The Effects of Ionizing Radiation on Mammalian Cells John E. Biaglow Case Western Reserve University, Cleveland, OH 44106 Human and animal cells. both normal and tnmoroeenic. " . can be grown in culture in uitro and studied for their responses to ionizing radiation (for reviews see (1-8)). I n uitro studies with cell cultures may involve cytotoxic and mutagenic effects of radiation. There is also a good deal of current interest in the effects of drug and radiation cornhinations on cell cytotoxicity. In addition. the effects of hormones and radioprotective agents are being actively pursued. For these studies the cells can be grown under various conditions such as log phase, plateau phase or growth-arrested and in multicellular arrays such as spheroids. Cells may also he grown a t lower density and concentrated before irradiation in order to duplicate tissue-like densities. Cells may he collected when they round up for division, or they may be chemically synchronized in order to study the effects of radiation alone or with drugs a t various staees of the cell cvcle. u An important advancement in understanding the nature and severity of radiation damage to mammalian cells was accomplished by the introduction of several techniques to measure the survival of single cells (1-4). These techniques provided the first opportunity to quantify the biological effects of radiation on a cellular basis. The introduction of these survival techniquesnk
