Optical investigations on double stranded ribonucleic acid from turnip yellow mosaic virus

Summary TYMV-dsRNA has been studied by ORD and CD. The spectra indicate a highly ordered secondary structure which disappears upon heating or titrating to acid pH. No distinct acid structure as found for DNA could be observed.Melting profiles of TYMV-dsRNA show a strong dependence on ionic strength which is analogous to synthetic polynucleotide complexes. Upon storage for several months the melting points drop considerably, without change in the ORD spectra. The two sets of melting points obtained for TYMV-dsRNA compare well with the results obtained in the literature: two series of melting points have been found for ds-RNA of a wide variety of origins. If plotted as a function of their G-C content, these data fall on two different lines with different slopes.It is suggested that ds-RNA might exist in two different helical forms and that TYMV-dsRNA might undergo a conformational change in solution upon storage.Boursier du Commissariat à l'Energie Atomique.     

The phylogenetic position of early hexapod lineages: morphological data contradict molecular data

Abstract. A review of different studies on the phylogenetic relationships of the early Hexapoda lineages shows that analyses based on molecular sequence data have led to labile and sometimes incongruous results, introducing doubt as to the reliability of the cladograms as a whole. In a recent analysis using molecular data, the Collembola, usually considered as early branching hexapods, appear to occupy a position outside the assemblage of Crustacea and Insecta, leading to the rejection of the traditional view of hexapod monophyly. However, many morphological features, as well as the results of cladistic analyses based on morphological and developmental information, contradict these conclusions. More generally, it appears that in the present state of the analytical strategies, hypotheses concerning arthropod phylogenies obtained from morphological and developmental criteria and combined analyses involving molecular and morphological data provide more reliable results than those generated by molecular information alone.     

Effets Inhibiteurs de Protéines Chromatiniennes non Histoniques Homospécifiques,sur la Morphogenèse d'Embryons d'Amphibiens Urodèles

Résumé Des protéines chromatiniennes non histoniques (PCNH) ont été injectées dans le blastocèle de blastulas âgées dePleurodèles waltlii préalablement ponctionnées. Les PCNH extraites du foie de la même espèce exercent un effet très fortement inhibiteur sur la morphogenèse: dans 75% des cas, la gastrulation est inhibée, mais les germes peuvent survivre 8 à 10 jours sans manifester de nécroses cellulaires et des mitoses continuent à se dérouler sporadiquement. Ces embryons montrent un affaiblissement très marqué de l'adhésivité inter-cellulaire, en rapport avec l'inhibition des mouvements morphogénétiques de la gastrulation. Les autres germes gastrulent avec du retard et de manière anormale, la neurulation est fortement perturbée, le tube nerveux est inachevé ou très réduit, la chorde et les somites sont mal différenciés. En revanche, les PCNH hétérospécifiques, extraites d'une autre espèce animale (foie de rat et de poulet, ascite de rat), sont pratiquement sans action sur ce même matériel. L'effet inhibiteur spécifique ainsi mis en évidence est comparé avec celui qui a été étudié sur des cultures de cellules embryonnaires de Pleurodèle et d'Axolotl en différenciation.Les niveaux où pourrait s'exercer l'action des PCNH sont envisagés, les effets observés dans le présent travail étant plus marqués au niveau de l'adhésivité intercellulaire.

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Inhibitory effects of homospecific non-histone chromatin proteins on morphogenesis of urodele amphibian embryos

Summary Non-histone chromosomal proteins (NHCP) were injected into the blastocoel of advanced blastulae fromPleurodeles waltlii which were previously punctured. NHCP extracted from the liver of the same amphibian species bring very strongly inhibitory effects on morphogenesis: gastrulation is prevented in 75% of cases, but the embryos can survive for 8 to 10 days without showing any necrotic cells, and cell divisions still occur sporadically. Intercellular adhesivity is strongly impaired in such embryos, in connection with inhibition of morphogenetic movements. Gastrulation is delayed and abnormal in other embryos, and neurulation is severely disturbed, the neural tube being unclosed or much reduced in size and the notochord and somites poorly differentiated. In contrast, NHCP extracted from other animal species (rat and chicken liver, rat ascites) have practically no effects onPleurodeles embryos. Species-specific inhibitory effects are thus demonstrated and compared with those which were previously studied on cultures of differentiating embryonic cells fromPleurodeles waltlii andAmbystoma mexicanum. The possible levels at which NHCP act are discussed, the changes in intercellular adhesivity being noted as more conspicuous in the present experiments.

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Ce travail a été réalisé dans le cadre de l'E. R. A. n^o 327, de l'A. T. P. n^o 439910 du Centre National de la Recherche Scientifique et du Contrat n^o 711019 de l'I. N. S. E. R. M.     

Site-directed mutagenesis of dicarboxylic acid residues of the penicillin-binding module of the Escherichia coli penicillin-binding protein 3

Abstract The glutamic acid E396, aspartic acid D409 and glutamic acid E411 residues of the Escherichia coli penicillin-binding protein 3 were each converted into an alanine residue. As deduced from penicillin-binding and complementation experiments, none of these dicarboxylic acid residues is involved in the mechanism of acylation by penicillin and none of them is essential for the in vivo functioning of the PBP. The mutation E396, however, causes an increased thermolability of the protein.     

Sequence of a gene encoding a (poly ManA) alginate lyase active on Pseudomonas aeruginosa alginate

Abstract To overcome problems associated with Western blotting of denatured proteins, we have used quantitative immunoelectrophoretic techniques to perform functional analysis of the Neisseria gonorrhoeae common antigen. Using these techniques, we show (a) that Neisseria gonorrhoeae expresses an antigen that is cross-reactive with the common antigen of Pseudomonas aeruginosa and Legionella micdadei and with the GroEl-like protein of Chlamydia , and (b) that this N. gonorrhoeae common antigen has lectin-like activity and can be precipitated with three different sugars immobilized on agarose beads: α- d -glucosamine, maltose and fucose.     

Etablissement des relations de dominance-soumission chez les bovins domestiques III. Effet de l'expérience sociale

An evaluation of social experience in the establishment of dominance-submission relationships was attempted using 20 animals in various constellations of 4. The establishment of rank-order in 5 groups of inexperienced heifers upon their first contact with strangers was compared with that in 20 groups consisting of the same animals in different arrangements upon their second to their fifth encounter with strangers. With experience, the various types of agonistic interactions were differently utilized, contact-forming and fighting time were reduced, the social order was more rapidly and firmly established, and fighting often dispensed with.     

Cloning and characterization of a cDNA encoding a Rab1-like small GTP-binding protein from Petunia hybrida

The cloning of small GTP-binding proteins from Petunia hybrida was performed using a PCR-based strategy. Degenerate primers were designed from the DTAGQE and FMETSA consensus sequences. Three different cDNAs were amplified. The deduced polypeptide sequences PhPCRGP1 and PhPCRGP2 were homologous to RB11_HUMAN and PhPCRGP3 to RAB1A_HUMAN. Using PhPCRGP3 as a probe, 8 identical clones were selected from a Petunia leaf cDNA library. They all encode the same 22.5 kDa polypeptide, PhRAB1, able to bind GTP in vitro and 72% identical to RAB1A_HUMAN. Hybridizable mRNAs encoding PhRAB1 accumulated preferentially in opened flowers.