The comparative pathogenicity of four serovars of Actinobacillus (Haemophilus) pleuropneumoniae

The pathogenicity of 2 isolates of each of serovars 7, 3, 1 and 2 of Actinobacillus pleuropneumoniae was tested by intranasal inoculation into 60, 6-week-old large white pigs. Four dose rates varying from 0.27 to 560 x 10(6) organisms per pig with 10-fold serial dilutions were used. Surviving pigs were necropsied 7 days after inoculation. The proportion of pigs dying and developing gross lesions following infection was significantly greater for pigs given serotype 1 than for each of the other 3 serotypes, which did not differ significantly from each other. Twelve of 16 pigs given either of the 2 isolates of serovar 1 died after acute illness and 1 of 44 pigs given either of the 2 isolates each of serovars 7, 3 and 2 died. Pigs given serovar 1 showed high temperatures, severe respiratory distress, frothy haemorrhagic nasal discharge and weight loss. Lung lesions were produced in all 16 pigs given serovar 1, in 7 of 14 pigs given serovar 7, 7 of 14 pigs receiving serovar 3 and in 5 of 16 pigs given serovar 2. The lethal infections were characterised by a severe acute fibrinohaemorrhagic necrotising pleuropneumonia, whereas non-lethal cases had lung lesions ranging from necrotising purulent pleuropneumonia to abscessation. Significant differences between isolates in proportions of tissues culture positive for A. pleuropneumoniae for serovars 7 and 2, but not for serovars 3 and 1 suggested that isolates may vary in virulence within serovars, but more detailed studies are needed to clarify this point.     

教师教学质量评估研究

本着以人为本、求真务实的理念,根据教育评价理论,运用数理统计原理,采用高阶综合评价方法对评估原则、体系建构、评估指标等进行分析研究,建构教师教学质量评估模型。     

Why implantation of bio‐loggers may improve our understanding of how animals cope within their natural environment

Bio‐loggers are miniaturized autonomous devices that record quantitative data on the state of free‐ranging animals (e.g. behavior, position and physiology) and their natural environment. This is especially relevant for species where direct visual observation is difficult or impossible. Today, ongoing technical development allows the monitoring of numerous parameters in an increasing range of species over extended periods. However, the external attachment of devices might affect various aspects of animal performance (energetics, thermoregulation, foraging as well as social and reproductive behavior), which ultimately affect fitness. External attachment might also increase entanglement risk and the conspicuousness of animals, leaving them more vulnerable to predation. By contrast, implantation of devices can mitigate many of these undesirable effects and might be preferable, especially for long‐term studies, provided that the many challenges associated with surgical procedures can be mastered. Implantation may then allow us to gather data that would be impossible to obtain otherwise and thereby may provide new and ecologically relevant insights into the life of wild animals. Here, we: (i) discuss the pros and cons of attachment methods; (ii) highlight recent field studies that used implanted bio‐loggers to address eco‐physiological questions in a wide range of species; and (iii) discuss logger implantation in light of ethical considerations.     

广灵驴成纤维细胞系的建立及其相关生物学特性研究

试验旨在建立广灵驴成纤维细胞库,以期在细胞水平上对广灵驴进行保护。本研究以1月龄广灵驴耳缘皮肤组织为试验材料,采用组织块贴壁法进行成纤维细胞培养,建立了广灵驴耳缘皮肤组织成纤维细胞系,并对其相关生物学特性进行了鉴定。结果发现,试验所建立的广灵驴成纤维细胞系大多数细胞呈长梭形,部分细胞呈三角状或星型。在培养过程中,广灵驴原代成纤维细胞在贴壁4 d时开始有细胞从组织边缘游离出来,贴壁14 d后,细胞汇合率达到80%,可以进行第一次传代培养;细胞生长态势良好,生长曲线呈典型的S型曲线;细胞冻存复苏后活率有所下降,但生长状态良好。细胞分裂中期染色体数2n=62,说明成功建立了广灵驴成纤维细胞系。通过本方法建立的广灵驴成纤维细胞系为后续广灵驴的相关研究奠定了基础。     

崇明东滩不同演替阶段湿地土壤有机碳汇聚能力的差异性及其微生物机制

旨在阐明崇明东滩不同演替阶段湿地土壤有机碳汇聚能力的差异性及其机制,以期为优化湿地的管理与保育措施,进而保持和提升湿地的碳汇功能提供理论指导和决策依据。研究结果表明,4个不同演替阶段湿地土壤有机碳含量和微生物呼吸强度有显著差异(P<0.05),中高潮滩处的土壤有机碳汇聚能力最高,这是由于其具有较高的有机碳输入(植物枯落物)和相对较低的碳输出(土壤呼吸)。PCR-DGGE分析和系统进化树结果表明,4个不同演替阶段土壤的微生物群落结构存在差异,一些特异性优势菌的存在可能是影响土壤微生物呼吸强度,并最终影响土壤有机碳汇聚能力的重要原因。出现在高潮滩的噬纤维菌和假单胞属菌具有较高降解纤维素等有机质的能力,它们的存在可能强化了高潮滩的土壤呼吸作用,从而降低了高潮滩土壤的有机碳汇聚能力。     

广西城乡居民收入差距与经济增长关系的实证研究

选用城镇居民人均可支配收入、农村居民人均纯收入和环比经济增长率3项指标,根据1980～2009年统计年鉴中的时序数据,运用ADF检验、Granger因果关系检验等方法对广西城乡居民收入与经济增长的关系进行分析。结果表明,库兹涅茨的经济增长与收入差距关系的理论不适于解释广西出现的城乡收入差距扩大的现象,＂滴流效应＂对缓解城乡收入的持续扩大也不会产生明显的效果。广西城乡居民收入差距扩大更多的是受到发展政策和城乡分割的经济体制制约而并非经济发展本身的影响。只有推进经济体制改革、打破城乡阻隔才是缩小城乡收入差距的最佳途径。     

氨基酸对基因表达的影响

氨基酸除了作为蛋白质合成底物外 ,氨基酸在体内还发挥着其它重要的营养生理功能 ,例如作为糖异生的底物、作为神经递质和信号转导的前体及蛋白质周转的调节剂等。然而 ,大量研究证实氨基酸还作为营养信号分子调控着许多调节细胞功能和氨基酸代谢的基因的表达。氨基酸主要是通过影响DNA的转录和mRNA的稳定性和翻译而调控基因的表达。但是 ,氨基酸调控基因表达的分子机制仍然不十分清楚     

温度与饲料蛋白质水平对吉富品系尼罗罗非鱼(Oreochromis nilotica)幼鱼生长和血清生长激素水平的影响

采用中心复合试验设计和响应曲面分析方法,在试验室条件下,研究了温度(20～34℃)和饲料蛋白质水平(25％ ～ 50％)对吉富品系尼罗罗非鱼(Oreochromis nilotica)幼鱼生长、饲料效率和血清生长激素(GH)水平的影响.试验期为56 d.随着温度和饲料蛋白质水平的上升,特定生长率、饲料效率和血清GH水平均呈先上升后下降的变化趋势.温度与饲料蛋白质水平的一次效应对特定生长率、饲料效率和血清GH水平有显著影响(P＜0.05);温度和饲料蛋白质水平的二次效应与互作效应对饲料效率和血清GH水平有显著影响(P＜0.05),温度与蛋白质水平对特定生长率无互作效应(P＞0.05).高温与饲料高蛋白质水平会降低饲料效率和血清GH水平.因子与响应值间二次多项回归方程的决定系数分别达到0.958、0.955和0.875(P ＜0.01),可用于预测.温度/饲料蛋白质水平最优组合为29.9 ℃/40.3％,此时,特定生长率和饲料效率均较高,分别为2.748％/d和77.5％,其可靠性达0.888.温度对特定生长率、饲料效率和血清GH水平影响较饲料蛋白质明显.血清GH水平与特定生长率相关性较低,而与饲料效率呈正相关.因此,建议在罗非鱼幼鱼的培育中,按照上述温度与饲料蛋白质组合安排生产,以提高罗非鱼养殖效益.     

Stocking rate effects on the worm burdens of Angora goats and Merino sheep

Worm egg counts of yearling Angora or Merino wethers grazing in mixed flocks at either 4/ha or 8/ha were observed over a 5 month period. Based on faecal egg counts infection levels in the sheep increased for the first 3 months and then decreased as the animals developed resistance. Egg counts in the goats did not decrease during the experiment. Post mortem worm counts indicated that there was a significant host species--stocking rate interaction on worm burdens of Haemonchus contortus adults and Ostertagia circumcincta adults and larvae. Goats had more H. contortus and O. circumcincta adults than sheep at the 8/ha stocking rate. At 4/ha goats had fewer O. circumcincta fourth stage larvae than sheep. There was no stocking rate effect on the numbers of Trichostrongylus axei or T. colubriformis. Sheep had more T. axei and fewer T. colubriformis than goats.