Calcium ion currents mediating oocyte maturation events

During maturation, the last phase of oogenesis, the oocyte undergoes several changes which prepare it to be ovulated and fertilized. Immature oocytes are arrested in the first meiotic process prophase, that is morphologically identified by a germinal vesicle. The removal of the first meiotic block marks the initiation of maturation. Although a large number of molecules are involved in complex sequences of events, there is evidence that a calcium increase plays a pivotal role in meiosis re-initiation. It is well established that, during this process, calcium is released from the intracellular stores, whereas less is known on the role of external calcium entering the cell through the plasma membrane ion channels. This review is focused on the functional role of calcium currents during oocyte maturation in all the species, from invertebrates to mammals. The emerging role of specific L-type calcium channels will be discussed

Etude microscopique de poteries anciennes du Negev et du Sinaï.

The mineralogical composition of ancient pottery found in the Negev and Sinaï has been studied under the polarising microscope in roughly 330 sections. The pétrographie microscopical method frequently enables the obtaining, in a relatively short time, of a great amount of information concerning the mineralogical composition and texture of the sherds relfecting the potter's technique, the origin of the raw materials, the binding and tempering materials used, and the approximate temperature of the firing ; and occasionally concerning specific details particular to certain sites, and, finally anomalies no doubt related to conditions of exchange between people. Pottery belonging to the Timna area consists of three types designated by Rothnberg under the names "Negev", "Common "and "Midian". The "Midian" type that is characterized by a highly superior technique is described in detail. The Sinaï pottery usually reflects the geological environment of the sites. A number of anomalies are incontestably related to exchanges ? Probably commercial - between sites relatively distant from one another. Certain sites belonging neither to the Negev or Sinaï and that are of particular significance for the archeologist, such as the Ghassul site and the Egyptian sites of Nagada, have been studied in detail.La composition minéralogique des poteries anciennes du Negev et du Sinaï a été étudiée au microscope polarisant sur environ 330 sections minces. La méthode microscopique pétrographique permet souvent d'obtenir en un temps relativement court un grand nombre d'informations sur la composition minéralogique et la texture des tessons qui reflètent la technique du potier ; sur l'origine des matières premières : liant et dégraissant ; sur la température approximative de la cuisson ; parfois sur des détails spécifiques à certains sites et enfin sur des anomalies liées sans doute à des relations d'échange entre les hommes. Les poteries de la région de Timna comportent trois types désignés par Rothenberg sous les noms de "Negev", "Common", "et "Midian". Le type "Midian" qui se distingue par une technique très supérieure est décrit en détail. Les poteries du Sinaï reflètent en général l'environnement géologique des sites. Certaines anomalies montrent indubitablement des liaisons probablement commerciales entre sites relativement éloignés. Certains sites n'appartenant pas au Negev ni au Sinaï qui ont une signification particulière pour les archéologues, tels, celui de Ghassul et les sites égyptiens de Nagada ont été étudiés en détail.Slatkine A. Etude microscopique de poteries anciennes du Negev et du Sinaï.. In: Paléorient, 1978, vol. 4. pp. 113-130

Statistical properties of visible and infrared beams retroreflected through a turbulent atmosphere

Statistical properties of HeNe and CO/sub 2/ laser beams retroreflected through a turbulent atmosphere are investigated experimentally for round paths of 1 km and 12 km. Both heterodyne and direct detection are used

Acquisition of meiotic competence in growing mouse oocytes is controlled at both translational and posttranslational levels

Full-grown mouse oocytes spontaneously resume meiosis in vitro when released from their follicular environment. By contrast, growing oocytes are not competent to resume meiosis; the molecular basis of meiotic competence is not known. Entry into M phase of the eukaryotic cell cycle is controlled by MPF, a catalytically active complex comprising p34cdc2 kinase and cyclin B. Incompetent oocytes contain levels of cyclin B comparable to those in competent oocytes, while their level of p34cdc2 is markedly lower; p34cdc2 accumulates abruptly at the end of oocyte growth, at the time of meiotic competence acquisition. We show here that this change in p34cdc2 concentration is not secondary to a corresponding change in the concentration of the cognate mRNA, indicating that translational control may be involved. Microinjection of translatable p34cdc2 mRNA into incompetent oocytes yielded high levels of the protein, but it did not lead to resumption of meiosis. Similarly, microinjection of cyclin B1 mRNA resulted in accumulation of the protein, but not in the acquisition of meiotic competence. By contrast, the microinjection of both p34cdc2 and cyclin B1 mRNAs in incompetent oocytes induced histone H1 and MAP kinase activation, germinal vesicle breakdown, and entry into M-phase including the translational activation of a dormant mRNA. Thus, endogenous cyclin B1 in incompetent oocytes is not available for interaction with p34cdc2, suggesting that a posttranslational event must occur to achieve meiotic competence. Microinjection of either p34cdc2 or cyclin B1 mRNAs accelerated meiotic reinitiation of okadaic acid-treated incompetent oocytes. Taken together, these results suggest that acquisition of meiotic competence by mouse oocytes is regulated at both translational and posttranslational levels