玉米叶绿体atpB及atpE基因在大肠杆菌中的表达

本实验构建了在大肠杆菌中能表达玉米叶绿体ＣＦ１完整β亚基、缺失Ｎ端２３个氨基酸残基的β亚基以及完整ε亚基的表达质粒。ＳＤＳ－聚丙烯酰胺凝胶电泳及Ｗｅｓｔｅｒｎｂｌｏｔ实验表明,在分别含这些表达质粒的细菌中β、ε亚基蛋白的合成量在诱导３ｈ后即达到饱和,其含量各占细菌体总蛋白的１０％左右。这些表达产物在细菌体中形成不溶性的包含体。可通过对菌体蛋白的分级分高,将表达产物溶于５ｍｏｌ／Ｌ的尿素溶液中。     

L-异亮氨酸和甘氨酸对大肠杆菌表达与分泌邻苯二酚2,3-双加氧酶的作用

证实了甘氨酸与L-异亮氨酸对大肠杆菌表达邻苯二酚2,3-双加氧酶(CatO_2ase)的促进作用和甘氨酸促使该酶分泌至胞外培养基中的作用.产酶量高低和分泌量多少与培养基种类、甘氨酸和L-异亮氨酸的浓度以及培养时间等因素有关.在甘氨酸存在的情况下,胞壁对溶菌酶的敏感性有所增加,超微形态似有变化,还存在其他物质的伴随分泌,故甘氨酸可能是引起细胞壁结构的改变而导致邻苯二酚2,3-双加氧酶等胞内容物被动分泌至胞外.     

精子介导鱼类基因转移和聚合酶链反应检测技术

金鱼精子与美洲大绵ｗｅｉ的抗冻蛋白基因一起保温３０分钟后,再与卵子受精,共获得１４５尾成鱼和若干胚胎。从胚胎和成鱼中提取ＤＮＡ经聚合酶链反应（ＰＣＲ法）扩增和Ｓｏｕｔｈｅｒｎ ｂｌｏｔ分子杂交表明,外源的抗冻蛋白基因进入了部分受体鱼的染色体组内。测定了４５尾一年龄实验鱼中,有１２尾显示出明确的杂交带,阳性率为２６％。     

Flow-induced detachment of red blood cells adhering to surfaces by specific antigen-antibody bonds.

Fixed spherical swollen human red blood cells of blood type B adhering on a glass surface through antigen-antibody bonds to monoclonal mouse antihuman IgM, adsorbed or covalently linked on the surface, were detached by known hydrodynamic forces created in an impinging jet. The dynamic process of detachment of the specifically bound cells was recorded and analyzed. The fraction of adherent cells remaining on the surface decreased with increasing hydrodynamic force. For an IgM coverage of 0.26%, a tangential force on the order of 100 pN was able to detach almost all of the cells from the surface within 20 min. After a given time of exposure to hydrodynamic force, the fraction of adherent cells remaining increased with time, reflecting an increase in adhesion strength. The characteristic time for effective aging was approximately 4 h. Results from experiments in which the adsorbed antibody molecules were immobilized through covalent coupling and from evanescent wave light scattering of adherent cells, imply that deformation of red cells at the contact area was the principal cause for aging, rather than local clustering of the antibody through surface diffusion. Experiments with latex beads specifically bound to red blood cells suggest that, instead of breaking the antigen-antibody bonds, antigen molecules were extracted from the cell membrane during detachment.     

Aggregation efficiency of activated normal or fixed platelets in a simple shear field: effect of shear and fibrinogen occupancy.

Shear rate can affect protein adsorption and platelet aggregation by regulating both the collision frequency and the capture efficiency (alpha). These effects were evaluated in well defined shear field in a micro-couette for shear rate G = 10 - 1000 s-1. The rate of protein binding was independent of G, shown for adsorption of albumin to latex beads and PAC1 to activated platelets. The initial aggregation rate for ADP-activated platelets in citrated platelet-rich plasma followed second order kinetics at the initial platelet concentrations between 20,000 and 60,000/microliters. alpha values, which dropped nearly fivefold for a 10-fold increase in G, were approximately proportional to G-1, contrary to a minor drop predicted by the theory that includes protein cross-bridging. Varying ADP concentration did not change alpha of maximally activated platelet subpopulations, suggesting that aggregation between unactivated and activated platelets is negligible. Directly blocking the unoccupied but activated GPIIb-IIIa receptors without affecting pre-bound Fg on "RGD"-activated, fixed platelets (AFP) by GRGDSP or Ro 43-5054 eliminated aggregation, suggesting that cross-bridging of GPIIb-IIIa on adjacent platelets by fibrinogen mediates aggregation. Alpha for AFP remained maximal (approximately 0.24) over 25-75% Fg occupancy, otherwise decreasing rapidly, with a half-maximum occurring at around 2% occupancy, suggesting that very few bound Fg were required to cause significant aggregation.     

Expression of the hepatitis delta virus large and small antigens in transgenic mice.

Simultaneous infection with hepatitis delta virus (HDV) and hepatitis B virus (HBV) in humans is often associated with severe viral liver disease including fulminant hepatitis. Since HBV is thought to be noncytopathic to the hepatocyte, the enhanced disease severity observed during dual infection has been attributed to either simultaneous immune responses against the two viruses or direct cytotoxic effects of HDV products on the hepatocyte or both. To examine these alternate possibilities, we produced transgenic mice that express the small and large delta antigens (HDAg) in hepatocyte nuclei at levels equal to those observed during natural HDV infection. No biological or histopathological evidence of liver disease was detectable during 18 months of observation, suggesting that neither the large nor small form of HDAg is directly cytopathic to the hepatocyte in vivo.     

卧龙自然保护区野生大熊猫繁殖研究

本文分析了１９７８－１９９２年在卧龙自然保护区五一棚研究区内的野生大熊猫繁殖情况,结果表明：野生大熊猫雌体６．５岁初发情,７．５岁交配产仔,２０岁繁殖基本停止;雄体７．５岁初发情,８．５岁能获交配权,２０岁繁殖基本停止。年繁殖率为６２．５％,其中单胞胎为５８．３３％,双胞胎为４．１７％。此外,１９８３年冷箭竹开花枯死,延迟了大熊猫的发情期,这可能与竹了开后大熊猫觅食行为改变及摄入影响繁殖的微量元素     

麦迪霉素产生菌酮基还原酶基因的研究

将麦迪霉素产生菌基因文库中与放线紫红索酮基还原酶基因actⅢ有同源性的4·0kb DNA片段克隆到质粒载体pWHM3中,构成重组质粒pCB4。将质粒pCB4转入酮基还原酶基因缺陷菌株——加利利链霉菌ATCC3167l中,得到转化子。转化子发酵产物经TLC和HPLC分析证明是阿克拉菌酮,与加利利链霉菌原株ATCC31133的产物相同,说明麦迪霉素产生菌酮基还原酶基因互补了加利利链霉菌ATCC31671中缺陷的酮基还原酶基因,使其恢复了产生阿克拉菌酮的能力。4．Okb DNA片段插入方向相反的重组质粒pCBR4在加利利链霉菌ATCC31671中发酵产物经TLC分析证明也是阿克拉菌酮,这说明4．0kbDNA片段中麦迪霉素产生菌酮基还原酶基因具有自身的启动子。对4．0kb DNA片段进行了限制酶酶切分析,建立了其酶切图谱。以actⅢ基因为探针,经分子杂交以及亚克隆和DNA转化实验,将麦迪霉索产生菌酮基还原酶基因定位于BssH Ⅱ—BamH Ⅰ 1．3kb DNA片段上。对1．3kb DNA片段核苷酸序列分析结果表明：此1．3kbDNA片段中含有一个独立的ORF,起始密码ATG,终止密码TAG,含783bp;在起始密码上游有GGAGG5个核苷酸SD序列;此ORF编码260个氨基酸,与actⅢ基因编码的261个氨基酸相似性为77．4%,相同性为66．7％,对麦迪霉素产生苗酮基还原酶基因的可能作用进行了讨论。     

强噪声暴露后听觉脑干电反应及皮层电反应的变化

为了观察噪声作用豚鼠后,在暂时性或移和永久性阈移期间,听觉末梢和听觉各级中枢电反庆的变化规律,我们进行了６２ｄ的测定。听神经电反应振幅减小２９％（Ｐ＜０．０５）,耳蜗核电反应振幅减小２８％（Ｐ＜０．０５）,上橄榄核电反应反而增加２１％（Ｐ＜０．０５）,中脑下丘的电反应振幅进而增大３７％（Ｐ＜０．０５）,听觉皮层电反应振幅却意外地增加１３１％（Ｐ＜０．００１）。这说明强噪声（１２５ｄＢ １５０ｍｉｎ