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991.
992.
993.
Effects of grazing and rainfall variability on root and shoot decomposition in a semi-arid grassland
Marcus Giese Ying Zhi Gao Ying Zhao Qingmin Pan Shan Lin Stephan Peth Holger Brueck 《Applied soil ecology》2009,41(1):8-18
Overgrazing increasingly affects large areas of Inner Mongolian semi-arid grasslands. Consequences for ecosystem functions and, in particular, for the decomposition as a key process of ecosystem carbon (C) and nitrogen (N) cycling are still unclear.We studied the effects of grazing on shoot and root decomposition with the litter bag method in a long-term grazing exclosure (UG79), a moderate winter grazed (WG) and a long-term heavily grazed site (HG). We separated the effects of local environmental factors and litter quality as altered by grazing. Growing seasons of average and very low precipitation allowed us to study the effect of inter annual rainfall variability on decomposition.Grazing-induced differences in environmental factors of the three studied grassland sites had no effect on decay rates of shoot and root dry mass. Also differences in litter quality among the grazing sites were not reflected by root decomposition dynamics. The accelerated shoot decay at site HG could not clearly be linked to litter quality parameters. Shoot decay rates were more or less constant, even under very dry conditions. This indicates the possibility of photodegradation (solar UV-B radiation) to control aboveground decomposition in this semi-arid ecosystem. By selecting the best predictors of root decomposition from regression analysis, we found that soil water content was the best parameter explaining the dynamics.Net N immobilization was generally not detected during the decay process of shoot and root. It is likely, when root decomposition is strongly reduced in dry periods, shoot decomposition becomes relatively more important for nutrient cycling. A separate analysis of shoot and root decay dynamics is required in order to describe C and N cycling in this semi-arid grassland. The grazing impact on C and N fluxes through decomposition of plant material likely exhibits a strong interaction with seasonal rainfall pattern. 相似文献
995.
TLC—UV法测定银杏叶中槲皮素的含量 总被引:1,自引:0,他引:1
建立了银杏叶黄酮类成分槲皮素的薄支析测定方法,分析条件:硅胶GF254薄层,展开剂为苯-醋酸乙酯-丙酮-甲酸(10:8:2:1,体积比),无水乙醇作解吸溶剂,吸光度检测波长360nm。结果表明:该法精确、重现性好和线性范围宽。 相似文献
996.
AIM: To investigate the effect and mechanism of fluvastatin on the migration induced by platelet derived growth factor-BB (PDGF-BB) and endothelin-1 (ET-1) in cultured vascular smooth muscle cells (VSMCs). METHODS: Cultured VSMCs derived from spontaneously hypertensive rats (SHR) were used. Cell migration was determined by modified Boyden chamber assays. Intracellular free calcium ([Ca2+]i) was measured with fluorescent Ca2+ indicator Fura-2/AM. RESULTS: PDGF-BB and ET-1 significantly induced VSMCs migration, which was inhibited by pretreatment of VSMCs with fluvastatin (10-9-10-5 mol/L) in a dose-dependent manner, and the peak inhibition rate of migration induced by PDGF-BB and ET-1 was over 86.67%. Fluvastatin also attenuated the increase in [Ca2+]i induced by PDGF-BB and ET-1, with a peak inhibition rate of 86.76% and 65.32%, respectively. CONCLUSION: PDGF-BB and ET-1 promote migration of VSMCs from SHR.Fluvastatin may have direct inhibitory effects on cell migration induced by PDGF-BB and ET-1. The increase in [Ca2+]i may acts as intracellular signaling in the migration in response to PDGF-BB and ET-1 in VSMCs. 相似文献
997.
AIM: The purpose of this study is to elucidate the relationship between apolipoprotein (apo) E polymorphism and plasma lipid profiles and HDL subclasses in obesity. METHODS: apoE genotype was assayed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The subclasses of serum HDL in 93 obese subjects and 96 nonobese subjects were determined by two-dimensional gel electrophoresis conjunction with immunodetection method. RESULTS: apoE3/3 genotypes and allele ε3 frequency in obese group and the control group were both the highest, but no significant difference. In obese group, the genotype of apoE2 had higher serum apoE/aopCⅢ, HDL2a and lower apoB100, apoCⅢ, HDL3c levels compared with the genotype of apoE3 (P<0.05). In control group, the genotype of apoE2 had higher serum TC and apoE levels, but lower HDL3b level compared with the genotype of apoE3 (P<0.05). CONCLUSION: Polymorphism of the ApoE gene is associated with the distribution of HDL particles in obesity. Allele of ε2 carrier may slow the tendency of HDL particals shifted towards smaller sizes. 相似文献
998.
为克隆和研究猪细胞因子及相关基因,应用建库试剂盒成功构建了猪细胞因子cDNA表达文库。采取健康猪外周血及淋巴结,分离单个核细胞,经LPS PHA联合刺激不同时间后,提取总RNA。将各组样品混合,分离纯化mRNA。反转录合成cDNA第一链和第二链,与EcoRI和HindⅢ接头连接。酶切和过柱分级分离后,与λScreen载体连接,经体外包装转染E.coliER1647宿主菌,进行文库容量测定和扩增。以扩增文库的DNA为模板,利用已知基因引物克隆猪IL-2和IL-4的cDNA并进行测序。结果表明,成功构建了猪细胞因子cDNA文库,文库原始库容量为8×105,插入片段在300~2 000 bp,扩增得到特定的IL-2和IL-4基因,说明文库质量高、代表性强,为进一步从文库中筛选未知细胞因子及相关基因提供了有效的工具。 相似文献
999.
利用细胞培养、原位杂交、免疫组化、图像分析等技术研究缺氧与肉鸡肺动脉平滑肌细胞癌基因c-fos和c-myc表达的关系,进一步阐明缺氧与以肺动脉增殖重塑为特征的肉鸡腹水综合征的关系。结果显示,缺氧显著引起肺动脉平滑肌细胞内癌基因c-fos和c-mycmRNA的表达(c-fosmRNA:常氧组为144.6±20.2,缺氧组为198.1±32.8,P<0.01;c-mycmRNA:常氧组为125.4±18.8,缺氧组为167.1±22.4,P<0.01)。缺氧显著引起肺动脉平滑肌细胞内癌基因c-fos和c-myc蛋白的表达(c-fos蛋白:常氧组为150.9±33.2,缺氧组为225.9±37.0,P<0.01;c-myc蛋白:常氧组为162.1±28.5,缺氧组为228.8±33.4,P<0.01)。结果表明缺氧能够明显诱发肉鸡肺动脉平滑肌细胞内癌基因c-fos、c-myc的转录和表达,是启动肺动脉平滑肌细胞增殖的重要原因。本研究阐明缺氧是以肺动脉重塑为特征的肉鸡腹水综合征的主要诱因。 相似文献
1000.
试验选用360只健康1日龄艾维茵肉仔鸡(公、母混养),采用2×2×3三因子析因化设计,将360只试验雏鸡随机分成12组,每组设3个重复,每个重复10只鸡。锌的添加浓度为50、100mg/kg,铁的添加浓度为30、60mg/kg,维生素A的添加浓度为1500、3000、6000IU/kg。测定了肉仔鸡血清、肝脏谷胱甘肽过氧化物酶(GSH-Px)活性,过氧化氢酶(CAT)活性、铜锌超氧化物歧化(酶CuZn-SOD)活性,丙二醛(MDA)含量,以此来研究不同水平的锌、铁、维生素A同时添加,三者在肉仔鸡血清、肝脏抗氧化功能方面的互作效应。结果表明:锌、铁与维生素A三者互作对提高肉仔鸡血清CuZn-SOD活性影响极显(著P<0.01),对提高肉仔鸡肝脏GSH-Px活性和降低MDA含量影响极显(著P<0.01)。这说明锌、铁、维生素A三者之间在肉仔鸡抗氧化方面存在协同效应。 相似文献