Studies on the Organization of the Brush Border in Intestinal Epithelial Cells

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 addition, negative staining shows that thc rods are composed of aligncd particles of roughly 60 A, consistent with thc appcarance of the core in tissue scction, where 60-A fibrils are characteristic. The shccts are covered by non-aligned particles of approximately thc same size. Sectioned preparations show that the core fraction contains predominantly fibrous material with some mcmbranous contamination and that the coat fraction is apparently composcd exclusively of elongated sacs with a unit membrane structure. Some details of the structurc of thc core are evident in cases whcrc the compact rod appears to be looscned, revealing a doubled strand. The strand is approximately 350 A widc; the compact rod is roughly twice this width. With negative staining the strand shows a dense central region. Thc morphological identification presented hcrc is consistent with the distribution of enzymic activity among the density gradient fractions dcscribed in the preceding paper.

The Fine Structure of the Microvilli of Isolated Brush Borders of Intestinal Epithelial Cells

“…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 .…”

Control of jejunal sucrase and maltase activity by dietary sucrose of fructose in man

“…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.…”

Studies on the Organization of the Brush Border in Intestinal Epithelial Cells

“…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).…”