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PubMed2003

Errors in the particle flux measurement data relevant to solar energetic particle spectra.

Systematical errors of the spacecraft measured high-energy particle fluxes are analyzed. The errors are shown to be inherent to most of the measurements made to be the monitoring of the high-energy radiation in the space. The level of the systematic errors of the measurements varies with energy, thus resulting in distortions of the solar energetic particle spectra based on the measurement data. The erroneous experimental data have resulted in spurious estimates of space radiation environment and give rise to erroneous physical conclusions.

Cosmic Radiation↗
PubMed2002

Possible application of an imaging plate to space radiation dosimetry.

Fading correction plays an important role in the application of commercially available BaBrF:Eu2+ phosphors: imaging plates (IP) to dosimetry. We successfully determined a fading correction equation, which is a function of elapsed time and absolute temperature, as the sum of several exponentially decaying components having different half-lives. In this work, a new method was developed to eliminate a short half-life component by annealing the IP and estimating the radiation dose with the long half-life components. Annealing decreases the effect of fading on the estimated dose, however, it also causes the loss of photo-stimulated luminescence (PSL). Considering an IP as an integral detector for a specific period of up to one month, the practically optimum conditions for quantitative measurement with two types of IP (BAS-TR and BAS-MS) were evaluated by using the fading correction equation, which was obtained after irradiation with a 244Cm source as the alpha-ray source having a specific radioactivity of 1,638.5 Bq/cm2 including beta and gamma-ray (alpha energy of 5.763 and 5.805 MeV). Annealing at 80 degrees C for 24 hours after irradiation for one month using BAS-MS should minimize the effect of the elapsed time, resulting in sufficient sensitivity. The results demonstrate new possibilities for radiation dosimetry offered by the use of an IP.

Cosmic Radiation↗
PubMed1999

Space radiation concerns for manned exploration.

Spaceflight exposes astronaut crews to natural ionizing radiation. To date, exposures in manned spaceflight have been well below the career limits recommended to NASA by the National Council of Radiation Protection and Measurements (NCRP). This will not be the case for long-duration exploratory class missions. Additionally. International Space Station (ISS) crews will receive higher doses than earlier flight crews. Uncertainties in our understanding of long-term bioeffects, as well as updated analyses of the Hiroshima. Nagasaki and Chernobyl tumorigenesis data, have prompted the NCRP to recommend further reductions by 30-50% for career dose limit guidelines. Intelligent spacecraft design and material selection can provide a shielding strategy capable of maintaining crew exposures within recommended guidelines. Current studies on newer radioprotectant compounds may find combinations of agents which further diminish the risk of radiation-induced bioeffects to the crew.

Aerospace Medicine↗
PubMed2000

Responses of TLD Mg2SiO4:Tb and radiophotoluminescent glass to heavy charged particles and space radiation.

The LET dependences of thermoluminescence dosimeters of Mg2SiO4:Tb (TLMS) and radiophotoluminescent glass dosemeters (RPLG) were examined using high energy, heavy ion beams. TLMS kept its efficiency below 10 keV micrometer-1 and decreased almost linearly with the logarithm of LET for higher LET particles. The efficiency of RPLG decreased more gradually than TLMS although its reduction was observed at a lower LET region around 0.5 keV micrometer-1. Accordingly, the ratio of TLMS to RPLG valued showed a maximum peak around 20 keV micrometer-1 of LET. The results obtained with both dosemeters in the 40 day space mission in the Russian space station Mir showed that not only dose level but also radiation quality were varying considerable in the Mir Core Module.

Cosmic Radiation↗
PubMed1999

Chromosome mechanics of fungi under spaceflight conditions--tetrad analysis of two-factor crosses between spore color mutants of Sordaria macrospora.

Spore color mutants of the fungus Sordaria macrospora Auersw. were crossed under spaceflight conditions on the space shuttle to MIR mission S/MM 05 (STS-81). The arrangement of spores of different colors in the asci allowed conclusions on the influence of spaceflight conditions on sexual recombination in fungi. Experiments on a 1-g centrifuge in space and in parallel on the ground were used for controls. The samples were analyzed microscopically on their return to earth. Each fruiting body was assessed separately. Statistical analysis of the data showed a significant increase in gene recombination frequencies caused by the heavy ion particle stream in space radiation. The lack of gravity did not influence crossing-over frequencies. Hyphae of the flown samples were assessed for DNA strand breaks. No increase in damage was found compared with the ground samples. It was shown that S. macrospora is able to repair radiation-induced DNA strand breaks within hours.

Ascomycota↗
PubMed2004

Ecological study of solar radiation and cancer mortality in Japan.

Geographic observation of the increased mortality of some cancers at higher latitudes has led to a hypothesis that vitamin D produced after exposure to solar radiation has anti-carcinogenic effects. However, it is unclear whether such association would be observed in countries like Japan, where fish consumption, and therefore dietary vitamin D intake, is high. Pearson correlation coefficients were calculated between averaged annual solar radiation levels for the period from 1961 through 1990 and cancer mortality in the year 2000 in 47 prefectures in Japan, with adjustments for regional per capita income and dietary factors. A moderate, inverse correlation with solar radiation was observed for cancers of the esophagus, stomach, colon, rectum, pancreas, and gallbladder and bile ducts in both sexes (correlation coefficient, ranging from -0.6 to -0.3). The results of this study support the hypothesis that increased exposure to solar radiation reduces the risk of cancers of the digestive organs.

Body Burden↗
PubMed2005

Stability of chromosome aberrations in the blood lymphocytes of astronauts measured after space flight by FISH chromosome painting.

Follow-up measurements of chromosome aberrations in the blood lymphocytes of astronauts were performed by FISH chromosome painting at various intervals from 5 months to more than 5 years after space flight and compared to preflight baseline measurements. For five of the six astronauts studied, the analysis of individual time courses for translocations revealed a temporal decline of yields with half-lives ranging from 10 to 58 months. The yield of exchanges remained unchanged for the sixth astronaut during an observation period of 5 months after flight. These results may indicate complications with the use of stable aberrations for retrospective dose reconstruction, and the differences in the decay time may reflect individual variability in risk from space radiation exposure.

Astronauts↗
PubMed1997

[An analysis of radiation risk for manned space flight in low-earth orbits with medium inclination].

The radiation risk for manned space flight in the orbit with altitude <500km and inclination 40 degrees-50 degrees was analyzed. The doses of several anomalously large solar proton events (SPE) were estimated from the measured doses during the SPE where the spectral parameters were known. The result shows that the radiation risk is not serious for the mission with above orbital parameters.

Cosmic Radiation↗
PubMed1967

The results of biological studies made on board the Voskhod and Voskhod 2 spaceships.

The biological effects of flight and outer space factors were studied on biological specimens of various organization, viz. spiderwort microspores, dry seeds of the pine tree, wheat, onion and of other higher plants as well as on lysogenic bacteria and wine flies. Furthermore, lysogenic bacteria were studied for the effectiveness of a number of well known ray-proof substances (such as mercaptopropylamine, 5-methoxytriptamine, etc.). The specimens were secured in special containers both on board the spaceships and in the hip pockets of the astronaut Leonov's spacesuit. Biological effectiveness of the factors was evaluated by means of cytogenic, genetic and microbiological procedures. The analysis of the data obtained has shown that under the impact of the complex of flight and outer space factors, including ionizing radiation, both qualitative and quantitative changes occurred in the hereditary structures of some of the specimens, viz.: wheat seeds, spiderwort microspores and lysogenic bacteria. These changes were similar to the effects recorded in the flights of Vostok-2, 3, 6. As compared to the controls, an enlargement was found in the cells of wheat sprout radicles, accompanied by chromosome rearrangements (N. L. Deloney et al.). Increased phage production by lysogenic bacteria (N. N. Zhukov-Verezhnikov, N. I. Rybakov et al.) and impairment of the mitosis mechanism in the spiderwort macrospores were demonstrated (N. L. Deloney, etc.). Higher frequency of dominant lethals and more frequent than normal chromosome indivergence in the wine flies were recorded. Quantitatively, the recorded drifts were insignificant (as was the case with the 'Vostok' spaceships' flights). Of interest are the results of the experiments on spiderwort microspores carried out with B. B. Yegorov's participation. The data obtained show that 1) during the mitosis stage spiderwort microspores show differing sensitivity to the space flight factors, and that 2) the mitosis stages support the previous hypothesis that impairment of the mitosis mechanism is due to the state of weightlessness, while chromosome rearrangements are chiefly induced by the effects of the complex of factors related to the take-off and touch-down stages of the flight. (N. L. Deloney et al.). The analysis of beta-mercaptopropylamine and 5-methoxytriptamine tests indicates that these substances significantly reduce the phage producing activities of the lysogenic bacteria not only blocking the induced phage production but reducing the amount of spontaneous phage production as well (N. N. Zhukov-Verezhnikov, N. I. Rybakov et al.). Thus, the results of biological experiments on various specimens with differing degrees of radiosensitivity agree well among themselves and are consistent with the data on the dosage of space radiation.

Bacteria↗
PubMed1985

Utilisation of the European Retrieval Carrier Eureca for life science research.

Eureca, the European Retrieval Carrier, is a reusable free-flying platform, which will be launched to 500 km altitude and retrieved by the Shuttle. up to 6 months later at 300 km. The first mission of Eureca is dedicated to research in the fields of life sciences and material sciences. The experimental hardware of the first mission will consist of a variety of processing chambers for crystal growth and equipment for biological investigations viz plant growth and protein crystallization, and there is the possibility to perform experiments in the field of exobiology. The Eureca mission offers the opportunity for long time exposure of material and of terrestrial origin to the unique environment of space or to selected factors of it, such as the radiation environment, the space vacuum, extreme temperatures and microgravity conditions.

Biological Science Disciplines↗
PubMed2002

Radiation quality and tissue-specific microenvironments following exposure to 1 GeV/amu Fe.

This paper summarizes quantitative in vivo laminin immunofluorescence analysis of mammary glands and skin epithelial structures from mice exposed to 1 GeV/amu Fe ions. Digital confocal microscopic images were quantified and linked to the rough "core-penumbra" Fe track physical description. Comparison to gamma-ray sparsely ionizing radiation suggested the core of the Fe track being responsible for a biological response only seen with energetic Fe particles. Conclusions for modeling in vivo responses to radiation were then implied.

Animals↗
PubMed2003

Changes in biomarkers from space radiation may reflect dose not risk.

This presentation evaluates differences between radiation biomarkers of dose and risk and demonstrates the consequential problems associated with using biomarkers to do risk calculations following radiation exposures to the complex radiation environment found in deep space. Dose is a physical quantity, while risk is a biological quantity. Dose does not predict risk. This manuscript discusses species sensitivity factors, tissue weighting factors, and radiation quality factors derived from relative biological effectiveness (RBE). These factors are used to modify dose to make it a better predictor of risk. At low doses, where it is not possible to measure changes in risk, biomarkers have been used incorrectly as an intermediate step in predicting risk. Examples of biomarkers that do not predict risk are reviewed. Species sensitivity factors were evaluated using the Syrian hamster and the Wistar rat. Although the frequency of chromosome damage is very similar in these two species, the Wistar rat is very sensitive to radiation-induced lung cancer while the Syrian hamster is very resistant. To illustrate problems involved in using tissue weighting factors, rat trachea and deep lung tissues were compared. The similar level of chromosome damage observed in these two tissues would predict that the risk for cancer induction would be the same. However, even though large numbers of deep lung tumors result from inhaled radon, under the same exposure conditions there has never been a tracheal tumor observed. Finally, the Relative Biological Effectiveness (RBE) used to generate "quality factors" that convert exposure and dose from different types of radiation to a single measure of risk, is discussed. Important risk comparisons are done at very low doses, where the response to the reference radiation has been shown to either increase or decrease as a function of dose. Thus, the RBE and the subsequent risk predicted is more dependent on the background response of the endpoint and the shape of the dose response to the reference radiation than it is on the radiation type of interest. A large study using micronuclei as biomarkers following exposure to different energies of mono-energetic neutrons, x-rays and gamma rays delivered at very low doses (0.0 to 0.10 Gy) is reported. As additional biomarkers of risk involved in critical steps in the carcinogenic process are developed, it may become possible to base risk estimates on biological change rather than the radiation energy deposition or dose.

Animals↗
PubMed2002

Molecular targets in cellular response to ionizing radiation and implications in space radiation protection.

DNA repair systems and cell cycle checkpoints closely co-operate in the attempt of maintaining the genomic integrity of cells damaged by ionizing radiation. DNA double-strand breaks (DSB) are considered as the most biologically important radiation-induced damage. Their spatial distribution and association with other types of damage depend on radiation quality. It is believed these features affect damage reparability, thus explaining the higher efficiency for cellular effects of densely ionizing radiation with respect to gamma-rays. DSB repair systems identified in mammalian cells are homologous recombination (HR), single-strand annealing (SSA) and non-homologous end-joining (NHEJ). Some enzymes may participate in more than one of these repair systems. DNA damage also triggers biochemical signals activating checkpoints responsible for delay in cell cycle progression that allows more time for repair. Those at G1/S and S phases prevent replication of damaged DNA and those at G2/M phase prevent segregation of changed chromosomes. Individuals with lack or alterations of genes involved in DNA DSB repair and cell cycle checkpoints exhibit syndromes characterized by genome instability and predisposition to cancer. Information reviewed in this paper on the basic mechanisms of cellular response to ionizing radiation indicates their importance for a number of issues relevant to protection of astronauts from space radiation.

Animals↗
PubMed1975

Peculiarities of biological action of hadrons of space radiation.

Biological investigations in space enable one to make a significant contribution on high-energy hadrons to biological effects under the influence of factors of space flights. Physical and molecular principles of the action of high-energy hadrons are analysed. Genetic and somatic hadron effects produced by the secondary radiation from 70 GeV protons have been studied experimentally. The high biological effectiveness of hadrons, great variability in biological effects, and specifically of their action, are associated with strong interactions of high-energy hadrons. These are the probability of nuclear interaction with any atom nucleus, generation of a great number of secondary particles (among them, probably, highly effective multicharged and heavy nuclei, antiprotons, pi(-)-mesons), and the spatial distribution of secondary particles as a narrow cone with extremely high density of particles in its first part. The secondary radiation generated by high- and superhigh-energy hadrons upon their interaction with the spaceship is likely to be the greatest hazard of radiation to the crew during space flights.

Bacteriophage T4↗