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Li R.,Zhejiang Academy of Agricultural Sciences | He L.,National Shanghai Center for New Drug Safety Evaluation and Research | Wei W.,Zhejiang Academy of Agricultural Sciences | Hao L.,Southwest University for Nationalities | And 3 more authors.
Food Control | Year: 2015

In this study, chlorpyrifos residue levels in field crops of rice, maize and soybean were investigated according to the "Guideline on Pesticide Residue Trials" of China. On the basis of the residual results, human dietary risks were further evaluated. Chlorpyrifos residues of harvest grains were firstly prepared by QuEChERS method and analyzed using Gas Chromatography Tandem Mass Spectrometry (GC-MS/MS). Dietary risks were assessed by a deterministic approach. The median residues in field trials of rice, maize and soybean were 0.617, 0.0227 and 0.0136 mg kg-1, respectively. The highest residues in field trials of rice, maize and soybean were 3.23, 0.114 and 0.102 mg kg-1, respectively. Chronic intake assessment indicated that only 39.0% of acceptable daily intake (ADI, 0-0.01mg kg bw-1day-1) was consumed through rice, maize and soybean. The acute hazard indexes (aHI) of adults was 26.1% of acute reference dose (ARfD, 0-0.1 mg kg bw-1) and aHI of children was 63.5% of ARfD in dietary exposure assessment through rice, maize and soybean consumption. Single pathway risk assessment indicated that chlorpyrifos application on field crops in manner of the good agricultural practices didn't pose public health risks. © 2014 Elsevier Ltd. Source


Zhang Y.,Soochow University of China | Li H.,National Shanghai Center for New Drug Safety Evaluation and Research | Pu Y.,Soochow University of China | Gong S.,Soochow University of China | And 3 more authors.
Journal of Pineal Research | Year: 2015

Although melatonin receptors are widely expressed in the mammalian central nervous system and peripheral tissues, there are limited data regarding the functions of melatonin in cerebellar Purkinje cells. Here, we identified a novel functional role of melatonin in modulating P-type Ca2+ channels and action-potential firing in rat Purkinje neurons. Melatonin at 0.1 μm reversibly decreased peak currents (IBa) by 32.9%. This effect was melatonin receptor 1 (MTR1) dependent and was associated with a hyperpolarizing shift in the voltage dependence of inactivation. Pertussis toxin pretreatment, intracellular application of QEHA peptide, and a selective antibody raised against the Gβ subunit prevented the inhibitory effects of melatonin. Pretreatment with phosphatidylinositol 3-kinase (PI3K) inhibitors abolished the melatonin-induced decrease in IBa. Surprisingly, melatonin responses were not regulated by Akt, a common downstream target of PI3K. Melatonin treatment significantly increased protein kinase C (PKC) activity 2.1-fold. Antagonists of PKC, but not of protein kinase A, abolished the melatonin-induced decrease in IBa. Melatonin application increased the membrane abundance of PKCδ, and PKCδ inhibition (either pharmacologically or genetically) abolished the melatonin-induced IBa response. Functionally, melatonin increased spontaneous action-potential firing by 53.0%; knockdown of MTR1 and blockade of P-type channels abolished this effect. Thus, our results suggest that melatonin inhibits P-type channels through MTR1 activation, which is coupled sequentially to the βγ subunits of Gi/o-protein and to downstream PI3K-dependent PKCδ signaling. This likely contributes to its physiological functions, including spontaneous firing of cerebellar Purkinje neurons. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd. Source


Sun Y.,Shanghai JiaoTong University | Shi N.,Shanghai Pudong New District Zhoupu Hospital | Li H.,National Shanghai Center for New Drug Safety Evaluation and Research | Liu K.,Shanghai Pudong New District Zhoupu Hospital | And 3 more authors.
Cellular Signalling | Year: 2014

Although ghrelin receptors have been demonstrated to be widely expressed in the central nervous system and peripheral tissues of mammals, it is still unknown whether ghrelin functions in cerebellar Purkinje neurons. In this study, we identified a novel functional role for ghrelin in modulating P-type Ca2+ channel (P-type channel) currents (IBa) as well as action-potential firing in rat Purkinje neurons. Our results show that ghrelin at 0.1μM reversibly decreased IBa by ~32.3%. This effect was growth hormone secretagogue receptor 1a (GHS-R1a)-dependent and was associated with a hyperpolarizing shift in the voltage-dependence of inactivation. Intracellular application of GDP-β-S and pretreatment with pertussis toxin abolished the inhibitory effects of ghrelin. Dialysis of cells with the peptide QEHA (but not the scrambled peptide SKEE), and a selective antibody raised against the G-protein αo subunit both blocked the ghrelin-induced response. Ghrelin markedly increased protein kinase A (PKA) activity, and intracellular application of PKI 5-24 as well as pretreatment of the cells with the PKA inhibitor KT-5720 abolished ghrelin-induced IBa decrease, while inhibition of PKC had no such effects. At the cellular level, ghrelin induced a significant increase in action-potential firing, and blockade of GHS-R1a by BIM-28163 abolished the ghrelin-induced hyperexcitability. In summary, these results suggest that ghrelin markedly decreases IBa via the activation of GHS-R1a, which is coupled sequentially to the activities of Go-protein βγ subunits and the downstream PKA pathway. This could contribute to its physiological functions, including the spontaneous firing of action potentials in cerebellar Purkinje neurons. © 2014 Elsevier Inc. Source


Li R.,Institute of Quality and Standard for Agro products | He L.,National Shanghai Center for New Drug Safety Evaluation and Research | Zhou T.,Agriculture and Agri Food Canada | Ji X.,Institute of Quality and Standard for Agro products | And 3 more authors.
Analytical and Bioanalytical Chemistry | Year: 2014

A rapid, specific, and sensitive method based on modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) coupled to gas chromatography tandem mass spectrometry (GC-MS/MS) was developed and validated for simultaneous determination of chlorpyrifos (CP) and its metabolite 3,5,6-trichloro-2- pyridinol (TCP) in duck muscle. The residues of CP and TCP were extracted by acidified acetonitrile. The fat layer of the extract was removed under-20 °C, then the organic layer was evaporated. The analytes were derivatized by N-(tert-butyldimethylsilyl)-Nmethyltrifluoroacetamide (MTBSTFA) and cleaned up by a mixture of 150 mg MgSO4, 25 mg graphitized carbon black (GCB), and 50mg N-propylethylenediamine (PSA) to remove interference. The final extract was analyzed by GC-MS/MS. Recovery values at the spiking concentrations ranged from 86.2 to 92.3 % for CP and from 74.8 to 81.8 % for TCP, with relative standard deviations (RSDs) lower than 9.5 and 12.3, respectively. The correlation coefficients of CP (from 2 to 2,000 μg/kg) and TCP (from 1 to 1,000 μg/kg) were equal to or higher than 0.998. The limits of detection (LODs) were 0.3 and 0.15 μg/kg, and the limits of quantification (LOQs) were 1.0 and 0.5 μg/kg for CP and TCP in duck muscle, respectively. The average intra- and inter-day accuracy ranged from 84.6 to 91.2 % for CP and 75.6 to 82.3 % for TCP, and the intra- and inter-day precisions were from 5.8 to 8.2 % for CP and 6.5 to 11.9 % for TCP. Furthermore, the CP and TCP residues in duck muscle samples were detected for dietary risk assessment using the validated method. Source


Li R.,Zhejiang Academy of Agricultural Sciences | Wei W.,Zhejiang Academy of Agricultural Sciences | He L.,National Shanghai Center for New Drug Safety Evaluation and Research | Hao L.,Southwest University for Nationalities | And 3 more authors.
Journal of Agricultural and Food Chemistry | Year: 2014

Chlorpyrifos is a widely used organophosphorus pesticide in agricultural crops (including food) and animal feeds in China, resulting in heavy contamination. Many studies have focused on the food-processing effects on chlorpyrifos removal, but sufficient information is not observed for feed-processing steps. Here, chlorpyrifos residual behaviors in field crops and its transfers in duck pellet feed-processing steps were evaluated. In field trials, the highest residues for rice grain, shelled corn, and soybean seed were 12.0, 0.605, and 0.220 mg/kg, respectively. Residues of all rice grain and about half of shelled corn exceeded the maximum residue limits (MRLs) of China, and five soybean seeds exceeded the MRL of China. Chlorpyrifos residue was reduced 38.2% in brown rice after the raw rice grain was hulled. The residue in bran increased 71.2% after milling from brown rice. During the squashing step, the residue reduced 73.8% in soybean meal. The residues reduced significantly (23.7-36.8%) during the process of granulating for rice, maize, and soybean products. Comparatively, the grinding process showed only limited influence on chlorpyrifos removal (<10%). The residues of duck pellet feeds produced from highly contaminated raw materials ofthis study were 1.01 mg/kg (maize-soybean feed) and 3.20 mg/kg (rice-soybean feed), which were much higher than the generally accepted value (>0.1 mg/kg) for animal feeding. Chlorpyrifos residues were removed significantly by processing steps of pellet feeds, but the residue of raw materials was the determining factor for the safety of duck feeding. © 2014 American Chemical Society. Source

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