title: Plasticity of monkey triceps muscle fibers in microgravity conditions.
abstract: We examined the changes in functional properties of triceps brachii skinned fibers from monkeys flown aboard the BION 11 satellite for 14 days and after ground-based arm immobilization. The composition of myosin heavy chain (MHC) isoforms allowed the identification of pure fibers containing type I (slow) or type IIa (fast) MHC isoforms or hybrid fibers coexpressing predominantly slow (hybrid slow; HS) or fast (hybrid fast) MHC isoforms. The ratio of HS fibers to the whole slow population was higher after flight (28%) than in the control population (7%), and the number of fast fibers was increased (up to 86% in flight vs. 12% in control). Diameters and maximal tensions of slow fibers were decreased after flight. The tension-pCa curves of slow and fast fibers were modified, with a decrease in pCa threshold and an increase in steepness. The proper effect of microgravity was distinguishable from that of immobilization, which induced less marked slow-to-fast transitions (only 59% of fast fibers) and changed the tension-pCa relationships.
authors: Laboratoire de Plasticité Neuromusculaire, Université des Sciences et Technologies de Lille 1, F-59655 Villeneuve d'Ascq Cedex, France.
authors: P
authors: P
authors: Kischel
authors: L
authors: L
authors: Stevens
authors: V
authors: V
authors: Montel
authors: F
authors: F
authors: Picquet
authors: Y
authors: Y
authors: Mounier
mesh_terms: D000818:Animals; D007103:Immobilization; D008253:Macaca mulatta; D009119:Muscle Contraction / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000032:analysis*; D020033:Protein Isoforms / Q000032:analysis; D012016:Reference Values; D013026:Space Flight; D014893:Weightlessness
chemical_list: D020033:Protein Isoforms; D018995:Myosin Heavy Chains