Predictable weathering of puparial hydrocarbons of necrophagous flies for determining the postmortem interval: a field experiment using Chrysomya rufifacies.

Preadult development of necrophagous flies is commonly recognized as an accurate method for estimating the minimum postmortem interval (PMImin). However, once the PMImin exceeds the duration of preadult development, the method is less accurate. Recently, fly puparial hydrocarbons were found to significantly change with weathering time in the field, indicating their potential use for PMImin estimates. However, additional studies are required to demonstrate how the weathering varies among species. In this study, the puparia of Chrysomya rufifacies were placed in the field to experience natural weathering to characterize hydrocarbon composition change over time. We found that weathering of the puparial hydrocarbons was regular and highly predictable in the field. For most of the hydrocarbons, the abundance decreased significantly and could be modeled using a modified exponent function. In addition, the weathering rate was significantly correlated with the hydrocarbon classes. The weathering rate of 2-methyl alkanes was significantly lower than that of alkenes and internal methyl alkanes, and alkenes were higher than the other two classes. For mono-methyl alkanes, the rate was significantly and positively associated with carbon chain length and branch position. These results indicate that puparial hydrocarbon weathering is highly predictable and can be used for estimating long-term PMImin.

Time of death revealed by hydrocarbons of empty puparia of Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae): a field experiment.

Determination of the postmortem interval (PMI) is crucial for investigating homicide. However, there are currently only limited methods available. Especially, once the PMI exceeds the duration of pre-adult development of the flies with the adult emergence, its determination is very approximate. Herein, we report the regular changes in hydrocarbon composition during the weathering process of the puparia in the field in Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae), one of the common species of necrophagous flies. Correlation analysis showed that the relative abundance of nearly all of the branched alkanes and alkenes decreased significantly with the weathering time. Especially, for 9 of the peaks, over 88% of the variance in their abundance was explained by weathering time. Further analysis indicated that the regular changes caused mainly by the different weathering rates of various hydrocarbons. Additionally, the weathering rates were found to depend on the chemical structure and molecular weight of the hydrocarbons. These results indicate strongly that hydrocarbon analysis is a powerful tool for determining the weathering time of the necrophagous fly puparia, and is expected to markedly improve the determination of the late PMI.

Chronic alcoholism-mediated impairment in the medulla oblongata: a mechanism of alcohol-related mortality in traumatic brain injury?

Alcohol-related traumatic brain injury (TBI) is a common condition in medical and forensic practice, and results in high prehospital mortality. We investigated the mechanism of chronic alcoholism-related mortality by examining the effects of alcohol on the synapses of the medulla oblongata in a rat model of TBI. Seventy adult male Sprague-Dawley rats were randomly assigned to either ethanol (EtOH) group, EtOH-TBI group, or control groups (water group, water-TBI group). To establish chronic alcoholism model, rats in the EtOH group were given EtOH twice daily (4 g/kg for 2 weeks and 6 g/kg for another 2 weeks). The rats also received a minor strike on the occipital tuberosity with an iron pendulum. Histopathologic and ultrastructure changes and the numerical density of the synapses in the medulla oblongata were examined. Expression of postsynaptic density-95 (PSD-95) in the medulla oblongata was measured by ELISA. Compared with rats in the control group, rats in the chronic alcoholism group showed: (1) minor axonal degeneration; (2) a significant decrease in the numerical density of synapses (p < 0.01); and (3) compensatory increase in PSD-95 expression (p < 0.01). Rats in the EtOH-TBI group showed: (1) high mortality (50%, p < 0.01); (2) inhibited respiration before death; (3) severe axonal injury; and (4) decrease in PSD-95 expression (p < 0.05). Chronic alcoholism induces significant synapse loss and axonal impairment in the medulla oblongata and renders the brain more susceptible to TBI. The combined effects of chronic alcoholism and TBI induce significant synapse and axon impairment and result in high mortality.

Haplotypes of 20 Y-chromosomal STRs in a population sample from southeast China (Chaoshan area).

In this study, 20 Y-specific short tandem repeat (STR) loci (DYS434, Y-GATA-A10, Y-GATA-H4, DYS438, DYS439, DYS443, DYS444, DYS446, DYS447, DYS448, DYS456, DYS458, DYS460, DYS520, DYS531, DYS557, DYS622, DYS630, DYS635(Y-GATA-C4), and DYS709) were analyzed in 158 unrelated healthy men from southeast China by three fluorescence-labeled multiplex polymerase chain reaction systems. The Y-STR multiplexes developed have followed the published nomenclature and International Society for Forensic Genetics (ISFG) guidelines for STR analysis. Gene diversity ranged from 0.2506 at DYS434 to 0.8034 at DYS447. A total of 157 different haplotypes were observed, and among these, 156 were unique, while 1 was found two times. The haplotype diversity value calculated from all 20 loci combined was 0.9997, which is informative. Furthermore, 80 father-son pairs, previously confirmed by autosomal STR analysis, were typed using the same 20 Y-STR loci, and four mutation events were identified at the Y-GATA-H4, DYS439, DYS456, and DYS458 loci, giving an average mutation rate of 0.25% per locus per generation (95% confidence interval 0.09-0.54). These results including the haplotype data at 20 Y-STR loci would enrich Chinese genetic informational resources and provide useful information in forensic practice.

[Twenty Y-STR locus multiplex amplification and genetic polymorphism analysis in Han population in Chaoshan area].

OBJECTIVE: To study genetic polymorphisms of 20 Y-chromosomal short tandem repeats (STR) in Chaoshan Han population, and to evaluate their value in forensic science. METHODS: Twenty Y-specific STR loci (DYS434, Y-GATA-A10, Y-GATA-H4, DYS438, DYS439, DYS443, DYS444, DYS446, DYS447, DYS448, DYS456, DYS458, DYS460, DYS520, DYS531, DYS557, DYS622, DYS630, DYS635 and DYS709) were amplified by using three fluorescence-labeled multiplex PCR systems and were analyzed by ABI310 genetic analyzer. One hundred and fifty-eight unrelated male individuals of Han population in Chaoshan area were investigated to determine the distribution of allele frequencies and haplotype. RESULTS: The Y-STR multiplexes developed had followed the published nomenclature and ISFG guidelines for STR analysis. Gene diversity ranged from 0.2506 at DYS434 to 0.8034 at DYS447. A total of 157 different haplotypes were observed, and among these, 156 were unique, while 1 was found for two times. The haplotype diversity value calculated from all 20 loci combined was 0.999998. None of Y-STR allele mutation was observed in the 30 father/ son pairs confirmed by autosomal STR analysis. CONCLUSION: The results indicate that the 20 Y-STR loci are highly polymorphic and fathership genealogy inheritance are stable. The three fluorescence-labeled multiplex amplification systems that we constructed are suitable for forensic individual identification and paternity testing in Chaoshan area.