Detection with the light and electron microscopes of a carbohydrate - rich cell coat at the surface of cells in the rat.

Over fifty cell types were examined under the light microscope after staining of rat tissues with the periodic acid - Schiff technique for detection of glycoproteins, and colloidal iron at low pH for detection of acidic carbohydrates. With both techniques, nearly all cells investigated were outlined by a thin band of stained material. In epithelia, the stained layer was usually interrupted where two adjacent plasma membranes fused to form tight junctions. This finding indicated that the layer was not part of the plasma membrane itself but rather a "cell coat" located on its outer surface. [...