[TESTING THE PROTECTIVE PROPERTIES OF ARGON DURING SUBACUTE EXPOSURE TO HYPOXIC HYPOXIA].

Previously it has been shown that argon has a stimulating effect on biological processes including, specifically, strong protective properties during exposure to acute (1-4 hrs.) hypoxic hypoxia. Experiments with animals under hypoxia gradually growing over 3 to 7 days may give insight into mechanisms of the argon protective action.

[Cytogenetic investigations of mice marrow cells after isolated chronic exposure to radiation and chemical factors, and combined sequential exposure to these factors].

The article presents data on chromosomal aberrations in bone marrow cells of mice following isolated exposure to gamma-radiation and chemical factor within the existing MPCs for piloted spacecraft, and also combined sequential exposure in the ranges predicted for interplanetary missions. In the event of chronic exposure the relative number of chromosomal aberrations goes up till reaching plateau and is governed strictly by the mathematical dependence on effective residual gamma-dose and effective damage of organism from inhaled chemical factor. Sequential exposure to the radiation and chemical factors within the ranges specified for orbital and remote space missions caused a tangible reduction of the speed of cytogenetic damages reparation in postexposure period which may be interpreted as depletion of the body reserve and compensatory-recovery potential.

[Morphologic changes in mice trachea, bronchi and lungs after prolonged combined radiation and inhaled chemical exposure].

Investigations of morphology and morphometry of the breathing organs (trachea, bronchi and lungs) and immunogenesis of mice subject to a combined sequential exposure to fractionated external γ-irradiation by the total dose of 350 cGy and a mix of acetone, ethanol and acetaldehyde in MPCs for piloted spacecrafts simulating the estimated levels in crewed exploration missions were conducted. Morphologic changes in the breathing organs of animals after space missions point to immunogenesis activation and appearance of a "structural trace" as a chronic inflammation with the growth of fibrous connective tissue in tracheal, bronchial and lung walls, increase in volume fractions of glands and vessels and reduction in loose fibrous connective tissue. Formation of the fibrous connective tissue was particularly noticeable in respiratory parts of the breathing organs suggesting a high risk of long-term adverse effects.

[Adaptation processes in mice during chronic combined exposure to radiation and chemical compounds (acetone, ethanol, acetaldehyde) innate to exploration missions].

The paper reports the results of experimental investigation with mice subjected to 63-day of daily 10-fold fractionated gamma-irradiation at the total dose of 350 cGy followed by 70-day exposure to chemical mixture (acetone, ethanol, acetate aldehyde) at close to maximum permissible concentrations innate to piloted space vehicles (MPCpsv). Measured levels of radiation and known radiation sensitivity of mice were used to model absorbed dose to cosmonauts on an exploration mission. Functional shifts in the hematopoietic system and changes in biochemical parameters of erythrocytes indicative of energy exchange and redox potential were tracked up during the combined radiation-chemical exposure and 90 days of recovery.

[Evaluation of the risk of delayed adverse effects of chronic combined exposure to radiation and chemical factors with the purpose to ensure safety in orbital and exploration space missions].

The work had the aim to anatomize the existing issues with providing safety in extended orbital and exploration missions for ensuing estimation of actual values of the total radiation risk for the crew, and risks of other delayed effects of simultaneous exposure to ionizing radiation and chemical pollutants in cabin air, and a number of other stressful factors inevitable in space flight. The flow of chronic experiments for separate and combined studies with reproduction of air makeup and radiation doses in actual orbital and predicted exploration missions is outlined. To set safety limits, new approaches should be applied to the description of gradual norm degradation to pathologies in addition to several generalized quantitative indices of adaptation and straining of the regulatory systems, as well as of effectiveness of the compensatory body reserve against separate and combined exposure.