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  • 1990-1994  (4)
  • 1980-1984  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Characterization of the Quisqualate Receptor Linked to Phosphoinositide Hydrolysis in Neurocortical Cultures (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb01192.x
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  • 2
    Electronic Resource
    Electronic Resource
    Role of Glycine in the N-Methyl-d-Aspartate-Mediated Neuronal Cytotoxicity (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb02329.x
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  • 3
    Electronic Resource
    Electronic Resource
    6,7-Dinitroquinoxaline-2,3-Dione Blocks the Cytotoxicity of N-Methyl-D-Aspartate and Kainate, but Not Quisqualate, in Cortical Cultures (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb08828.x
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  • 4
    Electronic Resource
    Electronic Resource
    Differential Binding Properties of Adenosine Receptor Agonists and Antagonists in Brain (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 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
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb04752.x
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  • 5
    Electronic Resource
    Electronic Resource
    S-100-Mediated Inhibition of Brain Protein Phosphorylation (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 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
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb09048.x
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  • 6
    Electronic Resource
    Electronic Resource
    Increased Phosphorylation of a Membrane Protein Consequent to Amygdaloid Kindling (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 43 (1984), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1471-4159.1984.tb06693.x
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  • 7
    Electronic Resource
    Electronic Resource
    Chemical Pathways of Peptide Degradation. VII. Solid State Chemical Instability of an Aspartyl Residue in a Model Hexapeptide (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 901-908 
    Details
    ISSN: 1573-904X
    Keywords: lyophilization ; lyophilized formulations ; factorial experimental design ; Asp-hexapeptide ; solid state chemical stability ; formulation development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chemical stability of an Asp-hexapeptide (Val-Tyr-Pro-Asp-Gly-Ala) in lyophilized formulations was evaluated as a function of multiple formulation variables–specifically pH of the bulk solution, temperature, moisture content, and type of bulking agent (amorphous vs. crystalline). The disappearance of the starting Asp-hexapeptide in the solid state conformed to pseudo-first-order reversible kinetics. This type of degradation profile was accounted for by the product distribution. The factorial experimental design of this study allowed statistical analysis of the effects of individual formulation variable (main effects) as well as those of two-factor interactions on the degradation of the Asp-hexapeptide. Analysis of Variance (ANOVA) calculations of the main effects indicated that while the influence of pH of the starting solution was not statistically significant, residual moisture level, temperature, and, especially, type of bulking agent had a significant impact on the solid state chemical reactivity of the hexapeptide. Furthermore, depending on which type of excipient was used in the lyophilized formulations, residual moisture level and temperature could be important stability variables. These types of factorial experiments have proven to be useful in the rapid identification of significant formulation variables in a given system and, consequently, in optimization of formulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018998312503
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