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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 34 (1980), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Cell dissociates from embryonic chick dorsal root ganglia, incubated for 6 h with 22Na+, accumulated four to six times more radioactivity in the absence than in the presence of Nerve Growth Factor (NGF). The accumulation of radioactivity paralleled the external Na+ concentration, indicating that the cells may have been reaching equilibrium with the medium. Delayed presentation of NGF to 22Na+-loaded cells caused a rapid loss of radioactivity, even with extracellular 22Na+ still present, demonstrating that NGF caused an overall efflux of Na+ rather than an accelerated equilibration. The Na+ exclusion from 22Na+-loaded cells was dependent upon NGF concentration. Use of nutrient-rich medium, serum, and certain hormones and other proteins did not prevent the Na+ accumulation in the absence of NGF or its reversion by delayed NGF administration. Incubation of the ganglionic cells with ouabain or dinitrophenol during the 22Na+ loading period (no NGF) increased the rate, but not the magnitude, of loading. The same incubation carried out in a Na+-free medium and followed by 22Na+ presentation resulted in fast radioactive loading that was identical to that occurring in drug-free, NGF-deprived cells and was not prevented by presentation of NGF together with the 22Na+. These data are consistent with a model in which NGF acts through a Na+ pump rather than by restricting Na+ influxes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 32 (1979), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Nerve growth factor (NGF) at 10 B.U./ml produced a 5-fold increase in the concentration of cyclic AMP 10min after addition to freshly excised embryonic chick dorsal root ganglia (DRG). The presence of NGF at 10 B.U./ml, but not 1 B.U./ml, over a 6 h incubation in nutrient-free medium prevented this cyclic AMP increase when the DRG were again challenged with NGF (10 B.U./ml) after the 6 h. Incubation of DRG for 6 h at 37°C without NGF did not prevent the cyclic AMP response from occurring when NGF was presented at this time. The basal cyclic AMP concentration, however, decreased by 65–75% during the course of the 6 h incubation, and the continuous presence of NGF (10 B.U./ml) was unable to prevent this. When NGF was added to 6-h NGF-deprived DRG, the time for maximum cyclic AMP increase decreased from 15min to 6min with increasing NGF concentrations from 1 to 50 B.U./ml, although the relative magnitude of the cyclic AMP increase was essentially the same (approx 3-fold) at these NGF concentrations.Attempts were made to correlate the cyclic AMP response in NGF-deprived DRG with another rapid response resulting from administration of NGF to NGF-deprived DRG, namely, the reactivation of hexose uptake. The cyclic AMP and permeation responses both occurred on the same time scale (5-15 min), and both responded to increasing concentrations of NGF with a decreasing time to achieve maximal effect. A temporal relationship between cyclic AMP and membrane permeability was noted, but it could not be ruled out that it might reflect difficulties in methodology and/or inadequacy in current knowledge of the underlying mechanisms.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 21 (1973), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —An enzyme from rat brain catalysing the synthesis of the histidine-containing dipeptides carnosine and homocarnosine (l.-histidine: β-alanine ligase (AMP) [EC 6.3.2.11]) was purified about 30-40-fold from a 100,000 g supernatant. Assays were conducted by measuring the incorporation of L-[14C]histidine into carnosine and homocarnosine isolated by paper electrophoresis from the incubation mixture. The ratios of specific activities for the formation of carnosine and homocarnosine were not significantly different for the various purification steps. This was taken as evidence of one enzyme synthesizing both dipeptides. In studying the properties of this enzyme, a pH optimum of 7.4 was shown for carnosine synthesis. The concentrations of amino acid substrates giving maximal synthesis of both dipeptides were in the physiological range found for rat brain. An apparent requirement for ATP, Mg2+, and DPN was seen for dipeptide synthesis. A substrate dependent, enzymecatalysed 32PPi-ATP exchange reaction was observed, suggesting the formation of an aminoacyl-AMP intermediate. Certain other nucleoside triphosphates could substitute for the ATP; this effect showed a specificity toward the dipeptide being synthesized. The apparent requirement for DPN was quite specific, with a number of related compounds having no effect. The stoichiometry of enzyme-catalysed carnosine synthesis was studied. A one to one relationship between carnosine formed and ATP hydrolysed was demonstrated. However, the ratio between carnosine synthesized and DPN hydrolysed was about 6 to 1, indicating a catalytic role for the DPN. The breakdown of DPN did not occur with enzyme alone but was dependent on the presence of substrate.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The intracellular concentrations of a number of amino acids were measured in a normal clone of rat glioma cells, and in several independently derived clones selected for gross deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). A significant, approx 2-fold increase in the concentration of free glycine was observed in both mutagenized and non-mutagenized HGPRT deficient clones. The increase in glycine was independent of the phase of cell growth. A similar increase did not occur in HGPRT deficient lymphoblasts.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 27 (1976), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The kinetic parameters of monoamine oxidase (MAO; E.C 1.4.3.4) and catechol-O-methyl-transferase (COMT; EC 2.1.1.6) were evaluated in extracts of adrenergic and non-adrenergic mouse neuroblastoma cells and in rat glioma cells. Using the naturally-occurring substrates tyramine, tryptamine, serotonin and norepinephrine, the affinity of MAO for a given substrate was independent of the presence of the catecholaminergic pathway or cell type used, with apparent Km values ranging from 8–14 μM for tryptamine to 510–580 μM for norepinephrine. The MAO activity in glioma cells was substantially greater than in either neuroblastoma clone, but Vmax values varied little with substrate among cell lines. Both the neuronal and glial COMT had a similar Km for I-norepinephrine (200μM); the corresponding Vmax values were also similar among the different cell lines, but represented only 2–10% of the maximal MAO activity. Neuroblastoma and glioma cells, when grown from early logarithmic to stationary phase, showed no significant changes in specific activity of either MAO or COMT. Growth of cells for 3 days with 1 mM-N6,O2′ -dibutyryl adenosine-3′,5′-cyclic monophosphate resulted in no marked change in either MAO or COMT activity.These results suggest that in neurons neither MAO nor COMT plays a major role in the type of transmitter inactivation that is analogous to that of acetylcholinesterase in cholinergic synapses. The occurrence of considerable MAO and acetylcholinesterase activities in glioma cells may indicate a role for these cells in neurotransmitter inactivation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 26 (1976), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The intracellular concentrations of a number of amino acids were compared in a parental line of mouse neuroblastoma cells, a line selected for gross deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and in a revertant line containing the enzyme selected from the deficient line. Most prominent was the increased concentration of free glycine and to a lesser extent glutamic acid in enzyme-deficient cells. The increase in glycine was eliminated after restoration of the HGPRT activity.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Amyloid β-peptide (Aβ) is the main component of senile plaques which characterize Alzheimer's disease and may induce neuronal death through mechanisms which include oxidative stress. To date, the signalling pathways linking oxidant stress, a component of several neurodegenerative diseases, to cell death in the CNS are poorly understood. Melastatin-like transient receptor potential 2 (TRPM2) is a Ca2+-permeant non-selective cation channel, which responds to increases in oxidative stress levels in the cell and is activated by oxidants such as hydrogen peroxide. We demonstrate here that Aβ and hydrogen peroxide both induce death in cultured rat striatal cells which express TRPM2 endogenously. Transfection with a splice variant that acts as a dominant negative blocker of TRPM2 function (TRPM2-S) inhibited both hydrogen peroxide- and Aβ-induced increases in intracellular-free Ca2+ and cell death. Functional inhibition of TRPM2 activation by the poly(ADP-ribose)polymerase inhibitor SB-750139, a modulator of intracellular pathways activating TRPM2, attenuated hydrogen peroxide- and Aβ-induced cell death. Furthermore, a small interfering RNA which targets TRPM2, reduced TRPM2 mRNA levels and the toxicity induced by hydrogen peroxide and Aβ. These data demonstrate that activation of TRPM2, functionally expressed in primary cultures of rat striatum, contributes to Aβ- and oxidative stress-induced striatal cell death.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 695 (1993), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: A large body of experimental data suggests that neurotrophic molecules and/or substances that facilitate their action could be pharmaceutical agents for neurodegenerative pathologies. In particular, it has been demonstrated that nerve growth factor (NGF) exerts a physiological role for forebrain cholinergic neurons, while brain-derived neurotrophic factor (BDNF) seems to play a relevant role in rescuing dopaminergic neurons following damage. In addition, gangliosides are reported to potentiate neurotrophic factor effects in vitro as well as in vivo. In this study we examined the effects of the monosialoganglioside GM1 in different experimental models. The responsiveness of forebrain cholinergic neurons following NGF ± GM1 was evaluated by assessing choline acetyltransferase (ChAT) activity in hippocampus, septal area and striatum of behaviorally impaired 24-month-old rats. NGF was intracerebroventricularly (i.c.v.) infused for 2 weeks while GM1 was given systemically for 3 weeks, starting from the beginning of NGF infusion. Moreover, the possible protective effects of GM1 were assessed following exposure of cultured cerebellar granule cells and dopaminergic mesencephalic neurons to different doses of 6-OH-DOPA, a metabolite of the dopamine pathway which has excitotoxic properties and has been hypothesized to participate in the pathology of Parkinson's disease. GM1 treatment to aged rats was seen to potentiate the NGF-induced increase of ChAT activity in the striatum ipsilateral to the NGF infusion. Moreover, in the striatum contralateral to the NGF infusion, GM1 increased ChAT activity above the control values, whereas NGF treatment alone did not affect enzymatic activity. GM1 treatment of cerebellar granule cells and mesencephalic neurons counteracted the dose-and time-dependent neurotoxidty of 6-OH-DOPA. These data support the notion that GM1 might prove useful in treating those pathological conditions where trophic factor deficits and/or cxcitotoxin-related toxicity play an important role.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-4927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neonatal mouse dorsal root ganglionic (DRG) cell dissociates were cultured in a synthetic medium with horse serum or the serum-free supplement N1 (insulin, transferrin, progesterone, putrescine, selenium). Serum-supplemented cultures with added nerve growth factor (NGF) yielded neurons, small flat and spindle cells (Schwann) and large flat cells (fibroblastic elements). However, in serum-free, N1-supplemented medium plus exogenous NGF, neurons and Schwann cells predominated, with very few large flat cells. In the N1 medium most Schwann cells assumed a typical spindle shape and were associated with neuritic processes when neurons were present. Upon addition of serum, virtually all of the Schwann cells appeared to abandon physical contact with the neurites and develop a more flattened morphology. In N1 medium without NGF (no neurites), most Schwann cells still assumed a spindle shape and formed characteristic chain-like associations. Autoradiographic techniques, as well as numerical analyses, demonstrated that in N1 medium Schwann cells were able to proliferate when associated with neurites but only slightly so in their absence. These Schwann cells showed a marked increase in proliferation when serum was added regardless of the presence or absence of neurites. The above observations may provide a basis for the preparation of purified Schwann cells, alone or in combination with their neurons.
    Type of Medium: Electronic Resource
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