ISSN:0148-639X    

DOI:10.1002/mus.880020302

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

年代:1979

数据来源: WILEY

摘要:

AbstractElectrophysiologic properties of biopsied normal and diseased intercostal muscle fibers were examined using intracellular microelectrode techniques. The resting potentials of all diseased muscle fibers were found to be depolarized. Those from Duchenne dystrophy patients showed the largest depolarization, followed by those from patients with myotonic muscular dystrophy, myotonia congenita, and motor neuron disease. All of the diseased fibers except those from myotonia congenita patients demonstrated an impaired ability to generate action potentials. In the latter fibers, the higher‐than‐normal membrane resistance was associated with hyperexcitability. When the membrane was hyperpolarized to the normal range, however, action potential characteristics in all fibers were near normal, except in motor neuron disease. All action potentials were blocked by tetrodotoxin. These findings—i.e., that all fibers were capable of generating action potentials when hyperpolarized, and that all action potentials were blocked by tetrodotoxin—suggest the relative intactness, in the disease studied here, of the regenerative sodium conductance me

ISSN:0148-639X    

DOI:10.1002/mus.880020303

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

年代:1979

数据来源: WILEY

摘要:

AbstractImmunization of groups of rats with 0.1–100 μg of acetylcholine receptor (AChR) purified from the electric organ ofTorpedo californicaresulted in dose‐dependent (1) loss of acetylcholine receptor from the rats' muscles, (2) binding of antibodies to many of the receptors remaining in muscle, and (3) production of antibodies in serum capable of cross‐reacting with receptor solubilized from rat muscle. Addition of antibodies from rats immunized with electric organ acetylcholine receptors to muscle cells in culture caused loss of receptor by accelerating the rate of receptor degradation. Monovalent antibody fragments did not accelerate degradation unless antiantibody was added to cross‐link the monovalent antibody fragments bound to receptors. This indicates that cross‐linking of receptors by antibody molecules triggers accelerated receptor degradation, leading to receptor loss. The rate of increase in receptor destruction due to antigenic modulation observed in vitro appears sufficient to account for the extent of receptor loss observed in vivo. Endocytosis of antibody cross‐linked receptors may be a rate‐limiting step common to antigenic modulation in vit

ISSN:0148-639X    

DOI:10.1002/mus.880020304

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

年代:1979

数据来源: WILEY

摘要:

AbstractTreatment of patients with D‐penicillamine (D‐P) has been associated with a syndrome similar to myasthenia gravis (MG). To explore this association, we examined the effects of D‐P on neuromuscular transmission in rat muscle. In the first experiment, bath‐applied D‐P had no significant effect on either miniature endplate potential (MEPP) amplitude or action potential (AP) amplitude. Endplate potential (EPP) amplitude and spontaneous MEPP frequency decreased significantly at concentrations approximately 40 times the maximum human therapeutic level. In the second experiment, rats receiving D‐P by daily injections for 33 to 37 days did not differ from controls in any of the measured electrophysiologic characteristics. Electron microscopy of muscle endplates from rats treated with D‐P showed no evidence of degeneration or simplification. In all cases, thymus histology by light microscopy was normal, and no antireceptor antibodies were found. Thus, D‐P has a mild direct presynaptic effect on neuromuscular transmission at high concentrations, but this effect is too small to account for the weakness seen in the myasthenia‐like s

ISSN:0148-639X    

DOI:10.1002/mus.880020305

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

年代:1979

数据来源: WILEY

摘要:

AbstractTo study the basis for the myasthenic illness that develops in some patients receiving D‐penicillamine (D‐P), we measured neuromuscular transmission in D‐P‐treated guinea pigs. Treated animals manifested edrophonium chloride–repairable decremental responses to 30‐Hz nerve stimulation (8.5% ± 1.5%—mean ± SEM; N = 16) compared with the response in saline‐treated control animals (−0.3% ± 0.85%, N = 10, p<0.005). Posttetanic phenomena were studied in 5 treated animals; 3 revealed posttetanic exhaustion. Miniature endplate potential (MEPP) amplitudes were significantly reduced in 11 treated animals (0.612 ± 0.016 mV) compared with 6 controls (0.713 ± 0.024 mV, p<0.01). The MEPP frequency appeared reduced in treated animals. Both MEPP amplitude and MEPP frequency correla

ISSN:0148-639X    

DOI:10.1002/mus.880020306

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

年代:1979

数据来源: WILEY

摘要:

AbstractWe compared the freeze‐fracture morphology of the plasmalemma of the pectoralis major muscle taken from normal and dystrophic chickens at adult, embryonic, and early posthatching stages. Developmental changes were more conspicuous in surface caveolae than in intramembranous particles. The most striking differences between normal and dystrophic muscles were seen in the densities of the caveolae (17/μm2in the normal adult; 30/μm2in the dystrophic adult) and in their distribution (rectangular pattern in normals; random arrangement in dystrophics). These differences had already become significant at seven days posthatching and before the appearance of clinical symptoms. This is the earliest developmental stage at which morphologic abnormalities of plasmalemma have been reported for dystrophic muscle. Variations of surface topography and caveolar morphology, presumably representing secondary changes, were common in adult dystrophic mus

ISSN:0148-639X    

DOI:10.1002/mus.880020307

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

年代:1979

数据来源: WILEY

摘要:

AbstractAging in the rodent is accompanied by a progressive loss of skeletal muscle fibers. The muscle twitch also becomes slower, probably as a result of fibertype conversion from “fast‐twitch” to “slow‐twitch.” The loss of muscle fibers precedes signs of obvious weakness and appears to involve the loss of entire functioning motor units. In the mouse, this loss of motor units correlates with a loss of axons from the innervating n

ISSN:0148-639X    

DOI:10.1002/mus.880020308

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

年代:1979

数据来源: WILEY

摘要:

AbstractMyoadenylate deaminase (adenosine monophosphate deaminase—AMPDA) was recently shown to be deficient in a group of patients by use of a histochemical and biochemical method based on the elaboration of ammonia by this enzyme as it deaminates 5′ AMP. We have confirmed the utility of this histochemical method and the existence of persons deficient in AMPDA through the use of an unrelated assay technique. The lack of enzyme activity is not associated with any inhibitory activity in the muscles of patients with this disorder. The clinical diversity of these patients suggests that this lack may represent a normal variant or a subclinical state rather than an actual disease. The occurrence of AMPDA deficiency in both sexes points to possible autosomal inherita

ISSN:0148-639X    

DOI:10.1002/mus.880020309

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

年代:1979

数据来源: WILEY

摘要:

AbstractMyelin‐forming Schwann cells in the peripheral nervous system characteristically surround and myelinate only single axons. Polyaxonal myelination is an anomaly of this one‐to‐one relationship whereby one normal‐appearing Schwann cell myelinates multiple axons. We examined the ventral roots and the proximal sciatic and posterior tibial nerves of developing normal mice and of dy2J/dy2Jdystrophic mice with proximal failure of myelination. Polyaxonal myelination was a rare feature in normal nerves. Examples of polyaxonal myelination were observed six times more often in dystrophic than in normal mice and were most abundant in proximal sciatic nerves. Polyaxonal myelination could result from either an axonal or a Schwann‐cell abnormality, or it may be the nonspecific response of uncommitted Schwann cells to an early failure of my

ISSN:0148-639X    

DOI:10.1002/mus.880020310

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

年代:1979

数据来源: WILEY

摘要:

AbstractMuscle breakdown and repair were measured by metabolic balance techniques in a patient with polymyositis who was being treated with prednisolone and azathioprine. Changes in body muscle mass that had been estimated from nitrogen and phosphorus balances correlated with anthropometric assessments of thigh muscle mass and quadriceps strength. Decline in muscle strength was associated with a net rate of muscle breakdown of 148 g/day. Recovery was associated with a net rate of muscle repair of up to 100 g/day. Early reduction in corticosteroid treatment appeared to enhance the rate of repair. Changes in the isometric contraction force of the quadriceps muscle (but not in clinical symptoms, plasma creatine kinase [CK] or erythrocyte sedimentation rate [ESR]) were found to reliably indicate whether the muscle was in a state of breakdown or repair. Treatment of the individual patient may be quantitatively monitored by metabolic balance studies or, more simply, by measurement of muscle strength.

ISSN:0148-639X    

DOI:10.1002/mus.880020311

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

年代:1979

数据来源: WILEY