bluuebunny/crossref_metadata_2025 huggingface dataset:
15-Deoxy-Δ12,14-prostaglandin J2 and peroxisome proliferator-activated receptor γ (PPARγ) levels in term placental tissues from control and diabetic rats: modulatory effects of a PPARγ agonist on nitridergic and lipid placental metabolism
Authors: Capobianco E. , Jawerbaum A. , Romanini M. C. , White V. , Pustovrh C. , Higa R. , Martinez N. , Mugnaini M. T. , Soñez C. , Gonzalez E.
Published: April 2005

15-Deoxy-Δ12,14-prostaglandin J2 (15dPGJ2) is a peroxisome proliferator-activated receptor γ (PPARγ) ligand that regulates lipid homeostasis and has anti-inflammatory properties in many cell types. We postulated that 15dPGJ2 may regulate lipid homeostasis and nitric oxide (NO) levels in term placental tissues and that alterations in these pathways may be involved in diabetes-induced placental derangements. In the present study, we observed that, in term placental tissues from streptozotocin-induced diabetic rats, 15dPGJ2 concentrations were decreased (83%) and immunostaining for nitrotyrosine, indicating peroxynitrite-induced damage, was increased. In the presence of 15dPGJ2, concentrations of nitrates/nitrites (an index of NO production) were diminished (40%) in both control and diabetic rats, an effect that seems to be both dependent on and independent of PPARγ activation. Exogenous 15dPGJ2 did not modify lipid mass, but decreased the incorporation of 14C-acetate into triacylglycerol (35%), cholesteryl ester (55%) and phospholipid (32%) in placenta from control rats, an effect that appears to be dependent on PPARγ activation. In contrast, the addition of 15dPGJ2 did not alter de novo lipid synthesis in diabetic rat placenta, which showed decreased levels of PPARγ. We conclude that 15dPGJ2 modulates placental lipid metabolism and NO production. The concentration and function of 15dPGJ2 and concentrations of PPARγ were altered in placentas from diabetic rats, anomalies probably involved in diabetes-induced placental dysfunction.
Zinc inhibition of γ-aminobutyric acid transporter 4 (GAT4) reveals a link between excitatory and inhibitory neurotransmission
Authors: Cohen-Kfir Einav , Lee William , Eskandari Sepehr , Nelson Nathan
Published: April 2005

γ-Aminobutyric acid (GABA) transporters (GATs) play an important role in inhibitory neurotransmission by clearing synaptically released GABA and by maintaining low resting levels of GABA in synaptic and extrasynaptic regions. In certain brain regions, vesicular zinc is colocalized and coreleased with glutamate and modulates the behavior of a number of channels, receptors, and transporters. We examined the effect of zinc on expressed GATs (GAT1, GAT2, GAT3, and GAT4) inXenopus laevisoocytes by using tracer flux and electrophysiological methods. We show that zinc is a potent inhibitor of GAT4 (Kiof 3 μM). Immunolocalization of GAT4 in the hippocampus revealed dense localization in the CA1 and CA3 regions of the hippocampus, regions which are known to be heavily populated by zinc-containing glutamatergic neurons. The results suggest a physiological role of synaptically released zinc in the hippocampus, because zinc released from hyperactive glutamatergic neurons may simultaneously bring about elevated GABAergic inhibition. Therefore, this mode of zinc function signifies a link between excitatory and inhibitory neurotransmission and may play a neuroprotective role against glutamate-induced excitotoxicity.
Conjugacy class asymptotics, orbital integrals, and the Bernstein center: the case of 𝑆𝐿(2)
Authors: Moy Allen , Tadić Marko
Published: April 2005

The Bernstein center of a reductive p-adic group is the algebra of conjugation invariant distributions on the group which are essentially compact, i.e., invariant distributions whose convolution against a locally constant compactly supported function is again locally constant complactly supported. In the case of

S
L
(
2
)

SL(2)

, we show that certain combinations of orbital integrals belong to the Bernstein center and reveal a geometric reason for this phenomenon.
Caspase-resistant Golgin-160 Disrupts Apoptosis Induced by Secretory Pathway Stress and Ligation of Death Receptors
Authors: Maag Rebecca S. , Mancini Marie , Rosen Antony , Machamer Carolyn E.
Published: April 2005

Golgin-160 is a coiled-coil protein on the cytoplasmic face of the Golgi complex that is cleaved by caspases during apoptosis. We assessed the sensitivity of cell lines stably expressing wild-type or caspase-resistant golgin-160 to several proapoptotic stimuli. Cells expressing a caspase-resistant mutant of golgin-160 were strikingly resistant to apoptosis induced by ligation of death receptors and by drugs that induce endoplasmic reticulum (ER) stress, including brefeldin-A, dithiothreitol, and thapsigargin. However, both cell lines responded similarly to other proapoptotic stimuli, including staurosporine, anisomycin, and etoposide. The caspase-resistant golgin-160 dominantly prevented cleavage of endogenous golgin-160 after ligation of death receptors or induction of ER stress, which could be explained by a failure of initiator caspase activation. The block in apoptosis in cells expressing caspase-resistant golgin-160 could not be bypassed by expression of potential caspase cleavage fragments of golgin-160, or by drug-induced disassembly of the Golgi complex. Our results suggest that some apoptotic signals (including those initiated by death receptors and ER stress) are sensed and integrated at Golgi membranes and that golgin-160 plays an important role in transduction of these signals.
Coronin-1 Function Is Required for Phagosome Formation
Authors: Yan Ming , Collins Richard F. , Grinstein Sergio , Trimble William S.
Published: April 2005

Coronin-1 is an actin-associated protein whose function in actin dynamics has remained obscure. All coronin proteins have a variable N-terminal domain, followed by WD repeats and a C-terminal coiled-coil dimerization domain. Transfection of coronin-1-GFP into RAW 264.7 cells revealed that coronin rapidly and transiently associates with the phagosome. To determine if coronin is involved in mammalian phagocytosis we used a dominant-negative approach by expressing only the central WD domains. However, this caused cell rounding and dissociation from the substratum, hampering analysis of their phenotype. We therefore developed TAT-fusion constructs of coronin-1 WD domains to acutely introduce the recombinant protein fragment into live cells. We show that although TAT-WD has no effect on binding of opsonized RBCs to RAW 264.7 cells, receptor clustering or several downstream signaling events, lamellipodial extensions, and actin accumulation at the base of the bound particle were diminished. Furthermore, Arp3 accumulation at the phagosome was impaired after TAT-WD treatment. Interestingly, whereas coronin-1 also accumulates at the sites of actin remodeling associated with Salmonella invasion, TAT-WD had no effect on this process. Together, our data demonstrates that coronin-1 is required for an early step in phagosome formation, consistent with a role in actin polymerization.
The Conserved Mec1/Rad53 Nuclear Checkpoint Pathway Regulates Mitochondrial DNA Copy Number inSaccharomyces cerevisiae
Authors: Taylor Sean D. , Zhang Hong , Eaton Jana S. , Rodeheffer Matthew S. , Lebedeva Maria A. , O'Rourke Thomas W. , Siede Wolfram , Shadel Gerald S.
Published: April 2005

How mitochondrial DNA (mtDNA) copy number is determined and modulated according to cellular demands is largely unknown. Our previous investigations of the related DNA helicases Pif1p and Rrm3p uncovered a role for these factors and the conserved Mec1/Rad53 nuclear checkpoint pathway in mtDNA mutagenesis and stability in Saccharomyces cerevisiae. Here, we demonstrate another novel function of this pathway in the regulation of mtDNA copy number. Deletion of RRM3 or SML1, or overexpression of RNR1, which recapitulates Mec1/Rad53 pathway activation, resulted in an approximately twofold increase in mtDNA content relative to the corresponding wild-type yeast strains. In addition, deletion of RRM3 or SML1 fully rescued the ∼50% depletion of mtDNA observed in a pif1 null strain. Furthermore, deletion of SML1 was shown to be epistatic to both a rad53 and an rrm3 null mutation, placing these three genes in the same genetic pathway of mtDNA copy number regulation. Finally, increased mtDNA copy number via the Mec1/Rad53 pathway could occur independently of Abf2p, an mtDNA-binding protein that, like its metazoan homologues, is implicated in mtDNA copy number control. Together, these results indicate that signaling through the Mec1/Rad53 pathway increases mtDNA copy number by altering deoxyribonucleoside triphosphate pools through the activity of ribonucleotide reductase. This comprises the first linkage of a conserved signaling pathway to the regulation of mitochondrial genome copy number and suggests that homologous pathways in humans may likewise regulate mtDNA content under physiological conditions.
Microtubules Are Dispensable for the Initial Pathogenic Development but Required for Long-Distance Hyphal Growth in the Corn Smut FungusUstilago maydis
Authors: Fuchs Uta , Manns Isabel , Steinberg Gero
Published: April 2005

Fungal pathogenicity often involves a yeast-to-hypha transition, but the structural basis for this dimorphism is largely unknown. Here we analyze the role of the cytoskeleton in early steps of pathogenic development in the corn pathogen Ustilago maydis. On the plant yeast-like cells recognize each other, undergo a cell cycle arrest, and form long conjugation hyphae, which fuse and give rise to infectious filaments. F-actin is essential for polarized growth at all these stages and for cell-cell fusion. Furthermore, F-actin participates in pheromone secretion, but not perception. Although U. maydis contains prominent tubulin arrays, microtubules are neither required for cell-cell recognition, nor for cell-cell fusion, and have only minor roles in morphogenesis of yeast-like cells. Without microtubules hyphae are formed, albeit at 60% reduced elongation rates, but they reach only ∼50 μm in length and the nucleus fails to migrate into the hypha. A similar phenotype is found in dynein mutants that have a nuclear migration defect and stop hyphal elongation at ∼50 μm. These results demonstrate that microtubules are dispensable for polarized growth during morphological transition, but become essential in long-distance hyphal growth, which is probably due to their role in nuclear migration.
Human papillomavirus 16 virus-like particles use heparan sulfates to bind dendritic cells and colocalize with langerin in Langerhans cells
Authors: Bousarghin Latifa , Hubert Pascale , Franzen Elisabeth , Jacobs Nathalie , Boniver Jacques , Delvenne Philippe
Published: April 2005

Langerhans cells (LC), the immature dendritic cells (DC) that reside in epithelial tissues are among the first immune cells to encounter human papillomavirus (HPV) and are not activated by HPV virus-like particles (VLPs) in contrast to DC. The notion that the differences in response to HPV VLPs between LC and DC are associated with different types of cell binding and intracellular trafficking has been addressed. Inhibition experiments with heparin and sodium chlorate showed that heparan sulfates are necessary for HPV 16 VLPs to bind to DC but not to LC. Electron microscopy analysis demonstrated a colocalization of HPV 16 VLPs and langerin, which is expressed only by LC. This colocalization was observed on the cell surface but also in cytoplasmic vesicles. As anti-langerin antibodies, HPV 16 VLPs were associated with a faster entry kinetics in LC, as reflected by the fact that VLPs were observed near the nuclear membrane of LC within 10 min whereas more than 60 min were needed in DC. However, no difference between LC and DC was observed for the endocytosis pathway. HPV 16 VLPs entered in both DC and LC by a clathrin-dependent-pathway and were then localized in large cytoplasmic vesicles resembling endosomes.
Phenotypic analysis of human immunodeficiency virus type 1 Rev trimerization-interface mutants in human cells
Authors: Trikha Roochi , Brighty David W.
Published: April 2005

Nuclear export of unspliced and incompletely spliced human immunodeficiency virus type 1 mRNA is mediated by the viral Rev protein. Rev binds to a structured RNA motif known as the Rev-response element (RRE), which is present in all Rev-dependent transcripts, and thereby promotes entry of the ribonucleoprotein complex into the nuclear-export pathway. Recent evidence indicates that a dimerization interface and a genetically separable ‘trimerization’ interface are required for multimeric assembly of Rev on the RRE. In this report, the effect of mutations within the trimerization interface on Rev function was examined in mammalian cells. All trimerization-defective Rev molecules had profoundly compromised Rev function and a range of localization defects was observed. However, despite the potential for formation of heterodimers between functional and non-functional Rev proteins, trimerization-defective Rev mutants were unable to inhibit wild-type Rev function in a trans-dominant-negative manner.
RNA interference of rotavirus segment 11 mRNA reveals the essential role of NSP5 in the virus replicative cycle
Authors: Campagna Michela , Eichwald Catherine , Vascotto Fulvia , Burrone Oscar R.
Published: April 2005

Rotavirus genomes contain 11 double-stranded (ds) RNA segments. Genome segment 11 encodes the non-structural protein NSP5 and, in some strains, also NSP6. NSP5 is produced soon after viral infection and localizes in cytoplasmic viroplasms, where virus replication takes place. RNA interference by small interfering (si) RNAs targeted to genome segment 11 mRNA of two different strains blocked production of NSP5 in a strain-specific manner, with a strong effect on the overall replicative cycle: inhibition of viroplasm formation, decreased production of other structural and non-structural proteins, synthesis of viral genomic dsRNA and production of infectious particles. These effects were shown not to be due to inhibition of NSP6. The results obtained strengthen the importance of secondary transcription/translation in rotavirus replication and demonstrate that NSP5 is essential for the assembly of viroplasms and virus replication.
More recent swine vesicular disease virus isolates retain binding to coxsackie–adenovirus receptor, but have lost the ability to bind human decay-accelerating factor (CD55)
Authors: Jimenez-Clavero Miguel A. , Escribano-Romero Estela , Ley Victoria , Spiller O. Brad
Published: April 2005

Swine vesicular disease virus (SVDV) evolved from coxsackie B virus serotype 5 (CVB5) in the recent past, crossing the species barrier from humans to pigs. Here, SVDV isolates from early and recent outbreaks have been compared for their capacity to utilize the progenitor virus receptors coxsackie–adenovirus receptor (CAR) and decay-accelerating factor (DAF; CD55). Virus titre of CVB5 and SVDV isolates It′66 and UK′72 on human HeLa cells was reduced by pre-incubation with either anti-DAF or anti-CAR antibodies; however, recent SVDV isolates R1072, R1120 and SPA′93 did not infect HeLa cells lytically. CVB5 and SVDV infection of the pig cell line IB-RS-2 was inhibited completely by anti-CAR antibodies for all isolates, and no reduction was observed following pre-incubation of cells with anti-pig DAF antibodies. Expression of human DAF in the pig cell line IB-RS-2 enhanced the virus titre of early SVDV isolates by 25-fold, but had no effect on recent SVDV isolate titre. Binding of radiolabelled CVB5 to IB-RS-2 cells was increased seven- to eightfold by expression of human DAF and binding of early SVDV isolates was increased 1·2–1·3-fold, whereas no increase in binding by recent SVDV isolates was mediated by human DAF expression. Addition of soluble hDAF-Fc inhibited CVB5, but not SVDV, infection of pig cells. Pre-incubation of all viruses with soluble hCAR-Fc blocked infection of IB-RS-2 pig cells completely; titration of the amount of soluble hCAR-Fc required to block infection revealed that early isolate UK′72 was the least susceptible to inhibition, and the most recent isolate, SPA′93, was the most susceptible.
Apoptotic events induced by human rhinovirus infection
Authors: Deszcz Luiza , Gaudernak Elisabeth , Kuechler Ernst , Seipelt Joachim
Published: April 2005

HeLa and 16HBE14o−bronchial epithelium cells infected with human rhinovirus serotype 14 (HRV14) were found to exhibit typical apoptotic morphological alterations, such as cell contraction and nuclear condensation. These events coincided with high-molecular-weight DNA fragmentation, activation of caspase-9 and caspase-3 and poly(ADP–ribose) polymerase cleavage. Caspase activation was preceded by cytochromectranslocation from the mitochondria to the cytoplasm, indicating that apoptosis caused by HRV14 infection was triggered predominantly via the mitochondrial pathway. Apoptosis did not affect HRV14 replication per se, but it facilitated the release of newly formed virus from cells. As apoptosis was fully induced at the time of maximal accumulation of progeny HRV14, it is postulated that apoptosis contributed to the destabilization of the cell and facilitated viral progeny release.
Epstein–Barr virus EBNA3 proteins bind to the C8/α7 subunit of the 20S proteasome and are degraded by 20S proteasomes in vitro, but are very stable in latently infected B cells
Authors: Touitou Robert , O'Nions Jenny , Heaney Judith , Allday Martin J.
Published: April 2005

A yeast two-hybrid screen using EBNA3C as bait revealed an interaction between this Epstein–Barr virus (EBV)-encoded nuclear protein and the C8 (α7) subunit of the human 20S proteasome. The interaction was confirmed by glutathione S-transferase (GST) pull-down experiments and these also revealed that the related proteins EBNA3A and EBNA3B can bind similarly to C8/α7. The interaction between these viral proteins and GST–C8/α7 was shown to be significantly more robust than the previously reported interaction between C8/α7 and the cyclin-dependent kinase inhibitor p21WAF1/CIP1. Co-immunoprecipitation of the EBNA3 proteins with C8/α7 was also demonstrated after transfection of expression vectors into B cells. Consistent with this ability to bind directly to an α-subunit of the 20S proteasome, EBNAs 3A, 3B and 3C were all degraded in vitro by purified 20S proteasomes. However, surprisingly, no sign of proteasome-mediated turnover of these latent viral proteins in EBV-immortalized B cells could be detected, even in the presence of gamma interferon. In actively proliferating lymphoblastoid cell lines, EBNAs 3A, 3B and 3C appear to be remarkably stable, with no evidence of either de novo synthesis or proteasome-mediated degradation.
Mobility of the hepatitis C virus NS4B protein on the endoplasmic reticulum membrane and membrane-associated foci
Authors: Gretton Sarah N. , Taylor Annette I. , McLauchlan John
Published: April 2005

The hepatitis C virus (HCV) non-structural protein NS4B induces morphological changes in the endoplasmic reticulum (ER) membrane that may have a direct role in viral RNA replication. A chimeric GFP–NS4B fusion protein located to the ER membrane and to foci that were attached to the ER. Thesemembrane-associatedfoci (MAFs) could be related to the membrane alterations observed in cells that replicate HCV RNA. The relationship of MAFs to pre-existing cellular structures is not known. Indirect immunofluorescence analysis demonstrated that they did not contain a cellular marker for vesicles, which have been implicated in the replication of other viruses. From photobleaching studies to examine diffusion of NS4B, the GFP-tagged protein had reduced mobility on MAFs compared with on the ER membrane. This slower mobility suggested that NS4B is likely to form different interactions on MAFs and the ER.
Temperature-sensitive mutants of enterovirus 71 show attenuation in cynomolgus monkeys
Authors: Arita Minetaro , Shimizu Hiroyuki , Nagata Noriyo , Ami Yasushi , Suzaki Yuriko , Sata Tetsutaro , Iwasaki Takuya , Miyamura Tatsuo
Published: April 2005

Enterovirus 71 (EV71) is one of the major causative agents of hand, foot and mouth disease and is sometimes associated with serious neurological disorders. In this study, an attempt was made to identify molecular determinants of EV71 attenuation of neurovirulence in a monkey infection model. An infectious cDNA clone of the virulent strain of EV71 prototype BrCr was constructed; temperature-sensitive (ts) mutations of an attenuated strain of EV71 or of poliovirus (PV) Sabin vaccine strains were then introduced into the infectious clone.In vitroandin vivophenotypes of the parental and mutant viruses were analysed in cultured cells and in cynomolgus monkeys, respectively. Mutations in 3D polymerase (3Dpol) and in the 3′ non-translated region (NTR), corresponding totsdeterminants of Sabin 1, conferred distinct temperature sensitivity to EV71. An EV71 mutant [EV71(S1-3′)] carrying mutations in the 5′ NTR, 3Dpoland in the 3′ NTR showed attenuated neurovirulence, resulting in limited spread of virus in the central nervous system of monkeys. These results indicate that EV71 and PV1 share common genetic determinants of neurovirulence in monkeys, despite the distinct properties in their original pathogenesis.
Evidence from nature: interspecies spread of heron hepatitis B viruses
Authors: Lin Li , Prassolov Alexej , Funk Anneke , Quinn Laura , Hohenberg Heinz , Frölich Kai , Newbold John , Ludwig Arne , Will Hans , Sirma Hüseyin , Steinbach Falko
Published: April 2005

Heron hepatitis B viruses (HHBVs) in three subspecies of free-living great blue herons (Ardea herodias) from Florida, USA, were identified and characterized. Eight of 13 samples were positive in all assays used, whereas sera from egrets, which are also members of the family Ardeidae, were negative in the same assays. Comparative phylogenetic analysis of viral DNA sequences from the preS/S region of previously reported and novel HHBV strains isolated from captive grey herons (Germany) and free-ranging great blue herons (USA), respectively, revealed a strong conservation (95 % sequence similarity) with two separate clusters, implying a common ancestor of all strains. Our data demonstrate for the first time that different subspecies of herons are infected by HHBV and that these infections exist in non-captive birds. Phylogenetic analysis and the fact that the different heron species are geographically isolated populations suggest that lateral transmission, virus adaptation and environmental factors all play a role in HHBV spreading and evolution.
Entry of the vaccinia virus intracellular mature virion and its interactions with glycosaminoglycans
Authors: Carter Gemma C. , Law Mansun , Hollinshead Michael , Smith Geoffrey L.
Published: April 2005

Vaccinia virus (VACV) produces two distinct enveloped virions, the intracellular mature virus (IMV) and the extracellular enveloped virus (EEV), but the entry mechanism of neither virion is understood. Here, the binding and entry of IMV particles have been investigated. The cell receptors for IMV are unknown, but it was proposed that IMV can bind to glycosaminoglycans (GAGs) on the cell surface and three IMV surface proteins have been implicated in this. In this study, the effect of soluble GAGs on IMV infectivity was reinvestigated and it was demonstrated that GAGs affected IMV infectivity partially in some cells, but not at all in others. Therefore, binding of IMV to GAGs is cell type-specific and not essential for IMV entry. By using electron microscopy, it is demonstrated that IMV from strains Western Reserve and modified virus Ankara enter cells by fusion with the plasma membrane. After an IMV particle bound to the cell, the IMV membrane fused with the plasma membrane and released the virus core into the cytoplasm. IMV surface antigen became incorporated into the plasma membrane and was not left outside the cell, as claimed in previous studies. Continuity between the IMV membrane and the plasma membrane was confirmed by tilt-series analysis to orientate membranes perpendicularly to the beam of the electron microscope. This analysis shows unequivocally that IMV is surrounded by a single lipid membrane and enters by fusion at the cell surface.
Coordination of Nuclear and Mitochondrial Genome Expression during Mitochondrial Biogenesis in Arabidopsis
Authors: Giegé Philippe , Sweetlove Lee J. , Cognat Valérie , Leaver Christopher J.
Published: April 2005

Mitochondrial biogenesis and function require the regulated and coordinated expression of nuclear and mitochondrial genomes throughout plant development and in response to cellular and environmental signals. To investigate the levels at which the expression of nuclear and mitochondrially encoded proteins is coordinated, we established an Arabidopsis thaliana cell culture system to modulate mitochondrial biogenesis in response to sugar starvation and refeeding. Sucrose deprivation led to structural changes in mitochondria, a decrease in mitochondrial volume, and a reduction in the rate of cellular respiration. All these changes could be reversed by the readdition of sucrose. Analysis of the relative mRNA transcript abundance of genes encoding nuclear and mitochondrially encoded proteins revealed that there was no coordination of expression of the two genomes at the transcript level. An analysis of changes in abundance and assembly of nuclear-encoded and mitochondrially encoded subunits of complexes I to V of the mitochondrial inner membrane in organello protein synthesis and competence for protein import by isolated mitochondria suggested that coordination occurs at the level of protein-complex assembly. These results further suggest that expression of the mitochondrial genome is insensitive to the stress imposed by sugar starvation and that mitochondrial biogenesis is regulated by changes in nuclear gene expression and coordinated at the posttranslational level.
Numerical modelling of interface scattering of seismic wavefield from a random rough interface in an acoustic medium: comparison between 2D and 3D cases
Authors: Makinde Wasiu , Favretto‐Cristini Nathalie , De Bazelaire Eric
Published: April 2005

Seismic wavefield scattering from a statistically randomly rough interface in a multilayered piecewise homogeneous medium is studied in 3D. The influence of the surface roughness on the scattered wavefield is analysed numerically by using a finite‐difference operator in the acoustic domain. Since interface scattering in the real practical sense is a 3D physical phenomenon, we show in this work that the scattering response of a randomly rough interface is not the same in 3D situations as in the 2D cases described in some earlier works. For a given interface roughness height in 3D, an interface roughness height at least three times greater is required to produce an equivalent phase scattering effect in 2D situations, for a given correlation length of the interface roughness scale. Based on observations from spectral analysis, we show that scattering results principally in de‐phasing and frequency band‐limiting of the incident wavefront, the frequency band‐limiting properties being comparable to cases reported in the literature for absorption and thin‐layer filtering. The interface scattering phenomenon should be critically considered when using amplitude and phase information from seismic signal during inversion processes.
A radiomagnetotelluric survey on an oil‐contaminated area near the Brazi Refinery, Romania
Authors: Tezkan B. , Georgescu P. , Fauzi U.
Published: April 2005

Scalar radiomagnetotelluric measurements were carried out on a contaminated test area close to the Brazi Refinery in Romania in order to detect and to monitor a 1 m thick oil layer expected at 5 m depth. Radio transmitters broadcasting in a frequency range from 10 kHz to 300 kHz were selected to observe the apparent resistivity and the phase data associated with the E‐ and B‐polarizations. They were located parallel and perpendicular to the assumed strike direction of the contamination plume. The data were interpreted by a 2D inversion technique from which the conductivity structure of the area was derived. The 2D inversion models of all profiles on the contaminated area show a poor‐conductivity zone above the groundwater table which could be associated with the oil contamination.

A first attempt was also made to monitor the contaminated layer: the radiomagnetotelluric measurements were repeated on the same profiles a year later, but this time in a dry period, not in a rainy one. The 2D inversion results of the measurements in the dry period indicate that the high‐resistivity layer moved closer to the surface. Additional reference measurements were then carried out on a non‐contaminated area situated at a distance from the refinery, in the opposite direction to the flow of the groundwater. These reference measurements were used for the derivation of the unperturbed geology and they were also compared with the measurements of the contaminated test area. There is a significant difference in the frequency dependences of the apparent resistivities of the reference and contaminated areas, which could indicate a contamination at shallow depth. The 2D inversion results show the increase of resistivity at a depth of about 5 m beneath the contaminated area where the oil contamination is expected according to the information from the boreholes.
A field test of imaging properties of rotational invariants of the magnetotelluric impedance tensor
Authors: Szarka László , Ádám Antal , Menvielle Michel
Published: April 2005

A part of the Békés Basin (an extensional sub‐basin of the Pannonian Basin, where the basement under thick Pannonian sediments is well known from deep boreholes and from seismic measurements, and where many magnetotelluric (MT) soundings have been carried out for frequencies ranging from 1 to 10−3 Hz) was selected as a test area to assess the imaging performances of various apparent‐resistivity definitions computed with rotational invariants of either the real part of the complex impedance tensor, or its imaginary part, or both. A comparison (based on earlier 3D numerical studies) has been made between the magnetotelluric images obtained in this way and the depths to the high‐resistivity basement, as known from boreholes and seismic investigations. The correlation coefficient between the series of basement depth values at 39 MT sites and the apparent‐resistivity values was found to be stronger and high correlation appeared at a shorter period when it was computed with apparent resistivities based on the real tensor rather than with apparent resistivities based on the imaginary tensor. In the light of our studies, ρReZ and the impedance phase seem to be more informative than any other combination of magnetotelluric interpretation parameters.
Multi‐refractor imaging with stacked refraction convolution section
Authors: De Franco Roberto
Published: April 2005

Multi‐refractor imaging is a technique for constructing a single two‐dimensional image of a number of refractors by stacking multiple convolved and cross‐correlated reversed shot records. The method is most effective with high‐fold data that have been obtained with roll‐along acquisition programs because the stacking process significantly improves the signal‐to‐noise ratios. The major advantage of the multi‐refractor imaging method is that all the data can be stacked to maximize the signal‐to‐noise ratios before the measurement of any traveltimes. However, the signal‐to‐noise ratios can be further increased if only those traces that have arrivals from the same refractor are used, and if the correct reciprocal times or traces are employed.

A field case study shows that multi‐refractor imaging can produce a cross‐section similar to the familiar reflection cross‐section with substantially higher signal‐to‐noise ratios for the equivalent interfaces.
The Continuity–Change Duality in Narrative Texts of Organizational Identity*
Authors: Chreim Samia
Published: April 2005

abstract This paper focuses on how continuity and change are managed discursively in narrative texts of organizational identity and thus helps move forward the discussion about persistence and change in organizational identity. The study reports on the content, context and authorial elements of the evolving narrative composed by a Canadian bank's senior managers. The analysis indicates that the discursive strategies employed by organizational authors to establish confluence (or simultaneous continuity and change) include the selective reporting of elements from the past, present and future, the juxtaposition of the ‘modern and attractive’ with the ‘outdated and undesirable’, the persistent use of expansive labels that allow the addition and subtraction of meanings attached to the labels, and the importation of selected themes from the wider macro‐discourses. In keeping with the view that organizations are plurivocal, evolving narratives of the organization in the business press are also presented. These narratives contribute themes that are at times concordant with senior managers’ accounts and thus confirm the value of the changes in identity elaborated by management; at other times, press accounts are discordant with senior managers’ narratives and provide alternative evaluations of the changes. The paper concludes with reflections on the indeterminacy of both organizational identity – for the texts that constitute it remain open to multiple readings and to subsequent re‐writing that continually destabilize it – and the narrative research enterprise that falls short of providing comprehensive and incontrovertible accounts of the voices that constitute organizations.
Language and the Circuits of Power in a Merging Multinational Corporation
Authors: Vaara Eero , Tienari Janne , Piekkari Rebecca , Säntti Risto
Published: April 2005

abstract  We argue in this paper that corporate language policies have significant power implications that are easily overlooked. By drawing on previous work on power in organizations (Clegg, 1989), we examine the complex power implications of language policy decisions by looking at three levels of analysis: episodic social interaction, identity/subjectivity construction, and reconstruction of structures of domination. In our empirical analysis, we focus on the power implications of the choice of Swedish as the corporate language in the case of the recent banking sector merger between the Finnish Merita and the Swedish Nordbanken. Our findings show how language skills become empowering or disempowering resources in organizational communication, how these skills are associated with professional competence, and how this leads to the creation of new social networks. The case also illustrates how language skills are an essential element in the construction of international confrontation, lead to a construction of superiority and inferiority, and also reproduce post‐colonial identities in the merging bank. Finally, we also point out how such policies ultimately lead to the reification of post‐colonial and neo‐colonial structures of domination in multinational corporations.
Does the Natural‐Resource‐Based View of the Firm Apply in an Emerging Economy? A Survey of Foreign Invested Enterprises in China*
Authors: Chan Ricky Y. K.
Published: April 2005

abstract  This study explores whether enterprises operating in China benefit from the practice of the tenets of the natural‐resource‐based view of the firm (NRVF). To this end, a conceptual model is proposed that depicts the major determinants and consequences of the practice of NRVF. By and large, the survey data collected from foreign invested enterprises (FIEs) in China confirm the validity of the proposed model, and suggest that the NRVF is applicable in the world's largest and fastest‐growing emerging economy. These results remind FIEs in China of the opportunities to enhance corporate environmental and financial performance through the adoption of environmental strategies. Various regression and multi‐group analyses conducted in this study further reveal significant moderating influences of perceived environmental uncertainties, operating mode, and firm size on the process of achieving company‐wide ecological sustainability.
Offshoring in the New Global Political Economy
Authors: Levy David L.
Published: April 2005

abstract  This essay challenges claims by economists and management scholars that ‘offshoring’ is simply another form of trade with mutual benefits. I argue that reducing wages through offshoring leads to wealth creation for shareholders but not necessarily for countries and employees, and that many displaced workers have difficulty ‘trading up’ to higher skilled jobs. Offshoring is a new phenomenon that entails the organizational and technological ability to relocate specific tasks and coordinate a geographically dispersed network of activities. It decouples the linkages between economic value creation and geographic location. The result is the creation of global commodity markets for particular skills and a shift in the balance of market power among firms, workers, and countries.
Influence of seasonally adjusted exposure to cold and darkness on cognitive performance in circumpolar residents
Authors: PALINKAS LAWRENCE A. , MÄKINEN TIINA M. , PÄÄKKÖNEN TIINA , RINTAMÄKI HANNU , LEPPÄLUOTO JUHANI , HASSI JUHANI
Published: April 2005

The effects of seasonally adjusted 24‐h exposure to cold and darkness on cognitive performance in urban circumpolar residents was assessed in 15 male subjects who spent three 24‐h periods in a climatic chamber at 65° latitude during the winter (January–March) and/or summer (August–September). Each subject was exposed to three different environmental conditions in random order: (1) 22 °C temperature and 500 lx lighting; (2) 10 °C temperature and 500 lx lighting; and (3) 10 °C temperature and 0.5–l lx lighting. Accuracy on an addition‐subtraction task was significantly greater in the summer than in the winter (p= 0.038), while accuracy on a repeated acquisition task was significantly greater in the winter than in the summer (p < 0.001). Independent of season, exposure to cold and darkness was significantly associated with a decline in response time on five cognitive tests, an improvement in accuracy on three tests measuring complex cognitive tasks, and a decline in accuracy on two tests measuring simple tasks. Increased performance on complex tasks may result from increased arousal in response to the combination of cold temperatures and dim light characteristic of the winter in urban circumpolar settings.
Different working memory capacity in normal young adults for visual and tactile letter recognition task
Authors: BLISS IRINA , HÄMÄLÄINEN HEIKKI
Published: April 2005

Thirty‐nine young adult participants performing the visual and tactile n‐back working memory task were compared. In the visual task, letters were presented on a computer screen and in the tactile task, plastic letters embedded on a board were explored tactually. The amount of incorrect responses increased with increasing memory load in both tasks, but was significantly lower in the visual task. Subgrouping the participants with extreme performances into “skilled” and “poor” performers showed that the best performance was found among “skilled” visual performers, and the worst one among “poor” tactile performers. There was more interindividual variation among tactile than visual performance. We conclude that tactile working memory capacity, measured here by letter recognition and letter memory, is generally more limited and shows more variability than visual memory in normal sighted participants.
Orthography as a handicap? A direct comparison of spelling acquisition in Danish and Icelandic
Authors: JUUL HOLGER , SIGURDSSON BALDUR
Published: April 2005

Spelling of cross‐linguistically very similar nonwords was compared in 115 Danish and 77 Icelandic children (primarily 3rd and 4th graders). Danish children made more errors than Icelandic children on word medial consonant doublets and on word initial consonant clusters, even when the groups compared were matched on simpler spelling tasks. These results suggest that the acquisition of phonemic encoding skills is slower in “deep” orthographies such as Danish than in more “transparent” orthographies such as Icelandic. The effect of orthography was expected for consonant doublets because of the relatively more complex sound‐letter correspondences in Danish. For consonant clusters, however, sound‐letter correspondences are perfectly regular in both languages. The study thus points to the conclusion that even the mastery of regular sound‐letter correspondences may be delayed in deep orthographies.
Nonparametric Estimation of Spatial Segregation in a Multivariate Point Process: Bovine Tuberculosis in Cornwall, UK
Authors: Diggle Peter , Zheng Pingping , Durr Peter
Published: April 2005

The paper is motivated by a problem in veterinary epidemiology, in which spatially referenced breakdowns of bovine tuberculosis are classified according to their genotype and year of occurrence. We develop a nonparametric method for addressing spatial segregation in the resulting multivariate spatial point process, with associated Monte Carlo tests for the null hypothesis that different genotypes are randomly intermingled and no temporal changes in spatial segregation. Our spatial segregation estimates use a kernel regression method with bandwidth selected by a multivariate cross-validated likelihood criterion.
Semiparametric Estimation of the Duration of Immunity from Infectious Disease Time Series: Influenza as a Case-Study
Authors: Xia Yingcun , Gog Julia R. , Grenfell Bryan T.
Published: April 2005

An important epidemiological problem is to estimate the decay through time of immunity following infection. For this purpose, we propose a semiparametric time series epidemic model that is based on the mechanism of the susceptible–infected–recovered–susceptible system to analyse complex time series data. We develop an estimation method for the model. Simulations show that the approach proposed can capture the non-linearity of epidemics as well as estimate the decay of immunity. We apply our approach to influenza in France and the Netherlands and show a rapid decline in immunity following infection, which agrees with recent spatiotemporal analyses.
A Nonparametric Bayesian Model for Inference in Related Longitudinal Studies
Authors: Müller Peter , Rosner Gary L. , Iorio Maria De , MacEachern Steven
Published: April 2005

We discuss a method for combining different but related longitudinal studies to improve predictive precision. The motivation is to borrow strength across clinical studies in which the same measurements are collected at different frequencies. Key features of the data are heterogeneous populations and an unbalanced design across three studies of interest. The first two studies are phase I studies with very detailed observations on a relatively small number of patients. The third study is a large phase III study with over 1500 enrolled patients, but with relatively few measurements on each patient. Patients receive different doses of several drugs in the studies, with the phase III study containing significantly less toxic treatments. Thus, the main challenges for the analysis are to accommodate heterogeneous population distributions and to formalize borrowing strength across the studies and across the various treatment levels. We describe a hierarchical extension over suitable semiparametric longitudinal data models to achieve the inferential goal. A nonparametric random-effects model accommodates the heterogeneity of the population of patients. A hierarchical extension allows borrowing strength across different studies and different levels of treatment by introducing dependence across these nonparametric random-effects distributions. Dependence is introduced by building an analysis of variance (ANOVA) like structure over the random-effects distributions for different studies and treatment combinations. Model structure and parameter interpretation are similar to standard ANOVA models. Instead of the unknown normal means as in standard ANOVA models, however, the basic objects of inference are random distributions, namely the unknown population distributions under each study. The analysis is based on a mixture of Dirichlet processes model as the underlying semiparametric model.
ON HISTORY CONSIDERED AS EPIC POETRY
Authors: BERMEJO BARRERA JOSÉ CARLOS
Published: April 2005

This essay defines history as an interaction of three elements: description, evocation, and expression. These three elements should interact and combine without any of them over‐whelming the remaining two. In combining the three elements, history carries on from epic poetry, which was its source. Highlighting the three elements reveals the ways history synthesizes the three historical stages outlined by Comte, namely, the theological, the metaphysical, and the scientific.
THE ENDURING POWER OF RACISM: A RECONSIDERATION OF WINTHROP JORDAN'S WHITE OVER BLACK
Authors: SHORE LAURENCE
Published: April 2005

As a history of the origins and development of American racism, White over Black received great acclaim upon its publication in 1968. Deeply researched and covering some 650 pages, it eschewed professional jargon and offered a deft prose style and close attention to matters of sexuality in revealing the origins and lasting influence of racist attitudes arising from Englishmen's impressions of blacks before they became, preeminently, slaves in North America. Jordan's careful weighing of evidence and causation made readers appreciate what he believed his evidence repeatedly demonstrated about white Americans’ attitudes toward African‐Americans: “the power of irrationality in men.” Despite the initial acclaim and scholarly achievement, White over Black soon lost pace with the curve of politics and academic fashion. By the mid‐1970s, the post‐World War II liberal consensus on racial issues had disintegrated, and professional historians were writing principally for other professional historians. Within a decade after its publication, White over Black was relegated to the wasteland of the “suggested supplemental reading list.” However, the book's grasp of the fundamental historical issues requiring explanation has received recent affirmation from influential scholarly and political quarters. A dispassionate review of the literature leading up to and following White over Black's publication indicates that Jordan's emphasis on the causal contribution of racist attitudes to the rise of African slavery in British North America was on target. Moreover, Jordan's appreciation that academic historians should write for nonprofessionals is now widely held inside the academy. The historical accuracy and cogency of expression of Jordan's perspective on race and slavery make White over Black worth reexamining.
THE GHOST OF BIG HISTORY IS ROAMING THE EARTH1
Authors: Spier Fred
Published: April 2005

Maps of Time: An Introduction to Big History. By David Christian.
THE STATE OF HISTORY AND THE EMPIRE OF METAPHYSICS1
Authors: Hunter Ian
Published: April 2005

The Limits of History. By Constantin Fasolt.