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At least 613 records · Page 34Linked to original sources
PubMed1978

Rapid determination of atenolol in human plasma and urine by high-pressure liquid chromatography.

A rapid, specific, high-pressure liquid chromatographic determination of atenolol in plasma and urine was developed. This method employs the high sensitivity of fluorescence detection together with selective extraction and reversed-phase chromatography to measure concentrations as low as 20 ng of drug/ml of plasma with a coefficient of variation of 3.91%. The assay is specific enough to be valid in the presence of plasma and urine substances. The detection limit (i.e., three times baseline noise) is 3 ng/ml.

Atenolol↗
PubMed1978

Interference in assays for hydralazine in humans by a major plasma metabolite, hydralazine pyruvic acid hydrazone.

The present study showed that published spectrophotometric and GLC methods for hydralazine in plasma do not distinguish between the drug and a major plasma metabolite, hydralazine pyruvic acid hydrazone. These methods involve the acid treatment of the sample, which hydrolyzes that hydrazone back to hydralazine. A specific GLC assay for the hydrazone was developed and involves its selective extraction from plasma and transformation to 3-trifluoromethyl-s-triazolo[3,4-a]phthalazine. This derivative could be sensitively measured by GLC using an electron-capture detector. With this procedure, it was shown that most "apparent hydralazine" in plasma is the hydrazone, which forms rapidly from hydralazine and endogenous pyruvic acid. Previous work indicated that the hydrazone was inactive when administered intravenously to rabbits.

Chromatography, Gas↗
PubMed1979

High-performance liquid chromatographic determination of ketoprofen in blood and urine.

A rapid, simple determination was developed for ketoprofen in biological fluids using high-performance liquid chromatography. The method requires selective extraction of this antirheumatic medicament and an internal standard with ether from the previously acidified plasma and urine. After evaporation of the ether, the residue is taken up by methanol and analyzed by reversed-phase liquid chromatography with detection at 254 nm. A concentration as low as 0.1 microgram/ml can be determined with a 0.5-ml sample.

Chromatography, High Pressure Liquid↗
PubMed1980

High-pressure liquid chromatographic determination of salicylsalicylic acid, aspirin, and salicylic acid in human plasma and urine.

A high-pressure liquid chromatographic method was developed for the separation and quantitation of salicylsalicylic acid (I), aspirin (II), and salicylic acid (III) in human plasma and urine. The method for plasma involves the selective extraction of I--III and an internal standard, alpha-phenylcinnamic acid, into methylene chloride from acidified plasma, followed by evaporation of the organic phase and dissolution of the residue in methanol. A 25-microliter aliquot is analyzed on a reversed-phase column with UV detection. Urine is treated similarly with hexane as the extracting solvent. If 300 nm is used as the monitoring wavelength, the assays of I and III are linear over the concentration range of 1--150 microgram/ml in both plasma and urine. If 280 nm is used as the monitoring wavelength, II can be quantitated along with I and III; however, detector sensitivities of I and III are two to three times greater at 300 nm. The accuracy and precision of the methods for I--III are adequate for clinical pharmacokinetic studies. Following therapeutic doses of I in humans, the method was applied successfully to the determination of I and III in plasma and urine.

Anti-Inflammatory Agents↗
PubMed1981

High-pressure liquid chromatographic determination of viloxazine in human plasma and urine.

A rapid, specific, high-pressure liquid chromatographic method is presented for the determination of viloxazine in plasma and urine. This method employs the high sensitivity of fluorescence detection with selective extraction and reversed-phase chromatography to measure concentrations as low as 25 ng/ml of plasma and 1.0 microgram/ml of urine. Known metabolites of viloxazine do not interfere with the analysis, and experience with several hundred samples in a bioavailability study demonstrated the applicability and reliability of the method.

Chromatography, High Pressure Liquid↗
PubMed1982

Analysis of conjugated estrogens in a vaginal cream formulation by capillary gas chromatography.

A capillary gas-chromatographic method is described for the quantitative analysis of nine equine estrogens in a vaginal cream formulation. The sodium sulfate ethers of the estrogens were selectively extracted from the formulation, subjected to enzyme hydrolysis, and derivatized to their oxime-trimethylsilyl esters. Resolution of the resulting derivatives was achieved on short (15 m) capillary column, wall-coated with cyanopropylmethyl silicon stationary phase.

Chromatography, Gas↗
PubMed1985

Radioimmunoassay for the 7-hydroxy metabolite of trifluoperazine and its application to a kinetic study in human volunteers.

A hapten derivative of the 7-hydroxy metabolite of trifluoperazine, 7-hydroxy-10-[[3-[4-(2-carboxyethyl)-1-piperazinyl]propyl]]-2 -tri-fluromethyl-10H-phenothiazine, was synthesized and coupled to bovine serum albumin. Immunization of New Zealand white rabbits with this drug-protein conjugate resulted in the production of antisera, one of which was subsequently utilized in the development of an RIA procedure. The described RIA for the first time enables the quantitation of the 7-hydroxy metabolite of trifluoperazine in human plasma after oral administration of single and therapeutic doses of trifluoperazine, in which 20 pg of the nonconjugated 7-hydroxy metabolite in 200 microL of plasma can be measured with a CV of less than 3% in B/Bo readings. Similar results were obtained by this assay procedure with or without the selective extraction of the 7-hydroxy metabolite and in the presence or absence of a large excess of trifluoperazine and other suspected major metabolites, such as the sulfoxide and N4'-oxide metabolites. This RIA procedure, together with a previously developed RIA for trifluoperazine, was used to directly determine plasma concentrations of trifluoperazine and its 7-hydroxy metabolite after administration of a single 5-mg oral dose of trifluoperazine to six healthy male volunteers. The mean +/- SD for the peak concentration (Cmax), the time to Cmax, the area under the curve from 0 to 24 h and, the apparent terminal elimination half-life for the 7-hydroxy metabolite were found to be 0.86 +/- 0.2 ng/mL, 6.2 +/- 1.6 h, 11.1 +/- 4.9 ng . h/mL, and 10.6 +/- 5.7 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

A modified, sensitive liquid chromatographic method for measurement of propranolol with fluorescence detection.

A simple, sensitive, and rapid fluorometric-high-performance liquid chromatographic method for quantitating human and animal plasma and blood levels of propranolol has been developed. The procedure, which requires microliter volumes of triethylamine in the mobile phase mixture and microliter volumes of plasma or blood (50-100 microL), may be applied in routine clinical analysis as well as in pharmacokinetic studies using small laboratory animals. A single, selective extraction step precedes the analysis. The limiting concentration that can be detected is 1 ng/mL.

Chromatography, High Pressure Liquid↗
PubMed1989

Competitive protein binding assay for piritrexim.

A competitive protein binding assay for piritrexim (PTX, 1) that makes use of a commercially available radioassay kit for methotrexate has been developed. After it is selectively extracted from plasma, PTX competes with [125l]methotrexate for binding to dihydrofolate reductase isolated from Lactobacillus casei. Free drug is separated from bound drug by adsorption to dextran-coated charcoal. Piritrexim is measurable over a range of 0.01 to 10.0 micrograms/mL in plasma with a coefficient of variation less than 15%. The limit of sensitivity of the assay is approximately 2 ng/mL. An excellent correlation between this assay and a previously published HPLC method was found. published HPLC method was found.

Antineoplastic Agents↗
PubMed1991

A sensitive radioligand binding assay for timolol in plasma.

A sensitive and reproducible radioreceptor assay (RRA) is described for the determination of low picogram levels of timolol in plasma. The plasma or serum samples (1 mL) are prepared by selectively extracting timolol with lipophilic solvents or, alternatively, only plasma (serum) proteins are precipitated prior to binding assay. The recovery of timolol is at least 90% during the sample preparation. In the radioligand binding assay, timolol and the nonselective beta-antagonist [3H](-)-CGP-12177 compete for the binding sites present in the rat reticulocyte membranes. The detection limit for timolol (30 pg/mL) exceeds 50 times the sensitivity of the GC-MS techniques for timolol. The RRA results and GC results obtained from the same clinical samples correlate excellently (r = 0.99). There was no evidence for interference caused by timolol metabolites in the RRA. Timolol concentrations in plasma following its oral and even ocular administration were possible to monitor using the RRA. The method can be modified to also measure several other beta-antagonist drugs in picogram per milliliter quantities.

Adrenergic beta-Antagonists↗
PubMed1992

Pharmacokinetic characterization and tissue distribution of the new glucocorticoid soft drug loteprednol etabonate in rats and dogs.

Loteprednol etabonate, a new glucocorticoid soft drug with a characteristic chloromethyl ester function in the 17 beta-position, is currently in the early phases of clinical development. As the basis for human trials, this study describes a new reversed-phase high-performance liquid chromatographic method for the determination of levels of drug in plasma and urine samples and assesses the pharmacokinetic properties of loteprednol etabonate in dogs and rats. Intravenous administration of loteprednol etabonate (5 mg/kg) to dogs revealed a terminal half-life of 2.8 h, a volume of distribution of 3.7 L/kg, and a total body clearance of 0.9 L/h/kg. Intact loteprednol etabonate was not detectable in the urine. After oral administration of the drug (5 mg/kg) to dogs, only metabolites, but no intact drug, were found in the plasma, an indication for a high first-pass effect. A pronounced binding of the drug to plasma protein (> 90%) and a high erythrocyte-buffer partition coefficient of 7.8 were determined in vitro. Preliminary information about tissue distribution and possible metabolic pathways were obtained in rats after oral administration of a 14C-labeled loteprednol etabonate suspension (5 mg/kg). pH-selective extraction into ethyl acetate revealed three distinguishable fractions: (1) a neutral lipophilic fraction, presumably intact drug, (2) an acidic, lipophilic fraction, and (3) a hydrophilic nonextractable fraction. Levels of intact drug and metabolites were highest in liver and kidney, whereas significantly lower levels were found in other investigated organs (lung, brain, heart).(ABSTRACT TRUNCATED AT 250 WORDS)

Androstadienes↗
PubMed1995

Development and application of a specific and sensitive radioimmunoassay for trihexyphenidyl to a pharmacokinetic study in humans.

A radioimmunoassay (RIA) for trihexyphenidyl was developed through the use of a bovine thyroglobulin conjugate of trihexyphenidyl hemisuccinate. Immunization of New Zealand white rabbits with this drug-protein conjugate yielded antisera, for which the antibody titer and specificity were evaluated. An antiserum that had the highest titer and minimal cross-reactivities to major metabolites of trihexyphenidyl, such as trihexyphenidyl N-oxide (2%), hydroxytrihexyphenidyl (1%), and the antipsychotic drugs fluphenazine (< 1%), flupenthixol (< 1%), chlorpromazine (< 1%), and haloperidol (< 1%), was selected for development of a RIA. The described RIA enables the quantitation of 7.8 pg of trihexyphenidyl in 200 microL of human plasma with a mean coefficient of variation of < 6% across the range of the standard curve. Assay specificity was further demonstrated by comparison of results obtained directly and after selective extraction of trihexyphenidyl from replicate samples. This RIA procedure was applied to the analysis of steady state plasma samples obtained from patients undergoing treatment with trihexyphenidyl (2-8 mg) and plasma samples obtained from eight healthy male volunteers after administration of a single 4 mg oral dose of the drug. The results of the latter single dose studies demonstrated that the mean +/- SD for the peak concentration (Cmax), the time to Cmax (Tmax), the rate of absorption (Ka), and the area under the curve from 0 to 72 h (AUC0-72) were found to be 7.15 +/- 2.58 ng/mL, 1.32 +/- 0.58 h, 2.07 +/- 0.93 1/h, and 201 +/- 71 ng h/mL, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Toxicity and trichothecene production by Fusarium acuminatum subsp. acuminatum and Fusarium acuminatum subsp. armeniacum.

The toxicity of cultures of Fusarium acuminatum subsp. acuminatum and Fusarium acuminatum subsp. armeniacum grown on Weet-Bix medium was assessed using a chick bioassay. Thirty-nine of 45 cultures of F. a. armeniacum tested produced at least 50% mortality in the chick bioassay. In contrast, of the 26 cultures of F. a. acuminatum tested, only nine produced at least 50% mortality. Selected extracts of both subspecies were analyzed by gas chromatography after clean-up and hydrolysis for the four main trichothecene families, namely; nivalenol (NIV), deoxynivalenol (DON), scirpentriol (Sctol), and T-2 tetraol (T-2tol). Levels of up to 500 micrograms/g and 7 micrograms/g of T-2tol were detected in F. a. armeniacum and F. a. acuminatum extracts respectively. Four cultures each of F. a. armeniacum and F. a. acuminatum were also grown on two solid media (Weet-Bix and Vermiculite) and two liquid media (MYRO and GYEP). Culture extracts were again tested for toxicity and analyzed for trichothecene production. Cultures of F. a. armeniacum grown on the solid media and on MYRO produced the highest toxicity. Levels of up to 168, 129, 150, and 8 micrograms/g of T-2tol were detected in cultures of F. a. armeniacum on Weet-Bix, Vermiculite, MYRO, and GYEP respectively. In contrast, only trace amounts of T-2tol were detected in extracts of F. a. acuminatum on all media. Sctol levels of less than 0.5 microgram/g were also detected in some cultures of both subspecies on solid media, but only F. a. armeniacum produced trace levels of Sctol on liquid media.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Trace determination of organotin compounds in water, sediment and mussel samples by low-pressure gas chromatography coupled to tandem mass spectrometry.

A fast method for the determination of eight organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), tetrabutyltin (TeBT), monophenyltin (MPhT), diphenyltin (DPhT), triphenyltin (TPhT) and tetraphenyltin (TePhT), in water, sediments and mussels, was developed using low-pressure gas chromatography/tandem mass spectrometry (LPGC/MS/MS). The method is based on sodium diethyldithiocarbamate (DDTC) complexation of the ionic organotins, followed by extraction of the target matrices and derivatization by a Grignard reagent, as described in a previously published method for water samples. Solid-phase extraction was selected as extraction method from water samples after comparison with liquid-liquid extraction, but extraction of the OTs from sediment and mussel samples was performed using toluene. Matrix-matched calibration standards were used to minimize matrix effects. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, detection limit (LOD), quantitation limit (LOQ), precision, and recovery were determined. Recoveries of OTs in spiked matrices ranged from 86-108% in water and from 78-110% in sediments and mussels, with precision values lower than 18%. Detection limits ranged from 0.1-9.6 ng L(-1) in water, and 0.03-6.10 microg kg(-1) in the other matrices. The present implementation of LPGC rather than conventional capillary GC permitted use of large-volume injection and reduced analysis time by a factor of two. The proposed methodology was applied to the determination of OTs in real samples of water, marine sediments and mussels from the west coast of the Mediterranean Sea (Spain).

Animals↗
PubMed2003

Gas chromatography/mass spectrometry for the characterization of organic materials in frescoes of the Monumental Cemetery of Pisa (Italy).

The paper deals with the application of two analytical procedures, based respectively on on-line pyrolysis in the presence of hexamethyldisilazane followed by gas chromatography/mass spectrometric analysis (Py/GC/MS) and on selective extractions and microwave-assisted hydrolysis followed by GC/MS determination. These procedures give reliable data on the organic composition of micro-samples; moreover, when applied to the same micro-sample, they give comparable data on natural substances, and complementary information on synthetic compounds and degradation products. The two methods were used to characterise the organic matter present in several samples taken from scenes of the frescoes 'Giudizio Universale' and the 'Ascensione' by Bonamico Buffalmacco in the Monumental Cemetery of Pisa. The observed hydrophobicity of their surfaces, which hampers traditional means of restoration, is explained by the formation of a polymeric network due to reactions between a synthetic polymer used as adhesive, the proteinaceous material (animal glue and casein), and formaldehyde.

Adhesives↗
PubMed1999

Development of a capillary electrophoresis assay based on free sulfate determination for the direct monitoring of sulfoesterase activity.

A capillary electrophoresis assay of sulfoesterase activity was developed that overcomes the main drawbacks encountered with the usual methods for sulfate determination in complex biological medium. Conditions are described allowing direct measurement of inorganic sulfate that is enzymatically produced in the reaction mixture. The main features of this method are electrokinetic sample introduction, which allows selective extraction of sulfate from the matrix into the separation capillary, counter-electroosmotic flow migration mode, indirect absorbance detection and use of an internal standard for quantitative performances. Likewise, perfect linearity was obtained for concentrations of sulfate up to 40 ppm. The limits of detection and quantification were 0.2 and 0.6 ppm, respectively. The run-to-run and day-to-day precision are 1 and 4.5%, respectively, for sulfate concentrations varying from 35 ppm down to 1 ppm. The accuracy was established for the synthetic p-nitrocatechol sulfate substrate by comparison with the classical spectrophotometric assay. The method was applied to the kinetic monitoring of the activity of a sulfoesterase extracted from the marine mollusc Pecten maximus on fucoidan, a bioactive sulfated fucose-based polysaccharide derived from brown algae. For the first time, a sulfoesterase activity was shown to be effective on such sulfated polysaccharides.

Animals↗
PubMed1993

Structure of the herpes simplex virus capsid. Molecular composition of the pentons and the triplexes.

The molecular anatomy of the herpes simplex virus (HSV-1) capsid has been examined by conventional electron microscopy, cryoelectron microscopy combined with three-dimensional image reconstruction, and scanning transmission electron microscopy (STEM). Studies were carried out with purified capsids before and after treatment with urea and guanidine hydrochloride (GuHCl) at concentrations that maintain the capsid's icosahedral geometry, but selectively extract certain of its protein components. Treatment with 6.0 M urea was found to remove the pentons quantitatively from the capsid vertices, but it caused no appreciable loss of hexons. Penton loss was correlated with solubilization of a small amount of VP5, the major HSV-1 capsid protein, and the amount solubilized (6.1%) was in good agreement with the amount expected (6.3%) if pentons are each composed of five copies of VP5. We conclude that the pentons, like the hexons, are composed of VP5, which exists as a pentamer at the capsid vertices (the pentons) and as a hexamer in all other capsomers (the hexons). Control capsids and capsids extracted with 2.0 M GuHCl (G2.0 capsids) were examined by cryoelectron microscopy and the resulting images were employed to compute three-dimensional reconstructions. Also, the masses of control and G2.0 capsids were determined by dark-field STEM and the results were used to calculate copy numbers for the proteins present. The three-dimensional reconstructions showed that control and G2.0 capsids are similar in structure, except that G2.0 capsids lack all 12 pentons and 120 of the 320 trigonal nodules or "triplexes" that connect HSV-1 capsomers in groups of three. The missing triplexes are the ten closest to each capsid vertex. Thus, the tightness with which triplexes are bound to the VP5 matrix varies according to position on the T = 16 icosahedral surface lattice, those closest to the pentons being most easily detached. Biochemical analyses revealed partial loss of the minor capsid proteins VP19 and VP23 in G2.0 compared to control capsids. Taking into account the STEM data on capsid protein stoichiometry, we propose that HSV-1 triplexes are heterotrimers composed of one copy of VP19 and two copies of VP23.

Capsid↗
PubMed2001

Multiple procyclin isoforms are expressed differentially during the development of insect forms of Trypanosoma brucei.

Transmission of Trypanosoma brucei by the tsetse fly entails several rounds of differentiation as the parasite migrates through the digestive tract to the salivary glands of its vector. Differentiation of the bloodstream to the procyclic form in the fly midgut is accompanied by the synthesis of a new coat consisting of EP and GPEET procyclins. There are three closely related EP isoforms, two of which (EP1 and EP3) contain N-glycans. To identify the individual EP isoforms that are expressed early during synchronous differentiation in vitro, we exploited the selective extraction of GPI-anchored proteins and mass spectrometry. Unexpectedly, we found that GPEET and all isoforms of EP were coexpressed for a few hours at the onset of differentiation. At this time, the majority of EP1 and EP3 molecules were already glycosylated. Within 24 hours, GPEET became the major surface component, to be replaced in turn by glycosylated forms of EP, principally EP1, at a later phase of development. Transient transfection experiments using reporter genes revealed that each procyclin 3' untranslated region contributes to differential expression as the procyclic form develops. We postulate that programmed expression of other procyclin species will accompany further rounds of differentiation, enabling the parasite to progress through the fly.

3' Untranslated Regions↗