Signaling life and death in the thymus: timing is everything

T lymphocytes are generated in the thymus, where developing thymocytes must accept one of two fates: They either differentiate or they die. These fates are chiefly determined by signals that originate from the T cell receptor (TCR), a single receptor complex with a remarkable capacity to decide between distinct cell fates. This review explores TCR signaling in thymocytes and focuses on the kinetic aspects of ligand binding, coreceptor involvement, protein phosphorylation, and mitogen-activated protein kinase (MAPK) activation. Understanding the logic of TCR signaling may eventually explain how thymocytes and T cells distinguish self from nonself, a phenomenon that has fascinated immunologists for 50 years.     

Discovery of a viral NLR homolog that inhibits the inflammasome

The NLR (nucleotide binding and oligomerization, leucine-rich repeat) family of proteins senses microbial infections and activates the inflammasome, a multiprotein complex that promotes microbial clearance. Kaposi's sarcoma-associated herpesvirus (KSHV) is linked to several human malignancies. We found that KSHV Orf63 is a viral homolog of human NLRP1. Orf63 blocked NLRP1-dependent innate immune responses, including caspase-1 activation and processing of interleukins IL-1β and IL-18. KSHV Orf63 interacted with NLRP1, NLRP3, and NOD2. Inhibition of Orf63 expression resulted in increased expression of IL-1β during the KSHV life cycle. Furthermore, inhibition of NLRP1 was necessary for efficient reactivation and generation of progeny virus. The viral homolog subverts the function of cellular NLRs, which suggests that modulation of NLR-mediated innate immunity is important for the lifelong persistence of herpesviruses.     

Confirmation of the Carolina slate belt as an exotic terrane

An assemblage of Middle Cambrian Atlantic faunal province trilobites has been found in the rocks of the Carolina slate belt near Batesburg, South Carolina. Geologic and paleomagnetic data suggest that the Carolina slate belt and the adjacent Charlotte belt constitute an exotic terrane that was accreted to North America in early to middle Paleozoic time.     

The scaling of animal space use

Space used by animals increases with increasing body size. Energy requirements alone can explain how population density decreases, but not the steep rate at which home range area increases. We present a general mechanistic model that predicts the frequency of interaction, spatial overlap, and loss of resources to neighbors. Extensive empirical evidence supports the model, demonstrating that spatial constraints on defense cause exclusivity of home range use to decrease with increasing body size. In large mammals, over 90% of available resources may be lost to neighbors. Our model offers a general framework to understand animal space use and sociality.     

Spray drift as influenced by meteorological and technical factors

BACKGROUND: The objective of this study was to investigate spray drift from a conventional field sprayer as influenced by meteorological and technical factors, and to provide spray operators with data on which to base sound judgements when applying pesticides. The study was conducted in grazing fields and cereal crops. RESULTS: Interpreting the results from 15 field trials under varying meteorological conditions using different boom heights and driving speeds indicates that, during normal spraying conditions, the most decisive factors influencing the total spray drift (TSD) will be boom height and wind speed, followed by air temperature, driving speed and vapour pressure deficit. One important finding was that TSD (within the encompassed range of meteorological conditions and a boom height of 0.4 m) could be expressed as a simple function of the fraction of droplets ≤ 100 µm. In cereal crops: TSD = 0.36 + 0.11× [fr. (d ≤ 100 µm)] and in grazing fields, TSD = 1.02 + 0.10× [fr. (d ≤ 100 µm)]. In most cases a fraction of the airborne drift passed over the 6 m sampling mast located 5 m downwind of the spray swath. CONCLUSIONS: Under specified conditions, the present results indicate a simple relation between the total spray drift and volume fractions of droplets ≤ 100 µm. Given the nozzle type, it was concluded that the most decisive factors determining TSD are wind speed and boom height. Evaluating the relative importance of the meteorological and technical factors contributes to increasing knowledge in this field of research. Copyright © 2011 Society of Chemical Industry     

Topographic controls on the invasion of Pteronia incana (Blue bush) onto hillslopes in Ngqushwa (formerly Peddie) district,Eastern Cape,South Africa

The role of topographic factors in the invasion of hillslopes by Pteronia incana, an unpalatable shrub, was investigated. The study combined field observations with image analysis based on high-resolution infrared imagery. A Digital Elevation Model (DEM) of 20 m spatial resolution was used to derive terrain parameters. The Topographic Wetness Index (WI), a component of the TOPMODEL, was derived from the DEM and its relationship with the spatial distribution of P. incana was explored. The absence/presence of P. incana was noted to be strongly influenced by slope angle and aspect. The probability for P. incana occurrence increased with slope steepness and southerly slope orientation. Abandoned and grazing lands were identified as the main invasion hotspots on hillslopes. The combined influence of slope gradient and aspect, and land use was noted to have promoted the invasion. This is borne out by the concentration of the invasion on abandoned steep slopes with a southerly orientation.     

Birds in Western Australian wheatbelt reserves—implications for conservation

Bird species richness in 22 reserves in the Western Australian wheatbelt was shown to be related not to isolation from adjacent uncleared land, either spatially or with time since clearing of land in their vicinity, but to area of reserve and certain reserve habitat variables. The nature of these relationships was examined with multiple regression analysis. Reserve area was the most important variable, except in some passerine groups, where numbers of plant species, vegetation associations, and plant life form and density classes in each vegetation stratum were, separately, more important than area. Eighty-two percent of the variation in the number of bird species was explained by area of reserve and number of plant species, indicating the importance of floristics to the total bird assemblage within reserves. The number of formations present (the broadest vegetation structural grouping used) did not explain any of the variation in species numbers in any of the bird groupings.There were more resident passerine species present in wheatbelt reserves than there were breeding passerine species on similar-sized southwestern Australian late-Pleistocene/Holocene islands, although the species versus area relationship of the resident habitat-specific passerines (P₅ group) was very similar to that of the island land-bird faunas. The P₅ species group contained many species which probably responded to wheatbelt reserves as islands; some of these species may fail to persist in the wheatbelt in the long term. Twenty-three species usually resident in reserves and 15 ‘non-residents’ were identified as being ‘vulnerable’ or of uncertain conservation status in the wheatbelt.Some vegetation formations within reserves were more important to birds than others; woodlands were most important both to resident and transient species. Most species do not appear to distinguish between shrublands and heaths as major habitats; Species richness versus formation area relationship suggest that insular patchiness for birds in the wheatbelt was manifest at the level of vegetation formations. Reserves as small as 80 ha were important sanctuaries for birds in the wheatbelt, although 1500 ha was considered a minimum area of reserve to conserve a local avifauna. Reserves of the order of 30,000–94,000 ha were required to contain most of the avifauna of the wheatbelt.