Effects of external irradiation of pregnant female rats on viability, growth and fertility of the offspring

Ionization within individual cells is produced when tissues are exposed to high levels of radiation; this may lead to cell damage or death of the cells. Both x-rays and gamma rays are electromagnetic radiations which are thought of as being physically identical, the difference in name indicating only a difference in origin. The interaction of electromagnetic radiation with matter changes in character as the energy increases. In the low energy region, the interaction is chiefly by the photoelectron process in which each individual photon loses its entire energy in a single collision with an electron. In the intermediate energy region, both the photoelectric effect and Compton scattering are significant, the latter involving multiple, degrading collision of a single photon with several electrons. The Compton effect becomes more significant, and the photoelectric effect less significant, as the energy increases. Above 1.02 mev* a third process is observed; this is the "pair production" process in which a single photon produces a positron and a negatron at the same time. The electrons produced by these three processes are responsible for ionization within the individual cells. Ordinarily, x-rays are in the low energy region, and interact chiefly by the photoelectric process, whereas gamma rays from cobalt-60 are in the high energy region, where a considerable amount of the initial energy loss is by the Compton process.

This study was initiated to determine the effects of gamma ray exposure of pregnant female rats on pre- and postnatal viability, growth and fertility of the irradiated offspring. It was hoped that the data obtained in this study would aid in designing further comparable type studies currently in progress with cattle and swine.