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Biomedical subjects

W J Dorson

Publications and source records attributed to W J Dorson.

At least 19 recordsLinked to original sources
PubMed1989

Metabolic adjustments to dynamic hypoxic hypoxemia in feline brain tissue.

Three different metabolic models were incorporated in a compartmental simulation of brain tissue pO2 response to rapid changes in arterial pO2. The first was the frequently utilized constant metabolism assumption. The second model was a 4-step kinetic simplification of glucose conversion to CO2 with an intermediate reversible reaction of pyrovate to lactate. The most sophisticated model was a new 11-step reaction scheme with the same start and end points accounting for glycolysis, the tricarboxylic acid cycle, and oxidative phosphorylation. A unique representation was derived for the oxygen consumption depending on reduced cytochrome a3+(3) consistent with diverse observations in the literature. The theoretical predictions were compared to previously published cortical tissue pO2 recordings from detailed experiments with pentobarbital anesthetized cats. The 11-step metabolic model invariably provided the best match between the theoretical calculations and the observed responses. These results indicate that cellular metabolism rapidly adjusts to changes in O2 in a manner which reduces the tissue pO2 fluctuation. In concert with the large compensatory arterial blood flow response there was extensive damping of intracellular pO2 compared to arterial O2 changes.

Animals↗
PubMed1979

Present status of the hemofiltration/molecular separation artificial kidney.

The hemofiltration/molecular separation (HFMS) artificial kidney concept, first proposed over a decade ago, involves continuous ultrafiltration from the blood stream followed by cleansing of the filtrate, with subsequent return to the body. Thus, the system is completely self-contained and portable. During recent preclinical trials on nephrectomized canines, HFMS was better than hemodialysis (HD) in several important ways. First, the removal or clearance of middle molecules was better with 0.34 m(2) HFMS than with 1 m(2) HD. Significant phosphate clearance was achieved, and the removal rate for creatinine was the same as that for urea. This uniform clearance extends to even higher molecular weight solutes and could potentially result in improved patient response. It mimics the real kidney, whereas membrane-limited dialysis undergoes a logarithmic decrease of clearance with molecular weight. This is due to the fact that solute transport through the membrane involves solution into its matrix followed by diffusion, and solute diffusivity decreases with molecular volume. In order to achieve this potential for hemofiltration-based systems, however, there are stringent requirements on both the membrane and the plasma proteins allowed to accumulate on the membrane surface.

Animals↗
PubMed1975

Ultrafiltration of molecules through deposited protein layers.

A naturally deposited protein layer is shown to be highly compressible as witnessed by its resistance to the passage of both water and dissolved molecules. This protein layer can easily be much more important than the underlying membrane. Hydrodynamic methods can be employed to control this protein layer, even to the extreme of its extinction in a continuous flow system. The rejection properties are shown to be a function of both the tracer molecular weight and type. Some of the physical property variations are reviewed for plasma amd serum as a function of protein concentration.

Amino Acids↗
PubMed1975

Correlation of pulsed flow vortex shedding.

Flow visualization experiments were performed leading to the development of a correlation for the vortex shedding from indentations perpendicular to the main stream flow and caused by the addition of a pulsed flow component. The peak pulse flow rate required for vortex shedding greatly exceeds the condition for flow reversal in the channel when the steady flow rate is low while the vortex shedding occurs close to the flow reversal condition when the steady flow rate is very high. The empirical correlation should be useful in assessing the practicality of utilizing this technique to augment mass transport in membrane separation processes. Vortex shedding provides substantial transport augmentation in the ultrafiltration of a flowing plasma stream, and recommendations for further study are outlined to improve our understanding of this phenomena.

Blood Flow Velocity↗