Attenuation of virulence of Lawsonia intracellularis after in vitro passages and its effects on the experimental reproduction of porcine proliferative enteropathy

Non-pathogenic Lawsonia intracellularis variants have been obtained through multiple passages in cell culture but there is no information regarding the number of passages necessary to attenuate a pathogenic isolate. The present study evaluated the susceptibility of pigs to L. intracellularis after 10, 20 and 40 passages in vitro. Three groups (six animals/group) were inoculated with pure culture of L. intracellularis on passage 10, 20 or 40 and one group with placebo. The animals were monitored for clinical signs, fecal shedding and serological IgG response during 28 days post-inoculation. Gross and histologic lesions and the level of infection based on the amount of L. intracellularis-specific antigen in the intestinal mucosa identified by immunohistochemistry were evaluated in two animals from each group on days 14, 21 and 28. Animals inoculated with passages 10 and 20 demonstrated proliferative lesions typical of porcine proliferative enteropathy associated with the presence of Lawsonia-specific antigen in the intestinal mucosa. Passage 40-inoculated pigs did not show proliferative lesions or presence of Lawsonia antigen at any time point throughout the study. Similar patterns of the fecal shedding were observed in passage 10 and 20-infected pigs but those infected with passage 40 shed for a short period. Serological IgG responses in passage 10 and 20-inoculated pigs were detected from day 14 post-infection but not at all in passage 40-inoculated animals. These results demonstrate attenuation of the virulence properties of L. intracellularis between 20 and 40 cell passages in vitro. This information will be valuable for design of future experimental models and for studying the mechanisms involved in the attenuation of L. intracellularis virulence.     

食品化学创新型实验教学体系的构建简

以食品组成成分为主线,将实验内容划分为基础型、综合设计型、创新型3个层次,构建创新型实验教学体系.通过课内与课外实验结合、理论教学与实验教学结合、实验教学与科研相结合的教学模式,培养学生创新能力和科学研究能力,为应用型本科院校改革食品化学实验教学提供指导和借鉴.     

昆虫实践在生物技术专业实验教学改革中的应用

结合昆虫学领域的发展现状,将昆虫实践应用于生物技术专业实验课程的教学改革中。通过对生物技术专业实验环节进行教学改革,及时更新教育教学的发展思路,将科研与教学有机结合,昆虫实践已在教学中取得良好的反馈效果。通过对昆虫实验教学环节的改革,优化了实验指导方法,通过电化教学与昆虫学实践研究相融合,调动学生学习实验课程的主动性,激发学生的学习热情,注重学生动手能力的培养,大大提高了昆虫实验课的教学质量。     

农学专业农业昆虫学理论和实验教学实践

针对农林院校农学专业昆虫学的教学现状,从优化教学大纲,加强理论课堂教学,实验教学突出学生主体性,改革考核体系几方面,提出了农业昆虫学课程理论和实践教学改革,以培养学生的主观能动性和综合素质,提高其解决农业生产中实际问题的能力。     

消费者对转基因食品的消费偏好研究

转基因食品自问世以来在各个国家都饱受争议。消费者对转基因食品的消费偏好是转基因食品推广的基础。在前人的研究基础上,采用实地实验的方法来研究消费者的消费偏好。同时,在实地实验中加入风险偏好的测量实验,研究消费者的风险偏好对转基因食品消费偏好的影响。研究结果表明,消费者对转基因食品的消费偏好有明显的下降,风险偏好程度对转基因食品的消费态度并没有显著的影响。     

生态学实验课程类型设计的探讨与实践

以楚雄师范学院新建本科生物技术专业生态学实验课程类型设计的探索历程为例,在总结该校生态学实验课程类型设计的经验和教训的基础上,探讨了正确设计高校实验课程类型的路径和方法。     

“试验设计与数据处理”教学改革探讨——基于本科生毕业论文常见问题的分析

“试验设计与数据处理”是食品类专业的一门重要课程。在分析毕业论文存在问题的基础上,找出这些问题存在的原因并寻求解决办法,为提高“试验设计与数据处理”课程的教学质量和教学效果提供参考和依据。     

新农科背景下《生物统计学与试验设计》教学模式改革

《生物统计学与试验设计》是种子科学与工程专业重要的专业基础课和专业主干课,是一门实践性较强的工具性学科,在教学过程中,逐步建立了以培养新型农林人才为目标的课程教学体系,教学方法多元化、重视实践教学、强化过程性考核,对学生实践能力的培养收到较好的教学效果。     

Detection of Leishmania infantum DNA by real-time PCR in saliva of dogs

This study developed a real-time quantitative PCR (qPCR) assay to detect L. infantum kinetoplast DNA (kDNA) in canine saliva. The qPCR showed an efficiency of 93.8%, a coefficient of correlation of 0.996 and a detection limit of 0.5 fg/reaction (0.005 parasites), although it detected until 0.25 fg/reaction (0.0025 parasites). When samples from 12 dogs experimentally infected with L. infantum were collected, L. infantum kDNA was detected at 16-weeks post-infection (wpi) in 41.7% and 91.7% of saliva and bone marrow samples, respectively, and at 47-wpi in 75% of both samples. L. infantum kDNA can be detected by qPCR in canine saliva, with lower sensitivity in the early stages of infection and a lower parasite load estimation compared to bone marrow. However, saliva had similar sensitivities to bone marrow in the later stages of the infection and could be used to detect L. infantum kDNA being aware of its limitations.