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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    FEBS Letters 249 (1989), S. 199-206 
    ISSN: 0014-5793
    Keywords: Ca^2^+ ; Fura-2 ; Macrophage ; Platelet-activating factor
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 424 (1993), S. 448-455 
    ISSN: 1432-2013
    Keywords: Na+/Ca2+ exchange ; Macrophages ; Platelet-activating factor ; Lymphocytes ; Anti-CD3 antibody ; Fura-2 ; Sodium-binding benzofuran isophthalate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In two blood cell types, peritoneal murine macrophages and Jurkat cells (a human T cell line), we have examined whether a Na+/Ca2+ exchange was present and what could be its functional importance. In nonstimulated macrophages, the intracellular Ca2+ concentration, [Ca2+]i, was unchanged when Li+ was substituted for external Na+. However, after stimulation by platelet-activating factor (PAF), the Ca2+ response was larger when the extracellular solution contained Li+ rather than Na+ ions. In stimulated macrophages, the rate of Ca2+ extrusion was smaller in a Li+-than in a Na+-containing medium. The net electrochemical gradient for ionic movements through the Na+/Ca2+ exchanger, during the course of the response of macrophages to PAF, was determined by combining the measurements of membrane potential (in patch-clamp), of [Ca2+]i (with fura-2), and of the intracellular Na+ concentration (with sodium-binding benzofuran isophthalate). These results show that macrophages possess a Na+/Ca2+ exchange that only functions as a Ca2+ extruder, and this only when [Ca2+]i has been increased, for instance following PAF stimulation. In T lymphocytes, before or after stimulation by an anti-CD3 antibody, no Na+/Ca2+ activity could be detected by measuring either [Ca2+]i, or the rate of Ca2+ extrusion. Even if a Na+/ Ca2+ exchanger was present in these cells, its equilibrium potential would be such that it would not allow Ca2+ influx but only Ca2+ extrusion.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2013
    Keywords: Calcium stores ; Platelet-activating factor ; Uridine 5′-triphosphate ; Adenosine 5′-triphosphate ; Macrophages ; Fura-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Ca2+ movements between intracellular stores, the cytoplasm and external solution were analysed in murine peritoneal macrophages stimulated by various agonists. The Ca2+ content of intracellular stores was estimated from the amplitude of Ca2+-transients elicited by ionomycin applied in Ca2+-free solution. Both uridine 5′-triphosphate (UTP) and platelet-activating factor (PAF) triggered the release of Ca2+ followed by a sustained influx, during which intracellular stores remained totally empty. In contrast, in the continuous presence of adenosine 5′-triphosphate (ATP), Ca2+ was initially released and then rapidly sequestered again by the stores. ATP-induced store refilling was not related to cell depolarization or to an increase in the intracellular Na+ concentration (two specific consequences of ATP stimulation which are not induced by PAF and UTP). Store refilling was not caused by a signal that ATP would fail to induce (e.g. as a result of receptor desensitization), but was positively controlled by ATP, even in the simultaneous presence of a concentration of PAF which, on its own, would have caused a persistent store depletion. The hypothesis that the signal delivered by ATP involves the sequential activation of phospholipase D and protein kinase C is consistent with the present pharmacological evidence. However, although we found conditions in which Ca2+ stores did not refill in the presence of ATP, this maintained store depletion was not accompanied by a sustained Ca2+ response similar to that elicited by PAF or UTP, suggesting that store depletion is a condition which is necessary, but not sufficient, for inducing Ca2+ influx.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2013
    Keywords: Macrophages ; Calcium ; Fura-2 ; Cyclic GMP ; Platelet-activating factor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of cyclic GMP on the release of calcium from intracellular stores, induced in murine peritoneal macrophages by either ATP or platelet-activating factor, were studied by microfluorimetry with fura-2. When macrophages were incubated for 10–20 min with 10 μM LY83583, an inhibitor of guanylate cyclase, the rise in intracellular calcium induced by agonist application was strongly depressed. This inhibition of the response to platelet-activating factor could be reversed by the addition of 0.1 mM cyclic 8-bromo-GMP. In the presence of cyclic 8-bromo-GMP, the decay of the calcium transient was speeded. Furthermore, when two calcium transients were evoked within 1 min by stimulating the cells with 10 μM ATP, the second calcium transient was more depressed than the first one in the presence of LY83583. These findings are compatible with the hypothesis that cyclic GMP is necessary for the activation of the calcium pump of the intracellular stores.
    Type of Medium: Electronic Resource
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