Noninnervated cultured chick embryonic heart cells are depolarized by veratridine (10(-5) 10(-6) g/ml) within a few minutes to membrane potentials of -12 +/- 2 mv. Action potentials and beating cease. Before depolarization begins, the repolarizing phase of the action potential is prolonged and leads to a long-lasting depolarizing afterpotential, probably due to a holding open of Na(+) channels....

Thin strips of frog ventricle were isolated and bathed for 15 min in a solution containing 140 mM KCl, 5 mM Na(2)ATP, 3 mM EDTA, and 10 mM Tris buffer at pH 7.0. The muscle was then exposed to contracture solutions containing 140 mM KCl, 5 mM Na(2)ATP, 1 mM MgCl(2), 10 mM Tris, 3 mM EGTA, and CaCl(2) in amounts to produce concentrations of free calcium from 10(-4.8)M to 10(-9)M. The muscles dev...

PURPOSE Crystalloid fluid and vasoactive drugs are used in the early treatment of sepsis. The purpose of the present study was to examine how these drugs alter plasma volume expansion, peripheral edema, and urinary excretion. METHODS Twenty-five anesthetized sheep were made septic by cecal puncture and a short infusion of lipopolysaccharide. After 50 min, a slow infusion of isotonic saline wa...

Changes of 42K efflux (J23K) caused by ouabain and/or furosemide were measured in isolated epithelia of frog skin. From the kinetics of 42K influx (J32K) studied first over 8-9 h, K+ appeared to be distributed into readily and poorly exchangeable cellular pools of K+. The readily exchangeable pool of K+ was increased by amiloride and decreased by ouabain and/or K+-free extracellular Ringer solu...

Neurotransmitters can modulate the release of other neurotransmitters from presynaptic nerve terminals, as has been described for "presynaptic inhibition" in the spinal cord (Eccles, 1964). Catecholamine and 5-hydroxytryptamine can alter the release of acetylcholine (ACh) from pre ganglionic nerve terminals in sympathetic ganglia (Christ and Nishi, 1971; Kuba et al. 1981; Hirai and Koketsu, 198...

The effect of zinc was studied on isolated frog gastrocnemius muscle wich stimulated directly or indirectly and perfused with Ringer containing calcium(Ca2+) deplated Ca2 +. N.ischiadicus-gastrocnemius muscles were obtained from 15 frogs. Isometric force generated in response to supramaximal electrical stimulation measured a transducer peak tension(Pt), contraction time(CT) total time(TCT) anal...

sylvania School of Medicine, Philadelphia. Reprint requests: Dr. Morad, Department of Physlology/G4, University of Pennsylvania, Philadelphia 19104 FIGUBE 1. Effect of increased calcium on overshoot of action potential in frog ventricle. Two photographically superimposed records obtained in presence of 0.2 and 3 mM Ca Ringer, respectively. From Niedergerke and Orkand.2 Calcium and Cardiac Elect...