Biomedical subjects

F Wagner

Publications and source records attributed to F Wagner.

238 records · Page 14Linked to original sources

PubMedDate not supplied

Marine biosurfactants, II. Production and characterization of an anionic trehalose tetraester from the marine bacterium Arthrobacter sp. EK 1.

Within a screening for biosurfactants we could isolate various n-alkanes utilizing marine bacteria which were capable of synthesizing glycolipids. One strain was identified as Arthrobacter sp. EK 1 which produced trehalose lipids. After purification by column and thick layer chromatography the main fraction, an anionic 2,3,4,2'-trehalose tetraester, was obtained. The chain lengths of fatty acids ranged from 8 up to 14, furthermore succinate could be detected. Since the place of substitution of succinate has so far not been cited in literature, a definitive structural elucidation was carried out chemically by hydroboration and by 1H, 2D1H, 13C and 13C-1H correlation NMR measurements. All investigations confirmed the exact position of succinate at C 2 atom of trehalose. After improvement of growth conditions the production of the trehalose tetraester increased up to 4.8 milligrams during a fermentation in 20 l bioreactor under nitrogen limitation.

Animals↗

PubMedDate not supplied

Marine biosurfactants, III. Toxicity testing with marine microorganisms and comparison with synthetic surfactants.

Eight synthetic and nine biogenetic surfactants were tested on their toxicity. Because of their possible application as oil dispersants against oil slicks on sea, the test organisms used were marine microorganisms (mixed and pure cultures of bacteria, microalgae, and protozoa). Bacterial growth was hardly effected or stimulated, whilst that of algae and flagellates was reduced. All substances tested were biodegraded in sea water. The bioluminescence of Photobacter phosphoreum (Microtox test) was the most sensitive test system used. A ranking shows that most biogenetic surfactants were less toxic than synthetic surfactants. No toxicity could be detected with the glucose-lipid GL, produced by the marine bacterium Alcaligenes sp. MM1.

Animals↗

PubMedDate not supplied

Investigation of tetherable distilbazolium compounds as fluorescent probes in nanostructured silica sol-gel materials.

Distibazolium dyes are investigated by steady-state and time-resolved fluorescence techniques in a series of low- and high-viscosity polar solvents and in a silica sol-gel matrix. In all solvents and the sol-gel matrix, an interplay of photoinduced switching between different cis-trans isomers and solvation dynamics is observed. Even in a viscous solution (glycerol) and in silica gel, cis-trans isomerization is solvent-controlled. Whereas in glycerol the solvation results in a time-dependent fluorescence Stokes shift, the solvation-induced spectral heterogeneity in silica gel is mostly static, possibly due to a close proximity of dye molecules to the silica surfaces of the nanopores. Compared to low-viscosity solvents, where the cis-trans isomerization process takes place with a solvent-dependent rate on the timescale of about 120-150 ps, it slows down to about 1100-1400 ps in glycerol and about 1500 ps in a sol-gel matrix. Additionally, fluorescence kinetics of the dyes in the sol-gel reveals the presence of a range of different "frozen-in" conformers exhibiting a broad spectrum of lifetimes from 20 to 300 ps.

Journal Article↗

PubMedDate not supplied

The influence of gastrointestinal agents on resorption and metabolism of cyclosporine after heart transplantation: experimental and clinical results.

The clinical effectiveness of cyclosporine is limited by changes in resorption and metabolism of cyclosporine and by possible drug interactions. This study examined the influence of five gastrointestinal agents on duration and resorption of cyclosporine and dosage/level relations: cimetidine, famotidine, pirenzepine, aluminum hydroxide, and omeprazole. These gastrointestinal agents were studied in 64 rat experiments, in which the impact of each single drug and of drug combinations on cyclosporine resorption and metabolism was tested. A standardized dosage of cyclosporine was given orally, and the duration was calculated for the maximum whole blood level of cyclosporine to be achieved; the dosage/level quotient was calculated. Cimetidine, famotidine, pirenzepine, and combination treatment prolonged duration of cyclosporine resorption. Furthermore, cimetidine, famotidine, and omeprazole lowered the dosage/level quotient, thus leading to higher cyclosporine levels with the same dosage; pirenzepine increased the dosage/level quotient. For clinical comparison, 163 heart transplant patients who had received standard triple-drug immunosuppressive therapy were analyzed. The time interval until a therapeutic cyclosporine level was achieved and the dosage/level quotient were once again calculated. Similar to the results in the animal experiments, cimetidine and famotidine significantly delayed the resorption of cyclosporine; cimetidine, famotidine, and omeprazole lowered the cyclosporine dosage/level quotient, thus leading to higher cyclosporine levels with the same dosage. Aluminum hydroxide did not lead to any changes in the resorption or metabolism of cyclosporine. Most examined gastrointestinal agents, and particularly H2-blocking drugs, led to significant prolongation of cyclosporine resorption and cyclosporine level alterations. The initial prolongation of cyclosporine resorption was successfully avoided by intravenous administration of cyclosporine for the first 4 postoperative days in 40 consecutive patients.

Absorption↗