Differentiation of photoreceptors in cultured optic vesicles from embryos of Rana esculenta

Optic vesicles from embryos of Rana esculenta at a stage corresponding to stage 19 in the development of Rana pipiens were cultured for 15 days. The eyes which differentiated in vitro were much smaller than controls of the same age, due partly to the absence of the vitreous body. In many specimens a well-stratified retina surrounded by a layer of pigmented cells was found. The features of all the components of the retinal layers are described. The complete differentiation of photoreceptors, including their outer segments, is the most interesting result obtained in these organ cultures, and is in contrast with the observations previously reported for retinal tissue cultures. The authors suggest that the source of the material (amphibia instead of birds or mammals) is the main reason for this discrepancy. Frog embryo cells are practically self-sufficient since they are endowed with nutritional substances, amongst which Vit. A and antioxidative agents (Vit. E and ascorbic acid) have been indicated as the most important factors for the structural organization and integrity of the outer segments. The role played by the pigment epithelium is also discussed.