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11.
EPR studies of Mn2+ binding to bovine pancreatic deoxyribonuclease I show that the enzyme can bind three Mn2+ ions at pH 7.5 and 2 degrees. Two sites bind Mn2+ strongly, with a Kd of 10(-4)M, and the third binds Mn2+ weakly, with a Kd of 10(-3)M. Ca2+ competes with the two strong sites, whereas Mg2+ competes only with one of them, indicating that both sites are not equivalent. Mn2+ binding to DNA has been confirmed by EPR measurements. Two types of sites, with different affinities for Mn2+ binding, were found on DNA molecules, one with a Kd of 1.2 times 10(-4)M and the other with a Kd of 10(-3)M. Mg2+ ions can displace Mn2+ from the high affinity sites, but not from the low affinity sites. These results suggest the Mn2+ binds not only to the phosphate groups, but also to the electron donor groups of the base rings. 相似文献
12.
William J. Sutherland Rosalind Aveling Thomas M. Brooks Mick Clout Lynn V. Dicks Liz Fellman Erica Fleishman David W. Gibbons Brandon Keim Fiona Lickorish Kathryn A. Monk Diana Mortimer Lloyd S. Peck Jules Pretty Johan Rockström Jon Paul Rodríguez Rebecca K. Smith Mark D. Spalding Femke H. Tonneijck Andrew R. Watkinson 《Trends in ecology & evolution》2014
13.
Liz Kisslov Nurit HadadMarina Rosengraten Rachel Levy 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2012,1821(9):1224-1234
Cytosolic phospholipase A2α (cPLA2α) up-regulation has been reported in human colorectal cancer cells, thus we aimed to elucidate its role in the proliferation of the human colorectal cancer cell line, HT-29. EGF caused a rapid activation of cPLA2α which coincided with a significant increase in cell proliferation. The inhibition of cPLA2α activity by pyrrophenone or by antisense oligonucleotide against cPLA2α (AS) or inhibition of prostaglandin E2 (PGE2) production by indomethacin resulted with inhibition of cell proliferation, that was restored by addition of PGE2. The secreted PGE2 activated both protein kinase A (PKA) and PKB/Akt pathways via the EP2 and EP4 receptors. Either, the PKA inhibitor (H-89) or the PKB/Akt inhibitor (Ly294002) caused a partial inhibition of cell proliferation which was restored by PGE2. But, inhibited proliferation in the presence of both inhibitors could not be restored by addition of PGE2. AS or H-89, but not Ly294002, inhibited CREB activation, suggesting that CREB activation is mediated by PKA. AS or Ly294002, but not H-89, decreased PKB/Akt activation as well as the nuclear localization of β-catenin and cyclin D1 and increased the plasma membrane localization of β-catenin with E-cadherin, suggesting that these processes are regulated by the PKB pathway. Similarly, Caco-2 cells exhibited cPLA2α dependent proliferation via activation of both PKA and PKB/Akt pathways. In conclusion, our findings suggest that the regulation of HT-29 proliferation is mediated by cPLA2α-dependent PGE2 production. PGE2via EP induces CREB phosphorylation by the PKA pathway and regulates β-catenin and cyclin D1 cellular localization by PKB/Akt pathway. 相似文献
14.
Sensitivity analysis, the study of how ecological variables of interest respond to changes in external conditions, is a theoretically well‐developed and widely applied approach in population ecology. Though the application of sensitivity analysis to predicting the response of species‐rich communities to disturbances also has a long history, derivation of a mathematical framework for understanding the factors leading to robust coexistence has only been a recent undertaking. Here we suggest that this development opens up a new perspective, providing advances ranging from the applied to the theoretical. First, it yields a framework to be applied in specific cases for assessing the extinction risk of community modules in the face of environmental change. Second, it can be used to determine trait combinations allowing for coexistence that is robust to environmental variation, and limits to diversity in the presence of environmental variation, for specific community types. Third, it offers general insights into the nature of communities that are robust to environmental variation. We apply recent community‐level extensions of mathematical sensitivity analysis to example models for illustration. We discuss the advantages and limitations of the method, and some of the empirical questions the theoretical framework could help answer. 相似文献
15.
Ivana Rosenzweig Matthew J. Kempton William R. Crum Martin Glasser Milan Milosevic Sandor Beniczky Douglas R. Corfield Steven C. Williams Mary J. Morrell 《PloS one》2013,8(12)
The full impact of multisystem disease such as obstructive sleep apnoea (OSA) on regions of the central nervous system is debated, as the subsequent neurocognitive sequelae are unclear. Several preclinical studies suggest that its purported major culprits, intermittent hypoxia and sleep fragmentation, can differentially affect adult hippocampal neurogenesis. Although the prospective biphasic nature of chronic intermittent hypoxia in animal models of OSA has been acknowledged, so far the evidence for increased ‘compensatory’ neurogenesis in humans is uncertain. In a cross-sectional study of 32 patients with mixed severity OSA and 32 non-apnoeic matched controls inferential analysis showed bilateral enlargement of hippocampi in the OSA group. Conversely, a trend for smaller thalami in the OSA group was noted. Furthermore, aberrant connectivity between the hippocampus and the cerebellum in the OSA group was also suggested by the correlation analysis. The role for the ischemia/hypoxia preconditioning in the neuropathology of OSA is herein indicated, with possible further reaching clinical implications. 相似文献
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17.
Hansford Kayleigh M. McGinley Liz Wilkinson Samantha Gillingham Emma L. Cull Ben Gandy Sara Carter Daniel P. Vaux Alexander G. C. Richards Simon Hayes Alister Medlock Jolyon M. 《Experimental & applied acarology》2021,84(3):593-606
Experimental and Applied Acarology - Assessing the risk of tick-borne disease in areas with high visitor numbers is important from a public health perspective. Evidence suggests that tick presence,... 相似文献
18.
Human Ecology - I address a contentious element in forest property relations to illustrate the role of ownership in protecting and expanding of forest cover by examining the extent to... 相似文献
19.
Alena Bartukov Arinawa Liz Filartiga Tom Herben Jianqiang Qian Jitka Klimeov 《Annals of botany》2021,127(7):931
Background and AimsRoot sprouting (RS), i.e. the ability to form adventitious buds on roots, is an important form of clonal growth in a number of species, and serves as both a survival strategy and a means of spatial expansion, particularly in plants growing in severely and recurrently disturbed habitats. Occurrence and/or success of plants in severely and recurrently disturbed habitats are determined by two components, namely the ability to produce adventitious buds on roots and the vigour of their production. As mechanisms behind different magnitudes of RS remain unclear, our study investigates: (1) whether the presence or absence of specific tissues in roots can promote or limit RS; and (2) whether there is some relationship between RS ability, RS vigour and species niche.MethodsWe studied RS ability together with RS vigour in 182 Central European herbaceous species under controlled experimental conditions. We used phylogenetic logistic regressions to model the presence of RS, RS vigour, the relationship between RS and anatomical traits and the relationship between RS and parameters of species niches.Key ResultsA quarter of herbs examined were able to produce adventitious buds on roots. They were characterized by their preference for open dry habitats, the presence of secondary root thickening and the occurrence of sclerified cortical cells in roots. Root sprouting vigour was not associated with any specific anatomical pattern, but was correlated with the environmental niches of different species, indicating that preferred disturbed and dry habitats might represent a selection pressure for more vigorous root sprouters than undisturbed and wet habitats.ConclusionsOur study shows that sprouting from roots is quite common in temperate dicotyledonous herbs. Two components of RS – ability and vigour – should be considered separately in future studies. We would also like to focus more attention on RS in herbs from other regions as well as on external forces and internal mechanisms regulating evolution and the functions of RS in both disturbed and undisturbed habitats. 相似文献
20.
K. Göran Ronquist Bo Ek Jane Morrell Anneli Stavreus-Evers Bodil Ström Holst Patrice Humblot Gunnar Ronquist Anders Larsson 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013