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Ines Burkard

Publications and source records attributed to Ines Burkard.

5 recordsLinked to original sources
PubMed2006

Lipoprotein distribution and biological variation of 24S- and 27-hydroxycholesterol in healthy volunteers.

24S- and 27-hydroxycholesterol are obligatory intermediates of cholesterol catabolism and play an important role in the maintenance of whole-body cholesterol homeostasis. Using an HPLC-MS method for oxysterol quantification, the distribution of esterified and unesterified oxysterols in lipoprotein subfractions as well as the influence of daytime, food intake and menstrual cycle on oxysterol concentrations were investigated in healthy volunteers. Moreover, reference intervals for 24S- and 27-hydroxycholesterol in plasma as well as the corresponding levels for 27-hydroxycholesterol in the HDL subfraction were established in 100 healthy volunteers. Both circulating oxysterols are mainly transported in association with HDL and LDL--primarily in the esterified form. No significant diurnal changes and no variations during menstrual cycle of either absolute or cholesterol-related plasma levels were detected. In contrast to 24S-hydroxycholesterol in plasma and 27-hydroxycholesterol in the HDL subfraction, the 95% reference intervals of 27-hydroxycholesterol both in plasma and the non-HDL subfraction were higher in males than in females. The concentrations of 27-hydroxycholesterol in plasma and the non-HDL subfraction showed strong positive correlations with the concentrations of cholesterol, non-HDL cholesterol and triglycerides. Our data on the lipoprotein distribution of oxysterols as well as on their intra- and inter-individual variation set the stage for future clinical studies.

Adult↗
PubMed2005

Differentiated quantification of human bile acids in serum by high-performance liquid chromatography-tandem mass spectrometry.

Determination of quantitative changes in the pattern of serum bile acids is important for the monitoring of diseases affecting bile acid metabolism. A sensitive and specific high-performance liquid chromatography (HPLC)-MS/MS method was developed for the differentiated quantification of unconjugated as well as glycine- and taurine-conjugated cholic, chenodeoxycholic (CDCA), deoxycholic (DCA), ursodeoxycholic (UDCA) and lithocholic acid (LCA) in serum samples. After solid-phase extraction and reversed-phase HPLC separation, detection of the conjugated bile acids was performed using electrospray ionization (ESI)-MS/MS and selected reaction monitoring mode, whereas unconjugated bile acids were determined by ESI-MS and selected ion monitoring mode. The within-day and between-day coefficients of variation were below 7% for all bile acids and the recovery rates of the extraction procedure were between 84.9 and 105%. The developed method was applied to a group of 21 healthy volunteers and preliminary reference intervals in serum were established. In patients with drug-induced cholestasis, an elevation of primary bile acids has been shown.

Adult↗
PubMed2004

Determination of 24S- and 27-hydroxycholesterol in plasma by high-performance liquid chromatography-mass spectrometry.

24S-Hydroxycholesterol (24S-OH-Chol) and 27-hydroxycholesterol (27-OH-Chol) are oxidized derivatives of cholesterol and of potential diagnostic interest because their circulating levels may reflect the cholesterol metabolism of the brain and macrophages, respectively. We developed a sensitive and specific HPLC-MS method for the quantification of 24S-OH-Chol and 27-OH-Chol in human plasma. In contrast to currently available procedures based on gas chromatography-mass spectrometry, this methodology offers the advantage that no time-consuming derivatization is needed. After saponification, solid-phase extraction, and HPLC separation under reversed-phase column conditions, detection by MS was performed using atmospheric pressure chemical ionization and selected ion monitoring mode. The standard curves were linear throughout the calibration range for both oxysterols. Within-day and between-day coefficients of variation were less than 9%, and the recoveries ranged between 98% and 103%. The quantification limits were 40 and 25 microg/l for 24S-OH-Chol and 27-OH-Chol, respectively. Mean values for both oxysterols were determined in plasma from 22 healthy volunteers. The sensitive and selective HPLC-MS method described here combined with the appropriate workup procedure allow the quantification of 24S-OH-Chol and 27-OH-Chol in plasma samples, for example in clinical studies to elaborate the clinical usefulness of these two oxysterols.

Chromatography, High Pressure Liquid↗
PubMed2002

Different activities of type I interferons on hepatitis B virus core promoter regulated transcription.

The type I interferons (IFNs) are a group of closely related cytokines which have different signal transduction pathways and different biological activities. Using transient transfection of human hepatoma cells with reporter plasmids containing the firefly/renilla luciferase genes under the control of the HBV-Enhancer (Enh) I, Enh II and core promoter we have investigated the biological activities of 10 recombinant (r) type I IFNs on transcription. Low concentrations of IFN (0.025 ng/ml) had a significant and specific inhibitory effect but the potencies of the different recombinant type I IFNs differed markedly with IFNalpha8 and IFNbeta being six-fold more potent than the least effective subtype (IFNalpha1). However, the addition of IFNalpha5-the subtype produced predominantly in the human liver-did not cause any synergistic effects.The non-natural consensus IFN displayed a more pronounced inhibition of HBV-regulated transcription than IFNalpha8 or IFNalpha2 but not IFNbeta. The INF-induced inhibitory effect was not dependent on the presence of the HBV-Enh1 and in particular of an interferon stimulated response element (ISRE)-like sequence. The characterization of different effects among type I interferons on HBV-regulatory elements may implicate an IFN-subtype-specific role for the pathogenesis and treatment of HBV-infection.

Cell Line↗