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Plasma
Kinds of Plasma Terms modified by Plasma Selected AbstractsDO PLASMA NON-ESTERIFIED FATTY ACIDS AND INSULIN RESISTANCE CONTRIBUTE TO IMPAIRED ENDOTHELIAL FUNCTION IN NEPHROTIC SYNDROME?NEPHROLOGY, Issue 1 2002G. Dogra [source] Verification of the 2D Tokamak Edge Modelling Codes for Conditions of Detached Divertor PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-5 2010V. Kotov Abstract The paper discusses verification of the ITER edge modelling code SOLPS 4.3 (B2-EIRENE). Results of the benchmark against SOLPS 5.0 are shown for standard JET test cases. Special two-point formulas are employed in SOLPS 4.3 to analyze the results of numerical simulations. The applied relations are exact in frame of the equations solved by the B2 code. This enables simultaneous check of the parallel momentum and energy balances and boundary conditions. Transition to divertor detachment is analyzed quantitatively as it appears in the simulations in terms of the coupled momentum and energy balance (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Accumulation Process of High-Z Impurity in Toroidal Rotating Tokamak PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-5 2010K. Hoshino Abstract The accumulation process of high-Z impurity in toroidal rotating tokamak plasma is investigated. A new inward pinch of high-Z impurity due to the ionization/recombination processes is derived using an analytic model. This inward pinch is driven by the large deviation of a drift orbit from a magnetic surface and the resultant variation of the charge state along the drift orbit. The pinch velocity increases with increasing toroidal rotation speed in both the co-direction and the ctr-direction. The inward pinch expected by the analytic model is really observed in the numerical simulation using the IMPGYRO code (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Equation of State of Strongly Coupled Quark,Gluon Plasma , Path Integral Monte Carlo ResultsCONTRIBUTIONS TO PLASMA PHYSICS, Issue 7-8 2009V.S. Filinov Abstract A strongly coupled plasma of quark and gluon quasiparticles at temperatures from 1.1Tc to 3Tc is studied by path integral Monte Carlo simulations. This method extends previous classical nonrelativistic simulations based on a color Coulomb interaction to the quantum regime. We present the equation of state and find good agreement with lattice results. Further, pair distribution functions and color correlation functions are computed indicating strong correlations and liquid-like behavior (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Longitudinal Dust Lattice Shock Wave in a Strongly Coupled Complex Dusty PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2008S. Ghosh Abstract The effect of hydrodynamical damping that arises due to the irreversible processes within the system have been studied on 1D nonlinear longitudinal dust lattice wave (LDLW) in homogeneous strongly coupled complex (dusty) plasma. Analytical investigation shows that the nonlinear wave is governed by Korteweg-de Vries Burgers' equation. This hydrodynamical damping induced dissipative effect is responsible for the Burgers' term that causes the generation of shock wave in dusty plasma crystal. Numerical investigation on the basis of the glow-discharge plasma parameters reveal that LDLW exhibits both oscillatory and monotonic shock. The shock is compressive in nature and its strength decreases (increases) with the increase of the shielding parameter , (characteristic length L). The effects of dust-neutral collision are also discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ion Particle Transport in the Tokamak Edge PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-3 2008W. M. Stacey Abstract A generalized pinch-diffusion transport relation previously derived from momentum conservation is combined with the continuity equation to derive a "generalized diffusion theory" for ion particle transport in the tokamak plasma edge inside the separatrix. The resulting generalized diffusion coefficients are evaluated for a representative experiment. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Emission Intensity Enhancement of DC Arc Plasma Induced by External Oscillating Magnetic FieldCONTRIBUTIONS TO PLASMA PHYSICS, Issue 10 2007M. M. Stoiljkovi Abstract Direct current (dc) arc plasma with continuous aerosol supply was coupled with an external oscillatingmagnetic field of a few tens of mT and a frequency of up to 1 kHz. Such configuration was used to alter the plasma-related radiative properties. The magnetic field was oriented perpendicularly to the electric field in the plasma and forced the arc column to oscillate as a whole with respect to the surrounding atmosphere. The magnitude of the appliedmagnetic.eld controls the amplitude of the oscillatory motion. Several parameters that can contribute to the radiative properties of the plasma were investigated (arc current, composition of aerosol introduced into the plasma, amplitude and frequency of the magnetic field applied). Spectral emission from different zones of the plasma column was measured by optical emission spectroscopy (OES). In comparison to steady-state plasma, the applied magnetic field induces an intensity enhancement of emission of the most analytes considered. The intensity enhancement is strongly affected by the amplitude and frequency of plasma column oscillations, i.e. by plasma column velocity. Also, intensity enhancement depends on the plasma zone observed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of Cathode and Anode Voltage on an Ion Sheath Thickness in a Magnetically Confined Diffusion PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 10 2007M. Kr. Abstract This article reports about the ion sheath thickness variation occurring in front of a negatively biased plate immersed in the target plasma region of a double plasma device. The target plasma is produced due to the local ionization of neutral gas by the high energetic electrons coming from the source region (main discharge region). It is observed that for an increase in cathode voltage (filament bias voltage) in the source region, the ion flux into the plate increases. As a result, the sheath at the plate contracts. Again, for an increase in source anode voltage (magnetic cage bias), the ion flux to the plate decreases. As a result, the sheath expands at the plate. The ion sheath formed at the separation grid of the device is found to expand for an increase in cathode voltage and it contracts for an increase in the anode voltage of the main discharge region. One important observation is that the applied anode bias can control the Bohm speed of the ions towards the separation grid. Furthermore, it is observed that the ion current collected by the separation grid is independent of changes in plasma density in the diffusion region but is highly dependent on the source plasma parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermally Conducting Partially Ionized Plasma in a Variable Magnetic FieldCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3 2007S. Shaikh Abstract An infinitely extending homogenous partially ionized plasma endowed with several physical mechanisms and permeated by a variable magnetic field is considered. The combined effect of these parameters, namely, Hall currents, finite conductivity, ion viscosity, collision with neutrals and thermal conductivity on the gravitational instability of the plasma is studied. It is found that the several mechanisms play different physical roles in the perturbed problem. Jeans' Criterion is analyzed in the framework of Tsallis' statistics for possible modifications due to the presence of nonextensive effects. A simple generalization of the Jeans' criterion is obtained and the standard values are obtained in the limiting case q = 1, q being the nonextensive parameter. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparison of Two Methods of Interpretation of LangmuirProbe Data for an Inductively Coupled Oxygen PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2006T. H. Chung Abstract The Langmuir probe technique has some drawback in applying to electronegative plasma since it is difficult to interpret the probe I , V data. The positive ion flux to the probe is modified due to the presence of negative ions. In this study, an inductively coupled oxygen RF plasma is employed to perform the Langmuir probe measurement of the electronegative discharge. Plasma parameters are obtained from Langmuir probe measurement using two different methods which are based on electron energy distribution function (EEDF) integrals, and the method based on the fluid model for the modified ion flux, respectively. The EEDF is measured by a double differentiation of the I , V characteristics according to the Druyvesteyn formula. The electron densities estimated based on the two methods are compared. The EEDF integral method gives little higher values than the modified ion flux method. It is observed that at low pressure the EEDF is close to a Maxwellian. Generally, as the pressure increases, the distributions switch to bi-Maxwellian and to Druyvesteyn, and suggest some depletion of electrons with larger energies. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Dielectric Characteristics for Radio Frequency Waves in a Laboratory Dipole PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4 2006N. I. Grishanov Abstract Transverse and parallel dielectric permittivity elements have been derived for radio frequency waves in a laboratory dipole magnetic field plasma. Vlasov equation is resolved for both the trapped and untrapped particles as a boundary value problem to define their separate contributions to the dielectric tensor components. To estimate the wave power absorbed in the plasma volume the perturbed electric field and current density components are decomposed in a Fourier series over the poloidal angle. In this case, the dielectric characteristics can be analyzed independently of the solution of the Maxwell's equations. As usual, imaginary part of the parallel permittivity elements is necessary to estimate the electron Landau damping of radio frequency waves, whereas imaginary part of the transverse permittivity elements is important to estimate the wave dissipation by the cyclotron resonances. Computations of the imaginary part of the parallel permittivity elements are carried out in a wide range of the wave frequencies. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Sheath in Front of a Negatively Biased Collector that Emits Electrons and is Immersed in a Two Electron Temperature PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2005T. Gyergyek Abstract An extension of a recently published [Gyergyek T., ,er,ek M. Contrib. Plasma Phys., 45, (2005), 89] one dimensional fluid model of the sheath formation in front of a floating electrode (collector) that emits secondary electrons and is immersed in a two-electron temperature nonmagnetized, collisionless plasma is presented. The electron velocity distribution function is assumed to be a two-temperature maxwellian, while the singly charged positive ions and the emitted electrons are assumed to be monoenergetic. It is assumed that the electrons in the pre-sheath potential drop obey the Boltzmann relation, so that a larger fraction of the hot than of the cool electrons can penetrate to the sheath edge. Our model predicts that the collector can in some cases have 3 and in some cases, when the emission of electrons from the collector is critical, even 5 different floating potentials at the same hot to cool electron temperature and density ratios very far away from the collector. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Presheath in Fully Ionized Collisional Plasma in a Magnetic FieldCONTRIBUTIONS TO PLASMA PHYSICS, Issue 7 2005B. Alterkop Abstract The quasineutral presheath layer at the boundary of fully ionized, collisional, and magnetized plasma with an ambipolar flow to an adjacent absorbing wall was analyzed using a two fluid magneto-hydrodynamic model. The plasma is magnetized by a uniform magnetic field B, imposed parallel to the wall. The analysis did not assume that the dependence of the particle density on the electric potential in the presheath is according to the Boltzmann equilibrium, and the dependence of the mean collision time , on the varying plasma density within the presheath was not neglected. Based on the model equations, algebraic expressions were derived for the dependence of the plasma density, electron and ion velocities, and the electrostatic potential on the position within the presheath. The solutions of the model equations depended on two parameters: Hall parameter (, ), and the ratio (, ), where , = ZTe /(ZTe + Ti ), and Te , Ti and Z are the electron and ion temperatures and ionicity, respectively. The characteristic scale of the presheath extension is several times ri /, , where ri is the ion radius at the ion sound velocity. The electric potential could have a non monotonic distribution in the presheath. The ions are accelerated to the Bohm velocity (sound velocity) in the presheath mainly near the presheath-sheath boundary, in a layer of thickness ,ri /, . The electric field accelerates the ions in the whole presheath if their velocity in the wall direction exceeds their thermal velocity. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Detection and Analysis of Strong Oscillating Electric Fields in a Picosecond Laser Plasma with the Help of Plasma Satellites of X-ray Spectral LinesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2005V. S. Belyaev Abstract X-ray lines of ions in a solid target interacting with picosecond laser pulses of the intensity ,3 × 1017 W/cm2 were studied on the "Neodim" laser facility. We observed X-ray Ly, emission spectra of hydrogen-like fluorine ions. Satellite lines were also recorded, evidencing the presence of intense plasma oscillations with an amplitude of the electric field larger than 108 V/cm and a frequency of about 1015 s,1. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fluid Model of a Sheath Formed in Front of an Electron Emitting Electrode Immersed in a Plasma with Two Electron TemperaturesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 2 2005T. Gyergyek Abstract The formation of a sheath in front of a negatively biased electrode (collector) that emits electrons is studied by a one-dimensional fluid model. Electron and ion emission coefficients are introduced in the model. It is assumed that the electrode is immersed in a plasma that contains energetic electrons. The electron velocity distribution function is assumed to be a sum of two Maxwellian distributions with two different temperatures, while the ions and the emitted electrons are assumed to be monoenergetic. The condition for zero electric field at the collector is derived. Using this equation the dependence of electron and ion critical emission coefficients on various parameters - like the ratio between the hot and cool electron density, the ratio between hot and cool electron temperature and the initial velocity of secondary electrons - is calculated for a floating collector. A modification of the Bohm criterion due to the presence of hot and emitted electrons is also given. The transition between space charge limited and temperature limited electron emission for a current-carrying collector is also analyzed. The critical potential, where this transition occurs, is calculated as a function of several parameters like the Richardson emission current, the ratio between the hot and cool electron density, the ratio between hot and cool electron temperature and the initial velocity of secondary electrons. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Screening Breakdown in a Plasma by Two Laser Fields and Strong DC Magnetic FieldCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005D. F. Miranda Abstract The effective static dielectric constant of an electron plasma system in the simultaneous presence of two electromagnetic waves and a strong DC magnetic field is calculated. It is found that as the difference ,, of the two electromagnetic wave frequencies matches the plasma frequency ,, a breakdown in screening occurs thereby increasing the plasma heating rate via the external fields due to inverse Bremmstrahlung. An application is made by considering the typical parameters of a hot plasma. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Experimental Studies of MHD Dynamics in a RFP Magnetically Confined PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2004J. R. Drake Abstract Studies of non-linear dynamics of MHD tearing modes in the EXTRAP reversed-field pinch experiments [1] have demonstrated such phenomena as mode rotation, phase-locking and wall locking. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Prolonged exposure to inhaled nitric oxide transiently modifies tubular function in healthy piglets and promotes tubular apoptosisACTA PHYSIOLOGICA, Issue 4 2009W. Go, dzik Abstract Aim:, Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator. We hypothesized that those piglets exposed to prolonged iNO react with a modified renal function. Methods:, Randomized, placebo-controlled exposure to 40 p.p.m. iNO (30 h) in piglets (n = 20). Plasma and urine were sampled during three periods (first and second 12 h periods, and finally a 6 h period). We measured urine volumes, plasma and urine electrolytes (UNa, UK, UCl), plasma creatinine and urea. We calculated creatinine clearance (Ccr), and fractional excretions of sodium and potassium (FENa, FEK) and urinary excretions of electrolytes (UENa, UEK, UECl). Haemodynamic data were recorded and renal tubular apoptosis detected. Results:, For the first 12 h, certain parameters significantly increased in the iNO group (mean ± SD): UNa (mmol L,1), 87.7 (±35.0) vs. 39.3 (±22.9), UCl (mmol L,1) 80.4 (±32.8) vs. 48.0 (±26.7), FENa (%) 2.1 (±0.8) vs. 0.7 (±0.5), FEK (%) 31.7 (±7.0) vs. 20.7 (±12.3), as well as UENa (mmol) 61.0 (±21.1) vs. 27.6 (±17.9) and UECl (mmol) 57.3 (24.5) vs. 37.6 (29.0). These changes were absent in the second and third periods of the study. Significant differences in percentage of apoptotic cell nuclei in the renal cortex and medulla were found after iNO exposure: 39% vs. 15%. Conclusion:, Exposure to 40 p.p.m. iNO in healthy anaesthetized piglets has a transient natriuretic effect that disappears after 12 h. We also found evidence of renal tubular apoptosis promotion after 30 h of iNO. [source] Enantioselective analysis of ketamine and its metabolites in equine plasma and urine by CE with multiple isomer sulfated ,-CDELECTROPHORESIS, Issue 15 2007Regula Theurillat Abstract CE with multiple isomer sulfated ,-CD as the chiral selector was assessed for the simultaneous analysis of the enantiomers of ketamine and metabolites in extracts of equine plasma and urine. Different lots of the commercial chiral selector provided significant changes in enantiomeric ketamine separability, a fact that can be related to the manufacturing variability. A mixture of two lots was found to provide high-resolution separations and interference-free detection of the enantiomers of ketamine, norketamine, dehydronorketamine, and an incompletely identified hydroxylated metabolite of norketamine in liquid/liquid extracts of the two body fluids. Ketamine, norketamine, and dehydronorketamine could be unambiguously identified via HPLC fractionation of urinary extracts and using LC-MS and LC-MS/MS with 1,mmu mass discrimination. The CE assay was used to characterize the stereoselectivity of the compounds' enantiomers in the samples of five ponies anesthetized with isoflurane in oxygen and treated with intravenous continuous infusion of racemic ketamine. The concentrations of the ketamine enantiomers in plasma are equal, whereas the urinary amount of R -ketamine is larger than that of S -ketamine. Plasma and urine contain higher S - than R -norketamine levels and the mean S -/R -enantiomer ratios of dehydronorketamine in plasma and urine are lower than unity and similar. [source] Pharmacokinetics of carisbamate (RWJ-333369) in healthy Japanese and Western subjectsEPILEPSIA, Issue 8 2009Peter Zannikos Summary Purpose:, To compare the pharmacokinetics of carisbamate (RWJ-333369) in healthy Japanese and Western adults, and to comparatively assess carisbamate safety and tolerability between the two populations. Methods:, An open-label study was conducted in 24 Japanese and 24 Caucasian healthy subjects. Subjects received a single oral dose of 250 mg carisbamate on day 1 followed by a 3-day washout period; twice-daily dosing of 250 mg carisbamate on days 5,8; subsequently, 500 mg on days 9,12 and a single dose of 500 mg on day 13. Plasma samples were collected for a pharmacokinetic analysis on days 1, 8, and 13. Plasma and urine samples were analyzed for carisbamate and its urinary metabolites by liquid-chromatography-mass-spectrometry. Results:, Following a single dose, carisbamate Cmax and area under the curve (AUC) geometric mean ratios were 16.4% and 28.8% higher in Japanese than in Caucasians, respectively; these differences were statistically significant and their 90% confidence intervals (CIs) fell outside of the 80,125% limits, which are considered not to be of clinical significance. With dose,body weight normalization, Cmax and AUC were similar in Japanese and Caucasian subjects and the 90% CIs were within the 80,125% boundaries. Carisbamate was well tolerated, and its mean oral clearance and half-life were similar in both groups, ranging from 35.1,41.4 ml/h/kg and 11.5,12.8 h. Discussion:, Carisbamate plasma exposure (AUC) and Cmax in Japanese subjects is ,20,25% higher than in Caucasians due to a higher mg/kg dose. After body weight normalization, carisbamate pharmacokinetics was similar between Japanese and Caucasian subjects following single and multiple dosing, and showed the same dose proportionality. [source] Pharmacokinetics of Levetiracetam and Its Enantiomer (R)-,-ethyl-2-oxo-pyrrolidine acetamide in DogsEPILEPSIA, Issue 7 2001Nina Isoherranen Summary: ,Purpose: The new antiepileptic drug, levetiracetam (LEV, ucb LO59), is a chiral molecule with one asymmetric carbon atom whose anticonvulsant activity is highly enantioselective. The purpose of this study was to evaluate and compare the pharmacokinetics (PK) of LEV [(S)-,-ethyl-2-oxo-pyrrolidine acetamide] and its enantiomer (R)-,-ethyl-2-oxo-pyrrolidine acetamide (REV) after i.v. administration to dogs. This is the first time that the pharmacokinetics of both enantiomers has been evaluated. Methods: Optically pure LEV and REV were synthesized, and 20 mg/kg of individual enantiomers was administered intravenously to six dogs. Plasma and urine samples were collected until 24 h, and the concentrations of LEV and REV were determined by an enantioselective assay. The levels of 2-pyrrolidone- N -butyric acid, an acid metabolite of LEV and REV, were determined by high-performance liquid chromatography (HPLC). The data were used for PK analysis of LEV and REV. Results: LEV and REV had similar mean ± SD values for clearance; 1.5 ± 0.3 ml/min/kg and volume of distribution; 0.5 ± 0.1 L/kg. The half-life (t1/2) and mean residence time (MRT) of REV (t1/2, 4.3 ± 0.8 h, and MRT, 6.0 ± 1.1 h) were, however, significantly longer than those of LEV (t1/2, 3.6 ± 0.8 h, and MRT, 5.0 ± 1.2 h). The renal clearance and fraction excreted unchanged for LEV and REV were significantly different. Conclusions: In addition to the enantioselective pharmacodynamics, ,-ethyl-2-oxo-pyrrolidine acetamide has enantioselective PK. The enantioselectivity was observed in renal clearance. Because REV has more favorable PK in dogs than LEV, the higher antiepileptic potency of LEV is more likely due to intrinsic pharmacodynamic activity rather than to enantioselective PK. [source] Rectal Absorption of Lamotrigine Compressed TabletsEPILEPSIA, Issue 7 2000Angela K. Birnbaum Summary: Purpose: Interruption of oral drug administration poses a significant clinical problem for antiepileptic drugs that have no parenteral formulation. If a drug is absorbed rectally, rectal administration can be a useful alternative when the oral route of administration is not possible. The purpose of this study was to compare the single-dose pharmacokinetics of la-motrigine (LTG) compressed tablets after rectal and oral administration in healthy volunteers. Methods: A single LTG compressed tablet (100 mg) was administered orally and rectally to 12 volunteers in this single-dose, two-period, crossover study with a 2-week washout between doses. For rectal administration, tablets were crushed and suspended in 10 mL of water. Plasma samples were collected from 0 to 120 hr after each dose and analyzed for LTG by an HPLC method developed for this investigation. Results: LTG plasma concentrations were lower after rectal administration versus oral administration. The average area under the curve was 28.90 ± 9.5 ,g/mL/hr after rectal administration and 51.71 ± 19.2 ,g/mL/hr after oral administration. The average maximum LTG concentration was 0.53 ± 0.14 ,g/mL after rectal administration and 1.45 ± 0.35 ,g/mL after oral administration. The relative bioavailability for LTG compressed tablets was 0.63 ± 0.33 for rectal administration. There were no drug-related rashes or serious side effects. Conclusions: LTG suspension prepared from LTG compressed tablets is absorbed rectally, although not to the same extent or rate as when given orally. [source] Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horsesEQUINE VETERINARY JOURNAL, Issue S36 2006C. A. WILLIAMS Summary Reasons for performing study: Vitamin E is the most commonly supplemented antioxidant in horses; however, previous research is not conclusive as to the recommended level for exercising horses. Objective: To evaluate the effects of 3 levels of vitamin E supplementation on oxidative stress and vitamin/antioxidant status in intensely exercised horses to determine the optimal level of vitamin E supplementation. Methods: Twelve unfit Standardbreds were divided into 3 groups, supplemented orally with 0 (CON), 5000 (MOD), or 10,000 (HI) iu/day of DL-,-tocopheryl acetate. The 3 times 3 Latin square design consisted of three 4 week supplementation periods with 4 week wash out periods between. After each period, horses underwent a treadmill interval exercise test. Blood samples were collected and heart rate (HR) measured before, during and after exercise. Data were analysed using ANOVA with repeated measures in SAS. Results: The CON group had lower HR throughout the test compared to the MOD and HI groups (P<0.05). There was an increase in plasma retinol (RET), ,-carotene (BC), red blood cell total glutathione and glutathione peroxidase with exercise (P<0.05), but all groups returned to baseline after 24 h. Plasma ,-tocopherol (TOC) increased from baseline with exercise (P<0.0001) in all groups; treatment differences were observed at 24 h (P<0.05). The HI and CON groups had lower BC compared to the MOD group (P = 0.05). Conclusions: Horses supplemented with vitamin E, at nearly 10-times the 1989 NRC recommended level, did not experience lower oxidative stress compared to control horses. Additionally, lower plasma BC levels observed in the HI group, which may indicate that vitamin E has an inhibitory effect on BC metabolism. Potential relevance: Supplementation above control levels is not more beneficial to oxidative stress and antioxidant status in intensely exercising horses; indeed, levels 10 times in excess may be detrimental to BC and should be avoided. [source] Application of a constant blood withdrawal method in equine exercise physiology studiesEQUINE VETERINARY JOURNAL, Issue 6 2001P. BARAGLI Summary The aim of the present study was to test a constant blood withdrawal method (CBWM) to collect blood samples from horses during treadmill exercise. CBWM was performed in 4 Standardbreds and 5 Haflinger horses. A peristaltic pump was used to control blood aspiration from an i.v. catheter via an extension line. Blood was collected using an automatic fractions collector, with a constant delay time between the drawing of blood and sample collection. Blood withdrawal using CBWM was made during a treadmill standardised exercise test (SET). A blood flow of 12 ml/min was used and samples collected every 60 s during the entire period of exercise. The volume of blood collected in each sample tube was 12.1 ± 0.2 ml, with a delay time of mean ± s.d. 25.3 ± 0.8 s. Plasma lactate kinetics based on measurement of lactate in each fraction showed an exponential increase during the first 13 min of exercise (10.5 min of SET and 2.5 min recovery). The peak plasma lactate concentration was observed between 2.5 and 5.5 min after the end of SET. CBWM permits the kinetics of lactate and other blood-borne variables to be studied over time. This method could be a valuable aid for use in studying equine exercise physiology. [source] Plasma angiopoietin-1, angiopoietin-2 and Tie-2 in breast and prostate cancer: a comparison with VEGF and Flt-1EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 10 2003G. J. Caine Abstract Background, Angiogenesis is essential for tumour growth and metastasis, and is coordinated by several classes of growth factors mediating their effect through receptors linked, in turn, to tyrosine kinase. These growth factors include angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF), which act through receptors Flt-1 and Tie-2. Materials and methods, In order to further determine abnormalities in levels of Ang-1, Ang-2, Tie-2, sFlt-1 and VEGF in human cancer (and their interrelationships), these molecules were measured in plasma from 30 patients with breast cancer, 30 patients with prostate cancer and 12 healthy controls per cancer group. Results, In breast cancer, levels of Ang-1 (P = 0·0005), Ang-2 (P = 0·0173), Tie-2 (P = 0·0001), and VEGF (P = 0·0001) were all significantly raised, and plasma levels of sFlt-1 (P = 0·045) were significantly reduced compared with controls. However, in prostate cancer, only levels of VEGF and Tie-2 were significantly higher (both P= 0·001). There were no significant differences between levels of any molecule between the two groups of cancer. The only difference between the healthy control groups was lower Ang-1 in the women compared with men. Significant correlations were found between levels of Ang-1 and Tie-2 both in breast (r = 0·498, P= 0·005) and prostate cancer (r = 0·643, P= < 0·001). Angiopoietin-1 was also positively correlated with Ang-2 in both breast (r = 0·422, P= 0·02) and prostate cancer (r = 0·543, P= 0·002). Conclusions, Abnormal levels of Ang-1, Ang-2 and their receptor, Tie-2, are present in breast and prostate cancer, and their interrelationships may be important in the pathophysiology of these conditions. [source] Brain angiotensin-converting enzymes: role of angiotensin-converting enzyme 2 in processing angiotensin II in miceEXPERIMENTAL PHYSIOLOGY, Issue 5 2008Khalid M. Elased Angiotensin (Ang)-converting enzyme 2 (ACE2) metabolizes Ang II to the vasodilatory peptide Ang(1,7), while neprilysin (NEP) generates Ang(1,7) from Ang I. Experiments used novel Surface Enhanced Laser Desorption Ionization-Time of Flight (SELDI-TOF) mass spectroscopic (MS) assays to study Ang processing. Mass spectroscopy was used to measure proteolytic conversion of Ang peptide substrates to their specific peptide products. We compared ACE/ACE2 activity in plasma, brain and kidney from C57BL/6 and NEP,/, mice. Plasma or tissue extracts were incubated with Ang I or Ang II (1296 or 1045, m/z, respectively), and generated peptides were monitored with MS. Angiotensin-converting enzyme 2 activity was detected in kidney and brain, but not in plasma. Brain ACE2 activity was highest in hypothalamus. Angiotensin-converting enzyme 2 activity was inhibited by the specific ACE2 inhibitor, DX600 (10 ,m, 99% inhibition), but not by the ACE inhibitor, captopril (10 ,m). Both MS and colorimetric assays showed high ACE activity in plasma and kidney with low levels in brain. To extend these findings, ACE measurements were made in ACE overexpressing mice. Angiotensin-converting enzyme four-copy mice showed higher ACE activity in kidney and plasma with low levels in hypothalamus. In hypothalamus from NEP,/, mice, generation of Ang(1,7) from Ang I was decreased, suggesting a role for NEP in Ang metabolism. With Ang II as substrate, there was no difference between NEP,/, and wild-type control mice, indicating that other enzymes may contribute to generation of Ang(1,7). The data suggest a predominant role of hypothalamic ACE2 in the processing of Ang II, in contrast to ACE, which is most active in plasma. [source] Micropatterning: Patterned Hydrogels for Controlled Platelet Adhesion from Whole Blood and Plasma (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Mater. Poly(ethylene glycol)-based hydrogel coatings patterned with selected proteins can be utilized to control and study the adhesion of human blood platelets with excellent precision, as presented by B. Liedberg et al. on page 2396. This frontispiece shows how imaging surface plasmon resonance is used in combination with fluorescence microscopy to investigate the platelet adhesion process in undiluted blood plasma. [source] Patterned Hydrogels for Controlled Platelet Adhesion from Whole Blood and PlasmaADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Tobias Ekblad Abstract This work describes the preparation and properties of hydrogel surface chemistries enabling controlled and well-defined cell adhesion. The hydrogels may be prepared directly on plastic substrates, such as polystyrene slides or dishes, using a quick and experimentally simple photopolymerization process, compatible with photolithographic and microfluidic patterning methods. The intended application for these materials is as substrates for diagnostic cell adhesion assays, particularly for the analysis of human platelet function. The non-specific adsorption of fibrinogen, a platelet adhesion promoting protein, is shown to be completely inhibited by the hydrogel, provided that the film thickness is sufficient (>5,nm). This allows the hydrogel to be used as a matrix for presenting selected bioactive ligands without risking interference from non-specifically adsorbed platelet adhesion factors, even in undiluted whole blood and blood plasma. This concept is demonstrated by preparing patterns of proteins on hydrogel surfaces, resulting in highly controlled platelet adhesion. Further insights into the protein immobilization and platelet adhesion processes are provided by studies using imaging surface plasmon resonance. The hydrogel surfaces used in this work appear to provide an ideal platform for cell adhesion studies of platelets, and potentially also for other cell types. [source] Lamotrigine pharmacokinetic/pharmacodynamic modelling in ratsFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 6 2005M.M. Castel-Branco Abstract The aim of this study was to perform a pharmacokinetic/pharmacodynamic (PK/PD) modelling of lamotrigine following its acute administration to rats. Adult male Wistar rats were given 10 mg/kg of lamotrigine intraperitoneally. Plasma and brain samples were obtained at predetermined times over 120 h post-dose and analysed by liquid chromatography. The anticonvulsant profile against maximal electroshock seizure stimulation was determined over 48 h after dosing. As a linear relationship between lamotrigine plasma and brain profiles was observed, only the plasma data set was used to establish the PK/PD relationship. To fit the effect,time course of lamotrigine, the PK/PD simultaneous fitting link model was used: the pharmacokinetic parameters and dosing information were used in the one-compartment first-order model to predict concentrations, which were then used to model the pharmacodynamic data with the sigmoid Emax model, in order to estimate all the parameters simultaneously. The following parameters were obtained: Vd = 2.00 L/kg, kabs = 8.50 h,1, kel = 0.025 h,1, ke0 = 3.75 h,1, Emax = 100.0% (fixed), EC50 = 3.44 mg/L and , = 8.64. From these results, it can be stated that lamotrigine is extensively distributed through the body, its plasma elimination half-life is around 28 h and a lamotrigine plasma concentration of 3.44 mg/L is enough to protect 50% of the animals. When compared with humans, the plasma concentrations achieved with this dose were within the therapeutic concentration range that had been proposed for epileptic patients. With the present PK/PD modelling it was possible to fit simultaneously the time-courses of the plasma levels and the anticonvulsant effect of lamotrigine, providing information not only about the pharmacokinetics of lamotrigine in the rat but also about its anticonvulsant response over time. As this approach can be easily applied to other drugs, it becomes a useful tool for an explanatory comparison between lamotrigine and other antiepileptic drugs. [source] Efficiency of combined methotrexate/chloroquine therapy in adjuvant-induced arthritisFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 4 2005M.A.R.C.P. Silva Abstract The present study evaluates the effects of methotrexate (MTX) and chloroquine (CQ), and of combined MTX + CQ treatment, on the inflammatory response and on plasma and liver phosphatase and transaminase activities, employing an adjuvant-induced arthritis model in rats. Arthritis was induced by the intradermal injection of a suspension of Mycobacterium tuberculosis in mineral oil into the plantar surface of the hind paws. Development of the inflammatory response was assessed over a 21-day period. Animal groups received either: (i) MTX, administered i.p., weekly, in 0.15, 1.5, 3, 6 or 12 mg/kg doses; (ii) CQ, given intragastrically, in daily 25 or 50 mg/kg doses; or (iii) MTX + CQ, administered in two combinations (MTX1.5 mg/kg + CQ50 mg/kg, or MTX6 mg/kg + CQ50 mg/kg). At the end of the experimental period, the animals were anesthetized and killed, blood and liver samples were collected and prepared for measurement of acid and alkaline phosphatase (AP, ALP), and aspartate (AST) and alanine aminotransferase (ALT) activities. MTX at 6 and 12 mg/kg reduced the inflammatory response while CQ had no effect. MTX6 mg/kg + CQ50 mg/kg reduced the inflammatory response similar to MTX12 mg/kg, without affecting the bone marrow. Plasma AP and liver ALP activities were very elevated in the arthritic rats. While MTX treatment partially reduced both plasma AP and liver ALP activities at all doses used in the arthritic rats, CQ treatment reduced plasma AP, but increased liver AP activity. MTX + CQ treatment decreased plasma AP and liver ALP activities in the arthritic rats to control values. Plasma and liver AST activities were unaltered in the arthritic rats, and were unaffected by treatment. However, plasma and liver ALT activities were significantly reduced in the arthritic rats. While MTX or CQ treatment did not alter plasma transaminase activity in the arthritic rats, after MTX + CQ treatment, plasma ALT activity returned to normal values. In conclusion, the present data suggest that MTX + CQ treatment provides more effective anti-inflammatory protection against adjuvant-induced arthritis than does MTX alone, reverting the alterations in enzyme activities induced by this inflammatory disease in rats. 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