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.

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.

scholarly journals Cell junctions and locomotion of the blastoderm edge in gastrulating chick and quail embryos

1985 ◽  
Vol 78 (1) ◽  
pp. 191-204
Author(s):  
L. Andries ◽  
F. Harrisson ◽  
R. Hertsens ◽  
L. Vakaet
Keyword(s):  
Gap Junctions ◽  
Tight Junctions ◽  
Functional Organization ◽  
Freeze Fracture ◽  
Leading Edge ◽  
Proximal Part ◽  
Cell Junctions ◽  
Vitelline Membrane ◽  
Thin Sections ◽  
Marginal Cells

The blastoderm edge migrates by the active locomotion of a multilayer of epithelial cells, the so-called margin of overgrowth (MO), that uses the vitelline membrane as its substratum. The structural unity formed by the margin of overgrowth cells and their rapid migration suggest coordination of locomotion between individual cells. Using transmission electron microscopy of thin sections and freeze-fracture, we attempted to determine if the pattern of junctions of the migrating margin of overgrowth is related to the suggested cell—cell cooperation between individual cells in this region. In the leading edge there are large areas of closely apposed cell membranes. Incipient desmosomes and small gap junctions were observed. Tight junctions consisted of isolated strands or isolated networks of tight-junctional strands. In the proximal part of the margin of overgrowth the size of the gap junctions increased and the desmosomes were fully developed. Tight-junctional strands were either isolated or arranged into an isolated network. A broad belt of tight junctions was observed at the transition between margin of overgrowth and non-marginal cells. The distribution of the junctional elements in the MO suggests that junctions contribute to the maintenance of the structural and functional organization of the margin of overgrowth. Furthermore, the spatial distribution of the junctions might give information about the mechanism of locomotion of the margin of overgrowth.

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.

Vascular Biology, Thromboresistance, and Inflammation

2006 ◽  
Author(s):  
Richard C. Becker ◽  
Frederick A. Spencer
Keyword(s):  
Endothelial Cells ◽  
Cardiovascular System ◽  
Vascular Endothelium ◽  
Vascular Endothelial Cells ◽  
Surface Membrane ◽  
Single Layer ◽  
Intercellular Junctions ◽  
Cell Junctions ◽  
Luminal Surface ◽  
Internal Layers

The delivery of vital substrate to metabolically active tissues and vital organs is achieved and maintained by the cardiovascular system including the heart, macrovasculature, and microvasculature. This life-sustaining process requires a normally functioning vascular endothelium—a multifunctional organ system composed of physiologically responsive cells responsible for vasomotion (vascular tone), thromboresistance, and inflammoresistance. Simply by virtue of its anatomic location, the vascular endothelium is functionally complex. It defines the intra- and extravascular components, serves as a selectively permeable barrier, and provides a continuous lining to the cardiovascular system. The location of the vascular endothelium is vital to its biologic interactions with cells found within the circulation and to the vessel wall itself. The surface activity is augmented in the microcirculation, also known as the resistance bed, where the ratio of endothelial surface to circulating blood is maximal. In most vertebrates, vascular endothelial cells form a single layer of squamous lining cells (0.1–0.5 μm in thickness) joined by intercellular junctions. The cells themselves are polygonal (varying between 10 and 50 μm) and are positioned in the long axis of the vessel, orienting the cellular longitudinal dimension in the direction of blood flow. The endothelial cell has three surfaces: luminal (nonthrombogenic), subluminal (adhesive), and cohesive. The luminal surface is devoid of electron-dense connective tissue. It does, however, possess an exterior coat (or glycocalyx), consisting primarily of starches and proteins secreted by the endothelial cells. Plasma proteins, including lipoprotein lipase, α2-macroglobulin, heparin cofactor II, antithrombin, and albumin, as well as small amounts of fibrinogen and fibrin are adsorbed to the luminal surface. The surface membrane itself adds significantly to thromboresistance by carrying a negative charge that repels similarly charged circulating blood cells. The subluminal (or abluminal) surface adheres to subendothelial connective tissues. Small processes penetrate through a series of internal layers to form myoendothelial junctions with subjacent smooth muscle cells. The cohesive component of the vascular endothelium connects individual endothelial cells to one another by cell junctions of two basic types: occluding (tight) junctions and communicating (gap) junctions. Occluding junctions represent a physical link between adjacent cells, sealing the intercellular space.

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.

Development of intercellular junctions in the pulmonary epithelium of the foetal lamb

1978 ◽  
Vol 32 (1) ◽  
pp. 307-324
Author(s):  
E.E. Schneeberger ◽  
D.V. Walters ◽  
R.E. Olver
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Tight Junctions ◽  
Lung Development ◽  
Light And Electron Microscopy ◽  
Intercellular Junctions ◽  
Intercellular Spaces ◽  
Thin Sections ◽  
Epithelial Tight Junctions ◽  
Foetal Lamb

The integrity of epithelial tight junctions in foetal mammalian lungs is essential to maintain the unique ionic composition of lung liquid, and to prevent leakage of serum proteins into peripheral air spaces. In the present study the development of intercellular junctions of the lining epithelium of foetal lamb lungs during gestation was examined by light and electron microscopy. Both thin sections and freeze-fracture replicas were examined by electron microscopy. By 39 days of gestation, epithelial tight junctions consist of a minimum of 3.1 +/− 1.6 (s.D.) and a maximum of 5.8 +/− 2.0 discontinuous rows of particles and short segments of strands on P face ridges and in complementary E face grooves, while from 58 to 76 days they are composed of a network of 4.3 +/− 1.6 to 7.7 +/− 1.9 focally interrupted P face strands. Complementary replicas show that many of the discontinuities on the P face are due to separation of junctional particles on to the E face during fracturing, and not to an absence of junctional particles. From 76 days to term, epithelial tight junctions (exclusive of upper airway epithelium which was not examined) resemble those of adult lungs, and consist of a continuous network of 4.5 +/− 2.0 to 7.5 +/− 2.5 P face strands and complementary particle-free grooves. Permeability measurements, published elsewhere, indicate that the epithelium is functionally ‘tight’ from 69 days onwards. Tight junctions in peripheral air-space epithelium, therefore, are structurally continuous and functionally ‘tight’ early in foetal lung development, and form seals at one end of long, narrow intercellular spaces; these features may be important for coupled ion and water transport. When the bounding epithelial cells become flattened, these narrow intercellular spaces remain intact as a result of complex interdigitations of adjacent cell membranes. Desmosomes were present throughout gestation near the abluminal side of the tight junctions and occasionally near the base of the intercellular space. These junctions may serve to connect cells to each other at a time when tight junctions may be mechanically weak. In addition, gap junctions are associated with tight junctions from the glandular through the canalicular stages of lung development. They disappear by 120 days when the epithelial cells are differentiated.

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.

scholarly journals Intercellular junctions and transfer of small molecules in primary vascular endothelial cultures.

1982 ◽  
Vol 92 (1) ◽  
pp. 183-191 ◽  
Author(s):  
D M Larson ◽  
J D Sheridan
Keyword(s):  
Gap Junctions ◽  
Small Molecules ◽  
Tight Junctions ◽  
Lucifer Yellow ◽  
Primary Cultures ◽  
Freeze Fracture ◽  
Cell Transfer ◽  
Isolated Cells ◽  
Thin Sections ◽  
Cell To Cell Transfer

The ultrastructure of gap and tight junctions and the cell-to-cell transfer of small molecules were studied in primary cultures and freshly isolated sheets of endothelial cells from calf aortae and umbilical veins. In thin sections and in freeze-fracture replicas, the gap and tight junctions in the freshly isolated cells from both sources appeared similar to those found in the intimal endothelium. Most of the interfaces in replicas had complex arrays of multiple gap junctions either intercalated within tight junction networks or interconnected by linear particle strands. The particle density in the center of most gap junctions was noticeably reduced. In confluent monolayers, after 3-5 days in culture, gap and tight junctions were present, although reduced in complexity and apparent extent. Despite the relative simplicity of the junctions, the cell-to-cell transfer of potential changes, dye (Lucifer Yellow CH), and nucleotides was readily detectable in cultures of both endothelial cell types. The extent and rapidity of dye transfer in culture was only slightly less than that in sheets of freshly isolated cells, perhaps reflecting a reduced gap junctional area combined with an increase in cell size in vitro.

scholarly journals Ultrastructural localization of blood-retinal barrier breakdown in diabetic and galactosemic rats.

1990 ◽  
Vol 38 (9) ◽  
pp. 1341-1352 ◽  
Author(s):  
S A Vinores ◽  
R McGehee ◽  
A Lee ◽  
C Gadegbeku ◽  
P A Campochiaro
Keyword(s):  
Tight Junctions ◽  
Retinal Pigment ◽  
Cell Junctions ◽  
Capillary Endothelium ◽  
Intercellular Spaces ◽  
Blood Retinal Barrier ◽  
Cytoplasmic Staining ◽  
Rpe Cells ◽  
Perinuclear Cytoplasm ◽  
Brb Breakdown

Breakdown of the blood-retinal barrier (BRB) is an early event in diabetic and galactosemic rats, but the location and nature of the specific defect(s) are controversial. Using an electron microscopic immunocytochemical technique, the retinas of normal, diabetic, and galactosemic rats were immunostained for endogenous albumin. Normal rats showed little evidence of BRB breakdown at either the inner barrier (retinal vasculature) or the outer barrier (retinal pigment epithelium) (RPE). In diabetic and galactosemic rats, as was true in human diabetics, BRB breakdown occurred predominantly at the inner BRB, but in some cases at the outer barrier as well. Treatment with the aldose reductase inhibitor sorbinil largely prevented BRB failure in galactosemic rats. In the inner retina of diabetic and galactosemic rats, albumin was frequently demonstrated on the abluminal side of the retinal capillary endothelium (RCE) in intercellular spaces, basal laminae, pericytes, ganglion cells, astrocytes, and the perinuclear cytoplasm of cells in the inner nuclear layer. Albumin did not appear to cross RCE cell junctions; however, it was occasionally seen in RCE cytoplasm of galactosemic rats. In the outer retina, albumin was frequently detected in the subretinal space, in the intercellular space between photoreceptors, and in the perinuclear cytoplasm of photoreceptor cells, but was only infrequently found in the RPE cells constituting the barrier. Albumin derived from the choroidal vasculature did not appear to cross the tight junctions of the RPE. These findings suggest that specific sites of BRB compromise are infrequent but that once albumin has crossed the RCE or RPE it freely permeates the retinal tissue by filling intercellular spaces and permeating the membranes of cells not implicated in BRB formation. The diffuse cytoplasmic staining of some RCE and RPE cells suggests that the predominant means of BRB breakdown in diabetes and galactosemia involves increased focal permeability of the surface membranes of the RCE and RPE cells rather than defective tight junctions or vesicular transport.

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).

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