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PubMed1999

Solid-phase extraction and high-performance liquid chromatographic determination of articainic and its metabolite articainic acid in human serum.

A new method is described using solid-phase extraction (SPE) for preconcentration of articaine and the metabolite articainic acid and high-performance liquid chromatography (HPLC) for the determination of both compounds in human serum. Articaine and articainic acid were extracted in one step with SDB-RPS disk cartridges after precipitation of the serum proteins by perchloric acid. The HPLC separation was then performed on a reversed-phase C8 column using phosphate buffer-acetonitrile (88:12, v/v). UV absorption at 274 nm was used for measuring the analytes with a low limit of quantitation of about 10 ng/ml, which is appropriate for pharmacokinetic studies of low dose submucosal injections of the local anaesthetic agent articaine hydrochloride in dentistry.

Anesthetics, Local↗

PubMed2003

Acute effects of gabapentin and pregabalin on rat forebrain cellular GABA, glutamate, and glutamine concentrations.

The effects of antiepileptic drugs, gabapentin, pregabalin and vigabatrin, on brain gamma-aminobutyric acid (GABA), glutamate and glutamine concentrations were studied in Long Evans rats using proton magnetic resonance spectroscopy (MRS) of perchloric acid extracts. Cellular glutamate concentrations significantly decreased by 7% (P<0.05) 2 hours after intraperitoneal injection of 100mg/kg gabapentin and 4% (P<0.05) with 1000 mg/kg. No differences were observed in cellular GABA and cellular glutamine concentrations in rats treated with gabapentin. Pregabalin, an analogue of gabapentin, significantly decreased cellular glutamate concentrations by 4% (P<0.05), while no effect was observed on cellular GABA or glutamine concentrations in the healthy rat forebrain. Vigabatrin, used as a positive control to increase GABA levels, produced a 50% increase in cellular GABA compared to saline treated rats (P<0.003). Although, gabapentin and pregabalin are anticonvulsants designed to mimic GABA, these drugs do not raise cellular GABA levels acutely but modestly decreased cellular glutamate levels in our healthy rat forebrain model.

Acetates↗

PubMed2002

Simple method for determination of paraquat in plasma and serum of human patients by high-performance liquid chromatography.

A simple and fast HPLC system is presented for quantifying paraquat in human plasma and serum using 1,1'-diethyl-4,4'-bipyridyldiylium (diethyl paraquat) as an internal standard. An octadecyl-silica column is used with an eluent of 10% acetonitrile (v/v) containing sodium 1-octanesulphonic acid (3.0 mM) and a diethylamine-orthophosphoric acid buffer (pH 3). Unlike with other techniques, sample treatment requires only the precipitation of protein contents by 6% perchloric acid (v/v) in methanol. The method has a limit of detection of 0.1 microg/ml and is linear up to 10 microg/ml. The serum of four patients and the plasma of one patient with paraquat intoxication's were analysed and positive identification and quantification was readily achieved. One of those patients survived, partially given the rapid disclosure of his levels of paraquat. Therefore, this method is suitable for quantification of paraquat in toxicological samples. It may be used as a prognostic tool in critical case detoxification and to quickly identify potentially salvageable patients for enrollment in new hemofiltration studies.

Chromatography, High Pressure Liquid↗

PubMed1967

A study of the sulphur amino acids of rat tissues.

1. In a study of the metabolism of l-[(35)S]methionine in vivo, the labelled sulphur compounds of rat liver and brain were separated first by ion-exchange chromatography into two fractions containing (i) free sulphur amino acids such as methionine, cystathionine, cyst(e)ine and homocyst(e)ine and (ii) glutathione. 2. Two-dimensional paper chromatography with butan-1-ol-acetic acid or propionic acid-water in the first direction and 80% acetone or acetone-ethyl methyl ketone-water in the second direction was found superior to other solvent systems for separating the sulphur amino acids. 3. At 10min. after injection of [(35)S]methionine only a small part of the (35)S was found combined in free methionine or other free sulphur amino acids. 4. Evidence was obtained of the presence of adenosyl[(35)S]methionine and adenosyl[(35)S]homocysteine in perchloric acid extracts of rat liver and brain. 5. The trans-sulphuration pathway was active in brain as well as in liver.

Amino Acids↗

PubMed1987

Modified extraction 2-thiobarbituric acid method for measuring lipid oxidation in poultry.

A simple and accurate objective test for monitoring lipid oxidation in poultry products is needed. Thiobarbituric acid (TBA) values of cooked poultry meat were determined by a distillation method and by a modified extraction method. Perchloric acid was used in the extraction method to release TBA reactive substances from the meat. The maximum absorption wavelength of the TBA-malonaldehyde complex was 531 nm. The TBA values for cooked chicken and turkey were highly correlated (r = .91) for both the extraction and distillation methods. Sensory scores of warmed-over flavor in precooked poultry were highly correlated with TBA values in both the distillation (r = .83) and extraction (r = .85) methods. Results indicate that the extraction method is faster, easier to perform, and as accurate as the distillation method for monitoring lipid oxidation in poultry.

Animals↗

PubMed1989

Quantitative determination of verapamil and metabolites in human serum by high-performance liquid chromatography and its application to biopharmaceutic investigations.

A specific and sensitive high-performance liquid chromatographic method for the quantitative analysis of verapamil and N-desmethylverapamil in human serum is described. The analytes were extracted from serum using diethylether under alkaline conditions, followed by back extraction into dilute hydrochlorid acid for chromatographic analysis on a reversed-phase column with a mobile phase consisting of acetonitrile, water and perchloric acid at a flow rate of 1 l/min. The analytes were detected by fluorescence detection, the influence of temperature on retention is discussed. The method is linear, quantitative and reproducible for two calibration ranges in serum (2.5 ng/ml-100 ng/ml and 12.5 ng/ml-500 ng/ml) using peak area ratios analyte/internal standard for quantification. At ultimate sensitivity, concentrations down to 250 pg/ml could be assayed. The method was selective to 6 other metabolites of verapamil and common exogenous interferences. It was applicated to the serum samples of a comparative 120 mg - verapamil hydrochloride tablet single dose two-way cross-over study comprising 18 volunteers. The pharmacokinetic data for both formulations are presented.

Biopharmaceutics↗

PubMed1967

Effect of some proteins on the yeast cell membrane.

Yeast cells, Candida utilis, in water suspension and in the absence of electrolytes were found to be very sensitive to several proteins of moderate size, including ribonuclease, protamine, lysozyme, bovine serum albumin, cytochrome c, and myoglobin. Viability ceases rapidly, and ultraviolet-absorbing compounds (260 mmu) and the amino acid pool are released into the medium. The ultraviolet-absorbing material appears to be the nucleotide and coenzyme fraction usually extracted by 0.2 n perchloric acid at low temperature. The ribonucleic acid fraction remains in the cell ghosts and can be released by ribonuclease. The enzymatic properties of some of these proteins have no relation to their damaging effect on the cell membrane. Poly-l-lysine shows the same activity.

Amino Acids↗

PubMed2004

Spectroscopic investigation of the adsorption and oxidation of thiourea on polycrystalline Au and Au(111) in acidic media.

In the present paper, a systematic electrochemical investigation on thiourea (TU) electrooxidation was developed on polycrystalline and (111) single-crystal gold electrodes in 0.1 M perchloric acid. The combination of cyclic voltammetry with in situ Fourier transform infrared spectroscopy (FTIRS) and differential electrochemical mass spectrometry techniques have allowed the nature of the species formed during the electroadsorption and electrooxidation of TU to be established. FTIRS experiments were performed in D2O to clean up the region of the H2O bending around 1600 cm(-1). It was concluded that TU adsorbs tilted on the surface in the 0.05-0.40 VRHE potential range. A dual-path reaction mechanism was evidenced in the oxidation process. The first pathway takes place from adsorbed TU at E > 0.40 VRHE and implies the formation of [Au(I)-(TU)2]+, which is oxidized to NH2CN and S0 at E > 0.80 VRHE. In a following oxidation step at E > 1.20 V, N2, CO2, and HSO4-/SO4(2-) were produced. The second parallel reaction occurs from TU in solution at E > 0.50 VRHE to form (TU)2(2+). All these species were characterized from the spectroscopic experiments. Similar results were obtained for both surfaces.

Journal Article↗

PubMed1985

Method for determining the lung burden of talc in rats and mice after inhalation exposure to talc aerosols.

A method has been developed to quantitate talc lung burdens in rats and mice after inhalation exposure to talc aerosols. The method is based on acid-insoluble magnesium (Mg) determination by flame atomic absorption. Precipitating protein from homogenates of lungs of unexposed rodents with 5% perchloric acid and washing with 5% trichloroacetic acid removed the soluble and naturally occurring Mg. This resulted in residual Mg content averaging 0.43 micrograms Mg per g lung in rats and less than 0.1 microgram Mg per g lung in mice for young rodents less than 12 weeks old. Rodents 12-18 months old had residual mean (+/- SD) Mg contents of 3.4 +/- 2.0 micrograms Mg per g rat lung (n = 17) and 6.5 +/- 2.9 micrograms Mg per g mouse lung (n = 12). Thus, the background residual acid-insoluble Mg content in rodent lungs appears to increase with age. Negligible quantities of Mg were extracted directly from the talc treated by these procedures. Adding 50-2000 micrograms talc to lungs from unexposed rodents, followed by the sample treatment, gave mean (+/- SD) Mg recoveries of 89 +/- 12% (n = 19) for rat lungs and 96 +/- 26% (n = 15) for mouse lungs. The lung burden of talc in rodents exposed to talc aerosols for 6 h per day, 5 days per week for 4 weeks was determined. Mean lung burdens in rats were 77, 187, and 806 micrograms talc per g lung (n = 10) for exposures at 2.3, 4.3, and 17 mg talc m-3, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗

PubMed2006

Effect of perchlorate on the fluorescence of protonated 2,2'-bipyridine.

Interaction between the monocation of an aromatic amine, 2,2'-bipyridine and perchlorate anion was studied. The protonation process by perchloric acid has been followed by the changes in the UV absorption spectra and in the fluorescence emission. Addition of lithium perchlorate with increasing amount results in a significant increase in the fluorescence of 2,2'-bipyridine (the bipyridyl cation). This increase in fluorescence indicates that the rotation in the protonated monocation is hindered in the presence of perchlorate. We assume that this hindrance is due to the formation of the BpH+.ClO4- ion-pair.

2,2'-Dipyridyl↗

PubMedDate not supplied

A micromethod for the on-column methylation of valproic acid by gas-liquid chromatography.

We described a simple procedure for the flash heater methylation of valproic acid and cyclohexylacetic acid (internal standard) by gas-liquid chromatography (GLC). A small volume (100 microL) of sample is acidified with 10% perchloric acid and extracted into hexane. An aliquot is back extracted into 5% tetramethylammonium hydroxide (TMH). A 1 microL sample of the TMH layer is injected into the GLC equipped with flame ionization detector (FID) and a 6 ft x 2 mm i.d. - nickel column packed with 3% OV-17 on 80/100 mesh Supelcoport. The injector temperature is set at 350 degrees C to ensure methylation. Recoveries are greater than 95% of theoretical value. The linearity for calibration points between 15 and 180 microgram/mL is excellent (coefficient of correlation and determination greater than 0.9999). The procedure is rapid and sensitive and does not require a dedicated column in the gas chromatograph.

Chromatography, Gas↗

PubMed1990

Analysis of human tumor associated Thomsen-Friedenreich antigen.

The Thomsen-Friedenrich (TF) antigen is a precursor structure of MN blood group antigens and is also expressed by about 90% of human carcinomas. The immunodominant group of TF antigen [beta-galactosyl(1-3)-alpha-N-acetylglactosamine] is present in cryptic form in normal RBC and is revealed by neuraminidase treatment. A murine monoclonal antibody (Mab 49H.8) developed against neuraminidase treated human RBC was reactive against a variety of human tumors. We have characterized the human tumor associated TF antigen detected by this antibody from a human transitional bladder carcinoma cell line (647V), a human colon adenocarcinoma cell line (LS174T), and a pleural effusion fluid of a breast adenocarcinoma patient (PE 89). A heterologous sandwich radioimmunoassay for TF antigen was developed using Mab 49H.8 as the catcher and 125I-peanut agglutinin as the probe. Detergent extracts of 647V and LS174T cells, media conditioned by culturing these cells, and PE 89 were shown to contain the antigen by this assay. The specificity of the antigen capture by Mab 49H.8 in this assay was demonstrated by its selective inhibition by nitrophenyl-beta-D-galactoside, phenyl-beta-D-galactoside, and a TF hapten. Preliminary studies on TF antigen in serum samples using this assay showed that about 53.7% of the carcinoma samples contained an antigen concentration greater than 200 units/ml whereas for 90.9% of the normal samples the antigen concentration was below 200 units/ml. These studies demonstrated that the TF antigen is shed by the tumor cells both in vitro and in vivo. The TF antigen was sensitive to treatment with alkali (0.1 M NaOH for 5 h at 37 degrees C) and periodate (10 mM sodium periodate for 1 h at room temperature), was resistant to acidic pH (50 mM acetate buffer, pH 4.5, for 5 h at 37 degrees C), and could be extracted with perchloric acid (0.6 M for 1 h at 4 degrees C). The antigen was shown to be a high molecular weight glycoprotein (Mr greater than 1,000,000) by gel filtration chromatography. The density of the antigen was estimated to be about 1.35 g/ml by cesium chloride density gradient centrifugation. The antigen could be isolated from conditioned media by a combination of affinity chromatography and gel filtration with an overall purification of about 61,432-fold and a final recovery of 53.2%.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗

PubMed1997

Effects of increasing times of incomplete cerebral ischemia upon the energy state and lipid peroxidation in the rat.

Different times of incomplete cerebral ischemia (2, 4, 6, 8, 10 and 30 min) were induced by bilateral common carotid artery occlusion in anesthetized rats to evaluate the time course of changes in lipid peroxidation and energy metabolism. Analysis of malondialdehyde (used to assess the levels of lipid peroxidation), ascorbic acid, oxypurines, nucleosides, nicotinic coenzymes and high-energy phosphates, was carried out by high-performance liquid chromatography on neutralized perchloric acid extract of brain tissue. Under the present experimental conditions, malondialdehyde, nicotinic coenzymes and ATP catabolites (oxypurines and nucleosides) were affected by increasing times of ischemia, with respect to control sham-operated rats. In particular, the concentration of malondialdehyde, undetectable in control brains, increased from 1.26 nmol/g wet weight after 2 min of carotid clamping to 13.42 nmol/g wet weight at the end of 30 min of incomplete cerebral ischemia. The presence of oxidative stress was further supported by ascorbic acid depletion, which was particularly significant after 10 and 30 min of incomplete ischemia. Carotid clamping provoked an imbalance between energy production and consumption that was evidenced by a reduction in ATP and GTP concentrations and an increase in ATP degradation products such as AMP, oxypurines and nucleosides. A decrement in the sum of adenine nucleotides and the energy charge potential indicated a progressive malfunctioning of energy-producing metabolic cycles. A possible contribution to such a severe change in energy state might be related to depletion of NAD and NADP, particularly noticeable after the longest incomplete brain ischemia times, that should have provoked a consequent lessening of oxido-reductive reactions. Bilateral carotid clamping causes a significant reduction in brain oxygen and substrate supply that results in inhibition of energy metabolism and triggering of oxygen-radical-induced lipid peroxidation.

Animals↗

PubMed1992

High-performance liquid chromatographic determination of catecholamines and their precursor and metabolites in human urine and plasma by postcolumn derivatization involving chemical oxidation followed by fluorescence reaction.

A high-performance liquid chromatographic method for the determination of catecholamines and their precursor and metabolites [amino compounds (norepinephrine, epinephrine, dopamine, normetanephrine, metanephrine, 3-methoxytyramine, and L-DOPA), acidic compounds (3,4-dihydroxyphenylacetic acid, vanillyl-mandelic acid, and homovanillic acid), and alcoholic compound [4-hydroxy-3-methoxyphenyl)ethylene glycol)] in human urine and plasma. Urine and plasma samples deproteinized with perchloric acid in the presence of isoproterenol and 3,4-dihydroxyphenylpropanoic acid (internal standards) are fractionated by solid-phase extraction on a strong cation-exchange resin cartridge (Toyopak IC-SP S) into two fractions (amine fraction and acid-alcohol fraction). The compounds in each fraction are separated by an ion-pair reversed-phase chromatography on a TSK gel ODS-80TM with isocratic elution and on-line derivatized by periodate oxidation followed by a fluorescence reaction using meso-1,2-diphenylethylenediamine. The detection limits (S/N = 5) vary from 0.5 to 95 pmol/ml, depending on the compounds.

Adult↗

PubMed1986

Quantitation of total MHPG in the rat brain using a non enzymatic hydrolysis procedure. Effects of drugs.

An acid-catalyzed procedure has been used to hydrolyze MHPG-sulfate in homogenates of rat brain. The samples (in 0.4 mol/L perchloric acid) are treated for 3 min. at 100 degrees C in a water bath and aliquots are injected into a reversed phase HPLC system. Detection is achieved fluorimetrically. The absolute detection limit for MHPG is 150 pg, which allows the reliable determination of either free or total MHPG in rat brain in concentrations down to 15 ng/g, using the described procedure. The concentration of total MHPG found in the brains of saline-treated rats are 101 +/- 21 ng/g (mean +/- S.D.) which is in a good accordance with the concentration value for the same samples obtained using a GC-MS method (115 +/- 19 ng/g). Rats treated with clonidine (300 micrograms/Kg, i.p.) or yohimbine (10 mg/Kg, i.p.) showed brain concentrations of total MHPG of 68 +/- 22 ng/g and 299 +/- 85 ng/g, respectively. The utility of this method for the analysis of brain regions or brain nuclei (e.g. locus coeruleus) is also shown.

Animals↗

PubMed1992

Improved method for the determination of 5,6-dihydroxytryptamine and 5,7-dihydroxytryptamine in tissue using high-performance liquid chromatography with electrochemical detection.

A liquid chromatographic method with electrochemical detection is described for the determination of the 5-hydroxytryptamine (5-HT) neurotoxins 5,6-dihydroxytryptamine (5,6-DHT) and 5,7-dihydroxytryptamine (5,7-DHT) in rat brain tissue. This method has also been used for the determination of 5-hydroxyindoleacetic acid, homovanillic acid and 5-HT in other tissue samples. The method is based on extraction of the indoles from brain samples with perchloric acid followed by reversed-phase liquid chromatography with electrochemical detection. The detection limit is 1 ng per 100 mg of tissue. This paper describes a quick and reliable method of assaying the 5-HT neurotoxins 5,6-DHT and 5,7-DHT in brain tissue, which is improved compared to currently available assays.

5,6-Dihydroxytryptamine↗

PubMed1992

High-performance liquid chromatographic analysis of the anticancer drug oxantrazole in rat whole blood and tissues.

A reversed-phase high-performance liquid chromatographic (HPLC) assay was developed for the antitumor anthrapyrazole analogue, oxantrazole (OX), in rat whole blood and tissues. Blood samples were mixed with equal volumes of a 25% (w/v) aqueous solution of L-ascorbic acid, whereas tissue samples were homogenized with 1.5-3 volumes of an L-ascorbic acid-methanol-water (1:10:1, w/v/v) mixture to prevent oxidative degradation of OX. Samples were then treated with 60% (v/v) perchloric acid (25-30 microliters/ml of stabilized sample) to precipitate proteins, and centrifuged, with the resultant supernatants analyzed on HPLC utilizing a C8 column. The mobile phase for blood and urine samples consisted of 8% (v/v) glacial acetic acid, 13% (v/v) acetonitrile, 79% (v/v) water, 0.16% (w/v) sodium acetate, and 0.05% (w/v) L-ascorbic acid (final pH 2.7), and was pumped at 1.8 ml/min. Tissue samples were eluted at 2 ml/min with a mobile phase consisting of 8% (v/v) glacial acetic acid, 12% (v/v) acetonitrile, 80% (v/v) water, 0.16% (w/v) sodium acetate, and 0.0;5% (w/v) L-ascorbic acid. OX and internal standard were detected at 514 nm and had retention times of 2.3 and 3.1 min, respectively. The limit of quantitation of OX was 25-50 ng/g. Recovery of OX from biological samples ranged from 50 +/- 0.9% in spleen to 102.8 +/- 1.8% in RG-2 glioma. The analytical method was applied to a pharmacokinetic study in rats.

Animals↗

PubMed1980

Mass spectrometric technique for the determination of N-phosphonoacetyl-L-aspartic acid in serum.

N-Phosphonoacetyl-L-aspartic acid (PALA), a potent inhibitor of aspartic acid transcarbamylase, is now undergoing Phase I clinical trials. Initial experiments revealed that PALA is not metabolized to phosphonoacetic acid (PAA) in humans. Thus PALA may be quantified in serum after in vitro conversion to PAA. Serum is deproteinized with perchloric acid, lipid extracted with methylene chloride, hydrolyzed with 8 N hydrochloric acid at 100 degrees for 3 h, and evaporated to dryness with nitrogen. The residue is silylated, and PAA is quantified by monitoring the (M + 1)+ ions of the protonated molecular ions of trimethylsilyl derivatives of PAA and phosphonopropionic acid (internal standard) obtained in chemical ionization with methane. Limit of detection is 0.5 microM (150 ng/ml) PALA using 1 ml serum. PALA was given by continuous infusion to cancer patients at various doses. Maximum levels of PALA (50-500 microM range) were obtained at the end of infusion, followed in most cases by biexponential decay. Persistent residual PALA levels (5 microM for 48 h after infusion) correlated with increased toxicity.

Antineoplastic Agents↗