Search Results
Results 601 - 650 of 1819
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Espey M G - - 1999
Chronic hyperactivation of excitatory amino acid pathways in the CNS of patients infected with HIV-1 may contribute to the pathogenesis of HIV-1-associated dementia complex. However, no correlation between the concentration of glutamate in CSF (mean 3.3 micromol/L) and either HIV-1 infection or HIV-1-associated dementia complex was observed. The results clarify ...
Qu H - - 1999
The effect of thiopental on glutamate metabolism was studied by 13C magnetic resonance spectroscopy. Cerebral cortical astrocytes were incubated with 0.5 mM [U-13C]glutamate for 2 hr in the presence of 0.5 or 1 mM thiopental. Labeled glutamate, glutamine, aspartate, and glutathione were observed in cell extracts, and glutamine, aspartate, and ...
Kanamatsu T - - 1999
The 13C-label incorporation into glutamate, glutamine, aspartate and gamma-aminobutyric acid (GABA) from [2-13C] glucose was measured by 13C nuclear magnetic resonance (NMR) spectroscopy to directly examine the effects of ammonia on the activity of pyruvate carboxylase (i.e., the anaplerotic pathway) and the amino acid metabolism in the rat brain in ...
Carrigan C N - - 1999
Twenty-six quinoline-2,4-dicarboxylic acids (QDC's) were synthesized by a modified Doebner-von Miller pathway and tested as inhibitors against the glutamate vesicular transport (GVT) protein. The QDC's were active as inhibitors with the most potent QDC's found to contain halogens at the 6-/8-position, a hydroxyl at the 8-position, or a tethered aromatic ...
Hasebe M - - 1999
BACKGROUND: Glutamine (GLN) plays many important roles for the enterocytes in health and disease, but no liquid enteral products contain GLN because of its instability. We hypothesized that glutamate (GLU) may replace GLN in supplementation to an enteral diet, and compared the metabolic effect of GLU and GLN on the ...
Phillis J W - - 1999
This study analyzed the effects of pre-existing hyperglycemia on the extracellular levels of glutamate, other amino acids and free fatty acids, including arachidonic acid, in the ischemic/reperfused rat cerebral cortex, using a cortical cup technique. Forebrain cerebral ischemia (20 min) was induced by four vessel occlusion. Glucose (3.4 g/kg) was ...
Sakata K - - 1999
N-Methyl-D-aspartate (NMDA) receptor subtypes epsilon 1 and zeta 1 were coexpressed in Xenopus oocytes for the investigation of the magnitude of augmentation of the L-glutamate response by 20 common L-amino acids and their 19 D-isoforms. Simultaneous application of L- and D-alanine, -cysteine, and -serine, or glycine and L-glutamate potentiated the ...
Samartsev V N - - 1999
Study of the uncoupling effect of various saturated fatty acids (from caprylic to palmitic) revealed that the glutamate recoupling effect was more pronounced in the case of short chain fatty acids, whereas recoupling of mitochondria by carboxyatractylate was more effective in the case of long chain fatty acids. The overall ...
Calik P - - 1999
The metabolic fluxes through the central carbon pathways in the bioprocess for serine alkaline protease (SAP) production by Bacillus licheniformis were calculated by the metabolic flux-based stoichiometric model based on the proposed metabolic network that contains 102 metabolites and 133 reaction fluxes using the time profiles of citrate, dry cell, ...
Bremaeker ND - - 1999
Amphipholis squamata is a polychromatic luminescent ophiuroid. The effects of amino acids ( &ggr; -aminobutyric acid, GABA, taurine, glycine and glutamate), N-methyl-d-aspartate (NMDA) and the invertebrate neuropeptides Antho-RFamide, FMRFamide and SALMFamides S1 and S2 were tested on acetylcholine-induced luminescence from isolated arms of clear and black specimens of Amphipholis squamata. ...
Niebroj-Dobosz I - - 1999
OBJECTIVES: In amyotrophic lateral sclerosis (ALS), a neurodegenerative disease of unknown origin, excitotoxic mechanisms are supposed to be involved. Divergent results are, however, presented either because of the heterogeneity of this disease, and/or different methodologies used to evaluate the excitotoxic amino acids content. The results of the most sensitive high ...
Tirosh O - - 1999
Elevated levels of extracellular glutamate have been linked to reactive oxygen species mediated neuronal damage and brain disorders. Lipoic acid is a potent antioxidant that has previously been shown to exhibit neuroprotection in clinical studies. A new positively charged water soluble lipoic acid amide analog, 2-(N,N-dimethylamine) ethylamido lipoate HCl (LA-plus), ...
Nakagawa M - - 1999
In vertebrate visual pigments, a glutamic acid serves as a negative counterion to the positively charged chromophore, a protonated Schiff base of retinal. When photoisomerization leads to the Schiff base deprotonating, the anionic glutamic acid becomes protonated, forming a neutral species that activates the visual cascade. We show that in ...
Phillis J W - - 1999
The contributions of sodium and chloride ions and of osmotic stresses to the ischemia-evoked efflux of excitotoxic and other amino acids were explored using a rat four vessel occlusion model. Replacement of Na+ with choline or N-methyl-D-glucamine (NMDG) and of Cl- with sulfate or gluconate was used to evaluate the ...
Sitar S M - - 1999
BACKGROUND: Glutamate transporters located in the plasma membrane of cerebral astrocytes take up excitatory neurotransmitters from the synaptic cleft. In diseases characterized by oxidative stress, the extracellular glutamate concentration increases and contributes to neuronal death. The authors wanted to determine whether propofol defends brain cells against oxidant-induced changes in their ...
Hylland P - - 1999
The crucian carp is one of the few vertebrates that has the ability to survive long periods of anoxia. A devastating event in the anoxic mammalian brain is a massive release of excitatory neurotransmitters, particularly glutamate. Using microdialysis to measure extracellular levels of several amino acid neurotransmitters and related compounds ...
Kaehler S T - - 1999
Hyperforin is the main antidepressant component of hypericum perforatum (St. John's Wort). Using the push-pull superfusion technique we tested whether hyperforin influences extracellular concentrations of neurotransmitters in the rat locus coeruleus. Hyperforin (10 mg/kg, i.p.) not only enhanced the extracellular levels of the monoamines dopamine, noradrenaline and serotonin, but also ...
Dames S A - - 1999
The pKa values of eight glutamic acid residues in the homotrimeric coiled coil domain of chicken matrilin-1 have been determined from 2D H(CA)CO NMR spectra recorded as a function of the solution pH. The pKa values span a range between 4.0 and 4.7, close to or above those for glutamic ...
Estevez A Y - - 1999
A cortical cup model with continuous perfusion of artificial cerebrospinal fluid (containing 134 mM NaCl) was used to investigate the effects of anion channel blockers on the hyposmotically-induced release of amino acids from the in vivo rat cerebral cortex. The hyposmotic stimulus (25 mM NaCl) evoked a release of taurine, ...
Winkler B S - - 1999
The purpose of the present experiments was to evaluate the contribution of the glutamate-glutamine cycle in retinal glial (Müller) cells to photoreceptor cell synaptic transmission. Dark-adapted isolated rat retinas were superfused with oxygenated bicarbonate-buffered media. Recordings were made of the b-wave of the electroretinogram as a measure of light-induced photoreceptor ...
Bianchi L - - 1999
A HPLC method, involving pre-column derivatisation with o-phthalaldehyde and fluorescence detection, is described. It allows the resolution of aspartate, glutamate, taurine and GABA, in a single run with detection limits of 3.2, 1.7, 1.4 and 2 fmol/microl of perfusate, respectively. It is sufficiently sensitive and rapid (15 min) for the ...
Sasaki K - - 1999
We have previously demonstrated that bilobalide, a constituent of the Ginkgo biloba extract, possesses anticonvulsant activity, and suggested that the mechanism of its anticonvulsant action involves modulation of y-aminobutyric acid (GABA)-related neuronal transmission. This study examined the effects of bilobalide on the level of GABA and glutamate, the activity and ...
Smythies J - - 1999
This paper presents a new theory of the biochemical basis of learning and neurocomputation. It has now been determined that excitatory synapses on dendritic spines in the brain are continually being formed and removed. This requires a neurochemical mechanism. There is evidence to suggest that the redox state of the ...
Schröeder H - - 1999
Previous studies have proposed that there is an increase in the density of glutamate binding sites after pentylenetetrazol (PTZ) kindling, whereas the glutamate release is not altered. Little is known about the time course of these changes. Therefore, we studied 3H-L-glutamate binding to hippocampal membranes and K+-stimulated 3H-D-aspartate release from ...
Tseng E E - - 1999
BACKGROUND: Prolonged hypothermic circulatory arrest (HCA) results in neurologic injury, but the mechanism of this injury is unknown. This study was undertaken to measure quantitatively intracerebral excitatory amino acids and citrulline, an equal coproduct of nitric oxide, during HCA. We hypothesized that HCA resulted in higher levels of glutamate, aspartate, ...
Rowbury R J - - 1999
Escherichia coli became more acid tolerant following incubation for 60 min in a medium containing L-glutamate at pH 7.0, 7.5 or 8.5. Several agents, including cAMP, NaCl, sucrose, SDS and DOC, prevented tolerance appearing if present with L-glutamate. Lesions in cysB, hns, fur, himA and relA, which frequently affect pH ...
Bucheli P - - 1999
A methodology for flavor and composition assessment of processed tomato juice samples was developed using a wide range of commercial processing tomato varieties (Lycopersicon esculentum) grown in Spain and the United States. Fruitiness intensity was found by a trained panel to best describe overall tomato flavor. For two consecutive years, ...
Rowbury R J - - 1999
Several metabolites and salts including glucose, L-glutamate, L-aspartate, FeCl3, KCl and L-proline induce acid tolerance at neutral external pH (pHo) in log phase Escherichia coli. For induction by glucose and L-glutamate, the processes are independent of integration host factor (IHF), H-NS, CysB, ferric uptake regulator (Fur) and RelA. For most ...
Tomita M - - 1999
Soy sauce was found to contain promoters of sediment formation at 60 degrees C, one of which has previously been identified as L-glutamic acid 5-n-butyl ester. Isomers and homologues of L-glutamic acid 5-n-butyl ester (n-propyl, isopropyl, n-butyl, isobutyl, and sec-butyl esters of L-glutamic acid) were synthesized using 80% (w/w) sulfuric ...
Ramezani M - - 1999
The utilization of D- and L-amino acids with acidic, basic or polar side chains was demonstrated by HPLC. Two species of the anaerobe Fusobacterium utilized D-lysine and the L isomers of glutamate, glutamine, histidine, lysine and serine. Only F. varium used L-arginine, D-glutamate and D-serine as substrates, whereas F. nucleatum ...
Cornish J L - - 1999
This study investigated the effect of ionotropic glutamate receptor agonist or antagonist administration into the nucleus accumbens on the maintenance of cocaine self-administration and the reinstatement of cocaine-seeking behavior. The stimulation of alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid or N-methyl-D-aspartate glutamate receptors in the nucleus accumbens with either alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid or 1-aminocyclobutane-cis-1,3-dicarboxylic acid, respectively, ...
Ferreira J - - 1999
This study investigates the antinociceptive and antihyperalgesic action caused by i.p., i.t. or i.c.v. injections of amiloride when assessed against formalin, capsaicin-induced licking, acetic acid-induced writhing and glutamate-induced hyperalgesia in mice. The systemic, spinal and supraspinal administration of amiloride causes dose-related antinociception when assessed against acetic acid-induced writhing, formalin and ...
Niculescu-Duvaz D - - 1998
Four new potential self-immolative prodrugs derived from phenol and aniline nitrogen mustards, four model compounds derived from their corresponding fluoroethyl analogues and two new self-immolative linkers were designed and synthesized for use in the suicide gene therapy termed GDEPT (gene-directed enzyme prodrug therapy). The self-immolative prodrugs were designed to be ...
Griffin J L - - 1998
Excitatory amino acids are an important cause of cell death in the hypoxic and ischaemic brain. Neuronal glutamate stores are depleted rapidly in hypoxia, but alanine production rises under such conditions and has been suggested to be a potential precursor of glutamate. To test this hypothesis, we have investigated amino ...
Tran-Dinh S - - 1998
A new mathematical model, based on the observation of 13C-NMR spectra of two principal metabolites (glutamate and aspartate), was constructed to determine the citric acid cycle flux in the case of high aspartate transaminase activity leading to the formation of large amounts of labeled aspartate and glutamate. In this model, ...
Roseth S - - 1998
The specificity of the vesicular L-glutamate carrier was characterized using dyes with biphenyl and amino- and sulphonic acid substituted naphthyl groups, structurally similar to the specific vesicular L-glutamate inhibitor Evans Blue. The dye Trypan Blue was the most potent inhibitor; the IC50 value was determined to be 49 nM. Naphthol ...
Håberg A - - 1998
Astrocytes play a pivotal role in cerebral glutamate homeostasis. After 90 minutes of middle cerebral artery occlusion in the rat, the changes induced in neuronal and astrocytic metabolism and in the neuronal-astrocytic interactions were studied by combining in vivo injection of [1-13C]glucose and [1,2-13C]acetate with ex vivo 13C nuclear magnetic ...
Vaccari A - - 1998
We aimed to ascertain whether pyrethroid insecticides could influence the vesicular transport of the excitatory amino acid glutamate. The incubation of rat cortical synaptic vesicles with resmethrin and permethrin, consistently stimulated both ATP-dependent and -independent uptake of [3H]glutamate, while not evoking depletion of its vesicular content. Both processes were counteracted ...
Wang S - - 1998
This study was conducted to document the glutathione (GSH) cycle (interorgan circulation of GSH) in broilers in vivo. Two experiments were conducted on 36 anesthetized male broilers (n = 6 per treatment) implanted with cannulae in the carotid artery, hepatic portal, and hepatic veins. Plasma GSH, glutamate, cysteine, cystine, and ...
Dumka V K - - 1998
Possible central modulation of acute peripheral inflammation by putative amino acid neurotransmitters was investigated in rats by adopting formalin induced pedal inflammation as an experimental model. Out of five amino acids (GABA, glycine, DL-alanine, L-glutamic acid and L-aspartic acid) tested, intracerebroventricular (icv) administration of GABA and L-aspartic acid produced significant ...
Ohtani S - - 1998
There are no reports on rates of amino acid racemization in bones. To investigate the possibility of estimating age by evaluating amino acid residue racemization in human bones, a heating experiment was performed and the rate of aspartic acid racemization was determined using the Arrhenius equation. Assuming an annual mean ...
Zielke H R - - 1998
Metabolic compartmentation of amino acid metabolism in brain is exemplified by the differential synthesis of glutamate and glutamine from the identical precursor and by the localization of the enzyme glutamine synthetase in glial cells. In the current study, we determined if the oxidative metabolism of glutamate and glutamine was also ...
Arsenian M - - 1998
Cardioplegic solutions rich in the hydrophilic, basic amino acids, glutamate and aspartate, have enhanced myocardial preservation and left ventricular function. This has been demonstrated in assorted animal preparations involving ischemia with and without reperfusion. Published clinical data, though limited, strongly support the contention that these amino acids have myocardial protective ...
Quertemont E - - 1998
Excitatory amino acid neurotransmission within the amygdala has been implicated in learning associations between external stimuli and intrinsic reward values, such that it may play a key role in conditioned drug effects. In the present studies, the responses of the excitatory amino acids, aspartate and glutamate, together with the neuromodulatory ...
Gundersen V - - 1998
To elucidate the role of aspartate as a signal molecule in the brain, its localization and those of related amino acids were examined by light and electron microscopic quantitative immunocytochemistry using antibodies specifically recognizing the aldehyde-fixed amino acids. Rat hippocampal slices were incubated at physiological and depolarizing [K+] before glutaraldehyde ...
Valli M J - - 1998
A series of N1-substituted derivatives of (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC) has been prepared as constrained analogs of gamma-substituted glutamic acids and examined for their effects at recombinant metabotropic glutamate receptor (mGluR) subtypes in vitro. Appropriate substitution of the N1 position of 2R,4R-APDC resulted in the identification of a number of selective group ...
Barron J T - - 1998
The effect of inhibition of the malate-aspartate shuttle on the cytoplasmic NADH/NAD ratio and NADH redox state and its corresponding effects on mitochondrial energetics in vascular smooth muscle were examined. Incubation of porcine carotid arteries with 0. 4 mmol amino-oxyacetic acid an inhibitor of glutamate-oxaloacetate transaminase and, hence the malate-aspartate ...
Aral Y Z - - 1998
BACKGROUND: In many neurological disorders, injury to neurons may be due in part to overstimulation of the receptors for the excitatory amino acids glutamate and aspartate. The same excitotoxic mechanism and high aspartate levels in experimental studies led to this study of the concentrations of glutamate and aspartate and zinc, ...
Clerici C - - 1998
BACKGROUND AND AIMS: A new amino acid derivative of 5-aminosalicylic acid, 5-ASA-glutamate, releases 5-aminosalicylic acid independently of the action of bacterial azoreductases or adapt intestinal pH. In this study, 5-ASA-glutamate was compared with sulphasalazine with respect to: 1) therapeutic action, 2) effects on the synthesis of eicosanoids, 3) regional release ...
Okamura T - - 1998
We found a new reaction of aspartic acid dehydrogenation, catalyzed by NADP(+)-dependent aspartate dehydrogenase, in vitamin B12-producing Klebsiella pneumoniae IFO 13541. The enzyme, which was purified from a crude extract of K.pneumoniae IFO 13541, catalyzes the oxidative deamination of aspartic acid to form oxaloacetic acid. This enzyme had a molecular ...
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