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Query: CAS:7440-70-2 (calcium)
 333,191 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In contrast to most systems in which oocyte activation is triggered by the fertilizing sperm, Sicyonia ingentis oocytes are activated by seawater Mg2+ during spawning. S. ingentis oocytes were spawned into Mg(2+)-free seawater and microinjected with the fluorescent Ca2+ indicator Fluo-3 to study the effects of added Mg2+ on intracellular Ca2+ levels. The Mg2+ induced a wave of fluorescence across the oocyte that traveled at a speed of 13 +/- 3 microns/sec. Extracellular Ca2+ was not required for induction of the wave. Treatment with Ca2+ ionophore in Mg(2+)-free medium or a localized injection (0.3% oocyte volume) of 3-5 microM Ca2+ also initiated the wave; injection of 250 mM Mg2+ (up to 1.5% oocyte volume) had no effect. Microinjection of 750 microM EGTA (final) suppressed the Mg(2+)-induced wave, while an identical concentration of EDTA had no inhibitory effect. Subsequent to the initial Mg(2+)-induced intracellular Ca2+ increase, a second Ca2+ increase was observed at approximately 15 min postspawning; the timing of this second increase appeared to be independent of when the Mg(2+)-induced wave was initiated, thus an event associated with spawning may be involved. While oocytes in normal seawater were monospermic, those in Mg(2+)-free seawater were polyspermic, suggesting a role for the Mg(2+)-induced Ca2+ wave in regulating sperm entry into the oocyte.
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PMID:Extracellular Mg2+ induces an intracellular Ca2+ wave during oocyte activation in the marine shrimp Sicyonia ingentis. 162 59

The effects of acute (3 h) and chronic (30 h) in vivo infusions of Escherichia coli endotoxin on the Ca2+ homeostasis of rat spleen cells was investigated. Conditions were established for obtaining reliable estimates of [Ca2+]i in these cells using the newly-developed Ca2+ indicator Fluo-3. The resting [Ca2+]i of splenocytes and T lymphocyte-enriched preparations were 119 +/- 35 and 102 +/- 31 nM, respectively. Treatment of the cells with concanavalin A (Con A) resulted in a rapid increase in [Ca2+]i. The magnitude of the increase was positively correlated with the concentration of Con A, whereas the time required to reach the maximum [Ca2+]i was inversely related to the amount of Con A. The peak [Ca2+]i was attained more rapidly in splenocytes (i.e. less than or equal to 30 s) than in the T cell-enriched fraction (i.e. 1.5-2.0 min). Both the resting [Ca2+]i and the Con A-induced increase in [Ca2+]i were similar to values previously reported for other lymphocyte cell types using different Ca2+ indicators, thereby supporting the values obtained with Fluo-3. Infusions of saline or endotoxin prior to the isolation of the cells did not result in significant alterations of either resting [Ca2+]i or the cells' response to Con A. Since chronic infusions of endotoxin have previously been shown to cause a reduction in blastogenic responsiveness of splenocytes to Con A, these data suggest that the endotoxin-induced lesion occurs distal to the mobilization of intracellular Ca2+.
Cell Calcium 1992 Feb
PMID:The effect of endotoxemia on concanavalin A induced alterations in cytoplasmic free calcium in rat spleen cells as determined with Fluo-3. 163 10

Ca2+ agonists induce Ca2+ waves and other non-uniform Ca2+ patterns in the cytosol of epithelial cells. To define subcellular Ca2+ transients in the cytosol of hepatocytes we examined Fluo-3-loaded isolated rat hepatocyte couplets using confocal microscopy. Optical sections of less than 1 micron in thickness were observed in couplets, and fluorescence from cytosolic Ca2+ signals was readily distinguished from nuclear, mitochondrial, and lysosomal fluorescence. The nature of the noncytosolic components of the fluorescent images was verified by double labelling with the mitochondrial dye DiOC6(3) and with the lysosomal marker acridine orange. Using the line scanning mode of confocal microscopy, measurements of cytosolic Ca2+ were made with a frequency of up to 250 Hz and without significant bleaching. It was found that phenylephrine-induced Ca2+ signals generally began at the basal pole of the hepatocytes, then spread to the canaliculus at average speeds of 80 micron/s. These findings demonstrate the utility of confocal line scanning microscopy for detecting rapid changes in the subcellular distribution of cytosolic Ca2+ in hepatocyte couplets, and suggest that phenylephrine-induced Ca2+ waves radiate in a basal-to-apical direction in this cell type.
Cell Calcium 1992 Feb
PMID:Subcellular distribution of cytosolic Ca2+ in isolated rat hepatocyte couplets: evaluation using confocal microscopy. 163 11

A possible role for the PI-linked CD14 molecule in human monocyte and granulocyte signal mediation was investigated. Using flow cytometry and the fluorescent indicators Fluo-3 and dihydrorhodamine-123 it was shown that crosslinking of the CD14 molecule induces an increase in monocyte and granulocyte cytoplasmic calcium concentration and monocyte H2O2 production. These responses were found to be independent of IgG Fc receptors and suggest an intrinsic signal mediating capacity of the CD14 molecule.
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PMID:Signal transduction in human monocytes and granulocytes through the PI-linked antigen CD14. 169 12

GnRH stimulates LH release by increasing intracellular Ca2+ ([Ca2+]i). Melatonin is known to inhibit GnRH-stimulated LH release from neonatal rat pituitary cells. In the present report, the issue of whether melatonin acts through [Ca2+]i was addressed. [Ca2+]i was studied in cells in suspension, using Fluo-3 as a fluorescent indicator. In neonatal rat pituitary cells, melatonin inhibited the GnRH-induced [Ca2+]i increase in a dose-dependent manner; the GnRH-induced increase in [Ca2+]i was inhibited 40% by 100 nM melatonin. The relative potencies of several indoles as inhibitors of the GnRH stimulation of [Ca2+]i in neonatal pituitary cells (2-iodo-melatonin greater than melatonin greater than 6-hydroxymelatonin) correlate with their known potencies to inhibit LH release and with their binding affinity to high affinity melatonin receptors, which indicates that these receptors probably mediate the effects of melatonin. Further support for this interpretation comes from the observation that melatonin does not inhibit the GnRH effect on [Ca2+]i in cells obtained from adolescent rat pituitary glands, which lack melatonin receptors and are insensitive to melatonin as an inhibitor of GnRH-stimulated LH release. The possible involvement of an inhibitory G-protein was also investigated by studying the effects of pertussis toxin. Pretreatment with pertussis toxin antagonized the effects of melatonin on [Ca2+]i and LH release. This indicates that melatonin may inhibit the GnRH-induced increase in [Ca2+]i through a mechanism involving a pertussis toxin-sensitive G-protein. To examine the role of extracellular Ca2+ in this effect, the effects of melatonin were examined in a low Ca2+ medium. Under these conditions, the effect of melatonin was markedly reduced, which indicates that melatonin may act by inhibiting Ca2+ influx. These observations indicate that melatonin inhibits GnRH stimulation of [Ca2+]i in neonatal rat gonadotrophs, and this probably explains the inhibitory action of melatonin on GnRH stimulation of LH release.
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PMID:Melatonin inhibits gonadotropin-releasing hormone-induced elevation of intracellular Ca2+ in neonatal rat pituitary cells. 173 18

1. ATP was puff applied to cells of a mesodermal stem cell line, C3H10T1/2, and the responses were studied by whole-cell patch clamp recording. 2. In 91% of the cells (90/99), K+ current lasting for tens of seconds was observed after several seconds latency. The current showed outward rectification. In 10% of the cells (9/99), ATP induced Cl- current which also lasted for tens of seconds after several seconds latency, but showed little rectification. In 6% of these cells (5/99), both K+ and Cl- currents were induced by ATP. 3. The K+ current induced by ATP was dose dependent, with a Kd of 0.4 microM. The effects of ATP analogues were tested at a concentration of 20 microM. ADP and ATP-gamma-S induced the K+ current, while AMP and adenosine did not. alpha, beta-Methylene ATP produced a diminished K+ current. 4. The ATP-induced K+ current was not observed when EGTA in the internal solution was raised from 0.1 to 5 mM. In Fluo-3-loaded cells, an increase in intracellular Ca2+ concentration induced by the application of ATP was observed, and the time course was similar to the induced K+ current. Both the increase in intracellular Ca2+ and the K+ current were induced by ATP even in Ca(2+)-free external solution. Ryanodine (50 microM) in the external solution did not affect the ATP response, and application of 10 mM-caffeine alone to the external solution did not induce any response. 5. The variance of the steady-state fluctuations in the course of the ATP-induced slow K+ current was analysed. The single-channel conductance was estimated as 2.7 pS at 0 mV with external and internal K+ concentrations of 5 and 140 mM respectively. The K+ current was not affected by apamin at concentrations of up to 1 microM but was reduced to one-third by 140 mM-tetraethylammonium (TEA). 6. It was concluded that puff-applied ATP has two main effects in the mesodermal stem cells: an increase in the intracellular Ca2+ concentration and a succeeding hyperpolarization due to the Ca(2+)-activated K+ conductance which is present in this cell. The significance of the increase in intracellular Ca2+ caused by ATP is discussed.
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PMID:Properties of ionic currents induced by external ATP in a mouse mesodermal stem cell line. 179 49

The aim of this study was to investigate signal transduction through the two Fc receptors for IgG on human granulocytes. Using flow cytometry and the calcium indicator Fluo-3, we measured changes in leucocyte cytoplasmic calcium concentrations following cross-linking of cellular Fc receptors with specific antibodies. Two different approaches were used in order to study the two Fc receptors independently of each other. One was to avoid the presence of IgG Fc fragments, capable of binding to both types of receptors. The other was to use leucocytes from a patient with paroxysmal nocturnal haemoglobinuria (PNH) deficient in granulocyte FcRIII. In contrast to earlier reports, both approaches showed that the two types of IgG Fc receptors on granulocytes are capable of increasing cytoplasmic free calcium concentrations independently of each other. The results suggest that free cytoplasmic calcium ions are involved in the signal transduction pathway of both types of IgG Fc receptors on human granulocytes.
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PMID:The IgG FcRII and the PI-linked IgG FcRIII trigger cytoplasmic calcium fluxes independently in human granulocytes. 182 73

High pressure (100-150 MPa) increases the intensity and polarization of fluorescence of FITC-labeled Ca(2+)-ATPase in a medium containing 0.1 mM Ca2+, suggesting a reversible pressure-induced transition from the E1 into an E2-like state with dissociation of ATPase oligomers. Under similar conditions but using unlabeled sarcoplasmic reticulum vesicles, high pressure caused the reversible release of Ca2+ from the high-affinity Ca2+ sites of Ca(2+)-ATPase, as indicated by changes in the fluorescence of the Ca2+ indicator, Fluo-3; this was accompanied by reversible inhibition of the Ca(2+)-stimulated ATPase activity measured in a coupled enzyme system of pyruvate kinase and lactate dehydrogenase, and by redistribution of Prodan in the lipid phase of the membrane, as shown by marked changes in its fluorescence emission characteristics. In a Ca(2+)-free medium where the equilibrium favors the E2 conformation of Ca(2+)-ATPase the fluorescence intensity of FITC-ATPase was not affected or only slightly reduced by high pressure. The enhancement of TNP-AMP fluorescence by 100 mM inorganic phosphate in the presence of EGTA and 20% dimethylsulfoxide was essentially unaffected by 150 MPa pressure at pH 6.0 and was only slightly reduced at pH 8.0. As the enhancement of TNP-AMP fluorescence by Pi is associated with the Mg(2+)-dependent phosphorylation of the enzyme and the formation of Mg.E2-P intermediate, it appears that the reactions of Ca(2+)-ATPase associated with the E2 state are relatively insensitive to high pressure. These observations suggest that high pressure stabilizes the enzyme in an E2-like state characterized by low reactivity with ATP and Ca2+ and high reactivity with Pi. The transition from the E1 to the E2-like state involves a decrease in the effective volume of Ca(2+)-ATPase.
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PMID:The effect of high pressure on the conformation, interactions and activity of the Ca(2+)-ATPase of sarcoplasmic reticulum. 183 34

We have applied several novel technologies to investigate the role of cytosolic free calcium [Ca2+]i in signal transduction in guard cells of Commelina communis L. Fluorescence ratio imaging and photometry together with the fluorescent Ca2+ indicator Indo-1 were used to directly visualise and measure dynamic spatial and temporal changes in [Ca2+]i in response to various exogenous stimuli. More subtle manipulation of the Ca2+ signal transduction pathway was achieved through the use of photoactivateable, caged Ca2+ and caged inositol-1,4,5-triphosphate (InsP3) released directly into the cytoplasm of the guard cell after microinjection. In these experiments, changes in [Ca2+]i were simultaneously monitored with the fluorescent Ca2+ indicator, Fluo-3. Resting levels of [Ca2+]i (100-200 nM) increased in response to elevated [Ca2+]e, lowering [K+]e, application of the ionophore A-23187 or cytosolic release of either Ca2+ or InsP3 from their caged forms. Stomatal closure was triggered if [Ca2+]i increased above a threshold of about 600 nM. Abscisic acid (ABA) had little effect on [Ca2+]i in the majority of cells studied, being elevated in only a minority of cells investigated. However, stomatal closure occurred in all cases after ABA application. This suggests that ABA acts through both Ca(2+)-independent and Ca(2+)-dependent pathways. The imaging data revealed a substantial heterogeneity in [Ca2+]i within the guard cell. Cytoplasmic regions, particularly near the nucleus, often showed marked elevations and sometimes oscillations. The origin and kinetics of the Ca2+ fluxes leading to the dynamic spatial patterns is discussed along with several new approaches directed towards identification of the source of the Ca2+. These methods include optical sectioning and 3-D reconstruction of both the endomembrane system and [Ca2+]i in living guard cells using confocal microscopy. Overall, our data is consistent with multiple sources for [Ca2+]i, including uptake across the plasma membrane and InsP3- or Ca(2+)-induced Ca2+ release from internal stores.
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PMID:Visualisation and measurement of the calcium message in guard cells. 184 7

Due to the participation of intracellular free calcium in the mechanisms of vascular smooth muscle contraction, and its importance in the physiopathology of essential arterial hypertension, its possible role in pre-eclampsia physiopathology, was investigated as a cellular model, platelets, were use, as they are similar to vascular smooth muscle cells. The study purpose was to investigate if intracellular concentration of ionized calcium is greater in the patients with pre-eclampsia than in normotensive pregnant women, and also, if there exists a correlation between intracellular calcium concentrations and arterial tension, Seven pre-eclamptic patients, diagnosed by the following criteria: arterial tension greater than or equal to 130/90 mmHg, edema and proteinuria, between 20 to 35 years of age, during the third trimester of gestation, without personal nor family antecedents of hypertension; none of them received treatment at the time, were studied. As control group seven normotensive pregnant women, equal by chronologic and gestational age, were included. Intracellular calcium in platelets was measured by Fluo-3-Am, and arterial blood pressure with conventional sphygmomanometer. Intracellular calcium and arterial blood pressure values, were compared, in both groups by Student's t, and analysis of lineal regression between intracellular calcium and mean arterial blood pressure, was done. Intracellular calcium was significantly greater in patients with pre-eclampsia, than the ones in the control group (142 +/- 5.6 vs 110 +/- 14 p less than 0.0001). Mean arterial blood pressure was also significantly greater in patients with pre-eclampsia (114 +/- 5 vs 83 +/- 3 p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Importance of free intracellular calcium in the physiopathology of pre-eclampsia]. 187 25


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