Johne's disease of sheep in the South Island of New Zealand

Bracken fern (Pteridium esculentum) was harvested from two sites LB and TB one of which (TB) was on a central North Island New Zealand farm where bovine enzootic haematuria (BEH) was known to occur. The fern was dried, ground and incorporated (25% w/w) into a pelleted diet and fed to female rats for a total of 162 days. Fifteen weeks later when the rats were autopsied it was found that numerous tumours, mainly of the ileum and urinary bladder were present in the animals fed the bracken fern from the TB site. Neoplasms were found in 85% of rats from the TB group compared with 11% in the LB group while only a single tumour (a haemangioma of the uterus) was observed in the controls. In all, there were neoplasms in 42, 5 and 1 organ/s from the TB, LB and control rat groups respectively (p<0.001). Analysis of the fern and pellets for ptaquiloside, the carcinogen in bracken fern, showed much higher levels present in the material from the TB site. There was 26 and 2270 μg ptaquiloside/g of dried fern and, for the pellets from the same fern, 6.5 and 355 μg ptaquiloside/g of pellets, for one collection from the LB and TB sources respectively.     

逆流运动对多鳞四须鲃幼鱼活动代谢及体内盐酸诺氟沙星残留的影响

以多鳞四须鲃(Barbodes schwanenfeldi)幼鱼(体质量90.3 g±10.1 g)为研究对象,设置0 BL/s和2.0 BL/s两种流速条件,使用自制的活动代谢和游泳行为同步测定装置测定不同时段幼鱼的摆尾频率和耗氧率。在此基础上,按鱼体质量以每天50 mg/kg口服盐酸诺氟沙星的剂量连续7 d投喂药饵,研究了两种流速对停药后多鳞四须鲃肌肉组织盐酸诺氟沙星残留的影响。结果表明,实验期间无论哪个时段,2.0 BL/s流速下多鳞四须鲃摆尾频率和耗氧率均显著大于静水组(P0.05);同一流速下多鳞四须鲃摆尾频率和耗氧率随养殖时间的延长有逐渐降低趋势。与静水对照组相比,停药后各时间点(1 d、2 d、4 d)2.0 BL/s流速组鱼肌肉盐酸诺氟沙星含量均显著减少(P0.05),在停药第6 d已低于检出限,而静水对照组则在停药12 d才低于检出限。研究结果说明适当的水流刺激可以诱导鱼类进行逆流运动,促进鱼体代谢和加速药物残留的排除。     

浅议东莞百悦尚城园林景观工程施工与设计的对接问题

园林工程施工效果要达到充分体现设计思想和理念的目的,必须解决好施工与设计的对接问题,其关键在于分析施工、设计与市场的偏差及其出现的原因,并采取措施和方法尽量消除或减少偏差。     

Effect of chemical and physical treatments on the inactivation of Macrobrachium rosenbergii nodavirus and extra small virus

White tail disease (WTD) is found to cause immense economic losses in hatcheries, with mortalities often reaching 100% within 4 or 5 days. The pathogenic agents have been identified as Macrobrachium rosenbergii nodavirus (MrNV) associated with extra small virus (XSV), which are 27 and 15 nm in diameter respectively. The effects of some chemical disinfectants hydrogen ions (pH), heat and ultraviolet (UV) irradiation on the inactivation of MrNV and XSV were investigated. The viral inoculum exposed to UV irradiation for a period of 5 min and more was totally inactivated and failed to cause mortality in postlarvae of prawn. The viruses were totally inactivated by this high pH (8.5, 9 and 10). The viral suspension treated with sodium hypochloride, formalin, Benzalkonium chloride and Benzethonium chloride at the concentration of 200 ppm caused 100% mortality in postlarvae of prawn. Iodine was found to be effective to inactivate MrNV and XSV at the concentration of 100 ppm or more, whereas the viral suspension treated with iodine at the concentration of 50 ppm or less caused mortality in postlarvae. The infected postlarvae in treated and positive control groups showed positive by RT‐PCR for these viruses.     

甜菜夜蛾细胞色素P450(CYP9A11)与3种杀虫剂的结合机理研究

细胞色素P450(以下简称CYP)与昆虫的抗药性密切相关。本研究运用AutoDock分子对接技术和分子力学泊松-波尔兹曼表面积法(molecular mechanics Poisson-Boltzmann surface area,MM-PBSA)结合自由能计算方法,分析了甜菜夜蛾CYP9A11与3种杀虫剂结合的作用位点、作用力类型和大小。结果表明:CYP9A11与毒死蜱结合形成两个氢键,有8个氨基酸残基参与形成疏水作用力,二者结合自由能为-3659.80 kJ/mol;CYP9A11与灭多威结合形成5个氢键,有3个氨基酸残基形成疏水作用力,结合自由能为-470.92 kJ/mol;CYP9A11中有7个氨基酸残基与氯氰菊酯结合形成疏水作用力,结合自由能为-473.44 kJ/mol。范德华力是CYP9A11与毒死蜱结合的主要驱动力,极性溶剂化能是CYP9A11与氯氰菊酯和灭多威结合的主要驱动力,这些结果为阐明甜菜夜蛾CYP9A11与3种杀虫剂的结合机理提供了参考。     

休闲农业网设计开发及促进休闲农业产业的发展

中国休闲农业的健康发展,需要农业休闲产品与目标消费群体之间实现有效的供需对接。"互联网+"发展模式已经渗透到社会、生产和生活等的诸多方面,对旅游农业产业的发展起到了推动作用。该文以农业部创办的中国休闲农业网和去农庄网为例,分析了休闲农业网站的模块设计、栏目设置、内容浏览次数等,考察这2个网站的实际建设成效,并提出相应的网站建设建议,探索如何使用互联网技术更好地推动中国休闲农业与乡村旅游的发展。     

杀虫晶体蛋白Cry1Ac与其配体N-己酰半乳糖胺的对接研究

利用同源建模得到杀虫晶体蛋白Cry1Ac的三维结构,之后模拟其与配体N-已酰半乳糖胺的对接,预测关键的氨基酸残基：N482、Q506、S501、L505和V483。Cry1Ac的虚拟突变体与N-已酰半乳糖胺之间的分子对接分析结果表明,R466、R468、R470和R472可能对维持Cry1Ac的DomainⅢ稳定构象起着重要作用。N482和Q506两个残基均含有酰氨基,在对接中易于形成多个氢键,这对稳定对接具有重要作用。研究结果可提供一些有用的信息,用于指导杀虫晶体蛋白的理性设计。     

牛尾毛中稳定性碳同位素组成变化规律研究

 【目的】研究牛尾毛中稳定性碳同位素组成随饲料改变的变化规律,确证牛尾毛一旦长成,其中的稳定性碳同位素不再与其它部分的进行交换,每段毛发记录的同位素信息可反映毛发生长时的饲料信息。【方法】设计控制饲料配比的牛模型试验,利用同位素比率质谱仪测定不同段位牛尾毛中的δ13C值,分析不同段位牛尾毛的δ13C值随饲料改变的变化趋势,以及牛尾毛中的δ13C值与饲料、牛个体的关系。【结果】随着牛生育过程中饲料成分的改变,不同段位牛尾毛中碳同位素组成有极显著差异,而且饲料对牛尾毛中碳同位素组成的影响远大于个体对其的影响;分段取得的牛尾毛δ13C值与其饲料δ13C值、C4植物饲料比例呈极显著相关（P＜0.01）,而不分段的牛尾毛δ13C值与饲料碳同位素组成相关性不显著。【结论】牛尾毛一旦长成,其中的稳定性碳同位素不再与其它部分进行交换,每段毛发的同位素信息可反映牛在毛发生长时的饲料信息,牛尾毛可以看作是记录牛饲料改变信息的档案库。     

Effect of age at castration on behavioural response to subsequent tail docking in lambs

Objective To investigate the effects of age at castration on the subsequent behavioural response to tail docking. Study design Randomised prospective blinded experimental study. Animals Forty‐five male lambs were admitted to the study at birth. Methods The lambs were allocated into two groups for castration by rubber ring at 1 (1D, n = 20) or 10 (10D, n = 25) days of age. Following castration both groups of lambs were tail‐docked by rubber ring at between 26 and 34 days of age. Their behavioural responses to tail docking were recorded by video for 30 minutes before (n = 11) and 30 minutes after (n = 45) tail docking. Statistical differences were tested using anova with Mann‐Whitney post‐hoc testing. Results Two data sets were removed resulting in n = 19 and = 24 at 1D and 10D, respectively. A significant increase in the incidence of active and abnormal postural behaviour was seen in both groups after tail docking. Three behaviours were significantly different (p < 0.05) between the two groups. These behaviours were rolling, standing unsteadily and the total proportion of time standing with abnormal posture. These behaviours all had greater incidence in the lambs castrated at 1D of age. Conclusions Lambs castrated at 1D appeared to perceive a greater intensity of pain after subsequent tail docking than lambs castrated at 10D. Clinical relevance The timing of a single noxious stimulus in young animals can affect subsequent pain perception.