Hepato- and cardiotoxicity of Fusarium verticillioides (F. moniliforme) isolates from Southern African maize

Molecular and epigenetic modes of Fumonisin B1 mediated toxicity and carcinogenesis and detoxification strategies

Fumonisin B₁ (FB₁) is a natural contaminant of agricultural commodities that has displayed a myriad of toxicities in animals. Moreover, it is known to be a hepatorenal carcinogen in rodents and may be associated with oesophageal and hepatocellular carcinomas in humans. The most well elucidated mode of FB₁-mediated toxicity is its disruption of sphingolipid metabolism; however, enhanced oxidative stress, endoplasmic reticulum stress, autophagy, and alterations in immune response may also play a role in its toxicity and carcinogenicity. Alterations to the host epigenome may impact on the toxic and carcinogenic response to FB₁. Seeing that the contamination of FB₁ in food poses a considerable risk to human and animal health, a great deal of research has focused on new methods to prevent and attenuate FB₁-induced toxic consequences. The focus of the present review is on the molecular and epigenetic interactions of FB₁ as well as recent research involving FB₁ detoxification.

Sphingolipid Effects on the Plasma Membrane Produced by Addition of Fumonisin B1 to Maize Embryos

Fumonisin B1 is a mycotoxin produced by Fusarium verticillioides that modifies the membrane properties from animal cells and inhibits complex sphingolipids synthesis through the inhibition of ceramide synthase. The aim of this work was to determine the effect of Fumonisin B1 on the plant plasma membrane when the mycotoxin was added to germinating maize embryos. Fumonisin B1 addition to the embryos diminished plasma membrane fluidity, increased electrolyte leakage, caused a 7-fold increase of sphinganine and a small decrease in glucosylceramide in the plasma membrane, without affecting phytosphingosine levels or fatty acid composition. A 20%-30% inhibition of the plasma membrane H+-ATPase activity was observed when embryos were germinated in the presence of the mycotoxin. Such inhibition was only associated to the decrease in glucosylceramide and the addition of exogenous ceramide to the embryos relieved the inhibition of Fumonisin B1. These results indicate that exposure of the maize embryos for 24 h to Fumonisin B1 allowed the mycotoxin to target ceramide synthase at the endoplasmic reticulum, eliciting an imbalance of endogenous sphingolipids. The latter disrupted membrane properties and inhibited the plasma membrane H+-ATPase activity. Altogether, these results illustrate the mode of action of the pathogen and a plant defense strategy.

Preliminary Study on the Use of Chitosan as an Eco-Friendly Alternative to Control Fusarium Growth and Mycotoxin Production on Maize and Wheat

The objectives of the present study were to determine the combined effects of chitosan and water activity (a_W) on growth and mycotoxin production in situ on the two most important Fusarium species (F. proliferatum and F. verticillioides) present on maize, and on F. graminearum, the main pathogen causing Fusarium head blight on wheat. Results showed that low-molecular-weight chitosan with more than 70% deacetylation at the lowest dose used (0.5 mg/g) was able to reduce deoxynivalenol (DON) and fumonisin (FBs) production on irradiated maize and wheat grains. Growth rates of F. graminearum also decreased at the lowest chitosan dose used (0.5 mg/g), while F. verticillioides and F. proliferatum growth rates were reduced at 0.98 a_W at the highest chitosan dose used (2 mg/g). Since mycotoxins are unavoidable contaminants in food and feed chains, their presence needs to be reduced in order to minimize their effects on human and animal health and to diminish the annual market loss through rejected maize and wheat; in this scenario, pre- and post-harvest use of chitosan could be an important alternative.

Fusarium verticillioides: Advancements in Understanding the Toxicity, Virulence, and Niche Adaptations of a Model Mycotoxigenic Pathogen of Maize

The importance of understanding the biology of the mycotoxigenic fungus Fusarium verticillioides and its various microbial and plant host interactions is critical given its threat to maize, one of the world's most valuable food crops. Disease outbreaks and mycotoxin contamination of grain threaten economic returns and have grave implications for human and animal health and food security. Furthermore, F. verticillioides is a member of a genus of significant phytopathogens and, thus, data regarding its host association, biosynthesis of secondary metabolites, and other metabolic (degradative) capabilities are consequential to both basic and applied research efforts across multiple pathosystems. Notorious among its secondary metabolites are the fumonisin mycotoxins, which cause severe animal diseases and are implicated in human disease. Additionally, studies of these mycotoxins have led to new understandings of F. verticillioides plant pathogenicity and provide tools for research into cellular processes and host-pathogen interaction strategies. This review presents current knowledge regarding several significant lines of F. verticillioides research, including facets of toxin production, virulence, and novel fitness strategies exhibited by this fungus across rhizosphere and plant environments.

Possible Role of Phosphatidylcholine and Sphingomyelin on Fumonisin B1-mediated Toxicity

A major corn-related mycotoxin, fumonisin B1 (FB1), continues to attract attention of researchers as well as risk-assessors due to the diverse toxicological characteristics, including distinct target tissues in different animal species and opposite susceptibility in males and females in mice and rats. More than thirty years passed since the structure identification as a sphingoid-like chemical, but the causal mechanism of the toxicity remains obscure in spites of extensive studies. Considerable amounts of knowledge have been accumulated on the biochemical/toxicological actions of FB1, but the influence on lipid dynamics and mobilization in the body has not been focused well in relation to the FB1-mediated toxicity. Considerable influences of this toxin on mobilization of sphingolipids and phospholipids and also on adaptive changes in their compositions in tissues are implicated from recent studies on FB1-interacting ceramide synthases. Accumulated patho-physiological data also suggest a possible role of hepatic phospholipid on FB1-mediated toxicity. Thus, a mechanism of FB1-mediated toxicity is discussed in relation to the mobilization of phospholipids and sphingolipids in the body in this context.

Health Risks Associated with Exposure to Filamentous Fungi

Filamentous fungi occur widely in the environment, contaminating soil, air, food and other substrates. Due to their wide distribution, they have medical and economic implications. Regardless of their use as a source of antibiotics, vitamins and raw materials for various industrially important chemicals, most fungi and filamentous fungi produce metabolites associated with a range of health risks, both in humans and in animals. The association of filamentous fungi and their metabolites to different negative health conditions in humans and animals, has contributed to the importance of investigating different health risks induced by this family of heterotrophs. This review aims to discuss health risks associated with commonly occurring filamentous fungal species which belong to genera Aspergillus, Penicillium and Fusarium, as well as evaluating their pathogenicity and mycotoxic properties.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging of ochratoxin A and fumonisins in mold-infected food

RATIONALE

Mycotoxins are toxic secondary metabolites produced by various fungi. Their distribution within contaminated material is of high interest to obtain insight into infection mechanisms and the possibility of reducing contamination during food processing.

METHODS

Various vegetable foodstuffs were infected with fungi of the genera Fusarium and Aspergillus. The localization of the produced mycotoxins was studied by matrix-assisted laser desorption/ionization time-of flight mass spectrometry imaging (MALDI-MSI) of cryosections obtained from infected material. The results were confirmed by high-performance liquid chromatography/electrospray ionization triple quadrupole mass spectrometry (HPLC/MS/MS).

RESULTS

The mycotoxins ochratoxin A (OTA) and fumonisins of the B- and C-series (FB₁ , FB₂ , FB₃ , FB₄ , FC₁ , FC_2/3 , and FC₄ ) as well as partially hydrolyzed fumonisins (pHFB₁ , pHFB₂ , pHFB₃ , pHFC₁ , and pHFC_2/3 ) could successfully be detected by MALDI-MSI in mold-infested foodstuffs. The toxins are distributed differently in the material: OTA is co-localized with visible fungal spoilage while fumonisins could be detected throughout the whole sample.

CONCLUSIONS

This work shows the applicability of MALDI-MSI to mycotoxin analysis. It has been demonstrated that the analyzed mycotoxins are differently distributed within moldy foodstuffs. These findings show the potential of MALDI-MSI for the localization of these hazardous compounds in various plant tissues. Copyright © 2016 John Wiley & Sons, Ltd.

Mycotoxicological research in South Africa 1910-2011

The British mycologist, I.B. Pole-Evans, was appointed as the first South African government mycologist in 1905 following the Anglo-Boer War (1899-1902). The Onderstepoort Veterinary Research Institute was founded in 1908 with the Swiss veterinarian, Arnold Theiler, as the first director. Thus, the stage was set for the commencement of mycotoxicological research when the Union of South Africa came into being in 1910. The first accounts of this pioneering research appeared in the 'Seventh and eight reports of the Director of Veterinary Research, Union of South Africa. 1918' in which D.T. Mitchell reported on the experimental reproduction of the neurotoxic syndrome, diplodiosis, in cattle with pure cultures of Stenocarpella maydis (= Diplodia zea) isolated by P.A. Van der Bijl and grown on sterile maize kernels. This is the first report of the experimental reproduction of a veterinary mycotoxicosis with a pure culture of a fungus in South Africa and possibly in the world. This seminal research was followed by a great deal of multidisciplinary research on veterinary mycotoxicoses as well as human syndromes in which fungal toxins are suspected to be involved, taxonomy of mycotoxigenic fungi and chemistry of mycotoxins in South Africa. The mycotoxicoses studied in South Africa include the following (more or less in chronological order): diplodiosis, Paspalum staggers, aflatoxicosis, human hepatocellular carcinoma, ochratoxicosis, lupinosis, facial eczema, tremorgenic mycotoxicosis, hyperoestrogenism, stachybotryotoxicosis, ergotism, leukoencephalomalacia and human oesophageal cancer. A major breakthrough in mycotoxicological research was made in South Africa in 1988 with the isolation and chemical characterisation of the carcinogenic fumonisins produced by Fusarium verticillioides in maize. Current research at the PROMEC Unit of the South African Medical Research Council on the risk assessment of fumonisins and intervention methods to reduce fumonisin intake by rural populations on a maize staple diet is highlighted. This paper concludes with a selected list of mycotoxicological publications by South African mycologists/plant pathologists, veterinarians and chemists/biochemists.

Comparative pathologic changes in broiler chicks on feed amendedwith Fusarium proliferatum culture material or purified fumonisinB1 and moniliformin*

Feed amended with autoclaved culture material (CM) of Fusarium proliferatum containing fumonisin B1 (FB1) (61-546 ppm), fumonisin B2 (FB2) (14-98 ppm) and moniliformin (66-367 ppm) was given to 228 male chicks in three separate feeding trials. In a fourth feeding trial, purified FB1 (125 and 274 ppm) and moniliformin (27 and 154 ppm) were given separately and in combination (137 and 77 ppm, respectively). Chicks that died during the trial periods, survivors and controls were subjected to postmortem examination. Specimens (liver, kidney, pancreas, lung, brain, intestine, testis, bursa of Fabricius, heart and skeletal muscle) were examined grossly and preserved for subsequent histopathologic and ultrastructural examination. Prominent gross lesions in affected birds fed diets amended with CM or purified FB1 and moniliformin included ascites, hydropericardium, hepatopathy, nephropathy, cardiomyopathy, pneumonitis, gizzard ulceration, and enlarged bursa of Fabricius filled with caseous material. The various concentrations of FB1 and moniliformin in the amended rations produced well-defined dose-response lesions in all groups in all four trials. Histopathologic changes included hemorrhage, leucocytic infiltration, fatty change or infiltration, individual cell necrosis and fibrosis in liver, kidneys, lungs, heart, intestines, gizzard, bursa of Fabricius and pancreas. Edema and hemorrhage were prominent in brains of treated birds. Ultrastructural changes included cytoplasmic and nuclear enlargement of cells in affected liver, lungs, kidneys, heart and pancreas. There were thickened membranes of the smooth endoplasmic reticulum, dilation of the rough endoplasmic reticulum with loss of ribosomes and vacuolated or deformed mitochondria.

Dimorphic fungus characteristic of fumonisin-producing strains of Fusarium moniliforme from Zhejiang

Fusarium moniliforme and its fumonisins have been shown to be carcinogenic in lab animals and have been linked to high incidences of human esophageal cancer. In this study we report the dimorphic fungus characteristic of fumonisin-producing strains of F. moniliforme from foodstuffs in Zhejiang, China. All of the twenty strains of F. moniliforme shown produce fumonisin B1 475.9-6322.2 micrograms/g in corn medium. These strains of F. moniliforme form yeast-like colonies in Sabouraud's agar plates contained 9% NaCl at 37 degrees C incubator and shows mostly budding reproduction. In blood agar plates these strains of F. moniliforme appear grass-green haemolytic reactions. This is the first report that yeast-like growth, dimorphic pathogenic fungus feature is found in F. moniliforme. These results suggest that it is also important to program epidemiological surveys of F. moniliforme as a primary pathogenic fungus, while proceeding to produce mycotoxins of F. moniliforme in food hygiene.

Fusaric acid and modification of the subchronic toxicity to rats of fumonisins in F. moniliforme culture material

Fumonisins and fusaric acid (FA) are mycotoxins produced by Fusarium moniliforme and other Fusarium which grow on corn. Fumonisins cause animal toxicities associated with F. moniliforme and, like F. monliforme, they are suspected human oesophageal carcinogens. Toxic synergism was obtained by simultaneous administration of FA and fumonisin B1 to chicks in ovo. To determine the effect of FA on in vivo toxicity of F. moniliforme culture material (CM), male rats (12 groups, n = 5/ group) were fed diets containing 0.025, 0.10 or 2.5% CM (providing dietary levels of 3.4, 18.4 or 437 ppm fumonisins, respectively) to which, at each CM level, 0, 20, 100 or 400 ppm FA were added. Additionally, an FA control group was fed 400 ppm FA only and an untreated control group was given neither FA nor culture material. Apoptosis and other effects consistent with those caused by fumonisins were present in the kidneys of animals fed 0.025% or more CM and in the livers of animals fed 2.5% CM. FA was without effect. No differences between the untreated and FA control groups were noted and no differences among the four groups (0-400 ppm FA) fed 0.025% CM, the four groups fed 0.10% CM or the four groups fed 2.5% CM were apparent. Thus, FA exerted no synergistic, additive or antagonistic effects on the subchronic in vivo toxicity of fumonisin-producing F. moniliforme.

[Investigation and evaluation of fumonisin contamination of native and imported cereals]

Cereal varieties cultivated in Germany, such as wheat, rye, grain-maize, barley, and oats were analyzed for fumonisins, including also imported maize from Argentina. In a total of 410 wheat samples and 140 rye samples of two harvesting years (1993, 1994) and in random samples of barley and oats no fumonisins were detected at all. In german grain-maize of 1993, only low fumonisin contents (17-33 ng/g) were detected occasionally. Some grainmaize samples of the 1994 harvest contained significantly higher fumonisin amounts, partly up to the mg/kg-range, which obviously is due to the extremely high temperatures during summer. In some samples of variety tests of the country the fumonisin B1 content amounted up to 4828 ng/g and the total fumonisin content (FB1-FB3) up to 7132 ng/g respectively. In 1994 a total of 317 native grain-maize samples was tested, of it 109 samples of German cultivation and 208 samples from variety tests of different federal states. Maize samples from Baden-Württemberg, which are representative to the maize harvest of this state, had a fumonisin contamination of 14%, the mean value of the contaminated samples amounting to 206 ng/g. Of the imported maize from Argentina, all the investigated 21 samples had a fumonisin content (FB1-FB3) of 14-1106 ng/g, the mean fumonisin content amounting to 175 ng/g.

Developmental effects of fumonisin B1 in mice

Developmental and toxic effects of aqueous extracts of F. moniliforme culture material containing known levels of fumonisin B1 were recently reported in mice and included maternal hepatotoxicity and lethality, maternal body weight gain reduction, increased embryonic resorptions, reduced offspring body weights, and fetal malformations including cleft palate, hydrocephalus, malformed ribs and incomplete digital and sternal ossification. These studies also suggested that the effects of the fungal extract on the mouse offspring may be mediated via maternal effects. The contribution of fumonisin B1 (FB1), a major toxic metabolite of F. moniliforme, in the induction of these effects was evaluated in this study by administering 0 to 100 mg pure FB1/kg of body weight on gestational days (GD) 7 through 15 to pregnant Charles River CD1 mice and assessing maternal health and fetal development till the end of gestation. Doses of 25 mg/kg or higher of pure FB1 induced maternal liver lesions (mostly necrotic changes), associated with ascites and increased hepatocytic nuclear diameter. Fumonisin doses of 50 mg/kg or higher also resulted in significantly increased maternal ALT on GD12, and reduced offspring bodyweights on GD18. Increased resorptions and decreased numbers of live offspring were only evident at 100 mg FB1/kg body weight. Offspring exhibited dose-dependent increase in the incidence and severity of hydrocephalus of both the lateral and third ventricles at doses of 25 mg/kg or higher. Doses of 25 mg/kg or higher also increased the sphinganine/sphingosine (Sa/So) ratios in maternal but not fetal livers. These results suggest that FB1 may be a developmental toxicant accounting for most but not all earlier reported effects of F. moniliforme culture extract. Association of FB1 effects on the offspring with maternal hepatoxicity and with alteration of Sa/So ratio in maternal but not fetal liver supported the earlier claim that FB1 effects on the mouse offspring are mediated by maternal hepatotoxicity.

Fungi associated with herbal drug plants during storage

Samples of sundried herbal drug plant parts stored for sale were purchased from four herbal markets located in Ibadan, Nigeria. The plant parts were analysed for mycoflora associated with their storage. Fungal colony counts ranged from 0.60 x 10(2) to 3.50 x 10(2) within the period of the survey. Twenty eight fungal species were isolated with the species of Aspergillus niger, A. flavus, Fusarium moniliforme, Trichoderma viride, Penicillium expansum and Mucor fragilis being the dominant ones. There were marked differences between the flora obtained on fresh plant parts and those stored for sale. The results obtained showed that herbal drug plant pieces stored for sale in the markets are hazardous for human health. There is therefore the need for some form of quality control and decontamination before they are used for herbal drug preparations.

Subchronic toxic effects of Fusarium moniliforme and fumonisin B1 in rats and mice

Fumonisins are mycotoxins produced by the fungi Fusarium moniliforme, F. proliferatum, and other Fusarium species. Fumonisin B1, the most commonly found fumonisin, causes the fatal diseases equine leukoencephalomalacia and porcine pulmonary edema. Fumonisins are suspected human carcinogens because of the extraordinarily high incidences of esophageal cancer coincidentally found in areas of southern Africa and China where F. moniliforme-contaminated corn is consumed as a dietary staple. The subchronic (up to 90 days) effects of F. moniliforme-contaminated corn, corn cultures of this fungus, and purified fumonisin B1 (FB1) in rats and mice were systematically studied to determine target organs, characterize organ-specified lesions, and obtain dose-response data. The liver is a target organ in both species. Serum chemical findings indicative of hepatocellular injury and morphological findings, including apoptosis, appeared qualitatively similar in both species. The kidney is also a target organ in rats, but not mice. Lesions which include apoptosis and cellular degeneration are predominately found in the outer medella. Results of several investigations showed that the kidney was consistently affected at lower doses than the liver. The "no-observed-effect" level for nephropathy in rats was also consistently lower in males than females, suggesting a sex-related difference in nephrotoxic response to fumonisins. Other findings suggest that toxigenesis may be mediated by disruption of de novo sphingolipid biosynthesis. Hepatic and renal sphingolipid profiles, specifically sphinganine concentration and sphinganine-to-sphingosine ratio, were altered in rats fed FB1 at levels that did not cause serum chemical, organ weight, or histopathological evidence of toxicity.

Fumonisin toxicity and metabolism studies at the USDA. Fumonisin toxicity and metabolism

Fumonisins are responsible for many of the toxic effects of the common corn fungus, Fusarium moniliforme. They are acute renal and liver toxins in rats, and have tumor promoting activity. Fumonisin B1 is poorly absorbed, rapidly excreted, and persists in small amounts in the liver and kidney. Fumonisins are specific inhibitors of ceramide synthase, and the toxic effects they produce may be related to their ability to disrupt sphingolipid metabolism, resulting in a myriad of problems in cell regulation and communication. In this paper, research that has been conducted on F. monilforme and the fumonisins at the USDA's Russell Research Center is reviewed.

Effect of thermal processing on the stability of fumonisins

Fumonisins, a group of mycotoxins produced by Fusarium moniliforme in corn, have been implicated in several animal and human diseases. F. moniliforme and the fumonisins are an area of incresing concern for corn producers and consumers. Consequently, there is interest in reducing human and animal exposure to these fungal toxins. Studies of the effects of biological, chemical, and physical treatments on the reduction of fumonisin levels in food have shown variable results. Work was conducted at the U.S. Food and Drug Administration, National Center for Food Safety and Technology, to determine the effects of thermal processing on fumonisins B1 (FB1) and B2 (FB2) in an aqueous buffer. Parameters that were studied included processing time (0-60 min), processing temperature (100-235 degrees C), and buffer pH (4, 7, and 10). The rate and extent of fumonisin decomposition increased with processing temperature. Less than 27% of FB1 and less than 20% of FB2 were lost when processing temperatures were less than or equal to 125 degrees C for 60 min. After 60 min at 150 degrees C, losses of FB1 and FB2 were 80-90% at pH 4, 18-30% at pH 7, and 40-52% at pH 10. At temperatures greater than or equal to 175 degrees C, more than 80% of FB1 and FB2 was lost after 60 min. These results indicate that foods reaching temperatures greater than 150 degrees C during processing may have lower fumonisin levels. More work is needed to quantitate the effects of different processing operations (baking, extrusion, frying) on the fumonisin content of corn-based foods.

Sphingosine-related mycotoxins in plant and animal diseases

The AAL-toxins and fumonisins are a group of chemically related phytotoxic congeners produced by Alternaria alternata f. sp. lycopersici and Fusarium moniliforme, respectively, that also are widespread mycotoxins with important health implications. These mycotoxins, which bear a structural relationship to the sphingoid base, sphingosine, also incite maladies in animals ranging from neoplasms to renal, neural, and hepatic necrosis. A. alternata f. sp. lycopersici causes the Alternaria stem canker disease in tomatoes, while F. moniliforme causes pink ear rot of maize and is associated with post-harvest contamination of many different food staples. These toxins are potent inhibitors of ceramide synthase in plants and animals. Sphingoid bases are mediators of signal transduction leading to neoplasms and necrosis in animals. Significant inhibition of ceramide synthase in microsomal preparations of tomato occurs at 20 nM with an I50in the range of 35–40 nM for both AAL-toxin, TA, and fumonisin, FB1. In plants, specific alterations of physiological processes associated with cellular response to these toxins appears to be required for cell death. A net decrease in sucrose influx to treated leaves occurs within 4 h of AAL-toxin treatment. Untreated leaves of toxin-resistant and -sensitive isolines of tomato show significant differences in sucrose transport capacity. Exogenous application of sucrose transport inhibitors mimicked AAL-toxin symptoms and enhanced cell death in susceptible lines of tomato. Conversely, the accumulation of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACQ occurred in 1 h and increased rapidly during the next 6 h after exposure to AAL-toxin. ACC accumulation is followed by a burst in ethylene within 12 h. Application of specific inhibitors of ethylene synthesis or ethylene action results in a decrease in toxin-induced cell death. These toxins appear to be useful tools for defining biochemical and molecular features common to induced cell death in both plants and animals. Key words: AAL-toxins, fumonisins, mycotoxins, host-selective toxins, Alternaria stem canker, Alternaria alternata, Fusarium moniliforme.

Subchronic toxicity of fumonisin B1 to male and female rats

Fumonisins are a class of mycotoxins produced by Fusarium moniliforme and other Fusarium spp. These compounds are widely distributed in corn. Equine leukoencephalomalacia, pulmonary oedema in swine, and nephrotoxicity, hepatotoxicity and liver cancer in male rats, all of which are caused by toxic F. moniliforme, have been experimentally reproduced using fumisin B1 (FB1) (ca 90-94% purity). To investigate the effect of purified (> or = 99% purity) FB1, to compare the effects of FB1 in males and females, and to obtain dose-response information for FB1, three rats per sex were fed diets containing 0, 15, 50 or 150 FB1 for 4 weeks. Serum chemical, organ weight and histopathological evidence showed that 150 mg/kg FB1 was hepatotoxic in both sexes. Nephrosis was found in males fed > or = 15 mg/kg and females fed > or = 50 mg/kg FB1. Altered sphingolipid profiles, specifically increased free sphinganine concentrations and increased sphinganine:sphinogosine ratios, were found in the liver, kidney, serum and urine of FB1-fed rats. These findings support the hypothesis that in vivo toxicity caused by fumonisins may result from altered sphingolipid metabolism.

Developmental effects of fumonisin B1-containing Fusarium moniliforme culture extract in CD1 mice

Pregnant Charles River CD1 mice were treated with a semipurified extract of Fusarium moniliforme culture containing 0, 12.5, 25, 50 or 100 mg FB1/kg each day orally (diluted in distilled water) between gestational days (GD) 7 and 15 to evaluate the developmental toxicity of FB1. Following sacrifice of dams on GD 18, litters were examined for gross abnormalities and divided equally for skeletal or visceral examination by routine techniques. Significant maternal mortality was observed at doses of 50 and 100 mg FB1/kg. Dose-dependent decreases in maternal body weight gains, number of live offsprings per litter, and mean body weight of the offspring were produced at FB1 doses of 25 mg/kg or higher. The percentage of implants resorbed increased at all doses in a dose-dependant manner. A dose-dependant increase, except at the lowest dose tested, in the incidence of ossification deficits involving digits and sternum, short and wavy ribs, and hydrocephalus of lateral and third ventricles was also evident. Cleft palate was seen only at the highest FB1 dose. Maternal intoxication manifested as a dose-dependant increase in the severity of ascites associated mainly with increased histopathologic scores reflecting hepatocellular damage at day 18. Concommittant increases in serum alanine amino transferase (ALT) on GD 12, reflecting parenchymal liver cell damage, was also observed at all doses above 12.5 mg of FB1/kg. These results suggest that FB1-containing F. moniliforme culture extract is developmentally toxic in mice, and that this toxicity may be mediated by maternal hepatotoxicity.

Taxonomy, biology, and clinical aspects of Fusarium species

There are several taxonomic systems available for identifying Fusarium species. The philosophy used in each taxonomic system is discussed as well as problems encountered in working with Fusarium species in culture. Fusarium species are toxigenic, and the mycotoxins produced by these organisms are often associated with animal and human diseases. The implications for the association of the carcinogens, fumonisins, produced by Fusarium moniliforme and other Fusarium species with human diseases are discussed. Foreign-body-associated fusarial infection such as keratitis in contact lens wearers, onychomycosis, skin infections, and disseminated multiorgan infections are discussed. Disseminated fusarial hyalohyphomycosis has emerged as a significant, usually fatal infection in the immunocompromised host. Successful outcome is determined by the degree of immunosuppression, the extent of the infection, and the presence of a removable focus such as an indwelling central venous catheter. These infections may be clinically suspected on the basis of a constellation of clinical and laboratory findings, which should lead to prompt therapy, probably with one of the newer antifungal agents. Perhaps the use of such agents or the use of colony-stimulating factors may improve the outcome of this devastating infection. However, until new approaches for treatment develop, effective preventive measures are urgently needed.

Mortality in broiler chicks on feed amended with Fusarium proliferatum culture material or with purified fumonisin B1 and moniliformin

Two hundred twenty-eight male chicks (Columbia x New Hampshire) were given feed amended with autoclaved culture material (CM) of Fusarium proliferatum Containing fumonisin B1 (FB1), fumonisin B2 (FB2) and moniliformin in 3 separate feeding trials. Purified FB1 and moniliformin were given separately and in combination in a fourth feeding trial. Birds were given amended rations at day 1 (Trial 1 and 4), day 7 (Trial 2), and day 21 (Trial 3) and their respective ration was given for 28 days (Trial 1), 21 days (Trial 2), 7 days (Trial 3), and 14 days (Trial 4). FB1 concentrations were 546, 193, and 61 ppm; FB2 were 98, 38 and 14 ppm; and moniliformin were 367, 193, and 66 ppm in the first 3 feeding trial regimens. Chicks in Trial 4 were given dietary concentrations of purified FB1 at 274 and 125 ppm, and moniliformin at 154 and 27 ppm. FB1 and moniliformin, both alone and in combination, produced dose-responsive clinical signs, reduced weight gains and mortality in chicks. Age of birds given amended feeds had little difference in the clinical response; however, those given the rations from days 7 or 21 were slightly less susceptible than those given rations beginning at 1 day of age. Additive effects were noted when the toxins were given in combination. When toxins were given separately, adverse effects took longer to occur. A system to monitor pattern and rate of defecation (RD) was developed for assessing the chicks' approach to feed, water and heat source as illness progressed. Our results indicate that chicks fed corn heavily infected with F. proliferatum under field conditions could suffer acute death similar to that described for 'spiking mortality syndrome' during the first 3 weeks of age.

Fumonisin toxicosis in swine: clinical and pathologic findings

From a series of experimental studies with pigs (12-16 kg), either pulmonary edema or liver failure emerged as a distinct pathogenetic expression of fumonisin B1 (FB1) toxicosis. The primary determinant as to which pathogenetic consequence developed was the quantity (dose) of the mycotoxin fed or intubated per kilogram of body weight per day. Pigs intubated with a minimum of 16 mg FB1/kg/day developed severe interlobular edema with or without hydrothorax and variably severe pulmonary edema. Pigs intubated with < 16 mg FB1/kg/day or pigs fed diets containing 200 mg FB1/kg of feed developed marked icterus and hepatocellular necrosis. The spectrum of degrees of severity of pulmonary edema observed in the experimental pigs allowed rational speculation regarding evolution of the pathologic changes.

A preliminary investigation on renal and hepatic toxicity in rats fed purified fumonisin B1

Fumonisins are metabolites of Fusarium moniliforme and other Fusarium spp. Fumonisin B1 (FB1) was hepatocarcinogenic (50 ppm, > or = 90% purity) when fed to male rats; however, neither the effects of FB1 on females nor the relationship between dietary FB1 levels and toxicity in rats has been reported. Male and female rats (three per sex per group) were fed diets fortified with 0, 15, 50 or 150 ppm FB1 (> or = 99% purity) for 4 weeks. There were no differences in general appearance or behavior among groups and significant differences in weight gain or food consumption were not found. Histopathological examinations and serum chemical profiles, including significant increases in triglycerides, cholesterol, and alkaline phosphatase, confirmed that 150 ppm FB1 was hepatotoxic to both sexes. Cortical nephrosis was found in males fed > or = 15 ppm and females fed > or = 50 ppm FB1. Both hepatic and renal lesions were consistent with those found in rats consuming F. moniliforme-infected corn. Thus, highly purified FB1 is unequivocally capable of inducing the subchronic liver and kidney lesions attributed to F. moniliforme.

Taxonomy and biology of Fusarium moniliforme

Fusarium moniliforme is one of the most prevalent fungi associated with basic human and animal dietary samples such as corn. This fungus has been suspected of being involved in human and animal diseases since its original description. Fusarium moniliforme is in the section Liseola along with F. proliferatum, F. subglutinans, and F. anthophilum. Cultural mutation often occurs when F. moniliforme is grown on a medium rich in carbohydrates. Mutants may be either the mycelial or pionnotal type and often lose virulence and the ability to produce toxins. Toxins produced by F. moniliforme are fusaric acid, fusarins, gibberellins, moniliformin, and fumonisins. The fumonisins are produced most often when F. moniliforme grows on corn. Fusarium moniliforme causes ear rot and stalk rot of corn and infection of corn kernels by this fungus is widespread. Infection of developing corn kernels may occur through the silks, through holes and fissures in the pericarp or at points where the pericarp is torn by the emerging seedling, and as a result of systemic infection of the corn plant by F. moniliforme. These models of infection as well as infestation of the kernel surface are important factors when considering the production of fumonisins in corn.

Subchronic toxicological investigations of Fusarium moniliforme-contaminated corn, culture material, and ammoniated culture material

The fungus Fusarium moniliforme is ubiquitous on corn throughout the world and is a likely co-contaminant on corn infested with aflatoxin-producing Aspergillus flavus. Ammoniation has been used to detoxify aflatoxin-contaminated commodities. To determine the effect of ammoniation on the toxic potential of Fusarium moniliforme, male Sprague-Dawley rats were fed either diets containing 10% sound corn, ammoniated corn, corn culture material of hepatotoxic F. moniliforme strain MRC 826 (CM), or ammoniated CM for four weeks. They were observed for signs of toxicity and hematological, serum chemical and histopathological evaluations were made. Groups of male Balb/c mice were fed diets fortifies with 10% sound corn or CM for four weeks and evaluated by serum chemical and histopathological means to determine the suitability of mice as a model species for investigation of F. moniliforme-induced hepatotoxicity. Ammoniation was ineffective for detoxification of the CM. Hepatotoxicity and renal toxicity of CM and ammoniated CM were qualitatively similar, although renal tubular lesions appeared more advanced in rats fed ammoniated CM. Adrenal cortical cellular vacuolation was also found in CM and ammoniated CM-fed rats, while focal seminiferous tubular degeneration and aspermia were found only in the testes of ammoniated CM-fed rats. Fumonisin B1 concentrations of the CM and ammoniated CM diets averaged 99 and 75 ppm, respectively. CM containing 99 ppm fumonisin B1 also produced hepatotoxicity in mice similar to that found in CM-fed rats. Thus, mice may be useful for investigations of F. moniliforme-induced hepatotoxicity.

Fumonisins: isolation, chemical characterization and biological effects

The fumonisin B mycotoxins (FB1 and FB2) have been purified and characterized from corn cultures of Fusarium moniliforme strain MRC 826. Fumonisin B1 (FB1), the major fumonisin produced in culture, has been shown to be responsible for the major toxicological effects of the fungus in rats, horses and pigs. Recent investigations on the purification of compounds with chromatographic characteristics similar to FB1 have led to the identification of two new fumonisins, FB3 and FB4. Fumonisins A1 and A2, the N-acetyl derivatives of FB1 and FB2 respectively, were also purified and shown to be secondary metabolites of the fungus. Short-term carcinogenesis studies in a rat liver bioassay indicated that over a period of 15 to 20 days, at dietary levels of 0.05-0.1%, FB2 and FB3 closely mimic the toxicological and cancer initiating activity of FB1 and thus could contribute to the toxicological effects of the fungus in animals. In contrast, no biological activity could be detected for FA1 under identical experimental conditions. These studies and others have indicated that the fumonisin B mycotoxins, although lacking mutagenicity in the Salmonella test or genotoxicity in the DNA repair assays in primary hepatocytes, appear to induce resistant hepatocytes similar to many known hepatocarcinogens.

The implications of naturally occurring levels of fumonisins in corn for human and animal health

Contamination of corn with the fungus Fusarium moniliforme and its secondary metabolites, the fumonisins, has been associated with several human and animal diseases. This paper summarizes present knowledge and presents new data on the levels of fumonisins present in foods and feeds associated with these diseases as well as in commercial corn and corn-based products. The doses of fumonisins to which humans and animals consuming these products would be exposed are compared with those doses known to produce LEM in horses and hepatocarcinogenesis in rats. It is concluded that the known naturally occurring levels of fumonisins present a potential threat to human and animal health and realistic tolerance levels need to be set.

Fumonisin-induced pulmonary edema and hydrothorax in swine

Pulmonary edema and hydrothorax were observed in mature swine that died approximately 5 days after consuming corn screenings. These postmortem observations were reproduced in younger pigs that died within 1 week when fed the corn screenings under experimental conditions. Additionally, pulmonary edema and hydrothorax were induced in a pig that died after receiving 4 daily intravenous injections of fumonisin B1, a toxic metabolite produced by Fusarium moniliforme.

Characterization of an epizootic of pulmonary edema in swine associated with fumonisin in corn screenings

In 1989, corn screenings were associated with acute interstitial pulmonary edema, hydrothorax, and death in swine. Attack rate was 5-50%, case fatality rate was 50-90%, and clinical course was 1-2 days. Screenings from farms with pigs affected with pulmonary edema contained 20-330 micrograms fumonisin B1 per gram. Screenings containing 92 micrograms fumonisin B1 per gram fed to weanling pigs caused pulmonary edema and death. Sterilized corn inoculated with Fusarium moniliforme and diluted 1:1 with clean corn contained fumonisin B1 (17 micrograms/g) and caused acute pulmonary edema when fed for 5 days. Survivors developed subacute hepatotoxicosis with individual hepatocellular necrosis, hepatomegalocytosis, and increased numbers of mitotic figures. Similar liver lesions occurred in pigs given fumonisin B1 intravenously at 0.8 mg/kg body weight for 14 days.

Production of fumonisins by Fusarium moniliforme strains from various substrates and geographic areas

Strains of Fusarium moniliforme from different geographic areas and from corn and other substrates were tested for the ability to produce fumonisins in culture. The test results indicate that the potential exists for production of fumonisins by such strains in agricultural commodities and other substrates in widespread geographic areas.

Toxicity and moniliformin production by four recently described species of Fusarium and two uncertain taxa

Four recently described species. Fusarium nygamai, F. dlamini, F. beomiforme and F. napiforme and two uncertain taxa, F. nygamai from millet in Africa and Fusarium species from rice with Bakanae disease, were tested for toxicity and moniliformin production. Cultures grown on autoclaved corn were fed to groups of four one-day-old ducklings for 14 days. Isolates that caused the death of 3 or 4 out of 4 ducklings were considered to be toxic and analyzed for moniliformin. All 15 isolates of F. dlamini tested were nontoxic. The other taxa contained some isolates that were toxic to ducklings and produced moniliformin in corn cultures. This is the first report of moniliformin production by F. beomiforme (200-890 micrograms/g), and F. napiforme (16-388 micrograms/g), and by F. nygamai not obtained from millet in Africa (15-874 micrograms/g). The highest production of moniliformin was obtained from the 19 isolates of F. nygamai from millet in Africa (4300-18,200 micrograms/g) and the 15 isolates from rice with Bakanae disease (2300-19,300 micrograms/g). The taxonomic position of these two uncertain taxa should be re-evaluated.

Comparative studies of hepatotoxicity and fumonisin B1 and B2 content of water and chloroform/methanol extracts of Fusarium moniliforme strain MRC 826 culture material

Fusarium moniliforme has been associated with several diseases including equine leukoencephalomalacia, human esophageal cancer and hepatotoxicity/hepatocarcinogenicity in laboratory animals. The potential health risks to animals and humans posed by F. moniliforme contaminated grains cannot be assessed until the toxins are identified and toxicologically evaluated. As part of a systematic approach to identifying the hepatotoxins produced by F. moniliforme, diets containing aqueous and chloroform/methanol (1:1) extracts of F. moniliforme strain MRC 826 culture material (CM) and/or the extracted CM residues were fed to male Sprague-Dawley rats for four weeks. Serum alanine aminotransferase, aspartate amino-transferase and alkaline phosphatase activities were increased after two and four weeks and microscopic liver lesions were found in those animals fed aqueous CM extract and the CM residue after chloroform/methanol extraction. Fumonisins B1 and B2 were extracted from the CM by water, but not chloroform/methanol, and were present in the toxic diets at concentrations of 93-139 and 82-147 ppm, respectively. Nontoxic diets contained less than or equal to 22 ppm fumonisin B1 and less than or equal to 65 ppm fumonisin B2.

Pulmonary edema and hydrothorax in swine produced by fumonisin B1, a toxic metabolite of Fusarium moniliforme

Pulmonary edema and hydrothorax were observed in mature swine that died approximately 5 days after consuming corn screenings. These postmortem observations were reproduced in younger swine (16-24 kg) that died within 1 week when fed the corn screenings under experimental conditions. Additionally, pulmonary edema and hydrothorax occurred in a pig (7.1 kg) that died after receiving 4 daily intravenous injections of fumonisin B1. A fungus was isolated from the corn screenings that is identical to Fusarium moniliforme MRC-826 in colony morphology and under microscopic examination.

Effects of temperature and incubation period on production of fumonisin B1 by Fusarium moniliforme

The kinetics of the production of fumonisin B1 (FB1) by Fusarium moniliforme MRC 826 in corn cultures was investigated as a function of fungal growth at various incubation temperatures. The growth rate of F. moniliforme, as measured by ergosterol concentration, was higher at 25 degrees C than at 20 degrees C, reaching a stationary phase after 4 to 6 weeks in both cases. FB1 production commenced after 2 weeks during the active growth phase, continued to increase during the stationary phase, and decreased after 13 weeks. The overall maximal yield of FB1 (17.9 g/kg, dry weight) was obtained in corn cultures incubated at 20 degrees C for 13 weeks, but it was not significantly (P greater than 0.05) higher than the maximum yield (16.5 g/kg, dry weight) obtained at 25 degrees C after 11 weeks. However, a significantly (P less than 0.05) higher mean yield was detected at 25 degrees C (9.5 g/kg, dry weight) than at 20 degrees C (8.7 g/kg, dry weight). Production reached a plateau after 7 weeks of incubation at 25 degrees C or 9 weeks of incubation at 20 degrees C. The maximal production of FB1 at 30 degrees C was very low (0.6 g/kg, dry weight). FB1 was also found to be heat stable, as there was no reduction in the FB1 concentration after boiling culture material of F. moniliforme MRC 826.

Inhibition of protein synthesis in rat primary hepatocytes by extracts of Fusarium moniliforme-contaminated corn

Mycological screening of two separate lots of corn samples that caused field cases of equine leukoencephalomalacia (ELEM) revealed heavy contamination with the fungus Fusarium moniliforme. Neutral and acidic fractions of a chloroform-methanol (1:1, v/v) extract of the corn were evaluated for toxicity using rat primary hepatocytes. The extracts had little effect on the release of lactate dehydrogenase from the hepatocytes, and were without effect on unscheduled DNA synthesis, indicating low cell lethality and lack of genotoxicity. However, neutral extracts of the corn were found to contain potent inhibitor(s) of protein synthesis as measured by incorporation of [3H]valine into the hepatocytes. When an isolate of F. moniliforme obtained from the corn samples or an isolate of F. moniliforme from South Africa that had previously been shown to cause ELEM (MRC 826) were grown on autoclaved seed corn, neutral extracts of the culture materials similarly inhibited protein synthesis. Whether the compound(s) responsible for inhibition of protein synthesis is associated with any of the toxic syndromes associated with F. moniliforme remains to be determined. The use of primary hepatocytes may be a useful bioassay for elucidating biologically active secondary metabolites of fungi.

Hepatotoxicity and renal toxicity in rats of corn samples associated with field cases of equine leukoencephalomalacia

Currently there is no convenient bioassay to determine the potential toxicity of corn naturally contaminated with Fusarium moniliforme. A short-term bioassay would be useful for future investigations aimed at isolating as yet unidentified toxins produced by this fungus. Two groups of five male Sprague-Dawley rats were each fed one of two F. moniliforme contaminated corn samples, designated CS-1 and CS-2, that were associated with separate field cases of equine leukoencephalomalacia (ELEM). A control group, also consisting of five male rats, was fed uncontaminated seed corn. All animals survived to the end of the study and there were no apparent differences in appearance or behaviour among groups. Weight loss and irregular food consumption occurred in all groups and probably resulted from nutritional deficiencies inherent in the corn diets. Hepatocellular degeneration, necrosis and hyperplasia as well as biliary hyperplasia were found in the test groups only and were attributed to F. moniliforme. Serum transaminase and alkaline phosphatase activities in animals fed CS-1 and CS-2 for 4 wk were significantly increased compared with the controls, while serum bilirubin concentration was increased only in the CS-1 group. Tubular nephrosis was also present in the renal cortex of all animals fed CS-1 and CS-2. These effects may have been related to fumonisins B1 and B2, recently discovered metabolites of F. moniliforme, that were found in both CS-1 and CS-2. Short-term studies of this type may be useful in screening naturally-contaminated grains and other materials for hepatotoxic metabolites produced by F. moniliforme.

Investigations on the spectral interactions of fusarin C with rat liver microsomal cytochrome P-450

1. The spectral interaction of a mutagenic fungal metabolite, fusarin C, with rat liver microsomal cytochrome P-450 was investigated using a method which determines competitive inhibition between substrates eliciting the same type of spectral change. The strong u.v. absorption of fusarin C in the region where the spectral changes of cytochrome P-450 are monitored prevented direct binding studies. 2. The conversion of fusarin C to fusarin PM1 by the microsomal carboxylesterase was effectively inhibited by either decreasing the temperature during the binding studies or by addition of NaF (20 mM) during the enzymic inhibition investigations. 3. Fusarin C competitively inhibited the binding of the type II substrate aniline, yet the enzymic hydroxylation reaction of aniline was inhibited in a non-competitive manner. 4. Although the C-13/C-14 epoxide group of fusarin C is necessary for mutagenicity, an additional metabolic step is required. The present data indicated that fusarin C may interact with cytochrome P-450 in a similar way to aniline.

Fumonisins--novel mycotoxins with cancer-promoting activity produced by Fusarium moniliforme

Cultures on corn of Fusarium moniliforme MRC 826 are known to cause leukoencephalomalacia in horses and to be toxic and hepatocarcinogenic in rats. Culture material of this F. moniliforme isolate has also been shown to exhibit cancer-promoting activity in a short-term cancer initiation-promotion bioassay with diethylnitrosamine-initiated rats and the induction of gamma-glutamyl-transpeptidase-positive (GGT+) foci as an endpoint after 4 weeks of promotion. This bioassay was used as a monitoring system to isolate cancer-promoting compounds from cultures of F. moniliforme MRC 826. Culture material was successively extracted with ethyl acetate and CH3OH-H2O (3:1). Most of the cancer-promoting activity was recovered in the CH3OH-H2O extract and remained in the aqueous phase following partitioning of this extract between CH3OH-H2O (1:3) and CHCl3. The CH3OH-H2O fraction was chromatographed on an Amberlite XAD-2 column, and the active fraction was eluted with CH3OH. This fraction was chromatographed on a silica gel column with CHCl3-CH3OH-CH3COOH (6:3:1) as eluent and further purified on a C18 reverse-phase column. Two pure compounds were isolated, and these have been chemically characterized and given the trivial names fumonisin B1 and B2. At least 2 g of the major compound fumonisin B1 was purified from 1 kg of culture material. Fumonisin B1 in the diet (0.1%) significantly (P less than 0.001) induced the formation of GGT+ foci in the livers of initiated as well as noninitiated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Production of moniliformin by Canadian isolates of Fusarium

Twenty-eight Canadian isolates of Fusarium were tested for their ability to produce moniliformin in corn. Both F. moniliforme (2/6 isolates) and F. subglutinans (11/15 isolates) produced the mycotoxin, while F. graminearum did not. Field-corn inoculated with F. moniliforme M3783 was able to support production of both moniliformin and fusarin C.

Hepatitis in vervet monkeys caused by Fusarium moniliforme

The fungus Fusarium moniliforme Sheldon is a common contaminant of maize (Zea mays L.) intended for human and animal consumption throughout the world. Culture material of F. moniliforme MRC 826, isolated from home-grown maize in an area in Transkei, southern Africa, with a high rate of human oesophageal cancer, was highly toxic to vervet monkeys (Cercopithecus pygerythrus). Ten monkeys were fed a standard primate diet which contained various amounts of culture material for 180 days. Two control monkeys received the standard diet without culture material. Pathological changes observed in liver biopsies taken by laparotomy were characterized by focal disturbance of the trabecular structure, degeneration and necrosis of hepatocytes, mononuclear infiltration, and in severe cases by cirrhosis. Biochemical changes, particularly increases in liver enzyme activities in serum, paralleled the liver damage seen by light microscopy. The acute, subacute and chronic toxic hepatitis induced in various degrees in all the monkeys fed fungal culture material showed close similarity with human viral hepatitis. The lesions also have some similarities to those induced in primates by aflatoxin, but differ in several respects. Ultrastructural nuclear and nucleolar changes caused by F. moniliforme, i.e. marginal clumping of chromatin and large nucleoli with segregation of fibrillar and granular components, suggested some similarity with the changes reported to be caused by aflatoxin and some other hepatocarcinogens. A long-term feeding experiment in vervet monkeys with F. moniliforme MRC 826 and attempts to isolate and chemically characterise the hepatotoxic metabolite(s) produced by this fungus are being continued.

Fusarin C production by North American isolates of Fusarium moniliforme

A liquid culture medium was developed to screen North American isolates of Fusarium moniliforme Sheldon and Fusarium subglutinans (Wollenw. and Reink.) Nelson, Toussoun, and Marasas for their ability to produce fusarin C. Parameters which were important for the optimal biosynthesis of fusarin C included pH (3.0 to 4.0), aeration, and sugar concentration (30 to 40%). Of seven sugars tested, sucrose and glucose were the best carbohydrate sources for mycotoxin production, resulting in levels of fusarin C of greater than 60 ppm (greater than 60 micrograms/g) in liquid culture (28 degrees C; 7 days). A time-course study of fusarin C production was done over a 21-day period, during which time pH values, glucose concentrations, nitrogen levels, and fungal biomass were determined. Of the two Fusarium spp. studied, 13 of 16 isolates of F. moniliforme produced fusarin C in liquid medium (14 of 16 in corn), while none of the 15 isolates of F. subglutinans studied was found to produce the compound. Levels of fusarin C produced by Fusarium sp. isolates growing on corn ranged from 18.7 to 332.0 micrograms/g.

Primary liver cancer and oesophageal basal cell hyperplasia in rats caused by Fusarium moniliforme

Fusarium moniliforme Sheldon is one of the most prevalent fungi associated with maize throughout the world. A correlation has been found between the incidence of F. moniliforme in home-grown maize and the human oesophageal cancer rate in Transkei, southern Africa. Culture material on maize of F. moniliforme strain MRC 826, isolated from maize in a high-risk area for oesophageal cancer in Transkei, was either freeze-dried or oven-dried and fed to groups of 20 inbred male BD IX rats on a life-long basis. At a dietary level of 8%, both types of culture material were hepatotoxic and caused 100% mortality. Hepatic lesions in rats that died were characterized by cirrhosis, nodular hyperplasia and bile-duct proliferation. At a dietary level of 4% for 286 days followed by 2% for the remainder of the experiment, both types of culture material were hepatocarcinogenic and caused hepatocellular carcinoma in 80% and ductular carcinoma of the liver in 63% of the rats surviving more than 450 days. Only one of 30 such rats did not have a primary hepatic carcinoma. No hepatocellular or ductular carcinomas occurred in the controls. Hepatocellular carcinomas in the experimental rats invariably developed in severely cirrhotic livers showing nodular hyperplasia. Adenofibrosis also developed concurrently with hepatocellular carcinoma. A higher incidence of basal cell hyperplasia occurred in the oesophageal epithelia of rats fed freeze-dried than in those fed oven-dried material. The chemical nature of the hepatotoxic and hepatocarcinogenic mycotoxin(s) produced by F. moniliforme is unknown.