Radiobiology and Radiation Safety

RADIOGENIC BREAST CANCER RISK PROJECTION FOR THE GEORGIAN FEMALE POPULATION

Giorgi Ormotsadze — 2024-06-26

This paper presents the results of the initial stage of the research cycle, aimed at adapting the methodology for assessing radiogenic risk to the specifics of the Georgian population. This adaptation aims to equip practicing radiologists, medical workers, and nuclear and radiation safety regulators with appropriate theoretical and methodological bases. Data from the National Center for Disease Control and Public Health of Georgia for 2017-2019, regarding the age structure of breast cancer incidence among the female population of Georgia, and demographic data from the National Statistical Office of Georgia for 2017-2019, were used. Comparative analysis utilized data from The Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute (NCI) of the USA and Cancer Statistics in Korea. Competing risk methodology was employed to estimate the age-conditional and lifetime baseline risk (LBR) of developing breast cancer. The US National Cancer Institute's DevCan 6.9.0 software was used for computation. The methodology described in the 2006 report of the National Academies of Sciences' BEIR VII Committee was used to estimate the age-conditional and Lifetime Attributable Risk (LAR) of radiogenic breast cancer. US National Cancer Institute software RadRat (version 4.3.1) and the R package for lifetime attributable risk estimation (LARisk) were used for computation. Monte Carlo simulation techniques were applied to estimate uncertainties in risk and subjective uncertainties under various assumptions. It was revealed that the lifetime baseline cancer risk for the hypothetical population of Georgia is 6.5% (95% CI: 6.2%-6.9%), for the US white non-Hispanic female population is 14.1% (95% CI: 13.99%-14.23%), and for the Korean female population, it is approximately 4.2%. For women in Georgia, the United States, and Korea irradiated with a dose of 10 mGy, the lifetime attributable risk is approximately the same, varying between 120-140 cases per 100,000 persons. The Lifetime Fractional Risk (LFR), defined as the ratio of lifetime attributable risk to lifetime baseline risk, is 3.5 times higher in the American white non-Hispanic female population than in Korea, and 2 times higher than in the female population of Georgia.

NUCLEOLAR DYNAMICS: REARRANGEMENT OF NUCLEOLUS ASSOCIATED CONDENSED CHROMATIN UNDER DNA DAMAGE INDUCED BY DIFFERENT DOSES OF γ-IRRADIATION

Lili Nadaraia — 2024-06-26

The nucleolus, a vital nuclear compartment, orchestrates ribosome biogenesis by producing polycistronic transcripts. It integrates gene-rich chromosomal domains, forming nucleolus-associated DNA (naDNA) or nucleolus-associated chromatin (NAC). The nucleolus hosts molecular machinery that guides the transcription of ribosomal genes (r-genes), pre-rRNA processing, and ribosome assembly. These are organized into nucleolar components (NCs). NAC, consisting of intra-nucleolar condensed chromatin (ICC) and peri-nucleolar condensed chromatin (PCC), is less studied, and its functional significance in establishing and maintaining the global nucleolar structure still needs to be elucidated. Previous studies demonstrated the spatiotemporal reorganization of NAC by inhibiting rRNA synthesis with DNA intercalating compound - actinomycin D (AMD), leading to profound changes in ICC and PCC. This study explores the structural reorganization of NAC under severe DNA damage induced by γ-irradiation. The focus is on ICC and PCC to investigate whether physically damaged naDNA retains the ability to move/contract, similar to the chemical inhibition observed with AMD. Histone H2B-GFP permanently transfected He-La cells were utilized for their stability and suitability for time-lapse imaging. γ-Irradiation was applied at 10 Gy (Gray) and 30 Gy doses, followed by post-irradiation imaging for 24-72 hours. Two approaches were employed: post-irradiation LSM imaging of fixed and living cells (time-lapse LSM). The structural organization of NAC, ICC network, and PCC shell were analyzed to understand the spatial changes induced by γ-irradiation. The study reveals that γ-irradiation-induced NAC inactivation dynamics mirror changes observed with AMD-induced rRNA synthesis inhibition. Under both regimes (10 Gy and 30 Gy) of γ-irradiation, ICC structures coalesce, forming more significant and more prominent clumps that migrate toward the PCC shell. This research provides insights into the dynamics of nuclear and nucleolar changes induced by severe DNA damage. The observed similarities between chemical inhibition and γ-irradiation effects on nucleolus-associated chromatin emphasize its significance in nucleolar organization. The study contributes to understanding the spatial changes in nucleolar structure under different modes of cellular stress.

STUDYING THE IMPACT OF UBIQUITIN ON RADIATION-INDUCED DAMAGE TO GENES THROUGH BIOINFORMATIC METHODOLOGIES

Irine Ioramashvili — 2024-06-26

Understanding the intricacies of cellular responses to radiation exposure is crucial for advancing radiobiology and developing effective strategies against radiation-induced pathologies. The annual radiation dose, sourced from natural and human-made sources, underscores the critical nature of this problem. Ubiquitination, as a pivotal process in protein regulation, holds the potential for alterations post-irradiation, impacting cellular recovery. The unique features of ubiquitin, beyond protein degradation, position it as one of the key players in comprehending cellular responses to radiation exposure.
Our studies, employing bioinformatic methods, have revealed the potential use of ubiquitin in the context of radiation-induced cell exposure. We conducted an analysis to assess the commonality in the genetic spectrum between genes damaged by radiation and genes associated with ubiquitin. This study utilizes RNA sequencing to identify differentially expressed genes in mice subjected to irradiation. Our investigation delves into the impact of irradiation on ubiquitin-related genes, on various functions such as chromosome segregation and organelle fission. The heightened expression of genes associated with the cell cycle suggests the foundational role of ubiquitin-related genes in organism recovery after radiation exposure. The study not only contributes to advancements in radiobiology but also offers direction for developing preventive strategies against radiation-induced pathologies.

ARE THE "LOW DOSES" TRUE LOW?

Oleksandr Mikhyeyev — 2024-06-24

The article states that the Chernobyl accident caused only a quantitative change in the pre-existing spectrum of radiobiological problems in the direction of increasing attention to the theoretical and practical issues of the effect of chronic ionizing radiation on biological objects of different levels of structural and functional organization. It is believed that chronic radiation influences biological objects in the so-called "low doses", the quantitative measure of which, however, is determined by subjectively chosen criteria. The article considers two main aspects of the problem of "low doses": firstly, to establish a relationship between these doses and subthreshold doses and, secondly, to show the role of heterogeneous tropism of biological structures in relation to their ability to absorb radionuclides from the environment, which contributes to the formation of uneven dose loads.

INFLUENCE OF Mn(II) IONS ON FROZEN AND GAMMA IRRADIATED SPIRULINA PLATENSIS

Eter Gelagutashvili — 2024-06-24

The influence of Mn(II) ions on frozen Spirulina platensis at -80°C and -20°C and high-dose irradiated 137Cs (400 kGy) was studied using a UV–Visible spectrometer. The absorption process was relatively fast in small concentrations of Mn(II) in the case of interaction with irradiated Spirulina platensis. However, for frozen Spirulina platensis, the absorption decrease was regarded as very slow. It was shown that the effect of Mn(II) ions on Spirulina platensis constituents (chlorophyll a, phycocyanin, carotenoids) under various conditions is different.

A NEW APPROACH TO THE CALCULATION OF THE CARCINOGENIC RADIOGENIC RISK

Oleksandr Mikhyeyev — 2024-06-24

A new method of calculating the carcinogenic risk factor (CRF) in accordance with the influence of ionizing radiation is proposed based on data concerning the level of spontaneous DNA degradation. It is shown that the CRF value can be at least 2 orders of magnitude less than the generally accepted values of this parameter. Accordingly, the costs of radiation protection can be reduced to the same extent. The specified estimates were obtained using assumptions about the non-threshold action of ionizing radiation and the linear dependence of 'dose-effect' on the parameter of carcinogenic action, and may be overestimated for this reason.

GIGANTISM OF PHOTOSYNTHESIZING ORGANS IN DECIDUOUS AND CONIFEROUS TREE SPECIES UNDER CONDITIONS OF ELEVATED BACKGROUND OF IONIZING RADIATION

Oleksandr Mikhyeyev — 2024-06-24

The research results on the effects of indirect action of ionizing radiation on tree species according to morphological parameters are presented. The phenomenon of gigantism in the needles of Pinus silvestris and Picea excelsa was observed at absorbed doses in the range of 2-10 Gy. In this case, the shoots carrying numerous large buds were distinguished by very large needles, the length of which was 1.5-2.5 times greater than the control values. The phenomenon of gigantism in the leaf apparatus, particularly in needles, served as a basis for considering the possible role of integral reactions to irradiation, which could be expressed in the radiation modification of physiologically normal correlative interactions between different parts and organs of the plant. The assumption that radiomorphoses in the form of giant leaf blades are caused by the reproductive death of cells of individual apical meristems, resulting in disrupted trophic interactions in the irradiated plant, is justified.

STUDY OF THE RADIONUCLIDE ABSORPTION IN TO THE VEGETATIVE ORGANS OF GRAPES TO INCREASE THE EFFICIENCY OF SOIL MECHANICAL DECONTAMINATION

Nazi Ivanishvili — 2024-06-24

Several man-made accidents at nuclear power plants and nuclear tests in recent years have highlighted the need to develop countermeasures that can effectively reduce the absorption of radionuclides by grape plants in viticulture. These measures should be cost-effective and easy to implement in everyday agricultural practice. To evaluate these parameters, we conducted experiments on 137Cs contaminated soil. Our studies revealed the dynamics of the distribution of radionuclide contamination across the vegetative parts of the grapevine, the research also highlights the significance of vertical zone depth for the penetration of radiocesium into the plant. It was concluded that shifting the depth of the space between the rows of the vineyard by the deep plow makes it possible to move the soil layer contaminated with radionuclides into relatively deep layers, which will significantly reduce the penetration of radionuclides into the grape plant.

INVESTIGATION OF RADON RADIOACTIVE EMISSION IN NATURAL WATERS OF VILLAGE KVEMO KHVITI (GEORGIA)

Lela Mtsariashvili — 2024-06-24

In the present work it was studied the content of radioactive gas radon - Rn-222 in the number of sources of surface water located nearby to village Kvemo Khviti, (Gori Municipality) in the territory of so-called Kartli artesian basins. Research was carried out during a year once a quarter. Radon detector RAD7 was used for determining radon content. It was established, that radon content in water considerably changes depending on the source location as well as on water type too. So, for example, radon content in various sources of water was within the limits from several units of Bq/L up to 10 Bq/L. A comparison with literary data has been carried out.