Gap and septate junctions in the excitable endoderm of Polyorchis penicillatus (Hydrozoa, Anthomedusae)

1979 ◽  
Vol 36 (1) ◽  
pp. 391-400
Author(s):  
M.G. King ◽  
A.N. Spencer
Keyword(s):  
Epithelial Cells ◽  
Action Potential ◽  
Gap Junctions ◽  
Intercellular Space ◽  
Septate Junctions ◽  
Impulse Conduction ◽  
Polyorchis Penicillatus ◽  
Morphological Basis ◽  
En Face ◽  
Electron Lucent

The morphological basis of impulse conduction in a jellyfish epithelium was investigated. Lanthanum impregnation of endodermal canal and endodermal lamella verified the existence of true gap junctions in Polyorchis. In both transverse and en face sections of gap junctions, electron-lucent globules, with a width of 7–8 nm and a spacing of about 11 nm, are evident. Gap-junctions are concentrated at the peripheral canal margin and septate junctions are localized around the canal lumen. Epithelial cells of the endodermal canals are capable of conducting a non-decrementing action potential. It is suggested that endodermal spike propagation, which can mediate ‘crumpling’ behaviour, is dependent upon low-resistence ionic pathways provided by gap-junctions and upon sealing of the intercellular space from saline extracellular fluids by septate junctions.

scholarly journals THE STRUCTURAL ORGANIZATION OF THE SEPTATE AND GAP JUNCTIONS OF HYDRA

1972 ◽  
Vol 52 (2) ◽  
pp. 397-408 ◽  
Author(s):  
Arthur R. Hand ◽  
Stephen Gobel
Keyword(s):  
Gap Junctions ◽  
Intercellular Space ◽  
Structural Organization ◽  
Barrier Properties ◽  
Ruthenium Red ◽  
Septate Junction ◽  
Intercellular Coupling ◽  
Lanthanum Hydroxide ◽  
Septate Junctions ◽  
Large Numbers

The septate junctions and gap junctions of Hydra were studied utilizing the extracellular tracers lanthanum hydroxide and ruthenium red. Analysis of the septate junction from four perspectives has shown that each septum consists of a single row of hexagons sharing common sides of 50–60 A. Each hexagon is folded into chair configuration. Two sets of projections emanate from the corners of the hexagons. One set (A projections) attaches the hexagons to the cell membranes at 80–100-A intervals, while the other set (V projections) joins some adjacent septa to each other. The septate junctions generally contain a few large interseptal spaces and a few septa which do not extend the full length of the junction. Basal to the septate junctions the cells in each layer are joined by numerous gap junctions. Gap junctions also join the muscular processes in each layer as well as those which connect the layers across the mesoglea. The gap junctions of Hydra are composed of rounded plaques 0.15–0.5 µ in diameter which contain 85-A hexagonally packed subunits. Each plaque is delimited from the surrounding intercellular space by a single 40-A band. Large numbers of these plaques are tightly packed, often lying about 20 A apart. This en plaque configuration of the gap junctions of Hydra contrasts with their sparser, more widely separated distribution in many vertebrate tissues. These studies conclude that the septate junction may possess some barrier properties and that both junctions are important in intercellular adhesion. On a morphological basis, the gap junction appears to be more suitable for intercellular coupling than the septate junction.

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 Cardiac macrophages prevent sudden death during heart stress

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Junichi Sugita ◽  
Katsuhito Fujiu ◽  
Yukiteru Nakayama ◽  
Takumi Matsubara ◽  
Jun Matsuda ◽  
...  
Keyword(s):  
Sudden Cardiac Death ◽  
Sudden Death ◽  
Gap Junctions ◽  
Adrenergic Receptor ◽  
Cardiac Death ◽  
Connexin 43 ◽  
Pressure Overload ◽  
Impulse Conduction ◽  
Cardiac Impulse ◽  
Medical Need

AbstractCardiac arrhythmias are a primary contributor to sudden cardiac death, a major unmet medical need. Because right ventricular (RV) dysfunction increases the risk for sudden cardiac death, we examined responses to RV stress in mice. Among immune cells accumulated in the RV after pressure overload-induced by pulmonary artery banding, interfering with macrophages caused sudden death from severe arrhythmias. We show that cardiac macrophages crucially maintain cardiac impulse conduction by facilitating myocardial intercellular communication through gap junctions. Amphiregulin (AREG) produced by cardiac macrophages is a key mediator that controls connexin 43 phosphorylation and translocation in cardiomyocytes. Deletion of Areg from macrophages led to disorganization of gap junctions and, in turn, lethal arrhythmias during acute stresses, including RV pressure overload and β-adrenergic receptor stimulation. These results suggest that AREG from cardiac resident macrophages is a critical regulator of cardiac impulse conduction and may be a useful therapeutic target for the prevention of sudden death.

A novel form of cellular communication among thymic epithelial cells: intercellular calcium wave propagation

2003 ◽  
Vol 285 (5) ◽  
pp. C1304-C1313 ◽  
Author(s):  
O. K. Nihei ◽  
A. C. Campos de Carvalho ◽  
D. C. Spray ◽  
W. Savino ◽  
L. A. Alves
Keyword(s):  
Wave Propagation ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Gap Junctions ◽  
Thymic Epithelial Cells ◽  
Calcium Wave ◽  
Thymic Epithelial Cell ◽  
Calcium Waves ◽  
Thymic Nurse Cells ◽  
Epithelial Cell Lines

We here describe intercellular calcium waves as a novel form of cellular communication among thymic epithelial cells. We first characterized the mechanical induction of intercellular calcium waves in different thymic epithelial cell preparations: cortical 1-4C18 and medullary 3-10 thymic epithelial cell lines and primary cultures of thymic “nurse” cells. All thymic epithelial preparations responded with intercellular calcium wave propagation after mechanical stimulation. In general, the propagation efficacy of intercellular calcium waves in these cells was high, reaching 80-100% of the cells within a given confocal microscopic field, with a mean velocity of 6-10 μm/s and mean amplitude of 1.4- to 1.7-fold the basal calcium level. As evaluated by heptanol and suramin treatment, our results suggest the participation of both gap junctions and P2 receptors in the propagation of intercellular calcium waves in thymic nurse cells and the more prominent participation of gap junctions in thymic epithelial cell lines. Finally, in cocultures, the transmission of intercellular calcium wave was not observed between the mechanically stimulated thymic epithelial cell and adherent thymocytes, suggesting that intercellular calcium wave propagation is limited to thymic epithelial cells and does not affect the neighboring thymocytes. In conclusion, these data describe for the first time intercellular calcium waves in thymic epithelial cells and the participation of both gap junctions and P2 receptors in their propagation.

scholarly journals Evidence for two physiologically distinct gap junctions expressed by the chick lens epithelial cell.

1986 ◽  
Vol 102 (1) ◽  
pp. 194-199 ◽  
Author(s):  
T M Miller ◽  
D A Goodenough
Keyword(s):  
Epithelial Cell ◽  
Epithelial Cells ◽  
Gap Junctions ◽  
Cell Communication ◽  
Cell Types ◽  
Lens Epithelial Cell ◽  
Dye Transfer ◽  
Fiber Cells ◽  
Junctional Permeability ◽  
Different Cell Types

Lens epithelial cells communicate with two different cell types. They communicate with other epithelial cells via gap junctions on their lateral membranes, and with fiber cells via junctions on their apices. We tested independently these two routes of cell-cell communication to determine if treatment with a 90% CO2-equilibrated medium caused a decrease in junctional permeability; the transfer of fluorescent dye was used as the assay. We found that the high-CO2 treatment blocked intraepithelial dye transfer but not fiber-to-epithelium dye transfer. The lens epithelial cell thus forms at least two physiologically distinct classes of gap junctions.

Ca2+ regulation of gap junctional coupling in lens epithelial cells

2001 ◽  
Vol 281 (3) ◽  
pp. C972-C981 ◽  
Author(s):  
Grant C. Churchill ◽  
Monica M. Lurtz ◽  
Charles F. Louis
Keyword(s):  
Epithelial Cells ◽  
Gap Junctions ◽  
Direct Action ◽  
Hill Coefficient ◽  
Lens Epithelial Cells ◽  
Alexa Fluor ◽  
Agonist Stimulation ◽  
Junctional Coupling ◽  
Gap Junctional ◽  
Gap Junctional Coupling

The quantitative effects of Ca2+signaling on gap junctional coupling in lens epithelial cells have been determined using either the spread of Mn2+ that is imaged by its ability to quench the fluorescence of fura 2 or the spread of the fluorescent dye Alexa Fluor 594. Gap junctional coupling was unaffected by a mechanically stimulated cell-to-cell Ca2+wave. Furthermore, when cytosolic Ca2+ concentration (Ca[Formula: see text]) increased after the addition of the agonist ATP, coupling was unaffected during the period that Ca[Formula: see text] was maximal. However, coupling decreased transiently ∼5–10 min after agonist addition when Ca[Formula: see text] returned to resting levels, indicating that this transient decrease in coupling was unlikely due to a direct action of Ca[Formula: see text] on gap junctions. An increase in Ca[Formula: see text] mediated by the ionophore ionomycin that was sustained for several minutes resulted in a more rapid and sustained decrease in coupling (IC50 ∼300 nM Ca2+, Hill coefficient of 4), indicating that an increase in Ca[Formula: see text]alone could regulate gap junctions. Thus Ca[Formula: see text]increases that occurred during agonist stimulation and cell-to-cell Ca2+ waves were too transient to mediate a sustained uncoupling of lens epithelial cells.

Observations on the nephridial system of the cestode Moniezia expansa (Rud., 1805)

Parasitology ◽  
1969 ◽  
Vol 59 (2) ◽  
pp. 449-459 ◽  
Author(s):  
R. E. Howells
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Connective Tissue ◽  
Intercellular Space ◽  
Technical Assistance ◽  
Light And Electron Microscopy ◽  
Flame Cell ◽  
Research Scholarship ◽  
Research Facilities

The nephridial system of M. expansa has been studied using light and electron microscopy, and a number of histochemical techniques have been used on sections of the worm. The organization of the nephridial system and the fine structure of the flame cells and the nephridial ducts are described. Pores, which connect the nephridial lumen to the intercellular space of the connective tissue, exist at the junction of a flame cell and a nephridial duct. These pores may be considered nephrostomes and the system therefore is not protonephridial as defined by Hyman (1951).The epithelium lining the nephridial ducts has a structure which suggests that it is metabolically active. It is postulated that the beating of the cilia of the flame cells draws fluid into the ducts via the nephrostomes, with absorption and/or secretion of solutes being carried out by the epithelial cells of the duct walls. The function of the nephridial system is discussed.I am grateful to Professor James Brough for the provision of research facilities at the Department of Zoology, University College, Cardiff, andtoDrD. A. Erasmus for much helpful advice during the course of the work. I wish to thank Professors W. Peters and T. Wilson for critically reading the manuscript and Miss M. Williams and Mr T. Davies for expert technical assistance.I also wish to thank the Veterinary Inspector and his staff at the Roath Abattoir, Cardiff, for their kind co-operation and assistance in obtaining material.The work was carried out under the tenure of an S.R.C. research scholarship.

Epithelial Cells of Nasal Mucosa Express Functional Gap Junctions of Connexin 43

2003 ◽  
Vol 123 (2) ◽  
pp. 314-320 ◽  
Author(s):  
Te-huei Yeh ◽  
Mao-chang Su ◽  
Chuan-jen Hsu ◽  
Yue-hsiang Chen ◽  
Shiann-yann Lee
Keyword(s):  
Epithelial Cells ◽  
Gap Junctions ◽  
Nasal Mucosa ◽  
Connexin 43
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