Sequence Analysis and Expression of the Attachment and Fusion Proteins of Canine Distemper Virus Wild-Type Strain A75/17

The biological properties of wild-type A75/17 and cell culture-adapted Onderstepoort canine distemper virus differ markedly. To learn more about the molecular basis for these differences, we have isolated and sequenced the protein-coding regions of the attachment and fusion proteins of wild-type canine distemper virus strain A75/17. In the attachment protein, a total of 57 amino acid differences were observed between the Onderstepoort strain and strain A75/17, and these were distributed evenly over the entire protein. Interestingly, the attachment protein of strain A75/17 contained an extension of three amino acids at the C terminus. Expression studies showed that the attachment protein of strain A75/17 had a higher apparent molecular mass than the attachment protein of the Onderstepoort strain, in both the presence and absence of tunicamycin. In the fusion protein, 60 amino acid differences were observed between the two strains, of which 44 were clustered in the much smaller F2 portion of the molecule. Significantly, the AUG that has been proposed as a translation initiation codon in the Onderstepoort strain is an AUA codon in strain A75/17. Detailed mutation analyses showed that both the first and second AUGs of strain A75/17 are the major translation initiation sites of the fusion protein. Similar analyses demonstrated that, also in the Onderstepoort strain, the first two AUGs are the translation initiation codons which contribute most to the generation of precursor molecules yielding the mature form of the fusion protein.     

Speech Rhythms and Multiplexed Oscillatory Sensory Coding in the Human Brain

Cortical oscillations are likely candidates for segmentation and coding of continuous speech. Here, we monitored continuous speech processing with magnetoencephalography (MEG) to unravel the principles of speech segmentation and coding. We demonstrate that speech entrains the phase of low-frequency (delta, theta) and the amplitude of high-frequency (gamma) oscillations in the auditory cortex. Phase entrainment is stronger in the right and amplitude entrainment is stronger in the left auditory cortex. Furthermore, edges in the speech envelope phase reset auditory cortex oscillations thereby enhancing their entrainment to speech. This mechanism adapts to the changing physical features of the speech envelope and enables efficient, stimulus-specific speech sampling. Finally, we show that within the auditory cortex, coupling between delta, theta, and gamma oscillations increases following speech edges. Importantly, all couplings (i.e., brain-speech and also within the cortex) attenuate for backward-presented speech, suggesting top-down control. We conclude that segmentation and coding of speech relies on a nested hierarchy of entrained cortical oscillations.     

A Natural Large Chromosomal Inversion in Lactococcus lactis Is Mediated by Homologous Recombination between Two Insertion Sequences

Comparative analysis of chromosomal macrorestriction polymorphism of the two closely related Lactococcus lactis subsp. cremoris strains MG1363 and NCDO763 revealed the presence of a large inversion covering half of the genome. To determine what kind of genetic element could be implicated in this rearrangement, the two inversion junctions of MG1363 and NCDO763 chromosomes were cloned and characterized. Nucleotide sequence analysis showed the presence of one copy of the lactococcal IS905 element in each junction. Each copy of this element contained the same nucleotide mutation that inactivates the putative transposase. Comparison of the sequences surrounding the insertion sequence demonstrated that the large inversion arose from a single-step homologous recombination event between the two defective copies of the IS905 element. The large inversion presumably conferred no selective disadvantage on strain NCDO763 because this rearrangement did not alter the oriC-terC symmetry of the chromosome and the local genetic environment.     

Autoregulation of the nar operon encoding nitrate reductase in Escherichia coli

Summary Nitrate reductase is demonstrated to exert an autogenous control on its own synthesis. This effect requires the participation of the molybdenum cofactor. Use of strains in which the control region of the nar operon is mutated reveals two loci in this region: one, affected in strain LCB94, is common to both autoregulation and induction by nitrate while the other, mutated in strain LCB188, is specific for the induction by nitrate. It is proposed that the autogenous control prevents the unnecessary accumulation of the nitrate reductase subunits in the cytoplasm.     

Docking Study of Ligands into the Colchicine Binding Site of Tubulin

Cancer is a major cause of mortality in developed countries, following only cardiovascular diseases. Death of cancerous cells can be achieved by stopping mitosis and the antimitotic class of drugs formed by the spindle poisons can be used for this purpose. Their role is to disorganize the mitotic spindle by targeting its main constituent, the microtubules, themselves made of heterodimers of α and β-tubulin. They disrupt the dynamics of the microtubules either by stabilizing them, as do paclitaxel or epothilones, or destabilizing them, as do colchicine. The binding site of colchicine seems to lie between the two units of the tubulin dimer. Here, we report on the characterization of this site by the docking of a series of reference compounds, and the subsequent docking of ligands prepared in our laboratory.     

Discovery of SAR184841, a potent and long-lasting inhibitor of 11β-hydroxysteroid dehydrogenase type 1, active in a physiopathological animal model of T2D

Starting from 11β-HSD1 inhibitors that were active ex vivo but with Cyp 3A4 liability, we obtained a new series of adamantane ureas displaying potent inhibition of both human and rodent 11β-HSD1 enzymes, devoid of Cyp 3A4 interactions, and rationally designed to provide long-lasting inhibition in target tissues. Final optimizations lead to SAR184841 with good oral pharmacokinetic properties showing in vivo activity and improvement of metabolic parameters in a physiopathological model of type 2 diabetes.     

DNA methylation as a key process in regulation of organogenic totipotency and plant neoplastic progression?

Summary Progressive loss of organogenic totipotency appears to be a common event in long-term plant tissue culture. This loss of totipotency, which has been proposed to be a typical trait of plant neoplastic progression, is compared to some mechanisms that occur during the establishment of animal differentiation-resistant cancer lines in vitro. Evidence is presented that alteration in DNA methylation patterns and expression of genes occur during long-term callus culture. An effect of the auxin, 2,4-dichlorophenoxyacetic acid, in the progressive methylation, is moreover suggested. Methylation of genes relevant to cell differentiation and progressive elimination of cells capable of differentiation is proposed as being responsible for this progressive loss of organogenic potential. Finally, the epigenetic alteration (DNA methylation) that occurs during prolonged periods of culture may induce other irreversible genetic alterations that ultimately make the loss of totipotency irreversible.     

Modeling landscape structure constraints on species dispersal with a cellular automaton: Are there convergences with empirical data?

Landscapes are typically complex systems which do not necessarily allow performing large scale field experiments. A lot of studies hence analyzed correlations between landscape structure and species distribution. However, empirical data integrate a non-reducible part of contingency, which implies a major issue: the generalization of results. In such complex contexts, modeling can be useful since it allows isolating factors and it can play the role of reference for comparisons. In this perspective, we modeled plant species dispersal within a hedgerow network with a simple cellular automaton. In parallel we studied empirically plant species distribution in hedgerows to see whether both, results from the model and results from empirical data were convergent. Results showed that the cellular automaton was characterized by non-linear responses, corresponding to different levels of landscape constraints. Furthermore, convergences were found between the theoretical model and empirical data, in terms of differential responses of plant species to landscape structure, according to dispersal type and habitat specialization. Finally examining past landscape structure, the theoretical model and empirical data converged, demonstrating that past landscape patterns are particularly relevant in terms of statistical explanation of plant species distribution. We conclude that cellular automata were relevant formalizations of dispersal processes at the landscape level.     

Migratory Birds Reinforce Local Circulation of Avian Influenza Viruses

Migratory and resident hosts have been hypothesized to fulfil distinct roles in infectious disease dynamics. However, the contribution of resident and migratory hosts to wildlife infectious disease epidemiology, including that of low pathogenic avian influenza virus (LPAIV) in wild birds, has largely remained unstudied. During an autumn H3 LPAIV epizootic in free-living mallards (Anas platyrhynchos) — a partially migratory species — we identified resident and migratory host populations using stable hydrogen isotope analysis of flight feathers. We investigated the role of migratory and resident hosts separately in the introduction and maintenance of H3 LPAIV during the epizootic. To test this we analysed (i) H3 virus kinship, (ii) temporal patterns in H3 virus prevalence and shedding and (iii) H3-specific antibody prevalence in relation to host migratory strategy. We demonstrate that the H3 LPAIV strain causing the epizootic most likely originated from a single introduction, followed by local clonal expansion. The H3 LPAIV strain was genetically unrelated to H3 LPAIV detected both before and after the epizootic at the study site. During the LPAIV epizootic, migratory mallards were more often infected with H3 LPAIV than residents. Low titres of H3-specific antibodies were detected in only a few residents and migrants. Our results suggest that in this LPAIV epizootic, a single H3 virus was present in resident mallards prior to arrival of migratory mallards followed by a period of virus amplification, importantly associated with the influx of migratory mallards. Thus migrants are suggested to act as local amplifiers rather than the often suggested role as vectors importing novel strains from afar. Our study exemplifies that a multifaceted interdisciplinary approach offers promising opportunities to elucidate the role of migratory and resident hosts in infectious disease dynamics in wildlife.