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We used a simple quadrat analysis to globally categorise the spatial distribution of Drosophila melanogaster individuals. Individuals were spatially aggregated and this was not only due to sexual attraction. This aggregation seemed to be maintained during dispersal, hence explaining the great variability of this behaviour observed in our work and by other authors. Thus, individuals are expected to...
Higher plant mitochondria contain a genetic system with a genome, transcription and translation processes, which have to be logistically integrated with the two other genomes in the nucleus and the plastid. In plant mitochondria, after transcripts have been synthesised, at least in some cases by a phage-type RNA polymerase, they have to go through a complex processing apparatus, which depends on protein...
Though feedforward activation (FA) is a little known principle of control in metabolic networks, there is one well-known example; namely, the activation of pyruvate kinase (PK) by fructose-1,6-biphosphate (FBP) in glycolysis. The effects of this activation on the enzyme’s kinetics are well characterised, but its possible role in glycolytic control has not been determined, and, experimentally, there...
L’étude du pollen et des macrorestes de deux séquences sédimentaires d’un sixième site (la gouille 1 800 m) de l’étage subalpin de la chaîne des Hurtières complète une précédente étude qui modélisait la mise en place des étages de végétation à l’échelle d’un massif circonscrit dans le domaine intermédiaire des Alpes françaises du Nord. Neuf datations AMS de macrorestes végétaux terrestres étayent...
Most prokaryotic genomes display strand compositional asymmetries, but the reasons for these biases remain unclear. When the distribution of gene orientation is biased, as it often is, this may induce a bias in composition, as codon frequencies are not identical. We show here that this effect can be estimated and removed, and that the residual base skews are the highest at third base codon positions...
Myosin-binding protein C (MyBP-C) is thought to play structural and/or regulatory role in striated muscles. The cardiac isoform of MyBP-C is one of the disease genes associated with familial hypertrophic cardiomyopathy and most of the mutations produce COOH truncated proteins. In order to determine the consequences of these mutations on myosin filament organization, we have characterized the effect...
The effect of a novel acyl-coenzyme A : cholesterol acyltransferase (ACAT) inhibitor on cholesterol metabolism was studied in hamsters. Oral administration of F12511 (10 mg/kg/d) for 4 weeks produced a decrease in dietary cholesterol absorption (–18 %) and in the liver concentration of esterified cholesterol (–75 %), as compared with control values in untreated hamsters. While the hepatic expression...
This study gathers the first data concerning the arthropod assemblages associated with Erica arborea L. and E. scoparia L. It demonstrates that it is necessary to sample at least ten Erica scoparia L. to give a representative image of its arthropod assemblage. This study reveals that neither plant size nor architecture nor floristic environment can explain the different patterns of colonisation of...
Les capacités compétitives de végétaux ont été interprétées à partir de la mesure de leurs caractéristiques morphologiques en conditions de compétition interspécifique. Ces mesures ont été réalisées grâce à des cultures expérimentales en compétition interspécifique de quatorze plantes adventices avec une espèce domestiquée et cultivée à grande échelle : le blé d’hiver (Triticum aestivum var Darius)...
The aim of this study was to determine the dioecious or monoecious condition of Fitzroya cupressoides and Pilgerodendron uviferum. The study area lies west of the Nahuel Huapi National Park in northern Patagonia (Argentina), where these species form mixed stands. One hundred individuals of each species were studied over three successive years. The nature and position in the crown of their reproductive...
Serotonin (5-hydroxytryptamine, 5-HT) is a well-known neurotransmitter and immunomodulator, which has been reported to affect the function of cells in the immune system. The purpose of the herein reported experiments was to investigate whether serotonin could regulate the proliferation of a human T lymphoblastic leukemia cell line (CCRF-CEM cells) and to characterize the 5-HT receptor(s) involved...
Afin de tester si les mutations responsables du daltonisme sont transmises plus fréquemment par des pères âgés, un recensement exhaustif des naissances dans la région de Namur a permis d’isoler un échantillon de 225 garçons descendant de grands-pères maternels ayant dépassé 45 ans à la naissance de leur fille. L’incidence de daltonisme a été comparée entre ce groupe de cas et trois groupes témoins...
The concept of multistationarity has become essential for understanding cell differentiation. For this reason theoretical biologists have more and more frequently to determine the steady values, often multiple, of systems of non-linear differential equations. It is well known that iteration processes of current use converge or not towards a fixed point depending on the absolute value of the slope...
Protein interactions within a multimolecular complex can result in information and energy transfer between proteins. This can lead in turn to the emergence of novel functions of some proteins of the complex. Various examples of this situation can be found in the scientific literature. This is probably the case for prion protein, chloroplast phosphoribulokinase bound to glyceraldehyde phosphate dehydrogenase,...
Three pectin methyltransferases (PMT5, PMT7, PMT18; EC 2.1.1.6.x) were solubilized from the endo-membrane complex of flax cells, with 0.05 % Triton X-100. After a 3 step-chromatography procedure, PMT7 and PMT5 were purified to apparent homogeneity. PMT5 and PMT7 differed regarding their optimum pH (5 or 7), the methyl acceptor (low or highly methylesterified pectin), their focusing pH range (6–7 or...
L’analyse pollinique à haute résolution d’une nouvelle séquence sédimentaire tardiglaciaire d’un site collinéen (Les Ételles 700 m) de la chaîne des Hurtières (Alpes du Nord) est présentée. Dix datations AMS de macrorestes végétaux terrestres étaient la chronologie de la mise en place des différentes communautés végétales et leurs évolutions. Une comparaison avec les courbes isotopiques des lacs suisses...
Basées sur l’inversion de fractions de trouées (modèle de Poisson de distribution du feuillage), trois méthodes optiques utilisant le Demon, le Plant Canopy Analyzer LAI-2000 (PCA) et les photographies hémisphériques zénithales ont été comparées pour estimer l’ouverture de la canopée (CO) et l’indice foliaire (LAI) dans une forêt mature, neutrophile, de chêne, hêtre et charme sur mull de l’est de...
The present study is the first comprehensive phylogeny of the class of the Phaeophyceae. For 67 species representing all orders of the class, the sequences of the 3’-end of the small and the 5ˈ-end of the large subunit nrRNA genes were aligned and analysed. A further analysis based on sequences of the 3’-end of the small and of the complete sequences of the 28S gene of the large subunits was also...
The methodology used by previous authors to resolve the relationships of the elopomorphan taxa is criticized. The morphological characters that have been proposed to support the monophyly of the Elopomorpha are reviewed and it is shown that most of them are weak. A new hypothesis of relationships is proposed on the basis of nucleotidic sequences of ribosomal RNA 18S, 16S and 12S. In order to really...
La détermination du sexe présente une importance considérable dans l’analyse de caractéristiques écologiques propres à certaines espèces non exploitées, notamment l’évolution des systèmes de reproduction et le contrôle du sex-ratio de la descendance par des avortements sélectifs, en fonction de divers paramètres maternels. Nous avons mis au point une méthode de sexage précoce (dès la deuxième semaine...
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