一些因子对七星瓢虫咽侧体活性的影响(英文)

七星瓢虫(Coccmella septimpunctata)为了适应环境的变化,通过咽侧体产生保幼激素的活动调节其生殖作用。为了探索内外因素对咽侧体活动的影响,应用放射化学法及免疫电泳测定了食物、卵巢发育、脑神经肽、保幼激素类似物对卵黄发生期成虫保幼激素生物合成及血淋巴中卵黄原蛋白含量的影响。结果表明咽侧体活性受上述各种因子的影响。咽侧体活性与卵黄原蛋白含量及卵母细胞生长密切相关,说明有反馈作用。食物的质与量影响着咽侧体活性的变化。低剂量外源保幼激素类似物处理成虫则可促使咽侧体活性的变化。脑分泌的神经肽(allatotropin)可活化咽侧体。这些结果表明雌瓢虫保幼激素的生产主要是受起源于脑的促咽侧体信号的调节作用。     

毛喉萜对人胃癌细胞BGC－823中蛋白激酶C及其亚类的影响

以人胃癌细胞ＢＧＣ－８２３为模型,研究了毛喉萜（ｆｏｒｓｋｏｌｉｎ）对胃癌细胞中蛋白激酶Ｃ活性及其亚类基因表达的作用,同时也观察了毛喉萜对癌基因ｃ－ｊｕｎ及抑癌基因ｐ５３表达的影响．结果表明,２×１０~（－５）ｍｏｌ／Ｌ毛喉萜处理ＢＧＣ－８２３细胞７２ｈ,细胞质、膜和细胞核ＰＫＣ活性下降,ＰＫＣ亚类β,γ基因表达被抑制,癌基因ｃ－ｊｕｎ的表达也明显降低,而抑癌基因ｐ５３表达升高,上述变化可能是毛喉萜抑制胃癌细胞增殖等生理效应的重要分子事件。     

Transformation and pp60v-src autophosphorylation correlate with SHC-GRB2 complex formation in rat and chicken cells expressing host-range and kinase-active, transformation-defective alleles of v-src.

The biochemical properties of several pp60v-src substrates believed to participate in src-mediated transformation were examined in cells expressing a kinase-active, transformation-defective v-src allele (v-src-F172 delta/Y416F) and its parental allele, v-src-F172 delta, a host-range--dependent allele that transforms chicken cells to a fusiform morphology, but does not transform rat cells. Because pp60v-src-F172 delta is dependent on autophosphorylation for transforming ability, these alleles provide a unique opportunity to examine the role of pp60v-src autophosphorylation in regulating substrate interactions. Increased pp125FAK tyrosine phosphorylation and high levels of pp60v-src-associated phosphotidylinositol-3' kinase activity were detected specifically in chicken cells exhibiting round, refractile transformation but not in cells transformed to a fusiform morphology. Increased pp125FAK kinase activity, but not increased pp125FAK tyrosine-phosphorylation correlated with pp60v-src autophosphorylation and increased anchorage-independent growth. Thus, pp125FAK and PI3'K may participate in morphological transformation by v-src. Furthermore, association of phosphorylated SHC with the adapter GRB2 correlated with increased anchorage-independent growth (and autophosphorylation) in both rat and chicken cells independent of the morphological phenotype induced. Therefore, host-range dependence for transformation may be regulated through association of SHC with GRB2, thus implicating SHC as a crucial substrate for src-dependent transformation.     

Activation of MEK family kinases requires phosphorylation of two conserved Ser/Thr residues.

MEK is a family of dual specific protein kinases which activate the extracellular signal-regulated kinases by phosphorylation of threonine and tyrosine residues. MEK itself is activated via serine phosphorylation by upstream activator kinases, including c-raf, mos and MEK kinase. Here, we report the activation phosphorylation sites of human MEK1 and yeast STE7 kinase as determined by a combination of biochemical and genetic approaches. In human MEK1, substitution of either serine residue 218 or 222 with alanine completely abolished its activation by epidermal growth factor-stimulated Swiss 3T3 cell lysates or immunoprecipitated c-raf, suggesting that both serine residues are required for MEK1 activation. Phosphopeptide analysis demonstrated that serine residues 218 and 222 of human MEK1 are the primary sites for phosphorylation by c-raf. These two serine residues are highly conserved in all members of the MEK family, including the yeast STE7 gene product, a MEK homolog in the yeast mating pheromone response pathway. Mutation of the corresponding residues in STE7 completely abolished the biological functions of this gene. These data demonstrate that MEK is activated by phosphorylation of two adjacent serine/threonine residues and this activation mechanism is conserved in the MEK family kinases.     

Vibrational analysis of nucleic acids. I. The phosphodiester group in dimethyl phosphate model compounds: (CH3O)2PO2-, (CD3O)2PO2-, and (13CH3O)2PO2-.

Normal coordinate analyses and vibrational assignments are presented for the dimethyl phosphate anion [(CH3O)2PO2-] and its deuteriomethyl [(CD3O)2PO2-] and carbon-13 [(13CH3O)2PO2-] derivatives in the gauche-gauche conformation. The dimethyl phosphate anion, which is the simplest model for the nucleic acid phosphodiester moiety, exhibits many of the spectral complexities of DNA and RNA and has previously resisted a complete and consistent vibrational analysis. In the present study we make use of new experimental data on the dimethyl phosphate isotopomers, including Raman depolarization measurements, to develop a consistent valence force field for normal modes of the C--O--P--O--C phosphodiester network and its hydrogenic substituents, as well as for stretching and bending modes of the O--P--O network of the anionic phosphodioxy group (PO2-). The force field established for dimethyl phosphate incorporates one significant nonbonded force constant, introduced from ab initio calculations, to account for interaction between the two ester C--O bonds. This study resolves previous problematic assignments for conformation-sensitive symmetric (in-phase) and asymmetric (out-of-phase) skeletal stretching modes of the ester linkages and demonstrates substantial anharmonicity in the hydrogen-stretching vibrations of the methyl substituents. New assignments are proposed for Raman bands of the phosphodioxy group, which may serve as potential indicators of structure and interaction of the DNA phosphates.     

Brucella abortus catalase is a periplasmic protein lacking a standard signal sequence.

A periplasmic catalase has been purified and cloned from Brucella abortus. The functional enzyme is a tetramer with a subunit molecular weight of 55,000. All evidence indicates that a typical N-terminal signal sequence is not associated with the export of this protein to the periplasm.     

黑曲霉突变株葡萄糖淀粉酶的化学组成及其光谱学性质

黑曲霉突变株葡萄糖淀粉酶中一型GAI舍糖量为17.6%。氨基酸分析表明,天门冬氨酸和谷氨酸(包括酰胺)占20.3%,苏氨酸和丝氨酸占25.1%,三种碱性氨基酸占6%。紫外光谱在278nm和250nm处分别有最大和最小吸收;其荧光光谱的最大激发波长和发射波长分别为284nm与342nm;远紫外CD谱表现为一双负峰;在溶液中的构象是α-螺旋10.6%,β折叠16.3%和无规卷曲73.1%。     

污染预测的非线性参数模型

本文探索了Cr~（3 ）,Cr~（6 ）溶液浓度与绿豆幼苗根过氧化物酶活性之间的相关关系,建立了线性与非线性的数学模型,经相关指数,剩余标准差检验,找出了拟合度比较高的非线性参数模型．本文的结果为利用过氧化物酶活性增长率作为水环境受重金属污染的生物监测指标提供了理论依据．     

农田林网化地区近地面层廓线特征研究

大面积林网化地区近地面层大气的系留气球观测发现,近地面层大气的风、温、湿分为两层,即下边界层和扰动边界层,其厚度和廓线分布与理查逊数有关,在中性天气条件下均满足对数分布规律,边界层（特别是扰动边界层）内的摩擦速度Ｕ．＂与旷野对比点的摩擦速度Ｕ０增大１个数量级,而粗糙度Ｚ＂０增大２个数量级,甚至更大。