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141.
Glyphosate determination in liver is challenging due to this particular molecule/matrix combination. Glyphosate is a very polar molecule and liver composition is highly variable between individuals and species. Since 2014, the Multiannual Control Program (MACP) of the European Union (EU) demands to analyse glyphosate in food of animal origin on a voluntary basis. Moreover, this analysis will be mandatory in 2017. This paper describes a robust and easily transferable method for glyphosate quantification in liver of animal origin by means of liquid chromatography–tandem mass spectrometry (LC-MS/MS). An intensive clean-up was used to eliminate matrix interferences and was combined with a derivatization step which ensures good retention of glyphosate on a conventional reverse-phase LC column. This method allows to meet the MACP requirements without a time-consuming change in the set-up of the routinely used LC-MS/MS system. Furthermore, it allows the use of an LC column and mobile phases often used in multi-residue analysis. The analytical method was validated according to the SANCO/12571/2013 criteria. Isotopic dilution was used to quantify glyphosate, leading to mean apparent recoveries of 115 and 101 % for the low (0.025 mg kg?1) and the high (0.250 mg kg?1) fortification levels, respectively. At both levels, the relative standard deviation was below 10 %. The limit of quantification of 0.025 mg kg?1 was found to be satisfactory as it was below the maximum residue level (MRL) value set at 0.050 mg kg?1 for glyphosate in liver. It is also the lowest MRL for all commodity types.  相似文献   
142.
The mechanisms underlying the beneficial effect observed in diabetic rats after treatment with a commercially available β-glucan-enriched extract (BGEE) were examined. Multiple low-dose streptozotocin (STZ) diabetes was used (40 mg STZ/kg) as a model for type 1 diabetes. BGEE was administered daily (80 mg/kg) for 4 weeks, starting from the last day of the STZ treatment. In vitro and in vivo experiments suggest that significant free radical scavenging and antioxidant activities of BGEE were responsible for a systemic adjustment of the redox disturbance and reduction of DNA damage in the liver and kidney of diabetic rats. BGEE-treated diabetic rats also displayed increased Akt kinase activity and decreased pro-caspase-3 degradation, implying that BGEE mediates its beneficial effects through activation of the cellular pro-survival pathway. We conclude that β-glucan administration under diabetic conditions promotes a systemic improvement that can be expected to increase the organism’s resistance to the onset of diabetic complications.  相似文献   
143.
144.
A liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of six major ergot alkaloids, ergometrine, ergosine, ergotamine, ergocornine, ergokryptine and ergocristine, as well as their corresponding epimers in food and feed samples. The method involves extraction under alkaline conditions and subsequent clean-up by applying a simple and rapid liquid–liquid partitioning procedure prior to LC–MS/MS analysis. Evaluation of the method revealed good linearity, accuracy and precision. The limits of quantification varied from 0.1 to 1 μg/kg depending on the analyte and matrix. The average extraction and clean-up recoveries in different matrices were between 45 (only for ergometrine in biscuit) and 90%. The uncertainty associated with the analytical method was not higher than 51% and 30%, at concentration levels of 2.5 and 150 μg/kg respectively. Analyte epimerization proved to be minimal during the analytical procedure. The method has been successfully applied to the determination of ergot alkaloids in some Belgian food and feed commodities. Ergot alkaloids were found in 104 out of 122 samples investigated. Ergosine was the most frequently occurring alkaloid, while the highest levels were observed for ergotamine, ergocristine or ergosine, depending on the product type. The total alkaloid content in positive samples varied from 1 to 1145 μg/kg.  相似文献   
145.
A scheme for applying an averaging method to the problem of convection in a two-layer system with an interface under the influence of high-frequency vibration is proposed. The derivation of the averaging equations is given, and the stability of the equilibrium of the averaged problem is considered. Long-wavelength asymptotics of steady and oscillatory instability are constructed. The results of numerical calculations for acetonitrile?Cn-hexane and silicone oil?Cfluorinert systems are given. The directions in which the investigation of thermovibrational convection in problems with free surfaces and interfaces can be continued, are indicated.  相似文献   
146.
Inversion of polarization lidar sensing data based on the form of the lidar sensing equation with allowance for contributions from multiple-scattering calls for a priori information on the scattering phase matrix. In the present study the parameters of the Stokes vectors for various propagation media, including those with the scattering phase matrices that vary along the measuring range, are investigated. It is demonstrated that, in spaceborne lidar sensing, a simple parameterization of the multiple-scattering contribution is applicable and the polarization signal's characteristics depend mainly on the lidar and depolarization ratios, whereas differences in the angular dependences of the matrix components are no longer determining factors. An algorithm for simultaneous reconstruction of the profiles of the backscattering coefficient and depolarization and lidar ratios in an inhomogeneous medium is suggested. Specific features of the methods are analyzed for the examples of interpretation of lidar signal profiles calculated by the Monte Carlo method and are measured experimentally.  相似文献   
147.
Colloidal type II CdTe/CdSe nanocrystals were synthesized by sequential addition of a tri-n-octylphosphine telluride (TOPTe)/TOP solution and several shell-precursor solutions to a CdO/TOP solution; the shell-precursor solutions consisted of CdO and TOPSe in TOP. For the growth of the CdTe core, the TOPTe/TOP solution was swiftly added to the CdO/TOP solution at a higher temperature (300 degrees C) than the growth temperature (250 degrees C). For the growth of the CdSe shell, in contrast, the CdO/TOPSe/TOP solution was slowly added to the CdTe/TOP solution at a lower temperature than the growth temperature (200-240 degrees C). The temporal evolution of the optical properties of the growing core-shell nanocrystals was monitored in detail. During the growth of the CdSe shell, the core-shell nanocrystals exhibited interesting changes in photoluminescence (PL) properties. The highest PL efficiency (approximately 38 %) was detected from core-shell nanocrystals with a CdSe shell thickness of 0.4-0.5 nm (indicated by TEM); the formation of the first monolayer is proposed. Our synthetic approach is well suited to a practical realization of engineering materials with bandgaps in the near-IR and IR spectral ranges.  相似文献   
148.
Genetically encoded probes have become powerful tools for non-invasive monitoring of ions, distributions of proteins and the migration and formation of cellular components. We describe the functional expression of two molecular probes for non-invasive fluorescent monitoring of intracellular Cl ([Cl]i) and the functioning of glycine receptor (GlyR) channels. The first probe is a recently developed cyan fluorescent protein-yellow fluorescent protein-based construct, termed Cl-Sensor, with relatively high sensitivity to Cl (Kapp approximately 30mM). In this study, we describe its expression in retina cells using in vivo electroporation and analyse changes in [Cl]i at depolarization and during the first three weeks of post-natal development. An application of 40mM K+ causes an elevation in [Cl]i of approximately 40mM. In photoreceptors from retina slices of a 6-day-old rat (P6 rat), the mean [Cl]i is approximately 50mM, and for P16 and P21 rats it is approximately 30-35mM. The second construct, termed BioSensor-GlyR, is a GlyR channel with Cl-Sensor incorporated into the cytoplasmic domain. This is the first molecular probe for spectroscopic monitoring of the functioning of receptor-operated channels. These types of probes offer a means of screening pharmacological agents and monitoring Cl under different physiological and pathological conditions and permit spectroscopic monitoring of the activity of GlyRs expressed in heterologous systems and neurons.  相似文献   
149.
We have designed and synthesized a new functional (amino reactive) highly efficient fluorescent molecular switch (FMS) with a photochromic diarylethene and a rhodamine fluorescent dye. The reactive group in this FMS -N-hydroxysuccinimide ester- allows selective labeling of amino containing molecules or other materials. In ethanolic solutions, the compound displays a large fluorescent quantum yield of 52 % and a large fluorescence modulation ratio (94 %) between two states that may be interconverted with red and near-UV light. Silica nanoparticles incorporating the new FMS were prepared and characterized, and their spectroscopic and switching properties were also studied. The dye retained its properties after the incorporation into the silica, thereby allowing light-induced reversible high modulation of the fluorescence signal of a single particle for up to 60 cycles, before undergoing irreversible photobleaching. Some applications of these particles in fluorescence microscopy are also demonstrated. In particular, subdiffraction images of nanoparticles were obtained, in the focal plane of a confocal microscope.  相似文献   
150.
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