A fine structural study of divalent cation-mediated epithelial union with connective tissue in human oral mucosa

The effects of alpha and beta adrenergic agonists and cyclic adenosine 3':5'-monophosphate on epidermal metabolism

Continuously regenerating stratified squamous epithelia form an interesting model for examining mechanisms controlling the balance between rates of cell formation and cell maturation and death. In vitro assays of rates of glycolysis and amino acid incorporation of epidermal sheets free from dermal contamination were used to examine rates of metabolism in both normal and hyperplastic epidermis after treatment with various adrenergic agonists and cAMP. Epinephrine and isoproterenol over the concentration range of 1 x 10(-9) to 1 x 10(-5) M depressed the rates of glycolysis and amino acid incorporation in normal epidermis. Dibutyryl cyclic AMP produced a 73 to 78% depression in metabolic activity and its action was enhanced by the addition of theophylline. The alpha adrenergic agonist norepinephrine produced similar reductions. When epidermal samples were treated with hexadecane to induce a mild hyperplasia, depressant effects of isoproterenol and epinephrine were lost, but dibutyryl cyclic AMP and norepinephrine still reduced metabolic activity. The results suggest that adrenergic agents and their putative second messenger cAMP cause reductions in epidermal metabolic activity, an effect similar to their effects on cell proliferation, and that increased rates of proliferation are associated with loss of beta adrenergic responsiveness of the epidermis.

Langerhans cells in dermoid cysts: transmission electron microscopic, cytochemical and immunofluorescent observations

Langerhans cells were detected in squamous, stratified epithelia lining human dermoid cysts. Their presence was assayed by ATPase staining and reactivity with heteroantisera against "Ia-like" antigens. Transmission electron microscopic studies demonstrated variations in the numbers of cells showing Birbeck granules in epithelia with different degrees of keratinization. Indeterminate cells (i.e. lacking granules), were more frequent in epithelia showing combined mucous and keratinizing differentiation. Membrane-coating-granules and keratohyalin granules were present in epithelia containing Langerhans cells with clearly identifiable Birbeck granules. Interepithelial mast cells were observed in epithelia with mucous differentiation. A relationship between Langerhans cells and keratinization was suggested. Such non-immune functions are compatible with the known macrophage characteristics of the cell.

The basement membrane complex of the human corneal epithelium

The present report reviews the fine structure of the basement membrane zone or complex in the normal human cornea and describes its alterations in cases of early and acute keratoconus. In normal human cornea the basement membrane zone is formed by a basal lamina (with a lamina lucida and a lamina densa), "special fibrils", collagen fibrils and assemblies of filaments. These components are less evident in the central region of the cornea than in its periphery. In early stages of keratoconus the basement membrane zone is thickened and the lamina densa displays an irregular course. In acute keratoconus, the basement membrane zone is also thickened and includes a large number of "special fibrils" as well as bundles of "microfibrils" (oxytalan fibers). The conclusion that the basement membrane complex of the corneal epithelium is equivalent to the epidermal-dermal junction of the skin is discussed.

Permeability of gingival sulcular epithelium in the development of scorbutic gingivitis

Young adult nonhuman primates were initially fed an ascorbic-acid free diet and, subsequently, a diet with a suboptimal level of the vitamin. Following approximately 12 weeks of this dietary regime, five of seven experimental animals of the gingival sulcular epithelium to 3H-inulin, but not to 14C-butyric acid or 14C-urea, had increased significantly (+86%, P less than 0.01) in the experimental group as compared to ad libitum or pair-fed controls. This defect in the intercellular permeability barrier of the sulcular epithelium could have contributed to the pathogenesis of scorbutic gingivitis.

Glycosaminoglycans of human gingival epithelium and connective tissue

The glycosaminoglycan (GAG) components of the proteoglycans (PG) in the epithelial and connective tissue extracellular compartments of human gingivae have been determined. Following proteolytic digestion of the separated tissues. GAG were identified electrophoretically. These were hyaluronic acid (HA), heparan sulfate (HS), dermatan sulfate (DS) and chondroitin-4 sulfate (ChS-4). Neither ChS-6 nor keratan sulfate (KS) was observed. Confirmation of the nature of the molecular species was obtained by the use of Streptomyces hyaluronidase, chondroitinase AC II and degradation with nitrous acid. Quantitatively, the major GAG component of the epithelial specimens was HS (59.6%), whilst DS (60.6%) constituted the major GAG of human gingival connective tissue.

Scanning electron microscope histochemistry: the use of backscattered electrons to identify epidermal Langerhans cells in the scanning electron microscope

Epidermal sheets reacted for ATPase were examined in the scanning electron microscope and images based on atomic number contrast formed by collecting the backscattered electrons. Langerhans cells lying within the tissue were revealed and could be related to surface structures by reference to conventional secondary electron images.

An examination of the relationship between experimentally altered rates of epidermal proliferations and rates of epidermal metabolism assayed in vitro

Continuously regenerating stratified squamous epithelia form an interesting model for examining mechanisms controlling the balance between rates of cell formation and cell maturation and death. Previous investigations of epidermal metabolism have been mainly based on single enzyme assays which may not form a reliable guide to changing rates of flux through metabolic pathways. Methods for in vitro assays of rates of glycolysis, protein synthesis and RNA synthesis of epidermal sheets free from dermal contamination were developed and used to examine rates of epidermal metabolism after experimental alteration of rates of epidermal proliferation. Starvation resulted in a 45-53% reduction in the in vivo epidermal labeling index and a 49-56% reduction in glycolysis and incorporation of amino acids assayed in vitro. Induction of epidermal hyperplasia with hexadecane resulted in a 4-fold increase in labeling index, a 6-fold increase in vitro glycolysis and a 3 to 4-fold increase in in vitro assays of incorporation of amino acids and uridine. Hyperplastic epidermis also showed an increased rate of incorporation of histidine (a marker for keratokyalin synthesis) relative to leucine (a marker for basal cell protein synthesis) indicating a change in maturation. The results suggest mechanisms linking rates of cell proliferation and death and indicate the possible value of such assays investigating these mechanisms.

A method for studying epithelial-mesenchymal interactions in human oral mucosal lesions

A system has been developed for examining connective tissue influence on keratinization of normal and leukoplakic human oral epithelia. Paired biopsy specimens of normal and leukoplakic mucosa were left intact or were incubated in 1 mM EDTA to permit epithelial-connective tissue separation and various recombinations of the epithelium and connective tissue. The tissues were transplanting to subdermal sites of "nude" (nu/nu) mice and were protected by polyethylene capsules. 44% of implants performed were recovered apparently vital. Preexisting structure was retained after epithelial-connective tissue separation and self-recombination. Cross-recombined specimens showed changes in patterns of keratinization including changes of keratinized leukoplakic epithelium to a non-keratinized type.

Histomorphologic evaluation of scleral grafts in experimental bony defects

This study was undertaken in order to evaluate and compare the effectiveness and fate of the nonautogenous scleral graft in relation to similar grafts of bone marrow and epithelium-free connective tissue grafts from the palate. One hundred round osseous defects 2 mm in diameter, were surgically created in the calveria of 25 rats. Three defects in each animal were filled with the various graft materials obtained from isogenic rats sacrificed at the time of preparation of the bony defects. The fourth defect was left empty as a control. The animals were sacrificed at varying periods of time up to 150 days. Histomorphologic evaluation of the graft sites demonstrated the following: (a) Scleral grafts had effected a functionally adequate repair, without apparent histopathologic changes. (b) Fresh bone marrow provided the greatest osteogenic activity when used as a graft implant. The sclera had an insignificant osteogenic activity when used as a graft implant. The sclera had an insignificant osteogenic potential. (c) Epithelium-free connective tissue was the least effective, both as an osteogenic or functionally adequate graft.

Developmental changes in the protein profile of cornifying lingual epithelium

Epithelia from the tongue dorsum of 14- to 21-day embryos, 21-day embryos, 3-week-old, and adult rats were separated from their connective tissues by incubation in balanced salt solution containing EDTA. Aliquots from total extracts of these tissues were electrophoresed on sodium dodecyl sulfate-polyacrylamide gels. Scans of gels stained with fast green (FG) revealed more than 20 peaks. Ten major peaks ranging from apparent molecular weights (MW) of 120,000 to 14,000 daltons comprised about 70% of the total protein on each gel. This report focuses primarily on two pairs of peaks, arbitrarily numbered 2 and 3 (MWs 71,000 and 69,000) and 9 and 10 (MWs 17,500 and 14,000). Peaks 9 and 10 predominated in the 15-day embryos where they comprised about 30% of the total protein. As development proceeded, there was a gradual shift in the protein profile in favor of peaks 2 and 3 until on the 20th day the relative amounts of these peaks reached a maximum and peaks 9 and 10 decreased in relative amounts. The protein profile on the 20th fetal day resembled that of the 3-week-old rats and the adults. The rise in the relative amounts of peaks 2 and 3 coincided with the morphologic appearance of large numbers of tonofilaments and the onset of cornification. When the gel was stained by a procedure specific for sulfhydryl groups, peaks 9 and 10 were especially reactive after the 18th day; plainmetric analysis revealed that these had twice the relative affinity for this stain than for FG whereas other peaks had equal or less affinity. The incorporation of [3H]cystine into peaks 9 and 10 was relatively greater than into the other proteins.

Use of scanning electron microscopy for the study of human epidermal melanocytes

A method is presented which makes it possible to study melanocytes in situ in the human epidermis by means of scanning electron microscopy. Melanocytes are located both under and wedged between the basal epidermocytes. The dendrites describe a short course in the dermo-epidermal (d-e) junction and then ascend and disappear into the spaces between the epidermocytes. As a rule, the surface of the cells is smooth. However, proliferations such as blebs and microvilli can sometimes be observed on the surface, particularly on that of the round, adendritic cells. Contact between the melanocytes in the d-e junction is only occasionally seen.

Patterns of mitosis in hamster epidermis

Alignment of the flattened keratinizing cells of the upper strata of mammalian epidermis leads to the formation of columnar units of structure. In mouse epidermis, mitoses have been found to occur relatively infrequently in the region beneath the center of each cell column where a non-keratinocyte dendritic cell, usually with freatures typical of an epidermal Langerhans cell, is situated. The observed pattern of mitosis could therefore be due either to displacement of central keratinocytes by Langerhans cells or indicate some control of keratinocyte proliferation related either to the Langerhans cells or to the over-lying cell columns. No relationship exists between the position of Langerhans cells and epidermal cell columns in hamster epidermis but measurement of the position of mitosis has shown a reduced frequency of occurrence of mitosis beneath the central region. This pattern of mitosis is therefore unrelated to Langerhans cells and appears to reflect differences in the mitotic potential of basal keratinocytes which could be associated with feedback from the overlying cell columns or with an intrinsic pattern of basal cell activity.

Rapid regeneration of the dermal-epidermal junction after partial separation by vacuum: an electron microscopic study

A process of rapid repair of dermal-epidermal adherence, as found in experiments with interrupted suction, was investigated electron microscopically. Biopsies in different stages of the process of suction blister formation and of the repair process were studied. Results show that suction blister formation occurs by successive detachment of hemidesmosomes from the basement membrane, and that, after partial separation of the epidermis from the dermis, a rapid regeneration of the dermal-epidermal junction takes place. This regeneration process apparently consists of two steps: realignment of basal cells to the basement membrane accompanied by autophagocytosis of detached hemidesmosomes, and de novo formation of hemidesmosomes. The time required for this structural regeneration corresponds well with the speed of the functional repair of dermal-epidermal adherence measured with the technique of interrupted suction.

Ordered structure of the epidermis

Recent reports on the ordered structure of the epidermis are reviewed. The regular relationship between Langerhans cells and cell columns in the mouse is not typical of the epidermis of other animals. The pattern of mitotic activity previously described in mouse epidermis has also been demonstrated in the hamster, which suggests control of keratinocyte activity rather than the exclusion of keratinocytes from the central region beneath cell columns. These findings are discussed in relation to mechanisms which may be responsible for the formation of cell columns.

Cytochemical identification of ATPase-positive langerhans cells in EDTA-separated sheets of mouse epidermis

Sheets of epidermis for incubation to demonstrate ATPase activity were obtained from specimens of mouse footpad using EDTA as the separation medium. The use of EDTA in place of the NaBr method previously described, resulted in a greatly reduced incubation time, precise localization of reaction product and preservation of ultrastructural detail. A population of closely and regularly spaced ATPase-positive dendritic cells was demonstrated by light microscopy. Electron microscopy demonstrated that, with short incubation times, reaction product was found only in the extracellular space adjacent to dendritic cells, the majority of which possessed the typical ultrastructural features of Langerhans cells.

Spatial distribution of mitosis in mouse epidermis

The cells of the upper strata of mammalian epidermis are flattened and aligned to form regular columnar units. It has been suggested that the position of the smaller underlying basal cells is related to the overlying cell columns. Examination of the position of metaphase figures in sheets of mouse epidermis indicated that mitosis occurs principally in cells lying just within the periphery of the cell columns but that there is no alignment of interphase basal cells within the columnar peripheries which could account for this position of mitosis.