Search results for "Muscle Contraction"

Postmenopausal hormone replacement therapy modifies skeletal muscle composition and function: a study with monozygotic twin pairs

2009

We investigated whether long-term hormone replacement therapy (HRT) is associated with mobility and lower limb muscle performance and composition in postmenopausal women. Fifteen 54- to 62-yr-old monozygotic female twin pairs discordant for HRT were recruited from the Finnish Twin Cohort. Habitual (HWS) and maximal (MWS) walking speeds over 10 m, thigh muscle composition, lower body muscle power assessed as vertical jumping height, and maximal isometric hand grip and knee extension strengths were measured. Intrapair differences (IPD%) with 95% confidence intervals (CI) were calculated. The mean duration of HRT use was 6.9 ± 4.1 yr. MWS was on average 7% (0.9 to 13.1%, P = 0.019) and muscle…

The effects of metoclopramide on acetylcholine release and on smooth muscle response in the isolated guinea-pig ileum

1982

The effects of metoclopramide on smooth muscle contraction and on release of acetylcholine were studied in the guinea-pig myenteric plexus longitudinal muscle preparation. Acetylcholine was determined either as endogenous acetylcholine, or as labelled transmitter from strips preloaded with 3H-choline. Metoclopramide caused an increase in resting tension of longitudinal muscle as well as an increase in resting output of either endogenous or labelled acetylcholine. Tetrodotoxin abolished the metoclopramide-evoked increase in transmitter release. The increase in smooth muscle tension was clearly related to the increase in resting output. The effects of metoclopramide on both longitudinal muscl…

2020

Even though the acute effects of pre-exercise static stretching and dynamic muscle activity on muscular and functional performance have been largely investigated, their effects on the corticospinal pathway are still unclear. For that reason, this study examined the acute effects of 5×20 s of static stretching, dynamic muscle activity and a control condition on spinal excitability, corticospinal excitability and plantar flexor neuromuscular properties. Fifteen volunteers were randomly tested on separate days. Transcranial magnetic stimulation was applied to investigate corticospinal excitability by recording the amplitude of the motor-evoked potential (MEP) and the duration of the cortical s…

Tetrandrine and Isotetrandrine, Two Bisbenzyltetrahydroisoquinoline Alkaloids from Menispermaceae, with Rat Uterine Smooth Muscle Relaxant Activity

1992

Abstract The effects of two bisbenzyltetrahydroisoquinoline alkaloids, 1S, 1′S tetrandrine and its isomer 1R, 1′S isotetrandrine, were investigated in rat isolated uterus in order to identify the mechanism of relaxant action and to study the influence of the absolute configuration on the activity of these alkaloids. Both inhibited the uterine contraction induced by high K+, acetylcholine and oxytocin. In Ca2+-free medium, isotetrandrine relaxed the sustained contraction induced by oxytocin but tetrandrine did not. The relaxant effects of the alkaloids may be due to blockade of calcium influx through specific channels. Tetrandrine and isotetrandrine modify the calcium channel in a nonreversi…

α-Adrenoceptor Interaction of Tetrandrine and Isotetrandrine in the Rat: Functional and Binding Assays

1998

Abstract The action of 1S,1′S-tetrandrine, a bisbenzyltetrahydroisoquinoline alkaloid, on α1-adrenoceptors has been compared with that of its isomer 1R,1′S-isotetrandrine. The work includes binding assays to analyse the affinity of these products for the [3H]prazosin binding site of rat cerebral cortical membranes and functional studies on rat isolated aorta to examine the effects of both alkaloids on intracellular calcium processes related or not to α-adrenoceptor activation. A radioligand receptor-binding study showed that both compounds interacted with the α1-adrenoceptors displacing [3H]prazosin from the specific binding site. The Ki values (inhibition constants) were 0.69±0.12 and 1.6±…

Inhibitory influence of chromogranin A N-terminal fragment (vasostatin-1) on the spontaneous contractions of rat proximal colon

2005

Very little is known about the role played by CGA and its fragments in the gastrointestinal physiology. We have studied the role of CGA N-terminal fragments in the regulation of intestinal smooth muscle contractility by measuring the influence of recombinant CGA 1-78 (VS-1) and synthetic CGA 7-57 peptides on the spontaneous mechanical activity of rat proximal colon in vitro. The mechanical activity was recorded as changes in the intraluminal pressure. VS-1 (0.1-30 nM) and CGA 7-57 (10-300 nM) produced concentration-dependent inhibitory effects, characterized by a progressive decrease in the mean amplitude of circular muscle spontaneous contractions, without affecting the resting tone. The r…

Training the Vertical Jump to Head the Ball in Soccer

2012

R esearchers involved in the training methodology to improve jump ability proposed a variety of techniques and exercise modalities (22,15,4). Nevertheless, the question on what percentage of training should be dedicated to strength and what to power seems unresolved. First of all, to better understand the matter, we have to stress the difference between strength and power. Generally speaking, in athletics, the rate of force development (RFD) is much more important than strength alone; the average RFD (mRFD) can be estimated as the ratio Fmax/Tmax, where Tmax is the time to reach the peak force, whereas Fmax is the maximum force. This ratio is also named explosive strength, commonly computed…

Vitamin and Mineral Supplementation and Neuromuscular Recovery after a Running Race

2006

International audience; Purpose: This double-blind study investigated the effects of vitamin and mineral complex supplementation on the neuromuscular function of the knee-extensor muscles after a prolonged trail running race. Methods: Twenty-two well-trained endurance runners took either placebo (Pl group) or vitamins and minerals (Vm group) for 21 d before the race and for 2 d after the race. Maximal voluntary contractions (MVC) and surface EMG activity of the vastus lateralis (VL) muscle were recorded before (pre) and 1 h (post), 24 h (post 24) and 48 h (post 48) after the race. Central activation ratio (CAR), neural (M-wave), and contractile (muscular twitch) properties of the quadriceps…

Effects of a vitamin D3 analogue in a rat model of bladder outlet obstruction

2006

OBJECTIVES To explore the effect of the vitamin D3 analogue, BXL-628, on some of the consequences of bladder outlet obstruction (BOO), e.g. hypertrophy and loss of contractile function, as vitamin D3 and BXL-628 inhibit prostate and bladder cell growth in vitro, and there are receptors for vitamin D in rat and human bladder. MATERIAL AND METHODS In female rats, BOO was produced by a standardized method; one group received daily BXL-628 (150 µg/kg per day) and the remaining rats received vehicle. Sham-operated rats received BXL-628 or vehicle. After 2 weeks, the conscious rats were assessed by cystometry. Plasma calcium levels were determined and in vitro contractility assessed at the end of…

Terminal tendon cell differentiation requires the glide/gcm complex.

2004

International audience; Locomotion relies on stable attachment of muscle fibres to their target sites, a process that allows for muscle contraction to generate movement. Here, we show that glide/gcm and glide2/gcm2, the fly glial cell determinants, are expressed in a subpopulation of embryonic tendon cells and required for their terminal differentiation. By using loss-of-function approaches, we show that in the absence of both genes, muscle attachment to tendon cells is altered, even though the molecular cascade induced by stripe, the tendon cell determinant, is normal. Moreover, we show that glide/gcm activates a new tendon cell gene independently of stripe. Finally, we show that segment p…