Objectives
Previous studies have shown that long-duration exposure to microgravity causes significant bone loss. In the absence of gravity, bone mass decreases in the load-bearing regions of the skeleton. This space condition mimics osteoporosis, a medical condition characterized by brittle bones. By learning more about the process of bone mineral loss and recovery, researchers hope to be able to implement effective countermeasures in space, and develop more effective treatments for those who suffer from bone disorders.
The objectives of this experiment were: (1) determine the regional losses in bone mineral density and lean body mass of the crewmembers of each of the Phase 1 Shuttle-Mir flights, (2) determine the regional rate and extent of recovery of the bone mineral and lean tissue in the above crewmembers, (3) determine the muscle strength of the lower extremities and back before and after flight, and relate muscle strength data to the bone loss during flight and to the degree and rate of bone recovery postflight, and (4) determine the levels of serum and urinary markers of bone metabolism before and after flight.
Shuttle-Mir Missions Approach
Strength testing was performed pre- and postflight using a LIDO isokinetic dynamometer. Peak torque was measured for muscle groups in the legs and back. Testing time points were the same as for DEXA scans.
Serum and urinary markers of bone metabolism were measured pre- and postflight. Urine was collected over a 24-hour period; serum was collected by a fasting blood draw. Urine markers included total calcium, pyridium cross-links, n-telopeptide, hydroxyproline and creatinine. Serum markers included total and ionized calcium, pH, calcitonin, parathyroid hormone (PTH), osteocalcin, total and bone-specific alkaline phosphatase and vitamin D. Testing time points were L-30, L-7, R+0 (landing day), R+7, R+14 and R+180 days.
Calcium kinetics testing was conducted pre-, in- and postflight during the NASA-6 and NASA-7 missions. The 22-day protocol included collection of urine, blood, saliva and fecal samples (fecal samples were not collected in flight, however) and the administration of stable calcium isotopes at the beginning of the 22-day test protocol. Testing time points (start of the 22-day protocol) were L-45 days, FD 28 (flight day 28), FD 96, R+3 days, R+6 months, and R+12 months. Samples were analyzed to determine the levels of the stable isotopes administered for this protocol (44Ca and 42Ca).
Results Earth Benefits Publications Principal Investigators
Viktor Oganov, M.D., Ph.D. Co-Investigators
Mir-21/NASA-2, Mir-22/NASA-3, Mir-23/NASA-4, Mir-24/NASA-5, Mir-25/NASA-6, Mir 26/NASA-7
Dual energy x-ray absorptiometry (DEXA) scans were obtained pre- and postflight using a Hologic QDR 2000 whole densitometer (U.S.) or QDR 1000W densitometer (Russia). Bone mineral density data were obtained from scans of the whole body, lumbar spine, proximal femur (hip) and calcaneous (heel). Whole body and regional measurements of lean tissue mass (LTM) were obtained from the whole body scans. Testing time points were L-60 (60 days prior to launch), L-30, R+5 (5 days after landing), R+180, R+360, R+720 and R+1080 days.
Preliminary DEXA findings on the crewmembers whose data have been analyzed to date indicate that the regional bone changes are similar to those documented in the 18 cosmonauts studied previously, both in terms of the variability in bone loss among individuals, as well as the site-specific variability in bone loss within a given individual. One NASA crewmember has shown complete bone density recovery at 6 months. All other NASA crewmembers still show significant losses with incomplete recovery. Muscle strength results will be correlated with bone density results during the 3-year recovery period and reported at a later date. Preliminary bone marker findings are not available at this time.
By learning more about the process of bone mineral loss and recovery, researchers hope to implement effective countermeasures in space and develop more effective treatments for those who suffer from bone disorders, such as osteoporosis.
Shackelford, L., Feiveson, A., Spector, E., LeBlanc, A., and Oganov, V. ''Prediction of femoral neck bone mineral density change in space.'' 12th Man in Space Symposium, Washington, DC (June, 1997).
Linda C. Shackelford, M.D.
NASA/Johnson Space Center
Institute of Biomedical Problems
Adrian LeBlanc, Ph.D.
Helen Lane, Ph.D.
Scott M. Smith, Ph.D.
Steve Siconolfi, Ph.D.
Boris Morukov, M.D.
Inessa B. Koslovskaya, M.D.
 |
Curator:
Julie Oliveaux
Responsible NASA Official: John Uri |
Page last updated: 07/16/1999
.gif)