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Electrocardiograms were recorded in 13 mice, from birth up to 57 days of age; during this period the heart rate, at rest, showed a marked increase (from 310 to 797 beats/min), occurring in two waves. Recordings of the intracellular electrical activity in the atria disclosed a different temperature dependence of the resting membrane potential, action(More)
Isometric twitches and intra- and extracellular electrical activity were recorded at various driving rates from lizard ventricles, either in the normal inotropic state, or in a hypodynamic state induced by perfusing at a high flow rate for a long time. Electron micrographs were obtained from hearts fixed immediately after dissection and from preparations(More)
The analysis of the staircases in lizard ventricle, that was the object of the preceding paper, has been extended to the hypodynamic condition, induced by the prolonged perfusion of the ventricular preparation at high flow rate. For comparison, the effects of lowered [Ca]0 on the normal ventricle as well as of raised [Ca]0 on the hypodynamic ventricle have(More)
The effect exerted by different doses (50 to 500 mg/kg body weight, or 1 or perfusing solution) of the lyophilised secretion of B. gabonica venom glands has been studied -by intracellular electrodes- on the electrical activity of atrial and ventricular cells from guinea-pigs hearts, by using both open-chested animals and isolated preparations. Noticeable(More)
Lizard ventricles induced to hypodynamia by the high flow rate of the perfusing solution were submitted either to brief periods of cooling (from 20 to 25 degrees C), or to a prolonged hypothermic incubation (35 h at 4 degrees C) followed by a recovery at room (20 degrees C) or reduced (15 degrees C) temperature. Isometric rested state contractions as well(More)