title: DNA supercoiled domains and radiosensitivity of subpopulations of human peripheral blood lymphocytes.
abstract: Enriched human B- and T-lymphocyte subpopulations were isolated by means of a Percoll step gradient centrifugation procedure. 60Co gamma-irradiation dose-response curves for these subpopulations were obtained by applying a modified nucleoid sedimentation technique, which was also employed for the determination of the superhelical content by means of ethidium bromide intercalation. Although a similarity in the average superhelical density of B- and T1-lymphocytes was shown, B-lymphocytes exhibited a more pronounced reduction in sedimentation ratio, suggesting a higher radiosusceptibility than the T1-lymphocytes. By applying the single hit kinetics of the target theory to the dose-response curves, an estimation of the supercoil domain sizes was made: B- cells, 5.5 X 10(9), 1.78 X 10(9) and 7.78 X 10(8) D; T-cells, 4.55 X 10(9), 1.75 X 10(9) and 7.67 X 10(8) D. The differences in radiosensitivity of lymphocyte subpopulations can not, therefore, be entirely ascribed to differences in DNA superstructure.
mesh_terms: D001402:B-Lymphocytes / Q000032:analysis / Q000528:radiation effects*; D002470:Cell Survival; D003037:Cobalt Radioisotopes; D004278:DNA, Superhelical / Q000032:analysis / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004996:Ethidium / Q000494:pharmacology; D005720:Gamma Rays; D006801:Humans; D066298:In Vitro Techniques; D007364:Intercalating Agents; D011836:Radiation Tolerance; D013601:T-Lymphocytes / Q000032:analysis / Q000528:radiation effects*
chemical_list: D003037:Cobalt Radioisotopes; D004278:DNA, Superhelical; D007364:Intercalating Agents; D004996:Ethidium