64 research outputs found
Development of an online SPEâLCâMS-based assay using endogenous substrate for investigation of soluble epoxide hydrolase (sEH) inhibitors
Soluble epoxide hydrolase (sEH) is a promising therapeutic target for the treatment of hypertension, pain, and inflammation-related diseases. In order to enable the development of sEH inhibitors (sEHIs), assays are needed for determination of their potency. Therefore, we developed a new method utilizing an epoxide of arachidonic acid (14(15)-EpETrE) as substrate. Incubation samples were directly injected without purification into an online solid phase extraction (SPE) liquid chromatography electrospray ionization tandem mass spectrometry (LCâESIâMSâMS) setup allowing a total run time of only 108 s for a full gradient separation. Analytes were extracted from the matrix within 30 s by turbulent flow chromatography. Subsequently, a full gradient separation was carried out on a 50X2.1 mm RP-18 column filled with 1.7 Όm coreâshell particles. The analytes were detected with high sensitivity by ESIâMSâMS in SRM mode. The substrate 14(15)-EpETrE eluted at a stable retention time of 96â±â1 s and its sEH hydrolysis product 14,15-DiHETrE at 63â±â1 s with narrow peak width (full width at half maximum height: 1.5â±â0.1 s). The analytical performance of the method was excellent, with a limit of detection of 2 fmol on column, a linear range of over three orders of magnitude, and a negligible carry-over of 0.1% for 14,15-DiHETrE. The enzyme assay was carried out in a 96-well plate format, and near perfect sigmoidal doseâresponse curves were obtained for 12 concentrations of each inhibitor in only 22 min, enabling precise determination of IC50 values. In contrast with other approaches, this method enables quantitative evaluation of potent sEHIs with picomolar potencies because only 33 pmol Lâ1 sEH were used in the reaction vessel. This was demonstrated by ranking ten compounds by their activity; in the fluorescence method all yielded IC50ââ€â1 nmol Lâ1. Comparison of 13 inhibitors with IC50 values >1 nmol Lâ1 showed a good correlation with the fluorescence method (linear correlation coefficient 0.9, slope 0.95, Spearmanâs rho 0.9). For individual compounds, however, up to eightfold differences in potencies between this and the fluorescence method were obtained. Therefore, enzyme assays using natural substrate, as described here, are indispensable for reliable determination of structureâactivity relationships for sEH inhibition
Reduction in Cholesterol Absorption Is Enhanced by Stearate-Enriched Plant Sterol Esters in Hamsters
Consumption of plant sterol esters reduces plasma LDL cholesterol concentration by inhibiting intestinal cholesterol absorption. Commercially available plant sterol esters are prepared by esterifying free sterols to fatty acids from edible plant oils such as canola, soybean, and sunflower. To determine the influence of the fatty acid moiety on cholesterol metabolism, plant sterol esters were made with fatty acids from soybean oil (SO), beef tallow (BT), or purified stearic acid (SA) and fed to male hamsters for 4 wk. A control group fed no plant sterol esters was also included. Hamsters fed BT and SA had significantly lower cholesterol absorption and decreased concentrations of plasma non-HDL cholesterol and liver esterified cholesterol, and significantly greater fecal sterol excretion than SO and control hamsters. Cholesterol absorption was lowest in hamsters fed SA (7.5%), whereas it was 72.9% in control hamsters. Cholesterol absorption was correlated with fecal sterol excretion (r = â0.72, P \u3c 0.001), liver cholesterol concentration (r = 0.88, P \u3c 0.001), and plasma non-HDL cholesterol concentration (r = 0.85, P \u3c 0.001). A multiple regression model that included each sterol ester type vs. cholesterol absorption indicated that intake of steryl stearate was the only dietary component that contributed significantly to the model (R2 = â0.75, P \u3c 0.001). Therefore, our results demonstrate that BT and SA are more effective than SO in reducing cholesterol absorption, liver cholesterol, and plasma non-HDL cholesterol concentration, suggesting that cardioprotective benefits can be achieved by consuming stearate-enriched plant sterol esters
Estimation of the burden of varicella in Europe before the introduction of universal childhood immunization
Exploration of scalp surface lipids reveals squalene peroxide as a potential actor in dandruff condition
Techniques de report et d'assemblage hétérogÚne. Exemples de réalisation, perspectives
RF characterisation and modelling of AlGaAs/GaAs HBT for 1.8 GHz applications
For power applications, AlGaAs/GaAs heterojunction bipolar transistors (HBT's)
were found to present high efficiency and linearity at high density RF power. We report
power performances in S-band of a 6 à 60 ”m2 one emitter finger HBT
fabricated in our laboratory. At 1.8Â GHz, when tuned for maximum efficiency, each
transistor delivered a CW output power of 0.5Â W (150Â kW/cm2) and a power-added
efficiency of 62% and 80% in class AB and C operation respectively.
The physical model based on technological and measured parameters
incorporates temperature dependence for most of its parameters. It has been easily
used to analyse DC and RF power characteristics in class AB mode and to determine
input and output optimum matching cells. Good agreement between simulated and
experimental results support the validity of the model
Passive enhanced safety surveillance for Vaxigrip and Intanza 15 ”g in the United Kingdom and Finland during the northern hemisphere influenza season 2015/16.
Auswirkungen von KrankheitsaktivitÀtskriterien auf die Wahl von Therapieintervallen in klinischen Studien bei Patienten mit neovaskulÀrer altersbedingter Makuladegeneration (nAMD)
Validation of a LCâAPCI-MS/MS method for quantification of methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenylpyraline (EMDP) in infant plasma following protein precipitation
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