Interleukin-1 receptor antagonist reduces mortality from endotoxin shock

About five out of 1,000 patients admitted to hospital develop bacterial sepsis leading to shock, the mortality rate for which is high despite antibiotic therapy. The infection results in hypotension and poor tissue perfusion, and eventually leads to the failure of several organ systems. Bacterial endotoxin is thought to be the direct cause of shock in Gram-negative sepsis, because it can cause shock in animals, and antibodies against endotoxin prevent Gram-negative shock in animals and in humans. But, the symptoms of septic shock are the result of the actions of host cytokines induced by the endotoxin. The cytokine interleukin-1 has been implicated as an important mediator of septic shock because it can induce tachycardia and hypotension and act synergistically with tumour necrosis factor to cause tissue damage and death. We now report that a specific interleukin-1 receptor antagonist reduces the lethality of endotoxin-induced shock in rabbits, indicating that interleukin-1 does indeed play an important part in endotoxin shock.     

New species and a new combination of Mentzelia section Bartonia (Loasaceae) from the Colorado Plateau

A new species, Mentzelia (sect. Bartonia ) cronquistii , subfamily Mentzelioideae, is described and a new combination, M. (sect. Bartonia ) marginata (Osterhout) is made. These two species of the Colorado Plateau are closely related to each other, but their relationships to other species in section Bartonia are obscure.     

Dynamic responses of a British Columbian forest-grassland interface to prescribed burning

Ponderosa pine Pinus ponderosa and Douglas-fir Pseudotsuga menziesii forests in the Interior of British Columbia, Canada, are adjacent to grasslands. Forest ingrowth and tree encroachment, mainly due to fire suppression, represent threats to both forest and ranching industries in the region. The use of prescribed burning for ecological restoration is being practiced, but the associated ecosystem effects of restoration treatments have been little studied in the region. We used a randomized complete block design in a prescribed burning experiment. Tree survival and the responses of understory vegetation to burning were monitored for 3 years. The transect method along with crown projection areas (onto the ground) were used in comparisons between areas inside and outside of the burned area. Fire was effective in eliminating small ponderosa pine (dbh Artemisia tridentata ssp. wyomingensis was observed in grassland sites, while reduction in rabbitbrush Chrysothamnus nauseosus in the forest was observed. Data trends indicate that 3 years after burning, total biomass and forb biomass increased in grasslands, but graminoid biomass in forests was reduced and total understory biomass was not affected by burning. Burning also reduced the shrub component in these ecosystems. While aboveground biomass production may be enhanced by burning in grasslands, the impact of burning on forest understory was minimal and burning may result in reduction of graminoids. Therefore, burning can be used to control tree encroachment and forest ingrowth in this region. Management plans must incorporate topography, species diversity, and tree survival to target areas that are most susceptible to tree encroachment and to achieve desired results. Extended monitoring is necessary to determine the long-term effects of burning on species diversity in and productivity of these ecosystems.     

Glycoprotein organization of Chikungunya virus particles revealed by X-ray crystallography

Chikungunya virus (CHIKV) is an emerging mosquito-borne alphavirus that has caused widespread outbreaks of debilitating human disease in the past five years. CHIKV invasion of susceptible cells is mediated by two viral glycoproteins, E1 and E2, which carry the main antigenic determinants and form an icosahedral shell at the virion surface. Glycoprotein E2, derived from furin cleavage of the p62 precursor into E3 and E2, is responsible for receptor binding, and E1 for membrane fusion. In the context of a concerted multidisciplinary effort to understand the biology of CHIKV, here we report the crystal structures of the precursor p62-E1 heterodimer and of the mature E3-E2-E1 glycoprotein complexes. The resulting atomic models allow the synthesis of a wealth of genetic, biochemical, immunological and electron microscopy data accumulated over the years on alphaviruses in general. This combination yields a detailed picture of the functional architecture of the 25?MDa alphavirus surface glycoprotein shell. Together with the accompanying report on the structure of the Sindbis virus E2-E1 heterodimer at acidic pH (ref. 3), this work also provides new insight into the acid-triggered conformational change on the virus particle and its inbuilt inhibition mechanism in the immature complex.     

Two Earth-sized planets orbiting Kepler-20

Since the discovery of the first extrasolar giant planets around Sun-like stars, evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered has a radius 1.42 times that of the Earth's radius (R(⊕)), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R(⊕)) and the other smaller than the Earth (0.87R(⊕)), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star. Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate. The outer planet could have developed a thick water vapour atmosphere.