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Biomedical subjects

A Verniory

Publications and source records attributed to A Verniory.

At least 37 records · Page 2Linked to original sources
PubMed1975

A model for sieving of macromolecules by the glomerular membrane of the kidney.

The transport of water and of macromolecules across the glomerular membrane of the kidney depends on the membrane parameters (radius, length and number of pores) as well as on the hydrostatic and oncotic pressures on either side of the membrane. The filtration pressure decreases along the capillary loops from afferent to efferent end. Water and solute flows are thus given by a system of two differential equations. The sieving coefficient of the macromolecules is the ratio of solute to water flow. In the program described the differential equations are solved by the Runge-Kutta method (fourth order). Rosenbrock's method of minimization is used to adjust the theoretical to the experimental sieving coefficients. The pore radius, total pore area per unit of path length and conductance of the membrane, as well as the intracapillary hydrostatic pressure and its gradient can thus be determined.

Biological Transport↗
PubMed1975

The role of membrane parameters and of filtration pressure in the determination of the shape of the polyvinylpyrrolidone sieving curve. An in vitro and in vivo study.

The theoretical equations describing the transport of a solute across a porous membrane predict that the shape of the sieving curve (ratio of solute concentrations in filtrate and filtrand versus molecular size) depends not only on the porosity of the membrane but also on the filtration pressure. This has been verified experimentally on an artificial membrane (Amicon XM-50). This model has been used to interpret the effects of angiotensin II on the shape of the glomerular 125I PVP sieving curve. The mean effective filtration pressure is increased by the intrarenal perfusion of angiotensin II.

Angiotensin II↗
PubMed1973

Measurement of the permeability of biological membranes. Application to the glomerular wall.

The transport equation describing the flow of solute across a membrane has been modified on the basis of theoretical studies calculating the drag of a sphere moving in a viscous liquid undergoing Poiseuille flow inside a cylinder. It is shown that different frictional resistance terms should be introduced to calculate the contributions of diffusion and convection. New sieving equations are derived to calculate r and A(p)/Deltax (respectively, the pore radius and the total area of the pores per unit of path length). These equations provide a better agreement than the older formulas between the calculated and the experimental glomerular sieving coefficients for [(125)I]polyvinylpyrrolidone (PVP) fractions with a mean equivalent radius between 19 and 37 A. From r and A(p)/Deltax, the mean effective glomerular filtration pressure has been calculated, applying Poiseuille's law. A value of 15.4 mm Hg has been derived from the mean sieving curve obtained from 23 experiments performed on normal anesthetized dogs.

Biological Transport↗
PubMed1971

The measurement of glomerular filtration pressure from sieving data for macromolecules.

It is possible to derive the GFP from sieving data by two means and with the following qualifications: 1. Assuming the membrane isoporous, it is possible to calculate GFP by applying Poiseuille's law. The analysis of the sieving curve should then be limited to molecules with a radius between 21 and 41 A. 2. Assuming a log-normal distribution of pore radii, it is possible to obtain a value for GFP by computation. In this case the values for phi higher than 0.7 will not be considered in the calculation of sigmaE used to determine the most satisfactory adjustment of the calculated sieving curve to the experimental data. Although the second method allows a perfect adjustment of the curves, it gives more scattered results than the first for the calculation of GFP. However, a close correlation exists between both sets of results.

Animals↗