大肠杆菌棉子糖操纵子α—半乳糖苷酶表达的调节控制

The alpha-galactosidase, coded for by the first structural gene rafA in the plasmid determined raf operon was an inducible enzyme. In contrast to lac or mel operon, raf operon has more strict structural specificity for inducers. The enzyme can be induced by melibiose and raffinose, or weakly by D-galactose, but not by structurally related sugars such as lactose, PNPG etc.. The alpha-galactosidase forming capacity as function of growth curve reached a single peak at the end of the logarithmic phase of the growth. The structure and regulation of raf operon is similar to those of lac operon. The repressormor-mediated negative control plays a major role in the regulation of raf operon, and cAMP-CAP mediated positive control is also involved in the regulation. When 0.4% glucose was added into the medium with other carbon sources, the expression of the enzyme was repressed by 2-3 fold. Transient catabolite repression has been observed neither in inducible nor constitutive alpha-galactosidase expression. Based on alpha-galactosidase assay, in mutant strains CA8306(cya) and CA8445 (cya, crp) the expression level of raf operon was only 9% and 2.5% of that in wild type strain respectively. The glucose effect or the repression in cya mutant can be abolished by 1-5 mmol cAMP. The constitutive alpha-galactosidase expression in cya and cry double mutant (CA8445) remains repressible by glucose, but irreversible by cAMP, suggesting cAMP-CAP complex is not the exclusive mediator of the catablite repression.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of human epidermal growth factor (hEGF) on splanchnic circulation in dogs

The effect of intravenous administration of human epidermal growth factor on the splanchnic blood flows was examined in anesthetized dogs, using an ultrasonic transit-time volume flow meter. Human epidermal growth factor (0.1, 0.5 and 1 microgram/kg) significantly increased blood flows in the portal vein (36.9 +/- 7.4% at 1 microgram/kg) and the superior mesenteric artery (49.0 +/- 16.8% at 1 microgram/kg). Systemic blood pressure monitored simultaneously was significantly decreased (8.4 +/- 1.2% at 1 microgram/kg). This study is the first to demonstrate that intravenous administration of epidermal growth factor increases the portal venous blood flow.     

Interleukin-1 inhibits PGE2 binding to macrophage-like P388D1 cells by a cyclic AMP-independent process.

The interaction between interleukin IL-1 alpha and PGE2 on P388D1 cells has been investigated. Preincubation of murine macrophage-like cells, P388D1, with IL-1 alpha (0-73 pM) reduced the binding of PGE2 to these cells in a concentration-dependent manner. Scatchard analysis showed that IL-1 alpha decreased the PGE2 binding by lowering both the high and low affinity receptor binding capacities (from 0.31 +/- 0.02 to 0.12 +/- 0.01 fmol/10(6) cells for the high affinity receptor binding sites and from 2.41 +/- 0.12 to 1.51 +/- 0.21 fmol/10(6) cells for the low affinity receptor binding sites). However, the dissociation constants of the receptors of the IL-1 alpha-treated cells remained unchanged. Inhibition of PGE2 binding by IL-1 alpha did not involve changes in either protein phosphorylation or intracellular cyclic AMP levels. Our data clearly show that IL-1 alpha inhibits the binding of PGE2 to monocytes/macrophages and may thereby counter the immunosuppressive actions of PGE2.     

人体基因组随机单拷贝顺序的分离及其在染色体上的定位

本文从构建杂种细胞14-7-1的基因组文库出发,用种特异的探针分离出含有人体基因组顺序的重组子,并进一步分析了其中13个克隆,得到8个单拷贝顺序。通过与已建立的杂种细胞克隆分布板杂交以及染色体的原位杂交方法,将1个单拷贝顺序FD11-1定位在11p11-q11上。由于已经报道在11号染色体上具有3个连锁群,它们分别位于11p15、11p13和11q13上,因此,FD11-1有可能为11号染色体连锁基因图的建立提供1个有意义的座位。     

Molecular cloning of a metallothionein-like gene from Nicotiana glutinosa L. and its induction by wounding and tobacco mosaic virus infection.

The cloning and characterization of genes expressed in plant disease resistance could be an initial step toward understanding the molecular mechanisms of disease resistance. A metallothionein-like gene that is inducible by tobacco mosaic virus and by wounding was cloned in the process of subtractive cloning of disease resistance-response genes in Nicotiana glutinosa. One 530-bp cDNA clone (KC9-10) containing an open reading frame of 81 amino acids was characterized. Genomic Southern blot hybridization with the cDNA probe revealed that tobacco metallothionein-like genes are present in few or in one copy per diploid genome. Northern blot hybridization detected strong induction of a 0.5-kb mRNA by wounding and tobacco mosaic virus infection, but only mild induction was detected when copper was tested as an inducer. Methyl jasmonate, salicylic acid, and ethylene were also tested as possible inducers of this gene, but they had no effect on its expression. The possible role of this gene in wounded and pathogen-stressed plants is discussed.     

细胞骨架对凝血酶诱导人血小板分泌反应的调节(英文)

本文利用血小板表面外露的GMP-140为血小板分泌反应的特异性标志,通过放射免疫分析法定量测定血小板表面GMP-140分子数,研究了细胞骨架抑制剂对凝血酶诱导血小板分泌反应的影响。结果表明,凝血酶激活使血小板表面GMP-140的外露明显增加,反应迅速,并在一定范围内呈剂量和时间依赖性;而ADP刺激则几乎不引起GMP-140外露的增加。凝血酶激活前加入不同的细胞骨架抑制剂处理可产生不同的效应:细胞松驰素B(肌动蛋白微丝抑制剂)可明显上调凝血酶诱导的GMP-140外露;而秋水仙素(微管抑制剂)则下调GMP-140的外露;两者同时处理仍呈现明显的上调作用。提示凝血酶作为一种强激活剂,不仅可通过受体-G蛋白-第二信使的途径启动血小板分泌反应,而且可能经诱导肌动蛋白微丝的形成对分泌反应起反馈性负调节作用。微管的存在则可能对凝血酶诱导的分泌反应起促进作用。虽然两种细胞骨架的作用相反,但以微丝的作用为主,两者间无相互拮抗现象。