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Biomedical subjects

T Nambara

Publications and source records attributed to T Nambara.

At least 73 records · Page 4Linked to original sources
PubMed1988

Studies on steroids. CCXXXIII. Separation and characterization of bile acid disulphates in human urine by high-performance liquid chromatography.

The separation of disulphates of cholate, chenodeoxycholate, deoxycholate and ursodeoxycholate and their glyco and tauro conjugates has been carried out by high-performance liquid chromatography (HPLC) on a reversed-phase column. The chromatographic behaviour of bile acid disulphates was dependent on the position of the sulphate and hydroxy groups and the structure of the side-chain. The method has been applied to the separation and characterization of disulphates in biological fluids without prior deconjugation. The disulphate fraction was obtained from a urine specimen by passing it through a Sep-Pak C18 cartridge, followed by group separation by ion-exchange chromatography on a lipophilic gel, piperidinohydroxypropyl-Sephadex LH-20. Subsequent resolution into individual disulphates was attained by HPLC on Radial-Pak A and Cosmosil 5C18 columns. Taurochenodeoxycholate 3,7-disulphate and taurodeoxycholate 3,12-disulphate in human urine were unequivocally identified on the basis of their behavior in HPLC using mobile phases of different pH.

Bile Acids and Salts↗
PubMed1988

A facile one-step synthesis of delta 1,4-3-keto bile acid esters by iodoxybenzene and benzeneselenic anhydride.

A facile one-step conversion of stereoisomeric methyl 3-hydroxycholanoates to 1,4-dien-3-one, by treatment in boiling toluene with iodoxybenzene catalyzed by benzeneselenic anhydride, is described. The direct oxidation-dehydrogenation at C-3 is applicable to other cholanoates (hyodeoxycholic, chenodeoxycholic, ursodeoxycholic, deoxycholic, and cholic) when the hydroxyl groups at C-6, C-7, or C-12 are protected. Without protection at C-6 and C-7, the products from hyodeoxycholic, chenodeoxycholic, ursodeoxycholic, and cholic esters are complex mixtures, whereas, methyl deoxycholate yields the 1,4-dien-3,12-dione cleanly.

Benzene Derivatives↗
PubMed1988

Potential bile acid metabolites. 13. Improved routes to 3 beta, 6 beta- and 3 beta, 6 alpha-dihydroxy-5 beta-cholanoic acids.

New synthetic routes to three possible stereoisomers of hyodeoxycholic (3 alpha, 6 alpha-dihydroxy-5 beta-cholanic) acid are described. The principal reactions involved were inversion at C-3 of 3 alpha-hydroxy-6-oxo derivatives with diethyl azodicarboxylate-triphenylphosphine-formic acid and with N,N-dimethylformamide, without allomerization to the more stable 5 alpha form. On the basis of physical and chromatographic data, previously reported 3 beta, 6 alpha-dihydroxy-5 beta-cholanic acid and its methyl ester are shown to be C-3 epimeric mixtures. The 13C nuclear magnetic resonance spectra were of key importance in characterizing the stereoisomers and estimating their purity.

Chemical Phenomena↗
PubMed1987

Sensitive ferrocene reagents for derivatization of thiol compounds in high-performance liquid chromatography with dual-electrode coulometric detection.

Three N-substituted maleimides possessing ferrocene as an electrophore were prepared and evaluated for pre-column derivatization of thiol compounds in high-performance liquid chromatography with dual-electrode coulometric detection. The utility of these reagents was investigated by employing N-acetyl-L-cysteine as a model compound. Among the three, N-(ferrocenyl) maleimide was the most favourable reagent with respect to reactivity, stability and electrochemical properties. The dual-electrode coulometric detection of the adduct showed high selectivity and sensitivity with a detection limit of 0.06 pmol. The proposed method is applicable to the determination of glutathione in biological specimens.

Adult↗
PubMed1987

Studies on steroids. CCXXIX. Separation and characterization of catechol oestrogen glucuronides in urine of pregnant women by high-performance liquid chromatography.

The separation and characterization of catechol oestrogen glucuronides in the urine of pregnant women by high-performance liquid chromatography with electrochemical detection is described. The urine samples from pregnant women were passed through Amberlite XAD-2 and Sep-Pak C18 columns and subsequented to ion-exchange chromatography on piperidinohydroxypropyl Sephadex LH-20 to isolate the oestrogen glucuronide fraction. The subsequent resolution into individual oestrogen glucuronides was achieved by high-performance liquid chromatography on a reversed-phase column. 2-Hydroxyoestrone 2-glucuronide and 4-hydroxyoestrone 4-glucuronide were identified on the basis of their behaviour in high-performance liquid chromatography with three different mobile phases. Derivatization of two glucuronides with 2-ferrocenylethylamine, followed by chromatographic separation and measurement of hydrodynamic voltammograms with an electrochemical detector was carried out for unequivocal identification. Enzymatic cleavage of the glucuronoside linkage followed by the identification of deconjugated catechol oestrogens by high-performance liquid chromatography with electrochemical detection further supported the structural assignment of these metabolites. The ratio between the amounts of 2-hydroxyoestrone 2-glucuronide and 4-hydroxyoestrone 4-glucuronide excreted in the urine of pregnant women was found to be ca. 5:1.

Chromatography, High Pressure Liquid↗
PubMed1987

Determination of isofloxythepin in biological fluids by gas chromatography-mass spectrometry.

A method for the determination of isofloxythepin in biological fluids by gas chromatography-mass spectrometry is described. Isofloxythepin was readily converted into the trimethylsilyl ether by treatment with N,O-bis(trimethylsilyl)trifluoroacetamide. This derivative was separated on a 5% OV-101 column and determined, employing newly prepared isofloxythepin-d7 as an internal standard. Clean-up of isofloxythepin in blood and urine was efficiently achieved by back-extraction with hexane or hexane-toluene (9:1) under acidic and basic conditions, while isofloxythepin glucuronide in biological fluids was isolated by ion-exchange chromatography on Dowex 50W-X4 resin. The detection limit of isofloxythepin by this method was 50 pg. The blood and urine levels of isofloxythepin after oral administration of the drug to dogs were monitored by the proposed method.

Animals↗
PubMed1987

Sensitive method for determination of captopril in biological fluids by gas chromatography-mass spectrometry.

A sensitive method for the determination of captopril in blood and urine by gas chromatography-mass spectrometry is described. In order to prevent oxidative degradation of captopril, its sulph-hydryl group was immediately protected by treatment with N-ethylmaleimide (NEM), and the resulting NEM adduct was then converted into the bis(pentafluorobenzyl) derivative. Derivatized captopril was separated on a 2% OV-1 column, exhibiting a single peak of the correct theoretical shape. The detection limit was estimated to be 100 pg by using S-benzylcaptopril as an internal standard. The blood level and urinary excretion of unchanged captopril orally administered to dogs were determined by the proposed method. In addition, epimerization of the proline moiety and formation of the sulphoxide or sulphone through the esterification step are also described.

Captopril↗
PubMed1987

Studies on steroids. CCXXVII. Separation and determination of bile acid 7- and 12-sulphates in urine by high-performance liquid chromatography with fluorescence labelling.

A method for the characterization and determination of bile acid 7- and 12-sulphates in urine without prior deconjugation is described. The sulphate fraction was obtained from an urine specimen by passing it through a Sep-Pak C18 cartridge, followed by group separation by ion-exchange chromatography on a lipophilic gel, piperidinohydroxypropyl Sephadex LH-20. Bile acid 7- and 12-sulphates were derivatized quantitatively into the fluorescent compounds through the hydroxyl group at C-3 by treatment with 1-anthroyl nitrile in the presence of quinuclidine in acetonitrile. Subsequent resolution into individual 7- and 12-sulphates was attained by high-performance liquid chromatography (HPLC) on a Cosmosil 5C18 column using 0.3% potassium phosphate buffer (pH 4.0)-methanol (1:3) as a mobile phase. The 3-(1-anthroyl) derivatives of 7- and 12-sulphates were monitored by fluorescence detection. Taurochenodeoxycholate 7-sulphate in human urine was unequivocally identified on the basis of behaviour in HPLC using mobile phases of different pH values. The present method has proved to be applicable to the characterization and quantification of bile acid 7- and 12-sulphates in human urine.

Bile Acids and Salts↗
PubMed1987

Capillary gas chromatography of hydroxylated bile acid stereoisomers of the allo and normal series.

Relative retention times and methylene unit (MU) values were determined for 56 bile acids of the allo (5 alpha, A/B-trans) and normal (5 beta, A/B-cis) series, which differ from one another in the number, position and configuration of the hydroxyl groups at positions C-3, C-6, C-7 and/or C-12. The bile acids were derivatized to their methyl ester O-trimethylsilyl ethers (Me-TMS) and methyl ester O-dimethylethylsilyl ethers (Me-DMES), and chromatographed on fused-silica capillary columns, chemically bonded with non-selective OV-1 and selective PEG-20M liquid phases. Of the four possible combinations of derivatives and columns examined, Me-DMES on OV-1 and Me-TMS on PEG-20M were most suitable. The differences in the MU values between the 5 alpha- and 5 beta-series, and between the Me-DMES and Me-TMS ether derivatives, are also summarized. These retention data would be helpful in the identification of closely related bile acid stereoisomers or for estimation of their structures. photolysis.

Bile Acids and Salts↗
PubMed1987

Studies on steroids. CCXXVIII Trace analysis of bile acids by gas chromatography-mass spectrometry with negative ion chemical ionization detection.

A suitable derivatization method for the trace analysis of bile acids by gas chromatography (GC) in combination with negative ion chemical ionization (NICI) mass spectrometry is described. Of various derivatives for the carboxyl group, the pentafluorobenzyl (PFB) ester provided the highest value of the ratio of the negative to the positive ion current. A characteristic carboxylate anion [M - 181]- was produced as the most abundant ion by the loss of the PFB group in NICI. The PFB esters were further derivatized to the dimethylethylsilyl (DMES) ethers, whereby lithocholic acid, deoxycholic acid, chenodeoxycholic acid, ursodeoxycholic acid and cholic acid were distinctly separated by GC on a cross-linked methyl silicone fused-silica capillary column. The detection limit for the PFB-DMES derivatives of dihydroxylated bile acids was 2 fg when the fragment ion was monitored at m/z 563 in the NICI mode using isobutane as a reagent gas.

Bile Acids and Salts↗
PubMed1987

Determination of chinoform in biological fluids and nervous tissues of the dog by gas chromatography-mass spectrometry.

A sensitive gas chromatographic-mass spectrometric method for the determination of 5-chloro-7-iodo-8-hydroxyquinoline (chinoform, clioquinol) in biological fluids and nervous tissues is described. Chinoform was converted into the pentafluorobenzyl ether, which was separated on a 10% Dexsil 300GC column and determined by the use of chinoform-d4 as an internal standard. The clean-up of chionoform in plasma and urine was efficiently achieved by extracting with benzene, while the drug in the tissue was pretreated successively by extraction with 12.5% v/v pyridine-benzene, separation on a Clin-Elut cartridge and adsorption on alumina. The quantitation limit of chinoform was 100 pg, and the recovery rates of chinoform added to plasma and tissue were 98% and 92%, respectively. The chinoform levels in biological fluids and tissues in dogs after prolonged administration of the drug at a dose of 400 mg/kg/day were measured by the proposed method. The plasma level and tissue distribution of chinoform are also discussed.

Animals↗
PubMed1987

Fluorescence and chemiluminescence enzyme immunoassays of 17 alpha-hydroxyprogesterone in dried blood spotted on filter paper.

Enzyme immunoassays for 17 alpha-hydroxyprogesterone (17-OHP) were developed. Horseradish peroxidase (HRP), glucose oxidase (GOD), invertase (INV) and glucose-6-phosphate dehydrogenase (G6PDH) were used as label enzymes. Double antibody coated beads or tubes were used for separating the bound and free fractions. Antisera used were prepared by using 4-carboxyethylthio-17-OHP and 3-carboxymethyl oxime-17-OHP-bovine serum albumin as immunogens. The bridge heterologous system was more sensitive than other site heterologous and homologous systems. The minimum amounts of 17-OHP detected were 0.25 and 1.0 pg/tube for fluorescence EIAs using HRP and GOD, and 0.1, 10 and 0.1 pg/tube for chemiluminescence EIAs using GOD, INV and G6PDH, respectively. The reproducibility and correlation with RIA were also studied. The present study demonstrates the feasibility of a neonatal screening for congenital adrenal hyperplasia.

17-alpha-Hydroxyprogesterone↗
PubMed1987

Production and characterization of monoclonal antibodies to 17 alpha-hydroxyprogesterone.

Hybridoma clones producing antibodies to 17 alpha-hydroxyprogesterone (17-OHP) were established by using a 17-OHP-bovine serum albumin conjugate as an immunogen. Six representative IgG-class monoclonal antibodies of high affinity (10(8)-10(9) M-1) showed differential reactivities with several structurally related steroids. Two enzyme immunoassay (EIA) systems (fluorescence EIA and micro-EIA) for 17-OHP using OHP 4B2.2.3, which showed the lowest cross-reactivity with other steroids, were established. The micro-EIA system was shown to be applicable to the mass-screening of congenital adrenal hyperplasia.

17-alpha-Hydroxyprogesterone↗