Type A-trichothecenes - Quantitative analysis using LC-MS and occurrence in Austrian maize and oats.

During this study a method was developed for the quantitative determination of diacetoxyscirpenol (DAS), T-2 toxin and HT-2 toxin using deuterated T-2 toxin (T-2 d3 toxin) as an internal standard. The described method involves a clean up step of maize extract by the use of Mycosep® 227 columns a chromatographic separation on a Zorbax® bonus-RP-column (2,1×150mm) and the detection and quantification step on a mass spectrometer in SIM (Selected Ion Monitoring) mode.Data on the occurrence of three type A trichothecenes in Austrian maize, maize silage and oats were collected. It could be shown that maize and silage samples harvested in 2002 were only contaminated to a small extent with T-2 toxin (8% of the maize, 0% of the silage) and with HT-2 toxin (30% of the maize, 18% of the silage). But most of the analysed oats samples showed significant levels of T-2 toxin (64%) or HT-2 toxin (82%).

Simultaneous quantification of A-trichothecene mycotoxins in grains using liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry.

An approach for simultaneous determination of the main type A-trichothecenes by liquid chromatography and atmospheric pressure chemical ionization mass spectrometry is described. Parameters for coupling of LC-MS such as cone voltage, nebulizing temperature and the LC flow-rate, were optimized to provide detection of mycotoxins with maximum sensitivity. Furthermore, the effects of cone voltage and temperature on the fragmentation pattern of the tested toxins were studied. Main type A-trichothecenes such as T-2 Toxin, HT-2 Toxin, acetyl T-2 Toxin, diacetoxyscirpenol, monoacetoxyscirpenol (15-acetoxyscirpenol) and neosolaniol were separated on a reversed-phase narrow bore C18 column, using a linear gradient and a flow-rate of 0.3 ml/min. Mass spectra were obtained in positive ion mode for confirmation and quantitation. The method involves extraction and purification of toxins by using multifunctional Mycosep columns. Deuterated T-2 Toxin was used as an internal standard. A linear working range between 80 and 500 microg/kg in matrix with an acceptable correlation coefficient was observed. The developed method was validated by using a blank oats sample. The detection limit in the matrix was found to be between 50 and 85 microg/kg in selected ion mode for all tested A-trichothecenes. Recovery data were found to be between 77 and 101%. Within run and day-to-day precision were determined as having comparable levels to those found using GC methods. Furthermore, the matrix effect was investigated by comparing the internal standard versus the external standard method in quantification studies. In addition, the developed method was applied for the analysis of naturally contaminated oats, maize, barley and wheat samples.

Investigation on the biodegradability of mycotoxins nivalenol (NIV) and deoxynivalenol (DON) in a rusitec fermentor and their monitoring by HPLC/MS.

Biodegradation of two B-trichothecenes nivalenol (NIV) and deoxynivalenol (DON) have been studied in a RUSITEC (rumen simulation technique) system. The fermentation studies were carried out in vessels containing the rumen fluid. To reach steady state an adaptation period of one week was carried out. The mycotoxin standards were then added into the fermentor in a concentration of 1ppm NIV and 2ppm DON. The kinetics of NIV and DON biodegradability during the fermentation process were monitored by using a rapid HPLC method combined with a mass spectrometer and an atmospheric pressure chemical ionisation (APCI(-)) interface. Also the effect of mycotoxin addition on different parameters such as ammonia production, pH, gas production and volatile fatty acids have been studied.

Study on biodegradation of some A- and B-trichothecenes and ochratoxin A by use of probiotic microorganisms.

In vitro biodegradation experiments were done using some probiotic microorganisms. DifferentSaccharomyces cerevisiae, Lactobacilli andBacilli strains were tested for their ability to degrade Nivalenol (NIV), Deoxynivalenol (DON), Diacetoxyscirpenol (DAS), T2-Toxin and Ochratoxin A (OTA). The concentrations of selected mycotoxins were in the range of natural occurring toxin contaminations (1ppm for NIV and DON, 500ppb for DAS and T-2 and 50ppb for OTA). No alteration of concentrations could be registered for the tested trichothecenes. The best results could be achieved in experiments with OTA by up to 94% detoxification. Influence of toxins on colony forming unit of all tested microorganisms were recorded. Especially T-2 toxin and DAS have a slowing effect on growth of some strains.

An associative memory that can form hypotheses: a phase-coded neural network.

Nonlinear associative memories as realized, e.g., by Hopfield nets are characterized by attractor-type dynamics. When fed with a starting pattern, they converge to exactly one of the stored patterns which is supposed to be most similar. These systems cannot render hypotheses of classification, i.e., render several possible answers to a given classification problem. Inspired by von der Malsburg's correlation theory of brain function, we extend conventional neural network architectures by introducing additional dynamical variables. Assuming an oscillatory time structure of neural firing, i.e., the existence of neural clocks, we assign a so-called phase to each formal neuron. The phases explicitly describe detailed correlations of neural activities neglected in conventional neural network architectures. Implementing this extension into a simple self-organizing network based on a feature map, we present an associative memory that actually is capable of forming hypotheses of classification.