The Clinical Sequence of Physiological Effects of Ionizing Radiation in Animals

Abstract

This paper summarizes experiments to be reported in detail in the Manhattan Project Technical Series on physiological and biochemical measurements on irradiated animals. Every kind of ionizing radiation is similar in its clinical action, whether it be penetrating external radiation or internal radiation from deposited radioactive material. Nearly every organ system is affected by lethal doses of radiation. Some effects are direct, some indirect as a result of toxic agents or of hypoxia, infections and other secondary factors. No single clinical reaction is peculiarly specific for irradiation damage. The clinical picture and the conditions resulting in death vary with the dose rate and the duration of exposure for both external and internal irradiation. Six patterns are recognized: (1) at very high dose rates animals die within a few mins.; (2) at median lethal doses all animals show sickness in the first few hrs. and some (e.g., rabbits) may die with cardiovascular failure during the first day; (3) early acute deaths (4-6 days) appear to be associated with dehydration; (4) most acute deaths occur 2-3 wks. after exposure ; they are characterized by extreme leucopenia, damage to blood forming organs, gastro-intestinal tract, and terminal symptoms indicative of a toxemia; (5) subacute deaths result from several mos. of exposure at low dose rates; there may be severe anemia and emaciation; (6) chronic deaths occur after several hundred days of very low dosage; the most common sign is tumor induction.