Ravidomycin is a yellow antitumor antibiotic produced by Streptomyces ravidus. Ravidomycin shows strong antitumor activity against P388 lymphocytic leukemia, the colon 38 tumor, and the CD8Fl mammary tumor. It is also very active against Gram positive bacteria. Biosynthetic studies have shown that the aglycone unit comes from the folding of a polyketide chain with the vinyl unit arising from propionic acid. Since this vinyl functionality is believed to playa role in the antitumor activity of the antibiotic, it is of interest to elucidate the stereochemical selectivity in its formation from propionic acid. The synthesis of (R) and (S)-L2-²H₁ j propionate, incorporation of the labelled material, and chemical analysis of the resulting antibiotic was be used to determine the stereochemistry of formation of the vinyl side chain. It was found that propionate was incorporated with ravidomycin with stereospecific loss of the 2-(pro-R)-proton. / Master of Science

Polycyclic (or polynuclear) aromatic hydrocarbons (PAHs) are environmental pollutants produced during the incomplete combustion of organic matter. Since many of these compounds have been shown to be mutagenic and/or carcinogenic, an investigation was initiated into determining the PAH content and mutagenicity of the ash that remains after sugar cane crop burning, and the soot deposited on toll booths by vehicle exhaust emissions. Due to the large amount of sugar cane farming in the Natal coastal region and that the favoured method of disposing unwanted leafy trash is crop burning, concern was expressed as to the nature of the residue that is formed. PAHs have been identified in the residues from combusted wood and straw and, due to their intrinsic similarity to sugar cane, it was considered that the burning of sugar cane could generate PAHs. It is well documented that vehicle exhaust emissions exhibit mutagenic properties and PAHs have been identified as the major contributors of this observed mutagenicity. Since a toll plaza is an area of high traffic density, it was considered to be an ideal location for an investigation into the build-up of particles emitted by the passing vehicles, and to study to what extent the operators are exposed to harmful compounds. In addition, this sample acted as a control, since the detection of PAHs and mutagenic activity in the soot would be an indication that the correct experimental techniques were being employed. Samples were collected on site. The sugar cane ash was collected off a field immediately after burning had taken place, and the soot was collected either by scraping the toll booth walls and surrounding areas or by wiping the surfaces with cotton wool swabs. The organic portion of the samples was separated from the inorganic and carbonaceous substances by extraction into a suitable solvent; the use of both acetone and dichloromethane was investigated. The extracts were divided into two portions - one was used for the analysis of PAHs and the other for determining mutagenic activity. Analysis for PAHs involved subjecting the extracts to a sample clean-up routine and the use of a number of analytical techniques to characterise the components. The mutagenic properties of the samples were investigated by means of two bacterial mutagenicity tests: the Salmonella typhimurium assay (the Ames test) and a new commercially available test kit, the SOS Chromotest. A number of PARs were identified in the extracts by means of reverse phase high performance liquid chromatography (HPLC) with both ultraviolet and fluorescence detection, the latter being the more sensitive method. Mutagenic activity was detected for both samples in the Ames test and for the toll booth soot in the SOS Chromotest, and this observed mutagenicity was attributed to the presence of the PAHs. / Thesis (M.Sc.)-University of Natal, Durban, 1992.

by Chan Sze Sze. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 193-218). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstracts --- p.ii / 摘要 --- p.v / Contents --- p.viii / List of figures --- p.xv / List of tables --- p.xix / Abbreviations --- p.xxii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- The North Tsing Yi Abandoned Shipyard area --- p.1 / Chapter 1.2 --- Polycyclic aromatic hydrocarbons (PAHs) in the site --- p.3 / Chapter 1.2.1 --- Characteristics of PAHs --- p.3 / Chapter 1.2.2 --- Sources of PAHs --- p.8 / Chapter 1.2.3 --- Environmental fates of PAHs --- p.9 / Chapter 1.2.4 --- Biodegradation of PAHs --- p.10 / Chapter 1.2.5 --- Toxicity of PAHs --- p.13 / Chapter 1.2.6 --- PAHs contamination in Hong Kong --- p.14 / Chapter 1.2.7 --- Soil decontamination assessment in Hong Kong --- p.16 / Chapter 1.2.8 --- Environmental standards of PAHs --- p.18 / Chapter 1.2.9 --- Remediation technology of PAHs --- p.21 / Chapter 1.2.9.1 --- Bioremediation --- p.22 / Chapter 1.3 --- Heavy metals in the site --- p.28 / Chapter 1.3.1 --- "Characteristics of copper, lead and zinc" --- p.29 / Chapter 1.3.2 --- "Sources of copper, lead and zinc" --- p.32 / Chapter 1.3.3 --- "Environmental fates of copper, lead and zinc" --- p.34 / Chapter 1.3.4 --- "Toxicities of copper, lead and zinc" --- p.36 / Chapter 1.3.5 --- "Copper, lead and zinc contamination in Hong Kong" --- p.39 / Chapter 1.3.6 --- "Environmental standards of copper, lead and zinc" --- p.40 / Chapter 1.3.7 --- Remediation technology of heavy metal --- p.42 / Chapter 1.3.7.1 --- Chemical method --- p.42 / Chapter 1.3.7.2 --- Biological method --- p.43 / Chapter 1.3.7.3 --- Stabilization and Solidification --- p.45 / Chapter 1.4 --- Aim of study --- p.47 / Chapter 1.5 --- Objectives --- p.47 / Chapter 1.6 --- Research Strategy --- p.47 / Chapter 1.7 --- Significance of study --- p.48 / Chapter 2 --- Materials and Methods --- p.49 / Chapter 2.1 --- Soil Collection --- p.49 / Chapter 2.2 --- Characterization of soil --- p.49 / Chapter 2.2.1 --- Sample preparation --- p.49 / Chapter 2.2.2 --- "Soil pH, electrical conductivity & salinity" --- p.50 / Chapter 2.2.3 --- Total organic carbon contents --- p.51 / Chapter 2.2.4 --- Soil texture --- p.51 / Chapter 2.2.5 --- Moisture --- p.53 / Chapter 2.2.6 --- Total nitrogen and total phosphorus --- p.53 / Chapter 2.2.7 --- Available nitrogen --- p.53 / Chapter 2.2.8 --- Available phosphorus --- p.54 / Chapter 2.2.9 --- Soil bacterial and fungal population --- p.54 / Chapter 2.2.10 --- Extraction of PAHs and organic pollutants --- p.55 / Chapter 2.2.10.1 --- Extraction procedure --- p.55 / Chapter 2.2.10.2 --- GC-MS condition --- p.56 / Chapter 2.2.10.3 --- Preparation of mixed PAHs stock solution --- p.56 / Chapter 2.2.11 --- Oil and grease content --- p.57 / Chapter 2.2.12 --- Total Petroleum Hydrocarbons (TPH) --- p.57 / Chapter 2.2.13 --- Total heavy metal analysis --- p.58 / Chapter 2.2.14 --- Toxicity characteristic leaching procedure (TCLP) --- p.59 / Chapter 2.2.15 --- Extraction efficiency --- p.59 / Chapter 2.3 --- Production of mushroom compost --- p.60 / Chapter 2.4 --- Characterization of mushroom compost --- p.62 / Chapter 2.4.1 --- Enzyme assay --- p.62 / Chapter 2.4.1.1 --- Laccase assay --- p.62 / Chapter 2.4.1.2 --- Manganese peroxidase assay --- p.62 / Chapter 2.5 --- Addition of mushroom to soil on site --- p.63 / Chapter 2.5.1 --- Transportation of mushroom compost to Tsing Yi --- p.63 / Chapter 2.5.2 --- Mixing of mushroom compost and soil --- p.64 / Chapter 2.6 --- Soil Monitoring --- p.64 / Chapter 2.6.1 --- On site air and soil measurements --- p.64 / Chapter 2.6.1.1 --- Air temperature and moisture --- p.64 / Chapter 2.6.1.2 --- Light intensity --- p.64 / Chapter 2.6.1.3 --- UV intensity --- p.65 / Chapter 2.6.1.4 --- Rainfall --- p.65 / Chapter 2.6.1.5 --- Soil temperature --- p.65 / Chapter 2.6.2 --- Soil chemical characteristic --- p.65 / Chapter 2.6.3 --- Relative residue pollutant (%) --- p.65 / Chapter 2.7 --- Toxicity of treated soil --- p.66 / Chapter 2.7.1 --- Seed germination test --- p.66 / Chapter 2.7.2 --- Indigenous bacterial toxicity test --- p.67 / Chapter 2.7.3 --- Fungal toxicity test --- p.68 / Chapter 2.7.3.1 --- Preparation of ergosterol standard solution --- p.70 / Chapter 2.8 --- Soil Washing --- p.70 / Chapter 2.8.1 --- Optimization of soil washing --- p.70 / Chapter 2.8.1.1 --- Effect of hydrochloric acid concentration --- p.70 / Chapter 2.8.1.2 --- Effect of incubation time --- p.71 / Chapter 2.9 --- Phytoremediation --- p.71 / Chapter 2.10 --- Mycoextraction --- p.72 / Chapter 2.11 --- Integrated bioextraction --- p.72 / Chapter 2.12 --- Cementation --- p.73 / Chapter 2.13 --- Glass encapsulation --- p.73 / Chapter 2.14 --- Statistical analysis --- p.74 / Chapter 3 --- Results --- p.75 / Chapter 3.1 --- Characterization of soil --- p.75 / Chapter 3.2 --- Characterization of mushroom compost --- p.78 / Chapter 3.2.1 --- Enzyme activity --- p.78 / Chapter 3.2.2 --- Total nitrogen and total phosphorus contents --- p.78 / Chapter 3.3 --- Soil monitoring --- p.79 / Chapter 3.3.1 --- Initial pollutant content in biopile and fungal treatment soils --- p.79 / Chapter 3.3.2 --- On site air and soil physical characteristics --- p.81 / Chapter 3.3.2.1 --- Soil temperature and air temperature --- p.81 / Chapter 3.3.3 --- Soil chemical characteristic --- p.84 / Chapter 3.3.3.1 --- Effect of type of treatment on total petroleum hydrocarbon content --- p.85 / Chapter 3.3.3.2 --- Effect of type of treatment on oil and grease content --- p.87 / Chapter 3.3.3.3 --- Soil pH --- p.89 / Chapter 3.3.3.4 --- Moisture --- p.91 / Chapter 3.3.3.5 --- Electrical conductivity --- p.92 / Chapter 3.3.3.6 --- Salinity --- p.93 / Chapter 3.3.3.7 --- Microbial population --- p.95 / Chapter 3.3.3.8 --- Removal of organopollutant PAHs in biopile and fungal treatment --- p.98 / Chapter 3.3.3.9 --- Effect of type of treatment on residual PAHs at Day 4 --- p.104 / Chapter 3.3.3.10 --- Effect of type of treatment on residual PAHs at peak levels --- p.107 / Chapter 3.3.3.11 --- Effect of type of treatment on residual organopollutants at the end of treatments --- p.109 / Chapter 3.3.3.12 --- Effect of type of treatment on total nitrogen and phosphorus contents --- p.111 / Chapter 3.3.3.13 --- Effect of type of treatment on physical and chemical properties of soil --- p.113 / Chapter 3.4 --- Toxicity of treated soil --- p.116 / Chapter 3.4.1 --- Seed germination test --- p.116 / Chapter 3.4.2 --- Indigenous bacterial toxicity test --- p.120 / Chapter 3.4.3 --- Fungal toxicity test --- p.125 / Chapter 3.5 --- Soil washing --- p.129 / Chapter 3.5.1 --- Optimisation of soil washing --- p.129 / Chapter 3.5.1.1 --- The effect of hydrochloric acid concentration --- p.129 / Chapter 3.5.1.2 --- The effect of incubation time --- p.134 / Chapter 3.6 --- Mycoextraction --- p.139 / Chapter 3.7 --- Phytoextraction and integrated bioextraction --- p.146 / Chapter 3.8 --- Cementation --- p.153 / Chapter 3.9 --- Glass encapsulation --- p.158 / Chapter 4 --- Discussion --- p.160 / Chapter 4.1 --- Characterization of soil --- p.160 / Chapter 4.2 --- Characterization of mushroom compost --- p.162 / Chapter 4.2.1 --- Enzyme activity --- p.162 / Chapter 4.2.2 --- Total nitrogen and total phosphorus contents --- p.163 / Chapter 4.3 --- Soil monitoring --- p.163 / Chapter 4.3.1 --- Initial pollutant content in biopile and fungal treatment soil --- p.163 / Chapter 4.3.2 --- On site air and soil physical characteristics --- p.164 / Chapter 4.3.3 --- Soil chemical characteristic --- p.164 / Chapter 4.3.3.1 --- Soil pH --- p.164 / Chapter 4.3.3.2 --- Moisture --- p.165 / Chapter 4.3.3.3 --- Electrical conductivity --- p.165 / Chapter 4.3.3.4 --- Salinity --- p.166 / Chapter 4.3.3.5 --- Microbial population in biopile and fungal treatments --- p.166 / Chapter 4.3.3.6 --- Removal of organopollutant PAHs in biopile and fungal treatments --- p.168 / Chapter 4.3.3.7 --- Effect of type of treatment on residual PAHs at peak levels --- p.170 / Chapter 4.3.3.8 --- Effect of type of treatment on residual oil and grease and TPH contents --- p.171 / Chapter 4.3.3.9 --- Effect of type of treatment on total nitrogen and phosphorus contents --- p.172 / Chapter 4.3.3.10 --- Effect of type of treatment on physical and chemical properties of the soil --- p.173 / Chapter 4.4 --- Toxicity of treated soil --- p.174 / Chapter 4.5 --- Summary of Pleurotus pulmonarius mushroom compost on organopollutant remediation --- p.177 / Chapter 4.6 --- Soil washing --- p.178 / Chapter 4.7 --- Mycoextraction --- p.180 / Chapter 4.8 --- Phytoextraction and integrated bioextraction --- p.182 / Chapter 4.9 --- Cementation --- p.184 / Chapter 4.10 --- Glass encapsulation --- p.185 / Chapter 4.11 --- "Summary of physical, chemical and biological heavy metal removal treatments" --- p.186 / Chapter 4.12 --- Future studies --- p.187 / Chapter 5 --- Conclusion --- p.190 / Chapter 6 --- References --- p.193

Zou, Huiling. / Thesis submitted in: November 2008. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 159-176). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.vi / Table of contents --- p.viii / List of tables --- p.x / List of figures --- p.xiii / Abbreviations --- p.xv / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Background --- p.1 / Chapter 1.1.1 --- Physicochemical properties of polycyclic aromatic hydrocarbons --- p.1 / Chapter 1.1.2 --- Sources of PAHs --- p.4 / Chapter 1.1.3 --- Toxicity of PAHs --- p.5 / Chapter 1.1.4 --- Fate of PAHs in environment --- p.6 / Chapter 1.1.5 --- Soil physicochemical and microbiological properties --- p.16 / Chapter 1.1.6 --- Geography and climate of Hong Kong --- p.17 / Chapter 1.1.7 --- Traffic status in Hong Kong --- p.17 / Chapter 1.1.8 --- Research status in Hong Kong --- p.18 / Chapter 1.2 --- "Significant, objectives and outline of this study" --- p.18 / Chapter 1.2.1 --- Research significance --- p.18 / Chapter 1.2.2 --- Research objectives and thesis outline --- p.19 / Chapter Chapter 2 --- PAH concentrations and their seasonal variations in roadside soils in Hong Kong / Chapter 2.1 --- Introduction --- p.20 / Chapter 2.2 --- Materials and methods --- p.22 / Chapter 2.2.1 --- Soil sampling --- p.22 / Chapter 2.2.2 --- Soil physicochemical properties analysis --- p.24 / Chapter 2.2.3 --- Soil PAH analysis --- p.25 / Chapter 2.2.3.1 --- Extraction of PAHs --- p.25 / Chapter 2.2.3.2 --- Cleanup and concentration of the extract --- p.25 / Chapter 2.2.3.3 --- Determination of PAHs --- p.26 / Chapter 2.2.3.4 --- Calibration standards and recovery --- p.26 / Chapter 2.2.4 --- Statistical analysis --- p.28 / Chapter 2.3 --- Results and discussion --- p.29 / Chapter 2.3.1 --- Soil PAH contents and their relationships with soil physicochemical properties and AADT --- p.29 / Chapter 2.3.1.1 --- Soil PAHs --- p.29 / Chapter 2.3.1.2 --- Soil physicochemical properties --- p.38 / Chapter 2.3.1.3 --- Relationships of PAH contents with soil physicochemical properties and AADT --- p.39 / Chapter 2.3.2 --- Seasonal variations of PAH contents of roadside soils --- p.50 / Chapter 2.4 --- Conclusion --- p.56 / Chapter Chapter 3 --- "PAH concentrations in roadside vegetation, dusts and soils" / Chapter 3.1 --- Introduction --- p.58 / Chapter 3.2 --- Materials and methods --- p.59 / Chapter 3.2.1 --- Sampling --- p.59 / Chapter 3.2.2 --- Soil physicochemical properties analysis --- p.60 / Chapter 3.2.3 --- PAHs analysis --- p.60 / Chapter 3.2.3.1 --- Extraction of PAHs --- p.60 / Chapter 3.2.3.2 --- Cleanup and concentration of the extract --- p.60 / Chapter 3.2.3.3 --- Determination of PAHs --- p.61 / Chapter 3.2.3.4 --- Calibration standards and recovery --- p.61 / Chapter 3.2.4 --- Statistical analysis --- p.61 / Chapter 3.3 --- Results and discussion --- p.62 / Chapter 3.3.1 --- Soil physicochemical properties --- p.62 / Chapter 3.3.2 --- PAH concentrations --- p.62 / Chapter 3.3.2.1 --- Soil PAHs --- p.62 / Chapter 3.3.2.2 --- Dust PAHs --- p.65 / Chapter 3.3.2.3 --- Vegetation PAHs --- p.71 / Chapter 3.3.3 --- PAH profile --- p.80 / Chapter 3.3.4 --- PAH sources --- p.83 / Chapter 3.3.5 --- PCA and HCA --- p.88 / Chapter 3.3.6 --- "Relationships of PAH contents between vegetation, dust and soil, and soil physicochemical properties and AADT" --- p.99 / Chapter 3.4 --- Conclusion --- p.124 / Chapter Chapter 4 --- Vertical and horizontal distribution of PAHs in roadside soil and their influences on soil microbial characteristics / Chapter 4.1 --- Introduction --- p.126 / Chapter 4.2 --- Materials and methods --- p.127 / Chapter 4.2.1 --- Sampling --- p.127 / Chapter 4.2.2 --- Soil physicochemical properties analysis --- p.128 / Chapter 4.2.3 --- Soil microbial biomass carbon analysis --- p.128 / Chapter 4.2.4 --- Soil microbial community analysis --- p.128 / Chapter 4.2.5 --- Soil enzyme activity analysis --- p.129 / Chapter 4.2.6 --- Soil PAH analysis --- p.130 / Chapter 4.2.7 --- Statistical analysis --- p.130 / Chapter 4.3 --- Results and discussion --- p.131 / Chapter 4.3.1 --- Vertical distribution --- p.131 / Chapter 4.3.2 --- Horizontal distribution --- p.137 / Chapter 4.3.3 --- Influences of roadside soil PAH on microbial characteristics --- p.142 / Chapter 4.4 --- Conclusion --- p.153 / Chapter Chapter 5 --- General conclusion / Chapter 5.1 --- Summary of findings --- p.155 / Chapter 5.2 --- Limitations of the study --- p.157 / Chapter 5.3 --- Implications for further studies --- p.158 / References --- p.159

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 102-117). Also available on the World Wide Web.

Since 2008, large numbers of Nile crocodile (Crocodylus niloticus) carcasses were found in the Kruger National Park (KNP), South Africa. Most of the crocodile carcasses were found in the Olifants Gorge, which is situated below the Letaba and Olifants river confluence, before the Mozambique border and Massingir Dam. The Massingir Dam is an important resource and it plays a significant role in the welfare of the local Mozambican population. Autopsies performed on the crocodiles indicated that the adipose tissue colour changed from normal white to yellow and this is usually a sign of pansteatitis. Pansteatitis is caused by lipid peroxidation in an organism and it is characterised by the lack of vitamin E. This disease is recognisable by the hardening of the fatty tissue and yellow discolouration, and is mostly associated with aquatic organisms from polluted ecosystems. There are speculations that the crocodile fatalities may be associated with the Massingir Dam that backed up into the Olifants Gorge after flooding. After the dam was reconstructed, it flooded the Olifants Gorge, causing it to act like a localised sediment trap as the water flow slowed down and as a result, caused pollutants to build-up. Sediment samples were collected from selected rivers and ponds within the KNP. These samples were analysed for selected elements, persistent organic pollutants (POPs), and polycyclic aromatic hydrocarbons (PAHs). The sediment samples were analysed in Norway for POPs and PAHs with the use of a high-resolution gas chromatography/mass spectrometry (GC/MS) and the heavy metals were analysed in South Africa with the use of inductively-coupled plasma mass spectrometry (ICP/MS). In order to identify which elements may have affected the health of the crocodiles, a series of sediment quality indices were used. These indices made it possible to determine which elements may have been involved. The order of probability of heavy metals causing harm was Se>As>Ni>Cr>Cu>I>V>Mn>Co>Fe>Cd>Hg>Zn>Pb>Ba>U. The data was compared to selected international guidelines. All the information was used to determine which of the sampled sites had the highest contamination. The sites sampled with the highest concentrations were in the Crocodile, Nkomati, Olifants, and Letaba Rivers. Concentrations of the elements, POPs, and PAHs were also quantifiable in the Olifants Gorge. The following elements (Fe, Co, Cu, Cr, Pb, V, As, and Ni) were quantified at elevated levels and may therefore have caused negative effects on the crocodiles in the Olifants Gorge. These elevated concentrations, in combination with the dramatic change in the physical environment due to the dam, could have added additional stress that may have contributed to the observed crocodile mortalities in the Olifants Gorge. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Since 2008, large numbers of Nile crocodile (Crocodylus niloticus) carcasses were found in the Kruger National Park (KNP), South Africa. Most of the crocodile carcasses were found in the Olifants Gorge, which is situated below the Letaba and Olifants river confluence, before the Mozambique border and Massingir Dam. The Massingir Dam is an important resource and it plays a significant role in the welfare of the local Mozambican population. Autopsies performed on the crocodiles indicated that the adipose tissue colour changed from normal white to yellow and this is usually a sign of pansteatitis. Pansteatitis is caused by lipid peroxidation in an organism and it is characterised by the lack of vitamin E. This disease is recognisable by the hardening of the fatty tissue and yellow discolouration, and is mostly associated with aquatic organisms from polluted ecosystems. There are speculations that the crocodile fatalities may be associated with the Massingir Dam that backed up into the Olifants Gorge after flooding. After the dam was reconstructed, it flooded the Olifants Gorge, causing it to act like a localised sediment trap as the water flow slowed down and as a result, caused pollutants to build-up. Sediment samples were collected from selected rivers and ponds within the KNP. These samples were analysed for selected elements, persistent organic pollutants (POPs), and polycyclic aromatic hydrocarbons (PAHs). The sediment samples were analysed in Norway for POPs and PAHs with the use of a high-resolution gas chromatography/mass spectrometry (GC/MS) and the heavy metals were analysed in South Africa with the use of inductively-coupled plasma mass spectrometry (ICP/MS). In order to identify which elements may have affected the health of the crocodiles, a series of sediment quality indices were used. These indices made it possible to determine which elements may have been involved. The order of probability of heavy metals causing harm was Se>As>Ni>Cr>Cu>I>V>Mn>Co>Fe>Cd>Hg>Zn>Pb>Ba>U. The data was compared to selected international guidelines. All the information was used to determine which of the sampled sites had the highest contamination. The sites sampled with the highest concentrations were in the Crocodile, Nkomati, Olifants, and Letaba Rivers. Concentrations of the elements, POPs, and PAHs were also quantifiable in the Olifants Gorge. The following elements (Fe, Co, Cu, Cr, Pb, V, As, and Ni) were quantified at elevated levels and may therefore have caused negative effects on the crocodiles in the Olifants Gorge. These elevated concentrations, in combination with the dramatic change in the physical environment due to the dam, could have added additional stress that may have contributed to the observed crocodile mortalities in the Olifants Gorge. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

<p>Subteratogenic and other low-level chronic exposures to toxicant mixtures are an understudied threat to environmental and human health. It is especially important to understand the effects of these exposures for contaminants, such as polycyclic aromatic hydrocarbons (PAHs) a large group of more than 100 individual compounds, which are important environmental (including aquatic) contaminants. Aquatic sediments constitute a major sink for hydrophobic pollutants, and studies show PAHs can persist in sediments over time. Furthermore, estuarine systems (namely breeding grounds) are of particular concern, as they are highly impacted by a wide variety of pollutants, and estuarine fishes are often exposed to some of the highest levels of contaminants of any vertebrate taxon. Acute embryonic exposure to PAHs results in cardiac teratogenesis in fish, and early life exposure to certain individual PAHs and PAH mixtures cause heart alterations with decreased swimming capacity in adult fish. Consequently, the heart and cardiorespiratory system are thought to be targets of PAH mixture exposure. While many studies have investigated acute, teratogenic PAH exposures, few studies have longitudinally examined the impacts of subtle, subteratogenic PAH mixture exposures, which are arguably more broadly applicable to environmental contamination scenarios. The goal of this dissertation was to highlight the later-life consequences of early-life exposure to subteratogenic concentrations of a complex, environmentally relevant PAH mixture.</p><p>A unique population of Fundulus heteroclitus (the Atlantic killifish or mummichog, hereafter referred to as killifish), has adapted to creosote-based polycyclic aromatic hydrocarbons (PAHs) found at the Atlantic Wood Industries (AW) Superfund site in the southern branch of the Elizabeth River, VA, USA. This killifish population survives in a site heavily contaminated with a mixture of PAHs from former creosote operations. They have developed resistance to the acute toxicity and teratogenic effects caused by the mixture of PAHs in sediment from the site. The primary goal of this dissertation was to compare and contrast later-life outcomes of early-life, subteratogenic PAH mixture exposure in both the Atlantic Wood killifish (AW) and a naïve reference population of killifish from King’s Creek (KC; a relatively uncontaminated tributary of the Severn River, VA). Killifish from both populations were exposed to subteratogenic concentrations of a complex PAH-sediment extract, Elizabeth River Sediment Extract (ERSE), made by collecting sediment from the AW site. Fish were reared over a 5-month period in the laboratory, during which they were examined for a variety of molecular, physiological and behavioral responses. </p><p>The central aims of my dissertation were to determine alterations to embryonic gene expression, larval swimming activity, adult behavior, heart structure, enzyme activity, and swimming/cardiorespiratory performance following subteratogenic exposure to ERSE. I hypothesized that subteratogenic exposure to ERSE would impair cardiac ontogenic processes in a way that would be detectable via gene expression in embryos, and that the misregulation of cardiac genes would help to explain activity changes, behavioral deficits, and later-life swimming deficiencies. I also hypothesized that fish heart structure would be altered. In addition, I hypothesized that the AW killifish population would be resistant to developmental exposures and perform normally in later life challenges. To investigate these hypotheses, a series of experiments were carried out in PAH-adapted killifish from Elizabeth River and in reference killifish. As an ancillary project to the primary aims of the dissertation, I examined the toxicity of weaker aryl hydrocarbon receptor (AHR) agonists in combination with fluoranthene (FL), an inhibitor of cytochrome P4501A1 (CYP1A1). This side project was conducted in both Danio rerio (zebrafish) and the KC and AW killifish.</p><p>Embryonic gene expression was measured in both killifish populations over an ERSE dose response with multiple time points (12, 24, 48, and 144 hours post exposure). Genes known to play critical roles in cardiac structure/development, cardiac function, and angiogenesis were elevated, indicating cardiac damage and activation of cardiovascular repair mechanisms. These data helped to inform later-life swimming performance and cardiac histology studies. Behavior was assessed during light and dark cycles in larvae of both populations following developmental exposure to ERSE. While KC killifish showed activity differences following exposure, AW killifish showed no significant changes even at concentrations that would cause overt cardiac toxicity in KC killifish. Juvenile behavior experiments demonstrated hyperactivity following ERSE exposure in KC killifish, but no significant behavioral changes in AW killifish. Adult swimming performance via prolonged critical swimming capacity (Ucrit) demonstrated performance costs in the AW killifish. Furthermore, swimming performance decline was observed in KC killifish following exposure to increasing dilutions of ERSE. Lastly, cardiac histology suggested that early-life exposure to ERSE could result in cardiac structural alteration and extravasation of blood into the pericardial cavity.</p><p>Responses to AHR agonists resulted in a ranking of relative potency for agonists, and determined which agonists, when combined with FL, caused cardiac teratogenesis. These experiments showed interesting species differences for zebrafish and killifish. To probe mechanisms responsible for cardiotoxicity, a CYP1A-morpholino and a AHR2-morpholino were used to mimic FL effects or attempt to rescue cardiac deformities respectively. Findings suggested that the cardiac toxicity elicited by weak agonist + FL exposure was likely driven by AHR-independent mechanisms. These studies stand in contrast to previous research from our lab showing that moderate AHR agonist + FL caused cardiac toxicity that can be partially rescued by AHR-morpholino knockdown.</p><p>My findings will form better characterization of mechanisms of PAH toxicity, and advance our understanding of how subteratogenic mixtures of PAHs exert their toxic action in naïve killifish. Furthermore, these studies will provide a framework for investigating how subteratogenic exposures to PAH mixtures can impact aquatic organismal health and performance. Most importantly, these experiments have the potential to help inform risk assessment in fish, mammals, and potentially humans. Ultimately, this research will help protect populations exposed to subtle PAH-contamination.</p> / Dissertation

Within the last few decades, epidemiological evidence has linked exposure to air pollution, both its particles and its organic components, with cardiovascular disease (CVD) progression. CVD is a life long disease with the disruption of the endothelium being the inaugural event in this inflammatory process. The vascular endothelium is extremely susceptible to environmental insults given its tremendous surface area and that it is in constant contact with blood and components circulating within the blood, including xenobiotics. The endothelium is important as a barrier from blood constituents however, dysfunction of this barrier leads to the influx of lymphocytes and granulocytes that lead to the fatty build‐up characteristic of atherosclerosis. The studies presented in this dissertation tested the hypothesis that two unique environmental contaminants, alumina nanoparticles and benzo[a]pyrene (B[a]P), lead to increased endothelial cell dysfunction, characterized by increased adhesion molecule expression. Alumina nanoparticles induced vascular cell adhesion molecule‐1 (VCAM‐1), intercellular adhesion molecule‐1 (ICAM‐1), and E‐selectin (ELAM‐1), as well as increased monocyte adhesion to activated endothelium. Polystyrene nanoparticles did not elicit this response. B[a]P induced ICAM‐1 expression, but only after toxification by aryl hydrocarbon receptor (AhR) controlled enzymes. Silencing of either AhR or the membrane microdomains called caveolae attenuated the B[a]P‐induced ICAM‐1 response. It was also shown that the induction of ICAM‐1 occurred by signaling through MEK, p‐38 MAPK, and activator protein‐1 (AP‐1). These data provide a novel mechanism by which air pollutants like B[a]P may cause increased atherosclerosis and describe a new toxicant, alumina nanoparticles, as a possible threat for the development of inflammatory diseases, such as atherosclerosis. Little is known about dietary interventions capable of alleviating xenobiotic‐induced toxicity. Nutrition is an obtainable and inexpensive means of possible preventative therapy. With this in mind, it was also hypothesized that plant polyphenols, such as flavonoids, can down‐regulate B[a]P‐induced ICAM‐1. Selective flavonoids, containing both a 4’ B‐ring hydroxyl substitution and a 2‐3 C‐ring double bond, protected against B[a]P‐induced ICAM‐1 activation, however this protection did not correlate with the flavonoid’s antioxidant capacity.

ABSTRACT To compare the degree of biodegradation of petroleum hydrocarbons in sediments from Ikarama and Okwori in the Niger delta, Nigeria, concentrations of n-alkanes and polycyclic aromatic hydrocarbons in the sediments were measured. Analysis was conducted with gas chromatography using mass spectrometry detector. While the decrease in concentrations of n-alkanes and polycyclic aromatic hydrocarbons confirmed the process of biodegradation in the sediments it was not solely fit to substantiate the degree of biodegradation in the sediments. Hence the percentage proportion of n-alkanes and polycyclic aromatic hydrocarbons was used. The degree of biodegradation of n-alkanes in both Okwori and Ikarama was almost similar. However, it was observed that polycyclic aromatic hydrocarbons were biodegraded in Okwori sediments than Ikarama sediments and this indicates the degree of biodegradation of petroleum hydrocarbons impacted sediments in Okwori is greater than that of Ikarama.