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.

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.

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.

Morphological Changes of Intercellular Junctions in the Rat Submandibular Gland Treated by Long-term Repeated Administration of Isoproterenol

1987 ◽  
Vol 66 (8) ◽  
pp. 1303-1309 ◽  
Author(s):  
T. Inoue ◽  
H. Yamane ◽  
T. Yamamura ◽  
M. Shimono
Keyword(s):  
Gap Junctions ◽  
Tight Junctions ◽  
Morphological Changes ◽  
Freeze Fracture ◽  
Acinar Cells ◽  
Intercellular Junctions ◽  
Repeated Administration ◽  
Experimental Conditions ◽  
Significant Difference

Long-term repeated administration of isoproterenol (lPR) 2 mg/100 g bw, once daily for ten days, resulted in morphological changes in the intercellular junctions of rat submandibular glands, which were investigated by means of the freeze fracture technique. A significantly increased number of tight-junctional strands was present. These junctional strands extended much deeper toward the basal membrane than those in normal acinar cells. The basal frontier strands that branched from the networks of tight junctions were elongated and had either free-endings or terminal loops, which were more frequently observed in the IPR-treated acinar cells than in untreated acinar cells. Some of the strands of tight junctions were connected to small gap junctions. The diameters of gap junctions were not significantly different from those of control acinar cells. However, smooth areas devoid of particles were found intermingling with the usual packed particles in irregularly shaped small gap junctions. There was no significant difference between the desmosomes of IPR-treated and untreated acinar cells, in terms of either morphology or distribution. These changes in junctional morphology in the IPR-treated acinar cells resemble those seen in salivary glands during development, and in some experimental conditions including tumorous changes.

scholarly journals Development of cell junctions in sea-urchin embryos

1983 ◽  
Vol 62 (1) ◽  
pp. 27-48
Author(s):  
E. Spiegel ◽  
L. Howard
Keyword(s):  
Epithelial Cells ◽  
Basement Membrane ◽  
Digestive Tract ◽  
Sea Urchin ◽  
Freeze Fracture ◽  
Cell Junctions ◽  
Septate Junctions ◽  
Thin Sections ◽  
Sea Urchin Embryos ◽  
Lanthanum Tracer

The development of cell junctions in sea-urchin embryos has been investigated using thin sections, lanthanum-tracer and freeze-fracture techniques. Three types of desmosomes are present: belt desmosomes and spot desmosomes, which attach cells to each other, and hemi-desmosomes, which attach cells to the basement membrane. Two types of septate junctions are present: the straight, unbranched, double-septum septate, which is present in epithelial cells throughout embryogenesis, and the pleated, anastomosing, single-septum septate. The latter is formed only on cells that have invaginated to the interior of the embryo to form the digestive tract. The pleated junctions are shown to replace the straight junctions that were originally present before the cells migrated to the interior. It is suggested that these pleated septates may be specialized for digestive processes, since they are developed just prior to feeding and are retained in the adult intestine. Tricellular junctions, which join the bicellular junctions of three adjoining cells, have been identified in the embryo and in the adult intestine. Evidence for the presence of gap junctions was not obtained, but there are indications of their presence.

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.

Intercellular Junctions in Fanft-Induced Transitional Cell Carcinomas in Tissue Culture, In situ Freeze-Fracture Studies

1977 ◽  
Vol 35 ◽  
pp. 594-595
Author(s):  
Bendicht U. Pauli ◽  
Ronald S. Weinstein
Keyword(s):  
Tissue Culture ◽  
Transitional Cell ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Cell Junctions ◽  
Biological Behavior ◽  
Rat Urinary Bladder ◽  
Solid Tissues ◽  
Bladder Carcinomas

Junctional abnormalities have been described in electron microscopy studies of a broad spectrum of human and animal tumors (for review, see Ref. 1). In such studies, quantitative and qualitative descriptions have been related to tumor morphology and, occasionally, to tumor biological behavior. Few investigations have attempted to correlate changes in junction ultrastructure with dynamic aspects of malignant transformation since such studies would be difficult to carry out in solid tissues. Further, until recently, methods available for freeze-fracturing tissue cultures were cumbersome and limited in their applications.In this study, we have examined the ultrastructure of cell junctions in tissue culture lines derived from chemical carcinogen induced epithelial tumors, using a novel freeze-fracture technique. The ultrastructure of the cultures was contrasted with comparable solid tumors, as described elsewhere (2). We examined four cell lines in continuous culture (AY27, AY32, AY33, AY34), which we grew from FANFT-induced Fischer rat urinary bladder carcinomas (3), and a fifth line derived from subcutaneously transplanted rat bladder carcinoma (CN27T).

Types of intercellular junctions in teleost ovarian follicles (plecoglossus altivelis)

1978 ◽  
Vol 36 (2) ◽  
pp. 556-557
Author(s):  
K. Toshimori ◽  
C Ōura ◽  
F Yasuzumi
Keyword(s):  
Electron Microscope ◽  
Gap Junctions ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Ovarian Follicles ◽  
The Other ◽  
Follicle Cells ◽  
Plecoglossus Altivelis ◽  
Zonula Occludens ◽  
Intramembraneous Particles

In animal ovarian follicles, many investigators have reported various types of intercellular junctions such as desmosome (macula adherens), gap junction (nexus) and tight junction (zonula occludens). Between adjacent follicle cells, though both desmosomes and gap junctions were clearly presented, no tight junctions were ellucidated by electron microscope excepting Adams and Hertig (guinea pig;1964) and Espey and Stutts (rabbit;1972). On the other hand, between the oocyte and follicle cells, though desmosmes or desmosome-like areas were shown, no gap junctions were recognized to exist excepting Amsterdam et al. (1976) who suggested the presence of small gap junctions on rat oocyte surfaces and Anderson and Albertini (1976) who showed the presence of aggregations of intramembraneous particles on the oocyte surfaces in mouse, rat, rabbit and monkey. Types of intercellular junctions in animal ovarian follicles were not completely understood, because few workers applied freeze-fracture technique to demonstrate junctions excepting Anderson and Albertini (1976).

MP26 is a lens junctional protein: Analysis with monoclonal antibodies

1984 ◽  
Vol 42 ◽  
pp. 118-121
Author(s):  
Ross Johnson ◽  
Jane Sas ◽  
Catherine Nelson ◽  
Sue Schik ◽  
Brad Quade ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Freeze Fracture ◽  
Cell Movement ◽  
Protein Analysis ◽  
Cell Junctions ◽  
Major Protein ◽  
Definitive Answer ◽  
Junction Protein ◽  
Junctional Protein

Investigators with interests in cell junctions, and gap junctions in particular, have been intrigued over the last 5-10 years by the extensive junctional specializations found in the lens. Attention has focused on the suggested role of MP26 as the major protein component. The fundamental question has been whether the abundant junctions seen with thin-section or freeze-fracture analyses correspond to lens “gap junctions.” That is, do these cell surface specializations between lens fiber cells provide for the direct cell-to-cell movement of small molecules? Unfortunately, we still lack a definitive answer to the question. For some investigators, enthusiasm waned when protein analysis uncovered no homology between MP26 and a major liver gap junction protein. However, we have much to learn about the nature and role of the lens junction.

The Langerhans receptor of Oikopleura (Tunicata: Larvacea)

1979 ◽  
Vol 59 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Q. Bone ◽  
K. P. Ryan
Keyword(s):  
Epithelial Cells ◽  
Gap Junctions ◽  
Mechanical Stimulation ◽  
Action Potentials ◽  
Electrical Synapses ◽  
Locomotor Rhythm ◽  
Receptor Cells ◽  
Stimulation Of

The bristle-bearing receptors on either side of the trunk in Oikopleura are connected to the caudal ganglion by the axons of central cells which form electrical synapses (gap junctions) at the bases of the receptor cells. The same axons also form similar synapses with epithelial cells adjacent to the receptors. Direct mechanical stimulation of the receptor processes evokes changes in the locomotor rhythm of the same kind as evoked by action potentials propagated in the epithelial cells. This remarkable arrangement is suggested to be a consequence of the reduced numbers of cells in larvaceans.

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