<p> Over the last several decades declines in pollinator populations, especially those of wild bees and other insects, have raised awareness of the economic impact pollination services have for crop production. This awareness and concern was heightened by an ongoing loss of millions of managed honey bee colonies since the early 1950s. Colonies are used predominantly for pollination services in fruit and vegetable crops. During 2007, an unusually large overwintering loss in colonies that was not characterized by the presence of dead bees was termed colony collapse disorder (CCD), a syndrome in which hives lacked sufficient worker caste bees to maintain the queen and brood. Potential factors hypothesized to be associated with CCD include parasite infestations (e.g., <i>Varroa </i> mite) and pathogen infections (<i>Nosema</i> spp. fungus and viruses), insecticide exposure (especially to the neonicotinoid class), and poor nutrition owing to a reduction in landscape areas containing high quality floral resources. Although no one stressor has been definitively associated with CCD, possible interactions among them have only recently been studied. Of particular interest are possible interactions of <i>Nosema </i> spp. with neonicotinoid insecticide exposure. The main objective of this dissertation was an examination of these potential interactions using a combination of literature analysis, empirical study of <i>Nosema</i> infection prevalence in adult bees, and simulation modeling of the combined effects of several stressors on worker population abundance. After the introduction, the dissertation is divided into four chapters addressing the following objectives: (1) Comparison of regulatory procedures for risk assessment of insecticides potentially impacting honey bees in the United States and in the European Union; (2) Analysis of published literature that document potential interactions between bee pathogens, parasites, and neonicotinoid insecticide residues; (3) Analysis of field-collected apiary bees for prevalence of <i>Nosema </i> spores in association with land uses and the presence of neonicotinoid residues; (4) Use of the honey bee colony model BEEHAVE to predict colony collapse in the presence of pathogens and insecticide-induced mortality. Results of the various analyses suggest a need for modifying risk assessment procedures to include the interaction of pesticide residues with parasite/pathogen stressors. </p><p>

Several trace metals have been shown to modify cell injury as indicated by reduction of observable pathological tissue changes after metal ion supplementation. An example of this is zinc ion induced protection against some of the liver injury caused by a single injection of carbon tetrachloride (CCl₄) to male Sprague-Dawley rats. Carbon tetrachloride liver injury is associated with membrane labilization as indicated by lysosomal and endoplasmic reticulum anomalies. Depressed hepatic levels of NADPH are observed during CCl₄ poisoning. Lipid metabolism is also impaired due to CCl₄ administration to animals. These biochemical manifestations of CCl₄ hepatotoxicity were studied in the presence of zinc ions in order to understand the mechanisms of the zinc protective effect against CCl₄ injury. The effect of zinc ions on the stability of rat liver lysomes was studied. Zinc was added by several methods: (1) feeding the animals a high zinc diet, (2) infusion of zinc into the liver in situ through the portal vein, or (3) by adding zinc to the lysosomal fraction either before or after isolation of this fraction from rat liver homogenates. By all techniques, addition of zinc reduced the release of β-glucuronidase from liver lysosomes, indicating increased stability of the suborganelles. The zinc induced protection against CCl₄ liver damage was evident in observations made using both light microscopy and electron microscopy. The increased release of lysosomal β-glucuronidase observed in the CCl₄ treated rats was significantly reduced by zinc administration. Also, decreases in microsomal protein synthesis and seromucoid levels due to the CCl₄ treatment were significantly ameliorated by zinc. Thus, disruption of lysosomal and endoplasmic reticulum membranes, one of the earliest signs of CCl₄ hepatotoxicity, appeared to be inhibited by pretreating the animals with zinc chloride. Depressed hepatic levels of NADPH are observed in rats administered CCl₄. Zinc chloride pretreatment of these rats significantly increased the NADPH levels in the liver. Since zinc ions bind NADPH, then the protective effect of zinc against CCl₄ toxicity may be due to stabilization of the pyridine nucleotide by zinc and the subsequent prevention of CCl₄ induced alterations of biochemical reactions dependent upon NADPH. Zinc chloride pretreatment of CCl₄ treated rats significantly reduced the CCl₄ induced hepatic triacylglycerol accumulation. Concomitant with this event is the appearance of elevated levels of newly synthesized triacylglycerols in the serum of the CCl₄ treated rats given zinc above that of the CCl₄ treated rats. Hepatic triacylglycerol synthesis is unchanged by CCl₄ or zinc treatment. Hepatic phospholipid levels which are depressed by the CCl₄ hepatotoxin are not affected by zinc treatment. However, the synthesis of phospholipids in the livers of rats treated with CCl₄ plus zinc is significantly increased. The lipid changes induced by CCl₄ and zinc dosing of rats are indicative of alterations in liver membranes thus affecting hepatic liver transport mechanisms. On the basis of the data presented, the effects of zinc ions on CCl₄ hepatotoxicity are discussed and applied to understanding the regulating role of metal ions in tissue injury. The protective effects of zinc ions against CCl₄ hepatotoxicity suggest a relationship between the zinc nutritional status of animals exposed to environmental contaminants, and the expression of the ensuing tissue damage.

"August 2002" / Bibliography: leaves 141-176. / ix, 179 leaves : ill. (some col.) ; 30 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Changes in maternal-foetal zinc homeostasis resulting in a foetal deficiency may be an important contributing factor in ethanol-realted teratogenicity. Ethanol induces expression of hepatic metallothionein, causing zinc transfer from the plasma to the liver. Rodent studies show that changes in plasma zinc correlate with a high incidence of abnormal fetuses in MT+/+ mice. Demonstrates a clear link between maternal hepatic MT induction, decreased foetal zinc supply, and teratogenicity, which has major implications for binge alcohol consumption in early pregnancy. The demonstration that zinc treatment is effective in preventing teratogenicity indicates potential treatment strategies. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 2003

Indiana University-Purdue University Indianapolis (IUPUI) / Fetal alcohol spectrum disorders (FASD) is the leading neurodevelopment deficit in children born to women who drink alcohol during pregnancy. The hippocampus and cortex are among brain regions vulnerable to alcohol-induced neurotoxicity, and are key regions underlying the cognitive impairment, learning and memory deficits shown in FASD individuals. Hippocampal and cortical neuronal differentiation and maturation are highly influenced by both intrinsic transcriptional signaling and extracellular cues. Epigenetic mechanisms, primarily DNA methylation and histone modifications, are hypothesized to be involved in regulating key neural development events, and are subject to alcohol exposure. Alcohol is shown to modify DNA methylation and histone modifications through altering methyl donor metabolisms. Recent studies in our laboratory have shown that alcohol disrupted genome-wide DNA methylation and delayed early embryonic development. However, how alcohol affects DNA methylation in fetal hippocampal and cortical development remains elusive, therefore, will be the theme of this study. We reported that, in a dietary alcohol-intake model of FASD, prenatal alcohol exposure retarded the development of fetal hippocampus and cortex, accompanied by a delayed cellular DNA methylation program. We identified a programed 5-methylcytosine (5mC) and 5-hydroxylmethylcytosine (5hmC) cellular and chromatic re-organization that was associated with neuronal differentiation and maturation spatiotemporally, and this process was hindered by prenatal alcohol exposure. Furthermore, we showed that alcohol disrupted locus-specific DNA methylation on neural specification genes and reduced neurogenic properties of neural stem cells, which might contribute to the aberration in neurogenesis of FASD individuals. The work of this dissertation suggested an important role of DNA methylation in neural development and elucidated a potential epigenetic mechanism in the alcohol teratogenesis.