Epidermal growth factor-like immunoreactivity in the buccopharyngeal mucous glands of Xenopus laevis tadpoles

We report epidermal growth factor (EGF)-like and epidermal growth factor receptor (EGFR)-like immunoreactivity in the buccopharyngeal mucous glands of Xenopus laevis larvae. EGF-like immunostaining was heaviest at the apices of the secretory cells of these glands. Immunostaining for EGFR-like protein was also observed in the mucosal lining of the alimentary tract. This staining was heaviest in cells lining the foregut but was almost absent in cells from the hindgut. A potential role for an orally secreted EGF homologue in anuran amphibians is discussed. Wassersug (1986) hypothesized the existence of a metamorphic inhibitory agent, produced by larval buccopharyngeal mucous glands, which could indirectly link food ingestion to the endocrine control of metamorphosis. The presence of EGF-like immunoreactivity in the oral mucous glands of X. laevis larvae, as well as the presence of EGFR-like immunoreactivity in the gut wall of this tadpole, satisfies many of the criteria for Wassersug's regulatory agent. It remains to be shown that EGF (or an anuran EGF homologue) has a direct inhibitory effect on anuran metamorphosis when administered via an orogastric route.     

Inhibition of return to object-bound location in identification and localization tasks]

The Langerhans cell is one of the antigen-presenting cells in the immune system. To study the presence of cutaneous Langerhans cells in prurigo nodularis, age- and sex-matched prurigo nodularis patients and healthy volunteer skin biopsies were investigated by an HLA-DR and S-100 immunohistochemical double staining method. The results showed that the HLA-DR- and S-100-immunoreactive (IR) Langerhans cells were altered in prurigo nodularis epidermis and dermis. The number of epidermal Langerhans cells in the prurigo nodularis patients was decreased in five and increased in two cases. In the dermis, the HLA-DR- and S-100-IR cells were apparently more numerous than in the controls. In the involved skin there were also more S-100-IR coarse nerve fibres in the dermis as compared to controls. The results indicate that dermal Langerhans cells (HLA-DR and S-100 double-labeled) as well as other dermal HLA-DR- and S-100-IR dendritic cells, but most likely not epidermal Langerhans cells, may be critically involved in the development or persistence of prurigo nodularis.     

Advantage of the presence of living dermal fibroblasts within in vitro reconstructed skin for grafting in humans

Methods for serial cultivation of human keratinocytes can provide large quantities of epidermal cells, which have the potential of restoring the vital barrier function of the epidermis in extensive skin defects such as burns. To investigate the value of combining an epidermis with a dermal component, fibroblasts originated from the superficial dermis were used to seed a collagen lattice as described by E. Bell (dermal equivalent). Beginning in 1981, we grafted 18 patients (burns and giant nevi) using 35 grafts 10 x 10 cm in size. In the course of this work, the original technique was modified and improved as experience was gained. We began by using small skin biopsy samples as a source of keratinocytes cultured on a dermal equivalent before grafting in a one-step procedure, but this gave poor cosmetic results, because of a nonhomogeneous epidermalization. We then chose to cover the graft bed using a two-step procedure. The first step consisted of grafting a dermal equivalent to provide a dermal fibroblast-seeded substrate for subsequent in vivo epidermalization by cultured epidermal sheets. Whatever the epidermalization technique used, a living dermal equivalent applied to the graft bed was found to reduce pain, to provide good hemostasis, and to improve the mechanical and cosmetic properties of the graft. A normal undulating dermal-epidermal junction reappeared by 3 to 4 months after grafting and elastic fibers were detectable 6 to 9 months after grafting. As a result of the biosynthesis of these products, the suppleness (e.g., elasticity) of the grafts was closer to that of normal skin than the cicatricial skin usually obtained with epidermal sheets grafted without the presence of living dermal cells. This rapid improvement of the mechanical properties of the graft could be attributed to the presence of fibroblasts cultured from the dermis and seeded into the collagen matrix.     

Induction of hair growth in ear wounds by cultured dermal papilla cells

In the adult hair follicle the dermal papilla plays a crucial role in the dermal-epidermal interactions that control hair production and events of the growth cycle. It has previously been shown that cultured cells from rat vibrissa follicle dermal papillae can stimulate hair growth when implanted into amputated follicles. This study investigated the effects of implanting low-passage cultured papilla cells into small incisional wounds in the rat ear pinna. The groups of fibers that emerged from wound sites were much larger than local hairs, and often had vibrissa-type characteristics. Later-passage papilla cells or cultured skin fibroblasts failed to elicit the same response. Histology revealed that big follicles were formed when papilla cells were trapped between the cut edges of the epidermis. Abnormally large follicles were seen at wound sites many months post-operatively. Independent of epidermal influence, cultured papilla cells in the wound dermis formed rounded papilla-like aggregates that also persisted until biopsy. A previously described method of wrapping papilla cells in glabrous epidermis was less successful in percentage terms but resulted in the production of one very large vibrissa-type follicle and fiber. These results further illustrate that the inductive powers and developmental information retained by cultured dermal papilla cells parallel the properties of their embryonic precursors; the findings may have implications for human hair growth.     

Formation of the dermal chromatophore unit (DCU) in the tree frog Hyla arborea

In the tadpole of the tree frog Hyla arborea, the color of the dorsal skin was dark brown. Dermal melanophores, xanthophores, and iridophores were scattered randomly under the subepidermal collagen layer (SCL). After metamorphosis, the dorsal color of the animal changed to green and the animal acquired the ability of dramatic color change, demonstrating that the dermal chromatophore unit (DCU) was formed at metamorphosis. Fibroblasts invaded the SCL and divided it into two parts: the stratum spongiosum (SS) and the stratum compactum (SC). The activity of collagenase increased at metamorphosis. The fibroblasts appeared to dissolve the collagen matrix as they invaded the SCL. Then, three types of chromatophores migrated through the SCL and the DCU was formed in the SS. The mechanism how the three types of chromatophores were organized into a DCU is uncertain, but different migration rates of the three chromatophore types may be a factor that determines the position of the chromatophores in the DCU. Almost an equal number of each chromatophore type is necessary to form the DCUs. However, the number of dermal melanophores in the tadpoles was less than the number of xanthophores and iridophores. It was suggested that epidermal melanophores migrated to the dermis at metamorphosis and developed into dermal melanophores. This change may account for smaller number of dermal melanophores available to form the DCUs.     

Sendai virus fusion activity as modulated by target membrane components

It is generally known that the anuran stomach begins to express pepsinogens (Pg) during metamorphosis. To clarify the mechanisms of differentiation of Pg-producing cells, we examined immunohistochemically the epithelial transformation from larval to adult form in Xenopus laevis stomach at the cellular level. At the beginning of metamorphic climax, concomitantly with the modification of the basement membrane, apoptotic cells labelled by TUNEL suddenly increased in number in the entire epithelium except for the primordia of adult epithelial cells in the basal region of larval glands. Subsequently, with the development of connective tissue, the adult epithelial cells actively proliferated and replaced the larval cells from the basal to the luminal region. Following the start of morphogenesis of adult glands, Pg-producing cells became differentiated in newly formed adult glands, but not in the adult surface epithelium. We then developed an organ culture system and examined effects of thyroid hormone (TH) on the differentiation of Pg-producing cells in X. laevis stomach in vitro. In the presence of TH, just as in spontaneous metamorphosis, Pg-producing cells differentiated from the adult epithelial primordia after the apoptosis of larval epithelial cells. In contrast, in the absence of TH, neither apoptotic larval cells no Pg-producing cells were detected. Therefore, we conclude that TH triggers organ-autonomously the entire process leading to the differentiation of Pg-producing cells in X. laevis stomach. In addition, the strict localization of Pg-producing cells in the adult glands both in vivo and in vitro suggests the correlation between the differentiation of Pg-producing cells and morphogenesis of the glands surrounded by the developed connective tissue.     

Antioxidant defense mechanisms in murine epidermis and dermis and their responses to ultraviolet light

A comprehensive comparison of antioxidant defenses in the dermis and epidermis and their response to exposure to ultraviolet (UV) irradiation has not previously been attempted. In this study, enzymic and non-enzymic antioxidants in epidermis and dermis of hairless mice were compared. Enzyme activities are presented both as units/gram of skin and units/milligram of protein; arguments are presented for the superiority of skin wet weight as a reference base. Catalase, glutathione peroxidase, and glutathione reductase (units/gram of skin) were higher in epidermis than dermis by 49%, 86%, and 74%, respectively. Superoxide dismutase did not follow this pattern. Lipophilic antioxidants (alpha-tocopherol, ubiquinol 9, and ubiquinone 9) and hydrophilic antioxidants (ascorbic acid, dehydroascorbic acid, and glutathione) were 24-95% higher in epidermis than in dermis. In contrast, oxidized glutathione was 60% lower in epidermis than in dermis. Mice were irradiated with solar light to examine the response of these cutaneous layers to UV irradiation. After irradiation with 25 J/cm2 (UVA + UVB, from a solar simulator), 10 times the minimum erythemal dose, epidermal and dermal catalase and superoxide dismutase activities were greatly decreased. alpha-Tocopherol, ubiquinol 9, ubiquinone 9, ascorbic acid, dehydroascorbic acid, and reduced glutathione decreased in both epidermis and dermis by 26-93%. Oxidized glutathione showed a slight, non-significant increase. Because the reduction in total ascorbate and catalase was much more severe in epidermis than dermis, it can be concluded that UV light is more damaging to the antioxidant defenses in the epidermis than in the dermis.     

Origin of the epidermis in parasitic platyhelminths

The epidermis of members of the major parasitic taxon Neodermata is distinctive among flatworms, being a syncytial, insunk, non-ciliated epidermis that develops through a wholesale replacement of larval epidermis at metamorphosis when the larva attacks a host. How it arose in evolution from what must have been a turbellarian-like ancestor is not immediately evident. While many turbellarian flatworms have also adopted a symbiotic way of life, the literature on ultrastructure of epidermis in these symbionts shows quite a variety of morphologies, many not so different from that of their free-living relatives. Various turbellarians do have syncytial or insunk epidermises or reduction of epidermal ciliation as is characteristic of the Neodermata, but co-occurrence in a single turbellarian of all features common to neodermatans has not been reported. Urastoma cyprinae, for example, which is ectosymbiotic on bivalves, has a ciliated cellular epidermis that is little different from what is known of epidermises of its free-living relatives. The endoparasitic Anoplodium hymanae, from the coelom of sea cucumbers, also bears a ciliated cellular epidermis, as is typical of many other rhabdocoels, but it shows marked phagocytic activity as well as incorporation of endosymbiotic bacteria. The closest similarity to neodermatan epidermis is that of the turbellarian Genostoma kozloffi, an ectosymbiont of the crustacean Nebalia: covering the bulk of the body is a non-ciliated syncytium with multiple branching connections to insunk nucleated portions, much as in epidermis of adult neodermatans and, on its ventral surface, is a field of ciliated cellular insunk epidermis resembling the epidermis of some larval neodermatans. Developmental clues to the origin of the neodermatan epidermis can be seen in turbellarian embryos. Before hatching, embryos of proseriate and triclad embryos go through 3 generations of epidermis, each replacing the next; 2 generations of epidermis are reported in the literature on rhabdocoel embryos. This process of replacement parallels the epidermal replacement that larval neodermatans undergo at metamorphosis. Ultrastructural study of developing acoel, polyclad and macrostomid embryos shows that they, too, have epidermal replacement and growth through immigration of deeper-lying cells, comparable to the processes seen in higher flatworms. Succession of distinct generations of epidermis in such animals as the proseriates, triclads and rhabdocoels is probably an adaptation to development of ectolecithal eggs, providing the means for the embryo to use yolk that resides in vitellocytes, outside its blastomeres. We propose that the Neodermata has taken advantage of this developmental mechanism, producing successive generations of epidermal cells even in its larval stages, to counter the defenses of hosts.     

Ultrastructure of the secretory cells of the submucosal glands in the human maxillary sinus

Tissue samples obtained from the lateral wall of the maxillary sinuses of five patients were examined by light microscopical, histochemical, and ultrastructural techniques. Submucosal glands were tubulo-alveolar mixed glands. The acini consisted of either all serous or all mucous cells, or a mixture of both. Serous granules were stained by toluidine blue, or by hematoxylin and eosin (H and E), but showed little or no reaction with periodic acid-Schiff (PAS) or Alcian blue. Mucous granules were pale in toluidine blue or H and E preparations, and consisted primarly of acid mucosubstances, as demonstrated by their staining reaction with PAS and Alcian blue. At the electron microscope level, the serous granules were either homogeneously dense, or showed a substructure consisting of at least two layers of distincly different electron-opacity. Typical mucous droplets consisted of a fibrillar network dispersed in a translucent matrix. A second secretory product was present in the mucous cells in the form of elongated, membrane-bounded structures containing numerous parallel filaments, which measured about 55 A in diameter. The mucous droplets and the filamentous bodies appear to arise from the opposite faces of the Golgi complex in the mucous cells. The filamentous bodies showed a pronounced tendency to fuse with the mucous droplets. All acini were surrounded by a well-defined myoepithelial layer and contained intercellular nerve terminals.     

The major excretory/secretory protease from Lucilia cuprina larvae is also a gut digestive protease

The larvae of the fly Lucilia cuprina excrete or secrete a chymotrypsia (LCTb) onto the skin of sheep to facilitate the establishment of the larval infestation. A combination of immunoblotting and RT-PCR approaches has established that this protease is also a gut digestive protease. LCTb is synthesized primarily in the cardia, a small highly specialized organ located at the anterior end of the midgut and by midgut cells. There is also some expression by the hindgut but no expression by salivary glands. Excretion of LCTb with waste products or regurgitation of the gut contents of the larvae may explain how this protease is transferred from the larval gut onto ovine skin. LCTb is first expressed in eggs and constitutively expressed throughout each larval instar, but is not expressed in pupae or adult flies. It is concluded that LCTb could be involved in the establishment of larvae on sheep skin as well as acting as a general gut digestive enzyme.     

A composite CMV-IE enhancer/beta-actin promoter is ubiquitously expressed in mouse cutaneous epithelium

In most existing transgenic mouse models developed for the study of specific genes in the skin, the goal has been to target transgene expression to defined populations of cells in the cutaneous epithelium. Keratin promoters have been especially useful for this purpose. In some instances, however, it may be desirable to express a transgene in all the cells of the cutaneous epithelium. Since no ubiquitously expressed promoter sequences had previously been identified, we used lacZ reporter transgenes to test two enhancer/promoter sequences for ubiquitous expression in the skin of adult transgenic mice. We find that a CMV enhancer/CMV promoter is not active in most cell types in the skin, whereas a CMV enhancer/modified beta-actin promoter sequence is active in the suprabasal and basal cells of the epidermis as well as in the epithelial cells of the hair follicles, sebaceous glands, and the dermal papillae.     

Apoptosis, necrosis, and proliferation: possible implications in the etiology of keloids

Keloids are collagenous lesions acquired as a result of abnormal wound heating. In this study we have assessed the potential role of proliferation, apoptosis, and necrosis in keloids. Samples were immunolabeled for proliferating cell nuclear antigen or DNA strand breaks or stained with acridine orange. Proliferating cells were observed in the basal layer of the epidermis and fibroblasts in the dermis, the numbers of the latter being increased in comparison with normal skin. No proliferating cells were observed in the central region of the keloid. In normal skin, apoptotic cells were restricted to the basal layer of the epidermis. In keloid samples, numerous apoptotic cells were observed in the epidermis and dermis; the number and distribution of positive cells decreased more distal to the keloid lesion. Apoptotic endothelial cells of a small proportion of blood vessels in the dermis were also observed. Evidence of necrosis was also seen in the dermis. These results suggest that, with maturity, progressive cell degeneration primarily by apoptosis results in clearance of certain cellular populations resulting in the typical keloid lesion. However, the persistence of fibroblast proliferation at the dermal/keloid interface propagates the fibrosis.     

Isolation of unstable myosins and the analysis of light chains by capillary electrophoresis

Dendritic cells marked by protein S-100 (S-100) antiserum in the suprabasal layers of the epidermis have previously been identified to be Langerhans' cells. In this study, S-100 immunoreactive cells have been investigated in psoriatic lesioned skin during and after peptide T treatment. Peptide T is an octapeptide with affinity for the CD4 receptor. Nine patients were intravenously infused with peptide T, 2 mg in 500 ml saline per day for 28 days. Sections from involved skin before, every week during, and after the treatment were processed by indirect immunofluorescence using S-100 antiserum. Before the treatment the epidermal Langerhans' cells were numerically decreased or even completely gone in the involved skin of psoriasis as compared to skin from normal healthy controls, while the dermal dendritic cells instead were increased and gathered in cell clusters around vascular structures. Four of the nine patients had histopathological improvements after the peptide T treatment, and, in those cases, the dendritic cells in the dermis were reduced in number, and the Langerhans' cells in the epidermis were numerically increased as well as even reversed to normal position and morphology. These changes in the distribution and density of Langerhans' cells represent their rearrangement during the course of psoriasis and/or the remission after peptide T treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epidermal and dermal phospholipids of the human eyelid: a 31P nuclear magnetic resonance spectroscopy study

The phospholipids of the skin are difficult to quantify because they represent only a small fraction of the skin tissue. In this study, 31P nuclear magnetic resonance, which permits precise profiling of these phospholipids, was used to compare the phospholipids of upper eyelid epidermal and dermal lipid extracts (n = 13 profiles). Phospholipid profiles included alkylacylphosphatidylcholine (AAPC), dihydrosphingomyelin (DHSM), diphosphatidylglycerol (cardiolipin), ethanolamine plasmalogen (EPLAS), lysophosphatidylcholine, phosphatidic acid, phosphatidylcholine (PC), phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, sphingomyelin, and uncharacterized phospholipids (U1 and U2, particularly enriched in the epidermis). The computed phospholipid metabolic index (n = 86 indexes) findings can be summarized as follows: a lower content of the en-ol and ether phospholipids in the epidermis relative to the dermis, internal compensation among the component phospholipids so as to maintain the choline functional group ratio, and a greater concentration of hydroxyl-containing functional groups in the epidermis. A membrane index (fmem) value of -0.37 for the epidermis deviated considerably from the value of -0.06 characteristic of living membranes and the dermis. The production of the reduced phosphatides, EPLAS and AAPC, indicates the use of alternative pathways between the two tissues. Relative to the dermis, increased PC in the epidermis coupled with decreased DHSM, EPLAS, and AAPC are factors enabling the epidermis of eyelid tissue to be an effective water barrier.     

Diagnosis of deep vein thrombosis, an overview

This article reviews the role of dendritic cells in cutaneous immunity. Langerhans cells (LC) found in the epidermis are the best-characterized dendritic cell population. They have the ability to process antigen in the periphery, transport it to the draining lymph nodes (DLN) where they are able to cluster with, and activate, antigen-specific naive T cells. During migration LC undergo phenotypic and functional changes which enable them to perform this function. There are other less well-characterized dendritic cells including dendritic epidermal T cells, dermal dendrocytes and dermal "LC-like' cells. Although there is no evidence that dendritic epidermal T cells (DETC) can present antigen or migrate to lymph nodes, they do influence the intensity of cutaneous immune responses to chemical haptens. Antigen-presenting cells (APC) in the dermis may provide alternative routes of antigen presentation which could be important in the regulation of skin immune responses. Therefore, dendritic cells are vital for the induction of immune responses to antigens encountered via the skin. LC are particularly important in primary immune responses due to their ability to activate naive T cells. The faster kinetics of secondary responses, and the ability of nonprofessional APC to induce effector function in previously activated cells, suggest that antigen presentation in the DLN may be less important in responses to previously encountered antigens. In these secondary responses, dendritic and nondendritic APC in the skin may directly induce effector functions from antigen-specific recirculating cells.     

Prolactin alters the expression of integumental glycoconjugates in the red-spotted newt, Notophthalmus viridescens

Prolactin (PRL)-mediated changes in the texture and secretory activity of the skin in adult red-spotted newts may involve alterations in the distribution and/or expression of structural and secretory epidermal glycoconjugates. To explore this possibility, skin samples were obtained from groups of conditioned animals that had received injections of either ovine prolactin or amphibian saline over a 14-day period. Glycoconjugates within the epidermis and cutaneous glands were examined by means of lectin histochemistry using a panel of eight HRP-labelled lectins. PRL increased levels of sialic acid and n-acetylglucosamine in the stratum corneum. In contrast, glycoconjugates containing fucose, galactose, n-acetylgalactosamine, and galactose-(1,3)-n-acetylgalactosamine were decreased by PRL within both glands and epidermis. These results suggest that the integumental effects associated with prolactin in the red-spotted newt are mediated, at least in part, through the alteration of epidermal and glandular glycoconjugates.     

Age-related changes in morphology and secretory responses of male rat lacrimal gland

This study investigates the differences in the outward appearance and morphology of lacrimal glands, the morphology within the lacrimal acinar cells and the secretion of protein from acinar cells of young (3-5 months) and aged (20 and 24 months) male rats. The appearance of the glands, as seen by the naked eye, differed between the three age-groups. The lacrimal gland of young animals was a smooth pink tissue, while the tissue from aged animals appeared lobular and white in colour, thought to result from infiltration of fatty/connective tissue. Glands from 24 month old animals had a more pronounced lobular appearance than the glands from 20 month old animals. Light microscopy studies revealed that as the animals aged there was evidence of progressive morphological changes. These changes included thickening of the connective tissue sheath, chronic inflammation with increased infiltration by mast cells, patchy destruction of ductal and vascular tissues, enlargement of lacrimal ducts, luminal swelling of the acini, and changes in acinar type. Electron microscopy (EM) studies revealed the presence of 3 types of acini in the rat lacrimal gland: acini which contained only protein secretory granules (serous acini), acini which contained protein and mucous secretory granules (seromucous acini), and acini which contained only mucous secretory granules (mucous acini). In young glands the majority of acini were serous with a few seromucous acini and even fewer mucous acini. In aged glands there were significant reductions in serous acini (ANOVA; P < 0.01) when compared to the young glands. In 20-month-old glands, there were marked increases in the percentage occurrence of seromucous acini, while in 24 month old glands, there were large increases in the relative number of mucous acini. Qualitative EM studies demonstrated that the typical acini from young glands contained numerous protein secretory granules. Ageing was associated with a progressive loss of protein (serous) secretory granules. Furthermore, marked changes and patchy destruction of the endoplasmic reticulum and Golgi apparatus were observed in acini of glands from aged rats when compared to acini of glands from young rats. Measurement of total protein output from acini revealed a significant (Student's t-test, P < 0.05) decrease in protein secretion from aged glands compared to glands from young animals. These results suggest that not only is there considerable structural damage, chronic inflammation and mast cell infiltration to the lacrimal gland with ageing, but also possible redifferentiation of acini from serous to seromucous and then to mucous acini. Furthermore, the results also suggest a reduction or an inability of the acini to synthesise and to secrete protein from glands of aged animals compared to glands of young rats. All of these changes appear to occur more rapidly as the rats mature between 20 and 24 months. These findings provide a morphological basis to explain the phenomenon of reduced tear/protein secretion with ageing.     

Endogenous skin fluorescence includes bands that may serve as quantitative markers of aging and photoaging

Aging and photoaging cause distinct changes in skin cells and extracellular matrix. Changes in hairless mouse skin as a function of age and chronic UVB exposure were investigated by fluorescence excitation spectroscopy. Fluorescence excitation spectra were measured in vivo, on heat-separated epidermis and dermis, and on extracts of mouse skin to characterize the absorption spectra of the emitting chromophores. Fluorescence excitation spectra obtained in vivo on 6 wk old mouse skin had maxima at 295, 340, and 360 nm; the 295 nm band was the dominant band. Using heat separated tissue, the 295 nm band predominantly originated in the epidermis and the bands at 340 and 360 nm originated in the dermis. The 295 nm band was assigned to tryptophan fluorescence, the 340 nm band to pepsin digestable collagen cross-links fluorescence and the 360 nm band to collagenase digestable collagen cross-links fluorescence. Fluorescence excitation maxima remained unchanged in chronologically aged mice (34-38 wk old), whereas the 295 nm band decreased in intensity with age and the 340 nm band increased in intensity with age. In contrast, fluorescence excitation spectra of chronically UVB exposed mice showed a large increase in the 295 nm band compared with age-matched controls and the bands at 340 and 350 nm were no longer distinct. Two new bands appeared in the chronically exposed mice at 270 nm and at 305 nm. These reproducible changes in skin autofluorescence suggest that aging causes predictable alterations in both epidermal and dermal fluorescence, whereas chronic UV exposure induces the appearance of new fluorphores.