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J Cell Biol. Aug 1, 1969; 42(2): 392–403.
PMCID: PMC2107669
PARTICIPATION OF THE RETINAL PIGMENT EPITHELIUM IN THE ROD OUTER SEGMENT RENEWAL PROCESS
Richard W. Young and Dean Bok
From the Department of Anatomy and the Jules Stein Eye Institute, University of California at Los Angeles, Center for the Health Sciences, Los Angeles, California 90024
Received January 16, 1969; Revised March 10, 1969
Abstract
The disposal phase of the retinal rod outer segment renewal process has been studied by radioautography in adult frogs injected with tritiated amino acids. Shortly after injection, newly formed radioactive protein is incorporated into disc membranes which are assembled at the base of the rod outer segment. During the following 2 months, these labeled discs are progressively displaced along the outer segment owing to the repeated formation of newer discs. When the labeled membranes reach the end of the outer segment, they are detached from it. They subsequently may be identified in inclusion bodies within the pigment epithelium by virtue of their content of radioactivity. These inclusions have been termed phagosomes. Disc membrane formation is a continuous process, but the detachment of groups of discs occurs intermittently. The detached outer segment fragments become deformed, compacted, undergo chemical changes, and are displaced within the pigment epithelium. Ultimately, the material contained in the phagosomes is eliminated from the cell. In this manner the pigment epithelium participates actively in the disposal phase of the rod outer segment renewal process.
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