Effect of Radiation on the RNA Metabolism of the Central Nervous System

Abstract

In spite of numerous studies on the effects of radiation on the central nervous system, the pathogenesis and mechanism of radiation injury to the nervous tissue are still little understood (1-4). Furthermore, the great discrepancy of dose requirements leading to physiological responses on the one hand and, on the other, to pathomorphological changes in the central nervous system has not been satisfactorily explained (5-8). The recent advances of cytochemical techniques have drawn particular attention to the relationship between Nissl substance and ribonucleic acid (RNA). Alteration of RNA content and chromatolysis of Nissl substance in the neuron, under pathological conditions, were observed by several investigators to precede obvious histomorphological changes indicative of neuronal changes (9-12). The application of microautoradiographic techniques can lead to an extension of these observations. Autoradiographically labeled substances can be followed within the single cell and its compartments, resulting in direct information on the dynamics of physiochemical activity in cells. Tritium-labeled cytidine has been used in various laboratories to study the rate and time course of RNA synthesis on a single-cell level with autoradiographic techniques (13-16). Deoxyribonucleic acid synthesis in the mature nervous tissue, with tritiated thymidine as a specific precursor, was identified only in microglias, astrocytes, oligodendron glias, and subependymal cells and not in any neurons nor in the choroid plexus cells (17-19). In the present study, therefore, tritiated cytidine was used to detect changes in