Browsing by Subject "Natural Products Chemistry and Pharmacognosy"
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Item Lifelong vs. Late Life Tocopherol on Learning and Memory in Mice(2004-05-01) McDonald, Shelley R.; Michael Forster; Glenn DillonMcDonald, Shelley R., Lifelong vs. late life tocopherol on learning and memory in mice. Doctor of Philosophy (Biomedical Sciences), May, 2004, 132 pp., 1 table, 14 figures, bibliography, 122 titles. The purpose of these studies was to determine if vitamin E supplementation, a well-studied antioxidant, could improve the cognitive functions of old mice either by preventing age-dependent impairments or reversing age-related dysfunction. Cellular oxidative stress is believed to be a causal factor in senescence, and the brain appears to be particularly susceptible to oxidative damage because of a relatively high rate of reactive oxygen species generation without commensurate levels of antioxidant defenses. If oxidative stress indeed plays a role in age-related brain dysfunction, then it can be predicted that experimental interventions capable of lowering oxidative stress would either prevent or restore function. This was tested using apolipoprotein E-deficient mice, which have an increased susceptibility to neuronal oxidative damage, maintained on 3 different doses (2 mg/kg, 20 mg/kg, or 200 mg/kg/day) of dl-α-tocopheryl acetate (vitamin E) via supplemented food pellets from 8 weeks of age throughout behavioral testing when 6 or 18 mo of age. A separate experiment used wild type mice 24 months of age to examine whether or not a combination of vitamin E (123 mg/kg/day) with coenzyme Q10 (200 mg/kg/day) which leads to higher tissue levels of vitamin E, could improve brain functions in old mice. Mice were tested on multiple behavioral tasks that required utilization of various components of memory and learning, as well as sensorimotor testing. The highest dose of vitamin E prevented the decline of spatial memory in old apolipoprotein E-deficient mice, but did not prevent age-related impairments in learning and memory for discriminated escape. When old wild type mice were treated with the combined vitamin E and coenzyme W10, the mice learned and remembered to avoid a preemptive shock significantly more than old mice treated with vitamin E or coenzyme Q10 alone. A followup experiment with higher doses of coenzyme Q10 alone (250 or 500 mg/kg/day) resulted in no cognitive improvements. No treatments improved sensorimotor performance.Item Neuroprotective properties of Phytoestrogens(2012-12-01) Brock, Courtney Anne; Singh, MeharvanWomen make up nearly two thirds of total Alzheimer’s cases in the United States. It has been speculated that the loss of endogenous estradiol during menopause is, at least in part, what renders the post-menopausal brain more vulnerable to the effects of aging and Alzheimer’s Disease. While hormone therapy can potentially thwart some of the undesirable consequences and increased risks associated with menopause, women are increasingly rejecting hormone therapy and seeking alternative therapy. There is a strong in interest in phytoestrogens as an alternative to traditional hormone therapy. Phytoestrogens are naturally occurring estrogen like compounds derived from plants which have been shown to have a variety of health benefits. Their effects in the brain however are not fully understood. It was my goal to evaluate the effect of phytoestrogens on brain cells as it relates to neuroprotection. We initially assessed the ability of genistein, the most abundant phytoestrogen found in soy, to protect brain cells against age-associated insults in vitro using the hippocampal cell line (HT22 cells), a cortical cell line (HCN-1A cells), and primary slice cultures of the cerebral cortex. The results of these experiments were such that genistein was protective in the explant model and HCN-1A cells, but not in the HT22 cells suggesting that certain key players must be present for genistein to elicit neuroprotective effects. Based on the known estrogen receptor (ER) profiles for the models used in our study, we hypothesized that ER profiles may dictate the effects of phytoestrogens on brain cells. As such, we evaluated male and female C57/Bl6 mice at 3 different ages for ER expression profile and the effects that a phytoestrogen diet had on BDNF, used in this study as a surrogate marker of neuroprotection. Results showed that phytoestrogens’ effects on the brain differ between the cortex and the hippocampus and are dependent upon the sex of the animal and age at which the diet was initiated. From our results we have proposed a mechanism by which phytoestrogens differentially elicit their effects in the brain. The data presented herein provides valuable insight into phytoestrogens’ effects on the brain.Item The Effect of Late-Life Antioxidant Supplementaion on Brain Function(2007-10-01) Shetty, Ritu A.; Forster, Michael J.; Sumien, Nathalie; Singh, MeharvanShetty, Ritu A., The effect of late-life antioxidant supplementation on brain function. Doctor of Philolosophy (Biomedical Sciences), October, 2007, 229 pp., 5 tables, 18 figures, bibliography, 284 titles. Purpose: Aging is associated with mild to moderate loss in brain function over time. These functional losses are thought to involve reversible changes disrupting important cellular signaling processes. One of the theories that proposes to explain the reversible losses of function is the ‘oxidative stress’ hypothesis of aging. According to the oxidative stress hypothesis, there is an inherent cellular imbalance between production of oxidants and antioxidative defenses that increases with age and that leads to an increase in oxidative damage to macromolecules that are involved in crucial cell functions. Previous studies have established a link between these cellular changes associated with aging and the impairments in cognitive and psychomotor function. Further it has also been suggested that dietary interventions can modulate the level of oxidative stress, reducing oxidative damage and perhaps even ameliorate age-related dysfunction. Most interventions have been implemented relatively early in life and maintained until old age. However, the current studies were based on the rationale that interventions initiated in late-life could potentially lower oxidative damage and thereby alter cellular components responsible for functional impairments. Methods: In study I, separate groups of young (4 months) and old mice male C57BL/6 (18 months) were fed a control diet or a diet supplemented with low (105 mg/kg/day) or high (368 mg/kg/day) concentrations of CoQ10 for a period of 15 weeks. After 6 weeks on the diets, the mice were subjected to a battery of age-sensitive behavioral tests. In study II, separate groups of male C57BL/6 young mice aged 3-4 months and old mice 17-18 months (total of n=124) were fed ad libitum either a control diet (cyclodextrin in base diet), or the same diet supplemented with D- α-tocopheryl acetate (Toc) (200 mg/kg body wt/day), or with CoQ10 (148 mg/kg body wt/day) or a diet containing a combination of CoQ and Toc (200 mg/kg body wt/day + 148 mg/kg body wt/day) for a period of 13-14 weeks. In both studies mice were subjected to a battery of behavioral tests that required utilization of various component of memory and learning and sensorimotor reflexes. Results: In study I, low CoQ10 failed to improve cognitive and psychomotor function in old mice. However, the high CoQ10 marginally helped the old mice to navigate in the swim maze task with greater efficiency than control mice but did not affect their performance in probe trials. Conversely, the high CoQ10 diet selectively impaired the spatial performance in young mice in probe trials. The results from study I indicated that intake of CoQ10 initiated in late-life had minimal beneficial effects on behavior function. In study II, an age-associated decline of behavioral functioning was observed; however CoQ10 treatment failed to improve the performance of mice in any of the age-sensitive tests. Moreover, young mice supplemented with a high CoQ diet performed poorly in the probe trial in a swim maze task, suggesting a possible deleterious effect. The results from study II indicated that there was a significant improvement in performance of old mice in the coordinated running and the learning ability in discriminated avoidance task when supplemented with Toc or with a combination of CoQ10 and Toc. Conclusions: In conclusion, these studies suggest that benefits of single antioxidant supplementation when initiated late in life are limited; however dietary supplementation with a combination of antioxidants has a greater impact in reversing age-related decline in behavioral function.