bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of collagen crosslinking in the increased stiffness of avian dystrophic muscle
Authors: Feit Howard , Kawai Masataka , Mostafapour A. Shanaz 
Published: January 2005

AbstractThe resting tension and stiffness in the range of sarcomere lengths 2.4–3.6 μm were studied in highly inbred normal and dystrophic chicken pectoral muscle bundles, and the results were compared with the collagen content and the extent of crosslinkage of the collagen. All parameters increased in the order normal homozygote (003/003) < heterozygote (003/433) < dystrophic homozygote (433/433) chickens, with the data from the heterozygotes being halfway between the two homozygotes, thus exhibiting a semidominant inheritance pattern. In separate experiments, lathyrism was induced by treating normal (412/412) and dystrophic (413/413) chickens with α‐acetoaminonitrile, an inhibitor of lysyl oxydase, the enzyme responsible for the initiation of collagen crosslinkage formation. These experiments showed that the tension and stiffness in response to passive stretch did not change with lathyrism in normal muscles, whereas the tension and stiffness decreased significantly with lathyrism in dystrophic muscles. The collagen content did not change with lathryrism in both normal and dystrophic muscles. These results indicate that the increased content of collagen crosslinkages is the basis for the increased resting tension and stiffness in the dystrophic muscles of the chicken, and that the effects can be reversed by treatment with an inhibitor of collagen crosslinkage formation.
Accumulation of collagen and altered fiber‐type ratios as indicators of abnormal muscle gene expression in the mdx dystrophic mouse
Authors: Marshall P. A. , Williams P. E. , Goldspink G. 
Published: January 2005

AbstractThe growth and development of the X‐linked muscular dystrophy mutant mouse (mdx) was compared with a control group from 3 weeks to 1 year old. Quantitative cytological analysis of the soleus muscle revealed cycles of degeneration, regeneration, and hypertrophy, and at any one time it was difficult to assess the extent of the disease based on muscle fiber size. One noticeable difference even in the youngest muscles studied was the reduced numbers of slow oxidative fibers and the increased number of fast glycolytic fibers in the mdx soleus muscles. The collagen of the connective tissue components of selectively stained sections was determined by computerized image analysis. Marked accumulation of collagen was found in both the endomysium and perimysium of the dystrophic muscles as compared with age‐matched controls. Since the mdx mouse is a result of the same type of genetic defect as in human Duchenne muscular dystrophy, this model could thus be used to assess the effectiveness of various therapeutic approaches, including gene therapy using muscle fibrosis and fiber type proportions as the indicators.
Focal nerve injury: Guidance factors during axonal regeneration
Authors: Thomas P. K. 
Published: January 2005

AbstractRegeneration of axons after nerve injury is not random but is often not precise, particularly after injuries that involve nerve transection. The factors that guide regenerating axons toward appropriate terminations are complex, but developments in neurobiology are beginning to indicate the mechanisms that are involved. These include neurotrophic and neurite promoting factors, chemotactic influences from peripheral tissues, and the properties of the extracellular matrix. Understanding these mechanisms may indicate means of improving functional recovery after nerve injury.
SFEMG improvement with remission in the cancer‐associated Lambert–Eaton myasthenic syndrome
Authors: Oh Shin J. 
Published: January 2005

AbstractIn two patients with the Lambert–Eaton myasthenic syndrome (LEMS) and small‐cell lung carcinoma (SLLC), therapy for LEMS was effective when combined with cancer therapy. The serial SFEMG tests showed a corresponding improvement with remission of the LEMS and proved to be a better and earlier indicator of the changing clinical status than the repetitive nerve stimulation test. Thus, we conclude that the SFEMG is useful in the follow‐up evaluation of patients with this condition.
Adynamia episodica hereditaria: What causes the weakness?
Authors: Ricker Kenneth , Camacho Luis M. , Grafe Peter , Lehmann‐Horn Frank , Rüdel Reinhardt 
Published: January 2005

AbstractThe cause of weakness was investigated in a patient with adynamia episodica hereditaria without myotonia. A pattern of exercise and rest produced episodes of hyperkalemic periodic paralysis. In addition, local muscle weakness was induced by forearm cooling. Investigations on isolated intercostal muscle demonstrated that a high potassium concentration in the bathing solution triggered a noninactivating membrane current causing depolarization of the muscle fibers. This current was carried by sodium as it could be inhibited by tetrodotoxin. The abnormal sodium conductance led to an increase of sodium within the fibers. This was demonstrated directly by intracellular recordings. Weakness induced by rest after exercise and cold‐induced weakness appeared to have different pathomechanisms. In the cold, the muscle fibers retained a normal resting potential, but their excitability was reduced and their mechanical threshold was increased. These findings also provide evidence that the mechanism of cold‐induced weakness in adynamia episodica is distinctly different from the cold‐induced weakness that occurs in paramyotonia congenita.
The effects of taurine on pharmacologically induced myotonia
Authors: Camerino Diana Conte , De Luca Annamaria , Mambrini Mercede , Ferrannini Ermanno , Franconi Flavia , Giotti Alberto , Bryant Shirley H. 
Published: January 2005

AbstractTaurine reduces the excitability of striated muscle fibers by increasing the membrane conductance to chloride ions (GCI). This action was tested on rats made myotonic by drugs that block GCI by different mechanisms. Experiments were made “in vivo” using electromyographic (EMG) recordings and “in vitro” with intracellular microelectrode recordings from extensor digitorum longus muscle fibers. Taurine did not antagonize the myotonic discharges produced in vivo by anthracene‐9‐carboxylic acid, nor did it restore GCI lowered in vitro by this agent. However, when myotonia was chronically induced by 20,25 diazacholesterol, taurine given chronically in vivo or acutely in vitro antagonized the EMG myotonia as well as the reduced GCI and increased excitability of single fibers. We conclude that taurine acts directly on chloride channels to modify their kinetics. Our findings suggest that further clinical studies on the use of taurine in muscle disease involving abnormal excitability or chloride channel function will be useful.
Role of nerve and tension in maturation of posthatching slow‐tonic muscle in chicken
Authors: Gardahaut Marie‐France C. , Rouaud Thierry P. , Renaud Didier , Khaskiye Ahmad , Le Douarin Georges H. 
Published: January 2005

AbstractThe role of motor innervation and muscle tension in the posthatching maturation of the slow‐tonic anterior latissimus dorsi (ALD) muscle of the chicken has been investigated. Modification of the muscle tension was obtained either by maintaining ALD in a shortened state or by stretching, after or without denervation. In denervated as well as in innervated ALD, shortening resulted in atrophy and inhibition of developmental change in muscle fiber population. In contrast, stretch causes hypertrophy, transformation of all 3B fibers, increase in SM2 isomyosin expression, and decrease in Ca2+‐activated myosin ATPase in innervated or denervated ALD. On the other hand oxidative activity in ALD fibers was strikingly reduced after denervation even in presence of stretch‐induced hypertrophy. This study suggests that a passive stretch can be involved in some, but not all, changes in ALD characteristics occurring after denervation and may be also involved in normal posthatching development of the slow‐tonic muscle. Possible clinical implications of these results in relation to treatments for preventing muscle atrophy resulting from immobilization or disuse are suggested.
The positive inotropic effect of epinephrine on skeletal muscle: A brief review
Authors: Williams Jay H. , Barnes William S. 
Published: January 2005

AbstractChronic and acute administration of epinephrine or related sympathomimetic agents are typically prescribed for the treatment of clinical disorders such as hypotension, anaphylactic and allergic reactions, and bronchial asthma. In addition to its effects on these infirmaties and on carbohydrate metabolism, epinephrine also exerts a positive inotropic effect on fast‐contracting skeletal muscle in a variety of animal species. At present, the precise mechanisms responsible for the inotropic effect are not known. This communication reviews the positive inotropic effects of epinephrine on fastcontracting skeletal muscle and discusses possible mechanisms which might mediate this phenomenon. Epinephrine potentiates muscle twitches via the second messenger, cAMP, secondary to hormone binding to membrane‐bound beta‐receptors. Cyclic AMP then acts to increase carbohydrate metabolism, alter sodium/potassium exchange, phosphorylate myosin isozymes, and/or alter intracellular calcium exchange. Based on theoretical grounds, the first three mechanisms can be excluded. Therefore, it is tentatively hypothesized that the effect is due to cAMP‐enhanced calcium exchange within the muscle fiber and/or to increased influx of extracellular calcium. This notion is consistent with the mechanism of the positive inotropic effects of epinephrine on cardiac tissue. If this hypothesis is correct, it would also suggest a role, at least under some conditions, for extracellular calcium in the process of skeletal muscle excitation–contraction coupling.
Far‐field and cortical somatosensory evoked potentials in motor neuron disease
Authors: Zanette Giampietro , Polo Alberto , Gasperini Marcella , Bertolasi Laura , De Grandis Domenico 
Published: January 2005

AbstractWe examined median somatosensory evoked potentials (SEPs) in 26 patients with sporadic motor neuron disease (MND). SEPs were recorded with multiple scalp derivations, using both the midfront and the earlobe as references for each subject. Central conduction time (CCT) was abnormal in three patients, but only when using the midfront reference. Moreover, an exclusive alteration of the early prerolandic potentials potentials (absent or delayed P20 and/or P22) was noted using the earlobe reference in amyotrophic lateral sclerosis and in progressive bulbar palsy (54% and 50% of patients, respectively) but not in progressive muscular atrophy. These findings correlated with clinical evidence of upper motor neuron signs and with the severity of the disease. In agreement with recentviews regarding the sources of the early anterior cortical responses, neuronal loss in the motor cortex may be considered as affecting the generator sites of these potentials.
Conduction block in neuropathies with necrotizing vasculitis
Authors: Ropert Angèle , Metral Stéphane 
Published: January 2005

AbstractThirty‐two patients with a mononeuropathy multiplex associated with a systemic necrotizing vasculitis were studied. The main abnormality was a loss of motor and sensory axons confirmed by electrophysiological and histological methods. A conduction block was observed in five patients, but only one was at a usual site of compression. Based on previous pathological studies and the experimental data in human and animals, the mechanism of the block is proposed to be ischemic. It is suggested that a conduction block in one nerve in a neuropathy with two or more individual nerves affected and with electrophysiological features of axonal degeneration may be due to a vasculitis.
Limits of normal nerve function during high‐frequency stimulation
Authors: Robinson Lawrence R. , Nielsen Viggo Kamp 
Published: January 2005

AbstractWe studied the effects of prolonged high‐frequency stimulation in normal rat tail nerves. Nerves could conduct impulses at 50 Hz for 5 hours without complete conduction block. However, over time there was a significant decrease in amplitude and increase in latency of the compound nerve action potential (CNAP), which gradually became desynchronized. Changes were influenced by the frequency of stimulation. When stimulating over 30 minutes at 20, 50, 100, and 143 Hz the amplitude decreased to 89%, 79%, 67%, and 65% of baseline values, respectively, whereas the latency was only significantly increased at 100 and 143Hz. All changes were reversible upon cessation of stimulation. Changes could not be attributed to focal block at the site of stimulation. These changes in the CNAP may reflect functional limitations of the axon membrane which may have pathophysiological implications for the study of neuropathies and focal nerve lesions.
Acoustic and surface EMG diagnosis of pediatric muscle disease
Authors: Barry Daniel T. , Gordon Kevin E. , Hinton George G. 
Published: January 2005

AbstractThe ratio of acoustic myography (AMG) amplitude to surface electromyography (EMG) amplitude is proposed as a measure of mechanical output compared with electrical activity of the contractile system. AMG to EMG ratios were measured from 16 children with muscle disease diagnosed by clinical criteria, EMG, and/or muscle biopsy. These were compared with the ratios from 11 normal volunteers spanning the same age range (7‐16 years). AMG to EMG ratios were significantly (P > 0.01) different for the two populations. Using a linear discriminant function to define the normal range for AMG to EMG ratios yielded a sensitivity of 82% (13 of 16 abnormals diagnosed) and a specificity of 91% (10 of 11 normals). These findings suggest that surface recordings may provide significant diagnostic information in muscle disease. The accuracy may be improved further by using additional muscles (e.g., paraspinals) and evoked twitches.
On the specificity of the acetylcholinesterase defect in dystrophic mice
Authors: Skau Kenneth A. 
Published: January 2005

AbstractThe tetrameric form of acetylcholinesterase (AChE) in ReJ/129 dystrophic mice was demonstrated to be absent from endplate‐poor regions of skeletal muscle but present in endplate‐rich regions. Skeletal muscle secreted normal amounts of this form of AChE. Visceral organs had normal amounts and distribution of the AChE molecular forms. These results suggest that the AChE defect in dystrophic mice is limited to skeletal muscle, and the defect does not reflect an abnormality of AChE synthesis but probably reflects an inability to incorporate the enzyme into skeletal muscle membranes.
EMG evaluation of the floppy infant: Differential diagnosis and technical aspects
Authors: Jones H. Royden 
Published: January 2005

AbstractElectromyographic examination of the newborn and young infant provides a relatively uncommon challenge to most electromyographers. The usual reason for referral for electromyographic studies in the newborn and young infant is to evaluate a floppy baby. The electromyographer must not only be aware of important differences in normal physiologic parameters but must also be familiar with a spectrum of diseases that are not typically encountered in the adult. The results of electromyography must also be correlated with the normal maturation of neuromuscular function. Although the most common pathophysiologic mechanisms affecting the peripheral motor unit are infantile motor neuron disease and the congenital myopathies, a large number of other disease entities warrant careful consideration.
A comparison of magnetic and electrical stimulation of spinal nerves
Authors: Evans B. A. , Daube J. R. , Litchy W. J. 
Published: January 2005

AbstractThe utility of the magnetic coil for stimulation of the cervical spinal nerves was compared to electrical stimulation by a monopolar needle cathode placed onto the spinal lamina in six volunteers. No statistical difference in average amplitudes or areas of evoked CMAPs was found although the size of the magnetic coil evoked potentials was less at C7–8 in several subjects. Electrical stimulation resulted in depolarization at a more proximal site. Electrical stimulation was associated with more discomfort, especially at C5–6. We conclude that electrical stimulation using a monopolar needle as the cathode is the superior technique for the clinical electrophysiologic study of the proximal brachial plexus and cervical spinal nerves.
A noninvasive procedure to detect muscle weakness in the mdx mouse
Authors: Carlson C. G. , Makiejus R. V. 
Published: January 2005

AbstractThe forward pulling tension exerted by individual mice was measured nearly isometrically in a simple apparatus designed to determine whole body tension (WBT). WBT determinations on control (C57BI10/SnJ) and experimental (C57BI10‐mdx) mice indicate muscle weakness which lasts throughoout the lifespan of mdx mice. Direct muscle stimulation experiments in vivo also showed significant decreases in peak twitch and tetanic tensions in adult mdx muscle with no obvious alterations in twitch time course or in twitch: tetanus rations. We suggest that the noninvasive WBT procedure may be used to partially assess various therapies on this murine model of Duchenne muscular dystrophy.
Schwartz–Jampel syndrome: II. Na+ channel defect causes myotonia
Authors: Lehmann‐Horn Frank , Iaizzo Paul A. , Frane Christian , Hatt Hanns , Spaans Frank 
Published: January 2005

AbstractSkeletal muscle fibers from a patient with Schwartz–Jampel syndrome were studied in vitro. The fibers had normal resting membrane potentials, but their resting [Ca2+]i was elevated. The resting potentials were unstable and spontaneous depolarizations caused twitching in all fibers. Stimulated contractions were characterized by markedly slowed relaxation which was due to electrical after‐activity. Neither curare (0.7 μM), tocainide (50 μM), nor phenytoin (80 μM) had an effect on the myotonic activity. In contrast, procainamide (200 μM) suppressed the hyperexcitability without affecting the twitch amplitude. The steady‐state current‐voltage relation was normal in 5 fibers, but altered in 3 others. These latter fibers had an increased specific membrane resistance owing to a decreased Cl‐ conductance. The Na+ channels were investigated in the cell‐attached patch clamp mode. In all patches on either type of fiber, depolarizing pulses elicited delayed, synchronized openings of Na+ channels. These abnormal openings occurred even after the surface membrane repolarized. We hypothesize that these altered membrane conductances are responsible for the hyperexcitability and the associated slowed relaxation.
Invited review: Peripheral neuropathy in Sjogren' syndrome
Authors: Kaplan Jerry G. , Rosenberg Richard , Reinitz Elizabeth , Buchbinder Shalom , Schaumburg Herbert H. 
Published: January 2005

AbstractOur experience and review of the literature reveal that Sjogren' syndrome (SS) is an important, poorly recognized cause of peripheral neuropathy. Several forms of peripheral nerve dysfunction occur in SS including trigeminal sensory neuropathy, mononeuropathy multiplex, distal sensory neuropathy, distal sensorimotor peripheral neuropathy and a pure sensory neuronopathy syndrome. Rarely, chronic relapsing inflammatory polyneuropathy and multiple cranial neuropathies appear. Clinical evidence of glandular in volvement is often minimal or absent when patients with SS develop peripheral neuropathy; and the diagnosis of the underlying condition is elusive. We review clinical and laboratory features of this disorder and suggest appropriate evaluation of patients with neuropathy and suspected SS.
Insulin effects in denervated and non‐weight‐bearing rat soleus muscle
Authors: Tischler Marc E. , Satarug Soisungwan , Eisenfeld Steven H. , Henriksen Erik J. , Rosenberg Sara B. 
Published: January 2005

AbstractPrevious reports indicated that glucose uptake in denervated muscle is resistant to insulin, while in non‐weight‐bearing (unweighted) muscle this effect of insuling is enhanced. To extend the comparison of these differences, insulin effects on amino acid uptake and protein metabolism were studied in soleus muscles subjected to denervation or unweighting. Denervated muscle showed insulin resistance of both 2‐deoxy[1,2‐3H] glucose and ‐[methyl‐3H]aminoisobutyric acid uptake whereas unweighted muscle showed an increased or normal response, respectively. Atrophy was greater in denervated than in unweighted muscle, apparently due to faster protein degradation by insulin was generally less in denervated than in unweighted muscle, apparently due to faster protein degradation. The stimulation of protein synthesis and the inhibition of protein degradation by insulin was generally less in denervated than in unweighted muscle. Since metabolic measurements in denervated‐unweighted muscles did not differ from those in denervated‐weight‐bearing muscles, effects of denervation must be independent of leg posture.
A theoretical calculation of the electric field induced by magnetic stimulation of a peripheral nerve
Authors: Roth Bradley J. , Cohen Leonardo G. , Hallett Mark , Friauf Walter , Basser Peter J. 
Published: January 2005

AbstractA mathematical model is presented that predicts the electric field induced in the arm during magnetic stimulation of a peripheral nerve. The arm is represented as a homogeneous, cylindrical volume conductor. The electric field arises from two sources: the time‐varying magnetic field and the accumulation of charge on the arm surface. In magnetic stimulation both of these contributions are significant. The magnitude of the electric field is greatest near the surface of the arm, and is well localized. Various coil orientations are examined; the smallest electric fields are induced when the coil is perpendicular to the arm surface, the largest when the coil is parallel. These results are consistent with many experimental observations in the literature, and aid in the basic understanding of magnetic stimulation of the peripheral nervous system.
Neuromuscular transmission in the mdx mouse
Authors: Nagel Alexandre , Lehmann‐Horn Frank , Engel Andrew G. 
Published: January 2005

AbstractThe mdx mouse is an animal model for human Duchenne dystrophy. In both disorders, the muscle fiber plasma membrane is rendered selectively vulnerable by dystrophin deficiency. In both disorders there are also ultrastructural abnormalities involving the postsynaptic membrane of the neuromuscular junction. The object of this electrophysiologic study was to determine whether the observed ultrastructural abnormalities at the mdx neuromuscular junction are associated with an abnormality of neuromuscular transmission. In comparison with age‐matched control mice, the mdx mice show an abnormal, age‐dependent decrease of the amplitude of the miniature end‐plate potential and aconcomitant increase in the quantal content of the end‐plate potential. Consequently, the safety margin of neuromuscular transmission is not impaired.