Kurochkina V. Cytogenetic efficacy of isotope cesium-137 in human peripheral blood lymphocytes in model experiments in vitro

The dissertation is dedicated to the study of the cytogenetic efficiency of the 137Cs radioisotope in human peripheral blood lymphocytes in in vitro model experiments for biological dosimetry of its external and internal impacts in relatively low doses. The significance of the study is determined by the need of the for cytogenetic assessment of radiation doses for victims of emergency radiation situations, when 137Cs is main dose-forming radioisotope. Own calibration dependence of "dose-effect" was obtained for the frequency of unstable chromosomal exchanges (dicentrics and centric rings) with the accompanying paired fragment in human lymphocytes during acute external γ-irradiation of blood samples with a 137Cs source in the dose range of 0.09 - 1.0 Gy in vitro For the first time, experimental and for calculating models (using the Monte Carlo method based on the GEANT-4 library) were developed and created for prolonged external and/or internal irradiation of blood samples with the radioisotope 137Cs in relatively low (up to 0.54 Gy) doses in vitro under conditions close to in vivo. It was shown that during prolonged external irradiation of human blood samples with the radioisotope 137Cs (in the dose range of 0.09-0.53 Gy) in vitro under conditions close to in vivo, with an increase in the absorbed dose, the frequency of unstable chromosomal aberrations in lymphocytes increases linearly. The frequency of chromatid-type aberrations is determined at the same level, which probably exceeds spontaneous. For the first time, it was found that during prolonged internal irradiation of blood with 137Cs (0.10 - 0.54 Gy) in vitro under conditions close to in vivo with an increase in the absorbed dose in lymphocytes, the frequency of aberrations of both chromosomal and chromatid types increases linearly. Greater cytogenetic efficiency of the 137Cs radioisotope was revealed in the case of internal irradiation compared to external irradiation in the same range of doses with an equivalent dose rate on G0 blood lymphocytes. For the first time, it has been proven that the greater cytogenetic efficiency of internal irradiation of human blood lymphocytes with 137Cs in vitro is due to the combined effect of the radioisotope on cells during their contamination (in a state of mitotic rest) and during their cultivation (in a state of proliferation) to obtain metaphase plates. For accurate determination of cytogenetic efficiency of internal 137Cs irradiation relative to its external effect on human peripheral blood lymphocytes in vitro, it is proposed to correct the output of aberrations during cell cultivation according to the cytogenetic study protocol.