Browsing by Subject "Rats"
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Item Effects of perfluorooctanesulfonate (PFOS) on thyroid hormone status in rats(2009-07) Chang, Shu-ChingPerfluorooctanesulfonate (PFOS) is an environmentally stable and accumulative compound that has been found to be distributed worldwide in humans and wildlife. Although PFOS exposure has been associated with hypothyroxinemia without a compensatory elevation of thyrotropin (TSH) in the laboratory studies; human biomonitoring studies did not report any association between serum PFOS concentrations and serum thyroid hormones either. Because thyroid hormones have numerous important roles in growth and brain developments, the differences between human and laboratory rat thyroid hormone data in the presence of PFOS raise the questions of whether PFOS interferes with the thyroid homeostasis as well as whether laboratory rats serve as an appropriate model to study thyroid biology. This thesis investigated the effect of PFOS on thyroid hormone status in rats. Rats receiving PFOS appeared to maintain a euthyroid state despite significant reductions in serum total thyroid hormones and enhanced thyroid hormone turnover, likely due to competition for binding sites between PFOS and thyroid hormones in rat serum that can systematically introduces a negative bias when conventional analog methods were used to determine serum free thyroxine levels. The binding competition between PFOS and thyroid hormones did not appear to interfere with the central H-P-T axis because the ability of the pituitary to respond to hypothalamic thyrotropin-releasing hormone to release TSH in response to decreased thyroid hormone production after treatment with propylthiouracil was not altered in rats by co-treatment with PFOS. PFOS administration to maternal rats during gestation and lactation has no clear adverse effect with regards to thyroid morphology, thyroid hormone status, thyroid cell proliferation, and liver gene expression in rat offspring.In conclusion, PFOS treatment does not appear to suppress the physiological thyroid hormone status in rats.Item The effects of wheat class and processing on markets of colon cancer risk in carcinogen-treated rats.(2009-02) Islam, AjmilaA previous study in this laboratory found that hard red wheat is more effective than soft white wheat in reducing colon cancer risk, regardless of processing state, based on fewer aberrant crypt foci (ACF), a morphological marker of colon cancer risk. Here we examined the effect of wheat class (red vs. white) and processing (whole vs. refined) on reducing markers of colon cancer risk during the early and late promotion stage of colon cancer development. Rats adapted to a basal diet were treated twice with the colon-specific carcinogen, dimethylhydrazine (DMH). After the last dose of carcinogen, rats were divided into either the basal diet or the wheat flour-based diet groups. Both hard red and soft white wheat flour significantly reduced morphological markers such as ACF, and sialomucin producing ACF (SiM-ACF), an ACF with greater tumorigenic potential, compared to the basal diet. These reductions occurred equally with whole and refined wheat. Both hard red and soft white wheat diets significantly reduced a biochemical marker of risk, beta-catenin accumulated crypts (BCAC), compared to the basal diet, but hard red wheat did so to a greater degree. Only hard red wheat significantly reduced a marker of stem cells mutation, metallothionein positive crypts, compared to soft white wheat. Hard red wheat caused regression of ACF, suggesting it can reduce the risk level of colon cancer. Overall, hard red wheat reduced colon cancer risk more than soft white wheat, regardless of processing state. The differences between wheat flours were greater in the late promotion stage.Item Effects of wheel running on cocaine seeking in rats: behavior and neurobiology(2014-12) Zlebnik, NatalieCocaine addiction is a pervasive public health problem, but currently there are no highly effective treatments to reduce its extent or duration. Emerging research in humans and animals suggests that aerobic exercise may decrease drug use and prevent relapse. This set of experiments focused on the use of exercise as a behavioral treatment for cocaine addiction using rodent (rat) models of relapse. Concurrent access to a voluntary running wheel decreased reinstatement of cocaine-seeking behavior in response to a cocaine injection (Experiments 1-3), cocaine-paired cues (Experiment 2-3), and the pharmacological stressor yohimbine (Experiment 2). Wheel running during the withdrawal period also prevented incubation of cocaine seeking or time-dependent increases in reactivity to cocaine-paired cues, a situation that often precipitates relapse (Experiment 5). Further, using pharmacological treatments such as progesterone (Experiment 2) or atomoxetine (Experiment 3) in combination with wheel running led to an additive treatment effect, suggesting a larger role for exercise as a singular or adjunct treatment in the prevention of cocaine relapse. While these behavioral models have revealed exercise to be an efficacious method to attenuate cocaine-motivated behaviors, long-term wheel running also changed cocaine-induced activation of brain reward circuitry (Experiment 4). Using c-Fos immunohistochemistry to evaluate neuronal activation, results demonstrated that exercising and control rats showed differential activation of the nucleus accumbens, caudate putamen, and prefrontal cortex in response to an acute cocaine injection. These results suggest that exercise may alter reactivity to cocaine by inducing plasticity in the mesolimbic dopamine system. Overall, results across these experiments have demonstrated that aerobic exercise has the ability to attenuate activation of the neurobiological substrates of addiction in addition to robustly reducing relapse to cocaine-seeking behavior.Item The Systemic Effect of local Injection of clodronate on orthodontic tooth movement in rats(2013-06) Issa, Omar MohamedClodronate is a non N-containing bisphosphonate that inhibits osteoclast maturation and function. The aim of the study was to assess the systemic effect of local administration of Clodronate on orthodontic tooth movement on rats. Two groups of Sparague-Dawley rats were used. Rats in the experimental group were injected with 50 µl of Clodronate solution on the same side every 3 days for 3 weeks and those in the control group received 50 µl saline solution at the same schedule. Two NiTi-coil springs exerting a constant 50 gm-force, were activated across the span from the central incisors to the first right and left maxillary molars. As the first molar tipped mesially, a diastema between the first and second molars was created. A histomorphometric analysis was used to calculate the mineral apposition rate (MAR) and the diastema between the maxillary first and second molars. The results indicate that (i) average diastema was less in Clodronate injection side group (ii) MAR was less in Clodronate injection side (iii) neither the appliance placement nor the injection inhibited the rat's ability to gain weight. Further study is necessary to determine the reproducibility of these effects.