ELECTRON MICROSCOPE STUDIES OF THE STRUCTURE OF THE MICROVILLI ON PRINCIPAL EPITHELIAL CELLS OF RAT JEJUNUM AFTER TREATMENT IN HYPO- AND HYPERTONIC SALINE

Immersion of the intestinal tissue, from rat jejunum, in hypertonic saline produced very rapid changes in all regions of the epithelial cells, but the apical region was apparently unaffected by hypotonic solutions for at least ½ hour. In both cases, blistering of the microvilli was taken as the first sign of degenerative changes which finally resulted in a breakdown to large vesicular particles. Consideration of both normal and modified tissue indicates that the core of the microvillus contains either paired strands or tubular structures. Lateral cross-fibres extended from the core to the microvillus membrane and may be an essential part of the supporting structure of the microvillus. Densitometer traces across the microvillus membrane at various stages of modification indicated that this membrane might include a 75 A unit membrane structure with additional components associated at either surface. Interruptions in the membrane were apparently expanded by the hypotonic solutions and these might possibly be distinguished from preparative artefacts.

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ER-annulate lamellar associations of mucosal epithelial cells of the rat jejunum

Cell and Tissue Research ◽

10.1007/bf00218719 ◽

1976 ◽

Vol 175 (3) ◽

Cited By ~ 10

Author(s):

D.K. Jasper

Keyword(s):

Epithelial Cells ◽

Rat Jejunum

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M1731 Sphingosine-1-Phosphate Regulates Barrier Function in Cultured Intestinal Epithelial Cells and Murine Intestinal Tissue

Gastroenterology ◽

10.1016/s0016-5085(08)61901-0 ◽

2008 ◽

Vol 134 (4) ◽

pp. A-407

Author(s):

Ruiyun Li ◽

Jose Greenspon ◽

Emily Bellavance ◽

Rex Sun ◽

Lan Xiao ◽

...

Keyword(s):

Epithelial Cells ◽

Barrier Function ◽

Intestinal Epithelial Cells ◽

Intestinal Epithelial ◽

Intestinal Tissue ◽

Sphingosine 1 Phosphate

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The estrogen-dependent c-JunER protein causes a reversible loss of mammary epithelial cell polarity involving a destabilization of adherens junctions.

The Journal of Cell Biology ◽

10.1083/jcb.132.6.1115 ◽

1996 ◽

Vol 132 (6) ◽

pp. 1115-1132 ◽

Cited By ~ 108

Author(s):

I Fialka ◽

H Schwarz ◽

E Reichmann ◽

M Oft ◽

M Busslinger ◽

...

Keyword(s):

Growth Factor ◽

Epithelial Cells ◽

Target Genes ◽

Egf Receptor ◽

Mammary Epithelial ◽

Breast Development ◽

Beta Catenin ◽

Epithelial Polarity ◽

Tubular Structures ◽

Tissue Organization

Members of the epidermal growth factor (EGF) receptor family are known to be specifically involved in mammary carcinogenesis. As a nuclear target of activated receptors, we examined c-Jun in mammary epithelial cells. For this, we used a c-JunER fusion protein which was tightly controlled by estrogen. Activation of the JunER by hormone resulted in the transcriptional regulation of a variety of AP-1 target genes. Hormone-activated JunER induced the loss of epithelial polarity, a disruption of intercellular junctions and normal barrier function and the formation of irregular multilayers. These changes were completely reversible upon hormone withdrawal. Loss of epithelial polarity involved redistribution of both apical and basolateral proteins to the entire plasma membrane. The redistribution of E-cadherin and beta-catenin was accompanied by a destabilization of complexes formed between these two proteins, leading to an enrichment of beta-catenin in the detergent-soluble fraction. Uninduced cells were able to form three-dimensional tubular structures in collagen I gels which were disrupted upon JunER activation, leading to irregular cell aggregates. The JunER-induced disruption of tubular structures was dependent on active signaling by growth factors. Moreover, the effects of JunER could be mimicked in normal cells by the addition of acidic fibroblast growth factor (aFGF). These data suggest that a possible function of c-Jun in epithelial cells is to modulate epithelial polarity and regulate tissue organization, processes which may be equally important for both normal breast development and as initiating steps in carcinogenesis.

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The core planar cell polarity gene, Vangl2 , directs adult corneal epithelial cell alignment and migration

Royal Society Open Science ◽

10.1098/rsos.160658 ◽

2016 ◽

Vol 3 (10) ◽

pp. 160658 ◽

Cited By ~ 11

Author(s):

Amy S. Findlay ◽

D. Alessio Panzica ◽

Petr Walczysko ◽

Amy B. Holt ◽

Deborah J. Henderson ◽

...

Keyword(s):

Cell Migration ◽

Epithelial Cells ◽

Cell Polarity ◽

Corneal Epithelium ◽

Planar Cell Polarity ◽

Corneal Epithelial Cell ◽

Corneal Epithelial Cells ◽

Corneal Epithelial ◽

The Core

This study shows that the core planar cell polarity (PCP) genes direct the aligned cell migration in the adult corneal epithelium, a stratified squamous epithelium on the outer surface of the vertebrate eye. Expression of multiple core PCP genes was demonstrated in the adult corneal epithelium. PCP components were manipulated genetically and pharmacologically in human and mouse corneal epithelial cells in vivo and in vitro . Knockdown of VANGL2 reduced the directional component of migration of human corneal epithelial (HCE) cells without affecting speed. It was shown that signalling through PCP mediators, dishevelled, dishevelled-associated activator of morphogenesis and Rho-associated protein kinase directs the alignment of HCE cells by affecting cytoskeletal reorganization. Cells in which VANGL2 was disrupted tended to misalign on grooved surfaces and migrate across, rather than parallel to the grooves. Adult corneal epithelial cells in which Vangl2 had been conditionally deleted showed a reduced rate of wound-healing migration. Conditional deletion of Vangl2 in the mouse corneal epithelium ablated the normal highly stereotyped patterns of centripetal cell migration in vivo from the periphery (limbus) to the centre of the cornea. Corneal opacity owing to chronic wounding is a major cause of degenerative blindness across the world, and this study shows that Vangl2 activity is required for directional corneal epithelial migration.

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Neurulation and the cortical tractor model for epithelial folding

Development ◽

10.1242/dev.96.1.19 ◽

1986 ◽

Vol 96 (1) ◽

pp. 19-49

Author(s):

Antone G. Jacobson ◽

George F. Oster ◽

Garrett M. Odell ◽

Louis Y. Cheng

Keyword(s):

Epithelial Cells ◽

Computer Simulations ◽

Dynamic Structure ◽

Mesenchymal Cells ◽

Epithelial Morphogenesis ◽

Apical Region ◽

New Model ◽

Epithelial Sheet ◽

Epithelial Sheets ◽

Placode Formation

We present here a new model for epithelial morphogenesis, which we call the ‘cortical tractor model’. This model assumes that the motile activities of epithelial cells are similar to those of mesenchymal cells, with the added constraint that the cells in an epithelial sheet remain attached at their apical circumference. In particular, we assert that there is a time-averaged motion of cortical cytoplasm which flows from the basal and lateral surfaces to the apical region. This cortical flow carries with it membrane and adhesive structures that are inserted basally and resorbed apically. Thus the apical seal that characterizes epithelial sheets is a dynamic structure: it is continuously created by the cortical flow which piles up components near where they are recycled in the apical region. By use of mechanical analyses and computer simulations we demonstrate that the cortical tractor motion can reproduce a variety of epithelial motions, including columnarization (placode formation), imagination and rolling. It also provides a mechanism for driving active cell rearrangements within an epithelial sheet, while maintaining the integrity of the apical seal. Active repacking of epithelial cells appears to drive a number of morphogenetic processes. Neurulation in amphibians provides an example of a process in which all four of the above morphogenetic movements appear to play a role. Here we reexamine the process of neurulation in amphibians in light of the cortical tractor model, and find that it provides an integrated view of this important morphogenetic process.

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

Journal of Cell Science ◽

10.1242/jcs.8.3.573 ◽

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.

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