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At least 1,549 records · Page 86Linked to original sources
PubMed1995

Collagen and stretch modulate autocrine secretion of insulin-like growth factor-1 and insulin-like growth factor binding proteins from differentiated skeletal muscle cells.

Stretch-induced skeletal muscle growth may involve increased autocrine secretion of insulin-like growth factor-1 (IGF-1) since IGF-1 is a potent growth factor for skeletal muscle hypertrophy, and stretch elevates IGF-1 mRNA levels in vivo. In tissue cultures of differentiated avian pectoralis skeletal muscle cells, nanomolar concentrations of exogenous IGF-1 stimulated growth in mechanically stretched but not static cultures. These cultures released up to 100 pg of endogenously produced IGF-1/micrograms of protein/day, as well as three major IGF binding proteins of 31, 36, and 43 kilodaltons (kDa). IGF-1 was secreted from both myofibers and fibroblasts coexisting in the muscle cultures. Repetitive stretch/relaxation of the differentiated skeletal muscle cells stimulated the acute release of IGF-1 during the first 4 h after initiating mechanical activity, but caused no increase in the long-term secretion over 24-72 h of IGF-1, or its binding proteins. Varying the intensity and frequency of stretch had no effect on the long-term efflux of IGF-1. In contrast to stretch, embedding the differentiated muscle cells in a three-dimensional collagen (Type I) matrix resulted in a 2-5-fold increase in long-term IGF-1 efflux over 24-72 h. Collagen also caused a 2-5-fold increase in the release of the IGF binding proteins. Thus, both the extracellular matrix protein type I collagen and stretch stimulate the autocrine secretion of IGF-1, but with different time kinetics. This endogenously produced growth factor may be important for the growth response of skeletal myofibers to both types of external stimuli.

Animals↗
PubMed1988

[An electromyographic study on elevation of the shoulder joint].

To quantitatively analyze the electromyographic activity of the shoulder girdle muscles during elevation of the arm, the action potentials of nine muscles were integrated over 10-degree intervals of corresponding elevation angle. The trapezius, supraspinatus and deltoideus (anterior and middle fibers) muscles showed high activity and their activity increased in accordance with the magnitude of the elevation angle. The integrated EMG activity in the trapezius, supraspinatus and deltoideus (middle and posterior fibers) muscles increased as the plane of elevation was changed from the sagittal plane to the frontal plane. The correlation between the calculated work and the integrated EMG activity during scapular abduction from 0 to 90 degrees was analyzed. The regression coefficients of the trapezius, supraspinatus and deltoideus (anterior and middle fibers) muscles were higher than those of other muscles. The correlation coefficient of the supraspinatus was significantly lower than those of the trapezius, deltoideus and pectoralis major muscles.

Adolescent↗
PubMedDate not supplied

Myopathy of the deep pectoral muscle in broiler breeder hens.

Myopathy of the pectoralis profundus and ambiens muscles was found in chickens from 5 flocks of broiler breeder hens. Histological lesions in the muscles varied from steatosis to loss of striations, fragmentation of fibers, and mineral deposition. A clinical response followed oral medication with vitamin E and selenium although analysis showed that selenium and vitamin E levels in the feed were normal. The possible relation between myopathy and Cassia seed in the feed is discussed.

Animals↗
PubMed1985

Selected muscle and nerve extracts contain an activity which stimulates myoblast proliferation and which is distinct from transferrin.

Extracts from normal chicken anterior latissimus dorsi and dystrophic pectoralis major muscles and from normal chicken sciatic nerves induce a growth stimulation in chicken and rat myogenic cell cultures. Transferrin is only partially responsible for the observed stimulation since the addition of the extracts to transferrin-saturated cultures induces a further growth response and extracts from which transferrin has been removed by immunoabsorption still retain a substantial portion of their stimulation activity. The active fractions of muscle and nerve extracts display heat, acid, and organic solvent inactivation. Gel filtration of ammonium sulfate fractionated activity from the anterior latissimus dorsi muscle suggests the presence of a growth factor in the molecular weight range of 10,000 to 30,000.

Animals↗
PubMed1987

Myomesin and M protein: differential expression in embryonic fibers during pectoral muscle development.

By applying immunocytochemistry using monoclonal antibodies, we found that the myofibrillar M band of both presumptive type-I and -II fibers in the pectoralis major muscle of chickens contains two high-molecular-weight proteins, i.e., myomesin (Mr, 185,000) and M protein (Mr, 165,000), early in embryonic development (7 days in ovo), even though adult type-I fibers lack M protein. The developmental expression of M protein is unusual in that, from 10 to 14 days in ovo, it is gradually suppressed not only in presumptive type-I fibers but also in presumptive type-II fibers formed from primary-generation myotubes. This latter suppression is transient, as M protein is expressed in all adult type-II fibers derived from both the primary- and second-generation myotubes. Myomesin, on the other hand, is continuously expressed in all myotubes throughout development. This finding shows that myomesin and M protein expression is regulated independently in different myotube populations, and that the suppression of M protein in primary-generation myotubes accounts for the delayed accumulation of M protein during development, as previously revealed by biochemical analysis. Presumptive type-I fibers, which form in the deep portion of the muscle, become concentrated in a narrow band known as the red strip.

Aging↗
PubMed1982

Correlation between the protein and mRNA levels for myosin light chains and tropomyosin subunits during chick fast muscle development in vivo.

Using myosin light chains and tropomyosin subunits as representative myofibrillar proteins, we have characterized their isoprotein forms and also correlated them with the accumulation of the corresponding mRNAs during development of a fast muscle in chicken, viz, pectoralis. Both slow and fast myosin light chain isoforms, except fast myosin light chain LC3, and the two subunits of tropomyosin are present in early embryonic muscle. During development, the slow myosin light chains and beta-tropomyosin appear in reduced amounts in pectoralis muscle and finally they disappear in adult muscle. Translation studies with total cellular RNA from developing muscle indicates that while the protein levels of the above isoforms, in general, correlate with the accumulation of corresponding mRNAs, for LC3, additional post-transcriptional control appears to modulate the expression of this isoprotein skeletal muscle development in vivo.

Aging↗
PubMed1980

Muscle flap reconstruction of shoulder defects.

Defects of the shoulder area pose difficult problems for the hand surgeon, especially when associated with irradiation or exposed, infected bone. The development of muscle and myocutaneous flaps has greatly simplified the reconstruction of such defects. This report discusses the use of the pectoralis and the latissimus flaps for this purpose, with case examples and emphasis upon technique and applications.

Adult↗
PubMed2006

Alternative bi-pectoral muscle flaps for postoperative sternotomy mediastinitis.

Suppuration, mediastinitis, and disruption of median sternotomy are all rare, but nevertheless severe complications. We propose a simple mobilization of the two pectoralis major muscles for use as flaps to fill the sternal defect without the need for humeral detachment or a second cutaneous incision. These will be supplied from both the thoracoacromial vessels and the perforating arteries of the nongrafted internal mammary artery (IMA). Our technique is quick and easy, giving excellent results. Furthermore, by maintaining the perforating branches, we also preserve the nongrafted IMA.

Cardiac Surgical Procedures↗
PubMed1999

Effects of abdominal belts on intra-abdominal pressure, intra-muscular pressure in the erector spinae muscles and myoelectrical activities of trunk muscles.

OBJECTIVE: To evaluate the effects of abdominal belts on lifting performance, muscle activation, intra-abdominal pressure and intra-muscular pressure of the erector spinae muscles. DESIGN: Simultaneous measurement of intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles was performed during the Valsalva maneuver and some isometric lift exertions. BACKGROUND: While several hypotheses have been suggested regarding the biomechanics of belts and performance has been found to increase when lifting with belts, very little is known about the modulating effects on trunk stiffness. At present, there is no reason to believe that spine tolerance to loads increases with belts. METHODS: An abdominal belt designed for weightlifting was used. Intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles and myoelectric activities of trunk muscles (erector spinae, rectus abdominis and external oblique) were measured simultaneously during the Valsalva maneuver as well as three types of isometric lifting exertions (arm, leg and torso lift). A paired t-test was used to analyze for statistical differences between the two conditions (without-belt and with-belt) in intra-abdominal pressure, intra-muscular pressure of the erector spinae muscles and in the integrated EMG of the trunk muscles. RESULTS: Intra-muscular pressure of the erector spinae muscles increased significantly by wearing the abdominal belt during Valsalva maneuvers and during maximum isometric lifting exertions, while maximum isometric lifting capacity and peak intra-abdominal pressure were not affected. Integrated EMG of rectus abdominis increased significantly by wearing the abdominal belt during Valsalva maneuvers (after full inspiration) and during isometric leg lifting. CONCLUSIONS: Wearing abdominal belts raises intra-muscular pressure of the erector spinae muscles and appears to stiffen the trunk. Assuming that increased intra-muscular pressure of the erector spinae muscles stabilizes the lumbar spine, wearing abdominal belts may contribute to the stabilization during lifting exertions.

Abdominal Muscles↗