bluuebunny/crossref_metadata_2025 huggingface dataset:
Confidence intervals for the amount of heterogeneity in meta‐analysis
Authors: Viechtbauer Wolfgang
Published: February 2006

Effect size estimates to be combined in a systematic review are often found to be more variable than one would expect based on sampling differences alone. This is usually interpreted as evidence that the effect sizes are heterogeneous. A random‐effects model is then often used to account for the heterogeneity in the effect sizes. A novel method for constructing confidence intervals for the amount of heterogeneity in the effect sizes is proposed that guarantees nominal coverage probabilities even in small samples when model assumptions are satisfied. A variety of existing approaches for constructing such confidence intervals are summarized and the various methods are applied to an example to illustrate their use. A simulation study reveals that the newly proposed method yields the most accurate coverage probabilities under conditions more analogous to practice, where assumptions about normally distributed effect size estimates and known sampling variances only hold asymptotically. Copyright © 2006 John Wiley & Sons, Ltd.
Business environment and entrepreneurial activity in Nigeria: implications for industrial development
Authors: Agboli Mary , Christian Ukaegbu Chikwendu
Published: February 2006

Commonsense suggests, and academic studies agree, that an ameliorative business environment enables entrepreneurial activity and boosts enterprise performance. This paper examines the business environment in southeast Nigeria, using two separate but complementary studies. Defined in terms of infrastructure, access to credit, bureaucratic practices and regulatory policy, the business environment in southeast Nigeria is stressful, and so has the capacity to limit entrepreneurial activity. This stressful business environment, which is a nationwide phenomenon, poses obstacles to Nigeria's industrial development.
Beyond the plantation: Mauritius in the global division of labour
Authors: Lincoln David
Published: February 2006

Mauritius' position within the global division of labour has changed considerably since the country gained its independence from Britain in 1968. This reflects change in the country's employment structure and a re-articulation within global chains of production. In a transformation led by the state, the formerly plantation-based economy has become a predominantly service- and manufacturing-based one. Mauritius has since set its sights on becoming a ‘cyber-island’, a regional hub for computer-based service provision. In charting this developmental route, the Mauritian state has had recourse to favourable socio-historical conditions. By highlighting these cultural influences on the globalisation of the Mauritian economy, this study affirms the value of analysing new divisions of labour as an aspect of the centuries-old process of globalisation.
Politics, donors and the ineffectiveness of anti-corruption institutions in Uganda
Authors: Tangri Roger , Mwenda Andrew M.
Published: February 2006

Elite corruption in Uganda constitutes an essential means of consolidating the present government in power. Political leaders have therefore shown little commitment to act to curb practices that could affect their political support. Instead, anti-corruption institutions have been influenced and controlled whenever they threatened to expose the corrupt ways of Uganda's state elites. Donors have also for many years been reluctant to use their substantial economic assistance to press the government to confront wrongdoing by state elites. They have not wanted to undermine a government which they have held up as one of the most successful in Africa in carrying out donor-sponsored economic reforms. But by giving large amounts of aid to a corrupt and quasi-authoritarian government, as well as being reticent in their public criticism of abuse of power and corruption, donors have abetted the actions of Uganda's leaders in weakening those bodies that could hold them responsible for abusing their public positions.
Performance Studies and Po-chang’s Ox: Steps to a Paradoxology of Performance
Authors: Kershaw Bez
Published: February 2006

Invited by NTQ to review two recent books on performance studies – Jon McKenzie's Perform or Else: from Discipline to Performance and Richard Schechners's Performance Studies: an Introduction – Baz Kershaw found himself in a Catch-22 situation: given the vast territories they claimed for the discipline, how could a short survey do them justice? Yet more perplexing, how might a close analysis of their diffusive visions proceed, even in a longer essay? Struck by their common use of air disasters as denouements and their respective publication dates just six months before and after 9/11, he uses these and other homologies as a route into exploring the ethical and political implications for the new century of the arguments employed by the two texts. Drawing on the philosophical innovation of ‘dialetheism’, which deploys paradox to stretch the bounds of classical logic, he also considers the books' differences and suggests a kind of de-territorialized reconciliation through his notion of a ‘paradoxology’ of performance. He offers the resulting search for depth in surfaces, beginnings in endings, presence in absences, and truth in contradictions as an exemplification of philosopher Po-chang's aphorism about the quest for Buddha's nature: ‘It’s much like riding an ox in search of the ox.’ Baz Kershaw holds the Chair of Drama at Bristol University. His many publications include Engineers of the Imagination (Methuen, 1990), The Politics of Performance (Routledge, 1992), and The Radical in Performance (Routledge, 1999), and he is editor of The Cambridge History of British Theatre: Volume 3, Since 1895 (CUP, 2005). He is also Director of the AHRC-funded major research project PARIP – Practice as Research in Performance.
Stanislavsky, Spirituality, and the Problem of the Wounded Actor
Authors: Lloyd Benjamin
Published: February 2006

In the following article Benjamin Lloyd uses the work of the noted Swiss psychologist Alice Miller to propose a new archetype – ‘the wounded actor’, a person in the throes of a narcissistic disorder, as defined by Miller in her book The Drama of the Gifted Child. He suggests that conventional actor training will not help the wounded actor, but that the re-introduction of spirituality into the acting-class curriculum may do so. In this light he looks at Stanislavsky's writings about spirituality, focusing on the chapter in An Actor Prepares called ‘Communion’. Linking Stanislavsky's spirituality to the writings and thought of Leo Tolstoy, he explores the reasons why the spiritual nature of Stanislavsky's work has not been generally explored in the West, and suggests some ways in which acting teachers may introduce spiritual concerns into their curricula. Benjamin Lloyd teaches at Villanova University. His The Actor's Way: a Journal of Self-Discovery in Letters is due for publication later this year by Allworth Press, New York, and he is currently facilitating a workshop on possible intersections between Quaker spiritual practice and theatre-making called ‘Revival: Meetings for Theatre’.
Death and Beyond in J. B. Priestley's Johnson Over Jordan
Authors: Friedman Alan W.
Published: February 2006

Just as the imminence of the Second World War overshadowed the first production of J. B. Priestley's ‘modern morality play’, Johnson Over Jordan, in 1939, so did the disaster of 9/11 its only major revival, at the West Yorkshire Playhouse in 2001. Both productions boasted a major actor – respectively Ralph Richardson and Patrick Stewart – in the title role of a play which continued Priestley's search to find a theatrical style for his own metaphysical enquiries into the nature of time and the boundaries of human mortality. In this article, Alan W. Friedman sets the play in the context of western attitudes towards death and the nature of an afterworld, and relates these to Johnson's own journey after his funeral through rewindings of his past life towards some sort of reconciliation with its ending. Alan W. Friedman is Thaman Professor of English in the University of Texas, Austin, and has also taught at universities in England, Ireland, and France. He has published numerous articles and books, the latter including Multivalence: the Moral Quality of Form in the Modern Novel (Louisiana State UP, 1978), William Faulkner (Frederick Ungar, 1984), Fictional Death and the Modernist Enterprise (Cambridge UP, 1995), and (edited with Charles Rossman and Dina Sherzer) Beckett Translating/Translating Beckett (Pennsylvania State UP, 1987).
Effect of Mg/Ca ratio in seawater on shell composition in shallow benthic foraminifera
Authors: Segev Einat , Erez Jonathan
Published: February 2006

The ratio of magnesium to calcium (Mg/Ca) in CaCO3 shells of foraminifera is widely used to determine paleotemperatures. However, Mg/Ca is highly variable within and between species, suggesting a strong physiological influence on the incorporation of Mg2+ into the shells. While most field and laboratory calibrations have focused on the effect of temperature, we chose to study the effect of ambient Mg/Ca on the calcification process and the final shell composition. We cultured two species of symbiont‐bearing benthic foraminifera, Amphistegina lobifera and Amphistegina lessonii, in seawater with different Mg/Ca ratios. Electron probe analysis of the shell Mg/Ca revealed a positive (but not entirely linear) correlation with Mg/Ca in the culturing media with slightly different curves for each species. Partition coefficients of Mg2+ (DMg) in the calcite shells showed a decrease by a factor of roughly 2 between the lowest and highest Mg/Ca in the ambient water. This was previously demonstrated in inorganic calcite precipitation experiments. However, the biogenic DMg was significantly lower than the inorganic one, suggesting a physiological mechanism that reduces Mg/Ca at the calcification site. Unlike inorganic experiments that display a dependence of DMg on the kinetics of precipitation, the biogenic DMg is not correlated with the rate of calcification. Both DMg and calcification rates in our experiment were sensitive to the Mg/Ca ratio rather than the concentration of either Ca2+ or Mg2+. The largest addition of CaCO3 was obtained at Mg/Ca of 1, and not at present‐day seawater ratio (Mg/Ca = 5). This may reflect the Mg/Ca that prevailed during the Eocene (Mg/Ca ∼ 1.5), when this genus evolved.
Shell‐instability generated waves by low energy electrons on converging magnetic field lines
Authors: Sundkvist D. , Vaivads A. , Bogdanova Y. V. , Krasnoselskikh V. V. , Fazakerley A. , Décréau P. M. E.
Published: February 2006

Wave emissions at electron cyclotron harmonics and at frequencies above the local plasma frequency are commonly observed in different magnetospheric regions. We show that such emissions when observed in the cusp, mantle or polar cap can be generated by shell‐type electron distributions. We present an example of observations of such shell type distributions having positive slope in velocity space at low energies, about 10 eV. Numerical calculations of wave growth rate based on the observed particle distributions show that the shell‐instability can generate electrostatic and electromagnetic wave modes: whistler waves, electron cyclotron harmonics, upper‐hybrid as well as the RX mode. Local wave spectra observations are consistent with the presence of all those wave modes in data. A possible connection between low and high frequency waves is discussed. Our results clearly show the importance of detailed studies of the lowest energy electrons.
El Niño–Southern Oscillation drives North Atlantic Oscillation as revealed with nonlinear techniques from climatic indices
Authors: Mokhov I. I. , Smirnov D. A.
Published: February 2006

Based on the nonlinear techniques for estimation of coupling between oscillatory systems, we investigate the dynamics of climatic modes characterizing global and the Northern Hemisphere (NH) processes. In particular, indices of the North Atlantic Oscillation (NAO) and El Niño–Southern Oscillation (ENSO) for 1950–2004 are analyzed. The methods based on phase dynamics modeling and nonlinear “Granger causality” are used. We infer that ENSO affects NAO during the last half a century with confidence probability higher than 0.95. The influence is characterized with time delay in the range from a couple of months up to three years and increases during the last decade.
An extension of rate and state theory to poromechanics
Authors: Karner Stephen L.
Published: February 2006

Laboratory results on granular media have lead to fundamental theoretical developments (such as poroelasticity, rate‐ and state‐variable friction) that have found widespread application. This paper presents results from laboratory experiments that help constrain and combine these theories. Data from triaxial deformation experiments on quartz sand aggregates are used to illustrate stress‐dependent behavior of poroelastic parameters (e.g., the Biot‐Willis coefficient). The results from both volumetric compaction and frictional shear experiments are well described by poroelasticity as well as rate‐ and state‐variable friction. The combination of these constitutive relations may provide a powerful tool that can be used in numerical models that couple mechanical, hydraulic, and temporal processes in the descriptions of granular deformation.
Photochemical oxidation and changes in molecular composition of organic aerosol in the regional context
Authors: Robinson Allen L. , Donahue Neil M. , Rogge Wolfgang F.
Published: February 2006

This paper presents evidence that condensed‐phase organic compounds are significantly oxidized in regional air masses and in locations affected by regional transport, especially during the summer. The core of the paper examines a large data set of ambient organic aerosol concentrations for removal of reactive compounds relative to less‐reactive compounds. The approach allows visualization of both photochemistry and mixing of emissions from multiple sources in order to differentiate between the two phenomena. The focus is on hopanes and alkenoic acids, important markers for motor vehicle and cooking emissions. Ambient data from Pittsburgh, PA and the Southeastern United States contain evidence for significant photochemical oxidation of these compounds in the summertime. There is a strong seasonal pattern in the ratio of different hopanes to elemental carbon consistent with oxidation. In addition, measurements at rural sites indicate that hopanes are severely depleted in the regional air mass during the summer. Alkenoic acids also appear to be photochemically oxidized during the summertime; however, the oxidation rate appears to be much slower than that inferred from laboratory experiments. The significance of photochemistry is supported by rudimentary calculations which indicate substantial oxidation by OH radicals and ozone on a time scale of a few days or so, comparable to time scales for regional transport. Oxidation is non‐linear; therefore it represents a very substantial complication to linear source apportionment techniques such as the Chemical Mass Balance model.
On the long‐term context for late twentieth century warming
Authors: D'Arrigo Rosanne , Wilson Rob , Jacoby Gordon
Published: February 2006

Previous tree‐ring–based Northern Hemisphere temperature reconstructions portray a varying amplitude range between the “Medieval Warm Period” (MWP), “Little Ice Age” (LIA) and present. We describe a new reconstruction, developed using largely different methodologies and additional new data compared to previous efforts. Unlike earlier studies, we quantify differences between more traditional (STD) and Regional Curve Standardization (RCS) methodologies, concluding that RCS is superior for retention of low‐frequency trends. Continental North American versus Eurasian RCS series developed prior to merging to the hemispheric scale cohere surprisingly well, suggesting common forcing, although there are notable deviations (e.g., fifteenth to sixteenth century). Results indicate clear MWP (warm), LIA (cool), and recent (warm) episodes. Direct interpretation of the RCS reconstruction suggests that MWP temperatures were nearly 0.7°C cooler than in the late twentieth century, with an amplitude difference of 1.14°C from the coldest (1600–1609) to warmest (1937–1946) decades. However, we advise caution with this analysis. Although we conclude, as found elsewhere, that recent warming has been substantial relative to natural fluctuations of the past millennium, we also note that owing to the spatially heterogeneous nature of the MWP, and its different timing within different regions, present palaeoclimatic methodologies will likely “flatten out” estimates for this period relative to twentieth century warming, which expresses a more homogenous global “fingerprint.” Therefore we stress that presently available paleoclimatic reconstructions are inadequate for making specific inferences, at hemispheric scales, about MWP warmth relative to the present anthropogenic period and that such comparisons can only still be made at the local/regional scale.
Identification of a novel p300-specific-associating protein, PRS1 (phosphoribosylpyrophosphate synthetase subunit 1)
Authors: Kaida Atsushi , Ariumi Yasuo , Baba Keiko , Matsubae Masami , Takao Toshifumi , Shimotohno Kunitada
Published: February 2006

CBP [CREB (cAMP-response-element-binding protein)-binding protein] and p300 play critical roles in transcriptional co-activation, cell differentiation, proliferation and apoptosis. Multiple transcription factors associate with CBP/p300. With the exception of the SYT oncoprotein, no proteins have been identified that specifically associate with p300, but not CBP. In the present study, we isolated a novel p300-associated protein for which no interaction with CBP was observed by GST (glutathione S-transferase) pull-down assay using Jurkat cell lysates metabolically labelled with [35S]methionine. This protein bound the KIX (kinase-inducible) domain of p300. Following resolution by two-dimensional acrylamide gel electrophoresis, we identified the KIX-domain-bound protein by MS analysis as PRS1 (phosphoribosylpyrophosphate synthetase subunit 1), a protein essential for nucleoside biosynthesis. This is the first report to demonstrate the existence of a p300 KIX-domain-specific-interacting protein that does not interact with CBP. Thus p300 may play a role in the regulation of DNA synthesis through interactions with PRS1.
Enhanced catabolism of mitochondrial superoxide/hydrogen peroxide and aging in transgenic Drosophila
Authors: Bayne Anne-Cécile V. , Mockett Robin J. , Orr William C. , Sohal Rajindar S.
Published: February 2006

The generation of superoxide anion radicals (O2•−) and hydrogen peroxide (H2O2) during mitochondrial respiration has been widely postulated to be causally linked to the aging process. The hypothesis that a specific enhancement of mitochondrial O2•−/H2O2 catabolism would delay age-associated physiological changes and extend the lifespan was tested by simultaneous overexpression of MnSOD (manganese superoxide dismutase) and catalase, ectopically targeted to the mitochondrial matrix of transgenic Drosophila melanogaster. The increased activities of these antioxidative enzymes resulted in a decrease of mitochondrial H2O2 release and enhancement of free methionine content. The MnSOD/mitochondrial catalase transgenic flies displayed an enhanced resistance to experimental oxidative stress, induced by dietary H2O2 administration or by exposure to 100% ambient oxygen. However, the lifespan of the flies was decreased, by up to 43%, and this effect coincided with (i) an overall decrease in physical fitness, as measured by the speed of walking, and (ii) an agerelated decrease in mitochondrial state 3 (ADP-stimulated) respiration. These findings support the notion that mitochondrial O2•−/H2O2 production at physiological levels is essential for normal biological processes leading to the attainment of a normal lifespan.
Brown recluse spider (Loxosceles reclusa) venom phospholipase D (PLD) generates lysophosphatidic acid (LPA)
Authors: Lee Sangderk , Lynch Kevin R.
Published: February 2006

Envenomation by the brown recluse spider (Loxosceles reclusa) may cause local dermonecrosis and, rarely, coagulopathies, kidney failure and death. A venom phospholipase, SMaseD (sphingomyelinase D), is responsible for the pathological manifestations of envenomation. Recently, the recombinant SMaseD from Loxosceles laeta was demonstrated to hydrolyse LPC (lysophosphatidylcholine) to produce LPA (lysophosphatidic acid) and choline. Therefore activation of LPA signalling pathways may be involved in some manifestations of Loxosceles envenomation. To begin investigating this idea, we cloned a full-length cDNA encoding L. reclusa SMaseD. The 305 amino acid sequence of the L. reclusa enzyme is 87, 85 and 60% identical with those of L. arizonica, L. intermedia and L. laeta respectively. The recombinant enzyme expressed in bacteria had broad substrate specificity. The lysophospholipids LPC, LPI (18:1-1-oleyol lysophosphatidylinositol), LPS, LPG (18:1-1-oleoyl-lysophosphatidylglycerol), LBPA (18:1-1-oleoyl-lysobisphosphatidic acid) (all with various acyl chains), lyso-platelet-activating factor (C16:0), cyclic phosphatidic acid and sphingomyelin were hydrolysed, whereas sphingosylphosphorylcholine, PC (phosphatidylcholine; C22:6, C20:4 and C6:0), oxidized PCs and PAF (platelet-activating factor; C16:0) were not hydrolysed. The PAF analogue, edelfosine, inhibited enzyme activity. Recombinant enzyme plus LPC (C18:1) induced the migration of A2058 melanoma cells, and this activity was blocked by the LPA receptor antagonist, VPC32183. The recombinant spider enzyme was haemolytic, but this activity was absent from catalytically inactive H37N (His37→Asn) and H73N mutants. Our results demonstrate that Loxosceles phospholipase D hydrolyses a wider range of lysophospholipids than previously supposed, and thus the term ‘SMaseD’ is too limited in describing this enzyme.
Characterization of chito-oligosaccharides prepared by chitosanolysis with the aid of papain and Pronase, and their bactericidal action against Bacillus cereus and Escherichia coli
Authors: Vishu Kumar Acharya B. , Varadaraj Mandyam C. , Gowda Lalitha R. , Tharanathan Rudrapatnam N.
Published: February 2006

Papain (from papaya latex; EC 3.4.22.2) and Pronase (from Streptomyces griseus; EC 3.4.24.31) caused optimum depolymerization of chitosan at pH 3.5 and 37 °C, resulting in LMMC (low molecular mass chitosan) and chito-oligomeric–monomeric mixture. The yield of the latter was 14–16% and 14–19% respectively for papain- and Pronase-catalysed reactions, depending on the reaction time (1–5 h). HPLC revealed the presence of monomer(s) and oligomers of DP (degree of polymerization) 2–6, which was also confirmed by matrix-assisted laser-desorption ionization–time-of-flight MS. Along with the chito-oligomers, the appearance of only GlcNAc (N-acetylglucosamine) in Pronase-catalysed chitosanolysis was indicative of its different action pattern compared with papain. Fourier-transform infrared, liquid-state 13C-NMR spectra and CD analyses of chito-oligomeric–monomeric mixture indicated the release of GlcNAc/GlcNAc-rich oligomers. The monomeric sequence at the non-reducing ends of chito-oligomers was elucidated using N-acetylglucosaminidase. The chito-oligomeric–monomeric mixture showed better growth inhibitory activity towards Bacillus cereus and Escherichia coli compared with native chitosan. Optimum growth inhibition was observed with chito-oligomers of higher DP having low degree of acetylation. The latter caused pore formation and permeabilization of the cell wall of B. cereus, whereas blockage of nutrient flow due to the aggregation of chito-oligomers–monomers was responsible for the growth inhibition and lysis of E. coli, which were evidenced by scanning electron microscopy analysis. The spillage of cytoplasmic enzymes and native PAGE of the cell-free supernatant of B. cereus treated with chito-oligomeric–monomeric mixture further confirmed bactericidal activity of the latter. Use of papain and Pronase, which are inexpensive and easily available, for chitosanolysis, is of commercial importance, as the products released are of considerable biomedical value.
Modulation of differential transcription of tRNA genes through chromatin organization
Authors: Parthasarthy Akhila , Gopinathan Karumathil P.
Published: February 2006

In higher eukaryotes, tRNA multigene families comprise several copies encoding the same tRNA isoacceptor species. Of the 11 copies of a tRNA1Gly family from the mulberry silkworm Bombyx mori, individual members are differentially transcribed in vivo in the B. mori-derived BmN cell lines and in vitro in silk gland nuclear extracts. These genes have identical coding regions and hence harbour identical internal control sequences (the A and B boxes), but differ significantly in their 5′ and 3′ flanking regions. In the present study, we demonstrate the role of chromatin structure in the down-regulation of the poorly expressed copy, tRNA1Gly-6,7. Distinct footprints in the 5′-upstream region of the poorly transcribed gene in vitro as well as in vivo suggested the presence of nucleosomes. A theoretical analysis of the immediate upstream sequence of this gene copy also revealed a high propensity of nucleosome formation. The low transcription of tRNA1Gly-6,7 DNA was further impaired on assembly into chromatin and this inhibition was relieved by externally supplemented TFIIIC with an associated histone acetyltransferase activity. The inhibition due to nucleosome assembly was absent when the 5′-upstream region beyond −53 nt was deleted or entirely swapped with the 5′-upstream region of the highly transcribed gene copy, which does not position a nucleosome. Footprinting of the in vitro assembled tRNA1Gly-6,7 chromatin confirmed the presence of a nucleosome in the immediate upstream region potentially masking TFIIIB binding. Addition of TFIIIC unmasked the footprints present on account of the nucleosome. Our studies provide the first evidence for nucleosomal repression leading to differential expression of individual members from within a tRNA multigene family.
Identification of the hydrophobic strand in the A–B loop of leptin as major binding site III: implications for large-scale preparation of potent recombinant human and ovine leptin antagonists
Authors: Niv-Spector Leonora , Gonen-Berger Dana , Gourdou Isabelle , Biener Eva , Gussakovsky Eugene E. , Benomar Yackir , Ramanujan Krishnan V. , Taouis Mohammed , Herman Brian , Callebaut Isabelle , Djiane Jean , Gertler Arieh
Published: February 2006

Interaction of leptin with its receptors resembles that of interleukin-6 and granulocyte colony-stimulating factor, which interact with their receptors through binding sites I–III. Site III plays a pivotal role in receptors' dimerization or tetramerization and subsequent activation. Leptin's site III also mediates the formation of an active multimeric complex through its interaction with the IGD (immunoglobulin-like domain) of LEPRs (leptin receptors). Using a sensitive hydrophobic cluster analysis of leptin's and LEPR's sequences, we identified hydrophobic stretches in leptin's A–B loop (amino acids 39–42) and in the N-terminal end of LEPR's IGD (amino acids 325–328) that are predicted to participate in site III and to interact with each other in a β-sheet-like configuration. To verify this hypothesis, we prepared and purified to homogeneity (as verified by SDS/PAGE, gel filtration and reverse-phase chromatography) several alanine muteins of amino acids 39–42 in human and ovine leptins. CD analyses revealed that those mutations hardly affect the secondary structure. All muteins acted as true antagonists, i.e. they bound LEPR with an affinity similar to the wild-type hormone, had no agonistic activity and specifically inhibited leptin action in several leptin-responsive in vitro bioassays. Alanine mutagenesis of LEPR's IGD (amino acids 325–328) drastically reduced its biological but not binding activity, indicating the importance of this region for interaction with leptin's site III. FRET (fluorescence resonance energy transfer) microscopy experiments have documented that the transient FRET signalling occurring upon exposure to leptin results not from binding of the ligand, but from ligand-induced oligomerization of LEPRs mediated by leptin's site III.
The selective recruitment of mRNA to the ER and an increase in initiation are important for glucose-stimulated proinsulin synthesis in pancreatic β-cells
Authors: Greenman Isabel C. , Gomez Edith , Moore Claire E. J. , Herbert Terence P.
Published: February 2006

Glucose acutely stimulates proinsulin synthesis in pancreatic β-cells through a poorly understood post-transcriptional mechanism. In the present study, we demonstrate in pancreatic β-cells that glucose stimulates the recruitment of ribosome-associated proinsulin mRNA, located in the cytoplasm, to the ER (endoplasmic reticulum), the site of proinsulin synthesis, and that this plays an important role in glucose-stimulated proinsulin synthesis. Interestingly, glucose has greater stimulatory effect on the recruitment of proinsulin mRNA to the ER compared with other mRNAs encoding secretory proteins. This, as far as we are aware, is the first example whereby mRNAs encoding secretory proteins are selectively recruited to the ER and provides a novel regulatory mechanism for secretory protein synthesis. Contrary to previous reports, and importantly in understanding the mechanism by which glucose stimulates proinsulin synthesis, we demonstrate that there is no large pool of ‘free’ proinsulin mRNA in the cytoplasm and that glucose does not increase the rate of de novo initiation on the proinsulin mRNA. However, we show that glucose does stimulate the rate of ribosome recruitment on to ribosome-associated proinsulin mRNA. In conclusion, our results provide evidence that the selective recruitment of proinsulin mRNA to the ER, together with increases in the rate of initiation are important mediators of glucose-stimulated proinsulin synthesis in pancreatic β-cells.
αB-crystallin-assisted reactivation of glucose-6-phosphate dehydrogenase upon refolding
Authors: Kumar M. Satish , Reddy P. Yadagiri , Sreedhar B. , Reddy G. Bhanuprakash
Published: February 2006

αB-crystallin, a small heat-shock protein has been shown to prevent the aggregation of other proteins under various stress conditions. We have investigated the role of αB-crystallin in the reactivation of denaturant [GdmCl (guanidinium chloride)]-inactivated G6PD (glucose-6-phosphate dehydrogenase). Studies indicate that unfolding and inactivation of G6PD by GdmCl proceeds via formation of a molten globule-like state at low concentrations of GdmCl, which was characterized by having maximum surface hydrophobicity and no catalytic activity. At high concentrations of GdmCl, G6PD was completely unfolded, which upon dilution-induced refolding yielding 35% of original activity. In contrast, no activity was recovered when G6PD was refolded from a molten globule-like state. Interestingly, refolding of completely unfolded G6PD in the presence of αB-crystallin resulted in 70% gain of the original activity, indicating that αB-crystallin assisted in enhanced refolding of G6PD. Intriguingly, αB-crystallin was unable to reactivate G6PD from a molten globule-like state. Size-exclusion chromatography data indicate that αB-crystallin-assisted reactivation of completely unfolded G6PD is concomitant with the restoration of the native structure of G6PD. Nonetheless, αB-crystallin failed to reactivate G6PD from preformed aggregates. Moreover, methylglyoxal-modified α-crystallin, which occurs in aged and diabetic cataract lenses, was less efficient in the reactivation of denaturant inactivated G6PD. Diminished chaperone-like activity of α-crystallin due to post-translational modifications may thus result in the accumulation of aggregated/inactivated proteins.
Carbonic anhydrase (Nce103p): an essential biosynthetic enzyme for growth of Saccharomyces cerevisiae at atmospheric carbon dioxide pressure
Authors: Aguilera Jaime , Van Dijken Johannes P. , De Winde Johannes H. , Pronk Jack T.
Published: February 2006

The NCE103 gene of the yeast Saccharomyces cerevisiae encodes a CA (carbonic anhydrase) that catalyses the interconversion of CO2 and bicarbonate. It has previously been reported that nce103 null mutants require elevated CO2 concentrations for growth in batch cultures. To discriminate between ‘sparking’ effects of CO2 and a CO2 requirement for steady-state fermentative growth, we switched glucose-limited anaerobic chemostat cultures of an nce103 null mutant from sparging with pure CO2 to sparging with nitrogen gas. This switch resulted in wash-out of the biomass, demonstrating that elevated CO2 concentrations are required even under conditions where CO2 is produced at high rates by fermentative sugar metabolism. Nutritional analysis of the nce103 null mutant demonstrated that growth on glucose under a non-CO2-enriched nitrogen atmosphere was possible when the culture medium was provided with L-aspartate, fatty acids, uracil and L-argininine. Thus the main physiological role of CA during growth of S. cerevisiae on glucose-ammonium salts media is the provision of inorganic carbon for the bicarbonate-dependent carboxylation reactions catalysed by pyruvate carboxylase, acetyl-CoA carboxylase and CPSase (carbamoyl-phosphate synthetase). To our knowledge, the present study represents the first full determination of the nutritional requirements of a CA-negative organism to date.
NuMA is a major acceptor of poly(ADP-ribosyl)ation by tankyrase 1 in mitosis
Authors: Chang William , Dynek Jasmin N. , Smith Susan
Published: February 2006

Tankyrase 1 is a PARP [poly(ADP-ribose) polymerase] that localizes to multiple subcellular sites, including telomeres and mitotic centrosomes. Previous studies demonstrated that cells deficient in tankyrase 1 suffered a block in resolution of sister telomeres and arrested in early anaphase [Dynek and Smith (2004) Science 304, 97–100]. This phenotype was dependent on the catalytic PARP activity of tankyrase 1. To identify critical acceptors of PARsylation [poly(ADP-ribosyl)ation] by tankyrase 1 in mitosis, tankyrase 1 immunoprecipitates were analysed for associated PARsylated proteins. We identified NuMA (nuclear mitotic apparatus protein) as a major acceptor of poly(ADP-ribose) from tankyrase 1 in mitosis. We showed by immunofluorescence and immunoprecipitation that association between tankyrase 1 and NuMA increases dramatically at the onset of mitosis, concomitant with PARsylation of NuMA. Knockdown of tankyrase 1 by siRNA (small interfering RNA) eliminates PARsylation of NuMA in mitosis, confirming tankyrase 1 as the PARP responsible for this modification. However, even in the absence of tankyrase 1 and PARsylation, NuMA localizes to spindle poles. By contrast, siRNA knockdown of NuMA results in complete loss of tankyrase 1 from spindle poles. We discuss our result in terms of a model where PARsylation of NuMA by tankyrase 1 in mitosis could play a role in sister telomere separation and/or mitotic progression.
D-Amino acid residue in a defensin-like peptide from platypus venom: effect on structure and chromatographic properties
Authors: Torres Allan M. , Tsampazi Chryssanthi , Geraghty Dominic P. , Bansal Paramjit S. , Alewood Paul F. , Kuchel Philip W.
Published: February 2006

The recent discovery that the natriuretic peptide OvCNPb (Ornithorhynchus venom C-type natriuretic peptide B) from platypus (Ornithorynchus anatinus) venom contains a D-amino acid residue suggested that other D-amino-acid-containing peptides might be present in the venom. In the present study, we show that DLP-2 (defensin-like peptide-2), a 42-amino-acid residue polypeptide in the platypus venom, also contains a D-amino acid residue, D-methionine, at position 2, while DLP-4, which has an identical amino acid sequence, has all amino acids in the L-form. These findings were supported further by the detection of isomerase activity in the platypus gland venom extract that converts DLP-4 into DLP-2. In the light of this new information, the tertiary structure of DLP-2 was recalculated using a new structural template with D-Met2. The structure of DLP-4 was also determined in order to evaluate the effect of a D-amino acid at position 2 on the structure and possibly to explain the large retention time difference observed for the two molecules in reverse-phase HPLC. The solution structures of the DLP-2 and DLP-4 are very similar to each other and to the earlier reported structure of DLP-2, which assumed that all amino acids were in the L-form. Our results suggest that the incorporation of the D-amino acid at position 2 has minimal effect on the overall fold in solution.
Nogo-B is a new physiological substrate for MAPKAP-K2
Authors: Rousseau Simon , Peggie Mark , Campbell David G. , Nebreda Angel R. , Cohen Philip
Published: February 2006

The neurite outgrowth inhibitor protein Nogo is one of 300 proteins that contain a reticulon homology domain, which is responsible for their association with the endoplasmic reticulum. Here we have found that the Nogo-B spliceform becomes phosphorylated at Ser107 in response to lipopolysaccharide in RAW264 macrophages or anisomycin in HeLa cells. The phosphorylation is prevented by SB 203580, an inhibitor of SAPK2a (stress-activated protein kinase 2a)/p38α and SAPK2b/p38β, and does not occur in embryonic fibroblasts generated from SAPK2a/p38α-deficient mice. Nogo-B is phosphorylated at Ser107in vitro by MAPKAP-K2 [MAPK (mitogen-activated protein kinase)-activated protein kinase-2] or MAPKAP-K3, but not by other protein kinases that are known to be activated by SAPK2a/p38α. The anisomycin-induced phosphorylation of Ser107 in HeLa cells can be prevented by ‘knockdown’ of MAPKAP-K2 using siRNA (small interfering RNA). Taken together, our results identify Nogo-B as a new physiological substrate of MAPKAP-K2.
Piecewise affine models of chaotic attractors: The Rössler and Lorenz systems
Authors: Amaral Gleison F. V. , Letellier Christophe , Aguirre Luis Antonio
Published: February 2006

This paper proposes a procedure by which it is possible to synthesize Rössler [Phys. Lett. A 57, 397–398 (1976)] and Lorenz [J. Atmos. Sci. 20, 130–141 (1963)] dynamics by means of only two affine linear systems and an abrupt switching law. Comparison of different (valid) switching laws suggests that parameters of such a law behave as codimension one bifurcation parameters that can be changed to produce various dynamical regimes equivalent to those observed with the original systems. Topological analysis is used to characterize the resulting attractors and to compare them with the original attractors. The paper provides guidelines that are helpful to synthesize other chaotic dynamics by means of switching affine linear systems.
Spectroscopic characterization of the ground and low-lying electronic states of Ga2N via anion photoelectron spectroscopy
Authors: Sheehan Sean M. , Meloni Giovanni , Parsons Bradley F. , Wehres Nadine , Neumark Daniel M.
Published: February 2006

Anion photoelectron spectra of Ga2N− were measured at photodetachment wavelengths of 416nm(2.978eV), 355nm(3.493eV), and 266nm(4.661eV). Both field-free time-of-flight and velocity-map imaging methods were used to collect the data. The field-free time-of-flight data provided better resolution of the features, while the velocity-map-imaging data provided more accurate anisotropy parameters for the peaks. Transitions from the ground electronic state of the anion to two electronic states of the neutral were observed and analyzed with the aid of electronic structure calculations and Franck-Condon simulations. The ground-state band was assigned to a transition between linear ground states of Ga2N−(XΣg+1) and Ga2N(XΣu+2), yielding the electron affinity of Ga2N, 2.506±0.008eV. Vibrationally resolved features in the ground-state band were assigned to symmetric and antisymmetric stretch modes of Ga2N, with the latter allowed by vibronic coupling to an excited electronic state. The energy of the observed excited neutral state agrees with that calculated for the AΠu2 state, but the congested nature of this band in the photoelectron spectrum is more consistent with a transition to a bent neutral state.
Ferroelectric domains and twinning in high-quality SrBi2Ta2O9 single crystals
Authors: Amorín H. , Shvartsman V. V. , Bdikin I. K. , Costa M. E. V. , Kholkin A. L. , Pertsev N. A.
Published: February 2006

The domain structure of high-quality SrBi2Ta2O9 (SBT) single crystals is investigated by x-ray diffraction and piezoelectric force microscopy. Both ferroelectric 180° domains and ferroelastic 90° domains (twins) are revealed at room temperature. Remarkably, coexisting domains of two types form a well-defined “herringbone” structure with mostly flat 90° walls. Formation of the observed complex domain pattern is attributed to a two-stage process associated with the presence of separate ferroelastic and ferroelectric phase transitions in SBT.
Static and dynamic properties of the interface between a polymer brush and a melt of identical chains
Authors: Pastorino C. , Binder K. , Kreer T. , Müller M.
Published: February 2006

Molecular-dynamics simulations of a short-chain polymer melt between two brush-covered surfaces under shear have been performed. The end-grafted polymers which constitute the brush have the same chemical properties as the free chains in the melt and provide a soft deformable substrate. Polymer chains are described by a coarse-grained bead-spring model, which includes excluded volume and backbone connectivity of the chains. The grafting density of the brush layer offers a way of controlling the behavior of the surface without altering the molecular interactions. We perform equilibrium and nonequilibrium molecular-dynamics simulations at constant temperature and volume using the dissipative particle dynamics thermostat. The equilibrium density profiles and the behavior under shear are studied as well as the interdigitation of the melt into the brush, the orientation on different length scales (bond vectors, radius of gyration, and end-to-end vector) of free and grafted chains, and velocity profiles. The obtained boundary conditions and slip length show a rich behavior as a function of grafting density and shear velocity.
Infrared spectroscopy of HCN-salt complexes formed in liquid-helium nanodroplets
Authors: Lewis William K. , Miller Roger E.
Published: February 2006

Rotationally resolved infrared spectra are reported for the binary complexes of HCN and LiF, LiCl, NaF, and NaCl, formed in helium nanodroplets. Stark spectroscopy is used to determine the dipole moments for these complexes. Ab initio calculations are also reported for these complexes, revealing the existence of several different isomers of these binary systems. In the frequency region examined in this experimental study we only observe one of these, corresponding to the salt binding to the nitrogen end of the HCN molecule. The experimental rotational constants, dipole moments, and vibrational frequency shifts are all compared with the results from ab initio calculations for this isomer.
Asymptotic form of the density profile for Gaussian and Laguerre random matrix ensembles with orthogonal and symplectic symmetry
Authors: Forrester P. J. , Frankel N. E. , Garoni T. M.
Published: February 2006

In a recent study we have obtained correction terms to the large N asymptotic expansions of the eigenvalue density for the Gaussian unitary and Laguerre unitary ensembles of random N×N matrices, both in the bulk and at the soft edge of the spectrum. In the present study these results are used to similarly analyze the eigenvalue density for Gaussian and Laguerre random matrix ensembles with orthogonal and symplectic symmetry. As in the case of unitary symmetry, a matching is exhibited between the asymptotic expansion of the bulk density, expanded about the edge, and the asymptotic expansion of the edge density, expanded into the bulk. In addition, aspects of the asymptotic expansion of the smoothed density, which involves delta functions at the endpoints of the support, are interpreted microscopically.
On the motion of a heavy rigid body in an ideal fluid with circulation
Authors: Borisov Alexey V. , Mamaev Ivan S.
Published: February 2006

We consider Chaplygin's equations [Izd. Akad. Nauk SSSR 3, 3 (1933)] describing the planar motion of a rigid body in an unbounded volume of an ideal fluid while circulation around the body is not zero. Hamiltonian structures and new integrable cases are revealed; certain remarkable partial solutions are found and their stability is examined. The nonintegrability of the system describing the motion of a body in the field of gravity is proved and the chaotic behavior of the system is illustrated.
Enhanced piezoelectric and pyroelectric effects in single-phase multiferroic Bi1−xNdxFeO3 (x=0–0.15) ceramics
Authors: Yuan G. L. , Or Siu Wing
Published: February 2006

Single-phase multiferroic Bi1−xNdxFeO3 (x=0–0.15) ceramics are polarized and their piezoelectric and pyroelectric effects are reported. The success in polarizing the ceramics originates from low electrical conductivities controlled predominantly by the Poole-Frenkel conduction mechanism. Limited internal traps due to reduced oxygen vacancies in the ceramics result in sufficiently low leakage current densities of <30mA∕m2 even at a high electric field of 145kV∕cm. The piezoelectric d33 coefficients of the ceramics before and after annealing at 550°C for 4h are measured to be ∼28 and ∼24pC∕N, respectively. These values are higher than those of most major lead-free high-temperature piezoelectric ceramics.
Electromechanical properties of poly(vinylidene-fluoride-chlorotrifluoroethylene) copolymer
Authors: Li Zhimin , Wang Yuhong , Cheng Z.-Y.
Published: February 2006

The electromechanical response of poly(vinylidene-fluoride-chlorotrifluoroethylene) [P(VDF-CTFE)] copolymers with 9 mol % (CT9) and 12 mol % CTFE (CT12) is reported. The CT12 (at room temperature) exhibits an electrostrictive strain response of more than 5% and a piezoelectric constant d33 of 140pC∕N at a dc bias of 70MV∕m. It is found that about 70% of crystalline regions in P(VDF-CTFE) is at the nonpolar phase and that the CT9 has a crystallinity about 25% higher than the CT12. The difference in electromechanical performance between the CT9 and CT12 cannot be completely explained using the structure/conformation change alone. It is believed that the contribution of the interfacial layers to the polarization and electrostrictive strain response plays an important role.
Spectral signature of native CN bonds for bacterium detection and identification using femtosecond laser-induced breakdown spectroscopy
Authors: Baudelet Matthieu , Guyon Laurent , Yu Jin , Wolf Jean-Pierre , Amodeo Tanguy , Fréjafon Emeric , Laloi Patrick
Published: February 2006

A sample of Escherichia coli has been analyzed by laser-induced breakdown spectroscopy (LIBS) using femtosecond pulses. The spectrum shows strong CN molecular bands due to the direct ablation of native CN molecular bonds from the bacteria in contrast with weak atomic lines from carbon. The native nature of the observed CN bonds is supported by the kinetic behavior of the CN band head which rapidly decays with a time constant of 94 ns, while for a pure graphite sample the CN band head increases with a delay of 450 ns due to recombination with the ambient air. Moreover, about hundred resolved lines belonging to 12 atomic or molecular species are recorded, providing a valuable spectral signature to identify the bacterium.