[Characteristics of muscle following denervation, in myotonia congenita and in protopathic muscle diseases; findings on the significance of galvanotonus & myotonus].
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Denervation↗
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Muscle fiber recovery functions studied with double pulse stimulation.
Direct electrical stimulation with paired pulses at varied intervals was used to study the propagation velocity and action potential amplitude recovery functions (VRF and ARF) of single muscle fibers. Following a subnormal period with slowed conduction, most of the muscle fibers tested in healthy subjects showed a period of supernormal propagation velocity starting at 3 to 12 ms, with a peak between about 5 and 15 ms, a mean increase of 7%, and an approximately logarithmic decay toward 1 second. The onset of supernormality was earlier in muscle fibers from patients with muscular dystrophy and significantly delayed in those from denervated muscles. Denervated muscle fibers also had a significantly longer refractory period.
Action Potentials↗
[Action of acid cathepsins on the myosin and sarcoplasmic proteins of normal and denervated rat muscles].
The activity of acid cathepsins in extracts of the healthy and denervated rat muscles was determined, using the proper and homologous sarcoplasmic proteins and myosin as substrates. Splitting of the sarcoplasmic proteins produces a 50% increase and that of myosin produces a 110% increase in the activity of acid cathepsins of the denervated muscles as compared to that of healthy ones. Substrates isolated from the healthy and denervated muscles are splitted by acid cathepsins with the same intensity.
Animals↗
Calcium binding capacity and calcium sensitive protein content in denervated frog muscles.
Total and ionic calcium content, calcium binding capacity of sarcoplasmic proteins and calcium insensitive proteins were examined in atrophying leg muscles of frog after 1-5 months period of denervation. Different muscles showed different levels of atrophy and the total calcium content varied with reference to the type of muscle. Ionic calcium levels doubled in the gastrocnemius muscle after three months denervation. Calcium binding capacity of proteins and calcium insensitive proteins decreased rapidly up to four months after denervation in the gastrocnemius muscle. However no significant changes in the levels of calcium binding capacity and calcium insensitive proteins were found with reference to the type of muscle. Since total calcium content remains constant and wet muscle mass (expressed as atrophy) decreased markedly, an apparent increase in calcium concentration occurs in each muscle on denervation.
Animals↗
Regenerating and denervated human muscle fibers and satellite cells express neural cell adhesion molecule recognized by monoclonal antibodies to natural killer cells.
The monoclonal antibodies anti-Leu-19 and anti-NKH-1 recognize the CD56 differentiation antigen expressed on natural killer (NK) cells and on a T-cell subset. Because CD56 is an isoform of neural cell adhesion molecule (N-CAM), we examined its expression on human muscle using antibodies to Leu-19, NKH-1, and purified N-CAM in an immunohistochemical, immunoblot, and immunoprecipitation study on 70 muscle biopsy specimens from various muscle diseases and on human muscle in tissue culture. Anti-Leu-19, anti-NKH-1, and anti-N-CAM had identical immunoreactive patterns. In tissue sections, they specifically recognized the satellite cells and the regenerating or newly denervated muscle fibers; in tissue cultures, they immunoreacted with myoblasts and myotubes; and in the homogenates of myopathic muscle and cultured myotubes, they immunoprecipitated the same glycoprotein of 145- to 220-kd. The study concludes that (1) the commercially available monoclonal antibodies to NK cells, Leu-19 and NKH-1, are immunocytochemical markers for the satellite cells and the regenerating or newly denervated muscle fibers complementing conventional techniques in the diagnosis of patients with neuromuscular disorders; and (2) the CD56 is a common antigen shared by NK cells and muscle fibers during certain stages of muscle maturation, regeneration, or denervation. When expressed in the muscle, CD56 may facilitate the adhesion of cytotoxic lymphocytes to the muscle and play a role in muscle fiber injury.
Antibodies, Monoclonal↗
The effects of glycerol detubulation, of manganese ions, of dantrolene and of nitrate ions on the responses of isolated chronically denervated soleus muscles of the mouse to acetylcholine.
1 In the isolated chronically denervated soleus muscle of the mouse acetylcholine produced a biphasic contraction. 2 In muscles detubulated by glycerol treatment, the first phase of the acetylcholine contraction was almost abolished, but the second was only slightly reduced or was unaffected. 3 Manganese ions (10 mM) reduced the first phase of the acetylcholine response, but enhanced the second. 4 Dantrolene sodium (5.94 x 10(-5) M) reduced the first phase of the acetylcholine response, but not the second. 5 Nitrate ions (118 mM) augmented the first phase but not the second. 6 It was concluded that the first phase requires the excitation-contraction-coupling sequence: membrane depolarization-T-tubules-Ca2+ release from sarcoplasmic reticulum. In contrast, the second phase appears to occur independently of these processes.
Acetylcholine↗
Functional and histologic effects of a free nonvascularised muscle graft implanted into a reinnervated muscle after prolonged denervation.
Striated muscle atrophy and degeneration, which increase with the delay of denervation, represent two of the main causes for poor recovery following delayed nerve repair. The present study, using a rat model, tests the hypothesis that an adjunction of small, free, nonvascularised muscle grafts of contralateral healthy triceps into a chronically denervated triceps improves muscle regeneration and recovery following sciatic nerve repair delayed for 3 months. Our experiments seem to show a relative increase in mechanical properties in animals in which free muscle graft into the triceps was performed 3 weeks following nerve repair. The improvement of the regenerative process of muscles which have suffered a long period of denervation should be considered as an additional therapeutic procedure in the case of late nerve repair.
Animals↗
Concanavalin-A binding to acetylcholine receptors: identification of two forms of receptor in denervated rat muscle.
The interaction of the nicotinic acetylcholine receptor from denervated rat muscle (AChR, solubilized in Triton X-100) and Concanavalin-A (Con-A) was studied by soluble Con-A competing with the binding of AChR to agarose immobilized Con-A, by immuno-precipitation of Con-A-AChR complexes and by inhibition of alpha-bungarotoxin binding to AChR. Results showed that Con-A bound to 85% of all AChR molecules at multiple cooperative binding sites. Con-A caused a partial inhibition of toxin binding to a maximum of 41% of receptors, but only when AChR was first incubated with Con-A before toxin labeling and not when the order was reversed. The blockade of toxin labeling was reversed when the Con-A-AChR complexes were treated with mannose (0.75 M). Receptor-Con-A complexes in which toxin binding was not inhibited showed saturation binding of toxin with a decreased apparent affinity. A sub-population of AChR prepared by affinity purification on Lens Culinaris lectin-agarose columns was 100% inhibited from toxin binding when preincubated with Con-A. We conclude that receptors from denervated rat muscle which bind Con-A (85% of the total AChR) contain two major subpopulations of AChR in the approximate proportions 6:4 that can be distinguished by interactions with lectins having specificity for mannose.
Animals↗
[Calcium transport and ATPase activity of sarcoplasmic reticulum in normal and denervated rabbit muscles].
The properties of sarcomplasmic reticulum Ca-pump from normal and denervated rabbit muscles were investigated. Ca+2 ion transport in denervated muscle reticulum was subject to Michaelis-Menten kinetics. The rate of fast Ca2+ outflux from the vesicles was enhanced after denervation; this caused a decrease in the transport efficiency and an increase of the "basic" ATP-ase. At the same time the rate of Ca2+ accumulation and the Ca-ATP-ase transport activity were enhances by a factor of 1.5. Kinetic properties of the denervated sarcoplasmic reticulum proved to be closely related to the features of the excitation-contraction cycle in these muscles.
Adenosine Triphosphatases↗
Regeneration in grafts of normal and denervated rat muscles. Contractile properties.
The soleus or extensor digitorum longus muscles of young rats were freely garfted into the bed of the corresponding contralateral muscle. The grafts were of normal muscle or muscles which had been denervated for 14 days. Grafts of normal muscle were characterized by little or no contractile activity for the first 2-4 days after transplantation. In contrast, denervated grafts contracted weakly, but consistently, throughout this early period. The patterns of contraction were complex. In early transplants, the contractions were due entirely to surviving muscle fibers in the graft, and the contractile characteristics were those of denervated muscle fibers. After the first week, contractions of newly regenerating muscle fibers within the grafts were superimposed upon and later took over those from the fibers that survived the original transplantation. The contraction times approached those of the normal soleus or extensor muscles during the second month after grafting, and the grafts contracted like fast or slow muscles.
Animals↗
[Electrodiagnostic and histochemical studies on the effect of electric stimulation on the atrophy of denervated laryngeal muscles in animal experiments].
UNLABELLED: Electrodiagnostic and histometric investigations have been carried out on 56 adult male rabbits following unilateral paralysis of the recurrent laryngeal nerve. Exponential current impulses were externally applied. The excitation threshold was determined endoscopically and also described graphically in terms of the excitation intensity as a function of time (I/t-curves). The diagnostic results thus obtained permit determination of the corresponding excitation parameters for therapy. The success of the therapy was evaluated from histometric data on type I and type II fibres of the vocalis and the posterior cricoarytenoid muscles. RESULTS: 1. The stimulation of denervated laryngeal muscles by external application of exponential current impulses is selective. 2. The extent of the neurogenous atrophy of denervated muscles following paralysis of the recurrent nerve can be diagnosed electrically. 3. This atrophy could be significantly reduced by proper choice of stimulation parameters within the time span of the experiment (28 days).
Animals↗
Presynaptic localization of the small conductance calcium-activated potassium channel SK3 at the neuromuscular junction.
Small conductance, calcium-activated potassium channels (SK channels) are present in most neurons, in denervated muscles and in several non-excitable cell types. In excitable cells SK channels play a fundamental role in the generation of the afterhyperpolarization which follows an action potential, thereby modulating neuronal firing and regulating excitability. To date, three channel subunits (SK1-3) have been cloned from mammalian brain. Since SK3 only has been shown to be expressed in muscles upon denervation, this channel may be involved in hyperexcitability and afterhyperpolarization observed in muscle cells in the absence of the nerve. Using confocal microscopy and SK3 specific antibodies, we demonstrate that SK3 immunoreactivity is present at the rat neuromuscular junction in denervated but also in innervated muscles. In denervated muscle fibers, SK3 is localized in the extrajunctional as well as the junctional plasma membrane, where it appears to be less abundant in the acetylcholine receptor-rich domains, corresponding to the crests of the postsynaptic folds. In innervated muscles, SK3 is not detectable in the muscle fiber but is present at the neuromuscular junction and seems to be localized presynaptically in the motor nerve terminals. Axonal accumulation of SK3 immunoreactivity occurs above and below a ligature of rat sciatic nerve, indicating that the SK3 protein is transported in both directions along the axons of the motor neurons. During rat development SK3 immunoreactivity is not found at the neuromuscular junction until day 35 of postnatal development when SK3 first appears in the motor neuron terminals. These results indicate that SK3 channels are components of the presynaptic compartment in the mature neuromuscular junction, where they may play an important regulatory role in synaptic transmission.
Age Factors↗
Caffeine contractures in denervated frog muscle.
Caffeine contracture tension, effect of caffeine on the resting membrane potential, and caffeine influx in normal and denervated frog sartorius muscle have been investigated. Peak caffeine contracture tension is increased after denervation at all caffeine concentrations. The percentage increases in tension are highest for lower caffeine concentrations. The caffeine concentration required for half maximum tension is decreased from about 3.6 mM in control muscles to 2.6 mM in denervated muscles. Caffeine at 3.5 mM produces a depolarization of about 6 mV in control muscles and 16mV in denervated muscles. The large contracture tensions observed in denervated muscles are not due to the greater depolarization produced by the drug in denervated muscles since innervated muscles depolarized to the same level by external K+ do not enhance caffeine contracture tension. Both control and denervated muscles are highly permeable to caffeine. The increases in sarcoplasmic reticulum development ( Moscatello et al. 1965) and calcium content ( Picken and Kirby 1976) promoted by denervation may explain the larger tension elicited by caffeine in denervated muscles.
Animals↗
DENERVATION OF MUSCLE IN MYASTHENIA GRAVIS. ROPORT OF A PATIENT WITH MYASTHENIA GRAVIS FOR 47 YEARS AND HISTOCHEMICAL SIGNS OF DENERVATION.
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Adenosine Triphosphatases↗
A comparison of fibrillation in denervated skeletal muscle of the anaesthetized rat and guinea-pig.
We have used intracellular recording in vivo to study fibrillation (spontaneous repetitive membrane activity) in extensor digitorum longus (fast twitch) and soleus (slow twitch) muscles of the anaesthetized rat and guinea-pig denervated for periods of about 10 to 60 days. The proportion of fibres fibrillating in the guinea-pig soleus was greater than 50% in most animals up to the longest period of denervation (65 days). Fibrillation was rarely found in rat soleus after three weeks of denervation. Its incidence in the extensor digitorum longus muscles of both species was intermediate. The mean frequency of fibrillation was higher in guinea-pig extensor digitorum longus (16 Hz) and soleus (8 Hz) than in the rat extensor digitorum longus (3 Hz) and soleus (2 Hz). The resting membrane potentials of the denervated muscles were less than normal and correlated inversely with the frequency of fibrillation but not with the incidence of fibrillation: in rat soleus, many fewer fibers were fibrillating at a given membrane potential than in the other three muscles. The incidence of fibrillation was compared with previously reported tensions of the four denervated muscles and was found to have the same rank order. We suggest that fibrillation may reduce atrophy (and hence tension loss) of denervated muscle, which may have implications for artificial stimulation. Fibrillation frequency was directly related to changes in twitch speed of the four muscles after denervation.
Animals↗
[Experimental study of morphology and electrophysiology on denervated skeletal muscle].
OBJECTIVE: In order to provide the scientific basis to find out a practical and effective method to evaluate the degree of muscle atrophy and a better method of prevention and treatment of skeletal muscle atrophy. METHODS: Forty-two adult Spray-Dawley rats were used and the model of denervated gastrocnemius muscle was established by cutting off the tibial nerve. The muscle wet weight, diameter and cross section area of myocyte were measured. The motor end-plate, fibrillation potential amplitude and frequency of denervated skeletal muscle were observed. RESULTS: The muscle wet weight rapidly reduced within 4 weeks. Afterwards, it maintained about 30 per cent of normal value, and the diameter and cross section area of myocyte progressively reduced. The motor end-plate slightly changed within 4 weeks, but its degeneration accelerated in 6 weeks and disappeared after 16 weeks. The fibrillation potential amplitude was maximum at 2 weeks and it progressively reduced after 12 weeks of muscle denervation. The changes of amplitude and frequency were consistent with the degeneration of end-plate. CONCLUSION: The muscle wet weight, diameter and cross section area of myocyte, fibrillation potential amplitude and frequency could be considered as the morphological and electrophysiological indexes of muscle atrophy degree. It's suggested that the repairing operation of peripheral nerve should be performed before the disappearance of motor end-plate.
Animals↗
Increased glucocorticoid/androgen receptor ratios in denervated striated muscle.
Cytosolic glucocorticoid (GR) and androgen receptors (AR) were evaluated at varying time intervals (1-28 days) post-denervation in rat bulbocavernosus/levator ani muscles and the receptor content in the unilaterally denervated muscles compared to the contralateral innervated muscles. Rats were adrenalectomized 3 days prior to GR or castrated 24 h prior to AR determinations. Receptor analyses were performed using charcoal adsorption. Lowered AR were noted in the denervated muscles during very early time periods post-denervation while increased GR were not observed until later. During later post-denervation intervals relative increases or decreases in receptors were dependent on the basis of data expression (cytosolic protein or DNA). The GR to AR ratio was consistently higher in denervated muscles regardless of the basis of comparison, however. We conclude that decreased responsiveness to anabolic stimuli may play a role in the atrophic process.
Adrenalectomy↗
Reparative myogenesis in long-term denervated skeletal muscles of adult rats results in a reduction of the satellite cell population.
This study, conducted on 25-month denervated rat hindlimb muscles, was directed toward elucidating the basis for the poor regeneration that is observed in long-term denervated muscles. Despite a approximately 97.6% loss in mean cross-sectional area of muscle fibers, the muscles retained their fascicular arrangement, with the fascicles containing approximately 1.5 times more fibers than age-matched control muscles. At least three distinct types of muscle fibers were observed: degenerating, persisting (original), and newly formed (regenerated) fibers. A majority of newly formed fibers did not appear to undergo complete maturation, and morphologically they resembled myotubes. Sites of former motor end-plates remained identifiable in persisting muscle fibers. Nuclear death was seen in all types of muscle fibers, especially in degenerating fibers. Nevertheless, the severely atrophic skeletal muscles continued to express developmentally and functionally important proteins, such as MyoD, myogenin, adult and embryonic subunits of the nicotinic acetylcholine receptor, and neural-cell adhesion molecule. Despite the prolonged period of denervation, slow and fast types of myosin were found in surviving muscle fibers. The number of satellite cells was significantly reduced in long-term denervated muscles, as compared with age-matched control muscles. In 25-month denervated muscle, satellite cells were only attached to persisting muscle fibers, but were never seen on newly formed fibers. Our data suggest that the absence of satellite cells in a population of immature newly formed muscle fibers that has arisen as a result of continuous reparative myogenesis may be a crucial, although not necessarily the only, factor underlying the poor regenerative ability of long-term denervated muscle.
Age Factors↗