摘要:

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 lesion

ISSN:0148-639X    

DOI:10.1002/mus.880130402

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

年代:1990

数据来源: WILEY

摘要:

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 twitche

ISSN:0148-639X    

DOI:10.1002/mus.880130403

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

年代:1990

数据来源: WILEY

摘要:

AbstractA 22‐year‐old male was studied 3½–&4½ years after a traumatic section‐avulsion amputation of the left upper extremity at the level of the distal humerus. The arm was reattached after a cold ischemia time of 4–5 hours and good vascularization was obtained. The ulnar nerve was repaired early with an end‐to‐end juncture while the median and radial nerves were repaired after seven months delay using a combination of vascularized radial nerve and nonvascularized sural nerve grafts. Some intrinsic hand muscle function had recovered. Pin‐prick and touch sensation was present in all digits, although localization of touch stimulation was poor. Evoked motor responses had recovered by 25–50% of control amplitude in ulnar‐innervated and by 10–25% in median‐innervated muscles. Amplitudes of sensory responses from digit V had recovered by 25% and from digits I and III by 1–5%. Fast‐adapting touch receptors had become reinnervated. There was electrophysiological evidence of aberrant sensory regeneration and of abnormal connections between sensory and motor fibers. Digital blood flow measurements suggested the presence of vascular obstruction in vessels of the replanted upper extremity. However, the digital vasconstriction during cold exposure indicated regeneratio

ISSN:0148-639X    

DOI:10.1002/mus.880130404

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe onset and pattern of muscle precursor replication in minced skeletal muscle isografts were examined autoradiographically in 22 BALBc and 23 Swiss mice. Tritiated thymidine was injected into mice at various times after grafting to label replicating muscle precursors and regenerated muscle isografts removed 14 days after grafting when labeled precursors had fused into myotubes. Analysis of labeled myotube nuclei in regenerated minced isografts showed a difference between the onset of DNA synthesis in muscle precursors of the two strains, although precursor proliferation peaked around day 5 and was greatly reduced by day 8 in both strains. The onset and duration of muscle precursor replication was similar to that seen in isografts of intact whole muscles: however, precursor proliferation was delayed and protracted compared with injured muscles. This autoradiographic model enables quantitative investigations of muscle precursor behavior in vivo, with clinical potential for improving muscle regeneration after severe injury, transplantation, and some myopathies.

ISSN:0148-639X    

DOI:10.1002/mus.880130405

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

年代:1990

数据来源: WILEY

摘要:

AbstractDistribution of conduction velocities (DCV) of sensory fibers in sural nerve was investigated in three patients with n‐hexane poisoning. Measurements were made at 1–2 months, 4–9 months, and at 11, 23, and 36 months after ending exposure. A sural nerve biopsy was obtained from one of the patients. The results indicated the characteristic changes of n‐hexane toxicity: myelinated nerve fiber degeneration and paranodal swelling, resulting in changes in the fiber diameter distribution. The DCV documented these changes. After removal from toxic exposure, varying degrees of recovery were studied clinically and evaluated with nerve conduction parameters. The DCV reflects the pathological changes in nerve in toxic neuropathy due to n

ISSN:0148-639X    

DOI:10.1002/mus.880130406

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

年代:1990

数据来源: WILEY

摘要:

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 membra

ISSN:0148-639X    

DOI:10.1002/mus.880130407

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

年代:1990

数据来源: WILEY

摘要:

AbstractA patient with slow muscle relaxation but without accompanying motor unit or myotonic electrical activity had a unique staircase twitch response to repeated nerve stimulation. During 1‐Hz stimulation, twitches recorded by measurement of the ankle dorsiflexor group displayed progressively increasing relaxation times with successive stimuli (37% increase) unlike the progressively decreasing relaxation time of the normal response (12–37% decrease). The response may be diagnostic of this unusual myopathy; the test methods are noninvasive and easily tolera

ISSN:0148-639X    

DOI:10.1002/mus.880130408

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

年代:1990

数据来源: WILEY

摘要:

AbstractRecent studies of patients with mitochondrial myopathies suggest the existence of both muscle‐specific and developmentally regulated isoforms of cytochromecoxidase (COX), the terminal enzyme complex of the electron transport chain. To investigate the temporal pattern of gene expression of nuclear genes for COX in developing muscle, the steady‐state levels of COX mRNA in total RNA from a satellite cell‐derived mouse muscle cell line, C2C12, were analyzed and compared with COX mRNA levels in mature rat skeletal muscle. Undifferentiated myoblasts, myotubes just after fusion (early myotubes), and fully differentiated, contractile, striated myotubes (late myotubes) were analyzed for mRNA levels for four of the 10 different nuclear‐encoded COX subunits: IV, Vb, VIc and VIII‐liver. Of these, IV, Vb and VIc are identical in both bovine heart and liver, whereas subunit VIII has heart and liver isoforms. In C2C12 myoblasts, the level of mRNA for subunits IV, Vb, and VIII‐liver is equal to or greater than the level in tissues such as brain, skeletal muscle, and liver. As myoblasts fuse and differentiate into myotubes, the levels of mRNA for these subunits undergo radically different changes. Transcripts for subunits IV and Vb accumulate to higher levels during myogenesis. The level of subunit VIII transcripts decreases during myogenesis, providing additional evidence that subunit VIII has tissue‐specific isoforms in the rat. Little mRNA for COX VIc was detected in either the C2C12 cell line or in primary embryonic rat myoblasts or myotubes in culture in spite of high levels in adult skeletal muscles, suggesting that subunit VIc may have both fetal and adult isofor

ISSN:0148-639X    

DOI:10.1002/mus.880130409

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

年代:1990

数据来源: WILEY

摘要:

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.

ISSN:0148-639X    

DOI:10.1002/mus.880130410

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

年代:1990

数据来源: WILEY

摘要:

AbstractAlpha‐actinin is a muscle protein located along the Z‐disc. Incubation of frog muscle with the calcium ionophore, A23187, can decrease the immunogold labelling of alpha‐actinin.14Pyridostigmine (PYR) is an inhibitor of acetylcholinesterase, which causes disruption of Z‐discs only in the region of the motor endplate. This is probably due to excess influx of calcium ions, leading to activation of proteases. Pretreating animals with the calcium channel blocker diltiazem can significantly reduce damage to the Z‐discs at the motor endplate caused by PYR. It was of interest to determine whether the distribution of alpha‐actinin had been altered following PYR administration and whether diltiazem could prevent those changes. There was less alpha‐actinin labelling at the motor endplate compared to away from this region for all treatment groups. Animals administered diltiazem showed less labelling compared to PYR, but with no disruption of Z‐discs at the motor endplate following diltiazem. Pretreatment with diltiazem reduced the incidence of Z‐disc damage, but the degree of alpha‐actinin labeling at the endplate was less than that seen with diltiazem alone. The greater effect seen at the endplate implies that neuromuscular activity is an important factor. The drugs may be causing a reduction in alpha‐actinin labelling by

ISSN:0148-639X    

DOI:10.1002/mus.880130411

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

年代:1990

数据来源: WILEY