Histological sections showing the photoreceptor layer of 13-month-old wild-type and nba retinas. (A) A section from the retina of a wild-type fish. In the light adapted retina, the rods (r) sit distal to the cones (c). Processes from the pigment epithelium (PE) extend between the outer segments of the rods. (B-D) Sections from the central retina of one nba fish showing the variability of degeneration seen in various regions of the affected retina (see text for details). in, inner nuclear layer; ip, inner plexiform layer. Arrows in B indicate the large lipid droplets in PE. [Bar = ≈100 μm (A) and 80 μm (B-D).]

Photographs of live embryos (A-D) and histological sections of the brain and retinas (E-H) of wild-type (Left) and homozygous nba (Right) fish. (A and B) Photograph of 2.5-day-old wild-type and nba embryos. Note the smaller eye (arrow) and blood cells that have pooled in the heart (asterisk) in nba fish. (C and D) Acridine orange staining of 2.5-day-old wild-type and nba embryos. Brightly staining apoptotic cells are seen in the retina (arrow) and tectum (arrowhead) in nba fish. Asterisks indicate nonspecific staining of yolk cells. (E and F) Transverse sections through the brain and retina of 2.5-day-old wild-type and nba embryos. Note the darkly stained dying cell in both the retina (arrows) and tectum (arrowheads) in nba fish. (G and H) Transverse sections of 3.5-day-old wild-type and nba embryos. By this time most of the retinal cells have degenerated (arrows), and the tectum continuous to show evidence of cell death (arrowheads) in nba fish. [Bar = ≈250 μm (A-D) and 100 μm (E-H)].