横断山地区果蝇三新种(双翅目：果蝇科)

横断山地区果蝇三新种（双翅目：果蝇科）张文霞,梁醒财（北京大学生命科学学院北京１００８７１）（中国科学院昆明动物研究所昆明６５０２２３）’果蝇属果蝇亚属Ｄｒｏｓｏｐｈｉｌａ（Ｄｒｏｓｏｐｈｉｌａ）的ｍｅｌａｎｄｅｒｉ种组由Ｗｈｅｅｌｅｒ１９４９年建立...     

囊萼紫草属与滇紫草属花粉形态比较研究

本文借助光学显微镜和扫描电镜研究了囊萼紫草属3种和滇紫草属12种植物的花粉形态。囊萼紫草属的花粉为哑铃形或茧形,中等大小,P／E比为1．6一1．67,三孔沟,内孔横长;具小刺状纹饰。滇紫草属的花粉为近长球形或近卵球形,P／E为l—1．23;三孔沟或三合沟孔,内孔一般纵长,具皱波状纹饰,在皱波上具密集的小瘤或微颗粒。从花粉形态的角度,本文支持把囊萼紫草属从滇紫草属(广义)中分离出来的观点。值得注意的是,在滇紫草属的花粉中首次观察到了一种比较少见且特化的花粉即单极三合沟孔的花粉。     

蚤数量与宿主数量和气象因子的关系

根据内蒙古自治区鄂托克旗和鄂托克前旗1975一1989年长爪沙鼠密度、蚤指数监测数据和本地区气象站的,项气象因子资料,分别求出了蚤指数与鼠密度的直线和曲线的回归模型,与气象因子的最优回因子集模型和标准回归模型,给出了鼠蚤因子和气象因子间的典型棺关分析。结论：宿主数量变化导致蚤指数变化;气象因子综合影响蚤指数;相对湿度和地表温度是影响蚤数量变动的重要因子;气象因于对蚤指数的影响大于对鼠密度的影响。     

Isolation and characterization of mosquito ferritin and cloning of a cDNA that encodes one subunit

Ferritin, an iron storage protein, was isolated from larvae and pupae of Aedes aegypti grown in an iron-rich medium. Mosquito ferritin is a high molecular weight protein composed of several different, relatively small, subunits. Subunits of molecular mass 24, 26, and 28 kDa are equally abundant, while that of 30 kDa is present only in small amounts. The N-terminal sequence of the 24 and 26 kDa subunits are identical for the first 30 amino acids, while that of the 28 kDa subunit differs. Studies using antiserum raised against a subunit mixture showed that the ferritin subunits were present in larvae, pupae, and adult females, and were increased in animals exposed to excess iron. The antiserum also was used to screen a cDNA library from unfed adult female mosquitoes. Nine clones were obtained that differed only in a 27 bp insertion in the 3′ end. Rapid amplification of cDNA ends (RACE) was used to obtain the complete protein coding sequence. A putative iron-responsive element (IRE) is present in the 5′-untranslated region. The deduced amino acid sequence shows a typical leader sequence, consistent with the fact that most insect ferritins are secreted, rather than cytoplasmic proteins. The sequence encodes a mature polypeptide of 20,566 molecular weight, smaller than the estimated size of any of the subunits. However, the sequence exactly matches the N-terminal sequences of the 24 and 26 kDa subunits as determined by Edman degradation. Of the known ferritin sequences, that of the mosquito is most similar to that of somatic cells of a snail. © 1995 Wiley-Liss, Inc.     

The expression of biologically active human p53 in Leishmania cells: a novel eukaryotic system to produce recombinant proteins.

We have investigated the use of Leishmania cells as a novel eukaryotic expression system for the production of recombinant protein. These cells are easy to maintain, requiring no CO2 incubator or shaker, and can be grown in standard tissue culture media. Leishmania cells can be readily transfected with plasmid DNA by electroporation and transformants selected with antibiotic resistance. Recent studies have shown that it is possible to express foreign genes in Leishmania for the purpose of understanding the biology of this protozoan cell. In the present study we report the use of this system as a means of producing a biologically functional human p53 protein. The conformation of the p53 protein is critical for its ability to bind specific DNA sequences. It is demonstrated that Leishmania-synthesized human p53 is phosphorylated and can bind specifically to its enhancer DNA sequence. These data demonstrate that Leishmania may represent a simple eukaryotic expression system for the production of biologically active recombinant proteins.     

Human DNA helicase IV is nucleolin, an RNA helicase modulated by phosphorylation

The cDNA encoding human DNA helicase IV (HDH IV), a 100-kDa protein which unwinds DNA in the 5′ to 3′ direction with respect to the bound strand, was cloned and sequenced. It was found to be identical to the human cDNA encoding nucleolin, a ubiquitous eukaryotic protein essential for pre-ribosome assembly. HDH IV/nucleolin can unwind RNA-RNA duplexes, as well as DNA-DNA and DNA-RNA duplexes. Phosphorylation of HDH IV/nucleolin by cdc2 kinase and casein kinase II enhanced its unwinding activity in an additive way. The Gly-rich C-terminal domain possesses a limited ATP-dependent duplex-unwinding activity which contributes to the helicase activity of HDH IV/nucleolin.     

Chromosomal localization and molecular characterization of 53 cosmid-derived bovine microsatellites

Gene mapping in cattle has progressed rapidly in recent years largely owing to the introduction of powerful genetic markers, such as the microsatellites, and through advances in physical mapping techniques such as synteny mapping and fluorescence in situ hybridization (FISH). Microsatellite markers are often not physically mapped because they are generally isolated from small insert plasmid libraries, which makes their chromosomal localization inefficient. In this report we describe the FISH mapping of a large group of cosmid-derived bovine microsatellite markers, as our contribution to the European mapping initiative, BovMap. One objective of BovMap is to develop a set of anchored loci for the cattle genome map.Two cosmid libraries were screened with probes corresponding to the (AC) _n microsatellite motif. Positive clones were mapped by FISH, and then a subset was further analyzed by sequencing the region flanking the microsatellite repeat. In total, 58 clones were hybridized with chromosomes and identified loci on 22 of the 31 different bovine chromosomes. Three clones contained satellite DNA. Two or more markers were placed on 12 chromosomes. Sequencing of the microsatellites and flanking regions was performed directly from 43 cosmids, as previously reported (Ferretti et al. Anim. Genet. 25, 209–214, 1994). Primers were developed for 39 markers and used to describe the polymorphism associated with the corresponding loci.