Volume 69, Nº 1 (2024)

The paper dwells upon the key outcomes of the 70-th Session of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) which took place during 19-23 June 2023. Experts from 30 UNSCEAR Member-states as well as the representatives of international organizations participated in the work of the Session. Within the framework of the meetings of the working group and subgroups the documents on the following projects were discussed: R.757 “Second primary cancer after radiotherapy”, R.758 “Epidemiological studies of radiation and cancer”, R.759 “Evaluation of public exposures to ionizing radiation from natural and other sources”, R.760 “Evaluation of diseases of the circulatory system from radiation exposure” and R.761 “Nervous system effects of ionizing radiation”. The Committee also discussed interim reports: UNSCEAR/70/7 “Implementation of the Strategy to improve collection, analysis and dissemination of data on radiation exposure (including consideration of the Committee’s ad hoc working group on sources and exposure)”, UNSCEAR/70/8 “Implementation of the Committee’s Future Programme of Work and proposals for 2025‒2029 period (including consideration of the Committee’s ad hoc working group on effects and mechanisms)”, working materials for this document “Terms used by the United Nations Scientific Committee on the Effects of Atomic Radiation”, UNSCEAR/70/9 “Implementation of public information and outreach strategy for 2020–2024” and Report to the UN General Assembly.

Aim: To study the patterns of changes in the number of foci of phosphorylated DNA double-strand break repair proteins H2AX (γH2AX) and ATM (pATM) in cultured human mesenchymal stem cells (MSCs) 1‒48 hours after exposure to X-ray radiation at doses of 40, 80, 160 and 250 mGy.

Material and methods: We used the primary culture of human MSCs, obtained from the collection of LLC “BioloT” (Russia). Cells were irradiated using a RUB RUST-M1 X-ray biological unit (Diagnostika-M LLC, Moscow, Russia) equipped with two X-ray emitters at a dose rate of 40 mGy/min (voltage of 100 kV, an anode current of 8 mA, and a 1.5 mm Al filter) and 4 °C temperature. To quantify the yield of γH2AX and pATM foci immunocytochemical staining was carried out with the use of γH2AX and pATM antibody respectively. Statistical analysis of the obtained data was carried out using the statistical software package Statistica 8.0 (StatSoft). To assess the significance of differences between samples, Student’s t-test was used.

Results: It was shown that the kinetics of changes in the number of γH2AX foci after irradiation at doses of 160 and 250 mGy and low (40‒80 mGy) doses are significantly different. In contrast to the significant (50‒60 %) decrease in the number of γH2AX foci observed 6 hours after irradiation at doses of 160 and 250 mGy, after irradiation at low doses, no significant decrease in γH2AX foci was observed at this time point. Analysis of the colocalization of γH2AX foci with pATM foci indicates that the mechanisms for maintaining a high number of γH2AX foci 24‒48 hours after low-dose irradiation are ATM independent. A hypothesis has been put forward to explain the phenomenon of maintaining the number of γH2AX foci 24‒48 hours after irradiation in low doses by replicative stress caused by stimulation of proliferation against the background of hyperproduction of free radicals, resulting in additional formation of DNA double-strand breaks and phosphorylation of H2AX by ATR kinase.

Relevance: A number of researchers consider the study of the radioprotective properties of non-toxic or low-toxic natural substances to be a promising direction. A special place among them is occupied by antioxidants and participants in the basic reactions of metabolism. In order to avoid methodological errors when performing these studies, it is necessary to conduct a number of additional experiments. For example, in order to study the properties of various substances on cell cultures using tablet readers, it is first necessary to make sure that these substances do not affect the ability of cells to adsorb to the bottom of the wells of the tablet and do not interfere with cell proliferation. And if such an influence is detected, further experiments with these substances should be planned taking into account the information received.

Purpose: To search the effect of ascorbic, malic and succinic acids on the ability of lung adenocarcinoma cells (A549) to adhere in a 96-well plate, followed by the onset of proliferation by fluorescence registration method using Hoechst-33342 fluorophore.

Methodology: The experiment was carried out in a 96-well tablet. The working concentration of Hoechst-33342 was 1 μg/ml (1.62 μM). Fluorescence was recorded at a wavelength of 460 nm when the samples were excited by light with a wavelength of 355 nm. In an experiment to study the effect of ascorbate, malate and succinate on cell adhesion and proliferation, 20,000 cells and a solution of one of these substances in a working concentration of 2 mM were introduced into the cells of the tablet. The number of cells in the wells was estimated based on the fluorescence of Hoechst-33342 after a day of incubation.

Result: In samples containing 2 mM succinic acid and ascorbic acid, a statistically significant decrease in the intensity of fluorescence was observed compared with a sample that did not contain the drug. This suggests that these compounds negatively affect the growth properties of the A549 culture: they inhibit cell adhesion or slow down their proliferation.

Scope of the results and conclusions:The results obtained are necessary for the methodologically correct planning of the most detailed studies on the A549 cell line model using fluorescent methods, including studies on the radioprotective properties of ascorbate, malate and succinate under the influence of rare ionizing and neutron radiation.

Background: The issue of assessing the features of factors affecting the formation of radiation doses of astronauts while in orbit of the Moon and on its surface remains insufficiently studied, which is important for ensuring the anti-radiation safety of astronauts on lunar missions.

Purpose: To analyze the factors influencing the formation of the radiation dose of astronauts at the stage of finding the spacecraft in orbit of the Moon and the lander on its surface.

Material and methods: The features of the dose load levels on astronauts at the stages of the Moon’s orbit and on the Moon’s surface are analyzed and generalized, calculation methods are used taking into account the orbit of the spacecraft around the Moon, the anti-radiation properties of the materials of the lander and spacesuit and the time spent in them during a short-term lunar mission.

Results: The total radiation doses of astronauts for 14 days, calculated according to dosimetric measurements during the years of low solar activity (2009 and 2018‒2019), are 19.5‒23.2 mSv for astronauts staying in a spacecraft in lunar orbit, and from 22,7 to 24,0 mSv for astronauts on the Lunar surface, depending on the mass thickness of the protection at the maximum permissible 250 mSv for 1 month. An increase in the mass thickness of the anti-radiation protection of the lander in the equivalent of aluminum from 1.5 to 3-5 g/cm² and the lunar spacesuit in the equivalent of aluminum from 0.2 to 0.5‒1 g/cm² will reduce the total radiation dose of astronauts no more than 1.3 times during a 14-day stay on the surface of the moon. The results indicate that in order to minimize the radiation doses that astronauts receive during a lunar mission, it is important to take into account the forecast of solar activity in order to optimize the launch time of the spacecraft in the «windows» with minimal levels of radiation exposure.

Conclusion: When predicting radiation hazard levels for astronauts during a short-term lunar mission, it is necessary to assess the levels of exposure to cosmic ionizing radiation both in the orbit of the Moon, depending on the lunar trajectory of the spacecraft, and on the surface of the Moon, taking into account the time spent in the lunar module and in a spacesuit, as well as levels of solar activity. It is important to take into account the analyzed features of the formation of cosmonauts’ radiation doses while orbiting the Moon and on its surface when predicting the time limits of the lunar mission, anti-radiation protection of astronauts and their compliance with the regulatory limits of exposure.

Purpose: To conduct a comparative retrospective analysis of the results of cytogenetic studies of workers at facilities using ionizing radiation in 2003 and 2018.

Material and methods: The material for the study was the venous blood of workers at facilities using ionizing radiation. The study was conducted on conditionally healthy workers (n = 11), of which 2 groups were formed: the control group (blood sampling and cytogenetic study of blood lymphocytes were carried out in 2003) and the study group (blood sampling was carried out in 2018). For all examined individuals, blood lymphocytes were cultured and standard cytogenetic analysis followed by statistical processing of the results.

Results: A comparative retrospective analysis showed that in the study group (2018) compared to the control group (2003), the frequency of chromatid fragments was reduced (p = 0.0452). The frequencies of other types of cytogenetic disorders studied (aberrant cells, chromosomal fragments, dicentric and circular chromosomes) do not differ between groups.

Cytogenetic abnormalities in blood lymphocytes are a highly sensitive measure of the degree of radiation exposure in the early and late periods after exposure and can be used as a biological indicator of ionizing radiation.

The absence of differences in indicators of radiation exposure markers may be due to the large interval of time that elapsed after irradiation until the moment of examination (15 years), during which lymphocytes with chromosomal aberrations were eliminated from the blood. In the future, for the completeness of the retrospective analysis and the accuracy of the result, it is planned to conduct a study on a larger sample with a shorter time interval between cytogenetic studies.

Conclusion: The result of this work allows us to supplement the understanding of the mutation process in the somatic cells of individuals exposed to ionizing radiation in the course of professional activities and indicates genotoxicity.

Introduction: Uranium, which is the raw material basis of the nuclear industry, is capable of causing adverse medical and biological consequences for workers who come into contact with its compounds in the course of their professional activities. In order to study this effect and to study in detail the biomedical consequences of the effects of uranium compounds on the body of personnel of nuclear power facilities, it is necessary to form a cohort of persons engaged in work with uranium compounds. One of the key elements of the uranium conversion technology carried out within the framework of sublimation production is the production of raw uranium hexafluoride for subsequent isotopic enrichment.

Purpose: To form and characterize a cohort of sublimate production of the personnel of the Siberian Chemical Plant involved in work with uranium compounds in the period 1953–2000.

Material and methods: The source of information was the regional medical dosimetric register of Seversk Biophysical Research Center, containing information on all current and former employees of the Siberian Chemical Plant (about 65,000 people) from the moment of the company’s foundation to the present.

Results: A cohort of Siberian Chemical Plant workers involved in work with uranium compounds in the period 1953–2000 has been formed and described. The cohort consists of 577 people (475 men and 102 women). Biomedical information and dosimetric information about the employees included in the cohort are included in the created database of the personnel of the Siberian Chemical Plant involved in working with uranium compounds in the period 1953–2000.

Conclusion: The formed cohort and database will allow conducting epidemiological studies to assess the morbidity and mortality of personnel due to malignant neoplasms, as well as making scientifically sound conclusions about the role of uranium compounds in the occurrence and mortality due to malignant neoplasms.

Purpose: To demonstrate the effectiveness of water bolus, combined with individual immobilization for the treatment of lesions in the pedal region of the foot on a patient with isolated cutaneous T-cell lymphoma lesions.

Material and methods: Construction of individual immobilization devices, simultaneously functioning as a bolus, in two clinical cases of T-cell cutaneous lymphoma radiation therapy in the pedal region of the foot, along with 3D-CRT and VMAT treatment planning, accompanied by retrospective evaluation of interfractional motion.

Results: The proposed methodology demonstrates the effectiveness of the individual immobilization devices in minimizing interfractional motion, as well as the benefit of the bolus effect of the device in achieving optimal dose distribution in the treatment of superficial T-cell lymphoma lesions.

Purpose: To study the capabilities of the new radiopharmaceutical ^99mTc-sentiscan in the visualization of sentinel lymph nodes in patients with breast cancer.

Material and methods: A survey of 178 people diagnosed with breast cancer. Patients were divided into two groups depending on the route of administration of the radiopharmaceutical. The day before surgical treatment, all subjects were injected with a radiopharmaceutical using a syringe with an activity of no more than 120 MBq, in a volume of 0.3‒0.4 ml. The visualized sentinel lymph nodes were marked on the skin using a patented device – «Device for external marking of sentinel lymph nodes during radionuclide visualization». Intraoperative search for sentinel lymph nodes was carried out using gamma detectors Gamma-Finder II or Radical, followed by urgent histological examination.

Results: Radioisotope visualization of sentinel lymph nodes using the domestic radiopharmaceutical ^99mTc-sentiscan: in the first group (the drug was administered peritumorally) was 100 %, the average number of visualized lymph nodes in this group was 2.2; in the second group (the drug was administered subareolarly) ‒ 99.1 %, the average number of visualized lymph nodes ‒ 2.6. In the first group of patients, metastatic lesions of sentinel lymph nodes were detected in 8 cases (13.1 %), and in the second group ‒ in 14 (11.9 %). All lymph nodes were mapped in the axillary region on the side of the tumor process.

Conclusion: The possibility of the radiopharmaceutical ^99mTc-sentiscan for the identification and biopsy of sentinel lymph nodes in patients with breast cancer was assessed. The use of the domestic ^99mTc-sentiscan makes it possible to visualize sentinel lymph nodes in patients with breast cancer and detect their location in 99.1‒100 % of cases. Taking into account the results obtained, the expanded indications for the use of the radiopharmaceutical and the cost of the kits, ^99mTc-sentiscan is more preferable for use in clinical practice.

Purpose: Conducted research was aimed at studying of microdistribution of ²³⁹Pu particles in liver tissues of former MAYAK PA workers. Current research is a continuation of studies of microdistribution of ²³⁹Pu particles in lung tissues of former MAYAK PA workers that were conducted earlier and published.

Material and methods: Neutron-induced track method was utilized for studying the distribution of sizes of ²³⁹Pu nanoparticles. At Southern Urals Biophysics Institute this method was improved, optimized and adapted for studying of plutonium microdistribution in biological tissues.

Liver samples studying started in 2020. Samples were chosen from Radiobiology Human Tissue Repository SUBI. Liver samples from Voronezh regional pathology and anatomical bureau and Tobolsk regional hospital #3 were obtained within the search of contemporary liver tissues.

Application of liver samples on track detectors and their assembling into plastic box for following irradiation in nuclear reactor at Joint stock company “Institute of Nuclear Materials” was provided similarly to lung samples. Standart pathohistological techniqes were applied. The thickness of liver slides was 5 micrometers.

Basic track count was conducted on the results of 36-minute etching. Single tracks and stars were counted. Stars with high density of tracks that exceeded counting abilities were counted on the results of 9-minute etching either directly (if all tracks were distinct) or in accordance with patent for invention RU 2733491 C2 that enables to calculate the number of tracks in a star by distinct peripheral tracks.

Results: This study quantitatively compares ²³⁹Pu microdistribution in liver of three deceased former Mayak PA workers who were exposed to ²³⁹Pu by inhalation and three deceased subjects who had been never employed at Mayak PA (from Ozyorsk, Voronezh, Tobolsk). The comparison is made utilizing neutron-activation method of measurement. The results are compared to the results of less-sensitive autoradiographic method. The study demonstrated that the most of ²³⁹Pu activity in liver is concentrated in liver lobules. ²³⁹PuO₂ nanoparticles found didn’t exceed the size of 20 nm. Track density for three liver samples of subjects who had been never employed at Mayak PA differed for less than two times.