The state of the microcirculatory bed after total ischaemia of the brain. An experimental ultrastructural study.

The study was focused on the changes in morphological structure of cerebral microcirculation after two stages of 7 min dog's total brain ischaemia followed by 24 recirculation. In the first experimental group (brain blood pressure 2.5-3.0 kPa), there was observed ultrastructural picture of damaged microvessels, including dilated and irregularly shaped lumens, thick finger-like endothelial processes, dark osmiophilic cytoplasm of the endothelial cells with light spaces, clusters of ribosomal structures, impairment of endoplasmic reticulum and mitochondria, dilated tight junctions, irregular and thickened basement membranes. The alteration of astrocytes consisted of accumulation of beta-glycogen particles and lipofuscin and altered lysosomal structures. On the other hand, in the second experimental group (brain blood pressure 1.0-1.5 kPa) the signs of impaired microcirculation were found. Type A pattern of vessel damage was delineated by dilated capillary lumen, despite the presence of marked perivascular oedema. Type B represented the no-reflow phenomenon. Type C was defined by a conspicuous lobular nucleus of endothelial cells obstructing the lumen of the capillary. Type D was characterized by ischemically damaged erythrocytes, despite the adequate perfusion fixation. Finally, type E included necrotic endothelial cells and endothelial blebs.