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PubMed1986

Application of high-field 1H-NMR spectroscopy for the study of perifused amphibian and excised mammalian muscles.

Frog sartorius and gastrocnemius muscles were perifused at 20 degrees C, the intracellular pH (pHi) and the concentration of phosphocreatine were determined in the resting muscle by 1H-NMR spectroscopy at 470 MHz; values of pHi = 7.31 +/- 0.05 (n = 7) and concentration of phosphocreatine = 20.4 +/- 1.1 mumol/g wet wt. (n = 6) were found. The hydrolysis of phosphocreatine and the simultaneous increase in lactate upon perifusion with 10 mM caffeine (in Ringer's solution) was followed with a time resolution of 1 min. Lactate increased at a rate of 1.0 mumol/g per min, but no pHi change was recorded during the time monitored. The lower limit for the buffering capacity of the muscle cytosol was estimated to be 16.7 mumol/g muscle per pH unit from the uncertainty in pHi determination (+/- 0.03 pH units) and from the amount of lactate produced and phosphocreatine hydrolyzed. Changes in pHi, lactate concentration and fatty acyl chain intensity were monitored by 1H-NMR spectroscopy at 361 MHz in ischemic rat skeletal muscle, excised and stored at 20 degrees C. The resonances in the 1H-NMR spectrum of a human skeletal muscle perchloric acid extract are reported and tentatively assigned.

Animals↗

PubMed1972

The interaction between caffeine and calcium in the desensitization of muscle postjunctional membrane receptors.

The interaction between caffeine and calcium on the rate of desensitization of muscle postjunctional membrane (PJM) receptors during the sustained application of 0.27 mM carbamylcholine (CARB) has been studied in vitro on the sartorius muscle of the frog. The rate of PJM repolarization with CARB added to the solution bathing the muscle or the recovery of the effective transmembrane resistance (EMR) during the microperfusion of CARB directly onto the end-plate region of individual fibers was used as an index of the rate of desensitization. Caffeine (1.5 mM) increased the rate of PJM repolarization with bulk application of CARB in a 1.8 or 10 mM calcium Ringer solution but had no effect on PJM repolarization in a calcium-deficient, 4 mM magnesium Ringer solution. For EMR measurements the preparation was rendered mechanically quiescent by repeated challenges with isotonic KCl during an exposure of several hours to a calcium-free, 4 mM magnesium-1 mM EGTA Ringer solution. In these fibers, the microperfusion of 0.27 mM CARB together with 1.8 mM calcium plus 1.5 mM caffeine significantly increased the rate of EMR recovery above that observed in the absence of caffeine. Raising the calcium concentration to 10 mM had a similar effect; however, no additional increase was noted by the inclusion of 1.5 mM caffeine. It is suggested that the major role of caffeine in PJM desensitization is to increase the calcium permeability of the surface membrane. The transmembrane movement of calcium and the consequent intracellular accumulation of calcium is seen as a critical factor in controlling the rate of PJM desensitization.

Animals↗

PubMed1994

Arteriolar network response to pressure reduction during sympathetic nerve stimulation in cat skeletal muscle.

Previous studies in this laboratory have shown that autoregulation of blood flow and dilation of midsized (second-order) arterioles were significantly enhanced during sympathetic nerve stimulation of cat sartorius muscle apparently because of a greater myogenic response of the arterioles. Quite typically, blood flow increased with arterial pressure reduction to 80, 60, and 40 mmHg (superregulation) during sympathetic nerve stimulation. To determine the contribution of the various orders of arterioles to the enhanced autoregulation, we measured diameters in all orders of arterioles and measured red cell velocity in first-, second-, and third-order arterioles. Without sympathetic nerve stimulation, all orders of arterioles except the first order dilated to pressure reduction, but flow autoregulation was weak. With sympathetic nerve stimulation, arteriolar dilation to pressure reduction was significantly enhanced in all six orders of arterioles, and flow rose significantly. The resistance change in the arteriolar network during pressure reduction as calculated from diameter changes was greatest in third- and fourth-order arterioles. Experimentally determined flow changes to pressure reduction and to sympathetic nerve stimulation were quantitatively similar to those predicted from diameter changes in a model of the arteriolar network. Calculated wall shear stress (from viscosity and shear rate) for first-, second-, and third-order arterioles decreased during pressure reduction with and without sympathetic nerve stimulation. We concluded that endothelium-mediated dilation due to shear stress would tend to oppose autoregulation of blood flow to a similar degree under both circumstances.

Animals↗

PubMed1980

Volumetric growth of muscle fibers in ducks.

Pekin and Muscovy breeds of domestic ducks were reared from hatching to 10 weeks. Males and females of each breed were killed at weekly intervals and sartorius muscles were removed after the onset of rigor mortis. Fiber diameters were measured from macerated preparations after fixation with formaldehyde. All volumetric data were corrected to a common sarcomere length. Longitudinal and radial growth of muscles reached their maximum velocity during the fourth and fifth weeks, respectively. In Muscovies, heavier muscles in males relative to females were due to increased muscle length and cross sectional area. Faster early growth of Pekins relative to Muscovies was due to muscle length and fiber diameter. Histochemical analysis of supracoracoideus muscles frozen immediately postmortem showed that both adenosine triphosphatase and succinate dehydrogenase activity were negatively correlated with muscle fiber cross sectional area.

Adenosine Triphosphatases↗

PubMed1986

Capillary recruitment and heterogeneity of microvascular flow in skeletal muscle before and after contraction.

The two objectives of this study were to evaluate the spatial distribution of velocities measured simultaneously in a population of capillaries at the surface of a sartorius muscle in anesthetized frogs, and to estimate the cross-sectional density of capillaries perfused with red cells in this muscle at rest and after supramaximal stimulation. In each of 10 muscles studied, the mean velocity associated with this distribution increased significantly after the stimulation (overall increase from 0.12 mm/sec in control to 0.46 mm/sec at the peak of hyperemia). The coefficient of variation (i.e., ratio of standard deviation to mean velocity), however, decreased, indicating that the individual velocities became relatively more homogeneous and that microvascular adjustments occurred at the capillary level. Additionally, the proportion of capillaries with zero or very low velocities (0-0.1 mm/sec) was reduced practically in all muscles suggesting an improved oxygen exchange after every stimulation. In contrast to these consistent velocity responses in all muscles, capillary recruitment was detected only in 5 out of 10 muscles (overall density increase from 104 to 134 cap/mm2). This partial occurrence of recruitment (range, 23-149%) was associated with control mean velocities less than 0.1 mm/sec. Since, in light of the velocity data, the absence of recruitment in the 5 remaining muscles did not necessarily signify the lack of microvascular adjustments at the capillary level, it is proposed that more sensitive indexes, such as the reduction in the proportion of low flow capillaries and the increase in relative homogeneity, be used in addition to or instead of recruitment, to describe more completely the microvascular response to stimulation.

Animals↗

PubMed1981

[Neurotrophic control of frog skeletal muscle following parenteral administration of colchicine].

A study was made of the membrane potential, electric properties and membrane sensitivity of individual muscle fibers to acetylcholine, as well as of electrophysiological characteristics of evoked and spontaneous transmitter release in myoneural synapses of the frog sartorius muscle after parenteral administration of colchicine. After two weeks the decrease in the membrane potential and appearance of junctional sensitivity of muscle fibers to acetylcholine were observed without any changes in the electrical properties of the electrogenic membrane. Concurrently the number of synapses with low values of the quantum composition of EPP increased. Meanwhile spontaneous transmitter release was not affected. It is suggested that denervation-like changes in the muscle were caused by the direct action of the alkaloid on nerve terminals but not on the muscle.

Acetylcholine↗

PubMed1998

Endoscopic subcutaneous neurovascular lower-extremity myofascial flap harvesting for genitourinary reconstruction.

Neurovascular myofascial flaps have been widely utilized when healthy tissues outside the anatomic confines of the pelvis are necessary for complex genitourinary reconstructions. Myofascial flaps have great potential in providing support and tone to the bladder neck in a model of total urinary incontinence. Two muscles were evaluated for minimally invasive harvesting utilizing an adult rabbit and human cadaveric model: the gracilis, because of its neurovascular supply and length, and the sartorius, because of its location. Three adult New Zealand White rabbits were prepared and draped in sterile fashion after general anesthesia. Bilateral 2-cm incisions were made over the origins of the gracilis and sartorius muscles. Dissection times were entered in a database on a personal computer for paired Student t-tests. Special techniques for dissection included utilization of a 5-mm subcutaneous dissector/retractor and reticulated scissors and dissector. Once the tissues were harvested, rotational angles of the functional arcs around the origins of the gracilis and sartorius flaps were measured, as were the lengths of the muscular flaps from the proximal pedicle to the free distal end. Initial positioning of the myofascial flap at the bladder neck was investigated in this nonsurvival study. Blood loss was estimated before the animals were humanely sacrificed. The possibilities of minimally invasive genitourinary reconstruction are numerous. Both flaps can be dissected endoscopically and have rotational angles allowing transfer to more cephalad positions in the groin or intra-abdominally. Further studies are needed to establish the efficacy of the myofascial graft for minimally invasive genitourinary reconstructions.

Animals↗

PubMedDate not supplied

Effect of halothane on isometric twitch and tetanus response and the associated heat production in striated muscle of frogs.

The purpose of these investigations was to determine the effect of halothane on isometric contraction of striated muscle and to measure the associated heat production. This basic information is necessary before studies more directly relating to malignant hyperthermia are undertaken. Sartorius muscles were isolate from Rana pipiens during winter and summer months. It appears from these experiments that there is a prolongation of the relaxation phase of the twitch and tetanus responses with low concentrations of halothane, with a more diffuse effect on the contractile process evident at higher administered concentrations. The results of heat measurements, using a sensitive thermopile-galvanometer system, are compatible with the hypotheses that this effect on relaxation could result from either an interference with calcium reuptake by the sarcoplasmic reticulum or an increased affinity of the troponintropomyosin complex for available calcium.

Animals↗

PubMed1983

Effects of verapamil on indirect muscle twitch responses.

The effects on indirectly elicited muscle twitch amplitude associated with the calcium (slow) channel blocker, verapamil, with or without pancuronium were investigated using isolated bullfrog sciatic nerve-sartorius muscle preparations. Verapamil (2-8 mM) produced a dose-related depression of indirect muscle twitch height (P less than 0.05). Twitch response was depressed 11% below control by the lowest concentration employed and 86% by the highest concentration. Pancuronium (0.07 mM) depressed neuromuscular function 35% below control (P less than 0.05). The combination of 5 mM or 8 mM verapamil with 0.07 mM pancuronium caused significantly greater degrees of depression than either drug alone. Verapamil produced significant depression of twitch height in vitro in relatively high concentrations. The mechanism of action remains unknown. Verapamil possesses pharmacologic properties that may be unrelated to slow (calcium) channel inhibition. The reduction of muscle twitch height caused by verapamil alone (5 mM) could not be antagonized by neostigmine, calcium, or frequent washings.

Animals↗

PubMed1989

Localized heterogeneity of red cell velocity in skeletal muscle at rest and after contraction.

Using intravital video microscopy, the present study focussed on a detailed analysis of Vrbc heterogeneity in a 2.4 x 1.8 x 0.15 surface volume of a frog sartorius muscle, before and after supramaximal contraction. Heterogeneity of Vrbc was evaluated (1) for an entire population of capillaries seen in this volume, (2) for a series of optical cross-sections, (3) along a series of longitudinal muscle strips, and (4) in terms of an asymmetry ratio for pairs of concurrent capillaries surrounding a muscle fibre. All four types of analysis showed an increased Vrbc homogeneity after contraction. Velocities became more homogeneous along rather than across muscle fibres. The mean asymmetry ratio became significantly larger during post-contraction hyperemia suggesting that each fibre receives a more uniform blood supply that will contribute to an improved exchange of materials across the capillary wall. The analysis of localized Vrbc heterogeneity provides new means of pinpointing the sources of perfusion heterogeneity. It enables, therefore, a specific experimental intervention that is aimed at an improved perfusion under both normal and abnormal conditions.

Animals↗

PubMed1984

Changes in intracellular pH and inorganic phosphate concentration during and after muscle contraction as studied by time-resolved 31P-NMR. Alkalinization by contraction.

The changes in intracellular pH and concentration of inorganic phosphate (Pi) were studied during and after contraction of bullfrog sartorius muscles by using 31P-NMR. The intracellular pH was 7.04 in resting muscles at 4 degrees C and an alkalinization by as much as 0.08 pH unit occurred following 5 s tetanic contraction. During the recovery period after contraction the increased level of intracellular pH returned to the resting level, the time course of which coincided with that of the recovery of the Pi concentration. Based on the changes in the intracellular pH and Pi concentration, the buffering power was estimated to be 18 mM/pH unit.

Animals↗

PubMed1998

Z/I and A-band lattice spacings in frog skeletal muscle: effects of contraction and osmolarity.

A-band and Z-line/I-band lattice spacings were measured by small-angle X-ray diffraction from relaxed and isometrically-contracting whole frog sartorius muscles with lattice spacings reduced or swollen by changing the osmolarity of the bathing solution. A-band spacing increased by approximately 3% upon isometric contraction at reduced lattice spacings (245-356 mOsm) and decreased by approximately 1% at swollen spacings (172 mOsm), similarly to the behaviour of skinned muscles upon changing from the relaxed state to rigor. The Z/I lattice underwent a significant lattice expansion (3-8%) upon isometric contraction at all osmolarities, in qualitative agreement (but quantitative disagreement) with results from electron microscopy on mammalian skeletal muscle. Lattice areas calculated for the Z/I and A-band lattices indicate a barrel-shaped sarcomere in the resting state, which may provide a partial explanation for how longitudinal forces produced in the A-band can produce a radial expansive force in the Z-line during contraction. The radial component of cross-bridge stiffness was calculated from the A-band data for contracting muscle, using a lattice stability model incorporating structural, osmotic and electrostatic forces. The calculations gave a radial cross-bridge stiffness during contraction of about 9 x 10(5) N m-2, and outward radial force per thick filament in normal Ringer's solution of 6 x 10(-9) N, corresponding to a radial force per cross-bridge of 10(-11) N.

Animals↗

PubMed1979

Binding of scorpion toxin to receptor sites associated with sodium channels in frog muscle. Correlation of voltage-dependent binding with activation.

Purified scorpion toxin (Leiurus quinquestriatus) slows inactivation of sodium channels in frog muscle at concentrations in the range of 17-170 nM. Mono[125I]iodo scorpion toxin binds to a single class of sites in frog sartorius muscle with a dissociation constant of 14 nM and a binding capacity of 13 fmol/mg wet weight. Specific binding is inhibited more than 90% by 3 microM sea anemone toxin II and by depolarization with 165 mM K+. Half-maximal inhibition of binding is observed on depolarization to -41 mV. The voltage dependence of scorpion toxin binding is correlated with the voltage dependence of activation of sodium channels. Removal of calcium from the bathing medium shifts both activation and inhibition of scorpion toxin binding to more negative membrane potentials. The results are considered in terms of the hypothesis that activation of sodium channels causes a conformational change in the scorpion toxin receptor site resulting in reduced affinity for scorpion toxin.

Animals↗

PubMed1988

An electronic mechanism in the action of drugs, ATP, transmitters and other cardinal adsorbents. II. Effect of ouabain on the relative affinities for Li+, Na+, K+, and Rb+ of surface anionic sites that mediate the entry of Cs+ into frog ovarian eggs.

Ouabain enhanced the inhibitory effects of Li+, Na+, and K+ on the rate of Cs+ permeation into frog ovarian eggs while it reduced the inhibiting effect of Rb+. The data agree with earlier demonstrated effects of ouabain on the rank order of selective accumulation of the five alkali-metals in frog muscles and on the relative effectiveness of glycine, Li+, Na+, K+, Rb+, and Cs+ in inhibiting the rate of entry of Cs+ into frog sartorius muscle. In all three cases, the ouabain behaved as an electron-donating cardinal adsorbent (EDC) causing a rise of the electron density (c-value) of the beta- and gamma-carboxyl groups in the cell cytoplasm (for selective accumulation) and on the cell surface (for selective ion permeation). Explanations based on the association-induction hypothesis were offered why an EDC like ouabain does not initiate cell activation (like veratridine does) and why Ca++ and tetradotoxin delays or inhibits physiological and artificial cell activation.

Animals↗

PubMed1984

The effect of the ATP analogue AMPPNP on the structure of crossbridges in vertebrate skeletal muscles: X-ray diffraction and mechanical studies.

Adenylylimidodiphosphate (AMPPNP), a nonhydrolysable analogue of ATP, has been used to arrest the crossbridge cycle of muscular contraction in one of its hypothetical intermediate states. Whole frog sartorius muscles were chemically demembranated, and it was found possible to cycle such skinned muscles reversibly between the relaxed and rigor states. The effect of binding of AMPPNP on the structure and spatial arrangement of the crossbridges of such muscles was studied using low-angle X-ray diffraction, with simultaneous recording of the mechanical effects, starting from the rigor state. Saturating concentrations of MgAMPPNP produce a characteristic decrease of about 50% in the original rigor isometric tension with a concomitant increase in muscle length by 0.13%. The equatorial X-ray diffraction pattern is modified in the following way: the lattice dimensions and the intensity of the (10) equatorial reflection do not change, while the intensity of the (11) equatorial reflection increases slightly. These observations of very small equatorial changes could be explained by assuming that in these muscles (as distinct from others such as rabbit psoas) the analogue does not produce a significant degree of detachment of crossbridges; that is, there are only AMPPNP-modified attached ones. The changes in the meridional X-ray diffraction pattern are more pronounced: the meridional reflection at 14.5 nm decreases in intensity, and the meridional reflection at 7.2 nm increases considerably: the intensity of all the actin-based off-meridional layer-lines decreases. There are no signs of the characteristic relaxed layer-lines, and the changes in the layer-line intensities are probably due to there being a single population of AMPPNP-modified attached crossbridges, rather than a mixture of attached and detached crossbridges. Thus the AMPPNP X-ray pattern, both equatorially and meridionally, is somewhat similar to the rigor one, indicating that most of the crossbridges remain attached. On the other hand, the fact that there are some changes in the layer-line intensities of the AMPPNP frog pattern, without the appearance of any signs of a relaxed equatorial pattern, indicates that the attached crossbridges are in a structural state that is different from rigor, one is not seeing, apparently, simply a mixture of rigor and relaxed states. Our tentative interpretation of this result is that there may be a structural change in the crossbridge near to the junction with S2, with less significant changes occurring in the parts of the crossbridge close to actin.

Adenosine Triphosphate↗

PubMed2006

Successful management of recalcitrant groin lymphorrhoea with the combination of intraoperative lymphatic mapping and muscle flap.

Recalcitrant groin lymphorrhoea in high-risk patients remains a problem. In this report, a cardiac transplant patient with recalcitrant groin lymphorrhoea was successfully treated with a combination of intraoperative lymphatic mapping and sartorius muscle flap. We believe that the combined use of these two treatment options offers a more effective approach for surgical treatment of recalcitrant groin lymphorrhoea and should be considered when managing this difficult clinical problem, especially in high-risk patients.

Groin↗

PubMed1976

Spectrophotometric studies on the pH of frog skeletal muscle. PH change during and after contractile activity.

The spectral characteristics of the pH-sensitive dyes neutral red (NR) and bromcresol purple (BCP) were utilized for studies of the changing intracellular pH (pHi) of sartorius muscles from Rana pipiens, both during the course of an isometric twitch and during recovery metabolism subsequent to a train of twitches. The information from the two dissimilar dyes correlated to confirm the methodology. Neither the fast realkalinization observed during a twitch nor the slow alkalizing phase of recovery metabolism was affected in an obvious manner when phosphocreatine (PC) hydrolysis was blocked by 1-fluoro-2,4-dinitrobenzene (FDNB). Iodoacetic acid (IAA) did inhibit the slow acidic phase of recovery metabolism. The conclusion is made that alkalizing reactions other than PC breakdown must be considered as operative at these levels of activity. Hypertonic solutions altered twitch tension and time course without altering the pHi shifts observed until approximately 75% of the twitch amplitude was abolished. Multiple effects of hypertonic solutions as the muscle approach tonic equilibrium are proposed.

Animals↗

PubMed2001

Normal conduction of surface action potentials in detubulated amphibian skeletal muscle fibres.

1. The influence of the transverse (T) tubules on surface action potential conduction was investigated by comparing electrophysiological and confocal microscopic assessments of tubular changes in osmotically shocked and control fibres from frog sartorius muscle. 2. The membrane-impermeant fluorescent dye, di-8-ANEPPs spread readily from the bathing extracellular solution into the tubular membranes in control, intact fibres. Prior exposure of muscles to a hypertonic glycerol-Ringer solution, its replacement by an isotonic Ca(2+)-Mg(2+) Ringer solution and cooling sharply reduced such access. In contrast, dye application in the course of this osmotic shock procedure stained the large tubular vacuoles hitherto associated with successful muscle detubulation. 3. Conduction velocities in intact, control fibres (1.91 +/- 0.048 m s(-1), mean +/- S.E.M., n = 32 fibres) agreed with earlier values reported at room temperature (18-21 degrees C) and were unaffected by prior episodes of steady cooling to 8-10 degrees C (1.91 +/- 0.043 m s(-1), n = 30). 4. Cooling to 11.5 degrees C reduced these velocities (1.47 +/- 0.081 m s(-1), n = 25) but action potential waveforms still included early overshoots and the delayed after-depolarizations associated with tubular electrical activity. 5. In contrast, action potentials from cooled, superficial fibres in osmotically shocked muscles lacked after-depolarization phases implying tubular detachment. Their mean conduction velocities (1.62 +/- 0.169 m s(-1), n = 25) were not significantly altered from values obtained in untreated controls or in intact fibres in muscle similarly treated with glycerol, in direct contrast to earlier results. 6. Cooling produced similar reductions in maximum rates of voltage change dV/dt in action potentials from all fibre groups with lower rates of change shown by detubulated fibres. 7. Use of an antibody to a conserved epitope of the alpha-subunit of voltage-gated sodium channels suggested a concentration of sodium channels close to the mouths of the T tubules. 8. These electrophysiological and anatomical findings are consistent with a partial independence of electrical events in the transverse tubules from those responsible for the rapid conduction of surface regenerative activity. 9. The findings are discussed in terms of a partial separation of the electrical activity propagated over the surface membrane, from the initiation of propagated activity within the T tubules, by the triggering of the sodium channels clustered selectively around the mouths of the T tubules.

Action Potentials↗