Entity

Time filter

Source Type


He H.,CAS Shenyang Institute of Applied Ecology | Lu H.,CAS Shenyang Institute of Applied Ecology | Zhang W.,CAS Shenyang Institute of Applied Ecology | Hou S.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | Zhang X.,CAS Shenyang Institute of Applied Ecology
Journal of Soils and Sediments | Year: 2011

Purpose: Amino acids are highly associated with biogeochemical cycling and represent an important potential source and sink of carbon (C) and nitrogen (N) in terrestrial ecosystems. Tracing the isotope dynamics of amino acids can improve the understanding of the origin and transformation of amino acids in soil matrix at process-levels; hence, the liquid chromatographic/mass spectrometric (LC/MS) method to evaluate 13C or 15N enrichment in amino acids is necessary to be established. Materials and methods: Laboratory incubations of a Mollisol (sampled from 0-20 cm) were conducted with either 15NH4 + plus glucose or NH4 + plus U-13C-glucose as substrates. The substrates were added weekly until the soils were sampled after 1 and 4 weeks, respectively. The soil samples were then ground to <0.25 mm and hydrolyzed to release amino acids. After being purified, the amino acids were derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate and then identified by LC/MS. The air-dried original soil was used as control and analyzed in the same assay. The amino acids were quantified based on the total current ion chromatograms. To fractionate and quantify the C and N isotopes in the amino acids, the intensities of the quasi-molecular peaks and the minor fragments were measured under both scan and selective ion monitoring modes. Results and discussion: The intensities of the corresponding isotope fragments in amino acids increased significantly after labile substrate addition, indicating the 15N and 13C incorporation into soil amino acids, including both free and proteinaceous or peptide forms during the incubations. The synchronous utilization of glucose was dominant to structure amino acid skeleton and the conversion from NH4 + to multi-nitrogen-containing amino acids exhibited the same pattern. The isotope enrichment in the amino acids was calculated according to the relative intensity increase of the isotope fragment and expressed as atom percentage excess (APE). The amount of isotope-labeled amino acids was furthermore differentiated from the native portion based on both APE and the concentration of individual compounds. Conclusions: The isotope-based LC/MS technique was useful to assess 15N and 13C enrichment in soil amino acids at relative high levels. The quantification of isotope incorporation makes it possible to evaluate the C or N turnover velocity of individual amino acids induced by the available substrates. Furthermore, the differentiation between the labeled and unlabeled amino acids was quite helpful to investigate the synthesis-decomposition dynamics of amino acid pools and explore the pathways of biological transformation of soil amino acids. © 2011 Springer-Verlag. Source


Lin L.H.,Shenyang Pharmaceutical University | Lin L.H.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | Duan M.Y.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | Chen G.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | And 3 more authors.
Talanta | Year: 2015

A simple, specific and reproducible liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of pyraoxystrobin in rat plasma and tissues. Chromatographic separation was achieved on a Zorbax Extend-C18 column (50×2.1 mm I. D., 3.5 μm), using a gradient mobile phase consisting of acetonitrile and 0.1% aqueous formic acid (v/v) at a flow rate of 0.5 mL min-1. Pyraoxystrobin and picoxystrobin (internal standard) were detected without interference in the selected reaction monitoring (SRM) mode with positive electrospray ionization. Further, the method was validated following FDA guideline. The calibration curves for plasma and tissues were linear over a concentration range of 1.00-200 ng mL-1, with lower limits of quantitation of 1.00 ng mL-1. Mean extraction recoveries in plasma and tissues ranged from 101.4% to 108.2% and from 49.1% to 59.4%, respectively. The intra-day and inter-day precision in plasma and tissues were within 9.9% and 8.9%, and the intra-day and inter-day accuracy ranged from 88.7% to 110.7% and 93.2% to 108.7%, respectively. Finally, the validated method was successfully applied to toxicokinetics and tissue distribution studies after oral administration of pyraoxystrobin to rats. © 2015 Elsevier B.V. All rights reserved. Source


Zhao J.,Shenyang Pharmaceutical University | Cai L.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | Wang J.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | Wu Y.,Shenyang Pharmaceutical University | And 2 more authors.
Experimental and Toxicologic Pathology | Year: 2011

To evaluate the endocrine-mediated effects of flumorph, we performed the uterotrophic assay, the Hershberger assay, and the repeated 28-day oral toxicity study based on the OECD draft protocols. In the uterotrophic assay, female ovariectomized SD rats were subcutaneously injected with flumorph at doses of 0, 50, 150, and 500mg/kg on each of 3 days, and no changes were observed. In the Hershberger assay, castrated male SD rats were administered with flumorph by oral gavage at doses of 0, 50, 150, and 500mg/kg/day for 10 consecutive days, and no abnormal changes were observed. However, in the repeated 28-day oral toxicity study, flumorph was orally administered at doses 0, 30, 100, and 300mg/kg/day for at least 28 days, a significantly increase in T4 value in male rats and TSH value in female rats were detected in the highest dosage group, respectively. Besides, the flumorph administration increase liver weights, produce hepatocellular diffuse fatty degeneration, and effect biochemical parameters related to liver function in male and/or female rats in dosed groups. Therefore, flumorph is concluded to have thyroid disruption effects and is likely a thyroid disrupter, but the further studies are needed for hazard identification. © 2009 Elsevier GmbH. Source


Lin L.,Shenyang Pharmaceutical University | Lin L.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | Yu W.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | Pang Y.,Supervision and Test Center for Pesticide Safety Evaluation and Quality Control | And 4 more authors.
Analytical and Bioanalytical Chemistry | Year: 2014

A simple, sensitive, and reliable liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed for determination of pyraoxystrobin in rat plasma and applied to a toxicokinetics study. The separation was performed by gradient elution on a Luna 5 μ C18 (2) 100 Å column (50×4.6 mm I.D., 5 μm) with mobile phase: water (0.1 % formic acid, v/v)/acetonitrile (0.1 % formic acid, v/v), followed by quantification with a mass detector in multiple reaction monitoring (MRM) mode using ESI as an interface. The calibration curve was linear over a concentration range of 1.00-200 ng/mL. The recovery for pyraoxystrobin ranged from 101.4 to 108.2 %. The intraday bias and precision ranged from -9.3 to 8.1 % and from 0.7 to 8.4 %, respectively, and the interday bias and precision ranged from -0.3 to 4.0 % and from 4.4 to 7.2 %, respectively. The toxicokinetics of pyraoxystrobin after single 100 and 1,000 mg/kg oral doses were studied in rats. © 2014 Springer-Verlag Berlin Heidelberg. Source

Discover hidden collaborations