X-lrradiation Studies 

 on the Mammalian Retina 



Werner K. Xoellj 



Roswell Park Memorial Institute 

 Buffalo, New York 



Our studies on the effects of x-irradiation originate from our concern with 

 mammalian retinal cells and their susceptibilities to poisons as related to the 

 function of the retina and to hereditary retinal diseases i Noell, 1951-1959 >. 



The retinal cells of main interest are the \isual cells, particularly the rod 

 cell, which in Fis,. 1 is depicted as elaborated by Sjostrand 1956). De 

 Robertis > 1956 i. and others. It comprises a sensory endino;. the rod, which 

 has an outer and an inner se2,ment. a nuclear region, \aryin2' somewhat in 

 location, and a fiber which terminates in a «ynapse of unusual morpholo.oic 

 arranoement with the bipolar cell. The outer se2,ment contains the photo- 

 sensitive pigment, rhodopsin. and is the site of the primary \-isual e\ents. It 

 consists of closely packed thin discs, which probably deri\e trom foldings of 

 the plasma membrane, and lacks cytoplasm and the enzymes of the respira- 

 tory and glycolytic systems ( Lowry <t al, 1956 ) . The inner segment seems to 

 be the site of high metabolic acti\ ities. It is rich in enzymes, and its distal half is 

 filled with mitochondria. In the rabbit, the distal part of the inner segment is 

 the only region of the visual cell which contains mitochondria and, therefore, 

 is the principal, and probably only, region capable of reducing oxygen. In the 

 mouse and rat. one additional mitochondrion is located within the synaptic 

 ending. Hence, glycolytic reactions may generally be of greater significance 

 for the \isual cell than for other cells. Indeed, the mammalian retina is 

 known for its high glycolytic acti\ity in the presence of oxygen. Its metabo- 

 lism resembles that of cancer tissue much more than that of the brain, of 

 which it is ontogenetically a part. 



X-irradiation af^^cts the rod cells of the mammalian retina selecti\ely, 

 killing them, but not other retinal cells. This selectivity has been observed 

 with rabbit, rat, dog. and monkey. Predominant efTectiveness on the rod 

 cells is not an exclusive property of x-irradiation. but is characteristic of 

 intravenous iodoacetate. a poison well known for its inhibitory effect on 



* Supported by a U.S. Public Health Grant. 



t Present address: University of Buffalo Medical School. 



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