Date of Graduation

1997

Document Type

Dissertation/Thesis

Abstract

As translocations increase in popularity for use as a biodosimeter for prior radiation exposure, information on the possible decline of these 'stable' aberrations over time is desperately needed. This study is the first to assess the stability of radiation-induced chromosome aberrations in vivo over the life span of a rodent model. C57BL/6 female mice were given an acute dose of 0, 1, 2, 3 or 4 Gy {dollar}\\sp{lcub}137{rcub}{dollar}Cs of 8 weeks of age. Metaphase chromosome preparations were made from peripheral blood and bone marrow samples which were taken from 4 mice in each dose group at 1, 8, 15 and 30 days, 2 months, 3 months and every 3 months thereafter until 21 months post-exposure. Aberrations were detected by painting chromosomes 2 and 8. While the frequency of translocations did not decrease in the bone marrow, we found that there was a significant decrease in translocations in the peripheral blood of mice exposed to 3 or 4 Gy during the first 2 months after irradiation, beyond which time the frequency remained constant. Both reciprocal and non-reciprocal translocations were found to increase with age in the peripheral blood of unexposed control animals. As expected of unstable aberrations, dicentrics decreased rapidly in both tissues. Clonal expansion of cells bearing stable aberrations was found to be a confounding factor that contributed significantly to the variation among exposed as well as unexposed mice. When the data are corrected for the presence of clones, biodosimetry after 1 year is much improved revealing a significant difference between the doses that was not evident when the uncorrected data was analyzed. Additional studies are needed to further improve biodosimetry in humans by incorporating statistical corrections for the confounding factors elucidated in this study.

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