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F E Evans

Publications and source records attributed to F E Evans.

At least 19 recordsLinked to original sources
PubMed1997

Characterization of DNA adducts in Chinese hamster ovary cells treated with mutagenic doses of 1- and 3-nitrosobenzo[a]pyrene and the trans-7,8-diol-anti-9,10-epoxides of 1- and 3-nitrobenzo[a]pyrene.

The environmental contaminants 1- and 3-nitrobenzo[a]pyrene (1- and 3-nitro-BaP) are mutagens in Chinese hamster ovary (CHO) cells with exogenous metabolic activation. Previous studies demonstrated the potent direct-acting mutagenicity of the oxidized metabolites, trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydro-1-nitrobenzo[a] pyrene (1-NBaPDE) and trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9, 10-tetrahydro-3-nitrobenzo[a]pyrene (3-NBaPDE), and the partially nitroreduced metabolites, 1- and 3-nitrosobenzo[a]pyrene (1- and 3-NO-BaP). In this study, we have identified the major adduct formed by incubation of calf thymus DNA with 1-NBaPDE and used this standard in conjunction with other adduct standards to characterize the 32P-postlabeled DNA adducts produced by 1- and 3-nitro-BaP metabolites in CHO cultures. The major adduct from 1-NBaPDE exposure was 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-1- nitrobenzo[a]pyrene; from 3-NBaPDE, 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-3- nitrobenzo[a]pyrene; from 1-NO-BaP, 6-(deoxyguanosin-N2-yl)-1-aminobenzo[a]pyrene; and from 3-NO-BaP, 6-(deoxyguanosin-N2-yl)-3-aminobenzo[a]pyrene. For comparison, the adducts formed by trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and the related nitroreduced derivative 6-nitrosobenzo[a]pyrene were also examined. The nitrobenzo[a]pyrene DNA adducts described in this study are proposed to be involved in the mutagenicity of 1- and 3-nitro-BaP upon either oxidative or reductive metabolism.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1997

Metabolism of metolachlor by the fungus Cunninghamella elegans.

The metabolism of metolachlor[2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-met hyl ethyl)acetamide]by the fungus Cunninghamella elegans ATCC 36112 was determined. Thesix metabolites identified comprised 81% of the total[14C]-metolachlor metabolized by C. elegans. Thesemetabolites were separated by reversed-phase high-performance liquidchromatography and identified by 1H nuclear magnetic resonance, UV, and atmospheric pressure chemical ionization (APCI) mass spectraltechniques. Metabolites I and II were identified as stereoismers of2-chloro-N-[2-ethyl-6-hydroxymethylphenyl)]-N-(2-hydroxy-1-me thylet hyl)acetamide. Metabolites III and IV have been tentatively identified as stereoismers of2-chloro-N-[2-(1-hydroxyethyl)-6-methylphenyl]-N-(2-methoxy-1-++ +methy lethyl)acetamide. Metabolites V and VI were identified as stereoismers of2-chloro-N-(2-ethyl-6-hydroxy-methylphenyl)-N-(2-methoxy-1-me thylet hyl)acetamideand 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-hydroxy-1-methylethyl)acetam ide, respectively. The fungus Cunninghamellaelegans was able to biotransform metolachlor. Multiple site oxidation ofmetolachlor by C. elegans occurred predominantly byO-demethylation of the N-alkyl side chain and benzylichydroxylation of the arylalkyl side chain.

Acetamides↗
PubMed1996

Formation of mammalian metabolites of cyclobenzaprine by the fungus, Cunninghamella elegans.

The fungus, Cunninghamella elegans, was used as a microbial model of mammalian drug metabolism to biotransform a tricyclic antidepressant, cyclobenzaprine. Seventy-five percent of this drug at a concentration of 1 mM was metabolized within 72 h by C. elegans grown on Sabouraud dextrose broth. Milligram amounts of fungal metabolites were isolated by reversed-phase high performance liquid chromatography (HPLC) and their structures were characterized by 1H NMR spectroscopy, mass spectrometry, and UV spectroscopy analyses. The major fungal metabolites of cyclobenzaprine were 2-hydroxycyclobenzaprine (59%), N-desmethylcyclobenzaprine (21%), cyclobenzaprine trans-10,11-dihydrodiol (5%), N-desmethyl-2-hydroxy-cyclobenzaprine (3%), 3-hydroxycyclobenzaprine (3%), and cyclobenzaprine N-oxide (1%). These fungal metabolites were used as standards to investigate the metabolism of cyclobenzaprine by rat liver microsomes. Rat liver microsomes also biotransformed cyclobenzaprine to produce similar metabolites as the fungus. The isotope labeling of 2-hydroxycyclobenzaprine by 18O2 and the trans-configuration of the dihydrodiol suggested that these reactions were catalyzed by cytochrome P-450 monooxygenases in C. elegans. These results also demonstrated that the fungal biotransformation system could be used to predict and synthesize the mammalian drug metabolites.

Amitriptyline↗
PubMed1996

Fungal metabolism of 2-nitrofluorene.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are direct-acting mutagens and carcinogens that are considered a risk to human health. We investigated the metabolism of 2-nitrofluorene by the fungus Cunninghamella elegans ATCC 36112. At 144 h of incubation, C. elegans had metabolized about 81% of the [9-14C]-2-nitrofluorene, resulting in 6 metabolites. The major metabolites were separated by reversed-phase high-performance liquid chromatography and identified by 1H NMR, ultraviolet (UV)-visible, and mass spectral analyses as 2-nitro-9-fluorenol, 2-nitro-9-fluorenone, 6-hydroxy-2-nitrofluorene, and sulfate conjugates of 7-hydroxy-2-nitro-9-fluorenone and 7-hydroxy-2-nitrofluorene. 2-Nitro-9-fluorenol accounted for about 62% of the total metabolism. For comparison with the microbial system, experiments with liver microsomes of rats pretreated with 3-methyl-cholanthrene were conducted. Microsomal incubations indicated formation of phenolic and ring-hydroxylated products of 2-nitrofluorene. 2-Nitrofluorene and hydroxylated metabolites have been previously implicated as direct-acting mutagens in bacterial assays and have shown sister chromatid exchanges in vivo in bone marrow cells and in vitro in ovary cells and unscheduled DNA synthesis in mammalian studies. Previous studies with other PAHs using C. elegans have shown that the phenols and glucoside and sulfate conjugates of phenols are generally less mutagenic than the parent. The results from the metabolism of 2-nitrofluorene by C. elegans suggests the detoxification potential of this fungus.

Animals↗
PubMed1996

Biotransformation of quinoxaline by Streptomyces badius.

Quinoxaline, a mutagenic azaarene produced in foods during cooking, was added to cultures of Streptomyces badius ATCC 39117. After 24 h, the cultures were extracted with ethyl acetate. Two major metabolites were purified by liquid chromatography and identified by mass spectrometry and nuclear magnetic resonance spectroscopy as 3,4-dihydro-2(1H)-quinoxalinone and 2(1H)-quinoxalinone.

Biotransformation↗
PubMed1995

Identification of two N2-deoxyguanosinyl DNA adducts upon nitroreduction of the environmental mutagen 1-nitropyrene.

1-Nitropyrene, the most abundant nitro-polycyclic aromatic hydrocarbon in the environment, is a known mammalian and bacterial mutagen and a tumorigen in animals. Early studies on DNA adduct characterization for 1-nitropyrene identified N-(deoxyguanosin-8-yl)-1-aminopyrene as the major product from the modification of calf thymus DNA with N-hydroxy-1-aminopyrene, the activated metabolite from nitroreduction of 1-nitropyrene. In this paper, we report the identification of two N2-deoxyguanosinyl adducts, in addition to N-(deoxyguanosin-8-yl)-1-aminopyrene, formed from the reaction of N-hydroxy-1-aminopyrene, prepared in situ, with calf thymus DNA. These DNA adducts were identified as 6-(deoxyguanosin-N2-yl)-1-aminopyrene and 8-(deoxyguanosin-N2-yl)-1-aminopyrene. The two N2-deoxyguanosinyl adducts were also identified in an ascorbic acid-catalyzed activation of 1-nitrosopyrene and in the mammary gland of female Sprague-Dawley rats administered 1-nitropyrene. The DNA adducts were also formed when 1-nitropyrene was metabolized by xanthine oxidase in the presence of calf thymus DNA, and when 1-nitropyrene was activated by rat liver microsomes and cytosols, as well as from DNA isolated from Salmonella typhimurium suspension cultures incubated with 1-nitropyrene.

Animals↗
PubMed1995

Biotransformation of amitriptyline by Cunninghamella elegans.

A fungal biotransformation system as an in vitro model for mammalian drug metabolism was investigated. Amitriptyline, a widely used antidepressant, was effectively biotransformed within 72 hr by the filamentous fungus, Cunninghamella elegans. Eight major metabolites in HPLC elution order (11-hydroxyamitriptyline N-oxide, 11-hydroxynortriptyline, 11-hydroxyamitriptyline, 10-hydroxyamitriptyline, 3-hydroxyamitriptyline, 2-hydroxyamitriptyline, nortriptyline, and amitriptyline N-oxide) were produced at estimated molar ratios of 2:1:10:0.6:0.1:1.2.5:0.5, respectively. These metabolites were isolated by HPLC and identified by UV/MS analyses, as well as NMR spectroscopic analysis for most of these metabolites. In some cases, they were also compared with authentic standards. Glucose, culture age, and substrate concentration significantly affected the extent of amitriptyline metabolism. Kinetic studies indicated that nortriptyline and 11-hydroxyamitriptyline were produced as initial major metabolites. The hydroxylated metabolite was excreted from mycelia, but amitriptyline and its N-demethylated metabolite, nortriptyline, were not. An 18O2 labeling experiment showed that the oxygen atoms in 11-hydroxyamitriptyline and 2-hydroxyamitriptyline were derived from molecular oxygen. The cytochrome P450 inhibitors SKF 525-A (1.5 mM), metyrapone (2.0 mM), and 1-aminobenzotriazole (1.0 mM) inhibited the biotransformations of amitriptyline by 50, 75, and 95%, respectively. A microsomal preparation was shown to catalyze the 11-hydroxylation of amitriptyline, which was inhibited by SKF 525-A and carbon monoxide. The similarities of amitriptyline metabolism in C. elegans and in humans and rats are discussed.

Amitriptyline↗
PubMed1994

Identification of a novel, N7-deoxyguanosine adduct as the major DNA adduct formed by a non-bay-region diol epoxide of benzo[a]pyrene with low mutagenic potential.

A metabolite of benzo[a]pyrene, 9-r,10-t-dihydroxy-7,8-c-oxy-7,8,9,10- tetrahydrobenzo[a]pyrene (BPDE-III), that is not thought to be involved in carcinogenesis has nevertheless been shown to bind extensively to DNA in vitro. The adducts formed by this non-bay-region diol epoxide in Chinese hamster ovary cells are much less mutagenic than those formed by an isomeric diol epoxide that is carcinogenic. We have isolated and characterized three major adducts formed by in vitro reaction of BPDE-III with DNA. The major adduct, accounting for over half of the total is formed by reaction of BPDE-III with the N7 position of dGuo and is recovered after enzymatic digestion as an N7-Gua adduct. A second major adduct involves the N2 position of dGuo, while the third adduct is tentatively identified as a C8-substituted dGuo. Little or no reaction with deoxyadenosine residues is detected. The N7 adduct is unstable in DNA at 37 degrees C and is released as the modified base with a half-life of about 24 h. This adduct lability apparently leads to single-strand breaks and alkali-sensitive sites in the DNA and may account in part for some of the biological properties of BPDE-III adducts. This represents the first description of an N7-dGuo adduct that is formed in DNA as the major adduct by a diol epoxide derived from a carcinogenic polycyclic aromatic hydrocarbon.

Animals↗
PubMed1994

Fungal metabolism of 3-nitrofluoranthene.

We investigated the metabolism of 3-nitrofluoranthene by filamentous fungus, Cunninghamella elegans ATCC 36112. Cunninghamella elegans metabolized about 72% of the 3-nitro[3,4-14C]fluoranthene added during 144 h of incubation to 2 major metabolites. These metabolites were separated by reversed-phase high-performance liquid chromatography and identified as 3-nitrofluoranthene-8-sulfate and 3-nitrofluoranthene-9-sulfate by 1H nuclear magnetic resonance, UV-visible, and mass spectral techniques. These results, in conjunction with previous studies on the fungal metabolism of fluoranthene, indicate that the nitro substituent at the C-3 position of fluoranthene sterically hinders epoxidation and shifts metabolism to the C-8 and C-9 positions. Since the phenolic microsomal metabolites of 3-nitrofluoranthene are mutagenic, the formation of sulfate conjugates of 8- and 9-hydroxy-3-nitrofluoranthene by C. elegans suggests that the fungal metabolic pathways may be beneficial for detoxification of this ubiquitous pollutant.

Carcinogens↗
PubMed1994

Metabolism of 7-nitrobenz[a]anthracene by intestinal microflora.

Pure cultures of anaerobic intestinal bacteria and mixed fecal microflora from human, rat, mouse, and pig were screened for the ability to metabolize 7-nitrobenz[a]anthracene (7-NO2BA). Based on analysis by high-performance liquid chromatography (HPLC) and by ultraviolet (UV), mass, and nuclear magnetic resonance (NMR) spectral techniques, the compounds were identified as 7-aminobenz[a]anthracene (7-NH2BA) and benz[a]anthracene 7,12-dione (dione). Identification of 7-NH2BA as a metabolite of 7-NO2BA indicates that the anaerobic intestinal bacteria are capable of reducing 7-NO2BA to potentially bioactive intermediates. The reductive capacities of the mixed intestinal microflora were generally greater than those of pure cultures. Thus, metabolism of 7-NO2BA in the intestinal tract may be underestimated if pure cultures are used as the sole method for evaluating the potential hazard.

Animals↗
PubMed1994

DNA adducts and carcinogenicity of nitro-polycyclic aromatic hydrocarbons.

We have been interested in the structure-activity relationships of nitro-polycyclic aromatic hydrocarbons (nitro-PAHs), and have focused on the correlation of structural and electronic features with biological activities, including mutagenicity and tumorigenicity. In our studies, we have emphasized 1-, 2-, 3-, and 6-nitrobenzo[a]pyrenes (nitro-B[a]Ps) and related compounds, all of which are derived from the potent carcinogen benzo[a]pyrene. While 1-, 2-, and 3-nitro-B[a]P are potent mutagens in Salmonella, 6-nitro-B[a]P is a weak mutagen. In vitro metabolism of 1- and 3-nitro-B[a]P has been found to generate multiple pathways for mutagenic activation. The formation of the corresponding trans-7,8-dihydrodiols and 7,8,9,10-tetrahydrotetrols suggests that 1- and 3-nitro-B[a]P trans-7,8-diol-9,10-epoxides are ultimate metabolites of the parent nitro-B[a]Ps. We have isolated a DNA adduct from the reaction between 3-nitro-B[a]P trans-7,8-diol-anti9,10-epoxide and calf thymus DNA, and identified it as 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-3-ni tro-B[a]P . The same adduct was identified from in vitro metabolism of [3H]3-nitro-B[a]P by rat liver microsomes in the presence of calf thymus DNA. A DNA adduct of 3-nitro-B[a]P formed from reaction of N-hydroxy-3-amino-B[a]P, prepared in situ with calf thymus DNA was also isolated. This adduct was identified as 6-(deoxyguanosin-N2-yl)-3-amino-B[a]P. The same adduct was obtained from incubating DNA with 3-nitro-B[a]P in the presence of the mammalian nitroeductase, xanthine oxidase, and hypoxanthine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Activation of retinal rod cGMP-gated channels: what makes for an effective 8-substituted derivative of cGMP?

Analogs of cGMP bearing diverse substituents at the C8 position of the guanine ring system have been shown to activate the cGMP-activated channel of retinal rods at concentrations lower than cGMP itself. In an effort to understand this behavior, we synthesized eight novel C8-substituted derivatives and tested their ability to activate channels in excised patches from salamander rod outer segments. We express the effectiveness of each analog as a ratio (in brackets) of the concentration required to open half of the channels in a patch to that required of 8-Br-cGMP, previously shown to be about 10 times more effective than cGMP. Five of the derivatives contained a thio substitution at C8: n-propylthio-cGMP [0.61], sulfoethylthio-cGMP [0.90], carboxyethylthio-cGMP [0.97], aminoethylthio-cGMP [2.8], and (trimethylamino)ethylthio-cGMP [8.5]. Three of the derivatives contained an amino substitution at C8: carboxyethylamino-cGMP [22], n-propylamino-cGMP [25], and aminoethylamino-cGMP [230]. The results indicate that thio-substitution at C8 produces more effective analogs than does amino-substitution, regardless of the chemical nature of the terminal functional group. Derivatives containing neutral and apolar tails opened channels at much lower concentrations than their positively-charged counterparts with the same C8 substituent. Analogs having negatively-charged tails were also more effective than those with positive charge but not quite as effective as those with neutral tails.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambystoma↗
PubMed1993

Products formed from the in vitro reaction of metabolites of 3-aminochrysene with calf thymus DNA.

3-Aminochrysene, a mutagenic geometric isomer of the mutagenic and carcinogenic aromatic amine 6-aminochrysene, has been synthesized and its metabolic activation studied by characterization of the products formed from the reaction of metabolites with calf thymus DNA. DNA adducts produced by 3-aminochrysene via N-oxidation were examined by preparing 3-nitrosochrysene and incubating the nitroso derivative with calf thymus DNA in the presence of ascorbic acid (to generate the N-hydroxy derivative) at pH 5. The major adduct, as determined by 1H-NMR and thermospray-mass spectrometry of the modified nucleoside obtained after enzymatic hydrolysis of the modified DNA, was N-(deoxyguanosin-8-yl)-3-aminochrysene. Thus, the reaction of N-hydroxy-3-aminochrysene with DNA differs from that of N-hydroxy-6-aminochrysene, which had previously been shown to generate N-(deoxyguanosin-8-yl)-6-aminochrysene, 5-(deoxyguanosin-N2-yl)-6-aminochrysene and N-(deoxyinosin-8-yl)-6- aminochrysene as major adducts. 32P-Postlabeling analysis of DNA treated with 3-aminochrysene in the presence of liver microsomes from rats pretreated with phenobarbital indicated an adduct pattern identical to that seen with DNA that had been treated with 3-nitrosochrysene and ascorbic acid. However, DNA treated with 3-aminochrysene (3-AC) in the presence of liver microsomes from rats pretreated with 3-methylcholanthrene contained a major adduct that was chromatographically distinct from N-(deoxyguanosin-8-yl)-3-aminochrysene.

Animals↗
PubMed1993

Formation of the adduct 6-(deoxyguanosin-N2-yl)-3-amino-benzo[a]pyrene from the mutagenic environmental contaminant 3-nitrobenzo[a]pyrene.

3-Nitrobenzo[a]pyrene (3-nitro-B[a]P) is a potent bacterial mutagen as a result of nitroreduction. Reaction of N-hydroxy-3-amino-B[a]P, prepared in situ from reduction of 3-nitro-B[a]P with calf thymus DNA, was studied. After enzymatic digestion of the DNA, the resulting modified nucleosides were analyzed by thermospray HPLC-MS and high-resolution proton NMR spectroscopy. The major adduct was identified as 6-(deoxyguanosin-N2-yl)-3-amino-B[a]P. The same adduct was obtained from incubation of DNA with 3-nitro-B[a]P in the presence of the mammalian nitroreductase xanthine oxidase, and hypoxanthine. These data indicate that a mammalian nitroreductase can metabolize 3-nitro-B[a]P to an activated derivative that reacts with DNA to give a novel adduct distant from the site of N-hydroxylation.

Animals↗
PubMed1993

Identification of metabolites from the degradation of fluoranthene by Mycobacterium sp. strain PYR-1.

Mycobacterium sp. strain PYR-1, previously shown to extensively mineralize high-molecular-weight polycyclic aromatic hydrocarbons in pure culture and in sediments, degrades fluoranthene to 9-fluorenone-1-carboxylic acid. In this study, 10 other fluoranthene metabolites were isolated from ethyl acetate extracts of the culture medium by thin-layer and high-performance liquid chromatographic methods. On the basis of comparisons with authentic compounds by UV spectrophotometry and thin-layer chromatography as well as gas chromatography-mass spectral and proton nuclear magnetic resonance spectral analyses, the metabolites were identified as 8-hydroxy-7-methoxyfluoranthene, 9-hydroxyfluorene, 9-fluorenone, 1-acenaphthenone, 9-hydroxy-1-fluorenecarboxylic acid, phthalic acid, 2-carboxybenzaldehyde, benzoic acid, phenylacetic acid, and adipic acid. Authentic 9-hydroxyfluorene and 9-fluorenone were metabolized by Mycobacterium sp. strain PYR-1. A pathway for the catabolism of fluoranthene by Mycobacterium sp. strain PYR-1 is proposed.

Biodegradation, Environmental↗
PubMed1993

Biotransformation of fluorene by the fungus Cunninghamella elegans.

The metabolism of fluorene, a tricyclic aromatic hydrocarbon, by Cunninghamella elegans ATCC 36112 was investigated. Approximately 69% of the [9-14C]fluorene added to cultures was metabolized within 120 h. The major ethyl acetate-soluble metabolites were 9-fluorenone (62%), 9-fluorenol, and 2-hydroxy-9-fluorenone (together, 7.0%). Similarly to bacteria, C. elegans oxidized fluorene at the C-9 position of the five-member ring to form an alcohol and the corresponding ketone. In addition, C. elegans produced the novel metabolite 2-hydroxy-9-fluorenone.

Biodegradation, Environmental↗
PubMed1992

Life-threatening acute respiratory distress in late pregnancy.

Acute severe ventilatory failure from any cause is always a critical emergency. In advanced pregnancy, such an episode is particularly hazardous. The management of a pregnant patient who presented with an acute episode of respiratory distress is described. Although this was though initially to be an asthmatic attack, there was evidence of upper airway obstruction caused by an enlarged thyroid. The major complicating factors and aetiology are discussed.

Acute Disease↗