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  • 1980-1984  (10)
  • 1
    Electronic Resource
    Electronic Resource
    Pyruvate Carboxylase Activity in Primary Cultures of Astrocytes and Neurons (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 41 (1983), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The activity of the pyruvate carboxylase was determined in brains of newborn and adult mice as well as primary cultures of astrocytes, of cerebral cortex neurons, and of cerebellar granule cells. The activity was found to be 0.25 ± 0.14, 1.24 ± 0.07, and 1.75 ± 0.13 nmol min−1 mg−1 protein in, respectively, neonatal brain, adult brain, and astrocytes. Neither of the two types of neurons showed any detectable enzyme activity (i.e., 〈 0.05 nmol min−1 mg−1). It is therefore concluded that pyruvate carboxylase is an astrocytic enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb00849.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Homo-β-Proline and Other Heterocyclic GAB A Analogues on GABA Uptake in Neurons and Astroglial Cells and on GABA Receptor Binding (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 37 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Two groups of GABA (γ-aminobutyric acid) analogues, one comprising derivatives of β-proline and the other compounds structurally related to nipecotic acid, were investigated as potential inhibitors of high-affinity GABA transport in neurons and glial cells, as well as displacers of GABA receptor binding. In addition to cis-4-hydroxynipecotic acid, which is known as a potent inhibitor of GABA uptake, homo-β-proline was the only compound which proved to be a potent inhibitor of glial as well as neuronal GABA uptake. IC50 values for GABA uptake into glial cells and brain cortex “prisms” were 20 and 75 μM, respectively, and the IC50 value obtained for GABA uptake into cultured neurons was 10 μM. A kinetic analysis of the action of homo-β-proline on GABA uptake into cultured astrocytes and neurons showed that this compound acts as a competitive inhibitor of GABA uptake in both cell types. From the apparent Km values, Ki values for homo-β-proline of 16 and 6 μM could be calculated for glial and neuronal uptake, respectively. This mechanism of action strongly suggests that homo-β-proline interacts with the GABA carriers. Furthermore, homo-β-proline also displaced GABA from its receptor with an IC50 value of 0.3 μM. The cis-4-hydroxynipecotic acid analogues, cis- and trans-4-mercaptonipecotic acid, had no inhibitory effect on glial or neuronal GABA uptake. Other SH reagents, PCMB, NEM and DTNB, were shown to be relatively weak inhibitors of GABA uptake into cultured astrocytes, suggesting that SH groups are not directly involved in the interaction between GABA and its transport carrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb06320.x
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  • 3
    Electronic Resource
    Electronic Resource
    Induction by Hydrocortisone of Glutamine Synthetase in Mouse Primary Astrocyte Cultures (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 36 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Glutaminc synthetase activity was investigated in developing primary astroglial cultures established from newborn mouse cerebral hemispheres. Between the 2nd and 4th week of culture there was little change in activity under our standard culturing conditions; however, when hydrocortiwne (10 μM) was added to the cultures for 48 h, the enzyme activity increased two- to fourfold, depending upon the age of the culture, with maximum response in 2-week-old cultures. The addition of dibutyryl cyclic AMP (dRcAMP) to the culture medium caused morphological differentiation of the astroglial cells but eliminated the response of the cells to hydrocortisone. Culturing in elevated serum levels, which delays morphological differentiation and inhibits astroglial cytodifferentiation after exposure to dBcAMP, shifted the time of maximal response to hydrocortisone from 2 to 3 weeks and prevented the abolishment of glutamine synthetase induction by dBcAMP. The induction of glutamine synthetase by hydrocortisone was prevented by actinomycin D (0.5 μg/ml), indicating its dependence upon RNA and protein synthesis. The present work thus confirms reports in the literature that hydrocortisone induces glutamine synthetase in neural tissues, but differs from the findings of Moscona and co-workers in the chick retina that intact tissues are required for the induction to occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb02388.x
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  • 4
    Electronic Resource
    Electronic Resource
    High-Affinity Uptake of (RS)-Nipecotic Acid in Astrocytes Cultured from Mouse Brain. Comparison with GABA Transport (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 34 (1980), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: (RS)-Nipecotic acid is taken up into cultured astrocytes by a saturable high-affinity transport system with a Km, of 28.8 ± 2.8 μM and a Vmax of 0.294 ± 0.022 nmol × min−1× [mg cell protein]−1. The uptake which represents a net inward transport was sodium-dependent, requiring translocation of one sodium ion for each molecule of nipecotic acid taken up. The most potent inhibitors of GABA uptake into astrocytes (GABA, (R)-nipecotic acid, (3RS,4SR)-4-hydroxynipecotic acid, and guvacine) were shown to be potent inhibitors of nipecotic acid uptake (IC50) 20, 25, 25, and 50 μm respectively), GABA being a competitive inhibitor. (S)-2,4-Diaminobutyric acid was a more efficient inhibitor than β-alanine of glial uptake of (RS)-nipecotic acid. It is concluded that astroglial uptake of (RS)-nipecotic acid and GABA is mediated by the same transport system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1980.tb09673.x
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  • 5
    Electronic Resource
    Electronic Resource
    Piperidine-4-sulphonic Acid, a New Specific GAB A Agonist (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 34 (1980), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1980.tb11211.x
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  • 6
    Electronic Resource
    Electronic Resource
    Glial Marker Enzymes (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 15 (1982), S. 0 
    Details
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3083.1982.tb03772.x
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  • 7
    Electronic Resource
    Electronic Resource
    Characterization of L-glutamate uptake into and release from astrocytes and neurons cultured from different brain regions (1982)
    Springer
    Experimental brain research 47 (1982), S. 259-269 
    Details
    ISSN: 1432-1106
    Keywords: Glutamate uptake ; Glutamate analogues ; Sodium dependency ; Glutamate release ; Cultured astrocytes ; Cultured neurons ; Brain regions ; Granule cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The uptake of L-glutamate was studied in astrocytes cultured from different brain areas of newborn rats as well as in two different cultures of neurons obtained from mouse brain. Both astrocytes and neurons exhibited high-affinity glutamate uptake with Km values ranging from 34 [μM to 82 μM. Vmax values for astrocytes cultured from the different brain regions were: prefrontal cortex: 13.9; occipital cortex: 11.4; neostriatum: 27.3 and cerebellum: 5.8 nmol · min−1 · mg−1 cell protein. For cerebellar granule cells and cerebral cortical neurons the Vmax values were found to be 10.2 and 5.9 nmol · min−1 · mg−1 cell protein, respectively. The effect on L-glutamate uptake in astrocytes cultured from prefrontal cortex and in cultured cerebellar granule cells of a series of compounds structurally related to glutamate was studied, and detailed kinetic analyses of the inhibitory patterns of three potent inhibitors were performed. L-aspartate and L-aspartate-β-hydroxamate were found to be competitive inhibitors of L-glutamate uptake in both cell types with Ki values for astrocytes of 60 μM and 91 [μM, respectively, and for granule cells of 48 μM and 72 μM, respectively. D-aspartate was found to be a mixed-type noncompetitive inhibitor of L-glutamate uptake in astrocytes (K;: 106 μM), but in granule cells this compound showed simple competitive inhibition with a Ki of 49 μM. Sodium dependency of L-glutamate uptake in both cell types was studied at a series of Lglutamate and Na+ concentrations. It was found that the uptake of glutamate in astrocytes is coupled with one Na+ ion in contrast to two Na+ ions in granule cells. The Km value for sodium was found to be 15 mM in both cell types. It was shown that release of exogenously supplied [3H] -L-glutamate from cerebel lar granule cells could be stimulated in a Ca2+-dependent manner by high concentrations (55 mM) of K+. In contrast to this no K+-induced release of glutamate could be demonstrated in cultured astrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239385
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  • 8
    Electronic Resource
    Electronic Resource
    Comparison between (RS)-nipecotic acid and GABA transport in cultured astrocytes: Coupling with two sodium ions (1981)
    Springer
    Neurochemical research 6 (1981), S. 257-266 
    Details
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The sodium ion dependency of the uptake of (RS)-nipecotic acid into astrocytes in primary cultures has been studied by performing kinetic analysis at different sodium ion concentrations (16–151 mM).V max of the saturable component of the astroglial (RS-nipecotic acid uptake is clearly affected by the sodium ion concentration whereasK m surprisingly remains unaffected. At high (RS)-nipecotic acid concentrations (≧50 μM), uptake rates as a function of the sodium ion concentration were clearly sigmoid. This sigmoid shape was not obvious at lower concentrations of (RS)-nipecotic acid. The calculated Hill coefficients corresponding to all (RS)-nipecotic acid concentrations studied were approximately two. From these results it is concluded that (RS)-nipecotic acid uptake into astrocytes in primary cultures, like astroglical GABA uptake, requires the binding of at least two sodium ions per (RS)-nipecotic acid molecule transported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00964041
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  • 9
    Electronic Resource
    Electronic Resource
    Properties of phosphate activated glutaminase in astrocytes cultured from mouse brain (1982)
    Springer
    Neurochemical research 7 (1982), S. 761-770 
    Details
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Astrocytes in primary cultures contain a relatively high activity, of phosphate activated glutaminase, although it is significantly lower than that of synaptosomal enriched preparations. The relatively high glutaminase activity in the astrocytes appears not to be caused by substrate induction, since a 10-fold variation in the glutamine concentration of the culture medium does not affect the activity. Of the reaction products, only glutamate inhibits astrocytic glutaminase whereas that of synaptosomal enriched preparations is inhibited by both glutamate and ammonia. Similar to the synaptosomal enzyme, glutaminase in astrocytes is inhibited about 50% by N-ethylmaleimide, indicating N-ethylmaleimide-sensitive and-insensitive compartments of the enzyme. Calcium activates glutaminase in astrocytes as in synaptosomes, by promoting phosphate activation. Except for the lower activity and the lack of effect of ammonia, the properties of the astroglial glutaminase has been found to be no different from that of the synaptosomal one. The relatively unrestrained astroglial glutaminase may, however, argue against the concept of a glutamine cycle operating in a stoichiometric manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00965528
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of uptake and release processes ford- andl-aspartate in primary cultures of astrocytes and cerebellar granule cells (1983)
    Springer
    Neurochemical research 8 (1983), S. 231-243 
    Details
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The uptake ofl-andd-aspartate was studied in astrocytes cultured from prefrontal cortex and in granule cells cultured from cerebellum. A high affinity uptake system forl- andd-aspartate was found in both cell types, and the two stereoisomers exhibited essentially the sameK m - andV max -values in bouth astrocytes (l-aspartate:K m 77 μM;V max 11.8 nmol×min−1×mg−1;d-aspartate:K m 83 μM;V max 14.0 nmol×min−1×mg−1) and granule cells (l-aspartate:K m 32 μM;V max 2.8 nmol ×min−1×mg−1;d-aspartate:K m 26 μM;V max 3.0 nmol×min−1×mg−1). To investigate whetherl-glutamate,l-aspartate andd-aspartate use the same uptake system a detailed kenetic analysis was performed. The uptake kinetics of each one of the three amino acids was studied in the presence of the two other amino acids, and no essential differences between the uptake characteristics of the amino acids were found. In addition to the uptake studies the release ofD-aspartate from cerebellar granule cells was investigated and compared withl-glutamate release. A Ca2+-dependent, K+-induced release was found for both amino acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00963923
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