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[en] Complete text of publication follows. Since 1987 till the present time, at the Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, studies on the effect of low-dose low-level irradiation on biophysical and biochemical parameters of the genetic and membrane apparatus of cells of organs of exposed animals are being carried out. We investigated the structural parameters of the genome (by the method of DNA binding to nitrocellulose filters), structural parameters of nuclear, microsomal, mitochondrial, and plasmic (synaptic and erythrocyte) membranes (by the method of spin probes localized in various layers of membranes), the composition and oxidation degree of membrane lipids, and the functional activity of cells - the activity of enzymes, relationship between isozymic forms, and regulating properties. We investigated also the effect of low-level irradiation on the sensitivity of cells, biopolymers, and animals to subsequent action of various damaging factors, including high-dose irradiation. The animals were exposed to a source of 137Cs γ-radiation at the dose-rates 41.6 x 10-3, 4.16 x 10-3, and 0.416 x 10-3 mGy. The doses were varied from 6 x 10-4 to 1.2 Gy. As a result of the studies performed, the following conclusions were made: 6. Low radiation doses affect actively the metabolism of animals and man. 7. Over certain dose ranges, low-level irradiation is even more effective than acute high level. 8. The dose-effect dependence of irradiation may be nonlinear, nonmonotonic, and polymodal in character. 9. Doses that cause the extreme effects depend on the irradiation dose-rate (intensity); they are lower at a lower intensity. 10. Low-dose irradiation causes changes (mainly, enhancement) in the sensitivity to the action of other damaging factors. We explain the nonlinear and nonmonotonic dose-effect dependence that we obtained in our experiments with low-dose low-level irradiation by changes in the relationship between damages and reparation of the damages. With this kind of low-level irradiation, the reparative systems either are not initiated (induced), or function inadequately, or are initiated with a delay, i.e., when the exposed object has already received radiation damages. Recently, the absence of reparation at low irradiation doses was verified on the cell level, and the complex character of the dose dependence was confirmed. Previously, we published a similar scheme of dependence of damages on irradiation dose, which was different for different dose ranges. According to the scheme, the quantitative characteristics were similar for the doses that differed by several orders of magnitude; in a certain dose range, the effect may have an opposite sign.The results obtained and supported by numerous experiments are important because the above dose dependences made it possible to come to conclusion about a radiogenic or non-radiogenic character of changes observed in an irradiated organism. The indisputable conclusion that if the effect increases with the dose it is evidence for its radiogenic nature is by no means in favor of an opposite statement, i.e., that the absence of a direct dose-effect dependence but its nonmonotonic character is evidence for the absence of a relation of the effect to irradiation. The controversial conclusions of International and Russian organizations stem mainly from the underestimation and misunderstanding of the effects of ultra-low and low irradiation doses, reluctance to apply other criteria to assess the consequences of irradiation on human health, and conviction (groundless) that low doses cause either no damages or such minor damages that they may be neglected and disregarded. In the lecture, data that elucidate the above controversies will be presented.
[en] Complete text of publication follows. The low level exposure to alpha radiation emitted from radon and its progeny in general environment and the dwellings has received continuing attention as the radon has been found to be ubiquitous radioactive air pollutants to which all the organisms (e.g. bacteria, plants or animals including humans) are exposed everyday to varying amounts of ionizing radiation. These radiations are spontaneously emitted by naturally occurring radioactive material like 238U and 232Th, ever since their existence on earth. The exposure to alpha radiation emitted from radon poses health hazards not only to the workers at industrial units like thermal power plants, gas fired power plants, coal fields and oil fields but also to the dwellers in normal houses in their surroundings. Radon being an inert gas can easily disperse into the atmosphere immediately on its release. The solid alpha active decay products of radon like 218Po and 214Po become airborne and get themselves attached to the aerosols, dust particles and water droplets suspended in the atmosphere. When inhaled during breathe, these solid decay products along with air may get deposited in the tracho-bronchial and pulmonary region of lungs resulting in the continuous irradiation of the cells which may be the cause of lung cancer. In the present work, we report on the estimation of the radon concentration, annual exposure and annual effective doses received by the workers working in the interior environment of some industrial units like thermal power plants and different types of dwellings of North India. For these measurements we have used the alpha sensitive solid-state nuclear track detector (SSNTD). The results indicate an increase in radiation dose received by the workers in thermal power plants due combustion of coal as compared with normal dwellings.
[en] Complete text of publication follows. Objective: The objective of this study is to detect the noble proteins that were functionally regulated by change of arginine methylation through irradiation of the low dose. The increase of the arginine methylation which is induced by low dose gamma-ray will have meaningful Introduction: Exposure of cells to low doses of radiation has well documented biological effect, but the underlying regulatory mechanisms are still poorly understood. Arginine methylation is a post translational modification that results in the formation of asymmetrical and symmetrical dimethylated arginines. Post-translational methylation of arginine residues of proteins involved in a growing number of cellular processes, including transcriptional regulation, cell signaling, RNA processing and DNA repair, biological influence. Methods: Human normal cell line Chang-liver was irradiation by gamma-ray of 0.02Gy, 0.2Gy. After irradiation, cells were incubated for 4h, 8h, 24h, and then harvested to prepare protein extracts. ASYM24(anti-dimethyl-Arginine, asymmetric) antibody was used to Western blot and immunoprecipitation. Proteins that show different degrees of intensity between the two samples were analyzed by Mass spectrometry. Results: We detected increased asymmetric arginine methylation of two proteins at 24h after a dose of 0.2Gy irradiation. The mass spectrometry identified that it is 27kDa and 73kDa proteins. The 27kDa is hypothetical protein that function does not know. The 73kDa protein is Mortalin, a member of the Heat shock 70 protein family, which correlate with the radioresistance response, control of cell proliferation and act as a chaperone. Conclusion: Low dose radiation induces the change of asymmetric arginine methylation modification of arginine residues of hypothetical protein and mortalin. We expect that increase of arginine methylation in mortarin and hypothetical protein correlates with the radioresistance, the functional study for these proteins is necessary to clarify the biological effects in radioadaptive response.
[en] Complete text of publication follows. It was experimentally showed, that the exposure to low doses of ionizing radiation (IR) result in over-production of oxygen derived free radicals with inverse dose-rate effect. The oxidative stress that follows, especially cell membrane damage, was considered by Petkau, as crucial step in the induction of radiation injuries. From clinical research and practice with other unexposed patients is known that this type of cell damage can lead to an impairment of cellular function and can cause many free-radicals mediated diseases, such as atherosclerosis, damage of heart muscles, inflammatory and immuno-reactive lesions, senile dementia, cancer, etc. The aim of this paper is to investigate if occupational exposure to low doses of IR change the redox status of exposed personnel, and if so, is it the additional risk factor for free-radicals mediated diseases. Subjects: 77 medical workers, devided in two groups: 44 occupationally exposed to ionizing radiation (E), and 33 controls (C), matched in age, gender, habits-daitary, alcohol consumption, smoking and exposure time, were examined. Methods: Radiation dose accumulated over years was calculated on the basis of individual TL-dose records. Superoxide-anion and MDA production, as well as SOD (MnSOD, CuZnSOD) and GSH activity were determined in blood samples spectrophotometrically. Results: Significantly higher incidence of cataract, and higher, but not significant, incidence of cardiovascular diseases was noticed in exposed. Our results also confirmed significantly higher superoxide and MDA production (p=0.0049, 0.000028, respectively), as well as, increased activity of MnSOD and CuZnSOD (p0.0105, 0.001, respectively), and decreased level of GSH (p=0.0599) in exposed. Conclusions: Our results showed that low doses of IR could induce oxidative stress and for that reason could be considered as additional risk factor for free radical-mediated diseases. Further epidemiological studies are needed for final result.
[en] Complete text of publication follows. Objective: The experimental data presented in the report put some clarity into the ongoing polemics about possibility of induction of harmful non-carcinogenic effects in human body as a result of exposure to low doses of radiation. The denial of this possibility is based on the fact that traditionally studied genotoxic effects cannot be the cause of this pathology: the incidence of these effects in exposure to low doses of radiation is fairly low; the effects are not overt in critical slowly regenerating tissues, since they can only be morphologically manifested in actively growing cell populations. Methods: Endothelium of myocardial and alveolar capillaries were studied ultra-structurally in 236 rats irradiated by a wide range of X-ray doses (0,25;0,5;2,25;4,5;9;30;48;100) and 28 intact control animals. Studies were conducted during 12-18 months. The material consisted of 2-3 portions from various parts of myocardium and lung. From each portion, sections were prepared, in which all capillary sections were analyzed and ultra-structure of all lining capillary endotheliocytes (their number most often was more than 100) was studied. In each animal the percentage of non-viable endotheliocytes with signs of generalized organoid destruction, damage of plasmalemma and nuclear structures was accounted. Results: Irradiation of rat to low and higher doses caused significant (up to 7 times) increase number of endothelial cells with various ultra-structural damages (from relatively light ones to in the cell death). Even the lowest dose - 0,25 Gy produce an increasing degeneration, intracellular lysis and defects of mitochondria. We found unusual features of postradiational endothelium changes: dose independence, necessity of revealing the long-term, non-mutational cellular effects, massive involvement of cells, early development of the maximum effect already after the low dose irradiation. These special somatic effects, unlike genotoxic effects, are not connected to cell division. They appear according to the principle 'all or nothing' in low doses of radiation (in mammals less than 1 Gy). In slowly regenerating tissues these effects (we called them 'alternative effects' result in various subcellular disorders (mostly cytoplasmic). An irreversible change of intracellular homeostasis and dystrophic processes occur within a few hours after exposure. This can result in morphological and functional changes in tissues (depopulation), thus providing for the development of non-carcinogenic somatic consequences of low-dose irradiation. Presumably the changes of this kind are responsible for pathogenesis of the remote somatic disorders following a moderate radiation exposure. The alternative effects are based on special hidden non-mutational alterations. Unlike the traditionally studied alterations they involve all cells of the population and can be inherited by all off-springs (at least in F1). This substantially broadens our notion of biological and applied significance of this phenomenon. Conclusion: The most typical manifestation of alternative effects is a persistently increasing predisposition of cells to damage and death. It is likely that other manifestations are also possible, including a non-specific increase of likelihood (due to impairment of reparation capability) of genome damage. This could give a better insight into the problem of biological risks of cancer transformation and occurrence of hereditary disorders after exposure to low-dose irradiation. It is essential that different biological organisms may develop alternative effects not only due to radiation but other kinds of exposure. This represents a substantial ecological importance of alternative effects and requires development of new methods of assessment of external factors.
[en] Complete text of publication follows. The effects of ionizing radiation can be viewed at all levels of biological organization, ranging from the molecular to ecosystem level. Effects on organisms can be traced to molecular and cellular responses, as radiation impact does not necessarily lead to observable effects on specimens, population or ecosystem. This is because the measurable attributes of the levels differ, despite the fact that all levels are interrelated. The cytogenetic effects of radioactive and conventional pollution as they are recorded in organisms of natural ecosystem and the apportionment of causes to each kind of pollutants is a relative new field in radioecological research. There is limited evidence on field observations in international literature; even there is a lot of evidence in concerning laboratory experiments. The study of in situ effects of ionizing radiation in the cytogenetic level is the key for determining the radiological status of the ecosystem considered, based on the relation: concentration of pollutant in abiotic components and/or bioaccumulation → dose rate → effect on organism at the cellular level. Several field studies on the comparative effects of ionizing radiation and chemical pollution in some selected areas in the Mediterranean, the Black Sea and in inland waters combined with laboratory experiments have shown a conceptual model of response of organisms, which is unique for ionizing radiation and chemical pollution. This model is based on the effects of different pollutants on aquatic biota (Crustacea, Polychaeta, Oligochatea, Fish embryos etc), as they have been recorded at the cellular level. The environmental assessment of an aquatic ecosystem with regards to ionizing radiation in comparison to effects of chemical pollutants is based on determining the distribution frequency of chromosomal aberrations induced in cells of natural populations. Cytogenetic methods are used in pollution research because of their high sensitivity in terms of the determination of effects of the pollutant impact. Because the impact at the cytogenetic level is not discriminated according to the primary agent, the search for the 'responsibility attribution' is based on statistics i.e. the distribution pattern of the observed aberrations and the types of chromosome aberration, as well.
[en] Complete text of publication follows. The radioprotective effects of the naturally occurring compound chlorogenic acid has been investigated against mortality induced by gamma irradiation in mice. Chlorogenic acid administrated at single doses of 100, 200 and 400 mg/kg 1 and 24 h prior to lethal dose of gamma irradiation (8.5 Gy). At 30 days after treatment, the percentage of animal survival in each group was: control, 20%; 100 mg/kg, 20% and 15%; 200 mg/kg, 45% and 15%; 400 mg/kg, 25% and 35% for 1 h and 24 h treatment prior gamma irradiation, respectively. Percentage of survival increased in animal treated with this agent at 200 mg/kg at 1 h statistically compared with irradiated alone group. Other doses of chlorogenic acid have not showed any enhanced survival at 1 and 24 h before irradiation. Chlorogenic acid exhibited concentration-dependent activity on 1, 1-diphenyl 2-picrylhydrazyl free radical to show strong antioxidant activity. It appeared that chlorogenic acid with antioxidant activity reduced mortality induced by gamma irradiation.
[en] Complete text of publication follows. A potential accident involving the transport of spent nuclear fuel along the Norwegian coastline has been choosen for evaluation of a dose assessment methodology. The accident scenario assumes that the release the radioactivity takes place under water and that there is free exchange of water between the spent fuel and the sea. The inventory has been calculated using the ORIGEN programme. Radioecological consequences are provided by the NRPA compartment model which includes the processes of advection of radioactivity between compartments and water-sediment interactions. The contamination of biota is further calculated from the radionuclide concentrations in filtered seawater in the different water regions. Doses to man are calculated on the basis of radionuclide concentrations in marine organisms, water and sediment and dose conversion factors. Collective dose-rates to man, doses to the critical groups, concentration of radionuclides in biota/sea-foods and doses to marine organisms were calculated through the evaluation of radioecological consequences after accidents. Results of calculations indicate that concentrations of radionuclides for some marine organisms can exceed guideline levels. At the same time collective dose rates to man as well as doses to a critical group are not higher than guideline levels. Comparison of results from calculations with provisional benchmark values suggests that doses to biota are in most cases unlikely to be of concern. However, to some marine organisms can be much higher than the screening dose of 10 μGyh over long periods. It is apparent that water-sediment distribution coefficients and concentration factors constitute the main sources of uncertainties in the present case. It is important to note that knowledge gaps concerning the influence of relatively low dose to populations of marine organisms over long time periods (many generations) substantially constrain the accessor's ability to evaluate with any great certainty, statistically significant effects on such organisms.
[en] Complete text of publication follows. Natural sources of radioactivity are all around us, and man-made radioactive materials are a vital part of medicine and industry. Exposure to some radiation, natural or man-made, is inevitable. Sixty-eight percent of our exposure to natural sources of radiation usually comes from radon, a colorless, tasteless, and odorless gas that comes from the decay of uranium found in nearly all soils. Radioactive radon gas is widely considered to be a health hazard by environmental agencies in the United States and in Europe. Yet despite the warnings of these agencies, thousands of people annually expose themselves to radon for therapeutic purposes, in facilities ranging from rustic old mines, to upscale spas and clinics. Moreover, while modern biomedicine has been enormously successful in the treatment of acute illnesses, it has dealt less well with chronic illnesses. In living with radiation, we must understand the risks and benefits. In order to assess the risk at high doses, LNT hypothesis of ICRP (and consequently also of IAEA, EU, NCRP, BEIR VI, etc.) is used. Current radiation risk estimates, drawn by linear extrapolation, from high dose and dose rate of radiation from very high and complex miner's data orders of magnitude down to completely different current mining conditions, residential radon doses and dose-rates, and a multitude of other confounding factors, even very careful epidemiological studies have not demonstrated any cancerogenic radon effects up to levels around 1000 Bq/m3, or ca. 7 times the EPA limit. This paper addresses the possibility that the LNT model may not be applicable for low doses of radon, and that low doses of radon may in fact be beneficial for certain chronic illnesses. There are growing numbers of studies indicating an inverse relationship between cancer occurrence and low dose environmental radon exposure, as well as numerous studies examining the therapeutic effects of low dose radiation. This protective or beneficial effect, called hormesis, has gained recognition by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). A large body of anecdotal evidence in support of hormesis exists, in the form of thousands of people who annually use radon spas worldwide. Moreover, there are also recent studies which indicate that not only lung cancer, but also other cancers including childhood leukemia are substantially lower in high natural background and radon than in low-dose areas. Similar effects have also been recently observed in Kerala/India, Russia, etc. - usually with the explanation that it is not the radiation level, but other factors such as industrial pollution and living habits, which far outweigh any possible small detrimental radiation effects beyond statistical detection - if they should exist at all. Regarding over ground radon, it may be concluded that the radon balneology remains an important therapy against painful joint diseases, etc., with a hypothetical minor negative radiation effect certainly negligible compared to the benefits. In the present work, a comprehensive study of the available literature, data and reports of various radiation exposure and protection studies will be presented. In summary, an analysis of all available data shows that, with a few exceptions such as early miners, the human health effects of radon are most likely to be substantially more beneficial than harmful.
[en] Complete text of publication follows. Purpose: To provide results of dose and dose rate measurements, modeling and analysis for the high Radon 'inverse' dose-rate effect (IDRE), adaptive response (AR) , Bystander Effects (BE), Hyper-radiosensitivity and dose induced radioresistance (HRS/IRR) and the low LET IDRE. Methods: Radon progeny particle diameters decrease at high Radon levels, due to increased neutralization rates. Underground miners data are used to confirm lung dose effects. An adaptive response Microdose Model formulated from the microdose concepts of Feinendegen and his cohorts, is extended to include BE and applied to IDRE, AR and BE experimental data. Results: Analysis of underground miners data conclusively supports a factor of 4.3 in lung dose from increased deposition in the nasel passages, negating BE as cause of the Lubin et al (1995) high Radon lung cancer IDRE. This negates support of BE as major concern at domestic Radon levels and high LET galactic radiations for manned Mars mission. AR Microdose Model use for mammography X-rays shows single Specific Energy Hits, at very low dose rates to the cell nucleus, activates AR protection against spontaneous neoplastic transformations of a factor of 2 further supporting Redpath (2007) of no deleterious cancer risk from mammography X-rays and a dose/dose-rate coupling. IRR in HRS/IRR is from increased repair capability 'triggered' at a very low dose of 15 cGy. The 'triggering' is shown in low LET IDRE with G2/M checkpoint arrest. The correlation suggest IRR in both HRS/IRR and low LET IDRE dose and dose rate radio-protection are from the activation of same increased repair rate protective mechanisms i.e. dose/dose-rate coupling. In examination of LDR Brachytherapy, it's plausible the high excess post-treatment complications, especially for cervix cancer, compared to HDR Brachytherapy is from a high-radiosensitivity for the decaying permanent implant sources below the IDRE threshold with a possible factor of 10 excess dose to connective tissue and organs. Finally, a method for measuring the changes in endogenic cell capabilities to carry-out increased radio-protective processes i.e. separate decreased direct damage (greater ROS scavenging) and the increased repair rates (increased damage recognition, increased damage site location, increased repair mobilization and finally increased repair of the actual damage). This method shows for low LET IDRE no decreased direct damage occurs and significant increased repair occurs. After the 'triggered' threshold and transition of IDRE protection against cell killing, a larger fraction of cell damage produces viable mutations. This suggests that the cells bio-chemically conclude it is senseless to provide protection against potentially mutations in the low dose rate region if all the cells are being killed. Conclusions: The BE does not cause the underground miners high Radon IDRE. Single Specific Energy nucleus hits at very low dose rates activate adaptive response protection of spontaneous neoplastic transformations from mammography X-rays. A dose and dose-rate coupling is modeled. A correlation between the 'triggering' of the transition of the radio-protection for the Hyper-radiosensitivity and dose induced radio-resistance effect (HRS/IRR) and the low LET 'inverse' dose-rate effect (IDRE) as if they are from same radioprotective mechanisms. Possible excess connective tissue and organs damage occurs from low LET IDRE in LDR Brachytherapy treatments with permanent implants.