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PubMed2002

Separation of detubulation and vacuolation phenomena in amphibian skeletal muscle.

Sartorius muscle fibres from cold-adapted Rana temporaria were exposed to variants of an established detubulation procedure (Koutsis et al. (1995) J Muscle Res Cell Motil 16, 519-528) to test the extent to which detubulation and tubular vacuolation phenomena could be separated using different conditions of osmotic shock. A control procedure was optimised to a 28-min exposure to 400 mM glycerol-Ringer. This was followed by a recovery step involving its replacement by a Ca2+/Mg(2+)-Ringer solution and steady cooling over 30 min from room temperature (approximately 18 degress C) to approximately 10 degress C, followed by the restoration of the normal Ringer solution. This procedure successfully abolished the action potential after-depolarisation component, reflecting a loss of tubular conduction ('detubulation') in 74.3 +/- 5.9% of the fibres studied. Omitting the cooling during the recovery step sharply reduced the incidence of detubulation. So did omitting either the high-[Ca2+] and/or [Mg2+] in the recovery solutions in test procedures, but to significantly different extents (P < 5%). Yet trapping of fluorescent Sulfhorhodamine B dye in 'closed' vacuoles persisted albeit with reduced proportions of fibre volume occupied by vacuoles. Furthermore, the variations in recovery conditions produced similar levels of vacuolation despite smaller vacuole sizes in the cooled fibres (P < 0.05). These findings demonstrate that fibre vacuolation and detubulation are phenomena that are potentially separable through varying the conditions of osmotic shock, with detubulation requiring significantly more stringent conditions than vacuolation.

Action Potentials↗

PubMed1968

The dual effect of lithium ions on sodium efflux in skeletal muscle.

Sartorius muscle cells from the frog were stored in a K-free Ringer solution at 3 degrees C until their average sodium contents rose to around 23 mM/kg fiber (about 40 mM/liter fiber water). Such muscles, when placed in Ringer's solution containing 60 mM LiCl and 50 mM NaCl at 20 degrees C, extruded 9.8 mM/kg of sodium and gained an equivalent quantity of lithium in a 2 hr period. The presence of 10(-5)M strophanthidin in the 60 mM LiCl/50 mM NaCl Ringer solution prevented the net extrusion of sodium from the muscles. Lithium ions were found to enter muscles with a lowered internal sodium concentration at a rate about half that for entry into sodium-enriched muscles. When sodium-enriched muscles labeled with radioactive sodium ions were transferred from Ringer's solution to a sodium-free lithium-substituted Ringer solution, an increase in the rate of tracer sodium output was observed. When the lithium-substituted Ringer solution contained 10(-5)M strophanthidin, a large decrease in the rate of tracer sodium output was observed upon transferring labeled sodium-enriched muscles from Ringer's solution to the sodium-free medium. It is concluded that lithium ions have a direct stimulating action on the sodium pump in skeletal muscle cells and that a significantly large external sodium-dependent component of sodium efflux is present in muscles with an elevated sodium content. In the sodium-rich muscles, about 23% of the total sodium efflux was due to strophanthidin-insensitive Na-for-Na interchange, about 67% being due to strophanthidin-sensitive sodium pumping.

Animals↗

PubMed1984

The sarcomere length dependence of the rate of heat production during isometric tetanic contraction of frog muscles.

Heat production and force have been measured as a function of sarcomere length between 1.6 and 3.0 microns during isometric tetani at 0 degree C for two types of frog muscle: sartorius and extensor longus digiti iv (e.l.d. iv). Stable heat rate declines linearly with increasing sarcomere length above 2.20 microns for both e.l.d. iv and sartorius muscles. In sartorius muscle stable heat rate remains at or near its maximum value between 1.75 and 2.20 microns while force decreases. In e.l.d. iv muscle, both stable heat rate and force decline linearly as sarcomere length decreases below 2.20 microns.

Animals↗

PubMed2005

Muscle fiber and motor unit behavior in the longest human skeletal muscle.

The sartorius muscle is the longest muscle in the human body. It is strap-like, up to 600 mm in length, and contains five to seven neurovascular compartments, each with a neuromuscular endplate zone. Some of its fibers terminate intrafascicularly, whereas others may run the full length of the muscle. To assess the location and timing of activation within motor units of this long muscle, we recorded electromyographic potentials from multiple intramuscular electrodes along sartorius muscle during steady voluntary contraction and analyzed their activity with spike-triggered averaging from a needle electrode inserted near the proximal end of the muscle. Approximately 30% of sartorius motor units included muscle fibers that ran the full length of the muscle, conducting action potentials at 3.9 +/- 0.1 m/s. Most motor units were innervated within a single muscle endplate zone that was not necessarily near the midpoint of the fiber. As a consequence, action potentials reached the distal end of a unit as late as 100 ms after initiation at an endplate zone. Thus, contractile activity is not synchronized along the length of single sartorius fibers. We postulate that lateral transmission of force from fiber to endomysium and a wide distribution of motor unit endplates along the muscle are critical for the efficient transmission of force from sarcomere to tendon and for the prevention of muscle injury caused by overextension of inactive regions of muscle fibers.

Adult↗

PubMed1986

Effects of carbon dioxide and tetanus duration on relaxation of frog skeletal muscle.

Sartorius and semitendinosus muscles of the frog Rana temporaria (0 degrees C) were stimulated under isometric (fixed-end) conditions and force during stimulation and relaxation was recorded. Relaxation time was assessed by measuring the time from the last stimulus until force declined to 90% or 50% of its value at that time. The relaxation time increased linearly with concentration of CO2 in the Ringer's solution (pH 7.2), whereas, at constant CO2, relaxation was hardly affected by changes in extracellular HCO3- and pH. This is consistent with the view that CO2 enters the cells, but H+ and HCO3- do not, and that entry of CO2 causes intracellular acidification and slows relaxation. For tetani lasting between 0.5 and 5s, relaxation is slower the longer the tetanus; further increase in tetanus duration to 10 s has little additional effect. The presence of 3.3 mmol 1(-1) CO2 in the Ringer's solution has a small effect on relaxation after a brief tetanus, but greatly slows relaxation as tetanus duration increases. Experiments with paired tetani (conditioning and test) showed that relaxation from a test tetanus was slower if a conditioning tetanus was given. However, the size of this effect was independent of muscle length during the conditioning tetanus. After a conditioning tetanus, an interval of many minutes is required for the muscle to recover its ability to relax quickly from a test tetanus. The results indicate that changes in metabolite levels caused by contraction itself are not responsible for the slowing of relaxation. Possible mechanisms of the effects of CO2 on relaxation are discussed.

Animals↗

PubMed1990

Evidence of the co-activation of alpha-motoneurones and static gamma-motoneurones of the sartorius medialis muscle during locomotion in the thalamic cat.

The activity in alpha and gamma efferent axon populations and in group I and group II afferent fibre populations innervating a flexor muscle, the sartorius medialis, was observed during spontaneous locomotor movements in the thalamic cat. Multi-unit discharges of each kind of fibre were obtained by electronic sorting of the action potentials from the overall activity of a thin, intact branch of the sartorius medialis nerve. The following results were obtained: (1) The gamma-motoneurones have a phasic behaviour characterized by a single discharge period during the hip flexion (swing phase of the step-cycle). (2) The gamma-motoneurones are co-activated with the homonymous alpha-motoneurones. (3) Between rhythmic alpha and gamma discharges, i.e. during the hip extension (stance phase of the step cycle), both alpha- and gamma-motoneurones were normally silent. However, in 5 out of 17 experiments, a few units of the gamma population fired at very low frequency. (4) Two observations indicate that the gamma-motoneurones that are co-activated with the alpha-motoneurones by central locomotor commands are predominantly of the static type. In actual locomotion, the rhythmic fusimotor discharges over-compensate the depressor effect on the firing rate of the group II afferents of the unloading of muscle spindles by the active shortening of the parent muscle. In fictive locomotion, when the transmission of the excitation is blocked by selective curarization in alpha skeleto-motor junctions alone, the rhythmic fusimotor discharges elicit in-phase modulations not only of the group I but also of the group II fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

[Restoration of an infected hip joint with sartorius-plasty].

For treatment of infected hip joints we use the proximally based sartorius muscle. After ligation of the vessels in the distal part of the muscle, the sartorius muscle is elevated and transposed to the floor of the deep joint cavity. By completely filling the space defect, reinfection of the osteomyelitic cavity is prevented. In addition, the transposed muscle flap directs optimal blood perfusion to the hypoxemic capsule tissue via its own vascular pedicle.

Aged↗

PubMed1989

Effect of potassium propionate on free and bound acetylcholine in frog muscle.

Frog sartorius muscles were homogenized under various conditions which allowed, by means of mass spectrometry, the measurement of total ACh, and different ACh compartments in the tissue: 'bound', 'free-1' and 'free-2' ACh. Bound ACh presumably corresponded to the vesicular compartment, and the free-1 and free-2 fractions to the cytoplasmic compartments of ACh. Stimulation of ACh release by La3+ ions for 60 min caused a decrease of both bound and free-2 ACh, but at 20 min bound ACh was reduced much more than free-2 ACh. Stimulation of ACh release by isotonic potassium propionate (KPr) solution for only 5 min caused a decrease of bound ACh, in contrast to free-1 and free-2 ACh which were not significantly changed. When muscles after 5 min stimulation in KPr were allowed to recover in normal Ringer, free-1 ACh did not change, but free-2 and bound ACh increased; after 180 min in Ringer bound ACh had recovered to control values. When ACh synthesis was prevented by hemicholinium-3 during recovery of the muscles in Ringer, bound ACh increased at the expense of free-2 ACh. In deuterium labeling experiments, in which the Ringer contained choline-d9, much more ACh-d9 was formed in stimulated than in unstimulated muscles. It appeared that almost all newly formed ACh was ACh-d9, since no significant synthesis of unlabeled ACh (ACh-d0) took place. Yet again, the amount of bound ACh-d0 significantly increased, apparently at the expense of preformed free-2 ACh-d0.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1963

The concentration dependence of sodium efflux from muscle.

Frog sartorius muscles subjected to overnight loading with Na(+) in K-free Ringer in the cold were subsequently labeled with Na(24) and then immersed in choline Ringer and the efflux of Na(24) followed for 4 hours. The initial efflux of Na(+) appeared to be 17 pmole/cm(2) sec.; this value was maintained for 20 minutes and was followed by an abrupt decline to about 9 pmole/cm(2) sec. This latter rate was maintained for the next 20 minutes of efflux. The efflux then declined gradually with time and reached values of the order of 0.1 pmole/cm(2) sec. The back addition of counts lost from muscles enabled one to calculate the relationship between efflux and [Na](i) for muscle. This roughly approximates an S-shaped curve with a value at half-saturation of about 17 mmole Na per liter of fiber water. The efflux-concentration curve is closely described by assuming that 3 Na(+) are transported per carrier cycle.

Animals↗

PubMed1983

Cobalt uptake and localization of putative calcium binding sites in striated muscle.

Frog sartorius muscles were soaked overnight in saline containing 50 mM cobalt and subsequently fixed with or without precipitation of intracellular cobalt by exposure to ammonium sulfide. Treated fibers and appropriate controls were embedded in plastic in the usual manner. Thick sections (3-4 micrometers) of each sample were treated with silver in order to intensify precipitated cobalt. The samples were then resectioned for ultrastructural examination. Fibers exposed to cobalt with or without precipitation had normal ultrastructure; indeed, the transverse lines of the A-zone and M-band appeared to be more obvious after exposure to cobalt than in control samples. Exposure to silver produced numerous silver grains only in those samples that contained precipitated cobalt. The distribution of silver grains after intensification matched expected calcium binding sites. Silver grains were abundant over membranes of the sarcoplasmic reticulum, sarcolemma, mitochondria, and nucleus and rare or absent from filaments and sarcoplasm. This technique appears to be generally useful for locating intracellular calcium binding sites.

Animals↗

PubMed1976

[Comparison of the compliance of resting and contracting muscle].

Frog sartorius muscles are stretched at rest and during maximal tetanic contractions. Parallel compliance decreases when the length increases. The relationship between compliance and length is linear in double-logarithmic scale. The compliance of the active muscle (tetanic contraction) is not related to the length. The series-compliance is calculated from the parallel compliance and the active one. It increases with the length of muscle. These results are discussed on the basis of the sliding-filaments theory.

Animals↗

PubMed1978

[Effect of fatigue on the compliance series of isolated muscles].

Frog sartorius muscles are stretched at rest and during tetanic contractions, and series-compliance of normal muscle is compared to that of a fatigued one. The series-compliance is calculated from the parallel compliance and the active one. The compliance decreases when the tension increases and becomes quite constant for the highest levels of tension. These results are discussed on the basis of the sliding filaments theory.

Animals↗

PubMedDate not supplied

[Direct proof of the existence of Ca2+-induced structural changes in miosin-containing thick filaments of vertebrate skeletal muscles].

Frog sartorius muscles were skinned with the help of detergent Triton X-100 in relaxing solution and then rigorized in the solution free of ATP and calcium (Ca2+-free rigor). Some of the X-ray diffraction patterns obtained from such muscles differed drastically from the patterns of usual "calcium" rigor state of the muscle. Analysis of the X-ray diffraction patterns of Ca2+-free rigor state of the muscle allows the following conclusions to be made. (1) It is proved that the so-called forbidden meridional reflections localised in groups at the successive orders of the repeat period of about 430 A are due to diffraction on the lattice formed by minor proteins of the thick filaments. This must be taken into account while interpreting the intensity changes of the meridional 143 and 215 A reflections in the contracting muscle. (2) The shafts of the myosin-containing filaments may exist in two different structural states; the transition between these states takes place on the change of calcium concentration. (3) The deflection of myosin cross-bridges from the shafts of the filaments is possible at either of two conformations of the myosin shafts. (4) The formation of actomyosin rigor-complexes does not necessarily leads to a structural change in the myosin filament. (5) Existence of Ca2+-induced structural changes in the thick filaments indicates possible myosin-linked regulations in the vertebrate skeletal muscle alongside with the actin-linked ones.

Animals↗

PubMed1968

Effects of nerve cross-union on fast-twitch and slow-graded muscle fibres in the toad.

1. A method is described for resolving isometric tetanic tension developed by fast-twitch and slow-graded components of heterogeneous toad muscles. This makes use of the difference in threshold for excitation of low threshold nerve fibres which normally innervate the fast-twitch muscle fibres and high threshold nerve fibres which innervate slow-graded muscle fibres.2. The sartorius muscle contains only fast-twitch muscle fibres whereas the posterior semitendinosus (PST) contains both fast-twitch and slow-graded muscle fibres, the latter contributing 10-15% of the maximum isometric tetanic tension.3. Following surgical cross-union of nerve to sartorius and PST muscles, both the fast-twitch and slow-graded muscle fibre components of the PST are reinnervated by low threshold nerves originally innervating sartorius fast-twitch fibres, and sartorius fast-twitch muscle fibres are reinnervated by both low threshold and high threshold nerves formerly supplying the fast-twitch and slow-graded muscle fibre components of the PST.4. The characteristic mechanical responses of fast-twitch muscle fibres and slow-graded muscle fibres were not transformed up to 134 and 200 days respectively following nerve cross-union.5. PST nerve partially innervated the sartorius muscle whereas sartorius nerves completely innervated the PST muscle. Isometric tetanic tension declined markedly during repetitive indirect stimulation of cross-innervated sartorius muscles, whereas the tetanic contractions of cross-innervated PST showed a plateau of tension and resembled the response of normal muscles.6. Normal, cross-innervated and self-innervated PST muscles gave sustained contractures in the presence of acetylcholine whereas PST muscles denervated for 120 days gave phasic contractures similar to those of normal, cross-innervated and self-innervated sartorius muscles.

Journal Article↗

PubMed1984

Discriminant effects of behaviorally active and inactive analogs of phencyclidine on membrane electrical excitability.

The discriminant effects of several behaviorally active and inactive analogs of phencyclidine [PCP; 1-(phenylcyclohexyl) piperidine] and the actions of PCP and three Ca-channel antagonists were examined on electrical excitability in frog and crayfish skeletal muscles. In frog sartorius muscle, 1-[1-(2-thienylcyclohexyl)piperidine (TCP; 100 microM), a behaviorally active analog of PCP, increased action potential duration nearly 9-fold, blocked delayed rectification and at 0.5 to 1 microM also increased the quantal release of transmitter. A partial blockade of delayed rectification and slight prolongation of the action potential occurred with 1-(p-fluorophenylcyclohexyl)piperidine (p-F-PCP; 100 microM), which possesses about 25% of the behavioral activity of PCP. Of the remaining p-phenyl- substituted analogs which never exhibited more than 10% of the behavioral potency of PCP, only 1-(1-p-nitrophenylcyclohexyl)piperidine (p-NO2-PCP; 100 microM) produced a frequency-dependent prolongation of the action potential but, like the p-methoxy-, p-chloro- and p-methyl- analog, it did not block delayed rectification. The order of potencies of these analogs in blocking delayed rectification, prolonging the muscle action potential and in affecting alternation impairment and response rate depression is therefore: PCP much greater than TCP greater than p-F-PCP much greater than p-CH3-PCP = p-CH3O-PCP = p-Cl-PCP = p-NO2-PCP. Like PCP and its behaviorally active analogs, verapamil (50 microM) and bepridil (50 microM), two Ca-channel blockers, also blocked delayed rectification in frog sartorius muscles whereas nifedipine (50 microM), another Ca-channel blocker, did not.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1983

Sea nettle (Chrysaora quinquecirrha) nematocyst venom: mechanism of action on muscle.

The cellular mechanism of toxicity of sea nettle nematocyst venom was studied in the isolated, perfused frog ventricle and the isolated frog sartorius muscle. The venom depolarized both cardiac muscle fibers and sartorius fibers and shortened the duration of the ventricular action potential. Sodium content was increased, potassium content was decreased and magnesium content was unaltered in both tissues upon exposure to venom. Calcium content increased in heart ventricle, twitch tension decreased and a contracture developed. The calcium content of venom-treated, quiescent sartorius muscles was not changed from control. In stimulated sartorius muscles, tetanus tension fell during venom treatment, the twitch response was variable and no contracture was seen. Venom-treated sartorius muscles incubated with 5 mM Rb+, Cs+ or Li+ took up twice the amount of each cation as did control muscles. Sea nettle venom decreased the resistance of black lipid membranes in discrete steps, each step corresponding to a transfer of about 2 X 10(7) ions/sec at a potential of 20 mV in Ringer's solution. It was concluded that a component of sea nettle venom forms a monovalent cation channel in cardiac skeletal muscle surface membranes that allows a rapid influx of sodium into the cell.

Animals↗

PubMed1975

Energy liberation and chemical change in frog skeletal muscle during single isometric tetanic contractions.

Recent data obtained from Rana temporaria sartorius muscles during an isometric tetanus indicate that the time-course of phosphocreatine (PC) splitting cannot account for the total energy (heat + work) liberation (Gilbert et al. 1971. J. Physiol. (Lond.) 218:)63). As this conclusion is important to an understanding of the chemical energetics of contraction, similar experments were performed on unpoisoned, oxygenated Rana pipiens sartorius muscles. The muscles were tetanized (isometrically) at 0 degrees C for 0.6, 1, or 5 s; metabolism was rapidly arrested by freezing the muscles with a specially designed hammer apparatus, and the frozen muscles were chemically analyzed. Comparable myothermal measurments were made on frogs from the same batch. Results of these experiments indicate: (a) The energy liberation parallels the PC and ATP breakdown with a proportionality constant of 10.7 kcal/mol; (b) comparably designed experiments with sartorius muscles of R. temporaria revealed that the ratio of energy liberation to PC splitting was significantly greater than that observed in R. pipiens sartorius muscles; (c) there is no systematic difference between experiments in which metabolism was arrested by the hammer apparatus and others using a conventional immersion technique.

Adenosine Triphosphate↗

PubMed1987

Ion permeation through single channels activated by acetylcholine in denervated toad sartorius skeletal muscle fibers: effects of alkali cations.

The gigaohm seal technique was used to study ion permeation through acetylcholine-activated channels in cell-attached patches of the extrajunctional membrane of chronically denervated, enzyme-treated cells from the sartorius muscle of the toad Bufo marinus. The most frequently occurring channel type (greater than 95% of channel openings), provisionally classified as 'extrajunctional,' had a chord conductance of approximately 25 pS under normal conditions (-70 mV, 11 degrees C, Normal Toad Ringer's). The less frequently observed channel type (less than 5% of channel openings), classified as a 'junctional' type, had a conductance of 35 pS under the same conditions, and a similar null potential. In many patches, a small percentage (usually less than 2%) of openings of the extrajunctional channel displayed a lower conductance state. The shape of the I-V curves obtained for the extrajunctional channel depended on the predominant extracellular cation. For Cs and K, the I-V curves were essentially linear over the voltage range +50 to -150 mV across the patch, suggesting that the potential independent component of the energy profile within the channel was symmetrical. For Li, the I-V curve was very nonlinear, displaying a significant sublinearity at hyperpolarized potentials. Both an electrodiffusion and a symmetrical uniform four-barrier, three-site rate-theory model provided reasonable fits to the data, whereas symmetrical two-barrier, single-site rate-theory models did not. For the alkali cations examined, the relative permeability sequence was PCs greater than PK greater than PNa greater than PLi--a "proportional" selectivity sequence. This was different from the single channel conductance sequence which was found to be gamma K greater than gamma Cs greater than gamma Na greater than gamma Li implying that ions do not move independently through the channel. The relative binding constant sequence for the channel sites was found to be a "polarizability" sequence, i.e., KLi greater than KCs greater than KNa greater than KK. There was an inverse relationship between the relative binding constant and the relative mobility for the cations examined. Under conditions when the single-channel conductance was relatively high, the conductance at depolarized potentials was lower than that predicted by both electrodiffusion and rate theory models, suggesting that there was a rate-limiting access step for ions, from the intracellular compartment into the channel.

Acetylcholine↗