PETECHIAL HEMORRHAGE IN THE CILIARY PROCESSES OF THROMBOCYTOPENIC RABBITS - ELECTRON-MICROSCOPIC STUDY

Thrombocytopenia was induced in rabbits by giving 6.6-Gy γ-irradiation to their whole bodies. The animals were in good condition 10 days later when the level of circulating platelets was below 15,000/μl of blood. Petechial bleeding was found principally in the ciliary processes of the rabbits' eyes. Ultrastructural examination of the bleeding vessels revealed changes in the endothelium: an increased number of vacuoles and vesicles, and multiple luminar projections. No such changes were found in the vessels of the ciliary body base or in the iris. The diapedesis of red cells apparently took place through narrow passages in the endothelial cells. Interendothelial cell junctions appeared normal and no large discontinuities in the endothelium were found in the sections studied. When a similar dose of irradiation was directed toward an animal's head region with the rest of the body shielded, the ultrastructure of the ciliary processes did not differ from that of normal animals. © 1979.