Relevance of lipid polar headgroups on boron-mediated changes in membrane physical properties

Using liposomes composed of either brain phosphatidylcholine (PC), or binary mixtures of PC and phosphatidylserine (PS), galactolipids (GL), phosphatidylinositol (PI), cardiolipin (CL), phosphatidic acid (PA), or phosphatidylethanolamine (PE), we investigated the effects of graded amounts of boric acid (B, 0.5-1000 microM) on the following membrane physical properties: (a) surface potential, (b) lipid rearrangement through lateral phase separation, (c) fluidity, and (d) hydration. Incubation of the different populations of vesicles with B was associated with a small, but statistically significant, increase in membrane surface potential in PC, PC:PS, PC:GL, PC:PI, PC:PA, and PC:PE liposomes. B-induced lipid lateral rearrangement through lateral phase separation in PC, PC:PA, and PC:PE liposomes; but had no effects on PC:PS, PC:GL, and PC:PI liposomes. In PC liposomes B affected membrane fluidity at the water-lipid interface without affecting the hydrophobic core of the bilayer. In all the other binary liposomes studied, B increased membrane fluidity in both, the hydrophobic portion of the membrane and in the anionic domains. The above was associated with a decrease in the fluidity of the cationic domains. B (10-1000 microM) decreased membrane hydration regardless the composition of the liposomes. The obtained results demonstrate the ability of B to interact with membranes, and induce changes in membrane physical properties. Importantly, the extent of B-membrane interactions and the consequent effects were dependent on the nature of the lipid molecule; as such, B had greater affinity with lipids containing polyhydroxylated moieties such as GL and PI. These differential interactions may result in different B-induced modulations of membrane-associated processes in cells.     

Interactions between land use,habitat use,and population increase in greater snow geese: what are the consequences for natural wetlands?

The North American greater snow goose population has increased dramatically during the last 40 years. We evaluated whether refuge creation, changes in land use on the wintering and staging grounds, and climate warming have contributed to this expansion by affecting the distribution, habitat use, body condition, and migration phenology of birds. We also reviewed the effects of the increasing population on marshes on the wintering grounds, along the migratory routes and on the tundra in summer. Refuges established before 1970 may have contributed to the initial demographic increase. The most important change, however, was the switch from a diet entirely based on marsh plants in spring and winter (rhizomes of Scirpus/Spartina) to one dominated by crops (corn/young grass shoots) during the 1970s and 1980s. Geese now winter further north along the US Atlantic coast, leading to reduced hunting mortality. Their migratory routes now include portions of southwestern Québec where corn production has increased exponentially. Since the mid‐1960s, average temperatures have increased by 1–2.4°C throughout the geographic range of geese, which may have contributed to the northward shift in wintering range and an earlier migration in spring. Access to spilled corn in spring improved fat reserves upon departure for the Arctic and may have contributed to a high fecundity. The population increase has led to intense grazing of natural wetlands used by geese although these habitats are still largely undamaged. The foraging in fields allowed the population to exceed limits imposed by natural marshes in winter and spring, but also prevented permanent damage because of their overgrazing.     

A review of dietary stilbenes: sources and bioavailability

Stilbenes are a class of phenolic metabolites found in various edible plants, such as grapevine, berries and peanuts. Their bioactivitiy and their potential benefits for human health have been the subject of several studies. Among all identified stilbenes, resveratrol has been particularly studied and results from literature showed that it presents several biological activities, including antioxidant, anti-inflammatory and antiproliferative effects. Likewise, some researches focused on other stilbenes and highlighted similar biological activity for those compounds. However, stilbenes present a high diversity in their phenolic structures (various chemical substituents and polymerization) which is a determining factor of their absorption and metabolism rates. Consequently, this could affect the effectiveness of stilbenes in vivo. In this context, an evaluation of the bioavailability and metabolism of stilbenes is necessary to move forward with pharmacological and clinical studies. Hence, this review aims to present recently obtained data and results concerning stilbenes sources and bioavailability, as a contribution to the valorization of the role of dietary stilbenes in the human diet.     

Direct targeting and rapid isolation of BAC clones spanning a defined chromosome region

To isolate genes of interest in plants, it is essential to construct bacterial artificial chromosome (BAC) libraries from specific genotypes. Construction and organisation of BAC libraries is laborious and costly, especially from organisms with large and complex genomes. In the present study, we developed the pooled BAC library strategy that allows rapid and low cost generation and screening of genomic libraries from any genotype of interest. The BAC library is constructed, directly organised into a few pools and screened for BAC clones of interest using PCR and hybridisation steps, without requiring organization into individual clones. As a proof of concept, a pooled BAC library of approximately 177,000 recombinant clones has been constructed from the barley cultivar Cebada Capa that carries the Rph7 leaf rust resistance gene. The library has an average insert size of 140 kb, a coverage of six barley genome equivalents and is organised in 138 pools of about 1,300 clones each. We rapidly established a single contig of six BAC clones spanning 230 kb at the Rph7 locus on chromosome 3HS. The described low-cost cloning strategy is fast and will greatly facilitate direct targeting of genes and large-scale intra- and inter-species comparative genome analysis.Edwige Isidore and Beatrice Scherrer contributed equally to the work.     

Domain 3 of NS5A protein from the hepatitis C virus has intrinsic alpha-helical propensity and is a substrate of cyclophilin A

Nonstructural protein 5A (NS5A) is essential for hepatitis C virus (HCV) replication and constitutes an attractive target for antiviral drug development. Although structural data for its in-plane membrane anchor and domain D1 are available, the structure of domains 2 (D2) and 3 (D3) remain poorly defined. We report here a comparative molecular characterization of the NS5A-D3 domains of the HCV JFH-1 (genotype 2a) and Con1 (genotype 1b) strains. Combining gel filtration, CD, and NMR spectroscopy analyses, we show that NS5A-D3 is natively unfolded. However, NS5A-D3 domains from both JFH-1 and Con1 strains exhibit a propensity to partially fold into an α-helix. NMR analysis identifies two putative α-helices, for which a molecular model could be obtained. The amphipathic nature of the first helix and its conservation in all genotypes suggest that it might correspond to a molecular recognition element and, as such, promote the interaction with relevant biological partner(s). Because mutations conferring resistance to cyclophilin inhibitors have been mapped into NS5A-D3, we also investigated the functional interaction between NS5A-D3 and cyclophilin A (CypA). CypA indeed interacts with NS5A-D3, and this interaction is completely abolished by cyclosporin A. NMR heteronuclear exchange experiments demonstrate that CypA has in vitro peptidyl-prolyl cis/trans-isomerase activity toward some, but not all, of the peptidyl-prolyl bonds in NS5A-D3. These studies lead to novel insights into the structural features of NS5A-D3 and its relationships with CypA.     

Field chronobiology of a molluscan bivalve: how the moon and sun cycles interact to drive oyster activity rhythms

The present study reports new insights into the complexity of environmental drivers in aquatic animals. The focus of this study was to determine the main forces that drive mollusc bivalve behavior in situ. To answer this question, the authors continuously studied the valve movements of permanently immersed oysters, Crassostrea gigas, during a 1-year-long in situ study. Valve behavior was monitored with a specially build valvometer, which allows continuously recording of up to 16 bivalves at high frequency (10?Hz). The results highlight a strong relationship between the rhythms of valve behavior and the complex association of the sun-earth-moon orbital positions. Permanently immersed C. gigas follows a robust and strong behavior primarily driven by the tidal cycle. The intensity of this tidal driving force is modulated by the neap-spring tides (i.e., synodic moon cycle), which themselves depend of the earth-moon distance (i.e., anomalistic moon cycle). Light is a significant driver of the oysters' biological rhythm, although its power is limited by the tides, which remain the predominant driver. More globally, depending where in the world the bivalves reside, the results suggest their biological rhythms should vary according to the relative importance of the solar cycle and different lunar cycles associated with tide generation. These results highlight the high plasticity of these oysters to adapt to their changing environment.     

Neural correlates of ongoing conscious experience: both task-unrelatedness and stimulus-independence are related to default network activity

The default mode network (DMN) is a set of brain regions that consistently shows higher activity at rest compared to tasks requiring sustained focused attention toward externally presented stimuli. The cognitive processes that the DMN possibly underlies remain a matter of debate. It has alternately been proposed that DMN activity reflects unfocused attention toward external stimuli or the occurrence of internally generated thoughts. The present study aimed at clarifying this issue by investigating the neural correlates of the various kinds of conscious experiences that can occur during task performance. Four classes of conscious experiences (i.e., being fully focused on the task, distractions by irrelevant sensations/perceptions, interfering thoughts related to the appraisal of the task, and mind-wandering) that varied along two dimensions ("task-relatedness" and "stimulus-dependency") were sampled using thought-probes while the participants performed a go/no-go task. Analyses performed on the intervals preceding each probe according to the reported subjective experience revealed that both dimensions are relevant to explain activity in several regions of the DMN, namely the medial prefrontal cortex, posterior cingulate cortex/precuneus, and posterior inferior parietal lobe. Notably, an additive effect of the two dimensions was demonstrated for midline DMN regions. On the other hand, lateral temporal regions (also part of the DMN) were specifically related to stimulus-independent reports. These results suggest that midline DMN regions underlie cognitive processes that are active during both internal thoughts and external unfocused attention. They also strengthen the view that the DMN can be fractionated into different subcomponents and reveal the necessity to consider both the stimulus-dependent and the task-related dimensions of conscious experiences when studying the possible functional roles of the DMN.     

Sex‐specific allelic transmission bias suggests sexual conflict at MC1R

Sexual conflict arises when selection in one sex causes the displacement of the other sex from its phenotypic optimum, leading to an inevitable tension within the genome – called intralocus sexual conflict. Although the autosomal melanocortin‐1‐receptor gene (MC1R) can generate colour variation in sexually dichromatic species, most previous studies have not considered the possibility that MC1R may be subject to sexual conflict. In the barn owl (Tyto alba), the allele MC1R_WHITE is associated with whitish plumage coloration, typical of males, and the allele MC1R_RUFOUS is associated with dark rufous coloration, typical of females, although each sex can express any phenotype. Because each colour variant is adapted to specific environmental conditions, the allele MC1R_WHITE may be more strongly selected in males and the allele MC1R_RUFOUS in females. We therefore investigated whether MC1R genotypes are in excess or deficit in male and female fledglings compared with the expected Hardy–Weinberg proportions. Our results show an overall deficit of 7.5% in the proportion of heterozygotes in males and of 12.9% in females. In males, interannual variation in assortative pairing with respect to MC1R explained the year‐specific deviations from Hardy–Weinberg proportions, whereas in females, the deficit was better explained by the interannual variation in the probability of inheriting the MC1R_WHITE or MC1R_RUFOUS allele. Additionally, we observed that sons inherit the MC1R_RUFOUS allele from their fathers on average slightly less often than expected under the first Mendelian law. Transmission ratio distortion may be adaptive in this sexually dichromatic species if males and females are, respectively, selected to display white and rufous plumages.