Studies of the Effect of Rapidly Delivered, Massive Doses of Gamma-Rays on Mammals

Abstract

Effects of massive doses of gamma radiation on mammals were studied using multikilocurie amounts of Ba140-La140 as radiation sources. Depending on total dose and dose rate, the hyperacute radiation syndrome consisted of 4 phases: (1) a transient ataxic phase beginning immediately and lasting about 5 minutes, (2) a lethargic phase, the time of onset and duration of which were dependent on radiation dose, (3) an excited, hyperactive, convulsive phase, and (4) a terminal phase. The median survival times of mice, rats, and monkeys were determined. Dose response curves for the 3 spp. were qualitatively similar with 3 segments of response. The first segment between 650 and 1200 r, median survival time was dose dependent. In the second segment, median survival time was essentially constant over the dose range of 1200 to 10,000 r for rodents and 1000 to 6000 r for monkeys. The third segment was a region in which median survival time was again dose dependent and death was mediated through the central nervous system. Tissues in rats following massive doses of radiation showed unusual changes in such radio-resistant organs as liver and kidney. The time of appearance of pathological changes following massive doses appeared no shorter than that following radiation doses near the LD5030 range. Hematological changes were similar to those observed in the more conventional dosage range. The principal difference was the persistence of above normal neutrophil counts following doses of 25,000, 50,000, and 100,000 r. This may be due to destruction of the mechanism normally responsible for removing damaged cells from the circulating blood. Effects of high doses of radiation on serum K, Na. Cl, Ca, Mg, urea nitrogen, specific gravity, total protein, and sulfhydryl levels were studied. Although changes in some biochemical systems were seen, they could not be correlated with the radiation syndrome. Cysteine had a syner-gistic action in producing radiation death of rats exposed to 100,000 r.