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Biomedical subjects

W Baumann

Publications and source records attributed to W Baumann.

At least 19 recordsLinked to original sources
PubMed1998

Monitoring of cellular signalling and metabolism with modular sensor-technique: the PhysioControl-Microsystem (PCM).

Microsensors provide instruments particularly suited for the noninvasive analysis of cell and tissue cultures. The outstanding benefit lies in the passive behaviour of continuously working transducers, which in turn allows the dynamic recording of function-specific cellular processes. The microsensor system presented in this paper is a modular arrangement of various planar and non-planar sensor elements surrounding small cell culture chambers. An optic access to the cultures (e.g. for high resolution light microscopy and spectro-photometric techniques) enables a parallel and comparative data acquisition. The system was originally designed for biomedical research in chemotherapy and pharmacology but it proved to be an effective device both for toxicological and environmental research.

Biosensing Techniques↗
PubMed1998

On-line control of cellular adhesion with impedance measurements using interdigitated electrode structures.

Critical parameters to be assessed in cell culture are the number of viable cells and cell viability. Growth, product formation, toxicity effects and the overall success of cell culture can depend largely on these. With interdigitated electrode structures (IDES) adherent cells are cultured directly on a pair of interdigitated electrodes, and the impedance of the system gives insight into the adhesive behaviour of the cells. The signal is influenced by the changes in number, growth and morphological behaviour of adherently growing cells, mainly owing to the insulating effects of the cell membranes. Five different cell lines are used, and their divergent behaviour is monitored over a period of four days, from inoculation of the cells to killing of the cells at the end of the experiments. Even when the cells from close monolayers, great fluctuations in the impedance signal can be observed. Nevertheless, for a more complete description of cellular systems, other parameters, such as acidification and respiration, have to be included in the measuring system.

Biosensing Techniques↗
PubMed1998

Microsensor-aided measurements of cellular signalling and metabolism on tumor cells. The cell monitoring system (cms(R)).

Microsensors provide instruments particularly suited for the rapid, noninvasive and on-line analysis of cell and tissue cultures. The microsensor system presented in this paper is a modular arrangement of various planar and nonplanar sensor elements for the measurement of physiological parameters of cell cultures. An optic access to the cultures (e.g. for light microscopy and spectrophotometric techniques) is also provided for a parallel and comparative data acquisition. The system was originally designed for biomedical research in chemotherapy (predicative chemotherapy assays) and pharmacology but it turned out to be also an effective tool for toxicological and environmental research.

Biosensing Techniques↗
PubMed1997

Monitoring of cellular behaviour by impedance measurements on interdigitated electrode structures.

A new method for on-line and real-time monitoring of concentration, growth and physiological state of cells in culture is described. This biosensor is based on impedance measurements of adherently growing cells on interdigitated electrode structures (IDES). The measurements can be performed for several days as there is no detectable electrical influence on the cells. The versatility of this new sensor is shown with some exemplary experiments. Cell density, growth and long-term behaviour of cells on the electrodes clearly change the impedance of the IDES. Both, the global influence of serum components (deprivation of foetal bovine serum) and the toxic effects of heavy metal ions (cadmium) result in changes of the sensor signal and can be visualized.

Animals↗
PubMed1997

Influence of inertia on intersegment moments of the lower extremity joints.

The calculation of three-dimensional intersegment moments of the lower extremity modelled as a system of rigid bodies-during human locomotion with the help of an inverse dynamics approach is one of the main strategies to describe the local kinetics of a human motion. From the numerical point of view, the resultant intersegment moment consists of different contributions; the moment of ground reaction force, the moment dependent on the weights of the segments and two inertia dependent parts, the moment of inertia force and the rate of change of angular momentum (with respect to the segments centre of gravity). For running with a horizontal velocity of 5 m s(-1), the calculation of the moment of inertia force can be neglected for the ankle but is important for the hip. Looking at the knee, this contribution is needed if the touch down phase is of special interest. The rate of change of angular momentum-with respect to the segments centre of gravity-can be neglected for all joints of the lower extremity.

Adult↗
PubMed1996

[Microsensory systems in cell biology basic research and medical diagnostics].

The development of an integrated sensor system, called the physiocontrol microsystem, is presented. It is suited for microscopy, and works with both adherent cell types and cultures growing in suspension, as well as with tissue biopsies. The central part, a miniaturized culture chamber equipped with differently constructed microsensors, allows continuous observation of important physiological parameters even in the course of long-lasting experiments. Besides a description of the physical components, the study provides a summary of selected applications of the physiocontrol microsystem in basic cellular research and biomedical diagnostics.

Animals↗
PubMed1994

[Biomechanical stress analysis of the lower extremity].

Within the field of prevention and rehabilitation, a detailed knowledge of the internal stresses and strains, for example the forces acting on and within joints, muscular force, is desirable or indispensable. The complex analysis of movements described here is based on a biomechanical model that takes into account the results of research done by F. Pauwels showing that muscular activity helps reduce the loading of tubular bones. The principle of functional adaptation provides a reasonable explanation for the "muscular redundence" of the locomotory system, and forms the basis for the calculation of internal loads. The results of the analysis include muscular and joint forces and the stresses within femur and tibia. The required anatomical data were for the most part obtainable directly from the test subject by magnetic resonance imaging. The calculated muscular forces are in good agreement with EMG measurements.

Biomechanical Phenomena↗
PubMed1993

[Magnetic resonance tomography in data collection in biomechanics].

Invasive measurement of internal loads is either not possible at all, or is extremely difficult. A non-invasive method for use in the clinical setting might be the computer-aided simulation of a mechanical model. All the geometrical data required can be obtained, at a level of accuracy not previously attainable, with the aid of magnetic resonance imaging.

Biomechanical Phenomena↗
PubMed1992

[Stress on the upper ankle joint in tennis-specific forms of movement].

The permanently increasing number of injuries in tennis, which are mainly located at the lower extremity, indicates that the internal load e.g. applicated to the ankle during certain movements might be a critical factor. In the present study the relationship between calculated ankle load and muscle forces appearing during tennis techniques performed in a laboratorial setup and some varying parameters such as playing surface, footwear and individual differences in movement structure were investigated. It could be shown that on a felt tennis floor due to its frictional characteristics the midfootstriking subject produced the highest ankle load, while the heelstriking technique reduces the load as well as the change of the playing surface to a floor with loose granulate. In addition it should be considered that external forces (e.g. gained from a force plate) must not be used as predictors for internal load. The presented data show that the model-aided load calculation (MALC) from two trials with similar ground reaction forces leads to completely different values of e.g. the ankle-joint force.

Ankle Injuries↗
PubMed1991

[Comparison of the bioequivalence of two allopurinol preparations].

Allopurinol generally is considered to be a problematic substance as to its bioavailability. To prove the quality, the in-vivo bioequivalence of an allopurinol (CAS 315-30-0) preparation (Cellidrin 300) in comparison to the standard preparation has been investigated. Both products were bioequivalent with regard to all relevant parameters such as AUC, tmax and Cmax.

Adult↗
PubMed1991

[Hepatitis B virus DNA. Current diagnosis in children with chronic hepatitis B].

After cloning the hepatitis B virus genome molecular hybridization techniques have been established for detection of HBV-DNA in serum and liver tissue. HBV-DNA is presently the most sensitive marker of viral replication and infectivity, which was previously related to the presence of HBeAg in serum and HBcAg in liver cells. HBV-DNA is usually analysed by dot blot-, Southern blot- and in situ hybridization techniques. The study of HBV-DNA has become a valuable part of the routine diagnostic in chronic hepatitis B, providing a more reliable estimation of viral replication and contagiousness and better parameters for severity and prognosis of the chronic infection.

Blotting, Southern↗
PubMed1990

Cellular cytotoxicity against autologous hepatocytes in children with different forms of chronic hepatitis B.

Cell-mediated immune reactions play the most important role in the pathogenesis of chronic viral and auto-immune hepatitis. Cellular cytotoxicity (CC) of peripheral blood lymphocytes against autologous hepatocytes isolated from liver biopsies was studied in 29 children with different types of hepatitis B surface antigen (HBsAg)-positive hepatitis. Children with chronic hepatitis B showed higher cytotoxicity than control patients. However, a correlation of cytotoxicity to serum amino-transferases, HBeAg-/Anti-HBe-status, and hepatitis B virus DNA in serum could not be found. Children with a higher percentage of hepatitis B core antigen (HBcAg) expression in their liver tissue presented lower CC values, and vice versa. This supports the hypothesis that virus elimination occurs via T-cell attack against HBcAg expressing hepatocytes. Furthermore, children with a longer duration of chronic hepatitis B had considerably higher cytotoxicity values. Possibly, CC plays a role in perpetuating liver damage after infection with hepatitis B virus.

Adolescent↗
PubMed1990

Diagnostic significance of epithelioid granulomas in Crohn's disease in children. Multicenter Paediatric Crohn's Disease Study Group.

Out of 528 children with Crohn's disease in a Multicenter Paediatric Crohn's Disease Study Group, 37 cases had epithelioid granulomas but did not fulfill defined radiographic criteria of the disease. Follow-up studies including clinical, biochemical, radiological, endoscopic, and histological investigations were done in these patients. Initially, all patients showed clinical symptoms and 27 of them had biochemical signs of chronic inflammation. After a mean follow-up of 3 years, all 37 children treated for Crohn's disease got a complete upper gastrointestinal series with small bowel followthrough and 8 children in addition had barium enemas. Colonoscopies were done in 23 patients. Radiographic examination revealed Crohn's disease in 14 and endoscopy additionally confirmed Crohn's disease in 8 further cases. One child was diagnosed as having chronic granulomatous disease. Thirteen children still remained unclassified after these follow-up studies including radiographs and endoscopy. An interval of 3 years may in some cases be too short to express the complete radiographic pattern of Crohn's disease. Our studies demonstrate that in addition to initial radiological, endoscopic, and histological investigations, a thorough follow-up is necessary in early diagnosed patients. In these children, epithelioid granulomas are of high diagnostic validity preceding radiological changes of Crohn's disease often for years.

Adolescent↗
PubMed1990

Defective jejunal brush border membrane sodium/proton exchange in association with lethal familial protracted diarrhoea.

The spectrum of clinical disease associated with specific defects in jejunal brush border membrane sodium/proton exchange is poorly defined and only two patients have been described so far. Jejunal brush border membrane transport studies were performed in a boy who presented with lethal familial protracted diarrhoea in the first few days of life. Using jejunal brush border membrane vesicles prepared from conventional jejunal biopsy specimens, initial sodium uptake under H+ gradient conditions was found to be only 6% of the mean control value. In contrast, sodium stimulated glucose uptake was normal. Our data confirm the importance of a congenital defect in this exchanger as a cause of severe sodium-losing diarrhoea and extend the spectrum of disorders characterised by a specific defect in brush border membrane Na+/H+ exchange to include some forms of lethal familial protracted diarrhoea.

Biological Transport, Active↗
PubMed1990

[Hepatitis A, B, CMV, EBV and HIV infections in premature and term newborn infants following polytransfusion].

306 children who received polytransfusion or exchange transfusion between 1979 and 1983 and 104 age-matched controls were re-examined at a median age of 2.9 years for hepatitis A and B, CMV, EBV, and HIV infections. This retrospective study revealed no differences between transfused children and controls. HBsAg and anti-HIV were not detected. Two children were suspected of having hepatitis C. In both groups the incidence of positive CMV and EBV serologies was significantly increased in children from Mediterranean countries. Red cell concentrates were less frequently associated with CMV infection. These results confirm the exclusive recruitment of volunteer donors from a "healthy", mainly rural population and support the preferred use of red cell concentrates in paediatric patients.

Antibodies, Viral↗