Cell junctions in the developing compound eye of the desert locust Schistocerca gregaria

Development ◽  
1976 ◽  
Vol 36 (2) ◽  
pp. 409-423
Author(s):  
S. Eley ◽  
P. M. J. Shelton
Keyword(s):  
Gap Junctions ◽  
Compound Eye ◽  
Schistocerca Gregaria ◽  
Intercellular Junctions ◽  
Cell Junctions ◽  
Different Types ◽  
Undifferentiated Cells ◽  
Development Gap ◽  
Sequential Appearance ◽  
Subsequent Disappearance

Intercellular junctions in the developing retina of the locust Schistocerca gregaria have been examined by electron microscopy. Different types of junction appear in a well-defined sequence during development. Five stages of ommatidial development are described. Close junctions and punctate junctions are present throughout development. Gap junctions appear transiently amongst the undifferentiated cells, before clearly defined preommatidia can be distinguished. The subsequent disappearance of gap junctions may be correlated with cell determination. Lanthanum studies confirm these findings. The later sequential appearance of adhesive junction types is described. These include septate desmosomes and two types of desmosomes. In the fully differentiated ommatidium only two types of junction remain, these are: desmosomes and rhabdomeric junctions.

Cell junctions in the excitable epithelium of bioluminescent scales on a polynoid worm: a freeze-fracture and electrophysiological study

1980 ◽  
Vol 41 (1) ◽  
pp. 341-368
Author(s):  
A. Bilbaut
Keyword(s):  
Epithelial Cells ◽  
Gap Junctions ◽  
Action Potentials ◽  
Electrophysiological Study ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Cell Junctions ◽  
Functional Roles ◽  
Electrophysiological Properties ◽  
Current Passage

The bioluminescent scales of the polynoid worm Acholoe are covered by a dorsal and ventral monolayer of epithelium. The luminous activity is intracellular and arises from the ventral epithelial cells, which are modified as photocytes. Photogenic and non-photogenic epithelial cells have been examined with regard to intercellular junctions and electrophysiological properties. Desmosomes, septate and gap junctions are described between all the epithelial cells. Lanthanum impregnation and freeze-fracture reveal that the septate junctions belong to the pleated-type found in molluscs, arthropods and other annelid tissues. Freeze-fractured gap junctions show polygonal arrays of membrane particles on the P face and complementary pits on the E face. Gap junctions are of the P type as reported in vertebrate, mollusc and some annelid tissues. Intracellular current passage also induces propagated non-overshooting action potentials in all the epithelial cells; in photocytes, an increase of injected current elicits another response which is a propagated 2-component overshooting action potential correlated with luminous activity. This study shows the coexistence of septate and gap junctions in a conducting and excitable invertebrate epithelium. The results are discussed in relation to the functional roles of intercellular junctions in invertebrate epithelia. It is concluded that the gap junctions found in this excitable epithelium represent the structural sites of the cell-to-cell propagation of action potentials.

Cell junctions in the compound eye of the worker honey bee

1978 ◽  
Vol 36 (2) ◽  
pp. 608-609
Author(s):  
E. Nickel ◽  
G. Scheck
Keyword(s):  
Honey Bee ◽  
Compound Eye ◽  
Electrical Coupling ◽  
Extracellular Fluid ◽  
Green Light ◽  
Intercellular Junctions ◽  
Cell Junctions ◽  
Pigment Cells ◽  
Electron Microscopic ◽  
Double Peaks

The ommatidium of the compound eye of the honey bee consists of visual or retinula cells which form a fused rhabdom. Each ommatidium contains three types of receptors which are sensitive to u. v., blue or green light. The ommatidium is isolated from its neighbours by secondary pigment cells.Electrical recordings from single retinula cells have shown sensitivity curves with double peaks. Basicly these two peaks can arise from two different photopigments in one receptor cell or from electrical coupling between two receptor cells of different spectral sensitivity.The present electron microscopic study was carried out in order to search for Junctional specializations between different cells in the ommatidium of the worker bee. These junctions are of particular functional interest because of their role in restricting extracellular fluid movement as well as in electrical coupling between cells. In freeze-cleaved specimens intercellular junctions can be identified on the characteristic array and size of intramembranous particles.

scholarly journals Segmental differentiations of cell junctions in the vascular endothelium. The microvasculature.

1975 ◽  
Vol 67 (3) ◽  
pp. 863-885 ◽  
Author(s):  
M Simionescu ◽  
N Simionescu ◽  
G E Palade
Keyword(s):  
Gap Junctions ◽  
Tight Junctions ◽  
Vascular Endothelium ◽  
Intercellular Junctions ◽  
Cell Junctions ◽  
Capillary Endothelium ◽  
Thin Sections ◽  
Low Profile ◽  
Special Case

Small vascular units consisting of an arteriole, its capillaries, and the emerging venule (ACV units) were identified in the rat omentum and mesentery. They were fixed in situ and processed for electron microscopy either as whole units or as dissected segments. Systematic examination of the latter (in thin sections, as well as in freeze-cleaved preparations) showed that the intercellular junctions of the vascular endothelium vary characteristically from one segment to another in the microvasculature. In arterioles, the endothelium has continuous and elaborate tight junctions with interpolated large gap junctions. The capillary endothelium is provided with tight junctions formed by either branching or staggered strands; gap junctions are absent at this level. The pericytic venules exhibit loosely organized endothelial junctions with discontinuous low-profile ridges and grooves, usually devoid of particles. No gap junctions were found in these vessels. The endothelium of muscular venules has the same type of junctions (discontinuous ridges and grooves of low profile); in addition, it displays isolated gap junctions of smaller size and lower frequency than in arterioles. The term communicating junction (macula communicans) is proposed as a substitute for gap junctions, since the latter is inappropriate, in general, and confusing in the special case of the vascular endothelium.

scholarly journals Organization of cell junctions in the peritoneal mesothelium

1977 ◽  
Vol 74 (1) ◽  
pp. 98-110 ◽  
Author(s):  
M Simionescu ◽  
N Simionescu
Keyword(s):  
Gap Junctions ◽  
Cell Body ◽  
Intercellular Junctions ◽  
Cell Junctions ◽  
Cell Process ◽  
Staggered Arrangement ◽  
Peritoneal Mesothelium ◽  
General Geometry ◽  
Small Clusters ◽  
Rats And Mice

Intercellular junctions in the mesothelium of the visceral (mesentery and omentum), and parietal (diaphragm, pre-aortic, and iliac region) peritoneum were examined in rats and mice by using freeze-cleaved preparations. In addition to usual intercellular junctions (cell body junctions), special junctions are found between cell processes and the surface of the neighboring cell (cell process junctions). Cell body junctions are provided with tight junctions and communicating (gap) junctions. The former consist of one to two junctional strands which show a characteristic staggered arrangement, and focal discontinuities. In cell process junctions, the strands form loops or appear as short, free-ending elements; their polymorphism suggests considerable lability, probably in connection with their assembly and disassembly. The existence of free-ending strands indicates that such structures can be used as attachment devices without being concomitantly involved in the formation of occluding zonules. In both types of junctions, the strands can be resolved into bars, approximately 80- 100nm long, frequently provided with terminal enlargements and intercalated particles which occur singly or in small clusters. These particles are morphologically similar to those present in communicating (gap) junctions. The mesothelium is also provided with isolate composite macular junctions. Throughout the mesothelium, the cleavage plane follows the outer contour of junctional strands and particles, suggesting that strand-to-strand interactions in the apposed membranes are weaker than interactions between each strand and underlying cytoplasmic structures. In their general geometry and cleavage characteristics, the mesothelial junctions resemble the junctions found in the venular endothelium.

The application of freeze-fracture in the analysis of intercellular junctions in pleuro-pulmonary tumors

1990 ◽  
Vol 48 (3) ◽  
pp. 540-541
Author(s):  
T. M. Mukherjee ◽  
J. G. Swift
Keyword(s):  
Gap Junctions ◽  
Tight Junctions ◽  
Thin Section ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Squamous Cell Carcinomas ◽  
Cell Junctions ◽  
Thin Sections ◽  
Pulmonary Tumors ◽  
Diagnostic Importance

Thin section and freeze-fracture techniques have been used to examine the morphology of cell junctions in a variety of pleuro-pulmonary tumours with the aim of identifying features that may be of diagnostic importance or of significance in the development of the tumour. Freeze-fracture preparations are particularly useful for the analysis of cell junctions, since extensive face views of the interior of the cell membrane are exposed. This enables precise characterisation of the type of junctions present, their extent and their inter-relationships.Freeze-fracture replicas can reveal the presence of junctions that would be difficult or impossible to detect in thin sections. For example, desmosomes are a well-known feature in thin sections of squamous cell carcinomas, but these tumours may also have focal tight junctions and gap junctions (Figs. 1,2). The tight and gap junctions can occur separately (Fig.l), or in combination (Fig. 2). Similarly, in a recent study of a case of “Ewing’s sarcoma”, replicas showed the presence of unusual, elaborate focal tight junctions, a feature never suspected from the routine thin section studies of this tumour.

Quantitative EM of gap junction distribution in mutant drosophila wing discs

1983 ◽  
Vol 41 ◽  
pp. 720-721
Author(s):  
J.S. Ryerse
Keyword(s):  
Gap Junctions ◽  
Growth Control ◽  
Intercellular Junctions ◽  
Wing Disc ◽  
En Bloc ◽  
Metabolic Cooperation ◽  
Drosophila Wing ◽  
Adult Wing ◽  
Wing Discs ◽  
Wing Pouch

Gap junctions are intercellular junctions found in both vertebrates and invertebrates through which ions and small molecules can pass. Their distribution in tissues could be of critical importance for ionic coupling or metabolic cooperation between cells or for regulating the intracellular movement of growth control and pattern formation factors. Studies of the distribution of gap junctions in mutants which develop abnormally may shed light upon their role in normal development. I report here the distribution of gap junctions in the wing pouch of 3 Drosophila wing disc mutants, vg (vestigial) a cell death mutant, 1(2)gd (lethal giant disc) a pattern abnormality mutant and 1(2)gl (lethal giant larva) a neoplastic mutant and compare these with wildtype wing discs.The wing pouch (the anlagen of the adult wing blade) of a wild-type wing disc is shown in Fig. 1 and consists of columnar cells (Fig. 5) joined by gap junctions (Fig. 6). 14000x EMs of conventionally processed, UA en bloc stained, longitudinally sectioned wing pouches were enlarged to 45000x with a projector and tracings were made on which the lateral plasma membrane (LPM) and gap junctions were marked.

Structural modifications of intercellular junctions.

1978 ◽  
Vol 36 (2) ◽  
pp. 330-331
Author(s):  
J. Metz ◽  
M. Merlo ◽  
W. G. Forssmann
Keyword(s):  
Gap Junctions ◽  
Intercellular Junctions ◽  
Cell Isolation ◽  
Extrahepatic Cholestasis ◽  
Structural Modifications ◽  
Pancreatic Duct Ligation ◽  
Pancreatic Cells ◽  
Duct Ligation ◽  
Thin Sectioning ◽  
And Function

Structure and function of intercellular junctions were studied under the electronmicroscope using conventional thin sectioning and freeze-etch replicas. Alterations of tight and gap junctions were analyzed 1. of exocrine pancreatic cells under cell isolation conditions and pancreatic duct ligation and 2. of hepatocytes during extrahepatic cholestasis.During the different steps of cell isolation of exocrine pancreatic cells, gradual changes of tight and gap junctions were observed. Tight junctions, which formed belt-like structures around the apex of control acinar cells in situ, subsequently diminished, became interrupted and were concentrated into macular areas (Fig. 1). Aggregations of membrane associated particles, which looked similar to gap junctions, were intermixed within tight junctional areas (Fig. 1). These structures continously disappeared in the last stages of the isolation procedure. The intercellular junctions were finally separated without destroying the integrity of the cell membrane, which was confirmed with porcion yellow, lanthanum chloride and horse radish peroxidase.

scholarly journals Plectin ensures intestinal epithelial integrity and protects colon against colitis

2021 ◽  
Vol 14 (3) ◽  
pp. 691-702
Author(s):  
Alzbeta Krausova ◽  
Petra Buresova ◽  
Lenka Sarnova ◽  
Gizem Oyman-Eyrilmez ◽  
Jozef Skarda ◽  
...  
Keyword(s):  
Mechanical Stability ◽  
Intestinal Barrier ◽  
Intercellular Junctions ◽  
Protein Profiling ◽  
Cell Junctions ◽  
Intestinal Barrier Function ◽  
Intestinal Epithelial ◽  
Critical Determinant ◽  
In Vitro Feeding

AbstractPlectin, a highly versatile cytolinker protein, provides tissues with mechanical stability through the integration of intermediate filaments (IFs) with cell junctions. Here, we hypothesize that plectin-controlled cytoarchitecture is a critical determinant of the intestinal barrier function and homeostasis. Mice lacking plectin in an intestinal epithelial cell (IEC; PleΔIEC) spontaneously developed colitis characterized by extensive detachment of IECs from the basement membrane (BM), increased intestinal permeability, and inflammatory lesions. Moreover, plectin expression was reduced in the colons of ulcerative colitis (UC) patients and negatively correlated with the severity of colitis. Mechanistically, plectin deficiency in IECs led to aberrant keratin filament (KF) network organization and the formation of dysfunctional hemidesmosomes (HDs) and intercellular junctions. In addition, the hemidesmosomal α6β4 integrin (Itg) receptor showed attenuated association with KFs, and protein profiling revealed prominent downregulation of junctional constituents. Consistent with the effects of plectin loss in the intestinal epithelium, plectin-deficient IECs exhibited remarkably reduced mechanical stability and limited adhesion capacity in vitro. Feeding mice with a low-residue liquid diet that reduced mechanical stress and antibiotic treatment successfully mitigated epithelial damage in the PleΔIEC colon.

scholarly journals Targeting Cancer Cell Tight Junctions Enhances PLGA-Based Photothermal Sensitizers’ Performance In Vitro and In Vivo

Pharmaceutics ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 43
Author(s):  
Victoria O. Shipunova ◽  
Vera L. Kovalenko ◽  
Polina A. Kotelnikova ◽  
Anna S. Sogomonyan ◽  
Olga N. Shilova ◽  
...  
Keyword(s):  
Epithelial Mesenchymal Transition ◽  
3D Culture ◽  
Intercellular Junctions ◽  
Cell Junctions ◽  
Multicellular Spheroids ◽  
Mesenchymal Transition ◽  
Non Invasive ◽  
Order Of Magnitude

The development of non-invasive photothermal therapy (PTT) methods utilizing nanoparticles as sensitizers is one of the most promising directions in modern oncology. Nanoparticles loaded with photothermal dyes are capable of delivering a sufficient amount of a therapeutic substance and releasing it with the desired kinetics in vivo. However, the effectiveness of oncotherapy methods, including PTT, is often limited due to poor penetration of sensitizers into the tumor, especially into solid tumors of epithelial origin characterized by tight cellular junctions. In this work, we synthesized 200 nm nanoparticles from the biocompatible copolymer of lactic and glycolic acid, PLGA, loaded with magnesium phthalocyanine, PLGA/Pht-Mg. The PLGA/Pht-Mg particles under the irradiation with NIR light (808 nm), heat the surrounding solution by 40 °C. The effectiveness of using such particles for cancer cells elimination was demonstrated in 2D culture in vitro and in our original 3D model with multicellular spheroids possessing tight cell contacts. It was shown that the mean inhibitory concentration of such nanoparticles upon light irradiation for 15 min worsens by more than an order of magnitude: IC50 increases from 3 µg/mL for 2D culture vs. 117 µg/mL for 3D culture. However, when using the JO-4 intercellular junction opener protein, which causes a short epithelial–mesenchymal transition and transiently opens intercellular junctions in epithelial cells, the efficiency of nanoparticles in 3D culture was comparable or even outperforming that for 2D (IC50 = 1.9 µg/mL with JO-4). Synergy in the co-administration of PTT nanosensitizers and JO-4 protein was found to retain in vivo using orthotopic tumors of BALB/c mice: we demonstrated that the efficiency in the delivery of such nanoparticles to the tumor is 2.5 times increased when PLGA/Pht-Mg nanoparticles are administered together with JO-4. Thus the targeting the tumor cell junctions can significantly increase the performance of PTT nanosensitizers.

The distribution of non-synaptic intercellular junctions during neurone differentiation in the developing spinal cord of the clawed toad

Development ◽  
1975 ◽  
Vol 33 (2) ◽  
pp. 403-417
Author(s):  
Brian P. Hayes ◽  
Alan Roberts
Keyword(s):  
Spinal Cord ◽  
Gap Junctions ◽  
Neural Differentiation ◽  
Electrical Coupling ◽  
Intercellular Junctions ◽  
Ependymal Cells ◽  
Freedom Of Movement ◽  
Ventricular Cells ◽  
Vertebrate Embryos ◽  
Developing Spinal Cord

The distribution of intercellular junctions, other than synapses and their precursors, has beendescribed in the developing spinal cord of Xenopus laevis between the neurula andfree swimming tadpole stages. At the neurocoel, ventricular cells are joined in the apical contactzone by a sequence of junctions which usually has one or more intermediate junctions but often also includes close appositions, gap junctions and desmosomes. This apical complex is more diverse than that reported in other vertebrate embryos and between ependymal cells in the adult central nervous system. Gap junctions are also found between ventricular cells and their processes near the external cord surface. However, no other special junctions occur in this location under the basementlamella which surrounds the cord. Punctate intermediate junctions are generally distributed between undifferentiated and differentiating cells and their processes but were not found in neuropil after stage 28. These results are discussed in relation to cell movements during neural differentiation, possible effects on the freedom of movement of ions and molecules through extracellular pathways in the embryo, and possible intercytoplasmic pathways via gap junctions which may be responsible for the physiologically observed electrical coupling between neural tube cells.

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