International journal of radiation biology最新文献

Purpose: Plant mutation breeding is an alternative approach that employs physical or chemical mutagens to develop new crop cultivars, in contrast to traditional hybridization and selection. For effective use of ionizing radiation, which induces a high mutation frequency, it is crucial to assess the mutagenic response of the target crop. This study aimed to evaluate the mutagenic response of nine soybean cultivars to different types and doses of ionizing radiation, focusing on plant growth traits and biological indicators, such as antioxidant enzyme activities and lipid peroxidation.

Materials and methods: In this study, we assessed nine soybean cultivars exposed to varying doses of ionizing radiation (gamma rays and electron beams), determining the lethal dose 50 (LD₅₀) for survival rate and reduction dose 50 (RD₅₀) for shoot growth reduction. We also evaluated biological responses, including malondialdehyde (MDA) content and the activities of three antioxidant enzymes: ascorbate peroxidase (APX), superoxide dismutase (SOD), and peroxidase (POD).

Results: The average LD₅₀ and RD₅₀ were 248 Gy and 178 Gy for gamma rays and 359 Gy and 321 Gy for electron beams, respectively. At doses near the LD₅₀, MDA content showed a decreasing trend under both radiation types. Conversely, the activities of the three antioxidant enzymes generally decreased under gamma rays but increased under electron beams.

Conclusions: These findings demonstrate distinct growth and biological responses to gamma rays and electron beams, suggesting that the choice of radiation type and dose should be tailored to breeding objectives. This provides a practical basis for using electron beams as an alternative to gamma rays in soybean mutation breeding.

Purpose and introduction: A number of countries, including Canada, are researching the development of Small Modular nuclear Reactors (SMR) for electrical power generation. This paper aims to point impact assessors to other previous historical deployments of SMRs. These types of reactors could be used to power remote locations, for heavy industry applications, and for on-grid applications. One possible use for a SMR is to provide power to remote Arctic communities. Small nuclear reactors are not a new concept. The Americans constructed small nuclear reactors for remote areas in the 1960s, under the U.S. Army Nuclear Power Program, where they built and operated four reactors in remote regions of Alaska, Greenland, Antarctica, and in the Panama Canal Zone on a barge. More recently, Russia placed two nuclear reactors on a barge and towed it to a remote Arctic community to replace diesel power generation. It is now providing electricity to that remote location. Health Canada, a federal department of the Government of Canada, plays a role in human health risk assessment for major resource and infrastructure projects in Canada and is therefore interested in the history of SMRs and the potential radio-ecological consequences of future projects in terms of radiation dose received by humans. Because Health Canada also has a role in emergency preparedness, this paper also examines the historical issues around the AVR reactor, a high temperature gas cooled reactor, which is a SMR reactor type being considered in Canada.

Conclusions: This review paper provides a brief overview of SMRs in general and discusses potential challenges for modeling human health risk in remote locations. For example, in doing assessments for nuclear reactors, often an environmental transport model is used which is dependent on transfer factors which are determined from measurements. These transfer factors most likely will change in the Arctic environment.

Purpose: To explain the multiple high level scientific contributions of Miral Dizdaroglu to our understanding of oxidatively generated DNA damage, which plays a pivotal role in radiation chemistry and multiple human diseases, especially cancer.

Materials and methods: A literature review of Miral's contributions and his interactions with my research group.

Results: Miral was a pioneer in understanding the mechanisms, measurement and repair of damage to DNA (and, more recently, RNA) by free radicals and other reactive oxygen species (ROS), initially in radiation systems and later in biological systems, including the human body. My research group learned an enormous amount from him when I was privileged to work together with him and publish multiple joint papers. In this review, I describe the history of the field from my perspective and describe several of Miral's fundamental contributions, as well as some of the controversies surrounding his work.

Conclusion: Miral's research contributions were outstanding, and we have lost a major contributor to the field of oxidatively generated damage to nucleic acids.

Purpose: This pilot study investigated promoter DNA methylation in key DNA damage response (DDR) genes in individuals chronically exposed to low-dose ionizing radiation (LDIR) in Kerala, India.

Materials and methods: 26 healthy male residents of Kerala's high level natural radiation areas (HLNRA) were selected and stratified based on lifetime cumulative radiation dose (<100 mSv, n = 10; >100 mSv, n = 16). Promoter methylation of 16 DDR-related genes was assessed using Methylation Sensitive High resolution Melting (MS-HRM), with LINE-1 as a surrogate for global methylation. Gene expression of selected targets was measured by RT-qPCR.

Results: Global DNA methylation showed no significant difference across exposure groups. In contrast, promoters of RAD23B, DNMT3A, MRE11A, and BRCA1 were significantly hypermethylated in individuals with cumulative dose >100 mSv, with RAD23B showing the strongest correlation. Gene expression displayed high inter-individual variation with no dose-dependent changes or correlation with promoter methylation.

Conclusions: Chronic LDIR exposure induces significant hypermethylation in specific DDR genes like RAD23B, DNMT3A, MRE11A, and BRCA1, suggesting a possible selective modulation of DNA repair pathways. but direct functional impact on gene expression was not observed in this study. The observed promoter methylation and gene expression alterations provide preliminary evidence of epigenetic modifications in response to chronic LDIR.

Purpose: Radiation-induced meningiomas (RIMs) are an uncommon late complication of cranial irradiation that frequently display aggressive behavior. Although recent genomic and epigenomic studies have redefined sporadic meningiomas into four molecular groups with distinct biological and clinical characteristics, the same analysis has not yet been conducted on RIMs. This study sought to contextualize RIMs within the current methylation-based meningioma classification.

Methods: DNA methylation data from RIMs (n = 20) were integrated with a reference cohort of sporadic (n = 121) meningiomas previously used to define molecular subgroups. Molecular group membership was assigned using a supervised machine-learning approach. Copy-number alterations and pathway enrichment analyses were derived from methylation data, and clinical features were compared between RIMs and sporadic meningiomas.

Results: Supervised molecular classification assigned 70% RIMs to the hypermetabolic subtype. The RIM cohort demonstrated broad DNA hypomethylation enriched for metabolic and biosynthetic pathways. Copy-number profiling revealed widespread chromosomal instability, including recurrent 22q loss involving NF2 and SMARCB1 as well as PTEN, MYB, and C19MC, consistent with the copy number alterations observed in hypermetabolic meningiomas.

Conclusions: RIMs predominantly align with the hypermetabolic molecular group, characterized by metabolic pathway activation and genomic instability. This distribution indicates a distinct molecular profile compared with sporadic meningiomas.

Purpose: Ecological observations in the Chernobyl Exclusion Zone (CEZ) show that populations of large mammals, such as wolves, boars, and elks, have recovered and remain stable despite chronic exposure to radiation. This study applies the Whack-A-Mole (WAM) model-a dynamic, dose-rate-dependent mathematical model-to the CEZ environment to explain the observed ecological stability under persistent low-dose-rate exposure that conventional Linear Non-Threshold (LNT) models fail to predict.

Materials and methods: The WAM model explicitly incorporates removal processes of radiation-induced mutated cells, allowing evaluation of mutation frequency at steady state under chronic exposure. Using standardized parameters calibrated across species and reported dose rates from wolf tracking studies (external 10-35 mGy/y; internal + external up to 87 mGy/y), we calculated the time evolution and equilibrium values of mutation frequency in mammalian cells.

Results: The equilibrium value of the mutation frequency increased as the radiation dose increased. This increase, however, remained below 1% of the natural baseline even under the upper-end CEZ exposure (87 mGy/y). At mean (18.4 mGy/y) and maximum (35.9 mGy/y) external dose rates, increases were only +0.18% and +0.35%, respectively. The boundary between LNT-like linear behavior and WAM saturation occurred around 330 hours regardless of dose rate. In contrast, the LNT model predicts mutation accumulation at levels incompatible with the continued growth of wolf populations, contradicting ecological observations in the CEZ.

Conclusions: The WAM model characterizes the dynamics of mutation frequency under chronic exposure and provides a mechanistic interpretation compatible with the absence of population-level health effects observed in the CEZ. Observed molecular responses, including endogenous retrovirus (ERV) activation and immune alterations, represent functioning repair and removal mechanisms rather than pathological damage.

Purpose: This review summarizes the discoveries of 8-bromopurine nucleosides (8-Br-Pu), particularly 8-bromo-2'-deoxyadenosine (8-Br-dA) and 8-bromo-2'-deoxyguanosine (8-Br-dG), in chemistry and biology over the past two decades. It compiles available data on the reactions of hydrated electrons (e_aq^-) with various 8-bromopurines, as determined by pulse radiolysis and supported by theoretical studies. Three distinct mechanistic pathways are identified: dissociative electron attachment, sequential electron transfer-proton transfer, and concerted electron-proton transfer. This review also highlights the use of 8-Br-dA and 8-Br-dG in the synthesis of a library of 5',8-cyclopurine nucleosides (cPu) for quantifying them in genetic material and incorporating them into oligonucleotides (ODNs) for DNA repair research. Additionally, the summary covers the use of 8-Br-dA and 8-Br-dG embedded in various ODNs to study excess electron transfer (EET), their potential as radiosensitizers, and their formation in vivo via hypobromous acid.

Conclusion: Based on radiation chemistry, our understanding of the one-electron reduction of 8-Br-dA and 8-Br-dG has been enhanced substantially. This mechanistic background is crucial for a better understanding of and addressing their significant roles in the biological environment, such as DNA radiosensitizers for cancer radiation therapy or as biomarkers for early inflammation.

Purpose: Radiotherapy is a widely used cancer treatment, and radiation-induced fibrosis is a frequent late effect that can significantly reduce patients' quality of life. Many approaches for evaluating and grading radiation late damage, such as fibrosis, are based on semi-quantitative methods. This study aimed to characterize the histopathological changes associated with late radiation damage in mice after exposure to proton and photon irradiation, and to evaluate the applicability of stereological methods for quantitative assessment of these changes. Materials and Methods: A mouse leg model was used to evaluate and compare the potential radiation-induced functionality impairments with histopathological changes. Mice (n = 32) were subjected to a single high dose of photon (n = 18) or proton (n = 14) irradiation on the right foot, while the left, unirradiated leg served as a control. Late damage was assessed using a leg contracture assay, while histopathological changes were quantified using stereological point counting. Results: Proton- and photon-irradiated legs histologically showed a dose-dependent increase in connective tissue and epidermal thickness and reduced adipose tissue. Adipose tissue was replaced with connective tissue, adnexal structures disappeared, and the epidermis was altered. An association was found between leg contracture in the living mice and histopathological connective tissue changes, suggesting that fibrosis contributes to impaired joint mobility. However, discrepancies between histological findings and the leg contracture assay indicate that factors other than connective tissue changes, such as tendon damage and experimental uncertainties, influence joint movement. Conclusions: This study provides a quantitative approach for associating radiation effects in normal tissue with histopathological changes, offering a valuable model for investigating late radiation-induced damage. The study highlights the need for larger studies to fully elucidate the late side effects of proton and photon irradiation.

Purpose: In order to estimate the effect of radiation exposure on the workers of a uranium enterprise, teeth samples were collected for EPR dosimetry of tooth enamel from workers of uranium mines living in Shantobe settlement (Akmola region, Northern Kazakhstan) and from residents of this settlement who had never worked in the mine as a control.

Methods: The accumulated radiation doses in enamel were estimated based on the magnitude of the radiation-induced EPR signal in the samples. Excess (additional) doses were obtained after subtracting the contribution of natural radiation at typical levels during enamel age, and they were interpreted as caused by radiation in the work environment and by radioactive contamination of the territory.

Results: For the personnel of the uranium mining enterprise (17 teeth samples), the average excess dose was 90 ± 20 mGy (standard uncertainty of the average is indicated here and below). For the rest of the population who did not work at the mine (10 teeth samples), the average excess dose is estimated at 20 ± 12 mGy.

Conclusions: A higher mean dose and greater variation were observed for miners in comparison to non-mining people in the same settlement. These differences were likely due to the occupational exposure.

Purpose: This mini-review aims to synthesize current knowledge regarding radiation-induced effects on female fertility and reproductive capacity, and to identify knowledge gaps relevant to radiation protection.

Methods: We critically examined evidence from developmental biology, animal models, clinical studies, and epidemiological investigations. Key topics include germ cell and follicle biology, radiation dose thresholds, therapeutic exposures, and environmental and occupational contexts.

Results: Female germ cells are highly radiosensitive, with animal models indicating a mean lethal dose as low as 0.05-0.15 Gy in primordial oocytes. In humans, pelvic irradiation increases risks of acute ovarian failure, premature ovarian insufficiency, and infertility, depending on dose and age at exposure. Cranial irradiation further impairs fertility through damage to the hypothalamic-pituitary axis. In contrast, evidence from occupational and environmental exposures is scarce, with most studies addressing miscarriage or perinatal outcomes rather than infertility itself.

Conclusions: While advances in oncofertility research have clarified therapeutic risks, systematic data on environmental and occupational exposures are lacking. Strengthened prospective studies and integration of fertility-specific biomarkers are urgently needed to inform comprehensive radiation protection strategies.