一株假单胞菌(Pseudomonas sp.)产生的胞外脂酶

假单胞菌(Pseudomonas sp.)生长在一定的培养条件中能产生胞外脂酶。最适碳源为1.0%淀粉,氮源为1.0%蛋白胨。一些植物油,如橄榄油、糠油、菜油等能诱导脂酶的大量产生,诱导脂酶产生的橄榄油最适浓度为0.5%。无机离子在菌培养过程中对脂酶产率影响很大,K^+、Na^+、Mg^(2+)、Ca^(2+)等对脂酶产生有促进作用,而Mn^(2+)、Ba^(2+)、Zn^(2+)、Fe^(3+)、Co^(2+)、Cu^(2+)等则抑制脂酶产生。非离子表面活性剂(如tween、span及糖脂)能刺激胞外脂酶的产生。

胞外脂酶活力的检测法

介绍一种含一定浓度的橄榄油和Rhodamine B的琼脂平板脂酶检测法。该方法适用于筛选产脂酶的微生物菌种、检测菌体发酵液中脂酶活力以及其它样品中脂酶活力的大小。在该平板上,产脂酶菌体的菌落外围有微红色水解带。脂酶溶液浓度的对数与水解圈直径呈很好的线性关系。与滴定法及比色法相比较,该平板检测法简便、可靠、灵敏。

Insulin-like growth factor binding protein-5 influences pancreatic cancer cell growth

AIM： To investigate the functional significance of insulin-like growth factor binding protein-5 （IGFBP-5） overexpression in pancreatic cancer （PaC）.METHODS： The effects of IGFBP-5 on cell growth were assessed by stable transfection of BxPC-3 and PANC-1 cell lines and measuring cell number and DNA synthesis. Alterations in the cell cycle were assessed by flow cytometry and immunoblot analyses. Changes in cell survival and signal transduction were evaluated after mitogen and phosphatidylinositol activated protein kinase 3-kinase （PI3K） inhibitor treatment.RESULTS： After serum deprivation, IGFBP-5 expression increased both cell number and DNA synthesis in BxPC-3 cells, but reduced cell number in PANC-1 cells. Consistent with this observation, cell cycle analysis of IGFBP-5-expressing cells revealed accelerated cell cycle progression in BxPC-3 and G2/M arrest of PANC-1 cells. Signal transduction analysis revealed that Akt activation was increased in BxPC-3, but reduced in PANC-1 cells that express IGFBP-5. Inhibition of PI3K with LY294002 suppressed extracellular signal-regulated kinase-1 and -2 （ERK1/2） activation in BxPC-3, but enhanced ERK1/2 activation in PANC-1 cells that express IGFBP-5. When MEK1/2 was blocked, Akt activation remained elevated in IGFBP-5 expressing PaC cells; however, inhibition of PI3K or MEK1/2 abrogated IGFBP-5-mediated cell survival.CONCLUSION： These results indicate that IGFBP-5 expression affects the cell cycle and survival signal pathways and thus it may be an important mediator of PaC cell growth.