title: In-flight and postflight changes in skeletal muscles of SLS-1 and SLS-2 spaceflown rats.
abstract: Spacelab Life Sciences-1 and -2 provided skeletal muscles from rats dissected in flight for the first time and 2 h to 14 days postflight. The muscles permitted the distinguishing of 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 one-third of normal. The adductor longus (AL) and soleus muscles exhibited decreased myofiber areas that did not recover 14 days postflight. Doubling of the nonmyofiber area indicated interstitial edema in AL muscles 2.3 h postflight. Solei did not manifest edema postflight, and neither muscle showed edema in flight. Sarcomere eccentric contraction-like lesions were detected in 2.6% of AL myofibers 4.5 h postflight; lesions were absent earlier postflight and in flight. At 9 days postflight, these lesions were repaired but regenerating AL myofibers were present, which suggests that myofiber necrosis occurred 1-2 days postflight. These studies demonstrate that muscle atrophy occurs in microgravity, whereas interstitial edema and sarcomere lesions are postflight phenomena.
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Wisconsin, Milwaukee 53226, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Riley
authors.forename: S
authors.initials: S
authors.lastname: Ellis
authors.forename: G R
authors.initials: GR
authors.lastname: Slocum
authors.forename: F R
authors.initials: FR
authors.lastname: Sedlak
authors.forename: J L
authors.initials: JL
authors.lastname: Bain
authors.forename: B B
authors.initials: BB
authors.lastname: Krippendorf
authors.forename: C T
authors.initials: CT
authors.lastname: Lehman
authors.forename: M Y
authors.initials: MY
authors.lastname: Macias
authors.forename: J L
authors.initials: JL
authors.lastname: Thompson
authors.forename: K
authors.initials: K
authors.lastname: Vijayan
authors.forename: J A
authors.initials: JA
authors.lastname: De Bruin
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001284:Atrophy; D003238:Connective Tissue / Q000502:physiology / Q000648:ultrastructure; D006651:Histocytochemistry; D008297:Male; D008407:Mast Cells / Q000502:physiology / Q000648:ultrastructure; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology* / Q000648:ultrastructure; D015388:Organelles / Q000502:physiology / Q000648:ultrastructure; D011187:Posture / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000502:physiology / Q000648:ultrastructure; D013026:Space Flight; D014893:Weightlessness / Q000009:adverse effects