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Carbon monoxide poisoning associated with a propane-powered floor burnisher--Vermont, 1992.

On July 28, 1992, two employees of a pharmacy in Vermont fainted within four hours after arriving for work; at a local hospital emergency department, carbon monoxide (CO) poisoning was diagnosed based on elevated carboxyhemoglobin (HbCO) levels. The pharmacy was evacuated, and the remaining eight employees were transported to the hospital for evaluation. Further investigation by the Vermont Department of Health (VDH) revealed that, on July 24, one of the employees had fainted, but CO poisoning was not suspected, and vasovagal syncope was diagnosed. This report summarizes the investigation of these cases by VDH.

Adolescent↗

Preclinical comparison of bis-diketopiperazine-propane (dexrazoxane) and bis-diketopiperazine-ethane (antimet) on the adriamycin-cardiotoxic effect.

A cardiotoxic effect induced by adriamycin (by repeated i.v. administration to experimental rats in 7-day intervals of administration) begins to be manifested in the ECG record by prolongation of the S alpha T segment between days 14 and 20, on day 30 it is statistically significant. By means of this index, the known protective effect of dexrazoxane (the preparation Cardioxan) against adriamycin cardiotoxicity has been successfully confirmed in a four-week experiment. A comparative study (using the identical frequency of the dosing scheme and S alpha T segment as the decisive parameter) has revealed that antimet-as another original substance of the diketopiperazines group-also involves (though less significantly) protective effects against the toxic action of adriamycin.

Administration, Oral↗

Comparison of the effects of R-(-)-2-amino-1-(2,5-dimethoxy-4-methylphenyl) propane (DOM), r-(-)-2-amino-1-(2,5-dimethoxy-4-methylphenyl) butane (BL-3912A) and 5-hydroxytryptamine on non-innervated vascular smooth muscle.

Isolated strips of sheep umbilical arteries contracted in the presence of R-(-)-2-amino-1-(2,5-dimethoxy-4-methylphenyl) butane (BL3912A). These contractions faded over an hour period and at this time BL3912A antagonized contractions to R-(-)-DOM, 5-hydroxytryptamine (5-HT) but not to angiotensin. The initial contraction produced by BL3912A was antagonized by cinanserin, a 5-HT antagonist. These experiments indicate that BL3912A can be classified as a partial agonist of 5-HT receptors in sheep umbilical arteries.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗

Selective recognition of glutathiolated aldehydes by aldose reductase.

In this study, the selectivity and specificity of aldose reductase (AR) for glutathionyl aldehydes was examined. Relative to free aldehydes, AR was a more efficient catalyst for the reduction of glutathiolated aldehydes. Reduction of glutathionyl propanal [gammaGlu-Cys(propanal)-Gly] was more efficient than that of Gly-Cys(propanal)-Gly and gamma-aminobutyric acid-Cys(propanal)-Gly suggesting a possible interaction between alpha-carboxyl of the conjugate and AR. Two active site residues, Trp20 or Ser302, were identified by molecular modeling as potential sites of this interaction. Mutations containing tryptophan-to-phenylalanine (W20F) and serine-to-alanine (S302A) substitutions did not significantly affect reduction of free aldehydes but decreased the catalytic efficiency of AR for glutathiolated aldehydes. Combined mutations indicate that both Trp20 and Ser302 are required for efficient catalysis of the conjugates. The decrease in efficiency due to W20F mutation with glutathionyl propanal was not observed with gamma-aminobutyric-Cys(propanal)-Gly or Gly-Cys-(propanal)-Gly, indicating that Trp20 is involved in binding the alpha-carboxyl of the conjugate. The effect of the S302A mutation was less severe when gammaGlu-Cys(propanal)-Glu rather than glutathionyl propanal was used as the substrate, consistent with an interaction between Ser302 and Gly-3 of the conjugate. These observations suggest that glutathiolation facilitates aldehyde reduction by AR and enhances the range of aldehydes available to the enzyme. Because the N-terminal carboxylate is unique to glutathione, binding of the conjugate with the alpha-carboxyl facing the bottom of the alpha/beta-barrel may assist in the exclusion of unrelated peptides and proteins.

Aldehyde Reductase↗

Nitrogen limitation and nitrogen fixation during alkane biodegradation in a sandy soil.

We investigated nutrient limitations during hydrocarbon degradation in a sandy soil and found that fixed nitrogen was initially a limiting nutrient but that N limitation could sometimes be overcome by N2 fixation. Hydrocarbon biodegradation was examined in an unsaturated sandy soil incubated aerobically at 20 degrees C with propane or butane and various added nutrients. Propane and butane degradation proceeded similarly during the first 3 months of incubation. That is, bacteria in soil amended with N oxidized these hydrocarbons more rapidly than in controls without nutrient additions or in soil with added phosphate or trace minerals. Both propane- and butane-amended soil apparently became N limited after the initial available inorganic N was utilized, as indicated by a decrease in the rates of hydrocarbon degradation. After 3 months, propane and butane degradation proceeded differently. Bacteria in propane-degrading soil apparently remained N limited because propane degradation rates stayed low unless more N was added. In contrast, bacteria in butane-degrading soil appeared to overcome their N limitation because butane degradation rates later increased regardless of whether more N was added. Analyses of total N and acetylene reduction assays supported this apparent surplus of N in butane-amended soil. Total N was significantly (P < 0.01) higher in soil incubated with butane and no N amendments than in soil incubated with propane, even when the latter was amended with N. Acetylene reduction occurred only in butane-amended soil. These results indicate that N2 fixation occurred in butane-amended soil but not in propane-amended soil.

Acetylene↗

In vivo phenolic metabolites of N-alkylamphetamines in the rat. Evidence in favor of catechol formation.

The major in vivo metabolites of 1-phenyl-2-(n-propylamino)propane (N-n-propylamphetamine) in the rat were phenolic compounds, identified as 1-(4-hydroxyphenyl)-2-(n-propylamino)-propane (metabolite A) and 1-(4-hydroxy-3-methoxyphenyl)-2-(n-propylamino)propane (metabolite B) by gas chromatography-mass spectrometry, and by comparison with authentic synthetic samples of A and B. Metabolites A and B were formed from the substrate in 18.3% and 3.3% yields, respectively, and are excreted in the urine mainly in conjugated form. In vivo metabolism in the rat of the homolog, 1-phenyl-2-(n-butylamino)propane (N-n-butylamphetamine) resulted in the formation of two homologous metabolites in similar yields, which were tentatively identified, from their gas chromatographic and mass spectrometric behav-propane (metabolite A) and 1-(4-hydroxy-3-methoxyphenyl)-2-(n-propylamino)propane (metaboior and by comparison with metabolites A and B, as 2-(n-butylamino)-1-(4-hydroxyphenyl)propane (metabolite C) and 2-(n-butylamino)-1-(4-hydroxy-3-methoxyphenyl)propane (metabolite D). It is suggested that the methylated metabolites B and D were formed from metabolites A and C, respectively, via catecholamine intermediates.

Amphetamines↗

Aggregation and other intermolecular interactions of biological buffers observed by capillary electrophoresis and UV photometry.

Electrophoretic and photometric experiments strongly indicate that monovalent anions, which arise by deprotonation of the nitrogen atom in zwitterionic Good's buffers 3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid (CAPSO) and 3-morpholinopropanesulfonic acid (MOPS), spontaneously aggregate. Cationic migration of sanguinarine (SA) and chelerythrine (CHE) in highly alkaline 1,3-bis[tris(hydroxymethyl)methylamino]propane (Bis-Tris-propane), in which the concentration of cations of both alkaloids is negligible, may be explained by the existence of an aggregate, which contains uncharged sanguinarine or chelerythrine and one monovalent cation of Bis-Tris-propane at least. Tendency of tris(hydroxymethyl)aminomethane (Tris), bis (2-hydroxyethyl)iminotris(hydroxymethyl)methane (Bis-Tris) and Bis-Tris-propane cations to ion pairing with synthetic cluster borane anions and with fused silica markedly rises up with the size and charge of these cations. The drop in mobility of cluster borane compounds sometimes exceeds 50% of their mobility found at identical pH and ionic strength in buffers with sodium cation. The electroosmosis drop approached 70% if background electrolyte contained Bis-Tris-propane cations instead of sodium cations. Nitrate, taken as a model inorganic ion, and four randomly chosen organic anions interacted markedly less with Tris, Bis-Tris and Bis-Tris-propane cations than cluster borane anions. 2-(N-morpholino)ethanesulfonic (MES) acid anions present in background electrolyte affect the ion pairing of Tris, Bis-Tris and Bis-Tris-propane cations with anionic analytes and, in this way influence also mobilites of these anionic analytes. Limited hydrophilicity at least one of interacting species appears to be the most probable cause of observed intermolecular interactions of biological buffers.

Alkaloids↗

Stereoselective biosynthesis of chloroarylpropane diols by the basidiomycete Bjerkandera adusta: exploring the roles of amino acids, pyruvate, glycerol and phenyl acetyl carbinol.

Bjerkandera adusta produces many chlorometabolites including chlorinated anisyl metabolites (CAMs) and 1-arylpropane-1,2-diols (1, 2, 3, 4) as idiophasic metabolic products of L-phenylalanine. These diols are stereoselectively biosynthesized from a C7-unit (benzylic, from L-phenylalanine) and a C2-unit, of unknown origin, as predominantly erythro (1R,2S) enantiomers. Of the labeled amino acids tested as possible C2-units, at the 4-10 mM level, none were found to efficiently label the 2,3-propane carbons of the diols. However, glycine (2-13C), L-serine (2,3,3-d3) and L-methionine (methyl-d3) entered the biomethylation pathway. Neither pyruvate (2,3-13C2), acetate (1,2-13C2), acetaldehyde (d4) nor ethanol (ethyl-d5) labeled the 2,3-propane carbons of the diols at the 4-10 mM level. Pyruvate (2,3-13C2) and L-serine (2,3,3-d3) (which also entered the biomethylation pathway) did, however, effectively label the 2,3-propane carbons of the alpha-ketols and diols at the 40 mM level as evidenced by mass spectrometry. Glycerol (1,1,2,3,3-d5) also appeared to label one of the 2,3-propane carbons (ca. 5% as 2H2 in the C3 side chain) as suggested by mass spectrometric data and also entered the biomethylation pathway, likely via amino acid synthesis. Glycerol (through pyruvate), therefore, likely supplies C2 and C3 of the propane side chain with arylpropane diol biosynthesis. Incubation of B. adusta with synthetic [2-2H1, 2-18O]-glycerol showed that neither 2H nor 18O were incorporated in the alpha-ketols or diols. The oxygen atom on the C2 of the ketols/diols, therefore, does not appear to come from the oxygen atom on the C2 of glycerol. Glycerol, however, can readily form L-serine (which can then form pyruvate via PLP/serine dehydratase and involve transamination washing out the 18O label and providing the oxygen from water), and can then go on to label the C2-unit. Labeled alpha-ketol, phenyl acetyl carbinol (5) (PAC; ring-d(5), 2,3-13C2 propane) cultured with B. adusta leads to stereospecific reduction to the (1R,2S)-diol (6) (ring-d5 and 2,3-13C2); in all other metabolites produced, the 2,3-13C2) label is washed out. Incubation of the fungus with 4-fluorobenzaldehyde (13) produces a pooling of predominantly erythro (1R,2S) 1-(4'-fluorophenyl)-1,2-propane diol (18 as diacetate) (through the corresponding alpha-ketols 16, 17). Blocking the para-position with fluorine thus appears to prevent ring oxygenation and also chlorination, forcing the conclusion that para-ring oxygenation precedes meta-chlorination.

Acetone↗

Push-pull tests evaluating in situ aerobic cometabolism of ethylene, propylene, and cis-1,2-dichloroethylene.

In situ aerobic cometabolic transformations of ethylene, propylene, and cis-1,2-dichloroethylene (c-DCE), by microorganisms stimulated on propane, were examined in groundwater contaminated with c-DCE and trichloroethylene (TCE). In situ measurements were performed by conducting field push-pull tests, which consisted of injecting site groundwater amended with a bromide tracer and combinations of propane, dissolved oxygen (DO), nitrate, ethylene, propylene, c-DCE, and TCE into existing monitoring wells and sampling the same wells over time. Mass balance and transformation rate calculations were performed after adjusting for dilution losses using measured tracer concentrations. Initial rates of propane utilization were very low; rates increased substantially following sequential additions of propane and DO. Evidence that propane and DO additions had stimulated organisms expressing a propane monoxygenase enzyme system and that had the capability to transform chlorinated aliphatic hydrocarbons (CAHs) included: (1) the transformation of injected ethylene and propylene to the cometabolic byproducts ethylene oxide and propylene oxide, (2) the transformation of c-DCE, and (3) the inhibition of these transformations in the presence of coinjected acetylene, a known monoxygenase mechanism-based inactivator. These results suggest that a series of push-pull tests performed with nontoxic chemical probes can be useful for detecting and monitoring in situ aerobic cometabolism of CAHs.

Alkenes↗

Influence of high biomass concentrations on alkane solubilities.

Alkane solubilities were measured experimentally for high-density biomass. The resulting Henry's law constants for propane were found to decrease significantly for both dense yeast suspensions and an actual propane-degrading biofilm consortium. At the biomass densities of a typical biofilm, propane solubility was about an order of magnitude greater than that in pure water. For example, a dense biofilm had a propane Henry's law constant of 0.09+/-0.04 atm m(3) mol(-1) compared to 0.6+/-0.1 atm m(3) mol(-1) measured in pure water. The results were modeled with mixing rules and compared with octanol-water mixtures. Hydrogels (agar) and salts decreased the alkane solubility. By considering a theoretical solubility of propane in dry biomass, estimates were made of intrinsic Henry's law constants for propane in pure yeast and biomass, which were 13+/-2 and 5+/-2 atm kg biomass mol(-1) for yeast and biofilm consortium, respectively.

Agar↗

Toxicological investigation of liquid petroleum gas explosion: human model for propane/ethyl mercaptan exposures.

Four individuals died as the result of a propane explosion. As with many propane explosions, the question was raised as to the adequacy of the product's odorization after the autopsy studies had been conducted. In most cases, this question leads to litigation. Ethyl mercaptan is a widely used odorant for propane and was used in this instance. Three of the four victims had blood available at autopsy for study. Quantitative analyses of the victims' blood, obtained during autopsy, were performed using gas chromatography/mass spectrometry, without subjecting the samples to hydrolysis. These analyses determined the relative amounts of propane and ethyl mercaptan in the blood to be 90, 63, and 175 mL/m3 headspace, and 0.36, 0.34, and 0.77 microgram/L blood, respectively. Since mercaptans have been reported in human blood as products of metabolism, modeling studies were conducted to establish the validity of the autopsy data and to develop an autopsy toxicology protocol for investigating explosion deaths. When subjects were not exposed to an atmosphere containing ethyl mercaptan, dimethylsulfide was the only mercaptan detectable in their blood without severe hydrolysis prior to analysis. Metabolic ethyl mercaptan is sufficiently bound to be undetectable by the methods used without hydrolysis. Human subjects were exposed to a flammable mixture of air and propane odorized with ethyl mercaptan. The analyses of the blood from these subjects produced results which were comparable with those for the explosion victims, establishing that the question of odorant adequacy can be addressed at the autopsy of propane explosion victims. It is extremely important that the pathologist and toxicologist investigating gas explosion deaths recognize the valuable evidence existing in the victim's blood.

Autopsy↗

Identification of 4-(N,N-dipropylamino)benzaldehyde as a potent, reversible inhibitor of mouse and human class I aldehyde dehydrogenase.

As the physiologic roles for the different classes of aldehyde dehydrogenase (ALDH) enzymes are elucidated, the identification of specific, reversible inhibitors becomes of great pharmacologic interest. Previous structure-function studies identified dialkylamino substituted benzaldehyde compounds as a novel class of reversible inhibitors of class I ALDH. To examine further structural requirements for inhibition, we tested a series of 4-(N,N-dialkylamino)benzaldehyde analogs as inhibitors of propanal oxidation by mouse liver and human erythrocyte class I ALDH. 4-(N,N-dipropylamino)benzaldehyde (DPAB) was identified as the most potent, reversible inhibitor of propanal oxidation by class I ALDH in spectrophotometric enzyme assays. In kinetic studies, DPAB showed mixed-type inhibition with respect to the aldehyde substrates propanal, phenylacetaldehyde, benzaldehyde, and aldophosphamide. DPAB exhibited uncompetitive inhibition with respect to the cofactor NAD. Inhibition constants (Ki) for DPAB, estimated from Dixon plots, were 10 nM (propanal) and 77 nM (phenylacetaldehyde) for mouse ALDH and 3 nM (propanal) and 70 nM (phenylacetaldehyde) for human ALDH. These Ki values are 100-fold lower than those reported for class I specific inhibitors. At low (< 1 microM) DPAB concentrations, inhibition of propanal and aldophosphamide oxidation was > 75%, whereas inhibition of benzaldehyde (32%) and phenylacetaldehyde (19%) oxidation was reduced markedly. These results indicate that DPAB exhibits potent, reversible inhibition of mouse and human class I ALDH. The degree of inhibition was highly dependent on the structure of the aldehyde substrate.

Acetaldehyde↗

In situ infrared spectroscopic studies on the mechanism of the selective catalytic reduction of NO by C3H8 over Ga2O3/Al2O3: high efficiency of the reducing agent.

The partial oxidation of propane and the mechanism of selective catalytic reduction (SCR) of NO by propane over Ga2O3/Al2O3 in excess of O2 have been investigated using in situ Fourier transform infrared spectroscopy. An optimized Ga2O3/Al2O3 catalyst shows high activity and efficiency of the reducing agent propane (100% conversion of NO at 623 K, GHSV: 10,000 h(-1)). One molecule of propane converts more than 4 NO molecules to N2. The reaction starts with the partial oxidation of C3H8 by O2 and carboxylates (acetate, formate) are formed on the catalyst surface above 573 K. This oxidation represents the rate-determining step of the SCR reaction. These surface carboxylates represent a dominating intermediate and (easily) react with (adsorbed) NO forming nitrogen-containing organic species. The latter are proposed to react with NO to form N2. Total oxidation of propane was enhanced at temperatures above 773 K leading to decreased reductant efficiency. Surface nitrite and nitrate species can also be observed, but they were found to be spectators only. This could be concluded from the electron balance (conversion of propane relative to NO) and from the relative rates of the single reaction steps. On the basis of these investigations and stoichiometric calculations, a conclusive reaction mechanism is proposed.

Journal Article↗