RADIATION DEATH IN MAMMALS 



B. Rajewsky 



Max Planck - Institut fiir Biophysik, Frankfurt/Main 



DOSE AND SURVIVAL TIME 



The complete dose-mortality curves obtained on irradiating with X-rays 

 mice, rats, and guinea-pigs show several distinct ranges of total dose over 

 which the biological mechanism of bringing about death is different. This 

 fact is especially true for whole body irradiation. Figure 1, for example, repre- 

 sents the complete survival curve of white mice after a whole body irradiation 

 by roentgen rays. The final response to irradiation is generally the pre- 

 mature death of the animal. A special case arises when medium doses are 

 applied over a long period of time (for about one year or more), and if a very 

 small irradiation intensity is used. That is the field of carcinogenesis. Here 

 cancer is the cause of the death of animals, but in this case their mean survival 

 time has, in general, not been reduced considerably. If one looks at the entire 

 survival curve as it is reproduced in Figure 1, one notices first that the curve 

 covers the dose range from some lOOr to some 1 00,000 r. When small doses 

 (under lOOr) are applied, changes take place in the irradiated body, the 

 meaning of which as regards injury of the organism is still not known. They 

 can be recognized mainly by changes in the blood picture. In addition there 

 are some further observations which, however, did not lead to a well defined 

 conception so far as the mode of action of these radiation doses is concerned. 

 The very large doses of the order of magnitude of 200,000 r result in the 

 practically instantaneous death of the animals. Between these extremes 

 there are dose ranges which differ from one another in a distinctive way. 

 These ranges are approximately as follows : (7) lOOr to l,200r, {2) l,200r 

 to 1 5,000 r, {3) 1 5,000 r to about 30,000 r, {4) 30,000 r to about 1 00,000 r, 

 (5) exceeding 1 00,000 r. From the results available it can be concluded 

 that each of these dose ranges is connected with different mechanisms of 

 injury, w'hich finally cause the death of the animals. 



In the first dose range numerous changes occur in different hormonal and 

 other systems of the body. A large part of the observed symptoms is due 

 in this case to irritation of the haematopoietic system and its connections 

 with other functional centres of the organism. In this range an essential 

 part is played by the time intensity factor of the radiation effects. Here the 

 direct injury of cells is also of great importance. Especially regarding these 

 direct cellular effects and the effects of local irradiation we generally con- 

 sider this region as being the field of radiation therapy. This field is being 

 studied in greatest detail at the present time. The effects of doses under 

 lOOr, mentioned above, can probably also be classed in this range. 



In the second dose range final reaction to irradiation is independent 

 of the magnitude of the applied dose. The results of the investigations we 

 carried out show that the damage to certain organs and their functions pre- 

 dominate if compared with direct cell-damage and other injuries of the 



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