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排序方式: 共有1007条查询结果,搜索用时 31 毫秒
271.
Haskin LA Wang A Jolliff BL McSween HY Clark BC Des Marais DJ McLennan SM Tosca NJ Hurowitz JA Farmer JD Yen A Squyres SW Arvidson RE Klingelhöfer G Schröder C de Souza PA Ming DW Gellert R Zipfel J Brückner J Bell JF Herkenhoff K Christensen PR Ruff S Blaney D Gorevan S Cabrol NA Crumpler L Grant J Soderblom L 《Nature》2005,436(7047):66-69
Gusev crater was selected as the landing site for the Spirit rover because of the possibility that it once held a lake. Thus one of the rover's tasks was to search for evidence of lake sediments. However, the plains at the landing site were found to be covered by a regolith composed of olivine-rich basaltic rock and windblown 'global' dust. The analyses of three rock interiors exposed by the rock abrasion tool showed that they are similar to one another, consistent with having originated from a common lava flow. Here we report the investigation of soils, rock coatings and rock interiors by the Spirit rover from sol (martian day) 1 to sol 156, from its landing site to the base of the Columbia hills. The physical and chemical characteristics of the materials analysed provide evidence for limited but unequivocal interaction between water and the volcanic rocks of the Gusev plains. This evidence includes the softness of rock interiors that contain anomalously high concentrations of sulphur, chlorine and bromine relative to terrestrial basalts and martian meteorites; sulphur, chlorine and ferric iron enrichments in multilayer coatings on the light-toned rock Mazatzal; high bromine concentration in filled vugs and veins within the plains basalts; positive correlations between magnesium, sulphur and other salt components in trench soils; and decoupling of sulphur, chlorine and bromine concentrations in trench soils compared to Gusev surface soils, indicating chemical mobility and separation. 相似文献
272.
Steffens S Veillard NR Arnaud C Pelli G Burger F Staub C Karsak M Zimmer A Frossard JL Mach F 《Nature》2005,434(7034):782-786
Atherosclerosis is a chronic inflammatory disease, and is the primary cause of heart disease and stroke in Western countries. Derivatives of cannabinoids such as delta-9-tetrahydrocannabinol (THC) modulate immune functions and therefore have potential for the treatment of inflammatory diseases. We investigated the effects of THC in a murine model of established atherosclerosis. Oral administration of THC (1 mg kg(-1) per day) resulted in significant inhibition of disease progression. This effective dose is lower than the dose usually associated with psychotropic effects of THC. Furthermore, we detected the CB2 receptor (the main cannabinoid receptor expressed on immune cells) in both human and mouse atherosclerotic plaques. Lymphoid cells isolated from THC-treated mice showed diminished proliferation capacity and decreased interferon-gamma secretion. Macrophage chemotaxis, which is a crucial step for the development of atherosclerosis, was also inhibited in vitro by THC. All these effects were completely blocked by a specific CB2 receptor antagonist. Our data demonstrate that oral treatment with a low dose of THC inhibits atherosclerosis progression in the apolipoprotein E knockout mouse model, through pleiotropic immunomodulatory effects on lymphoid and myeloid cells. Thus, THC or cannabinoids with activity at the CB2 receptor may be valuable targets for treating atherosclerosis. 相似文献
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Marise Mangeney-Andréani Françoise Beaugé J. Nordmann R. Nordmann 《Cellular and molecular life sciences : CMLS》1981,37(6):545-546
Summary Addition of glucagon 5 min after ethanol was found to stimulate the rate of ethanol oxidation in hepatocytes isolated from starved rats. This stimulation is of the same order of magnitude as that mediated by asparagine. The glucagon effect is suppressed by antiproteolytic agents such as insulin or NH4Cl. The stimulatingeffect of glucagon on ethanol oxidation is probably liked to enhanced proteolysis andan elevated glutamate level in the hepatocytes.Acknowledgments. this investigation was supported by grants from the Institut de la Santé de la Recherche Médicale, the Scientific Council of the Faculté de Médecine Paris-Ouest and the Ecole Pratique des Hautes Etudes (3rd section). 相似文献
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Maria Luiza Beçak W. Beçak L. D. Vizotto 《Cellular and molecular life sciences : CMLS》1970,26(5):545-546
Resumen La ocurrencia de poliploidia ha sido relatada en anuros de la familia Ceratophrydidae incluyendo la especie tetraploideO. americanus (4n=44). En una área geográfica distinta, sin embargo, fue observada una población diploide deO. americanus (2n=22). Fueron obtenidos híbridos intraespecíficos triploides (3n=33) por cruzamiento de ejemplares diploides y tetraploides deO. americanus. 相似文献
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J. Coloma M. J. Gómez-Lechón M. D. García J. E. Feliu J. Báguena 《Cellular and molecular life sciences : CMLS》1981,37(9):941-943
Summary Primary cultures of adult rat liver parenchymal cells showed a progressive rise of gamma-glutamyl transpeptidase (GGT) activity (E.C. 2.3.2.2.) after the first 5 days of culture. The presence of dexamethasone and other synthetic glucocorticoids in the culture medium partially prevented this increase.Supported by a research grant (No. 12/180/76) from the Spanish Instituto Nacional de la Salud, Ministerio de Sanidad y Seguridad Social. 相似文献