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At least 37 records · Page 2Linked to original sources
PubMed1992

Serotonin-stimulated release of [3H]dopamine via reversal of the dopamine transporter in rat striatum and nucleus accumbens: a comparison with release elicited by potassium, N-methyl-D-aspartic acid, glutamic acid and D-amphetamine.

Release of preloaded radiolabeled dopamine ([3H]DA) elicited by several agents from terminal fields of mesolimbic and nigrostriatal projections in rats was compared. Several similarities between the two areas were observed. For example, potassium, which stimulates release both directly, through altering the potential across the membrane of the dopaminergic neuron, as well as indirectly, presumably by releasing endogenous excitatory neurotransmitters, exhibited some similarities to release stimulated by L-glutamate and N-methyl-D-aspartic acid. These included sensitivity to tetrodotoxin (TTX), Mg++ and Ca++. In contrast, release of [3H]DA stimulated by serotonin (5-HT), like that stimulated by D-amphetamine, depended upon a functional dopamine transport system and was less sensitive to TTX, Mg++ and Ca++. 5-HT-stimulated [3H]DA release in striatum (STR) and nucleus accumbens (NACC) was not modified by antagonists at 5-HT2 or 5-HT3 receptors. Differences were observed in release of [3H]DA from STR and NACC. Elevated potassium (20 mM) released about twice as much [3H]DA from NACC as it did from STR. 5-HT was also able to release more [3H]DA from NACC than from STR. Conversely, D-amphetamine released more [3H]DA from STR than from NACC. TTX increased release stimulated by potassium in STR, but decreased release stimulated by potassium in NACC. These observations suggest that receptor- and non-receptor-mediated mechanisms may contribute to regulation of [3H]DA release in mesolimbic and nigrostriatal areas of the brain. It is possible that endogenous 5-HT in STR or NACC acts as a local regulator of DA release acting via a transport-dependent mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Amphetamine↗
PubMed1980

Empirical calculations on cyclic dipeptides. Conformations of aspartic acid, glutamic acid and histidine residues.

Empirical conformational energy calculations were carried out for the dipeptides cyclo-(L-Asp-L-His) and cyclo-(L-Glu-L-His). The side chain conformations have been studied for various DKP ring structures, demonstrating that distortions can modify the stability of some conformations by favouring peptide backbone-side chain or side chain-side chain interactions. The carboxylic side chain of Asp and Glu residues can induce specific interactions with the imidazole ring or the peptide bond of the DKP ring which are not found for Ser or Thr. The necessity of including solute--solvent interactions to account for a more realistic conformational behaviour is discussed.

Dipeptides↗
PubMedDate not supplied

Glutamic acid and glutamic acid diethylester in tinnitus treatment.

Numerous recent findings indicate that in mammals glutamic acid (Glu) functions as the primary and secondary afferent cochlear transmitter, or at least as an agonist of the main transmitter. Glutamic acid diethylester (GDEE) is one of the known antagonists of Glu. A long term suppression of certain forms of tinnitus was observed dependent on the sequence, amount and perfusion rate upon i.v. application of Glu and GDEE. Consecutive controls with tinnitus detecting as well as blind studies helped to objectify the subjective sensations of the patients.

Glutamates↗
PubMed1977

Aspartic acid and glutamic acid levels in the cochlear nucleus after auditory nerve lesion.

Aspartic acid, glutamic acid and alanine were measured in the cochlear nucleus after lesioning the auditory nerve by cochlear ablation. Ultrastructural analysis of the cochlear nucleus showed that most primary auditory terminals were degenerating one day after cochlear ablation; the terminals were enlarged and the number of synaptic vesicles was reduced. Primary auditory terminals were virtually gone three days after cochlear ablation. Aspartic acid decreased after cochlear ablation in parallel with the morphological degeneration of the primary auditory terminals. The level of total aspartic acid in the cochlear nucleus had decreased more than 8% one day after cochlear ablation and more than 30% after two days, and remained at this level up to 28 days. Glutamic acid also decreased in the cochlear nucleus after cochlear ablation but not in parallel with the morphological degeneration of the primary auditory terminals. Following a slight increase one day after cochlear ablation, total glutamic acid decreased about 10% after two days and continued to decrease slowly through to day 28. Alanine dropped slowly after cochlear ablation and not in parallel with the degeneration of the primary terminals. Levels of other amino acids measured were unchanged or had increased two days after cochlear ablation. Aspartic acid and glutamic acid did not decrease in the superficial layers of the dorsal cochlear nucleus, an area receiving little or no primary innervation.

Alanine↗
PubMed2000

Two amino acids in glutamic acid decarboxylase act in concert for maintenance of conformational determinants recognised by Type I diabetic autoantibodies.

AIMS/HYPOTHESIS: Glutamic acid decarboxylase 65 is a major autoantigen in Type I (insulin-dependent) diabetes mellitus, autoimmune polyendocrine syndrome and stiff-man syndrome. These disorders are characterised by the presence of multiple autoantibodies to the autoantigen which can be distinguished in a variety of different ways. We have investigated the role of single amino-acid mutations in glutamic acid decarboxylase 65 in distinguishing the binding of serum antibodies and a variety of patient-derived human IgG monoclonal antibodies directed to different determinants of the autoantigen. METHODS: We identified a mutant of glutamic acid decarboxylase 65 that contained four single amino-acid mutations from the wild-type molecule. The role of these mutations was investigated by site-directed mutagenesis. We investigated the binding of patient-derived serum antibodies to glutamic acid decarboxylase 65 to a number of single and double amino-acid mutants using immunoprecipitation with labelled, recombinant antigen. To overcome the heterogeneity of different anti-glutamic acid decarboxylase 65 antibodies present in a patient's serum, the binding of a panel of eleven patient-derived human monoclonal antibodies recognising different determinants on the autoantigen was also studied. RESULTS: Two replacements in glutamic acid decarboxylase 65 at Asn247Ser and Leu574Pro were identified that preferentially influence the anti-glutamic acid decarboxylase 65 serum antibodies of Type I diabetic patients, without statistically significantly effecting those recognised in other disorders. Single or double amino-acid replacements Asn247Ser and Leu574Pro in the autoantigen showed differential affects on expression of epitopes recognised by the human monoclonals. The double replacement of Asn247Ser and Leu574Pro in glutamic acid decarboxylase 65 resulted in the loss of binding of all eleven human monoclonal antibodies, irrespective of their epitope recognition. In contrast, single replacement of Leu574Pro statistically significantly reduced the binding of some carboxyl terminal-directed antibodies such as MICA 1, MICA 3 and DP-A without influencing the binding of other monoclonals. Replacement of Asn247Ser did not, however, influence the binding of any patients serum or human monoclonal antibodies. CONCLUSION/INTERPRETATION: Two distantly spaced amino acids, Asn247 and Leu574 in glutamic acid decarboxylase 65 were identified that act in concert to greatly influence the conformational structure of the autoantigen and statistically significantly influence the binding of antibodies present in Type I diabetic sera. The single or double amino-acid mutants can be used to distinguish some anti-glutamic acid decarboxylase-65 autoantibodies and could prove useful in distinguishing Type I diabetic from autoimmune polyendocrine syndrome and stiff-man syndrome patients' sera as well as to study changes in antibody patterns during disease progression.

Amino Acid Sequence↗
PubMed1996

Free alanine, aspartic acid, or glutamic acid reduce the glycation of human lens proteins.

The amino acids lysine and glycine are reported to react with glucose at physiological pH and temperature and undergo non-enzymic glycation. Three other amino acids present in relatively larger amounts in the lens i.e. alanine, aspartic acid and glutamic acid were also found to undergo non-enzymic glycation as found by incorporation of uniformly labelled (U-[14C]) glucose into the amino acids. The glucose incorporation was 1.6 to 2.5% for alanine, 35 to 50% for aspartic acid and 2.3 to 3.3% for glutamic acid. Each amino acid of varying concentrations lowered the extent of in vitro glycation of lens proteins significantly in glucose-treated homogenates of normal lens from humans. The decrease in glycation for alanine was between 32 and 69%, that for aspartate was between 18 and 74%, and for glutamate was between 52 to 74%. Decreased glycation was greater for higher concentrations of glucose. Scavenging of intracellular glucose and decreasing the extent of glycation of lens proteins could be the mechanism of action by which the amino acids alanine, aspartic acid and glutamic acid could exercise a beneficial effect on cataract and diabetic retinopathy.

Alanine↗
PubMed2001

A theoretical study of electronic and structural states of neurotransmitters: gamma-aminobutyric acid and glutamic acid.

As a first approach to understanding the mechanism for the recognition of a ligand by its receptor, we first calculated the electronic and structural states of ionized gamma-aminobutyric acid (GABA) and ionized glutamic acid using the ab initio method with the 6-311++G (3df, 2pd) basis set. We paid special attention to the physicochemical characteristics of these molecules, such as the electric dipole moment, electrostatic potential, and electrostatic force. Even though GABA and glutamic acid are known to exert completely opposite influences in the mammalian brain by binding their specific receptors, the only difference in their chemical structures is that glutamic acid contains one more carboxyl group than GABA. As a result, we succeeded in showing that a difference of only one carboxyl group induces significant differences in the electronic and structural states between these molecules. These differences have a crucial influence on the electric dipole moments, the electrostatic potentials, and the electrostatic forces. The most remarkable finding of the present research is that the electrostatic potential formed by glutamic acid is composed of only negative parts, while that formed by GABA is separated into positive and negative parts. These results strongly suggest that GABA can approach either positively or negatively charged amino acids by adjusting its own orientation, while glutamic acid can approach only a positively charged binding site.

Chemical Phenomena↗