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  • 1
    ISSN: 1432-069X
    Keywords: Keys words Human skin ; Nude mouse ; Wound healing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It has been established that human skin grafted onto the nude mouse is able to regenerate after being subjected to a full-thickness wound. In the present work, we sought to determine the cells involved in the connective tissue repair process following superficial wounding. Two months after transplantation, superficial wounds were made at the center of the graft using mechanical dermabrasion. At various times thereafter, ranging from 2 days to 6 weeks, healing grafts were harvested and processed for immunohistological study with species-specific and cross-reacting antibodies directed against human or mouse antigens. The grafted human skin regenerated according to the following series of events. First, the human dermis underneath the scab became devoid of human fibroblasts while the surrounding human dermis preserved its own characteristics. The TUNEL reaction on early-phase healing wounds indicated that apoptosis occurred steadily within this area and could be the mechanism by which cells disappeared. Moreover, cell death was reduced when the wound was covered with an occlusive dressing. The human dermis beneath the wound was then invaded by mouse cells which deposited type I collagen on the human extracellular matrix and produced mouse granulation tissue at the surface above it. Human keratinocytes migrated over the mouse granulation tissue to reconstruct the epidermis. Eventually, the mouse granulation tissue was progressively invaded by human fibroblasts, which formed a human neodermis. The overall process appeared to depend upon several successive epithelial-mesenchymal interactions, which were not species-specific. This suggests that myofibroblasts arise from a specific subpopulation of fibroblasts, probably located at the interface between the dermis and adipose tissue, and that the granulation tissue is eventually remodeled by another population of fibroblasts present in the human dermis.
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  • 2
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background  For ethical and technical reasons, the in vivo biological effects of ultraviolet (UV) radiation on skin are difficult to study in human volunteers. The use of human skin grafted on to nude mice may circumvent this difficulty.Objectives  To investigate the effects of a single moderate UVB exposure on human skin grafted on to nude mice.Methods  Modifications of epidermal differentiation markers and patterns of keratin expression were assessed from 24 h to 14 days after a physiological UVB irradiation characterized by the induction of sunburn cells.Results  During the first 48 h postexposure, involucrin, loricrin, transglutaminase type I, filaggrin and keratin K2e expression were altered together with the formation of abnormal horny layers. Constitutive keratin K14 was increased while keratin K10 expression was delayed. Newly synthesized keratins K6, K16, K17 and K19 were induced in parallel with an increase in the epidermal proliferation rate. A progressive normalization of both keratinocyte proliferation and differentiation took place during the following days, reaching completion within 2 weeks.Conclusions  Exposure of human skin to a UVB dose corresponding to a mild sunburn reaction induces epidermal hyperproliferation and alterations of several constitutive differentiation markers, as well as a drastic modification in the pattern of epidermal keratins. Although these modifications were shown to be progressively reversed in a single exposure model, the data also suggest that subsequent UV exposures occurring during the recovery period may lead to potentially deleterious long-term consequences, such as photoageing and photocarcinogenesis. Grafted human skin appeared to be an attractive and promising model for investigating the biological consequences of UVB radiation in vivo.
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  • 3
    ISSN: 1434-6036
    Keywords: PACS. 75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects – 75.60.Jk Magnetization reversal mechanisms – 75.70.Ak Magnetic properties of monolayers and thin films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Magnetic exchange coupling has been observed for ultrathin films of yttrium iron garnet (Y3Fe5O12 or YIG). Single-crystalline YIG films were prepared on yttrium aluminium garnet (Y3Al5O12 or YAG) substrates by pulsed laser deposition. (111) and (110) oriented substrates were used. Film thicknesses were varied from 180 Å to 4600 Å. Epitaxial growth of YIG on YAG was obtained in spite of the lattice mismatch of 3%. Magnetic hysteresis loops recorded for ultrathin YIG films have a “bee-waist” shape and show a coupling between two different magnetic phases. The first phase is magnetically soft YIG. A composition study by secondary ion mass spectroscopy shows the second phase to be Y3Fe5-xAlxO12 due to the interdiffusion of Fe and Al at the film/substrate interface. This compound is known to be magnetically harder and to have weaker magnetization than YIG. The coupling of the two phases leads to a hysteresis loop displacement at low temperatures. This displacement varies differently with film thickness for two substrate orientations. Assuming an interfacial coupling, the maximal interaction energy is estimated to be about 0.17 erg/cm2 at 5 K for (111) oriented sample.
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  • 4
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: Electronic grade diamond is usually grown by Microwave Plasma assisted CVD froma hydrogen rich CH4/H2 mixture, hence hydrogen is likely to be incorporated during growth. Itmay thus affect the properties of the material. In this work, we present the state of the art on theunderstanding of the diffusion properties of hydrogen and of the hydrogen-dopant interactions indiamond. First, we show the existence of strong interactions between H and boron dopants indiamond. The formation of H-acceptor pairs results in the passivation of the acceptors. Further,we show that an excess of hydrogen in selected boron-doped diamond epitaxial layers can resultin the creation of H and boron-containing donors with a ionization energy of 0.36 eV (about halfthe ionization energy of phosphorus). At 300 K, the n-type conductivity of hydrogenated borondopeddiamond is several orders of magnitude higher than the conductivity of phosphorus-dopeddiamond. The formation process of these new donors is discussed
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  • 5
    ISSN: 1590-3478
    Keywords: Human ; Hypothalamus ; Anterior hypothalamic area ; Supraoptic nucleus ; Neurons ; Golgi impregnation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Sono state analizzate le caratteristiche morfologiche delle popolazioni cellulari impregnate con metodo di Golgi, nelle aree ipotalamiche anteriore (AHA) e sopraottica (SON) del cervello umano adulto. Per la prima volta vengono descritte quattro sottopopolazioni neuronali. I neuroni del tipo I sono stati osservati sia in AHA che in SON mentre gli altri tre sottotipi neuronali (tipi II – IV) sono stati trovati solo in SON. I neuroni di tipo I hanno soma allungato, triangolare o multipolare da cui emergono 2–5 dendriti primari con un numero ridotto di spine. Molti di questi neuroni in AHA hanno sottili ramificazioni dendritiche. I neuroni di tipo II presentano un soma tondeggiante o fusiforme e generalmente due ramificazioni dendritiche principali. Il tipo III è caratterizzato da neuroni multipolari con 3–5 ramificazioni dendritiche ricche di spine. I loro assoni presentano collaterali. Il tipo IV ha soma piccolo ed ovoidale con dendriti primari sottili e che non si ramificano. I neuroni osservati nei nuclei AHA e SON dell'uomo sono simili a quelli osservati nelle stesse aree di altre speci animali ad eccezione dei piccoli neuroni in SON e delle caratteristiche delle ramificazioni dendritiche dei neuroni di tipo I in AHA. Queste caratteristiche morfologiche non sono state precedentemente descritte.
    Notes: Abstract Morphological features of neuronal cell types in the anterior hypothalamic area (AHA) and supraoptic hypothalamic nucleus (SON) of the adult human brain were analysed in Golgi impregnated preparations. Four neuronal cell types were described for the first time in these human nuclei. Type I neurons were found in both the AHA and SON, while the other three cell types (types II–IV) were found only in the SON. Type I neurons had elongated, triangular or multipolar somata, which emitted 2–5 sparsely branching primary dendrites with a moderate number of fine spines. Also many of type I neurons in the AHA had thin dendritic side-branches. Type II neurons had round or fusiform somata, and two occasionally branching primary dendrites. Type III neurons were multipolar neurons with 3–5 densely spined and sparsely branching dendrites. Their axons had collaterals. Type IV neurons had very small ovoid somata with one smooth and unbranched primary dendrite. The neurons in the human AHA and SON were similar to those observed in the same areas in other mammalian species, except for the very small neurons in the SON and the thin dendritic side-branches of type I neurons in the AHA, that had not been previously described.
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  • 6
    ISSN: 1600-0625
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract:  Androgens have profound effects on the physiology of the sebaceous gland. Using the hamster ear sebaceous gland model, we performed a detailed kinetic study to clarify the mechanism of androgen action on sebaceous gland function. We demonstrated that the growth of sebaceous glands observed after androgen treatment was due to both an increase in sebocyte proliferation and a parallel induction of sebocyte terminal differentiation, as evidenced by the induction of the synthesis of specific sebaceous lipids such as cholesterol esters, triglycerides, and squalene. Accordingly, the effect of androgen treatment on the mRNA expression of several key enzymes involved in the synthesis of sebaceous lipids has been studied using semi-quantitative RT-PCR. Up-regulation by androgens of mRNA expression of HMG coenzyme A synthase and reductase, acetyl coenzyme A carboxylase (ACC), glycerol 3-phosphate acyl transferase (GPAT), and FAR-17c (stearoyl coenzyme A desaturase homologous), was demonstrated. Because sterol-response element(s) (SREs) are known to be present in the promoters of these genes, we analyzed the expression by RT-PCR and the activation of the transcription factor sterol regulatory element binding protein (SREBP) using immunoblotting experiments. Our results showed that SREBP-1 was up-regulated and rapidly activated after androgen treatment. Altogether, these results demonstrate for the first time that in sebaceous glands, in vivo, androgen regulates the synthesis of sebum lipids through the SREBP pathway.
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Unintentionally doped ZnO layers grown epitaxially on a sapphire substrate have been exposed either to a hydrogen or deuterium plasma. Secondary ion mass spectroscopy measurements performed subsequently showed a rapid diffusion of hydrogen in these layers. Furthermore, the presence of hydrogen in the ZnO samples is found to be responsible for nearly a factor of 3 increase in the free electron concentration. This effect is attributed to the hydrogen passivation of compensating acceptor impurities present in the as-grown ZnO layers. © 2002 American Institute of Physics.
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  • 8
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The n-type doping of diamond with phosphorus suffers from defects reducing the electron mobilities and inducing some degree of compensation. In addition, the relatively high ionization energy (0.6 eV) of phosphorus severely limits the electrical activity of the dopants. Here, we present two recent advances of the n-type doping of diamond. One is based on the significant reduction of the compensation ratio of highly compensated phosphorus-doped diamond by thermal annealings. The second one presents the possibility of converting p-type boron-doped diamond into n-type by deuterium diffusion and formation of deuterium-related shallow donors with ionization energy of 0.33 eV
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    British journal of dermatology 139 (1998), S. 0 
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Adapalene, a synthetic retinoid, is a new drug proposed for the treatment of acne patients. Studies on the in vitro and in vivo pharmacology of adapalene have shown that it is very active on cell and tissue proliferation and differentiation. Furthermore, adapalene has anti-inflammatory potential as determined by its anti-AP1 activity. Adapalene interacts selectively with the nuclear receptors RARβ and RARγ, and its activity on proliferation and differentiation can be blocked by a RARβ-γ antagonist. Because RARβ is not expressed in human keratinocytes, the effect of adapalene on the major cell type of the epidermis is certainly mediated by its interaction with RARγ. The unique pharmacological properties of adapalene may explain why, when compared to tretinoin, it has an improved therapeutic ratio due to its better tolerance.
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  • 10
    ISSN: 0167-2584
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
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