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Chen G.,U.S. Department of Agriculture | Liu G.,Shanghai Institute for Food and Drug Control
Sensing and Instrumentation for Food Quality and Safety | Year: 2011

Oxytetracycline residue in shrimp muscle was determined using a portable time-resolved analyzer. After extraction in EDTA-metaphosphoric acid and filtration, the analyte was cleaned up using hydrophilic-lipophilic balance cartridges. Europium-sensitized luminescence (ESL) was measured at λ ex = 385 nm and λ em = 620 nm. Recoveries were 80. 3 and 79. 7% at 100 ng g -1 and 2 μg g -1, respectively. The signal intensity was linear (r 2 ≥ 0.996) in each decade in the 5-5,000 ng g -1 range. Averaged relative standard deviation was ~2% and limit of detection was 8. 3 ng g -1. This instrument-method combination enabled sensitive in-situ quantification of OTC residue in shrimp. The ESL results were validated by HPLC-MS/MS. © 2012 Science+Business Media, LLC.

Chen G.,U.S. Department of Agriculture | Miao S.,Shanghai Institute for Food and Drug Control
Journal of Agricultural and Food Chemistry | Year: 2010

Residues of malachite green (MG), gentian violet (GV), and their leuco metabolites in channel catfish muscle were individually determined by HPLC using diode array and fluorescence detectors and confirmed by tandem mass spectrometry. This detection scheme obviates a PbO2 reactor that converts leuco forms to chromatic forms for absorbance detection, therefore eliminating uncertainties in oxidant depletion and data integrity. Extraction was performed once in pH 3 McIlvaine buffer and acetonitrile, followed by cleanup using a polymeric strong cation-exchange column. Liquid-liquid extraction was excluded to provide an environmentally responsible and relatively rapid protocol. Spectrometric limits of detection (LOD; S/N = 3) for MG (λ = 620 nm) and GV (λ = 588 nm) were 0.38 and 0.26 ng/g with 44.5-49.2% and 92.2-101.4% recoveries (1-10 ng/g, n = 6), respectively. Fluorometric LOD (S/N = 3) for LMG and LGV (λex = 266 nm, λem = 360 nm) were 0.10 and 0.09 ng/g with 74.3-84.5% and 80.6-86.5% recoveries (1-10 ng/g, n = 6), respectively. This simplified protocol saves costs and meets the sensitivity requirements set by the Food and Drug Administration and the European Union. © 2010 American Chemical Society.

Zhao H.,Fudan University | Jiang Y.,National Institute of Parasitic Diseases | Cao Q.,Fudan University | Hou Y.,Fudan University | Wang C.,Shanghai Institute for Food and Drug Control
Biology of Reproduction | Year: 2012

The physiological hypoxic condition favors the angiogenesis in the placenta. However, it remains unclear how hypoxia regulates the invasion of human extravillous trophoblast cells. In the present study, we first showed that alpha5 integrin expression increased and alpha1 integrin expression decreased in human extravillous trophoblast cells cultured in 1% oxygen as compared with control cells cultured in 8% oxygen. Further data showed that the neutralizing antibody against alpha5 integrin increased the invasion of human extravillous trophoblast cells and the neutralizing antibody against alpha1 integrin inhibited the invasion of human extravillous trophoblast cells. Human extravillous trophoblast cells cultured in 1% oxygen showed reduced invasive capacity, which can be effectively blocked by alpha5 integrin neutralizing antibody. Moreover, human extravillous trophoblast cells exposed to 1% oxygen demonstrated increased expression of transforming growth factor-beta3 (TGFB3), and recombinant human TGFB3 inhibited the invasion of human extravillous trophoblast cells in a dosedependent manner. The neutralizing antibodies against alpha5 integrin and TGFB3 markedly abrogated hypoxia-induced invasion inhibition in human extravillous trophoblast cells. These data indicate that hypoxia may inhibit the invasion of human extravillous trophoblast cells through inducing the integrin switch from alpha1 integrin to alpha5 integrin and promoting TGFB3 expression. © 2012 by the Society for the Study of Reproduction, Inc.

Chen G.,U.S. Department of Agriculture | Du Y.,Shanghai Institute for Food and Drug Control
Journal of Agricultural and Food Chemistry | Year: 2011

Danofloxacin (DANO) residue in bovine muscle was screened at 200 ng/g by terbium-sensitized luminescence (TSL) directly measured on 10 x 6 mm C18 sorbent strips. The analyte was first adsorbed on sorbent surface by immersion in defatted homogenates. After reagent application and desiccation, TSL was directly measured on sorbent surfaces at λex = 273 nm and λem = 546 nm. The luminescence intensity was linearly dependent on DANO concentration in the 0-1000 ng/g range (R2 = 0.9967). A threshold was established at x200 - 3σ 200, where x200 and σ200 are the mean and standard deviation, respectively, of the DANO signals at 200 ng/g. Among 48 blind samples randomly fortified at 0-1000 ng/g, 45 were screened correctly and 3 negative samples were presumed positive. This simple screening protocol has the potential to significantly reduce sample numbers and hence improve sample throughput and save assay costs. © 2011 American Chemical Society.

Xiong Y.,Zhejiang Chinese Medical University | Chen J.,China Pharmaceutical University | Guo D.,Shanghai Institute for Food and Drug Control
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2014

Nobiliside A (Nob) is a new triterpenoid saponin separated from Holothuria noblilis. In this article, a liquid chromatography-electrospray ionization-tandem mass spectrometry method was established to quantify Nob, a hemolytic saponin, in rat blood and tissue homogenates. Standard curves were linear (r= 0.9988-0.9995) over the range 50-5000. ng/mL in blood and 100-10000. ng/g in tissues. The lower limit of quantification (LLOQ) was 50. ng/mL for Nob. The novel method was rapid, accurate, highly sensitive and highly selective. Using this method, the pharmacokinetics and biodistribution of Nob liposome and Nob solution in Sprague-Dawley rats after a single intravenous dose of 1. mg/kg were then investigated. Nob was cleared slowly from circulation. There was no significant difference of the pharmacokinetic parameters in blood between Nob solution and Nob liposome. The highest AUC of Nob was observed in liver for the two groups, followed by spleen, lungs, kidney and heart. Compared with Nob solution, Nob liposome showed much higher AUC in liver and spleen and much lower AUC in kidney, heart and lung, which might be one important reason for the decreased toxicity of Nob. © 2014 Elsevier B.V.

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