Browsing by Subject "Optometry"
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Item Characterization and Activity of Endothelin Converting Enzyme-1 in Human Non-Pigmented Ciliary Epithelial Cells(1999-01-01) Finkley, Alvin; Thomas Yorio; S. Dan Dimitrijevich; Victoria J. RudickFinkley, Alvin, Characterization and Activity of Endothelin Converting Enzyme-1 in Human Non-Pigmented Ciliary Epithelial Cells. Master of Science (Biomedical Sciences). Endothelins (ETs) are potent vasoactive peptides, that are present in many ocular tissues including the ciliary epithelium where active ET-1 is produced from the precursor Big ET-1 by a membrane-bound metalloprotease, endothelin-converting enzyme (ECE). Although the role of ocular ET’s are uncertain, ETs have been shown to lower the intraocular pressure. In the current study, ET-1 and Big-ET-1 were detected in SV-40 transformed human ciliary epithelial (HNPE) cells by immunofluorescence suggesting the presence of ECE activity. The presence of ECE was confirmed by Western blotting using polyclonal antibodies against ECE-1 which detected a 124 KDa protein in the membrane fraction and not in the cytosol. Further characterization of the enzymatic activity of ECE (conversion of Big ET-1 to ET-1) was performed using a novel assay involving 121I-Big ET-1 (substrate; 2fmloe) and polyclonal antibodies specific for Big ET-1. Mean ECE-1 activity (expressed as the ratio of 121^1-ET-1 produced to the total 125^I-Big ET-1 incubated X 100) was measured and corresponded to: 26% (0.5 3±0.02 fmole, 1 hr), 63% (1.26±0.07 fmole, 3hr) and 66% (1.33±0.11 fmole, 24 hr) compared to blank controls at 13% (0.25±0.03 fmole). Thiorphan (2mM), an inhibitor of ECE, abolished ECE-1 activity. These results suggest that ECE-1 is localized in HNPE cells and is essential for the production of ET-1. The physiological importance of the proteolytic processing by ECE-1 in ocular tissue may reflect on how ET regulates intraocular pressure. Key Words: endothelin converting enzyme-1; endothelin-1; Big endothelin-1; ciliary epithelium; aqueous humor dynamics; intraocular pressure, Western blotting, ECE-1Item Characterization of the Bradykinn Receptor in Human Corneal Epithelium(1997-08-01) Wiernas, Terry Kirkham; Michael W. Martin; Glenn Dillon; Michael ForsterWiernas, Terry Kirkham, Characterization of the Bradykinin Receptor in Human Corneal Epithelium. Doctor of Philosophy (Biomedical Sciences), August, 1997, 255 pp., 5 tables, 39 figures, references, 137 titles. Bradykinin (BK) is a well-established mediator of inflammation. High levels of BK in human tears following ocular allergic provocation led to the hypothesis that BK receptors may exist on the corneal epithelium and could play a role in corneal inflammation and/or wound healing, in addition to other functions. To test this hypothesis, human corneal epithelial cells were cultured and used to conduct a series of studies to evaluate and characterize the BK receptor. Due to the limited supply and high cost of primary human corneal epithelial (P-CEPI) cells, in addition to the fact that these cells do not divide and proliferate over more than a few passages, SV40 virus-immortalized human CEPI cells (CEPI-17-CL4) were used as a model system. Extensive studies confirmed that the immortalized cells faithfully represented the primary cells. This study demonstrated the presence of BK receptors on corneal epithelial cells for the first time. The receptors were characterized as the B2 subtype and were found to be represented by an apparent single binding site. Furthermore, stimulation of these receptors was found to elicit concentration-dependent increases in both inositol phosphates, via activation of phospholipase C, and intracellular calcium mobilization. The rank order affinity of BK and its analogs as determined by binding assays was found to correlate well with the rank order potency of BK and its analogs in evoking the latter functional responses, which were blocked by two B2-receptor selective antagonists. A significant, concentration-dependent stimulation of [3H]thymidine uptake in CEPI cell DNA was elicited by BK which suggests a potential mitogenic effect of BK and a role in corneal wound healing. BK did not significantly affect the release of three pro-inflammatory cytokines, prostaglandin E2 or matrix metalloproteinase-1, and seemed to have an inhibitory effect on the release of tumor necrosis factor α. In conclusion, these studies have confirmed that CEPI-17-CL4 cells represent a good in vitro model of human corneal epithelium and have contributed to a better understanding of the ocular effects of BK and characterization of its receptor within the cornea.Item Characterization of the Serotonin Receptors in the Long Posterior Ciliary Artery of the Bovine Eye(2000-08-01) Landry, Theresa A.; Quist, Eugene; Martin, Michael; Pang, Iok-HouLandry, Theresa A., Characterization of the Serotonin Receptors in the Long Posterior Ciliary Artery of the Bovine Eye. Doctor of Philosophy (Biomedical Science), August 2000, 14 pp., 5 tables, 29 illustrations, bibliography, 104 titles. Vascular disease and vasospasm are implicated in the etiology of glaucoma. The long posterior ciliary (LPCA) is the major blood supply for the ciliary body including the ciliary processes that produce aqueous humor. Information about the pharmacological control of this vessel would be helpful in understanding its normal and pathologic function. Serotonin (5-HT) is a neurotransmitter that effectively constricts the LPCA. The objective of this research is to identify the serotonin receptor subtype responsible for the 5-HT induced vasoconstriction of the LPCA and to characterize the cellular mechanisms that mediate that contraction. Ring segments of the LPCA were dissected from bovine eyes and mounted on tungsten triangles attached to a force transducer. Changes in vascular tension were measured and recorded using a physiography recorder. Dose response curves with 5-HT, 5-HT 1-like agonist, 5-CT, and 5-HT2 agonist, α-methyl-5-HT, indicate that the 5-HT 1-like receptor contributed about 15.13% to the contraction and the 5-HT2 receptor contributed to 61.61%. The EC50 for the three agonists were 283 nM (5-HT), 336 nM (5-CT), and 1.7 μM (α-methyl-5-HT). Inhibition curves with selective antagonists indicate that the IC50 is (5-HT 1-like antagonist) and ketanserin (5-HT2 antagonist). Following incubation of the rings with diltiazem 10 μM or nifedipine 10μM, the response to 5-HT was reduced 65.*% and 61.7% respectively. Incubation in calcium free PB produced similar results. Ryanodine inhibited the 5-HT contraction by 58.1% and caffeine inhibited the response 100%. PKC inhibitors bisindolymaleimide II 1 μM, disindolylamalemide II 10 μM, chelerythrine 25 μM and H-7 5 μM decreased the 5-HT response by19.8%, 55.7%, 31.1% and 61.5% respectively. Incubation of the ring segments with one of three PLC antagonists, 2-NCDC 70 μM, U73122 0.5μM, or neomycin 5 mM, prior to the addition of 1 μM serotonin, significantly reduced the contraction of each vessel, p [less than] 0.0001. The 5-HT-induced vasoconstriction of the LPCA of the bovine eye is mediated through activation of both 5-HT2 and 5-HT 1-like receptors. The contraction is dependent on the mobilization of calcium and is mediated in part through PLC activated intracellular calcium release from IP3 sensitive stores.Item Clinical Internship with the Clinical Glaucoma/Viability Group at Alcon Research, Ltd.: The Use of Prostaglandin Analogues in the Treatment of Patients with Open-Angle Glaucoma (OAG) or Ocular Hypertension (OHT)(2003-12-01) Hall, Magali G.; Robert Wordinger; Richard Easom; Victoria RudickHall, Magali. Master of Science, Biomedical Sciences, December 2003. The use of Prostaglandin Analogues (PGAs) in the Treatment of Patients with Open-Angle Glaucoma (OAG) or Ocular Hypertension (OHT). Summary: Glaucoma is an ocular condition that causes damage to the optic nerve leading to a loss of visual function, and permanent blindness if left untreated. It is the leading cause of preventable blindness in the U.S. The main risk factor for glaucomatous optic neuropathy is elevated intraocular pressure (IOP), which can be controlled by pharmaceutical therapy, surgical therapy or both. Topical medication is usually recommended prior to surgical intervention. Objectives: This study had two main objectives. First, to determine the IOP lower safety and efficacy of three concentrations of a new prostaglandin analogues (PGA), and secondly to determine the incidence of ocular hyperemia with once-daily dosing of study medication compared to it’s vehicle and to latanoprost, a marketed PGA. Study Design: This was a Phase II, double-masked, dose-response study with five treatment arms (the three different concentrations of study drug), vehicle, and latanoprost. Study was conducted in fourteen days, with five study visits as follows: Screening and eligibility visit followed by three on-therapy visits scheduled on Day 1, Day 7, and Day 14. The primary efficacy variable was IOP measurements taken at four different time points on study visits. Results: Final data will not available in time to include in this paper.Item Development of a Subjective Comfort Questionnaire for Hydrogel Contact Lens Wearers(2003-12-01) Hays, Brian Hunter; Sheedlo, Harold; Stein, Jerry; Atiles, LuisThroughout this paper it is written that I would complete this study in its entirety. Due to time constraints and the length of this study, it was planned from the beginning that I would only accomplish the beginning phases, phases one and two. The reason why this paper was written this way, planning the complete research plan, is to aid the individuals that will finish this study in its entirety. I. Purpose. The purpose of this project is to develop a questionnaire that can be used as a tool to measure the subjective symptoms of ocular comfort or discomfort reported by soft contact lens wearers. After a questionnaire has been developed, it will be tested to determine its reliability and validity in capturing the ocular sensations experienced by hydrogel contact lens wearers. II. Overview of the study. The research for the study will be conducted in six phases while pursuing three specific aims. The phases will consist of: A. reviewing literature in the form of reported soft contact lens symptomatology and interviewing skill improvement, compiling and B. examining previously developed questionnaires, developing open-ended interview questions and collecting data from the field. C. developing preliminary questionnaire items based on data gained during the first phase. D. administering the preliminary questionnaire to receive feedback from volunteers with regards to each item’s appropriateness, and tallying the volunteer's responses to graphically analyze each item’s answer distribution. E. refining each item based on the data obtained during the third phase to create a revised draft of the questionnaire. F. determining if the revised draft conveyed and captured the ideas reported by the volunteers by receiving feedback after it is administered. G. demonstrating reliability and validity by psychometrically validating the questionnaire. During each administrational phase of the study (phases three, five and six) two groups of volunteers will be used to gain a broader spectrum of data. Each group will be composed of a sub-set of previously interviewed volunteers and a sub-set of new volunteers. Before any information is obtained, a confidentiality agreement will be discussed with each volunteer. All volunteers will be given a simple, easy to read informed consent form and a randomly assigned number.Item Effects of Intravitreal Endothelin-1 on Anterograde Axonal Transport in Rat Optic Nerve: Evaluating a Possible Mechanism for Glaucomatous Optic Neuropathy(2002-05-01) Stokely, Martha Elise Lambert; Thomas Yorio; Scott T. Brady; Glenn DillonStokely, Martha Elise Lambert, Effects of Intravitreal Endothelin-1 on Anterograde Axonal Transport in Rat Optic Nerve: Evaluating a possible mechanism for glaucomatous optic neuropathy. Doctor of Philosophy (Biomedical Sciences and Neuroscience), May 2002; 114 pages; 1 table; 12 figures; bibliography, 274 titles. Glaucoma presents a distinctive dysfunction in anterograde axonal transport that disproportionately affects the delivery of specific types of cargo(s) into the optic nerve. Previous models for pathogenesis of glaucoma have failed to provide an adequate mechanism to explain the characteristic cargo-selectivity. A new theoretical model, the “endothelin receptor-mediated model of neuropathogenesis,” was developed to explain the cargo-selective axonal transport dysfunction seen in glaucomtous optic neuropathy. In addition, a new experimental animal model, the “intravitreal endothlin/axonal transport” model was developed to test hypotheses generated by the new theoretical model. Intravitreal endothelin-1 significantly affected all of the known rate components and subcomponents of anterograde axonal transport in the rat optic nerve. Changes were seen in anterograde axonal transport in the rat optic nerve. Changes were seen in anterograde fast axonal transport for both the fastest moving small tubulovesicles, and slightly slower membrane bound organelles (MBOs), as well as in the slow transport of cytoplasmic matrix and cytoskeletal materials. Endothelin-1’s predominant effect was a severe depression in the mitochondrial subcomponent of fast anterograde axonal transport, which was most pronounced at 28 hours post-treatment. At that time, the effects of endothelin-1 were mimicked by endothelin-3, characteristic of the non-ischemic endothelin-B type of receptor. In addition, analysis of a cohort of 11 distinctive protein bands moving with the mitochondrial subcomponent demonstrated a cargo-selective effect of endothelin-1 and the delayed movement into the optic nerve for a chemically distinct subset of proteins, but not the majority of protein, in transport during this timeframe. These results appear to be consistent with what is known about the pathology of glaucomatous optic neuropathy and the neurochemistry of anterograde axonal transport and suggest that intravitreal may be an excellent model to study the mechanisms of neurodegeneration that occurs in glaucoma.Item Endothelin-1 Mediated Regulation of Extracellular Matrix Collagens- A Role in Pathology of Primary Open Angle Glaucoma(2007-11-01) Rao, Vidhya Ramachandiran; Thomas Yoroi; Neeraj Agarwal; Raghu KrishnamoorthyEndothelin -1 Mediated Regulation of Extracellular Matrix Collagens –A role in Pathology of Primary Open Angle Glaucoma. Vidhya R. Rao, Doctor of Philosophy. (Pharmacology and Neuroscience), November, 2007, 157 pp., 3 tables, 18 figures. Summary. Primary Open Angle Glaucoma (POAG) is a progressive optic neuropathy characterized by loss of retinal ganglion cells, optic nerve degeneration and characteristic extracellular matrix (ECM) remodeling of the optic nerve head. An increase in collagen type I and VI is observed at the level of lamina cribosa (LC), a distinct connective tissue region of optic nerve in POAG subjects. Extensive ECM remodeling with enhanced collagen deposition observed in POAG is consistent with the pathology of fibrosis. Mechanisms contributing to ECM remodeling in POAG is not known. Endothelin-1(ET-1), a potent vaso-active peptide plays a key role in glaucoma pathology. Intra-vitreal administration of ET-1 in animal models results in optic neuropathy, RGC apoptosis, axonal transport block and ONA activation. An upregulation of ET-1 and ETB receptors is observed in glaucomatous LC and animal models of glaucoma and ET-1 mediated detrimental effects in POAG appears to be mediated by ETB receptors. ET-1 initiatives and maintains enhanced collagen synthesis and deposition in various tissues under pathological conditions and is recognized as a potent profibrotic factor. In the present study we hypothesized that ET-1 increases extracellular matrix collagen deposition in lamina cribrosa and this change in ECM contributes to optic nerve fibrosis. We have demonstrated that cells of lamina cribrose (LC) cells, express functional ETA and ETB receptors. ET-1 increases intracellular calcium mobilization via ETA receptors and increases NO release by mechanisms involving both ETA and ETB receptors. Consistent with POAG pathology we have observed an upregulation ETB receptors in LC cells in response to chronic treatment with ET-1. LC cells also express prepro-ET-1, the primary gene transcript of ET-1. We have demonstrated for the first time that ET-1 exerts its profibrotic effects by enhancing collagen type I and type VI mRNA, protein synthesis, deposition and secretion in LC cells. ET-1 enhanced collagen deposition in LC cells appears to involve both ETA and ETB receptors, as both of the receptor antagonist, individually inhibit ET-1 mediated collagen synthesis. We have demonstrated that ET-1 also exerts its profibrotic effects in vivo by enhancing collagen deposition in rat optic nerve head. We have also observed an apparent decrease in ET-1 mediated collagen VI deposition in optic nerve heads of ETB deficient transgenic rats suggesting that ET-1 mediated collagen VI synthesis involves ETB receptor activation. In conclusion, endothlein-1 stimulates collagen synthesis and deposition both in vitro in LC cells as well as in vivo at the level of rat optic nerve head. ET-1 mediated increase in collage synthesis at the level of optic nerve head could render a fibrotic mechanism that contributes to the progression of POAG.Item Ergonomic Efficiency Field Evaluation of the C-03-35 Intraocular Lens Delivery System(2004-05-01) Kajtoch, Michael; Gwirtz, Patricia A.; Bens, Annita V.; Hileman, KendraObjective: The purpose of this post-market clinical investigation is to validate the ergonomic efficiency of the C-03-35 Intraocular Delivery System following cataract removal by phacoemulsification. The C-O-35 Delivery System is a newly approved device developed by Alcon Laboratories, Inc, which allows the delivery of the ACRYSOF Model SA60AS soft acrylic intraocular lens in a sterile, single-use and disposable unit that combines the hand piece plus the ACRYSOF intraocular lens-contained cartridge in an integrated system. This system is somewhat different from the predecessor MONARCH II Delivery System, which requires the surgeon to correctly insert the ACRYSOF intraocular lens into a cartridge and then assemble the cartridge into a reusable hand piece. The C-03-35 Delivery System eliminates these steps; therefore, it should decrease the risk of damage that may occur to the optic or the haptic as well as reducing surgery time. Materials and Methods: This study is an open label ergonomic assessment of the C-03-35 Delivery System that will be completed after the operative visit (performed on one eye only) of 120 patients by up to twelve investigators. The investigators will enroll patients requiring cataract extraction with intraocular lens implantation into the study that meet predetermined inclusion/exclusion criteria. Data Collection and Analysis: Upon concluding the surgical procedure, the investigator will complete a series of Case Report Forms consisting of questions assessing the ergonomic efficiency of the C-03-35 Delivery System. The Case Report Forms will comprise of questions regarding the optic and haptic placement, ease of use, as well as any adverse events that might have occurred. In addition, the investigator will complete an Exit Case Report Form once the patient concludes the study, is discontinued from the study, or if the patient fails to attend the follow-up visits. The required C-03-35 Case Report Form examination schedule is included in Appendix C. The information obtained from the Case Report Forms will then be entered into a clinical database. The safety information will be analyzed by the Biostatics Department by comparing the safety data obtained from the field evaluation to the Federal Food and Drug Administration’s standards called the FDA Grid of Historical Controls. The FDA Historical Grid provides pharmaceutical companies with performance guidelines by which the investigational test article is measured. In the case of intraocular lenses, the FDA Historical Grid provides standards for overall visual acuity (%20/40), best-case visual acuity (%20/40), and adverse events. Only adverse events will be compared to the FDA Historical Grid and analyzed for this field evaluation. The visual acuity parameters of the intraocular lens will not be analyzed in this study, since the C-03-35 Delivery System uses a FDA approved ACRYSOF Model SA60AS lens with established performance. In addition, the ergonomic efficiency questions such as ease of use will be summarized into a table. Although not currently on the protocol of the study, this information may also be further compared against the MONARCH II Delivery System analysis results, since safety as well as ergonomic efficiency data were also collected during that study. The FDA Grid of Historical Controls is included in Appendix D.Item Function of Differentially Expressed Intracellular Calcium Channels in Retinal Neurons(2008-05-01) Nixon, Everett Sheldon; Peter Koulen; Raghu Krishnamoorthy; Rong MaNixon, Everett, Function of differentially expressed intracellular calcium channels in retinal neurons. Doctor of Philosophy (Pharmacology and Neuroscience), May, 2008, pp154, 17 illustrations. The retina, a specialized part of the central nervous system (CNS) is the innermost layer of the eye responsible for capturing light and converting the light response into a signal that can be transmitted through the optic nerve and onto the brain for interpretation. The ability of the retina to perceive light is dependent on its sensory neurons and the neural circuitry present that initiate the primary stage of processing the image being visualized, which then transmits an electrical signal down the optic nerve to the brain for processing and ultimately visual perception. In the vertical pathway of the visual process that involves the photoreceptor cells, bipolar cells and the ganglion cells, glutamate is the main excitatory neurotransmitter. Communication between these cells is dependent upon the release of glutamate into the synaptic region within both the outer plexiform layer and inner plexiform layer, a process that is Ca2+ regulated. In neurons, Ca2+ regulates a plethora of processes such as gene expression, cell death, synaptic plasticity and neurotransmitter release since it serves as a critical intracellular messenger. In view of the involvement of Ca2+ in a variety of physiological processes, it is essential for the intracellular Ca2+ concentration to be tightly regulated within neuronal cell. Regulation of Ca2+ signaling within retinal neurons can occur via inositol 1,4,5-triphosphate (IP3) receptors (IP3Rs) and ryanodine receptors (RyRs). These receptors are involved in the release of Ca2+ from the intracellular stores such as the endoplasmic reticulum (ER) into the cytosol. IP3Rs and RyRs contribute substantially to cytosolic free Ca2+ concentration transients and thereby play an important role in neuronal function. The purpose of the study was to determine the role of mGluRs, IP3Rs and RyRs in increasing intracellular Ca2+ levels in retinal neurons as related to signaling and neurotransmitter release. The present study provides experimental evidence for the following mechanisms: -Activation of mGluR8 in photoreceptor cells reduced cytosolic Ca2+ concentration by inhibition of the voltage gated Ca2+ channels on the plasma membrane. –The distribution of IP3R and RyR isoforms was associated with cytosolic Ca2+ transients and the IP3R induced transients occurs by activation of group I mGluRs. –In rod bipolar cells, the main increase in cytosolic Ca2+ concentrations during depolarization is due to Ca2+ release from internal stores via activation of RyR. The results of the present study contribute to the understanding of intracellular Ca2+ signaling in retinal neurons and Ca2+ signaling mechanisms. This is of relevance for identifying mechanisms controlling neurotransmitter release and possible pharmacological targets in neurodegenerative retinal diseases characterized by Ca2+ dyshomeostasis.Item Histamine Induced Changes in Phospholipase C Activity, Calcium Mobilization, and Contractility in Human Ciliary Muscle Cells(1996-06-01) Markwardt, Kerry L.; Michael W. Martin; Thomas Yorio; Eugene QuistMarkwardt, Kerry L., Histamine induced changes in phospholipase C activity, calcium mobilization, and contractility in human ciliary muscle cells. Doctor of Philosophy (Biomedical Sciences), June, 1996. Histamine has long been known to be an important mediator of inflammation and autocoid throughout the body. It has been shown to cause the contraction of many types of smooth muscle. Due to its known presence in many ocular structures and aqueous humor especially during inflammatory states, it was hypothesized that histamine could have an effect on intraocular pressure (IOP). This could occur if histamine triggered events which ultimately lead to contraction of the ciliary muscle, since it is established that contraction of the ciliary muscle affects aqueous humor outflow. Therefore, it was hypothesized in this study, the histamine causes increases in inositol phosphate production and intracellular calcium in human ciliary muscle cells which ultimately leads to contraction. To test this hypothesis, human ciliary muscle (CM) cells were cultured and used in various experiments to determine the effect of histamine on inositol phosphate production, intracellular calcium mobilization, and contractility. This study, for the first time in CM cells, showed that histamine, via an H1 receptor subtype, caused dose dependent increases in both inositol phosphates and intracellular calcium. Furthermore, it was shown that these histamine-induced events ultimately lead to contraction of the CM cells. Combining the results from all our studies, the data indicate that in human CM cells, histamine via an H1 receptor, activates phospholipase C which generates inositol phosphates such as inositol triphosphate (IP3). IP3 binds to an IP3 sensitive receptor on the endoplasmic reticulum causing the initial release of calcium which is sufficient to cause contraction of the CM cells. The intracellular release of calcium is also involved in activating a calcium channel which allows the influx of extracellular calcium into the cell. The results of these studies suggest that histamine could potentially have an IOP lowering effect in the eye due to contraction of the ciliary muscle. Overall, these studies contribute to a better understanding of the effect of histamine on a key IOP regulating tissue in the eye.Item Impact of Intraocular Pressure Maintenance on Sight Preservation(2002-05-01) Ratliff, Marla D.; Susan Brown; Kristine A. Lykens; Claudia S. CogginRatliff, Marla D., Impact of Intraocular Pressure Maintenance on Sight Preservation. Master of Public Health (Health Services Research), May 2002, 35 pp., 3 tables, 1 figure, 40 titles. Purpose: The objective of the study was to review diurnal IOP control and its impact on sight preservation. Methods: This is a retrospective study used in patients with elevated IOP. Patient IOPs were measured every 4 hours over a 24-hour period. Qualified patients provided open label TRAVATAN to dose once a day for 2 weeks. Following 2 weeks of dosing, IOP measurements were taken every 4 hours for 36 hours. Additional IOP measurements were taken at 60 and 84 hours after the last dose of TRAVATAN. Results: The IOP changes from baseline were statistically significant (p≤0.0001) at all time points out to 36 hours. Even without additional dosing, substantial IOP reductions (6mm Hg) were maintained out to 84 hours. Conclusions: Use of TRAVATAN may have less impact on IOP maintenance due to non-compliance and missed doses. This could help prevent glaucomatous loss and preserve sight.Item In Vitro Effect of CNTF, FGF-9, IL-1α on Human Optic Nerve Head Astrocytes(2004-08-01) Tovar-Vidales, Tara; Wordinger, Robert J.; Alvarez-Gonzales, Rafael; Agarwal, NeerajTovar, Tara., In Vitro Effect of CNTF, FGF-9, and IL-1α on Human Optic Nerve Head Astrocytes. Master of Science (Biomedical Sciences), August 2004, 100 pp., 4 tables, 35 illustrations, bibliography, 163 titles. Glaucoma is a leading cause of blindness worldwide. A major risk factor for glaucoma is increased intraocular pressure that leads to pathological changes in the optic nerve head (ONH). Astrocytes within the ONH become activated in glaucoma and may create an environment detrimental to retinal ganglion cell axons. The factors that cause activation of the ONH astrocytes (ONA) are unknown, although there is evidence that CNTF, FGF-9, and IL-1α activate glial cells within the CNS. The purpose of this research was to determine if exogenous CNTF, FGF-9, and/or IL-1α activate human ONH astrocytes.Item Interleukin-1Alpha-Mediated Signaling Mechanisms in the Human Trabecular Meshwork(2000-12-01) Shade, Debra L.; Pang, Iok-Hou; Yorio, Thomas; Dillon, GlennShade, Debra L., Interleukin-1Alpha-Mediated Signaling Mechanisms in the Human Trabecular Meshwork. Doctor of Philosophy (Biomedical Sciences/Pharmacology), December, 2000, 140 pp., 13 tables, 30 figures, references, 156 titles. This research provides important insights into the means by which interleukin-1alpha (IL-1α) regulates TM cell functions and enhances aqueous outflow, thus lowering IOP. The studies reported herein represent the first known characterization of the central role of the AP-1 transcription factor pathway in IL-1α-mediated production of proMMP-3 by TM cells, as well as the first known evidence that IL-1α can also enhance TM phagocytosis. Using these results as a stepping stone, this research has furthermore led to the identification of “AP-1 activators” as a novel compound class which may be useful in the treatment of glaucoma; it also points to the potential for compounds which regulate MEK, p38, and PKCμ activity as additional means of treatment. Based on these results, it is postulated that such compounds would be expected to lower IOP via upregulations of MMP production, followed by ECM degradation, and potentially, enhanced clearance of degraded ECM via phagocytosis.Item Modulation of Manganese Superoxide Dismutase by 17-Beta Estradiol(2008-05-01) Gottipati, Srinivas; Thomas YorioGottipati, Srinivas. Modulation of manganese superoxide dismutase activity by 17-beta estradiol. Master of Science (Cell Biology and Genetics), May, 2008. We have previously reported that 17β-Estradiol (17β-E2) can protect human lens epithelial cells against oxidative stress by preserving mitochondrial function, acting as a positive regulator of the MAPK signal transduction pathway. While pERK plays a significant role in stabilizing the inner mitochondrial membrane to maintain the mitochondrial membrane potential during oxidative stress, the protective mechanisms activated by 17β-E2 are probably multifactorial acting via both genomic and non genomic pathways. This study examined the effects of 17β-E2 on the expression and activity of MnSOD, which is present exclusively in the mitochondria, as a possible mechanism by which it affords protection against oxidative stress. Our results demonstrate that 17β-E2 rapidly increases the activity of MnSOD in a time dependent manner. This augmentation of activity of MnSOD by 17β-E2 is seen in the absence of a corresponding increase in the mRNA and protein expression, thereby which estrogens protect the cells against oxidative stress will help us in developing estrogens to be useful therapies for the prevention of cataract in postmenopausal women and non feminizing estrogens may provide similar protection in men.Item Molecular Mechanisms of and Potential Therapies for Oxidative Damage to the Retinal Pigment Epithelium(2007-09-01) Wang, Zhaohui; Roque, Rouel S.; Wordinger, Robert J.; Das, HridayWang, Zhaohui, Molecular Mechanisms of and Potential Therapies for Oxidative Damage to the Retinal Pigment Epithelium. Doctor of Philosophy (Biomedical Sciences), September 2007, 161 pages, 34 illustrations, bibliography, 119 titles. Age-related macular degeneration (AMD), the most common cause of irreversible vision loss in the elderly, results mainly from degeneration of the retinal pigment epithelium (RPE) and loss of photoreceptor cells. Oxidative stress has been acknowledged as a leading cause of RPE degeneration and concomitant photoreceptor cell loss, but the exact role of reactive oxygen species (ROS) in RPE cell death remains to be established. Moreover, while mitogen-activated protein kinases (MAPKs) are suggested to be involved in RPE degeneration induced by oxidative stress, the precise functions and molecular mechanisms of MAPKs in RPE degeneration remain elusive. In spite of the numerous therapeutic modalities proposed for AMD, the treatment of AMD remains unsatisfactory. Recent studies suggesting stem cells as a potential source for trophic factors in damaged murine hearts led us to investigate a possible role for stem/progenitor cell-derived factors in protecting RPE cells from oxidative damage. Furthermore, human retinal progenitor cells promote RPE cell survival by regulating p42/p44 MAPK activity. When exposed to oxidative stress produced by glucose oxidase/glucose, human RPE cells exhibited membrane blebbing and cytoskeleton remodeling in the early phase of oxidative stress. Prolonged exposure to oxidative stress induced mitochondrial membrane potential depolarization, cell death and DNA condensation, but not DNA fragmentation. Furthermore, both p38 MAPK and p42/p44 MAPK were activated by oxidative injury. P38 MAPK inhibitor, but not p38 MAPK siRNA, inhibited RPE cell death induced by oxidative stress. Overexpression of constitutively active MEK1 inhibited RPE cell death exposed to oxidative damage. In contrast, interfering p42/p44 MAPK expression accelerated oxidative-stress induced RPE cell death. To investigate the effects of human retinal progenitor cells (hRPC) on RPE cells, we isolated and expanded hRPC in vitro. The hRPCs expressed markers of neuronal and retinal progenitor cells, and were capable of differentiating into neuronal phenotype in defined medium. In the presence of 10% fetal bovine serum, hPRC suppressed RPE cell death induced by oxidative damage. Furthermore, conditioned medium of hRPC induced activation of p42/p44 MAPK, and the protective effect of hRPC and conditioned medium was suppressed by p42/p44 MAPK inhibitor. Our studies increase our understanding of the molecular mechanisms that could be employed to rescue RPE cells from degeneration and support the therapeutic potential of retinal progenitor cells. It will provide further insight into molecular mechanisms of AMD and establish a foundation for the long-term prevention and treatment of AMDItem Osmoregulatory Alterations in Taurine Uptake by Cultured Human and Bovine Lens Epithelial Cells(2002-06-01) Schafer, Grant D.; Michael W. Martin; Neeraj AgarwalSchafer, Grant D., Osmoregulatory Alterations in Taurine Uptake by Cultured Human and Bovine Lens Epithelial Cells. Master of Science (Biomedical Sciences), July, 2002, 47 pp., 3 tables, 12 figures, bibliography, 43 titles. Purpose. Using cultured human lens epithelial cells (HLECs) and bovine lens epithelial cells (BLECs) and the nature of the relationship between taurine-concentrating capability and intracellular polyol accumulation or extracellular hypertonicity. Methods. The kinetic characteristics of taurine accumulation based upon the measurement in vitro [3H]-taurine uptake were compared in cultured HLECs and BLECs pre-exposed to either galactose-supplemented medium or extracellular hypertonicity. Results: The capacity to accumulate [3H]-taurine was significantly lowered after chronic (20 hour) incubation of cultured BLECs in 40 mmol/l galactose in contrast to HLECs. Inhibition of the intracellular taurine transport site appeared to be noncompetitive as there was a marked reduction in the Vmax without significant alteration in the Km. Galactitol content in BLECs exceeded five times that found in HLECs. The coadministration of the aldose reductase inhibitor, sorbinil with 40 mmol/l galactose completely prevented the inhibitory effect of galactose on [3H]-taurine uptake. Acute expression (3 hours) of HLECs and BLECs to a range of 10 to 40 mmol/l galactitol or 10 to 40 mmol/l galactose plus sorbinil-supplemented medium suggested by Dixon plot analysis that neither galactitol nor galactose interacted with the extracellular taurine transport site. In contrast, [3H]-taurine accumulation was markedly elevated in both HLECs and BLECs after chronic exposure to galactose-free medium made hyperosmotic by supplementation with sodium chloride. The enhanced taurine uptake capacity involved an increase in Vmax without significant change in the Km value. Conclusions: These results demonstrate lens epithelial cells express a taurine transporter protein capable of active uptake but predisposed to inhibition by intracellular galactitol when the sugar alcohol is present in high enough concentration to interfere with cell metabolism. Furthermore, lens epithelial cells respond to hypertonic stress by raising taurine transport activity.Item Photic Injury Promotes Photoreceptor Apoptosis via Nuclear and Mitochondrial Targeting of p75ICD, NRAGE and p53(2003-05-01) Srinivasan, Bhooma; Rouel S. Roque; Patrick Cammarata; Porunellor MathewSrinivasan, Bhooma., Photic injury promotes photoreceptor apoptosis via nuclear and mitochondrial targeting of p751ICD, NRAGE and p53. Doctor of Philosophy (Biomedical Sciences), May, 2003, 185 pp., 36 illustrations, bibliography, 256 titles. Retinal diseases involving photoreceptor cell degeneration such as Age-related Macular Degeneration (AMD) and Retinitis Pigmentosa (RP) remain some of the leading causes of blindness in the U.S. The changes in light-damaged retinas of laboratory animals resemble those in patients with degenerative retinal diseases, making photic injury widely accepted as a suitable model to study photoreceptor cell death. Intense light exposure to the retina leads to photoreceptor cell apoptosis but the molecular mechanisms remain known. Recent studies in our laboratory showed that photoreceptor cells express p76NTR, the low affinity neurotrophin receptor, and that p75NTR expression was upregulated in photoreceptor cells of Royal College of Surgeons (RCS) rats, a model of retinal degeneration. Earlier reports have also shown that photoreceptor cell death was decreased in p75NTR knock-out mice exposed to light as compared to wild type mice. These results suggest that p75NTR could be involved in photoreceptor cell death while signaling pathways employed by p75NTR in inducing cell death remain vague, the intracellular domain of p75NTR (p75ICD) has been shown to be sufficient to induce apoptosis, and adaptor proteins for p75NTR are necessary for cell death to occur. In this study, we have identified a novel signaling mechanism utilized by p75NTR in promoting apoptotic cell death of photoreceptor cells following photic injury. The mouse transgenic photoreceptor cell line (661w), exposed to intense light (1400fc) for 2-3h, exhibited increased expression of p75NTR, NRAGE (Neurotrophin receptor MAGE, a p75NTR adaptor protein), and TACE (Tumor necrosis factor-alpha converting enzyme, an alpha-secretase shown previously to promote shedding of several growth factors and cytokines including TNF-alpha). Furthermore, apoptotic cell death followed the increased levels of three proteins. Light-exposure also promoted the release of p75ICD by TACE, and increased association and nuclear translocation of p75ICD and NRAGE. The level of p53 was also increased in 661w cells following light exposure and binding of the p75ICD-NRAGE complex to p53 is required for translocation into the nucleus. P75ICD-NRAGE-p53 nuclear translocation appeared to be necessary for transcriptional activation of Bax and repression of Bc12. Moreover, mitochondrial targeting of p53 resulted in mitochondrial membrane permeability changes and release of cytochrome c. The use of TAPI, a TACE inhibitor, and of pifithrin, a p53 inhibitor, and overexpression of Bc12 suppressed apoptotic cell death of 661w cells after a light exposure. Our study shows that light exposure promotes apoptotic cell death of photoreceptor cells by activating novel signaling mechanisms involving the nuclear and mitochondrial targeting of p75NTR-NRAGE-p53. Our studies increase our understanding of the mechanisms that may be involved in photoreceptor degeneration and provide new molecular targets for the treatment of degenerative retinal diseases.Item Regulation of Endothelin-1 (ET-1) Synthesis and Secretion at the Outer Blood Retinal Barrier(2003-08-28) Narayan, Santosh; Thomas Yorio; Glenn Dillon; Michael W. MartinRegulation of Endothelin-1 (ET-1) Synthesis and Secretion at the Outer Blood-Retinal Barrier. Santosh Narayan, Department of Pharmacology & Neuroscience, University of North Texas Health Science Center Fort Worth, TX 76102. Summary The retinal pigment epithelium (RPE) constitutes the outer blood retinal barrier at the posterior segment of the eye. The RPE provides metabolic support to the photoreceptors in the neural retina. A breakdown in the barrier supported by RPE is a hallmark in several retinopathies including proliferative vitreoretinopathy, choroidal neovascularization and macular edema. Characteristic to all epithelial cells, mature RPE cells display a polarized phenotype both in culture (ARPE-19 cells) and in vivo, with specific apical and basolateral domains. This provides a testable model to study the RPE in vitro. The purpose of this study was to characterize the RPE as a source for endothelin-1, using both in vitro and in situ models. Endothelins (ET-1,-2, and -3) are known regulators of vascular tone, that are produced at sites close to their target, ET-1, being a potent vasoconstrictor may be involved in regulating blood supply to the choroid and the neural retina. We identified the RPE to be a major source for endothelin-1 (ET-1) in situ in the human retina as well as in pigmented and albino rat retinas. Additionally, using a cell-culture model of mature polarized ARPE-19 cells, we studied the synthesis and expression of ET-1 in response to muscarinic receptor stimulation, TNF-α and more recently to thrombin. We have identified other components involved in the synthesis and turnover of ET-1 in ARPE-19 cells including the proprotein convertase-furin, endothelin-converting enzyme-1 and its isoforms and the endothelin receptor B subtype. ARPE-19 cells grown on collagen filters helped determine if secretion of ET-1 was polarized or discriminative towards either the apical or basolateral surface. We consistently observed changes in cell shape and tight junction disassembly in ARPE-19 cells following TNF-α and thrombin addition. Additionally, thrombin caused an increase in preproET-1 mRNA at earlier time points that was dependent on the rhokinase (ROCK1/2) pathway. We report a novel signaling mechanism for regulating preproET-1 mRNA and mature ET-1 secretion in ARPE-19 cells that involves the thrombin receptor (protease activated receptor-1/PAR-1) dependent activation of the rho/ROCK1/2 signaling pathway that may also be involved in thrombin induced changes in the cytoskeleton. In conclusion, the RPE may be an important source for ET-1 at the posterior segment of the eye, secretion of which is greatly enhanced by substances that promote breakdown of blood retinal barriers, inflammation and changes in the RPE cytoskeleton. In conclusion, the RPE may be an important source for ET-1 at the posterior segment of the eye, secretion of which is greatly enhanced by substances that promote breakdown of blood retinal barriers, inflammation and changes in the RPE cytoskeleton. ET-1 secreted by the RPE, under physiological conditions may provide an autoregulatory mechanism for controlling blood flow at the outer blood retinal barrier. Excessive ET-1 secretion following breakdown of the barrier may either promote wound repair or may mediate further damage to the retina, the substrates of which are presently unknown. Future experimental approaches are planned to address these possibilities.Item Role of 14-3-3σ in Corneal Epithelial Differentiation(2008-05-01) Shankardas, Jwalitha; Dan S. Dimitrijevich; Porunelloor Mathew; Julian BorejdoEpithelial differentiation is a highly coordinated process that is essential for proper function of epithelia in their respective tissues. In the cornea epithelial differentiation is necessary to maintain transparency of the cornea, which is essential for vision. 14-3-3σ/stratifin is a proposed epithelial cell marker, which is up regulated in response to UV damage. This up-regulation causes the cells to arrest in G2/M phase so that DNA repair can take place. In a number of epithelial cancers 14-3-3σ has been shown to be down-regulated. The function of 14-3-3σ in the corneal epithelium and other stratified epithelial tissues other than the skin has not been studied. In the cornea are no reports of hyperplasia so it would be a good model to study the role of this protein. In this study, for the first time we have evaluated the expression of 14-3-3 family of proteins in the cornea. We have also shown the involvement of 14-3-3σ in the process of corneal epithelial differentiation in vitro using primary corneal epithelial cells and in vivo using the Er/+ mouse model. We have also been able to extend in vitro lifespan of corneal epithelial cells by down regulating 14-3-3σ expression. The down regulation also resulted in immortalization and generation of a corneal epithelial cell line. We have characterized and shown that this cell line is a suitable model to study signaling cascades involving corneal epithelial proliferation, differentiation and apoptosis. Preliminary data presented in this study also imply that ΔNp63 is an upstream regulator of 14-3-3σ expression.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.