Low-dose Γ-radiation Research Articles

Low-dose-rate induces more severe cognitive impairment than high-dose-rate in rats exposed to chronic low-dose γ-radiation.

Owing to the long penetration depth of gamma (γ)-rays, individuals working in ionizing radiation environments are chronically exposed to low-dose γ-radiation, resulting in cognitive changes. Dose rate significantly affects radiation-induced biological effects; however, its role in chronic low-dose γ-irradiation-induced cognitive impairment remains unclear. We aimed to investigate whether chronic low-dose γ-irradiation at low-dose-rate (LDR) could induce cognitive impairment and to compare the cognitive alteration caused by chronic low-dose γ-irradiation at LDR and high-dose-rate (HDR). The rats were exposed to γ-irradiation at a LDR of 6 mGy/h and a HDR of 20 mGy/h for 30 days (5 h/day). Functional imaging was performed to assess the brain inflammation and blood-brain barrier (BBB) destruction of rats. Histological and immunofluorescence analyses were used to reveal the neuron damage and the activation of microglia and astrocytes in the hippocampus. RNA sequencing was conducted to investigate changes in gene expression in hippocampus. The rats in the LDR group exhibited more persistent cognitive impairment than those in the HDR group. Furthermore, irradiated rats showed brain inflammation and a compromised BBB. Histologically, the number of hippocampal neurons were comparable in the LDR group but were markedly decreased in the HDR. Additionally, activated M1-like microglia and A1-like astrocytes were observed in the hippocampus of rats in the LDR group; however, only M1-like microglia were activated in the HDR group. Mechanistically, the PI3K-Akt signaling pathway contributed to the different cognitive function change between the LDR group and HDR group. Compared with chronic low-dose γ-irradiation at HDR, LDR induced more severe cognitive impairment which might involve PI3K/Akt signaling pathway.

Low dose γ-radiation induced effects on wax moth (Galleria mellonella) larvae

Larvae of the greater wax moth Galleria mellonella are common pests of beehives and commercial apiaries, and in more applied settings, these insects act as alternative in vivo bioassays to rodents for studying microbial virulence, antibiotic development, and toxicology. In the current study, our aim was to assess the putative adverse effects of background gamma radiation levels on G. mellonella. To achieve this, we exposed larvae to low (0.014 mGy/h), medium (0.056 mGy/h), and high (1.33 mGy/h) doses of caesium-137 and measured larval pupation events, weight, faecal discharge, susceptibility to bacterial and fungal challenges, immune cell counts, activity, and viability (i.e., haemocyte encapsulation) and melanisation levels. The effects of low and medium levels of radiation were distinguishable from the highest dose rates used – the latter insects weighed the least and pupated earlier. In general, radiation exposure modulated cellular and humoral immunity over time, with larvae showing heightened encapsulation/melanisation levels at the higher dose rates but were more susceptible to bacterial (Photorhabdus luminescens) infection. There were few signs of radiation impacts after 7 days exposure, whereas marked changes were recorded between 14 and 28 days. Our data suggest that G. mellonella demonstrates plasticity at the whole organism and cellular levels when irradiated and offers insight into how such animals may cope in radiologically contaminated environments (e.g. Chornobyl Exclusion Zone).

Concerted regulation of OPG/RANKL/ NF‑κB/MMP-13 trajectories contribute to ameliorative capability of prodigiosin and/or low dose γ-radiation against adjuvant- induced arthritis in rats

BackgroundProdigiosin (PDG) is a microbial red dye with antioxidant and anti-inflammatory properties, although its effect on rheumatoid arthritis (RA) remains uncertain. Also, multiple doses of low dose γ- radiation (LDR) have been observed to be as a successful intervention for RA. Thus, the purpose of this study was to investigate the ameliorative potential of PDG and/or LDR on adjuvant-induced arthritis (AIA) in rats. MethodsThe anti-inflammatory and anti-arthritic effects of PDG and/or LDR were examined in vitro and in vivo, respectively. In the AIA model, the arthritic indexes, paw swelling degrees, body weight gain, and histopathological assessment in AIA rats were assayed. The impact of PDG (200 µg/kg; p.o) and/or LDR (0.5 Gy) on the levels of pro- and anti-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-18, IL-17A, and IL-10) as well as the regulation of osteoprotegrin (OPG)/ receptor activator of nuclear factor κB ligand (RANKL)/ nuclear factor-κB (NF-κB)/MMP-13 pathways was determined. Methotrexate (MTX; 0.05 mg/kg; twice/week, i.p) was administered concurrently as a standard anti-arthritic drug. ResultsPDG and/or LDR markedly diminished the arthritic indexes, paw edema, weigh loss in AIA rats, alleviated the pathological alterations in joints, reduced the levels of pro-inflammatory cytokines IL-1β, TNF-α, IL-6, IL-18, IL-17A, and RANKL in serum and synovial tissues, while increasing anti-inflammatory cytokines IL-10 and OPG levels. Moreover, PDG and/or LDR down-regulated the expression of RANKL, NF-κBp65, MMP13, caspase-3, and decreased the RANKL/OPG ratio, whereas OPG and collagen II were enhanced in synovial tissues. ConclusionPDG and/or LDR exhibited obvious anti-RA activity on AIA.

Regulation of Sirtuin-3 and ERK1/2/p38MAPK by the combination Ga nanoparticles/γ-radiation low dosage: an effective approach for treatment of hepatocellular carcinoma

BackgroundSynthesized gallium nanoparticles synthesized by grape seed extract were characterized with spherical shape and size range less than100 nm, possessing the functional groups of the biological material. The purpose of this study is to evaluate gallium nanoparticles synthesized by grape seed extract, as an antitumor agent with low dose of γ-radiation against hepatocellular carcinoma in rats. Aim of workThis work aimed to evaluate the antitumor effect of gallium nanoparticles synthesized (GaNPs) by grape seed extract and the co-binded treatment with low dose of γ-radiation on hepatocellular carcinoma in rats, through evaluating their effect on signaling pathways and tumor markers. ResultsCytotoxic activity of GaNPs synthesized by grape seed extract was estimated by mediated cytotoxicity assay on HepG2 cell line that recorded IC50 of 388.8 μg/ml. To achieve these goals, eighty Wistar male rats (120−150 g) will be divided into eight groups, each of 10 rats. The animals are administered with diethylnitrosamine to induce hepatocellular carcinoma and then orally administered with GaNPs synthesized by grape seed extract (38.5 mg/kg) in combination with the exposure of the total body to a low dose of γ-radiation (0.5 Gy). The treatment modulated plasma vascular endothelial growth factor and alpha-fetoprotein. In addition, the immunoblotting results of nuclear factor-kappa beta showed a marked downregulation of extracellular signal-regulated kinase, mitogen-activated protein kinase, and c-Jun NH2-terminal kinase alongside, significantly elevating the level of Sirtuin-3 and caspase-3. ConclusionsIt can be concluded that the combined treatment with GaNPs synthesized by grape seed extract and low dose γ-radiation may have antineoplastic activity against hepatocarcinogenesis by inhibiting signal pathways extracellular signal-regulated kinase/mitogen-activated protein kinase/c-Jun NH2-terminal kinase and stimulating apoptotic protein.

Low-Dose Gamma Radiation Modulates Liver and Testis Tissues Response to Acute Whole Body Irradiation.

AimThis work aims to investigate whether the pre-exposure to low dose/low dose rate (40 mGy, 2.2 mGy/hour) γ-radiation as a priming dose can produce a protective effect against the subsequent high one (4 Gy, .425 Gy/minute).MethodsRats were divided into Group I (control), Group II (L); exposed to 40 mGy, Group III (H); exposed to 4 Gy, and Group IV (L+H); exposed to 40 mGy 24 hours before the exposure to 4Gy. The molecular and biochemical changes related to oxidative stress, DNA damage, apoptosis, and mitochondrial activity in the liver and testis were studied 4 hours after irradiation.ResultsExposure to 40 mGy before 4 Gy induced a significant increase in the levels of Nrf2, Nrf2 mRNA, TAC, and mitochondrial complexes I & II accompanied by a significant decrease in the levels of LPO, 8-OHdG, DNA fragmentation, TNF-α, caspase-3, and caspase-3 mRNA compared with H group.ConclusionExposure to low-dose γ-radiation before a high dose provides protective mechanisms that allow the body to survive better after exposure to a subsequent high one via reducing the oxidative stress, DNA damage, and apoptosis-induced early after irradiation. However, further studies are required to identify the long-term effects of this low dose.

Effects of Low-dose Gamma Radiation on Expression of Apoptotic Genes in Rat Peripheral Blood Lymphocyte.

Background: Exposure to high-dose ionizing radiation is known as a human carcinogen factor, but our information about the effects of low-dose ionizing radiation such as occupational exposures is limited. The main concern of scientific community is biological consequences due to low-dose radiations.Objective: This study aims to evaluate the effects of low-dose γ-radiation on expression changes of apoptotic genes (bax and bcl-2) in the rat peripheral blood lymphocytes.Material and Methods: In this experimental study, 42 adult male rats were classified into 6 groups, which was exposed to various doses values ranged from 20 mGy to 1000 mGy by γ-rays from a Co-60 source. Blood samples were provided for analysis of gene expression 24 h after gamma radiation by relative quantitative Reverse Transcription - Polymerase Chain Reaction (RT-PCR). Radiation sensitivity of rat lymphocytes was measured by the bax/bcl-2 ratio as a predictive marker for radio-sensitivity. Results: The results of this study showed that low dose of gamma radiation can induce down-regulation of bax in rat peripheral blood lymphocytes. Despite other mechanisms of cellular radio-protection, changes in expression of these apoptotic genes can be the primary pathway in responses of the lymphocytes radio-protection to the exposure. Our study revealed a significant decrease in the bax/bcl-2 ratio at 50 mGy dose compare to control and the other irradiated groups (p < 0.05).Conclusion: These results suggest that changes in the bax/bcl-2 ratio especially in radiation workers, as a key factor in apoptosis, can be considered as a biological marker in low-dose gamma radiation.

Metabolic Profiling of γ-Irradiated Barley Plants Identifies Reallocation of Nitrogen Metabolism and Metabolic Stress Response.

The favorable responses of crop species to low-dose γ irradiation can help to develop cultivars with increased productivity and improved stress tolerance. In the present study, we tried to reveal the candidate metabolites involved in growth stimulation of barley seedlings after applying low-dose γ-radiation (60Co) to seeds. Stimulating doses (5-20 Gy) provided a significant increase in shoot length and biomass, while relatively high dose of 100 Gy led to significant inhibition of growth. Gas chromatography–mass spectrometry metabolomic analysis uncovered several compounds that may take part in radiation hormesis establishment in irradiated plants. This includes molecules involved in nitrogen redistribution (arginine, glutamine, asparagine, and γ-aminobutyric acid) and stress-responsive metabolites, such as ascorbate, myo-inositol and its derivates, and free amino acids (l-serine, β-alanine, pipecolate, and GABA). These results contribute to the understanding of the molecular mechanisms of hormesis phenomenon.

Anticancer Activity of Fermented Solenostemm Aargel Extract and/or Low Dose Gamma Radiation Against Hepatocellular Carcinoma

For many decades the terrestrial plants are represent an infinitive source of bioactive substances as well as pharmaceutical components which play a main role in the discovering ,developing and manufacturing of anticancer and antibiotic drugs.Solenostemmaargel is a desert plant widely used in Arabic countries as antispasmodic, anti-inflammatory and anti-rheumatic agent. It also has anti-tumor activity. Aim: the present study was oriented to investigatethe hepato-protective effect of fermentedSolenostemmaargelleave extract (100amg/kg b.wt) and/or low dose γ-radiation (0.5Gy) againsthepatocellular carcinoma (HCC)developedin rats by injection of diethylnitrosamine. Results: the data obtained revealed that thepro-apoptotic agents (caspase 3 and cytochrome c) undergoes significant elevation in HCC rats received plant extract and/or γ-radiation compared to HCC rats.While,the vascular endothelial growth factor (VEGF), hypoxia inducible factor-α (HIF-α)and monocytichemotactic protein-1(MCP-1) were significantly decreased. Also, the activity of cyclooxygenase-2 (COX-2) was significantly decreased. Moreover, the histopathological analysis revealed that a mild improvement .In conclusion, the improvement emerged in HCC rats could be attributed to the potency of extract and/or γ- radiation by induce apoptosis and reduce angiogenesis.

Effects of Gamma-Radiation on DNA Damage in Onion (Allium cepa L.) Seedlings.

The effect of γ-radiation on the level of nuclear DNA damage in onion seedlings (Allium-test) was studied using the comet assay. DNA breaks were first found in cells of onion seedlings exposed to low-dose radiation (≤ 0.1 Gy). Dose dependence of DNA damage parameters showed nonlinear behavior: a linear section in the low-dose region (below 0.1 Gy) and a dose-independent plateau in the dose range between 1 and 5 Gy. Thus, the comet assay can be used to estimate the biological effects of low-dose γ-radiation on Allium cepa seedlings.

Radioactive particles in the Yenisei River floodplain (Russia): Characterization, leaching and potential effects in the environment

The operation of the Mining-and-Chemical Combine (MCC), the largest producer of weapons-grade plutonium in Russia, has resulted in radioactive contamination of the Yenisei River floodplain. Investigations carried out in Novosibirsk and Krasnoyarsk institutes have shown that the floodplain of the Yenisei downstream of the MCC is contaminated by radioactive particles (RP) of various types and activities. Analytical characterization of the RP showed that most of them were fuel particles, which were carried into the Yenisei after incidents at the MCC reactors. The plutonium and caesium isotope ratios (238Pu/239,240Pu; 137Cs/134Cs) vary substantially between the particles, indicating different source terms and time intervals when the RP were formed. In addition to fuel RP, there were particles that contained activation radionuclides. The experiment on dissolution of RP using the model solution (the simulated stomach fluid) showed different cumulative extractions of radionuclides from the particles: 60Co and 137Cs extractions were the lowest, the extracted fractions of europium and americium isotopes were the largest, and plutonium occupied an intermediate position. High concentrations of radionuclides in RP are sources of exposure of organisms in aquatic and terrestrial ecosystems to low radiation doses. The plant bioassays of the effects of γ-radiation from RP showed the effect of low doses of γ-radiation on growth parameters of aquatic plant Elodea canadensis growing in the Yenisei River floodplain. The presence of RP from different sources in the Yenisei River floodplain makes this region a unique site for studying environmental effects of the particles.

Chromosomal aberrations and micronuclei induced in onion (Allium cepa) by gamma-radiation

The Allium-test is commonly used to assess genotoxicity of chemical and physical factors. In the present study, the roots of germinating onion (Allium cepa) were exposed to 0.02–13 Gy of γ-radiation. The dose dependencies of the frequency of chromosomal aberrations and micronuclei were nonlinear. An increase in the frequency of chromosomal aberrations in germinating seed root cells was first found under exposure to low doses of γ-radiation (0.05 and 0.1 Gy). Micronuclei inductions at low doses of radiation were not significantly different from the control. Our study suggests that germinating onion seed roots are a sensitive bioassay material for assessing the genotoxic effects of low-dose γ-radiation.

G2-lymphocyte chromosomal radiosensitivity in patients with LPS responsive beige-like anchor protein (LRBA) deficiency

Lipopolysaccharide-responsive, beige-like anchor protein (LRBA) deficiency is an autosomal recessive primary immunodeficiency disease characterized by a CVID-like phenotype, particularly severe autoimmunity and inflammatory bowel disease. This study was undertaken to evaluate radiation sensitivity in 11 LRBA-deficient patients. Therefore, stimulated lymphocytes of the studied subjects were exposed to a low dose γ-radiation (100 cGy) in the G2 phase of the cell cycle and chromosomal aberrations were scored. Lymphocytes of age-sex matched healthy individuals used in the same way as controls. Based on the G2-assay, six (54.5%) of the patients had higher radiosensitivity score comparing to the healthy control group, forming the radiosensitive LRBA-deficient patients. This chromosomal radiosensitivity showed that these patients are predisposed to autoimmunity and/or malignancy, and should be protected from unnecessary diagnostic and therapeutic procedures using ionizing radiation and exposure to other DNA damaging agents.

Формирование слоев наноструктурированного пористого кремния при облучении малыми дозами γ-радиации

Формирование слоев наноструктурированного пористого кремния при облучении малыми дозами γ-радиации

Cellular adaptive response and regulation of HIF after low dose gamma-radiation exposure

Purpose: Cellular damage due to low dose of γ-radiation (≤0.1 Gy) is generally extrapolated from observing the effects at higher doses. These estimations are not accurate. This has led to uncertainties while assessing the radiation risk factors at low doses. Although there are reports on the radiation induced adaptive response, the mechanism of action is not fully elucidated, leading to the uncertainties. One of the outcomes of low dose radiation exposure is believed to be an adaptive response. The mechanism of adaptive response is not fully understood. Therefore, the study was undertaken to understand the role of hypoxia inducible factor (HIF) on radiation induced adaptive response.Materials and methods: Human breast cancer cell line MCF-7 cells pre-exposed to low dose γ-radiation (0.1 Gy; priming dose) were exposed to 2 Gy (challenging dose) 8 h after the priming dose and studied for the adaptive response. Cell death was measured by 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) assay and apoptosis was measured by fluorescence-activated cell sorting analysis. DNA damage was measured by alkaline comet assay. HIF transcription activity was assayed using transiently transfected plasmid having HIF consensus sequence and luciferase as the reporter gene.Results: Cells when exposed to 0.1 Gy priming dose 8 h prior to the higher dose (2 Gy; challenging dose) results in lower amount of radiation induced damages compared to the cells exposed to 2 Gy alone. Cobalt chloride treatment in place of priming dose also results in the protection to cells when exposed to challenging dose. There was up-regulation of HIF activity when cells were exposed to priming dose, indicating the role of HIF in radiation induced response.Conclusion: Results indicate the γ-radiation induced adaptive response. One of the mechanism proposed is up-regulation of HIF after low dose exposure, which protects the cells from damages when they are exposed to challenging dose of 2 Gy radiation.

Cytogenetic Effects of γ-Radiation in Onion (Allium cepa L.) Seedlings

The effect of γ-radiation on the cytogenetic parameters of root meristem cells of onion seedlings was studied in laboratory experiments (Allium-test). An increase in the overall frequency of chromosomal aberrations and micronucleus frequencies in seedling cells at low γ-radiation doses (≤0.1 Gy) was detected for the first time. At a maximum absorbed dose of 13 Gy, chromosomal aberrations were detected in the majority of cells in the anaphase and telophase stages of the cell cycle, and the number of cells with multiple aberrations increased. The main contribution to the overall frequency of chromosomal aberrations, in addition to multiple aberrations, is made by the bridge-type aberrations, fragments, and lagging chromosomes. The data obtained allow using the cytogenetic indices of Allium cepa seedlings to assess the biological effects of lowdose γ-radiation.

Effects of low-dose rate γ-irradiation combined with simulated microgravity on markers of oxidative stress, DNA methylation potential, and remodeling in the mouse heart.

PurposeSpace travel is associated with an exposure to low-dose rate ionizing radiation and the microgravity environment, both of which may lead to impairments in cardiac function. We used a mouse model to determine short- and long-term cardiac effects to simulated microgravity (hindlimb unloading; HU), continuous low-dose rate γ-irradiation, or a combination of HU and low-dose rate γ-irradiation.MethodsCardiac tissue was obtained from female, C57BL/6J mice 7 days, 1 month, 4 months, and 9 months following the completion of a 21 day exposure to HU or a 21 day exposure to low-dose rate γ-irradiation (average dose rate of 0.01 cGy/h to a total of 0.04 Gy), or a 21 day simultaneous exposure to HU and low-dose rate γ-irradiation. Immunoblot analysis, rt-PCR, high-performance liquid chromatography, and histology were used to assess inflammatory cell infiltration, cardiac remodeling, oxidative stress, and the methylation potential of cardiac tissue in 3 to 6 animals per group.ResultsThe combination of HU and γ-irradiation demonstrated the strongest increase in reduced to oxidized glutathione ratios 7 days and 1 month after treatment, but a difference was no longer apparent after 9 months. On the other hand, no significant changes in 4-hydroxynonenal adducts was seen in any of the groups, at the measured endpoints. While manganese superoxide dismutase protein levels decreased 9 months after low-dose γ-radiation, no changes were observed in expression of catalase or Nrf2, a transcription factor that determines the expression of several antioxidant enzymes, at the measured endpoints. Inflammatory marker, CD-2 protein content was significantly decreased in all groups 4 months after treatment. No significant differences were observed in α-smooth muscle cell actin protein content, collagen type III protein content or % total collagen.ConclusionsThis study has provided the first and relatively broad analysis of small molecule and protein markers of oxidative stress, T-lymphocyte infiltration, and cardiac remodeling in response to HU with simultaneous exposure to low-dose rate γ-radiation. Results from the late observation time points suggest that the hearts had mostly recovered from these two experimental conditions. However, further research is needed with larger numbers of animals for a more robust statistical power to fully characterize the early and late effects of simulated microgravity combined with exposure to low-dose rate ionizing radiation on the heart.

Antioxidant and antiapoptotic effects of sea cucumber and valsartan against doxorubicin-induced cardiotoxicity in rats: The role of low dose gamma irradiation

Doxorubicin (DOX) is a highly effective antineoplastic drug; however, the clinical use of DOX is limited by its dose dependent cardiotoxicity. This study was conducted to evaluate the cardioprotective effect of sea cucumber and valsartan against DOX-induced cardiotoxicity in rats. Also, the role of exposure to low dose γ radiation (LDR) on each of them was investigated, since LDR could suppress various reactive oxygen species-related diseases. Rats received DOX (2.5mg/kg, ip) in six equal injections over a period of 2weeks, sea cucumber (14.4mg/kg, p.o) and valsartan (30mg/kg, p.o) for 8 successive weeks. Exposure to LDR (0.5Gy) was performed one day prior to DOX. Results revealed that DOX administration elevated serum levels of aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatine kinase (CK-MB) and troponin-I as well as increased cardiac lipid peroxide content and myeloperoxidase (MPO) activity. Additionally, it increased cardiac expressions of iNOS and caspase-3, accompanied by reduction in cardiac total protein and glutathione (GSH) contents. Treatment with sea cucumber or valsartan improved the cardiotoxicity of DOX. Their adjuvant therapy with LDR offers an additional benefit to the cardioprotection of the therapeutic drugs. These results confirmed by histopathological examination. In conclusion, sea cucumber and valsartan alone or combined with LDR attenuated DOX-induced cardiotoxicity via their antioxidant and anti-apoptotic activities and thus might be useful in the treatment of human patients under doxorubicin chemotherapy.

Phosphoprotein profiles of candidate markers for early cellular responses to low-dose γ-radiation in normal human fibroblast cells.

Ionizing radiation causes biological damage that leads to severe health effects. However, the effects and subsequent health implications caused by exposure to low-dose radiation are unclear. The objective of this study was to determine phosphoprotein profiles in normal human fibroblast cell lines in response to low-dose and high-dose γ-radiation. We examined the cellular response in MRC-5 cells 0.5 h after exposure to 0.05 or 2 Gy. Using 1318 antibodies by antibody array, we observed ≥1.3-fold increases in a number of identified phosphoproteins in cells subjected to low-dose (0.05 Gy) and high-dose (2 Gy) radiation, suggesting that both radiation levels stimulate distinct signaling pathways. Low-dose radiation induced nucleic acid–binding transcription factor activity, developmental processes, and multicellular organismal processes. By contrast, high-dose radiation stimulated apoptotic processes, cell adhesion and regulation, and cellular organization and biogenesis. We found that phospho-BTK (Tyr550) and phospho-Gab2 (Tyr643) protein levels at 0.5 h after treatment were higher in cells subjected to low-dose radiation than in cells treated with high-dose radiation. We also determined that the phosphorylation of BTK and Gab2 in response to ionizing radiation was regulated in a dose-dependent manner in MRC-5 and NHDF cells. Our study provides new insights into the biological responses to low-dose γ-radiation and identifies potential candidate markers for monitoring exposure to low-dose ionizing radiation.

Radiation Stress Changes the Size of Side Population of Human Epithelial Cells.

Stem cell cultures are heterogeneous and include true stem cells and progenitor cells. True stem cells are identified by flow cytofluorometry as a cell subset characterized by low accumulation of fluorescent dye rhodamin-123 and forming a side population. Low-dose γ-irradiation (10-200 mGy) of human skin epithelial stem cells and epithelial H69 tumor cells to was followed by an increase in cell counts by day 7 after the exposure. In parallel, reduction of the side population to 4-30% from the control for epithelial stem cells on the next day after exposure and to 22-36% from the control for H69 cells in 3 days after exposure. The size of the side population remained reduced to 8-37% of that in the control cultures of epithelial stem cells and H69 cells for at least 7 days after exposure. The decrease of the side population fraction of cells was not caused by cell death, but could be due to radiation-induced activation of the signal pathways, regulating the velocity of autoregeneration of the pool of true stem cells and acceleration of their transition to the pool of rapidly proliferating progenitor cells, this leading to an increase in the total cell count in the studied cultures under the effect of low-dose γ-radiation.

Low doses of gamma-radiation induce SOS response and increase mutation frequency in Escherichia coli and Salmonella typhimurium cells

This study addresses use of two bacterial test systems (the Ames test and the SOS chromotest) to estimate the effects of low doses of γ-radiation. The most substantial increases in induction of SOS response and mutation frequencies were observed in the first 24h of exposure to γ-radiation as compared to the cells in the exposure-free control. Gamma-radiation also impaired growth and survival of S. typhimurium cells in the first 24h. The effects were attenuated at lower exposure doses and at longer exposure times. In the experiments conducted in this study, at 96h of exposure, the values of some of the γ-radiation effects were lower than the MID (minimum inducing dose) detection limits and, thus, were neglected. Long-term exposure to γ-radiation could also result in combined effects of γ-radiation and the death of cells in the culture.