DIFFERENCES IN SUSCEPTIBILITY TO WHOLE-BODY GAMMA IRRADIATION IN THE LAYERS OF THE RETINA OF BUFO

¹ Atomic Energy Project, School of Medicine, University of California at Los Angeles

1. Gamma irradiation doses of 10,000 r, 20,000 r, 30,000 r and 60,000 r were given to recently metamorphosed Bufo boreas halophilus. Toads receiving the two lower dosages were killed at the end of twenty-four hours and at six days. Those receiving the two higher dosages were all killed at twenty-four hours. Cell destruction was found in the inner nuclear and ganglionic layer of the retina but none was found in the outer nuclear layer nor in the rods and cones.

2. Destruction increased as the dosage increased. At doses of 10,000 r and 20,000 r, pyknotic nuclei were most abundant near the marginal portion of the retina, where the cells had been formed more recently than in the central portion. In animals that were given 60,000 r, pyknosis of retinal nerve cells was general and almost complete.

3. Divided daily doses of 10,000 r given six times, 20,000 r three times, and 30,000 r two times produced as much destruction as a single dose of 60,000 r. The amount of edema in these cases was never as great as that which was caused by a single dose of 60,000 r.

4. At the ora serrata where structural differentiation was not yet evident, cells interpreted as prospective nerve cells were destroyed while there was no destruction of prospective sensory cells of the outer nuclear layer.