignment might be a new twist in the developmental challenge facing local governments in South Africa. The thesis provides an overview of the Makana Municipality IDP and the degree to which is serving as one mechanism to address poverty in the Grahamstown urban area
- Full Text:
- Date Issued: 2006
An investigation of the in vitro anticancer properties of selected platinum compounds
- Authors: Du Plessis-Stoman, Debbie
- Date: 2006
- Subjects: Antineoplastic agents , Platinum compounds , Cancer -- Immunological aspects , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10334 , http://hdl.handle.net/10948/498 , http://hdl.handle.net/10948/d1012002 , Antineoplastic agents , Platinum compounds , Cancer -- Immunological aspects , Cancer -- Chemotherapy
- Description: This dissertation mainly deals with some biochemical aspects regarding the efficacy of novel platinum anticancer compounds, as part of a broader study in which both chemistry and biochemistry are involved. Various novel diamine and N-S donor chelate compounds of platinum II and IV have been developed in which factors such as stereochemistry, ligand exchange rate and biocompatibility were considered as additional parameters. In the first order testing, each of these compounds was tested with reference to their “killing” potential by comparing their rate of killing, over a period of 48 hours with those of cisplatin and oxaliplatin. Some 80 compounds were tested in this way. Although only a few could be regarded as equal to or even better than cisplatin and oxaliplatin, the testing of these compounds on cancer cells provided useful knowledge for the further development of novel compounds. Four of the better compounds, namely Y9, Y14, Y16 and Lt16.2 were selected for further studies to obtain more detailed knowledge of their anticancer action, including some flow cytometric studies. In addition to the above, cisplatin resistant cells were produced for each of the three different cell lines tested, namely, HeLa, HT29 and MCF7 cancer cell lines, by intermittent and incremental exposure to cisplatin (all the cell lines tested became resistant to cisplatin). Each of the selected compounds were exposed to the cells in the same manner, in order to attempt the induction of resistance against these compounds in the three cell lines tested (i.e. whether these cells will become resistant to the various compounds). Each of these selected platinum containing compounds were subsequently tested against the “cisplatin resistant” cell lines in order to determine their efficacy against such cells. One such compound could be singled out, since cervical cancer cells (HeLa cells) do not become resistant to it. This behaviour is similar to that of oxaliplatin against cervical cancer and colon cancer (HT29) cells (oxaliplatin is the number one treatment for colon cancer at present). This compound also proved to be more active against cisplatin resistant cell lines. It was found that all the compounds induced apoptosis in the cell lines tested as well as inhibit the DNA cycle at one or more phase. Finally, an effort was made to evaluate the different compounds by comparing them with respect to their properties relating to anticancer action.
- Full Text:
- Date Issued: 2006
- Authors: Du Plessis-Stoman, Debbie
- Date: 2006
- Subjects: Antineoplastic agents , Platinum compounds , Cancer -- Immunological aspects , Cancer -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10334 , http://hdl.handle.net/10948/498 , http://hdl.handle.net/10948/d1012002 , Antineoplastic agents , Platinum compounds , Cancer -- Immunological aspects , Cancer -- Chemotherapy
- Description: This dissertation mainly deals with some biochemical aspects regarding the efficacy of novel platinum anticancer compounds, as part of a broader study in which both chemistry and biochemistry are involved. Various novel diamine and N-S donor chelate compounds of platinum II and IV have been developed in which factors such as stereochemistry, ligand exchange rate and biocompatibility were considered as additional parameters. In the first order testing, each of these compounds was tested with reference to their “killing” potential by comparing their rate of killing, over a period of 48 hours with those of cisplatin and oxaliplatin. Some 80 compounds were tested in this way. Although only a few could be regarded as equal to or even better than cisplatin and oxaliplatin, the testing of these compounds on cancer cells provided useful knowledge for the further development of novel compounds. Four of the better compounds, namely Y9, Y14, Y16 and Lt16.2 were selected for further studies to obtain more detailed knowledge of their anticancer action, including some flow cytometric studies. In addition to the above, cisplatin resistant cells were produced for each of the three different cell lines tested, namely, HeLa, HT29 and MCF7 cancer cell lines, by intermittent and incremental exposure to cisplatin (all the cell lines tested became resistant to cisplatin). Each of the selected compounds were exposed to the cells in the same manner, in order to attempt the induction of resistance against these compounds in the three cell lines tested (i.e. whether these cells will become resistant to the various compounds). Each of these selected platinum containing compounds were subsequently tested against the “cisplatin resistant” cell lines in order to determine their efficacy against such cells. One such compound could be singled out, since cervical cancer cells (HeLa cells) do not become resistant to it. This behaviour is similar to that of oxaliplatin against cervical cancer and colon cancer (HT29) cells (oxaliplatin is the number one treatment for colon cancer at present). This compound also proved to be more active against cisplatin resistant cell lines. It was found that all the compounds induced apoptosis in the cell lines tested as well as inhibit the DNA cycle at one or more phase. Finally, an effort was made to evaluate the different compounds by comparing them with respect to their properties relating to anticancer action.
- Full Text:
- Date Issued: 2006
Application of the Baylis-Hillman reaction in the preparation of quinoline derivatives
- Authors: Pakade, Vusumzi Emmanuel
- Date: 2006 , 2013-06-11
- Subjects: Heterocyclic compounds -- Derivatives , Quinoline
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4442 , http://hdl.handle.net/10962/d1007669 , Heterocyclic compounds -- Derivatives , Quinoline
- Description: The reaction of various 2-nitrobenzaldehyde derivatives with methyl vinyl ketone (MVK) in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) has afforded the Baylis-Hillman adducts in moderate to good yield. Dissolution of the catalyst in the solvent before the addition of the aldehyde was observed to improve the yield. Reduction of the Baylis-Hillman adducts was effected by catalytic hydrogenation using a 10% palladium-on- carbon catalyst in ethanol to give quinoline and quinoline-N-oxide derivatives and, in some cases, acyclic reduction products. All products were characterised using NMR and, where appropriate, HRMS methods. Selected quinoline-N-oxides were successfully converted to their corresponding quinoline derivatives using phosphorus tribromide (PBr₃) and DMF as solvent. Conjugate addition of the benzylamine and piperidine nucleophiles to the Baylis-Hillman adducts was also investigated but proved problematic, with one of the substrates undergoing a retro-Baylis-Hillman reaction to afford the aldehyde in ca. 40% yield, but seemingly only traces of the required product. Perkin-type coupling of two 2-methylquinolines with benzaldehyde was successfully effected to afford the desired styrylquinoline derivatives confirming the potential of the Baylis-Hillman approach to the construction of the analogues of known HIV-1 integrase inhibitors. Three ¹³C NMR chemical shift prediction programmes, viz., Chem Window, neural network and HOSE (hierarchically ordered spherical description of environment) methods were applied to selected representative compounds prepared in the project. The results from the three programmes correlated reasonably well with the experimental carbon-13 chemical shift data for each of the selected compounds.
- Full Text:
- Date Issued: 2006
- Authors: Pakade, Vusumzi Emmanuel
- Date: 2006 , 2013-06-11
- Subjects: Heterocyclic compounds -- Derivatives , Quinoline
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4442 , http://hdl.handle.net/10962/d1007669 , Heterocyclic compounds -- Derivatives , Quinoline
- Description: The reaction of various 2-nitrobenzaldehyde derivatives with methyl vinyl ketone (MVK) in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) has afforded the Baylis-Hillman adducts in moderate to good yield. Dissolution of the catalyst in the solvent before the addition of the aldehyde was observed to improve the yield. Reduction of the Baylis-Hillman adducts was effected by catalytic hydrogenation using a 10% palladium-on- carbon catalyst in ethanol to give quinoline and quinoline-N-oxide derivatives and, in some cases, acyclic reduction products. All products were characterised using NMR and, where appropriate, HRMS methods. Selected quinoline-N-oxides were successfully converted to their corresponding quinoline derivatives using phosphorus tribromide (PBr₃) and DMF as solvent. Conjugate addition of the benzylamine and piperidine nucleophiles to the Baylis-Hillman adducts was also investigated but proved problematic, with one of the substrates undergoing a retro-Baylis-Hillman reaction to afford the aldehyde in ca. 40% yield, but seemingly only traces of the required product. Perkin-type coupling of two 2-methylquinolines with benzaldehyde was successfully effected to afford the desired styrylquinoline derivatives confirming the potential of the Baylis-Hillman approach to the construction of the analogues of known HIV-1 integrase inhibitors. Three ¹³C NMR chemical shift prediction programmes, viz., Chem Window, neural network and HOSE (hierarchically ordered spherical description of environment) methods were applied to selected representative compounds prepared in the project. The results from the three programmes correlated reasonably well with the experimental carbon-13 chemical shift data for each of the selected compounds.
- Full Text:
- Date Issued: 2006
Biomonitoring in two contrasting catchments
- Authors: Maseti, Pumza Penelope
- Date: 2006
- Subjects: Water quality biological assessment -- South Africa , Water quality management -- South Africa , Rivers -- South Africa , Freshwater fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6034 , http://hdl.handle.net/10962/d1006175 , Water quality biological assessment -- South Africa , Water quality management -- South Africa , Rivers -- South Africa , Freshwater fishes -- South Africa
- Description: The introduction of instream biological monitoring to water resources management has been an increasing trend world-wide. This monitoring uses biological field assessments of instream biota such as macroinvertebrates, fish and riparian vegetation as an integrated and sensitive tool for diagnosing the condition of the ecosystems and assessing ecological impacts. Biomonitoring information has become an important component in the overall assessment of water resources and is used to drive and direct processes of decision-making and management of water resources. The River Health Programme (RHP) was initiated in South Africa to serve as a source of information regarding the ecological status of river systems, in order to support rational management of these natural resources. In this study, biomonitoring indices (SASS5 and FAII) were used to assess the present ecological status of two rivers located in contrasting catchments of the Eastern Cape. The first river is the Buffalo River located in an urban and industrialized catchment. The second river is the Inxu River draining a rural and afforested catchment. SASS5 was used successfully in both rivers and the results based on water quality and SASS5 indicated that most sites selected on the upper catchment of the Buffalo River have a fair water quality with most sites selected on the lower catchment having a poor water quality. The Inxu River sites (both upper and lower catchment) based on SASS5 and water quality results have a good to fair water quality. The majority of sites sampled on both rivers systems had very low FAII scores and fell within a critically modified water quality category. This result may be due to the fact that these rivers have low fish diversities (either low natural diversity or low diversity due to the presence of alien fish species), poor water quality or inadequate sampling methods. Observations from this study suggest that this index may not be suitable for rivers with low fish diversity. A fish index that is usable to all ecoregions of South Africa with minor adaptations to suit local conditions is still needed, as the present FAII index does not meet these requirements.
- Full Text:
- Date Issued: 2006
- Authors: Maseti, Pumza Penelope
- Date: 2006
- Subjects: Water quality biological assessment -- South Africa , Water quality management -- South Africa , Rivers -- South Africa , Freshwater fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6034 , http://hdl.handle.net/10962/d1006175 , Water quality biological assessment -- South Africa , Water quality management -- South Africa , Rivers -- South Africa , Freshwater fishes -- South Africa
- Description: The introduction of instream biological monitoring to water resources management has been an increasing trend world-wide. This monitoring uses biological field assessments of instream biota such as macroinvertebrates, fish and riparian vegetation as an integrated and sensitive tool for diagnosing the condition of the ecosystems and assessing ecological impacts. Biomonitoring information has become an important component in the overall assessment of water resources and is used to drive and direct processes of decision-making and management of water resources. The River Health Programme (RHP) was initiated in South Africa to serve as a source of information regarding the ecological status of river systems, in order to support rational management of these natural resources. In this study, biomonitoring indices (SASS5 and FAII) were used to assess the present ecological status of two rivers located in contrasting catchments of the Eastern Cape. The first river is the Buffalo River located in an urban and industrialized catchment. The second river is the Inxu River draining a rural and afforested catchment. SASS5 was used successfully in both rivers and the results based on water quality and SASS5 indicated that most sites selected on the upper catchment of the Buffalo River have a fair water quality with most sites selected on the lower catchment having a poor water quality. The Inxu River sites (both upper and lower catchment) based on SASS5 and water quality results have a good to fair water quality. The majority of sites sampled on both rivers systems had very low FAII scores and fell within a critically modified water quality category. This result may be due to the fact that these rivers have low fish diversities (either low natural diversity or low diversity due to the presence of alien fish species), poor water quality or inadequate sampling methods. Observations from this study suggest that this index may not be suitable for rivers with low fish diversity. A fish index that is usable to all ecoregions of South Africa with minor adaptations to suit local conditions is still needed, as the present FAII index does not meet these requirements.
- Full Text:
- Date Issued: 2006
Community structure and predation impact of carnivorous macrozooplankton in the polar frontal zone (Southern Ocean), with particular reference to chaetognaths
- Authors: Lukáč, Danica
- Date: 2006
- Subjects: Zooplankton -- Antarctic Ocean , Chaetognatha
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5653 , http://hdl.handle.net/10962/d1005336 , Zooplankton -- Antarctic Ocean , Chaetognatha
- Description: The community structure and predation impact of carnivorous macrozooplankton (>2 cm; chaetognaths, medusae, ctenophores and mysids), with particular emphasis on the chaetognaths Eukrohnia hamata and Sagitta gazellae, were investigated during three surveys conducted in late austral summer (April/May) of 2001, 2004 and 2005 in the Polar Frontal Zone in the vicinity of the Prince Edward Islands (46º45’S, 37º50’E), Southern Ocean. The 2001 survey formed part of the Marion Offshore Variability Ecosystem Study (MOVES II), while the 2004 and 2005 surveys formed part of the Dynamics of Eddy Impacts on Marion’s Ecosystem study (DEIMEC III and IV respectively). Macrozooplankton samples were collected using WP-2, RMT-8 and Bongo nets. Results of the hydrographic survey indicated that the region of investigation, the Polar Frontal Zone (PFZ), is an area of high mesoscale variability. During the 2004 survey the Antarctic Polar Front (APF) and the Subantarctic Front (SAF) merged to form an intense frontal feature with subsurface temperature and salinity ranging from 8.5-7.5ºC and 34.15-33.88, respectively. A cyclonic cold core eddy, believed to have been spawned from the APF, was observed during the 2005 survey. Macrozooplankton abundance and biomass ranged from 0 to 43.731 ind. m⁻³, and from 0 to 41.55 mg wwt m⁻³ respectively, during the three surveys. Among the carnivorous macrozooplankton, chaetognaths (Eukrohnia hamata and Sagitta gazellae) were most prominent, contributing up to 85% of the total biomass during all three surveys. Elevated biomass values were found near and within the frontal feature during the 2004 survey, and also along the eddy edge during the 2005 survey. However, hierarchical cluster analysis did not reveal the presence of distinct zooplankton groupings associated with the various water masses encountered during the surveys and this is probably due to the high mesoscale variability in oceanographic conditions that are characteristic of the PFZ. The total average predation impact of the selected carnivorous macrozooplankton during the 2001, 2004 and 2005 surveys accounted for 4.93 ± 6.76%, 0.55 ± 0.51% and 4.88 ± 4.45 of the mesozooplankton standing stock, respectively. S. gazellae had the highest consumption rate in all three surveys, consuming up to 800 g Dwt 1000m⁻³d⁻¹ during the study. Of the two chaetognaths, E. hamata dominated the chaetognath standing stock. The combined abundance and biomass values of E. hamata and S. gazellae ranged from 0 to 43.73 ind. m⁻³ and from 0 to 41.551 mg wwt m⁻³ respectively, during the three surveys. Inter-annual variability in the chaetognath densities was apparent. Highest abundances and biomasses tended to be associated with specific water masses, confirming the existence of a relationship between zooplankton community structure and hydrographic conditions. Generally, about 90% of the chaetognaths contained no food in their guts. S. gazellae consumed a wider variety of prey. Oil droplets occurred in the guts of ≈ 51% of E. hamata. Cannibalism was low in both species, but greater in S. gazellae than E. hamata. During the three surveys, the feeding rate values of E. hamata and S. gazellae went up to 0.48 and 2.099 prey d⁻¹ respectively. S. gazellae also had a greater predation impact on the mesozooplankton standing stock than E. hamata. The mean predation impact of the chaetognaths combined was 0.31 ± 0.291%, 0.52 ± 0.28% and 0.53 ± 0.56% of the mesozooplankton standing stock during the 2001, 2004 and 2005 surveys, respectively. During all three surveys, the majority of individuals (≈ 76%) of the chaetognaths were at stage I maturity, suggesting that during the time of study the chaetognaths were not reproducing. In both species a significant difference (log-linear analysis, p < 0.05) in maturities between the years investigated was observed. In general, there were no differences in lengths and maturities between the different water masses encountered during the surveys. The lengths of E. hamata and S. gazellae ranged from 5 to 24 mm and from 9.4 to 63.6 mm, respectively.
- Full Text:
- Date Issued: 2006
- Authors: Lukáč, Danica
- Date: 2006
- Subjects: Zooplankton -- Antarctic Ocean , Chaetognatha
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5653 , http://hdl.handle.net/10962/d1005336 , Zooplankton -- Antarctic Ocean , Chaetognatha
- Description: The community structure and predation impact of carnivorous macrozooplankton (>2 cm; chaetognaths, medusae, ctenophores and mysids), with particular emphasis on the chaetognaths Eukrohnia hamata and Sagitta gazellae, were investigated during three surveys conducted in late austral summer (April/May) of 2001, 2004 and 2005 in the Polar Frontal Zone in the vicinity of the Prince Edward Islands (46º45’S, 37º50’E), Southern Ocean. The 2001 survey formed part of the Marion Offshore Variability Ecosystem Study (MOVES II), while the 2004 and 2005 surveys formed part of the Dynamics of Eddy Impacts on Marion’s Ecosystem study (DEIMEC III and IV respectively). Macrozooplankton samples were collected using WP-2, RMT-8 and Bongo nets. Results of the hydrographic survey indicated that the region of investigation, the Polar Frontal Zone (PFZ), is an area of high mesoscale variability. During the 2004 survey the Antarctic Polar Front (APF) and the Subantarctic Front (SAF) merged to form an intense frontal feature with subsurface temperature and salinity ranging from 8.5-7.5ºC and 34.15-33.88, respectively. A cyclonic cold core eddy, believed to have been spawned from the APF, was observed during the 2005 survey. Macrozooplankton abundance and biomass ranged from 0 to 43.731 ind. m⁻³, and from 0 to 41.55 mg wwt m⁻³ respectively, during the three surveys. Among the carnivorous macrozooplankton, chaetognaths (Eukrohnia hamata and Sagitta gazellae) were most prominent, contributing up to 85% of the total biomass during all three surveys. Elevated biomass values were found near and within the frontal feature during the 2004 survey, and also along the eddy edge during the 2005 survey. However, hierarchical cluster analysis did not reveal the presence of distinct zooplankton groupings associated with the various water masses encountered during the surveys and this is probably due to the high mesoscale variability in oceanographic conditions that are characteristic of the PFZ. The total average predation impact of the selected carnivorous macrozooplankton during the 2001, 2004 and 2005 surveys accounted for 4.93 ± 6.76%, 0.55 ± 0.51% and 4.88 ± 4.45 of the mesozooplankton standing stock, respectively. S. gazellae had the highest consumption rate in all three surveys, consuming up to 800 g Dwt 1000m⁻³d⁻¹ during the study. Of the two chaetognaths, E. hamata dominated the chaetognath standing stock. The combined abundance and biomass values of E. hamata and S. gazellae ranged from 0 to 43.73 ind. m⁻³ and from 0 to 41.551 mg wwt m⁻³ respectively, during the three surveys. Inter-annual variability in the chaetognath densities was apparent. Highest abundances and biomasses tended to be associated with specific water masses, confirming the existence of a relationship between zooplankton community structure and hydrographic conditions. Generally, about 90% of the chaetognaths contained no food in their guts. S. gazellae consumed a wider variety of prey. Oil droplets occurred in the guts of ≈ 51% of E. hamata. Cannibalism was low in both species, but greater in S. gazellae than E. hamata. During the three surveys, the feeding rate values of E. hamata and S. gazellae went up to 0.48 and 2.099 prey d⁻¹ respectively. S. gazellae also had a greater predation impact on the mesozooplankton standing stock than E. hamata. The mean predation impact of the chaetognaths combined was 0.31 ± 0.291%, 0.52 ± 0.28% and 0.53 ± 0.56% of the mesozooplankton standing stock during the 2001, 2004 and 2005 surveys, respectively. During all three surveys, the majority of individuals (≈ 76%) of the chaetognaths were at stage I maturity, suggesting that during the time of study the chaetognaths were not reproducing. In both species a significant difference (log-linear analysis, p < 0.05) in maturities between the years investigated was observed. In general, there were no differences in lengths and maturities between the different water masses encountered during the surveys. The lengths of E. hamata and S. gazellae ranged from 5 to 24 mm and from 9.4 to 63.6 mm, respectively.
- Full Text:
- Date Issued: 2006
Cytokine signalling functions of human soluble IgE receptors in peripheral blood mononuclear cells from normal and hyper-allergic individuals and in B-lymphoblastoid and monocytic cell lines
- Authors: Askew, Sandra Lyn
- Date: 2006
- Subjects: Ligands , Cell receptors , Cellular signal transduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10305 , http://hdl.handle.net/10948/455 , Ligands , Cell receptors , Cellular signal transduction
- Description: CD23 is a multifunctional receptor/ligand, found in a variety of cell types, such as human peripheral blood mononuclear cells (PBMCs), B-lymphoblastoid cell lines, mast cells and basophils. It is also found on a variety of haematopoietic cell lines. As the low-affinity receptor for immunoglobulin E (IgE), CD23 plays a role in antigen-presentation and macrophage activation. As a surface molecule cleaved from the cell membrane, soluble CD23 (sCD23) can act as an adhesion molecule and a cytokine. Perturbances of such molecular interactions may lead to various diseases such as allergies and other inflammatory diseases. It has been speculated that elevated levels of sCD23 may be used to bind secreted IgE, thus preventing it from binding to membrane CD23 on haematopoietic cells, preventing B cells from being activated into IgE producing cells. Signal transduction by sCD23 is dependent on cell subsets, ligands and co-factors required for its function. sCD23 plays a direct role in inducing tumour necrosis factor alpha (TNFα), interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β) and soluble IL-1 receptor from activated human monocytes and PBMCs in vitro. Recombinant forms of 25 and 37 kDa human sCD23 were produced by polymerase chain reaction (PCR)-cloning into pET23a, a bacterial expression vector. The proteins were expressed and refolded, followed by purification by gel filtration chromatography. The purified proteins were biochemically characterized to ensure purity and biological activity, by observing the binding to human IgE both in enzyme-linked immunosorbant assay (ELISA) and surface plasmon resonance (SPR) spectroscopy. ELISA showed KD values of 7.23 x 10-9M and 8.12 x 10-9M for the 25 and 37 kDa proteins, respectively. These values were significantly lower than that of Hibbert et al., (2005). SPR data obtained for the 25 kDa CD23 was not of reliable quality but SPR for the 33kDa sCD23 showed a KD of 1.18 x 10-7M, close to that of Hibbert et al., (2005), J. Exp. Med, 202: 751-760. To test the therapeutic potential of the recombinant molecule, a B-lymphoblastoid cell line (Raji), a pre-monocytic cell line (U937), and PBMCs from normal and hyper-allergic individuals were used. All cells showed no change in production of cytokines. It is essential to investigate further cytokine functions and production implicated by recombinant forms of sCD23, as well as binding of sCD23 to CD21 and CD11b/c, and in vivo IgE regulation before a conclusion can be drawn as to whether recombinant sCD23 is a potential therapeutic target against allergic disease.
- Full Text:
- Date Issued: 2006
- Authors: Askew, Sandra Lyn
- Date: 2006
- Subjects: Ligands , Cell receptors , Cellular signal transduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10305 , http://hdl.handle.net/10948/455 , Ligands , Cell receptors , Cellular signal transduction
- Description: CD23 is a multifunctional receptor/ligand, found in a variety of cell types, such as human peripheral blood mononuclear cells (PBMCs), B-lymphoblastoid cell lines, mast cells and basophils. It is also found on a variety of haematopoietic cell lines. As the low-affinity receptor for immunoglobulin E (IgE), CD23 plays a role in antigen-presentation and macrophage activation. As a surface molecule cleaved from the cell membrane, soluble CD23 (sCD23) can act as an adhesion molecule and a cytokine. Perturbances of such molecular interactions may lead to various diseases such as allergies and other inflammatory diseases. It has been speculated that elevated levels of sCD23 may be used to bind secreted IgE, thus preventing it from binding to membrane CD23 on haematopoietic cells, preventing B cells from being activated into IgE producing cells. Signal transduction by sCD23 is dependent on cell subsets, ligands and co-factors required for its function. sCD23 plays a direct role in inducing tumour necrosis factor alpha (TNFα), interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β) and soluble IL-1 receptor from activated human monocytes and PBMCs in vitro. Recombinant forms of 25 and 37 kDa human sCD23 were produced by polymerase chain reaction (PCR)-cloning into pET23a, a bacterial expression vector. The proteins were expressed and refolded, followed by purification by gel filtration chromatography. The purified proteins were biochemically characterized to ensure purity and biological activity, by observing the binding to human IgE both in enzyme-linked immunosorbant assay (ELISA) and surface plasmon resonance (SPR) spectroscopy. ELISA showed KD values of 7.23 x 10-9M and 8.12 x 10-9M for the 25 and 37 kDa proteins, respectively. These values were significantly lower than that of Hibbert et al., (2005). SPR data obtained for the 25 kDa CD23 was not of reliable quality but SPR for the 33kDa sCD23 showed a KD of 1.18 x 10-7M, close to that of Hibbert et al., (2005), J. Exp. Med, 202: 751-760. To test the therapeutic potential of the recombinant molecule, a B-lymphoblastoid cell line (Raji), a pre-monocytic cell line (U937), and PBMCs from normal and hyper-allergic individuals were used. All cells showed no change in production of cytokines. It is essential to investigate further cytokine functions and production implicated by recombinant forms of sCD23, as well as binding of sCD23 to CD21 and CD11b/c, and in vivo IgE regulation before a conclusion can be drawn as to whether recombinant sCD23 is a potential therapeutic target against allergic disease.
- Full Text:
- Date Issued: 2006
Decorating Asterisk : experiments in service creation for a multi-protocol telephony environment using open source tools
- Authors: Hitchcock, Jonathan
- Date: 2006
- Subjects: Asterisk (Computer file) , Internet telephony
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4635 , http://hdl.handle.net/10962/d1006539 , Asterisk (Computer file) , Internet telephony
- Description: As Voice over IP becomes more prevalent, value-adds to the service will become ubiquitous. Voice over IP (VoIP) is no longer a single service application, but an array of marketable services of increasing depth, which are moving into the non-desktop market. In addition, as the range of devices being generally used increases, it will become necessary for all services, including VoIP services, to be accessible from multiple platforms and through varied interfaces. With the recent introduction and growth of the open source software PBX system named Asterisk, the possibility of achieving these goals has become more concrete. In addition to Asterisk, a number of open source systems are being developed which facilitate the development of systems that interoperate over a wide variety of platforms and through multiple interfaces. This thesis investigates Asterisk in terms of its viability to provide the depth of services that will be required in a VoIP environment, as well as a number of other open source systems in terms of what they can offer such a system. In addition, it investigates whether these services can be made available on different devices. Using various systems built as a proof-of-concept, this thesis shows that Asterisk, in conjunction with various other open source projects, such as the Twisted framework provides a concrete tool which can be used to realise flexible and protocol independent telephony solutions for a small to medium enterprise.
- Full Text:
- Date Issued: 2006
- Authors: Hitchcock, Jonathan
- Date: 2006
- Subjects: Asterisk (Computer file) , Internet telephony
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4635 , http://hdl.handle.net/10962/d1006539 , Asterisk (Computer file) , Internet telephony
- Description: As Voice over IP becomes more prevalent, value-adds to the service will become ubiquitous. Voice over IP (VoIP) is no longer a single service application, but an array of marketable services of increasing depth, which are moving into the non-desktop market. In addition, as the range of devices being generally used increases, it will become necessary for all services, including VoIP services, to be accessible from multiple platforms and through varied interfaces. With the recent introduction and growth of the open source software PBX system named Asterisk, the possibility of achieving these goals has become more concrete. In addition to Asterisk, a number of open source systems are being developed which facilitate the development of systems that interoperate over a wide variety of platforms and through multiple interfaces. This thesis investigates Asterisk in terms of its viability to provide the depth of services that will be required in a VoIP environment, as well as a number of other open source systems in terms of what they can offer such a system. In addition, it investigates whether these services can be made available on different devices. Using various systems built as a proof-of-concept, this thesis shows that Asterisk, in conjunction with various other open source projects, such as the Twisted framework provides a concrete tool which can be used to realise flexible and protocol independent telephony solutions for a small to medium enterprise.
- Full Text:
- Date Issued: 2006
Designing for maintenance
- Authors: Syce, Melvin
- Date: 2006
- Subjects: Buildings -- Maintenance -- South Africa , Buildings -- Protection -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9670 , http://hdl.handle.net/10948/440 , http://hdl.handle.net/10948/d1011924 , Buildings -- Maintenance -- South Africa , Buildings -- Protection -- South Africa
- Description: This treatise is a study of the methodology and the thought processes followed when buildings are designed, in order to determine to what extent, if any, designers consider the need for buildings to be maintained long after they walk off site and part with the project. The concept of taking future maintenance requirements into account as part of the design process is referred to as “designing for maintenance” (DFM). It can be assumed that, from a professional perspective, designers must keep the client’s needs in mind when designing. Facilities managers face the challenge of balancing a budget with maintaining a functional building – a dream building would be a maintenance-free building. Armed with the knowledge of DFM it is hoped that future buildings will be designed in a manner that will facilitate maintenance, thereby achieving significant savings on the life cycle costing of buildings. Buys (2004) suggests that designers should adopt a more open-minded approach toward maintenance during the design stages of buildings. Maintenance, with reference to access, methods, material and funding, could benefit from this approach, with a positive effect on the life cycle costing of a building. In order of priority when starting a building project, the design process is at the top of the list. Because this process happens right at the outset of a project, it is important to address the level of maintenance awareness that goes into designing, at this stage. The research concludes that one of the methods which could have a permanent effect on designers’ awareness of DFM would be to include it in the subjects taught at schools where designers are trained. This idea was discussed with a number of lecturers in this field and they were all in favour of this approach. There is a perception that built environment practitioners and professionals such as architects and contractors in the various fields related to the built environment, often engage in their particular task as if they exist in isolation from the project as a whole and from the rest of the project team. However, it is becoming increasingly evident that all built environment aspects are interwoven and interlinked, and that all are part of a larger context. With reference to the built environment as a whole, no action or element exists in isolation from a larger web of activity. The challenge, to nurture within students an awareness of the range and interconnectedness of elements and processes that contribute to the holistic idea, rests with the educators in the design fields, because it is clear that the final impact of any project relies to a large extent on what was specified by the designers in terms of materials and construction methods. The impact of the world’s six billion inhabitants on the environment is clearly a critical issue but does little to influence the actions of most design professionals. Documented experiences should serve as valuable tools to guide designers towards making more educated decisions on building design. Built environment professionals should educate themselves about the range of issues involved in the analysis, design and production of the built environment and the interaction between these factors.
- Full Text:
- Date Issued: 2006
- Authors: Syce, Melvin
- Date: 2006
- Subjects: Buildings -- Maintenance -- South Africa , Buildings -- Protection -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:9670 , http://hdl.handle.net/10948/440 , http://hdl.handle.net/10948/d1011924 , Buildings -- Maintenance -- South Africa , Buildings -- Protection -- South Africa
- Description: This treatise is a study of the methodology and the thought processes followed when buildings are designed, in order to determine to what extent, if any, designers consider the need for buildings to be maintained long after they walk off site and part with the project. The concept of taking future maintenance requirements into account as part of the design process is referred to as “designing for maintenance” (DFM). It can be assumed that, from a professional perspective, designers must keep the client’s needs in mind when designing. Facilities managers face the challenge of balancing a budget with maintaining a functional building – a dream building would be a maintenance-free building. Armed with the knowledge of DFM it is hoped that future buildings will be designed in a manner that will facilitate maintenance, thereby achieving significant savings on the life cycle costing of buildings. Buys (2004) suggests that designers should adopt a more open-minded approach toward maintenance during the design stages of buildings. Maintenance, with reference to access, methods, material and funding, could benefit from this approach, with a positive effect on the life cycle costing of a building. In order of priority when starting a building project, the design process is at the top of the list. Because this process happens right at the outset of a project, it is important to address the level of maintenance awareness that goes into designing, at this stage. The research concludes that one of the methods which could have a permanent effect on designers’ awareness of DFM would be to include it in the subjects taught at schools where designers are trained. This idea was discussed with a number of lecturers in this field and they were all in favour of this approach. There is a perception that built environment practitioners and professionals such as architects and contractors in the various fields related to the built environment, often engage in their particular task as if they exist in isolation from the project as a whole and from the rest of the project team. However, it is becoming increasingly evident that all built environment aspects are interwoven and interlinked, and that all are part of a larger context. With reference to the built environment as a whole, no action or element exists in isolation from a larger web of activity. The challenge, to nurture within students an awareness of the range and interconnectedness of elements and processes that contribute to the holistic idea, rests with the educators in the design fields, because it is clear that the final impact of any project relies to a large extent on what was specified by the designers in terms of materials and construction methods. The impact of the world’s six billion inhabitants on the environment is clearly a critical issue but does little to influence the actions of most design professionals. Documented experiences should serve as valuable tools to guide designers towards making more educated decisions on building design. Built environment professionals should educate themselves about the range of issues involved in the analysis, design and production of the built environment and the interaction between these factors.
- Full Text:
- Date Issued: 2006
Development and assessment of azithromycin paediatric suppository formulations
- Authors: Mollel, Happiness
- Date: 2006
- Subjects: Azithromycin , Pediatrics , Clinical pharmacology , Pharmacokinetics , Suppositories , Drugs -- Dosage forms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3774 , http://hdl.handle.net/10962/d1003252 , Azithromycin , Pediatrics , Clinical pharmacology , Pharmacokinetics , Suppositories , Drugs -- Dosage forms
- Description: The use of the oral route of administration for the treatment of young children with antibiotics can at times be problematic since, factors such as nausea, vomiting, taste and/or smell, in addition to the challenges associated with the administration of suspensions, may contribute to poor patient compliance. In such cases, the use of the rectal route of administration may be appropriate. Therefore, suppositories containing 250 mg azithromycin (AZI) were manufactured and assessed for potential as an antibiotic suppository dosage form. Suppositories, containing AZI dihydrate were manufactured by the fusion method, using different grades of PEG, Witepsol® and Suppocire® bases. The rate and extent of AZI release was evaluated using USP apparatus I, and samples were analyzed using a validated HPLC method. Differences in the rate and extent of AZI release were observed with the greatest amount of AZI being released from PEG formulations. The rate and extent of AZI release from formulations manufactured using fatty bases were influenced by physicochemical properties, such as melting rate and hydroxyl value, of the bases. In addition drug partitioning appeared to favor the lipid phase and had a negative impact on AZI release characteristics. Two different formulation approaches were used in an attempt to increase the rate and extent of AZI release from fatty base formulations. The use of surfactants significantly increased AZI release from formulations manufactured with fatty bases with high hydroxyl values. The use of urea or Povidone K25 in combination with AZI as a physical mixture or solid dispersion did not increase the rate and extent of AZI release from the fatty suppositories, to any significant extent. The mechanism of drug release was evaluated using several mathematical models, including the Higuchi, Korsmeyer- eppas, Zero and, First order models. In addition, in vitro dissolution profiles were characterized by the difference and similarity factors, f1 and f2 and by use of the Gohel similarity factor, Sd. AZI release kinetics were best described by the Higuchi and Korsmeyer-Peppas models and the values of the release exponent, n, revealed that drug release was a consequence of the combined effects of AZI diffusion, rate of melting of the base and partitioning of the drug which can be considered to be anomalous release.
- Full Text:
- Date Issued: 2006
- Authors: Mollel, Happiness
- Date: 2006
- Subjects: Azithromycin , Pediatrics , Clinical pharmacology , Pharmacokinetics , Suppositories , Drugs -- Dosage forms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3774 , http://hdl.handle.net/10962/d1003252 , Azithromycin , Pediatrics , Clinical pharmacology , Pharmacokinetics , Suppositories , Drugs -- Dosage forms
- Description: The use of the oral route of administration for the treatment of young children with antibiotics can at times be problematic since, factors such as nausea, vomiting, taste and/or smell, in addition to the challenges associated with the administration of suspensions, may contribute to poor patient compliance. In such cases, the use of the rectal route of administration may be appropriate. Therefore, suppositories containing 250 mg azithromycin (AZI) were manufactured and assessed for potential as an antibiotic suppository dosage form. Suppositories, containing AZI dihydrate were manufactured by the fusion method, using different grades of PEG, Witepsol® and Suppocire® bases. The rate and extent of AZI release was evaluated using USP apparatus I, and samples were analyzed using a validated HPLC method. Differences in the rate and extent of AZI release were observed with the greatest amount of AZI being released from PEG formulations. The rate and extent of AZI release from formulations manufactured using fatty bases were influenced by physicochemical properties, such as melting rate and hydroxyl value, of the bases. In addition drug partitioning appeared to favor the lipid phase and had a negative impact on AZI release characteristics. Two different formulation approaches were used in an attempt to increase the rate and extent of AZI release from fatty base formulations. The use of surfactants significantly increased AZI release from formulations manufactured with fatty bases with high hydroxyl values. The use of urea or Povidone K25 in combination with AZI as a physical mixture or solid dispersion did not increase the rate and extent of AZI release from the fatty suppositories, to any significant extent. The mechanism of drug release was evaluated using several mathematical models, including the Higuchi, Korsmeyer- eppas, Zero and, First order models. In addition, in vitro dissolution profiles were characterized by the difference and similarity factors, f1 and f2 and by use of the Gohel similarity factor, Sd. AZI release kinetics were best described by the Higuchi and Korsmeyer-Peppas models and the values of the release exponent, n, revealed that drug release was a consequence of the combined effects of AZI diffusion, rate of melting of the base and partitioning of the drug which can be considered to be anomalous release.
- Full Text:
- Date Issued: 2006
Development and assessment of propranolol sustained release dosage forms separately and in combination with hydrochlorothiazide
- Authors: Chetty, Prakash
- Date: 2006
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3749 , http://hdl.handle.net/10962/d1003227
- Description: Hypertension is a chronic illness that is often undiagnosed and untreated leading to high mortality rates in South Africa. The use of diuretics such as hydrochlorothiazide and beta blockers such as propranolol has been advocated as first line therapy for the treatment of hypertension. The study and use of controlled release dosage forms for the treatment of various disease states has gained wide interest over the past two decades. The use of controlled release systems offers improved therapeutic efficiency over conventional immediate release dosage forms, the use of which at times have often led to poor patient adherence and decreased therapeutic efficiencies. The current research objective was to develop a sustained release multi-source product for propranolol such that once daily dosing would be achieved. In addition, the sustained release product was developed using Inderal® LA 80mg capsules as a reference product. In addition the development of a suitable immediate release hydrochlorothiazide tablet was undertaken to produce a combination dosage form. The use of two different technologies, namely direct compression and wet granulation were employed to develop the sustained release dosage form. The release of propranolol from these dosage forms was assessed using USP apparatus 1 with quantitation of the relevant dissolution samples using a validated high performance liquid chromatographic method. The release profiles from the prototype and subsequent products were subjected to model independent and model dependent analyses in order to compare them to the innovator product and to elucidate the mechanisms of drug release respectively. Dissolution test results reveal that dosage forms prepared from wet granulation showed better rate retardation and more appropriate release profiles than those prepared by direct compression techniques. The subsequent model independent and model dependent analysis show that a dosage form that is comparable to the innovator product has been developed, with drug release occurring by a diffusion type mechanism.
- Full Text:
- Date Issued: 2006
- Authors: Chetty, Prakash
- Date: 2006
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3749 , http://hdl.handle.net/10962/d1003227
- Description: Hypertension is a chronic illness that is often undiagnosed and untreated leading to high mortality rates in South Africa. The use of diuretics such as hydrochlorothiazide and beta blockers such as propranolol has been advocated as first line therapy for the treatment of hypertension. The study and use of controlled release dosage forms for the treatment of various disease states has gained wide interest over the past two decades. The use of controlled release systems offers improved therapeutic efficiency over conventional immediate release dosage forms, the use of which at times have often led to poor patient adherence and decreased therapeutic efficiencies. The current research objective was to develop a sustained release multi-source product for propranolol such that once daily dosing would be achieved. In addition, the sustained release product was developed using Inderal® LA 80mg capsules as a reference product. In addition the development of a suitable immediate release hydrochlorothiazide tablet was undertaken to produce a combination dosage form. The use of two different technologies, namely direct compression and wet granulation were employed to develop the sustained release dosage form. The release of propranolol from these dosage forms was assessed using USP apparatus 1 with quantitation of the relevant dissolution samples using a validated high performance liquid chromatographic method. The release profiles from the prototype and subsequent products were subjected to model independent and model dependent analyses in order to compare them to the innovator product and to elucidate the mechanisms of drug release respectively. Dissolution test results reveal that dosage forms prepared from wet granulation showed better rate retardation and more appropriate release profiles than those prepared by direct compression techniques. The subsequent model independent and model dependent analysis show that a dosage form that is comparable to the innovator product has been developed, with drug release occurring by a diffusion type mechanism.
- Full Text:
- Date Issued: 2006
Email meets issue-tracking: a prototype implementation
- Authors: Kwinana, Zukhanye N
- Date: 2006 , 2013-06-11
- Subjects: Microsoft Visual studio , Electronic mail systems , Computer networks , eXtreme programming , Computer software -- Development
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4614 , http://hdl.handle.net/10962/d1005644 , Microsoft Visual studio , Electronic mail systems , Computer networks , eXtreme programming , Computer software -- Development
- Description: The use of electronic mail (email) has evolved from sending simple messages to task delegation and management. Most mail clients, however, have not kept up with the evolution and as a result have limited task management features available. On the other hand, while issue tracking systems offer useful task management functionality, they are not as widespread as emails and also have a few drawbacks. This thesis reports on the exploration of the integration of the ubiquitous nature of email with the task management features of issue-tracking systems. We explore this using simple ad-hoc as well as semi-automated tasks. With these two working together, tasks can be delegated from email clients without needing to switch between the two environments. It brings some of the benefits of issue tracking systems closer to our email users.The system is developed using Microsoft VisuaI Studio.NET. with the code written in C#. The eXtreme Programming (XP) methodology was used during the development of the proof-of-concept prototype that demonstrates the integration of the two environments, as we were faced at first with vague requirements bound to change, as we better understood the problem domain through our development. XP allowed us to skip an extended and comprehensive initial design process and incrementally develop the system, making refinements and extensions as we encountered the need for them. This alleviated the need to make upfront decisions that were based on minimal knowledge of what to expect during development. This thesis describes the implementation of the prototype and the decisions made with each step taken towards developing an email-based issue tracking system. With the two environments working together, we can now easily track issues from our email clients without needing to switch to another system. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2006
- Authors: Kwinana, Zukhanye N
- Date: 2006 , 2013-06-11
- Subjects: Microsoft Visual studio , Electronic mail systems , Computer networks , eXtreme programming , Computer software -- Development
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4614 , http://hdl.handle.net/10962/d1005644 , Microsoft Visual studio , Electronic mail systems , Computer networks , eXtreme programming , Computer software -- Development
- Description: The use of electronic mail (email) has evolved from sending simple messages to task delegation and management. Most mail clients, however, have not kept up with the evolution and as a result have limited task management features available. On the other hand, while issue tracking systems offer useful task management functionality, they are not as widespread as emails and also have a few drawbacks. This thesis reports on the exploration of the integration of the ubiquitous nature of email with the task management features of issue-tracking systems. We explore this using simple ad-hoc as well as semi-automated tasks. With these two working together, tasks can be delegated from email clients without needing to switch between the two environments. It brings some of the benefits of issue tracking systems closer to our email users.The system is developed using Microsoft VisuaI Studio.NET. with the code written in C#. The eXtreme Programming (XP) methodology was used during the development of the proof-of-concept prototype that demonstrates the integration of the two environments, as we were faced at first with vague requirements bound to change, as we better understood the problem domain through our development. XP allowed us to skip an extended and comprehensive initial design process and incrementally develop the system, making refinements and extensions as we encountered the need for them. This alleviated the need to make upfront decisions that were based on minimal knowledge of what to expect during development. This thesis describes the implementation of the prototype and the decisions made with each step taken towards developing an email-based issue tracking system. With the two environments working together, we can now easily track issues from our email clients without needing to switch to another system. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2006
Feeding dynamics and distribution of the hyperiid amphipod, Themisto gaudichaudii (Guérin, 1828) in the polar frontal zone, Southern Ocean
- Authors: Lange, Louise
- Date: 2006
- Subjects: Themisto gaudichaudii -- Antarctic Ocean , Hyperiidae -- Antarctic Ocean , Zooplankton -- Antarctic Ocean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5696 , http://hdl.handle.net/10962/d1005382 , Themisto gaudichaudii -- Antarctic Ocean , Hyperiidae -- Antarctic Ocean , Zooplankton -- Antarctic Ocean
- Description: The population structure and feeding dynamics of the hyperiid amphipod, Themisto gaudichaudii, was investigated during two cruises of the South African National Antarctic Programme conducted in the Indian sector of the Polar Frontal Zone during austral autumn (April) 2004 and 2005. During the 2004 cruise the frontal features that delimit the PFZ converged to form a single distinctive feature. In 2005, the research cruise was conducted in the vicinity of a cold-core eddy which was spawned from the Antarctic Polar Front. Total mesozooplankton abundance and biomass during the 2004 study ranged from 55.19 to 860.57 ind. m⁻³, and from 2.60 to 38.42 mg dwt m⁻³, respectively. In 2005 the abundance and biomass ranged from 23.1 to 2160.64 ind. m⁻³, and from 0.76 to 35.16 mg dwt m⁻³, respectively. The mesozooplankton community was numerically dominated by copepods, pteropods, and ostracods during both surveys. The abundance and biomass of Themisto gaudichaudii in the region of investigation was < 0.2 ind. m⁻³ (range 0.01 to 0.15 ind. m⁻³) and < 0.06 mg dwt m⁻³ (range 0.02 to 0.06 mg dwt m⁻³) during 2004, while in 2005 the abundance and biomass of the amphipod ranged from < 0.01 to 0.2 ind. m⁻³ and < 0.01 to 0.04 mg dwt m⁻³, respectively. These values correspond to < 1% of the total mesozooplankton abundance and biomass during both surveys. T. gaudichaudii exhibited no significant spatial patterns in abundance, biomass and total length during both 2004 and 2005 (p > 0.05 in all cases). A key feature of the two investigations was the virtual absence of juveniles (total length < 15 mm) among the amphipod population, supporting the suggestion that they exhibit strong seasonal patterns in reproduction. Gut content analysis during both years indicated that for both the male and female amphipods’, copepods were the most prevalent prey species found in stomachs, followed by chaetognaths and pteropods. Results of electivity studies indicate that T. gaudichaudii is an opportunistic predator, generally feeding on the most abundant mesozooplankton prey. Results of in vitro incubations indicated that the total daily feeding rate of T. gaudichaudii during 2004 ranged from 11.45 to 20.90 ind. m⁻³ d⁻¹, which corresponds to between 0.12 and 1.64% of the total mesozooplankton standing stock. In 2005, the feeding rate ranged between 0.1 and 1.73% of the total mesozooplankton standing stock. The low predation impact of T. gaudichaudii during this study can be related to their low abundances and high interannual variability throughout the region of investigation.
- Full Text:
- Date Issued: 2006
- Authors: Lange, Louise
- Date: 2006
- Subjects: Themisto gaudichaudii -- Antarctic Ocean , Hyperiidae -- Antarctic Ocean , Zooplankton -- Antarctic Ocean
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5696 , http://hdl.handle.net/10962/d1005382 , Themisto gaudichaudii -- Antarctic Ocean , Hyperiidae -- Antarctic Ocean , Zooplankton -- Antarctic Ocean
- Description: The population structure and feeding dynamics of the hyperiid amphipod, Themisto gaudichaudii, was investigated during two cruises of the South African National Antarctic Programme conducted in the Indian sector of the Polar Frontal Zone during austral autumn (April) 2004 and 2005. During the 2004 cruise the frontal features that delimit the PFZ converged to form a single distinctive feature. In 2005, the research cruise was conducted in the vicinity of a cold-core eddy which was spawned from the Antarctic Polar Front. Total mesozooplankton abundance and biomass during the 2004 study ranged from 55.19 to 860.57 ind. m⁻³, and from 2.60 to 38.42 mg dwt m⁻³, respectively. In 2005 the abundance and biomass ranged from 23.1 to 2160.64 ind. m⁻³, and from 0.76 to 35.16 mg dwt m⁻³, respectively. The mesozooplankton community was numerically dominated by copepods, pteropods, and ostracods during both surveys. The abundance and biomass of Themisto gaudichaudii in the region of investigation was < 0.2 ind. m⁻³ (range 0.01 to 0.15 ind. m⁻³) and < 0.06 mg dwt m⁻³ (range 0.02 to 0.06 mg dwt m⁻³) during 2004, while in 2005 the abundance and biomass of the amphipod ranged from < 0.01 to 0.2 ind. m⁻³ and < 0.01 to 0.04 mg dwt m⁻³, respectively. These values correspond to < 1% of the total mesozooplankton abundance and biomass during both surveys. T. gaudichaudii exhibited no significant spatial patterns in abundance, biomass and total length during both 2004 and 2005 (p > 0.05 in all cases). A key feature of the two investigations was the virtual absence of juveniles (total length < 15 mm) among the amphipod population, supporting the suggestion that they exhibit strong seasonal patterns in reproduction. Gut content analysis during both years indicated that for both the male and female amphipods’, copepods were the most prevalent prey species found in stomachs, followed by chaetognaths and pteropods. Results of electivity studies indicate that T. gaudichaudii is an opportunistic predator, generally feeding on the most abundant mesozooplankton prey. Results of in vitro incubations indicated that the total daily feeding rate of T. gaudichaudii during 2004 ranged from 11.45 to 20.90 ind. m⁻³ d⁻¹, which corresponds to between 0.12 and 1.64% of the total mesozooplankton standing stock. In 2005, the feeding rate ranged between 0.1 and 1.73% of the total mesozooplankton standing stock. The low predation impact of T. gaudichaudii during this study can be related to their low abundances and high interannual variability throughout the region of investigation.
- Full Text:
- Date Issued: 2006
Feeding ecology, space use and habitat selection of elephants in two enclosed game reserves in the Eastern Cape Province, South Africa
- Authors: Roux, Candice
- Date: 2006
- Subjects: Shamwari Game Reserve (South Africa) , Kwandwe Game Reserve (South Africa) , Elephants -- South Africa -- Eastern Cape , Elephants -- Ecology -- South Africa -- Eastern Cape , Elephants -- Feeding -- South Africa -- Eastern Cape , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Behavior -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5699 , http://hdl.handle.net/10962/d1005385 , Shamwari Game Reserve (South Africa) , Kwandwe Game Reserve (South Africa) , Elephants -- South Africa -- Eastern Cape , Elephants -- Ecology -- South Africa -- Eastern Cape , Elephants -- Feeding -- South Africa -- Eastern Cape , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Behavior -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: The development of small (<300 km²), private game reserves has become a trend, not only in the Eastern Cape Province, but also elsewhere in South Africa as a result of a shift in land use practise from agriculture to ecotourism. The resultant re-introduction of elephants to many of these reserves has lead to management concerns because of the limited research on small reserves regarding their impact on the vegetation. In this study I assessed the space use, habitat selection, diet and impact of two elephant populations on the vegetation in the Eastern Cape Province between February 2004 and March 2005. Home range sizes were calculated using the kernel utilization distribution method. Home range sizes for elephants on Kwandwe were significantly larger during summer than winter (p<0.05). There was no significant difference between the home range sizes of the herds and males within a season and during summer the elephants utilized about 75 % of the reserve and only 54 % during winter. On Shamwari, the herd utilized about 92 % of the reserve during summer and 83 % during winter; while the males utilized 76 % of the reserve. Core areas for both elephant populations shrank from summer to winter and were concentrated around the permanent water sources on each reserve. Habitat selection was assessed using χ² tests and Bonferroni confidence intervals. On Kwandwe, there was a significant difference between observed and expected use of vegetation types (p<0.05) and karroid shrubland was strongly avoided by both herds during summer and winter. The preferred vegetation types of the males ranged from relatively open (short euphorbia thicket, bushclump karroid thicket and karroid shrubland) to completely open (old lands). On Shamwari, subtropical thicket, bontveld and montane grassland were avoided; while primary and secondary acacia thicket, riverine thicket and cultivated lands were preferred. The predominant vegetation type in the home ranges of herds on Kwandwe and Shamwari was subtropical thicket. The diet was assessed by direct observations over two seasons and dietary preferences were calculated. There was a significant difference in the frequency of occurrence of plants in the diet on the two reserves (p<0.05) and no significant effect of time of day or season (p>0.05). Seventeen woody plant species were utilized on Kwandwe and 23 species were utilized on Shamwari. Grass constituted a significantly greater percentage of the diet in summer than winter (p<0.05). Elephants on Kwandwe showed a selective preference for Ozoroa mucronata, Pappea capensis and Acacia karroo; while on Shamwari, A. karroo was selected. Transects were conducted in two different vegetation types on each reserve so as to assess the impact of elephant on the vegetation and damage scores were then calculated from these data. There was no significant effect of vegetation type or elephant density on mean damage scores in Kwandwe (p>0.05). Five hundred and seventy-eight plants were assessed in the subtropical thicket vegetation type and 225 plants were assessed in the savanna-type vegetation, with more than half the trees showing low levels of damage that could not only be attributed to elephants. Mean damage was highest for Portulacaria afra and Pappea capensis in subtropical thicket and for Rhus spp. in the savanna-type vegetation. On Shamwari, 408 plants were assessed in subtropical thicket and 215 in the savanna-type vegetation, with more than 70 % of trees showing low levels of damage. There was a significant effect of plant species and elephant density on the mean damage scores in subtropical thicket, with Aloe ferox showing more damage than the other plant species (p<0.01). In the savanna-type vegetation, A. karroo was the most severely damaged. Overall, damage was greater in the thicket vegetation type compared to the more open vegetation type on both reserves.
- Full Text:
- Date Issued: 2006
- Authors: Roux, Candice
- Date: 2006
- Subjects: Shamwari Game Reserve (South Africa) , Kwandwe Game Reserve (South Africa) , Elephants -- South Africa -- Eastern Cape , Elephants -- Ecology -- South Africa -- Eastern Cape , Elephants -- Feeding -- South Africa -- Eastern Cape , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Behavior -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5699 , http://hdl.handle.net/10962/d1005385 , Shamwari Game Reserve (South Africa) , Kwandwe Game Reserve (South Africa) , Elephants -- South Africa -- Eastern Cape , Elephants -- Ecology -- South Africa -- Eastern Cape , Elephants -- Feeding -- South Africa -- Eastern Cape , Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Behavior -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape
- Description: The development of small (<300 km²), private game reserves has become a trend, not only in the Eastern Cape Province, but also elsewhere in South Africa as a result of a shift in land use practise from agriculture to ecotourism. The resultant re-introduction of elephants to many of these reserves has lead to management concerns because of the limited research on small reserves regarding their impact on the vegetation. In this study I assessed the space use, habitat selection, diet and impact of two elephant populations on the vegetation in the Eastern Cape Province between February 2004 and March 2005. Home range sizes were calculated using the kernel utilization distribution method. Home range sizes for elephants on Kwandwe were significantly larger during summer than winter (p<0.05). There was no significant difference between the home range sizes of the herds and males within a season and during summer the elephants utilized about 75 % of the reserve and only 54 % during winter. On Shamwari, the herd utilized about 92 % of the reserve during summer and 83 % during winter; while the males utilized 76 % of the reserve. Core areas for both elephant populations shrank from summer to winter and were concentrated around the permanent water sources on each reserve. Habitat selection was assessed using χ² tests and Bonferroni confidence intervals. On Kwandwe, there was a significant difference between observed and expected use of vegetation types (p<0.05) and karroid shrubland was strongly avoided by both herds during summer and winter. The preferred vegetation types of the males ranged from relatively open (short euphorbia thicket, bushclump karroid thicket and karroid shrubland) to completely open (old lands). On Shamwari, subtropical thicket, bontveld and montane grassland were avoided; while primary and secondary acacia thicket, riverine thicket and cultivated lands were preferred. The predominant vegetation type in the home ranges of herds on Kwandwe and Shamwari was subtropical thicket. The diet was assessed by direct observations over two seasons and dietary preferences were calculated. There was a significant difference in the frequency of occurrence of plants in the diet on the two reserves (p<0.05) and no significant effect of time of day or season (p>0.05). Seventeen woody plant species were utilized on Kwandwe and 23 species were utilized on Shamwari. Grass constituted a significantly greater percentage of the diet in summer than winter (p<0.05). Elephants on Kwandwe showed a selective preference for Ozoroa mucronata, Pappea capensis and Acacia karroo; while on Shamwari, A. karroo was selected. Transects were conducted in two different vegetation types on each reserve so as to assess the impact of elephant on the vegetation and damage scores were then calculated from these data. There was no significant effect of vegetation type or elephant density on mean damage scores in Kwandwe (p>0.05). Five hundred and seventy-eight plants were assessed in the subtropical thicket vegetation type and 225 plants were assessed in the savanna-type vegetation, with more than half the trees showing low levels of damage that could not only be attributed to elephants. Mean damage was highest for Portulacaria afra and Pappea capensis in subtropical thicket and for Rhus spp. in the savanna-type vegetation. On Shamwari, 408 plants were assessed in subtropical thicket and 215 in the savanna-type vegetation, with more than 70 % of trees showing low levels of damage. There was a significant effect of plant species and elephant density on the mean damage scores in subtropical thicket, with Aloe ferox showing more damage than the other plant species (p<0.01). In the savanna-type vegetation, A. karroo was the most severely damaged. Overall, damage was greater in the thicket vegetation type compared to the more open vegetation type on both reserves.
- Full Text:
- Date Issued: 2006