Efficiency of embryonic development after Intra-Follicular and Intra-Oviductal transfer of in vitro and in vivo matured horse oocytes

In vivo techniques, such as intra-oviductal Oocyte Transfer (OT) and Intra-Follicular Oocyte Transfer (IFOT) can be considered as alternatives to bypass the lack of efficient superovulation treatments and the inadequacy of conventional in vitro fertilization techniques in the horse. We compared embryo production following transfer of in vivo recovered oocytes (1) into a recipient’s oviduct or (2) into her preovulatory follicle either immediately after ovum pick up or (3) after in vitro maturation. Recipients were inseminated with fresh semen of a stallion with a known normal fertility. Ten days after surgery, rates of embryos collected in excess to the number of ovulations were calculated and compared for each group. Embryo collection rates were 32.5% (13/40), 5.5% (3/55) and 12.8% (6/47) for OT, post-IVM and immediate IFOT respectively. OT significantly yielded more embryos than immediate and post-IVM IFOT did. We also showed that in vitro matured oocytes could succesfully be used for IFOT. Our results also suggest that improvement of the IFOT technique could turn it into an inexpansive and easy to perform procedure that could be an answer to the inefficiency of superovulation treatments in the mare

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International audienc

A hybrid characterization framework to determine the visco-hyperelastic properties of a porcine zona pellucida

The zona pellucida (ZP) is a specialized extracellular matrix surrounding the developing oocyte. This thick matrix consists of various types of glycoprotein that play different roles in the fertilization process. Nowadays, several techniques are available for assessing ZP's mechanical response. The basic assumption behind these methods is that the ZP behaves like an elastic body: hence, dissipative forces are neglected and Young's modulus remains unaffected by probe dynamics. However, dissipative forces are strongly regulated by the slippage of ZP chains past one another while reaction forces related to elastic deformations (driven by the ability of each chain to stretch) depend on the ZP structure (i.e. number of cross-links and distances between knots). Although viscous reaction forces generated by the ZP are one of the main factors regulating sperm transit, their peculiar behaviour along the ZP structure remains poorly understood and rarely investigated. In order to overcome this limitation, a novel visco-hyperelastic model describing the porcine ZP reaction forces generated by nanoindentations at different probe rates is developed and verified in this study. Visco-hyperelastic parameters of porcine ZP membranes are determined by means of a hybrid characterization framework combining atomic force microscopy nanoindentation measurements, nonlinear finite-element analysis and nonlinear optimization. Remarkably, it is possible to separate the contributions of hyperelastic and viscous terms to ZP mechanical response and evaluate the error made in the determination of ZP mechanical properties if viscous effects were not considered

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International audienc

Study on the visco-hyperelastic behavior of the zona pellucida

Chapitre 6Conference: SEM Annual Conference and Exposition on Experimental and Applied Mechanics, 2-5 June 2014, Greenville, USAThe zona pellucida (ZP) is a specialized extracellular matrix surrounding the developing oocyte. This thick matrix consists of different types of glycoprotein, which have different roles in fertilization. Nowadays several techniques are developed and refined to establish the ZP mechanical response. The assumption at the basis of these methods is that the ZP behaves like an elastic body, dissipative forces are neglected, and thus the Young modulus value remains unaffected by probe dynamics. On the contrary dissipative force are strongly regulated by the slippage of ZP chains past one another whereas the absolute reaction force value is mainly due to the architecture of the ZP structure (number of cross-links and distances between knots). Elastic deflection is then due to the ability of each chain to stretch, whereas viscous flow is caused by the sliding of the molecules over one another. Therefore viscous reaction forces generated by the ZP have to be considered one of the main player in regulating the sperm transit but their peculiar behavior along the ZP structure is still poorly understood. In this context, for the first time, we developed and verified a visco-hyperelastic model able to reproduce the ZP reaction force stressed at different probe rate

Les Hommes face aux sécheresses

Fléaux parmi les plus dévastateurs, les sécheresses marquent depuis longtemps et d'une façon périodique l'histoire des populations. Aujourd'hui, elles sont à la fois mieux connues gr âce au progrès scientifiques, et plus graves socialement parce que les hommes concernés sont plus nombreux. Mettant toujours à l'épreuve les autorités des pays atteints et entra înant souvent l'intervention de la communauté internationale, elles constituent un problème politique majeur. Comparant le Nordeste intérieur du Brésil et le Sahel africain, deux espaces récemment sinistrés, l'ouvrage analyse d'abord la géographie physique de l'accident : baisse des précipitations, appauvrissemenf de la couverture végétale, fragilisation de l'écosystème. Il décrit ensuite les réponses des hommes, que ce soit les adaptations paysannes ou les stratégies des Etats, les interventions des ONG (organisations non gouvernementales) ou les travaux des chercheurs. Il ressort de ce débat que, si certains milieux naturels sont vulnérables, la sécheresse est aussi un phénomène social : la réflexion multidisciplinaire peut alors aider à construire un meilleur équilibre entre les hommes et leur espace