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  • 1
    Electronic Resource
    Electronic Resource
    Phosphatidylinositol:myo-Inositol Exchange Activity in Intact Nerve Endings: Substrate and Cofactor Dependence, Nucleotide Specificity, and Effect on Synaptosomal Handling of myo-Inositol (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Micromolar concentrations of CMP produced a large increase in Mn2+ -dependent phosphatidylinositol:myo-inositol exchange activity in isolated nerve endings or synaptosomes. The apparent Km for CMP was 2 μM, and that for myo-inositol was 38 μM. Only cytidine nucleotides were capable of enhancing activity, and this effect is probably specific for CMP, because the synaptosomal preparation rapidly converted CTP or CDP to CMP. Manganese did not affect the uptake of myo-inositol into the synaptosomal cytosolic fraction or myo-inositol levels. Determinations of myo-inositol specific activity showed that the Mn2+-enhanced labeling of phosphatidylinositol was not accompanied by a decrease of label content in free myo-inositol. This lack of an effect on intrasynaptosomal myo-inositol and the dependence of exchange on cytidine nucleotides whereas cytidine itself was previously found to be without effect show that for the bulk of Mn2+-dependent exchange activity, it is the myo-inositol in the incubation medium that is being directly incorporated into membrane-bound phosphatidylinositol. Because CMP dependence is the hallmark of exchange catalyzed by CDP-diacylglycerol:inositol phosphatidyl transferase, this enzyme is likely to be responsible for most of the exchange activity in synaptosomes. The strong affinity of this exchange system for CMP suggests that endogenous levels of this nucleotide might support Mn2+-dependent exchange in the absence of added nucleotide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00620.x
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  • 2
    Electronic Resource
    Electronic Resource
    Galactose-1-phosphate uridyl transferase in density-fractionated erythrocytes (1989)
    Springer
    Human genetics 〈Berlin〉 82 (1989), S. 99-103 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Galactose-1-phosphate uridyl transferase (GALT), the deficient enzyme in classical galactosemia, was studied by Percoll-gradient age-fractionation of erythrocytes. For normal GALT, a rapid and substantial decrease in GALT activity and loss of most of two isozymes was found to occur in the reticulocyte fractions. The loss of activity was then followed by relative stabilization of both GALT-specific activity and microheterogeneity in mature and aging erythrocytes. When applied to the study of mutant GALT from galactosemic patients, the Percoll-gradient fractionation method permitted detection in the reticulocyte-enriched fractions of up to 5% of normal GALT-specific activity and an isoelectric focusing pattern essentially the same as that of normal GALT. Percoll-gradient fractionation of erythrocytes offers a simple and direct method to study characteristics of GALT activity and microheterogeneity in normal and galactosemic human erythrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00284037
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Characteristics of L-proline and sodium transport in renal brush border membranes isolated from 7-day-old and adult rats (1989)
    Springer
    Bioscience reports 9 (1989), S. 709-719 
    Details
    ISSN: 1573-4935
    Keywords: Ontogeny ; renal membrane transport ; proline ; sodium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract To explore the nature of differences in uptake by renal brush border vesicles from animals of different ages, vesicles were isolated from 7-day old and adult rats by a Mg-aggregation method. A number of criteria were compared in vesicles from the young and mature animals. The vesicles isolated from animals of both ages appear similar on electron microscopy, in response to osmotic changes, and in uptake kinetics for L-glucose. Despite these parameters which indicate no basic differences between the membranes of young and mature kidney, differences in proline and sodium handling are seen. When compared to the uptake pattern seen in vesicles from adult animals, the height of the sodium gradient-stimulated proline overshoot is diminished and sodium entry is faster in vesicles of the 7-day old rats. These are the same differences which were found in vesicles prepared by differential centrifugation from 7-day old animals. In addition, although sodium efflux was faster from vesicles of immature kidney and mirrored the faster sodium entry, proline efflux was slower. The data indicate a dissociation of proline and sodium fluxes in brush borders of the young rat kidney.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01114809
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Cystine-glutamate transport interactions in rat renal cortical tubules, brushborder vesicles, and cultured renal tubule cells (1986)
    Springer
    Bioscience reports 6 (1986), S. 113-119 
    Details
    ISSN: 1573-4935
    Keywords: amino acid transport ; renal tubule ; brushborder membrane ; cystine ; glutamate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Glutamate had no significant effect on the uptake of 0.025 mM cystine by isolated rat renal cortical tubules and brushborder membrane vesicles in contrast to lysine which significantly inhibits cystine transport. Glutamate, however, markedly inhibited cystine uptake by rat renal tubule cells grown in a serum-free, hormonally defined media for 5 days. Lysine also inhibited cystine transport in these cultured renal tubule cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01145186
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    Paper (German National Licenses)
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