Biomedical subjects

P Snabre

Publications and source records attributed to P Snabre.

3 recordsLinked to original sources

PubMed1990

Influence of altered phospholipid composition of the membrane outer layer on red blood cell aggregation: relation to shape changes and glycocalyx structure.

Reversible aggregation of erythrocytes was investigated after alteration of the phospholipid content in the membrane outer leaflet either by disturbance of endogenous transmembrane lipid asymmetry through changes in cellular free calcium, or by incorporation of exogenous lyso-derivatives. It was found that both calcium loading and lyso-phosphatidylcholine (LPC) addition induce a strong increase in red cell-red cell adhesive energy, whereas lyso-phosphatidylserine (LPS), added in the same amount as LPC, does not. Red cell morphological studies show differences in the shape change efficiency of LPS, LPC and calcium loading. However, it was further demonstrated that shape change is not directly responsible for the observed adhesive energy increase, since neuraminidase or trypsin treatment abolish this increase, even though the shape changes induced by alteration of phospholipid organization are not affected. The latter experiment strongly suggests that the red cell adhesive energy increase results from an alteration of the glycocalyx structure, which could be in turn a consequence of the shape change.

Calcium↗

PubMed1987

Cell disaggregation behavior in shear flow.

The disaggregation behavior of erythrocytes in dextran saline solution was investigated by a light reflectometry technique in a Couette flow and in a plane Poiseuille flow. Dextran concentration and mass average molecular weight of the polymer fraction strongly influence the shear stress dependence of the erythrocyte suspension reflectivity in shear flow and the critical hydrodynamic conditions (shear rate or shear stress) for near-complete cell dispersion. We investigated the influence of cell volume fraction and membrane deformability (heat treatment of the erythrocytes) on the reflectivity of the flowing suspension. This study indicates that the intercell adhesiveness and the shear stress are the only parameters that influence rouleau break-up in steady uniform shear flow, thus eliminating cell volume fraction and membrane deformability as possible factors. However, the critical cross-sectional average shear stress for near-complete cell dispersion through the flow cross-section is shown to depend on the flow pattern. The rotation of cells in a shear flow or the nonuniform shear field in Poiseuille flow indeed increases the flow resistance of cell aggregates. We give a theoretical description of the shear-induced cell disaggregation process in Couette flow and in plane Poiseuille flow. The quantitation of shear forces for cell dispersion provides a way for estimating the surface adhesive energy of the bridging membranes by fluid mechanical technique.

Cell Aggregation↗

PubMed1985

Aggregation of human red blood cells after moderate heat treatment.

The aggregation behaviour of normal and heat treated (48.4 degrees C, 48.8 degrees C, 49.5 degrees C) red blood cells (RBCs) suspended in dextran-saline solutions (Dx 70, Dx 173) was investigated by a laser light reflectometric method over a wide range of bridging energies. The characteristic times of rouleau formation were found to be increased after RBC heat treatment. The disaggregation shear stress is not significantly different between normal RBCs and heat treated RBCs. The loss of cell deformability is nevertheless shown to improve slightly the dissociation efficiency of the flowing liquid in a shear flow resulting in a small reduction of the disaggregation shear rate after heat treatment. Heat treatment is also shown to alter the structure of RBC network at equilibrium. These results indicate that heat induced alterations of erythrocytes only affects the mechanical properties of the cell membrane without significant changes in the macromolecular bridging energy.

Blood Viscosity↗