甘肃天祝牧区白牦牛乳脂肪中脂肪酸的分析     

妥彦峰  甘伯中  杭锋  宋馨 《乳业科学与技术》2013,36(4):23-27

以甘肃天祝地区3个牧场所产的白牦牛乳为研究对象,采用气相色谱-质谱联用检测方法,测定3个牧场所产白牦牛乳中脂肪酸含量,比较在枯草期、枯草末期、返青期、青草期4个时期及不同胎次的白牦牛所产牦牛乳中脂肪酸的构成及含量.结果表明:3个牧场白牦牛乳中乳脂肪酸含量差异不显著(P＞0.05);1～5胎次母白牦牛乳中脂肪酸含量差异不显著(P＞0.05).枯草期、枯草末期、返青期、青草期4个时期白牦牛乳中饱和脂肪酸(SFA)、不饱和脂肪酸(USFA)含量比值分别为1.86、1.75、1.62、1.32.随着气温的升高及牧草的成熟,白牦牛乳中饱和脂肪酸含量逐渐降低,而不饱和脂肪酸的含量逐渐升高.  相似文献   

Cu2+对蚯蚓和家兔AChE毒性研究     

张轶辉  崔小伟  毕亚玲  王波 《安徽农业科学》2011,39(25):15342-15344

采用体外试验方法,以蚯蚓和家兔为研究对象,分别测定了Cu2＋对二者AChE的半抑制浓度（IC50）和双分子速率Ki。结果表明,在抑制时间为10 min时Cu2＋对蚯蚓AChE和家兔脑部AChE的IC50分别为3.6和2.4 mmol/L;在IC50浓度的Cu2＋作用下,Cu2＋对家兔脑部AChE的Ki值较大,为Cu2＋对蚯蚓AChE的3.59倍,表明家兔脑部AChE较蚯蚓AchE对Cu2＋更为敏感。  相似文献   

乙酰胆碱酯酶的分离纯化及生物学研究进展     

叶东平  陈斌  何正波 《安徽农业科学》2011,39(7):3811-3814

乙酰胆碱酯酶在神经突触间隙中通过催化水解神经递质乙酰胆碱来维持神经冲动的正常传递,广泛存在于各种动物组织中,如脑、红血球、鱼肉组织和动物血清中。总结了最近国内外关于乙酰胆碱酯酶的研究进展,包括乙酰胆碱酯酶的提取、纯化和固定化研究,且综述了有关乙酰胆碱酯酶传感器的应用进展,以及在治疗疾病如阿尔茨海默病方面的应用,这将为以乙酰胆碱酯酶为目标的研究提供信息框架。  相似文献   

桃蚜高效氯氰菊酯抗药性与乙酰胆碱酯酶的关系   总被引：3，自引：0，他引：3  

杨帆  帅霞 《植物保护》2008,34(5):60-62

于室内对桃蚜进行高效氯氰菊酯抗药性筛选,选育至10代后抗性倍数增长到49.9倍。生化分析表明,抗性品系乙酰胆碱酯酶(AChE)活性均显著高于敏感品系。比较两个品系乙酰胆碱酶活性个体频率分布发现,更多的桃蚜个体向酶活性高的区域分布。酶动力学测定结果显示,抗性桃蚜酯酶对底物的Vmax、Km显著大于敏感品系。  相似文献   

尖膀胱螺对毒死蜱毒性的生物化学响应     

马军国  张榜军  李效宇 《水生态学杂志》2012,33(5):114-118

以尖膀胱螺作为试验动物,研究毒死蜱对尖膀胱螺抗氧化系统、乙酰胆碱酯酶和一氧化氮合酶的影响.通过预试验获得尖膀胱螺72 h LC50为243 μg/L,推算的安全浓度为16 μg/L,正式试验以16和121.5 μg/L浓度组分别暴露尖膀胱螺96 h.在第24、48和96 h分别取材,测定尖膀胱螺体内超氧化物歧化酶(SOD)、乙酰胆碱酯酶(AChE)、一氧化氮合酶(NOS)的活性和丙二醛(MDA)含量变化情况.结果显示,在推算的安全浓度(16 μg/L)暴露后,尖膀胱螺体内MDA含量和NOS活性在各时间段变化均不明显,而SOD和AChE活性在96 h被抑制;在高浓度组(121.5 μg/L),尖膀胱螺SOD呈现先上升后下降后又有所回升的趋势,MDA水平持续上升,NOS水平被显著性诱导,AChE活性则被显著性抑制,且在48 h时抑制作用最强.试验结果表明毒死蜱对尖膀胱螺抗氧化系统和神经中枢均产生一定的影响,提示尖膀胱螺可作为毒死蜱毒理学试验模型动物,同时MDA和AChE可作为毒死蜱毒性的生物标记物.  相似文献   

Separation of fine organic particles by a low-pressure hydrocyclone (LPH)     

《Aquacultural Engineering》2014

The separation performance of a low-pressure hydrocyclone was tested using fine organic particles from 1 to 700 μm. The dimensions of the low-pressure hydrocyclone were an inflow diameter of 30 mm, a cylinder length of 575 mm, an overflow diameter of 60 mm, an underflow diameter of 50 mm, a cylinder diameter of 335 mm and a cone angle of 68°. The low-pressure hydrocyclone was operated with a lower inlet pressure (average 1.38–5.56 kPa) that could be maintained under water level differences that ranged from 17.5 to 53.5 cm between the water surface of the feeding mass cylinder and the middle of the inlet pipe of the low-pressure hydrocyclone. By varying the inflow rate, underflow ratio and feed concentration, the separation performance of the low-pressure hydrocyclone was affected. The separation performances were determined from total separation efficiency and grade efficiency. Separation performances were determined according to the different inflow rates of 400, 600, 800 and 1000 ml s⁻¹ and their respective underflow ratios that ranged from 5% to 30%. The maximum total separation efficiencies for each inflow rate were 41%, 46% and 46% at 400, 800 and 1000 ml s⁻¹ inflow rates, respectively, and at underflow rates of 30% of the inflow rates. In addition, a total separation efficiency of 46% was employed at 600 ml s⁻¹ of inflow rate and with an underflow rate of 25% its inflow rate. As the feed concentration increased from 25 to 150 mg l⁻¹, the separation performances were gradually decreased. For the fine particles ranging 1–200 μm, the grade efficiency was higher at the higher inflow rate (higher than 600 ml s⁻¹) and higher underflow rate. However, for the coarse particles ranging 400–700 μm, the grade efficiency was higher at the lower inflow rate (lower than 600 ml s⁻¹) and higher underflow rate. The cut-point (d₅₀) values ranged from 30 to 200 μm for a feed size range of 1–700 μm. The Response Surface Method (RSM) model predicted an optimum operating inflow rate and underflow ratio of 721 ml s⁻¹ of inflow rate and 30%, respectively, for the low-pressure hydrocyclone at a maximum total separation efficiency. Based on these findings, further design and operating adaptation of low-pressure hydrocyclones used for fine solids removal in recirculating aquaculture systems is expected.  相似文献   

Plant functional types rather than climate or soil determine leaf traits in the forest biomes of eastern China     

Xiaoyun Zhan  Guirui Yu 《Scandinavian Journal of Forest Research》2018,33(1):14-22

Nitrogen (N) has great ecological importance, but the biogeographic pattern across forest biomes in China has only recently been explored. Here we conducted a systematic census of leaf C and N following the same protocol to explore the variations of leaf traits, and their possible responses to plant functional types (PFTs) and environmental factors. Results showed that leaf traits varied substantially across biomes, and the relationships of PFTs to climatic factors were stronger than those of PFTs versus soil nutrient proxies, indicating that plant species composition might be a better predictor of plant species distribution with climate than leaf traits. Soil nutrient proxies explained more variation of leaf traits than climate, which demonstrates that leaf traits reflect important aspects of plant responses to soil nutrients. Importantly, partial general linear models analyses found that PFTs showed the greatest direct influence for leaf traits, and climate and soil affected leaf traits mainly through the change in plant species composition rather than having direct impacts. Hence, we concluded that leaf traits were largely controlled by PFTs rather than climate or soil at the biome scale. The results favored the species composition hypothesis, indicating that leaf nutrient concentration is mainly determined by PFTs.  相似文献   

Effects of forest residue harvesting on short-term changes in soil solution chemistry     

Nicholas Clarke  Silje Skår  O. Janne Kjønaas  Kjersti Holt Hanssen  Tonje Økland  Jørn-Frode Nordbakken 《Scandinavian Journal of Forest Research》2018,33(3):299-307

Short-term (three to four years) effects of forest harvesting on soil solution chemistry were investigated at two Norway spruce sites in southern Norway, differing in precipitation amount and topography. Experimental plots were either harvested conventionally (stem-only harvesting, SOH) or whole trees, including crowns, twigs and branches were removed (whole-tree harvesting, WTH), leaving residue piles on the ground for some months before removal. The WTH treatment had two sub-treatments: WTH-pile where there had been piles and WTH-removal, from where residues had been removed to make piles. Increased soil solution concentrations of NO₃–N, total N, Ca, Mg and K at 30?cm depth, shown by peaks in concentrations in the years after harvesting, were found at the drier, less steep site in eastern Norway after SOH and WTH-pile, but less so after WTH-removal. At the wetter, steeper site in western Norway, peaks were often observed also at WTH-removal plots, which might reflect within-site differences in water pathways due largely to site topography.  相似文献   

Disturbance ecology benchmarks for Schima–Castanopsis forests in the central Himalayas     

Deepak B. Khatry 《Journal of Sustainable Forestry》2018,37(3):316-338

Roughly 2.8 billion people burn wood for basic energy needs, and traditional wood-fuel represents ~55% of global wood harvest. With increasing anthropogenic disturbance of natural forests, the “stability/fragility” paradigm of forest ecology is gradually being replaced by a “disturbance/recovery” paradigm. In order to understand effects of human-induced disturbances on natural forest ecosystems, and to plan for recovery of disturbed forests, appropriate metrics become necessary. Such metrics will aid in assessment and management of forests for carbon sequestration, biodiversity conservation, ecosystem health, and sustainability of natural resources. Such metrics are especially needed in “wood-fuel hotspots” of the world where over 275 million people live and harvest wood-fuel unsustainably. In this article, I provide metrics of human-induced disturbance in Nepal’s Schima–Castanopsis dominated forests and show relationships of disturbance intensity with forest structure and composition, site productivity potential, natural regeneration, and tree species diversity. Benchmark data were collected from survey of two protected reference forests and compared against three other forests representing a disturbance gradient. The Schima–Castanopsis association is a common dominant forest type in the warm temperate zone of the central Himalayas, and the findings from this study should have wider application.  相似文献   

Influence of staggered sown Spring sunflower (Helianthus Annuus L.) at varying intra–row spacing and applied–N on pre– and post–anthesis N dynamics and dry matter partitioning in Indo–Gangetic Plains Region     

Buta Singh Dhillon  Pawan Kumar Sharma  Anil Kumar Choudhary 《Communications in Soil Science and Plant Analysis》2018,49(16):2002-2015

In current study, dry–matter accumulation (DMA), pre– and post–anthesis nitrogen (N) accumulation, N translocation (NT) and dry–matter partitioning by sunflower seeds was investigated under three sowing dates (January 20, February 10 & March 2), two intra–row spacings (30 & 24 cm) and four nitrogen doses (0, 45, 60 & 75 kg ha^–1) in two alluvial soils. Early sowing resulted in higher DMA and NT; leading to higher nitrogen use efficiency (NUE) that could be associated with higher pre–anthesis N accumulation. The closer intra–row spacing resulted in higher DMA by all plant parts except seed. Each graded N dose improved DMA, but improvement in dry–matter partitioning to seed was significant up to 60 and 75 kg N ha^–1 during 2014 and 2015, respectively owing to higher NT under respective treatments. NUE was highest at 60 kg N ha^–1 during both years.  相似文献