Aflatoxin compromises development of the preimplantation bovine embryo through mechanisms independent of reactive oxygen production

Aflatoxin is a potent carcinogen often found in animal feedstuffs. Although it reportedly impairs development of the preimplantation pig embryo, it is not known whether it adversely affects development of the preimplantation bovine embryo. We conducted 3 experiments to investigate this possibility and determine whether deleterious effects of aflatoxin were caused by increased production of reactive oxygen species (ROS). Experiments were conducted with embryos produced in vitro and cultured after fertilization with various concentrations of aflatoxin. For experiment 1, embryos were treated with 0 (control), 40, 400, or 4,000 µg/L of aflatoxin B₁ (AFB₁). Treatment at all concentrations of AFB₁ tended to reduce cleavage rate, with the 2 highest concentrations having significant effects. As compared with the control, 40 µg/L AFB₁ reduced the percentage of oocytes becoming blastocysts and the percentage of cleaved embryos becoming blastocysts (19.7 vs. 8.1% and 30.3 vs. 14.3%, respectively). Complete inhibition of blastocyst formation occurred at concentrations of 400 and 4,000 µg/L of AFB₁. Experiments 2 and 3 involved a 2 × 2 factorial design with effects of AFB₁ (0 and 40 µg/L), the antioxidant Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, a water-soluble analog of vitamin E; 0 and 5 µM), and their interaction on production of ROS in putative zygotes (experiment 2) and development to the blastocyst stage (experiment 3). Production of ROS was increased by AFB₁, and this effect was reversed by Trolox. However, Trolox did not prevent the reduction in development to the blastocyst stage caused by AFB₁. Thus, the anti-developmental effects of AFB₁ are not caused solely by increased ROS production. Rather, other underlying mechanisms exist for the adverse effects of aflatoxin on embryonic development. Overall, results indicate the potential for feeding aflatoxin-contaminated feed to cause embryonic loss in cattle.     

去除食品中黄曲霉毒素的方法

本文介绍用机械碾磨、溶剂浸出、吸附、加热、放射、加酸碱、加NaC和氧化剂去除食品中黄曲霉毒素的方法。     

Chronic toxicological evaluation of dietary NovaSil Clay in Sprague-Dawley rats

NovaSil (NS) clay, a common anti-caking agent in animal feeds, has been shown to sorb aflatoxins in the GI tract and diminish their bioavailability and adverse effects in short-term animal studies. Based on this evidence, it is hypothesized that clay-based enterosorption of aflatoxins may be a useful strategy for the prevention of aflatoxicosis in human populations. However, the potential toxicity of long-term dietary exposure to NS has not been determined. In this research, 5-6-week-old male and female Sprague-Dawley rats were fed rations containing 0, 0.25, 0.5, 1.0, or 2.0% (w/w) levels of NS for 28 weeks. Analysis of the NS showed negligible levels of dioxin and furan contaminants. Total feed consumption, cumulative feed consumption, body weight, total body weight gain, feed conversion efficiency, cumulative feed conversion efficiency, and relative organ weights were unaffected in either sex at the doses tested. No NS-dependent differences in relative organ weights or gross or histopathological changes were observed. Analysis of hematological parameters, clinical chemistry, and selected vitamin and mineral levels revealed isolated significant differences between some treatments and control groups (mean corpuscular hemoglobin, serum Ca, serum vitamin A, and serum Fe). However, the differences observed in each case were not dose-dependent. These results suggest that dietary inclusion of NS at levels as high as 2.0% (w/w) does not result in overt toxicity. These findings (as well as others) support the use of NS clay for dietary intervention studies in human populations at high risk for aflatoxicosis.     

Are the Genes nadA and norB Involved in Formation of Aflatoxin G1?

Aflatoxins, the most toxic and carcinogenic family of fungal secondary metabolites, are frequent contaminants of foods intended for human consumption. Previous studies showed that formation of G-group aflatoxins (AFs) from O-methylsterigmatocystin (OMST) by certain Aspergillus species involves oxidation by the cytochrome P450 monooxygenases, OrdA (AflQ) and CypA (AflU). However, some of the steps in the conversion have not yet been fully defined. Extracts of Aspergillus parasiticus disruption mutants of the OYE-FMN binding domain reductase-encoding gene nadA (aflY) contained a 386 Da AFG₁ precursor. A compound with this mass was predicted as the product of sequential OrdA and CypA oxidation of OMST. Increased amounts of a 362 Da alcohol, the presumptive product of NadA reduction, accumulate in extracts of fungi with disrupted aryl alcohol dehydrogenase-encoding gene norB. These results show that biosynthesis of AFG₁ involves NadA reduction and NorB oxidation.     

高效液相色谱-光化学衍生法测定陈皮中黄曲霉毒素G2的不确定度评定

目的评定高效液相色谱法-光化学衍生法测定陈皮中黄曲霉毒素G2的含量的不确定度。方法参考中国药典四部通则2351黄曲霉毒素测定法第一法对陈皮进行提取,以C_(18)柱(4.6 mm×250 mm,5μm)为分析柱,甲醇:乙腈:水(30:12:58,V:V:V)为流动相进行洗脱,流速0.6 mL/min,柱温40℃,使用柱后光化学衍生器连接荧光检测器进行检测。找出影响不确定度的因素,对不确定度进行评估,并给出不确定度,如实反映测量的置信度和准确度。结果该批次陈皮样品中黄曲霉毒素G2的含量为0.08μg/kg,其实际含量可表示为(0.08±0.005)μg/kg (k=2)。结论黄曲霉毒素G2测定过程中主要影响因素为高效液相色谱仪的校准,其次为测量重复性,而样品溶液的配置与对照品溶液的稀释引入的不确定因素较小,天平称量引入的不确定因素可以忽略不计。