Ultrastrual Study on Changes of the Capillaries in Experimental Brain Infarcts of Rats

ABSTRACT

Experimental brain infarcts in rats were studied light and electron microscopically to investigate the factor(s) controlling contrast enhancement on CT scans of the infarcts. Brain infarction was induced by injection of fine autologous blood clots through the right internal carotid artery and the affected brain was processed for examination 1 day, 2 day, and 1, 2, 4, 6 and 8 weeks after the injection. The lesion of early, necro - degenerative stage(1 day to 1 week) showed structural disintegration of capillary endothelial cells with dissolution of tight junctions. The lesion of middle, regenerative stage(2 to 4 weeks) was characterized by proliferation of new capillaries, They had well - formed tight junctions and continuos basement membrane. The endothelial cells, however, had intraluminal villous projections and many pinocytotic vesicles, suggesting an increased permeability. The capillaries matured at late, reparative stage(8 weeks), appearing similar to those in normal brain tissue except that they were loosely surrounded by astrocytic foot processes. It was presumed that the ncreased permeability of new capillaries might play an important role for contrast enhancement observable clinically during the middle stage(2 to 4 weeks).