Theileria species (sable) causes significant mortalities in roan (Hippotragus equinus), and to a lesser extent, sable antelope (Hippotragus niger) yearly. Treatment of the condition and an ‘infect and treat’ vaccination method using a tick-derived stabilate both rely on the availability of buparvaquone, a naphthoquinone with anti-theilerial activity. As buparvaquone is a controlled drug which is not commercially available in South Africa, a viable commercial alternative prevention or treatment method is necessary to control this disease. This study explores the effectiveness of an alternative vaccination method using Theileria sp. (sable) infected in vitro cultured leukoblasts. A Theileria sp. (sable) containing cell line was initiated from lymph node biopsy material of an infected roan antelope and the parasite was successfully propagated in vitro. Attenuation is believed to have been achieved by 16 cycles of passage. Real time PCR suggests that the parasite was successfully transmitted via subcutaneous inoculation with this cell line to two naïve roan antelope. These two inoculated animals remained clinically unaffected by challenge with a tick stabilate used in the ‘infect and treat’ vaccination method. In contrast, the two unvaccinated control animals became clinically ill and required buparvaquone treatment after challenge. This pilot study provides enough evidence to encourage further investigation in the use of Theileria sp. (sable) infected cells as a potential vaccine. A field study involving more animals which are challenged by natural infection after inoculation is the proposed next step. / Dissertation (MMedVet)--University of Pretoria, 2010. / Paraclinical Sciences / unrestricted

Eucalyptus species form an integral part of the South African forestry industry and their uses extend from paper and pulp production to the synthesis of essential oils which are used in various cosmetic products. Throughout their lifetime these hosts are naturally challenged with various pests and pathogens, most of which cause devastating diseases. An approach to curb the spread of pathogens is to enhance the defence response of the host. Most of the information pertaining to defence against pathogens stems from studies conducted in model organisms such as Arabidopsis, however such information is scarce in woody species such as Eucalyptus. It is understood, from model systems, that once the pathogen is perceived by the host, a cascade of defences are initiated such as the activation of salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) signalling pathways. These pathways in turn activate the expression of genes involved in limiting the spread of the pathogen such as pathogenesis-related (PR) proteins. Certain PR genes have also been shown to be markers of the induction of a specific pathway e.g. PR2 is a marker for the SA pathway. This study aimed to elucidate marker genes specific to the SA (PR1, PR2 and PR5) and JA (PR3, PR4 and LOX) signalling pathways in Eucalyptus grandis using the genome sequence, bioinformatics tools and sequence information from other plant species. A co-phylogenetic approach using neighbour joining analysis and maximum likelihood was used to identify and add confidence in the selection of putative orthologs. Following the selection of orthologous markers, the expression profile of these candidate genes was assessed using Reverse transcriptase quantitative PCR (RT-qPCR). Transcript profiling was conducted under mock induction of the signalling pathways as well as under pathogen stress. For the mock induction of the pathways, the expression profiles of the putative marker genes were investigated under various concentrations of the inducer and at various time points. In the interaction with Chrysoporthe austroafricana it was observed that the SA signalling pathway could have a role in facilitating resistance due to the expression profile observed for EgrPR2. In the tolerant genotype (TAG5) this gene was induced at an earlier time point as opposed to the susceptible genotype (ZG14). These putative markers could provide a diagnostic tool for the screening of pathogen challenged eucalypts to determine which signalling pathway(s) are activated against various pathogens. In addition, this research adds to our knowledge of defence responses in E. grandis by elucidating genes that can be used as targets for improving resistance. Additionally this study provides a stepping stone for understanding mechanisms to curb future tree diseases. / Dissertation (MSc)--University of Pretoria, 2014. / Genetics / Unrestricted

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Breast cancer is the most prevalent type of cancer and second leading cause of death in women. Among others, the triple negative breast cancer (TNBC) is the most invasive as it has the highest recurrence and death rates with no targeted therapeutic available thus far. Epidermal Growth Factor Receptor (EGFR) is one of the important targets as more than fifty percent of the TNBC overexpress it but all the therapies designed against it have failed to show significant results. The juxtamembrane domain of EGFR has been explored comparatively recently and has been used to design a decoy peptide with the anticipation to affect the EGFR downstream functions. Previous research has shown it to cause cell death in cancer cells. This study is aimed towards deciphering the mechanism of action of the stapled form of this decoy peptide-SAH5. It presents evidence that the peptide leads to an immediate intracellular calcium release from the Inositol 1,4,5 triphosphate on the endoplasmic reticulum, an inhibition of which can rescue SAH5 induced cell death. The study also demonstrate that the peptide is able to increase the production of Reactive Oxygen Species (ROS) in mitochondria, part of which is triggered by the peptide-induced calcium release.

The main objective of this research was to determine the seed bank longevity of Melinis repens at two Southern Florida sites. Seeds were divided among different exposure levels (shade versus sun) and depths (surface versus buried) and tested for baseline viability using 2,3,5-Triphenyl-tetrazolium chloride. Statistical analysis determined that at the pine rockland site there was a significant interaction between time, exposure, and depth. The initial mean viability at this site declined from 49.71% to 11.26% and 13.06% for sun/buried seeds and sun/surface seeds, respectively, by month 8. The mean viability of shade/surface seeds and shade/buried seeds declined to 24.56% and 22.06% after 8 months. There were no significant effects in the Florida scrub. In order for land managers to completely remove this species from a site, treatment with herbicide will need to continue for a minimum of one year to effectively kill all viable seeds in the seed bank.

Speciation can be understood as a continuum occurring at different levels, from population to species. The recent molecular revolution in population genetics has opened a pathway towards understanding species evolution. At the same time, speciation patterns can be better explained by incorporating a geographic context, through the use of geographic information systems (GIS). Phaedranassa (Amaryllidaceae) is a genus restricted to one of the world’s most biodiverse hotspots, the Northern Andes. I studied seven Phaedranassa species from Ecuador. Six of these species are endemic to the country. The topographic complexity of the Andes, which creates local microhabitats ranging from moist slopes to dry valleys, might explain the patterns of Phaedranassa species differentiation. With a Bayesian individual assignment approach, I assessed the genetic structure of the genus throughout Ecuador using twelve microsatellite loci. I also used bioclimatic variables and species geographic coordinates under a Maximum Entropy algorithm to generate distribution models of the species. My results show that Phaedranassa species are genetically well-differentiated. Furthermore, with the exception of two species, all Phaedranassa showed non-overlapping distributions. Phaedranassa viridiflora and P. glauciflora were the only species in which the model predicted a broad species distribution, but genetic evidence indicates that these findings are likely an artifact of species delimitation issues. Both genetic differentiation and non-overlapping geographic distribution suggest that allopatric divergence could be the general model of genetic differentiation. Evidence of sympatric speciation was found in two geographically and genetically distinct groups of P. viridiflora. Additionally, I report the first register of natural hybridization for the genus. The findings of this research show that the genetic differentiation of species in an intricate landscape as the Andes does not necessarily show a unique trend. Although allopatric speciation is the most common form of speciation, I found evidence of sympatric speciation and hybridization. These results show that the processes of speciation in the Andes have followed several pathways. The mixture of these processes contributes to the high biodiversity of the region

The Tropical Andes make up Earth's most species-rich biodiversity hotspot for both animals and plants. Nevertheless, the ecological and evolutionary processes underlying this extraordinary richness remain uncertain. Here, we examine the processes that generate high richness in the Tropical Andes relative to other regions in South America and across different elevations within the Andes, using frogs as a model system. We combine distributional data, a newly generated time-calibrated phylogeny for 2,318 frog species, and phylogenetic comparative methods to test the relative importance of diversification rates and colonization times for explaining Andean diversity at different scales. At larger scales (among regions and families), we find that faster diversification rates in Andean clades most likely explain high Andean richness. In contrast, at smaller temporal and spatial scales (within family-level clades within the Andes), diversification rates rarely explain richness patterns. Instead, we show that colonization times are important for shaping elevational richness patterns within the Andes, with more species found in habitats colonized earlier. We suggest that these scale-dependent patterns might apply to many other richness gradients. Recognition of this scale dependence may help to reconcile conflicting results among studies of richness patterns across habitats, regions, and organisms.

Oomycetes are eukaryotic fungus-like microorganisms that are known to be pathogenic to plants and animals, causing both ecological and economic damage. Animal pathogenic oomycetes, such as Saprolegnia species are destructive pathogens to many aquatic organisms and are found in most parts of the world. Phytophthora species cause a number of plant diseases. Pythium are less understood as many of these species are saprotrophs which are not thought to be pathogenic. Oomycete research has focussed mainly towards the characterisation and control of pathogenic species with very little information on the ecology of Oomycetes. In this thesis, oomycete species were isolated from water samples collected from rivers in Scotland and Northern England. Baiting and water filtration were used to compare the reliability of both methods, and nested PCR was used to compare the number and types of species obtained in comparison to conventional culturing methodologies. The results suggest that water filtration provided a fast, reliable method for isolating abundant, hardier species such as Pythium undulatum, Saprolegnia diclina, Saprolegnia delica, and Saprolegnia ferax. Water chemistry, surrounding land use, seasonality and land elevation were found to be important factors in Oomycete diversity. Nested PCR of oomycetes directly from filters to obtain target DNA from organisms which are more difficult to culture or less numerous proved to be useful for some species, but will need more refinement of primer and methodologies to obtain species of interest. Sampling of the rivers resulted in the isolation of three new Pythium spp. isolated from the Rivers Spey and Dochart in Scotland. Phylogenetic analysis, infection studies, growth rates and microscopy were used to characterise these three species.

The Wrinkle-lipped free-tailed bat (T. plicata) in Thailand and the Brazilian free-tailed bat (T. brasiliensis) in south-central Texas are integral in the control of agricultural pests. The effect on the production of rice and cotton is determined by the bats consumption of a particular pest species in that region. In Thailand, it is the White-Backed Planthopper (Sogatella furcifera), while in south-central Texas, it is the cotton bollworm (Helicoverpa zea). The ecological service these bat species provide is measured in millions of dollars saved by farmers each year. Finally, a conclusion was made about which species had a greater effect on the economy when compared to each other.

Ischemic stroke is characterized by a disruption of blood supply to a part of the brain tissue, which leads to a focal ischemic infarct. The expression and activity of MMP-9 is increased in ischemic stroke and is considered to be one of the main factors responsible for damages to the cerebral vasculature, resulting in compromised blood-brain barrier (BBB) integrity. However, the regulatory mechanisms of MMP-9 expression and activity are not well established in ischemic stroke. Since hypoxia/ischemia and reperfusion generates reactive oxygen species (ROS), I hypothesize that ROS is one of factors involved in up-regulation of MMP-9 expression in brain cells and ROS-mediated effect may occur via MAPK signaling pathway. My study has provided the evidence that ROS is responsible for an increase in MMP-9 expression in astrocytes mediated via MAPK-AP1 signaling pathway. Preliminary studies with an in vitro model of the BBB suggest that inhibition of MMP-9 is a critical component of reducing ROS-induced BBB permeability.