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211.
Sandip K. Badyal Nina Bhanji Alap P. Chavda Hyun Suk Jung Roger Craig Andrew F. Irvine Igor L. Barsukov Clive R. Bagshaw 《Journal of molecular biology》2011,405(4):1004-7227
The interaction between the calcium-binding protein S100A4 and the C-terminal fragments of nonmuscle myosin heavy chain IIA has been studied by equilibrium and kinetic methods. Using site-directed mutants, we conclude that Ca2+ binds to the EF2 domain of S100A4 with micromolar affinity and that the Kd value for Ca2+ is reduced by several orders of magnitude in the presence of myosin target fragments. The reduction in Kd results from a reduced dissociation rate constant (from 16 s− 1 to 0.3 s− 1 in the presence of coiled-coil fragments) and an increased association rate constant. Using peptide competition assays and NMR spectroscopy, we conclude that the minimal binding site on myosin heavy chain IIA corresponds to A1907-G1938; therefore, the site extends beyond the end of the coiled-coil region of myosin. Electron microscopy and turbidity assays were used to assess myosin fragment filament disassembly by S100A4. The latter assay demonstrated that S100A4 binds to the filaments and actively promotes disassembly rather than just binding to the myosin monomer and displacing the equilibrium. Quantitative modelling of these in vitro data suggests that S100A4 concentrations in the micromolar region could disassemble myosin filaments even at resting levels of cytoplasmic [Ca2+]. However, for Ca2+ transients to be effective in further promoting dissociation, the elevated Ca2+ signal must persist for tens of seconds. Fluorescence recovery after photobleaching of A431/SIP1 cells expressing green fluorescent protein-myosin IIA, immobilised on fibronectin micropatterns to control stress fibre location, yielded a recovery time constant of around 20 s, consistent with in vitro data. 相似文献
212.
The pre-meiotic, meiotic and tetrad stages of development in microsporangia of Alsophila setosa were studied with particular emphasis on the early establishment of patterning in the microspore wall and the subsequent development of the sporoderm. The data obtained were compared with corresponding ontogenetic stages of Psilotum nudum. Tapetal behaviour was also examined. During the tetrad period, only one layer, a thin undulating sheet, appeared alongside the plasma membrane of the tetraspores, and this was evidently formed on a pre-patterned structure – a fibrillar layer, corresponding to a kind of primexine matrix. The early free microspores had a wavy plasma membrane with a parallel, sinusoidal, thin initial sporoderm layer. The proximal apertural fold was observed to be an extended outgrowth of this initial spore envelope. Sporoderm ontogeny during the tetrad period in Alsophila and Psilotum show some common points, but also fundamental differences, mainly in the relative timing of events: in Alsophila the end of the tetrad period is the starting point for exospore development, whereas in Psilotum the exospore is already complete at this stage. Considerable differences were also observed in the tapetum of the two species. 相似文献
213.
Daniela Pica Nina Bloecher Antonio Dell’Anno Alessandra Bellucci Tommaso Pinto Lisa Pola 《Biofouling》2013,29(6):696-709
Biofouling is one of the challenges that can strongly affect the finfish farm economy. Although several studies on biofouling in aquaculture have been conducted in the Mediterranean Sea, they focused on specific taxa or were limited to a particular period of sampling. The present study investigated for the first time the development, composition and variation in a biofouling community in a finfish farm with immersion time, season and depth. The results indicate that all these factors influence biofouling succession and recruitment. Moreover, the species that had a crucial role in structuring the community and in the farm cleaning activities were the ascidian Styela plicata and the bivalve Mytilus galloprovincialis. Compared with the literature data, the results highlight the heterogeneity in the composition of the biofouling present in the Mediterranean Sea. Moreover, such knowledge of the biofouling community could provide important information about management efforts and the costs that farmers will face when siting new fish farms. 相似文献
214.
Volodymyr Trotsiuk Florian Hartig Maxime Cailleret Flurin Babst David I. Forrester Andri Baltensweiler Nina Buchmann Harald Bugmann Arthur Gessler Mana Gharun Francesco Minunno Andreas Rigling Brigitte Rohner Jonas Stillhard Esther Thürig Peter Waldner Marco Ferretti Werner Eugster Marcus Schaub 《Global Change Biology》2020,26(4):2463-2476
The response of forest productivity to climate extremes strongly depends on ambient environmental and site conditions. To better understand these relationships at a regional scale, we used nearly 800 observation years from 271 permanent long‐term forest monitoring plots across Switzerland, obtained between 1980 and 2017. We assimilated these data into the 3‐PG forest ecosystem model using Bayesian inference, reducing the bias of model predictions from 14% to 5% for forest stem carbon stocks and from 45% to 9% for stem carbon stock changes. We then estimated the productivity of forests dominated by Picea abies and Fagus sylvatica for the period of 1960–2018, and tested for productivity shifts in response to climate along elevational gradient and in extreme years. Simulated net primary productivity (NPP) decreased with elevation (2.86 ± 0.006 Mg C ha?1 year?1 km?1 for P. abies and 0.93 ± 0.010 Mg C ha?1 year?1 km?1 for F. sylvatica). During warm–dry extremes, simulated NPP for both species increased at higher and decreased at lower elevations, with reductions in NPP of more than 25% for up to 21% of the potential species distribution range in Switzerland. Reduced plant water availability had a stronger effect on NPP than temperature during warm‐dry extremes. Importantly, cold–dry extremes had negative impacts on regional forest NPP comparable to warm–dry extremes. Overall, our calibrated model suggests that the response of forest productivity to climate extremes is more complex than simple shift toward higher elevation. Such robust estimates of NPP are key for increasing our understanding of forests ecosystems carbon dynamics under climate extremes. 相似文献
215.
Peter I. Whelan Nina Kurucz William J. Pettit Vicki Krause 《Journal of vector ecology》2020,45(1):118-126
The Northern Territory (NT) of Australia is currently free of the dengue mosquito Aedes (Stegomyia) aegypti (L). However, on 17 February 2004, two Ae. aegypti adults were captured in two routine CO2‐baited encephalitis virus surveillance traps in Tennant Creek, located 990 km south of Darwin in the NT. The detection triggered an immediate survey and control response undertaken by the NT Department of Health and Community Services, followed by a Commonwealth of Australia‐funded Ae. aegypti elimination program. This report details the methods and results of the detection and subsequent elimination activities that were carried out between 2004 and 2006, returning the NT to its dengue vector‐free status. There have been very few successful Ae. aegypti elimination programs in the world. This purposeful mosquito elimination for Australia was officially declared on 5 April 2006. 相似文献
216.
217.
218.
Anmol Kumar Jaakko Kopra K?rt Varendi Lauriina L. Porokuokka Anne Panhelainen Satu Kuure Pepin Marshall Nina Karalija Mari-Anne H?rma Carolina Vilenius Kersti Lillev?li Triin Tekko Jelena Mijatovic Nita Pulkkinen Madis Jakobson Maili Jakobson Roxana Ola Erik Palm Maria Lindahl Ingrid Str?mberg Vootele V?ikar T. Petteri Piepponen Mart Saarma Jaan-Olle Andressoo 《PLoS genetics》2016,12(1)
219.
Ying Liu Christoph Bachofen Yanjing Lou Zhi Ding Ming Jiang Xianguo Lü Nina Buchmann 《Journal of Plant Ecology》2021,14(2):337
温度变化和钾添加对扁秆藨草生长及繁殖的影响
人类活动导致的气候变暖和农业面源污染已被认为是影响湿地植物生长和繁殖的重要因素。为了预 测和缓解这些人类活动的影响,研究沼泽植物如何响应这些环境变化具有重要意义。本研究选取在欧亚 大陆广泛分布的莎草科球茎植物扁秆藨草(Bolboschoenus planiculmis)为研究对象,考察气温变化(恒温: 15、20、25 °C及交替温度:20/10和30/15 °C)和钾添加(0、1、3、9 和18 mmol/L)对其生长和繁殖性状 的影响。研究结果表明,高的恒温(20、25 °C)比高的交替温度(30/15 °C)更有利于扁秆藨草球茎的形成, 而地上生物量和株高一般在较高温度下(30/15、25 °C)达到最大值。扁秆藨草的繁殖和生长性状均与施钾量 呈驼峰型关系,最适施钾量在1–3 mmol/L K。高恒温效应和最适钾浓度的交互作用对繁殖性状的促进作 用最大,但是,较高的温度(30/15和25 °C)和0–9 mmol/L的钾浓度只促进了生长性状的生长。综上所述, 扁秆藨草的种群优势度可能受益于全球变暖和额外的钾添加。 相似文献
220.
We report the chemical synthesis of Fuc(12)Gal-O(CH2)7CH3 (1) an analog of the natural blood group (O)H disaccharide Fuc(12)Gal-OR. Compound 1 was a good substrate for recombinant blood group B glycosyltransferase (GTB) and was used as a precursor for the enzymatic synthesis of the blood group B analog Gal(3)[Fuc(12)]Gal-O(CH2)7CH3 (2). To probe the mechanism of the GTB reaction, kinetic evaluations were carried out employing compound 1 or the natural acceptor disaccharide Fuc(12)Gal-O(CH2)7CH3 (3) with UDP-Gal and UDP-GalNAc donors. Comparisons of the kinetic constants for alternative donor and acceptor pairs suggest that the GTB mechanism is Theorell-Chance where donor binding precedes acceptor binding. GTB operates with retention of configuration at the anomeric center of the donor. Retaining reactions are thought to occur via a double-displacement mechanism with formation of a glycosyl-enzyme intermediate consistent with the proposed Theorell-Chance mechanism. 相似文献