Mineral and nitrogen balance study observations: the second manned Skylab mission.

A metabolic study of the effects of space flight on various chemical elements, particularly those with special revelance to the musculoskeletal system, was carried out on the three astronauts of the SL-3 mission for 21 d preflight, during the 60 d flight phase, and for 17 d postflight. The study required of the cooperating crewmen quite constant dietary intake, continuous 24-hour urine collections and total fecal collections. Urinary calcium was significantly increased during flight in all three crewmen with man-to-man variation in pattern and amount; the degree of calcium loss was, in general, similar to that in the prior study of the 28-d Skylab flight (SL-2).

Mineral and nitrogen metabolic studies on Skylab flights and comparison with effects of earth long-term recumbency.

A metabolic study of the effects of space flight on various chemical elements, particularly those with special relevance to the musculo-skeletal system, was carried out on the nine astronauts who participated in the three Skylab flights of 28, 59 and 84 days in 1973-1974. The study required of the cooperating crewmen constant dietary intake, continuous 24-hour urine collections and total fecal collections for 21-31 days before each flight, throughout each flight and for 17-18 days post-flight. Increases in urinary calcium and negative calcium balances during space flight were generally similar to those found in previous immobilization and bedrest studies.

Metabolic and biochemical considerations of bone.

Recognition of the dynamic aspects of bone metabolism can lead to a unified concept involving endocrine and nutritional influences. Although most hormones can influence bone metabolism directly or indirectly, the principal ones involved in skeletal metabolism are parathyroid hormone, calcitonin and 1,25-dihydroxy-vitamin D. The actions of parathyroid hormone and 1,25-dihydroxy-vitamin D result in elevations of circulating extracellular fluid calcium concentration through actions directly on bone, intestine, and kidney.