THE ROLE OF ("ELLULAR DAMAGE IN THE 

 MAMMALIAN RADIATION SYNDROME 



E. Y. GRAYEVSKY, I. M. SHAPIRO, 

 M. M. K0N8TANTIN0VA AND N. F. BARAKINA 



A. N. Severtzov Institute of Ariimal Morphology, U.S.S.R. Academy 

 of Sciences, Moscow, U.S.S.R. 



SUMMARY 



The mass destruction of the cells of haematopoetic organs and of the intestine 

 is one of the most important causes of death in an irradiated animal. The death 

 of these cells is only observed in directly irradiated tissues not connected with 

 mitosis and is the result of the activity of the damaged intracellular substrate. 

 The destruction is not a direct consequence of the variation of the content of 

 nucleic acids in the nuclei. The regeneration of the irradiated tissues occurs from 

 potentially viable cells and is limited first of all by the number of cells having 

 lethal chromosome injuries and also by the reduced mitotic activity. Prophy- 

 lactic defensive agents exert their action at the cellular level. Most agents 

 protect by producing hypoxia in the radiosensitive tissues. Some sulphur- 

 containing protective agents do not reduce the content of oxygen in the tissvies. 



Various changes in a mammalian organism arise as a result of ex- 

 posure to ionizing radiation. It is evident, however, that only some 

 injuries play an important role in the mechanism of the radiation 

 reaction. At the present time radiation injury after exposure to doses 

 as high as 10 to 15,000 r is considered to be determined first of all by 

 the state of the haematopoietic and digestive systems. (This thesis is 

 supported by numerous experiments on shielding and local irradiation 

 which showed that peaks of mortality were related to damage to 

 haematopoietic organs and to different parts of the digestive system 

 (Maisin, et al., 1957; Quastler, 1956; Quastler and Zucker, 1959; 

 Rajevsky, 1956; Semenov and Fedorov, 1959). 



The analysis of changes in these radiosensitive systems shows that 

 the most characteristic feature of their reaction to iiTadiation is a 

 mass destruction of cells which occurs soon after exposure. Destructive 

 processes in some other organs (for example in the gonads) are of a 

 local significance and have no effect on the survival of irradiated ani- 

 mals. The understanding of the mechanism of radiation injury and the 

 elaboration of rational radiation protection require an investigation of 



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