An electron microscopic study of the vascular factor in hemorrhagic diathesis.

Experimental diapedetic hemorrhage (oozing) was produced by streptokinase in rabbits and the fine structures of mesenterial microvessels were observed. Diapedesis of erythrocytes was seen in the venular side of microcirculation. On the contrary, no diapedesis was seen in true capillary on the arteriolar side. Sticking of erythrocytes to venular wall prior to diapedesis was proved, electron microscopically, to be the state in which red blood cells were trapped in the gaps on the endothelial junction. It was considered to be the morphological findings of the prediapedetic state. Erythrocytes passed through gaps on the endothelial junctions with high plasticities under any diapedetic conditions mentioned above. Furthermore, in author's experiments by ruthenium red staining, erythrocytes were observed just passing through the basement membrane under electron microscopy, in spite of its high speed process. It was found that the basement membrane is a very important barrier in erythrocyte diapedesis.