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Identiifcation of tissues/body lfuids in forensic science is important for criminal cases investigation such as crime scene reconstruction, conclude the character of crime. Recently, many researches of Epigenetic shows that tissue speciifc differentially methylated regions(tDMRs) have the ability to as a biomarker for identiifcation of tissues/body lfuids. In this paper, we reviewed the study progress and summarized the probability, advantage and disadvantage as well as application value and the development direction of the application of DNA methylation in the aspect of identifying the tissues/ body lfuids source, aiming at providing a reference for the related research and application.
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Forensic medical talents with creative ability should have ability to find.analyze and solve problems from complex cases.According to teaching practice on the basis of PBL this article illustrates application methods of PBL teaching characters in the training of forensic medical talents with creative ability.
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Three SNaPshot multiplex assays were developed to test 23 coding region single nucleotide polymorphisms (SNPs) and one control region SNP outside hypervariable regions (HVR)I and II, which was aimed at increasing the discrimination power of the mitochondrial DNA (mtDNA) typing in forensic casework, and confirming haplogroup assignments of mtDNA profiles in both human population studies and medical research. The selected SNPs targeted the East Asian phylogeny. These multiplex assays were validated by comparing with the sequencing analysis of samples chosen randomly. The mtDNA variations of 100 unrelated individuals from the Wuhan population in China were examined and classified into 31 haplotypes, and the haplotype diversity was estimated to be 0.952. The multiplex SNaPshot method is rapid and robust, and suitable for large-scale screening studies of mtDNA variability.
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To study the relationship between the late postmortem interval (PMI) and trimethylamine-nitrogen (TMA-N) in postmortem tissues of cadaver, TMA-N in muscles, livers and kidneys of rats was measured at different postmortem intervals (PMI) by using a modified spectrophotometric method. The results indicated that the detection sensitivity of TMA-N was 1 mg/L, and there was a good linear correlation between the value of absorbance (A value) and TMA-N at the concentration of 1-10 mg/L (R (2) = 0.9991). Although TMA variation in muscles was different from that in inner organs during the time since death, TMA-N changes in cadaver tissues was positively correlated with PMI. During 2 to 7 d since death, the best correlation between PMI and TMA-N concentration was found in muscles. With PMI as an independent variable, the cubic polynomial regression equation was y= -0.457x(3)+6.519x(2)-24.574x+27.207 (R (2)=0.969). During 3 to 8 days since death, PMI was best correlated with TMA-N concentration in inner organs. With PMI as the independent variable, the cubic polynomial regression equation was y=0.509x(3)-9.153x(2)+55.727x-95.819 (R (2)=0.953). It was concluded that TMA-N in tissues could be used as a new estimator for late PMI. The method used in this study offered advantages such as accuracy, sensitivity, little samples required and wide PMI estimation.
Subject(s)
Cadaver , Forensic Pathology , Methylamines/analysis , Nitrogen/analysis , Pilot Projects , Postmortem Changes , Random Allocation , Rats, Sprague-Dawley , Spectrophotometry , Time FactorsABSTRACT
The changes of retinal nuclear DNA content in rats after death was detected and the relationship between degradation of retinal nuclear DNA and postmortem interval (PMI) was analyzed. Ninety healthy adult SD rats, female, weighing 250+/-10 g, were randomly divided into 15 groups. At 20 degrees C, the retinal cells were withdrawn every 2 h within 0 to 28 h after death and stained with Feulgen-Vans. Index of density (ID), integral absorbance (IA) and average absorbance (AA) in retinal nucleus were analyzed by image analysis system. And the obtained data were subjected to linear regression analysis by using SPSS12.0 software. The results showed that in retinal nucleus, AA and IA were gradually declined with the prolongation of PMI, while ID had an increased tendency. Within 28 h after PMI, the regression equations were as follows: Y(AA )=-0.009X(AA )+0.590 (R(2)=0.949), Y(IA )=-0.097X(IA )+18.903 (R(2)=0.968), Y(ID)=0.122X(ID)+2.246 (R(2)=0.951). It was concluded that retinal nuclear DNA after death in rats was degraded gradually and had a good correlation with PMI.
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The changes of retinal nuclear DNA content in rats after death was detected and the relationship between degradation of retinal nuclear DNA and postmortem interval (PM1) was analyzed. Ninety healthy adult SD rats, female, weighing 250±10 g, were randomly divided into 15 groups. At 20 ℃, the retinal cells were withdrawn every 2 h within 0 to 28 h after death and stained with Feulgen-Vans. Index of density (ID), integral absorbance (IA) and average absorbance (AA) in retinal nucleus were analyzed by image analysis system. And the obtained data were subjected to linear regression analysis by using SPSS 12.0 software. The results showed that in retinal nucleus, AA and IA were gradually declined with the prolongation of PMI, while ID had an increased tendency. Within 28 h after PMI, the regression equations were as follows: YAA=-0.009XAA+0.590 (R2=0.949), YIA=-0.097XIA+18.903 (R2=0.968), YID=0.122XID+2.246 (R2=0.951). It was concluded that retinal nuclear DNA after death in rats was degraded gradually and had a good correlation with PMI.
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Objective To detect nuclear DNA degradation of bone marrows and brains in rat cadavers at different temperatures,and develop a new parameter for estimating early postmortem interval(PMI).Methods The brain and bone marrow were taken out for every 4h,during 0~40h after death at 10℃ and 20℃,respectively.And the single cell gel electrophoresis(SCGE) was carried out to detect the nuclear DNA degradation.Linear regression analysis was used to assay the relationship of the comet parameter HeadDNA%,Tail Length(TL) and Olive TailMoment(TM) with PMI.Results Different decline degrees of comet HeadDNA% were found in both brain cells and bone marrow cells after death,the decline of HeadDNA% in brain cells at 20℃ was faster.Compared with degradation in marrow cells,the linear relation between degradation of brain cells and PMI was better.Conclusion with that of comet parameters TL and TM,the perfect linear relationship between HeadDNA% and PMI was also observed.Conclusion Brain tissues are more suitable for PMI estimation by detecting degradation of DNA with SCGE.The HeadDNA% is more valuable for PMI estimation than TL and TM.
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Objective To study the relationship between the mRNA degradation in the retinal cells of rat after death and postmortem interval(PMI) in order to provide a new methods of inferring PMI.Methods The level of ?-actin,Pgk1 and Rpl 4 mRNA in the retinal cell of rat were measured at different time(0,2,4,6,8,10, 12,14,16,18,20,22,24,26,28h)after death by compound fluorescence RT-PCR.The rats executed immediately were used as controls.Results Within 28h after death,the absorbance value of total RNA and the level of ?-actin,Pgk1 and Rpl 4 mRNA in the retinal cells decreased along with the prolongation of PMI.The equations of linear regression fitting the relationship between mRNA degradation and PMI were as follows:Y?-actin=-4436.205X?-actin+127581.7(r2=0.976),Ypgk1=-1993.884Xpgk1+57651.54(r2=0.973),YRpl 4=-1189.791XRpl 4+34533.46(r2=0.955).The return model had remarkable statistical significance(P
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Objective To observe the morphological change of retina and its affection on visual function after optic nerve crush in adult rat. Methods The models of optic nerve crush in rats were made. The change of retinas in different time (1,3 ,5 ,7,9,14,28,56,84d respectively) after injury were observed by light microscope, and the flash visual evoked potential (F-VEP) was recorded in normal and injured rats. Result The number of retinal ganglion cells (RGCs) was significantly reduced in the partial lesion of optic nerve crush compared with normal optic nerves without injury. The initial loss of RGCs was accelerated during 3-7days after nerve crush and then declined gradually by 14 days, and no change was observed after 28 days. The wave of F-VEP became lower and wider in one day after the crush, and the latency and amplitude of F-VEP declined gradually from one day to 14 days, and recovery response was observed by the time of 4 weeks after injury. Conclusion The secondary degeneration of RGCs following optic nerve crush is the important morphological foundation of fall of visual function, which have relativity with the regular decline of visual function.