Biomedical subjects

T Siebert

Publications and source records attributed to T Siebert.

3 recordsLinked to original sources

PubMed2005

ISOFIT: a model-based method to measure muscle-tendon properties simultaneously.

Estimation of muscle parameters specifying force-length and force-velocity behavior requires in general a large number of sophisticated experiments often including a combination of isometric, isokinetic, isotonic, and quick-release experiments. This study validates a simpler method (ISOFIT) to determine muscle properties by fitting a Hill-type muscle model to a set of isovelocity data. Muscle properties resulting from the ISOFIT method agreed well with muscle properties determined separately in in vitro measurements using frog semitendinosus muscles. The force-length curve was described well by the results of the model. The force-velocity curve resulting from the model coincided with the experimentally determined curve above approximately 20% of maximum isometric force (correlation coefficient R>0.99). At lower forces and thus higher velocities the predicted curve underestimated velocity. The stiffness of the series elastic component determined with direct experiments was approximately 10% lower than that determined by the ISOFIT method. Use of the ISOFIT method can decrease experimental time up to 80% and reduce potential changes in muscle parameters due to fatigue.

Algorithms↗

PubMed2002

Scorecard endoscopy: a pilot study to assess basic skills in trainees for upper gastrointestinal endoscopy.

BACKGROUND: The development of training models and structured training courses for endoscopic techniques provides practical experience. To assess individual performance and progress in this training we developed and tested a scorecard system. METHODS: Three test groups were compared: group 1, ten physicians without previous endoscopic experience; group 2, ten students, without endoscopic experience; group 3, a control group of experienced endoscopists. Groups 1 and 2 underwent 1 week of training with a theoretical introduction and practical demonstrations. They were assessed by the scorecard daily by an experienced tutor. The individual scores and learning curves of the two beginner groups were compared with those of the expert group using a biosimulation model was used. RESULTS: Each participant improved significantly during the 1-week course. Mean scores on the first day in groups 1-3 were, respectively, 26.7+/-10.7, 33.4+/-5.3, and 72.0+/-5.8, and on day 6 they were 62.2+/-6.6, 63.4+/-7.6, and 86.6+/-4.3. The difference between group 3 and the other two groups was significant but not that between groups 1 and 2. CONCLUSIONS: Training in endoscopy can be assessed using our training model and our scorecard protocol, which distinguishes between various levels of experience. In physicians beginning in the field of gastrointestinal endoscopy this approach could help to reduce risks to patients, shorten learning curves, and exclude unskilled individuals from further fruitless interventions.

Animals↗

PubMed1993

Detection and direct sequence identification of BCR-ABL mRNA in Ph+ chronic myeloid leukemia.

The reverse transcriptase-polymerase chain reaction (RT-PCR) for BCR-ABL mRNA is increasingly used to diagnose and monitor patients with Ph+ chronic myeloid leukemia (CML). We investigated an alternative approach to detect BCR-ABL mRNA in CML in order to overcome some of the potential drawbacks of RT-PCR. Nucleic acid sequence based amplification (NASBA) is a homogeneous, isothermal, in vitro process that provides the direct amplification of RNA. Peripheral blood from seven patients with Ph+ CML and Ph+ EM-2 cells were investigated by NASBA and RT-PCR. A nested set of four primers flanking the BCR-ABL junction was used in two serial NASBA reactions performed for 2 hours. The two methods were fully concordant for detection of transcripts with bcr3-abl2 and bcr2-abl2 junctions. Ethidium bromide fluorescence with NASBA indicated in repeated experiments that similar quantities of total RNA from patient material contained different amounts of BCR-ABL mRNA. The data suggest that direct amplification of RNA is suitable for identifying and monitoring patients with Ph+ CML and may provide a means to quantify BCR-ABL mRNA levels.

Base Sequence↗