ABSTRACT
The aim of this study was to elucidate the effects of 14- day hindlimb suspension (HS) and subsqquent reloading (3 or 7 days) on the m. soleus mass, muscle fiber cross-sectional area (CSA), soleus fiber properties and serum IGF-1 in rats. Rats were hindlimb suspended for 14 days or kept as controls (C, n = 7). Soleus muscles were isolated after HS (HS, n = 7) or after reambulation for either three (R3, n = 5) or seven days (R7, n = 6). Frozen serial sections of m. soleus were stained by primary monoclonal antibodies against MHCI. For measurement of concentration IGF-1 in the blood serum, test-system for IFA DSL-10-2800 Non-Extraction IGF-1 ELISA was used. Muscle mass was significantly reduced in HS (-35 %) but subsequently increased with reloading in R3 (-10 % to C) and was recovered to control values in R7 (+5 % to C). Fiber CSA was significantly reduced (-43 %) in HS and was greater in R7 than in HS and slightly greater than in R3. 14 days of HS resulted in a mean maximal tension reduced by 35 %. After 7 days of subsequent reloading the mean maximal specific tension was still low (-33 % to C) and didn't differ from HS level. The level in blood IGF-1 has obviously decreased during 14-day unloading by 48 %, remained at the same level in R3, and increased 10 fold in R7.
Subject(s)
Hindlimb Suspension , Insulin-Like Growth Factor I/analysis , Muscle Contraction , Muscle, Skeletal/metabolism , Muscular Atrophy/blood , Animals , Male , Muscle, Skeletal/pathology , Muscular Atrophy/etiology , Rats , Rats, WistarABSTRACT
The effects of creatine oral supplementation combined with a 10-week resistive training of morphometric, contractile and molecular characteristics of human vast lateral muscle fibers were studied. 2 groups consisting of 9 young healthy men each were involved in resistive training of knee extensors for 10 weeks. Volunteers of the first group received per os 20 g of creatine for the 1st week of training and 5 g for the rest of the experimental training period. We found a significant increase of slow and fast-twitch fiber size in both trained groups and a significant increase of Ca-sensitivity of skinned single fiber contractility in creatine-supplemented group. The serum creatine phosphokinase activity in blood samples taken 24 hours after exercise session increased in all stages of the experimental training in both groups. At the same time, the adaptive decrease of the after-exercise CK concentration was observed in the placebo but not in the creatine-supplemented group. The altered integrity of the subsarcolemmal dystrophin layer was revealed in both groups after training.
Subject(s)
Creatine/administration & dosage , Exercise/physiology , Muscle Fibers, Fast-Twitch/physiology , Muscle Fibers, Slow-Twitch/physiology , Muscle, Skeletal/physiology , Adult , Dystrophin/metabolism , Humans , Male , Muscle Fibers, Fast-Twitch/cytology , Muscle Fibers, Slow-Twitch/cytology , Muscle, Skeletal/cytology , Organ Size/drug effects , Organ Size/physiology , Sarcolemma/physiologyABSTRACT
Effect of functional unloading on the course of degenerative process in muscles was studied in dystrophin-deficient mdx mice. Head down-hanging of animals led to a significant decrease in the cross-section area of muscle fibers, increase in the percentage of fibers with centrally located nuclei and of Evans blue-stained fibers. Gravitation unloading of 12-month-old animals with pronounced manifestations of muscular dystrophy did not inhibit this pathological process.
Subject(s)
Hindlimb Suspension/physiology , Muscle Contraction/physiology , Muscle, Skeletal/cytology , Muscle, Skeletal/physiology , Muscular Dystrophy, Animal/pathology , Animals , Body Weights and Measures , Evans Blue , Male , Mice , Mice, Inbred C57BL , Mice, Inbred mdxABSTRACT
Muscle fiber composition of m. vastus lateralis has significant individual variability mainly depending on genetic factors. Present study shows analysis of association between polymorphisms of three muscle performance-related genes and muscle fiber type composition in 48 young healthy men. DNA was obtained from mouthwash samples by alkaline extraction. Polymorphism determination of PPARalpha, ACE and ACTN3 genes was performed using polymerase chain raction. Muscle fiber typing from m. vastus lateralis was performed using immunohistochemistry method. We found an association of increased frequency of intron 7 G allele of PPARalpha gene (93.9% vs 60.0%) and D allele of ACE gene (68.8% vs 34.4%) in the group with the highest proportion of slow-twitch fibers (56-70%) compared to the group with the lowest proportion (25-43%). Thus, PPARalpha and ACE genes can be considered as potential candidate genes for muscle fiber type determination.
