Carlos A Ojeda

Learn More
Voltage clamp experiments on isolated sheep Purkinje fibres showed an increase of the steady state outward membrane current, over the potential range −65 mV to −15 mV, in the presence of tetrodotoxin (TTX, 3 · 10−5 M). This “window” current is considered to be the steady state component of the fast sodium current (I Na), resulting from the crossover of the(More)
1. Properties of the 'pace-maker' current if in rabbit sino-atrial node have been investigated by voltage clamp of small preparations and compared with those of the iK2 current in the Purkinje fibre. Besides having a similar voltage range of activation and responding in a similar way to adrenaline, if resembles iK2 in other respects. 2. When external Na is(More)
The effects of organic and inorganic calcium antagonists on washed platelets from rat and human have been studied. Platelet aggregation was assessed by turbidimetry. Endogenous serotonin release was measured on the same sample by means of electrochemically treated carbon fiber electrodes. The organic calcium antagonist, nitrendipine, and the inorganic(More)
1. In sheep Purkinje fibre preparations, salicylate ions produce reversible changes in resting potential and in action potential duration. In most preparations these effects resemble those produced by -ow extracellular K concentration: the resting potential first increases and then decreases, the action potential is prolonged and eventually, low potential(More)
Washed rat platelets aggregation and endogenous serotonin release were studied after thrombin stimulation in the presence of different concentrations of Ca2+, Sr2+ or Ba2+. The extent of platelet aggregation and release was found to depend upon the external concentration of these cations. For all of them, an optimum concentration could be defined. Higher(More)
The presence of an Na/Ca exchange system in fasciculata cells of the bovine adrenal gland was tested using isolated plasmalemmal vesicles. In the presence of an outwardly Na(+) gradient, Ca(2+) uptake was about 2-fold higher than in K(+) condition. Li(+) did not substitute for Na(+) and 5 mM Ni(2+) inhibited Ca(2+) uptake. Ca(2+) efflux from Ca(2+)-loaded(More)
1. The outward currents underlying delayed rectification have been studied in frog auricular trabeculae with the double sucrose gap method.2. The results obtained in our experimental conditions allow us to discard the hypothesis of an accumulation of ions during the flow of the outward current.3. In most of the cases the delayed current is composed of two(More)
Voltage-activated Ca2+ currents, in zona fasciculata cells isolated from calf adrenal gland, were characterized using perforated patch-clamp recording. In control solution (Ca2+: 2.5 mm) a transient inward current was followed, in 40% of the cells, by a sustained one. In 20 mm Ba2+, 61% of the cells displayed an inward current, which consisted of transient(More)
1. In frog atrium, Cs ions block both the inward rectifieri K1 and the carbachol induced K currenti Cch. 2. Bothi K1 andi Cch display a high affinity for Cs with a K0.5 of 4×10−5 M fori k1 and of 8×10−5 M fori Cch atV=−50 mV. 3. Block of bothi K1 andi Cch is strongly voltage dependent. When fitted by the block model of Woodhull (1973), δ is >1 for the two(More)
K+ accumulation-depletion (AD) phenomena were found in single guinea pig ventricular myocytes using the patch-clamp method in whole cell configuration. We suggest that the cardiomyocyte transverse-axial tubular system (TATS) lumen is the restricted extracellular space where the K+ AD could take place. A three-dimensional (3D) reconstruction of the TATS in a(More)