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  • 1
    Electronic Resource
    Electronic Resource
    Phosphate and carbonate ester aging reactions with .alpha.-chymotrypsin. Kinetics and mechanism (1972)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 94 (1972), S. 2101-2109 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00761a050
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  • 2
    Electronic Resource
    Electronic Resource
    Glutamine synthetase of Bacillus stearothermophilus. Regulation, site interactions, and functional information (1976)
    s.l. : American Chemical Society
    Biochemistry 15 (1976), S. 1749-1755 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00653a024
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  • 3
    Electronic Resource
    Electronic Resource
    Interaction of extrinic fluoresence probes with E. coli glutamine synthetase (1977)
    Springer
    Cellular and molecular life sciences 33 (1977), S. 1016-1018 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Binding of 2-p-toluidinylnaphthalene-6-sulfonate (TNS) to adenylylated $$E_{\overline {11} } $$ glutamine synthetase is cooperative and time-dependent, with 3 dye sites per subunit. In fluorescence polarization experiments TNS and pyrene butyrate give normalized Perrin plots that indicate a symmetrical arrangement of dye excited state dipoles, relative to the rotational axis of the oblate ellipsoid of the dodecameric native enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01945941
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  • 4
    Electronic Resource
    Electronic Resource
    Chick brain glutamine synthetase and Mn2+−Mg2+ interactions (1987)
    Springer
    Neurochemical research 12 (1987), S. 1041-1047 
    Details
    ISSN: 1573-6903
    Keywords: Chick brain ; glutamine synthetase ; enzyme purification ; physico-chemical characteristics ; cation effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Glutamine synthetase (GS) from the chick brain was purified to apparent homogeneity by ammonium sulfate fractionation followed by affinity chromatography, electrofocusing and Sephadex G-150 chromatography. The purified enzyme showed a single band on sodium dodecyl sulfate analysis in polyacrylamide gel. By sedimentation equilibrium analysis and gel electrophoresis analysis, it was shown that the enzyme has a subunit molecular weight of 45,000 and a native molecular weight of 364,000, which is consistent with an octameric structure. Sedimentation analysis in the presence of Mg2+ revealed three different forms of macromolecules corresponding respectively to a monomer, a tetramer and an octamer. Among eight cations tested (Ca2+, Co2+, Fe2+, Li+, Mg2+, Mn2+, Ni2+, Zn2+) only Co2+, Mg2+ and Mn2+ supported GS activity; the order of activatory ability was Mg2+〉Co2+〉Mn2+. The maximum activating effect of Mn2+ occurs only within a very narrow range of concentration: with an excess of cation causing strong inhibition of GS activity. For each cation, maximal GS activity occurs at a defined cation/ATP ratio. A regulatory system in which Mn2+, modulates the Mg2+ dependent GS activity, is proposed; such cation interactions may be of significance in the intracellular control of glutamine synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00970934
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  • 5
    Electronic Resource
    Electronic Resource
    Concentrations of physiologically important metal ions in glial cells cultured from chick cerebral cortex (1988)
    Springer
    Neurochemical research 13 (1988), S. 45-50 
    Details
    ISSN: 1573-6903
    Keywords: Manganese ; magnesium ; metal ions ; glial cells ; glutamine synthetase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Energy dispersive x-ray fluorescence and atomic absorption spectroscopy were used to determine the concentrations of Mg, Ca, Mn, Fe, Zn, and Cu in primary cultures of astroglial cells from chick embryo cortex in chemically defined serum-free growth medium. The intracellular volume of cultured glia was determined to be 8.34 μl/mg protein. Intracellular Mn, Fe, Zn, and Cu in these cells were ca. 10–200 μM, or 20–200 times the concentrations in the growth medium. Mg2+ was 7 mM in glial cells, only four-fold higher than in growth medium. Glutamine synthetase (GS), compartmentalized in glia, catalyzes a key step in the metabolism of neurotransmitterl-glutamate as part of the glutamate/glutamine cycle between neurons and glia. Hormones (insulin, hydrocortisone, and cAMP) added to growth medium differentially altered the activity of GS and the intracellular level of Mn(II), but not Mg(II). These findings suggest the possibility that glutamine synthetase activity could be regulated in brain by the intracellular levels of Mn(II) or the ratio of Mn(II)/Mg(II), which may in turn be controlled indirectly by means of transport processes that respond to hormones or secondary metabolic signals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00971853
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  • 6
    Electronic Resource
    Electronic Resource
    Levels and sub-cellular distribution of physiologically important metal ions in neuronal cells cultured from chick embryo cerebral cortex (1988)
    Springer
    Neurochemical research 13 (1988), S. 1163-1167 
    Details
    ISSN: 1573-6903
    Keywords: Manganese ; cations ; neurons ; superoxide ; dismutase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Mg2+, Ca2+, Mn2+, Zn2+, and Cu content of neurons from chick embryo cortex cultivated in chemically defined serum free growth medium was determined by energy dispersive X-ray fluorescence and atomic absorption spectroscopy. The intracellular volume of cultured neurons was determined to be 2.73 μl/mg. Intracellular Mn2+, Fe2+, Zn2+, and Cu2+ in the cultivated neurons were 100–200 times the concentrations in the growth medium: Mg2+ and Ca2+ were 0.9 and 1.7 mM respectively, around 20 fold higher than in growth medium. Mg2+, Fe2+, Cu2+ and Zn2+ concentrations in neurons were in the range of ca. 300–600 μM, approximately 2–3 times the values previously reported in glial cells; Ca2+ and Mn2+ content of the neurons were higher by 5 and 10 fold respectively compared to glial cells. In neurons, the subcellular distribution of Fe2+, Cu2+, and Mn2+ follows the rank order: cytosol〉microsomes〉mitochondria; for Zn2+ the distribution differs as following: cytosol 〉mitochondria〉microsomes. Determination of the superoxide dismutase activities in the cultivated neurons indicated that the Mn2+ linked activity predominates whereas, the Cu-Zn dependent enzyme is dominant in glial cells. Enrichment of the culture medium with Mn2+ to 2.5 μM enhanced the Mn-SOD by approximately 33% but Cu2+−Zn2+ enzyme activity was not modified. The high Mn2+ content, the capacity to accumulate Mn2+, and the predominancy of the Mn−SOD form observed in neurons is in accord with a fundamental functional role for this metal ion in this type of brain cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00971634
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  • 7
    Electronic Resource
    Electronic Resource
    Combined effects of ethanol and manganese on cultured neurons and glia (1991)
    Springer
    Neurochemical research 16 (1991), S. 591-596 
    Details
    ISSN: 1573-6903
    Keywords: Ethanol ; manganese ; cell cultures ; neurons ; glial cells ; enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Manganese is essential for normal development and activity of the nervous tissue. Mn2+ ions are involved in protein synthesis and may prevent free radical damage. Since it is now established that alcohol degradation may produce free radicals, we studied the effect of Mn2+ on ethanol induced alterations using cultured nerve cells as an experimental model of the central nervous system. Neurons and glial cells were cultured from rat brain cortex; a tumoral rat glial cell line (C6) was also examined. We measured enzymatic markers of nerve cell maturation (enolase, glutamine synthetase) and superoxide dismutase, a scavenger of free radicals; all these enzymes being activated by Mn2+ ions. Only for the glial cell types an alcohol antagonizing effect was found when Mn2+ was combined with ethanol. Neurons were not sensitive to that Mn2+ effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00974879
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  • 8
    Electronic Resource
    Electronic Resource
    Modulation of Mn2+ accumulation in cultured rat neuronal and astroglial cells (1990)
    Springer
    Neurochemical research 15 (1990), S. 751-754 
    Details
    ISSN: 1573-6903
    Keywords: Glial cells ; Neurons ; Mn2+ accumulation ; K+-effect ; trace elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of physiological concentrations of K+ on Mn2+ accumulation were compared in rat glial cells and neurons in culture. Increasing the K+ concentration in growth medium increased significantly the Mn2+ level of the cultivated cells, with glial cells more affected than neurons. Ethanol markedly increased the Mn2+ accumulation within glia but not within neurons while ouabaïn caused inhibition of Mn2+ uptake with neurons and glial cells. A modulation of the total protein synthesis by Mn2+ and ethanol level in the growth medium was observed with glial cells. These data suggest that the mechanisms involved in Mn2+ accumulation in glial cells are different from those present in neurons. Moreover, the results are consistent with the hypothesis that Mn2+ plays a regulatory role in glial cell metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973657
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of manganese on the development of glial cells cultured from prenatally alcohol exposed rats (1995)
    Springer
    Neurochemical research 20 (1995), S. 435-441 
    Details
    ISSN: 1573-6903
    Keywords: Alcohol ; manganese ; development ; cell culture ; enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Maternal alcohol abuse is known to produce retardation in brain maturation and brain functions. Using cultured glial cells as a model system to study these effects of alcohol we found an alcohol antagonizing property for manganese (Mn). Mn was added to the alcohol diet (MnCl2 25 mg/l of 20% v/v ethanol) of pregnant rats. Glial cells were cultured during 4 weeks from cortical brain cells of pups born to these mothers. Several biochemical parameters were examined: protein levels, enzymatic markers of glial cell maturation (enolase and glutamine synthetase), superoxide dismutase a scavenger of free radicals produced during alcohol degradation. The results were compared to appropriate controls. A beneficent effect of Mn was observed for the pups weight which was no more significantly different from the control values. Protein levels, enolase and glutamine synthetase activities were increased mainly during the proliferative period when Mn was added to the alcohol diet compared to the only alcohol treated animals. This Mn effect was not found for superoxide dismutase in cultured glial cells but exists in the total brain of the 2 week-old offspring. In the total 2 and 4 week-old brain the alcohol induced decrease of enolase and glutamine synthetase was also antagonized by the Mn suplementation. Our data suggest that Mn may act as a factor overcoming at least partially some aspects of alcohol induced retardation of nerve cell development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973099
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