A Comparative Histological Study of Duodenal Damage Produced by Fission Neutrons and Co 60 Gamma-Rays

During the past several years experiments have been carried out at the Argonne National Laboratory to test the relative effectiveness of Co60 y-rays and fission neutrons on a number of biological objects (1). One of the comparative criteria utilized was the acute lethal action on mice exposed to single doses of these two radiations (2). After exposures to fission neutrons, mice showed a much earlier mortality mode than after comparable irradiation with Co60 y-rays. After neutron doses that were high enough to kill mice within the 30-day period after irradiation, a mortality peak was observed on the fifth or sixth day after exposure; a great majority of these neutron-irradiated mice died between the fourth and the ninth days. In contrast, the pattern after y-irradiation showed a pronounced peak of mortality around the thirteenth or fourteenth day after exposure. A specific intestinal radiation syndrome leading to death in 3 to 5 days has been described in several species of laboratory animals after exposure to large doses (1000 to 10,000 r) of X-rays (3-8). It seemed of interest to determine whether or not the early mortality mode characteristically following fission neutrons was also produced chiefly by intestinal damage. The object of this experiment was to compare both histologically and cytologically the small intestine of mice exposed to fission neutrons with that of animals exposed to Co60 y-irradiation.