Permeability of the epidermis and the phagocytic activity of keratinocytes. Ultrastructural studies with thorotrast as a marker

Skin Barriers in Dermal Drug Delivery: Which Barriers Have to Be Overcome and How Can We Measure Them?

Although, drugs are required in the various skin compartments such as viable epidermis, dermis, or hair follicles, to efficiently treat skin diseases, drug delivery into and across the skin is still challenging. An improved understanding of skin barrier physiology is mandatory to optimize drug penetration and permeation. The various barriers of the skin have to be known in detail, which means methods are needed to measure their functionality and outside-in or inside-out passage of molecules through the various barriers. In this review, we summarize our current knowledge about mechanical barriers, i.e., stratum corneum and tight junctions, in interfollicular epidermis, hair follicles and glands. Furthermore, we discuss the barrier properties of the basement membrane and dermal blood vessels. Barrier alterations found in skin of patients with atopic dermatitis are described. Finally, we critically compare the up-to-date applicability of several physical, biochemical and microscopic methods such as transepidermal water loss, impedance spectroscopy, Raman spectroscopy, immunohistochemical stainings, optical coherence microscopy and multiphoton microscopy to distinctly address the different barriers and to measure permeation through these barriers in vitro and in vivo.

A reverse Warburg metabolism in oral squamous cell carcinoma is not dependent upon myofibroblasts

BACKGROUND

The reverse Warburg effect describes the phenomenon that epithelial cancer cells take advantage of the metabolic machinery from nearby cancer-associated fibroblast, inducing them to produce lactate and ketones to fuel the high metabolic demands of the epithelial tumour tissues. This is in breast cancer observed as a lack of stromal caveolin-1 (CAV-1) and an increased expression of monocarboxylate transporter 4 (MCT-4) in the tumour stroma, with a concomitant increase in the expression of monocarboxylate transporter 1 (MCT-1) in the epithelial, tumour compartment. The lack of CAV-1 and increased expression of MCT-4 have been shown to have prognostic importance, primarily in patients with breast cancer. However, this phenomenon has only scarcely been described in oral squamous cell carcinoma (OSCC). Given the prognostic importance of myofibroblasts in OSCC, we also examined a potential relationship between the expression of MCT-4 and the presence of myofibroblasts.

METHODS

Paraffin-embedded tissues from 30 patients with OSCC were immunostained with antibodies towards MCT-1, MCT-4, Cav-1, GLUT-1, α-SMA, TOMM20 and KI-67, and evaluated for their specific epithelial and stromal expression.

RESULTS AND CONCLUSIONS

In patients with OSCC, we find an increased expression of MCT-1 and MCT-4 in both the epithelial and stromal compartment, with almost no overlap in their spatial expression. We found a large spatial overlap between α-SMA and MCT-1 in the stroma compartment, but no relationship between MCT-4 and myofibroblasts. Interestingly, we did not observe any relationship between the absence of CAV-1 and the presence of MCT-4 as has been shown in breast carcinomas.

Buccal bioadhesive drug delivery--a promising option for orally less efficient drugs

Rapid developments in the field of molecular biology and gene technology resulted in generation of many macromolecular drugs including peptides, proteins, polysaccharides and nucleic acids in great number possessing superior pharmacological efficacy with site specificity and devoid of untoward and toxic effects. However, the main impediment for the oral delivery of these drugs as potential therapeutic agents is their extensive presystemic metabolism, instability in acidic environment resulting into inadequate and erratic oral absorption. Parenteral route of administration is the only established route that overcomes all these drawbacks associated with these orally less/inefficient drugs. But, these formulations are costly, have least patient compliance, require repeated administration, in addition to the other hazardous effects associated with this route. Over the last few decades' pharmaceutical scientists throughout the world are trying to explore transdermal and transmucosal routes as an alternative to injections. Among the various transmucosal sites available, mucosa of the buccal cavity was found to be the most convenient and easily accessible site for the delivery of therapeutic agents for both local and systemic delivery as retentive dosage forms, because it has expanse of smooth muscle which is relatively immobile, abundant vascularization, rapid recovery time after exposure to stress and the near absence of langerhans cells. Direct access to the systemic circulation through the internal jugular vein bypasses drugs from the hepatic first pass metabolism leading to high bioavailability. Further, these dosage forms are self-administrable, cheap and have superior patient compliance. Developing a dosage form with the optimum pharmacokinetics is a promising area for continued research as it is enormously important and intellectually challenging. With the right dosage form design, local environment of the mucosa can be controlled and manipulated in order to optimize the rate of drug dissolution and permeation. A rational approach to dosage form design requires a complete understanding of the physicochemical and biopharmaceutical properties of the drug and excipients. Advances in experimental and computational methodologies will be helpful in shortening the processing time from formulation design to clinical use. This paper aims to review the developments in the buccal adhesive drug delivery systems to provide basic principles to the young scientists, which will be useful to circumvent the difficulties associated with the formulation design.

Mechanism of transepithelial elimination of elastic fibers in keratoacanthoma

Transepithelial elimination of elastic fibers is frequently seen in keratoacanthoma. However, the mechanism underlying this elastic fiber transport is not yet fully understood. We investigated the process by comparing the related features of 27 cases of keratoacanthoma, eight cases of squamous cell carcinoma and 11 cases of seborrheic keratosis (control). Microscopically, transepithelial elimination of elastic fibers was specifically observed in keratoacanthomas. Elastic fibers were surrounded by keratoacanthoma cell membrane and were ultrastructurally associated with hemidesmosomes and the basement membrane. Collagen fibrils were also observed within small, membrane-delineated vesicles within cells in the lower layers of the tumor. Also noted was strong expression of matrix metalloproteinase-1, which was detected by immunohistochemical analysis and in situ hybridization. Western blotting showed significantly stronger labeling of matrix metalloproteinase-1 in samples of keratoacanthoma than in normal epidermis. In contrast, squamous cell carcinomas and seborrheic keratosis exhibited none of the aforementioned characteristics. We propose that keratoacanthoma cells entrap, lift and eliminate elastic fibers as they proliferate and keratinize toward the epidermal surface, while simultaneously phagocytosing collagen fibrils. In that regard, matrix metalloproteinase-1 appears to play a key role in the degradation of collagen fibrils.

Rabbit IgG distribution in skin, spinal cord and DRG following systemic injection in rat

In order to determine the distribution of antibodies such as anti-NGF following systemic injection in neonates, immunocytochemical techniques were used to examine the localization of rabbit IgG in rat skin, DRG, and spinal cord after treatments with normal rabbit serum or purified rabbit IgG. Daily subcutaneous injections beginning on postnatal day 2 or on day 15 were given for three days. On the fourth day the animals were sacrificed and tissues were processed for rabbit IgG-IR. In the dorsal and ventral spinal cord, staining intensities suggest a substantial increase in the blood-brain barrier during the first two weeks after birth. Staining intensity in the epidermis of the glabrous skin from the hindpaw was substantially lower than in the adjacent dermis. In addition, IgG infrequently accumulated intracellularly in intensely stained patches in the epidermis. IgG was also able to reach relatively high intracellular concentrations in a small number of sensory neurons. The IgG staining pattern in the skin was similar when anti-NGF itself was administered to the animals. The results are discussed in the context of the effects of anti-NGF on the development of nociceptive afferents.

Endocytosis of fluorescent microspheres by human oesophageal epithelial cells: comparison between normal and inflamed tissue

This paper examines the presence and characteristics of endocytosis by oesophageal epithelial cells. Biopsy specimens from normal and inflamed oesophagus were incubated in organ culture with fluorescent microspheres (0.1 and 0.01 microns diameter). These markers were taken into early endosomes and the lysosomes of both the smaller differentiating prickle cells and the larger mature squamous cells. Confocal and electron microscopy showed that markers passed to the early endosomes and the lysosomes by endocytosis. The process was energy dependent. Larger, 1 micron microspheres adhered to the epithelial cells but were not phagocytosed. Disaggregated cells were analysed by flow cytometry. Microspheres were endocytosed in proportion to the concentration in the culture medium in a dose dependent manner. Cells from inflamed oesophagus were significantly smaller (p = 0.013) and took up significantly more microspheres than cells from normal biopsy specimens (p = 0.015). In conclusion, endocytosis occurs in oesophageal epithelial cells and is increased in inflammation.

The permeability of oral mucosa

In discussing permeability, we are describing one of the fundamental barrier functions of oral mucosa. Despite assumptions to the contrary, the oral mucosa is not a uniformly, highly permeable tissue like gut, but shows regional variation. The keratinized areas, such as gingiva and hard palate, are least permeable and nonkeratinized lining areas are most permeable. This variation appears to reflect differences in the types of lipid making up the intercellular permeability barrier in the superficial layers of the epithelium. Differences in permeability may be related to regional differences in the prevalence of certain mucosal diseases and can be utilized to advantage for local and systemic drug delivery.

Charge-selective permeability of dermo-epidermal junction: tracer studies with cationic and anionic ferritins

To investigate quantitatively the charge-selective permeability of the basement membrane (BM) of the dermo-epidermal junction (DEJ), tracer experiments using anionic and cationic ferritins were performed on an epidermal sheet, whose lamina densa was exposed on the dermal surface; its dermis was removed with forceps after the treatment of newborn rat skin with 10 mM dithiothreitol. The lamina densa and epidermal components of the sheets were electron microscopically well preserved, and anionic sites were ultrastructurally demonstrated on both the dermal and epidermal aspects of the lamina densa in the DEJ as clusters of cationic ferritins (CF) [isoelectric point (pI) greater than 9.5] or polyethyleneimine particles, indicating that the epidermal sheets were suitable for study of permeability. In tracer experiments, a large number of CF (pI 8.0-9.4) passed the lamina densa and formed clusters on both aspects of the lamina densa and in the intercellular space. The number of native anionic ferritins (NF) (pI 4.1-4.6) passing it was apparently much smaller than that of CF. When the epidermal sheets were pre-treated with protamine sulfate to neutralize the negative charges in the tissue, the number of NF penetrating the lamina densa was significantly larger than the number of those in the untreated sheet. These results indicate that the BM of the DEJ plays a role in a charge-selective filtration, although it is not as selective a barrier as the glomerular basement membrane.

Functional analysis of Ia antigen-bearing keratinocytes: mixed skin lymphocyte culture between Ia antigen-bearing Pam 212 cells and allogeneic and syngeneic splenic T cells

Keratinocytes express Ia antigens in various skin disorders, although the biological role of these Ia antigen-bearing (Ia+) keratinocytes remains unclear. We induced Ia antigens on Pam 212 murine keratinocyte cell line by interferon-gamma(IFN-gamma) and using these cells, we performed the mixed skin lymphocyte culture with syngeneic BALB/c or allogeneic C3H/He splenic T cells. Unexpectedly, Pam 212 cells were found to stimulate both syngeneic and allogeneic T cells irrespective of IFN-gamma treatment. However, both syngeneic and allogeneic T cells cultured with IFN-gamma-treated Pam 212 cells incorporated [3H]thymidine much more actively than those cultured with IFN-gamma-untreated Pam 212 cells. This stimulation was not inhibited by monoclonal anti-I-Ad antibody. Analysis of the responding T cells demonstrated that the syngeneic T-cell stimulation by IFN-gamma-treated Pam 212 cells occurred in both purified Lyt 1-T cells and Lyt 2- T cells. Furthermore, we found that the T cells cultured with the IFN-gamma-treated cells were composed of two morphologically different types of cells. Determination of their surface phenotype showed that the small cell population consisted of 57% Thy-1+, 23% Lyt-1+, 6% Lyt-2+, and 9% asialo-GM1+ cells, while the large cells consisted of 53% Thy-1+, 15% Lyt-1+, 9% Lyt-2+, and 24% asialo-GM1+ cells. These findings suggest that IFN-gamma-treated Pam 212 cells could stimulate more than one kind of splenic T cell populations.

Effects of ultraviolet irradiation on surface marker expression by epidermal immunocompetent cells and contact sensitization to dinitrofluorobenzene in mice

We studied the effects of ultraviolet (UV) irradiation on murine epidermal Ia-positive Langerhans cells (Ia + LC) and Thy-I-positive dendritic epidermal cells (Thy-I + dEC). We also studied contact hypersensitivity to dinitrofluorobenzene (DNFB) introduced through UV-treated epidermis. C3H/HeN mice were exposed to UVB or 8-methoxypsoralen plus UVA (PUVA). UVB and PUVA treatment led to a dramatic reduction in surface marker expression of both Ia + LC and Thy-I + dEC. High-dose UVB irradiation (360 J/m2) interfered with contact hypersensitivity to DNFB; the density of Ia + LC may thus be related to the sensitizing potential. In contrast, low-dose UVB (120 J/m2) and PUVA treatment had little effect on contact hypersensitivity despite a marked reduction in Ia + LC. The density of Thy-I + dEC appeared not to be associated with contact hypersensitivity. These results suggest that there may be a Langerhans cell density-independent mechanism for the induction of contact hypersensitivity.

Granulocyte-activating mediators (GRAM). II. Generation by human epidermal cells--relation to GM-CSF

In the present study we investigated the capability of human epidermal cells to generate granulocyte-activating mediators (GRAM). It could be shown that human epidermal cells as well as an epidermoid carcinoma cell line (A431) produce an epidermal cell-derived granulocyte-activating mediator (EC-GRAM) which stimulates human granulocytes to release significant levels of toxic oxygen radicals as measured by a lucigenin-dependent chemiluminescence (CL). For further characterization of EC-GRAM the A431 cell line was used. Supernatants of A431 cells usually contained maximal EC-GRAM levels within 24 h of incubation. Factor production was enhanced by bacterial lipopolysaccharide (LPS), but not by silica particles and PHA. Moreover, freeze-thaw lysates of A431 cells and extracts of heat-separated human epidermis contained significant levels of EC-GRAM. Preincubation of granulocytes with EC-GRAM resulted in an enhanced response to subsequent stimulation with the chemotactic peptide f-met-phe. In contrast EC-GRAM did not affect the response to PMA or zymosan particles. However, EC-GRAM treated granulocytes were unresponsive to restimulation with EC-GRAM. Upon high performance liquid chromatography (HPLC) gel filtration EC-GRAM eluted within two major peaks exhibiting a molecular weight of 17 kD and 44 kD.(ABSTRACT TRUNCATED AT 250 WORDS)

Different cellular reaction patterns of epidermal Langerhans cells after application of contact sensitizing, toxic, and tolerogenic compounds. A comparative ultrastructural and morphometric time-course analysis

BALB/c mice were treated with the irritants croton oil (0.5%, 20%), sodium lauryl sulfate (15%), and benzalkonium chloride (25%), the contact sensitizers 2,4-dinitrofluorobenzene (DNFB, 0.3%) and picryl chloride (PCl, 1%), and the tolerogen 2,4-dinitrothiocyanatebenzene (DNTB, 2%). All irritants used produced degenerative alterations of Langerhans cells (LCs). After application of 0.5% croton oil, however, this degeneration was preceded by an activation of the cells with increased number of mitochondria and enlargement of nuclei. The DNFB and PCl application in sensitizing doses to nonsensitized animals resulted in a cellular activation similar to that observed for 0.5% croton oil. In addition, these LCs showed enhanced adsorptive endocytosis as demonstrated by increased numbers of Birbeck granules and coated vesicles. The endocytotic activity was more pronounced in DNFB-sensitized animals. The DNTB at a concentration that induced tolerance to DNFB did not cause either cellular or endocytotic activation of LCs. These results demonstrate that the contact sensitizers DNFB and PCl induce characteristic cellular reaction patterns of LCs, which may be related to their sensitizing property.

Recombinant gamma interferon induces HLA-DR expression on squamous cell carcinoma, trichilemmoma, adenocarcinoma cell lines, and cultured human keratinocytes

We investigated the effects of recombinant human gamma interferon on the induction of HLA-DR expression by two human squamous cell carcinoma, three trichilemmoma, one eccrine carcinoma, two adenocarcinoma cell lines, and cultured human keratinocytes in vitro. None of eight epithelial cell lines or keratinocytes expressed HLA-DR without gamma interferon treatment. In contrast, pure gamma interferon (500 IU/ml, 72-h treatment) induced HLA-DR expression on 1/2 squamous cell carcinoma, 3/3 trichilemmoma, 2/2 adenocarcinoma cell lines, and 4/4 keratinocyte cell lines, as determined using a fluorescence-activated cell sorter. A maxillary squamous cell carcinoma line and an eccrine carcinoma cell line failed to express HLA-DR with gamma interferon treatment; however, the growth of cells was inhibited by gamma interferon treatment. By indirect immunoperoxidase techniques, tumor cells such as Bowen's disease and squamous cell carcinoma were found to express HLA-DR. Since HLA-DR expression has been shown to be important for various immune responses, these findings suggest that gamma interferon plays important roles in various immune-related skin diseases.

Differences in human skin between the epidermal growth factor receptor distribution detected by EGF binding and monoclonal antibody recognition

Two methods have been used to examine epidermal growth factor (EGF) receptor distribution in human scalp and foreskin. The first employed [125I]EGF viable explants and autoradiography to determine the EGF binding pattern while the second used a monoclonal antibody to the human EGF receptor to map the distribution on frozen skin sections of an extracellular epitope on the EGF receptor. The [125I]EGF binding experiments showed accessible, unoccupied EGF receptors to be present on the epidermal basal cells (with reduced binding to spinous cells), the basal cells of the hair shaft and sebaceous gland, the eccrine sweat glands, capillary system, and the hair follicle outer root sheath, generally similar in pattern to that previously reported for full-thickness rat skin and human epidermis. The same areas also bound EGF-R1 but in addition the monoclonal antibody recognized a cone of melanin containing presumptive cortex cells, excluding the medulla, lying around and above the upper dermal papilla of anagen hair follicles, epithelial cells around the lower dermal papilla region, and in some tissue samples the cell margins of the viable differentiating layers of the epidermis. In a control study, to clarify whether EGF-R1 could recognize molecules unrelated to the EGF receptor, the EGF binding and EGF-R1 recognition profiles were compared on cultures of SVK14 cells, a SV40 transformed human keratinocyte cell line. EGF binding and EGF-R1 monoclonal antibody distribution on these cells was found to be similar, indicating that, at least for SVK14 cells, EGF-R1 binding provides a reliable marker for EGF binding. Explanations for the discrepancies between these two methods for determining EGF receptor distribution in human skin are discussed, including the possibility that latent EGF receptors, unable to bind [125I]EGF, may be present in some differentiating epithelial compartments.

The Langerhans cell granule is an adsorptive endocytic organelle

The role of Langerhans cell granules (LCG) in adsorptive endocytosis was studied by using concanavalin A (Con A) and heterologous anti-epidermal cell serum (AES) as ligands. Isolated epidermal cells were obtained by trypsinization of guinea pig skin fragments and exposed to ferritin-conjugated Con A or AES followed by ferritin-conjugated second antibody at 37 degrees C for various times up to 30 min. Langerhans cells among the treated epidermal cells were observed by electron microscopy. Shortly after the incubation, a few LCG in the cell periphery were filled with ferritin particles in the bulb portion. After prolonged incubation, ferritin-containing LCG increased in number and seemed to move to the juxtanuclear area. The granules were derived from plasma membrane invaginations that collected ferritin particles in a saclike extension at the end. Some of these invaginations were apparently of coated pit origin. The contents in the bulb of LCG seemed to be delivered finally to intracellular degradation compartments. Our findings clearly demonstrate that LCG are an adsorptive endocytic organelle.

Direct and indirect immunofluorescent findings in dermatomyositis

Three skin biopsies (proximal nailfold, extensor forearm and buttock) and serum samples were studied by direct and indirect immunofluorescence, immunodiffusion and radioimmunoassay techniques in 6 patients with dermatomyositis. A variety of serologic and immunopathologic abnormalities was observed in the patients. Three of 6 patients had antinuclear antibodies (ANA) of a speckled pattern mixed with a peculiar dot pattern. Epidermal intercellular deposits of immunoglobulins were seen in the nailfold biopsies of 2 patients; one of them also had IgG deposits in the cytoplasm of epidermal cells. Forearm and buttock biopsies were negative.

Coated Langerhans cell granules in histiocytosis X cells

Histiocytosis X cells (HXC) and epidermal Langerhans cells (LC) are thought to be closely related because they share morphologic features and immunologic markers. One of these common markers, the LC granule, is an acknowledged morphologic criterion for the identification of these cell types, but its function and, thus, significance are as yet unknown. In this study, we report the presence of a fuzzy coat radiating from the cytoplasmic face of the LC granule membrane in HXC. This bristly coat is indistinguishable from that of coated vesicles and pits and, thus, represents a strong morphologic clue to the function of LC granules because coated structures have been shown to be involved in the selective transport of molecules in eukaryotic cells.

The sequence of events in the differentiation of the epidermis in fetal rats with particular reference to membrane-coating granules

The sequence of events in the establishment of a keratinised epidermis has been related to age and crown rump length in fetal rats. Differentiation of the epidermis occurs under cover of the periderm throughout gestation. Ten stages are defined between 12d intra-uterine life and birth. Membrane-coating granules (MCGs) appeared at 18d (Stage 4) after the appearance of tonofilaments but before the appearance of the first "fetal" keratohyaline granules (KHGs) at 19d (Stage 5). Measurement of the position of MCGs within the cells showed a less marked concentration near the superficial border of the cells than that found at later stages. As KHGs formed, exocytosis of MCGs occurred into the intercellular space immediately deep to the periderm. It is suggested that after 19d (Stage 5) the periderm serves to retain the contents of the MCGs in this space so providing the permeability barrier and that prior to that stage the periderm itself probably provides the permeability barrier of fetal skin.

A histological method for the visualization of the intercellular permeability barrier in mammalian stratified squamous epithelia

Mammalian epidermis and oral epithelial possess an intercellular permeability barrier which is located in the superficial region of the tissue. This study reports a staining reaction which appears to demonstrate a histological correlate of this functional property. Specimens of ear skin, palate, buccal and oesophageal mucosa and of cornea and bladder were obtained from adult rabbits and rats, bisected and either incubated in vitro with 2.5% horseradish peroxidase as a tracer or fixed and processed for light microscopy and stained with a modification of Hart's elastin stain. Examination of specimens prepared by each procedure showed a complementary staining pattern in the intercellular spaces of the stratum corneum or in the superficial region of the non-keratinized tissue. In the epidermis and oral and oesophageal epithelia, the region which excluded the tracer stained with the modified elastin stain. In contrast, the corneal and bladder epithelia neither excluded the tracer nor showed intercellular staining. This relationship between staining of the intercellular space and the exclusion of tracer suggests that the intercellular material in the superficial region of epithelia may be chemically altered to form a barrier substance, possibly as the result of the discharge of the contents of the membrane-coating granules which are present in all the epithelia examined except the cornea and bladder.

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.

Langerhans cells as macrophages in skin and lymphoid organs

Properties of epidermal Langerhans cell were compared with those of a number of other dendritic cells in lymphoid organs and of mononuclear phagocytes. Among the dendritic "reticulum" cells included were indeterminate cells from the epidermis, interdigitating "reticulum" cells from T-dependent areas of lymphoid tissue and thymus, follicular dendritic cells of Nossal, and the dendritic cells described by Steinman and Cohn. Interdigitating cells with typical Birbeck granules, in the thymus and in the paracortices of lymph nodes, which are morphologically indistinguishable from Langerhans cells and indeterminate dendritic cells in the epidermis, appear to belong to the same system and possibly represent a subpopulation of "macrophages." On the basis of their similarity to these other dendritic cells, we believe Langerhans cells may function in antigen presentation, lymphokine production, provision of a microenvironment for T lymphocytes, and prostaglandin secretion.

Hyaline bodies of odontogenic cysts: histological, histochemical and electron microscopic studies

Hyaline bodies of odontogenic cyst were examined by histological, histochemical and electron microscopic observations. They were seen only in odontogenic cysts and their prevalence was 6.9% in 576 cases of the cysts. They occurred most frequently within the epithelial lining, but a few bodies were observed in the connective tissue walls. Histochemical reactions of hyaline bodies were similar to those of dental cuticles, but differed from keratin. Ultrastructurally, hyaline bodies were typed into two forms: lamellated and homogeneous. The lamellated bodies were composed of alternate electron-dense and electron-lucent layers. The homogeneous bodies were occasionally formed around granular material, mineralized masses and cholesterol clefts. Hyaline bodies adjoined epithelial cells via a basal lamina-like structure and half-desmosomes. Epithelial cells containing well-developed, rough surfaced, endoplasmic reticulum were seen adjacent to hyaline bodies. Ferritin-like granules were found in the cytoplasm of epithelial cells near hyaline bodies. By electron probe X-ray microanalysis, inorganic elements within the ferritin-like granules were the same in constitution as those in the outermost electron-dense layer of the lamellated bodies. By scanning electron microscopy, hyaline bodies displayed ellipsoidal and stick-like shapes. The present study suggested that hyaline bodies are particular products formed by odontogenic epithelium.

The distribution and mobility of surface anionic groups of normal human oesophageal epithelium following interaction with cationized verritin

Oesophageal epithelial cells from biopsies from normal patients showed the presence of randomly distributed anionic groups, mostly sialic acid on the cell membrane in fixed material shown by cationized ferritin. When biopsies were pulse labelled, patching occurred in all three cell layers. Patching was energy dependent and did not occur at 4 degrees C. Pulse labelled material incubated on an unlabelled medium showed progressive loss of cationized ferritin from the cell membrane. This was mostly into the medium, although some was internalized in membrane profiles. A second pulse of cationized ferritin produced further patching suggesting regeneration of cell membrane. Superficial cells were leaky, but their organelles were not.

Ultrastructural studies of epidermis in acute radiation dermatitis. Basal lamina thickening and coated vesicles

Fine structural changes of keratinocytes by X-ray were examined in normal skin area around a lesion of Bowen's disease. The area was exposed to about 6000 r over 28 days. The findings were: a decreased number of desmosomes and microvilli, formation of cytoplasmic vaculoes with or without membrane, perinuclear aggregation of tonofibrils, intracytoplasmic desmosomes and gap junction, cytoplasmic occurrence of dense bodies, lipid droplet and glycogen particles, changes in mitochondria, endoplasmic reticulum and Golgi complex, and deep invagination of the nuclear membrane. Besides these, conspicuous in the present study were, changes in the basal lamina which consisted of multiplication, thickening and occasional detachment from basal cells, and frequent occurrence of coated vesicles along with the basal lamina alteration. Possible exocytotic nature of coated vesicles in X-ray irradiated keratinocytes is discussed.

Multiple clear-cell acanthoma (Degos): histochemical and ultrastructural study of two cases

Two patients with clear-cell acanthoma with multiple lesions are reported; histologic and histochemical findings are similar to previous descriptions. The ultrastructural study confirms the overload of glycogen in keratinocytes, associated with an increase of mitochondria and nuclear deformations. The abundance of Langerhans' cells is emphasized. Extrusion of glycogen by keratinocytes and its phagocytosis by Langerhans' cells is suggested.

A study of the permeability barrier in epidermis and oral epithelium using horseradish peroxidase as a tracer in vitro

Small biopsies of skin, and of keratinized and non-keratinized oral mucosa were incubated with horseradish peroxidase, fixed and reacted to demonstrate peroxidase activity at the light and electron microscope level. In all tissues peroxidase extended through the intercellular spaces of the epithelium up to, but not into, the stratum corneum of keratinized, or the superficial layer of non-keratinized, tissue. This distribution corresponds to that seen in studies using the tracer in vivo where the presence of an intercellular permeability barrier has been demonstrated in the upper cell layers. It is suggested that the method is a useful way of investigating the permeability of normal and pathological human epithelial tissues.

Langerhans cells at the sites of vaccinia virus inoculation

Langerhans cells in the epidermis at the sites of vaccina virus inoculation were studied with the electron microscope. The cells contained unusually increased numbers of the Langerhans cell granules. Such abnormal Langerhans cells have not been described except for in histiocytosis X. Vaccinia virus particles were found in the Langerhans cells, where they were located individually or embedded in the granular matrix or in lysosomes.

Trends in electron microscopy of skin

Some trends in electron microscopy of skin have emerged and should be pursued in the future. The fine structure and some basic cellular reaction patterns of epidermal cells are discussed to illustrate the interplay of morphologic, cytochemical, and tracer studies. Intracytoplasmic membranes and secretory granules, lysosomes and endocytic mechanisms, cytomembranes and cell surface specialization are discussed to show how these can be used to arrive at a more meaningful interpretation of structure. Despite all advances, however, a great deal more needs to be done before the details of skin structure are completely elucidated.

Some aspects of melanin biology: 1950-1975

Recent advances in the biology of mammalian pigmentation are reviewed. The multicellular epidermal melanin unit (melanocyte and associated pool of keratinocytes) rather than the melanocyte alone forms the focal point for melanin metabolism within mammalian epidermis. Within an epidermal melanin unit, melanosomes are synthesized by melanocytes and transferred to keratinocytes where they are degraded as they ascend to the epidermal surface. During the past 25 years, technical advances in biology and biochemistry have frosted a multidisciplinary approach to research on mammalian pigmentation. Emphasizing this perspective, we have examined the current state of knowledge of the form and function of epidermal melanin units from the levels of biologic organization ranging from the molecules relevant to melanin synthesis through the skin as a totally intergrated system. To an unusual degree, advances in melanin pigmentation have resulted from the integration of clinical medicine and basic science.

The role of Langerhans cells in allergic contact hypersensitivity. A review of findings in man and guinea pigs

Evidence in favor of a role for Langerhans cells in contact allergic hypersensitivity reactions has been reviewed. This includes mononuclear cell to Langerhans cell apposition and damage to some Langerhans cells at sites of specific challenge to a variety of contact allergens. Such apposition occurs in actively sensitized patients and guinea pigs and in passively sensitized guinea pigs. In addition, in passively sensitized guinea pigs Langerhans cells circulate in dermal vessels resembling lymphatics and are much increased in the dermis after challenge with the contact allergen. These observations, together with the existing knowledge that Langerhans cells occur in the lymph nodes and thymus, suggest that these cells may be involved not only in contact allergic reactions but also in other immunologic reactions, particularly in cell-mediated reactions in the skin.

Role of light in human skin color viariation

The major source of color in human skin derives from the presence within the epidermis of specialized melanin-bearing organelles, the melanosomes. Tanning of human skin on exposure to ultraviolet light results from increased amounts of melanin within the epidermis. Melanosomes synthesized by melanocytes are acquired by keratinocytes and transported within them to the epidermal surface. In some cases, the melanosomes are catobolized en route. New information indicates that the multicellular epidermal melanin unit (melanocyte and associated pool of keratinocytes) rather than the melanocyte alone is the focal point for the control of melanin metabolism within mammalian epidermis. Gross human skin color derives from the visual impact of the summed melanin pigmentation of the many epidermal melanin units. In theory, constitutive skin color in man designates the genetically-determined levels of melanin pigmentation developed in the absence of exposure to solar radiation or other environmental influences; facultative skin color or "tan" characterizes the increases in melanin pigmentation above the constitutive level induced by ultraviolet light. The details of genetic regulation of pigment metabolism within the epidermal melanin units are being clarified. In some mammals at least, the function of epidermal melanin units is significantly influenced by hormones which may be regulated by radiations received through the eyes. Based on an evolutionary history of the human family which exceeds ten million years, it is proposed that melanin pigmentation may have played a number of roles in human adaptions to changing biologic and physical environments.