Chemical and histochemical studies of normal and diseased human gastrointestinal tract. II. A comparison between histologically normal small intestine and Crohn's disease of the small intestine.

Comparative chemical and histochemical studies were performed on formalin-fixed, surgical specimens of human small intestine from cases of Crohn's disease and normal controls. The sialic acids of the crude glycoproteins isolated from normal ileum were significantly less neuraminidase-susceptible and more C4 substituted (P less than 0.01) than those of the glycoproteins isolated either from normal upper small intestine (duodenum and jejunum) or from cases of Crohn's disease of the ileum. Fractionation yielded two major sialic acid-containing fractions, eluting from DEAE-cellulose with 0.2 M or 0.3 M sodium chloride. Both fractions contained fucose, galactose, glucosamine and galactosamine in addition to sialic acids both with and without O-acyl substituents at position C4 and/or in the side-chain (side-chain O-acylated sialic acids were also detected by histochemical procedures). The fractions differed significantly from one another with respect to the neuraminidase susceptibility of their sialic acids (P less than 0.01), the percentage of C4 (P less than 0.01) and side-chain substituted sialic acids (P less than 0.05), and the molar fucose-sialic acid ratio (P less than 0.05). The O-acyl substitution patterns of the sialic acids of both the 0.2 M and 0.3 M fractions of the upper small intestine glycoproteins differed significantly from those of the corresponding fractions from normal ileum, while the sialic acids of the 0.2 M fractions from Crohn's disease of the ileum differed significantly from normal with respect to neuraminidase susceptibility (P less than 0.01) and percentage C4 substitution (P less than 0.01); the 0.3 M fractions differed only in the percentage of sialic acids substituted at C4. The differences between the sialic acids from the normal and Crohn's disease specimens were shown to be independent of either the anatomical origin of the specimen or the histopathological sub-group of the Crohn's disease specimens; no significant differences were noted between the sub-groups but all the sub-groups differed from normal.