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Results 601 - 650 of 1837
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Hoop B - - 1999
The ventilatory response to acute hypoxia in mammalian species is biphasic, an initial hyperventilatory response is followed by a reduction in ventilation within 2-3 min below the peak level (roll-off). Brain amino acid neurotransmitters also change during hypoxia. This study explores the role of neurotransmitters in anesthetized adult Sprague Dawley ...
Deane C M - - 1999
Asparagine and aspartate are known to adopt conformations in the left-handed alpha-helical region and other partially allowed regions of the Ramachandran plot more readily than any other non-glycyl amino acids. The reason for this preference has not been established. An examination of the local environments of asparagine and aspartic acid ...
Slusher B S - - 1999
We describe here a new strategy for the treatment of stroke, through the inhibition of NAALADase (N-acetylated-alpha-linked-acidic dipeptidase), an enzyme responsible for the hydrolysis of the neuropeptide NAAG (N-acetyl-aspartyl-glutamate) to N-acetyl-aspartate and glutamate. We demonstrate that the newly described NAALADase inhibitor 2-PMPA (2-(phosphonomethyl)pentanedioic acid) robustly protects against ischemic injury in ...
Phillis J W - - 1999
The effects of the phospholipase activator melittin on amino acid and free fatty acid release from the rat cerebral cortex were monitored and compared with those of a secretory PLA(2), using a cortical cup technique with topical application of these agents in artificial cerebrospinal fluid. Melittin (10 microg/ml; 3.5 microM) ...
Kulagina N V - - 1999
This paper describes electrochemical microsensors for the in vivo measurement of glutamate and ascorbate in the extracellular space of brain tissue. To prepare glutamate microsensors, carbon fiber microelectrodes (10 microns in diameter and 300-400 microns long) were modified with a cross-linked redox polymer film containing enzymes. The microsensors were coated ...
Pasantes-Morales H - - 1999
Amino acids play a role as osmolytes during the regulatory volume decrease subsequent to hyposmotic swelling, but less is known about its role when swelling occurs in isosmotic conditions. In this work we examined the efflux of labelled GABA, taurine and glutamate (traced as D-aspartate) from the chick retina, after ...
Verity C K - - 1999
Schistosomes utilise haemoglobin from ingested host erythrocytes as their main source of amino acids. Using reverse-transcriptase PCR, we detected transcripts encoding cathepsin D in eggs, miracidia, and adult male, female and mixed-sex Schistosoma japonicum. Using the synthetic fluorogenic peptide, o-aminobenzoyl-isoleucyl-glutamyl-phenylalanyl-p-nitro-phenylalanyl-a rgi nyl-leucine-NH2, and human haemoglobin as substrates, we detected cathepsin ...
Napper G A - - 1999
Glutamate and gamma-aminobutyric acid (GABA) are the dominant amino acids in the retina and brain. The manufacturing and degradation pathways of both of these amino acids are intricately linked with the tricarboxylic acid cycle leading to rapid redistribution of these amino acids after metabolic insult. Postmortem ischemia in mammalian retina ...
Jones P - - 1999
The transfer of label from 15N-alanine and 15N-glutamate into amino acids in incubated brain slices has been followed using gas chromatography/mass spectrometry (GC/MS). 15N from alanine appeared in both amino and amide groups of glutamine more rapidly than into aspartate, glutamate and GABA, which were all labeled at similar rates. ...
Sherwin A L - - 1999
Studies of neuroactive amino acids and their regulatory enzymes in surgically excised focally epileptic human brain are reviewed. Concentrations of glutamate, aspartate and glycine are significantly increased in epileptogenic cerebral cortex. The activities of the enzymes, glutamate dehydrogenase and aspartate aminotransferase, involved in glutamate and aspartate metabolism are also increased. ...
Viano J - - 1999
A survey of compositional characteristics of the aerial part of sheep's burnet (Sanguisorba minor ssp. muricata) growing in Mediterranean French pastures has been undertaken. Investigations with scanning electron microscopy gave the morphological structure of this plant, in particular for akene ornamentation. Taxonomic characters confirmed the identification of the muricata subspecies. ...
Kalloniatis M - - 1999
The dominant neurochemicals involved in encoding sensory information are the amino acid neurotransmitters, glutamate, gamma-aminobutyrate (GABA) and glycine, which mediate fast point-to-point synaptic transmission in the retina and other parts of the central nervous system. The relative abundance of these neurochemicals and the existence of neuronal and glial uptake mechanisms ...
Yang C S - - 1999
Glutamate is an important excitatory amino acid in central nervous system. We developed a method for in vivo, continuous and automatic monitoring of brain extracellular glutamate, as well as other amino acids in anesthetized rat. This method involves the use of microdialysis perfusion technique and a high-performance liquid chromatography system ...
Estevez A Y - - 1999
In an evaluation of the contribution of swelling-induced amino acid release, through the regulatory volume decrease (RVD) process, to cerebral ischemic injury, studies of the role of phospholipases and protein kinases in the response to hyposmotic stress were undertaken using an in vivo rat cortical cup model. Hyposmotic stress induced ...
Waagepetersen H S - - 1999
GABA, which is present in the brain in large amounts, is distributed among distinctly different cellular pools, possibly reflecting its multiple functions as metabolite, neurotransmitter, and neurotrophin. Its metabolic enzymes also exhibit heterogeneity, because glutamate decarboxylase exists in two isoforms with different subcellular distribution and regulatory properties. Moreover, recent evidence ...
Delaunay S - - 1999
To give clues about the respective importance of phosphoenol-pyruvate carboxylase (PEPc) and pyruvate carboxylase (Pc) in Corynebacterium glutamicum metabolism during a temperature triggered glutamic acid fermentation, PEPc activity was genetically amplified and Pc activity was suppressed by biotin limitation in the culture medium. In absence of Pc activity, glutamate production ...
Matsumoto M - - 1999
The occurrence of free D-amino acids and aspartate racemases in several hyperthermophilic archaea was investigated. Aspartic acid in all the hyperthermophilic archaea was highly racemized. The ratio of D-aspartic acid to total aspartic acid was in the range of 43.0 to 49.1%. The crude extracts of the hyperthermophiles exhibited aspartate ...
Fairbanks L D - - 1999
Leflunomide is an immunomodulatory drug which acts by inhibiting dihydroorotic acid dehydrogenase, the fourth enzyme of pyrimidine biosynthesis. We modified our high-performance liquid chromatography method to demonstrate that the principal metabolite in mitogen-stimulated human T-lymphocytes incubated with leflunomide was not dihydroorotic acid, but carbamoyl aspartate. Identification involved preparation of [14C]carbamoyl ...
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 ...
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