Inflight and postflight changes in skeletal muscles of sls-1 and
sls-2 spaceflown rats.
Riley, D. A., S. Ellis, G. R. Slocum, F. R. Sedlak, J. L. W. Bain, B.
B. Krippendorf, C. T. Lehman, M. Y. Macias, J. L. Thompson, K.
Vijayan, and J. A. De Bruin.
Department of Cellular Biology & Anatomy, Medical College of
Wisconsin, Milwaukee, Wisconsin 53226, USA
APStracts 2:0176A, 1995.
Spacelab Life Sciences 1 and 2 provided skeletal muscles from rats
dissected inflight for the first time and 2 hrs to 14 days
postflight. The muscles permitted distinguishing primary adaptations
to microgravity from secondary reloading-induced alterations. In
microgravity, rats adopted bipedal forelimb locomotion with the
hindlimbs relegated to grasping activities. On landing day, body
posture was abnormally low, and walking was stilted at a rate 1/3
normal. The adductor longus (AL) and soleus muscles exhibited
decreased myofiber areas which did not recover 14 days postflight.
Doubling of the nonmyofiber area indicated interstitial edema in AL
muscles 2.3 hrs postflight. Solei did not manifest edema postflight,
and neither muscle showed edema inflight. Sarcomere eccentric
contraction-like lesions were detected in 2.6% of AL myofibers 4.5
hrs postflight; lesions were absent earlier postflight and inflight.
At 9 days postflight, these lesions were repaired, but regenerating
AL myofibers were present, suggestive that myofiber necrosis occurred
1-2 days postflight. These studies demonstate that muscle atrophy
occurs in microgravity whereas interstitial edema and sarcomere
lesions are postflight phenomena.
Received 23 December 1994; accepted in final form 25 April 1995.
APS Manuscript Number A1329-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 2 May 1995.