The skin's barrier

The skin provides an effective barrier between the organism and the environment, preventing the invasion of pathogens and fending off chemical and physical assaults, as well as the unregulated loss of water and solutes. In this review we provide an overview of several components of the physical barrier, as well as how barrier function is regulated and altered in association with dermatoses. The physical barrier localized primarily in the stratum corneum (SC) and consists of protein-enriched cells (corneocytes with cornified envelope and cytoskeletal elements, as well as corneodesmosomes) and lipid-enriched intercellular domains. The nucleated epidermis, with its tight, gap and adherens junctions, additional desmosomes and cytoskeletal elements, also contributes to the barrier. Lipids are synthesized in the keratinocytes during epidermal differentiation and are then extruded into the extracellular domains, where they form lipid-enriched extracellular layers. The cornified cell envelope, a robust protein/lipid polymer structure, is located below the cytoplasmic membrane on the exterior of the corneocytes. Ceramides A and B, forming the backbone for the subsequent addition of free ceramides, free fatty acids and cholesterol in the SC, are covalently bound to cornified envelope proteins. Filaggrin is cross-linked to the cornified envelope and aggregates keratin filaments into macrofibrils. Cytokines, cAMP and calcium influence the formation and maintenance of barrier function. Changes in lipid composition and epidermal differentiation lead to a disturbed skin barrier, which allows the entry of environmental allergens, immunological reaction and inflammation in atopic dermatitis. A disturbed skin barrier is an important component in the pathogenesis of contact dermatitis, ichthyosis, psoriasis, and atopic dermatitis.

Stylostome formation in trombiculid mites (Acariformes: Trombiculidae)

Stylostomes of the trombiculid mite larvae Neotrombicula pomeranzevi (Schluger), Hirsutiella zachvatkini (Schluger), Miyatrombicula esoensis (Sasa and Ogata) and Euschoengastia rotundata (Schluger) (Acariformes: Trombiculidae), formed in the host skin during feeding of the parasites on their natural hosts (voles) were studied histologically and histochemically. A stylostome is a variously shaped tube formed of solidified mite saliva that extends from the mouthparts of the parasite through the epidermis into the dermis of the host, and allows the mite to obtain its liquid food. The first step of stylostome formation is deposition of an eosinophilic cone, to which the larva's chelicerae are glued. Organization of the stylostome depends on the mite species, and its walls may show weakly expressed longitudinal or transverse stratification. Histochemically, the stylostome is composed of complex glycoprotein with varying tinctorial properties through the width or the length of the stylostome's walls. Beneath the distal end of the stylostome, irrespectively of its localization either in the epidermis or in the dermis of the host, a feeding cavity is formed as a result of the action of the hydrolytic components of the mite's saliva forced through the stylostome into the wound. An inflammatory dermal reaction of moderate intensity is evolved during larval feeding and stylostome formation. It is manifested by the infiltration of the foci with neutrophiles, lymphocytes and macrophages and by dilation of capillaries of the terminal vessel bed and filling them by erythrocytes and other blood elements. Around the stylostome, necrosis of the epidermal cells occurs, leucocytes come to the damaged area and fuse with the necrotic epidermal cells, leading to the formation of the large scabs on the surface of the host's skin. In the case of E. rotundata, single capsules having a terminal opening and containing feeding larva are formed on the abdomen of the hosts. The walls of the capsules are composed of the mite's saliva flowing upon the surface of the host's skin. At the bottom of the capsule, a stylostome perforating the epidermis is also present.

Mutations in the fatty acid transport protein 4 gene cause the ichthyosis prematurity syndrome

Ichthyosis prematurity syndrome (IPS) is an autosomal-recessive disorder characterized by premature birth and neonatal asphyxia, followed by a lifelong nonscaly ichthyosis with atopic manifestations. Here we show that the gene encoding the fatty acid transport protein 4 (FATP4) is mutated in individuals with IPS. Fibroblasts derived from a patient with IPS show reduced activity of very long-chain fatty acids (VLCFA)-CoA synthetase and a specific reduction in the incorporation of VLCFA into cellular lipids. The human phenotype is consistent with Fatp4 deficiency in mice that is characterized by a severe skin phenotype, a defective permeability barrier function, and perturbed VLCFA metabolism. Our results further emphasize the importance of fatty acid metabolism for normal epidermal barrier function illustrated by deficiency of a member in the FATP family of proteins.

Neuroendocrine (Merkel Cell) Carcinomas of the Skin: An Ultrastructural Study of Nine Cases

Nine neuroendocrine tumors of the skin were examined by light and electron microscopy. The patients (7 males and 2 females) had an average age of 57 years. Seven tumors were located in the head and neck region. Light microscopic examination showed sheets of cells. In 4 cases, a tendency to form small groups of cells was observed. Contact with the epidermis was seen in only 2 cases. The dominant ultrastructural feature was the presence of cytoplasmic processes that contained membrane-bound granules 100-200 nm. Three tumors recurred locally, and in 7 patients, regional nodal metastases occurred. Three patients died of disseminated disease.

Exposure to gamma rays induces early alterations in skin in rodents: Mechanical, biochemical and structural responses

In this study, the effect of gamma rays has been investigated on the normal rat skin using biomechanical, biochemical and histological techniques. Seventeen male Wistar albino rats were divided into two groups (control (n=7) and irradiated (n=10)). The irradiated group was treated with a (60)Co gamma source at a dose of 10Gy at room temperature. Skin biomechanics were measured with tensile test using biomaterial testing machine and maximum load, stiffness, energy absorption capacity, ultimate stress, ultimate strain and elastic modulus were calculated. In the irradiated group, energy, strain and toughness were significantly lower than in the control group (p<0.05). However, strength, displacement, stiffness, stress and elastic modulus were similar to that of the control group (p>0.05). Catalase (CAT) activities and the levels of malondialdehyde (MDA) in the skin of rats were measured using the biochemical methods. MDA levels significantly increased whereas CAT activities decreased in the irradiated group as compared with the control group (p<0.05). Diameters of collagen fibers were measured by transmission electron microscopy. There was no significant difference (p>0.05) between control and irradiated groups for collagen fiber diameter. Thickness of epidermis was significantly lower than the control group. There were no changes in the epidermis between the irradiated group and the control group ultrastructurally. The results of this study show that the gamma irradiation has a significant effect on normal healthy skin.

Phytoliths analysis for the discrimination of Foxtail millet (Setaria italica) and Common millet (Panicum miliaceum)

Foxtail millet (Setaria italica) and Common millet (Panicum miliaceum) are the oldest domesticated dry farming crops in Eurasia. Identifying these two millets in the archaeobotanical remains are still problematic, especially because the millet grains preserve only when charred. Phytoliths analysis provides a viable method for identifying this important crop. However, to date, the identification of millet phytoliths has been questionable, because very little study has been done on their morphometry and taxonomy. Particularly, no clear diagnostic feature has been used to distinguish between Foxtail millet and Common millet. Here we examined the anatomy and silicon structure patterns in the glumes, lemmas, and paleas from the inflorescence bracts in 27 modern plants of Foxtail millet, Common millet, and closely related grasses, using light microscopy with phase-contrast and microscopic interferometer. Our research shows that five key diagnostic characteristics in phytolith morphology can be used to distinguish Foxtail millet from Common millet based on the presence of cross-shaped type, regularly arranged papillae, Omega-undulated type, endings structures of epidermal long cell, and surface ridgy line sculpture in the former species. We have established identification criteria that, when used together, give the only reliable way of distinguishing between Foxtail millet and Common millet species based on their phytoliths characteristics, thus making a methodological contribution to phytolith research. Our findings also have important implications in the fields of plant taxonomy, agricultural archaeology, and the culture history of ancient civilizations.

Exposure to heptachlor: evaluation of the effects on the larval and adult epidermis of Rana kl. esculenta

Widely used in the past against termites and soil insects, the chlorinated insecticide heptachlor (H) is a toxic contaminant which represents a risk for both terrestrial and aquatic organisms. Like many organochlorine pesticides, heptachlor and heptachlor epoxide (HE), with oxidation products synthesized by many plant and animal species, degrade slowly since many of the derived compounds are persistent. This increases the status of heptachlor as a hazardous pollutant. In the present experimental study we exposed specimens of Rana kl. esculenta, from the tadpole stage through to their complete metamorphosis, to three different concentrations of heptachlor (4, 40 and 400 ppb). Mortality and HE bioaccumulation were evaluated on all the experimental groups. Since amphibian integument directly interacts with the environmental constituents (water, air and soil), we investigated the toxic effects on the ventral epidermis of both tadpole and adult samples by employing such histo-cytopathological biomarkers as ultrastructural morphology, certain enzyme activities (acid and alkaline phosphatases, AcPase, and AlkPase; succinic dehydrogenase, SDH; alpha-naphtyl butyrate esterase, ANBE; nitric oxide synthase/NADPH diaphorase, NOS/NADPHd). Also, the levels of reactive oxygen species (ROS) in the different conditions were evaluated. The results obtained were of ecological relevance, in particular as regards the effects of this environmental toxicant on the samples of tadpole epidermis. Severe morphological alterations were observed in the larval epidermal cells (apical and skein cells), whereas the cell epidermis (keratinocytes and mitochondria-rich cells) of the adult survivors showed changes in enzyme activities, particularly those involved in the protective response to xenobiotic injury. In general, morpho-histochemical studies, analysis of HE bioaccumulation and mortality showed a relation to the H doses employed.

Label-free biomedical imaging with high sensitivity by stimulated Raman scattering microscopy

Label-free chemical contrast is highly desirable in biomedical imaging. Spontaneous Raman microscopy provides specific vibrational signatures of chemical bonds, but is often hindered by low sensitivity. Here we report a three-dimensional multiphoton vibrational imaging technique based on stimulated Raman scattering (SRS). The sensitivity of SRS imaging is significantly greater than that of spontaneous Raman microscopy, which is achieved by implementing high-frequency (megahertz) phase-sensitive detection. SRS microscopy has a major advantage over previous coherent Raman techniques in that it offers background-free and readily interpretable chemical contrast. We show a variety of biomedical applications, such as differentiating distributions of omega-3 fatty acids and saturated lipids in living cells, imaging of brain and skin tissues based on intrinsic lipid contrast, and monitoring drug delivery through the epidermis.

Two-photon laser-scanning fluorescence microscopy applied for studies of human skin

Two-photon laser scanning fluorescence microscopy (TPM) has been shown to be advantageous for imaging optically turbid media such as human skin. The ability of performing three-dimensional imaging without presectioning of the samples makes the technique not only suitable for noninvasive diagnostics but also for studies of topical delivery of xenobiotics. Here, TPM is used as a method to visualize both autofluorescent and exogenous fluorophores in skin. Samples exposed to sulforhodamine B have been scanned from two directions to investigate attenuation effects. It is shown that optical effects play a major role. Thus, TPM is excellent for visualizing the localization and distribution of fluorophores in human skin, although quantification might be difficult. Furthermore, an image-analysis algorithm has been implemented to facilitate interpretation of TPM images of autofluorescent features of nonmelanoma skin cancer obtained ex vivo. The algorithm was designed to detect cell nuclei and currently has a sensitivity and specificity of 82% and 78% to single cell nuclei. However, in order to detect multinucleated cells, the algorithm needs further development.

Plasmin induces degradation and dysfunction of laminin 332 (laminin 5) and impaired assembly of basement membrane at the dermal-epidermal junction

BACKGROUND

The epidermal basement membrane (BM), located at the dermal-epidermal junction (DEJ), plays important roles not only in adhesion between epidermis and dermis, but also in controlling skin functions. In sun-exposed skin, the BM becomes disrupted and multilayered. In order to explore the impairment of BM assembly, we have used a skin-equivalent (SE) as a model of BM damage and previously clarified the involvement of matrix metalloproteinases (MMPs) in impairment of BM assembly.

OBJECTIVES

In this work, we examined the role of urokinase-type plasminogen activator (uPA) and plasmin in impairment of BM assembly at the DEJ by using the SE, as ultraviolet irradiation to the skin increases uPA as well as MMPs.

METHODS

SEs were used as a model of formation and damage of BM. Human uPA was detected by enzyme-linked immunosorbent assay and zymography, and gelatinases such as MMP-2 and MMP-9 were detected by zymography. Human plasminogen was added at 0.06 micromol L(-1) (about 3% of plasma level) to increase plasmin to a pathological level. N-terminal peptide sequence analysis of plasmin-treated laminin 332 was carried out to identify alpha3, beta3 and gamma2 chains of laminin 332 and their cleavage sites of each chain. Plasmin-treated laminin 332 was analysed in keratinocyte adhesion activity and binding to type VII collagen.

RESULTS

Human uPA was detected in addition to MMP-2 and MMP-9, in conditioned medium of SE. Although the BM was well organized in the presence of an MMP inhibitor alone, the activated plasmin disorganized the BM even in the presence of the inhibitor. The impairment of BM assembly made the epidermis thinner as compared with that of a control cultured in the presence of MMP inhibitor, indicating that the BM affects the polarity and differentiation of the epidermis. The addition of aprotinin, a serine proteinase inhibitor, and tranexamic acid, a uPA-plasmin inhibitor, inhibited the plasmin-induced impairment of BM assembly and facilitated BM reorganization, thereby improving the epidermal structure. N-terminal peptide sequence analysis of plasmin-treated laminin 332 revealed the removal of a 5- or 10-kDa fragment, including the cell adhesion region, from the G3 domain of the alpha3 chain, and the LN domain, which binds to the noncollagenous 1 domain in type VII collagen, from the beta3 chain. Plasmin-treated laminin 332 showed lower keratinocyte adhesion activity and reduced binding to type VII collagen.

CONCLUSIONS

These results suggest that uPA and plasmin are involved in the impairment of BM assembly and epidermal differentiation, and that these effects arise at least partly through direct degradation of laminin 332.

Transmission electron microscopy of the preclinical phase of experimental phytophotodermatitis

OBJECTIVE

To examine the epidermis in induced phytophotodermatitis using transmission electron microscopy in order to detect histologic changes even before lesions are visible by light microscopy.

INTRODUCTION

In the first six hours after the experimental induction of phytophotodermatitis, no changes are detectable by light microscopy. Only after 24 hours can keratinocyte necrosis and epidermal vacuolization be detected histologically, and blisters form by 48 hours.

METHODS

The dorsum of four adult rats (Rattus norvegicus) was manually epilated. After painting the right half of the rat with the peel juice of Tahiti lemon, they were exposed to sunlight for eight minutes under general anesthesia. The left side was used as the control and exposed to sunlight only. Biopsies were performed immediately after photoinduction and one and two hours later, and the tissue was analyzed by transmission electron microscopy.

RESULTS

No histological changes were seen on the control side. Immediately after induction, vacuolization in keratinocytes was observed. After one hour, desmosomal changes were also observed in addition to vacuolization. Keratin filaments were not attached to the desmosomal plaque. Free desmosomes and membrane ruptures were also seen. At two hours after induction, similar changes were found, and granular degeneration of keratin was also observed.

DISCUSSION

The interaction of sunlight and psoralens generates a photoproduct that damages keratinocyte proteins, leading to keratinocyte necrosis and blister formation.

CONCLUSIONS

Transmission electron microscopy can detect vacuolization, lesions of the membrane, and desmosomes in the first two hours after experimental induction of phytophotodermatitis.

The epidermal basement membrane: structure, ontogeny and role in disease

Since many dermatological diseases affect the epidermal basement membrane zone (BMZ), there has been intense investigation into the role of epidermal BMZ constituents in various skin diseases, particularly subepidermal skin diseases. The epidermal BMZ consists of four major structural components--the basal cell plasma membrane, the lamina lucida, the lamina densa and the sublamina densa zone, which contains anchoring fibrils. The lamina lucida is composed of laminin, bullous pemphigoid antigen (a disease-specific glycoprotein identified by antibodies circulating in patients' sera), and other as yet poorly defined antigens which are identified by in vivo bound and circulating antibodies in the sera of patients with herpes gestationis, scarring pemphigoid and other conditions. The lamina densa consists of type IV collagen and KF-1 antigen (which is non-collagenous and is identified by a skin-specific monoclonal antibody). Knowledge of the structure and chemical composition of the BMZ is critical to an understanding of some of the genetic and immunologically mediated blistering skin diseases.

Effects of arotinoid ethyl ester on epithelial differentiation and proliferation

In recent years the search for new retinoids, safer and more potent than the available compounds, has led to the development of arotinoids. In preliminary clinical trials, arotinoid ethyl ester [(E)-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1- propenyl]benzoic acid ethyl ester; TTNPB ethyl ester] was found to be highly effective in the treatment of severe and etretinate-resistant dermatoses. Using adult hairless mice, embryonic mouse limb-bud cultures and keratinocyte cultures as experimental models, we have performed morphological, autoradiographic and biochemical studies on the effects of arotinoid ethyl ester on epithelial differentiation in vivo and in vitro. Arotinoid ethyl ester stimulates proliferation of both embryonic and adult mouse epidermis. However, it inhibits the differentiation of embryonic epidermis and enhances that of adult epidermis. Arotinoid ethyl ester induces a decrease in the cyclic AMP content of cholera toxin-stimulated keratinocytes but fails to alter cyclic AMP concentrations in keratinocytes not treated with cholera toxin.

Structure of the sexually dimorphic gland of Cycloramphus fuliginosus (Amphibia, Anura, Cycloramphidae)

Cycloramphus fuliginosus males (Amphibia, Leptodactylidae) have discoid glandular elevations on the abdominal inferior body region which are considered a characteristic of genus. In this work, this sexually dimorphic gland of C. fuliginosus was investigated by low vacuum scanning electron microscopy, light microscopy, and transmission electron microscopy. In this cycloramphid, the covered integument exhibits the basic structure: the epidermis, a keratinized squamous stratified epithelium with flask cells, and the dermis. The dermis is subdivided into spongious and compact dermal layers. In the iliac gland region, an aggregate of small mucous glands and larger syncytial tubuloalveolar glands occur in the spongious dermis, and they do not go beyond the Eberth-Katschenko layer limit. The adenocytes of the mucous gland produce neutral glycoproteins, in contrast to the larger tubuloalveolar glands that elaborate a proteinaceous secretion. Myoepithelial cells surround the alveoli, and play an important role in the secretion extrusion. The final secretion, elaborated by the iliac gland, is a mixture of mucus and protein. Both secretions are important to the cycloramphid biology, and may act as pheromone and/or as chemical parental care.

Effects of fibroblasts and microenvironment on epidermal regeneration and tissue function in long-term skin equivalents

In vitro generated skin models find growing interest as promising tools in basic research and clinical application in regenerative medicine. Here, we present further details of an improved long-term skin equivalent (SE) enabling mechanistic studies on skin reconstruction and epidermal function. Growth conditions of fibroblasts in a 3D scaffold were analysed to optimise the dermal microenvironment by providing an authentic dermal matrix for regular tissue reconstruction and function of cocultured keratinocytes. These SEs demonstrate sustained epidermal viability - over 12 weeks - with regular differentiation as substantiated by in vivo-like patterns of all differentiation products, exemplified here by the cornified envelope components loricrin and repetin. The continuous expression of all major tight junction components in the granular layer, shown here for ZO-1 in coherence with the presence of epidermal barrier lipids, and ultrastructural accumulation of lamellar bodies, collectively indicate proper epidermal barrier structures. Remarkably, cocultured keratinocytes exerted an ongoing proliferation-stimulating effect on fibroblasts colonising the scaffold comparable to a cocktail of fibroblast growth factors. Consequently, precultivation of dermal equivalents (DEs) in basal or growth factor-enriched media had only minor effects on the quality of epidermal regeneration in cocultures. As to the role of fibroblast numbers, complete absence of dermal cells resulted in atrophic epithelia but the effect of cell numbers as low as 5 x 10(4)cells/cm(2) on epidermal tissue quality equalled that of the standard density (2 x 10(5)cells/cm(2)). Surprisingly, precultivation of fibroblasts in the DEs for 7 days (standard) showed no better effect on epidermal tissue reformation as compared to 2 days whereas a precultivation period of 14 days resulted in atrophic epidermal and dermal tissue development. These data demonstrate, (i) the strict dependence of epidermal tissue regeneration on the presence of fibroblasts, (ii) the mutual keratinocyte-fibroblast interactions for cell proliferation and organogenesis, and (iii) the importance of the proper microenvironment for epidermal tissue function and supposedly for establishment of a stem cell niche in vitro.

Specific distribution of barrier-relevant ceramides in the emerging epidermis and the periderm/subperiderm during chicken embryogenesis

During mammalian embryogenesis the emerging epidermis is temporarily covered by an epithelial monolayer, the periderm. In chicken, a second epithelial layer, the subperiderm, located underneath the periderm develops in later embryogenesis. Together the periderm and the subperiderm are referred to as the PSP unit. The cells of the PSP unit are tightly connected by tight junctions (TJ), thereby providing the embryo with an impermeable bilayered diffusion barrier. The emerging epidermis assumes its barrier function by cornification beginning at embryonic day 17 (E17) before at E18 the PSP unit undergoes desquamation. Lipid analysis of both epithelia after their mechanical separation revealed a dramatic increase to about 100-fold values of barrier-relevant ceramides, i.e. those known to essentially contribute to the diffusion barrier of the cornified envelope, in the emerging epidermis between E17 and E19. In contrast, the content of barrier-relevant ceramides in the PSP unit remained at constantly low levels throughout embryogenesis. These data strongly argue in favour of different mechanisms for the barrier function of the two epithelia. TJ in the PSP unit provide the main diffusion barrier protecting the embryo until beginning of desquamation at E18. At this developmental stage the content of cornified envelope-specific ceramides is substantially elevated, thus enabling the epidermis to fulfil its function as the major diffusion barrier after desquamation of the PSP unit. The observation that barrier-relevant ceramides are formed prior to desquamation of the PSP unit points to a precisely regulated sequence in that desquamation does not occur until the lipid-based barrier of the cornified envelope is completed and suggests in addition that these lipids might be essential regulators of the interaction between the PSP unit and the emerging epidermis.

Granular chitin in the epidermis of nudibranch molluscs

Chitin is usually found in stiff extracellular coatings typified by the arthropod exoskeleton, and is not associated with the soft, flexible mollusc skin. Here, we show, however, that chitin in nudibranch gastropods (Opisthobranchia, Mollusca) occurs as intracellular granules that fill the epidermal cells of the skin and the epithelial cells of the stomach. In response to nematocysts fired by tentacles of prey Cnidaria, the epidermal cells of eolid nudibranchs (Aeolidacea) release masses of chitin granules, which then form aggregates with the nematocyst tubules, having the effect of insulating the animal from the deleterious action of the Cnidaria tentacles. Granular chitin, while protecting the animal, does not interfere with the suppleness and flexibility of the skin, in contrast to the stiffness of chitin armor. The specialized epidermis enables nudibranchs to live with and feed on Cnidaria.

Denervation of skin in neuropathies: the sequence of axonal and Schwann cell changes in skin biopsies

We compared the pathological changes in cutaneous axons and Schwann cells of individuals with nerve transection to the changes in patients with chronic neuropathies. Following axotomy there was segmentation of axons in the epidermis and dermis on the first day, and loss of axons from the skin was virtually complete by Day 11. Epidermal and small superficial dermal axons were lost before larger caliber and deeper dermal axons. Within the first 50 days following nerve transection, the denervated Schwann cells in the dermis were easily identified by their markers p75 and S100, but by 8 months they had largely disappeared. The chronic neuropathy patients had distally predominant fibre loss, with greater loss of epidermal and dermal fibres in the distal regions of the leg than proximal regions. Several patients had large axonal swellings, often alternating with axonal attenuation, even in regions with normal or nearly normal fibre densities. By electron microscopy the swellings contained accumulations of mitochondria and other particulate organelles as well as neurofilaments. These swellings are likely to represent predegenerative changes in sites of impaired axonal transport, and previous data indicate that the swellings presage fibre loss in the subsequent months. Some of the severely denervated regions had remaining Schwann cells, as judged by immunocytochemistry and by electron microscopy, but others lacked Schwann cells. By analogy with animal experiments, these regions are likely to have had more prolonged denervation. The distribution of axonal loss, the axonal swellings and the changes in Schwann cells all have implications for the design of clinical trials of agents intended to protect cutaneous innervation and to promote regeneration of cutaneous axons in peripheral neuropathies.

Morphological characterization of the venom secretory epidermal cells in the stinger of marine and freshwater stingrays

Marine and freshwater stingrays are characterized by the presence of one to three mineralized serrated stingers on the tail, which are covered by epidermal cells secreting venom. When these animals are dorsally touched, the stinger can be introduced into the aggressor by a whip reflex mechanism of the tail, causing severe mechanical injuries and inoculating the venom. Accidents in humans are frequent causing intense local pain, oedema and erythema. Bacterial secondary infection is also common. In addition, injuries involving freshwater stingrays frequently cause a persistent cutaneous necrosis. The exact localization of the venom secretory epidermal cells in the stinger is controversial, but it is known that it is preferentially located in the ventrolateral grooves. A comparative morphological analysis of the stinger epidermal tissue of different marine and freshwater Brazilian stingray species was carried out. The results indicate that in freshwater species there is a larger number of protein secretory cells, of two different types, spread over the whole stinger epidermis, while in marine species the protein secretory cells are located only around or inside the stinger ventrolateral grooves. These differences between the stingers of the two groups can justify the more severe envenomation accidents with the freshwater species when compared with the marine species.

Characterization of keratins and associated proteins involved in the corneification of crocodilian epidermis

Crocodilian keratinocytes accumulate keratin and form a corneous cell envelope of which the composition is poorly known. The present immunological study characterizes the molecular weight, isoelectric point (pI) and the protein pattern of alpha- and beta-keratins in the epidermis of crocodilians. Some acidic alpha-keratins of 47-68 kDa are present. Cross-reactive bands for loricrin (70, 66, 55 kDa), sciellin (66, 55-57 kDa), and filaggrin-AE2-positive keratins (67, 55 kDa) are detected while caveolin is absent. These proteins may participate in the formation of the cornified cell membranes, especially in hinge regions among scales. Beta-keratins of 17-20 kDa and of prevalent basic pI (7.0-8.4) are also present. Acidic beta-keratins of 10-16 kDa are scarce and may represent altered forms of the original basic proteins. Crocodilian beta-keratins are not recognized by a lizard beta-keratin antibody (A68B), and by a turtle beta-keratin antibody (A685). This result indicates that these antibodies recognize specific epitopes in different reptiles. Conversely, crocodilian beta-keratins cross-react with the Beta-universal antibody indicating they share a specific 20 amino acid epitope with avian beta-keratins. Although crocodilian beta-keratins are larger proteins than those present in birds our results indicate presence of shared epitopes between avian and crocodilian beta-keratins which give good indication for the future determination of the sequence of these proteins.

Identification of novel ciliogenesis factors using a new in vivo model for mucociliary epithelial development

Mucociliary epithelia are essential for homeostasis of many organs and consist of mucus-secreting goblet cells and ciliated cells. Here, we present the ciliated epidermis of Xenopus embryos as a facile model system for in vivo molecular studies of mucociliary epithelial development. Using an in situ hybridization-based approach, we identified numerous genes expressed differentially in mucus-secreting cells or in ciliated cells. Focusing on genes expressed in ciliated cells, we have identified new candidate ciliogenesis factors, including several not present in the current ciliome. We find that TTC25-GFP is localized to the base of cilia and to ciliary axonemes, and disruption of TTC25 function disrupts ciliogenesis. Mig12-GFP localizes very strongly to the base of cilia and confocal imaging of this construct allows for simple visualization of the planar polarity of basal bodies that underlies polarized ciliary beating. Knockdown of Mig12 disrupts ciliogenesis. Finally, we show that ciliogenesis factors identified in the Xenopus epidermis are required in the midline to facilitate neural tube closure. These results provide further evidence of a requirement for cilia in neural tube morphogenesis and suggest that genes identified in the Xenopus epidermis play broad roles in ciliogenesis. The suites of genes identified here will provide a foundation for future studies, and may also contribute to our understanding of pathological changes in mucociliary epithelia that accompany diseases such as asthma.

Expression of the keratinocyte lipid transporter ABCA12 in developing and reconstituted human epidermis

Serious defects in the epidermal keratinocyte lipid transporter ABCA12 are known to result in a deficient skin lipid barrier, leading to harlequin ichthyosis (HI). HI is the most severe inherited keratinizing disorder and is frequently fatal in the perinatal period. To clarify the role of ABCA12, ABCA12 expression was studied in developing human skin and HI lesions artificially reconstituted in immunodeficient mice. By immunofluorescent study, ABCA12 was expressed in the periderm of the early stage two-layered human fetal epidermis. After formation of a three-layered epidermis, ABCA12 staining was seen throughout the entire epidermis. ABCA12 mRNA expression significantly increased during human skin development and reached 62% of the expression in normal adult skin, whereas the expression rate of transglutaminase 1, loricrin, and kallikrein 7 remained low. We transplanted keratinocytes from patients with HI and succeeded in reconstituting HI skin lesions in immunodeficient mice. The reconstituted lesions showed similar changes to those of patients with HI. Our findings demonstrate that ABCA12 is highly expressed in fetal skin and suggest that ABCA12 may play an essential role under both the wet and dry conditions, including the dramatic turning point from a wet environment of the amniotic fluid to a dry environment after birth.

Poxvirus infection in a great tit (Parus major)

Four great tits (Parus major) with nodular lesions suggestive of poxvirus infections were observed in a garden in Vienna, Austria. One of the birds was submitted for examination. Because of its poor condition, the bird had to be euthanatized and was subsequently necropsied. An avipoxvirus infection was confirmed by histopathology, electron microscopy, and polymerase chain reaction and sequencing. This is the second report of naturally occurring poxvirus infection in great tits and the first of its kind in central Europe.

Hyaluronan in the epidermal and the dermal extracellular matrix: Its role in cutaneous hydric balance and integrity of anuran integument

New researches have revealed that hyaluronan (HA) is not a passive molecule. HA has being pointed out to participate in many processes, such as cell interactions, proliferating and migrating cell events and function as hydrate agent. The present study was undertaken to localize HA in Bufo ictericus integument providing a better understating for the role of cutaneous HA. Paraffinized sections were stained with haematoxylin-eosin and with 1% Alcian blue 8GX at pH 1.0 and 2.5. Alcianophilic reaction was visualized in both spongious dermis and Eberth-Katschenko layer. The mucus cells of mucus glands were also stained with AB methods. Besides these histological techniques, the localization of HA was performed using the FITC-labeled HA probe labeled with fluorescein isothiocyanate. In the extracellular matrix of spongious dermis, the reaction for HA was evident, being less intense in hypodermis and in pericellular keratinocyte matrix of the cornified tubercles regions. Thus, since HA was localized in the pericellular epidermal matrix and in the spongious dermis of anuran integument, it plays an important role in hydric balance, and is essential for integument integrity and functionality.