High Radiation Levels Research Articles

Radiotolerant endophytic bacteria and analysis of the effects of 137Cesium on the metabolome of Pantoea sp.

Some bacteria have developed mechanisms to withstand the stress caused by ionizing radiation. The ability of these radioresistant microorganisms to survive high levels of radiation is primarily attributed to their DNA repair mechanisms and the production of protective metabolites. To determine the effect of irradiation on bacterial growth, we propose to compare the metabolites produced by the irradiated isolates to those of the control (non-irradiated isolates) using mass spectrometry, molecular networking, and chemometric analysis. We identified the secondary metabolites produced by these bacteria and observed variations in growth following irradiation. Notably, after 48h of exposure to radiation, Pantoea sp. bacterial cells exhibited a significant 6-log increase compared to non-irradiated cells. Non-irradiated cells produce exclusively Pyridindolol, 1-hydroxy-4-methylcarbostyril, N-alkyl, and N-2-alkoxyethyl diethanolamine, while 5'-methylthioadenosine was detected only in irradiated cells. These findings suggest that the metabolic profile of Pantoea sp. remained relatively stable. The results obtained from this study have the potential to facilitate the development of innovative strategies for harnessing the capabilities of endophytic bacteria in radiological protection and bioremediation of radionuclides.

Antioxidant Systems in Extremophile Marine Fish Species

Living in extreme environments, marine organisms face constant exposure to a range of stressors, such as high radiation levels, fluctuations in temperature, and oxidative stress. Understanding extremophile fishes is crucial because it gives us valuable insights into the biochemical, physiological, and developmental processes that govern life, by observing how they operate under natural stressors. Among the most fascinating adaptations is the existence of specialised enzymes and compounds that function as potent antioxidants, successfully counteracting reactive oxygen species’ deleterious effects. In this review, we analysed the findings from several studies on Antarctic and deep-sea fish species, while highlighting the environmental stressors effects toward the antioxidant system. The antioxidant defences of the considered extremophile fishes have been extensively studied, but there is still much to learn to fully understand this complex system, while the relative research is still ongoing. Consequently, we are properly anticipating further advancements over the next few years about our understanding of crucial physiological processes that support cell survival.

Effects of temperature, chloride and perchlorate salt concentration on the metabolic activity of Deinococcus radiodurans

The extremophile bacterium Deinococcus radiodurans is characterized by its ability to survive and sustain its activity at high levels of radiation and is considered an organism that might survive in extraterrestrial environments. In the present work, we studied the combined effects of temperature and chlorine-containing salts, with focus on perchlorate salts which have been detected at high concentrations in Martian regolith, on D. radiodurans activity (CO2 production rates) and viability after incubation in liquid cultures for up to 30 days. Reduced CO2 production capacity and viability was observed at high perchlorate concentrations (up to 10% w/v) during incubation at 0 or 25 °C. Both the metabolic activity and viability were reduced as the perchlorate and chloride salt concentration increased and temperature decreased, and an interactive effect of temperature and salt concentration on the metabolic activity was found. These results indicate the ability of D. radiodurans to remain metabolically active and survive in low temperature environments rich in perchlorate.

Radioactivity as a driver of bacterial community composition in naturally radioactive mineral springs in the French Massif Central.

Some natural environments on Earth are characterised by high levels of radiation, including naturally radioelement enriched mineral springs in the French Massif Central. Therefore, naturally radioactive mineral springs are interesting ecosystems for understanding how bacterial populations in these springs have adapted to high levels of natural and chronic radioactivity over the very long term. The aim of this study was to analyse the bacterial communities of sediments from five naturally radioactive mineral springs in the French Massif Central, sampled in autumn 2019 and spring 2020, and to observe whether radionuclides, compared to other physicochemical parameters, are drivers of the bacterial community structuring in these extreme environments. Physicochemical measurements showed that two springs, Dourioux and Montagne had high radioelement concentrations/activities (uranium, thorium and radon). Analysis of the structure of the bacterial communities, by next generation sequencing based on 16S rRNA gene sequencing, showed that the presence of radionuclides in Dourioux and Montagne, did not lead to a reduction in bacterial diversity and richness compared to the other springs. However, Dourioux and Montagne were characterised by specific bacterial populations, whose presence correlates with the radioelement concentrations/activities measured in these springs. This suggests that radioelements could partly explain the structuring of bacterial communities in these springs. In addition, several of these operational taxonomic units (OTUs) specific to Dourioux and Montagne, mainly affiliated to Proteobacteria, Firmicutes, Acidobacteria, Actinobacteria, and Bacteroidetes, could be involved in the biogeochemistry of radionuclides through different mechanisms (biosorption, biomineralisation, bioaccumulation, and bioreduction), which would allow the development of other bacterial species sensitive to these metals/radioelements. In particular, the co-occurrence of sulphate and/or iron-reducing bacteria, capable of bioreducing uranium, with fermentative bacteria, releasing sources of organic carbons, reflects associations of bacteria with complementary functions that allow them to grow in this peculiar environment and maintain a high diversity in these extreme environments. This study has provided a better understanding of the structuring of bacterial communities exposed to ionising radiation for thousands of years in naturally radioactive environments.

Drivers of agrivoltaic perception in California and North Carolina

The last decade has seen dramatic growth in solar power. In some regions, the most favorable land for solar panels is farmland, which is often flat and exposed to high levels of irradiance. At the same time, the agricultural sector is faced with growing challenges, notably changing water availability and increasingly frequent extreme weather events. The combination of these trends presents an opportunity for a synergistic relationship between the agriculture and solar sectors: agrivoltaic systems (AVS). In AVS, solar panels are placed above and between crops, such that the same land produces both food and energy. This system has beneficial microclimate impacts, such as reduced evapotranspiration. Yet, despite these benefits there has been limited uptake of AVS. One reason may be hesitation on the part of farmers, whose perceptions of AVS have been explored little. This analysis seeks to address part of this gap by exploring the relationship between farmer perceptions and interest in AVS. A Likert scale survey was designed and distributed to farmers across two large, agriculturally productive states, North Carolina and California. Responses from the 41 participants who fully completed the survey suggest that farmers who perceive AVS as diversifying their income or whose goals include reducing water use are the most interested in installing AVS. Respondents also identified financial viability as a major concern, agreeing that upfront cost is a major barrier to AVS, and markets as the most influential driver of crop decisions. These findings provide insights for policymakers interested in expanding AVS, particularly in response to environmental stressors, such as water scarcity and extreme weather events. They also suggest the aspects of AVS that may be most important to farmers, and most effective in encouraging AVS uptake. This information can support efforts to promote AVS, contributing to sustainable agriculture.

Assessment on thermophysical properties of nano enhanced heat transfer fluid with hexagonal boron nitride nanoparticles for thermal management of photovoltaic thermal (PVT) system

One of the most promising sources of energy to meet demand and reduce pollution from fossil fuels is solar energy. To maximize energy conversion, solar technology efficiency, whether it comes from thermal systems, photovoltaic panels, or a hybrid known as photovoltaic-thermal (PVT) systems is critical. This work looks into the formulation and thermophysical of hBN-water nanofluids, with an emphasis on how they might be used as coolants in PVT systems to improve electrical performance. After a meticulous preparation process, the nanofluids exhibited exceptional stability, confirmed through visual inspection and zeta potential evaluation. Zeta potential analysis revealed consistent values across different temperatures and volume concentrations. Density decreased with temperature, while viscosity increased with volume concentration but decreased with temperature. Thermal conductivity showed a consistent increase with volume concentration and temperature. Through optimization, the 0.5 vol% concentration was identified as optimal for the PVT system. Compared to no coolant and water-based coolant scenarios, hBN-water nanofluids effectively regulated cell temperatures between 40.25°C and 46.34°C, demonstrating superior thermal conductivity and heat transfer properties. Moreover, the nanofluid coolant enhanced the PVT system's electrical performance. Open circuit voltage remained consistent (19.67 V to 20.81 V), short circuit current and output power improved with higher irradiance levels, and electrical efficiency, thermal efficiency and overall efficiency reached 5.73–5.88 %, 54.15–62.73 % and 59.88–68.62 % respectively These findings underscore the potential of hBN-water nanofluids in enhancing thermal management and electrical performance in solar energy systems. By minimizing thermal losses and maximizing electrical output, nanofluid coolants offer promising avenues for optimizing the efficiency of renewable energy technologies.

The hazardous protective glass material for gamma, neutrons, and behaviors of charged particles: Results of adding barium oxide concentrations

The objective of this research is to examine the effectiveness of gamma and neutron shielding, as well as to investigate the behavior of charged particles in glass compositions with the formula xBaO:5SnO2:10Na2O:10CaO:10Li2O: (65-x)SiO2. These glass compositions will be created using the melt quenching technique (MQT). The findings indicated that the physical characteristics, such as density and molar volume, exhibited a comparable pattern. The gamma-ray shielding capacity of the glass system was assessed by comparing it with theoretical, simulation, and experimental values obtained using WinXCom, PHITS (Particle and Heavy Ion Transport Code System) Monte Carlo simulation, and Compton scattering technique (CST), respectively. The results revealed that the total attenuation (μm), effective atomic number (Zeff), and electron density (Nel) exhibited a consistent increase with higher BaO contents. Additionally, this increase led to a decrease in scattering energy within the Compton energy range. The half-value layer (HVL) exhibited superior shielding characteristics compared to alternative substances. Furthermore, the addition of more BaO atoms in the glass structure results in an increased ability of the material to stop the motion of charged particles with larger mass. Conversely, lower concentrations of BaO demonstrate an efficient barrier against fast neutrons. The simulation revealed that BaO can be utilized as an additive in glass materials to enhance their radiation shielding properties in environments with high levels of radiation.

Protective effects of tauroursodeoxycholate against radiation-induced intestinal injury in a mouse model

In patients with high-level radiation exposure, gastrointestinal injury is the main cause of death. Despite the severity of damage to the gastrointestinal tract, no specific therapeutic option is available. Tauroursodeoxycholic acid (TUDCA) is a conjugated form of ursodeoxycholic acid that suppresses endoplasmic reticulum (ER) stress and regulates various cell-signaling pathways. We investigated the effect of TUDCA premedication in alleviating intestinal damage and enhancing the survival of C57BL/6 mice administered a lethal dose (15Gy) of focal abdominal irradiation. TUDCA was administered to mice 1 h before radiation exposure, and reduced apoptosis of the jejunal crypts 12 h after irradiation. At later timepoint (3.5 days), irradiated mice manifested intestinal morphological changes that were detected via histological examination. TUDCA decreased the inflammatory cytokine levels and attenuated the decrease in serum citrulline levels after radiation exposure. Although radiation induced ER stress, TUDCA pretreatment decreased ER stress in the irradiated intestinal cells. The effect of TUDCA indicates the possibility of radiation therapy for cancer in tumor cells. TUDCA did not affect cell proliferation and apoptosis in the intestinal epithelium. TUDCA decreased the invasive ability of the CT26 metastatic colon cancer cell line. Reduced invasion after TUDCA treatment was associated with decreased matrix metalloproteinase (MMP)-7 and MMP-13 expression, which play important roles in invasion and metastasis. This study shows a potential role of TUDCA in protecting against radiation-induced intestinal damage and inhibiting tumor cell migration without any radiation and radiation therapy effect.

A Reexamination of Peto's Paradox: Insights Gained from Human Adaptation to Varied Levels of Ionizing and Non-ionizing Radiation.

Humans have generally evolved some adaptations to protect against UV and different levels of background ionizing radiation. Similarly, elephants and whales have evolved adaptations to protect against cancer, such as multiple copies of the tumor suppressor gene p53, due to their large size and long lifespan. The difference in cancer protection strategies between humans and elephants/whales depends on genetics, lifestyle, environmental exposures, and evolutionary pressures. In this paper, we discuss how the differences in evolutionary adaptations between humans and elephants could explain why elephants have evolved a protective mechanism against cancer, whereas humans have not. Humans living in regions with high levels of background radiation, e.g. in Ramsar, Iran where exposure rates exceed those on the surface of Mars, seem to have developed some kind of protection against the ionizing radiation. However, humans in general have not developed cancer-fighting adaptations, so they instead rely on medical technologies and interventions. The difference in cancer protection strategies between humans and elephants/whales depends on genetics, lifestyle, environmental exposures, and evolutionary pressures. In this paper, we discuss how the differences in evolutionary adaptations between humans and elephants could explain why elephants have evolved a protective mechanism against cancer, whereas humans have not. Studying elephant adaptations may provide insights into new cancer prevention and treatment strategies for humans, but further research is required to fully understand the evolutionary disparities.

Detailed Monte Carlo simulations on secondary radiation emissions of polymer based neutron shielding materials

Since radiation safety is a sensitive issue in terms of health, this situation poses a significant problem. In order to raise awareness among researchers while preparing future studies on this problem, in this study, the interactions between fast neutrons and 10 different polymer-based shielding materials determined from the literature were modeled with the GEANT4 Monte Carlo code. The fast neutron shielding performances of the samples and the emitted secondary radiation and radioactivity have been reported. When evaluated number and mean energies of created particles, in order to solve this problem, the sum of the risk factors obtained by multiplying these values for each sample can provide us with the opportunity to make a more accurate evaluation. When these values are examined, sample P9 is at the top of the risk ranking with a value of 1823472, while sample P6 is at the bottom with a value of 146246. As a result, it has been revealed that these samples, which have good fast neutron shielding properties, also produce high levels of radiation and radioactive nuclei.

A numerical study of the R744 primary cooling system for ATLAS and CMS LHC detectors

A R744 (CO2) refrigeration system has been designed to cool down the Large Hadron Collider (LHC) silicon detectors ATLAS and CMS, located at CERN, Switzerland. The silicon detectors are subjected to high radiation levels. The system is composed of a pri- mary CO2 trans-critical booster vapor compression loop operated with piston compressors, and an oil-free liquid pumped loop on the evaporation side, to preserve the detectors. To ensure the system's reliability, the cooling facility is designed to operate under a parallel operation mode of several modular 70 kW plant units providing evaporation temperature as low as -53 °C. This layout, is also useful in case of components failure and maintenance. A numerical model is developed using a dynamic simulation software Dymola that is based on the open source Modelica modelling language. The simulation results are proven on a first demonstration plant (System A) experimentally to explore the systems control logic and to validate the reliability of the system before it is built on the detectors side. In this paper the models development is explained and the results of the experimental validation of the numerical model are shown.

Wildfire susceptibility mapping by incorporating damage proxy maps, differenced normalized burn Ratio, and deep learning algorithms based on sentinel-1/2 data: a case study on Maui Island, Hawaii

ABSTRACT Climate change has contributed to the recent increase in wildfire occurrences, vegetation failures, human health risks, physical damage, and economic losses. Wildfire susceptibility mapping is an essential technique for assessing areas prone to wildfires. In this study, we proposed the combination of the damage proxy map (DPM) and differenced normalized burn ratio (dNBR) method to generate a precise wildfire inventory map and used it to predict areas susceptible to wildfire. The wildfire susceptibility maps were produced using frequency ratio (FR), convolutional neural network (CNN), and long short-term memory (LSTM)-based deep learning and their performances were compared. We implemented the proposed method on Maui Island, Hawaii, where wildfires frequently occur. We started the process by generating a wildfire inventory map from 2019 to 2023 based on the DPM method applied to Sentinel-1 synthetic aperture radar (SAR) data combined with a dNBR map retrieved from Sentinel-2 data. The wildfire inventory was randomly divided into a training dataset (70%) and a testing dataset (30%). Fifteen wildfire-related factors, including topographical, meteorological, land use, environmental, and anthropological factors, were selected to predict wildfires. The wildfire-related factors were selected by conducting study literature and considering spatial correlation analysis based on the FR method, information gain ratio analysis (IGR), and multicollinearity assessment using tolerance (TOL) and variance inflation factor (VIF) metrics. The level of susceptibility of an area to wildfire is divided into five, namely very high, high, moderate, low, and very low. The FR, CNN, and LSTM produced wildfire susceptibility maps with similar patterns, significantly influenced by land use and rainfall factors. The highly susceptible areas are located on gentle slopes covered by agricultural land and unhealthy vegetation, and these areas have low rainfall intensity but receive high levels of solar radiation. Meanwhile, areas with relatively low susceptibility occur in forests with high levels of wet canopy evaporation. The prediction results were evaluated using the area under the receiver operating characteristic (ROC) curve (AUC), and the CNN performed slightly better than the FR and LSTM, with AUC values of 0.879, 0.877, and 0.870, respectively. Hence, the use of the CNN algorithm in the proposed method is appropriate, specifically for the study area. In addition, the susceptibility map provides information on susceptible areas on Maui Island, Hawaii, to increase public awareness.

A new cold cooling system using krypton for the future upgrade of the LHC after the long shutdown 4 (LS4)

Future silicon detectors for High Energy Physics Experiments will require operation at lower temperatures to cope with radiation damage of the sensors and consequent increase of the dark current, beyond the limit of the current CO2 evaporative cooling system. This, together with many other requirements such as mass minimization and high radiation hardness, pushes the need of a new advanced cooling technology. The new coolant shall be able to approach ultra-low temperatures below −60 °C, withstand high radiation levels while having cooling lines diameters comparable to the currently achieved with the CO2 technology. Among different natural working fluids, krypton appears as a promising coolant for the thermal management of future detectors in high-irradiated environments. The thermodynamic properties of krypton do not allow the use of a pumped loop cycle but rather impose a need of a novel cooling technology. A new ejector-supported krypton cycle is presented, highlighting the cycle dynamics involved due to the different temperature levels normally encountered during the detector lifetime.

MYB4, a member of R2R3-subfamily of MYB transcription factor functions as a repressor of key genes involved in flavonoid biosynthesis and repair of UV-B induced DNA double strand breaks in Arabidopsis

Plants accumulate flavonoids as part of UV-B acclimation, while a high level of UV-B irradiation induces DNA damage and leads to genome instability. Here, we show that MYB4, a member of the R2R3-subfamily of MYB transcription factor plays important role in regulating plant response to UV-B exposure through the direct repression of the key genes involved in flavonoids biosynthesis and repair of DNA double-strand breaks (DSBs). Our results demonstrate that MYB4 inhibits seed germination and seedling establishment in Arabidopsis following UV-B exposure. Phenotype analyses of atmyb4-1 single mutant line along with uvr8-6/atmyb4-1, cop1-6/atmyb4-1, and hy5-215/atmyb4-1 double mutants indicate that MYB4 functions downstream of UVR8 mediated signaling pathway and negatively affects UV-B acclimation and cotyledon expansion. Our results indicate that MYB4 acts as transcriptional repressor of two key flavonoid biosynthesis genes, including 4CL and FLS, via directly binding to their promoter, thus reducing flavonoid accumulation. On the other hand, AtMYB4 overexpression leads to higher accumulation level of DSBs along with repressed expression of several key DSB repair genes, including AtATM, AtKU70, AtLIG4, AtXRCC4, AtBRCA1, AtSOG1, AtRAD51, and AtRAD54, respectively. Our results further suggest that MYB4 protein represses the expression of two crucial DSB repair genes, AtKU70 and AtXRCC4 through direct binding with their promoters. Together, our results indicate that MYB4 functions as an important coordinator to regulate plant response to UV-B through transcriptional regulation of key genes involved in flavonoids biosynthesis and repair of UV-B induced DNA damage.

Impact of Solar Shading on Façades’ Surface Temperatures under Summer and Winter Conditions by IR Thermography

In warm climates with high levels of solar irradiation, solar shading plays a determinant role on buildings’ envelope performance, both during summer and winter conditions. In this research, an evaluation of the solar shading effect on sunny façades through IR thermography non-destructive testing was performed. Sunny and shaded areas revealed temperature differences of 7.4 °C in summer conditions and up to 1.2 °C in wintertime. Moreover, solar shading was shown to be beneficial not only for decreasing surface temperature in summertime but also for reducing convective air flow in wintertime. In addition, it was found that the prevalence of dense shadows, especially with non-reflective materials in louvres, is favorable. External Thermal Insulation Constructive Systems (ETICS) must be shadowed and the use of clear colors is recommended to reinforce homogeneity in the surface in wintertime and reduce solar absorptance in summertime. Under steady-state calculations, thermal losses can be reduced up to 30% at night in wintertime and up to 50–60% at daytime in summertime because of the shadowing. However, another important finding lied in the confirmation of the performance gap that arises between using air temperature, sol-air temperature and the actual surface temperature data, in such a way that the two former implied high levels of inaccuracy and overestimated the performance of the buildings compared to the actual behavior. Some of the main conclusions can be extrapolated to other circumstances.

Fusion neutron diagnostics with CVD diamond detectors

The measurement of Deuterium–Deuterium (DD) and Deuterium–Tritium (DT)-fusion neutrons is crucial for plasma diagnostics at nuclear fusion facilities, such as ITER. Elevated temperatures and high radiation levels challenge radiation detectors. Chemical Vapour Deposition (CVD) diamond withstands harsh environments and is a distinguished candidate for reliable plasma instrumentation (Angelone et al., 2021 and Passeri et al., 2021). Neutron-induced nuclear reactions on Carbon nuclei of diamond substrates are the basis for fusion neutron detection with CVD diamond detectors. DD-fusion neutrons have an energy of 2.45 MeV. The corresponding response function of diamond sensors is purely elastic scattering and has a characteristic shape. DT-fusion neutrons have 14.1 MeV kinetic energy, and their response function reveals different nuclear reactions. The 12C(n, α)9Be peak is the most prominent structure in this response function. The principles of neutron diagnostics with CVD diamond detectors are discussed in this paper and the measured response functions of diamond sensors for 2.45 MeV and 14.1 MeV neutrons are presented, as well as the fusion neutron measurement using a proton-recoil telescope.

Development of partitioned rectangular-shaped heat sink for photovoltaic thermal systems and performance evaluation using TiO2/Water-based nanofluids

The current study presents a partitioned rectangular-shaped heat sink for improving the PVT system performance. The experiment was examined under various experimental parameters. Five cooler block types with different dimensions were arranged to share the same total contact area with the panel back surface. These cooler blocks were placed in different arrangements, namely (PVT-I, PVT-II, PVT-III, PVT-IV, PVT-V), and studied comparatively using water. The dimensions and numbers of each cooler block arrangement were altered, while maintaining the same surface area in contact with the photovoltaic panel. Through the response surface methodology (RSM) optimization, the optimal arrangement with the best performance was determined, and then TiO2/nanofluid was applied to that arrangement with different volumetric concentrations. Using water, the highest electrical and thermal efficiencies were obtained by case PVT-III with values of 19.39 % and 63.72 %, respectively. This was followed by PVT-II, PVT-V, PVT-I, and PVT-IV in that order for electrical efficiency; and at the same time by PVT-II, PVT-I, PVT-IV, and PVT-V in that order for thermal efficiency. The RSM method recommended the optimal arrangement case as case PVT-III. By using nanofluid in that case arrangement, the highest electrical efficiency value was recorded upon using 0.3 wt% and operating the system at 1.5 L/m and 900 W/m2. Regarding the thermal efficiency results, in that case, the highest and lowest values were recorded upon using 0.3 wt% and 0.1 wt%, respectively, with values of 72.49 % and 31.19 %. Increasing the volumetric concentrations positively reflected on the system's performance, resulting in high efficiencies being achieved. In addition, the highest electrical efficiencies were obtained at high levels of solar irradiance and flow rates.

Non-Electrically Driven Acoustic Actuator

Nuclear power plants have high radiation levels and humans cannot work directly on them. Therefore, it is necessary to establish effective repair work methods. One promising approach is the use of disaster relief robots. However, strong radiation affects circuits and electronic devices. Because typical robots contain electrical circuits and are controlled by radio waves, they are difficult to use in highly radioactive environments. In this study, we propose a non-electrically driven acoustic actuator that does not use electronic circuits and is driven by sound waves. To realize this goal, we have investigated a sound wave drive using a cylindrical container.

Competition between phase ordering and phase segregation in the TixNbMoTaW and TixVNbMoTaW refractory high-entropy alloys

Refractory high-entropy alloys are under consideration for applications where materials are subjected to high temperatures and levels of radiation, such as in the fusion power sector. However, at present, their scope is limited because they are highly brittle at room temperature. One suggested route to mitigate this issue is by alloying with Ti. In this theoretical study, using a computationally efficient linear-response theory based on density functional theory calculations of the electronic structure of the disordered alloys, we study the nature of atomic short-range order in these multi-component materials, as well as assessing their overall phase stability. Our analysis enables direct inference of phase transitions in addition to the extraction of an atomistic, pairwise model of the internal energy of an alloy suitable for study via, e.g., Monte Carlo simulations. Once Ti is added into either the NbMoTaW or VNbMoTaW system, we find that there is competition between chemical phase ordering and segregation. These results shed light on observed chemical inhomogeneity in experimental samples, as well as providing fundamental insight into the physics of these complex systems.

Ultrastructural Analysis of Large Japanese Field Mouse (Apodemus speciosus) Testes Exposed to Low-Dose-Rate (LDR) Radiation after the Fukushima Nuclear Power Plant Accident.

Since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, great attention has been paid to the impact of chronic low-dose-rate (LDR) radiation exposure on biological systems. The reproductive system is sensitive to radiation, with implications connected to infertility. We investigated the testis ultrastructure of the wild large Japanese field mouse (Apodemus speciosus) from three areas contaminated after the FDNPP accident, with different levels of LDR radiation (0.29 µSv/h, 5.11 µSv/h, and 11.80 µSv/h). Results showed good preservation of the seminiferous tubules, comparable to the unexposed animals (controls), except for some ultrastructural modifications. Increases in the numerical density of lipid droplet clusters in spermatogenic cells were found at high levels of LDR radiation, indicating an antioxidant activity rising due to radiation recovery. In all groups, wide intercellular spaces were found between spermatogenic cells, and cytoplasmic vacuolization increased at intermediate and high levels and vacuolated mitochondria at the high-level. However, these findings were also related to the physiological dynamics of spermatogenesis. In conclusion, the testes of A. speciosus exposed to LDR radiation associated with the FDNPP accident showed a normal spermatogenesis, with some ultrastructural changes. These outcomes may add information on the reproductive potential of mammals chronically exposed to LDR radiation.