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排序方式: 共有245条查询结果,搜索用时 16 毫秒
101.
Eero J. Vesterinen Lasse Ruokolainen Niklas Wahlberg Carlos Peña Tomas Roslin Veronika N. Laine Ville Vasko Ilari E. Sääksjärvi Kai Norrdahl Thomas M. Lilley 《Molecular ecology》2016,25(7):1581-1594
Optimal foraging theory predicts that predators are selective when faced with abundant prey, but become less picky when prey gets sparse. Insectivorous bats in temperate regions are faced with the challenge of building up fat reserves vital for hibernation during a period of decreasing arthropod abundances. According to optimal foraging theory, prehibernating bats should adopt a less selective feeding behaviour – yet empirical studies have revealed many apparently generalized species to be composed of specialist individuals. Targeting the diet of the bat Myotis daubentonii, we used a combination of molecular techniques to test for seasonal changes in prey selectivity and individual‐level variation in prey preferences. DNA metabarcoding was used to characterize both the prey contents of bat droppings and the insect community available as prey. To test for dietary differences among M. daubentonii individuals, we used ten microsatellite loci to assign droppings to individual bats. The comparison between consumed and available prey revealed a preference for certain prey items regardless of availability. Nonbiting midges (Chironomidae) remained the most highly consumed prey at all times, despite a significant increase in the availability of black flies (Simuliidae) towards the end of the season. The bats sampled showed no evidence of individual specialization in dietary preferences. Overall, our approach offers little support for optimal foraging theory. Thus, it shows how novel combinations of genetic markers can be used to test general theory, targeting patterns at both the level of prey communities and individual predators. 相似文献
102.
Eero Asmala Lumi Haraguchi Hans H. Jakobsen Philippe Massicotte Jacob Carstensen 《Biogeochemistry》2018,137(1-2):93-104
Incubation experiments were performed to examine the processing of fresh autochthonous dissolved organic matter (DOM) produced by coastal plankton communities in spring and autumn. The major driver of observed DOM dynamics was the seasonally variable inorganic nutrient status and characteristics of the initial bulk DOM, whereas the characteristics of the phytoplankton community seemed to have a minor role. Net accumulation of dissolved organic carbon (DOC) during the 18-days experiments was 3.4 and 9.2 µmol l?1 d?1 in P-limited spring and N-limited autumn, respectively. Bacterial bioassays revealed that the phytoplankton-derived DOC had surprisingly low proportions of biologically labile DOC, 12.6% (spring) and 17.5% (autumn). The optical characteristics of the DOM changed throughout the experiments, demonstrating continuous heterotrophic processing of the DOM pool. However, these temporal changes in optical characteristics of the DOM pool were not the same between seasons, indicating seasonally variable environmental drivers. Nitrogen and phosphorus availability is likely the main driver of these seasonal differences, affecting both phytoplankton extracellular release of DOM and its heterotrophic degradation by bacteria. These findings underline the complexity of the DOM production and consumption by the natural planktonic community, and show the importance of the prevailing environmental conditions regulating the DOM pathways. 相似文献
103.
Plinio C. Casarotto Mykhailo Girych Senem M. Fred Vera Kovaleva Rafael Moliner Giray Enkavi Caroline Biojone Cecilia Cannarozzo Madhusmita Pryiadrashini Sahu Katja Kaurinkoski Cecilia A. Brunello Anna Steinzeig Frederike Winkel Sudarshan Patil Stefan Vestring Tsvetan Serchov Cassiano R.A.F. Diniz Liina Laukkanen Eero Castrén 《Cell》2021,184(5):1299-1313.e19
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104.
Päivi Kurttio Karri Seppä Kari Pasanen Toni Patama Anssi Auvinen Eero Pukkala Sirpa Heinävaara Hannu Arvela Timo Hakulinen 《Cancer epidemiology》2013,37(5):585-592
Aim: We studied whether incidence of all cancer sites combined was associated with the radiation exposure due to fallout from the Chernobyl accident in Finland. An emphasis was on the first decade after the accident to assess the suggested “promotion effect”. Methods: The segment of Finnish population with a stable residence in the first post-Chernobyl year (2 million people) was studied. The analyses were based on a 250 m × 250 m grid squares covering all of Finland and all cancer cases except cancers of the breast, prostate and lung. Cancer incidence in four exposure areas (based on first-year dose due to external exposure <0.1 mSv, 0.1–1.3, 0.3–0.5, or ≥0.5 mSv) was compared before the Chernobyl accident (1981–1985) and after it (1988–2007) taking into account cancer incidence trends for a longer period prior to the accident (since 1966). Results: There were no systematic differences in the cancer incidence in relation to radiation exposure in any calendar period, or any subgroup by sex or age at accident. Conclusion: The current large and comprehensive cohort analysis of the relatively low levels of the Chernobyl fallout in Finland did not observe a cancer promotion effect. 相似文献
105.
Geoffrey M. Malinga Anu Valtonen Philip Nyeko Eero J. Vesterinen Heikki Roininen 《Oecologia》2014,174(2):511-520
Although invasion risk is expected to increase with propagule pressure (PP), it is unclear whether PP-invasibility relationships follow an asymptotic or some other non-linear form and whether such relationships vary with underlying environmental conditions. Using manipulations of PP, soil fertility and disturbance, we tested how each influence PP-invasibility relationships for Lespedeza cuneata in a Kansas grassland and use recruitment curve models to determine how safe sites may contribute to plant invasions. After three growing seasons, we found that the PP-invasibility relationships best fit an asymptotic model of invasion reflecting a combination of density-independent and density-dependent processes and that seeds were aggregated within the plant community despite efforts to uniformly sow seeds. Consistent with some models, community invasibility decreased with enhanced soil fertility or reduced levels of disturbance in response to changes in the fraction of safe sites. Our results illustrate that disturbance and soil fertility can be a useful organizing principle for predicting community invasibility, asymptotic models are a reasonable starting point for modeling invasion, and new modeling techniques—coupled with classic experimental approaches—can enhance our understanding of the invasion process. 相似文献
106.
107.
Risto Siev?nen Christophe Godin Theodore M. DeJong Eero Nikinmaa 《Annals of botany》2014,114(4):599-603
A number of research groups in various areas of plant biology as well as computer science and applied mathematics have addressed modelling the spatiotemporal dynamics of growth and development of plants. This has resulted in development of functional–structural plant models (FSPMs). In FSPMs, the plant structure is always explicitly represented in terms of a network of elementary units. In this respect, FSPMs are different from more abstract models in which a simplified representation of the plant structure is frequently used (e.g. spatial density of leaves, total biomass, etc.). This key feature makes it possible to build modular models and creates avenues for efficient exchange of model components and experimental data. They are being used to deal with the complex 3-D structure of plants and to simulate growth and development occurring at spatial scales from cells to forest areas, and temporal scales from seconds to decades and many plant generations. The plant types studied also cover a broad spectrum, from algae to trees. This special issue of Annals of Botany features selected papers on FSPM topics such as models of morphological development, models of physical and biological processes, integrated models predicting dynamics of plants and plant communities, modelling platforms, methods for acquiring the 3-D structures of plants using automated measurements, and practical applications for agronomic purposes. 相似文献
108.
Tissue inhibitor of metalloproteinases 4 (TIMP4) is involved in inflammatory processes of human cardiovascular pathology 总被引:4,自引:2,他引:2
Koskivirta I Rahkonen O Mäyränpää M Pakkanen S Husheem M Sainio A Hakovirta H Laine J Jokinen E Vuorio E Kovanen P Järveläinen H 《Histochemistry and cell biology》2006,126(3):335-342
Tissue inhibitors of matrix metalloproteinases (TIMPs) comprise a family of four members, of which TIMP4 is characterized by being primarily restricted to cardiovascular structures. We demonstrate with immunohistochemical analysis of healthy human tissue that TIMP4 is present in medial smooth muscle cells and adventitial capillaries of arteries as well as in cardiomyocytes. Animal studies have suggested a role for TIMP4 in several inflammatory diseases and cardiovascular pathologies. We therefore examined whether TIMP4 is involved in human inflammatory cardiovascular disorders, specifically atherosclerosis, giant cell arteritis and chronic rejection of heart allografts. TIMP4 was most clearly visible in cardiovascular tissue areas populated by abundant inflammatory cells, mainly macrophages and CD3+ T cells. Using western blotting and immunocytochemistry, human blood derived lymphocytes, monocytes/macrophages and mast cells were shown to produce TIMP4. In advanced atherosclerotic lesions, TIMP4 was detected around necrotic lipid cores, whereas TIMP3 and caspase 3 resided within and around the core regions, indicating different roles for TIMP3 and TIMP4 in inflammation-induced apoptosis and in matrix turnover. In conclusion, the data demonstrate upregulation of TIMP4 in human cardiovascular disorders exhibiting inflammation, suggesting its future use as a novel systemic marker for vascular inflammation. 相似文献
109.
Lloyd-Price J Häkkinen A Kandhavelu M Marques IJ Chowdhury S Lihavainen E Yli-Harja O Ribeiro AS 《Journal of bacteriology》2012,194(7):1747-1752
Escherichia coli cells employ an asymmetric strategy at division, segregating unwanted substances to older poles, which has been associated with aging in these organisms. The kinetics of this process is still poorly understood. Using the MS2 coat protein fused to green fluorescent protein (GFP) and a reporter construct with multiple MS2 binding sites, we tracked individual RNA-MS2-GFP complexes in E. coli cells from the time when they were produced. Analyses of the kinetics and brightness of the spots showed that these spots appear in the midcell region, are composed of a single RNA-MS2-GFP complex, and reach a pole before another target RNA is formed, typically remaining there thereafter. The choice of pole is probabilistic and heavily biased toward one pole, similar to what was observed by previous studies regarding protein aggregates. Additionally, this mechanism was found to act independently on each disposed molecule. Finally, while the RNA-MS2-GFP complexes were disposed of, the MS2-GFP tagging molecules alone were not. We conclude that this asymmetric mechanism to segregate damage at the expense of aging individuals acts probabilistically on individual molecules and is capable of the accurate classification of molecules for disposal. 相似文献
110.
Strang-Karlsson S Kajantie E Pesonen AK Räikkönen K Hovi P Lahti J Heinonen K Järvenpää AL Eriksson JG Andersson S Paavonen EJ 《Chronobiology international》2010,27(9-10):1829-1842
The authors explored morningness-eveningness propensity in adults born prematurely at very low birth weight (VLBW; 1500g) and in controls born at term. At age 21 to 29 yrs, 184 participants completed the Morningness-Eveningness Questionnaire (MEQ). Compared with controls, VLBW adults scored higher in morningness propensity (group difference: 2.8 scores, 95% confidence interval: 0.1 to 5.5; p?=?.042). This finding was confined to those VLBW adults whose birth weight was not small for gestational age, and remained similar when adjusting for age, sex, and working conditions. The finding is potentially important, since morningness is associated with beneficial health outcomes. 相似文献