摘要:

AbstractMotor unit recruitment is the process by which different motor units are activated to produce a given level and type of muscle contraction. At minimal levels of muscle contraction (innervation), muscle force is graded by changes in firing rate (rate coding) of individual motoneurons (MNs). At higher levels of innervation, recruitment is accomplished by the addition of different motor units firing at or above physiologic tremor rate. During slowly graded and ballistic increases in force, motor units are recruited in rank order of their size. In addition to MN soma diameter, other factors contribute to the selectivity of MN activation. For la afferent MN activation in the cat, synaptic density and efficacy as well as specific membrane resistance are also rank ordered for slow, fatigue resistant, and fast fatigue motor units with slow motor units recruited first. The central drive for motor unit activation is distributed to all the MNs of the pool serving a given muscle. Size‐structure organization of the MN pool determines the order of recruitment and how MNs interact with each other. Disorders of the motor unit affect recruitment. A method for the clinical electromyographic assessment of recruitment is suggested. Assessment is made at three levels of innervation:minimal contractionfor onset and recruitment firing rates;moderate contractionrequired to maintain the limb against gravity for the maximum number of motor units, their firing rates, and motor unit spikes/s;maximal voluntarycontraction (MVC) for detection of high threshold enlarged motor units characteristic of reinnervation and completeness of the interference pattern (IP). Loss of muscle fibers results in early and excessive recruitment at minimal and moderate levels of innervation. Loss of motor units can result in both an increased rate and range of single motor unit firing at all levels of innervation. With reinnervation and enlargement of motor units, firing rates increase significantly and the interference pattern during MVC is incomplet

ISSN:0148-639X    

DOI:10.1002/mus.880140602

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe have demonstrated that maneuvers capable of reducing Ca influx into cells have beneficial effects in dystrophic hamsters and Duchenne muscular dystrophy. Since dantrolene inhibits Ca release from the sarcoplasmic reticulum, its effects on DMD was studied in 7 patients of 6 to 13 years of age (mean 10.8 years). Patients were studied for 4 years with tri‐monthly evaluations of manual muscle testing (MMT), functional activity, and serum CK and aldolase. During the first 2‐year period, no medicines were given and served as control. In the second 2‐year period, dantfblene 8 mg/kg/d was administered. No side effects were observed. In 1 patient, mild, weakness occurred that disappeared when the dose was reduced to 6 mg/kg/d. The 95% confidence limit for the difference in slopes of regression lines from tri‐monthly MMT was asymmetric in favor of dantrolerte in 5 of 7 patients. Serum CK did not differ between the first and second year of the control and treatment periods, respectively. However, it fell significantly from the second year of control to the first year of treatment (P= 0.003). The fall during the first year of treatment was significantly greater (P<0.01) than in age‐matched natural history controls during the same length of observation. There was a 3‐fold reduction in CK when the pooled values of the first and second year control vs. treatment periods were analyzed. No changes were observed in functional activity and serum aidolase. The data suggest that dantrolene reduces serum CK in DMD associated with a lessening trend in MMT de

ISSN:0148-639X    

DOI:10.1002/mus.880140603

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe thin afferent nerves were tested quantitatively by determining the thresholds of warmth and pricking pain to argon laser stimulation and by measuring the brain potentials related to pricking pain. In 27 patients with electrophysiologically verified carpal tunnel syndrome these parameters were measured from fingers 3 and 5 on both hands. All patients had had sensory symptoms ranging from 3 months to 25 years. Both the thresholds were elevated (P<0.05) at finger 3 compared to measurements from finger 5, and compared to finger 3 in a group of 39 controls. Four patients with symptoms for more than 7 years had thresholds below the control values. The power of the pain‐evoked brain potentials elicited from finger 3 was lower (P<0.05) compared to finger 5, and compared to the control group (P<0.01). No correlations were found between the measured parameters and the clinical electrophysiological investigation. The findings support previous assumptions that chronic low‐force compressions cause impairment of intraneural microcirculation, and hence can affect the function of the thin affere

ISSN:0148-639X    

DOI:10.1002/mus.880140604

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

年代:1991

数据来源: WILEY

摘要:

AbstractImmunohistochemical analysis of the inflammatory cells and complement C3 in the rat skeletal muscle was performed chronologically in bupivacaine‐induced myonecrosis. At 30 minutes after injection, polymorphonuclear leukocytes appeared and increased in number, with a peak value at 12 hours, while macrophages reached the highest level at 2 days. In contrast, T cells comprised only a small population. Two weeks after the injection, all types of the inflammatory cells returned to the normal level. Deposition of complement C3 was recognized at 60 minutes at the surface membrane of de erating muscle fiber. Our observation suggests the importance of both polymorphonuclear leukocytes and complement C3 in the early stage, and macrophages in the later stage of bupivacaine‐induced myonecrosis. In addition, our findings cast doubt on the pathological significance of T cells in this mo

ISSN:0148-639X    

DOI:10.1002/mus.880140605

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

年代:1991

数据来源: WILEY

摘要:

AbstractInvasive electromyography (EMG) of the paraspinal muscles is useful in clinical and research settings. No technique for localization of the needle in specific fascicles has been validated. Recent descriptions of the segmented innervation of the multifidus imply that such a technique would add greatly to the EMG determination of root level of a radiculopathy. We have developed a technique for localization which relies on palpation of bony structures and needle insertion at certain angles and depths. The technique was evaluated by injecting latex dye in 199 locations in 13 cadavers. Dissection demonstrated that the technique was accurate in 91 of 112 injections into specific fascicles of the multifidus (originating from different spinous processes), 39 of 43 injections into the longissimus, and 35 of 44 injections into the iliocostalis. Certain types of errors would not have occurred with the aid of EMG in vivo. When these are added to the correct injections, accuracy improves 97%, 93%, and 82%, respectively. The technique described here should be useful for kinesiological studies, biopsies and injections, as well as for the EMG confirmation of a radiculopathy.

ISSN:0148-639X    

DOI:10.1002/mus.880140606

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

年代:1991

数据来源: WILEY

摘要:

AbstractUltrasound (US) technique was applied to measure the thickness, crosssectional area (CSA), and internal structure of the quadriceps muscle ih 70‐to 80‐year‐old endurance and power athletes and untrained men. Isometric knee extension strength was higher in the power athletes than in the other groups. The mean values for thickness and CSA did not differ between the athletes and the untrained men. The intensity of the intramuscula echo was, however, lower and the echo reflected from the connective tissue septa and bone was higher in the athletes than in the untrained men. Both the CSA and internal structure of the muscle group correlated signifjaayntly with muscle strength and number of training kilometers per year. The resuits suggest that long‐term training maintains the muscle architecture and counteracts the age‐related replacement of contractile tissue by other tissues su

ISSN:0148-639X    

DOI:10.1002/mus.880140607

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe main component of the compound sensory action potential reflects the activity of large myelinated sensory fibers with diameters of greater than 9 μm. By recording the averaged potential using a needle electrode placed close to the nerve, small late components can be measured. The latency of these late components can be used to calculate minimum conduction velocity (CV); in normal subjects, average minimum CV is 15 m/s, correspending to conduction in fibers of about 4 μm in diameter. Minimum CV was measured in median, ulnar, and sural nerves of 187 patients with mild to severe neuropathic symptoms. A reduction in minimum CV was a sensitive measure of peripheral nerve dysfunction, often showing abnormalities when measures derived from the main component were normal. Patients with isolated abnormalities in minimum CV tended to have neuropathic symptoms but no signs of neuropathy. In addition, reduced minimum conduction velocity has implications for the pathology of different types of neuropathy. Slowing conducting potentials may originate from regenerating fibers, which may be of particular relevance in patients with neuropathic pai

ISSN:0148-639X    

DOI:10.1002/mus.880140608

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn murine muscular dystrophy, hindlimb muscle contains a functionally defective thiol protease inhibitor (TPI) which has been implicated in the onset and progression of the disease in mice. More recently, this protease inhibitor has been identified as parvalbumin, a calcium binding protein. In this study, a polyclonal antibody against mouse muscle parvalbumin was used to study the concentration and distribution of this protein in normal and dystrophic male mice at various ages. Immunodetection assays were used to screen extracts of hindlimb, forelimb, brain, heart, lung, liver, and kidney in 60‐day‐old normal and dystrophic male mice for parvalbumin content. Parvalbumin was detected in relatively high amounts in both hindlimb and forelimb muscle extracts, while much lower concentrations were detected in brains of normal and dystrophic animals. No parvalbumin was detected in the lung, liver, heart, or kidney extracts using the immunoassay. With aging, the parvalbumin concentration in hindlimb muscle of normal mice remained fairly constant for 90 days, whereupon the level increased at 120 days. In contrast, the parvalbumin concentration in hindlimb muscle of dystrophic mice decreased steadily with age to about 22%% of normal animals at 120 days. The parvalbumin content was also reduced in dystrophic br

ISSN:0148-639X    

DOI:10.1002/mus.880140609

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn rabbits, the tibial nerve was exposed in the lower thigh under general anesthesia and cooled in a metal trough at 1 to 2°C or 5°C for 2, 3, or 4 hours. Nerve conduction studies showed local failure of conduction at the site of cooling which persisted after rewarming, and which was followed by distal degeneration of affected fibers. No persistent conduction block was seen. Changes in maximal velocity indicated that the fastest‐conducting motor and afferent axons had been preferentially affected. Histological finding in nerves examined at different intervals after cooling confirmed the physiological evidence of primary axonal damage, affecting particularly large diameter fibers. Paranodal demyelination was inconspicuous and restricted to regions just proximal to sites of axonal degeneration. No segmental demyelination was seen. These results clarify previous uncertainties as to the time‐course and distribution of nerve damage after local cooling at temperatures just above freezing

ISSN:0148-639X    

DOI:10.1002/mus.880140610

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to examine the effects of 3 weeks of immobilization on the mechanical properties of motor units in a cat hindlimb muscle. The muscle, tibialis posterior, was immobilized in a shortened position. Motor units were classified as type FF, F(int), FR, or S. Force, axonal conduction velocity, fatigability, and proportions of motor unit types were compared in control and immobilized muscles. All properties exhibited some change after immobilization, including slower axonal conduction velocities, greater twitch forces, slower twitch contraction times, and greater tetanic forces. In addition, most motor units were less fatigable after immobilization. The number of motor units that could not be included in one of the four classification categories increased significantly after immobilization; these units exhibited normal axon conductivity but failed to produce measurable force or associated EMG. Short‐term immobilization induced a variety of physiological adaptations in neuromuscular processes that varied with motor unit typ

ISSN:0148-639X    

DOI:10.1002/mus.880140611

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

年代:1991

数据来源: WILEY