The toxicity of copper and nickel was measured in algal cultures of Selenastrum capricornutum and zooplankton cultures of Daphnia magna to determine if dissolved organic carbon (DOC) and/or calcium concentrations can influence toxicity of these two metals. Water samples were collected from the Raisin River (high DOC and high calcium), the St. Lawrence River (low DOC and high calcium), the Ottawa River (medium DOC and calcium) as well as two lakes in Nova Scotia. The concentration sufficient to kill half the population of Daphnia magna after 48h of exposure (LC50), and the inhibition of cell growth of S. capricornutum after 72 h of exposure (IC50) were used to determine the sensitivity of these species to copper or nickel toxicity in these 5 water samples. In Part 3, I showed that the protection against copper or nickel toxicity was reduced with UVB radiation even though the total DOC was reduced by only 18%. The role of EDTA in the toxicity of copper and nickel on S. capricornutum was investigated in part 4. (Abstract shortened by UMI.)

Dichlorodiphenyltrichloroethane (DDT) had been used in the Okavango delta, Botswana, since the 1950's for the control of malaria and sleeping sickness disease vectors. Concentrations of DDT were determined in water, plant material, invertebrates and fish samples. Isotopes of nitrogen (delta15N) were further used to infer organisms' trophic position and the level of biomagnification of total DDT (DDT and it's metabolites). Average concentrations of total DDT ranged from 0.04 ng.L-1 in water to 8.33 ng.g-1 (wet weight) in fish from the Okavango delta. As predicted from global distillation models, these concentrations are about 2 orders of a magnitude lower than the levels in fish from temperate and arctic regions of Canada, where DDT was banned in the early 1970s. The DDE metabolite was the most abundant fraction of total DDT. Although total DDT concentrations were higher in areas treated for malaria control than areas treated for tsetse control, these concentrations were driven by factors other than the historic application of the pesticide. Gaborone dam, an area where DDT had not been used, was sampled in order to compare total DDT levels to treated areas. Here, levels in fish were 3 times higher than in the Okavango delta but consistent with predictions from delta15N values. Lipid was also a significant predictor of DDT concentrations. Fattier and larger fish such as Hydrocynus vittatus and Synodontis sp. contained higher levels of DDT than those with less fat.

Halogenated aromatic hydrocarbons such as polychlorinated biphenyls (PCBs) comprise some of the most toxic and persistent environmental pollutants associated with various developmental and reproductive effects in mammals, birds and fish. Oxidative stress can modify beta-adrenoceptor (beta-AR) function. This thesis examines the effects PCBs on beta-AR function in an avian model. Injection of 1.6 mug PCB 126/kg egg into the air cell prior to incubation increased the % mortality and the incidence of abnormalities, including liver lesions and subcutaneous edema, in day 19 chicken (Gallus domesticus ) embryos. Hepatic lipid peroxidation and EROD activity were significantly increased in PCB 126-treated embryos. These results indicate that the dose of PCB 126 used in this study induced a significant toxic response in day 19 embryos. Pharmacological characterization of chick embryo hepatic beta-ARs showed that they preferentially bind mammalian beta2-agonists and antagonists. PCB 126 significantly decreased hepatic beta-AR affinity (Kd) compared to vehicle-treated embryos. There were, however, no significant differences between control and PCB 126-treated embryos, or control and vehicle-treated embryos. This suggests there is an effect of the corn oil vehicle. (Abstract shortened by UMI.)

Hatchery reared rainbow trout (Oncorhynchus mykiss) were caged at two locations in the St. Lawrence river near Cornwall, Ontario. One cage was anchored in an area of high polychlorinated biphenyl (PCB) contamination, within an iron enclosure near the General Motors Foundry at Massena, N.Y. during a dredging operation designed to remove PCB contaminated sediments from the river. A second control cage was placed in the Snye channel, known to have low PCB concentrations. Hatchery fish were sampled to provide a time 0 control, and fish from each site were collected following 21 and 41 day exposure. Plasma, muscle, bone, and liver were harvested and assayed to determine muscle PCB levels, plasma cortisol, electrolyte, lactate and glucose concentrations, bone calcium, muscle water and the activity of a variety of liver enzymes. Total PCB levels were significantly higher in fish muscle from the General Motors site but few differences were found in any of the physiological parameters. Levels of bone calcium decreased in fish exposed to high PCB levels, suggesting an effect of PCBs on either the thyroid or ultimobranchial bodies. Pyruvate kinase activity in the liver of PCB exposed fish suggests a shift in energy metabolism to a greater reliance on glycogenolysis. Both parameters require further study to determine the feasibility of their use as bioindicators of PCB stress.

Cisplatin (CP) is one of our most useful antineoplastic drugs. When CP is dissolved in human plasma, different metabolites are formed. We examined the interactions of CP and its metabolites, namely aquated CP (AP), monomethionine CP (MP), bismethionine CP (BP) and CP dissolved in plasma ultrafiltrate (UP) on the OV 2008 human ovarian cancer cell line. By clonogenic assays, cell survivals (%) with AP, CP, MP, BP and UP were 3.28 $\pm$ 0.73, 9.84 $\pm$ 0.99, 15.93 $\pm$ 1.11, 76.83 $\pm$ 2.13 and 13.11 $\pm$ 0.74, respectively. AP was the most cytotoxic species, and BP was the least cytotoxic species. Cellular platinum (ng/10$\sp6$ cells) accumulation after addition of 0.33 (#1), 1.6 (#2) and 2.5 (#3) mM of each species was:(UNFORMATTED TABLE OR EQUATION FOLLOWS)$$\vbox{\halign{#\hfil&&\enspace#\hfil\cr\lbrack Species\rbrack &CP &AP &MP &BP &UP\cr\cr \#1 &289$\pm$26 &1080$\pm$90 &138$\pm$5 &24$\pm$1 &187$\pm$26\cr \#2 &607$\pm$31 &4352$\pm$145 &372$\pm$8 &56$\pm$2 &498$\pm$69\cr \#3 &713$\pm$41 &6610$\pm$279 &710$\pm$8 &78$\pm$2 &711$\pm$96\cr}}$$(TABLE/EQUATION ENDS) There is a strong correlation between cytotoxicity of the platinum species and their cellular uptake (r = 0.997). Infrared spectroscopy (IR) was done on OV 2008 cells after one hour exposure to different concentrations of species. IR data suggest that MP induced more cellular changes than the other species. While bands of all CP metabolites attributed to the phosphate and amide II stretching indicate a frequency shift and intensity variation, those of methyl and methylene stretching vibrations of the cell membrane seem to be hardly affected. In conclusion, CP and its metabolites have different effects on OV 2008 cells.

Polychlorinated biphenyls (PCBs) are ubiquitously distributed in the aquatic and terrestrial environments, even though their production was stopped more than 20 years ago. The biochemical effects of PCBs are primarily initiated by the induction of drug metabolizing enzymes, especially cytochromes P450. In the first instance, these enzymes detoxify xenobiotics such as PCB congeners to facilitate their excretion from the animal. However, these processes are also known to generate more toxic metabolites, including the production of reactive oxygen species (ROS) which impact on cellular antioxidant defenses. Teleost fish contain an active endogenous antioxidant defense system, which consists of superoxide dismutase, catalase and the glutathione system. Apart from its antioxidant functions, glutathione (GSH) plays a major role in electrophilic conjugation of lipophilic conjugation (initiated by glutathione S-transferase, GST) and in the maintenance of cellular homeostasis. This thesis investigated the responses of drug metabolizing enzymes and endogenous antioxidant defenses in teleosts exposed to PCBs. The first field study showed that feral brown bullheads, harvested from the St. Lawrence River and contaminated with PCBs, had enhanced activities of ethoxyresorufin O-deethylase (EROD), a cytochrome P4501A (CYP1A) catalytic activity. GST activities were induced several fold in these River bullheads, which suggested active detoxication via GSH conjugation, although at the expense of tissue GSH content. A second field study involved the caging of hatchery reared rainbow trout at a PCB contaminated site. The trout showed significant accumulation of PCB congeners in skeletal muscle in the absence of changes in tissue drug metabolizing enzymes and antioxidant defenses. Endogenous antioxidant defenses were examined in rainbow trout and black bullheads. These systems were found to underlie age- and/or maturation-dependent changes. In a series of experiments, exogenous GSH was noted to serve as an efficient delivery agent of GSH to tissues in teleosts. This observation suggests that piscine GSH biochemistry differs from that of mammals, which respond poorly to exogenous GSH. This unique characteristic of the piscine GSH system could be important for fish husbandry while providing an interesting tool to study the biochemical effects of PCBs. A series of experiments found that a 3 day exposure of rainbow trout to 3,3$\sp\prime$,4,4$\sp\prime$-tetrachlorobiphenyl (TCB) had little impact upon tissue antioxidant defenses, while a 6 week exposure resulted in significant induction of activities of the conjugation enzyme UDP-glucuronosyltransferase, antioxidant enzymes activities and GSH levels in hepatic and extrahepatic tissues. However in both experiments TCB induced CYP1A metabolism. Additional experiments attempted to characterize to what extent tissue glutathione status influences basal and TCB induced hepatic CYP1A metabolism. Manipulation of tissue GSH content by either depletion (induced by L-buthionine- (S,R) -sulfoximine, BSO) or supplementation with pro-GSH agents (GSH and lipoate) revealed that glutathione status modified cytochrome P4501A at two stages, the CYP1A mRNA expression and the catalytic activity. This apparent cross-talk between the glutathione and cytochrome P450 systems suggested that glutathione homeostasis plays a major role in PCB induced metabolic alterations.

Introduction. Birth defects and low birth weight/preterm delivery are the leading causes of a infant mortality in the United States. However, their etiologies remain mostly unknown. There is evidence suggestive of a link between exposure to pesticides and reduced infant health. We sought to answer the question of whether spatial variation in the incidence of infant mortality in the general population is correlated with variation in agricultural pesticide use. Methods. We examined the variation during 1996--2001 among 48 U.S. states of rates of infant mortality due to birth defects, and rates of infant mortality due to low birth weight or preterm delivery. We also examined the incidence of 41 specific birth defects through 1989--2001 in 33 states. We related these variables to the rate of agricultural pesticide use per state. Results. After controlling for socio-economic and behavioural risk factors, among-state variation in the rate of pesticide use accounted for over one quarter of the variation in infant mortality rates due to birth defects (r2=0.29). We did not find a significant relationship between pesticide use and infant mortality due to low birth weight/preterm delivery. Conclusion. Our results support the hypothesis that adverse effects on infant health in the general population are associated with broad scale pesticide use. To overcome the inferential limitations of this study, further research using individual exposure and outcome data is needed.

Polycyclic aromatic hydrocarbons (PAHs) are environmental ovotoxicants commonly released in cigarette smoke and vehicle exhaust. PAHs have been shown to target small ovarian follicles (25-100 μm) after a single high dose. Once irreplaceable primordial follicles are depleted in the ovary, ovarian failure results. The occupational chemical, 4-vinylcyclohexene diepoxide (VCD), induces pre-mature ovarian failure in mice and rats. A direct comparison between the ovotoxicity caused by VCD and that of PAHs was made by calculating an initial ovotoxic index (OI = ED₅₀ x 15d) in ovarian follicles of mice and rats. There are two hypotheses to be tested, first is that oocyte destruction can be prevented with a single dose of VCD. Second, three constituents of cigarette smoke, PAHs: 3-methylchloranthrene (3-MC), 9,10-dimethylbenzanthracene (DMBA) and benzo[a]pyrene (BaP) after repeated low-dose exposure results in apoptosis similar to VCD. VCD is protective against the normal rate of atresia in primary ovarian follicles following exposure to a single dose of VCD, and the mRNA expression of the cell death gene bax paralleled the changes in atresia. Using the initial OI, repeated low dose exposures were shown to be more toxic (lower OI) in the ovary than that previously reported from a single high dose. Furthermore, the calculation of the initial OI demonstrated DMBA to be the most potent chemical tested by destroying primordial follicles at the lowest dose. PAHs were also found to target secondary follicles. In the present study, the PAHs were also found to be associated with apoptosis (increased bax mRNA - DMBA and 3-MC; decreased bcl-x(L) mRNA - DMBA), in mice ovarian follicles. Confocal microscopy was used to visualize proteins of gene products from the bcl-2 family Bax (cell death) and Bcl-x(L) (cell survival) in mice. Large primary follicles illustrated consistently increased ratios of Bax/Bcl-x(L) for the three chemicals tested. These results suggest that repeated low dose exposure make ovarian follicles more susceptible to PAHs-induced cellular changes. Taken together with the confocal data, DMBA may be working through a different pathway than VCD and 3-MC, or the ovotoxic effects of DMBA are so potent that the effects due to 3-MC and VCD appear lower, and that large primary follicles may be the critical follicle stage determining the cells fate. The results obtained in these experiments can predict the potential reproductive effects initiated by VCD and PAHs.

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