A fine structural study of human oral epithelium separated from the lamina propria by enzymatic action

Polypodium leucotomos extract inhibits glutathione oxidation and prevents Langerhans cell depletion induced by UVB/UVA radiation in a hairless rat model

In this report, we have addressed the effect of oral administration of a hydrophilic extract of the fern Polypodium leucotomos (PL) on the deleterious effects of ultraviolet radiation (UVR) on the levels of epidermal and plasmatic antioxidants in hairless rats. We have found that pretreatment with PL effectively reduced glutathione oxidation in both blood and epidermis, suggesting a potent systemic antioxidant effect. In addition, PL inhibited UVR-mediated Langerhans cell (LC) depletion. Our results demonstrate the efficacy of PL as an oral antioxidant and photoimmunoprotective agent and support its employment as a complement to topical sunscreens.

Variation in basement membrane topography in human thick skin

Samples of human plantar and palmar skin were excised and incubated in 20 mM EDTA after which the epidermis was gently separated from the dermis with the plane of separation occurring in the lamina lucida. Scanning electron microscopic examination of the dermal component revealed the classically described series of regularly spaced grooves and papillae that characterize the epidermal-dermal junction in thick skin. Primary dermal grooves exhibited evenly spaced tunnels that were originally occupied by sweat gland ducts. The basement membrane (basal lamina) in the primary grooves was relatively smooth but did exhibit a flattened, reticulated pattern at high magnifications. The basement membrane of secondary dermal grooves and papillae was in the form of numerous, elevated microridges off of which septae arose at roughly right angles. The surface appearance of the basement membrane in these areas was that of a honeycomb owing to the numerous compartments and recesses formed by the ridges and septae. Degradation of the basement membrane by trypsin demonstrated that the foundation for the highly folded and compartmentalized basement membrane was composed of dermal collagen fibrils, 60-70 nm in diameter, that were arranged in a series of variably sized, interconnected collagen bundles or walls. Epidermal basal cells extended cytoplasmic (foot) processes into two or more compartments, formed by the ridges and septae, which considerably amplified the basement membrane surface available for epidermal attachment. Scanning electron microscopic studies of the epidermal-dermal junction confirm the variable surface character of this interface previously reported by others using sectioned material.(ABSTRACT TRUNCATED AT 250 WORDS)

Degradation of the epidermal-dermal junction by proteolytic enzymes from human skin and human polymorphonuclear leukocytes

The degradation of normal human skin by the human polymorphonuclear leukocyte proteinases cathepsin G and elastase, and by a human skin chymotrypsin-like proteinase that appears to be a mast cell constituent, was examined. Enzymes were incubated with fresh, split-thickness skin for up to 8 h; the tissue was examined ultrastructurally and immunohistochemically using antibodies to known basement membrane constituents. In all cases, the primary damage observed was at the epidermal-dermal junction. Elastase degraded the lamina densa leaving scattered and disorganized anchoring fibrils, dermal microfibril bundles, and normal-appearing collagen fibers. Immunohistochemically, type IV collagen, laminin, KF1 antigen, and EBA antigen were absent. The bullous pemphigoid antigen was present and localized on the basal cells. Epidermal-dermal separation produced by the chymotrypsin-like proteinases, cathepsin G, and the human skin proteinase, was confined to the lamina lucida. The lamina densa and sub-lamina densa fibrillar network remained intact. The human skin chymotrypsin-like proteinase produced extensive epidermal-dermal separation, while cathepsin G, at comparable concentrations, produced only focal separations. Immunohistochemically, all antigens were present after incubation with enzyme. The bullous pemphigoid antigen, however, was found on the epidermal side of the split, while laminin was found on the dermal side. These results show that the epidermal-dermal junction is highly susceptible to neutral serine proteinases located in mast cells and polymorphonuclear leukocytes. Although all the proteinases produce epidermal-dermal separation, the patterns and extent of degradation are different. The distinctive patterns of degradation may provide a clue to the involvement of these proteinases in skin diseases.

Hemidesmosomal dimensions and frequency in experimental oral carcinogenesis: a stereological investigation

Connective tissue invasion by carcinomas results in a variety of morphological changes at the epithelial-connective tissue junction. In this report, hemidesmosomal size (-delta) and frequency (Ns) were quantified using established stereological methods. Following treatment of hamster cheek pouches with the chemical carcinogen DMBA, lesions defined as hyperplasias, dysplasias and carcinomas were evaluated using electron microscopical techniques. Untreated pouches served as controls. Stereological intersection counting procedures were used to quantify hemidesmosomes at the epithelial-connective tissue junction. During carcinogenesis, hemidesmosomal diameter decreased progressively, although the reductions were not statistically significant. Hemidesmosomal frequency also decreased progressively between control and carcinoma groups. Normal basal plasma membranes possessed approximately 8 hemidesmosomes/micron 2 whereas values were reduced to approximately 3/micron 2 in the carcinoma group. The reductions in hemidesmosomal frequency during carcinogenesis may reflect an increased motility of basal epithelial cells and a decreased adherence of basal cells to the adjacent lamina propria. The specificity of this alteration in the pathogenesis of malignancy can be readily determined by the application of stereological methods to various neoplastic and non-neoplastic lesions.

A quantitative study of lamina densa alterations in hamster cheek pouch carcinogenesis

Lesions produced by topical application of 0.5 per cent. DMBA to the hamster cheek pouch epithelium were classified as hyperplasia, dysplasia and carcinoma groups using strict histological criteria. Untreated epithelium served as a control. Tissue samples from five animals in each group were processed for electron microscopy and electron micrographs from the epithelial-connective tissue junction were obtained from 5 blocks per animal. The micrographs were subjected to stereological intersection counting to determine the relative surface (SSLD, BM) of lamina densa which was in normal relationship to the basal cell plasma membranes. Quantitative results indicated a progressive loss of lamina densa during carcinogenesis and this was accompanied by the extrusion of pseudopodia from the basal cells through the gaps. The pseudopodia were frequently related to peripheral cytoplasmic microfilaments. Quantitative data confirmed the progressive nature of this loss, with values for SSLD,BM being of the order of 98 per cent., 88 per cent., 76 per cent, and 42 per cent. for normal epithelium and for the hyperplastic, dysplastic and carcinomatous lesions respectively. The loss of lamina densa is discussed in relation to the specificity of the response and to the development of features indicative of motility in transforming cells.

Elastase +/- soybean trypsin inhibitor dissociation of rat oral mucosa: ultrastructural and oxidative metabolic destructive changes in isolated, epithelial and dermal mitochondria after dissociation

Epithelial and connective tissue compartments of rat oral mucosa were dissociated after incubation with elastase +/- soybean trypsin inhibitor (SBTI). Elastase + SBTI induced greater ultrastructural damage within the dissociated compartments than elastase alone. The basal lamina remained with the epithelial layer after elastase separation and was destroyed after exposure to elastase + SBTI. Isolated epithelial mitochondria were more severely damaged ultrastructurally after elastase + SBTI separation of the compartment than those prepared after exposure to elastase alone. Isolated fibroblast mitochondria were damage to the same extent after dissociation of the compartment with either medium. Oxidative metabolism and mitochondrial recoveries declined significantly after exposure to either dissociating medium. Cytochrome oxidase activity was significantly greater than succinic cytochrome c reductase in the control and experimental groups. Oxidative metabolism was found to be significantly greater in the connective tissue compartment than the epithelial compartment after dissociation of immature rat oral mucosa. Our data suggests that caution be utilized in assessing cellular viability and oxidative metabolism in tissue compartments immediately after their dissociation by proteolytic enzymes.

Ultrastructural alteration of trypsin- and pancreatin-separated embryonic rabbit palate epithelium and mesenchyme

The effects of 30- and 45-minute trypsin- and pancreatin-separation on embryonic rabbit palate epithelium and mesenchyme were studied with the electron microscope. Changes in epithelium included fragmentation of the basal lamina and formation of cytoplasmic blebs associated with the basal cell layer. Changes in mesenchymal cells were first evident at 45 min of incubation and included cell fragmentation, nuclear pyknosis, and dilation of extracellular space. Results indicate a differential susceptibility of mesenchyme to the separating agent.

Fine structure of the surfaces of the epithelium and mesenchyme of the newt limb regenerate, separated in salt solution: 14 to 25 days

Forelimbs of the newt Notophthalmus (Triturus) viridescens were amputated at the wrist, and at 14 to 25 days, the new limb regenerates were removed by a razor-blade cut. After incubation of the isolated regenerates in a medium containing only inorganic salts, the epithelium was removed easily from the underlying mesenchyme. The surfaces separated in the salt solution were examined using scanning and transmission electron microscopy to evaluate the completeness of the separation and the extent of tissue damage near the plane of separation. Rarely was an epithelial cell found clinging to the mesenchymal surface, supporting previous light microscopic observations. The most apparent morphological damage was sustained by the basal epithelial cell surfaces, which exhibited blebbing; the formation of vacant vesicles within the cytoplasm near the newly exposed plasma membranes; the structural disruption of some organelles; and the tearing away of fragments of the basal epithelial cell plasma membranes, which remained adherent to the mesenchymal surface during separation procedure. Examination of the structure of the epithelial-mesenchymal interface of intact regenerates showed that the plane of epithelial-mesenchymal separation was, for the most part, between the basal epithelial cell membrane and its substrate, an extracellular material which remained at the mesenchymal surface after separation. This substrate was in the form of an extracellular material closely adherent to the basal epithelial cell membrane at the distal tips of the regenerates; a developing basal lamina at the periphery of regenerates undergoing blastema accumulation; or a mature basal lamina at the base of digit stage regenerates. The usefulness of these separated tissues for future experimentation and the evaluation of the nature of the epithelial substratum throughout the course of limb regeneration are discussed.

Basement membrane changes under neoplastic oral mucous membrane. Ultrastructural observations, review of the literature, and a unifying concept

This study explores the morphologic nature of the basement membrane under neoplastic oral mucous membrane. Of particular interest is the progression of changes associated with dysplasia, carcinoma in situ, and invasive carcinoma. On the basis of a critical review of the literature and our own ultrastructural observations, we present a unifying concept for the development of these basement membrane changes. This concept proposes that neoplastic epithelial cells may produce a collagenolytic enzyme which is released into the epithelial intercellular spaces. This enzyme permeates to the basement membrane, causes breaks in the basement membrane, and focal loss of stromal area contiguous with intercellular spaces. The neoplastic basal cells develop pseudopodia that eventually extend through the breaks in the basement membrane. This concept suggests that the basement membrane changes herald the progression of carcinoma in situ to invasive carcinoma.

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.