Figure 6. Generation of recoverin-positive cells in the pars plana after retinal histogenesis in rd1 mice. Double-headed arrows indicate the pars plana. A: Cells positive for both BrdU (labeled at P6) and recoverin (arrowhead) were found in the P30 pars plana. Note that numerous cells in the neuroblast layer were labeled with BrdU at P6. B: Cells positive for both BrdU (labeled at P12) and recoverin (filled arrowhead) were identified in the pars plana at P30. A cell positive for BrdU but negative for recoverin is also present in the inset (open arrowhead). Only rare BrdU-positive cells, mostly blood cells (cells in the lower right corner), were identified in the retina, suggesting that gross retinal histogenesis was already complete by P12. Note that immunopositive cells in the peripheral retina showed an oblique alignment, which contrasted with those in the pars plana; the differential susceptibility of the retina and ciliary epithelium to mounting artifacts is one of the features that sometimes distinguished the cilioretinal border. C: Hematoxylin and eosin staining of eye section is from a P12 rd1 mouse. The box roughly corresponds to the area from which images A and B were obtained. D: Cells positive for both BrdU (labeled at P18) and recoverin (arrowhead) were identified in the P30 pars plana. E,F: The proportion (%) of cells positive for BrdU (injected at P6, P12, P18, and P24) among recoverin-positive cells in the P30 pars plana (E) and similarly in the pars plana of mice (enucleated at P9, P12, P20, and P30) after BrdU injection at P6 (F) are presented. After the number of recoverin-positive cells within 320-µm width of the pars plan were determined from a single optical scan (10.0 μm thick), the number of those also positive for BrdU were determined from the same image. Three independent images randomly obtained from the same eye were analyzed to calculate the proportion of BrdU-positive cells among recoverin-positive cells per animal. Average proportion (%; mean±SEM) for each category were determined from the following number of animals. The numbers of mice used in each experiment is summarized in Table 1. A dose of BrdU injected was 50 mg/kg. A and B are thick scans each merged from 3 scans (each scan was 10.0 μm thick) while D is also a thick scan but merged image from 2 scans (each scan was 3.9 μm thick). Scale bar equals 25 μm (D) and 50 μm in A, B, and C. Abbreviation: recoverin (Rcv).