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171.
172.
The aim of this study was to investigate (1) whether intestine endoparasites (Diphyllobothrium latum) accumulate trace elements related to its body size and (2) whether parasites bioconcentrate more trace elements than their host. Freshwater fish (rainbow trout Oncorhynchus mykiss) were sampled in the deep, oligotrophic and uncontaminated Lake Riñihue in Southern Chile. The element concentration of different organs (intestine, muscle, liver) and of the intestine endoparasites were analyzed using total reflection X-ray fluorescence spectrometry. The results showed that the mass fraction for Mn, Fe, Ni, Cu, and Pb decreased significantly with the body size (dry weight) of the endoparasite. Only Zn did not reveal such a relationship. Small parasites accumulated up to 80 times more Fe, Ni, Mn, Pb, and Cu than large parasites. Compared to the fish organs, small parasites accumulated in maximum 35 to 307 times more Mn, 5 to 255 times more Fe, 98 to 220 times more Ni, 3 to 175 times more Cu, and 0.4 to 12 times more Zn than the fish. Lead was only found in the endoparasite, but not in the fish organs. We conclude that (1) D. latum is a good indicator for trace element accumulation in fishes and that (2) small endoparasites are more sensitive as bioindicators because they showed higher bioconcentrations of trace metals than larger parasites. 相似文献
173.
Endo H Hayashi Y Kitani Y Ren H Hayashi T Nagashima Y 《Analytical and bioanalytical chemistry》2008,391(4):1255-1261
l-Lysine (l-Lys) in living bodies is critical for metabolism; therefore, determination of its levels in food is important. Most enzymatic
methods for l-Lys analysis are performed using l-lysine oxidase (LyOx), but commercially manufactured LyOx is generally not highly selective for l-Lys among amino acids. We previously isolated LyOx as an antibacterial protein secreted from the skin of the rockfish Sebastes schlegeli. In the present study, we developed an optical enzyme sensor system for rapid and continuous determination of l-Lys using this LyOx. The system comprised an immobilized LyOx membrane, an optical oxygen probe, a flow system, and a personal
computer. The amount of l-Lys was detected as a decrease in the oxygen concentration due to the LyOx reaction. The specificity of the sensor was examined
against various amino acids. The sensor response was specific for l-Lys. Good reproducibility was obtained in 58 assays. The response of the sensor using commercially prepared LyOx was unstable
compared with the response using LyOx isolated in our laboratory. Our sensor system could be used for 5 weeks without our
having to change the enzyme membrane. The calibration curve for a standard l-Lys solution was linear from 0.1 to 3.0 mmol L−1. One assay could be completed within 2 min. The sensor was applied to determine the l-Lys content in food samples such as bonito cooking water and scallop hepatopancreas. The values obtained using the sensor
and conventional high-performance liquid chromatography methods were well correlated. 相似文献
174.
175.
Environmentally friendly solid‐phase microextraction coupled with gas chromatography and mass spectrometry for the determination of biogenic amines in fish samples 下载免费PDF全文
Jie Huang Ning Gan Fangying Lv Yuting Cao Haiqing Tang 《Journal of separation science》2016,39(22):4384-4390
In this work, a facile and environmentally friendly solid‐phase microextraction assay based on on‐fiber derivatization coupled with gas chromatography and mass spectrometry was developed for determining four nonvolatile index biogenic amines (putrescine, cadaverine, histamine, and tyramine) in fish samples. In the assay, the fiber was firstly dipped into a solution with isobutyl chloroformate as derivatization reagent and isooctane as extraction solvent. Thus, a thin organic liquid membrane coating was developed. Then the modified fiber was immersed into sample solution to extract four important bioamines. Afterwards, the fiber was directly inserted into gas chromatography injection port for thermal desorption. 1,7‐Diaminoheptane was employed as internal standard reagent for quantification of the targets. The limits of detection of the method were 2.98–45.3 μg/kg. The proposed method was successfully applied to the detection of bioamines in several fish samples with recoveries ranging 78.9–110%. The organic reagent used for extraction was as few as microliter that can greatly reduce the harm to manipulator and environment. Moreover, the extraction procedures were very simple without concentration and elution procedures, which can greatly simplify the pretreatment process. The assay can be extended to the in situ screening of other pollutant in food safety by changing the derivatization reagent. 相似文献
176.
The concentration of polyacrylate (PA) used as a scale inhibitor was potentiometrically determined with a solid state copper ion-selective electrode after addition of Cu2+ as a probe. While the conventional methods monitor only the total concentration of PA, the proposed method measures the free, “effective” concentration of PA in equilibrium with species like Ca2+ and CaCO3. The slope of a potential response to PA was −40 mV decade−1 and the limit of detection was 10−6.3 M (= mol dm−3) at a probe concentration of 10−6 M. The system could be used to control the PA concentration just enough to prevent the scale formation in various circulating water systems. 相似文献
177.
Ch. Schlechtriem U. Focken K. Becker 《Isotopes in environmental and health studies》2013,49(2):135-140
For many ecological applications of stable carbon isotope techniques, it is necessary to separate the lipid and lipid-free fractions. The effect of different lipid extraction methods on the isotope signature of the remaining lipid-free matter as well as the lipid fraction was tested. A hot extraction form of the Soxhlet method using petrol-ether was compared with two liquid-liquid extraction methods for lipid determination described by Bligh and Dyer and Smedes. Solid samples of fish and different natural food items were subjected to extraction and the carbon isotope ratios in lipid and lipid-free matter determined by IRMS. All methods were suitable for lipid extraction from all samples analysed here and did not cause biologically relevant differences (>1) in carbon isotopic ratios, except the Bligh and Dyer extraction method using chloroform which caused systematic errors for δ 13C when applied to diatoms. 相似文献
178.
Huiping Jin 《Journal of Mathematical Analysis and Applications》2011,374(2):429-441
In this paper, we prove the existence of infinitely many quasiperiodic solutions for a class of coupled Duffing-type equations via KAM theorem. Moreover, the set of quasiperiodic solutions is of infinitely Lebesgue measure in the phase space. 相似文献
179.
The propulsion performance of a flexible plate undergoing an arbitrary harmonic motion in a two-dimensional and inviscid fluid is addressed. This plate being free of external forces, heaving and pitching cannot be imposed and are the results of recoil conditions on the body. Linear unsteady airfoil theory is first used to calculate the average thrust and power required for swimming. The propulsive performance is then discussed in terms of hydrodynamic efficiency, energy consumption and average swimming speed and two different asymptotic regimes are identified: the low-velocity regime and the high-velocity regime. The optimal swimming gaits are calculated in the different regimes as a function of the plate mass ratio and leading-edge suction. Finally an empirical non-linear model is proposed to complement the linear model and the optimal swimming modes are calculated and discussed within this framework. For a fixed number of degrees of freedom, it is found that the Strouhal number of the optimal mode is almost constant, independently of the swimming regime. 相似文献
180.
This paper describes a comprehensive non-linear multiphysics model based on the Euler–Bernoulli beam equation that remains valid up to large displacements in the case of electrostatically actuated Mathieu resonators. This purely analytical model takes into account the fringing field effects and is used to track the periodic motions of the sensing parts in resonant microgyroscopes. Several parametric analyses are presented in order to investigate the effect of the proof mass frequency on the bifurcation topology. The model shows that the optimal sensitivity is reached for resonant microgyroscopes designed with sensing frequency four times faster than the actuation one. 相似文献