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Delayed type IV muscle flap in a feline model.

The concept of delaying a skin flap is well established and has been implemented into plastic surgery practice for years. Some investigators have delayed musculocutaneous flaps to improve the perforator inflow. To our knowledge, the concept of delaying a muscle flap had previously never been tested in a model with segmental pedicles. Five cats each underwent 3 sequential operations providing them with a sartorius muscle whose blood supply was a single distal pedicle. The opposite leg was used as a control. Our delayed type IV muscle flap demonstrated perfusion to the proximal tip of the sartorius muscle without necrosis or loss of muscle mass (P < 0.0001). The control showed no evidence of perfusion beyond the distal portion of the muscle when infused through the distal pedicle. The delayed flap can survive on a distal blood supply that would not be adequate in a single-stage procedure. This flap has an increased arc of rotation that may provide solutions to difficult reconstructive problems in the groin, lower abdomen, genitalia, knee, proximal leg, and might be suitable as a free flap.

Animals↗

Electrolyte distribution in toad sciatic nerve and spinal cord.

The distribution of Na+, K+ and water was studied in spinal cord, sciatic nerve and sartorius muscle of the toad, Bufo arenarum (Hensel). Electrolyte assays and sodium washout curves were made. In sartorius muscle, extracellular water was estimated to account for 18.9% of total tissue weight and the intracellular concentrations of Na+ and K+ were 18.4 and 147.9 mEq/kg of intracellular water respectively. In spinal cord extracellular water was 17.2%, intracellular Na+ was 40.6 mEq/kg of water, and intracellular K+ was at a concentration of 134.5 mEq/kg. Interpretation of washout curves in sciatic nerve could not be as simple as in other tissues due to the connective sheath, and therefore electron micrograph measurements had to be made in order to estimate how much of the total tissue weight could be attributed to the sheath. Assuming that it had a water and electrolyte composition similar to that of plasma, the sheath corresponded to 22.3% of the nerves and contained a proportional fraction of Na+ and K+. These calculations left an 'excess' of Na+ and water to be distributed among the remaining components of sciatic nerve. Application of the pyroantimoniate histochemical technique for Na+ determination disclosed a large amount of precipitate among myelin lamellae both in sciatic nerve and in spinal cord. This might explain at least in part the distribution of the 'excess' Na+ in both nervous tissues.

Animals↗

A triple-barreled microelectrode for simultaneous measurements of intracellular Na+ and K+ activities and membrane potential in biological cells.

A triple-barreled Na+, K+-selective microelectrode was constructed with liquid ion exchangers for Na+ (monensin) and K+ (Corning #477317) to measure the intracellular Na+ and K+ activities ((Na)i and (K)i) of a single cell and its membrane potential (EM), simultaneously. The tip of the triple-barreled assembly was made less than 0.6 micron in outside diameter. Prior to in vivo measurements, some physiochemical properties of microelectrodes were examined in vitro for the slope constant, selectivity coefficient, electrical resistance, and pH effect, as well as measurements of the activity coefficient on ions in blood serum and Ringer solution. Carrying out direct micropunctures on single cells of the sartorius muscle and renal proximal tubule of bullfrogs in vivo, we obtained the following results: (1) In sartorius muscle, the average (Na)i was 14.8 mEq/liter, the (K)i 64.5 mEq/liter, and the EM -86.2 mV. (2) In proximal tubule cells, the average (Na)i, (K)i and EM were 16.8, 63.0 mEq/liter and -65.9 mV, respectively. (3) There were significant correlations in the proximal tubule between (K)i and EM, and inversely between (Na)i and EM, and between (Na)i and (K)i. These facts may somehow be related to both the activity of Na+-K+ exchange pump and the osmotic equilibrium of water across the membrane. Further, several problems inherent in the multibarreled microelectrode were discussed from the practical point of view.

Animals↗

The visualization of myosatellite cells in normal and denervated muscle: a new light microscopic staining technique.

A new light microscopic staining technique allows the visualization of satellite cells on the surface of myofibers. Either prior to or during fixation, whole frog sartorius muscles are bathed in an acidic buffered solution containing lead nitrate and subsequently exposed to ammonium sulfide. The staining of the satellite cells resulting from this procedure reveals their positions, and the outlines of their cell processes which occasionally branch. Electron microscopy shows that the staining is due to lead deposits localized between apposing membranes of satellite cells and associated myofibers. Prior exposure to N-ethyl-maleimide (NEM) does not alter the formation of the lead deposits on the satellite cell, but reduces the amount of Pb deposits on the muscle surface and connective tissue. This technique has been applied to determine the effects of denervation on the satellite cells of frog sartorius muscles. Four weeks after denervation, the number of satellite cells is essentially the same in both denervated muscles and the intact muscles of the contralateral side. However, denervation results in a subpopulation of satellite cells with altered shapes. They have elongated cytoplasmic processes which often branch. It is suggested that these supernumerary cytoplasmic processes represent an intermediate phase in the transition of satellite cells to myoblasts.

Animals↗

Elevated levels of polyneuronal innervation persist for as long as two years in reinnervated frog neuromuscular junctions.

When the nerve to an adult frog sartorius muscle is crushed, and axons are allowed to regenerate, the level of polyneuronal innervation at reinnervated neuromuscular junctions is higher than normal. With time, much of this polyneuronal innervation is reduced by the process of synapse elimination (Werle and Herrera, 1988). Using intracellular recording, we estimated the level of polyneuronal innervation in adult frog (Rana pipiens) sartorius muscles 2 years (range: 1.7-2.4 years) after crushing the sartorius nerve. We found that 27% (S.E. = 1.4%) of the junctions in muscles 2 years after reinnervation were polyneuronally innervated, whereas only 10% (S.E. = 1.2%) of the junctions in normal frog muscles were polyneuronally innervated. Thus, the synapse elimination that occurs following reinnervation does not restore the normal level of polyneuronal innervation. Histological comparisons of junctional structure between muscles 2 years after reinnervation and normal muscles revealed substantial differences. Reinnervated junctions had a greater length of synaptic gutter apposed by nerve terminal processes, more axonal inputs, more empty synaptic gutter, more instances of single synaptic gutters innervated by more than one axon, and longer lengths of nerve terminal processes that connect synaptic gutters within a junction. On the basis of this physiological and anatomical evidence, we conclude that nerve injury causes persistent changes in the pattern of muscle innervation.

Animals↗

The physostigmine depolarization potentiating effect of salicylate in frog skeletal muscle.

1) The frog's sartorius muscle was depolarized depending on the degree of concentration 2--4 times more intensely by physostigmine salicylate than by physostigmine sulphate. 2) In normal Ringer's solution, 1 mM physostigmine salicylate decreased the sensitivity of the membrane to potassium depolarization by about 90%. Under similar experimental conditions, physostigmine sulphate and Na salicylate, respectively, decrease the sensitivity of the membrane to potassium depolarization by about 30%. 3) The difference manifested in the depolarizing effect of salicylate and other physostigmine salts (chloride, sulphate, phosphate, formiate, acetate, monochloracetate, benzoate and para-oxy-benzoate) is expressed already at 1 mM concentration (about 10-fold), if the muscle had been equilibrated in chloride-free glucuronate or sulphate milieu. 4) The depolarization develops slowly. It takes 30--60 minutes for the new steady state to develop even in the superficial sartorius fibres. If depolarization has reached its maximum on an average 100 mV, the membrane potential remains unchanged for hours. 5) Depolarization ensues at an unchanged degree in the presence of Na-free (choline) Ringer as well as in the presence of 2X10(-8) g/ml tetrodotoxin; therefore, it is not a Na-dependent process. 6) Under the influence of 1 mM physostigmine salicylate the membrane's resistance to the inward potassium current increased about twofold, while the increase was only 15% to the outward potassium current. It is assumed that the salicylate anion is characteristically capable of potentiating the decreasing effect of physostigmine on potassium permeability, though the role of the metabolic effect of salicylate cannot be excluded.

Animals↗

Mechanism of neuromuscular blockade induced by phenthonium, a quaternary derivative of (-)-hyoscyamine, in skeletal muscles.

1. The mechanisms underlying the postjunctional blockade induced by phenthonium [N-(4-phenyl) phenacyl 1-hyoscyamine] were investigated in mammalian and amphibian muscles. This muscarinic antagonist was previously shown to enhance specifically the spontaneous acetylcholine (ACh) release at concentrations that blocked neuromuscular transmission. 2. In both rat diaphragm and frog sartorius muscles, phenthonium (Phen, 1-100 microM) depressed the muscle twitches elicited by nerve stimulation (IC50: 23 microM and 5 microM, respectively), and blocked the nerve-evoked muscle action potential. The neuromuscular blockade was not reversed after incubation with neostigmine. 3. Equal concentrations of Phen decreased the rate of rise and prolonged the falling phase of the directly elicited action potential in frog sartorius muscle fibres, indicating that the drug also affects the sodium and potassium conductance. 4. Phen (50 and 100 microM) protected the ACh receptor against alpha-bungarotoxin (BUTX) blockade in the mouse diaphragm allowing recording of endplate potentials and action potentials after 5 h wash with physiological salt solution. 5. Phen (10-100 microM) produced a concentration- and voltage-dependent decrease of the endplate current (e.p.c.), and induced nonlinearity of the current-voltage relationship. At high concentrations Phen also shortened the decay time constant of e.p.c (tau(e.p.c.)) and reduced its voltage sensitivity. 6. At the same range of concentrations, Phen also reduced the initial rate of [125I]-BUTX binding to junctional ACh receptors of the rat diaphragm (apparent dissociation constant = 24 microM), the relationship between the degree of inhibition and antagonist concentration being that expected for a competitive mechanism. 7. It is concluded that Phen affects the electrical excitability of the muscle fibre membrane, and blocks neuromuscular transmission through a mechanism that affects the agonist binding to its recognition site and ionic channel conductance of the nicotinic ACh receptor.

Animals↗

Natural probes for cholinergic sites: L-bebeerine actions on the neuromuscular transmission, the nicotinic receptor/ionic channel complex, and contraction of skeletal muscles.

The mechanisms underlying the muscle relaxant activity of 1-bebeerine (BB), a tertiary alkaloid isolated from the roots of Chondrodendron platyphyllum, were examined in mammalian and amphibian skeletal muscles. Injections of BB (0.05-1 g/kg, i.p.) in rats caused a dose-related flaccid paralysis and respiratory arrest at high doses. In isolated rat diaphragm and toad sartorius muscles, BB depressed the indirectly elicited muscle twitches (IC50: 228 microM and 5.4 microM, respectively, at 22 degrees C) and blocked the nerve-elicited muscle action potential. The neuromuscular blockade was not reversed by neostigmine (10 microM). High concentrations of BB (170 and 340 microM) caused muscle contracture unrelated to the junctional blockade, and intensified by increasing the bath temperature. Analysis of the contraction properties showed that BB (40 and 80 microM) increased the twitch/tetanus ratio (46% and 125%) and prolonged the relaxation time; the falling phase of the directly elicited action potential in toad sartorius muscle fibers was slower probably by a decreased potassium conductance. BB (0.1-340 microM) reduced the binding of [125l]alpha--bungarotoxin to the junctional ACh receptor of the rat diaphragm (IC50: 47.7 microM, at 37 degrees C. At low concentrations BB (1.5-15 microM) induced either opening or blockade of the ACh receptor-ionic channel. The results showed that BB blocked noncompetitively the neuromuscular transmission through a mechanism that affects the ACh recognition site and the ionic channel properties. The alkaloid also produced muscle contracture and changed the contractile properties through its extra-junctional action at the calcium handling by the sarcoplasmic reticulum or the contractile machinery.

Alkaloids↗

The inhibitory actions of eserine and ouabain on the K, Rb and Cs uptake in slow and fast twitch muscles of the rat.

Comparative, in vitro studies were carried out on the 42K, 86Rb, and 131Cs uptake in fast twitch extensor digitorum longus (EDL), slow twitch soleus (SOL) muscles of the rat, and in fast muscle (sartorius) of the frog. The inhibitory action of ouabain (10(-4) M) and eserine (10(-3) M) on the influxes of alkali cations was investigated. The rate of potassium influx in isolated EDL muscles was higher than that of SOL, while no difference could be found in 86Rb or 131Cs influx in the two types of mammalian muscles under in vitro condition. Ouabain inhibited to about the same extent the influx of K (25%) of both types of mammalian muscles and also in fast amphibian muscle. On the other hand, the eserine sensitive component of 42K influx in fast twitch mammalian muscle (EDL) was about one-fourth of the total influx and even less in slow twitch mammalian muscle (SOL), while in frog muscle it amounted to about two-third of the total. The "residual" potassium influx, which represents the influx remaining after simultaneous treatment of the muscles with cardiac glycoside and eserine was about half of the total in EDL and SOL, but it was only a fraction of it in the frog sartorius muscle. The results may be explained on the basis of the morphological differences of the transverse tubular and sarcoplasmic reticulum systems of fast and slow mammalian muscles.

Animals↗

Metabolic and myogenic factors in local regulation of the microcirculation.

Patterns of flow were recorded from individual capillaries of mesentery and muscle during autoregulation and reactive hyperemia. In cat mesentery at normal arterial pressure capillary blood flow was often periodic in nature. When arterial pressure was reduced periodicity was abolished and in certain cases mean flow increased. Elevation of venous pressure at this time caused restoration of flow periodicity and simultaneously a large fall in mean flow. Vasomotion and autoregulation in mesentery appear to be dependent on intravascular pressure per se. In cat sartorius muscle substantial increase in flow was seen in most capillaries during reactive hyperemia. In certain capillaries the pattern resembled the gross flow pattern while others showed a brief hyperemia and then a period of flow arrest that is presumably due to a strong precapillary vasoconstriction. The latter response is suggestive of a myogenic control while the former may be due to accumulation of metabolites. In frog pectoralis muscle reactive hyperemia was very prolonged in comparison to cat sartorius muscle. The general pattern of flow was consistent with the notion of a strong metabolic control mechanism. The three tissues studied provide examples of strong myogenic, strong metabolic, and combined metabolic and myogenic control of the microcirculation.

Animals↗

The influence of extracellular buffer concentration and propionate on lactate efflux from frog muscle.

Lactate efflux from frog sartorius muscles was measured following a lactate load of about 18 mumol X g-1 induced by a 4-min period of stimulation. Lactate efflux rate was buffer concentration dependent. The initial efflux rate increased from about 150 nmol X g-1 X min-1 in 1 mM MOPS buffer to 400 nmol X g-1 X min-1 in 25 mM MOPS buffer. The addition of 20 mM propionate reduced mean intracellular pH by about 0.2 units and increased lactate efflux rate by 70% at the highest buffer concentration and 400% at the lowest buffer concentration. The observed results are in reasonable agreement with predictions based on a model in which net efflux is limited by diffusion of both buffer and lactate in the extracellular space. Transmembrane lactate efflux appears to consist of two components, one of which is proton linked and carried either by undissociated lactic acid or coupled proton-lactate transport, the other being carried by independent lactate ions.

Animals↗

Active state of muscle in iodoacetate rigor.

Frog sartorius muscles, equilibrated to 2 x 10(-4)M iodoacetic acid-Ringer's solution and activated by a series of twitches or a long tetanus, perform a rigor response consisting in general of a contractile change which plateaus and is then automatically reversed. Isotonic rigor shortening obeys a force-velocity relation which, with certain differences in value of the constants, accords with Hill's equation for this relation. Changes in rigidity during either isotonic or isometric rigor response show that the capacity of the rigor muscle to bear a load increases more abruptly than the corresponding onset of the ordinarily recorded response, briefly plateaus, and then decays. A quick release of about 1 mm. applied at any instant of isometric rigor output causes the tension to drop instantaneously to zero and then redevelop, the rate of redevelopment varying as does the intensity of the load-bearing capacity. These results demonstrate that rigor mechanical responses result from interaction of a passive, undamped series elastic component, and a contractile component with active state properties like those of normal contraction. Adenosinetriphosphate is known to break down in association with development of the rigor active state. This is discussed in relation to the apparent absence of ATP splitting in normal activation of the contractile component.

Adenosine Triphosphate↗

The dependence on extent of shortening of the extra energy liberated by rapidly shortening frog skeletal muscle.

1. Pairs of frog sartorius muscles were stimulated for 2 sec at 0 degrees C, after 1 sec of isometric contraction, were released at a constant velocity. The total excess heat (shortening heat) and work associated with the release were determined by comparison with isometric control tetani. 2. Shortening heat and work production were non-linearly related to the distance shortened. There was proportionally more energy liberation for smaller releases. 3. The dependence of shortening heat on muscle length was investigated within the sarcomere length range 2.1--2.6 micrometer (as measured in resting muscle) and was found to be similar to that of isometric tension. 4. A simple model in which heat and work are produced in a two-state cycle can describe these and previous results concerning the energetics of rapidly shortening muscle.

Animals↗

ADENOSINE TRIPHOSPHATE: CHANGES IN MUSCLES DOING NEGATIVE WORK.

Frog sartorius muscles were isolated, treated with 1-fluoro-2, 4-dini-trobenzene at 0 degrees C, then stimulated tetanically at the length in situ and stretched with a Levin-Wyman ergometer during stimulation. The normal adenosine triphosphate breakdown during the tetanus was reduced by about half during the forced stretch. The tension was increased by about 70 percent, but resynthesis of adenosine triphosphate did not occur. Thus, on the basis of A. V. Hill's results, adenosine triphosphate is probably not the direct final energy source for muscular contraction, although it intimately participates in the process. The use of adenosine triphosphate during negative work was less than one-tenth that needed for positive work.

Adenosine Triphosphate↗

Variation in thin filament size in the skeletal muscle of the frog.

The sartorius muscle of Rana esculenta was fixed and dehydrated by different methods and cross-sections of sarcomeres of different lengths were examined by electron microscopy. The area within the outlines of the thin filaments in negatives was measured using a high-resolution television system and a graphics tablet or by using a microdensitometer and computer processing the images with a density threshold above the background level. In all specimens the area of the thin filaments in the I-bands was found to be larger than in the S-zones of the A-bands where the thick and thin filaments interpenetrate. The difference was statistically significant and independent of the length of the sarcomere. The results are in agreement with previous observations in glycerol-extracted fibres. It is suggested that the change in size of the thin filaments might be accounted for by some interaction with the thick filaments.

Actin Cytoskeleton↗

Effect of diazepam on calcium translocation during physiological muscle fatigue.

Stimulation of frog sartorius muscle at 1 Hz leads to an initial positive staircase during the first 120 twitches and is followed by a negative staircase. There is a net calcium influx into two distinct compartments within the muscle during the positive staircase. The two compartments are separated by measuring the calcium extracted from muscles soaked in strontium-Ringer for 15 min and the calcium remaining in the muscle. A net gain of extractable Ca++ (0.32 mumol/g wet wt.) and residual Ca++ (0.18 mumol/g) is observed during positive staircase. A loss in residual Ca++, a gain in extractable Ca++ and a net loss of Ca++ (0.09 mumol/g) to the bathing medium occur during the period preceding physiological muscle fatigue (60 to 120 twitches). Diazepam (EC50, 5.6 X 10(-6) M) causes a marked reduction in the latent period and increases the rate constant 2.6 times the control value for physiological muscle fatigue. A net loss of 0.31 mumol/g of Ca++ to the bathing medium occurs during the interval between 60 and 120 twitches. Diazepam increases net Ca++ efflux 3.5-fold during this interval when compared to control muscles. Diazepam does not affect the Ca++ gained during the positive staircase but accelerates the loss of calcium from the residual and the extractable compartments during the initial phase of physiological muscle fatigue. Physiological muscle fatigue is attributed to an accumulation of calcium in the transverse tubular network and an uncoupling of the muscle action potential from contraction.

Animals↗

Skeletal muscle relaxant properties of the aqueous extract of Portulaca oleracea.

The skeletal muscle relaxant properties of an aqueous extract of Portulaca oleracea were examined on the twitch and tetanus tension evoked by electrical stimulation using the rat phrenic nerve-hemidiaphragm and frog sciatic nerve-sartorius muscle preparations and on contractures induced by nicotinic agonists using the rat rectus abdominis muscle preparation. The extract (5-50 X 10(-4) g/ml) produced a dose-dependent initial enhancement, followed by a longer lasting depression of twitch tension as induced by indirect electrical stimulation (NS) as well as direct stimulation (MS) of the diaphragm and sartorius muscle preparations. The augmentation of twitch amplitude (MS) produced by the extract was not significantly antagonised or potentiated by d-tubocurarine (5-50 X 10(-8) M) or physostigmine (5-50 X 10(-8) M) at concentrations which blocked or potentiated NS-induced twitch contractions. Furthermore, tetrodotoxin (5 X 10(-7) g/ml) alone or in combination with d-tubocurarine did not significantly attenuate extract-induced augmentation of twitch contractions to MS. In addition, the depression of twitch tension due to NS was not antagonised by physostigmine but was reversed and/or abolished by Ca2+ (2-5 X 10(-3) M) or potassium thiocyanate (1 X 10(-3) M). Contractures induced by K+ (80 mM) or by tetanic stimulation (20-60 Hz) were significantly reduced by the extract whereas, contracture induced by caffeine (2.5-6.0 mM) was not affected. Ca2+-free Tyrode's solution and EDTA (1.25 X 10(-3) g/ml) potentiated extract-induced depression of twitch tension to MS. On the rectus abdominis, contractures induced by nicotinic agonists (acetylcholine, 3-500 X 10(-7) M; carbachol, 5-500 X 10(-7) M and nicotine, 5-500 X 10(-8) M) were significantly attenuated and/or abolished by the extract (5-10 X 10(-3) g/ml). These observations indicate that the aqueous extract possesses unique skeletal muscle relaxant properties which do not appear to involve interference with cholinoceptor mechanism(s). It appears that the mechanism of action of the extract may involve interference with Ca2+ mobilization in skeletal muscle.

Animals↗

Comparison of myosin isoenzymes from slow-tonic and fast-twitch fibers of frog muscle.

Myosin from distal cruralis bundle of triceps femoris composed of slow-tonic and fast-twitch fibers in an about 1 to 1 ratio, from rectus abdominis containing a lower proportion of slow-tonic fibers, and from a fast-twitch sartorius muscle of the frog, was characterized by means of polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate (SDS), electrophoresis in non-dissociating conditions, and determination of the ATPase activity. SDS-polyacrylamide gel electrophoresis failed to reveal the presence of any specific light chain in myosin from slow-tonic fibers. Light chains having the same mobilities as fast-twitch LC1 and LC2 were observed; as previously described by Focant and Reznik [15], myosin from tonic fibers appears, on the other hand, devoid of LC3. By electrophoresis in non-dissociating conditions myosin from sartorius muscle was resolved into three components which comigrated with the three myosin isoenzymes from the fast-twitch posterior latissimus dorsi muscle of the chicken. Preparations from rectus abdominis and from cruralis bundle were shown to contain an additional component of lower electrophoretic mobility. Its relative proportion in these two muscles suggests that it represents the slow-tonic fiber myosin isoenzyme. Analysis of proteolytic digestion patterns revealed differences in the heavy chain structure of the isoenzymes from slow and fast fibers, respectively. As indicated by ATPase measurements, fast-twitch myosin exhibits a higher catalytic activity than myosin from slow-tonic fibers, the difference being of the same order as that reported for myosins from slow and fast muscles of higher vertebrates.

Actomyosin↗