CELL DAMAGE IN THE MAMMALIAN RADIATION SYNDROME 



245 



It was sliowii on P. caudatum cultured as a single cell that this uni- 

 cellular organism recovered its abiUty to divide in a short time after 

 irradiation. Changes in the tempo of division were the same after ex- 

 posure of intact cells to 100,000 r as of those preliminarily irradiated with 

 high doses (Grayevsky and Zinovieva, 1958). 



Norm 



2 4 6 



Time after irradiation (days) 



Fig. 6. — Mitotic index of the epithelium of mouse cornea after X-irradiation. 



4. Realization of injury depends on the conditions of environment 

 after irradiation. Manifestation of radiation damage is related to a 

 function of the affected substrate. 



The conditions preventing the destruction of irradiated bone-marrow 

 cells were described above. It is possible to suppose that the repair of 

 such an injured but not functioning substrate may take place in these 

 particular conditions. The process of spontaneous recovery was found 

 in gametes of Drosophila (Llining, 1958) and in yeast (Korogodin, 

 1958). There are some data to show that the environment can promote 

 development of the damage of such nonfunctioning substrates. For 

 example, storage or germination of irradiated seeds in an atmosphere 

 of oxygen brings about the realization of some potential chromosome 

 breaks (Adams and Nilan, 1958; Caldecott et al., 1957). 



In some cases the injury to cells does significantly change after 

 irradiation, in this connection accumulation of damage occurs after 



