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991.
The virtual ecologist approach: simulating data and observers 总被引:3,自引:0,他引:3
Damaris Zurell Uta Berger Juliano S. Cabral Florian Jeltsch Christine N. Meynard Tamara Münkemüller Nana Nehrbass Jörn Pagel Björn Reineking Boris Schröder Volker Grimm 《Oikos》2010,119(4):622-635
Ecologists carry a well‐stocked toolbox with a great variety of sampling methods, statistical analyses and modelling tools, and new methods are constantly appearing. Evaluation and optimisation of these methods is crucial to guide methodological choices. Simulating error‐free data or taking high‐quality data to qualify methods is common practice. Here, we emphasise the methodology of the ‘virtual ecologist’ (VE) approach where simulated data and observer models are used to mimic real species and how they are ‘virtually’ observed. This virtual data is then subjected to statistical analyses and modelling, and the results are evaluated against the ‘true’ simulated data. The VE approach is an intuitive and powerful evaluation framework that allows a quality assessment of sampling protocols, analyses and modelling tools. It works under controlled conditions as well as under consideration of confounding factors such as animal movement and biased observer behaviour. In this review, we promote the approach as a rigorous research tool, and demonstrate its capabilities and practical relevance. We explore past uses of VE in different ecological research fields, where it mainly has been used to test and improve sampling regimes as well as for testing and comparing models, for example species distribution models. We discuss its benefits as well as potential limitations, and provide some practical considerations for designing VE studies. Finally, research fields are identified for which the approach could be useful in the future. We conclude that VE could foster the integration of theoretical and empirical work and stimulate work that goes far beyond sampling methods, leading to new questions, theories, and better mechanistic understanding of ecological systems. 相似文献
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995.
Julie B. Fiévet Christine Dillmann Dominique de Vienne 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,120(2):463-473
The genetic and molecular approaches to heterosis usually do not rely on any model of the genotype–phenotype relationship.
From the generalization of Kacser and Burns’ biochemical model for dominance and epistasis to networks with several variable
enzymes, we hypothesized that metabolic heterosis could be observed because the response of the flux towards enzyme activities
and/or concentrations follows a multi-dimensional hyperbolic-like relationship. To corroborate this, we used the values of
systemic parameters accounting for the kinetic behaviour of four enzymes of the upstream part of glycolysis, and simulated
genetic variability by varying in silico enzyme concentrations. Then we “crossed” virtual parents to get 1,000 hybrids, and
showed that best-parent heterosis was frequently observed. The decomposition of the flux value into genetic effects, with
the help of a novel multilocus epistasis index, revealed that antagonistic additive-by-additive epistasis effects play the
major role in this framework of the genotype–phenotype relationship. This result is consistent with various observations in
quantitative and evolutionary genetics, and provides a model unifying the genetic effects underlying heterosis. 相似文献
996.
Structure, allelic diversity and selection of Asr genes, candidate for drought tolerance, in Oryza sativa L. and wild relatives 总被引:1,自引:0,他引:1
997.
Effect of nitrate supply and mycorrhizal inoculation on characteristics of tobacco root plasma membrane vesicles 总被引:1,自引:0,他引:1
Martin Moche Stefanie Stremlau Lars Hecht Cornelia Göbel Ivo Feussner Christine Stöhr 《Planta》2010,231(2):425-436
Plant plasma membrane (pm) vesicles from mycorrhizal tobacco (Nicotiana tabacum cv. Samsun) roots were isolated with negligible fungal contamination by the aqueous two-phase partitioning technique as proven
by fatty acid analysis. Palmitvaccenic acid became apparent as an appropriate indicator for fungal membranes in root pm preparations.
The pm vesicles had a low specific activity of the vanadate-sensitive ATPase and probably originated from non-infected root
cells. In a phosphate-limited tobacco culture system, root colonisation by the vesicular arbuscular mycorrhizal fungus, Glomus mosseae, is inhibited by external nitrate in a dose-dependent way. However, detrimental high concentrations of 25 mM nitrate lead
to the highest colonisation rate observed, indicating that the defence system of the plant is impaired. Nitric oxide formation
by the pm-bound nitrite:NO reductase increased in parallel with external nitrate supply in mycorrhizal roots in comparison
to the control plants, but decreased under excess nitrate. Mycorrhizal pm vesicles had roughly a twofold higher specific activity
as the non-infected control plants when supplied with 10–15 mM nitrate. 相似文献
998.
Anjali Prabhu Qin Xu Michaele B. Manigrasso Moumita Biswas Elizabeth Flynn Radu Iliescu Edwin D. Lephart Christine Maric 《Steroids》2010,75(11):779-787
Our previous studies have shown that diabetes in the male streptozotocin (STZ)-induced diabetic rat is characterized by a decrease in circulating testosterone and concomitant increase in estradiol levels. Interestingly, this increase in estradiol levels persists even after castration, suggesting extra-testicular origins of estradiol in diabetes. The aim of the present study was to examine whether other target organs of diabetes may be sources of estradiol. The study was performed in male Sprague–Dawley non-diabetic (ND), STZ-induced diabetic (D) and STZ-induced diabetic castrated (Dcas) rats (n = 8–9/group). 14 weeks of diabetes was associated with decreased testicular (ND, 26.3 ± 4.19; D, 18.4 ± 1.54; P < 0.05), but increased renal (ND, 1.83 ± 0.92; D, 7.85 ± 1.38; P < 0.05) and ocular (D, 23.4 ± 3.66; D, 87.1 ± 28.1; P < 0.05) aromatase activity. This increase in renal (Dcas, 6.30 ± 1.25) and ocular (Dcas, 62.7 ± 11.9) aromatase activity persisted after castration. The diabetic kidney also had increased levels of tissue estrogen (ND, 0.31 ± 0.01; D, 0.51 ± 0.11; Dcas, 0.45 ± 0.08) as well as estrogen receptor alpha protein expression (ND, 0.63 ± 0.09; D, 1.62 ± 0.28; Dcas, 1.38 ± 0.20). These data suggest that in male STZ-induced diabetic rats, tissues other than the testis may become sources of estradiol. In particular, the diabetic kidney appears to produce estradiol following castration, a state that is associated with a high degree or renal injury. Overall, our data provides evidence for the extra-testicular source of estradiol that in males, through an intracrine mechanism, may contribute to the development and/or progression of end-organ damage associated with diabetes. 相似文献
999.
Thanemozhi G Natarajan Bhaskar V Kallakury Christine E Sheehan Margaret B Bartlett Natarajan Ganesan Anju Preet Jeffrey S Ross Kevin T FitzGerald 《Cancer cell international》2010,10(1):13
Background
MLL2, an epigenetic regulator in mammalian cells, mediates histone 3 lysine 4 tri-methylation (H3K4me3) through the formation of a multiprotein complex. MLL2 shares a high degree of structural similarity with MLL, which is frequently disrupted in leukemias via chromosomal translocations. However, this structural similarity is not accompanied by functional equivalence. In light of this difference, and previous reports on involvement of epigenetic regulators in malignancies, we investigated MLL2 expression in established cell lines from breast and colon tissues. We then investigated MLL2 in solid tumors of breast and colon by immunohistochemistry, and evaluated potential associations with established clinicopathologic variables. 相似文献1000.
April L Ellis Wensheng Pan Guang Yang Kim Jones Christine Chuang John M Whitelock Arthur A DeCarlo 《BMC biotechnology》2010,10(1):66