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Phylogeography and speciation in the genus arthroleptella
(University of the Western Cape, 2010) Turner, Andrew Alexander
Moss frogs are restricted to permanently moist terrestrial habitats in the south-western Cape Fold Mountains. There is a very close association between Arthroleptella distribution and Table Mountain Sandstone. Suitable habitats are generally occupied by allopatric populations of moss frogs. Comprehensive spatial sampling of moss frogs (genus Arthroleptella) in the Cape Floristic Region biodiversity hotspot yielded 192 new distribution records; 5 842 advertisement calls from 240 individual male frogs; 31 Rag-1, 76 16S, 54 12S sequences and morphological measurements of 90 specimens. There are many differences in male advertisement call and genetic sequences between populations on different mountain ranges, even over small distances. A mitochondrial and nuclear gene phylogeny of the southern African Pyxicephalidae places Natalobatrachus as the sister genus to Arthroleptella. Application of a Bayesian relaxed molecular clock model indicates that Arthroleptella arose between 20 and 39 Ma. Phylogenetic trees return two main clades within Arthroleptella: one consists of species which exhibit chirp-like calls and the second contains species with longer calls composed of a series of clicks. These two clades diverged between 19 and 22 Ma. There is a general pattern of strong phylogeographic structure with many small, isolated populations. Three species are identified within the Chirping clade and seven in the Clicking clade, including three undescribed species. This population structure is a result of the patchy distribution of suitable habitat and low vagility of the moss frogs. The distribution and speciation of moss frogs has been affected by drying and cooling climate change, changing geomorphology over the last 20 Ma and the increasing prevalence of fire over the last 5 Ma. An assessment of the threat status of each species according to IUCN criteria categorised one species as Least Concern, seven as Near Threatened, one as Vulnerable and one as Critically Endangered. The primary threats to Arthroleptella are invasive alien plants and increased fire frequencies and intensities.
Premature aging of the lungs of the offspring induced by maternal nicotine exposure during gestation and lactation: protective effects of tomato juice
(University of the Western Cape, 2012) Mutemwa, Muyunda
Tobacco smoking during pregnancy and lactation is a common habit and accounts for a significant percentage of fetal morbidity and mortality worldwide. The offspring is as a result exposed to nicotine through the blood and the milk of the mother. Nicotine is thus expected to interact with the developing fetus and the offspring of mothers who smoke or use NRT for smoking cessation, resulting in the interference with normal fetal and neonatal lung development. Maternal cigarette smoke or nicotine exposure produces adverse effects in the lungs of offspring, these include; intrauterine growth retardation, low birth weight, premature birth, reduced pulmonary function at birth, and a high occurrence of respiratory illnesses after birth. This study aimed at investigating the effects of maternal nicotine exposure during gestation and lactation on lung development in the offspring; to establish whether tomato juice can have protective effects on the fetal lung development and function in the offspring; and to determine if nicotine cases premature aging of the lungs of the offspring. It was therefore shown that maternal exposure to nicotine during gestation and lactation had no significant effect on the growth parameters of the offspring. Maternal nicotine exposure during gestation and lactation had no effect on the growth parameters of the offspring, but resulted in compromised lung structure and function. The morphometric results demonstrated decrease in alveolar number, increase in alveolar size, and decrease in lung parenchyma of the nicotine exposed animals showing a gradual deterioration of the lung parenchyma. Structural alterations include emphysematous lesions, where the latter was accompanied by an increase in alveolar size (Lm), and a decrease in the tissue volume of the lung parenchyma. Thickening of alveolar walls was also evident and serves as an indication of remodeling of the extracellular matrix, also a characteristic of emphysema. A consequence of the gradual deterioration of the lung parenchyma is a decrease in the alveolar surface area available for gas exchange. The present study showed that the emphysematous lesions were conceivably a result of a reduced rate of cell proliferation accompanied by the increase in senescent cells numbers in the alveolar walls of the exposed offspring. The data of this study suggests that maternal nicotine exposure during gestation and lactation induces premature aging of the lungs of the offspring rendering the lungs of the offspring more susceptible to disease later in life. Since these structural changes occurred later in the life of the offspring and long after nicotine withdrawal, it is suggested that it is programmed during gestation and lactation. Smoking and NRT result in an increased load of oxidants in the mother and fetus. It also reduces the level of anti-oxidants and thereby compromising the ability of the mother to protect the fetus. It is hypothesized that this oxidant antioxidant imbalance will program the lungs to age prematurely. The supplementation of the mother’s diet with tomato juice, rich in lycopene, other anti-oxidants such as vitamin C, as well as phytonutrients protected the lungs of the offspring against the adverse effects of maternal nicotine exposure. This supports the hypothesis mentioned above. The study further showed that the effects of grand-maternal nicotine exposure during gestation and lactation on the lungs of the F1 offspring is also transferred to the F2 offspring. This is most likely via the paternal and maternal germ line. Since tomato juice supplementation of the mother’s diet with tomato juice prevented the adverse effects of maternal nicotine exposure on the lungs of the offspring, it is conceivable that it will prevent transfer of these changes to the F2 generation.
Characterization of Candida species isolated from the oral mucosa of HIV-positive African patients
(University of the Western Cape, 2013) Abrantes, Pedro Miguel dos Santos
One of the most common HIV-associated opportunistic infections is candidiasis, caused by Candida albicans or other Candida species. In immune suppressed subjects, this commensal organism can cause an increase in patient morbidity and mortality due to oropharyngeal or systemic dissemination. Limited information exists on the prevalence and antifungal susceptibility of Candida species in the African continent, the most HIV-affected region globally and home to new and emerging drug resistant Candida species. The mechanisms of Candida drug resistance in the African continent have also not been described. In this study, 255 Candida species isolated from the oral mucosa of HIV-positive South African and Cameroonian patients were identified using differential and chromogenic media and their drug susceptibility profiles tested using the disk diffusion method and the TREK Sensititre system, an automated broth microdilution method. Candida cell wall fractions were run on SDSPAGE and HPLC-MS with the aim of identifying peptides specifically expressed by antifungal drug resistant isolates. Comparisons between the two groups of isolates revealed differences in Candida species prevalence and drug susceptibility with interesting associations observed between specific drug resistance and duration of ARV therapy. This study showed that fluconazole, the drug of choice for the treatment of candidiasis in the African continent, is not an effective therapy for most cases of Candida infection, and suggests that regional surveillance be implemented in the continent. A multiple-drug resistant Candida strain was identified in this study, a finding that has not previously been documented. The use of proteomics tools allowed for the identification of peptides involved in drug resistance and the elucidation of Candida colonization mechanisms in HIV-infected African patients.
Sperm mitochondria: species specificity and relationships to sperm morphometric features and sperm function in selected mammalian species
(University of the Western Cape, 2011) Maree, Liana
Numerous studies on mammalian spermatozoa have reported large variations in the dimensions of the main sperm structural components, namely the head, midpiece and flagellum. These variations in sperm architecture are believed to be adaptations for functioning of spermatozoa in complex environments outside the male reproductive system. The midpiece of the mammalian spermatozoon contains a varied number of mitochondria, but the reason for the marked difference in the size and structure of this sperm component is not clear. This study confirmed the variations in the sperm morphometry of seven selected mammalian species and revealed unique features of the sperm midpiece and sperm mitochondria of these seven species. Evaluation of several sperm kinematic parameters revealed the unique swimming characteristics of the different spermatozoa. The importance of using standardized motility parameters was highlighted as well as the assessment of different subpopulations of spermatozoa in order to produce more reliable and comparable data. Investigating the role of sperm mitochondria in human sperm metabolism indicated that these organelles are related to sperm function in terms of sperm motility. Furthermore, it was suggested that glycolysis and mitochondrial respiration are linked processes and that both are important for the maintenance of human sperm motility. By optimizing and employing standardized experimental procedures and analysis techniques, this study was able to confirm the species specificity of almost all the sperm parameters evaluated, while also elucidating the phylogenetic relatedness of the non-human primate species. In conclusion, the present study has confirmed that the various midpiece morphometry parameters are related to the remaining sperm morphometry parameters as well as to the sperm kinematic parameters. These proposed associations between the various sperm parameters were used to explain the sperm velocity of two hypothetical and morphologically different sperm structures. Therefore, the results of the current study support the idea of co-evolution between sperm components in mammalian spermatozoa and propose that the midpiece morphometry parameters that are selected for in these spermatozoa are midpiece volume, total number of mitochondrial gyres, thickness of the mitochondrial sheath and mitochondrial height.
Face-work and identities in a discussion about xenophobia
(University of the Western Cape, 2011) Bock, Zannie
International students arriving at the University of the Western Cape (UWC) from other African countries find themselves in a position of having to negotiate their identities and positions with their South African counterparts. The local students too are faced with the prospect of doing the same since they have to coexist with the former. This study aims to investigate how, in a discussion about xenophobia, a selection of UWC students perform face-work and negotiate or construct their identities as well as those of their coparticipants and position themselves in relation to each other. I was interested in exploring how the participants, who were representative of the two groups that clashed in the xenophobic attacks of 2008, would engage with each other while discussing this sensitive topic.The data was gathered during an open-ended discussion among four UWC postgraduate students in a casual, relaxed setting (my room on campus). The transcribed data was then analyzed using a combination of theoretical frameworks from Systemic Functional Linguistics (SFL) and Discourse Analysis. In particular, the SFL theory of modality(Halliday 1994) and Engagement (Martin and White 2005) and Goffman’s (1999[1967]) notion of face were used as tools of analysis.The analysis reveals that participants use a variety of linguistic choices and discourse strategies to maintain face during the discussion of this sensitive topic of xenophobia. The participants make an effort to take care of each other’s face (desires to be appreciated and left free of any imposition) and keep conflicts to a minimum even when they at times disagree and give incriminatory information about each other. It also reveals that the participants, in addition to maintaining face, also construct and negotiate identities which in turn help build in-group solidarity and provide a sense of belonging to them.