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Cat hindlimb motoneurons during locomotion. III. Functional segregation in sartorius.

Cat sartorius has two distinct anatomical portions, anterior (SA-a) and medial (SA-m). SA-a acts to extend the knee and also to flex the hip. SA-m acts to flex both the knee and the hip. The objective of this study was to investigate how a "single motoneuron pool" is used to control at least three separate functions mediated by the two anatomical portions of one muscle. Discharge patterns of single motoneurons projecting to the sartorius muscle were recorded using floating microelectrodes implanted in the L5 ventral root of cats. The electromyographic activity generated by the anterior and medial portions of sartorius was recorded with chronically implanted electrodes. The muscle portion innervated by each motoneuron was determined by spike-triggered averaging of the EMGs during walking on a motorized treadmill. During normal locomotion, SA-a exhibited two bursts of EMG activity per step cycle, one during the stance phase and one during the late swing phase. In contrast, every recorded motoneuron projecting to SA-a discharged a single burst of action potentials per step cycle. Some SA-a motoneurons discharged only during the stance phase, whereas other motoneurons discharged only during the late swing phase. In all cases, the instantaneous frequencygram of the motoneuron was well fit by the rectified smoothed EMG envelope generated by SA-a during the appropriate phase of the step cycle. During normal locomotion, SA-m exhibited a single burst of EMG activity per step cycle, during the swing phase. The temporal characteristics of the EMG bursts recorded from SA-m differed from the swing-phase EMG bursts generated by SA-a.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Effect of primycin on some electric properties of the frog skeletal muscle.

The effect of primycin, a guanidine-type antibiotic was studied on the electric properties and 42K+ uptake of the frog sartorius and semitendinosus muscle. Both in normal and choline chloride Ringer solution, primycin evoked a concentration and time dependent depolarization of the surface membrane of the muscle. This depolarization was significantly increased by Na ions. Primycin treatment was shown to evoke a dose-dependent decrease of the depolarization induced by 20 mM K+-Ringer. When the muscles were incubated in a Ringer solution containing choline chloride, during an incubation period of 30 min the uptake of 42K+ was decreased to 12% upon the exposure to 5 x 10(-6) mol primycin as compared to the control value. As the primycin-induced depolarization increased, the shape and amplitude of the action potentials elicited by square-wave electric impulses were altered and decreased, respectively. In sodium isaethionate Ringer 1--2 x 10(-6) M primycin induced a slow depolarization resulting in firing potentials. The results suggest that primycin depolarizes the surface membrane exclusively through the blockade of the resting K+ channels, the other phenomena being the results of this depolarizing effect.

Action Potentials↗

Chronic heat exposure alters protein turnover of three different skeletal muscles in finishing broiler chickens fed 20 or 25% protein diets.

Heat-exposed chickens exhibit a lower growth rate and a depressed protein retention which may result from an alteration in protein metabolism. A high-protein diet seems to be beneficial under hot conditions because it tends to improve growth. Effects of high ambient temperature (32 vs. 22 degrees C) and dietary crude protein (25 vs. 20%) on muscle protein turnover were investigated in finishing broiler chickens. At 5-6 wk of age, protein synthesis was measured in vivo in the Pectoralis major, Sartorius and Gastrocnemius muscles (flooding dose of [(3)H]-phenylalanine). Protein breakdown was determined in the same muscles as the difference between protein synthesis and deposition. Chronic heat stress markedly reduced protein synthesis, irrespective of muscle type (P < 0.05). This was mainly related to the lower capacity for protein synthesis (muscle RNA/Protein) (P < 0.01). Chronic heat exposure also decreased protein breakdown in the P. major and Sartorius; this effect was not observed in the GASTROCNEMIUS: Protein synthesis was more affected than breakdown, leading to reduced protein deposition, at least in the P. major and Gastrocnemius muscles. Increasing dietary protein content had no significant impact on muscle protein turnover. Particularly at 32 degrees C, the high-protein diet did not significantly modify either protein synthesis, ribosomal capacity or translational efficiency. However, it favored muscle protein deposition, which was probably related to reduced proteolysis. In conclusion, we showed that chronic heat exposure decreased muscle protein deposition, mainly by reducing protein synthesis. Under these conditions, the impaired protein synthesis was not restored by a 5% higher protein intake.

Animals↗

The effects of semitendinosus and gracilis harvest in anterior cruciate ligament reconstruction.

PURPOSE: There is significant debate concerning the morbidity of hamstring harvest for use during anterior cruciate ligament (ACL) reconstruction. We hypothesized that harvest of the semitendinosus and gracilis tendons for ACL reconstruction would result in no measurable hamstring weakness, but that abnormalities of the semitendinosus and gracilis muscle would be observed on magnetic resonance imaging (MRI) scans. TYPE OF STUDY: Case series. METHODS: Nine patients undergoing ACL reconstruction with doubled semitendinosus and gracilis tendons had MRI cross-sectional area measurements of both limbs made from axial images and muscle contour was studied on coronal images at 3 and 12 months. The semitendinosus, semimembranosus, gracilis, sartorius, and biceps muscles were evaluated. Isokinetic testing was performed on the operative and nonoperative legs at 60 degrees and 180 degrees per second at 6 and 12 months postoperatively. RESULTS: The gracilis cross-sectional area at 1 year averaged 2 cm2 on the operative side and 3.7 cm2 on the contralateral side. The semitendinosus averaged 2.1 cm2 on the operative side and 6.6 cm2 on the contralateral side at 1 year. Both of these differences were statistically significant (P < .05). In most cases, the semitendinosus muscle was retracted. Distally, the gracilis and occasionally the semitendinosus were blending with the gastrocnemius or sartorial fascia. The gracilis and semitendinosus in 1 case extended to near the original attachment site. Hamstring strength testing revealed a 26% deficit on the operative side at 60 degrees/second at 6 months and 16% at 180 degrees/second. At 12 months the mean 60 degrees/second deficit was 21% and the deficit at 180 degrees/second was 13%. CONCLUSIONS: At 1 year, the semitendinosus and gracilis muscles showed significant and persistent atrophy on the operative side and frequent retraction of the semitendinosus muscle belly. There were also hamstring strength deficits persisting at 1 year after the use of the tendons for ACL reconstruction. LEVEL OF EVIDENCE: Level IV.

Adult↗

Effect of citrate on the activities of 6-phosphofructokinase from nervous and muscle tissues from different animals and its relationships to the regulation of glycolysis.

1. Citrate inhibits the activities of phosphofructokinase from muscles and nervous tissues from different animals across the Animal Kingdom except for the insects. The enzymes from the flight muscle of nine different insects and the cerebral ganglion of the locust were investigated: no inhibition by citrate was observed. Inhibition was observed with the enzymes from both aerobic (e.g. pectoral muscle of pigeon) and anaerobic (e.g. fish muscle, pectoral muscle of the game birds) muscles. It is suggested that this inhibition is of physiological importance in decreasing the rate of glucose utilization in skeletal muscle of animals during starvation and/or prolonged exercise. 2. The rates of glucose utilization by the sartorius and gastrocnemius muscles of the frog were markedly decreased by ketone bodies. The latter elevated the glucose 6-phosphate and citrate contents of the gastrocnemius muscle, indicating that citrate inhibition of phosphofructokinase could be, in part, responsible for the decreased rate of glycolysis. 3. These findings provide evidence that the concept of the glucose-fatty acid-ketone-body cycle involves both aerobic and anaerobic skeletal muscle and nervous tissue from a wide range of animals except the insects. In the latter the concept of the cycle may not be applicable.

Adenosine Triphosphate↗

CT muscle scanning in the evaluation of patients with spinal muscular atrophy (SMA).

One hundred patients with spinal muscular atrophy (SMA) were assessed by CT scanning using a standardised technique. The spectrum of CT abnormality occurring in SMA was observed and by overall analysis the patients were divided into 4 groups. While the CT appearances of these groups correlated well with clinical assessment of severity of disease, the disease process was usually much more widespread than clinical examination suggested. CT abnormality was first observed in the leg and gluteal muscles, progressing to the posterior spinal, thigh, shoulder girdle and sternomastoid muscles. Hypertrophy of sartorius and gracilis was observed in a significant number of patients. Fascial planes were preserved in involved muscles in over half of the patients, even in late-stage disease. Asymmetrical muscle involvement was seen with increasing frequency as the disease process increased in extent as evaluated by CT scanning. There was no discernible difference in the CT appearances in those patients who clinically had limb-girdle, facioscapulohumeral or scapuloperoneal distribution of weakness.

Adolescent↗

Surgical anatomy of the variations of the arrangement of the tendons of the muscles of the pes anserinus in male adults.

The descriptions of the morphology of the human pes anserinus (the combined insertions of the tendons expansions of medial muscles of the thigh) vary on the arrangement of the muscles and tendons that originate the so-called "goose's foot". Although descriptions found in the literature include up to 7 muscles, most of the authors indicated this anatomical structure as formed only by the insertions of the gracilis, sartorius and semitendinosus muscles. Our aim is to find out in Brazilian male adult cadavers the most frequent disposition of the tendons for application in the orthopedic practice. So far, 60 inferior members of 30 cadavers from the laboratories of the Anatomy Departments of the Medical Schools of the Universities of Mogi das Cruzes and Santos were studied. The dissection was performed in cadavers fixed in 10% formaldehyde solution. The specimens were then drawn and photographed. In all 30 cadavers only 3 muscles participated in the formation of the pes anserinus but several variations were found in the disposition of the tendons. Applications of the anatomical knowledge of this tendinous arrangement were discussed.

Adult↗

Discharge patterns of gamma motoneurone populations of extensor and flexor hindlimb muscles during walking in the thalamic cat.

Two monopolar recordings of the whole activity in a fine nerve branch innervating the gastrocnemius lateralis (GL) or the sartorius medialis (SM) muscle were obtained during spontaneous walking in thalamic cats. Using a special electronic device, the potentials of several groups of efferent (alpha and gamma) and afferent (I and II) fibres constituting the whole nerve activity were separated. In the present paper we compare the data obtained for an ankle extensor (GL) and a hip-knee flexor (SM) during the step cycle. In both muscles the gamma motoneurone population is activated in parallel with the alpha motoneurone population. Usually, between the cyclic locomotor discharges, the GL gamma neurones are tonically active whereas the SM gamma neurones are silent. During muscle contraction, the group I and II afferent discharges are both length and gamma dependent, but the prevailing factor is the muscle shortening for the GL afferents and the cyclic gamma drive for the SM afferents. Both dynamic and static fusimotor efferents appear to be activated during muscle contraction, but on indirect evidence it is suggested that dynamic action prevails in GL spindles whereas static action dominates in SM spindles.

Animals↗

[The effect of dihydropyridines on the strontium and calcium content in frog muscle].

2,6-Dimethyl-3,5-dimethoxycarbonyl-4-(O-difluromethoxyphenyl)-1,4- dihydropyridine (ryodipine) (2 x 10(-4) M) significantly blocks the resting Sr++ uptake in sartorius and iliofibularis muscles of Rana temporaria without changes in Ca++ and Mg++ content. Dihydropyridine CGP (2.10(-4) M) increased both [Sp++] and [Ca++] (mumol/g dr. w.) by about 20 and 13%, respectively, as compared with paired control muscles, whereas [Mg++] remained unaffected. The [Sr++] changes are interpreted as specific dihydropyridine-effect on the Ca(++)-channels in the muscle membrane.

Animals↗

Heterogeneity of type 1 skeletal muscle fibers revealed by monoclonal antibody to slow myosin.

Monoclonal antibodies (McAbs) were generated against slow myosin from the chicken anterior latissimus dorsi (ALD) muscle and their reactivity was checked against fast (pectoralis), slow (ALD), cardiac (ventricular), and smooth (gizzard) myosins by radioimmunoassay (RIA), immunoautoradiography (immunoblots), and indirect immunofluorescence techniques. In RIAs, the McAb (ALD-58) described in this article reacted specifically with slow myosin, with only a weak cross-reactivity to cardiac myosin. In immunoblots against whole muscle homogenates and purified myosins, it bound selectively to the 200 Kd myosin heavy chain band. The ALD-58 antibody stained the fibers of the ALD muscle uniformly but gave three grades of reactions (strong, weak, and negative), with histochemically identified type 1 fibers of sartorius and gastrocnemius muscles demonstrating the immunological heterogeneity of myosins in type 1 skeletal muscle fibers.

Animals↗

Studies on the endoplasmic reticulum. III. Its form and distribution in striated muscle cells.

Several types of striated muscle have been examined by the technics of electron microscopy and the findings in myotome fibers of Amblystoma larvae, the sartorius, and cardiac muscle of the rat are reported on in some detail. Particular attention has been given to structural components of the interfibrillar sarcoplasm and most especially to a finely divided, vacuolar system known as the sarcoplasmic reticulum. This consists of membrane-limited vesicles, tubules, and cisternae associated in a continuous reticular structure which forms lace-like sleeves around the myofibrils. It shows a definable organization which repeats with each sarcomere of the fiber so that the entire system is segmented in phase with the striations of the associated myofibrils. Details of these repetitive patterns are presented diagrammatically in Text-figs. 1, 2, and 3 on pages 279, 283, and 288 respectively. The system is continuous across the fiber at the H band level and largely discontinuous longitudinally because of interruptions in the structure at the I and Z band levels. The structure of the system relates it to the endoplasmic reticulum of other cell types. The precise morphological relation of the reticulum to the myofibrils, with specializations opposite the different bands, prompts the supposition that the system is functionally important in muscle contraction. In this regard it is proposed that the membrane limiting the system is polarized like the sarcolemma and that the corresponding potential difference is utilized in the intracellular distribution of the excitatory impulse.

Animals↗

Histochemical determination of muscle fiber types in locomotor muscles of anuran amphibians.

1. A histochemical study using myosin ATPase, succinate dehydrogenase and alpha-glycerophosphate dehydrogenase reactions and a morphometric analysis with image analyser, was carried out in sartorius and gastrocnemius muscles of two anuran species, Rana perezi and Bufo calamita, that show different locomotor activities. 2. Four types of muscle fiber were found. There were interspecific variations in their proportions, with a predominance of oxidative muscle fibers in Bufo calamita. 3. These results agree with those obtained previously for the metabolic profile of several tissues from both species and point to a clear metabolic basis for the differences in locomotor activities between these two species.

Animals↗

Determination of extracellular space in amphibian muscle.

The volumes of distribution of inulin and dextran in the sartorius, stomach, and cardiac muscle of the frog agree rather closely. That these spaces represent the volume of extracellular water is supported by the observation that efflux of sucrose can be divided into a fast and a slow phase and that the fast-moving fraction corresponds closely with inulin space determined in the same muscle. These and other findings confirm that sugars and related substances penetrate slowly into part of the fiber water and that, therefore, their volume of distribution does not accurately represent the volume of extracellular water. The kinetics of efflux of sucrose is consistent with the assumption that the movement of sugars is determined by the resistance of the cell surface as well as by internal diffusion. In connective tissue, sucrose and inulin are excluded only from a small part of the total water.

Animals↗

Effects of testosterone on a sexually dimorphic frog muscle: repeated in vivo observations and androgen receptor distribution.

In the present study the sexually dimorphic, androgen-sensitive flexor carpi radialis muscle (FCR) in male Xenopus laevis was viewed repeatedly in vivo to assess the influence of testosterone on muscle fiber size over a period of up to 12 weeks. Regions of the muscle innervated by different spinal nerves responded differently to testosterone treatment. Muscle fibers innervated by spinal nerve 2 (SN2) hypertrophied within 7 days in frogs that had been castrated and given testosterone-filled implants. This initial hypertrophy was followed by a return to normal fiber size a week later, after which fiber size slowly increased again. In castrated males with empty implants, muscle fibers innervated by SN2 gradually atrophied. Fibers innervated by spinal nerve 3 (SN3) were not affected by androgen replacement or withdrawal. The sartorius, a control muscle that is neither sexually dimorphic nor particularly androgen sensitive, was also unaffected. The in vivo observations were confirmed by measurements of muscle fiber cross-sectional areas in frozen sections of whole forelimbs. At 8 and 12 weeks after castration, cross-sectional areas of fibers innervated by SN2 were significantly larger in frogs provided with testosterone than in castrates without testosterone. No difference was found in the SN3 region or in the anconeus caput scapulare (triceps), another control muscle. Immunocytochemistry employing an antibody against the androgen receptor (AR) indicated that the receptor is present in myonuclei of all muscles of the forelimb. While no difference in labeling intensity was detected, the number of AR-containing nuclei per muscle fiber cross-section was higher in fibers innervated by SN2 than in those innervated by SN3, and was yet lower in the triceps. This suggests that regulation of androgen sensitivity may occur via muscle fiber ARs, although an influence of the nerve may also contribute.

Animals↗

Siblings of Schwartz-Jampel syndrome with abnormal muscle computed tomographic findings.

Schwartz-Jampel syndrome (SJS) is a disorder characterized by myotonia, joint contractures, skeletal abnormalities, facial dysmorphism and growth retardation. We present two boys of ages 4 and 8 years with SJS. Their clinical, electromyographic and histopathological findings were similar to those described, except for computed tomography (CT) images that revealed diffuse high attenuation in sternocleidomastoid muscles and low attenuation in the paraspinal, quadriceps, sartorius, soleus and gastrocnemius muscles. This is the first report describing abnormal muscle CT findings associated with SJS. Additional studies of muscle CT might help to improve understanding of the pathogenesis of SJS.

Child↗

Perchlorate-induced alterations in electrical and mechanical parameters of frog skeletal muscle fibres.

The effect of the perchlorate anion (ClO4-) on the potential dependence of mechanical and electrical parameters was investigated in skeletal muscles fibres of the frog. Two main methods were employed: twitches and K contractures were induced in isolated fibres from the semitendinosus or iliofibularis muscle, and point voltage clamp was applied in sartorius and short toe muscle fibres. Twitch height was unaffected below 10(-4) M-ClO4-, it usually increased several-fold in the concentration range of 10(-3) to 10(-2) M-ClO4- and continued to rise slowly between 10(-2) and 10(-1) M-ClO4-. ClO4- caused a parallel shift of the activation curve, which relates peak force to membrane potential, towards more negative potentials by up to 40 mV (70 mM-ClO4-). The shift in force activation was not accompanied by a corresponding shift in the potential dependence of force inactivation. In the presence of ClO4-, maximum force development upon depolarization to -60 or -50 mV could be maintained for several minutes, suggesting that spontaneous relaxation after full depolarization is due to a potential-dependent inactivation process, and not to an exhaustion of Ca2+ release. ClO4- shifted the threshold for the initiation of the action potential only slightly towards more negative potentials (approximately 10 mV at 70 mM-ClO4-). Little or no shift was observed in the lower concentration range (less than 10 mM) where the threshold of force activation was shifted by about 20 mV. ClO4- slightly depressed the activation of the delayed rectifier without causing any distinct change in its threshold potential. Electrophoretic injection of ClO4- (internal ClO4- concentration ([ClO4-]i) approximately 1 mM) induced similar effects to those following external application of this anion, i.e. a shift of force activation towards more negative potentials. Of several other anions tested, only dichromate, which resembles ClO4-in its tetrahedal structure, similarly caused force activation after repolarization. We conclude that at low concentrations (less than 10 mM) ClO4- rather specifically improves excitation-contraction coupling by direct interference with the gating mechanism which activates Ca release from the sarcoplasmic reticulum. At higher concentrations, it may also influence potential-dependent membrane processes by adsorption to the outer surface of the membrane.

Action Potentials↗

[The structure of thick filaments on longitudinal sections of rabbit psoas muscle].

By means of electron microscopy the longitudinal sections of chemically skinned fibres of rigorised rabbit psoas muscle have been examined at pH of rigorising solutions equal to 6, 7, 8 (I = 0.125) and ionic strengths equal to 0.04, 0.125, 0.34 (pH 7.0). It has been revealed that at pH 6.0 the bands of minor proteins localization in A-disks were seen very distinctly, while at pH 7.0 and I = 0.125 these bands can be revealed only by means of antibody labelling technique. At the ionic strength of 0.34 (pH 7.0) the periodicity of 14.3 nm in thick filaments was clearly observed, which was determined by packing of the myosin rods into the filament shaft and of the myosin heads (cross-bridges) on the filament surface. The number of cross-bridge rows in the filament equals 102. A new scheme of myosin cross-bridge distribution in thick filaments of rabbit psoas muscle has been suggested according to which two rows of cross-bridges at each end of a thick filament are absent. The filament length equals 1.64 +/- 0.01 micron. It has been shown that the length of thick filament as well as the structural organization of their end regions in rabbit psoas muscle and frog sartorius one are different.

Animals↗

Gene expression of myofibrillar proteins in single muscle fibers of adult chicken: micro two dimensional gel electrophoretic analysis.

Using a micro two dimensional gel electrophoretic system and silver stain method, we examined the isoform patterns of myofibrillar proteins in single muscle fibers of adult chicken. Several isoforms of myosin light chains, tropomyosin, troponin T, troponin I, and troponin C were identified. Analysis of pectoral, anterior latissimus dorsi, sartorius and soleus muscle revealed that single fibers contained either fast or slow form of each of the troponin subunits, indicating that troponin exists as a 'homocomplex.' The form of troponin in a given cell was associated with that of myosin light chains. The form of tropomyosin, however, was not associated with those of myosin light chains and troponin, but was tissue specific. Overall, we found four combinations of isoforms of myosin light chains, troponin subunits and tropomyosin subunits. In adult dystrophic chicken the isoform patterns of tropomyosin and troponin T in single fibers of pectoral muscle markedly deviated from the normal patterns.

Animals↗