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PubMedDate not supplied

Antigen-induced antigen endocytosis in primitive reticular cells of connective tissue of innervated and denervated skeletal muscle from the allergized guinea pig.

Electron microscope studies demonstrated that soluble proteins (ferritin and horseradish peroxidase) administered in vitro to strips of guinea pig diaphragmatic muscle under physiological conditions were internalized by vesicles of primitive reticular cells (PRCs) found in the connective tissue. This endocytosis effect was enhanced when the muscle preparations were obtained from animals actively allergized to the protein. Denervation increased the occurrence of peroxidase-positive vesicles in the peroxidase-antiperoxidase system. These results suggest that the antigen-antibody interaction induces endocytosis directed to the specific antigen.

Animals↗
PubMed2006

Acetylcholine receptors and nerve terminal distribution at the neuromuscular junction of long-term regenerated muscle fibers.

Mdx mice are deficient in dystrophin and show muscle fiber regeneration. Changes in the distribution of acetylcholine receptors have been reported at the neuromuscular junction of mdx mice and may be a consequence of muscle fiber regeneration. In this study, we examined whether the distribution of receptors was still altered in long-term, regenerated muscle fibers from C57Bl/10 mice. The left sternomastoid muscle of adult mice was injected with 60 microl of lidocaine hydrochloride to induce muscle degeneration-regeneration. In some mice, the sternomastoid muscle was denervated at the time of lidocaine injection. After 90 and 150 days, the nicotinic acetylcholine receptors were labeled with rhodamine-alpha-bungarotoxin for confocal microscopy. At both intervals studied, the receptors were distributed in spots. In denervated-regenerated fibers, the receptors were distributed as regular branches similar to denervated muscles without lidocaine treatment. These findings suggested that nerve-dependent mechanisms were involved in the changes in receptor distribution seen in regenerated muscle fibers after lidocaine treatment, and that a similar phenomenon could explain the changes in receptor distribution seen in dystrophic muscle fibers.

Animals↗
PubMed1982

Induction of action potentials in fish red muscle by denervation.

The effects of denervation on the electrical membrane properties of fish red muscle were investigated. Forty to fifty hours after denervation, miniature endplate potentials disappeared abruptly and field stimulation of the nerve within the muscle failed to evoke endplate potentials, indicating that transmission failure occurred at this time. The membrane resistance of the red muscle fibre increased after denervation. Normally innervated fish red muscles do not generate action potentials in response to either nerve or direct muscle stimulation. However, approximately 3 weeks after nerve sectioning, action potentials could be induced in the muscles. The action potential was sodium-dependent, and was sensitive to tetrodotoxin. Actinomycin D injected in the early phase after operation suppressed the induction of the action potential. These results indicate that RNA synthesis is preliminary to the induction of the action potential mechanism, and that this mechanism is under neural control.

Action Potentials↗
PubMed1987

Glucocorticoid excess induces preferential depletion of myosin in denervated skeletal muscle fibers.

The combined effects of dexamethasone treatment (1 mg/Kg/day) plus denervation (DEX-DEN), were studied at 7, 13, and 28 days by microscopic, biochemical, and physiological techniques in plantaris and soleus muscles of adult rats. The results were compared with corresponding dexamethasone-treated (DEX) and denervated (DEN) muscles and appropriate controls. There was a significantly more marked atrophy of all fiber types in the DEX-DEN plantares at 7 and 13 days than in either DEX or DEN muscles. The degree of atrophy was greatest in type 2B fibers in DEX-DEN plantares. Electron microscopy revealed a severe preferential depletion of thick myofilaments in DEX-DEN plantares and solei but not in DEX or DEN muscles. The thick myofilament depletion in DEX-DEN muscles occurred in addition to a severe overall reduction of myofibrillar caliber. Gel electrophoresis showed a marked preferential decrease of myosin heavy chain in DEX-DEN plantares and solei, but not in either DEX or DEN muscles. Myosin light chains were also markedly reduced in DEX-DEN plantares and solei. In vitro physiological studies showed a marked reduction of the denervation-induced twitch potentiation in DEX-DEN solei. Maximal tetanic tension (20 Hz stimulation) per gram weight of muscle as well as the twitch-tetanus ratio was significantly reduced only in DEX-DEN solei in relation to controls. Myosin depletion in DEX-DEN muscles may be due to a severe preferential inhibition of its synthesis coupled with an accelerated catabolism.

Actins↗
PubMed1990

Effects of intermittent high frequency electrical stimulation on denervated EDL muscle of rabbit.

This study was performed to determine whether electrical stimulation can retard denervation-induced changes. The denervated extensor digitorum longus of the rabbit, a fast-twitch muscle, was stimulated at a rate mimicking its motoneuron firing pattern. The 100-Hz stimulation given intermittently subjected the muscle to a low mean total daily frequency of 1.6 Hz. Four weeks of stimulation resulted in no effect upon the denervated stimulated muscle. This stimulation protocol, therefore, is unable to substitute for the lost neuronal influence of the nerve. The muscle contralateral to the stimulated side showed physiological changes making it unsuitable to serve as a control.

Animals↗
PubMedDate not supplied

Distribution of different fibre types in human skeletal muscles. A statistical and computational model for the study of fibre type grouping and early diagnosis of skeletal muscle fibre denervation and reinnervation.

To define fibre type grouping in terms of random and non-random arrangements of the two fibre types, type 1 (ST) and type 2 (FT), we adopted the measure of counting the number of "enclosed fibres". The statistical properties of the number of enclosed fibres, and the number and size of groups of enclosed fibres were studied in computer-simulated muscle cross-sections, using a model based upon hexagonal-shaped fibres. The effects on the results of differences in the sizes of the muscle fibres were considered. The applicability of the model, and the derived results and methods of analysis were tested on 10 samples from a cross-section of a whole human muscle. The results show that the model can be applied to various shapes and sizes of muscle samples and various sizes of muscle fibres. The number of enclosed fibres within a muscle sample is the best of the three measures of non-randomness considered. A test is also described for assessing whether or not the observed number of enclosed fibres is random at a given significance level.

Biopsy, Needle↗
PubMed1981

Prostaglandin modulation of adrenergic vascular control during hemorrhagic shock.

This study was designed to evaluate 1) whether the initial compensatory skeletal muscle vascular constriction induced by hemorrhagic hypotension is primarily the result of increased adrenergic neural tone rather than circulating vasoconstrictor agents, and 2) whether the secondary skeletal muscle decompensatory vasodilation is caused by inhibitory action of prostaglandins on peripheral adrenergic nervous system. A constant-flow vascularly isolated double canine gracilis muscle preparation in which one muscle served as innervated control for the contralateral muscle was used. Dogs were subjected to standard stepwise hemorrhagic shock protocol. In series 1, perfusion pressures of control muscles were compared to denervated muscles with the result that innervated muscle perfusion pressures increased initially from 105 to 175 mmHg but subsequently fell significantly (P less than 0.05) to 147 mmHg. Only modest increases in perfusion pressures with no significant secondary fall were noted in denervated muscles. Series 2 compared innervated control perfusion pressures to pressures perfusing muscles pretreated with prostaglandin-synthesis inhibitor sodium meclofenamate (MCF). The MCF-treated muscle perfusion pressures rose to 260 mmHg where they remained without the secondary fall noted in control muscles. These data support the two hypotheses tested.

Animals↗
PubMed1986

Effect of protease inhibitors on skeletal muscle lysosomal enzyme activity and resting membrane potential.

Inhibition of lysosomal enzyme activity by protease inhibitors in denervated muscle was studied in vitro by incubating muscle homogenates with increasing concentrations of inhibitor and determining acid protease activity. Pepstatin was the most potent inhibitor of protease activity, followed in order of inhibitor potency by chloroquine, aprotinin, and leupeptin. The in vivo uptake of chloroquine or leupeptin by denervated muscle was greater than that of innervated muscle, and repeated administration of the drug led to a decrease in muscle N-acetylglucosaminidase activity. Repeated administration of chloroquine had no effect on resting membrane potential of muscle fibers in the soleus or extensor digitorum longus measured in vivo. Chloroquine attenuated the marked decrease in the resting membrane potential of the extensor 2.5 days after denervation, but had no effect on that of the denervated soleus. Possible involvement of proteases in lowering the membrane potential of denervated muscle is discussed.

Acetylglucosaminidase↗
PubMed1990

Myosin heavy chain isoform composition in striated muscle after denervation and self-reinnervation.

The total content of myosin heavy chains (MHC) and their isoform pattern were studied by biochemical methods in the slow-twitch (soleus) and fast-twitch (extensor digitorum longus) muscles of adult rat during atrophy after denervation and recovery after self-reinnervation. The pattern of fibre types, in terms of ultrastructure, was studied in parallel. After denervation, total MHC content decreased sooner in the slow-twitch muscle than in the fast-twitch. The ratio of MHC-1 and the MHC-2B isoforms to the MHC-2A isoform decreased in the slow and the fast denervated muscles, respectively. After reinnervation of the slow muscle, the normal pattern of MHC recovered within 10 days and the type 1 isoform increased above the normal. In the reinnervated fast muscle, the 2B/2A isoform ratio continued to decrease. Traces of the embryonic MHC isoform, identified by immunochemistry, were found in both denervated and reinnervated slow and fast muscles. A shift in fibre types was similar to that found in the MHC isoforms. Within 2 months of recovery a tendency to normalization was observed. The results show that (a) MHC-2B isoform and the morphological characteristics of the 2B-type muscle fibres are susceptible to lack of innervation, similar to those of type 1, (b) during muscle recovery induced by reinnervation the MHC isoforms and muscle fibres shift transiently to type 1 in the soleus and to type 2A in the extensor digitorum longus muscles, and (c) the embryonic isoform of MHC may appear in the adult skeletal muscles if innervation is disturbed.

Animals↗
PubMed1985

Neural nature of the time-dependent factor(s) involved in motor reinnervation.

The influence of a time interval between nerve transection and reimplantation into a foreign muscle on the effectiveness of reinnervation was studied in the rat. We evaluated the weight loss and the maximal twitch and tetanic tensions developed by the reinnervated muscle upon nerve stimulation 60 days after reimplantation (i) of an acutely severed nerve onto an acutely denervated muscle; (ii) of a chronically (20 days) severed nerve onto an acutely denervated muscle, and (iii) of an acutely severed nerve onto a chronically denervated muscle. The best recovery was obtained when a chronically severed nerve was implanted into an acutely denervated muscle. We conclude that a neural time-dependent factor(s) is involved in motor reinnervation.

Animals↗
PubMedDate not supplied

[Possible mechanism of metabolic disturbance in gastrocnemius muscle after denervation].

Under complete denervation of m. gastrocnemius by crushing of sciatic nerve it was established that the intensity of oxygen free radicals formation increased 3 times, lipid peroxidation intensity 2 times, and the activity of antioxidative enzymes (glutathione reductase, superoxide dismutase) increased by 30-50%. Under these conditions the content of sarcolemmal neutral lipids increases and that of phospholipids decreases, proteins disintegrate, muscle atrophy increases. The use of the substances stimulating growth of tissues (neurobolil and thyroxin) 3-5 times increases the activity of enzymes of antioxidant protection of glutathione oxidase and superoxide dismutase. Considerable decrease of lipids peroxidation is observed, and the level of the muscle atrophy decreases.

Anabolic Agents↗
PubMedDate not supplied

Suppression of sprouting at the neuromuscular junction by immune sera.

Injury of afferent motor axons or pathological loss of motoneurones from the spinal cord causes the remaining axons within a muscle to sprout and to reinnervate the denervated muscle fibres. Sprouting occurs at two sites along intramuscular axons, at nodes of Ranvier (nodal sprouting) and at the neuromuscular junction (terminal sprouting). Terminal sprouting is also produced by treatment with botulinum toxin and by other agents that render muscle inactive. The muscle probably provides a signal for terminal sprouting as restoration of muscle activity by direct electrical stimulation prevents sprouting. Such a signal might be a local change on the muscle fibre surface or a 'soluble' sprouting factor, although the failure to induce terminal sprouting in one muscle by denervating adjacent muscles argues against the latter hypothesis. I now report that rabbit antisera against a 56,000 (56K)-molecular weight protein secreted by denervated rat muscle suppress botulinum toxin-induced terminal sprouting in the mouse gluteus muscle. An immune response against this protein has also been detected in serum of patients with amyotrophic lateral sclerosis (ALS), a disease in which loss of motoneurones from the spinal cord is not accompanied by the degree of sprouting and reinnervation seen in other motoneurone diseases.

Amyotrophic Lateral Sclerosis↗
PubMed2002

The expression profile of myogenic transcription factors in satellite cells from denervated rat muscle.

The muscle-specific transcription factors of the MyoD family are altered after denervation. In order to determine whether this shift takes place in satellite cells (SC), we investigated the expression pattern of MyoD, myf5, myogenin, and MRF4 in SC. Hindlimb muscles of rats were denervated for 2 days to 4 weeks. SC were isolated, pooled and the transcription of all 4 factors was assessed by RT-PCR. Protein expression was assessed in histological sections of soleus and anterior tibial (TA) muscles; SC were identified by M-cadherin. Pooled SC from innervated muscles expressed myf5 mRNA, and very weakly MyoD and myogenin mRNA. MyoD and myogenin protein was found in only few SC. After denervation, pooled SC expressed myf5 mRNA, and very weakly myogenin and MRF4 mRNA. Myogenin protein was found in less than about 10% of the cells, whereas MRF4 protein was absent from SC. We conclude that the presence of myf5 and the absence of MyoD and MRF4 protein in SC after denervation indicated the quiescent state of the cell cycle. A subset of SC has additionally acquired myogenin. SC after denervation might be less easily recruited into the mitotic cycle than SC from normal muscle, rendering regeneration of denervated muscle less efficient than normal muscle.

Animals↗
PubMed1991

Morphology of long-term denervated rat soleus muscle and the effect of chronic electrical stimulation.

1. Rat soleus muscles were denervated for 6-10 months; some of these were chronically stimulated for the last 3-8 weeks before recording. The muscles were fixed at physiological lengths and embedded in epoxy resin. 2. Sections for light microscopy were stained with p-phenylenediamine. Denervation reduced the mean cross-sectional area of fibres to 3% of controls (peak at 20 microns2). The cross-sectional areas of the stimulated fibres had a peak at 70 microns 2. In light micrographs of denervated muscles, the total number of fibres appeared to be reduced; however not all fibres could be identified (see paragraph (3)). 3. In the electron microscope, many fibres showed disarrayed myofilaments. Few fibres had more or less normal cross-striations. Muscle fibres as small as 1 micron in diameter were seen. The smallest fibres did not contain myofilaments. Some unequivocally necrotic fibres were seen. 4. Most stimulated denervated fibres showed an almost normal sarcomere pattern. Scattered throughout the muscle were single fibres as small as 2 microns in diameter, but these were well organized and could be recognized in the light microscope. Few fibres were necrotic. Often fibres were serially arranged. Satellite cells were prominent. 5. It is concluded that in long-term denervated rat soleus the original fibres are lost and those seen are the result of repeated cycles of regeneration and necrosis. Stimulation maintains the sarcomeres and probably prevents secondary degeneration and necrosis.

Actin Cytoskeleton↗
PubMed2005

Mitochondria-associated apoptotic signalling in denervated rat skeletal muscle.

Apoptosis has been implicated in the regulation of denervation-induced muscle atrophy. However, the activation of apoptotic signal transduction during muscle denervation has not been fully elucidated. The present study examined the apoptotic responses to denervation in rat gastrocnemius muscle. Following 14 days of denervation, the extent of apoptotic DNA fragmentation as determined by a cytosolic nucleosome ELISA was increased by 100% in the gastrocnemius muscle. RT-PCR and immunoblot analyses indicated that Bax was dramatically upregulated while Bcl-2 was modestly increased; however, the Bax/Bcl-2 ratio was significantly increased in denervated muscles relative to control muscles. Analyses of ELISA and immunoblots from mitochondria-free cytosol extracts showed a significant increase in mitochondria-associated apoptotic factors, including cytochrome c, Smac/DIABLO and apoptosis-inducing factor (AIF). In addition to the upregulation of caspase-3 and -9 mRNA, pro-/cleaved caspase protein and proteolytic activity levels, the X-linked inhibitor of apoptosis (XIAP) protein level was downregulated. The cleaved product of poly(ADP-ribose) polymerase (PARP) was detected in muscle samples following denervation. Although we did not find a difference in the inhibitor of DNA binding/differentiation-2 (Id2) and c-Myc protein contents between the denervated and control muscles, the protein content of tumour suppressor p53 was significantly increased in both the nuclear and the cytosolic fractions with denervation. Moreover, denervation increased the protein content of HSP70, whereas the MnSOD (a mitochondrial isoform of superoxide dismutase) protein content was diminished, which indicated that denervation might have induced cellular and/or oxidative stress. Our data show that mitochondria-associated apoptotic signalling is upregulated during muscle denervation. We interpret these findings to indicate that apoptosis has a physiologically important role in regulating denervation-induced muscle atrophy.

Animals↗
PubMed1999

Anterograde transport of leukemia inhibitory factor within transected sciatic nerves.

Disappointing functional recovery following peripheral nerve repair can be improved by neurotrophic growth factors. Leukemia inhibitory factor (LIF) is unique in that it has independent neurotrophic and myotrophic actions. The aim of this study was to explain this finding by establishing the existence of anterograde axonal transport of LIF from the site of nerve division to denervated muscles. Using 125I LIF, administered topically via an entubulation repair of divided rat sciatic nerve, we monitored its subsequent distribution by measuring the radioactivity associated with nerve segments and denervated muscles. We established that LIF preferentially accumulated in denervated muscles, a process we could reduce by 70% after tightly ligating the intervening nerve, confirming the presence of anterograde axonal transport. This was most likely an active mode of transport that ceased approximately 24 h after nerve division, establishing a narrow clinical time frame within which the myotrophic action of LIF could be optimized following nerve repair.

Animals↗
PubMed1983

Increased activation effects of succinylcholine in neurological patients.

Succinylcholine, a depolarizing muscle relaxant with both activating and desensitizing effects, is used to facilitate endotracheal intubation. The activating effects were found to be above-normal on induction of anesthesia in 7 neurological patients: generalized muscle spasm in 1 myotonic patient, contractures or prolonged contractions in "anatomically" denervated muscles (1 patient), in "functionally" denervated muscles (1 patient) and in "centrally" denervated muscles (4 patients). One of these four presented hyperkalemia and cardiocirculatory collapse. It is important to differentiate these anomalous responses to succinylcholine from those occurring as early signs of rhabdomyolysis or malignant hyperthermia.

Adult↗
PubMed2005

Recovery of long-term denervated human muscles induced by electrical stimulation.

We investigated the restorative potential of intensive electrical stimulation in a patient with long-standing quadriceps denervation. Stimulation started 18 months after injury. After 26 months, the thighs were visibly less wasted. Muscle cross-sectional areas, measured by computerized tomography, increased from 36.0 cm(2) to 57.9 cm(2) (right) and from 36.1 cm(2) to 52.4 cm(2) (left). Knee torque had become sufficient to maintain standing without upper extremity support. Biopsies revealed evidence of both growth and regeneration of myofibers. The results suggest that electrical stimulation may offer a route to the future development of mobility aids in patients with lower motor neuron lesions.

Cauda Equina↗