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101.
Journal of Mathematical Biology - For structured populations with an annual breeding season, life-stage interactions and behavioral tactics may occur on a faster time scale than that of population... 相似文献
102.
John T Hancock Dan Henson Mukanthu Nyirenda Radhika Desikan Judith Harrison Mervyn Lewis Jenna Hughes Steven J Neill 《Plant Physiology and Biochemistry》2005,43(9):828-835
Hydrogen peroxide (H2O2) is now recognised as a key signalling molecule in eukaryotes. In plants, H2O2 is involved in regulating stomatal closure, gravitropic responses, gene expression and programmed cell death. Although several kinases, such as oxidative signal-inducible 1 (OXI1) kinase and mitogen-activated protein kinases are known to be activated by exogenous H2O2, little is known about the proteins that directly react with H2O2. Here, we utilised a proteomic approach, using iodoacetamide-based fluorescence tagging of proteins in conjunction with mass spectrometric analysis, to identify several proteins that might be potential targets of H2O2 in the cytosolic fraction of Arabidopsis thaliana, the most prominent of which was cytosolic glyceraldehyde 3-phosphate dehydrogenase (cGAPDH; EC 1.2.1.12). cGAPDH from Arabidopsis is inactivated by H2O2 in vitro, and this inhibition is reversible by the subsequent addition of reductants such as reduced glutathione (GSH). It has been suggested recently that Arabidopsis GAPDH has roles outside of its catalysis as part of glycolysis, while in other systems this includes that of mediating reactive oxygen species (ROS) signalling. Here, we suggest that cGAPDH in Arabidopsis might also have such a role in mediating ROS signalling in plants. 相似文献
103.
The most abundant β-amylase (EC 3.2.1.2) in pea (Pisum sativum L.) was purified greater than 880-fold from epicotyls of etiolated germinating seedlings by anion exchange and gel filtration chromatography, glycogen precipitation, and preparative electrophoresis. The electrophoretic mobility and relative abundance of this β-amylase are the same as that of an exoamylase previously reported to be primarily vacuolar. The enzyme was determined to be a β-amylase by end product analysis and by its inability to hydrolyze β-limit dextrin and to release dye from starch azure. Pea β-amylase is an approximate 55 to 57 kilodalton monomer with a pl of 4.35, a pH optimum of 6.0 (soluble starch substrate), an Arrhenius energy of activation of 6.28 kilocalories per mole, and a Km of 1.67 milligrams per milliliter (soluble starch). The enzyme is strongly inhibited by heavy metals, p-chloromer-curiphenylsulfonic acid and N-ethylmaleimide, but much less strongly by iodoacetamide and iodoacetic acid, indicating cysteinyl sulfhydryls are not directly involved in catalysis. Pea β-amylase is competitively inhibited by its end product, maltose, with a Ki of 11.5 millimolar. The enzyme is partially inhibited by Schardinger maltodextrins, with α-cyclohexaamylose being a stronger inhibitor than β-cycloheptaamylose. Moderately branched glucans (e.g. amylopectin) were better substrates for pea β-amylase than less branched or non-branched (amyloses) or highly branched (glycogens) glucans. The enzyme failed to hydrolyze native starch grains from pea and glucans smaller than maltotetraose. The mechanism of pea β-amylase is the multichain type. Possible roles of pea β-amylase in cellular glucan metabolism are discussed. 相似文献
104.
Phospholipid Fatty Acid Composition of the Syntrophic Anaerobic Bacterium Syntrophomonas wolfei 下载免费PDF全文
J. Michael Henson Michael J. McInerney P. Shawn Beaty Janet Nickels David C. White 《Applied microbiology》1988,54(6):1570-1574
The membrane phospholipid fatty acids (PLFAs) from several cocultures and a pure culture of Syntrophomonas wolfei were determined by capillary column gas chromatography. Cocultures of S. wolfei with a Desulfovibrio sp. contained PLFAs from both organisms, whereas PLFAs from a coculture with Methanospirillum hungatei contained very little biomass to analyze. The pure culture of S. wolfei grown on crotonate provided the best material for analysis of the PLFAs. The predominant PLFAs of S. wolfei were the monounsaturated 16:1ω7c and 16:1ω9c and the saturated 16:0 and 14:0. A low concentration of the diunsaturated 18:2ω6 was detected. The PLFA analysis provides additional information for consideration in the determination of the profile of PLFAs obtained from anaerobic environments. In addition, this information may aid in the understanding of the physiology and phylogeny of S. wolfei and other syntrophic bacteria. 相似文献
105.
D L Bratton E Dreyer J M Kailey V A Fadok K L Clay P M Henson 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(2):514-523
Recent studies suggest that cellular internalization of platelet-activating factor (PAF), a potent ether phospholipid mediator of inflammation, is modulated by, as yet undefined cellular mechanisms. Using an albumin extraction method, the internalization of PAF and several PAF analogues was studied in the resting and stimulated human neutrophil. Our data demonstrate that internalization of these analogues is largely dependent on the state of cellular activation and that the process is not specific for certain unique structural features of the PAF molecule including the 1-position ether linkage, 2-position acetyl substitution, or choline polar head group. Furthermore, the internalization process was shown not to be dependent on the PAF receptor, metabolism of the molecule, or the process of endocytosis. Data are presented to suggest that the route of internalization of PAF is enhanced transbilayer movement (flipping) across the plasma membrane occurring as a result of changes in membrane physical properties accompanying cellular activation. It is proposed that in addition to enhanced internalization of PAF, modulation of PAF biosynthesis and net release from the stimulated neutrophil may be consequences of enhanced transbilayer movement of PAF across the activated plasma membrane. 相似文献
106.
Exposure of phosphatidylserine on the surface of apoptotic lymphocytes triggers specific recognition and removal by macrophages. 总被引:75,自引:0,他引:75
V A Fadok D R Voelker P A Campbell J J Cohen D L Bratton P M Henson 《Journal of immunology (Baltimore, Md. : 1950)》1992,148(7):2207-2216
During normal tissue remodeling, macrophages remove unwanted cells, including those that have undergone programmed cell death, or apoptosis. This widespread process extends to the deletion of thymocytes (negative selection), in which cells expressing inappropriate Ag receptors undergo apoptosis, and are phagocytosed by thymic macrophages. Although phagocytosis of effete leukocytes by macrophages has been known since the time of Metchnikoff, only recently has it been recognized that apoptosis leads to surface changes that allow recognition and removal of these cells before they are lysed. Our data suggest that macrophages specifically recognize phosphatidylserine that is exposed on the surface of lymphocytes during the development of apoptosis. Macrophage phagocytosis of apoptotic lymphocytes was inhibited, in a dose-dependent manner, by liposomes containing phosphatidyl-L-serine, but not by liposomes containing other anionic phospholipids, including phosphatidyl-D-serine. Phagocytosis of apoptotic lymphocytes was also inhibited by the L isoforms of compounds structurally related to phosphatidylserine, including glycerophosphorylserine and phosphoserine. The membranes of apoptotic lymphocytes bound increased amounts of merocyanine 540 dye relative to those of normal cells, indicating that their membrane lipids were more loosely packed, consistent with a loss of membrane phospholipid asymmetry. Apoptotic lymphocytes were shown to express phosphatidylserine (PS) externally, because PS on their surfaces was accessible to derivatization by fluorescamine, and because apoptotic cells expressed procoagulant activity. These observations suggest that apoptotic lymphocytes lose membrane phospholipid asymmetry and expose phosphatidylserine on the outer leaflet of the plasma membrane. Macrophages then phagocytose apoptotic lymphocytes after specific recognition of the exposed PS. 相似文献
107.
Extracts of germinated barley (Hordeum vulgare L.) seeds of 41 different genotypes were analyzed for their activities of alpha-amylase, beta-amylase, alpha-glucosidase, and debranching enzyme and for their abilities to hydrolyze boiled soluble starch, nonboiled soluble starch, and starch granules extracted from barley seeds with water. Linear correlation analysis, used to quantitate the interactions between the seven parameters, revealed that boiled soluble starch was not a good substrate for predicting activities of enzymes functioning in in vivo starch hydrolysis as the extracts' abilities to hydrolyze boiled soluble starch was not correlated with their abilities to hydrolyze native starch granules. Activities of alpha-amylase and alpha-glucosidase were positively and significantly correlated with the seed extracts' abilities to hydrolyze all three starches. beta-Amylase was only significantly correlated with hydrolysis of boiled soluble starch. No significant correlations existed between debranching enzyme activity and hydrolysis of any of the three starches. Interactions between the four enzymes as they functioned together to hydrolyze the three types of starch were evaluated by path coefficient analysis. alpha-Amylase contributed to hydrolyses of all three starches primarily by its direct effect (noninteractive component). This direct contribution increased as the substrate progressed from the completely artificial boiled soluble starch, to the most physiologically significant substrate, native starch granules. alpha-Glucosidase contributed to the hydrolysis of boiled soluble starch primarily by its direct effect (noninteractive) yet contributed to starch granule hydrolysis primarily via its interaction with alpha-amylase (indirect effect). The contribution of beta-amylase to hydrolysis of boiled soluble starch was direct and it did not contribute significantly to hydrolysis of native starch granules. 相似文献
108.
Human CD8+ EMRA T cells display a senescence‐associated secretory phenotype regulated by p38 MAPK 下载免费PDF全文
Lauren A. Callender Elizabeth C. Carroll Robert W. J. Beal Emma S. Chambers Sussan Nourshargh Arne N. Akbar Sian M. Henson 《Aging cell》2018,17(1)
Cellular senescence is accompanied by a senescence‐associated secretory phenotype (SASP). We show here that primary human senescent CD8+ T cells also display a SASP comprising chemokines, cytokines and extracellular matrix remodelling proteases that are unique to this subset and contribute to age‐associated inflammation. We found the CD8+ CD45RA+CD27? EMRA subset to be the most heterogeneous, with a population aligning with the naïve T cells and another with a closer association to the effector memory subset. However, despite the differing processes that give rise to these senescent CD8+ T cells once generated, they both adopt a unique secretory profile with no commonality to any other subset, aligning more closely with senescence than quiescence. Furthermore, we also show that the SASP observed in senescent CD8+ T cells is governed by p38 MAPK signalling. 相似文献
109.
110.
William?R.?Henson Fong-Fu?Hsu Gautam?DantasView authors OrcID profile Marcus?Foston 《Biotechnology for biofuels》2018,11(1):339