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At least 19 recordsLinked to original sources
PubMed1979

Synthesis of the calcium transport ATPase of sarcoplasmic reticulum and other muscle proteins during development of muscles cells in vivo and in vitro.

The effect of medium Ca2+ concentration upon the concentration and the rate of synthesis of muscle proteins was investigated in chicken pectoralis muscle cultures. There is an easily identifiable class of muscle protein which includes the Ca2+-ATPase of sarcoplasmic reticulum, myosin, troponin C, ATP : creatine phosphotransferase, muscle specific actin, tropomysin 1 and 2, and muscle hemagglutinin, which show a large increase in concentration during normal development. The increased synthesis of these proteins was inhibited, without inhibition of cell proliferation, in culture media of relatively low Ca2+ concentration, 0.05--0.3 mM, where fusion was prevented. Similar medium Ca2+ concentration was required for the expression of all these proteins, suggesting their coordinate regulation. The proteins are denoted as 'calcium-modulated proteins'. The increased Ca2+ transport activity of sarcoplasmic reticulum in cultured chicken pectoralis muscle cells during development at 1.8 mM medium calcium concentration represents de novo synthesis of the Ca2+ transport ATPase, as shown by immunoprecipitation, active site labeling and direct identification of the Ca2+ transport ATPase on two-dimensional gel electropherograms of whole muscle homogenates. The concentration and the turnover rate of the majority of the muscle proteins is not affected significantly by medium Ca2+ concentration between 0.06 and 1.8 mM. It is proposed that increase in cytoplasmic free Ca2+ concentration during fusion plays a central role in the regulation of the synthesis of calcium-modulated proteins.

Acetylcholinesterase↗
PubMed1979

Muscle protein analysis. I. High-resolution two-dimensional electrophoresis of skeletal muscle proteins for analysis of small biopsy samples.

We have been developing a clinically useful method for high-resolution two-dimensional electrophoretic analysis of small (5--10 mg) human muscle biopsy samples with sufficient resolution to resolve the major contractile proteins and enzymes. Using rabbit psoas muscle as a model, we describe methods for sample preparation and two-dimensional electrophoresis. Basic proteins, which appear as streaks when conventional isoelectric focusing is used in the first dimension, are resolved through a modification of the nonequilibrium pH gradient electrophoresis method [Cell 12, 1133 (1977)]. In the two-dimensional patterns obtained from rabbit muscle, we identify the components of 10 enzymes and of myosin, actin, tropomyosin, and troponin. These patterns indicate charge heterogeneity in a large fraction of the proteins. Comparison of rabbit and normal human muscle patterns shows many similarities, but much additional work is required to confirm identifications. We conclude that analysis of small biopsy samples is feasible, but that all aspects of human sample acquisition, storage (when necessary), and preparation require thorough study before the method becomes routine in human muscle research and, ultimately, in the diagnosis of some muscle diseases.

Animals↗
PubMed1978

Turnover rates of muscle protein in cardiac and skeletal muscles of dog, fowl, rat and mouse: turnover rate related to muscle function.

Turnover rates of muscle protein in cardiac and skeletal muscle have been measured in dogs using a continuous infusion of 14C-tyrosine, and in fowls, rats and mice after a pulse label of either 3H-leucine or 3H-aspartate. In all species the total mixed protein from ventricle turned over the most rapidly. Tonic muscles predominantly comprised of red fibres were intermediate in rate and twitch muscles comprised of predominantly white fibres had the slowest rates of turnover. This same progression of turnover rates was also seen in myofibrillar and sarcoplasmic protein fractions and with myosin. The RNA concentrations of the muscle tissue were highly correlated with the turnover rates. It is suggested that the turnover rate of muscle protein is related to the function of the muscle.

Animals↗
PubMedDate not supplied

Turnover rates of muscle proteins in cardiac, skeletal, and smooth muscle: turnover rate related to muscle function.

The turnover rate of muscle proteins was related to the physiological function of the muscle in dogs, fowl, rats, and mice. The turnover rates of mixed muscle proteins were most rapid in cardiac muscle, intermediate in red tonic and mixed fiber-type muscles, and slowest in white twitch skeletal muscle. This same progression in turnover rates also was shown in the subcellular fractions of muscle-sarcoplasmic and myofibrillar proteins-as well as in purified proteins, myosin, and tropomyosin. The RNA concentration of muscle was highly correlated with the protein turnover rate, and the RNA activity, i.e., the translational efficiency of the RNA, was similar in the different muscle types.

Animals↗
PubMed1976

The relative importance of muscle protein synthesis and breakdown in the regulation of muscle mass.

The effects of growth-suppressing and muscle-wasting treatments on muscle protein turnover and amino acid concentrations were determined in vivo. All treatments depressed protein synthesis and some treatments depressed protein breakdown. Only prolonged starvation increased protein breakdown. Muscle protein mass is regulated primarily through alterations in protein synthesis in all except emergency conditions. The increased concentrations of the branched-chain amino acids indicate that they are unlikely to be involved in this regulation.

Animals↗
PubMed1975

Measurement of muscle protein synthetic rate from serial muscle biopsies and total body protein turnover in man by continuous intravenous infusion of L-(alpha-15N)lysine.

1. Five healthy male subjects were studied by continuous infusion of L-[alpha-15N]lysine over 20-30 h with timed blood and urine samples, and two or three percutaneous needle biopsies of vastus lateralis muscle. 2. A standard creatine-free diet, quantitatively related to body surface area, was given for 5 days before the infusion. The [15N]lysine was administered at a constant rate in an amino acid solution with a nitrogen content of 0-96 mol/l, which constituted the sole source of exogenous nitrogen during the infusion. 3. A plateau level of plasma free [15N]lysine enrichment was achieved after infusion for 14 h. The total plasma lysine flux calculated from the plateau was 7-3 mmol/h (range 4-8-9-6). Total body protein turnover calculated from the lysine flux was 3-5 g day-1 kg body wt.-1 (range 2-5-5-0). 4. Muscle sarcoplasmic and myofibrillar fractions were separated, purified and the 15N enrichment was measured. The sarcoplasmic protein fractional synthetic rate was calculated as 3-8%/day (range 2-2-5-1). The myofibrillar protein synthetic rate was 1-46%/day (range 1-09-2-44). 5. Muscle mass, calculated from 24 h creatinine excretion, was 33-7 kg (range 28-8-37-4), which represented 50-0% of body weight (range 38-9-58-1). Total muscle protein synthesis was calculated to account for 53-2% (range 39-5-62-1) of total body protein syntehsis. 6. The advantages and limitations of using continuous infusion of [15N]lysine in human subjects are discussed.

Adult↗
PubMedDate not supplied

[Effect of prolonged cold storage and subsequent heat treatment on the fractional composition of fish muscle proteins].

The effect of prolonged preservation at -18 degrees C and subsequent culinary heat treatment of the fractional composition of sarcoplasmatic and myofibrillar proteins in the muscles of mirror carp, pike and sheat-fish were studied by the method of gel-filtration on Sephadex G-100. Cold storage of the dish at -18 degrees C for 9 months was found to produce market changes in the qualitative and quantitative composition of muscle proteins. After culinary heat treatment the finished products have lost much of their original quality.

Animals↗
PubMed1978

Ntau-methylhistidine (3-methylhistidine) and muscle protein turnover: an overview.

Actin and myosin, the contractile proteins of skeletal muscle, are methylated following peptide bond synthesis, with production of Ntau-methylhistidine (3-methylhistidine, 3-MeHis). During intracellular breakdown of these proteins, the 3-MeHis is released and excreted in the urine. Studies on tissue distribution of 3-MeHis and on its qunatitative excretion following administration to rats and to man show that urinary output of this amino acid provides a reliable index of the rate of myofibrillar protein breakdown in the musculature of intact rats and human subjects. Estimates of the fractional rate of muscle protein breakdown based on 3-MeHis data are consistent with rates computed by other techniques. By this technique, it has been shown that the fractional rate of muscle protein breakdown is not significantly different in the elderly as compared with young adults. However, since muscle mass is less in the elderly, it makes a smaller contribution to whole body protein breakdown with aging in humans. Output of 3-MeHis diminishes in growing rats and obese human subjects with protein or energy restriction, though the initial response of myofibrillar protein breakdown in growing rats to protein and protein-energy restriction differs. Measurement of 3-MeHis excretion has also proved useful in exploring the effects of physical and thermal trauma on the rate of muscle useful in exploring the effects of physical and thermal trauma on the rate of muscle protein breakdown.

Aging↗
PubMed1978

Effects of age, sex and starvation on the turnover of plasma, liver and breast muscle proteins in the Japanese quail.

Half-lives of the plasma, liver and breast muscle proteins in female, old male, young male and starved young male Japanese quail were measured by following the changes in protein specific radioactivity over a period of 7 days. The female birds showed the shortest half-lives for plasma and liver proteins and very long half-lives for breast muscle proteins. Compared to the proteins from the female birds, the old and young male birds showed slightly longer half-lives for plasma and insoluble liver proteins and shorter half-lives for soluble liver and breast muscle proteins. Starved birds showed greatly increased half-lives for all proteins when compared to the corresponding proteins from the other groups of quail. In general, the trends shown for the turnover of proteins from plasma, liver and breast muscle of the four groups of quail were similar to turnovers reported for rats under similar treatment conditions.

Aging↗
PubMed1979

Ntau-methylhistidine in human skeletal and smooth muscle proteins.

1. Fifteen pieces of rectus abdominus muscle and fifteen pieces of taenia muscle were removed from patients undergoing various surgical procedures. 2. The muscles were extracted, hydrolysed and the content of Ntau-methylhistidine was measured. 3. The rectus muscles contained 3.13 +/- 0.7 mumols Ntau-methylhistidine/g fat-free dry solid and the taenia muscles 2.4 +/- 0.6 mumols/g fat-free dry solid. There was a statistically significant difference (P less than 0.05) between these values using the Student's unpaired tau test, although this could have been due to contamination of the taenia muscles with connective tissue. 4. The muscle content of Ntau-methylhistidine was at least 40% higher than the only other reported value and therefore the method of calculating muscle protein breakdown based on Ntau-methylhistidine excretion requires revision.

Aged↗
PubMed1975

Incorporation of leucine into human skeletal muscle proteins.

The in vitro incorporation of labelled leucine into human skeletal muscle proteins was studied with the aim to elucidate the relationship between the amino acid tissue pools and protein biosynthesis. The distribution volumes of leucine and cycloleucine in skeletal muscle tissue were similar but the equilibration time was shorter for leucine than for cycloleucine. The cellular uptake of leucine and cycloleucine was competitively inhibited by increased concentration of amino acids in the medium indicating an active transport. Optimal stimulation for incorporation of leucine into proteins was obtained at an amino acid concentration in the medium corresponding to 10 times that of normal human plasma. The incorporation of 14C-leucine into skeletal muscle proteins was linear before the total pool of free intracellular 14C-leucine and the incorporation rate of leucine calculated from the specific activity in the medium versus the amino acid concentration in the medium were different in the same experiment indicating a re-utilization of amino acids released at protein degradation. The results are compatible with the hypothesis that the proteolytically released amino acids have a competitive advantage for incorporation as compared with extra- and intracellular free amino acids. It is concluded that the amino acid pool which is in the immediate continuity with the protein biosynthesis sites equilibrates rapidly with the extracellular amino acid pool.

Amino Acids↗
PubMed1979

Effect of glucocorticoid administration on the rate of muscle protein breakdown in vivo in rats, as measured by urinary excretion of N tau-methylhistidine.

The role of glucocorticoids in regulating the rate of muscle protein breakdown was evaluated by measuring excretion of N(tau)-methylhistidine during administration of various doses of corticosterone to adrenalectomized rats. Groups of rats received daily subcutaneous injections of 0, 0.2, 0.5, 1.0, 5.0 or 10.0mg of corticosterone/day per 100g body wt. for 7 days, followed by 3 days without hormone treatment, after which they were killed. A group with intact adrenal glands served as an additional control. All animals were pair-fed with the untreated adrenalectomized group. No significant differences were noted in growth rate or N(tau)-methylhistidine excretion between the intact or adrenalectomized control groups, or those given 0.2, 0.5 and 1.0mg of corticosterone, whereas growth ceased and N(tau)-methylhistidine excretion rose markedly in the groups receiving 5 and 10mg of corticosterone. After these two high doses of corticosterone, but not after lower doses, there was a loss of weight of the gastrocnemius muscle per 100g of final body wt., but not of the soleus and extensor digitorum longus muscles. The two highest doses of corticosterone also resulted in an increase in liver weight per 100g of final body wt. Lower doses of corticosterone did not cause these changes. Plasma corticosterone concentrations, measured on the final day of injection and again at the time of killing, were decreased to near zero by adrenalectomy and were little raised by doses of 0.2 and 0.5mg daily, but were increased to within the normal range by the 1mg dose. At 5 and 10mg doses, plasma corticosterone concentrations were sustained at 2-3 times those of intact rats, and thus in the range reported for rats exposed to severe stress. Rats given 5 and 10mg doses of corticosterone had glycosuria, and showed considerably elevated concentrations of insulin in the plasma. It is concluded that plasma concentrations of glucocorticoids within the normal range do not regulate the rate of muscle protein breakdown, whereas excessive plasma concentrations of corticosteroids, equivalent to those observed in severe stress, can accelerate muscle protein breakdown.

Adrenalectomy↗
PubMed1979

Muscle protein degradation in premature human infants.

1. Myofibrillar protein degradation has been measured by the rate of 3-methylhistidine excretion in premature infants weighing between 635 g and 1295 g. Analyses were made in conjunction with 1--3 day nitrogen balance studies. 2. In 56 balance studies in 36 infants, total muscle protein breakdown varied between 0.70 and 2.58 (mean 1.05) g day-1 kg-1 body weight while the percentage of total muscle protein degraded each day was between 3.3 and 8.3 (mean 4.8). 3. Both total and fractional rates of protein breakdown showed highly significant negative correlations with nitrogen retention but no relationship to total energy input. 4. Protein degradation was higher than average in infants who were losing weight at the time of the balance study, lower in infants who were gaining weight and higher in those who died within 2 weeks of the analysis. 5. Myofibrillar protein breakdown was not different between infants fed orally and those receiving total parenteral nutrition. 6. Generally the effects of nitrogen and evergy status on muscle protein degradation in the premature infants are different from changes reported in adult human beings or adult rats. We suggest that this difference may be a consequence of the very limited energy reserves of the premature infant.

Aging↗
PubMed1978

Turnover of muscle protein in the fowl (Gallus domesticus). Rates of protein synthesis in fast and slow skeletal, cardiac and smooth muscle of the adult fowl.

Rates of protein synthesis in skeletal, cardiac and smooth muscle of fully grown fowl (Gallus domesticus) were determined in vivo by means of the constant infusion method using [14C]proline. In the anterior latissimus dorsi muscle, containing predominantly slow fibres, the average synthesis rate of non-collagen muscle proteins was 17.0 +/- 3.1% per day, a value higher than that obtained for cardiac muscle (13.8 +/- 1.3% per day) and for smooth muscle of the gizzard (12.0 +/- 1.9% per day). In the posterior latissimus dorsi muscle, containing predominantly fast fibres, synthesis rates were much lower (6.9 +/- 1.8% per day). In each case these average rates for the non-collagen protein were similar to the average rate for the sarcoplasmic and myofibrillar protein fractions. The RNA concentration of these four muscles showed that relative rates of protein synthesis were determined mainly by the relative RNA concentrations. The rate of protein synthesis per unit of DNA (the DNA activity) was similar in the two skeletal muscles, but somewhat lower in cardiac muscle and gizzard, possibly reflecting the larger proportion of less active cell types in these two muscles. These quantitative aspects of protein turnover in the two skeletal muscles are discussed in terms of the determination of ultimate size of the DNA unit, and in relation to muscle ultrastructure.

Animals↗
PubMed1979

The study of nitroxide radical active esters as spin labels on muscle protein actin.

Nitroxide radical active esters were used to label the muscle protein actin and to study the orientation dependence of the EPR spectra of the labelled protein. It is concluded that the labels are located at least at two different sites of the protein with strong polar environment and different mobilities. The EPR spectrum of the strongly immobilized labels exhibits orientation dependence, the N--O bond axis of the spin labels is nearly perpendicular to the long axis of the F-actin threads, and the labels undergo a rapid rotational motion about an axis directed perpendicular to the filament axis. The application of the nitroxide radical active esters may be useful in the study of ordered systems as muscle or muscle protein systems.

Actins↗
PubMed1978

The effects of starvation and refeeding on muscle protein synthesis and catabolism in the young rat.

We studied the effects of acute starvation and refeeding on muscle protein synthesis and degradation in young rats. As measures of synthesis, we determined muscle RNA concentration and the rate of incorporation of [14C]leucine into skeletal muscle protein (Sm). As an estimate of nitrogen retention we measured urea production (UrP). Starvation reduced these variables significantly. One refeeding period returned Sm to control values, only partially restored RNA concentration, and increased UrP. We determined the urinary excretion rate of 3-methylhistidine (3-MH) as a measure of the rate of myofibrillar protein degradation. Excretion of 3-MH was lowest in control and highest in starved rats. Refeeding decreased 3-MH excretion to a level midway between control and starved animals. Growth was attended by high rates of synthesis and low rates of degradation. Starvation depressed synthesis and increased degradation. With refeeding, synthesis increased and degradation decreased, compared with the starved state.

Animals↗
PubMed1977

Oxidative deterioration of the muscle proteins during nutritional muscular dystrophy in chicks.

Nutritional muscular dystrophy in the chick results from the simultaneous deficiency of vitamin E and cystine. Being a biological antioxidant, vitamin E might be functional in maintaining a proper redox state of the sulfur-containing amino acid in the proteins. The analyses of protein-bound sulfhydryls and disulfides at onset of muscular dystrophy in young chicks were carried out. The ratio of disulfide to sulfhydryls increased two- to three-fold in dystrophic muscle as compared to that in the control muscle proteins. Dystrophic and normal muscle proteins also were subjected to SDS-gel electrophoresis. Proteins of low molecular weight, supposedly derived from proteolysis, were present in the gels of the dystrophic muscle and absent in those of normal muscle extracts. As a result of these studies, a chemical model has been proposed to explain the oxidative deterioration of proteins in nutritional muscular dystrophy due to vitamin E deficiency.

Amino Acids, Sulfur↗