怎样正确购买受体牛

胚胎移植成功与否受体牛选择占有举足轻重的作用,下面谈谈怎样正确购买和选择受体牛。1品种受体牛品种的选择是做胚胎移植时应该首先考虑的问题。本地品种做受体会出现下列问题:受体牛体格小难产率高;由于都是役用牛产奶量很低,所产的牛乳不够犊牛吃;如是杂交牛,生殖器官发育往     

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.     

Inhibition of porcine circovirus type 1 and type 2 production in PK-15 cells by small interfering RNAs targeting the Rep gene

Porcine circovirus type 1 (PCV1) and type 2 (PCV2) are two genotypes of porcine circovirus. Both of them are presumed to be widespread in the swine population. Currently, there is no specific treatment for their infections. RNA interference (RNAi) is a sequence-specific RNA degradation mechanism mediated by small interfering RNA (siRNA), which represents a possible therapeutic application for the treatment of viral infections. In this study, three siRNA expression plasmids (pS-RepA, pS-RepB and pS-RepC) were generated to target three different coding regions of the Rep protein (Rep) of PCV. These siRNAs were used to inhibit PCV production in a porcine kidney cell line, PK-15 cells. Our results revealed that Rep gene expression was inhibited by pS-RepA, pS-RepB and pS-RepC to different degrees. Moreover, our study also showed that the production of PCV1 and PCV2 was reduced by these siRNAs. pS-RepC, which targets the middle region of Rep gene, proved to be the most efficient siRNA for inhibition of Rep expression and viral production. Taken together, our data suggest that RNAi could be investigated as a potential treatment for PCV infection.     

家蚕新品种“9903·801A×9902·812B”主要经济性状差异分析

通过对9903、801A、9902、812B组成的中日系各2对复交原种及8种不同交配型式的一代杂交种主要经济性状进行分析比较，了解到新品种“9903·801A×9902·812B”与对照黄鹤×朝霞之间差异显著，而8种交配型式之间差异不显著，为新品种的组配，鉴定及应用提供了参考。     

A computer program for calculation of doses and prices of injectable medications based on body weight or body surface area

A computer program (CalcAnesth) was developed with Visual Basic for the purpose of calculating the doses and prices of injectable medications on the basis of body weight or body surface area. The drug names, concentrations, and prices are loaded from a drug database. This database is a simple text file, that the user can easily create or modify. The animal names and body weights can be loaded from a similar database. After typing the dose and the units into the user interface, the results will be automatically displayed. The program is able to open and save anesthetic protocols, and export or print the results. This CalcAnesth program can be useful in clinical veterinary anesthesiology and research. The rationale for dosing on the basis of body surface area is also discussed in this article.     

L-选择素分子结构及功能的研究进展

近 1 0年来 ,由于分子生物学及相关学科的理论和技术的飞速发展 ,使得对L 选择素的分子结构、分子功能的研究更加深入。就其分子结构而言目前已经完全清楚 ,而功能与其相应的问题仍在研究和探索之中。作为受体的选择素 ,其功能的实现是在其与相应的配体结合之后。表达与调节是在细胞因子、炎症介质以及其他因素的作用下 ,细胞表面黏附分子表达的水平和构型可以发生改变 ,以调节免疫平衡。L 选择素通过白细胞表面的Ca2 依赖的凝集素结构域和胞内小片段激活酪氨酸酶p56lck和ras的信号途径进行跨膜信号转导。活化依赖和活化独立的脱落、生理和病理意义及基因改造对功能的影响等方面目前仍在进一步的研究之中     

一种澄清的低浓度桑果汁饮料的研制

本研究了桑果汁的澄清方法，确定了一种澄清低浓度桑果汁饮料的配方和工艺，也指出了该饮料的不足以及进一步研究需要解决的问题。     

短期禁牧对天山北坡蒿类荒漠群落特征及其稳定性的影响

本研究以天山北坡蒿类荒漠为研究对象,采用野外调查取样的方法,探讨不同区域荒漠围栏内外群落特征和物种多样性对禁牧的响应规律,分析禁牧对生态系统稳定性的影响。结果表明,1)禁牧能改变荒漠植被功能群结构,禁牧后不同生态经济类群群落盖度和生物量分别上升40.2%~57.0%和44.4%~81.0%;2)荒漠群落物种多样性指数对短期禁牧的响应较小,但从区域上看,玛纳斯荒漠放牧区Patrick丰富度指数、Shannon-Wiener多样性指数比博乐和奇台显著高16.7%~20.0%,而禁牧区Simpson优势度指数、Shannon-Wiener多样性指数、Pielou均匀度指数高了8.6%~17.7%;3)短期禁牧有利于荒漠群落稳定性的维持,且稳定性可能与禁牧年限和生态环境的变化均有一定的关系。因此,短期禁牧能显著提高荒漠草地生产力,有利于群落物种多样性和群落稳定性的维持。     

让警犬技术强警增效——记全国公安科技工作先进个人

2007年2月27日至28日,全国公安科技大会在北京举行。2月28日,大会对被授予"科技强警示范城市"称号的城市和公安科技"突出贡献奖"、"科技英才奖"、"科技先进集体"的获奖者和单位进行了表彰。中共中央政治局委员、国务委员、公安部部长周永康为受表彰单位和个人颁奖。周永康部长要求,公安机关要把科技强警作为“一把手工程”,加强领导,加大投入,完善公安科技管理机制,推动科技强警的深入开展。要树立人才资源是第一资源的观念,造就一支政治坚定、技术过硬、工作规范、作风严谨的公安科技队伍。广大公安科技工作者要发扬严谨求实、艰苦创业、团结协作、拼搏奉献的精神,学习新知识,掌握新技术,成为科技专家、技术能手。在警犬技术领域,就有这样一些政治坚定、技术过硬的科技专家、技术能手在平凡的警犬技术工作中,做出了不平凡的的贡献。大会的众多科技精英中,来自警犬技术战线的5名科技工作者荣获"全国公安科技工作先进个人"称号。他们分别是公安部警犬技术学校副校长李泰山、公安部南京警犬研究所科研管理科科长刘湖、公安部南昌警犬基地犬病防治所所长徐玉生、公安部昆明警犬基地副主任唐树生、新疆生产建设兵团公安局警犬基地主任张学坤。