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      Scanning Electron Microscopy after Cryofracture of Normal and Ischemic Rat Retinas

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          Abstract

          The authors described the use of scanning electron microscopy after cryofracture to analyze rat retinas after experimental ischemia-reperfusion sequence. In Sprague-Dawley albino rats, intraocular hypertony by cannulation of anterior chamber was performed for 1 h on one eye. The other eye served as control. After 48 h of reperfusion, retinas were dissected. They were frozen and fractured before ultrastructural analysis by a scanning electron microscope. In the ischemic eyes the thickness of the photoreceptors layer was reduced, through internal disorganization resulting in misalignment of rods. There was swelling of the outer segments, a loss of adhesion between segments and superficial necrosis. Scanning electron microscopy after cryofracture permitted an analysis of the external morphology of retinal cells and intercellular components, especially the outer layers.

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          Quantitation of ischemic damage in the rat retina.

           E. W. Hughes (1991)
          In order to determine thresholds for irreversible cellular injury in the rat retina, timed acute no-flow ischemic episodes of 30-180 min duration were produced by elevation of intraocular pressure (IOP) above systolic pressure. Quantitation of irreversible degeneration and cell loss following a 2-week post-ischemic interval was performed by computer-assisted measurements from histologic sections. Alterations of thickness of retinal layers and linear cell density were determined for ischemia of selected durations (30, 60, 80, 90, 120 and 180 min). Different thresholds were evident for inner and outer retinal damage. Neurons of the inner nuclear layers showed extensive loss with episodes at 60 min. Decrease in the thickness of the inner plexiform layer provided the best index of this inner nuclear damage. The outer retina was more resistant, with photoreceptors showing extensive damage only after 90 min in conjunction with pigment epithelial metaplasia and degeneration. Two-hour episodes produced full-thickness degeneration with loss of pigment epithelium and sparing of the peripheral retina. Greater sensitivity of the inner retina suggested problems with restoration of the retinal circulation. Horseradish peroxidase infusions did reveal central microcirculatory defects in retinal wholemounts of some specimens with episodes longer than 60 min. Refinements of the methods resulted in outcomes sufficiently reproducible for quantitative assessment of acute ischemic injury. The rat retina provides an economical basic tissue model of acute ischemic injury affecting neurons, glia, and microvasculature. Quantitation of this injury promises great utility in testing agents with potentially protective effects on acute ischemic injury.
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            Author and article information

            Journal
            ORE
            Ophthalmic Res
            10.1159/issn.0030-3747
            Ophthalmic Research
            S. Karger AG
            0030-3747
            1423-0259
            1998
            August 1998
            12 June 1998
            : 30
            : 4
            : 216-220
            Affiliations
            aHôpital Gabriel Montpied CHU, Service d’Ophtalmologie, Clermont-Ferrand, b Laboratoires IPSEN, Paris, c Université d’Auvergne, Facultés de Médecine et de Pharmacie, Clermont-Ferrand, France
            Article
            55478 Ophthalmic Res 1998;30:216–220
            10.1159/000055478
            9667052
            © 1998 S. Karger AG, Basel

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            Page count
            Figures: 5, References: 14, Pages: 5
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