Fetuin-A is a known inhibitor of vascular calcification in vitro. In arteries with calcification, there is increased immunostaining for fetuin-A. However, vascular smooth muscle cells (VSMC) do not synthesize fetuin-A, suggesting fetuin-A may be endocytosed to exert its inhibitory effects. To examine the mechanism by which fetuin-A is taken up in bovine VSMC (BVSMC), we examined living cells by...

The biologic role of calcium and guanosine 3':5'-monophosphate (cyclic GMP) in the immunologic secretion of lysosomal enzymes from human neutrophils was studied. Contact of neutrophils with zymosan-treated serum or the divalent cation ionophore A-23187, in the presence of extracellular calcium, resulted in beta-glucuronidase (beta-D-glucuronide glucuronosohydrolase, EC 3.2.1.31) secretion and a...

Considerable progresses have taken place, both in the methodology available to study changes in intracellular cytosolic calcium and in our understanding of calcium signaling cascades, but how calcium signals function in plant drought resistance is questionable. In plant cells, calcium plays roles as a second messenger coupling a wide range of extracellular stimuli with intracellular responses. ...

The transfer of calcium from mother to milk during lactation is poorly understood. In this report, we demonstrate that parathyroid hormone-related protein (PTHrP) production and calcium transport in mammary epithelial cells are regulated by extracellular calcium acting through the calcium-sensing receptor (CaR). The CaR becomes expressed on mammary epithelial cells at the transition from pregna...

The objective of this study was to elucidate the mechanisms associated with the reciprocal relation between magnesium and calcium on vascular smooth muscle tone in bovine pulmonary artery and vein. Rapid removal of magnesium from Krebs-bicarbonate medium used to bathe isolated rings of precontracted artery or vein caused transient endotheliumand calciumdependent relaxation and cyclic GMP accumu...

This study was designed to determine whether alpha-receptor-stimulated monovalent ionic fluxes in rat aorta required calcium, and, if so, whether both extracellular calcium and cellularly stored calcium are active. Calcium removal in the presence of 10 mM magnesium (to maintain membrane stability) inhibited the norepinephrine-stimulated increase in potassium-42 and chloride-36 efflux. However, ...

PURPOSE To characterize better the ameba-host interactions that may be involved with the pathogenesis of Acanthamoeba keratitis, the role of calcium (Ca2+) on the binding of Acanthamoeba polyphaga to extracellular matrix proteins was examined in vitro. METHODS The binding of a metabolically labeled A. polyphaga (CDC:0187:1) isolate from a case of human keratitis to collagen type IV, laminin, ...

In epilepsy, the GABA and glutamate balance may be disrupted and a transient decrease in extracellular calcium occurs before and during a seizure. Flow Cytometry based fluorescence activated particle sorting experiments quantified synaptosomes from human neocortical tissue, from both epileptic and nonepileptic patients (27.7% vs. 36.9% GABAergic synaptosomes, respectively). Transporter-mediated...

Primary hyperparathyroidism (PHPT) is a common endocrine neoplastic disorder caused by a failure of calcium sensing secondary to tumour development in one or more of the parathyroid glands. Parathyroid adenomas are comprised of distinct cellular subpopulations of variable clonal status that exhibit differing degrees of calcium responsiveness. To gain a clearer understanding of the relationship ...

Acetylcholine elicited a sustained contraction and an increase in potassium efflux in longitudinal muscle isolated from the guinea pig ileum. Stepwise increases in the calcium concentration of the bathing medium, from 0.06 to 36 mM generally reduced the increase in potassium efflux, but had a complex effect on the mechanical response. Contractions produced by high levels of acetylcholine became...