Jan H. Ravesloot

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The sinoatrial node initiates the heartbeat and controls the rate and rhythm of contraction, thus serving as the pacemaker of the heart. Despite the crucial role of the sinoatrial node in heart function, the mechanisms that underlie its specification and formation are not known. Tbx3, a transcriptional repressor required for development of vertebrates, is(More)
Primary cultures of embryonic chick osteoblasts consist of a heterogeneous cell population. Patch clamp measurements were done on 1- to 5-day-old osteoblasts, osteocytes, fibroblastlike cells, and cells that could not be classified on morphologic criteria. The measurements showed the omnipresence of depolarization-activated high-conductance channels in(More)
The Ca(2+)-activated Cl(-) current (I(Cl(Ca))) has been identified in atrial, Purkinje and ventricular cells, where it plays a substantial role in phase-1 repolarization and delayed after-depolarizations. In sinoatrial (SA) node cells, however, the presence and functional role of I(Cl(Ca)) is unknown. In the present study we address this issue using(More)
Patch-clamp measurements on freshly isolated embryonic chicken osteoclasts revealed three distinct types of voltage-dependent K+ conductance. The first type of conductance, present in 72% of the cells, activated at membrane potentials less negative than -30 to -20 mV and reached full activation at +40 mV. It activated with a delay, reached a peak value, and(More)
OBJECTIVES The proarrhythmic early afterdepolarizations (EADs) during phase-2 of the cardiac action potential (phase-2 EADs) are associated with secondary Ca2+-release of the sarcoplasmic reticulum. This makes it probable that the Ca2+-activated Cl- current [ICl(Ca)] is present during phase-2 EADs. Activation of ICl(Ca) during phase-2 of the action(More)
BACKGROUND In animal models of heart failure (HF), heart rate decreases as the result of an increase in intrinsic cycle length of the sinoatrial node (SAN). In this study, we evaluate the HF-induced remodeling of membrane potentials and currents in SAN cells. METHODS AND RESULTS SAN cells were isolated from control rabbits and rabbits with volume and(More)
OBJECTIVE Various cationic membrane channels contribute to the heterogeneity of action potential configuration between the transmural layers of the left ventricle. The role of anionic membrane channels is less intensively studied. We investigated the role of the Ca2+-activated Cl- current, ICl(Ca), in transmural electrical heterogeneity. METHODS AND(More)
Patch-clamp measurements done on excised membrane patches obtained from 1-5 day cultured embryonic chick osteoblasts, osteocytes, and periosteal fibroblasts revealed the existence of a high-conductance anion channel: 371 +/- 63 pS when measured under symmetrical 158 mM Cl- conditions. The channel frequently displayed subconductance levels. The ion(More)
The suprachiasmatic nucleus (SCN) is a major pacemaker for circadian rhythms in mammals. Photic entrainment of the circadian pacemaker is mediated by the retinohypothalamic tract (RHT). Most likely, excitatory amino acids function as neurotransmitters in this pathway. We have now investigated the effect of glutamate on the membrane potential of cultured SCN(More)
Calcium-activated potassium channels were found in embryonic chick osteoclasts using the patch-clamp technique. The activity of the channel was increased by both membrane depolarisation and an increase in intracellular Ca2+ concentration in the range 10(-5) to 10(-3) M. In the cell-attached-patch configuration the channel was only active at extreme(More)