ETHYL ALCOHOL REDUCTION OF SALMONELLA TYPHIMURIUM IN POULTRY FEED

This study was designed to evaluate the effect of ethyl alcohol as a potential treatment for reduction of Salmonella populations in poultry feed. Growth rate of S. typhimurium in tryptic soy broth was significantly reduced by addition of greater than 0.3% volume/volume of ethyl alcohol and growth was completely inhibited by addition of 5% ethyl alcohol. Ethyl alcohol concentrations of 20% volume/weight and greater significantly reduced initial S.typhimurium populations in poultry feed (for 20% treated, 2.31 ± 0.31 vs 3.39 ± 0.29 for untreated; P < 0.05). When feed treatment was administered either before or after inoculation of S. typhimurium with 60% ethyl alcohol or 0.04% buffered propionic acid, populations in feeds treated after inoculation were decreased to a nondetection level (< 1.0 log₁₀ CFU/g) by ethyl alcohol treatment but not by other treatments. Ethyl alcohol treatment may have the potential for reducing Salmonella spp. contamination in poultry feed.     

干扰素研究及应用进展

1957年,英国科学家Isaacs和Lindenmann利用鸡胚绒毛尿囊研究流感干扰现象时,发现一种能够干扰病毒繁殖的物质,称之为干扰素（IFN）,由于干扰素对许多疾病有很好的治疗作用,一直是医学领域研究的重要物质之一。现在干扰素已成功地用于肝炎、肿瘤治疗等方面。为了充分发挥干扰素的作用,人们稍用基因工程的方法来对干扰素的产量及功效进行改进,已达到更好的应用,因此基因工程干扰素越来越多地成了研究的重点。     

Interaction of Bruton's tyrosine kinase and protein kinase Ctheta in platelets. Cross-talk between tyrosine and serine/threonine kinases.

The nonreceptor Bruton's tyrosine kinase (Btk) has been previously shown to associate physically and functionally with members of the protein kinase C (PKC) family of serine/threonine kinases in a variety of cell types. Here we show evidence for a novel interaction between Btk and PKCtheta; in platelets activated through the adhesion receptors GP Ib-V-IX and GP VI. Alboaggregin A, a snake venom component capable of activating both receptors in combination, leads to tyrosine phosphorylation of Btk downstream of Src family kinases. Inhibition of Btk by the selective antagonist LFM-A13 causes a reduction in calcium entry, although secretion of 5-hydroxytryptamine is potentiated. Btk is also phosphorylated on threonine residues in a PKC-dependent manner and associates with PKCtheta; upon platelet activation by either alboaggregin A or activation of GP Ib-V-IX alone by von Willebrand factor/ristocetin. PKCtheta; in turn becomes tyrosine-phosphorylated in a manner dependent upon Src family and Btk kinase activity. Inhibition of Btk activity by LFM-A13 leads to enhancement of PKCtheta; activity, whereas nonselective inhibition of PKC activity by bisindolylmaleimide I leads to reduction in Btk activity. We propose a reciprocal feedback interaction between Btk and PKCtheta; in platelets, in which PKCtheta; positively modulates activity of Btk, which in turn feeds back negatively upon PKCtheta;.     

苹果园光能截获率的数学模型

应用气象学原理推导了不同纬度、不同栽植行向、不同树形的苹果园光能截获率的数学模型,给出在保证树冠基部外围日照时间大于25％总日照时间的条件下,生长季中充分截获光能的最佳树形、行距、冠高、冠径的优化组合方案。实例分析表明,计算结果与专家经验基本一致。本研究为果园合理栽植,充分利用光能,合理整形修剪提供理论依据与参考方案。     

毛乌素沙地南缘沙丘生物结皮对凝结水形成和蒸发的影响

在水分极度匮乏的荒漠生态系统,凝结水是除降雨之外最重要的水分来源之一,它对荒漠生态系统结构、功能和过程的维持产生重要的影响。为探明半干旱沙区生物结皮表面的凝结水形成和蒸发特征,采用自制的微型蒸渗计(直径7 cm、高5 cm的PVC管)实验观测了不同类型地表(裸沙、浅灰色藻类结皮、黑褐色藻类结皮和苔藓结皮)对凝结水形成和蒸发的影响。结果表明:(1)观测期间共有20次凝结水形成记录,除降雨天气外,几乎每天都能观测到水分凝结现象;(2)不同类型地表凝结水总量依次为(1.998±0.075),(2.326±0.083),(2.790±0.058)和(3.416±0.068) mm,生物结皮表面的凝结水总量显著大于裸沙(P < 0.05);随生物结皮的发育,不同类型生物结皮表面的凝结水总量呈增加的趋势,凝结水总量之间差异显著(P < 0.05);观测期间不同类型地表日平均凝结水量依次为(0.100±0.003),(0.116±0.004),(0.140±0.002)和(0.171± 0.003) mm,不同类型地表日平均凝结水量之间差异极显著(P < 0.01);(3)凝结水形成过程的观测结果显示,凝结水19:00开始形成,23:00-凌晨1:00形成不明显,1:00-7:00继续形成,除浅灰色藻类结皮外,太阳升出后在黑褐色藻类结皮和苔藓结皮表面继续形成少量的凝结水;凝结水7:30开始蒸发,10:30到11:00之间结束蒸发,凝结水在裸沙和浅灰色藻类结皮中的保持时间显著大于黑褐色藻类结皮和苔藓结皮中的保持时间(P < 0.05);(4)凝结水的形成受大气温度、地表温度、空气相对湿度和大气地表温度差等气象因素的影响,但其形成过程不与某一个气象因素呈简单的线性关系。     

人热休克蛋白gp96基因的克隆及其在大肠杆菌中的表达与纯化

热休克蛋白gp96是热休克蛋白90家族成员,能够引起非特异性和特异性免疫反应。得到大量高纯度的蛋白质是研究开发gp96的关键。然而重组的gp96容易在E．coli中降解,并在一定条件下形成多聚体。实验先将人gp96基因克隆到pET-30a载体上并在E．coli Blstar中表达,再经过亲和层析、阴离子交换、分子筛分别纯化gp96。最终去掉了大部分的降解片段和多聚体,得到一定量的可溶性gp96,为进一步研究其结构和功能打下一定的基础。     

'Calling Cards' method for high-throughput identification of targets of yeast DNA-binding proteins

We present a protocol for a novel method for identifying the targets of DNA-binding proteins in the genome of the yeast Saccharomyces cerevisiae. This is accomplished by engineering a DNA-binding protein so that it leaves behind in the genome a permanent mark -- a 'calling card' -- that provides a record of that protein's visit to that region of the genome. The calling card is the yeast Ty5 retrotransposon, whose integrase interacts with the Sir4 protein. If Sir4 is fused to a DNA-binding protein, it recruits the Ty5 integrase, which directs insertion of a Ty5 calling card into the genome. The calling card along with the flanking genomic DNA is harvested by inverse PCR and its genomic location is determined by hybridization of the product to a DNA microarray. This method provides a straightforward alternative to the 'ChIP-chip' method for determining the targets of DNA-binding proteins. This protocol takes approximately 2 weeks to complete.