THE HISTOCHEMICAL DEMONSTRATION OF O-ACYLATED SIALIC ACID IN GASTROINTESTINAL MUCINS THEIR ASSOCIATION WITH THE POTASSIUM HYDROXIDE-PERIODIC ACID-SCHIFF EFFECT

O-Acylated sialic acids have been demonstrated histochemically in the epithelial mucins of the lower end of the gastrointestinal tract. The potassium hydroxide-periodic acid-Schiff effect has been shown to be due, in most areas, to the presence of these O-acyl esters on the polyhydroxy side chains of sialic acid. The esters have been shown to hinder the removal of the sialic acids by either neuraminidase or acid hydrolysis unless tissues were pretreated with alcoholic potassium hydroxide. It is suggested that substitution at the C4 position is responsible for their neuraminidase resistance.