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L-glutamate diethyl ester and deaminated analogues as excitatory amino acid antagonists in rat cerebral cortex.

1. The effects of L-glutamate diethyl ester (GDEE) HCl, glutarate diethyl ester (GlrDEE) and glutarate dimethyl ester (GlrDME) on depolarizing responses to alpha-amino-3-hydroxy-5- methyl-4-isoxazolepropionate (AMPA), kainate (Kain), N-methyl-D-aspartate (NMDA) and quisqualate (Quis), and spontaneous paroxysmal discharges (SPDs) were examined. Experiments were performed on slices of rat cingulate cortex using the in vitro grease gap recording technique in nominally Mg(2+)-free Krebs medium. 2. GDEE HCl (3-14 mM) caused a concentration-dependent depolarization of the d.c. baseline potential. L-Glutamate (0.1-0.5 mM), HCl (15 mM) and sucrose (30 mM) also depolarized the baseline. GlrDEE (3-12 mM) and GlrDME (4-26 mM) had no consistent effect on baseline potential. 3. GDEE HCl (10 mM) had no effect on depolarizing responses to AMPA, Kain and NMDA, but caused potentiation of those to Quis with a dose-ratio of 0.53 (0.44-0.63) (n = 4). In two other experiments, where the depolarization of the baseline induced by GDEE HCl was large, a depression of Quis response amplitude was observed. 4. GlrDEE (10 mM) antagonized depolarizing responses to Kain, and to a lesser extent NMDA, with dose-ratios of 2.14 (1.92-2.38) and 1.61 (1.39-1.87), respectively. This concentration of GlrDEE had no effect on AMPA responses, but potentiated Quis responses, with a dose-ratio of 0.64 (0.58-0.71). 5. GlrDME (10 mM) antagonized depolarizing responses to Kain and to Quis, with dose-ratios of 1.66 (1.48-1.85) and 1.22 (1.15-1.29), respectively, and had no effect on responses to NMDA. 6. The SPDs were inhibited by GDEE HCI (IC50 6.7 +/- 0.37mM), GlrDEE (IC50 5.6 +/- 0.38 mM) and GlrDME (IC50 10.4 +/- 0.73 mM). 7. In conclusion, there is little evidence that GDEE HCI is an antagonist of the postsynaptic excitatory amino acid receptors in the rat neocortex, and its effects may result from its contamination with Lglutamate and increased osmolarity of the bathing medium at high concentrations. The deaminated analogues of GDEE are very weak Kain antagonists.

Amino Acids↗

Low molecular weight organic acids in the urine of the newborn.

The urinary excretion of seven selected low molecular weight organic acids in normal neonates was measured by gas chromatography. First and third to fourth day of life excretion of the following compounds was significantly unchanged: 3-OH-butyric acid (less than 13 mumol/mmol creatinine), succinic acid (approx. 43 mumol/mmol creatinine), adipic acid (approx. 12 mumol/mmol creatinine), 2-OH-glutaric acid (approx. 23 mumol/mmol creatinine), 3-OH-3-Me-glutaric acid (approx. 25 mumol/mmol creatinine) and citric acid (approx. 115 mumol/mmol creatinine). The excretion of 4-OH-phenyl-acetic acid increased during the first four days of life (from less than 8 mumol/mmol creatinine to approx. 20 mumol/mmol creatinine). It is postulated that urinary orgainc acid excretion in the neonate, which is clearly different from the adult urinary pattern, is a reflection of the specific neonatal metabolic situation, including a high fatty acid utilisation and a low protein catabolism.

Adipates↗

D-lysine catabolic pathway in Pseudomonas putida: interrelations with L-lysine catabolism.

The isolation of several mutant strains blocked in l-lysine degradation has permitted an assessment of the physiological significance of enzymatic reactions related to lysine metabolism in Pseudomonas putida. Additional studies with intact cells involved labeling of metabolic intermediates from radioactive l- or d-lysine, and patterns of enzyme induction in both wild-type and mutant strains. These studies lead to the conclusions that from l-lysine, the obligatory pathway is via delta-aminovaleramide, delta-aminovalerate, glutaric semialdehyde, and glutarate, and that no alternative pathways from l-lysine exist in our strain. A distinct pathway from d-lysine proceeds via Delta(1)-piperideine-2-carboxylate, l-pipecolate, and Delta(1)-piperideine-6-carboxylate (alpha-aminoadipic semialdehyde). The two pathways are independent in the sense that certain mutants, unable to grow on l-lysine, grow at wild-type rates of d-lysine, utilizing the same intermediates as the wild type, as inferred from labeling studies. This finding implies that lysine racemase in our strain, while detectable in cell extracts, is not physiologically functional in intact cells at a rate that would permit growth of mutants blocked in the l-lysine pathway. Pipecolate oxidase, a d-lysine-related enzyme, is induced by d-lysine and less efficiently by l-lysine. Aminooxyacetate virtually abolishes the inducing activity of l-lysine for this enzyme, suggesting that lysine racemase, although functionally inactive for growth purposes, may still have regulatory significance in permitting cross-induction of d-lysine-related enzymes by l-lysine, and vice versa. This finding suggests a mechanism in bacteria for maintaining regulatory patterns in pathways that may have lost their capacity to support growth. In addition, enzymatic studies are reported which implicate Delta(1)-piperideine-2-carboxylate reductase as an early step in the d-lysine pathway.

Acetates↗

Indirect coupling to Na+ of p-aminohippuric acid uptake into rat renal basolateral membrane vesicles.

Experiments with basolateral membrane vesicles prepared from rat kidney cortex were performed to study the mechanism by which p-aminohippuric acid (PAH) is taken up across the contraluminal membrane and is concentrated in proximal tubule cells. An inward Na+ gradient failed to stimulate [3H]PAH uptake compared with K+ or Li+ and did not cause intravesicular PAH accumulation above equilibrium distribution. In the absence of Na+, the dicarboxylates glutarate and suberate cis-inhibited and trans-stimulated [3H]PAH uptake, indicating a common transport system. In the presence of Na+, 10 microM glutarate in the incubation medium did not cis-inhibit, but rather stimulated [3H]PAH uptake and caused PAH accumulation above equilibrium distribution ("overshoot"). Li+ diminished this stimulation, but was without effect on [3H]PAH/PAH- and [3H]PAH/glutarate exchange. The data indicate the coexistence of a Na+ -coupled, Li+-sensitive transport system for dicarboxylates and a Li+ -insensitive PAH/dicarboxylate exchanger in the basolateral membrane. We propose that dicarboxylates are cotransported with Na+ into the cell and subsequently exchange for extracellular PAH at the basolateral membrane. PAH uptake is thereby indirectly coupled to Na+ via the Na+/dicarboxylate cotransporter.

Aminohippuric Acids↗

Screening newborns for multiple organic acidurias in dried filter paper urine samples: method development.

Screening urine for inherited and acquired organic acidurias in newborns has the potential of preventing severe disease, mental retardation, and death. A method for screening dried urine filter paper samples for acidic markers of at least 20 different metabolic conditions has been developed. These conditions include, among others, maple syrup urine disease; methylmalonic, propionic, isovaleric, glutaric, and hydroxymethylglutaric acidurias; methylcrotonylglycinuria; medium-chain acyl-CoA dehydrogenase deficiency; inherited vitamin responsive disorders B12, biotin, B2), and acquired deficiencies of these vitamins. The preparation of the urine extract is identical to the method we use to screen infants for neuroblastoma. Screening is based on a highly sensitive and specific determination of eight organic acid markers by an automated computerized gas chromatography mass spectrometry system using selected ion monitoring. The markers used for screening are methylmalonic acid, 2-hydroxyisocaproic acid, glutaric acid, propionylglycine, isovalerylglycine, 3-methylcrotonylglycine, hexanoylglycine, and 3-phenylpropionylglycine. The extraction efficiencies of these acids from dried filter paper were similar to extraction from water, ranging from about 40% to 80%, except for propionylglycine which showed a low extraction efficiency of 11-13%. The stability of these acids on filter paper exposed to room air and temperature over a period of 15 d was adequate for the use of this collection method for organic aciduria screening. Normal levels, adjusted to urinary creatinine, were established for these acids in 519 urine filter paper samples obtained from 3-wk-old newborns. This screening method was tested on samples obtained from 12 patients with known organic acidurias including stored urine filter paper collected at 3-wk of age from two infants later found to have organic acidurias.

Amino Acids↗

Transepithelial urate transport by avian renal proximal tubule epithelium in primary culture.

Birds are uricotelic, and because they excrete urate by renal tubular secretion, they provide a convenient model for examination of this process. Primary monolayer cultures of the isolated renal proximal tubule epithelium from the domestic chicken, Gallus gallus L., were mounted in Ussing chambers where several substrates/inhibitors of renal organic anion transporters were tested for the sidedness and specificity of their effects on transepithelial urate transport. Transepithelial electrical resistance, electrical potential and sodium-dependent glucose current were monitored to detect nonspecific effects. Under control short-circuited conditions the ratio of unidirectional fluxes of [(14)C]urate was found to be 3:1. Active net secretion was specifically inhibited by 1 mmol l(-1) probenecid and 10 mmol l(-1) para-aminohippuric acid (PAH). Bromocresol Green, cimetidine, nocodozole, cytochalasin D and ouabain also inhibited secretion but were toxic. Interstitial-side lithium (5 mmol l(-1)) and glutarate (1 mmol l(-1)) specifically blocked transport, but 10-100 micromol l(-1) glutarate had no effect. Interstitial estrone sulfate (ES) stimulated urate secretion at 10 micromol l(-1) but was inhibitory at 500 micromol l(-1). Active PAH secretion (5:1 flux ratio) was inhibited 34% by 330 micromol l(-1) urate. ES (500 micromol l(-1)) blocked the remainder. From the lumen side, glucose-free, Cl(-)-free and high K(+) (30 mmol l(-1)) solutions, or an alkaline pH of 7.7 had no effect on urate transport and neither did several compounds known to be uricosuric. Lumen-side methotrexate (500 micromol l(-1)) and MK571 (20 micromol l(-1)) strongly inhibited urate secretion. MK571 had no effect from the interstitial side. RT-PCR revealed mRNA for OAT1-, OAT3-, MRP2- and MRP4-like organic anion transporters in chicken proximal epithelium.

Animals↗

Inhibition of liver acetyl-coenzyme-A carboxylase by 2-tetradecanylglutarate.

In a previous study (A. ENDO, et al., J. Antibiotics 38: 599 approximately 604, 1985), 2-alkyl glutarate and its derivatives isolated from cultures of Gongronella butleri were shown to inhibit animal acetyl-CoA carboxylase. In the present communication, the inhibition of liver acetyl-CoA carboxylase was investigated with several 2-alkyl glutarate and 2-alkyl succinate analogs. Their inhibitory potency increased with the chain length of the alkyl moiety, and 2-tetradecanylglutarate was most potent among the inhibitors tested. Kinetic analysis indicated that inhibition by 2-tetradecanylglutarate was non-competitive with respect to the substrates, ATP, HCO3- and acetyl-CoA, and competitive with respect to the allosteric regulatory citrate, giving a Ki value of 40 microM. Sucrose density gradient centrifugation analysis showed that the citrate-induced polymerization of the enzyme was inhibited by 2-tetradecanylglutarate.

Acetyl-CoA Carboxylase↗

[Inner and outer immobilization of chloroplasts].

The effects of glutaric aldehyde on pea leave chloroplasts and their inactivation kinetics were studied. Optimization of the chloroplasts fixation by glutaric aldehyde resulted in a 5-fold increase of stability of the chloroplasts. Immobilization of the chloroplasts in agar-agar gels was performed; the ability of chloroplasts for photooxidation of H2O was thereby retained. Immobilization did not actually affect the stability of chloroplasts. The inactivation kinetics of fixed and immobilized chloroplasts are in good agreement with the previously described model for inactivation of native chloroplasts.

Aldehydes↗

[Application of tandem mass spectrometry in diagnosis of organic acidemias].

OBJECTIVE: The diagnosis of organic acidemia is very difficult and needs special test methods. Recently the tandem mass spectrometry has been used in screening for and diagnosis of this inborn error of metabolism. The aim of the present study was to utilize a dry blood filter paper method for acylcarnitines profiles test using tandem mass spectrometry in diagnosis of organic acidemias in high risk children. METHOD: One thousand patients (642 were males and 358 females) with high risk of inborn error of metabolism were studied, the median of their age was 2 years. The blood specimens were collected on filter paper, punched and extracted into methanol solution with stable isotope labeled internal standards of acylcarnitine, then derivatized with butanolic-HCI. After preparation, the samples were analyzed by tandem mass spectrometry. The volume of the acylcarnitines was calculated with special software. RESULTS: Forty patients (4.0%) were diagnosed as organic acidemias among the 1000 patients, including 20 methylmalonic acidemia, 6 propionic acidemia, 3 isovaleric acidemia, 3 glutaric acidemia type I, 3 glutaric acidemia type II, 2 biotinidas deficiency, 1 3-methylcrotonyl-CoA carboxylase deficiency, 1 3-hydroxy-3-methylglutaryl-CoA lyase deficiency, and 1 beta-keto thiolase deficiency. The common clinical symptoms and signs of these patients were motor and mental developmental retardation, spasm, lethargy, coma, hypotonia, vomiting, and feeding difficulty. Routine laboratory tests suggested metabolic acidosis, hyperammonemia, hyperlactacidemia, hypoglycemia, anemia, and abnormal liver function. CONCLUSION: A part of organic acidemias can be rapidly diagnosed by tandem mass spectrometry through acylcarnitine profiles analysis in dry blood filter paper. Combination of tandem mass spectrometry with urine gas chromatography mass spectrometry would improve more accurate diagnosis of organic acidemias.

Adolescent↗

[Electron dense substance of thylakoids in chloroplasts of tansy Tanacetum vulgare L].

An intrathylakoid electron opaque substance, further referred to as loculin, is found in 80-90 % of thylakoids of tansy leaf mesophyll chloroplasts at the stage of flower bud formation and flowering. Upon conventional isolation of chloroplasts in aqueous solution, and fixation in osmium solution alone, loculin is not retained in thylakoids. Preliminary fixation of leaves in glutaraldehyde makes it possible to isolate chloroplasts without injuring the envelope and stroma (glutar chloroplasts), and loculin is retained in thylakoids under these conditions. Upon prolonged incubation of glutar chloroplasts (for 24 h), loculin leaves thylakoids in the form of drops concentrating on the chloroplast envelope. Upon crossing the thylakoid membrane and chloroplast, loculin properties remain unchanged. It is assumed that loculin is an important metabolite necessary for active growth.

Chloroplasts↗

Organic anion secretion by winter flounder renal proximal tubule primary monolayer cultures.

Recent models of para-aminohippuric acid (PAH) transport by renal proximal tubule have been deduced from isolated membrane vesicles and stopped flow microperfusion. The flounder proximal tubule primary monlayer cultures mounted in Ussing chambers have provided a means to examine the relationship of these models to transepithelial transport. Unidirectional transepithelial 3H-PAH fluxes were determined in 12-day-old monolayers on floating collagen gels under continuously short-circuited conditions. The kinetic values of PAH secretory flux were complex. Over the range of 0.6 microM to 1.5 mM the K1/2 was 0.4 mM and Vmax was 80 nmol/cm2/h. Reabsorptive flux did not saturate. 1 mM probenecid inhibited 95% of the secretory flux (0.07 +/- 0.18 compared with control of 1.38 +/- 0.34 nmol/cm2/h at 10 microM PAH) and had no significant effect on reabsorptive flux (probenecid, 0.07 +/- 0.04; control, 0.05 +/- 0.01 nmol/cm2/h). 0.1 mM 4-acetamido-4'-isothiocyanalostilbene-2,2'-diasulfonic acid and 1 mM benzoylpropionic acid also significantly inhibited secretory flux (95 and 78%, respectively). These inhibitors appeared to be specific in that no effects on transepithelial potential difference, resistance or phlorizin-sensitive current were seen. Removal of Na during flux measurement reduced net PAH secretion to zero, and 1 mM ouabain reduced PAH secretory flux to 10% of control within 90 min with no effect on reabsorptive (leak) flux. Clamping transepithelial voltage to +/- 10 mV had no significant effect on PAH fluxes. Addition of glutarate to flounder saline significantly inhibited PAH secretory flux starting at 0.1 mM and caused 90% inhibition at 1 mM; no stimulation of transport was noted at any glutarate concentration.

Animals↗

[Effects of weak solutions of aldehydes on EEG changes in rats].

Alternations of EEG have been investigated after single intraarterial infusion of formaldehyde, glutaric aldehyde and its mixture in 50 adult male rats. The dissolved solutions of aldehydes were shown to have complicated inhibitive activity which consists of two phases. The first phase of EEG inhibition rapidly develops and it isn't very long in its duration. The second one is much more durable. Formaldehyde causes the first phase of inhibition in general, though glutaric aldehyde promotes especially the appearance of the second phase. The mixture of two aldehydes demonstrates synergic activity which is shown as significant increase of EEG inhibition as compared to individual inhibitive activity of aldehydes. The inhibitive influence of aldehydes is fully reversible, nonspecific and doesn't cause post-experimental disorders. The highest effect of brain protection from ischaemia damages coincides with development of maximum inhibition of specific brain functions during the second phase of EEG depression.

Aldehydes↗

Prevention of oxalate urolithiasis by some compounds.

Male Wistar rats were fed a basal diet, Purina Laboratory Chow, and an oxalate calculi-producing diet (CPD). The CPD was the basal diet containing 3 per cent glycolic acid. Sodium pyruvate, DL-alanine, alpha-keto glutaric acid, thiamine pyrophosphate, and L-glutamic acid were added to the CPD to determine their effectiveness in preventing calculi formation. The effectiveness of methyl glyoxal was determined by adding it to the drinking water. Rats fed CPD for 4 weeks developed calculi in the ureters, bladder, renal tubules, and/or renal pelvis and papilla. Rats in groups fed alanine and/or pyruvate had no calculi in their renal tubules or ureters; additionally, these rats had a significant reduction in incidence and amount of deposits in the renal pelvis and bladder. Rats in groups fed alpha-keto glutaric acid, thiamine pyrophosphate, L-glutamic acid, and methyl glyoxal developed equally or more severe oxalate urolithiasis than those on CPD alone. Results of this study show that either pyruvate or alanine at appropriate levels may be beneficial in preventing oxalate urolith formation.

Alanine↗

[Problems of environmental exposure to toxic effects of glutaraldehyde in medicine].

Glutaraldehyde is an antibacterial and antiviral agent commonly used for cleaning and disinfection of endoscopic equipment. The accepted glutaraldehyde air-concentration is 0.2 ppm. The irritant action, allergic potential and possible neurotoxicity of glutaral have been reported. Red eyes, cough, headache and running nose are most frequent symptoms of glutaral activity. The incidence of bronchial asthma and contact dermatitis has also been reported. In order to avoid occupational hazards of glutaraldehyde closed washing-disinfection systems, proper ventilation (20 cycles per hour), vapour recovery safety nozzle and neutralizing agent should be used.

Asthma↗

Biochemical investigation of young hospitalized Chinese children: results over a 7-year period.

During the seven years from January 1989 to December 1995, we investigated 2,269 Chinese infants and young children for metabolic disorders in Hong Kong. These young patients, all aged under 4 years and originated from southern China, were ill with no apparent cause and had clinical manifestations suggestive of inherited metabolic diseases. A spot urine and a plasma sample were obtained from each patient for biochemical analysis, including urinary organic acid identification and plasma amino acid analysis. Six cases of mucopolysaccharidosis, four multiple carboxylase deficiency, three 2-methylacetoacetyl CoA thiolase deficiency, two methymalonic aciduria, one glutaric aciduria type I, one glutaric aciduria type II, one a-oxoglutaric aciduria, and one case of orotic aciduria were detected. There were also single suspected cases of medium-chain acyl-CoA dehydrogenase deficiency and isovaleric aciduria. No primary amino acid disorder, such as phenylketouria and maple syrup urine disease, has been detected. Our results suggest that a different pattern of inherited metabolic diseases exists in the southern Chinese when compared with the Chinese in other regions of China.

Child, Preschool↗

Evidence of a single origin for the most frequent mutation (R402W) causing glutaryl-CoA dehydrogenase deficiency: identification of 3 novel polymorphisms and haplotype definition.

Glutaryl-CoA dehydrogenase (GCDH) deficiency causes glutaric aciduria type I (GA I), an inborn error of metabolism that is characterized clinically by dystonia and dyskinesia, biochemically by excretion of glutaric and 3-hydroxyglutaric acids in urine, and pathologically by neural degeneration of the caudate and putamen. To date, over 70 mutations in GCDH gene have been identified, single prevalent mutations have been found in communities in which GA I is particularly common, but generally GA I is heterogeneous. The most frequent mutation in Caucasians, R402W, has been identified in 12-16% of alleles. Here we report the frequency of mutation R402W in GA I Spanish patients, the characterization of three novel GCDH polymorphisms (IVS2+48T>C, IVS2-82T>G and 3'UTR 1518A>G) which, in combination with the two polymorphisms previously described (IVS2+64G>C, 1209G>T) gave rise to the first definition of GCDH haplotypes and their frequencies in control population. Linkage disequilibrium has been found between mutation R402W and a specific haplotype, suggesting a single origin for this mutation. Hum Mutat 15:207, 2000.

Amino Acid Substitution↗

Chelation-controlled radical chain reactions studied by electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry (ESI-MS) is a novel tool for the investigation of chemical reactions in solution and for the direct detection and identification of reactive intermediates. The tributyltin hydride mediated addition of tert-butyl iodide to dimethyl 2-cyclohexyl-4-methyleneglutarate (2) in the presence of Lewis acids was investigated by ESI-MS using a microreactor coupled on-line to an ESI mass spectrometer. For the first time we have been able to show that transient radicals in radical chain reactions can be detected unambiguously under steady-state conditions in the reaction solution and can be characterized by ESI-MS/MS and accurate mass determination. The detection of different heterodimer radical complexes by ESI-MS/MS has provided new insights into the mechanism of Lewis acid controlled radical chain reactions. Dimeric chelate complexes of glutarates, such as 2 and 3, and Lewis acids, like Sc(OTf)3, MgBr2OEt2 and LiClO4, were observed as well as higher aggregates with additional equivalents of Lewis acid. Evidence for a dynamic equilibrium of the complexes in solution was found by NMR spectroscopy. The ESI-MS investigation of the chelation of glutarate 2 with various Lewis acids has led to the conclusion that the tendency for Lewis acids to form dimeric chelate complexes and higher aggregates has an important effect on the stereoselective outcome of the radical reactions.

Journal Article↗

Improved liquid chromatography/mass spectrometric analysis of low molecular weight carboxylic acids by ion exclusion separation with electrospray ionization.

An improved, simple and sensitive analytical method for low molecular weight organic acids has been developed. A mixture of acetic, propionic, butyric, glycolic, lactic, 2-hydroxybutyric, malonic, succinic, glutaric, tartaric and citric acids was separated on a semi-rigid styrene-divinylbenzene copolymer-based H-type cation-exchange resin (ULTRON PS-80H) based on an ion exclusion chromatographic (IEC) mechanism, with detection using electrospray ionization mass spectrometry (ESI-MS). Formic or acetic acid was used as a mobile phase to separate the carboxylic acids within 15 min. For liquid chromatography/mass spectrometry (LC/MS), the ESI interface was used in both positive and negative ionization mode. ESI produced reasonable signals from positive ions, [M+NH(4)](+), of acetic, propionic and butyric acids and from negative ions, [M-H](-), of glycolic, lactic, 2-hydroxybutyric, malonic, succinic, glutaric, tartaric and citric acids. The effects of ionization parameters, source temperature, capillary voltage and cone voltage, on sensitivity and linearity were examined. Linear plots of peak area versus concentration were obtained over the range 0.1-20 ppm for MS detection. The detection limits of the target carboxylic acids calculated at signal-to-noise (S/N) ratio of 3 ranged from 9 to 59 ppb. The reproducibility of retention times and peak areas were 0.55-1.25 and 0.85-2.45%, respectively.

Carboxylic Acids↗