scholarly journals THE CELL JUNCTION IN A LAMELLIBRANCH GILL CILIATED EPITHELIUM

1970 ◽  
Vol 47 (2) ◽  
pp. 468-487 ◽  
Author(s):  
P. Satir ◽  
N. B. Gilula
Keyword(s):  
Cell Membrane ◽  
Smooth Endoplasmic Reticulum ◽  
Freshwater Mussel ◽  
Septate Junction ◽  
Cell Junction ◽  
Junctional Complex ◽  
Regional Differentiation ◽  
Ion Permeability ◽  
Membrane Surfaces ◽  
Entire Cell

The junctional complex in the gill epithelium of the freshwater mussel (Elliptio complanatus) consists of an intermediary junction followed by a 2–3 µ long septate junction. Homologous and heterologous cell pairs are connected by this junction. After fixation with 1% OsO4 containing 1% potassium pyroantimonate, electron microscopy of the gill reveals deposits of electron-opaque precipitate, specifically and consistently localized along cellular membranes. In both junctional and nonjunctional membrane regions, the precipitate usefully outlines the convolutions without obliterating the 150 A intercellular space, which suggests the rarity or absence of either vertebrate-type gap or tight junctions along the entire cell border. The precipitate appears on the cytoplasmic side of the limiting unit membranes of frontal (F), laterofrontal (LF), intermediate (I), lateral (L), and postlateral (PL) cells. The membrane surfaces of certain vesicles of the smooth endoplasmic reticulum, of multivesicular bodies, and of mitochondrial cristae contain precipitate, as does the nucleolus. In other portions of the cell, precipitate is largely absent. The amount of over-all deposition is variable and depends on the treatment of the tissue prior to fixation. Deposition is usually enhanced by pretreatment with 40 mM NaCl as opposed to 40 mM KCl, which suggests that the precipitate is in part sodium pyroantimonate. Treatment with 0.2 mM ouabain does not enhance deposition. Regional differentiation of cell membranes with respect to their ability to precipitate pyroantimonate is found in at least three instances: (a) between the ciliary membranes and other portions of the cell membrane: the precipitate terminates abruptly at the ciliary base, (b) between the LF and I cell borders: the precipitate is asymmetric, favoring the LF side of the junction, and (c) between the septate junctional membrane and adjacent membrane: the precipitate occurs periodically throughout the septate junction region with the periodicity corresponding to the spacing of the septa. This suggests that different regions of the cell membrane may have differing ion permeability properties and, in particular, that the septa may be the regions of high ion permeability in the septate junction.

The junctional complex in the intestine of Sagitta setosa (Chaetognatha): the paired septate junction

1980 ◽  
Vol 42 (1) ◽  
pp. 227-246
Author(s):  
M. Duvert ◽  
D. Gros ◽  
C. Salat
Keyword(s):  
Uranyl Acetate ◽  
The Other ◽  
Septate Junction ◽  
Junctional Complex ◽  
Outer Diameter ◽  
Central Ring ◽  
Straight Path ◽  
New Type ◽  
Pleated Sheet ◽  
Tight Formation

The junctional complex of the intestine of Sagitta setosa has been studied in tissues stained with uranyl acetate or after lanthanum impregnation, and by freeze-cleavage. All types of junctions have been characterized in both perpendicular and tangential planes. From the apex to the base of the cell the following junctions occur in this order: a zonula adhaerens; a septate junction where the septa occur in pairs; a pleated sheet septate junction; and numerous gap junctions of the A-type. From the upper part of the cells inwards to the septate junction, the membranes follow a relatively straight path. In the lower part of the cells the membranes are deeply interdigitating. At the intersection between 3 cells a very different junction is to be observed where small units, periodically disposed, bind the membranes of the 3 adjoining cells. Each unit is composed of 3 short segments which bind the cell membranes to a central ring 16.6 +/− 2.3 nm in outer diameter. The paired septate junction constitutes a new type. Its main features are that the septa are paired and occur in 2 formations, one the ‘loose formation’, with elements between the septa of each pair, and the other, a ‘tight formation’. After lanthanum impregnation, the thickness of each septum is seen to be about 3 nm and the undulation period 12.6 +/− 1.6 nm. On freeze-fractures 10-nm particles are found on crests on the PF face and in furrows on the EF face. The possible significance of this type of junction is discussed. The junctional complex described is analogous to those found in various invertebrate epithelia.

scholarly journals Permeability of a Cell Membrane Junction

1969 ◽  
Vol 53 (4) ◽  
pp. 498-515 ◽  
Author(s):  
A. L. Politoff ◽  
S. J. Socolar ◽  
W. R. Loewenstein
Keyword(s):  
Salivary Gland ◽  
Energy Metabolism ◽  
Cell Membrane ◽  
Oxidative Phosphorylation ◽  
Ion Permeability ◽  
Intracellular Injection ◽  
Gland Cells ◽  
Salivary Gland Cells ◽  
Junctional Permeability ◽  
A Cell

The ion permeability of the membrane junctions between Chironomus salivary gland cells is strongly depressed by treatments that are generally known to inhibit energy metabolism. These treatments include prolonged cooling at 6°–8°C, and exposure to dinitrophenol, cyanide, oligomycin, and N-ethylmaleimide. Intracellular injection of ATP appears to prevent depression of junctional permeability by dinitrophenol or to reverse it. Ouabain, azide, p-chloromercuriphenylsulfonic acid, reserpine, and acetazolamide fail to depress junctional permeability. Thus the ion permeability of the junctional membranes appears to depend on energy provided by oxidative phosphorylation. Possible energy-linked processes for maintaining junctional permeability are discussed, including processes involving transport of permeability-modifying species such as Ca++.

Serine proteases decrease intestinal epithelial ion permeability by activation of protein kinase Cζ

2009 ◽  
Vol 297 (1) ◽  
pp. G60-G70 ◽  
Author(s):  
Veronica A. Swystun ◽  
Bernard Renaux ◽  
France Moreau ◽  
Shoubin Wen ◽  
Michael A. Peplowski ◽  
...  
Keyword(s):  
Serine Proteases ◽  
Specific Inhibitor ◽  
Insoluble Fraction ◽  
Junctional Complex ◽  
Intestinal Epithelial ◽  
Ion Permeability ◽  
Protease Activated Receptors ◽  
Epithelial Barrier Function ◽  
Intestinal Pathology ◽  
Epithelial Cell Lines

Epithelial permeability to ions and larger molecules in the gut is essential for fluid balance, and its dysregulation contributes to intestinal pathology. We investigated the effect of digestive serine proteases on epithelial paracellular permeability. Trypsin, chymotrypsin, and elastase elicited sustained increases in transepithelial resistance (RTE) in polarized monolayers of three intestinal epithelial cell lines. This effect was reflected by decreases in paracellular conductances of Na+ and Cl− and a concomitant decrease in permeability to 3,000 molecular weight dextran. The enzyme activities of the proteases were required, yet activators of known protease-activated receptors (PARs) did not reproduce the effect of these proteases on RTE. PKCζ isoform-specific inhibitor significantly reduced the trypsin-induced increase in RTE whereas PKCζ activity was increased in cells treated with trypsin and chymotrypsin compared with control cells; this activity was reduced to control levels in the presence of PKCζ-specific inhibitor. Ca2+ chelators and pharmacological inhibitors of cell signaling support the role for PKCζ in the protease-induced effect. Finally, we showed that treatment with the serine proteases increased occludin immunostaining and zonula occludin-1 coimmunoprecipitation with occludin in the detergent-insoluble fraction of cell lysates, and these increases were ablated by pretreatment with PKCζ-specific inhibitor. This finding indicates increased insertion of occludin into the cell junctional complex. These data demonstrate a role for serine proteases in the facilitation of epithelial barrier function through a mechanism that is independent of PARs and is mediated by activation of PKCζ.

scholarly journals LIGAND-INDUCED MOVEMENT OF LYMPHOCYTE MEMBRANE MACROMOLECULES

1973 ◽  
Vol 137 (3) ◽  
pp. 675-689 ◽  
Author(s):  
Emil R. Unanue ◽  
Morris J. Karnovsky ◽  
Howard D. Engers
Keyword(s):  
Protein Synthesis ◽  
Cell Membrane ◽  
Cell Surface ◽  
Oxidative Phosphorylation ◽  
Cross Linking ◽  
Lymphocyte Membrane ◽  
Compact Zone ◽  
Entire Cell ◽  
Freeze Etching ◽  
Spleen Lymphocytes

Spleen lymphocytes were studied for the movement and interiorization of complexes of anti-Ig-surface Ig. The movement of the complex into a small, compact zone of the cell membrane (forming a cap) was inhibited by drugs that inhibited glycolysis and oxidative phosphorylation, but not by drugs that affected protein synthesis. Dead lymphocytes did not form caps. Freeze-etching techniques revealed that inhibited lymphocytes showed formation of multiple small complexes over the entire cell surface. Inhibitors of glycolysis and of oxidative phosphorylation also inhibited the interiorization and catabolism of radioiodinated anti-Ig. We hypothesize that cross-linking of all the surface Ig triggers the membrane movements that are required to pull the lattice into one zone of the cell.

scholarly journals α-catenin switches between a slip and a cooperative catch bond with F-actin to regulate cell junction fluidity

2020 ◽  
Author(s):  
C. Arbore ◽  
M Sergides ◽  
L. Gardini ◽  
F.S. Pavone ◽  
M. Capitanio
Keyword(s):  
Cell Membrane ◽  
Actin Cytoskeleton ◽  
Protein Unfolding ◽  
Solid Phase ◽  
Cell Junctions ◽  
Cell Junction ◽  
Laser Tweezers ◽  
Catch Bond ◽  
Membrane Cytoskeleton ◽  
Solid Phase Transition

α-catenin is a crucial protein at cell junctions that provides connection between the actin cytoskeleton and the cell membrane. At adherens junctions (AJs), α-catenin forms heterodimers with β-catenin that are believed to resist force on F-actin. Outside AJs, α-catenin forms homodimers that directly connect the cell membrane to the actin cytoskeleton, but their mechanosensitive properties are inherently unknown. Surprisingly, by using ultra-fast laser tweezers we found that a single α-β-catenin heterodimer does not resist force but instead slips along F-actin in the direction of force. Conversely, the action of 5 to 10 α-β-catenin heterodimers together with unidirectional force applied to F-actin engaged a molecular switch in α-catenin, which unfolded and strongly bound F-actin as a cooperative catch bond. Similarly, an α-catenin homodimer formed an asymmetric catch bond with F-actin triggered by protein unfolding under force. Our data reveal that α-catenin clustering together with intracellular tension engage a fluid-to-solid phase transition at the membrane-cytoskeleton interface.

scholarly journals Origin of subdiffusion of water molecules on cell membrane surfaces

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Eiji Yamamoto ◽  
Takuma Akimoto ◽  
Masato Yasui ◽  
Kenji Yasuoka
Keyword(s):  
Cell Membrane ◽  
Water Molecules ◽  
Membrane Surfaces

Plasma membranes, cell junctions and cuticle of the rectal chloride epithelia of the larval dragonfly Aeshna cyanea

1983 ◽  
Vol 59 (1) ◽  
pp. 159-182
Author(s):  
J. Kukulies ◽  
H. Komnick
Keyword(s):  
Gap Junctions ◽  
Structural Control ◽  
Plasma Membranes ◽  
Freeze Fracture ◽  
Septate Junction ◽  
Cell Junctions ◽  
Junctional Complex ◽  
Apical Region ◽  
Thin Sections ◽  
Aeshna Cyanea

The cell membranes and cell junctions of the rectal chloride epithelia of the larval dragonfly Aeshna cyanea were examined in thin sections and by freeze-fracture. These epithelia function in active ion absorption and maintain a high concentration gradient between the haemolymph and the fresh-water environment. Freeze-fracturing reveals fine-structural differences in the intramembraneous particles of the luminal and contraluminal plasma membranes of these epithelia, reflecting the functional diversity of the two membranes, which are separated by the junctional complex. The particle frequency of the basolateral plasma membranes is reduced after transfer of the larvae into high concentrations of environmental salinity. The junctional complex is located in the apical region and composed of three types of cell junctions: the zonula adhaerens, seen in freeze-fracture as a nearly particle-free zone; the extended and highly convoluted pleated septate junction and randomly interspersed gap junctions of the inverted type. Gap junctions also occur between the basolateral plasma membranes. They provide short-cuts in the diffusion pathway for direct and rapid co-ordination of the interconnected cell processes. Colloidal and ionic lanthanum tracer solutions applied in vivo from the luminal side penetrate through the cuticle via epicuticular depressions, but invade only the apical portion of the junctional complex. This indicates that the pleated septate junction constitutes a structural control of the paracellular pathway across the chloride epithelia, which are devoid of tight junctions. The structure of the pleated septate junctions is interpreted as a device for the extension of the diffusion distance, which is inversely related to the net diffusion. A conservative estimate of the total length of the junction, and the number and extension of septa reveals that the paracellular route exceeds the transcellular route by a factor of 50.

DISEASED RED BLOOD CELLS STUDIED BY ATOMIC FORCE MICROSCOPY

2002 ◽  
Vol 01 (05n06) ◽  
pp. 683-688 ◽  
Author(s):  
YONG CHEN ◽  
JIYE CAI ◽  
JINGXIAN ZHAO
Keyword(s):  
Lung Cancer ◽  
Atomic Force Microscopy ◽  
Cell Membrane ◽  
Erythrocyte Membrane ◽  
Mammalian Cells ◽  
Membrane Surface ◽  
Force Microscopy ◽  
Membrane Surfaces ◽  
Atomic Force ◽  
Mean Width

In recent years, many mammalian cells, especially erythrocytes because of simpleness of their membrane surfaces, were widely studied by atomic force microscopy. In our study, diseased erythrocytes were taken from patients of lung cancer, myelodisplastic syndrome (MDS), and so on. We obtained many clear topographical images of numerous erythrocytes, single erythrocyte, and ultramicrostructure of erythrocyte membrane surfaces from normal persons and patients. By studying the red cells of lung cancer patients, we found that many erythrocytes of lung cancer patient have changed into echinocytes. One erythrocyte has 10–20 short projections, most of which, with a mean width of 589.0 nm and a length of 646.7 nm, are on the edge of cell. The projections in the center of echinocytes are lodged and embedded, but in conventional model of echinocytes, the projections in the center stretch outside cell membrane, so a novel model of erythrocytes was designed in our paper. After observation of microstructure of MDS patient's erythrocyte membrane surface, we found that many apertures with different diameters of tens to hundreds nanometers appeared on the surface of cell membrane. It can be concluded that AFM may be widely applied in clinic pathological inspection.

scholarly journals 2P131 Aging of water molecules on cell membrane surfaces(07. Water & Hydration & Electrolyte,Poster)

2013 ◽  
Vol 53 (supplement1-2) ◽  
pp. S180
Author(s):  
Eiji Yamamoto ◽  
Takuma Akimoto ◽  
Masato Yasui ◽  
Kenji Yasuoka
Keyword(s):  
Cell Membrane ◽  
Water Molecules ◽  
Membrane Surfaces
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