Some Characteristics of Biological Damage Induced by Ionizing Radiations

Abstract

Radiobiological literature is reviewed. A number of examples are cited which appear to demonstrate clearly that a given form of biological damage proceeds by different pathways when induced by u.-v. radiation, ionizing radiation and radiomimetic chemicals. Ionizing radiations themselves do not form a homogeneous group since damage induced by X- and gamma-radiation is in general markedly affected by O2 tension and other environmental factors, whereas damage induced by neutrons and alpha-particles is either less affected or almost independent of environmental influences. The influence of the environmental factors often bears a close relationship to the influence of the same factors on the chemical changes induced by ionizing radiations. The influence of dissolved molecular O2 is a particular example. In other instances, cysteine protection, biochemical factors appear also to be involved. There appears to be little evidence that moderate doses of radiation directly and immediately interfere with most cellular metabolic activities. DNA synthesis may be an exception. A study of the conditions under which radiation induces metabolic disturbances suggests that, as regards many enzyme systems of the cell, the radiation affects the capacity for replacement rather than existing enzyme systems.