Transport pathway and uptake of microperoxidase in the junctional epithelium of healthy rat gingiva

Junctional epithelial uptake and transport of microperoxidase (MP, heme-undecapeptide) was investigated in the healthy gingivae of 24–26 day old rats. MP products were observed from the blood vessels in the junctional epithelium to the internal basement lamina (IBL) close to enamel surface via the intercellular spaces of junctional epithelial (JE) cells. The IBL was strongly stained with MP, but there was an abrupt stoppage of MP at the external basement lamina (EBL). The EBL seemed to act as a barrier against transport of MP from the gingival connective tissue into the junctional epithelium. MP was also found in the micropinocytotic vesicles and phagocytotic vacuoles of innermost JE cells. Neutrophils located in the intercellular spaces of JE cells showed positive reaction for both MP and/or endogenous peroxidase. These results suggest that gingival fluid is probably transuded from the blood vessels into the junctional epithelium, reaches the IBL via the intercellular spaces, and diffuses into the oral environment along the IBL, and that toxic and foreign materials are taken up by the micropinocytotic vesicles and phagocytotic vacuoles of JE cells and the neutrophils on their way to the oral environment.     

Correlated scanning and transmission electron microscopy of cell surfaces at various levels in human gingival epithelium.

The surfaces and cellular interdigitations of cells at defined levels in human gingival epithelium were investigated by correlated scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The epithelium of critical point-dried or freeze-dried specimens of gingiva was stripped with adhesive tape and the SEM and TEM appearances compared for each level. The undersurfaces of the epithelial cells removed by the adhesive tape were examined by SEM. Critical point-dried specimens were fractured vertically and the fractured epithelial surfaces examined by SEM. Epithelial cells stripped or scraped from the gingiva were also examined.The superficial surfaces of cells of the stratum corneum had a reticular pattern of ridges. Microvilli were present on their undersurface in a reciprocal arrangement. Desmosomes are included in these processes of the plasma membrane which are concluded to be remnants of the cellular interdigitation from a deeper level. Cell separation is an orderly process starting a few layers below the surface, and is possibly controlled by desmosomal attachments. At deeper levels the stripping tape technique uncovered isodiametric cells with fine processes, thought to be prickle or basal cells. Smooth featureless zones were detected at this level which, it is suggested, may represent portions of the basement membrane or cytoplasmic faces of intracellularly fractured keratinocytes. The fractured specimens enabled cells at different levels in the epithelium to be identified and their SEM appearances compared.     

Ultrastructure of the dento-gingival junction after gingivectomy

The lateral incisors of 2 cynomolgus monkeys were removed with the adjacent gingiva in situ at intervals of 12 to 49 days after gingivectomy. Electron microscopic examination of the specimens indicated that epithelial reattachment may occur in 12 days or less under these experimental conditions. Hemidesmosomes and a basement lamina were regenerated against enamel as well as coronal and root cementum surfaces. Reattachment appeared to occur against both morphologically normal and superficially altered cementum. Enamel lamellae extending through the thin coronal cementum layer were not disturbed during the surgical procedure. Hemidesmosomes appeared to regenerate more rapidly than the basement laminas against either the tooth surface or the gingival connective tissue.     

Two years oral use of chlorhexidine in man

Possible changes in the structure of human oral mucosa resulting from exposure to chlorhexidine were examined in biopsy specimens of palatal and gingival mucosa obtained from three groups of young adults who had rinsed for more than 1 year (a) once or (b) twice daily with 0.2 % chlorhexidine solution or (c) with a placebo mouthwash. Specimens were quenched in liquid nitrogen and cryostat sectioned perpendicular to the epithelial surface. Sections stained with hematoxylin and eosin were used to assess the degree of keratinization of epithelia and to measure the width of the stratum corneum. Sections treated with buffered alkaline solutions were used to expand and count the number of layers of cells in the stratum corneum.
All specimens examined showed evidence of keratinization and, in keeping with previous reports, palatal specimens were more frequently orthokeratinized than gingival specimens. Mean width of the stratum corneum of gingival specimens was approximately 13 μ m and of palatal specimens, 23 μ m. The mean number of layers of cells in the stratum corneum of the gingiva was approximately 10 and of the palate, approximately 12. Differences in the degree of keratinization and thickness of the stratum corneum between gingival and palatal specimens was statistically significant, but no statistically significant differences were found between the chlorhexidine-exposed and non-chlorhexidine-exposed palatal tissue in keratinization, layers of cells or thickness of the stratum corneum. Neither was there any statistical difference in the same parameters for the gingival specimens. The methods employed did not therefore detect any changes in the normal structure of keratinizing oral epithelia as a result of prolonged daily exposure to chlorhexidine.     

The structure of the interstitial surfaces of the epithelial basement membranes of mouse oral mucosa, gingiva and tongue.

It is known that the gaps between epithelium and the underlying connective tissue usually occur between the epithelial cells and the basement membrane, resulting in exposure of the cellular surface of the lamina densa. After dithiothreitol separation, the epithelia of oral mucosa, gingiva, and tongue were mechanically peeled off from the underlying connective tissues. This treatment severed the connections between the basement membrane and the underlying connective tissue and the anchoring fibrils were pulled off from the collagen layer. In contrast, connections between the epithelial cells and basement membrane were preserved, resulting in exposure of the interstitial surfaces of the laminae densae. Scanning electron-microscopic observations of those interstitial surfaces were possible using the specimens prepared as above. The basement membranes of these three oral epithelia were morphologically the same not only by transmission but also by scanning electron microscopy. Scanning electron-microscopic observations revealed that their laminae densae were composed of fine fibrils and demonstrated three-dimensionally the projection of the anchoring fibrils from the laminae densae to the interstitial side. These findings coincide with those for epidermal basement membrane, which had already been observed with the same method.     

Ultrastructure of glycogen-rich clear cell carcinoma of the palate

Abstract. Tissues from four local recurrences of a palatal tumor and regional lymph node metastases were studied by light microscopy while ultrastructural observations were made on the most recent tumor. The tumor was composed of solid sheets, clumps, and small nests of polyhedral epithelial cells with well-defined cell boundaries, clear cytoplasm, and cellular pleomorphism. Histochemical stains indicated the presence of abundant intracellular glycogen deposits in all tumor specimens examined. Ultrastructural observations revealed solid sheets of epithelial cells which lacked both surrounding basement lamina and ductal arrangements. The cytoplasm of the tumor cells was filled with P glycogen deposits and contained scattered bundles of tonofilaments and scant organelles. The transition between the glycogen-rich tumor cells and surface epithelium showed intervening cells which contained diffusely dispersed ribosomes and small amounts of glycogen. The tumor probably originated from surface epithelium.     

Electron microscopic features of the newly formed epithelial attachment after gingival surgery

Deciduous first molars with the buccal gingiva in situ were obtained from three year old cynomologus monkeys 2 months and 4 months after gingivectomy. Of the four specimens examined to date, all showed formation of a new epithelial attachment consisting of hemidesmosomes and a basement lamina. In some areas this attachment apparatus connected the cells directly to the tooth surface. In other areas, "cuticular" structures were interposed between the attachment apparatus and the tooth surface. Although the layers intervening between the attachment apparatus and the tooth surface may represent acquired pellicles, they may also be due to denaturation of superficial layers of cementum. Any factor affecting the integrity of the epithelial tissue, the attachment apparatus or these "cuticles" could result in breakdown of the epithelial attachment.     

Immunohistological study of wound healing in periodontal tissue of rats. Distribution of fibronectin and laminin after flap operation

This study describes the distribution of fibronectin and laminin in periodontal tissue of rats after a flap operation. After full thickness flaps were raised, the roots were surgically exposed and planed. Animals were sacrificed at 12 hours, and 1, 3, 5, 7, 14, 28 and 56 days after the wounding. The block specimens were fixed in formalin, decalcified with EDTA, made into serial paraffin sections, and examined after hematoxylin and eosin staining, after Masson-trichrome staining and by indirect immunofluorescence for the presence of fibronectin and laminin. After the wounding, fibronectin was detected in the fibrin clot, and the migratory epithelial cells crossed over this fibrin clot (12 hours-5 days). Fibronectin was deposited heavily in the granulation tissue. When the gingival connective tissue had matured, fibronectin diminished (5-14 days). On the root surface, a layer of fibronectin was present in the region where connective tissue fibers were oriented parallel to the root surface, while no fibronectin was seen at the site of reattachment of the regenerated collagen bundle (14-56 days). Laminin was present in the basement membrane of normal epithelium and blood vessels, but was absent from the internal basal lamina. After the wounding, laminin was absent from the basement membrane zone of the distal site of the migrating epithelium (1-3 days). Upon completion of wound reepithelialization at 5-7 days after wounding, laminin reappeared throughout the basement membrane except the internal basal lamina. These results suggest that fibronectin may be important in the regeneration of epithelium, connective tissue and connective tissue attachment during repair by functioning as an extracellular provisional matrix for migrating cells. On the other hand laminin may be important in maintaining the normal epithelium.     

Ultrastructure of intra-epithelial nerve endings in the hard palate of the rat, Rattus norvegicus

The ultrastructure is described of lanceolate and free nerve endings within the epithelium of the papillae of the intermolar palatal rugae, located either between the basement membranes and the bases of the epithelial cells, or suprabasally in the intercellular spaces of the epithelium. Cytoplasmic processes of epithelial cells invaginated the Schwann cells of the nerve endings; junctions between, or fusion of, the cell membranes of the epithelial cells and the Schwann cells were not found. The neurites of the nervous structures were characterized by numerous mitochondria, clear-cored vesicles and an axoplasmic reticulum. In lanceolate endings, asymmetric membrane densities existed between the neurite and its Schwann cell, the Schwann cell showing signs of pinocytotic activity at all sides of its plasma membrane. The basal lamina of the Schwann cell covering of the nerve endings appeared to be continuous with the basal lamina of the epithelium.     

Excision wounds in palatal epithelium in guinea pigs

abstract – Standardized excision wounds were made in the palatal mucosa of 112 adult, male guinea pigs in order to study the reaction to injury of orthokeratinized epithelium. The wound area was studied histologically 4, 6, 12, 24, 48, 72, 96 and 120 h postoperatively. Four and 6 h after wounding, a triangular eosinophilic «reactive zone» was found in the stratum granulosum and the upper half of stratum spinosum along the wound margins. This cellular reaction was interpreted as an «induced keratinization». After 12 h the reactive zone was delineated from the adjacent, normal epithelial cells by 2–4 rows of hyperchromatic, flattened cells – the demarcation zone. In the reactive zone a hypertrophic cell reaction was observed. The initial epithelial cell migration started from the lowest cell layers in the stratum spinosum and stratum basale 12 h postoperatively. The migrating epithelium moved out fan-shaped into the fibrin network under accumulations of granulocytes. The migrating cells showed few intercellular bridges, few tonofibril bundles, but many cytoplasmic granules and vacuoles. Both migrating cells and stratum spinosum cells along the wound margins exhibited erythro-phagocytosis. After 24 h and onwards the apices of the epithelial ridges along the wound margins turned away from the wound area indicating a sliding of the epithelial mass. Seventy-two hours postoperatively distinct changes were found in the stratum corneum up to 800–1000 microns from the wound. To the same extent stratum granulosum was replaced by a 10–12 cell layer wide demarcation zone. Ninety-six and 120 h postoperatively the migrating epithelial lips had fused. The epithelium in the wound area showed no differentiated stratification. The superficial cell layers consisted of remains of the reactive and demarcation zones which contained numerous granulocytes. No PAS-positive basement membrane was re-forrned within the period studied. From the basal cell layers downward multifocal cell migration was observed. At no stage of healing was glycogen demonstrated in the epithelium.     

Cell contacts in oral epithelia

Biopsies from normal, non-inflamed buccal gingiva, palatal gingiva, retromolar and upper vestibular mucosa were obtained from 12 adult patients for an electron microscopical investigation of cell contacts in the epithelial layers. The junctional complexes found were desmosomes, tight junctions and intermediate junctions. In parakeratotic or poorly keratinized epithelium (e.g. retromolar and vestibular mucosa, gingiva) the desmosomes maintained their typical appearance in all layers. In highly keratinized epithelium (e.g. palatal gingiva) the structure of the desmosomes changed in the stratum corneum to a three-layered structure between the thickened cell membranes. The tight junctions were classified as maculac occludentes in the basal layer and the stratum spinosum and as zonulae occludentes in the stratum granulosum and the stratum corneum. The intermediate junctions were rather numerous and of different length. The principal mode of attachment of clear cells to adjoining epithelial cells seemed to be of this type. At the tissue surface the orifices of the intercellular spaces were closed by tight junctions or modified desmosomes. No such junctional complexes were found at the orifices of the intercellular spaces to the basement membrane. In the light of the findings some permeability conditions of oral epithelia are discussed.     

Comparative ultrastructure of oral epithelium in fish and amphibia

The palatal epithelium and adjacent lamina propria of two species of fish and two species of amphibia were examined with the electron microscope. Corydoras posessed an orthogonal orientation of collagen fibres in the lamina propria. An unusual cell was described in the lamina profria of Bufo which contained large rhomboidal masses in the cytoplasm, possibly representing stored material. All four species studied contained abundant tonofilaments in the oral epithelium although they were not grouped to form tonofibrils as one sees in human oral mucosa. All species contained demosomes connecting the epithelial cells, and a basement lamina separating the basal cells from the lamina propria. Individual mucous cells were frequently observed in the epithelium. Dense granules, usually about 0.13 microns in diameter and of unknown composition were present in the palatal epithelium of Amphiuma. Specialized cells containing large amounts of arganualr endoplasmic reticulum oriented into a lattice-work of hollow tubes were visualized in the oral epithelium of Corydoras. The outer-most cells of the Corydoras palatal epithelium appeared to undergo a dehydration and compacting of cytoplasmic components which suggested a primative type of keratinization.     

Immunocytochemical localization of laminin in the epithelial rests of Malassez of immature rat molars.

Immediately after disruption of Hertwig's root sheath, epithelial cells were found near the root apex, singly or in groups of two or three cells. They were irregular in shape with only a partial lining of basal lamina. Immunoreactivity for laminin was intense in the basal lamina and weak between projections of the epithelial cells. In 5-week-old rats, the epithelial rests consisted of about five cells and still had an incomplete basal lamina with collagen fibrils in the intercellular spaces. Immunoreaction products were seen in the basal lamina and diffusely in the intercellular spaces. The epithelial rests of 9-week-old rats had more cells, an almost complete lining of basal lamina, and narrowed intercellular spaces. Immunoreaction products were seen in the basal lamina but not in the intercellular spaces. These findings indicate the basal lamina is involved in the formation of the epithelial rests.     

Macrophages in oral lichen planus

The presence and distribution of macrophages within 15 non-ulcerated lesions of oral lichen planus was investigated using an immunoperoxidase technique for the detection of the macrophage markers lysozyme and alpha 1 antitrypsin. All specimens contained mononuclear lysozyme and alpha 1 antitrypsin positive cells which were concentrated in a band immediately beneath the epithelium and often associated with areas of damaged basal cells. Cell counts revealed that 11% of the positive cells were in the epithelium and 89% in the lamina propria. Approximately 61% of all positive cells were found within a 125 micron wide zone centred on the basement membrane. These results suggest that in oral lichen planus macrophages are in close proximity to the epithelial basal cells, where cell damage occurs, and play a role in the pathogenesis of this condition.     

Relationship between fibronectin and lymphoid cells in buccal mucosa, labial salivary glands and palatine tonsil

The distribution of fibronectin in human buccal mucosa and labial salivary glands and its relationship to lymphoid cells was studied using an immunoperoxidase technique and monoclonal and polyclonal antibodies. In all specimens fibronectin was associated with basement membranes of epithelia, vascular endothelium and perineural sheaths. In histologically normal areas of buccal mucosa fibronectin was distributed as a sparse network in the superficial lamina propria. A more extensive network of fibronectin was found within the lamina propria of mucosal specimens infiltrated with T lymphocytes, whereas fibronectin was absent in areas occupied by B lymphocytes. A similar relationship between lymphocyte type and the presence of a fibronectin network was found in labial glands and palatine tonsil. Fibronectin was not detected within oral, salivary gland, tonsillar crypt or capsular epithelium.     

Relationship between fibronectin and lymphoid cells in buccal mucosa, labial salivary glands and palatine tonsil

The distribution of fibronectin in human buccal mucosa and labial salivary glands and its relationship to lymphoid cells was studied using an immunoperoxidase technique and monoclonal and polyclonal antibodies. In all specimens fibronectin was associated with basement membranes of epithelia. vascular endothelium and perincural sheaths. In historically normal areas of buccal mucosa fibronectin was distributed as a sparse network in the superficial lamina propria. A more extensive network of fibronectin was found within the lamina propria of mucosal specimens infiltrated with T lymphocytes, whereas fibronectin was absent in areas occupied by B lymphocytes. A sirelationship between lymphocyte type and the presence of a fibronectin network was found in labial glands and palatine tonsil. Fibronectin was not detected within oral, salivary gland, tonsillar crypt or capsular epithelium.     

Ultrastructure of odontogenic jaw cysts

The epithelial ultrastructure of six radicular cysts, four follicular cysts, and five keratocysts was studied with special attention to the epithelium-connective tissue junction, Inflammation was found to cause widened interepithelial cell spaces which often harbored inflammatory cells in the radicular and follicular cysts. The characteristic structures at the epithelium-connectivc tissue junction (plasma membrane, lamina lucida and basal lamina) were not affected by inflammation. Fibrous structures were seen to connect the basal lamina to the underlining collagenous connective tissue The keratocyst specimens, however, showed juxtaepithelial collagenolysis that was not associated with the degree of inflammation. Desmosomes were rare in the inflamed keratocysts' spinous layer but the cell-to-cell interactions still appeared close. Inflammatory cells were not detected within epithelium of the keratocyst specimens.     

Ultrastructure of odontogenic jaw cysts

The epithelial ultrastructure of six radicular cysts, four follicular cysts, and five keratocysts was studied with special attention to the epithelium-connective tissue junction. Inflammation was found to cause widened interepithelial cell spaces which often harbored inflammatory cells in the radicular and follicular cysts. The characteristic structures at the epithelium-connective tissue junction (plasma membrane, lamina lucida and basal lamina) were not affected by inflammation. Fibrous structures were seen to connect the basal lamina to the underlining collagenous connective tissue. The keratocyst specimens, however, showed juxtaepithelial collagenolysis that was not associated with the degree of inflammation. Desmosomes were rare in the inflamed keratocysts' spinous layer but the cell-to-cell interactions still appeared close. Inflammatory cells were not detected within epithelium of the keratocyst specimens.     

Immunolocalization of integrin alpha 6 beta 4 in mouse junctional epithelium suggests an anchoring function to both the internal and the external basal lamina.

The localization of the integrin alpha 6 beta 4, a transmembrane adhesion molecule associated with hemidesmosomes, was studied in mouse junctional epithelium (JE) by the use of monoclonal antibodies in indirect immunofluorescence microscopy. The results showed that the integrin a6 subunit was expressed throughout the JE and was localized to the cell membranes, including the aspects facing the internal and external basal laminae. The beta 4 subunit had a more restricted distribution. It was expressed only in cells facing the internal and the external basal laminae and had a basally polarized distribution. In other parts of gingival epithelium, both integrin subunits were mainly expressed at the basal aspects of basal epithelial cells. The basement membrane components, type IV collagen and laminin, could be detected only in the external basal lamina and in other basement membranes of gingival epithelium. The results indicate that the a6 beta 4 integrin, expressed in mouse JE, has a role in mediating the attachment of the cells to the basement membranes facing the connective tissue and the tooth.     

Immunoglobulin-bearing lymphocytes and polymorphonuclear leucocytes in recurrent aphthous ulcers in man.

Direct immunofluorescent techniques were used to study the number of immunoglobulin-bearing lymphocytes and polymorphonuclear leucocytes in specimens of mucosal lesions from 10 patients with recurrent aphthous ulcers. The proportion of immunoglobulin-coated cells in the peripheral blood of the 10 patients was also studied. Ten normal healthy controls were included. IgM-, IgD- and IgE-bearing lymphocytes and polymorphonuclear leucocytes were found in sections adjacent to the mucosal lesions. IgE-bearing peripheral blood lymphocytes were slightly but significantly increased in patients with recurrent aphthous ulcers. The recruitment of immunoglobulin-bearing lymphocytes and polymorphonuclear leucocytes into the lamina propria and their migration into the stratum spinosum of mucosa may be involved in the pathogenesis of these ulcers.