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排序方式: 共有491条查询结果,搜索用时 15 毫秒
81.
82.
Faure H Fontes JC Hebrard L Monteillet J Pirazzoli PA 《Science (New York, N.Y.)》1980,210(4468):421-423
An expedition under "Projet Rhéomarge" traced marine deposits along the Sénégal estuary. Leveled and dated samples have made it possible to reconstruct portions of paleogeoids of 6500, 5500, and 1800 years before present. The surfaces of these geoids show that the tilt across continental margins predicted by mathematical models is less than 1 meter from the coast to 120 kilometers inland. 相似文献
83.
Treusch S Hamamichi S Goodman JL Matlack KE Chung CY Baru V Shulman JM Parrado A Bevis BJ Valastyan JS Han H Lindhagen-Persson M Reiman EM Evans DA Bennett DA Olofsson A DeJager PL Tanzi RE Caldwell KA Caldwell GA Lindquist S 《Science (New York, N.Y.)》2011,334(6060):1241-1245
Aβ (beta-amyloid peptide) is an important contributor to Alzheimer's disease (AD). We modeled Aβ toxicity in yeast by directing the peptide to the secretory pathway. A genome-wide screen for toxicity modifiers identified the yeast homolog of phosphatidylinositol binding clathrin assembly protein (PICALM) and other endocytic factors connected to AD whose relationship to Aβ was previously unknown. The factors identified in yeast modified Aβ toxicity in glutamatergic neurons of Caenorhabditis elegans and in primary rat cortical neurons. In yeast, Aβ impaired the endocytic trafficking of a plasma membrane receptor, which was ameliorated by endocytic pathway factors identified in the yeast screen. Thus, links between Aβ, endocytosis, and human AD risk factors can be ascertained with yeast as a model system. 相似文献
84.
Murphy WJ Larkin DM Everts-van der Wind A Bourque G Tesler G Auvil L Beever JE Chowdhary BP Galibert F Gatzke L Hitte C Meyers SN Milan D Ostrander EA Pape G Parker HG Raudsepp T Rogatcheva MB Schook LB Skow LC Welge M Womack JE O'brien SJ Pevzner PA Lewin HA 《Science (New York, N.Y.)》2005,309(5734):613-617
The genome organizations of eight phylogenetically distinct species from five mammalian orders were compared in order to address fundamental questions relating to mammalian chromosomal evolution. Rates of chromosome evolution within mammalian orders were found to increase since the Cretaceous-Tertiary boundary. Nearly 20% of chromosome breakpoint regions were reused during mammalian evolution; these reuse sites are also enriched for centromeres. Analysis of gene content in and around evolutionary breakpoint regions revealed increased gene density relative to the genome-wide average. We found that segmental duplications populate the majority of primate-specific breakpoints and often flank inverted chromosome segments, implicating their role in chromosomal rearrangement. 相似文献
85.
Christelle Simon-Colin Yannick Gueguen Evelyne Bachere Achraf Kouzayha Denis Saulnier Nicolas Gayet Jean Guezennec 《Marine drugs》2015,13(6):3732-3744
Cultured pearls are the product of grafting and rearing of Pinctada margaritifera pearl oysters in their natural environment. Nucleus rejections and oyster mortality appear to result from bacterial infections or from an inappropriate grafting practice. To reduce the impact of bacterial infections, synthetic antibiotics have been applied during the grafting practice. However, the use of such antibiotics presents a number of problems associated with their incomplete biodegradability, limited efficacy in some cases, and an increased risk of selecting for antimicrobial resistant bacteria. We investigated the application of a marine antimicrobial peptide, tachyplesin, which is present in the Japanese horseshoe crab Tachypleus tridentatus, in combination with two marine bacterial exopolymers as alternative treatment agents. In field studies, the combination treatment resulted in a significant reduction in graft failures vs. untreated controls. The combination of tachyplesin (73 mg/L) with two bacterial exopolysaccharides (0.5% w/w) acting as filming agents, reduces graft-associated bacterial contamination. The survival data were similar to that reported for antibiotic treatments. These data suggest that non-antibiotic treatments of pearl oysters may provide an effective means of improving oyster survival following grafting procedures. 相似文献
86.
Increased pyrophosphate in fibroblasts and lymphoblasts from patients with hereditary diffuse articular chondrocalcinosis 总被引:2,自引:0,他引:2
The metabolic and genetic factors leading to deposition of calcium pyrophosphate crystals in cartilage of patients with chondrocalcinosis are not well understood. Analysis of cultured fibroblasts and lymphoblasts from 12 affected members of a large kindred showed a mean concentration of intracellular inorganic pyrophosphate two times greater than that in cells from unaffected family members or normal, unrelated volunteers. Increased intracellular pyrophosphate may, therefore, be a biochemical marker for the heterozygous expression of the chondrocalcinosis gene. 相似文献
87.
Jean François Emard Pierre Andre Jean -Pierre Thouez Jean Mathieu Camil Boily Michel Beaudry Andree Cholette Yves Robitaille Remi Bouchard Nicolas Daoud Francine Veilleux Denis Gauvreau 《Water, air, and soil pollution》1994,72(1-4):251-264
Accepting as founded the hypothesis of a multifactorial origin for the Alzheimer's disease (AD), we explore the possible links between the geographical distribution of AD cases according to their birth place and the geochemical profile of the Saguenay-Lac-Saint-Jean (SLSJ) territory in the province of Québec. The method used for factor analysis of correspondances (FAC) and another one based on the differences between the residential and municipal geochemical concentrations (DRMC) have been used for this purpose. The geochemical matrix of SLSJ relates the highest concentrations of nickel, copper and zinc to the sector surrounding the Jonquière municipality. Moreover, high concentrations of iron, lead and manganese were found in the northern sector of the Lac Saint-Jean. The DRMC method corroborates this strong correlation between iron, lead and manganese. Furthermore, these concentrations do not differ from the north-american geochemical standards. No single geochemical element seems to be associate with the spatial distribution of cases. It is, however, still possible that a certain synergistic effect between two or several elements could be implied in the development of the disease. According to the results of the soil analysis, there does not seem to be any association between the spatial distribution of cases and the concentration of aluminum, a chemical element that has been thought to be implied in the etiology of AD. These results are compared with those obtained by other workers in the micronesian islands, where abnormally high frequencies of amyotrophic lateral sclerosis and parkinsonism dementia have already been observed. 相似文献
88.
Basko D 《Science (New York, N.Y.)》2011,334(6056):610-611
89.
An in vitro system for adhesion and fusion of maize gametes 总被引:1,自引:0,他引:1
The development of in vitro fertilization systems in flowering plants is important for understanding and controlling the mechanisms of fertilization. Here a method is described in which isolated maize gametes fuse. In a medium containing 5 mM calcium chloride, sperm and egg cells adhere for several minutes and then fuse within 10 seconds. The method is specific to male-female gamete pairs and results in 80 percent fusion, whereas fusions with other combinations of gametic and mesophyllic cells are less frequent. Eggs fertilized in vitro do not fuse with additional male gametes, which suggests that a block to polyspermy exists. 相似文献
90.
Bibring JP Langevin Y Mustard JF Poulet F Arvidson R Gendrin A Gondet B Mangold N Pinet P Forget F Berthé M Bibring JP Gendrin A Gomez C Gondet B Jouglet D Poulet F Soufflot A Vincendon M Combes M Drossart P Encrenaz T Fouchet T Merchiorri R Belluci G Altieri F Formisano V Capaccioni F Cerroni P Coradini A Fonti S Korablev O Kottsov V Ignatiev N Moroz V Titov D Zasova L Loiseau D Mangold N Pinet P Douté S Schmitt B Sotin C Hauber E Hoffmann H Jaumann R Keller U Arvidson R Mustard JF Duxbury T 《Science (New York, N.Y.)》2006,312(5772):400-404
Global mineralogical mapping of Mars by the Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activité (OMEGA) instrument on the European Space Agency's Mars Express spacecraft provides new information on Mars' geological and climatic history. Phyllosilicates formed by aqueous alteration very early in the planet's history (the "phyllocian" era) are found in the oldest terrains; sulfates were formed in a second era (the "theiikian" era) in an acidic environment. Beginning about 3.5 billion years ago, the last era (the "siderikian") is dominated by the formation of anhydrous ferric oxides in a slow superficial weathering, without liquid water playing a major role across the planet. 相似文献