A blood capillaries-bridging cell type in adult mammalian brains

For the investigations we used coronal-sectioned series of adult brains from Wistar-rat, white mouse, cat, tree-shrew (Tupaia glis), and rhesus monkey (Macaca mulatta) in which the blood capillaries bridging cells (BCs) had been demonstrated by different silver-impregnation procedures (Golgi-Kopsch, Gallyas, Bär and Budi Santoso) and by complex staining with LFB + PAS + Hematoxylin, too. The BCs could be found in many cortical and subcortical brain areas of the 5 mammalian species under study. All investigated mammalian species showed the same morphological range of intercapillary bridges and BCs. Even between the individual brain regions as well as between the grey and white matter no difference could be determined. The BC is a small, generally spindle- or bell-shaped, rarely roundish cell bridging with its one or two smooth processes two capillaries ore precapillaries. The processes are usually attached to the blood vessels by disc- or pyramid-shaped thickenings. Usually, the bridged capillaries form bends with their crowns directed to one another. Only capillaries of the same stem were bridged. By reason of the striking morphological similarity of pericytes and BCs with regard to their soma shape, primary processes and chromatin-distribution patterns of their cell nuclei we consider the BCs as a subtype of pericytes. Our findings point to the following way of formation of the intercapillary bridges: The BC attached to the capillary either remains in this position and sends a process to another microvessel or withdraws from the vessel by means of a process and develops a second process at the opposite pole which grows towards a capillary.(ABSTRACT TRUNCATED AT 250 WORDS)