版纳鱼螈幼体和成体皮肤的结构

采用光镜和扫描电镜,对我国特有的珍稀濒危两栖动物版纳鱼螈Ichthyophis bannanicus幼体和成体的皮肤进行形态学和组织学观察.版纳鱼螈幼体和成体的皮肤均可分为表皮、真皮疏松层和真皮致密层;皮肤中含有粘液腺和颗粒腺;在不同发育阶段或同一个体的不同部位,其皮肤的各种组成成分在结构和厚度上存在着差异:成体和幼体都是头部的表皮最厚,尾部的最薄;幼体表皮各层细胞分化不明显,几无角化现象,成体表皮的各层细胞分化明显,表层细胞明显角化;成体躯干部皮肤最厚,头部最薄,幼体则是头部皮肤最厚,尾部最薄;幼体和成体的头部皮肤都分布有大量的粘液腺,颗粒腺分布较少;幼体的躯干部皮肤则主要分布着大量颗粒腺,尾部只有颗粒腺,未见粘液腺;成体躯干部和尾部皮肤均分布有大量的颗粒腺和粘液腺.     

Balancer Fine Structure of the Pleurodeles Larva

The paired balancers of larval Pleurodeles waltl, a urodelan species of the Amphibia, were investigated throughout their life span until final degeneration, using electron microscopy. The evidence from cellular ultrastructure illustrates the mucus-secreting function of these organs, and the outer epithelial cells actively synthesize muco-proteinaceous substance. An extensive granular endoplasmic reticulum and well developed Golgi complexes participate in the mucus manufacture. The balancer epidermis is also extensively innervated throughout by non-myelinated neurites, most of them without Schwann cells, a feature which argues strongly in favour of the organ also having a sensory function, whose nature has yet to be determined.     

Evaluation of Dermal Substitute in a Novel Co-Transplantation Model with Autologous Epidermal Sheet

The development of more and more new dermal substitutes requires a reliable and effective animal model to evaluate their safety and efficacy. In this study we constructed a novel animal model using co-transplantation of autologous epidermal sheets with dermal substitutes to repair full-thickness skin defects. Autologous epidermal sheets were obtained by digesting the basement membrane (BM) and dermal components from rat split-thickness skins in Dispase II solution (1.2 u/ml) at 4°C for 8, 10 and 12 h. H&E, immunohistochemical and live/dead staining showed that the epidermal sheet preserved an intact epidermis without any BM or dermal components, and a high percentage of viable cells (92.10±4.19%) and P63 positive cells (67.43±4.21%) under an optimized condition. Porcine acellular dermal matrixes were co-transplanted with the autologous epidermal sheets to repair full-thickness skin defects in Sprague-Dawley rats. The epidermal sheets survived and completely re-covered the wounds within 3 weeks. Histological staining showed that the newly formed stratified epidermis attached directly onto the dermal matrix. Inflammatory cell infiltration and vascularization of the dermal matrix were not significantly different from those in the subcutaneous implantation model. Collagen IV and laminin distributed continuously at the epidermis and dermal matrix junction 4 weeks after transplantation. Transmission electron microscopy further confirmed the presence of continuous lamina densa and hemidesmosome structures. This novel animal model can be used not only to observe the biocompatibility of dermal substitutes, but also to evaluate their effects on new epidermis and BM formation. Therefore, it is a simple and reliable model for evaluating the safety and efficacy of dermal substitutes.     

Figures of Eberth in the amphibian larval epidermis.

Figures of Eberth are prominent extensive filamentous structures in the basal epidermal cells of larval amphibians. They are compared and contrasted qualitatively and quantitatively in a number of species of the three groups of living amphibians. Fully developed Figures consist of massive skeins of tonofilaments oriented in three dimensions and hinged on hemidesmosomes within the cell. The overall appearance of the Figures is similar in anurans, urodeles and Ichthyophis among the apodans. However, in terms of size and number per unit length of the proximal cell margin, the hemidesmosomes and the thickness or their emergent skeins in anurans and Ichthyophis differ significantly from those parameters in urodeles, a feature that is presumably independent of cell size. Figures are poorly developed or missing in embryos of Typhlonectes, which has no larval stage in its life history. These ubiquitous skeletogenous structures in the aquatic larval amphibians, among other things, could be protective of underlying delicate tissues and act as a stabilizer in bodily movement during swimming. They could also serve as a reserve of cytokeratin for use during later cellular division and sloughing.     

Comparative structure of the epidermis in polychaetes (Annelida)

The polychaete epidermis generally consists of a single layer of supportive cells, gland cells and sensory cells. Except for the latter, this paper reviews the recent literature on the annelid epidermis, focussing on the mentioned cell types and the cuticle. The annelid epidermis is compared to that of Sipuncula, Echiura and Myzostomida. Supportive cells predominate in the polychaete epidermis. They show a high structural diversity even within single specimens. Ciliated cells are usually multiciliary and only two cases of monociliary epidermis cells are known. Unambigous epithilio-muscle cells are only described in feeding palps of a Magelona species. Secretory cells release a large number of gland products and some of them are essential for tube secretion. Rather pecularities of the cells and its arrangement within glands than the ultrastructure of the secretions is useful for phylogenetic considerations. One of the main components of the cuticle is collagen. Recent studies indicate that annelid cuticular collagen differs in several aspects from collagen of the connective tissue and might be of interest for systematics.     

Remarkable genetic homogeneity in unstriped, long-tailed Ichthyophis along 1500 km of the Western Ghats, India

The mountainous Western Ghats are part of a biodiversity hotspot and extend for about 1600 km, lying close and subparallel to the west coast of peninsular India. The region is a centre of diversity for amphibians, and recent preliminary work on some components of both caecilian (Gymnophiona) and frog (Anura) fauna is indicative of a high degree of local endemism. We investigated diversity in mitochondrial rRNA 12S and 16S sequences for long-tailed, unstriped Ichthyophis (Amphibia: Gymnophiona: Ichthyophiidae) that potentially represent four taxonomically confused and poorly known endemic caecilian species. Data were analysed for18 individuals from along c . 1500 km of the Western Ghats region. Genetic diversity is remarkably low, with a maximum uncorrected p -distance of 0.5%. These DNA sequences and new morphological data do not allow us to reject the null hypothesis that the sample comprises only a single, widely distributed, highly interconnected species. The phylogenetic signal among the data is extremely low. However, population genetic analyses reveal that the Palghat Gap, a c . 30 km discontinuity in the Western Ghats considered to be significant in the biogeography of other organisms occurring in this region, corresponds to a significant subdivision of long-tailed, unstriped Ichthyophis into two groups.     

The Study of Cutaneous Melanomas in Camargue‐Type Gray‐Skinned Horses (1): Clinical–Pathological Characterization

The clinical and pathological characteristics of cutaneous melanomas occurring in Camargue‐type gray‐skinned horses are reported. Examination of 83 tumor‐bearing horses revealed that the tumors occurred most frequently underneath the tail (93.9%) and at high rates in the peri‐anal region (43.0%), the lips (33.0%), and the eyelids (24.0%), but rarely in the vulva (3.8%). Tumorous lesions were characterized by the presence of either hemispheric nodules or large infiltrated plaques, or their combinations. Microscopic examination indicated that tumorous lesions were composed mostly of melanocytes and numerous melanophages and that component cells manifested a remarkable cellular atypia with anisocytosis and anisokarinosis. Pathological examination of lesions corresponding to earlier stages of the tumors disclosed that tumor formation and its related melanogenesis occurred in close topographical association with apocrine sweat glands, but not at the dermal–epidermal junction. Larger nodules of the tumors were often composed of a concentric deposition of cell layers, each being separated by dermal components from the epidermis. Because of the absence of their tropism toward the epidermis and their multiloculation, horse melanomas are considered to be different in their pathological characteristics from human melanomas.     

Ultrastructural observations on the embryonic development of the integument of Lacerta muralis (Lacertilia,Reptilia)

Integumentary development on the dorsal and ventral aspects of the body of 14, 21, 26, 33, and 40-day incubated embryos of the European Wall Lizard (Lacerta muralis) is described. While the earliest stages of epidermal differentiation resemble those reported for other tetrapods, precocious differentiation of dermal collagen more resembles that of anamniotes than that of birds and mammals. Anchoring complexes comprising cellular components, anchor filaments, and collagen are described, and their possible relationship to the formation of scale anlagen is discussed. The first embryonic epidermal generation differentiates beneath the periderm; most features of its histogenesis resemble those that have been described for the epidermis of adult squamates, but certain previously ignored organelles, including possible earlier β-keratin precursors, are reported. Different strategies regarding in ovo peridermal loss and posthatching shedding behavior are described and discussed in light of presently available data concerning control of cell differentiation in the squamate epidermis.     

Tail skin of the dipnoan Neoceratodus larva: fine structure and differentiation

The fine structure of the tail skin oflarval Neoceratodusforsteri , between stages 40 and 50 (Kemp, 1982), is described and where applicable specific cellular components are compared and contrasted with comparable ones in the skin of adult dipnoans, teleosts and larval and adult amphibians.
The epidermis of the early developing tail, within the range studied, differentiates a variety of different cell types. Surface epithelial lucent and vacuolated lucent cells and basal cells are distinguished, and goblet (mucous) cells, Merkel cells and macrophages appear in the epidermis towards the end of the series.
Below a poorly developed collagenous basement lamella, immature melanophores with premelanosomes are present, and likewise there are non–myelinated nerves, some striated muscle fibres, capillaries and mesenchymal fibroblasts.
The tail epidermis is innervated by naked neurites from the beginning of the series, and the earliest recognizable Merkel cell is in synaptic association with neurites.     

Scale Arrangement Pattern in a Lepidopteran Wing. 1. Periodic Cellular Pattern in the Pupal Wing of Pieris rapae

In most species of lepidopteran insects, anteroposterior rows formed by scales are arranged at regular intervals in the adult wing; within each row two kinds of scales are alternately arranged. To investigate the cellular basis for the scale arrangement pattern, we examined cell arrangement in the epidermal monolayer of the pupal wing of a small white cabbage butterfly, Pieris rapae , by scanning electron microscopy and light microscopy.
The arrangement of scale precursor cells, closely resembling that of scales in the adult wing, was observed in the wing epidermis of the early pupa. Scale precursor cells are proximodistally elongated and form anteroposterior rows. Within a row two kinds of scale precursor cells are nearly alternately arranged, which is not so precise as the alternation of scales in the adult wing. Individual rows of scale precursor cells are separated by rows of single or double undifferentiated general epidermal cells. Occasionally, arrangement abnormalities occur both in the adult and the pupal wing. The cellular basis for the regular spacing of scale rows is discussed.     

Expression and role of E- and P-cadherin adhesion molecules in embryonic histogenesis. II. Skin morphogenesis

Expression and the role of E- and P-cadherin in the histogenesis of the surface epidermis and hair follicles were examined using the upper lip skin of the mouse. P-cadherin is expressed exclusively in the proliferating region of these tissues, that is in the germinative layer of the surface epidermis, the outer root sheath and the hair matrix. E-cadherin is coexpressed in these layers but this molecule was also detected in non-proliferating regions such as the intermediate layer of the surface epidermis and the immature regions of the inner root sheath. Neither P- nor E-cadherin was detected in fully keratinized layers such as the horny layer of the surface epidermis, the outermost layer of the outer root sheath and the mature hair fibres. These two cadherins were not detected in dermal cells. We cultured pieces of the upper lip skin in vitro in the absence or presence of a monoclonal antibody to E-cadherin (ECCD-1) or to P-cadherin (PCD-1). In control cultures, skin morphogenesis normally occurred in a pattern whereby the hair follicles grew and dermal cells were condensed to form the dermal sheath. A mixture of ECCD-1 and PCD-1, however, induced abnormal morphogenesis in the skin in several respects. (1) The cuboidal or columnar arrangement of basal epithelial cells was distorted. (2) Hair follicles were deformed. (3) Condensation of dermal cells was suppressed, causing a homogeneous distribution of these cells. These results suggest that cadherins present in epidermal cells are involved not only in maintaining the arrangement of these cells but also in inducing dermal condensation.     

Electron microscopy of wound healing in the skin of Gasterosteus aculeatus

The process of healing of a small surgical incision in the skin of Gasterosteus aculeatus has been studied by electron microscopy. The wounds were made in the mid-ventral line where no muscle intervenes between the skin and the peritoneum. The epidermis moved in through the incision and spread outwards beneath the dermis; the migrating epithelial cells were shown to be phagocytic. The wound was closed when cells at the surface of the epidermis met across the gap, forming a plug of epidermal tissue which was then invaded by dermal tissue from either side. Formation of new basement membrane apparently depended on the interaction of epidermal and dermal components. Leucocyte types were identified by electron microscopy; acid phosphatase tests were positive in macrophages and in neutrophil granulocytes, negative in lymphocytes and in eosinophil granulocytes. These four types of leucocyte are present in normal skin; after wounding, more migrated into the epidermis from the blood. The number of neutrophils in the epidermis reached a peak 24 h after wounding and declined during the second day. The number of macrophages rose to a peak by the third day and returned to normal by day 8. The numbers of eosinophil granulocytes and of lymphocytes showed little change. Neutrophil granulocytes were shown to be phagocytic, although not to the same extent as the macrophages.     

The tentacles of Ichthyophis (Amphibia: Caecilia) with special reference to the skin

The skin of the paired tentacles of Ichthyophis consists of a cornified epidermis of 5–7 layers of epidermal cells, and a glandular dermis of ducted mucous glands, in association with collagen, blood vessels, fibroblasts, granulocytes, sparse melanophores and characteristic laminophores of unknown function. The epidermis is highly innervated at all levels below the stratum corneum by naked neurites, which originate as branches from large unmyelinated nerve bundles (and associated Schwann cells), located sub-epidermally, and which are part of the trigeminal cranial nerve. Myelinated nerves are also present below the epidermis, spatially associated with capillaries and glands. The study of the ultrastructure of the tentacle supports a concept of a sensory function, possibly tactile, though until further information from experimentation is available, any ideas on the specific nature of these sensory activities must remain speculative.     

The study of cutaneous melanomas in Camargue-type gray-skinned horses (1): clinical-pathological characterization

The clinical and pathological characteristics of cutaneous melanomas occurring in Camargue-type gray-skinned horses are reported. Examination of 83 tumor-bearing horses revealed that the tumors occurred most frequently underneath the tail (93.9%) and at high rates in the peri-anal region (43.0%), the lips (33.0%), and the eyelids (24.0%), but rarely in the vulva (3.8%). Tumorous lesions were characterized by the presence of either hemispheric nodules or large infiltrated plaques, or their combinations. Microscopic examination indicated that tumorous lesions were composed mostly of melanocytes and numerous melanophages and that component cells manifested a remarkable cellular atypia with anisocytosis and anisokarinosis. Pathological examination of lesions corresponding to earlier stages of the tumors disclosed that tumor formation and its related melanogenesis occurred in close topographical association with apocrine sweat glands, but not at the dermal-epidermal junction. Larger nodules of the tumors were often composed of a concentric deposition of cell layers, each being separated by dermal components from the epidermis. Because of the absence of their tropism toward the epidermis and their multiloculation, horse melanomas are considered to be different in their pathological characteristics from human melanomas.     

Wound healing and the haemocyte response in the skin of the Lesser octopus Eledone cirrhosa (Mollusca: Cephalopoda)

The general structure of the skin of the Lesser octopus, Eledone cirrhosa is described. The component regions and cell types being (1) the epidermis, composed of columnar cells with a border of microvilli on their external surface, mucous cells and secretory cells of an unknown type, abutting a non cellular basal lamina; (2) the dermis, containing the elements of the colour change system, vascular and neural processes and an a cellular matrix.
A sequential, morphological study of wound closure revealed three major mechanisms in the healing response; muscular contraction, a dermal cellular reaction and epidermal migration. The process of wound closure in Eledone is significantly slower than that seen, for example, in teleost fish (30 h rather than 30 min for the initiation of epidermal migration). The significance of these results in relation to the osmotic balance between seawater and the internal milieu of Eledone is discussed, together with their relevance to resistance against infection by pathogens.     

Cultured dermal papilla cells induce follicle formation and hair growth by transdifferentiation of an adult epidermis.

Adult rat pelage follicle dermal papilla cells induced follicle neogenesis and external hair growth when associated with adult footpad skin epidermis. They thus demonstrated a capacity to completely change the structural arrangement and gene expression of adult epidermis--an ability previously undocumented for cultured adult cells. Isolation chambers ensured that de novo follicle formation must have occurred by eliminating the possibility of cellular contributions, and/or inductive influences, from local skin follicles. These findings argue against previous suggestions of vibrissa follicle specificity, and imply that the potential for hair follicle induction may be common to all adult papilla cells.     

The epidermis and its degeneration in the larval tail and adult body of Rana temporaria and Xenopus laevis (Amphibia: Anura)

The tail epidermis of the larva and the body epidermis of adults of Rana temporaria and Xenopus laevis are described in terms of electron microscopy.
The activity of lysosomes (determined by the localization of acid phosphatase) in relation to autolysis and the process of cellular cornification, is considered during the periods of climactic disappearance of the larval tail and skin sloughing of adults. The results obtained generally correspond for both genera.
Larval tail epidermal cells completely disappear at metamorphic climax; those of the adult, which are shed, are replaced throughout life after each periodic sloughing. Nevertheless the mechanisms of their epidermal cell loss are comparable, though the level of lysosomal activity in larval tail epidermal cells is higher than in the adult body epidermis. This higher activity of lysosomal enzymes may facilitate the heavy necrosis which ensues in the larval tail at metamorphic climax.     

Human skin reconstructed in vitro as a model to study the keratinocyte, the fibroblast and their interactions: photodamage and repair processes

The protective role of the skin is provided by the two major compartments of the skin, dermis and epidermis. Both are affected in the long term by consequences of sun exposure such as skin photoaging and cancer development. Characterization of UV-induced skin response at cellular and molecular levels is needed for prevention or correction of these long term effects. The human skin reconstructed in vitro, comprising both a living dermal equivalent and a fully differentiated epidermis represents a predictive tool to characterize wavelength and cell type specific biological damage together with tissular distribution. While UVB directly affects epidermis, inducing DNA lesions and apoptotic sunburn keratinocytes, UVA radiation can directly target the dermal compartment through ROS generation, dermal fibroblasts alterations and extracellular matrix (ECM) modifications. Interactions between the two compartments have also been found, especially for MMP1 induction. In the normal population, photodamage can be repaired through specialized systems. Using skin cells from Xeroderma pigmentosum (XP, a photosensitive and cancer-prone disease), a DNA-repair deficient skin has been developed in vitro. Specific features due to intrinsic XP cell phenotype have been discovered, some of them being indicative of early steps of neoplasia and suggesting a particular role for stroma-epithelium interactions. Finally, human reconstructed skin can be used for approaches designed to regenerate photodamaged skin. The dermal-epidermal junction (DEJ), which is crucial for skin cohesion, is drastically altered in photo-aged skin. The three-dimensional skin model allowed to visualize the improving effects of vitamin C on the DEJ. Modified skin models, lacking one cell type, allowed us to determine the cellular origin of the different markers, their spatial localization, and the respective roles and interactions of keratinocytes and fibroblasts during DEJ formation. All together these studies give a global and tissular view concerning the effects of UV light on skin cells and emphazise the interest of such models for general aspects of cellular biology. By allowing the control of cells used to reconstruct the model and their origin, these studies make it possible to assess the respective role of the two major cellular actors of the skin as well as their interactions. Ongoing research about incorporating other cell types may certainly give rise to even more relevant models.     

The shift from aquatic to terrestrial phenotype in Lissotriton italicus: larval and adult remodelling of the skin

Morphology and ultrastructure of the skin of Lissotriton italicus (previously named Triturus italicus) have been described in different phases of its biological cycle: larval stage, metamorphic stage and adult stage with emphasis on modifications occurring between aquatic and terrestrial adults. In the present study, light microscopy and both scanning and transmission electron microscopy were employed to analyze the histological and cytological remodelling that occurs in the skin of L. italicus during metamorphosis. The ultrastructure of the larval epidermis is arranged into three principal layers comprising an external layer of pavement cells, a basal layer and 1-3 intermediate layers consisting of Leydig cells along with accessory cells and mitochondria-rich cells. By the onset of metamorphosis, morphological changes of the skin include stratification and flattening of epidermal layers and disappearance of typical larval cells. In both aquatic and terrestrial adult phases the thin, cornified epidermis shows the same general arrangement as found in other vertebrates with an external stratum corneum and a variable number of intermediate cell layers. During the terrestrial adult phase, the skin is characterized by the presence of numerous tubercles; moreover, the lower epithelium is thicker than in the aquatic phase. Ultrastructural analysis revealed no substantial differences in the cellular composition of the skin between aquatic and terrestrial phases.     

Structure of the dermal scales in gymnophiona (Amphibia)

Histology and cytology of dermal scales of the gymnophionans Ichthyophis kohtaoensis and Hypogeophis rostratus reveal their structure and the nature of their mineralization. Dermal scales are small flat disks set in pockets in the transverse ridges of the skin. Each pocket contains several scales of various sizes. A ring of “hypomineralization” of varying diameter may occur on scales of a particular dermal pocket but bears no relation to the diameter of these scales. Three different layers form the scales and are seen on sections perpendicular to the surface. The cells of the basal layer lie deepest. Each of the two or three more superficial fibrous layers is composed of bundles of fibres that are oriented in parallel. The orientation varies among layers. The striation of the fiber scales has a periodicity comparable to that of the surrounding dermal fibers. Squamulae form a discontinuous layer on the scale surface and are the only mineralized part of the scale. The minerals are deposited both on the collagen fibers passing from the fibrous layers into the squamulae, and in the interfibrillar spaces. Spherical concretions, either isolated or coalescent, reaching up to 1 μm, are found on the surface of the squamulae. The dermal scales of Gymnophiona present some analogies with those of evolved bony fishes. Their characteristics could make them an original model for the study of mineralization.