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Sensitivity of the postsynpatic membrane to acetylcholine, the resting membrane potential, input resistance, and membrane time constant of fast muscle fibers were measured in experiments on frogs. Complete immobilization of the animals with D-tubocurarine or local immobilization of a muscle with α-bungarotoxin was found not to affect these parameters of the muscle membrane, whereas denervation of the muscle widens the zone of postsynaptic sensitivity to acetylcholine, lowers the resting membrane potential, and increases the input resistance and time constant of the muscle membrane. These results are evidence that neurotrophic control of the frog fast muscle fiber membrane is achieved mainly by substances reaching the muscle via axoplasmic transport and not by the character of the neuronal discharge and motor activity or by synaptic acetylcholine. 相似文献
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Electrical properties of the membrane and sensitivity of the fibers to acetylcholine were investigated in the frog sartorius muscle after denervation and a single application of colchicine to the nerve. After both types of procedure the electrical properties showed similar changes and extrasynaptic sensitivity to acetylcholine appeared. No such changes took place in the fibers of the contralateral muscle. Injection of colchicine into the lymphatic sac did not affect the electrical properties of the membrane, but widened the zone of sensitivity to acetylcholine. The results are regarded as further evidence in support of the view that denervation-like changes after application of colchicine to the motor nerve, when the transmission of excitation of nerve to muscle is preserved, are the result of a disturbance of the supply of neurotrophic substances along the axon by means of axoplasmic transport.Kazan' Medical Institute. I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 550–557, September–October, 1980. 相似文献
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Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene locus, is expressed on the muscle fiber surface. One key to further understanding of the cellular function of dystrophin would be extended knowledge about its subcellular organization. We have shown that dystrophin molecules are not uniformly distributed over the humen, rat, and mouse skeletal muscle fiber surface using three independent methods. Incubation of single-teased muscle fibers with antibodies to dystrophin revealed a network of denser transversal rings (costameres) and finer longitudinal interconnections. Double staining of longitudinal semithin cryosections for dystrophin and alpha-actinin showed spatial juxtaposition of the costameres to the Z bands. Where peripheral myonuclei precluded direct contact of dystrophin to the Z bands the organization of dystrophin was altered into lacunae harboring the myonucleus. These lacunae were surrounded by a dystrophin ring and covered by a more uniform dystrophin veil. Mechanical skinning of single-teased fibers revealed tighter mechanical connection of dystrophin to the plasma membrane than to the underlying internal domain of the muscle fiber. The entire dystrophin network remained preserved in its structure on isolated muscle sarcolemma and identical in appearance to the pattern observed on teased fibers. Therefore, connection of defined areas of plasma membrane or its constituents such as ion channels to single sarcomeres might be a potential function exerted by dystrophin alone or in conjunction with other submembrane cytoskeletal proteins. 相似文献
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Potassium conductance of single muscle fibres from Rana esculenta was studied in isotonic K2SO4 solution under constant current conditions using double sucrose gap method. At room temperature the channel formation by gramicidin was much faster than that of the synthetic head to head covalently linked gramicidin dimer. The increase of temperature by 8-10 degrees C resulted in a considerable rise of both dimer- and gramicidin-induced conductances. The effect was much greater than in the case of bilayers indicating a remarkable entropy change in the muscle fibre membrane. The temperature dependence of adsorption was more pronounced than that of desorption: there was no effect on desorption of dimer and only 20% of the temperature-activated desorption of gramicidin irreversibly bound at room temperature. 相似文献
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Effect of aging on properties of motor unit action potentials in the rat medial gastrocnemius muscle
Piotr Krutki Iwona Ciechanowicz-Kowalczyk Dawid Łochyński Jan Celichowski 《Journal of electromyography and kinesiology》2013,23(5):1150-1157
The purpose of this study was to investigate whether age-related changes in motor unit (MU) contractile properties are reflected in parameters of motor unit action potentials (MUAPs). MUs of the medial gastrocnemius muscle were functionally isolated in anaesthetized Wistar rats. A control group of young animals (5–10 mo) was compared to two groups of old rats (24–25 mo and 28–30 mo). The basic contractile properties of MUs as well as the amplitude, total duration, peak-to-peak time, and number of turns within MUAPs were measured. Effects of aging were mainly observed for fast fatigable MUs (a prolongation of MUAPs and increased number of turns). The MUAP amplitude did not change significantly with aging in either MU type, but it correlated to the twitch or tetanic forces, which tended to increase with age, especially for slow MUs. We concluded that the prolongation of MUAPs and the greater incidence of signal turns was probably a result of a decrease in muscle fiber conduction velocity and/or an increase in their dispersion, and enlargement of MU territories – presumably caused by axonal sprouting of surviving motoneurons. The latter might also be responsible for the observed age-related tendency for a increase in MUAP amplitudes in slow MUs. 相似文献
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The conductance of single fibres from m. ileofibularis of Rana esculenta was studied in isotonic K2SO4 solution under constant--current conditions using the double sucrose gap method. The antibiotic gramicidin A effects a drastic increase of membrane conductance. Variation of the gramicidin-induced conductance with gramicidin concentration in the bathing solution (10(-8)-5,5 . 10(-7) M) was investigated. Gramicidin-induced conductance was proportional to the square of gramicidin concentration in the solution, as expected in a channel made of gramicidin dimer. 相似文献
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The short-term function of motor neurons is to integrate synaptic inputs converging onto the somato-dendritic membrane and to transform the net synaptic drive into spike trains. A set of voltage-gated ion channels determines the electro-responsiveness and thereby the motor neuron's input-output function. In addition, several of the decisive ion channels are transmitter controlled, which results in a flexible control of the input-output relationship. 相似文献
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J Kucera 《The journal of histochemistry and cytochemistry》1977,25(11):1260-1263
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Pleshchinskiĭ IN Babynina TV Egorova LI Eremeev AA 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》1999,85(11):1415-1419
When the rat spinal motor centre was activated by fixing the animal in a supine posture, the motor units of intact gastrocnemius muscle fired more frequently in the high-frequency range. Under conditions of the ischiatic nerve blockade, a shift to an increase in the background firing frequency of the motor units related to intact gastrocnemius muscle seems to be related to increased motoneurone excitability occurring because of the contralateral denervation. 相似文献
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In 28 experiments on cat papillary muscles the effect of mesocain (generically related to lidocaine) was studied on transmembrane currents (rapid inward INa, slow inward Isi, outward Io), on the configuration and (dV/dt)max of the action potential, on the refractory period and on isometric tension. The experiments were performed using either voltage clamp method (double sucrose gap) or microelectrode technique. All three transmembrane currents are inhibited by mesocain in a dose-dependent manner. The effect becomes measurable at 10(-6) mol/1 on INa, at 10(-5) mol/1 on Isi and at 5 X 10(-5) mol/1 on Il. INa is blocked at 10(-3) mol/1 concentration. These changes correlate with the measured alterations of action potentials: i.e. a decreased (dV/dt) max and overshoot, lower voltage and shortening of the plateau phase, slower rate of late repolarizaion. The negative inotropic effect appeared with the same treshold concentration as Isi; at higher concentrations, however, this effect was relatively much greater. The recovery of excitability measured by the interval-dependence of (dV/dt) max was prolonged 5 times on the average by mesocain at 10(-4) mol/1 and the effective refractory period was delayed beyond complete repolarization. It is concluded that the main effect of mesocain also involves a delayed kinetics of recovery from inactivation of the Na carrying system. 相似文献
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The data have been obtained that confirm the identity of the electrogenic mechanism of hyperpolarization by nanomolar concentrations of cholinergic ligands in the extrasynaptic region and endogenous nonquantal acetylcholine in the synaptic region of a skeletal muscle fiber. In both cases, this mechanism is realized through the involvement of the alpha2 isoform of Na, K-ATPase and operates in the absence of Na+ entry through membrane channels. At the same time, there are peculiar properties which take place under functional disorders. Thus, the effectiveness of this mechanism in the synaptic region selectively increases under rat hindlimb unloading and decreases in case of dystrophin deficit in mdx mice. The last fact suggests that dystrophin is a molecular component that is essential for the functioning of the electrogenic mechanism of local hyperpolarization of the end-plate membrane. 相似文献
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Fitts RH Desplanches D Romatowski JG Widrick JJ 《American journal of physiology. Regulatory, integrative and comparative physiology》2000,279(5):R1546-R1557
The purpose of this investigation was to understand how 14 days of weightlessness alters the cellular properties of individual slow- and fast-twitch muscle fibers in the rhesus monkey. The diameter of the soleus (Sol) type I, medial gastrocnemius (MG) type I, and MG type II fibers from the vivarium controls averaged 60 +/- 1, 46 +/- 2, and 59 +/- 2 microm, respectively. Both a control 1-G capsule sit (CS) and spaceflight (SF) significantly reduced the Sol type I fiber diameter (20 and 13%, respectively) and peak force, with the latter declining from 0.48 +/- 0.01 to 0.31 +/- 0.02 (CS group) and 0.32 +/- 0.01 mN (SF group). When the peak force was expressed as kiloNewtons per square meter (kN/m(2)), only the SF group showed a significant decline. This group also showed a significant 15% drop in peak fiber stiffness that suggests that fewer cross bridges were contracting in parallel. In the MG, SF but not CS depressed the type I fiber diameter and force. Additionally, SF significantly depressed absolute (mN) and relative (kN/m(2)) force in the fast-twitch MG fibers by 30% and 28%, respectively. The Ca(2+) sensitivity of the type I fiber (Sol and MG) was significantly reduced by growth but unaltered by SF. Flight had no significant effect on the mean maximal fiber shortening velocity in any fiber type or muscle. The post-SF Sol type I fibers showed a reduced peak power and, at peak power, an elevated velocity and decreased force. In conclusion, CS and SF caused atrophy and a reduced force and power in the Sol type I fiber. However, only SF elicited atrophy and reduced force (mN) in the MG type I fiber and a decline in relative force (kN/m(2)) in the Sol type I and MG type II fibers. 相似文献
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V K Rybal'chenko 《Ukrainski? biokhimicheski? zhurnal》1987,59(6):44-49
The effect of detergents on enzymic and barrier properties of membrane structures is studied in the plasma membrane fraction, postsynaptic membranes of smooth muscle cells and sterine bilipid membranes. The formation of hydrophylic pores in the membrane, as well as changes in the phase state of the lipid matrix and fluidity of lipid microenvironment of membrane enzymes are supposed. 相似文献