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961.
Carl D. Marti 《西北部美国博物学家》2011,46(2)
An investigation of the diet of the Common Barn-owl ( Tyto alba ) on Antelope Island, Great Salt Lake, Utah, yielded four mammal species not previously known to occur on any island in the Great Salt Lake ( Microtus pennsylvanicus, M. montanus, Ondatra zibethicus , and a Sorex sp.). Two other species, known from other islands, were added to the list of fauna of Antelope Island ( Perognathus parvus and Reithrodontomys megalotis ). The barn owl diet on Antelope Island was remarkably like that of barn owls feeding in farmlands adjacent to the Great Salt Lake despite major vegetational differences. 相似文献
962.
Streambed surveys were conducted along the upper Colorado River, Colorado, to describe the distributions of Claassenia sabulosa larvae in relation to current speed and to determine their diets. We also addressed diel feeding periodicity by sampling during both day and night. Claassenia sabulosa was more abundant in riffle habitats than in runs. A positive relationship existed between C. sabulosa abundance and stream current, with larval size increasing with current speed. Chironomidae, Baetidae, and Simulidae collectively accounted for 93% of the prey found in stonefly guts; however, these categories were not consumed equally by all C. sabulosa . Smaller C. sabulosa primarily ate chironomids, and larger individuals consumed more baetids. Only a slight difference existed in the percentage of empty guts between night- and day-collected stoneflies, and ranges of prey per gut at night were higher than those in the day, suggesting that these stoneflies may forage more intensively at night. 相似文献
963.
964.
965.
Christian Dölle Marc Niere Emilia Lohndal Mathias Ziegler 《Cellular and molecular life sciences : CMLS》2010,67(3):433-443
Poly-ADP-ribose polymerases (PARPs) use NAD+ as substrate to generate polymers of ADP-ribose. We targeted the catalytic domain of human PARP1 as molecular NAD+ detector into cellular organelles. Immunochemical detection of polymers demonstrated distinct subcellular NAD+ pools in mitochondria, peroxisomes and, surprisingly, in the endoplasmic reticulum and the Golgi complex. Polymers did not
accumulate within the mitochondrial intermembrane space or the cytosol. We demonstrate the suitability of this compartment-specific
NAD+ and poly-ADP-ribose turnover to establish intra-organellar protein localization. For overexpressed proteins, genetically
endowed with PARP activity, detection of polymers indicates segregation from the cytosol and consequently intra-organellar
residence. In mitochondria, polymer build-up reveals matrix localization of the PARP fusion protein. Compared to presently
used fusion tags for subcellular protein localization, these are substantial improvements in resolution. We thus established
a novel molecular tool applicable for studies of subcellular NAD metabolism and protein localization. 相似文献
966.
夏提姑丽·阿不都热依木 《中国西部科技》2009,8(15):47-48
公路基本建设事业的快速发展,对公路养护工程提出了更高的要求,公路养护不断遇到新的难题,面对困难和挑战。文章结合本地区公路养护实际工作实践,对公路养护管理存在的问题进行了分析,并探讨了相应对策。 相似文献
967.
本文建立了同时考虑轴颈径向位移和歪斜时的滑动轴承动力学模型.对于这种模型,油膜力将扩展为四个广义力分量.文章将相应的动力系数矩阵分解为对称和反对称两部分并讨论其物理性质.然后,本文推导得出该模型的正交变换矩阵,在此基础上导得各向同性的动力系数矩阵表达式,并讨论了诸元素的物理意义.文章最后引入动力系数椭圆的概念以分析非对称动力系数矩阵的变换性质. 相似文献
968.
Membrane depolarization causes many kinds of ion channels to open, a process termed activation. For both Na+ channels and Ca2+ channels, kinetic analysis of current has suggested that during activation the channel undergoes several conformational changes before reaching the open state. Structurally, these channels share a common motif: the central element is a large polypeptide with four repeating units of homology (repeats I-IV), each containing a voltage-sensing region, the S4 segment. This suggests that the distinct conformational transitions inferred from kinetic analysis may be equated with conformational changes of the individual structural repeats. To investigate the molecular basis of channel activation, we constructed complementary DNAs encoding chimaeric Ca2+ channels in which one or more of the four repeats of the skeletal muscle dihydropyridine receptor are replaced by the corresponding repeats derived from the cardiac dihydropyridine receptor. We report here that repeat I determines whether the chimaeric Ca2+ channel shows slow (skeletal muscle-like) or rapid (cardiac-like) activation. 相似文献
969.
Self peptides bound to self major histocompatibility complex (MHC) molecules have been implicated both in positive and in negative selection of T cells during intrathymic development. We report here that the novel MHC-restricted monoclonal antibody Y-Ae detects the MHC class II bound form of a major self peptide. Y-Ae binds approximately 12% of the relevant MHC class II molecules on self antigen presenting cells. The peptide detected by Y-Ae is one of several major peptides eluted from the MHC molecule. These data suggest that self peptides presented by self MHC class II molecules at densities sufficient to signal a CD4 T cell are of very limited complexity. Furthermore, as Y-Ae stains antigen presenting cells that mediate negative selection but not thymic cortical epithelial cells that drive positive selection, differential expression of self peptide:self MHC class II complexes may be a key feature of intrathymic selection. 相似文献
970.