Chronic irradiation effects in blood lymphocyte chromosomes of plutonium workers

155 23 Brandom, W., A. Bloom, P. Archer and R. Bistline, University of Denver, Denver, CO 80208, College of Physicians and Surgeons, Columbia University, N.Y., Colorado Medical Center, Denver, CO and Rockwell International, Golden, CO (U.S.A.) Chronic irradiation effects in blood lymphocyte chromosomes of plutonium workers We reported preliminary findings on the prevalence of structural chromosome aberrations in lymphocytes of 40 plutonium workers and controls at the 1st International Conferences on Environmental Mutagens (Mutation Res., 21 (1973) 211). The study is now increased to over 200 plutonium workers and controls (>30 000 cells). In most instances, the convention of scoring for dicentrics + ring chromosomes does not yield a good biological response indicator in this chronically irradiated population. The prevalence of dicentric + ring + inversion + translocation chromosome aberrations does yield a biological dose--response in our population and appears to be sensitive at low physical dose estimates. The somatic cell cytogenetic findings may prove of value to supplement physical, medical, demographic and environmental histories of these workers. This research was supported by the U.S. Energy Research and Development Administration under Contract No. E (29-2)-3639.

24 Brewen, J.G., Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tenn. 37830 {U.S.A.) Critical appraisal of methods in mutagenicity testing: Chromosome aberrations in mammals * It has often been assumed, and argued, that structural damage to chromosomes constitutes the majority of mutational events after treatment of a biological system with a mutagenic agent. Increasing research efforts seem to be validating this point of view for mammalian systems. If one wishes to make the further (somewhat tenuous) assumption that the mechanism of chromosome damage visible in the light microscope is the same as that associated with supposedly simple mutations, cytogenetic assays offer a simple and rapid means of mutagenicity testing. Based on these two assumptions a considerable investigation has been expended in evaluating the clastogenic effects of numerous mutagens and promutagens in an array of mammalian test systems. The questions posed are: " H o w sensitive and reliable are these systems?" and "Can refinements be made to existing systems, or are there alternative systems, that will increase the sensitivity and reliability of the testing?" A brief history of cytogenetic testing in mammals will be presented, with mention of the difficulties and pitfalls encountered. Some of the newer tech-