bluuebunny/crossref_metadata_2025 huggingface dataset:
The critical period for ethanol effects on cholinergic neuronal expression in neuroblast‐enriched cultures derived from 3‐day‐old chick embryo: NGF ameliorates the cholinotoxic effects of ethanol
Authors: Rahman Hafeez , Kentroti Susan , Vernadakis Antonia
Published: April 2003

Studies from our laboratory have established that ethanol exerts morphological and biochemical neurotoxic effects during early neuroembryogenesis in the chick brain both in ovo and in culture. In the present study, we further localized the critical period for ethanol effects on cholinergic neuronal expression using neuroblast‐enriched cultures derived from 3‐day‐old chick embryos. Moreover, we report that NGF attenuated the cholinotoxic effects of ethanol. We used the following experimental paradigms: cultures treated with ethanol alone either C0‐C3 or C4‐C10; NGF alone CO‐C4 or C4‐C10; ethanol and NGF given concomitantly; ethanol given first then replaced with NGF in the medium; or NGF given first then replaced with ethanol in the medium. The results revealed: (1) the cholinotoxic effect of ethanol occurs between culture days CO and C4 with day 3 appearing to be most critical. (2) similarly, the critical period for the cholinotoxic effects of NGF is during early neuroblast differentiation, culture days CO‐C4. (3) NGF can prevent the cholinotoxic effects of ethanol only if both ethanol and NGF are given concomitantly or if ethanol is given first, then culture is replaced with NGF‐containing medium.
Pattern of polyamines and related monoacetyl derivatives in chick embryo retina during development
Authors: Taibi G. , Schiavo M.R. , Calvaruso G. , Tesoriere G.
Published: April 2003

Polyamines and related monoacetyl derivatives were studied in chick embryo retina during development (6th–19th day). Putrescine, which is high in the first phase of retinogenesis, is necessary to sustain both tissue proliferation and via N‐acetylputrescine, γ‐aminobutyric acid synthesis. A later increase in spermidine and particularly spermine may play a role in the last phase of development when the retina reaches maturation. The presence of N‐acetylspermidine already at the 8th day indicates that in chick embryo retina, putrescine synthesis can depend on two separate pathways. The first involves ornithine decarboxylase activity; the second, spermidine/spermine N1‐acetlytransferase and probably polyamine oxidase that converts spermidine to putrescine via N1‐acetylspermidine.
Development of glutamate‐stimulated phosphatidylinositol metabolism in primary neuronal and astrocyte cultures
Authors: DeCoster Mark A. , Yourick Debra L.
Published: April 2003

It was the purpose of the present study to evaluate glutamate‐stimulated phosphatidylinositol metabolism in primary mixed astrocyte/neuron and neuron‐enriched cortical cultures through different stages of development in vitro. Glutamate (0–200 μM) stimulated inositol phosphate accumulation in a concentration‐dependent fashion at 6, 13 and 20 days in vitro. Pure astrocyte cultures exhibited glutamate‐stimulated phosphatidylinositol hydrolysis only at high concentrations (100–400 μM), indicating that these cells contribute little to the overall inositol phosphate accumulation measured in mixed neuronal cultures treated with low glutamate concentrations. Comparison of mixed neuronal cultures with and without antimitotic treatment revealed that increasing astrocyte number suppressed glutamate‐stimulated responses, presumably via glutamate uptake. In contrast to previous reports, glutamate‐stimulated inositol phosphate accumulation, when expressed as a function of cell number, increased with increasing days in vitro.
Plasticity of autonomic nerves: Differential effects of long‐term guanethidine sympathectomy on the sensory innervation of the rat uterus during maturation
Authors: Brauer M.M. , Lincoln J. , Milner P. , Sarner S. , Blundell D. , Passaro M. , Corbacho A. , Burnstock G.
Published: April 2003

The sensory nerves, containing substance P and calcitonin gene‐related peptide, and noradrenaline‐containing sympathetic nerves of the rat uterus were analyzed following long‐term sympathectomy with guanethidine in prepubertal (four weeks), young adult (eight weeks) and fully adult animals (18 weeks). Immunohistochemical and histochemical methods were used in association with nerve density measurements and biochemical assays. The main findings were as follows: (1) long‐term guanethidine treatment completely abolished the noradrenergic innervation of the uterine horn and parametrial tissue and markedly reduced the tissue levels of noradrenaline in both regions at the three ages analysed; (2) in the uterine hom guanethidine treatment had no effect on the tissue levels of either calcitonin gene‐related peptide or substance P or on the density of calcitonin gene‐related peptide‐containing nerves, at any of the three ages studied; (3) in the parametrial tissue increased levels of calcitonin gene‐related peptide were observed at 8 and 18 weeks of age, together with a significant increase in the density of calcitonin gene‐related peptide‐containing nerves. Substance P levels showed a transient increase in this tissue at eight weeks. In conclusion, long‐term sympathectomy with guanethidine resulted in an increase in calcitonin gene‐related peptide and substance P in sensory nerves in the parametrial tissue, but not in the uterine horn. The changes in the parametrial tissue only occurred after puberty. It is suggested that sensory nerves in the uterine horn may be less responsive to sympathetic denervation since loss of sympathetic nerves occurs as part of a normal physiological process during pregnancy in this region.
AKT1/PKBα is recruited to lipid rafts and activated downstream of PKC isotypes in CD3‐induced T cell signaling
Authors: Bauer Birgit , Jenny Marcel , Fresser Fiedrich , Überall Florian , Baier Gottfried
Published: April 2003

Protein kinase (PK) Cθ and Akt/PKBα cooperate in T cell receptor/CD28‐induced T cell signaling. We here demonstrate the recruitment of endogenous Akt1 and PKCθ to lipid rafts in CD3‐stimulated T cells. Further we show that Myr‐PKCθ mediates translocation of endogenous Akt1 to the plasma membrane as well as to lipid rafts, most likely explained by the observed complex formation of both protein kinases. In addition, in peripheral mouse T cells, the PKC inhibitor Gö6850 could partially block Akt1 activation in CD3‐induced signaling, placing PKC isotype(s) upstream of Akt1. However, T cells derived from PKCθ knockout mice were not impaired in CD3‐ or phorbol ester‐induced Akt1 activity. Taken together, the results of this study give new insights into the functional link of Akt1 and PKCθ in T cell signaling, demonstrating the co‐recruitment of the two kinases and showing a novel pathway leading to Akt1 transactivation where PKC isotype(s) are involved but PKCθ is not essential.
Transient receptor potential (TRPC) channels in human sperm: expression, cellular localization and involvement in the regulation of flagellar motility
Authors: Castellano Laura E , Treviño Claudia L , Rodrı́guez Delany , Serrano Carmen J , Pacheco Judith , Tsutsumi Vı́ctor , Felix Ricardo , Darszon Alberto
Published: April 2003

Capacitative Ca2+ entry is a process whereby the activation of Ca2+ influx through the plasma membrane is triggered by depletion of intracellular Ca2+ stores. Some transient receptor potential (TRPC) proteins have been proposed as candidates for capacitative Ca2+ channels. Recent evidence indicates that capacitative Ca2+ entry participates in the sperm acrosome reaction (AR), an exocytotic process necessary for fertilization. In addition, several TRPCs have been detected heterogeneously distributed in mouse sperm, suggesting that they may participate in other functions such as motility. Using reverse transcription‐polymerase chain reaction (RT‐PCR) analysis, RNA messengers for TRPC1, 3, 6 and 7 were found in human spermatogenic cells. Confocal indirect immunofluorescence revealed the presence of TRPC1, 3, 4 and 6 differentially localized in the human sperm, and immunogold transmission electron microscopy indicated that TRPC epitopes are mostly associated to the surface of the cells. Because all of them were detected in the flagellum, TRPC channel antagonists were tested in sperm motility using a computer‐assisted assay. Our results provide what is to our knowledge the first evidence that these channels may influence human sperm motility.
The isolated N‐terminal extracellular domain of the glucagon‐like peptide‐1 (GLP)‐1 receptor has intrinsic binding activity
Authors: Wilmen Andreas , Goke Burkhard , Göke Rudiger
Published: April 2003

The glucagon‐like peptide 1 (7–37)/(7–36) amide (GLP‐1) receptor belongs to a new subclass of seven transmembrane domain, G‐protein coupled receptors comprising several receptors for peptide hormones. The receptors of this family share many common motifs including a relatively large N‐terminal extracellular domain. The GLP‐1 receptor is presently attracting much attention, since it is the target protein of the antidiabetic gut hormone GLP‐1. To establish the functional significance of the N‐terminal part of the GLP‐1 receptor for ligand binding, the extracellular domain was isolated and purified. Utilizing CHL cells expressing the cloned GLP‐1 receptor, we demonstrate that the isolated, solubilized N‐terminal part of the receptor protein competes for GLP‐1 binding with the intact wild‐type receptor. Moreover, in cross‐linking experiments radiolabeled GLP‐1 was covalently attached to the isolated N‐terminus, thereby demonstrating direct physical interaction of both components. By Western blot analysis two specific bands were detectable, representing the N‐terminal receptor protein in the presence or absence of bound ligand. These data underline the significance of the N‐terminal domain of the GLP‐1 receptor for ligand binding.
Major increase in brain natriuretic peptide indicates right ventricular systolic dysfunction in patients with heart failure
Authors: Mariano‐Goulart Denis , Eberlé Marie‐Claude , Boudousq Vincent , Hejazi‐Moughari Azadeh , Piot Christophe , de Kerleau Charles Caderas , Verdier Régis , Barge Marie‐Luce , Comte Frédéric , Bressot Nicole , Rossi Michel , Kotzki Pierre‐Olivier
Published: April 2003

This study sought to investigate whether the presence of right ventricular systolic dysfunction with pre‐existing left ventricular systolic dysfunction is associated with higher plasma brain natriuretic peptide (BNP) levels, compared with patients with isolated left ventricular dysfunction. Eighty‐five patients referred for evaluation of isotopic ventricular function were prospectively included in the study. Left (LVEF) and right (RVEF) ventricular ejection fractions were evaluated by gated blood pool scintigraphy and compared with plasma BNP levels. BNP correlated negatively with LVEF, except in patients with ischaemic heart disease (P=0.09) and in patients with LVEF<40% (P=0.11). In contrast, BNP levels correlated negatively with RVEF for all subgroups. Among patients with RVEF<40%, no significant BNP difference was found between patients with or without additional left ventricular systolic dysfunction (P=0.51). Among patients with LVEF<40%, plasma BNP levels were significantly higher in patients with RVEF<40% than in patients with RVEF≥40% (P=0.004) whereas age, renal function, clinical findings, ventricular volumes, LVEF or medication were not significantly different. In conclusion, an important increase in BNP levels in patients with left ventricular systolic dysfunction should be considered by cardiologists as an indication of high risk of right ventricular dysfunction and should justify further investigation.
Construct Validation of the Self-Description Questionnaire II with a French Sample
Authors: Guérin Florence , Marsh Herbert W. , Famose Jean-Pierre
Published: April 2003

Summary: This investigation is a French validation of the Self-Description Questionnaire (SDQ) II, an instrument derived from the Marsh and Shavelson model and designed to measure adolescent self-concept. Previous theoretical and methodological considerations in SDQ research provided guidelines for the instrument “within-construct” validity. 480 students completed the questionnaire. Reliability and confirmatory factor analyses were used to demonstrate support for the good psychometric properties, the well-defined 11 facets of the multidimensional self-concept, the two remarkably distinct higher order academic areas, and the weak hierarchical ordering. Third-order HCFA models resulted in a hierarchical general self-concept modestly related to most nonacademic self-concepts and rather weakly to academic self-concepts. The present research strongly supports the multifaceted nature of self-concept, but cannot supply clear evidence for the usefulness of hierarchical representations of adolescent self-concept.
Mouse system-N amino acid transporter, mNAT3, expressed in hepatocytes and regulated by insulin-activated and phosphoinositide 3-kinase-dependent signalling
Authors: GU Sumin , LANGLAIS Paul , LIU Feng , JIANG Jean X.
Published: April 2003

Amino acid transporters are essential for normal cell function and physiology. In the present study, we report the identification and functional and regulatory characterization of a mouse system-N amino acid transporter, mNAT3. Expression of mNAT3 in Xenopus oocytes revealed that the strongest transport activities were preferred for l-alanine. In addition, mNAT3 is an Na+- and pH-dependent low-affinity transporter and it partially tolerates substitution of Na+ by Li+. mNAT3 has been found to be expressed predominantly in the liver, where it is localized to the plasma membrane of hepatocytes, with the strongest expression in those cells adjacent to the central vein, decreasing gradually towards the portal tract. Treatment of mouse hepatocyte-like H2.35 cells with insulin led to a significant increase in the expression of mNAT3, and this stimulation was associated closely with an increase in the uptake of l-alanine. Interestingly, this insulin-induced stimulatory effect on mNAT3 expression was attenuated by the phosphoinositide 3-kinase inhibitor LY294002, but not by the mitogen-activated protein kinase inhibitor PD98059, although both kinases were fully activated by insulin. The results suggest that insulin-mediated regulation of mNAT3 is likely to be mediated through a phosphoinositide 3-kinase-dependent signalling pathway. The unique expression pattern and insulin-mediated regulatory properties of mNAT3 suggest that this transporter may play an important role in liver physiology.
Anomalous hysteresis in magnetoresistive ceramic and film samples of (La0.8Sr0.2)1−xMn1+xO3 (0⩽x⩽0.4)
Authors: Dovgij V. T. , Linnik A. I. , Pashchenko V. P. , Derkachenko V. N. , Prokopenko V. K. , Turchenko V. A. , Davydeiko N. V. , Sycheva V. Ya. , Dyakonov V. P. , Klimov A. V. , Szymczak H.
Published: April 2003

A study is made of the external structure, magnetization, and magnetoresistive effect in ceramic samples of (La0.8Sr0.2)1−xMn1+xO3 annealed at 1150 and 1500 °C. It is shown that the additional annealing at 1500 °C leads to significant changes in the magnetization and increases the magnetoresistive effect by a factor of 2–3, depending on x. An “anomalous” magnetic hysteresis is observed on the initial parts of the magnetization curves in both ceramic and laser-deposited film samples. It is found that the value of the “anomalous” magnetic hysteresis depends on the composition of the samples (on x) and their annealing temperature. A mechanism for the appearance of the “anomalous” hysteresis is proposed, involving the presence and interaction of ferromagnetic and antiferromagnetic phases.
Eigenmodes of the electromagnetic field in the presence of a magnetic domain structure
Authors: Peschansky V. G. , Stepanenko D. I.
Published: April 2003

The spectrum of weakly damped eigenmodes of the electromagnetic field in metals in a quantizing magnetic field are determined under conditions such that a magnetic domain structure exists.
Discrete transformation for the matrix three-wave problem in three dimensional space
Authors: Leznov A. N. , Torres-Cordoba R.
Published: April 2003

Discrete transformation for three-wave problems is constructed in explicit form. Generalization of this system on the matrix case in three dimensional space together with corresponding discrete transformation is presented also.
Advanced tokamak profile evolution in DIII-D
Authors: Murakami M. , Wade M. R. , DeBoo J. C. , Greenfield C. M. , Luce T. C. , Makowski M. A. , Petty C. C. , Staebler G. M. , Taylor T. S. , Austin M. E. , Baker D. R. , Budny R. V. , Burrell K. H. , Casper T. A. , Choi M. , Ferron J. R. , Garofalo A. M. , Gorelov I. A. , Groebner R. J. , La Haye R. , Hyatt A. W. , Jayakumar R. J. , Kajiwara K. , Kinsey J. E. , Lao L. L. , Lohr J. , McCune D. , Pinsker R. I. , Politzer P. A. , Prater R. , St. John H. E. , West W. P.
Published: April 2003

Using off-axis electron cyclotron current drive (ECCD), self-consistent integrated advanced tokamak operation has been demonstrated on DIII-D [Plasma Physics and Controlled Nuclear Fusion Research, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159], combining high β (>3%) at high q (qmin>2.0) with good energy confinement (H89∼2.5) and high noninductive current fraction (fBS∼55%,fNI∼90%). Modification of the current profile by ECCD led to internal transport barrier formation even in the presence of type I edge localized modes. Improvements were observed in all transport channels, and increased peaking of profiles led to higher bootstrap current in the core. Separate experiments have shown the ability to maintain a nearly steady-state current profile for up to 1 s with qmin>1.5. Modeling indicates that this favorable current profile can be maintained indefinitely at a higher βN using tools available to the near-term DIII-D program. Modeling and simulation have become essential tools for the experimental program in interpreting the data and developing detail plans for new experiments.
On the uniform asymptotic expansion of the Legendre functions
Authors: Khusnutdinov Nail R.
Published: April 2003

A uniform expansion of the Legendre functions of large indices is considered by using the WKB approach. We obtain the recurrent formula for the coefficients of uniform expansion and compare them with the uniform expansion of the Bessel function.
On harmonic oscillators on the two-dimensional sphere S2 and the hyperbolic plane H2. II.
Authors: Rañada Manuel F. , Santander Mariano
Published: April 2003

The properties of several noncentral n=2 harmonic oscillators are examined on spaces of constant curvature. All the mathematical expressions are presented using the curvature κ as a parameter, in such a way that particularizing for κ>0, κ=0, or κ<0, the corresponding properties are obtained for the system on the sphere S2, the Euclidean plane E2, or the hyperbolic plane H2, respectively. First, the separability in several κ-dependent systems of coordinates, as well as the existence of four families of κ-dependent superintegrable potentials related with the harmonic oscillator, are studied. Then three harmonic oscillators (1:1, 2:1 and 12:1) are studied by using two different methods: superseparability and complex factorization. The second part deals with the problem of the existence of superintegrable but not superseparable systems. Several κ-dependent superintegrable harmonic oscillators with higher-order constants of motion are studied. The constants of motion are obtained by making use of the method of the complex factorization.
Fractional operators and special functions. I. Bessel functions
Authors: Durand Loyal
Published: April 2003

Most of the special functions of mathematical physics are connected with the representation of Lie groups. The action of elements D of the associated Lie algebras as linear differential operators gives relations among the functions in a class, for example, their differential recurrence relations. In this paper, we define fractional generalizations Dμ of these operators in the context of Lie theory, determine their formal properties, and illustrate their use in obtaining interesting relations among the functions. We restrict our attention here to the Euclidean group E(2) and the Bessel functions. We show that the two-variable fractional operator relations lead directly to integral representations for the Bessel functions, reproduce known fractional integrals for those functions when reduced to one variable, and contribute to a coherent understanding of the connection of many properties of the functions to the underlying group structure. We extend the analysis to the associated Legendre functions in a following paper.
Different operations on a single circuit: Field computation on an excitable chemical system
Authors: Ichino Takatoshi , Igarashi Yasuhiro , Motoike Ikuko N. , Yoshikawa Kenichi
Published: April 2003

Recently, it has been proposed that various kinds of time operations can be performed using an excitable field, mainly based on computer simulation. In this study, we performed experiments toward the realization of a time operation, such as time-difference detection. We used the photosensitive Belousov–Zhabotinsky reaction as a spatially distributed excitable field. We found that a single geometrical circuit can perform different operations with changes in the intensity of light illumination. The experimental results are discussed in relation to the idea of a non-Neumann-type computational device.
Study of the demixing transition in model athermal mixtures of colloids and flexible self-excluding polymers using the thermodynamic perturbation theory of Wertheim
Authors: Paricaud Patrice , Varga Szabolcs , Jackson George
Published: April 2003

Fluid phase separation in model athermal mixtures of colloids and polymers is examined by means of the first-order thermodynamic perturbation theory of Wertheim [M. S. Wertheim, J. Chem. Phys. 87, 7323 (1987); W. G. Chapman, G. Jackson, and K. E. Gubbins, Mol. Phys. 65, 1057 (1988)]. The colloidal particles are modeled simply as hard spheres, while the polymers are represented as chains formed from tangent hard-sphere segments. In this study the like (colloid–colloid, polymer–polymer) and unlike (polymer–colloid) repulsive interactions are treated at the same level of microscopic detail; we do not employ the common Asakura–Oosawa (AO) approximations which essentially involve treating the polymer as an ideal (noninteracting) chain. The effect of varying both the chain length and the diameter of the hard-sphere segments of the polymer on the fluid phase behavior of the model polymer–colloid system is investigated. We focus our attention on the stability of the fluid phase relative to a demixing transition into colloid-rich and polymer-rich fluid phases by using a spinodal instability analysis and determine the full coexistence boundaries (binodal). The colloid–polymer system represents the limit where the diameter of the colloid is much larger than the diameter of the segments making up the polymer chain. The precise segment/colloid diameter ratio at which liquid–liquid demixing first occurs is examined in detail as a function of the chain length of the polymer. In the case of moderately short chains the addition of polymer induces the “colloidal vapor–liquid” transition found in polymer–colloid systems, while for long chains a “polymeric vapor–liquid” transition is found. The diameter of the polymeric segments must lie between the AO limit (minimum diameter) and the so-called protein limit (maximum diameter) in order for the system to exhibit fluid–fluid phase separation. The maximum value of the segment diameter which induces phase separation is determined from a simple approximate stability analysis. The critical density of the demixing transitions is not found to tend to be zero for infinitely long polymers, but has a limiting value which depends on the diameter of the segment. An examination of the thermodynamic properties of mixing indicates that the fluid–fluid phase separation in such systems is driven by a large positive enthalpy of mixing which is induced by a large positive volume of mixing due to the unfavorable polymer–colloid excluded volume interactions. The enthalpy of mixing makes an unfavorable contribution to the overall Gibbs free energy (which is seen to counter the favorable entropy of mixing), giving rise to fluid–fluid immiscibility.
Semiconductor mirror for dynamic dispersion compensation
Authors: Isomäki A. , Vainionpää A. , Lyytikäinen J. , Okhotnikov O. G.
Published: April 2003

We report on a monolithic Gires–Tournois semiconductor interferometer used to generate a tunable delay. Controllable saturable absorption in optically pumped multiple-quantum-well semiconductor reflector was shown to provide promising means for rapid changing the group delay of the reflector, and represents an attractive form of dynamic dispersion compensation.
Problems in concurrent new product development: an in‐depth comparative study of three companies
Authors: Haque Badr
Published: April 2003

Concurrent engineering or concurrent new product development (CNPD) is gradually becoming the norm for developing and introducing new products to the market place. Through the use of three in‐depth case studies looks at the seldom discussed problems in CNPD implementation and day‐to‐day management, and tries to provide a clear picture of the current state of its development, at three companies in three different countries across Europe. Identifies a number of issues emerging from the study, in particular the lack of process understanding for a concurrent or integrated product development effort and the abundance of “organisational” factors as the main barrier to its success. The results identified both differences and commonalties in CNPD experiences between each of the three case study companies. The case studies highlight the importance of process management, with a focus on process modelling and analysis of organisational factors, to improve the existing implementations of CNPD.
Improved amino acid flexibility parameters
Authors: Smith David K. , Radivojac Predrag , Obradovic Zoran , Dunker A. Keith , Zhu Guang
Published: April 2003

Protein molecules exhibit varying degrees of flexibility throughout their three‐dimensional structures, with some segments showing little mobility while others may be so disordered as to be unresolvable by techniques such as X‐ray crystallography. Atomic displacement parameters, or B‐factors, from X‐ray crystallographic studies give an experimentally determined indication of the degree of mobility in a protein structure. To provide better estimators of amino acid flexibility, we have examined B‐factors from a large set of high‐resolution crystal structures. Because of the differences among structures, it is necessary to normalize the B‐factors. However, many proteins have segments of unusually high mobility, which must be accounted for before normalization can be performed. Accordingly, a median‐based method from quality control studies was used to identify outliers. After removal of outliers from, and normalization of, each protein chain, the B‐factors were collected for each amino acid in the set. It was found that the distribution of normalized B‐factors followed a Gumbel, or extreme value distribution, and the location parameter, or mode, of this distribution was used as an estimator of flexibility for the amino acid. These new parameters have a higher correlation with experimentally determined B‐factors than parameters from earlier methods.
Peptidase family U34 belongs to the superfamily of N‐terminal nucleophile hydrolases
Authors: Pei Jimin , Grishin Nick V.
Published: April 2003

Peptidase family U34 consists of enzymes with unclear catalytic mechanism, for instance, dipeptidase A from Lactobacillus helveticus. Using extensive sequence similarity searches, we infer that U34 family members are homologous to penicillin V acylases (PVA) and thus potentially adopt the N‐terminal nucleophile (Ntn) hydrolase fold. Comparative sequence and structural analysis reveals a cysteine as the catalytic nucleophile as well as other conserved residues important for catalysis. The PVA/U34 family is variable in sequence and exhibits great diversity in substrate specificity, to include enzymes such as choloyglycine hydrolases, acid ceramidases, isopenicillin N acyltransferases, and a subgroup of eukaryotic proteins with unclear function.
Crystal structures of a pantothenate synthetase from M. tuberculosis and its complexes with substrates and a reaction intermediate
Authors: Wang Shuishu , Eisenberg David
Published: April 2003

Pantothenate biosynthesis is essential for the virulence of Mycobacterium tuberculosis, and this pathway thus presents potential drug targets against tuberculosis. We determined the crystal structure of pantothenate synthetase (PS) from M. tuberculosis, and its complexes with AMPCPP, pantoate, and a reaction intermediate, pantoyl adenylate, with resolutions from 1.6 to 2 Å. PS catalyzes the ATP‐dependent condensation of pantoate and β‐alanine to form pantothenate. Its structure reveals a dimer, and each subunit has two domains with tight association between domains. The active‐site cavity is on the N‐terminal domain, partially covered by the C‐terminal domain. One wall of the active site cavity is flexible, which allows the bulky AMPCPP to diffuse into the active site to nearly full occupancy when crystals are soaked in solutions containing AMPCPP. Crystal structures of the complexes with AMPCPP and pantoate indicate that the enzyme binds ATP and pantoate tightly in the active site, and brings the carboxyl oxygen of pantoate near the α‐phosphorus atom of ATP for an in‐line nucleophilic attack. When crystals were soaked with, or grown in the presence of, both ATP and pantoate, a reaction intermediate, pantoyl adenylate, is found in the active site. The flexible wall of the active site cavity becomes ordered when the intermediate is in the active site, thus protecting it from being hydrolyzed. Binding of β‐alanine can occur only after pantoyl adenylate is formed inside the active site cavity. The tight binding of the intermediate pantoyl adenylate suggests that nonreactive analogs of pantoyl adenylate may be inhibitors of the PS enzyme with high affinity and specificity.
Stator-Rotor Interactions in a Transonic Compressor—Part 2: Description of a Loss-Producing Mechanism
Authors: Gorrell Steven E. , Okiishi Theodore H. , Copenhaver William W.
Published: April 2003

A previously unidentified loss producing mechanism resulting from the interaction of a transonic rotor blade row with an upstream stator blade row is described. This additional loss occurs only when the two blade rows are spaced closer together axially. Time-accurate simulations of the flow and high-response static pressure measurements acquired on the stator blade surface reveal important aspects of the fluid dynamics of the production of this additional loss. At close spacing the rotor bow shock is chopped by the stator trailing edge. The chopped bow shock becomes a pressure wave on the upper surface of the stator that is nearly normal to the flow and that propagates upstream. In the reference frame relative to this pressure wave, the flow is supersonic and thus a moving shock wave that produces an entropy rise and loss is experienced. The effect of this outcome of blade-row interaction is to lower the efficiency, pressure ratio, and mass flow rate observed as blade-row axial spacing is reduced from far to close. The magnitude of loss production is affected by the strength of the bow shock and how much it turns as it interacts with the trailing edge of the stator. At far spacing the rotor bow shock degenerates into a bow wave before it interacts with the stator trailing edge and no significant pressure wave forms on the stator upper surface. For this condition, no additional loss is produced.
Measurement and Prediction of the Influence of Catalytic and Dry Low NOx Combustor Turbulence on Vane Surface Heat Transfer
Authors: Ames Forrest E. , Wang Chao , Barbot Pierre A.
Published: April 2003

New combustion systems developed for low emissions have produced substantial changes to the characteristics of inlet turbulence entering nozzle guide vanes. This paper documents the characteristics of turbulence generated by mock combustion system configurations representative of recently developed catalytic and dry low NOx combustors. Additionally, heat transfer rates are determined on the surface of a vane subjected to inlet turbulence generated by these mock combustor configurations. Six different inlet turbulence conditions with levels ranging up to 14% are documented in this study and vane heat transfer rates are acquired at exit chord Reynolds numbers ranging from 500,000 to 2,000,000. Heat transfer distributions show the influence of turbulence level and scale on heat transfer augmentation and transition. Cascade aerodynamics are well documented and match pressure distributions predicted by a commercial CFD code for this large-scale low-speed facility. The vane pressure distribution could be characterized as a conventional or fully loaded distribution. This comprehensive data set is expected to represent an excellent test case for vane heat transfer predictive methods. Predictive comparisons are shown based on a two-dimensional boundary layer code using an algebraic turbulence model for augmentation as well as a transition model.
RENORMALIZATION GROUP IMPROVING THE EFFECTIVE ACTION: A REVIEW
Authors: HOCHBERG DAVID , PÉREZ-MERCADER JUAN , MOLINA-PARÍS CARMEN , VISSER MATT
Published: April 2003

The existence of fluctuations together with interactions leads to scale-dependence, in the couplings of quantum field theories for the case of quantum fluctuations, and in the couplings of stochastic systems when the fluctuations are of a thermal or statistical nature. In both cases the effects of these fluctuations can be accounted for by solutions of the corresponding renormalization group equations. In this review, we show how the renormalization group equations are intimately connected with the effective action: given the effective action we can trivially extract the renormalization group equations; given the renormalization group equations the effects of these fluctuations can be included in the classical action by using what is known as improved perturbation theory (wherein the bare parameters appearing in tree-level expressions are replaced by their scale-dependent running forms). The improved action can then be used to reconstruct the effective action, up to finite renormalizations, and up to gradient terms.
THE STATIONARY INSTABILITY IN QUASI-REVERSIBLE SYSTEMS AND THE LORENZ PENDULUM
Authors: CLERC M. , COULLET P. , TIRAPEGUI E.
Published: April 2003

We study the resonance at zero frequency in presence of a neutral mode in quasi-reversible systems. The asymptotic normal form is derived and it is shown that in the presence of a reflection symmetry it is equivalent to the set of real Lorenz equations. Near the critical point an analytical condition for the persistence of an homoclinic curve is calculated and chaotic behavior is then predicted and its existence verified by direct numerical simulation. A simple mechanical pendulum is shown to be an example of the instability, and preliminary experimental results agree with the theoretical predictions.
A NOTE ON THE TOTALLY TRANSITIVE GRAPH MAPS STABILITY OF PWL CELLULAR
Authors: ALSEDÀ LL. , RÍO M. A. DEL , RODRÍGUEZ J. A.
Published: April 2003

We study the totally transitive graph maps which have periodic points. In particular we show that the cofiniteness of the set of periods characterizes these maps among transitive graph maps.
BIFURCATIONS AND CHAOTIC OSCILLATIONS IN AN AUTOMATIC CONTROL RELAY SYSTEM WITH HYSTERESIS
Authors: ZHUSUBALIYEV ZHANYBAI T. , SOUKHOTERIN EVGENIY A. , RUDAKOV VADIM N. , KOLOKOLOV YURI V. , MOSEKILDE ERIK
Published: April 2003

The dynamics of relay system with hysteresis is investigated. Systems of this type have a broad range of applications for power control and temperature regulation or in order to obtain highly stabilized electric or magnetic fields. Examples are power supplies for radio-electronics, computer equipment or spacecrafts, test stands for investigations of high- or low-temperature superconductivity, electron microscopes, and nuclear magnetic resonance tomographs. We first describe a general approach to determine stable and unstable periodic orbits for systems with hysteresis. Considering a concrete example of a four-dimensional relay system with hysteresis we hereafter determine the regions of periodic and chaotic oscillations in parameter space. The regularities in the occurrence of periodic motions are studied, and the associated bifurcations are described. The causes of nondeterminate (i.e. chaotic) dynamics are discussed and the influence of an external noise signal is analyzed.
RESPONSE PROPERTIES OF A SINGLE CHAOTIC NEURON TO STOCHASTIC INPUTS
Authors: KUROIWA JOUSUKE , NARA SHIGETOSHI , AIHARA KAZUYUKI
Published: April 2003

Response properties of a single chaotic neuron to stochastic inputs are investigated by means of numerical simulations in the context of a nonlinear dynamical approach to analyzing chaotic behaviors of a neuron. We apply six kinds of stochastic inputs with the same mean rate but different correlations of interspike intervals, whose timings are determined by a stochastic process, namely, Markovian processes and Gaussian/Poisson random processes. From numerical evaluations of entropy and conditional entropies with respect to interspike intervals of outputs, it is shown that interspike intervals of outputs represent dynamical structures of each input. Numerical calculations of Lyapunov exponents, trajectories of dynamics and return plots of internal states make meaningful difference in dynamical properties of the model depending on inputs even if mean interspike intervals of outputs are almost the same values. In order to extract dynamical features of outputs, we calculate a time-delayed space representation of output responses to inputs, and the results provide different trajectories in a time-delayed phase space, which reflect a higher order statistical feature of inputs, amplifying their feature differences. For signals containing noise, the behaviors of the model do not suffer degradation, showing robustness to noise in the inputs. As conclusion, our results show that dynamical properties of inputs can be extracted with clear difference of response properties of the model, that is, the model gives a variety of the amplitude and the interspike intervals of outputs depending on inputs. In other words, the model can realize dynamical sampling of inputs with sensitivity of response properties to inputs and robustness to inputs with noise.
BIFURCATIONS OF LIMIT CYCLES IN A Z3-EQUIVARIANT VECTOR FIELD OF DEGREE 5
Authors: CHAN H. S. Y. , CHUNG K. W. , LI JIBIN
Published: April 2003

A concrete numerical example of Z3-equivariant planar perturbed Hamiltonian vector field of fifth degree having 23 limit cycles and a configuration of compound eyes are given, by using the bifurcation theory of planar dynamical systems and the method of detection functions. It gives rise to the conclusion: the Hilbert number H(5) ≥ 23 for the second part of Hilbert's 16th problem.
Neonatal Lymphocytes Dominate against Lymphocytes of Their Own Mother but Not against Allogenic Maternal or Adult Lymphocytes in Bidirectional Mixed Lymphocyte Cultures
Authors: Brune Thomas , Beier Kirsten , Exeler Rita , Harms Erik , Louwen Frank
Published: April 2003

Objective: Recent studies have shown a regular prenatal transfer of maternal immunocompetent cells into the fetal circulation. However, these cells engraft and proliferate only in a few exceptional cases if the fetus reaches an immunocompetent state. Thus the fetus has to have an immunologic defense mechanism against the engraftment of maternal cells. In the current study we investigated whether the fetus has such an immune defense and whether this defense mechanism specifically attacks cells of the mother. Patients, Material and Methods: Blood samples were obtained from 15 mothers and 15 newborns directly after delivery. We compared individual vitality and spontaneous cytotoxicity between fetal and maternal lymphocytes in a cell ratio of 1:1 in nonstimulated bidirectional mixed lymphocyte cultures (MLC). The distribution of each cell population within the MLC was visualized by fluorescence in situ hybridization and X/Y-DNA probes. This was compared to MLCs between unrelated fetal and maternal as well as between unrelated adult lymphocytes. Results: After 72 h, a significant cell shift was observed only in the MLC with neonatal lymphocytes mixed with cells of their own mother; there was a significantly higher number of neonatal cells (0.71 vs. 0.29) present. All other groups continued to have a cell distribution of 1:1. Conclusion: Our results show that neonatal lymphocytes specifically dominate against maternal but not allogenous maternal or adult lymphocytes in nonstimulated bidirectional MLCs.
Test Amnioinfusion to Determine Suitability for Serial Therapeutic Amnioinfusion in Midtrimester Premature Rupture of Membranes
Authors: Tan L.-K. , Kumar S. , Jolly M. , Gleeson C. , Johnson P. , Fisk N.M.
Published: April 2003

Objective: To evaluate whether a test amnioinfusion procedure is useful in selecting cases of midtrimester preterm premature rupture of membranes (PPROM) which may benefit from serial amnioinfusions if the initial fluid is retained. Study Design: The Centre for Fetal Care database between 1992 and 2000 was reviewed for women with PPROM <26 weeks who had undergone amnioinfusion. Amniotic fluid index (AFI) was assessed before and after a test amnioinfusion procedure. Those who retained fluid ≧48 h underwent serial AFI assessment with a view to serial amnioinfusion when oligohydramnios recurred. Results: Eighty-five amnioinfusion procedures were performed in 60 women with oligohydramnios. Nineteen of these women presented with confirmed PPROM at a median gestation of 19 (range 15–22) weeks and severe olighohydramnios (median AFI 1, range 0–3 cm), in whom 20 test amnioinfusions were carried out. Two amnioinfusions were abandoned during the procedure because of fetal bradycardia and both mothers opted for termination of pregnancy. Only 4 women retained fluid during the test amnioinfusion, 1 of whom miscarried at 19 weeks before serial amnioinfusion could be started. The remaining 3 underwent a median of 4 (range 1–6) serial amnioinfusion procedures; none had evidence of pulmonary hypoplasia. Thirteen (68%) leaked fluid within 48 h; within this group there was 1 subsequent miscarriage and 9 pregnancy terminations. The remaining 3 pregnancies resulted in livebirths 2 of which had pulmonary hypoplasia with 1 early neonatal death. Overall survival was poor (4/19), largely attributed to the high incidence of terminations in the presence of persistent severe oligohydramnios. In continuing pregnancies reaching viability survival was 67% (4 of 6). Conclusion: Three quarters of women with mid-trimester PPROM lose fluid at test amnioinfusion and therefore would not be suitable candidates for serial amnioinfusion. However, if infused fluid is retained, this allows subsequent serial amnioinfusion and prolongation of pregnancy in about 75%, with an attendant decrease in the risk of pulmonary hypoplasia. However, even successful serial amnioinfusion remains associated with procedure-related complications (i.e. chorioamnionitis, placental abruption) which themselves may predispose to preterm delivery.
Stroke in Parents Who Lost a Child: A Nationwide Follow-Up Study in Denmark
Authors: Li Jiong , Johnsen Søren P. , Olsen Jørn
Published: April 2003

The association between psychological stress and stroke remains uncertain. We therefore examined whether or not one of the most extreme psychological stressors, the death of a child, was associated with the risk of stroke in a nationwide population-based follow-up study. All 21,062 parents who lost a child in Denmark during 1980–1996 were compared with 293,745 parents who had not lost a child. The overall adjusted relative risk (RR) of stroke was 1.00 (95% CI = 0.83–1.20) among the exposed after up to 18 years of follow-up. The RRs for fatal stroke and nonfatal stroke were 0.69 (95% CI = 0.37–1.26) and 1.03 (95% CI = 0.85–1.24), respectively. The RRs for hemorrhagic and nonhemorrhagic stroke were 1.02 (95% CI = 0.77–1.36) and 0.94 (95% CI = 0.74–1.20), respectively. The risk of stroke did not differ irrespective of whether the death of the child was unexpected or not. The death of a child was not associated with any substantially increased risk of stroke in the bereaved parents.
Death with Functioning Graft in Living Donor Kidney Transplantation: Analysis of Risk Factors
Authors: El-Agroudy Amgad E. , Bakr Mohamed A. , Shehab El-Dein Ahmed B. , Ghoneim Mohamed A.
Published: April 2003

Background: Death with a functioning graft (DWF) has been reported as a major cause of graft loss after renal transplantation. It has been reported to occur in 9–30%. Methods: From March 1976 to January 2002, a total of 1,400 living donor renal transplants were performed in our center. Out of 257 reported deaths among our patients, 131 recipients died with functioning grafts after a mean period of 53.4 ± 53.2 months. Results: DWF patients account for 27% of all graft losses in our series. The mean age was 34.9 + 10.6 (range 8–62 years), 98 of them were male and 33 were female. The original kidney disease was GN in 9, PN in 24, PCK in 5 and nephrosclerosis in 8 patients. Acute rejection episodes were diagnosed in 84 patients (63.1). The post-transplant complications encountered were hypertension in 78 patients (59.5%), diabetes mellitus in 30 patients (22.9%), medical infections in 68 (51.5%), hepatic complications in 30 (22.9%) and malignancy in 17 patients (13%). The main causes of death in these patients were infections in 46 (35.6%), cardiovascular in 23 (17.6%), liver cell failure in 15 patients (11.4%) and malignancy in 8 (6.1%). The mean serum creatinine was 2 ± 0.6 mg/dl at last follow-up before death. Conclusion: We conclude that the relatively higher mortality in renal transplantation is, in part, due to co-morbid medical illness, pre-transplant dialysis treatment, and factors uniquely related to transplantation, including immunosuppression and other drug effects. DWF must be in consideration when calculating graft survival.
Influence of upper‐tropospheric inertial stability on the convective transport of momentum
Authors: Mecikalski J. R. , Tripoli G. J.
Published: April 2003

This study verifies the apparent high positive correlation between environmental and convection‐relative inertial stability, and the transport of momentum by deep convection. We evaluate the hypothesis that convection structurally aligns itself to best access the region of lowest upper‐tropospheric inertial stability, while forming the lowest convective updraught‐relative inertial stability.

A numerical experiment evaluates variations in the structure, behaviour and momentum‐transport characteristics of deep convection across the tropical‐plume genesis region in the eastern Pacific. This unique region forms as a precursor to tropical‐plume genesis, and possesses spatially varying very‐low upper‐tropospheric inertial stability (the potential vorticity locally reaches zero, or becomes slightly negative, in the northern hemisphere).

Our results show that the vertical transport of horizontal momentum is predictable, given knowledge of the inertial‐stability fields immediately surrounding the convection. It is conjectured that the preferred mode of convective organization (squall‐line dominated versus more three‐dimensional) near the intertropical convergence zone is a function of the ambient inertial stability. Therefore, as the convection organizes itself, it selects the most efficient access to regions of lowest inertial stability to enable its upper‐tropospheric outflow. Copyright © 2003 Royal Meteorological Society