Role of DNA damage in the formation of radiation damage to chromosomes

The data are reviewed on the role of various DNA lesions in the formation of structural damages to chromosomes. The concepts are developed that the molecular damages to nuclear DNA induce chromosome mutagenesis.     

Effect of secondary radiation from 70-GeV protons and gamma quanta on chromosomes of Chinese hamster cells as dependent on the cell cycle stage

In cultured Chinese hamster cells, no decrease in the number of chromosome aberrations was noted after exposure thereof to 70 GeV protons at the late S-phase as opposed to early one. It is suggested that high biological effectiveness of this type of radiation is associated with its inhibiting effect of cytogenetic damages repair.     

Low doses of radiation decrease the level of spontaneous and gamma-induced chromosomal mutagenesis in bone marrow cells of mice in vivo

Low doses of ionizing radiation are known to induce adaptive response (AR), which is characterized in most cases by temporary nature, though the possibility of long-term persistence of AR is not ruled out. In this investigation we studied the effect of low doses of gamma-radiation on both high-dose radiation-induced and spontaneous level of cytogenetic damage throughout the life of mice. SHK male mice 2 months old were used. Priming doses of 0.1 and 0.2 Gy (0.125 Gy/min, gamma-radiation from 60Co) were used. A challenging dose of 1.5 Gy (1 Gy/min) was used in the experiments using a routine AR experimental design. The frequency of micronucleated polychromatic erythrocytes in bone marrow cells of primed, primed and challenged, and control groups was assessed at various times of animal life span. It was shown that: a) single low-dose gamma-irradiation induces a cytogenetic AR which can be revealed at 1, 3, 6, 9, 12 months after priming; b) single low-dose gamma-irradiation decreases the cytogenetic damage to a level below the spontaneous rate at the end of lifetime (20 months) of animals; c) ability to induce adaptive response does not depend on the age of animals at the moment of priming irradiation. In conclusion, the mechanisms underlying AR not only protect from chromosome damage induced by high-dose irradiation but also may play a role in spontaneous mutagenesis during aging of animals.     

Peculiarities of the effect of low-dose-rate radiation simulating high-altitude flight conditions on mice in vivo

In the present work, the effect of a low-dose rate of high-LET radiation in polychromatic erythrocytes of mice bone marrow was investigated in vivo. The spectral and component composition of the radiation field used was similar to that present in the atmosphere at an altitude of about 10 km. The dose dependence, adaptive response, and genetic instability in the F₁ generation born from males irradiated under these conditions were examined using the micronucleus test. Irradiation of the mice was performed for 24 h per day in the radiation field behind the concrete shield of the Serpukhov accelerator. Protons of 70 GeV were used over a period of 15–31 days, to accumulate doses of 11.5–31.5 cGy. The experiment demonstrated that irradiation of mice in vivo in this dose range leads to an increase in cytogenetic damage to bone marrow cells, but does not induce any adaptive response. In mice pre-irradiated with a dose of 11.5 cGy, an increase in sensitivity was observed after an additional irradiation with a dose of 1.5 Gy. The absence of an adaptive response suggests existence of genetic instability.     

Hypofractionated irradiation of the solid form of Ehrlich ascites carcinoma in mice by a thin scanning proton beam

The dynamics of the growth of Ehrlich ascites carcinoma in mice of the SHK line exposed to hypofractionated high-dose irradiation by a thin scanning proton beam has been analyzed for different irradiation volumes and different time intervals (from 4 to 24 hours) between two 30-Gy fractions. Irradiation of the gross tumor volume and the planned target volume was performed within the Bragg peak; the energy of protons at the outlet of the accelerator ranged from 85 to 100 MeV. Hypofractionated irradiation of the gross tumor volume of Ehrlich ascites carcinoma resulted in a more pronounced antitumor effect than the irradiation of the planned target volume. The effect did not depend on the interval between the irradiation episodes.     

Low-Intensity Femtosecond Radiation Activates the Natural Defenses of Mice in vivo

Doklady Biochemistry and Biophysics - The possibility of induction of cytogenetic damage in the bone marrow, changes in the cellularity of lymphoid organs and blood composition in mice irradiated...     

Distribution of DNA radiation damage throughout the cells and its comparison with cytogenetic injury

The distribution of DNA lesions induced by irradiation of Chinese hamster fibroblast cells with different doses was determined by the cytochemical method in situ and compared with the number of cytogenetic damages caused by the same doses. The results obtained indicate that not all the DNA lesions but only those occurred in the structurally important chromosome sites initiate chromosome mutagenesis.     

DNA damage and repair in Chinese hamster fibroblasts exposed to gamma and secondary radiation generated by 70 GeV protons

The cytochemical study of DNA damage and repair in a Chinese hamster fibroblast culture exposed to gamma-rays and secondary radiation from 70 GeV protons showed no significant differences between the two types of radiation.     

The effect of infrared and X-ray radiation on the production of reactive oxygen species in blood and induction of cytogenetic damage in the bone marrow of mice in vivo

The goal of the present work was to study the effect of infrared light (IRL) at a wavelength of 850 nm modulated by a frequency of 101 Hz with a mode of power 22 mW/cm2 and X-rays with a voltage of 200 kV at a dose rate of 1 Gy/min on the production of reactive oxygen species (ROS) in blood cells using luminol-dependent chemiluminescence, as well as on the induction of a cytogenetic damage in bone marrow cells of mice by the in vivo micronucleus test. The experiments performed have shown: 1) the level of the ROS production in blood of the mice exposed to IRL and X-rays at an adapting dose of 0.1 Gy reaches the peak value after 0.5 h and drops to the ROS level in untreated animals 5 h after either exposure; 2) irradiation of mice with IRL and X-rays at a dose of 0.1 Gy induces adaptive responses both in blood cells and bone marrow cells of mice. These adaptive responses were revealed only 5 h after both exposures, when the level of ROS production decreased to the ROS level in untreated animals; they are equal in magnitude and dynamics and persist up to 2 months.     

Correlation between the duration of radiation adaptive response in bone marrow cells of mice and the dose of gamma-irradiation in vivo

The dependence between the adaptive response and adaptive dose was studied on the basis of cytogenetic damage in polychromatic erythrocytes of bone marrow cells in mice after a low dose gamma-irradiation in vivo. The adaptive response to doses of 0.1 and 0.2 Gy was found to be retained for at least two months after irradiation. However, the adaptive dose of 0.4 Gy did not induce prolonged adaptive response.