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PubMed1990

Research note: simultaneous histochemical determination of three fiber types in single sections of broiler skeletal muscles.

A staining procedure used for simultaneously determining three different fiber types in single sections of bovine, porcine, or ovine skeletal muscle was modified for use with broiler skeletal muscle. The modification involved acid-preincubation of muscle sections at a pH of 4.15 followed by staining for reduced nicotinamide adenine dinucleotide (NADH) tetrazolium reductase enzyme and for acid-stable myosin-adenosine triphosphatase enzyme activity, respectively. Four broiler muscles were selected for fiber-type determination of fast (alpha), slow (beta), red, aerobic (R), or white, anaerobic (W) properties. The anterior latissimus dorsi muscle was composed almost entirely of beta-R fibers while the pectoralis superficialis muscle was composed almost entirely of alpha-W fibers. The sartorius and posterior latissimus dorsi muscles were much more heterogeneous in fiber-type distribution, exhibiting all three types of fibers (alpha-W, alpha-R, and beta-R).

Aluminum Silicates↗
PubMed1993

Activity of ornithine decarboxylase in muscle of Japanese quail in hypergravity conditions.

Ornithine decarboxylase (ODC) is the rate limiting enzyme in the synthesis of polyamines which are generally required for animal cell proliferation. Because of many different stimuli changing the activity of ODC, the effect of hypergravity on muscle ODC activity in Japanese quail was investigated. Adult Japanese quail cockerels were exposed to 2G in the centrifuge permanently for 96 hours. The activity of ODC was determined by radioisotopic method in supernatant of homogenised breast and fibular muscles (m. pectoralis minor, m.superficialis fibularis). The activity of ODC was higher in breast muscle than in the fibular muscle in both, control and experimental groups. Exposition of quail to hypergravity evokes approximately 2 fold increase of ODC activity in both breast and fibular muscles. The results suggest that 96 hours of permanent hypergravitation (2G) caused activation of polyamine synthesis and their involvement in biochemical processes of adaptation to hypergravity.

Adaptation, Physiological↗
PubMedDate not supplied

Optimization of pacing parameters for conditioned latissimus dorsi muscle in cardiomyoplasty.

Synchronous paced contractions of latissimus dorsi muscle pedicle (LDM) around the heart improve ventricular function in dynamic cardiomyoplasty. To optimize assistance and prolong pacemaker battery life, the LDM should be stimulated with the lowest energy pacing parameters (PP) that will produce maximal muscle contraction. Muscle fractional shortening (FS) and duration of contraction (CT) were studied in conditioned, fatigue-resistant LDM of six goats. Fractional shortening and CT were determined at increasing amplitude, (A, 1-6v); pulse width, (PW, 60-450 musec); and frequency, (F, 5-130 Hz). Maximal rate of contraction was determined by pacing at higher rates. Maximal FS plateaued after V, 2.4 +/- .6v; PW, 125 +/- 47 musec; and F, 36 +/- 9 Hz. Mean CT for all PP was significantly longer (p less than or equal to 0.001) than the burst length (185 msec). Increasing F resulted in CT, which peaked at 460 +/- 59 msec. Increasing rate of contraction demonstrated that over 87 beats per minute the muscle fails to achieve complete relaxation, and, therefore, maximal FS.

Animals↗
PubMedDate not supplied

Perineural leads and burst stimulation optimize contraction of skeletal muscle.

Electrode position and stimulation mode were hypothesized to be independent variables for the contractile response of skeletal muscle. Perineural and intramuscular electrodes were tested with single and burst pulse generators. Voltage requirements and muscle force generation were measured. Perineural leads improved the efficiency of stimulation for muscle contraction and yielded reduced threshold and plateau voltages compared to intramuscular leads. There were no differences between the different types of perineural leads. Burst stimulation had a wider range of voltage for muscle fiber recruitment and was confirmed to elicit greater maximal force than single stimulation.

Animals↗
PubMedDate not supplied

Breathing pattern and efficiency of the respiratory muscles in healthy prematures and in prematures with respiratory distress syndrome.

The relationship between the compliance of the respiratory system (Crs), measured by mouth occlusion technique, and the the breathing pattern, the central inspiratory activity, and the performance of the respiratory muscles respectively, was studied in healthy prematures and in prematures presenting with the respiratory distress syndrome. With decreasing Crs, respiratory rate, instantaneous minute-ventilation, airway pressure at 0.1 s after end-expiratory occlusion (P0.1), effective inspiratory impedance, the average rate of change of the pressure generated during the inspiratory effort against closed airways, and the work of breathing increased; inspiratory and expiratory times decreased overproportionally. We conclude that the changes in lung mechanics predispose prematures with a Crs of less than 1 ml X cmH2O-1 to develop respiratory failure because they cannot perform the respiratory work demanded by intact central regulation mechanisms.

Airway Resistance↗
PubMed1990

Cortical outflow to proximal arm muscles in man.

Corticospinal influences on two antagonistic muscles of the shoulder were studied in 6 normal volunteers. Recordings were made of the discharges of single motor units from the deltoid and pectoralis major muscles and poststimulus time histograms constructed following either anodal electrical or magnetic cortical stimulation via the scalp. Contralateral anodal stimulation caused narrow short-latency peaks of excitation in motor units from both muscles, probably indicative of the arrival of the D or direct corticospinal volley. The size of the peaks led to estimates of the underlying excitatory postsynaptic potentials (EPSP) amplitude of 5.5 mV for the deltoid and 2.2 mV for the pectoralis motor units. Magnetic stimulation over the vertex caused multiple early peaks of excitation in motor units from both muscles but these peaks began at a greater latency than those produced by anodal stimulation. Additionally, magnetic cortical stimulation (and, occasionally, contralateral anodal stimulation) caused a previously undescribed period of medium latency excitation in both muscles. These medium latency periods of excitation differed from the earlier events in that they occurred independently of the direction of current flow in the magnetic coil. This raises the possibility that they are the consequence of stimulation of bilaterally distributed cortical motor outflow pathways. The short-latency excitation strongly suggests that, in man, corticomotoneuronal projections exist to proximal as well as distal muscles of the contralateral arm. The strength of the projection to deltoid assessed by this method is similar to that to an intrinsic muscle of the hand and significantly larger than that to its antagonist, pectoralis. The possible bilateral organization of the additional medium-latency projection to these proximal arm muscles may contribute to two characteristic clinical features after a unilateral cerebral lesion, such as stroke: the relative sparing of proximal arm strength compared with distal and, secondly, ipsilateral weakness.

Adult↗
PubMed1990

Turkey muscle growth and focal myopathy.

Muscle structure and blood enzyme activity were studied to 16 wk of age in lines of turkeys selected for rapid growth. The body and carcass weights were measured, frozen sections of breast and leg muscles examined, and plasma creatine kinase (CK) levels determined. Muscle weights were usually proportional to BW except for the relatively larger superficial pectoralis (SP) muscles in the most rapidly growing line. Damaged muscle fibers were found in all muscles examined, especially in the SP of the breast, the gastrocnemius (GA), and other muscles of the leg; these damages became more common from 10 to 16 wk of age. There were more degenerating muscle fibers and higher levels of plasma CK in the rapidly growing lines than in a slower growing unselected line. The findings support the idea that a focal myopathy, unrelated to deep pectoral myopathy or to inherited muscular dystrophy of the chicken, is associated with rapid growth of turkeys.

Animals↗
PubMed2000

Anatomy and histochemistry of flight muscles in a wing-propelled diving bird, the Atlantic puffin, Fratercula arctica.

Twenty-three species within the avian family Alcidae are capable of wing-propelled flight in the air and underwater. Alcids have been viewed as Northern Hemisphere parallels to penguins, and have often been studied to see if their underwater flight comes at a cost, compromising their aerial flying ability. We examined the anatomy and histochemistry of select wing muscles (Mm. pectoralis, supracoracoideus, latissimus dorsi caudalis, coracobrachialis caudalis, triceps scapularis, and scapulohumeralis caudalis) from Atlantic puffins (Fratercula arctica) to assess if the muscle fiber types reveal the existence of a compromise associated with "dual-medium" flight. Pectoralis was found to be proportional in size with that of nondiving species, although the supracoracoideus was proportionally larger in puffins. Muscle fiber types were largely aerobic in both muscles, with two distinct fast-twitch types demonstrable: a smaller, aerobic, moderately glycolytic population (FOg), and a larger, moderately aerobic, glycolytic population (FoG). The presence of these two fiber types in the primary flight muscles of puffins suggests that aerial and underwater flight necessitate a largely aerobic fiber complement. We suggest that alcids do not represent an adaptive compromise, but a stable adaptation for wing-propelled locomotion both in the air and underwater.

Animals↗
PubMed2000

Tissue-specific regulation of thyroid hormone receptor mRNA isoforms and target gene proteins in domestic ducks.

Skeletal muscles are important target tissues for thyroid hormone action. The present study examines the influence of thyroid status on muscle growth and tissue-specific expression of thyroid receptor (TR) mRNA isoforms in a commercial strain of the domestic duck (Anas platyrhynchos). Four groups (n=5) of 1-week-old ducklings were rendered either hypothyroid by treatment with methimazole (6 mg 100 g(-1) body mass or 12 mg 100 g(-1) body mass), or hyperthyroid by treatment with methimazole (6 mg 100 g(-1) body mass) in combination with thyroid hormones (5 microg thyroxine (T(4)) and tri-iodothyronine (T(3)) 100 g(-1) body mass or 10 microg T(4) and T(3) 100 g(-1) body mass). Serum and tissue samples (cardiac, pectoralis and semimembranosus leg muscle, liver, pituitary and cerebral cortex) were collected from these four groups, and from a group of untreated controls, at 8 weeks of age. Development of duckling morphology was retarded in methimazole-treated birds compared with that in euthyroid controls, as evidenced by differences in skeletal dimensions, primary feather length, and body and muscle masses. Body mass was lower by 18%, and relative masses of cardiac and pectoralis muscles were lower by 28% and 32% respectively. Heterologous oligonucleotides for TR alpha, TR beta 0, TR beta2 and the housekeeping gene beta-actin were derived from chicken sequences. RT-PCR showed that TR alpha mRNA was expressed in all tissues but was not significantly affected by any of the experimental treatments. TR beta 0 mRNA expression was significantly lower in the leg muscles of ducklings treated with 12 mg methimazole 100 g(-1) body mass (0.109+/-0.047 TR:beta-actin ratio, P<0.05) compared with that in euthyroid controls (0.380+/-0.202), but was unaltered in the pectoralis and cardiac muscles. Expression of TR beta 0 mRNA was significantly higher in pectoralis (by 3.5-fold, P<0. 05), cardiac (by 4.2-fold, P=0.003) and leg (by 4.0-fold, P<0.001) muscles of ducklings treated with thyroid hormones compared with those in euthyroid controls (0.098+/-0.019, 0.822+/-0.297 and 0. 38+/-0.202 TR:beta-actin respectively). Only the pituitary gland expressed significant levels of TR beta 2 mRNA.

Animals↗
PubMed1992

Complete primary structure and tissue expression of chicken pectoralis M-protein.

M-Protein (165 kDa) is a structural constituent of myofibrillar M-band in striated muscle. We generated a monoclonal antibody which recognized a 165-kDa protein from chicken pectoralis muscle in immunoblot analysis and stained the M-band under immunofluorescence microscopy. By screening a lambda gt11 cDNA library from chicken embryonic pectoralis muscle with this antibody, we isolated a cDNA clone encoding the M-protein. Northern blot analysis showed that M-protein mRNA is expressed in pectoralis and cardiac muscle but not in gizzard smooth muscle or non-muscle tissues. Moreover, the anterior latissimus dorsi muscle, which consists almost exclusively of slow fiber types, contains no detectable levels of the mRNA. The full-length cDNA sequence predicted a 1,450-amino acid polypeptide with a calculated molecular weight of 163 x 10(3). The encoded protein contains several copies of two different repetitive motifs: five copies of fibronectin type III repeats are in the middle part of the predicted molecule, and two and four copies of the immunoglobulin C2-type repeats are located toward the NH2-terminal and COOH-terminal regions, respectively. This indicates that M-protein, along with other thick filament-associated proteins such as C-protein, twichin, and titin, belongs to the superfamily of cytoskeletal proteins with immunoglobulin/fibronectin repeats.

Amino Acid Sequence↗
PubMedDate not supplied

Freeze-fracture study of muscle plasmalemma in normal and dystrophic chickens.

We compared the freeze-fracture morphology of the plasmalemma of the pectoralis major muscle taken from normal and dystrophic chickens at adult, embryonic, and early posthatching stages. Developmental changes were more conspicuous in surface caveolae than in intramembranous particles. The most striking differences between normal and dystrophic muscles were seen in the densities of the caveolae (17/micron2 in the normal adult; 30/micron2 in the dystrophic adult) and in their distribution (rectangular pattern in normals; random arrangement in dystrophics). These differences had already become significant at seven days posthatching and before the appearance of clinical symptoms. This is the earliest development stage at which morphologic abnormalities of plasmalemma have been reported for dystrophic muscle. Variations of surface topography and caveolar morphology, presumably representing secondary changes, were common in adult dystrophic muscle.

Animals↗
PubMed1985

Effects of phosphate on the contractile properties of fast and slow muscle fibres from an Antarctic fish.

Single fast myotomal fibres and small bundles of slow fibres (from the adductor pectoralis profundus muscle) were isolated from the Antarctic teleost Notothenia neglecta. Fibres were skinned by a brief detergent treatment. The effects of phosphate on the mechanical properties and ATPase activity of fast and slow fibres were studied. 20 mM-phosphate inhibited maximum isometric tension in slow fibres by 34%, but by only 11% in fast fibres. A half-maximal response was obtained at approximately 5 mM-phosphate. These concentrations are within the range measured in muscle, and the effect is probably of physiological significance. This species is of particular interest, since there is evidence that the energy supply to the fast muscle is largely based on phosphocreatine breakdown, which would result in large changes in intracellular phosphate concentration during exercise. The maximum contraction velocity of both fast and slow fibres was not affected by 10 mM-phosphate, nor was the ATPase activity of the slow fibres during isometric contraction. The phosphate-induced depression in tension in slow fibres was associated with a proportional decrease in stiffness. The rate of force recovery after rapid, small amplitude stretches and releases was increased by phosphate, as was the rate of rise of force during stretch activation. The results are discussed with reference to the different patterns of energy supply for contraction in muscle, and an attempt is made at explaining the data in terms of changes in cross-bridge kinetics.

Adenosine Triphosphatases↗