Abstract:Two of the fractions obtained by density gradient centrifugation of Tris-disrupted brush borders from hamster intestinal mucosa have been identified as the microvillus cores and their surrounding membranous coats, respectively. This identification has the following morphological basis. In shadowed preparations one fraction (cores) appears as rounded, compact rods, and thc other fraction (coats) appears as flattened shects. Both rods and sheets have dimensions appropriate to the idcntities assigncd to them. In … Show more
“…Although in our ultrasonicated material we have found no evidence for such strands, the "fibrils" described by Overton et al . (17) appear to resemble our filaments .…”
“…Although in our ultrasonicated material we have found no evidence for such strands, the "fibrils" described by Overton et al . (17) appear to resemble our filaments .…”
“…In the few studies available, human intestinal cell turnover has been estimated at 2-5 days (21)(22)(23)(24) contact with the enzyme site because the disaccharidases are located in the brush border. Furthermore, techniques are now being developed which enable the separation of the brush border from the rest of the intestinal mucosa (25,26). Thus, one might be able ultimately to isolate and purify these enzymes in man.…”
A B S T R A C T The specific effect of dietary sugars on jejunal disaccharidase activity in seven normal nonfasted male volunteers was studied. The sugars tested were sucrose, maltose, lactose, glucose, fructose, and galactose. Comparisons were made of the effects of each sugar in an isocaloric liquid diet.In all subjects, sucrose feeding, as compared to glucose feeding, significantly increased jejunal sucrase (S) and maltase (M) activities, but not lactase (L) activity. The S/L and M/L ratios increased to a significant degree.Fructose feeding, in two subjects, gave results similar to sucrose when comparing fructose and glucose diets. One subject was fed lactose, galactose, and maltose. These sugars, compared to glucose, did not increase disaccharidase activity. Fructose appears to be the active principle in the sucrose molecule.These results demonstrate that specific dietary sugars can alter enzyme activity in the small intestine of man in a specific fashion. Sucrose and fructose are able to regulate sucrase and maltase activity. Dietary alteration of intestinal enzymes may represent a suitable system for studying the regulation of enzyme activity in man.
“…1 is a photograph of a representative gradient showing the position of the bands obtained. Bands C and D of the gradient have been studied with the electron microscope, and the morphology of their components is described in the accompanying paper (16).…”
Section: Separation Of Components Of Brush Bordersmentioning
Brush borders isolated from the epithelial cells of hamster jejunum have been dissociated by treatment with 1 M Tris(hydroxymethyl)aminomethane into several subfractions which can be separated by means of centrifugation on glycerol density gradients. Investigation of the chemical specificity of disrupting agents suggests that the amino group of Tris, in its positively charged state, is involved. Five individual bands or fractions have been routinely recovered from density gradients. The distribution of alkaline phosphatase and maltase activities among these fractions has been studied and the results indicate that both enzymes are predominantly associated with one fraction which has been identified in a companion paper as being composed of the membranes of the brush border microvilli. A fibrillar material of unidentified origin has also been obtained from Tris-disrupted brush borders.
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