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Intercellular junctions and the permeability barrier in the junctional epithelium
Author(s) -
Saito Isamu,
Watanabe Osamu,
Kawahara Hironori,
Igarashi Yuichi,
Yamamura Takeo,
Shimono Masaki
Publication year - 1981
Publication title -
journal of periodontal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.31
H-Index - 83
eISSN - 1600-0765
pISSN - 0022-3484
DOI - 10.1111/j.1600-0765.1981.tb02012.x
Subject(s) - tight junction , cell junction , epithelium , cytoplasm , septate junctions , ultrastructure , barrier function , anatomy , junctional epithelium , gap junction , intracellular , biology , chemistry , microbiology and biotechnology , biophysics , cell , genetics
The morphology and distribution of intercellular junctions were studied in the clinically normal junctional epithelium of dogs by freeze‐fracture and thin sectioning. Desmosomes were found in cells of the coronal and apical regions of the junctional epithelium. The occurrence values for desmosomes were low in comparison with those of other oral epithelia. Gap junctions were also observed in cells of the junctional epithelium, often in association with desmosomes. These were usually small, their diameter varying between 0.2 and 0.7 μm. Relatively large ones were found in the cells of the coronal region. Tight junctions were observed only in the intermediate cells of the coronal region, forming small, discrete maculae occludentes. Numerous dense PTA‐positive granules were observed in the peripheral cytoplasm of the intermediate and superficial cells. In freeze‐fracture replicas, hemispherical structures were also observed at the periphery of the cytoplasm. Because of similarities in their size and location, the hemispherical structures probably correspond to the dense granules. Freeze‐fracture images such as elevated membranes seem to reveal exocytosis. The hypothesis is put forward that the dense granules are related to the physiological permeability barrier in the junctional epithelium. However, it is doubtful that the epithelium provides a complete barrier function because of the vast extent of the intercellular spaces and the sparseness of desmosomes.