Search results for "Muscle Contraction"

Evidence for extrinsic control of oesophageal primary peristalsis.

1985

AbstractThe role of both peripheral and central mechanism in the control of primary peristalsis was studied in pigeon cervical oesophagus.The results from the transection of oesophageal muscular wall and of extrinsic nerves suggest that :i) primary peristalsis is programmed centrally.ii) extrinsic motor input is carried in glossopharyngeal nerves and distributed separately at each oesophageal level through intramural neurons.iii) intramural neurons do not seem capable of propagating the peristaltic sequence irrespective of the central control.

Differences in cardiorespiratory and neuromuscular responses between voluntary and stimulated contractions of the quadriceps femoris muscle.

2006

The aim of this study was to compare respiratory gas exchange variables and muscle fatigue between equal-intensity (i.e., same force output) electrostimulated and voluntary contractions of the quadriceps muscle (46+/-10% of maximal voluntary force). Twelve healthy men served as volunteers. Oxygen consumption, ventilation and respiratory exchange ratio were recorded during the exercise bouts. Muscle fatigue was quantified as the exercise-induced reduction in maximal voluntary force. The average oxygen consumption (11+/-3 versus 8+/-2 mL min(-1)kg(-1)), ventilation (23+/-4 versus 16+/-2 L min(-1)) and respiratory exchange ratio (0.96+/-0.02 versus 0.85+/-0.01) were significantly higher during…

Hypoxia-induced dysfunction of rat diaphragm

2004

Contains fulltext : 47331.pdf (Publisher’s version ) (Closed access) Oxidants may play a role in hypoxia-induced respiratory muscle dysfunction. In the present study we hypothesized that hypoxia-induced impairment in diaphragm contractility is associated with elevated peroxynitrite generation. In addition, we hypothesized that strenuous contractility of the diaphragm increases peroxynitrite formation. In vitro force-frequency relationship, isotonic fatigability, and nitrotyrosine levels were assessed under hypoxic (Po(2) approximately 6.5 kPa) and hyperoxic (Po(2) approximately 88.2 kPa) control conditions and also in the presence of authentic peroxynitrite (60 min), ebselen (60 min), and t…

Influence of endothelial nitric oxide on neurogenic contraction of human pulmonary arteries.

1995

The present study was designed to investigate the contribution of the endothelium and that of the L-arginine pathway on the contractile responses of isolated human pulmonary arteries to electrical field stimulation (EFS) and noradrenaline. Isometric tension was measured in artery rings obtained from portions of human lung after thoracic surgery for removal of lung carcinoma (18 patients). Electrical field stimulation (EFS) induced frequency-dependent contractions of isolated human pulmonary arteries which were abolished by tetrodotoxin, guanethidine and prazosin (all at 10(-6) M). The increases in tension were of greater magnitude in arteries denuded of endothelium. NG-nitro-L-arginine meth…

Evidence for a negative inotropic effect of obesity in human myocardium?

2009

Objective: The present study was performed as an attempt to analyze the relationship between body weight and human myocardial performance. As overweight is frequently associated with hypertension, stenosis of epimyocardial coronary arteries and other factors that influence myocardial performance, the experimental model of isolated human atrial myocardium was selected. Atrial contractile performance does neither depend on the extent of stenosis of epicardial coronary arteries nor on the degree of hypertension and its secondary pathology. Methods:Rightatrialmusclepreparations(0.5 6 mm)of183patientsundergoingcoronaryarterybypasssurgerywereelectricallystimulatedat optimal length. Active tension…

Direct effect of cigarette smoke on human pulmonary artery tension.

2010

The effect of chronic cigarette smoke on pulmonary artery (PA) tension has been studied extensively; nevertheless, the direct effect of cigarette smoke is poorly understood. We investigated the direct effect of cigarette smoke extract (CSE) on PA tension in non-smokers, smokers, and COPD patients in vitro. PA samples from 35 patients who underwent lung resection were examined by measuring isometric tension in response to increasing serotonin concentrations. CSE dose dependently inhibited the response to serotonin in smokers and COPD patients, and to a lesser extent in non-smokers. CSE-induced relaxation was similarly inhibited by the nonspecific nitric oxide synthase (NOS) inhibitor l-NOARG…

Muscarinic M2 receptors in acetylcholine-isoproterenol functional antagonism in human isolated bronchus

2002

The muscarinic functional antagonism of isoproterenol relaxation and the contribution of muscarinic M2 receptors were examined in human isolated bronchus. In intact tissues, acetylcholine (ACh) precontraction decreased isoproterenol potency and maximal relaxation (−log EC50 shift = −1.49 ± 0.16 and Emax inhibition for 100 μM ACh = 30%) more than the same levels of histamine contraction. The M2receptor-selective antagonist methoctramine (1 μM) reduced this antagonism in ACh- but not histamine-contracted tissues. Similar results were obtained for forskolin-induced relaxation. After selective inactivation of M3 receptors with 4-diphenylacetoxy- N-(2-chloroethyl)piperadine hydrochloric acid (3…

Pharmacological activity of new histamine analogues.

1974

Stretch-shortening cycle: a powerful model to study normal and fatigued muscle.

2000

Stretch-shortening cycle (SSC) in human skeletal muscle gives unique possibilities to study normal and fatigued muscle function. The in vivo force measurement systems, buckle transducer technique and optic fiber technique, have revealed that, as compared to a pure concentric action, a non-fatiguing SSC exercise demonstrates considerable performance enhancement with increased force at a given shortening velocity. Characteristic to this phenomenon is very low EMG-activity in the concentric phase of the cycle, but a very pronounced contribution of the short-latency stretch-reflex component. This reflex contributes significantly to force generation during the transition (stretch-shortening) pha…

Preferential Type II Muscle Fiber Damage From Plyometric Exercise

2012

Context: Plyometric training has been successfully used in different sporting contexts. Studies that investigated the effect of plyometric training on muscle morphology are limited, and results are controversial with regard to which muscle fiber type is mainly affected. Objective: To analyze the skeletal muscle structural and ultrastructural change induced by an acute bout of plyometric exercise to determine which type of muscle fibers is predominantly damaged. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: Eight healthy, untrained individuals (age = 22 ± 1 years, height = 179.2 ± 6.4 cm, weight = 78.9 ± 5.9 kg). Intervention(s): Partici…