山奈酚对三硝基丙酸诱导氧化应激胎鼠的影响

试验旨在研究山奈酚对三硝基丙酸诱导亲代小鼠氧化应激从而对子代胎鼠氧化应激和抗氧化能力的作用.42只亲代小鼠分为3组:对照组、氧化应激模型组、抗氧化剂组,试验重复3次.测定妊娠20d后的子代胎鼠肝脏、肺脏和心脏3个器官中的总超氧化物歧化酶(T-SOD)活力、谷胱甘肽过氧化物酶(GSH-Px)活力、总抗氧化能力(T-AOC...     

Pathogenesis of experimental bovine spongiform encephalopathy (BSE): estimation of tissue infectivity according to incubation period

This paper reports the results of tissue infectivity assays of bovine spongiform encephalopathy (BSE) agent in orally exposed cattle at stages during the incubation period. Estimations of the titre of infectivity in central nervous system (CNS), certain peripheral nerve ganglia and distal ileum tissue were made according to time post exposure from the relationship between incubation period and dose for RIII mice and C57bl mice using data from titrations of brain material from cases of BSE. The rate of increase of infectivity in the bovine CNS was then estimated, taking into account these tissue infectivity titres, the variability of the brain titre of clinical field cases of BSE, and the probability density of the expected number of months before clinical onset of each infected bovine. The doubling time for CNS was shown to equal 1.2 months. The titre in the thoracic dorsal root ganglia (DRG) was, on average, approximately 1 log units less than CNS, and cervical DRG approximately 0.5 log less than thoracic DRG. The pattern of increase of infectivity in the distal ileum is that of an initial increase up to 14-18 months post exposure, followed by a decrease, which is likely to be highly variable between animals. These results will be informative for future risk assessments of BSE, especially in relation to reviewing current control measures.     

基于灰色预测模型的重庆市生态足迹动态分析与预测

生态足迹是近年来定量评估生态可持续发展的一种方法。以重庆统计年鉴为主要数据来源,对重庆市2000--2007年的生态足迹进行了时间序列的测度,并运用灰色预测模型对重庆市2008--2012年生态足迹做出预测。结果表明：2000--2007年,重庆市人均生态足迹从1．162226hm^2增加到1．576941hm^2;人均生态承载力从0．487810hm^2下降到0．447831hm^2;生态赤字从0．674416hm^2增加到1．129111hm^2,生态赤字持续扩大,预测2012年人均生态赤字将达到1．617362hm^2。对此提出了一些对策：控制人口数量,提高人口质量;增加科技财政投入,提高单位面积生物生产量;控制环境污染;做好土地利用总体规划,严格粹制非农律设用她规模;引导人们合理消着,提高瓷源利用率。     

断奶日龄对仔猪心肌、背最长肌和半腱肌抗氧化功能的影响

为研究不同断奶日龄对仔猪心肌、背最长肌和半腱肌抗氧化功能的影响,试验选取受试仔猪24头,随机分为4个处理,每个处理6个重复,每个重复1头仔猪,各处理仔猪分别在14日龄、21日龄、28日龄和35日龄断奶,所有仔猪在42日龄宰杀取样.测定仔猪相应组织的MDA含量和抗氧化酶活性.结果表明,随着断奶日龄的推迟,仔猪心肌、背最长肌和半腱肌中MDA含量逐渐降低,35日龄断奶组仔猪心肌MDA含量显著低于14日龄组（P＜0.05）,28日龄和35日龄断奶组背最长肌和半腱肌MDA含量显著低于14日龄组（P＜0.05）;与28日龄和35日龄断奶组相比,14日龄断奶组心肌T-SOD、GSH-Px活性（P＜0.05）以及半腱肌GSH-Px活性均显著降低（P＜0.05）,各断奶日龄组仔猪背最长肌抗氧化酶活性无显著差异.以上结果提示,仔猪断奶日龄越早,其肌肉组织脂质过氧化反应越强,抗氧化功能越低.     

Impact on soil physical properties of using large-grain legumes for catch crop cultivation under different tillage conditions

In Central Europe, various plant species including large-grain legumes and their mixtures are grown as catch crops, particularly between grains harvested early and subsequent summer crops. This article investigates the question of how soil structure in the topsoil is influenced when catch cropping with large-grain legumes (experimental factor A: without catch crop, with catch crop) under different ploughless tillage conditions during catch crop seeding (experimental factor B: deep tillage/25–30 cm, shallow tillage/8–10 cm). Five one-year trials were performed using standard machinery at various sites in Germany. Soil core samples extracted from the topsoil in the spring after catch crop cultivation served to identify air capacity, saturated hydraulic conductivity and precompression stress. The above-ground and below-ground biomass yields of the catch crops were also determined at most of the sites. In addition, the soil compaction risk for the working steps in the experiments was calculated using the REPRO model.The dry matter yield of the catch crops varied considerably between the individual trial sites and years. In particular, high levels of dry matter were able to form in the case of early seeding and a sufficient supply of precipitation. The soil structure was only rarely affected positively by catch crop cultivation, and catch crops did not contribute in the short term to loosening already compacted topsoils. In contrast, mechanical soil stresses caused by driving over the ground and additional working steps used in cultivating catch crops often led to lower air capacity in these treatments. This is consistent with the soil compaction risks calculated using the REPRO model, which were higher in the treatments with catch cropping. Catch crop cultivation also only resulted in improved mechanical stability at one location. The positive effect of deep ploughless tillage on air capacity and saturated hydraulic conductivity, however, became more clearly evident regardless of catch crop cultivation. In order for catch crop cultivation with large-grain legumes to be able to have a favourable impact on soil structure, it is therefore important that cultivating them does not result in any new soil compaction. In the conditions evaluated, deep tillage was more effective at loosening compacted topsoil than growing catch crops.     

青海省海东市1961-2015年气温变化趋势和演变特征

为了研究近55年来青海省海东市气温变化的特点及其规律,利用海东市5气象站1961-2015年的气温资料,使用线性趋势、Mann-Kendall突变检验和累积距平法等方法进行分析研究。结果表明：55年来海东市年平均气温、最高气温和最低气温呈极显著的增温趋势,年际增长率分别为0.33℃/10a、0.33℃/10a和0.43℃/10a,从年代际变化来看,平均气温和最低气温(最高气温)在20世纪90年代到21世纪00年代(80年代到90年代)增暖趋势明显;四季平均气温、最高气温和最低气温均呈显著的增温趋势,存在着非对称性变化的特点,以最低气温增温更明显,冬季增温对年平均气温增高贡献最大,三者增温的强弱在时间和空间上均表现出不一致性;海东市年平均气温20世纪90年代中后期的增暖是一突变现象,突变开始的具体时间是1996-1997年,最高气温于1993年发生了突变。     

成都市水资源生态足迹及承载力时空演变研究

利用水资源生态足迹模型对成都市2000-2015年水资源生态足迹与生态承载力进行了研究.结果表明,成都市历年水资源生态足迹值在2000-2012年呈上升趋势,受成都市节水政策和产业转型影响, 2013年相对降低, 2014年和2015年趋于平缓;水资源生态承载力与降水量呈正相关关系,相关系数达0.952,旱情灾害影响成都市生态承载力水平, 2006年与2009年的干旱使成都市水资源产生生态赤字;万元GDP水资源生态足迹值逐年下降,成都市水资源利用效率16年间增长6.8倍;成都市各区县人均水资源生态足迹分布不均且在2013-2015年变化较大,成都市规划发展的工业城市人均水资源生态足迹值高,各区县处于人均水资源生态盈余状态,但数值逐年下降,水生态安全保障降低;改变产业结构、提高水资源利用效率、增强水利设施对干旱等自然灾害的应对能力是成都市水资源可持续利用的基本途径.     

基于土地综合承载力的西安市适度人口测度

[目的]测度和分析西安市2001—2011年的适度人口及其变化情况,探讨人口承载力变化的特征与原因,提出优化对策。[方法]食品承载力模型、生态足迹模型、改进的经济承载力模型和改进的综合承载力模型。[结果]2001—2011年,西安市的适度人口数量及结构呈现出阶段性变化;2004年开始,西安市人口承载赤字一直存在,并在经历一个快速增长阶段后出现缓和趋势;西安市经济人口承载力较强,而食品和生态人口承载力不足。[结论]提高区域综合承载力,土地承载是基础,经济承载是关键,生态承载是限制。     

三江源区不同季节放牧草场天然牧草营养价值评定及载畜量研究

为探究三江源区不同季节放牧草场天然牧草营养供给潜力和载畜量,选用3头安装永久性瘤胃瘘管的成年大通牦牛为瘤胃液供体动物,采用概略养分分析法和体外产气法,结合产草量对放牧草场牧草进行综合评定并确定其载畜量。结果表明,1)夏、秋及冬春放牧草场的可食风干草的最高产量分别为(123.83±17.88),(256.88±29.90)和(246.83±66.73) g/m²。2)夏、秋及冬春草场天然牧草的最高粗蛋白(CP)含量分别为(12.69±0.13)%,(10.54±1.22)%和(8.65±0.64)%,其含量随牧草生长而逐渐降低;夏、秋及冬春草场天然牧草EE的最高含量分别为(2.95±0.10)%,(4.38±0.17)%及(3.74±0.70)%;NDS含量的变化趋势与CP一致,而NDF和ADF含量的变化与CP相反,随牧草生长含量不断增加。3)体外发酵pH和氨氮浓度均在正常范围内;夏季草场牧草的48 h产气量、24 h产气估测消化能(DM)、代谢能(ME)和有机物质降解率(OMD)的最大值分别为(57.50±4.27) mL、(9.32±0.59) MJ/kg、(7.98±0.62) MJ/kg和(57.93±3.23)%;秋季草场牧草分别为(54.67±5.35) mL、(8.83±0.64) MJ/kg、(7.47±0.68) MJ/kg及(55.26±3.52)%;冬春草场牧草分别为(58.83±4.51) mL、(9.56±0.60) MJ/kg、(8.24±0.63) MJ/kg及(52.69±5.14)%。4)无补饲条件下,夏、秋及冬春天然放牧草场载畜量分别按数量载畜量、数量载畜量和DCP载畜量核算放牧科学,其最适载畜量分别为7.05,19.51和2.47 SU/hm²;有良好补饲情况下,夏、秋及冬春天然放牧草场载畜量按DCP载畜量、ME载畜量和ME载畜量核算放牧科学,其最适载畜量分别为14.85,29.00和5.03 SU/hm²。因此,三江源区牧草产量和品质季节性差异大,能-氮不平衡,通过补饲可以使夏、秋及冬春放牧草场的载畜量分别提高1.1,0.5和1.0倍左右,有利于促进当地畜牧业发展和生态保护。     

THREE-DIMENSIONAL MULTISLICE HELICAL COMPUTED TOMOGRAPHY TECHNIQUES FOR CANINE EXTRA-HEPATIC PORTOSYSTEMIC SHUNT ASSESSMENT

The purpose of the present study was to investigate the feasibility and usefulness of three-dimensional (3D) multislice computed tomography (CT) angiography with maximum intensity projection (MIP) and volume rendering (VR) in six dogs with clinical and sonographic findings suggestive of portosystemic shunt. Furthermore, we aimed to estimate the diameter of the portal vein and shunt vessels. MIP and VR reconstructions were performed for each patient and the origin and insertion of all shunt vessels were detected. In addition, 3D reconstructions allowed excellent depiction of vascular morphology and topography. All diagnoses and vessel measurements were confirmed by surgery. 3D multidetector CT angiography is a promising, noninvasive, and accurate method of evaluating dogs with suspected portosystemic shunts.