Contractile properties of standard and nerve-intact muscle grafts in the rat

The contractile properties of standard and nerve-intact grafts of extensor digitorum longus muscles of rats were compared in vitro. Fourteen days after grafting, the time to peak tension and the half-relaxation times of nerve-intact grafts were shorter than those of standard grafts, but both were longer than control values. By 60 days, these variables attained normal values. At every sample period, the tetanic tensions of nerve-intact grafts were higher than those of standard grafts. Even at the early sampling periods, the twitch-tetanic tension ratios of nerve-intact grafts were close to normal values, whereas those of standard grafts were higher than normal. Stabilized nerve-intact grafts had a larger mass and greater maximum tetanic tension development than standard grafts, but were more fatigable. Compared with control EDL muscles, stable nerve-intact grafts show no differences except for lessened fatigability, whereas standard grafts demonstrate significant functional deficits.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50136/1/880080511_ftp.pd

Protein synthesis in skeletal muscle following acute exhaustive exercise

Cell-free and whole-tissue protein synthesis was studied in skeletal muscle of untrained male guinea pigs that had undergone a treadmill run to exhaustion. Experiments using explants from the gastrocnemius muscle maintained in organ culture demonstrated that the ability of the acutely exercised muscle to incorporate amino acids into protein had increased. Compared to polyribosomes prepared from several lower hind limb muscles of nonexercised guinea pigs, polyribosomes from the same muscle in exhausted guinea pigs had incorporated almost 50% more radioactive leucine into protein. However, the polysome profiles of control and exercised muscle were identical, and no difference in the total polysome RNA content could be detected. The efficiency of in-vitro protein synthesis using washed membrane-bound polyribosomes (microsomes) isolated from acutely exercised skeletal muscle was 50% greater than with microsomes from rested control muscle.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50128/1/880020403_ftp.pd

Injury To Skeletal Muscles Of Mice By Forced Lengthening During Contractions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109942/1/eph1989745661.pd

Power Output of Fast and Slow Skeletal Muscles of MDX (Dystrophic) and Control Mice After Clenbuterol Treatment

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72380/1/j.1469-445X.2000.02018.x.pd

Neuroanastomosis of orthotopically transplanted palmaris longus muscles

Palmaris longus (PML) muscles of rhesus monkeys were transplanted, with or without anastomosis of the median nerve, to the nerve stump of the autograft. Because PML autografts revascularize spontaneously, vascular anastomoses were not performed. Muscle fibers regenerated in all autografts with neuroanastomosis, but in only three of eight autografts without neuroanastomosis. Five autografts without neuroanastomosis were replaced by noncontractile connective tissue. Growth and differentiation of muscle fibers into three fiber types and development of capillarity were analyzed histochemically, and succinate oxidase activity of whole-muscle homogenates was determined. None of these measures reached values for control PML muscles within 100 days of transplantation. In comparison to control muscles, autografts had slower times to peak tension and less absolute tension, but similar tension per square centimeter of muscle fiber cross-sectional area. Monkey PML autografts with neuroanastomosis were similar in structure and function to cat extensor digitorum longus autografts that had not had neuroanastomosis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50127/1/880020107_ftp.pd

Motor unit function in skeletal muscle autografts of rats

Standard and nerve-intact grafts of the extensor digitorum longus (EDL) muscles of rats do not fully recover control values for maximum tetanic tension (Po). We compared the physiologic properties of motor units from standard and nerve-intact EDL grafts of rats with those of control EDL muscles. Standard grafts were completely removed and replaced in their original site. For nerve-intact grafts all physical connections were severed except for the nerve. Isometric contractile properties of whole muscles and single motor units were measured in situ 75 and 50 days after surgery for standard and nerve-intact grafts, respectively. Motor units from both types of grafts showed a mean and distribution for time-to-peak twitch tension (TPT) not different from control motor units. The absolute Po of nerve-intact grafts showed a greater recovery than the standard grafts, but was still significantly lower than the control value. The average decrease in the Po of motor units from nerve-intact grafts of 16% was not different from the decrease in the Po of the total EDL graft which suggests no loss of motor units in nerve-intact grafts. In standard grafts, the 57% decrease in Po for the whole muscle was attributable to a 20% decrease in the average tension development per motor unit and a 45% decrease in the number of motor units. These differences suggest a more complete reinnervation of the nerve-intact grafts than standard grafts.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24834/1/0000260.pd

Effect of an acute dose of omega-3 fish oil following exercise-induced muscle damage

Purpose The purpose of this double-blind, placebo-controlled study was to examine the effect of two fish oil supplements, one high in EPA (750 mg EPA, 50 mg DHA) and one low in EPA (150 mg EPA, 100 mg DHA), taken acutely as a recovery strategy following EIMD. Methods Twenty-seven physically active males (26 ± 4 year, 1.77 ± 0.07 m, 80 ± 10 kg) completed 100 plyometric drop jumps to induce muscle damage. Perceptual (perceived soreness) and functional (isokinetic muscle strength at 60° and 180° s−1, squat jump performance and countermovement jump performance) indices of EIMD were recorded before, and 1, 24, 48, 72, and 96h after the damaging protocol. Immediately after the damaging protocol, volunteers ingested either a placebo (Con), a low-EPA fish oil (Low EPA) or a high-EPA fish oil (High EPA) at a dose of 1 g per 10 kg body mass. Results A significant group main effect was observed for squat jump, with the High EPA group performing better than Con and Low EPA groups (average performance decrement, 2.1, 8.3 and 9.8%, respectively), and similar findings were observed for countermovement jump performance, (average performance decrement, 1.7, 6.8 and 6.8%, respectively, p = 0.07). Significant time, but no interaction main effects were observed for all functional and perceptual indices measured, although large effect sizes demonstrate a possible ameliorating effect of high dose of EPA fish supplementation (effect sizes ≥0.14). Conclusion This study indicates that an acute dose of high-EPA fish oil may ameliorate the functional changes following EIMD

AGE-RELATED CHANGES IN THE STRUCTURE AND FUNCTION OF SKELETAL MUSCLES

1.  For animals of all ages, during activation of skeletal muscles and the subsequent contraction, the balance between the force developed by the muscle and the external load determines whether the muscle shortens, remains at fixed length (isometric) or is lengthened. With maximum activation, the force developed is least during shortening, intermediate when muscle length is fixed and greatest during lengthening contractions. During lengthening contractions, when force is high, muscles may be injured by the contractions. 2.  ‘Frailty’ and ‘failure to thrive’ are most frequently observed in elderly, physically inactive people. A ‘frail’ person is defined as one of small stature, with muscles that are atrophied, weak and easily fatigued. The condition of ‘failure to thrive’ is typified by a lack of response to well-designed programmes of nutrition and physical activity. 3.  With ageing, skeletal muscle atrophy in humans appears to be inevitable. A gradual loss of muscle fibres begins at approximately 50 years of age and continues such that by 80 years of age, approximately 50% of the fibres are lost from the limb muscles that have been studied. For both humans and rats, the observation that the timing and magnitude of the loss of motor units is similar to that for muscle fibres suggests that the mechanism responsible for the loss of fibres and the loss of whole motor units is the same. The degree of atrophy of the fibres that remain is largely dependent on the habitual level of physical activity of the individual. 4.  ‘Master athletes’ maintain a high level of fitness throughout their lifespan. Even among master athletes, performance of marathon runners and weight lifters declines after approximately 40 years of age, with peak levels of performance decreased by approximately 50% by 80 years of age. The success of the master athletes and of previously sedentary elderly who undertake well-designed, carefully administered training programmes provide dramatic evidence that age-associated atrophy, weakness and fatigability can be slowed, but not halted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75382/1/j.1440-1681.2007.04752.x.pd

Dystrophin‐deficient mdx mice display a reduced life span and are susceptible to spontaneous rhabdomyosarcoma

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154288/1/fsb2fj067353com.pd

Revascularization of skeletal muscle transplanted into the hamster cheek pouch: Electron microscopy

Revascularization of bundles of skeletal muscle fibers transplanted into the cheek pouch of hamsters was examined previously by intravital and light microscopy. Some blood vessels survived the ischemia of transplantation and revascularization resulted from the growth of surviving vessels. We have now examined the cellular events of graft revascularization by electron microscopy (EM). Approximately 20 skeletal muscle fibers were autografted into the hamster cheek pouch. Segments of the graft were prepared for EM from 0.5 to 5 days after transplantation. At 0.5 day, the endothelial cells of surviving blood vessels had short processes extending from them. By 1.0 day, some endothelial cells had separated. At 1.5 days, many endothelial cells were undergoing mitosis. Blood vessels at 2 to 2.5 days were of narrow diameter and most were densely packed with erythrocytes. Circulation was reestablished between 2.5 and 3 days. The fine structure of the blood vessels changed little after 3 days except for a decrease in the number of vesicles in the endothelial cell cytoplasm and the formation of normal endothelial cell injections. After 5 days, blood vessels were larger in diameter, but otherwise similar to control capillaries. We conclude that, despite the initial absence of circulation, surviving blood vessels underwent a rapid, orderly sequence of growth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25167/1/0000605.pd