Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Intercellular Junctions”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1977

Ultrastructure and distribution of intercellular junctions in corneal endothelium.

The intercellular junctions of the corneal endothelium has been studied in rabbit, monkey and human eyes. A union of apposing outer leaflets (tight junction) is usually found near the apical end of the intercellular clefts. However, evidence from lanthanum tracer studies indicates that the tight junctions do not seal the intercellular clefts completely. In addition to tight junctions, the presence of gap junctions or nexuses is demonstrated in all three species studied.

Animals↗
PubMed1975

[Highly permeable intercellular junctions in normal and transformed fibroblast cultures].

Intercellular junctions permeable to ions and fluorescein Na were studied with the aid of intracellular microelectrodes in the cultures of normal and transformed mouse-embryo and hamster-embryo fibroblast-like cells. Normal cells were effectively coupled by the highly permeable junctions. In cultures of 7 types of transformed cells, 3 types of coupling were detected: effective, decreased, and fully reduced couplings. The degree of uncoupling was not correlated with morphological patterns of malignization and tumorogeneity of transformed cultures. The decrease of permeability of intercellular junctions to ions and small molecules is concluded not to be necessary for malignization.

Animals↗
PubMed1977

Intercellular junctions in the central nervous system of insects.

The intercellular junctional complexes in the central nervous system (CNS) from a variety of insect species have been examined by thin-sectioning and freeze-fracturing techniques. Of particular concern has been the fine-structural basis of the blood-brain barrier observed to be present in the outer perineurial layer around the avascular insect CNS. The basis of this has been found in the form of tight junctions (zonulae occludentes) present both in sections and in replicas of the perineurium. In the latter, they appear as one or two simple linear ridges, lying parallel to the outer surface, which occasionally display overlapping. The complex geometry of the interdigitating perineurial cells apparently permits such a relatively simple series of ridges to function as a barrier, since tracers are found not to penetrate beyond this level into the underlying nervous tissue. Such evidence is supported by microprobe X-ray analysis of lanthanum-incubated tissues, the perineurium compared with the glia-ensheathed axons showing the presence and absence of lanthanum, respectively. Possible physiological mechanisms that could operate 'in vitro' to maintain the blood-brain barrier are also considered. Other intercellular junctions such as desmosomes, septate junctions and gap junctions are found in the perineurial layer too, the last exhibiting EF particle plaques and PF pits. Glia-glia junctions also occur in some insect species; they include desmosomes, inverted gap junctions and occasional tight junctions. Septate, gap and tight junctions are also found on the membranes of tracheoles penetrating the CNS. Short, ridge-like elaborations and other particle arrays are found on the PF on the axon surfaces and the significance of these structures is discussed.

Animals↗
PubMedDate not supplied

Intercellular junctions in the differentiating rat otocyst.

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.

Animals↗
PubMed1979

Freeze-fracture study of the epidermal cells of a teleost with particular reference to intercellular junctions and permeability to tracer.

The plasmatic membranes, the intercellular junctions and the intercellular spaces of the epidermis of the fish Pimelodus maculatus were studied by freeze-fracture and by lanthanum methods. The observations has confirmed the presence of desmosomes. Gap junctions were not found and the tight junctions can be seen very rarely, arranged to form small discrete maculae. The finger-print pattern due to the microridges of the apical plasma membrane of the superficial cells was studied by direct replicas. The tracer penetrates all the intercellular epidermal spaces but failed to penetrate the dermis, suggesting the presence of a barrier at the dermo-epidermal level.

Animals↗
PubMed1979

Ultrastructure of intercellular junctions in the rat exocrine pancreas stimulated by pancreozymin.

Intercellular junctions in the exocrine pancreas, through which pancreatic enzymes may leak out from the lumen into the intercellular spaces, were studied in the rat by means of electron microscopy using tannic acid as a tracer and freeze-fracture methods as well as conventional thin sections. In thin sections and freeze-fracture replicas from the pancreas stimulated or not stimulated by exogenous pancreozymin, tight junctions were located between adjacent cells of the acinus or duct at the level just below the lumen. Observation of freeze-fracture replicas revealed that the number of strands or furrows in the tight junction did not differ significantly between the two groups but the width of the tight junction area was narrower and the distance between neighboring strands or furrows in the junction was smaller in the stimulated pancreas than in the control pancreas. Tannic acid, the molecular weight of which is smaller than that of pancreatic enzymes, could not pass beyond the tight junction area into the lumen. This study suggests that the pancreatic enzymes can not leak out from the glandular lumen into the intercellular spaces by dissociation of intercellular junctions even if the pancreas is stimulated by a high concentration of pancreozymin.

Animals↗
PubMed1975

Intercellular junctions of rat endocardium.

The ultrastructure of the intercellular junctions of rat endocardium has been characterized following lanthanum exposure in vitro and uranyl acetate staining en bloc. The interendothelial clefts of the endocardium run either a relatively straight or convoluted course and posses one or two loci where the plasma membranes are in close apposition or form punctate fusions. Elongate restrictions, that exhibit hexagonal arrays of subunits following lanthanum immersion (gap junctions), are also present in the intercellular endocardial clefts. The occurrence of interendothelial clefts of endocardium lacking occlusive foci can account for the permeability properties of ventricular endocardium, where the direction of diffusion of macromolecules has been attributed to pressure gradients between ventricular cavity and myocardium. The relationship of gap junctions to possible electrical phenomena within the endocardium is also discussed.

Animals↗
PubMedDate not supplied

Intercellular junctions in the organ of Corti.

The intercellular junctions between adjacent supporting cells and between apposed hair and supporting cells in the organ of Corti of cat and human were studied. At the endolymphatic surface, the intercellular space was closed by a series of tight junctions (zonula occludens), whereas there were no tight junctions at the basilar membrane surface of the neuroepithelium. Beneath the adlumenal zonula occludens between adjacent supporting cells, a zonula adherens (intermediate junction, "desmosone") was found. Many gap junctions joined apposed supporting cells both within apposed hair and supporting cells, membrane specialization sharing the morphological characterics of both the macula adherens and zonula adherens was found. Between cells, there were short areas of parallel limiting membranes separated by a 20A intercellular space. These areas were suggestive but not characteristic of gap junctional specialization. The functional significance of the junctional specialization between cells in the organ of Corti is discussed.

Animals↗
PubMed1977

Intercellular junctional complexes of the rat seminiferous tubules: a freeze-fracture study.

This paper provides a description of the intercellular junctions in the rat testis, as observed using the freeze fracture technique. These intercellular junctions were categorized into four general types: Sertoli cell tight junctions, myoid cell tight junctions, gap junctions, and "heterogeneous junctions." The Sertoli cell tight junctions had a mean depth of 3.1 micron in the basal to apical direction, and contained 25 to 50 (average: 36) parallel rows of particulate sealing elements. The myoid cell tight junction was neither continuous nor extensive, but focal in nature. Interestingly the sealing elements of this junction, like those of the Sertoli cell tight junction, were quite particulate in nature. Typical gap junctions were observed between Sertoli cells where they were intercalated between the parallel rows of the Sertoli cell tight junction. The most interesting observation was the identification of gap junction-like structures, in various stages of formation, on germ cell membrane fracture faces, both in the basal and adluminal compartments. Lastly, the unusual "heterogeneous junction" was observed on large membrane fracture faces in close proximity to cells in the adluminal compartment, presumably between Sertoli cells. These junctions appeared to consist of both tight and gap junction elements.

Animals↗
PubMed1979

Intercellular junctions in FANFT-induced carcinomas of rat urinary bladder in tissue culture: in situ thin-section, freeze-fracture, and scanning electron microscopy studies.

This paper describes a set of simple methods for comparative light and electron microscopy studies on tissue cultured tumour cells derived from both noninvasive and invasive carcinogen-induced rat urinary bladder carcinomas. Cells are grown on Thermanox plastic coverslips and fixed in situ. Each plastic coverslip is then divided with scissors into four parts: the first is processed for light microscopy, the second for thin-section electron microscopy, the third for freeze-fracture electron microscopy, and the fourth for scanning electron microscopy. In some experiments, portions of the culture which have first been examined by light microscopy are subsequently prepared for electron microscopy. In this way, the culture conditions are kept constant and comparison of structural features (i.e. intercellular junctions) by several preparative techniques is possible. Noninvasive and invasive rat bladder tumour cells, characterized by numerous pleomorphic microvilli, have normal zonulae occludentes at the apices of lateral surfaces of tumour cells in all cultures. In some areas of invasive tumour cells, occludens junctions are focally attenuated, consisting of only one or two strands, and occasionally the strands are discontinuous. Gap junctions, type PF-1, as well as numerous demosomes are present in all cell lines. Thus, intercellular junctions in noninvasive and invasive rate bladder epithelial cell lines bear a striking resemblance to those previously described in the comparable solid primary tumours. These culture systems may be useful for studying factors which influence the formation of intercellular junctions during malignant transformation.

Animals↗
PubMed1979

Junctional intercellular communication pattern of cultured human breast cancer cells.

Junctional intercellular communication between several established human breast cancer cell lines and a variety of mammalian cells has been examined. All the cancer cell lines were found to be either noncommunicators or nonselective communicators. This contrasts with normal human mammary epithelium which shows selectivity in junctional communication. Loss of selectivity in junctional communication appears to be a general feature of cultured human breast cancer cells.

Animals↗
PubMed1978

Alterations of intercellular junctions in acinic cell carcinoma of the canine pancreas.

Intercellular junctions in spontaneous canine pancreatic acinic cell adenocarcinomas were compared to those in control canine pancreas. The neoplastic cells displayed proliferation and fragmentation of tight junctions and reduction in size and number of gap junctions. Marked decrease in desmosomal density was observed only in the poorly differentiated carcinoma. In the well differentiated carcinomas a few of the desmosomes were characteristic of those found in squamous cells. No quantatitive or qualitative differences in cell junctions were noted between primary and metastatic tumor.

Adenocarcinoma↗
PubMed1977

Intercellular junctions in "shock lung". A freeze-fracture study.

Intercellular junctions in the alveolar epithelium and in the capillary endothelium in lung from five dogs after hemorrhagic shock (mean blood pressure, 40 mm. Hg for 3 hours) and from five control dogs were observed in the electron microscope using the freeze-fracture technique. Following shock zonulae occludentes (tight junctions) in the alveolar epithelium showed alterations in substructure that were not present in control animals. These changes were morphologically similar to those reported in junctions altered after exposure to osmotic gradients with marked degradation and disappearance of junctional strands. The appearance of tight junctions in the capillary endothelium, which were of a rather poorly organized "leaky" type in control animals, was generally unaltered after shock. Disintegration and disappearance of junctional strands in "focal" regions, however, were occasionally observed. The increased pulmonary capillary permeability observed physiologically after hemorrhagic shock could be explained by such alterations of endothelial zonulae occludentes.

Animals↗
PubMed1977

Intercellular junctions of antennal gland epithelial cells in the crayfish, Orconectes virilis. A freeze-fracture study.

Labyrinth and nephridial canal cells of the crayfish (Orconectes virilis) antennal gland possess two types of intercellular junctions revealed by freeze-fracture studies. Apical margins of the cells are connected by long septate junctions. In replicas, these junctions consist of many parallel rows of 80--140 A intramembrane particles situated on the PF membrane face (EF and PF fracture faces of Branton et al., 1975). Rows of pits are found on the EF fracture face and are deemed complementary to the rows of particles. Moreover, lateral margins of basal regions of the epithelial cells are attached by many intercellular junctions. These contacts are characterized in thin plastic sections by a narrow dense cytoplasmic plaque located subjacent to the plasma membrane at sites of adjoined cells, and 5 to 12 fine strands of dense material that extend across the intercellular gap between adjoined cells. In freeze-fracture replicas, EF intramembrane faces basal to the region of the plasma membrane containing septate junctions exhibit numerous discoid clusters of particles. The particle aggregates, assumed to represent freeze-cleave images of adhering junctions, range from 900 to 3,700 A in diameter, with individual particles about 185 A in diameter. These junctions appear to connect epithelial cell processes formed by basal infoldings of the plasmalemma, and occur between adiacent cells as well as adiacent processes of a single cell. The discrete aggregates of particles resemble replicated desmosomes (Shienvold and Kelly, 1974) and hemi-desmosomes (Shivers, 1976); therefore, they probably do not constitute a basis for electrical coupling between antennal gland epithelial cells.

Animals↗
PubMed1978

Freeze-etching observation on the development of intercellular junctions of the duodenal epithelial cells in the chick embryo.

Development of intercellular junctions in duodenal epithelium in the chick embryo was studied by electron microscopy using the thin-section and freeze-fracture techniques. Incomplete tight junctions are already seen in 6 and 7 day old embryos at the apical portion of the lateral plasma membrance, and consist of 1-7 strands, their mean depth measuring 0.2 micron. This corresponds to a "very leaky type" (CLAUDE and GOODENOUGH) of tight junction. Ridges on the PF are discontinuous and rarely cross or link. The tight junctions extend basally at the place where more than three epithelial cells are in contact. On the lateral plasma membrane, particle-aggregates suggesting primitive gap junctions are already recognized. Some are dense aggregations of 3-5 membrane-particles with a halo free of the particles and others are rather loose aggregations of 5-10 particles with an indistinct halo. In 9 day old embryos, the ridges of the tight junction become more discontinuous, although the frequency of the linkage of the neighboring ridges increases. The compartments bounded by the tight junctional strands are angular. These strands become continuous and the facets surrounded by them are roundish in 12 day old embryos. The presumptive immature gap junctions show a characteristic polygonal pattern in 9 day old embryos and gradually increase in size. Mature tight junctions and typical gap junctions of 0.3-0.4 micron diameter are seen after 18 days of incubation. The strands number 6-8 and the depth of the tight junction measures about 0.4 micron in 18 day old embryos. In the chick embryo duodenal epithelium, the tight and gap junctions develop independently from each other without any direct interaction between them.

Animals↗
PubMed1978

Intercellular junctions in the ciliary epithelium.

The fine structure of the intercellular junctions in the ciliary epithelium of rhesus monkeys and rabbits was studied with conventional electron microscopy of thin-sectioned specimens and the freeze-fracturing technique. In the rhesus monkey, a zonula occludens, zonula adhaerens, gap junctions, and desmosomes interconnect the nonpigmented cells, whereas gap junctions, puncta adhaerentia, and desmosomes connect pigmented to nonpigmented cells, and pigmented cells to one another. In the rabbit, desmosomes are absent between nonpigmented cells, and substituted for by puncta adhaerentia. The zonula occludens between nonpigmented cells greatly varies in its complexity in different regions of the cell perimeter, and in places, it may consist of very few intramembrane strands; this suggests that the ciliary epithelium is relatively leaky to ions and small molecules. Gap junctions are ubiquitous in the ciliary epithelium and particularly numerous at the interface between pigmented and nonpigmented layers; this finding indicates that the cells of the ciliary epithelium are joined in a metabolic syncytium. All gap junctions are characterized by the crystalline configuration which is typical of the uncoupled state; furthermore, in specimens fixed by immersion, they may be caused by uncoupling and take place in the time interval elapsing between interruption of the blood supply and arrival of the fixative fluid. Puncta adhaerentia resemble zonulae adhaerentes in their structural details but are macular in shape instead of encompassing the cell perimeter in a beltlike fashion. In contrast with desmosomes, the intercellular cleft of puncta adhaerentia has an irregular width and contains opaque material, but this never gives rise to the central band typical of desmosomes. On the inner aspect of the junctional membranes, there is a layer of fluffy material but no plaque of insertion for a bundle of tonofilaments. Finally, puncta adhaerentia have no representation in the interior of the plasmalemma and are intimately associated with cytoplasmic microfilaments. They probably anchor to the plasmalemma the contractile apparatus of the ciliary epithelial cells.

Animals↗