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Biomedical subjects

M A Quilliam

Publications and source records attributed to M A Quilliam.

At least 37 records · Page 2Linked to original sources
PubMed1992

Ionspray mass spectrometry of marine toxins. IV. Determination of diarrhetic shellfish poisoning toxins in mussel tissue by liquid chromatography/mass spectrometry.

An improved liquid chromatographic/mass spectrometric (LC/MS) method utilizing gradient elution and ion-spray ionization is described for the sensitive determination of okadaic acid and dinophysistoxin-1, the principal toxins implicated in cases of diarrhetic shellfish poisoning. The method was used to confirm the presence of both toxins, together with a recently identified isomer of okadaic acid, dinophysistoxin-2, in various samples of cultivated blue mussels (Mytilus edulis) from Canadian and European waters. The method provided a mass detection limit of 0.4 ng for each toxin, thus allowing detection of 40 ng per g of whole mussel tissue (or approximately 10 ng/g if only the digestive glands were used in the assay). Quantitative results obtained by LC/MS were in good agreement with those obtained by derivatization and high-performance liquid chromatography with fluorescence detection.

Animals↗
PubMed1992

C60 and C70 fullerene isomers generated in flames. Detection and verification by liquid chromatography/mass spectrometry analyses.

Fullerenes C60 and C70, generated by combustion, have been shown previously to be produced in controlled laminar flames accompanied by other compounds having fullerene-like characteristics. Analysis of these additional compounds by high-performance liquid chromatography, coupled on-line with mass spectrometry has identified them as isomers of the C60 and C70 fullerenes. The newly observed isomers have characteristic UV spectra and are thermally unstable, undergoing conversion to the more stable fullerenes with a half-life of about 1 h in boiling toluene (111 degrees C). Isomers of C60 and C70 fullerenes previously have been studied theoretically, but not observed experimentally. The flame-generated material also contains C60O and C70O compounds, as well as C76 and higher carbon clusters.

Carbon↗
PubMed1992

Detection of new 7-O-acyl derivatives of diarrhetic shellfish poisoning toxins by liquid chromatography-mass spectrometry.

A novel method for the detection of acylated diarrhetic shellfish poisoning toxins is reported. Direct determination of these compounds is possible using high performance liquid chromatography coupled with ion-spray mass spectrometry. An extract, purified from the digestive glands of toxic mussels (Mytilus edulis) contaminated with okadaic acid, dinophysistoxin-1, and a recently reported analog, dinophysistoxin-2, was also shown to contain small amounts of dinophysistoxin-3, a mixture of 7-O-acyl ester derivatives of dinophysistoxin-1. In addition, acyl ester derivatives of okadaic acid and dinophysistoxin-2 were also detected by direct LC-MS analysis and confirmed by analysis of their hydrolysis products. This is the first report of the detection of other naturally occurring 7-O-acyl esters similar to dinophysistoxin-3.

Acylation↗
PubMed1992

An idiotypic-anti-idiotypic competitive immunoassay for quantitation of okadaic acid.

A competitive indirect enzyme-linked immunosorbent assay for the measurement of okadaic acid, a marine toxin, was developed. The assay uses a murine monoclonal anti-idiotypic antibody bearing an internal image of okadiac acid epitope to capture an anti-okadaic acid monoclonal antibody in the presence of free okadaic acid. Bound anti-okadaic acid antibody is detected with peroxidase-conjugated anti-mouse immunoglobulin antiserum. If present, free toxin will lessen the amount of anti-okadaic acid antibody binding to its corresponding anti-idiotypic antibody in a dose-dependent manner that can be quantified from the standard curve. The assay permits reliable measurement of okadaic acid in the 9-81 ng/ml range. The intra- and interassay coefficients of variation in the measurement of OA in the toxin spiked mussel samples averaged 9% and 12%, respectively. The assay is rapid, accurate, reproducible and relatively simple to perform. It may be of potential use to laboratories involved in monitoring the toxin levels in plankton, seafood or sponges.

Animals↗
PubMed1991

Determination of sulfonamides by liquid chromatography, ultraviolet diode array detection and ion-spray tandem mass spectrometry with application to cultured salmon flesh.

Ion-spray mass spectrometry was investigated for the analysis of 21 antibacterial sulfonamide drugs. All of the sulfonamides analyzed gave positive ion mass spectra with abundant protonated molecules and no fragmentation. Tandem mass spectrometry (MS-MS) using collision-induced dissociation provided structural information, allowing the identification of common fragmentation pathways and the differentiation of isomeric and isobaric sulfonamides. A reversed-phase high-performance liquid chromatographic method was developed, using gradient elution and ultraviolet diode-array detection (DAD), enabling the separation of 16 of the sulfonamides. Combined liquid chromatography (LC)-MS was accomplished using the ion-spray interface. Analyses of a mixture of sulfonamide standards were performed with gradient elution and the mass spectrometer configured for full-scan acquisition, selected-ion monitoring, or selected-reaction monitoring. Procedures for the analysis of sulfadimethoxine (SDM), a representative sulfonamide used in the aquaculture industry, are described. The presence of SDM in cultured salmon flesh was confirmed at levels as low as 25 ng/g by a combination of LC-DAD and LC-MS-MS.

Animals↗
PubMed1990

Analysis of domoic acid and related compounds by mass spectrometry and gas chromatography/mass spectrometry as N-trifluoroacetyl-O-silyl derivatives.

A method is presented for the analysis of shellfish tissue for domoic acid, a neurotoxic amino acid responsible for cases of amnesic shellfish poisoning. Tissue extracts are first taken through a two-stage solid-phase extraction clean-up, using reversed-phase and strong cation exchange cartridges. A two-stage derivatization, using N-methyl-bis-trifluoroacetamide followed by either N-methyl-tert-butyldimethylsilyltrifluoroacetamide or N, O-bis-trimethylsilyltrifluoroacetamide, is then used to produce an N-trifluoroacetyl-O-silyl derivative which can be analyzed by mass spectrometry with introduction via direct inlet probe, moving-belt liquid chromatograph/mass spectrometer interface, or capillary column gas chromatography. The N-trifluoroacetyl-O-tert-butyldimethylsilyl derivative, which has good stability towards hydrolysis, provides a spectrum well suited to gas chromatography/mass spectrometry (GC/MS) using selected ion recording. GC/MS data for two related compounds, kainic acid and dihydrokainic acid, are also reported. The latter is used as an internal standard for quantification of domoic acid, although the method reported is intended primarily for confirmation of the toxin and related compounds in shellfish tissue.

Chromatography, Gas↗
PubMed1990

Chemistry, biology, and toxicology of domoic acid and its isomers.

The causative agent of toxicity in cultured mussels from a localized area of eastern Prince Edward Island has been identified as domoic acid, a neuroexcitatory amino acid. The toxin was isolated by a number of different bioassay-directed separation techniques including high-performance liquid chromatography (HPLC), high-voltage paper electrophoresis (HVPE), and ion-exchange chromatography, and characterized by a number of spectroscopic techniques including ultraviolet, infrared, mass spectrometry, and nuclear magnetic resonance. The isolation and purification methods are described in detail and some new analytical data for domoic acid are reported. A plankton bloom at the time of the outbreak gave positive mouse bioassays and consisted almost entirely of the pennate diatom, Nitzschia pungens f. multiseries. A positive correlation was found between the number of N. pungens cells and the concentration of domoic acid in the plankton. N. pungens f. multiseries isolated from Cardigan Bay produced domoic acid de novo during stationary phase culture at levels (1 to 10 pg/cell) comparable to values estimated for N. pungens in the plankton samples. We conclude that N. pungens was the major source of the domoic acid in toxic mussels in eastern Prince Edward Island. The recurrence, in November 1988, of a monospecific bloom of N. pungens and the presence of domoic acid in plankton and mussels reinforces this conclusion.

Animals↗
PubMed1989

Liquid chromatographic determination of domoic acid in shellfish products using the paralytic shellfish poison extraction procedure of the association of official analytical chemists.

Domoic acid, the recently discovered toxic substance found in contaminated mussels from an area in eastern Prince Edward Island (Canada) was extracted from mussel tissue using the procedure of the Association of Official Analytical Chemists for paralytic shellfish poisons. This involved a 5-min boiling of the sample with 0.1 M hydrochloric acid then cooling and centrifuging. An aliquot of the supernatant was diluted ten to one-hundred times with water, filtered and analysed by reversed-phase liquid chromatography with a mobile phase consisting of acetonitrile-water (12:88) at pH 2.5 and an absorption wavelength of 242 nm. The detection limit was about 0.5 mg/kg domoic acid in seafood samples. The technique was successfully applied to a variety of commercially purchased shellfish and shellfish products.

Animals↗
PubMed1989

Ion-spray mass spectrometry of marine neurotoxins.

Ion-spray mass spectrometry was investigated for the analysis of three marine neurotoxins: domoic acid, saxitoxin and tetrodotoxin. All three compounds gave positive-ion spectra with abundant ions of protonated molecules and no significant fragmentation. Domoic acid gave a negative-ion spectrum with a strong [M-H]- ion. Tandem mass spectrometry provided useful fragment-ion spectra for all compounds. Detection limits for flow injection analyses with selected-ion monitoring were determined to be 30 pg for saxitoxin, 100 pg for domoic acid and 200 pg for tetrodotoxin. Combining liquid chromatography with ion-spray mass spectrometry allowed the determination of domoic acid and some of its isomers in toxic shellfish tissue extracts.

Kainic Acid↗
PubMed1988

Determination of polycyclic aromatic compounds by high-performance liquid chromatography with simultaneous mass spectrometry and ultraviolet diode array detection.

A major problem in the determination of polycyclic aromatic compounds (PACs) in environmental samples is the extreme complexity of the extracts, even after extensive fractionation. The combination of high-performance liquid chromatography (HPLC) with simultaneous mass spectrometry (MS) and ultraviolet diode array detection (DAD) is a powerful tool for the identification and quantitation of such species with a high degree of confidence. HPLC allows the selective separation of a wide variety of PACs, including thermally labile and high molecular weight compounds. Electron ionization MS with the moving belt interface provides high sensitivity and selectivity, as well as structural information such as molecular weight, functional groups, and elemental composition. The diode array detector helps to differentiate isomeric structures and confirm compound identity.

Chromatography, High Pressure Liquid↗
PubMed1986

Identification of the DNA adduct formed by metabolism of 1,8-dinitropyrene in Salmonella typhimurium.

The incubation of [3H]1,8-dinitropyrene with Salmonella typhimurium TA98NR followed by isolation of the DNA from these cells, hydrolysis of the DNA to nucleosides, butanol extraction of the hydrolysate and purification by reversed-phase liquid chromatography afforded a single product. Calf thymus DNA, after treatment with N-hydroxyl-1-amino-8-nitro-pyrene, was hydrolyzed, extracted and purified in a similar fashion to give a single compound which was shown to be the deoxyguanosine derivative 1-N-(2'-deoxyguanosin-8-yl)-amino-8-nitropyrene by a combination of proton n.m.r. and u.v.-vis. spectroscopy and fast atom bombardment mass spectrometry. The DNA adducts formed in vivo and in vitro exhibited identical chromatographic and chemical behavior. Under acidic or basic conditions in the vivo and in vitro adducts were converted to identical products. Reduction of the adduct gave a new, highly fluorescent product that had a fluorescence emission spectrum identical to that of 1,8-diaminopyrene.

Chromatography, High Pressure Liquid↗
PubMed1985

Identification of polycyclic aromatic compounds in mutagenic emissions from steel casting.

Workers in ferrous foundries show increased risk of lung cancer. In the steel casting process hot metal is poured into sand moulds solidified with organic binders, producing a plume of smoke containing a variety of organic compounds and showing strong mutagenicity in the Salmonella/S9 assay. We have collected the emissions produced when steel is poured into an experimental sand mould solidified with oil, clay and cereal, a widely used binder system. The organic constituents of these emissions have been fractionated by preparative reverse-phase high performance liquid chromatography (HPLC) and mutagenic fractions have been analysed by capillary column gas chromatography/mass spectrometry (GC/MS). Of the 65 compounds for which mass spectra are reported, 54 have been tentatively identified as alkyl derivatives of polycyclic aromatic compounds. Many compounds of this class are known to be carcinogenic and mutagenic. In addition, several unsubstituted polycyclic aromatic hydrocarbons, including the carcinogenic benz[a]anthracene and benzo[a]pyrene, were found to be present.

Air Pollutants, Occupational↗
PubMed1984

On auxotrophy for pyrimidines of respiration-deficient chick embryo cells.

Chick embryo cells treated with chloramphenicol are inherently resistant to the growth-inhibitory effect of the drug when cultured in the presence of tryptose phosphate broth. The cells were found to be auxotrophic for pyrimidines and the presence in the broth of compounds of pyrimidine origin is demonstrated by chromatographic procedures and mass spectral analyses. They are in the form of ribonucleosides, ribonucleotides and pyrimidine-containing oligoribonucleotides. To understand the mechanism responsible for pyrimidine auxotrophy, the activity of enzymes involved in the pyrimidine biosynthetic pathway was determined. Measurement of the conversion of dihydroorotic acid to orotic acid in cell-free extracts revealed that chloramphenicol-treated chick embryo cells are deficient in dihydroorotate dehydrogenase activity. The data in vitro are supported by studies on the nutritional requirements of the respiration-deficient cells and by the incorporation in vivo of labelled dihydroorotic acid into the acid-insoluble fraction of the cells. Although the activity of the dehydrogenase in vitro is decreased by 95%, the enzyme is present in chloramphenicol-treated cells and its activity is unmasked by the artificial electron acceptor menadione. A study of the activity of other enzymes of the pyrimidine biosynthetic pathway demonstrated that their activity is comparable to that in control cells. The present results indicate that auxotrophy for pyrimidines results from the inhibition of the flow of electrons along the mitochondrial electron transport chain.

Animals↗
PubMed1984

Metabolism of 1,8-dinitropyrene by Salmonella typhimurium.

Earlier work has shown that many nitroaromatic and nitroheterocyclic compounds are directly 'activated' to their ultimate mutagenic forms through the action of bacterial nitroreductase enzymes. However, in the case of 1,8-dinitropyrene (DNP) and certain other nitroarenes the pathway of activation is more complex and neither the identity of the ultimate mutagens nor the nature of the DNA adducts formed are known. We now show that Salmonella typhimurium strains TA98 and TA1538, which are sensitive to DNP and have wild type nitroreductase complements, do metabolize DNP to 1-amino-8-nitropyrene (ANP) and 1,8- diaminopyrene (DAP) but that these compounds are much weaker mutagens than DNP. These two strains (TA98 and TA1538) contain two separable components of nitroreductase activity as determined using nitrofurazone as the substrate. The major component, at least, is capable of reducing both 1-nitropyrene (NP) and DNP although the rates are much lower than with nitrofurazone. TA98NR , a mutant of TA98 that is resistant to nitrofurazone and NP but not to DNP, lacked the major nitroreductase but retained two minor components. In contrast, a mutant ( DNP6 ) which is resistant to DNP (but not to NP) contained a full complement of nitroreductases. When the metabolism of [3H]DNP by crude extracts of TA98 was re-examined, previously undetected metabolites were found. These were more polar than DAP and ANP and were also seen when TA98NR was used as the source of enzyme. These metabolites were not formed when enzymes from TA98DNP6 or TA98NR / DNP6 were used. This work supports the notion that some enzymic activity other than (or in addition to) nitroreductase is required for the activation of DNP and that the new polar metabolites may be related to this process.

Chromatography, High Pressure Liquid↗
PubMed1981

Amaranth suppresses the mutagenicity of 2-acetylaminofluorene by lowering the concentration of NADPH in top agar.

Addition of 1 mg amaranth (FD&C Red No. 2) to the top agar of Salmonella/S9 assay plates decreased the yield of revertants induced by 20 micrograms 2-acetylaminofluorene (AAF) by over 50% and additional amaranth completely eliminated the mutagenic response. Similar suppression of AAF mutagenicity was seen with sulfonazo III, another azo dye. The suppressive effect of amaranth was greatest at low S9 concentrations and decreased as the amount of S9 was increased. When N-hydroxyacetylaminofluorene (N-OH-AAF) was used as mutagen, amaranth had little or no effect on either the number of revertants obtained or the S9 optimum. Similarly, 1-naphthylamine-4-sulfonic acid (a reduction product of amaranth) did not significantly affect the mutagenicity of AAF. The rate of metabolism of [14C]AAF by the S9 preparations was shown to be markedly decreased by amaranth, as were the levels of both the phenolic metabolites and of N-OH-AAF. Thus, it appeared that amaranth acts by blocking the conversion of AAF to N-OH-AAF and that this effect is caused by the amaranth itself and not by its constituent amines. Further experiments indicated that amaranth greatly decreased the levels of NADPH formed in reaction mixtures comparable to S0 mix in top agar and that such reaction mixtures also metabolized amaranth to colourless compounds. It appears likely that in top agar, NADPH reacts with amaranth at a fast enough rate to limit severely the level of the reduced co-factor (which must be formed from NADPH+ by the action of endogenous glucose-6-phosphate dehydrogenase) and thus decreases the rate of activation of mutagens by other NADPH-dependent processes.

2-Acetylaminofluorene↗
PubMed1981

Metabolism of 1-nitropyrene and formation of DNA adducts in Salmonella typhimurium.

1-Nitropyrene is slowly reduced by intact cells of Salmonella typhimurium to yield 1-aminopyrene and N-acetyl-1-aminopyrene plus six unidentified minor products. When the bacteria are exposed to tritiated 1-nitropyrene, increasing amounts of radioactivity become bound to DNA as the nitropyrene is metabolized. Enzymatic hydrolysis of the labelled DNA yields low molecular weight labelled compounds which probably represent nucleoside adducts formed by the reaction of nitropyrene metabolites with DNA. Results with appropriate mutant strains indicate that bacterial nitroreductases are involved in activating nitropyrene to a reactive intermediate that binds to DNA and that nitropyrene adducts in DNA are subject to excision repair.

Biotransformation↗