Cycl AMP concentrations were elevated and acrosome reactions were induced in intact sea urchin spermatozoa by Nigericin, A23187, and pH 9.0 seawater. To determine whether or not the metabolism of cyclic AMP was being altered in sperm heads, the heads were mechanically separated from the flagella, and the flagella-less heads were then isolated by differential centrifugation. The isolated heads c...

Exposure of PC12 cells to reagent peroxynitrite promotes the release of arachidonic acid (AA) mediated by activation of phospholipase A(2) [Guidarelli, Palomba and Cantoni (2000) Br. J. Pharmacol. 129, 1539-1542]. We now present experimental evidence consistent with the notion that this response is not directly triggered by peroxynitrite but, rather, by reactive oxygen species generated at the ...

The Ca2+-sensitive photoprotein aequorin (Mr = 20,000) was introduced into human blood platelets by incubation with 10 mM EGTA and 5 mM ATP. Platelet cytoplasmic and granule contents were retained during the loading procedure, and platelet morphology, aggregation, and secretion in response to agonists were normal after aequorin loading. Luminescence indicated an apparent resting cytoplasmic ion...

BACKGROUND The role of platelet activating factor (PAF) in asthma remains controversial. The priming effect of PAF on leukotriene B4 (LTB4) release, 5-lipoxygenase activity, and intracellular calcium levels in asthmatic neutrophils was examined. METHODS LTB4 and other lipoxygenase metabolites in neutrophils obtained from 17 asthmatic patients and 15 control subjects were measured by reverse p...

BACKGROUND In a variety of disease states, endothelium-dependent vasodilation is abnormal. Reduced nitric oxide (NO) production, increased destruction of NO by superoxide, diminished cellular levels of L-arginine or tetrahydrobiopterin, and alterations in membrane signaling have been implicated. We examined these potential mechanisms in human vessels. METHODS AND RESULTS Relaxations to acetyl...

Low concentrations of calcium and magnesium ions have been shown to influence microtubule assembly in vitro. To test whether these cations also have an effect on microtubules in vivo, specimens of Actinosphaerium eichhorni were exposed to different concentrations of Ca++ and Mg++ and the divalent cation ionophore A23187. Experimental degradation and reformation of axopodia were studied by light...

We measured changes of cytosolic Ca2+ concentration during chondrogenesis, which occurs in high-density cultures (HDC) of chondrifying chicken mesenchymal cells. A significant, transient elevation was detected in Fura-2-loaded cells on day 3 of culturing, when majority of chondrogenic cells of HDC become differentiated. This 140 nM peak of cytosolic Ca2+ concentration is a result of increased C...

Nitric oxide is an endothelium-derived relaxing factor. Conversion of L-arginine to nitric oxide follows mediator-induced elevation of endothelial cytosolic calcium concentration. However, not all endothelium-dependent vasodilatation is caused by endothelium-derived relaxing factor, and few studies have correlated changes in vascular tone with measurement of free cytosolic calcium concentration...

Hyperkalemic solutions are widely used to preserve organs for transplantation and for cardiac surgery. The present study was designed to test the hypothesis that hyperkalemia may alter endothelial function through a non-nitric oxide (NO) pathway, since preliminary studies have shown that the NO pathway may not be affected. Porcine coronary artery rings were studied in organ chambers. After incu...