HISTOLOGICAL CHANGES AFTER IRRADIATION 1125 



types: (1) the functional and degenerative morphological changes and 

 subsequent repair occurring shortly after irradiation and (2) the develop- 

 ment of gastric ulcers some weeks later. 



In rabbits, after total-body irradiation with 800 r of 200-kv X rays, 

 some degenerate cells and absence of mitoses are seen early in the necks of 

 the fundic glands. Mitoses reappear after 17 hours but are not normal 

 until 5 days later. The surface epithelium and the cardiac and pyloric 

 glands are much more resistant. In the fundic glands some of the 

 parietal cells show wrinkling of the nuclear membrane, or pyknosis, and 

 vacuolization of the cytoplasm from 2 hours to 5 days in some cells, but 

 only during the first day in the majority of them. The more severely 

 affected mucous and zymogenic cells show pyknosis for 5 days. Zymogen 

 granules are absent from 2 hours to 5 days, and are, for the most part, 

 irregular in size and number until 9 days (Pierce, 1948). Hemorrhages 

 may occur, especially in the lamina propria (Engelstad, 1938). 



There is agreement that irradiation causes a marked decrease in gastric 

 secretion with a great decrease in acidity and relatively little change in 

 pepsin content (Desjardins, 1931). It is noteworthy that in dogs the 

 parietal cells, presumably the source of hydrochloric acid precursors, are 

 not greatly damaged, in contrast to the destructive changes and loss of 

 zymogen granules in the chief cells (Dawson, 1925). This decrease in 

 production of acid after irradiation, which may last for some weeks, is the 

 basis for the treatment of gastric ulcers by large doses of X rays (Palmer 

 and Templeton, 1939). Many but not all authors report a decrease in 

 secretion of gastric mucus. 



The production of ulcers of the stomach by irradiation has been noted 

 in man and animals (Delbet et at., 1909; Engelstad, 1938; Rickettsial, 

 1949). They develop after a latent period of several weeks or more and 

 usually occur singly along the lesser curvature. They may be shallow or 

 may penetrate all the tunics of the organ and lead to perforation. Scar- 

 ring and healing of the ulcers may occur after many months. It has been 

 suggested that the failure to heal sooner is due to the inhibition of pro- 

 liferation of connective tissue cells resulting from irradiation. 



There are minor differences of opinion as to the relative sensitivity of 

 the small intestine as compared with other tissues and organs (Friedman, 

 1942). Part of this absence of unanimity is due to our inability to com- 

 pare dosages used in much of the experimental material before 1930, to 

 differences in species, and to large gaps in the series of animals reported by 

 many investigators. Nevertheless, the majority of authors agree that 

 the small intestine is more sensitive than the stomach and that it is only 

 slightly more resistant than lymphatic tissue. 



Parts of the epithelium of the duodenum of the rabbit, more sensitive to 

 radiation than any other part of the gastrointestinal tract, show marked 

 degenerative changes 30 minutes after exposure to 800 r of X rays (total 



