Disappearance of eggs during gestation in a viviparous snake (Vipera aspis) detected using non-invasive techniques

The number of eggs released at ovulation may be greater than the number of offspring born, if some of these ovulated eggs and/or embryos disappear during gestation. Although this process can potentially exert significant effects on reproductive output, logistical problems have discouraged studies on the disappearance of eggs and embryos in most kinds of vertebrates. Nuclear Magnetic Resonance (NMR) imaging and ultrasound Doppler-imaging have not been applied previously to such questions. Using these techniques, we monitored changes in the female’s oviduct through gestation in a viviparous snake. We documented a case of disappearance of two ovulated eggs (from a litter of four) in the aspic viper, Vipera aspis. The female ovulated four normal-sized eggs, two of which contained living embryos when examined by NMR and ultrasound Doppler-imaging early in gestation. Subsequent NMR imaging midway through gestation showed the same situation, but a third imaging session immediately prior to parturition revealed that the oviducts contained only the two live embryos. The two nonviable eggs had disappeared. The female gave birth to the two live offspring, with no evidence of any additional material. These data thus offer the strongest evidence so far available for egg disappearance (resorption?) during gestation in reptiles. More generally, NMR imaging offers a valuable tool for investigating processes inside the body cavity, where direct observation is otherwise difficult or impossible. The technique does not require sacrifice of the animals, and hence allows dynamic investigations over time

Application de la R.M.N. des milieux orientes a l'etude de phospholipides en dispersions aqueuses

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Fast and Ultrafast Quantitative 2D NMR: Vital Tools for Efficient Metabolomic Approaches

International audienceNuclear magnetic resonance (NMR) offers great potential for quantitative analysis of metabolic samples, but accurate and precise quantitative analysis is often made difficult by a high degree of spectral overlap. Multi-dimensional NMR offers an interesting alternative, as it provides a much better discrimination of resonances. However, its use for quantitative analysis is limited by its long acquisition duration and its multi-impulsional character. Nevertheless, numerous improvements in the quantitative performance of 2D NMR have been made during the past decade, facilitating a wide range of applications. This review assesses the recent contributions brought to the field of quantitative 2D NMR, and provides a survey of recent studies of metabolic samples using this methodology. The ongoing need for developing and optimizing powerful tools is first examined. It highlights the necessity of reducing the experimental duration, resulting in a fast 2D NMR approach. This methodology is then described, relying on recent applications to metabolic samples. The last section of the chapter describes a more recent approach, ultrafast 2D NMR, which makes it possible to record multi-dimensional spectra in a single scan. The principles and the analytical performances of this novel methodology are described, as well as its perspectives in terms of quantitative analysis

Développement de la RMN quantitative du carbone 13 en abondance naturelle

NANTES-BU Sciences (441092104) / SudocSudocFranceF

Sensitivity losses and line shape modifications due to molecular diffusion in continuous encoding ultrafast 2D NMR experiments

Recent ultrafast techniques make it possible to obtain multidimensional (nD) NMR spectra in a single scan. These ultrafast methods rely on a spatial encoding process based on radiofrequency (RF) pulses applied Simultaneously with magnetic field gradients. Numerous approaches have been proposed in the past few years to perform this excitation process, most of them relying on a continuous excitation of the spins throughout the whole sample. However, the resolution and sensitivity of ultrafast nD spectra are often reduced by molecular diffusion effects due to the presence of gradients during the excitation process. In particular, increasing the excitation period is necessary to improve the resolution in the ultrafast dimension, but it leads to high sensitivity losses due to diffusion. In order to understand better and to limit molecular diffusion effects, a detailed theoretical and experimental study of the various continuous ultrafast excitation processes is carried out in the present Study. New numerical Simulations Of ultrafast echo line shapes are presented and compared to experimental data. The evolution of the signal intensity with the excitation process duration is also simulated and compared to experimental intensity losses. The different excitation schemes are compared in order to determine the best excitation conditions to perform 2D ultrafast experiments with optimum resolution and sensitivity. The experimental and theoretical results put in evidence the efficiency of the multi-echo scheme. (C) 2008 Elsevier Inc. All rights reserved

Appréciation de la quantité et de la répartition des tissus adipeux et musculaires dans les produits animaux par imagerie par résonance magnétique

Ce mémoire a pour but de mieux cerner les potentialités et les limites de l'imagerie de résonance magnétique nucléaire " bas champ " pour caractériser et quantifier la répartition anatomique des tissus adipeux et musculaires dans les produits animaux. Cette recherche a donc nécessité de mettre au point et d'optimiser des techniques d'acquisition et de traitement des images IRM en comparant les résultats ainsi obtenus à ceux en vigueur, méthodes longues, fastidieuses et parfois dépendante du manipulateur, telles que la dissection ou les méthodes de dosage par extraction chimique. Deux produits modèles, le porc et la truite Fario, ont été étudiés pour appréhender différents aspects de l'étude de la répartition des tissus adipeux.The aim of this thesis is to better understand the potentialities and the limits of magnetic resonance imaging (MRI) at low field to characterise and quantify the anatomic repartition of adipose and muscular tissues in animal products..NANTES-BU Sciences (441092104) / SudocRENNES-Agrocampus-Bibl. SPA (352382310) / SudocSudocFranceF

Le signal de référence ERETIC pour la mesure par RMN du deutérium en abondance naturelle ( application aux arômes)

Ce mémoire présente la mise en place de plusieurs protocoles de mesure par RMN-2H des abondances isotopiques spécifiques (Ai), au moyen du signal de référence électronique ERETIC. La méthode présente les mêmes caractéristiques en termes de précision et de justesse que la référence interne chimique classique (TMU). Les contraintes et inconvénients rencontrés avec une référence chimique sont ainsi évités : superposition de pics, solubilité, prix, pollution de l'échantillon... Un protocole, nommé "à TR court", met à profit les caractéristiques de la méthode ERETIC, où la relation TR >= 5.T1 pour une erreur systématique de 0,7 % n'est plus vérifiée. Ainsi, la durée totale d'expérience peut être divisée par 4. Cette étude établit également une méthode d'authentification du salicylate de méthyle et de la caféine. L'observation des Ai distingue le composé naturel du synthétique, et dans le cas du salicylate de méthyle, son origine botanique.In the present dissertation we developed a methods for a thermodynamical analysis and control of a synthesis of new materials in a solid state. We based it on the abilities of the irreversible processes thermodynamics and on the experimental analysis techniques (such as DSC-TG, XRD, SEM, etc.). We applied that methods to two kinds of problems with a practical application: i) the LiCoPO4 synthesis; and ii) the PdSe2, PdTe2 and PtTe2 phase transitions under high pressure. Thanks to our study we prepared a pure LiCoPO4 with average particle size of 0.5 m. Moreover, we got the ability to prognosticate its particle size, obtained in a random thermal regime. Concerning the second problem we found the phase transition order under high pressure of the PdSe2, the PdTe2 and the PtTe2: first order one and no phase transition respectively. We also explored the phases stabilities in respect of pressure and temperature.NANTES-BU Sciences (441092104) / SudocSudocFranceF

Développements méthodologiques en RMN 2D ultrarapide pour l étude de métabolismes

Ultrafast (uf) 2D NMR is a very promising methodology enabling the acquisition of 2D NMR spectra in a single scan. The main goal of this work is to develop quantitative methods based on uf 2D NMR and to apply them to the quantification of metabolites in biological mixtures. Based on ultrafast 2D NMR, we developed a quantitative Multi-Scan-Single-Shot (M3S) strategy, capable of measuring absolute metabolite concentrations in complex mixtures with a high precision in a reasonable time. The analytical performance of this methodology appears much higher than the one of its conventional counterpart. In particular, uf experiments are more immune to hardware temporal instabilities, thus leading to a higher precision. A first application to the determination of metabolite concentrations in breast cancer cell extracts is presented. Another part of this thesis considers the application of such methods to the determination of 13C site-specific enrichments in biological samples, an approach which is particularly useful in fluxomics. We have designed an ensemble of methods like uf hetero-nuclear J-resolved and 3D ufJCOSY for measuring specific 13C-enrichments in a very fast and accurate way, by using experiments based on ultrafast 2D NMR. Finally, the success of an analytical method stands in its capacity to be applied by other researchers and users. Therefore, to make this methodology implementable and applicable by non-specialists, we developed a simple routine capable of translating the conventional NMR acquisition parameters (spectral widths, transmitter frequencies) into specific uf parameters (gradients and chirp pulse parameters).La RMN 2D ultrarapide (uf) est une méthodologie prometteuse permettant l obtention de spectres RMN 2D en un seul scan. L objectif principal de ce travail est de développer des méthodes quantitatives basées sur la RMN 2D uf, et de les appliquer à la quantification de métabolites dans des échantillons biologiques. Ainsi, en nous basant sur la RMN 2D uf, nous avons développé une stratégie multi-scan permettant de déterminer les concentrations absolues de métabolites dans des mélanges complexes, avec une précision élevée en un temps raisonnable. Les performances analytiques de cette approche sont nettement supérieures à celles de la RMN 2D conventionnelle. En particulier, les expériences ultrarapides sont mieux immunisées contre les instabilités temporelles de l appareillage, d où une meilleure précision. Une première application à la détermination des concentrations de métabolites dans des extraits cellulaires de cancer du sein est présentée. Une autre partie de ce travail consiste à développer et appliquer des méthodes uf pour la détermination d enrichissements isotopiques 13C site-spécifiques, dans le domaine de la fluxomique. Nous avons mis au point plusieurs méthodes ultrarapides (RMN J-résolue hétéronucléaire, ufJCOSY 3D) pour la mesure rapide, précise et juste de ces enrichissements. Enfin, le succès d une méthode analytique dépend fortement de son exportabilité. Afin de faciliter son implémentation par d autres utilisateurs, nous avons développé une interface permettant de convertir les paramètres d acquisition RMN conventionnels (largeurs spectrales, fréquences RF) en paramètres spécifiques aux expériences ultrarapides (gradients et impulsions à fréquence variable).NANTES-BU Sciences (441092104) / SudocSudocFranceF