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At least 19 recordsLinked to original sources
PubMedDate not supplied

Magnetic resonance imaging examination of denervated muscle.

Denervated muscles due to lumbar radiculopathy, peroneal axonal neuropathy and hypoglossal neuropathy were studied with magnetic resonance imaging (MRI). Denervated muscle was clearly distinguished from normal muscle by its higher intensity signal. Comparison of the resulting signal intensity of the muscle using various imaging parameters suggests an alteration in water macromolecular binding. These preliminary findings indicate that MRI may be useful in the noninvasive in vivo diagnosis and study of the effects of denervation on muscle.

Humans↗
PubMed1987

Clenbuterol, a beta 2-agonist, retards atrophy in denervated muscles.

Denervated soleus, anterior tibialis, and gastrocnemius muscles, but not the extensor digitorum longus, contained 95-110% more protein after 2-3 wk of treatment with the adrenergic beta 2-receptor agonist, clenbuterol, than denervated controls. In addition, the twofold difference in the protein content of denervated solei was paralleled by similar changes in contractile strength and muscle fiber cross-sectional area. In contrast, when the innervated contralateral muscles were examined, the extensor digitorum longus and anterior tibialis showed relatively small increases in protein of 32 and 19%, respectively, whereas the soleus and gastrocnemius were unaffected. The magnitude of the effects of clenbuterol in sparing the mass and functional capacity of denervated muscle suggests that this agent may be important in studies of neuromuscular diseases and disuse atrophy.

Animals↗
PubMed1985

Parvalbumin in cross-reinnervated and denervated muscles.

The extensor digitorum longus (EDL) muscle was cross-reinnervated by the soleus (SOL) nerve, leading to the well-known transformation toward a slow muscle. Nine weeks after the operation, the quantitative analysis of the Ca2+-binding protein, parvalbumin (PV), using high-performance liquid chromatography, showed a threefold reduction of PV in the cross-reinnervated EDL muscle. Denervation of the EDL muscle, which leads to an increase of the half-relaxation time, resulted in a 20% decrease of the PV concentration within 4 days. This significant lower PV level was detectable prior to any change of the myofibrillar adenosine triphosphatase (ATPase). Normal PV concentrations were reached after 9 weeks following self-reinnervation of the EDL muscle. The experiments support the view that PV is involved in the relaxation of rat fast skeletal muscles and that its expression is dependent on nerve-muscle interaction. Since PV changes preceded histochemical changes after denervation, this protein may be a sensitive marker for early stages of neuromuscular disturbances.

Adenosine Triphosphatases↗
PubMed1991

Real-time sonography of acute and chronic muscle denervation.

Presented are real-time ultrasound findings in partially and completely denervated muscles of 30 patients with focal neuropathy and various other disorders of the second motor neuron. Sonographic scans of affected muscles are analyzed in conjunction with unaffected muscles of the same individual, under identical examination conditions. Initial pathological ultrasound changes could be detected as soon as 2 weeks after an acute neurogenic lesion. In denervation, the echodensity of the muscle was high and the normal intramuscular pattern was decomposed. Findings were more intense in severe and longstanding denervation. Ultrasound-indicated pathology correlated highly (chi-square: P less than 0.001) with pathological spontaneous activity detected by electromyography. Focal and systemic neuropathies showed no differences in ultrasound pathology. Six cases with central motor palsy had normal sonograms. Poor spatial resolution of real-time ultrasonography--as compared with CT and MRI--is compensated by its bedside availability, frequent repeatability without patient risk and discomfort, and its in vivo correlation of muscle morphology with muscle function.

Adult↗
PubMed1992

Levels of mRNA coding for motoneuron growth-promoting factors are increased in denervated muscle.

Partial denervation of skeletal muscle induces sprouting of axons remaining within the muscle, possibly as a result of increased synthesis by denervated muscle fibers of motoneuron growth-promoting factors. Direct verification of this hypothesis has not been possible because the molecules responsible are not unambiguously characterized. We used Xenopus oocytes as a functional assay for mRNAs coding for secreted growth factors: preparations of mRNA from innervated and denervated neonatal muscle were injected into oocytes. Three days later, oocytes injected with denervated muscle mRNA expressed increased levels of nicotinic acetylcholine receptor and voltage-dependent sodium channels at their membrane. Proteins secreted by the same oocytes were tested for their effects on (i) neurite outgrowth from embryonic chicken ventral spinal cord neurons; (ii) survival in mixed culture of embryonic chicken motoneurons identified using the SC1 antibody; and (iii) survival of embryonic motoneurons purified by panning on SC1 antibody. In all three assays, media conditioned by oocytes injected with mRNA from denervated muscle contained significantly higher levels of biological activity than did those from oocytes injected with innervated muscle mRNA or water. mRNA was prepared from muscle at different times after denervation: a maximal increase was obtained already after 1 day, consistent with an involvement in sprouting. Synthesis of motoneuron growth-promoting factors is thus regulated by denervation in a parallel fashion to that of other key components of the neuromuscular junction.

Animals↗
PubMed1975

Evidence for myoblastic potential of satellite cells in denervated muscle.

The failure of denervated muscle to undergo effective regeneration, despite reported increases in the number of muscle satellite cells, warranted an investigation of the viability and myoblastic capacity of these cells present in denervated muscle. Four types of satellite cells present in muscle denervated for three weeks are described, based on their ultrastructure and relationship to their principal fiber. The increased number of ribosomes, including helically arranged polysomes; the number of Golgi complexes; the presence of microtubules; the branching subsarcolemmal tubular system; and the appearance of regularly arranged 96 A microfilaments with diffuse electron dense areas are structural features of satellite cells that are similar to those of developing myoblasts in growing and regenerating muscle. The electron microscopic observations suggest that "activated" satellite cells do have myoblastic potential. Possible explanations for the ultimate failure of denervated muscle to regenerate include: 1) the inability of the muscle to produce satellite cells rapidly enough to keep pace with muscle degeneration; 2) a cytotoxic effect produced by the degenerating muscle fiber on the satellite cell; and 3) the inability of satellite cells to form stable, mature multinucleated fibers in the absence of the trophic effect of the nerve.

Animals↗
PubMed1974

Ultrastructural changes in the muscle cells of denervated muscles of rat.

The ultrastructural changes taking place in the diaphragm and plantaris of rat are followed up from the 3rd hour to 24th week after section of the peripheral nerve. The latter is either sectioned, or crushed. It is found out that the initial changes, consisting in an increase of the number of ribosomes and certain degree of mitochondrial destruction, are observed as early as the first 24 hours after denervation. The postdenervational changes are traced up to the occurrence of reinnervation with restoration of the myoneural junctions. A description is ade of the changes in the various organelles of the muscle cell, and of the appearance of spheromembranous bodies, hellical complex and destruction of the contractile apparatus. Differences in the course of the post-denervational process in the diaphragm and plantaris are outlined. The results obtained are discussed and comparatively studied with literature data.

Actins↗
PubMed1985

Partial purification from mammalian peripheral nerve of a trophic factor that ameliorates atrophy of denervated muscle.

Atrophy in a denervated muscle results from the disuse caused by paralysis of the muscle, and from the loss of special nerve-derived trophic substances. Crude preparations of protein from rat or sheep sciatic nerves have been shown to prevent the nondisuse atrophy of the rat's extensor digitorum longus muscle when injected into the denervated muscle daily for 1 week. Aqueous extracts of sheep sciatic nerves were fractionated by gel-liquid chromatography. After each step of purification, the trophic activities of the various fractions were assayed in the rat. Cross-sectional areas of type IIB muscle fibers in the denervated extensor digitorum longus were measured to determine which injected fraction contained the active principle. Affinity chromatography on concanavalin A-agarose revealed that the trophic substance was a glycoprotein. Further fractionation by gel filtration indicated that the active substance had a molecular weight in the range of 90,000 to 130,000. Ion-exchange chromatography on DEAE-cellulose yielded an active fraction containing substances with isoelectric points between 7.0 and 7.2, determined by polyacrylamide gel isoelectric focusing. This active fraction was resolved into 15 bands on sodium dodecyl sulfate-gel electrophoresis. Two bands had apparent molecular weights of 91,300 and 127,400. The active factor was shown thus to be a glycoprotein, molecular weight approximately 100,000, isoelectric point approximately 7.0. It may be one of two protein bands that are similar to it in molecular weight.

Animals↗
PubMed1986

Motoneurone survival activity in extracts of denervated muscle reduced by prior stimulation of the muscle.

Inactivation of skeletal muscle by denervation increases motoneurone survival activity in extracts of skeletal muscle. The present investigation shows that electrical stimulation of denervated muscle decreases motoneurone survival activity in extracts of these muscles. The result suggests that motoneurone survival is dependent on a factor(s) in muscle whose synthesis and/or release is regulated by muscle contraction.

Animals↗
PubMed1989

Regeneration of muscle axons in the frog is directed by diffusible factors from denervated muscle and nerve tubes.

In the frog, peripheral muscle axons regenerate after a lesion to reinnervate the original synaptic sites on muscle fibers. Previous experiments in the frog have shown that satellite cells of the nerve tube direct the outgrowth of regenerating muscle axons over distances of many millimeters. In the present experiments, denervated muscle was used as a target for regenerating muscle axons. Muscle and satellite cells of the nerve tube also were placed in filters to determine if their influence on axonal outgrowth was exerted by diffusible factors. Filters were used with a pore size of 0.22 micron. With this pore size, target cells were isolated from physical contact with the surrounding cells; yet an exchange of fluids--and therefore of molecules released by the target cells--could occur across the filter. In the presence of denervated muscle or satellite cells of the nerve tube in filters, regenerating axons turn and grow toward the target cells. This influence on the direction of axonal outgrowth was produced over distances of 6 mm by muscles and 4 mm by cells of the nerve tubes. This directed outgrowth is in marked contrast to the random pattern of outgrowth in the absence of the targets. The present findings set the stage for tissue culture experiments in which the phenomena observed in vivo can be analyzed in terms of mechanisms. The present finding that denervated muscle attracts regenerating axons means that sufficient material may be available for the characterization and isolation of the relevant molecules.

Animals↗
PubMed1987

Cell accumulation in the junctional region of denervated muscle.

If skeletal muscles are denervated, the number of mononucleated cells in the connective tissue between muscle fibers increases. Since interstitial cells might remodel extracellular matrix, and since extracellular matrix in nerve and muscle plays a direct role in reinnervation of the sites of the original neuromuscular junctions, we sought to determine whether interstitial cell accumulation differs between junctional and extrajunctional regions of denervated muscle. We found in muscles from frog and rat that the increase in interstitial cell number was severalfold (14-fold for frog, sevenfold for rat) greater in the vicinity of junctional sites than in extrajunctional regions. Characteristics of the response at the junctional sites of frog muscles are as follows. During chronic denervation, the accumulation of interstitial cells begins within 1 wk and it is maximal by 3 wk. Reinnervation 1-2 wk after nerve damage prevents the maximal accumulation. Processes of the cells form a multilayered veil around muscle fibers but make little, if any, contact with the muscle cell or its basal lamina sheath. The results of additional experiments indicate that the accumulated cells do not originate from terminal Schwann cells or from muscle satellite cells. Most likely the cells are derived from fibroblasts that normally occupy the space between muscle fibers and are known to make and degrade extracellular matrix components.

Animals↗
PubMed1988

Spinal cord TRH deficiency is associated with incomplete recovery of denervated muscle in the rat.

The raphe-spinal pathway, which contains co-localized serotonin (5-HT), thyrotropin-releasing hormone (TRH), and several TRH-prohormone-derived non-TRH peptides, projects to the ventral horn of the spinal cord. Pharmacologic ablation of this pathway with the 5-HT neurotoxin, 5,7-dihydroxytryptamine, in neonatal rats resulted in deficient recovery of plantar foot muscles, functionally denervated with botulinum toxin type A. Failure of reinnervation was suggested by slower and incomplete recovery of the plantar foot compound muscle action potential amplitude and by a reduced mean diameter of plantar foot muscle fibers in ablated rats. These findings indicate that deprivation of alpha motor neurons from descending raphe-spinal input interferes with their ability to respond to muscle-derived signals for reinnervation.

5,7-Dihydroxytryptamine↗
PubMed1989

Fibrillatory activity and other membrane changes in partially denervated muscles.

Rat soleus muscles were partially or totally denervated by sectioning the radicular nerve L5 or the radicular nerves L3 through L6, respectively. Three days after these procedures, fibrillation potentials were not observed in the case of partial denervation, whereas they were clearly detectable after total denervation. At later times, spontaneous spike activity also developed in the partially denervated muscles. The difference in time of onset of fibrillation between partially and totally denervated muscles was confirmed by a more gradual increase in the number of acetylcholine receptors and a greater sensitivity to tetrodotoxin of the former muscles. These differences between partially and totally denervated muscles are interpreted on the basis of the different amounts of nerve breakdown products generated in the two situations.

Acetylcholine↗
PubMedDate not supplied

Insulin binding in denervated muscle.

Insulin binding was measured in rat muscle following denervation. There was a 40% reduction in the number of high-affinity insulin receptors, with no change in the insulin binding Kd. Selected muscles showed a 40%-60% reduction in weight during this period. The down-regulation in the number of insulin receptors may contribute to the mechanism of muscle atrophy following denervation.

Animals↗