To study the mechanism of granule centralization in platelets, we permeabilized with saponin in either EGTA (5 mM) or calcium (1 or 10 microM). Under all conditions, platelets retained 40-50% of their total actin and greater than 70% of their actin-binding protein (ABP) but lost greater than 80% of talin and myosin to the supernatant. Thin sections of platelets permeabilized in EGTA showed a mi...

When starved wild-type amoebae of Dictyostelium discoideum were washed and incubated in 1 mM-EGTA, their ability to induce soluble cyclic AMP phosphodiesterase (PD) activity in response to either millimolar cyclic AMP or a series of nanomolar cyclic AMP pulses was reduced by 55-75%. Supplementation of EGTA-treated cells with exogenous Ca2+ stimulated PD induction in a dose-dependent fashion (EC...

Simultaneous measurements of electrical activity and light absorbance have been made on nerve cell bodies from Archidoris monteryensis injected with indicator dyes. pH indicators, phenol red and bromocresol purple, and arsenazo III, which under normal conditions is primarily a calcium indicator have been employed. Voltage clamp pulses which induced calcium influx caused an absorbance decrease o...

Seven strains of normal human cells (fibroblastic, skin epithelioid, and amniotic) ceased to proliferate in medium depleted of free calcium ion by titration with ethylenebis(oxyethylenenitrilo)tetraacetic acid (EGTA), whereas the growth of 9 of 10 human melanoma cell lines was not affected. Fibroblasts showed a rapid drop in thymidine pool size and decreased incorporation of thymidine and uridi...

Using immunocytochemistry and Northern blot analysis, we investigated the role of cell morphology and reorganization of the cytoskeleton in the expression of transforming growth factor-beta 1 (TGF-beta 1) in human dermal fibroblasts. Disruption of the cytoskeleton was induced by three different agents--trypsin, ethyl-eneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), or cyt...

Removal of Ca(2+) from tobacco suspension cell medium has two immediate effects on cytosolic Ca(2+) fluxes: (i) externally derived Ca(2+) influx (occurring in response to cold shock or hypo-osmotic shock) is inhibited, and (ii) organellar Ca(2+) release (induced by a fungally derived defense elicitor, caffeine, or hypo-osmotic shock) is elevated. We show here that the enhanced release of intern...

1. We have investigated the prediction of a relationship between the magnitude of activity-dependent increases in postsynaptic calcium and both the magnitude and direction of synaptic plastic change in the central nervous system. 2. Activity-dependent increases in calcium were buffered to differing degrees using a range of concentrations of EGTA and the effects on synaptic plasticity were asses...