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H Lauer

Publications and source records attributed to H Lauer.

8 recordsLinked to original sources
PubMed2003

Fusion of small unilamellar vesicles onto laterally mixed self-assembled monolayers of thiolipopeptides.

Monolayers of the thiolipopeptide NH(2)-Cys-Ala-Ser-Ala-Ala-Ser-Ser-Ala-Pro-Ser-Ser-(Myr)Lys(Myr)-OH (III) were formed on gold surfaces by self-assembly, mixed with a lateral spacer of the same peptide composition, NH(2)-Cys-Ala-Ser-Ala-Ala-Ser-Ser-Ala-Pro-Ser-Ser-Lys-OH (I). Different mixing ratios were employed ranging from 0.1 to 1, corresponding to 10-100% thiolipopeptide. These self-assembled monolayers (SAMs) were then exposed to a suspension of liposomes with the aim of forming lipid bilayers as a function of the mixing ratio. A clear optimum with respect to homogeneity and electrical properties of the membranes was obtained in the middle region (0.5) of mixing ratio, as revealed by surface plasmon resonance spectroscopy, impedance spectroscopy, and fluorescence microscopy. The combination of these methods was shown to be a powerful tool, although a true lipid bilayer was not obtained. Instead, vesicle adsorption was shown to be the predominant process, and FRAP (fluorescence recovery after photobleaching) measurements showed that the films were not fluid on the micrometer length scale.

Lipoproteins↗
PubMed1998

Volumetric object modeling for surgical simulation.

Surgical simulation has many applications in medical education, surgical training, surgical planning and intra-operative assistance. However, extending current surface-based computer graphics methods to model phenomena such as the deformation, cutting, tearing or repairing of soft tissues poses significant challenges for real-time interactions. This paper discusses the use of volumetric methods for modeling complex anatomy and tissue interactions. New techniques are introduced that use volumetric methods for modeling soft-tissue deformation and tissue cutting at interactive rates. An initial prototype for simulating arthroscopic knee surgery is described which uses volumetric models of the knee derived from 3-D magnetic resonance imaging, visual feedback via real-time volume and polygon rendering, and haptic feedback provided by a force-feedback device.

Arthroscopy↗
PubMed1991

[Combination intestinal lavage: a conservative procedure for colonoscopy].

The purpose of this study was to optimize the cleaning for colonoscopy. We compared a combination of senna pods and Goleytely solution to the exclusive ingestion of 7 litres of Goleytely solution. Test parameters were the score of visual assessment in five regions of the large bowel, the distension of the abdomen, concentration of hydrogen and methane in intestinal gases and subjective informations about abdominal complaints. We concluded from 80 colonoscopies that the combined procedure was almost identical with the cleaning by voluminal ingestions of Goleytely solution. There were no differences in the scores of visual assessment or concerning the intestinal gases. The additional administration of simethicone resulted in a statistically significant decrease of foam production. Thus, the combination of senna pods, a reduced ingestion of Goleytely solution supplemented with simethicone can be recommended for colonoscopy.

Adult↗
PubMed1986

Naturally occurring conjugated bile acids, measured by high-performance liquid chromatography, in human, dog, and rabbit bile.

The aim of this study was to determine the biliary pattern of conjugated bile acids after stimulation of their enterohepatic circulation. Conjugated bile acids were separated by reversed-phase ion-pair chromatography without prior derivatization. A MicroPak SP-C18-IP-4 column was used as non-polar matrix, and an ionic alkyl compound, tetrabutylammonium phosphate, was added to the mobile phase, which was a mixture of acetonitrile and water. Quantification was made by UV absorption at 210 nm with external standardization. In fourteen human patients with external biliary drainage after papillotomy there was preferential glycine conjugation. The mean values were 36.5% for glycocholic acid, 33% for glycochenodeoxycholic acid, and 10.0% for glycodeoxycholic acid. Only 15.2% of the biliary bile acids were taurine metabolites. Conjugates of ursodeoxycholic acid were below 2.1%. In most cases, conjugated lithocholic acid was not detected. Within 4 h after ingestion of a standardized meal there were no significant changes in the biliary bile acid pattern. In four dogs (beagles), glycine-conjugated bile acids were lacking. The mean values were 74.3% for taurocholic acid, 14.9% for taurodeoxycholic acid, and 5.3% for taurochenodeoxycholic acid. In six rabbits, 87.4% of biliary bile acids was identified as glycodeoxycholic acid and 5.3% as glycocholic acid. In conscious dogs, as well as in rabbits, the stimulation of biliary secretion by cholecystokinin and/or secretin had no effect on the biliary bile acid spectrum. Evidently, there is a difference in the biliary composition of conjugated bile acids between humans, dogs, and rabbits. Because of the different physicochemical behaviour of glycine- and taurine-conjugated bile salts, it seems difficult to compare the therapeutic effect of gallstone dissolution in various species.

Animals↗
PubMed1983

Measurement of conjugated bile acids by ion-pair high-performance liquid chromatography.

Vhe quantitatively most important conjugated bile acids in man were separated by reversed-phase ion-pair chromatography without prior derivatization. As non-polar matrix an Ultrasphere I.P. column (C18) was used, and an ionic alkyl compound, tetrabutylammonium phosphate, was added to the mobile phase, which was a mixture of acetonitrile and water. Under these conditions, the glycine and taurine conjugates of cholic acid, chenodeoxycholic acid and deoxycholic acid were separated within 15 min. At 214 nm, the minimum measurable concentration was 1.3-2.0 nmol/ml. The average recovery from bile was 94%. In ten patients with biliary drainage an average of 79.5% of the bile acids were glycine conjugates.

Bile↗
PubMed1969

[Not Available].

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History, Early Modern 1451-1600↗