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Even though reptiles are threatened worldwide, few studies address their conservation, especially snakes. The goal of our study was to measure the genetic structure of a widely distributed temperate reptile, the smooth snake Coronella austriaca using eight microsatellite markers in two different areas at the core (Alsace, north-eastern France) and at the edge (Wallonia, southern Belgium) of its range. We sampled 506 individuals in 38 localities (respectively 10 and 28). Analysis of genetic structure conducted with a clustering method detected three clusters in Alsace, one group gathering all populations but two. In Wallonia, differentiation was observed on both sides of the Meuse river and in the Southern Ardenne region (southernmost sampling sites). Spatial autocorrelation analysis showed that individuals share parental relationship up to a distance of 2.8 km in Alsace and up to 10 km in Wallonia. Isolation by distance was detected in Wallonia but the distance explained a very limited part of the differentiation (r = 0.033), whereas no isolation-by-distance pattern was detected in Alsace. Even though genetic differentiation between populations separated by large rivers, highways, or crop fields was detected, dispersal between populations seem currently sufficient to avoid any kind of genetic drift in both regions. These results are strongly contrasting with a previous study in England, suggesting sharp local variation of genetic structuring and diversification between location within the same species, probably related to the position in the distribution area and different densities.

International audience; Optical full-field measurement methods such as Digital Image Correlation (DIC) are increasingly used in the field of experimental mechanics, but they still suffer from a lack of information about their metrological performances. To assess the performance of DIC techniques and give some practical rules for users, a collaborative work has been carried out by the Workgroup "Metrology" of the French CNRS research network 2519 "MCIMS (Mesures de Champs et Identification en Mécanique des Solides / Full-field measurement and identification in solid mechanics, http://www.ifma.fr/lami/gdr2519)". A methodology is proposed to assess the metrological performances of the image processing algorithms that constitute their main component, the knowledge of which being required for a global assessment of the whole measurement system. The study is based on displacement error assessment from synthetic speckle images. Series of synthetic reference and deformed images with random patterns have been generated, assuming a sinusoidal displacement field with various frequencies and amplitudes. Displacements are evaluated by several DIC packages based on various formulations and used in the French community. Evaluated displacements are compared with the exact imposed values and errors are statistically analyzed. Results show general trends rather independent of the implementations but strongly correlated with the assumptions of the underlying algorithms. Various error regimes are identified, for which the dependence of the uncertainty with the parameters of the algorithms, such as subset size, gray level interpolation or shape functions, is discussed.

This paper presents experimental tensile test results obtained on flat aluminum magnesium alloy samples on a hard machine. The mechanical response, kinematic fields and acoustic emissions were simultaneously obtained in an experimental setup. Propagation instabilities associated with the Portevin-Le-Châtelier effect were observed as localized intense strain increment bands. Depending on the strain rate, A, B or C types were studied on the basis of stress drops, acoustic emission and strain fields. Then the band characteristics (position, orientation, width, thickness reduction, intensity, acoustic emission, principal strain direction) were presented in various strain rate conditions.

We have examined the spatiotemporal aspects of PRL-induced Ca2+ signals using high-speed fluo-3 confocal imaging. We found that PRL stimulated Ca2+ entry and intracellular Ca2+ mobilization. Ca2+ influx was seen as a peripheral increase in [Ca2+]i without amplification in the nucleus region. Intracellular Ca2+ mobilization was seen as a propagating intracellular calcium wave with a strong amplification in the nuclear region. The amplitude of PRL-induced Ca2+ increases would be sufficient to stimulate cell proliferation. Furthermore, PRL induced an increase in [3H]thymidine incorporation. These data suggest that PRL would be able to induce mitogenesis through a Ca2+-dependent pathway.

The effects of gonadotropin-releasing hormone (GnRH) and GnRH-associated peptide (GAP) on cytosolic free calcium concentration ([Ca(2+)](i)) were investigated in 20 human nonfunctioning pituitary adenomas. We divided these tumors into three classes according to their response pattern to hypothalamic peptides. In type I adenomas (8 out of 20 adenomas), GnRH and GAP mobilized intracellular calcium ions stored in a thapsigargin (TG)-sensitive store. For the same concentration of agonist, two distinct patterns of GnRH-GAP-induced Ca(2+) mobilization were observed (1) sinusoidal oscillations, and (2) monophasic transient. The latter is followed by a protein kinase C (PKC)-dependent increase in calcium influx through L-type channels. In type II adenomas (7 out of 20 adenomas), GnRH and GAP only stimulate calcium influx through dihydropyridine-sensitive Ca(2+) channels by a PKC-dependent mechanism. TG (1 μM) did not affect [Ca(2+)](i) in these cells, suggesting that they do not possess TG-sensitive Ca(2+) pools. All the effects of GnRH and GAP were blocked by an inhibitor of phospholipase C (PLC), suggesting that they were owing to the activation of the phosphoinositide turnover. Type I and type II adenoma cells showed spontaneous Ca(2+) oscillations that were blocked by dihydropyridines and inhibition of PKC activity. GnRH and GAP had no effect on the [Ca(2+)](i) of type III adenoma cells that were also characterized by a low resting [Ca(2+)](i) and by the absence of spontaneous Ca(2+) fluctuations. K(+)-induced depolarization provoked a reduced Ca(2+) influx, whereas TG had no effect on the [Ca(2+)](i) of type III adenoma cells. The variety of [Ca(2+)](i) response patterns makes these cells a good cell model for studying calcium homeostasis in pituitary cells.

We show that the simultaneous coupling of two laser scanning non-linear microscopies (2-photon excited fluorescence and third harmonic generation microscopy) give functional and morphological information for improving our understanding on intracellular calcium flows.

Electrical activity in non-neuronal cells can be induced by altering the membrane potential and eliciting action potentials. For example, hormones, nutrients and neurotransmitters act on excitable endocrine cells1. In an attempt to correlate such electrical activity with regulation of cell activation, we report here direct measurements of cytosolic free Ca2+ changes coincident with action potentials. This was achieved by the powerful and novel combination of two complex techniques, the patch clamp2 and micro-fluorimetry using fura 2 methodology3,4. Changes in intracellular calcium concentration were monitored in single cells of the pituitary line GH3B6. We show that a single action potential leads to a marked transient increase in cytosolic free calcium. The size of these short-lived maxima is sufficient to evoke secretory activity. The striking kinetic features of these transients enabled us to identify oscillations in intracellular calcium concentration in unperturbed cells resulting from spontaneous action potentials, and hence provide an explanation for basal secretory activity. Somatostatin, an inhibitor of pituitary function5, abolishes the spontaneous spiking of free cytosolic Ca2+ which may explain its inhibitory effect on basal prolactin secretion. Our data therefore demonstrate that electrical activity can stimulate Ca2+-dependent functions in excitable non-neuronal cells.