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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Applied categorical structures 2 (1994), S. 315-329 
    ISSN: 1572-9095
    Schlagwort(e): Primary 18A40 ; Secondary 18A30 ; 13B30 ; Monoreflection ; functorial ring of quotients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract It is shown that, in a category with a specified class ℳ of monics and under some mild hypothesis,there is a monoreflection maximum among those whose reflection maps lie in ℳ. Thus, for example, any variety, and “most” SP-classes in a variety, have both amaximum monoreflection and amaximum essential reflection (which might be the same, but frequently aren't, and which might be the identity functor, but frequently aren't). And, for example, under some mild hypotheses, beneath each “completion” lies a maximum monoreflection, so that, for example, any “category of rings” has amaximum functorial ring of quotients.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-4919
    Schlagwort(e): Stypopodium flabelliforme ; 14-keto-stypodiol diacetate ; DU-145 cell line ; microtubule assembly ; cell proliferation ; plasminogen activator (u-PA) ; tumor invasiveness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract We investigated the effects of the drug 14-keto-stypodiol diacetate (SDA) extracted from the seaweed product Stypopodium flabelliforme, in inhibiting the cell growth and tumor invasive behavior of DU-145 human prostate cells. In addition, the molecular action of the drug on microtubule assembly was analyzed. The effects of this diterpenoid drug in cell proliferation of DU-145 tumor cells in culture revealed that SDA at concentrations of 5 μM decreased cell growth by 14%, while at 45 μM a 61% decrease was found, as compared with control cells incubated with the solvent but in the absence of the drug. To study their effects on the cell cycle, DU-145 cells were incubated with increasing concentrations of SDA and the distribution of cell-cycle stages was analyzed by flow cytometry. Interestingly, the data showed that 14-keto-stypodiol diacetate dramatically increased the proportion of cells in the G2/M phases, and decreased the number of cells at the S phase of mitosis, as compared with appropriate controls. Studies on their action on the in vitro assembly of microtubules using purified brain tubulin, showed that SDA delayed the lag period associated to nucleation events during assembly, and decreased significantly the extent of polymerization. The studies suggest that this novel derivative from a marine natural product induces mitotic arrest of tumor cells, an effect that could be associated to alterations in the normal microtubule assembly process. On the other hand, a salient feature of this compound is that it affected protease secretion and the in vitro invasive capacity, both properties of cells from metastases. The secretion of plasminogen activator (u-PA) and the capacity of DU-145 cells to migrate through a Matrigel-coated membrane were significantly inhibited in the presence of micromolar concentrations of SDA. These results provide new keys to analyze the functional relationships between protease secretion, invasive behavior of tumor cells and the microtubule network.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Acta applicandae mathematicae 27 (1992), S. 55-65 
    ISSN: 1572-9036
    Schlagwort(e): 13B30 ; 54C99 ; commutative ring ; fraction-dense ring ; fraction dense space
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A fraction-dense (semi-prime) commutative ring A with 1 is one for which the classical quotient ring is rigid in its maximal quotient ring. The fraction-dense f-rings are characterized as those for which the space of minimal prime ideals is compact and extremally disconnected. For Archimedean lattice-ordered groups with this property it is shown that the Dedekind and order completion coincide. Fraction-dense spaces are defined as those for which C (X) is fraction-dense. If X is compact, then this notion is equivalent to the coincidence of the absolute of X and its quasi-F cover.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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