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  • 1
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Dry skin and eczema only seldomly occur in workers in the Danish fish-processing industry (FPI) during work, when their fingers and palms have a low skin surface temperature, low transepidermal water loss (TEWL), and a high capacitance. However, shortly after work, when the skin temperature has become normal, TEWL levels increase to above normal, and capacitance decreases to below normal, followed by the development of dry skin or chapping, which subsequently revert to normal over a period of hours. These observations suggest that workers in the FPI may have a delect in skin barrier function, which is, however, masked by a low skin temperature, resulting in misleadingly low TEWL levels during work. To test this hypothesis, we disrupted the permeability barrier in hairless mice with topical acetone, and exposed the treated skin to ice for 3–5h. Although TEWL rates immediately after cold exposure were low, suggesting normal barrier recovery, TEWL increased to levels slightly above pre-cold exposure levels (i.e. levels just after the barrier was disrupted with acetone) when the skin temperature reverted to normal (≥ 15min). The changes in TEWL were paralleled by equivalent changes in percutaneous penetration of the electron-dense tracer lanthanum nitrate. This indicates that cold masks a defective barrier, and inhibits barrierrepair. After a few hours at ambient temperatures, normal barrier recovery was observed. Electron microscopy revealed empty or partially empty lamellar bodies during the first 30 min post-cold exposure. After 1 h the majority of nascent LBs displayed normal morphology. Moreover, histochemical studies showed a delayed reappearance of stratum corneum intercellular lipids following cold exposure. These results demonstrate that cold exposure prevents barrier recovery after acetone disruption, and provide an explanation for the occupatonal dermatosis observed in the fish-processing industry and related occupations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 126 (1992), S. 0 
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Lamellar body secretion results in the delivery of a selected array of hydrolytic enzymes to the extracellular domains of stratum corneum (SC). Deposition and activation of these enzymes in the interstices presumably is associated with the transformation of lamellar body-derived lipids from a relatively polar to a non-polar mixture, as well as the degradation of other non-lipid intercellular substrates. To determine whether abnormal desquamation might result from failure of hydrolytic enzyme delivery to the SC interstices, we localized one catabolic enzyme, acid lipase, previously shown to be a reproducible marker for the lamellar body secretory system, by cytochemical methods within the epidermis of selected human (congenital ichthyosiform erythroderma, CIE) and animal (essential fatty-acid deficient (EFAD) mouse epidermis and mouse tail epidermis) models associated with abnormal scaling or unusual SC retention. In addition, we compared the persistence of desmosomes within normal SC vs. the various models. Normal human and murine epidermis displayed abundant lipase activity both in lamellar bodies (LB) and in association with secreted lamellar body contents in the SC interstices. Despite normal quantities of LB in CIE, EFAD, and mouse tail epidermis, lipase activity was markedly deficient both in LB and in the SC intercellular domains. These studies support the hypothesis that normal desquamation is mediated by enzymatic modulations in lipid and/or protein content of the SC interstices, and that some forms of pathological or excessive scaling may be due to desmosomal persistence that results from defective or limited delivery of lamellar body-derived, hydrolytic enzymes to the SC intercellular domains
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 130 (1994), S. 0 
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary Prior studies have demonstrated a Ca2+ gradient within the epidermis, with the highest concentration in the outer nucleated layers, disappearance of the Ca2+ gradient when the permeability barrier is acutely disrupted, and reappearance of the Ca2+ gradient in parallel with barrier repair, and disruption of the gradient in psoriasis. These observations suggest that integrity of the permeability barrier may maintain the epidermal Ca2+ gradient. To determine further whether a functional barrier is crucial for maintaining the Ca2+ gradient, we examined Ca2+ distribution by ion-capture cytochemistry in essential-fatty-acid-deficient (EFAD) and topical-lovastatin-treated mice, which display a chronic barrier abnormality. In both models, loss of the Ca2+ gradient occurred due to increased cytosolic Ca2+ in the lower epidermis, which normally displays a paucity of Ca2+. Moreover, artificial barrier restoration for 48 h with a water vapour-impermeable wrap normalized the Ca2+distribution pattern. Acute barrier disruption also leads to the loss of the Ca2+ gradient, but in contrast with the chronic models, loss of the gradient was due to decreased Ca2+ in the upper epidermis. Occlusion with a vapour-impermeable wrap blocked restoration of the Ca2+ gradient after acute barrier disruption. These results demonstrate that chronic barrier disruption increases Ca2+ in the epidermis, and blockade of water flux normalizes Ca2+ distribution, whereas acute barrier disruption leads to loss of Ca2+, and blockade of water flux prevents the return of Ca2+. We conclude: (i) that the epidermal Ca2+ reservoir is derived from the movement of fluids and Ca2+ across the basement membrane, and (ii) that the integrity of the permeability barrier maintains the epidermal Ca2+gradient.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 128 (1993), S. 0 
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The stratum corneum, the permeability barrier between the internal milieu and the environment, is composed of fibrous protein-enriched corneocytes and a lipid-enriched intercellular matrix. The lipids are a mixture of sphingolipids, cholesterol and free fatty acids, which form intercellular membrane bilayers. Lipid synthesis occurs in the keratinocytes in all nucleated layers of the epidermis, and the newly synthesized lipids are delivered by lamellar bodies to the interstices of the stratum corneum during epidermal differentiation. Disruption of barrier function by topical acetone treatment results in an increase in the synthesis of free fatty acids, sphingolipids and cholesterol in the living layers of the epidermis, leading to barrier repair. Cholesterol and sphingolipid synthesis are regulated by the rate-limiting enzymes HMG CoA reductase and serine palmitoyi transferase (SPT). respectively. Acute barrier disruption leads to an increase in both enzymes, but with a different time curve: increase in HMG CoA reductase activity begins at 1.5 h, whereas the increase in SPT activity occurs 6 h after barrier impairment. Topical application of HMG CoA reductase or SPT inhibitors after acetone treatment delays barrier repair, providing further evidence for a role of cholesterol and sphingolipids in epidermal barrier function. Repeated application of lovastatin to untreated skin results in disturbed barrier function accompanied by increased DNA synthesis and epidermal hyperplasia. Therefore, we have examined the specific relationship between barrier function and epidermal DNA synthesis. After acute and chronic disturbances not only lipid, but also DNA synthesis, is stimulated. Thus, stimulation of DNA synthesis leading to epidermal hyperplasia may be a second mechanism by which the epidermis repairs defects in barrier function. The link between barrier function and both lipid and DNA synthesis is supported further by occlusion studies. Artificial barrier repair by latex occlusion prevents an increase in both lipid and DNA synthesis. In addition, increased epidermal lipid and DNA synthesis in essential fatty-acid deficiency can be reversed by topical applications of the n-6 unsaturated fatty acids, linoleic or columbinic acid. These studies may be of relevance in understanding the pathogenesis of hyperproliferative skin diseases, such as ichthyosis, psoriasis, atopic dermatitis, and irritant contact dermatitis.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Pharmaceutical and Biomedical Analysis 12 (1994), S. 719-722 
    ISSN: 0731-7085
    Keywords: Size exclusion chromatography ; bloat. ; poloxalene ; poloxamer ; polyethylene ; polypropylene ; rumenal tympany
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Molecular Cell Research 930 (1987), S. 193-200 
    ISSN: 0167-4889
    Keywords: (Keratinocyte) ; Sterol synthesis ; Vitamine D status
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Crop science 38 (1998), S. 1685-1687 
    ISSN: 1435-0653
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Previous work has shown that tissue cultures initiated from mature embryos of a specific experimental oat (Avena sativa L.) line, Gaf/Park, can be genetically engineered and fertile plants regenerated. The objectives of this study were to investigate the initiation of tissue cultures from mature embryos of 16 elite North American spring oat cultivars and to determine whether these tissue cultures can be used to produce transgenic plants. Fifteen of the genotypes tested produced at least some embryogenic callus that was similar in appearance to transformable callus. The elite cultivar Belle was tested to determine whether it could be genetically engineered. From 30 microprojectile bombardment treatments, 17 independently genetically engineered tissue cultures were produced that regenerated fertile, transgenic plants. These results indicate that the mature embryo-derived tissue culture system will be useful for genetically engineering elite oat cultivars.
    Type of Medium: Electronic Resource
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