The Fine-Structural Organization of the Brush Border of Intestinal Epithelial Cells

1971 ◽  
Vol 8 (3) ◽  
pp. 573-599
Author(s):  
T. M. MUKHERJEE ◽  
L. A. STAEHELIN
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Brush Border ◽  
Intestinal Epithelial Cells ◽  
Membrane Surface ◽  
Intestinal Epithelial ◽  
The Core ◽  
Unit Structure ◽  
Terminal Web ◽  
Freeze Etching

The fine structure of the brush border of intestinal epithelial cells of the mouse has been studied with both normal sectioning and freeze-etching techniques. Freeze-etching reveals the plasma membrane of the microvilli as consisting of a continuous layer, that is split during the cleaving process, in which numerous particles, 5-9 nm in diameter, are embedded, while other particle-like structures, with diameters of 7-10 nm, appear attached to the true outer membrane surface. The mucopolysaccharide surface coats of the microvilli show up more clearly in sectioned material than in freeze-etched specimens. Inside each microvillus 2 different filament systems can be demonstrated: (1) bundles of fairly closely packed and straight core microfilaments, which lead into the tip of the microvillus, and (2) short cross-filaments. Under suitable conditions the core microfilaments display a sub-unit structure with a repeating distance of approximately 6 nm. The diameter of a microfilament can vary along its length from 6 to 11 nm. Two strands of globular particles wound helically around each other seem to make up each microfilament. These and other data support the idea that the core microfilaments are actin-like. No substructure has been found on the cross-filaments, which have an orientation approximately radial to the axis of the microvilli and seem to be attached at one end to the core microfilaments and at the other to the inner surface of the microvillous membrane. The interwoven terminal web filaments also show no substructure. They form a continuous flexible platform-like structure into which the bundles of core microfilaments extend. Some terminal web filaments appear attached to the plasma membrane between the microvilli. It is suggested that the core microfilaments represent mechanical supporting elements and that the terminal web and cross-filaments are tensile elements of the brush border. In addition all 3 filament systems may also be involved in possible contractile movements of the microvilli.

scholarly journals Localization of actin and microfilament-associated proteins in the microvilli and terminal web of the intestinal brush border by immunofluorescence microscopy.

1978 ◽  
Vol 79 (3) ◽  
pp. 839-845 ◽  
Author(s):  
A Bretscher ◽  
K Weber
Keyword(s):  
Epithelial Cells ◽  
Indirect Immunofluorescence ◽  
Brush Border ◽  
Immunofluorescence Microscopy ◽  
Intestinal Epithelial Cells ◽  
Intestinal Epithelial ◽  
Indirect Immunofluorescence Microscopy ◽  
Terminal Web ◽  
Intestinal Brush Border ◽  
Associated Proteins

Indirect immunofluorescence microscopy was used to localize microfilament-associated proteins in the brush border of mouse intestinal epithelial cells. As expected, antibodies to actin decorated the microfilaments of the microvilli, giving rise to a very intense fluorescence. By contrast, antibodies to myosin, tropomyosin, filamin, and alpha-actinin did not decorate the microvilli. All these antibodies, however, decorated the terminal web region of the brush border. Myosin, tropomyosin, and alpha-actinin, although present throughout the terminal web, were found to be preferentially located around the periphery of the organelle. Therefore, two classes of microfilamentous structures can be documented in the brush border. First, the highly ordered microfilaments which make up the cores of the microvilli apparently lack the associated proteins. Second, seemingly less-ordered microfilaments are found in the terminal web, in which region the myosin, tropomyosin, filamin and alpha-actinin are located.

Surface Charge on Human Colinic Epithelial Cells as Shown by Ferritin Labelling

1972 ◽  
Vol 30 ◽  
pp. 266-267
Author(s):  
T. M. Mukherjee
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Brush Border ◽  
Negative Charge ◽  
Intestinal Epithelial Cells ◽  
Conclusive Evidence ◽  
Surface Coat ◽  
Intestinal Epithelial ◽  
Luminal Surface ◽  
Metabolic Activities

Recent observations suggest the glycoprotein surface coat of the intestinal epithelial cells to be involved in the metabolic activities of the absorptive cells. In fact such considerations led Crane to speculate and include the “glycocalyx” as an essential component of the “digestive absorptive surface”. In spite of such speculations no conclusive evidence in support of this contention has yet been obtained. One such speculation has been that the surface coat because of its high negative charge is responsible for the adsorption of materials prior to their terminal breakdown and absorption. To test this hypothesis a study was undertaken to reveal the charge distribution over the luminal surface, of the brush border plasma membrane, i.e. the region of the “glycocalyx”.

scholarly journals Characterization and localization of myosin in the brush border of intestinal epithelial cells

1978 ◽  
Vol 79 (2) ◽  
pp. 444-453 ◽  
Author(s):  
MS Mooseker ◽  
TD Pollard
Keyword(s):  
Ionic Strength ◽  
Epithelial Cells ◽  
Atpase Activity ◽  
Brush Border ◽  
Intestinal Epithelial Cells ◽  
Gel Filtration ◽  
Intestinal Epithelial ◽  
Terminal Web ◽  
Brush Borders ◽  
Low Ionic Strength

The brush border of intestinal epithelial cells consists of a tightly packed array of microvilli, each of which contains a core of actin filaments. It has been postulated that microvillar movements are mediated by myosin interactions in the terminal web with the basal ends of these actin cores (Mooseker, M.S. 1976. J. Cell. Biol. 71:417-433). We report here that two predictions of this model are correct: (a) The brush border contains myosin, and (b) myosin is located in the terminal web. Myosin is isolated in 70 percent purity by solubilization of Triton-treated brush borders in 0.6 M KI, and separation of the components by gel filtration. Most of the remaining contaminants can be removed by precipitation of the myosin at low ionic strength. This yield is approximately 1 mg of myosin/30 mg of solubilized brush border protein. The molecule consists of three subunits with molecular weights of 200,000, 19,000, and 17,000 daltons in a 1:1:1 M ratio. At low ionic strength, the myosin forms small, bipolar filaments with dimensions of 300 X 11nm, that are similar to filaments seen previously in the terminal web of isolated brush borders. Like that of other vertebrate, nonmuscle myosins, the ATPase activity of isolated brush border myosin in 0.6 M KCI is highest with EDTA (1 μmol P(i)/mg-min; 37 degrees C), intermediate with Ca++ (0.4 μmol P(i)/mg-min), and low with Mg++ (0.01 μmol P(i)/mg-min). Actin does not stimulate the Mg-ATPase activity of the isolated enzyme. Antibodies against the rod fragment of human platelet myosin cross-react by immunodiffusion with brush border myosin. Staining of isolated mouse or chicken brush borders with rhodamine-antimyosin demonstrates that myosin is localized exclusively in the terminal web.

scholarly journals Unique Regulation of Enterocyte Brush Border Membrane Na-Glutamine and Na-Alanine Co-Transport by Peroxynitrite during Chronic Intestinal Inflammation

2019 ◽  
Vol 20 (6) ◽  
pp. 1504 ◽  
Author(s):  
Subha Arthur ◽  
Palanikumar Manoharan ◽  
Shanmuga Sundaram ◽  
M Rahman ◽  
Balasubramanian Palaniappan ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Intestinal Inflammation ◽  
Intestinal Epithelial Cells ◽  
Rabbit Model ◽  
Intestinal Epithelial ◽  
Mechanism Of Inhibition ◽  
Chronic Intestinal Inflammation

Na-amino acid co-transporters (NaAAcT) are uniquely affected in rabbit intestinal villus cell brush border membrane (BBM) during chronic intestinal inflammation. Specifically, Na-alanine co-transport (ASCT1) is inhibited secondary to a reduction in the affinity of the co-transporter for alanine, whereas Na-glutamine co-transport (B0AT1) is inhibited secondary to a reduction in BBM co-transporter numbers. During chronic intestinal inflammation, there is abundant production of the potent oxidant peroxynitrite (OONO). However, whether OONO mediates the unique alteration in NaAAcT in intestinal epithelial cells during chronic intestinal inflammation is unknown. In this study, ASCT1 and B0AT1 were inhibited by OONO in vitro. The mechanism of inhibition of ASCT1 by OONO was secondary to a reduction in the affinity of the co-transporter for alanine, and secondary to a reduction in the number of co-transporters for B0AT1, which were further confirmed by Western blot analyses. In conclusion, peroxynitrite inhibited both BBM ASCT1 and B0AT1 in intestinal epithelial cells but by different mechanisms. These alterations in the villus cells are similar to those seen in the rabbit model of chronic enteritis. Therefore, this study indicates that peroxynitrite may mediate the inhibition of ASCT1 and B0AT1 during inflammation, when OONO levels are known to be elevated in the mucosa.

scholarly journals Intermediate Filaments Interact with Dormant Ezrin in Intestinal Epithelial Cells

2005 ◽  
Vol 16 (9) ◽  
pp. 4096-4107 ◽  
Author(s):  
Flavia A. Wald ◽  
Andrea S. Oriolo ◽  
M. Llanos Casanova ◽  
Pedro J.I. Salas
Keyword(s):  
Epithelial Cells ◽  
Intermediate Filaments ◽  
Brush Border ◽  
Antisense Rna ◽  
Apical Membrane ◽  
Intestinal Epithelial Cells ◽  
Intestinal Epithelial ◽  
Undifferentiated Cells ◽  
Responsive Element

Ezrin connects the apical F-actin scaffold to membrane proteins in the apical brush border of intestinal epithelial cells. Yet, the mechanisms that recruit ezrin to the apical domain remain obscure. Using stable CACO-2 transfectants expressing keratin 8 (K8) antisense RNA under a tetracycline-responsive element, we showed that the actin-ezrin scaffold cannot assemble in the absence of intermediate filaments (IFs). Overexpression of ezrin partially rescued this phenotype. Overexpression of K8 in mice also disrupted the assembly of the brush border, but ezrin distributed away from the apical membrane in spots along supernumerary IFs. In cytochalasin D-treated cells ezrin localized to a subapical compartment and coimmunoprecipitated with IFs. Overexpression of ezrin in undifferentiated cells showed a Triton-insoluble ezrin compartment negative for phospho-T567 (dormant) ezrin visualized as spots along IFs. Pulse-chase analysis showed that Triton-insoluble, newly synthesized ezrin transiently coimmunoprecipitates with IFs during the first 30 min of the chase. Dormant, but not active (p-T567), ezrin bound in vitro to isolated denatured keratins in Far-Western analysis and to native IFs in pull-down assays. We conclude that a transient association to IFs is an early step in the polarized assembly of apical ezrin in intestinal epithelial cells.

scholarly journals STUDIES ON THE ORGANIZATION OF THE BRUSH BORDER IN INTESTINAL EPITHELIAL CELLS

1965 ◽  
Vol 26 (3) ◽  
pp. 687-691 ◽  
Author(s):  
Alexander Eichholz ◽  
Robert K. Crane
Keyword(s):  
Epithelial Cells ◽  
Brush Border ◽  
Intestinal Epithelial Cells ◽  
Companion Paper ◽  
Density Gradients ◽  
Intestinal Epithelial ◽  
Fibrillar Material ◽  
Brush Borders ◽  
Individual Bands ◽  
Positively Charged

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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