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排序方式: 共有10000条查询结果,搜索用时 12 毫秒
941.
Günther Klonner Johannes Wessely Andreas Gattringer Dietmar Moser Iwona Dullinger Karl Hülber Sabine B. Rumpf Svenja Block Oliver Bossdorf Marta Carboni Luisa Conti Wayne Dawson Emily Haeuser Martin Hermy Tamara Münkemüller Madalin Parepa Wilfried Thuiller Sebastiaan Van der Veken Kris Verheyen Mark van Kleunen Franz Essl Stefan Dullinger 《Ecography》2019,42(9):1548-1557
Climate warming is supposed to enlarge the area climatically suitable to the naturalization of alien garden plants in temperate regions. However, the effects of a changing climate on the spread of naturalized ornamentals have not been evaluated by spatially and temporarily explicit range modelling at larger scales so far. Here, we assess how climate change and the frequency of cultivation interactively determine the spread of 15 ornamental plants over the 21st century in Europe. We coupled species distribution modelling with simulations of demography and dispersal to predict range dynamics of these species in annual steps across a 250 × 250 m raster of the study area. Models were run under four scenarios of climate warming and six levels of cultivation intensity. Cultivation frequency was implemented as size of the area used for planting a species. Although the area climatically suitable to the 15 species increases, on average, the area predicted to be occupied by them in 2090 shrinks under two of the three climate change scenarios. This contradiction obviously arises from dispersal limitations that were pronounced although we assumed that cultivation is spatially adapting to the changing climate. Cultivation frequency had a much stronger effect on species spread than climate change, and this effect was non‐linear. The area occupied increased sharply from low to moderate levels of cultivation intensity, but levelled off afterwards. Our simulations suggest that climate warming will not necessarily foster the spread of alien garden plants in Europe over the next decades. However, climatically suitable areas do increase and hence an invasion debt is likely accumulating. Restricting cultivation of species can be effective in preventing species spread, irrespective of how the climate develops. However, for being successful, they depend on high levels of compliance to keep propagule pressure at a low level. 相似文献
942.
Mark D. Stenglein Elliott R. Jacobson Li-Wen Chang Chris Sanders Michelle G. Hawkins David S-M. Guzman Tracy Drazenovich Freeland Dunker Elizabeth K. Kamaka Debbie Fisher Drury R. Reavill Linda F. Meola Gregory Levens Joseph L. DeRisi 《PLoS pathogens》2015,11(5)
Arenaviruses are one of the largest families of human hemorrhagic fever viruses and are known to infect both mammals and snakes. Arenaviruses package a large (L) and small (S) genome segment in their virions. For segmented RNA viruses like these, novel genotypes can be generated through mutation, recombination, and reassortment. Although it is believed that an ancient recombination event led to the emergence of a new lineage of mammalian arenaviruses, neither recombination nor reassortment has been definitively documented in natural arenavirus infections. Here, we used metagenomic sequencing to survey the viral diversity present in captive arenavirus-infected snakes. From 48 infected animals, we determined the complete or near complete sequence of 210 genome segments that grouped into 23 L and 11 S genotypes. The majority of snakes were multiply infected, with up to 4 distinct S and 11 distinct L segment genotypes in individual animals. This S/L imbalance was typical: in all cases intrahost L segment genotypes outnumbered S genotypes, and a particular S segment genotype dominated in individual animals and at a population level. We corroborated sequencing results by qRT-PCR and virus isolation, and isolates replicated as ensembles in culture. Numerous instances of recombination and reassortment were detected, including recombinant segments with unusual organizations featuring 2 intergenic regions and superfluous content, which were capable of stable replication and transmission despite their atypical structures. Overall, this represents intrahost diversity of an extent and form that goes well beyond what has been observed for arenaviruses or for viruses in general. This diversity can be plausibly attributed to the captive intermingling of sub-clinically infected wild-caught snakes. Thus, beyond providing a unique opportunity to study arenavirus evolution and adaptation, these findings allow the investigation of unintended anthropogenic impacts on viral ecology, diversity, and disease potential. 相似文献
943.
Recombination has an impact on genome evolution by maintaining chromosomal integrity, affecting the efficacy of selection, and increasing genetic variability in populations. Recombination rates are a key determinant of the coevolutionary dynamics between hosts and their pathogens. Historic recombination events created devastating new pathogens, but the impact of ongoing recombination in sexual pathogens is poorly understood. Many fungal pathogens of plants undergo regular sexual cycles, and sex is considered to be a major factor contributing to virulence. We generated a recombination map at kilobase-scale resolution for the haploid plant pathogenic fungus Zymoseptoria tritici. To account for intraspecific variation in recombination rates, we constructed genetic maps from two independent crosses. We localized a total of 10,287 crossover events in 441 progeny and found that recombination rates were highly heterogeneous within and among chromosomes. Recombination rates on large chromosomes were inversely correlated with chromosome length. Short accessory chromosomes often lacked evidence for crossovers between parental chromosomes. Recombination was concentrated in narrow hotspots that were preferentially located close to telomeres. Hotspots were only partially conserved between the two crosses, suggesting that hotspots are short-lived and may vary according to genomic background. Genes located in hotspot regions were enriched in genes encoding secreted proteins. Population resequencing showed that chromosomal regions with high recombination rates were strongly correlated with regions of low linkage disequilibrium. Hence, genes in pathogen recombination hotspots are likely to evolve faster in natural populations and may represent a greater threat to the host. 相似文献
944.
Hazel J. Jenkins Mark J. Hancock Simon D. French Chris G. Maher Roger M. Engel John S. Magnussen 《CMAJ》2015,187(6):401-408
Background:Rates of imaging for low-back pain are high and are associated with increased health care costs and radiation exposure as well as potentially poorer patient outcomes. We conducted a systematic review to investigate the effectiveness of interventions aimed at reducing the use of imaging for low-back pain.Methods:We searched MEDLINE, Embase, CINAHL and the Cochrane Central Register of Controlled Trials from the earliest records to June 23, 2014. We included randomized controlled trials, controlled clinical trials and interrupted time series studies that assessed interventions designed to reduce the use of imaging in any clinical setting, including primary, emergency and specialist care. Two independent reviewers extracted data and assessed risk of bias. We used raw data on imaging rates to calculate summary statistics. Study heterogeneity prevented meta-analysis.Results:A total of 8500 records were identified through the literature search. Of the 54 potentially eligible studies reviewed in full, 7 were included in our review. Clinical decision support involving a modified referral form in a hospital setting reduced imaging by 36.8% (95% confidence interval [CI] 33.2% to 40.5%). Targeted reminders to primary care physicians of appropriate indications for imaging reduced referrals for imaging by 22.5% (95% CI 8.4% to 36.8%). Interventions that used practitioner audits and feedback, practitioner education or guideline dissemination did not significantly reduce imaging rates. Lack of power within some of the included studies resulted in lack of statistical significance despite potentially clinically important effects.Interpretation:Clinical decision support in a hospital setting and targeted reminders to primary care doctors were effective interventions in reducing the use of imaging for low-back pain. These are potentially low-cost interventions that would substantially decrease medical expenditures associated with the management of low-back pain.Current evidence-based clinical practice guidelines recommend against the routine use of imaging in patients presenting with low-back pain.1–3 Despite this, imaging rates remain high,4,5 which indicates poor concordance with these guidelines.6,7Unnecessary imaging for low-back pain has been associated with poorer patient outcomes, increased radiation exposure and higher health care costs.8 No short- or long-term clinical benefits have been shown with routine imaging of the low back, and the diagnostic value of incidental imaging findings remains uncertain.9–12 A 2008 systematic review found that imaging accounted for 7% of direct costs associated with low-back pain, which in 1998 translated to more than US$6 billion in the United States and £114 million in the United Kingdom.13 Current costs are likely to be substantially higher, with an estimated 65% increase in spine-related expenditures between 1997 and 2005.14Various interventions have been tried for reducing imaging rates among people with low-back pain. These include strategies targeted at the practitioner such as guideline dissemination,15–17 education workshops,18,19 audit and feedback of imaging use,7,20,21 ongoing reminders7 and clinical decision support.22–24 It is unclear which, if any, of these strategies are effective.25 We conducted a systematic review to investigate the effectiveness of interventions designed to reduce imaging rates for the management of low-back pain. 相似文献
945.
Tulika Sarma Athanasia Koutsouris Jiang Zhu Yu Aleksandar Krbanjevic Thomas J. Hope Mark M. Rasenick 《The Journal of biological chemistry》2015,290(16):10045-10056
Signals that activate the G protein Gαs and promote neuronal differentiation evoke Gαs internalization in rat pheochromocytoma (PC12) cells. These agents also significantly increase Gαs association with microtubules, resulting in an increase in microtubule dynamics because of the activation of tubulin GTPase by Gαs. To determine the function of Gαs/microtubule association in neuronal development, we used real-time trafficking of a GFP-Gαs fusion protein. GFP-Gαs concentrates at the distal end of the neurites in differentiated living PC12 cells as well as in cultured hippocampal neurons. Gαs translocates to specialized membrane compartments at tips of growing neurites. A dominant-negative Gα chimera that interferes with Gαs binding to tubulin and activation of tubulin GTPase attenuates neurite elongation and neurite number both in PC12 cells and primary hippocampal neurons. This effect is greatest on differentiation induced by activated Gαs. Together, these data suggest that activated Gαs translocates from the plasma membrane and, through interaction with tubulin/microtubules in the cytosol, is important for neurite formation, development, and outgrowth. Characterization of neuronal G protein dynamics and their contribution to microtubule dynamics is important for understanding the molecular mechanisms by which G protein-coupled receptor signaling orchestrates neuronal growth and differentiation. 相似文献
946.
Zhu Z Burnett CM Maksymov G Stepniak E Sierra A Subbotina E Anderson ME Coetzee WA Hodgson-Zingman DM Zingman LV 《Biochemical and biophysical research communications》2011,(4):637-641
The cardiovascular system operates under demands ranging from conditions of rest to extreme stress. One mechanism of cardiac stress tolerance is action potential duration shortening driven by ATP-sensitive potassium (KATP) channels. KATP channel expression has a significant physiologic impact on action potential duration shortening and myocardial energy consumption in response to physiologic heart rate acceleration. However, the effect of reduced channel expression on action potential duration shortening in response to severe metabolic stress is yet to be established. Here, transgenic mice with myocardium-specific expression of a dominant negative KATP channel subunit were compared with littermate controls. Evaluation of KATP channel whole cell current and channel number/patch was assessed by patch clamp in isolated ventricular cardiomyocytes. Monophasic action potentials were monitored in retrogradely perfused, isolated hearts during the transition to hypoxic perfusate. An 80–85% reduction in cardiac KATP channel current density results in a similar magnitude, but significantly slower rate, of shortening of the ventricular action potential duration in response to severe hypoxia, despite no significant difference in coronary flow. Therefore, the number of functional cardiac sarcolemmal KATP channels is a critical determinant of the rate of adaptation of myocardial membrane excitability, with implications for optimization of cardiac energy consumption and consequent cardioprotection under conditions of severe metabolic stress. 相似文献
947.
Vivi Andasari Alf Gerisch Georgios Lolas Andrew P. South Mark A. J. Chaplain 《Journal of mathematical biology》2011,63(1):141-171
The ability of cancer cells to break out of tissue compartments and invade locally gives solid tumours a defining deadly characteristic.
One of the first steps of invasion is the remodelling of the surrounding tissue or extracellular matrix (ECM) and a major
part of this process is the over-expression of proteolytic enzymes, such as the urokinase-type plasminogen activator (uPA)
and matrix metalloproteinases (MMPs), by the cancer cells to break down ECM proteins. Degradation of the matrix enables the
cancer cells to migrate through the tissue and subsequently to spread to secondary sites in the body, a process known as metastasis.
In this paper we undertake an analysis of a mathematical model of cancer cell invasion of tissue, or ECM, which focuses on
the role of the urokinase plasminogen activation system. The model consists of a system of five reaction-diffusion-taxis partial
differential equations describing the interactions between cancer cells, uPA, uPA inhibitors, plasmin and the host tissue.
Cancer cells react chemotactically and haptotactically to the spatio-temporal effects of the uPA system. The results obtained
from computational simulations carried out on the model equations produce dynamic heterogeneous spatio-temporal solutions
and using linear stability analysis we show that this is caused by a taxis-driven instability of a spatially homogeneous steady-state.
Finally we consider the biological implications of the model results, draw parallels with clinical samples and laboratory
based models of cancer cell invasion using three-dimensional invasion assay, and go on to discuss future development of the
model. 相似文献
948.
Major locus and other novel additive and epistatic loci involved in modulation of isoflavone concentration in soybean seeds 总被引:4,自引:0,他引:4
Gutierrez-Gonzalez JJ Vuong TD Zhong R Yu O Lee JD Shannon G Ellersieck M Nguyen HT Sleper DA 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,123(8):1375-1385
Seeds of soybean [Glycine max (L.) Merr.] accumulate more isoflavones than any tissue of any plant species. In other plant parts, isoflavones are usually
released to counteract the effects of various biotic and abiotic stresses. Because of the benefits to the plant and positive
implications that consumption may have on human health, increasing isoflavones is a goal of many soybean breeding programs.
However, altering isoflavone levels through marker-assisted selection (MAS) has been impractical due to the small and often
environmentally variable contributions that each individual quantitative trait locus (QTL) has on total isoflavones. In this
study, we developed a Magellan × PI 437654 F7-RIL population to construct a highly saturated non-redundant linkage map that encompassed 451 SNP and SSR molecular markers
and used it to locate genomic regions that govern accumulation of isoflavones in the seeds of soybean. Five QTLs were found
that contribute to the concentration of isoflavones, having single or multiple additive effects on isoflavone component traits.
We also validated a major locus which alone accounted for up to 10% of the phenotypic variance for glycitein, and 35–37% for
genistein, daidzein and the sum of all three soybean isoflavones. This QTL was consistently associated with increased concentration
of isoflavones across different locations, years and crosses. It was the most important QTL in terms of net increased amounts
of all isoflavone forms. Our results suggest that this locus would be an excellent candidate to target for MAS. Also, several
minor QTLs were identified that interacted in an additive-by-additive epistatic manner, to increase isoflavone concentration. 相似文献
949.