The Flash Mode of Proton Irradiation in the Bragg Peak Partly Spares the Embryogenesis of the Quail

Abstract

The study of biological effects of high-dose-rate ionizing radiation using animal models remains an urgent problem. In the work, a comparison of proton-induced damage to embryos (the 9th post-fertilization day) and 1-day-old baby chicks (the 18th post-fertilization day) from irradiated eggs of Japanese quail (Coturnix coturnix japonica) irradiated in and outside the Bragg peak with the conventional and ultra-high dose rate D (CONV D < 1 Gy/s, FLASH D [~]100 Gy/s and single-pulse flash - SPLASH D [~]106 Gy/s, respectively) was carried out. The following criteria were used: survival, body weight and body length of embryos, weight of chicks, percentage of erythrocytes with anomalies (with micronuclei, without nuclei, with two nuclei), and the speed of movement of 1-day-old chicks in the open field test. The largest number of dead embryos was recorded after irradiation with 7 and 14 Gy in the plateau region of the proton trajectory. By the criteria of body weight and length, as well as the number of erythrocytes with micronuclei in 9-day-old embryos from eggs irradiated with a dose of 8.5 Gy in the Bragg peak, FLASH and SPLASH modes were found to be the least traumatic compared with the CONV mode. The weight of chicks from eggs irradiated with a dose of 4 Gy in the Bragg peak did not differ from the control and did not depend on the irradiation mode. The lowest death incidence and the smallest number of abnormal erythrocytes were recorded after FLASH and SPLASH irradiation; in chicks that hatched from eggs irradiated in the CONV mode, a tendency for an increase in the number of abnormal erythrocytes was observed. The speed of movement of chicks from FLASH- and SPLASH-irradiated eggs was comparable with that from unirradiated eggs, and chicks from eggs irradiated in the CONV mode were less active than chicks from unirradiated eggs and eggs irradiated in the other regimes. Thus, the irradiation of eggs with a beam of accelerated protons in the Bragg peak in the FLASH/SPLASH modes is less damaging for healthy tissues and for the development of embryos and chicks on the cellular, anatomical, and physiological levels.