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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
    l-[35S]CYSTINE UPTAKE BY RAT BRAIN SYNAPTOSOMES (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 33 (1979), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The uptake of [35S]cystine at 37°C by synaptosomal fractions isolated from adult rat cerebrum can be divided into two components. About 60% of the uptake is due to binding to synaptosomal proteins while the remainder exists as a free amino acid pool. Chemical analysis of this soluble component indicates that considerable reduction of cystine to cysteine occurs with 75% or more of the labeled molecular species being cysteine. The process involved in the uptake into the soluble pool was composed of two saturable systems with apparent Km values of 0.14 and 1.4 mm. The low Km system was sodium and oxygen independent but inhibited by dinitrophenol. Dibasic amino acids, lysine, arginine and ornithine, did not inhibit cystine uptake. The characteristics of cystine uptake by synaptosomes from newborn brain are very similar to those of adult brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1979.tb05214.x
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  • 3
    Electronic Resource
    Electronic Resource
    DEVELOPMENTAL AND OTHER ASPECTS OF [35S]CYSTEINE TRANSPORT BY RAT BRAIN SYNAPTOSOMES (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 33 (1979), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Cysteine uptake by rat brain synaptosomes occurs by active transport. The uptake by synaptosomes isolated from newborn brain is slower and the concentration gradient achieved is lower than that observed in adult tissue. Synaptosomal fractions from both adult and newborn rat brains accumulate cysteine by two saturable systems. The calculated parameters show that the maximum rates of cysteine uptake in adult synaptosomes are approximately twice that observed in newborn synaptosomes for both the high and low affinity systems. The uptake by the high affinity system is sodium dependent and is inhibited by glycine and dibasic amino acids. Uptake by synaptosomes from 14-day-old animals is close to that observed in adult tissue. The uptake of cysteine differs greatly from that of cystine since the oxidized form, cystine, is taken up more slowly by systems with low affinities which are sodium independent, do not interact with dibasic amino acids and are independent of age.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1979.tb05277.x
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental Galactose Toxicity: Effects on Synaptosomal Phosphatidylinositol Metabolism (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 Experimental galactose toxicity was induced by weaning rats onto an isocaloric 40% galactose diet. Synaptosomes were prepared from cerebra of rats at 2-9 weeks post-weaning and incubated with [33P]Pi and myo-[2-3H]inositol in the presence or absence of 0.2 mM-acetylcholine. The acetylcholine-stimulated [33P]Pi labeling of phosphatidylinositol and the changes in amounts of phosphatidylinositol were similar in the normal and galactose-toxic rats; however, acetylcholine-stimulated myo-[2-3H]inositol labeling of phosphatidylinositol was markedly decreased in the galactose-toxic rats. The impairment of acetylcholine-stimulated myo-[2-3H]inositol incorporation into phosphatidylinositol observed after 2 weeks on the diet did not vary after more prolonged exposure to galactose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb04475.x
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  • 5
    Electronic Resource
    Electronic Resource
    A NEW INCUBATION TECHNIQUE FOR THE STUDY OF SYNAPTOSOMAL TRANSPORT (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 30 (1978), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A simple, inexpensive method is described for the incubation and study of transport in synaptosomes. This method avoids the many potential sources of error inherent in the methods currently in use. The transport of two sugars and two amino acids has been studied, using this system, and the resulting data is compared to similar studies already published by others. A steady-state was achieved and maintained for 60 min independent of tissue concentration, except in the case of γ-aminobutyric acid. An analysis of the entry kinetics of 2-deoxy-d-glucose has been performed, the results indicating that the present method offers the advantage of substantially increasing oxygenation and hence, efficiency of the uptake. Using α-aminoisobutyric acid, analysis of substrate flux within the system was performed, illustrating the utility of the method. The specific advantages offered by the technique over other methods in use are discussed. It is concluded that adequate oxygenation of the synaptosome during study is essential to reliable results and can easily be achieved by means of the methodology described in this report.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1978.tb06545.x
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  • 6
    Electronic Resource
    Electronic Resource
    Uptake of L-[14C]Proline by Isolated Rat Brain Capillaries (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 40 (1983), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Rat brain capillaries exhibit concentrative uptake of l-proline. The uptake is mediated by two saturable systems, one with a Km of 0.11 mM and another with a Km of 5.9 mM. Entry also occurred by diffusion, especially at high substrate concentrations. The saturable high-affinity system is sodium-dependent, with a Km for sodium of 36 mM. Proline uptake is not inhibited by lysine, but is inhibited by phenylalanine, glycine and leucine. α-Methylaminoisobutyric acid (MeAIB), a model for sodium-requiring transport systems, is a competitive inhibitor of the low-Km system. b-2-Aminobicyclo-[2, 2, 1]-heptane-2-carboxylic acid (BCH), a model for nonsodium-dependent transport, however, also inhibited proline uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb11285.x
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  • 7
    Electronic Resource
    Electronic Resource
    On the Ability of Galactose to Influence Hexose and Amino Acid Uptake by Isolated Rat Brain Capillaries (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 40 (1983), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The uptake of glucose, 2-deoxyglucose, proline, methionine, and α-methylamino isobutyric acid was studied in brain capillaries preincubated with 50 mM galactose either in vitro or isolated from galactose-fed rats. The uptake was not decreased in both cases. The linear rate of glucose oxidation by capillaries was also not altered by preincubation with galactose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb13579.x
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  • 8
    Electronic Resource
    Electronic Resource
    Uptake of l-[35S]Cystine by Isolated Rat Brain Capillaries (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 35 (1980), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Adult rat brain capillaries were isolated by a simplified procedure and showed an enrichment of the marker enzyme, γ-glutamyltranspeptidase. The uptake of [35S]cystine at 37°C by this preparation can be divided into two components, a sodium- and energy-dependent transport process for the free amino acid pool, with an apparent Km of 36 μm, and a binding process, with an apparent Km of 1.13 mm. Chemical analysis of the amino acid pool indicates that cystine is the major form of intracapillary 35S. Cystine transport was not inhibited by lysine, but glycine, α-methylaminoisobutyric acid and β-2-aminobicyclo-[2,2,1]-heptane-2-carboxylic acid were inhibitory to a small extent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1980.tb06281.x
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  • 9
    Electronic Resource
    Electronic Resource
    ON THE UPTAKE OF INOSITOL BY RAT BRAIN SYNAPTOSOMES (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 31 (1978), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The uptake of inositol by rat brain synaptosomes occurs via an unsaturable process that even at substrate concentrations as low as 1 μM is unable to achieve a concentration gradient indicative of active transport. Dinitrophenol, ouabain and cytochalasin B did not affect uptake of the cyclitol. The data indicate that inositol uptake by rat synaptosomes occurs by diffusion or by a system with an affinity so low it is difficult to discern. The low capacity, saturable inositol uptake system observed in rabbit brain slices may reflect a species difference or uptake by elements of the slice other than neuronal membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1978.tb00133.x
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  • 10
    Electronic Resource
    Electronic Resource
    A CONCEPT OF THE MECHANISM OF SULFONYLUREA-INDUCED HYPOGLYCEMIA BASED ON STUDIES OF GLUCOSE AND PENTOSE DISPOSITION IN MAN (1957)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 71 (1957), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1957.tb54578.x
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