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961.
X-chromosome linked inhibitor of apoptosis, XIAP, is cellular caspase inhibitor and a key regulator of apoptosis. We and others have previously shown that XIAP expression is regulated primarily at the level of protein synthesis; the 5′ untranslated region (UTR) of XIAP mRNA contains an Internal Ribosome Entry Site (IRES) that supports cap-independent expression of XIAP protein during conditions of pathophysiological stress, such as serum deprivation or gamma irradiation. Here, we show that XIAP is encoded by two distinct mRNAs that differ in their 5′ UTRs. We further show that the dominant, shorter, 5′ UTR promotes a basal level of XIAP expression under normal growth conditions. In contrast, the less abundant longer 5′ UTR contains an IRES and supports cap-independent translation during stress. Our data suggest that the combination of alternate regulatory regions and distinct translational initiation modes is critical in maintaining XIAP levels in response to cellular stress and may represent a general mechanism of cellular adaptation. 相似文献
962.
Tsai MT Chern TC Chuang JH Hsueh CW Kuo HS Liau CJ Riley S Shen BJ Shen CH Wang DW Hsu TS 《PloS one》2010,5(11):e13292
Early data from the 2009 H1N1 pandemic (H1N1pdm) suggest that previous studies over-estimated the within-country rate of spatial spread of pandemic influenza. As large spatially resolved data sets are constructed, the need for efficient simulation code with which to investigate the spatial patterns of the pandemic becomes clear. Here, we present a significant improvement to the efficiency of an individual-based stochastic disease simulation framework commonly used in multiple previous studies. We quantify the efficiency of the revised algorithm and present an alternative parameterization of the model in terms of the basic reproductive number. We apply the model to the population of Taiwan and demonstrate how the location of the initial seed can influence spatial incidence profiles and the overall spread of the epidemic. Differences in incidence are driven by the relative connectivity of alternate seed locations. The ability to perform efficient simulation allows us to run a batch of simulations and take account of their average in real time. The averaged data are stable and can be used to differentiate spreading patterns that are not readily seen by only conducting a few runs. 相似文献
963.
Background
Urbanization is a major cause of habitat fragmentation worldwide. Ecological and conservation theory predicts many potential impacts of habitat fragmentation on natural populations, including genetic impacts. Habitat fragmentation by urbanization causes populations of animals and plants to be isolated in patches of suitable habitat that are surrounded by non-native vegetation or severely altered vegetation, asphalt, concrete, and human structures. This can lead to genetic divergence between patches and in turn to decreased genetic diversity within patches through genetic drift and inbreeding.Methodology/Principal Findings
We examined population genetic patterns using microsatellites in four common vertebrate species, three lizards and one bird, in highly fragmented urban southern California. Despite significant phylogenetic, ecological, and mobility differences between these species, all four showed similar and significant reductions in gene flow over relatively short geographic and temporal scales. For all four species, the greatest genetic divergence was found where development was oldest and most intensive. All four animals also showed significant reduction in gene flow associated with intervening roads and freeways, the degree of patch isolation, and the time since isolation.Conclusions/Significance
Despite wide acceptance of the idea in principle, evidence of significant population genetic changes associated with fragmentation at small spatial and temporal scales has been rare, even in smaller terrestrial vertebrates, and especially for birds. Given the striking pattern of similar and rapid effects across four common and widespread species, including a volant bird, intense urbanization may represent the most severe form of fragmentation, with minimal effective movement through the urban matrix. 相似文献964.
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968.
Parasitic sex-ratio distorters are a major selective force in the evolution of host mating behaviour and mate choice. Here, we investigate sperm limitation in the amphipod Gammarus duebeni and the impact of the microsporidian sex-ratio distorter Nosema granulosis on sperm allocation strategies. We show that males become sperm limited after three consecutive matings and provide uninfected, high fecundity, females with more sperm than infected females. We show that sperm limitation leads to a decrease in female productivity. The outcome of sex-ratio distortion has been shown theoretically to be sensitive to the mating limits of males. Our results indicate that strategic sperm allocation under male rarity will have a greater impact on infected females and has the potential to regulate spread of parasitic feminisers in host populations. 相似文献
969.
A Mycobacterium tuberculosis membrane protein called Mycobacterium cell entry protein (Mce1A) was previously shown to mediate the uptake of nonpathogenic Escherichia coli and latex beads by nonphagocytic mammalian cells. Here we characterize further the in vitro invasive activity of Mce1A using colloidal gold nanoparticles and fluorescent latex microspheres. Mce1A-coated colloidal gold particles induced plasma membrane invagination and entered membrane-bound compartments inside HeLa cells. Few of the protein-coated particles were also found in the cytosol compartment. Cytochalasin D and nocodazole inhibited the uptake by HeLa cells, indicating that rearrangement of both microtubules and microfilaments was necessary for the uptake. The functional domain of Mce1A for invasion was narrowed to a highly basic 22-amino acid sequence termed Inv3. A synthetic Inv3 peptide stimulated uptake of colloidal gold particles as well as latex microspheres by HeLa cells. A chimeric protein composed of Inv3 sequence at the N terminus of beta-galactosidase appeared to stain the nuclear membrane, suggesting that it entered the HeLa cell cytoplasm. These observations suggest that the cell uptake activity of Mce1A is confined to a small peptide domain located in the core region of the protein. Inv3 could be used to ferry any protein in fusion with it into mammalian cells and may serve as a potent nonviral delivery system. 相似文献
970.
In arid and semi-arid regions of the southwestern United States and other parts of the world, flows of historically ephemeral
streams are now perennially dominated by municipal and/or industrial effluent discharges, particularly in urbanized watersheds.
Because effluent-dominated and dependent water bodies have previously received limited scientific study, we reviewed select
contemporary topics associated with water quality of ephemeral streams receiving effluent flows. Our findings indicate that
these ecosystems present numerous challenges to aquatic scientists and water resources managers, including: 1) appropriate
ecosystems or upstream conditions used reference sites in biomonitoring are difficult to locate or do not exist; 2) water
quality criteria, particularly for metals, are dramatically influenced by unique site-specific stream and land use conditions;
3) effluent-dominated streams represent worse-case scenarios for evaluating and predicting aquatic responses to emerging contaminants
(e.g., pharmaceuticals and personal care products); 4) low-flow and drought conditions often preclude effective biomonitoring
and water quality interpretation, or skew ambient assessment results; 5) chemical-physical water quality parameters (e.g.,
dissolved oxygen, conductivity, temperature) are dramatically altered by effluent and stormwater characteristics; and 6) beneficial
reuse of reclaimed effluent waters potentially conflict with sustainability of ecological integrity. Subsequently, we recommend
several water quality research priorities for effluentdominated water bodies. 相似文献