The Breadth and Titer of Maternal HIV-1-Specific Heterologous Neutralizing Antibodies Are Not Associated with a Lower Rate of Mother-to-Child Transmission of HIV-1

It has been hypothesized that neutralizing antibodies (NAbs) should have broad specificity to be effective in protection against diverse HIV-1 variants. The mother-to-child transmission model of HIV-1 provides the opportunity to examine whether the breadth of maternal NAbs is associated with protection of infants from infection. Samples were obtained at delivery from 57 transmitting mothers (T) matched with 57 nontransmitting mothers (NT) enrolled in the multicenter French perinatal cohort (ANRS EPF CO1) between 1990 and 1996. Sixty-eight (59.6%) and 46 (40.4%) women were infected by B and non-B viruses, respectively. Neutralization assays were carried out with TZM-bl cells, using a panel of 10 primary isolates of 6 clades (A, B, C, F, CRF01_AE, and CRF02_AG), selected for their moderate or low sensitivity to neutralization. Neutralization breadths were not statistically different between T and NT mothers. However, a few statistically significant differences were observed, with higher frequencies or titers of NAbs toward several individual strains for NT mothers when the clade B-infected or non-clade B-infected mothers were analyzed separately. Our study confirms that the breadth of maternal NAbs is not associated with protection of infants from infection.     

Caractérisation des peuplements de macroinvertébrés benthiques à l’aide de la carte auto-organisatrice (SOM)

Macrobenthic organisms are much used nowadays as bio-indicators for their ability to reflect different disturbances of aquatic ecosystems. However, they have never been used to assess the ecological status of the lagoons of Benin. The current study aims at revealing the ecological state of the lagoon of Porto-Novo through the study of changes in the settlement of benthic organisms collected in this lagoon. The sampling was carried out from July 2007 to June 2009 on a frequency of four seasons of collection per year. The self-organizing map (SOM) of Kohonen has been used for various patterns of distribution of collected organisms. A discriminant analysis (AFD) has allowed the identification of the parameters that govern the patterns observed in this environment. Four groups of macrobenthic communities emerged that were well predicted (75%). The distribution of benthic macro invertebrates of this lagoon is therefore zonal, seasonal and discriminated by variables of mineralization and sediment grain size. The difference in taxonomic richness corresponds to environmental conditions of stations appearing more or less stable and highlighting a gradient of the stress on organisms. Places with unstable conditions are affected by human activities due to their proximity to homes that are enriched in organic matter. These places are full of polluted-tolerant species such as the Gastropods Potamididae, Cirratulidae Polychaetes, Diptera Chironomidae and Oligochaeta. The macrobenthic fauna, which is well differentiated in the groups, is then subjected to human disturbance.     

High‐Throughput DNA sequencing of ancient wood

Reconstructing the colonization and demographic dynamics that gave rise to extant forests is essential to forecasts of forest responses to environmental changes. Classical approaches to map how population of trees changed through space and time largely rely on pollen distribution patterns, with only a limited number of studies exploiting DNA molecules preserved in wooden tree archaeological and subfossil remains. Here, we advance such analyses by applying high‐throughput (HTS) DNA sequencing to wood archaeological and subfossil material for the first time, using a comprehensive sample of 167 European white oak waterlogged remains spanning a large temporal (from 550 to 9,800 years) and geographical range across Europe. The successful characterization of the endogenous DNA and exogenous microbial DNA of 140 (~83%) samples helped the identification of environmental conditions favouring long‐term DNA preservation in wood remains, and started to unveil the first trends in the DNA decay process in wood material. Additionally, the maternally inherited chloroplast haplotypes of 21 samples from three periods of forest human‐induced use (Neolithic, Bronze Age and Middle Ages) were found to be consistent with those of modern populations growing in the same geographic areas. Our work paves the way for further studies aiming at using ancient DNA preserved in wood to reconstruct the micro‐evolutionary response of trees to climate change and human forest management.     

Imprints of multiple glacial refugia in the Pyrenees revealed by phylogeography and palaeodistribution modelling of an endemic spider

Mediterranean mountain ranges harbour highly endemic biota in islandlike habitats. Their topographic diversity offered the opportunity for mountain species to persist in refugial areas during episodes of major climatic change. We investigate the role of Quaternary climatic oscillations in shaping the demographic history and distribution ranges in the spider Harpactocrates ravastellus, endemic to the Pyrenees. Gene trees and multispecies coalescent analyses on mitochondrial and nuclear DNA sequences unveiled two distinct lineages with a hybrid zone around the northwestern area of the Catalan Pyrenees. The lineages were further supported by morphological differences. Climatic niche‐based species distribution models (SDMs) identified two lowland refugia at the western and eastern extremes of the mountain range, which would suggest secondary contact following postglacial expansion of populations from both refugia. Neutrality test and approximate Bayesian computation (ABC) analyses indicated that several local populations underwent severe bottlenecks followed by population expansions, which in combination with the deep population differentiation provided evidence for population survival during glacial periods in microrefugia across the mountain range, in addition to the main Atlantic and Mediterranean (western and eastern) refugia. This study sheds light on the complexities of Quaternary climatic oscillations in building up genetic diversity and local endemicity in the southern Europe mountain ranges.     

A genetic analysis of neural progenitor differentiation

Genetic mechanisms regulating CNS progenitor function and differentiation are not well understood. We have used microarrays derived from a representational difference analysis (RDA) subtraction in a heterogeneous stem cell culture system to systematically study the gene expression patterns of CNS progenitors. This analysis identified both known and novel genes enriched in progenitor cultures. In situ hybridization in a subset of clones demonstrated that many of these genes were expressed preferentially in germinal zones, some showing distinct ventricular or subventricular zone labeling. Several genes were also enriched in hematopoietic stem cells, suggesting an overlap of gene expression in neural and hematopoietic progenitors. This combination of methods demonstrates the power of using custom microarrays derived from RDA-subtracted libraries for both gene discovery and gene expression analysis in the central nervous system.     

Regulation of glycine receptor diffusion properties and gephyrin interactions by protein kinase C

Glycine receptors (GlyRs) can dynamically exchange between synaptic and extrasynaptic locations through lateral diffusion within the plasma membrane. Their accumulation at inhibitory synapses depends on the interaction of the β-subunit of the GlyR with the synaptic scaffold protein gephyrin. An alteration of receptor-gephyrin binding could thus shift the equilibrium between synaptic and extrasynaptic GlyRs and modulate the strength of inhibitory neurotransmission. Using a combination of dynamic imaging and biochemical approaches, we have characterised the molecular mechanism that links the GlyR-gephyrin interaction with GlyR diffusion and synaptic localisation. We have identified a protein kinase C (PKC) phosphorylation site within the cytoplasmic domain of the β-subunit of the GlyR (residue S403) that causes a reduction of the binding affinity between the receptor and gephyrin. In consequence, the receptor's diffusion in the plasma membrane is accelerated and GlyRs accumulate less strongly at synapses. We propose that the regulation of GlyR dynamics by PKC thus contributes to the plasticity of inhibitory synapses and may be involved in maladaptive forms of synaptic plasticity.     

Activation of nicotinic cholinergic receptors prevents ventilator-induced lung injury in rats

Respiratory distress syndrome is responsible for 40 to 60 percent mortality. An over mortality of about 10 percent could result from additional lung injury and inflammation due to the life-support mechanical ventilation, which stretches the lung. It has been recently demonstrated, in vitro, that pharmacological activation of the alpha 7 nicotinic receptors (α7-nAChR) could down regulate intracellular mediators involved in lung cell inflammatory response to stretch. Our aim was to test in vivo the protective effect of the pharmacological activation of the α7-nAChR against ventilator-induced lung injury (VILI). Anesthetized rats were ventilated for two hours with a high stretch ventilation mode delivering a stroke volume large enough to generate 25-cmH(2)O airway pressure, and randomly assigned to four groups: pretreated with parenteral injection of saline or specific agonist of the α7-nAChR (PNU-282987), or submitted to bilateral vagus nerve electrostimulation while pre-treated or not with the α7-nAChR antagonist methyllycaconitine (MLA). Controls ventilated with a conventional stroke volume of 10 mL/kg gave reference data. Physiological indices (compliance of the respiratory system, lung weight, blood oxygenation, arterial blood pressure) and lung contents of inflammatory mediators (IL-6 measured by ELISA, substance P assessed using HPLC) were severely impaired after two hours of high stretch ventilation (sham group). Vagal stimulation was able to maintain the respiratory parameters close to those obtained in Controls and reduced lung inflammation except when associated to nicotinic receptor blockade (MLA), suggesting the involvement of α7-nAChR in vagally-mediated protection against VILI. Pharmacological pre-treatment with PNU-282987 strongly decreased lung injury and lung IL-6 and substance P contents, and nearly abolished the increase in plasmatic IL-6 levels. Pathological examination of the lungs confirmed the physiological differences observed between the groups. In conclusion, these data suggest that the stimulation of α7-nAChR is able to attenuate VILI in rats.     

Intraspecific variability in leaf traits strongly affects alder leaf decomposition in a stream

This study assessed the intraspecific variability of senescent leaves of alder (Alnus glutinosa Gaertn.) and the effects of this variability on leaf decomposition in streams. Leaves were collected at five geographically distant locations in Europe. We analyzed 10 batches of leaf samples for seven quantitative leaf traits as well as leaf decomposition rate in coarse and fine mesh bags exposed in a single stream. The geographic origin of leaf samples largely explained the observed variation in litter quality and decomposition rate. Phosphorus (0.034–0.187%) and lignin (3.9–18.7%) concentrations in leaves varied widely. Together, these two traits accurately predicted leaf decomposition rate (r²=84.1%). Intraspecific variation in leaf decomposition rate was within a range similar to that reported for interspecific variation among co-occurring riparian plant species in Europe. Our study demonstrates extensive intraspecific variability in leaf traits on a continental scale, which can have enormous effects on major ecosystem processes such as leaf decomposition.