Bases moléculaires et cellulaires de l'invasion des cellules épithéliales intestinales par Shigella flexneri

A key step in the pathogenesis of shigellosis is the capacity of the causative bacteria, shigellae, to invade colonic and rectal epithelial cells in humans. This invasive process encompasses several steps: entry into epithelial cells by induction of a macropinocytic event caused by secreted Ipa proteins. The bacterium then escapes from the vacuole and reaches the cytoplasmic compartment in which it divides rapidly and becomes motile via the expression of a surface protein, IcsA, whose polar localization achieves directed polymerization of actin filaments that push the bacterial body forward. Bacteria then engage the inner face of the cellular membrane in the junctional area and form protrusions allowing their passage into the adjacent cell. Lysis of the double membrane eventually allows access to the cytoplasmic compartment of the adjacent cell, thus providing the bacterium with a very efficient mechanism of epithelial colonization.     

Familles moléculaires et réactions croisées en allergie

Le risque pour une personne de développer des manifestations allergiques est plus grand si elle a des antécédents familiaux d’allergie: on parle de terrain atopique.     

Ganglion sentinelle et détection moléculaire du statut ganglionnaire

Sentinel lymph node (SLN) biopsy is the most used practice in breast cancer, in absence of clinical or radiological evidence of node metastasis for stage T0, T1 and T2 until 3 cm tumours. About 20,000 patients each year could benefit from a SLN biopsy in France. Nevertheless, the mean rate of second surgical procedure is of 10 to 17%. Two techniques (OSNA^® et GeneSearch?) are actually available in France. Their principle is based upon an intraoperative diagnosis of the presence or absence of metastasis in the SLN, using a rapid, quantitative, accurate molecular assay. The literature shows that those tests have the advantage of being more sensitive (frequently greater than 95%) than the classical techniques of frozen section diagnosis. The concordance with histopathological examination is high too (> 90%). For some of the patients, these techniques avoid a second surgery, reduce the cost of the management and shorten the initiation of treatment. In the future, this approach could become a standard.     

Relations phylogénétiques chez les marchantiales (Hepaticae). Incongruence apparente entre données morphologiques et moléculaires

A cladistic analysis of the order Marchantiales based on morphological characters (43 characters) did not agree with the classification in current use. Molecular sequences of nuclear-encoded 26S rRNA genes of seven species of the order and two out-groups (1254–1299 bp) were analysed to solve this contradiction. Results between morphologial and sequence data are conflicting. The combination of the two data sets shows that a weighting of the morphological data corresponding to equal contributions of the two sets resolves contradiction. We demonstrate that the structure of two data sets can be compatible even if the resultant trees are incongruent. Addition of a few compatible data (for instance, via character weighting) can result in congruent trees. The taxonomic incongruence we observed could illustrate a case of too limited molecular sampling.     

Classification des souches du groupeBacillus thuringiensis par la détermination de l'antigène flagellaire

Summary The serological study of 26 new strains ofBacillus thuringiensis (of which the biochemical features are also given) makes it possible to classify these strains into: 1^o Strains which are in concordance with the six serotypes previously described. 2^o Strains which have a new H antigen. Here, we describe two new serotypes: serotype 7 (aizawai), serotype 8 (morrisoni). On the other hand, the serological study of five new strains ofB. thuringiensis belonging to serotype 4 shows that the H₄ antigen must be divided into ?sub-factors?: ?4 a, 4b? to be found in the strains sotto, dendrolimus, T.84-A, L (Grig) and ?4 a, 4 c? to be found in the strains Pil 94, 1748 and Rhodesia. Table 6 gives the present statute of theB. thuringiensis strains' classification by the flagellar agglutination technic.

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Avec la collaboration technique deM. Lechevallier etT. Le Borgne. Nous remercions vivement les collègues qui ont bien voulu nous adresser des cultures et nous nous tenons à la disposition de tous ceux qui seraient intéresés par la détermination de l'antigène H de leurs souches. Nous remercions également notre collègueLe Minor pour ses précieux conseils.     

Génétique moléculaire de la transposition du bras long du chromosome x sur l'y lors de la spéciation humaine

Five cosmidic probes (7 b; 8 j; 22 b; CB 16 and 115 i 1) recognizes site of simple-copy DNA sequence homology between the human X and Y chromosomes. Genomic DNAS restricted with Eco RI from the great apes (Gorilla and Pan) were examined for sequences homologous to these probes, by molecular hybridization studies. Experiments reported here revealed, by genetic dosage with sex, that the great apes have homologous sequences of these five probes on their X chromosomes only. The simplest explanation of these results is that the corresponding sequences were transposed from the X chromosome to the Y chromosome after the human line diverged, like probe pDP 34 for locus DXY S1 (Page et al., 1984).     

Systématique moléculaire des phlebotominae : étude pilote. paraphylie du genre phlebotomus

Phylogenetic relationships among Phlebotominae were inferred through a pilot study using parsimony analysis of the D2 domain of ribosomal DNA sequences: 455 pairs of bases were sequenced in nine species of Phlebotomine sandflies which belong to the genera Lutzomyia, Phlebotomus and Sergentomyia. Two taxa are used as outgroups: Psychoda sp. and Nemapalpus flavus which is the sister group of the Phlebotominae. The South American genus Lutzomyia appears to be monophyletic. The Mediterranean species Sergentomyia dentata is its sister group and is not clustered with the Old World genus Phlebotomus. The latter is a paraphyletic genus with an early individualisation of the branch including the closely related subgenera Phlebotomus and Paraphlebotomus, and a late individualisation of the subgenus Larroussius. These results have some consequences on the biogeography of the leishmaniasis in the Old World.     

Classification moléculaire des cancers du sein : utilité en clinique

In spite of the progress of treatments and the discovery of targeted therapies, breast cancer remains the leading cause of cancer mortality among women. It is also the first cancer to get benefits from target therapies against hormone receptors and now HER2. The anatomoclinical classification used to optimize the therapeutics is not always accurate and is a cause of overtreatments or of inappropriate treatments. Tumour cells genomic studies have shown the relationship between genomic alterations and the prognosis and the efficacy of treatments. The molecular classification which results from those studies allowed the emergence of numerous diagnostic tests. They use different technologies and different clinical approaches which should allow a better classification in order to be able to propose a personalized therapy. In this review, eight molecular tests are estimated compared to their scientific validation and to their clinical utility. Protein assays are also reviewed as uPA/PAI-1, the only prognostic marker validated with a level of evidence 1.     

Aspects moléculaires de la spermatogenèse: la réparation post-réplication de l’ADN et le système ubiquitine

Ubiquitin is a ubiquitous and highly conserved protein of 76 amino acid residues, that can be covalently attached to cellular acceptor proteins through a multi-step enzymatic pathway. Mono- or poly-ubiquitination of proteins can lead to protein degradation or modification of protein activity. The ubiquitin system is essential to all eukaryotic cells. Many components of the complex ubiquitin system show remarkable evolutionary conservation, from yeast to mammalian species. Interestingly, during gametogenesis, many specialized and important aspects of the ubiquitin system become apparent. TheHR6B gene is a mammalian, autosomal homolog of theSaccharomyces cerevisiae geneRAD6 encoding a ubiquitin-conjugating enzyme.RAD6 in yeast is required for a variety of cellular functions, including sporulation, DNA repair, and mutagenesis. Male infertility inHR6B knockout mice is associated with impairment of spermatogenesis. Components of the ubiquitin system appear to be involved in different steps and processes during gametogenesis, including control of meiosis, and reorganization of chromatin structure.