Biomedical subjects

M Nyssen

Publications and source records attributed to M Nyssen.

At least 19 recordsLinked to original sources

PubMed1991

[Statistical value of the various mathematical models in rhinomanometry].

By means of rhinomanometry, analogue physiological transnasal pressure and corresponding flow signals are simultaneously recorded during quiet nasal breathing. In order to describe the sigmoid shaped pressure/flow curves or relationship, several mathematical models have been developed. In this study, the authors wanted to demonstrate which model best describes the curvilinearity of the pressure/flow curves. By their approach, they found that polynomial models like delta p = K0 + K1V + K2V2 as well as the Broms' polar coordinate model best fit the recorded pressure/flow data. Since the parameters and exponents of such a model characterize the degree of laminar and turbulent behaviour of transnasal flow, a diagnostic potential may be offered in the future, to qualify and quantify the phenomenon of nasal obstruction.

Humans↗

PubMed1991

Optimal sample frequency in computerized rhinomanometry. Development and method.

The authors studied the pressure/flow signals generated during active anterior rhinomanometry of 25 subjects, presenting a normal transnasal breathing. By means of a Fourier transformation, the frequency content of these signals was analyzed. This investigation demonstrated clearly that signals with a frequency of more than 50 Hz no longer yield any further information about the transnasal ventilation.

Adult↗

PubMed1985

Specific cytochemical stains in the image analysis of subcellular organelles.

This paper describes our work concerning densitometry and morphometry of subcellular structures in thin sections. The techniques of automatic image analysis were applied to light and electron microscopic observations of enzymatically stained lysosomes, renal brush borders and mitochondria (in human and rat kidney) and peroxisomes (in human liver). To obtain significant measurements of the enzymatic activity, specific staining techniques were developed and applied, including an improved staining of acid phosphatase for lysosomes. Optical densities were obtained by videodensitometry and electron densities of peroxisomes were obtained by digitizing and processing scanning transmission electron microscopic images. In subsequent steps, delineations and parameter estimation are performed by software. Included was an examination of delineation techniques, which showed improved results from the use of a newly developed local boundary search algorithm. The combination of these techniques was used to study changes in peroxisome and lysosome compartment in liver and kidney, some results of which are also reported.

Acid Phosphatase↗

PubMed1984

A computerized mathematical model of arterial thrombi recorded by light transmission.

For several years, the formation and evolution of thrombi in small arteries of rats has been quantitatively studied at the laboratory of PHYSIOLOGY and PHYSIOPATHOLOGY at the V.U.B. Global size parameters can be determined by projecting the image of a small arterial segment onto photosensitive cells. The transmitted light intensity is a measure for the thrombotic phenomenon. This unique method permitted extensive in vivo study of the platelet-vessel wall interaction and local thrombosis. We actually attempt to refine the spatial resolution of these measurements in order to get information on texture and form of the thrombotic mass at any stage of its evolution. Therefore a thorough understanding of how light propagates through non hemolyzed blood is essential. Application of results from Twersky's multiple scattering theory, combined with appropriate border conditions and parameter values was attempted. It is well known that the erythrocytes are mostly aligned in the direction of the blood flow. In order to explain the measured intensity profiles, we had to postulate alignment in the plane perpendicular to the flow as well. The theoretical predictions are in good agreement with the experimental values if we assume almost perfect alignment of the erythrocytes such that their short axes are pointing in the direction of the center of the artery. Conclusive evidence of the interaction between local flow properties and light transmission could be found by observing arteries with perturbated flow.

Animals↗

PubMed1975

[Detection and determination of alpha-feto-protein in human serum. Use in hepato-gastroenterology].

The presence of alpha-foeto-protein (A.F.P.) was sought in the serum of 520 patients, suffering from various digestive disorders, using two methods: double immuno-diffusion and counter immuno-electrophoresis on cellogel--a more sensitive technique. A.F.P. was detected on 90 of the 520 patients. A.F.P. was measured by radial immunodiffusion or by electro-immunodiffusion on cellogel. Study of the values obtained in various kinds of hepatic disorders indicates that high levels (more than 10 mg/1) are seen almost solely in association with primary carcinoma of the liver, whilst lower levels (less than 10 mg/1) are found in the majority of hepatic disorders, without having any precise significance. The interest of the clinician should therefore be directed not towards the presence or absence of A.F.P. but to its level, which alone is significant.

Adenoma, Bile Duct↗

PubMed1973