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 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 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.

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.

Tight and gap junctions in the intestinal tract of tunicates (Urochordata): a freeze-fracture study

1986 ◽  
Vol 84 (1) ◽  
pp. 1-17
Author(s):  
N.J. Lane ◽  
R. Dallai ◽  
P. Burighel ◽  
G.B. Martinucci
Keyword(s):  
Gap Junctions ◽  
Tight Junctions ◽  
Thin Section ◽  
Intestinal Tract ◽  
Freeze Fracture ◽  
Intestinal Cells ◽  
Fracture Profile ◽  
Tracer Studies ◽  
Septate Junctions ◽  
Fracture Study

The intestinal tracts from seven different species of tunicates, some solitary, some colonial, were studied fine-structurally by freeze-fracture. These urochordates occupy an intermediate position phylogenetically between the vertebrates and the invertebrates. The various regions of their gut were isolated for examination and the junctional characteristics of each part investigated. All the species examined exhibited unequivocal vertebrate-like belts of tight-junctional networks at the luminal border of their intestinal cells. No septate junctions were observed. The tight junctions varied in the number of their component strands and the depth to which they extended basally, some becoming loose and fragmented towards that border. The junctions consisted of ridges or rows of intramembranous particles (IMPs) on the P face, with complementary, but offset, E face grooves into which IMPs sometimes fractured. Tracer studies show that punctate appositions, the thin-section correlate of these ridge/groove systems, are sites beyond which exogenous molecules do not penetrate. These junctions are therefore likely to represent permeability barriers as in the gut tract of higher chordates. Associated with these occluding zonular junctions are intermediate junctions, which exhibit no identifiable freeze-fracture profile, and macular gap junctions, characterized by a reduced intercellular cleft in thin section and by clustered arrays of P face particles in freeze-fractured replicas; these display complementary aggregates of E face pits. The diameters of these maculae are rarely very large, but in certain species (for example, Ciona), they are unusually small. In some tissues, notably those of Diplosoma and Botryllus, they are all of rather similar size, but very numerous. In yet others, such as Molgula, they are polygonal with angular outlines, as might be indicative of the uncoupled state. In many attributes, these various junctions are more similar to those found in the tissues of vertebrates, than to those in the invertebrates, which the adult zooid forms of these lowly chordates resemble anatomically.

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.

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.

scholarly journals A freeze-fracture and lanthanum tracer study of the complex junction between Sertoli cells of the canine testis.

1978 ◽  
Vol 76 (1) ◽  
pp. 57-75 ◽  
Author(s):  
C J Connell
Keyword(s):  
Tight Junctions ◽  
Sertoli Cells ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Septate Junction ◽  
Septate Junctions ◽  
Thin Sections ◽  
En Face ◽  
Lanthanum Tracer ◽  
Complex Junction

What appear to be true septate junctions by all techniques currently available for the cytological identification of intercellular junctions are part of a complex junction that interconnects the Sertoli cells of the canine testis. In the seminiferous epithelium, septate junctions are located basal to belts of tight junctions. In thin sections, septate junctions appear as double, parallel, transverse connections or septa spanning an approximately 90-A intercellular space between adjacent Sertoli cells. In en face sections of lanthanum-aldehyde-perfused specimens, the septa themselves exclude lanthanum and appear as electron-lucent lines arranged in a series of double, parallel rows on a background of electron-dense lanthanum. In freeze-fracture replicas this vertebrate septate junction appears as double, parallel rows of individual or fused particles which conform to the distribution of the intercellular septa. Septate junctions can be clearly distinguished from tight junctions as tight junctions prevent the movement of lanthanum tracer toward the lumen, appear as single rows of individual or fused particles in interlacing patterns within freeze-fracture replicas, and are seen as areas of close membrane apposition in thin sections. Both the septate junction and the tight junction are associated with specializations of the Sertoli cell cytoplasm. This is the first demonstration in a vertebrate tissue of a true septate junction.

Intercellular Junctions in the Differentiating Rat Otocyst

1979 ◽  
Vol 88 (4) ◽  
pp. 540-544 ◽  
Author(s):  
Khalid M. Khan ◽  
William F. Marovitz
Keyword(s):  
Gap Junctions ◽  
Tight Junctions ◽  
Intercellular Space ◽  
Early Stage ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Junctional Complex ◽  
Luminal Surface ◽  
Lanthanum Tracer

Intercellular junctions between cells of the rat otocyst on the 12th day of gestation were studied using lanthanum tracer and freeze-fracture techniques. At the luminal surface, the intercellular space is closed by a series of tight junctions. Gap junctions are also present between cells both within and below the luminal junctional complex. The presence of tight and gap junctions at this early stage in the differentiating otocyst is probably essential for the development of a normally functioning adult ear.

Gap junctions in the prothoracic glands of the tobacco hornworm, Manduca sexta

1992 ◽  
Vol 50 (1) ◽  
pp. 706-707
Author(s):  
Ji-da Dai ◽  
M. Joseph Costello ◽  
Lawrence I. Gilbert
Keyword(s):  
Gap Junctions ◽  
Small Molecules ◽  
Manduca Sexta ◽  
Freeze Fracture ◽  
Cell Communication ◽  
Cellular Level ◽  
Thin Sections ◽  
Prothoracic Glands ◽  
Polyhydroxylated Steroids ◽  
Stimulation Of

Insect molting and metamorphosis are elicited by a class of polyhydroxylated steroids, ecdysteroids, that originate in the prothoracic glands (PGs). Prothoracicotropic hormone stimulation of steroidogenesis by the PGs at the cellular level involves both calcium and cAMP. Cell-to-cell communication mediated by gap junctions may play a key role in regulating signal transduction by controlling the transmission of small molecules and ions between adjacent cells. This is the first report of gap junctions in the PGs, the evidence obtained by means of SEM, thin sections and freeze-fracture replicas.

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