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J P Freeman

Publications and source records attributed to J P Freeman.

At least 73 records · Page 4Linked to original sources
PubMed1989

Analysis, characterization, and purification: requirements for toxicological evaluation of 1,4-dithiane.

1,4-Dithiane is an organo-sulfur chemical associated with production and storage of munitions. Toxicological evaluation of this chemical was scheduled in rats because of the paucity of such information. Prerequisite for the evaluation was the development of gas chromatographic procedures using flame ionization detection to determine the purity of the test chemical and to certify the concentration and stability of the chemical in the dosage form, sesame oil. Mass and nuclear magnetic resonance spectrometry procedures are described for assessing the structural character and purity of the test chemical. A procedure for the purification of the test chemical and data concerning its solubility in various solvents are also presented.

Chromatography, Gas↗
PubMed1989

Identification of a novel metabolite in phenanthrene metabolism by the fungus Cunninghamella elegans.

The metabolism of phenanthrene by the fungus Cunninghamella elegans was investigated. Kinetic experiments using [9-14C]phenanthrene showed that after 72 h, 53% of the total radioactivity was associated with a glucoside conjugate of 1-hydroxyphenanthrene (phenanthrene 1-O-beta-glucose). This metabolite was isolated by reversed-phase high-performance liquid chromatography and characterized by the application of UV absorption, 1H nuclear magnetic resonance, and mass spectral techniques. The results show that aromatic ring oxidation followed by glucosylation is a predominant pathway in the metabolism of the polycyclic aromatic hydrocarbon phenanthrene by C. elegans.

Acetylation↗
PubMed1988

Pyrene degradation by a Mycobacterium sp.: identification of ring oxidation and ring fission products.

The degradation of pyrene, a polycyclic aromatic hydrocarbon containing four aromatic rings, by pure cultures of a Mycobacterium sp. was studied. Over 60% of [14C]pyrene was mineralized to CO2 after 96 h of incubation at 24 degrees C. High-pressure liquid chromatography analyses showed the presence of one major and at least six other metabolites that accounted for 95% of the total organic-extractable 14C-labeled residues. Analyses by UV, infrared, mass, and nuclear magnetic resonance spectrometry and gas chromatography identified both pyrene cis- and trans-4,5-dihydrodiols and pyrenol as initial microbial ring-oxidation products of pyrene. The major metabolite, 4-phenanthroic acid, and 4-hydroxyperinaphthenone and cinnamic and phthalic acids were identified as ring fission products. 18O2 studies showed that the formation of cis- and trans-4,5-dihydrodiols were catalyzed by dioxygenase and monooxygenase enzymes, respectively. This is the first report of the chemical pathway for the microbial catabolism of pyrene.

Biodegradation, Environmental↗
PubMed1987

Characterization, purification, and analysis of solvent yellow 33 and solvent green 3 dyes.

Thin-layer chromatography and high-performance liquid chromatography (HPLC) with linear photodiode array detection (LPDA) were used to separate impurities from two commercial dyes. Gravity flow liquid chromatography was used to purify reference standards of the dyes. Normal phase HPLC with LPDA detection was used to determine purities of submitted samples by comparing responses to those of the reference standards. Electron impact mass spectrometry and nuclear magnetic resonance were utilized to confirm structures of the dyes and their impurities.

Anthraquinones↗
PubMed1987

Naphthalene biodegradation in environmental microcosms: estimates of degradation rates and characterization of metabolites.

Naphthalene biodegradation was investigated in microcosms containing sediment and water collected from three ecosystems which varied in past exposure to anthropogenic and petrogenic chemicals. Mineralization half-lives for naphthalene in microcosms ranged from 2.4 weeks in sediment chronically exposed to petroleum hydrocarbons to 4.4 weeks in sediment from a pristine environment. Microbiological analysis of sediments indicated that hydrocarbon-utilizing microbial populations also varied among ecosystems and were 5 to 12 times greater in sediment after chronic petrogenic chemical exposure than in sediment from an uncontaminated ecosystem. Sediment from an ecosystem exposed to agricultural chemicals had a mineralization half-life of 3.2 weeks for naphthalene and showed about a 30-fold increase in heterotrophic bacterial populations in comparison to uncontaminated sediments, but only a 2- to 3-fold increase in hydrocarbon-degrading bacteria. Analysis of organic solvent-extractable residues from the microcosms by high-pressure liquid chromatography detected polar metabolites which accounted for 1 to 3% of the total radioactivity. Purification of these residues by thin-layer chromatography and further analysis by gas chromatography-mass spectrometry indicated that cis-1,2-dihydroxy-1,2-dihydronaphthalene, 1-naphthol, salicylic acid, and catechol were metabolites of naphthalene. These results provide useful estimates for the rates of naphthalene mineralization in different natural ecosystems and on the degradative pathway for microbial metabolism of naphthalene in freshwater and estuarine environments.

Biodegradation, Environmental↗
PubMed1986

Microbial metabolism of pyrene.

The isolation and identification of pyrene metabolites formed from pyrene by the fungus Cunninghamella elegans is described. C. elegans was incubated with pyrene for 24 h. Six metabolites were isolated by reversed-phase high-performance liquid (HPLC) and thin-layer chromatography (TLC) and characterized by the application of UV absorption, 1H-NMR and mass spectral techniques. C. elegans hydroxylated pyrene predominantly at the 1,6- and 1,8-positions with subsequent glucosylation to form glucoside conjugates of 1-hydroxypyrene, 1,6- and 1,8-dihydroxypyrene. In addition, 1,6- and 1,8-pyrenequinones and 1-hydroxypyrene were identified as metabolites. Experiments with [4-14C]pyrene indicated that over a 24-h period, 41% of pyrene was metabolized to ethyl acetate-soluble metabolites. The glucoside conjugates of 1-hydroxypyrene, 1,6- and 1,8-dihydroxypyrene accounted for 26%, 7% and 14% of the pyrene metabolized, respectively. Pyrenequinones accounted for 22%. The results indicate that the fungus C. elegans metabolized pyrene to non-toxic metabolites (glucoside conjugates) as well as to compounds (pyrenequinones) which have been suggested to be biologically active in higher organisms. In addition, there was no metabolism at the K-region of the molecule which is a major site of enzymatic attack in mammalian systems.

Animals↗
PubMed1986

Biodegradation of tert-butylphenyl diphenyl phosphate.

The biodegradation of tert-butylphenyl diphenyl phosphate (BPDP) was examined in microcosms containing sediment and water from five different ecosystems as part of our studies to elucidate the environmental fate of phosphate ester flame retardants. Biodegradation of [14C]BPDP was monitored in the environmental microcosms by measuring the evolution of 14CO2. Over 37% of BPDP was mineralized after 8 weeks in microcosms from an ecosystem which had chronic exposure to agricultural chemicals. In contrast, only 1.7% of BPDP was degraded to 14CO2 in samples collected from a noncontaminated site. The exposure concentration of BPDP affected the percentage which was degraded to 14CO2 in microcosms from the two most active ecosystems. Mineralization was highest at a concentration of 0.1 mg of BPDP and was inhibited with 10- and 100-fold higher concentrations of BPDP in these microcosms. Indigenous heterotrophic and BPDP-utilizing microbial populations and phosphoesterase enzyme activities were highest in sediments which had the highest biodegradation of BPDP. We observed adaptive increases in both microbial populations and phosphoesterase enzymes in some sediments acclimated to BPDP. Chemical analyses of the residues in the microcosms indicated undegraded BPDP and minor amounts of phenol, tert-butylphenol, diphenyl phosphate, and triphenyl phosphate as biodegradation products. These data suggest that the microbial degradation of BPDP results from at least three catabolic processes and is highest when low concentrations of BPDP are exposed to sediment microorganisms of eutrophic ecosystems which have high phosphotri- and diesterase activities and previous exposure to anthropogenic chemicals.

Animals↗
PubMed1985

Fungal metabolism of tert-butylphenyl diphenyl phosphate.

The fungal metabolism of tert-butylphenyl diphenyl phosphate (BPDP) was studied. Cunninghamella elegans was incubated with BPDP for 7 days, and the metabolites formed were separated by thin-layer, gas-liquid, or high-pressure liquid chromatography and identified by 1H nuclear magnetic resonance and mass spectral techniques. C. elegans metabolized BPDP predominantly at the tert-butyl moiety to form the carboxylic acid 4-(2-carboxy-2-propyl)triphenyl phosphate. In addition, 4-hydroxy-4'-(2-carboxy-2-propyl)triphenyl phosphate, triphenyl phosphate, diphenyl phosphate, 4-(2-carboxy-2-propyl)diphenyl phosphate, 2-(4-hydroxyphenyl)-2-methyl propionic acid, and phenol were detected. Similar metabolites were found in the 28 fungal cultures which were examined for their ability to metabolize BPDP. Experiments with [14C]BPDP indicated that C. elegans metabolized 70% of the BPDP after 7 days and that the ratio of organic-soluble metabolites to water-soluble metabolites was 8:2. The results indicate that fungi preferentially oxidize BPDP at the alkyl side chain and at the aromatic rings to form hydroxylated derivatives. The trace levels of mono- and diaryl metabolites and the low level of phosphotriesterase activity measured in C. elegans indicate that phosphatase cleavage is a minor pathway for fungal metabolism of BPDP.

Biodegradation, Environmental↗
PubMed1985

Fungal metabolism and detoxification of the nitropolycyclic aromatic hydrocarbon 1-nitropyrene.

Nitropolycyclic aromatic hydrocarbons are ubiquitous environmental pollutants, many of which are potent mutagens in bacterial and mammalian cells and carcinogenic to rodents. In this study, we investigated the fungal metabolism of 1-nitropyrene and determined the mutagenic activity of the metabolites toward Salmonella typhimurium TA98, TA98NR, and TA100. Cunninghamella elegans metabolized 1-nitropyrene to form glucoside conjugates of 6-hydroxy-1-nitropyrene and 8-hydroxy-1-nitropyrene. The metabolites were isolated by reversed-phase high-pressure liquid chromatography and characterized by application of UV absorption, 1H-nuclear magnetic resonance, and mass spectroscopy. Mutagenicity assays performed on samples extracted from incubations of C. elegans with 1-nitropyrene indicated that mutagenic activity decreased with time. Consistent with the loss in mutagenic activity, the glucoside conjugates of 6- and 8-hydroxy-1-nitropyrene were nonmutagenic in the Salmonella reversion assay. The results indicate that the fungus C. elegans metabolizes 1-nitropyrene to detoxified products.

Biodegradation, Environmental↗
PubMed1985

Mechanism of microsomal metabolism of benzene to phenol.

The mechanism of microsomal hydroxylation of benzene to phenol has been studied by examining the microsomal metabolism of the specifically deuterated derivative 1,3,5-[2H3]benzene. Evidence for the formation of the following four products was obtained: 2,3,5-[2H3]phenol, 3,5-[2H2]phenol, 2,4,6-[2H3]phenol, and 2,4-[2H2]phenol. The presence of 2,3,5-[2H3]phenol and 2,4-[2H2]phenol shows that, in the microsomal metabolism of benzene to phenol, a NIH shift had occurred. A deuterium isotope effect (kH/kD) of approximately 4 was detected in both the meta- and para-deuterated phenols. This finding indicates that cyclohexadienone, formed either by isomerization of the epoxide or directly from the enzyme-substrate complex, is a major intermediate in the metabolism of benzene to phenol.

Animals↗
PubMed1984

Quantitative determination of dexamethasone in human plasma by stable isotope dilution mass spectrometry.

An analytical method for the quantitation of nanogram to subnanogram amounts of dexamethasone is described. Dexamethasone was isolated from human plasma using a C18-bonded reverse-phase cartridge, purified by subsequent normal-phase HPLC, and the corresponding trimethylsilyl derivative analyzed by gas chromatography-mass spectrometry (GC-MS). The quantitation by isotope-dilution MS was carried out by selected-ion monitoring on the (M + 1)+ ion of the trimethylsilyl derivative of dexamethasone and its stable isotopically labeled diluent, [ 13C6 ,2H3]dexamethasone (681 and 690 m/z, respectively). Methane was used as the GC carrier gas and as the chemical-ionization reagent gas. The sensitivity of the method, judged from the lower limit of detection of the mass spectrometer, was at approximately 100 pg. The inter- and intraassay coefficients of variation (CV) determined at two different concentrations were 3.83 and 3.78% for 2 ng/mL and 2.64 and 1.29% for 5 ng/mL, respectively. Plasma concentration profiles for dexamethasone following a single 1-mg iv and a 2-mg oral dose of dexamethasone administered 24 h apart to two healthy volunteers are presented. The mass fragmentographic method described here is useful for bioavailability and pharmacokinetic studies of the synthetic glucocorticoid.

Administration, Oral↗
PubMed1984

Evidence for an arene oxide-NIH shift pathway in the transformation of naphthalene to 1-naphthol by Bacillus cereus.

Bacillus cereus ATCC 14579 transformed naphthalene predominately to 1-naphthol. Experiments with [14C]naphthalene showed that over a 24 h period, B. cereus oxidized 5.2% of the added naphthalene. 1-Naphthol accounted for approximately 80% of the total metabolites. B. cereus incubated with naphthalene under the presence of 18O2 led to the isolation of 1-naphthol that contained 94% 18O. The metabolism of [1-2H]- and [2-2H]-naphthalene by B. cereus yielded 1-naphthol which retained 95% and 94% deuterium, respectively, as determined by mass spectral analysis. NMR spectroscopic analysis of the deuterated 1-naphthol formed from [1-2H]-naphthalene indicated an NIH shift mechanism in which 19% of the deuterium migrated from the C-1 to the C-2 position. The 18O2 and NIH shift experiments implicate naphthalene-1,2-oxide as an intermediate in the formation of 1-naphthol from naphthalene by B. cereus.

Bacillus cereus↗
PubMed1984

Synthesis, spectral analysis, and mutagenicity of 1-, 3-, and 6-nitrobenzo[a]pyrene.

The mutagenic environmental pollutants 1-, 3-, and 6-nitrobenzo[a]pyrene were synthesized. Nitration of 7,8,9,10-tetrahydrobenzo[a]pyrene with sodium nitrate in trifluoroacetic acid and acetic anhydride at ambient temperature gave a mixture of 1-, 3-, and 6-nitro-7,8,9,10-tetrahydrobenzo[a]pyrene, which was separated by chromatography. Dehydrogenation of the isolated nitrotetrahydrobenzo[a]pyrenes with 2,3-dichloro-4,5-dicyano-1,6-benzoquinone produced 1-, 3-, and 6-nitrobenzo[a]pyrene in high yield. Comparison of the spectral data of these compounds with those obtained from direct nitration of benzo[a]pyrene confirmed that 1- and 3-nitrobenzo[a]pyrenes are indeed the minor products of the latter reaction. This confirmation also verifies that 1- and 3-nitrobenzo[a]pyrene were the minor nitrated products of benzo[a]pyrene formed in model air atmospheres. The 1-, 3-, and 6-nitrobenzo[a]pyrene were mutagenic in Salmonella typhimurium tester strains TA98 and TA100 in the presence of a mammalian microsomal (S9) activating system. Both 1- and 3-nitrobenzo[a]pyrene, but not 6-nitrobenzo[a]pyrene, were also direct-acting mutagens in these strains. However, only 6-nitrobenzo[a]pyrene exhibited weak mutagenic activity when tested in Chinese hamster ovary cells, while only 3-nitrobenzo[a]pyrene produced a concentration-dependent decrease in cellular survival.

Benzopyrenes↗
PubMed1984

Determination of N-nitrosamines and N-nitrosamine precursors in rubber nipples from baby pacifiers by gas chromatography-thermal energy analysis.

N-Nitrosamines and precursors are present in rubber products in which the accelerators and stabilizers used in the vulcanization process were derived from dialkylamines. Research was performed to develop data concerning the presence of N-nitrosamines and precursors so that the health significance of the exposure problem related to infant ingestion of these chemicals could be properly assessed. Volatile N-nitrosamines were determined in cut-up pacifier nipples by extraction with dichloromethane followed by concentration in a Kuderna-Danish evaporator, high-temperature mineral oil purge and trap, and analysis by gas chromatography--thermal energy analysis (GC-TEA). N-nitrosodibutylamine (NDBA) was the principal N-nitrosamine found, with concentrations up to 427 ppb. N-Nitrosamines and precursors in cut-up and intact nipples were determined by GC-TEA after a single extraction with artificial saliva. NDBA was the principal nitrosamine found, at levels up to 1040 ppb, while dibutylamine (DBA) was the principal precursor found, at levels up to 3890 ppb. The persistence of these compounds in intact nipples was determined by multiple artificial saliva extractions. Amounts of NDBA and DBA found after 15 artificial saliva extractions of intact pacifier nipples totalled 824 ppb and 15.6 ppm, respectively. N-Nitrosamine levels generally showed a gradual decrease in concentration with each extraction, whereas no consistent trend could be determined for concentrations of precursors.

Bottle Feeding↗
PubMed1984

Transformation of 1- and 2-methylnaphthalene by Cunninghamella elegans.

Cunninghamella elegans metabolized 1- and 2-methylnaphthalene primarily at the methyl group to form 1- and 2-hydroxymethylnaphthalene, respectively. Other compounds isolated and identified were 1- and 2-naphthoic acids, 5-hydroxy-1-naphthoic acid, 5-hydroxy-2-naphthoic acid, 6-hydroxy-2-naphthoic acid, and phenolic derivatives of 1- and 2-methylnaphthalene. The metabolites were isolated by thin-layer and reverse-phase high-pressure liquid chromatography and characterized by the application of UV-visible absorption, 1H nuclear magnetic resonance, and mass spectral techniques. Experiments with [8-14C]2-methylnaphthalene indicated that over a 72-h period, 9.8% of 2-methylnaphthalene was oxidized to metabolic products. The ratio of organic-soluble in water-soluble metabolites at 2 h was 92:8, and at 72 h it was 41:59. Enzymatic treatment of the 48-h aqueous phase with either beta-glucuronidase or arylsulfatase released 60% of the metabolites of 2-methylnaphthalene that were extractable with ethyl acetate. In both cases, the major conjugates released were 5-hydroxy-2-naphthoic acid and 6-hydroxy-2-naphthoic acid. The ratio of the water-soluble glucuronide conjugates to sulfate conjugates was 1:1. Incubation of C. elegans with 2-methylnaphthalene under an 18O2 atmosphere and subsequent mass spectral analysis of 2-hydroxymethylnaphthalene indicated that hydroxylation of the methyl group is catalyzed by a monooxygenase.

Kinetics↗
PubMed1984

Effects of a fluoro substituent on the fungal metabolism of 1-fluoronaphthalene.

The metabolism of 1-fluoronaphthalene by Cunninghamella elegans ATCC 36112 was studied. The metabolites were isolated by reverse-phase high-pressure liquid chromatography and characterized by the application of UV absorption, 1H nuclear magnetic resonance, and mass spectral techniques. C. elegans oxidized 1-fluoronaphthalene predominantly at the 3,4- and 5,6-positions to form trans-3,4-dihydroxy-3,4-dihydro-1-fluoronaphthalene and trans-5,6-dihydroxy-5,6-dihydro-1-fluoronaphthalene. In addition, 1-fluoro-8-hydroxy-5-tetralone, 5-hydroxy-1-fluoronaphthalene, and 4-hydroxy-1-fluoronaphthalene as well as glucoside, sulfate, and glucuronic acid conjugates of these phenols were formed. Circular dichroism spectra of the trans-3,4- and trans-5,6-dihydrodiols formed from 1-fluoronaphthalene indicated that the major enantiomers of the dihydrodiols have S,S absolute stereochemistries. In contrast, the trans-5,6-dihydrodiol formed from 1-fluoronaphthalene from 3-methylcholanthrene-treated rats had Cotton effects that are opposite in sign (R,R) to those formed by C. elegans. The results indicate that the fungal monooxygenase-epoxide hydrolase systems are highly stereoselective in the metabolism of 1-fluoronaphthalene and that a fluoro substituent blocks epoxidation at the fluoro-substituted double bond, decreases oxidation at the aromatic double bond that is peri to the fluoro substituent, and enhances metabolism at the 3,4- and 5,6-positions of 1-fluoronaphthalene.

Animals↗
PubMed1982

Separation of some natural and synthetic corticosteroids in biological fluids and tissues by high-performance liquid chromatography.

A high-performance liquid chromatography (HPLC) technique was developed for the determination of radiolabeled triamcinolone acetonide (TAC), cortisol and their metabolites in rhesus monkey plasma, urine and tissue samples. After protein precipitation, the parent compounds and metabolites were simultaneously resolved using a single-column reversed-phase HPLC system. TAC was subsequently verified by mass spectrometry and TAC glucuronide was tentatively identified by enzymatic hydrolysis and mass spectrometry of the hydrolysis product. The endogenous hormones, cortisol and cortisone were presumptively identified by cochromatography with authentic standards on two different HPLC systems and positively identified by reverse-isotope recrystallization. Other metabolites of both compounds were detected by selective enzymatic hydrolysis and HPLC. This method is rapid and reproducible with a total recovery greater than 80%.

Adrenal Cortex Hormones↗