Regeneration of the Neural Portion of the Retina from Pigment Cells in Adult Urodele Eyes. ∗

Abstract

In previous experiments on grafted adult salamander eyes, it has been shown by the author, 1 , 2 , 3 that degeneration of the neural elements of the retina is followed by regeneration. The retina can be regenerated with subsequent return of vision at least 4 times in the same eye repeatedly transplanted. 2 The functional patterns associated with each of the retinal quadrants are reestablished and the visuomotor responses of the host are determined by the orientation of the graft. 4 , 5 , 6 , 7

Regeneration of the retina in amphibians especially in larval urodeles has been reported previously by other investigators. As to its source of origin iris tissue has been claimed by some authors. 8 Retinal tissue at the ciliary margin 8 , 11 and ganglion cells in the fully differentiated retina 12 have been proposed as the source. One of the above mentioned investigators 8 believed that the regenerating retina in larval urodeles could also be derived from the pigmented epithelial layer.

An extensive study has been made to settle the question of the source of origin of the regenerating neural portion of the retina in the eye of the adult urodele, Triturus v. viridescens. In various groups of experiments over 500 grafts of iris tissue have been placed in the aqueous and vitreous chambers of the eye. None of them has given rise to retinal tissue. A detailed study was made of the degeneration and regeneration of the retina in 200 grafted eyes preserved at close intervals for at least 3 months after operation. Degeneration spreads throughout the neural retina during the first 3 weeks. In some cases destruction proceeds at different rates in various parts of the same eye and when degeneration overlaps early stages of regeneration it is more difficult to obtain a clear picture of the origin of the new retina.