小鼠骨骼肌细胞核DNA降解与死亡时间的关系

目的　监测小鼠死后骨骼肌核内DNA降解的情况 ,探讨死后细胞核DNA降解的一般规律。方法　建立小鼠死亡模型 ,在死后 72h内 ,以 12h的间隔取骨骼肌样本进行单细胞凝胶电泳 ,在荧光显微镜下测量彗星图像 ,并作统计学分析。结果　机体死后 ,骨骼肌细胞在电泳图像上出现了明显的彗星形拖尾 ,L/W比值随死亡时间而逐渐增大 ,二者呈一定的线性关系。结论　单细胞凝胶电泳技术可以应用于早期死亡时间推断。     

人脾脏细胞核DNA含量与死亡时间关系的图像分析

目的研究人脾脏细胞DNA含量改变与死亡时间的关系。方法选取36例已知死亡时间的人体脾脏,在死后5～36h内逐时进行细胞学涂片、Feulgen Vans染色观察,并用图像分析系统,测定脾脏细胞核积分光密度、平均灰度等灰度参数,所得数据用SPSS软件分析。结果在5～36h内平均光密度、积分光密度、平均灰度均值均与死亡时间显著性相关,并得出对应的回归方程,其中平均光密度、积分光密度随死亡时间的延长而逐渐减小、平均灰度逐渐增大。结论人脾脏细胞核DNA含量改变呈现一定规律,与死亡时间明显相关。     

肋软骨及牙髓细胞DNA含量与PMI的相关性

目的探讨人死后肋软骨及牙髓细胞平均DNA含量与死亡时间(PMI)的相关性,寻求推断PMI的新方法。方法应用细胞图像分析技术分析高温(30～35℃)及低温(15～20℃)环境下人死后0～15d两种组织细胞平均DNA含量的降解情况。结果两种组织细胞平均DNA含量随死后时间的延长而逐步降解,其中低温组牙髓细胞平均DNA含量的降解在死后0～4d内有一个降解平台期。统计分析两组温度下两种组织细胞平均DNA含量与PMI有显著的负相关性(P<0.01)。结论依据两种组织细胞平均DNA含量的降解可进行PMI推断。     

应用DNA3’末端转移推测死亡时间

目的根据机体死后组织细胞DNA降解规律,研究其与死亡时间之间的关系.方法SD大鼠处死后,在不同死亡时间段取肝、肾、脾组织提取DNA.根据DNA3′末端转移的方法(TdT法)将dUTP结合到DNA的3′末端,检测反应剩余的dUTP量,从而推测机体死后不同时间段DNA的降解情况.结果经对剩余dUTP检测发现,dUTP的剩余量随死亡时间延长而减少,说明DNA降解与死亡时间存在一定的关系.结论根据机体死后DNA降解规律可用于早期死亡时间的推测.     

DNA含量变化与死亡时间推断的研究进展

在法医学实践中,死亡经历时间的推断具有重要的实践价值,但其准确推断却一直是法医学实践的难题,因而也一直是法医学研究的热点。法医DNA技术是近年来发展起来的在分子水平进行死亡时间推断的新技术、新方法,同传统方法相比,具有很大的优势,本文对该技术提出的背景、发展、优缺点以及发展前景进行综述,着重对DNA含量变化与其相关性的研究进展进行讨论。     

岷江上游民族地区生态环境退化与整治研究

在过去几十年 ,由于人口超过环境承载量 ,人们生产方式和生活方式落后 ,以及生态脆弱等诸多因素 ,导致岷江上游民族地区生态环境退化 ,如植被 ,草场 ,土地的退化及自然灾害频繁发生等。目前 ,区域贫困和生态环境退化已形成了恶性循环。本文根据生态环境退化的现状和人为活动的特点 ,提出了生态环境恢复和整治的对策 ,为岷江上游民族地区生态屏障的构建提出新思路。     

Assessing the performance of quantity and quality metrics using the QIAGEN Investigator® Quantiplex® pro RGQ kit

The Quantiplex® Pro RGQ kit quantifies DNA in a sample, supports the detection of mixtures and assesses the extent of DNA degradation based on relative ratios of amplified autosomal and male markers. Data show no significant difference in the accuracy and sensitivity of quantification between this and the Promega PowerQuant® System, both detecting the lowest amount of DNA tested, 4 pg. Laboratory controlled mixed male:female DNA samples together with mock sexual assault samples were quantified across a range of mixture ratios. Analysis software detected mixed DNA samples across all ratios for both quantification kits. Subsequent STR analysis using the Investigator® 24Plex QS Kit was able to corroborate mixture detection down to 1:25 male:female DNA ratios, past which point mixtures appeared identical to single-source female samples. Analysis software also detected laboratory degraded DNA samples, with data showing a positive trend between the Degradation Index (DI) and length of time of sonication. When used on ancient remains the assay was able to triage samples for further analysis, and STR profiles were concordant with DNA quantification results in all instances. STR analyses of laboratory-controlled sensitivity, mixture, and degradation studies supports the quality metric obtained from quantification. These data support the use of the Quantiplex® Pro RGQ kit for sample screening and quantification in forensic casework and ancient DNA studies.     

Temperature‐Dependent Postmortem Changes in Human Cardiac Troponin‐T (cTnT): An Approach in Estimation of Time Since Death

Estimation of time of death is an indispensible requirement of every medico‐legal autopsy, but unfortunately, there is not a single method by which it could be determined accurately. This study focused on the temperature‐dependent postmortem degradation of cardiac troponin‐T and its association with postmortem interval (PMI) in human. The analysis involved extraction of the protein, separation by denaturing gel electrophoresis (SDS‐PAGE), and visualization by Western blot using cTnT‐specific monoclonal antibodies. The area of the bands within a lane was quantified by scanning and digitizing the image using Gel Doc (Universal Hood). The results indicate a characteristic banding pattern among human cadavers (n = 6) and a pseudo‐linear relationship between percentage of cTnT degradation and the log of the time since death (r > 0.95), which can be used to estimate the postmortem interval. The data presented demonstrate that this technique can provide an extended time range during which PMI can be more accurately estimated.     

Mitochondrial DNA Extraction from Burial Soil Samples at Incremental Distances: A Preliminary Study

Preservation variance of soil DNA is neglected in the literature, and exceptional cases exaggerate amplification capabilities. This study sought to amplify a short mitochondrial fragment (212 bp) specific to Sus scrofa domesticus from the soil surrounding decomposing pig remains from an open‐air locale. Samples collected above the body at incremental distances after 145 days of initial placement yielded pig DNA. A secondary sampling was collected in 2017, approximately 768 days after burial. Inhibition tests corroborated that pig DNA was no longer present in the soil resulting in a loss of original DNA between 145 and 768 days. The results provide evidence that genetic material leaches out radially from the source and DNA fragments longer than 200 bp do not persist in soil for a relatively short timeframe in western Montana. The conclusions support the collection of soil in crime scene investigation procedures within the first few months of decomposition.     

Latent Fingermark Aging Patterns (Part IV): Ridge Width as One Indicator of Degradation

This fourth article of the series is taking an in‐depth analysis at the visible aging of latent fingermarks regarding changes in ridge widths over time. The objective is to quantify and statistically describe significant ridge size variations under controlled indoor conditions. The effect of three environmental variables are examined: type of secretion (sebaceous‐ and eccrine‐rich) and type of substrate (glass and polystyrene) when aged in three light conditions (direct natural light, shade, and dark). Prior to width measurements, fresh and aged fingermarks were powdered with titanium dioxide (TiO₂) and sequentially photographed at predetermined times over 6 months. Three independent observers measured the ridges from thirty predetermined locations using strategically placed intersecting lines on the print. Results indicate that fingermarks deposited on glass are more resilient to degradation compared with those deposited on plastic. The presence of direct natural light plays a negligible role on degradation compared to secretion and substrate types.