Search results for "Muscle Contraction"
showing 10 items of 569 documents
Selective inhibition of calcium entry induced by benzylisoquinolines in rat smooth muscle.
1992
Abstract The mechanism of relaxant activity of six benzylisoquinolines was examined in order to determine the minimal structural requirements that enable these compounds to have either a non-specific action like papaverine or an inhibitory activity on calcium entry via potential-operated channels. All the alkaloids tested totally or partially relaxed KCl-depolarized rat uterus and inhibited oxytocin-induced rhythmic contractions. Only glaucine and laudanosine inhibited K+-induced uterine contractions more than oxytocin-induced uterine contractions. In Ca+-free medium, sustained contractions induced by oxytocin or vanadate were relaxed by the alkaloids tested except for glaucine and laudanos…
Effects of dopamine in isolated rat colon strips.
2005
The aim of the present work is to investigate the effects of dopamine on isolated rat colon strips, and whether dopamine receptors are involved in these effects. Experiments on spontaneous motility and under potassium contraction were performed with dopamine and isoprenaline, both in the absence and presence of antagonists (distal colon strips, isotonic recording, Tyrode solution, 31 °C, 1 g of resting tension). At higher concentration (10–4mol/L), dopamine abolished spontaneous motility of the rat colon and this effect was not modified by antagonists. In isolated rat colon strips that were depolarized with potassium, dopamine produced concentration-dependent relaxation, without significant…
Substance P inactivation by transglutaminase in vitro.
1992
Gamma(glutamyl5)spermine derivative of substance P (Spm-SP) was synthesized in vitro in the presence of purified guinea pig liver transglutaminase and Ca2+. The spermine adduct of the neuropeptide was purified by HPLC on a reversed-phase column and characterized by fast atom bombardment mass spectrometry. The biological activities of Spm-SP were tested by assaying, in comparison with substance P, its ability to induce both the contractions of smooth muscle in vitro and the edema formation in vivo. Spm-SP was shown not to elicit contractile responses in the isolated rat stomach strip and duodenum and not to antagonize the spasmogenic effect evoked by the native neuropeptide. Furthermore, Spm…
Effects of intermittent high frequency electrical stimulation on denervated EDL muscle of rabbit.
1990
This study was performed to determine whether electrical stimulation can retard denervation-induced changes. The denervated extensor digitorum longus of the rabbit, a fast-twitch muscle, was stimulated at a rate mimicking its motoneuron firing pattern. The 100-Hz stimulation given intermittently subjected the muscle to a low mean total daily frequency of 1.6 Hz. Four weeks of stimulation resulted in no effect upon the denervated stimulated muscle. This stimulation protocol, therefore, is unable to substitute for the lost neuronal influence of the nerve. The muscle contralateral to the stimulated side showed physiological changes making it unsuitable to serve as a control.
Neuromuscular electrical stimulation: a new therapeutic option for chronic diseases based on contraction-induced myokine secretion
2019
Myokines are peptides known to modulate brain neuroplasticity, adipocyte metabolism, bone mineralization, endothelium repair and cell growth arrest in colon and breast cancer, among other processes. Repeated skeletal muscle contraction induces the production and secretion of myokines, which have a wide range of functions in different tissues and organs. This new role of skeletal muscle as a secretory organ means skeletal muscle contraction could be a key player in the prevention and/or management of chronic disease. However, some individuals are not capable of optimal physical exercise in terms of adequate duration, intensity or muscles involved, and therefore they may be virtually deprived…
Combination of hormone replacement therapy and high physical activity is associated with differences in Achilles tendon size in monozygotic female tw…
2009
Estrogen concentration has been suggested to play a role in tendon abnormalities and injury. In physically active postmenopausal women, hormone replacement therapy (HRT) has been suggested to decrease tendon diameter. We hypothesized that HRT use and physical activity are associated with Achilles tendon size and tissue structure. The study applied cotwin analysis of fourteen 54- to 62-yr-old identical female twin pairs with current discordance for HRT use for an average of 7 yr. Achilles tendon thickness and cross-sectional areas were determined by ultrasonography, and tendon structural organization was analyzed from the images using linear discriminant analysis (LDA). Maximal voluntary and…
Effects of hormone replacement therapy and high-impact physical exercise on skeletal muscle in post-menopausal women: a randomized placebo-controlled…
2001
An age-related decline in muscle performance is a known risk factor for falling, fracture and disability. In women, a clear deterioration is observed from early menopause. The effect of hormone replacement therapy (HRT) in preserving muscle performance is, however, unclear. This trial examined the effects of a 12-month HRT and high-impact physical exercise regimen on skeletal muscle in women in early menopause. A total of 80 women aged 50–57 years were assigned randomly to one of four groups: exercise (Ex), HRT, exercise+HRT (ExHRT) and control (Co). The exercise groups participated in a high-impact training programme. The administration of HRT (oestradiol/noretisterone acetate) or placebo …
Influence of Vascular Load on Plasma Endothelin-1, Cytokines and Catecholamine Levels in Essential Hypertensives
1998
In vitro studies demonstrated a relationship between ET-1 and basic Fibroblast Growth Factor (bFGF), and of bFGF with Platelet Derived Growth Factor (PDGF). The present study was carried out to investigate in vivo the behaviour after vascular stress of circulating ET-1, bFGF and PDGF, and catecholamines, and their relationship. In 12 healthy normotensives (NTs) and 15 essential hypertensives (Ehs) venous blood samples to determine circulating ET-1, bFGF and PDGF, and catecholamine (EPI and NE) levels were drawn before and at the third minute of a handgrip test. Blood pressures (BP) and heart rate were automatically recorded before starting, and at 1, 2, and 3 minutes during the test. The NT…
Perivascular nerve fiber α-synuclein regulates contractility of mouse aorta: A link to autonomic dysfunction in Parkinson's disease
2010
Parkinson's disease and other neurodegenerative disorders associated to changes in alpha-synuclein often result in autonomic dysfunction, most of the time accompanied by abundant expression of this synaptic protein in peripheral autonomic neurons. Given that expression of alpha-synuclein in vascular elements has been previously reported, the present study was undertaken to determine whether alpha-synuclein directly participates in the regulation of vascular responsiveness. We detected by immunohistochemistry perivascular nerve fibers containing alpha-synuclein in the aorta of mice while aortic endothelial cells and muscular fibers themselves did not exhibit detectable levels of this protein…
Kinin receptors in human vascular tissue: their role in atheromatous disease
1997
Using samples of many human blood vessels, obtained at autopsy and specific antibodies directed to peptide sequences of the kinin B1 and B2 receptors, we demonstrate the localisation of these receptors within the human vascular system using standard immunolabelling techniques. In large elastic arteries and veins, kinin receptors are present only in the endothelial cells whereas in all muscular arteries and arterioles, these receptors are present in both the endothelial and smooth muscle cells. The identification of kinin receptors in human blood vessels confirms that kinins may modulate both vascular permeability and contractility. The incidental finding at histology, of patchy atheromatous…