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Prolonged weightlessness and calcium loss in manData have been accumulated from a series of studies in which men have been subjected to weightlessness in orbital space flight for periods of up to 12 weeks. These data are used to predict the long term consequences of weightlessness upon the skeletal system. Space flight induced a loss of calcium which accelerated exponentially from about 50 mg/d at the end of 1 week to approx. 300 mg/d at the end of 12 weeks. The hypercalciuria reached a constant level within 4 weeks while fecal calcium losses continued to increase throughout the period of exposure. This apparent diminution of gastrointestinal absorptive efficiency was accompanied by a slight decline in the plasma level of parathyroid hormone and a slight elevation in the plasma level of calcium and phosphorus. Although losses in mineral from the calcaneus were closely correlated with the calcium imbalance, no changes were detected in the mineral mass of the ulna and radius. From the data presented it is concluded that the process of demineralization observed in space flight is more severe than would be predicted on the basis of observations in immobilized, bed rested, or paralyzed subjects. It is, moreover, suggested that the process may not be totally reversible.
Document ID
20040115154
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Rambaut, P. C.
(NASA Johnson Space Center Houston TX United States)
Johnston, R. S.
Date Acquired
August 21, 2013
Publication Date
September 1, 1979
Publication Information
Publication: Acta astronautica
Volume: 6
Issue: 9
ISSN: 0094-5765
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
Skylab 2 Project
short duration
Skylab 4 Project
manned
Flight Experiment
Skylab 3 Project
long duration

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