Accumulation of poly-(hydroxybutyrate) by a non-sulfur photosynthetic bacterium,Rhodobacter sphaeroides RV at different pH

Summary Effect of pH of culture media on intracellular accumulation of poly-(hydroxybutyrate) (PHB) by a non-sulfur photosynthetic bacterium, Rhodobacter sphaeroides strain RV was studied in pH-stat cultures. Sub-optimal pH for growth, 8.0 or 8.5 gave the higher content of PHB rather than optimal pH 7.5 for growth. These results show that growth and PHB accumulation of the bacteria can be controlled by pH of culture media.     

Induction of a Nerve Growth Factor-Sensitive Kinase that Phosphorylates the DNA-Binding Domain of the Orphan Nuclear Receptor NGFI-B

Abstract: Nerve growth factor (NGF) induces the synthesis and the phosphorylation of the orphan nuclear receptor NGFI-B in PC12 cells. Previous work has shown that phosphorylation, by protein kinase A, of a specific serine in the DNA-binding domain inhibits its binding to the NGFI-B response element. Also, cytoplasmic extracts from PC12 cells phosphorylate this serine, and phosphorylation is greater in extracts from cells treated with NGF. The present work describes the induction, identification, and partial purification of a kinase (termed NGFI-B kinase I) from PC12 cell extracts that catalyzes this phosphorylation. Phosphorylation of the DNA-binding domain with this purified preparation inhibits its binding to the NGFI-B response element. The kinase is rapidly activated by treatment of the cells with NGF, and the activation lasts for at least several hours. It also is activated by fibroblast growth factor and epidermal growth factor (EGF), but the activation by EGF is quite transient. The kinase requires Mg²⁺ but will use Mn²⁺. The molecular mass of the kinase is 95–100 kDa, and it is different from protein kinase A, Fos kinase, or pp90 ^rsk . Comparison with a partially purified preparation of cyclic AMP response element-binding protein kinase, however, indicates that the two are either very similar or identical.     

超氧化物歧化酶切割超螺旋DNA的活性

在体外系统中,发现超氧化物歧化酶(SOD)具有切割超螺旋DNA的活性. 猪血和牛血Cu/Zn-SOD以及烟草Mn-SOD都能将超螺旋DNA转变为非超螺旋结构的缺刻环状DNA,进一步产生线状DNA. 它们只作用于超螺旋DNA而不作用于线状DNA. 这个事实排除了SOD样品中污染核酸酶的可能性. 用H₂O₂、胍基抑制或蛋白酶降解的实验结果表明,这两种酶的活性中心处于酶蛋白的不同部位.     

生物实验数据的某些非线性分析方法

简要介绍常用的非线性动力学参量,结合生物学实验数据的特点,给出几种最新的分析方法.     

Subnuclear Trafficking of Glucocorticoid Receptors In Vitro: Chromatin Recycling and Nuclear Export

We have used digitonin-permeabilized cells to examine in vitro nuclear export of glucocorticoid receptors (GRs). In situ biochemical extractions in this system revealed a distinct subnuclear compartment, which collects GRs that have been released from chromatin and serves as a nuclear export staging area. Unliganded nuclear GRs within this compartment are not restricted in their subnuclear trafficking as they have the capacity to recycle to chromatin upon rebinding hormone. Thus, GRs that release from chromatin do not require transit through the cytoplasm to regain functionality. In addition, chromatin-released receptors export from nuclei of permeabilized cells in an ATP- and cytosol-independent process that is stimulated by sodium molybdate, other group VI-A transition metal oxyanions, and some tyrosine phosphatase inhibitors. The stimulation of in vitro nuclear export by these compounds is not unique to GR, but is restricted to other proteins such as the 70- and 90-kD heat shock proteins, hsp70 and hsp90, respectively, and heterogeneous nuclear RNP (hnRNP) A1. Under analogous conditions, the 56-kD heat shock protein, hsp56, and hnRNP C do not export from nuclei of permeabilized cells. If tyrosine kinase inhibitors genistein and tyrphostin AG126 are included to prevent increased tyrosine phosphorylation, in vitro nuclear export of GR is inhibited. Thus, our results are consistent with the involvement of a phosphotyrosine system in the general regulation of nuclear protein export, even for proteins such as GR and hnRNP A1 that use distinct nuclear export pathways.     

Possible role of macrophage-derived soluble mediators in the pathogenesis of encephalomyocarditis virus-induced diabetes in mice.

Pancreatic islets from DBA/2 mice infected with the D variant of encephalomyocarditis (EMC-D) virus revealed lymphocytic infiltration with moderate to severe destruction of pancreatic beta cells. Our previous studies showed that the major population of infiltrating cells at the early stages of infection is macrophages. The inactivation of macrophages prior to viral infection resulted in the prevention of diabetes, whereas activation of macrophages prior to viral infection resulted in the enhancement of beta-cell destruction. This investigation was initiated to determine whether macrophage-produced soluble mediators play a role in the destruction of pancreatic beta cells in mice infected with a low dose of EMC-D virus. When we examined the expression of the soluble mediators interleukin-1 beta (IL-1beta), tumor necrosis factor alpha (TNF-alpha), and inducible nitric oxide synthase (iNOS) in the pancreatic islets, we found that these mediators were clearly expressed at an early stage of insulitis and that this expression was evident until the development of diabetes. We confirmed the expression of these mediators by in situ hybridization with digoxigenin-labelled RNA probes or immunohistochemistry in the pancreatic islets. Mice treated with antibody against IL-1beta or TNF-alpha or with the iNOS inhibitor aminoguanidine exhibited a significant decrease in the incidence of diabetes. Mice treated with a combination of anti-IL-1beta antibody, anti-TNF-alpha antibody, and aminoguanidine exhibited a greater decrease in the incidence of disease than did mice treated with one of the antibodies or aminoguanidine. On the basis of these observations, we conclude that macrophage-produced soluble mediators play an important role in the destruction of pancreatic beta cells, resulting in the development of diabetes in mice infected with a low dose of EMC-D virus.     

非酶促转氨测定蛋白质相对分子量及研究空间结构的变化

在非酶促转氨过程中测定生成甘氨酸的量,计算蛋白质的相对分子量是一种方便、节省经费和快速的方法,该方法的应用不受蛋白分子量大小的限制。非酶促转氨的另一产物２－羰化氨基酸可作为制备各种喹喔啉衍生物的原料。苯丙氨酸非酶促形成的苯丙酮酸与邻苯二胺反应生成３－苯基－２－羰基喹喔啉。该产物在３６３ｎｍ具有荧光发色性质。胰岛素及不同一级结构的短肽２－羰酰衍生物和２－喹喔啉衍生物的荧光在盐酸胍和不同ＰＨ训的变化各     

心肺压力感受器持续卸荷对前臂血流、血管阻力及心率变异性谱的影响

低压值下体负压（ＬＢＮＰ）可仅使心肺压力感受器卸荷。采用－２ｋＰａＬＢＮＰ实验结果表明：ＬＢＮＰ既不引起动脉血压变化,也不引起心率改变,但却引起基础胸阻抗（Ｚ。）从对照的２１．８±０．４升高到２２．５±０．５Ω（Ｐ＜０．０１）,前臂血管阻力（ＦＶＲ）从１２．３±０．９升高到１９．９±１．４Ｕ（Ｐ＜０．０１）,前臂血流（ＦＢＦ）从对照时７．１±０．５降低到４．３±０．３ｍｌ·ｍｉｎ￣（－１）·１００ｍｌ￣（－１）,心率变异性谱（ＨＲＶ）未发生任何变化,即心肺压力感受器卸荷时心脏自主神经活动水平与均衡性不受影响。由于ＦＶＲ和ＦＢＦ的变化可间接反映外周血管交感传出活动水平,上述实验结果提示,心肺压力感受器对外周血管及心脏自主神经活动的调节可能存在机能分化现象。     

被子植物系统发育研究的现状与展望

为植物界最大的类群—被子植物建立一个能真正反映植物的进化历史和系统发育（phylogeny）的分类系统一直是许多植物系统学家和进化学家所向往的。到目前为止,已经提出的被子植物分类系统至少有二十多个。问题在于这样的分类系统能否说已符合于系统发育的要求？要回答这个问题,首先必须弄清系统发育的真正含义是什么。