ABSTRACT
The dose response of the number of micronuclei in cytokinesis-blocked (CB) lymphocytes after in vitro irradiation with -rays and neutrons in the 5 dose ranges was studied for a heterogeneous population of 4 donors. One thousand binucleated cells were systematically scored for micronuclei. Measurements performed after irradiation showed a dose-dependent increase in micronuclei(MN) frequency in each of the doctors studied. The dose-response curves were analyzed by a linear-quadratic model, frequencies per 1000 CB cells were (0.31+/-0.049) D+(0.0022+/-0.0002) D2+(13.19+/-1.854) (r2=1.000, X2=0.7074, p=0.95) following irradiation, and (0.99+/-0.528) D+(0.0093+/-0.0047) D2+(13.31+/-7.309) (r2=0.996, X2=7.6834, p=0.11) following neutrons irradiation (D is irradiation dose in cGy). The relative biological effectiveness (RBE) of neutrons compared with -rays was estimated by best fitting linear-quadratic model. In the micronuclei frequency between 0.05 and 0.8 per cell, the RBE of neutrons was 2.37+/-0.17. Since the MN assay is simple and rapid, it may be a good tool for evaluating the y-ray and neutron response.
Subject(s)
Humans , Lymphocytes , Neutrons , Relative Biological Effectiveness , Tissue DonorsABSTRACT
The evaluation of radiation-induced DNA double strand breaks(DSB) was made following irradiation of human lymphocytes, murille lymphocytes and EL-4 leukemia cells over a wide dose range of 60Co g-rays. In lipopolysacchande(LPS) or phytohemagglutinin(PHA)-stimulated murine lymphocytes, the slopes of the strand scission factor(SSF) revealed that lymphocytes with LPS increased DNA DSB formation by a factor of 1.432 (p<0.005). Furthermore, strand break production was relatively inefficient in the T lymphocytes compared to the B lymphocytes. And EL-4 leukemia cells were found to form significantly more DNA DSB to a greater extent than normal lymphocytes (p<0.705). The in vitro studies of the intrinsic radiosensitivity between human lymphocytes and murine lymphocytes showed similar phasic kinetics. However, murine lymphocytes were lower in DNA DSB formation and higher in the relative radiation dose of 10 percent DNA strand breaks at 3.5 hours following g-irradiation than human lymphocytes. Though it is difficult to interpret these results, these differences may be result from environmental and genetic factors. From our data, if complementary explanations for this difference will be proposed, the differences in the dose-effect relationship for the induction of DSB between humans and mice must be related to interspecies variations in the physiological condition of the peripheral blood in vitro and not to differences in the intrinsic radiation sensitivity of the lymphocytes. These results can be estimated on the basis of dose-effect correlation enabling the interpretation of clinical response and the radiobiological parameters of cytometrical assessment.
Subject(s)
Animals , Humans , Mice , B-Lymphocytes , DNA , Kinetics , Leukemia , Lymphocytes , Radiation Tolerance , T-LymphocytesABSTRACT
The filter elution technique was used to assay Co-60 g ray-induced DNA single-strand breaks (SSB) in EL 4 mouse leukemia cell and spleen lymphocyte. The lymphocytes were stimulated with lipopolysaccharide (LPS, 20 mug/ml) to label [3H] thymidine. EL 4 cells and lymphocytes in suspension were exposed at 0degree C to gy, 1 gy, 5 gy, 10 gy of Co-60 radiation and elution procedure was performed at PH 12.1. The number of DNA single-strand breaks increased with increasing doses of g rays. The strand scission factor (SSF) was estimated in each experiment (eluted volume 21 ml. The slope for EL 4 cells was 0.01301+/-0.00096 gy-1(n=5) and the slope for lymphocytes was 0.01097+/-0.00091 gy-1(n=5). The slopes were significantly different (p<0.005). Thus EL 4 cells were more sensitive to induction of DNA SSB by ionizing radiation than lymphocytes.