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排序方式: 共有1874条查询结果,搜索用时 15 毫秒
981.
982.
Kullander K Butt SJ Lebret JM Lundfald L Restrepo CE Rydström A Klein R Kiehn O 《Science (New York, N.Y.)》2003,299(5614):1889-1892
Local circuits in the spinal cord that generate locomotion are termed central pattern generators (CPGs). These provide coordinated bilateral control over the normal limb alternation that underlies walking. The molecules that organize the mammalian CPG are unknown. Isolated spinal cords from mice lacking either the EphA4 receptor or its ligand ephrinB3 have lost left-right limb alternation and instead exhibit synchrony. We identified EphA4-positive neurons as an excitatory component of the locomotor CPG. Our study shows that dramatic locomotor changes can occur as a consequence of local genetic rewiring and identifies genes required for the development of normal locomotor behavior. 相似文献
983.
The myxomycetes are a group of protists that form a monophyletic taxon in the phylum Amoebozoa. Evidence of their evolutionary success is the fact that they account for more species (ca. 900 are currently recognized) than the combined total for the rest of the Amoebozoa. Moreover, myxomycetes are present in every terrestrial environment investigated to date and also, as amoebae or flagellated cells, in aquatic environments where they cannot form fruiting bodies. Even if culture-based methods tend to underestimate their occurrence in soil, myxomycetes probably account for ∼50% of soil amoebae. The emergence of molecular-based methods has revolutionized our concepts of biodiversity, but myxomycetes are conspicuously absent from all environmental surveys. Herein we show that this is due to their highly diverging SSU rRNA gene sequences, which contain numerous Group I introns.Further proof comes from a recent study that used a massive sequencing approach without primer bias to amplify RNAs. The results obtained show that the mycetozoans (myxomycetes along with dictyostelids and protostelids) are indeed a dominant group of soil protozoans. 相似文献
984.
985.
Gabriella Sonnante Anna Vittoria Carluccio Roser Vilatersana Domenico Pignone 《Genetic Resources and Crop Evolution》2007,54(3):483-495
The evolutionary history of artichoke and cultivated cardoon and their relationships to wild allies of the genus Cynara are not fully understood yet. To try resolve the evolutionary patterns leading to the domestication of these two crops, a
study of molecular evolution was undertaken. The species C. cardunculus, including artichoke, cultivated and wild cardoon, together with four wild Cynara species were taken into consideration. Internal (ITS) and external (ETS) rDNA transcribed spacers were used as markers of
nuclear genome, the psbA-trnH spacer as a marker of chloroplast genome. Sequences were analysed using phylogenetic analysis packages. Molecular data indicate
that the whole genus is quite recent and that the domestication of artichoke and cultivated cardoon, crops diverging for reproduction
system and use, are independent events which diverge in time and space. As for wild Cynara species, an evolutionary pattern consistent with their present geographical distribution was hypothesized in relation to
the climatic changes occurring in the Mediterranean during the last 20 millennia: C. humilis and C. cornigera appeared to have differentiated first, C. syriaca and C. baetica were differentiated in a second period, while C. cardunculus showed to be the most recent and plastic species. The high plasticity of C. cardunculus has not only allowed its nowadays wide distribution, but has also given the potential for domestication.
Dedicated to the memory of Richard Neville Lester (1937–2006) who greatly contributed to the understanding of the evolution,
domestication, and genetic resources of eggplants as well as to the biosystematics and taxonomy of allied species.
IGV Publication N. 78 of the Institute of Plant Genetics, CNR 相似文献
986.
Anna Peterson 《Agriculture and Human Values》2000,17(1):95-106
This review essay examines several recentbooks about agriculture, including two books on thelinks between cultural and biological diversity intraditional agriculture, two books on the US farmcrisis, and a collected volume examining globalaspects of agricultural restructuring andsustainability. Finally, a history of ``alternative'agriculture provides a framework for thinking aboutthe ways the different cases shed light on the complexrelations between tradition and innovation inagriculture. A historical perspective highlights theextent to which ``alternative' is a relative term. Themonocrop, ``factory' mode that dominate US agriculturetoday certainly differs from what has characterizedfarming for most of history and in most of the world.Small-scale, more or less organic, diversified farms,which appear so ``alternative' in the present context,have until lately counted as the norm, here andelsewhere. These books also highlight both the dangersof the currently dominant industrial agriculture andthe potential for genuine alternatives. 相似文献
987.
Lyuksyutova AI Lu CC Milanesio N King LA Guo N Wang Y Nathans J Tessier-Lavigne M Zou Y 《Science (New York, N.Y.)》2003,302(5652):1984-1988
Commissural neurons in the mammalian dorsal spinal cord send axons ventrally toward the floor plate, where they cross the midline and turn anteriorly toward the brain; a gradient of chemoattractant(s) inside the spinal cord controls this turning. In rodents, several Wnt proteins stimulate the extension of commissural axons after midline crossing (postcrossing). We found that Wnt4 messenger RNA is expressed in a decreasing anterior-to-posterior gradient in the floor plate, and that a directed source of Wnt4 protein attracted postcrossing commissural axons. Commissural axons in mice lacking the Wnt receptor Frizzled3 displayed anterior-posterior guidance defects after midline crossing. Thus, Wnt-Frizzled signaling guides commissural axons along the anterior-posterior axis of the spinal cord. 相似文献
988.
C Del Bo' P Riso A Brambilla C Gardana A Rizzolo P Simonetti G Bertolo D Klimis-Zacas M Porrini 《Journal of agricultural and food chemistry》2012,60(36):9298-9304
Blueberries ( Vaccinium corymbosum L.) are rich sources of phenolics and anthocyanins (ACNs). We investigated the absorption of ACNs after consumption of one portion (300 g) of minimally processed blueberry purée (P) obtained from blanched (BL) or unblanched (NB) berries. A repeated-measures, crossover design study was conducted on healthy human volunteers. Blood was drawn between baseline and 24 h after BL-P or NB-P consumption, while urine were collected from the day before the experiment up to 48 h. Total plasma ACN content was not significantly different, while phenolics content was higher in BL-P with respect to NB-P. The maximum ACN absorption in plasma was observed after 1.5 h from the intake of the purées and was significantly higher (p ≤ 0.05) after the intake of BL-P. Both products increased the excretion of hippuric acid in urine. In conclusion, blanching had no significant effect on total ACN content and enhanced their absorption from minimally processed purées. 相似文献
989.
Water, Air, & Soil Pollution - A submerged membrane bioreactor (MBR) was used to treat two types of petrochemical wastewater: olefin process wastewater and total petrochemical wastewater.... 相似文献
990.
Peñalvo JL Adlercreutz H Uehara M Ristimaki A Watanabe S 《Journal of agricultural and food chemistry》2008,56(2):401-409
Lignans constitute a group of phytochemicals widely distributed in the human diet. Once ingested, most dietary lignans are metabolized by the gut microflora to enterolactone and enterodiol, also known as enterolignans. Together with isoflavones and coumestrol, enterolignans have been traditionally classified as phytoestrogens, plant-derived compounds that exhibit estrogen-like activity. In addition to a higher intake of vegetables, many studies have suggested that the presence of phytoestrogens in the Japanese diet is one of the factors that might explain the reduced incidence of certain chronic diseases in Japanese populations compared with Western countries. Being a vegetable-based diet, exposure to dietary lignans should be high, but to assess this exposure, a lignan food database is required. Stable isotope-dilution gas chromatography coupled with mass spectrometry was used to quantify six plant lignans in 86 food items commonly consumed in Japan. These data will complement the previous databases and most importantly expand the knowledge of occurrence of lignans in food to Eastern diets. 相似文献