[Photocarcinogenicity of 8-methoxypsoralen and aflatoxin B1].
Explore the source record for details and available documents.
Aflatoxin B1↗
SEARCH · Search PubMed
Results for “Aflatoxin B1”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
[An observation on hepatocarcinogenesis in rat by longterm feeding with minimal doses of aflatoxin B1].
Explore the source record for details and available documents.
Aflatoxin B1↗
Monoclonal antibody-based enzyme linked immunosorbent assay of aflatoxin B1, T-2 toxin, and ochratoxin A in barley.
Aflatoxin B1 (B1), T-2 toxin (T2), and ochratoxin A (OA) were assayed in a single extract from barley grain by using competitive enzyme linked immunosorbent assays (ELISAs) with monoclonal antibodies. B1 and T2 monoclonal antibodies were conjugated to horseradish peroxidase for direct competitive ELISA while an indirect competitive ELISA was used for OA determination. The competitive ELISA detected 0.1 ng/mL of B1, 10 ng/mL of T2, or 1 ng/mL of OA. Acetonitrile-0.5% KCl-6% H2SO4 (89 + 10 + 1) extracts of barley grain either were diluted 1:10 for direct assay or were subjected to a simple liquid-liquid cleanup procedure to concentrate the extract 10:1 before assay. For cleanup, water was added to the acetonitrile extract to partition water-soluble interfering substances, and then the mycotoxins were re-extracted with chloroform. The chloroform extract was evaporated to dryness and redissolved in Tris HCl buffer for ELISA. The mean recoveries from barley spiked with 4-60 ng/g of B1, 50-5000 ng/g of T2, and 5-500 ng/g of OA were, respectively, 93.8, 80.6, and 95.8%. The mean within-assay, inter-assay, and subsample coefficients of variation by ELISA of barley grain colonized with toxigenic fungi were less than 12% for B1 and OA but as high as 17% for T2.
Aflatoxin B1↗
Binding characteristics of bovine serum albumin-aflatoxin B1 to polystyrene microtiter plates: importance of hapten to carrier protein molar ratio.
Binding characteristics of bovine serum albumin-aflatoxin B1 conjugates with high (1:54), medium (2:25) and low (1:9) hapten to carrier molar ratios, to the polystyrene microtiter plates are influenced by the stoichiometry of the hapten (Aflatoxin B1) to the carrier protein (bovine serum albumin). Conjugates with optimal hapten to carrier molar ratios (1:25) showed a better binding capacity to the polystyrene microtiter plate as compared to the conjugates with the high molar ratios in a non-competitive ELISA for aflatoxin B1. Denaturation of the conjugate with molar ratio of 1:54 in order to enhance its binding capacity, however, did not result in any significant improvement.
Aflatoxin B1↗
Phage-displayed peptides that mimic aflatoxin B1 in serological reactivity.
AIMS: To test phage-displayed random peptide libraries as sources of peptides that mimic the binding of aflatoxin B1 to monoclonal antibodies raised against the toxin. METHODS AND RESULTS: For two of the three MAbs tested, clones were obtained by panning, producing phage that bound specifically to MAb 13D1-1D9 (MAb 24; specific for aflatoxins B1 and G1) and MAb 6E12-1E9 (MAb 13; specific for aflatoxins B1, G1 and B2) in ELISA. The amino acid sequences of the binding peptides varied. Those binding to MAb 24 contained the sequence of '...YMD...', and those that bound to MAb 13 contained the dipeptide 'PW'. Mimotope phage was used in a competition ELISA format for assaying aflatoxin concentrations. CONCLUSION: The results show that mimotope preparations are effective substitutes for pure toxin in these ELISA procedures. SIGNIFICANCE AND IMPACT OF THE STUDY: These results should contribute significantly to enhancing the safety and diminishing the costs of aflatoxin assays.
Aflatoxin B1↗
Purification and characterization of a hepatic mitochondrial cytochrome P-450 active in aflatoxin B1 metabolism.
We have previously shown that phenobarbital (PB) increases hepatic mitochondrial cytochrome P-450 (P-450) content and also the ability to metabolize hepatocarcinogen, aflatoxin B1 [Niranjan, B. G., Wilson, N. M., Jefcoate, C. R., & Avadhani, N. G. (1984) J. Biol. Chem. 259, 12495-12501]. In the present study, we have purified a mitochondrial-specific P-450 with an apparent molecular mass of 52 kdaltons (termed P-450mt3) from PB-induced rat liver using a combination of hydrophobic and ion exchange column chromatography procedures. Polyclonal antibody to P-450mt3 failed to cross-react with P-450mt1 and P-450mt2 purified from beta-naphthoflavone- (BNF) induced rat liver mitochondria. Furthermore, P-450mt3 shows an N-terminal amino acid sequence (Ala-Ile-Pro-Ala-Ala-Leu-Arg-Thr-Asp) different from those of both P-450mt1 and P-450mt2, as well as microsomal P-450b. The polyclonal antibody to P-450mt3 cross-reacted with a P-450 of comparable size purified from uninduced mitochondria. These two isoforms, however, showed difference with respect to catalytic properties and amino acid composition. In vitro reconstitution experiments show that P-450mt3 can actively metabolize diverse substrates including (dimethylamino)antipyrine, benzphetamine, and aflatoxin B1 but shows a low vitamin D3 25-hydroxylase activity. The mitochondrial P-450 from uninduced livers, on the other hand, shows relatively high [229 pmol min-1 (nmol of P-450)-1] vitamin D3 25-hydroxylase activity but a considerably lower ability for aflatoxin B1 metabolism and no detectable activity for (dimethylamino)antipyrine and benzphetamine metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)
Aflatoxin B1↗
Aflatoxicol: major aflatoxin B1 metabolite in rat plasma.
Aflatoxicol, a carcinogenic metabolite of the foodborne carcinogen aflatoxin B1 previously known only as a bioreduction product in vitro, was identified as the major aflatoxin metabolite in the plasma of Sprague-Dawley rats, a susceptible species, that had been doses orally or intravenously with aflatoxin B1 labeled with carbon-14. Alfatoxicol, however, was not detected in the plasma of similarly dosed mice and monkeys, which are both resistant to aflatoxin B1-induced cardinogenesis. The formation of aflatoxicol both in vitro and in vivo may be an indicatory of species sensitivity to aflatoxin-induced carcinogenesis and may be useful in the prediction of human susceptibility.
Aflatoxins↗
Inhibition of mitochondrial DNA synthesis by aflatoxin B1 and dimethylnitrosamine.
The acute and subchronic effects of aflatoxin B1 and dimethylnitrosamine (DMN) on in vitro incorporation of thymidine-3H into DNA (mt-DNA) from mouse liver mitochondria were studied after single injection or after one month or three months of weekly injection. Both carcinogens induced 50% decreases in mt-DNA synthesis acutely, with a 50% decrease in synthesis of high molecular weight mt-DNA. Subchronic administration of aflatoxin B1 inhibited mt-DNA synthesis by 54% with elution profiles similar to the controls. DMN showed only a 29% inhibition of mt-DNA synthesis at one month increasing to 55% at three months.
Aflatoxins↗
Aflatoxins, B1, B2, G1, G2 in primary liver cell carcinoma.
Aflatoxin B1, B2, G1, G2 levels were determined in sera of 20 patients with primary liver cell carcinoma (CC). Values of B1 above 0.15 microgram/ml were obtained in sera of three patients. Hepatitis B surface antigen (HBsAg) was detected in only 35% of patients. 50-90% of serum levels were cleared in 24 h in three patients studied. Although it is inconclusive as to the carcinogenic potential of aflatoxins in adult man, foodstuffs should be protected from excessive aflatoxin contamination.
Adult↗
Metabolic activation of aflatoxin B1 by liver tissue from male fischer F344 rats of various ages.
The effect of aging on the ability of the liver to activate chemical procarcinogens was studied using 12-, 18-, and 27-month-old male Fischer F344 rats. The cytochrome P-450 content of the S9 and microsomal fractions of the liver decreased approximately 30% between 12 and 18 months of age. The structural conformation of cytochrome P-450 in microsomes from 12-, 18-, and 27-month-old rats was studied using electron-spin resonance spectroscopy. An age-related decrease in the amount of cytochrome P-450 ferric iron in the liver microsomes was observed. The conversion of the chemical procarcinogen aflatoxin B1 to mutagenic compounds by the S9 and microsomal fractions of liver was measured using the Salmonella typhimurium bioassay. A 40-50% decrease in the metabolic activation of aflatoxin B1 was observed between 12 and 18 months of age. However, the activation of aflatoxin B1 did not change after 18 months of age. The age-related decrease in the activation of aflatoxin B1 by liver appears to be due to a decrease in the metabolic activity of the mixed-function oxidase system.
Aflatoxin B1↗
The major metabolite of aflatoxin B1 in the rat is a glutathione conjugate.
[14C]aflatoxin B1 (AFB1) was injected i.p. into female Wistar rats. Half of the dose was eliminated into the bile mostly as polar non-extractable metabolites. Among these a glutathione conjugate was the main component. The same conjugate was formed when rat liver postmitochondrial supernatant was incubated with AFB1 and [3H]glutathione. The conjugate was purified by ion exchange chromatography, gel-filtration and thin layer chromatography (TLC). It was tentatively identified as 2,3-dihydro-2-(S-glutathionyl)-3-hydroxy aflatoxin B1 (AFB1-GSH-conjugate). This structure was derived mainly from amino acid analysis, ultraviolet spectra and the enzymatic requirements for its formation in in vitro experiments. In the rat this detoxification product of the potentially ultimate reactive AFB1-epoxide constitutes about 10% of the administered dose and thus underlines the quantitative importance of this activating pathway.
Aflatoxins↗
Metabolic activation and bacterial mutagenicity of aflatoxin B1 in two different test systems.
The metabolism of aflatoxin B1 (AFB1) by liver post-mitochondrial supernatant fraction from phenobarbitone treated male albino rats in liquid suspension and soft-agar plate incorporation bacterial mutation assay systems has been studied. The AFB1 concentration used was in the range of those added to bacterial mutagenicity tests with this mycotoxin. Three oxidative metabolites of AFB1 viz the Tris derivative of AFB1 8,9-diol (derived from the 8,9-epoxide), aflatoxin Q1 (AFQ1) and M1 (AFM1) were observed. The metabolite profile and time course of formation were qualitatively similar in both assay systems. The rate and overall formation of metabolites in the soft-agar system was approximately one half that in the liquid suspension system which was reflected in decreased AFB1 induced bacterial mutation in the former system. The AFB1 metabolite profile in these in vitro systems did not mirror completely the reported in vivo profile seen in the rat, as aflatoxin P1 (AFP1) and a glutathione conjugate were not detected. No evidence was found for a prolongation of metabolism in the soft-agar system.
Aflatoxin B1↗
Functional impairment of rat Kupffer cells induced by aflatoxin B1 and its metabolites.
Contamination of food with mycotoxins is a major health problem. Impairment of several immune functions has been repeatedly reported in animals fed with contaminated fodder. Since the liver is a major target of toxicity by aflatoxins, the effects of aflatoxins B1, and its hepatic metabolites Q1 and M1 on Kupffer cell function was investigated in vitro. Aflatoxin B1 induced significant (P < 0.05) inhibition of phagocytosis, intracellular killing of Candida albicans, and intrinsic anti-Herpes virus activity at concentrations as low as 0.01 pg ml-1. Aflatoxin Q1 and M1 had similar effects on phagocytosis and microbicidal activity, but were two- to ten-fold less potent than aflatoxin B1.
Aflatoxin B1↗
[Photolysis of aflatoxin B1 in the presence of pyridine N-oxide].
Aflatoxin B1 (AFB1) photolysis in presence of pyridine N-oxide was studied. It was established that AFB1 ethanol solution irradiated with UV-light lambda = 362 nm demonstrated an increase of the fluorescence as a result of appearance of AFB1 product which was formed by pyridine N-oxide oxygen binding to AFB1 molecules in position 2,3.
Aflatoxin B1↗
Rapid thin layer chromatographic method for determining aflatoxin B1, ochratoxin A, and zearalenone in corn.
A multimycotoxin thin layer chromatographic method is described for the analysis of corn. Aflatoxins are extracted from the samples with acetonitrile-water, and sodium bicarbonate is added to separate the acidic ochratoxin from zearalenone and aflatoxin B1. After chloroform extraction, 1N NaOH is added to separate zearalenone and aflatoxin B1. The separated mycotoxins are spotted on TLC plates, which are then examined under ultraviolet light. The following recoveries (%) were obtained for corn samples: aflatoxin B1 71, ochratoxin A 87, and zearalenone 85. The limits of detection for the respective mycotoxins were 2, 40, and 200 ppb.
Aflatoxins↗
Carcinogen-nucleic acid interactions: equilibrium binding studies of aflatoxins B1 and B2 with DNA and the oligodeoxynucleotide d(ATGCAT)2.
Equilibrium binding is believed to play an important role in directing the subsequent covalent attachment of many carcinogens to DNA. We have utilized UV spectroscopy to examine the non-covalent interactions of aflatoxin B1 and B2 with calf thymus DNA, poly(dAdT):poly(dAdT), and poly(dGdC):poly(dGdC), and have utilized NMR spectroscopy to examine non-covalent interactions of aflatoxin B2 with the oligodeoxynucleotide d(ATGCAT)2. UV-VIS binding isotherms suggest a greater binding affinity for calf thymus DNA and poly(dAdT):poly(dAdT) than for poly(dGdC):poly(dGdC). Scatchard analysis of aflatoxin B1 binding to calf thymus DNA in 0.1 M NaCl buffer indicates that binding of the carcinogen at levels of bound aflatoxin less than 1 carcinogen per 200 base pairs occurs with positive cooperativity. The cooperative binding effect is dependent on the ionic strength of the medium; when the NaCl concentration is reduced to 0.01 M, positive cooperativity is observed at carcinogen levels less than 1 carcinogen per 500 base pairs. The Scatchard data may be fit using a "two-site" binding model [L.S. Rosenberg, M.J. Carvlin, and T.R. Krugh, Biochemistry 25, 1002-1008 (1986)]. This model assumes two independent sets of binding sites on the DNA lattice, one a high affinity site which binds the carcinogen with positive cooperativity, the second consisting of lower affinity binding sites to which non-specific binding occurs. NMR analysis of aflatoxin B2 binding to d(ATGCAT)2 indicates that the aflatoxin B2/oligodeoxynucleotide complex is in fast exchange on the NMR time scale. Upfield chemical shifts of 0.1-0.5 ppm are observed for the aflatoxin B2 4-OCH3, H5, and H6a protons. Much smaller chemical shift changes (less than or equal to 0.06 ppm) are observed for the oligodeoxynucleotide protons. The greatest effect for the oligodeoxynucleotide protons is observed for the adenine H2 protons, located in the minor groove. Nonselective T1 experiments demonstrate a 15-25% decrease in the relaxation time for the adenine H2 protons when aflatoxin B2 is added to the solution. This result suggests that aflatoxin B2 protons in the bound state may be in close proximity to these protons, providing a source of dipolar relaxation. Further experiments are in progress to probe the nature of the aflatoxin B1 and B2 complexes with polymeric DNA and oligodeoxynucleotides, and to establish the relationship between the non-covalent DNA-carcinogen complexes observed in these experiments, and covalent aflatoxin B1-guanine N7 DNA adducts.
Aflatoxin B1↗
Evaluation of particulate air samplers for airborne aflatoxin B1.
Five air samplers (Millipore, all-glass impinger, centrifugal, Andersen, and absorbent cotton) were evaluated for their ability to collect airborne grain particles contaminated with aflatoxin B1. Corn dust containing 100 micrograms aflatoxin B1/g was aerosolized within a containment system. Each device sampled 100 I air, thus exchanging the air in the chamber two times. Aflatoxin B1 was extracted from all sampling matrices and was detected and quantitated with thin-layer chromatography and scanning fluorodensitometry. The highest efficiency was obtained with the Millipore sampler, while the efficiencies of the centrifugal and the cotton samplers were almost identical. Efficiency of an Andersen was less, with no toxin recovered from an all-glass impinger. Measurement of particle size was accomplished with the Andersen sampler.
Aerosols↗
Quantitative tritium exchange of [3H] aflatoxin B1 during penetration through isolated human skin.
Tritium labelled aflatoxin B1 ([G-3H]AFB1) underwent an almost total tritium exchange with water during penetration through isolated human skin. The process was not enzymatic and the site of exchange appeared to be within the epidermis. The mechanism which mediated this extensive exchange was not determined. However, the tritium in [G-3H]AFB1 was found to be very susceptible to chemical conditions which favored carbanion formation at the alpha-carbon of the cyclopentenone ring. The relative effectiveness of the various solvents in mediating the loss of the tritium label was 1 N3NaOH much greater than methanol greater than 1 N HCl greater than water. This work serves as a warning that [G-3H]AFB1 can easily undergo significant changes in specific activity in biological tissues and under relatively mild experimental conditions. It is possible that conditions within the skin favor carbanion formation.
Aflatoxin B1↗