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PubMed2005

Differential osmotic behavior of water components in living skeletal muscle resolved by 1H-NMR.

Using frog sartorius muscle, we observed transverse relaxation processes of (1)H-NMR signals from myowater. The process could be well described by four characteristic exponentials: the extremely slow exponential of relaxation time constant T(2) > 0.4 s, the slow one of T(2) approximately 0.15 s, the intermediate one of 0.03 s < T(2) < 0.06 s, and the rapid one of T(2) < 0.03 s. Addition of isotonic extracellular solution affected only the extremely slow exponential, linearly increasing its amplitude and gradually increasing its T(2) toward that of the bulk solution (1.7 s). Therefore, this exponential should represent extracellular surplus solution independently of the other exponentials. At two thirds to three times the isotonicity, the amplitude of the intermediate exponential showed normal osmotic behavior in parallel with the volume change of the myofilament lattice measured with x-ray diffraction. In the same tonicity range, the amplitude of the rapid exponential showed converse osmotic behavior. Lower tonicities increased the amplitude of only the slow exponential. Studied tonicities did not affect the T(2) values. The distinct osmotic behavior indicated that each characteristic exponential could be viewed as a distinct water group. In addition, the converse osmotic behavior suggested that the rapid exponential would not be a static water layer on the macromolecule surface.

Animals↗

PubMed1975

[Effect of insulin of frog skeletal muscle respiration].

The respiration of the isolated frog sartorius muscle was measured polarographically. The endogenous respiration was seen to increase by 8 and 6 times in 20 mM KCL and 0.05 mM 2,4-DNP, resp., and by 40 percent in 10mM pyruvate or lactate. Insulin stimulated the endogemous respiration from 27 to 38 mm-3 O2/hr. per gramm of wet weight. In the excess of exogenous lactate and pyruvate, the degree of the insulin stimulated respiration did not change. It is suggested that the increase of the endogenous respiration by insulin cannot be accounted for by the mobilization of the substrate of glycolysis.

Animals↗

PubMed1977

Dual end-plate potentials at the single neuromuscular junction of the adult frog.

Electrophysiological evidence is presented that at least 30 percent of sartorius muscle fibres of adult frogs are innervated by two or more axons at a single end-plate zone. In these fibres, increasing stimulation of the common sartorius nerve led to the appearance of two or more distinct levels of end-plate potentials (e.p.p.) (or currents, measured by the voltage clamp technique). They had an identical time course, reversal potential and delay to nerve stimulation. When the recording microelectrode was moved along the same fibre and reinserted, both components of e.p.p. decreased proportionally. This indicated that both components of e.p.p. originated very closely to each other on the muscle fibre, presumably in one end-plate zone. Many fibres of the sartorius muscle of adult frogs therefore possess polyneural innervation of a single end-plate zone, which is otherwise typical for early stages of ontogenesis.

Animals↗

PubMed1979

Muscular fatigue and rate of tension development.

The effects of long-term fatigue upon maximal force and peak rate of tension development (PRTD) (dF/dt max) are studied in man (elbow flexors), in the rat (pseudo-isolated gastrocnemius muscle) and in the frog (isolated sartorius muscle). The muscles are fatigued by voluntary anisometric anisotonic contractions against an elastic resistance in man, and by maximal tetanic contractions in the frog and the rat. In man, the excitation level of the muscle is controlled by the integrated surface EMG of the biceps brachii. In the animals, the muscles are stimulated by a neurostimulator. The PRTD and the maximal isometric force are measured during fatigue tests. In man, frog and rat, the maximal voluntary isometric torque or the maximal force and the PRTD decrease initially more or less rapidly according to the power developed during the fatigue process, and then less rapidly. The relationship between PRTD and maximal force is linear in the animals and curvilinear in man. The variations of maximal force and PRTD are discussed in relation to the level of excitation of the muscles and of the composition in different motor units types and their spatio-temporal recruitment. From a biomechanical point of view, it seems necessary to study the behavior of the series elastic component during the evolution of long term fatigue.

Animals↗

PubMed1988

Differential expression of the Ca2+-binding protein parvalbumin during myogenesis in Xenopus laevis.

We have used immunocytological techniques to examine the developmental expression of the Ca2+-binding protein parvalbumin in Xenopus laevis embryos. Western blot experiments show that at least three different forms of parvalbumin are expressed during embryogenesis; the tadpole tail expresses one form, adult brain expresses another, mylohyoid muscle expresses both, and gastrocnemius and sartorius muscles express these two plus a third form. Parvalbumin (PV) is first detectable by immunofluorescence at stages 24-25 of development, a time when myotomal muscles are differentiating and contractile activity occurs spontaneously in embryos. At metamorphosis, PV is expressed in developing limb muscles. While the majority of skeletal muscle fibers express high levels of PV in both embryos and adults, a second fiber type has no detectable PV. The arrangement of PV-containing fibers is stereotyped in each muscle group examined. Histochemical staining of tadpole muscles indicate that PV-containing fibers correspond to fast-twitch skeletal muscles, whereas those without PV correspond to slow-twitch muscles. During tail resorption at metamorphosis, PV appears to be extruded from dying tail muscle cells and taken up by phagocytic cells.

Animals↗

PubMed1985

Muscle paralyzing effect of the juice from the trunk of the banana tree.

The effect of an extract from the trunk of the banana tree (Musa sapientum) was investigated in isolated skeletal muscle preparations from the chick, mouse and frog using twitch tension and intracellular recording techniques. The extract produced, in the same concentration range and after an initial period of twitch augmentation, paralysis of skeletal muscle in both directly and indirectly stimulated preparations. It also had a dose-dependent stimulant effect on the muscle causing a contracture. The neuromuscular blockade was reversed by calcium, but only when added before complete paralysis of the muscle. On the other hand, neostigmine usually hastened the blockade and aggravated the contracture. The frequency of the miniature endplate potential in the mouse phrenic nerve-diaphragm preparation greatly increased initially, declining to an elevated plateau. Effects on quantal content of endplate potentials (e.p.p.s) were studied in the transected mouse phrenic nerve-hemidiaphragm using trains of e.p.p.s. In the presence of the extract, only a few e.p.p. trains could normally be evoked, probably due to nerve terminal block. When quantal content could be measured at low concentrations of the extract, an increase was usually obtained. Muscle action potentials in the frog sartorius muscle were decreased in amplitude until no further potentials could be generated. The results suggest that the nature of the block produced by the extract resembles that of a potent local anaesthetic with an initial atypical labilizing effect on cell calcium rather than a conventional curariform block.

Action Potentials↗

PubMed2001

Superiorly based rectus abdominis wraparound flap for axillofemoral graft sepsis.

Prosthetic vascular graft sepsis, although uncommon, can lead to catastrophic sequelae for life and limb. Axillofemoral grafts are predisposed to sepsis and perigraft seromas because of their length, subcutaneous tunneling, and infrainguinal anastomosis, and are often performed in elderly, debilitated patients. The authors detail the use of a superiorly based rectus abdominis muscle flap, in combination with a sartorius muscle flap to salvage a Szilagy/Samson grade III septic axillounifemoral graft. The superiorly based rectus abdominis wraparound muscle flap should be considered a salvage option for select cases of sepsis involving axillofemoral grafts.

Aged↗

PubMed1985

Succinyl derivatives of N-tris (hydroxymethyl) methyl-2-aminoethane sulphonic acid: their effects on the frog neuromuscular junction.

Succinic anhydride (SA) dissolved in Ringer solution buffered with N-tris (hydroxymethyl) methyl-2-aminoethane sulphonic acid (SA-TES solution) potentiates the depolarizing action of acetylcholine (ACh, 10-40 microM) on frog muscle and the tension induced by bath application of this agonist. Applied from one side of a double-barrelled micropipette, SA-TES increases the amplitude of iontophoretically elicited ACh potentials. The potentiation of the effects of ACh by SA-TES does not involve changes in either the activity of the ACh esterase or the input resistance of the muscle membrane. For depolarizations of frog sartorius muscle, dose-response relationships obtained for ACh concentrations from 0.5 to 20 microM indicate that SA-TES increases the apparent affinity of ACh by a factor of 3. SA-TES exerts an "accelerating' effect on the responses elicited by bath-applied ACh; i.e., it increases the rate of depolarization when ACh is added to the bath and the rate of repolarization upon washing out. These effects are particularly marked in preparations treated with neostigmine (3 microM). SA-TES does not potentiate the depolarizing action of agonists which do not contain an ester group. Moreover, the time course of the responses elicited by these compounds is not influenced by SA-TES. SA-TES fails to influence significantly the effects of the neurally released transmitter. Only a 10% increase in the average amplitude of the endplate potentials was observed. SA hydrolyzes in about 30 min at room temperature; however the SA-TES solution retains its activity for several weeks. Succinate is inactive, and so is SA in Ringer buffered with phosphate. The SA-TES solution contains seven succinyl-TES derivatives, which were separated by ion-exchange chromatography and paper chromatography. At concentrations between 1 to 150 microM, these succinyl-TES derivatives affected the ACh-induced contraction of frog rectus abdominus muscle. The most abundant derivative potentiated the action of high doses of ACh, but was inhibitory at lower ones. The other derivatives were mostly inhibitory. These results are discussed in terms of two hypotheses. One postulates the presence of a diffusion barrier formed by groups that bind ACh and are saturated by SA-TES. The other assumes that SA-TES acts directly on the ACh receptor exerting its potentiating effect through a cooperative mechanism.

Acetylcholine↗

PubMed1969

The kinetics of mechanical activation in frog muscle.

1. The kinetics of mechanical activation were examined in muscle fibres of the frog's sartorius muscle, using a voltage clamp to control membrane potential, tetrodotoxin to eliminate electrical activity and microscopic observations to determine the mechanical threshold.2. The strength-duration curve was determined over a range of membrane potentials varying between -52 mV (rheobase) and +90 mV. At 4 degrees C the critical duration was about 11 msec at -30 mV, 4 msec at 0 mV and 2 msec at +40 mV.3. For pulses where V > -10 mV the threshold criterion at 4 degrees C was that the ;area above -30 mV' must exceed about 120 mV msec.4. The effect of a brief subthreshold pulse declines with a time constant of about 3 msec at -100 mV and about 8 msec at -85 mV at 4 degrees C.5. Although the strength-duration curve is well fitted by assuming a first-order mechanism in which the rate of release of activator increases with membrane potential, other experiments show that the over-all mechanism is probably second order in time.6. A short pulse must be at least 50% threshold if it is to give a visible contraction when added to a long pulse which is just below rheobase.7. Delayed rectification was conspicuous with medium or long pulses which were just below the mechanical threshold, but short pulses could give contraction without turning on any appreciable potassium conductance.8. The Appendix extends Falk's (1968) treatment of the charging of the tubular system under a voltage clamp.

Animals↗

PubMed1981

Intracellular chloride activity in mammalian ventricular muscle.

The intracellular chloride activity (formula, see text) of quiescent rabbit right papillary muscle was measured with ion-selective microelectrodes (ISE) made with Corning 477315 liquid ion-exchange resin. The (formula, see text) was 9.8 +/- 2.4 (SD) mM, a value significantly greater than the 6.1 +/- 0.6 mM expected from passive distribution. The chloride equilibrium potential (ECl) was -64.4 +/- 6.6 mV, while membrane potential was -75.9 +/- 2.2 mV and significantly negative to ECl. These values are corrected for a nonchloride signal detected by the ISE. An apparent (formula, see text) of 4.8 +/- 0.6 mM was measured after exposure to Cl-free media for 1 h. Since isotopic chloride was totally washed out by this time, the apparent (formula, see text) in Cl-free media was interpreted as interference and subtracted from the (formula, see text) measured in other media. The conclusion that chloride is not passively distributed is supported by the observation that the (formula, see text) increase in high potassium media was smaller than predicted. In contrast to findings in papillary muscle, (formula, see text) of frog sartorius muscle was consistent with passive distribution, if it is assumed that interference was less than 0.5 mM.

Animals↗

PubMed1985

[Anterior approach in total hip arthroplasty].

The anterior approach to the hip is first between the tensor muscle of fascia lata and the sartorius muscle, then laterally to the vastus externus. Desinsertion of the fascia lata from the ilium is necessary in only slightly more than one half of the cases, and it is always limited. Access to the capsule is wide and, provided one works on an orthopaedic operating table, the manoeuvres required to dislocate the joint and expose the femoral head and neck, then the cotyloid cavity, are simple. Closure is easy, and because the trochanter has not been sectioned, early rehabilitation is possible.

Hip↗

PubMed1984

Intramuscular pH and energy changes in muscle.

Intracellular pH (pHi) and buffering power of unstimulated sartorius muscle (frog) were measured with pH-sensitive microelectrodes. The mean pHi for muscle was about 0.3 units more acid than the extracellular pH in the range 7.0 to 7.2. The buffer power was 44.0 +/- SE 7.1 mM/pH unit for 19 fibres with pHi 6.83 +/- SE 0.05.

Animals↗

PubMed2004

Detubulation experiments localise delayed rectifier currents to the surface membrane of amphibian skeletal muscle fibres.

Ionic currents in intact and detubulated frog sartorius muscle fibres were compared at room temperature using a loose-patch voltage clamp configuration in four experimental groups. The test fibres (i) were detubulated by a previously established osmotic shock protocol that involved the introduction and withdrawal of extracellular glycerol followed by exposure to Ca2+/Mg2+-Ringer solution and cooling. The control fibres were spared osmotic shock and (ii) simply studied in normal Ringer solution, (iii) exposed to 30 min of steady cooling to 9-10 degrees C before electrophysiological study or (iv) exposed to and studied in glycerol-Ringer solution. The presence or absence of detubulation was confirmed for all the experimental groups through assessing for the abolition or otherwise of the delayed after-depolarisation normally associated with action potential propagation into the transverse (T) tubules. All fibre groups showed similar resting potentials (-80 to -90 mV) thus ensuring consistent baseline voltages from which the voltage clamp steps were imposed. The intact muscle fibres in the three control groups (ii)-(iv) spared osmotic shock showed both inward Na+ and delayed rectifier outward (K+) currents. In contrast, patches from detubulated muscle fibres in the test group (i) showed only delayed outward currents, consistent with contrasting contributions to Na+ and K+ currents from regions of membrane affected or spared by the detubulation procedure. Nevertheless, the voltage dependence, maximum steady state amplitudes and timecourses of the delayed outward currents were conserved through all the experimental groups. These findings suggest that the surface as opposed to the tubular membrane contributes the greater part of the delayed rectifier current in amphibian skeletal muscle.

Action Potentials↗

PubMed1978

Stimulation of the Na+ pump by hypotonic solutions in skeletal muscle.

The fractional loss of 22 Na+ from frog sartorius muscle is increased when the tonicity of the external solution is reduced. The effect, which is larger the lower the osmolarity, exhibits the following characteristics: (1) quick onset and reversibility, (2) is not reduced in the absence of external Na+, (3) is completely abolished by strophanthidin (3. 10-5 M), (4) is neither the result of membrane depolarization nor K+ accumulation in the extracellular space.

Animals↗

PubMed1990

The study of energy metabolism in denervated skeletal muscle with 31P-NMR.

1. The denervated frog sartorius muscle showed a decrease in the energy store more than that in the control. 2. In the caffeine contractures, both the denervated and the innervated muscles showed similar sequential changes in the relative concentration of phosphocreatine (PCr) to beta-adenosine triphosphate (beta-ATP) and inorganic phosphate (Pi) to beta-ATP. Instead, the intracellular pH value of the denervated muscle was lower than that of the control. 3. It is suggested that phosphate metabolism of the denervated muscle during contracture shows little difference from that of the control, nevertheless, the buffering capacity is decreased in the early stage of atrophy.

Animals↗

PubMed1988

Heat changes during transient tension responses to small releases in active frog muscle.

Tension and heat production were measured in frog sartorius muscles in response to small shortening ramps (releases) at high and moderate speed. Transient tension responses to fast releases (0.1 to 0.4 mm in 1 or 4 ms) were similar to the tension transients length-clamped single fibers. Tension time courses during releases at 25 mm/s were like fiber responses calculated from the first two phases of the step responses (Ford et al., 1977). We conclude that similar crossbridge transitions produce tension transients observed in whole muscles and single fibers. Heat was absorbed during rapid tension recovery after fast releases and during the later part of releases at 25 mm/s. Variation of heat absorption with release size was compared with that of crossbridge movement predicted by the Huxley-Simmons hypothesis of force generation (Huxley and Simmons, 1971). Agreement between the two supports the conclusion that heat is absorbed by the crossbridge transitions responsible for rapid tension recovery after release. The results indicate that the entropy change of these transitions is positive.

Animals↗

PubMed1988

Effect of carbon dioxide on heat production of frog skeletal muscles.

1. Maintenance heat produced in tetani of frogs' sartorius muscles (Rana japonica) was measured under various values of intracellular pH (pHi) brought about by increasing the CO2 concentration in Ringer solution. The pHi values were measured using 31P nuclear magnetic resonance from the chemical shifts of the inorganic phosphate resonance. The pHi was 7.10 +/- 0.009 (mean +/- S.E. of the mean, n = 10) in the gas mixture of 5% CO2/95% O2 at 4 degrees C and it was reduced to 6.44 +/- 0.001 (n = 23) in 45% CO2. 2. As CO2 was increased, the maximum force was decreased and relaxation was prolonged. This is in accordance with the results of Edman & Mattiazzi (1981) and Curtin (1986). 3. An increase in CO2 induced a reduction of the maintenance heat production, which can be divided into stable and labile heats (Aubert, 1956). The stable heat, which is produced with a steady rate during contraction, was decreased as CO2 was increased. The labile heat, which is produced with an exponentially declining rate, was not significantly altered by increasing CO2 within the range studied. 4. The effect of previous contractile activity on the labile heat production, i.e. the time course of repriming of the labile heat, could be described by an equation with two exponential terms in 5% CO2 in accordance with the result of Peckham & Woledge (1986). The time course of repriming of the labile heat was not affected by increasing CO2 to 20%.

Animals↗

PubMed1979

The extracellular compartments of frog skeletal muscle.

1. Detailed studies of solute efflux from frog sartorius muscle and single muscle fibres were carried out in order to characterize a 'special region' (Harris, 1963) in the extracellular space of muscle and determine whether this 'special region' is the sarcoplasmic reticulum. 2. The efflux of radioactive Na, Cl, glusose, 3-O-methylglucose, xylose, glycine, leucine, cycloleucine, Rb, K, inulin (mol. wt. 5000) and dextran (mol. wt. 17,000) from previously loaded muscles was studied. In all cases except dextran the curve had three components, a rapid (A) component which could be equated with efflux from the extracellular space proper, a slow (C) component representing cellular solute and an intermediate (B) component. The distribution space for the B component was 8% of muscle volume in summer frogs and 12% in winter frogs and appeared to be equal for all compounds studied. We tested the hypothesis that the B component originated from the sarcoplasmic reticulum. 3. The C component was missing from the dextran curves. Both dextran and inulin entered the compartment of origin of the B component (compartment B) to the same extent as small molecules. 4. For all compounds studies, the efflux rate constant for the A component could be predicted from the diffusion coefficient. For the B component the efflux rate constant was 6--10 times slower than that for the A component but was still proportional to the diffusion coefficient for the solute in question. 5. When Na and sucrose efflux from single fibres was followed, a B component was usually observed. The average distribution space for this component was small, averaging 1.5% of fibre volume. There was no difference between the average efflux rate constants for Na and sucrose. 6. In an appendix, the constraints placed on the properties of a hypothetical channel between the sarcoplasmic reticulum and the T-system by the linear electrical parameters of frog skeletal muscle are derived. It is shown that the conductance of such a channel must be less than 0.06 x 10(-3) mohs/cm2 of fibre membrane. 7. The conductance between compartment B and the extracellular space can be calculated from the efflux rate constants for Na, K and Cl. The value obtained was 5 x 10(-3) mhos/cm2 of fibre membrane or 100 times the limiting value for the conductance of the T-SR junction. 8. The finding that there is a B component in the efflux curves for large molecular weight substances like inulin and dextran and the small size of the B component in efflux curves from single muscle fibres indicate that the 'speical region' of the extra-cellular space of frog muscle is not the sarcoplasmic reticulum. This conclusion is confirmed by a calculation of the conductance between the B compartment and the extracellular space. The value obtained is incompatible with predicted electrical properteis of the SR-T-tubule junction...

Animals↗