Biomedical subjects

E Bayer

Publications and source records attributed to E Bayer.

114 records · Page 7Linked to original sources

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Mass transfer in chromatographic columns studied by PFG NMR.

Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) is applied to study convective and diffusional transport in chromatographic columns packed with totally porous support particles. Here stagnant zones exist in the particle pores, and diffusional mass-transfer limitations between fluid molecules diffusing in the intraparticle pore network and flowing in the interparticle void space are detected quantitatively. Axial displacement probability distributions were measured for water over a range of Peclet numbers and observation times, with diffusion lengths between 0.15 and 0.91 times the average support particle diameter. The transition towards complete diffusional exchange is demonstrated, thereby also revealing the development of the classical convective dispersion process in a packed bed of (porous) particles.

Candy↗

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Dangerous chemicals.

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Environmental Pollutants↗

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In vivo metabolism of [4-13C]phenacetin in an isolated perfused rat liver measured by continuous flow 13C NMR spectroscopy.

Continuous flow 13C NMR spectroscopy has been used for the first time to monitor the metabolism of a 13C labeled drug in an isolated liver. Continuous and almost immediate information on the metabolite formation could be obtained using 13C labeled phenacetin without alteration of the biological system. The data are consistent with those observed by conventional techniques (HPLC, aliquot 13C NMR measurements). From the biological point of view the sensitivity of continuous flow 13C NMR spectroscopy is still low (10(-3) M). The results presented demonstrate however that non-invasive and non-radioactive real time monitoring of drug metabolism in intact organs is possible.

Animals↗

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Comparative luminescence of rat liver Cu-thionein and its chemically synthesized alpha-domain.

A peptide corresponding to the alpha-domain of rat liver metallothionein-2 was chemically synthesized employing the solid phase peptide synthesis technique. Its luminescence properties that depend on the coordinated Cu(I) have been studied using luminescence spectrometric titration in the presence of Cu(I). Unlike the intact metallothionein which has been converted into the Cu species, the emission and excitation spectra of the Cu-alpha-fragment showed a red shift by 20 nm and 65 nm, respectively, suggesting a more compact and stable luminophore in the alpha-domain. Saturation of Cu(I) coordination was reached in the presence of 6.5 mol eq Cu(I) when the alpha-fragment was used and 12 mol eq Cu(I) were specifically bound by the intact metallothionein. The emission bands were homogeneous and no decline of the cluster structure was observed when excessive Cu(I) was added after saturation. A rearrangement of the Cu-cluster in metallothionein during its formation seems to be plausible.

Amino Acid Sequence↗

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Capillary gas chromatographic analysis of amino acids by enantiomer labeling.

The optical isomers of amino acids can be easily separated by gas chromatography using capillary columns coated with the chiral polysiloxane peptide, Chirasil-Val. Quantitative trace amino acid analysis in complex mixtures such as biological fluids, sea water, or protein hydrolysates can be achieved by enantiomer labeling: The D-amino acid enantiomers, which do not occur naturally, are added to the sample prior to analysis as internal standards. Because the D-enantiomers show the same physical and chemical properties as the natural L-enantiomers, they are ideal standard references. In routine analysis, the derivatization is achieved with a new automated derivatization robot. The D-standard serves as overall internal standard for the whole analytical procedure from sample enrichment to derivatization, chromatography, and response of the detector.

Amino Acids↗

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Penetration of gentamicin into heart valves, subcutaneous and muscular tissue of patients undergoing open heart surgery.

Concentrations of gentamicin in plasma, heart valves, subcutaneous tissue and muscle were determined in 38 patients undergoing open heart surgery. Gentamicin reached peak levels in plasma and tissue within 60 min after a 5 min intravenous bolus injection of 1.5 mg/kg body weight. Subcutaneous and muscle concentrations varied between 0.51 microgram/g and 2.1 microgram/g. Gentamicin peak concentrations in cardiac valvar tissue wre 3.6 mug/g between 2 and 5 hours after administration; gentamicin heart valve concentrations varied between 1.2 microgram/g and 1.59 microgram/g. Gentamicin tissue concentrations during open heart surgery are high enough to inhibit most Klebsiella/Enterobacter and Staphylococcus aureus and epidermidis strains. However Gentamicin heart valve concentrations do not exceed 1.5 microgram/g for more than 1 h, which may explain treatment failures of patients with endocarditis.

Cardiac Surgical Procedures↗