[Ultrastructure of cellular features permitting the regulation of human cerebral cortex microcirculation]

Microglia-like cells and endothelial cells may influence capillary blood output. 1) Microglia-like cells are sometimes interposed between two endothelial processes with which they are nexus-linked. In this position, they protude in vascular lumen which is considerably reduced. 2) Endothelial cells present no contractile filaments but their nucleus and surrounding cytoplasm may protude in vascular lumen, constituting a "coussinet-like" structure. Thus, regulation by specialized structures observed by Legait in brain arteries seems to occur even in the smallest ramifications of brain cortical vessels.