Comparison of Application of MD-VF-Auto SEM Method and Plankton Gene Multiplex PCR System in the Diagnosis of Drowning.

OBJECTIVES: To compare the application effect of microwave digestion - vacuum filtration - automated scanning electron microscopy (MD-VF-Auto SEM) method and plankton gene multiplex PCR system in the diagnosis of drowning. METHODS: Lung, liver and kidney tissue of 10 non-drowning cases and 50 drowning cases were prepared for further MD-VF-Auto SEM method analysis and plankton gene multiplex PCR system analysis. The positive detection rate of the two methods in each tissue was calculated. RESULTS: The positive rate of the MD-VF-Auto SEM method detecting diatoms in drowning cases was 100%, and few diatoms were detected in the liver and kidney tissues of 6 non-drowning cases. By using the plankton gene multiplex PCR system, the diatom positive rate of drowning cases was 84%, and all the non-drowning cases were negative. There were significant differences in the positive rate of the liver, kidney tissues between MD-VF-Auto SEM method and plankton gene multiplex PCR system (P<0.05), as well as the total positive rate of cases. However, no significant differences were found in the positive rates of lung tissues (P>0.05). CONCLUSIONS: MD-VF-Auto SEM method is more sensitive than plankton gene multiplex PCR system in diatom test. But the plankton gene multiplex PCR system can also detect plankton other than diatoms. Combination of the two methods can provide a more reliable basis for the diagnosis of drowning.

Development of the nine X-STR loci typing system and genetic analysis in three nationality populations from China.

This study is to develop a new multiplex polymerase chain reaction (PCR) system that simultaneously amplifies the nine X-chromosome short tandem repeats loci in the same PCR reaction, and to explore their polymorphism and mutation rate among three nationality populations from China. These loci included DXS6854, DXS9902, DXS6809, GATA172D05, HPRTB, DXS7423, DXS6807, DXS8378, and DXS8377. The samples of 890 (484 males and 406 females) unrelated individuals from Guangdong Han population, Xinjiang Uigur, and Inner-Mongolia Mongol were successfully analyzed using this multiplex system. The allele frequencies and mutation rates of the nine loci were investigated, and the comparison of allele frequency distribution among different populations was performed. There were 87 alleles for all the loci, and six to 18 alleles for each locus observed by our new multiplex PCR system. Polymorphism information content was 0.4998-0.9101, and power of discrimination in females was 0.6518-0.9846. Five cases with mutation of above loci were detected in 5,310 meioses. Pair-wise comparisons of allele frequencies distribution showed significant differences for most loci among different populations. Our results indicate that this multiplex system is very useful for identification analysis, and that the information about polymorphism and mutation rate is necessary for forensic application in three nationality populations from China.