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PubMed2004

Formation and stability of complex organic compounds in space environments.

Complex organic compounds have been found in extraterrestrial bodies such as meteorites and comets. We confirmed the formation of complex organic compounds that contained amino acid precursors from a mixture of carbon monoxide (or methanol), ammonia and water by radiation or UV. Molecular weights of the complex organics were several thousands. Stability of the complex precursors was studied. When free amino acids were irradiated with gamma rays or synchrotron radiation, they easily decomposed. The complex precursors were, however, much more stable than free amino acid against irradiation. We propose to examine the formation and alteration of amino acid precursors in space by using exposed facility of ISS.

Amino Acids↗
PubMed1999

Application of real-time radiation dosimetry using a new silicon LET sensor.

A new type of real-time radiation monitoring device, RRMD-III, consisting of three double-sided silicon strip detectors (DSSDs), has been developed and tested on-board the Space Shuttle mission STS-84. The test succeeded in measuring the linear energy transfer (LET) distribution over the range of 0.2 keV/micrometer to 600 keV/micrometer for 178 h. The Shuttle cruised at an altitude of 300 to 400 km and an inclination angle of 51.6 degrees for 221.3 h, which is equivalent to the International Space Station orbit. The LET distribution obtained for particles was investigated by separating it into galactic cosmic ray (GCR) particles and trapped particles in the South Atlantic Anomaly (SAA) region. The result shows that the contribution in dose-equivalent due to GCR particles is almost equal to that from trapped particles. The total absorbed dose rate during the mission was 0.611 mGy/day; the effective quality factor, 1.64; and the dose equivalent rate, 0.998 mSv/day. The average absorbed dose rates are 0.158 mGy/min for GCR particles and 3.67 mGy/min for trapped particles. The effective quality factors are 2.48 for GCR particles and 1.19 for trapped particles. The absorbed doses obtained by the RRMD-III and a conventional method using TLD (Mg(2)SiO(4)), which was placed around the RRMD-III were compared. It was found that the TLDs showed a lower efficiency, just 58% of absorbed dose registered by the RRMD-III.

Calibration↗
PubMed2003

Radiation risk and human space exploration.

Radiation protection is essential to enable humans to live and work safely in space. Predictions about the nature and magnitude of the risks posed by space radiation are subject to very large uncertainties. Prudent use of worst-case scenarios may impose unacceptable constraints on shielding mass for spacecraft or habitats, tours of duty of crews on Space Station, and on the radius and duration of sorties on planetary surfaces. The NASA Space Radiation Health Program has been devised to develop the knowledge required to accurately predict and to efficiently manage radiation risk. The knowledge will be acquired by means of a peer-reviewed, largely ground-based and investigator-initiated, basic science research program. The NASA Strategic Plan to accomplish these objectives in a manner consistent with the high priority assigned to the protection and health maintenance of crews will be presented.

Aerospace Medicine↗
PubMed1998

Energetic neutron and gamma-ray spectra under the earth radiation belts according to "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686" orbital complex and "CORONAS-I" satellite data.

The spectra of neutrons >10 MeV and gamma-rays 1.5-100 MeV under the Earth Radiation Belts, restored from the data, obtained onboard orbital complex "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686", are presented. The spectra shapes are similar to those for albedo neutrons and gamma-rays, but absolute values of their fluxes (0.2 cm-2 s-1 for neutrons, 0.8 cm-2 s-1 for gamma-rays at the equator and 1.2 cm-2 s-1, 1.9 cm-2 s-1, accordingly, at L=1.9) are several times as large. It is possibly explained by the fact that most of the detected particles were produced by the cosmic ray interactions with the orbital complex matter. Neutron and gamma-ray fluxes obtained from "CORONAS-1" data are near those for albedo particles.

Cosmic Radiation↗
PubMed1977

Apollo-Soyuz Test Project on biorhythm of zone-forming fungi: preliminary work.

The purpose of the experiment was to study general and local effects of space flight factors on the rhythm of cellular activity and on the morphological and genetic properties of biological objects. The Pushchino strain, Actinomyces levoris Kras 17-225A-IBFM, isolated at the Institute of Biological Physics, Moscow, was chosen as the main biological object. Under appropriate conditions it gives distinct and continuous rings of spore formation reflecting its intrinsic high degree of synchronism in changing its reproduction forms seen with the unaided eye as transparent rings (vegetative growth) alternate with convex white rings (spore-formation growth). As an additional test object, a film culture of bacteriophage T4Br+ developed at the institute was used. The strains were placed together in one bioblock together with plastic detectors for detecting nuclear particles. The film culture of bacteriophage enabled us to amplify the area of registration of local radiation effects by studying the genetic effects of these: frequency of mutations, induced radiation, their spectrum, subsequent revertability under the action of chemical mutagens with known mechanisms of action on DNA molecules.

Actinomyces↗
PubMed1983

Effect of HZE particles and space hadrons on bacteriophages.

The effect of high energy (HZE) particles and high energy hadrons on T4Br+ bacteriophage was analyzed. The experiments were done in orbital flight, on high mountains, on an accelerator, and with an alpha particle source. We studied the survival rate of the bacteriophage, the mutation frequency, the mutation spectrum and the revertability under the action of chemical mutagens with a known mechanism of action on DNA. It was found that the biological efficiency of HZE particles and high energy hadrons is greater than that of gamma radiation. The spectra of mutations produced by these mutations and the mechanisms of their action are also different. These effects were local, because of the mode of interaction of the radiant energy with biological objects, and depended on the linear energy transfer (LET). The modes have now been experimentally defined.

Alpha Particles↗
PubMed1983

Genetic risks associated with radiation exposures during space flight.

The genetic risks associated with manned space flight are judged to be of little significance to the general population. The risks may be significant to the irradiated individual, particularly if one focuses attention on the incidence of dominant and chromosomal mutations that are expressed in the first generation offspring. Even so, the risk is not increased to a great extent by the low linear energy transfer (LET) component of the space radiations. It is the presumed high LET component, neutrons especially, that would make the major contribution to the risk, because the relative biological effectiveness (RBE) values for this component, relative to low dose-rate photon irradiation, are between 10 and 40, depending upon the particular genetic effect and dose-rate comparison. The appropriate RBE value would probably be 20 or greater, so that even small neutron doses become magnified in their contribution. Under the assumed condition of protracted exposure to 8 rads of low LET radiation and 2 rads of high LET radiation, or from 48 to 88 rem, the individual's risk of transmitting a new dominant mutation that will be expressed in his immediate offspring is estimated to increase by at least 4% and as much as about 40%. The HZE-particle component is not expected to make a significant contribution to the total risk.

Aerospace Medicine↗
PubMed2005

Fragmentation of 1 GeV/nucleon iron ions in thick targets relevant for space exploration.

We have measured charged nuclear fragments produced by 1 GeV/nucleon 56Fe ions interacting with aluminium, polyethylene and lead. These materials are relevant for assessment of radiation risk for manned space flight. The data will be presented in a form suitable for comparison with models of nuclear fragmentation and transport, including linear energy transfer (LET) spectrum, fluence for iron and fragments, event-tack- and event-dose-averaged LET, total dose and iron contribution to dose.

Aluminum↗
PubMed1997

[Comparison of predictive methods of Sugi (Cryptomeria) atmospheric pollen counts using mean temperature, solar radiation and male flowering index--an example of Toyama Prefecture].

The previous years mean temperature of July, total solar radiation of July and August and the male flowering index were used to predict atmospheric pollen counts. We examined the adaptability of these predictions and we get following results: 1. Following good harvest years of male flower, atmospheric pollen counts predicted by previous year's mean temperature of July and the total solar radiation of July and August are higher than the actual atmospheric pollen count. 2. Prediction of atmospheric pollen counts by factors within the previous five years are more exact because matured Cryptomeria forests are increasing yearly. 3. There are few errors in prediction by the flowering index because the flower index reflects the actual harvest of male flower.

Air↗
PubMed2005

Ground-based research with heavy ions for space radiation protection.

Human exposure to ionizing radiation is one of the acknowledged potential showstoppers for long duration manned interplanetary missions. Human exploratory missions cannot be safely performed without a substantial reduction of the uncertainties associated with different space radiation health risks, and the development of effective countermeasures. Most of our knowledge of the biological effects of heavy charged particles comes from accelerator-based experiments. During the 35th COSPAR meeting, recent ground-based experiments with high-energy iron ions were discussed, and these results are briefly summarised in this paper. High quality accelerator-based research with heavy ions will continue to be the main source of knowledge of space radiation health effects and will lead to reductions of the uncertainties in predictions of human health risks. Efforts in materials science, nutrition and pharmaceutical sciences and their rigorous evaluation with biological model systems in ground-based accelerator experiments will lead to the development of safe and effective countermeasures to permit human exploration of the Solar System.

Animals↗
PubMed2001

Chromosome aberrations in the blood lymphocytes of astronauts after space flight.

Cytogenetic analysis of the lymphocytes of astronauts provides a direct measurement of space radiation damage in vivo, which takes into account individual radiosensitivity and considers the influence of microgravity and other stress conditions. Chromosome exchanges were measured in the blood lymphocytes of eight crew members after their respective space missions, using fluorescence in situ hybridization (FISH) with chromosome painting probes. Significant increases in aberrations were observed after the long-duration missions. The in vivo dose was derived from the frequencies of translocations and total exchanges using calibration curves determined before flight, and the RBE was estimated by comparison with individually measured physical absorbed doses. The values for average RBE were compared to the average quality factor (Q) from direct measurements of the lineal energy spectra using a tissue-equivalent proportional counter (TEPC) and radiation transport codes. The ratio of aberrations identified as complex was slightly higher after flight, which is thought to be an indication of exposure to high-LET radiation. To determine whether the frequency of complex aberrations measured in metaphase spreads after exposure to high-LET radiation was influenced by a cell cycle delay, chromosome damage was analyzed in prematurely condensed chromosome samples collected from two crew members before and after a short-duration mission. The frequency of complex exchanges after flight was higher in prematurely condensed chromosomes than in metaphase cells for one crew member.

Chromosome Aberrations↗
PubMed2002

The response of tissue-equivalent proportional counters to heavy ions.

The paper presents a theoretical model for the response of a tissue-equivalent proportional counter (TEPC) irradiated with charged particles. Heavy ions and iron ions in particular constitute a significant part of radiation in space. TEPCs are used for all space shuttle and International Space Station (ISS) missions to estimate the dose and radiation quality (in terms of lineal energy) inside spacecraft. The response of the tissue-equivalent proportional counters shows distortions at the wall/cavity interface. In this paper, we present microdosimetric investigation using Monte Carlo track structure calculations to simulate the response of a TEPC to charged particles of various LET (1 MeV protons, 2.4 MeV alpha particles, 46 MeV/nucleon 20Ne, 55 MeV/nucleon 20Ne, 45 MeV/nucleon 40Ar, and 1.05 GeV/nucleon 56Fe). Data are presented for energy lost and energy absorbed in the counter cavity and wall. The model calculations are in good agreement with the results of Rademacher et al. (Radiat. Res. 149, 387-389, 1998), including the study of the interface between the wall and the sensitive region of the counter. It is shown that the anomalous response observed at large event sizes in the experiment is due to an enhanced entry of secondary electrons from the wall into the gas cavity.

Aerospace Medicine↗
PubMed1984

Radiation measurements aboard Spacelab 1.

The radiation environment inside Spacelab 1 was measured by a set of passive radiation detectors distributed throughout the volume inside the module, in the access tunnel, and outside on the pallet. Measurements of the low-LET (linear energy transfer) component obtained from the thermoluminescence detectors ranged from 102 to 190 millirads, yielding an average low-LET dose rate of 11.2 millirads per day inside the module, about twice the low-LET dose rate measured on previous flights of the space shuttle. Because of the higher inclination of the orbit (57 degrees versus 28.5 degrees for previous shuttle flights), substantial fluxes of highly ionizing HZE particles (high charge and energy galactic cosmic rays were observed, yielding an overall average mission dose-equivalent of about 150 millirems, more than three times higher than measured on previous shuttle missions.

Cosmic Radiation↗
PubMed1999

DNA damage formation and p53 accumulation in mammalian cells exposed to the space environment.

To determine the effects of the space environment on gene instability from the point of view of human health for long-term stays in space, we have studied the formation of DNA strand breaks and the induction of gene expression in mammalian cells. We previously measured DNA damage in human cultured cells and the accumulation of a tumor suppressor gene product, p53, in muscle and skin of rats after space flight, and the relative importance of microgravity and space radiation in causing these effects remains to be clarified. Our results suggest that the p53 pathway may play a role in safeguarding genomic stability against the stressful space environment. We review here the present knowledge on cellular stress signaling and present our space experimental data. The importance of the stress response to the space environment is also discussed.

Animals↗
PubMed2006

On-board TLD measurements on MIR and ISS.

This paper presents results from dosimetric measurements made aboard the Mir space station and the International Space Station (ISS) using the Pille portable thermoluminescent dosemeter (TLD) system. This paper includes the dosimetry mapping and automatic readout (trapped and untrapped components) results from Mir and ISS. The mean dose rate in 2001-2003 was 7 microGy h(-1). Using the hourly measuring period in automatic mode, doses from both galactic (independent of South Atlantic Anomaly--SAA) and SAA components were determined during Euromir'95 experiment. The mean total dose rate was 12.5 microGy h(-1), while the SAA contribution was 6.2 microGy h(-1). A similar measurement was performed on ISS in 2001 and in 2003. Both the manual and automatic measurements show a significant decrease in dose rate in 2001 in comparison to 1995-1997 due to the change in solar activity. For determination of the high linear energy transfer contribution from the radiation field during the ISS mapping experiment, three CR-39 plastic nuclear track detectors (PNTDs) were co-located with each TL detector. Analysis of the combined TLD and PNTD measurements showed a typical mean TLD efficiency of 84%, a dose contribution <10 keV microm(-1) of 17%, and an average quality factor of 1.95.

Cosmic Radiation↗
PubMed1990

Medical considerations for extending human presence in space.

The prospects for extending the length of time that humans can safely remain in space depend partly on resolution of a number of medical issues. Physiologic effects of weightlessness that may affect health during flight include loss of body fluid, functional alterations in the cardiovascular system, loss of red blood cells and bone mineral, compromised immune system function, and neurosensory disturbances. Some of the physiologic adaptations to weightlessness contribute to difficulties with readaptation to Earth's gravity. These include cardiovascular deconditioning and loss of body fluids and electrolytes; red blood cell mass; muscle mass, strength, and endurance; and bone mineral. Potentially harmful factors in space flight that are not related to weightlessness include radiation, altered circadian rhythms and rest/work cycles, and the closed, isolated environment of the spacecraft. There is no evidence that space flight has long-term effects on humans, except that bone mass lost during flight may not be replaced, and radiation damage is cumulative. However, the number of people who have spent several months or longer in space is still small. Only carefully-planned experiments in space preceded by thorough ground-based studies can provide the information needed to increase the amount of time humans can safely spend in space.

Adaptation, Physiological↗
PubMed1981

A review and comparative analysis of the biological damage induced during space flight by HZE particles and space hadrons.

We have studied the somatic and genetic effects of heavy ions (HZE particles) and the very high energy hadrons of space radiation on various organisms ranging in complexity from bacteriophage to man. Experimental data were obtained in space, on high mountains and in a proton accelerator at energies of 76 GeV. In all these experiments local micro- and macroradiational damage was observed. This damage was characterized by severity over large local regions and for the most part was due to cascades of secondary particle bundles resulting from the collision of very high energy space hadrons with atomic nuclei rather than from cellular hits from relatively low energy single HZE particles. At present there does not appear to be any effective way to provide shielding against these cosmic hadrons.

Animals↗