Unconditional small-sample confidence intervals for the odds ratio

The traditional approach to 'exact' small-sample interval estimation of the odds ratio for binomial, Poisson, or multinomial samples uses the conditional distribution to eliminate nuisance parameters. This approach can be very conservative. For two independent binomial samples, we study an unconditional approach with overall confidence level guaranteed to equal at least the nominal level. With small samples this interval tends to be shorter and have coverage probabilities nearer the nominal level.     

戈壁生态系统蚁穴微生境对大型土壤动物多样性的影响

收获蚁蚁穴是戈壁生态系统中重要的微生境, 它通过汇集凋落物和改善土壤环境强烈影响动植物的分布及多样性。鉴于此, 本文选择戈壁荒漠收获蚁(Messor desertus)蚁穴为研究对象, 于2020年5月、6月和10月利用陷阱法调查了蚁穴及毗邻裸地大型土壤动物的种类组成及数量变化, 并分析其影响要素。结果表明: (1) 10月, 蚁穴和裸地间大型土壤动物群落组成存在显著差异, 而5月和6月二者间相差较小, 10月(62.9%)蚁穴和裸地大型土壤动物的平均相异性高于5月(34.8%)和6月(39.3%); (2) 5月, 蚁穴大型土壤动物均匀度指数显著低于裸地, 6月, 蚁穴大型土壤动物活动密度和类群丰富度均显著高于裸地, 10月, 蚁穴大型土壤动物类群丰富度和多样性指数均显著高于裸地; (3)荒漠收获蚁蚁穴显著提高了其他食性土壤动物的活动密度及类群丰富度, 还增强了捕食性和非捕食性土壤动物的相互作用关系并改变了荒漠收获蚁与蚁穴大型土壤动物类群的种间相互作用关系; (4) pRDA排序结果表明, 土壤电导率、全氮和粉粒含量是影响蚁穴和裸地大型土壤动物分布的主要土壤因子。总之, 戈壁生态系统荒漠收获蚁蚁穴微生境提高了大型土壤动物多样性, 改变了大型土壤动物类群间的营养和非营养关系, 这会影响大型土壤动物的营养结构及其功能。     

沈阳市大气微生物的研究Ⅲ．大气真菌粒子浓度及其分布

本研究用ＡＮＤＥＲＳＥＮ生物粒子采样器在沈阳市对大气真菌粒子浓度及其分布进行了一年的观测。结果表明,沈阳市大气真菌粒子年平均浓度为１７９７个／ｍ￣３。四季中,秋季大气真菌粒子浓度高,为２８５８个／ｍ３;春季低,为１０９４个／ｍ￣３。在不同地点中,造纸厂大气真菌粒子浓度明显高,为５７８０个／ｍ￣３。一天中的７：００,１９：００为大气真菌粒子浓度的高峰时,１３：００为低谷时。大气真菌粒子的浓度分布是单峰型,高峰在第３、４级,峰值为５３５个／ｍ￣３。造纸厂大气真菌粒子浓度分布的高峰在第５级,小粒子浓度比其余地点明显高。     

核糖体蛋白rpS6在核仁中的定位与其磷酸化无关

核糖体蛋白S6(rpS6)是核糖体小亚基40S的一个组成成分。在该研究中,利用免疫荧光和邻位连接技术证明rpS6不仅是核糖体小亚基的组成成分,而且还可与核仁中的U3核蛋白复合体的标志性蛋白Mpp10共定位并且存在相互作用。rpS6蛋白的C端有5个丝氨酸磷酸化位点,为了研究rpS6蛋白在核仁中的分布是否与其磷酸化有关,构建了rpS6蛋白的两个突变体rpS6A和rpS6D分别与EGFP和HA的融合蛋白。rpS6A是将C端的5个丝氨酸位点全部突变为丙氨酸;rpS6D是将C端的5个丝氨酸位点全部突变为天冬氨酸。研究表明:rpS6、rpS6A和rpS6D与EGFP和HA的融合蛋白均可分布在核仁中,与内源性rpS6蛋白的分布情况一致,说明rpS6蛋白在核仁中的定位与其磷酸化无关,为探索rpS6蛋白在核仁中的功能奠定了良好的基础。     

氮素对长江中下游温室切花百合外观品质影响的模拟研究

氮素是影响花卉生长与外观品质的重要营养元素。定量研究氮素对温室切花百合外观品质的影响,可为切花百合氮素管理提供决策支持。以百合‘索邦’和‘西伯利亚’为材料,根据不同定植期、生长中后期不同速效氮素水平处理试验,以冠层累积吸收辐热积(PTI)为发育尺度,以现蕾期叶片累积氮含量为植株氮素特征指标,定量分析氮素对切花百合外观品质指标(叶面积指数、株高、出叶数、第1花蕾长度与第1花蕾直径)和出花率的动态影响。在此基础上,建立氮素对切花百合外观品质影响的模拟模型,并用独立的试验数据对模型进行检验。结果表明,模型对叶面积指数、株高、出叶数、第1花蕾长度、第1花蕾直径、一级花、二级花、三级花和四级花的预测效果较好,预测值与实测值之间基于1∶1线的决定系数(r2)分别为0.92、0.85、0.86、0.91、0.88、0.88、0.88、0.91和0.91,相对回归估计标准误(rRMSE)分别为0.09、0.10、0.14、0.13、0.12、0.18、0.15、0.18和0.21。研究建立的模型为长江中下游地区温室切花百合生产中氮素的优化管理提供了模型工具,也为露地栽培切花百合生产中氮素的优化管理提供了参考。     

Thymoquinone protects human retinal pigment epithelial cells against hydrogen peroxide induced oxidative stress and apoptosis

Oxidative stress in retinal pigment epithelium (RPE) cells may contribute to the progression of age-related macular degeneration. Thymoquinone (TQ), an active component derived from Nigella sativa, possesses antioxidative effect. However, the role of TQ in RPE cells under oxidative stress condition remains unclear. The present study aimed to examine the protective effect of TQ against hydrogen peroxide (H₂O₂)-induced oxidative stress in human RPE cells. Our results showed that TQ improved the cell viability and apoptosis in H₂O₂-induced ARPE cells. We also found that the levels of reactive oxygen species and malondialdehyde induced by H₂O₂ were reduced after the pretreatment of TQ. In addition, the inhibitory effect of H₂O₂ on the glutathione (GSH) level and superoxide dismutase activity was markedly attenuated by TQ pretreatment. Moreover, TQ enhanced the activation of Nrf2/heme oxygenase 1 (HO-1) signaling pathway in H₂O₂-induced ARPE cells. Knockdown of Nrf2 abolished the protective effect of TQ on H₂O₂-induced oxidative damage. These results suggested that TQ protected ARPE cells from H₂O₂-induced oxidative stress and apoptosis via the Nrf2/HO-1 signaling pathway.     

Drug-tolerant cancer cells show reduced tumor-initiating capacity: depletion of CD44 cells and evidence for epigenetic mechanisms

Cancer stem cells (CSCs) possess high tumor-initiating capacity and have been reported to be resistant to therapeutics. Vice versa, therapy-resistant cancer cells seem to manifest CSC phenotypes and properties. It has been generally assumed that drug-resistant cancer cells may all be CSCs although the generality of this assumption is unknown. Here, we chronically treated Du145 prostate cancer cells with etoposide, paclitaxel and some experimental drugs (i.e., staurosporine and 2 paclitaxel analogs), which led to populations of drug-tolerant cells (DTCs). Surprisingly, these DTCs, when implanted either subcutaneously or orthotopically into NOD/SCID mice, exhibited much reduced tumorigenicity or were even non-tumorigenic. Drug-tolerant DLD1 colon cancer cells selected by a similar chronic selection protocol also displayed reduced tumorigenicity whereas drug-tolerant UC14 bladder cancer cells demonstrated either increased or decreased tumor-regenerating capacity. Drug-tolerant Du145 cells demonstrated low proliferative and clonogenic potential and were virtually devoid of CD44(+) cells. Prospective knockdown of CD44 in Du145 cells inhibited cell proliferation and tumor regeneration, whereas restoration of CD44 expression in drug-tolerant Du145 cells increased cell proliferation and partially increased tumorigenicity. Interestingly, drug-tolerant Du145 cells showed both increases and decreases in many "stemness" genes. Finally, evidence was provided that chronic drug exposure generated DTCs via epigenetic mechanisms involving molecules such as CD44 and KDM5A. Our results thus reveal that 1) not all DTCs are necessarily CSCs; 2) conventional chemotherapeutic drugs such as taxol and etoposide may directly target CD44(+) tumor-initiating cells; and 3) DTCs generated via chronic drug selection involve epigenetic mechanisms.