Showing papers on "Skeletal muscle published in 1971"
TL;DR: A kinetic analysis of the effect of the inhibitor on the phosphorylation of casein by skeletal muscle protein kinase indicates that it interacts noncompetitively with respect to ATP, the protein substrate, and adenosine 3',5'-monophosphate.
815 citations
TL;DR: A model system is proposed for the regulation of skeletal muscle phosphorylase kinase by Ca2+ in vivo, and the consequent linking of the process of glycogenolysis to that of muscle contraction.
384 citations
TL;DR: To determine the relationship between temperature and respiration, the consumption of isolated rat skeletal muscle mitochondria was measured at temperatures between 25 and 45 C in vitro and the results confirmed that increasing temperature had a negative effect on respiration.
Abstract: E. BEYER. Temperature, skeletal muscle mitochondrid functions, and oxygen debt. Am. J* Physiol. 220(4): 1053-1059. 1971 .-Compared to resting liver and skeletal muscle tempera- tures of 38.6 and 36.0 C, respectively, postexercise values were 43.4 and 44,l C in viva. To determine the relationship between temperature and respiration, the 02 consumption of isolated rat skeletal muscle mitochondria was measured at temperatures between 25 and 45 C in vitro. Increasing temperature had
255 citations
TL;DR: Evidence is presented for the existence of more than a single type of regulatory or cAMP-binding subunit in muscle in rabbit skeletal muscle.
232 citations
TL;DR: In the animals surviving 4 months or longer the end-plates of soleus fibres were similar to the normal for that muscle though nerve terminals were scattered along muscle fibres and many had no sole-plate nuclei near them and in gastrocnemius some end- plates were normal in appearance but others had unusually few and shallow subneural folds.
211 citations
TL;DR: It is submitted that a new, more flexible approach to fiber typing is needed to appreciate the dynamic nature of the muscle cell, and that the histochemically demonstrable “fiber types” merely reflect each muscle fiber's constitution at a given moment in time.
202 citations
TL;DR: It is suggested that adenosine may play a role in the metabolic regulation of skeletal muscle blood flow, whereas ATP, ADP, AMP, and P1 may not.
Abstract: Experiments were performed on isolated frog sartorius muscle and in situ dog skeletal muscle to determine whether adenine nucleotides and their degradation products are released during contraction in concentrations capable of producing arteriolar dilation ATP was not detectable (>10 -8 M) in the bathing solution of the resting or contracting frog sartorius muscle. Inorganic phosphate (P 1 ) in the muscle bath increased from 9 x 10 -5 M to 28 x 10 -5 M with 30 minutes of contraction (2 Hz) or with rest. With the dog hindlirnb preparation, ATP, ADP, and AMP were not detectable (>5 x 10 ⊟8 M in the venous blood collected after 5 minutes of ischemic contraction whereas P 1 was present at a concentration of 3.7 x 10 x8 M. Arterial blood levels required to elicit detectable vasodilation for ATP, ADP, AMP, and P 1 were 28.7 x 10 -8 M, 27.1 x 10 -8 M 31.4 x 10 -8 M and 7.2 ⊠ 10 -4 M respectively. The adenosine concentration in dog muscle increased from 0.7 to 1.5 nmole/g with ischemic contraction, and hypoxanthine and inosine increased from 4.5 to 8.5 nmole/g and 2.0 to 5.5 nmole/g, respectively. The adenosine concentration in venous plasma collected from the hiodlimb immediately after termination of the irchemic contraction period was 2.2 x 10 -7 MM as compared to 0.4 x 10 -7 M in control venous and arterial blood samples. Hypoxanthine and inosine concentrations in venous blood increased 22- and 270-fold, respectively, foflowing ischemic contraction. The calculated interstitial fluid adenosine concentration was twice the arterial concentration of adenosine required to elicit maximal arteriolar dilation. These findings suggest that adenosine may play a role in the metabolic regulation of skeletal muscle blood flow, whereas ATP, ADP, AMP, and P 1 may not.
202 citations
TL;DR: Studies of the binding of labelled α-bungarotoxin to mouse skeletal muscle endplates have allowed the quantification of acetylcholine receptor sites at the post-synaptic membrane.
Abstract: Studies of the binding of labelled α-bungarotoxin to mouse skeletal muscle endplates have allowed the quantification of acetylcholine receptor sites at the post-synaptic membrane.
191 citations
186 citations
TL;DR: Histochemical evaluation of three skeletal muscles of the chick in early postnatal development shows that there are two basic fiber types based on myosin ATPase activity, and it is suggested that skeletal muscle fibers be classified as αR, αW, and βR according to ATPase and oxidative enzyme activities.
182 citations
TL;DR: It is suggested that this defect may be a generalized cellular abnormality which is a common quality of serious illnesses and the mechanisms which might account for the elevation of intracellular Na(+) and a depression of Em independent of changes in intra-extracellular K(+) ratios.
Abstract: The resting membrane potential difference (Em) of skeletal muscle was measured in 26 normal human subjects, 7 patients with mild illness, and 21 patients with severe, debilitating medical disorders. A closed transcutaneous approach to the muscle was made by needle puncture and the Em was measured utilizing standard Ling electrodes. Measurements revealed an Em of -88 +/-3.8 mv in healthy subjects and -89 +/-2.1 mv in patients hospitalized for minor medical problems. The mean Em in 21 in-hospital patients, judged to be severely ill clinically from a variety of causes, was -66.3 +/-9.0 mv. Open deltoid muscle biopsies were performed in 7 of the healthy subjects and in 13 of the severely ill group. Estimation of the intra-extracellular water partition was made by calculating the chloride space from the previously measured Em. Analysis of the muscle samples revealed no significant difference in the intra-extracellular potassium ratios of the two groups biopsied. Intracellular Na(+) concentrations were uniformly increased in the muscle samples of the severely ill subjects and averaged 42.3% higher than those of the normal subjects. The mechanisms which might account for the elevation of intracellular Na(+) and a depression of Em independent of changes in intra-extracellular K(+) ratios are discussed and it is suggested that this defect may be a generalized cellular abnormality which is a common quality of serious illnesses.
TL;DR: The results suggest that liver phosphofructokinase is less suited for anaerobic energy production than the skeletal muscle enzyme and may not be subject to the same control mechanism in vivo.
TL;DR: Myoblasts obtained from newborn rat skeletal muscle undergo changes in vitro before fusion into multinucleated fibers, and a change from an inhibitory to a permissive medium results in the onset of very intense cell fusion after a lag period of about 18 h.
TL;DR: It was concluded that denervation produces a genuine reduction in the rate of rise of the action potential in muscle fibre.
Abstract: Redfern, P. and S. Thesleff, Action potential generation in denervated rat skeletal muscle. I. Quantitative aspects. Acta physiol. scand. 1971. 81. 557–564.
Action potential generation was studied at various periods up to one week after denervation in individual muscle fibres of the extensor digitorum longus muscles of the adult rat. To allow a comparison of action potential generation at various stages of denervation, it was necessary to establish adequate conditions for spike generation. It was found that when fibres were locally polarized to a level of -90 to -100 mV, and the external calcium concentrations was increased to 4 mM, the peak rate of rise and the overshoot of the action potential were maximal. Between 30 and 40 hrs following section of the motor nerve, the mean maximal rate of rise of action potentials, recorded under the aforementioned conditions, was reduced by about one third, and remained at about this reduced level during the subsequent days. Two days after denervation the resting membrane potential was reduced from a mean of 82 mV in innervated muscle to a mean of 68 mV, and remained at about this level for the remaining 5 days studied. The electrical time constant and the input resistance of the muscle fibres gradually increased during the 7 days following denervation, the time constant by about 70 % and the input resistance by about 50 %. With anodal polarization in denervated muscle no significant correlation was found between the resting membrane potential and the maximal peak rate of rise of the spike. It was concluded that denervation produces a genuine reduction in the rate of rise of the action potential in muscle fibre.
TL;DR: The variations in changes of contractile behavior in muscles undergoing CH are explained by the varying degree of overlap of the filaments known to be affected by sarcomere length related to lengthening or shortening of the muscle.
TL;DR: The capacity to perform aerobic work is related to the utilization and mobilization of fatty acids from extramuscular sources and the obvious importance of local tissue stores of substrate such as glycogen and triglycerides for the energy metabolism was discussed.
Abstract: Twenty‐four fasting male subjects exercised until exhaustion on a bicycle at a relative workload of about 70% of the workload at heart rate 170 per min. Muscle tissue was obtained by needle biopsy from the lateral femoral muscle before and after exercise.—The average work time was 99 min. The muscle triglyceride concentration decreased during the exercise from 10.4 to 7.8 μmoles per gram and that of glycogen from 10.4 to 3.4 mg per gram. The concentration of phospholipids in the muscle remained unchanged.‐The amount of fatty acids and of glucose which were oxidized during the exercise was calculated from the oxygen uptake and the respiratory quotient and found to be 39 % and 61 % respectively of the caloric output. It was estimated that the muscle triglyceride and plasma free fatty acids (FFA) contributed about 2/3 and 1/3 respectively of the fatty acids oxidized. Similar calculations showed that muscle glycogen covered about 2/3 of the amount of glucose oxidized.—A number of correlation coefficients were calculated between the various parameters studied. There was no correlation between the triglyceride and glycogen content of the muscle. The amount of work performed was correlated to the glycogen (r = 0.60) and to the triglyceride (r = − 0.53) content of the muscle. These two muscle substrates could be used to predict the work performance by multiple linear regression analysis with an error of only 17 % and with a multiple correlation coefficient of 0.774.—The work performance was positively correlated to the amount of fatty acids oxidized but negatively correlated to the decrease in muscle triglycerides which suggests that the capacity to perform aerobic work is related to the utilization and mobilization of fatty acids from extramuscular sources.The obvious importance of local tissue stores of substrate such as glycogen and triglycerides for the energy metabolism was discussed.
TL;DR: Evidence is provided that the processes of post-denervation changes occur in the following temporal sequence: a) partial depolarization of the postsynaptic muscle membrane; b) a decrease and subsequent cessation of the spontaneous transmitter release preceded in some fibres by a transient increase in m.e.p. frequency; c) appearance of extrajunctional ACh sensitivity; d) increase in the transverse resistance of a unit area of the muscle membrane.
Abstract: The first alteration noted after denervation of the extensor digitorum longus muscles of rats was a decrease in resting membrane potential (RMP) which occurred at about 2h. The exact time course of this membrane depolarization was dependent upon the intramuscular length of the degenerating nerve stump. The decrease in RMP occurred prior to any detectable alteration in adenosine triphosphate and phosphocreatine content of the muscle. Prior to failure of spontaneous transmitter release, which occurred 10 h after denervation, some muscle fibres showed an increase in frequency of the miniature end-plate potentials (m.e.p.p.) with no alterations in amplitude and shape of the single potentials. Appearance of areas sensitive to acetylcholine (ACh) on the extra-junctional membrane occurred at 24 h after crushing the motor nerve. At 48 h after denervation a high ACh-sensitivity appeared at the muscle-tendon region, but was not detected in the majority of the muscle fibres studied midway between end-plate region and muscle-tendon area. The transverse resistance of a unit area of the muscle membrane was increased 3 days after denervation. These results provide evidence that the processes of post-denervation changes occur in the following temporal sequence: a) partial depolarization of the postsynaptic muscle membrane; b) a decrease and subsequent cessation of the spontaneous transmitter release preceded in some fibres by a transient increase in m.e.p.p. frequency; c) appearance of extrajunctional ACh sensitivity; d) increase in the transverse resistance of a unit area of the muscle membrane. It is suggested that the motor nerve releases more than one neurotrophic substance.
TL;DR: Cyclic 3',5'-adenosine monophosphate can be measured directly in crude tissue extracts by its stimulation of the rate of phosphorylation of casein catalyzed by skeletal muscle protein kinase.
TL;DR: Tissue culture of neural tumour cells with skeletal muscle provides a model for the early stages of synapse formation, but functional synaptic transmission has not yet been seen.
Abstract: Tissue culture of neural tumour cells with skeletal muscle provides a model for the early stages of synapse formation. Functional synaptic transmission, however, has not yet been seen.
TL;DR: Acute rhabdomyolysis was observed as a new complication of intravenous heroin-adulterant injections in four men, and in one case an unusual picture consistent with tubular aggregates was demonstrated.
Abstract: Acute rhabdomyolysis was observed as a new complication of intravenous heroin-adulterant injections in four men. Clinical features included generalized muscle tenderness, edema, and profound weakness. Myoglobinuria was detected by a specific immunological method which measured levels up to 3.25 mg/ml. Serum myoglobin levels as high as 0.310 mg/ml were found, with serum creatine phosphokinase levels up to 14,000 units. Needle electromyography showed myopathic motor unit potentials in all muscles tested, most marked proximally. Histologic examination demonstrated acute myolysis, and in one case an unusual picture consistent with tubular aggregates. Renal failure occurred in two patients, one of whom survived. Resolution of weakness varied from two to six weeks. The process recurred in one patient following a subsequent heroin injection.
TL;DR: The fatty acid content of the neutral lipids is high in 16:0 + 18:0 and is less unsaturated than that of mitochondria or fragmented sarcoplasmic reticulum, which are very similar.
TL;DR: Cardiac light chains from both bovine and sheep hearts contain the same thiol sequence which is present in the “alkali” light chains of rabbit and sheep skeletal myosin but have two extra thiol sequences (peptides B and C).
Abstract: Differences have been observed in the thiol sequences of light chains from cardiac and skeletal muscle myosins. Cardiac light chains from both bovine and sheep hearts contain the same thiol sequence (peptide A) which is present in the “alkali” light chains of rabbit and sheep skeletal myosin, but have two extra thiol sequences (peptides B and C). Chemical similarities have been demonstrated between myosin light chains from cardiac and slow skeletal muscle.
TL;DR: Observations identify localized mechanical abnormalities during recovery from myocardial ischemia which may be important in the syndrome of acute coronary heart disease.
Abstract: A B S T R A C T The mechanical behavior of isolated cat, rat, and dog ventricular muscle was examined during hypoxia and after reoxygenation. During hypoxia, an early abbreviation of tension duration was followed by a decline in the rate of tension development. After reoxygenation, a marked, early prolongation of tension development and relaxation time was invariably observed with little, if any, increase in peak tension. As recovery progressed, the duration of contraction gradually shortened as tension returned to control levels. This phenomenon was also observed in the intact dog heart after release of a coronary artery ligature. Isometric tension gauges sewn to ischemic portions of the left ventricle demonstrated that after reinstitution of coronary flow, segment tension duration "outlasts" the duration of left ventricular pressure development and is associated with ventricular irritability. Epicardial electrograms showed shortening of the QT interval within the ischemic segment with prolongation of the QT interval after release of the coronary ligature. Prolongation of tension development during recovery from hypoxia was not observed in experiments with rat skeletal muscle. These observations identify localized mechanical abnormalities during recovery from myocardial ischemia which may be important in the syndrome of acute coronary heart disease.
TL;DR: The polymyxin antibiotics are inactivated in vitro by tissues because they are bound to phospholipids of cell membranes, and a method that liberates bound drug in an active form from tissues permitted study of distribution and persistence in vivo.
Abstract: The polymyxin antibiotics are inactivated in vitro by tissues because they are bound to phospholipids of cell membranes. A method that liberates bound drug in an active form from tissues permitted study of distribution and persistence in vivo. Studies using single injections in the rabbit showed that bound drug persists in liver, kidney, brain, heart, muscle, and lung for as long as 72 hr. Accumulation in tissue but not in serum was noted on repeated injection, with persistence for at least five days after seven daily injections. Free polymyxin B was detectable in liver, kidney, muscle, and brain and persisted for many days in muscle and brain. Free colistimethate was detectable in all tissues other than brain and persisted for many days in liver, kidney, and muscle. Colistimethate appears to be incompletely converted in vivo to the parent compound, colistin. These observations may account for differences in toxicity and chemotherapeutic efficacy of polymyxin B and colistimethate.
TL;DR: The present study suggests that there is slow diffusion of myoblast contents (ribosomes and, possibly, other materials) into the myotube when cells destined to fuse are grown in monolayer cultures at the fine structural level.
Abstract: The process of myoblast fusion was observed in embryonic chick skeletal muscle cells grown in monolayer cultures at the fine structural level. At the first step, the sarcolemmas of cells destined to fuse are closely applied to each other. They are linked in some places by fasciae adherentes; in other places, engulfment of small processes of one cell by another is seen. At a somewhat more advanced stage of myogenesis, vesicles and tubules are formed between the adjacent cytoplasms; presumably, the apposed membranes have opened at several points and their edges have fused to each other. Finally, remnants of cell membranes (vesicles and tubules) disappear completely, and the confluent cytoplasm is formed. The cytoplasmic contents of the multinucleated cells are often poorly admixed, giving the cytoplasm a mosaic appearance in which different zones can be designated as arising from separate cells. This observation suggests, however, that there is slow diffusion of myoblast contents (ribosomes and, possibly, other materials) into the myotube. In agreement with the previous works at the light microscopic level, the present study suggests the occurence of fusion between mononucleated cells, between mononucleated cells and multinucleated myotubes, and between nascent multinucleated myotubes.
TL;DR: A mechanism for contraction in skeletal muscle is proposed in which the tension-generating site is located within the core of the thick (myosin) filament, specifically within the trypsin-sensitive hinge region of the myosin rod.
Abstract: A mechanism for contraction in skeletal muscle is proposed in which the tension-generating site is located within the core of the thick (myosin) filament, specifically within the trypsin-sensitive hinge region of the myosin rod. The force-developing mechanism is thought to be the transfer of energy from ATP splitting in the globular head of one molecule directly to the hinge region of an adjoining molecule, resulting in a phase transition from crystalline to amorphous within the hinge segment of the second molecule. Binding of MgATP at the actinmyosin interface is considered to be a release mechanism. The model leads to out-of-phase oscillating movement of the cross bridges.
TL;DR: If the distal stump of peripheral nerve is positioned in the proximity of the mince, motor units are believed to develop within 75 days, and stimuli applied to the nerve should elicit a contraction in the regenerate muscle.
Abstract: MINCED skeletal muscle regenerates with autotransplantation and homotransplantation in the rat1,2, and with heterotrans-plantation in the mouse3. If the distal stump of peripheral nerve is positioned in the proximity of the mince, motor units are believed to develop within 75 days, and stimuli applied to the nerve should elicit a contraction in the regenerate muscle (personal communication from Dr B. M. Carlson).