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941.
Bize P Piault R Moureau B Heeb P 《Proceedings. Biological sciences / The Royal Society》2006,273(1597):2063-2068
As fitness returns during a breeding attempt are context-dependent, parents are predicted to bias their food allocation within a brood from poor towards good condition nestlings when environmental conditions deteriorate. We tested this prediction in the Alpine swift and the European starling, two migratory bird species, by modifying an ultraviolet (UV) visual signal of condition in nestlings and exploring how parents allocate food to their young as the season progresses. We show in both species that: (i) UV light reflected by the body skin of offspring positively correlates with their stature (i.e. body mass and skeletal size) and (ii) parental favouritism towards young with more UV reflective skin gradually increases as the season progresses. Early-breeding parents supplied food preferentially to UV pale (i.e. small stature) nestlings, whereas late-breeding parents favoured UV bright offspring (i.e. large stature). These results emphasize that parents use UV signals of offspring condition to adjust their feeding strategies depending on the ecological context. 相似文献
942.
Implication of mitochondrial dysfunction and cell death in cold preservation--warm reperfusion-induced hepatocyte injury 总被引:3,自引:0,他引:3
Duval M Plin C Elimadi A Vallerand D Tillement JP Morin D Haddad PS 《Canadian journal of physiology and pharmacology》2006,84(5):547-554
Cold ischemia--warm reperfusion (CI/WR) injury of liver transplantation involves hepatocyte cell death, the nature and underlying mechanisms of which remain unclear. Isolated hepatocytes and isolated perfused livers were used to determine the prevalence of necrosis and apoptosis as well as mitochondrial dysfunction. In isolated cells, propidium iodide and Hoechst 33342 staining showed a cold-storage, time-dependent increase in necrosis, whereas apoptosis was minimal even after 48 h of hypothermia. Nonetheless, a progressive loss of mitochondrial membrane potential was observed. Translocation of mitochondrial cytochrome c toward microsomes occurred within 24 h of CI/WR, with cytochrome c reaching the cytosol later. Mitochondria isolated from whole livers subjected to CI/WR also display reduced metabolic parameters and increased susceptibility to swelling. These events are associated with increased activity of major initiator (caspase 9) and effector (caspase 3) caspases. The results demonstrate that CI/WR induces mitochondrial dysfunction in isolated cells and in the whole organ; only in the latter is that sufficient to trigger the classical mitochondrial pathway of apoptosis. Our study also provides evidence for the involvement of endoplasmic reticulum stress in CI/WR hepatocyte injury. Combined protection of mitochondria and endoplasmic reticulum may thus represent an innovative therapeutic avenue to enhance liver graft viability and functional integrity. 相似文献
943.
We examined the effect of sustained stream bank seepage during base flow conditions on the pore water nitrogen biogeochemistry
of two riparian zones in lowland agricultural areas in southern Ontario, Canada. Nitrate, ammonium and dissolved oxygen concentrations
in riparian subsurface water over a two-year period showed well-organized spatial patterns along stream bank seepage flow
paths that extended seasonally up to 25 m inland. High levels of dissolved oxygen and NO3− in stream inflow were depleted rapidly at the stream bank interface suggesting the occurrence of aerobic microbial respiration
followed by denitrification. A zone of NH4+ accumulation persisted in more anaerobic sediments inland from the bank margin, although the magnitude and intensity of the
pattern varied seasonally. A bromide tracer and NO3− co-injection at the stream bank interface indicated that bank seepage occurred along preferential flow paths in a poorly
sorted gravel layer in the two riparian zones. Depletion of NO3− in relation to co-injected bromide confirmed that the bank margin was a hot spot of biogeochemical activity within the riparian
zone. Conceptual models of humid temperate riparian zones have focused on nitrogen biogeochemistry in relation to hillslope
to stream hydrologic flow paths. However, our results suggest that sustained stream bank inflow during low flow conditions
can exert a dominant control on riparian nitrogen cycling in lowland landscapes where level riparian zones bounded by perennial
streams receive limited subsurface inflows from adjacent slopes. 相似文献
944.
Experimental demonstration of the impact of hard and soft selection regimes on polymorphism maintenance in spatially heterogeneous environments† 下载免费PDF全文
Romain Gallet Virginie Ravigné 《Evolution; international journal of organic evolution》2018,72(8):1677-1688
Predicting and managing contemporary adaption requires a proper understanding of the determinants of genetic variation. Spatial heterogeneity of the environment may stably maintain polymorphism when habitat contribution to the next generation can be considered independent of the degree of adaptation of local populations within habitats (i.e., under soft selection). In contrast, when habitats contribute proportionally to the mean fitness of the populations they host (hard selection), polymorphism is not expected to be maintained by selection. Although mathematically established decades ago, this prediction had never been demonstrated experimentally. Here, we provide an experimental test in which polymorphic populations of Escherichia coli growing in heterogeneous habitats were exposed to hard and soft selection regimes. As predicted by theory, polymorphism was preserved longer under soft selection. Complementary tests established that soft selection slowed fixation processes and could even protect polymorphism in the long term by providing a systematic advantage to rare genotypes. 相似文献
945.
Giuseppe Arena Madi Yann Cissé Samuel Pyrdziak Laurent Chatre Romain Riscal Maryse Fuentes Jamie Jon Arnold Markus Kastner Laurie Gayte Christelle Bertrand-Gaday Kevin Nay Claire Angebault-Prouteau Kerren Murray Beatrice Chabi Christelle Koechlin-Ramonatxo Béatrice Orsetti Charles Vincent François Casas Laurent Le Cam 《Molecular cell》2018,69(4):594-609.e8
946.
Suspension cultures of oil palm (Elaeis guineensis Jacq.) were established in a medium with 80 or 100 mg.l–1 2,4-dichlorophenoxyacetic acid and 1 g.l–1 activated charcoal, from calli producing embryogenic cells and protruding proembryos. The suspension was composed of meristematic clumps, breaking away and giving rise to new smaller aggregates. Under the best conditions, the initial weight increased about 4 fold in one month. Embryo differentiation was achieved when plating the clumps either directly, or after a phase in hormone-free liquid medium. In the second case, early maturation occurred in liquid medium. Secondary embryogenesis was reduced, and up to 18.1 % embryos formed shoots. Rooted plants were sucessfully transferred to soil.Abbreviations BAP
6-benzylaminopurine
- NAA
-naphthaleneacetic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid 相似文献
947.
Emilie Vassal-Stermann Albert Duranton Annie F. Black Gayane Azadiguian Julien Demaude Hugues Lortat-Jacob Lionel Breton Romain R. Vivès 《PloS one》2012,7(10)
Proteoglycans (PGs) are critically involved in major cellular processes. Most PG activities are due to the large interactive properties of their glycosaminoglycan (GAG) polysaccharide chains, whose expression and fine structural features are tightly controlled by a complex and highly regulated biosynthesis machinery. Xylosides are known to bypass PG-associated GAG biosynthesis and prime the assembly of free polysaccharide chains. These are, therefore, attractive molecules to interfere with GAG expression and function. Recently, we have developed a new xyloside derivative, C-Xyloside, that shares classical GAG-inducing xyloside activities while exhibiting improved metabolic stability. We have previously shown that C-Xyloside had beneficial effects on skin homoeostasis/regeneration using a number of models, but its precise effects on GAG expression and fine structure remained to be addressed. In this study, we have therefore investigated this in details, using a reconstructed dermal tissue as model. Our results first confirmed that C-Xyloside strongly enhanced synthesis of GAG chains, but also induced significant changes in their structure. C-Xyloside primed GAGs were exclusively chondroitin/dermatan sulfate (CS/DS) that featured reduced chain size, increased O-sulfation, and changes in iduronate content and distribution. Surprisingly, C-Xyloside also affected PG-borne GAGs, the main difference being observed in CS/DS 4-O/6-O-sulfation ratio. Such changes were found to affect the biological properties of CS/DS, as revealed by the significant reduction in binding to Hepatocyte Growth Factor observed upon C-Xyloside treatment. Overall, this study provides new insights into the effect of C-Xyloside on GAG structure and activities, which opens up perspectives and applications of such compound in skin repair/regeneration. It also provides a new illustration about the use of xylosides as tools for modifying GAG fine structure/function relationships. 相似文献
948.
Simó Graells Srdjan Aćimović Giorgio Volpe Romain Quidant 《Plasmonics (Norwell, Mass.)》2010,5(2):135-139
Electron beam induced deposition (EBID) is used to grow on a transparent substrate plasmonic antennas formed by gold nanorods. We first discuss the influence of the growth parameters on the geometrical homogeneity of the structures. The optical response of optimized rods with different aspect ratios are measured using scattering spectroscopy. The optical data show antenna resonances in good agreement with 3D numerical simulations for pure gold antennas, validating EBID as a novel relevant technique for the fabrication of plasmonic nanostructures. 相似文献
949.
Schuck PF Tonin A da Costa Ferreira G Viegas CM Latini A Duval Wannmacher CM de Souza Wyse AT Dutra-Filho CS Wajner M 《Cellular and molecular neurobiology》2007,27(1):147-160
Growing evidence indicates that some metabolites derived from the kynurenine pathway, the major route of l-tryptophan catabolism, are involved in the neurotoxicity associated with several brain disorders, such as Huntington’s disease,
Parkinson’s disease and Alzheimer’s disease, as well as in glutaryl-CoA dehydrogenase deficiency (GAI). Considering that the
pathophysiology of the brain damage in these neurodegenerative disorders is not completely defined, in the present study,
we investigated the in vitro effect of l-kynurenine (Kyn), kynurenic acid (KA), 3-hydroxykynurenine (3HK), 3-hydroxyanthranilic acid (3HA) and anthranilic acid (AA)
on some parameters of energy metabolism, namely glucose uptake, 14CO2 production from [U-14C] glucose, [1-14C] acetate and [1,5-14C] citrate, as well as on the activities of the respiratory chain complexes I–IV and Na+,K+-ATPase activity in cerebral cortex from 30-day-old rats. We observed that all compounds tested, except l-kynurenine, significantly increased glucose uptake and inhibited 14CO2 production from [U-14C] glucose, [1-14C] acetate and [1,5-14C] citrate. In addition, the activities of complexes I, II and IV of the respiratory chain were significantly inhibited by
3HK, while 3HA inhibited complexes I and II activities and AA inhibited complexes I–III activities. Moreover, Na+,K+-ATPase activity was not modified by these kynurenines. Taken together, our present data provide evidence that various kynurenine
intermediates provoke impairment of brain energy metabolism. 相似文献
950.
Florent Levavasseur Patrice K. Kouakou Julie Constantin Romain Cresson Fabien Ferchaud Romain Girault Vincent Jean-Baptiste Hélène Lagrange Sylvain Marsac Sylvain Pellerin Sabine Houot 《Global Change Biology Bioenergy》2023,15(2):224-238
Energy cover crops for biogas production through anaerobic digestion (AD) are inserted between two primary crops. They replace either bare soil or nonharvested cover crops, and their management is usually intensified to produce more biomass. They allow the production of renewable energy as well as digestate, used as an organic fertilizer, without directly competing with food production. Because of the increased biomass production and export and of the return of a digested biomass to the soil, the impact of energy cover crops on soil organic carbon (SOC) is questioned. The objective of this paper was to study the difference in SOC stocks induced by the introduction of energy cover crops for AD coupled with the application of the resulting amount of digestate. We used the AD model Sys-Metha combined with the soil C model AMG to simulate SOC stocks for 13 case studies in France, with scenarios comparing different intercrop management practices, with or without cover crops, harvested or not. Our results indicated that the higher biomass production of energy cover crops (from 6.7 to 11.1 t DM ha−1) in comparison with nonharvested cover crops (2 t DM ha−1) or bare soil led to higher humified C input (belowground input and digestate), despite the high C fraction exported in AD. This resulted in an increase in SOC stocks in comparison with nonharvested cover crops or bare soil (from 0.01 to 0.12 t C ha−1 year−1 over 30 years). The uncertainties in the model parameters did not modify these results. However, in the case of equal biomass production between energy cover crops and nonharvested cover crops, SOC stocks would be lower with energy cover crops. 相似文献