Cell signaling and heat shock protein expression

Exposure of cells and organs to heat shock is associated with numerous changes in various cellular metabolic parameters and overexpression of proteins collectively known as heat shock proteins (HSP). In this communication we review the cell-signaling events that are altered in response to heat shock as they relate to the subsequent induction of HSP 70 kd (HSP-70) expression. We also review the mechanisms by which HSP-70 is involved in conferring cytoprotective effects. The possibility of altering HSP expression through manipulations of the cell-signal process has clinical importance.The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Department of the Army or Department of Defense.     

The role of context on alpha-helix stabilization: host-guest analysis in a mixed background peptide model.

The helix content of a series of peptides containing single substitutions of the 20 natural amino acids in a new designed host sequence, succinyl-YSEEEEKAKKAXAEEAEKKKK-NH2, has been determined using CD spectroscopy. This host is related to one previously studied, in which triple amino acid substitutions were introduced into a background of Glu-Lys blocks completely lacking alanine. The resulting free energies show that only Ala and Glu- prove to be helix stabilizing, while all other side chains are neutral or destabilizing. This agrees with results from studies of alanine-rich peptide modela, but not the previous Glu-Lys block oligomers in which Leu and Met also stabilize helix. The helix propensity scale derived from the previous block oligomers correlated well with the frequencies of occurrence of different side chains in helical sequences of proteins, whereas the values from the present series do not. The role of context in determining scales of helix propensity values is discussed, and the ability of algorithms designed to predict helix structure from sequence is compared.     

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。     

薏苡胚乳传递细胞的超微结构

传粉后１０ ｄ,薏苡（Ｃｏｉｘ ｌａｃｒｙｍ ａ－ｊｏｂｉＬ．）颖果基部胚乳最外层传递细胞具长而多的壁内突,第二层细胞的壁内突较第一层的短而少,均具瓣裂的细胞核、丰富的线粒体、粗糙内质网、核糖体、产生小泡的高尔基体及与壁内突质膜相连的、含深色物质的囊泡。线粒体分布于壁内突附近或其间。授粉后２５ ｄ,第一、二层细胞壁内突发达,几乎充满了细胞,但细胞器可见。第四层传递细胞具树枝状及网状的壁内突,大量线粒体、具质体膜的淀粉粒、脂体存在壁内突附近或壁内突的间隙内。高尔基体常见,仅见很少的片段内质网。第五层传递细胞具短的壁内突、较大的淀粉粒及许多小蛋白质体。两个时期的第一、二层细胞内均未观察到胞间连丝。授粉后２５ ｄ,第四层及以上的传递细胞的细胞壁和呈网状的壁内突均含有胞间连丝。还讨论了各种细胞器的作用及各层传递细胞的功能     

滇藏常绿杜鹃亚属的修订

常绿杜鹃亚属Subgenus Hymenanthes是由K.Koch（1872）根据Blume（1826）建立的Genus Hymenanthes改级组合而成。但长期以来人们一直沿用了Maximowicz（1870）所建立的、后由Koehne（1893）修订过的Subgenus Eurhododendron这一亚属名称,直到最近D.F.Chamberlain（1978,1979,1982）对该亚属的名称才作了正式订正。     

Production of Ethanol from d-Xylose by Using d-Xylose Isomerase and Yeasts

d-Xylulose, an intermediate of d-xylose catabolism, was observed to be fermentable to ethanol and carbon dioxide in a yield of greater than 80% by yeasts (including industrial bakers' yeast) under fermentative conditions. This conversion appears to be carried out by many yeasts known for d-glucose fermentation. In some yeasts, xylitol, in addition to ethanol, was produced from d-xylulose. Fermenting yeasts are also able to produce ethanol from d-xylose when d-xylose isomerizing enzyme is present. The results indicate that ethanol could be produced from d-xylose in a yield of greater than 80% by a two-step process. First, d-xylose is converted to d-xylulose by xylose isomerase. d-Xylulose is then fermented to ethanol by yeasts.     

羧基化多壁碳纳米管、混合盐及其复合胁迫对水稻幼苗生理特性的影响

将水稻（Oryza sativa L.）幼苗悬浮培养于含有羧基化多壁碳纳米管MWCNTs-COOH（0、2.5、5.0、10.0 mg/L）、50 mmol/L混合盐（1NaCl：9Na₂SO₄：9NaHCO₃：1Na₂CO₃）,以及MWCNTs-COOH+混合盐的复合溶液中,10 d后检测叶片生理生化指标变化,研究MWCNTs-COOH复合盐碱胁迫对水稻幼苗的毒性及生态风险。结果显示,与对照组相比,MWCNTs-COOH单一组诱导下水稻叶片O₂^·-和H₂O₂的产生不明显,而混合盐组和混合盐+MWCNTs-COOH复合组均诱导了O₂^·-和H₂O₂产物的大量累积。MWCNTs-COOH与混合盐复合后,加剧了O₂^·-和H₂O₂的累积,并有明显的浓度效应。活性氧（ROS）作为信号分子在一定程度上诱导了各处理组部分抗氧化酶（SOD、CAT、POD、APX）活性的升高;与混合盐组相比,低浓度混合盐+MWCNTs-COOH复合组中叶绿素a和胡萝卜素含量呈一定程度的升高;MWCNTs-COOH与混合盐复合后,抑制了叶片中可溶性糖（SS）和脯氨酸（Pro）的合成,致使相对电导率（REC）和丙二醛（MDA）含量显著升高。上述抗氧化酶活性及叶绿素a和胡萝卜素含量的升高对缓解水稻叶片氧化损伤、维持正常的光合电子传递及对过剩光能的热耗散是有益的,是水稻幼苗重要的防御机制。本研究表明MWCNTs-COOH单一处理在一定程度上诱导了水稻叶片的氧化胁迫和应激响应,与混合盐复合后加剧了叶片的氧化胁迫和应激损伤。     

大蒜病毒检测用抗血清制备的研究

本文报告了从阿城大蒜田间感染病叶片中分离了大蒜病毒,用聚乙二醇沉淀法提取的抗原浓度高于差速离心法.制备的抗血清效价达1024以上.电镜观察粗提纯的病毒粒子,呈线状,长度为516～846nm占46.9%,1142～1525nm占40.6%.     

寡聚脱氧核苷酸d(G-C)_3的激光喇曼谱及其分析

用改进的固相磷酰三酯法合成了oligo-d(G-C)_3。以氩离子激光为激发光源,波长488nm.,在室温条件下,分别测定了纯化后的oligo-d(G-C)_3和其组分单体5’-dGMP和5’-dCMP的激光喇曼谱。观察到被测定的物质在300-2500cm~(-1)频率区间,各自都有其特征的谱形和喇曼峰。5’-dGMP和5’-dCMP谱中大多数特征峰在寡聚体的谱中消失,而在oligo-d(G-C)_3谱中出现了几处新的喇曼峰。经查证,峰832,851和899cm~(-1)系糖-磷酸主链的特征喇曼峰,另外几处峰与DNA的构象有关。实验结果表明oligo-d(G-C)_3在水溶液中(室温)主要以B-构象存在。