bluuebunny/crossref_metadata_2025 huggingface dataset:
Deletion of the Gibberella fujikuroi glutamine synthetase gene has significant impact on transcriptional control of primary and secondary metabolism
Authors: Teichert S. , Schönig B. , Richter S. , Tudzynski B.
Published: September 2004

In Gibberella fujikuroi, the gibberellin (GA) and bikaverin biosynthesis are under control of nitrogen metabolite repression. However, the signalling components acting upstream of AREA are still unknown. We investigated the role of glutamine synthetase (GS) both as an enzyme and as a possible regulator in the nitrogen regulation system. We cloned and replaced the GS‐encoding gene, glnA‐Gf. The mutants grow with a phenotype different from the wild type in the presence of glutamine. They were unable to express nitrogen‐repressed GA and bikaverin biosynthetic genes even under nitrogen starvation conditions. Complementation with the glnA‐Gf wild‐type copy fully restored GS activity, the expression of secondary metabolism genes, and the production of GAs and the red pigment, bikaverin. In order to find more target genes of GS, differential cDNA‐screening and differential hybridization of macroarrays were performed using cDNA from the wild type and ΔglnA mutant as probes. Several genes were dramatically up‐ or downregulated in the mutant. Among them are genes involved in N‐ and C‐catabolism, and in transcriptional and translation control. Some of these genes are also under AREA control. Treatment with the GS inhibitor l‐methionine sulphoximine resulted in similar expression patterns as in the glnA mutant with ammonium as nitrogen source, whereas glutamine can overcome the up‐ or downregulation of most but not all of the target genes. These findings suggest that not only glutamine, but also GS itself might play an important role in nitrogen metabolite repression.
A mycobacterial virulence gene cluster extending RD1 is required for cytolysis, bacterial spreading and ESAT‐6 secretion
Authors: Gao Lian‐Yong , Guo Su , McLaughlin Bryant , Morisaki Hiroshi , Engel Joanne N. , Brown Eric J.
Published: September 2004

Initiation and maintenance of infection by mycobacteria in susceptible hosts are not well understood. A screen of Mycobacterium marinum transposon mutant library led to isolation of eight mutants that failed to cause haemolysis, all of which had transposon insertions in genes homologous to a region between Rv3866 and Rv3881c in Mycobacterium tuberculosis, which encompasses RD1 (Rv3871–Rv3879c), a known virulence gene cluster. The M. marinum mutants showed decreased virulence in vivo and failed to secrete ESAT‐6, like M. tuberculosis RD1 mutants. M. marinum mutants in genes homologous to Rv3866‐Rv3868 also failed to accumulate intracellular ESAT‐6, suggesting a possible role for those genes in synthesis or stability of the protein. These transposon mutants and an ESAT‐6/CFP‐10 deletion mutant all showed reduced cytolysis and cytotoxicity to macrophages and significantly decreased intracellular growth at late stages of the infection only when the cells were infected at low multiplicity of infection, suggesting a defect in spreading. Direct evidence for cell‐to‐cell spread by wild‐type M. marinum was obtained by microscopic detection in macrophage and epithelial monolayers, but the mutants all were defective in this assay. Expression of M. tuberculosis homologues complemented the corresponding M. marinum mutants, emphasizing the functional similarities between M. tuberculosis and M. marinum genes in this region that we designate extRD1 (extended RD1). We suggest that diminished membranolytic activity and defective spreading is a mechanism for the attenuation of the extRD1 mutants. These results extend recent findings on the genomic boundaries and functions of M. tuberculosis RD1 and establish a molecular cellular basis for the role that extRD1 plays in mycobacterial virulence. Disruption of the M. marinum homologue of Rv3881c, not previously implicated in virulence, led to a much more attenuated phenotype in macrophages and in vivo, suggesting that this gene plays additional roles in M. marinum survival in the host.
Genetic mapping in the human malaria parasite Plasmodium falciparum
Authors: Su Xin‐zhuan , Wootton John C.
Published: September 2004

The Plasmodium falciparum genome sequence has boosted hopes for a new era of malaria research and for the application of comprehensive molecular knowledge to disease control, but formidable obstacles remain: ≈ 60% of the predicted P. falciparum proteins have no known functions or homologues, and most life cycle stages of this haploid eukaryotic parasite are relatively intractable to cultivation and biochemical manipulation. Genetic mapping based on high‐resolution maps saturated with single‐nucleotide polymorphisms or microsatellites is now providing effective strategies for discovering candidate genes determining important parasite phenotypes. Here we review classical linkage studies using laboratory crosses and population associations that are now amenable to genome‐wide approaches and are revealing multiple candidate genes involved in complex drug responses. Moreover, mapping by linkage disequilibrium is practicable in cases where chromosomal segments flanking drug‐selected genes have been preserved in populations during relatively recent P. falciparum evolution. We discuss the advantages and limitations of these various genetic mapping strategies, results from which offer complementary insights to those emerging from gene knockout experiments and/or high‐throughput genomic technologies.
Gaseous fluxes of peroxyacetyl nitrate (PAN) into plant leaves
Authors: TEKLEMARIAM T. A. , SPARKS J. P.
Published: September 2004

Peroxyactyl nitrate (PAN) is the most abundant of the gaseous organic nitrates produced from the photochemistry of hydrocarbons and NOx (i.e. ozone and smog production). PAN is known to be toxic to plants and also as a reservoir for the transport nitrogen dioxide in the troposphere. Here, the effect of vegetation on PAN deposition was investigated in four plant species by measuring leaf fluxes of PAN in a dynamic leaf chamber using atmospheric PAN fumigations between 0.7 and 18 nmol mol−1. A linear relationship was observed between PAN flux and ambient PAN mixing ratio for all species. Depending on the species, measured PAN flux varied between 11 and 24 pmol m−2 s−1. Measured fluxes of PAN accounted for 12–48% of the PAN flux predicted solely from modelled stomatal conductance to PAN, suggesting the presence of a mesophyllic resistance to PAN uptake. The brief (approximately 5–10 min) exposure to PAN during uptake measurements did not affect photosynthesis, transpiration or conductance to water vapour. Increasing stomatal resistance by varying the vapour pressure gradient between the leaf chamber and leaf internal air space led to a corresponding drop in PAN uptake. Varying leaf nitrogen and total leaf–ascorbate concentrations did not appear to influence PAN uptake as had been reported for other reactive odd‐nitrogen gases. Measured and model‐predicted PAN fluxes were offset, but correlated suggesting that PAN flux could be estimated using established stomatal conductance algorithms.
Polyamines Regulate Both Transcription and Translation of the Gene Encoding Ornithine Decarboxylase Antizyme in Mouse
Authors: Nilsson Jonas , Koskiniemi Satu , Persson Kent , Grahn Birgitta , Holm Ingvar
Published: September 2004

The degradation of ornithine decarboxylase (ODC) is mediated by antizyme, a protein regulated by the end‐products of ODC activity, the polyamines. High levels of polyamines induce a +1 ribosomal frameshift in the translation of the rat antizyme message leading to the expression of a full‐length protein. We have studied whether the regulation of antizyme expression occurs only at the level of translation or whether polyamine levels also affect the transcription of the antizyme gene. Thus, we have cloned and sequenced the mouse homologues of the rat ODC‐antizyme gene and cDNA. Northern blot analysis shows that although high concentrations of polyamines do not affect the steady‐state levels of antizyme message in L1210 leukemia cells, polyamine depletion using 2‐(difluoromethyl)ornithine [Orn(F2Me)] leads to a marked decrease in mRNA levels. Results of transient transfections of luciferase‐reporter‐gene constructs driven by antizyme promoter fragments in untreated and Orn(F2Me)‐treated Balb/C 3T3 cells indicate that the transcription of the antizyme gene is altered upon polyamine depletion. The amount of antizyme protein on Western blots was also altered by polyamine depletion and addition, and the polysomal distribution of antizyme message suggests a general translational increase of the message when polyamine concentrations are high. These results indicate a role for polyamines in the transcriptional and translational regulation of ornithine decarboxylase antizyme.
Information Transfer in Multienzyme Complexes
Authors: Lebreton Sandrine , Gontero Brigitte , Avilan Luisana , Ricard Jacques
Published: September 2004

Oxidized phosphoribulokinase is almost inactive in its isolated state but becomes active when associated with glyceraldehyde‐3‐phosphate dehydrogenase. There is therefore an information transfer that takes place between these two enzymes. However, when the complex dissociates, free oxidized phosphoribulokinase is even more active than when it is associated with glyceraldehyde‐3‐phosphate dehydrogenase. This means that glyceraldehyde‐3‐phosphate dehydrogenase exerts an imprinting effect upon phosphoribulokinase which persists for a while after the parting of the two proteins.

Various methods derived from statistical thermodynamics can be used to estimate the fraction of energy transferred from glyceraldehyde‐3‐phosphate dehydrogenase to phosphoribulokinase and which alters the kinetic parameters of the latter enzyme. In the complex, the decrease of the free energy associated with the binding of ribulose 5‐phosphate is larger than that of ATP. This implies that the mutual association of the two enzymes facilitates the binding of the former substrate but is without effect on that of the latter. The main effect exerted by the association of the two enzymes is to decrease by about 10 kJ/ mol the height of the energy barrier of the catalytic process.

Phosphoribulokinase keeps an imprinting effect exerted by glyceraldehyde‐3‐phosphate dehydrogenase after the parting of the two enzymes. Part of the energy transferred from one protein to the other is used to decrease slightly the apparent binding free energy of the two substrates of phosphoribulokinase by about 1.5 kJ/mol. Whereas the previous association of the two enzymes does not significantly alter substrate binding to phosphoribulokinase, it greatly affects catalysis and decreases by about 16 kJ/mol the height of the energy barrier pertaining to this step.

Therefore, within multienzyme complexes, information and energy can be transferred between proteins. Statistical thermodynamics offers the possibility of estimating how this energy is used to alter the various kinetic parameters of the reaction.
Critical Residues of Chlamydomonas reinhardtii Ferredoxin for Interaction with Nitrite Reductase and Glutamate Synthase Revealed by Site‐Directed Mutagenesis
Authors: García‐Sánchez M. Isabel , Gotor Cecilia , Jacquot Jean‐Pierre , Stein Mariana , Suzuki Akira , Vega José M.
Published: September 2004

Incubation of wild‐type ferredoxin (Fd) with Chlamydomonas reinhardtii crude extract in the presence of a carboxyl activator resulted in the formation of a unique 1:1 covalent complex with nitrite reductase. However, glutamate synthase was able to form two covalent complexes of Fd: GOGAT with 1:1 and 2:1 stoichiometries. These complexes were functional only when reduced methyl viologen was used as electron donor. Kinetic studies of complex formation suggested the presence of two Fd‐binding domains with similar affinity for Fd in the glutamate synthase molecule. Using site‐directed mutagenesis with recombinant Fd, we have shown that Fd‐Glu91 is directly involved in Fd interaction with glutamate synthase and nitrite reductase. Moreover, a negative core of residues in the α1 helix of Fd was also critical in binding the enzymes. These data highlight the analogy in the Fd‐binding sites of nitrite reductase and glutamate synthase, which may compete for the electrons coming from the photo synthetic chain.
Tryptamine as Substrate and Inhibitor of Lentil Seedling Copper Amine Oxidase
Authors: Medda Rosaria , Padiglia Alessandra , Agro Alessandro Finazzi , Pedersen Jens Z. , Lorrai Anita , Floris Giovanni
Published: September 2004

Copper amine oxidase from lentil seedlings was shown to be able to catalyze the oxidative deamination of the indoleamines tryptamine, 5‐hydroxytryptamine, and 5‐methoxytryptamine. These compounds showed saturation kinetics with Km values as normal substrates, but their oxidation led to irreversible loss of enzyme activity suggesting a covalent interaction with the enzyme, most probably through its cofactor 6‐hydroxydopa (2,4,5‐trihydroxyphenylalanine). These indoleamines acted as irreversible inhibitors of the enzyme only in the absence of oxygen but they brought about changes in the electronic spectra of the enzyme both in aerobiosis and in anaerobiosis. This study reports on the mechanism by which these compounds inhibit lentil amine oxidase which involves first the oxidation of indoleamines bound to 6‐hydroxydopa followed by the formation of an irreversible covalent derivative. The same inhibitory mechanism could possibly lead to inactivation of mammalian amine oxidases involved in serotonin neurotransmitter metabolism in conditions of ischemia or hypoxia.
Detection of Lipopolysaccharide(LPS)‐Binding Membrane Proteins by Immuno‐Coprecipitation with LPS and Anti‐LPS Antibodies
Authors: El‐Samalouti Volker T. , Schletter Jens , Brade Helmut , Brade Lore , Kusumoto Shoichi , Rietschel Ernst T. , Flad Hans‐Dieter , Ulmer Artur J.
Published: September 2004

In this study we describe a general method for the detection and characterization of endotoxin‐(lipopolysaccharide, LPS)‐binding membrane proteins. In the past, experimental procedures to detect LPS‐binding sites on cells were generally performed with chemically modified LPS derivates. Since any modification of a ligand may lead to a modification of its binding characteristics, the results of those studies are controversial.

In our assay, cell membrane preparations are treated with free lipid A, the endotoxic center of LPS, in the presence of normal human serum. After binding of lipid A, membrane proteins are solubilized by mild detergent treatment without disruption of the lipid A‐protein complexes. Addition of anti‐(lipid A) mAbs and subsequent adding of protein A agarose lead to the precipitation of complexes of lipid A and its binding proteins. By SDS/PAGE and western blot, these precipitates can be screened for the presence of LPS/lipid A‐binding proteins. We describe the use of this method for the immuno‐coprecipitation of lipid A (or LPS) with an 80‐kDa LPS‐binding membrane protein (LMP80), which we have previously identified on several human cells. In addition, CD14, the well‐known functional LPS receptor on monocytes and macrophages, can be detected.

By means of this immuno‐coprecipitation approach we could demonstrate binding of either purified LPS preparations or synthetic lipid A to these LPS/lipid A‐binding membrane proteins at physiological pH under conditions in which the proteins are in their natural membranous environment.
Haemoglobin Synthesis in Erythropoietin‐Stimulated J2E Cells Does not Require Increased Numbers of Transferrin Receptors
Authors: Callus Bernard A. , Busfield Samantha J. , Rossi Enrico , Tilbrook Peta A. , Chappell David , Morgan Evan H. , Klinken S. Peter
Published: September 2004

Changes in transferrin‐receptor numbers and iron utilisation were monitored during erythropoietin‐induced maturation of J2E erythroid cells. Uptake of transferrin and iron doubled 24 h after exposure to erythropoietin, due to a twofold rise in surface transferrin receptors. In addition, a tenfold increase in iron incorporation into haem was observed after erythropoietin stimulation, as iron taken up from transferrin was directed towards haem biosynthesis and away from storage in ferritin. The rise in iron chelation into haem correlated extremely well with haemoglobin synthesis. However, the increase in numbers of transferrin receptors was not essential for haemoglobin synthesis; rather, it was linked with a burst in proliferation stimulated by erythropoietin. We have shown previously that amiloride blocks erythropoietin‐enhanced proliferation of J2E cells, but potentiates maturation [Callus, B. A., Tilbrook, P. A., Busfield, S. J. & Klinken, S. P. (1995) Exp. Cell Res. 219, 39–46]. Here we demonstrate that amiloride suppressed the hormone‐induced increase in transferrin receptors, whereas the enhanced incorporation of iron into haem was not inhibited. Similarly, when sodium butyrate was used to induce differentiation of J2E cells, proliferation ceased and surface transferrin receptors remained unaltered, while haemoglobin production was accelerated. It was concluded from these experiments that the erythropoietin‐stimulated rise in transferrin receptors during the final stages of J2E cell maturation is linked to cell division, and is not essential for haemoglobin synthesis.
High‐Molecular‐Mass and Low‐Molecular‐Mass Kininogens Block Plasmin‐Induced Platelet Aggregation by Forming a Complex with Kringle 5 of Plasminogen/Plasmin
Authors: Selim Tarek E. , Ghoneim Hayam R. , Uknis Audrey B. , Colman Robert W. , DeLa Cadena Raul A.
Published: September 2004

We have previously demonstrated a low‐affinity (0.8 μM, non‐covalent complex formation between high‐molecular‐mass kininogen (HK) and plasminogen (Plg) which prevented Plg interaction with glioma and endothelial cells. We have now extended our previous observations by exploring the potential complex formation between Plg and low‐molecular‐mass kininogen (LK) and between LK and HK with Plg cleaved with human neutrophil elastase (HNE). Plg cleavage by HNE (PlgHNE) yielded kringles gun 1–3, kringle 4 and mini‐plasminogen. PlgHNE was subjected to SDS/PAGE under non‐reducing conditions, followed by western blotting, and incubated with either 125I‐HK or 125I‐LK. Autoradiograms revealed that 125I‐HK bound to miniplasminogen and to kringles 1–3 but not to kringle 4 and the presence of 10 mM 6‐aminohexanoic acid (Ahx) disrupted only the interaction with kringles 1–3. In contrast, 125I‐LK bound to miniplasminogen but not to kringles 1–3 or 4 and Ahx had no effect at all. The complex formation of either HK (0.67 μμM) or LK (3 μM) with Plg (1.5 μM) did not affect its conversion to plasmin by tissue plasminogen activator (t‐PA) (100/ml) in the presence of a tissue plasminogen stimulator (0.14 μM). However, the rate of conversion of plasminogen to plasmin by t‐PA was affected when platelets were added to the reaction mixture. Since HK (0.83 μM) has been shown to inhibit plasmin‐induced platelet aggregation, we investigated whether this inhibitory property is found within the heavy chain shared by HK and LK. We found that LK inhibited plasmin‐induced platelet aggregation, but a 4‐fold molar excess was required when compared to HK. Compared to plasmin, 3–5‐fold molar excess of miniplasmin is required to induce platelet aggregation, indicating the important role of kringles 1–3 for plasmin interactions with these cells. These results indicate that HK and LK‐mediated inhibition of plasmin‐induced platelet aggregation is likely due to complex formation with kringle 5 without interfering with plasmin's active site. We found an additional interaction between HK and kringles 1–3 enhancing the inhibitory effect, presumably by interfering with plasmin's interaction with platelets. This HK and LK‐associated modulation of plasmin‐induced platelet aggregation may serve as a template to develop synthetic peptides as novel therapeutic agents to prevent some of the plasmin‐associated thrombocytopenia seen during thrombolytic therapy.
Kinetics of Membrane‐Bound Nitrate Reductase A from Escherichia Coli with Analogues of Physiological Electron Donors
Authors: Giordani Roger , Buc Jean , Cornish‐Bowden Athel , Cárdenas Maria Luz
Published: September 2004

We have compared the steady‐state kinetics of wild‐type nitrate reductase A and two mutant forms with altered β subunits. To mimic conditions in vivo as closely as possible, we used analogues of the physiological quinols as electron donors and membranes with overexpressed nitrate reductase A in preference to a purified αβγ complex. With the wild‐type enzyme both menadiol and duroquinol supply their electrons for the reduction of nitrate at rates that depend on the square of the quinol concentration, menadiol having the higher catalytic constant. The results as a whole are consistent with a substituted‐enzyme mechanism for the reduction of nitrate by the quinols.

Kinetic experiments suggest that duroquinol and menadiol deliver their electrons at different sites on nitrate reductase, with cross‐inhibition. Menadiol inhibits the duroquinol reaction strongly, suggesting that menaquinol may be the preferred substrate in vivo. To examine whether electron transfer from menadiol and duroquinol for nitrate reduction requires the presence of all of the Fe‐S centres, we have studied the steady‐state kinetics of mutants with β subunits that lack an Fe‐S centre. The loss of the highest‐potential Fe‐S centre results in an enzyme without menadiol activity, but retaining duroquinol activity; the kinetic parameters are within a factor of two of those of the wild‐type enzyme, indicating that this centre is not required for the duroquinol activity. The loss of a low‐potential Fe‐S centre affects the activity with both quinols: the enzyme is still active but the catalytic constants for both quinols are decreased by about 75%, indicating that this centre is important but not essential for the activity.

The existence of a specific site of reaction on nitrate reductase for each quinol, together with the differences in the effects on the two quinols produced by the loss of the Fe‐S centre of +80 mV, suggests that the pathways for transfer of electrons from duroquinol and menadiol are not identical.
Methylmalonyl‐CoA Decarboxylase from Propionigenium Modestum
Authors: Bott Michael , Pfister Karin , Burda Patricie , Kalbermatter Oliver , Woehlke Günther , Dimroth Peter
Published: September 2004

Methylmalonyl‐CoA decarboxylase catalyses the only energy‐conserving step during succinate fermentation by Propionigenium modestum: the decarboxylation of (S)‐methylmalonyl‐CoA to propionyl‐CoA is coupled to the vectorial transport of Na+ across the cytoplasmic membrane, thereby creating a sodium ion motive force that is used for ATP synthesis. By taking advantage of the sequence similarity between the β‐subunits of other Na+‐transport decarboxylases, a portion of the P.modestumβ‐subunit gene was amplified by PCR with degenerated primers. The cloned PCR product then served as homologous probe for cloning suitable fragments from genomic DNA. Sequence analysis of a 3.7‐kb region identified four genes which probably form a transcriptional unit, mmdADCB. Remarkably, a mmdE gene which is present in the homologous mmdADECB cluster from Veillonella parvula and encodes the 6‐kDa δ‐subunit, is missing in P.modestum. By sequence comparisons, the following functions could be assigned to the P.modestum proteins: MmdA (56.1 kDa; α‐subunit), carboxyltransferase; MmdB (41.2 kDa; β‐subunit), carboxybiotin‐carrier‐protein decarboxylase; MmdC (13.1 kDa; γ‐subunit), biotin carrier protein. MmdD (14.2 kDa; δ‐subunit) presumably is essential for the assembly of the complex, as shown for the corresponding V.parvula protein. Methylmalonyl‐CoA decarboxylase was solubilized from membranes of P.modestum with n‐dodecylmaltoside and enriched 15‐fold by affinity chromatography on monomeric avidin resin. The purified protein was composed of four subunits, three of which were identified by N‐terminal sequence analysis as MmdA, MmdD, and MmdC. The purified enzyme exhibited a specific activity of up to 25 U/mg protein and an apparent Km value for (S)‐methylmalonyl‐CoA of ≈ 12 μM. Compared to the five‐subunit complex of V.parvula, the four‐subunit enzyme of P.modestum appeared to be more labile, presumably a consequence of the lack of the ε‐subunit.
Residual strength of unidirectional fibre‐metal laminates based on JC toughness of C(T) and SE(B) specimens: comparison with M(T) test results
Authors: CASTRODEZA E. M. , BASTIAN F. L. , IPIÑA J. E. PEREZ
Published: September 2004

Fibre‐metal laminates (FMLs) are structural composites designed with the aim of producing very low fatigue crack‐propagation rate, damage‐tolerant and high‐strength materials, if compared to aeronautical Al alloys. Their application in aeronautical structures demands a deep knowledge of a wide set of mechanical properties and technological values, including both fracture toughness and residual strength. The residual strength of FMLs have been traditionally determined by using wide centre‐cracked tension panels M(T). The use of this geometry requires large quantities of material and heavy laboratory facilities. In this work, fracture toughness ( JC) of some unidirectional FMLs laminates was measured using a recently proposed methodology for critical fracture toughness evaluation on compact tension C(T) and single‐edge bend SE(B) specimens. Additionally, residual strength values of wider M(T) specimens with different widths (W from 150 to 200 mm) and several crack to width ratios (2a/W) were experimentally obtained. Some experimental residual strength values of M(T) specimens (W from 150 to 400 mm and different 2a/W ratios) of Arall were also obtained from the bibliography. Based on JC results from C(T) and SE(B) specimens, and either using or not using crack‐tip plasticity corrections, the residual strengths of the M(T) specimens were predicted and compared to the experimental ones. The results showed good agreement, especially when crack‐tip plasticity corrections were applied.
Fatigue of beta titanium alloy at 20, 482 and 648 °C
Authors: SOLIMINE P. A. , LISSENDEN C. J.
Published: September 2004

Fatigue life of fibrous metal matrix composites is limited by the distribution of fibre strengths, the fibre‐matrix interfacial strength, and the fatigue resistance of the matrix. The aim of this work is to provide fatigue results for a beta titanium alloy over a range of temperatures and stresses that can be used as input for predicting fatigue life of a titanium matrix composite. Stress controlled tests having fatigue ratios between −1 and −0.2 were conducted on a limited number of samples machined from unreinforced laminated Ti‐15Mo‐3Al‐2.7Nb‐0.2Si (TIMETAL®21S) sheets to represent as closely as possible the in situ matrix material. Stress control was used to enable quantification of strain ratcheting for tensile mean stresses and a fast loading rate was used to minimize time‐dependent (creep) deformation. Stress amplitude‐life data at 20, 482 and 648 °C for fully reversed loading are well fit by a power law. Normalizing the stress amplitude with respect to the power law coefficient appears to account for the temperature dependence of the S–N curves. As the tests had large strains and lives were in the low‐cycle fatigue range, strain range at the half‐life was also correlated to life. For tensile mean stress cycling at 482 and 648 °C, the rate of strain ratcheting per cycle increased to failure; shakedown was not observed.
Quantifying 3H‐thymidine incorporation rates by a phylogenetically defined group of marine planktonic bacteria (Bacteriodetes phylum)
Authors: Van Mooy Benjamin A. S. , Devol Allan H. , Keil Richard G.
Published: September 2004

The rate of [3H‐methyl] thymidine (3H‐TdR) incorporation into DNA has been applied extensively to measure cell production by bacterial communities in aquatic environments. Here we describe a method to quantify 3H‐TdR incorporation by specific, phylogenetically defined members of the bacterial community. The method involves selectively capturing DNA from targeted groups of bacteria and then quantifying its 3H radioactivity. The method was applied to measure 3H‐TdR incorporation by the members of the phylum Bacteriodetes whose members, which include the Cytophaga‐Flavobacter cluster, are ubiquitous in coastal waters. 3H‐labelled DNA from Bacteriodetes was selectively biotinylated in PCR‐like reactions that contained a Bacteriodetes‐specific 16S rRNA gene primer, thermostable DNA polymerase and biotinylated dUTP. The biotinylated DNA was then captured on streptavidin‐coated beads and its 3H radioactivity determined by scintillation counting. We have termed this method ‘selective nucleic acid polymerase‐biotinylation and capture’ or ‘SNAP‐BAC’. Internal 33P‐labelled DNA standards were used to quantify the recovery of 3H‐labelled DNA from the SNAP‐BAC reactions. The method was verified by successfully targeting Bacteriodetes in simple laboratory mixtures of 3H‐labelled DNA extracted from pure cultures of Bacteriodetes and γ‐proteobacteria. Field application of this method in Puget Sound and off the Washington coast determined that Bacteriodetes were responsible for 56 ± 17% and 32 ± 5% of community 3H‐TdR incorporation (1.3 ± 0.3 and 9.9 ± 1.7 pmol l−1 h−1) at these two locations.
Molecular evidence that plastids in the toxin‐producing dinoflagellate genus Dinophysis originate from the free‐living cryptophyte Teleaulax amphioxeia
Authors: Janson Sven
Published: September 2004

Some species of the dinoflagellate genus Dinophysis form red tides and are toxin producers with a great environmental impact. The dinoflagellates as a group display high plastid diversity. Several cases indicate that plastids have been replaced. In the case of the genus Dinophysis, the plastids show characteristics of a plastid originating from a cryptophyte. Recent molecular evidence showed that the plastid indeed originates from a cryptophyte, but the source could not be identified to species or genus level. The data presented here show that both a 799 bp region of the psbA gene and 1221 bp region of the 16S rRNA gene from Dinophysis spp. are identical to the same loci in Teleaulax amphioxeia SCCAP K434. This strongly indicates that the plastid was acquired recently in Dinophysis and may be a so‐called kleptoplastid, specifically originating from a species of Teleaulax.
Low archaeal diversity linked to subseafloor geochemical processes at the Lost City Hydrothermal Field, Mid‐Atlantic Ridge
Authors: Schrenk Matthew O. , Kelley Deborah S. , Bolton Sheryl A. , Baross John A.
Published: September 2004

The recently discovered Lost City Hydrothermal Field (LCHF) represents a new type of submarine hydrothermal system driven primarily by exothermic serpentinization reactions in ultramafic oceanic crust. Highly reducing, alkaline hydrothermal environments at the LCHF produce considerable quantities of hydrogen, methane and organic molecules through chemo‐ and biosynthetic reactions. Here, we report the first analyses of microbial communities inhabiting carbonate chimneys awash in warm, high pH fluids at the LCHF and the predominance of a single group of methane‐metabolizing Archaea. The predominant phylotype, related to the Methanosarcinales, formed tens of micrometre‐thick biofilms in regions adjacent to hydrothermal flow. Exterior portions of active structures harboured a diverse microbial community composed primarily of filamentous Eubacteria that resembled sulphide‐oxidizing species. Inactive samples, away from regions of hydrothermal flow, contained phylotypes related to pelagic microorganisms. The abundance of organisms linked to the volatile chemistry at the LCHF hints that similar metabolic processes may operate in the subseafloor. These results expand the range of known geological settings that support biological activity to include submarine hydrothermal systems that are not dependent upon magmatic heat sources.
Financial Liberalization and Corporate Investments: Evidence from Korean Firm Data*
Authors: Koo Jaewoon , Shin Sunwoo
Published: September 2004

This paper examines whether financial liberalization procedures introduced in Korea in the early 1990s succeeded in relaxing financing constraints on firms. Because external funds are more costly than internal funds in an imperfect capital market, corporate investments depend on the availability of internal funds. As financial liberalization mitigates constraints on firms, the sensitivity of investments to cash flow can be reduced. Using panel data on Korean firms, we found that cash‐flow effects on investment spending decreased drastically during the liberalization period. In particular, small, non‐chaebol and established firms that were severely constrained gained most from liberalization. Chaebol firms appeared to lose preferential access to credit after liberalization.
Flying Ducks? Girls’ Schooling in Rural Vietnam: A Revisit
Authors: Liu Amy Y.C.
Published: September 2004

In Vietnam, girls are colloquially referred to as ‘flying ducks’ as they are regarded as a loss to the family upon marriage. Using the Vietnam Living Standards Surveys of 1992–1993 and 1997–1998, the method of Doiron and Riddell (1994) is applied to decompose the probability gap of being in school to explore gender differences in children's education and changes over time. The unexplained component is found to account for most of the observed gender probability gap in each period. Over time, however, the gap has narrowed. The explained component (namely, household income and children's involvement in housework or work activities) contributes to the narrowing gap. Cutting the indirect cost of education for girls (forgone contribution in work and housework) is crucial in ensuring girls have the same education opportunities as boys do.
Introduction to the Special Issue Work Habits and Work Styles: Volition in Education
Authors: Corno Lyn
Published: September 2004

This introduction to the special issue describes concepts and research principles from modern psychological theories of self-regulation that are relevant to the subject of work habits and work styles in school. Modern systems-based and situated views of volitional functioning are applicable to practice in clinical settings as well as education, but practitioners are not well acquainted with this body of work. The article discusses the assessment and development of volitional competence in students, showing teachers and policy makers how attention to the psychology of volition in education may be used to enhance academic work habits and work styles.
The Interplay of Aspirations, Enjoyment, and Work Habits in Academic Endeavors: Why is it So Hard to Keep Long-Term Commitments?
Authors: Schallert Diane Lemonnier , Reed Joylynn Hailey , Turner Jeannine E.
Published: September 2004

This article describes our interest in bringing together students’ emotions and their motivation for academic work as these play out across the school year. We explore three main issues. First, we consider what some view as an incompatibility between students’ use of established work habits (volitional strategies) and real enjoyment of academic tasks (what we call involvement). Rather than seeing these two approaches as diametrically opposed, we show how volitional control can be useful in getting a student to experience involvement in a task. Conversely, we consider how involvement itself can be an incentive to students’ use of volitional strategies. A second issue has to do with students realizing that long-term goals may require different volitional strategies than short-term goals. Finally, we discuss the need to encourage students to develop the habit of seeking enjoyment in academic tasks because the goal of enjoyment focuses them on the rewards of deep concentration rather than on the elation of having finished a task.
Motivational Influences on Student Participation in Classroom Learning Activities
Authors: Turner Julianne C. , Patrick Helen
Published: September 2004

This study examined how one type of student work habit—classroom participation—is related to a combination of both student factors (math achievement, personal achievement goals, perceptions of classroom goal structures, and teacher support) and features of the classroom context (teachers’ instructional practices, average perceptions of classroom goal structures). We focused on the participation of two students in mathematics class during both sixth and seventh grades. Differential teacher expectations, calling patterns, and instructional and motivational support and nonsupport interacted with beliefs and behaviors of both students, and those interactions were associated with different patterns of participation each year. Results suggest that student participation is malleable rather than stable and emphasize the potential of teacher practices to both support and undermine the development of student work habits.
Examining Features of Tasks and Their Potential to Promote Self-Regulated Learning
Authors: Perry Nancy , Phillips Lynda , Dowler Judy
Published: September 2004

The term “self-regulated” is used to describe learners who have highly effective learning and work habits. They are successful in and beyond school. This investigation examines whether and how teachers, who are masters at supporting young students’ development of self-regulated learning (SRL), can mentor student teachers to design tasks and develop practices that promote elementary school students’ SRL. Nineteen student teachers were paired with 19 mentor teachers in a cohort that emphasized SRL theory and practice. In general, student teachers remained with the same mentors throughout their teacher education program and were supported by faculty associates and researchers who also had expertise in promoting SRL. Researchers observed mentor and student teachers teaching, videotaped professional seminars, and collected samples of student teachers’ reflections, lesson plans and unit plans. Data indicate some student teachers designed tasks and implemented practices that promote SRL and that mentors’ practices accounted for 20% of the variance observed in the student teachers’ practices. Finally, the complexity of the tasks that mentors and student teachers designed was strongly predictive of opportunities for students to develop and engage in SRL.
Expressing inter‐link constraints in OWL knowledge bases
Authors: Russomanno David J. , Kothari Cartik R.
Published: September 2004

Abstract: In this paper the Web Ontology Language (OWL) is examined to instantiate expert system knowledge bases intended for semantic Web applications. In particular, OWL is analyzed for expressing Unified Modeling Language (UML) representations that have been augmented with propositional logic asserted as inter‐link constraints. The motivation is ultimately to provide declarative propositional logic constraints that can be represented in UML and declaratively implemented using OWL and other constructs to realize semantic Web knowledge base repositories and databases to facilitate expert system applications. The results of this paper show that OWL is sufficient for capturing most inter‐link constraints asserted on generalization/specialization instances; however, OWL alone is inadequate for representing some inter‐link constraints asserted on associations. We propose enhancements to OWL via RDF extensions for the reification of associations into classes. These extensions mitigate all concerns that were identified in OWL as part of this study. The result is increased support of declarative constraint representations, which can be expressed in knowledge bases in the context of the semantic Web.
Mechanical Failure of an Implant‐Retained Bar: A Clinical Report
Authors: Masri Radi , Driscoll Carl F.
Published: September 2004

This clinical report describes the mechanical failure of an implant‐retained bar where the bar fractured midway between two implants. The location of the fracture is not typical for implant‐retained bars. Possible causes of the fracture are discussed. The prosthodontic treatment provided to manage the mechanical failure and prevent it from recurring is also discussed.
Predictable Investment Horizons and Wealth Transfers among Mutual Fund Shareholders
Authors: JOHNSON WOODROW T.
Published: September 2004

This study analyzes the distribution of investment horizons in a large, proprietary panel of all shareholders in one no‐load mutual fund family. A proportional hazards model shows that there are observable shareholder characteristics that enable the fund to predict reliably on the day each account is opened whether the account will be short term or long term. Simulations show that the liquidity costs imposed on the fund by the expected short‐term shareholders are significantly greater than those imposed by the expected long‐term shareholders. Combining these results, the analysis argues that mutual funds do not provide equitable liquidity‐risk insurance.
Investment–Cash Flow Sensitivities: Constrained versus Unconstrained Firms
Authors: MOYEN NATHALIE
Published: September 2004

From the existing literature, it is not clear what effect financing constraints have on the sensitivities of firms' investment to their cash flow. I propose an explanation that reconciles the conflicting empirical evidence. I present two models: the unconstrained model, in which firms can raise external funds, and the constrained model, in which firms cannot do so. Using low dividends to identify financing constraints in my generated panel of data produces results consistent with those of Fazzari, Hubbard, and Petersen; using the constrained model produces results consistent with those of Kaplan and Zingales.
Correlated Trading and Location
Authors: FENG LEI , SEASHOLES MARK S.
Published: September 2004

This paper analyzes the trading behavior of stock market investors. Purchases and sales are highly correlated when we divide investors geographically. Investors who live near a firm's headquarters react in a similar manner to releases of public information. We are able to make this identification by exploiting a unique feature of individual brokerage accounts in the People's Republic of China. The data allow us to pinpoint an investor's location at the time he or she places a trade. Our results are consistent with a simple, rational expectations model of heterogeneously informed investors.
Characteristics, Contracts, and Actions: Evidence from Venture Capitalist Analyses
Authors: KAPLAN STEVEN N. , STRÖMBERG PER
Published: September 2004

We study the investment analyses of 67 portfolio investments by 11 venture capital (VC) firms. VCs describe the strengths and risks of the investments as well as expected postinvestment actions. We classify the risks into three categories and relate them to the allocation of cash flow rights, contingencies, control rights, and liquidation rights between VCs and entrepreneurs. The risk results suggest that agency and hold‐up problems are important to contract design and monitoring, but that risk sharing is not. Greater VC control is associated with increased management intervention, while greater VC equity incentives are associated with increased value‐added support.
Monitoring as a Motivation for IPO Underpricing
Authors: ARUǦASLAN ONUR , COOK DOUGLAS O. , KIESCHNICK ROBERT
Published: September 2004

Brennan and Franks (1997) and Stoughton and Zechner (1998) provide contrasting arguments for why monitoring considerations create incentives for managers to underprice their firms' IPOs (initial public offerings). Like Smart and Zutter (2003), we examine these arguments using a sample of U.S. IPOs. However, we find evidence that the determinants of initial returns, institutional shareholdings, and post‐IPO likelihood of acquisition are not consistent with these arguments. Thus, we conclude that monitoring considerations are not important determinants of IPO underpricing.
The KwaZulu‐Natal Health Promotion Model
Authors: Uys Leana R. , Majumdar Basanti , Gwele Nomthandaso S.
Published: September 2004

Purpose

: To describe a health promotion model aimed at assisting primary health care nurses to incorporate health promotion into their practice.

Organizing Structure

: The model is based on empowering people through a systematic, planned, needs‐driven curriculum with comprehensive content, using interactive teaching in small groups, and linking the groups with external resources. The process involves identifying and engaging partners, planning the project, implementing it, and then disengaging.

Methods

: The implementation of this model in a province of South Africa, KwaZulu‐Natal, in a collaborative project involving two universities and the state health services, changed the practice of the primary health care nurses involved. They worked with women's groups over 3 years and changed both their own perspectives and the lives of the women.

Conclusions

: Unless nurses have an implementation model available to them, they frequently focus only on illness needs of people and do not participate in health promotion.
Symptom Clusters in Oncology Patients and Implications for Symptom Research in People with Primary Brain Tumors
Authors: Armstrong Terri S. , Cohen Marlene Z. , Eriksen Lillian R. , Hickey Joanne V.
Published: September 2004

Purpose

: To provide a critical analysis of the state of the science of research on symptom clusters in the general oncology population, compared to symptom research in the primary brain tumor population.

Organizing Construct

: Symptoms are a multidimensional experience that include perceptions of the frequency, intensity, distress, and meaning as symptoms occur and are expressed. A symptom can influence the occurrence and meaning of other symptoms.

Methods

: Literature pertaining to symptom presentation in people with primary brain tumors and the occurrence of multiple symptoms and symptom clusters in patients with cancer was reviewed and analyzed.

Findings

: Symptoms occur in clusters in general oncology patients, and these clusters have been shown to influence functional status. The potential effect of tumor biology on symptom clusters is shown by the cluster of symptoms theorized to be associated with proinflammatory cytokine production. In patients with primary brain tumors, few researchers have examined the occurrence of symptoms at the time of diagnosis. Studies to date are retrospective and descriptive and were conducted before the use of modern imaging techniques. Studies of symptom clusters have not been reported for patients with primary brain tumors.

Conclusions

: Symptom clusters have recently been identified in the general oncology population and might provide a new strategy for assessment and intervention. Neurologic symptoms in patients with primary brain tumors are those related to increased intracranial pressure and those that are location‐dependent within the brain. Therefore, application of the symptom cluster paradigm to guide research is warranted.