An ultrastructural study of the complex carbohydrates of the mouse posterior vitreoretinal juncture

The content and distribution of complex carbohydrates of the posterior vitreoretinal juncture of the mouse eye were examined by electron microscopy. Eyes were fixed 24 hr or 192 hr in glutaraldehyde or glutaraldehyde and cetylpyridinium chloride (CPC) and then block-stained with cationic dyes. Globular material of intermediate electron density was found in the basement membrane of the retina and on collagen fibrils in the vitreous cortex with CPC fixation and disappeared after Streptomyces hyaluronidase digestion. More of this material was found at the juncture of the basement membrane and the vitreous body with alcian blue than with the other cationic dyes after the shorter fixation period. After prolonged fixation, all of the cationic dyes revealed a thick layer of globular material on the basement membrane. A finely filamentous network associated with the globular material was revealed by glutaraldehyde fixation and alcian blue staining. Some laminated bodies were found at the vitreoretinal juncture after block-staining. Neither the finely filamentous material nor the laminated material was sensitive to the hyaluronidase. It is suggested that the globular material is hyaluronic acid, which is more labile along the basement membrane than toward the inner vitreous cortex. The finely filamentous network may be formed of oligosaccharide chains associated with vitreous proteins. The laminated bodies may be formed of lipid and complex carbohydrates of an otherwise uncharacterized mixture. The various complex carbohydrates form parts of a vitreoretinal-juncture layer that may participate in the known chemical, cellular, and mechanical barrier functions of this region.