SEARCH · PubMed Health

Results for “Aflatoxin B1”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources

PubMed1979

Conditions for induction of bacteriophage from lysogenic Bacillus megaterium with aflatoxin B1.

The present study was conducted to determine whether or not aflatoxin B1 was an effective inducing agent for lysogenic bacteria and to characterize some of the parameters involved in induction. A lysogenic strain of Bacillus megaterium (NRRL-B-3695) and an indicator strain of this species (NRRL-B-3694) were used. Cultures of the lysogenic strain were incubated for various periods of time in the presence of aflatoxin B1. Plaque-forming units as well as colony-forming units were then determined. Results of the present study indicated that bacteriophage lysogenizing B. megaterium could be induced with aflatoxin B1. The optimum concentration for induction was 25 micrograms of toxin per ml of early-log-phase culture. Evidence suggested that: (i) higher concentrations of aflatoxin B1 formed hydrophobic complexes which would not efficiently induce B. megaterium; (ii) the toxic effect of aflatoxin B1 severely limited the number of cells which could be induced prior to killing action of the toxin; and (iii) concentrations less than 25 micrograms of aflatoxin B1 per ml were not efficient inducers of bacteriophage production nor did they demonstrate the toxic effect observed at higher concentrations.

Aflatoxins↗

PubMed1986

Clinical and pathologic changes in acute bovine aflatoxicosis: rumen motility and tissue and fluid concentrations of aflatoxins B1 and M1.

Effects of aflatoxin on bovine rumen motility were determined by radiotelemetric techniques. Aflatoxin altered amplitude and/or frequency of rumen contractions in steers given dosages of 0.2, 0.4, 0.6, or 0.8 mg of aflatoxin/kg of body weight. Effects of aflatoxin on rumen motility were dose dependent. An increase in elimination time of aflatoxin from rumen contents was observed in steers given the aflatoxin dosages of 0.4 to 0.8 mg/kg. The increase in elimination time of this toxin facilitates diagnostic capabilities for detecting bovine aflatoxicosis by obtaining rumen contents for analysis for aflatoxin. Aflatoxin M1 was detected in rumen contents from steers at 2 hours after aflatoxin was administered. Thus, intraruminal metabolism of aflatoxin B1 to M1 may occur.

Acute Disease↗

PubMed1977

Species comparison of in vitro metabolism of aflatoxin B1.

The metabolism of [14C]aflatoxin B1 by 9000 X g supernatant fraction of livers of duck, rat, mouse, monkey, and humans was compared by incubating the compound and liver fractions in the presence of cofactors and air for 30 min. The incubation medium was extracted with chloroform, and the soluble metabolites were separated on thinlayer plates and quantified; radioactivity remaining in the aqueous phase was determined in order to quantify metabolism to water-soluble derivatives. Duck, monkey, and human livers were most active in total conversion, each metabolizing approximately 80% of available substrate in 30 min. Rat and mouse livers had lower activites, metabolizing 15 to 20%. Duck liver produced mainly (60%) chloroform-insoluble derivatives, but all other species produced larger quantities of chloroform-soluble than insoluble metabolites. Aflatoxin Q1 was the principle chloroform-soluble metabolite produced by monkey, human, and rat liver, whereas duck liver produced mainly aflatoxicol in that fraction. Aflatoxin P1 was produced by monkey, human, and mouse liver, but not by duck and rat. The chromatographic region containing M1 and B2alpha contained low levels of radioactivity in all species except human. No consistent pattern of metabolism emerged which could be correlated with species differences in response to aflatoxin B1 toxicity or carcinogenicity.

Adult↗

PubMed1991

Metabolism of aflatoxin B1 by Petroselinum crispum (parsley).

On administration of aflatoxin B1 to whole parsley (Petroselinum crispum) plants, a derivative was formed, which was shown to be aflatoxicol by its chromatographic properties and mass spectrometry. Optimum conditions for the production of the derivative was on the second day after administration of the toxin to the plants, which were 90 days old after germination. Cell-free preparations of parsley were found not to produce aflatoxicol A from added aflatoxin B1; instead they formed two new derivatives, which from chromatographic properties, were shown to be more polar than either aflatoxin B1 or aflatoxicol A.

Aflatoxin B1↗

PubMed1980

Aflatoxin B1 in hepatocellular carcinoma.

The aflatoxin B1 content of liver tissue was measured in patients who died from chronic liver disease [hepatocellular carcinoma (HCG) (5), schistosomal liver fibrosis (1), chronic aggressive hepatitis (1)] and compared with fifteen controls who died of motor traffic accidents (10), drowning (1), malnutrition (1), idiopathic cardiomegaly (1) and lung infection (2). Significant levels of aflatoxin B1 were found in hepatocellular carcinoma patients who were also hepatitis B surface antigen (HBsAg) negative. Histology showed HCC arising in macronodular cirrhosis.

Adult↗

PubMed1988

Effects of various inducers on the activities of cytochrome P-450-mixed function oxidases and aflatoxin B1 activation in microsomes of hamster livers.

The effects of various inducers on the activities of drug-metabolizing enzymes including aflatoxin B1 activation were studied in Syrian golden hamsters. Activity for aflatoxin B1 was determined by aflatoxin B1-DNA adducts formation. The treatments of hamsters with 3-methylcholanthrene, alpha-naphthoflavone and benzo(a)pyrene elevated markedly the activity for aflatoxin B1 by 2460, 1380 and 450%, respectively. Phenobarbital induced slightly and isosafrole and ethanol did not induce the activity for aflatoxin B1. Pregnenolone-16 alpha-carbonitrile decreased aflatoxin B1 activation to 51% of that of the non-treated animals. These results were in good accordance with the induction rate of a form of cytochrome P-450 (P-450AFB) which has potent activity to aflatoxin B1. Characteristics in the induction of mixed function oxidases of hamsters by these inducers, especially in respect to benzo(a) pyrene metabolizing enzyme, seemed to differ from those of rats. These results suggest that the activity for aflatoxin B1 in hamster is inducible by 3-methylcholanthrene-type inducers and that hamster is a suitable animals model to study the mechanism of aflatoxin B1-hepatocarcinogenesis.

Aflatoxin B1↗

PubMedDate not supplied

[Incidence of chromosome aberrations in the bone marrow of monkeys and their progeny after exposure to aflatoxin B1].

A mutagenic effect of aflatoxin B1 (AFB1) was studied in somatic cells of primates. It is shown that AFB1 elevates the chromosome aberration frequency in bone marrow cells of two monkey species: Macaca mulatta and Papio hamadryas. Genome mutations were found in these experimental primates simultaneously with chromosome aberrations. The AFB1-induced chromosome aberrations were revealed at least during two years of the study. The fact of the chromosome aberration frequency increase was established in Macaca babies born from females who received AFB1 in pregnancy.

Aflatoxin B1↗

PubMed1977

Structural identification of the major DNA adduct formed by aflatoxin B1 in vitro.

The covalent binding of the hepatocarcinogen aflatoxin B1 by rat liver microsomes to calf thymus DNA resulted in a binding level equal to one aflatoxin residue per 60 DNA nucleotides. An aflatoxin derivative-guanine adduct was efficiently liberated from DNA with formic acid. Analytical reversed-phase high-pressure liquid chromatography of the DNA hydrolysate revealed that approximately 90% of the carcinogen bound to DNA could be accounted for as a single component. Preparative high-pressure liquid chromatography was used to isolate sufficient quantities of the adduct for structural analysis from large quantities (340 mg) of DNA. A combination of spectral and chemical data indicates that the major product of the interaction of metabolically activated aflatoxin B1 and DNA is 2,3-dihydro-2-(N7-guanyl)-3-hydroxyaflatoxin B1 with the guanine and hydroxyl functions possessing a trans configuration. The structural data support the hypothesis that the putative 2,3-oxide of aflatoxin B1 is quantitatively important as an intermediate in the binding of aflatoxin B1 to nucleic acids.

Aflatoxins↗

PubMed1990

Comparative action of aflatoxin B1 in mammalian airway epithelium.

Aflatoxin B1 (AFB1) is thought to be an occupational risk factor for airway carcinogenesis where exposure to AFB1-laden grain dusts is common. Since activation of AFB1 is catalyzed by cytochromes P-450 associated with the smooth endoplasmic reticulum, we compared the response to AFB1 in cultured tracheal epithelium from species with abundant (rabbit and hamster) and scarce (rat and monkey) distributions of smooth endoplasmic reticulum in nonciliated tracheal epithelial cells. Explants from each species, incubated in medium containing 0.5 microM [14C]-AFB1 for selected intervals up to 24 h, were compared on the basis of binding of [14C]-AFB1 to tracheal DNA, amount and type of AFB1 metabolites in the medium, ultrastructurally determined population densities of epithelial cells, and distribution of bound material in epithelium as determined by autoradiographic grain densities. Cultures derived from rabbits were most active in metabolic conversion and formation of AFB1-DNA adducts, followed by those from hamsters, rats, and monkeys. Rabbit tracheal epithelium formed a significantly greater proportion of glutathione conjugates, while that from hamster formed a greater amount of AFB1-dihydrodiol, compared to rats and monkeys. The monkey formed significantly greater proportions of aflatoxin Q1 and the rabbit more aflatoxicol, compared to other species. There was selective degeneration and accumulation of labeled material in nonciliated cells in both rabbits and hamsters but not in rats or monkeys. Explants from rabbit tracheas were much more susceptible to cytotoxic injury and had higher autoradiographic grain densities than explants from hamsters. We conclude that the presence of smooth endoplasmic reticulum-containing nonciliated epithelial cells is qualitatively associated with the activation and toxicity of AFB1.

Aflatoxin B1↗

PubMed1987

Studies of immune function of CD-1 mice exposed to aflatoxin B1.

The immunotoxic potential of aflatoxin B1 (AFB1), a secondary metabolite of Aspergillus flavus and a known animal hepatocarcinogen, was evaluated in CD-1 mice. Male mice received 0, 0.03, 0.145 or 0.70 mg/kg of AFB1 orally every other day for 2 weeks in a corn oil:ethanol vehicle. Splenic lymphocytes were cultured in the presence of lipopolysaccharide (LPS), phytohemagglutinin (PHA), or pokeweed mitogen (PWM). A dose-related inhibition of [3H]thymidine uptake in lymphocyte cultures, with or without the above mitogens, was observed after 2 weeks of AFB1 exposure. Synthesis of DNA was decreased in mixed lymphocyte cultures. Primary antibody production by splenic cells, from animals challenged with a T-dependent antigen (sheep red blood cells), was affected by AFB1. No effects were observed, however, when animals were challenged with a T-independent antigen (LPS). A dose-related suppression of a delayed-type hypersensitivity reaction to keyhole limpet hemocyanin was observed. The results suggested that AFB1 was immunotoxic in CD-1 mice.

Aflatoxin B1↗

PubMed1991

Analysis of ras gene mutations in rainbow trout liver tumors initiated by aflatoxin B1.

The suspect human hepatocarcinogen aflatoxin B1 (AFB1) is a well-known potent initiator of hepatic tumors in rainbow trout (Oncorhynchus mykiss). Both hepatocellular carcinomas and mixed hepatocellular/cholangiocellular carcinomas are induced by AFB1 in trout, with the mixed form predominating. We previously isolated two c-ras genes from trout liver cDNA, and in the present study we analyzed DNA from 14 AFB1-induced trout liver tumors for point mutations in exon 1 of both genes. Using the polymerase chain reaction (PCR) and oligonucleotide hybridization methods, a high proportion (10/14) of the AFB1-initiated tumor DNAs showed evidence of activating point mutations in the trout c-Ki-ras gene. Of the 10 mutant ras genotypes, seven were codon 12 GGA----GTA transversions, two were codon 13 GGT----GTT transversions, and one was codon 12 GGA----AGA transition. Nucleotide sequence analysis of cloned PCR products from four of these tumor DNAs provided definitive evidence for two codon 12 GGA----GTA mutations, one codon 12 GGA----AGA mutation, and one codon 13 GGT----GTT mutation, in complete agreement with the oligonucleotide hybridization results. No mutations were detected in exon 1 of a second trout ras gene also expressed in liver, nor in DNA from control livers. This is the first report of experimentally induced ras gene point mutations in a lower vertebrate fish model. The results indicate that the hepatocarcinogen AFB1 induces c-Ki-ras gene mutations in trout similar to those in rat liver tumors.

Adenoma, Bile Duct↗

PubMed1987

Isolation and characterization of the major serum albumin adduct formed by aflatoxin B1 in vivo in rats.

Aflatoxin B1 (AFB1) was shown to react primarily with one or more lysine residues in serum albumin (SA), accounting for more than half of the total binding to this protein. The radioactivity associated with SA following administration of [U-14C]AFB1 to rats was cleared with a half-life of 2.5 days, which is not significantly different from the half-life of unmodified albumin in the normal rat. The product isolated from a Pronase digest of in vivo-modified SA was identical by chromatographic retention time and u.v. and mass spectroscopy to the synthetic product obtained by the acylase-catalyzed deacetylation of the reaction product of N alpha-acetyl-L-lysine with 8,9-dihydro-8,9-dibromo-AFB1. The latter was characterized by u.v., fluorescence, 500 MHz 1H-n.m.r. and fast atom bombardment mass spectrometry. The spectral data strongly support a structure in which the terminal dihydrofuran ring of AFB1 has been converted to a pyrrolinone ring. It is proposed that the initial adduct is formed by condensation of the dialdehyde tautomer of 8,9-dihydro-8,9-dihydroxy-AFB1, with the epsilon-amino group of lysine, to form a Schiff base, and that the Schiff base undergoes an Amadori rearrangement to an alpha-amino ketone. The pyrrolinone ring is formed by condensation of the amino group with the remaining aldehyde to yield the final product. The purified product was relatively stable but was shown to decompose significantly under the conditions used to isolate it from modified SA.

Aflatoxin B1↗

PubMed1991

Comparative biotransformation of aflatoxin B1 in mammalian airway epithelium.

Aflatoxin B1 (AFB1) appears to be a risk factor for upper respiratory tumors in individuals occupationally exposed to AFB1-contaminated grain dusts. To study the potential effects of this mycotoxin in the upper airways, the metabolism of AFB1 was investigated in tracheal cultures and purified tracheal microsomes from rabbit, hamster and rat. These species differ in the proportion of P450-containing non-ciliated epithelial (NC) cells in the upper airway (17, 41, 0% respectively). Cultures from the rabbit produced the highest level of the AFB1 metabolites AFB1-dihydrodiol (AFB1-diol), GSH-AFB1, AFM1, AFB2a and the highest tracheal microsomal pentoxyresorufin-O-dealkylase (PROD) activity (an indicator of that P450 activity which activates AFB1) and greater cytosolic GSH-transferase activity compared to hamster and rat. Tracheal microsomal epoxide hydrolase activity, AFB1-diol production, cytochrome P450 content, P450 reductase and ethoxyresorufin-O-dealkylase (EROD) activity (an indicator of AFB1 detoxification) were highest in the hamster. Although the overall metabolic activity in rat tracheal epithelium was low, PROD-related activity appeared to predominate. Conjugation with GSH was the major detoxification pathway in rabbit and rat upper airways, although levels of AFB1-GSH and activities of glutathione transferase were significantly lower in the rat than in the rabbit and hamster. Hydrolysis of the putative AFB1-2,3-epoxide via epoxide hydrolase appeared to be the major AFB1 detoxification pathway in hamster tracheal epithelium as indicted by corresponding high tracheal microsomal AFB1-diol production and EH activity compared to rabbit and rat. Glucuronide and sulfate conjugates of AFB1 and its metabolites were formed in tracheal explant cultures from these three species, although amounts formed were minor. These results indicate that rabbit upper airway epithelium contains metabolic activity primarily involved in AFB1 activation, whereas AFB1 detoxification pathways predominante in hamster. Furthermore, the characteristics of carcinogen metabolism are not predictable based solely on airway morphology.

Aflatoxin B1↗

PubMed2001

Co-occurrence of aflatoxins B1, B2, G1, G2, zearalenone and fumonisin B1 in Brazilian corn.

Two hundred and fourteen unprocessed corn samples (1997-98 harvest), collected at wholesale markets in different regions in Brazil, were surveyed for the occurrence of mycotoxins. The samples were analysed for aflatoxins B1, B2, G1, G2, zearalenone and fumonisin B1 using in-house validated methods. The occurrence of aflatoxin B1, zearalenone and fumonisin B1 was found in 38.3, 30.4 and 99.1% of the samples, respectively. Aflatoxin B1, zearalenone and fumonisin B1 contamination levels varied from 0.2 to 129, 36.8 to 719, and 200 to 6100 microg/kg, respectively. The co-occurrence of the two carcinogenic mycotoxins aflatoxin B1 and fumonisin B1 was observed in 100% of the aflatoxin-contaminated samples (82 samples). Co-occurrences of aflatoxin B1: zearalenone: fumonisin B1 and aflatoxin B1: aflatoxin B2: fumonisin B1 were found in 18 and 43 samples, respectively.

Aflatoxin B1↗

PubMedDate not supplied

Distribution and clearance of aflatoxins B1 and M1 in turkeys fed diets containing 50 or 150 ppb aflatoxin from naturally contaminated corn.

Turkeys were fed a diet containing 50 or 150 ppb aflatoxin for 11 or 13 weeks or fed these diets for 11 weeks and then the control diet for 1 or 2 weeks. Aflatoxins B1 and M1 were found in liver, kidney, gizzard, and feces of poults fed the diets for 11 or 13 weeks. However, in turkeys fed the control diet for 1 or 2 weeks after the 11-week feeding trial, no residues of aflatoxin were found in the feces or tissues, except for some aflatoxin B1 remaining in detectable amounts in the gizzard. No mortality was attributable to aflatoxin, and there were no notable differences among groups in weight gains, feed conversion, or histopathologic changes in selected tissues. The response to a second inoculation with sheep erythrocytes was significantly lower in poults given dietary aflatoxin than in controls. This reduced antibody response was not observed when a Pasteurella multocida vaccine was administered.

Aflatoxin B1↗

PubMed1988

Hepatocellular uptake of aflatoxin B1 by non-ionic diffusion. Inhibition of bile acid transport by interference with membrane lipids.

Aflatoxin B1 permeates isolated rat hepatocytes by non-ionic diffusion. Its uptake is neither saturable nor influenced by metabolic energy and not inhibited by treatment of cells with proteases. The initial rate of aflatoxin B1 uptake measured at 7 degrees C is between 40 and 50% compared to that at 37 degrees C. However, after an incubation period of 7 minutes identical equilibrium uptake is reached at both temperatures. The apparent activation energies, calculated for aflatoxin B1 uptake by Arrhenius diagrams ranged between 1.69 and 4.5 kcal/mol. A Q10 value of 1.34 was calculated for a temperature interval of 7-17 degrees C but decreased to 1.05 for the interval of 27-37 degrees C. Liposomes or lipoproteins added to the cell suspension inhibited the aflatoxin B1 uptake into hepatocytes. Liposomes mainly composed of unsaturated fatty acids bind twice as much aflatoxin B1 as those composed of saturated ones, indicating that the lipophilicity of the mycotoxin is crucial in the determination of its uptake into liver cells. At concentrations above 5 micrograms/ml, aflatoxin B1 inhibited the carrier-mediated uptake of cholic acid and of phalloidin into hepatocytes. This effect was reversible and abolished by washing the cells after preincubation with aflatoxin. In concentrations below 5 micrograms/ml the uptake of phallotoxin and cholic acid was however stimulated by 15-25%. These results indicate, that a carrier-mediated uptake into hepatocytes via the multispecific bile salt transporter is not responsible for the organoselective clearance of aflatoxins by the liver. On the other hand, the cholestatic effect of aflatoxin B1 results at least partially from the inhibition of the multispecific bile acid transport system. This inhibition may arise from affinity of aflatoxins to lipid domains of the cell membrane.

Aflatoxin B1↗

PubMed1987

Human aflatoxin B1 metabolism: an investigation of the importance of aflatoxin Q1 as a metabolite of hepatic post-mitochondrial fraction.

The metabolism of aflatoxin B1 by the post-mitochondrial fraction of human autopsy or biopsy liver and monkey necropsy liver was investigated. Aflatoxin Q1, a hydroxy metabolite of B1, was produced by 18 of 22 human liver samples and by 5 of 7 species of non-human primates investigated. Human specimens from both sexes, ages 20-80 years, with a variety of hepatic histological and historical influences produced this metabolite. Aflatoxin Q1 was of variable quantitative importance. Yields seldom exceeded 10% of initial B1. However, based upon its persistent formation in vitro, these studies identify the need to clarify the role of Q1 in aflatoxin epidemiology.

Adult↗

PubMed1976

Interaction of aflatoxin B1 with some biologically important substances.

The interaction of aflatoxin B1 with a number of biologically important substances has been investigated by spectrophotometric and fluorimetric techniques. The ultra-violet absorption of tryptophan, adenosine, RNA and DNA were altered by the addition of aflatoxin B1. Some amino-acids, purine and pyrimidine derivatives, bovine-serum albumin and DNA quenched the fluorescence of aflatoxin B1. Fluorescence polarization data suggested that the interaction of aflatoxin B1 with bovine-serum albumin was stronger than that with DNA.

Adenosine↗