Platelet adhesion to artificial surfaces: consequences of flow, exposure time, blood condition, and surface nature.
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Artificial Organs↗
Biomedical subjects
E F Leonard
Publications and source records attributed to E F Leonard.
Light microscopic visualization of plasma intrusion into microporous hollow fibers.
An immunohistochemical method has been developed to describe the pattern and extent of plasma intrusion into hydrophobic microporous membranes. Even though these membranes have very high calculated capillary intrusion pressures, they fill with plasma, sometimes during short-term use and routinely over the time spans characteristic of extracorporeal membrane oxygenation applications. It is not clear whether intrusion is widespread and caused by operating procedure or general properties of the membrane or localized and caused by defects in the membrane. The staining method reported here depends upon the fact that plasma proteins appear on pore walls only where the pores have been contacted by plasma. The selected plasma protein can be revealed, in sections viewed under the light microscope, by the immunospecific attachment of colloidal gold particles covered with an appropriate antibody. The particles are made visible by using them to nucleate precipitation of silver. Data are reported for Celanese polypropylene hollow fibers: 1) uniformly wetted with plasma; 2) locally intruded by centrifuging a plasma filled fiber covering a range of radii in a hematocrit centrifuge; and 3) locally intruded by wetting out the fiber with a "microdrop" of alcohol followed by saline, then plasma. In all instances, intruded and unintruded regions were distinguished clearly and unequivocally.
Biocompatible Materials↗
A dynamic method for setting roller pumps nonocclusively reduces hemolysis and predicts retrograde flow.
In general, roller pumps are set almost occlusively despite evidence that nonocclusive settings cause less hemolysis. Almost-occlusive settings are used because of the concern that forward flow would not be accurately known if retrograde flow were allowed to occur through a nonocclusive gap. This article presents a dynamic method for setting roller pumps nonocclusively that overcomes the many difficulties of the "drop method" for setting occlusion. Studies were conducted to determine the effect of nonocclusive settings on pump flow and hemolysis generated; the results suggest that roller pumps can and should be set more nonocclusively than is the currently accepted standard to reduce pump related hemolysis without greatly affecting pump performance. The dynamic method allows retrograde flow to be easily predicted and corrected with an increase in pump speed.
Extracorporeal Circulation↗
Controlling receptor-ligand contact to examine kinetics of T cell activation.
A method for controlling the contact of cell-surface receptors with immobilized ligands has been developed. Cells are trapped in an asymmetric liquid film that can be quantitatively thinned by reducing the film's capillary pressure. Ligands adsorbed to the liquid-solid interface are forced into increasingly tighter contact with the cells as the air-liquid interface is drawn down. Controlling the degree of thinning allows study of repulsive forces, and controlling its time course produces a definite time 0 for analyzing signal transduction. This system was tested by examining the time course of calcium mobilization in T cells upon activation with anti-CD3 antibody at different dilutions and ionic strengths. The averaged calcium transient of the responding cells was essentially the same for each condition. However, the fraction of responding cells decreased with anti-CD3 dilution, and indicated that the critical ligand density for T cell activation lies between approximately 35 and 70 molecules of anti-CD3 per microm2. Decreasing the medium's ionic strength from the normal value of 157 mM to 57 mM did not affect either the average calcium response profile or the fraction of responding cells, but strongly affected receptor-ligand contact, decreasing the percent of spontaneous activation from 38% to 5%. Such an imposed decrease sets the stage for film thinning to impose much greater control of receptor-ligand contact.
Animals↗