Identification of the mammalian Not gene via a phylogenomic approach.

Despite the great morphological diversity of early embryos, the underlying mechanisms of gastrulation are known to be broadly conserved in vertebrates. However, a number of genes characterized as fulfilling an essential function in this process in several model organisms display no clear ortholog in mammalian genomes. We have devised an in silico phylogenomic approach, based on exhaustive similarity searches in vertebrate genomes and subsequent bayesian phylogenetic analyses, to identify such missing genes, presumed to be highly divergent.

European doctorate in biotechnology: Added value for european academia and industry.

It has long been recognized that educational programs and degrees are not equivalent across Europe. Add to this the fact that Europe consists of many different cultures and languages, then it is not surprising that the free circulation of scientists and their job market in the European Union is severely restricted. This is one of several debated causes for the crisis in European biotechnology, which is in danger of succumbing to the competition of North America, Japan, and some of the developing countries.

In vivo functional analysis of ezrin during mouse blastocyst formation.

During mouse blastocyst formation, a layer of outer cells differentiates in less than 48 h into a functional epithelium (the trophectoderm). Ezrin, an actin-binding structural component of microvilli in epithelial cells, is also involved in signal transduction and ionic pump control. In the mouse embryo, ezrin becomes restricted to the apical cortex of all blastomeres at compaction and of outer cells at later stages.

A major posttranslational modification of ezrin takes place during epithelial differentiation in the early mouse embryo.

The preimplantation development of the mouse embryo leads to the formation of two populations of cells: the trophectoderm, which is a perfect epithelium, and the inner cell mass. The divergence between these two lineages is the result of asymmetric divisions, which can occur after blastomere polarization at compaction. The apical pole of microvilli is the only asymmetric feature maintained during mitosis and polarity is reestablished only in daughter cells that inherit all or a sufficient part of this pole.

Ezrin becomes restricted to outer cells following asymmetrical division in the preimplantation mouse embryo.

During preimplantation development in the mouse, two phenotypically distinct cell populations appear at the 16-cell stage: nonpolarized inner cells that give rise to the inner cell mass and polarized outer cells that give rise mainly to the trophectoderm. The divergence of these two cell lineages is due to asymmetrical cell divisions during the transition from the 8- to the 16 cell stage which can occur following blastomere polarization. During compaction, at the 8-cell stage, cytoplasmic organelles accumulate in the apical domain, a surface pole of microvilli forms, and blastomeres flatten onto one another.

Evidence of singlet oxygen evolution by whole living cells of Chlamydomonas reinhardtii.

The oxygen evolved by Chlamydomonas reinhardtii in the light is measured simultaneously with a Clark electrode and with the nitrosodimethylaniline-imidazole colorimetric method which is specific for singlet oxygen. Experiments with wild-type and FuD7 mutant cells (unable to synthesize the D1 protein of Photosystem II), with dichlorophenyldimethylurea (which blocks electron transfer from Photosystem II to Photosystem I) and with dibromothymoquinone (which diverts electrons from their normal path between the two photosystems), as well as with hydroxylamine (an inactivator of the water-splitting part of Photosystem II and a competitor of water for electron donation to it), all point to the dependence of detected singlet oxygen on photolysis of water by Photosystem II.

Cell adhesion and gap junction formation in the early mouse embryo are induced prematurely by 6-DMAP in the absence of E-cadherin phosphorylation.

Compaction of the mouse embryo, which takes place at the 8-cell stage, is dependent upon the adhesion molecule E-cadherin (uvomurulin), but does not require protein synthesis, suggesting that post-translational modification(s) is (are) implicated in the setting up of this phenomenon. The demonstration recently that E-cadherin is phosphorylated at the 8-cell stage just before compaction supports this theory. In this work we used 6-dimethylaminopurine, a serine-threonine kinase inhibitor, to investigate the role of protein phosphorylation in compaction of mouse embryos.

gamma-Tubulin is present in acentriolar MTOCs during early mouse development.

gamma-Tubulin, a recently discovered member of the tubulin superfamily, is a peri-centriolar component considered to be essential for microtubule nucleation. Mouse oocytes and early embryos lack centrioles until the blastocyst stage. Thus, early mouse embryos allowed us to study the location of gamma-tubulin in animal cells in the absence of centrioles.

Bacteriorhodopsin "detergent-monomers," blue shift and velocity of light-dark adaptation.

Bacteriorhodopsin was incubated in various detergent solutions. Absorbance, circular dichroism and size of fragments obtained were investigated. Among all the detergents used, only Triton-X-100 and Nonidet P 40 led to monomers of bacteriorhodopsin.

Complex formation between chlorophyll a and cytochrome c: surface properties at the air-water interface. Absorbance, fluorescence and fluorescence-lifetime in Langmuir-Blodgett films.

The binding of cytochrome c to an insoluble monolayer of chlorophyll a was studied. Surface pressure (II), surface potential (delta V) and [14C]cytochrome c surface-concentration (gamma) isotherms were measured versus molecular area (sigma) in mixed films. Compared to the successive-addition method, this procedure allows the formation of homogeneous mixed films.

Cell polarity and microtubule organisation during mouse early embryogenesis.

We have studied the distribution and the role of microtubules in the major developmental events occurring during early development of the mouse. These events are the setting up of asymmetries within blastomeres, the process of asymmetrical cell division and the changes in cellular organisation taking place during epithelial differentiation.

Cytoskeleton organization during oogenesis, fertilization and preimplantation development of the mouse.

The organization and role of the cytoskeletal networks (mainly microtubules and microfilaments) during oogenesis, fertilization and preimplantation development of the mouse are described given the importance of cell-cell interactions and of the subcellular organization in events leading to the formation of the first two lineages of the mouse embryo.

Molecular cloning and characterization of comC, a late competence gene of Bacillus subtilis.

comC is a Bacillus subtilis gene required for the development of genetic competence. We have cloned a fragment from the B. subtilis chromosome that carries comC and contains all the information required to complement a Tn917lac insertion in comC.

Light adaptation of bacteriorhodopsin in the presence of valinomycin and potassium. pH-dependence.

In the presence of valinomycin and K(+), bacteriorhodopsin undergoes (i) a decrease of its maximum absorbance, (ii) a blue shift of the maximum wavelength of both the light and the dark adapted forms. However (iii) a normal light adaptation is maintained and (iv) the retinal-retinal interactions are not perturbed. The role of valinomycin as a K(+)-carrier allowing a H(+)-K(+) competition as well as the stabilization of the deprotonated Schiff-base (linking retinal to the apo-opsin) is shown and discussed.

T-antigen-independent replication of polyomavirus DNA in murine embryonal carcinoma cells.

Expression of wild-type polyomavirus (Py) is restricted in murine embryonal carcinoma (EC) cells. The block appears to be located at the level of early transcription. Since no T antigen is produced, we investigated the fate of viral DNA upon infection of these cells; we showed that wild-type Py DNA replicates efficiently in all EC cells, probably via a T-antigen-independent mechanism.

Purification of cardiolipin for surface pressure studies.

Thin-layer chromatography and surface pressure-area isotherms of commercial bovine cardiolipins showed that the samples contained contaminants. They were purified by TLC and their purity was checked by chromatography and by their monolayer properties. The molecular area of cardiolipin and its purification yield depend upon the fatty acid composition, particularly the degree of unsaturation.

Interactions of CF1, the coupling factor of photophosphorylations, with chloroplast lipids. Monolayers studies.

Surface pressure and surface potential of monolayers at a water-air interface show no polar interactions between the chloroplast total lipids and the polar protein CF1. The two components are perfectly miscible in mixed monolayers. It follows that CF1 interacts with the hydrophobic parts of the lipid molecules and that, in vivo, CF1 could penetrate in the hydrophobic core of the membranes.

Temperature dependent expression of polyoma virus in murine embryonal carcinoma cells.

At 37 degrees C, undifferentiated murine teratocarcinoma cells (PCC4) are resistant to infection with SV40 and Polyoma virus. When infection is carried out at 31 degrees C, these cells become fully susceptible to a variety of polyoma virus strains, including wt, ts-a, and hr-t; they also display an increased susceptibility to polyoma virus mutants (PyE.C.

Chlorophylls attached to lipid and protein globules, absorption and fluorescence spectra, photo-oxidation.

The precipitation of chlorophylls upon lipid and protein globules suspended in an aqueous buffer yields a partial model of photosynthetic membranes. The absorption and fluorescence spectra of the model are investigated as well as the photo-oxidation of the chlorophylls (bleaching) by dissolved oxygen. It is shown that pigment--pigment interactions occur in such systems, by (a) the appearance of absorption bands characteristic of crystalline or highly ordered chlorophyll at high pigment concentrations, (b) the chlorophyll a-type of fluorescence of systems containing chlorophyll a and chlorophyll b where the latter is selectively excited, and (c) the kinetics of photo-oxidation which suggest that chlorophylls can only be bleached when they are dimerized.