Effect of α-Particle Microbeam Irradiation on the Synthesis of Deoxyribonucleic Acid in Tissue Culture

DATA concerning the effects of irradiation on cell components are of considerable importance in the elucidation of the role of possible toxic mediators in radiation damage 1 . We have compared the formation of DNA in cells with nuclei and cytoplasm separately irradiated in order to estimate the contribution of toxic substances, formed after irradiation of cytoplasm, to nuclear damage. DNA synthesis was investigated because this process is known to be the most radiosensitive in a cell, and also because this high sensitivity is thought largely to be a result of the sensitivity of kinases located in the nucleus 2 and of DNA molecules themselves 3 .