Human Skeletal Muscle In Response Research Articles

Angiotensin-converting enzyme genotype affects the response of human skeletal muscle to functional overload

Angiotensin-converting enzyme genotype affects the response of human skeletal muscle to functional overload

The human adult skeletal muscle transcriptional profile reconstructed by a novel computational approach.

By applying a novel software tool, information on 4080 UniGene clusters was retrieved from three adult human skeletal muscle cDNA libraries, which were selected for being neither normalized nor subtracted. Reconstruction of a transcriptional profile of the corresponding tissue was attempted by a computational approach, classifying each transcript according to its level of expression. About 25% of the transcripts accounted for about 80% of the detected transcriptional activity, whereas most genes showed a low level of expression. This in silico transcriptional profile was then compared with data obtained by a SAGE study. A fairly good agreement between the two methods was observed. About 400 genes, highly expressed in skeletal muscle or putatively skeletal muscle-specific, may represent the minimal set of genes needed to determine the tissue specificity. These genes could be used as a convenient reference to monitor major changes in the transcriptional profile of adult human skeletal muscle in response to different physiological or pathological conditions, thus providing a framework for designing DNA microarrays and initiating biological studies.

Exercise Stimulates c-Jun NH2Kinase Activity and c-Jun Transcriptional Activity in Human Skeletal Muscle

Exercise causes selective changes in gene expression leading to alterations in the structure and function of human skeletal muscle. However, little is known about the specific signaling pathways that enable exercise to modulate gene regulatory events. We determined the effects of exercise on c-Jun NH2-terminal kinase (JNK) activity, a signaling molecule involved in the regulation of transcription. Biopsies of vastus lateralis muscle were taken from eight subjects at rest and after 60 min of cycle ergometer exercise. Exercise increased JNK activity in all subjects (5.9 ± 1.8 fold above basal). JNK activation was associated with an increased expression of its downstream nuclear target c-JunmRNA. When two additional subjects were studied using a one-legged exercise protocol, JNK activity increased only in the exercising leg, indicating that exercise-induced JNK signaling represents an intrinsic response of the contracting muscle, rather than a systemic response to exercise. These studies demonstrate that the JNK pathway may serve as a link between contractile activity and transcriptional responses in human skeletal muscle.

Cardiac troponin T isoforms expressed in renal diseased skeletal muscle will not cause false-positive results by the second generation cardiac troponin T assay by Boehringer Mannheim

The purpose of this study was to determine whether the two monoclonal anti-cardiac troponin T (cTnT) antibodies (MAbs) used in the second generation cTnT assay by Boehringer Mannheim (BM, capture Ab, M11.7; detection Ab, M7) would detect cTnT isoforms expressed in human skeletal muscle in response to chronic renal disease (CRD). cTnT expression was examined in skeletal muscle biopsies obtained from 45 CRD patients, as well as nondiseased human heart (n = 3) and skeletal muscle (n = 3). cTnT proteins were resolved by modified 7.5% sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose, and probed with the following anti-cTnT MAbs: M11.7; M7; JS-2, Lakeland Biomedical; and 13-11, Duke University. All four antibodies detected the cTnT isoforms (Ta, Te) expressed in human myocardium. In 20 of 45 skeletal muscle biopsies, MAb M11.7 recognized its epitope in one to three proteins, molecular mass 34-36 kDa, designated Te, Td, and Tc; the strongest signal was that of Te. The same proteins were recognized by MAbs JS-2 and 13-11. The BM M7 antibody did not detect the cTnT isoforms in the molecular mass range of 34-36 kDa. However, MAb M7 did detect a cTnT isoform, molecular mass 39 kDa, in 2 of 45 biopsies. This isoform had an electrophoretic mobility similar to the predominant heart cTnT isoform, Ta. We conclude that cTnT isoforms are expressed in the skeletal muscle of CRD patients. However, given the epitopes recognized by the BM MAbs M7 and M11.7 and the variable presence of these cTnT isoforms in skeletal muscle, the second generation BM cTnT assay will not detect these isoforms if they are released from skeletal muscle into the circulation.

Analytical Performance of the Sanofi Access® Cardiac Troponin-I Procedure

Troponin-I (TnI), a regulatory protein of the thin filaments of striated muscle, is part of the troponin complex (I, T, C) involved in the calcium-sensitive switch that regulates the interaction of actin and myosin in these tissues (1). TnI exists in three isoforms: one for slow-twitch, one for fast-twitch, and one for cardiac muscle. Cardiac TnI (cTnI) is differentiated from the skeletal muscle isoform by a significant difference in amino acid sequence (2). cTnI is not expressed in human fetal skeletal muscle or in adult human skeletal muscle in response to any pathological stimuli but is specific to cardiac muscle. Consequently, an increasing interest has been paid to this protein as a marker of myocardial injury (3)(4). Several different immunoassays have been reported for quantification of cTnI in serum. They use two cTnI-specific monoclonal antibodies, do not show cross-reactivity with skeletal muscle TnI or other cardiac proteins, and are not …

Contraction specific changes in passive torque in human skeletal muscle.

The present investigation examined passive torque and electromyographic response in human skeletal muscle during passive static stretch within 60 s after maximal repetitive eccentric and concentric contractions. Passive torque (Nm) offered by the hamstring muscle group was measured during passive knee extension in a modified dynamometer in 10 subjects. The distal thigh was elevated to 0.52 rad from horizontal and the backrest was positioned at 1.57 rad. The lever arm moved the leg passively at 0.09 rad s-1 from a starting position of 1.48 rad below horizontal to the final position where it remained stationary for 90 s. Gross electrical activity of the human hamstring muscle group was recorded simultaneously. The effect of concentric or eccentric contraction was tested on separate days. Two stretch manoeuvres with a 45 min hiatus were administered on a control and experimental side. The experimental side performed 40 maximal effort repetitive concentric or eccentric hamstring muscle contractions at 1.05 rad s-1 prior to the second stretch. Passive torque during the 90 s stretch declined 30-35% on the experimental and control side in all stretches, P < 0.001, without a significant effect of prior contraction mode. Passive peak and final torques were lower on the experimental side, P < 0.01 after concentric contractions. Passive peak and final torques remained unchanged after eccentric contractions on the experimental side. The low level EMG response of the hamstring muscle during the stretch was unchanged after maximal repetitive concentric or eccentric contractions. These data demonstrate acute contraction specific alteration in passive torque in human skeletal muscle, which cannot be accounted for by EMG activity. Furthermore, the lack of difference on the control side implies that one 90 s stretch has no effect on passive torque of the muscle 45 min later.

Hypertrophic response of human skeletal muscle to strength training in hypoxia and normoxia.

The purpose of this study was to test the hypothesis that work-induced skeletal muscle hypertrophy may be reduced by training in chronic hypobaric hypoxia compared to normoxia. Five healthy males [mean age 34.4 (SEM 2.2) years] performed strength training of the elbow flexors for 1 month, at altitude (A) (5050 m) and with the same absolute loads at sea level (SL), 8 months later. The EF cross-sectional area (CSA), determined at mid-arm by nuclear magnetic resonance imaging, increased by 11.3 (SEM 3.7)% (P < 0.05) at A and 17.7 (SEM 4.5)% (P < 0.05) at SL. Isometric maximal voluntary contraction (MVC) increased by 9.5 (SEM 2.6)% (P < 0.05) at A and 13.6 (SEM 2.4)% (P < 0.05) at SL. The CSA and MVC changes in A were significantly smaller than at SL (P < 0.05). Muscle specific tension did not change in either condition. No changes in muscle plus bone or MVC of the untrained, controlateral arm were observed. Thus, although there was no indication of muscle wasting at A, the hypertrophic response of skeletal muscle when trained in chronic hypoxia seemed to be significantly lower than that produced in normoxia. This effect could have arisen either from a direct depression of protein synthesis and/or hormonal changes provoked by hypoxia.

Factors which influence alterations of phosphates and pH in exercising human skeletal muscle: Measurement error, reproducibility, and effects of fasting, carbohydrate loading, and metabolic acidosis

Previous studies have shown considerable variability in the metabolic response of human skeletal muscle during a standardized exercise protocol. The goal of these studies was to investigate the factors responsible for the broad range of metabolic changes produced by fatiguing exercise. Experiments were performed to quantitate the measurement error of 31P nuclear magnetic resonance spectroscopy of human muscle, the reproducibility of changes within a single subject, and the effects of fasting, carbohydrate loading, and metabolic acidosis. The results show that none of these factors appear to be responsible for the wide variation between subjects. However, the effects of training and genetic factors were not investigated and are likely to be responsible for the substantial variability between subjects.

The effects of benzamil on in vitro contracture responses of human skeletal muscle to halothane

1. 1. Inhibition of sodium-calcium exchange using 100 μM benzamil caused contracture development of in vitro skeletal muscle samples from humans susceptible to malignant hyperthermia, but not of samples from normal individuals. 2. 2. This dose of benzamil increased the contracture response of both types of muscle to halothane. 3. 3. At a concentration of 1 μM, benzamil significantly reduced the contracture response to halothane of muscle from malignant hyperthermia individuals. 4. 4. The implications for the role of sodium-calcium exchange in skeletal muscle calcium homeostasis and the pathophysiology of malignant hyperthermia are discussed.

Mammalian stress response: cell physiology, structure/function of stress proteins, and implications for medicine and disease.

Mammalian stress response: cell physiology, structure/function of stress proteins, and implications for medicine and disease.

Response of human skeletal muscle to the anabolic steroid stanozolol.

Response of human skeletal muscle to the anabolic steroid stanozolol.

Adaptive response of human skeletal muscle to simulated hypergravity condition

The mechanical behaviour of leg extensor muscles of five international-level athletes was evaluated during 13 months training period. Drop jumps, average mechanical power during 15 S continuous jump, and vertical jumps performed with and without extra weights were used to measure explosive power characteristics. The data recorded in vertical jumps was utilized for construction of force-velocity relationship (F-V curve). The athletes did not show improvement in any of the variables studied after 12 months of intensive systematic training programme. It was assumed that the subjects already had reached their upper limit of performance. However, after that the athletes underwent a simulated 3 weeks high-gravity period. The hypergravitational condition was created by wearing a special vest filled with extra loads (11% of BW). The vest was used from morning to evening. No changes in the ordinary training programme were allowed. After the simulated high-gravity conditioning period significant improvement in almost all the variables studied was observed (P less than 0.05-0.001). Vertical jump performance was enhanced from 44.3 to 54.9 cm. The F-V curve remained stable all year but after hypergravity period shifted markedly to the right. The drastic improvement was attributed to be caused by a fast adaptation to the new functional requirements (I.I g). Therefore, once the biological adaptation occurred the mechanical behaviour of the athlete's leg extensor muscle was similar to that which could be experienced in a field at low gravity condition (0.9 g). Adaptive response to the hypergravity conditioning was speculated to occur mainly at neurogenic level and less in myogenic component.

Quantitative estimation of anaerobic and oxidative energy metabolism and contraction characteristics in intact human skeletal muscle in response to electrical stimulation.

A set up for electrical stimulation of the human quadriceps femoris muscle and registration of tension is described. Normal values for the frequency-tension relations and relaxation time are presented. There was no relationship between contraction characteristics and fibre type distribution. Muscle tissue was sampled after electrical stimulation by percutaneous biopsy technique. Phosphocreatine (PCr) decreased during a 75 s isometric contraction from 76 mmol per kg dry muscle down to a mean value of 9 mmol. Lactate increased during the same time period from 5 mmol per kg dry muscle to 100 mmol. At end of contraction there was a rapid resynthesis of PCr with a half time of about 20 s while the lactate content decreased slowly. The relaxation time of the muscle was prolonged from 38 ms, in non-fatigued muscle, to 128 ms after 75 s of isometric contraction. The relaxation time was normalized after the contraction at the same rate as the resynthesis of PCr. It is proposed that the relationship between PCr and lactate of contracting muscle can be used as an index of glycolytic capacity and that the rate of resynthesis of PCr after contraction is a measure of oxidative capacity. Relaxation time measurements alone may be used as a non-invasive estimation of the oxidative capacity.

The Electrical Response of Human Skeletal Muscle to Passive Stretch

A refined technique of electromyography and electronic analysis was utilized to determine the responses of several muscle groups to passive stretch. Distinctive responses were obtained in the soleus and long head of the triceps humeri. In the normal person these had a definite relationship with the phase of the stretch cycle, were about fifty microvolts in amplitude initially, and diminished on repeated stretching. In patients with disease characterized by hyperirritability of the skeletal musculature, the same responses were obtained in the same muscles. However, in these subjects the initial amplitude averaged 100 microvolts and repeated stretching produced a marked increase in amplitude and duration of the discharge. In all subjects the responses were confined to multiple discrete areas within the muscle bulk. The gastrocnemius and the lateral head of the triceps were silent to repeated stretching. A few scattered non-potentiating discharges were found in the anterior tibial muscle of some of the diseased patients. The possible sources of error in the investigation are considered and discussed in relation to the findings. These results correlated well with tentative criteria for the presence of tonic muscle fibers, based on recent indentification of tonic anterior horn cells in the cat. Further investigation in clinical syndromes seems warranted. The activity in the patients with neuromuscular disorders appeared to be analogous to the activity of the tonic motoneurons in decerebrate preparations. The experimental results indicate some duality of function in the skeletal musculature of the human being.

Reflex changes in vasoconstrictor tone in human skeletal muscle in response to stimulation of receptors in a low‐pressure area of the intrathoracic vascular bed

Reflex changes in vasoconstrictor tone in human skeletal muscle in response to stimulation of receptors in a low‐pressure area of the intrathoracic vascular bed

Reflex vasodilatation in human skeletal muscle in response to heating the body

The Journal of PhysiologyVolume 106, Issue 3 p. 271-278 ArticleFree Access Reflex vasodilatation in human skeletal muscle in response to heating the body H. Barcroft, H. BarcroftSearch for more papers by this authorW. McK. Bonnar, W. McK. BonnarSearch for more papers by this authorO. G. Edholm, O. G. EdholmSearch for more papers by this author H. Barcroft, H. BarcroftSearch for more papers by this authorW. McK. Bonnar, W. McK. BonnarSearch for more papers by this authorO. G. Edholm, O. G. EdholmSearch for more papers by this author First published: 31 July 1947 https://doi.org/10.1113/jphysiol.1947.sp004210Citations: 30AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume106, Issue3July 31, 1947Pages 271-278 RelatedInformation