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551.
羊草草地生长季放牧山羊采食量和食性选择 总被引:12,自引:1,他引:12
在松嫩平原羊草草地,通过控制放牧实验对山羊的时限采食量和食性选择进行了研究。结果表明:(1)5-9月份,山羊的时限(1h)采食量平均为0.42kg干物质,其季节动态为5月份最低,随季节推移不断增大,8月份达到最大,9月份又有所减小;时限采食量基本上随放牧率减小而增大,但在最低放牧率小区有所减小。(2)山羊的食性选择随季节推移和放牧率不同而变化。(3)山羊对20-25cm高度草层的选择性最高;各高度草层的食性选择指数随季节推移和放牧率不同而变化;山羊对不同植物的高度选择性存在差异,但高度选择指数的最大值都在15-30cm范围内。 相似文献
552.
Huang SH Long M Wu CH Kwon-Chung KJ Chang YC Chi F Lee S Jong A 《The Journal of biological chemistry》2011,286(40):34761-34769
Cryptococcus neoformans is a neurotropic fungal pathogen, which provokes the onset of devastating meningoencephalitis. We used human brain microvascular endothelial cells (HBMEC) as the in vitro model to investigate how C. neoformans traverses across the blood-brain barrier. In this study, we present several lines of evidence indicating that C. neoformans invasion is mediated through the endocytic pathway via lipid rafts. Human CD44 molecules from lipid rafts can directly interact with hyaluronic acid, the C. neoformans ligand. Bikunin, which perturbs CD44 function in the lipid raft, can block C. neoformans adhesion and invasion of HBMEC. The lipid raft marker, ganglioside GM1, co-localizes with CD44 on the plasma membrane, and C. neoformans cells can adhere to the host cell in areas where GM1 is enriched. These findings suggest that C. neoformans entry takes place on the lipid rafts. Upon C. neoformans engagement, GM1 is internalized through vesicular structures to the nuclear membrane. This endocytic redistribution process is abolished by cytochalasin D, nocodazole, or anti-DYRK3 (dual specificity tyrosine-phosphorylation-regulated kinase 3) siRNA. Concomitantly, the knockdown of DYRK3 significantly reduces C. neoformans invasion across the HBMEC monolayer in vitro. Our data demonstrate that the lipid raft-dependent endocytosis process mediates C. neoformans internalization into HBMEC and that the CD44 protein of the hosts, cytoskeleton, and intracellular kinase-DYRK3 are involved in this process. 相似文献
553.
SarA is an essential positive regulator of Staphylococcus epidermidis biofilm development 总被引:6,自引:0,他引:6
Tormo MA Martí M Valle J Manna AC Cheung AL Lasa I Penadés JR 《Journal of bacteriology》2005,187(7):2348-2356
554.
为揭示我国西藏高原湖泊原生动物群落结构特征及垂直分布格局,于2017年11月及2018年5月和9月,在巴松措中心分7层设置采样点,利用25号浮游生物网采集原生动物。采用活体观察和固定染色相结合的方法,共鉴定到原生动物195种(其中春季86种,夏季93种,秋季80种),隶属于2门11纲24目43科59属。其中以肉鞭门种类较丰富,砂壳类纤毛虫占优势。垂直分布的物种组成和群落结构复杂表现为:表层>中层>底层,物种多样性、丰富度和优势度指数表现为:表层>中层>底层,均匀度指数大多数为1;季节分布的物种组成和群落结构群复杂程度表现为:夏季>春季>秋季,物种多样性、丰富度指数表现为:夏季>秋季>春季,优势度指数表现为:夏季>秋季>春季,均匀度指数表现为:秋季>春季>夏季;优势物种和群落结构都会随水深的增加而减少。总体呈现出物种多样性较低、均匀度较高,具有明显的时空异质性。 相似文献
555.
556.
A. Ambrose 《BMJ (Clinical research ed.)》1903,1(2195):228-229
557.
Two populations of Anadara senilis were sampled periodicallyin a lagoon of Senegal. Spatfall occurs in summer during therainy season. Population density decreases from about 50, 000.m2,two months after spatfall, down to 6, 750 one year later and750 after 28 months. The average growth, measured on the surfaceof the shell, following the umbo rim axis is 0.8 mm per month.The main reduction in growth rate occurs in winter and endsby the deposition of a growth ring. A second growth reductiontakes place during the rainy season and sometimes ends by aweak growth ring. The microgrowth increments are conspicuousand widest during spring equinox. They are not directly relatedto the tidal cycle, but it was impossible to determine if theyhave a tidal or a daily periodicity. (Received 11 February 1990; accepted 16 July 1993) 相似文献
558.
Ambrose L. Lockwood 《BMJ (Clinical research ed.)》1940,1(4131):401-403
559.
Emily Dong Cynthia Lam Danming Tang Salina Louie Mandy Yim Ambrose J. Williams William Sawyer Shirley Yip Joseph Carver Ali AlBarakat Joni Tsukuda Brad Snedecor Shahram Misaghi 《Biotechnology journal》2021,16(4):2000230
Complex recombinant proteins are increasingly desired as potential therapeutic options for many disease indications and are commonly expressed in the mammalian Chinese hamster ovary (CHO) cells. Generally, stoichiometric expression and proper folding of all subunits of a complex recombinant protein are required to achieve the desired titers and product qualities for a complex molecule. Targeted integration (TI) cell line development (CLD), which entails the insertion of the desired transgene(s) into a predefined landing-pad in the CHO genome, enables the generation of a homogeneous pool of cells from which clonally stable and high titer clones can be isolated with minimal screening efforts. Despite these advantages, using a single transgene(s) configuration with predetermined gene dosage might not be adequate for the expression of complex molecules. The goal of this study is to develop a method for seamless screening of many vector configurations in a single TI CLD attempt. As testing vector configurations in transient expression systems is not predictive of protein expression in the stable cell lines and parallel TI CLDs with different transgene configurations is resource-intensive, we tested the concept of randomized configuration targeted integration (RCTI) CLD approach for expression of complex molecules. RCTI allows simultaneous transfection of multiple vector configurations, encoding a complex molecule, to generate diverse TI clones each with a single transgene configuration but clone specific productivity and product qualities. Our findings further revealed a direct correlation between transgenes’ configuration/copy-number and titer/product quality of the expressed proteins. RCTI CLD enabled, with significantly fewer resources, seamless isolation of clones with comparable titers and product quality attributes to that of several parallel standard TI CLDs. Therefore, RCTI introduces randomness to the TI CLD platform while maintaining all the advantages, such as clone stability and reduced sequence variant levels, that the TI system has to offer. 相似文献
560.
The seagrass Halophila stipulacea Forsskål, native to the Red Sea, is an invasive species in the Mediterranean that was recently observed offshore Grenada, in the Caribbean. Here, we document the presence of this seagrass in Dominica and St. Lucia, demonstrating it has spread across part of the eastern Caribbean. H. stipulacea in Dominica was present in seven locations along the west coast covering more than 22.9 ha of the benthos, at depths from 2 to 18 m. Populations were concentrated in or adjacent to bays frequented by recreational or commercial boats, likely vectors for the introduction. Morphological features varied from bed to bed, with depth being the predominant driving factor. H. stipulacea had a rapid mean lateral bed expansion rate of 0.5 cm d−1, with a maximum rate of >6 cm d−1. H. stipulacea patches often occurred exclusive of the otherwise dominant seagrasses of the Caribbean. The potential for the expansion of H. stipulacea, combined with its tolerance for a wide spectrum of environmental conditions, positions it as a potential threat to local and regional biodiversity. 相似文献