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1
Chan, Fion. « Kampen mot aflatoxin : En litteraturstudie som synliggör förekomsten av aflatoxin i Västafrika ». Thesis, Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-46049.
Texte intégralRésumé :
Aflatoxin is a poisonous mold that has spread around the world, posing a threat to food security and the agricultural economy. A total of 4,5 million people are in danger of being exposed to aflatoxins on a long-term basis around the world. Acute toxicity is caused by consuming significant amounts of toxins in a short period of time, which can lead to death in the worst cases, whereas chronic toxicity is caused by consuming small quantities over a longer period of time, which can lead to low birth weight, immunosuppression, restricted growth in children, and liver cancer in the worst cases. The occurrence of aflatoxins in West Africa was recognized, studied, and investigated in this paper based on a literature review. The findings demonstrate that large levels of aflatoxins have been found in West African raw materials and food and the human body. Children under the age of five, pregnant women, and breastfeeding mothers are the most vulnerable to aflatoxins. Furthermore, the findings reveal that the majority of the population is unaware of aflatoxins and its health implications. Inadequate governmental systems, low societal development, lack of access to health care, a low educated population, climate variability and climate change, high levels of illiteracy, and a lack of laboratories are only a few of the many obstacles that the region has in limiting aflatoxins concentrations. Sorting procedures, the use of tarpaulins, and seminars have all helped raise awareness and knowledge and reduce contamination and consumption of aflatoxin-contaminated foods. This study argues that a multi-sectoral strategy is needed to promote food security and local education. Increased limitations and regulations and higher standards may be able to help limit aflatoxin contamination and exposure.
2
Watson, A. J. « Aflatoxin biosynthesis in Aspergillus ». Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267259.
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3
Cervino, Christian. « Entwicklung von immunanalytischen, chromatographischen und massenspektrometrischen Methoden zur Bestimmung von Aflatoxinen in Lebensmitteln ». München Hieronymus, 2009. http://d-nb.info/994958935/04.
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4
Mariutti, Lilian Regina Barros 1973. « Aflatoxinas em produtos de tomate : avaliação de metodologia analitica e de ocorrencia ». [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254717.
Texte intégralRésumé :
Orientador : Lucia Maria Valente SoaresDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Um recente relato da presença de Aspergillus flavus e Aspergillus parasiticus em polpa de tomate industrializada brasileira motivou preocupações quanto a possível presença de micotoxinas em produtos de tomate nacionais. Aspergillus fIavus e Aspergillus parasiticus são conhecidos produtores de aflatoxinas, uma família de toxinas com propriedades hepatotóxicas, mutagênicas, teratogênicas e carcinogênicas. No presente trabalho foi adaptado e avaliado um método para determinação de aflatoxinas em produtos de tomate por cromatografia de camada delgada com detecção por comparação visual com padrões. Para verificar a possível contaminação de produtos de tomate comercializados com aflatoxinas foram analisadas 63 amostras de produtos de tomate (polpa, extrato, purê, catchup, tomate desidratado e tomate seco conservado em óleo) provenientes de 5 Estados e uma do exterior, compreendendo 29 marcas. A avaliação do método para determinação das aflatoxinas em produtos de tomate resultou em uma recuperação médía de 86%, para as quatro aflatoxinas, em dois níveis de adição. Os limites de detecção para as aflatoxinas B1, B2, G1 e G2 variaram entre 2 e 7 mg/Kg dependendo do tipo de produto. As aflatoxinas não foram detectadas em nenhuma das amostras analisadas
Abstract: A recent report on the presence of Aspergillus flavus and Aspergillus parasiticus in tomato pulp from a Brazilian plant caused concern about the possible presence of mycotoxins in tomato products from local plants. Aspergillus flavus and Aspergillus parasiticus are known producers of aflatoxins, a group of toxins with hepatotoxic, mutagenic, teratogenic, and carcinogenic properties. In the present work a thin layer chromatographic method with visual detection for the determination of aflatoxins in tomato products was adapted and evaluated. In order to verify a possible contamination of tomato products with aflatoxins, 63 samples of tomato products (pulp, paste, purée, catsup, dehydrated tomato and dried tomatoes in oil preserve) from 5 states and one from abroad, totaling 29 brands, were analyzed. The method evaluation showed an average recovery of 86%, for all four aflatoxins, at two levels of addition. The detection limits for the aflatoxins 81, 82, G1 e G2 ranged from 2 and 7 mg/Kg depending on the type of product. Aflatoxins were not detected in any of the samples analyzed.
Mestrado
Mestre em Ciência de Alimentos
5
Cotty, Peter J. « Aflatoxin Contamination : Variability and Management ». College of Agriculture, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/208346.
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Mapping aflatoxin contamination in the field reveals that most toxin occurs in relatively few, highly contaminated, bolls. Several studies suggest that protection of early bolls from pink bollworm damage will eliminate many of these highly contaminated bolls. Early harvest will also help reduce aflatoxin contamination. However, the crop must still be carefully managed after harvest because toxin content of mature bolls can increase very rapidly.
6
Cotty, P. J., D. R. Howell, C. Bock et A. Tellez. « Aflatoxin Contamination of Bt Cottonseed ». College of Agriculture, University of Arizona (Tucson, AZ), 1997. http://hdl.handle.net/10150/211132.
Texte intégralRésumé :
Transgenic Bt cotton may have reduced susceptibility to aflatoxin contamination as a result of pink bollworm resistance. During 1995 and 1996, Bt cottonseed from several commercial fields in Arizona contained aflatoxin levels unacceptable for dairy use. Comparison of cottonseed with and without BGYF (bright-green-yellow fluorescence) from one highly contaminated (> 6,000 ppb aflatoxin Bj) Bt seed lot indicated that most contamination probably resulted from exposure of mature cotton to high humidity. Seed exhibiting BGYF was repeatedly detected in Bt cottonseed lots but, pink bollworm exit holes were not observed in the field. A field plot test in 1996 demonstrated high resistance among Bt cultivars to both pink bollworm damage and formation of BGYF seed cotton. These observations suggest that resistance to pink bollworm will result in reduced aflaaoxin contamination when pink bollworm pressure coincides with conditions conducive to Aspergillus flavus infection. However, Bt cultivars are not resistant to aflatoxin increases occurring after boll opening and large quantities aflatoxin can form during this period. If insect control provided by Bt cultivars leads growers to hold crops in the field longer, most advantages of Bt cotton in aflatoxin management may be lost. Combined use of Bt cultivars and atoxigenic strains of A. flavus may result in the most reliable control of aflatoxin contamination.
7
Waltman, Lindsey. « Effect of Squestering Agents on Aflatoxin in Milk of Dairy Cows Fed Aflatoxin-contaminated Diets ». NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-07172008-121019/.
Texte intégralRésumé :
Three experiments (EXP) were conducted to determine the potential of experimental sequestering agents, clays or non-digestible yeast oligosaccharides, to reduce milk aflatoxin concentration in lactating Holstein cows consuming aflatoxin. All EXP included two periods in a randomized block design. Cows were fed an aflatoxin-contaminated total mixed ration (TMR) for both periods of all trials. During the first period, cows received no sequestering agents in the TMR, but agents were included in the TMR for the second period. EXP 1 and 2 consisted of two 7 d periods with 12 cows per treatment. Milk aflatoxin (AFM1) concentrations were analyzed by HPLC for milk samples collected on d 5 to 7 and d 11 to 13. Two treatments in EXP 1 were: 1) control (no sequestering agent n=12), and 2) 100g/cow/day Lallemand n=12. Four treatments in EXP 2 were: control (no sequestering agent) n=12, 2) 10g/cow/day MTB-100® (2004) n=12 (Alltech, Inc., Nicholasville, KY), 3) 10g/cow/day MTB-100® 2006 n=12 (Alltech, Inc., Nicholasville, KY) n=12, and 4) 10g/day/cow Alltech experimental (Alltech, Inc., Nicholasville, KY) n=12. EXP 3 consisted of two 8 d periods and included 14 cows. Milk samples from d 4 to 8 and d 11 to 16 were analyzed for AFM1 concentrations by ELISA. Three treatments in EXP 3 were: 1) control (no sequestering agent) n=4, 2) MTB-100® 2006 (Alltech, Inc., Nicholasville, KY) n=5 and 3) Astra-Ben 20A® (AB-20A®) (Prince Agri Products, Inc., Quincy, IL) n=5.For all EXPs, the percent differences in AFM1 concentrations between periods 1 and 2 were calculated. All percent differences were normalized using a correction factor that converted values for controls to zero. The changes from zero (%) due to sequestering agents were considered significant at P < 0.05. In EXP 1, the addition of a mixture of NYO-A and diatomite-montmorillonite resulted in a 5.2% numerical increase in AFM1 concentration. In EXP 2, MTB-100® (2004), MTB-100® (2006), and Alltech experimental product resulted in 8.0%, 6.2%, and 9.5% numerical increases in AFM1 concentrations respectively. In EXP 3, MTB-100® (2006) resulted in a 5.1% numerical decrease in AFM1 concentrations, and AB-20A® resulted in a 60.4% significant decrease in AFM1 concentrations. In summary, the AB-20A® in EXP 3 reduced AFM1 concentrations (P=0.01). There were no significant changes (P>0.25) in AFM1 concentrations in response to sequestering agents other than AB-20A®.
8
Navas, Sandra Aparecida. « Possivel exposição de crianças as aflatoxina M1 e ocratoxina A, atraves do leite materno, na cidade de São Paulo ». [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256162.
Texte intégralRésumé :
Orientador: Delia B. Rodriguez-AmayaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Tendo em vista o fato das crianças serem mais sensíveis aos efeitos adversos de aflatoxina M1 (AFM1) e ocratoxina A (OTA) comparativamente aos adultos, este trabalho teve como objetivo padronizar metodologia para determinação de AFM1 e OTA em leite matemo, avaliar a incidência das citadas toxinas em Banco de Leite Humano do Hospital Regional Sul, da cidade de São Paulo, e correlacionar os resultados obtidos com a alimentação consumida pelas mães. Os métodos estabelecidos para a determinação de AFM1 e OT A envolveram extração da AFM1 com metanol e OT A com bicarbonato de sódio 1 % e metanol, seguido da limpeza por colunas de imunoafinidade com anticorpos especificos para cada micotoxina e separação por cromatografia líquida de alta eficiência e quantificação com detector de fluorescência. A confirmação de AFM1 foi realizada através da reação de derivatização com ácido trifluoroacético (TFA) e para OTA por meio da reação de derivatização com ácido clorídrico concentrado (HCI). O método estabelecido para AFM1 apresentou porcentagem de recuperação e coeficiente de variação de 93,6% e 17,S%, respectivamente para a contaminação de 0,01 ng/mL. Para o método de OTA, os valores correspondentes são 83,9% e 14,1% no mesmo nível de contaminação (0,01 ng/mL). O limite de quantificação para ambos os métodos foi de 0,01 ng/mL. Do total de SO amostras analisadas, apenas uma continha a AFM1 (2% do total), em nível de 0,024 ng/mL e duas com OTA (4% do total), em nível de 0,011 e 0,024 ng/mL. Portanto, houve baixa incidência de AFM1 e OTA em leite materno proveniente do Banco de Leite do Hospital Regional Sul da cidade de São Paulo
Abstract: Since infants are more susceptible than adults to the adverse effects of aflatoxin M1 (AFM1) and ochratoxin A (OTA) , this work was carried out to establish and evaluate methods for the determination of AFM1 and OT A in human milk collected by the Human Milk Bank of the Southern Regional Hospital, city of São Paulo, and correlate the incidence of these mycotoxins to the mothers' diets, information obtained through a questionnaire. The methods established for the determination of AFM1 and OT A involved the extraction of AFM1 with methanol and OT A with 1 % sodium bicarbonate and methanol, followed by clean-up with immunoaffinity columns with antibodies specific for each mycotoxin and quantification by high performance liquid chromatography with a fluorescent detector. Confirmation of the identity of AFM1 was carried out by derivatization with trifluoroacetic acid (TFA) and of OT A by derivatization with concentrated hydrochloric acid (HCI). The method established for AFM1 had mean recovery percentage and coefficient of variation of 93.6% and 17.5%, respectively, at the contamination levei of 0.01 ng/mL. For the OTA method, the corresponding values were 83.9% and 14.1% at the same levei of contamination. The limit of quantification for both methods was 0.01 ng/mL. Of a total of 50 samples analyzed, only one was contaminated with AFM1 (2%), at 0.024 ng/mL and two with OTA at 0.011 and 0.024 ng/ml. There was low incidence of AFM1 and OT A, therefore, in human milk from the Milk Bank of the Southern Regional Hospital, city of São Paulo
Mestrado
Mestre em Ciência de Alimentos
9
Stroud, Jillian Summer. « The Effect of Feed Additives on Aflatoxin in Milk of Dairy Cows Fed Aflatoxin-Contaminated Diets ». NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-07262006-181138/.
Texte intégralRésumé :
Sixty lactating Holstein cows were used in a replicated block experiment to determine the efficacy of eight feed additives to reduce the transfer of aflatoxin (AF) from feed to milk. Six cows were allocated to each treatment group and 12 to a control group. All cows were fed the same aflatoxin-contaminated total mixed ration (TMR) with either no additive (control) or one of eight additives at 0.5% of the TMR dry matter (DM). Milk samples were collected twice daily to evaluate changes in milk AF concentration, milk AF excretion (milk AF concentration × milk yield); and AF transfer from feed to milk (AF excretion as a percentage of AF intake). All changes were expressed as percentages and calculated relative to the control group which defined zero change. Four of the eight additives resulted in significant reductions (P < 0.05) in milk AF concentration, secretion, and AF transfer ranging from 34.98-40.39%, 36.36-52.28%, and 34.45-48.44%, respectively. Dry matter intake (DMI) was significantly reduced (P < 0.001) by the consumption of AF, while milk production was not affected during the same time period. Neither DMI nor milk production were affected by the addition of treatment products to the diet when compared to control (P > 0.05).
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Rodríguez, Blanco María. « Mycotoxin risk in dairy farms : feedstuffs contamination, aflatoxin transference to milk and thermal stability of aflatoxin M1 ». Doctoral thesis, Universitat de Lleida, 2019. http://hdl.handle.net/10803/667885.
Texte intégralRésumé :
Les micotoxines són metabòlits secundaris tòxics produïts per fongs filaments que poden contaminar una àmplia varietat de productes agrícoles tant en etapes precollita com en etapes postcollita. La gestió de la contaminació per micotoxines durant la cadena de producció de la llet és essencial per evitar la presència d'aflatoxina M1 (AFM1) en la llet com a conseqüència de l'exposició d'animals productors de llet a pinsos contaminats per aflatoxina B1 (AFB1). L'objectiu d'aquesta tesi va ser l'estudi de la contaminació per micotoxines en pinsos i ingredients per a pinsos per a vaques lleteres i la seva transferència a la llet. La presència d'aflatoxines i micotoxines de Fusarium es va avaluar mitjançant l'anàlisi de mostres de ració total barrejada (TMR) i diferents tipus d'ensitjats per a vaques lleteres. Mostres de llet procedents de vaques alimentades amb les mostres de TMR recollides es van analitzar per estimar la transferència de AFB1 en el pinso a AFM1 en la llet. Per saber si el tractament tèrmic afecta el contingut de AFM1 en la llet durant el seu processat, es van provar diferents tractaments tèrmics en llet contaminada natural i artificialment.Las micotoxinas son metabolitos secundarios tóxicos producidos por hongos filamentos que pueden contaminar una amplia variedad de productos agrícolas tanto en etapas precosecha como en etapas poscosecha. La gestión de la contaminación por micotoxinas durante la cadena de producción de la leche es esencial para evitar la presencia de aflatoxina M1 (AFM1) en la leche como consecuencia de la exposición de animales productores de leche a piensos contaminados por aflatoxina B1 (AFB1). El objetivo de esta tesis fue el estudio de la contaminación por micotoxinas en piensos e ingredientes para piensos para vacas lecheras y su transferencia a la leche. La presencia de aflatoxinas y micotoxinas de Fusarium se evaluó mediante el análisis de muestras de ración total mezclada (TMR) y diferentes tipos de ensilados para vacas lecheras. Muestras de leche procedentes de vacas alimentadas con las muestras de TMR recogidas se analizaron para estimar la transferencia de AFB1 en el pienso a AFM1 en la leche. Para saber si el tratamiento térmico afecta al contenido de AFM1 en la leche durante su procesado, se probaron diferentes tratamientos térmicos en leche contaminada natural y artificialmente.
Mycotoxins are toxic secondary metabolites produced by filamentous fungi which can contaminate a wide variety of agricultural commodities either at pre-harvest or post-harvest stages. Through the milk supply chain, the management of mycotoxin contamination is essential in order to avoid the presence of aflatoxin M1 (AFM1) in milk as a consequence of the exposure of lactating animals to aflatoxin B1 (AFB1)-contaminated feed. The aim of this Thesis was to evaluate the mycotoxin contamination of feed and feed ingredients for dairy cows and their transference to milk. The occurrence of aflatoxins and Fusarium mycotoxins was evaluated through the analysis of total mixed ration (TMR) samples and different types of silages for dairy cows. Milk samples collecting from cows fed with the sampled TMR were analysed so as to estimate the transference of AFB1 form feed to AFM1 in milk. In order to know whether heat treatment affect to the AFM1 content in milk during processing, different heat treatments were tested in artificially and naturally contaminated milk.
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Saad, Anwar Mudher. « The use of aflatoxin M1 monitoring for studying levels of exposure to aflatoxin for mothers and children ». Thesis, University of Surrey, 1992. http://epubs.surrey.ac.uk/843217/.
Texte intégralRésumé :
The present study was carried out in Abu Dhabi to evaluate the levels of contamination of mother's milk with the 4-hydroxy metabolite of aflatoxin B1. More than 22 nationalities living in Abu Dhabi were chosen as donors for this study. These different nationalities have different food habits. Most of those donors with the exception of U.A.E. have come to U.A.E. at ages 18 - 35 years. Their previous food habits have been looked into in comparison with the present style of life in U.A.E. The present study revealed that mother's milk is showing an increase in the level of aflatoxin contamination. The level of AFM; in mother's milk was as high as 3 ng / ml and, from 445 mother donors, AFM1 was detected in 99.5% of mother's breast milk. Analysis of the data shows no significant correlation between nationalities and total fat content of mother's milk with the level of AFM1. However, a detailed analysis of the composition of the milk fat revealed that milk rich in saturated fatty acid may be associated with high level of aflatoxin M1. In contrast milk containing high AFM1 usually had low levels of linoleic acid. High concentration of Lactose, the sole carbohydrate in human milk, has no association with AFM1 levels. It was found that a high protein content in the diet may be associated with high AFM1, in the mother's milk. Clearly the interaction between dietary factors, the presence of AFB1 in the diet, and the physiology of milk production are complex.
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Gouas, Doriane. « Association entre le mutant p.R249S de p53 et la protéine HBx du virus de l’hépatite B dans les carcinomes hépatocellulaires ». Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10280.
Texte intégralRésumé :
La mutation R249S (mutant p.R249S) du gène TP53, caractéristique de l'exposition à l'aflatoxine B1 (AFB1), est la plus fréquente dans les carcinomes hépatocellulaires (CHC) et est dans la plupart des cas associée à une infection chronique par le virus de l'hépatite B (VHB). En effet, il existe une synergie entre ces deux facteurs de risque, augmentant ainsi le risque de développer un CHC. Dans une première partie, nous avons étudié les mécanismes moléculaires de cette synergie dans différents modèles cellulaires puis dans une deuxième partie nous avons utilisé une approche épidémiologique pour étudier l'interaction entre la mutation R249S et le VHB. Nous avons tout d'abord montré que p.R249S avait perdu ses fonctions liées à p53wt. D'autre part, p.R249S était capable de former un complexe protéique avec l'oncoprotéine virale HBx dans les cellules de CHC PLC/PRF/5. Dans la deuxième partie de ce travail, nos résultats montrent que la mutation R249S est détectable dans l'ADN du sérum de sujets asymptomatiques de Gambie rurale (Afrique de l'Ouest). Notre travail met en évidence des variations temporelles quantitatives de la mutation R249S. Ces variations dépendent des niveaux d'exposition d'AFB1 mais également de la présence du VHB, suggérant une interaction entre l'AFB1 et le VHB. Enfin, dans une autre étude menée en Gambie et basée sur le recrutement de sujets ayant développés un CHC ou non (contrôles) nos résultats montrent que la mutation R249S est fortement associée au gène HBX complet dans les CHC. Cette association pourrait ainsi expliquer en partie l'effet synergique observé entre l'AFB1 et le VHB. A terme, une cible critique pourrait être identifiée pour des interventions préventives ou thérapeutiques précoces sur les CHC dans les régions de forte incidenceR249S mutation (mutant p.R249S) of TP53 gene, characteristic of the exposure to aflatoxin B1, is the most frequent TP53 mutation in hepatocellular carcinoma (HCC) and is highly associated with chronic hepatitis B virus infection (HBV). Indeed, a synergistic effect exists between these two main risk factors, thus increasing the risk to develop HCC. In a first part, we have studied the molecular mechanisms of this synergy in different cellular models and then, in a second part we have used an epidemiology-based approach to investigate the interaction between the R249S mutation and HBV. Firstly, we have shown that p.R249S has lost p53wt functions. Moreover, p.R249S formed a protein complex with the oncoprotein HBx from HBV in the HCC cell line PLC/PRF/5. In the second part, our results show that R249S mutation is detectable in plasma DNA of asymptomatic subjects from the rural Gambia (West Africa). Our work shows quantitative variations of R249S mutation that are dependent on the levels of exposition to AFB1 but also on the presence of HBV, suggesting an interaction between AFB1 and HBV. Finally, in another study performed in The Gambia and based on subjects with HCC or not (controls), our results show that R249S mutation is highly associated with HBX complete gene in HCC. Therefore this association could explain in part the synergistic effect observed between AFB1 and HBV. Eventually, a critical target may be identified for preventive or early therapeutic interventions on HCC of high-incidence regions
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Apolinario, Letícia de Araujo. « Efeito da lectina ArtinM na hepatocarcinogênese induzida por Aflatoxina B1 ». Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/17/17143/tde-23042018-112514/.
Texte intégralRésumé :
ArtinM é uma lectina ligante a carboidrato D-manose que se interage a receptores de células fagocíticas induzindo a produção de mediadores pró- inflamatórios relacionados à resposta imune antitumoral. Aflatoxinas são micotoxinas produzidas por fungos do gênero Aspergillus. A Aflatoxina B1 (AFB1) é a toxina sintetizada mais abundantemente e a que apresenta o maior poder toxigênico, sendo capaz de induzir carcinoma hepatocelular (CHC) em humanos. O objetivo deste estudo foi investigar o papel da lectina ArtinM na hepatocarcinogênese induzida pela AFB1 em ratos. Setenta e dois ratos recém-desmamados foram divididos em três grupos: Controle - animais tratados com veículo; AFB1 - animais intoxicados com AFB1; AFB1+ArtinM - animais tratados com AFB1 e ArtinM. Ratos Wistar foram intoxicados por gavagem com 400 ?g de AFB1 por quilograma de ração ingerida durante três meses, enquanto o grupo AFB1+ArtinM recebeu adicionalmente três doses da lectina por via subcutânea (50 ?g por quilograma de peso do animal por dose) nos 45, 60 e 75 após inicio do experimento. Animais foram eutanasiados 3 e 12 meses após início das gavagens. A expressão hepática de proteínas relacionadas à hepatocarcinogênese foi avaliada por técnicas de imunohistoquímica, Western blotting e PCR em tempo real nos animais eutanasiados após 3 meses de intoxicação. A incidência de lesões pré-neoplásicas e de tumores hepáticos foi mensurada 3 e 12 meses após início das gavagens, respectivamente. Os animais tratados com ArtinM apresentaram maior expressão hepática de proteínas supressoras tumorais além de redução do número de focos pré-neoplásicos e de tumores hepáticos em relação aos animais que receberam apenas a micotoxina. Conclui-se, portanto, que ArtinM possui efeito protetor durante o processo de hepatocarcinogênese induzida por AFB1.ArtinM is a D-mannose carbohydrate-binding lectin that interacts with phagocytic cell receptors inducing the production of pro-inflammatory mediators related to the antitumor immune response. Aflatoxins are mycotoxins produced by fungi of the genus Aspergillus. Aflatoxin B1 (AFB1) is the toxin most abundantly synthesized and the one with the highest toxigenic power, being able to induce hepatocellular carcinoma (HCC) in humans. The aim of this study was to investigate the role of ArtinM lectin in AFB1-induced hepatocarcinogenesis in rats. Seventy-two newly weaned rats were divided into three groups: Control - vehicle-treated animals; AFB1 - animals poisoned with AFB1; AFB1 + ArtinM - animals treated with AFB1 and ArtinM. Wistar rats were gavage-poisoned with 400 ?g AFB1 per kilogram of ration fed for three months, while the AFB1 + ArtinM group received three subcutaneous doses of the lectin (50 ?g per kilogram of animal weight per dose) 45, 60 and 75 days after the start of the experiment. Animals were euthanized 3 and 12 months after initiation of treatments. Hepatic expression of hepatocarcinogenesis-related proteins was assessed by immunohistochemistry, Western blotting, and realtime PCR in euthanized animals after three months of intoxication. The incidence of pre-neoplastic lesions and liver tumors was measured 3 and 12 months after the start of treatments, respectively. Animals treated with ArtinM had fewer pre-neoplastic foci and hepatic tumors than the animals that receiving mycotoxin alone, as well as showing greater hepatic expression of tumor suppressor proteins. It is concluded, therefore, that ArtinM has a protective effect during the process of hepatocarcinogenesis induced by AFB1.
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Mota, Monique Matias. « Diferentes níveis vitamínicos na dieta de frangos de corte ». Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/74/74131/tde-19032013-094024/.
Texte intégralRésumé :
Foi realizado um experimento no aviário experimental do Departamento de Zootecnia da Universidade de São Paulo (USP), na Faculdade de Zootecnia e Engenharia de Alimentos (FZEA), em Pirassununga/SP com o objetivo de avaliar o efeito de dois níveis vitamínicos (comercial e OVN) com ou sem aflatoxina em dietas de frangos de corte no período de 1 a 42 dias. Foram utilizados 1800 pintinhos, machos, Cobb 500, distribuídos em um delineamento inteiramente casualizado em esquema fatorial 2 x 2 x 2 (2 níveis vitamínicos - comercial e OVN, 2 níveis de aflatoxina - 0 ppm e 0,5 ppm, e 2 níveis de adsorventes - 0 e 10 kg/ton), totalizando 8 tratamentos com 15 repetições de 15 aves cada. As dietas foram fornecidas fareladas e a base de milho e farelo de soja, formuladas segundo os níveis praticados por uma integradora da região. Para avaliar o desempenho foram analisados o consumo de ração, ganho de peso e conversão alimentar de 1 a 49 dias. Para avaliação de carcaça (rendimento de carcaça, peito e pernas), determinação de incidência de BBS e determinação do peso das vísceras abdominais e coração foram abatidas duas aves por repetição aos 45 dias. Os resultados mostraram que frangos de corte, machos, alimentados com nível OVN de vitaminas, apresentaram melhor ganho de peso, conversão alimentar, rendimento de carcaça e peito quando comparado com o nível comercial de vitaminas (P<0,05) e que as dietas contendo 0,5 ppm de aflatoxinas resultaram em menor ganho de peso, rendimento de carcaça, porcentagem de peito e aumentou o tamanho do coração e fígado do animal (P<0,05). O uso de 10kg/ton de adsorvente só apresentou resultado positivo no final da vida dos animais (dos 39 a 49 dias) (P<0,05) e somente na conversão alimentar. Esse estudo permite concluir que a aflatoxina resulta em perdas de desempenho e rendimento de carcaças e que o fornecimento de níveis ótimos de vitaminas melhora os resultados dessas características. O uso de adsorventes se mostrou inviável nesse estudo.An experiment was conducted in an experimental aviary the Department of Animal Science, University of São Paulo (USP), the Faculty of Animal Science and Food Engineering (FZEA) in Pirassununga/SP, to evaluate the performance, carcass characteristics and weight of offal in broiler chickens fed with two levels of vitamins (commercial and VNO) with or without aflatoxin in broiler diets. Were used 1800 chicks, male, Cobb 500 distributed in a completely randomized 2 x 2 x 2 factorial arrangement (two vitamin levels, two levels of aflatoxin and two levels of adsorbents), totaling eight treatments with 15 replicates of 15 birds each. Diets were fed mash and corn and soybean meal, formulated according to the levels charged by an integrator in the region. To evaluate the performance were analyzed feed intake, weight gain, feed conversion from 1 to 49 days. For evaluation of carcass yield (carcass, breast and legs), determination of the incidence of BBS and determination of the weight of the abdominal viscera and heart were killed two birds per replicate at 45 days. The results showed that broilers, males fed VNO level of vitamins showed better weight gain, feed conversion, carcass yield and breast when compared to the commercial level of vitamins (P<0.05) and that diets intoxicated with 0.5 ppm of aflatoxin resulted in less weight gain, carcass yield, percentage of breast and increased the size of the heart and liver of the animal (P<0.05). The use of adsorbent 10kg/ton only had a positive result at the end of life of animals (from 39 to 49 days) (P<0.05) and only in the feed. This study indicates that aflatoxin results in loss of performance and carcass yield and the provision of optimal levels of vitamins improved the results of these characteristics. The use of adsorbents in this study proved to be unfeasible.
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Abdel-Hadi, Ahmed. « Molecular ecology of aspergillus section flavi species : approaches to understand the role of aflatoxin genes in aflatoxin biosynthesis ». Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/5571.
Texte intégralRésumé :
This is the first study to integrate and correlate the effect of ecophysiological factors on the life cycle of Aspergillus flavus by carrying out complementary work on gene expression of the aflatoxin gene cluster, with growth, sporulation and phenotypic toxin production. This information was used to understand the role of ecological factors on key biosynthetic genes and examine the use of such information for control of aflatoxin production using RNA interference. Ecological studies showed the profiles for growth, sporulation and aflatoxin B1 (AFB1) production with optimum ranges of water activity (aw) and temperature for AFB1 production being identified. A. flavus grew faster at 0.99 aw at all temperatures, but optimally at 30-35°C. The highest amount of asexual conidia was produced at 0.95 aw followed by 0.90 aw and then 0.99 aw at all temperatures examined. Interestingly, the partitioning of AFB1 into biomass, medium and spores showed that at 0.99 aw, about 50% of the mycotoxin was present in the biomass and the medium, with very little present in the spores. However, as water stress was imposed there was a switch to a significantly higher channelling of AFB1 (about 45%) into the spores, especially at 0.95 and 0.93 aw levels. A microarray analysis was used to examine the effect of aw x temperature interactions on the relative expression of the aflatoxin gene cluster for the first time using A. flavus NRRL 3357. This showed that under mild stress conditions (20°C/0.99 aw) several of the cluster genes, in particular aflS and aflJ, were highly induced concomitant with high levels of phenotypic AFB1 production. Highest amounts of AFB1 were produced in all conditions where aflS expression was elevated. When the ratio between the normalised expression data of the aflS/aflR genes was generated, high ratios were obtained at 25°C and 30°C at 0.99 and 0.95 aw and low ratios at 25°C and 30°C at 0.90 aw. This is in agreement with the AFB1 production profile. Cont/d.
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Kachapulula, Paul W., et Paul W. Kachapulula. « Aflatoxin-Producing Fungi and Contamination in Zambia ». Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/625642.
Texte intégralRésumé :
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.
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Probst, Claudia. « Fungi Associated with Aflatoxin Contamination in Africa ». Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/201499.
Texte intégralRésumé :
Aflatoxins are secondary metabolites produced by members of the fungal genus Aspergillus. Immunosuppressive and carcinogenic activities of these toxins negatively impact human health especially in developing countries. Severity of contamination is influenced by both fungal community structure and the environment to which the crop is exposed either prior to or after harvest. In 2004, a severe episode of lethal human aflatoxicosis occurred in the Eastern Province of Kenya. Analysis of fungal community structure revealed that this event was caused by a previously unknown fungal lineage closely resembling the S strain morphotype of Aspergillus flavus. Fungal communities associated with maize produced in affected regions of Kenya were invariably dominated by the new fungal lineage and its incidence was strongly correlated with maize aflatoxin content. Analyses of fungal communities of maize grown in adjacent Kenyan provinces showed that incidences of the new lineage are limited outside the Eastern Province where the aflatoxicoses outbreaks occurred. Multi-locus phylogenetic analyses suggest the newly identified Kenyan lineage is closely related to the B and G aflatoxin producing species A. minisclerotigenes, and more distantly related to both the A. flavus S strain and an unnamed taxon with similar morphology endemic in West Africa (strain SBG). Sequence analyses of the cypA aflatoxin biosynthesis gene identified a previously unknown 2.2 kb deletion unique to the Kenyan lineage and coherent with its phylogenetic placement. A polyphasic approach was used to study aflatoxin-producing fungal communities, with emphasis on occurrence of fungi with S strain morphology, in Sub-Saharan Africa. Four phylogenetically distinct groups of fungi with S strain morphology were identified with restrictions to West Africa (strain SBG) or Central and East Africa (A. flavus S strain, A. minisclerotigenes, the new lineage). Aflatoxin production in synthetic media was a poor predictor of aflatoxin production in viable maize grain. An in vitro assay was developed to predict the aflatoxin-producing potential of fungal isolates in maize. This screen was used to identify atoxigenic isolates of A. flavus with potential value for biological control within highly toxic Aspergillus communities associated with maize production in Kenya. These atoxigenic isolates have potential value for mitigating aflatoxin contamination in Kenya.
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Eichelberger, J. Michael. « Aflatoxin B1 Metabolism in Mammalian Pulmonary Tissue ». DigitalCommons@USU, 1997. https://digitalcommons.usu.edu/etd/3981.
Texte intégralRésumé :
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.
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Mencarelli, Mariangela <1982>. « Practical implications of aflatoxin contamination in corn ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4885/4/Tesi_Dott.sa_Mencarelli_M.pdf.
Texte intégralRésumé :
Aflatoxin (AFL) contamination of corn is a serious economic and food security issue. Although a variety of technical solutions for reducing AFL contamination of corn have been proposed, only a few have produced satisfactory results. A successful approach is a biocontrol strategy consisting of using non-flatoxigenic strains of Aspergillus flavus to replace indigenous AFL-producing isolates. The main objective of the present thesis was to investigate the dynamic and contamination of AFL/A. flavus in corn in Northern Italy. The study also investigated the role of the key-pest of corn, the European Corn Borer (ECB), on AFL contamination and dispersal of A. flavus propagules in corn. Finally, the study evaluated the feasibility of bioplastic-based granules entrapping a non-aflatoxigenic A. flavus strain for the biocontrol of this fungus in corn.
The 2-year field study demonstrated the efficacy of the bioplastic formulation to reduce AFL contamination in corn. More precisely, although AFL contamination varied among the two years, application of 15 and 30 kg ha-1 of granules reduced AFL contamination to up 60 and 85% in 2009 and 2010 respectively. Microbiological analysis showed that the relative abundance of non-aflatoxigenic soil isolates significantly increased after 1 month from granules application (mid-May) and throughout the corn-growing season. These findings were consistent with data obtained using a bioplastic-based bait specifically developed to selectively isolate Aspergilli from soil and other environmental samples. In addition, field and laboratory evaluations showed that the level of damages produced by ECB larvae were not significantly correlated to A. flavus infestation and AFL contamination.
Taking together, these findings demonstrated that AFL contamination of corn in Northern Italy was variable, but above the EU limit for human consumption. First proposed in the USA, this study showed the practical possibility of this formulation to be use for reducing AFL contamination in corn in the EU.
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Mencarelli, Mariangela <1982>. « Practical implications of aflatoxin contamination in corn ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4885/.
Texte intégralRésumé :
Aflatoxin (AFL) contamination of corn is a serious economic and food security issue. Although a variety of technical solutions for reducing AFL contamination of corn have been proposed, only a few have produced satisfactory results. A successful approach is a biocontrol strategy consisting of using non-flatoxigenic strains of Aspergillus flavus to replace indigenous AFL-producing isolates. The main objective of the present thesis was to investigate the dynamic and contamination of AFL/A. flavus in corn in Northern Italy. The study also investigated the role of the key-pest of corn, the European Corn Borer (ECB), on AFL contamination and dispersal of A. flavus propagules in corn. Finally, the study evaluated the feasibility of bioplastic-based granules entrapping a non-aflatoxigenic A. flavus strain for the biocontrol of this fungus in corn.
The 2-year field study demonstrated the efficacy of the bioplastic formulation to reduce AFL contamination in corn. More precisely, although AFL contamination varied among the two years, application of 15 and 30 kg ha-1 of granules reduced AFL contamination to up 60 and 85% in 2009 and 2010 respectively. Microbiological analysis showed that the relative abundance of non-aflatoxigenic soil isolates significantly increased after 1 month from granules application (mid-May) and throughout the corn-growing season. These findings were consistent with data obtained using a bioplastic-based bait specifically developed to selectively isolate Aspergilli from soil and other environmental samples. In addition, field and laboratory evaluations showed that the level of damages produced by ECB larvae were not significantly correlated to A. flavus infestation and AFL contamination.
Taking together, these findings demonstrated that AFL contamination of corn in Northern Italy was variable, but above the EU limit for human consumption. First proposed in the USA, this study showed the practical possibility of this formulation to be use for reducing AFL contamination in corn in the EU.
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Gorayeb, Teresa Cristina Castilho [UNESP]. « Avaliação das condições críticas para o surgimento de Aflatoxina na cadeia de processamento de amendoim (Arachis hypogaea L.) ». Universidade Estadual Paulista (UNESP), 2007. http://hdl.handle.net/11449/90775.
Texte intégralRésumé :
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gorayeb_tcc_me_sjrp.pdf: 727819 bytes, checksum: c7b2371e2daddf295fbcad8a255c30b7 (MD5)Este trabalho visa fornecer às autoridades sanitárias e ao setor industrial elementos que possam contribuir para a prevenção do perigo químico aflatoxina em amendoim (Arachis hypogaea L.) e seus derivados. O estudo foi realizado em três partes: A Parte A, compreendeu a elaboração dos planos APPCC (Análise dos Perigos e Pontos Críticos de Controle) no processamento das indústrias de beneficiamento de grãos de amendoim (Empresa A) e de fabricação de doces de amendoim (Empresa B), identificando as etapas do processo que apresentam pontos críticos de controle (PCC) para o perigo químico aflatoxina. Observou-se que nos dois processos não há nenhum método que consiga destruir, ou mesmo reduzir os teores, da micotoxina. Assim, restam manter rigorosos controles e monitoramentos em cada PCC quanto aos índices de aflatoxina e de umidade dos grãos como medidas preventivas para prevenir e reduzir a possibilidade de infestação dos grãos por fungos e conseqüente produção de aflatoxina. As etapas de recepção dos grãos, secagem, armazenamento e transporte são as que requerem maior atenção na cadeia de beneficiamento. Para a indústria de doces, as etapas mais críticas são as de recepção e armazenamento de grãos e de doces e o transporte. Na Parte B, foram obtidas as isotermas de sorção até o equilíbrio higroscópico de três variedades de amendoim (Runner IAC 886, Caiapó e Tatu Vermelho), para uma ampla faixa de umidade relativa e temperaturas controladas. Verificou-se que o equilíbrio higroscópico dos três amendoins é diretamente proporcional à umidade relativa do ar e decrescente com o aumento de temperatura, para uma mesma umidade relativa. A variedade Caiapó apresentou uma umidade de equilíbrio menor que as outras variedades, podendo-se dizer que a quantidade de lipídeos e carboidratos...
The purpose of this work is to provide technical information to the authorities and industries on aflatoxin production and prevention measures in peanuts (Arachis hypogaea L.) and its products. The work was divided in three parts: Part A: HACCP (Hazard Analysis and Control of Critical Points) plans elaboration in two industries, one of post-harvest treatment of peanuts (Industry A) and another of peanuts candy products (Industry B). Critical Control Points (CCP) for aflatoxin were indentified, and it was observed that no process measure is available to eliminate or even reduce the toxin. Thus, rigid monitoring and control on aflatoxin content must be carried on to avoid fungus infestation and hence toxin production. The process steps of raw peanuts reception, drying, storage and transportation are critical for Industry A. For Industry B, the most important steps are reception and storage of both raw peanuts and candies. Part B: sorption isotherms for three peanuts varieties (Runner IAC 886, Caiapó e Tatu vermelho) were obtained, for wide relative humidity (RH) and temperature (T) ranges. Hygroscopic equilibrium is directly proportional to RH and conversely proportional to T. Caiapó variety presented the lowest equilibrium moisture content (EMC), confirming that lipids and carbohydrates quantities area correlated to EMC. The Modified Halsey model was the best on representing the experimental sorption data. Part C: microbiological experiments were carried out to assess fungus growth and aflatoxin production in String bean and kernels of Runner IAC 886 peanuts. Two concentrations of Aspergilus flavus spores 104 e 106 spores/mL, were inoculated, two storage periods were used 15 and 30 days, three relative humidities were employed 75 %, 84 % and 90 %, and three temperature were applied 25, 30 and 35º C. Growth analysis was assessed by counting spores ...(Complete abstract click electronic access below)
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Ruadrew, Sayan. « Characterization of aflatoxin contamination of foods and identification of food components that protect against aflatoxin-mediated toxicity and mutagenicity ». Thesis, Glasgow Caledonian University, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687407.
Texte intégralRésumé :
Aflatoxins (AFs) are a group of mycotoxins produced by moulds of Aspergillus genus which contaminate food commodities of tropical and sub-tropical countries. The aims of this study are to assess the extent of AF contamination of foods in the UK that originated in Asia and to identify components of Thai foods that may protect against the toxicity of AFs. Examination of 12 commercial, dried Asian foods showed that long grain rice, fragrant rice, peanuts, black beans and black pepper contained Aspergillus spp. which were identified as A. parasiticus (afiatoxigenic), A. versicolor, A. ustus, A.niger and A. ochraceus. These commodities contained undetectable AFs. Jasmine brown rice and crushed chilli contained 14.7 and 11.4 IJglkg of AFs, respectively, in the absence of Aspergillus. AFBl, the most toxigenic AFs was detected in crushed chilli (lO.7IJglkg) so Aspergillus was present at some stage of food production, particularly pre-harvest stage. Cross contamination during food processing is one of possible cause of AFs contamination in these commodities. These results indicate direct and indirect risks of exposure to AFs from these products since AFs fOlmation is possible in Aspergillus-contaminated crops and AFs can be carried throughout the food chain. Hence an alternative strategy to mitigate toxicity of ingested AFs is required. One possibility is by using food components to modulate the harm from ingested AFs by altering AF metabolism and mutagenesis. In this study, the effectiveness of the compounds in Thai culinary herb, fingerroot (Boesenbergia rotunda) were investigated. A crude methanol extract (ME) of fingerroot was analysed and found to contain ~ 15 putative flavonoids as major components of which pinocembrin, pinocembrin chalcone, cardamonin, pinostrobin, 4-hydroxypanduratin A and panduratin A were identified by HPLC and LC-MS. The ME significantly inhibited fonnation of mutagenic/carcinogenic metabolite of AFBl (AFB1-epoxide, AFBO) in a cell-free metabolic system (Model 1) and also suppressed mutagenicity of AFBl in Salmonella/microsomal assay (Model 2). These inhibitory properties of the ME might be related to its indigenous flavonoids which could modulate activities of AFB1 -metabolising enzymes (CYPIA2, 3A4). Purified flavonoids (cardamonin, apigenin, pinostrobin) were found to affect AFB 1 toxicity to some extent in both models, but their potencies were much lower than the ME particularly in the Salmonella model and evidence is provided that suggests that Reactive Oxygen Species rather than AFBO are the mutagenic entities in this assay. This also suggests that fingerroot contains effective metabolic modulators that were not identified. Consumption of fmgerroot could provide a combination of potential phytochemicals that protect against aflatoxin-mediated toxicity by altering AF metabolism at the initial stages of enzymatic activation.
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Edwards, Melanie Love. « Genotypic and phenotypic characterization of response to aflatoxin and secondary traits in maize ». Texas A&M University, 2006. http://hdl.handle.net/1969.1/3828.
Texte intégralRésumé :
One major problem facing maize producers in the southern US is
contamination with the mycotoxin aflatoxin, produced by Aspergillus
flavus (Link:fr). Aflatoxin is a serious threat to human and animal
health, with no resistant commercial hybrid available.
Development of resistance to aflatoxin production has several major
limitations. Aflatoxin is highly variable both across and within
environments, even under inoculation, requiring several locations and
replications for breeding. Additionally, there is no screening method that
is reliable, rapid, inexpensive, and allows for high throughput.
Several secondary traits, such as kernel texture, kernel integrity, husk
cover, and visible ear rot, have previously shown to be related to
aflatoxin accumulation. These traits are easily characterized in the field and are candidates for indirect selection if they are correlated to
aflatoxin concentration.
Root lodging, a plantÂs inability to maintain upright stature, is another
complex characteristic of root related traits that traditionally is selected
for indirectly. It can greatly reduce harvestable yield. It is affected by
morphological traits and environmental conditions, but its genetic
components are little understood.
This dissertation comprises three studies presented in chapters II, III,
and IV. Chapter II involved white and yellow hybrid maize trials as well
as quality protein maize trials from several years across Texas
environments. Data was analyzed both per and across location to
determine repeatability of response to aflatoxin. Additionally, aflatoxin
levels were correlated to several secondary characteristics (female
flowering, endosperm texture, husk cover, and ear rot ratings) to
determine usefulness in indirect selection.
Chapter III was a phenotypic evaluation of a recombinant inbred line
(RIL) mapping population, which was derived from divergent parental
inbreds Tx811 and CML176. The trials were conducted in two Texas
locations, and phenotypic data for aflatoxin concentration, kernel integrity, endosperm texture, female flowering date, and root lodging was
collected. Variance components for these traits and genetic and
phenotypic correlations were determined.
Chapter IV was a genotypic evaluation of the Tx811/CML176 mapping
population using simple sequence repeat markers. Genotypic and
phenotypic data were combined to identify quantitative trait loci (QTL)
and epistatic interactions for response to aflatoxin and for root lodging.
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Shenasi, Mariam H. « Studies on the formation of mycotoxins, microbial interaction and biochemical composition during ripening stages of different cultivars of date fruit from the United Arab Emirates ». Thesis, Glasgow Caledonian University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251239.
Texte intégral
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Verheecke, Carol. « Modulation of Aflatoxin B1 production by Aspergillus flavus ». Phd thesis, Toulouse, INPT, 2014. http://oatao.univ-toulouse.fr/14149/1/verheecke.pdf.
Texte intégralRésumé :
Mycotoxins are toxic contaminants of foodstuffs produced by a wide range of fungal species. Aflatoxins are the only mycotoxins carcinogenic for humans. They are mainly produced by the Aspergillus genus and can be found at each step of the agrofood chain (e.g. field, storage, process). Due to climate changes, France is starting to be exposed to aflatoxins. In order to limit the consumer exposure, many prevention or decontamination techniques have been developed. To this aim, we started the development of a biocontrol against aflatoxins accumulation for maize field application. Actinomycetes, are soil-borne bacteria that has already been commercialized as biocontrol. In Petri dishes, we studied the in vitro interaction between some actinomycetes and Aspergillus flavus, the main aflatoxins producer. We revealed that the interaction reduced the aflatoxins content (monitored by HPLC). Moreover, some bacterial isolates were able to reduce pure-aflatoxin B1 added in the medium. To understand this mechanism, adsorption tests has been conducted. Otherwise, RT-qPCR methodology was used to study the impact of Streptomyces-Aspergillus sp. on aflatoxin gene expression. Finally, the current knowledge of the impact of environmental factors (temperature, water activity and incubation time) on aflatoxins production was supplemented.
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Knowles, Tim C., Vic Wakimoto, Del Wakimoto et Mike Keavy. « Aflatoxin Contamination of Bt and Non-Bt Cottonseed ». College of Agriculture, University of Arizona (Tucson, AZ), 1998. http://hdl.handle.net/10150/210387.
Texte intégralRésumé :
Transgenic Bt cotton varieties that are resistant to pink bollworm should sustain less feeding damage to bolls and cottonseed, compared to non-Bt varieties that are more susceptible to feeding damage by pink bollworm larvae. Prior to boll opening, the aflatoxin producing fungus Aspergillus flavus cannot penetrate undamaged cotton bolls. Thus resistance to pink bollworm could result in reduced aflatoxin contamination under high pink bollworm pressure. Cottonseed aflatoxin levels of Bt and non-Bt varieties were compared at various planting and harvest dates. Bt and non-Bt cotton varieties had similar cottonseed aflatoxin levels. Long season production systems favored high cottonseed aflatoxin levels, compared to short season production systems, regardles of the cotton variety grown.
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Emara, Hamdy Aly. « Production of aflatoxin by Aspergillus parasiticus and its control ». Thesis, University of Stirling, 1996. http://hdl.handle.net/1893/3461.
Texte intégralRésumé :
The aim of the present work was to investigate aflatoxin levels in various food commodities and to study its production by Aspergillus parasiticus in culture to find out the possible ways to control it. Of 40 food samples collected from Abha region, Saudi Arabia, only 25% were contaminated with aflatoxins. Oil-rich commodities had the highly contaminated commodities by fungi and aflatoxins while spices were free from afatoxins. The optimal pH for the growth of A. parasiticus and its productivity of aflatoxin B, was found at 6.0, while the best incubation conditions were found at 30°C for 10 days. D-glucose was the best carbon source for fungal growth, as well as aflatoxin production. Corn steep liquor, yeast extract and peptone were the best nitrogen sources for both fungal growth and toxin production. (NH4)2HPO4 (1.55 gL-1) and NaNO2 (1.6 gL-1) reduced fungal growth and toxin production with 37.7% and 85%, respectively. Of ten amino acids tested, asparagine was the best for aflatoxin B, production. Zn2+ and Co2+ supported significantly both fungal growth, as well as aflatoxin B, production at the different tested concentrations. Zn2+ was effective when added to A. parasiticus growth medium at the first two days of the culture age. The other tested metal ions gave variable effects depending on the type of ion and its concentration. Water activity (a ) was an important factor controlling the growth of A. parasiticus and toxin production. The minimum aW for the fungal growth was 0.8 on both coffee beans and rice grains, while aW, of 0.70 caused complete inhibition for the growth and aflatoxin B, production. H202 is a potent inhibitor for growth of A. parasiticus and its productivity of toxins. Incubation with NaHCO3 and C6H5000Na converted aflatoxin B, to a water-soluble form which returned to aflatoxin B, by acid treatment. Black pepper, ciliated heath, cuminum and curcuma were the most inhibitory spices on toxin production. Glutathione, quinine, EDTA, sodium azide, indole acetic acid, 2,4-dichlorophenoxy acetic acid, phenol and catechol were inhibitory for both growth, as well as, aflatoxin B, production. Stearic acid supported the fungal growth and decreased the productivity of AFBI gradually. Lauric acid is the most suppressive fatty acid for both fungal growth and aflatoxin production, but oleic acid was the most potent supporter. Vitamin A supported the growth but inhibited aflatoxin B, production. Vitamins C and D2 were also repressive particularly for aflatoxin production. The present study included determining the activities of some enzymes in relation to aflatoxin production in A. parasiticus culture during 20 days. Glycolytic enzymes and pyruvate-generating enzymes seems to be linked with aflatoxin B, production. Also, pentose-phosphate pathway enzymes may provide NADPH for aflatoxin B, synthesis. The decreased activities of TCA cycle enzymes particularly from 4th day of growth up to 10th day were correlated with the increase of aflatoxin B, production. All the tested enzymes as well as aflatoxin B, production were inhibited by either catechol or phenol.
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Nkama, I. « The fate of aflatoxin during the processing of rice ». Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375370.
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Kaya, Celiker Hande. « Mid-Infrared Spectral Characterization of Aflatoxin Contamination in Peanuts ». Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77219.
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Contamination of peanuts by secondary metabolites of certain fungi, namely aflatoxins present a great health hazard when exposed either at low levels for prolonged times (carcinogenic) or at high levels at once (poisonous). It is important to develop an accurate and rapid measurement technique to trace the aflatoxin and/or source fungi presence in peanuts. Thus, current research focused on development of vibrational spectroscopy based methods for detection and separation of contaminated peanut samples.
Aflatoxin incidence, as a chemical contaminant in peanut paste samples, was investigated, in terms of spectral characteristics using FTIR-ATR. The effects of spectral pre-processing steps such as mean-centering, smoothing the 1st derivative and normalizing were studied. Logarithmic method was the best normalization technique describing the exponentially distributed spectral data. Spectral windows giving the best correlation with respect to increasing aflatoxin amount led to selection of fat associated spectral bands. Using the multivariate analysis tools, structural contributions of aflatoxins in peanut matrix were detected. The best region was decided as 3028-2752, 1800-1707, 1584-1424, and 1408-1127 cm-1 giving correlation coefficient for calibration (R2C), root mean square error for calibration (RMSEC) and root mean square error for prediction (RMSEP) of 98.6%, 7.66ppb and 19.5ppb, respectively. Applying the constructed partial least squares model, 95% of the samples were correctly classified while the percentage of false negative and false positive identifications were 16% and 0%, respectively.
Aspergillus species of section Flavi and the black fungi, A. niger are the most common colonists of peanuts in nature and the majority of the aflatoxin producing strains are from section Flavi. Seed colonization by selected Aspergillus spp. was investigated by following the chemical alterations as a function of fungal growth by means of spectral readouts. FTIR-ATR was utilized to correlate spectral characteristics to mold density, and to separate Aspergillus at section, species and strain levels, threshold mold density values were established. Even far before the organoleptic quality changes became visually observable (~10,000 mold counts), FTIR distinguished the species of same section. Besides, the analogous secondary metabolites produced increased the similarity within the spectra even their spectral contributions were mostly masked by bulk peanut medium; and led to grouping of species producing the same mycotoxins together.
Aflatoxigenic and non-aflatoxigenic strains of A. flavus and A. parasiticus were further studied for measurement capability of FTIR-ATR system in discriminating the toxic streams from just moldy and clean samples. Owing to increased similarity within the collected spectral data due to aflatoxin presence, clean samples (having aflatoxin level lower than 20 ppb, n=44), only moldy samples (having aflatoxin level lower than 300 ppb, n=28) and toxic samples (having aflatoxin level between 300-1200 ppb, n=23) were separated into appropriate classes (with a 100% classification accuracy).
Photoacoustic spectroscopy (PAS) is a non-invasive technique and offers many advantages over more traditional ATR system, specifically, for in-field measurements. Even though the sample throughput time is longer compared to ATR measurements, intact seeds can be directly loaded into sample compartment for analysis. Compared to ATR, PAS is more sensitive to high moisture in samples, which in our case was not a problem since peanuts have water content less than 10%. The spectral ranges between: 3600-2750, 1800-1480, 1200-900 cm-1 were assigned as the key bands and full separation between Aspergillus spp. infected and healthy peanuts was obtained. However, PAS was not sensitive as ATR either in species level classification of Aspergillus invasion or toxic-moldy level separation. When run for separation of aflatoxigenic versus non-aflatoxigenic batches of samples, 7 out of 54 contaminated samples were misclassified but all healthy peanuts were correctly identified (15 healthy/ 69 total peanut pods).
This study explored the possibility of using vibrational spectroscopy as a tool to understand chemical changes in peanuts and peanut products to Aspergillus invasion or aflatoxin contamination. The overall results of current study proved the potential of FTIR, equipped with either ATR or PAS, in identification, quantification and classification at varying levels of mold density and aflatoxin concentration. These results can be used to develop quality control laboratory methods or in field sorting devices.Ph. D.
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Thakare, Dhiraj, Jianwei Zhang, Rod A. Wing, Peter J. Cotty et Monica A. Schmidt. « Aflatoxin-free transgenic maize using host-induced gene silencing ». AMER ASSOC ADVANCEMENT SCIENCE, 2017. http://hdl.handle.net/10150/623199.
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Aflatoxins, toxic secondary metabolites produced by some Aspergillus species, are a universal agricultural economic problem and a critical health issue. Despite decades of control efforts, aflatoxin contamination is responsible for a global loss of millions of tons of crops each year. We show that host-induced gene silencing is an effective method for eliminating this toxin in transgenic maize. We transformed maize plants with a kernel-specific RNA interference (RNAi) gene cassette targeting the aflC gene, which encodes an enzyme in the Aspergillus aflatoxin biosynthetic pathway. After pathogen infection, aflatoxin could not be detected in kernels from these RNAi transgenic maize plants, while toxin loads reached thousands of parts per billion in nontransgenic control kernels. A comparison of transcripts in developing aflatoxin-free transgenic kernels with those from nontransgenic kernels showed no significant differences between these two groups. These results demonstrate that small interfering RNA molecules can be used to silence aflatoxin biosynthesis in maize, providing an attractive and precise engineering strategy that could also be extended to other crops to improve food security.
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Changbumrung, Jiraratana Thesasilpa Supranee. « Aflatoxin in milk from Bangkok and northeast Thailand mothers / ». Abstract, 1999. http://mulinet3.li.mahidol.ac.th/thesis/2542/42E-JiraratanaT.pdf.
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Sudini, Hari Kishan Huettel Robin Norton. « Soil microbial community structure and aflatoxin contamination of peanuts ». Auburn, Ala., 2009. http://hdl.handle.net/10415/1875.
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Henry, Kevin. « The conversion of versicolorin to sterigmatocystin in aflatoxin biosynthesis ». Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068167.
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Cotty, P. J., et L. S. Lee. « Aflatoxin Contamination of Cottonseed From Pink Bollworm Damaged Bolls ». College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/204861.
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Aflatoxin contamination of cottonseed from bolls damaged by the pink bollworm was compared with contamination of cottonseed from undamaged bolls. Cottonseed produced in pink bollworm damaged bolls was the predominant source of aflatoxin contaminated cottonseed.
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Heimbecher, Susan Klara 1954. « AFLATOXIN M₁ ANALYSIS : EFFECTS OF FORMALDEHYDE AND STORAGE CONDITIONS ». Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/291858.
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Romero, Alessandra de Cássia. « Mensuração de biomarcador de exposição às aflatoxinas em fluidos biológicos ». Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/11/11141/tde-17072008-135001/.
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As aflatoxinas são substâncias naturais que apresentam efeitos tóxicos aos humanos e são reconhecidamente carcinogênicas. Estas substâncias podem estar presentes na dieta humana ou, em casos específicos, no ar respirado. Desta maneira, a exposição humana às aflatoxinas é objeto de muita preocupação. Uma das maneiras mais eficazes de avaliar a exposição humana as aflatoxinas é através da mensuração da presença de biomarcadores da exposição a estas substâncias em fluidos biológicos. Dentre as possibilidades de biomarcadores de exposição às aflatoxinas tem-se que aflatoxina M1 (AFM1), presente na urina e leite humano, é considerada um biomarcador válido. Assim sendo, o objetivo deste trabalho de pesquisa foi avaliar a presença de AFM1 em amostras de urina provenientes de indivíduos residentes na região urbana e rural da cidade de Piracicaba-SP, assim como, de leite de gestantes de Piracicaba e cidades da região. Nos indivíduos doadores de amostras de urina foi levantado também o padrão de ingestão de alimentos com alto risco de conter aflatoxinas, através da aplicação de inquéritos de freqüência alimentar e recordatórios 24 horas. A análise de AFM1 em urina e leite foi realizada por cromatografia liquida de alta eficiência (CLAE) com detecção por fluorescência. A extração e purificação do extrato foram realizadas com auxílio de colunas de imunoafinidade. No total 69 amostras de urina e 18 de leite foram analisadas. Entre as amostras de urina detectou-se a presença de AFM1 em 54 (78%) das amostras, com concentrações variando de 1,8 até 39,9 pg/mL. Não foi observada diferença estatística entre as concentrações médias detectadas entre urinas de indivíduos da zona urbana e rural, bem como no nível de consumo de produtos de risco. Apesar das concentrações de AFM1 detectadas serem inferiores as concentrações médias reportadas em outros países a freqüência de amostras positivas foi bastante elevada mostrando que as populações estudadas estão sendo expostas às aflatoxinas. Assim, melhores avaliações dos níveis de exposição necessitam ser realizados considerando que a amostragem utilizada foi pontual, pode existir variação de contaminação sazonal com aflatoxinas na dieta e a contaminação é heterogênea dentro no alimento. Não foi observada uma correlação entre o nível do consumo de produtos de risco e as concentrações detectadas em amostras de urina. Apenas uma amostra de leite apresentou contaminação detectada; entretanto, o nível de contaminação estava entre o limite de detecção (LD) e o limite de quantificação (LQ).Aflatoxins are natural substances that present toxic and carcinogenic effects to humans. These substances may be present in human diet or, in specific cases, in the breathing air. Thus, the human exposition to aflatoxins is object of concern. One of the most effective ways to evaluate human exposition to aflatoxins is to measure the presence of biomarkers in biological fluids. Among the possibilities of aflatoxin presence biomarkers, the aflatoxin M1 (AFM1), present in human urine and milk, is considered a valid biomarker. The objective of this work was to evaluate the presence of AFM1 in urine samples from individuals who live in urban and rural areas in the county of Piracicaba, state of São Paulo, Brazil, and in milk of pregnant women from Piracicaba and neighbor cities. Urine-donor individuals were researched in relation to the ingestion of food with high risk of containing aflatoxins through the application of a food frequency questionnaire and 24-hour recall. The analysis of AFM1 in urine and milk was performed through high-performance liquid chromatography (HPLC) with fluorescence detection. The extract purification and extraction were performed with the aid of immunoaffinity columns. Overall, 69 urine and 18 human breast milk samples were analyzed. Among urine samples, the presence of AFM1 was detected in 54 (78%), with concentrations ranging from 1.8 to 39.9 pg/mL. No statistical difference was observed between average concentrations detected in the urine of individuals from urban and rural areas, as well as the consumption of aflatoxin risky food. Although the AFM1 concentrations detected are lower than those reported for other countries, the frequency of positive samples was quite high, showing that the populations studied are exposed to aflatoxins. Thus, further evaluations on the exposition levels should be performed, and considering that the sampling used in this work was punctual, there may be seasonal contamination variations in diet and the contamination level is heterogeneous within a food. No correlation between the consumption of risky food and concentrations detected in urine samples was observed. Only one milk sample presented detected contamination; however, the contamination level was between the limit of detection (LOD) and the limit of quantification (LOQ).
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Gorayeb, Teresa Cristina Castilho. « Avaliação das condições críticas para o surgimento de Aflatoxina na cadeia de processamento de amendoim (Arachis hypogaea L.) / ». São José do Rio Preto : [s.n.], 2007. http://hdl.handle.net/11449/90775.
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Resumo: Este trabalho visa fornecer às autoridades sanitárias e ao setor industrial elementos que possam contribuir para a prevenção do perigo químico aflatoxina em amendoim (Arachis hypogaea L.) e seus derivados. O estudo foi realizado em três partes: A Parte A, compreendeu a elaboração dos planos APPCC (Análise dos Perigos e Pontos Críticos de Controle) no processamento das indústrias de beneficiamento de grãos de amendoim (Empresa A) e de fabricação de doces de amendoim (Empresa B), identificando as etapas do processo que apresentam pontos críticos de controle (PCC) para o perigo químico aflatoxina. Observou-se que nos dois processos não há nenhum método que consiga destruir, ou mesmo reduzir os teores, da micotoxina. Assim, restam manter rigorosos controles e monitoramentos em cada PCC quanto aos índices de aflatoxina e de umidade dos grãos como medidas preventivas para prevenir e reduzir a possibilidade de infestação dos grãos por fungos e conseqüente produção de aflatoxina. As etapas de recepção dos grãos, secagem, armazenamento e transporte são as que requerem maior atenção na cadeia de beneficiamento. Para a indústria de doces, as etapas mais críticas são as de recepção e armazenamento de grãos e de doces e o transporte. Na Parte B, foram obtidas as isotermas de sorção até o equilíbrio higroscópico de três variedades de amendoim (Runner IAC 886, Caiapó e Tatu Vermelho), para uma ampla faixa de umidade relativa e temperaturas controladas. Verificou-se que o equilíbrio higroscópico dos três amendoins é diretamente proporcional à umidade relativa do ar e decrescente com o aumento de temperatura, para uma mesma umidade relativa. A variedade Caiapó apresentou uma umidade de equilíbrio menor que as outras variedades, podendo-se dizer que a quantidade de lipídeos e carboidratos ...(Resumo completo, clicar acesso eletrônico abaixo)Abstract: The purpose of this work is to provide technical information to the authorities and industries on aflatoxin production and prevention measures in peanuts (Arachis hypogaea L.) and its products. The work was divided in three parts: Part A: HACCP (Hazard Analysis and Control of Critical Points) plans elaboration in two industries, one of post-harvest treatment of peanuts (Industry A) and another of peanuts candy products (Industry B). Critical Control Points (CCP) for aflatoxin were indentified, and it was observed that no process measure is available to eliminate or even reduce the toxin. Thus, rigid monitoring and control on aflatoxin content must be carried on to avoid fungus infestation and hence toxin production. The process steps of raw peanuts reception, drying, storage and transportation are critical for Industry A. For Industry B, the most important steps are reception and storage of both raw peanuts and candies. Part B: sorption isotherms for three peanuts varieties (Runner IAC 886, Caiapó e Tatu vermelho) were obtained, for wide relative humidity (RH) and temperature (T) ranges. Hygroscopic equilibrium is directly proportional to RH and conversely proportional to T. Caiapó variety presented the lowest equilibrium moisture content (EMC), confirming that lipids and carbohydrates quantities area correlated to EMC. The Modified Halsey model was the best on representing the experimental sorption data. Part C: microbiological experiments were carried out to assess fungus growth and aflatoxin production in String bean and kernels of Runner IAC 886 peanuts. Two concentrations of Aspergilus flavus spores 104 e 106 spores/mL, were inoculated, two storage periods were used 15 and 30 days, three relative humidities were employed 75 %, 84 % and 90 %, and three temperature were applied 25, 30 and 35º C. Growth analysis was assessed by counting spores ...(Complete abstract click electronic access below)
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Jelena, Krulj. « Potencijal biosinteze aflatoksina B1 u različitim vrstama Triticum spp ». Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2019. https://www.cris.uns.ac.rs/record.jsf?recordId=108224&source=NDLTD&language=en.
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Prisustvo plesni i mikotoksina u hrani predstavlja višestruku opasnost, kako sa aspekta bezbednosti hrane, tako i sa aspekta globalne trgovine. Učestalost i intenzitet pojave plesni na uzorcima zrna hlebne pšenice i spelte prikupljenih u regionu Vojvodine određeni su nakon žetve tokom trogodišnjeg perioda (2015-2017). Istraživanja su obuhvatila identifikaciju i karakterizaciju 38 izolata A. flavus primenom polifaznog pristupa koji uključuje klasične mikrobiološke i molekularne metode. Ispitivanjem potencijala biosinteze AFB1 izolata A. flavus utvrđeno je da su dva izolata poreklom sa zrna hlebne pšenice pokazala aflatoksigeni potencijal. Veštačka inokulacija različitih Triticum vrsta: hlebne pšenice, spelte, korasan i hibrida pšenice toksigenim izolatama izvršena je u fazi cvetanja u cilju poređenja otpornosti ovih vrsta na pojavu A. flavus i produkciju AFB1. Visok nivo AFB1 (256 μg/kg) je kvantifikovan samo u zrnu spelte, dok kod drugih Triticum vrstama, zrno nije bilo kontaminirano AFB1 (<LOD). Određivanjem fizičko-hemijskih karakteristika plevičastih omotača Triticum vrsta potvrđen je njihov potencijalni uticaj na rast i razvoj A. flavus i biosintezu AFB1. Efekti različitih temperatura (15, 23, 30 i 37°C) i aktivnosti vode (0,85; 0,90; 0,95 i 0,99) na biosintezu AFB1 ispitani su na veštački inokulisanim uzorcima spelte sa plevičastim omotačima kao i prethodno oljuštenim zrnima. Optimalni uslovi za biosintezu tj. uslovi pri kojima je ostvaren najveći prinos AFB1 bili su temperatura 30 °C i aw 0,99 u svim tipovima uzoraka (zrna spelte inkubirana bez plevičastih omotača - ZBPO, plevičasti omotači - PO i zrna nakon ljuštenja tj. oljuštena zrna - OZ). Rezultati su pokazali da je prisustvo plevičastih omotača bilo zaštitna barijera za razvoj infekcije i akumulaciju AFB1 u zrnu. Matematički modeli, razvijeni primenom faktora sa visokom značajnošću kao što su temperatura skladištenja i aktivnost vode, mogu biti korišćeni u predviđanju akumulacije AFB1 u zrnu spelte što predstavlja ključni korak u proceni rizika. Ispitivanjem uticaja različitih nivoa kontaminacije spelte AFB1 u poređenju sa kontrolnim nekontaminiranim uzorkom ukazano je na smanjenje određenih parametara tehnološkog kvaliteta i potencijalne gubitke pecivnih svojstava speltinog brašna pri sadržaju AFB1 od 50 μg/kg i 250 μg/kg.The presence of fungi and mycotoxins in food presents a multiple risk, both from the aspect of food safety and from the aspect of global trade. The frequency and incidence of mycobiota on common wheat and spelt grains samples collected in the region of Vojvodina were determined after harvest during the three-year period (2015-2017). The research covered the identification and characterization of 38 A. flavus isolates using a polyphase approach including classical microbiological and molecular methods. Testing the A. flavus isolates for AFB1 biosynthesis, it was found that two isolates originating from wheat grains possess the aflatoxigenic potential. Artificial inoculation of different Triticum species: common wheat, spelt, khorasan and hybrid wheat with toxigenic isolates was carried out in the flowering stage in order to compare the resistance of these species to the occurrence of A. flavus and the production of AFB1. The highest AFB1 level (256 μg/kg) was determined only in the dehulled spelt grains, in comparison to other species where AFB1 was not detected in dehulled grains. In order to investigate the impact of wheat hulls on development of A. flavus, including the biosynthesis of toxic fungal metabolites, physico-chemical and structural properties of different Triticum spp. hulls were characterized. The effects of different temperatures (15, 23, 30 and 37 ° C) and water activity (0.85; 0.90; 0.95 and 0.99) on AFB1 biosynthesis were examined on artificially inoculated hull-less as well as hulled spelt grains. The optimal conditions for AFB1 biosynthesis (the conditions in which the highest AFB1 yield was achieved) were temperature 30 °C and 0.99 aw in the all tested spelt samples (hull-less grain, dehulled grains and hulls). Accumulation of AFB1 was significantly higher in hull-less than in dehulled grains that implicate the protective effect of spelt hulls. Mathematical models, developed using high-significance factors such as storage temperature and water activity, can be used to predict the accumulation of AFB1 in spelt grains, which is a key step in risk assessment. By examining the influence of different levels contamination levels of spelt grain with AFB1 and comparing to the control (uncontaminated) sample, the reduction in certain technological quality parameters and the potential loss of dough properties of spelt flour with AFB1 content of 50 μg/kg and 250 μg/kg was pointed out.
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Mayfield, Kerry L. « Preharvest aflatoxin in maize genotypes under inoculation with Aspergillus flavus ». [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1184.
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Kannewischer, Ines. « Smectite clay adsorbents of aflatoxin B1 to amend animal feed ». [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1202.
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Corn, Rebecca Joann. « Response to aflatoxin and grain composition of exotic maize germplasm ». [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1963.
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Holmberg, Victor. « Exponering av Aflatoxin B1 i enhögriskpopulation för ventrikelcancer isydöstra Nicaragua ». Thesis, Örebro universitet, Institutionen för läkarutbildning, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-36992.
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Harrison, Joanne Clare. « Immunological and HPLC detection of aflatoxin Bâ†1-DNA adducts ». Thesis, University of York, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304060.
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Melanitou, Maria A. « Sulphur dried figs in Greece : technological aspects and aflatoxin contamination ». Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760676.
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Almaghrabi, Merfat Abdulrahman. « Detection and determination of aflatoxin in food and human serum ». Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15345/.
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Rawal, Sumit. « Mechanisms of the Extreme Sensitivity of Turkeys to Aflatoxin B1 ». DigitalCommons@USU, 2010. https://digitalcommons.usu.edu/etd/568.
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The pathogenesis of hepatotoxic and hepatocarcinogenic actions of the mycotoxin aflatoxin B1 (AFB1) involves initial bioactivation by microsomal cytochrome P450s (P450) to a reactive and electrophilic intermediate, exo-aflatoxin B1-8,9-epoxide (exo-AFBO). Poultry, especially turkeys, are extremely sensitive to AFB1, a condition associated with efficient epoxidation by P450s. The purpose of this research was to 1) discover and characterize the P450s in turkey liver responsible for AFB1 bioactivation, and 2) determine the relative importance of these P450s in turkey liver. Initial investigations led to the discovery of CYP1A5. We then identified CYP3A37, a human CYP3A4 homologue from turkey liver, which along with CYP1A5 plays an important role in the bioactivation of AFB1 to exo-AFBO. The E. coli-expressed CYP3A37 possessed striking similarities to human CYP3A4, in terms of its catalytic activities and the kinetics of AFB1 oxidation. After the discovery of CYP3A37, further research evaluated its relative importance to CYP1A5, with respect to the epoxidation of AFB1, to determine which of the homologues bioactivated relatively low "real world" AFB1 concentrations, reflective of the potential dietary exposure. Using antibodies directed to both the enzymes as tools in immuno-inhibition experiments, we determined that CYP1A5 contributes to about 98% of the exo-AFBO formation at the low AFB1 concentrations (0.1 µM), which led us to conclude that CYP1A5 is likely the dominant homologue involved in the extreme sensitivity of the turkeys to AFB1. CYP3A37 also efficiently epoxidated AFB1, but only at high concentrations of this mycotoxin, not likely to be achievable in turkey liver in vivo. Our research has helped shed light on the relative importance of CYP1A5 and CYP3A37 in the bioactivation of AFB1 to the toxic exo-AFBO, and thus on the mechanisms of the extreme sensitivity of turkeys to AFB1. Given that AFB1 is a ubiquitous component of corn-based poultry feed and contamination is practically unavoidable, we conducted further studies evaluating the chemopreventive action of probiotic bacteria, Lactobacillus, on AFB1 toxicity in turkeys. Probiotic bacteria are known to bind AFB1, thus reducing its bioavailability. A mix of probiotic bacteria provided protection against key endpoints of aflatoxicosis, like AFB1-induced reduction in body and liver weights. Our data demonstrate that Lactobacillus was protective against aflatoxicosis in turkeys, thus validating its use as a possible chemopreventive, thereby helping alleviate the significant annual losses to the poultry industry due to feed contamination by AFB1.
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Saraiva, Otavio Jaconi. « Determinação da aflatoxinas M1 em queijos coloniais comercializados na região Vale do Taquari-RS ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/174522.
Texte intégralRésumé :
A Aflatoxina M1 (AFM1) é um metabólito tóxico que pode ser secretado no leite de animais contaminados com Aflatoxina B1 (AFB1). A ingestão do produto contaminado pode causar efeitos adversos de forma aguda ou crônica, sendo necessária não somente sua detecção, mas quantificação para um consumo seguro dos alimentos. Como os queijos coloniais são oriundos de pequenas propriedades rurais, muitas sem uma efetiva fiscalização e que são não somente consumidos pela família, mas também comercializados principalmente em pequenos estabelecimentos às margens de rodovias, este trabalho visa justamente avaliar o índice de contaminação em queijos coloniais produzidos artesanalmente comercializados em estabelecimentos às margens de rodovias de grande fluxo no vale do Taquari. Foram analisadas 15 amostras de queijos comercializados em estabelecimentos comerciais às margens das rodovias BR 386 e RS 287 na região do vale do Taquari, no estado do Rio Grande do Sul. A metodologia empregada na análise de Aflatoxina M1 envolveu uma partição líquido-líquido na etapa de extração e purificação e Enzimaimunoensaio em fase sólida (ELISA) para detecção e quantificação. O limite mínimo de detecção foi 16 ng/Kg (0,016 μg/Kg) e a avaliação da eficiência do método foi superior a 90% no teste de recuperação. Todas as amostras analisadas apresentaram níveis de AFM1, sendo que quatro delas apresentaram níveis superiores ao limite máximo toleradoestabelecido pela Comunidade Européia( 0,25μgKg). Nenhuma das amostras apresentou níveis superiores ao limite máximo tolerado definido pela legislação nacional (2,5 μg/Kg). Estes dados indicam a necessidade de um melhor controle na produção de queijos coloniais, principalmente das condições em que foram obtidas a matéria prima para o seu manufaturamento.Aflatoxin M1 (AFM1) is a toxic metabolite that can be secreted into the milk of animals infected with Aflatoxin B1 (AFB1). Ingestion of the contaminated product may cause acute or chronic adverse effects, requiring not only its detection, but quantification for safe consumption of food. As the colonial cheeses come from small rural properties, many without an effective inspection and that are not only consumed by the family, but also marketed mainly in small establishments along roadsides, this work aims precisely to evaluate the contamination index in produced colonial cheeses traded in establishments along the banks of high-flow roads in the Taquari valley. Fifteen samples of cheeses marketed in commercial establishments along the BR 386 and RS 287 highways in the Taquari valley region in Rio Grande do Sul State were analyzed. The methodology used in the analysis of Aflatoxin M1 involved a liquid-liquid partition in step extraction and purification and solid phase enzyme immunoassay (ELISA) for detection and quantification. The minimum detection limit was 16 ng / kg (0.016 μg / kg) and the efficiency evaluation of the method was over 90% in the recovery test. All samples analyzed showed levels of AFM1, four of which presented levels above the maximum tolerated limit established by the European Community (0.25 μg kg). None of the samples had levels above the maximum tolerated limit defined by national legislation (2,5 μg / kg). These data indicate the need for a better control in the production of colonial cheeses, mainly from the conditions in which the raw material was obtained for its manufacture.
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Bovo, Fernanda. « Avaliação da eficiência de bactérias ácido-láticas para descontaminação de aflotoxina M1 ». Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/74/74132/tde-11082011-085506/.
Texte intégralRésumé :
O objetivo do trabalho foi avaliar a capacidade de cepas de bactérias ácido-láticas (BAL) em remover a aflatoxina M1 (AFM1) em solução tampão fosfato salina (TFS) e em amostras de leite. Nos ensaios com TFS, verificou-se a influência do tempo de contato (15 min. ou 24 horas) entre as células de sete cepas de BAL e AFM1, as diferenças entre a eficiência de remoção das bactérias viáveis e inviabilizadas termicamente, e a estabilidade do complexo BAL/AFM1 formado. As três cepas de BAL com maior percentual (> 33%) de remoção da AFM1 nos ensaios com TFS foram re-avaliadas utilizando-se leite UHT (ultra-high-temperature) desnatado artificialmente contaminado com AFM1. Para isso, foram utilizadas somente células inviabilizadas termicamente, verificando-se o efeito da temperatura (4ºC ou 37ºC) sobre a capacidade de remoção da toxina por 15 minutos. A remoção média da AFM1 pelas cepas de BAL em TFS variou entre 5,60±0,45 e 45,67±1,65% (n=3), sendo que as células inviáveis obtiveram percentuais de remoção de AFM1 significativamente maiores que as células viáveis, em ambos os tempos de contato analisados (15 min. ou 24 horas), não havendo diferença significativa entre os tempos. Observou-se que o complexo BAL/AFM1 obtido nos ensaios com TFS é instável, pois 40,57±4,66 a 87,37±1,82% da AFM1 retida pela bactéria foram recuperados em solução após a lavagem do complexo com TFS. As três cepas de BAL com maior percentual de remoção da AFM1 em TFS (Lactobacillus rhamnosus, Lactobacillus delbrueckii spp. bulgaricus e Bifidobacterium lactis) não apresentaram diferenças significativas nos ensaios com leite UHT a 37ºC. Somente B. lactis apresentou maior capacidade de remover a AFM1 do leite UHT a 4ºC. Os resultados demonstraram que a remoção de AFM1 empregando-se as BAL em alimentos é viável para reduzir as concentrações da toxina a níveis seguros. Entretanto, estudos adicionais são necessários a fim de investigar os mecanismos envolvidos na remoção da toxina pelas BAL com vistas à aplicação em indústrias de alimentos.The purpose of this study was to evaluate the ability of strains of lactic acid bacteria (LAB) to remove aflatoxin M1 (AFM1) in phosphate buffer saline (PBS) and in milk samples. In the assays with PBS, the influence of contact time (15 min. or 24 hours) between the cells of seven LAB strains and AFM1 was evaluated, as well as the differences between the removal efficiency of viable and non-viable (heat-killed) bacteria, and the stability of AFM1/LAB complex produced. The three LAB strains with the highest percentage (> 33%) of AFM1 removal in the tests with PBS were reevaluated using UHT (ultra-high-temperature) skimmed milk spiked with AFM1. For these assays, only non-viable bacterial cells were used for checking the effect of temperature (4ºC or 37ºC) on the toxin removal capacity during 15 min. The mean AFM1 removal by LAB strains in PBS ranged from 5.60±0.45 and 45.67±1.65% (n=3). Non-viable cells showed AFM1 removal percentages significantly higher than viable cells in both contact times (15 min. or 24 hours), although there were not significant differences between these contact times. The AFM1/LAB complex resulted from the tests with PBS was unstable, as 40.57±4.66 to 87.37±1.82% of AFM1 retained by the bacteria were recovered in solution after washing the complex with PBS. The three LAB strains with the highest percentage of AFM1 removal in the PBS assays (Lactobacillus rhamnosus, Lactobacillus delbrueckii spp. bulgaricus and Bifidobacterium lactis) showed no significant differences in the UHT skimmed milk assays at 37ºC. Only B. lactis had greater ability to remove AFM1 in UHT milk at 4ºC. The results demonstrated that the removal of AFM1 by using LAB in foods is viable to reduce the toxin concentrations until safe levels. However, additional studies are needed to investigate the mechanisms involved in the toxin removal by LAB aiming its application in food industries.
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Nogueira, Jeronimo de Alencar. « Mutação pontual do códon 249 do TP53 no carcinoma hepatocelular ». Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/5/5147/tde-02042008-134033/.
Texte intégralRésumé :
Mutação 249Ser no TP53 no Carcinoma Hepatocelular (CHC), frequente em países da África e Ásia, é uma evidência molecular de exposição à aflatoxina. O objetivo deste estudo é analisar a freqüência de 249Ser em 74 amostras de CHC no Brasil. A mutação foi analisada por RFLP e sequenciamento. A presença de vírus da hepatite B (VHB) foi analisada por PCR em tempo real. 249Ser foi encontrada em 13/74 (28%) e VHB em 13/74 (16%). A mutação foi encontrada em maior freqüência em tumores indiferenciados (OR = 2,415, IC = 1,001 - 5,824). O tamanho médio de tumores com 249Ser foi de 9,4 cm contra 5,5 cm de amostras sem a mutação (p=0,012). Não foi encontrada relação entre VHB e 249Ser. Os resultados indicam que 249Ser é um fator importante na carcinogênese do CHC no Brasil sendo associada à uma forma maior e menos diferenciada de tumor.TP53 249Ser mutation has been proved a molecular evidence for aflatoxin-related Hepatocellular Carcinoma (HCC) and is frequent in Africa and Asia. The aim of our study was to analyze the frequency of 249Ser mutation in HCC from Brazil. We studied 74 samples of paraffin embedded HCC. 249Ser mutation was analyzed by RFLP and sequencing. Presence of HBV DNA was determined by Real-Time PCR. 249Ser was found in 21/74 (28%) samples while HBV DNA was found in 13/74 (16%). Poorly differentiated HCC was more likely to have 249Ser mutation (OR = 2.415, IC = 1.001 - 5.824). The mean tumor size of 249Ser HCC was 9.4 cm versus 5.5cm on wild type (p=0.012). HBV DNA was not related with 249Ser. Results indicate that 249Ser is an important factor of HCC carcinogenesis in Brazil and is associated with large and poorly differentiated tumors.
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Carão, Agatha Cristina de Pinho. « Determinação de biomarcadores de aflatoxina B1 e aplicabilidade na avaliação da eficiência de adsorventes em frangos de corte ». Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/10/10135/tde-11052016-172125/.
Texte intégralRésumé :
As aflatoxinas são metabólitos secundários produzidos por fungos toxigênicos das espécies Aspergillus flavus, A. parasiticus e A. nomius. São amplamente encontradas em matérias-primas de rações animais, em especial o milho, e têm a capacidade de levar a quadros clínicos agudos ou crônicos de aflatoxicose, caracterizados por, desde a morte por hepatite aguda até a diminuição do desempenho zootécnico por diminuição de peso ou consumo de ração. A aflatoxina B1 tem sido considerada o metabólito mais perigoso, uma vez que possui alto poder hepatotóxico, além de ser mutagênica e carcinogênica. Atualmente a ciência trabalha rumo à descoberta de substâncias que sejam indicadoras confiáveis de contaminação por componentes tóxicos em homens e em animais, os chamados biomarcadores, que medem uma mudança celular, biológica ou molecular em um meio biológico (tecidos humanos, células ou fluídos) que fornecem informação a respeito de uma doença ou exposição a uma determinada substância. Sua detecção pode auxiliar na identificação, no diagnóstico e no tratamento de indivíduos afetados que podem estar sob risco, mas ainda não exibem os sintomas. Sendo assim, com o auxílio de análises que confirmem a patogenicidade da aflatoxina B1 (determinação da atividade de enzimas hepáticas, da avaliação da função renal, de hematologia, da dosagem de minerais séricos e da avaliação de desempenho zootécnico), o objetivo deste trabalho foi avaliar a aplicabilidade da determinação de resíduos hepáticos de aflatoxinas e do aduto sérico AFB1-lisina na avaliação da eficiência de adsorventes em frangos de corte. Utilizou-se 240 pintos de 1 dia, machos, de linhagem Cobb 500®, distribuídos aleatoriamente em 4 dietas experimentais: Controle Negativo: Ração Basal (RB); RB + 0,5% de adsorvente ((aluminosilicato de cálcio e sódio hidratado/HSCAS); RB + 0,5% de adsorvente + 500 µg de AFB1/kg de ração e; RB + 500 µg de AFB1/kg de ração.Os resultados experimentais mostram que o efeito deletério da AFB1, na concentração utilizada, é mais pronunciado que os efeitos protetores do HSCAS sobre os parâmetros de saúde dos animais. Não houve ação efetiva do adsorvente utilizado sobre quase nenhuma variável estudada, apenas para a redução das lesões histopatológicas em fígado, na redução da concentração de gama-glutamiltransferase (GGT), fósforo e aumento da contagem de hemáceas aos 21 dias de idade. Porém, influenciou positivamente a redução de resíduos hepáticos de aflatoxina G1 aos 21 dias e as concentrações de AFB1-lisina sérica aos 21 e aos 42 dias de idade. Estes dados são importantes porque permite concluir que, embora sintomatologicamente o HSCAS não tenha exercido função efetiva, molecularmente foi capaz de mostrar de eficácia sobre os alguns biomarcadores de aflatoxinas no organismo das avesAflatoxins are secondary metabolites produced by toxigenic fungi of the species Aspergillus flavus, A. parasiticus and A. nomius. They are widely found in raw materials of animal feed, in particular corn, and have the ability to lead to clinical cases of acute or chronic aflatoxicosis, characterized by acute hepatites leading to death until lower performance by decreased weight or feed intake. Aflatoxin B1 has been considered the most dangerous metabolite, since it has high hepatotoxic power, besides being mutagenic and carcinogenic. Nowadays science works toward the discovery of substances that are reliable indicators of contamination by toxic components in humans and animals, called biomarkers, which measure a cell change, biological or molecular in a biological medium (human tissues, cells or fluids) that provide information regarding a disease or exposure to a particular substance. Its detection can assist in the identification, diagnosis and treatment of affected individuals who may be at risk, but still do not exhibit symptoms. Thus, with the help of analysis that confirm aflatoxin B1 pathogenicity (determination of liver enzymes activity, assessment of renal function, hematology, dosage of serum minerals and evaluation of animal performance), the objective of this work was to evaluate the applicability of the determination of aflatoxin liver residues and serum AFB1-lysine adduct in the evaluation of the adsorbents efficiency in broiler chickens. Two hundred and fourty day-old male chicks, Cobb 500® lineage, were randomly distributed into 4 experimental diets: Negative Control: Basal Feed (BF); BF + 0.5% adsorbent (hydrated sodium calcium aluminosilicate/HSCAS); RB + 0.5% adsorbent + 500 µg AFB1/kg of feed; and RB +500 µg AFB1/kg of feed. The experimental results show that the deleterious effect of AFB1, at the concentration used, is more pronounced that the protective effects of HSCAS on animal health parameters. There was no effective action of the adsorbent used on almost any variable studied, only for the reduction of the histopathological lesions in the liver, reduction of gamma-glutamyltransferase (GGT) and phosphorus concentration, and increased count of red blood cells at 21 days. However, influenced positively the reduction of aflatoxin G1 liver residues at 21 days and the concentrations of serum AFB1-lysine at 21 and 42 days. These are important data because they allow to conclude that, although symptomatically the HSCAS has not exercised effective function, molecularly was able to show some efficacy on aflatoxin biomarkers in the birds body