Jewish Hospital

About: Jewish Hospital is a healthcare organization based out in Cincinnati, Ohio, United States. It is known for research contribution in the topics: Antigen & Population. The organization has 3881 authors who have published 3414 publications receiving 123044 citations.

Stimulus-secretion coupling in beta-cells of transplantable human islets of Langerhans. Evidence for a critical role for Ca2+ entry.

Abstract: With human islets isolated for transplantation, we examined the applicability to humans of a metabolic fuel hypothesis of glucose transduction and a Ca 2+ hypothesis of depolarization-secretion coupling, both previously proposed for rodent islet β-cells. We report that several features of human β-cell physiology are well accounted for by these hypotheses. With whole-islet perifusion, we demonstrated that insulin secretion induced by glucose, tolbutamide, or elevated K + is dependent on extracellular Ca 2+ . Insulin release induced by these secretagogues is enhanced by the dihydropyridine Ca 2+ channel agonist BAYk8644 and depressed by the dihydropyridine Ca 2+ -channel antagonist nifedipine. All of the aforementioned secretagogues provoke increases in cytosolic free Ca 2+ , which are dependent on extracellular Ca 2+ and are altered by the dihydropyridine drugs. Individual β-cells in the islet display diminished resting membrane conductance, graded depolarization, and complex electrical patterns, including bursts of action potentials in response to stimulatory concentrations of glucose or tolbutamide. Individual islet β-cells display voltage-dependent Ca 2+ currents that are activated at membrane potentials traversed during the excursion of the action potential. In most cells, the Ca 2+ currents are enhanced by BAYk8644 and depressed by nifedipine at concentrations that have parallel effects on secretagogue-induced increases in cytosolic Ca 2+ and insulin secretion. These survey studies should provide the basis for more detailed investigations of the relationship of voltage-dependent ionic currents to electrical activity patterns and of electrical activity patterns to granule exocytosis in single human β-cells.

Regulation of paracellular permeability in Caco-2 cell monolayers by protein kinase C.

Abstract: Caco-2 cells are an enterocyte-like cell line derived from a human colonic adenocarcinoma. Paracellular permeability was assessed in monolayers of these cells by transmonolayer resistance and by the permeation of [3H]mannitol across the monolayer. Paracellular permeability was increased by the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (50 nM), carbachol (500 microM), and the combination of carbachol (50 microM) and monolein (100 microM), an inhibitor of diacylglycerol kinase, as manifested by a decrease in transmonolayer resistance and an increase in mannitol permeation. The effects of all of these stimuli on transmonolayer resistance were inhibited by staurosporine (3 nM), an inhibitor of PKC. The effects of carbachol plus monolein were also inhibited by atropine (0.1 microM), a muscarinic antagonist. Treatment of the monolayers with each of the stimuli was associated with translocation of PKC activity from cytosol to a membrane-associated state. Stimulation of Caco-2 cell monolayers with phorbol myristate acetate or with the combination of carbachol and monolein was also associated with phosphorylation of the MARCKS protein, an endogenous substrate of PKC. These data support the hypothesis that intestinal paracellular permeability is regulated by the activity of enterocyte PKC and demonstrate that the increase in paracellular permeability induced by binding of carbachol to the muscarinic receptor is mediated by activation of PKC.

The carboxy terminus of tissue factor pathway inhibitor is required for interacting with hepatoma cells in vitro and in vivo.

Abstract: Tissue factor pathway inhibitor (TFPI) is a plasma Kunitz-type serine protease inhibitor that directly inhibits coagulation Factor Xa and also inhibits tissue factor-initiated coagulation. Normal human plasma TFPI exists both as the full-length molecule and as variably carboxy-terminal truncated forms. We reported recently that the low density lipoprotein receptor-related protein mediates the cellular degradation of TFPI after TFPI binding to the hepatoma cell surface. To examine whether the carboxy terminus of TFPI was required for interacting with hepatoma cells, a mutant of TFPI lacking the third Kunitz-type domain and basic carboxy terminus was generated. We found that this mutant, TFPI-160, did not compete with full-length 125I-TFPI-160 for binding to hepatoma cells. We were also unable to demonstrate specific binding of 125I-TFPI-160 to hepatoma cells at 4 degrees C. At 37 degrees C, significantly less 125I-TFPI-160 was internalized and degraded via low density lipoprotein receptor-related protein than full-length 125I-TFPI. Full-length 125I-TFPI binding to hepatoma cells could be inhibited > 90% by heparin and other highly charged molecules. Since TFPI, but not TFPI-160, was capable of effectively binding to cultured hepatoma cells, the fates of TFPI and TFPI-160 in vivo were examined. Both 125I-TFPI and 125I-TFPI-160 disappeared rapidly from the circulation after their intravenous administration into rats. The initial plasma half-life of 125I-TFPI was approximately 30 s whereas the half-life of 125I-TFPI-160 was approximately 4 min. 125I-TFPI was cleared predominantly by the liver. In contrast, 125I-TFPI-160 accumulated in the outer cortex of the kidney. Using microscopic autoradiography, we demonstrate that 125I-TFPI clearance is largely hepatocellular, whereas 125I-TFPI-160 accumulates mainly in the cells of the kidney proximal tubules. Together our findings demonstrate that the carboxy-terminal region(s) distal to amino acid 160 of TFPI mediates TFPI binding to hepatoma cells both in vitro and in vivo.