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Results for “Intercellular Junctions”

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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↗
PubMed1990

Gap junctional intercellular communication (GJIC) in rat glioma cells--characterizations to detect inhibitors of metabolic cooperation.

Gap junctional intercellular communication (GJIC) as measured by metabolic cooperation was examined in a rat glioma cell line P98F47. X-ray induced mutants of P98F47 cells were grown in 6-thioguanine selective medium (6TG medium) to separate 6TG-resistant HGPRT- mutant cells (6TGr). By co-culturing 200 6TGr cells with varied high densities of the wild type 6TG-sensitive cells (6TGs), it was found that the recovery of 6TGr cells depended on the density of 6TGs cells. Higher densities of 6TGs cells reduced the recovery of 6TGr cells. These results demonstrate the ability of P98F47 cells to perform metabolic cooperation which is indicative of GJIC. When metabolic cooperation was inhibited, increased recovery of 6TGr cells was observed. Presented results also demonstrate metabolic cooperation between P98F47 glioma cells and normal rat glial cells. Effect of tumor promoting chemicals on metabolic cooperation of P98F47 cells was studied. 3H-uridine nucleotide autoradiography technique was used to confirm the above observations. The results suggest that these cells may provide the basis for an in vitro assay specially to study brain tumor promoters and neurotoxins.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1987

Formation, distribution and dissociation of intercellular junctions in the lens.

A 70,000 Mr membrane protein (MP70) has previously been identified as a specific component of lens intercellular junctions. In this paper we use anti-MP70 immunofluorescence microscopy of dissected fibre bundles to study the formation, distribution and dissociation of junctional plaques in the outer cortex region of the sheep lens. Abundant, small junctional plaques are assembled de novo in the broad sides of the elongating fibres near the equatorial lens periphery. In fully elongated, pole-to-pole fibres, junctional plaques are generally larger, and while dispersed on the broad sides of the fibres in the equatorial lens plane, these junctions line up in the middle of the broad and narrow sides of the fibres in the lens polar regions. This precisely defined positioning is independent of junction size and hence cannot solely be explained by the constraints of fibre width. Junctional plaques fragment to smaller sizes and MP70 is cleaved to MP38 in mature, enucleated fibres located in the deeper portions of the lens outer cortex. These results demonstrate a dynamic aspect of lens intercellular junctions and show that they are positioned in a precise fashion, possibly in association with other membrane or cytoskeletal components.

Animals↗
PubMed1997

The biological conditions of assessment of ethylene glycol-induced inhibition of gap junctional intercellular communication by metabolic cooperation assay.

Ethylene glycol (EG) has been previously shown to inhibit gap junctional intercellular communication. In this paper we examine conditions under which the effect of EG on gap junctional communication is assessed by metabolic cooperation assay. The later, after the start of metabolic cooperation assay, EG was added, the lower its inhibitory effect was. If treatment with EG began 12 h or even later after plating of cells, no significant effect on gap junctional communication was observed. Short EG treatments (2-8 h) induced a reversible inhibition of cell-to-cell communication, provided that the cells could communicate freely after the drug was removed. However, if further cell-to-cell communication was excluded, the effect of short exposures was irreversible. Using Scrape loading method we observed that after a 60 min exposure to EG the standard gap junctional intercellular communication was completely restored in a few hours.

Animals↗
PubMed1989

Morphology of fungiform papillae in canine lingual epithelium: location of intercellular junctions in the epithelium.

The localization and structure of intercellular junctions and barriers in the extragemmal epithelium of canine fungiform papillae were determined by using both morphological and electrophysiological methods. Gap junctions were located in all epithelial strata with the exception of the stratum corneum, suggesting that the epithelium functions as a syncytium. The extracellular space of the stratum corneum was composed of a discontinuous, three-dimensional network of tight junctions, modified desmosomes, and lamellar bodies. A zonula occludens, which stops the penetration of lanthanum, is present in the uppermost layer of the stratum granulosum. In freeze-fracture replicas, tight junctions appear as extended networks of ridges of variable thickness on the PF fracture face and complementary grooves on the EF fracture face. The relatively high resistance pathway resulting from the layers of corneocytes and networks of tight junctions and lamellar bodies in the stratum corneum is bypassed by the low-resistance pathway provided by the taste pore.

Animals↗
PubMed1987

Intercellular junctions of the ciliary epithelium in anterior uveitis.

The intercellular junctions of the anterior ciliary and iridial epithelia of the inflamed rabbit eye were examined by use of an ultrastructural tracer, conventional electron microscopy, and the freeze-fracture technique. In normal control eyes, intravascularly injected horseradish peroxidase was prevented from entering the posterior chamber by the zonulae occludentes of the nonpigmented ciliary epithelium. In freeze-fracture studies these junctions appeared as a series of 5-12 branching and anastomosing strands on the P-fracture face, which were complemented by a network of shallow grooves with discontinuous rows of particles at their bases on the E-fracture face. Gap junctions were abundant, particularly between the apical surfaces of the pigmented and nonpigmented layers where they were accompanied by discontinuous tight junctional strands. In eyes inflamed by intravitreal injection of E. coli 055:B55 endotoxin, peroxidase leaked into the posterior chamber primarily from the crests of anterior ciliary and iridial processes. Freeze-fracture electron microscopy of these same areas demonstrated primarily a simplification in junctional complexity and reduction in the number of occluding strands. Severe junctional disorganization and complete junctional fragmentation were rarely seen. A profound reduction in the complement of gap junctions was observed particularly between the apical surfaces of the pigmented and nonpigmented layers. The possible functional significance of the observed changes is discussed.

Animals↗
PubMed1988

Glycyrrhetinic acid derivatives: a novel class of inhibitors of gap-junctional intercellular communication. Structure-activity relationships.

Glycyrrhetinic acid was shown previously to inhibit intercellular gap-junctional communication between human fibroblasts. In the present study 31 derivatives of glycyrrhetinic acid were tested for their ability to inhibit communication. Eight of the compounds inhibited communication with high potency (IC50 less than 3 microM) and showed low toxicity, properties which suggest they may be useful pharmacological probes for studies of gap-junction function.

Cell Communication↗
PubMed1984

Intercellular junctions of the iris epithelia in Macaca mulatta.

The intercellular junctions in the anterior myoepithelium and posterior pigmented epithelium of the rhesus monkey iris were examined using an ultrastructural tracer, conventional electron microscopy, and the freeze-fracture technique. Within the anterior myoepithelium the lateral cell margins were joined by puncta adhaerentia, desmosomes, and gap junctions. The distribution of the puncta adhaerentia and desmosomes was restricted to the apico-lateral region of these cells. Joining the apical surface of the anterior myoepithelium and posterior pigmented epithelium gap junctions, puncta adhaerentia, and desmosomes also were present. Adjacent posterior pigmented epithelial cells were joined by an apico-lateral junctional complex, which consisted of a zonula occludens, zonula adhaerens, and gap junction. These cells also were connected by one or more desmosomes. Intravenously injected horseradish peroxidase, which diffused from the ciliary body stroma, was prevented from reaching the posterior chamber by the presence of the zonulae occludentes between adjacent posterior pigmented epithelial cells. Their presence was confirmed using the double replica method of freeze-fracturing. The zonulae occludentes appeared as a continuous series of branching and anastomosing strands of particles on the P-fracture face, which were complemented on the E-fracture face by a series of shallow grooves. These junctions varied in complexity from one to eight or more strands indicating that they are analogous in both location and degree of permeability to the zonulae occludentes present in the nonpigmented ciliary epithelium.

Animals↗
PubMed1995

Differing effects of various cryoprotectants on intercellular junctions of epithelial (MDCK) cells.

The effects of 30 min exposure to 10% v/v cryoprotectant (glycerol, dimethyl sulfoxide, or propane-1,2-diol) on intercellular junctions were investigated in monolayers of epithelial (MDCK) cells. The cells were grown on microporous membrane filters and transepithelial resistance was monitored as an index of junction integrity. At 22 degrees C, Me2SO had the least effect of the three cryoprotectants, causing a gradual fall in transepithelial resistance of only 17% in 30 min. This compares with falls of 50% in 15 min and 37% over 30 min, respectively, with glycerol and propane-1,2-diol. At 0 degrees C, however, propane-1,2-diol had no effect on transepithelial resistance, whereas the effect of Me2SO was now similar to that of glycerol, viz. a sustained reduction in resistance of approximately 30% throughout the 30-min exposure. The results could not be explained solely in terms of osmotic effects and suggested that the cryoprotectants were directly affecting components of the junctional complex or associated elements of the cytoskeleton. During removal of the cryoprotectants by two-step dilution, changes in transepithelial resistance showed little consistency between the different cryoprotectants. This suggested that the pattern of change was dictated more by the state of the junctions immediately before removal of the cryoprotectants, with each cryoprotectant having affected the junctions to different extents and perhaps by different mechanisms, than by the removal of cryoprotectant itself. Thus, intercellular junctions in epithelial sheets were affected by even modest concentrations of cryoprotectant, but the effect was influenced by the type of cryoprotectant and by temperature of exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
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↗
PubMedDate not supplied

Ultrastructural peculiarities of intercellular junctions in bronchopulmonary carcinomas.

Six bronchopulmonary carcinomas of various histological types (macrocellular, epidermoid) were electronmicroscopically studied on bronchial biopsy samples. The scarcity of intercellular junctions was observed in all of them, especially in carcinoma types or zones (i.e. of epidermoid carcinoma) less differentiated. Close and gap junctions, zonulae adherentes and maculae adherentes dominated the structure of poorly differentiated carcinomas, while the differentiated types also presented frequent desmosomes. Also the reduction of intercellular junctions frequency was accompanied by their ultrastructural aberrations. The ultrastructural changes observed were correlated to the capacity for invasion of investigated carcinomas without reducing this basic property of cancer cells to the former.

Carcinoma, Squamous Cell↗
PubMed1996

Expression of intercellular junctions during preimplantation development of the human embryo.

A total of 74 human embryos were stained with gap junction protein specific anti-peptide antibodies an antibodies to the desmosomal protein desmoplakin to reveal the expression pattern of intercellular junctions during preimplantation development. Prior to implantation, the human embryo expresses predominantly connexin (Cx43)-containing gap junctions. Gap junctions were first detected in apposing cell membranes at the 4-cell stage and became increasingly organized as development proceeded. In normal blastocysts, trophectoderm (TE) cells were linked by dense arrays of gap junctions while inner cell mass (ICM) cells were linked by small, punctate gap junctions. Gap junctions containing Cx32 or Cx26 were observed occasionally in the TE of late blastocysts. Desmosomes appeared between outer cells prior to cavitation and were retained in the TE, but not in the ICM. Levels of gap junction protein expression were variable in morphologically normal embryos at the same stage, suggesting that a normal appearance may not be a reliable indicator of future viability. Morphologically normal embryos often possessed multinucleate, apoptotic and decompacting cells. They could show either extensive, disorganized over-expression or reduced expression of gap junction protein. The results fit the view that only embryos destined to survive display an organized pattern of intercellular junctions.

Blastocyst↗
PubMed1997

Triazine derivatives inhibit rat hepatocarcinogenesis but do not enhance gap junctional intercellular communication.

We report here novel candidate chemopreventive agents active against experimental hepatocarcinogenesis. The triazine derivatives 6-(2-chlorophenyl)-2,4-diamino-1,3,5-triazine (2CPDAT), 6-(3-chlorophenyl)-2,4-diamino-1,3,5-triazine (3CPDAT), 6-(4-chlorophenyl)-2,4-diamino-1,3,5-triazine (4CPDAT), 6-(4-pyridyl)-2,4-diamino-1,3,5-triazine (PyDAT), and 6-(pyridine N-oxid-4-yl)-2,4-diamino-1,3,5-triazine (PyNODAT), synthesized in our laboratory, in addition to 6-(2,5-dichloro-phenyl)-2,4-diamino-1,3,5-triazine (DCPDAT), or irsogladine, which is a widely used anti-ulcer drug, were investigated for potential chemopreventive effects in a rat liver medium-term bioassay system. A significant inhibitory influence on enzyme-altered liver foci was found for 2CPDAT, 3CPDAT, 4CPDAT, and PyNODAT, but not for DCPDAT or PyDAT. The involvement of gap junctional intercellular communication in the inhibition was studied, but no change in gap junctional intercellular communication capacity in rat liver cells in vitro or in gap junction protein (connexin 32) expression in rat liver in vivo was noted. These results indicate that, although these irsogladine analogues exert inhibitory effects on rat liver carcinogenesis, their action is independent of modification of gap junctional intercellular communication.

Animals↗
PubMed1985

Intercellular junctions and the cardiac intercalated disk.

Cardiac muscle cells are equipped with three distinct types of intercellular junction--gap junctions, "spot" desmosomes, and "sheet" desmosomes (or fasciae adherentes)--located in a specialized portion of the plasma membrane, the intercalated disk. Gap junctions are responsible for electrical coupling and the transfer of small molecules between cells, whereas the desmosomelike junctions (also known as adherens junctions) provide strong intercellular adhesion. The adhesion sites formed by the "spot" desmosome anchor the intermediate-filament cytoskeleton of the cell; those formed by the fascia adherens anchor the contractile apparatus. An understanding of the ultrastructure of these junctions helps explain how they carry out their functions, and new observations in this field have been made through the application of ultrarapid freezing techniques in conjunction with freeze-fracture electron microscopy. With recent findings from biochemical and immunocytochemical studies, this understanding is now being extended to the molecular level.

Animals↗
PubMed2004

[Influence of acetylcholine on cytoplasma Ca2+ signals and gap junctional intercellular communication of rat hippocampus cells].

OBJECTIVE: To investigate the influence of acetylcholine (Ach) on gap junctional intercellular communication in rat hippocampus. METHODS: Ach was applied to primary co-cultured hippocampus neurons and glial cells. Laser scanning confocal microscopy was used to monitor the change of Ca(2+) in the cytoplasma. The effect of Ach on gap junctional intercellular communication(GJIC) was measured by scrape loading method. RESULTS: Ach(0.05-0.10 mmol/L) induced all changes in cytoplasmic Ca(2+) concentration and calcium waves and calcium oscilation in cytoplasma. The Ca(2+) change could be blocked by scopolamine. Using scrape-loading method, we found GJIC notably enhanced 60 h after applying Ach to these cultured cells. CONCLUSION: Ach can enhance GJIC in hippocampus cells.

Acetylcholine↗
PubMed1997

Changes in gap junctional intercellular communication in mouse skin carcinogenesis.

Gap junction intercellular communication (GJIC) has been measured in cell lines that represent different stages of chemically induced mouse skin carcinogenesis. No significant difference in GJIC, as measured by dye spread, was found in cultures of normal keratinocyte, papilloma or squamous carcinoma cell lines. There was no correlation, in this system, between the presence of a mutant Ha-ras gene and down-regulation of communication. There was, however, a marked decrease in GJIC (80-90%) on progression from squamous to spindle carcinoma cells. Measurement of GJIC in somatic cell hybrids shows that the genetic defect responsible for this down-regulation is recessive and is common to two independently isolated spindle cell lines. No abnormalities were found in the spindle cells in expression of connexin 43, a cell component involved in gap junction formation and permeability. However, expression of E-cadherin, a cell-cell adhesion molecule implicated in the process of gap junction formation, was missing in the spindle carcinoma cells. Introduction of an E-cadherin cDNA into the spindle cells partially restored junctional communication without causing any noticeable alterations in cell morphology. During the study a non-tumourigenic keratinocyte line, a sub-clone of a normal keratinocyte line, was also found to have a low level of GJIC. However, the defect in this line was shown, by genetic complementation in somatic cell hybrids, to be different from that in the spindle carcinoma cell lines. Consistent with these data, analysis by immunofluorescence shows an abnormal distribution of connexin 43 in these cells.

Animals↗
PubMed2000

Intercellular junctions: downstream and upstream of Ras?

Most human tumors are of epithelial origin, and these tumors gradually lose their epithelial character in a process termed the epithelial-mesenchymal transition. Approximately 40% of human tumors have activating mutations in one of the three RAS genes. Given these statistics, it is critically important to understand the role of Ras signaling in the epithelial-mesenchymal transition. This review considers the mechanisms and effectors through which Ras may regulate intercellular junction formation in epithelial cells. Conversely, intercellular junction proteins themselves may play a role in regulating Ras activation and signaling.

Animals↗
PubMed1993

Concurrent analysis of intracellular glutathione content and gap junctional intercellular communication.

The potential for performing dual analysis of intracellular glutathione levels and assessment of gap junctional intercellular communication with thiol-specific fluorescent probes in anchored cells was evaluated. Gap junction-mediated diffusion of monochlorobimane and 5-chloromethylfluorescein diacetate following intracellular loading and conjugation with glutathione was compared with 5-carboxyfluorescein diacetate (which is routinely used in laser cytometry to monitor intercellular communication) by means of fluorescence recovery after photobleaching using a variety of communication-competent and communication-incompetent cells. The rate of diffusion of fluorescence among communication-competent cells was inversely proportional to the size of the fluorescent probe employed. The thiol-specific probes were also employed to monitor depletion and synthesis of glutathione following treatments to inhibit glutathione synthesis or consume glutathione by adduct formation. Analysis of gap junctional intercellular communication following glutathione depletion revealed a direct correlation between glutathione levels and intercellular communication. These studies support the utility of the thiol-specific probes to monitor the respective role of cellular glutathione and intercellular communication in the mechanisms of cellular injury.

Animals↗