Browsing by Subject "vision"
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Item Gracy, Robert, PhD.(1994-01-26) Gracy, Robert; Hailey, BlakeDr. Gracy, Associate Dean of Basic Sciences and Research, recounts the process of bringing TCOM and North Texas together. Interviewed by Blake Hailey, January 26, 1994Item Mechanisms of Photoreceptor Cell Apoptosis(2000-05-01) Crawford, Matthew John; Neeraj Agarwal; Victoria Rudick; Raghu KrishnamoorthyCrawford, Matthew John, Mechanisms of Photoreceptor Cell Apoptosis. Doctor of Philosophy (Biomedical Sciences), May 2000; 168 pp; 3 tables; 23 figures; bibliography, 282 titles. Photoreceptor cell death mediated by programmed cell death pathways is responsible for many disease states of the retina, which result in vision loss. Examples of this include retinal dystrophies and age-related macular degeneration. Correspondingly, the understanding of programmed cell death, or apoptosis, in these cells is important in the formulation of preventative and treatment options. The goals of this dissertation are to characterize a suitable in vitro photoreceptor cell model and explore the molecular mechanisms resulting in apoptotic cell death secondary to oxidative cell death paradigm. Means of interrupting the cell death process were also investigated. An immortalized clonal mouse retinal cell line was shown to express photoreceptor-specific genes and proteins by RT-PCR amplification, Western blot analysis, and immunocytochemical localization. Exposing these cultured cells to visible light resulted in oxidative stress, as exhibited by elevated malonyldialdehyde and reduced gluthathione levels, as well light exposure-dependent apoptosis was shown using multiple techniques which identified fragmentation of chromosomal DNA, a key finding in the apoptotic cell death process. Molecular regulators of apoptotic cell death, including bcl-2 family proto-oncogenes and the nuclear transcription factor NF-kB, were found to be important in oxidative stress-induced pathogenesis of 661 W photoreceptor cells. mRNA and protein levels of the anti-apoptotic proto-oncogene bcl-2 declined following oxidative stress disturbing the balance proto-oncogene regulators and initiating the apoptotic pathway. The nuclear transcription factor NF-kB was found to be constitutionally expressed in the photoreceptor cells with its down-regulation during apoptosis. Permanent transfection of the photoreceptor cells with bcl-2 gene imparted protection from apoptosis and sustained NF-kB levels. The results presented in this dissertation help define the molecular mechanisms which occur during apoptosis of photoreceptor cells. Photo-oxidative stress results in programmed cell death mediated through changes in NF-kB binding activity and bcl-2 family genes. The involvement of caspase-1 in the degradation of NF-kB and the execution of apoptosis is also demonstrated. Over-expression of the proto-oncogene bcl-2 interrupts the apoptotic events, protecting against down-modulation of NF-kb binding activity and cell death. Our proposed mechanism for apoptosis in photoreceptor cells provides several points at which targeted gene expression (bcl-2 or NF-kB), or pharmaceuticals (anti-oxidants, caspase inhibitors, or calcium channel blockers) may prevent apoptotic cell death.Item Role of Nonfeminizing Estrogen Analogues in Neuroprotection of Rat Retinal Ganglion Cells Against Glutamate-Induced Cytotoxicity(2007-05-01) Kumar, Domalapalli Maneesh; Agarwal, Neeraj; Gracy, Robert; Garner, MargaretKumar, Domalapalli Maneesh, Role of Nonfeminizing Estrogen Analogues in Neuroprotection of Rat Retinal Ganglion Cells against Glutamate-Induced Cytotoxicity, Doctor of Philosophy (Cell Biology and Genetics), May, 2007, 210 pp., 3 tables, 23 figures, bibliography, 427 titles. Retinal ganglion cell death has been determined to be the final common pathway in glaucoma. Continuous loss of retinal ganglion cells results in irreversible progressive visual field deterioration that culminates in blindness. No effective therapy is currently available to reverse retinal ganglion cell loss. Therefore, preventing the loss of retinal ganglion cells is a logical approach to maintaining vision in effected individuals. Of the methods of investigation, in vivo models of ganglion cell death provide a physiological system in which to study neuroprotective drugs and their effects, but these systems are inefficient for initial screening studies. We have addressed this by utilizing the RGC-5 clonal rat retinal ganglion cell line. Glutamate treatment of RGC-5 cells induces apoptotic death which can be attenuated by pretreatment with the anti-oxidants N-acetyl cysteine and thiourea, implicating oxidative stress as a major component of glutamate’s cytotoxicity. Also antioxidants, estrogens have been demonstrated to be potent neuroprotectants in a variety of in vitro and in vivo models of neurodegeneration. Estrogens’ antioxidant capacity has been attributed to the ability of the phenolic A ring to quench and resonance stabilize oxidative free radicals. It is also known that the estrogen A ring is responsible for binding of these hormones to estrogen receptors, producing feminizing phenotypes. The feminizing effects of estrogens narrow or preclude their use as neuroprotectants in males, and in females that may be predisposed to their deleterious effects. To address these shortcomings we screened 13, non-feminizing, non-receptor binding estrogen analogues in our glutamate-induced RGC-5 model of oxidative stress-induced cell death. The most effective of these drugs was ZYC-3. ZYC-3 was synthesized by the addition of an adamantly group to the C2 position on the A ring of estrone. This modification produced a neuroprotective compound with potency and efficacy at least equal to the prototypical estrogen, 17β-estradiol, but with no appreciable binding affinity for estrogens receptors α or β. Our preliminary findings suggest that ZYC-3 enhances glutathione synthesis and blocks mitochondrial apoptotic pathways. However, as a novel drug we are naïve to its effects on cellular physiology and as to how it affords neuroprotection. Understanding how this drug regulates cellular destructive and protective mechanisms could lead to further innovations in drug design and in methods to prevent retinal ganglion cell degeneration. In vivo studies of this drug may then form the bridge to a better clinical approach to managing ocular disorders in which ganglion cell loss is the culprit for vision loss. Although promising, evidence supporting the application of estrogen analogues in models of ocular neurodegenerative diseases are nearly non-existent. It is our objective to study the neuroprotective effects of ZYC-3 in glaucomatous models with the goal of maintaining retinal ganglion cell viability and preventing vision loss.Item The Association between Obesity, Cognition, and Visual Function(2011-05-01) Currie-Elolf, Lauren M.; Nathalie SumienPurpose: Obesity is an adverse health condition characterized by excessive weight gain. Aside from the pathological conditions most commonly associated with obesity, recent epidemiological studies have suggested that obesity may be associated with impaired learning and memory. Previous research has linked inflammation and oxidative stress, cellular changes that occur consequent to obesity, to impaired cognitive function. Obese rodent models have been established and are commonly used for obesity-related research; however, with respect to the effect of obesity on cognitive function, the data remain inconclusive. In these studies, two obese mouse models, representing two obesity-inducing causes: genetic vs. environment, were behaviorally characterized in order to determine which model was best suited to study behavioral and cellular changes associated with obesity. Furthermore, a suitable model needed to be identified to carry on studies focusing on the relation between aging and obesity, as one would predict an exacerbation of the impairment in old obese models with age. The current studies were also based on the rationale that a dietary intervention at mid-life would ameliorate behavioral and biochemical changes observed with obesity. Methods: In study I, separate groups of 6-month old male and female C57BL/6 and leptin-deficient (ob/ob) were subjected to a battery of behavioral tests for motor, cognitive and visual function. In study II, separate groups of male C57BL/6 mice aged to 6- or 12-months were fed ad libitum either a control diet or a high-fat diet since 6- weeks of age. In a subset of the aged mice, a dietary intervention was introduced such that these mice were switched from the high-fat diet to the control diet at 6-months of age. Mice were subjected to a battery of behavioral tests at 6- or 12-months that required utilization of various component of memory, learning and visual function. Results: In study I, cognitive impairments were observed in the obese mice, and were exacerbated in female mice. While overall spatial learning was unaffected, male and female ob/ob mice performed worse on an active avoidance paradigm, indicating frontal cortical impairment. The ob/ob mice also performed worse on vision-associated tests. The results from this study suggested that obesity impairs cognitive and visual function in a sex-dependent manner. In study II, increased anxiety was observed in diet-induced obese mice; however, spontaneous activity, spatial capacity and performance on the active avoidance paradigm were unaffected. The dietary intervention reversed the effect of obesity on anxiety-like behaviors, but failed to improve cognitive and motor function. Visual impairments were observed in diet-induced obese mice, and these impairments were exacerbated with age. The results from study II indicated that diet- induced obese mice could be used to study the effects of obesity on visual, but not cognitive function. Conclusions: Overall, the hypothesis that obesity impairs cognitive function and exacerbates age-related impairments was not supported and the dietary intervention had minor effects. However, in both models, obesity impaired visual function and it was exacerbated at older ages. These findings suggest that ob/ob and diet-induced obese mice are valid animal models for investigating obesity-induced visual disorders.