Browsing by Author "Van Wyk, Johannes H."

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    Lizard epidermal gland secretions I : chemical characterization of the femoral gland secretion of the sungazer, Cordylus giganteus
    (Springer Verlag, 2007-09) Louw, Stefan; Burger, B. V.; Le Roux, Maritha; Van Wyk, Johannes H.
    The giant girdled lizard or sungazer, Cordylus giganteus, is endemic to South Africa. It has been suggested that in this species, as in other lizard species, epidermal glands in the femoral, pre-cloacal regions, and cloacal glands are the main sources of semiochemicals and that these secretions could play an important role at different levels of the social biology of the animals. To gain a better understanding of the nature of the femoral gland secretions of the sungazer, characterization of the constituents of the secretions was carried out. By using GC-MS analysis, in conjunction with auxiliary techniques, such as solventless sample introduction and trimethylsilyl derivatization, 53 relatively involatile compounds, including carboxylic acids, alcohols, ketones, esters, and steroids, were identified in the secretions of both sexes. The study showed that the secretions of male and female sungazers contain only semi-volatile chemicals.
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    Lizard epidermal gland secretions II : chemical characterization of the generation gland secretion of the sungazer, Cordylus giganteus
    (American Chemical Society and American Society of Pharmacognosy, 2011-06) Louw, Stefan; Burger, B. V.; Le Roux, Maritha; Van Wyk, Johannes H.
    In lizards, the epidermal glands of the femoral and precloacal regions are involved in the production of semiochemicals. In addition to its femoral glands, the giant girdled lizard, or sungazer, Cordylus giganteus, which is endemic to South Africa, has generation glands as an additional potential source of semiochemicals. These epidermal glands are described as glandular scales that overlay the femoral glands and are included in the normal epidermal profile located in the femoral (thigh) and anterior antebrachial (fore-leg) regions of the male sungazer. GC-MS analysis of the generation gland secretions and the trimethylsilyl derivatives of some of the steroidal constituents was employed to identify 59 constituents, including alkenes, carboxylic acids, alcohols, ketones, aldehydes, esters, amides, nitriles, and steroids. The quantitative differences of the volatile constituents of the fore- and hind-leg generation glands were compared between individuals. This is the first report on the chemical composition of generation glandular material of lizards. © 2011 The American Chemical Society and American Society of Pharmacognosy.
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    Pharmaceutical and personal care products (PPCPs) as endocrine disrupting contaminants (EDCs) in South African surface waters
    (South African Water Research Commission, 2017-10) Archer, Edward; Wolfaardt, Gideon M.; Van Wyk, Johannes H.
    Globally, water resources are under constant threat of being polluted by a diverse range of man-made chemicals, and South Africa is no exception. These contaminants can have detrimental effects on both human and wildlife health. It is increasingly evident that several chemicals may modulate endocrine system pathways in vertebrate species, and these are collectively referred to as endocrine disrupting contaminants (EDCs). Although the endocrine-disrupting effect of water pollutants has been mainly linked to agricultural pesticides and industrial effluents, other pollutants such as pharmaceuticals and personal care products (PPCPs) are largely unnoticed, but also pose a potentially significant threat. Here we present for the first time in a South African context, a summarised list of PPCPs and other EDCs detected to date within South African water systems, as well as their possible endocrine-disrupting effect in-vitro and in-vivo. This review addresses other factors which should be investigated in future studies, including endocrine disruption, PPCP metabolites, environmental toxicology, and antibiotic resistance. The challenges of removing EDCs and other pollutants at South African wastewater treatment works (WWTWs) are also highlighted. The need for focused research involving both in-vitro and in-vivo studies to detect PPCPs in water systems, and to delineate adverse outcome pathways (AOPs) of priority PPCPs to aid in environmental impact assessment (EIA), are discussed.