摘要:

AbstractThe physiologic and histologic principles underlying clinical electromyographic studies are briefly reviewed as an introduction to the normal and abnormal findings in human subjects. Technical aspects of recordings as well as the specific types of discharges and their, significance are discussed.

ISSN:0148-639X    

DOI:10.1002/mus.880140802

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractAn endogenous inhibitor for calcium‐activated neutral protease (CANP) from skeletal and cardiac muscles of muscular dystrophic hamsters (UMX 7.1) was compared with that from normal control animals at 4 and 10 weeks of age by Western blotting using antibody raised against CANP inhibitor. Fragmented CANP inhibitor was found in dystrophic skeletal muscles in all cases at both ages, while only intact inhibitor was detected in the skeletal muscle of the normal hamsters. A total absence of intact inhibitor was shown in one 10‐week‐old dystrophic hamster. In contrast, there was little difference in CANP inhibitor from heart between dystrophic and control hamsters at 4 weeks. However, fragmentation similar to that in skeletal muscle was seen in the heart inhibitor in a few of the 10‐week‐old dystrophic

ISSN:0148-639X    

DOI:10.1002/mus.880140803

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractSubjects with at least one sensory action potential (SAP) amplitude greater than 2 SD above the age‐matched mean during standard nerve conduction tests were evaluated for evidence of spinal cord disease. From a total of 153 subjects, 16 had at least one large amplitude SAP and 12 of 16 (75%) had a documented myelopathy. While a mechanism has yet to be determined, this observation suggests that SAP amplitudes greater than 2 SD above normal may be correlated with clinical evidence of injury to the central nervous syste

ISSN:0148-639X    

DOI:10.1002/mus.880140804

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractMagnetic resonance imaging (MRI) of the muscles was performed in patients with polymyositis and dermatomyositis. Lesions with high intensity on T2‐weighted image, but normal intensity on T1‐weighted image, were observed in 7 of 8 patients in the active stage of the disease. Following clinical improvement with corticosteroid therapy in 4 patients, the high intensity lesions reverted to normal. The high intensity lesions seen on T2‐weighted image in the active stage may represent edema and inflammation of the muscle. MRI of the muscle may serve as a diagnostic tool and be useful for follow‐up of the patients with polymyositis or dermatom

ISSN:0148-639X    

DOI:10.1002/mus.880140805

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractSomatosensory evoked potentials (SEPs) were recorded from the scalp in man to magnetic stimulation of various skeletal muscles. The potentials consisted of several components, the earliest of which decreased in latency as the stimulated site moved rostrally, ranging from 46 msec for stimulation of the gastrocnemius, to 14 msec for stimulation of the deltoid. Experiments were performed to distinguish the mechanisms by which magnetic stimulation of the muscle was effective in evoking these cerebral potentials. For the gastrocnemius, the intensity of the magnetic stimulus needed for evoking cerebral potentials was less than that required for activating mixed or sensory nerves in proximity to the muscle belly (eg, posterior tibial nerve in the popliteal fossa, sural nerve at the ankle). Vibration of the muscle or passive lengthening of the muscle, procedures which activate muscle spindles, were accompanied by a significant attenuation of the potentials evoked by magnetic stimulation of the muscle. Anesthesia of the skin underlying the stimulating coil had no effect on the latency or amplitude of the early components of the magnetically evoked potentials, whereas electrically evoked potentials from skin electrodes were abolished. Thus, the cerebral potentials accompanying magnetic stimulation of the muscle appear to be due to activation of muscle afferents. We suggest that magnetic stimulation of muscle can provide a relatively simple method for quantifying the function of muscle afferents originating from a wide variety of skeletal musculature.

ISSN:0148-639X    

DOI:10.1002/mus.880140806

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractTwo processes account for most instances of ulnar neuropathy at the elbow: compression in the retroepicondylar groove, and compression by the humeroulnar aponeurotic arcade joining the two heads of the flexor carpi ulnaris. While conventional electrodiagnostic criteria may localize an ulnar neuropathy to the elbow, separating retroepicondylar compression from humeroulnar arcade compression is more difficult. In 130 cadaver elbows, we examined the relationships between the medial epicondyle, flexor carpi ulnaris, and ulnar nerve. The humeroulnar arcade lay from 3 to 20 mm distal to the medial epicondyle, the intramuscular course of the nerve through the flexor carpi ulnaris ranged from 18 to 70 mm, and the nerve exited the flexor carpi ulnaris 28 to 69 mm distal to the medial epicondyle. In 6 specimens, dense fibrous bands bridged directly between the medial epicondyle and the olecranon proximal to the cubital tunnel proper; accessory epitrochleoanconeus muscles were present in 14 specimens: both may cause ulnar neuropathy at the elbow. Anatomical variations may contribute to the difficulty in separating causes of ulnar neuropathy at the elbow.

ISSN:0148-639X    

DOI:10.1002/mus.880140807

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractDirect 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.

ISSN:0148-639X    

DOI:10.1002/mus.880140808

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA comparison has been made between the responses of denervated mouse soleus muscles to direct electrical stimulation, as reported by earlier workers, and to incubation with supraphysiological concentrations of insulin. The parameters of interest were resting membrane potential (RMP), qualities of the active state, the amount of alpha bungarotoxin (BUTX) binding, and chemosensitivity, as measured by the strength of acetylcholine (ACh)‐induced contractures. In all aspects, the changes recorded after insulin, were in the same direction as with direct stimulation, however, owing to the time limitations of in vitro testing were smaller. It is suggested that the effects of electric shocks on denervated muscles are the result of activation of the insulin receptor, or some similar macromolecule, which appears to be sensitive to the membrane potential. The possible interrelations between acetylcholine and insulin receptors in neurotrophic control are discusse

ISSN:0148-639X    

DOI:10.1002/mus.880140809

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractMeasurements were done on the biceps muscles of 6 healthy volunteers to record simultaneously the surface electromyogram (EMG) and vibromyogram (VMG) by means of a piezoelectric device (accelerometer). The VMG is generated by mechanical waves due to the contraction mechanism and often measured as sound. The frequency spectrum and integrated value (IEMG and IVMG) of both signals were calculated. Both IEMG and IVMG showed a clear linear correlation with force, although at high forces, the variability of the VMG became rather high. Two series of experiments were performed to study the EMG and VMG changes in relation to changes induced by fatigue: (1) during constant force at 50% of the maximal voluntary contraction (MVC) and recovery; (2) for one 1 minute during declining force at MVC. The main finding was that the IVMG was related to the absolute force, irrespective of the fatigue state of the muscle. In contrast, the IEMG showed the well‐known changes during fatigue, such as an increase during endurance. The spectral changes of the two measurements also showed a divergence. The spectra of the EMG shifted to lower frequencies in both fatigue protocols. In contrast, the spectra of the vibratory signal did not shift, except for several measurements at MVC. However, the shape did change to a somewhat flatter spectrum with less pronounced peaks. Possible explanations for this different behavior are discussed. It is concluded that the vibratory energy generated by the contraction mechanism is linearly related to force. Changes induced by fatigue do not alter this relationship: this contrasts with the behavior of the EMG. The combination of these two measurements give supplemental information regarding the state of the working muscl

ISSN:0148-639X    

DOI:10.1002/mus.880140810

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractIntact muscle fibers or resealed fiber segments from 7 patients with recessive generalized myotonia were studied in vitro. All fibers had normal resting membrane potentials and normal resting [Ca2+]iseveral hours after removal. Contractions were characterized by slowed relaxation which was due to electrical after‐activity. Often spontaneous depolarizations were recorded intracellularly. In all fibers, the steady state voltage‐current relationship was abnormal, due to a reduced Cl2+conductance. However, this conductance ranged from 0% to 66% of the total membrane conductance, whereas, in normal muscle, it was 80%. Theoretically, myotonic after‐discharges would not appear until the Cl−conductance is below 20%. Thus, the membrane hyperexcitability must be due to another defect, at least in the preparations in which the Cl−conductance was only slightly reduced. In all patches from all patients investigated with the patch clamp technique, we observed reopenings of the Na+channels throughout depolarizing pulses (such behavior was absent in normal muscle). If a patch was polarized to potentials less negative than the resting potential, the duration of the reopenings increased. We conclude that a combination of reduced Cl−conductance and the reopenings of Na+channels underlie the electrical afteractivity in recessive generaliz

ISSN:0148-639X    

DOI:10.1002/mus.880140811

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY