The Structure and Permeability of Integument

SYNOPSIS. The skin is a heterogeneous, multimembrane systemwith multiple diffusion pathways and potentially numerous rate-limitingbarriers for specific molecules that are exchanged with theenvironment. A broad survey of animals indicates that integumentarycoverings are morphologically, biochemically and embryologicallydiverse but with common themes of adaptation. The evolutionaryproliferation of intercellular junctions, fibrous or mineralizedprotective barriers, and lipoid waterproofing barriers emphasizethe generality of diffusion limitations. However, the regulationof specific exchange processes such as the flux rates of respiratorygases entails a complex interaction of multiple factors affectingboth diffusion and perfusion limitations. Consideration of specificpathways and rate limitations for diffusion of various substancessuggests that the permeation of skin by specific molecules canbe partially independent of other exchange processes. Our understandingof regulated permeability is, however, lacking in mechanisticand integrated analysis in most cases. Comprehensive understandingof the integument as a regulatory pathway of communication withthe environment will require comparative studies of specifictransport pathways, their rate-limiting resistances, and theinteractions as well as individual regulation of transportedmolecules.     

Integument initiation and testa development in some Cruciferae

This study has shown for the first time that the middle layer (or layers) of the outer integument is (are) of subdermal derivation in at least some taxa of the Cruciferae. The outer integument is initiated in the Cruciferae in three different ways, viz. subdermally (Brassica, Sinapis) , partly subdermally and partly dermally (Lunaria) , or completely dermally (Capsella). These differences in initiation are reflected in the structure of the mature testa. The inner integument is completely of dermal derivation and originally two cell-layers thick, but may become more than two-layered during the ovule and seed maturation by periclinal divisions of the inner cell layer. The consequences of the ontogeny of the integuments for the terminology and interpretation of the mature testa is discussed.     

家蚕幼虫血细胞密度变化成因及血细胞密度与耐高温性的关系

[目的]血细胞是昆虫血淋巴免疫的主导者.调查家蚕Bombyx mori幼虫血细胞密度变化和成因、血细胞密度与家蚕抗性的关系,是研究家蚕血细胞相关的免疫调控和抗性育种的重要组成.[方法]用细胞计数板统计家蚕品种大造不同龄期(4龄第1-4天、5龄第1-8天和上蔟期)幼虫10 μL血淋巴中的血细胞数目并计算血细胞密度,利用I...     

Eicosanoids mediate insect hemocyte migration

Hemocyte migration toward infection and wound sites is an essential component of insect defense reactions, although the biochemical signal mechanisms responsible for mediating migration in insect cells are not well understood. Here we report on the outcomes of experiments designed to test the hypotheses that (1) insect hemocytes are able to detect and migrate toward a source of N-formyl-Met-Leu-Phe (fMLP), the major chemotactic peptide from Escherichia coli and (2) that pharmaceutical modulation of eicosanoid biosynthesis inhibits hemocyte migration. We used primary hemocyte cultures prepared from fifth-instar tobacco hornworms, Manduca sexta in Boyden chambers to assess hemocyte migration toward buffer (negative control) and toward buffer amended with fMLP (positive control). Approximately 42% of negative control hemocytes migrated toward buffer and about 64% of positive control hemocytes migrated toward fMLP. Hemocyte migration was inhibited (by >40%) by treating hornworms with pharmaceutical modulators of cycloxygenase (COX), lipoxygenase and phospholipase A2 (PLA2) before preparing primary hemocyte cultures. The influence of the COX inhibitor, indomethacin, and the glucocorticoid, dexamethasone, which leads to inhibition of PLA2, was expressed in a dose-dependent way. The influence of dexamethasone was reversed by injecting arachidonic acid (precursor to eicosanoid biosynthesis) into hornworms before preparing primary hemocyte cultures. The saturated fatty acid, palmitic acid, did not reverse the inhibitor effect. These findings support both our hypotheses, first that insect hemocytes can detect and respond to fMLP, and second, that insect hemocyte migration is mediated by eicosanoids.     

高等植物珠被绒毡层的研究

绒毡层是植物孢子体向配子体世代转换的"哺乳组织",其研究对于揭示植物配子体发育的调控机制具有重要意义。对花药绒毡层的发育过程已有一些研究,而对珠被绒毡层的研究积累相对较薄弱。对菊科(Compositae)、柴胡(Bupleu-rum)、大车前(Plantago major)、柱花草(Stylosanthes)等草本植物的研究表明,因珠被发育过程和结构复杂,珠被绒毡层结构也较花药绒毡层复杂,其发育模式因植物不同而异,有单珠被绒毡层和双珠被绒毡层两种类型;珠被绒毡层异常生长会导致胚珠败育。木本植物珠被绒毡层,特别是裸子植物的珠被绒毡层在国内外的研究报道不多。     

五唇兰珠被细胞的超微结构观察

应用透射电镜对五唇兰(Doritis pulcherrima)珠被细胞进行超微结构观察。结果表明,授粉38d后,五唇兰外珠被细胞尚保持完好,而内珠被细胞开始退化;线粒体内嵴减少或消失,内质网上的核糖体数量减少,液泡增加,在新形成的液泡内含有膜状结构和模糊的细胞器,但核膜完整,与细胞程序死亡的部分特征相似。     

Integument of Kamptozoa Barentsia discreta Busk, 1886

The integument of the colonial species Barentsia discreta has been investigated in the present work. On its greater length the integument is presented by a monolayered unciliated epithelium covered by a layer of microvillar cuticle. The floor of the atrial cavity and the frontal surface of tentacles is lined by ciliated epidermis covered by a protocuticle. Sensitive and secretory cells are present in the epidermis.     

Vergleichende Untersuchungen am Integument von Hetero- und Eutardigraden

Zusammenfassung Licht- und elektronenmikroskopische Untersuchungen am Integument vonEchiniscus testudo (Heterotardigrada),Milnesium tardigradum, Hypsibius oberhaeuseri undMacrobiotus hufelandi (Eutardigrada) lassen acht, mindestens jedoch sechs Schichten erkennen, die in Anlehnung an Baccetti und Rosati (1971) benannt werden, wobei eine Homologie beiE. testudo nicht sicher ist.BeiE. testudo bildet die innere sklerotisierte Epicuticula ein Hohlraumsystem, dessen Wände von ca. 150 Å breiten Kanälen durchzogen werden. Die dorsalen Einsenkungen der Panzerplatten besitzen einen zentralen 500 Å breiten Kanal. Ventral ist die äußere Epicuticula mehrfach geschichtet. Ein darunterliegender Röhrchensaum und die weitgehend reduzierte innere Epicuticula lassen andere Permeabilitätseigenschaften vermuten. Die Intracuticula zeigt vertikale Filamente. Wachsschicht und innere Lage der Intracuticula sind morphologisch nicht eindeutig zu identifizieren. Die einschichtige Epidermis ist reich an Lipidtropfen, freien Ribosomen und granulärem endoplasmatischem Reticulum. Manche Zellen sind kontrastreicher.Besondere Cuticula-Bildungen der drei Eutardigraden sind die epicuticulären Einsenkungen vonM. hufelandi, in deren Bereich die innere Epicuticula fehlt, die dorsale und laterale Skulpturierung vonH. oberhaeuseri, die eine Bildung der Epicuticula ist, und die epicuticulären Kanäle vonM. tardigradum. Die Proticula aller untersuchten Tardigraden-Arten besitzt keine Porenkanäle.Die Epidermis vonM. hufelandi besteht aus einem einschichtigen Epithel. Seine Zellen enthalten zahlreiche membranbegrenzte osmiophile Einschlüsse, die die Färbung der Tiere bedingen. Einzelne Zellen fallen durch ihren hohen Kontrast und zahlreichere Organellen auf.Die Cuticula der Eutardigraden zeigt in allen Fällen eine morphologisch vergelichbare Schichtenfolge. Die Cuticula vonE. testudo, die Besonderheiten aufweist, kann jedoch aufgrund charakteristischer Merkmale (z. B. die äußere Lage der Intracuticula) vielleicht in den Vergleich einbezogen werden.

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Comparative studies on the integument of Hetero- and Eutardigrada

Summary The structure of the integument ofEchiniscus testudo (Heterotardigrada),Milnesium tardigradum, Hypsibius oberhaeuseri andMacrobiotus hufelandi (Eutardigrada) was studied by light and electron microscopy. In all species the cuticle consists of 6–8 layers and can adequately be described following the terminology of Baccetti and Rosati (1971). This perhaps does not apply toE. testudo.InE. testudo the inner sclerotized epicuticle reveals a labyrinthine structure due to lacunae with numerous channels of about 150 Å in diameter. The central canals in the depressions of the dorsal plates have a diameter of 500 Å. The outer epicuticle of the ventral cuticle is formed by several layers. Basally there is a tubular layer of channels and an almost reduced epicuticle. Thus the permeability of the cuticle is supposed to be altered. In the intracuticle vertically oriented filaments occur. The inner layer of the intracuticle and the wax-layer cannot be properly distinguished. The one-layered epidermis contains many lipid droplets, ribosomes and rough ER. Some of the cells are rather electron-dense.Peculiar cuticular structures inM. hufelandi appear as cup-shaped depressions of the epicuticle, and here the inner epicuticle is absent. A similarly typical feature is the structured and sculptured dorsal and lateral epicuticle ofH. oberhaeuseri and the channels of the epicuticle inM. tardigradum. In all species investigated there are no pore canals in the procuticle.InM. hufelandi there is a single layer of epidermal cells, which contain many osmiophilic grana ensheathed by membranes. These grana cause the colour of the animal. Some of the cells contain more organelles and ribosomes and show a strong contrast.In spite of some cuticular peculiarities inE. testudo, perhaps this Heterotardigrade species fits into the general pattern of cuticle morphology of Tardigrada.

Veränderter Teil einer Dissertation des Fachbereichs Biologie der Universität Münster. Die Arbeit wurde von Herrn Prof. Dr. R. Altevogt angeregt.     

Immunohistochemical Demonstration of Transferrin and Transferrin Receptor in Mammalian Integument

The present study demonstrates the distribution of transferrin and the transferrin receptor in the integument of eleven wild mammalian species using immunohistochemical methods. Both substances were regularly found in or near the peripheral cells of the sebaceous glands, especially of dense-haired animals. The transferrin receptor was also detectable in the epidermis, the secretory portion of tubular apocrine glands, and the outer epithelium of primary hair follicles. Transferrin as well as the transferrin receptor reacted strongly in macrophages of the papillary dermis only in the common seal. The results obtained are discussed with regard to possible biological functions in the skin of the substances demonstrated. Keywords: immunohistochemistry, integument, mammals, transferrin, transferrin receptor     

Intrinsic Pigment-Cell Stimulating Activity in the Catfish Integument

In keeping with the concept that local factors in the vertebrate integument affect the expression of pigment cells, the present study was directed toward demonstrating the existence of such factors in the skin of the channel catfish, Ictalurus punctatus. This species has a dark dorsal surface in marked contrast to an almost white midventral surface. Pieces of skin from these two surfaces were used to condition culture media, which were in turn bioassayed using the Xenopus neural tube explant system (Fukuzawa and Ide, 1988, Dev. Biol. 129:25). A certain number of neural crest cells grow out from the explant, and many of these are melanized in a culture medium of Steinberg's basic salt solution (BSS). When the BSS was conditioned with either dorsal or ventral skin, a profound increase in both the number of crest cells emigrated from the neural tubes and the percentage of melanized cells was observed. The effects of dorsal skin were stronger than those of ventral skin and were evident on a dose/response basis. Initial fractionation of conditioned BSS with DEAE ion exchange chromatography produced fractions of particular potency in the stimulation of melanogenesis. A similarly conditioned medium based upon Leibovitz's L-15 was used in the primary culture of mature chromatophores, namely, melanophores, iridophores, and xanthophores from tadpoles of Rana pipiens. Both dorsal and ventral conditioned media stimulated iridophores and xanthophores, but seemed to have little or no effect on tadpole melanophores. A melanization inhibiting factor (MIF) from the ventral surface of adult frogs has been suggested as the basis for the light colored ventrum of amphibians, and although the present experiments were not designed to study catfish MIF, the possible existence of such a factor in this species was supported by the results. The total results of this investigation are discussed in the light of the possible presence of a melanization inhibiting factor (MIF) of greater prevalence in the ventrum and a melanization stimulatory factor (MSF) of greater prevalence in the dorsal integument. It is suggested that the light-colored ventral surface of the catfish and other poikilotherms may result from the presence of higher levels of MIF than MSF. Thus, the expression of melanophores is inhibited while that of iridophores is enhanced. In contrast, higher levels of MSF over MIF in the dark dorsal surface would result in melanophore stimulation and inhibition of iridophore expression.     

Das Schicksal der Melanoblasten im Integument verschiedener Taubenrassen

Ohne ZusammenfassungZur Durchführung der Untersuchungen standen Mittel der Deutschen Forschungsgemeinschaft zur Verfügung.     

Differentiation of the Opercular Integument in Rana pipiens

The opercular skin develops in its own specific fashion differing from other areas of the integument previously studied. It remains typically larval until it is sloughed off.
The opercular integument first deviates from the common skin development pathway at stage XV [1] when the rough endoplasmic reticulum. proliferates to form a large part of the cytoplasm and is accompanied by numerous large mitochondria. The Golgi apparatus becomes very large and many vesicles are found in the cytoplasm.
The mitochondria become large and swollen with atypical structure. The cytoplasm becomes highly vesiculated. Degeneration begins at the dermal edge of the basement lamella and proceeds toward the epidermis, being marked by the disorientation of collagen fibrils.
Epidermal cells become progressively more necrotic having cytoplasm consisting mainly of residual bodies and vesicles: the nucleus is the last cellular structure to undergo autolysis.
The dermal cells are the first to be lost (stages XVIII–XIX). The opercular integument is shed as a sheet of cells at stage XX when the forelimbs emerge. The necrotic zone of the opercular integument appears to stop at the junction of the body skin and the skin of the forelimb.     

Integument and the Environment Glandular Composition, Function, and Evolution

SYNOPSIS Integumcntirv secietory cells and glands inveitebiateanimals are systemati cally surveyed and basic attnbutes ofthen adaptive evolution are outlined Moi phogenetic lines ofsecretory epideimal cells are fundamentaland present a pnmaiydichotomy between mucous and piotcinaceous stem lines Adaptiveevolution of integumentary glandulir cells can not be sepaiatedfrom the cytogenesis and evolution of other synthetically activeepideimal cells including thosewhich seciete without havinga glandulii moiphology Glandular microevolutionny patterns aiecoirelated with evolving intciactions between enviionment andoiganism and aie mterpietible only on the basis of studies lntegiaungthe appioaches ind techniques of diffciuit zoological spornllics     

Plasmatocyte-spreading peptide influences hemocyte behavior via eicosanoids

Hemocyte-spreading behavior is required for expressing a cellular immune response, nodulation, which clears the vast majority of invading microbes from circulation. The nodulation response is completed by a layer of plasmatocytes, which spread over the nodule and initiate a malanization process leading to darkened nodules. Plasmatocyte-spreading peptide (PSP), the first reported insect cytokine, is responsible for mediating the spreading and attachment of some subclasses of plasmatocytes to nodules. Prostaglandins (PGs), one group of eicosanoids formed from arachidonic acid (AA), also mediate plasmatocyte spreading (PS), although the potential interactions between the PSP and PG signal transduction pathways have not been investigated. We tested our hypothesis that PSP acts via biosynthesis of eicosanoids, specifically PGs, in the beet armyworm, Spodoptera exigua. In this study, we report that (1) PSP and PGE(2) independently stimulated Ca(++)-dependent PS, (2) inhibitors of PG biosynthesis reversibly blocked PS, (3) dsRNA silencing the gene encoding proPSP blocked PS, which was rescued by PSP and by AA, (4) PSP-stimulated PS was reversibly impaired by inhibitors of PG biosynthesis, and (5) the inhibitor-impaired spreading was rescued by AA. Taken together, these points strongly support our model showing that PSP acts via a plasmatocyte-surface receptor, which stimulates biosynthesis of the PGs responsible for mediating plasmatocytes spreading.     

Integument and epidermal sensory structures of Myzostoma cirriferum (Myzostomida)

Summary The fine structure of the integument of Myzostoma cirriferum is described with special attention to the integument sensory areas. Hypotheses about the function and a functional model of these are proposed. The integument consists of an external pseudostratified epithelium with cuticle (the epidermis) covering a parenchymo-muscular layer (the dermis). The dermis includes two types of cells: muscular fibers of the double obliquely striated type and parenchymal cells. Differences occur in the epidermis, which consists either of a large non-innervated myoepithelial area (viz. the regular epidermis). or of several rather localized sensory-secretory areas associated with discrete nerve proceses (viz. the sensory epidermis). The regular epidermis is made up of three types of cell: covering cells, ciliated cells and myoepithelial cells. The sensory epidermis shows small or marked structural variations from the regular epidermis. Small variations occur in the cirri, the buccal papilla, the body margin, the parapodia and the parapodial folds where nerve processes insinuate between epidermal cells. They are thought to be mechanoreceptor sites that could give information on the structural variations of the host's integument and participate in the recognition of individuals of the same species. The sensory epidermis differs markedly from the regular eidermis in the four pairs of lateral organs. Each lateral organ consists of a villous and ciliated dome-like central part, surrounded by a peripheral fold. The epidermis of the fold's inner part (viz. the part facing the central dome) is made up of secretory cells, while that of the fold's outer part is similar to the regular epidermis. The epidermis of the dome includes vacuolar cells, sensory cells and a different type of secretory cell. Lateral organs are presumed to be both chemoreceptors and mechanoreceptors. They could allow the myzostomids to recognize the host's integument and prevent them from shifting on the surrounding inhospitable substrate.     

Yellow Marking and Pteridine Contents in the Integument of Albino Armadillidium vulgare

The albino mutant strain in the woodlice, Armadillidium vulgare, was investigated with respect to the yellow patterns on the dorsal integument. Pigment cells were observed with electron microscope in order to determine the cell types of yellow markings. Quantitative analyses of pteridines in the albino were carried out by HPLC. The result indicated that the albino integument contain sepiapterin, biopterin, pterin, isoxanthopterin as in the wild type and the red mutant strain. The total amount of the four pteridines in the albino was about half as much as that in the red phenotype for both males and females, respectively. Males and females showed almost the same totals and ratios of the four pteridines in the albino and red phenotypes. Therefore, pteridine contents in both phenotypes of A. vulgare may not be related to the activity of androgenic gland hormone. Yellow chromatophores of the albino and red phenotypes were morphologically identical, emitting a yellow fluorescence. These cells contained numerous electron-lucent pigment organelles which were similar to pteridine granules of the wild type.     

Caterpillars have evolved lungs for hemocyte gas exchange

Since insect blood usually lacks oxygen-carrying pigments it has always been assumed that respiratory needs are met by diffusion in the gas-filled lumen of their tracheal systems. Outside air enters the tracheal system through segmentally arranged spiracles, diffuses along tubes of cuticle secreted by tracheal epithelia and then to tissues through tracheoles, thin walled cuticle tubes that penetrate between cells. The only recognized exceptions have been blood cells (hemocytes), which are not tracheated because they float in the hemolymph. In caterpillars, anoxia has an effect on the structure of the hemocytes and causes them to be released from tissues and to accumulate on thin walled tracheal tufts near the 8th (last) pair of abdominal spiracles. Residence in the tufts restores normal structure. Hemocytes also adhere to thin-walled tracheae in the tokus compartment at the tip of the abdomen. The specialized tracheal system of the 8th segment and tokus may therefore be a lung for hemocytes, a novel concept in insect physiology. Thus, although as a rule insect tracheae go to tissues, this work shows that hemocytes go to tracheae.     

A cell membrane-associated lectin of the oyster hemocyte

The presence of a lectin in association with hemocytes of the American oyster, Crassostrea virginica, has been demonstrated by utilizing a microhemagglutination assay. The plasma membrane association of this lectin is shown by its copurification with the plasma membrane fraction of disrupted hemocytes, using sucrose density gradient centrifugation, and also by the binding of ¹²⁵I-labeled glycoproteins to intact hemocytes at 4°C. Based upon agglutinating spcificity for a range of vertebrate erythrocytes, both untreated and enzyme-treated, along with hemagglutination-inhibition assays and crossed-absorption tests, it is apparent that there are also two serum (soluble) lectins, each having a distinct serological agglutination specificity, and that the hemocyte membrane-associated lectin has a specificity that is identical with one of these two serum lectins. It is proposed that the hemocyte membrane-associated lectin may be a true integral membrane protein, and therefore may function as a membrane receptor in nonself recognition by molluscan hemocytes.     

The Development of the Integument Spatial, Temporal, and Phylogenetic Factors

SYNOPSIS The development of hair teeth and feathers is leviewedin the context ot experimental manipulation of dermal epideimalinteractions The inductive role of the del mis is described,and the consequences of altering the ages and sources of theinteracting tissue components is demonstrated The importanceof examining the developmental capibilities of these tissuesafter disruption of the dermal epidermal inteiface as well asin intact explants is discussed In addition the role of thebasement membrane m establishing and stabilizing integumentaldenvatrves and the role of collagen synthesis and depositionisexamined