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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Based on radioligand binding and electrophysiological studies, quinoxalinediones such as 6,7-dinitroquinoxaline-2,3-dione (DNQX) have been shown to be potent competitive antagonists at the quisqualate and kainate subtypes of the glutamate receptor. In this report we have examined the effects of DNQX on excitatory amino acid neurotoxicity and evoked neurotransmitter release. DNQX was found to be a potent neuroprotective agent against glutamate and N-methyl-D-aspartate (NMDA) neurotoxicity. The data suggest that this neuroprotective activity of DNQX is due to its antagonism of the coagonist activity of glycine at the NMDA receptor–channel complex. The specificity of DNQX for the glycine site associated with the NMDA receptor–channel complex was confirmed in radioligand binding and neurotransmitter release studies. DNQX also prevented kainate neurotoxicity and kainate-evoked neurotransmitter release, presumably by direct competition for the kainate receptor. DNQX, however, did not prevent quisqualate neurotoxicity, suggesting that a novel quisqualate-preferring receptor insensitive to DNQX may mediate quisqualate toxicity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Current evidence indicates that glutamate acting via the N-methyl-d-aspartate (NMDA) receptor/ion channel complex plays a major role in the neuronal degeneration associated with a variety of neurological disorders. In this report the role of glycine in NMDA neurotoxicity was examined. We demonstrate that NMDA-mediated neurotoxicity is markedly potentiated by glycine and other amino acids, e.g., d-serine. Putative glycine antagonists HA-966 and 7-chlorokynurenic acid were highly effective in preventing NMDA neurotoxicity, even in the absence of added glycine. The neuroprotective action of HA-966 and 7-chlorokynurenic acid, but not that of NMDA antagonists 3-(2-carboxypiperazine-4-yl)propylphosphonate and MK-801, could be reversed by glycine. These results indicate that glycine, operating through a strychnine-insensitive glycine site, plays a central permissive role in NMDA-mediated neurotoxicity.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 43 (1984), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The phosphorylation of both particulate and soluble proteins in the amygdala was examined in electrically kindled rats. In animals receiving electrical stimulation in the left amygdala for 5–6 days that displayed electrical after-discharges but no motor seizures, no changes were observed in the phosphorylation of either particulate or soluble proteins. In animals stimulated for 20–21 days where major motor seizures were produced, the phosphorylation of a protein having a molecular weight of 45,000 (45K) was markedly increased. The phosphorylation of this protein was increased in both the right (unstimulated) and left (stimulated) amygdala. Major motor seizures induced by electroconvulsive shocks, however, did not alter phosphorylation of this protein. Phosphorylation of the 45K protein was stimulated by calcium and calmodulin. The 45K protein is a major phosphoprotein of amygdala, representing 3.2% of the total particulate phosphoproteins in control animals and 7.4% in the kindled animals. In the presence of calcium-calmodulin, 16.2% of net protein phosphorylation was accounted for by the 45K protein.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Activation of phosphoinositide metabolism is an early event in signal transduction for a number of neurotransmitters and hormones. In primary cultures of rat neurocortical cells, various excitatory amino acids stimulate inositol phosphate production with a rank order of potency of quisqualate 〉 ibotenate 〉 glutamate 〉 kainate, N-methyl-d-aspartate 〉 α-amino-3-hydroxyl-5-methyl-4-isoxazole propionate. This response to excitatory amino acids was insensitive to a variety of excitatory amino acid antagonists including 6-cyano-7-nitroquinoxaline-2,3-dione, 3–3(2-carboxypiperazine-4-yl)propyl-l-phosphonate, and 2-amino-4-phosphonobutyrate. The individual responses of quisqualate-, ibotenate-, and kainate-stimulated inositol phosphate production were not additive. These results suggest that phosphoinositide metabolism activated by excitatory amino acids is mediated by a unique quisqualate-preferring receptor that is not antagonized by known N-methyl-d-aspartate and non-N-methyl-d-aspartate antagonists, and is relatively insensitive to α-amino-3-hydroxyl-5-methyl-4-isoxazole propionate.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We have identified and partially purified an acidic, heat-stable, noncalmodulin protein from bovine brain cytosol that stimulates Ca2+ -dependent phosphorylation of an Mr 90K substrate in crude rat brain synaptic membranes. We show that this modulator of phosphorylation (MOP) enhances Ca2+ - and phospholipid-dependent protein kinase (C kinase) phosphorylation of this 90K substrate. The 90K substrate is a higher Mr form of an 87K substrate that is a major C kinase substrate in rat brain. The Ca2+-dependent phosphorylation of both substrates is inhibited by the Ca2+-binding proteins S-100 and calmodulin. Both substrates yield phosphopeptide fragments of Mr 9K and 13K after limited proteolysis with V8 protease. Two-dimensional polyacrylamide gel electrophoresis reveals that they have similar acidic iso-electric points (pI 5.0). MOP enhances Ca2+-dependent phosphorylation of the 90K substrate whereas the phosphorylation of 87K is diminished. This reciprocal relationship suggests that the mobility of the 87K substrate in sodium dodecyl sulfate-polyacrylamide gels is decreased to 90K with increasing phosphorylation. MOP may be a novel protein modulator of C kinase-mediated phosphorylation in the nervous system.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 41 (1983), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of the glial-specific, calcium-binding, S-100 protein on brain membrane and supernatant protein phosphorylation were assessed. S-100 concentrations as low as 5 μg/ml caused a marked inhibition of the phosphorylation of a soluble brain protein having a molecular weight of 73,000 daltons (73K). This protein was designated the S-100 protein-modulated phosphoprotein (SMP). Half-maximal inhibition of the phosphorylation of SMP by S-100 was obtained at concentrations of 12 μg/ml (0.57 (μM). The inhibition of SMP phosphorylation by S-100 was calcium-dependent, with a calculated calcium Ka of 2.0 ± 0.3 μM. SMP phosphorylation was also inhibited by calmodulin, but only partially and with a much lower potency. The inhibition of SMP phosphorylation by S-100 was not inhibited by fluphenazine, whereas the effect of calmodulin was. SMP was found in many brain areas, with the highest levels seen in the corpus callosum. Various peripheral tissues, such as kidney; liver; and pineal, pituitary, and adrenal glands, did not contain detectable SMP levels. At higher S-100 concentrations, 〉10μg/ml, the phosphorylation of several other soluble proteins was markedly inhibited. These proteins have molecular weights of 56K, 50K, and 47K. The phosphorylation of these proteins was enhanced by calmodulin. These data suggest that the S-100 protein may function to modulate the phosphorylation of brain proteins in a manner analogous to (although in a reciprocal fashion) that of calmodulin.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 41 (1983), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The binding properties of N6-cydohexyl [3H]adenosine ([3H]CHA) and 1, 3-diethyl-8-[3H]phenyl-xanthine ([3H]DPX) in rat forebrain membrane are compared. The kinetic parameters of binding for each ligand are quite distinct, with [3H]CHA displaying two populations of binding sites (KD= 0.4 ± 0.05 nM and 4.2 ± 0.3 nM; Bmax= 159 ± 17 and 326 ± 21 fmol/mg protein), whereas [3H]DPX yielded monophasic Scatchard plots (KD= 13.9 ±1.1 nM;Bmax= 634 ± 27 fmol/mg protein). The metals copper, zinc, and cadmium are potent inhibitors of [3H]CHA binding, with respective IC50 concentrations of 36 [μM, 250 )μM, and 70 μM. Copper is a much less potent inhibitor of [3H]DPX binding (IC50= 350 μM). The inhibitory effect of copper on both [3H]CHA and [3H]DPX binding is apparently irreversible, as membranes pretreated with copper cannot be washed free of its inhibitory effect. The inhibitory effect of both copper and zinc on [3H]CHA binding was reversed by the guanine nucleotide Gpp(NH)p. [3H]DPX binding is only partially inhibited by zinc and cadmium (60% of specific binding remains unaffected), suggesting that this adenosine receptor ligand binds to two separate sites. Guanine nucleotides had no effect on the inhibition of [3H]DPX binding by either copper or zinc. Differential thermal and proteolytic denaturation profiles are also observed for [3H]CHA and [3H]DPX binding, with the former ligand binding site being more labile in both cases. Stereospecificity is observed in the inhibition of both [3H]CHA and [3H]DPX binding, with l-N-phenylisopropyladenosine (PIA) being 50-fold more potent than d-PIA in both cases. Evidence is therefore provided that adenosine receptor agonists and antagonists have markedly different binding properties to brain adenosine receptors.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 70 (2005), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: : Convective heat transfer coefficient (hp) between fluid and particle in continuous tube flow were compared for 2 configurations of holding tubes: one conventional having a circular cross section (CHT) and the other having noncircular cross section (NCHT). A stream of plastic spheres was fed into the holding tube to simulate a food system with particulates. Live vegetative cells of Bacillus stearothermophilus were immobilized in aqueous gellan cubes and injected into the holding tubes with water as a carrier medium. The observed inactivation levels were compared with predicted values calculated from transient heat transfer equations solved by an explicit finite difference technique. Mean effective hp values ranged from 400 to 2500 W/m2.K for the NCHT and 350 to 1700 W/m2.K for the CHT at a Reynolds numberrpanging from 6000 to 13000. The difference in hp levels between the 2 configurations increased with the flow rate and temperature. Although no relation was observed between hp values and liquid to particle relative velocity, a trend between pipe Reynolds number and hp values was observed. The presence of a large number of particles in the holding tube significantly influenced hp values. Keywords: heat transfer coefficients, holding tube, Reynolds number, particle
    Type of Medium: Electronic Resource
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