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Biomedical subjects

M Bres

Publications and source records attributed to M Bres.

7 recordsLinked to original sources
PubMed1986

Regurgitation in gorillas: possible model for human eating disorders (rumination/bulimia).

Regurgitation and reingestion behavior in gorillas is compared with two human disorders, rumination and bulimia. Eighty-four percent of captive gorillas that are more than 5 years old regurgitate and reingest. Comparisons are made on the basis of ontogeny, context, motor pattern, and intervention. There are more similarities between regurgitation and reingestion and rumination than between regurgitation and reingestion and bulimia. Regurgitation and reingestion resembles bulimia in parental/infant separation, lack of eating control, methods of induction, and some aspects of motor pattern. Regurgitation and reingestion resembles rumination in disrupted maternal/infant communication, context of the behavior (enjoy the taste of the regurgitant), several aspects of motor pattern, and treatment (increased food volume).

Animals↗
PubMed1985

Stochastic simulation of Taylor's dispersion in the airways.

A stochastic simulation was devised in order to obtain a more correct solution of the phenomenon of convection combined with axial and radial diffusion, which is also called Taylor's dispersion, as it could occur in the pulmonary tract. The fit with Aris' moments which can be deemed as a reference since they are obtained analytically without approximation, was quite good. On the other hand, Taylor's solution usually led to large discrepancies with these moments. Taylor's stipulation that his solution be used only under certain conditions was therefore confirmed. This solution is not applicable in the lungs.

Diffusion↗
PubMed1982

Computer simulation of ternary diffusion in distal airways of the human lung.

Gaseous diffusion plays a fundamental role in the terminal generations of airways for respiratory physiology. It has been proposed as a prime mechanism underlying stratified inhomogeneity in the alveolar space. Nevertheless, the diffusion phenomenon in the lung has often been studied using Fick's law which is only valid for binary diffusion. Under conditions of more than two gases in a mixture, the appropriate equations for diffusion are those of Stefan. In respiration, diffusion involves at least three gases (O2, CO2 and N2), and in physiological experiments complex mixtures including heavy or light gases (SF6, He) are often added to enhance the effect of diffusion. We present in this paper the features of ternary diffusion and solve the appropriate equations for the non-steady state by a finite difference method. The simulation was performed using two models derived from the anatomical data of Weibel and Hansen-Ampaya. Moreover, four initial conditions most often encountered during current respiratory physiology tests, were used for the computations. Therefore in these four situations, O2-N2-He, O2-N2-Ar, O2-N2-SF6 and O2-N2-CO2 combinations were used. Our results showed that for each case mentioned above the oxygen acted differently in ternary diffusion owing to the specific nature of the components of each mixture. Moreover, the behaviour of each component in ternary diffusion was very different from that of binary diffusion. However, this difference may be negligible when the subject breathed normal air.

Computers↗
PubMed1980

On-line computation of dead space and nitrogen clearance curve.

This work is aimed at getting on-line values of dead space and nitrogen clearance curves during washout experiments performed during continuous oxygen inhalation. An analog computer was built and connected to standard numeric implements, sending to them the processed signals from the measuring instruments. This solution seems to give at the same time good accuracy and good versatility at the lowest cost both in time and money.

Computers↗
PubMed1977

Three-gas diffusion--experimental and theoretical study.

The purpose of this work was to compare experimental diffusion among three gases with the solution given by Stefan's equations to understand better how this phenomenon can work in the multicomponent alveolar gas. Experiments were performed in a cylinder full of beads open at one end and closed at the other in which a mixture of oxygen with helium or argon or sulphur hexafluoride could diffuse with ambient air through the open end. We solved Stefan's equations for the non-steady state by a finite-difference method and applied them to our experimental conditions with diffusion coefficients we had measured in binary experiments. We then made experiments and calculations to show the influence of the beads on gas transport. Provided that diffusion is the only phenomenon, experimental and theoretical curves are very close together. Moreover beads nearly stop motions due to vortices or small differences of density. We conclude that: Stefan's equations should replace Fick's equations when more than two gases are involved. One should bear in mind the possible influence of gravity and devise diffusion experiments accordingly. In small spaces such as alveoli the influence of gravity must be negligible compared to diffusion.

Diffusion↗