Zinc ions block the intracellular calcium release induced by caffeine in guinea-pig taenia caeci

Zn²⁺ in low concentrations (0.005–0.1 mM) inhibited the transient contractions in response to caffeine (25 mM) in a dose-dependent manner in smooth muscle of intact guinea-pig taenia caeci. At Zn²⁺ concentrations higher than 0.1 mM, caffeine did not elicit any response. After saponin-treatment of the fibres, which leaves the Ca²⁺ storage sites intact, caffeine contraction was completely inhibited by Zn²⁺ at a relatively low concentration (0.03 mM). However, in Triton-X-100-treated fibres, in which the Ca²⁺ release sites are destroyed, the contraction could be induced in the presence of Zn²⁺ by an increase in Ca²⁺. In conclusion, Zn²⁺ can block the intracellular Ca²⁺ release from caffeine-sensitive release sites in taenia caeci.     

The effect of intracellular potassium ions on active sodium efflux in frog sartorius muscle

Zusammenfassung Radioaktive Untersuchungen zeigen. dass intrazelluläre K⁺-Ionen den aktiven Na⁺-Austausch hemmen.     

Changes in transmitter release at frog neuromuscular junction induced by 4-aminopyridine]

4-aminopyridine (4-AP) at micromolar concentrations, increases the end-plate potential amplitude in curarized preparations and the mean quantal content in every preparation tested, but the spontaneous release is not modified by 4-AP. These results can explain the anticurare activity observed in the wole animal or in vitro. 4-AP prolongs the falling phase of the muscle action potential without change in the muscle membrane potential.     

Role of calcium in the histamine release induced by D-galactosamine from rat mast cells

Summary Rat peritoneal mast cells were isolated and purified by differential centrifugation in Ficoll. Cells pooled from three to four rats were suspended at approximately 10⁶ cells/ml in a buffered salt solution and incubated for 1 h at 37°C in 300 l volumes in the absence or presence (9×10^–4 M) of calcium chloride. Addition of D-galactosamine hydrochloride (DGM; 2.8×10^–4 M) caused (in addition to basal release) a mean ±SEM percent histamine release of 15.7±5.2 in the presence of Ca⁺⁺ and 19±4.9 in the absence of Ca⁺⁺ (p>0.05). It is suggested that D-galactosamine does not require extracellular Ca⁺⁺ for the release of histamine from the rat mast cell.A preliminary analysis of these results was presented at the International Symposium on calcium entry blockers and tissue protection, Rome, 15–16 March 1984.     

Role of calcium in the histamine release induced by D-galactosamine from rat mast cells

Rat peritoneal mast cells were isolated and purified by differential centrifugation in Ficoll. Cells pooled from three to four rats were suspended at approximately 10(6) cells/ml in a buffered salt solution and incubated for 1 h at 37 degrees C in 300 microliter volumes in the absence or presence (9 X 10(-4) M) of calcium chloride. Addition of D-galactosamine hydrochloride (DGM; 2.8 X 10(-4)M) caused (in addition to basal release) a mean +/- SEM percent histamine release of 15.7 +/- 5.2 in the presence of Ca++ and 19 +/- 4.9 in the absence of Ca++ (p greater than 0.05). It is suggested that D-galactosamine does not require extracellular Ca++ for the release of histamine from the rat mast cell.     

Fluxes of magnesium and calcium during induced activity of frog sartorius muscle

Resumen La representación del influjo de Ca y de Mg en músculo esquelético en reposo de rana as cualtitativamente differente; sin embargo la magnitud de dicho influjo as inicialmente similar. Estímulo mediante pulsos eléctricos o cafeina aumenta significamente el influjo de Ca pero no el de Mg durante un período de 10 min.     

Inhibition of sodium transport in frog skin by cardiac glycosides of different molecular structure

p 19-OM no- . ; — .     

Endothelium-dependent relaxation induced by sodium fluoride in the rabbit ear artery

Sodium fluoride (NaF) produced concentration-dependent relaxation of isolated rabbit ear artery precontracted with norepinephrine. In contrast, an arterial preparation with the endothelium rubbed off did not relax, but contracted in response to NaF. NaF-induced relaxation was not influenced by indomethacin but was inhibited by methylene blue or NG-monomethyl-L-arginine. The results indicate that NaF relaxes the artery by releasing a so-called EDRF.     

Endothelium-dependent relaxation induced by sodium fluoride in the rabbit ear artery

Summary Sodium fluoride (NaF) produced concentration-dependent relaxation of isolated rabbit ear artery precontracted with norepinephrine. In contrast, an arterial preparation with the endothelium rubbed off did not relax, but contracted in response to NaF. NaF-induced relaxation was not influenced by indomethacin but was inhibited by methylene blue or N^G-monomethyl-L-arginine. The results indicate that NaF relaxes the artery by releasing a so-called EDRF.     

Localization of sodium ions in dog submandibular gland tissue by the use of potassium pyroantimonate

Résumé Des glandes sousmaxillaires de chiens ont été coupées en morceaux et mises dans un fixatif composé de 2% KSB(OH)₆ et soit de 6.25% d'aldéhyde glutarique, soit de 2% d'osmium et préparées pour l'examen au microscope électronique. Quand les tissus sont fixés à l'aldéhyde glutarique, le précipité est principalement extracellulaire. Par contre, avec le fixatif à l'osmium, le précipité est plus diffus et se trouve partout dans la cellule. Cependant, on ne peut pas se fier à cette méthode pour localiser des ions de sodium in vivo.     

Demonstration of increased in vitro autolytic activity in a denervated muscle of frog

Zusammenfassung Es wird gezeigt, dass die erhöhte autolytische Abbaugeschwindigkeit im denervierten Muskel von Bedeutung für den Proteinumsatz ist und immer noch das zentrale Problem der Veränderungen darstellt, die bei Denervierung — hier Durchschneidung des Ischiadicus — auftreten.