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At least 919 records · Page 51Linked to original sources
PubMed1983

Formation of imine derivatives between tris(hydroxymethyl)-aminomethane and saturated 3-oxo steroids during conventional work up of biological samples dissolved in Tris-HCl buffers.

Extraction with organic solvents of Tris-HCl buffer solutions containing microgram amounts of saturated 3-oxo-steroids, followed by evaporation of the organic solvent, produce a condensation product identified as the Tris-3-imino-derivative of the steroid. The yields range between 20-40%. The conditions governing the formation of the derivatives have been explored.

Chemical Phenomena↗
PubMed1994

The trace analysis of musk xylene in biological samples: problems associated with its ubiquitous occurrence.

Musk xylene (1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene) (MX), a synthetic musk often used in fragrances has previously been described to occur in human tissue. In this article a specific and sensitive method for the determination of MX in blood is described. It includes a simple clean-up by silica gel adsorption chromatography followed by GC/MS detection with negative chemical ionisation (NCI) and multiple ion detection of the molecular ion and M-30. The absolute detection limit in the MID-mode was 50 fg of MX. 11 human blood samples of 3 individuals were analysed to elucidate the suitability of this method. The MX concentrations ranged from 66 to 270 pg/g plasma or 12 to 49 ng/g blood lipids, respectively. In the course of the method evaluation the hazard of sample contamination during the clean-up procedure was investigated and MX was found to be present in several materials in the laboratory. Some of these contamination sources could be eliminated.

Adult↗
PubMed1995

Mercury in environmental and biological samples from a gold mining area in the Amazon region of Brazil.

A massive increase in gold mining in the Amazon region of Brazil has led to an enormous discharge of metallic mercury into the aquatic ecosystem. To investigate the dispersion, total and inorganic mercury concentrations were measured in water, fish and animal tissues, and in blood, urine and hair from members of the local populations. Mercury concentrations in river water, sediments and fish were high compared with those of non-contaminated areas. Cattle and pigs kept in the area and with access to the contaminated rivers had concentrations of mercury of 0.1-1.28 micrograms/g and 11.7-15.7 micrograms/l in hair and blood, respectively. These results are approximately twice those measured in specimens from control animals. Mean mercury concentrations in blood, urine and hair of residents were increased at 11.4 micrograms/l, 22.8 micrograms/l and 4.3 micrograms/g, respectively, and the urine mercury of workers from the gold mining sites were up to 155 micrograms/l. The results demonstrate widespread contamination of the environment by mercury with transfer of the metal to fish and animals used for food, and into the inhabitants of the region. Further investigations for possible adverse health effects need to be undertaken.

Animals↗
PubMed1980

Rapid extraction of oxygenated metabolites of arachidonic acid from biological samples using octadecylsilyl silica.

A rapid procedure for the efficient extraction of prostaglandins, thromboxanes and hydroxy fatty acids from urine, plasma and tissue homogenates has been developed. Fractions containing these substances are acidified and passed through a column of octadecylsilyl silica, which retains oxygenated metabolites of arachidonic acid. Phospholipids, proteins and very polar materials either are not retained or can be eluted with dilute aqueous ethanol. Nonpolar lipids and monohydroxy fatty acids are then eluted with petroleum ether or benzene. Subsequent elution of the column with methyl formate gives a fraction containing prostaglandins and thromboxanes which is much less contaminated with extraneous material than that obtained by conventional extraction of aqueous media with organic solvents. The methyl formate can be removed rapidly under a stream of nitrogen and the components of the sample purified directly by high pressure liquid chromatography (HPLC). An improved method for the purification of prostaglandins and TXB2 by HPLC on silica columns is reported.

Animals↗
PubMed1981

A method for the estimation of amino acid radioactivity in biological samples.

A method for quantitative estimation of total radioactivity present in the free amino acid fraction of tissue samples has been described. Samples deproteinized with cold acetone were extracted, in acidic medium, with ethyl ether (peroxide free); after centrifugation, the aqueous phase was used for amino acid derivatization at 40 degrees C for 15 h with 1-fluoro-2,4-dinitrobenzene in bicarbonate-buffered medium. Aliquots of the derivatized samples were acidified and extracted twice again with ethyl ether. The combined organic phases were placed in glass scintillation vials, dried, and used for the determination of its radioactivity, corresponding to the radioactivity present in the free amino acid fraction of the sample. Deproteinized samples of rat blood plasma, as well as hen egg white and yolk were tested after addition of known quantities of 14C-labelled amino acids or glucose, for validation of the method. No glucose radioactivity was found in any of the extracted samples. All radioactivity added to the samples in the form of 14C-labelled alanine, glutamic acid, leucine and phenylalanine was quantitatively recovered in the derivatized fraction; only a fraction of arginine radioactivity was recovered.

Amino Acids↗
PubMed1987

A novel fluorometric assay for quantitative analysis of dihydrofolate reductase activity in biological samples.

In an effort to study the level of dihydrofolate reductase (DHFR), the main molecular target of antifolate drugs, in healthy and malignant tissues of human origin, a new and convenient fluorometric enzymatic assay has been developed. The technique measures the overall decrease in fluorescence emission at 454 nm (lambda ex = 342 nm) due to the contributions from coenzyme oxidation and substrate reduction. This technique was developed by using an enzyme purified from beef liver. All criteria of quality were checked: sensitivity, reproducibility and specificity made it suitable for low activity measurements. It was successfully applied to human tissue crude extracts.

Animals↗
PubMed1987

A novel method for the rapid detection of specific nucleotide sequences in crude biological samples without blotting or radioactivity; application to the analysis of hepatitis B virus in human serum.

The detection of a little as 0.2 pg (60,000 molecules) of hepatitis B viral (HBV) DNA in human serum samples in 4 h has been demonstrated using a solution-hybridization and bead-capture method. An amplification method based on chemically crosslinked oligodeoxyribonucleotides was coupled with a horseradish peroxidase-labeling scheme for the ultimate detection of the analyte. Two sets of HBV complementary synthetic oligodeoxyribonucleotide probes containing one of two types of single-stranded (ss) overhangs were employed. These ss overhangs were used to capture the probe-analyte complex onto a bead and subsequently to label it. Detection was achieved with either a chemiluminescent or colorimetric output substrate for the enzyme. Only in the presence of the virus was label specifically bound to the support. The assay was relatively unaffected by either sample composition or by the presence of heterologous nucleic acids.

Base Sequence↗
PubMed1990

Rapid detection of pseudorabies virus genomic sequences in biological samples from infected pigs using polymerase chain reaction DNA amplification.

The presence of the pseudorabies virus (PRV) genome in infected hosts has previously been studied by standard hybridization techniques, which showed the viral genome to be present at very low levels in infected tissues. The recently introduced polymerase chain reaction (PCR) procedure provides an alternative and rapid means of amplifying small quantities of specific DNA sequences. We applied this technique to a study of pigs infected by PRV. The sequence selected for amplification consisted of 222 base pairs lying in the gene coding for the glycoprotein gp50. We used a pair of 20-mer oligonucleotides flanking this sequence as primer and a cloned Stu-Nde fragment containing the sequence as target DNA. To avoid the tedious DNA extraction procedure we performed PCR directly on disrupted cells and detected specific amplification after 25 cycles of PCR with the thermostable Taq DNA polymerase. Amplified products were detected by gel electrophoresis directly. Nasal samples from experimentally and naturally infected pigs were tested by this PCR technique. When compared with tissue culture and serological tests, detection by gel electrophoresis of PCR amplified fragments provided excellent specificity and sensitivity. We concluded that PCR amplification will be a valuable tool for rapid diagnosis of PRV infection in pigs, taking less than 1 h to complete.

Animals↗
PubMed1985

Liquid chromatographic determination of indecainide, a new antiarrhythmic drug, and its major metabolite, desisopropyl indecainide, in biological samples.

A simple, sensitive, and selective method for the determination of indecainide and its metabolite, desisopropyl indecainide, in human plasma (or serum) and urine is described. The compounds are extracted from alkalinized plasma or urine samples with ethyl acetate--hexane (9:1); the solvent is evaporated under nitrogen and the residue is reconstituted in the mobile phase. The compounds are chromatographed on a Zorbax C8 column, using 0.25 M ammonium acetate--acetonitrile--methanol--tetrahydrofuran (60:20:16:4) as the eluent at 1.5 ml/min. The effluent is monitored at 270 nm or by using a fluorescence detector (lambda exc 270 nm, lambda em 315 nm).

Anti-Arrhythmia Agents↗