Figure 10.

S334ter-7 rats - Light micrographs of the outer retina at ages ranging from P4 (A) to P30 (L). Ages given on the micrographs. Regions of eye: (A–D and F–H), superior posterior; (E) superior peripheral; (I, K) inferior posterior; (J) inferior peripheral; (L) inferior ora serrata. (A) Pyknotic nuclei (arrows) are seen in the developing outer nuclear layer (ONL) at P4, and then many of the innermost immature PR nuclei in the ONL rapidly become pyknotic at P6 (B), P7 (C), P8 (D) and P10 (E). At these same ages, many displaced PR nuclei (d) are present in the IPS (B–E). Beginning at about P8, pyknotic nuclei rapidly disappear (D–F), so that by P12 in the superior posterior retina, there is a loss of PRs (F), which becomes more extensive at P15 (G) and P21 (K). A cluster of PRs persists at the ora serrata at P30 (L). Invading cells, presumptive microglia, (arrowheads) that are presumably phagocytic and remove pyknotic cells are widely present in the inner part of the ONL at most ages, with some in the subretinal space (E). Pyknotic displaced PR nuclei are present in the IPS (1), and the RPE apparently participates in the removal of dead cells by phagocytosis (2). Once PR inner and OSs disappear (G, H), the IPS is filled with RPE cell processes (pep). c, cone nucleus; r, rod nucleus. Magnification bar = 20 μm.