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PubMed2000

Comparison of silver-ion high-performance liquid chromatographic quantification of free and methylated conjugated linoleic acids.

Silver-ion high-performance liquid chromatography was used to fractionate a mixture of conjugated linoleic acid (CLA) isomers (as the free fatty acids, CLAFFA) in commercial CLA mixtures and biological samples. Due to the unchanged retention mechanism, it was assumed that the elution order of the isomers remained the same as that of methyl esters separated on the same column. The most abundant isomers, cis/trans 10, 12-18:2 and cis/trans 9,11-18:2, were separated better as free acids on a single column than in the methyl ester form. Quantification of the CLA standard was used as the reference profile to evaluate different methylation methods commonly used to prepare CLA methyl esters for quantitation. Acid-and base-catalyzed derivatization methods resulted in CLA intraisomerization and losses in total conjugated dienes content. Acid (HCl and BF3) methylations significantly elevated the level of trans,trans isomers and significantly reduced the cis/trans isomers. Base methylation, tetramethylguanidine/methanol, resulted in loss of trans,trans isomers, and a substantial loss of total underivatized conjugated dienes. Other catalysts such as the trimethylsilyldiazomethane produced additional peaks of unidentified artifacts. The analysis of CLAFFA appears to provide more accurate quantification of CLA isomers in commercial and biological samples.

Adipose Tissue↗
PubMed2005

Trans and positional ethylenic bonds in two dominant isomers of eicosapentaenoic acid from the freshwater sponge Baicalospongia bacillifera.

Reinvestigation of the current FA composition of the regional freshwater sponge Baicalospongia bacillifera showed that the main measured isomer of EPA (14% of the total FA now detected) is, in fact, an unusual 5Z,8Z,11Z,14Z,18E-EPA. Two other isomers of this acid also present were identified as a novel 5Z,8Z,11Z,15Z,18E-EPA and the common methylene-interrupted 5Z,8Z,11Z,14Z,17Z-EPA (usually written simply as EPA). Isolation of these acids as their methyl ester derivatives was accomplished with the use of a combination of silver-ion column chromatography and HPLC. The structure of the two new compounds was deduced from GC-MS and detailed NMR data. Partial hydrazine reduction of all three isolated EPA esters followed by separation of cis/trans isomers of the resulting monoenoic acids and GC-MS analysis of their dimethyl disulfide adducts were used for determination of the configuration and position of the double bonds. We may assume that the sponge B. bacillifera cannot receive these unusual EPA isomers directly from food sources (e.g., algal diatoms), and accordingly restructuring of ordinary EPA to novel acids may take place in the sponge tissue.

Animals↗
PubMed1989

Indirect determination of O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothioate in air at low concentrations.

This paper describes an indirect method for the quantification of the toxic military agent O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothioate (VX) in the vapor state in air or other similar gases at ng/m3 levels. The method begins with the passage of a gaseous sample through a filter impregnated with silver fluoride to convert the VX vapor to ethyl methylphosphonofluoridate. The latter compound is then trapped on a bed of Chromosorb 106, transferred to a smaller bed of the same sorbent, and desorbed thermally into a gas chromatograph equipped with a flame-photometric detector. The method is comparable in sensitivity to the principal alternative method, which is based on cholinesterase inhibition, and it is less subject to interference from common organic solvents and other cholinesterase inhibitors. The detection limit was found to be limited by, and therefore dependent on, the nature and extent of any background substances that produced a significant chromatographic signal or response at the retention time of the analyte. In the absence of such substances, the instrument provided a response to 0.19 ng of VX that was thirty times larger than the peak-to-peak noise amplitude on the chromatographic base line. Moreover, the method bias (i.e., 100% minus the percent VX recovery) was found to depend on VX concentration, with estimates of agent recovery ranging from 83% at a VX concentration of 0.67 ng/m3 to 104% at a concentration of 0.084 ng/m3. The relative standard deviation varied with VX concentration and with the nature of the test that was performed to estimate it. It ranged from 2.1% in one VX vapor-challenge test to 17% in an experiment involving spiked sampling tubes, and it was generally lower at the higher VX test concentrations.

Cholinesterase Inhibitors↗
PubMed1981

Inhibition of platelet lipoxygenase by toluene-3,4-dithiol and other ferric iron chelators.

Arachidonate lipoxygenase, obtained from the soluble, cytoplasmic fraction of sonicated human platelets was strongly inhibited by toluene-3,4-dithiol and dithizone, agents which form strong complexes with ferric but not ferrous ions. Weak inhibition was noted with the less specific iron chelator ortho-phenanthroline and with potassium cyanide. There was not inhibition with the ferrous iron chelating agents 2,2' dipyridyl nor with bathophenanthroline or EDTA. These findings suggest that platelet lipoxygenase activity depends on ferric iron.

Arachidonate Lipoxygenases↗
PubMed1993

The interference of cysteine thiols in the detection of glycated and non-glycated proteins by modified silver staining after sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

In the previous study a staining intensification of in vitro glycated collagen type I versus a non-glycated one after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under a modified silver staining procedure was observed (Hodny, Z., Struzinsky, R. and Deyl, Z. (1992) J. Chromatogr. 578, 53-62). While investigating the specificity of this stain to glycation product(s) on protein we have observed that a great number of proteins (e.g. bovine serum albumin) was sensitive to this stain even in a non-glycated state. It is proposed from results of the analysis of amino acid composition of these proteins that their better stainability correlates with the amount of cysteine present in the protein. Modification of SH groups by iodoacetamide (or N-ethylmaleimide) had an inhibitory effect on the staining of bovine serum albumin (and some other proteins) in its 'native' state but had no visible inhibitory effect on their staining in the glycated state. However, the positive staining response of a great number of components from cellular lysates even after iodoacetamide treatment indicates the existence of further chemical groups (either of protein or nucleic acid origin) participating in this silver staining method.

Collagen↗
PubMed1987

Fluorine-19 NMR spectroscopic studies of the metabolism of 5-fluorouracil in the liver of patients undergoing chemotherapy.

Fluorine-19 nuclear magnetic resonance allows direct observation of fluorinated drugs and their metabolites in the human body without background signal from the tissue. A well-known fluorinated chemotherapeutic drug, 5-fluorouracil, and its metabolites were observed noninvasively in the liver of three patients undergoing cancer chemotherapy. Spectra were obtained at 1.5 T with a surface coil centered over the right lobe of the patient's liver. Administration of 1.5 gm of 5-fluorouracil was done after positioning in the magnet. Serial spectra, collected over a 2-h period, revealed both the nature of the metabolites present in the liver, and the time course of each patient's metabolism. These observations represent the first noninvasive NMR study of drugs in human patients and show the feasibility of using in vivo F-19 NMR spectroscopy for human studies of fluorinated compounds.

Female↗
PubMedDate not supplied

Genotoxicity of mercury used in chromosome aberration tests.

The purpose of this study was to investigate the genotoxic effects of Hg released from dental amalgams. The chromosome aberration test was conducted using original extracts and their diluted solutions of conventional type amalgam and high copper amalgam. The concentrations of Hg, Cu and Ag in the original extract of high copper amalgam were 17.64, 7.97 and 43.90 microM, respectively. Those in the original extract of conventional type amalgam were 20.63, 7.87 and 14.79 microM, respectively. 10 and 30 microM Hg(2+) were also used for comparison. The frequency of chromosome aberrations was below 5% with 0 microM Hg(2+) and with a triple dilution of high copper amalgam extract, containing 5.88 microM Hg, 14.63 microM Cu and 2.65 microM Ag. However, 9.5% of the cells showed chromosome aberrations with a quadruple dilution of conventional type amalgam, containing 5.15 microM Hg, 3.69 microM Cu and 1.96 microM Ag. The amount of Hg in the quadruple dilution of conventional type amalgam was less than that in the triple dilution of high copper amalgam extract and 10 microM Hg(2+). A concentration of 30 microM Hg(2+) caused 34.5% of the cells to show chromosome aberrations while with a two-thirds dilution of high copper amalgam extract, containing 11.76 microM Hg, 29.26 microM Cu and 5.31 microM Ag, 58.5% of the cells showed chromosome aberrations. A two-thirds dilution of high copper amalgam extract induced more chromosome aberrations than 30 microM Hg(2+), although the amount of Hg was less than 30 microM Hg(2+). A triple dilution of conventional type amalgam extract, original extracts of conventional type amalgam and high copper amalgam and 100 microM Hg(2+) were induced few metaphases. It was revealed that the conventional type amalgam induced chromosome aberrations with quadruple dilution where cell viability was about 80% and that the high copper amalgam induced a high level of chromosome aberrations with the two-thirds dilution. The effects of low level Hg on humans are not clear.

Animals↗
PubMed2003

A new method for preparing powders for transmission electron microscopy examination.

In this paper we describe a novel method to prepare powder specimens for transmission electron microscopy examination. The powder samples are embedded in a metallic matrix by a route based on the plastic flow of a soft metal, using a small laboratory type hand driven hydraulic press. The resulting composites are processed with the conventional procedure based on grinding polishing and ion beam milling. The resulting TEM specimens have a self-supporting structure, good thermal and electrical conductivity while showing a well-polished surface resulting from the ion milling process. The method can be applied to a large variety of samples with sufficiently strong mechanical properties; a few examples are reported. The limits, mainly due to the mechanical toughness of the powder, are discussed.

Copper↗
PubMedDate not supplied

Benchmarking of linear and nonlinear approaches for quantitative structure-property relationship studies of metal complexation with ionophores.

A benchmark of several popular methods, Associative Neural Networks (ANN), Support Vector Machines (SVM), k Nearest Neighbors (kNN), Maximal Margin Linear Programming (MMLP), Radial Basis Function Neural Network (RBFNN), and Multiple Linear Regression (MLR), is reported for quantitative-structure property relationships (QSPR) of stability constants logK1 for the 1:1 (M:L) and logbeta2 for 1:2 complexes of metal cations Ag+ and Eu3+ with diverse sets of organic molecules in water at 298 K and ionic strength 0.1 M. The methods were tested on three types of descriptors: molecular descriptors including E-state values, counts of atoms determined for E-state atom types, and substructural molecular fragments (SMF). Comparison of the models was performed using a 5-fold external cross-validation procedure. Robust statistical tests (bootstrap and Kolmogorov-Smirnov statistics) were employed to evaluate the significance of calculated models. The Wilcoxon signed-rank test was used to compare the performance of methods. Individual structure-complexation property models obtained with nonlinear methods demonstrated a significantly better performance than the models built using multilinear regression analysis (MLRA). However, the averaging of several MLRA models based on SMF descriptors provided as good of a prediction as the most efficient nonlinear techniques. Support Vector Machines and Associative Neural Networks contributed in the largest number of significant models. Models based on fragments (SMF descriptors and E-state counts) had higher prediction ability than those based on E-state indices. The use of SMF descriptors and E-state counts provided similar results, whereas E-state indices lead to less significant models. The current study illustrates the difficulties of quantitative comparison of different methods: conclusions based only on one data set without appropriate statistical tests could be wrong.

Algorithms↗
PubMed2004

Hybridization of oligonucleotide-modified silver and gold nanoparticles in aqueous dispersions and on gold films.

Functionalization of silver and gold nanoparticles by 12mer-thiolated homo-oligonucleotides, SA and ST (containing only adenine or thymine, respectively), and their hybridization and dehybridization in aqueous dispersions have been described. In addition, ST and SA were self-assembled onto gold films and hybridized with their complementary pairs, unlabeled or labeled by gold and silver nanoparticles. The base pairing between DNA strands and the types of oligonucleotides (adenine or thymine) attached to the nanoparticles was detected by Polarization Modulated Fourier Transform Infrared Reflection Absorption Spectroscopy (PM-FTIRRAS).

Adenine↗