Search results for " Muscle"

Die Wirkung von Theophyllin, Coffein und Theobromin auf Kontraktionskraft, Erregbarkeit, Refrakt�rzeit und Spontanfrequenz des isolierten Herzmuskels…

1956

In the electrically driven papillary muscle of the cat's right ventricle theophylline, caffeine and theobromine exerted a positive inotropic action. Log. dose-effect regression lines for the three drugs were parallel; the effect of theophylline was significantly greater than those of caffeine and theobromine. The range of concentrations used was 1/32–1/2 mM/1.

�ber den Mechanismus der positiv inotropen Wirkung von Theophyllin am Warmbl�terherzen

1971

In order to further elucidate the mechanism of the positive inotropiceffect of theophylline (T) in mammalian cardiac muscle, the influence of T on contractile force, extracellular space,45Ca uptake,45Ca release, and total myocardial calcium concentration was investigated in isolated, electrically driven (frequency 170 beats/min) or quiescent left guinea-pig atria. The investigations were performed in Tyrode solution containing 0.45 mM CaCl2. T concentration was 5×10−4 g/ml. Under these conditions, T exerted maximal positive inotropic but no toxic effects, that is, it did not cause contractures or arrythmias within 60 min (Fig. 1). The experiments provide evidence that T increases the rate o…

Die Reversibilität der Wirkung von Digitoxin, Strophanthidin und Strophanthidin-3-bromazetat am Papillarmuskel und einer mikrosomalen Na+-K+-aktivier…

1969

The reversibility of the inhibitory action of strophanthidin, strophanthidin-3-bromoacetate, and digitoxin on the Na+-K+-ATPase activity (microsomal fraction, guinea-pig brain) was compared with the rate of decline of their positive inotropic effects (papillary muscle, guinea-pig heart) after exposure to drug-free solution. The actions of strophanthidin and digitoxin were easily reduced on both systems. Strophanthidin-3-bromoacetate, however, was found to have an irreversible blocking effect on the transport ATPase, whereas its inotropic action could be rapidly abolished.

Barnidipine block of L-type Ca2+ channel currents in rat ventricular cardiomyocytes

2000

The effects of barnidipine and nifedipine on L-type Ca2+ current (ICa(L)) were investigated in ventricular cardiomyocytes from rats. Both barnidipine and nifedipine reduced ICa(L) in a concentration and voltage dependent manner; the EC50 were 80 and 130 nM at a holding potential of −80 mV, respectively, and 18 and 6 nM at −40 mV, respectively. Both drugs induced a leftward shift of the steady-state inactivation curve of ICa(L). Using a twin pulse protocol, the relationships between the amount of block of ICa(L) by either drug, seen during the second pulse, and the length of the first pulse were described by monoexponential functions reflecting onset of block, dependent on drug concentration…

Die α-Glycerophosphat-Oxydation des Heuschreckenbrustmuskels (Locusta migratoria)

1956

The conditions were studied for the glycerophosphate oxidation by homogenate from locust flight muscle, and the O2-consumption was measured. Maximal oxidation rates were found with 0.087m glycerophosphate, 8 × 10−6m cytochromec, 7 × 10−6m DPN and pH 7.5. The production of dihydroxyacetone phosphate is followed by further oxidation steps, as could be shown by estimation of the different fractions of acid-soluble phosphate. Comparative studies were made on different insects and vertebrates. The rate of succinate oxidation by insect muscle was found to be ten times higher than that of vertebrate muscle. The relation of glycerophosphate oxidation to succinate oxidation is quite different in ins…

Extracellular ATP Increases <i>L</i>-Carnitine Transport and Content in C2C12 Cells

2008

Extracellular ATP regulates cell proliferation, muscle contraction and myoblast differentiation. ATP present in the muscle interstitium can be released from contracting skeletal muscle cells. <i>L</i>-Carnitine is a key element in muscle cell metabolism, as it serves as a carrier for fatty acid through mitochondrial membranes, controlling oxidation and energy production. Treatment of C2C12 cells with 1 mmol/l of ATP induced a marked increase in <i>L</i>-carnitine uptake that was associated with an increase in <i>L</i>-carnitine content in these cells. These effects were found to be dependent on the density of the cultured cells and on the dose of ATP. The…

Beneficial effects of l-carnitine in myoblastic C2C12 cells

2003

L-Carnitine is a key molecule in the transfer of fatty acid across mitochondrial membranes. Bioavailable L-carnitine is either provided by an endogeneous biosynthesis or after intestinal absorption of dietary items containing L-carnitine. After intestinal absorption or hepatic biosynthesis, L-carnitine is transferred to organs whose metabolism is dependent upon fatty acid oxidation, such as skeletal muscle. To cross the muscle plasma membrane, there are several transporters involved. Among those transporters, OCTN2 is actually the only one to have been clearly characterized. Zidovudine is a commonly used inhibitor of human immunodeficiency virus (HIV) replication. Zidovudine has many side e…

P1 and P2 receptors in the rat duodenal smooth muscle

1989

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.

Kinetische Analyse der Calcium-Kompartimente im Meerschweinchenherzen unter Kontrollbedingungen und Strophanthineinwirkung

1974

A quantitative analysis of myocardial Ca-metabolism was carried out on isolated, isovolumetric (10 ml/min) perfused guinea pig hearts by combined determinations of the total Ca-content and kinetics of 45Ca-efflux (collecting period 60 min) (Fig. 1). The kinetics of 45Ca-uptake was estimated by extrapolating 45Ca-efflux curves of heart muscles isotopically loaded for different times (2, 5, 10, 30 60 min) to the end of the loading-period (Fig. 2).