bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Medium Exchange Schedules on Metabolic, Growth, and GM‐CSF Secretion Rates of Genetically Engineered NIH‐3T3 Cells
Authors: Caldwell Jerry , Locey Betty , Clarke Michael F. , Emerson Stephen G. , Palsson Bernhard O.
Published: March 2005

The metabolic and secretory characteristics of NIH‐3T3 fibroblasts transfected with a cDNA encoding human granulocyte‐macrophage colony stimulating factor (GM‐CSF) were examined as a function of the culture medium exchange schedule. The rates of glucose and glutamine consumption and of lactate and ammonia production were measured over exchange schedules ranging from complete medium replacement weekly (1/week) to complete medium replacement daily (7/week). All measured metabolic rates increased with increased medium exchange rates and accelerated sharply between exchange rates of 3.5/week and 7/week. The lactate/glucose and ammonia/glutamine yield coefficients, however, remained invariant at about 1.9 and 1.0 mol/mol, respectively, under all medium perfusion conditions. A shift‐up in medium perfusion rates from 3.5/week to 7/week resulted in increased metabolic rates that resembled those observed in the cultures that were exchanged at the 7/week rate throughout, showing that the metabolic rates could be directly controlled by the perfusion rate. Differential regulation of medium versus serum perfusion demonstrated that increased NIH‐3T3 cell metabolism was directly proportional to the serum flux to which the cells were exposed. Thus a limiting serum component is responsible for the altered metabolic and growth rates. The GM‐CSF production by the transfected 3T3 cells was stable but exhibited substantial transient increases during periods of cell proliferation, demonstrating that the secretion of transfected gene products can be highly modulated even when the cDNA is driven from a constitutive promoter. These studies show that the metabolic and secretory behavior of genetically engineered cells is influenced by the medium exchange schedule.
Identifying Rate‐Controlling Enzymes in Metabolic Pathways without Kinetic Parameters
Authors: Delgado Javier P. , Liao James C.
Published: March 2005

The flux control coefficients, originally defined by Kacser and Burns, provide a sound theoretical basis for identifying rate‐controlling enzymes in metabolic pathways. However, the calculation of these quantities requires kinetic parameters, which are usually unavailable in practical systems. This article presents a method for evaluating the flux control coefficients by using measurements of metabolite concentrations in a transient state. The basis of this approach is the relationship identified here between transient fluxes and the flux control coefficients. Principal component analysis in the form of singular value decomposition is used to identify such relationships and evaluate the flux control coefficients. The approach does not require kinetic parameters and depends only on the knowledge of pathway stoichiometry, which is generally available.
Solubility of Globular Proteins in Polysaccharide Solutions
Authors: Guo Meining , Narsimhan Ganesan
Published: March 2005

A statistical thermodynamic model based on the lattice model proposed by Baskir et al. (1987) was employed to predict the solubilities of globular proteins such as ovalbumin and lysozyme at their isoelectric points in dextran solutions of different molecular weights. The model accounted for protein‐polysaccharide and polysaccharide‐solvent interactions as well as entropy of mixing, and it employed simplifying assumptions such as a linear homogeneous polysaccharide molecule and a spherical globular protein molecule of uniform surface properties. The protein‐polysaccharide interaction parameter χs, obtained by fitting the model to experimental data for one molecular weight of dextran, was found to be 0.132 and 0.115 for ovalbumin and lysozyme, respectively. Solubilities of ovalbumin and lysozyme in dextran solutions of different molecular weights exhibited a shallow maximum at intermediate dextran concentrations and compared well with model predictions. Protein solubility was found to be very sensitive to protein‐polysaccharide interactions and increase with more favorable protein‐polysaccharide interactions (larger χs), less favorable polysaccharide‐solvent interactions (larger χ), smaller size protein molecule, and lower molecular weight polysaccharide.
Immobilization of Escherichia coli JM103[pUC8] in κ‐Carrageenan Coupled with Recombinant Protein Release by in Situ Cell Membrane Permeabilization
Authors: Ryan Wen , Parulekar Satish J.
Published: March 2005

Immobilization of Escherichia coli JM103[pUC8] was carried out with κ‐carrageenan as the support matrix. Substantial natural excretion of β‐lactamase, attributable to the less intact membrane of plasmid‐harboring cells, was observed in immobilized cell cultures. Nevertheless, a significant portion of the β‐lactamase produced was retained in the cells. As compared to suspension cultures, much higher β‐lactamase activities, especially in the extracellular liquid, and much longer retention of plasmid‐bearing cells (improved plasmid stability) were observed in immobilized cell cultures. Further enhancement in excretion of the recombinant protein (β‐lactamase) was achieved by permeabilization of cell membrane by periodic exposure of the immobilized cell cultures to ethylenediaminetetraacetic acid (EDTA). While the presence of EDTA led to some suppression of cell growth in suspension cultures, cell growth in gel beads was not affected by EDTA to the same extent, possibly due to lesser exposure of immobilized cells to EDTA. Exposure of immobilized cell cultures to EDTA presumably inhibited plasmid replication and led in turn to diversion of cellular resources for the support of expression of plasmid genes. Indeed, treatment of the immobilized cell cultures with EDTA resulted in increased production of β‐lactamase when compared to the enzyme production in EDTA‐free cultures. More frequent addition of EDTA increased the period of retention of plasmid‐bearing cells in these cultures but did not have any noticeable adverse effect on synthesis of β‐lactamase. Improvement in plasmid stability in EDTA‐treated immobilized cell cultures was ascribed to the reduction in the growth rate differential between plasmid‐free and plasmid‐bearing cells, since plasmid‐free cells were subject to more reduction in specific growth rate than were plasmid‐bearing cells.
Convective Mass Transfer in Large Porous Biocatalysts: Plant Organ Cultures
Authors: Prince C. L. , Bringi V. , Shuler M. L.
Published: March 2005

The importance of convective contributions to the total rate of mass transfer into porous biological catalysts has been insufficiently appreciated. For liquid systems, diffusion within large particles is generally slow relative to reaction, especially for sparingly soluble nutrients such as oxygen. We report experimental evidence demonstrating that oxygen consumption within porous root culture clumps is normally restricted by the rate of convective mass transfer within the clump. Increasing liquid flow rates around spheres of entangled rootlets induces higher rates of internal convective mass transfer and gives rise to increased total rates of oxygen consumption. Minimum external velocities for full nutrient sufficiency on the interior are not predicted well by creeping external flow models and, especially for larger biocatalysts, inertial effects must be taken into account. For higher Reynolds number external flow, form drag may be used to suggest the dependence of internal convection on external flow conditions. The minimum external liquid velocity for nutrient sufficiency is then seen to be a strong and unpredictable function of catalyst size and catalyst density. Implications for organ culture reactor design are discussed.
Effect of Self‐Association on the Transport of α‐Chymotrypsin across Microporous Membranes
Authors: Zanapalidou R. H. , Domach M. M.
Published: March 2005

The dependence of the rate of α‐chymotrypsin transport across microporous, polycarbonate membranes on enzyme concentration was investigated. It was of interest to determine whether self‐association, the extent of which is concentration‐dependent, would have a significant effect on the mass transfer coefficient. When the enzyme was solubilized in pH 6.2 and I 0.2 buffer, a significant decrease in the mass transfer coefficient accompanied an increase in solute concentration. Furthermore, when the pH and ionic strength of the solvent were altered, it was found that the concentration dependence of the mass transfer coefficient reflected the degree of self‐association known to occur in the different solvents. An analysis of the potential effects of osmotic backflow and excluded volume indicates that self‐association is responsible for the observed changes in the mass transfer coefficient. From the practical standpoint, these results suggest that self‐association could be promoted in order to alter a solute's rejection coefficient, and membrane transport studies could complement the results of moving boundary and light scattering experiments.
Concentration of Spirulina Suspensions by Radial Migration with Flow Through Vertical Tees
Authors: Rakow Allen L. , Fernald Daniel
Published: March 2005

Suspensions of Spirulina platensis, a microalga, were pumped in laminar flow through vertical tubes. Reynolds numbers in the high end of the laminar regime were maintained along with sufficient length of tube in most cases to allow the particles to migrate to a region close to the tube axis. An equidiameter tee‐branch was employed to direct the dilute outer region of the flow through the branches while the central region of concentrated particles flowed on through the main channel. A 0.01 % dry mass (DM) suspension can be concentrated 100‐fold in a 650‐μm diameter system to approximately 1 % DM in the equivalent of 6 passes (the upper limit of concentration on the basis of a rod exclusion model is about 2.5% DM). The concentration factor decreases exponentially with inlet concentration ranging from a value near 3 at low inlet concentration to a value near 1 at the highest concentration tested to date.
Catalytic Peptide Synthesis by Trypsin Modified with Polystyrene in Chloroform
Authors: Ito Yoshihiro , Fujii Hajime , Imanishi Yukio
Published: March 2005

Trypsin was modified with a hydrophobic synthetic polymer, polystyrene. The attachment was achieved by first coupling free amines in the trypsin with azobis(4‐cyanovaleric acid) and then irradiating the product in the presence of styrene. Decomposition of the azo structure provided free radical initiation of styrene polymerization, with the trypsin thus becoming part of the end group for the polymer chain initiated. That the modified trypsin retained catalytic activity when dissolved in chloroform was demonstrated by using it to catalyze the formation of a peptide linkage between amino acids. The catalytic reaction was stereoselective.
Fractional Factorial Study of Hybridoma Behavior. 2. Kinetics of Nutrient Uptake and Waste Production
Authors: Gaertner John G. , Dhurjati Prasad
Published: March 2005

A fractional factorial experimental method was used to identify important variables and variable interactions which affect nutrient uptake and waste production. The variables studied include glucose, glutamine, base medium, lactate, and ammonium. Cellular glucose uptake was stimulated by glucose and glutamine and inhibited by lactate. Glucose, base medium, and glutamine all had large stimulative effects on lactate production. Glucose uptake and lactate production both exhibited Monod‐type dependencies on the glucose concentration. Ammonium production was sensitive to the glucose and lactate concentrations at levels below about 8 and 20 mM, respectively. Mathematical descriptions of glucose uptake and of lactate and ammonium production were developed. These experimental results have significant implications for the optimization of hybridoma growth in bioreactors.
Modeling and Simulation of Anaerobic Wastewater Treatment and Its Application to Control Design: Case Whey
Authors: Ryhiner Gerhard B. , Heinzle Elmar , Dunn Irving J.
Published: March 2005

Modeling and simulation of the anaerobic treatment of whey wastewater was studied. A model inpluding five groups of organisms, whey substrate, butyric, propionic, and acetic acids, CO2, H2, and CH4, was developed for single‐ and two‐stage anaerobic fluidized bed reactors. It included thermodynamic limitations for the acetogenesis reaction, acid‐base equilibria of dissociating compounds (organic acids and CO2) for variable and constant pH situations, gas‐liquid phase mass transfer, and measurement dynamics. The model was adequate to describe both the steady‐state and dynamic behavior of the reactors and was used to study various control schemes. In all cases the feed flow rate was the manipulated variable. Controls of pH, dissolved hydrogen, and organic acids were all successful in simulation and experiment. Simulations were used to determine optimal control parameters for conventional proportional—integral (PI) or proportional—integral—differential (PID) control. The experimentally found optimal values were in close agreement with predetermined simulated values. Simple control using gas analysis results did not give stable control, either in the simulation or in the experiment.
A Computer Model Based on Reaction‐Diffusion Equations for the Growth of Filamentous Fungi on Solid Substrate
Authors: Molin Paul , Gervais Patrick , Lemiere Jean‐Pierre
Published: March 2005

A model of two reaction‐diffusion equations for biomass production and glucose consumption was developed. Experiments were carried out in order to estimate the different constants of the model and to compare the behavior of the system using two species of fungi, Rhizopus oligosporus and Trichoderma viride T.S. A mathematical study of the equations was performed. The model provides good predictive values, and the parameters have a precise biological significance. From the study of the phase plane biomass‐glucose, in the case of Rhizopus oligosporus the existence of a secondary metabolism for the growth when glucose consumption is almost complete is proposed.
Modeling of Isotope Distributions and Intracellular Fluxes in Metabolic Networks Using Atom Mapping Matrices
Authors: Zupke C. , Stephanopoulos G.
Published: March 2005

The modeling of isotope distributions can be used to evaluate intracellular fluxes and to investigate cellular metabolism. A method of modeling isotope distributions in biochemical networks that addresses some of the shortcomings of conventional methods is presented. Matrix equations representing steady state isotope balances are formulated for each metabolite and solved iteratively via computer. The key feature of this method is the use of atom mapping matrices, which decouple the generation of the steady state equations from the details of the transfer of carbon atoms from reactants to products. The use of atom mapping matrices results in a clear, intuitive description of metabolic networks that is easy to develop, check, and modify. A network representing energy metabolism in a hybridoma cell line was developed and presented as an example of the method. A program that uses the atom mapping matrix method to calculate the isotope distribution in the network as a function of the intracellular fluxes was written. Calculations showed that a single nuclear magnetic resonance (NMR) experiment with 13C‐labeled glucose should be able to uniquely determine two important TCA cycle flux ratios. These results demonstrate how in vitro NMR can be used to study cellular metabolism or to validate the flux estimates obtained from other methods.
A Mathematical Model To Predict the Partitioning of Peptides and Peptide‐Modified Proteins in Aqueous Two‐Phase Systems
Authors: Eiteman Mark A. , Hassinen Cynthia , Veide Andres
Published: March 2005

A mathematical procedure was developed to predict the partition coefficients of the peptides AIIP, AWWP, AIIPAIIP and AWWPAWWP in poly(ethylene glycol) (PEG)/ phosphate aqueous two‐phase systems from amino acid hydrophobicities. In general, peptides containing tryptophan partition more into the PEG‐enriched upper phase than analogous peptides containing isoleucine. Specifically, as the PEG concentration difference between the phases increased in a PEg/potassium phosphate aqueous two‐phase system, the peptide AIIP was observed to have a partition coefficient ranging from 1.2 to 1.6, AIIPAIIP from 2.4 to 5.7, AWWP from 13.5 to 32.2, and AWWPAWWP from 43 to 170. The model was extended to predict the partitioning of a staphylococcal protein A derivative (ZZ) modified with these four peptides. As predicted, the protein modified with isoleucine‐containing peptides had lower partition coefficients than the protein modified with tryptophan‐containing peptides. The partition coefficient of the ZZ protein ranged from 0.35 to 0.20, that of ZZAIIPAIIP from 0.58 to 0.48, and that of ZZAWWPAWWP from 3.5 to 5.3 in these systems. The results show that short peptide handles can significantly enhance the partitioning of proteins in aqueous two‐phase systems. The relationship between the model and the surface exposure of peptide handles and the utility of the model to aid in the design of such handles to enhance purifications are also discussed.
Measurement of Adhesion and Spreading Kinetics of Baby Hamster Kidney and Hybridoma Cells Using an Integrated Optical Method
Authors: Li S. ‐Y. , Ramsden J. J. , Prenosil J. E. , Heinzle E.
Published: March 2005

A novel optical method was used for quantitative characterization and continuous measurement of both the adhesion and spreading of mammalian cells on inorganic surfaces. It is based upon the effective refractive index change caused by cells when they adhere to a planar optical waveguide. We have applied this technique to measure the kinetics of the adhesion and spreading processes of baby hamster kidney (BHK) cells adhering to surfaces coated with fibronectin and under different culture conditions (PBS, medium, serum, EDTA). In comparison, hybridoma cells are only adsorbed to the surface and do not spread at all. Moreover, this technique also allows the mass of an adsorbed protein adlayer to be determined very precisely and thus provides a valuable tool for screening suitable substrata as well as determining the influence of different culture conditions on cell adhesion and spreading. This sensitive test for substrate influence could be important in toxicity tests using adherent animal cells.
Dynamic Mixing and Oxygen Transfer in Small, Airlift Loop Bioreactors: Model and Experimental Verification
Authors: Fraser Randall D. , Ritchie Brian J. , Hill Gordon A.
Published: March 2005

A mechanistic model for mixing and mass transfer in both airlift bubble column and loop bioreactors is described. The model is a useful design tool to improve oxygen‐transfer characteristics. It is shown that the model fits mixing and mass‐transfer experimental data closely. The model confirms that the overall oxygen‐transfer coefficient in the riser of a loop airlift fermentor is similar to that in bubble columns and that lower measured transfer rates are due solely to the dead volume in the downcomer. The effects of parameters such as mass‐transfer coefficient, aeration rate, dispersion coefficient, sparger rotation speed, and liquid circulation velocity are presented in terms of both the liquid‐ and gas‐phase oxygen concentrations.
NDVI‐indicated decline in desertification in China in the past two decades
Authors: Piao Shilong , Fang Jingyun , Liu Hongyan , Zhu Biao
Published: March 2005

In this study, we explore the trend in desertification in China from 1982 to 1999 by investigating the changes in area and normalized difference vegetation index (NDVI) of arid and semiarid regions, using NDVI time series data sets and climatic variables. We use Thornthwaite moisture index (Im) to define the arid and semiarid region as Im ≤ −40 and −40 < Im ≤ −20, respectively. Rainy season NDVI (May to October NDVI) increased in most areas of arid and semiarid regions over the past two decades, accounting for 72.3% and 88.2% of total area of arid and semiarid regions, respectively. Compared to that in the early 1980s, the area of arid and semiarid regions decreased by 23 × 104 km2 (6.9%) and 7 × 104 km2 (7.9%) by the end of the 1990s, suggesting a reversal of desertification processes in these two climate regions. Transformation from warm‐arid to warm‐wet climate and weakened disturbance from human activities may be the major causes of this declined trend.
Interannual temperature variability in the tropical Pacific and Lagrangian heat transport pathways
Authors: Holland Christina L. , Mitchum Gary T.
Published: March 2005

In a previous study we found that volume variability during an El Niño–Southern Oscillation (ENSO) event is well described by variations in, and redistribution of, the heat content for any given region within the tropical Pacific. In this study we use numerical model temperature and velocity fields in a Lagrangian analysis of heat content variability. These three‐dimensional fields are used to examine specific warm and cool anomaly regions by computing trajectories back through time to the origins of the anomalously warm or cool water. In particular, we find that three distinct pathways are important in creating and maintaining the warm eastern equatorial anomaly, including pathways in the basin interior in both hemispheres. After this warm anomaly at peak ENSO, off‐equatorial anomalies form both in the eastern Pacific and in the far western Pacific. The west Pacific off‐equatorial cool anomalies are attributed to ENSO variations in the Ekman pumping in those regions.
Short‐timescale thermohaline variability and residual circulation in the central segment of the coastal upwelling system of the Ría de Vigo (northwest Spain) during four contrasting periods
Authors: Piedracoba S. , Álvarez‐Salgado X. A. , Rosón G. , Herrera J. L.
Published: March 2005

Sixteen hydrographic surveys were carried out in the middle segment of the Ría de Vigo (northwest Spain) at 3‐ to 4‐day intervals during February, April, July, and September 2002 (four surveys per period). Simultaneously, an acoustic Doppler current profiler (ADCP) mooring recorded the velocity profile. Combination of direct current measurements with the output of an inverse model based on the time course of the distributions of salinity and temperature allowed an objective analysis of the effect of the meteorological forces on the hydrodynamics of the Ría. Remote shelf winds explained more than 65% of the variability of the subtidal circulation, which responded immediately to this forcing (lag time, <2 days). Shelf winds created a simple two‐layered circulation pattern, with a surface outgoing current under northerly winds and a surface ingoing current under southerly winds. A three‐layered circulation developed during the transitions from northerly to southerly winds and vice versa. At the same time, an empirical orthogonal function (EOF) analysis demonstrated the lack of contribution of local winds to the subtidal dynamics of the ría. Continental runoff and heat exchange with the atmosphere explained less than 5% and 25% of the variability observed in the subtidal circulation of the Ría de Vigo.
Pathology of Monin‐Obukhov similarity in the stable boundary layer
Authors: Cheng Yinguo , Parlange Marc B. , Brutsaert Wilfried
Published: March 2005

The performance of Monin‐Obukhov similarity (MOS) theory has been investigated for four types of events of transient physical processes in the stable nocturnal boundary layer during the Cooperative Atmosphere‐Surface Exchange Study‐99 (CASES‐99). These four types were internal gravity waves, Kelvin‐Helmholtz (K‐H) shear instability, a density current, and a low‐level jet. It was found that the MOS theory generally holds whenever a new equilibrium is reached or recovered during or after these events but fails in the period of transition or the developing stage of the events with newly generated turbulence. Specifically, MOS was found to hold during the entire process of the nonbreaking internal gravity waves and during the well‐developed stages both of the density current and of the low‐level jet. It was found not valid during the process of the K‐H instability and the developing stages of the density current. Characteristic features of these four types of events are also presented and analyzed.
Extending the SeaWiFS chlorophyll data set back 50 years in the northeast Atlantic
Authors: Raitsos Dionysios E. , Reid Philip C. , Lavender Samantha J. , Edwards Martin , Richardson Anthony J.
Published: March 2005

Phytoplankton play a key role in biogeochemical cycling and climate processes. Precise quantitative measurements of chlorophyll‐a (Chl‐a), a measure of phytoplankton biomass, have only been available globally since 1997 from the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS). In the North Atlantic, semi‐quantitative measurements of chlorophyll (Phytoplankton Color Index, PCI) for >50 years have been collected by the Continuous Plankton Recorder. Here we demonstrate a significant correlation between PCI and SeaWiFS Chl‐a from 1997–2002. Combining both time series allows quantification of the stepwise increase in biomass in the mid‐1980s; this regime shift corresponded to a 60% increase in Chl‐a. This was a result of an 80% increase in Chl‐a during winter, alongside a smaller summer increase. This new high‐resolution data set on the monthly variation of Chl‐a in the North Atlantic since 1948 is now available for the development and validation of climate models, and for interpretation of ecological changes related to climate.
Highly localized strain fields due to planar defects in epitaxial SrBi2Nb2O9 thin films
Authors: Boulle A. , Guinebretière R. , Dauger A.
Published: March 2005

Thin films of (00l) oriented SrBi2Nb2O9 epitaxially grown on SrTiO3 by sol-gel spin coating have been studied by means of high-resolution x-ray diffraction reciprocal space mapping. It is shown that these materials contain highly localized heterogeneous strain fields due to imperfect stacking faults (i.e., faults that do not propagate throughout the crystallites building up the film). In the film plane, the strain fields are confined to 11 nm wide regions and characterized by a vertical displacement of 0.18c (where c is the cell parameter) showing that the stacking faults are mainly composed of one additional (or missing) perovskite layer. Prolonged thermal annealing at 700 °C strongly reduces the density of stacking faults and yields a more uniform strain distribution within the film volume without inducing significant grain growth.
Short-range magnetic correlation with Kondo-lattice behavior in Ce3Ir2Ge2 and superconductivity in La3Ir2Ge2
Authors: Li D. X. , Nimori S. , Homma Y. , Shiokawa Y. , Tobo A. , Onodera H. , Haga Y. , Onuki Y.
Published: March 2005

We present the results of the magnetic susceptibility, magnetization, specific-heat, and electrical resistivity measurements on rare-earth iridium germanides Ce3Ir2Ge2 and La3Ir2Ge2, crystallizing in the La3Ni2Ga2-type orthorhombic crystal structure. The results reveal that Ce3Ir2Ge2 is a Kondo-lattice system showing characteristic −lnT dependence of magnetic resistivity at high temperatures, while there does not exist evident sign of long-range magnetic ordering at least down to 1.8 K. Instead, a short-range magnetic correlation occurs at about 3.5 K. The La-based compound was found to be a type-II superconducting material with a relatively high critical temperature TC=4.7K. A number of the relevant parameters, such as lower critical field, upper critical field, coherence length, penetration depth, and Ginzburg–Landau parameter, were estimated for the La3Ir2Ge2 sample.
Optical defect centers and surface morphology of isotopically enriched diamond layers in designer diamond anvils
Authors: Peterson Randolph S. , Baker Paul A. , Catledge Shane A. , Vohra Yogesh K. , Weir Samuel T.
Published: March 2005

We have studied optical defect centers and surface morphology of isotopically enriched layers grown on diamond anvils by microwave plasma chemical vapor deposition for applications as designer diamond anvils in high-pressure diamond anvil cell devices. Various mixtures of methane isotopes were used to grow homoepitaxial diamond with C13 molar fractions of 0.01, 0.41, 0.83, and 0.99 as determined from Raman spectroscopy. Defect centers were studied at temperatures between 80 and 320K using micro-photoluminescence (PL) spectroscopy with an argon ion and krypton laser excitation source. The defect spectra were dominated by zero phonon lines (ZPL) from nitrogen-related defect centers at nominal energies of 1.945eV (640nm defect) and 2.156eV (575nm defect), especially for the non-(100) surfaces. Polished (100) surfaces fluoresced weakly. ZPL’s at 1.77 and 1.68eV are observed, but not for all isotopically mixed samples. The 1.77eV ZPL appears to be associated from the original diamonds, while the 1.68eV ZPL is known to originate with silicon-based defects. Atomic force microscopy of as-grown isotopically enriched layers show rough growth steps in areas with surface roughness of hundred nanometers and smooth areas with surface roughness of few nanometers. Our studies indicate that (100) polished surfaces of isotopically enriched designer diamonds with low concentration of nitrogen defect centers can be fabricated for a variety of applications in high pressure research.
Epitaxial La0.7Sr0.3MnO3 thin films with two in-plane orientations on silicon substrates with yttria-stabilized zirconia and YBa2Cu3O7−δ as buffer layers
Authors: Goh Wei Chuan , Yao Kui , Ong C. K.
Published: March 2005

Epitaxial La0.7Sr0.3MnO3 (LSMO) thin films were fabricated on silicon substrates by pulsed laser deposition utilizing yttria-stabilized zirconia (YSZ) and YBa2Cu3O7−δ (YBCO) films as buffer layers. Structural characterization showed that the epitaxial LSMO films were (001) oriented with two in-plane orientations and exhibited a columnar growth structure. In contrast, when LSMO was deposited directly on the YSZ∕Si substrate without the YBCO template layer, it was characterized as a mixture of randomly oriented polycrystalline grains and (001)-oriented grains, without the columnar growth structure. The role of the YBCO layer for achieving the c-axis-oriented epitaxial LSMO film by introducing the dual-in-plane orientation mechanism on the YSZ∕Si substrate has been analyzed. In addition, it was found that the LSMO film with the dual-in-plane orientations on the YBCO∕YSZ∕Si substrate exhibited a much lower resistivity compared to the LSMO film directly deposited on the YSZ∕Si substrate. This effect is attributed to the existence of the randomly oriented grains in the latter, which resulted in more significant electron scattering at the grain boundaries. The higher density of grain boundaries in the LSMO film on YSZ∕Si also led to a substantially higher magnetoresistance.
Microstructure and exchange coupling in nanocrystalline Nd2(FeCo)14B∕α-FeCo particles produced by spark erosion
Authors: Tang Y. J. , Parker F. T. , Harper H. , Berkowitz A. E. , Vecchio K. , Rohatgi A. , Ma Bao-Min
Published: March 2005

Exchange spring magnet particles of Nd2(FeCo)14B∕α-FeCo were prepared by spark erosion. X-ray diffraction and Mössbauer studies showed that the particles are composed of about ∼85vol% of Nd2(FeCo)14B and ∼13vol% of α-FeCo with negligible other phases. No oxide was found in these particles. Transmission electron micrographs indicated that the grain sizes of the Nd2(FeCo)14B and α-FeCo phases are ∼10–50nm, and are compatible with effective exchange coupling between the hard and soft phases. The intergrain exchange coupling was also observed in ΔM measurements.
Formation of nanosized BaIrO3 precipitates and their contribution to flux pinning in Ir-doped YBa2Cu3O7−δ quasi-multilayers
Authors: Hänisch J. , Cai C. , Hühne R. , Schultz L. , Holzapfel B.
Published: March 2005

Structural and transport measurements for quasimultilayers of Ir-doped YBa2Cu3O7−δ prepared by pulsed-laser deposition are presented. Due to metallic Ir doping, BaIrO3 particles form during film growth. These nanosized particles, having a perovskite structure, grow epitaxially in cube-on-cube relationship inside the film. A strong increase in pinning force density and, hence, Jc was found.
A New Synthesis for Antifungal α-Sulfone Disulfides
Authors: Langler Richard Francis , McNamara Robert Antle , O'Connor Paul Eric , MacQuarrie Stephanie Lee
Published: March 2005

An α-ester disulfide is shown to be a useful precursor for the
preparation of several α-sulfone disulfides. These new α-sulfone
disulfides are all fungitoxic against Aspergillus niger
and Aspergillus flavus.
RSO2CH2SSCH9
Parathyroid hormone decreases renal vitamin D receptor expressionin vivo
Authors: Healy Kevin D. , Vanhooke Janeen L. , Prahl Jean M. , DeLuca Hector F.
Published: March 2005

The vitamin D receptor (VDR) is a nuclear transcription factor responsible for mediating the biological activities of 1,25-dihydroxyvitamin D3[1,25(OH)2D3]. Renal and parathyroid gland VDR content is an important factor in calcium homeostasis, vitamin D metabolism, and the treatment of secondary hyperparathyroidism and renal osteodystrophy. In these tissues, VDR expression is highly regulated by the calcium and vitamin D status. Although 1,25(OH)2D3up-regulates VDR expression, hypocalcemia and vitamin D deficiency result in drastically reduced expression of the receptor. The generation of 25-hydroxyvitamin D3-1α-hydroxylase-null mice, which are incapable of endogenously producing 1,25(OH)2D3, has allowed us to investigate the influence of parathyroid hormone (PTH) on VDR expression independent of PTH-mediated increases in 1,25(OH)2D3. Administration of human PTH (1-34) (110 μg/kg per day) for 48 h reduced renal VDR levels from 515 to 435 fmol/mg protein (15%,P< 0.03) in wild-type mice. In the 25-hydroxyvitamin D3-1α-hydroxylase-null mice, PTH administration strongly reduced renal VDR levels, from 555 to 394 fmol/mg protein (29%,P< 0.001). These results demonstrate that PTH is a potent down-regulator of VDR expressionin vivo.
Effects of Skin Pigmentation on Pulse Oximeter Accuracy at Low Saturation
Authors: Bickler Philip E. , Feiner John R. , Severinghaus John W.
Published: March 2005

Background

It is uncertain whether skin pigmentation affects pulse oximeter accuracy at low HbO2 saturation.

Methods

The accuracy of finger pulse oximeters during stable, plateau levels of arterial oxygen saturation (Sao2) between 60 and 100% were evaluated in 11 subjects with darkly pigmented skin and in 10 with light skin pigmentation. Oximeters tested were the Nellcor N-595 with the OxiMax-A probe (Nellcor Inc., Pleasanton, CA), the Novametrix 513 (Novametrix Inc., Wallingford, CT), and the Nonin Onyx (Nonin Inc., Plymouth, MN). Semisupine subjects breathed air-nitrogen-carbon dioxide mixtures through a mouthpiece. A computer used end-tidal oxygen and carbon dioxide concentrations determined by mass spectrometry to estimate breath-by-breath Sao2, from which an operator adjusted inspired gas to rapidly achieve 2- to 3-min stable plateaus of desaturation. Comparisons of oxygen saturation measured by pulse oximetry (Spo2) with Sao2 (by Radiometer OSM3) were used in a multivariate model to determine the interrelation between saturation, skin pigmentation, and oximeter bias (Spo2 - Sao2).

Results

At 60-70% Sao2, Spo2 (mean of three oximeters) overestimated Sao2 (bias +/- SD) by 3.56 +/- 2.45% (n = 29) in darkly pigmented subjects, compared with 0.37 +/- 3.20% (n = 58) in lightly pigmented subjects (P < 0.0001). The SD of bias was not greater with dark than light skin. The dark-light skin differences at 60-70% Sao2 were 2.35% (Nonin), 3.38% (Novametrix), and 4.30% (Nellcor). Skin pigment-related differences were significant with Nonin below 70% Sao2, with Novametrix below 90%, and with Nellcor at all ranges. Pigment-related bias increased approximately in proportion to desaturation.

Conclusions

The three tested pulse oximeters overestimated arterial oxygen saturation during hypoxia in dark-skinned individuals.
Classic Benzodiazepines Modulate the Open–Close Equilibrium in α1β2γ2Lγ-Aminobutyric Acid Type A Receptors
Authors: Rüsch Dirk , Forman Stuart A.
Published: March 2005

Background

Classic benzodiazepine agonists induce their clinical effects by binding to a site on gamma-aminobutyric acid type A (GABAA) receptors and enhancing receptor activity. There are conflicting data regarding whether the benzodiazepine site is allosterically coupled to gamma-aminobutyric acid binding versus the channel open-close (gating) equilibrium. The authors tested the hypothesis that benzodiazepine site ligands modulate alpha1beta2gamma2L GABAA receptor gating both in the absence of orthosteric agonists and when the orthosteric sites are occupied.

Methods

GABAA receptors were recombinantly expressed in Xenopus oocytes and studied using two-microelectrode voltage clamp electrophysiology. To test gating effects in the absence of orthosteric agonist, the authors used spontaneously active GABAA receptors containing a leucine-to-threonine mutation at residue 264 on the alpha1 subunit. To examine effects on gating when orthosteric sites were fully occupied, they activated wild-type receptors with high concentrations of a partial agonist, piperidine-4-sulfonic acid.

Results

In the absence of orthosteric agonists, the channel activity of alpha1L264Tbeta2gamma2L receptors was increased by diazepam and midazolam and reduced by the inverse benzodiazepine agonist FG7142. Flumazenil displayed very weak agonism and blocked midazolam from further activating mutant channels. In wild-type receptors activated with saturating concentrations of piperidine-4-sulfonic acid, midazolam increased maximal efficacy.

Conclusions

Independent of orthosteric site occupancy, classic benzodiazepines modulate the gating equilibrium in alpha1beta2gamma2L GABAA receptors and are therefore allosteric coagonists. A Monod-Wyman-Changeux coagonist gating model quantitatively predicts these effects, suggesting that benzodiazepines minimally alter orthosteric ligand binding.
Efficacy and Safety of Single and Repeated Administration of 1 Gram Intravenous Acetaminophen Injection (Paracetamol) for Pain Management after Major Orthopedic Surgery
Authors: Sinatra Raymond S. , Jahr Jonathan S. , Reynolds Lowell W. , Viscusi Eugene R. , Groudine Scott B. , Payen-Champenois Catherine
Published: March 2005

Background

Intravenous acetaminophen injection (paracetamol) is marketed in Europe for the management of acute pain. A repeated-dose, randomized, double-blind, placebo-controlled, three-parallel group study was performed to evaluate the analgesic efficacy and safety of intravenous acetaminophen as compared with its prodrug (propacetamol) and placebo. Propacetamol has been available in many European countries for more than 20 yr.

Methods

After orthopedic surgery, patients reporting moderate to severe pain received either 1 g intravenous acetaminophen, 2 g propacetamol, or placebo at 6-h intervals over 24 h. Patients were allowed "rescue" intravenous patient-controlled analgesia morphine. Pain intensity, pain relief, and morphine use were measured at selected intervals. Safety was monitored through adverse event reporting, clinical examination, and laboratory testing.

Results

One hundred fifty-one patients (intravenous acetaminophen: 49; propacetamol: 50; placebo: 52) received at least one dose of study medication. The intravenous acetaminophen and propacetamol groups differed significantly from the placebo group regarding pain relief from 15 min to 6 h (P < 0.05) and median time to morphine rescue (intravenous acetaminophen: 3 h; propacetamol: 2.6 h; placebo: 0.8 h). Intravenous acetaminophen and propacetamol significantly reduced morphine consumption over the 24-h period: The total morphine doses received over 24 h were 38.3 +/- 35.1 mg for intravenous acetaminophen, 40.8 +/- 30.2 mg for propacetamol, and 57. 4 +/- 52.3 mg for placebo, corresponding to decreases of -33% (19 mg) and -29% (17 mg) for intravenous acetaminophen and propacetamol, respectively. Drug-related adverse events were reported in 8.2%, 50% (most of them local), and 17.3% of patients treated with intravenous acetaminophen, propacetamol, and placebo, respectively.

Conclusion

Intravenous acetaminophen, 1 g, administered over a 24-h period in patients with moderate to severe pain after orthopedic surgery provided rapid and effective analgesia and was well tolerated.
Pseudomonas pachastrellae sp. nov., isolated from a marine sponge
Authors: Romanenko Lyudmila A. , Uchino Masataka , Falsen Enevold , Frolova Galina M. , Zhukova Natalia V. , Mikhailov Valery V.
Published: March 2005

Two Gram-negative, non-fermentative, non-denitrifying, non-pigmented, rod-shaped bacteria that were motile by means of polar flagella, designated strains KMM 330T and KMM 331, were isolated from a deep-sea sponge specimen and subjected to a polyphasic taxonomic study. The new isolates exhibited 16S rRNA gene sequence similarity of 99·9 %, and their mean level of DNA–DNA relatedness was 82 %. Phylogenetic analysis based on their 16S rRNA gene sequences placed the strains within the genus Pseudomonas as an independent deep clade. Strain KMM 330T shared highest sequence similarity (96·3 %) with each of Pseudomonas fulva NRIC 0180T, Pseudomonas parafulva AJ 2129T and Pseudomonas luteola IAM 13000T; sequence similarity to other recognized species of the genus Pseudomonas was below 95·7 %. The marine sponge isolates KMM 330T and KMM 331 could be distinguished from the other recognized Pseudomonas species based on a unique combination of their phenotypic characteristics, including growth in 8 or 10 % NaCl, the absence of pigments, the inability to denitrify and lack of carbohydrate utilization. On the basis of phylogenetic analysis, physiological and biochemical characterization, strains KMM 330T and KMM 331 should be classified as a novel species of the genus Pseudomonas, for which the name Pseudomonas pachastrellae sp. nov. is proposed. The type strain is KMM 330T (=JCM 12285T=NRIC 0583T=CCUG 46540T).
Occurrence and Antibiotic Resistance of Mesophilic Aeromonas in Three Riverine Freshwaters of Marrakech, Morocco
Authors: Imziln Boujamaa
Published: March 2005

I n order to evaluate the impact of pollution and sewage on the occurrence and antibiotic resistance of mesophilic aeromonads in riverine freshwaters of Marrakech, samples were collected from three rivers (Oukaimeden, Ourika, and Tensift) upstream and downstream from the principal bordering villages. During a 2-year study, indicators of pollution increased dramatically in the downstream waters. Bacterial indicators (faecal coliforms and faecal streptococci) correlated with mesophilic aeromonads only in heavily polluted waters. In low and moderately polluted sources, densities of mesophilic aeromonads were independent of water quality indicators and did not correlate statistically with faecal indicators. Average counts of Aeromonas in low and heavily polluted waters were 2.5 × 103 and 2.1 × 106 colony forming units per 100 ml, respectively. The biochemical identification of 841 isolates indicated a predominance of A. caviae in heavily and moderately polluted water and sediment. A. hydrophila was dominant only in low polluted waters and when the temperature was below 12°C. High densities of A. sobria were found in low, moderately polluted, or cleaned waters and when the water temperature was above 18°C. All selected isolates (total = 841) were tested for antibiotic susceptibility against 21 antibiotics. Antibiotic resistance frequencies recorded were: ampicillin and amoxicillin, 100%; novobiocin, 96%; cefalotin, 81%; colistin, 72%; sulfamethoxazole, 40%; cefamandole, 37%; polymyxin B, 23%; trimethoprim, 17%; erythromycin, 15%; streptomycin, 8%; amoxicillin-clavulanate, 5%. Resistance to cefotaxime, kanamycin, gentamycin, chloramphenicol, tetracycline, oxytetracycline, nalidixic acid, rifampicin, or trimethoprim-sulfamethoxazole was found to be <5%. Antibiotic resistance rates did vary according to the source of a strain’s isolation, and high numbers of antibiotic resistant strains were recorded in polluted samples. Since no correlation between mesophilic aeromonads and conventional faecal pollution indicators was observed in low or moderately polluted waters, and since these freshwaters are used for domestic supply, we propose the use of mesophilic aeromonads as complementary water pollution indicators to ensure the safety of water.
Heat Shock Protein 70 Neutralizes Apoptosis-Inducing Factor
Authors: Kroemer Guido
Published: March 2005

Programmed cell death (apoptosis) is the physiological process responsible for the demise of superfluous, aged, damaged, mutated, and ectopic cells. Its normal function is essential both for embryonic development and for maintenance of adult tissue homeostasis. Deficient apoptosis participates in cancerogenesis, whereas excessive apoptosis leads to unwarranted cell loss accounting for disparate diseases including neurodegeneration and AIDS. One critical step in the process of apoptosis consists in the permeabilization of mitochondrial membranes, leading to the release of proteins which normally are secluded behind the outer mitochondrial membrane[1]. For example, cytochrome c, which is normally confined to the mitochondrial intermembrane space, is liberated from mitochondria and interacts with a cytosolic protein, Apaf-1, causing its oligomerization and constitution of the so-called apoptosome, a protein complex which activates a specific class of cysteine proteases, the caspases[2]. Another example concerns the so-called apoptosis-inducing factor (AIF), another mitochondrial intermembrane protein which can translocate to the nucleus where it induces chromatin condensation and DNA fragmentation[3].
Pesticides Are Involved With Population Declines of Amphibians in the California Sierra Nevadas
Authors: Sparling Donald W. , Fellers Gary , McConnell Laura
Published: March 2005

Several species of frogs and toads are in serious decline in the Sierra Nevada Mountains of California. These species include the threatened red-legged frog (Rana aurora), foothill yellow-legged frog (R. boylii), mountain yellow-legged frog (R. muscosa), Cascades frog (Rana cascadae), western toad (Bufo boreas) and Yosemite toad (B. canorus). For many of these species current distributions are down to 10% of historical ranges [1,2]. Several factors including introduced predators [3,4,5], habitat loss [2], and ultraviolet radiation [6] have been suggested as causes of these declines. Another probable cause is air-borne pesticides from the Central Valley of California. The Central Valley, especially the San Joaquin Valley, is a major agricultural region where millions of pounds of active ingredient pesticides are applied each year (http://www.cdpr.ca.gov/dprdatabase.htm). Prevailing westerly winds from the Pacific Coast transport these pesticides into the Sierras [7,8].
Gene Silencing and Antigenic Variation in Malaria Parasites
Authors: Deitsch Kirk W.
Published: March 2005

Malaria remains one of the most important infectious diseases in the world today, infecting 300 to 500 million people yearly and resulting in 1 to 2 million deaths, primarily of young African children[1]. The most severe form of this disease is caused by infection with the mosquito borne protozoan parasite Plasmodium falciparum. This parasite lives by invading and multiplying within the red blood cells of its host, causing disease through anemia resulting from red cell destruction, and also through modifications made to the surface of infected red cells. These modifications make infected cells cytoadherent or “sticky”, allowing them to adhere to the walls of blood vessels, leading to obstruction of blood flow and such clinical manifestations as the often fatal syndrome of cerebral malaria[2]. In addition, parasites are capable of undergoing antigenic variation, a process of continually changing the identity of proteins on the surface of infected cells and thus avoiding the immune response mounted by the host[3]. This process promotes a long term, persistent infection that is difficult to clear.