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L Bass

Publications and source records attributed to L Bass.

At least 55 records · Page 3Linked to original sources
PubMed1983

Saturation kinetics in hepatic drug removal: a statistical approach to functional heterogeneity.

Extraction of drugs and other substrates from blood passing through the intact liver (or other capillary beds), inferred from samples taken at the organ inlet and outlet, is influenced by two kinds of heterogeneity of capillaries: transverse and longitudinal with respect to the direction of blood flow. The transverse heterogeneity is exemplified by arteriovenous shunts of the extracting system; the longitudinal one by zones of liver function. These two clinically interesting examples are among transverse and longitudinal distributions of capillary properties that can be inferred from the way the organ transforms the influx of a substance (or of a pair of substances interacting via liver cells) into the outflux over a range of input concentrations or of rates of blood flow. Mathematical and statistical ideas recently developed to implement this program in terms of saturation kinetics of uptake are reviewed and elucidated in relation to key experiments, data analysis, and statistical hypothesis testing.

Animals↗
PubMed1983

A Bayesian analysis of capillary heterogeneity in the intact pig liver.

Published experimental data on the steady elimination of galactose by five isolated perfused pig livers are interpreted in terms of a model of hepatic uptake, in which the functional properties of the individual liver capillaries (hepatic sinusoids) are not identical. Kinetic parameters, including the Michaelis constant for the local enzyme-substrate interaction, are determined for each preparation on the basis of this model and are compared with previously obtained values based on an earlier model in which the sinusoids were assumed to be functionally identical. Posterior distributions of the degree of functional heterogeneity and the value of the Michaelis constant are given for the case where the livers are considered as a statistically homogeneous group. The degree of functional heterogeneity of the capillaries is found to be consistent with previous independent estimates.

Animals↗
PubMed1979

The physiologic basis for clearance measurements in hepatology.

Three hepatic clearance regimes (flow-limited, general, and enzyme-limited) can be defined from a model of hepatic perfusion-elimination relationships. Substances that can be used for clearance measurements can thus be classified into three categories according to the relation between their kinetic elimination constants (Vmax, Km) and hepatic blood flow. The pathophysiologic and clinical importance of the clearance regimes is discussed with special emphasis on the effect of changes in hepatic blood flow and liver function. The criteria for choosing test substances within each regime are stated. This choice depends on the object of study for a clearance measurement (blood flow, drug elimination, liver function). Only the enzyme-limited clearance regime is suited for direct assessment of quantitative liver function ('true clearance'), while the other regimes depend more or less on blood flow.

Animals↗