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991.
Dominique Jolly I. Colin Prentice Raymonde Bonnefille Aziz Ballouche Martin Bengo Patrice Brenac Guillaume Buchet David Burney Jean-Pierre Cazet Rachid Cheddadi Therese Edorh Hilaire Elenga Saida Elmoutaki Joel Guiot Fouzia Laarif Henry Lamb Anne-Marie Lezine Jean Maley Muaka Mbenza Odile Peyron Maurice Reille Isabelle Reynaud-Farrera Guy Riollet Jim C. Ritchie Emile Roche Louis Scott Immaculate Ssemmanda Herbert Straka Mohammed Umer Elise Van Campo Sikiminywa Vilimumbalo Annie Vincens Martyn Waller 《Journal of Biogeography》1998,25(6):1007-1027
Biome reconstruction from pollen and plant macrofossil data provides an objective method to reconstruct past vegetation. Biomes for Africa and the Arabian peninsula have been mapped for 6000 years bp and provide a new standard for the evaluation of simulated palaeovegetation distributions. A test using modern pollen data shows the robustness of the biomization method, which is able to predict the major vegetation types with a high confidence level. The application of the procedure to the 6000 years data set (pollen and plant macrofossil analyses) shows systematic differences from the present that are consistent with the numerous previous regional and continental interpretations, while providing a more extensive and more objective basis for such interpretations. Madagascar, eastern, southern and central Africa show only minor changes in terms of biomes, compared to present. Major changes in biome distributions occur north of 15°N, with steppe in many low-elevation sites that are now desert, and temperate xerophytic woods/scrub and warm mixed forest in the Saharan mountains. These shifts in biome distributions imply significant changes in climate, especially precipitation, between 6000 years and present, reflecting a change in monsoon extent combined with a southward expansion of Mediterranean influence. 相似文献
992.
993.
Carbapenemases are beta-lactamases that hydrolyze most beta-lactams including carbapenems. Carbapenemases are classified in four molecular classes; those belonging to class A are the chromosomally-encoded and clavulanic acid-inhibited IMI, NMC-A and SME, identified in Enterobacter cloacae and Serratia marcescens; the plasmid-encoded KPC enzymes identified in Enterobacteriaceae (and rarely in Pseudomonas aeruginosa); and the GES-type enzymes identified in Enterobacteriaceae and P. aeruginosa. The class B enzymes are the most clinically-significant carbapenemases; they are metallo-beta-lactamases, mostly of the IMP and the VIM series. They have been reported worldwide and their genes are plasmid- and integron-located, hydrolyzing all beta-lactams with the exception of aztreonam. One single plasmid-mediated AmpC beta-lactamase, CMY-10, identified in an Enterobacter aerogenes isolate, has been shown to be a cephaslosporinase with some carbapenemase properties. Finally, the class D carbapenemases are being increasingly reported, mostly in Acinetobacter baumannii, and they compromise the efficacy of imipenem and meropenem significantly. 相似文献
994.
Mohammad Nazim Uddin Patrice Dunoyer Gregory Schott Salina Akhter Chunlin Shi William J. Lucas Olivier Voinnet Jae-Yean Kim 《Nucleic acids research》2014,42(12):7971-7980
RNA silencing is an evolutionarily conserved mechanism triggered by double-stranded RNA that is processed into 21- to 24-nt small interfering (si)RNA or micro (mi)RNA by RNaseIII-like enzymes called Dicers. Gene regulations by RNA silencing have fundamental implications in a large number of biological processes that include antiviral defense, maintenance of genome integrity and the orchestration of cell fates. Although most generic or core components of the various plant small RNA pathways have been likely identified over the past 15 years, factors involved in RNAi regulation through post-translational modifications are just starting to emerge, mostly through forward genetic studies. A genetic screen designed to identify factors required for RNAi in Arabidopsis identified the serine/threonine protein kinase, TOUSLED (TSL). Mutations in TSL affect exogenous and virus-derived siRNA activity in a manner dependent upon its kinase activity. By contrast, despite their pleiotropic developmental phenotype, tsl mutants show no defect in biogenesis or activity of miRNA or endogenous trans-acting siRNA. These data suggest a possible role for TSL phosphorylation in the specific regulation of exogenous and antiviral RNA silencing in Arabidopsis and identify TSL as an intrinsic regulator of RNA interference. 相似文献
995.
Sonia Jego Denise Salvert Leslie Renouard Masatomo Mori Romain Goutagny Pierre-Hervé Luppi Patrice Fort 《PloS one》2012,7(12)
The recently discovered Nesfatin-1 plays a role in appetite regulation as a satiety factor through hypothalamic leptin-independent mechanisms. Nesfatin-1 is co-expressed with Melanin-Concentrating Hormone (MCH) in neurons from the tuberal hypothalamic area (THA) which are recruited during sleep states, especially paradoxical sleep (PS). To help decipher the contribution of this contingent of THA neurons to sleep regulatory mechanisms, we thus investigated in rats whether the co-factor Nesfatin-1 is also endowed with sleep-modulating properties. Here, we found that the disruption of the brain Nesfatin-1 signaling achieved by icv administration of Nesfatin-1 antiserum or antisense against the nucleobindin2 (NUCB2) prohormone suppressed PS with little, if any alteration of slow wave sleep (SWS). Further, the infusion of Nesfatin-1 antiserum after a selective PS deprivation, designed for elevating PS needs, severely prevented the ensuing expected PS recovery. Strengthening these pharmacological data, we finally demonstrated by using c-Fos as an index of neuronal activation that the recruitment of Nesfatin-1-immunoreactive neurons within THA is positively correlated to PS but not to SWS amounts experienced by rats prior to sacrifice. In conclusion, this work supports a functional contribution of the Nesfatin-1 signaling, operated by THA neurons, to PS regulatory mechanisms. We propose that these neurons, likely releasing MCH as a synergistic factor, constitute an appropriate lever by which the hypothalamus may integrate endogenous signals to adapt the ultradian rhythm and maintenance of PS in a manner dictated by homeostatic needs. This could be done through the inhibition of downstream targets comprised primarily of the local hypothalamic wake-active orexin- and histamine-containing neurons. 相似文献
996.
997.
The present report describes a simple method to selectively extract free fatty acids and analyze them by capillary gas-liquid chromatography. The procedure is based on the use of fumed silicon dioxide. In the presence of plasma, this material induces a rapid rise in the viscosity of the mixture and presents the ability to trap large particles such as emulsified lipids and lipoproteins. Albumin-bound fatty acids are thus left in the aqueous media. We present applications of our procedure for the analysis of free fatty acids in 0.2 ml of plasma from rat or human. By comparison with the method utilizing thin-layer chromatography for the separation of fatty acids and gas chromatography analysis, the present method has been found to be reliable and simple. The recovery of linoleic acid was 92.1 +/- 8.2%, a value which is about twice better than that obtained with the procedure using thin-layer chromatography. In particular, long-chain polyunsaturated fatty acids were better preserved. Our procedure does not require the use of organic solvents and its simplicity and reproducibility make it suitable for routine specific determination of the composition of free fatty acids in biological samples. 相似文献
998.
999.
C. Weingarten A. Moufti J.F. Desjeux T.T. Luong G. Durand J.P. Devissaguet F. Puisieux 《Life sciences》1981,28(24):2747-2752
We prepared an insulin liposome suspension by hot dispersion (50 °C) of a lipid mixture comprising dipalmitoyl phosphatidylcholine (DPPC) and cholesterol (7:2 molar ratio) in an 80 UI/ml acid bovine insulin solution, followed by two minutes of cold sonification (4 °C). Free insulin was removed by ultracentrifugation and the washed insulin liposomes were resuspended in a 1% aqueous saline solution (pH 3). Administration of these liposomes in the buccal cavity of normal rats caused clear hypoglycemia (?37% of the initial glycemia after one hour and ?44% after hours), but the solution was inactive when introduced by a strictly intragastric route. Hypoglycemic effects were also obtained when a mixture containing a liposome suspension devoid of insulin and 10 UI/100 g b.w. of free insulin was given by the buccal route (?56% of initial glycemia one hour later and ?55% after hours). These results show that the route of liposomal insulin administration strongly influences its biological effects. 相似文献
1000.