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U.S. Department of Energy
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The development of in vitro mutagenicity testing systems using T-lymphocytes

Technical Report ·
OSTI ID:5625685

During the past four months we have continued our study of in vitro induction of mutations in human T-lymphocytes and molecular characterization of these induced mutations. Our primary effort has involved determination of the size of deletion events involving the hprt gene. We have analyzed 57 mutants for codeletion of 20 different Xq26 region anonymous DNA probes. We have now ordered the five probes which show codeletion in some mutants, relative to the hprt gene. We are now investigating the physical size of these deletions by us of pulsed field electrophoresis. We have also studied a unique type of deletion mutation found in cord blood samples. This mutation involves a specific deletions of exons 2 and 3, with breakpoints at identical sites in introns 1 and 3. Thirteen mutants from 10 newborns have been shown to have characteristics consistent with a V(D)J recombinase mediated mutational event. As part of our study of the induction of mutations by in vitro exposure to gamma irradiation, we have investigated the effect of inhibiting DNA repair by use of incubation in cytosine arabinoside/release with deoxycytidine. We have also continued our study of in vivo mutation frequencies in humans exposed to ionizing irradiation in the course of radioimmunoglobulin therapy (RIT) for cancer. The mutant frequencies are elevated in the post-RIT patients and 40% of the mutations involve deletions/rearrangements of the hprt gene with total gene deletions predominating (17.6% of the mutations). The fraction of mutants with these structural alterations correlated with the cumulative amount of radioactivity received, providing a possible indicator of total in vivo chronic exposure to ionizing irradiation.

Research Organization:
Vermont Univ., Burlington, VT (USA)
Sponsoring Organization:
DOE; USDOE, Washington, DC (USA)
DOE Contract Number:
FG02-87ER60502
OSTI ID:
5625685
Report Number(s):
DOE/ER/60502-5; ON: DE91012283
Country of Publication:
United States
Language:
English