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. The data suggest that fibrinogen causes an increase in blood viscosity and a departure from Newtonian behavior by interacting with erythrocytes to form cell aggregates which can be dispersed by shear stress.

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. An increase in shear stress deforms the normal erythocytes and lowers the suspension viscosity, but has no influence on the viscosity of the hardened cell suspension. In blood with high cell percentages, the shear deformation of normal RBC's plays an important role in reducing viscosity and facilitating flow at high shear stresses.

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The intravenous injection of Escherichia coli endotoxin (3 mg/kg) into dogs caused an increase in lymph flow from the thoracic duct. The lymph concentrations of macromolecules (dextran with mol. wt. of 250,000, albumin-I131, and endogenous proteins) increased and the lymph-to-plasma ratios approached 1. These results indicate that E. coli endotoxin causes an increase in capillary permeability to both the fluid and the macromolecules in plasma. The increase in capillary permeability for albumin-I131 was greater than that for dextran with mol. wt. of 250,000. Eighty minutes after endotoxin, the lymph flow returned to normal, but albumin-I131 and dextran injected at this time were still transferred into the thoracic duct lymph at enhanced rates.