bluuebunny/crossref_metadata_2025 huggingface dataset:
AAEE minimonograph #28: Injury to peripheral motor nerves
Authors: Miller Robert G.
Published: January 2005

Nerve injury triggers a sequence of electrophysiological events dependent upon changes occurring both at the neuromuscular junction and the muscle membrane. The time course of these physiologic and morphologic alterations is reviewed in light of recent information provided by studies of extrajunctional acetylcholine receptors, axoplasmic transport, and freeze‐fracture electron microscopy. A thorough knowledge of these changes is essential to understanding the clinical impact of nerve injury.
Torpedo monoclonal antibodies react with components of the human peripheral nervous system
Authors: Bjornskov Elizabeth K. , Stephenson Diane T. , Kushner Pinky Drosten
Published: January 2005

A panel of 141 monoclonal antibodies, generated to the Torpedo ray cholinergic nerve terminal preparation, were tested for binding to components of human nerve and muscle. Tested by immunofluorescence, 13 of the antibodies reacted with components of the human intercostal nerve, and 9 bound either muscle or blood vessels in a diversity of staining patterns. Results indicate that the antibodies identifiy a spectrum of different antigens. Some of the antibodies that cross react with the human nervous system have been studied in the ray and rat. In the human peripheral nerve and muscle, their cytochemical distribution is consistent with what has been observed in these other species. These antibodies, therefore, are likely to identify components of the neuromuscular junction that have been conserved in evolution from elasmobranches to humans. The antibodies identified here are potentially useful tools for a molecular examination of human nerves and muscles in pathological conditions.
Growth of skeletal muscle from patients with amyotrophic lateral sclerosis transplanted into nude mice
Authors: Gulati Adarsh K. , Rivner Michael H. , Shamsnia Morteza , Swift Thomas R. , Sohal Gurkirpal S.
Published: January 2005

We studied the fate of skeletal muscle obtained from patients with amyotrophic lateral sclerosis (ALS) after transplantation into immunodeficient nude mice. The transplanted muscle consistently survived in the nude mice without immunological rejection. The myofibers in these muscles underwent degeneration, followed by regeneration, maturation, and eventual functional innervation by the mouse motor neurons. The ability to grow diseased human muscle successfully over a prolonged period in nude mice offers an in vivo model to study the etiology of ALS and possibly of other neuromuscular disorders.
Myoplasmic free [Ca2+] during a malignant hyperthermia episode in swine
Authors: Löapez Jose R. , Allen Paul D. , Alamo Lorenzo , Jones Donald , Sreter Frank A.
Published: January 2005

Malignant hyperthermia (MH) is a genetic syndrome usually initiated by exposure to volatile anesthetic agents or depolarizing neuromuscular blocking agents. We have used Ca2+‐selective microelectrodes to measure in vivo the intracellular ionized calcium ([Ca2+]i) in skeletal muscle fibers of MH‐susceptible swines before and during hyperthermic episodes and also after dantrolene administration. The animals were anesthetized with thiopental and fentanyl and maintained with a mixture of nitrous oxide (66%) and oxygen (34%). The malignant hyperthermic episode was triggered by exposure to halothane. Determinations of [Ca2+]i during the episode show an increase from 0.44 ± 0.01 μM ± SEM, n = 20 to 8.44 ± 0.68 μM (mean ± SEM, n = 10). Administration of dantrolene (2 mg/kg) during the hyperthermic episode reduces [Ca2+]i to 0.17 + 0.01 μM (mean ± SEM, n = 10) and reverses the clinical symptoms. These results show that the MH episode is associated with an increase in the myoplasmic free Ca2+ concentration and that the therapeutic effect of dantrolene is related to a decrease in [Ca2+]i.
Central motor conduction times using transcranial stimulation and F Wave latencies
Authors: Robinson Lawrence R. , Jantra Puangepeth , MacLean Ian C.
Published: January 2005

The purpose of this study was to determine central motor conduction times between the motor cortex and the C8 spinal cord level (MC/C8), the motor cortex and S1 cord level (MC/S1), and C8 and S1 (C8/S1). We stimulated 29 normal subjects with a transcranial high voltage (300–500 V), short duration spike wave form (time constant 50 μsec) and recorded over the hypothenar or calf muscles. F Wave and M response latencies were used to estimate peripheral conduction time. The mean MC/C8 conduction time was 4.4 ± 0.6 msec. Out of 26 subjects tested, 14 had discernable responses in the calf. The mean MC/S1 conduction time was 13.1 ± 2.5 msec, and the mean estimated C8/S1 conduction time was 8.5 ± 2.3 msec. This technique accurately measures conduction time from the motor cortex to the cervical anterior horn cells but is less reliable for monitoring conduction to the sacral cord. These values will facilitate future studies in patients with suspected lesions of the descending motor pathways.
Transient weakness and altered membrane characteristic in recessive generalized myotonia (Becker)
Authors: Rüdel Reinhardt , Ricker Kenneth , Lehmann‐Horn Frank
Published: January 2005

The isometric force of arm and leg muscles was studied in five unrelated patients with recessive generalized myotonia (Becker). The symptom of myotonia was present mainly in the legs, whereas transient weakness was the prominent symptom in the arms. Tocainide improved both symptoms, although it improved the stiffness more than the weakness. A specimen of intact muscle fibers was excised from the external intercostal muscle of one of the patients. The resting potential of the fibers was normal, but on injection of depolarizing current the fibers responded with repetitive action potentials. In normal interstitial fluid the current‐voltage relationship was N‐shaped, with a region of negative slope between −70and −55 mV. Replacement of chloride by an impermeant anion changed this relationship very little, suggesting an abnormally small chloride conductance. The potassium current through the inward‐going rectifier was larger than normal. The force of tetanic contractions of a rested bundle was not sustained but fell quickly to a plateau that increased with repeated stimulation. The relaxation of a rested tetanus was slow and accompanied by spontaneous electrical activity. In subsequent contractions the relaxation became faster and electrical after‐activity decreased. However at 23°C the speed of relaxation was always high despite a large amount of electrical after‐activity. The electrical instability of the membrane and the transient weakness can be explained on the basis of the N‐shaped membrane characteristic.
Effects of chronic prednisolone treatment on post junctional membrane responses to agonist
Authors: Ribera Angeles B. , Nastuk William L.
Published: January 2005

Using frogs treated 1 month with prednisolone, we studied responses of the muscle postjunctional membrane to acetylcholine and carbamylcholine. In control muscles following a bath application of 3 μM neostigmine or 30 μM pyridostigmine, there was an increased depolarization response to iontophoretically applied acetylcholine or carbamylcholine. Results with prednisolone‐treated frog muscle were essentially identical. In some fibers of prednisolone‐treated muscle there was a decrementing response to repetitive iontophoretic application of carbamylcholine. Prolonged administration of prednisolone may accelerate desensitization of acetylcholine receptors during repetitive application of agonist.
Lumbar radiculopathy after spinal fusion for scoliosis
Authors: Harper C. Michel , Daube Jasper R. , Litchy William J. , Klassen Rudolph A.
Published: January 2005

In 184 patients with no preoperative neurologic deficit who underwent operation for idiopathic scoliosis, somatosensory evoked potential monitoring was used. Four patients had neurologic deficits postoperatively. Two patients developed mild signs of intraspinal lesions involving upper motor neurons at high lumbar levels that resolved over 3–5 months. These patients and two others developed evidence of unilateral, moderate, lower motor neuron damage that was confirmed on electromyography. No changes in somatosensory evoked potentials occurred in these patients. Lumbar root damage may be difficult to recognize after operation and should be considered in patients with neurologic deficit after scoliosis surgery.
The myotonic mouse mutant ADR: Electrophysiology of the muscle fiber
Authors: Mehrke Gerhard , Brinkmeier Heinrich , Jockusch Harald
Published: January 2005

The hereditary neuromuscular syndrome of the mouse, “arrested development of righting response” (ADR), is characterized by after‐contractions of skeletal muscle. In order to analyze the etiology of this hereditary defect, mutant and wildtype muscle fibers were studied by intracellular recording. Direct stimulation of ADR muscle fibers elicited runs of action potentials of 1–5 seconds duration, with declining amplitudes and varying frequencies. The electrical after‐activity coincided with after‐contractions of the fiber, and both phenomena could be suppressed by the membrane‐stabilizing drug tocainide. Since similar runs of APs were observed with wildtype muscle in chloride‐free medium, the possible involvement of chloride conductance in the ADR syndrome was studied. Although membrane time constants in wildtype muscle were 4 times prolonged in chloride‐free medium, those of ADR muscle were only 1.4 times longer. This finding indicated a drastic reduction of chloride conductance of the ADR muscle membrane. We conclude that ADR is a myotonia, related in its etiology to hereditary myotonias of man.
The membrane lipid and fatty acid composition of erythrocyte ghosts from three patients with paramyotonia congenita
Authors: Marx Alexander , Szymanska Grażyna , Melzner Ingo , Rüdel Reinhardt
Published: January 2005

The membrane lipid and fatty acid composition of red blood cell ghosts from three paramyotonia patients was investigated. Cholesterol and total phospholipid contents were not different from the controls, but the sphingomyelin content was reduced, and this was compensated for by an increase in phosphatidylcholine. Thus, the molar ratios of phosphatidylcholine/sphingomyelin and phophatidylcholine/phosphatidylethanolamine were greater than normal. The saturated fatty acids in the total phospholipids were increased so that the ratio of saturated/unsaturated fatty acids was 1.4–1.6 versus 1.1–1.2 in the controls. The polyunsaturated fatty acids comprised only 22–26% of the fatty acids versus 31–32% in controls. The reduction in content of unsaturated fatty acids concerned all phospholipid classes in one patient and only the choline phospholipids in the two other patients who were related to each other. The pattern of the fatty acids in the C2‐position of the glycerophospholipids reflected the finding in the total phospholipids. Thus, an alteration of the activity of the acyl‐CoA: 1‐monoacylphosphoglyceride‐acyltransferase seems unlikely. The results support the notion of a generalized membrane defect in paramyotonia congenita, although the degree of abnormality in the fatty acid pattern was not correlated with the severity of the clinical symptoms.
Normal myoblast injections provide genetic treatment for murine dystrophy
Authors: Law Peter K. , Goodwin Tena G. , Wang Mary G.
Published: January 2005

A treatment has been developed to alleviate muscle weakness in murine dystrophy. Cultured myoblasts from genetically normal mouse embryos were injected into the right soleus of 20‐day‐old normal or dystrophic mice. Hosts and donors were immunocompatible but exhibited different genotype markers. Donor cells produced GPI‐1CC. Host cells produced GPI‐1BB. When compared with contralateral controls 6 months postoperatively, test dystrophic solei exhibited greater cross‐sectional area, total fiber number, wet weight, and twitch and tetanus tensions. They contained more normal‐appearing and less abnormal‐appearing fibers. Their mean fiber resting potential was similar to that of normal controls. Presence of GPI‐1CC with or without the hybrid isozyme GPI‐IBC in these mucles implied the survival and development of donor myoblasts into normal myofibers, and fusion of normal myoblasts with dystrophic satellite cells to form genetically mosaic myofibers. Injection of fibroblasts instead of myoblasts caused detrimental effects.
Drug‐induced myotonia in human intercostal muscle
Authors: Kwiecińaski Hubert , Lehmann‐Horn Frank , Rüdel Reinhardt
Published: January 2005

The myotonia‐inducing effects of furosemide and clofibrate, two widely used pharmaceutical agents, were investigated in excised human external intercostal muscle. The effects of anthracene‐9‐carboxylic acid (9‐AC), a well‐known myotonia‐producing chemical, were also tested for comparison. In the presence of these drugs the electrical threshold was lowered, and a constant current pulse produced multiple spiking. Short trains of direct stimuli were often followed by after‐activity, and this caused a myotonia‐like prolongation of muscle contraction. Voltage‐clamp experiments showed that 0.05 mM anthracene‐9‐carboxylic acid, 1 mM furosemide, and 1 mM clofibrate decreased the chloride conductance of the muscle fiber membrane to 14, 18, and 40%, respectively, of the normal value, and the myotonia‐inducing potency of the 3 drugs was correlated with the decreased chloride conductance. The potassium currents were not affected by these compounds.
Adult human masseter muscle fibers express myosin isozymes characteristic of development
Authors: Butler‐Browne G. S. , Eriksson P.‐O. , Laurent C. , Thornell L.‐E.
Published: January 2005

Masseter muscle biopsies were obtained from nine patients undergoing orthognatic surgery or surgery for parotid tumors. A detailed enzyme‐histochemical and immunocytochemical study of these muscles was performed using antibodies specific to the various isozymes of the myosin heavy chain (MHC) in order to identify the MHC isozymes that were present in the different fiber types. The contractile proteins in these same biopsies were analyzed by two‐dimensional gel electrophoresis, native pyrophosphate gel electrophoresis, and by an immunopolypeptide mapping approach. These studies have shown that there is a very heterogeneous distribution of the myosin isozymes, with many fibers containing more than one myosin type. We also present evidence that in addition to adult fast and slow myosin, the human masseter muscle contains two proteins, neonatal MHC and embryonic myosin light chain, that are characteristic of developing muscle.
Changes in denervated skeletal muscle of amiodarone‐fed mice
Authors: Costa‐Jussà Frederic R. , Guevara Ana , Brook Gary A. , Duchen Leo W. , Jacobs Jean M.
Published: January 2005

Prolonged dosing of mice with amiodarone produced a myopathy characterized by autophagic vacuolation and phospholipid inclusions. A previous morphological study had shown that amiodarone did not affect the rate of nerve regeneration after sciatic nerve crush. In the present study, reinnervation was assessed by the reappearance of miniature endplate potentials that confirmed that axonal regeneration and motor reinnervation was not affected by amiodarone. However, there was a marked delay in the recovery of motor function in the amiodarone‐treated mice. Denervation was found to induce an extensive necrosis of muscle fibers in the deeper parts of fast‐twitch muscles. Histochemical studies showed that type 1 fibers were spared, necrosis affecting mainly type 2 fibers with relatively high oxidative enzyme activity (fast‐twitch oxidative fibers). Biochemical studies showed a significant increase in the amount of amiodarone and its metabolite in denervated muscle of amiodarone‐treated mice when compared with contralateral, normally innervated muscles.
Prognostic value of electrodiagnosis in Guillain‐Barré syndrome
Authors: Miller Robert G. , Peterson Gordon W. , Daube Jasper R. , Albers James W.
Published: January 2005

This study was designed to identify clinical and electrodiagnostic indicators of prognosis in Guillain‐Barré syndrome (GBS). Sixty severe GBS patients (all bedfast, 22 ventilator dependent) were analyzed clinically and with standard electromyography and nerve conduction studies. Both ventilator dependence and rapid evolution of weakness were more common in patients with a poor prognosis. The most powerful predictor of a poor outcome was reduced mean compound muscle action potential amplitude (less than 10% of the lower limit of normal).
Investigation of scoliosis in duchenne dystrophy using computerized tomography
Authors: Stern L. M. , Clark B. E.
Published: January 2005

In order to determine the role of the spinal muscles in the etiology of the scoliosis associated with Duchenne muscular dystrophy, we carried out a study of 16 children using computerized tomography. Scans were taken at the level of the 9th dorsal and the 3rd lumbar vertebrae. Density readings were taken in the medial and lateral portions of the erector spinae. The results confirmed the loss of muscle and replacement by fat which was greater on the concave side. The density differences between the convex and concave sides correlated with the degree of curvature measured by Cobb's method. Computed tomography may offer a prognostic indicator in the development of scoliosis.
Therapeutic trial of isaxonine in duchenne muscular dystrophy
Authors: Heckmatt J. Z. , Hyde S. A. , Gabain A. , Dubowitz V.
Published: January 2005

A randomized double‐blind therapeutic trial of isaxonine was completed over a 2‐year period for 20 ambulant boys with Duchenne muscular dystrophy aged 5 1/2–10 years. The effect of the drug was monitored by measurement of walking times over 28 and 150 ft, motor ability score, MRC score based on 32 muscle groups, and myometry of 7 muscle groups. The drug had no significant effect on the progression of the disease. The trial had statistical power comparable to previous larger‐scale multicenter trials. This reflected the low variability in the patients in relation to the magnitude of the overall deterioration. Measurements of muscle force (myometry and MRC score) had much greater statistical power than measurements of function (motor ability score and walking times) as analyzed by our methods. These observations have important implications for the design of future trials.
Axonal branching following crush lesions of peripheral nerves of rat
Authors: Toft Peter B. , Fugleholm Kåre , Schmalbruch Henning
Published: January 2005

Branching of myelinated and unmyelinated nerve fibers in normal and regenerating peroneal and soleus nerves was studied by light and electron microscopy. There were at most 2% more myelinated and 13% more unmyelinated axons in the distal as compared with the proximal nerve segments. Two to four weeks after a crush lesion the distal axons became 2–3 times more numerous; thereafter their number decreased. The number of axons in the proximal nerve segment did not change. The number of myelinated sprouts in most regenerated nerves equalled the number of myelinated fibers in the proximal nerve, while the number of unmyelinated axons after 12–19 weeks was 18–60% higher than normal. Branching was not restricted to the crush region. The results indicate that following a crush lesion all axons branch but only branches of unmyelinated fibers persist for a prolonged period of time. It is tentatively suggested that regenerating axons branch when searching for a target and that when contact is made with the target this prevents additional branching and eliminates redundant branches. Myelinated axons are guided by existing Schwann cells, whereas unmyelinated axons do not follow predetermined pathways; this may explain their greater tendency to form permanent branches.
Selected IgG rapidly induces Lambert–Eaton myasthenic syndrome in mice: Complement independence and EMG abnormalities
Authors: Lambert Edward H. , Lennon Vanda A.
Published: January 2005

Antibodies in individual patients with the Lambert–Eaton myasthenic syndrome (LES) differ in their reactivity with mouse motor nerve terminals. Of 26 LES patients' sera injected a single time into mice, 3 caused a highly significant reduction in stimulus‐dependent quantal release (m) of acetylcholine (ACh) (to 6, 33, and 42 quanta per impulse at 1 Hz, respectively; mean for 10 control sera, 100 quanta at 1 Hz). The most potent serum (LES‐A) was fully effective in mice deficient in complement component C5 and in mice depleted of complement components C3→C9 by cobra venom factor. A single i.v. injection of serum reduced m in direct proportion to log dose. Responses to K+ depolarization and increasing concentrations of Ca2+ were like those observed in human LES.

With LES‐A serum, or its IgG, m was reduced near maximally in 1 day and plateaued in 3–4 days. Recovery began after day 8; m was in the normal range by day 20–30. Electromyographic (EMG) abnormalities were not seen until m fell below 40 quanta per impulse at 1 Hz. Below 10 quanta, clinical signs of weakness appeared, and the EMG abnormalities were those classically associated with LES: a marked reduction of compound muscle action potential to a single nerve stimulus in rested muscle, a further decrement during stimulation at slow rates, but marked facilitation during rapid repetitive stimulation.
Axonal transport of choline acetyltransferase and 6‐phosphofructokinase activities in genetically diabetic mice
Authors: Calcutt Nigel A. , Willars Gary B. , Tomlinson David R.
Published: January 2005

This study examined the anterograde axonal transport of activities of the cytoplasmic enzymes choline acetyltransferase and 6‐phosphofructokinase in genetically diabetic C57BL/Ks (db/db) mice and their nondiabetic (+/?) littermates. Diabetic mice exhibited marked reductions in the accumulation of both choline acetyltransferase and 6‐phosphofructokinase activity against a constriction of the left sciatic nerve (38% and 51% of nondiabetic values, respectively). Enzyme activities per unit length of unconstricted nerve were not different from those of nondiabetic mice. The nerves of diabetic mice did not accumulate measurable amounts of sorbitol or fructose and showed no myo‐inositol depletion. Thus this study concludes that, in diabetic mice, the deficits in anterograde axonal transport of these two enzymes do not arise from the accumulation of sorbitol and fructose nor from depletion of nerve free myo‐inositol.
The binding of lipoproteins to human muscle cells: Binding and uptake of LDL, HDL, and α‐tocopherol
Authors: Gurusinghe Asitha , de Niese Michael , Renaud Jean‐Francois , Austin Lawrence
Published: January 2005

The specific binding of low‐density lipoprotein (LDL) to cells and its subsequent uptake into these cells is well documented, but little is known of the LDL binding and uptake by skeletal muscle. Lipoproteins are the major transporters of tocopherols, deficiencies of which have been associated with a number of muscle diseases of animals. Their possible implication in human muscle diseases prompted our investigation of LDL and high‐density lipoprotein (HDL) binding and uptake into human muscle cells in culture. Cultured human muscle cells were used at both the myoblast and myotube stage. They were incubated with LDL or HDL which were labelled by protein iodination or with (3H) α‐tocopherol and receptor binding and cell uptake characteristics established. LDL binds to both myoblasts and myotubes, but the binding affinity increases significantly with the more highly differentiated cells. This binding appears to be specific to LDL receptors.

The LDL is taken into the muscle cell and protein is degraded, as with other types of cells. HDL also binds to muscle cells, but there is no evidence of internalization. α‐Tocopherol is transferred to muscle‐cells from both LDL and HDL, but the transfer is not dependent on lipoprotein internalization. HDL is effective as a means of transport of α‐tocopherol to muscle cells, but LDL appears to be about one order more effective.
Metabolic myopathy in canine muscle‐type phosphofructokinase deficiency
Authors: Giger Urs , Argov Zohar , Schnall Mitch , Bank William J. , Chance Britton
Published: January 2005

In vivo 31phosphorus nuclear magnetic resonance spectroscopy (P‐NMR) on the anterior tibialis muscle was used to investigate the metabolic myopathy of inherited muscle‐type phosphofructokinase (PFK) deficiency in four (homozygous) dogs who had mild exercise intolerance, rare muscle cramps, increased serum creatine kinase activity, but no myoglobinuria. During isometric muscle work induced by indirect electrical stimulation, and subsequent recovery, changes in the ratio of phosphocreatine (PCr) and inorganic phosphates (Pi) were comparable in muscle of PFK‐deficient and normal dogs and indicated a large capacity for arobic oxidative phosphorylation in canine muscle. The progressive accumulation of sugar phosphates (PME) during graded exercise clearly demonstrated the glycolytic block in PFK‐deficient dogs. During a muscle contracture, induced by acute muscle stimulation, PFK‐deficient muscle became completely depleted of PCr and ATP, accumulated large amounts of PME, and recovered very slowly. We conclude that PFK‐deficient dogs have a metabolic myopathy that demonstrated some but not all the features recognized in the human disorder.
Scanning electron microscopic study of denervated and reinnervated neuromuscular junction
Authors: Matsuda Yoshiro , Oki Sadaaki , Kitaoka Kenji , Nagano Yoji , Nojima Motoo , Desaki Junzo
Published: January 2005

Morphological changes of the subneural apparatus (SNA) during denervation and reinnervation are demonstrated using the hamster peroneus Iongus muscie. One week after nerve section, synaptic grooves (SGs) were more shallow, with lowered sarcoplasmic ridges. After 4 weeks, the whole SNA area was elevated above the sarcolemma as a flat plate, which persisted as a fusiform bulge for more than 8 weeks. There was a rapid and progressive decrease in the number of junctional folds (JFs) and slit‐to‐pit transformation of their openings. There was no trace of the SNA after 16 weeks. By 4 weeks after nerve suture, SGs were flattened but did not form the plate‐like elevation. Many shallow pit‐like JFs still persisted. At 10 weeks, deep SGs started to be restored with an increased number of deep slit‐like JFs. The SNA recovered its normal structural organization by the week 20. However, a few pit‐like vestigial JFs were present outside the groove.
AAEE case report #17: Peripheral neuropathy in monoclonal gammopathy of undetermined significance
Authors: Donofrio Peter D. , Kelly John J.
Published: January 2005

Monoclonal gammopathy of undetermined significance (MGUS) is the most common paraproteinemia associated with polyneuropathy. Although the clinical and electrodiagnostic manifestations most resemble those of chronic inflarnmatory demyelinating polyneuropathy, some patients manifest a pure sensory neuropathy or neuronopathy. The M protein is usually IgM, and its concentration in serum is low. Nerve pathology from patients with demyelinating disease shows a reduction of large myelinated fibers and segmental demyelination with remyelination. In some cases, the M protein possesses antibody activity against components of the myelin sheath or axon. These neuropathies may respond to treatment with steroids, immunosuppressant agents, and plasma exchange.
Calcium sensitivity of fast‐and slow‐twitch human muscle fibers
Authors: Ruff Robert L.
Published: January 2005

Muscle fibers from the lateral gastrocnemius muscles of five normal adult males were chemically skinned (sarcolemma disrupted) and each fiber was divided into two parts for histochemical determination of fiber type and calcium‐induced tension measurements. The calcium concentration associated with half‐maximal tension was 2.5 μM for fast‐twitch and 1.3–1.4 μM for slow‐twitch fibers. Fast‐oxidative‐glycolytic (type 2A) and fast‐glycolytic (type 2B) fibers had similar calcium sensitivities. Maximum tensions (kg/ cm2) were 2.24 for fast‐twitch and 2.19 for slow‐twitch fibers.
Porcine malignant hyperthermia: Halothane effects on force generation in skeletal muscles
Authors: Gallant Esther M. , Goettl Virginia M.
Published: January 2005

Halothane‐induced malignant hyperthermia (MH) is thought to result from a defect in the regulation of cytosolic calcium concentration in MH‐susceptible (MHS) skeletal muscle. Such a defect might be expected to alter the time course of contractile responses. To test this hypothesis, isolated intact cell bundles from external intercostal and common digital extensor muscles of normal and MHS pigs were stimulated electrically to elicit twitch and tetanic tension in the presence and absence of halothane (2.5%). Time intervals measured for both twitches and tetani were (1) the latent period between the stimulus and tension increase, (2) the time to peak tension, and (3) the half‐relaxation time. In contrast to previous reports, halothane had no effect on any measured time course parameter of twitches of either type of normal or MHS muscle, nor did the twitches of MHS and normal muscles differ in any parameter in the absence of halothane. However, the tetanic tension relaxation in both types of MHS muscle was markedly slowed by halothane, whereas in normal muscles there was little change. The slower rate of relaxation induced by halothane in MHS muscles suggests that halothane, either directly or indirectly, enhances the release or slows the removal of calcium in intact MHS muscles following maximal activation. This slowed tetanus relaxation could be of use in identification of MHS individuals.
Myasthenic U‐shaped decrement in multifocal cervical radiculopathy
Authors: Gilchrist James M. , Sanders Donald B.
Published: January 2005

A middle‐aged man with lymphomatous meningitis developed acute cervical radiculopathy. Repetitive stimulation of an affected nerve revealed a “U‐Shaped” decrement. The decrement was absent 10 days later. We hypothesize that the decrement was secondary to simultaneous denervation of many motor units and disappeared as denervation became complete in those motor units.
Ankle dorsiflexor twitch properties in malignant hyperthermia
Authors: Quinlan John G. , Iaizzo Paul A. , Lambert Edward H. , Gronert Gerald A.
Published: January 2005

A noninvasive method to diagnose malignant hyperthermia (MH) was sought. To this end, in vivo isometric twitch properties of the ankle dorsi‐flexor muscles were studied in three groups: (1) MH‐susceptible patients (n = 12), (2) relatives (n = 12) of MH‐susceptible patients who were judged to be MH resistant, and (3) a group of normal volunteers (n = 42) chosen from the community. Twitch properties were studied under resting state conditions and with 1 or 2 Hz stimulation to produce the negative staircase twitch response. There was a high degree of overlap between the ranges of the measured twitch parameters of all groups. Thus, the techniques presented in this study have no value in diagnosing susceptibility to MH. Several physiological features of human isometric twitch properties were demonstrated: (1) slowing of twitch speed with advancing age, (2) strong positive correlation between body weight and twitch torque, and (3) a negative staircase response typical of that described in other mammalian twitch studies.
Malignant hyperthermia: Effects of halothane on the surface membrane
Authors: Iaizzo Paul A. , Lehmamn‐Horn Frank , Taylor Stuart R. , Gallant Esther M.
Published: January 2005

We studied the electrical properties of intact muscle fibers from normal and malignant hyperthemia‐susceptible (MHS) pigs. Resting membrane potentials, action potentials, and current‐voltage relationships were measured with without the presence of halothane. There were no changes in the resting potentials or the specific membrane conductances at any concentration of halothane in either the normal or MHS fibers. The current‐voltage relationships of normal and MHS fibers did not differ. Contractures were observed in MHS muscle when the concentration of halothane was ≥0.8%. These halothane‐induced contractures were not associated with depolarization of the surface membrane. Contractures were not observed in normal muscle even at concentrations of 6.0% halothane. In contrast, halothane altered the shape of the action potentials of both MHS and normal fibers. However these changes were significantly greater in MHS fibers, occurred at much lower concentrations, and were partially prevented by preincubation in 10 μM dantrolene.
Myophosphorylase B deficiency and malignant hyperthermia
Authors: Isaacs Hyam , Badenhorst Margaret E. , Sautoy Cheryl Du
Published: January 2005

A 6‐year‐old boy was examined with the dual purpose of establishing whether he had malignant hyperthermia (MH) and to investigate his complaint of excessive muscle fatiguability. In the course of such investigations, McArdle's disease was diagnosed, and the patient was also identified as an MH‐positive reactor.
Principal component analysis of the features of concentric needle EMG motor unit action potentials
Authors: Nandedkar Sanjeev D. , Sanders Donald B.
Published: January 2005

Motor unit action potentials (MUAPs) were recorded from the biceps muscle of normal subjects and of patients with nerve of muscle diseases. Principal component analysis of the MUAP amplitude, area, area/amplitude ratio, duration, and the number of turns and phases produced three components that among them contained 90% of the variance of the data set. Thus the dimensionality of data was reduced from six to three. The first component reflected changes in the size of the MU, whereas the second reflected variations in the arrival time at the recording electrode of the action potentials of muscle fibers in the motor unit. The third factor reflected local loss of muscle fibers within the MU territory. Patterns of variations in the three components were different in patients with neuropathy and myopathy.
Studies of water permeability and proteins of erythrocyte membranes in patients with Duchenne muscular dystrophy
Authors: Benga Gheorghe , Popescu Octavian , Pop Victor I. , Ionescu Iulian , Muresan Ana , Borza Victoria , Hodâacrnâu Adriana , Popescu Mihai , Serbu Ana Maria , Benga Ileana
Published: January 2005

The characteristics of water permeability of erythrocytes from 54 Duchenne muscular dystrophy (DMD) patients and age‐matched controls have been determined by a pulse nuclear magnetic resonance (NMR) technique. A decreased permeability of erythrocyte membrane in DMD was definitely found at all temperatures between 15 and 42°C, with normal values for the activation energy of water diffusion. No differences between DMD and control subjects in the pattern of erythrocyte membrane polypeptides separated by two‐dimensional electrophoresis could be detected. The findings are discussed in relation to the molecular mechanisms of water diffusion across erythrocyte membrane and the problem of erythrocyte membrane abnormalities in DMD. A new interpretation of erythrocyte membrane alterations is proposed based on the recent findings regarding the molecular pathology of DMD.
Biochemical characteristics of free and junctional sarcoplasmic reticulum and of transverse tubules in human skeletal muscle
Authors: Damiani Ernesto , Barillari Alfredo , Tobaldin Gianantonio , Pierobon Sandra , Margreth Alfredo
Published: January 2005

The microsomal fraction of normal human skeletal muscle was subfractionated by isopycnic sucrose‐density centrifugation, using the procedure originally described by Saito et al.38 for rabbit fast muscle, and specific markers of the junctional face membrane of terminal cisternae (TC) (ryanodine receptor, high‐molecular‐weight feet proteins and membrane‐associated calcium‐binding protein calsequestrin), of the sarcoplasmic reticulum (SR) Ca‐pump membrane (chicken antibody to rabbit Ca‐ATPase), and of transverse tubules (TT) (dihydropiridine receptor, membrane cholesterol), respectively. The results show that isolated TC from human skeletal muscle share extensive morphological characteristics, protein composition, as well as Ca‐release properties with rabbit TC, as tested with an inhibitor (Ruthenium red) and an activator (doxorubicin) of SR Ca‐release. The Ca‐pump membrane of human muscle SR, in distinction to rabbit fast muscle SR, showed a relatively low specific activity of the Ca‐ATPase, as expected from the mixed fiber composition of human muscles, but shared the presence of minor protein components, such as a Con A binding protein of about 57 kDa and blue‐staining peptides in the 170–120 kDa range of molecular weights. Human muscle TT, as isolated from the same sucrose gradient, demonstrated a high affinity (3H)‐dihydropiridine binding activity in the range of previously reported values for purified TT from rabbit skeletal muscle.
Electrodiagnosis of human colchicine myoneuropathy
Authors: Kuncl Ralph W. , Cornblath David R. , Avila Orlando , Duncan Greg
Published: January 2005

Colchicine may produce a neuromuscular disorder even when given in customary doses. We report the electrodiagnostic features in eight pathologically proven cases of colchicine‐induced myoneuropathy. Myopathic motor unit potentials and early recruitment were found in proximal limb and truncal muscles, frequently with fibrillations, positive sharp waves, or complex repetitive discharges. These electromyographic findings correlated with the course of the weakness, which rapidly resolved within weeks of drug discontinuation, indicating that the major functional disturbance in the patients was myopathy. The accompanying signs of axonal neuropathy persisted longer, with little functional consequence. Although often misrecognized as polymyositis, colchicine myoneuropathy was identifiable by the rapid clinical and electrophysiologic improvement following drug withdrawal as well as by its distinctive morphology.
Mdx muscle grafts retain the mdx phenotype in normal hosts
Authors: Morgan Jennifer E. , Coulton Gary R. , Partridge Terence A.
Published: January 2005

Whole muscle grafts were made between mdx and normal mice to investigate whether the mdx myopathic lesion is intrinsic to mdx muscle or is a property of its environment. Grafts were examined between 20 and 101 days. Unequivocal necrotic muscle fibers and/or newly formed basophilic myotubes were noted in 8 of 16 grafts of mdx muscle made in normal hosts but in none of 16 grafts of normal muscle made in mdx hosts. In older grafts, the proportion of centrally nucleated fibers and variability of fiber diameter were both higher in mdx muscle grafted into normal hosts than in normal muscle grafted into either mdx or normal hosts. Analysis of the glucose‐6‐phosphate isomerase (GPI) isoenzyme content of the grafts indicated that the muscle formed was predominantly of donor origin. These findings provide evidence that the mdx lesion is a primary myopathy rather than secondary to an extramuscular primary lesion.
Effect of diltiazem on 2,4‐D‐induced myotonia in rats
Authors: Al‐Rajeh Saad , Iyer Vasudeva , Olson William H.
Published: January 2005

Myotonia is characterized by prolonged contraction (delay in onset of relaxation) of skeletal muscle fibers with characteristic electromyographic findings. Calcium channel blocking drugs may be expected to reduce myotonia, should they promote the onset of relaxation in a contracted skeletal muscle. This study was aimed at evaluating the effect of diltiazem, a calcium channel blocking agent, on myotonia induced by 2,4‐dichlorophenoxyacetic acid (2,4‐D).

In rat diaphragm, exposed to 2.5 mM 2,4‐D in a tissue bath, myotonia was quantified by documenting the contraction time in response to direct stimulation with supramaximal electric stimuli. At the peak of myotonia, different concentrations of diltiazem were added to the tissue bath and the effect on evoked contraction studied over a period of 6 minutes. A concentration of 5 × 10−5M was found to be the most effective, causing a decrease in contraction time of more than 90% in 3 minutes in 100% of specimens (n = 7).

The above findings raise the possibility of using diltiazem as an antimyotonic agent.
Changes in muscle fiber conduction velocity, mean power frequency, and mean EMG voltage during prolonged submaximal contractions
Authors: Arendt‐Nielsen Lars , Mills Kerry R. , Forster Allan
Published: January 2005

Average muscle fiber conduction velocity, mean power frequency, and mean EMG voltage have been measured in human vastus lateralis during prolonged isometric knee extensions at 10, 20, 30, and 40% of the maximum knee extension force. During contractions at 10 and 20% of maximum force, conduction velocity and mean power frequency rose as the contraction progressed, whereas the conduction velocity and mean power frequency fell at 30 and 40% of the maximum force. The mean EMG voltage rose during the contractions, with steeper increases for higher forces. It is argued that two principal factors influence the EMG during prolonged submaximal contractions: firstly, the fatigue of current active motor units, and, secondly, recruitment of fresh motor units. These factors act in opposition to muscle fiber conduction velocity. Recruitment gives an increase in average conduction velocity, whereas fatigue provokes a slowing in conduction velocity.
Electromyography in congenital nemaline myopathy
Authors: Wallgren‐Pettersson Carina , Sainio Kimmo , Salmi Tapani
Published: January 2005

To clarify the discrepancies between earlier reports of electromyography (EMG) in congenital nemaline myopathy (CNM), conventional electromyography was done on 13 patients with CNM, and results were compared with those of 18 earlier EMG examinations of the same patients. Fiber density was measured in 10 patients with a computerized method and neuro‐muscular jitter in 3 with single‐fiber EMG. With age, the EMG abnormality progressed, and “neuropathic” EMG features developed in distal muscles. In 9 of 10 patients fiber density was higher than normal. In two of three patients jitter was abnormal. Motor (13 of 13 patients) and sensory (3 of 3 patients) nerve conduction velocities were normal. Our results seem to explain the conflicting reports of EMG in CNM. We conclude that active degeneration and regeneration of muscle fibers takes place in CNM and suggest that the “neuropathic” motor unit potentials seen in our patients may be secondary to myopathic disease activity.
Cross‐reactivity of an antineurofilament antibody with a troponin‐T isoform
Authors: Takagi Michito , Takano‐Ohmuro Hiromi , Nakamura Toshitaka , Kawahara Hajime , Shimizu Teruo , Obinata Takashi , Kohama Kazuhiro
Published: January 2005

Histochemical examination has revealed that a monoclonal antibody raised against the 200‐kilodalton (kd) subunit of neurofilament reacts not only with neural tissue but with type 1 and type 2C fibers of skeletal muscle. To identify the cross‐reactive substance(s), rat soleus muscle, which includes type 1 and type 2C fibers, was separated into a soluble fraction and an insoluble myofibrillar fraction. Western blot analysis demonstrated that the antibody reacted with 30‐kd and 36‐kd polypeptides in the soluble fraction and with a 38‐kd polypeptide in the insoluble fraction. We isolated a fraction that contained the 38‐kd polypeptide from the insoluble fraction. The material in this fraction bound to F‐actin. Two‐dimensional electrophoresis of the fraction showed that the 38‐kd polypeptide was part of the group of isoforms of troponin‐T, which was identified by a monoclonal antibody developed against troponin‐T. Thus, we conclude that this antineurofilament antibody recognizes one of the isoforms of troponin‐T in type 1 and type 2C fibers.
Hypokalemic paralysis in two patients with paramyotonia congenita (PC) and known hyperkalemic/exercise‐induced weakness
Authors: Streib Erich W.
Published: January 2005

Two male patients from a single family with known PC and “potassium sensitivity” developed hypokalemic paralysis following generalized anesthesia. These patients confirm previous similar observations. It's significance and management are discussed.
Nerve conduction studies in the superficial in the superficial radial nerve entrapment syndrome
Authors: Spindler Henery A. , Dellon A. Lee
Published: January 2005

This report reviews the ssyndrome of entrapment of the superficial branch of the radial nerve (SBRN) in the forearm, and electrodiagnostic techniques to aid in diagnosis are presented. Normal mean radial sensory conduction in the forearm was found to be 61.4 ± 3.1 m/sec. Three patients are presented. In two of these comparison of conduction in the SBRN to the lateral antebrachial cutanious nerve (LACN) and contralateral SBRN was abnormal, whereas the absolute SBRN conduction appeared normal. Normal LACN‐SBRN difference in the same arm was 1.9 ± 1.6 m/sec, with a range of 0–7.0 m/sec; mean SBRN difference in opposite arms of the same subject was 1.8 ± 1.6 m/sec.
Rat and human Schwann cells in vitro can synthesize and express MHC molecules
Authors: Armati P. J. , Pollard J. D. , Gatenby P.
Published: January 2005

The expression of MHC class I and II molecules on cultured rat and human Schwann cells (SCs) was studied to determine whether these molecules could be synthesized by SCs in the absence of T cells. Normal rat and human SCs in vitro expressed low levels of class I MHC, but this was markedly increased by incubation with interferon gamma (IFN‐γ). Untreated SCs of rat or human origin did not express detectable class II MHC molecules, but after 48 hours incubation with IFN‐γ 100 U/ml, 20% of rat SCs and 90% of human SCs were class II positive. Immunoelectron microscopy confirmed the surface expression of MHC molecules on SCs and demonstrated class II MHC within endocytotic vesicles. These findings provide further evidence for an immunological role for SCs as antigen presenting cells or as targets for cytotoxic T cells.
Effect of clenbuterol on normal and denervated muscle growth and contractility
Authors: Agbenyega Edward Tsiri , Wareham Anthony Clive
Published: January 2005

The reported anabolic action of some β2 agonists may have clinical applications in certain muscle wasting states. Administration of clenbuterol (2mg/kg diet for 14 days) to rats resulted in a limited degree of hypertrophy of normal muscles; the effect was more pronounced on fast‐twitch muscles than on slow‐twitch muscles. The anabolic effect was greatest in denervated muscles, where it was significantly more effective on the slow‐twitch type. Clenbuterol significantly improved the contractile properties of denervated slow‐twitch muscle, reverting them toward normal, but had little effect on contractile properties of denervated fast‐twitch muscle. Such differential effects of clenbuterol must be taken into consideration in the evaluation of any future human intervention study.
Polyneuropathy in lithium intoxication
Authors: Vanhooren Geert , Dehaene Ides , Van Zandycke Michel , Piessens Frans , Vandenbergh Vic , Van Hees Johan , Lammens Martin , Carton Herwig
Published: January 2005

Two patients developed acute sensorimotor polyneuropathy after intoxication with lithium carbonate. Nerve conduction studies, electromyography, and sural nerve biopsy proved it to be an axonal neuropathy. Recovery of muscle strength, reflexes, and sensory function started weeks after discontinuation of lithium therapy. One patient fully recovered within a year. In the literature we found nine other cases of lithium polyneuropathy.
The expression of myosin light chains and tropomyosin in human muscle biopsies with histochemical type 1 and type 2 fiber deficiency
Authors: Giometti Carol S. , Danon Moris J.
Published: January 2005

Two‐dimensional gel electrophoresis (2DE) was used to compare the protein composition of human muscle biopsies that were shown by histochemical staining to be deficient in either type 1 or type 2 fibers. Distinct quantitative differences were found in the myofibrillar protein composition of muscle from a 43‐year‐old woman with proximal limb weakness that showed almost total absence of type 1 fibers and muscle from a 2.5‐year‐ girl with congenital myopathy in which there was severe lack of type 2 fibers. These data indicate that human type 1 and type 2 muscle fibers express distinct isoforms of myosin light chains and α‐tropomyosin.