scholarly journals VARIATIONS IN TIGHT AND GAP JUNCTIONS IN MAMMALIAN TISSUES

1972 ◽  
Vol 53 (3) ◽  
pp. 758-776 ◽  
Author(s):  
Daniel S. Friend ◽  
Norton B. Gilula
Keyword(s):  
Smooth Muscle ◽  
Gap Junctions ◽  
Tight Junctions ◽  
Adrenal Cortex ◽  
Freeze Fracture ◽  
Junctional Complex ◽  
Exocrine Glands ◽  
Rat Pancreas ◽  
Zonula Occludens ◽  
Mammalian Tissues

The fine structure and distribution of tight (zonula occludens) and gap junctions in epithelia of the rat pancreas, liver, adrenal cortex, epididymis, and duodenum, and in smooth muscle were examined in paraformaldehyde-glutaraldehyde-fixed, tracer-permeated (K-pyroantimonate and lanthanum), and freeze-fractured tissue preparations. While many pentalaminar and septilaminar foci seen in thin-section and tracer preparations can be recognized as corresponding to well-characterized freeze-fracture images of tight and gap junction membrane modifications, many others cannot be unequivocally categorized—nor can all freeze-etched aggregates of membrane particles. Generally, epithelia of exocrine glands (pancreas and liver) have moderate-sized tight junctions and large gap junctions, with many of their gap junctions basal to the junctional complex. In contrast, the adrenal cortex, a ductless gland, may not have a tight junction but does possess large gap junctions. Mucosal epithelia (epididymis and intestine) have extensive tight junctions, but their gap junctions are not as well developed as those of glandular tissue. Smooth muscle contains numerous small gap junctions The incidence, size, and configuration of the junctions we observed correlate well with the known functions of the junctions and of the tissues where they are found.

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.

Possible role of gap junctions in activation of myometrium during parturition

1978 ◽  
Vol 235 (5) ◽  
pp. C168-C179 ◽  
Author(s):  
R. E. Garfield ◽  
S. M. Sims ◽  
M. S. Kannan ◽  
E. E. Daniel
Keyword(s):  
Smooth Muscle ◽  
Gap Junctions ◽  
Freeze Fracture ◽  
Normal Pregnancy ◽  
Pregnant Rats ◽  
Junction Formation ◽  
Synchronous Contraction ◽  
Do So

Gap junctions between smooth muscle cells of the myometrium of pregnant rats were found only immediately prior to, during and immediately after parturition by quantitative thin-section and freeze-fracture microscopy. Ovariectomy of 16- to 17-days-pregnant rats resulted in premature termination of pregnancy and the appearance of gap junctions. Methods that prolonged normal pregnancy in rats or maintained pregnancy in ovariectomized animals (progesterone treatment) prevented the appearance of gap junctions. Gap junctions formed in tissues incubated for 24--96 h in vitro without any hormonal influence. We propose that gap junctions are essential for normal labor and delivery for synchronous contraction of the muscle of the uterus. We present a model for control of parturition that may apply to other animals including humans. The model proposes: 1) the possible roles progesterone, prostaglandins, or estrogens may play in initiating gap-junction formation; 2) that the formation of gap junctions is a necessary step in activation of the myometrium leading to labor; and 3) that agents used to stimulate or inhibit labor may do so by affecting gap junctions.

scholarly journals A freeze-fracture study on the developing satellite cells of spinal ganglia in the chick embryo

1988 ◽  
Vol 46 (1) ◽  
pp. 6-9
Author(s):  
Claudio A. Ferraz de Carvalho ◽  
Ciro F. da Silva
Keyword(s):  
Chick Embryo ◽  
Gap Junctions ◽  
Tight Junctions ◽  
Small Groups ◽  
Satellite Cells ◽  
Freeze Fracture ◽  
Fracture Analysis ◽  
Spinal Ganglia ◽  
Pinocytotic Vesicles ◽  
Fracture Study

A freeze-fracture analysis of the satellite cells of spinal ganglia of the chick embryo was performed in 8 successive stages of development, from the 5th incubation day to hatching. The characteristic laminar disposition of the cells were first observed on the 7th day. Tight junctions were found at the 20th incubation day. Small groups or irregular aggregates of particles, but not gap junctions, were described on the 7th and 8th days. Pinocytotic vesicles were pointed out in the different stages considered.

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.

Structure, biochemistry, and assembly of epithelial tight junctions

1987 ◽  
Vol 253 (6) ◽  
pp. C749-C758 ◽  
Author(s):  
B. Gumbiner
Keyword(s):  
Tight Junction ◽  
Tight Junctions ◽  
Plasma Membranes ◽  
Freeze Fracture ◽  
Lateral Diffusion ◽  
Junctional Complex ◽  
Epithelial Cell Layer ◽  
Dependent Cell ◽  
Freeze Fracture Electron Microscopy ◽  
Dynamic Structures

The zonula occludens (ZO), also referred to as the tight junction, forms the barrier to the diffusion of molecules and ions across the epithelial cell layer through the paracellular space. The level of electrical resistance of the paracellular pathway seems to depend on the number of strands in the ZO observed by freeze-fracture electron microscopy (EM). The ZO also forms the boundary between the compositionally distinct apical and basolateral plasma membrane domains because it is a barrier to the lateral diffusion of lipids and membrane proteins that reside in the extracytoplasmic leaflet of the membrane bilayer. In contrast to its appearance in transmission EM, the tight junction is not a fusion between the outer membrane leaflets of neighboring cells. Rather it consists of protein molecules, including the newly discovered protein ZO-1 and probably others, which bring the plasma membranes into extremely close apposition so as to occlude the extracellular space. Very little is known about the assembly of tight junctions, but several kinds of evidence suggest that they are very dynamic structures. Other elements of the epithelial junctional complex including the zonula adherens (ZA), the Ca2+-dependent cell adhesion molecule uvomorulin, or L-CAM, and actin filaments of the cytoskeleton may participate in the assembly of the ZO.

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.

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).

scholarly journals ASSEMBLY OF GAP JUNCTIONS DURING AMPHIBIAN NEURULATION

1974 ◽  
Vol 62 (1) ◽  
pp. 32-47 ◽  
Author(s):  
Robert S. Decker ◽  
Daniel S. Friend
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Freeze Fracture ◽  
Ruthenium Red ◽  
Junctional Complex ◽  
Translational Movement ◽  
Pile Up ◽  
Neuroepithelial Cells ◽  
Solitary Domains ◽  
Number Of Particles

Sequential thin-section, tracer (K-pyroantimonate, lanthanum, ruthenium red, and horseradish peroxidase), and freeze-fracture studies were conducted on embryos and larvae of Rana pipiens to determine the steps involved in gap junction assembly during neurulation. The zonulae occludentes, which join contiguous neuroepithelial cells, fragment into solitary domains as the neural groove deepens. These plaque-like contacts also become permeable to a variety of tracers at this juncture. Where the ridges of these domains intersect, numerous 85-Å participles apparently pile up against tight junctional remnants, creating arrays recognizable as gap junctions. With neural fold closure, the remaining tight junctional elements disappear and are replaced by macular gap junctions. Well below the junctional complex, gap junctions form independent of any visible, preexisting structure. Small, variegated clusters, containing 4–30 particles located in flat, particle-free regions, characterize this area. The number of particles within these arrays increases and they subsequently blend together into a polygonally packed aggregate resembling a gap junction. The assembly process in both apical and basal regions conforms with the concept of translational movement of particles within a fluid plasma membrane.

Sign in / Sign up

Export Citation Format

Share Document