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  • 1
    Electronic Resource
    Electronic Resource
    MYELIN BASIC PROTEIN PHOSPHATASE ACTIVITY IN RAT BRAIN (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Previous work from this and other laboratories has demonstrated phosphorylation of myelin BP in vivo and in vitro. The rapid turnover of BP phosphate has suggested the presence of a phosphatase. The present studies have identified two BP phosphatases. One is present in the cytosol of rat brain homogenate. It has the highest specific activity (37 pmol/min/mg) and total activity of BP phosphatase present in any subcellular fraction. The partially purified cytosol enzyme can readily dephosphorylate soluble 32P-labelled BP but is only half as effective in dephosphorylating membrane-bound BP. Conversely, the phosphatase which remains associated with highly purified myelin is 2.3 times as effective on BP in the membrane (7.2 pmol/min/mg) as on soluble BP (3.2 pmol/min/mg). The myelin phosphatase is tightly bound to the membrane and cannot be removed with concentrated salt solutions. During development the specific activity of the cytosol phosphatase remains constant. The specific activity of the myelin phosphatase, however, is twice as high during the period of maximum myelin formation (6.8 pmol/min/mg at 18 days) as it is in adult myelin (3.2 pmol/min/mg at 12 weeks).In order to compare enzyme effectiveness under the various conditions employed in these studies, we have assumed that both soluble and particulate substrates are phosphorylated at equivalent sites on the polypeptide. We have further assumed that soluble and/or particulate substrates are dephosphorylated at equivalent sites on the polypeptide chain and that the various particulate and soluble enzymes have comparable access to the substrate. Within the limitations of these assumptions, our data suggest myelin phosphatase may play a significant role in phosphate turnover of BP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1977.tb03920.x
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  • 2
    Electronic Resource
    Electronic Resource
    HEXOSE MONOPHOSPHATE PATHWAY IN SYNAPSES (1970)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 17 (1970), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Synaptosomes isolated from rat cerebral cortex converted [l-14C]glucose more rapidly than [6-24C]glucose to ,14CO2. The ratio of C-l: C-6 in 14CO2 was 3-9, thus suggesting that the hexose monophosphate shunt (HMP) pathway was functional in synapses in vitro. When changes in the ratio of C-l: C-6 in 14CO2 were used as an index of shunt activity, glucose oxidation by this route was stimulated by electron acceptors as well as by neurohormones, including norepinephrine, acetylcholine and serotonin. Brain mince also exhibited a C-l: C-6 ratio of 3-2 when short (15 min) incubations were employed. Negative results previously reported are attributable to prolonged incubation during which depletion of NADP or randomization of the labelled carbons in radioactive glucose could have occurred. Our experiments excluded the incorporation of glucose into macromolecules as a specific role for the hexose monophosphate pathway. The generation of NADPH for numerous metabolic reactions including the maintenance of membrane SH groups and the oxidation and hydroxylation reactions may represent the functions of the hexose monophosphate in synaptosomes and account for its stimulation by neurohormones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1970.tb11386.x
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis de novo of purines in slices of rat brain and liver (1970)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 17 (1970), 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.1471-4159.1970.tb00509.x
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  • 4
    Electronic Resource
    Electronic Resource
    PYRIMIDINE SYNTHESIS IN TISSUE CULTURE (1968)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 15 (1968), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Myelinated cerebellar tissue culture (organ culture) was used to assess the salvage and de novo pathways of pyrimidine synthesis in mammalian brain. Radioactive orotic acid and carbamyl aspartic acid were readily incorporated into UMP and into perchloric acid-insoluble RNA. The incorporation was effectively blocked by azauridine. Neither radioactive sodium bicarbonate or citrulline was incorporated into UMP or blocked by azauridine. [3H]Uridine, on the other hand, rapidly entered the cultures, was incorporated into UMP and perchloric acid-insoluble material, and was partially inhibited by azauridine. The failure to demonstrate activity of carbamyl phosphate synthetase suggests the potential importance of the salvage pathway and the likely dependence of the brain upon exogenous and endogenous pyrimidine precursors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1968.tb05925.x
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  • 5
    Electronic Resource
    Electronic Resource
    CHOLINERGIC SITES IN SKELETAL MUSCLE: INTERACTION WITH CONCANAVALIN A (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract– The interaction of normal and denervated skeletal muscle cholinergic sites with the lectin concanavalin A and concanavalin A-Sepharose are detailed. Concanavalin A blocks the binding of 125I-α-bungarotoxin to both the high and low affinity sets of cholinergic sites described previously. The characteristics of the block of 125I-α-bungarotoxin binding to the high affinity set (acetylcholine receptor) is not competitive. The data suggest that the concanavalin binds multivalently to the macro-molecular complex containing the ACh receptor site and sterically prevents the α-bungarotoxin binding. The interaction of both sets of cholinergic sites with concanavalin A-Sepharose was also studied. The macromolecule(s) containing both the high and low affinity sets of sites bind to the concanavalin A-Sepharose. The data indicate a multivalent association with the affinity resin. Following the affinity procedure, a partial purification in both sets of sites is effected. The equilibrium binding of 125I-diiodo-α-bungarotoxin to the preparations from the affinity procedure (both normal and denervated muscle) was examined. The KD of the α-bungarotoxin binding to the high affinity sets of sites (acetylcholine receptor) in both normal and denervated preparations changes from ∼10−9mol/l to ∼ 10−10 mol/l following purification. No change in the KD of the α-bungarotoxin binding to the low affinity set of sites was observed following purification. The 125l-α-bungarotoxin binding to the partially purified acetylcholine receptor was blocked by unlabelled α-bungarotoxin, concanavalin A, d-tubocurarine and carbamylcholine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1976.tb02637.x
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  • 6
    Electronic Resource
    Electronic Resource
    Phosphatidyl inositol turnover in muscle membranes following denervation (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), 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.1471-4159.1974.tb10760.x
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  • 7
    Electronic Resource
    Electronic Resource
    THE EFFECTS OF ELECTROSHOCK SEIZURES ON POTASSIUM TRANSPORT WITHIN SYNAPTOSOMES FROM RAT BRAIN (1972)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 19 (1972), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —Potassium transport was assessed within synaptic terminals isolated from cerebral cortices of rats which experienced one or two maximal electroshock (ES) convulsions daily. No significant change in endogenous K content was present after 2 consecutive days of ES-seizures. However, K decreased 22 % and 41 % after 4 and 6 days of convulsions respectively. After 6 days, synaptosomes from ES rats were able to accumulate K to the same extent as controls and were inhibited by ouabain to an equivalent extent (50%). When these synaptosomes from ES rats were preloaded with high concentrations of K, K leaked out at an increased rate. When diphenylhydantoin (DPH) was administered intraperitoneally from the second to the sixth day of ES-convulsions, the decrease in endogenous K induced by chronic convulsions was corrected. In ion-free media or with 50 mM Na, DPH had no effects on the enhanced efflux of K observed in vitro after ES-seizures. However, with high Na (50–100 mm) and low K (0.2–1 mm) DPH stimulated K uptake but did not affect the ouabain inhibition. Under conditions optimal for K uptake (50 mm Na and 10 mm K), DPH did not affect K accumulation but it prevented in vitro ouabain inhibition. Our results indicate that repeated ES-convulsions decreased K content within isolated nerve terminals by enhancing its passive leakage. In vivo DPH prevented the effects of ES-seizures by stimulating the Na-K pump and not by directly blocking the K leak.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1972.tb06208.x
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  • 8
    Electronic Resource
    Electronic Resource
    INCORPORATION OF [14C]GLUCOSAMINE INTO SYNAPTOSOMES IN VITRO (1971)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 18 (1971), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Synaptosomes isolated from rat cerebral cortex by zonal centrifugation in-corporated radioactive glucosamine into macromolecules in vitro as glucosamine, galactosamine, N-acetylneuraminic acid, and glucuronic acid. The largest percentage of incorporated radioactivity was recovered in the particulate fraction in which radioactive carbohydrates were bound in covalent linkage requiring acid hydrolysis or enzymatic digestion for release. Less than 20 per cent of the particulate radioactivity represented incorporation into gangliosides. Some 20 per cent of the radioactivity was incorporated into proteins as glucosamine, identified in hydrolysates by paper chromatography and by the amino acid analyser. After incubation, radioactivity was demonstrable in the proteins as sialic acid by paper chromatography and specific enzymic digestion; and as glucuronic acid by chromatography, electrophoresis, and digestion with hyaluronidase.Incorporation of carbohydrate was stimulated by sodium and potassium at concentrations demonstrated to enhance incorporation of amino acids, and involved the macro-molecules of all subsynaptosomal fractions. Significant incorporation of radioactivity was found in the synaptic plasma membrane. The synthesis of glycoproteins was suggested by simultaneous incorporation of [14C]glucosamine and [3H]leucine into glycopeptides subsequently hydrolysed and subjected to polyacrylamide gel electrophoresis and two-dimensional paper chromatography and electrophoresis. Such studies demonstrated that amino acids and carbohydrates may be incorporated into glycoproteins of the synaptic membrane and suggest the possibility of local synthesis as well as modification of material brought to the nerve ending by axoplasmic flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1971.tb09593.x
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  • 9
    Electronic Resource
    Electronic Resource
    THE CONTRIBUTION OF AXOPLASMIC FLOW IN OPTIC NERVE AND PROTEIN SYNTHESIS WITHIN THE OPTIC TECTUM TO SYNAPTIC MEMBRANE PROTEINS OF THE CHICK OPTIC TECTUM (1973)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 20 (1973), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In the 5-day-old chick, radioactive leucine was incorporated into proteins of synaptosomal and subsynaptosomal fractions both by fast axoplasmic flow and synthesis within the optic tectum. The distribution of radioactivity in subsynaptosomal fractions suggested that both pathways contribute to the protein constituents of each fraction. The relative contributions to each fraction were similar except for the supernatant proteins, for which fast axoplasmic flow contributed less than the synthesis within the optic tectum. The qualitative contribution of fast flow and synthesis within the optic tectum to the synaptic membrane fraction was distinctive. Fast axoplasmic flow preferentially labelled the high molecular weight proteins, whereas synthesis within the optic tectum labelled a larger percentage of smaller molecular weight proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1973.tb00286.x
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  • 10
    Electronic Resource
    Electronic Resource
    Trophic Factors in Neurologic Disease (1988)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Medicine 39 (1988), S. 193-201 
    Details
    ISSN: 0066-4219
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.me.39.020188.001205
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