This study investigated the effects of the Triffid weed Chromolaena odorata on small and large mammals in Hluhluwe-iMfolozi Park. C. odorata is a widespread invasive alien plant that poses threat to the highly maintained natural vegetation in HiP and most other protected areas in KwaZulu-Natal. Following the opinion that the effects of invasive alien plants on all levels of biodiversity need to be recognised for their effective control, we compared small and large mammal species richness and diversity between areas with differing C. odorata invasion durations, areas with differing clearing times and an area with no history of invasion as a control area. Small mammal trapping was done using Sherman live traps and mark-recapture techniques. Track counts were used to estimate large mammal species abundance, richness and diversity. The control area had higher small mammal species richness and diversity than the invaded areas, which suggests that invaded areas were not suitable habitats for small mammals. It was also found that small and large mammal species richness and diversity decreased with the increase in invasion duration, which shows that the more time C. odorata is left to establish the more disturbance it causes to the habitat. We found the uninvaded treatment to have the highest diversity of large mammal species than all the invaded treatments, which suggests that large mammalian species show some degree of avoidance to the invaded areas. We also found that there were significant differences between the treatments with regard to large mammal species diversity indices. Some of the large mammalian species appeared to neither avoid nor prefer invaded areas. It is hypothesized that they use invaded areas to hide away from predators as most of them fall prey to many carnivores. Also, C. odorata invaded areas could provide suitable shelter from climatic extremes. The treatments cleared of C. odorata showed an increase in both small and large mammalian species richness and diversity, suggesting that clearing of this plant helps in rehabilitation of the ecosystem. However, large mammal species composition in the cleared treatments remained different to preinvasion state, which suggests that the habitat may remain changed for a long time after clearing. Managers of conservation areas should therefore prioritise alien plant removal in order to maintain healthy ecosystems. / Dissertation (MSc (Wildlife Management))--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Recently nanoparticles (NPs) have been introduced and used in combination with therapeutic approaches to develop nanotechnology-enabled medicine. These nanostructures allow for the exploitation of the physiochemical properties which may be beneficial in cancer treatment. The use of NPs in nanomedicine has proven successful in modern chemotherapeutics and has demonstrated promising potential in in vivo and in vitro radiosensitization studies. This is a baseline study aimed to determine the cytotoxic effects of AuNPs for potential radiosensitization analysis. The study analysed the effects of different AuNP sizes (30, 50 and 80nm), concentrations (5, 10 and 15 μg/ml) over various time periods in CHOK1 and A549 cells.

Recently, the occurrence of a mammalian endocannabinoid ligand N-arachidonoylethanolamide (anandamide, AEA, NAE20:4), was reported in early land plants. Unlike seed plants, bryophytes such as Physcomitrella patens possess unique fatty acid composition that includes long-chain fatty acids such as arachidonic acid (AA, 20:4) and eicosapentaenoic acid (EPA, 20:5). We performed targeted lipid profiling to discovere long-chain N-acylethanolamines (NAEs) and their corresponding N-acylphosphatidylethanolamine (NAPE) precursors in Physcomitrella and Selaginella. In protonemal tissues, N-arachidonyl-PE and N-20:5-PE contributed to about 49 % and 30 %, respectively. Matured gametophytes on the other hand showed a 12 % increase in N-20:4-PE and 20 % decline in N-20:5-PE, relative to NAPE content in protonemata. In all haploid developmental stages analyzed, NAE20:4 levels contributed to ~ 23 % of the total NAE while NAE 20:5 remained as a minor component (5 %). Interestingly, in Selaginella moellendorffi, an early vascular plant, N-18:2-PE species was most abundant and 20C-NAEs were present in trace amounts. To understand biological implications of anadamide, we examined the effects of exogenously applied AEA and its corresponding fatty acid (AA) on moss protonemata growth. Both AEA and AA inhibit growth of gametophytes and protonemata in a dose dependent manner, while AEA exclusively affected actin-mediated tip growth. Additionally, we identified moss ortholog for NAPE-hydrolyzing phospholipase D (NAPE-PLD) enzyme that likely generates AEA and a fatty acid amide hydrolase (FAAH) that catabolizes AEA. Both putative PpNAPEPLD and PpFAAH are expressed in E. coli for further characterization. Our data demonstrates the occurrence of evolutionarily conserved NAE metabolic pathway in the moss, with unique composition. Functional and evolutionary implications of this mammalian endocannabinoid in early land plants, however, remains elusive.

Control of gene expression is essential for synthetic biology. Drug-inducible systems allow for gene expression levels to be precisely regulated through the administration of exogenous chemical inducers, and by combining these systems, more complex circuits with multiple inputs and outputs can be designed. However, the number of existing orthogonal drug-inducible systems is limited. Therefore, there remains a need for new, small-molecule-inducible systems that are orthogonal to both existing systems and native cellular function. Here, we focus on the development and applications of two small-molecule inducible systems for use in basic research, synthetic systems, and therapeutics: the ligand-inducible connection (LInC) system and the HaXS8-inducible system. In the LInC system, the NS3/4a protease from hepatitis C virus is used to regulate the linkage between genetically fused DNA-binding elements and transcriptional effector domains, which remain linked only in the presence of an NS3/4a protease inhibitor. The antiviral drugs which are used as inhibitors for NS3-based systems provide ideal small-molecule inputs for synthetic biology applications, as they are designed to be orthogonal to native biological function and have been tested for clinical use in humans. We demonstrate the construction and validation of a LInC transcription factor (TF) system, as well as further extension of the system with an “all-in-one” single vector design. We then continue on to describe the application of a small molecule (HaXS8) heterodimer system based on the SNAP-tag and HaloTag domains to control gene expression and protein behavior. We demonstrate the construction and validation of several HaXS8-inducible proteins, including TFs, Cre recombinase, and caspase-9. Together, our work on these two systems provides additional orthogonal methods of small molecule-inducible gene expression and protein function for use in control of cellular behavior. / 2024-05-23T00:00:00Z

<p> Dihydrofolate reductase from a subline of the L1210 lymphoma was purified by affinity chromatography using substituted Sepharose -4B to which was coupled methotrexate, a specific, tight binding inhibitor of the enzyme. The purified enzyme was subjected to disc gel electrophoresis at pH 8.5. At least two bands of activity were detected on the gel by the formation of a reduced formazan. Their ratios were dependent on enzyme concentration. Similar bands were found in the presence of EDTA (10^-6M), 4M and SM urea. When a substrate, NADPH (5xl0^-5M), was added to the buffers used in electrophoresis, three bands of enzyme activity were present in a fixed ratio which was independent of enzyme concentration. Protein bands showed a different but constant ratio. When folate replaced dihydrofolate as substrate in the assay mixture, the bands of activity corresponded at high concentrations of the enzyme. When activity was detected in the presence of an increasing concentration of methotrexate, different inhibition of the bands resulted. Preliminary experiments with crude extracts of the same subline gave activity profiles with multiple peaks.</p> / Thesis / Master of Science (MSc)

<p> The present investigation was concerned with mitochondrial energy transfer reactions and their relationship to mitochondrial structural integrity. Experiments with azide demonstrated a close relationship between oxidative phosphorylation and large amplitude mitochondrial volume changes. Azide inhibited energy transfer and energy-linked mitochondrial swelling by competing with adenine nucleotide for a site on the terminal phosphorylating enzyme. As a permeant anion azide exerted secondary effects on mitochondrial structure and function.</p> <p> Experiments with mitochondria treated with phlorizin and phloretin emphasized the importance of Mg++ as a controlling factor in maintaining the integrity of mitochondrial energy transfer processes. The results indicated that these compounds interfered directly with oxidative phosphorylation, and that mitochondrial swelling was either a consequence of impaired energy transfer, or a separate phenomenon.</p> / Thesis / Doctor of Philosophy (PhD)

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No description available.

An adequate supply of oxygen (02) is essential to the survival of all higher organisms. The mammalian carotid body, located at the common carotid artery senses blood levels of 0 2, carbon dioxide (C02) and acidity. Glomus cells, or type I cells in the carotid body are the main 0 2-sensors which regulate blood p02 via reflex control of ventilation. The carotid body secretes multiple neurotransmitters including dopamine (DA), which is potentiated during low p02 levels and is thought to modulate sensory signaling by apposing afferent nerve fibers. Catecholamine (CA) release is also critical for the animal's ability to survive hypoxic stress associated with the birthing process and the transition to extrauterine life. However, the source for this CA release (primarily epinephrine; EPI) is from adrenal chromaffin cells. The primary 02-sensor in both adrenal chromaffin cells and carotid body type I cells is unknown. One potential candidate is the cytochrome b55s/NADPH oxidase complex that generates the respiratory burst in phagocytes. To test this hypothesis, cultured adrenal medulla chromaffin cells and intact carotid bodies from wild type (WT) and oxidase deficient (OD) mice (knockout gp91 phox, the glycoprotein subunits in the NADPH oxidase complex) were investigated. High performance liquid chromatography and immunocytochemistry were used to quantify amine release in these two chemoreceptors following exposure to hypoxia. Both WT and OD chromaffin cells and carotid bodies responded to the hypoxic challenge with increased monoamine secretion. Norepinephrine and epinephrine were the principal amines released from chromaffin cells, compared to dopamine and serotonin from carotid bodies. These findings suggest that NADPH oxidase is not the primary 02- sensor in either chemosensory system. Quantification of monoamine secretion in intact carotid body from mouse and rat was also compared under basal conditions and after exposure to hypoxia and acid/hypercapnia (pH 7.10). Significantly larger amounts of basal serotonin was secreted from mouse carotid body as compared to the rat. Interestingly, serotonin release was potentiated by hypoxia in mouse carotid body, but this was not observed in the rat. Additionally, ratio of basal level serotonin-to-dopamine secretion was significantly higher in mouse than rat CB. Surprisingly, acid/hypercapnic (pH 7.1 0) had no detectable effect on amine secretion from either mouse or rat carotid body. / Thesis / Master of Science (MSc)

Perturbations of the complex intrinsic and extrinsic factors that contribute to cellular differentiation can have many consequences ranging from dedifferentiation to cell death. The overall objective of my research is to investigate the factors that contribute to the maintenance of mature midbrain neurons and glia. In order to address this objective, I first carried out a detailed immunocytochemical analysis to demonstrate that histone deacetylase inhibitor (HDACI) treatment of differentiated midbrain neurons in culture results in an overall destabilization of neuronal phenotype, which leads to caspase-independent cell death. GFAP positive astrocytes are refractory to the effects of HDACI treatment, suggesting that inhibition of HDACs has differential effects on neurons and glia. HDACI treatment alone was not sufficient to induce neuronal dedifferentiation as evidenced by RT-PCR analysis of stem/progenitor markers, and recovery experiments. Finally, I demonstrate that cortical neurons do not undergo cell death in response to HDACI treatment, suggesting that there may be microenvironmental factors that promote the susceptibility of midbrain neurons to the neurotoxic effects of HDACI. In the second part of this thesis I determined the molecular mechanism that was at least partly responsible for the effects of HDACI treatment on midbrain neurons. Gene expression profiling of HDACI treated midbrain cultures revealed a strong down-regulation of immune related factors. This observation is supported by the loss of microglia in HDACI treated midbrain cultures. I also provide evidence that Toll-like receptor (TLR) signaling, likely through the activation of Interleukin-6 (IL-6) expression, mediates HDAC-dependent neuronal survival. These data provide new evidence that the neuroimmune system is an extrinsic regulator for the homeostasis and survival of neurons.