石蜡包埋人体组织STR检验的探讨

目的 探讨普通甲醛对人体组织DNA的影响及提高STR检出率的手段。方法 取少量石蜡包埋组织。65℃水浴脱蜡。Chelex-100法提取DNA，PCR扩增，循环次数分别为28次和28＋6次，扩增产物经310型测序检测。结果 普通甲醛固定5d以内的组织基本上可检出Amel及15个STR基因座，固定时间延长，检出率下降；PCR循环次数增加，灵敏度增加，但有错误分型的情况。结论 普通甲醛固定时间长短直接影响PCR—STR的检验，减少模板量有利于PCR反应成功，PCR次数为28＋6时，灵敏度增加。但应谨慎判读结果，以免错误分型。     

石蜡包埋人体组织STR检验的探讨

目的探讨普通甲醛对人体组织DNA的影响及提高STR检出率的手段。方法取少量石蜡包埋组织,65℃水浴脱蜡,Chelex-100法提取DNA,PCR扩增,循环次数分别为28次和28 6次,扩增产物经310型测序检测。结果普通甲醛固定5d以内的组织基本上可检出Amel及15个STR基因座,固定时间延长,检出率下降;PCR循环次数增加,灵敏度增加,但有错误分型的情况。结论普通甲醛固定时间长短直接影响PCR-STR的检验,减少模板量有利于PCR反应成功,PCR次数为28 6时,灵敏度增加,但应谨慎判读结果,以免错误分型。     

HE染色切片组织的STR检测及法医学应用

目的建立并优化HE染色切片组织STR分型方法,评估HE染色切片组织的STR分型有效性。方法用QIAgen法提取2例尸检人体的心、肝、肺、肠等8种组织的HE染色切片DNA,用TaqMan荧光探针法通过荧光域值循环数(Ct值)测定获得各提取液中的DNA质量浓度,以阳性内对照(internal posi-tive control,IPC)监测PCR过程中的抑制水平。再用Identifiler试剂盒扩增,在3100-Avant上进行STR片段分析。结果在本研究建立优化的STR分型技术条件下,8种人体组织的HE染色切片DNA提取液质量浓度均可达到1ng/μL以上,其IPC的Ct值提示无PCR抑制剂。HE染色切片组织的STR分型有效性与石蜡包埋组织相当,其DNA随时间延续而缓慢降解。结论在一定保存时限内,HE染色切片的DNA质和量可以满足STR分型检测需要,但受残余甲醛固定剂的影响,HE染色切片的分型成功率随保存时间延长而降低。     

人体组织在非缓冲福尔马林固定剂中的STR检测时限

目的评估经非缓冲福尔马林固定不同时间后的人体组织STR分型有效性,了解各种人体组织在非缓冲福尔马林固定剂中可获得完全STR分型位点的时限。方法市售40%福尔马林溶液经1∶9稀释后在室温(15～20℃)下固定人体组织,不同时间后取样。以QIAamp DNA法和IQTMDNA System法提取DNA,用quantifiler humanTaqman探针法进行DNA定量,用常规16 STR位点的AmpFSTR identifiler kit和短小片段9 STR位点的AmpFSTR Min-iFiler kit进行PCR扩增,在3100遗传分析仪进行扩增DNA片段长度检测,用GeneMapper ID v3.2对STR位点检出率进行分析。结果福尔马林固定时间、组织类型以及DNA提取方法、PCR的DNA模板终浓度均影响非缓冲福尔马林固定后人体组织STR分型效能。DNA提取用QIAgen法为优,DNA模板终浓度的最佳范围在1～3ng/μL。各类型组织在非缓冲福尔马林固定剂中的降解速率有差异,肺组织的降解速率最慢,肝、肠组织最快。固定时间在4d内的组织可以获得常规STR的完整位点数;固定时间在15d内的组织可以获得miniSTR的完整位点数。结论非缓冲福尔马林固定人体组织时间是影响STR分型的最主要因素,其次组织类型、提取方法、DNA模板浓度及STR基因座的选择也是此类降解样品成功检测的关键因素。     

石蜡包埋人体组织DNA分型的研究

目的研究石蜡包埋人体组织的DNA提取方法对其STR分型的影响,并建立石蜡包埋组织的DNA提取方法。方法经不同预处理条件后采用Chelex-100法提取石蜡包埋人体组织中的DNA,用不同的反应体系进行STR复合扩增检验。结果经福尔马林固定、石蜡包埋的人体组织直接采用Celex-100法提取DNA与65℃水浴除蜡后采用Celex-100法提取DNA均可获得满意的DNA分型。结论该方法简便易行,实验效果好,适合检案。     

Triton X-100快速提取甲醛固定、石蜡包埋组织内DNA的方法

目的建立一种快速提取甲醛固定、石蜡包埋组织内DNA的方法。方法利用TritonX-100一步提取甲醛固定、石蜡包埋组织内DNA,并具体研究了不同浓度TritonX-100对提取后DNA-STR分型效果的影响。结果成功地一步提取出甲醛固定、石蜡包埋组织内DNA,浓度为1%的TritonX-100提取效果较好。结论利用TritonX-100提取甲醛固定、石蜡包埋组织内的DNA,为快速提取DNA提供了有效的途径,是法科学领域中一种值得推荐的方法。     

采用SNP分型方法对甲醛固定组织进行个体识别

目的通过对X染色体SNP遗传标记的检测,探讨甲醛固定组织块的DNA分型策略。方法提取甲醛固定组织块的DNA,在用SinofilerTM试剂盒、MiniFilerTM试剂盒检测未能获得分型结果的情形下,采用多重PCR和飞行质谱技术对X染色体上的51个SNP位点进行分型检测。结果对于常染色体STR、miniSTR分型失败的甲醛固定组织块,X-SNP分型获得成功。结论对于甲醛固定组织块等微量、降解的生物学检材,若常染色体STR基因座分型失败,可尝试进行SNP位点的分型,以获得更多的遗传信息。     

氨基比林血痕预试验处理血痕后样本的DNA定量

目的：探讨氨基比林血痕预试验处理血痕后样本DNA含量的变化及对STR分型检测的影响。方法10名健康无关个体EDTA抗凝血液制成滤纸血痕,氨基比林血痕预试验检测,按试验后血样干燥保存时间分30 min、1 h、3 h、6 h、12 h、24 h共6个实验组,并采用磁珠法、QIAcube DNA纯化法、Chelex-100法三种方法提取样本DNA,应用荧光定量PCR检测样本DNA含量,PCR-STR荧光技术进行STR分型。结果提取方法相同时,氨基比林血痕预试验后血样随干燥保存时间的延长,样本DNA含量呈逐渐降低的趋势。保存时间相同时,不同DNA提取方法间,样本DNA含量差异也有统计学意义。90.56%样本均可获得16个STR基因座明确分型。结论氨基比林血痕预试验对血痕样本DNA有损伤,24 h内多可获有效STR分型。磁珠法提取样本DNA进行STR分型,效果最好。     

一次性牙刷上脱落细胞的DNA提取及STR分型

目的研究一次性使用牙刷上脱落细胞的DNA提取和STR分型。方法对一次性使用牙刷的采集方法、采集部位、DNA提取方法、存放时间对STR分型的影响进行比对研究。结果割取法可获得较高浓度的DNA,30例中检出9个以上基因座达27例,与擦拭法存在统计学差异（P〈0.05）。Chelex-100法、DNA IQTM法检出9个以上基因座分别为26例、24例,STR分型结果无统计学意义（P〉0.05）。提取牙刷的前、后部三束刷毛检出9个以上基因座分别达27例、28例,STR分型结果无统计学意义（P〉0.05）;放置1天、1周、1个月、3个月、6个月的时间后检出9个以上基因座分别为28例、27例、22例、12例、7例。结论割取法提取一次性牙刷上的脱落细胞进行STR分型效果良好;放置时间越长的牙刷,检出率越低。     

甲醛固定石蜡包埋组织DNA提取方法比较

目的比较甲醛固定石蜡包埋尸检组织中三种提取DNA的方法对DNA质量的影响,寻找一种操作简便、污染较少、经济实用的石蜡包埋组织中提取DNA的方法。方法选取经甲醛固定石蜡包埋的心肌组织20例,分别以二甲苯脱蜡-酚氯仿法、改良TES水浴脱蜡-酚氯仿法、试剂盒法提取DNA,进行电泳分析、紫外分光光度计测定A260/A280值及PCR扩增。结果改良TES水浴脱蜡-酚氯仿法抽提DNA法、二甲苯脱蜡-酚氯仿法分别与试剂盒法所提取DNA的A260/A280值相比较,均有显著性意义（P〈0.01）。二甲苯脱蜡-酚氯仿法、改良TES水浴脱蜡-酚氯仿法所提取DNA的A260/A280值相比较,无显著性意义（P〉0.05）。以改良TES水浴脱蜡-酚氯仿法所得DNA为模板,扩增的目的条带亮度与阳性对照相当。结论结果证实改良TES水浴脱蜡-酚氯仿法简便有效,所用试剂价格低廉,是一种经济实用的石蜡包埋组织DNA提取方法。     

Analysis of DNA profiles extracted from degraded samples from archival of formalin fixed tissue included in paraffin (FFTIP) and hairs

The possibility of studying DNA extracted from archival of formalin fixed tissue included in paraffin (FFTIP) enables valuable retrospective investigations. However, according to some authors it is difficult to obtain genomic DNA of good quality, since the process of fixation often results in fragmentation of DNA. In order to evaluate the quality and quantity of DNA extracted, necropsy samples of FFTIP (spleen/lung) and hairs, with or without bulbs, were analyzed using three methods of extraction (QIAamp DNA mini, QIAamp DNA micro-kit and phenol–chloroform followed by microcon YM-30). The amount of DNA recovered was quantified by spectrophotometer. The β-actin, amelogenin gene and the profiles of STR were analyzed. Based on experimental results, a general guideline concerning the appropriate extraction method according to the tissue and the quantity of the starting material for the analysis of DNA from FFTIP and hairs could be suggested.     

福尔马林固定组织SNP与STR检测的比较

目的检测经长期福尔马林固定的组织降解情况,并比较组织中SNP与STR的检出率。方法本文对24例经福尔马林固定、-20℃保存5年的组织样本,采用Quantifiler?Trio DNA定量试剂盒检测样本DNA的降解系数及浓度,运用55-SNPs SNa Pshot复合分型体系和Power Plex?21试剂盒分别进行SNP与STR检测。结果大部分样本降解系数在1~8,发生不同程度的降解。与未降解样本相比,SNP分型完全一致,检出率为100%;其中8例样本STR分型存在33个等位基因丢失,降解系数均大于2.6,且75.8%的等位基因片段长度大于300bp。当样本检测出16个STR基因座时,似然率与54个SNP相当。当样本检出大于17个STR时,似然率大于54个SNP。STR基因座片段长度与等位基因检出率之间呈负相关。除2例样本降解系数较小却发生等位基因丢失外,其余样本降解系数与等位基因检出率之间呈负相关。结论经福尔马林长期固定的组织DNA易降解,检测SNP明显优于STR,但需要更多的SNP以提高个体识别能力。     

福尔马林固定石蜡包埋组织中DNA提取

由于甲醛介导的DNA损伤和石蜡对DNA提取的阻碍作用,使得常规DNA提取方法很难从福尔马林固定石蜡包埋组织(FFPET)中获取高质量的DNA。近年来,众多学者的研究表明,通过改良预处理方法,优化蛋白酶K消化作用,简化DNA提取步骤,纯化DNA提取物等,可以有效提高FFPET中提取的DNA质量,为FFPET的DNA分析奠定了基础。     

Highly sensitive HLA-DNA typing from formalin-fixed and paraffin-embedded tissue samples

Nucleotide sequences have been determined for more than 1700 different alleles at the core of the human leukocyte antigen (HLA) system. The highly polymorphic character of these genes affects adaptive immune response and is also useful for forensic applications. HLA typing from formalin-fixed and paraffin-embedded tissue provides abundant useful information for both clinical settings and forensic investigations. This study, which investigated the potential use of DNA from formalin-fixed and paraffin-embedded tissue samples in an HLA PCR sequence-specific primer and probe (SPP) system, showed that tissue fixed in formalin for less than 3 days and embedded in paraffin can serve as a useful source of DNA for PCR-SPP typing kits.     

Multiple interchanging of tissue samples in cases of breast cancer

Due to the suspicion of a gynaecologist, a pathologist was suspected of incorrect diagnoses in cases of breast cancer and the interchanging of tissue samples. Many women applied to the attorney's bureau to clarify the reproaches. The privately owned laboratory for pathology was searched and 926 histological slides, roughly the same number of paraffin blocks and about 20 formalin fixed tissue samples were confiscated. Together with other confiscated material, at least 1236 histological slides and additional 249 paraffin blocks had to be sorted. Histological slides and paraffin blocks were matched with patients as far as possible following the laboratory book. Many of the warranted samples which were diagnosed as containing the carcinoma by the pathologist were missing. A total of 160 samples were chosen and rediagnosed by two independent pathologists. The formalin fixed tissue was negative for DNA most likely due to storage in formalin for years. Most of the histological slides were positive for DNA. On the whole, 18 expertises about histological findings and the DNA results were given. In some cases only DNA results could be presented, as previous experts had only performed DNA examinations without controlling the histological diagnosis. In six cases a carcinoma could be confirmed and the DNA profile matched with patient's DNA; in seven cases a carcinoma was confirmed without match with the patient; in two cases the carcinoma could not be confirmed in the presented samples. A jurisdictional solution was impossible because the accused pathologist died during the investigation. In conclusion, it must be stated that a DNA examination of histological slides should never be performed without a rediagnosis of an independent pathologist and photographic documentation of the findings. Whenever possible, material should be left on the slide.     

DNA genotyping of unbuffered formalin fixed paraffin embedded tissues

Formalin-induced DNA degradation was studied at different fixation times (3, 7, 16 and 32 days) each on 10 formalin fixed paraffin embedded tissues (FFPET) stored for 15 years at room temperature.The four different extraction protocols used in this study showed that Chelex100 extracts performed the best at 3 and 7 days of formalin fixation (DFF) (with regard to the quantity and the quality of the DNA). However, Qiamp extracts showed better results for long sized alleles, as well for single polymerase chain reaction (PCR) amplifications after 16 and 32 DFF, as for multiplex PCR at shorter fixation times. DNA degradation is expressed by the size of the amplified alleles, only 100 bp templates surviving after 32 DFF (AMG locus). Single locus amplifications (CD4 and FES/FPS alleles) performed better than multiplex PCR (ProfilerPlus), with nearly 100% positive results at 7 DFF. In both types of amplifications, the success rate decreased proportionally with the time of formalin fixation and, consequently, with the size of the required DNA template.     

Histologic detection of fat emboli

We describe a procedure for detection of fat emboli in formalin fixed tissue using osmium tetroxide postfixation. Intravascular fat in tissue postfixed in osmium tetroxide, embedded in epoxy or paraffin, and stained with toluidine blue, hematoxylin, or Oil Red O is more easily visualized than in frozen tissue that is stained with Oil Red O. With these methods, fat emboli may be detected years after the initial autopsy.     

Identification of N,N-dimethylamphetamine formed by methylation of methamphetamine in formalin-fixed liver tissue by multistage mass spectrometry

Methamphetamine is methylated in the presence of unbuffered formalin solutions within hours at room temperature. The product, N,N-dimethylamphetamine, is also found in human liver exposed to methamphetamine followed by incubation with formalin. In the present study, a direct mass spectrometric method was developed to identify N,N-dimethylamphetamine in human liver before and after treatment with formalin. Human liver samples were obtained from four deaths that were investigated by the West Virginia Office of Chief Medical Examiner. Full toxicological analysis was conducted on samples from the decedents and methamphetamine was among the positive findings in each case. The method used to expose liver tissue to formaldehyde involved treating a small piece of liver from each case with formalin solution (20% v/v) for 24 h at room temperature. The formalin treated tissues were homogenized and the resulting suspension was sonicated for 5 min, and then centrifuged. Supernatant aliquots were directly analyzed by electrospray ionization (ESI) mass spectrometry without chromatographic isolation. Positive ion multistage mass spectra recorded in MS, MS/MS and MS/MS/MS (MS3) modes were used to confirm the presence of N,N-dimethylamphetamine and methamphetamine in the mixture. Liver tissue not treated with formalin did not contain a detectable level of N,N-dimethylamphetamine. Decreases in methamphetamine concentrations in liver tissue resulting from treatment with formalin were measured using deuterium-labeled methamphetamine as internal standard. The method can be completed in less than 2 h on thawed tissue. The results suggest that the process of fixing tissues with formalin may lead to false negative findings for methamphetamine.     

Paternity-testing on paraffin-embedded abortion tissue: preparation of fetal cells may be indispensable

In a case of sexual abuse, a paternity test was performed on paraffin embedded abortion material. STR typing was successful only after isolating fetal tissue from the abortion-material and separately extracting DNA from the excised fetal cells. Examination with five STRs led to a paternity index of 332, confirming the abuse that had resulted in pregnancy.