Mitochondria have a very large capacity to accumulate Ca(2+) during cell stimulation driven by the mitochondrial membrane potential. Under these conditions, [Ca(2+)](M) (mitochondrial [Ca(2+)]) may well reach millimolar levels in a few seconds. Measuring the dynamics of [Ca(2+)](M) during prolonged stimulation has been previously precluded by the high Ca(2+) affinity of the probes available. We...

Maitotoxin (MTX) activates Ca(2+)-permeable nonselective cation channels and causes a dramatic increase in cytosolic free Ca(2+) concentration ([Ca(2+)](i)) in every cell examined to date, but the molecular identity of the channels involved remains unknown. A clue came from studies of a structurally related marine toxin called palytoxin (PTX). PTX binds to the plasmalemmal Na(+)-K(+)-ATPase (NK...

Treatment of sarcoplasmic reticulum vesicles with diethylpyrocarbonate in the presence of a large excess of reagent, at pH 6.2 and at room temperature, reveals both a fast- and a slow-reacting population of protein residues. The loss of the Ca(2+)-ATPase activity is mainly associated with the fast-reacting population being partially sensitive to hydroxylamine. There is also an effect on the Ca(...

The metabolism, flagellar beating, and acrosome reaction of spermatozoa are regulated by ion flux across the plasma membrane. As is true of most cells, swimming sperm maintain intracellular Ca(2+) concentrations at submicromolar levels. Here we describe a K(+)-dependent Na(+)/Ca(2+) exchanger (suNCKX) from sea urchin sperm. The suNCKX is phylogenetically related to other NCKXs, which use high r...

this study was carried out to investigate the effects of 1, 25-dihydroxycholecalciferol (1, 25 (oh)2 d3) and root hydroalcoholic extract of withania somnifera (ws) root on performance, mineral retention, bone mineralisation and mechanical characteristics of broiler chicks. treatments were arranged factorially (2×3×2) consisted of a positive control with adequate ca and a negative control diet (...

Free [Ca ] inside the sarcoplasmic reticulum ([Ca ]SR) is difficult to measure yet critically important in controlling many cellular systems. In cardiac myocytes, [Ca ]SR regulates cardiac contractility. We directly measure [Ca ]SR in intact cardiac myocytes dynamically and quantitatively during beats, with high spatial resolution. Diastolic [Ca ]SR (1 to 1.5 mmol/L) is only partially depleted ...

Genetic alterations in Ca(2+) channel subunits can be used to study the interaction among channel subunits and their roles in channel function. P/Q- and N-type Ca(2+) channels reside at the presynaptic terminal and control the release of neurotransmitter at mammalian central synapses. We used fluorescence imaging techniques to investigate presynaptic Ca(2+) currents and neurotransmitter release...