Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants (1992) / Chapter Skim
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'PHYSIOLOGICAL CHANGES DURING SPACEFLIGHT'
'PHYSIOLOGICAL CHANGES DURING SPACEFLIGHT'
Pages 49-58
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From page 49... ...
Because a correlation appears to exist between the duration of exposure and the frequency and intensity of the effects, the issues of duration of the spaceflights and of the microgravity environment remain the critical variables in attempting to establish safe levels of exposure to potentially toxic chemicals. Risk assessment of chemicals begins with biological studies conducted in animals and humans on earth.
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From page 50... ...
While the overall rate of calcium loss in Skylab astronauts was 0.4% of total body calcium per month, the loss was estimated to be 10 times greater in the lower extremities than in the rest of the body (based on bed-rest studies of calcium losses by metabolic balance compared with decrease in bone calcium density)
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From page 51... ...
. All mechanical procedures tested thus far have been ineffective including exercise with the Exer Genie pulley apparatus, static and intermittent compression of the length of the body from shoulders to feet, static and intermittent lower-body negative pressure, and impact loading up to 36 Ib to the bottom of the heel 40 times per minute for up to 8 hr daily.
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From page 52... ...
These considerations suggest that research ought to be continued on urinary-tract stone formation in relation to microgravity as a significant possibility during long spaceflight. The likelihood of such an occurrence may be small, especially if care is taken to maintain abundant urine volumes; nevertheless, such stone formation might be catastrophic to health and function for the astronaut involved and thus to success of the particular flight.
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From page 53... ...
As shown in rats that are suspended (hind limb unloaded) , loading and stretching of otherwise inactive leg muscles prevented muscle atrophy and stimulated protein synthesis; the addition of electrical stimulation increased protein synthesis markedly.
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From page 54... ...
However, this adaptation becomes inappropriate upon return to normal gravity. Postflight circulatory studies demonstrate decreased orthostatic tolerance, decreased physical work capacity, and lowered exercise stroke volume and cardiac output in the sitting position.
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From page 55... ...
In an unmanned Russian spaceflight, the weights of lymph nodes and spleens of rats flown for 22 days were reported to be markedly reduced, compared with those of controls on earth, because of a marked decrease of lymphocytes in these organs. The effects were found to be reversible since the organs returned to normal 27 days postflight(Durnovaetal., 1977)
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From page 56... ...
The high phosphate content of meat may partially protect against the effect of high protein intake increasing urinary calcium. At the same time, the negative nitrogen balance associated with muscle atrophy in weightlessness should not be accentuated by encouraging too low a protein intake.
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From page 57... ...
Too high an intake of phosphorus will exert some binding effect on calcium in the intestine and tend to inhibit calcium absorption. Since no studies have been done on the effects of spaceflight on the metabolism of any of the trace elements, no comment can be made other than that care should be taken that space diets contain trace elements in the amounts recommended in the U.S.
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From page 58... ...
Reduction in the total list of available food items should simplify both the strategy of storage of multiple food packages in a long-flying spacecraft and the ability of travelers to retrieve desired items with a minimum of difficulty and time. The space station will need to provide for testing of currently available and newly formulated items for long-term durability and acceptability.
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