亚硒酸钠对交链孢酚诱发DNA单链断裂和脂质过氧化的影响

本文采用碱性洗脱-DNA荧光分析法及硫代巴比妥酸反应法,研究了亚硒酸钠(Na_2SeO_3)对交链孢酚(alternariol,AOH)诱发DNA单链断裂和脂质过氧化的影响。结果表明,在人胚食管上皮组织或人胚肺2BS细胞株接触AOH前4小时,在培养基内加10~(-5)或10~(-6)M Na_2SeO_3能显著抑制AOH诱导的DNA单链断裂和脂质过氧化反应;Na_2SeO_3与AOH同时处理对AOH的上述诱变性作用无显著抑制作用,10~(-4)MNa_2ScO_3可诱发人胚肺2BS细胞株DNA单链断裂。结果提示硒能抑制AOH的诱变性,但高浓度硒有毒性作用。     

Copper

Copper is an essential trace element, which is an important catalyst for heme synthesis and iron absorption. Following zinc and iron, copper is the third most abundant trace element in the body. Copper is a noble metal, like silver and gold. Useful industrial properties include high thermal and electrical conductivity, low corrosion, alloying ability, and malleability. Most of the metallic copper appears in electrical applications. Copper is a constituent of intrauterine contraceptive devices and the release of copper is necessary for their contraceptive effects. The average daily intake of copper in the US is about 1 mg Cu with the primary source being the diet. The bioavailability of copper from the diet is about 65–70% depending on a variety of factors including chemical form, interaction with other metals, and dietary components. The biological half-life of copper from the diet is 13–33 days with bilary excretion being the major route of elimination. Copper sulfate is a gastric irritant that produces erosion of the lining of the gastrointestinal tract. Chronic copper toxicity is rare and primarily affects the liver. Wilson's disease and Indian childhood cirrhosis are examples of severe chronic liver disease that results from the genetic predisposition to the hepatic accumulation of copper. The serum copper concentration ranges up to approximately 1.5 mg/L in healthy persons. Gastrointestinal symptoms occur at whole blood concentrations near 3 mg Cu/L. Chelating agents (CaNa₂EDTA, BAL) are recommended in severe poisoning, but there are little pharmacokinetic data to evaluate the effectiveness of these agents.     

Biomonitoring of concurrent mycotoxin exposure among adults in Sweden through urinary multi-biomarker analysis

Mycotoxin producing moulds may contaminate numerous agricultural commodities either before harvest or during storage. A varied diet consisting of different foods may therefore be contaminated with a range of mycotoxins. The aim of the present study was to study concurrent exposure to mycotoxins through urinary multi-biomarker analysis, as well as its possible associations with the diet.Urinary samples from 252 adults, participating in the Swedish national dietary survey Riksmaten 2010–11, were collected together with a 4-day diet record. Concurrent mycotoxin exposure was studied using a multi-biomarker LC-MS/MS method. The results revealed that exposure to mycotoxins is common and concurrent exposure to more than one toxin was found in 69% of the study population. However, when comparing the number of toxins detected with the reported consumption data it was difficult to distinguish food patterns which would indicate an increased risk of exposure to many mycotoxins simultaneously.This is the first study to investigate concurrent mycotoxin exposure and urinary levels of fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), nivalenol (NIV), ochratoxin A (OTA), zearalenone (ZEA), α-zearalenol (α-ZOL), β-zearalenol (β-ZOL) and de-epoxydeoxynivalenol (DOM-1) among adults in Sweden.     

Integration of Crop Management and Genetics for Control of Preharvest Aflatoxin Contamination of Corn

Aflatoxin contamination of corn in the field is influenced by several factors. In the southern U.S., insect populations are usually large every year. Drought caused by warmer and drier than normal weather is conducive to A. flavus infection and aflatoxin contamination of corn, Zea mays L. When loose‐husked hybrids are used in the southern U.S., they accentuate insect damage and aflatoxin contamination. The development and breeding of “southern‐type” hybrids is essential for control of preharvest aflatoxin contamination. Molecular biotechnology may make an impact on tackling the complexity of preharvest aflatoxin contamination of corn. Integration of crop management tactics and genetic strategies, conventional or molecular, may constrain the problem and help southern corn growers produce a quality, profitable crop.     

Unlocking the Secrets Behind Secondary Metabolism: A Review of Aspergillus flavus from Pathogenicity to Functional Genomics

Aspergillus flavus has received a considerable amount of attention due to its ability to produce aflatoxin, a secondary metabolite that is both immunosuppressive and carcinogenic to animals and humans. Research on aflatoxin over the last 40 years has made it one of the best studied fungal secondary metabolites. In spite of the large volume of research in this area, many unanswered questions remain concerning the genetic regulation of aflatoxin production and the molecular signals that intimately associate the synthesis of aflatoxin with specific environmental and nutritional conditions. It is anticipated that the tools now available in the field of genomics will build upon our existing knowledge and provide answers to some of these questions. Complete genome sequences are now available for a number of fungal species that are closely related to A. flavus. This information can be used along with current genomic analyses in A. flavus to more closely examine the biosynthesis and regulation of secondary metabolism. The intent of this review is to summarize the large body of knowledge that exists from many years of research on A. flavus, with the hope that this information in the light of new genomic studies may bring scientists closer to unraveling the web of regulatory circuits that govern aflatoxin biosynthesis. Specifically, scientific findings in the following areas will be presented: classification and phylogenetic analyses of A. flavus, population biology, ecology and pathogenicity in agricultural environments, classical genetics including linkage group and mutant analyses, gene clusters, regulation of aflatoxin biosynthesis, and genomics.     

New perspectives for the application of bioplastic materials in the biocontrol of Aspergillus flavus in corn

Mycotoxins are secondary metabolites produced by certain filamentous fungi that can contaminate a large variety of agricultural commodities before and after harvest. Among different mycotoxins, aflatoxins and especially aflatoxin B1 are of particular concern because they are potent natural carcinogens. Aflatoxin-producing fungi, mainly Aspergillus flavus and A. parasiticus, are ubiquitous, being commonly isolated from agricultural soil and crop debris. Although many aspects of the ecology of aflatoxin-producing fungi have been elucidated, control of aflatoxin contamination of agricultural crops remains a difficult task. Agronomical practices promoting general plant health have shown variable and more frequently limited success in preharvest control of aflatoxin contamination. Competitive replacement of indigenous toxigenic soil isolates is considered a more promising and effective approach. This biocontrol strategy is based on field application of a large number of propagules of nontoxigenic strains of A. flavus. Biocontrol strains are typically formulated as inoculated or spore-coated grain seeds. More recently, efforts to explore new approaches and technologies have resulted in the development of other practical solutions, including a bioplastic-based formulation. This formulation originally developed in 2008, consists of bioplastic granules entrapping spores of the nontoxigenic biocontrol strain, A. flavus NRRL 30797. Laboratory and field studies that have been conducted until now have clearly shown that granules of the starch-based bioplastic Mater-Bi^® are effective in delivering this biocontrol strain. In addition to having a satisfactory shelf life, the granules are easy to prepare, handle, and apply to agricultural fields. More importantly, this novel bioplastic formulation is capable of efficiently reducing aflatoxin contamination of corn. The bioplastic Mater-Bi^® can also have other applications. For instance, rods or granules prepared using a slightly modified Mater-Bi^® bioplastic matrix can be used to selectively isolate A. flavus from soil and corn kernels.     

Determination of ochratoxin A in human urine by solid-phase microextraction coupled with liquid chromatography-fluorescence detection

A new method for the determination of ochratoxin A (OTA) in human urine samples has been developed using solid-phase microextraction (SPME) interfaced with liquid chromatography-fluorescence detection (LC-FD). This method is simpler and cheaper compared to the most widely adopted clean-up procedures for OTA extraction from urine (usually based on immunoaffinity columns). Briefly, urine samples, diluted 1:5 with phosphate buffer (10 mM, pH 3), were partitioned against chloroform and the aqueous phase extracted by a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber. The fiber was then "statically" desorbed, through a SPME interface, into a LC system operating in isocratic conditions. The linear range investigated in urine was 0.01-1 ng/ml. Within-day R.S.D.% in urine spiked at 0.1 and 1 ng/ml were 3.9 and 1.9, respectively, whereas the between-days R.S.D.% were 5.5 and 3.0, respectively. The limits of detection (LOD) and quantitation (LOQ) calculated at a signal-to-noise ratio of 3 and 10 (noise calculated peak to peak on a blank chromatogram at the OTA retention time) were 0.01 and 0.05 ng/ml, respectively.     

Mycotoxin-induced depletion of intracellular glutathione and altered cytokine production in the human alveolar epithelial cell line A549

Mould exposure has been associated with asthma and other inflammatory airway conditions. However, cellular effects of inhaled mould components are not well understood. We hypothesised that host defence mechanisms, such as production of cytokines (TGFbeta1, IL-6 and IL-8) and the intracellular antioxidant glutathione (GSH), could be adversely affected by different concentrations of mycotoxins. We studied the effects of citrinin and gliotoxin on lipopolysaccharide (LPS)-stimulated alveolar epithelial cells (A549). Cytokines in cell culture supernatants were analysed by ELISA and levels of GSH were measured by colorimetric (absorbance) determination. We found that GSH decreased in a dose- and time-dependent manner when cells were exposed to citrinin in particular. TGFbeta1 was moderately reduced at low mycotoxin concentrations but elevated at higher sub-toxic concentrations. A tendency for an inverse relationship between TGFbeta1 and GSH levels was observed. IL-6 and IL-8 were not significantly reduced at non-toxic mycotoxin concentrations. Thus, reduced epithelial GSH and TGFbeta1 levels combined with elevated IL-6 and IL-8 levels may result in increased pro-inflammatory activity during mycotoxin exposure. We suggest that this mechanism can contribute to inflammation in mould exposure.     

Aquilegia vulgaris L. extract counteracts oxidative stress and cytotoxicity of fumonisin in rats

Exposure to fumonisins (FB) is known to have toxic and carcinogenic effects in different animal species, and to express toxicity in cells via the induction of oxidative stress. The aim of the current study was to evaluate the protective effects of the ethanol extract of Aquilegia vulgaris L. against the oxidative stress and the genotoxicity using micronucleus assay and random amplified polymorphism DNA (RAPD-PCR) in FB-treated rats. Sixty mature female Sprague-Dawley were divided into six treatment groups and treated for 4 weeks as follow: the control group, the group fed FB-contaminated diet (200 mg/kg diet), the groups treated orally with the extract (5 and 10 mg/kg bw) and the groups fed FB-contaminated diet and treated with the extract at the two doses. The results showed that treatment with FB alone disturbed lipid profile in serum, increases Sa/So ratio, induces micronucleated polychromatic erythrocytes (Mn-PCEs) in bone marrow, increases DNA and RNA in liver accompanied with significant changes in histological picture The extract alone at the two tested doses did not induce any significant changes in the biochemical or histological picture. The combined treatment showed significant improvements in all biochemical, cytogenetic parameters tested and histological pictures in the liver tissues. Moreover, this improvement was more pronounced in the group received the high dose of the extract. It could be concluded that the ethanol extract of A. vulgaris induced its protective effect via the increase in the antioxidant capacity, inhibition of lipid peroxidation and scavenging of free radicals.