Development and validation of molecular methodologies for identification of biological traces from crime scenes

This study aimed to develop a methodology to identify biological fluids in sexual assault cases through mRNA markers. Biological fluid samples such as blood, saliva, and semen were collected from volunteers and submitted to RT-qPCR reactions with specific primers for the biomarkers HTN3 (saliva), ALAS (blood) andTGM4 (semen). The Melting (Tm) of each biological fluid was analyzed and the result inferred a high specificity capable of differentiating such traces. Biplex systems were generated to improve trace analysis in a single qPCR reaction.     

不同方式标记非放射性探针原位杂交效果评价

目的比较不同方式标记非放射性探针的原位杂交效果。方法通过两种方法标记地高辛随机引物DNA探针和反意RNA探针,在大鼠损伤模型的皮肤组织上进行原位杂交。结果两种探针均可满足要求,以反意RNA探针在阳性染色深度和背景方面效果更佳。结论RNA探针在杂交效果方面优于DNA探针。     

Spatial and temporal influences on bacterial profiling of forensic soil samples

Bacterial content may be helpful in differentiating forensic soil samples; however, the effectiveness of bacterial profiling depends on several factors, including uniqueness among different habitat types, the level of heterogeneity within a habitat, and changes in bacterial communities over time. To examine these, soils from five diverse habitats were tested over a 1 year period using terminal restriction fragment length polymorphism (TRFLP) analysis. Soil samples were collected at central locations monthly, and 10 feet in cardinal directions quarterly. Similarity indices were found to be least related among habitats, while the greatest bacterial similarities existed among collection locations within a habitat. Temporally, however, bacterial content varied considerably, and there was substantial overlap in similarity indices among habitats during different parts of the year. Taken together, the results indicate that while bacterial DNA profiling may be useful for forensic soil analysis, certain variables, particularly time, must be considered.     

Evaluating the use of hypoxia sensitive markers for body fluid stain age prediction

To augment DNA profiling and body fluid identification techniques efforts are being made to increase the amount of information available from a crime scene stain, which includes efforts to identify externally visible characteristics through phenotypic analysis. A key question surrounding crime scene stains is the length of time between deposition of the stain and its subsequent recovery, in that is the stain recovered related to the incident in question or from a previously deposited stain number of weeks earlier? The inability to answer this fundamental question has a detrimental effect upon the successful completion of a criminal investigation. Once a body fluid leaves the body, the oxygen concentration in the environment changes; therefore, it may be that this change could cause a change in the expression of hypoxia-sensitive biomarkers. Here, a range of bloodstains, liquid saliva and liquid semen samples were collected at 0 days, 7 days, 14 days, 21 days and 28 days of degrading at room temperature (19–22 °C), before undergoing total RNA extraction and cDNA synthesis. Blood was recovered from filter paper with 3 mm², with saliva and semen being left in their tubes and swabbed at the appropriate times. All samples then underwent quantitative PCR targeting Vascular Endothelial Growth Factor A (VEGFA) and Hypoxia-Inducible Factor 1 Alpha (HIF1A), with B-Actin (ACTB) as a reference gene. A range of linear and quadratic correlation values was obtained from the qPCR data and used to develop a predictive model with a mean absolute deviation (MAD) of 4.2, 2.1, and 5 days for blood, saliva, and semen respectively. Blind testing indicated that a stain age prediction model based upon VEGFA with ACTB as a reference gene could be used on samples up to four weeks old with a margin of error ranging from 2 days through to 5 days. While a sizeable potential time frame exists using this model; this represents a significant step towards the target of having an accurate stain age prediction model.     

Detection of microRNAs in DNA Extractions for Forensic Biological Source Identification

Molecular‐based approaches for biological source identification are of great interest in the forensic community because of a lack of sensitivity and specificity in current methods. MicroRNAs (miRNAs) have been considered due to their robust nature and tissue specificity; however, analysis requires a separate RNA extraction, requiring an additional step in the forensic analysis workflow. The purpose of this study was to evaluate miRNA detection in blood, semen, and saliva using DNA extraction methods commonly utilized for forensic casework. RT‐qPCR analysis revealed that the tested miRNAs were consistently detectable across most tested DNA extraction methods, but detection was significantly reduced compared to RNA extracts in some biological fluids. DNase treatment was not necessary to achieve miRNA‐specific results. A previously developed miRNA panel for forensic body fluid identification was evaluated using DNA extracts, and largely demonstrated concordance with results from samples deriving from RNA extracts of semen, blood, and saliva.     

Leaders Without Borders: Familiarity as a Moderator of Transnational Source Cue Effects

The role of source cue effects in transnational persuasion (in which a foreign actor attempts to persuade an audience in another jurisdiction) is largely unexplored in both the political communication and international relations literatures. This article investigates transnational source cue effects using two source cue experiments that test the persuasiveness of German chancellor Angela Merkel and UK prime minister David Cameron in a Canadian context. The experiments were embedded in an online survey administered to student participants at a Canadian university in January 2011. As might be expected, the foreign leaders exerted positive source cue effects among participants who held positive impressions of the leaders and backlash effects among those who held strongly negative impressions. These effects, however, were moderated by participants’ level of political awareness, with the largest effects observed among participants who had an intermediate level of awareness. It is argued that this nonlinear moderating effect can be attributed to the countervailing effects of attitude stability and source familiarity (both of which are associated with political awareness) on individuals’ susceptibility to source cue effects. Finally, cueing David Cameron had approximately equivalent source cue effects on participants’ attitudes towards government spending on foreign aid and welfare, suggesting that foreign leaders may be able to move opinion on domestic as well as on foreign policy issues. Overall, these results validate existing models of source cue effects in a transnational context and point to the scope and limitations of national leaders’ ability to engage in direct public diplomacy.

[Supplementary material is available for this article. Go to the publisher's online edition of Political Communication for the following free supplemental resources: Appendix: Question Wordings for Survey Experiments; Table A1: Balance Tests for Afghanistan and Cameron Cue Experiments; and Table A2: Underlying Salience of Domestic and Foreign Policy Spending.]     

Trizol法大鼠心肌总RNA提取方法探讨

目的 探讨大鼠心肌总RNA的提取方法,为今后法医学研究和实践工作提供参考.方法 用Trizol法,严格注意无RNA酶操作,通过裂解组织,分离、沉淀RNA而提取大鼠心肌总RNA,并用分光光度计、凝胶电泳及RT-PCR检测结果.结果 Trizol法能获得较高纯度和产量的完整总RNA.结论 Trizol法是提取总RNA可靠有效的方法,可望在法医学领域有较广的应用.     

基因沉默的研究进展

基因沉默(genesilencing)是指生物体中特定基因由于种种原因不表达或者表达减少的现象。基因沉默发生在两种水平上,一种是由于DNA甲基化、异染色质化以及位置效应等引起的转录水平上的基因沉默;另一种是转录后基因沉默。RNA干扰(RNAi)是一种新发现的通过dsRNA介导的特异同源靶基因途径,RNAi的应用有望成为一种防治疾病的新方法。