FACTORS INFLUENCEING IN VIVO SISTER CHROMATID DIFFERENTIATION AND EXCHANGES IN BONE MARROW CELLS OF MICE AND HAMSTER

Exposure of mice to high temperature and humidity (34°C and 70% relative humidity) during and following BrdUrd/Faurd i/p injections yielded a significantly (p<.01) higher percentage of differentiated metaphases and induced higher sister chromatid exchanges (SCEs) but had no effect on mitotic index and chromosome aberrations. FdUrd and MMC produced a dose dependent increase in SCEs. With higher doses FdUrd affected the differential chromatid staining, whereas MMC not only affected the chromatid differential staining but also produced a number of pulverized metaphases. Unlike MMC, MMS did not appear to produce an additive effect with BrdUrd in inducing SCEs. Both the mice and hamsters, administered with 40 µg/g BrdUrd, 2 µg/g FdUrd or 50 mg BrdUrd tablet by implantation, showed similar baseline SCE values. A partially paraffin coated BrdUrd tablet (50 mg) was found to be most suitable for animals with a wide range of body weights.