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PubMed2006

[Changes in muscle satellite cells in denervated and innervated muscles].

OBJECTIVE: To explore the rule of changes in the myoblast stem cells (satellite cells) in the denervated and innervated muscles and to find out the cellular mechanism of the changes in the muscle morphology and function. METHODS: The denervated muscle-atrophy models were established from 27 Wistar rats aged 1 month. One to six months after operation, examinations of the histology, histochemistry, and morphology were performed on the specimens from the bilateral triceps muscle of the calves of 3 rats in each month. Meanwhile, examination of the cell biology was performed on the specimens from the bilateral triceps muscle of the calves of 1 rat 1, 2 and 3 weeks after operation, and monthly for 1-6 months after operation. The innervation models were established from 35 Wistar rats aged 1 month. Immediately after the denervation, and monthly for 1-6 months after operation, 5 denervated rats underwent the nerve implantation. The changes in the electrophysiological index were observed dynamically until 8 weeks after the nerve implantation. RESULTS: After the denervation, the muscle wet weight and the muscle cell area decreased rapidly, but the content of the collagen fibers increased gradually. The number of the nucleus in the period of proliferation was the greatest 3-4 months after the denervation, and then decreased rapidly. The muscle satellite cells began to increase obviously 3 weeks after the denervation, but 2 months later they decreased rapidly and 4 months later the number of the cells was the smallest. Four to five weeks after innervation, the muscle action potential could be induced, and the best innervation effect could be achieved in the implanted nerve after the 2-3 months on denervation, and at this time the differentiation ability of the satellite cells was the strongest. CONCLUSION: Four months after the denervation of the skeletal muscle, an extremely small number of the satellite cells can make the muscle enter the irreversible atrophy. However, when the innervation is performed 2-3 months after the denervation, the actively-growing satellite cells can promote a better functional recovery of the atrophic muscle.

Animals↗
PubMed1985

Force and membrane potential in acetylcholine and potassium contractures of denervated mouse muscles.

Depolarization and contracture force (P) provoked by acetylcholine (ACh) and by K ions were studied in bundles dissected from mouse soleus muscles that had been denervated for 4-7 days. Cl-free solutions were used. The muscle fibres were depolarized by solutions containing 150 mM K or 10 microM ACh to nearly zero mV resulting in maximum P (Pmax). Threshold P was produced when the membrane was depolarized to more than about -60 mV by both agents. 50% Pmax was produced by [K] causing the membrane to depolarize to -42 mV, whereas a potential more positive than -20 mV was required for 50% Pmax to be produced when ACh was used. The rate of depolarization was always higher for ACh than for K. Pretreatment by 0.05 microM ACh (about threshold for P) did not affect the P-[K] relation appreciably showing that ACh did not "stabilize" the membrane. Nearly equal P was provoked by successive applications of just suprathreshold agent concentrations when the order of application was ACh----K but not with the reverse order. Hypertonicity (by addition of 300 mM sucrose to all solutions) caused PACh to decrease and PK to increase. It was concluded that the ACh receptors are located in the surface membrane of the muscle fibres, not in the T-system membranes.

Acetylcholine↗
PubMed1987

The effect of caffeine on normal and denervated gastrocnemius muscles of Uromastix hardwickii.

The effect of time and 5 mM caffeine was studied on the maximum twitch tension of the normal and 11-13 days denervated gastrocnemius muscles of Uromastix hardwickii. The maximum twitch tension was found to decrease with time and it remained about 68% of initial after 60 minutes at 20 degrees C. Five mM caffeine only produced potentiation in normal and denervated muscles while there was no contracture in either muscle. Although caffeine increased the overall contraction and relaxation times in control muscles, it was more effective on the contraction time of the denervated muscles in which the contraction time increased with time. Denervated muscles were seen to be less sensitive to caffeine as the contraction times increased with time (at about 30-40 minutes) in these muscles while in normal control muscles the contraction time increased immediately. The action of caffeine in relation to these effects is discussed.

Animals↗
PubMed1985

The fate of proliferating cells in skeletal muscle after denervation or tenotomy: an autoradiographic study.

During the first 7 days after denervation or tenotomy of skeletal muscle there is increased cell proliferation, as measured autoradiographically by [3H]thymidine incorporation. By 21 days most of the labelled cells have disappeared. The present experiment was designed to measure residual levels of labelling in skeletal muscles at 21 days after denervation or tenotomy, when [3H]thymidine had been available for the first 7 days. This was to determine the fate of cells labelled at 7 days and to detect whether continued cell proliferation had occurred during the intervening period, as evidenced by the dilution of nuclear label. Tibialis anterior muscles of 16 mice were denervated, tenotomized or sham-operated, and the animals injected with a single daily pulse of [3H]thymidine for the first 7 days only. In denervated muscle the 11% of muscle nuclei and 41% of connective tissue nuclei labelled at 7 days had decreased to 2 and 13%, respectively, by 21 days. These values were still significantly higher than in 21 day controls (0.2 and 1.9%, respectively). In muscle nuclei (myonuclei and satellite cell nuclei) there was a significant decrease in the amount of label per nucleus. This was interpreted as evidence of continued cell proliferation. However, this did not produce an increase in numbers of muscle nuclei. It was concluded that: there was turnover of satellite cells and possibly myonuclei, the latter probably through continued division and incorporation of satellite cells; and the extra satellite cells and myonuclei produced were probably extruded from the fibre to the extracellular space.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

L-glutamate and potassium-induced contractures in denervated cockroach muscles.

1. The effects of denervation on the mechanical responses to various concentrations of L-glutamate in retractor unguis muscle of cockroach (Perilpaneta americana) was examined, comparing them with contractures induced by high potassium saline. 2. The dose-response curve was shifted to the lower concentrations of L-glutamate after 9 days of denervation. 3. Following a transient increase in the maximum contracture tension, it decreased with days after denervation and reached a constant level by several days. However, from 16 to 20 days after denervation, the tension ratios of the maximum glutamate to potassium contractures were significantly higher than that of the innervated muscles. 4. A sustained contracture was observed on and after treatment of L-glutamate in the denervated muscle. Pretreatment of the muscle by concanavalin A facilitated to induce L-glutamate contracture. 5. It was suggested that the sensitivity of the muscle membrane to L-glutamate was increased in the denervated muscle.

Animals↗
PubMed1993

Inactivity induces muscle hypertrophy and redistribution of myosin isozymes in chicken anterior latissimus dorsi muscle.

Denervation of the anterior latissimus dorsi (ALD) muscle causes transient muscle fibre hypertrophy and leads to an increase of the SM1 myosin isoform. We tested whether the changes that take place after denervation can be attributed to loss of muscle activity which follows denervation. Neuromuscular activity was prevented by blocking the acetylcholine receptors with alpha-bungarotoxin and thereby paralysing the muscle. Following this treatment, we found increased muscle weight and pronounced hypertrophy of muscle fibres. Also, the proportion of SM1 isomyosin was decreased. Due to the multiple innervation of ALD muscle fibres it is possible to paralyze only part of the muscle. When only a region of the muscle was paralysed a local hypertrophy of fibres was detected, and the change from SM1 to SM2 was most pronounced in the area where activity was blocked. Removal of muscle activity resulted in changes similar to those that occurred after denervation.

Animals↗
PubMed1984

Prevention of denervation atrophy in muscle: mammalian neurotrophic factor is not transferrin.

Atrophy in a denervated muscle results from the disuse caused by paralysis of the muscle, and from the loss of special neurotrophic substances. Daily injections of proteins extracted from rats' sciatic nerves have been shown to prevent the non-disuse atrophy of rats' muscles denervated for 7 days. The trophic factor from chicken sciatic nerve which stimulates differentiation in aneural chick muscle in vitro has been purified and found to be closely similar to transferrin. We undertook to determine whether the trophic properties of mammalian nerve extract on denervated rats' muscles in vivo were due to the presence of serum transferrin in the extract. Atrophy was measured as the reduction in cross-sectional areas of type IIB fibers in the extensor digitorum longus muscle. Muscles denervated for 7 days and injected daily with 1 of several doses of iron-conjugated rat transferrin exhibited a rate of atrophy equivalent to that in denervated muscles that either were not treated or were injected with saline. Denervated muscles injected with crude extract of rats' sciatic nerves had significantly less atrophy than their controls. Removal of transferrin from the crude extract by immunoaffinity chromatography did not diminish its ameliorative effects on denervated muscle. Therefore, the trophic action of mammalian nerve extract on denervated rats' muscles in vivo is not due to the presence of serum transferrin in the extract.

Animals↗
PubMed1988

Adaptation of sarcolemmal action potential mechanisms to chronic depolarization in denervated skeletal muscle.

Action potential properties were studied in rat extensor digitorum longus fibers, at different times after locally setting the membrane to a holding potential of -90 mV. Whereas in normal muscles holding potential duration had little effect on the action potential, the holding potential duration markedly influenced membrane excitability in the fibers previously depolarized by increasing the K+ concentration of the bathing medium. In this case, when the holding potential was prolonged from 20 to 180 s, action potential overshoot, maximum rate of rise, and maximum rate of fall increased 1.8-, 3.1-, and 1.8-fold, respectively. In the denervated muscle, overshoot and maximum rate of fall were dependent on the duration of holding potential application until denervation day 6, whereas maximum rate of rise was affected throughout the duration of this study (15 days of denervation). However, 180-s application of -90 mV holding potential elicited about a 2-fold increase of maximum rate of rise in the earlier denervation stages, and only a 1.5-fold increase at later times. These observations suggest that ultra-slow processes of Na+ conductance inactivation were less effective after 6 days of denervation. Correspondingly, extensor digitorum longus fibers acquired the ability to generate action potentials at a depolarized holding potential. The partial removal of ultra-slow Na+ inactivation after muscle denervation could substantially contribute to a general process of membrane adaptation, resulting in the capacity of voltage-dependent ion channels to operate in a condition of chronic depolarization.

Action Potentials↗
PubMed2001

Expression and neural control of myogenic regulatory factor genes during regeneration of mouse soleus.

Given the importance of the myogenic regulatory factors (MRFs) for myoblast differentiation during development, the aims of this work were to clarify the spatial and temporal expression pattern of the four MRF mRNAs during soleus regeneration in mouse after cardiotoxin injury, using in situ hybridization, and to investigate the influence of innervation on the expression of each MRF during a complete degeneration/regeneration process. For this, we performed cardiotoxin injury-induced regeneration experiments on denervated soleus muscle. Myf-5, MyoD, and MRF4 mRNAs were detected in satellite cell-derived myoblasts in the first stages of muscle regeneration analyzed (2--3 days P-I). The Myf-5 transcript level dramatically decreased in young multinucleated myotubes, whereas MyoD and MRF4 transcripts were expressed persistently throughout the regeneration process. Myogenin mRNA was transiently expressed in forming myotubes. These results are discussed with regard to the potential relationships between MyoD and MRF4 in the satellite cell differentiation pathway. Muscle denervation precociously (at 8 days P-I) upregulated both the Myf-5 and the MRF4 mRNA levels, whereas the increase of both MyoD and myogenin mRNA levels was observed later, in the late stages of regeneration (30 days P-I). This significant accumulation of each differentially upregulated MRF during soleus regeneration after denervation suggests that each myogenic factor might have a distinct role in the regulatory control of muscle gene expression. This role is discussed in relation to the expression of the nerve-regulated genes, such as the nAChR subunit gene family. (J Histochem Cytochem 49:887-899, 2001)

Animals↗
PubMed1978

Alkaline phosphatase activity in normal and denervated skeletal muscle.

Changes in the specific activity of alkaline phosphatase in the normal and denervated skeltal muscle have been studied both histochemically as well as biochemically for a maximum period of 8 weeks of its postnatal development. In the normal muscle, a heterogenous population of fibres with respect to the enzyme distribution is observed. Relatively higher levels of enzyme in the denervated muscle and also the proliferation of extrafibillar connective tissue in the diseased muscle show its specific association with the lytic processes.

Alkaline Phosphatase↗
PubMed1984

Lysosomes in skeletal muscle following denervation. Time course of horseradish peroxidase uptake and increase of lysosomal enzymes.

The in-vivo uptake of exogenously applied horseradish peroxidase and the activities of the lysosomal enzymes acid phosphatase and cathepsin D were studied histochemically and/or biochemically in innervated and 2-14 day-denervated tibialis anterior muscles of the mouse. The biochemically determined uptake of horseradish peroxidase showed a large increase already 4 days after denervation. The activities of the lysosomal enzymes increased in a more gradual fashion, and only cathepsin D showed an increase in activity when expressed as total activity per muscle. Histochemically horseradish peroxidase was found to be localized in muscle fibres in characteristic spindle-shaped segments after denervation. The main increase in the number of such segments per transverse section of the muscle occurred between 3 and 6 days after denervation. In serial sections these segments frequently showed positive staining also for acid phosphatase. It is concluded that exogenously applied horseradish peroxidase is taken up into the lysosomal system, which after denervation becomes organized into characteristic spindle-shaped segments in the muscle fibres. The endocytic activity of muscle fibres increases early after denervation. This is followed by a more gradual increase in activity of lysosomal enzymes and finally by an organization of the lysosomal system into characteristic spindle-shaped segments. The results are compatible with the working hypothesis that increased endocytosis may initiate lysosomal activation in denervated skeletal muscle.

Acid Phosphatase↗
PubMed1992

Reinnervation of denervated skeletal muscles by grafted dorsal root ganglion.

We examined whether or not the cervical dorsal root ganglion (DRG) of the rat, when isografted and connected to the distal stump of the severed common peroneal nerve, could survive, project axons to the denervated leg muscles, and exert beneficial influences to delay the degeneration of the denervated muscles. Rats in which the muscles were similarly denervated but no DRG was grafted served as the control. After a postoperative period of 72 to 286 days, histological study showed that nerve cells at the superficial part of the grafted DRG survived. Indirect electrical stimulation via the distal stump of the common peroneal nerve produced no contraction of the muscles, indicating that no functional neuromuscular contacts had been reestablished. Direct stimulation of the denervated muscles did elicit contraction, and the isometric twitch and tetanic tensions were significantly much higher in the experimental rats with a grafted DRG than in the control rats. Cholinesterase-silver staining indicated the presence of axons in the denervated muscles, but the axons did not terminate on endplates. Compared with the control muscles, the experimental muscles had significantly more axons, and had atrophied less as indicated by muscle wet weight and histological appearance. These results indicate that the sensory axons can delay the weakening and atrophy of muscles after denervation. We suggest that the sensory axons may exert certain trophic influence on the denervated muscle fibers, though the actual mechanism is unknown.

Animals↗
PubMed1999

The adaptive response of MyoD family proteins in overloaded, regenerating and denervated rat muscles.

Using Western blot analysis, we investigated whether the amount of myogenic regulatory factors differs in slow-type and fast-type muscles. In addition, we examined the adaptive response of myogenic regulatory factor protein in the overloaded rat muscles by the ablation of synergists, in the regenerating muscles following bupivacaine injection and in the denervated muscle. The amount of myogenin protein in the slow-type muscle was markedly greater. In contrast, the proteins MyoD and Myf-5 were selectively accumulated in the fast-type muscles. A gradual down-regulation of MyoD and Myf-5 proteins was detected in the denervated fast-type muscles, but not in the myogenin protein content. A rapid down-regulation of myogenic regulatory factor protein was observed both of the mechanically overloaded and in the regenerating muscles. These results indicate that the fast-type-specific gene expression in muscle is modulated by MyoD and Myf-5 proteins and suggest that myogenin protein plays an important role in the reconstruction of damaged neuromuscular connections.

Adaptation, Physiological↗
PubMed2006

Denervation does not change the ratio of collagen I and collagen III mRNA in the extracellular matrix of muscle.

Denervation or inactivity is known to decrease the mass and alter the phenotype of muscle and the mechanics of tendon. It has been proposed that a shift in the collagen of the extracellular matrix (ECM) of the muscle, increasing type III and decreasing type I collagen, may be partially responsible for the observed changes. We directly investigated this hypothesis using quantitative real-time PCR on muscles and tendons that had been denervated for 5 wk. Five weeks of denervation resulted in a 2.91-fold increase in collagen concentration but no change in the content of collagen in the muscle, whereas in the tendon there was no change in either the concentration or content of collagen. The expression of collagen I, collagen III, and lysyl oxidase mRNA in the ECM of muscle decreased (76 +/- 1.6%, 73 +/- 2.3%, and 83 +/- 3.2%, respectively) after 5 wk of denervation. Staining with picrosirius red confirmed the earlier observation of a change in staining color from red to green. Taken with the observed equivalent decreases in collagen I and III mRNA, this suggests that there was a change in orientation of the ECM of muscle becoming more aligned with the axis of the muscle fibers and no change in collagen type. The change in collagen orientation may serve to protect the smaller muscle fibers from damage by increasing the stiffness of the ECM and may partly explain why the region of the tendon closest to the muscle becomes stiffer after inactivity.

Animals↗
PubMed1984

Increased cytosolic androgen receptor binding in rat striated muscle following denervation and disuse.

We investigated the effects of denervation and disuse on cytosolic androgen receptor binding by rat striated muscle. Denervation of the extensor digitorum longus and tibialis anterior muscles caused a 40-50% increase in cytosolic androgen receptor concentration with no change in apparent binding affinity. This effect was evident at 6 h postdenervation, maximal at 24 h, and declined to 120% of the control level 72 h after denervation. A 40% increase in cytosolic androgen receptor concentration was also noted 24 hr after denervation of the hormone-sensitive levator ani muscle. The effect of denervation on androgen receptors was not blocked by in vivo injection of cycloheximide; therefore, de novo receptor synthesis probably is not involved in the observed increase. Disuse, produced by subperineurial injection of tetrodotoxin into the tibial and common peroneal branches of the sciatic nerve, mimicked the effect of denervation on androgen receptor binding, suggesting that neuromuscular activity is important in regulation of receptor concentration. Possible mechanisms subserving this effect are discussed.

Animals↗
PubMedDate not supplied

Surface EMG and motor unit activity of partially denervated human muscle during fatiguing submaximal isometric contraction.

The extent to which the normal fatigue compensatory mechanisms are disturbed in partially denervated muscles was investigated in human patients. Surface EMG, as well as motor unit electrical and mechanical activity, were analyzed from the partially denervated first interosseous muscle, during fatiguing isometric submaximal contraction. The EMG power and frequency changes which reveal the local fatigue process of healthy muscle have not been systematically found. Motor unit firing rate changes were rather normal and twitch contraction time did not increase during the fatiguing exercise. Differences between normal and partially denervated muscles could be explain by the occurrence of a central fatigue process more or less important in neurogenic lesions.

Adult↗
PubMed2001

Comparative study of different surgical procedures using sensory nerves or neurons for delaying atrophy of denervated skeletal muscle.

To observe the effect of sensory components on muscle atrophy, 4 surgical procedures applying sensory nerves or neurons to the denervated muscle were conducted in a rat model: sensory nerve implantation (group B), sensory motor nerve crossover (group C), dorsal root ganglia implantation (group D), and implantation of preganglionically avulsed sensory nerve (group E). Rats with complete denervation served as controls (group A). The degree of muscle atrophy was evaluated after surgery by fibrillation potential amplitude, muscle wet weight, muscle fiber cross-sectional area, collagen content, and protein content. Compared with group A, the results in groups B, D, and E were superior 1 month after surgery and the results in groups B, C, and E were superior 3 months after surgery. Implantation of normal or preganglionically avulsed sensory nerve delayed atrophy. Dorsal root ganglia implantation only had a short-term trophic influence. In the animal model setting, sensory motor nerve crossover is effective only after it is maintained for at least 3 months.

Animals↗
PubMed1990

The study of energy metabolism in denervated skeletal muscle with 31P-NMR.

1. The denervated frog sartorius muscle showed a decrease in the energy store more than that in the control. 2. In the caffeine contractures, both the denervated and the innervated muscles showed similar sequential changes in the relative concentration of phosphocreatine (PCr) to beta-adenosine triphosphate (beta-ATP) and inorganic phosphate (Pi) to beta-ATP. Instead, the intracellular pH value of the denervated muscle was lower than that of the control. 3. It is suggested that phosphate metabolism of the denervated muscle during contracture shows little difference from that of the control, nevertheless, the buffering capacity is decreased in the early stage of atrophy.

Animals↗