Protonation and stability of the globular domain of influenza virus hemagglutinin.

A partial dissociation of the HA1 subunits of influenza virus hemagglutinin (HA) is considered to be the initial step of conformational changes of the HA ectodomain leading to a membrane fusion active conformation (L. Godley, J. Pfeifer, D. Steinhauer, B. Ely, G. Shaw, R. Kaufman, E. Suchanek, C. Pabo, J.J. Skehel, D.C. Wiley, and S. Wharton, 1992, Cell 68:635-645; G.W. Kemble, D.L.Bodian, J. Rose, I.A. Wilson, and J.M. White, 1992, J. Virol. 66:4940-4950). Here, we explore a mechanism that provides an understanding of the physical and chemical basis for such dissociation and relies on two essential observations. First, based on the x-ray structure of HA from X31 (I.A. Wilson, J.J. Skehel, and D.C. Wiley, 1981, Nature 289:366-373), and by employing techniques of molecular modeling, we show that the protonation of the HA1 subunits is enhanced at the conditions known to trigger conformational changes of the HA ectodomain. Second, we found that the dependence of the calculated relative degree of protonation of the HA1 domain on temperature and pH is similar to that observed experimentally for the conformational change of HA assessed by proteinase K sensitivity. We suggest that at the pH-temperature conditions typical for the conformational change of HA and membrane fusion, dissociation of the HA1 subunits is caused by the enhanced protonation of the HA1 subunits leading to an increase in the positive net charge of these subunits and, in turn, to a weakened attraction between them.     

多巴胺(DA)和去甲肾上腺素(NE)在文昌鱼神经系统和性腺中的免疫细胞化学定位

用免疫细胞化学ABC法对多巴胺（DA）和去甲肾上腺素（ＮＥ）的文昌鱼神经系统和性腺中进行定位研究。免疫反应结果显示：ＤＡ和ＮＥ免疫阳性神经细胞广泛分布在文昌鱼端脑后部、中脑前部和中部以及脊髓,我们还观察到,在文昌鱼漏斗部也有ＤＡ免疫阳性神经细胞及其纤维;在中脑中部,ＮＥ免疫阳性神经细胞及其纤维与另一个神经细胞相接触。此餐,文昌鱼精巢和卵巢中也存在ＤＡ和ＮＥ免疫阳性物,研究结果表明,ＤＡ和ＮＥ可有像在鱼类中那样,参与调节文昌鱼哈氏窝上皮细胞的分泌活动以及性腺发育。     

Diversity and compatibility of peanut (Arachis hypogaea L.) bradyrhizobia and their host plants

A high degree of genetic diversity among 125 peanut bradyrhizobial strains and among 32 peanut cultivars collected from different regions of China was revealed by using the amplified fragment length polymorphism (AFLP) technique. Eighteen different peanut bradyrhizobial genotypes and six peanut cultivars were selected for symbiotic cross-inoculation experiments. The genomic diversity was reflected in the symbiotic diversity. The peanut cultivars varied in their ability to nodulate with the strains used. Some cultivars had a more restricted host range than the others. Also the strains displayed a range of nodulation patterns. In yield formation there were clear differences between the plant cultivar/bradyrhizobium combinations. There was good compatibility between some peanut bradyrhizobial strains and selected cultivars, with inoculation resulting in well-nodulated, high-yielding symbiotic combinations, but no plant cultivar was compatible with all strains used. The strains displayed a varying degree of effectiveness, with some strains being fairly effective with all cultivars and others with selected ones. The AFLP genotypes of the strains did not explain the symbiotic behavior, whereas the yield formation of the plant cultivars was more related to the genotype. It is concluded that to obtain optimal nitrogen fixation efficiency of peanut in the field, compatible plant cultivar-bradyrhizobium combinations should be selected either by finding inoculant strains compatible with the plant cultivars used, or plant cultivars compatible with the indigenous bradyrhizobia.     

生后雌性小鼠下丘脑室旁核内ER—β表达的免疫组化研究

研究发现小鼠下丘脑室旁核(PVN)内雌激素β受体(ER-β)的表达与在大鼠等一些实验动物脑PVN的表达有差异,提示其在小鼠PVN内的表达可能有特定的生理意义。为了深入探讨ER—β在小鼠PVN内的功能,本文采用硫酸镍铵增强显色的免疫组化SP法研究了ER—β在生后雌性小鼠PVN内的表达。结果发现ER—β免疫阳性物质主要见于PVN的大细胞部,在小细胞部和背侧帽部免疫阳性细胞数目较少。免疫阳性物质主要位于细胞核内,未发现明显的胞浆或突起阳性,但在发育的某些时期可见免疫阳性细胞核局部呈现阴性反应。最高表达见于生后早期(第1—9天),随后表达降低,生后一个月即达到成年水平。PVN内ER-β的表达模式表现为生后早期表达高、随后降低,提示在该部位ER—β可能主要参与了对生后早期PVN的神经内分泌活动以及神经结构的发育与完善的调控,并可能与生后早期动物的应激、体重增加和脂肪代谢等有关。     

利用RACE技术扩增大豆抗病基因同源cDNA 5′末端序列

利用抗病基因保守序列筛选大豆cDNA文库,获得一抗病基因同源cDNA片段,命名为KR3-1。根据KR3-1设计两个基因特异引物（GSP 和 NGSP）,分别与通用引物(UPM)和巢式通用引物（NUP）共同扩增,成功地克隆到了该基因的5′末端序列。该扩增片段长447 bp,与已知序列重叠部分为129 bp。 Abstract:Based on part of a known partial cDNA sequence of a disease resistance gene homolog,KR3-1,obtained by screening a cDNA library from soybean,5′-RACE-PCR was carried out with gene specific primers and universal primers.After the nested PCR reaction,an amplified fragment of 447 bp in length which overlapped the known KR3-1 sequence by 129 bp was obtained subsequently.Thus,a 5′ cDNA end of KR3 was successfully cloned.     

白细胞介素-2对心肌负性肌力作用机制的探讨

为研究白细胞介素-2（IL-2）对心肌的负性肌力作用的可能机制,本采用酶解分离成年大鼠心室肌细胞,用细胞内双波长荧光系统和膜片钳全细胞记录检测细胞膜钙离子通道和细胞内酸碱度（pHi）及钙水平的变化,分别以fura-2/AM和BCECF/AM作为细胞内钙离子和氢离子荧光指示剂。结果：（1）IL-2(2.5-200U/ml）浓度依赖性地降低单个心室肌细胞电刺激诱导的钙瞬变幅度,使舒张末钙水平升高,选择性κ-阿片受体阻断剂nor-BNI(10nmol/L）可阻断IL-2对心肌细胞内钙的作用;（2）用200U/ml的IL-2灌流10min后,与对照组相比膜片钳全细胞记录的L-型钙电流无明显改变;（3）用200U/ml的IL-2灌流后,与对照组相比Mn^2 对fura-2/AM的淬灭率无明显改变。（4）IL-2(200U/ml）使大鼠心室肌细胞pHi降低,其作用可被选择性κ-阿片受体阻断剂nor-BNI(10nmol/L）所减弱。结论：IL-2引起的心室肌细胞pHi降低可能是其负性肌力作用机制之一,细胞膜上L-型钙离子通道可能不参与IL-2降低心肌收缩力的作用;细胞膜上的阿片受体可能介导IL-2对心肌的负性肌力作用。     

Expression of vde Gene Integrated Into Tobacco Genome in Antisense and Overexpressed Ways

Violaxanthin de-epoxidase (VDE) is localised in the thylakoid lumen of chloroplasts and catalyses de-epoxidation of violaxanthin into antheraxanthin and zeaxanthin. Tobacco vde gene was inserted into a binary vector pCAMBIA1301 with the hygromycin resistant gene for selection in antisense and overexpressed ways. Two constructs with antisense and overexpressed vde gene were introduced in tobacco (Nicotiana tabacum L.) using Agrobacterium tumefaciens strain LBA4404, PCR and Southern blot analyses demonstrated that the exogenous gene was integrated into genome of tobacco plants. VDE activity assay and HPLC analysis of pigments showed that the vde gene was expressed in the overexpressed transformants, whereas suppressed in the antisense ones. The chlorophyll fluorescence measurements proved that the contents of VDE in transgenic plants have a significant function in non-photochemical quenching.     

草地螟第三个暴发周期的发生特点、成因及防治对策

分析了1949年以来草地螟3次周期性大暴发的原因。通过对1979-2001年康保县23年草地螟系统监测资料的分析,重点剖析了草地螟第3个暴发周期发生特点、成因,认为种群数量、气候和耕作制度是导致草地螟暴发的重要原因,并提出防治对策。     

苦豆子生物碱对小菜蛾体内部分杀虫剂代谢酶活性的影响

以苦豆子Sophora alopecuroids 7种生物碱和小菜蛾Plutella xylostella幼虫为试材,研究了该生物碱对小菜蛾体内降解杀虫剂的羧酸酯酶、磷酸酯酶、谷胱甘肽-S-转移酶活性的影响。结果表明: 野靛碱和苦豆碱对羧酸酯酶活性有显著的抑制,为可逆抑制类型的非竞争性抑制作用;野靛碱等5种生物碱对酸性磷酸酯酶有明显的抑制,野靛碱对碱性磷酸酯酶有弱抑制作用;其中野靛碱等3种生物碱对谷胱甘肽-S-转移酶有明显的抑制作用。     

大叶黄杨叶片内部光能利用梯度

采用一种新方法来测量大叶黄杨叶片（Euonymus japonicusT.)内部的绝对光能利用效率梯度曲线。该方法基于光声光谱的深度分析（Depth-Analysis)理论,并结合了光纤微探测器的叶片光梯度测量结果。日本小檗（Berberis thunbergii DC.)叶片的光声光谱扫描显示了深度分析的精确性。实验结果表明：叶片内部利用光能效率最低处在栅栏组织和海绵组织之间（入射光能0.026%-660nm红光）;越靠近叶片的上表皮和下表皮,显示出叶片组织利用光能效率有上升的趋势（分别为0.092%和0.036%)。因此,不同叶肉组织绝对光能利用效率是不同的,该实验结果直接证实了Han和Vogelmann(1999)所提出的假设。