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F Baumgart

Publications and source records attributed to F Baumgart.

25 records · Page 2Linked to original sources
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↗
PubMedDate not supplied

Biomechanical comparison of bending and torsional properties in retrograde intramedullary nailing of humeral shaft fractures.

OBJECTIVE: To establish whether the bending and torsional stiffness of an implanted nail are influenced by nail design and nail-bolt interface, this study compared two implanted retrograde nail systems: the AO/ASIF unreamed humeral nail (UHN) and the Russell-Taylor (RT) nail. DESIGN: Pair randomization. SETTING: Mechanical laboratory testing. SPECIMENS: Twelve pairs of freshly harvested cadaveric humeri. METHODS: Transverse fractures were simulated with a standardized midshaft osteotomy and a three-millimeter gap. Both nails were proximally and distally interlocked. The RT nail has a single interlock at its base and tip. The UHN has double interlocking both proximally and distally. The screw hole design of the RT nail features slots, whereas the UHN has round screw holes. MAIN OUTCOME MEASURES: Anteroposterior and mediolateral bending stiffness and torsional stiffness. RESULTS: The RT nail showed higher bending stiffness in anteroposterior and mediolateral bending. Large differences were seen in the torsional characteristics: for the first 30 degrees, the RT nail showed a much lower resistance against torsion than the UHN. Analysis of variance of stiffness at four, six, and eight newton-meters showed statistical significance (p < 0.0001). Torsional stiffness, defined as the slope of a straight line approximated to between 75 and 100 percent of the maximum torque, was very similar in both nails. CONCLUSION: The torsional differences between the two nail systems are attributable to the nail-bolt interface of the RT nail. This dynamic system allows a clinically relevant degree of movement. The greater resistance to rotatory forces of the UHN is explained by the fact that the interlocking at its tip and base creates a static rather than a dynamic system.

Biomechanical Phenomena↗
PubMedDate not supplied

Activation of human auditory cortex in retrieval experiments: an fMRI study.

In a previous functional magnetic resonance (fMRI) study, a subdivision of the human auditory cortex into four distinct territories was achieved. One territory (T1a) exhibited functional specialization in terms of a foreground-background decomposition task involving matching-to-sample monitoring on tone sequences. The present study more specifically determined whether memory-guided analysis of tone sequences is part of the T1a specialization. During the encoding periods, an arbitrary and unfamiliar four-tone-sequence (melody) played by one instrument was presented. The melody-instrument-combination was different in each period. During subsequent retrieval periods, learned and additional combinations were presented, and the tasks were either to detect the target melodies (experiment I) or the target instruments (experiment II). T1a showed larger activation during the melody retrieval. The results generally suggest that (1) activation of T1a during retrieval is determined less by the sound material than by the executed task, and (2) more specifically, that memory-guided sequential analysis in T1a is dominant over recognition of characteristic complex sounds.

Acoustic Stimulation↗