Browsing by Subject "PCB"
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Item Alterations in thyroid hormone status in Atlantic croaker (Micropogonias undulatus) exposed to Aroclor 1254 and selected PCB congeners(2006-05) LeRoy, Kimberly Dale; Khan, Izhar A.Many studies in animals and humans have demonstrated that exposure topolychlorinated biphenyls (PCBs) can interfere with the normal function of the thyroid system. In this study, Atlantic croaker (Micropogonias undulatus) were exposed to a PCB mixture (Aroclor 1254) or one of three individual congeners (ortho-PCB 153, ortho-PCB 47 or planar PCB 77) in the diet for 30 days to investigate the effects of PCBs on thyroidal status. Thyroid hormones, thyroxine (T4) and triiodothyronine (T3) were extracted from plasma samples and measured with an enzyme-linked immunosorbent assay. Both male and female croaker exposed to the PCB mixture Aroclor 1254 (0.2 and 1.0 mg/kg body wt/day) had decreased plasma levels of total T3 when compared to the parallel control groups, but the effects on total T4 levels were inconsistent. Exposure to PCB 153 (0.1 and 1.0 mg/kg body wt /day) significantly lowered both T4 and T3, while PCB 47 at the same doses had no effect on thyroid hormone levels. Fish exposed to PCB 77 had no effect on T4 or T3 levels except an increase in T4 levels at the highest dose employed (0.1 mg/kg body weight/day). However, this dose of PCB 77 caused partial loss of appetite and may be too high to be relevant for the effects observed after exposure to Aroclor 1254 considering the fact that it constitutes only 0.31% of the PCB mixture. The results of the present study demonstrate that exposure to synthetic endocrine disrupting chemicals, such as PCBs at the higher end of environmentally realistic concentrations can have profound effects on the thyroidal status of Atlantic croaker. The ability of Aroclor 1254, as well as ortho-PCB 153, to consistently disrupt the natural homeostasis of the thyroid system in croaker is an important finding that contributes to a better understanding of PCB endocrine toxicity in teleosts.Item Endocrine-disrupting chemicals alter embryonic brain development and adult neurobehavioral phenotypes(2020-04-28) Hernandez, Morgan Elizabeth; Gore, Andrea C., 1964-; Crews, David; Dominguez, Juan; Champagne, Frances; Melamed, EstherEndocrine-disrupting chemicals are detectable in nearly every environment on the planet. Humans and wildlife are exposed to myriad of these pollutants throughout their life. Because these chemicals interfere with hormone systems in the body, exposure to them during early life development can have a severe impact on later neurobiological and reproductive health. In this dissertation, I investigated how prenatal exposure to two specific EDCs affected the organization of the embryonic brain and changed neuromolecular and behavioral phenotypes in adulthood. The weakly estrogenic mixture of polychlorinated biphenyls (PCBs), Aroclor 1221 (A1221), and the antiandrogenic fungicide vinclozolin (VIN) offer insight through their different mechanisms of interrupting normal endocrine function. I hypothesized that these chemicals would affect the brain and behavior of adult rats in a sex- and compound-specific manner. The first study in this dissertation demonstrates that prenatal exposure to these EDCs can disrupt an important sociosexual behavior in adult rats together with changes in the patterns of expression of associated genes. More specifically, in a test of sociosexual preference, adult rats failed to demonstrate the sex-typical preference for a mate after prenatal exposure to PCBs or VIN in males, and PCBs in females. The second study extends the previous findings by probing for deficits in the ability to distinguish between and/or prefer odorants that convey information about a mate’s fitness, i.e., hormonal status. I deduced that while changes to odor preference strongly resemble the mate preference phenotype, odor discrimination ability is not impaired. However, the activation of the ventrolateral portion of the ventromedial nucleus, a brain region known to regulate mate preference behavior, was altered by PCB exposure in females, suggesting that improper central processing of odor signals may explain some of the results. In the third study, I found that PCB exposure shifted the timing of the hormone-sensitive process of embryonic neurogenesis in the ventromedial nucleus but not the preoptic area. Taken together, these studies demonstrate a possible mechanism by which an EDC can change brain organization and functionally transfer the effects of a prenatal exposure into adulthood.Item The effects of gestational exposure to endocrine-disrupting chemicals on the adult social behavior in male and female rats(2018-06-13) Reilly, Michael Patrick; Gore, Andrea C., 1964-; Crews, David; Vasquez, Karen; Dominguez, Juan; Richburg, JohnEndocrine disrupting chemicals (EDC) exposures during critical periods of development influence neuronal development and the manifestation of sexually dimorphic behaviors that emerge in adulthood. Among these behaviors, social information processing is sexually dimorphic and regulated by sex steroids. Oxytocin and vasopressin serve as primary neurotransmitters mediating these behaviors; these neuroendocrine circuits are hormone sensitive and potential targets of prenatal EDC exposures. In dissertation, I assess the effects of gestational exposure to EDCs on the social behavior of male and females later in adulthood. A weakly estrogenic PCB mixture, Aroclor 1221, was administered to pregnant Sprague-Dawley rat dams during the time when the hypothalamus undergoes sexual differentiation. The brains of these animals were also used to quantify the presence of oxytocin or vasopressin in the two main regions of production: the paraventricular nucleus (PVN) and the supraoptic nucleus (SON). Another experiment extended this treatment paradigm to encompass a longer period of gestational development, added another EDC treatment group (Vinclozolin), and looked at similar behavioral outcomes. Lastly, I provide a novel way of modeling complex social behaviors in a laboratory setting. Through all of this work, we show that the sexes are differentially susceptible to endocrine disruption by PCBs or vinclozolin. Additionally, we provide evidence that the traditional choice models of social behavior in the rodent may not be reflective of how an animal behaves in a more complex, naturalistic, environment.