Search results for "Muscle Contraction"

Zur Wirkung von Oxytocin auf einen autorhythmischen glatten Gefässmuskel

1972

The influence of oxytocine on the spontaneously contractile portal vein of the rat has been investigated. This octapeptide decreases the active tension and abolished it completely at a concentration of 5×10−7g/ml. The effect is not caused by an adrenergic mechanism but by a direct action on the smooth muscle cell.

Effects ofThymus species extracts on rat duodenum isolated smooth muscle contraction

1989

The diethylether, ethylacetate and butanolic extracts from Thymus webbianus and Thymus leptophyllus were tested for spasmolytic activity. Pre-incubation of the isolated rat duodenum with these extracts for 10 min produced a concentration-dependent inhibition of acetylcholine-induced contractions. This effect was at least ten times greater with the apolar extracts than with the polar extracts.

Histamine inhibits spontaneous activity of the uterus of the progesterone-treated rat

1993

Adrenoceptor-mediated changes of excitation and contraction in isolated heart muscle preparations.

1989

The inotropic effects of sympathetic stimulation on the heart are mainly ascribed to the activation of beta-adrenoceptors. However, several findings suggest that alpha-adrenoceptors also may help mediate the inotropic response to catecholamines under certain conditions. The onset of the positive inotropic effect mediated by beta-adrenoceptors occurs within seconds and is associated with a faster rate of relaxation. Both beta 1- and beta 2-adrenoceptors are stimulatorily coupled to the enzyme adenylate cyclase, thereby leading to the generation of cyclic AMP. Cyclic AMP increases the slow inward calcium current and enhances the uptake of calcium into the sarcoplasmic reticulum. GTP-binding p…

Evidence that ATP or a related purine is an excitatory neurotransmitter in the longitudinal muscle of mouse distal colon

2007

Background and purpose: This study analysed the contribution of the purinergic system to enteric neurotransmission in the longitudinal muscle of mouse distal colon. Experimental approach: Motor responses to exogenous ATP and to nerve stimulation in vitro were assessed as changes in isometric tension. Key results: ATP induced a concentration-dependent contraction, reduced by 4-[[4-formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]-2-pyridinyl]azo]-1,3-benzene disulphonic acid (PPADS), suramin, P2Y purinoreceptor desensitisation with adenosine 5’-O-2-thiodiphosphate (ADPβS), and atropine, but unaffected by P2X purinoceptor desensitisation with α,β-methylene ATP (α,β-meATP) and by 2,2-dimethyl…

Relaxant effects of antidepressants on human isolated mesenteric arteries

1999

Aims The therapeutic action of tricyclic agents may be accompanied by unwanted effects on the cardiovascular system. The evidence for the effects on vascular and nonvascular smooth muscle comes from animal studies. Whether these studies can be extrapolated to human vessels remains to be determined. Therefore, the present study was designed to investigate the influence of amitriptyline, nortriptyline and sertraline on the contractile responses of human isolated mesenteric arteries to electrical field stimulation, noradrenaline and potassium chloride. Methods Arterial segments (lumen diameter 0.8–1.2 mm) were obtained from portions of the human omentum during the course of 41 abdominal operat…

Elektrische Registrierung der Druckanstiegsbeschleunigung und ihre Beziehung zur isometrischen Kontraktion des linken Herzventrikels

1967

Aus der zweimaligen Differentiation der Ventrikeldruckkurve nach der Zeit ergibt sich die Druckanstiegsbeschleunigung. Dieser Parameter wurde mittels RC-Glieder bei der Kontraktion des linken Ventrikels der Katze registriert. Sein Maximum lag in der Phase der isometrischen Kontraktion. Die maximale Druckanstiegsbeschleunigung nahm bei Erhohung der isometrischen Kontraktion starker zu als die maximale Druckanstiegsgeschwindigkeit. Es wird gefolgert, das zwischen der Kraft der isometrischen Kontraktion und der maximalen Druckanstiegsbeschleunigung eine Proportionalitat besteht.

Effect of angular velocity on soleus and medial gastrocnemius H-reflex during maximal concentric and eccentric muscle contraction.

2009

At rest, the H-reflex is lower during lengthening than shortening actions. During passive lengthening, both soleus (SOL) and medial gastrocnemius (MG) H-reflex amplitudes decrease with increasing angular velocity. This study was designed to investigate whether H-reflex amplitude is affected by angular velocity during concentric and eccentric maximal voluntary contraction (MVC). Experiments were performed on nine healthy men. At a constant angular velocity of 60 degrees /s and 20 degrees /s, maximal H-reflex and M-wave potentials were evoked at rest (i.e., H(max) and M(max), respectively) and during concentric and eccentric MVC (i.e., H(sup) and M(sup), respectively). Regardless of the muscl…

Theoretical and experimental behaviour of the muscle viscosity coefficient during maximal concentric actions

1994

The aim of this study was to calculate the theoretical variation of the nonlinear damping factor (B) as a function of the muscle shortening velocity, and then to compare the theoretical values with the experimental data obtained on both the elbow flexor and the ankle extensor muscles. The theoretical variation of the B factor was determined from a muscle model consisting of a contractile component in parallel with a viscous damper both in series with an elastic component, and by using, the characteristic equation of the force velocity curve. In this muscle model, the viscous element modelled the inability of the muscle to generate as big a contracting force (while shortening) as possible un…

Force-, power-, and elasticity-velocity relationships in walking, running, and jumping

1980

Ground reaction forces and mechanical power were investigated when the subjects walked normally, while they were racing or running at four speeds, and when they performed the running long jump take-off. In addition, the apparent spring constants of the support leg in eccentric and concentric phases were investigated at the four running speeds, during the running long jump take-off, and in the triple jump. Six club level track and field athletes, four national level long jumpers, and six national level triple jumpers took part in the study. Cinematographic technique and a mathematical model of hopping (Alexander and Vernon 1975) were employed in the analysis. Force and power values were foun…