Electron Microscopic Study on the Initial Effect of γ-Irradiation on the Chromatin Structure of L Cells

Abstract

Mouse L cells are γ-irradiated at a dose of 1 Mrad, and ultrathin sections of the cells are examined by electron microscopy. The distance between chromatin fibers in diffused chromatin regions in the irradiated nuclei is essentially identical with the non- irradiated control. In contrast, an increase of the distance between the chromatin fibers is observed in the excess of Ca ions in irradiation.