Effects of Mycotoxins on the Intestine

Mycotoxins are secondary metabolites produced by several fungal species. They can contaminate human food and animal feed, and have been a threat for thousands of years. The gastrointestinal tract is the first target when ingesting mycotoxin-contaminated food or feed. As unlikely as it sounds, the investigations concerning the effects of mycotoxins on the intestine are still in their early stages. This book gathers the most recent advances related to the characterization of the intestinal toxicity of mycotoxins. Substantial data assembled on the damage caused to a number of histological structures and functions of the intestine remove any remaining doubt about this organ being a primary target for the toxicity of mycotoxins. An interesting overview of the detrimental effects of mycotoxins on the gut-hosted microbiota—now regarded as a fully-fledged organ associated with the gut—is also given. Finally, outstanding contributions in this book address questions relating to the suitability of current regulations to protect against alterations of the intestine, and to the efficacy assessment of new detoxification strategies using the intestinal toxicity of mycotoxins as a relevant endpoint

An iterative study of time independent induction effects in magnetohydrodynamics

International audienceWe introduce a new numerical approach to study magnetic induction in flows of an electrically conducting fluid submitted to an external applied field B-0. In our procedure the induction equation is solved iteratively in successive orders of the magnetic Reynolds number Rm. All electrical quantities such as potential, currents, and fields are computed explicitly with real boundary conditions. We validate our approach on the well known case of the expulsion of magnetic field lines from large scale eddies. We then apply our technique to the study of the induction mechanisms in the von Karman flows generated in the gap between coaxial rotating disks. We demonstrate how the omega and alpha effects develop in this flow, and how they could cooperate to generate a dynamo in this homogeneous geometry. We also discuss induction effects that specifically result from boundary conditions

Development of a pig jejunal explant culture for studying the gastrointestinal toxicity of the mycotoxin deoxynivalenol: histopathological analysis

The digestive tract is a target for the mycotoxin deoxynivalenol (DON), a major cereals grain contaminant of public health concern in Europe and North America. Pig, the most sensitive species to DON toxicity, can be regarded as the most relevant animal model for studying the intestinal effects of DON. A pig jejunal explants culture was developed to assess short-term effects of DON. In a first step, jejunal explants from 9-13 week-old and from 4-5 week-old pigs were cultured in vitro for up to 8 hours. Explants from younger animals were better preserved after 8 hours, as assessed by morphological scores and by villi lengths. In a second step, dose-related alterations of the jejunal tissue were observed, including shortened and coalescent villi, lysis of enterocytes, oedema. After 4h of DON exposure of explants from 4-5 week-old pigs, a no-effect concentration level of 1 µM was estimated (corresponding to diet contaminated with 0.3 mg DON/kg) based on morphological scores, and of 0.2 µM based on villi lengths. In conclusion, our data indicate that pig intestinal explants represent a relevant and sensitive model to investigate the effects of food contaminants

The food contaminant deoxynivalenol, decreases intestinal barrier permeability and reduces claudin expression

The gastrointestinal tract represents the first barrier against food contaminants as well as the first target for these toxicants. Deoxynivalenol (DON) is a mycotoxin that commonly contaminates cereals and causes various toxicological effects. Through consumption of contaminated cereals and cereal products, human and pigs are exposed to this mycotoxin. Using in vitro, ex vivo, and in vivo approaches, we investigated the effects of DON on the intestinal epithelium. We demonstrated that, in intestinal epithelial cell lines from porcine (IPEC-1) or human (Caco-2) origin, DON decreases trans-epithelial electric resistance (TEER) and increases in a time and dose-dependent manner the paracellular permeability to 4 kDa dextran and to pathogenic Escherichia Coli across intestinal cell monolayers. In pig explants treated with DON, we also observed an increased permeability of intestinal tissue. These alterations of barrier function were associated with a specific reduction in the expression of claudins, which was also seen in vivo in the jejunum of piglets exposed to DON-contaminated feed. In conclusion, DON alters claudin expression and decreases the barrier function of the intestinal epithelium. Considering that high levels of DON may be present in food or feed, consumption of DON-contaminated food/feed may induce intestinal damage and has consequences for human and animal health

Estimating Potential Infection Transmission Routes in Hospital Wards Using Wearable Proximity Sensors

Contacts between patients, patients and health care workers (HCWs) and among HCWs represent one of the important routes of transmission of hospital-acquired infections (HAI). A detailed description and quantification of contacts in hospitals provides key information for HAIs epidemiology and for the design and validation of control measures. We used wearable sensors to detect close-range interactions ("contacts") between individuals in the geriatric unit of a university hospital. Contact events were measured with a spatial resolution of about 1.5 meters and a temporal resolution of 20 seconds. The study included 46 HCWs and 29 patients and lasted for 4 days and 4 nights. 14037 contacts were recorded. The number and duration of contacts varied between mornings, afternoons and nights, and contact matrices describing the mixing patterns between HCW and patients were built for each time period. Contact patterns were qualitatively similar from one day to the next. 38% of the contacts occurred between pairs of HCWs and 6 HCWs accounted for 42% of all the contacts including at least one patient, suggesting a population of individuals who could potentially act as super-spreaders. Wearable sensors represent a novel tool for the measurement of contact patterns in hospitals. The collected data provides information on important aspects that impact the spreading patterns of infectious diseases, such as the strong heterogeneity of contact numbers and durations across individuals, the variability in the number of contacts during a day, and the fraction of repeated contacts across days. This variability is associated with a marked statistical stability of contact and mixing patterns across days. Our results highlight the need for such measurement efforts in order to correctly inform mathematical models of HAIs and use them to inform the design and evaluation of prevention strategies

Mycotoxines et éléments traces métalliques : co-contamination et toxicité croisée.

Ce numéro est constitué d’articles issus du colloque « Contaminants alimentaires – approches émergentes pour connaître et prévenir le risque » qui s’est tenu à Paris le 19 décembre 2018.Food safety is a major concern worldwide. Most of the toxicological data concern the effects of foodcontaminant when present alone; however, food and feedstuff are usually contaminated by more thanone toxic compound. In this study, we focused on the contamination and toxicity of the mixture betweena metallic chemical element, cadmium (Cd) and a mycotoxin, deoxynivalenol (DON). Their individualand combined cytotoxicity were first investigated in human cell lines from kidney, intestine, blood andliver. The types of interactions, determined by the combination index method, revealed the interaction isorgan specific. When looking more precisely at the intestine, we observed that the interaction betweenDON and Cd on the barrier function varied according to the dose and duration of exposure. Theexpression of junctional proteins was greatly reduced in any exposed cells, with a greater effect with themixture in DON+Cd. In vivo, intestine of rat exposed to DON, Cd or both, showed a higher lesionalscore and lower junctional-proteins expression than control animals. Taken together, our resultsdemonstrate that combined exposure to DON and Cd can induces more effect than a single exposureThey also reveal the complexity of the interaction between food contaminantsLa sécurité sanitaire des aliments est une préoccupation majeure. La plupart des donnéestoxicologiques concernent les effets des contaminants alimentaires présents seuls. Cependant, lesaliments sont généralement contaminés simultanément par plusieurs toxiques. Nous sommesintéressés à la contamination et à la toxicité du mélange d'un élément trace métallique, le cadmium (Cd)et d'une mycotoxine, le déoxynivalénol (DON). Leur cytotoxicité a d'abord été étudiée dans différenteslignées cellulaires humaines d'origine rénale, intestinale, sanguine et hépatique. L'analyse desinteractions, par l'indice de combinaison, montre que le type d'interaction est organe-spécifique. Uneanalyse plus fine sur l'intestin montre que l'interaction entre ces deux contaminants sur la fonction debarrière varie en fonction de la dose et de la durée d'exposition. L'expression des protéines de jonctionest réduite sur les cellules exposées aux contaminants, avec une réduction plus importante pour lemélange. In vivo, l'intestin des rats exposés au DON, au Cd ou au mélange a montré un score lésionnelplus élevé et une expression plus faible des protéines de jonction que les contrôles. De façon globale,nos résultats montrent qu'une exposition au mélange DON et Cd peut induire effets plus importantsqu'une exposition à un seul de ces contaminants. Ils révèlent également la complexité des interactionsentre les contaminants alimentaires

Induction in a von Karman flow driven by ferromagnetic impellers

We study magnetohydrodynamics in a von K\'arm\'an flow driven by the rotation of impellers made of material with varying electrical conductivity and magnetic permeability. Gallium is the working fluid and magnetic Reynolds numbers of order unity are achieved. We find that specific induction effects arise when the impeller's electric and magnetic characteristics differ from that of the fluid. Implications in regards to the VKS dynamo are discussed.Comment: 14 pages, 7 figure

Long-term memory in experiments and numerical simulations of hydrodynamic and magnetohydrodynamic turbulence

International audienceWe analyze time series stemming from experiments and direct numerical simulations of hydrodynamic and magnetohydrodynamic turbulence. Simulations are done in periodic boxes, but with a volumetric forcing chosen to mimic the geometry of the flow in the experiments, the von Kármán swirling flow between two counterrotating impellers. Parameters in the simulations are chosen to (within computational limitations) allow comparisons between the experiments and the numerical results. Conducting fluids are considered in all cases. Two different configurations are considered: a case with a weak externally imposed magnetic field and a case with self-sustained magnetic fields. Evidence of long-term memory and 1/f noise is observed in experiments and simulations, in the case with weak magnetic field associated with the hydrodynamic behavior of the shear layer in the von Kármán flow, and in the dynamo case associated with slow magnetohydrodynamic behavior of the large-scale magnetic field

Robust estimate of dynamo thresholds in the von Kármán sodium experiment using the extreme value theory

International audienceWe apply a new threshold detection method based on the extreme value theory (EVT) to the von Kármán sodium (VKS) experiment data. The VKS experiment is a successful attempt to get a dynamo magnetic field in a laboratory liquidmetal experiment. We first show that the dynamo threshold is associated with a change of the probability density function of the extreme values of the magnetic field. This method does not require the measurement of response functions from applied external perturbations and thus provides a simple threshold estimate. We apply our method to different configurations in the VKS experiment, showing that it yields a robust indication of the dynamo threshold as well as evidence of hysteretic behaviors. Moreover, for the experimental configurations in which a dynamo transition is not observed, the method provides a way to extrapolate an interval of possible threshold values