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PubMed2002

Effect of aestivation on muscle characteristics and locomotor performance in the green-striped burrowing frog, Cyclorana alboguttata.

The Green-striped burrowing frog, Cyclorana alboguttata survives extended drought periods by burrowing underground and aestivating. These frogs remain immobile within cocoons of shed skin and mucus during aestivation and emerge from their burrows upon heavy rains to feed and reproduce. Extended periods of immobilisation in mammals typically result in muscle atrophy and a decrease in muscle performance. We examined the effect of aestivation and hence prolonged immobilisation, on skeletal muscle mass, in vitro muscle performance, and locomotor performance in C. alboguttata. Frogs were aestivated in soil for 3 months and were compared with control animals that remained active, were fed, and had a continual supply of water. Compared to the controls, the wet mass of the gastrocnemius, sartorius, gracilus major, semimembranosus, peroneus, extensor cruris, tibialis posticus and tibialis anticus longus of aestivators remained unchanged indicating no muscle atrophy. The in-vitro performance characteristics of the gastrocnemius muscle were maintained and burst swimming speed was unaffected, requiring no recovery from the extended period of immobilisation associated with aestivation. This preservation of muscle size, contractile condition and locomotor performance through aestivation enables C. alboguttata to compress their life history into unpredictable windows of opportunity, whenever heavy rains occur.

Animals↗
PubMed1993

A correlation between quantal content and decay time of endplate currents in frog muscles with intact cholinesterase.

1. The relationship between quantal content and prolongation of endplate currents (EPC) was studied in the frog sartorius with intact synaptic acetylcholinesterase. 2. The prolongation of EPC was more pronounced in endplates with a higher quantal content both before and after potentiation of quantal release by 4-aminopyridine (4-AP). When the quantal content of EPC was lowered, either by high Mg2+ or repetitive stimulation, the EPC decay constant was reduced. 3. A certain critical value of about 120 quanta per nerve impulse was found, at which point the decay of EPC remained constant even through the quantal content was reduced further. 4. The reduction in both density and number of postsynaptic receptors, produced by alpha-bungarotoxin and (+)-tubocurarine led to a profound reduction in EPC decay during the progressive fall in EPC amplitude in both 4-AP-treated and -untreated endplates. Both drugs are known to produce a shortening of EPC in anti-cholinesterase (anti-ChE)-treated muscles, due to a decrease in receptor density and less frequent repetitive binding of ACh. 5. It is assumed that the prolongation of multiquantal EPC is caused by an increased ACh concentration near the receptors, which may provide the opportunity for repetitive binding even with full cholinesterase activity. The critical quantum content of about 120 might be the number of quanta at which the probability of multiple release at single active zones is increased above zero.

4-Aminopyridine↗
PubMed1987

Ultrasound propagation in anisotropic soft tissues: the application of linear elastic theory.

Linear elastic theory has served well in modeling the mechanical properties of numerous materials. In modeling ultrasonic wave propagation in biological soft tissues, an isotropic model has usually been employed. Many tissues, however, possess a lower order of symmetry, and the speed of sound in muscle is known to vary with the direction of propagation. In this study, by applying linear regression to acoustic microscopic data from seven frog sartorius specimens, four observable elastic constants associated with a transversely isotropic model were obtained. The average values of these constants were c11 = 2.64, c13 = 3.39 and c33 = 4.40 Nm-2 for resting muscles and c11 = 2.65, c13 = 3.43 and c33 = 4.57 Nm-2 for muscles undergoing tetanic contraction, where '1' and '3' represent the transverse and longitudinal axes, respectively. In all cases, c44 was 0, indicating a minimal contribution from longitudinal shear. For all seven specimens, the model of transverse isotropy provided a better fit of the data than that of isotropy.

Animals↗
PubMed2002

The effectiveness of muscle flaps for the treatment of prosthetic graft sepsis.

The objective of this study was to assess the efficacy and reliability of muscle flaps in the treatment of prosthetic graft sepsis. A retrospective analysis was performed to assess the outcome of all patients with prosthetic graft sepsis who were treated with a muscle flap at Groote Schuur Hospital between January of 1991 and July of 2000. The specific end points studied were flap survival, limb salvage rate, and mortality. A total of 27 muscle flaps were raised to cover 24 sites of graft sepsis in 21 patients. Twenty-five flaps were performed primarily and two secondarily. The mortality rate was zero. Limb salvage was achieved in 15 of 21 patients (71 percent), with no recurrent sepsis after an average follow-up period of 36 months. The groin was the most common site of infection, with an 86 percent incidence. Eighteen sartorius flaps were raised in the groin. Seventeen of the 18 sartorius flaps survived (94 percent), and a 71 percent limb salvage was achieved with no recurrent sepsis after 36 months of follow-up. This series supports the use of muscle flaps for the treatment of prosthetic graft sepsis. The sartorius flap has been shown to be reliable as a flap in the groin, with successful limb salvage in the majority of patients.

Adolescent↗
PubMed1994

[The thermoregulatory activity of the skeletal muscle motor units in the cat under conditions of sympathetic denervation].

Thermoregulatory activity of motor units was investigated in the cat mm sartorius and semitendinosus on the 7th and 14th days after lumbar sympathectomy. The EMG pattern did not change after gangliotomy but a statistically significant prolongation of the interspike intervals occurred on the 7th day indicating a growing instability of the motoneuronal pool activity. These changes tended to restore on the 14th day. Processes affecting the thermoregulatory activity of the motor units after sympathetic denervation, are discussed.

Animals↗
PubMed1977

Muscle structure and function in the goose, quail, pheasant, guinea hen, and chicken.

1. Metabolic functions, fiber composition and, in some cases, mitochondrial morphology have been investigated in the pectoralis major and sartorius of the goose, quail, pheasant, guinea-hen, broiler chicken and laying hen. 2. In the pectoralis only two types of fibers, red and white twitch fibers, are found in all birds studied except in the quail, where a third twitch fiber also occurs. Red fibers form the main part in the quail and goose, white fibers in the rest. In the sartorius at least three types of fibers, two twitch and one tonus are found in all birds except in the guinea-hen where only two fibers can be found. 3. The metabolic pattern of the muscles, based on determination of specific activities of metabolic key enzymes, varies greatly among the birds. Three groups can be discerned from the ratio between aerobic and anaerobic activities or between fatty acid oxidation and carbohydrate metabolism. The metabolic patterns are reflected in the fiber combinations of the muscles. 4. The size and number of the mitochondria vary among different animals and different fiber types. The metabolism of red and white fibers is discussed.

Animals↗
PubMed1976

[Responses of the neuromuscular synapses of chronically desympathized frog muscles to tetanic nerve stimulation].

7--14 days after unilateral section of the abdominal sympathetic trunk, the quantum content of the end plate potential (e.p.p.) in the m. sartorius of the frog decreased. The facilitation and fluctuations of the e.p.p. amplitude during train of stimuli (20, 50, 100/sec) became more obvious. Noradrenaline (5-10(-6) g/ml) increased the amplitude of a single e.p.p. and the facilitation during repetitive stimulation. The effect of noradrenaline in sympathectomized muscles was more obvious than in the control muscles. After the noradrenaline administration, the fourfold increase of calcium concentration did not change the amplitude of e.p.p.s or the time course of the facilitation. The mechanism of depolarization--secretion coupling in the nerve terminal seems to be impaired by the sympathectomy.

Animals↗
PubMed2000

The use of selective electrical stimulation of the quadriceps to improve standing function in paraplegia.

Persons with spinal cord injury (SCI) can benefit significantly from functional neuromuscular stimulation (FNS) systems for standing if manual tasks can be performed while upright. Using FNS to sufficiently activate the knee extensors to rise from a sitting position often results in inadvertent activation of the rectus femoris and/or sartorius, which flex the hip. In this study, intramuscular electrodes implanted in the vastus lateralis and medialis of four subjects with SCI were used to activate these muscles individually and simultaneously to measure knee extension moment. Support forces applied to the arms and feet were measured while upright to quantify the effects of recruiting rectus femoris and/or sartorius. In three of the four subjects, vastus lateralis, by itself, generated adequate knee extension moment for rising from a chair and to maintain static standing. Simultaneous activation of the vastus lateralis and medialis using a bifurcated electrode generated adequate knee extension moment in one subject, and was within 10% of the required moment in another. While upright, activation of the rectus femoris resulted in arm support force increases of 4-11% body weight, while deactivation resulted in arm support force decreases of 6-9% body weight. The results indicate that selective activation of the vastus lateralis, individually or in combination with vastus medialis, can improve current FNS standing systems by reducing the arm support forces required to remain upright.

Biomechanical Phenomena↗
PubMed1991

Distribution of motoneurons supplying cat sartorius and tensor fasciae latae, demonstrated by retrograde multiple-labelling methods.

Sartorius (SART) and tensor fasciae latae (TFL) in the cat hindlimb are functionally heterogeneous muscles with regions that differ in their skeletal actions and electromyographic recruitment during normal activity. The topographical organization of motoneurons supplying different regions of SART or TFL has been investigated by exposing cut nerve branches supplying different peripheral territories to a combination of retrograde tracers, including Fast Blue (FB), Fluorogold (FG), and horseradish peroxidase (HRP). Motoneurons supplying medial, central, and anterior regions of SART were intermixed extensively throughout a single columnar nucleus located in the ventrolateral part of segments L4 and L5. With this column, motoneurons supplying medial SART tended to lie more rostrally than those supplying anterior regions, but the gradient was modest and showed some cat-to-cat variation. Two major branches entered anterior SART at different proximodistal levels. When these two branches were exposed to different tracers, most motoneurons contained a single tracer; only a few double-labelled cells were apparent. The labelling suggests that anterior SART may contain two separate, in-series divisions of motor units. In TFL, motoneurons supplying nerve branches to posterior, central, and anterior parts of the muscle were intermingled indiscriminately in a single ventrolateral cell column in L6 and rostral L7. These results suggest that topographical organization in lumbar motor nuclei does not always reflect the highly ordered biomechanical and functional specialization evident in the peripheral organization of the muscles themselves.

Amidines↗
PubMed1996

High performance liquid chromatography purification and amino acid sequence of toxins from the muscarinic fraction of Tityus discrepans scorpion venom.

Tityus discrepans venom was fractionated by gel filtration on Sephadex G-50 column. The peptides in fraction II from Sephadex were further purified by high performance liquid chromatography, through a C4 reverse-phase column. Lethality of purified peptides was determined by injection into mice and crabs, and their effects were verified electrophysiologically on frog (Hyla crepitans) sartorius neuromuscular junction. Toxins having retention times between 39.6 and 40.7 min depolarized the muscle membrane and caused acetylcholine release at the endplate. The toxin eluted at 42.67 min increased the frequency of miniature endplate potentials without depolarizing muscle fibres. The four most active toxins were reduced, carboxymethylated and sequenced by automatic Edman degradation and named TdII-1 to II-4. Toxin gamma from Tityus serrulatus venom and the toxins from T. discrepans venom were found to be structurally distinct. TdII-1 to II-4 lack the pancreatic effects of T. serrulatus' toxin gamma; yet, the five toxins act on Na+ channels.

Acetylcholine↗
PubMed1992

The variation of isometric energy rates with muscle length: a distribution-moment model analysis.

The Distribution-Moment Model of skeletal muscle, which has been enhanced recently to make possible the calculation of chemical energy release (E) and heat production (H) rates [1], is applied to isometric muscle. Under steady-state isometric conditions the model predicts a simple relation between the energy rates and the muscle length, namely (E/Emax) = (H/Hmax) = [1 + B alpha(symbol see text)]/[1 + B], where (symbol see text) is the ratio of muscle length to the "optimal" length at which maximal isometric tension is produced, and alpha (symbol see text) is a function numerically equal to the ratio of the tetanic isometric force to its maximum value. The single dimensionless constant in this relation, B, can be calculated from model parameters characterizing muscle dynamics at the optimum length, and has a value near unity for frog sartorius at 0 degrees C. The predicted behavior is shown to agree reasonably well with experimental measurements of heat production and phosphocreatine (PCr) hydrolysis. The model relates the isometric energy rates to PCr hydrolysis in (1) cross-bridge interactions, and (2) calcium pumping into the sarcoplasmic reticulum.

Biomechanical Phenomena↗
PubMed2005

Orientation of tendons in vivo with active and passive knee muscles.

Tendon orientations in knee models are often taken from cadaver studies. The aim of this study was to investigate the effect of muscle activation on tendon orientation in vivo. Magnetic resonance imaging (MRI) images of the knee were made during relaxation and isometric knee extensions and flexions with 0 degrees , 15 degrees and 30 degrees of knee joint flexion. For six tendons, the orientation angles in sagittal and frontal plane were calculated. In the sagittal plane, muscle activation pulled the patellar tendon to a more vertical orientation and the semitendinosus and sartorius tendons to a more posterior orientation. In the frontal plane, the semitendinosus had a less lateral orientation, the biceps femoris a more medial orientation and the patellar tendon less medial orientation in loaded compared to unloaded conditions. The knee joint angle also influenced the tendon orientations. In the sagittal plane, the patellar tendon had a more anterior orientation near full extension and the biceps femoris had an anterior orientation with 0 degrees and 15 degrees flexions and neutral with 30 degrees flexions. Within 0 degrees to 30 degrees of flexion, the biceps femoris cannot produce a posterior shear force and the anterior angle of the patellar tendon is always larger than the hamstring tendons. Therefore, co-contraction of the hamstring and quadriceps is unlikely to reduce anterior shear forces in knee angles up to 30 degrees . Finally, inter-individual variation in tendon angles was large. This suggests that the amount of shear force produced and the potential to counteract shear forces by co-contraction is subject-specific.

Adult↗
PubMed1985

[Role of calcium ions and cyclic nucleotides in neurotrophic control of the membrane properties of muscle fibers in the frog].

Subcutaneous injections of caffeine, calcium ionophore X537A or cAMP did not affect the changes of input resistance (R0) and time constant (T) of membrane caused by denervation of the frog m. sartorius but prevented the MP decrease and ACh sensitivity spread. Injections of cGMP did not affect the denervation changes of R0 and MP but increased the ACh sensitivity. The neurotrophic control of frog muscle membrane properties seems to depend on calcium and involve the cyclic nucleotides system.

Animals↗
PubMed1997

Effects of 20 days of bed rest on physiological cross-sectional area of human thigh and leg muscles evaluated by magnetic resonance imaging.

The present study was to investigate the effects of 20 days of bed rest on morphological characteristics of lower limb skeletal muscles. Ten sedentary volunteers (5 males and 5 females) were participating in this study. Magnetic resonance imaging techniques were used to measure the physiological cross-sectional areas (PCSAs) of the major muscles and muscle groups of the lower limb. Consecutive images were taken from the right thigh and leg of subjects, and muscle volumes (MV), muscle length, and fiber length were calculated. PCSA of each muscle was determined as MV times the cosine of the angle of fiber pennation divided by fiber length. PCSA of knee extensor and flexor muscles were significant reduced during and after bed rest. MV and PCSA of individual muscles in the knee extensors decreased by -5.1 % to -8.0%. In knee flexors, MV and PCSA in biceps femoris (long head), semitendinosus, semimembranosus, and sartorius decreased during and after bed rest. MV and PCSA in medial and lateralis [correction of andateralis] gastrocnemius, and soleus were remarkably reduced by -9.4 to -10.3% after bed rest. The results suggest that there is a great variability of muscle atrophy in the lower limb muscle groups or individual muscle after bed rest and that the plantar flexors primarily affected.

Adult↗