Alteration in the rheologic properties of Plasmodium knowlesi--infected red cells. A possible mechanism for capillary obstruction.

Red cells parasitized by Plasmodium knowlesi concentrate within the microcirculation of many organs including cerebral capillaries in rhesus monkeys. The possibility that P. knowlesi could alter the rheologic properties of red cells so that they are trapped within capillaries was investigated in the present study.

Abnormal rheology of oxygenated blood in sickle cell anemia.

The viscosity of oxygenated blood from patients with sickle cell anemia (Hb SS disease) was found to be abnormally increased, a property which contrasts with the well recognized viscous aberration produced by deoxygenation of Hb SS blood. Experiments designed to explain this finding led to considerations of deformation and aggregation, primary determinants of the rheologic behavior of erythrocytes as they traverse the microcirculation. Deformability of erythrocytes is in turn dependent upon internal viscosity (i.

Blood viscosity: influence of erythrocyte aggregation.

The addition of purified canine or bovine fibrinogen to suspensions of canine erythocytes in Ringer solution caused an increase in viscosity and the formation of aggregates of erythocytes. Both of these effects became increasingly pronounced as the fibrinogen concentration was raised, and they approached plateaus with 1 gram of fibrinogen per 100 milliliters. An increase in shear rate (or shear stress) reduced both the effect on viscosity and the aggregate size.

Blood viscosity: influence of erythrocyte deformation.

Suspensions of canine and human erythocytes hardened with acetaldehyde differ from the suspensions of normal erythrocytes with respect to their rheological behavior. Normal erythrocytes can be packed by centrifugation so that the sediment volume is nearly 100 percent cells, but the hardened erythrocytes (RBC's) can be packed only to approximately 60 percent cells. At the same cell percentage the viscosity of the hardened RBC suspension is higher than that of the suspension of normal erythocytes.