Light micrographs of retinal sections from 3-month-old male mice of different genotypes. The densely stained photoreceptor nuclei layer is indicated in each panel by a white vertical bar. A, Homozygousrds retina (rds). Up to three rows of photoreceptor nuclei are present. B, Homozygousrds retina expressing the Bcl-2 transgene (rds:bcl). Up to six rows of nuclei are present.C, Homozygous rds retina expressing the normal rds/peripherin transgene (rds:113). Up to eight rows of nuclei are present. D, Homozygousrds retina expressing the normal rds/peripherin plus Bcl-2 transgenes (rds:113+bcl). Up to eight rows of nuclei are present. ris, Rod inner segment layer;ros, rod outer segment layer. Magnification, 400×.