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F Baumgart

Publications and source records attributed to F Baumgart.

6 recordsLinked to original sources
PubMed1991

Identification of amino acid substitutions in the lipopeptide surfactin using 2D NMR spectroscopy.

It is generally accepted that surfactin, being produced by various Bacillus subtilis strains, is a cyclic lipopeptide built from the heptapeptide L-Glu-L-Leu-D-Leu-L-Val-L-Asp-D-Leu-L-Leu and a beta-hydroxy fatty acid with variable chain length of 13 - 15 carbon atoms. We investigated surfactin from Bacillus subtilis ATCC 21332 and OKB 105, dissolved in pyridine and methanol, with two-dimensional H NMR spectroscopy. In the NH-fingerprint region, 21 well resolved cross peaks are observed instead of the expected seven cross peaks for the given heptapeptide. We were able to assign all proton signals to 21 amino acids, to identify three heptapeptides, and thus to prove the existence of structural analogues of surfactin. In the major fraction A, the peptide sequence is as given above. In fractions B and C, the C-terminal leucine is replaced by valine and isoleucine, respectively.

Amino Acid Sequence↗
PubMed1991

31P nuclear magnetic resonance spectroscopy, histology and cytokinetics of a xenografted hypopharynx carcinoma following treatment with cisplatin: comparison in three sublines with increasing resistance.

The changes in the phosphorus metabolism of a xenografted hypopharynx carcinoma (Hyp 1), sensitive to cisplatin (CDDP), were compared to those occurring in two sublines of the tumour, characterised by moderate or high resistance to CDDP (Hyp 1/H and Hyp 1/R) following, i.p. administration of 4, 8 or 12 mg CDDP/kg-1. The investigations were performed by in vivo 31P nuclear magnetic resonance (NMR) spectroscopy. Parallel to the NMR experiments, the cytokinetic and histological alterations in the tumours were studied under the same experimental conditions. No mentionable differences in the levels of the main phosphorus-containing metabolites could be detected between the three tumour lines before treatment. Following application of CDDP, the alterations in the NMR spectra were clearly related to the degree of tumour response. The most sensitive and earliest marker of tumour regression was a decrease in the phosphomonoester/phosphodiester ratio, parallelled by a gradual increase in the phosphocreatine/inorganic phosphorus quotient. In the resistant tumour lines Hyp 1/H and Hyp 1/R non-responding tumours showed alterations in the 31P NMR spectrum which were similar to those observed during uninfluenced tumour growth. Marked changes in the 31P NMR spectrum were always associated with severe cytotoxic lesions following therapy. The results suggest that the changes detected by 31P NMR spectroscopy following chemotherapy with CDDP are response-specific.

Animals↗
PubMed1990

["Mixing" of implants, a basic problem].

The so-called "mixing" of implants and instruments of different producers in hospitals leads to some risks. The use of standardized implant materials (e.g. stainless steel ISO 5832/1) by different producers is necessary but not sufficient for combining an osteosynthesis plate and a bone screw from different sources. The design, the dimensions and tolerances, the manufacturing, the quality control, the well tested applicational technique can be different too for the implants and the necessary instruments as well. This may lead to damage, failure or fracture of the biomechanical system called "osteosynthesis", that means failure of the therapy. Finally the patient pays for the problems. Some examples illustrate the potential problems for the involved staff or institutions. The use of a unique consistent well tested and approved set of implants and instruments must be recommended strongly to avoid any additional risk.

Biocompatible Materials↗
PubMed1978

[On Dwyer's scoliosis operation using memory alloy wire (author's transl)].

In Dwyer's spinal column correction a titanium cable is stretched from vertebra to vertebra by a special clamp and secured to each vertebra with screws and clips. It is suggested to replace the titanium wire with wire consisting of the memory alloy NiTi. This will permit the prestretched wire to be tensioned by heating it to 60 deg C after it has been fixed at its ends in the vertebrae. The functional principle of the NiTi memory wire was demonstrated in an experiment carried out on a plastic model. This consists of 8 plastic vertebrae with 30 mm sides which are connected by interposed wedge-shaped soft rubber discs, giving the model a curved shape. Memory wire prestretched by 7% is led through eylets on the convex side and fixed at the ends. On being heated (electrically in this experiment for the sake of simplicity), the wire shortens, righting the model so that it assumes a straight shape. The authors also describe in detail the manufacture of the alloy, i.e. the melting and shaping operations, as well as the properties of the material, that is, the stress-strain and strain-temperature relationships and the transformation temperatures, as well as mechanical problems.

Alloys↗
PubMedDate not supplied

31P NMR spectroscopy of a xenografted hypopharynx carcinoma: effects of tumor growth and treatment with cisplatin on the tumor phosphorus metabolism, histology and cytokinetics.

A xenografted hypopharynx carcinoma growing subcutaneously in nude mice was studied by in vivo 31P NMR spectroscopy during uninfluenced growth and following treatment with cisplatin (CDDP). Parallel to the NMR experiments, the cytokinetic and histological changes in the tumor were investigated. The most significant change in the growing tumor was a decline in the level of phosphocreatine (PCr), whereas the tumor pH did not change. Following treatment with CDDP (4, 8 and 12 mg/kg), a dose-dependent decrease in the level of phosphomonoesters (PME) took place, whilst no dose dependence could be observed for the increase of PCr. the pH shifted to alkaline only after administration of the highest CDDP dose. Tumor cytokinetics revealed a cell arrest at the G1/S boundary 24 h after chemotherapy. At this time, the histological sections showed a dilatation of capillaries, whereas first necroses appeared on day 3. The proliferative activity of the tumor showed a sharp decline 24 h after CDDP application, followed by a revival of cell proliferation that was proportional to the dose applied between days 5 and 7. This increase in proliferative activity was paralleled by a marked increase in the PME/phosphodiesters ratio. Thus, in the tumor investigated the PME were the best indicators of tumor response to therapy. A precise correlation between the cytokinetic data and the re-energization of the tumor was not possible because histological changes, which may contribute to improved tumor energy status took place at the same time.

Animals↗