两种奶牛功能性添加剂效果对比试验

选取泌乳期高产和低产奶牛各18头。高产和低产中各随机选取9头在日粮中添加纤维素复合酶,添加量为0．1kg／t精料;其余18头在日粮中添加酵母培养物,添加量为2kg／t精料。结果显示,高产组饲喂纤维素复合酶的奶牛试验期第35天时产奶量显著高于饲喂酵母培养物的奶牛（P=0．024）,低产组饲喂纤维素复合酶的奶牛试验期内产奶量呈稳步上升趋势;高产组饲喂纤维素复合酶的奶牛乳脂率在试验期28天显著高于同组中饲喂酵母培养物的奶牛（P=0．022）,乳蛋白率在试验第7天（P=0．044）和第28天（P=0．018）显著高于同组中饲喂酵母培养物的奶牛。     

Latent class analysis of the diagnostic characteristics of PCR and conventional bacteriological culture in diagnosing intramammary infections caused by Staphylococcus aureus in dairy cows at dry off

Background

Staphylococcus aureus is one of the most common causes of intramammary infections in dairy cows at dry off. Reliable identification is important for disease management on herd level and for antimicrobial treatment of infected animals. Our objective was to evaluate the test characteristics of PathoProof ™ Mastitis PCR Assay and bacteriological culture (BC) in diagnosing bovine intramammary infections caused by S. aureus at dry off at different PCR cycle threshold (Ct)-value cut-offs.

Methods

Sterile quarter samples and non-sterile composite samples from 140 animals in seven herds were collected in connection with the dairy herd improvement (DHI) milk recording. All quarter samples were analyzed using BC whereas all composite samples were analyzed with PathoProof ™ Mastitis PCR Assay. Latent class analysis was used to estimate test properties for PCR and BC in the absence of a perfect reference test. The population was divided into two geographically divided subpopulations and the Hui-Walter 2-test 2-populations model applied to estimate Se, Sp for the two tests, and prevalence for the two subpopulations.

Results

The Se for PCR increased with increasing Ct-value cut-off, accompanied by a small decrease in Sp. For BC the Se decreased and Sp increased with increasing Ct-value cut-off. Most optimal test estimates for the real-time PCR assay were at a Ct-value cut-off of 37; 0.93 [95% posterior probability interval (PPI) 0.60-0.99] for Se and 0.95 [95% PPI 0.95-0.99] for Sp. At the same Ct-value cut-off, Se and Sp for BC were 0.83 [95% PPI 0.66-0.99] and 0.97 [95% PPI 0.91-0.99] respectively. Depending on the chosen PCR Ct-value cut-off, the prevalence in the subpopulations varied; the prevalence increased with increasing PCR Ct-value cut-offs.

Conclusion

Neither BC nor real-time PCR is a perfect test in detecting IMI in dairy cows at dry off. The changes in sensitivity and prevalence at different Ct-value cut-offs for both PCR and BC may indicate a change in the underlying disease definition. At low PCR Ct-value cut-offs the underlying disease definition may be a truly/heavily infected cow, whereas at higher PCR Ct-value cut-offs the disease definition may be a S. aureus positive cow.     

桑树试管苗生根因素研究

提高试管苗生根率是桑树快速繁殖的关键因素。本实验调查桑子叶试管苗在各种不同条件下的生根情况，探索桑树试管苗的最佳生根条件。实验表明，以1／2MS＋IBA1或1／4MS＋IBA1为基本培养基，肌醇浓度为0.15-0.3g/l，在光照强度2000LX，光照时间12小时，培养温度28℃的培养条件下，桑试管苗平均生根率可达98％，驯化后移栽的成活率在96％以上。     

GDNF对海仁酸损伤体外培养新生大鼠背根神经节神经元的影响

N1无血清培养基原代分离培养新生大鼠背根神经节（dorsal root ganglion DRG)神经元，用兴奋性毒素海仁酸（kainic acidKA)损伤体外培养细胞后，加入胶质源性神经营养因子（glial-derived neurotrophic factor,GDNF)作用。最后通过MTT法检测，细胞总蛋白测定，胎盘兰染色计数，形态学观察等方法研究分析GDNF对兴奋性毒素海仁酸损伤后大鼠DRG神经元的活性，存活及突起生长的影响，结果表明：GDNF对体外正常生长的DRG神经元的存活，活性及突起生长没有明显的促进作用。而在海仁酸损伤后，GDNF对其存活和活性有明显的促进作用。但对突起生长没有明显的影响。     

添加不同酵母培养物对瘤胃纤维分解菌群和纤维素酶活的影响

用3种酵母培养物(YC- 1、YC 2和YC- 3)分别饲喂4头带有永久性瘤胃瘘管的肉牛,研究培养物对瘤胃发酵、纤维分解酶活性和3种纤维分解菌数量的影响,结果表明:YC 2处理的乙酸、丙酸、丁酸和总 VFA浓度显著高于对照组(P<0 .05),YC 1和YC 3处理的乙酸/丙酸比例显著降低(P<0 .01);各处理均能显著提高瘤胃内羧甲基纤维素酶、水杨苷酶和木聚糖酶的活性(P<0 .01);各处理都显著提高黄化瘤胃球菌的相对比例(P<0 .01),16SrRNA特异性寡聚核苷酸探针杂交法分析测定结果表明 3 种纤维分解菌在瘤胃细菌中所占比例为 3. 80%±0 .2%。     

胚胎干细胞的研究进展

胚胎干细胞来源于附植前胚胎的内细胞团或附植后胎儿的原始生殖细胞具有发育全能性的细胞。本文从它的研究概况、生物学特性、胚胎干细胞的分离培养与建系等方面做一概述。     

跨文化交际与“红楼梦”的“情”文化

当今社会，跨文化交际活动日趋频繁。一直以来跨文化交际研究主要集中于不同国家民族的主流文化之间，对于同一文化中的不同群体间的跨文化交际研究相对较少。而中国古典名著“红楼梦”对众多人物间纷繁复杂的关系的描写正体现了这种跨文化交际。在研究分析这些交际的同时，笔者发现这些跨文化交际与书中的“情”文化有着密不可分的联系。可以说，“情”文化奠定了跨文化交际成功的基础。本文尝试对“红楼梦”一书中这种群体间跨文化交际进行初步的探讨，并在此基础上剖析“情”文化对于跨文化交际的重要性，从文学作品中提炼出对社会语言学有价值的东西。     

小白菜小孢子培养胚状体的诱导

21个小白菜品种小孢子培养结果表明:适宜的花蕾长为2.5~3.5mm,花瓣与花药长度比为1/2~3/4;0.05~0.10 mg.L-1的细胞分裂素能促进小孢子胚的发生,高于此浓度的细胞分裂素对小孢子胚的产生有抑制作用,并使小孢子胚向畸形化发展;0.05mg.L-16-BA 0.10 mg.L-1NAA的配比可以明显提高成熟胚的比例。     

Root zone temperature alters storage root formation and growth of sweetpotato

Large mounds amended with plant residues are a common cultivation method for sweetpotato (Ipomoea batatas) in the western parts of the Papua New Guinea highlands, with a suggested benefit of elevated root zone temperature (RZT) from decomposition. This study aimed to evaluate whether RZT affects the formation and growth of sweetpotato storage roots. Experiments evaluated the effects of a constant elevated RZT on the Beauregard cultivar and of a short‐term increase in RZT on the Beauregard and Northern Star cultivars. Plants were grown in 18‐L pots divided into a control compartment (constant RZT at 20°C) and a treated compartment (RZT at 30, 40 or 50°C). Constant elevated RZT was maintained until harvest, while short‐term increase in RZT occurred in weeks 2 and 3 only. Constant elevated RZT did not affect the total number of storage roots, but RZT of 30°C and above reduced the dry‐biomass of storage roots. The short‐term increase in RZT did not alter the total number or dry‐biomass of storage roots in Beauregard, while both of these attributes were reduced at RZT of 40°C or above in Northern Star. Elevated RZT inhibited dry‐biomass accumulation of storage root, with a more pronounced impact at constant elevated RZT. These results demonstrate that any benefits of the mound culture on sweetpotato yield production do not arise through the influence of temperature elevation.     

Factors involved in Agrobacterium tumefaciens-mediated gene transfer into Pinus nigra Arn. ssp. salzmannii (Dunal) Franco

Cotyledons from dissected sterile embryos of salgareño pine (Pinus nigra Arn. ssp. salzmannii (Dunal) Franco) were inoculated with different disarmed Agrobacterium tumefaciens strains harbouring the binary vector p35SGUSint. The transient expression of a β-glucuronidase gene (uidA) was studied, using a histochemical staining procedure. Nineteen days after inoculation, the activity of β-glucuronidase was detected in epidermal and subepidermal layers of cotyledonary explants. The EHA105 strain harbouring a disarmed agropine-type Ti-plasmid (pTiBO542) was the most effective for gene transfer of the uidA gene. The effects of exudates and extracts from 0-day-old embryos on induction of vir gene expression in A. tumefaciens were also examined. The results of this study showed that salgarño pine embryo exudates contain a substance(s) that induce vir gene expression, in similar way to that observed with 100 μM acetosyringone (AS).All these findings suggest that T-DNA processing and transfer might take place when Agrobacterium infects suitable tissues of salgareño pine.