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1.
Summary During molt-induced atrophy of the pectoralis muscle of the Giant Canada Goose (Branta canadensis maxima), the zinc content of the muscle was significantly reduced (p0.0139), though the concentration of zinc per unit weight of muscle appeared higher (p0.0232). Zinc lost from the muscle during molt could be utilized for growth of the new flight feathers.Acknowledgments. Funds for this study were obtained from an operating grant awarded to J. C. G. by the Natural Sciences and Engineering Research Council of Canada. 相似文献
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通过对二战后世界经济发展的回顾与分析,论述了技术革命与全球化和在此进程中产生的问题:“精简”,以及由此带来的社会影响。介绍了西方国家学者关于解决上述问题的不同建议和主张,进而提出了自己的观点和对策。 相似文献
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Nussbaum JM Schilling S Cynis H Silva A Swanson E Wangsanut T Tayler K Wiltgen B Hatami A Rönicke R Reymann K Hutter-Paier B Alexandru A Jagla W Graubner S Glabe CG Demuth HU Bloom GS 《Nature》2012,485(7400):651-655
Extracellular plaques of amyloid-β and intraneuronal neurofibrillary tangles made from tau are the histopathological signatures of Alzheimer's disease. Plaques comprise amyloid-β fibrils that assemble from monomeric and oligomeric intermediates, and are prognostic indicators of Alzheimer's disease. Despite the importance of plaques to Alzheimer's disease, oligomers are considered to be the principal toxic forms of amyloid-β. Interestingly, many adverse responses to amyloid-β, such as cytotoxicity, microtubule loss, impaired memory and learning, and neuritic degeneration, are greatly amplified by tau expression. Amino-terminally truncated, pyroglutamylated (pE) forms of amyloid-β are strongly associated with Alzheimer's disease, are more toxic than amyloid-β, residues 1-42 (Aβ(1-42)) and Aβ(1-40), and have been proposed as initiators of Alzheimer's disease pathogenesis. Here we report a mechanism by which pE-Aβ may trigger Alzheimer's disease. Aβ(3(pE)-42) co-oligomerizes with excess Aβ(1-42) to form metastable low-n oligomers (LNOs) that are structurally distinct and far more cytotoxic to cultured neurons than comparable LNOs made from Aβ(1-42) alone. Tau is required for cytotoxicity, and LNOs comprising 5% Aβ(3(pE)-42) plus 95% Aβ(1-42) (5% pE-Aβ) seed new cytotoxic LNOs through multiple serial dilutions into Aβ(1-42) monomers in the absence of additional Aβ(3(pE)-42). LNOs isolated from human Alzheimer's disease brain contained Aβ(3(pE)-42), and enhanced Aβ(3(pE)-42) formation in mice triggered neuron loss and gliosis at 3 months, but not in a tau-null background. We conclude that Aβ(3(pE)-42) confers tau-dependent neuronal death and causes template-induced misfolding of Aβ(1-42) into structurally distinct LNOs that propagate by a prion-like mechanism. Our results raise the possibility that Aβ(3(pE)-42) acts similarly at a primary step in Alzheimer's disease pathogenesis. 相似文献
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分析了抗生素类药物盐酸环丙沙星对水中不同食物链水生生物包括小球藻、发光菌、大型蚤、孔雀鱼的影响,其急性毒性EC50或者LC50数值分别为20.61,63.27,135.15,365.00 mg·L-1。毒性作用规律结果显示,随着生物链等级的升高,生物对环丙沙星的耐受程度升高。将综合评价因子(PEC/PNEC)作为环境风险表征参数,对大连开发区污水处理厂排水及大连湾沿海养殖区中存在的盐酸环丙沙星进行风险分析,发现盐酸环丙沙星在沿海养殖区水域中的环境风险高于污水处理厂排水。小球藻的综合评价因子数值范围最大,可作为评价水体中盐酸环丙沙星残留风险等级的生物标志物。 相似文献
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禽流感的暴发使得禽类免疫系统的研究显得愈加迫切.而以其他种属的同源β2-微球蛋白作为模板进行结构解析,不能解析鸡β2-微球蛋白(Chβ2m)的晶体结构.为了利用硒原子的反常散射获取Chβ2m晶体X射线衍射的相位信息.本研究以pET21a为表达载体,E coli BL21(DE3)为宿主菌,在含有硒代甲硫氨酸的M9培养基中,用IPTG诱导表达硒代甲硫氨酸Chβ2m.包涵体经提取和稀释复性法复性之后,通过分子筛层析和Resource Q阴离子交换层析进行纯化,产物经SDS-PAGE检验纯度达98%以上.利用悬滴气相扩散法采用与Chβ2m蛋白晶体生长相同的条件.获得了衍生物可供衍射的晶体.通过北京同步辐射装置收集数据,最高分辨率至1.9 A. 相似文献
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Low beta diversity of herbivorous insects in tropical forests 总被引:1,自引:0,他引:1
Novotny V Miller SE Hulcr J Drew RA Basset Y Janda M Setliff GP Darrow K Stewart AJ Auga J Isua B Molem K Manumbor M Tamtiai E Mogia M Weiblen GD 《Nature》2007,448(7154):692-695
Recent advances in understanding insect communities in tropical forests have contributed little to our knowledge of large-scale patterns of insect diversity, because incomplete taxonomic knowledge of many tropical species hinders the mapping of their distribution records. This impedes an understanding of global biodiversity patterns and explains why tropical insects are under-represented in conservation biology. Our study of approximately 500 species from three herbivorous guilds feeding on foliage (caterpillars, Lepidoptera), wood (ambrosia beetles, Coleoptera) and fruit (fruitflies, Diptera) found a low rate of change in species composition (beta diversity) across 75,000 square kilometres of contiguous lowland rainforest in Papua New Guinea, as most species were widely distributed. For caterpillars feeding on large plant genera, most species fed on multiple host species, so that even locally restricted plant species did not support endemic herbivores. Large plant genera represented a continuously distributed resource easily colonized by moths and butterflies over hundreds of kilometres. Low beta diversity was also documented in groups with differing host specificity (fruitflies and ambrosia beetles), suggesting that dispersal limitation does not have a substantial role in shaping the distribution of insect species in New Guinea lowland rainforests. Similar patterns of low beta diversity can be expected in other tropical lowland rainforests, as they are typically situated in the extensive low basins of major tropical rivers similar to the Sepik-Ramu region of New Guinea studied here. 相似文献
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Dawson MA Prinjha RK Dittmann A Giotopoulos G Bantscheff M Chan WI Robson SC Chung CW Hopf C Savitski MM Huthmacher C Gudgin E Lugo D Beinke S Chapman TD Roberts EJ Soden PE Auger KR Mirguet O Doehner K Delwel R Burnett AK Jeffrey P Drewes G Lee K Huntly BJ Kouzarides T 《Nature》2011,478(7370):529-533
10.
Cancer immunotherapy comes of age 总被引:1,自引:0,他引:1
Activating the immune system for therapeutic benefit in cancer has long been a goal in immunology and oncology. After decades of disappointment, the tide has finally changed due to the success of recent proof-of-concept clinical trials. Most notable has been the ability of the anti-CTLA4 antibody, ipilimumab, to achieve a significant increase in survival for patients with metastatic melanoma, for which conventional therapies have failed. In the context of advances in the understanding of how tolerance, immunity and immunosuppression regulate antitumour immune responses together with the advent of targeted therapies, these successes suggest that active immunotherapy represents a path to obtain a durable and long-lasting response in cancer patients. 相似文献