Speaker
Dr
Vladimir Potetnya
(Medical Radiological Research Center)
Description
Cytogenetic studies of neutron dose rate effect were carried out at the BARS-6 pulse reactor (IPPE, Obninsk, Russia) using human lymphocytes in G0 and G1 (15 hours after PGA stimulation) stages. Blood samples in plastic tubes were irradiated in water/ice-filled flasks with unfiltered radiation (Dn/Dg=1.5-2) from two unshielded metallic active zones. Equal doses in the range 0.3-1.8 Gy were given at the exposure time of 65 microsecond (burst) or during 1 hour (protracted irradiation mode). Metaphase preparations of the 1st mitosis were conventionally stained. Aberrations recorded were dicentrics, centric and acentric rings, and excess acentric fragments. In both stages the same dependences were observed: the efficiency of the protracted irradiation was higher for induction of all types of chromosomal aberrations (CA), total CA yield, and cells with CA as compared with the burst irradiation. The temperature of irradiation (20oC or 0oC) did not affect the results. The cytogenetic efficiency difference was highest for the induction of dicentrics (1.81/G1,1.78/G0), followed by total CA yields (1.64/G1, 1.44/G0), acentric rings, and was the least for the induction of centric rings and excess acentrics (ca. 1.1).Thus, an inverse dose rate effect for the induction of CA in human lymphocytes exposed to reactor radiation at dose rates of 0.8-4.5∙cGy/min or 0.5-2.7 MGy/min was observed. The dose curves were fitted by linear equations in G0 for all CA types and by linear-quadratic equations in G1 for dicentrics and total CA. The yield of CA in lymphocytes was higher at G0 stage than at G1 for both irradiation modes which was in line with known data for neutrons. For both irradiation modes an overdispersion of chromosomal aberration distributions in cells was observed. We may speculate that accompanying gamma-radiation (35-40% of the dose) induces multiple SSBs resulting in relaxation of supercoiled DNA/chromatin making it more susceptible to neutron lesion formation and fixation. This process is, perhaps, of little importance during the short burst because chromatin has not enough time to relax. Other studies at this reactor showed that pulse irradiation was more effective - CA in mice bone marrow, concentration of malonic dialdehyde in lyposomes, nearly isoeffective - yeast and bacteria survival, albumin peroxides, thymus cell death, less effective - G(Fe) in Fricke solution, suggesting that the neutron DRE depends on the complex interplay of different mechanisms.
Primary author
Dr
Vladimir Potetnya
(Medical Radiological Research Center)
Co-authors
Prof.
Aleksandr Sevankaev
(Medical Radiological Research Center)
Dr
Ekaterina Koryakina
(Medical Radiological Research Center)
Dr
Olga Potetnya
(Medical Radiological Research Center)
Prof.
Stepan Ulianenko
(Medical Radiological Research Center)
