Study on the relationship between postmortem interval and electrical conductivity of different tissues / 中国法医学杂志

Objective To determine the electrical conductivity of cerebrum, liver, lung and muscle of rats at different postmortem intervals for investigating the relationship between EC and PMI. Methods Healthy Sprague-Dawley rats were sacrificed and kept at constant temperature of 25°C. Cerebrum, lung, liver and muscle were extracted at different PMIs of immediate (0d), 1d, 2d, 3d, 4d, 5d, 6d and 7d, and their extraction liquids were prepared with ultrapure water at the ratio of 1g:10mL. EC were separately determined for different tissues and organs. The relationships between EC of different tissues and organs and PMI were analyzed and their regression functions were established. The characteristics of EC values for four tissues and organs were compared and their decomposition processes were discussed. Results EC of brain and muscle showed no significant changes within 1d, and increased rapidly during 2~7d; but EC of liver and lung started to increase within 1d and increased rapidly during 2~7d.The relationship between EC of different tissues and organs and PMI were well fitted with cubic equations and liver gained the highest coefficient (R2=0.96). Additional, the EC of four organs presented various increasing laws in different periods of PMI. Conclusion The EC of cerebrum, lung, liver and muscle of rats were well fitted with PMI and the determination of EC of cadaver tissues can be expected to become an effective method for PMI estimation in forensic practice.

Molecular identification of five common Sarcophagidae species of necrophagous flies from Luoyang / 中国法医学杂志

Objective To identify the common Sarcophagidae species of necrophagous flies in Luoyang by DNA barcoding and 28S ribosomal RNA(28S rRNA) gene and evaluate its effectiveness for forensic practice. Methods Eighteen Sarcosaprophagous flies were collected and classified by entomologists with traditional morphological characteristics. The DNA of flies was extracted with Chelex-100 method. The fragments of mitochondrial cytochromec oxidase subunit I (COI) and 28S rRNA gene were amplified and sequenced. Twenty corresponding species (China and South Korea) were loaded from Barcode of Life Data System (BOLD) and added to the alignment. All the sequences were analyzed by MEGA 7.0 software package for nucleotide composition, genetic distance computation and phylogenetic tree construction. Results Eighteen Sarcosaprophagous flies were classified into 5 species of 3 genera. The result of amplification with 18 samples showed that length of the obtained COI and 28S rRNA gene sequences were 646bp and 721bp, respectively. And the result of alignment on BLAST online showed that index of similarity of the same species was above 99%. The thirty-eight COI sequences of Sarcosaprophagous flies were clustered into five groups by a neighbor-joining (NJ) tree on value of Bootstrap 1000. The intraspecific difference in COI was 0 to 0.022 while the interspecific difference ranged from 0.057 to 0.090 excluding Sarcophaga Africa and Sarcophaga haemorrhoidalis, which was 0~0.086. The NJ tree of 28S rRNA showed Sarcophaga peregrine and Sarcophaga portschinskyi sequences were obviously clustered into two groups and the others a group. Conclusion For the five sarcophagous flies in this study, the DNA barcoding based on COI gene were able to effectively identify the Sarcophaga peregrine, Sarcophaga dux and Sarcophaga portschinskyi, while 28S rRNA gene can only differentiate Sarcophaga peregrine from others. DNA barcoding based on COI gene and 28S rRNA gene can be used as supplemental molecular markers for identifying these species.

Relationship between Electrical Conductivity and Decomposition Rate of Rat Post-mortem Skeletal Muscle / 法医学杂志

Objective T o analyze the relationship am ong electrical conductivity (E C ), total volatile basic nitrogen (T V B-N ), w hich is an index of decom position rate for m eat production, and postm ortem inter-val (PM I). T o explore the feasibility of E C as an index of cadaveric skeletal m uscle decom position rate and lay the foundation for PM I estim ation. Methods H ealthy Sprague-D aw ley rats w ere sacrificed by cervical vertebrae dislocation and kept at 28℃. M uscle of rear lim bs w as rem oved at different PM I, ho-m ogenized in deionized w ater and then skeletal extraction liquid of m ass concentration 0.1 g/m L w as prepared. E C and T V B-N of extraction liquid w ere separately determ ined. T he correlation betw een E C (x1) and T V B-N (x2) w as analyzed, and their regression function w as established. T he relationship be-tw een PM I (y) and these tw o param eters w ere studied, and their regression functions w ere separately established. Results T he change trends of E C and T V B-N of skeletal extraction liquid at different PM I w ere alm ost the sam e, and there w as a linear positive correlation betw een them . T he regression equation w as x2=0.14 x1-164.91 (R2=0.982). E C and T V B-N of skeletal m uscle changed significantly w ith PM I, and the regression functions w ere y=19.38 x13-370.68 x12+2526.03 x1-717.06 (R2=0.994), and y=2.56 x23-48.39 x22+330.60 x2-255.04 (R2=0.997), respectively. Conclusion E C and T V B-N of rat postm ortem skeletal m uscle show sim ilar change trends, w hich can be used as an index for decom position rate of cadaveric skeletal m uscle and provide a m ethod for further study of late PM I estim ation.

Research Progress on Forensic Entomotoxicology / 法医学杂志

Forensic entom otoxicology is a branch of forensic m edicine, w hich applies entom ology, toxicology and other related studies to solve the poisoning cases. It has an obvious advantage in the investigation on poisoning death. B ased on the expounding definition and research of entom otoxicology, this paper review s research progress and application value in som e aspects of forensic m edicine, such as the effects of drugs/toxins on the growth and developm ent of sarcosaphagous insects and the qualitative and quantitative analysis of the drugs/toxins in the poisoned body tissue.

A study on SNP polymorphisms in the hypermethylated region upstream of the human H19 gene / 中国法医学杂志

Objective To establish a simple and high-performance analytical technique for detecting DNA methylation markers and SNPs simultaneously,and obtain the population genetics data of some SNPs in the hypermethylated region upstream of the human H19 gene.Methods The haplotypes of H19FR1 and H19FR2 which located in the promoter region upstream of the human H19 gene were investigated from 232 unrelated Chinese individuals living in Wuhan by means of PCR and subsequent denaturing gradient gel electrophoresis(DGGE).Based on the methylation status of the genomic DNA,selective detection of the parental alleles for H19FRs was examined by using the methylation-sensitive restriction enzyme(msRE) Hpa II or Hha I.Results Five haplotypes and nine phenotypes were observed for H19FR1 in Chinese Han population in Wuhan,and the power of discrimination(DP),polymorphism information content(PIC) and probability of paternity exclusion(PE) were 0.803,0.58 and 0.322 respectively.For the H19FR2,two haplotypes and three phenotyes were detected,and the DP,PIC and PE were 0.626,0.37 and 0.162 respectively.Sequencing results showed that there were 3 SNPs,a7342g,a7357g and g7547a,and one g7351c point mutation in H19FR1.In the H19FR2,there was only one SNP,a8097g.The msRE,HpaⅡ or HhaⅠ,could digest the maternal allele,and only a single band derived from the paternal allele was detected by post-digestion PCR-DGGE(PDP-DGGE) technique.Conclusion PDP-DGGE is a simple,sensitive and effective technique for analyzing DNA methylation status and SNPs simultaneously,and can be used for discriminating the parental origin of alleles.

Age related changes in 5-methylcytosine content in human peripheral leukocytes by HPLC / 中国法医学杂志

Objective To investigate age-dependent variation of 5-methylcytosine (5-mC) content in human peripheral leukocytes.Methods 94 healthy individuals (50 males and 44 females) of ages varying from 4 to 87 years were dividied into six groups by age: age under 20 years, age between 20 to 30 years, age between 30 to 40 years, age between 40 to 50 years, age between 50 to 60 years and age beyond 60 years. Their 5-mC content in human peripheral leukocytes were analyzed by HPLC.Results The 5-mC content of age between 50 to 60 years (mean age 54.7) and age beyond 60 years (mean age 71.7) are statistically not significant, but statistically highly significant (P