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Biomedical subjects

W A Hunt

Publications and source records attributed to W A Hunt.

At least 109 records · Page 6Linked to original sources
PubMed1969

Calculations of pulsatile flow across bifurcations in distensible tubes.

A simple method is given for extending across junctions the numerical methods previously used to study fluid flow in nonuniform, nonbranching, distensible tubes. Calculations with this method suggest that the ratio of downstream to upstream cross-sectional areas and the pressure wave velocity ratio in mammals are optimal for energy transfer across the junction.

Biophysical Phenomena↗
PubMed1968

On the shape of the erythrocyte.

A model is postulated which attributes the distinctive biconcave shape of the human erythrocyte to a balance of forces acting on the membrane. The forces considered are electrostatic forces due to a charge distribution on the membrane, a hydrostatic pressure difference acting across the membrane, and forces arising from a constant tension in the membrane. A numerical study indicates that the postulated model will produce an equilibrium shape which is very similar to the observed shape of the human erythrocyte.

Cell Membrane↗
PubMed1966

A theory of fluid flow in compliant tubes.

Starting with the Navier-Stokes equations, a system of equations is obtained to describe quasi-one-dimensional behavior of fluid in a compliant tube. The nonlinear terms which cannot be shown to be small in the original equations are retained, and the resulting equations are nonlinear. A functional pressure-area relationship is postulated and the final set of equations are quasi-linear and hyperbolic, with two independent and two dependent variables. A method of numerical solution of the set of equations is indicated, and the application to cases of interest is discussed.

Biophysical Phenomena↗
PubMed1966

Numerical hydrodynamic calculations of catheter characteristics.

The theory of fluid flow in compliant tubes developed in a previous paper is applied to a catheter, and the results of various calculations are compared with experiment. When a parabola is used for the unknown velocity profile, the calculated gains are too high. Agreement is slightly improved by using more reasonable profiles. It is shown that there exists a functional relationship between the parameter gamma and the nondimensional parameter alpha(10) which gives reasonable agreements with all the experimental data considered. The theory of Womersley is applied to the catheter, and the calculated gains are larger than those observed experimentally. A form for the frictional force suggested by Lambossy is used in some further calculations.

Biophysical Phenomena↗
PubMed1966

Peaking of the pressure pulse in fluid-filled tubes of spatially varying compliance.

Calculations are made for a fluid-filled tube with characteristics approximately those found physiologically. The pressure variation, diameter, and compliance at the input end are as measured by Lawton for the abdominal aorta of a dog. After a 30 cm-long input section of constant k (=dp/dA), the tube is taken to stiffen by approximately the amount measured by Patel et al., i.e., k increases by a factor of 5 over the next 40 cm. The cross-section remains constant. Pressure and velocity wave forms are calculated at 8 stations spaced at 10-cm intervals down the tube. The pressure pulse leading edge is found to become steeper in the stiffening section. The peak height of the pressure pulse is found to increase by about 50% and the velocity pulse to decrease by about 30% as the disturbance propagates over a distance of 70 cm. These values agree qualitatively with the experimental physiological values given by McDonald. Most of the pressure peaking takes place upstream of the stiffening section.

Animals↗
PubMedDate not supplied

Regional differences in high-affinity choline uptake in brain after acute and chronic treatment with ethanol.

A single dose of ethanol has been shown to affect both striatal and hippocampal high-affinity choline uptake. This effect is probably mediated through effects of ethanol on acetylcholine release. Choline uptake has also been shown to be altered in ethanol-dependent animals, and these effects may be coupled to alterations in dopamine neurons which are produced by chronic ethanol feeding and withdrawal.

Acetylcholine↗
PubMedDate not supplied

Ethanol-induced taste aversions: lack of involvement of acetaldehyde and the area postrema.

Two experiments were run to evaluate the role of acetaldehyde and the area postrema in the acquisition of an ethanol-induced conditioned taste aversion. An ethanol-induced taste aversion was observed in male Sprague-Dawley rats with a dose of 4 g/kg. PO, but not after doses of 1 or 2 g/kg. Pretreatment with 4-methylpyrazole (8 mg/kg, IP), which itself did not induce an aversion as compared to pyrazole (68 mg/kg, IP) that did, and/or prior application of lesions of the area postrema had no influence on the development of an ethanol-induced taste aversion. The results indicate that ethanol-induced taste aversion learning does not result from the metabolism of ethanol to acetaldehyde and does not, like other toxins, involve the mediation of the area postrema.

Acetaldehyde↗
PubMedDate not supplied

A role for behavioral sensitization in uncontrolled ethanol intake.

The processes that underlie the transition from controlled to uncontrolled consumption of ethanol are unknown. Behavioral sensitization is proposed as one of these processes and occurs with repeated administration of psychomotor stimulants whereby both behavioral and neurochemical responses to the drugs are progressively enhanced. Because ethanol shares some actions in common with these drugs, chronic exposure to ethanol may intensify its reinforcing properties. The effect of ethanol on several behavioral models suggests that behavioral sensitization may develop especially in the presence of environmental cues. Thus, a research opportunity exists to study factors that contribute to an increasing probability of progressively higher ethanol consumption. Knowledge of these factors will lead to a better understanding of why some people drink uncontrollably.

Alcohol Drinking↗