PHYSIOLOGY OF RADIATION INJURY 1005 



Obviously, the extent to which adaptive and defensive mechanisms are 

 successful will depend, for the most part, upon the magnitude of the 

 stress. The nonspecific potentiation of one stress by another may be 

 interpreted on this basis. These considerations apply to the high-energy 

 radiations, which, because of their distribution, usually result in* fairly 

 extensive injury. It has been shown, for example, that hypophysectomy 

 (Patt et al., 1948), adrenal insufficiency (Cronkite and Chapman, 1950; 

 Edelmann, 1951b; Kaplan et al., 1951), infection (Taliaferro el al., 1945; 

 Shechmeister and Bond, 1951 ; Shechmeister el al., 1950), trauma (Brooks, 

 1951), exhaustive exercise (Stapleton and Curtis, 1946; Kimeldorf 

 et al., 1950), and nutritional deficiencies (Johnson et al., 1946; Jennings, 

 1949) enhance the susceptibility to irradiation and, conversely, that 

 irradiation increases the toxicity resulting from many of these conditions. 

 Moderate degrees of stress, however, may be well tolerated by minimally 

 irradiated animals (W. W. Smith, 1951; W. W. Smith and Smith, 1951b; 

 F. Smith and Smith, 1951). Of interest from the point of view of war 

 disaster, is the recent finding by Brooks (1951) that 100 r total-body X 

 irradiation, which by itself is nonlethal, increases the mortality of dogs 

 from 14 to 75 per cent following a standardized surface burn. 



ACUTE RADIATION SYNDROME 



The symptom complex appearing within several weeks after irradiation 

 of large areas of the body and the way it develops may be considered 

 pathognomonic of radiation exposure (Shields Warren and Bowers, 

 1950; Howland and Warren, 1947; Jacobson et al., 1949d; Painter and 

 Brues, 1949; Hempelmann, 1950; Shields Warren and Brues, 1950; 

 Bowers, 1951; Cronkite, 1951; Hempelmann et al., 1952). The relatively 

 mild discomfort of clinical radiation sickness, which is sometimes seen 

 after therapeutic exposure, should be distinguished from the more serious 

 and complex events of the acute radiation syndrome, of which it is a part. 

 It is well to recall that chronic effects, e.g., anemia, neoplasia, lenticular 

 opacities, and "premature aging" 2 may appear in survivors of the acute 

 injury, or after protracted or repeated irradiation. The more chronic 

 sequelae do not, however, constitute as discrete an entity as the acute 

 syndrome. The pattern in man is, in general, similar to that observed 

 experimentally. Our knowledge of acute radiation injury in man is 

 based largely upon studies of the Japanese bomb casualties (Howland 

 and Warren, 1947; Liebow et al., 1949) and of persons injured by acci- 

 dental nuclear reactions (Hempelmann et al., 1952). Data relating to 

 the Japanese victims are necessarily incomplete and complicated by the 



2 Shortening of life span is generally thought of as if it involved an acceleration of the 

 aging process. In fact, it rests almost entirely on statistical data and so is analogous 

 to semilethal effects in Drosophila (Brues and Sacher, 1952). 



