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Zhang C.,Nanjing Institute of Supervision and Testing on Product Quality | Shen Y.,U.S. Center for Disease Control and Prevention | Dong M.,Nanjing Agricultural University
Food Control

Staphylococcal food poisoning (SFP) is characterized by diarrhea and vomiting resulting from the ingestion of staphylococcal enterotoxins (SEs) contaminated foods. The genome-located enterotoxin gene cluster (egc) encodes superantigens performed different clinical severities than traditional SEs. In this study, we identified 336 Staphylococcus aureus isolates from various foods in China and investigated the presences of egc, 5 classical SE genes, accessory gene regulator (agr) and sarA. Subsequently, the egc subtypes were assayed and the mRNA expression of egc and relative genes in the cell cycle were analyzed in selected isolates. As a result, egc was more prevalent than all traditional SE genes in foodborne S. aureus isolates, and egc1 was the predominant subtype. During the growth cycle, the expression patterns of egc and those of traditional SE genes were similar in tested isolates: the enterotoxin mRNAs peaked at the post-exponential growth phase and then rapidly decreased. Simultaneously, the agr system was activated and the sarA expression was enhanced. However, ZJY58, the only selected isolate which did not harbor agr, performed significantly lower peak of egc expression than other isolates. Hence, these data of gene typing and expression described a general profile of egc in food-derived S. aureus, and would have potential use in the control of SFP. © 2012. Source

Zhang C.,Nanjing Southeast University | Zhang C.,Nanjing Institute of Supervision and Testing on Product Quality
Food Control

Techniques for species assay are potent tools for the supervision of meat adulteration. Matsunaga et al. have established a reliable multiplex PCR method to identify chicken, beef, pork and mutton species in meat products. However, this method was not sensitive enough in the assay of further-processed meats. Here, we attempted 2 strategies, semi-nested multiplex PCR and shortening primers, to enhance the sensitivity of multiplex PCR. As the semi-nested multiplex PCR, first PCR was performed by a pair of common primers, and the product was used as the template of second multiplex PCR. This method lowered the limit of detection (LOD) of multiplex PCR by 3 orders of magnitude, and effectively identified meat species in further-processed foods. The LOD of semi-nested multiplex PCR reached 1 pg of DNA per reaction, which was 10-fold lower than a standardized Real-time PCR method. In contrast, multiplex PCR using truncated primers could hardly meet identical efficiency on different templates, and failed to improve the method sensitivity. The semi-nested multiplex PCR established in this study would be practical in the control of meat adulteration, and could benefit QC of meat manufacture. © 2012 Elsevier Ltd. Source

Chen X.,CAS Beijing Institute of Acoustics | Lin H.-Q.,Nanjing Institute of Supervision and Testing on Product Quality
Xitong Fangzhen Xuebao / Journal of System Simulation

In order to provide the lifelike vessels noise signal for passive sonar, the noise continuous spectrum was characterized by benchmark spectral class and spectrum-shaped table, the noise line spectrum was characterized by line spectrum frequency, amplitude and phase, the noise time-varying modulating spectrum was characterized by shaft frequency and blade frequency. And a realistic, high efficiency and controllable simulation algorithms were given. The real-time simulation of stationary continuous spectrum noise was achieved though autocorrelation function, AR coefficient and autoregressive filter. The real-time simulation of line spectrum was achieved in the form of sum of a series of sine wave through calculation of amplitude, frequency and phase of line spectrum. The real-time simulation of time-varying modulating spectrum was achieved through autoregressive algorithm of stationary continuous spectrum, time-varying modulating function of fluctuation pulse train and the modulation of noise continuous spectrum. The algorithms have been implemented on the DSP platform with TS101 processor and successfully applied in a variety of sonar test equipment and sonar simulation system. © Right. Source

Zhu Q.,Nanjing Normal University | Sun C.,Nanjing Normal University | Sun C.,Nanjing University of Science and Technology | Yan J.,Nanjing Normal University | And 4 more authors.
Australian Journal of Chemistry

Three kinds of novel facile fabrication routes to prepare Au-F127 nanocolloids with different morphologies including rambutan-like Au-F127 hybrid nanospheres, Au@F127 core-shell nanostructure, and multiple shapes of Au nanosheets are reported. The different Au-F127 nanocolloids are characterised by transmission electron microscopy, electron diffraction patterns, and UV-vis spectroscopy. The different formation mechanisms of the Au-F127 nanocolloids with different morphologies are discussed. The intrinsic properties and application potential of Au-F127 nanocolloids are determined by their size, shape, composition, and structure. A biosensor made of rambutan-like Au-F127 hybrid nanospheres exhibited a good electrocatalytic activity for the reduction of hydrogen peroxide. The Au@F127 core-shell nanoparticles exhibited good blood compatibility attributable to the surface hydrophilicity of the F127 layer. These strategies open up the exciting possibility of using F127 in synthesis of gold nanomaterials of variable morphology, and provide a promising platform for biomedical applications in future. Source

Gao F.,Capital Medical University | Gao F.,Beijing Centers for Diseases Control and Prevention | Zhao Y.,Nanjing Institute of Supervision and Testing on Product Quality | Shao B.,Capital Medical University | And 3 more authors.
Chinese Journal of Chromatography (Se Pu)

An analytical method was established for the simultaneous determination of 42 pesticides and veterinary drugs in milk by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UPLC-Q-TOF-MS). The target compounds are the commonly used drugs including 13 pesticides and 29 veterinary drugs. The QuEChERS (Quick, Easy, Cheap, Effective, Rugged/ and Safe) method was used for sample preparation. The analytes in milk samples were extracted with acetonitrile containing 1.0% (v/v) formic acid, and were salted out by adding anhydrous sodium sulfate and potassium chloride. After that, the extract solution was purified by dispersive solid phase extraction with C18 sorbent. In the chromatographic analysis of 42 target compounds were separated on an ACQUITY UPLC™ BEH C18 column with the gradient elution using the mobile phases of acetonitrile and water containing 0.1% formic acid. MSE(where E represents collision energy) acquisition under positive ion mode was performed to obtain accurate relative molecular masses and fragment ions. As a result, the limits of quantification (LOQ, S/N = 10) of the target compounds were from 1 μg/kg to 100 μg/kg in milk. The average recoveries of the 42 analytes spiked at three concentration levels were ranged from 68.2% to 129.1% with the relative standard deviations of 2.8% - 30.8%. This method can be applied to the analysis of the 42 pesticides and veterinary drugs in milk due to its fastness, simplicity and relatively high sensitivity. © 2010 Editorial Office of Chinese Journal of Chromatography, Dalian Institute of Chemical Physics, CAS. Source

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