scholarly journals Reflexive gap junctions. Gap junctions between processing arising from the same ovarian decidual cell.

1976 ◽  
Vol 69 (2) ◽  
pp. 495-501 ◽  
Author(s):  
J C Herr
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Gap Junction ◽  
Decidual Cell ◽  
Hexagonal Array ◽  
Decidual Cells

Ajacent processes on ovarian decidual cells were shown by electron microscopy to form gap junctions with one another. Micrographs of tissues preserved with lanthanum included in the fixative confirm the hexagonal array and 2-4 nm gap which characterize gap junctions. It is suggested that these gap junctions may play a role in the process of merocrine secretion from the peduncular processes of ovarian decidual cells. The term reflexive gap junction is introduced to describe gap junctions between adjacent processes from the same cell.

scholarly journals Electron microscopy and functional analysis of recombinant innexin gap junctions

2014 ◽  
Vol 70 (a1) ◽  
pp. C851-C851
Author(s):  
Atsunori Oshima ◽  
Tomohiro Matsuzawa ◽  
Kazuyoshi Murata ◽  
Kouki Nishikawa ◽  
Yoshinori Fujiyoshi
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Gap Junction ◽  
Single Particle ◽  
Particle Analysis ◽  
Single Particle Analysis ◽  
Dye Transfer ◽  
Gap Junction Channels ◽  
Class Average ◽  
Detergent Micelles

Innexin is a molecular component of invertebrate gap junctions, which have an important role in neural and muscular electrical activity in invertebrates. Although the structure of vertebrate connexin26 was revealed by X-ray crystallography [1], the structure of innexin channels remains poorly understood. To study the structure of innexin gap junction channels, we expressed and purified Caenorhabditis elegans innexin-6 (INX-6) gap junction channels, and characterized their molecular dimensions and channel permeability using electron microscopy (EM) and a fluorescent dye transfer assay, respectively [2]. Negative-staining and thin-section EM of isolated INX-6 gap junction plaques revealed a loosely packed hexagonal lattice. We performed single particle analysis of purified INX-6 channels with negative-staining and cryo EM. Based on the negative-stain EM images, the class average of the junction form had a longitudinal height of 220 Å, a channel diameter of 110 Å in the absence of detergent micelles, and an extracellular gap space of 60 Å, whereas the class average of the hemichannels had diameters of up to 140 Å in the presence of detergent micelles. Cryo EM images revealed rotational peaks that could be related to the INX-6 subunits. Structural analysis of the reconstituted INX-6 channels with single particle analysis and electron tomography suggested that the oligomeric number of the INX-6 channel was distinct from that of the dodecameric connexin channel. Dye transfer experiments indicated that the INX-6-GFP-His channels were permeable to 3-kDa and 10-kDa dextran-conjugated tracers. These findings indicate that INX-6 channels have a characteristic oligomer component that differs from that in connexin gap junction channels.

scholarly journals Calcium-mediated changes in gap junction structure: evidence from the low angle X-ray pattern.

1983 ◽  
Vol 97 (5) ◽  
pp. 1459-1466 ◽  
Author(s):  
P N Unwin ◽  
P D Ennis
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Gap Junction ◽  
Rat Liver ◽  
X Ray Diffraction ◽  
X Ray ◽  
Controlled Environments ◽  
Free Media ◽  
Junction Structure ◽  
Lattice Dimension

Rat liver gap junctions were isolated in Ca2+-free media and analyzed in controlled environments by x-ray diffraction of partially oriented pellets. Different treatments of the same preparations were compared. The ordered hexagonal lattices gave rise to detail that was sensitive to low Ca2+ concentrations (0.05 mM), but not to Mg2+ (up to 0.16 mM) or pH (between 6.0 and 8.0). The major Ca2+-mediated responses were reductions in the intensity of the (1, 0) peak and in the off-equatorial contributions to the (2, 1) peak, and changes of scale equivalent to a decrease (approximately 2%) in lattice dimension, but an increase (approximately 4%) in the dimension perpendicular to the lattice. A simple structural interpretation of these findings is that Ca2+ induces the subunits of the channel-forming assembly, the connexon, to align more nearly parallel to the channel, thereby causing the connexon to become slightly longer and more radially compact. The rearrangement is of the same nature as one found under less physiological circumstances by electron microscopy (Unwin, P. N. T., and G. Zampighi, 1980, Nature (Lond.)., 283:545-549), and may be part of a coordinated mechanism by which the channel closes.

scholarly journals Visualization of Annular Gap Junction Vesicle Processing: The Interplay between Annular Gap Junctions and Mitochondria

2018 ◽  
Author(s):  
Cheryl L. Bell ◽  
Teresa I. Shakespeare ◽  
Sandra A. Murray
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Gap Junction ◽  
Connexin 43 ◽  
Cell Communication ◽  
Super Resolution ◽  
Protective Role ◽  
Annular Gap ◽  
Transmission Electron ◽  
Junction Proteins

It is becoming clear that in addition to gap junctions, playing a role in cell-cell communication, gap junction proteins, connexins, located in cytoplasmic-compartments may have other important functions. Mitochondrial connexin 43 (Cx43) is increased after ischemic preconditioning and has been suggested to play a protective role in the heart. How Cx43 traffics to the mitochondria and the interactions of mitochondria with other Cx43-containing structures are unknown. In this study, immunocytochemical, super-resolution and transmission electron microscopy were used to detect cytoplasmic Cx43-containing structure and to demonstrate their interactions with other cytoplasmic organelles. The most prominent cytoplasmic Cx43-containing structures, annular gap junctions, were demonstrated to form intimate associations with lysosomes as well as with mitochondria. Surprisingly, the frequency of associations between mitochondria and annular gap junctions was greater than that between lysosomes and annular gap junctions. The benefits of annular gap junction/mitochondrial associations are not known. However, it is tempting to suggest that the contact between annular gap junction vesicles and mitochondria facilitates Cx43 deliver to the mitochondria. Furthermore, it points to the need for investigating trafficking of Cx43 to cytoplasmic compartments and annular gap junction as more than only a vesicle destined for degradation.

scholarly journals Visualization of Annular Gap Junction Vesicle Processing: The Interplay Between Annular Gap Junctions and Mitochondria

2018 ◽  
Vol 20 (1) ◽  
pp. 44 ◽  
Author(s):  
Cheryl Bell ◽  
Teresa Shakespeare ◽  
Amber Smith ◽  
Sandra Murray
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Gap Junction ◽  
Connexin 43 ◽  
Cell Communication ◽  
Super Resolution ◽  
Protective Role ◽  
Annular Gap ◽  
Transmission Electron ◽  
Junction Proteins

It is becoming clear that in addition to gap junctions playing a role in cell–cell communication, gap junction proteins (connexins) located in cytoplasmic compartments may have other important functions. Mitochondrial connexin 43 (Cx43) is increased after ischemic preconditioning and has been suggested to play a protective role in the heart. How Cx43 traffics to the mitochondria and the interactions of mitochondria with other Cx43-containing structures are unclear. In this study, immunocytochemical, super-resolution, and transmission electron microscopy were used to detect cytoplasmic Cx43-containing structures and to demonstrate their interactions with other cytoplasmic organelles. The most prominent cytoplasmic Cx43-containing structures—annular gap junctions—were demonstrated to form intimate associations with lysosomes as well as with mitochondria. Surprisingly, the frequency of associations between mitochondria and annular gap junctions was greater than that between lysosomes and annular gap junctions. The benefits of annular gap junction/mitochondrial associations are not known. However, it is tempting to suggest, among other possibilities, that the contact between annular gap junction vesicles and mitochondria facilitates Cx43 delivery to the mitochondria. Furthermore, it points to the need for investigating annular gap junctions as more than only vesicles destined for degradation.

A New Junctional Structure in the Epithelia of Insects of the Order Dictyoptera

1972 ◽  
Vol 10 (3) ◽  
pp. 683-691
Author(s):  
N. E. FLOWER
Keyword(s):  
Epithelial Cells ◽  
Gap Junctions ◽  
Gap Junction ◽  
Tight Junctions ◽  
Hexagonal Array ◽  
Septate Junctions ◽  
New Type ◽  
Junctional Complexes ◽  
Junctional Structure

The junctional complexes in the epithelia of insects of the order Dictyoptera have been investigated using the freeze-etch technique. As well as septate junctions, a new type of junction has been identified and the name ‘inverted gap junction’ proposed. The patch-like distribution of the inverted gap junctions basal to and often closely associated with septate junctions is very similar to the form of gap junctions and their relationship to tight junctions in vertebrates. This suggests that the inverted gap junctions, like normal gap junctions, could perform a communicating function between epithelial cells. The following features distinguish inverted gap junctions from normal gap junctions in freeze-etch preparations: (i) the arrays of particles and holes within inverted gap junctions appear on B- and A-type faces respectively, i.e. on the opposite faces to the particles and holes in gap junctions; (ii) the particles within inverted gap junctions appear to lie in rows which anastomose to form an irregular net, and not in an hexagonal array, as occurs in gap junctions.

scholarly journals Spontaneous Abortion and Chikungunya Infection: Pathological Findings

Viruses ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 554
Author(s):  
Natália Salomão ◽  
Michelle Brendolin ◽  
Kíssila Rabelo ◽  
Mayumi Wakimoto ◽  
Ana Maria de Filippis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Spontaneous Abortion ◽  
Ultrastructural Changes ◽  
Rt Pcr ◽  
Chorionic Villi ◽  
Decidual Cells ◽  
Hofbauer Cells ◽  
Hematoxylin And Eosin ◽  
Maternal Fetal Transmission

Intrauterine transmission of the Chikungunya virus (CHIKV) during early pregnancy has rarely been reported, although vertical transmission has been observed in newborns. Here, we report four cases of spontaneous abortion in women who became infected with CHIKV between the 11th and 17th weeks of pregnancy. Laboratorial confirmation of the infection was conducted by RT-PCR on a urine sample for one case, and the other three were by detection of IgM anti-CHIKV antibodies. Hematoxylin and eosin (H&E) staining and an electron microscopy assay allowed us to find histopathological, such as inflammatory infiltrate in the decidua and chorionic villi, as well as areas of calcification, edema and the deposition of fibrinoid material, and ultrastructural changes, such as mitochondria with fewer cristae and ruptured membranes, endoplasmic reticulum with dilated cisterns, dispersed chromatin in the nuclei and the presence of an apoptotic body in case 1. In addition, by immunohistochemistry (IHC), we found a positivity for the anti-CHIKV antibody in cells of the endometrial glands, decidual cells, syncytiotrophoblasts, cytotrophoblasts, Hofbauer cells and decidual macrophages. Electron microscopy also helped in identifying virus-like particles in the aborted material with a diameter of 40–50 nm, which was consistent with the size of CHIKV particles in the literature. Our findings in this study suggest early maternal fetal transmission, adding more evidence on the role of CHIKV in fetal death.

scholarly journals Two Drosophila Innexins Are Expressed in Overlapping Domains and Cooperate to Form Gap-Junction Channels

2000 ◽  
Vol 11 (7) ◽  
pp. 2459-2470 ◽  
Author(s):  
Lucy A. Stebbings ◽  
Martin G. Todman ◽  
Pauline Phelan ◽  
Jonathan P. Bacon ◽  
Jane A. Davies
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Ectopic Expression ◽  
In Vivo Studies ◽  
Electrophysiological Properties ◽  
Gap Junction Channels ◽  
Overlapping Domains ◽  
In Vitro Data

Members of the innexin protein family are structural components of invertebrate gap junctions and are analogous to vertebrate connexins. Here we investigate two Drosophila innexin genes,Dm-inx2 and Dm-inx3 and show that they are expressed in overlapping domains throughout embryogenesis, most notably in epidermal cells bordering each segment. We also explore the gap-junction–forming capabilities of the encoded proteins. In pairedXenopus oocytes, the injection of Dm-inx2mRNA results in the formation of voltage-sensitive channels in only ∼ 40% of cell pairs. In contrast, Dm-Inx3 never forms channels. Crucially, when both mRNAs are coexpressed, functional channels are formed reliably, and the electrophysiological properties of these channels distinguish them from those formed by Dm-Inx2 alone. We relate these in vitro data to in vivo studies. Ectopic expression ofDm-inx2 in vivo has limited effects on the viability ofDrosophila, and animals ectopically expressingDm-inx3 are unaffected. However, ectopic expression of both transcripts together severely reduces viability, presumably because of the formation of inappropriate gap junctions. We conclude that Dm-Inx2 and Dm-Inx3, which are expressed in overlapping domains during embryogenesis, can form oligomeric gap-junction channels.

Postjunctional supersensitivity of the rat vas deferens and gap junctions

1976 ◽  
Vol 54 (3) ◽  
pp. 412-416 ◽  
Author(s):  
D. M. Paton ◽  
J. Buckland-Nicks ◽  
A. Johns
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Spontaneous Activity ◽  
Vas Deferens ◽  
Rat Vas Deferens ◽  
Sprague Dawley ◽  
Glutaraldehyde Fixation ◽  
Sprague Dawley Rats

Tissues from the duodenum and vas deferens of Sprague–Dawley rats were examined of the rat vas deferens and gap junctions. Can. J. Physiol. Pharmacol. 54, 412–416. by electron microscopy after glutaraldehyde fixation and postosmication. Gap junctions (nexuses) were readily demonstrated in the duodenum in both control and reserpine treated animals (1.0 mg/kg per day for 7 days). However, gap junctions could not be demonstrated in vas deferens. It is concluded that the postjunctional supersensitivity and spontaneous activity induced by reserpine in vas deferens, does not result from the formation of gap junctions.

Freeze-fracture studies of frog atrial fibres

1976 ◽  
Vol 22 (2) ◽  
pp. 427-434
Author(s):  
F. Mazet ◽  
J. Cartaud
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Outer Membrane ◽  
Electrical Coupling ◽  
Freeze Fracture ◽  
Present Knowledge ◽  
Inner Membrane ◽  
Freeze Fracturing ◽  
Morphological Variant ◽  
Characteristic Features

The freeze-fracturing technique was used to characterize the junctional devices involved in the electrical coupling of frog atrial fibres. These fibres are connected by a type of junction which can be interpreted as a morphological variant of the “gap junction” or “nexus”. The most characteristic features are rows of 9-nm junctional particles forming single or anastomosed circular profiles on the inner membrane face, and corresponding pits on the outer membrane face. Very seldom aggregates consisting of few geometrically disposed 9-nm particles are found. The significance of the junctional structures in the atrial fibres is discussed, with respect to present knowledge about junctional features of gap junctions in various tissues, including embryonic ones.

Investigation of the roles of Ca2+ and InsP3 diffusion in the coordination of Ca2+ signals between connected hepatocytes

2001 ◽  
Vol 114 (11) ◽  
pp. 1999-2007
Author(s):  
Caroline Clair ◽  
Cécile Chalumeau ◽  
Thierry Tordjmann ◽  
Josiane Poggioli ◽  
Christophe Erneux ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Significant Role ◽  
Signaling Molecules ◽  
Rat Hepatocyte ◽  
Inositol 1,4,5 Trisphosphate ◽  
Gap Junction Coupling ◽  
Junction Coupling ◽  
Insp3 Receptor

Glycogenolytic agonists induce coordinated Ca2+ oscillations in multicellular rat hepatocyte systems as well as in the intact liver. The coordination of intercellular Ca2+ signals requires functional gap-junction coupling. The mechanisms ensuring this coordination are not precisely known. We investigated possible roles of Ca2+ or inositol 1,4,5-trisphosphate (InsP3) as a coordinating messengers for Ca2+ spiking among connected hepatocytes. Application of ionomycin or of supra-maximal concentrations of agonists show that Ca2+ does not significantly diffuse between connected hepatocytes, although gap junctions ensure the passage of small signaling molecules, as demonstrated by FRAP experiments. By contrast, coordination of Ca2+ spiking among connected hepatocytes can be favored by a rise in the level of InsP3, via the increase of agonist concentrations, or by a shift in the affinity of InsP3 receptor for InsP3. In the same line, coordination cannot be achieved if the InsP3 is rapidly metabolized by InsP3-phosphatase in one cell of the multiplet. These results demonstrate that even if small amounts of Ca2+ diffuse across gap junctions, they most probably do not play a significant role in inducing a coordinated Ca2+ signal among connected hepatocytes. By contrast, coordination of Ca2+ oscillations is fully dependent on the diffusion of InsP3 between neighboring cells.

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