Time filter

Source Type

of Le Mans, Italy

Brillouet J.-M.,French National Institute for Agricultural Research | Romieu C.,Montpellier SupAgro | Schoefs B.,University of Le Mans | Solymosi K.,Eotvos Lorand University | And 5 more authors.
Annals of Botany | Year: 2013

Background and AimsCondensed tannins (also called proanthocyanidins) are widespread polymers of catechins and are essential for the defence mechanisms of vascular plants (Tracheophyta). A large body of evidence argues for the synthesis of monomeric epicatechin on the cytosolic face of the endoplasmic reticulum and its transport to the vacuole, although the site of its polymerization into tannins remains to be elucidated. The aim of the study was to re-examine the cellular frame of tannin polymerization in various representatives of the Tracheophyta.MethodsLight microscopy epifluorescence, confocal microscopy, transmission electron microscopy (TEM), chemical analysis of tannins following cell fractionation, and immunocytochemistry were used as independent methods on tannin-rich samples from various organs from Cycadophyta, Ginkgophyta, Equisetophyta, Pteridophyta, Coniferophyta and Magnoliophyta. Tissues were fixed in a caffeine-glutaraldehyde mixture and examined by TEM. Other fresh samples were incubated with primary antibodies against proteins from both chloroplastic envelopes and a thylakoidal chlorophyll-carrying protein; they were also incubated with gelatin-Oregon Green, a fluorescent marker of condensed tannins. Coupled spectral analyses of chlorophyll and tannins were carried out by confocal microscopy on fresh tissues and tannin-rich accretions obtained through cell fractionation; chemical analyses of tannins and chlorophylls were also performed on the accretions.Key Results and ConclusionsThe presence of the three different chloroplast membranes inside vacuolar accretions that constitute the typical form of tannin storage in vascular plants was established in fresh tissues as well as in purified organelles, using several independent methods. Tannins are polymerized in a new chloroplast-derived organelle, the tannosome. These are formed by pearling of the thylakoids into 30 nm spheres, which are then encapsulated in a tannosome shuttle formed by budding from the chloroplast and bound by a membrane resulting from the fusion of both chloroplast envelopes. The shuttle conveys numerous tannosomes through the cytoplasm towards the vacuole in which it is then incorporated by invagination of the tonoplast. Finally, shuttles bound by a portion of tonoplast aggregate into tannin accretions which are stored in the vacuole. Polymerization of tannins occurs inside the tannosome regardless of the compartment being crossed. A complete sequence of events apparently valid in all studied Tracheophyta is described. © 2013 The Author. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

Rousseau P.,University of Angers | Rousseau P.,French Institute of Health and Medical Research | Mahe G.,University of Angers | Mahe G.,French Institute of Health and Medical Research | And 7 more authors.
Microvascular Research | Year: 2011

Objective: Both spatial variability and temporal variability of skin blood flow are high. Laser speckle contrast imagers (LSCI) allow non-contact, real-time recording of cutaneous blood flow on large skin surfaces. Thereafter, the observer can define different sizes for the region of interest (ROI) in the images to decrease spatial variability and different durations over which the blood flow values are averaged (time of interest, TOI) to decrease temporal variability. We aimed to evaluate the impact of the choices of ROI and TOI on the analysis of rest blood flow and post occlusive reactive hyperemia (PORH). Methods: Cutaneous blood flow (CBF) was assessed at rest and during PORH. Three different sizes of ROI (1mm2, 10mm2 and 100mm2), and three different TOI (CBF averaged over 1s, 15s, and 30s for rest, and over 1s, 5s and 10s for PORH peak) were evaluated. Inter-subjects and intra-subjects coefficient of variations (inter-CV and intra-CV) were studied. Results: The inter-subject variability of CBF is about 25% at rest and is moderately improved when the size of the ROI increases (inter-CV=31%, for 1s and 1mm2 versus inter-CV=23%, for 15s and 100mm2). However, increasing the TOI does not improve the results. The variability of the PORH peak is lower with an inter-CV varying between 11.4% (10s and 100mm2) and 21.6% (5s and 1mm2). The lowest intra-CV for the CBF at rest was 7.3% (TOI of 15s on a ROI of 100mm2) and was 3.1% for the PORH peak (TOI of 10s on a ROI of 100mm2). Conclusion: We suggest that a size of ROI larger than 10mm2 and a TOI longer than 1s are required to reduce the variability of CBF measurements both at rest and during PORH peak evaluations at the forearm level. Many technical aspects such as comparison of laser speckle contrast imaging and laser Doppler imaging or the effect of skin to head distance on recorded values with LCSI are required to improve future studies using this fascinating clinical tool. © 2011 Elsevier Inc.

Lecouteux B.,University Of Grenoble Alpes | Linares G.,University of Avignon | Esteve Y.,University of Le Mans | Gravier G.,French National Center for Scientific Research
IEEE Transactions on Audio, Speech and Language Processing | Year: 2013

Combining automatic speech recognition (ASR) systems generally relies on the posterior merging of the outputs or on acoustic cross-adaptation. In this paper, we propose an integrated approach where outputs of secondary systems are integrated in the search algorithm of a primary one. In this driven decoding algorithm (DDA), the secondary systems are viewed as observation sources that should be evaluated and combined to others by a primary search algorithm. DDA is evaluated on a subset of the ESTER I corpus consisting of 4 hours of French radio broadcast news. Results demonstrate DDA significantly outperforms vote-based approaches: we obtain an improvement of 14.5% relative word error rate over the best single-systems, as opposed to the the 6.7% with a ROVER combination. An in-depth analysis of the DDA shows its ability to improve robustness (gains are greater in adverse conditions) and a relatively low dependency on the search algorithm. The application of DDA to both A and beam-search-based decoder yields similar performances. © 2006-2012 IEEE.

Schwenk H.,University of Le Mans
Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH | Year: 2013

Language models play a very important role in many natural language processing applications, in particular large vocabulary speech recognition and statistical machine translation. For a long time, back-off n-gram language models were considered to be the state-of-art when large amounts of training data are available. Recently, so called continuous space methods or neural network language models have shown to systematically outperform these models and they are getting increasingly popular. This article describes an open-source toolkit that implements these models in a very efficient way, including support for GPU cards. The modular architecture makes it very easy to work with different data formats and to support various alternative models. Using data selection, resampling techniques and a highly optimized code, training on more than five billions words takes less than 24 hours. The resulting models achieve reductions in the perplexity of almost 20%. This toolkit has been very successfully applied to various languages for large vocabulary speech recognition and statistical machine translation. By making available this toolkit we hope that many more researchers will be able to work on this very promising technique, and by these means, quickly advance the field. Copyright © 2013 ISCA.

Mahe G.,University of Angers | Mahe G.,French Institute of Health and Medical Research | Haj-Yassin F.,University of Angers | Rousseau P.,University of Angers | And 7 more authors.
Microvascular Research | Year: 2011

Background: Laser Speckle contrast imaging (LSCI) allows non-contact, real-time recording of cutaneous blood flow (CBF). Different distances from laser-head to skin (distances L-S) can be chosen by the operator to perform these recordings. We aimed to evaluate the impact of different Distances L-S on the analysis of rest blood flow and post-occlusive reactive hyperemia (PORH). Methods: Four distances L-S (10, 15, 20, and 30cm) were evaluated in a random order in 11 healthy subjects. We analyzed the concordance between each recording at each distance L-S. We compared CBF results (absolute values and cutaneous vascular conductance (CBF divided by mean arterial pressure)) obtained for each distance L-S. The intra-subject coefficients of variation due to distances L-S (intra-CV, in%) were also studied. Results: The mean "r" (standard deviation) cross-correlation coefficient was 0.99 (0.00) between each CBF trace issued from different distance L-S. Both kinds of CBF results, at rest and for PORH peak, show non-significant differences when the distance L-S is modified. The intra-CV varies from 5.9% to 8.6% at rest and from 5.6% to 9.1% for the PORH peak. Conclusion: Distance L-S neither influences SBFR at rest, nor at peak post-occlusive hyperemia in the 10-30cm interval using LSCI. © 2011 Elsevier Inc..

Discover hidden collaborations