Isolation of two novel myb-like genes from Arabidopsis and studies on the DNA-binding properties of their products

Two novel myb-like genes (atmyb6 and atmyb7) were isolated from an Arabidopsis thaliana cDNA library. The entire proteins or the Myb domains encoded by the genes were expressed as fusion proteins in Escherichia coli. The DNA-binding domain of the murine c-Myb was also expressed in the same way for use in comparative studies. The fusion proteins were examined for their DNA-binding activity using the animal c-Myb DNA-binding site (MBS) and the binding site of the maize P gene product (PBS). The Myb domain of Atmyb6 bound to PBS more efficiently than to MBS. Complete Atmyb6 and Atmyb7 proteins preferentially bound to PBS but not MBS. This suggests that the in vitro binding consensus sequences for both Atmyb6 and Atmyb7 are similar to PBS. The binding of the Myb domain of Atmyb6 to both PBS and MBS raises the possibility that the protein recognizes multiple sequences in vivo. The third α-helix and three adjacent amino acids in the third repeat (R3) of c-Myb were replaced with the analogous sequence of Atmyb6 to create a chimeric Myb protein. This chimeric protein bound to PBS with a low affinity but failed to bind to MBS. Thus the binding pattern of the chimeric Myb protein is similar to that of the Atmyb6. This result suggests that the last 20 amino acids in the R3 repeat of Atmyb6 play a major role in DNA-binding.     

薯蓣皂甙元分离工艺的研究及其综合利用

采用“分离法加工薯蓣植物”的工艺技术是将薯蓣根茎带水磨碎,在水中筛分,将各有用成分分开后,分别采用适宜的方法加工利用。本文报道利用薯蓣植物盾叶薯蓣（ＤｉｏｓｃｏｒｅａｚｉｎｇｉｂｅｒｅｎｓｉｓＣ．Ｈ．Ｗｒｉｇｈｔ）和穿龙薯蓣（ＤｉｏｓｃｏｒｅａｎｉｐｐｏｎｉｃａＭａｋｉｎｏ）制取薯蓣皂甙元（Ｄｉｏｓｇｅｎｉｎ）和药用酵母粉（Ｓａｃｃｈａｒｏｍｙｃｅｓｓｉｃｃｕｍ）的方法。     

DNA-dependent RNA polymerases from Schneider 2-L cells of Drosophila. I. Preliminary characterization

The DNA-dependent RNA polymerases of Schneider 2-L cells of Drosophila melanogaster are described. These cells contain five readily detectable forms of this enzyme, polymerases I_a, I_b, III_a, II, and III_b, which elute from DEAE-Sephadex at 0.08, 0.12, 0.15, 0.20, and 0.22 m ammonium sulfate, respectively. RNA polymerases III_a and III_b, which each constitute about 5–10% of the total RNA polymerase activity in Drosophila embryos, are found to constitute 30 and 10%, respectively, of the total polymerase activity in cultured cells. The two form III polymerases are further characterized by in vitro response to divalent cations and ionic strength, template utilization, and sensitivity to -amanitin. Verification of the class III designation of these two polymerases is provided by their sensitivity to only very high levels of -amanitin (50% inhibition at approximately 800 µg/ml), their 10-fold greater activity on poly[d(A–T)], and their elution from DEAE-cellulose at lower ionic strengths than from DEAE-Sephadex.This work was supported by the Natural Sciences and Engineering Research Council.     

由大肠杆菌中提取重组猪生长激素的研究

 本文通过研究提出了一种由大肠杆菌细胞中提取重组猪生长激素的方法。提取回收率为52.4％,纯度为94.1％,具有生物学活性。     

山西朔县种子植物区系及其生态经济意义

朔县(现朔州市朔城区)植物种属相对丰富,具有维管束植物938种,隶属于420属,105科。其植物区系主要起源于古北大陆;种子植物属的地理成分复杂多样,以温带成分占绝对优势,具有典型的温带草原性质;与相邻地区植物区系的比较分析表明,联系最为密切的是蒙古草原植物区系,其次是黄土高原植物区系。该县植物资源利用应采取的对策是:既要合理开发利用,又要加强物种的保护。     

发展生态渔业,保护水域环境——朱湖水体生态农业初探

渔业是大农业的一环。在充分合理的利用好水体自然资源,大力发展水产品生产的同时,认真保护好水域生态环境,这不仅是渔业的问题,也完全符合环保这项基本国策。研究渔业生态,发展生态渔业也是当今水产养殖发展的主要方向。“水体生态农业”是依据生态学原理,生态     

急进高海拔时健康人夜间睡眠、呼吸状态和血氧饱和度的变化

在海拔2300m选择健康成年男性5人,急进抵海拔4660m,用多导监测仪分别在两地连续7h监测夜间睡眠、呼吸状态和血氧饱和度变化,进行自身对比。结果发现:(1)急进高海拔后,总睡眠时间、有效睡眠指数、Ⅲ～Ⅳ期深睡眠均较中度高原减少(p<0.01);总觉醒时间、Ⅰ～Ⅱ期浅睡眠高海拔较中度高原增多(p<0.05):(2)急进高海拔后,有3名健康人出现周期性呼吸,其中1名健康者出现周期性呼吸119次,伴有中枢性睡眠呼吸暂停,最低Sao_2为78％;(3)同海拔高度夜间睡眠时与清醒时Sao_2相比较,中度高原下降4.2％,高海拔下降11.2％(p<0.01);高海拔与中度高原夜间清醒时Sao_2相比较下降7.4％,睡眠时下降14.4％(p<0.001)。结果提示:(1)睡眠加重了高原人原有的低氧血症;(2)低氧血症导致睡眠结构的紊乱和睡眠质量的降低;(3)睡眠中出现的周期性呼吸,应视为机体的一种自我保护机制;(4)频发的周期性呼吸或睡眠呼吸暂停将影响大脑机能。