An immunohistochemical study of regenerating newt retinas.

Light-microscopical examination was carried out to investigate the emergence and development of several classes of immunoreactive cells in regenerating retinas of the adult newt (Triturus pyrrhogaster) after total retinal ablation. Immunoreactive proliferating cell nuclear antigen (ir-PCNA, a marker for replicating cells) was present in nuclei of all neuroblasts in the early mono-layered to several-layered stages (15-20 days after retinal ablation; days 15-20), but was lost progressively in an intermediate-to-central/peripheral order as cells and layers increased (days 20-25). Cells, which had lost ir-PCNA, began to separate to form the outer nuclear, inner nuclear and ganglion cell layers around days 25-30 (the cell separation stage). Finally, the location of ir-PCNA was restricted to a band of neuroblast cells at the retinal margin (days 30-35) as seen in intact adult retinas. Visinin-immunoreactive (ir) cells, mainly destined to be cones, appeared first singly or as clusters at the most distal layer in the intermediate region of retinas multi-layered with PCNA-ir neuroblasts, which was followed by appearance of opsin-ir rod outer segments and tyrosine hydroxylase-ir amacrine cells around the cell separation stage. Shortly later, cells respectively immunoreactive to glutamic acid decarboxylase, neuropeptide Y, serotonin, glucagon, glutamine synthetase, glial fibrillary acidic protein, substance P and protein kinase C were found to emerge also in an intermediate-to-central/peripheral sequence. Some of the glucagon-ir cells appeared to be of an interplexiform type.