Impact of manipulation of glycerol/diol dehydratase activity on intestinal microbiota ecology and metabolism

Glycerol/diol dehydratases (GDH) are enzymes that catalyse the production of propionate from 1,2-propanediol, and acrolein from glycerol. Acrolein reacts with dietary carcinogenic heterocyclic amines (HCA), reducing HCA mutagenicity, but is itself also an antimicrobial agent and toxicant. Gut microbial GDH activity has been suggested as an endogenous acrolein source; however, there is limited information on the potential of the intestinal microbiota to have GDH activity, and what impact it can have on the intestinal ecosystem and host health. We hypothesized that GDH activity of gut microbiota is determined by the abundance and distribution of GDH-active taxa and can be enhanced by supplementation of the GDH active Anaerobutyricum hallii, and tested this hypothesis combining quantitative profiling of gdh, model batch fermentations, microbiota manipulation, and kinetic modelling of acrolein formation. Our results suggest that GDH activity is a common trait of intestinal microbiota shared by a few taxa, which was dependent on overall gdh abundance. Anaerobutyricum hallii was identified as a key taxon in GDH metabolism, and its supplementation increased the rate of GDH activity and acrolein release, which enhanced the transformation of HCA and reduced fermentation activity. The findings of this first systematic study on acrolein release by intestinal microbiota indicate that dietary and microbial modulation might impact GDH activity, which may influence host health.     

Mechanisms of Functional and Physical Genome Reduction in Photosynthetic and Nonphotosynthetic Parasitic Plants of the Broomrape Family

Nonphotosynthetic plants possess strongly reconfigured plastomes attributable to convergent losses of photosynthesis and housekeeping genes, making them excellent systems for studying genome evolution under relaxed selective pressures. We report the complete plastomes of 10 photosynthetic and nonphotosynthetic parasites plus their nonparasitic sister from the broomrape family (Orobanchaceae). By reconstructing the history of gene losses and genome reconfigurations, we find that the establishment of obligate parasitism triggers the relaxation of selective constraints. Partly because of independent losses of one inverted repeat region, Orobanchaceae plastomes vary 3.5-fold in size, with 45 kb in American squawroot (Conopholis americana) representing the smallest plastome reported from land plants. Of the 42 to 74 retained unique genes, only 16 protein genes, 15 tRNAs, and four rRNAs are commonly found. Several holoparasites retain ATP synthase genes with intact open reading frames, suggesting a prolonged function in these plants. The loss of photosynthesis alters the chromosomal architecture in that recombinogenic factors accumulate, fostering large-scale chromosomal rearrangements as functional reduction proceeds. The retention of DNA fragments is strongly influenced by both their proximity to genes under selection and the co-occurrence with those in operons, indicating complex constraints beyond gene function that determine the evolutionary survival time of plastid regions in nonphotosynthetic plants.     

Atlas-Guided Cluster Analysis of Large Tractography Datasets

Diffusion Tensor Imaging (DTI) and fiber tractography are important tools to map the cerebral white matter microstructure in vivo and to model the underlying axonal pathways in the brain with three-dimensional fiber tracts. As the fast and consistent extraction of anatomically correct fiber bundles for multiple datasets is still challenging, we present a novel atlas-guided clustering framework for exploratory data analysis of large tractography datasets. The framework uses an hierarchical cluster analysis approach that exploits the inherent redundancy in large datasets to time-efficiently group fiber tracts. Structural information of a white matter atlas can be incorporated into the clustering to achieve an anatomically correct and reproducible grouping of fiber tracts. This approach facilitates not only the identification of the bundles corresponding to the classes of the atlas; it also enables the extraction of bundles that are not present in the atlas. The new technique was applied to cluster datasets of 46 healthy subjects. Prospects of automatic and anatomically correct as well as reproducible clustering are explored. Reconstructed clusters were well separated and showed good correspondence to anatomical bundles. Using the atlas-guided cluster approach, we observed consistent results across subjects with high reproducibility. In order to investigate the outlier elimination performance of the clustering algorithm, scenarios with varying amounts of noise were simulated and clustered with three different outlier elimination strategies. By exploiting the multithreading capabilities of modern multiprocessor systems in combination with novel algorithms, our toolkit clusters large datasets in a couple of minutes. Experiments were conducted to investigate the achievable speedup and to demonstrate the high performance of the clustering framework in a multiprocessing environment.     

Influence of T-2 and HT-2 Toxin on the Blood-Brain Barrier In Vitro: New Experimental Hints for Neurotoxic Effects

The trichothecene mycotoxin T-2 toxin is a common contaminant of food and feed and is also present in processed cereal derived products. Cytotoxic effects of T-2 toxin and its main metabolite HT-2 toxin are already well described with apoptosis being a major mechanism of action. However, effects on the central nervous system were until now only reported rarely. In this study we investigated the effects of T-2 and HT-2 toxin on the blood-brain barrier (BBB) in vitro. Besides strong cytotoxic effects on the BBB as determined by the CCK-8 assay, impairment of the barrier function starting at low nanomolar concentrations were observed for T-2 toxin. HT-2 toxin, however, caused barrier disruption at higher concentrations compared to T-2 toxin. Further, the influence on the tight junction protein occludin was studied and permeability of both toxins across the BBB was detected when applied from the apical (blood) or the basolateral (brain) side respectively. These results clearly indicate the ability of both toxins to enter the brain via the BBB.     

Die Bedeutung elektrophoretischer Proteinanalysen bei phytopathogenen Pilzen als Hilfsmittel zu ihrer taxonomischen Charakterisierung

Sunflower is one of the most important oilseed crops, which is grown in many countries. Increasing demand to use sunflower oil has expanded the under cultivation area throughout the world. Sunflower viruses have been reported as one of the pathogens that reduce the quantity and the quality of this product in a number of countries. In our research to study the occurrence and distribution of viruses in sunflower fields of Iran, 562 samples were collected from different fields in Kerman and Isfahan provinces during growing seasons from 2009 to 2011. Potato virus Y (PVY), Cucumber mosaic virus (CMV) and Tomato spotted wilt virus (TSWV) were detected by double antibody sandwich enzyme-linked immunosorbent assay. Also, numbers of samples were positive for infection to potyviruses (except PVY) in antigen-coated-plate enzyme-linked immunosorbent assay test using potyviruses general antiserum. Infected plants had symptoms like mosaic, yellowing, deformation, necrotic and chlorotic lesions and mottling on leaves and stunting. The infection rates of potyviruses, PVY, CMV and TSWV in Isfahan province were 33, 22, 4.18 and 3.25% of collected samples, respectively. The corresponding rates for samples from Kerman province were 15, 5, 0.8 and 0.4% of collected samples. According to these results, viral infection in Isfahan province was more than surveyed in Kerman province during the mentioned period of three years. Furthermore, generally there was a decrease in the percentage of viral infection during this three growing seasons in both provinces. This is the first report of the detection of CMV and TSWV in sunflower fields of Isfahan and Kerman and first report of PVY in Isfahan.     

Phylogenetic position and delimitation of the moss family Plagiotheciaceae in the order Hypnales

The phylogenetic position and generic composition of the moss family Plagiotheciaceae were explored using DNA sequence data from three genomes: plastid trnL‐F and rps4, mitochondrial nad5 intron and nuclear ITS1‐5.8S‐ITS2. Our phylogenetic analyses included 35 terminals from Plagiotheciaceae and 71 outgroup taxa from a representative set of hypnalean moss families. The family Plagiotheciaceae is resolved in the early‐diverging Hypnales grade, together with Fontinalaceae, Habrodontaceae and several genera which are mainly distributed in the area of the former Gondwanan supercontinent. However, monophyly of the family can only be attained if the three Southern Hemisphere genera, Acrocladium, Catagonium and Rhizofabronia, are excluded. Ancestral state reconstruction for eight morphological characters reveals that many characters used to delimit the family, such as a lack of pseudoparaphyllia and rhizoids inserted in the leaf axils, were already present in the ancestor of Hypnales. Dispersal–vicariance analysis suggests that Plagiotheciaceae and Fontinalaceae have their ancestral distributions in the area of the former Laurasian supercontinent. As the analyses also reveal a Gondwanan distribution for the ancestor of Hypnales in general, Plagiotheciaceae and Fontinalaceae represent the first diverging Laurasian lineages in the order. © 2013 The Linnean Society of London     

Computational biomechanics of a lumbar motion segment in pure and combined shear loads

Anterior shear has been implicated as a risk factor in spinal injuries. A 3D nonlinear poroelastic finite element model study of a lumbar motion segment L4-L5 was performed to predict the temporal shear response under various single and combined shear loads. Effects of nucleotomy and facetectomy as well as changes in the posture and facet gap distance were analyzed as well.     

Lipid Segregation and Membrane Budding Induced by the Peripheral Membrane Binding Protein Annexin A2

The formation of dynamic membrane microdomains is an important phenomenon in many signal transduction and membrane trafficking events. It is driven by intrinsic properties of membrane lipids and integral as well as membrane-associated proteins. Here we analyzed the ability of one peripherally associated membrane protein, annexin A2 (AnxA2), to induce the formation of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂)-rich domains in giant unilamellar vesicles (GUVs) of complex lipid composition. AnxA2 is a cytosolic protein that can bind PI(4,5)P₂ and other acidic phospholipids in a Ca²⁺-dependent manner and that has been implicated in cellular membrane dynamics in endocytosis and exocytosis. We show that AnxA2 binding to GUVs induces lipid phase separation and the recruitment of PI(4,5)P₂, cholesterol and glycosphingolipids into larger clusters. This property is observed for the full-length monomeric protein, a mutant derivative comprising the C-terminal protein core domain and for AnxA2 residing in a heterotetrameric complex with its intracellular binding partner S100A10. All AnxA2 derivatives inducing PI(4,5)P₂ clustering are also capable of forming interconnections between PI(4,5)P₂-rich microdomains of adjacent GUVs. Furthermore, they can induce membrane indentations rich in PI(4,5)P₂ and inward budding of these membrane domains into the lumen of GUVs. This inward vesiculation is specific for AnxA2 and not shared with other PI(4,5)P₂-binding proteins such as the pleckstrin homology (PH) domain of phospholipase Cδ1. Together our results indicate that annexins such as AnxA2 can efficiently induce membrane deformations after lipid segregation, a mechanism possibly underlying annexin functions in membrane trafficking.