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PubMed2003

Detection of enterovirus in human skeletal muscle from patients with chronic inflammatory muscle disease or fibromyalgia and healthy subjects.

Enterovirus RNA has been found previously in specimens of muscle biopsy from patients with idiopathic dilated cardiomyopathy, chronic inflammatory muscle diseases, and fibromyalgia or chronic fatigue syndrome (fibromyalgia/chronic fatigue syndrome). These results suggest that skeletal muscle may host enteroviral persistent infection. To test this hypothesis, we investigated by reverse transcription-polymerase chain reaction (RT-PCR) assay the presence of enterovirus in skeletal muscle of patients with chronic inflammatory muscle diseases or fibromyalgia/chronic fatigue syndrome, and also of healthy subjects. Three of 15 (20%) patients with chronic inflammatory muscle diseases, 4 of 30 (13%) patients with fibromyalgia/chronic fatigue syndrome, and none of 29 healthy subjects was found positive. The presence of VP-1 enteroviral capsid protein was assessed by an immunostaining technique using the 5-D8/1 monoclonal antibody; no biopsy muscle from any patient or healthy subject was found positive. The presence of viral RNA in some muscle biopsies from patients exhibiting muscle disease, together with the absence of VP-1 protein, is in favor of a persistent infection involving defective viral replication.

Adult↗

PubMed1987

Frequency of bifurcated muscle fibers in hypertrophic rat soleus muscle.

The total number of bifurcated and nonbifurcated fibers were counted in rat soleus muscles induced to hypertrophy by surgical ablation of the gastrocnemius and plantaris muscles. Sham-operated and normal soleus muscles served as controls. Every muscle fiber within the entire muscle was individually examined and counted with the aid of a dissecting microscope following a 10-12 hour nitric acid digestion of the connective tissue. The results show that the total number of muscle fibers in the hypertrophic soleus did not differ significantly from the control. The frequency of bifurcated fibers observed in the control muscles was significantly greater than has been previously reported, and their frequency in the hypertrophic muscles, although slightly increased, was not significantly different from control values. These data confirm that fiber hypertrophy is not accompanied by hyperplasia, and they further suggest that bifurcated fibers probably play an insignificant role during muscle adaptation to hypertrophy due to their very low frequency.

Animals↗

PubMed1996

Smooth muscle alpha-actin downregulation in cultured chick aortic smooth muscle and neural crest cells is associated with altered cell shape.

A modified CXL retrovirus was used to clone an antisense smooth muscle alpha-actin ribozyme sequence adjacent to the reporter lacZ sequence. The virus was applied to downregulate alpha-actin expression in cultured smooth muscle cells obtained from chicken aortic arch and cultured neural crest cells. After infection with the ribozyme-containing CXL retrovirus both the smooth muscle and neural crest cells showed beta-galactosidase activity accompanied by a reduction of smooth muscle alpha-actin-positive fibers. Double staining of beta-galactosidase and smooth muscle alpha-actin using immunohistochemistry revealed that single cells infected with the CXL/ribozyme showed little to no smooth muscle alpha-actin protein. The absence of smooth muscle alpha-actin was associated with a distinct change in cellular morphology of the cultured cells, suggesting that expression of smooth muscle alpha-actin in cultured neural crest cells may be associated with cytoskeletal elements rather than vascular smooth muscle phenotype.

Actins↗

PubMed2001

Electroporation-facilitated delivery of plasmid DNA in skeletal muscle: plasmid dependence of muscle damage and effect of poloxamer 188.

Electroporation has been reported to facilitate naked DNA gene transfer in skeletal muscle, but has also been implicated in the pathogenesis of electrical injuries. To assess the effects of electroporation on gene transfer, mouse quadriceps muscles were injected with the luciferase reporter plasmid VR1255 and electroporated with caliper electrodes. Intramuscular luciferase expression was increased 10- to 70-fold by electroporation, depending on the DNA dose and injection volume used. In the absence of plasmid DNA injection, electroporation of quadriceps muscles resulted in rapid elevations in serum creatine phosphokinase activity, but did not elicit visible muscle damage. However, in muscles injected with plasmid DNA and electroporated, visible lesions consistently developed in the areas proximal to electrode placement when field strengths optimal for gene transfer (300 volts/cm) were applied. The development of muscle lesions was independent of plasmid transgene expression and required the presence of plasmid in the muscle during electroporation. Co-injection of poloxamer 188 (pluronic F68) with VR1255 substantially reduced elevations in serum creatine phosphokinase activity following electroporation, but did not inhibit the development of muscle lesions. In non-electroporated muscles, co-injection of poloxamer 188 increased luciferase expression threefold. Poloxamer 188 may thus constitute a useful excipient for intramuscular delivery of naked DNA.

Animals↗

PubMed1993

Shoulder muscle load and muscle fatigue among industrial sewing-machine operators.

Physiological responses to physical work were assessed for 29 female industrial sewing-machine operators during an 8-h working day under ordinary working conditions. During sewing-machine work, the average (left and right) static load in the trapezius muscle was 9% of the maximal electromyogram (EMG) amplitude (% EMGmax), while the average mean load was 15% EMGmax, and the average peak load was 23% EMGmax. The static load level was unrelated to the muscle strength of the sewing-machine operators, which for the group as a whole was within the normal range. The load levels remained unchanged during the working day, while changes in the EMG mean power frequency and zero crossing frequency rate occurred, both indicating the development of muscle fatigue in left and right trapezius muscle during the working day. In line with this, the rating of perceived exertion in the shoulder and neck region increased during the working day. Dividing the group of sewing-machine operators into two groups, those with the highest frequency and those with the lowest frequency of shoulder/neck troubles showed that the former group had significantly lower muscle strength, despite the fact that no differences in the surface EMG during sewing were found between the two groups. It was concluded that industrial sewing-machine work involves a pattern of shoulder muscle activity which induces fatiguing processes in the shoulder and neck regions. Furthermore, since the static shoulder muscle load was independent of muscle strength, factors other than working posture may be of significance for the static shoulder muscle load.

Adult↗

PubMed1991

Evidence of fibre hyperplasia in human skeletal muscles from healthy young men? A left-right comparison of the fibre number in whole anterior tibialis muscles.

Cross-sections (thickness 10 microns) of whole autopsied left and right anterior tibialis muscles of seven young previously healthy right-handed men (mean age 23 years, range 18-32 years) were prepared for light-microscope enzyme histochemistry. Muscle cross-sectional area and total number of fibres, mean fibre size (indirectly determined) and proportion of the different fibre types (type 1 and type 2 on basis of myofibrillar adenosine triphosphatase characteristics), in each muscle cross-section were determined. The analysis showed that the cross-sectional area of the left muscle was significantly larger (P less than 0.05), and the total number of fibres was significantly higher (P less than 0.05), than for the corresponding right muscle. There was no significant difference for the mean fibre size or the proportion of the two fibre types. The results imply that long-term asymmetrical low-level daily demands on muscles of the left and the right lower leg in right-handed individuals provide enough stimuli to induce an enlargement of the muscles on the left side, and that this enlargement is due to an increase in the number of muscle fibres (fibre hyperplasia). Calculations based on the data also explain why the underlying process of hyperplasia is difficult, or even impossible, to detect in standard muscle biopsies.

Adaptation, Physiological↗

PubMed1986

Motor unit fibre density in extremely hypertrophied skeletal muscles in man. Electrophysiological signs of muscle fibre hyperplasia.

Single fibre electromyography (SFEMG) was performed on the left quadriceps, extensor digitorum communis, and biceps brachii muscles of four highly trained bodybuilders (BB). Muscle fibre areas, as assessed from biopsy samples, were similar in the BB as in age-matched habitually active male controls despite large differences in limb circumferences. This indicates a greater muscle fibre number in BB. An abnormally high muscle fibre density (FD) was recorded in two subjects exposed to extremely severe exercise for 14 years or longer, while those with normal FDs had been training extensively for a considerably shorter time (4-6 years). The abnormal FD was due either to an ephaptic transmission of action potentials between adjacent muscle fibres, or a muscle fibre hyperplasia, or most probably a combination of both, in response to a long-term functional overload. From the present results one cannot say whether the suggested muscle fibre hyperplasia had any major influence on the muscle hypertrophy per se, since all BB possessed large muscle volumes.

Adult↗

PubMed2004

Electrodynamic smooth muscle sphincter: development and biomechanical evaluation of a novel porcine artificial smooth muscle sphincter in a new in vitro stoma simulator.

AIM: Many authors have suggested that the activity of the enteric inhibitory nerves is important in regulating normal gastrointestinal motility and inducing smooth muscle relaxation. Hitherto, no experimental or clinical models exist that transfer these physiological aspects to creating an autologous artificial sphincter for the treatment of major incontinence. Therefore, this study was performed to determine the contractile and relaxant capacity of gastrointestinal muscle types and to investigate the efficiency of a novel smooth muscle sphincter, based on the non-adrenergic, non-cholinergic (NANC) receptive relaxation under electrical field stimulation (EFS). METHODS: For the first step, the isometric tension from isolated circular porcine fundus and colon muscle strips was recorded during pharmacological stimulation (TTX, L-NNA and atropine) and EFS. As a result, a continent electrodynamic smooth muscle sphincter (ESMS) was created by wrapping a fundus muscle flap around an isolated segment of porcine distal colon. The EFS of the free nerve fibers of the flap was realized using a circular platinum wire electrode. Parameters such as threshold of continence, intra/preluminal pressure and fluid passage were analyzed in a newly designed in vitro stoma simulator. RESULTS: Electrical field stimulation produced a maximal and voltage-dependent fundus relaxation to --12.4 mN/mm(2) (frequency of 40 Hz, pulse duration, train duration and voltage of 5 ms, 1 s and 60 mA respectively), which were abolished by N-nitro-L -arginine (L-NNA; 10(-4) M) in a dose-dependent manner, confirming that relaxant responses were mediated by NANC nerves. The results of eight ESMS showed that circular electrical stimulation of the muscle flap caused muscle relaxation with a concomitant and effective reduction in the occlusion pressure. CONCLUSION: The NANC-induced relaxation mechanism of porcine fundus preparations could be transferred to an efficient smooth muscle sphincter with a high threshold of continence and electrically controlled defecation.

Anal Canal↗

PubMed2000

Muscle enlargement in sumo wrestlers includes increased muscle fascicle length.

Skeletal muscle architecture was measured in 28 college sumo wrestlers (Sumo) and 30 control subjects. Pennation angle (PAN) and muscle thickness (MTH) of the triceps long head (TL), vastus lateralis (VL) and gastrocnemius medialis (MG) and lateralis (LG) muscles were measured by B-mode ultrasonography, and fascicle length (FAL) was estimated. Sumo wrestlers had a significantly greater percentage body fat [mean (SD) 33.9 (9.4)%], fat mass [41.7 (18.5) kg], and fat-free mass [76.8 (7.5) kg] than the controls [15.6 (2.5)%, 9.3 (2.4) kg, and 49.9 (6.2) kg, respectively]. MTH was between 18 and 35% greater in sumo wrestlers than in controls. The sumo wrestlers had a significantly greater PAN in the TL, MG and LG muscles than did the controls, but not in the VL. There were significant correlations between PAN and MTH for the sumo wrestlers (r values from 0.33 to 0.57), suggesting that PAN is a function of the relative state of muscle enlargement. FAL was greater (P < 0.01) in the Sumo group for TL (7.26 cm vs 6.13 cm), VL (10.01 cm vs 6.97 cm) and MG (6.41 cm vs 5.53 cm) than in the controls, but not for LG (7.61 cm vs 7.04 cm). Relative FAL correlated significantly with MTH for these muscles in the Sumo group [r values from 0.45 (P < 0.05) to 0.71 (P < 0.01)]. There appear to be architectural differences in the muscle fascicles between sumo wrestlers and controls, with sumo wrestlers having longer fascicles. A greater FAL appears to limit the degree of change in PAN associated with the extreme muscle enlargement seen in sumo wrestlers. This architectural alteration may ultimately improve the expression of the force/cross-sectional area relationship with extreme muscle enlargement.

Adaptation, Physiological↗

PubMed1979

Effect of isolated inferior oblique muscle myectomy in the management of superior oblique muscle palsy.

Thirty-three patients with superior oblique palsy were treated with an inferior oblique myectomy temporal to the inferior rectus muscle. The mean effect of surgery was 11.91 +/- 1.38 in all positions of gaze and for all age groups. The operative result in both children and adults was the same. The mean effect of surgery correlated with the size of the preoperative hyperdeviation in the fields of action of both inferior and superior oblique muscles. Inferior oblique muscle myectomy was followed by return of normal function to the superior oblique muscle in 63% of cases. Ocular torticollis was eliminated in 90% of the patients. Persistent overaction of inferior oblique muscle was encountered in three patients. Postoperative underaction of the myectomized muscle was not observed in any of our patients. A myectomy is recommended as a primary procedure in patients with superior oblique muscle palsy when the direct antagonist is overacting and the hyperdeviation is 10 to 15 prism diopters or more in primary position or the fields of action of the paretic superior oblique muscle or the overacting inferior oblique muscle.

Adolescent↗

PubMed1984

Regeneration of mouse peripheral nerves in degenerating skeletal muscle: guidance by residual muscle fibre basement membrane.

The part played by basement membrane in the guidance of peripheral nerve growth in vivo has been assessed by examining the capacity of degenerating mouse muscle to support the regeneration of the cut sciatic and saphenous nerves. Ethanol and formaldehyde-fixed gluteus maximus muscles were implanted around the contralateral cut nerves. The subsequent nerve growth into the degenerating muscle was assessed by silver staining after 3, 4 and 10 days. By 4 days, linear axonal growth was seen, parallel to the length of the muscle fibres, and coinciding with the onset of degeneration of the sarcoplasm. Transverse sections of the 10 day preparations showed that over 90% of linearly growing axons were located inside the remaining sheaths of muscle fibre basement membrane. This relationship was confirmed by electron microscopy of ruthenium red-stained preparations. Both motor and sensory axons were able to grow in this manner, for electrophysiological testing revealed the presence of motor axons from the sciatic nerve, while the saphenous nerve contains only sensory axons. Identical growth was seen at 10 days in muscles caused to degenerate by incubation in distilled water. However, linear growth did not occur in live-innervated and glutaraldehyde-fixed muscles, in which muscle fibre architecture was preserved. It is concluded that basement membrane derived from muscle can promote peripheral nerve regeneration. Furthermore, both motor and sensory axons show a strong preference for growth along its inner surface, the basal lamina.

Animals↗

PubMed1985

Muscle development in the grasshopper embryo. III. Sequential origin of the flexor tibiae muscle pioneers.

The flexor (FlTi) and extensor (ETi) tibiae are antagonist muscles located in the femur of the metathoracic leg of the grasshopper. Both are complex, consisting of an array of bundles of muscle fibers connecting the ectoderm of the wall of the femur with their respective apodemes. In the previous paper (E. E. Ball and C. S. Goodman, 1985, Dev. Biol. 111, 399-416) we described the embryonic development of the ETi muscle, focusing in particular on its syncytial origin from a giant supramuscle pioneer which later divides into an array of individual muscle pioneers. Here we describe the embryonic development of the FlTi muscle. In contrast to the development of the ETi muscle, the array of individual muscle pioneers for the FlTi does not have a syncytial origin but rather arises by sequential recruitment from the mass of smaller, undifferentiated mesoderm cells. The FlTi MPs first appear as two cells symmetrically placed on the corners of the FlTi apodeme at around 37%. A third MP is then added between these two; this third MP later dies. Subsequent growth occurs by symmetrical addition of MPs distally along the sides of the developing apodeme and by enlargement of the individual MPs. Initially each MP contains only a single nucleus; by about 50% there are at least two to three nuclei per MP and each is surrounded by a cluster of smaller, undifferentiated mesoderm cells. Each MP develops into a bundle of muscle fibers by a cycle of fusion and division. The individual mesoderm cells surrounding each MP fuse with it starting at about 60%. At the same time, the large MP begins to divide into smaller muscle fibers.

Animals↗

PubMed1984

Soluble age-related factors from skeletal muscle which influence muscle development.

Successful regeneration of damaged striated muscle in adult mice is dependent on the regeneration of newly differentiated myofibers from proliferating satellite cells and inhibition of scar tissue formation by fibroblasts. As with most tissues, the ability of skeletal muscle to regenerate decreases in older animals. In this study, we have analysed soluble extracts from intact and regenerating skeletal muscle from mice of different ages for their ability to affect avian myogenesis in tissue culture. We were interested in determining whether an age-dependent difference could be detected with this tissue culture bioassay system. Total cell proliferation in the cultures, measured by [3H]thymidine incorporation was increased equally by muscle extracts from both young and older mice but the resulting cell populations differed in proportion of cell types. The ratio of myoblasts to fibroblasts was significantly greater in cultures exposed to extracts from younger mouse muscle as compared with cultures exposed to extracts from older animals. This age-related activity was found to reside in a low molecular weight (MW) (greater than 12 kD) component of the extract. This fraction had dissimilar effects on myoblasts and fibroblasts. Relative to saline controls, myoblast proliferation was increased and fibroblast proliferation decreased. The low MW fraction from younger mouse muscle extracts stimulated myogenic cell proliferation and myotube formation to a greater extent than the similar fraction prepared from older mouse muscle. Conversely, younger mouse muscle fractions had significantly greater inhibitory activity against fibroblast proliferation than did older mouse muscle fractions.

Age Factors↗

PubMed1975

Mechanisms of cell-mediated myotoxicity. Morphological observations in muscle grafts and in muscle exposed to sensitized spleen cells in vivo.

Fragments of rectus abdominis muscle or diaphragm from AKR or Prince Henry mice were transplanted beneath the skin of the anterior abdominal wall of BALB/C mice and were examined by light and electron microscopy 1-23 days after transplantation. Observations were made on the mode of entry of lymphoid cells into grafts, the nature of the inflammatory cells present in grafts and the interactions between mononuclear cells and regenerating muscle fibres during the rejection phase 7-14 days after transplantation. Lymphoid cells were found to migrate through the endothelium of venules and to enter the space between the basement lamina and the plasma membrane of muscle fibres to make contacts of varying degrees of complexity with the muscle cell membrane. Evidence of penetration of lymphoid cells into muscle fibres (emperipolesis) was found and was usually associated with signs of damage to the muscle fibre. Interactions between mononuclear cells and mature muscle fibres were studied after inoculation of sensitized spleen cells into the musculature of the tongue in mice. Both lymphoid cells and mononuclear phagocytes were found to invade muscle fibres by penetrating the basement lamina. The muscle cell membrane was usually broken down in zones of invasion by mononuclear cells but generally remained intact at sites of invasion by lymphoid cells.

Animals↗

PubMed1990

Expression of muscle-specific isozymes of phosphorylase and creatine kinase in human muscle fibers cultured aneurally in serum-free, hormonally/chemically enriched medium.

Primary cultures of muscle cells derived from a biopsied adult human skeletal muscle were grown up to 6 weeks in a hormonally/chemically enriched serum-free medium. The expression of muscle-specific isozymes of creatine kinase, glycogen phosphorylase, and phosphoglycerate mutase, indicative of muscle cell maturation, was studied after 1, 4 and 6 weeks of growth. The maturation of muscle fibers cultured in serum-free medium was comparable to that achieved by muscle fibers cultured in medium containing 10% serum and supplemented with growth factors (insulin, epidermal growth factor, and fibroblastic growth factor) and was greater than that achieved in medium containing 10% serum only. Our study demonstrates that adult human muscle can be cultured aneurally for a long period of time in a serum-free medium, and that it can achieve a high degree of maturation. This study provides an important basis for investigations related to: (1) assessment of the influence of individual components of the medium on human muscle maturation in culture; (2) studies of regulation of abnormal gene expression in diseased human muscle cultured in serum-fre medium.

Adult↗

PubMed2005

Muscle-derived interleukin-6--a possible link between skeletal muscle, adipose tissue, liver, and brain.

Accumulating evidence exists that regular exercise offers protection against chronic disorders such as cardiovascular diseases, type 2 diabetes, dementia, and depression. Although acute and chronic exercise has numerous consequences, it is still discussed how contracting skeletal muscles mediate metabolic and physiological effects of benefits on health. For years the search for the stimulus that initiates and maintains the change of excitability or sensibility of the regulating centers in exercise has been progressing. For lack of more precise knowledge, it has been called the 'work stimulus,' 'the work factor' or 'the exercise factor.' In other terms, the big challenge for muscle and exercise physiologists has been to determine how muscles signal to central and peripheral organs. Recently, we identified that muscle fibers produce and release the cytokine IL-6 into the circulation during exercise. We further proposed that IL-6 and other cytokines, which are produced and released by skeletal muscles, exerting their effects in other organs of the body, should be named 'myokines.' In line with that adipokines have been suggested as a term, which is restricted to cover cytokines and other peptides which are produced and secreted by adipocytes, we suggest that the term "myokines" should be used exclusively to describe cytokines or other peptides, which are produced and released by muscle fibers per se. Myokines may represent the link from working muscle to other organs such as the adipose tissue, the liver, and the vascular compartments. Here, we review the literature on muscle- and brain-derived IL-6. We further suggest that myokines may also provide an explanation as to how regular muscle activity influences mood, performance, and cognitive function.

Adipose Tissue↗

PubMed2005

The effect of physical training on workload, upper leg muscle function and muscle areas in patients with chronic heart failure.

OBJECTIVE: To investigate the effect of physical training (PTr) on upper leg muscle area, muscle strength and muscle endurance expressed as upper leg muscle function (ULMF) in relation to exercise performance in CHF. DESIGN: Randomised to a training (TG) or control group (CG). SETTING: Outpatient cardiac rehabilitation centre of community hospital. PATIENTS: 77 CHF patients (59 men and 18 women), NYHA class II/III, age 59.8+/-9.3 years, LVEF 27+/-8%. Sixteen patients dropped out during the intervention period, 61 patients (M/F:46/15) completed the study. INTERVENTION: PTr (combined strength and endurance exercises) four times per week, twice supervised and twice at home, during 26 weeks. MAIN OUTCOME MEASURES: LVEF, body composition, daily physical activity, exercise performance, upper leg muscle area and isokinetic leg muscle variables. RESULTS: Workload and peak oxygen consumption decreased in the CG (-4.1% and -4%) but increased in the TG (+5% and +4%) following PTr (p<0.05, ANOVA repeated measures). Hamstrings area decreased in the CG and did not change in the TG (p<0.05, ANOVA repeated measures). ULMF improved in the TG, but remained unchanged in the CG (+13.0% and 0.0, respectively, p<0.05; ANOVA repeated measures). At baseline and after intervention nearly 60% of the variance in maximal workload was explained by ULMF and quadriceps muscle area (multiple regression analysis). CONCLUSIONS: In CHF patients, home-based training in conjunction with a supervised strength and endurance training program is safe, feasible and effective and does not require complex training equipment. Physical training prevented loss of hamstrings muscle mass and improved exercise performance by enhancing muscle strength and endurance.

Exercise↗

PubMed1999

Tissue-specific distribution of breast-muscle-type and leg-muscle-type troponin T isoforms in birds.

In order to show the tissue-specific distribution of troponin T (TnT) isoforms in avian skeletal muscles, their expression was examined by electrophoresis of the breast and leg muscles of seven avian species and immunoblotting with the antiserum against fast skeletal muscle TnT. It has been reported in the chicken that breast-muscle-type (B-type) and leg-muscle-type (L-type) TnT isoforms are expressed specifically in the adult breast and leg muscles, respectively. Their differential expression patterns were confirmed in all birds examined in this study. The expression of a segment encoded by the exon x series of TnT was also examined by immunoblotting with the antiserum against a synthetic peptide derived from the exon x3 sequence, because the segment has been shown to be included exclusively in the B-type, but not in the L-type TnT. The expression of the segment was found only in the breast muscle, but not in the leg muscle of all birds examined. TnT cDNA sequences from the duck breast and leg muscles were determined and showed that only B-type TnT had an exon x-related sequence, suggesting that the expression of B-type TnT containing the exon x-derived segment is conserved consistently in the birds.

Amino Acid Sequence↗