Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The influence of a variety of metabolic factors on DNA excision repair was examined in studies involving measurements of damaged base removal, repair replication, and size of the resulting resynthesized regions or repair patches.;First, ultraviolet light (UVL)- and dimethylsulfate (DMS)-induced excision repair was examined in quiescent and lectin-stimulated bovine lymphocytes. Upon mitogenic stimulation, UVL-induced repair increased by a factor of 2 to 3, and reached this maximum 2 days before the onset of DNA replication. However, DMS-induced repair increased sevenfold in parallel with DNA replication. Repair patch sizes were smaller for DMS-induced damage reflecting patches of 7 nucleotides in quiescent lymphocytes compared to 20 nucleotides induced by UVL. The patch size increased during lymphocyte stimulation until one day prior to the peak of DNA replication when patch sizes of 45 and 35 nucleotides were produced in response to UVL- and DMS-induced damage, respectively. At the peak of DNA replication, the patch sizes were equal for both damaging agents at 34 nucleotides. In the second study, a small amount of repair replication was observed in undamaged quiescent and concanavalin A-stimulated bovine lymphocytes as well as in human T98G glioblastoma cells. No increase in repair was found early during lectin stimulation; however, repair replication did increase with longer times of mitogen stimulation. Confluent T98G cell DNA was found to contain fivefold to tenfold more repair replication than unstimulated lymphocytes. Repair incorporation doubled in the presence of hydroxyurea. Thirdly, the enhanced repair replication induced by the poly(ADP-ribose) polymerase inhibitor, 3-aminobenzamide, (3-AB), could not be correlated either with an increased rate of repair in the presence of 3-AB or with the use of hydroxyurea in the repair protocol. Finally, treatment of unstimulated lymphocytes with hyperthermia was accompanied by decreased repair replication while the repair patches remained constant at 20 nucleotides.;These results are discussed in terms of differences in precursor pools, changes in enzymatic activities, and alterations in chromatin structure which could influence the amount and accessibility of damage.



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