Search results for "Muscle Contraction"
showing 10 items of 569 documents
Mechanical jumping power in young athletes.
1987
Mechanical jumping power was determined for 286 young male athletes representing six sports events and ranging in calendar and skeletal ages from 8.8 to 17.1 and from 7.8 to 18.1 years, respectively. The subjects performed successive maximal vertical jumps on a contact mat for 30 s. The number of jumps and their cumulative flight time after 15 and 30 s were used for calculations of mechanical power. The jumping performances of the young athletes were found to be reproducible from the age of 10-12 years in respect to the angular displacement of the knee and duration of contact. Absolute mechanical power, as well as power related to body weight, increased with calendar and skeletal ages. Of t…
Effect of isometric strength training of mechanical, electrical, and metabolic aspects of muscle function.
1978
Monozygous twin pairs (two female and four male) were used in a strength training study so that one member of each pair served as training subject (TS) and the other members as nonexercising controls (CS). TS trained four times a week for 12 weeks with maximal isometric knee extensions of the right leg. The parameters studied included muscle strength, endurance time, electromyographic activity, and activities of several key enzymes in nonoxidative and oxidative muscle metabolism. The results disclosed that in addition to a 20% increase in isometric knee extension strength in the trained leg of TS, an average increase of 11% was observed in strength of TS untrained leg. CS did not demonstrat…
Muscle strength in male athletes aged 70-81 years and a population sample.
1991
Muscle strength characteristics of different muscle groups were studied in active male strength-trained (ST, n = 14), speed-trained (SP, n = 16), and endurance-trained (EN, n = 67) athletes aged between 70 and 81 years. A population sample of similar age (n = 42) served as a control group. The isometric forces for hand grip, arm flexion, knee extension, trunk extension, and trunk flexion were higher for the athletes than the controls and higher for the ST than EN group. The SP athletes showed higher values in knee extension and trunk flexion than the EN group. When the isometric muscle forces were related to lean body mass, significant differences still existed between the athletes and cont…
Gastric relaxation induced by apigenin and quercetin: Analysis of the mechanism of action
2009
Abstract Aims Recently, flavonoids have been shown to cause murine gastric relaxation. In the present study we examined the mechanism of action underlying gastric relaxation induced by apigenin and quercetin in isolated mouse stomach. Main methods The mechanical activity from the whole stomach was detected as changes in the endoluminal pressure and the response to increasing concentrations of both flavonoids were tested before and after different pharmacological treatments. Key findings Apigenin and quercetin-induced a concentration-dependent gastric relaxation, apigenin being more potent than quercetin. The responses were unaffected by 2′5′dideoxyadenosine, an inhibitor of adenylate cyclas…
In vitro tracheal hyperresponsiveness to muscarinic receptor stimulation by carbachol in a rat model of bleomycin-induced pulmonary fibrosis
2006
Summary 1 Bleomycin-induced lung injury is widely used as an experimental model to investigate the pathophysiology of pulmonary fibrosis but the alterations in the pharmacological responsiveness of airways isolated from bleomycin-exposed animals has been scarcely investigated. The aim of this study was to examine the in vitro tracheal responses to muscarinic receptor stimulation with carbachol in a rat bleomycin model. 2 Concentration–response curves to carbachol (10 nm to 0.1 mm) were obtained in tracheal rings isolated from Sprague–Dawley rats 14 days after endotracheal bleomycin or saline. The intracellular calcium signal in response to carbachol (10 μm) was measured by epifluorescence m…
Effects of papaverine on human isolated bladder muscle
1990
Papaverine is a non-specific smooth muscle relaxant and is thought to act at a site beyond the receptor sites on the cell membrane. In this study the relaxing properties of papaverine were tested in isolated muscle strips from the human bladder dome. In carbachol-induced contractions papaverine, even in high concentrations of 10(-4) mol/l had virtually no effects on peak tension generation, whereas the fading was accelerated and the steady state tension at 30 min. was reduced by about 54%. In contrast, high potassium-induced contractions were relaxed by papaverine in a concentration-dependent way; a concentration of papaverine of 10(-4) mol/l produced full relaxation. These findings might p…
Tetrodotoxin-dependent effects of menthol on mouse gastric motor function.
2013
Menthol, the main active constituent of peppermint oil, exerts gut spasmolytic effects, although its mechanism of action remains unclear. We investigated the effects of menthol on gastric emptying and spontaneous- or evoked- mechanical activity of whole murine stomach. Gastric emptying was calculated after i.p. administration of menthol (50mg/Kg). Responses induced by menthol on gastric intraluminal pressure and evoked-cholinergic contractions were analyzed in vitro. Menthol decreased the gastric emptying rate. In vitro, menthol (0.3-30 mM) produced a concentration-dependent relaxation of whole stomach, that was significantly reduced by tetrodotoxin or ω-conotoxin GVIA. The gastric relaxant…
Differentiation of calcium antagonists with respect to their effects in normal and skinned taenia caeci preparations
1987
Abstract In taenia preparations, depolarized by a K+-rich medium, Ca2+ caused contraction and cinnarizine (0.4–100 μM), trifluoperazine (2–100 μM) and verapamil (0.02–10 μM) caused concentration-dependent antagonism of Ca2+, displacing the Ca2+ log concentration-effect curve to the right and depressing the maximal response. Equieffective (IC75) antispasmogenic concentrations were selected. The antispasmogenic effects of verapamil were readily offset by removing the drug from the bathing fluid but those of the other drugs were not. The calcium antagonists (antispasmogenic IC75) were then tested for spasmolytic activity in tissues generating tension in response to the EC80 of Ca2+. Verapamil …
Modulation by nitric oxide of spontaneous mechanical activity in rat proximal colon.
1999
Summary 1 In order to examine the role of nitric oxide (NO) in the tonic neural inhibition in rat proximal colon, the effects of Nω-nitro- l-arginine methyl ester (L-NAME) were studied on the spontaneous contractions of circular muscle (monitored as intraluminal pressure changes) and of longitudinal muscle (detected as isometric tension changes). 2 L-NAME (3 × 10−−6–3 × 10−−4 m) caused a concentration-dependent increase in the amplitude of circular contractions, without affecting those of longitudinal muscle. This effect was prevented by l-arginine (1–5 × 10−−3 m), but not d-arginine. 3 In the presence of tetrodotoxin (10−−6 m), which per se induced increase of the pressure waves, L-NAME (1…
Angiotensin II contractile effects in mouse colon: role for pre- and post-junctional AT1A receptors
2013
Aim This study investigates whether a local renin–angiotensin system (RAS) exists in mouse colon and whether angiotensin II (Ang II) may play a role in the regulation of the contractile activity. Methods Isometric recordings were performed in vitro on the longitudinal muscle of mouse proximal and distal colon. Transcripts encoding for RAS components were investigated by RT-PCR. Results Ang II caused, in both preparations, a concentration-dependent contractile effect, antagonized by losartan, AT1 receptor antagonist, but not by PD123319, AT2 receptor antagonist. The combination of losartan plus PD123319 caused no change on the Ang II-induced contraction than losartan alone. Tetrodotoxin, neu…