ISSN:0148-639X    

DOI:10.1002/mus.880150202

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe relationship between the discharge frequencies of motoneurons and the voluntary force at high contraction strengths (50% to 100%maximum) was determined for tibialis anterior with the ankle: (i) at 90° (control length) and (ii) this angle reduced by about 15° (short length), an amount sufficient to reduce the maximal voluntary force by about 35%. In the shortened position, twitch contraction and half‐relaxation times were reduced by 11% and 18%, respectively. At both muscle lengths, the ability to activate the muscle fully by voluntary effort was confirmed by twitch interpolation. Motor unit firing rates were recorded during isometric voluntary contractions lasting 10 seconds, performed at 50%, 75%, and 100% maximal force. At each length, discharge rates varied in proportion to the relative force exerted. Despite the difference in twitch contractile speed at the two lengths, no significant differences were found between motoneuron discharge rates recorded at each muscle length during maximal or submaximal contracti

ISSN:0148-639X    

DOI:10.1002/mus.880150203

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to quantify the changes in motor‐unit action potentials (MUAP) and force during a standard motor‐unit fatigue test. MUAP waveforms were characterized by the measurement of amplitude, duration, area, and shape (as reflected in a coefficient of proportionality). Fatigue‐resistant motor units exhibited small, but statistically significant, changes in MUAP amplitude and area during the fatigue test, whereas fatigable motor units displayed variable changes in MUAP amplitude, duration, and area. For all motor‐unit types, the coefficient of proportionality did not change, and hence the change in MUAP area was proportional to the combined changes in amplitude and duration. The between‐ and withintrain changes in MUAP were also distinct for the fatigue‐resistant and fatigable motor units. Although several mechanisms could be responsible for the changes in the MUAP as the fatigue test proceeded, the dissociation of the time courses for MUAP and force indicated that these MUAP changes were not the principal reason for the decline in force under these

ISSN:0148-639X    

DOI:10.1002/mus.880150204

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

年代:1992

数据来源: WILEY

摘要:

AbstractSingle fiber electromyography (SFEMG) measurements of fiber density and jitter are used in the diagnosis of a variety of peripheral nervous system disorders. However, the normal values of these measurements for most muscles and age groups are not well documented in the literature. We present a retrospective and prospective multicenter collection of SFEMG jitter and fiber density data from control subjects obtained for the purpose of defining reference values for many muscles and different ages. The data and calculated upper limits for fiber density, individual pair jitter, and mean jitter are presented for each muscle in tabular and graphical format, for different age groups.

ISSN:0148-639X    

DOI:10.1002/mus.880150205

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to determine the concentration of Ca2+–ATPase and Na+‐K+–ATPase in biopsies from vastus lateralis muscle of 24 patients, who underwent a diagnostic contracture test for susceptibility to malignant hyperthermia (MH). Ca2+–ATPase was quantified as the Ca2+‐dependent32P incorporation in whole muscle homogenates. Na+‐K+–ATPase was quantified as the [3H]ouabain‐binding capacity in intact muscle samples. These methods avoid isolation of membranes, a procedure that may influence the results due to interindividual variation in recovery. The results show that both enzymes can be determined in (frozen) muscle biopsies weighing 50 mg. Neither the concentration of Ca2+–ATPase nor that of Na+‐K+–ATPase differed in biopsies from subjects diagnosed as susceptible (MHS) or nonsusceptible (MHN) to MH. Our data support the view that changes in the concentration of Ca2+–ATPase and/or Na+‐K+–ATPase do not play a primary rol

ISSN:0148-639X    

DOI:10.1002/mus.880150206

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe fiber density in the deltoid, extensor digitorum communis, and first dorsal interosseous muscles was measured using SFEMG in 11 patients with acute and chronic inflammatory demyelinating polyneuropathy. The fiber density was increased in 58% of the muscles studied. The deltoid muscle was the most abnormal of the 3 muscles studied. There was no correlation with the clinical syndrome, with conduction block or slowed motor conduction, or with the distribution of weakness. Changes were noted even in patients studied within 3 weeks of presentation, suggesting that reinnervation begins soon after the onset of the disease.

ISSN:0148-639X    

DOI:10.1002/mus.880150207

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe describe a new neuromuscular disorder in the kyphoscoliotic mouse mutant (ky). Mice were killed at ages from birth to 210 days, and tissues were taken for standard light microscopy, histochemistry, nerve ending studies, and electron microscopy. At birth a few myofibers showed phagocytosis ultrastructurally. Between 6 and 25 days there was prominent necrosis and regeneration in soleus, gracilis, paraspinal, and back muscles. At 47 days, these muscles were atrophic and necrosis and regeneration were rare. At 136 days, all muscle groups, including head muscles, showed some degree of myofiber atrophy and gracilis was fibrotic. Prominent intramuscular axonal sprouting was present from 31 days. Peripheral nerves and anterior horn cells were normal. The findings indicate a neuromuscular basis of hereditary kyphoscoliosis in the mouse. The animal may be useful as a model of human muscle disease and scoliosis.

ISSN:0148-639X    

DOI:10.1002/mus.880150208

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

年代:1992

数据来源: WILEY

摘要:

AbstractContemporary equipment used for nerve conduction studies is usually capable of computerized measurement of latency, amplitude, duration, and area of nerve and muscle action potentials and resulting conduction velocities. Abnormalities can be due to technical error or disease. Identification of technical error is a major element of quality control in electromyography, and artificial intelligence could be useful for this purpose. We have developed a coupled knowledge‐based prototype system (QUALICON) to assess the correctness of recording and stimulating characteristics in routine conduction studies. QUALICON extracts numeric features from CMAPs or SNAPs, which are translated into symbolic form to drive a Bayesian network. The network uses high‐level knowledge to infer the quality of stimulating and recording electrode placement as well as polarity and stimulus strength making recommendations as to the likely technical error when abnormal potentials are detected. A preliminary assessment shows that QUALICON performs as well as manual assessment performed by profession

ISSN:0148-639X    

DOI:10.1002/mus.880150209

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

年代:1992

数据来源: WILEY

摘要:

AbstractClenbuterol has been shown to ameliorate denervation‐induced atrophy and, therefore, clearly has therapeutic potential in the treatment of muscle wasting conditions in man. Previous studies have used dosages in rats which would be unacceptable in clinical practice, but the present results show that denervated muscle has a greater sensitivity to the drug than innervated or cardiac muscle. Fiber hypertrophy and an increase in protein and RNA content could be observed in denervated muscles but not in innervated muscles at a dose of 10 μg/kg body weight. When considered on a metabolic body weight basis, the effective dose in rats and the "safe" dose in man are surprisingly comparable. The observations imply that there is good reason to suppose that clenbuterol could be effective in ameliorating similar wasting conditions in m

ISSN:0148-639X    

DOI:10.1002/mus.880150210

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe values obtained from two different macro EMG methods were compared, and found to be different. Normally, macro electromyography (EMG) is performed with a modified single fiber (SF) needle using the SF potential as a trigger; a new method recommends a modified concentric needle and triggers on the concentric EMG signal. The concentric macro EMG has a 40% to 50% smaller amplitude and area values than data obtained with a SF macro EMG needle. The different values are the result of variant spatial relationships of the respective needles to the motor unit under stud, and may be due to a recruitment‐dependent bias resulting from different trigger properties of the two methods. The concentric macro EMG needle can be used to estimate motor unit size, to scan the unit, and to investigate its different concentric EMG signal

ISSN:0148-639X    

DOI:10.1002/mus.880150211

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

年代:1992

数据来源: WILEY