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Biomedical subjects

O S Hum

Publications and source records attributed to O S Hum.

9 recordsLinked to original sources
PubMed1985

Thrombogenetic studies of bioprosthetic heart valve surfaces. I. In vitro platelet adhesion in a static system.

Contact angle measurements, histological examinations and platelet adhesion tests on native and glutaraldehyde-treated porcine aortic valve leaflets, are reported. Contact angles measured with water or saline on native and treated leaflets do not differ appreciably. Values of less than 10 degrees for both the dry and wet leaflets were observed. Histological examination of the native and fixed tissue surfaces was carried out with both optical and scanning electron microscopy. Native leaflet surfaces appeared to be smoother with longer and straighter fibres beneath the surface than treated leaflets. Platelet adhesion tests were performed with fresh, non-anticoagulated human whole blood as well as with platelet suspension. Static platelet adhesion tests were carried out by depositing droplets of blood on the test surface. The blood droplets were washed off after a contact time of 2 minutes for whole blood and up to 32 minutes for platelet suspension. The adhering platelets were microscopically observed and counted. The platelet density on the native leaflets was found to be significantly higher than on the treated tissues. However, the platelet density did not vary with glutaraldehyde concentration in the range from 0.2 to 1.0% (v/v).

Animals↗
PubMed1982

Effect of surface roughness on platelet adhesion under static and under flow conditions.

Normal blood clots when exposed to surfaces other than endothelial. Various unsuccessful attempts have been made to find a synthetic material that is compatible with blood. Both platelets and clotting factors are involved in thrombosis at foreign surfaces. The authors are concerned with platelet adhesion as a first step in thrombus formation. The determination of the number of platelets adhering per unit area, therefore, appears to be a useful criterion for the choice of appropriate biomaterials contacting blood. However, laboratory tests are often carried out with specially prepared, well-defined biomaterials with a smooth surface, whereas biomaterials in clinical use may have a variable degree of roughness. In this paper the authors present data on platelet adherence to a hydrophilic (glass) and to a hydrophobic (silane) material, with smooth and rough surfaces. Additional data are presented that document the extent of platelet adhesion to a wide range of smooth polymer materials having a large variation in surface hydrophobic quality. There was no difference in platelet adherence between the smooth and rough surfaces when tested under static conditions. When the surfaces were tested in a laminar flow cell, the addition of roughness caused a decrease in platelet adhesion on the hydrophilic surface and an increase in platelet adhesion on the hydrophobic surface.

Animals↗
PubMed1980

Kinetic and thermodynamic aspects of platelet adhesion from suspension to various substrates.

Kinetics of platelet adhesion from suspension to various substrates leads to Langmuir isotherm types of curves, both for suspensions in which the platelets were isolated by means of gel filtration as well as by centrifuging and washing. The level of platelet adhesion increases with increasing surface tension of the substrate. These results cannot be explained on the basis of the theoretical transport model of Ruckenstein et al. The plot of the platelet adhesion at equilibrium vs. gamma SV brings the observations in yet closer agreement with thermodynamic predictions based on free energy calculations than was found previously for the adhesion of platelets after short contact times between platelet suspension and substrate.

Animals↗
PubMed1977

Platelet adhesion to solid surfaces. The effects of plasma proteins and substrate wettability.

Platelet adhesion tests were performed using protein-free washed pig platelet suspensions in conjunction with a simple open-static method on smooth, well-defined protein-coated glass and polymer surfaces and bare glass and polymer surfaces. A normalization technique was introduced in an attempt to correct day-to-day variations in platelet reactivity. Protein coatings reduced platelet adhesion (to glass as well as polymer surfaces) to such a low level that the platelet density on one protein/substrate combination could not be distinguished from that on any other protein/substrate combination. Specifically, albumin and fibrinogen behaved identically regardless of the substrate on which they were coated. The addition of albumin and gamma-globulin to the platelet-suspension also significantly reduced platelet adhesion to glass surfaces. Whereas the extent of platelet adhesion from protein-free suspensions to bare glass and polymer surfaces depended on their wettability, the presence of specific chemical groups in the proteins, such as (-CONH-), may have an overriding effect on platelet adhesion to solid surfaces.

Blood Proteins↗