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PubMed1993

A new HPLC method for pidotimod plasma levels determination.

This paper describes a HPLC method for the determination of Pidotimod (3-L-pyroglutamyl-L-thiazolidine-4-carboxylic acid; PGT/1A), a new biological response modifier, in plasma. The column was an Aminex Ion Exclusion HPX 874 with a PRP precolumn, the mobile phase was 0.05% sulfuric acid-acetonitrile (88:12, v/v), the flow rate was 0.6 ml/min, the detection wavelength was 210 nm. Plasma (1 ml) was added with internal standard (Oxiracetam, concentration 400 micrograms/ml) (50 microliters) and 35% perchloric acid (100 microliters). The supernatant (0.5 ml) was added with mobile phase (0.5 ml) and, after centrifugation, injected into the column. The retention times of Pidotimod and Oxiracetam were 16.5 and 13.8 min. respectively. The method was validated for recovery, accuracy and reproducibility. The results after oral administration of 800 mg of Pidotimod in male volunteers were also given. This method is better than that previously described because it utilizes an internal standard and reaches a lower detection limit.

Adult↗

PubMed1999

Age-dependent differences in glutamate-induced phosphorylation systems in rat hippocampal slices.

Glutamate receptor induced changes in the activity of different phosphorylation systems were measured in hippocampal slices from 12- and 56-day-old rats, by determining the endogenous phosphorylation of 2.5% perchloric acid (PCA) soluble proteins. We identified among these proteins an 85, 80 kDa and the tau protein as specific substrates for protein kinase A (PKA), MARCKS, and neurogranin as specific substrates for protein kinase C (PKC), and prostaglandin-D-synthase as substrate for casein kinase II (CKII). In addition, a 35 kDa protein was phosphorylated by calcium/calmodulin dependent kinase II and protein kinase C and a 21 kDa protein was a substrate for all investigated kinases. The basal endogenous phosphorylation of 2.5% PCA soluble proteins changed during development qualitatively and quantitatively. Thus, the phosphorylation degree of nearly all proteins declines during maturation. Activation of mGluR induced an increased phosphorylation of PKA, PKC, and CKII substrates in hippocampal slices from 12-day-old rats, but in slices of 56-day-old rats only PKA and to a lower extent PKC substrates were affected. In contrast, stimulation of NMDA receptors led to an enhancement of CKII and PKA dependent phosphorylation only in slices of young animals, whereas the endogenous phosphorylation of some proteins in adult slices was actually decreased. These data showing developmental changes in the coupling of metabotropic and ionotropic glutamate receptors to different phosphorylation systems are discussed in the light of altered physiological properties of the mature hippocampus.

Aging↗

PubMed1989

Very rapid assay of gamma-aminobutyric acid in mouse brain regions within 3 minutes by high-performance liquid chromatography with electrochemical detection.

For assay of gamma-aminobutyric acid (GABA) in brain tissue, a very rapid and simple chromatographic procedure using high-performance liquid chromatography (HPLC) with electrochemical detection (ECD) in combination with precolumn o-phthalaldehyde (OPA) derivatization is described. Perchloric acid extracts of the tissue were mixed with OPA/beta-mercaptoethanol solution and the mixture was injected onto the HPLC system. The present method permits GABA assay within less than 3 min in one chromatographic run. Up to 100 samples a working day can be analyzed in the present method. The present method has been applied to the measurement of GABA levels in discrete brain regions of mice treated with aminooxyacetic acid and isoniazid.

Aminooxyacetic Acid↗

PubMed1997

No effect of glutamate on metabolic disturbances in hippocampal slices of mature fetal guinea pigs after transient in vitro ischemia.

The involvement of glutamate in the development of cerebral metabolic disturbances in mature fetuses after transient ischemia was studied using a hippocampal slice model. We investigated the effects of exogenously applied glutamate or glutamate antagonists on the recovery of energy metabolism and protein synthesis rate (PSR) in hippocampal slices of mature guinea pigs after in vitro ischemia. The slices were incubated in a thermostatically controlled flow-through chamber and gassed with carbogen (95% O2/5% CO2). In vitro ischemia was induced by transferring the slices to an aglycemic, artificial cerebrospinal fluid (aCSF) equilibrated with 95% N2/5% CO2. In a first set of experiments slices were exposed to 10 mM glutamate during a 20-40 min period of in vitro ischemia. In a second set slices were incubated in aCSF containing MK-801 (100 microM) or kynurenic acid (0.5 mM) 30 min before, during and 2 h after in vitro ischemia. After a 12 h recovery phase, the concentrations of adenylates in the slices were measured by HPLC after extraction with perchloric acid. PSR was calculated from the rate of incorporation of [14C]leucine into tissue proteins. Neither glutamate nor glutamate antagonists had any effect on the postischemic recovery of energy metabolism and PSR when applied during in vitro ischemia. It is therefore concluded that glutamate does not play a major role in the development of metabolic disturbances in hippocampal slices from mature guinea pig fetuses subjected to transient in vitro ischemia.

Adenosine Triphosphate↗

PubMed2003

Detection and amplification of a small enantiomeric imbalance in alpha-amino acids by a helical poly(phenylacetylene) with crown ether pendants.

We have designed a novel stereoregular poly(phenylacetylene) bearing the bulky crown ether as the pendant (poly-1) for the amino acid binding site. The polymer forms a one-handed helix upon complexation with l-amino acid perchlorates, and the complexes exhibit an induced circular dichroism (ICD) with the same Cotton effect signs in the polymer backbone region through a significant cooperative interaction. Poly-1 is highly sensitive to the amino acid chirality and can detect an extremely small enantiomeric imbalance in alpha-amino acids (less than 0.005% enantiomeric excess of alanine, for example).

Acetylene↗

PubMed1999

Gastric juice ascorbic acid is related to Helicobacter pylori infection but not ethnicity.

BACKGROUND: Maori and Pacific Island ethnic groups in New Zealand have a high risk for gastric cancer. Low levels of gastric juice ascorbic acid (vitamin C) have been suggested to be a risk factor for gastric cancer. Previous studies have shown that gastric juice ascorbic acid may be independently associated with both ethnicity and Helicobacter pylori infection. This study aimed to examine the interrelationship between H. pylori and ethnicity in New Zealand. METHODS: Gastric juice was collected into 70% perchloric acid preservative and stored at -80 degrees C. Ascorbic acid was analysed by high-performance liquid chromatography using ion-pair chromatography and electrochemical detection. Inflammation and atrophy was graded from biopsies from multiple sites in the antrum and body. Gastric juice was collected from 89 patients during routine endoscopy. RESULTS: There was a wide range of measured gastric juice ascorbic acid from 0.001 to 410 microg/mL. The median concentration of ascorbic acid for H. pylori-negative patients was 1.78 microg/mL (n = 57) and 0.12 microg/mL (n = 32) for H. pylori-positive patients (P = 0.001). Gastric juice ascorbic acid concentration was not associated with age, endoscopic diagnosis or intestinal metaplasia, but was significantly associated with the degree of acute inflammation (P = 0.01) and the presence of atrophy (P = 0.04). The median ascorbic acid concentration for European patients was 0.92 microg/mL (n = 44) and 0.09 microg/mL (n = 38) for Maori and Pacific Island ethnic groups combined (P = 0.1). Multiple step-wise regression analysis showed that only H. pylori infection was a significant factor for predicting ascorbic acid concentrations (r2 = 0.12). CONCLUSIONS: This study has confirmed that gastric juice ascorbic acid concentration is lower in the presence of H. pylori infection.

Adult↗

PubMed1983

Role of 5-hydroxytryptamine (serotonin) in oral glucose intolerance.

The aim of the present study was to investigate the metabolic base of psychoneurological symptoms, most notably tiredness and loss of concentration ability, appearing after carbohydrate-rich meals and during oral glucose tolerance tests. Such metabolic changes may be the cause of many accidents attributed to the "human factor". Oral glucose tolerance tests (OGTT) were performed in healthy volunteers, divided into symptomatic (n = 21) and symptom-free (n = 15) groups. Since the symptoms arising during OGTT simulate those in alcohol intoxication, a method for clinical examination of alcohol intoxication was used to separate symptom-free from symptomatic subjects. Comparison of blood glucose concentrations during OGTT revealed the symptomatic group to have higher concentrations in blood samples taken 15 min (p less than 0.05), 30 min (p less than 0.01), 45, 60 and 90 min (p less than 0.05) after intake of glucose than those having no symptoms. The symptoms began when the glucose concentration was at maximum, some 38 min (mean value) following the ingestion of glucose. The symptomatic subjects demonstrated a normal assimilation rate of glucose (mean 1.7 %/min) as tested with intravenous glucose tolerance tests and the differences in blood glucose concentrations between the groups is concluded to depend on the rate of absorption of glucose from the intestinal tract. The enterochromaffine cells of the intestinal tract are the site of biosynthesis, storage and release of 5-hydroxytryptamine (5-HT) (serotonin). In whole blood practically all of the 5-HT is of thrombocytic origin. Thrombocytes are thought to be peripheral models of 5-HT neurons in regard to 5-HT uptake, storage release and metabolism. Thrombocytes have a mechanism for 5-HT uptake analogous to the reuptake mechanism for 5-HT in the serotonergic nerve terminals. The whole blood 5-HT changes parallel changes in the 5-HT concentrations of the neurons. In this work 5-HT concentrations were measured during OGTT in whole blood to ascertain the possible relation between 5-HT changes and glucose absorption. For this purpose a reliable, fluorometric method for 5-HT was developed with the following improvements: In whole EDTA-blood the oxidation of 5-HT was prevented with ascorbic acid. The oxidation of hemoglobin iron to ferri-iron was prevented with carbon monoxide, because 5-HT, being a phenol, will otherwise form a complex with ferri-iron. Proteins were precipitated with perchloric acid and the supernatant neutralized before purification of 5-HT by cation exchange.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1999

The strict molybdate-dependence of glucose-degradation by the thermoacidophile Sulfolobus acidocaldarius reveals the first crenarchaeotic molybdenum containing enzyme--an aldehyde oxidoreductase.

In order to investigate the effects of trace elements on different metabolic pathways, the thermoacidophilic Crenarchaeon Sulfolobus acidocaldarius (DSM 639) has been cultivated on various carbon substrates in the presence and absence of molybdate. When grown on glucose (but neither on glutamate nor casein hydrolysate) as sole carbon source, the lack of molybdate results in serious growth inhibition. By analysing cytosolic fractions of glucose adapted cells for molybdenum containing compounds, an aldehyde oxidoreductase was detected that is present in the cytosol to at least 0.4% of the soluble protein. With Cl2Ind (2,6-dichlorophenolindophenol) as artificial electron acceptor, the enzyme exhibits oxidizing activity towards glyceraldehyde, glyceraldehyde-3-phosphate, isobutyraldehyde, formaldehyde, acetaldehyde and propionaldehyde. At its pH-optimum (6.7), close to the intracellular pH of Sulfolobus, the glyceraldehyde-oxidizing activity is predominant. The protein has an apparent molecular mass of 177 kDa and consists of three subunits of 80.5 kDa (alpha), 32 kDa (beta) and 19.5 kDa (gamma). It contains close to one Mo, four Fe, four acid-labile sulphides and four phosphates per protein molecule. Methanol extraction revealed the existence of 1 FAD per molecule and 1 molybdopterin per molecule, which was identified as molybdopterin guanine dinucleotide on the basis of perchloric acid cleavage and thin layer chromatography. EPR-spectra of the aerobically prepared enzyme exhibit the so-called 'desulpho-inhibited'-signal, known from chemically modified forms of molybdenum containing proteins. Anaerobically prepared samples show both, the signals arising from the active molybdenum-cofactor as well as from the two [2Fe-2S]-clusters. According to metal-, cofactor-, and subunit-composition, the enzyme resembles the members of the xanthine oxidase family. Nevertheless, the melting point and long-term thermostability of the protein are outstanding and perfectly in tune with the growth temperature of S. acidocaldarius (80 degrees C). The findings suggest the enzyme to function as a glyceraldehyde oxidoreductase in the course of the nonphosphorylated Entner-Doudoroff pathway and thereby may attribute a new physiological role to this class of enzyme.

Aldehyde Oxidoreductases↗

PubMed1979

[Determination of radioactive and stable cobalt in marine biological materials (author's transl)].

Studies were made to develop the method for rapid determination of radioactive and stable cobalt in a single specimen of marine biological materials. The sample was dried, ashed, and dissolved in acid. The cobalt was extracted with 1-nitroso-2-naphthol benzene and determined by absorptiometry on the benzene phase. Then, the organic solution was evaporated to dryness, and the residue was treated with nitric-perchloric acid mixture to decompose any organic matter, and taken up with hydrochloric acid. The cobolt was extracted from the solution with TIO A-toluene, and the radioactive cobalt was determined by liquid scintillation counting on the toluene phase. Examinations were made on the chemical yield and on the decontamination factor of the fission product nuclides. Analysis were made on the marine biological samples of Urazoko Bay, Fukui prefecture. Agreement of the radioactive cobalt data between that by the present method and that by Ge(Li) gamma ray spectometry was good. Also, the stable cobalt value by the present method agreed well with that by neutron activation analysis method.

Animals↗

PubMed1988

Simultaneous determination of four monoamine metabolites and serotonin in cerebrospinal fluid by "high-performance" liquid chromatography with electrochemical detection; application for patients with Alzheimer's disease.

We describe an optimized, sensitive assay procedure for simultaneously determining 3-methoxy-4-hydroxyphenylglycol, 3,4-dihydroxyphenylacetic acid, and serotonin in human lumbar cerebrospinal fluid. The assay is based on liquid chromatography with an electrochemical detection system equipped with a newly developed, highly sensitive graphite electrode. Before assay, samples are deproteinized with perchloric acid, 0.2 mol/L. The within- and between-day CVs were less than 2.5% and 6.7%, respectively, for all compounds. The lower limits of detection for 3-methoxy-4-hydroxyphenylglycol and 3,4-dihydroxyphenylacetic acid were 0.5 pg and for the other three analytes 1.5 pg per injection. Preliminary data on monoaminergic metabolites by the current assay showed that concentrations of dopaminergic and serotonergic metabolites were significantly (P less than 0.05) lower in patients with Alzheimer's disease than in the age-matched controls. In addition, the concentration of 3,4-dihydroxyphenylacetic acid correlated significantly (P less than 0.01) with that of homovanillic acid, suggesting that monitoring either of these metabolites in cerebrospinal fluid can be used as an index of central dopaminergic activity.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1981

Analytical determination of purity of 1-piperidinocyclohexanecarbonitrile and its hydrobromide salt.

A common contaminant of illicit phencyclidine, 1-piperidinocyclohexanecarbonitrile (I), is a very weak base compared to tertiary amines such as phencyclidine, 1-(cyclohexenyl)piperidine, and piperidine. Compound I and its hydrobromide salt can be selectively detected and quantitated in the presence of synthetic contaminants by nonaqueous titration with perchloric acid in acetonitrile. This method allows direct assay of I under conditions where decomposition is not observed.

Drug Contamination↗

PubMed1989

Indirect determination of tungstate in rat tissues by atomic absorption spectrometry.

An indirect method is described for the determination of tungsten as tungstate in tissue samples by atomic absorption spectrometry (AAS). Tungstate forms a stable ion-association complex [Fe(dipy)3]2+WO4(2-) (dipy = 2,2'-dipyridyl) in acidic solution, which can be extracted into chloroform with an efficiency of higher than 98%. The extract can be analysed for iron (and hence indirectly for WO4(2-] by flame AAS after stripping back into 60% perchloric acid. The calibration graph is linear up to 19 p.p.m. of WO4(2-) and the limit of detection is 0.17 p.p.m. Many foreign ions do not interfere and the method has been applied successfully to the determination of tungstate in rattus norvegicus tissue samples.

Animals↗

PubMed1986

High mobility group proteins in ram spermatids.

The four major high mobility group proteins HMG 1, 2, 14 and 17, HMG 19B and histone H1(0) were identified in the ram testis by their extraction and solubility characteristics and by their electrophoretic mobilities. HMG 14 and 17 were isolated by chromatography and amino acid analysis revealed that they were similar to their calf thymus analogues. A protein, named 2R and co-extracted with HMG 14, was also purified and analysed. Electrophoretic analyses of the proteins extracted by 0.75 M perchloric acid (PCA) or by 0.35 M NaCl from round and non-round spermatids, separated by centrifugal elutriation, showed that the four major HMG proteins disappear from nuclei in the oldest round spermatids, at the time the nuclear content of protein 2R and histone H1(0) increases in spermatids. Ubiquitin and HMG 19B were present in the round and elongating spermatids, but not in elongated spermatids which contained only protamine. The relation was considered between several protein changes and genetic inactivation and structural reorganization of the spermatid chromatin.

Amino Acids↗

PubMed1995

Determination of dopexamine hydrochloride in human blood by high-performance liquid chromatography with electrochemical detection.

A method is described for the determination of dopexamine hydrochloride at concentrations of 5 to 100 ng/ml in human blood using electrochemical detection. The method uses a Hypersil ODS column and a mobile phase containing heptane sulphonate, orthophosphoric acid, diisopropylamine and disodium EDTA. Blood samples are stabilised immediately after collection by the use of dipotassium EDTA and a high concentration of sodium metabisulphite. The sample preparation procedure consists of a simple de-proteinisation with perchloric acid. The method is accurate, with inter-assay accuracies ranging from 100 to 104%, and is free of interference by blood from different individuals. Known and potential metabolites of dopexamine hydrochloride and a wide range of drugs do not interfere with the method. The method is precise with inter-assay coefficients of variation of 10.6% at 5 ng/ml and of less than 4.2% at higher concentrations. Stabilised blood samples may be stored for over six months at -25 degrees C prior to analysis.

Adrenergic beta-Agonists↗

PubMed1981

Paper chromatographic separation of phosphate esters, tricarboxylic cycle acids and amino acids in extracts from malaria parasites.

A paper chromatographic method for the separation and identification of complex mixtures of phosphate esters, tricarboxylic cycle acids and amino acids in biological extracts is described. The method has been applied to the investigation of carbohydrate metabolism pathways in the intraerythrocytic, simian malaria parasite Plasmodium knowlesi; on treatment of parasitized erythrocytes with [U-C14]glucose, a perchloric acid extract was prepared and separated by chromatography on Whatman 31 ET filter-paper. A simple procedure for the measurement of the specific activities of radioactive compounds without prior elution from the chromatographic support is also described.

Amino Acids↗

PubMed2002

Stability of ascorbic acid in serum and plasma prior to analysis.

INTRODUCTION: The stability of ascorbic acid in serum and plasma prior to analysis was studied. METHODS: Blood samples were collected from ten healthy subjects into Vacutainer tubes containing either dipotassium EDTA, lithium-heparin or no additive. Ascorbic acid was analysed following immediate separation and preservation of samples, following delayed separation for 2 h and after delayed deproteinization and preservation for 2, 5 and 8 h. Deproteinization and preservation were achieved using a solution containing perchloric acid, EDTA and dithiothreitol. Ascorbic acid was analysed by high-performance liquid chromatography. RESULTS: Blood collected into EDTA and separated, deproteinized and preserved immediately gave the highest yield of ascorbic acid. Loss of analyte after delayed separation was least for EDTA tubes (median 7%, range 4-13%), followed by lithium-heparin (median 18%, range 10-32%) and serum (median 26%, range 14-50%). Immediate separation of samples but delayed deproteinization and preservation also resulted in substantial losses of ascorbic acid. CONCLUSION: Minimum loss of ascorbic acid is achieved if blood is collected into tubes containing dipotassium EDTA and separated within 2 h, followed by immediate deproteinization and preservation.

Analysis of Variance↗

PubMed1988

Direct 19F NMR spectroscopic observation of 5-fluorouracil metabolism in the isolated perfused mouse liver model.

A direct analysis of 5-fluorouracil (FUra) metabolism in the isolated perfused mouse liver was carried out using 19F NMR spectroscopy. In livers treated with low (30 mg/kg body weight (b.w.] or high (180 mg/kg b.w.) doses of FUra, with (180 mg/kg b.w.) or without thymidine (dThd), FUra was rapidly catabolized to alpha-fluoro-beta-ureidopropionic acid (FUPA) and alpha-fluoro-beta-alanine (FBAL), the latter usually becoming by far the major catabolite. The first catabolite of FUra, 5,6-dihydro-5-fluorouracil (5FUH2), was never detected both in the liver and in perchloric acid (PCA) extracts. In the latter, it was generally split into three signals, the major one being attributed to 5-fluorouridine-5'-monophosphate. Moreover, when the liver was treated with high doses of FUra and dThd, a signal for fluoronucleoside was observed in the liver, in PCA extracts and in perfusate where it was attributed to 5-fluoro-2'-deoxyuridine (FdUrd). The injection of concurrent dThd with the high dose of FUra led to a marked reduction of catabolism due to competitive inhibition of dihydrouracil dehydrogenase. Moreover, a significant formation of FdUrd was noticed whereas 5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP) was not detected. dThd therefore inhibits the conversion of FdUrd to FdUMP.

Animals↗

PubMed1982

NMR studies of malaria. 31P nuclear magnetic resonance of blood from mice infected with Plasmodium berghei.

High resolution 31P-NMR has been used for the non-invasive observation of metabolites and metabolic rates in blood of normal mice and of mice infected with Plasmodium berghei, the causative agent of malaria. 31P-NMR was used to quantitate levels of 2,3-diphosphoglycerate in whole cells as a function of the degree of parasitemia and yielded good agreement with the results of enzymatic assays. The time-dependence of 31P metabolites was monitored in both normal and infected erythrocytes, greater rates of decay of 2,3-diphosphoglycerate being observed in malarial blood which correlate with the level of parasitemia. Very high metabolic rates of infected cells render measurement of intracellular pH unreliable on freshly drawn whole blood. When appropriate measures are taken to avoid this complication, no difference is observed in the intracellular pH of parasitized and non-parasitized erythrocytes from infected animals. In both normal and parasitized mice the intraerythrocytic pH is more acidic than that of the suspending medium by 0.15 pH unit at 25 degrees C. Unlike free-living protozoa, the parasitic protozoan Plasmodium does not contain detectable levels of phosphonates or polyphosphates, in either whole cells or perchloric acid extracts thereof.

2,3-Diphosphoglycerate↗