scholarly journals A new method for excitation-contraction uncoupling in frog skeletal muscle.

1978 ◽  
Vol 78 (3) ◽  
pp. 782-784 ◽  
Author(s):  
J del Castillo ◽  
G Escalona de Motta
Keyword(s):  
Electrical Activity ◽  
Prolonged Exposure ◽  
Neuromuscular Block ◽  
Ringer Solution ◽  
Mechanical Activity ◽  
Sartorius Muscle ◽  
Nerve Branch ◽  
Miniature Endplate Potentials ◽  
Endplate Potentials ◽  
Frog Sartorius

The mechanical activity of frog sartorius muscle fibers can be uncoupled from the electrical activity of their surface membranes by immersing the preparation in Ringer solution containing either 1.5 or 2.0 M of formamide for 15--20 min. This uncoupling is not reversed when the muscle is transferred to normal frog Ringer solution. Formamide does not affect the electrical activity of the sciatic nerve branch, and both endplate potentials and miniature endplate potentials may be recorded from the uncoupled muscles. Prolonged exposure to formamide, beyond the time needed to paralyze, causes neuromuscular block.

Effect of Hypertonicity on Augmentation and Potentiation and on Corresponding Quantal Parameters of Transmitter Release

1999 ◽  
Vol 81 (3) ◽  
pp. 1428-1431 ◽  
Author(s):  
Hong Cheng ◽  
Michael D. Miyamoto
Keyword(s):  
Nerve Stimulation ◽  
Transmitter Release ◽  
Ringer Solution ◽  
Hypertonic Solution ◽  
Repetitive Nerve Stimulation ◽  
Quantal Transmitter Release ◽  
Before And After ◽  
Miniature Endplate Potentials ◽  
Endplate Potentials ◽  
Made In

Effect of hypertonicity on augmentation and potentiation and on corresponding quantal parameters of transmitter release. Augmentation and (posttetanic) potentiation are two of the four components comprising the enhanced release of transmitter following repetitive nerve stimulation. To examine the quantal basis of these components under isotonic and hypertonic conditions, we recorded miniature endplate potentials (MEPPs) from isolated frog ( Rana pipiens) cutaneous pectoris muscles, before and after repetitive nerve stimulation (40 s at 80 Hz). Continuous recordings were made in low Ca2+ high Mg2+ isotonic Ringer solution, in Ringer that was made hypertonic with 100 mM sucrose, and in wash solution. Estimates were obtained of m (no. of quanta released), n (no. of functional release sites), p (mean probability of release), and vars p (spatial variance in p), using a method that employed MEPP counts. Hypertonicity abolished augmentation without affecting potentiation. There were prolonged poststimulation increases in m, n,and p and a marked but transient increase in vars p in the hypertonic solution. All effects were completely reversed with wash. The time constants of decay for potentiation and for vars p were virtually identical. The results are consistent with the notion that augmentation is caused by Ca2+ influx through voltage-gated calcium channels and that potentiation is due to Na+-induced Ca2+ release from mitochondria. The results also demonstrate the utility of this approach for analyzing the dynamics of quantal transmitter release.

Intracellular pH recovery from lactic acidosis of single skeletal muscle fibres

1988 ◽  
Vol 66 (12) ◽  
pp. 1560-1564 ◽  
Author(s):  
Y. E. Allard
Keyword(s):  
Skeletal Muscle ◽  
Lactic Acid ◽  
Intracellular Ph ◽  
Buffer Capacity ◽  
Ringer Solution ◽  
Sartorius Muscle ◽  
Muscle Fibres ◽  
Diffusion Limited ◽  
Skeletal Muscle Fibres ◽  
Frog Sartorius

Intracellular pH (pHi, measured with H+-selective microelectrodes, in quiescent frog sartorius muscle fibres was 7.29 ± 0.09 (n = 13). Frog muscle fibres were superfused with a modified Ringer solution containing 30 mM HEPES buffer, at extracellular pH (pHo) 7.35. Intracellular pH decreased to 6.45 ± 0.14 (n = 13) following replacement of 30 mM NaCl with sodium lactate (30 mM MES, pHo 6.20). Intracellular pH recovery, upon removal of external lactic acid, depended on the buffer concentration of the modified Ringer solution. The measured values of the pHi recovery rates was 0.06 ± 0.01 ΔpHi/min (n = 5) in 3 mM HEPES and was 0.18 ± 0.06 ΔpHi/min (n = 13) in 30 mM HEPES, pHo 7.35. The Na+–H+ exchange inhibitor amiloride (2 mM) slightly reduced pHi recovery rate. The results indicate that the net proton efflux from lactic acidotic frog skeletal muscle is mainly by lactic acid efflux and is limited by the transmembrane pH gradient which, in turn, depends on the extracellular buffer capacity in the diffusion limited space around the muscle fibres.

Effect of Cooling on Neuromuscular Transmission in the Frog

1958 ◽  
Vol 192 (3) ◽  
pp. 464-470 ◽  
Author(s):  
Choh-Luh Li ◽  
Peter Gouras
Keyword(s):  
Critical Temperature ◽  
Neuromuscular Junction ◽  
Nerve Stimulation ◽  
Neuromuscular Transmission ◽  
The Other ◽  
Sartorius Muscle ◽  
Single Muscle ◽  
Miniature Endplate Potentials ◽  
Endplate Potentials ◽  
Muscle Responses

Recording with intracellular electrodes from endplate regions of frogs sartorius muscle showed that at –1°C miniature endplate potentials still occurred and that the resting membrane potentials differed very little from those recorded at room temperatures. The miniature potentials, however, were decreased in frequency and increased in amplitude by cooling; and at about 5°C, the amplitude began to fall while the frequency continued to be low. It was also at about 5°C that the muscle responses to nerve stimulation frequently consisted of endplate potentials only. Upon rewarming spike potentials again appeared. These observations suggest that there is a critical temperature for neuromuscular transmission, below which impediment of impulse transmission began; and in the frog it is 5°C. The experiments also demonstrated that during the process of cooling a blockage of impulses at one neuromuscular junction and transmission across the other in a single muscle fiber could occur.

scholarly journals Multimodal Distribution of Frog Miniature Endplate Potentials in Adult, Denervated, and Tadpole Leg Muscle

1974 ◽  
Vol 64 (1) ◽  
pp. 85-103 ◽  
Author(s):  
Mahlon E. Kriebel ◽  
Cordell E. Gross
Keyword(s):  
Mean Amplitude ◽  
Sartorius Muscle ◽  
Integer Multiple ◽  
Major Mode ◽  
Mepp Amplitude ◽  
The Mean ◽  
Almost All ◽  
Increasing Temperature ◽  
Miniature Endplate Potentials ◽  
Endplate Potentials

Amplitude histograms of spontaneous miniature endplate potentials (MEPPs) from adult sartorius muscle cells show a definite bimodality with the mean amplitude of the larger mode five to seven times that of the smaller mode which accounted for 2–5 % of the total MEPPs. Histograms were plotted after high frequency MEPP generation induced by increasing temperature, increasing external calcium or nerve stimulation. These plots showed a reversible left-shift of the major mode as well as a reversible increase in the proportion of small mode MEPPs. Repeated challenges shifted almost all MEPPs into the small mode. An increase in the percentage of small mode MEPPs also occurred spontaneously during the course of denervation before the quiescent period and some of the histogram profiles showed multiple modes whose means were integer multiples of the small mode mean. In the early stages of hind leg development the greatest proportion of MEPPs were of the small mode size; as metamorphosis progressed, the histograms showed a definite multimodality with the mean of each mode being an integer multiple of the small mode mean and with the proportion of MEPPs in each mode about the same. During tail resorption the percentage of larger MEPPs increased until the adult histogram profile was reached. Thus, the changes in MEPP amplitude histograms over the course of metamorphosis are the reverse of those found with denervation.

scholarly journals The Movement of Thallium Ions in Muscle

1960 ◽  
Vol 43 (4) ◽  
pp. 759-773 ◽  
Author(s):  
L. J. Mullins ◽  
R. D. Moore
Keyword(s):  
Ringer Solution ◽  
Sartorius Muscle ◽  
Muscle Twitch ◽  
External Concentration ◽  
Irreversible Damage ◽  
Toxic Heavy Metal ◽  
Tenfold Increase ◽  
Internal Concentration ◽  
High Concentrations ◽  
Frog Sartorius

Measurements have been made of the fluxes of thallous ions (Tl+) across the membrane of frog sartorius muscle fibers. These show that at an external concentration of 74 µM the influx is about 270 x 10-15 moles/cm.2 sec., while the efflux from a muscle with an internal concentration equal to the above is 5 x 10-15 moles/cm.2 sec. The efflux is increased of the order of 300-fold during a muscle twitch, and Tl+ reach a steady-state distribution between fiber water and Ringer solution that is very close to the corresponding ratio for K+. High concentrations of Tl+ depolarize the membrane about 58 mv. for a tenfold increase in external concentration. The results obtained are consistent with the view that the muscle fiber membrane cannot distinguish between the toxic heavy metal Tl+ and K+, provided that the concentrations of the former ion are kept low. High concentrations of Tl+, if allowed to act for an appreciable period of time, lead to irreversible damage to muscle.

scholarly journals Electrical Properties and Excitation-Contraction Coupling in Skeletal Muscle Treated with Ethylene Glycol

1972 ◽  
Vol 60 (2) ◽  
pp. 221-236 ◽  
Author(s):  
Carlos Sevcik ◽  
Toshio Narahashi
Keyword(s):  
Membrane Potential ◽  
Ethylene Glycol ◽  
Control Level ◽  
Membrane Resistance ◽  
Ringer Solution ◽  
Resting Membrane Potential ◽  
Sartorius Muscle ◽  
Frog Sartorius ◽  
Specific Membrane ◽  
Normal Ringer

The contractility of the frog sartorius muscle was suppressed after treatment with a Ringer solution added with ethylene glycol (EGR). No contraction was elicited by nerve stimulation when the muscle was brought back to normal Ringer solution after having been soaked in 876 mM EGR for 4 hr or in 1095 mM EGR for 2 hr. However, the action potential of normal amplitude was generated and followed by a depolarizing afterpotential. The resting membrane potential was slightly decreased from the mean normal value of –91.1 mv to –78.8 mv when 1095 mM EGR was used, and to –82.3 mv when 876 mM EGR was used, but remained almost constant for as long as 2 hr. The afterpotential that follows a train of impulses and a slow change in membrane potential produced by a step hyperpolarizing current (so-called "creep") were suppressed after treatment with ethylene glycol. The specific membrane capacity decreased to about 50% of the control values while the specific membrane resistance increased to about twice the control values Therefore, the membrane time constant remained essentially unchanged. The water content of the muscle decreased by about 30% during a 2 hr immersion in 1095 mM EGR, and increased by about 30% beyond the original control level after bringing the muscle back to normal Ringer. The intracellular potassium content did not change significantly during these procedures. Some differences between the present results and those obtained with glycerol are discussed.

scholarly journals SELECTIVE DISRUPTION OF THE SARCOTUBULAR SYSTEM IN FROG SARTORIUS MUSCLE

1968 ◽  
Vol 39 (2) ◽  
pp. 451-467 ◽  
Author(s):  
Brenda Eisenberg ◽  
Robert S. Eisenberg
Keyword(s):  
Extracellular Space ◽  
Skeletal Muscles ◽  
Muscle Fibers ◽  
Ringer Solution ◽  
Sartorius Muscle ◽  
Normal Muscle ◽  
Tubular System ◽  
Sarcotubular System ◽  
Reliable Marker ◽  
Frog Sartorius

Skeletal muscles which have been soaked for 1 hr in a glycerol-Ringer solution and then returned to normal Ringer solution have a disrupted sarcotubular system. The effect is associated with the return to Ringer's since muscles have normal fine structure while still in glycerol-Ringer's. Karnovsky's peroxidase method was found to be a very reliable marker of extracellular space, filling 98.5% of the tubules in normal muscle. It was interesting to note that only 84.1% of the sarcomeres in normal muscle have transverse tubules. The sarcotubular system was essentially absent from glycerol-treated muscle fibers, only 2 % of the tubular system remaining connected to the extracellular space; the intact remnants were stumps extending only a few micra into the fiber. Thus, glycerol-treated muscle fibers provide a preparation of skeletal muscle with little sarcotubular system. Since the sarcoplasmic reticulum is not destroyed and the sarcolemma and myofilaments are intact in this preparation, of the properties of the sarcolemma may thus be separated from those of the tubular system.

scholarly journals A Study on the Electrical Resistance of the Frog Sartorius Muscle

1966 ◽  
Vol 49 (5) ◽  
pp. 897-912 ◽  
Author(s):  
Otto Schanne ◽  
Hiroshi Kawata ◽  
Bärbel Schäfer ◽  
Marc Lavallée
Keyword(s):  
Muscle Fiber ◽  
Potassium Concentration ◽  
Membrane Resistance ◽  
Ringer Solution ◽  
Effective Resistance ◽  
Sartorius Muscle ◽  
Cable Model ◽  
Frog Sartorius Muscle ◽  
Electrode Resistance ◽  
Frog Sartorius

Four different methods of measuring the resistance of a muscle fiber have been applied to the frog sartorius muscle. The methods, in which the resistance of the microelectrode entered the calculation of the effective resistance of the fiber, resulted in values which were 8 times higher than the resistance values obtained with methods independent of the electrode resistance. A simple cable model of a muscle fiber could not account for the discrepancy in the effective resistance found in these measurements; therefore, an enlarged cable model for a muscle fiber has been proposed, and its biological implications have been discussed. The effective resistance (measured with the two different groups of methods) decreased when the potassium concentration in the bath increased. Using the proposed enlarged cable model for the interpretation of these results, it is shown that not only the membrane resistance but also the myoplasmic resistance decreases with an increasing potassium concentration in the Ringer solution.

scholarly journals Initial Heat Production in Isometric Frog Muscle at 15°C

1973 ◽  
Vol 62 (3) ◽  
pp. 271-285 ◽  
Author(s):  
Allan Fraser ◽  
Francis D. Carlson
Keyword(s):  
Heat Production ◽  
Sarcomere Length ◽  
Heat Rate ◽  
Frog Muscle ◽  
Mechanical Activity ◽  
Sartorius Muscle ◽  
Cooling Phase ◽  
Frog Sartorius ◽  
Initial Heat ◽  
Rest Length

An infrared radiation-detecting system was used to measure initial heat production in bull frog sartorius muscle at 15°C. Numerous tests with the system showed that thermal artifacts were not noticeable. Many previous measurements with myothermic thermopiles were corroborated with this method. In addition, a cooling phase as large as 0.39 of peak exothermicity was found during and after relaxation. Cooling diminished with both increasing sarcomere length and increasing duration of mechanical activity. No large rapid increase in heat rate accompanied a 0.6 reactivation at the peak of twitch tension. Above rest length, initial heat rate and the heat produced up to the peak of tension decreased nearly proportionally with overlap of myofilaments, while the total twitch initial heat decreased slightly.

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