BIOMEDICAL AND ENVIRONMENTAL SCIENCES DIVISIONS Organization These two Divisions function with common administrative staff, support functions and facilities within the Biomedical and Environmental Research Program. The Biomedical Sciences Division deals with the mechanism, detection and minimization of potential long-term health impacts, with primary emphasis on mutagenic, carcinogenic and reproductive biologic effects, and on analytical cytology as a tool for analysis of such effects. Mutagenesis and carcinogenesis are probably the most sensitive and important deleterious health effects of concern to DOE. They involve long latent periods and profound consequences, and they operate through a multitude of physical and chemical mechanisms. To understand and ameliorate such effects requires a thorough knowledge of genetics and cancer biology, the development of tools to detect mutagenesis and incipient carcinogenesis in man, and the large-scale application of these advances to occupational medicine and human epidemiology. Current LLL efforts emphasize two approaches: 1) reliable, sensitive assays for specific toxic substances using animal, cellular and microbial systems; and 2) detection methods that can indicate mutagenic and early, reversible carcinogenic changes in readily obtainable samples of blood and urine from individual people. The reproductive system is crucial for perpetuation of the species and is exquisitely responsive to toxicologic damage. Current LLL studies indicate that rodent and monkey oocytes at one stage of development are the most sensitive cells in the body to radiation and to certain energy-related chemicals. Spermatogenesis remains highly vulnerable throughout adult life and our studies show that in animals and man it provides an important assay for mutagenic and other taxicologic activity. Continuing research in these two gametogenic systems deals with mechanism of effect, dose-response relationships, species differences including primates and man, and broad application as potential monitoring systems. Analytical cytology is the science and technology of probing cells for their physical, morphological, chemical and functional properties. At LLL emphasis is placed on two complementary approaches: 1) cell measurements and sorting by flow cytometry, and 2) cell measurement and discrimination by scanning microscopy and computer-based image analysis. These approaches offer high resolution, quantitation and automated highcapacity processing and have been coupled to a rich, rapidly growing diversity of cytochemical cellular probes. They are being applied to cancer diagnosis, to chromosome analysis, to sperm analysis, and to identifying somatic mutations as rare, highly specific events in single cells.