Quantitative Determination of Microcystins in Rat Plasma by LC-ESI Tandem MS

A rapid and sensitive method was developed and validated for the determination of MCYST (microcystin)-RR, -LR, and [Dha(7)] MCYST-LR in rat plasma by liquid chromatography-tandem mass spectrometry. The analytes were extracted from rat plasma by protein precipitation, followed by solid-phase extraction. Liquid chromatography with electrospray ionization mass spectrometry, operating in selected reaction monitoring (SRM) mode, was used to quantify MCYST-RR, -LR, and [Dha(7)] MCYST-LR in rat plasma. The recoveries for each analyte in rat plasma ranged from 70.8 to 88.7%. The calibration curve was linear within the range from 0.005 to 1.25 mu g mL(-1). The limit of detection were 1.4, 1.0, 0.6 ng mL(-1) for MCYST-RR, -LR, and [Dha(7)] MCYST-LR. The overall precision was determined on three different days. The values for within- and between-day precision in rat plasma were within 15%. This method was applied to the identification and quantification of microcystins in rat plasma with acute exposure of microcystins via intravenous injection.

LC determination of amino acids in rat plasma with fluorescence detection: Application to exercise physiology

An LC method for the determination of 20 amino acids (AAs), using 1,2-Benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) as fluorescent labeling reagent, has been validated and applied for the analysis of AAs in rat plasma at three different states concerning exercise physiology. Identification of AA derivatives was carried out by LC-MS with electrospray ion (ESI), and the MS-MS cleavage mode of the representative tyrosine (Tyr) derivative was analyzed. Gradient elution on a Hypersil BDS C-18 column gave good separation of the derivatives. Excellent linear responses were observed and good compositional data could be obtained from as little as 50-200 mu L of plasma samples. The contents of 20 AAs in rat plasma of three groups (24 rats, group A: quiet state, group B: at exercising exhaust, group C: 12 h after exercising exhaust) exhibited evident difference corresponding to the physiological states. Facile BCEOC derivatization coupled with LC-FLD-ESI-MS analysis allowed the development of a highly sensitive method for the quantitative analysis of trace level of AAs from plasma or other biochemical samples.

Distribution of microcystins in various organs (heart, liver, intestine, gonad, brain, kidney and lung) of Wistar rat via intravenous injection

The distribution of microcystins (MCs) in various tissues of Wistar rats was studied under laboratory conditions. Rats were injected intravenously (i.v.) with extracted MCs at a dose of 80 mu g MC-LRequivalent/kg body weight. MCs concentrations in various tissues were detected at 1, 2. 4, 6, 12 and 24 h post-injection using liquid chromatography-mass spectrometry (LC-MS). The highest concentration of MCs was found in kidney (0.034-0.295 mu g/g dry weight), followed by lung (0.007-0.067 mu g/g dry weight), stomach (0.010-0.058 mu g/g dry weight) and liver (0.003-0.052 mu g/g dry weight). The maximum MCs content in the whole body of rat, 2.9% of the injected dose, was observed at 2 h post-injection. MCs concentration was higher in kidney than in liver during the experiment, and two peaks of MCs concentration (at 2 and 24 h, respectively) were observed in kidney, indicating that MCs can be excreted directly via kidney of rat. Though heart, intestine, spleen, brain, gonad and stomach contained less than 0.2% of injected MCs during the whole experiment stage, the presence of MCs in these tissues represents potential damage to them. (c) 2008 Elsevier Ltd. All Fights reserved.

Effects of prolonged exposure to context following contextual fear conditioning on synaptic properties in rat hippocampal slices

Acute stressful events enhance plasma corticosterone release and profoundly affect synaptic functions, which are involved in the development of stress-related cognitive and mental disorders. However, how exposure to stressful context immediately after str

The profound effects of microcystin on cardiac antioxidant enzymes, mitochondrial function and cardiac toxicity in rat

Deaths from microcystin toxication have widely been attributed to hypovolemic shock due to hepatic interstitial hemorrhage, while some recent studies suggest that cardiogenic complication is also involved. So far, information on cardiotoxic effects of MC has been rare and the underlying mechanism is still puzzling. The present study examined toxic effects of microcystins on heart muscle of rats intravenously injected with extracted MC at two doses, 0.16LD(50) (14 mu g MC-LReq kg(-1) body weight) and 1LD(50) (87 mu g MC-LReq kg(-1) body weight). In the dead rats, both TTC staining and maximum elevations of troponin I levels confirmed myocardial infarction after MC exposure, besides a serious interstitial hemorrhage in liver. In the 1LD(50) dose group, the coincident falls in heart rate and blood pressure were related to mitochondria dysfunction in heart, while increases in creatine kinase and troponin I levels indicated cardiac cell injury. The corresponding pathological alterations were mainly characterized as loss of adherence between cardiac myocytes and swollen or ruptured mitochondria at the ultrastructural level. MC administration at a dose of 1LD(50) not only enhanced activities and up-regulated mRNA transcription levels of antioxidant enzymes, but also increased GSH content. At both doses, level of lipid peroxides increased obviously, suggesting serious oxidative stress in mitochondria. Simultaneously. complex I and III were significantly inhibited, indicating blocks in electron flow along the mitochondrial respiratory chain in heart. In conclusion, the findings of this study implicate a role for MC-induced cardiotoxicity as a potential factor that should be considered when evaluating the mechanisms of death associated with microcystin intoxication in Brazil. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

Sequential ultrastructural and biochemical changes induced in vivo by the hepatotoxic microcystins in liver of the phytoplanktivorous silver carp Hypophthalmichthys molitrix

Up to now, in vivo studies on the toxic effects of microcystins (MCs) on the ultrastructures of fish liver have been very limited. The phytoplanktivorous silver carp was injected i.p. with extracted hepatotoxic microcystins (mainly MC-RR and -LR) at a dose of 1000 mu g MC-LReq. kg(-1) body weight, showing a time-dependent ultrastructural change in liver as well as significant increases in enzyme activity of plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH). We observed for the first time the occurrence of a large amount of activated secondary lysosomes, which might be an adaptive mechanism to eliminate or lessen cell damage caused by MCs through lysosome activation. Quantitative and qualitative determinations of MCs in the liver were conducted by HPLC and LC-MS2, respectively. MCs concentration in the liver reached the maximum (114.20 mu g g(-1) dry weight) after 3 h post-injection, and then rapidly dropped to 7.57 mu g g(-1) dry weight at 48 h, indicating a deputation of 99% accumulated MC-LReq. On the other hand, a decrease trend in glutathione (GSH) concentration was observed in the liver of silver carp while the activity of glutathione S-transferase (GST) increased significantly after injection. The high tolerance of silver carp to MCs might be due to the high basic GSH level in their liver, and/or an increased GSH synthesis. (C) 2007 Elsevier Inc. All rights reserved.

Three-Dimensional Modeling of Heat Transfer and Fluid Flow in Laminar-Plasma Material Re-Melting Processing

Modeling study is performed concerning the heat transfer and fluid flow for a laminar argon plasma jet impinging normally upon a flat workpiece exposed to the ambient air. The diffusion of the air into the plasma jet is handled by using the combined-diffusion-coefficient approach. The heat flux density and jet shear stress distributions at the workpiece surface obtained from the plasma jet modeling are then used to study the re-melting process of a carbon steel workpiece. Besides the heat conduction within the workpiece, the effects of the plasma-jet inlet parameters (temperature and velocity), workpiece moving speed, Marangoni convection, natural convection etc. on the re-melting process are considered. The modeling results demonstrate that the shapes and sizes of the molten pool in the workpiece are influenced appreciably by the plasma-jet inlet parameters, workpiece moving speed and Marangoni convection. The jet shear stress manifests its effect at higher plasma-jet inlet velocities, while the natural convection effect can be ignored. The modeling results of the molten pool sizes agree reasonably with available experimental data.

Propagation Properties of Electromagnetic Wave in a Plasma Slab

In this paper, the calculated results about the propagation properties of electromagnetic wave in a plasma slab are described. The relationship of the propagation properties with frequencies of electromagnetic wave, and parameters of plasma (electron temperature, electron density, dimensionless collision frequency and the size of the plasma slab) is analyzed.

Destruction of Chemical Agents in a Plasma Reactor with Working Gas of Hydrogen

THE FORMATION MECHANISM OF THE VITRIFIED SLAG IN A PLASMA ARC REACTOR FOR HAZARDOUS WASTE TREATMENT

Various hazardous wastes with additives have been vitrified to investigate the formation mechanism of the glassy slag by a 30 kW DC plasma-arc reactor developed by the Institute of Mechanics, Chinese Academy of Sciences. The average temperature in the reaction area is controlled at 1500°C. The chemical compositions of three sorts of fly ashes are analyzed by XRF (X-Ray Fluorescence). Fly ashes with vitrifying additives can be vitrified to form glassy slag, which show that the ratio of the whole oxygen ions to the whole network former ions in glass (R) is appropriate in the range of 2~3 to form durable vitrified slag. In this experiment, the arc power is controlled below 5 kW to inhibit waste evaporation. To enhance the effects of heat transfer to wastes, ferrous powder has been added into the graphite crucible, which aggregates as ingot below the molten silicate after vitrification. The slag fails to form glass if the quenching rate is less than 1 K/min. Therefore, the slag will break into small chips due to the sharp quenching rate, which is more than 100 K/sec.

Electron acceleration by an intense short-pulse laser in underdense plasma

Electron acceleration from the interaction of an intense short-pulse laser with low density plasma is considered. The relation between direct electron acceleration within the laser pulse and that in the wake is investigated analytically. The magnitude and location of the ponderomotive-force-caused charge separation field with respect to that of the pulse determine the relative effectiveness of the two acceleration mechanisms. It is shown that there is an optimum condition for acceleration in the wake. Electron acceleration within the pulse dominates as the pulse becomes sufficiently short, and the latter directly drives and even traps the electrons. The latter can reach ultrahigh energies and can be extracted by impinging the pulse on a solid target. (C) 2003 American Institute of Physics.

Photon-photon scattering in a plasma channel

The Heisenberg-Euler correction due to photon-photon scattering, a still unverified quantum electrodynamics effect, on electromagnetic wave interaction inside a plasma channel is investigated theoretically. From a signal laser beam in the relativistic overdense plasma channel, photon-photon scattering can produce a detectable output beam of different frequency and polarization. (C) 2003 American Institute of Physics.

Relativistic channel-coupling focusing enhanced nonlinear guiding of an intense laser beam in a plasma channel

We employ the variational method to study the optical guiding of an intense laser beam in a preformed plasma channel without using the weakly relativistic approximation. Apart from the dependence on the laser power and the nonlinear channel strength parameter, the beam focusing properties is shown also to be governed by the laser intensity. Relativistic channel-coupling focusing, arising from the coupling between relativistic self-focusing and linear channel focusing, can enhance relativistic self-focusing but its strength is weaker than that of linear channel focusing. (C) 2008 Elsevier B.V. All rights reserved.