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

An increase in intracellular Ca2+ concentration ([Ca2+]) and morphological were simultaneously observed by epifluorescence and differential interference contrast (DIC) microscopy during fertilization of the sand dollar, Clypeaster japonicus. [Ca2+], which was detected by a Ca2+ indicator, Fluo-3, initially increased just beneath the sperm-attached site on the egg surface 8.6 sec after attachment. The increase spread into the egg as a concentric sphere to the egg center and, thereafter, propagated in the egg cytoplasm as a planar wave rather than a spherical wave. It reached the site opposite the initiation site across the egg 24.2 sec after initiation. The fertilization envelope (FE) began to elevate 10.3 sec after the initiation of the increase in [Ca2+] and 21.2 sec after sperm attachment.
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PMID:Simultaneous investigation of intracellular Ca2+ increase and morphological events upon fertilization in the sand dollar egg. 239 3

Fluo-3, one member of a family of new fluorescent Ca2+ indicators excitable at wavelengths in the visible (Minta, A., Kao, J. P. Y., and Tsien, R. Y. (1989) J. Biol. Chem. 264, 8171-8178), has been tested in living cells. We demonstrate that fluo-3 can be loaded into fibroblasts and lymphocytes by incubation with the pentaacetoxymethyl ester of the dye and that the ester is hydrolyzed intracellularly to yield genuine fluo-3 capable of indicating changes in [Ca2+]i induced by agonist stimulation. Fluo-3 can also be microinjected into fibroblasts along with photolabile compounds such as nitr-5 and caged inositol trisphosphate for photorelease experiments. Fluo-3 permits continuous monitoring of [Ca2+]i without interference with use of UV-sensitive caged compounds. A procedure for combined use of ionophore and heavy metal ions in end-of-experiment calibration of fluo-3 intensities to give [Ca2+]i is also described.
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PMID:Photochemically generated cytosolic calcium pulses and their detection by fluo-3. 249 9

The free cytosolic Ca2+ concentration ([Ca2+]i) of cultured cerebral cortex neurons was determined using a fluorescent Ca2+ chelator (Fluo-3) after exposure of the neurons to glutamate. Mature neurons (8 days in culture) responded within 45 s to 100 microM glutamate by an increase in [Ca2+]i from 75 to 340 nM, an increase that during the following 6 min of exposure reached 400 nM. This increase in [Ca2+]i could not be reversed by removal of glutamate. In the absence of extracellular CaCl2, only part of the initial, rapid, glutamate-induced increase in [Ca2+]i was observed in these neurons. In contrast to these findings, neurons cultured for only 2 days (immature neurons) exhibited only a small (from 75 to 173 nM) increase in [Ca2+]i after exposure to 100 microM glutamate, and this rapid increase in [Ca2+]i tended to decline on prolonged exposure to glutamate. Moreover, after removal of glutamate, the increase in [Ca2+]i was fully reversible. Pharmacological characterization of the response to glutamate in mature neurons showed that the N-methyl-D-aspartate (NMDA) receptor antagonists phencyclidine and D-2-amino-5-phosphonovalerate phosphonovalerate blocked 75 and 90%, respectively, of the response, whereas the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione had little effect.
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PMID:Glutamate-induced increase in intracellular Ca2+ in cerebral cortex neurons is transient in immature cells but permanent in mature cells. 257 Jan 29

1. Cultured hippocampal neurons were recorded with a patch pipette containing 100 microM of the calcium indicator Fluo-3, and one of their dendrites, carrying dendritic spines, was visualized with a x100, 1.3-numerical aperture oil objective. Calcium spikes evoked by depolarizing the somata and changes in free dendrite and spine calcium concentrations ([Ca]d and [Ca]s, respectively) were monitored with a cooled charge-coupled device (CCD) camera, acquiring images at a rate of 17-20 ms per frame. In the majority of spine-dendrite pairs, [Ca]s rose faster and to a higher level than the adjacent [Ca]d. Likewise, topical application of glutamate evoked a faster and larger change in [Ca]s than in [Ca]d. The rise of intracellular calcium concentration in response to a depolarizing current pulse, but not in response to glutamate, was reduced in the presence of the calcium antagonist verapamil in both dendrites and spines. It is suggested that dendritic spines possess voltage-gated calcium channels.
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PMID:Fast imaging of [Ca]i reveals presence of voltage-gated calcium channels in dendritic spines of cultured hippocampal neurons. 747 52

Laser scanning confocal microscopy in combination with the fluorescent calcium indicators Fluo-3 and Fura-Red was employed to estimate the intracellular concentration of free calcium ions in individual olfactory receptor neurons and to monitor temporal and spatial changes in the Ca(2+)-level upon stimulation. The chemosensory cells responded to odorants with a significant increase in the calcium concentration, preferentially in the dendritic knob. Applying various stimulation paradigma, it was found that in a population of isolated cells, subsets of receptor neurons display distinct patterns of responsiveness.
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PMID:Calcium signals in olfactory neurons. 748 45

It has been shown that supraphysiological concentrations of asparagine and hypoosmotic shock stimulate ornithine decarboxylase activity in cultured cancer cells by increasing the synthesis and the half-life of the enzyme protein. Since extracellular Ca2+ is essential for the action of asparagine and is also important for cell volume regulation in certain cell types, aspects of Ca2+ physiology in asparagine-treated H-35 rat hepatoma cells were investigated. The initial rate of influx of 45Ca increased from 0.25 to 1.04 nmol/min/mg protein immediately after exposure to 10 mM asparagine. With a one-minute lag the efflux rate also increased 2.2-fold over a five minute period. Asparagine did not cause a net-gain in cellular Ca2+ as measured by 45Ca equilibration, nor did it have any effect on the cytosolic free Ca2+ as measured by Fura-2 fluorescence spectroscopy and Fluo-3 fluorescence confocal microscopy.
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PMID:Membrane Ca2+ fluxes in rat hepatoma cells exposed to a supraphysiological concentration of asparagine. 749 52

Vascular endothelial cells (ECs) can undergo dramatic phenotypic and functional alterations in response to humoral and cellular stimuli. These changes promote endothelial participation in the inflammatory response through active recruitment of immune effector cells, increased vascular permeability, and alteration in vascular tone. In an attempt to define early events in lymphocyte-mediated EC signaling, we investigated cytosolic-free calcium (Ca2+) changes in single, Fluo-3-labeled human umbilical vein ECs (HUVECs), using an ACAS interactive laser cytometer. Of all lymphocyte subsets tested, allogeneic CD3-, CD56+ natural killer (NK) cells uniquely elicited oscillatory EC Ca2+ signals in cytokine (interleukin [IL]-1- or tumor necrosis factor [TNF])-treated ECs. The induction of these signals required avid intercellular adhesion, consisted of both Ca2+ mobilization and extracellular influx, and was associated with EC inositol phosphate (IP) generation. Simultaneous recording of NK and EC Ca2+ signals using two-color fluorescence detection revealed that, upon adhesion, NK cells flux prior to EC. Lymphocyte Ca2+ buffering with 1,2-bis-5-methyl-amino-phenoxylethane-N,N,N'-tetra-acetoxymethyl acetate (MAPTAM) demonstrated that lymphocyte fluxes are, in fact, prerequisites for the adhesion-dependent EC signals. mAb studies indicate that the beta 2 integrin-intercellular adhesion molecule (ICAM)-1 adhesion pathway is critically involved. However, ICAM-1 antisense oligonucleotide inhibition of IL-1-mediated ICAM-1 hyperinduction had no effect on EC Ca2+ signaling in lymphocyte-EC conjugates, indicating that additional cytokine-induced EC alteration is required. These experiments combine features of lymphocyte-endothelial interactions, intercellular adhesion, EC cytokine activation and transmembrane signaling. The results implicate the IP/Ca2+ second messenger pathway in EC outside-in signaling induced by cytotoxic lymphocytes, and suggest that these signals may play a role in EC alteration by lymphocyte adhesion.
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PMID:Lymphocyte adhesion-dependent calcium signaling in human endothelial cells. 753 70

The ability of the ectodermal cells to be induced and to differentiate toward neural tissue, called neural competence, is acquired shortly before gastrulation and lost during late gastrula stages in Pleurodeles waltl embryos. We have examined ectodermal cells' neural competence in relation to the evolution of the density of L-type calcium channels using the fluorescent labelled dihydropyridine probe (STBodipy-DHP). We find that the appearance of dihydropyridine sensitive calcium channels (L-type Ca2+ channels) is correlated with the acquisition of neural competence by the ectoderm cells. The highest density of these channels is reached when competence of the ectoderm is optimal. Conversely, the decrease of L-type Ca2+ channel density occurs simultaneously with the normal loss of competence. In addition, we show that these channels are functional since stimulation by S(-)-Bay K 8644 triggered an increase in [Ca2+]i revealed by fluorescence measurements using Fluo-3. This increase in [Ca2+]i is a function of the L-type Ca2+ channels' density. We propose that the molecular basis of the gain and loss of neural competence is linked to the presence of L-type Ca2+ channels in ectodermal cell membranes of Pleurodeles waltl embryos.
Cell Calcium 1995 Mar
PMID:In vivo labelling of L-type Ca2+ channels by fluorescent dihydropyridine: correlation between ontogenesis of the channels and the acquisition of neural competence in ecotderm cells from Pleurodeles waltl embryos. 754 70

This study aimed at testing if, and under which conditions, long-lasting cytosolic calcium responses can be induced in dissociated embryonic brain cells exposed to alpha-amino-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor agonists. Rat brainstem cells (gestation days 13-14; mean crown-rump lengths 8-11 mm) were mechanically dissociated and loaded with the fluorescent calcium marker Fluo-3 after in vitro delays ranging from 20 min to 6 days. The cells were exposed to various concentrations of AMPA, domoic acid or kainic acid. The evoked fluorescence changes, indicating variations of cytosolic calcium, were recorded and analysed either with a video-microscope or a laser cytometer. Even at the earliest stages, non-desensitizing (or partly desensitizing) calcium responses to AMPA were found. In addition, sequential exposure to AMPA followed either by domoic acid, or by AMPA in the presence of aniracetam, revealed the existence of cells bearing predominantly desensitizing receptors. The non-desensitizing as well as desensitizing response components were blocked by 6,7-dinitroquinoxaline-2,3-dione (DNQX). When the experiments were conducted at 24 degrees C, the cytosolic calcium levels generally returned close to pre-stimulus baseline levels after washout. In contrast, when the working temperature was slightly raised (to 27 degrees C), complex secondary calcium rises were observed not only during prolonged stimulation, but also after short agonist application. The calcium modulation might be correlated with some form of cellular "learning" in the embryonic brain. Under particular conditions, where the regulation processes are either switched off by cell programmes or simply overloaded, the cascade of events comprising secondary calcium rises may lead to cell death.
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PMID:AMPA elicits long-lasting, partly hypothermia-sensitive calcium responses in acutely dissociated or cultured embryonic brainstem cells. 754 83

Spontaneous Ca2+ waves were visualized in quiescent cardiomyocytes loaded with the Ca(2+)-sensitive fluorescent probe, Fluo-3, and imaged by laser confocal microscopy. No sarcomere shortening was detected during wave propagation. This type of Ca2+ waves began at the periphery or in a central region of a myocyte and propagated the length of the cell in one or two directions. The average velocity of wave propagation was 32 microns/sec and the estimated concentration of Ca2+ oscillated from 124, at the bottom, to 311 nM, at the pick of the wave. Ca2+ waves were not confined to a single cell but could spread from cell to cell. These results describe a type of spontaneous Ca2+ waves which does not induce a contractile response in cardiomyocytes.
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PMID:Spontaneous calcium waves without contraction in cardiac myocytes. 757 44


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