To replicate, the trypomastigote form of Trypanosoma cruzi must invade host cells. Since a role for Ca2+ in the process of cell invasion by several intracellular parasites has been postulated, changes in the intracellular Ca2+ concentration in T. cruzi trypomastigotes and in tissue culture L6E9 myoblasts during their interaction were studied at the single cell level using digital imaging fluore...

Lead (Pb) is a known nephrotoxic element. Recently we have proved that subcellular Ca2+ redistribution is involved in Pb-induced apoptosis in primary cultures of rat proximal tubular (rPT) cells, but the underlying mechanism remains to be elucidated. Firstly, data showed that Pb triggers endoplasmic reticulum (ER) stress response in rPT cells, as evidenced by the elevations of ER stress markers...

We hypothesized that endotoxin would impair agonist-induced calcium (Ca2+) mobilization in rat mesangial cells, owing to the induction of nitric oxide synthase (NOS) and augmented nitric oxide (NO) synthesis. We measured basal and bradykinin-induced peak free cytosolic Ca2+ concentrations through microspectrofluorimetry with fura-2 in confluent mesangial cells, and assayed conditioned medium fo...

Suspensions of aspirin-treated, 32P-prelabelled, washed platelets containing ADP scavengers in the buffer were activated with either phorbol 12,13-dibutyrate (PdBu) or the Ca2+ ionophore A23187. High concentrations of PdBu (greater than or equal to 50 nM) induced platelet aggregation and the protein kinase C (PKC)-dependent phosphorylation of proteins with molecular masses of 20 (myosin light c...

Fas receptor is a member of the tumor necrosis factor-alpha family of death receptors that mediate physiologic apoptotic signaling. To investigate the molecular mechanisms regulating calcium mobilization during Fas-mediated apoptosis, we have analyzed the sequential steps leading to altered calcium homeostasis and cell death in response to activation of the Fas receptor. We show that Fas-mediat...

Intracellular free Ca2+ concentrations were monitored in vascular smooth muscle cells (VSMC) using the Ca2+-sensitive dye fura II. Superfusion of VSMC with platelet-activating factor (S-PAF; 1-100 nM) increased cytosolic Ca2+ in a dose-dependent manner. The response was transient and returned to base line even though the agonist was still present. A second, higher dose of PAF did not elicit a r...

Many hormones, neurotransmitters, and secretagogues act by increasing the intracellular free Ca2+ concentration in target cells. The initial event following binding of agonists to specific receptors in the plasma membrane involves a receptor-mediated activation of a guanosine nucleotide-binding protein (G protein), which induces a Ca2+-independent activation of phospholipase C. This novel, pres...

Ca2+ is the most universal second messenger in cells from the very first moment of fertilization. In all animal species, fertilized eggs exhibit massive mobilization of intracellular Ca2+ to orchestrate the initial events of development. Echinoderm eggs have been an excellent model system for studying fertilization and the cell cycle due to their large size and abundance. In preparation for fer...

Sodium nitroprusside (SNP) is an endothelium-independent relaxant agent and its effect is attributed to its direct action on the vascular smooth muscle (VSM). Endothelium modulates the vascular tone through the release of vasoactive agents, such as NO. The aim of this study was to investigate the contribution of the endothelium on SNP vasorelaxation, NO release and Ca2+ mobilization. Vascular r...