普洱茶发酵过程中外源接种黄曲霉产毒研究

以云南大叶种晒青茶为原料,接种产毒黄曲霉进行模拟普洱茶发酵试验,并在发酵结束时通过LC-MS/MS法对茶样进行黄曲霉毒素检测,研究普洱茶发酵过程中黄曲霉的生长及产毒情况。结果表明,在普洱茶发酵过程中,接种的黄曲霉能在茶叶中生长繁殖,初期生长较快,但随发酵时间的延长,黄曲霉在茶叶中的生长明显受到抑制,其数量逐渐下降。发酵终止时,未在茶样中检测出黄曲霉毒素。     

Fungi and Maize Seed Biodeterioration in Storage

研究了真菌与玉米种子在不同贮藏条件下的生物劣变关系．结果表明：在含水１６．６％的玉米种子上生长的主要真菌是曲霉菌,而在含水１３．６％和１０．３％的玉米种子中则为根霉菌、曲霉菌、镰刀菌和青霉菌．研究中还发现,不同贮藏条件下,玉米种子中还含有０～７．６６ｎｇ／ｇ的黄曲霉毒素,这种毒素将会影响种子的生活力、发芽率和活力．     

牛乳中黄曲霉毒素M1检测方法的研究进展

近年来由于国内外乳品安全问题层出不穷,作为乳品中广泛存在的一类剧毒物——黄曲霉毒素越发地引起了人们的关注。黄曲霉毒素具有强烈的致癌性、致畸性及诱变性,已被证实可对人和动物的健康造成极大伤害,牛乳中以其代谢产物黄曲霉毒素M1最为常见。本文阐述了牛乳中黄曲霉毒素M1的来源与危害,并重点介绍了对其检测方法的研究进展。     

Aflatoxin in maize,a multifaceted answer of Aspergillus flavus governed by weather,host-plant and competitor fungi

Aspergillus section Flavi is able to produce aflatoxins (AFs) in vitro down to 0.85 a_w with a potential maximum occurring between 0.95 and 0.99 a_w, while in the field AFs increased significantly with kernel humidity below 0.95 a_w. In order to clarify this apparent discrepancy, a 3-year field trial with artificial inoculation of maize ears with Aspergillus flavus strains was organised. The co-occurrence of Aspergillus section Flavi and Gibberella fujikuroi species complex (Gfsc) was observed. The incidence of A. flavus was significantly influenced by the year and negatively related to Gfsc incidence. In 2012, when the highest temperature and the lowest rain were registered, aflatoxin B₁ (AFB₁) content was the highest and a_w < 0.95 in kernels was measured early throughout the growing season. In 2013 and 2014, the temperature was lower and rain more abundant, and a_w decreased below 0.95 only close to harvest and AFB₁ contamination was limited. The possibility of describing/predicting reasonably well a_w dynamic based on temperature, (degree day) was confirmed. With a_w > 0.95, a positive correlation between AFB₁ production rate and a_w was found, but a negative correlation resulted with a_w < 0.95. Other factors than a_w play a role, but a_w = 0.95 should be considered as an indicator of suitable conditions for rapid aflatoxin accumulation.     

Clinicopathological findings of an episode of mycotoxicosis in horses

This report of mycotoxicosis in horses describes the clinical signs, post-mortem findings, histopathological findings and prognosis following the accidental feeding of mycotoxin contaminated fodder to the horses at a farm over a 3-year period. Variable clinical signs viz. weight loss, height retardation in foals, episodes of sudden weakness and staggering gait, ulceration in the oral cavity and at mucocutaneous junctions, yawning, decreased appetite to complete anorexia, rectal prolapse, and failure of blood clotting were observed in many horses at an organised equine farm over a period of 2–3 years. Post-mortem examination of these cases revealed liver cirrhosis and pathological changes in other organs too. On examination of the fodder, it was observed that pearl millet fodder fed to the animals had ergot infestation. On laboratory investigation of the fodder, aflatoxins levels ranged from 24 ppb to 70 ppb in pearl millet fodder. The analysis eventually led to discontinuation of the pearl millet fodder. On follow-up for 2 years, no new cases of hepatic cirrhosis were seen. Most of the horses at the farm including those that had shown high levels of serum gamma glutamyl transferase (GGT) and weight loss, recovered completely. The present episode demonstrates that there is a need for regular monitoring of cereal fodders of horses in subtropical and tropical areas to avoid mycotoxicosis. In the present episode, monitoring serum/plasma GGT levels was found to be a sensitive biochemical indicator to identify liver damage caused by mycotoxins.     

Intravenous regional analgesia for surgery of the limbs in goats

Intravenous regional analgesia (IVRA) has been achieved in twelve West African Dwarf (WAD) goats in a total of 35 trials with 2 per cent lidocaine hvdrochloride without any significant complications.

Experimental analgesia was effected 25 times on the limbs of seven goats. Analgesia was also produced 10 times on the limbs of five goats and a major orthopaedic procedure (amputation) performed on the anaesthetized limbs and digits. The analgesia produced was found to be adequate for the procedure.

The comparative values of this method of regional analgesia are discussed.     

Mycotoxin Genetics and Gene Clusters

Fungi produce low molecular weight secondary metabolites such as antibiotics and mycotoxins. Antibiotics cure diseases whereas mycotoxins cause diseases in plants, animals and human beings. Species such as Aspergillus, Fusarium, Penicillium and Stachybotrys are known to produce mycotoxins that accumulate in processed foods and feeds, although the incidence of infection occurs before processing, during the active growth of the organism. Among the mycotoxins, aflatoxins produced by Aspergillus flavus and A. parasiticus have been extensively studied at the molecular level. A complex biosynthetic pathway involving sixteen steps is mediated by individual major genes. These fungi have eight linkage groups, but the aflatoxin/sterigmatocystin (AF/ST) metabolic pathway genes have been mapped to only three linkage groups; ten of them belong to linkage group VII, and one of each to linkage group II and VIII. These genes are involved in both the regulatory and biosynthetic pathways and are clustered on the respective chromosomes. Clustering of genes in fungi indicates an evolutionary trend among genes that orchestrate gene function. Being linked together they segregate as a unit, thereby conferring a selective advantage to the organism. The evolution of gene clusters takes place through vertical or horizontal gene transfer. In fungi, horizontal gene transfer is most effective. Functionally, the mechanism of evolution of mycotoxin gene clusters in fungi seems to be similar to the evolution of a super-gene. The possible implications of evolutionary parallelism of gene clusters and super-genes is briefly explored.     

Pesticide Use and Mycotoxin Production in Fusarium and Aspergillus Phytopathogens

The major mycotoxigenic species of Fusarium and Aspergillus phytopathogens have been identified in this review. Since fungicides are widely used to control crop diseases caused by these fungi, it is pertinent to assess efficacy with respect to mycotoxin production. In both laboratory studies with pure cultures of phytopathogens and field trials with crop plants, the overall evidence concerning the effectiveness of fungicides is contradictory and in certain cases somewhat unexpected. In particular, at sub-lethal doses of a number of fungicides including carbendazim, tridemorph, difenoconazole and tebuconazole with triadimenol, mycotoxin production from Fusarium phytopathogens may increase. Furthermore, the efficacy of propiconazole and thiabendazole in the control of deoxynivalenol production from F. graminearum is not consistent. Evidence has been presented to suggest, for the first time, that fungicide-resistance in F. culmorum may be accompanied by a more persistent pattern of mycotoxin production. The limited evidence on the effects of fungicides on mycotoxin production in Aspergillus species is also conflicting. Under laboratory conditions, miconazole and fenpropimorph have been shown to increase aflatoxin production from A. parasiticus. Moreover, fenpropimorph increased production of the more toxic aflatoxin B1. Since fungal infection of plant products is often preceded by insect damage, there is interest in the effectiveness of insecticides to reduce infestation, infection and mycotoxin contamination. Additionally, insecticides may be effective in their own right, causing a direct effect on mycotoxin synthesis. The bulk of the evidence relates to effects on aflatoxin (AF) components B1, B2, G1 and G2. Under laboratory conditions, AFB1 production was most resistant to inhibition by insecticides, followed by AFG1, AFG2 and AFB2. This pattern of inhibition was particularly consistent for the organophosphorus insecticides. In one field study, Bux and carbaryl were considerably more effective than naled in reducing AFB1 contamination of maize kernels. It is concluded that if pesticide control is to be more effective in the future, additional criteria may be required in developing evaluation protocols for candidate compounds. In particular, the issue of fungicide-resistance in relation to mycotoxin production needs to be addressed in a concerted programme of research. Additionally, the potential of breeding and selecting cultivars resistant to disease caused by toxigenic fungi needs to be exploited in a parallel search for an environmentally acceptable solution to the question of mycotoxin contamination of plant products.     

Flavonoids as Flower Pigments: The Formation of the Natural Spectrum and its Extension by Genetic Engineering

Preharvest aflatoxin contamination of maize (Lea mays L.) gram by Aspergillns spp. is a concern to both producers and consumers of maize. Aflatoxms are carcinogenic to animals and have been linked to liver cancer in humans. The most desirable solution for eliminating or reducing aflatoxin contamination is to identify and/or develop sources of resistance. However, only a few genetic studies, which utilized a limited amount of genetic material, have been conducted. A thorough review and consolidation of information from these studies was deemed necessary. The purpose of this paper is to present a current, critical review on aspects of infection by Aspergillus, role of insects, inoculation techniques, and sources and genetics of resistance as they relate to aflatoxin production in maize. Damage to maize kernels by insects, especially the European corn borer (Ostrinia nubilalis Hübner), fall armyworm (Spodoptera frugiperda J. E. Smith), and corn ear-worm (Helicoverpa zea Boddie), has been associated with high aflatoxin levels. Artificial inoculation techniques that damage maize kernels generally result in the highest and most consistent aflatoxin levels. Although, a relatively large amount of maize germplasm has been screened for resistance and varying levels of resistance have been identified, additional germplasm needs to be systematically evaluated. To date, there are no known genotypes with complete resistance. Results from the few genetic studies indicated that additive genetic effects controlled resist-Preharvest aflatoxin contamination of maize (Zea mays L.) gram by Aspergillns spp. is a concern to both producers and consumers of maize. Aflatoxms are carcinogenic to animals and have been linked to liver cancer in humans. The most desirable solution for eliminating or reducing aflatoxin contamination is to identify and/or develop sources of resistance. However, only a few genetic studies, which utilized a limited amount of genetic material, have been conducted. A thorough review and consolidation of information from these studies was deemed necessary. The purpose of this paper is to present a current, critical review on aspects of infection by Aspergillus, role of insects, inoculation techniques, and sources and genetics of resistance as they relate to aflatoxin production in maize. Damage to maize kernels by insects, especially the European corn borer (Ostrinia nubilalis Hübner), fall armyworm (Spodoptera frugiperda J. E. Smith), and corn ear-worm (Helicoverpa Zea Boddie), has been associated with high aflatoxin levels. Artificial inoculation techniques that damage maize kernels generally result in the highest and most consistent aflatoxin levels. Although, a relatively large amount of maize germ-plasm has been screened for resistance and varying levels of resistance have been identified, additional germplasm needs to be systematically evaluated. To date, there are no known genotypes with complete resistance. Results from the few genetic studies indicated that additive genetic effects controlled resistance to aflatoxin contamination in maize. Aflatoxin production on maize grain appeared to be greatly influence by the environment. Further genetic studies, utilizing additional germplasm, are warranted for a better understanding of the nature of resistance to asflatoxin contamination in maize. Future research needs and plans relative to resistance to aflatoxin contaminaton in maize are presented.