β-phenylethyl isothiocyanate-mediated apoptosis in hepatoma HepG2 cells

-Phenylethyl isothiocyanate (PEITC) is a promising chemoprotective compound that is routinely consumed in the diet as its glucosinolate precursor. Previous studies have shown that PEITC can inhibit phase I enzymes and induce phase II detoxification enzymes along with apoptosis in vitro. The detailed mechanisms involved in the apoptotic cascade, however, have not been elucidated. In the present study, we demonstrate that PEITC can induce apoptosis in hepatoma HepG2 cells in a concentration- and time-dependant manner as determined by TUNEL positive and SubG1 population analysis. Caspase-3-like activity and poly(ADP-ribosyl)polymerase cleavage increased during treatment with 20 µM PEITC; high concentrations, however, induced necrosis. Pre-treatment with Z-VAD-FMK and the caspase-3-specific inhibitor Ac-DEVD-CHO prevented PEITC-induced apoptosis, as determined by caspase-3-like activity and DNA fragmentation. Additional investigations also showed that at concentrations of 5-C10 µM PEITC, DNA synthesis was inhibited and G2/M phase cell cycle arrest occurred, correlating with an alteration in cyclin B1 and p34^cdc2 protein levels. Furthermore, we also demonstrate a concentration- and time-dependant burst of superoxide (O₂^-) in PEITC-treated cells. However, pre- and co-treatment with the free radical scavengers Trolox, ascorbate, mannitol, uric acid and the superoxide mimetic manganese (III) tetrakis (N-methyl-2-pyridyl) porphyrin failed to prevent PEITC-mediated apoptosis. Taken together, these results suggest that PEITC potently induces apoptosis and cell cycle arrest in HepG2 cells and that the generation of reactive oxygen species appears to be a secondary effect.Received 23 December 2002; accepted 22 April 2003     

ERKs are the point of divergence of PKA and PKC activation by PTHrP in human skin fibroblasts

Parathyroid hormone-related peptide (PTHrP) receptors, coupled to trimeric G proteins, operate in most target cells through at least three different transduction routes: Gαs-mediated stimulation of adenylylcyclase (AC), Gαq-mediated activation of phospholipase Cβ (PLC) and mitogen-activated protein kinase (MAPK) activation. In this study we investigated the relative role of different pathways in human skin fibroblast prolifera-tion. Using chemical inhibitors and activators of signal transduction, we demonstrated that: (i) AC/cAMP and PLC/1,4,5 inositol triphosphate/diacylglycerol second-messenger systems are simultaneously activated following PTHrP binding to its receptors; (ii) the mitogenic response to PTHrP derives from a balance between two counteracting pathways – an activating route mediated by protein kinase C (PKC) and an inhibitory route mediated by protein kinase A (PKA); (iii) PTHrP mitogenic effects are largely dependent on MAPKs, whose activity can be modulate d by both PKA and PKC. Our results indicate that MAPKs are common targets of both transduction routes and, at the same time, their point of divergence in mediating PTHrP dual and opposite mitogenic effects. Received 2 August 2002; received after revision 10 September 2002; accepted 18 October 2002 RID="*" ID="*"Corresponding author.     

基于Shell脚本的IBM Cell／B．E．模拟环境的自动安装与测试

本文针对IBM Cell/B.E 模拟环境的构建提出了一种借助Shell脚本创建的方法,解决了模拟环境构建中所面临的图形系统的自动启动与配置、License的自动确认、软件的自动安装与配置等问题,并给出了实例测试验证该方法的正确性.这为今后研究和使用IBM Cell/B.E模拟环境提供了一种尝试性的解决方案.     

A reappraisal of the hormonal regulation of larval fat body histolysis in femaleDrosophila melanogaster

The histolysis of larval fat body cells in adult femaleDrosophila melanogaster was examined in wild type and mutant animals. The fat body cells of wild type (Canton-S),apterous ^56f homozygotes,apterous ^78jts homozygotes and heterozygotes,apterous ⁴/+, ecdysoneless¹ homozygotes and heterozygotes all underwent histolysis normally during the 72 h following adult eclosion. Only in the case ofap ⁴/ap⁴ adults did the cells fail to histolyze normally. The fat body cells of both diapausing and non-diapausing wild type females underwent histolysis at the same rate. Attempts to demonstrate histolysis in vitro were unsuccessful, even in the presence of juvenile hormones (JHs), larval ring glands, or adult ovaries. In all strains other than theap ⁴ homozygotes, a significant proportion of larval fat body cells were dead at any time while theap ⁴/ap⁴ animals, almost all cells remained viable. It is postulated that fat body cell lysis following eclosion is not a JH-mediated event, but is elicited by an as yet unidentified factor(s), possibly originating in the ovary.     

高稳定性便于再生的苯酚微生物传感器

这种传感器的细胞固定化是左氢电极膜表面紧贴一层包埋着茁芽丝孢酵母的海藻胶层,再在凝胶层上覆盖一片透析膜,该传感器的基本特性除类似或略优于透析膜包装的传感器外,还具有两个很重要的特点:稳定性高,可反复使用3个月以上;便于培养处理,使因热或化学因子而失活的传感器获得再生。     

Cell size of mammalian myocardia is not related to physiological demand

Morphological characteristics of myocardial ventricular myocytes have been evaluated from 5 mammalian orders with resting heart rates ranging from 51 to 475 bpm. The purpose was to determine if morphological characteristics of the myocardia are related to the functional demand imposed on the cell as represented by the resting heart rate. Cell size is a constant among mammals of different sizes which have different physiological demands. In contrast, there is more mitochondrial area and less myofibrillar area per cell in animals with rapidly beating hearts than in animals with slower heart rates. Additionally, the mean cross sectional area of individual myofibrils is 30% larger in the cow as compared to the mouse. These findings combined with our previous studies indicate that the different functional requirements of myocardia from different mammalian orders are satisfied by intracellular adaptations of both a structural and biochemical nature.     

Increased apoptosis in differentiating p27-deficient mouse embryonic stem cells

In mouse embryonic stem (mES) cells, the expression of p27 is elevated when differentiation is induced. Using mES cells lacking p27 we tested the importance of p27 for the regulation of three critical cellular processes: proliferation, differentiation, and apoptosis. Although cell cycle distribution, DNA synthesis, and the activity of key G1/S-regulating cyclin-dependent kinases remained unaltered in p27-deficient ES cells during retinoic acid-induced differentiation, the amounts of cyclin D2 and D3 in such cells were much lower compared with normal mES cells. The onset of differentiation induces apoptosis in p27-deficient cells, the extent of which can be reduced by artificially increasing the level of cyclin D3. We suggest that the role of p27 in at least some differentiation pathways of mES cells is to prevent apoptosis, and that it is not involved in slowing cell cycle progression. We also propose that the pro-survival function of p27 is realized via regulation of metabolism of D-type cyclin(s).Received 25 February 2004; received after revision 5 April 2004; accepted 15 April 2004     

Opposite roles of protein kinase C isoforms in proliferation, differentiation, apoptosis, and tumorigenicity of human HaCaT keratinocytes

We have previously shown that the protein kinase C (PKC) system plays a pivotal role in regulation of proliferation and differentiation of the human keratinocyte line HaCaT which is often used to assess processes of immortalization, transformation, and tumorigenesis in human skin. In this paper, using pharmacological and molecular biology approaches, we investigated the isoform-specific roles of certain PKC isoenzymes (conventional cPKC and ; novel nPKC and ) in the regulation of various keratinocyte functions. cPKC and nPKC stimulated cellular differentiation and increased susceptibility of cells to actions of inducers of apoptosis, and they markedly inhibited cellular proliferation and tumor growth in immunodeficient mice. In marked contrast, cPKC and nPKC increased both in vitro and in vivo growth of cells and inhibited differentiation and apoptosis. Our data present clear evidence for the specific, antagonistic roles of certain cPKC and nPKC isoforms in regulating the above processes in human HaCaT keratinocytes.Received 13 January 2004; received after revision 18 February 2004; accepted 25 February 2004     

端粒、端粒酶和肿瘤、细胞衰老

端粒和端粒酶是现代生物学研究的热点,端粒的缺失与细胞的衰老,端粒酶的活性与细胞的老化及癌化均有密切的关系.文章综述了端粒和端粒酶的结构和功能及其与细胞衰老及肿瘤的关系,并在此基础之上展望了端粒酶在抗衰老、抑制肿瘤等方面的应用.     

一种小型PEM燃料电池流量系统的建模与控制

给出了一种小型质子交换膜燃料电池流量系统的控制模型,根据此模型应用基于CMAC神经元网络的自适应PID控制算法以实现燃料电池阴极和阳极侧压力的协调控制。同时将这种控制算法在一种基于ARM微处理器的硬件平台和可视化的监控组态软件平台(netcon系统)上予于实现。仿真结果和实验结果具有良好的一致性,实际应用效果表明此控制系统运行可靠,使用方便,具有很强的实用价值。