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  • 1
    Electronic Resource
    Electronic Resource
    Presence of Kynurenic Acid in the Mammalian Brain (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 51 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Kynurenic acid, a tryptophan metabolite able to antagonize the actions of the excitatory amino acids, has been identified and measured for the first time in the brain of mice, rats, guinea pigs, and humans by using an HPLC method. Its content was 5.8 ± 0.9 in mouse brain, 17.8 ± 2.0 in rat brain, 16.2 ± 1.5 in guinea pig brain, 26.8 ± 2.9 in rabbit brain, and 150 ± 30 in human cortex (pmol/g wet wt, mean ± SE). The regional distribution of this molecule was uneven. In rats, guinea pigs, and rabbits, the brainstem was the area richest in this compound. Tryptophan administration (100–300 mg/kg, i.p.) to rats resulted in a significant increase of the brain content of kynurenic acid. Similarly, 1 h after probenecid administration (200 mg/kg, i.p.), the brain content of kynurenate increased by fourfold, thus suggesting that its turnover rate is relatively fast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb04852.x
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  • 2
    Electronic Resource
    Electronic Resource
    Increase in the Content of Quinolinic Acid in Cerebrospinal Fluid and Frontal Cortex of Patients with Hepatic Failure (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Quinolinic acid (QUIN), an excitotoxic tryptophan metabolite, has been identified and measured in human cerebrospinal fluid (CSF) using a mass-fragmentographic method. Furthermore, its content has been evaluated in frontal cortex obtained at autopsy from the cadavers of patients who died after hepatic coma. During the coma, the concentration of QUIN in the CSF was 152 ± 38 pmol ml-1. In contrast, the concentration in control patients affected by different pathologies was 22 ± 7 pmol ml-1. In the frontal cortex of patients who died after episodes of hepatic encephalopathy, the content of QUIN was three times higher than in controls (2.6 ± 0.6 versus 0.80 ± 0.08 nmol/g wet weight). As a result of these investigations we are now able to extend our previous observations on the increase of QUIN in the brains of rats used as experimental models of hepatic encephalopathy to man. QUIN should therefore be added to the list of compounds possibly involved in the pathogenesis and symptomatology of brain disorders associated with liver failure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb13071.x
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  • 3
    Electronic Resource
    Electronic Resource
    Content of Quinolinic Acid and of Other Tryptophan Metabolites Increases in Brain Regions of Rats Used as Experimental Models of Hepatic Encephalopathy (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: The content of the tryptophan metabolites quinolinic acid (QUIN), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) was measured in various brain areas of rats bearing a portocaval anastomosis (PCA) for 4 weeks, using mass fragmentography or HPLC. In these animals, the content of the excitotoxic compound QUIN increased by 75% in the cortex and 125% in the cerebellum. The content of 5-HT increased by 27% in the brainstem. No changes occurred in other brain areas. On the other hand, the content of 5-HIAA increased by 66% in the cortex, 65% in the caudate, 64% in the hippocampus, 120% in the diencephalon, and 185% in the brainstem. Probenecid administration caused a larger increase of 5-HIAA accumulation in various brain areas of PCA-bearing rats than in those of sham-operated controls. The cortical content of QUIN and 5-HIAA increased after administration of ammonium acetate (7 mmol/kg), whereas an equimolar amount of sodium acetate was inactive. These results confirm that profound changes in the disposition of tryptophan occur in the brains of experimental animals used as models of hepatic encephalopathy. Furthermore, this study adds the excitotoxic compound QUIN to the list of molecules possibly involved in the pathogenesis of this brain disorder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb13052.x
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  • 4
    Electronic Resource
    Electronic Resource
    Nicotinylalanine Increases the Formation of Kynurenic Acid in the Brain and Antagonizes Convulsions (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Kynurenic acid (KYNA) was quantified in the extracellular spaces of the rat hippocampus using microdialysis and HPLC (fluorimetric detection) to study the possible role of this tryptophan metabolite in the modulation of the function of the N-methyl-D-aspartate (NMDA) receptor. Addition of probenecid (1 mM), which is an inhibitor of the organic acid transport system, to the Ringer's solution perfusing the dialysis probe increased the KYNA concentration in the dialysate from 10.4 ± 0.9 to 48 ± 6 nM. Addition of 2 mM aminooxyacetic acid, a nonspecific inhibitor of KYNA synthesis, reduced this concentration by 50%. These data suggest that KYNA is continuously synthesized in the rat hippocampus. Nicotinylalanine (NAL), 200–400 mg/kg i.p., an analogue of kynurenine that is able to direct the flow of tryptophan metabolites toward the synthesis of KYNA, significantly increased the KYNA concentration in the hippocampal dialysate and significantly potentiated the effect of tryptophan on the accumulation of KYNA in the brain and other organs. This increase resulted in pharmacological actions compatible with an antagonism of the NMDA receptors. In fact, NAL antagonized sound-induced seizures and prevented death in DBA/2 mice. Pretreatment of the mice with D-serine (100 μg intracerebroventricularly), a glycine agonist and a competitive antagonist of KYNA, completely prevented the anticonvulsive action of NAL. These data suggest that changes in the extracellular concentration of KYNA in the brain are associated with a modulation of NMDA receptor function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb10097.x
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  • 5
    Electronic Resource
    Electronic Resource
    Induction of Ornithine Decarboxylase by N-Methyl-D-Aspartate Receptor Activation Is Unrelated to Potentiation of Glutamate Excitotoxicity by Polyamines in Cerebellar Granule Neurons (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 60 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Polyamines positively modulate the activity of the N-methyl-d-aspartate (NMDA)-sensitive glutamate receptors. The concentration of polyamines in the brain increases in certain pathological conditions, such as ischemia and brain trauma, and these compounds have been postulated to play a role in excitotoxic neuronal death. In primary cultures of rat cerebellar granule neurons, exogenous application of the polyamines spermidine and spermine (but not putrescine) potentiated the delayed neurotoxicity elicited by NMDA receptor stimulation with glutamate. Furthermore, both toxic and nontoxic concentrations of glutamate stimulated the activity of ornithine decarboxylase (ODC)—the key regulatory enzyme in polyamine synthesis—and increased the concentration of ODC mRNA in cerebellar granule neurons but not in glial cells. Glutamate-induced ODC activation but not neurotoxicity was blocked by the ODC inhibitor difluoromethylornithine. Thus, high extracellular polyamine concentrations potentiate glutamate-triggered neuronal death, but the glutamate-induced increase in neuronal ODC activity may not play a determinant role in the cascade of intracellular events responsible for delayed excitotoxicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03292.x
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  • 6
    Electronic Resource
    Electronic Resource
    Neuroendocrine Axis and Behavioral Stress (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 741 (1994), 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.1749-6632.1994.tb39663.x
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  • 7
    Electronic Resource
    Electronic Resource
    Hypothalamic-Pituitary-Adrenal Axis in Neuropsychiatric Disorders (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 741 (1994), 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.1749-6632.1994.tb39668.x
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  • 8
    Electronic Resource
    Electronic Resource
    Alterations during Positive Selection in the Thymus of nackt CD4-Deficient Mice (2000)
    Oxford, UK : Blackwell Science Ltd
    Scandinavian journal of immunology 52 (2000), S. 0 
    Details
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The T-cell repertoire is shaped by the positive and negative selection of immature CD4+ CD8+ double positive (DP) thymocytes. Positive selection of DP T cells to the CD4+ CD8− and CD4− CD8+ simple positive (SP) lineages is a multistep process which involves cellular interactions between thymocytes and stromal cells. Mutant nackt (nkt/nkt) mice have been shown to have a deficiency in the CD4+ CD8− T-cell subset both in the thymus and in the periphery. The present report suggests that nkt/nkt mice present alterations in early steps of positive selection because they show decreases in the percentages of CD69+ and CD5+ cells within the DP subset. Experiments involving bone marrow transfer and thymic chimeras demonstrate that the thymic epithelium of nkt/nkt mice is involved in the alterations registered during positive selection and dictates the ultimate fate of CD4+ SP cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3083.2000.00818.x
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  • 9
    Electronic Resource
    Electronic Resource
    The Release and Neosynthesis of Glutamic Acid Are Increased in Experimental Models of Hepatic Encephalopathy (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 effects of ammonium ions on the release of glutamic acid from the rat cerebral cortex were measured in vivo using cortical cups and a multiple ion detection technique. The neosynthesis of this amino acid from glucose was also studied in two experimental models of hepatic encephalopathy: (1) rats receiving large amounts of ammonium acetate (i.p.) and (2) rats with a surgically constructed portocaval anastomosis. Intraperitoneal administration of 8 mmol/kg of ammonium acetate increased the cortical release of glutamic acid from 9.1.0.8 to 19.2 (nmol. cm−2. min−1). Moreover, 20 min after ammonium acetate administration the rate of incorporation of 13C2, originating from [13C]glucose, into glutamic acid increased by 65%. In several brain areas of rats bearing a portocaval anastomosis and fed ad libitum for 4 weeks, the content of glutamic acid slightly increased and the rate of formation of [13C2]glutamate from [13C]glucose approximately doubled. These results indicate that ammonium ions increase the release and the formation of glutamic acid in the brain. The resulting increased concentration of this amino acid in the extracellular spaces may be one of the mechanisms of ammonia toxicity in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb08057.x
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  • 10
    Electronic Resource
    Electronic Resource
    Cisapride and erythromycin prokinetic effects in gastroparesis due to type 1 (insulin-dependent) diabetes mellitus (1997)
    Oxford UK : Blackwell Science Ltd.
    Alimentary pharmacology & therapeutics 11 (1997), S. 0 
    Details
    ISSN: 1365-2036
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Erythromycin, a macrolide antibiotic, has been shown to have gastric prokinetic effects and has been proposed as an alternative therapeutic option for diabetic gastroparesis. However, its efficacy has not yet been compared with that of other prokinetic drugs.〈section xml:id="abs1-2"〉〈title type="main"〉Aims:The purpose of the present study was to compare the effects of erythromycin (250 mg 60 min before meals) and cisapride (10 mg 30 min before meals) on gastric emptying of healthy subjects and insulin-dependent diabetics.〈section xml:id="abs1-3"〉〈title type="main"〉Patients and methods:Six type 1 diabetic patients with a previous scintigraphic demonstration of gastroparesis and five healthy subjects were recruited for the study. Gastric emptying was scintigraphically studied by labelling the solid component of a standard test meal. Three scintigraphic studies, spaced at least 3 days apart, were carried out on each subject, basally and after erythromycin or cisapride.〈section xml:id="abs1-4"〉〈title type="main"〉Results:Cisapride significantly accelerated gastric emptying in both the healthy subjects and the diabetic patients without any significant effect on the lag-time, whereas erythromycin in addition to a significant improvement of the overall gastric emptying also showed a pronounced effect on the lag-time in both groups (controls 25 ± 5 vs. 37 ± 8 min, P≤0.04; diabetics 65 ± 11 vs. 112 ± 16 min, P〈0.03).〈section xml:id="abs1-5"〉〈title type="main"〉Conclusions:Erythromycin may represent an effective therapeutic alternative to more established forms of treatment in patients with diabetic gastroparesis, especially when other drugs have failed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2036.1997.00177.x
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