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F.J. Giblin, J.B. Runco, M.T. Cheng, J.C. Blanks; Effects of Hyperbaric Oxygen in vivo on the Pigmented Mouse Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):458.
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Purpose: It is believed that molecular oxygen may play a role in the progression of certain retinal degenerative diseases, such as macular degeneration. It was shown previously (Yamada, H. et al., J. Cell. Physiol., 179:149, 1999) that exposure of mice to normobaric 75% oxygen continuously for one week produced photoreceptor (PR) degeneration. The purpose of this study was to investigate the effects of intermittent hyperbaric oxygen (HBO) treatment of mice on retinal PR cells, and to determine the earliest point resulting in tissue damage, as well as the characteristics of the PR damage. The HBO conditions were similar to those that are used to treat human patients therapeutically for various diseases, such as poor-healing wounds. Methods: Twenty-four normal mice (B612956F1) were used: four mice served as controls and were exposed to room air while the other twenty were treated in an HBO chamber with 100% oxygen at three atmospheres for three hours in the dark, three times a week, for up to 20 weeks. Mice were sacrificed at various times over the experimental period. The eyes were enucleated, fixed and prepared for light microscopy. Results: In the control, the outer nuclear layer (ONL) consisted of 9-13 rows of nuclei at the posterior region of the retina. Over the twenty-week period of HBO treatment, there was a drastic reduction in the number of PR cells, primarily in the posterior retina, while the peripheral retina showed much less damage. After the first week of oxygen exposure, the ONL consisted of 8-10 layers of PR cell nuclei at the posterior region of the retina. After the second week, only 5-10 layers of PR cell nuclei existed and by the third week, only 4-8 layers of PR cell nuclei remained. From the fourth to the twentieth week, the ONL consisted of approximately 4-6 layers of PR nuclei. Rods were misaligned, and swelling of the inner segments, outer segments, and ONL was evident. Nuclei were often present in the outer plexiform layer, possibly due to migrating nuclei from the ONL and/or the inner nuclear layer. Conclusions: Treatment of pigmented mice with HBO produces significant damage to retinal photoreceptor cells beginning within the first two weeks. This model may prove to be useful for investigating oxidative mechanisms of retinal degeneration.
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