984 RADIATION BIOLOGY 



injury and cell death. The same considerations may well apply to other 

 metabolic phenomena. Respiration of all segments of the small intestine 

 is inhibited several hours after exposure of the rat to 700 r (Barron et al., 

 1947). Oxygen consumption is essentially normal at 24 hours, but is 

 again depressed on the third day. Anaerobic glycolysis is apparently 

 unaffected at all intervals. 



A decrease in dry weight of the intestinal mucosa occurs during the 

 first two days after irradiation; this is not observed in nonirradiated 

 pair-fed controls (Ross and Ely, 1949a). In contrast, similar weight 

 losses have been detected in the gastrointestinal tract of X-rayed and 

 fasted rats at 4 days (Painter, 1948) . Although sodium space is increased 

 by some 50 per cent in both the irradiated and fasted animals, total water 

 content is not changed significantly. The increase in sodium space may 

 be related in part to an increase in extracellular fluid volume, and also to 

 an exchange of sodium for potassium in the intestinal cells (Painter and 

 Pullman, 1950). Radiosensitive tissues, in general, show an initial 

 decrease in sodium and potassium followed by an increase in the former 

 (Bowers and Scott, 1951a, b). 



Anorexia and weight loss have been observed in a number of species and 

 are reasonably good indicators of the severity of radiation injury (Prosser, 

 Painter, Lisco, et ah, 1947; Ely and Ross, 1947). A transient diminution 

 in food intake has been noted by Smith, Tyree, Patt, and Bink (1951) in 

 the rat after only 50 r delivered to the whole body. After dosages of 

 250 to 10,000 r, food consumption drops to less than 10 per cent of normal 

 on the first day. Although the initial anorexia is rather similar over a 

 wide dosage range, recovery varies more or less directly with the magni- 

 tude of exposure, being more rapid after 250 r than after 500 r and non- 

 existent after 1000 r. With median lethal irradiation, food intake may 

 return toward normal after a few days, only to decrease again several 

 days before death. This is perhaps suggestive of some recovery in the 

 gastrointestinal tract during the intermediate period. Anorexia appar- 

 ently accounts for all or most of the weight loss that is seen after exposure 

 to penetrating radiation (Ely and Ross, 1947; Smith, Tyree, Patt, and 

 Bink, 1951). Observations made on a few rats after external irradia- 

 tion reveal a decreased food intake for the first week or two, followed by an 

 increase above the normal that is maintained until death (Anderson, 

 1946). Body weight, however, falls progressively, perhaps as a result of 

 extensive fluid loss. 



Anorexia, vomiting, and diarrhea are generally not observed in animals 

 after exposure of regions remote from the abdomen and are thought to be 

 a result of direct injury of the digestive tract. Symptoms of the same 

 general nature have been seen clinically after X irradiation of extra- 

 abdominal areas with dosages far below those employed experimentally. 

 The severity of the clinical reaction has been related to the size of the 



