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Biomedical subjects

R J Bing

Publications and source records attributed to R J Bing.

At least 19 recordsLinked to original sources
PubMed1995

Intracellular translocation of endothelial nitric oxide synthase by lysophosphatidylcholine.

The amphiphile lysophosphatidylcholine (LPC) modulates the activity of membrane-associated enzymes such as phospholipase A2, adenylate and guanylate cyclases and ATPase. LPC also relaxes vascular smooth muscle through production of nitric oxide. On the basis of reports that bradykinin translocates nitric oxide synthase (NOS) from the membrane to the cytosol, we investigated whether a similar translocation occurs with LPC. It was found that LPC translocated NOS from the membrane to the cytosolic fraction. Total NOS activity remained at the control level.

Amino Acid Oxidoreductases↗
PubMed1995

Immunohistochemistry in the identification of nitric oxide synthase isoenzymes in myocardial infarction.

OBJECTIVE: Inducible nitric oxide synthase (iNOS) activity, as measured by conversion of L-14C-arginine to L-14C-citrulline is significantly increased in infarcted rabbit myocardium as compared to healthy myocardium 48 h after coronary occlusion. The aim of this study was to localise the nitric oxide synthase (NOS) isoforms in normal myocardium and compare these findings with NOS activity in cells of the infarcted region. METHODS: Activities of NOS isoforms were enzymatically assayed in normal and infarcted myocardium. Localisation of NOS was performed on identical sections using specific monoclonal IgG antibodies against endothelial constitutive (cNOS) and macrophage inducible (iNOS) nitric oxide synthase. In addition, macrophages were identified using fluorescein conjugated ChromPure rabbit IgG, Fc fragment. RESULTS: iNOS activity increased significantly in infarcted as compared to normal myocardium [0.42(SEM 0.03) v 0.85(0.08) fmol.microgram-1.min-1, P = 0.02, respectively]. However, cNOS did not increase significantly in infarcted regions [0.18(0.04) v 0.24(0.06) fmol.microgram-1.min-1; P = 0.16, respectively]. cNOS was immunohistochemically localised in endothelial and endocardial cells in normal and infarcted tissues. The presence of iNOS activity in macrophages in infarcted myocardium was identified immunohistochemically. Cardiomyocytes and neutrophils did not label with the antibodies to cNOS and iNOS. CONCLUSIONS: (1) Infiltrating macrophages are the main site of increased iNOS activity in infarcted rabbit myocardium. (2) cNOS activity is not significantly increased in infarcted tissues as compared to normal myocardium. (3) Neutrophils and cardiomyocytes do not express NOS immunoreactivity in infarcted and normal rabbit myocardium.

Amino Acid Oxidoreductases↗
PubMed1994

Inducible nitric oxide synthase activity in myocardium after myocardial infarction in rabbit.

The activity of nitric oxide synthase (NOS) in infarcted and noninfarcted rabbit myocardium was determined. NOS activity, as measured by conversion of [14C]arginine to [14C]citrulline, was significantly higher in the infarcted area of myocardium (22.7 +/- 3.7 fmol/mg as compared to 7.67 +/- 1.0 in noninfarcted area). NOS activity within the area of risk remained on control level. Increased inducible NOS activity was observed on the first postoperative day and persisted for at least 14 days; it declined 3 weeks after infarction. Citrulline formation was inhibited by N-omega-nitro-L-arginine and N-omega-monomethyl-L-arginine The localization of NOS by monoclonal anti-NOS antibody indicates mononuclear cells/macrophages as the likely source of the enzyme. The concentrations of tumor necrosis factor-alpha and interleukin-1 beta were not increased in peripheral blood or myocardium.

Amino Acid Oxidoreductases↗
PubMed1994

Dexamethasone inhibits the expression of an inducible nitric oxide synthase in infarcted rabbit myocardium.

Infarcted areas of rabbit myocardium show relatively higher inducible nitric oxide synthase activity, measured by the conversion of L-[14C]arginine to L-[14C]citrulline. The principal finding in this study is that dexamethasone (2 mg/kg) prevents the induction of inducible nitric oxide synthase in heart muscle when given before, or even 3 hr after coronary artery ligation. Additionally cyclic GMP levels remain unchanged following treatment with dexamethasone. It is possible that the enhanced production of nitric oxide by inducible nitric oxide synthase accounts, at least in part, for the depression of myocardial contractility seen in myocardial infarction and in other clinical conditions.

Amino Acid Oxidoreductases↗
PubMed1994

The production of nitric oxide in endothelial cells by amphiphiles.

Lysophosphatidylcholine, an endogenous detergent is an endothelium-dependent smooth muscle relaxant, which acts through the release of nitric oxide. It is known to activate a number of membrane-bound enzymes. Because of the relationship between detergent action, relaxation of endothelium-intact rabbit aortic strips and the release of nitric oxide, we considered the possibility that other amphiphiles also produce nitric oxide from endothelial cells. We therefore investigated the effect of digitonin on relaxation of precontracted rabbit aortic strips and the release of nitric oxide from freshly harvested bovine endothelial cells as determined by chemiluminescence. We found that both digitonin and LPC release nitric oxide and that this process is inhibited by the NO synthase inhibitor N omega-Nitro-L-Arginine Methyl Ester (L-NNAME).

Animals↗
PubMed1994

Effect of amphiphiles on nitric oxide synthase in endothelial cells.

Amphiphiles are known to modulate the activity of ATPase, phospholipase A2, adenylate and guanylate cyclase amongst others and relax vascular smooth muscle. The effect of two amphiphiles, lysophosphatidylcholine (LPC) and digitonin on the activity of nitric oxide synthase (NOS), as measured by conversion of radiolabeled L-arginine to L-citrulline, has been studied. Neither digitonin (0.01 mmol/l) nor LPC (0.01 mmol/l) influenced NOS activity in endothelial cell homogenates. Digitonin but not LPC stimulated NOS in intact endothelial cells. NOS activity was markedly inhibited by L- but not by D-omega-nitroarginine (D-NNA, 0.1 mmol/l). L-NNA or D-NNA data demonstrate no effect of amphiphiles on isolated NOS. NOS activation may occur as a result of detergent action on the membrane.

Amino Acid Oxidoreductases↗
PubMed1992

The effect of immune mediators (cytokines) on the release of endothelium-derived relaxing factor (EDRF) and of prostacyclin by freshly harvested endothelial cells.

The effect of recombinant tumor necrosis factor and other cytokines stimulated by LPS (lipopolysaccharide), on the release of endothelial-derived relaxing factor and of prostacyclin was investigated using freshly harvested endothelial cells attached to plastic microcarrier beads. The results show that the cytokines failed to interfere with the release of EDRF and prostacyclin under the conditions of these experiments.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

A simplified method for the determination of nitric oxide in biological solutions.

A new simplified procedure for determination of nitric oxide (NO) in biological solutions is described utilizing a new reducing system of nitric oxide prior to chemiluminescence. Advantages of the new method makes heating of the reducing solution unnecessary and avoids cooling and condensation of generated vapors. Only traces of acid with a high boiling point are used. The method permits analysis of small sample volumes (200 microL). The basal production of nitric oxide by freshly harvested endothelial cells ranged from 100 to 880 picomoles.

Animals↗
PubMed1992

Cytokine production from freshly harvested human mononuclear cells attached to plastic beads.

The release of tumor necrosis factor (TNF), interleukin-1 beta (IL-1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) from freshly harvested monocytes and lymphocytes attached to plastic beads was investigated. Previous studies had shown that freshly harvested endothelial cells attached to microcarrier beads release an endothelium-derived relaxing factor. Attachment of freshly harvested lymphocytes and monocytes to plastic beads created a dense network, consisting of 25% monocytes and 75% lymphocytes as shown by flow cytometry. Viability of cells was 90%. Monocytes were characterized by phagocytosis and non-specific esterase stain. Freshly harvested cells stimulated with lipoprotein lipase (LPS) released TNF and IL-1. Non-stimulated cells also produced GM-CSF five hours after collection of blood.

Cell Aggregation↗
PubMed1992

Dopa: then and now.

Explore the source record for details and available documents.

Dihydroxyphenylalanine↗
PubMed1991

Release of prostacyclin, endothelium-derived relaxing factor and endothelin by freshly harvested cells attached to microcarrier beads.

Cultured endothelial cells have been used in the past as a source of endothelium-derived relaxing factor (EDRF) and of prostacyclin (PGI2). Although cell cultures are essential for observation of prolonged exposure to media or when there is delayed response, they are time consuming and sterile conditions are essential. In the present study, we report that endothelial cells, freshly harvested from bovine aortas, readily attached themselves to cytodex-3 microcarrier beads and released an endothelium-derived relaxing factor (EDRF), prostacyclin (PGI2) and increased the amount of cyclic GMP in vascular smooth muscle. Attachment to microcarrier beads was essential since it increased the surface area and the number of attached cells and permitted collection of cell free filtrates because of the formation of dense networks of cells and beads. As a result superfusion of cells and beads on the filter did not dislodge bound cells which remain on the filter. Conditioned filtrates from freshly harvested endothelial cells attached to microcarrier beads caused marked relaxation of endothelium-deprived bovine pulmonary artery strips. The degree of relaxation depended on the number of cells; maximal relaxation occurred with 50 million cells at ED50 of 14 million. High values of cyclic GMP were found in vascular smooth muscle exposed to conditioned filtrate. The calcium ionophore A23187 further increased the amount of cyclic GMP. Large amounts of PGI2 were released by freshly harvested endothelial cells particularly after stimulation with the calcium ionophore. In contrast, endothelin production by freshly harvested cells attached to microcarrier beads was barely detectable after 30 min incubation and was beyond the limit of detection by bioassay procedures. Freshly harvested endothelial cells attached to microcarrier beads appear to be a useful adjunct to tissue cultures under specific experimental conditions.

Animals↗
PubMed1991

The effect of lysophosphatidylcholine on coronary and renal circulation in the rabbit.

It has been shown that different lysophosphatidylcholines (LPC) possess relaxing properties in vascular strips. We report on the effect of intraatrial injection of LPC micelles into white New Zealand rabbits. Changes in renal and coronary flow were determined by radioactive microspheres. Coronary blood flow increased significantly following administration of LPC, while no significant changes were observed in renal blood flow, cardiac output and myocardial contractility. Coronary, renal and total vascular resistance, as well as mean arterial pressure, dropped significantly. Cardiac arrhythmia and hemolysis were not noted. The results demonstrate the vasorelaxant effect of LPC in vivo.

Animals↗
PubMed1991

Reduction of biological effluents in purge and trap micro reaction vessels and detection of endothelium-derived nitric oxide (edno) by chemiluminescence.

Various analytical approaches have been used to measure endothelium-derived nitric oxide (NO). We have detected NO in perfusates with a sample size as low as 2 ml after acidification with 4 N HC1 to pH less than 2 at 25 degrees C by using a Nitric Oxide Analyser (Sievers, Colorado). This procedure had the advantage that the detectable level of NO was enhanced by the self-decomposition of HNO2 when the PH less than pKa of NHO2 (pKa = 3.15) and also the reaction temperature of 25 degrees C substantially increased the half-line of NO. Palmer, et al., measured NO released by cultured porcine endothelial cells by chemiluminescence after passing cell effluents continuously at a rate of 5 ml/min into 75 ml of 1% sodium iodide in glacial acetic acid. The larger volumes involved in this method for continuous refluxing, made it less desirable for the detection of endothelium-derived nitric oxide. Feelisch et al. utilized the activation of soluble guanylate cyclase, as well as, the quantitative oxidation of oxyhemoglobin to methemoglobin in aqueous solutions by NO as a means of measuring nitric oxide. We describe here a modification of our earlier micromethod which now enables us to detect NO after complete reduction with glacial acetic acid and sodium iodide. A comparison of the two procedures indicate that while freshly prepared NO standard solutions gave identical chemiluminescence response with and without reduction, effluents from bovine intrapulmonary artery under basal conditions gave substantially higher values upon reduction.

Animals↗
PubMed1991

The use of microcarrier beads in the production of endothelium-derived relaxing factor by freshly harvested endothelial cells.

This study is concerned with the use of freshly harvested bovine endothelial cells attached to microcarrier beads in the production of the endothelium-derived relaxing factor (EDRF). The results are compared to production of EDRF by endothelial cells grown in tissue cultures. We found that freshly harvested cells attach themselves to microcarrier beads within minutes. This results in large surface/area volume ratio and permits superfusion of cells suspension on a filter (pore size of 25-30 microns), resulting in cell free filtrate. When superfusing an endothelium-deprived pulmonary artery strip, the effluent causes relaxation; the response depends on the number of superfused endothelial cells. The number of viable freshly harvested cells attached to microcarrier beads in 5 ml Krebs-Henseleit solution is small (30%), as compared to almost 100% for cultured cells. Despite this difference, percent relaxation induced for the same number of viable cells is identical for both groups. Scanning electromicrographs confirm anchorage of endothelial cells to microcarrier beads. While cultured cells cover the entire surface and are individually attached, freshly harvested cells are anchored as cell aggregates leaving some of the surface free. Attachment of freshly harvested endothelial cells to microcarrier beads offers an alternative for the study of the role of endothelial cells in the production of vasoactive substances.

Animals↗