Effect of x-irradiation and beta emanation on circulation in the hamster cheek pouch.

The small venules of the hamster cheek pouch were rendered susceptible to hemorrhage by total body x-irradiation, cheek pouch x-irradiation and beta emanations from strontium-90 glass beads imbedded in the cheek pouch, as determined by negative pressure and moccasin venom tests. Petechiae were formed without vessel rupture and ceased without formation of platelet plug or fibrin clot. Increased susceptibility to petechiae preceded thrombocytopenia. Endothelial damage was indicated by increased leukocytic adhesiveness to walls of venules. Vasodilation, tortuosity, newlyformed capillaries, and occasional "sausage-shaped" segments of constriction in arterioles were characteristic vascular responses. Near death, erythrocytes circulated in aggregates varying from typical rouleau formation to discrete masses, resembling "sludged blood" but without formation of occluding thrombi.