EFFECTS OF VERY SMALL DOSES OF IONIZING RADIATION AND HYPOMAGNETIC FIELD CHANGE PHYSIOLOGICAL CHARACTERISTICS OF HIGHER PLANT SEEDS.

Effects of a 40-times weakened geomagnetic field and its combination with low a- and y-radiation doses on the physiological characteristics of higher plant seeds and water redox properties were studied. Germination rate was found decreased and seedlings development retarded equally when exposure to the hepomagnetic field was direct or mediated by water. Besides, water-mediated irradiation by low y-doses moderated and by low a-doses augmented the negative HMF effect on seeds growth. In other words, ionizing radiation dominated in this combination. The redox potential of water (ROP) was noted to rise due to low-intensity a-radiation (9Pu) that was nonlinear and polymodal. Comparing to a-irradiation, the range of ROP changes due to y-irradiation ('37Cs) was narrow which was reflected in growth processes in seeds. Water ROP increases as the magnetic field induction attenuates which implies a natural reduction of water molecules internal energy and bettering of water oxidative qualities. In our view, this was the cause for retarded seed germination. Water is believed to be the determinant for the factors in this study as their effects on seeds were modified by changes in water qualities and structure.

[Effect of an altered magnetic field on the development of great ramshorn Planorbarius corneus (Gastropoda, Planorbidae)].

Effects of a 100-300-fold attenuated geomagnetic field on the embryonic development of great ramshorn Planorbarius corneus and water oxidation-reduction properties were studied in a hypomagnetic chamber. The hypomagnetic field was largely favorable to the P. corneus development. Specifically, teratogenic effects were less massive, i.e. embryos that had known no other environment but hypomagnetism were characterized by low death rate. The agility index grew in embryos on the stages of late veliger and post-metamorphosis. A sharp increase of the magnetic field to the normal strength resulted in rapid death of embryos and juvenile mollusks (virtually, their growth was arrested). Type of induction was dependent on adaptation of juvenile P. corneus to a magnetic field. Mollusks grown in the normal geomagnetic field would prefer the conditions with maximal induction, whereas mollusks developed in the hypomagnetic chamber, on the contrary, chose the conditions with minimal induction. The oxidation-reduction potential of water increased as magnetic induction attenuated pointing to a natural decline in internal energy of water molecules due, as we see it, to inhibition of the mollusk embryonic development.

[Radiation situation prognosis for deep space: reactions of water and living systems to chronic low-dose ionizing irradiation].

The authors review the findings of researches into the effects of low-dose ionizing irradiation on diverse biological objects (embryonic Japanese quails, Aspergillus niger, Spirostomum ambiguum Ehrbg., mesenchymal stem cells from mouse marrow, dry higher plants seeds, blood lymphocytes from pilots and cosmonauts). Model experiments with chronic exposure to ionizing radiation doses comparable with the measurements inside orbital vehicles and estimations for trips through the interplanetary space resulted in morphological disorders (embryonic Japanese quails, Aspergillus niger), radiation hormesis (Aspergillus niger, MSCs from mouse marrow), increase in the seed germination rate, inhibition of Spirostomum spontaneous activity, DNA damages, chromosomal aberrations, and increase of the blood lymphocytes reactivity to additional radiation loading. These facts give grounds to assume that the crucial factor in the radiation outcomes is changes in liquid medium. In other words, during extended orbiting within the magnetosphere region and interplanetary missions ionizing radiation affects primarily liquids of organism and, secondarily, its morphofunctional structures.

[Spatial distribution of local absorbed doses inside the Russian segment of the International Space Station].

The article discusses the procedure of operational radiation safety monitoring with the use of portable Pille-MKS dosimeters, presents the results of ISS dose measurements from September 22, 2003 (after Pille deployment on board the ISS) to March 16, 2011 (completion of the ISS-25 mission). The necessity of continuous dynamic tracking of the radiation environment in ISS compartments arises from the character and uniqueness of space ionizing radiation effects on crew. Radiation loading in the ISS compartments was analyzed and results of using different dosimeters were compared. Experimental radiation studies of the ISS piloted compartments are needed for reliable prediction of doses for the crew that still defy precise estimation.

[Effects of low doses of ionizing radiation on substrate and germination of higher plants seeds].

The investigation had the aim to evaluate the effects of low doses (< 1-10 cGy) of ionizing radiation on the physical-chemical qualities of high-purification water. It had also the goal to study germination rate and energy and sprouting of four species of higher plants exposed directly and indirectly (watering) to alpha- and beta-radiation from radionuclids sources. When compared with intact water, after exposure to beta-particles electrical currents in water-filled containers consistently tended upward and downward after exposure to alpha-particles. Radiation-induced changes in water parameters were observed throughout the experiment with higher plant seeds. Evaluation of the effect of irradiated water on sprouting showed that plant sensitivity varied with species and depended on type of radiation particles. Neither alpha- nor beta particles affected the wheat sprouts; however, both types of particles inhibited growth of mustard and accelerated growth of lentil and haricot Mash as compared with control crops. The investigation suggests that plant species for space greenhouses should be selected with account of their radioresistance and radiosensitivity.

[New approaches to diagnostics and identification of possible damages in normal humans under the conditions of microgravity and exposure to low doses of radiation].

The issues of radiation risk evaluation were addressed in the investigation of cytogenetic and molecular-biological changes in lymphocytes of cosmonauts and pilots of high-altitude airplanes. The goal was to determine individual sensitivity to the flight conditions and an additional factor (lymphocyte exposure to 1 Gy in situ), and adaptability as an index of induction of cell and organism resistance to extreme conditions.

[Individual cytogenetic and molecular-biological characteristics of lymphocytes in blood of pilots and cosmonauts].

The purpose of this paper was the investigation of the pilots and of cosmonauts individual sensitivity to the fly conditions, to the additional irradiation (in the dose of 1 Gy), the adaptive response manifestation (in the doses 0.05 and 0.5 Gy). The DNA comet assay (the double strand DNA breaks was determined) and the method of unstable chromosome aberrations in metaphase was used. The human blood lymphocytes was the object of investigation. The significant individual differences were discovered in pilots and in cosmonauts in the initial DNA damage; in the sensitivity to the additional irradiation. The frequency of the adaptive response induction was decreased in the pilots in the comparison with the control group. The adaptive response was registered in cosmonauts (3 men). It is supposed that DNA damage, chromosome aberrations, sensitivity to the additional irradiation, the adaptive response manifestations can be used as biological markers of individual risk disease.

[Characteristics of micromycets Fusarium oxysporum recovered from an artificial soil for space greenhouse after chronic exposure to low doses of ionizing radiation].

Growth and development of Fusarium oxysporum intact strain and strains subjected to irradiation by low gamma-neutron doses were studied during cultivation on intact substrate and substrate irradiated by a gamma-source at 29 microGy. There was a striking difference in growth and sporification between the strains cultivated on irradiated and intact substrates. Irradiated Fusarium oxysporum strains exhibited manifest antagonism to one another and the non-irradiated strain. Electroconductivity of substrate after gamma-irradiation at low doses was noted to slow down markedly. The authors come to the conclusion that nutrient molecules may become more available to micromycets because of alteration of proton activity in consequence of preliminary irradiation.

[Effect of chronic exposure to low doses of ionized radiation on embryonal development of the Japanese quail].

Experiments on Japanese quail embryogenesis on a background of chronic exposure to gamma- and neutron doses comparable with the doses of ionized radiation inside the orbital space stations Mir and ISS, and exploration vehicles gave evidence that permanent absorption of low gamma-doses (0,15 cgy/d) did not impact development of the Japanese quail embryos. On the contrary, the neutron dose of 200 microgy/d imparted by the neutron flux of 30 particles/cm2s was hazardous to embryos as it caused morphological disorders in 12% of embryos.

[Main results of the Biorisk experiment on the International Space Station].

To get better appreciation of the margins of phenotypic adaptation and genotypic changes in bacteria-fungi associations within the typical microbiota residing on structural materials of space-flown equipment, developed were a program and hardware for a series of experiments under the general name BIORISK. Protocol of each experimental cycle is based on the well-proven method of exposure of "passive" samples of materials (Biorisk-KM), microorganisms-materials systems inside the ISS service module (Biorisk-MSV), and microorganisms-materials systems on the outside of the ISS SM (Biorisk-MSN). Each six months the samples are returned to the laboratory in conjunction with crew rotation. Already the first in-hand data from the experiment point to the dramatic effect of space flight on growth, reproduction, and biological properties of test microbes and fungi. Thus, the activity of enzymes that characterize the pathogenic potential (RNA-ase and DNA-ase), and resistance of microorganisms to aseptic agents were found increased.

[Effect of the spaceflight radiation factor on the growth of Brassica pekinensis and micromycetes Fusarium oxysporum].

The effects of chronic exposure in the combination of low-dose gamma- and neutron radiation on growth of Brassica pekinensis (lour) Rupr, var. Khibinskaya, and micromycetes of Fusarium oxysporum, a representative of soil microflora were stadied. Seeds, water and vegetating plants raised from previously irradiated seeds were subjected to radiation exposure. The gamma-neutron dose rate was -0.013 sGy/d and the neutron flux was -20 n/cm2 d. Growth of Brassica pekinensis and of Fusarium oxysporum on the background of weak chronic ionizing irradiation by radioactive nuclides was noticeably changed when compared with the growth in the normal radiation environment. The radiosensitivity of Fusarium oxysporum isolated from the artificial soil following 60-d exposure was far higher than the radioactivity of the culture isolated from non-irradiated soil. Fusarium oxysporum isolated from the irradiated soil failed to form spores normally even when cultivated in a non-irradiated nutrient substrate without further exposure. These peculiarities persisted at least for four months. 15-mo gamma- and neutron exposure of Brassica pekinensis seeds held in storage for 5 years retained their original germinating capacity, whereas the non-irradiated seeds suffered deprivation of this quality. It was noticed that the Brassica pekinensis reaction on chronic exposure of low doses was markedly dependent on the growth conditions non-related directly with the radiation background.

[Some results of radiaton monitoring of the ISS Russian Segment in 2000-2005].

Dynamics of the ISS RS radiation environment was studied using the data of daily (operative) monitoring and personal dose measurements during 11 increments in the period between August 1, 2000 and October 28, 2005 overlapping the maximum phase of the 23rd solar cycle. It was shown that personal absorbed doses varied within the range of measurements of dual wavelength radiometer R-16, a component of the ISS radiation monitoring system. Power of the absorbed doses fell in the range of 0.017 to 0.02 cGy/day and was solar-dependent.

[Effects of low-dose accelerated charged particles of varying LET on cytogenetic changes in comeal epithelium cells in mice]. / Vliianie nizkikh doz uskorennykh zariazhennykh chastits s razlichnymi LPE na tsitogeneticheskie izmeneniia v kletkakh épiteliia rogovitsy myshei.

Effects of low-dose heavy charged particles (HCP) of varying LET on quantitative and qualitative changes in chromosomes of the comeal epithelium cells were studied in mice. Cytogenetic damages in the comeal epithelium cells were analyzed after irradiation by ions of helium and carbon with an energy of 300 MeV/nucleon (LET = 1.36 and 12.6 keV/microm), and 137Cs gamma-rays with the doses from 5 to 200 Gy. Accelerated nuclei were shown to be more effective. On the basis of aberrant mitosis rate, RBE values for helium and carbon ions in 24, 72 and 120 hrs. after irradiation were 6.0; 3.6 and 2.2 for helium ions and 7.0; 3.8 and 2.4 for carbon ions, respectively. The dose region of 20-30 Gy turned to be dose-independent. It was established that the period of chromosomal aberration sustenance in cells is also LET-dependent.

The features of radiation dose variations onboard ISS and Mir space station: comparative study.

The dynamics of the ISS-measured radiation dose variations since August 2000 is studied. Use is made of the data obtained with the R-16 instrument, which consists of two ionization chambers behind different shielding thicknesses. The doses recorded during solar energetic particle (SEP) events are compared with the data obtained also by R-16 on Mir space station. The SEP events in the solar maximum of the current cycle make a much smaller contribution to the radiation dose compared with the October 1989 event recorded on Mir space station. In the latter event, the proton intensity was peaking during a strong magnetic storm. The storm-time effect of solar proton geomagnetic cutoff decreases on dose variations is estimated. The dose variations on Mir space stations due to formation of a new radiation belt of high-energy protons and electrons during a sudden commencement of March 24, 1991 storm are also studied. It was for the first time throughout the ISS and Mir dose measurement period that the counting rates recorded by both R-16 channels on ISS in 2001-2002 were nearly the same during some time intervals. This effect may arise from the decreases of relativistic electron fluxes in the outer radiation belt.

[Influence of chronic exposure to low doses of space ionizing radiation on the character of formation of microbial assemblage in the habitat of orbital station]. / Vliianie khronicheskogo oblucheniia nizkimi dozami kosmicheskogo ioniziruiushchego izlucheniia na kharakter formirovaniia mikrobnogo soobshchestva v srede obitaniia orbital'nykh stantsii.

Statistically valid relations between radiation conditions in compartments of MIR station and the micromicete population (CFU number) on the surface of the equipment and the interior have been established. It was found that in conditions of a chronic exposure to space radiation the number of CFU increased in one thousand and more times with increasing of absorbed dose rate from 200 up to 1000 microGy/day. The results of land-based model experiments confirmed morphological changes in the "flight" strains of funguses under exposure to low doses of gamma (100-800 microGy/day) and neutron (0.2-2 neutron/cm2.s) radiation. It was found that the morphological changes in the control (museum) cultures of funguses of the same species, which were expressed in the weak increase of vegetative mycelium, were detected only after repeated gamma- and gamma + neutron irradiation.

[Effects of 10-day long exposure to gamma irradiation at low doses on bone marrow cells in mice]. / Effekt 10-sutochnogo gamma-oblucheniia v nizkikh dozakh na kostnomozgovye kletki myshi.

Effects of ten day long exposure to gamma-irradiation at low doses (mean dose rate of 1.5-2.0 m Gy/day, total dose of 15 m Gy) on hemopoietic (CFU-S) and stromal (CFU-F) progenitor cells from murine bone marrow were examined. The CFU-F content measured as in vitro fibroblastic colony number showed 1.5-4.5-fold increase. Additionally, the size of ectopic marrow transplants evaluated by counting myelokariocytes and CFU-S numbers also increased. No significant changes of CFU-S proliferation rate were found.

Radiation dose measurements aboard the Mir using the R-16 instrument.

NASA: Data from the R-16 radiation dosimeter mounted to the outside of the Mir space station are analyzed to determine the radiation environment and absorbed radiation dose inside Mir during the 22nd solar cycle. The outcome of the analysis demonstrated that data could be collected over a long period, dynamics of the daily mean absorbed doses correlated well with parameters of solar activity, seasonal variations of absorbed doses during the solar cycle were clearly observed, during periods of unfavorable conditions the absorbed dose rate within the living modules can reach up to 30 mrad/min for more than 10 minutes, and overall, the radiation environment inside the space station was low.^ieng

[Effect of continuous gamma-radiation at low doses on clonogenic hemopoietic (CFU-S) and stromal (CFU-F) bone marrow cells ]. / Effekt nepreryvnogo gamma-oblucheniia v nizkikh dozakh na klonogennye krovetvornye (KOE-S) i stromal'nye (KOE-F) kletki kostnogo mozga.

We studied the effects of low doses of continuous gamma-irradiation (Co60, 10 days, mean daily dose power 1.5-2.0 mGy, total dose 15 mGy) on hemopoietic and stromal progenitor cells of murine bone marrow. The content of hemopoietic clonogenic cells representing a "younger" (CFU-S-11) and more "mature" (CFU-S-7) categories in the compartment of stem cells was determined in the bone marrow. The state of bone marrow stroma was estimated by the method of in vitro cloning according to the number of progenitor cells that form colonies of fibroblasts (CFU-F) and by the method of ectopic transplantation according to the capacity of stroma of organizing and building new hemopoietic territories. Continuous gamma-irradiation at low doses, that were by one order of magnitude lower than those inducing hermesis, exerted a stimulating effect on both hemopoietic (CFU-S) and stromal (CFU-F) progenitor cells. The number of CFU-S in the compartment of stem cells of the bone marrow markedly increased and they formed larger hemopoietic territories but these cells appeared to create a qualitatively different microenvironment, which stimulated the proliferation of CFU-S.

[The assessment of radiation hazards in the "MIR" and ISS orbits from the data of vehicle and personal dosimetric monitoring]. / Otsenka radiatsionnoi opasnosti dlia chlenov ékipazhei orbital'noi stantsii "Mir" i Mezhdunarodnoi kosmicheskoi stantsii na osnove dannykh bortovogo i individual'nogo dozimetricheskogo kontrolia.

The paper describes the procedure of estimating total radiation risk to crewmembers during lifetime and possible lifetime reduction in consequence of participation in the Mir and ISS missions in different periods of the solar activity. The procedure includes analysis of data of vehicle and personal dosimetry, and calculations of radiation doses in various Mir compartments and accumulated by body tissues of cosmonauts. Calculated doses showed good consistency with the doses measured with R-16 on board Mir and personal dosimeters. To a first approximation, estimation of doses to cosmonauts and radiation risk as a result of participation in ISS missions took into account similarity of the Mir and ISS basal modules (geometry, dimensions and mass values) and was performed with the use of the space station shielding model that had been described elsewhere. The model of ISS radiation shielding will be updated as data of dosimetry of ISS compartments and phantom studies are available.

[Effect of space flight factors on health of cosmonauts in the near and late term after space flights]. / Izuchenie vliianiia faktorov kosmicheskogo poleta na zdorov'e kosmonavtov v blizhaishie i otdalennye sroki posle kosmicheskikh poletov.

Cytogenetical studies of cosmonauts' peripheral blood lymphocytes after space flights on MIR orbital station showed a statistically significant increase in the yields of radiation-induced chromosomal aberrations. However, similar studies with in vitro irradiation of biological objects with accelerated charged particles are of great importance for elucidation of the nature of cytogenetical damage induced in vivo. It is also important to investigate the structure of cosmonatus' diseases over their life, in particular, lens opacities and oncological diseases. Thus, the purpose of the investigations planned is to study cytogenetical damage in blood lymphocytes from cosmonauts after space flights on the ISS in vivo, as well as in donor blood lymphocytes after in vitro exposure to accelerated charged particles. The tasks of the project are as follows: determination of the yields and types of chromosomal aberrations in cosmonauts' blood lymphocytes before and after space flights, comparative studies of biological effects induced in vitro by different types of ionizing radiation in human blood lymphocytes in ground experiments, assessment of cytogenetical risks, analysis of the structure of cosmonatus' diseases comparing with that of whole population, study of the mortality and frequency of cataracts and oncological diseases in cosmonauts. The results to be obtained will be used for setting of health norms applied to the influence of radiations of different types, and for elaboration of measures to reduce health risks from space flight factors.