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Toxins, Volume 3, Issue 8 (August 2011), Pages 932-1064

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Research

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Open AccessArticle Expression Profiling of Non-Aflatoxigenic Aspergillus parasiticus Mutants Obtained by 5-Azacytosine Treatment or Serial Mycelial Transfer
Toxins 2011, 3(8), 932-948; doi:10.3390/toxins3080932
Received: 25 May 2011 / Revised: 19 July 2011 / Accepted: 26 July 2011 / Published: 2 August 2011
Cited by 10 | PDF Full-text (210 KB) | HTML Full-text | XML Full-text
Abstract
Aflatoxins are carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. Previous studies found that repeated serial mycelial transfer or treatment of A. parasiticus with 5-azacytidine produced colonies with a fluffy phenotype and inability to produce aflatoxins. To understand
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Aflatoxins are carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. Previous studies found that repeated serial mycelial transfer or treatment of A. parasiticus with 5-azacytidine produced colonies with a fluffy phenotype and inability to produce aflatoxins. To understand how these treatments affect expression of genes involved in aflatoxin production and development, we carried out expressed sequence tag (EST)-based microarray assays to identify genes in treated clones that are differentially expressed compared to the wild-type. Expression of 183 genes was significantly dysregulated. Of these, 38 had at least two-fold or lower expression compared to the untreated control and only two had two-fold or higher expression. The most frequent change was downregulation of genes predicted to encode membrane-bound proteins. Based on this result we hypothesize that the treatments cause changes in the structure of cellular and organelle membranes that prevent normal development and aflatoxin biosynthesis. Full article
(This article belongs to the Special Issue Aflatoxins 2011)
Open AccessArticle Incidence of Fusarium Species and Mycotoxins in Silage Maize
Toxins 2011, 3(8), 949-967; doi:10.3390/toxins3080949
Received: 1 June 2011 / Revised: 18 July 2011 / Accepted: 20 July 2011 / Published: 4 August 2011
Cited by 24 | PDF Full-text (528 KB) | HTML Full-text | XML Full-text
Abstract
Maize is frequently infected by the Fusarium species producing mycotoxins. Numerous investigations have focused on grain maize, but little is known about the Fusarium species in the entire plant used for silage. Furthermore, mycotoxins persist during the ensiling process and thus endanger feed
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Maize is frequently infected by the Fusarium species producing mycotoxins. Numerous investigations have focused on grain maize, but little is known about the Fusarium species in the entire plant used for silage. Furthermore, mycotoxins persist during the ensiling process and thus endanger feed safety. In the current study, we analyzed 20 Swiss silage maize samples from growers’ fields for the incidence of Fusarium species and mycotoxins. The species spectrum was analyzed morphologically and mycotoxins were measured by LC-MS/MS. A pre-harvest visual disease rating showed few disease symptoms. In contrast, the infection rate of two-thirds of the harvest samples ranged from 25 to 75% and twelve different Fusarium species were isolated. The prevailing species were F. sporotrichioides, F. verticillioides and F. graminearum. No infection specificity for certain plant parts was observed. The trichothecene deoxynivalenol (DON) was found in each sample (ranging from 780 to 2990 µg kg−1). Other toxins detected in descending order were zearalenone, further trichothecenes (nivalenol, HT-2 and T-2 toxin, acetylated DON) and fumonisins. A generalized linear regression model containing the three cropping factors harvest date, pre-precrop and seed treatment was established, to explain DON contamination of silage maize. Based on these findings, we suggest a European-wide survey on silage maize. Full article
(This article belongs to the Special Issue Trichothecenes)
Open AccessArticle Enzyme-Linked Immunosorbent-Assay for Deoxynivalenol (DON)
Toxins 2011, 3(8), 968-978; doi:10.3390/toxins3080968
Received: 8 May 2011 / Revised: 28 June 2011 / Accepted: 14 July 2011 / Published: 4 August 2011
Cited by 11 | PDF Full-text (217 KB) | HTML Full-text | XML Full-text
Abstract
Deoxynivalenol (DON), one of the trichothecene mycotoxins, is a worldwide contaminant of wheat and barley, especially when infected by Fusarium graminearum, the causative agent of an epidemic wheat disease called Fusarium Head Blight. Because of the high risk of DON ingestion and
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Deoxynivalenol (DON), one of the trichothecene mycotoxins, is a worldwide contaminant of wheat and barley, especially when infected by Fusarium graminearum, the causative agent of an epidemic wheat disease called Fusarium Head Blight. Because of the high risk of DON ingestion and the possibility of frequent exposure, it is important to develop a rapid and highly sensitive method for easy identification and quantification of DON in grain samples. In this study, we have developed an indirect competitive enzyme-linked immunosorbent assay (ELISA) to detect DON in wheat. We conjugated 3-O-Hemisuccinyl-DON (3HS-DON) to Bovine serum albumin (BSA) and Ovalbumin (OVA), and obtained DON-specific mice antisera. The indirect competitive ELISA revealed that the optimal concentration of mice serum and the coated antigen was 1/1600 and 1/1500, respectively. The antiserum cross-reacted with the trichothecenes 3-acetyl-DON and T-2 toxin, reaching about 55.2% and 6.3%, respectively, as compared with DON. Results showed that the assay could be performed satisfactorily using an extraction buffer containing less than 15% methanol. Recovery from DON was 82–93% in grains. The linear detection range of DON in grains was between 0.01 and 100 μg/mL. Full article
(This article belongs to the Special Issue Trichothecenes)
Open AccessArticle Mechanism of Lethal Toxin Neutralization by a Human Monoclonal Antibody Specific for the PA20 Region of Bacillus anthracis Protective Antigen
Toxins 2011, 3(8), 979-990; doi:10.3390/toxins3080979
Received: 29 April 2011 / Revised: 7 July 2011 / Accepted: 4 August 2011 / Published: 9 August 2011
Cited by 5 | PDF Full-text (302 KB) | HTML Full-text | XML Full-text
Abstract
The primary immunogenic component of the currently approved anthrax vaccine is the protective antigen (PA) unit of the binary toxin system. PA-specific antibodies neutralize anthrax toxins and protect against infection. Recent research has determined that in humans, only antibodies specific for particular determinants
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The primary immunogenic component of the currently approved anthrax vaccine is the protective antigen (PA) unit of the binary toxin system. PA-specific antibodies neutralize anthrax toxins and protect against infection. Recent research has determined that in humans, only antibodies specific for particular determinants are capable of effecting toxin neutralization, and that the neutralizing epitopes recognized by these antibodies are distributed throughout the PA monomer. The mechanisms by which the majority of these epitopes effect neutralization remain unknown. In this report we investigate the process by which a human monoclonal antibody specific for the amino-terminal domain of PA neutralizes lethal toxin in an in vitro assay of cytotoxicity, and find that it neutralizes LT by blocking the requisite cleavage of the amino-terminal 20 kD portion of the molecule (PA20) from the remainder of the PA monomer. We also demonstrate that the epitope recognized by this human monoclonal does not encompass the 166RKKR169 furin recognition sequence in domain 1 of PA. Full article
(This article belongs to the Special Issue Anthrax Toxin)
Open AccessArticle Molecular Analysis of the Interaction of the Snake Venom Rhodocytin with the Platelet Receptor CLEC-2
Toxins 2011, 3(8), 991-1003; doi:10.3390/toxins3080991
Received: 6 July 2011 / Revised: 21 July 2011 / Accepted: 8 August 2011 / Published: 10 August 2011
Cited by 3 | PDF Full-text (687 KB) | HTML Full-text | XML Full-text
Abstract
The Malayan pit viper, Calloselasma rhodostoma, produces a potent venom toxin, rhodocytin (aggretin) which causes platelet aggregation. Rhodocytin is a ligand for the receptor CLEC-2 on the surface of platelets. The interaction of these two molecules initiates a signaling pathway which results
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The Malayan pit viper, Calloselasma rhodostoma, produces a potent venom toxin, rhodocytin (aggretin) which causes platelet aggregation. Rhodocytin is a ligand for the receptor CLEC-2 on the surface of platelets. The interaction of these two molecules initiates a signaling pathway which results in platelet activation and aggregation. We have previously solved the crystal structures of CLEC-2 and of rhodocytin, and have proposed models by which tetrameric rhodocytin may interact with either two monomers of CLEC-2, or with one or two copies of dimeric CLEC-2. In the current study we use a range of approaches to analyze the molecular interfaces and dynamics involved in the models of the interaction of rhodocytin with either one or two copies of dimeric CLEC-2, and their implications for clustering of CLEC-2 on the platelet surface. Full article
(This article belongs to the Special Issue Snake Venoms)
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Review

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Open AccessReview Monoclonal Antibody Therapies against Anthrax
Toxins 2011, 3(8), 1004-1019; doi:10.3390/toxins3081004
Received: 10 June 2011 / Revised: 6 August 2011 / Accepted: 10 August 2011 / Published: 15 August 2011
Cited by 40 | PDF Full-text (197 KB) | HTML Full-text | XML Full-text
Abstract
Anthrax is a highly lethal infectious disease caused by the spore-forming bacterium Bacillus anthracis. It not only causes natural infection in humans but also poses a great threat as an emerging bioterror agent. The lethality of anthrax is primarily attributed to the
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Anthrax is a highly lethal infectious disease caused by the spore-forming bacterium Bacillus anthracis. It not only causes natural infection in humans but also poses a great threat as an emerging bioterror agent. The lethality of anthrax is primarily attributed to the two major virulence factors: toxins and capsule. An extensive effort has been made to generate therapeutically useful monoclonal antibodies to each of the virulence components: protective antigen (PA), lethal factor (LF) and edema factor (EF), and the capsule of B. anthracis. This review summarizes the current status of anti-anthrax mAb development and argues for the potential therapeutic advantage of a cocktail of mAbs that recognize different epitopes or different virulence factors. Full article
(This article belongs to the Special Issue Anthrax Toxin)
Open AccessReview Population Structure and Genetic Diversity of the Fusarium graminearum Species Complex
Toxins 2011, 3(8), 1020-1037; doi:10.3390/toxins3081020
Received: 1 June 2011 / Revised: 11 August 2011 / Accepted: 12 August 2011 / Published: 19 August 2011
Cited by 25 | PDF Full-text (222 KB) | HTML Full-text | XML Full-text
Abstract
The Fusarium graminearum species complex (Fg complex) consists of phylogenetically distinct species some of which cannot be discriminated based on their morphology. Their chemotypes and geographic distributions are dramatically different, and these highlight the challenges that Fusarium head blight (FHB) poses to
[...] Read more.
The Fusarium graminearum species complex (Fg complex) consists of phylogenetically distinct species some of which cannot be discriminated based on their morphology. Their chemotypes and geographic distributions are dramatically different, and these highlight the challenges that Fusarium head blight (FHB) poses to plant disease specialists and plant breeders, thereby requiring that quarantine officials employ molecular diagnostic tools in their active surveillance programs. Molecular marker technologies play essential roles in species identification of the Fg complex, and they are being used widely to assess the genetic diversity of the clade. The utility, applicability and limitations of molecular methods for assessing the population structure and genetic diversity within the Fg complex are discussed with suitable examples. Knowledge gained from these studies will provide a baseline for monitoring changes in FHB pathogen diversity and mycotoxin potential over time, both of which are critical to the ultimate control and elimination of this economically devastating disease. Full article
(This article belongs to the Special Issue Trichothecenes)
Open AccessReview Modes of Action of Microbially-Produced Phytotoxins
Toxins 2011, 3(8), 1038-1064; doi:10.3390/toxins3081038
Received: 28 July 2011 / Revised: 15 August 2011 / Accepted: 17 August 2011 / Published: 22 August 2011
Cited by 41 | PDF Full-text (1296 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
Some of the most potent phytotoxins are synthesized by microbes. A few of these share molecular target sites with some synthetic herbicides, but many microbial toxins have unique target sites with potential for exploitation by the herbicide industry. Compounds from both non-pathogenic and
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Some of the most potent phytotoxins are synthesized by microbes. A few of these share molecular target sites with some synthetic herbicides, but many microbial toxins have unique target sites with potential for exploitation by the herbicide industry. Compounds from both non-pathogenic and pathogenic microbes are discussed. Microbial phytotoxins with modes of action the same as those of commercial herbicides and those with novel modes of action of action are covered. Examples of the compounds discussed are tentoxin, AAL-toxin, auscaulitoxin aglycone, hydantocidin, thaxtomin, and tabtoxin. Full article

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