The cationic dye Alcian blue has been used to demonstrate protein-polysaccharide com plexes at the level of nerve tissue (1,2). The results obtained in the capillary wall when this dye was applied to mouse brain and examined in the electron microscope are the object of the present report.
The central nervous system of normal adult mice was fixed either by vascular perfusion or by immersion with 4% glutaraldehyde-0.1M sodium cacodylate-0.1 M sucrose at pH 6.8 followed by the same procedure using the same fixative but with the addition of 0.5% Alcian blue. After fixation, tissue was immersed in 1% OsO4-0.1M phosphate buffer pH 7.2, dehydrated by graded ethanol and embedded in Araldite. Ultrathin sections were doubly stained with uranyl acetate and lead citrate. The complete procedure has been denominated GABOUL method (3).
The submicroscopic study of cerebral and cerebellar capillaries showed the presence of a thin line of GABOUL positive material attached to the outer layer of the asymmetric luminal membrane of endothelial cells (endocapillary layer) (Fig. 1).