Search PubMed⌕ Search

Biomedical subjects

N J Gooderham

Publications and source records attributed to N J Gooderham.

At least 55 records · Page 3Linked to original sources
PubMed1990

Mutagenesis of mouse intestine in vivo using the Dlb-1 specific locus test: studies with 1,2-dimethylhydrazine, dimethylnitrosamine, and the dietary mutagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline.

The ability of three model carcinogens, 1,2-dimethylhydrazine, dimethylnitrosamine, and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, to induce mutation in a novel in vivo assay in mouse intestine has been examined. The assay is based on mutations at the Dlb-1 locus which determines the tissue specific pattern of expressio of the binding site for the lectin Dolichos biflorus agglutinin. In C57BL/6J x SWR F1 mice Dlb-1 mutants are recognized as clones of epithelial cells not staining with a peroxidase conjugate of D. biflorus agglutinin. Chronic administration of 1,2-dimethylhydrazine (20 mg/kg/week s.c. for 10 weeks) induced Dlb-1 mutants, whereas administration of a single dose did not. Similarly, chronic dimethylnitrosamine treatment p.o. (0.001% in drinking water for 8 weeks) induced Dlb-1 mutants, but acute administration did not. In contrast, neither chronic nor acute treatment of the mice with 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline induced Dlb-1 mutations. The activities of 1,2-dimethylhydrazine, dimethylnitrosamine, and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline in the Dlb-1 assay more accurately reflect their carcinogenic potential than do many in vitro bioassays.

1,2-Dimethylhydrazine↗
PubMed1990

In vitro translational activity of messenger-RNA isolated from mice treated with the interferon inducer, polyriboinosinic acid.polyribocytidylic acid.

Treatment of mice with interferon and interferon inducers causes down regulation of a number of hepatic proteins. In a previous publication it was demonstrated that these treatments depress hepatic protein synthesis and increase protein degradation, particularly of the endoplasmic reticulum Gooderham NJ and Mannering GJ, Arch Biochem Biophys 250: 418-425, 1986. In the present study the effects of polyriboinosinic acid.polyribocytidylic acid (poly IC) treatment on mouse hepatic RNA levels and the translation of this RNA in a cell-free system were examined. Poly IC treatment of mice increased hepatic poly (A+) RNA levels. The translation of isolated poly(A+)RNA was evaluated at various intervals after the administration of poly IC. Translation was marginally increased at 3-6 hr after treatment and depressed after 12-18 hr. Antibodies were employed to examine the effects of poly IC treatment on specific polypeptides in order to evaluate the in vitro translation of mRNAs for tyrosine aminotransferase and albumin; translation of these proteins was biphasic with pronounced depression. These studies indicate that in vivo interferon may regulate gene expression by altering levels of hepatic proteins via increased transcription and decreased translation.

Animals↗
PubMed1989

Detection and measurement of MeIQx in human urine after ingestion of a cooked meat meal.

A gas chromatographic-mass spectrometric assay has been developed for the measurement of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in urine. The method employs capillary column gas chromatography, electron capture negative-ion chemical ionization mass spectrometry, a stable isotope-labelled analogue of MeIQx as internal standard and has a limit of detection of 5 pg MeIQx/ml urine. Six subjects consumed a fried beef meal and urine was collected before and after this event. While no MeIQx could be detected in urine collections made prior to meat consumption, the 12-h urine collections of all six subjects made after the meal contained the amine. When the amounts of MeIQx measured in the urine collections were compared to the quantities of amine ingested in the fried beef, it was found that 1.8-4.9% of the oral dose was excreted unchanged in urine. Metabolic studies in animals lead us to believe that MeIQx in the diet is efficiently absorbed and extensively biotransformed.

Gas Chromatography-Mass Spectrometry↗
PubMed1988

An assay for 2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline and 2-amino-3,4,8-trimethylimidazo-[4,5-f]quinoxaline in fried beef using capillary column gas chromatography electron capture negative ion chemical ionization mass spectrometry.

A gas chromatographic/mass spectrometric assay has been developed for the simultaneous measurement of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) in fried beef. The method employs capillary column gas chromatography, electron capture negative ion chemical ionization mass spectrometry and a stable isotope labelled analogue of MeIQx as common internal standard. Two patties of lean minced beef which had been cooked separately were analysed and found to contain both compounds (patty 1:2.4 ng MeIQx g-1 meat, 1.2 ng DiMeIQx g-1 meat; patty 2:1.3 ng MeIQx g-1 meat, 0.5 ng DiMeIQx g-1 meat). Neither compound was present in the meat prior to cooking.

Animals↗
PubMed1988

Measurement of MeIQx and DiMeIQx in fried beef by capillary column gas chromatography electron capture negative ion chemical ionisation mass spectrometry.

A gas chromatographic-mass spectrometric assay has been developed for the simultaneous measurement of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) in fried beef. The method employs capillary column gas chromatography, electron capture negative ion chemical ionisation mass spectrometry and a stable isotope labelled analogue of MeIQx (the synthesis of which is described) as common internal standard. Two patties of lean minced beef which had been cooked separately were analysed and found to contain both compounds (patty 1-2.4 ng MeIQx/g meat, 1.2 ng DiMeIQx/g meat; patty 2-1.3 ng MeIQx/g meat, 0.5 ng DiMeIQx/g meat). Neither compound was present in the meat prior to cooking.

Animals↗
PubMed1987

Metabolism of the mutagen MeIQx in vivo: metabolite screening by liquid chromatography-thermospray mass spectrometry.

2-Amino-3,8-dimethylimidazo(4,5-f)quinoxaline (MeIQx) is a potent mutagen found in cooked food. MeIQx and its isotopically labelled (13C, 15N2 and 14C) analogues were synthesised and used for metabolic studies in vivo. An equimolar mixture of MeIQx and its 13C, 15N2 stable isotope labelled analogue (containing tracer amounts of 14C-MeIQx) was given intraperitoneally to mice. Some 67% of the radioactivity was eliminated in urine and faeces within 24h. Four radiolabelled species were observed when urine was analysed by HPLC, corresponding to unchanged MeIQx and three more polar metabolites. Urine was analysed directly by HPLC-thermospray mass spectrometry. Four signals were observed containing the characteristic 1:1 isotopic doublet, corresponding to unchanged MeIQx, an MeIQx glucuronide, and two uncharacterized metabolites.

Animals↗
PubMed1987

Trp-P-2 is not detectable in cooked meat and fish.

A gas chromatographic-mass spectrometric assay has been developed for the measurement of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in cooked meat and fish. The method employs capillary column gas chromatography, electron capture negative ion chemical ionisation mass spectrometry, a deuterated analogue of Trp-P-2 as internal standard and has a limit of detection of 0.1 ng Trp-P-2/g food. Four different meats and three types of fish, cooked either by frying on an electric hotplate or by charcoal broiling, were analysed for Trp-P-2. No Trp-P-2 was detected in any of the samples. The assay was modified to give an improved limit of detection of 25 pg Trp-P-2/g food and fried ground beef was re-examined. Once again, no Trp-P-2 was detected in this cooked meat.

Animals↗
PubMed1987

The metabolism of N-benzyl-4-substituted anilines: factors influencing in vitro C- and N-oxidation.

N-Benzyl-4-substituted anilines are metabolized by N-debenzylation, aniline-ring hydroxylation and N-oxidation. Factors affecting metabolism of these secondary anilines have been studied in vitro. Enzymes responsible for C- and N-oxidation are present mainly in the liver, but also occur in lung and kidney and are localized in the endoplasmic reticulum. Quantitative and qualitative species differences were observed in microsomal N-benzylaniline metabolism. In hamsters and mice N-debenzylation is the major route of metabolism. In guinea pig and rabbit, ring hydroxylation is the major pathway whereas the rat uses both pathways to equal extents. The hamster has particularly high N-oxidase activity. A sex difference in microsomal N-benzylaniline metabolism is evident in rats but not mice. Kinetic constants for C- and N-oxidation of N-benzylanilines are reported.

Aniline Compounds↗
PubMed1986

Depression of cytochrome P-450 and alterations of protein metabolism in mice treated with the interferon inducer polyriboinosinic acid X polyribocytidylic acid.

Treatment of mice with the interferon inducer polyriboinosinic acid X polyribocytidylic acid [poly(IC)] results in the depression of several hepatic proteins. In this study we examined synthesis and degradation of the proteins of liver cell organelles in mice treated with poly(IC). Effects on synthesis were determined by using [14C]- and L-[3H]leucine incorporation into control and poly(IC)-treated mice, respectively. At selected times after poly(IC) treatment the 3H/14C ratio was established for preparations of nuclei, mitochondria, lysosomes, smooth endoplasmic reticulum, rough endoplasmic reticulum, and 105,000g supernatant (cytosol). Time-dependent alterations in de novo protein synthesis were greatest in lysosomal and rough endoplasmic reticular fractions; both were depressed 9 h after treatment. The effects of poly(IC) on protein degradation were determined with [14C]bicarbonate. Poly(IC) treatment decreased the time required for disappearance of 50% of 14C-labeled protein (t1/2) of smooth and rough endoplasmic reticula. Examination of endoplasmic reticulum marker enzymes showed depression of cytochromes P-450 and b5 from 9 h onward after poly(IC) administration. Tyrosine aminotransferase activity was elevated 6 h after treatment with poly(IC), and then depressed after 9 h. The other organelle marker enzymes were not affected significantly. We conclude that poly(IC) decreases the content of proteins of the hepatic endoplasmic reticulum, including certain cytochrome P-450 isozymes, by decreasing rates of protein synthesis and increasing rates of protein degradation.

Amino Acids↗
PubMed1985

Microsomal N- and C-oxidation of 4-substituted N-benzylanilines.

Using direct specific analytical techniques microsomal metabolism of N-benzyl-4-substituted anilines has been investigated and found to include both N- and C-oxidation. N-Debenzylation was observed with all substrates and species examined. N-Oxidation usually yielded aryl nitrones, although the N-hydroxy derivative of the 4-chloro-substituted substrate was identified in some species. This is the first direct evidence of microsomal N-hydroxylation of a secondary aniline. The metabolic formation of amides from these secondary amines was observed and is believed to be a novel class of metabolite for these substrates.

Aniline Compounds↗
PubMed1985

Depression of the hepatic cytochrome P-450 monooxygenase system by treatment of mice with the antineoplastic agent 5-azacytidine.

The effects of 5-azacytidine (5-AC) administration on the hepatic cytochrome P-450 systems of mice were studied. A single i.p. dose of 5-AC (25 mg/kg) to male Swiss-Webster mice caused about a 50% depression of microsomal cytochromes P-450 and b5 and of ethylmorphine N-demethylase and ethoxycoumarin O-deethylase activities. Depression was greatest 24 h after treatment; by 48 to 72 h, cytochromes and drug metabolism had returned to near control values. Reduced nicotinamide adenine dinucleotide phosphate-cytochrome c reductase activity was also depressed by 5-AC, whereas reduced nicotinamide adenine dinucleotide-cytochrome c reductase was not. Incubation of 5-AC with microsomes produced no effect on drug metabolism. The prolongation of hexobarbital sleeping time by 5-AC showed that drug metabolism is also impaired by 5-AC in vivo. These studies may have important clinical implications when certain drugs are coadministered with 5-AC.

Animals↗
PubMed1984

The application of reversed-phase high-performance liquid chromatography to in vitro drug metabolism studies with N-alkylarylamines.

Analytical procedures have been investigated for the separation, detection, identification and quantitation of some metabolites of N-benzyl-4-substituted anilines. Techniques based on gas-liquid chromatography were investigated and found to be unsatisfactory. By the use of reversed-phase high-performance liquid chromatography with gradient and ion-pairing techniques, methods were devised for the simultaneous analyses of a variety of metabolites. The method involves minimum sample work-up (acetonitrile precipitation) and allows easy and prompt analysis in biological media avoiding undue decomposition of unstable metabolites.

Amines↗
PubMed1981

The in vitro metabolism of N,N-dimethylaniline by guinea pig and rabbit tissue preparations.

A study of the in vitro metabolism of N,N-dimethylaniline using guinea pig and rabbit preparations and GLC techniques has confirmed N-demethylation and N-oxidation and established ring hydroxylation as metabolic routes. Whereas N-demethylation and N-oxidation are major routes of metabolism, ring hydroxylation is a comparatively minor pathway. Like N-demethylase and N-oxidase, the 4-hydroxylase has been shown to be a microsomal enzyme. The major ring hydroxylated product of N,N-dimethylaniline is N,N-dimethyl-4-aminophenol; N-methyl-4-aminophenol is subsequently formed. The apparent Km and V max values for N-demethylation, N-oxidation and 4-hydroxylation, are presented for both the guinea pig and the rabbit.

Aniline Compounds↗