Glutamine Synthetase in the Normal and Dystrophic Mouse Retina

activity in the chick embryo retina has proved to be a useful system for studying control mechanisms in animal cells (6, 12, 2, 21). The enzyme activity rises rapidly late in embryonic development (16) and can be induced prematurely both in culture and in ovo by a variety of steroids (10, 11, 7). Piddington and Moscona (9) have shown that the time of GS development coincides with structural maturation in the chick retina; in addition, they have reported that steroids which induce GS activity in the retina concomitantly induce these morphological changes. An obvious implication is the possible existence of a connection between the appearance of GS and the morphological changes. To investigate this possibility and to attempt to determine the role of GS in the developing retina, it would be advantageous to localize the enzyme within the retina. At present, however, there is no histochemical technique for identifying the site of GS activity in tissues. Utilizing a partially inbred strain of mice with inherited retinal degeneration and normal littermate controls, we have now determined that GS probably is distributed throughout the retina. We have also shown that the parallel between GS development and final