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151.
Reactive oxygen species (ROS), generated as a result of various reactions, control an array of cellular processes. The role of ROS during megakaryocyte (MK) development has been a subject of interest and research. The bone marrow niche is a site of MK differentiation and maturation. In this environment, a gradient of oxygen tension, from normoxia to hypoxia results in different levels of ROS, impacting cellular physiology. This article provides an overview of major sources of ROS, their implication in different signaling pathways, and their effect on cellular physiology, with a focus on megakaryopoiesis. The importance of ROS-generating oxidases in MK biology and pathology, including myelofibrosis, is also described. 相似文献
152.
Philip A. Fay Alexia M. Kelley Andrew C. Procter Dafeng Hui Virginia L. Jin Robert B. Jackson Hyrum B. Johnson H. Wayne Polley 《Ecosystems》2009,12(5):699-714
Field studies of atmospheric CO2 effects on ecosystems usually include few levels of CO2 and a single soil type, making it difficult to ascertain the shape of responses to increasing CO2 or to generalize across soil types. The Lysimeter CO2 Gradient (LYCOG) chambers were constructed to maintain a linear gradient of atmospheric CO2 (~250 to 500 μl l−1) on grassland vegetation established on intact soil monoliths from three soil series. The chambers maintained a linear daytime
CO2 gradient from 263 μl l−1 at the subambient end of the gradient to 502 μl l−1 at the superambient end, as well as a linear nighttime CO2 gradient. Temperature variation within the chambers affected aboveground biomass and evapotranspiration, but the effects
of temperature were small compared to the expected effects of CO2. Aboveground biomass on Austin soils was 40% less than on Bastrop and Houston soils. Biomass differences between soils resulted
from variation in biomass of Sorghastrum nutans, Bouteloua curtipendula, Schizachyrium scoparium (C4 grasses), and Solidago canadensis (C3 forb), suggesting the CO2 sensitivity of these species may differ among soils. Evapotranspiration did not differ among the soils, but the CO2 sensitivity of leaf-level photosynthesis and water use efficiency in S. canadensis was greater on Houston and Bastrop than on Austin soils, whereas the CO2 sensitivity of soil CO2 efflux was greater on Bastrop soils than on Austin or Houston soils. The effects of soil type on CO2 sensitivity may be smaller for some processes that are tightly coupled to microclimate. LYCOG is useful for discerning the
effects of soil type on the CO2 sensitivity of ecosystem function in grasslands.
Author Contributions: PF conceived study, analyzed data, and wrote the paper. AK, AP analyzed data. DH, VJ, RJ, HJ, and WP
conceived study, and conducted research. 相似文献
153.
Tanja Pejovic Nupur T Pande Motomi Mori Paulette Mhawech-Fauceglia Christina Harrington Solange Mongoue-Tchokote Daniel Dim Christopher Andrews Amy Beck Yukie Tarumi Jovana Djilas Fabio Cappuccini Otavia Caballero Jiaqi Huang Samuel Levy Alexia Tsiamouri Joanna Cain Grover C Bagby Robert L Strausberg Andrew J Simpson Kunle O Odunsi 《Translational oncology》2009,2(4):341-349
154.
Marie Genet Alexia Stokes Thierry Fourcaud Joanne E. Norris 《Ecological Engineering》2010,36(3):265-275
The influence of plant diversity on slope stability was investigated at early phases of succession in a mixed forest in Sichuan, China. The first phase comprised big node bamboo (Phyllostachys nidularia Munro) only. In the second phase, bamboo co-existed with deciduous tree species and in the third phase, deciduous species existed alone. Root density at different depths and root tensile strength were determined for each species. The factor of safety (FOS) was calculated for slopes with and without vegetation for each succession phase. For phase 2, FOS was determined for different species mixtures and positions. In phase 3, simulations were performed with a single tree at the top, middle or toe of the slope. Due to its shallow root system, bamboo contributed little to slope stability. In simulations with the tree at the top or middle of the slope, FOS decreased because tree weight added a surcharge to the slope. FOS increased with the tree at the bottom of the slope. Different mixtures of species along the slope had no influence on FOS. Differences in root tensile strength between species played a small role in FOS calculations, and tree size and density were the most important factors affecting slope stability, excluding hydrological factors. 相似文献
155.
A Numerical Investigation into the Influence of Soil Type and Root Architecture on Tree Anchorage 总被引:11,自引:2,他引:9
The influence of root morphology and soil type on the mechanical behaviour of tree anchorage was investigated through numerical
modelling. We developed a simple computer program to construct three-dimensional virtual root architectural patterns. This
tool was used to build four schematic patterns: heart-, tap-, herringbone- and plate-like root systems. Each of these rooting
types was characterized by specific branching characteristics. However, the total volume (proportional to the wood biomass)
and material properties were kept constant. The finite element method was used to calculate the mechanical response of root/soil
systems when the stem was subjected to bending forces. The overturning resistance of the four schematic root patterns was
determined in four different idealistic soil types. These soils were based on Mohr–Coulomb plasticity models. Results showed
that soil internal friction modified the position of the rotation axis during tilting of the root/soil plate. Rooting depth
was a determinant parameter in sandy-like soils. Overturning resistance was greatest in heart- and tap-root systems whatever
the soil type. However, the heart root system was more resistant on clay-like soil whereas the tap root system was more resistant
on sandy-like soil. Herringbone and plate root systems were twice as less resistant on clay soils and 1.5 times less resistant
on sandy soils when compared to heart and tap-like structures. 相似文献
156.
157.
Amir-Moazami O Alexia C Charles N Launay P Monteiro RC Benhamou M 《The Journal of biological chemistry》2008,283(37):25514-25523
Engagement of the IgE receptor (FcepsilonRI) on mast cells leads to the release of preformed and newly formed mediators as well as of cytokines. The signaling pathways responsible for these responses involve tyrosine phosphorylation of multiple proteins. We previously reported the phosphorylation on tyrosine of phospholipid scramblase 1 (PLSCR1) after FcepsilonRI aggregation. Here, PLSCR1 expression was knocked down in the RBL-2H3 mast cell line using short hairpin RNA. Knocking down PLSCR1 expression resulted in significantly impaired degranulation responses after FcepsilonRI aggregation and release of vascular endothelial growth factor, whereas release of MCP-1 was minimally affected. The release of neither leukotriene C4 nor prostaglandin D2 was altered by knocking down of PLSCR1. Analysis of FcepsilonRI-dependent signaling pathways revealed that whereas tyrosine phosphorylation of ERK and Akt was unaffected, tyrosine phosphorylation of LAT was significantly reduced in PLSCR1 knocked down cells. Tyrosine phosphorylation of phospholipase Cgamma1 and consequently the mobilization of calcium were also significantly reduced in these cells. In nonactivated mast cells, PLSCR1 was found in part in lipid rafts where it was further recruited after cell activation and was constitutively associated with Lyn and Syk but not with LAT or Fyn. Altogether, these data identify PLSCR1 as a novel amplifier of FcepsilonRI signaling that acts selectively on the Lyn-initiated LAT/phospholipase Cgamma1/calcium axis, resulting in potentiation of a selected set of mast cell responses. 相似文献
158.
159.
This paper brings both intertemporal and age-dependent features to a theory of population policy at the macro-level. A Lotka-type renewal model of population dynamics is combined with a Solow/Ramsey economy. We consider a social planner who maximizes an aggregate intertemporal utility function which depends on per capita consumption. As control policies we consider migration and saving rate (both age-dependent). By using a new maximum principle for age-structured control systems we derive meaningful results for the optimal migration and saving rate in an aging population. The model used in the numerical calculations is calibrated for Austria. 相似文献
160.
Contribution of protein kinase A and protein kinase C pathways in ultraviolet B-induced IL-8 expression by human keratinocytes 总被引:2,自引:0,他引:2
We have previously demonstrated that treatment of the human keratinocyte cell line NCTC 2544 with a UVB dose equivalent to 1h exposure (100 mJ/cm2) results in a significant increase of IL-8 production. In this study, we use specific inhibitors to investigate the role of both PKA- and PKC-mediated pathways in the regulation of UVB-induced IL-8 expression in NCTC 2544 cell line. We show here that the treatment of irradiated human keratinocytes with PKA inhibitors [H89 and PKA inhibitor (PKAi)] induced a significant decrease of IL-8 production at both mRNA and protein levels. However, the regulation of IL-8 production seems to be mediated via a cAMP-independent PKA pathway, since drugs known to enhance cAMP concentrations [PGE2, cholera toxin and dibutyryl cAMP] decrease IL-8 production in irradiated cells by down-regulating NF-kappa B activation in response to UVB radiation. Using PMA (a potent pharmacological activator of PKC) and calphostin C (a specific PKC inhibitor), we demonstrated an up-regulation of IL-8 in NCTC 2544 cells and a down-regulation of the cytokine in UVB-irradiated cells, respectively. We also observed that in our experimental conditions, staurosporine, an inhibitor of both PKC and PMA-stimulated cellular responses, does not involve PKC inhibition in irradiated cells and significantly decreased NF-kappa B activity in response to UVB radiation. Finally, we concluded that a cAMP-independent PKA activation and a PKC-associated pathway are probably involved in the regulation of UVB-induced IL-8 synthesis in human keratinocytes. 相似文献