匹配在观察性研究中的作用——有向无环图视角

匹配是观察性研究中选择研究对象的一种常用方法,具有控制混杂因素、提高统计效率等作用,但其控制混杂因素的作用在不同观察性研究中并不一致,匹配在队列研究中能够消除匹配变量的混杂偏倚,但在病例对照研究中匹配本身并不能消除混杂偏倚。在匹配性病例对照研究选择匹配变量时,研究者可能并不能准确判断该变量是否为混杂变量,若误将真实情况为非混杂因素的变量进行匹配,则会形成过度匹配,造成统计效率下降或引入难以避免的偏倚或增加工作量等;若将真实情况为混杂因素的变量遗漏不予匹配,则会造成混杂偏倚。有向无环图是一种直观的展示不同流行病学研究设计、变量间复杂因果关系的可视化图形语言。本文从有向无环图视角分析匹配在不同观察性研究设计中的作用、匹配性病例对照研究中欲匹配变量的选择标准制定,为今后流行病学研究设计提供一定的参考建议。     

复合诱变筛选avermectins高产菌株

由Streptomyces avermitilis初始菌株经过自然分离可以得到三种不同类型的菌株，即灰色粉末型、白色和光秃型。其中灰色粉末型产素水平最高，摇瓶发酵效价达到6835．1μg／ml，B1组分达到56．3％。经过紫外线和亚硝基胍对初始菌株的孢子的诱变及对其原生质体的诱变再生。并且经过异亮氨酸和链霉素的定向筛选，得到的高产菌株摇瓶发酵效价达到8542．9μg／ml，B。组分达到64．9％；同时通过对高产菌株进行传代培养检验其传代稳定性，结果表明，传代3代后，菌株开始退化，并且其发酵效价有比较显著的下降。     

Use of the tail moment of the lymphocytes to evaluate DNA damage in human biomonitoring studies.

The Comet assay has gained increasing popularity for use in human biomonitoring or epidemiologic studies; however, one of the shortcomings of the Comet assay is a lack of agreement on a single appropriate Comet parameter that is capable of adequately describing observed DNA damages. Among the tail parameters of Comet features, the most frequently used are the tail moments (both the Olive tail moment and the extent tail moment), the tail DNA, and the tail length. Some studies comparing Comet parameters have been found in cell toxicity research, but there are few comparative studies that use human biomonitoring or epidemiologic data. In this study, we evaluate those four tail parameters in both high and low DNA damaged cells with the use of epidemiologic data. To do this, a new graphical approach, the so-called quantile dispersion graphs (QDGs) are used. In a comparison of an exposed group and a control group, either the tail moment or tail DNA is preferable to the tail length. With respect to providing smaller variability in quantiles for the amount of DNA damage, however, the tail moment is the preferred parameter for both groups. Moreover, the tail moment provides the most stable estimates for DNA damage because it has a larger degree of uniformity in quantile dispersions. To study high degrees of damage from toxic exposure using B cells or G cells, however, the tail DNA showed more significant discrepancies than the other parameters, in terms of both the mean differences and the graphical differences between the two groups. In view of this result, it is suggested that both the tail moment and the tail DNA be presented as tail parameters in human biomonitoring studies.     

Learning from nature – Novel synthetic biology approaches for biomaterial design

Many biomaterials constructed today are complex chemical structures that incorporate biologically active components derived from nature, but the field can still be said to be in its infancy. The need for materials that bring sophisticated properties of structure, dynamics and function to medical and non-medical applications will only grow. Increasing appreciation of the functionality of biological systems has caused biomaterials researchers to consider nature for design inspiration, and many examples exist of the use of biomolecular motifs. Yet evolution, nature’s only engine for the creation of new designs, has been largely ignored by the biomaterials community. Molecular evolution is an emerging tool that enables one to apply nature’s engineering principles to non-natural situations using variation and selection. The purpose of this review is to highlight the most recent advances in the use of molecular evolution in synthetic biology applications for biomaterial engineering, and to discuss some of the areas in which this approach may be successfully applied in the future.     

Altered patterns of directed connectivity within the reading network of dyslexic children and their relation to reading dysfluency

Reading is a complex cognitive skill subserved by a distributed network of visual and language-related regions. Disruptions of connectivity within this network have been associated with developmental dyslexia but their relation to individual differences in the severity of reading problems remains unclear. Here we investigate whether dysfunctional connectivity scales with the level of reading dysfluency by examining EEG recordings during visual word and false font processing in 9-year-old typically reading children (TR) and two groups of dyslexic children: severely dysfluent (SDD) and moderately dysfluent (MDD) dyslexics. Results indicated weaker occipital to inferior-temporal connectivity for words in both dyslexic groups relative to TRs. Furthermore, SDDs exhibited stronger connectivity from left central to right inferior-temporal and occipital sites for words relative to TRs, and for false fonts relative to both MDDs and TRs. Importantly, reading fluency was positively related with forward and negatively with backward connectivity. Our results suggest disrupted visual processing of words in both dyslexic groups, together with a compensatory recruitment of right posterior brain regions especially in the SDDs during word and false font processing. Functional connectivity in the brain’s reading network may thus depend on the level of reading dysfluency beyond group differences between dyslexic and typical readers.     

Dynamic path analysis – a useful tool to investigate mediation processes in clinical survival trials

When it comes to clinical survival trials, regulatory restrictions usually require the application of methods that solely utilize baseline covariates and the intention‐to‐treat principle. Thereby, much potentially useful information is lost, as collection of time‐to‐event data often goes hand in hand with collection of information on biomarkers and other internal time‐dependent covariates. However, there are tools to incorporate information from repeated measurements in a useful manner that can help to shed more light on the underlying treatment mechanisms. We consider dynamic path analysis, a model for mediation analysis in the presence of a time‐to‐event outcome and time‐dependent covariates to investigate direct and indirect effects in a study of different lipid‐lowering treatments in patients with previous myocardial infarctions. Further, we address the question whether survival in itself may produce associations between the treatment and the mediator in dynamic path analysis and give an argument that because of linearity of the assumed additive hazard model, this is not the case. We further elaborate on our view that, when studying mediation, we are actually dealing with underlying processes rather than single variables measured only once during the study period. This becomes apparent in results from various models applied to the study of lipid‐lowering treatments as well as our additionally conducted simulation study, where we clearly observe that discarding information on repeated measurements can lead to potentially erroneous conclusions. Copyright © 2015 John Wiley & Sons, Ltd.     

日本血吸虫(中国大陆株)表达基因的分离和EST序列测定

目的 运用表达标签技术（ＥＳＴ方法）,从ＳｊｃＤＮＡ文库中分离、鉴定血吸虫表达基因序列。方法 应用ＥＳＴ方法,人ＳｊｃＤＮＡ文库中随机挑出单个重组克陲 ＰＣＲ直接序列分析,通过互联网将获得的ＥＳＴ序列送入ＮＣＢＩＧｅｎＢａｎｋ进行同源性检素,并将发现的未知基因ＥＳＴ序列送入ＮＣＢＩｄｂＥＳＴ以获得ＧｅｎＢａｎｋ进入号。结果 分离了１００个ＳｊＧｅｎＢａｎｋ中已知的血吸虫基因序列,１９个为未知基因序