Herpesvirus Glycoproteins Undergo Multiple Antigenic Changes before Membrane Fusion

Herpesvirus entry is a complicated process involving multiple virion glycoproteins and culminating in membrane fusion. Glycoprotein conformation changes are likely to play key roles. Studies of recombinant glycoproteins have revealed some structural features of the virion fusion machinery. However, how the virion glycoproteins change during infection remains unclear. Here using conformation-specific monoclonal antibodies we show in situ that each component of the Murid Herpesvirus-4 (MuHV-4) entry machinery—gB, gH/gL and gp150—changes in antigenicity before tegument protein release begins. Further changes then occurred upon actual membrane fusion. Thus virions revealed their final fusogenic form only in late endosomes. The substantial antigenic differences between this form and that of extracellular virions suggested that antibodies have only a limited opportunity to block virion membrane fusion

A Holistic Landscape Description Reveals That Landscape Configuration Changes More over Time than Composition: Implications for Landscape Ecology Studies

International audienceBackground: Space-for-time substitution—that is, the assumption that spatial variations of a system can explain and predict the effect of temporal variations—is widely used in ecology. However, it is questionable whether it can validly be used to explain changes in biodiversity over time in response to land-cover changes.Hypothesis: ere, we hypothesize that different temporal vs spatial trajectories of landscape composition and configuration may limit space-for-time substitution in landscape ecology. Land-cover conversion changes not just the surface areas given over to particular types of land cover, but also affects isolation, patch size and heterogeneity. This means that a small change in land cover over time may have only minor repercussions on landscape composition but potentially major consequences for landscape configuration.Methods: sing land-cover maps of the Paris region for 1982 and 2003, we made a holistic description of the landscape disentangling landscape composition from configuration. After controlling for spatial variations, we analyzed and compared the amplitudes of changes in landscape composition and configuration over time.Results: For comparable spatial variations, landscape configuration varied more than twice as much as composition over time. Temporal changes in composition and configuration were not always spatially matched.Significance: The fact that landscape composition and configuration do not vary equally in space and time calls into question the use of space-for-time substitution in landscape ecology studies. The instability of landscapes over time appears to be attributable to configurational changes in the main. This may go some way to explaining why the landscape variables that account for changes over time in biodiversity are not the same ones that account for the spatial distribution of biodiversity

Complex temporal climate signals drive the emergence of human water-borne disease

Predominantly occurring in developing parts of the world, Buruli ulcer is a severely disabling mycobacterium infection which often leads to extensive necrosis of the skin. While the exact route of transmission remains uncertain, like many tropical diseases, associations with climate have been previously observed and could help identify the causative agent's ecological niche. In this paper, links between changes in rainfall and outbreaks of Buruli ulcer in French Guiana, an ultraperipheral European territory in the northeast of South America, were identified using a combination of statistical tests based on singular spectrum analysis, empirical mode decomposition and cross-wavelet coherence analysis. From this, it was possible to postulate for the first time that outbreaks of Buruli ulcer can be triggered by combinations of rainfall patterns occurring on a long (i.e., several years) and short (i.e., seasonal) temporal scale, in addition to stochastic events driven by the El Nino-Southern Oscillation that may disrupt or interact with these patterns. Long-term forecasting of rainfall trends further suggests the possibility of an upcoming outbreak of Buruli ulcer in French Guiana

The Physics of Core-Collapse Supernovae

Supernovae are nature's grandest explosions and an astrophysical laboratory in which unique conditions exist that are not achievable on Earth. They are also the furnaces in which most of the elements heavier than carbon have been forged. Scientists have argued for decades about the physical mechanism responsible for these explosions. It is clear that the ultimate energy source is gravity, but the relative roles of neutrinos, fluid instabilities, rotation and magnetic fields continue to be debated.Comment: Review article; 17 pages, 5 figure

The methylmercury cycle in Little Rock Lake during experimental acidification and recovery

The cycle of waterborne methylmercury (meHg) in Little Rock Lake is characterized by a period of accumulation during summertime (when the lake is warm and open to the atmosphere) and a period of decline during winter (when the lake is scaled by ice). We followed this cycle for 16 yr. during which time the lake was acidified with H,SO., and then allowed to recover naturally as part of a long-term field experiment on acidic rain. Mass balance Was used to quantify meHg sources and sinks during acidification and recovery. Although year-to-year variability in the Summertime accumulation of meHg was high during both acidified and de-acidified years (C.V. = 0.7 and 0.5, respectively), oil average 65% more meHg accumulated in the water column during acidification. Most of the meHg mass accumulated in the anoxic hypolimnion (> 70%). even though the hypolimnion constituted < 5% of the lake volume. In hypolininetic waters, we observed a direct correlation between the maximum meHg concentration and the sulfate deficit for each year (r(2) = 0.5-0.9) and a direct correlation between meHg and sulfide concentrations (r(2) = 0.7). Sulfide was directly related to dissolved organic carbon at concentrations between 300 and 600 mu mol L-1 carbon (C). Seasonal changes in waterborne H-(II), meHg, and sulfate reduction covaried with the atmospheric deposition of Hg-(II) and SO42-. Across all years, the interaction term [SO42- X Hg-(II)] explained 70% of the variation in the meHg accumulation rate during summer. These results indicate that meHg production was co-mediated by several simultaneously occurring processes that affect the supply of Hg-(II) substrate to the anoxic hypolimnion and the activity of methylating bacteria that are present there. They imply that meHa levels in lakes may respond to future changes in atmospheric Hg deposition in a rapid but complex way, modulated by environmental variables that can interact synergistically with Hg-(II) supply. Such variables include sulfate in acid rain, organic carbon ill terrestrial runoff, and temperature

A reflection on the origins, evolution, and future of PRAGMA

All of the papers in this special collection have been shaped by and/or have helped shape PRAGMA. This paper, a reflection on PRAGMA, will provide additional technical, scientific and human context to many of these papers. We hope to illustrate that it is the people who set directions by following their interests or posing questions, who make progress by honoring their commitments, and who build community by establishing open communications and trust

Landscape-Scale Variation in Taxonomic Diversity in Four Groups of Aquatic Organisms: The Influence of Physical, Chemical, and Biological Properties

We evaluated several factors influencing the taxonomic richness of macrophytes, benthic invertebrates, snails, and fish in a series of northern Wisconsin lakes. We chose the study lakes to decouple the potential effects of ionic strength of lake water and stream connection, two factors that are usually highly correlated and therefore have been confounded in previous studies. In addition, our study lakes covered a wide range in a variety of characteristics, including residential development, abundance of exotic species, nutrient concentrations, predator abundance, and lake size. Species richness within each of the four taxonomic groups was significantly positively related to ionic strength (as measured by specific conductance); we also found secondary associations with other variables, depending on the specific group of organisms. The relationship between richness and lake area was dependent on the specific conductance of the lake and the vagility of the organisms; less vagile groups of organisms showed stronger and steeper species-area relationships in low-conductivity lakes. Further, after variance owing to specific conductance was removed, the presence of stream connections was positively related to species richness for fish, snails, and macrophytes as well as familial richness in benthic invertebrates. Our results indicate that lakes with relatively more groundwater input have lower extinction rates for all four groups of taxa and that lakes with stream inlets and outlets have enhanced immigration rates for fish, snails, benthic invertebrate families, and macrophytes. These findings link processes of immigration and extinction of four groups of organisms of varying vagility to landscape-level hydrologic characteristics related to the glacial history of the region