The unique properties of the confocal Scanning Laser Ophthalmoscope [cSLO] have been exploited in tandem with computer-aided image analysis to detect and quantify macular lesions. Healthy volunteers and patients with macular ischaemia, oedema and hole formation underwent fluorescein angiography, tomography and indirect mode imaging using the cSLO. For macular ischaemia, a computer program has been developed to identify poorly perfused areas based on fluorescence and temporal data extracted systematically from fluorescein angiograms. These parametric images, <I>viz</I>., <I>maximum fluorescence, time-to-maximum </I>and <I>ischaemia</I>, combine physiological with anatomical data. The ischaemia program has been validated using a human Gold Standard on a panel of five angiograms using Receiver Operator Characteristic analysis. The program performs favourably against a panel of ophthalmologists for angiograms of diabetic retinopathy. Computer algorithms have been developed for extracting topographical features from tomographic images of macular lesions causing thickening or thinning, such as oedema and holes. The information has been presented as <I>topography </I>and <I>thickness</I> parametric images. The novel <I>thickness</I> images show three-dimensional data in an easily assimilable form. The indirect mode technique readily reveals retinal and subretinal lesions, including macular oedema, macular hole, choroidal naevi and retinal pigment epithelial detachment without the need for any specialised viewing equipment or image processing. We have made significant progress towards developing a research and potential clinical tool for the detection and accurate quantification of macular pathology to facilitate the better understanding, diagnosis and clinical management of these blinding conditions.

No description available.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1991. / Includes bibliographical references (leaves 213-225) / Microfiche. / xvii, 225 leaves, bound ill. 29 cm

Glaucoma is a devastating blinding disease, caused by retinal ganglion cell (RGC) loss via apoptosis and clinically associated with raised intraocular pressure (IOP). Mainstream theories of glaucoma's pathogenesis detail loss of RGCs via indirect links to lOP; including mechanodistortion of optic nerve axons, trophic factor deficiency, ischaemia or excitotoxicity. A novel concept in the pathogenesis of glaucoma is that pressure alone could be a direct stimulus for RGC loss. Currently available glaucoma treatments are solely aimed at lowering lOP. Reduction ofIOP has been shown to reduce glaucomatous progression however RGC losses continue. Neuroprotection is an emerging field of research offering hope to neurodegenerative diseases, including glaucoma. This thesis investigated known glaucoma therapeutics with suggested neuroprotective activity in an in vitro glaucoma model using the RGC-5 cell line. To evaluate therapies, a suitable in vitro model was initially evaluated. The RGC-5 cell line was immunochemically demonstrated to possess NSE, a neuronal marker and Thy-1, an RGC marker. Glutamate excitotoxicity was investigated however excessive concentrations were required to cause significant in vitro RGC-5 cytotoxicity. Using a modified hydrostatic pressure model, reproducible pressure-induced RGC-5 apoptosis was demonstrated. Apoptosis was detected using cell morphology and confirmed with both early (caspase-3 and annexin V) and late (TUNEL) apoptotic markers. Despite the advantages of rapid, objective quantification, results indicated that flow cytometry of RGC-5 cells was not technically possible. I defined a modified laser scanning cytometry protocol, allowing for objective apoptosis quantification of TUNEL stained cells. Brimonidine is postulated to mediate receptor mediated RGC protection. Experiments conducted for this thesis, were the first to immunochemically demonstrate alpha2 adrenergic receptor expression on human RGCs and the RGC-5 cell line, suggesting direct cell mediated protection on the target neuron of glaucoma is possible and that the RGC-5 line is a useful in vitro target for experimentation. Both brimonidine and betaxolol were shown to confer protection to the RGC-5 cell line from pressure-induced apoptosis, under defined conditions. These results suggest that these drugs may confer direct cell-mediated protection, rather than indirect protection conferred via other retinal or glial cells, the anterior segment, the vasculature or some other means.

Thesis (Ph.D.)--University of Alabama at Birmingham, 2009. / Title from first page of PDF file (viewed on June 10, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Hong Kong, 1994. / Includes list of author's publication (leaves viii-xiv). Includes bibliographical references (leaves 253-281).

No description available.

Peripherin, a membrane protein with an apparent molecular weight of 34 kDa, has been previously localized to the rim region of the vertebrate rod photoreceptor disk membrane using monoclonal antibodies and immunocytochemical labelling techniques. As an initial step in determining the structure and function of this protein, cDNA containing its coding sequence has been cloned and sequenced. A bovine retinal ʎgtll expression library was screened with antiperipherin monoclonal antibodies, and a 583 base pair clone was initially isolated. The remaining part of the coding sequence was obtained from subsequent rescreenings of the same library and an independent ʎgt10 library. A C-terminal CNBr fragment of peripherin was purified by immunoaffinity chromatography and reverse phase high-performance liquid chromatography. The amino acid sequence of the isolated C-terminal peptide and the N-terminal sequence analysis of immunoaffinity purified peripherin are in agreement with the cDNA sequence. At the amino acid level, the sequence of peripherin has 92.5% sequence identity to the gene proposed to be responsible for the retinal degeneration slow defect in mice (Travis et al.(1989) Nature 338, 70-73) The differences between the two sequences can be attributed to species differences. The identity of the retinal degeneration slow gene product and its intracellular localization were previously unknown. The cDNA sequence of peripherin predicts that there are possibly four transmembrane domains. On the basis of immunocytochemical studies and sequence analysis, the hydrophilic C-terminal segment containing the antigenic sites for the antiperipherin monoclonal antibodies has been localized on the cytoplasmic side of the disk membrane. There are three consensus sequences for asparagine linked glycosylation. Deglycosylation studies have indicated that at least one of these sites is utilized. The complete coding sequence of peripherin was expressed in COS-1 cells. Western blot analysis of the expressed peripherin suggest that it exists as a homodimer in the absence of a reducing agent. The possible function of peripherin in relation to its primary structure is discussed. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Retinitis pigmentosa (RP) is a collection of inherited retinal degenerations that afflicts 50,000- 100,000 people in the United States. The hallmark pathology of RP is apoptosis of photoreceptor cells. Currently there is no treatment for this disease. The equivalent light hypothesis states that some RP mutations cause retinal degeneration by mimicking a continuous phototransduction signal. We tested this hypothesis in transducin knockout (TKO-/-) mice, deficient for the a - subunit of transducin, the heterotrimeric G-protein which mediates light signaling in photoreceptors. Methods: We used light microscopy to compare the retinal morphology of TKO-/- and wild-type (TKO+/+) mice: 1) exposed to continuous bright light, or 2) crossed with mice carrying three different rhodopsin mutations leading to retinal degeneration: A) Proline347Serine (P347S), B) Valine20Giycine, Proline23Histidine, Proline27Leucine (VPP), and C) Lysine296Giutamic acid (K296E). Results: We predicted two types of photoreceptor cell apoptosis: 1) signal-dependent mutants in which degeneration was blocked in the absence of transducin, and 2) signal-independent mutants, not affected by the presence or absence of transducin signaling. To our surprise,we found three classes of retinal degeneration: 1) the VPP triple mutant caused photoreceptor apoptosis, at the same rate, regardless of the presence or absence of a-transducin, 2) the P347S and K296E opsin mutants caused an accelerated rate of degeneration on the TKO -/- background as compared to on the TKO+/+ background, and 3) the damaging effects of continuous light were retarded on the null transducin background. These data support the equivalent light hypothesis as a mechanism for some, but not all forms of retinal degeneration. Thus, the cellular signal that triggers photoreceptor apoptosis can occur either upstream or downstream of transducin signaling. Classifying different types of mutations that lead to photoreceptor cell death will be important for determining effective therapies for different classes of human retinal degeneration. / 2031-01-01

Purpose. In the genetically defective Royal College of Surgeons (RCS) rat model for retinal degeneration, a breakdown occurs in the retinal pigment epithelial (RPE) cell tight junctions just as the photoreceptors begin to degenerate. These experiments sought to determine the impact of the RPE genetic defect on this alteration in the RPE cell tight junctions. Methods. Retinal pigment epithelial cell cultures prepared from RCS and control rats were treated with hormonally defined medium (HDM), base medium conditioned by RCS or control retinas, or unconditioned base medium. The tight junctions formed by these cultures were assayed functionally by measuring transepithelial electrical resistance and permeability. Junction structure was evaluated by immunolocalization of the tight junction protein zonula occludens I and of the junction-associated actin microfilaments. Results. Retinal pigment epithelial cultures from dystrophic rats formed structurally and functionally normal tight junctions when maintained in hormonally defined medium. The junctions remained stable when the medium bathing the apical surface was switched to base medium preconditioned by normal retinas. In contrast, cultures treated with medium preconditioned by degenerating dystrophic retinas or with unconditioned medium exhibited a breakdown in their tight junctions. Conclusions. Retinal pigment epithelial cells isolated from dystrophic RCS rats can form tight junctions normally in vitro. Normal, but not dystrophic, retinas release factors that support RPE tight junctions. Therefore, the junctional abnormality seen in dystrophic rat RPE cells in vivo is probably caused by the loss of trophic factors normally provided by the healthy neural retina rather than by a direct effect of the genetic defect on the tight junctions.