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At least 451 records · Page 25Linked to original sources
PubMed2006

Mercury analysis of acid- and alkaline-reduced biological samples: identification of meta-cinnabar as the major biotransformed compound in algae.

The biotransformation of Hg(II) in pH-controlled and aerated algal cultures was investigated. Previous researchers have observed losses in Hg detection in vitro with the addition of cysteine under acid reduction conditions in the presence of SnCl2. They proposed that this was the effect of Hg-thiol complexing. The present study found that cysteine-Hg, protein and nonprotein thiol chelates, and nucleoside chelates of Hg were all fully detectable under acid reduction conditions without previous digestion. Furthermore, organic (R-Hg) mercury compounds could not be detected under either the acid or alkaline reduction conditions, and only beta-HgS was detected under alkaline and not under acid SnCl2 reduction conditions. The blue-green alga Limnothrix planctonica biotransformed the bulk of Hg(II) applied as HgCl2 into a form with the analytical properties of beta-HgS. Similar results were obtained for the eukaryotic alga Selenastrum minutum. No evidence for the synthesis of organomercurials such as CH3Hg+ was obtained from analysis of either airstream or biomass samples under the aerobic conditions of the study. An analytical procedure that involved both acid and alkaline reduction was developed. It provides the first selective method for the determination of beta-HgS in biological samples. Under aerobic conditions, Hg(II) is biotransformed mainly into beta-HgS (meta-cinnabar), and this occurs in both prokaryotic and eukaryotic algae. This has important implications with respect to identification of mercury species and cycling in aquatic habitats.

Chlorophyta↗
PubMed1999

On-line dialysis-SPE-CE of acidic drugs in biological samples.

A fully automated method is presented for the determination of acidic drugs in urine and serum using on-line dialysis-solid-phase extraction (SPE)-capillary electrophoresis (CE) with UV detection. With non-steroidal anti-inflammatory drugs (NSAIDs) as test compounds, detection limits in the biological samples were 0.05-1.0 microgram ml-1. Calibration plots were linear over two orders of magnitude and the within-day and between-day repeatability were better than 10%. The CE capillary and SPE column were used for over 500 analyses; the dialysis membrane was replaced after 250 analyses. A general protocol for dialysis-SPE-CE which can be used for amphoteric and acidic drugs was devised. The present results show that this protocol has general validity and can be recommended for future work on other classes of drugs.

Acids↗
PubMed2002

High-sensitivity analyses of metabolites in biological samples by capillary electrophoresis using dynamic pH junction-sweeping.

Emerging fields of biochemical research, such as metabolomics, present challenges to current separation technologies because of the large number of metabolites present in a cell and their often low (submicromolar) concentration. Although capillary electrophoresis (CE) holds great promise as the method of choice for high-resolution separations of biological samples, it suffers from poor concentration sensitivity, especially with the use of UV detection. In CE, sweeping and dynamic pH junction represent two complementary on-line focusing techniques that have been used for sensitivity enhancement of hydrophobic and weakly acidic analytes, respectively. However, the application of either the sweeping or dynamic pH junction technique alone might, in some cases, be less effective for the analysis of certain sample mixtures. Recent work in the development of a hyphenated dynamic pH junction-sweeping technique is presented as an effective on-line method of preconcentration suitable for both hydrophilic (anionic) and hydrophobic (neutral) analytes. Sensitive analyses of flavin metabolites by CE with laser-induced fluorescence (LIF) detection is demonstrated in various biological matrixes, including cell extracts of Bacillus subtilis, pooled human plasma, as well as heat-deproteinized flavoenzymes. Enhanced analyte band narrowing and improved sensitivity is achieved for flavins using dynamic pH junction-sweeping compared to either sweeping or dynamic pH junction alone. This results in over a 1200-fold improvement in sensitivity relative to conventional injection methods, giving a limit of detection (LOD, defined as S/N = 3) of about 4.0 x 10(-12) M. Strategies for sensitive and more comprehensive analyses of other cell metabolites, including nucleotides, coenzymes, and steroids, are also discussed when using on-line focusing techniques in conjunction with multiplexed CE and UV detection.

Bacillus subtilis↗
PubMed1993

1H editing of 2-deuterated exogenous and natural endogenous D-glucose in biological samples.

A spin-echo based 1H homonuclear pulse sequence, enabling the selective editing of homonuclear first-order J-multiplet types, is presented and analyzed. Its effectiveness in quantification applications is assessed. Its potential usefulness in the quantitative distinction between 2-deuterated and natural D-glucose in biological samples is briefly discussed, with emphasis on studies of hexose metabolism conducted in vitro.

Absorption↗
PubMed1997

An acid-treatment method for the enhanced detection of GDNF in biological samples.

Glial cell line-derived neurotrophic factor (GDNF), a distant member of the transforming growth factor-beta (TGFbeta) family, is a protein that is essential for the survival of dopaminergic, motor, and peripheral neurons. To facilitate its study, we and others have developed sensitive (low pg/ml) enzyme-linked immunosorbant assays (ELISA) to quantitate endogenous concentrations of GDNF, along with neurotrophin-3 (NT-3) and nerve growth factor (NGF). However, endogenous tissue levels of GDNF in adult animals are not readily detected by ELISA and do not correlate well with message RNA. Based upon previously described methods for the extraction of TGFbeta from tissue samples, we have developed an acid-treatment procedure to allow the quantification of total endogenous GDNF. This procedure also was evaluated for use when measuring total endogenous levels of NT-3 and NGF from biological samples. The acid-treatment procedure increases the detectable amounts of GDNF, NT-3, and NGF in all tissue samples and most of the serum samples tested. Moreover, these values were as much as 35 times greater than those detected using traditional extraction buffers. Such elevated concentrations likely resulted from the acid treatment promoting the dissociation of ligands from receptors or binding proteins, thereby making more of the analyte available to be measured in the ELISA. These findings indicate that appropriate sample treatment is essential for the measurement of total endogenous neurotrophic factors.

Acids↗
PubMed1978

Quantitative determination of styrene in biological samples and expired air by gas chromatography-mass spectrometry (selected ion monitoring).

Styrene, phenylethylene, is an oily liquid of commercial importance in the manufacture of various plastics, rubbers, resins, and insulating materials. A gas chromatographic-mass spectrometric method is described for the determination of low levels of styrene in biological samples. The procedure utilizes an internal standard and specificity is gained by monitoring selected ions.

Adipose Tissue↗
PubMed1998

Guidelines for mineral fibre analyses in biological samples: report of the ERS Working Group. European Respiratory Society.

Microscopic techniques for analysing asbestos fibres in lung tissue and bronchoalveolar lavage have provided major information in the understanding of asbestos-related diseases. These analyses are increasingly applied for clinical work and medicolegal problems. Differences in sampling, preparation and counting techniques, definitions of reference populations and expression of results have caused major difficulties in comparing results from different laboratories. Therefore it appeared necessary to set a goal to harmonize these analyses between the European laboratories active in this field. This article summarizes the work of a European Respiratory Society working group with participation from nine European laboratories. The five main issues touched upon are: 1) definitions of control populations and reference levels; 2) sampling, preparation and analytical techniques; 3) asbestos fibres in lung tissues in different pathologies; 4) asbestos bodies in lung tissue, bronchoalveolar lavage and sputum; and 5) basis for the interpretation of fibres and asbestos bodies in biological samples. These guidelines indicate the crucial importance of several factors for the interpretation of the results; namely, adequate sampling, comparable analytical procedures and expression of the results, the use of well-defined reference populations, and a comprehensive understanding of the factors affecting the fibre retention and the dose-responses associated with the different asbestos-related diseases.

Asbestos↗
PubMed1989

Direct electrochemical determination of glucose oxidase in biological samples.

An electrochemical method for the quantitation of glucose oxidase in murine plasma and tissues has been developed. Instead of oxygen, this method uses benzoquinone as an artificial cosubstrate of glucose oxidase. The quantitative detection of the enzymatically produced hydroquinone by controlled-potential amperometry allows measurement of glucose oxidase concentrations in biological samples. The use of an internal standard corrects for all possible interfering effects. We demonstrated a 10-fold increase in sensitivity, as well as the ability to work in turbid media, in comparison to spectrophotometric methods.

Animals↗
PubMed1998

Determination of ropivacaine and [2H3]ropivacaine in biological samples by gas chromatography with nitrogen-phosphorus detection or mass spectrometry.

Bioanalytical methods for determining the total concentration of the new local anaesthetic drug ropivacaine in blood plasma, urine and tissues are presented. Ropivacaine is a drug mainly used in connection with surgery and for post-operative pain relief. The biological samples were prepared using liquid-liquid extraction and analysed using capillary gas chromatography with nitrogen-phosphorus detection or mass spectrometry. The methods are highly selective and reliable with a between-day precision, given as the relative standard deviation, generally below 6%. More than 20000 samples have been analysed using the methods described.

Amides↗
PubMed1991

Evaluation of gas chromatographic columns for the determination of methylmercury in aqueous head space extracts from biological samples.

Several gas chromatographic columns were evaluated for the determination of methylmercury in aqueous solution. The goal of the study was to further decrease the detection limit of the recently developed method of head space gas chromatography with microwave-induced plasma detection (HS-GC-MIP) for the determination of methylmercury in biological samples. The columns were first evaluated using gas chromatography with electron-capture detection (ECD). At the same time, the column efficiencies for the determination of ethyl- and phenylmercury were also studied. Of the packed columns the stationary phase used previously in HS-GC-MIP, AT-1000, yielded the best results. Better results were obtained with two wide-bore thick-film fused-silica open tubular (FSOT) columns, one of which was suitable for aqueous injections (Superox-FA) and the other for benzene or toluene (RSL-300). With these FSOT columns, absolute detection limits at the sub-picogram level were reached. A new HS-GC-MIP system was then constructed, which was adapted for the use of FSOT columns. As more sensitive measurements were obtained with a Superox-FA FSOT column than with an AT-1000 packed column using the GC-ECD system in the first part of this study, the FSOT column was evaluated in this HS-GC-MIP system for the determination of methylmercury in real tissue samples. It was demonstrated that the use of an FSOT column gives only a small decrease in the detection limit compared with a packed column; reconditioning of the FSOT column is, however, a disadvantage in routine measurements.

Chromatography, Gas↗
PubMed2003

Determination of aluminum in environmental and biological samples by reversed-phase high-performance liquid chromatography via pre-column complexation with morin.

Morin was used as a pre-column reagent for the determination of aluminum by RP-HPLC with fluorescence detection. This method has been successfully applied to direct determination of trace Al in environmental and biological samples. The response was linear from 6 x 10(-9) to 6 x 10(-5) M with a detection limit of 2 x 10(-9) M. In addition, the different Al complexes with morin were separated by the proposed HPLC procedure and their coordination ratios were depicted by molar-ratio method. The results showed that 1:1 and 2:1 Al-morin complexes formed.

Aluminum↗
PubMed2004

Performance of selective and differential media in the primary isolation of yeasts from different biological samples.

In view of the increase in yeast infections, especially polymicrobial ones, differential culture media have acquired increasing importance. The present study evaluated the Sabouraud chloramphenicol, Biggy agar, Pagano Levin agar and CHROMagar Candida media in terms of isolation, number of yeast colony forming units per plate, and inhibition of bacteria and filamentous fungi. To this end, we used 223 biological samples, including feces, and oral, vaginal and anal mucosae from 86 patients presenting or not symptoms of fungal infections. The four media did not differ significantly in terms of detection of yeast-positive cultures. The number of colony forming units per plate ranged from zero to 2.380, with a predominance of counts of 1 to 9 colonies per plate. No significant differences were observed among the four culture media in terms of number of colonies counted, for each kind of biological material. Fifteen species belonging to the genera Candida, Saccharomyces, Cryptococcus, Trichosporon and Rhodotorula were isolated, with C. albicans being the predominant species, followed by C. parapsilosis and R. rubra. CHROMagar Candida and Biggy agar were complementary in the isolation of the different species and favored a greater recovery of polymicrobial cultures. Pagano Levin agar isolated the smallest variety of species. Sabouraud chloramphenicol agar was the least effective in terms of bacterial inhibition and favored a greater development of filamentous fungi. The results suggest that more than one culture medium should be used for an adequate primary isolation.

Adult↗
PubMed1992

Quantitation of paraquat in biological samples by radioimmunoassay using a monoclonal antibody.

We have developed a sensitive and specific radioimmunoassay for the quantitative determination of paraquat in plasma, urine, and bronchoalveolar lavage fluid using a monoclonal antibody. The synthesis of the iodinated paraquat tracer is novel and less complicated than a previously reported method. Regardless of the type of biological sample analyzed, the sensitivity of the assay was 0.46 ng/ml in a 200-microliters aliquot. The results correlated well with those of another assay performed in a separate laboratory. Paraquat concentrations were determined in plasma and in urine of a dog over several days after the intravenous administration of 7.48 mg paraquat cation/kg and in bronchoalveolar lavage fluid obtained 34 hr after the 2-hr infusion was discontinued. Concentrations of paraquat measured ranged from 14.1 to 0.03 micrograms/ml in plasma and 2034 to 0.36 micrograms/ml in urine. Concentrations of paraquat in plasma obtained at various times after the ingestion of paraquat by three patients ranged from 51.0 to 0.010 micrograms/ml.

Animals↗
PubMed1985

Identification and quantification of 1-carboxysalsolinol and salsolinol in biological samples by gas chromatography--mass spectrometry.

1-Carboxysalsolinol was found to be present in rat striatum, human urine and caudate nucleus of post mortem human brain, according to capillary column gas chromatographic retention times and selected ion monitoring of the hexafluoropropionyl ester pentafluoropropyl derivative. Simultaneous quantification of 1-carboxysalsolinol and salsolinol was performed in biological samples using deuterium labelled internal standards. In human urine, the precision of the method was +/- 7.1% (coefficient of variation, n = 25) for 1-carboxysalsolinol at 15 pmol/ml and +/- 8.5% for salsolinol at 10 pmol/ml. According to enzymatic hydrolysis, 68% of 1-carboxysalsolinol was found as conjugates in urine, and the corresponding figure for salsolinol was 92%. In human caudate nucleus, the amounts of 1-carboxysalsolinol were found to be significantly greater in brains from alcoholics, who at autopsy had ethanol present in the blood, whereas alcoholics without blood ethanol levels at autopsy had significantly lower concentrations of salsolinol.

Adult↗
PubMed1990

Microtiter plate assay for the measurement of glutathione and glutathione disulfide in large numbers of biological samples.

By combining the least complicated and expedient methods of sample handling with the sensitivity and specificity of the GSH assay by enzymatic recycling and the small volumes and software capabilities of microtiter plate technology we have devised a rapid, sensitive, and easy assay for GSH and GSSG in biological samples. The assay is sensitive to 5 pmol in sample volumes of 50 microliters, although other volumes could be used. The use of a computer-driven microplate with software capable of linear kinetic data storage and analysis on each well, Maxline series microplate readers and Softmax software, enables the user not only to assay large numbers of samples per day but also to have immediate calculated results. We suggest by examples that measurements of total GSH as well as changes in GSH:GSSG in vitro and in vivo are feasible with this technology.

Animals↗
PubMed1991

Highly sensitive method for the determination of 5-fluorouracil in biological samples in the presence of 2'-deoxy-5-fluorouridine by gas chromatography-mass spectrometry.

A highly sensitive and convenient gas chromatographic-mass spectrometric (GC-MS) method is described for the determination of 5-fluorouracil in the presence of 2'-deoxy-5-fluorouridine (which breaks down into 5-fluorouracil during ordinary GC derivatization) in biological samples such as plasma and urine. After extraction with ethyl acetate, 5-fluorouracil and 5-chlorouracil, the latter being used as an internal standard, were converted into their tert.-butyldimethylsilyl derivatives by allowing the mixture to stand for 30 min at room temperature and were assayed by electron-impact ionization GC-MS. Under these conditions, 2'-deoxy-5-fluorouridine did not decompose or interfere with the determination of 5-fluorouracil. The assay method, including the extraction and tert.-butyldimethylsilyl derivatization of 5-fluorouracil, showed good linearity in the range 0-100 ng/ml for 5-fluorouracil in plasma (detection limit 0.5 ng/ml) and urine (detection limit 1 ng/ml). The usefulness of this method was demonstrated by determining plasma concentrations of 5-fluorouracil in rats treated intravenously with 5-fluorouracil and 2'-deoxy-5-fluorouridine.

Acetamides↗
PubMed2000

Determination of theophylline and its metabolites in biological samples by liquid chromatography-mass spectrometry.

Liquid chromatography-mass spectrometry (LC-MS) is a powerful tool for analysis of drugs and their metabolites. We used a column-switching system in combination with atmospheric pressure chemical ionization LC-MS (LC-APCI-MS) for the determination of theophylline and its metabolites in biological samples. The separation was carried out on a reversed-phase column using methanol-20 mM ammonium acetate as a mobile phase at a flow-rate of 1 ml/min in 30 min. In the mass spectrum, the molecular ions of these drugs and metabolites were clearly observed as base peaks. This method is sufficiently sensitive and accurate for the pharmacokinetic studies of these drugs.

Calibration↗