Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Alterations of extracellular matrix induced by tobacco smoke extract (2000)
    Springer
    Archives of dermatological research 292 (2000), S. 188-194 
    Details
    ISSN: 1432-069X
    Keywords: Key words Matrix metalloproteinase ; Extracellular ¶matrix ; Reactive oxygen species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Epidemiologic studies have indicated the association between tobacco smoking and skin aging, but the exact mechanism of tobacco smoke-induced premature skin aging is currently unknown. In this study, we investigated the alterations of collagen, matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in human fibroblasts treated with tobacco smoke extract. Human fibroblasts were exposed to different concentrations of water-soluble extract from tobacco smoke. Human fibroblasts irradiated with ultraviolet A1 (UVA1) were used as positive controls because the mechanism of UVA1-mediated MMP expression has been well characterized. The expression of MMP and TIMP was analyzed semiquantitatively following reverse transcriptase-polymerase chain reaction. Production of type I and type III collagens was detected by Western blotting and biosynthesis of new collagen was assessed by 3H-proline incorporation. Upon treatment with tobacco smoke extract or UVA1 irradiation, the expression of MMP-1 and MMP-3 mRNA was significantly increased in a dose-dependent manner. Maximum induction was observed with 25 μl/ml tobacco smoke extract. In contrast, the expression of TIMP-1 and TIMP-3 mRNA remained unchanged. Western blotting of the supernatant revealed that type I and type III collagens were decreased as compared with untreated controls. Collagen biosynthesis was significantly reduced by 40.1% following treatment with ¶25 μl/ml tobacco smoke extract. Sodium azide, l-ascorbic acid and Trolox (a water-soluble vitamin E) prevented both the UVA1- and the tobacco-induced alteration of MMP-1. These observations suggest that the imbalance of connective tissue matrix components might contribute to the molecular basis for premature skin aging in smokers. They also suggest that reactive oxygen species including singlet oxygen mediate this process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004030050476
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Structure/property relationships in LCP/PEI blends revealed with a new selective etching process (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 97-105 
    Details
    ISSN: 1435-1536
    Keywords: Liquidcrystalpolymer (LCP) ; polyethermide (PEI) ; structure ; etching ; processing behaviour ; rheology ; mechanical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An etching technique for making visible the morphology of blends composed of polyetherimide and a liquid crystalline fully aromatic copolyester (LCP) has been developed. The four organic solvents-tetrachloroethane, N-methylpyrrolidone (NMP), dimethylformamide (DMF) and dimethylacetamide (DMAc)-selectively etch the polyetherimide without attacking the LCP component. By adjusting the etching conditions to the respective conditions prevailing within the samples, all the four solvents yielded equally good results across the entire concentration range investigated (from 20/80 to 80/20 percent by weight of LCP/PEI). The viscosith of the LCPs decreases markedly with increasing shear rate. The large shear rate gradient from the mould edges to the centre results in different deformations of different volume elements within the melt. The resulting frozenin morphologies can be visualized with the new etching technique. This allows one to explain certain correlations between morphology and mechnical properties of the respective samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652175
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...