Aflatoxin B1 (AFB1) is a potent dietary hepatocarcinogen and may be a lung carcinogen when inhaled. To study the relative ability of lung and liver to metabolize AFB1, a susceptible (Swiss-Webster rat) and resistant species (Syrian golden hamster) were pretreated with inducing agents in order to identify specific AFB1 metabolizing enzymes in each tissue. Analysis of AFB1-exo-epoxide (AFBO) formation, O-dealkynation assays, and protein immunoblots demonstrated that cytochrome P450 (CYP) 1A proteins were overexpressed in both the lung and liver of hamsters pretreated with 3-methylchyolanthrene (3-MC). Only CYP1A1 was expressed in the lung and there was no indication that this protein was involved in AFB1 activation. CYP1A2, on the other hand, was induced in the liver and this correlated well with both increasing protein activity and AFBO formation. It would appear that CYP1A2 is important in activating AFB1 in hamster liver. Although the hamster is resistant as compared to the rat, AFBO formation was higher in both the lung and liver of the hamster compared to the rat. Glutathione S-transferase (GST) Yc subunits were detected in the lung and liver of both species but were not induced by the inducing agents used in these experiments. Following intratracheal injections of [3H]AFB1, in the rat, specific activity was localized in the liver. Only a fraction of the activity was detected in the lung. Of four inducing agents used, only pretratment with phenobarbital (PB) showed increased AFB1-DNA binding in either lung or liver. This correlated with increased CYP2B1 protein levels in both lung and liver, as well as increased CYP2B1 activity and AFBO formation in the liver. Cooxidation of AFB1 by purified prostaglandin H-synthase was shown to produce AFBO but microsomal fractions from rabbit lung and liver failed to show detectable levels of AFBO formation by this cooxidative pathway. Neither purified 5-lipoxygenase or cytosolic fractions from rabbit lung or liver showed detectable levels of LOX mediated cooxidation of AFB1 to AFBO. These studies demonstrate that hamster resembles the human in regard to AFB1 activation in the liver, but that a different as yet unknown enzyme is responsible for hamster lung AFB1 activation. Further evidence that the rat is a poor model for human AFB1 metabolism was demonstrated with the fact that rat activates AFB1 with CYP2B1, a protein unknown in humans.

Exotic germplasm has potential to provide new alleles for disease and insect resistance. US maize (Zea mays L.) currently lacks genetic resistance to Aspergillus flavus, a fungal pathogen that produces aflatoxin in maize kernels. Aflatoxin is one of the main limitations to maize production in hot, dry regions like the Southern US because of the harmful effects on humans and animals and subsequent marketing regulations. Two experiments were conducted to evaluate different exotic maize collections for response to aflatoxin. Exotic adapted maize lines, known as LAMA lines, were found to accumulate less aflatoxin than US hybrids in tests across Southern Texas. Exotic introgression lines developed by The International Center for Maize and Wheat Improvement (CIMMYT) including inbred lines, yellow hybrids, and white hybrids, were more resistant to aflatoxin than US inbred lines and hybrids in field trials in Texas, Georgia, and Mississippi. Another experiment evaluated the grain composition of hybrids with exotic adapted LAMA maize lines and a collection of US hybrids, quality protein maize (QPM) hybrids, and advanced breeding lines using near-infrared spectroscopy. Individual LAMA lines and advanced breeding lines have higher starch content than US hybrid checks. Starch content was the primary grain composition trait of interest as an enhanced-value market has emerged for high starch maize hybrids. Limited germplasm has been analyzed for grain composition because wet chemistry analysis methods required large sample sizes and were time and labor intensive. The near infrared spectroscopy (NIR) method requires a relatively small sample and is a non-destructive analysis method. In this study, NIR was effective at ranking genotypes based on starch, oil, and protein content of the grain.

Maize (Zea mays L.) is one of the main crops grown in the United States. Genetic improvement over the last century has seen a shift from using open-pollinated varieties to single cross hybrids. This has resulted in major grain yield gains and improved management methodologies. However, there is still concern about reduced genetic diversity in elite corn germplasm and the potential effects this could have on future maize productivity in the presence of numerous abiotic and biotic pressures. One solution to this issue is the incorporation of exotic germplasm into existing maize improvement programs. This exotic material must be evaluated and characterized because too much or poorly matched exotic material can lead to reduced productivity. The use of multiple environments representative to the target improvement area is the best way to determine the true potential of certain material. The objectives of this research were to: i) estimate the responses of hybrids to aflatoxin and their agronomic performance across a range of environments under inoculation with Aspergillus flavus; ii) identify the hybrids within each group that exhibit the lowest levels of contamination; iii) analyze the relationship between agronomic performance and aflatoxin accumulation; and iv) determine how Genotype x Environment interactions affect these traits. Agronomic data was collected in ten Texas environments in 2005 for hybrids created from yellow, white, and Quality Protein Maize material that was crossed with one of two elite temperate inbred testers, LH195 or LH210. Response to aflatoxin was measured in eight of these environments. U.S. commercial hybrids were used as checks. Significant differences between hybrids were observed at different environments for different traits. Overall the experimental hybrids had lower aflatoxin accumulation than the commercial checks. They also yielded lower and had lower test weights and 1000 kernel weights. However, there were some hybrids that were competitive with the commercial checks for these agronomic traits. The incorporation of this material into established U.S. lines could be beneficial with regards to aflatoxin accumulation and kernel quality, which could ultimately translate to higher yields and crop quality.

Exotic germplasm has potential to provide new alleles for disease and insect resistance. US maize (Zea mays L.) currently lacks genetic resistance to Aspergillus flavus, a fungal pathogen that produces aflatoxin in maize kernels. Aflatoxin is one of the main limitations to maize production in hot, dry regions like the Southern US because of the harmful effects on humans and animals and subsequent marketing regulations. Two experiments were conducted to evaluate different exotic maize collections for response to aflatoxin. Exotic adapted maize lines, known as LAMA lines, were found to accumulate less aflatoxin than US hybrids in tests across Southern Texas. Exotic introgression lines developed by The International Center for Maize and Wheat Improvement (CIMMYT) including inbred lines, yellow hybrids, and white hybrids, were more resistant to aflatoxin than US inbred lines and hybrids in field trials in Texas, Georgia, and Mississippi. Another experiment evaluated the grain composition of hybrids with exotic adapted LAMA maize lines and a collection of US hybrids, quality protein maize (QPM) hybrids, and advanced breeding lines using near-infrared spectroscopy. Individual LAMA lines and advanced breeding lines have higher starch content than US hybrid checks. Starch content was the primary grain composition trait of interest as an enhanced-value market has emerged for high starch maize hybrids. Limited germplasm has been analyzed for grain composition because wet chemistry analysis methods required large sample sizes and were time and labor intensive. The near infrared spectroscopy (NIR) method requires a relatively small sample and is a non-destructive analysis method. In this study, NIR was effective at ranking genotypes based on starch, oil, and protein content of the grain.

Bentonite clays have long been used as additives in animal feed, aiming to improve pellet quality and prevent caking. Certain bentonites are also capable of deactivating aflatoxin B_(1) (AfB_(1)) in feed by adsorption, therefore, detoxifying the feed. However, a 10–fold difference in adsorption capacity has been observed among selected bentonites. The major mineralogical and chemical properties of smectites in determining their adsorption capacities for AfB_(1) are still poorly understood. Improved knowledge of the key controlling factors of aflatoxin adsorption to bentonite clays is needed to guide the selection, modification, and application of the clays as aflatoxin binders. The objective of this study was to test a hypothesis that a smectite's selectivity and adsorption capacity for aflatoxin was mainly determined by the size matching requirement on interlayer surface domains and the aflatoxin molecules. Three approaches were used to vary the size of nanometer-scaled nonpolar domains in the interlayer of smectites: 1) exchanging interlayer cations, 2) selecting natural bentonites with different cation exchange capacities (CEC), and 3) reducing charge density of a high CEC smectite. Six bentonites were fractionated, with their major mineralogical and chemical properties determined. Clay suspensions saturated with different cations were tested for aflatoxin adsorption. Some aflatoxin-smectite complexes were prepared and analyzed with FTIR and XRD. AfB_(1) adsorption isotherms were fitted with Langmuir, modified Langmuir with adsorption dependent affinity, and exponential Langmuir models. Divalent exchange cations with low hydration energy in general resulted in a much higher adsorption capacity and affinity for all six natural bentonite clays. Cations with smaller hydration radii tended to further enhance the adsorption process for aflatoxin on smectites. Charge density of smectite had shown significant effects on the adsorption capacity, affinity, and the isotherm shape. Aflatoxin adsorption isotherms on the six natural smectites and the CEC-reduced 5OK samples by Hofmann and Klemen effects suggested that there is an optimal CEC range between 80~110 cmol(+)/kg for the best aflatoxin binding smectites. When the smectite has a CEC within this range, the mineral has the highest affinity and adsorption capacity for AfB_(1). The aflatoxin adsorption results after cation exchange treatment, selection of different CEC smectites, and the CEC reduction on 5OK confirmed the importance of size and polarity matching on the nanometer scale in smectites’ adsorption for AfB_(1). All clay samples tested in this study were capable of adsorbing aflatoxin into interlayers, and the charge density seemed to have no effect on bonding strength.

Techn. Hochsch., Diss.--Aachen, 2007.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 107-130).

This diploma thesis deals with the problem of aflatoxin in selected organs of fallow game, roe deer and for comparation of petty game with hare. The aim was to evaluate the free and preserve breeds at a sufficient amount of samples and to assess the suitability of a feeding.There were assessed the parenchymal tissues and kidneys and liver. It evaluated 176 collected biological tissues, including 118 from free places and 58 samples from specialized preserve.After the screening method RIA complemented by gas chromatography, were evaluated concentrations of aflatoxin B1. Diferences of feeding, which were assessed on based of results of evaluation in preserves.Subsequently the problem of submitting feeds was solved, and it was made a manual for submission of a feed.

No description available.

Aflatoxins are cancer-causing, immuno-suppressive mycotoxins that frequently contaminate important staples in Zambia including maize and groundnut. Managing aflatoxins begins with understanding the distribution of aflatoxins across the target region. Seventeen percent of crops from markets contained aflatoxin concentrations above allowable levels in Zambia, with the frequency of contamination in groundnut and maize highest in warmest regions of the country. Proper management of aflatoxin contamination requires a clear understanding of the etiologic agents of the observed contamination. Several species within Aspergillus section Flavi have been implicated as causal agents of aflatoxin contamination in Africa. In Zambia, A. parasiticus was the main etiologic agent of aflatoxin contamination of maize and groundnut, although fungi with S morphology also caused contamination. Aspergillus flavus L morphotype fungi were associated with reduced aflatoxins, suggesting natural biological control by atoxigenic strains may reduce aflatoxin contamination in Zambia. In addition to maize and groundnut, wild insects, fruits and fish are important sources of food and incomes in Zambia. Unfortunately, both insects and wild plants are susceptible to aflatoxin contamination. To evaluate the safety of wild insects and fruit, concentrations of aflatoxins and presence of aflatoxin-producers were assessed. Some species of wild fruits and insects were found to have unsafe levels of aflatoxins suggesting mitigation efforts should target these important foods of Zambia in addition to crops such as groundnut and maize. New lineages of aflatoxin-producing fungi have been described, and found associated with cases of aflatoxicoses in Kenya and elsewhere. Although A. parasiticus is highly frequent and an important etiologic agent of aflatoxin contamination, it is not known how this fungus is related to similar fungi elsewhere. A multigene phylogenetic analysis revealed at least two new groups divergent from known fungal species whose frequencies need to be modified if aflatoxin contamination of crops is to be reduced.