Accurate quantification of basal plasma levels of 3-nitrotyrosine and 3-nitrotyrosinoalbumin by gas chromatography-tandem mass spectrometry.

Measurement of 3-nitro-L-tyrosine (NO(2)Tyr) and protein-related 3-nitro-L-tyrosine in human plasma is associated with numerous methodological problems which result in highly divergent basal plasma levels often ranging within two orders of magnitude. Recently, we have described an interference-free GC-tandem MS-based method for NO(2)Tyr which yielded the lowest basal plasma NO(2)Tyr levels reported thus far. This method was extended to quantify protein-associated 3-nitrotyrosine and in particular 3-nitrotyrosinated albumin (NO(2)TyrALB) in human plasma.

Normal oxidative stress and enhanced lipoprotein resistance to in vitro oxidation in hypertriglyceridemia: effects of bezafibrate therapy.

Although there is evidence that hyperlipidemia and predominance of small dense low density lipoproteins (LDLs) are associated with increased oxidative stress, the oxidation status in patients with hypertriglyceridemia (HTG) has not been studied in detail. Therefore, we studied urinary levels of F(2)-isoprostanes (8-isoprostaglandin F(2alpha) and 2,3-dinor-5,6-dihydro-8-isoprostaglandin F(2alpha)) and susceptibility of very low density lipoproteins (VLDLs) and LDLs to oxidation ex vivo in 18 patients with endogenous HTG and 20 matched control subjects. In addition, the effects of 6 weeks of bezafibrate therapy were assessed in a double-blind, placebo-controlled, crossover trial.

Nebivolol decreases systemic oxidative stress in healthy volunteers.

Aims: Nebivolol is a selective, vasodilatory beta1-adrenergic receptor antagonist which has been suggested to possess additional antioxidative properties. The aim of the present study was to assess the actions of nebivolol in antihypertensive doses on systemic oxidative stress in healthy volunteers, reflected by 24 h urinary excretion of 8-iso-PGF2alpha.

Methods: In a double-blind, cross-over study, 12 healthy volunteers received 5 mg nebivolol once daily or placebo for a total of 7 days, separated by a wash out period of 2 weeks.

Tandem mass spectrometric quantification of 8-iso-prostaglandin F2alpha and its metabolite 2,3-dinor-5,6-dihydro-8-iso-prostaglandin F2alpha in human urine.

Whole body synthesis of F2-isoprostanes, a family of cyclooxygenase-independent eicosanoids formed by free-radical catalysed peroxidation, should be best assessed by quantifying their urinary metabolites. Two methods for the quantitative determination of F2-isoprostane metabolites in human urine performing either thin-layer chromatography (TLC) (method A) or high-performance liquid chromatography (HPLC) (method B) prior to GC-tandem MS are described. Method A allows for simultaneous quantification of 8-iso-PGF2alpha, one prominent member of the F2-isoprostane family, and its major urinary metabolite, 2,3-dinor-5,6-dihydro-8-iso-PGF2alpha.

Gas chromatographic-tandem mass spectrometric quantification of free 3-nitrotyrosine in human plasma at the basal state.

A fully validated gas chromatographic-tandem mass spectrometric (GC-tandem MS) method for the accurate and precise quantification of free 3-nitrotyrosine in human plasma at the basal state is described. In the plasma of 11 healthy humans a mean concentration of 2.8 nM (range 1.

Gas chromatographic-tandem mass spectrometric quantification of human plasma and urinary nitrate after its reduction to nitrite and derivatization to the pentafluorobenzyl derivative.

Gas chromatography-mass spectrometry (GC-MS) of nitrite as its pentafluorobenzyl derivative in the negative-ion chemical ionization mode is a useful analytical tool to quantify accurately and sensitively nitrite and nitrate after its reduction to nitrite in various biological fluids. In the present study we demonstrate the utility of GC-tandem MS to quantify nitrate in human plasma and urine. Our present results verify human plasma and urine levels of nitrite and nitrate measured previously by GC-MS.

Dietary L-arginine and alpha-tocopherol reduce vascular oxidative stress and preserve endothelial function in hypercholesterolemic rabbits via different mechanisms.

Vascular oxidative stress brought about by superoxide radicals and oxidized low-density lipoproteins (oxLDL) is a major factor contributing to decreased NO-dependent vasodilator function in hypercholesterolemia and atherosclerosis. We investigated whether chronic administration of L-arginine (2% in drinking water) or of alpha-tocopherol (300 mg/day) improves endothelium-dependent vasodilator function and systemic NO production, reduces vascular oxidative stress, and reduces the progression of atherosclerosis in cholesterol-fed rabbits with pre-existing hypercholesterolemia. Systemic NO production was assessed as urinary nitrate excretion; oxidative stress was measured by urinary 8-iso-PGF2alpha excretion in vivo, by lucigenin-enhanced chemiluminescence of isolated aortic rings ex vivo, and by copper-mediated LDL oxidation in vitro.

Specific and rapid quantification of 8-iso-prostaglandin F2alpha in urine of healthy humans and patients with Zellweger syndrome by gas chromatography-tandem mass spectrometry.

8-iso-Prostaglandin F2alpha (8-iso-PGF2alpha) is currently discussed as a potential index parameter of oxidative stress in vivo. We describe in this article a fully validated gas chromatographic-tandem mass spectrometric method for the quantitative determination of 8-iso-PGF2alpha in human urine. The method is highly specific and requires a single thin-layer chromatographic step for sample purification.

Gas chromatographic-tandem mass spectrometric determination of acetylsalicylic acid in human plasma after oral administration of low-dose aspirin and guaimesal.

A fully validated gas chromatographic-tandem mass spectrometric (GC-MS-MS) method is described for the accurate determination of acetylsalicylic acid (ASA) in human plasma after a single low-dose oral administration of aspirin or guaimesal, an ASA releasing prodrug. ASA and the newly prepared O-[2H3]-acetylsalicylic acid (d3-ASA) used as internal standard were determined in 100-microl aliquots of plasma by extractive pentafluorobenzyl (PFB) esterification using PFB bromide and tetrabutylammoniumhydrogen sulphate as the esterifying and ion-pairing agent, respectively, and by GC-MS-MS analysis in the negative-ion chemical ionization mode. The overall relative standard deviations were below 8% for ASA levels in the range 0-1 microg/ml plasma.

Fracture strength of type IV and type V die stone as a function of time.

Statement Of Problem: During the removal of casts from the impression there is the risk of stone fracture.

Purpose: This study evaluated the fracture resistance of four die stone materials at different time intervals.

Material And Methods: Additional silicone impressions were made of a maxillary master cast.