棘孢木霉葡聚糖酶基因Glu1的克隆及原核表达

从棘孢木霉(Trichoderma asperellum)ACCC30536中克隆获得一个葡聚糖酶基因Glu1,其cDNA全长984bp,编码327个氨基酸。该葡聚糖酶属于Glyco-hydro-12家族,推测为β-1,4-葡聚糖酶,与深绿木霉IMI 206040的Glycohydro-12家族蛋白(XP_013940397.1)有91%相似性,且亲缘关系较近。运用qRT-PCR技术检测9种诱导条件下棘孢木霉Glu1基因的表达水平,结果表明,Glu1基因能参与棘孢木霉对山新杨(Populus davidiana×P.alba var.pyramidlis)或杨树病原菌的识别。构建原核表达载体并获得重组蛋白rGlu1。酶活特性分析结果表明,该酶最适pH为4.5,最适温度为45℃,且酶活性随诱导时间延长逐渐升高,在5h达到稳定。     

四种菊酯类杀虫剂对枸杞蚜虫线粒体膜流动性的影响

为明确菊酯类杀虫剂对昆虫线粒体膜流动性的影响,以1,6-二苯基-1,3,5-己三烯（1,6-diphenyl-1,3,5-hexatriene,DPH）为荧光探剂,采用荧光偏振法研究了4种菊酯类杀虫剂对枸杞蚜虫Aphis sp.线粒体膜流动性的影响。结果表明,4种菊酯类杀虫剂对枸杞蚜虫线粒体膜流动性均有显著影响,其荧光偏振度显著增大,线粒体膜流动性显著减小。当药剂浓度为100 μmol/L时,对照组枸杞蚜虫线粒体膜的荧光偏振度为0.239,高效氯氰菊酯的影响最大,线粒体膜的荧光偏振度为0.315,联苯菊酯的影响最小,线粒体膜的荧光偏振度为0.287。4种菊酯类杀虫剂对线粒体膜流动性的影响都存在一定的浓度效应,当药剂浓度在0~100 μmol/L范围内,浓度越大影响越大。4种菊酯类杀虫剂在不同温度下对枸杞蚜虫线粒体膜流动性的影响不同,高效氯氰菊酯、联苯菊酯和甲氰菊酯对线粒体膜流动性的影响基本不受温度影响,而氯菊酯在高温条件下产生的影响大,在低温条件下产生的影响小,表现为明显的正温度系数。表明DPH可以作为荧光探剂研究枸杞蚜虫线粒体膜的流动性。     

生物素测定方法的应用现状

<正>生物素,又称维生素H,是一种水溶性B族维生素。生物素的测定方法很多,早在20世纪40年代,国外就报道了利用微生物法测定生物素的含量。随着科学技术的发展,国内外报道了许多新的测定方法,主要有同位素稀释法、     

Dynamic Changes of Microbial Community for Degradation of Lignocellulose

Dynamic changes of a microbial community for lignocellulose degradation were explored in details. Community composition and development were investigated by the means of denaturing gradient gel electrophoresis （DGGE）, and results showed that the microbial community was constituted of 14 kinds of bacteria and presented the fluctuation in some degrees with fermentation. Furthmore, the result of cluster analysis of DGGE pattern was accordant with growth curve, and the degradation process was divided into three stages： initial stage （0-12 h）, intermediate stage （24-144 h） and end stage （144-216 h）.     

水牛MFSD2A基因多态性及其与产奶性状的关联分析

【目的】研究水牛主要促进因子超家族成员2a(major facilitator superfamily domain containing 2a, MFSD2A)基因多态性,并筛选与水牛产奶性状相关联的SNP。【方法】采集383头健康水牛血液DNA,利用PCR扩增和Sequenom MassARRAY飞行时间质谱技术对SNP位点进行筛选及基因型检测,并进行遗传多样性、连锁不平衡(LD)和单倍型分析,以及对不同基因型和单倍型与水牛产奶性状进行关联分析。【结果】在水牛MFSD2A基因中检出7个SNPs位点,多态信息含量(PIC)均在0.25～0.40之间,属于中度多态,除g.8290 T>C位点外,其余位点均处于Hardy-Weinberg平衡状态(P>0.05);关联分析结果表明,这7个SNPs位点与305 d产奶量均显著关联(P<0.05),且突变杂合子基因型的305 d产奶量是3种基因型中最低的,g.568 C>G和g.701 A>G位点与乳脂率显著关联(P<0.05),乳脂率从大到小依次为突变纯合子>野生纯合子>突变杂合子,g.568...     

纵轴式掘进机截割减速器优化设计

针对纵轴式掘进机截割减速器常规设计中存在的体积较大、设计周期比较长、制造成本比较高等不足之处,建立以体积最小为最优化设计的数学模型,利用MATLAB工具箱的fmincon函数对目标进行优化设计,使得设计的减速器在满足结构强度和传动比要求的前提下,达到体积小、重量轻,从而为纵轴式掘进机截割减速器的优化设计提供了理论参考和借鉴。     

Effect of urea supplementation on performance and safety in diets of Dorper crossbred sheep

This study was conducted to evaluate the efficacy and safety of dietary urea in sheep rations having a 50:50 concentrate:roughage ratio. Sixty‐four Dorper × thin‐tailed Han crossbred ram lambs with an average body weight of 30.8 (±0.02) kg were randomly divided into four groups of 16 sheep each, and each group was fed one of the following diets: a basal diet (CON), or CON supplemented with 0.5% (0.5UTM), 1.5% (1.5UTM) or 2.5% (2.5UTM) urea. Growth performance, carcass characteristics, non‐carcass offals, meat quality and peptic tissue lesions were assayed. The average daily weight gains for CON, 0.5UTM, 1.5UTM and 2.5UTM were 216, 218, 200 and 170 g, respectively, with the CON and 0.5UTM groups higher than 2.5UTM group (p < 0.05). Sheep from the 2.5UTM treatment had a significantly lower dry matter intake (1.29 kg/day) than those from the CON and 0.5UTM treatments (1.42 and 1.43 kg/day, p < 0.05), and the feed conversion ratio in the 2.5UTM group was the highest (p < 0.05). Carcass characteristics, including shrunk body weight, empty body weight, hot carcass weight, dress percentage, and the absolute or relative weight (% body weight) of heart, liver, spleen, lung and kidney, were not altered by the treatments (p > 0.05). The muscular pH of 2.5UTM was higher than that of CON (5.68 vs. 5.52, p < 0.05), and shear force in 0.5UTM was lower compared with CON and 2.5UTM (p < 0.05). The anatomical structure lesions in kidneys became more serious with the increasing dietary urea concentrations, with the 2.5UTM animals showing the most severe lesions compared with CON animals. Therefore, supplementary urea as a non‐protein nitrogen source for sheep should not exceed 1.5% of ration having a 50:50 concentrate:roughage ratio to ensure efficacy and safety.     

Mutant-prevention concentrations of enrofloxacin for Escherichia coli isolates from chickens

OBJECTIVE: To investigate the development of enrofloxacin resistance among Escherichia coli isolates obtained from chickens by determining mutant-prevention concentrations (MPCs) and sequence the quinolone resistance-determining regions (QRDRs) of gyrA and parC genes in selected isolates. SAMPLE POPULATION: 15 chicken-derived E coli isolates. PROCEDURES: For all isolates, MPC and minimal inhibition concentration (MIC) of enrofloxacin were determined. The MPCs and maximum serum drug concentrations attained with enrofloxacin doses recommended for treatment of E coli infections in chickens were compared. Mutation frequencies and QRDR sequence changes in gyrA and parC were also determined. RESULTS: In 2 of 15 E coli strains, MPCs were low (0.016 and 0.062 microg/mL), MPC:MIC ratios were 2 and 4, and the GyrA and ParC proteins had no mutations. In 9 susceptible isolates with a GyrA point mutation, MPCs ranged from 2 to 16 microg/mL. For isolates with double mutations in GyrA and a single mutation in ParC, MPCs were > 32 microg/mL (several fold greater than the maximal plasma concentration of enrofloxacin in chickens); mutation frequencies were also much lower, compared with frequencies for single-mutation isolates. CONCLUSIONS AND CLINICAL RELEVANCE: For E coli infections of chickens, MPC appears to be useful for determining enrofloxacin-dosing strategies. The high MPC:MIC ratio may result in enrofloxacin-treatment failure in chickens infected with some wild-type gyrA E coli isolates despite the isolates' enrofloxacin susceptibility (MICs 0.125 to 1 microg/mL). For infections involving isolates with high MPCs, especially those containing mutations in gyrA and parC genes, treatment with combinations of antimicrobials should be adopted.     

棉田膜内与膜间土壤溶液含盐量的变化

用定期取表层土样测定其电导率和在不同深度埋设盐分传感器探头的方法 ,在作物生长季节内 ,监测了棉田膜内和膜间不同深度的土壤溶液含盐量变化。结果为 :1棉田膜内与膜间表层土壤和 1 0 cm、30 cm深土壤溶液含盐量变化较大 ,且规律相同。未灌水时上升 ,灌水后迅速下降。膜间未灌水期间的含盐量上升幅度大于膜内 ,灌水对膜内和膜间表土洗盐、1 0 cm、30 cm深土壤溶液含盐量的降低作用没有差别。降雨可引起膜内和膜间 1 0 cm深土壤溶液电导率的变化 ,这个影响也是膜间大于膜内。 2 60 cm深的土壤溶液不存在明显的盐分累积现象 ,灌水可使这里的土壤溶液含盐量缓慢降低 ,膜间的降低过程快于膜内     

牡丹类psDHN-YSK2基因全长cDNA的克隆与表达分析

为了获得牡丹类脱水素基因的全长cDNA序列,推测其在休眠解除进程中的生物学功能,以不同低温处理时间的牡丹花芽为供试材料,末端快速扩增方法克隆全长cDNA序列,实时定量PCR分析其表达模式。结果表明牡丹类脱水素基因全长cDNA序列为1187 bp,包括831 bp的开放阅读框,114 bp的5’非编码区和242 bp的3’非编码区。其编码的蛋白具有两个植物脱水素蛋白特征性K片段,根据Close的分类方法,属于YSK2类脱水素蛋白。系统发生分析表明psDHN-YSK2基因与葡萄亲缘关系最近。在花芽内休眠解除前期随着低温处理时间的延长psDHN-YSK2表达呈上调趋势。本研究克隆了牡丹psDHN-YSK2的全长cDNA序列,分析了其在花芽内休眠解除过程的表达趋势,暗示了其参与了牡丹花芽的内休眠过程。