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PubMed1997

Blockade of neuromuscular transmission by huwentoxin-I, purified from the venom of the Chinese bird spider Selenocosmia huwena.

Huwentoxin-I (HWTX-I) is a neurotoxic peptide purified from the venom of the Chinese bird spider Selenocosmia huwena. The effects of HWTX-I on neuromuscular transmission of vertebrate skeletal muscle have been investigated by means of twitch tension and electrophysiological techniques. On isolated mouse phrenic nerve-hemidiaphragm preparations, HWTX-I blocked the twitch responses to indirect, but not to direct, muscle stimulation. The time needed for complete block of the neuromuscular transmission was dose dependent. The transmission could be mostly restored by prolonged repeated washing with Tyrode's solution. If the preparation was pretreated with D-tubocurarine and then immersed in a mixed solution of D-tubocurarine and HWTX-I, the washout time necessary to restore the neuromuscular transmission was significantly decreased. Intracellular recording at the end-plate region of frog sartorius muscle revealed that HWTX-I could synchronously reduce the amplitude of the acetylcholine potential induced by ionophoretic application of acetylcholine as well as the amplitude of the end-plate potential evoked by nerve stimulation. Both of these effects eventually disappeared; however, both could be restored by prolonged washing. Experiments on Xenopus embryonic myocytes indicated that HWTX-I reduced the open probability of acetylcholine-induced channel activity, and finally blocked the channel. All of these results demonstrated that HWTX-I was a peptide neurotoxin and the postsynaptic nicotinic acetylcholine receptor was its site of action.

Acetylcholine↗
PubMed1988

Muscle flaps in the management of vascular grafts in contaminated wounds: an experimental study in dogs.

This study evaluates in an animal model the efficacy of muscle flaps in protecting the fabric vascular prosthesis when placed in contaminated wounds. A total of 20 adult mongrel dogs received a 2-cm interpositional polytetrafluoroethylene (PTFE) graft to each femoral artery at the groin level. During the surgical procedure, the wounds were inoculated with a Staphylococcus aureus suspension containing either 1 x 10(4) or 1 x 10(5) organisms per milliliter. In half the animals, the grafts were wrapped with a distally based sartorius muscle flap before a standard two-layer closure was completed. One month after the surgery, all the animals were sacrificed and quantitative cultures were performed of the grafts and wounds. The muscle flaps were capable of protecting the vascular prosthesis with inoculums up to 1 x 10(4) organisms (p less than 0.05), but at greater bacterial contamination their efficacy was no longer significant.

Animals↗
PubMed2004

Spindle cell lipoma in an intramuscular lipoma.

Intramuscular lipoma (IML) is a relatively common variant of lipomas. The most important sites for IML are the large muscles of the extremities. Spindle cell lipoma (SCL) is a rare and distinct variant of lipoma. Most SCL arise in the neck, shoulders or back. It has also been described in unusual sites, such as the oral cavity, larynx, bronchus, breast, orbit and extremities. However, localization of a SCL in an IML has not been described yet. Thus, we present the first SCL located in an IML, which was localized underneath the fascia and embedded within the left sartorius muscle of a 55-year-old man. Microscopically, the SCL component of the tumor was sharply circumscribed by a fibrous capsule and clearly separated from the IML in which it was localized. The collagen-forming spindle cells of the SCL showed neither atypia nor pleomorphism. These cells stained positive for CD34, while the mature fat tissue component of the SCL was positive for S-100 protein and negative for CD34. Spindle cells were negative for S-100 protein. Vimentin stained both components of the SCL, as well as the striated muscle fibers and mature fat tissue of the IML. In conclusion, careful morphological observation along with immunohistochemistry for CD34 and S-100 protein are essential to differentiate this rare tumor from lesions that enter the differential diagnosis.

Antigens, CD34↗
PubMed1976

Role of superficially membrane-bound calcium on excitation-contraction coupling in frog skeletal muscle.

Single fibers isolated from frog semitendinosus muscle continued to twitch for 5-8 min in calcium-free Ringer solution containing 1 mM ethylene glycol bis (beta-aminoethyl ether)-N, N'-tetraacetic acid (EGTA). Even after twitching was completely abolished, the tension of potassium contracture was not depressed, although the time course was markedly shortened. The resting potential recorded from single fibers 10 min after immersion in EGTA-Ringer solution decreased slightly. These fibers failed to generate action potential, however, in a whole sartorius muscle the self-exchangeable calcium was not significantly reduced by 1mM EGTA, while it was reduced by about 27% during the potassium contracture induced in the EGTA solution. From these results, it is suggested that the calcium bound on the surface sites of the transverse tubular membrane and the sarcolemma can serve as a trigger for the release of calcium from the sarcoplasmic reticulum and can produce a resting potential and maintain relatively long duration excitability under the condition of extracellular calcium deficiency.

Action Potentials↗
PubMed1981

The behavioral effects of phencyclidines may be due to their blockade of potassium channels.

The action of phencyclidine [1-(1-phenylcyclohexyl)piperidine; PCP] and its behaviorally active analog (m-amino-PCP) and of two behaviorally inactive analogs [m-nitro-PCP and 1-piperidinocyclohexanecarbonitrile (PCC)] were examined in this study. In a test of spatial alternation performance in rats, PCP and m-amino-PCP were much more potent behavior modifiers than were PCC and m-nitro-PCP. We studied the effects of the drugs on the ionic channels of the electrically excitable membrane and of the nicotinic acetylcholine (AcCho) receptors at the neuromuscular junction of frog skeletal muscle. All four compounds blocked the indirectly elicited muscle twitch and depressed the amplitude and rate of rise of directly elicited muscle action potentials. They also caused a voltage- and concentration-dependent decrease in the peak amplitude of the endplate current but did not react with the nicotinic AcCho receptor. These observations indicate that the four compounds have comparable blocking effects on the ionic channels associated with the nicotinic AcCho receptor. In contrast, the behaviorally active agents could be distinguished from behaviorally inactive ones by their effects on K+ conductance. PCP and m-amino-PCP blocked delayed rectification in frog sartorius muscles, prolonged the muscle action potential more than 2-fold, and markedly potentiated the directly elicited muscle twitch. The behaviorally active compound also blocked depolarization-induced 86Rb+ efflux from rat brain synaptosomes (presumably a measure of K+ conductance) and increased quantal content at the frog neuromuscular junction. In these actions, m-nitro-PCP was much less effective, and PCC was relatively ineffective. Because PCP and m-amino-PCP are much more potent behavior modifiers than PCC and m-nitro-PCP, we suggest that the behavioral effects of PCP and m-amino-PCP, may be due to a block of K+ conductance and enhancement of transmitter release at central neurons.

Action Potentials↗
PubMed1989

Functional aspects of calcium transport in sarcoplasmic reticulum vesicles derived from frog skeletal muscle treated with saponin.

To study the physiological aspects of the excitation-contraction cycle, saponin (10-100 micrograms ml-1) was used as a skinning agent on muscle and sarcotubular vesicles derived from fast muscles (sartorius and tibialis anterior) of Rana esculenta. The vesicles showed similar Ca2+-ATPase activity and similar protein profiles carried out by SDS-PAGE. Calcium transport in untreated vesicles and those treated with different concentrations of saponin seemed to have the same quantitative and qualitative parameters if the saponin was used in a range between 10 and 50 micrograms ml-1. Our results confirm that saponin may be considered to be a valid skinning agent for the external membranes of fast skeletal muscles.

Animals↗
PubMed1996

Activation of midlumbar neurones by afferents from anterior hindlimb muscles in the cat.

1. It has been suggested that a group of interneurones located in the midlumbar segments of the spinal cord might play a role in switching from the stance to swing phases of the step cycle during locomotion. We have further examined the input to these neurones from proprioceptive afferents to test whether the connections to these cells are consistent with this role. 2. Electrical stimulation of group I and group II afferents in branches of the femoral nerve which supply iliopsoas, the major hip flexor muscle, excited a large majority of intermediate zone midlumbar interneurones which receive input from quadriceps group II afferents. The central latencies and properties of the EPSPs indicate that both group I and group II afferents from iliopsoas make monosynaptic connections with many midlumbar interneurones. 3. Group II afferents from both the ankle flexor tibialis anterior and the digit dorsiflexor extensor digitorum longus excited midlumbar interneurones. Similarly, they were also excited by group II afferents from both of the two main anatomical divisions of the sartorius muscle. 4. The frequent and potent excitation of midlumbar neurones from group I and II afferents in iliopsoas suggests that they may be excited at the end of the stance phase of the step when these muscles are stretched. This possibility is discussed in relation to recent work on the functional control of the step cycle.

Animals↗
PubMed2006

Dermatomyositis, lobar panniculitis and inflammatory myopathy with abundant macrophages.

Dermatomyositis (DM) is a rare treatable muscle disorder with a reported favorable outcome in most patients. A localized skin/muscle involvement in a DM patient raises questions of definition and causes such as lymphoma, or relapse. We describe here a young treated DM patient who presented a focal biopsy-proven destructive myositis and dermatitis restricted to the left thigh 15 months after the onset of a treated dermatomyositis. There was evidence of subcutaneous lobular panniculitis, somewhat resembling cytophagic histocytic panniculitis associated with a focal inflammatory myopathy with abundant macrophages that destroyed the sartorius muscle. Mild signs of hemophagocytosis and T-CD3 lymphocytosis were present in the bone marrow, but no monoclonal T-lymphocyte expansion was observed, as searched by autoradiography of the totality of TcR Vgamma families. The patient improved with prednisone and azathioprine. We conclude that this focal complication suggests a continuum between dermatomyositis, CHP, and IMAM, the three syndromes where T-cell activation plays an important role.

Adult↗
PubMed1980

The effect of energy deprivation and hyperosmolarity upon tubular structures and electrophysiological parameters of muscle fibres.

The exhaustion of metabolically poisoned muscle fibres is accompanied by a one hundred-fold increase in potassium conductance. Under these conditions a normal membrane capacity was measured. Extracellular markers (lanthanum, ferritin) were traced in the transverse tubular system but not in the myoplasm or the sarcoplasmic reticulum. These results show that the structural integrity of surface and tubular membranes is fully maintained. The exhausted muscle can, therefore, be introduced as a suitable preparation for an analysis of the potassium channel, the alterations of ion concentrations in the restricted area of the T-system and other phenomena of physiological interest. Further experiments with extracellular markers dealt with the structure of the triads. Earlier measurements by other authors suggested a continuity between lumina of the T-system and the sarcoplasmic reticulum, at least after an exposure to hyperosmotic solutions. These results could not be confirmed.--In addition the distribution of fibre cross areas of sartorius muscle was analysed from cryosections.

Animals↗
PubMed1984

Heterogeneity of oxygen diffusion through hamster striated muscles.

We determined the O2 diffusion coefficients (DO2) and resting O2 consumptions for three hamster muscles with differing histochemical fiber type composition using a nonsteady-state technique. The muscles ranged from an oxidative muscle (soleus) to a glycolytic muscle (sartorius) with a third, the cheek pouch retractor, having mixed metabolic properties. We found that the DO2 of the soleus (corrected to 37 degrees C) was 2.59 +/- 0.33 X 10(-5) cm2/s, whereas the DO2 of the sartorius was 1.15 +/- 0.14 X 10(-5). The value for the retractor was between these two values (1.39 +/- 0.14 X 10(-5) cm2/s). In addition, we observed a linear correlation between DO2 and the percent of transverse cross-sectional area occupied by oxidative fibers, suggesting that the differences in DO2 can be accounted for by differences in their histochemical fiber type composition. In light of known differences in capillary density and maximal O2 demand, these data imply an interplay between capillarity and O2 diffusion rate resulting in an appropriate O2 delivery to meet each muscle's maximal O2 demand.

Animals↗
PubMed1996

Effects of growth hormone injection to embryos on growth and myosin heavy chain isoforms in growing turkeys (Meleagris gallopavo).

Effects of embryonic imprinting with growth hormone (GH) on growth and myosin heavy chain (MyHC) isoforms in pectoralis muscle were determined by injecting turkey embryos with ovine growth hormone (oGH) at a dose of 10 micrograms three times a day. Injections were made on days 20 and 26 (Treatment 1), days 14 and 20 (Treatment 2) or days 14 and 26 (Treatment 3) of incubation. In Treatment 1 poults, plasma GH concentrations were elevated at 3 days posthatch and in Treatment 3 poults, plasma GH concentrations were elevated at 15 days posthatch, as compared to control poults. At 4 weeks of age, in males, body weights, shank length and weights of pectoralis, gastrocnemius and sartorius muscles were increased in Treatment 3, and in females, body weights, shank length and weights of gastrocnemius muscle of female turkeys were increased in Treatment 1. The growth rate of female turkeys from 4 weeks through 16 weeks was increased by Treatment 1. Treatment 1 resulted in a delay in the transition from the embryonic MyHC isoform to the neonatal MyHC isoform and to the adult MyHC isoform. Treatment 3 induced an earlier appearance of the adult MyHC isoform. No effects on body and muscle growth and MyHC isoforms were observed by Treatment 2.

Animals↗
PubMed2001

Effects of dietary spirulina on meat colour in muscle of broiler chickens.

1. The present study was undertaken to determine the effects of dietary spirulina on growth performance and pigmentation in the muscle of growing broiler chickens and to examine the possibility that zeaxanthin in spirulina may affect yellow colour development in the meat. 2. Twenty-four, 21-d-old, male broiler chicks were fed an experimental diet containing spirulina at 0, 40, or 80 g/ kg for 16 d. No significant differences among treatments were observed in body weights, nor weights or yields (as a percentage of body weight) for any of the selected traits, including liver, abdominal fat, kidney and Pectoralis profundus. 3. Spectrocolourimetric analyses revealed that the redness of Pectoralis superficialis, profundus and Sartorius muscles reached a maximum in chicks fed the 40 g/kg spirulina diet, while the yellowness of all fillets, including the Semitendinosus muscle, increased in a sub-linear fashion with increased spirulina in the diet. The overall correlation between the yellowness and zeaxanthin content in the Pectoralis muscle was significant. 4. This study provides the first conclusive evidence that dietary spirulina influences both the yellowness and redness of broiler flesh and that the increments in yellowness with dietary spirulina content may possibly be reflected in the common yellow pigment related to the accumulation of zeaxanthin within the flesh.

Animal Feed↗
PubMed1987

Surplus acetylcholine and acetylcholine release in the rat diaphragm.

1. Skeletal muscles from rat, mouse and frog were incubated under different conditions and the amounts of acetylcholine (ACh) extractable from the tissue and released into the medium were determined by mass fragmentography. In some experiments measurements were made of the amounts of ACh ('bound' ACh) surviving in a muscle homogenate to which an excess of acetylcholinesterase had been added. In other experiments the membrane potentials, end-plate potentials (e.p.p.s), and miniature end-plate potentials (m.e.p.p.s) were studied. 2. During incubation in Ringer medium the ACh content of the rat hemidiaphragm usually did not change, but after inhibition of cholinesterase by soman the ACh content rose gradually from about 100 to 150 pmol to a plateau of about 400 pmol after 4 h. A similar formation of 'surplus ACh' after cholinesterase inhibition was found in the mouse diaphragm, but not in the frog sartorius muscle. 3. Surplus ACh accumulated predominantly in the end-plate region of the rat diaphragm. In muscles, 16-18 h after in vivo denervation, the capacity to form surplus ACh was decreased by more than 80%. 4. The amount of ACh diffusing from the resting hemidiaphragm into the incubation medium ('resting release') varied between 0.5 and 0.9 pmol min-1 in different experiments; it remained at the same level during accumulation of surplus ACh. It was reduced by more than 80% 16-18 h after denervation. 5. The amplitude of m.e.p.p.s and e.p.p.s did not increase while surplus ACh was accumulating. 6. Incubation of hemidiaphragms in Ringer solution containing [3H]choline caused the formation of [3H]ACh. Additional amounts of [3H]choline were incorporated into ACh when the nerve was stimulated for 60 min. However, incubation in the presence of soman (3,3-dimethyl-2-butylmethylphosphonofluoridate), in the absence of stimulation, did not cause an increase of the [3H]ACh content of the muscles. 7. From hemidiaphragms with active cholinesterase about 120 pmol ACh was lost after prolonged nerve stimulation or incubation with 50 mM-KCl in the presence of hemicholinium-3, and about 35 pmol remained in the tissue. In soman-treated muscles, containing surplus ACh, about as much ACh was released by nervous stimulation as from untreated hemidiaphragms, and much more ACh remained unreleased. 8. Transection of the muscle at both sides of the end-plate or incubation of intact muscles in the presence of 50 mM-KCl depolarized the muscle fibres to -35 and -31 mV, respectively. Surplus ACh was partially released by 50 mM-KCl, but not by muscle transection.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1990

Cross-bridge cycling theories cannot explain high-speed lengthening behavior in frog muscle.

The Huxley 1957 model of cross-bridge cycling accounts for the shortening force-velocity curve of striated muscle with great precision. For forced lengthening, however, the model diverges from experimental results. This paper examines whether it is possible to bring the model into better agreement with experiments, and if so what must be assumed about the mechanical capabilities of cross-bridges. Of particular interest is how introduction of a maximum allowable cross-bridge strain, as has been suggested by some experiments, affects the predictions of the model. Because some differences in the models are apparent only at high stretch velocities, we acquired new force-velocity data to permit a comparison with experiment. Using whole, isolated frog sartorius muscles at 2 degrees C, we stretched active muscle at speeds up to and exceeding 2 Vmax. Force during stretch was always greater than the peak isometric level, even during the fastest stretches, and was approximately independent of velocity for stretches faster than 0.5 Vmax. Although certain modifications to the model brought it into closer correspondence with the experiments, the accompanying requirements on cross-bridge extensibility were unreasonable. We suggest (both in this paper and the one that follows) that sarcomere inhomogeneities, which have been implicated in such phenomena as "tension creep" and "permanent extra tension," may also play an important role in determining the basic force-velocity characteristics of muscle.

Animals↗
PubMed1983

Potencies and channel properties induced by semirigid agonists at frog nicotinic acetylcholine receptors.

Structure-activity relationships were investigated in a series of semirigid nicotinic agonists. Three of the agonists, (-)-ferruginine methiodide, arecoline methiodide, and its ketonic analogue arecolone methiodide, were cyclic analogues of anatoxin-a, a potent, naturally occurring, bicyclic alkaloid. Two other cyclic agonists, (-)-cytisine and (+/-)-muscarone, and the simplest agonist, the tetramethylammonium ion, were also tested. Arecolone methiodide and (-)-ferruginine methiodide have been tested as nicotinic agonists for the first time. Relative potency was assayed by contracture on the rectus abdominis muscle of the frog Rana pipiens. Natural, (+)-anatoxin-a, the most active of all of the agonists, was more than twice as potent as racemic anatoxin-a. Arecolone methiodide ranked after anatoxin-a in potency, being 8.6 times more potent than carbamycholine. A correlation between nicotinic potency and steric requirements probably involves the position of positively charged groups out of the plane defined by the carbonyl group and its two substituents. Channel properties induced by the agonists were evaluated by Fourier analysis of the end-plate current noise that resulted when the agonists were iontophoretically applied to frog sartorius muscle fibers. Average channel lifetimes were exponential functions of membrane potential, but the voltage sensitivity of channel lifetime seemed to vary among the agonists. Channel conductance, which was independent of membrane potential, also varied significantly among the agonists. The average charge traversing the membrane through each open channel, calculated from the product of average channel lifetime and current, did not correlate with potency. Therefore, the dominant component of potency is the frequency of channel opening. No clear relationship between the structure of the agonist and channel lifetime or conductance was evident.

Alkaloids↗
PubMed1986

Effects of digoxin on diaphragmatic strength generation.

Contrary to hindlimb muscle, extracellular calcium plays an important role in diaphragmatic strength generation (J. Appl. Physiol. 58: 2054-61, 1985). Since the inotropic effect of digitalis appears to be related to cell membrane transport of calcium, we studied the effect of digoxin on diaphragmatic contractility in 20 anesthetized dogs. The diaphragm was electrically stimulated with intramuscular electrodes. The transdiaphragmatic pressure (Pdi) during supramaximal (50 V) 2-s stimulations applied over a frequency range of 10-100 Hz was measured with balloon catheters at functional residual capacity. Cardiac output was measured with a Swan-Ganz catheter and diaphragmatic blood flow (Qdi) by timed volume collections of left inferior venous effluent. The force generated by the sartorius muscle during electrical stimulations was studied concomitantly to Pdi. In 10 dogs (group A) 0.04 mg/kg of digoxin was infused in 10 min. In 10 other dogs (group B) 0.2 mg/kg was administered. All measurements were performed during control and 30, 60, 90, and 120 min after digoxin administration. In group A, digoxin plasmatic level at 60 min reached a therapeutic range in all dogs (1.8 +/- 0.3 ng/ml), whereas in group B, digoxin plasmatic level was higher (8 +/- 1.3 ng/ml). No significant change in cardiac output and Qdi was noted after administration of digoxin, either in the dogs of group A or those of group B.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Assessment of morbidity of semitendinosus and gracilis tendon harvest for ACL reconstruction.

This study evaluates the morbidity of harvest of both the semitendinosus and gracilis tendons for anterior cruciate ligament reconstruction on nine patients at a minimum of 3 year follow-up. Specifically, the effect on knee function, knee extension and flexion strength, the size of the individual posterior thigh muscles, and the extent of retraction of the semitendinosus and gracilis tendons were evaluated. At final follow-up, each patient was evaluated using the following functional scales: International Knee Documentation Committee (IKDC), Hospital for Special Surgery (HSS), Lysholm, and Tegner. Each patient also had a dynamometer evaluation and a comprehensive magnetic resonance imaging study of both the operated and nonoperated knees. The average functional evaluation scores were: HSS-47.9, Lysholm-88, and Tegner-0.27. The average percent quadriceps and hamstring strength of the operated compared with the nonoperated extremities were 93.7% and 95.3%, respectively; neither decrease was significant. Magnetic resonance imaging evaluation of the cross-sectional areas of the biceps femoris, semimembranosus, and sartorius muscles of both thighs at the same level above the joint were not significantly different. The distal-most insertion of the semitendinosus and gracilis tendons after harvest were always more proximal than the nonoperated side; the average difference was 26.7 mm (range: 11 to 32 mm) for the semitendinosus (unable to calculate in three patients) and 47.1 mm (range: 17 to 72 mm) for the gracilis. We conclude that tendon harvest of the semitendinosus and gracilis muscles does not significantly compromise function and strength despite a more proximal insertion of the retracted tendons. In addition, the majority of cases demonstrated some but never complete regrowth or scar formation of these tendon remnants.

Adult↗
PubMed1989

The nonoxime bispyridinium compound SAD-128 alters the kinetic properties of the nicotinic acetylcholine receptor ion channel: a possible mechanism for antidotal effects.

The effects of SAD-128 [1,1'-oxybis(methylene) bis 4-(1,1-dimethylethyl) pyridinium dichloride], a nonoxime bispyridinium compound, were investigated on the nicotinic acetylcholine receptor-ion channels of frog muscle fibers using end-plate current (EPC) and single channel current measurement techniques. SAD-128 decreased the EPC peak amplitude in a concentration-dependent manner and caused nonlinearity in the current-voltage plots. The time constant of EPC decay was prolonged by SAD-128 (10-200 microM) at potentials between +50 and -90 mV without loss of the single exponential decay. However, at -100 mV and below, biphasic decays of the EPCs were observed in the presence of the drug. The time constant of the fast phase of the EPC decay decreased, whereas that of the slow phase increased, with either hyperpolarization or increasing concentration of the drug. SAD-128 weakly inhibited acetylcholinesterase in frog sartorius muscle. At the single-channel current level, SAD-128 reduced the mean channel open time and produced a blocked state evidenced as an additional phase in the closed time distribution. The agent induced a biphasic burst time distribution whose fast component became faster and slow component slower with increasing concentration and hyperpolarization. The present study provides more details regarding the kinetics of the nicotinic acetylcholine receptor ion channel-blocking mechanisms and a correlation between single-channel currents and macroscopic events. The ability of SAD-128 to block the nicotinic acetylcholine receptor may underlie its efficacy in counteracting lethal effect of organophosphorus compounds.

Animals↗