Detection of molecules related to the GABAergic system in a single-cell eukaryote, Paramecium primaurelia.

Gamma-aminobutyric acid (GABA)-related molecules were identified in Paramecium primaurelia by immunocytochemical methods, and GABA(A) receptors by their histochemical BODIPY-binding sites. Confocal microscope analysis showed different localizations according to the stages of the developmental cycle. A comparison was made with the cholinergic molecules, such as the acetylcholine biosynthetic enzyme (choline acetyltransferase), in double-labelled cells by confocal microscopy. In vivo experiments suggested the involvement of GABA-related molecules in cell-cell interaction.

Treatment with vigabatrin may mimic alpha-aminoadipic aciduria.

PURPOSE: We describe a secondary effect of treatment with vigabatrin (VGB). A significant increase in alpha-aminoadipic acid (AAA) occurred in plasma and urine of VGB-treated children, thus mimicking a known rare metabolic disease, alpha-aminoadipic aciduria (AAAuria). METHODS: We studied eight children, aged from 3 months to 5 years, who were receiving VGB for drug-resistant partial epilepsies. Plasma and urine amino acids were assayed with ninhydrin detection on an automated Beckman 6300 analyzer. RESULTS: In eight out of eight children, there was a significant increase of AAA in plasma and in urine. Plasma values ranged from 7 to 8 microM (control values, < 5) and urinary values from 67 to 274 mmol/mol creatinine (control values, < 25). CONCLUSIONS: The concentrations of AAA in these VGB-treated children were as high as the concentrations found in the inherited metabolic disease, AAAuria. This could lead to incorrect diagnosis and to inappropriate genetic counseling. Thus whenever a genetic metabolic disease is suspected, amino acid chromatography testing should be performed before initiation of treatment with VGB.

Gamma-aminobutyric acid, its related enzymes and receptor-binding sites in the human ovary and fallopian tube.

The concentration of gamma-aminobutyric acid (GABA), the activities of related enzymes, i.e. glutamate decarboxylase and GABA transaminase, as well as the level of specific GABA binding sites were determined in ovaries and fallopian tubes obtained surgically from 31 women. None of the biochemical parameters examined showed a correlation with the age and hormonal background (serum estradiol and progesterone levels) of the patients. The respective ovarian and tubal values did not differ significantly in groups operated on because of uterine myoma and carcinoma. In organs from pregnant women, however, most GABAergic markers altered significantly. These findings indicate some gestation-related role for the ovarian and tubal GABA systems in humans.

GABAergic inhibition on dopamine cells of the fish retina: a [3H]dopamine release study with isolated fractions.

Inner retinal cells including dopamine (DA) cells were isolated and fractionated from the carp (Cyprinus carpio) retina by an enzyme cell dissociation and metrizamide gradient centrifugation method. When gamma-aminobutyric acid (GABA) antagonists (bicuculline and picrotoxin) were added into the perfusate over such a cell fraction, they stimulated the release of [3H]DA which had been preloaded in the cell fraction. The action of GABA antagonists was dose and Ca2+ dependent. Their minimal effective concentration was very low (0.5 microM). A similar action was elicited by high K+. In the presence of excess GABA, this stimulatory action of GABA antagonists and high K+ on [3H]DA release was completely abolished. To interpret the action of GABA antagonists on DA cells, isolated cell fractions were preincubated with GABAse. After such a treatment, the stimulatory effects of GABA antagonists and high K+ on [3H]DA release were differentiated from each other; the former disappeared whereas the latter remained unchanged. The data strongly suggest that GABA inhibits the DA release from retinal DA cells and thus the GABA antagonists affect [3H]DA release from cell fractions not by a direct membrane action but by a disinhibition mechanism via GABA receptors on the DA cell bodies.

Treatment of Huntington disease with gamma-acetylenic GABA an irreversible inhibitor of GABA-transaminase: increased CSF GABA and homocarnosine without clinical amelioration.

gamma-Acetylenic GABA (GAG, RMI 71.645), a potent irreversible inhibitor of gamma-aminobutyric acid transaminase, was given orally in various dosage schedules to 14 patients with Huntington disease. The biochemical effects of the drug on cerebrospinal fluid (CSF) concentrations of gamma-aminobutyric acid (GABA) and the GABA-containing dipeptide, homocarnosine, were measured in 10 of 14 patients. Treatment with GAG increased CSF concentrations of GABA and homocarnosine as compared to pretreatment values, suggesting that the drug increased brain GABA concentration. Despite this neurochemical effect, the clinical state was not improved. Except for single seizure episodes in five patients, GAG therapy was well tolerated. These results do not exclude the possibility that agents that augment CNS GABAergic function may prove useful in therapy of Huntington disease.

Anacystis nidulans mutants resistant to aromatic amino acid analogues.

Three classes of mutants of Anacystis nidulans were selected on the basis of resistance to fluorophenylalanine and 2-amino-3-phenylbutanoic acid. The most frequent type exhibited DAHP synthetase (7-phospho-2-keto-3-deoxy-D-arabino-heptonate-D-erythrose-4-phosphate-lyase [pyruvate phosphorylating], EC 4.1.2.15) activity identical to that of the parental strain. The second type was characterized by extremely low levels of the activity. The third type had a DAHP synthetase showing decreased sensitivity to inhibition by L-tyrosine. The enzyme was purified 140-fold from wild-type and feedback-insensitive strains, and the kinetics of the reaction was examined. The activity of the wild-type enzyme was inhibited 75% in the presence of 2.0 X 10-3 M tyrosine, and the altered enzyme was inhibited 10%. The following apparent constants were obtained from kinetic studies with partially purified wild-type enzyme: S0.5 for D-erythrose-4-phophate equal to 7.1 X 10-4 M; S0.5 for phosphoenolpyruvate equal to 1.4 X 10-4 M. Inhibition by tyrosine was mixed with respect to binding of both D-erythrose-4-phosphate and phosphoenolpyruvate. In addition, tyrosine promoted cooperative interactions in the binding of phosphoenolpyruvate. For the altered enzyme the following apparent constants were obtained: S0.5 for D-erythrose-4-phosphate equal to 7.1 X 10-4 M; S0.5 for phosphoenolpyruvate equal to 2.9 X 10-4 M. Inhibition by tyrosine was mixed with respect to D-erythrose-4-phosphate and competitive with respect to phosphoenolpyruvate. Tyrosine did not promote cooperative effects in the binding of phosphoenolpyruvate to the altered enzyme.