Initiation of cancer and other diseases by catechol ortho-quinones: a unifying mechanism

Exposure to estrogens is a risk factor for breast and other human cancers. Initiation of breast, prostate and other cancers has been hypothesized to result from reaction of specific estrogen metabolites, catechol estrogen-3,4-quinones, with DNA to form depurinating adducts at the N-7 of guanine and N-3 of adenine by 1,4-Michael addition. The catechol of the carcinogenic synthetic estrogen hexestrol, a hydrogenated derivative of diethylstilbestrol, is metabolized to its quinone, which reacts with DNA to form depurinating adducts at the N-7 of guanine and N-3 of adenine. The catecholamine dopamine and the metabolite catechol (1,2-dihydroxybenzene) of the leukemogen benzene can also be oxidized to their quinones, which react with DNA to form predominantly analogous depurinating adducts. Apurinic sites formed by depurinating adducts are converted into tumor-initiating mutations by error-prone repair. These mutations could initiate cancer by estrogens and benzene, and Parkinson's disease by the neurotransmitter dopamine. These data suggest a unifying molecular mechanism of initiation for many cancers and neurodegenerative diseases and lay the groundwork for designing strategies to assess risk and prevent these diseases. Received 4 September 2001; received after revision 28 November 2001; accepted 2 December 2001     

Recombinant PsbF from Synechococcus sp. PCC 7002 forms β:β homodimeric cytochrome b559

All organisms with oxygenic photosynthesis contain two photosystems:photosystem Ⅰ(PSⅠ)and photo-systemⅡ(PSⅡ),The minimal photosystem Ⅱ particles which are photochemically active contain three subunits:D1,D2 and cytochrome b559 (Cyt b559),The function of Cyt b559 remains unclear,We have successfully overxpressed the psbF gene,encoding the β subunit of Cyt b559,from a marine cyanobacterium Synechoccous sp.PCC 7002 as a fusion gene and obtained a redox-active from of Cyt b559,When the N-terminal GST protein of the fusion gene product was removed with thrombin ,the PsbF protein was still redox-active,suggesting that the recombinant PsbF can form dimer in Escherichia coli.The absorption spectra of either the oxidized from or the reduced form of both GST fusion protein and the purified PsbF dimer and the difference Spectra between the two forms are the same as that of the Cyt b559 isolated from the higher plants .Redox titration analysis of recombinant PsbF showed that the mid-point redox potential of the recombinant Cyt b559 was approximately 50 mV, which is close to the low potential of Cyt b559 ,The results are helpful to the understanding of locatlization and function of Cyt b559 on thylakoid membranes.Ⅰ     

航迹起始算法及性能仿真

在深入研究基于逻辑的航迹起始方法和基于Hough变换技术的航迹起始方法的基础上,把基于逻辑的方法和Hough变换法相结合,提出了基于目标运动状态的航迹起始算法。该算法首先利用目标的位置信息形成候选目标航迹,在候选目标航迹扩展过程中,利用来自同一个目标的量测数据在较短时间内(相邻2个采样周期)具有相同的运动状态,利用目标的运动状态对候选航迹进行检验。进行了性能比较仿真,仿真结果表明:该算法在正确航迹起始概率上和基于逻辑的方法相当,但其虚假航迹起始概率远低于其他航迹起始方法;并且对存储要求低,适于工程应用。     

基于模糊Hough变换的被动传感器系统航迹起始方法

提出一种基于模糊Hough变换(FHT)的被动传感器系统中的航迹起始方法。首先利用逻辑关系或规则初步排除鬼点,以降低计算复杂度,推导出被动传感器系统中的Hough变换形式。考虑到传感器系统误差和测量误差对检测结果的影响,将传感器系统获得的观测值模糊映射到参数空间,利用梯度信息降低计算消耗,求出参数空间的模糊累积矩阵,通过模糊推理确定出最终的航迹检测结果。实验结果表明,所提的模糊Hough变换方法能有效解决杂波环境下的航迹起始问题,且计算消耗小。     

低氮营养与激动素对离体黄瓜子叶花芽分化的影响

以黄瓜（ＣｕｃｕｎｉｓｓａｔｉｖｕｓＬ．）子叶为材料，探讨了低氮营养与激动素对子叶花芽分化的影响，总氮量为ＭＳ培养基的一半，ＮＯ＾－３／ＮＨ＾＋４比值为２：１时花芽分化受到显著促进，低浓度的激动素（０．１ｍｇ／Ｌ）对于叶花芽间接分化具有明显的促进作用，高浓度的激动素（１．５ｍｇ／Ｌ）则对花芽的直接分化有促进作用，低氮营养下施以０．１ｍｇ／Ｌ激动素的促进作用显著高于二者单独作用的效果，分期取样进行酶     

轴承钢中夹杂物与接触疲劳裂纹萌生的关系

通过在国产JPM—1型接触疲劳试验机上对国产GCr15、瑞典SKF及美国SAE52100三种类似的轴承钢进行的接触疲劳试验,观察到许多接触疲劳微裂纹及引起裂纹萌生的夹杂物。利用金相显微镜、扫描电镜观察并测量萌生裂纹的夹杂物形状、尺寸、位置,并用图相分析仪测定出夹杂物尺寸分布,从而找出轴承钢中夹杂物与接触疲劳裂纹萌生之间的定量关系,为提高轴承钢冶金质量,完善夹杂物评级标准提供科学依据。     

砂类盐渍土起胀含盐量的试验探讨

目前对盐渍土起胀含盐量的判定多是通过不同学者拟合的盐胀率计算公式反推算求得的,其结果莫衷一是,因此需采用试验方法予以明确.试验选择8种不同孔隙率(级配)的土样,在单次降温条件下观测其是否发生盐胀变形.通过试验发现:砂土起胀含盐量随着孔隙率增长呈现出先长后降的规律,这一规律在不同含水量条件下都有体现.这一现象与盐分在土颗粒间的结晶位置发生改变有关,孔隙率较小时,土壤饱和度较高,盐分多在孔隙内部结晶析出;当孔隙率增加后,土饱和度降低,盐分则转移到水膜较厚的颗粒接触点位置析出,因此启动盐胀所需盐分减少,起胀含盐量下降.     

紫外引发合成三元阳离子聚丙烯酰胺及其对雌酮的絮凝去除

通过紫外引发聚合技术制备了具有疏水特性的三元阳离子聚丙烯酰胺,并用于典型环境雌激素雌酮(E1)的分离和去除。由丙烯酰胺(AM)、丙烯酰氧基乙基三甲基氯化铵(DAC)和丙烯酰氧基乙基二甲基苄基氯化铵(AODBAC)单体合成三元共聚物(PADA),并采用傅里叶变换红外光谱(FT-IR),核磁共振氢谱(~1H NMR)和热失重/差示扫描量热仪(TG/DSC)分别对聚合物的结构和热分解性能进行表征。FT-IR和~~1H NMR结果表明聚合物成功合成。通过引入疏水性基团(苯基),TG/DSC分析观察到PADA热稳定性能提高。在最佳条件下(p H=7,絮凝剂用量为4.0 mg/L),用高效絮凝剂PADA-3(阳离子度为40%,特性黏度为6.30 d L·g~(-1))得到最佳E1絮凝性能(E1去除率90.1%,絮凝体积18.3μm,絮凝动力学22.69×10~(-4)s~(-1))。Zeta电位和絮体尺寸分析用于探究E1去除的絮凝机理。结果表明,E1去除过程中,电中和、吸附和架桥效应占主导地位。