Links between declining human male fertility (decreased sperm counts, increased incidence of both testicular cancer and genital abnormalities) and the increasing prevalence of endocrine disrupting chemicals (EDCs) in the environment have been reported. We aim to characterise the key developmental processes occurring during human fetal gonad development. Human fetal testis development was characterised by a transient increase in interstitial area proliferation between 13-19 weeks which was accompanied by an increase in steroidogenic acute regulatory protein (StAR) and steroidogenic enzymes. Androgen receptor was expressed by the peritubular myoid cells which had a high bcl-2:bax ratio, indicative of cell survival. Estrogen receptors ( and ) were localised to distinct cell populations. In the ovine gonad similar developmental processes occurred, and comparison with human ovarian development demonstrated interesting parallels. After optimisation, the explant culture system revealed that exposure to the insecticidal EDC dieldrin, at low (<1 ppb) doses reduced LH-stimulated testosterone output in the human fetal testis. This was accompanied by dose-specific changes to the testis proteome, alterations in bcl-2:bax ratios in favour of apoptosis and a down-regulation in StAR expression relative to the LH-treated controls. In conclusion, the processes of proliferation apoptosis, steroidogenesis and steroid action are crucial during fetal gonad development. We demonstrated that in utero exposure to dieldrin may cause reproductive dysfunction in adult life due to reduced steroidogenesis in the fetal gonad; mediated through a down-regulation in StAR expression and alterations in the regulation of gonadal apoptosis.

No description available.

Bibliography: leaves 186-210.

Perfluorooctanoate (PFOA) and Perfluorooctane sulfonate (PFOS) are two environmentally persistent perfluorinated compounds widely used for many industrial and consumer products due to their high thermal, oxidative resistance and surface repellence to water and oil. Their reproductive and developmental toxicity in lab animals and their persistence in environment have raised a serious concern for humans and animals. Trace amounts of these compounds have been found in water bodies, human blood, and wildlife samples. PFOA and PFOS are currently listed in Environmental Protection Agency's drinking water Contaminant Candidate List and in the list of Persistent Organic Pollutants in the Stockholm Convention. The strong covalent bond between carbon and fluorine present in PFOA and PFOS makes them stable and resistant to conventional treatment processes. Several advanced chemical processes can degrade PFOA and PFOS under high temperatures and pressures or other extreme conditions. However, the potential of biodegradation as a treatment technology for these compounds hasn't been developed successfully. This thesis focuses on evaluating the biodegradation potential of PFOA and PFOS. Fluoroacetate dehalogenase is an enzyme capable of defluorinating fluorinated aliphatic compounds. In this study, the potential of fluoroacetate dehalogenaseexpressing microorganisms to biodegrade PFOA and PFOS is examined. Two known fluoroacetate dehalogenase-expressing strains and fluoroacetate-degrading mixed cultures were used. The effect of ammonia in the enzyme activity was extended to study its effect on the biodegradation of PFOA and PFOS. Fluoride ions released during the mineralization of the PFOA and PFOS was used as a proof of biodegradation. The experiments with fluoroacetate dehalogenase-expressing strains and mixed culture consortia enriched from soil showed an increase in fluoride concentration in the solution thus indicating the possibility of successful biodegradation of PFOA and PFOS. Based on the fluoride ion content, it was also concluded that ammonia inhibits the enzyme activity in one of the two pure strains.

This study looks at the role that liberal economic norms are playing in international environmental negotiations on hazardous chemicals (including wastes), and the implications of these norms for the protection of the environment and human health from the thousands of chemicals on the market. The key trait of liberal economic norms in relation to global environmental governance is their assumption that the liberalisation of trade and finance and economic growth are both consistent with and necessary for environmental protection. From this assumption follows, for instance, the idea that states should adopt the "least-trade restrictive" measures required to protect the environment and human health. I argue that liberal economic norms are "hegemonic," in a Gramscian sense, in chemicals-related international environmental negotiations. This means that a wide range of actors, including those that do not necessarily accept the liberal economic perspective, are upholding liberal economic norms in their statements and proposals if not out of conviction then out of a perceived need to be realistic or persuasive. The most important implication of liberal economic hegemony is that it is widely assumed that human health and the environment can be effectively protected from the negative effects of hazardous chemicals even though the volume of chemicals and chemical-containing products being consumed is increasing at a spectacular rate. The issue of growing consumption of chemicals is therefore consistently framed as a problem of quality (hazardousness) rather than quantity. To understand consumption in this narrow sense is problematic, however, because there is considerable scientific uncertainty concerning the environmental and health effects of most of the chemicals on the market and because chemicals that pose minimal risks to the environment and human health might be very hazardous when they are being manufactured or upon becoming waste. In order to address the problem of hazardous chemicals effectively, it is necessary to challenge the hegemony of liberal economic norms in international environmental negotiations. This can be done, I conclude, by deepening a number of fissures in the hegemony of the liberal economic perspective that can be detected in the context of chemicals-related instruments.

This thesis describes the results of the analytical effort dealing with the products from the preliminary experimental runs using the Advanced Extruder Feeder Biomass Liquefaction Facility in the period from August 1985 to December 1986. Results of the analyses show that a low-oxygen crude wood oil could be produced over a wide range of temperatures, pressures, with or without carbon monoxide and with or without a sodium carbonate catalyst. The analytical procedures have been adapted to evaluate the crude wood oil by standard investigative procedures, including elemental analysis, nuclear magnetic resonance, infrared spectroscopy, gas chromatograph-mass spectrometry, and gas chromatography.

Many chemicals released into the environment are believed to disrupt normal endocrine functions in humans and animals. These endocrine disrupting chemicals (EDCs) affect reproductive health and development. A major group of EDCs that could be responsible for reproductive effects are those that mimic natural oestrogens, known as xeno-oestrogens. A number of in vivo and in vitro screening strategies are being developed to identify and classify xeno-oestrogens, in order to determine whether they pose a health risk to humans and animals. It is also important to be able to apply the assays to environmental samples for monitoring purposes. In South Africa information on the levels of EDCs in water is limited. While establishing the recombinant yeast screen bioassay (RCBA) using the yeast strain Sacchyromyces cerivisiae for oestrogenic activity, problems were experienced with contamination. Four South African laboratory water sources were assessed. From the results it was clear that the water used in the preparation of the medium for the assay was the source of oestrogenic contamination. Care should be taken to eliminate all possible sources of contamination in the test procedures to eliminate the reporting of false positive results. The fact that South African laboratory and surface waters tested positive for estrogenic activity has far reaching implications regarding reproductive and general health.

No description available.

This study looks at the role that liberal economic norms are playing in international environmental negotiations on hazardous chemicals (including wastes), and the implications of these norms for the protection of the environment and human health from the thousands of chemicals on the market. The key trait of liberal economic norms in relation to global environmental governance is their assumption that the liberalisation of trade and finance and economic growth are both consistent with and necessary for environmental protection. From this assumption follows, for instance, the idea that states should adopt the "least-trade restrictive" measures required to protect the environment and human health. I argue that liberal economic norms are "hegemonic," in a Gramscian sense, in chemicals-related international environmental negotiations. This means that a wide range of actors, including those that do not necessarily accept the liberal economic perspective, are upholding liberal economic norms in their statements and proposals if not out of conviction then out of a perceived need to be realistic or persuasive. The most important implication of liberal economic hegemony is that it is widely assumed that human health and the environment can be effectively protected from the negative effects of hazardous chemicals even though the volume of chemicals and chemical-containing products being consumed is increasing at a spectacular rate. The issue of growing consumption of chemicals is therefore consistently framed as a problem of quality (hazardousness) rather than quantity. To understand consumption in this narrow sense is problematic, however, because there is considerable scientific uncertainty concerning the environmental and health effects of most of the chemicals on the market and because chemicals that pose minimal risks to the environment and human health might be very hazardous when they are being manufactured or upon becoming waste. In order to address the problem of hazardous chemicals effectively, it is necessary to challenge the hegemony of liberal economic norms in international environmental negotiations. This can be done, I conclude, by deepening a number of fissures in the hegemony of the liberal economic perspective that can be detected in the context of chemicals-related instruments.

No description available.