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At least 127 records · Page 7Linked to original sources
PubMed1999

Effects of bilobalide on gamma-aminobutyric acid levels and glutamic acid decarboxylase in mouse brain.

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 the amount of glutamic acid decarboxylase (EC 4.1.1.15), and the function of GABA(A) receptors in the hippocampus, cerebral cortex and striatum of the mouse. GABA levels, glutamic acid decarboxylase activity, and the protein amount of 67 kDa glutamic acid decarboxylase in the hippocampus of mice treated with bilobalide (30 mg/kg, p.o., once a day for 4 days) were significantly higher than those in controls. However, there were no significant differences in glutamate levels or, the number and the dissociation constants of GABA(A) receptors in the hippocampus between control and bilobalide-treated mice. These results suggest that the anticonvulsant effect of bilobalide is due to elevation of GABA levels, possibly through potentiation of glutamic acid decarboxylase activity and enhancement of the protein amount of 67 kDa glutamic acid decarboxylase by bilobalide.

Animals↗
PubMed1984

[Effect of glutamic acid content of the diet on the catabolic rate of isotope-labeled glutamic acid in rats. 2. Time course of 14CO2 excretion following subcutaneous administration of 14C-glutamic acid].

40 rats with a body weight of 100 g received 7 semisynthetic diets with different contents of glutamic acid and one diet contained whole egg. A L-amino acid mixture corresponding to the pattern of egg protein was the protein source of the semisynthetic diets. Glutamic acid was supplemented successively from 0 to 58 mol-% of the total amino acid content. On the 8th day of experimental feeding the animals were labelled by subcutaneous injection of 14C-U-L-glutamic acid. Subsequently the CO2- and the 14CO2-excretion were measured for 24 hours. In this period 64 to 68% of the injected radioactivity were recovered as 14CO2. The curve pattern of 14CO2-excretion indicates two different processes of 14CO2-formation. One characterizing the direct degradation of glutamic acid to CO2 with a high rate constant and a second one with a lower rate constant characterizing the 14CO2-formation via metabolites of glutamic acid. 77% of the total 14CO2-excretion in 24 hours resulted from the direct oxidation of glutamic acid and 23% from the oxidation of intermediates. When 14CO2-formation was measured 10 to 24 hours after injection of 14C-glutamic acid a positive correlation to the content of glutamic acid in the diet was observed. The intestinal tissue contribute considerably to the catabolization of glutamic acid, however, there seems to exist an upper limit for this capacity.

Animal Feed↗
PubMed1985

[Effect of glutamic acid content in the diet on the catabolic rate of the isotope-labeled glutamic acid in rats. 4. Measurement of 14C-glutamic acid oxidation to 14CO2 with various energy sources in the diet].

48 male rats (body weight 80-100 g) were fed with 2 diets different in the glutamic acid content (diet I 2.42 and diet II 6.24% glutamic acid in the dry matter). The mixture of the other synthetic L-amino acids was adapted to the egg protein pattern corresponding 10% crude protein in the diet. Each diet was fed either on 73% or 98 to 104% of the energy maintenance requirement. After 7 days of experimental feeding 14C-U-L-glutamic acid was given to each group by intragastric infusion (i.g.), intraperitoneal (i.p.) or subcutaneous injection (s.c.), respectively, followed by a measurement of the CO2-and 14CO2-excretion during two subsequent periods of 3 hours. The CO2-excretion was lower in animals with restricted energy intake especially during the first 3 hour-period, which was started 2 hours after feed intake. The relative 14CO2-excretion (percent of the dose) was neither significantly influenced by the level of energy intake nor by the amount of dietary glutamic acid. The highest degradation rates of 14C-glutamic acid to 14CO2 were measured after i.g. application (more than 50%), followed by the i.p. injection (nearly 50%) and the lowest values were observed after s.c. injection (about 40%). These differences were only evident during the first CO2-absorption period. Furthermore the s.c. injection caused a lower specific radioactivity of CO2 compared with the data after i.g. and i.p. application. The results suggest the high metabolic activity of the intestinal tissue for glutamic acid.

Animal Feed↗
PubMed1979

Formation of delta-aminolevulinic acid from glutamic acid by a partially purified enzymes system from wheat leaves.

A method for partial purification of an enzyme system from greening wheat leaves which converts 14C-labeled glutamate to delta-aminolevulinic acid is described. The purification entails the successive use of anion and cation exchange, followed by molecular sieving. The enzyme system is unstable in crude form, but the stability is markedly increased after column chromatography on CM-cellulose. The pH profile and the cofactor requirements suggest that at least two enzymes are involved.

Aminolevulinic Acid↗
PubMed1987

Formation of delta-Aminolevulinic Acid from Glutamic Acid in Algal Extracts : Separation into an RNA and Three Required Enzyme Components by Serial Affinity Chromatography.

Extracts from plant chloroplasts and algae catalyze the conversion of glutamate to delta-aminolevulinic acid (ALA) in the first committed step of the tetrapyrrole biosynthetic pathway leading to chlorophylls, hemes, and bilins. The conversion requires ATP, Mg(2+), and NADPH as cofactors. Soluble extracts from Chlorella vulgaris have now been resolved into four macromolecular fractions, all of which are required to reconstitute activity. One fraction contains a low molecular weight RNA which can be separated from the protein components in an active high-speed supernatant by treatment with 1 molar NaCl followed by precipitation of the proteins with (NH(4))(2)SO(4) at 70% saturation. The proteins recovered from the (NH(4))(2)SO(4) precipitate are reactivated by addition of a fraction containing tRNAs isolated from Chlorella by phenol-chloroform extraction and DEAE cellulose chromatography. Three required protein fractions were resolved from the RNA-depleted (NH(4))(2)SO(4) precipitate by serial affinity chromatography on Reactive Blue 2-Sepharose and 2',5'-ADP-agarose. Glycerol was found to stabilize the enzyme activity during the separation process. The majority of the glutamate:tRNA ligase activity was associated with the fraction which was retained by Blue-Sepharose and not retained by ADP-agarose, in agreement with the reported properties of the affinity ligands. The active material in the fraction not retained by Blue-Sepharose eluted as a single component on gel filtration chromatography, with an apparent molecular weight of 67,000. The active component in the RNA fraction also eluted as a single component on gel filtration chromatography.

Journal Article↗
PubMed1987

Gamma-aminobutyric acid- and glutamic acid decarboxylase-immunoreactive neurons in the retina of different vertebrates.

The localization of gamma-aminobutyric acid (GABA)- and L-glutamate 1 carboxy-lyase (GAD)-immunoreactive neurons was compared in the skate, frog, pigeon, chicken, rabbit, and man. Horizontal cells show both GABA and GAD immunoreactivity in the skate, frog, and bird. Certain amacrine cells show GABA and GAD immunoreactivity in all species. The distribution of GABA- and GAD-immunoreactive cell bodies and cell processes was very similar, if not identical, in the skate and man. In the other species, cell populations with GAD immunoreactivity also showed GABA immunoreactivity. However, in the bird, frog, and rabbit, the GABA-immunoreactive amacrine cells were at least twice as numerous as the GAD-immunoreactive cells. In birds, the distributions of the GAD and GABA immunoreactivities were different in the sublayers of the inner plexiform layer. The reason for the difference is currently unknown. GABA-immunoreactive bipolar-like cells were seen in the frog.

Animals↗
PubMed1976

Antagonism of cortical excitation of striatal neurons by glutamic acid diethyl ester: evidence for glutamic acid as an excitatory transmitter in the rat striatum.

Rat striatal cells that were excited by cortical stimulation were found to respond to cortical stimulation with an average latency of 12 msec. Each response consisted of a variable number of spikes with, on the average, a less than 1:1 relationship between the stimulus and the number of spikes generated. Iontophoretic application of glutamic acid diethyl ester (GDEE), a substance reported to be a glutamate antagonist, at currents of +50 to +125 nA in the vicinity of neurons exicted by cortical stimulation, almost totally suppressed the excitation in 90% of the cells, and this suppression was fully reversible. All cells were excited by glutamate. GDEE also suppressed neuronal excitation produced by iontophoretic aspartate, glutamate and DL-homocysteic acid. It is concluded from this study that an excitatory amino acid, either aspartic or glutamic, may function as the transmitter in the corticostriate projection.

Animals↗
PubMed1991

Biological actions of beta-hydroxy-l-glutamic acid, a synthesized structural analogue of glutamic acid.

1. Biological actions of beta-hydroxy-L-glutamic acid (BHGA), a synthesized analog of L-glutamic acid (Glu), were examined using voltage-clamp, electrophysiological and binding assay techniques. 2. Application of BHGA to the voltage-clamped snail neurons elicited an inward current which was blocked by Na(+)-free saline but not by Co(2+)-substituted Ca(2+)-free saline in the voltage-clamped snail neurons. 3. This response exhibited a potency about 10 times stronger than Glu, and was not completely blocked by DL-2-amino-5-phosphonovaleric acid or kynurenic acid. 4. Intraventricular injection of BHGA caused burst discharges in the electrocorticograph (ECoG) of rats whose pattern was similar to that elicited by Glu, but quite different from the ECoG charges induced by NMDA, quisqualic acid, or kainic acid. 5. Receptor binding assays using specific radioactive ligands showed that the binding affinity of BHGA to the Glu receptor was different from that of other agonists tested.

Animals↗