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971.
白鱀豚饲养池水质某些理化因子的变动规律 总被引:1,自引:0,他引:1
自来水中的低量余氯对白暨豚无明显的刺激作用。豚池水温的变化情况与长江中、下游相似,极温对豚有不利影响。不同温度下,池水中磷酸盐含量的日增加率有显著差异,铵氮和硝酸盐氮的日增加系数相近,分别为0.327和0.2468,而亚硝酸盐氮的日增加系数在0.397—0.539之间,受温度的影响较大。池水有机物耗氧量增加不显著,含量与时间的相关式符合Y=aX~b型。缺少阳光照射是池水无机氮化合物增加较快、有机物分解较慢的原因之一。 相似文献
972.
无论对于自然的还是人为管理的生态系统,天气都是最重要的一种环境条件。用系统分析方法对生态系统进行的研究使天气模拟越来越成为非常必要的了。本文首先介绍了一个美国天气模拟模型(WGEN)的数学原理。它用马尔柯夫链和Γ-分布组成降水量子模型,产生逐日降水量。用弱平稳过程和调和分析为工具建立另一个子模型,产生逐日最高温度、最低温度和太阳辐射量。通过常规的统计学方法或灰靶白化方法可以估计模型参数。于是,就可由WGEN生出Alabama州天气模型ALWGEN和北京天气模型BJWGEN。考虑到篇幅有限,本文没有具体介绍上述估计方法,也只是扼要介绍了用Monte Carlo Bootstrap方法进行模型校验和验证的问题。最后,简单地讨论了天气模拟模型的应用。如IPM研究中的风险分析,生态系统管理决策,农业生态区域规划等课题,对天气模型都有现实的或潜在的需要。 相似文献
973.
用人上皮癌细胞系A 431细胞作为抗原免疫BalB/c小鼠,制备七株抗人表皮生长因子受体的单克隆抗体的杂交瘤,这些杂交瘤经三次亚克隆后仍能稳定地分泌单克隆抗体。对其中四株杂交瘤分泌的单克隆抗体进行了鉴定。免疫沉淀放射自显影结果示单克隆抗体3、101和176均可识别A 431细胞膜抗原MW为170000的蛋白质即EGF受体。单克隆抗体59可以识别低分化鼻咽癌细胞膜上EGF受体。单抗3、176和59等可抑制EGF与受体的特异结合,而101和94则不能抑制EGF与受体的结合。 用Protein-A Sepharose CL4B纯化了单抗,纯化的单抗主要为IgG_1亚类。用SDS聚丙烯酰胺凝胶电泳对纯化的单抗进行了纯度测定。 相似文献
974.
Expression of normal and mutant avian integrin subunits in rodent cells [published erratum appears in J Cell Biol 1989 Oct;109(4 Pt 1):1187]
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J Solowska J L Guan E E Marcantonio J E Trevithick C A Buck R O Hynes 《The Journal of cell biology》1989,109(2):853-861
We describe the expression of the beta 1 subunit of avian integrin in rodent cells with the purpose of examining the structure-function relationships of various domains within this subunit. The exogenous subunit is efficiently and stably expressed in 3T3 cells, and it forms hybrid heterodimers with endogenous murine alpha subunits, including alpha 3 and alpha 5. These heterodimers are exported to the cell surface and localize in focal contacts where both extracellular matrix and cytoskeleton associate with the plasma membrane. Hybrid heterodimers consisting of exogenous beta 1 and endogenous alpha subunits bind effectively and specifically to columns of cell-binding fragments of fibronectin. The exogenous avian beta 1 subunit appears to function as well as its endogenous murine equivalent, consistent with the high degree of conservation noted previously for integrins. In contrast, expression of a mutant form of avian integrin beta 1 subunit lacking the cytoplasmic domain produces hybrid heterodimers which, while efficiently exported to the cell surface and still capable of binding fibronectin, do not localize efficiently in focal contacts. This further implicates the cytoplasmic domain of the beta 1 subunit in interactions required for cytoskeletal organization. 相似文献
975.
Tang Peng Cho Yang Fang Long Lin Zhi Gang Wang Yang Lu He Jun Shen Guang Yuan Fu Jian Hong Wang Lin Guan Dong Liang Zhang Lei Luo Jing Jing Gong Ai Shen She Gao Hong Wang Dan Feng Ying Yan Pang Ke Leng Ying Feng Jun Mong Xian Tai 《Bioorganic & medicinal chemistry letters》2010,20(12):3565-3568
A series of novel azobicyclo[3.3.0]octane derivatives were synthesized and evaluated as dipeptidyl peptidase 4 (DPP-4) inhibitors. The effort resulted in the discovery of inhibitor 2a, which exhibited excellent efficacies in an oral glucose tolerance test. Introduction of methyl group (2j) could prolong the inhibition of serum DPP-4 activity. 相似文献
976.
Li Shuigen Li Jikai Li Xiufen Guan Yuan Chen Minmin Zhu Jianjun 《In vitro cellular & developmental biology. Plant》2021,57(2):235-247
In Vitro Cellular & Developmental Biology - Plant - Shoot regeneration from pluripotent cell masses is an important process for genetic improvement of Anthurium andraeanum through... 相似文献
977.
Ying Li Xiaojun Cai Yuqing Guan Lei Wang Shuya Wang Yueyan Li Ying Fu Xiaoyuan Gao Guohai Su 《PloS one》2016,11(2)
Adiponectin and miR-133a are key regulators in cardiac hypertrophy. However, whether APN has a potential effect on miR-133a remains unclear. In this study, we aimed to investigate whether APN could regulate miR-133a expression in Angiotensin II (Ang II) induced cardiac hypertrophy in vivo and in vitro. Lentiviral-mediated adiponectin treatment attenuated cardiac hypertrophy induced by Ang II infusion in male wistar rats as determined by reduced cell surface area and mRNA levels of atrial natriuretic peptide (ANF) and brain natriuretic peptide (BNP), also the reduced left ventricular end-diastolic posterior wall thickness (LVPWd) and end-diastolic interventricular septal thickness (IVSd). Meanwhile, APN elevated miR-133a level which was downregulated by Ang II. To further investigate the underlying molecular mechanisms, we treated neonatal rat ventricular myocytes (NRVMs) with recombinant rat APN before Ang II stimulation. Pretreating cells with recombinant APN promoted AMP-activated protein kinase (AMPK) phosphorylation and inhibited ERK activation. By using the inhibitor of AMPK or a lentiviral vector expressing AMPK short hairpin RNA (shRNA) cancelled the positive effect of APN on miR-133a. The ERK inhibitor PD98059 reversed the downregulation of miR-133a induced by Ang II. These results indicated that the AMPK activation and ERK inhibition were responsible for the positive effect of APN on miR-133a. Furthermore, adiponectin receptor 1 (AdipoR1) mRNA expression was inhibited by Ang II stimulation. The positive effects of APN on AMPK activation and miR-133a, and the inhibitory effect on ERK phosphorylation were inhibited in NRVMs transfected with lentiviral AdipoR1shRNA. In addition, APN depressed the elevated expression of connective tissue growth factor (CTGF), a direct target of miR-133a, through the AMPK pathway. Taken together, our data indicated that APN reversed miR-133a levels through AMPK activation, reduced ERK1/2 phosphorylation in cardiomyocytes stimulated with Ang II, revealing a previously undemonstrated and important link between APN and miR-133a. 相似文献
978.
979.
980.
Weiwen Zheng Ulla Rasmussen Siping Zheng Xiaodong Bao Bin Chen Yuan Gao Xiong Guan John Larsson Birgitta Bergman 《PloS one》2013,8(6)
Programmed cell death (PCD) is a genetically-based cell death mechanism with vital roles in eukaryotes. Although there is limited consensus on similar death mode programs in prokaryotes, emerging evidence suggest that PCD events are operative. Here we present cell death events in a cyanobacterium living endophytically in the fern Azolla microphylla, suggestive of PCD. This symbiosis is characterized by some unique traits such as a synchronized development, a vertical transfer of the cyanobacterium between plant generations, and a highly eroding cyanobacterial genome. A combination of methods was used to identify cell death modes in the cyanobacterium. Light- and electron microscopy analyses showed that the proportion of cells undergoing cell death peaked at 53.6% (average 20%) of the total cell population, depending on the cell type and host developmental stage. Biochemical markers used for early and late programmed cell death events related to apoptosis (Annexin V-EGFP and TUNEL staining assays), together with visualization of cytoskeleton alterations (FITC-phalloidin staining), showed that all cyanobacterial cell categories were affected by cell death. Transmission electron microscopy revealed four modes of cell death: apoptotic-like, autophagic-like, necrotic-like and autolytic-like. Abiotic stresses further enhanced cell death in a dose and time dependent manner. The data also suggest that dynamic changes in the peptidoglycan cell wall layer and in the cytoskeleton distribution patterns may act as markers for the various cell death modes. The presence of a metacaspase homolog (domain p20) further suggests that the death modes are genetically programmed. It is therefore concluded that multiple, likely genetically programmed, cell death modes exist in cyanobacteria, a finding that may be connected with the evolution of cell death in the plant kingdom. 相似文献