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Y. Li, L. Zhao, Y. Liu, Y. Song, A. M. Laties, M. M. LaVail, R. Wen; Loss of Cone Outer Segments in Transgenic Rats Carrying the Rhodopsin Mutation S334ter. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4492.
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In retinitis pigmentosa, the loss of rods is followed by cone degeneration. The present work investigates changes in cones after rod degeneration in transgenic rats carrying the rhodopsin mutation S334ter (line 3).
Rod degeneration was examined by light microscopy in semi-thin plastic sections. Cone outer segments and cell bodies were stained with peanut agglutinin lectin (PNA) or antibodies against rodent cone arrestin in whole-mount retinas, and examined by fluorescence confocal microscopy.
Rod degeneration occurred as early as postnatal day 8 (PD8) and was mostly complete by PD20. At PD10, cone outer segments were present across the entire retina and distributed evenly, as assessed by PNA staining. Loss of cone outer segments was detected as early as PD12, characterized by complete lack of PNA staining in small areas that formed round or irregularly shaped non-staining patches. The loss of PNA staining was progressive. By PD20, the non-staining patches became larger and more numerous, especially in the superior-posterior retina. In the non-staining patches, many cells were positive for cone arrestin except in the very center, indicating that cone cells were still present although they were not stained with PNA. The area of non-staining patches increased progressively with age. At 6 months of age, many patches merged and only a few PNA positive cells remained.
Loss of cone outer segments started soon after the initiation of rod degeneration. The loss of cone outer segments is concentrated in small areas where cone cell bodies are still present.
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