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541.
Marten Scheffer Remi Vergnon Egbert H. van Nes Jan G. M. Cuppen Edwin T. H. M. Peeters Remko Leijs Anders N. Nilsson 《PloS one》2015,10(10)
While species fulfill many different roles in ecosystems, it has been suggested that numerous species might actually share the same function in a near neutral way. So-far, however, it is unclear whether such functional redundancy really exists. We scrutinize this question using extensive data on the world’s 4168 species of diving beetles. We show that across the globe these animals have evolved towards a small number of regularly-spaced body sizes, and that locally co-existing species are either very similar in size or differ by at least 35%. Surprisingly, intermediate size differences (10–20%) are rare. As body-size strongly reflects functional aspects such as the food that these generalist predators can eat, these beetles thus form relatively distinct groups of functional look-a-likes. The striking global regularity of these patterns support the idea that a self-organizing process drives such species-rich groups to self-organize evolutionary into clusters where functional redundancy ensures resilience through an insurance effect. 相似文献
542.
Plasmids were constructed which contained two expression units encoding single-chain insulin precursors. Surprisingly, the total amount of insulin precursor produced was similar to that produced from plasmids containing a single expression unit. In this system, therefore, two expression cassettes can be brought to compete for the limited ability of the yeast cell for synthesis and secretion. Using genes encoding B(1-29)-A(1-21) and B(1-29)-Ala-Ala-Lys-A-(1-21), the slightly different precursors could be quantified individually after separation by high-performance liquid chromatography from the culture supernatant. The two-cassette system allowed a sensitive and well controlled comparison of parameters important for optimal expression of a heterologous gene in Saccharomyces cerevisiae. The system was used to compare two promoter constructions and also to evaluate the position of expression cassettes in the plasmid. Finally the codon usage in the gene to be expressed was found to influence its ability to compete for expression. 相似文献
543.
A quantitative analysis of the time- and voltage-dependent kinetics of the guard cell anion channel (GCAC1) current in guard cell protoplasts from Vicia faba was analyzed using the whole-cell patch clamp technique. The voltage-dependent steady-state activation of GCAC1 current followed a Boltzmann distribution. For the corresponding steady-state value of the activation variable a power of two was derived which yielded suitable fits of the time course of voltage-dependent current activation. The GCAC1 mediated chloride current could successfully be described in terms of the Hodgkin-Huxley equations commonly evoked for the Na channel in nerve. After step depolarizations from a potential in the range of the resting potential to potentials above the equilibrium potential for chloride an activation and also an inactivation could be described. The gating of both processes exhibited an inverse relationship on the polarity of the applied step potentials in the order of milliseconds. Deactivating tail currents decline exponentially. The presented analysis contributes to the understanding of the rising phase of the observed action potentials in guard cells of V. faba. Evidence is presented that the voltage-dependent kinetic properties of the GCAC1 current are different from those properties described for the excitable anion currents in the plasmalemma of Chara corallina (Beilby & Coster, 1979a).The authors gratefully acknowledge the encouragement of Dr. David Colquhoun to apply the Hodgkin-Huxley model to the GCAC1 channel. The work was in part supported by a grant of the Deutsche Forschungsgemeinschaft to R.H. and a grant of the Herman and Lilly Schilling Stiftung to H.-A.K. 相似文献
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546.
Marten Szibor Rolf Schreckenberg Zemfira Gizatullina Eric Dufour Marion Wiesnet Praveen K. Dhandapani Grazyna Debska-Vielhaber Juliana Heidler Ilka Wittig Tuula A. Nyman Ulrich Gärtner Andrew R. Hall Victoria Pell Carlo Viscomi Thomas Krieg Michael P. Murphy Thomas Braun Frank N. Gellerich Klaus-Dieter Schlüter Howard T. Jacobs 《Journal of cellular and molecular medicine》2020,24(6):3534-3548
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548.
Background
Global warming and the alteration of the global nitrogen cycle are major anthropogenic threats to the environment. Denitrification, the biological conversion of nitrate to gaseous nitrogen, removes a substantial fraction of the nitrogen from aquatic ecosystems, and can therefore help to reduce eutrophication effects. However, potential responses of denitrification to warming are poorly understood. Although several studies have reported increased denitrification rates with rising temperature, the impact of temperature on denitrification seems to vary widely between systems.Methodology/Principal Findings
We explored the effects of warming on denitrification rates using microcosm experiments, field measurements and a simple model approach. Our results suggest that a three degree temperature rise will double denitrification rates. By performing experiments at fixed oxygen concentrations as well as with oxygen concentrations varying freely with temperature, we demonstrate that this strong temperature dependence of denitrification can be explained by a systematic decrease of oxygen concentrations with rising temperature. Warming decreases oxygen concentrations due to reduced solubility, and more importantly, because respiration rates rise more steeply with temperature than photosynthesis.Conclusions/Significance
Our results show that denitrification rates in aquatic ecosystems are strongly temperature dependent, and that this is amplified by the temperature dependencies of photosynthesis and respiration. Our results illustrate the broader phenomenon that coupling of temperature dependent reactions may in some situations strongly alter overall effects of temperature on ecological processes. 相似文献549.
Kubin T Pöling J Kostin S Gajawada P Hein S Rees W Wietelmann A Tanaka M Lörchner H Schimanski S Szibor M Warnecke H Braun T 《Cell Stem Cell》2011,9(5):420-432
Cardiomyocyte remodeling, which includes partial dedifferentiation of cardiomyocytes, is a process that occurs during both acute and chronic disease processes. Here, we demonstrate that oncostatin M (OSM) is a major mediator of cardiomyocyte dedifferentiation and remodeling during acute myocardial infarction (MI) and in chronic dilated cardiomyopathy (DCM). Patients suffering from DCM show a strong and lasting increase of OSM expression and signaling. OSM treatment induces dedifferentiation of cardiomyocytes and upregulation of stem cell markers and improves cardiac function after MI. Conversely, inhibition of OSM signaling suppresses cardiomyocyte remodeling after MI and in a mouse model of DCM, resulting in deterioration of heart function after MI but improvement of cardiac performance in DCM. We postulate that dedifferentiation of cardiomyocytes initially protects stressed hearts but fails to support cardiac structure and function upon continued activation. Manipulation of OSM signaling provides a means to control the differentiation state of cardiomyocytes and cellular plasticity. 相似文献
550.
Levin Simon A. Anderies John M. Adger Neil Barrett Scott Bennett Elena M. Cardenas Juan Camilo Carpenter Stephen R. Crpin Anne-Sophie Ehrlich Paul Fischer Joern Folke Carl Kautsky Nils Kling Catherine Nyborg Karine Polasky Stephen Scheffer Marten Segerson Kathleen Shogren Jason van den Bergh Jeroen Walker Brian Weber Elke U. Wilen James 《Ecosystems》2022,25(3):697-711
Ecosystems - The increasing frequency of extreme events, exogenous and endogenous, poses challenges for our societies. The current pandemic is a case in point; but "once-in-a-century"... 相似文献