Quantitative screening for benzodiazepines in blood by dual-column gas chromatography and comparison of the results with urine immunoassay. (1/150)

A dual-column retention index method is described for quantitative gas chromatographic (GC) screening of 26 benzodiazepine drugs and metabolites in the blood using DB-5 and DB-17 capillary columns and electron capture detection. The method involves a one-step, small-scale liquid-liquid extraction with ethyl acetate and derivatization with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide with 1% tert-butyldimethylsilyl chloride. The results from the GC screening of 514 postmortem blood samples were compared to those obtained from urine immunoassay (Syva ETSplus with a 200-ng/mL cutoff). Both methods gave a negative result in 284 cases and a positive result in 149 cases. In 48 cases, urine was negative by immunoassay but blood was positive by GC. The opposite situation (blood negative, urine positive) was detected only in four cases. In 29 cases, an invalid result was obtained by urine by immunoassay: 26 blood samples of those cases were negative and three samples positive by GC. In postmortem forensic toxicology, the present GC method seems to be a good alternative to the common combination of urinary immunoassay followed by quantitative analysis of blood by chromatography.  (+info)

A high-performance liquid chromatographic method for the determination of monofluoroacetate. (2/150)

A simple isocratic high-performance liquid chromatographic (HPLC) method for the quantitative analysis of monofluoroacetic acid (MFA), the toxic substance of Dichapetalum cymosum, in plant material, rumen contents (gastric contents), and liver samples is described. A suitable HPLC column that gives optimum sensitivity, accuracy, precision, and separation of MFA is identified. A C-610 organic acid analysis column at ambient temperature with 0.02M H3PO4 as an eluent and ultraviolet detection at 210 nm is utilized to quantitate MFA. Using this method, the average percentage recovery in plant material, bovine liver, and rumen samples is 94.8%, and a detection limit of 12 microg/L is achievable.  (+info)

In vivo transposon mutagenesis of the methanogenic archaeon Methanosarcina acetivorans C2A using a modified version of the insect mariner-family transposable element Himar1. (3/150)

We present here a method for in vivo transposon mutagenesis of a methanogenic archaeon, Methanosarcina acetivorans C2A, which because of its independence from host-specific factors may have broad application among many microorganisms. Because there are no known Methanosarcina transposons we modified the mariner transposable element Himar1, originally found in the insect Hematobia irritans, to allow its use in this organism. This element was chosen because, like other mariner elements, its transposition is independent of host factors, requiring only its cognate transposase. Modified mini-Himar1 elements were constructed that carry selectable markers that are functional in Methanosarcina species and that express the Himar1 transposase from known Methanosarcina promoters. These mini-mariner elements transpose at high frequency in M. acetivorans to random sites in the genome. The presence of an Escherichia coli selectable marker and plasmid origin of replication within the mini-mariner elements allows facile cloning of these transposon insertions to identify the mutated gene. In preliminary experiments, we have isolated numerous mini-mariner-induced M. acetivorans mutants, including ones with insertions that confer resistance to toxic analogs and in genes that encode proteins involved in heat shock, nitrogen fixation, and cell-wall structures.  (+info)

Urinary metabolites of halothane in man. (4/150)

The urinary metabolites of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) were investigated in five individuals given trace doses (25 muCi), and in three individuals given large doses (1 mCi) of radioactively labeled 14C-halothane. The latter were donor subjects for heart transplant operations. Separation of the nonvolatile urinary metabolites of halothane was accomplished by chemical extraction, electrophoresis, ion-exchange and high-pressure liquid chromatography, and gas chromatography. Identification of the individual metabolites was by nuclear magnetic resonance and mass spectrometry. Three major metabolites were identified: trifluoroacetic acid, N-trifluoroacetyl-2-aminoethanol, and N-acetyl-S-(2-bromo-2-chloro-1,1-difluoroethyl)-L-cysteine. Smaller unidentified radioactive peaks were also found. The presence of both ethanolamide and cysteine conjugates of halothane is of concern. These urinary products imply the presence of reactive intermediates. The conjugation of such intermediates to proteins and phospholipids may give rise to the high-molecular-weight covalently bound metabolites demonstrated to be present in the liver following halothane anesthesia. Elucidation of the structures of the urinary metabolites provides information important to an understanding of halothane metabolism and its potential hepatotoxicity.  (+info)

Isolation of an aldehyde dehydrogenase involved in the oxidation of fluoroacetaldehyde to fluoroacetate in Streptomyces cattleya. (5/150)

Streptomyces cattleya is unusual in that it produces fluoroacetate and 4-fluorothreonine as secondary metabolites. We now report the isolation of an NAD(+)-dependent fluoroacetaldehyde dehydrogenase from S. cattleya that mediates the oxidation of fluoroacetaldehyde to fluoroacetate. This is the first enzyme to be identified that is directly involved in fluorometabolite biosynthesis. Production of the enzyme begins in late exponential growth and continues into the stationary phase. Measurement of kinetic parameters shows that the enzyme has a high affinity for fluoroacetaldehyde and glycoaldehyde, but not acetaldehyde.  (+info)

Selectivity of protein oxidative damage during aging in Drosophila melanogaster. (6/150)

The purpose of the present study was to determine whether oxidation of various proteins during the aging process occurs selectively or randomly, and whether the same proteins are damaged in different species. Protein oxidative damage to the proteins, present in the matrix of mitochondria in the flight muscles of Drosophila melanogaster and manifested as carbonyl modifications, was detected immunochemically with anti-dinitrophenyl-group antibodies. Aconitase was found to be the only protein in the mitochondrial matrix that exhibited an age-associated increase in carbonylation. The accrual of oxidative damage was accompanied by an approx. 50% loss in aconitase activity. An increase in ambient temperature, which elevates the rate of metabolism and shortens the life span of flies, caused an elevation in the amount of aconitase carbonylation and an accelerated loss in its activity. Exposure to 100% ambient oxygen showed that aconitase was highly susceptible to undergo oxidative damage and loss of activity under oxidative stress. Administration of fluoroacetate, a competitive inhibitor of aconitase activity, resulted in a dose-dependent decrease in the life span of the flies. Results of the present study demonstrate that protein oxidative damage during aging is a selective phenomenon, and might constitute a mechanism by which oxidative stress causes age-associated losses in specific biochemical functions.  (+info)

Trifluoromethyl ketone-based inhibitors of apoptosis in cerebellar granule neurons. (7/150)

A variety of aromatic trifluoromethyl ketone derivatives has been studied as inhibitors of apoptosis in cerebellar granule neurons (CGNs). Among them, alpha-trifluoromethyl diketone (2) and benzyl trifluoromethyl ketone (11) were found to be apoptosis inhibitors which can prevent a neurodegenerative disease. Compounds 2 and 11 showed neuroprotection effect on low K+-induced apoptosis in CGNs. Furthermore, these compounds effectively suppressed DNA fragmentation accompanied with apoptosis. The neuroprotection mode of 2 and 11 was not related to inhibition of caspase-3.  (+info)

Catalysis-linked inactivation of fluoroacetate dehalogenase by ammonia: a novel approach to probe the active-site environment. (8/150)

Fluoroacetate dehalogenase from Moraxella sp. B (FAc-DEX) catalyzes the hydrolytic dehalogenation of fluoroacetate and other haloacetates. Asp(105) of the enzyme acts as a nucleophile to attack the alpha-carbon of haloacetate to form an ester intermediate, which is subsequently hydrolyzed by a water molecule activated by His(272) [Liu, J.Q., Kurihara, T., Ichiyama, S., Miyagi, M., Tsunasawa, S., Kawasaki, H., Soda, K., and Esaki, N. (1998) J. Biol. Chem. 273, 30897-30902]. In this study, we found that FAc-DEX is inactivated concomitantly with defluorination of fluoroacetate by incubation with ammonia. Mass spectrometric analyses revealed that the inactivation of FAc-DEX is caused by nucleophilic attack of ammonia on the ester intermediate to convert the catalytic residue, Asp(105), into an asparagine residue. The results indicate that ammonia reaches the active site of FAc-DEX without losing its nucleophilicity. Analysis of the three-dimensional structure of the enzyme by homology modeling showed that the active site of the enzyme is mainly composed of hydrophobic and basic residues, which are considered to be essential for an ammonia molecule to retain its nucleophilicity. In a normal enzyme reaction, the hydrophobic environment is supposed to prevent hydration of the highly electronegative fluorine atom of the substrate and contribute to fluorine recognition by the enzyme. Basic residues probably play a role in counterbalancing the electronegativity of the substrate. These results demonstrate that catalysis-linked inactivation is useful for characterizing the active-site environment as well as for identifying the catalytic residue.  (+info)