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  • 1995-1999  (2)
  • 1980-1984
  • 129Xe NMR spectroscopy  (1)
  • Vesicle formation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Zeolite ZnY catalysts prepared by solid-state ion exchange (1998)
    Springer
    Catalysis letters 51 (1998), S. 213-218 
    Details
    ISSN: 1572-879X
    Keywords: zeolite ZnY ; solid-state ion exchange ; salt inclusion ; 129Xe NMR spectroscopy ; adsorption of carbon monoxide and xenon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolites ZnY with various overall zinc contents were prepared from mixtures of zeolite NH4Y and crystalline zinc chloride by solid-state ion exchange. The obtained materials were investigated with carbon monoxide, xenon, and nitrogen adsorption as well as with 129Xe NMR and XRF spectroscopy. From the results of these measurements, the zinc cation distributions between the different types of cages of the faujasite framework as well as between the crystallographic positions SIII and SII within the large voids (supercages) were quantitatively determined. The concentrations of zinc cations in the supercages of the presently prepared zeolites are considerably higher than in materials obtained from NaY by conventional wet ion exchange using aqueous zinc salt solutions. Experimental evidence is provided for salt inclusion under certain conditions of preparation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019009706584
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Intracellular localization, vesicular accumulation and kinetics of daunorubicin in sensitive and multidrug-resistant gastric carcinoma EPG85-257 cells (1995)
    Springer
    Virchows Archiv 426 (1995), S. 249-256 
    Details
    ISSN: 1432-2307
    Keywords: P-Glycoprotein ; Multidrug resistance ; Vesicle formation ; Daunorubicin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the human gastric carcinoma cell line EPG85-257P (parent) induction of resistance to daunorubicin (DAU) was achieved by selection with stepwise increased concentrations of the drug. The new vairant was named EPG85-257DAU and was shown to overexpress the mdr1 gene product 170 kDa P-glycoprotein (P-Gp) as demonstrated by immunocytochemistry and mdr1-specific RT-PCR. To investigate the intracellular pathway of DAU the subcellular distribution of this autofluorescent drug was studied in the resistant cells and compared to its chemosensitive counterpart EPG85-257P. When sensitive cells were exposed to DAU the drug rapidly accumulated in the nucleus until cell death. No redistribution of DAU to the cytoplasm was observed. In resistant cells exposed to the drug DAU also accumulated in the nucleus but to a lesser extent than in parent cells. Following exposure, nuclear fluorescence was observed to decrease over a time period of up to 48 h. Six hours after DAU exposure formation of fluorescent vesicle formation started in the perinuclear region and increased continously. After 48 h nuclear fluorescence was no longer detectable and DAU was located exclusively in vesicles. During this period the vesicles moved from the region of origin to the cell periphery. A pulse chase experiment showed, that vesicles may contain DAU derived from the nucleus. Treatment of EPG85-257DAU cells with DAU in conjunction with the chemosensitizer cyclosporin A (CsA) increased nuclear fluorescence without impairing vesicle formation. Disruption of microtubules by nocodazole led to an accumulation of vesicles in the perinuclear region indicating that microtubules are involved in vesicular transport. Treatment of EPG85-257DAU cells with the actin disruptor cytochalasin B led to accumulation of vesicles in the cell periphery indicating that actin may be involved in exocytosis. Uptake and efflux of DAU and rhodamin (RH) were determined in sensitive and resistant cells using a fluorescence activated cell sorter. Uptake of both compounds was distinctly lower in resistant than in sensitive cells. When resistant cells preloaded for 2 h with RH subsequently were incubated in drug free medium the substance was rapidly released indicating transmembrane transport by P-Gp. In contrast, despite expression of P-Gp in resistant cells no considerable release of DAU was observed for up to 2 h under the same experimental protocol. This indicates that in resistant cells intracellular DAU at least in part may be inaccessible for P-Gp and that vesicular drug transport appears to contribute to DAU resistance by removing intracellular DAU via exocytosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00191362
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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