Genotyping by sequencing suggests overwintering of Peronospora destructor in southwestern Québec,Canada

Several Peronospora species are carried by wind over short and long distances, from warmer climates where they survive on living plants to cooler climates. In eastern Canada, this annual flow of sporangia was thought to be the main source of Peronospora destructor responsible for onion downy mildew. However, the results of a recent study showed that the increasing frequency of onion downy mildew epidemics in eastern Canada is associated with warmer autumns, milder winters, and previous year disease severity, suggesting overwintering of the inoculum in an area where the pathogen is not known to be endogenous. In this study, genotyping by sequencing was used to investigate the population structure of P. destructor at the landscape scale. The study focused on a particular region of southwestern Québec—Les Jardins de Napierville—to determine if the populations were clonal and regionally differentiated. The data were characterized by a high level of linkage disequilibrium, characteristic of clonal organisms. Consequently, the null hypothesis of random mating was rejected when tested on predefined or nonpredefined populations, indicating that linkage disequilibrium was not a function of population structure and suggesting a mixed reproduction mode. Discriminant analysis of principal components performed with predefined population assignment allowed grouping P. destructor isolates by geographical regions, while analysis of molecular variance confirmed that this genetic differentiation was significant at the regional level. Without using a priori population assignment, isolates were clustered into four genetic clusters. These results represent a baseline estimate of the genetic diversity and population structure of P. destructor.     

Mycobacterium tuberculosis Lipoprotein LprG Binds Lipoarabinomannan and Determines Its Cell Envelope Localization to Control Phagolysosomal Fusion

Mycobacterium tuberculosis (Mtb) virulence is decreased by genetic deletion of the lipoprotein LprG, but the function of LprG remains unclear. We report that LprG expressed in Mtb binds to lipoglycans, such as lipoarabinomannan (LAM), that mediate Mtb immune evasion. Lipoglycan binding to LprG was dependent on both insertion of lipoglycan acyl chains into a hydrophobic pocket on LprG and a novel contribution of lipoglycan polysaccharide components outside of this pocket. An lprG null mutant (Mtb ΔlprG) had lower levels of surface-exposed LAM, revealing a novel role for LprG in determining the distribution of components in the Mtb cell envelope. Furthermore, this mutant failed to inhibit phagosome-lysosome fusion, an immune evasion strategy mediated by LAM. We propose that LprG binding to LAM facilitates its transfer from the plasma membrane into the cell envelope, increasing surface-exposed LAM, enhancing cell envelope integrity, allowing inhibition of phagosome-lysosome fusion and enhancing Mtb survival in macrophages.     

Plant extinction in New Caledonia: protection of sclerophyll forests urgently needed

The sclerophyll forests which once extended over the lowlands of the west coast of New Caledonia are now reduced to small fragments representing about 2% (10 000 ha) of their original area. Much of the remaining forests are degraded. Threats to sclerophyll forests come from land clearance, grazing by cattle or deer, and fire. In sclerophyll forests, 223 endemic phanerogam species occur and 59 of these are specific to this forest type. Several of the 59 specific species are known only from a few plants at a single locality and are critically endangered. Pittosporum tanianum sp. nov. became extinct shortly after its discovery in 1988, and becomes the first documented plant extinction in New Caledonia. A further 15 species of New Caledonian plants, not recorded for several decades, are discussed, and it is concluded that between 4 and 9 of them may be extinct. The existing reserves containing sclerophyll forests are inadequate to protect the remaining biodiversity of the forests. Four immediate steps needed to protect sclerophyll forests are (i) restoration of Leprédour Island; (ii) purchase and restoration of selected privately owned forests; (iii) management of publicly owned forest near Népoui; and (iv) ex situ conservation of certain species.     

A versatile tool for conditional gene expression and knockdown

Drug-inducible systems allowing the control of gene expression in mammalian cells are invaluable tools for genetic research, and could also fulfill essential roles in gene- and cell-based therapy. Currently available systems, however, often have limited in vivo functionality because of leakiness, insufficient levels of induction, lack of tissue specificity or prohibitively complicated designs. Here we describe a lentiviral vector-based, conditional gene expression system for drug-controllable expression of polymerase (Pol) II promoter-driven transgenes or Pol III promoter-controlled sequences encoding small inhibitory hairpin RNAs (shRNAs). This system has great robustness and versatility, governing tightly controlled gene expression in cell lines, in embryonic or hematopoietic stem cells, in human tumors xenotransplanted into nude mice, in the brain of rats injected intraparenchymally with the vector, and in transgenic mice generated by infection of fertilized oocytes. These results open up promising perspectives for basic or translational research and for the development of gene-based therapeutics.     

Global human footprint on the linkage between biodiversity and ecosystem functioning in reef fishes

Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas.     

n-3 Polyunsaturated fatty acids in animal models with neuroinflammation

Neuroinflammation is present in the majority of acute and chronic neurological disorders. Excess or prolonged inflammation in the brain is thought to exacerbate neuronal damage and loss. Identifying modulators of neuroinflammation is an active area of study since it may lead to novel therapies. Omega-3 polyunsaturated fatty acids (n-3 PUFA) are anti-inflammatory in many non-neural tissues; their role in neuroinflammation is less studied. This review summarizes the relationship between n-3 PUFA and brain inflammation in animal models of brain injury and aging. Evidence by and large shows protective effects of n-3 PUFA in models of sickness behavior, stroke, aging, depression, Parkinson's disease, diabetes, and cytokine- and irradiation-induced cognitive impairments. However, rigorous studies that test the direct effects of n-3 PUFA in neuroinflammation in vivo are lacking. Future research in this area is necessary to determine if, and if so which, n-3 PUFA directly target brain inflammatory pathways. n-3 PUFA bioactive metabolites may provide novel therapeutic targets for neurological disorders with a neuroinflammatory component.     

Degradation of RDX,TNT, and HMX during EPA 8330B Sample Processing and Analysis of Soils under Hydrated Lime or Dithionite-Based Chemical Remediation

The remediation efficiency of soils containing energetic materials (EM) is assessed using SW-846 USEPA Method 8330B. However, the extraction, which is performed by sonicating the soil samples in acetonitrile for several hours, could lead to additional degradation of EM during sample processing, and consequently, to an overestimation of remediation efficiency. To verify this, soil samples that were spiked with controlled amounts of EM were briefly exposed to remediation reagents, such as MuniRem® (a commercial sodium dithionite-based formulation) or hydrated lime, and analyzed using SW-846 USEPA Method 8330B. The most affected EM of this study was 2,4,6-trinitrotoluene (TNT), for which complete degradation was observed after exposure to hydrated lime or pH-buffered MuniRem®. Losses of 1,3,5-trinitro-1,3,5-triazinane (RDX) reached 30 ± 20% upon treatment with full pH-buffered MuniRem® and 90 ± 10% when exposed to lime. The concentrations of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) were near the method’s lower limit of quantification, and subjected to large errors, which prevented us from drawing any clear conclusions regarding its degradation under the studied experimental conditions. These results highlight the necessity of performing appropriate soil sample treatments to quench the remaining hydrated lime or sodium dithionite prior to the extraction and analysis steps with SW-846 USEPA Method 8330B. Quenching of remaining remediation reagents may possibly be also required for other remediation reagents and EM.     

Determinants of refusal of A/H1N1 pandemic vaccination in a high risk population: a qualitative approach

Background

Our study analyses the main determinants of refusal or acceptance of the 2009 A/H1N1 vaccine in patients with cystic fibrosis, a high-risk population for severe flu infection, usually very compliant for seasonal flu vaccine.

Methodology/Principal Findings

We conducted a qualitative study based on semi-structured interviews in 3 cystic fibrosis referral centres in Paris, France. The study included 42 patients with cystic fibrosis: 24 who refused the vaccine and 18 who were vaccinated. The two groups differed quite substantially in their perceptions of vaccine- and disease-related risks. Those who refused the vaccine were motivated mainly by the fears it aroused and did not explicitly consider the 2009 A/H1N1 flu a potentially severe disease. People who were vaccinated explained their choice, first and foremost, as intended to prevent the flu''s potential consequences on respiratory cystic fibrosis disease. Moreover, they considered vaccination to be an indirect collective prevention tool. Patients who refused the vaccine mentioned multiple, contradictory information sources and did not appear to consider the recommendation of their local health care provider as predominant. On the contrary, those who were vaccinated stated that they had based their decision solely on the clear and unequivocal advice of their health care provider.

Conclusions/Significance

These results of our survey led us to formulate three main recommendations for improving adhesion to new pandemic vaccines. (1) it appears necessary to reinforce patient education about the disease and its specific risks, but also general population information about community immunity. (2) it is essential to disseminate a clear and effective message about the safety of novel vaccines. (3) this message should be conveyed by local health care providers, who should be involved in implementing immunization.     

Mechanical properties of the porcine growth plate and its three zones from unconfined compression tests

The aim of the study was to determine intrinsic mechanical properties of the complete growth plate and its reserve, proliferative and hypertrophic zones. Growth plate disk samples from newborn swine's ulnae were tested using stress relaxation tests under unconfined compression. The Transversely Isotropic Biphasic Model (TIBPE) derived by [Cohen, B., Lai, W. M., Mow, V. C., 1998. A transversely isotropic biphasic model for unconfined compression of growth plate and chondroepiphysis. Journal of Biomechanical Engineering, 120, pp. 491–496] was used to extract intrinsic mechanical properties using a four-parameter optimization procedure. Significant differences were found for the transverse permeability k₁, the Poisson's ratio in the transverse plane ν₂₁, the out-of-plane Poisson's ratio ν₃₁ and the out-of-plane Young's modulus E₃ between the reserve zone and the proliferative zone as well as between the reserve zone and the hypertrophic zone. The same trends were obtained for the Young's modulus in the transverse plane E₁, but significant differences were also found between the reserve zone and the complete growth plate. The proliferative and hypertrophic zones are half as stiff as the reserve zone along the compression axis and about three times less stiff than the reserve zone in the transverse plane. These two zones are also three times as permeable as the reserve zone in the radial direction. The mechanical behavior of the newborn porcine distal ulna growth plate is non-uniform along its thickness. The reserve zone, with its greater zonal component at that development stage, has noteworthy effects on the complete growth plate intrinsic mechanical properties. This study provides, for the very first time, an investigation of the intrinsic mechanical properties of the reserve, proliferative and hypertrophic zones of the growth plate.