A) P6 retinal cell outgrowth from explant, 6 days in vitro . Note nuclear staining pattern of large, flat cells. Round, neuronal-like cells remain unstained (arrowhead). B) R28 cells immunoreactive for S-100 also exhibit a nuclear pattern (arrows). Approximately 50% of the cell population shows S-100 immunoreactivity. Scale Bar = 20 Ám. C) Western immunoblot for S-100: Lane 1) P6 retina, Lane 2) R28 cells. 3 minute chemiluminescent exposure.