Disc shedding in rodlike and conelike photoreceptors of tree squirrels

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Science  14 Mar 1975:
Vol. 187, Issue 4180, pp. 953-955
DOI: 10.1126/science.1145180


Electron microscopic observations suggest that the rodlike and conelike photoreceptors of diurnal tree squirrels shed outer segment discs. Twenty-four hours after injection of triated L-leucine, the rodlike photoreceptors show a band of radioactivity at the base of the outer segment. The conelike photoreceptor outer segments show only a pattern of diffuse labeling. These results strongly suggest that disc shedding can occur in photoreceptor outer segments in which proteins are diffusely renewed.