Jifeng Cai

Identification of forensically important sarcophagid flies (Diptera: Sarcophagidae) in China, based on COI and 16S rDNA gene sequences.

Abstract:  Insects attracted to cadavers may provide important indications of the postmortem interval (PMI). However, use of the flesh flies (Diptera: Sarcophagidae) for PMI estimation is limited as the species are often not morphologically distinct, especially as immatures. In this study, 23 forensically important flesh flies were collected from 13 locations in 10 Chinese provinces. Then, a 278‐bp segment of the cytochrome oxidase subunits one (COI) gene and a 289‐bp segment of the 16S rDNA gene of all specimens were successfully sequenced. Phylogenetic analysis of the sequenced segments showed that all sarcophagid specimens were properly assigned into four species (Boerttcherisca peregrina [Robineau‐Desvoidy, 1830], Helicophagella melanura [Meigen, 1826], Parasarcophaga albiceps [Meigen, 1826], and Parasarcophaga dux [Thompson, 1869]) with relatively strong supporting values, thus indicating that the COI and 16S rDNA regions are suitable for identification of sarcophagid species. The difference between intraspecific threshold and interspecific divergence confirmed the potential of the two regions for sarcophagid species identification.

Molecular characterization and expression pattern of an odorant receptor from the myiasis-causing blowfly, Lucilia sericata (Diptera: Calliphoridae)

The blowfly Lucilia sericata (Diptera: Calliphoridae) is a facultative ectoparasite that causes myiasis in both man and animals, leading to serious human health problems and economic losses in the livestock industry. Like other insects, olfaction of this species plays an important role in host location and is presumably mediated by a seven transmembrane receptor family. Here, we isolate and characterize LserOR1, which is the first candidate member of the odorant receptor gene family from L. sericata. LserOR1 displayed high amino acid conservation with previously identified Or83b orthologs from different insect species. The transcripts of LserOR1 were detected in the major olfactory organs including the antennae and maxillary palps, as well as in traditionally non-olfactory tissues such as the legs and female ovipositors. In developmental studies, a quantitative real-time PCR assay was developed and validated for determining the relative expression levels of LserOR1 during several stages. In contrast to its extremely high expression in the adult stage, LserOR1 expression was at the lowest level during the egg stage, and then increased to a peak through the first two larval stages before declining in the third-instar stage. These results suggest that a broadly expressed LserOR1 receptor is likely to be essential for olfactory sensory processes throughout the lifetime of L. sericata. The present study provides the information that may aid in the development of novel blowfly repellents using olfactory proteins as molecular targets.

Potential use of bacterial community succession for estimating post-mortem interval as revealed by high-throughput sequencing

Decomposition is a complex process involving the interaction of both biotic and abiotic factors. Microbes play a critical role in the process of carrion decomposition. In this study, we analysed bacterial communities from live rats and rat remains decomposed under natural conditions, or excluding sarcosaphagous insect interference, in China using Illumina MiSeq sequencing of 16S rRNA gene amplicons. A total of 1,394,842 high-quality sequences and 1,938 singleton operational taxonomic units were obtained. Bacterial communities showed notable variation in relative abundance and became more similar to each other across body sites during the decomposition process. As decomposition progressed, Proteobacteria (mostly Gammaproteobacteria) became the predominant phylum in both the buccal cavity and rectum, while Firmicutes and Bacteroidetes in the mouth and rectum, respectively, gradually decreased. In particular, the arrival and oviposition of sarcosaphagous insects had no obvious influence on bacterial taxa composition, but accelerated the loss of biomass. In contrast to the rectum, the microbial community structure in the buccal cavity of live rats differed considerably from that of rats immediately after death. Although this research indicates that bacterial communities can be used as a “microbial clock” for the estimation of post-mortem interval, further work is required to better understand this concept.

Identification of forensically important flesh flies based on a shorter fragment of the cytochrome oxidase subunit I gene in China

With the development of molecular identification, there has been a great deal of discussion about the feature of the mitochondrial DNA (mtDNA) fragments. Although longer fragments may minimize stochastic variation across taxa and be more likely to reflect broader patterns of nucleotide divergence, shorter fragments have many advantages, such as quick, easy and economical. Extensive application of long mtDNA segments for species identification cannot always be achieved as a result of constraints in time and money. In the present study, a molecular identification method involving the sequencing of a 272‐bp ‘barcode’ fragment of the mitochondrial cytochrome oxidase subunit I (COI) gene from 55 specimens, representing 7 Chinese sarcophagid species from varying populations, was evaluated. Phylogenetic analysis of the sequenced segments showed that all sarcophagid specimens were properly assigned into seven species, which indicated the possibility of separation congeneric species with the short fragments. The results of this research will be instrumental for the implementation of the Chinese Sarcophagidae database.

An investigation and pathological analysis of two fatal cases of cadmium poisoning

Pollution associated with population growth, and with industrial and urban development has led to a serious decline in the water quality of Chinese rivers. Cadmium (Cd) is recognized as one of the most toxic metals and is strongly accumulated by organisms. Humans are exposed to cadmium originating from the environment and from industrial pollution. In spite of thousands of published studies on Cd, there is little information on its pathological features seen in human autopsy. The gross and pathological findings of forensic autopsies of two case of cadmium poisoning are presented and related to an epidemiological investigation. In both cases, multiple organ damage was observed, involving brain, lung, liver, kidney, red blood cells, and platelets, which is consistent with reports in the literature. In particular, in both cases, transmission electron microscopy revealed a large number of dense lysosomal and phagocytic particles in the cytoplasm near the nucleus, indicating the need for a genotoxic study of cadmium. Our observations provide new clues for the future recognition and prevention of Cd poisoning.

A carbon dot-based hybrid fluorescent sensor for detecting free chlorine in water medium

A novel fluorescent sensor has been prepared for the quantitative detection of free chlorine in water medium. The sensor contains a fluorescent carbon dot (CD)–rhodamine B (RhB) nanohybrid, which exhibits their respective emission peaks at 445 and 580 nm under an excitation wavelength of 380 nm. The fluorescence of CDs could be quenched by free chlorine through the combination of chemical bonds and energy transfer while the peak of RhB almost remains constant, leading to color changes that can be recognized by the naked eye. The designed sensor could achieve the detection of free chlorine rapidly with a detection limit as low as 4 μM.

Identification of forensically important sarcophagid flies (Diptera: Sarcophagidae) in China based on COI and period gene

Unequivocal identification of insect specimens is an essential requirement in forensic entomology. With the development of molecular identification, spate of discussions about the feature of the DNA fragments have been raised. Relying solely on single DNA fragment for delimiting closely related species is supposed to be dangerous. Aiming at obtaining more reliable markers that might be universally used, we explore the utility of 700-bp COI fragment and 678-bp period gene fragment in the identification of Sarcophagidae (Diptera). Thirty-six sarcophagid fly specimens were collected from 19 locations in 11 Chinese provinces. Phylogenetic analysis of the sequenced segments showed that all sarcophagid specimens were properly assigned into nine species with relatively strong supporting values, which indicated the possibility of separation congeneric species with COI and period gene fragments. The difference between intraspecific threshold and interspecific divergence confirmed that the combination of nuclear and mitochondrial genes for species identification is much more accurate. The results of this research will be instrumental for implementation of the Chinese Sarcophagidae database.

Genetic polymorphism of 21 non-CODIS STR loci in the Chinese Mongolian ethnic minority.

In this research, we investigated the allele frequencies and forensic parameters of 21 non-, CODIS short tandem repeat (STR) loci (D6S474, D12ATA63, D22S1045, D10S1248, D1S1677, D11S4463, D1S1627, D3S4529, D2S441, D6S1017, D4S2408, D19S433, D17S1301, D1GATA113, D18S853, D20S482, D14S1434, D9S1122, D2S1776, D10S1435 and D5S2500) among 523 unrelated, Chinese Mongolians in the city of Tongliao, Horqin district, Inner Mongolia Autonomous Region.

Genetic polymorphism of 17 STR loci in Chinese population from Hunan province in Central south China

We selected 586 unrelated healthy individuals (338 males and 248 females) whose ancestors lived in Hunan Province for at least three generations. After informed consent in compliance with the ethical norms set by Chinese legislation was acquired, we obtained bloodstains from each of the subjects. The study was approved by the ethics committee of the Third Xiangya Hospital of Central South University, and was carried out following the guidelines for publication of population data required by the journal [1] and according to the International Society of Forensic Genetics (ISFG) recommendations [2]. The laboratory has passed through proficiency testing in the field of forensic science by the Institute of Forensic Science of Chinese Ministry of Justice. Genomic DNA was extracted from the bloodstains using the Chelex-100 and proteinase K protocol [3]. The quantity of the extracted DNA was determined spectrophotometrically. The 17 short tandem repeat (STR) loci included in the AmpFlSTR Identifiler PCR Amplification Kit (Applied Biosystems, USA) and the PowerPlex 16 Monoplex System Kit (Promega, USA) were respectively co-amplified according to the manufacturer’s instruction [4]. Amplification reactions were carried out using a GeneAmp PCR system 9700 (Applied Biosystems). Laboratory internal control standards and kit controls (negative control and 9947A) were used for quality control. The amplified products were separated by capillary electrophoresis on ABI PRISM 3130 Genetic Analyzers (Applied

Identification of forensically important blow fly species (Diptera: Calliphoridae) in China by mitochondrial cytochrome oxidase I gene differentiation

Abstract  Unambiguous and rapid sarcosaphagous insect species identification is an essential requirement for forensic investigations. Although some insect species are difficult to classify morphologically, they can be effectively identified using molecular methods based on similarity with abundant authenticated reference DNA sequences in local databases. However, local databases are still relatively incomplete in China because of the large land area with distinct regional conditions. In this study, 75 forensically important blow flies were collected from 23 locations in 16 Chinese provinces, and a 278‐bp segment of the cytochrome oxidase subunit I gene of all specimens was successfully sequenced. Phylogenetic analysis of the sequenced segments showed that all Calliphorid specimens were properly assigned into nine species with relatively strong supporting values, thus indicating that the 278‐bp cytochrome oxidase subunit one region is suitable for identification of Calliphorid species. The clear difference between intraspecific threshold and interspecific divergence confirmed the potential of this region for Calliphorid species identification, especially for distinguishing between morphologically similar species. Intraspecific geographic variations were observed in Lucilia sericata (Meigen, 1826) and Lucilia caesar (Linnaeus, 1758).