bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of bromosulphophthalein binding to human glutathione S-transferase A1-1: thermodynamics and inhibition kinetics
Authors: KOLOBE Doris , SAYED Yasien , DIRR Heini W.
Published: August 2004

In addition to their catalytic functions, GSTs (glutathione S-transferases) bind a wide variety of structurally diverse non-substrate ligands. This ligandin function is known to result in the inhibition of catalytic function. The interaction between hGSTA1-1 (human class Alpha GST with two type 1 subunits) and a non-substrate anionic ligand, BSP (bromosulphophthalein), was studied by isothermal titration calorimetry and inhibition kinetics. The binding isotherm is biphasic, best described by a set of two independent sites: a high-affinity site and a low-affinity site(s). The binding stoichiometries for these sites are 1 and 3 molecules of BSP respectively. BSP binds to the high-affinity site 80 times more tightly (Kd=0.12 μM) than it does to the low-affinity site(s) (Kd=9.1 μM). Binding at these sites is enthalpically and entropically favourable, with no linkage to protonation events. Temperature- and salt-dependent studies indicate the significance of hydrophobic interactions in the binding of BSP, and that the low-affinity site(s) displays low specificity towards the anion. Binding of BSP results in the release of ordered water molecules at these hydrophobic sites, which more than offsets unfavourable entropic changes during binding. BSP inhibition studies show that the binding of BSP to its high-affinity site does not inhibit hGSTA1-1. This site, located near Trp-20, may be related to the buffer-binding site observed in GSTP1-1. The low-affinity-binding site(s) for BSP is most probably located at or near the active site of hGSTA1-1. Binding to this site(s) results in non-competitive inhibition with respect to CDNB (1-chloro-2,4-dinitrobenzene) (KiBSP=16.8±1.9 μM). Given the properties of the H site and the relatively small size of the electrophilic substrate CDNB, it is plausible that the active site of the enzyme can simultaneously accommodate both BSP and CDNB. This would explain the non-competitive behaviour of certain inhibitors that bind the active site (e.g. BSP).
InsP3-mediated intracellular calcium signalling is altered by expression of synaptojanin-1
Authors: JOHENNING Friedrich W. , WENK Markus R. , UHLÉN Per , DeGRAY Brenda , LEE Eunkyung , de CAMILLI Pietro , EHRLICH Barbara E.
Published: August 2004

Phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] plays an important physiological role as a precursor for the InsP3-mediated intracellular calcium (Ca2+) signalling cascade. It also regulates membrane trafficking, actin function and transmembrane proteins. SJ-1 (synaptojanin-1), a phosphoinositide phosphatase, regulates the turnover of a PtdIns(4,5)P2 pool involved in clathrin and actin dynamics at the cell surface. We tested the interrelationship of this pool with PtdIns(4,5)P2 pools involved in Ca2+ signalling by expressing in Chinese-hamster ovary cells full-length SJ-1 or its 5-Pase (inositol 5-phosphatase) domain. SJ-1 significantly attenuated the generation of Ca2+ oscillations induced by ATP and the 5-Pase domain mimicked this effect. These changes correlated with increased PtdIns(4,5)P2 phosphatase activity of cellular extracts. Overexpression of the endoplasmic reticulum-anchored PtdIns(4)P phosphatase Sac1 did not affect Ca2+ oscillations, although it increased the Ca2+ efflux rate from intracellular stores. The ability of SJ-1 to alter intracellular Ca2+ signalling indicates a close functional interrelationship between plasma membrane PtdIns(4,5)P2 pools that control actin and endocytosis and those involved in the regulation of specific spatio-temporal Ca2+ signals.
Overexpression of inactive arylsulphatase mutants andin vitroactivation by light-dependent oxidation with vanadate
Authors: CHRISTIANSON Terri M. , STARR Chris M. , ZANKEL Todd C.
Published: August 2004

Arylsulphatases B (ASB) and A (ASA) are subject to a unique post-translational modification that is required for their function. The modification reaction, conversion of an active-site cysteine into a formylglycine, becomes saturated when these enzymes are overexpressed. We have removed the possibility of in vivo modification by expressing mutants of ASB and ASA in which the active-site cysteine is substituted with a serine. These mutants are expressed much more efficiently when compared with the native enzymes under identical conditions. The purified ASB mutant can then be converted into catalytically active ASB in vitro using vanadate and light.
Structural requirements of the glucocorticoid-response unit of the carbamoyl-phosphate synthase gene
Authors: SCHONEVELD Onard J. L. M. , GAEMERS Ingrid C. , DAS Atze T. , HOOGENKAMP Maarten , RENES Johan , RUIJTER Jan M. , LAMERS Wouter H.
Published: August 2004

The GRU (glucocorticoid-response unit) within the distal enhancer of the gene encoding carbamoyl-phosphate synthase, which comprises REs (response elements) for the GR (glucocorticoid receptor) and the liver-enriched transcription factors FoxA (forkhead box A) and C/EBP (CCAAT/enhancer-binding protein), and a binding site for an unknown protein denoted P3, is one of the simplest GRUs described. In this study, we have established that the activity of this GRU depends strongly on the positioning and spacing of its REs. Mutation of the P3 site within the 25 bp FoxA–GR spacer eliminated GRU activity, but the requirement for P3 could be overcome by decreasing the length of this spacer to ≤12 bp, by optimizing the sequence of the REs in the GRU, and by replacing the P3 sequence with a C/EBPβ sequence. With spacers of ≤12 bp, the activity of the GRU depended on the helical orientation of the FoxA and GR REs, with highest activities observed at 2 and 12 bp respectively. Elimination of the 6 bp C/EBP–FoxA spacer also increased GRU activity 2-fold. Together, these results indicate that the spatial positioning of the transcription factors that bind to the GRU determines its activity and that the P3 complex, which binds to the DNA via a 75 kDa protein, functions to facilitate interaction between the FoxA and glucocorticoid response elements when the distance between these transcription factors means that they have difficulties contacting each other.
Characterization of the first non-insect invertebrate functional angiotensin-converting enzyme (ACE): leech TtACE resembles the N-domain of mammalian ACE
Authors: RIVIÈRE Guillaume , MICHAUD Annie , DELOFFRE Laurence , VANDENBULCKE Franck , LEVOYE Angélique , BRETON Christophe , CORVOL Pierre , SALZET Michel , VIEAU Didier
Published: August 2004

Angiotensin-converting enzyme (ACE) is a zinc metallopeptidase that plays a major role in blood homoeostasis and reproduction in mammals. In vertebrates, both transmembrane and soluble ACE, containing one or two homologous active sites, have been characterized. So far, several ACEs from invertebrates have been cloned, but only in insects. They are soluble and display a single active site. Using biochemical procedures, an ACE-like activity was detected in our model, the leech, Theromyzon tessulatum. Annelida is the most distant phylum in which an ACE activity has been observed. To gain more insight into the leech enzyme, we have developed a PCR approach to characterize its mRNA. The approx. 2 kb cDNA has been predicted to encode a 616-amino-acid soluble enzyme containing a single active site, named TtACE (T. tessulatum ACE). Surprisingly, its primary sequence shows greater similarity to vertebrates than to invertebrates. Stable in vitro expression of TtACE in transfected Chinese-hamster ovary cells revealed that the leech enzyme is a functional metalloprotease. As in mammals, this 79 kDa glycosylated enzyme functions as a dipeptidyl carboxypeptidase capable of hydrolysing angiotensin I to angiotensin II. However, a weak chloride inhibitory effect and acetylated N-acetyl-SDKP (Ac SDAcKP) hydrolysis reveal that TtACE activity resembles that of the N-domain of mammalian ACE. In situ hybridization shows that its cellular distribution is restricted to epithelial midgut cells. Although the precise roles and endogenous substrates of TtACE remain to be identified, characterization of this ancestral peptidase will help to clarify its physiological roles in non-insect invertebrate species.
Number and activity of endothelial progenitor cells from peripheral blood in patients with hypercholesterolaemia
Authors: CHEN Jun Zhu , ZHANG Fu Rong , TAO Qian Min , WANG Xing Xiang , ZHU Jian Hua , ZHU Jun Hui
Published: August 2004

Hypercholesterolaemia contributes to atherosclerosis and coronary artery diseases by inducing endothelial cell injury and dysfunction. Recent studies have provided increasing evidence that EPCs (endothelial progenitor cells) participate in ongoing endothelial repair and postnatal neovascularization. However, the changes in EPCs in patients with hypercholesterolaemia have not been elucidated to date. Therefore we investigated the number and functional activity of EPCs in patients with hypercholesterolemia. Total MNCs (mononuclear cells) were isolated from 20 patients with hypercholesterolaemia and 20 matched control subjects. EPCs were characterized as adherent cells double-positive for DiI-LDL (1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanide percholate-labelled low-density lipoprotein) uptake and lectin binding by direct fluorescent staining under a laser scanning confocal microscope, and were characterized further by demonstrating the expression of KDR (kinase insert domain-containing receptor), CD34 and AC133 by flow cytometry. Proliferation, migration and in vitro vasculogenesis activity of EPCs were assayed using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay, modified Boyden chamber assay and an in vitro vasculogenesis kit respectively. EPC adhesion assay was performed by replating cells on fibronectin-coated dishes and then counting the adherent cells. As a result, the number of EPCs was significantly reduced in patients with hypercholes-terolaemia compared with that in control subjects (41.8±8.7 compared with 64.5±16.6 EPCs/×200 field respectively; P<0.05). The number of EPCs was inversely correlated with total cholesterol (r=−0.659, P<0.001) and LDL-cholesterol (r=−0.611, P<0.001) levels. In addition, the functional activities of isolated EPCs, such as proliferative, migratory, adhesive and in vitro vasculogenesis capacity, were also impaired. In conclusion, the results of the present study may state a novel pathophysiological mechanism of hypercholesterolaemia: the reduction of EPCs with decreased functional activity.
Vasoconstrictor products of cyclo-oxygenase activity limit acetylcholine-induced cutaneous vasodilatation in young men
Authors: HENDRY Ross G. , MARSHALL Janice M.
Published: August 2004

In healthy young men (age, 20–22 years), we tested the role of prostanoids produced by the COX (cyclo-oxygenase) pathway in cutaneous vasodilatation evoked in the finger by ACh (acetylcholine). To this end, changes in cutaneous RCF (red cell flux), recorded by the laser Doppler technique, evoked by a series of iontophoretic pulses of ACh were tested before and after oral aspirin (600 mg). Increases in RCF produced by successive pulses of ACh up to a mean change of 125.5±11.8 PU (perfusion units) were potentiated 30 min after aspirin (160.0±12.4 PU; P<0.05). By contrast, aspirin had no effect on increases in RCF evoked by iontophoretic application of the NO (nitric oxide) donor and endothelium-independent dilator sodium nitroprusside (mean increases in RCF were 73.8±9.8 PU before and 79.1±12.2 PU after aspirin). The ACh-evoked increases in RCF were also potentiated 3 h after oral administration of the antioxidant vitamin C (1000 mg; 139.1±15.4 PU before and 170.5±13.5 PU after vitamin C; P<0.05). We propose that, in healthy young men, cutaneous vasodilatation evoked in the finger by the endothelium-dependent dilator ACh is limited by constrictor products of the COX pathway, including PGH2 (prostaglandin H2), TXA2 (thromboxane A2) and/or superoxide anions. This effect of the COX products may be an early marker of the increased risk of cardiovascular disease in men compared with women.
N-terminal pro-atrial natriuretic peptide (N-ANP) and N-terminal pro-B-type natriuretic peptide (N-BNP) in the prediction of death and heart failure in unselected patients following acute myocardial infarction
Authors: SQUIRE Iain B. , O'BRIEN Russell J. , DEMME Bettina , DAVIES Joan E. , NG Leong L.
Published: August 2004

Elevated plasma natriuretic peptide levels after AMI (acute myocardial infarction) are associated with adverse outcome. The aim of the present study was to examine the relationship of plasma N-ANP (N-terminal pro-atrial natriuretic peptide) and N-BNP (N-terminal pro-B-type natriuretic peptide) with mortality and heart failure following AMI. We studied 403 patients with AMI. Blood was sampled for measurement of N-ANP and N-BNP on a single occasion between 72 and 96 h after symptom onset. Natriuretic peptide levels were related to all-cause mortality and heart failure episodes. During follow up (median, 462 days; range 5–764), 43 (10.7%), 25 (6.2%) and 49 (12.2%) patients suffered death, heart failure hospitalization and outpatient heart failure respectively. Only N-BNP (P<0.0005), N-ANP (P=0.005) and previous AMI (P=0.016) were independently predictive of death. N-BNP, but not N-ANP, predicted 30-day mortality. N-ANP, but not N-BNP, predicted mortality after 30 days. N-BNP was the better predictor of heart failure. N-ANP and N-BNP were above the median in 35 and 38 respectively, of 43 patients who later died. N-ANP, N-BNP, or both were above the median in 41 out of 43 patients. Of 25 patients hospitalized with heart failure, N-ANP and N-BNP was above the median in 20 and 24 respectively, and one or other was elevated in all cases. Above-median N-ANP predicted 36 and N-BNP predicted 41 out of 49 episodes of outpatient heart failure. One or other peptide was above the median in 45 out of 49 patients. Our results indicate that N-BNP predicts 30-day and N-ANP >30-day mortality. We conclude that consideration of both N-ANP and N-BNP identifies a greater number of patients at risk of death or heart failure than either peptide alone.
Stability and transport properties of multiple-patch quasiequilibria
Authors: Schoemaker R. M. , Clercx H. J. H. , van Heijst G. J. F.
Published: August 2004

A novel subclass of exact solutions to the Euler equations in two dimensions has been put forward recently [D. Crowdy, “A class of exact multipolar vortices,” Phys. Fluids 11, 2556 (1999)]. The solutions show vortical equilibria which can be described by only two parameters. The first one designates the multipolar aspect of these equilibria, i.e., the number of point vortices involved, while the other parameter signatures the shape of the finite area of uniform vorticity in which the point vortices are embedded. The main aspect of these equilibria is that the vortical configuration is static, meaning that the velocity induced at the patch edge, outside the vortical area, and also at the locations of the point vortices is zero. We show with numerical experiments that quite remarkably the linearly stable equilibria of Crowdy seem to mix very efficiently in contrast to the unstable vortex solutions. In the second part of this paper we report on the dynamics, stability, and mixing properties of similar vortex systems where the point vortices are regularized to vortex patches (with uniform vorticity). Several of these multiple-patch vortices turn out to be remarkably stable, although the regularization itself should be considered as a (symmetric) perturbation of Crowdy’s multipolar solutions.
Growth and physiological responses of six barley genotypes to waterlogging and subsequent recovery
Authors: Pang Jiayin , Zhou Meixue , Mendham Neville , Shabala Sergey
Published: August 2004

In this study, the growth response of 6 barley genotypes of different origin (3 from China, 2 from Australia, 1 from Japan) to waterlogging and subsequent recovery was evaluated in 2 different soil types, an artificial potting mix and a Vertosol. A range of physiological measurements was assessed, to develop a method to aid selection for waterlogging tolerance. Plants at the 3 or 4 expanded leaf stages were subjected to waterlogging for 3 weeks followed by 2 weeks of recovery. Both shoot and root growth was negatively affected by waterlogging. As waterlogging stress developed, chlorophyll content, CO2 assimilation rate, and maximal quantum efficiency of photosystem II (Fv/Fm) decreased significantly. The adverse effect of waterlogging was most severe for genotype Naso Nijo, intermediate for ZP, Gairdner, DYSYH, and Franklin, and least for TX9425 in both trials. Studies of the root anatomy suggested that such a contrasting behaviour may be partially due to a significant difference in the pattern of aerenchyma formation in barley roots. The adverse effects in stressed plants were alleviated after 2 weeks of drainage for all genotypes. In general, TX9425 continued to grow better than other varieties, whereas recovery of Naso Nijo was extremely slow. It is suggested that screening a small number of lines for waterlogging tolerance could be facilitated by selecting genotypes with least pronounced reduction of photosynthetic rate or total chlorophyll content, and for a larger number of lines, chlorophyll fluorescence is the most appropriate tool.
Over-cropping lucerne with wheat: effect of lucerne winter activity on total plant production and water use of the mixture, and wheat yield and quality
Authors: Humphries A. W. , Latta R. A. , Auricht G. C. , Bellotti W. D.
Published: August 2004

Two field experiments in southern Australia investigated a farming system of over-cropping wheat (Triticum aestivum L.) into established lucerne (Medicago sativa subsp. L.) varieties of different winter activity ratings. The study was completed at Roseworthy, South Australia, and Katanning, Western Australia, between August 2000 and May 2003 in seasons receiving below average and average rainfall. Comparative lucerne persistence and biomass, wheat biomass, grain yield and protein contents, and soil water contents were measured. Wheat grain yield was reduced by 13–63% by over-cropping lucerne compared with wheat monoculture. Winter-dormant lucerne (winter activity Classes 0.5 and 2) reduced the yield penalty compared with winter-active varieties (Classes 6 and 10) in 2 of the 4 evaluations. The positive response to applying N at sowing in the second year of over-cropping wheat at Katanning was greatest in the most winter-dormant lucerne treatment (winter activity 0.5). Soil water contents were similar under the lucerne/wheat over-cropping and lucerne monoculture treatments irrespective of lucerne winter activity. Deficits of up to 43 mm at Roseworthy and 88 mm at Katanning were measured in the 0–200-cm soil profile at the start of the third summer of the study. The study shows that it can be more efficient in terms of land area to over-crop wheat into lucerne than to grow monocultures on separate parcels of land akin to phase farming. The improved productivity of over-cropping is associated with the separation of growth patterns of winter wheat and summer-active lucerne. This farming system offers great potential for improving sustainability and productivity in southern Australian cropping rotations.
Growth and development of stock (Matthiola incana) under salinity
Authors: Heuer Bruria , Ravina Israela
Published: August 2004

Stock plants (Matthiola incana) are oil plants rich in omega-3 linolenic acid. The possibility of irrigating stock plants with saline water was tested under greenhouse conditions. High salinity levels affect plant growth expressed as plant height and accumulation of fresh weight. This is also true for the number of flowers and fruits and for seed yield. It can be concluded that irrigation of stock with saline water is feasible and could be recommended as an alternative approach to save fresh water.
Simulating lupin development, growth, and yield in a Mediterranean environment
Authors: Farré Imma , Robertson Michael J. , Asseng Senthold , French Robert J. , Dracup Miles
Published: August 2004

Simulation of narrow-leafed lupin (Lupinus angustifolius L.) production would be a useful tool for assessing agronomic and management options for the crop. This paper reports on the development and testing of a model of lupin development and growth, designed for use in the cropping systems simulator, APSIM (Agricultural Production Systems Simulator). Parameters describing leaf area expansion, phenology, radiation interception, biomass accumulation and partitioning, water use, and nitrogen accumulation were obtained from the literature or derived from field experiments. The model was developed and tested using data from experiments including different locations, cultivars, sowing dates, soil types, and water supplies. Flowering dates ranged from 71 to 109 days after sowing and were predicted by the model with a root mean square deviation (RMSD) of 4–5 days. Observed grain yields ranged from 0.5 to 2.7 t/ha and were simulated by the model with a RMSD of 0.5 t/ha. Simulation of a waterlogging effect on photosynthesis improved the model performance for leaf area index (LAI), biomass, and yield. The effect of variable rainfall in Western Australia and sowing date on yield was analysed using the model and historical weather data. Yield reductions were found with delay in sowing, particularly in water-limited environments. The model can be used for assessing some agronomic and management options and quantifying potential yields for specific locations, soil types, and sowing dates in Western Australia.
A preliminary genetic study of the social biology of feral pigs in south-western Australia and the implications for management
Authors: Hampton Jordan , Pluske John R. , Spencer Peter B. S.
Published: August 2004

A combination of demographic and genetic data was collected from 354 feral pigs (Sus scrofa), caught using standard trapping methods in south-western Australia, to provide preliminary information on their social biology. This included attempts to identify the putative parentage of 172 juvenile and foetal pigs, characterisation of the genetic mating system observed, and examination of the demographics of those individuals captured by current trapping methods. Findings revealed that in south-western Australia (a) feral pigs displayed moderately polygynous, but not polyandrous, mating behaviour, (b) breeding boars were significantly heavier than non-breeding boars, (c) the most reproductively successful boars, large individuals weighing >90 kg, moved the furthest in order to secure paternity, and (d) that a large proportion of breeding adults, particularly boars, were not captured under the standard trapping method employed. Ultimately, these data may be useful for the improvement of existing control programs, and exotic disease preparedness strategies.
Membrane lipids of symbiotic algae are diagnostic of sensitivity to thermal bleaching in corals
Authors: Tchernov Dan , Gorbunov Maxim Y. , de Vargas Colomban , Narayan Yadav Swati , Milligan Allen J. , Häggblom Max , Falkowski Paul G.
Published: August 2004

Over the past three decades, massive bleaching events of zooxanthellate corals have been documented across the range of global distribution. Although the phenomenon is correlated with relatively small increases in sea-surface temperature and enhanced light intensity, the underlying physiological mechanism remains unknown. In this article we demonstrate that thylakoid membrane lipid composition is a key determinate of thermal-stress sensitivity in symbiotic algae of cnidarians. Analyses of thylakoid membranes reveal that the critical threshold temperature separating thermally tolerant from sensitive species of zooxanthellae is determined by the saturation of the lipids. The lipid composition is potentially diagnostic of the differential nature of thermally induced bleaching found in scleractinian corals. Measurements of variable chlorophyll fluorescence kinetic transients indicate that thermally damaged membranes are energetically uncoupled but remain capable of splitting water. Consequently, a fraction of the photosynthetically produced oxygen is reduced by photosystem I through the Mehler reaction to form reactive oxygen species, which rapidly accumulate at high irradiance levels and trigger death and expulsion of the endosymbiotic algae. Differential sensitivity to thermal stress among the various species of
Symbiodinium
seems to be distributed across all clades. A clocked molecular phylogenetic analysis suggests that the evolutionary history of symbiotic algae in cnidarians selected for a reduced tolerance to elevated temperatures in the latter portion of the Cenozoic.
An accelerated assay for the identification of lifespan-extending interventions in
Drosophila
melanogaster
Authors: Bauer Johannes H. , Goupil Stephan , Garber Graham B. , Helfand Stephen L.
Published: August 2004

Recent advances in aging research have uncovered genes and genetic pathways that influence lifespan in such diverse organisms as yeast, nematodes, flies, and mice. The discovery of genes and drugs that affect lifespan has been delayed by the absence of a phenotype other than survivorship, which depends on the measurement of age at death of individuals in a population. The use of survivorship to identify genetic and pharmacological interventions that prolong life is time-consuming and requires a large number of homogeneous animals. Here, we report the development of an assay in
Drosophila melanogaster
using the expression of molecular biomarkers that accelerates the ability to evaluate potential lifespan-altering interventions. Coupling the expression of an age-dependent molecular biomarker to a lethal toxin reduces the time needed to perform lifespan studies by 80%. The assay recapitulates the effect of the three best known environmental life-span-extending interventions in the fly: ambient temperature, reproductive status, and calorie reduction. Single gene mutations known to extend lifespan in the fly such as
Indy
and
rpd3
also extend lifespan in this assay. We used this assay as a screen to identify drugs that extend lifespan in flies. Lipoic acid and resveratrol were identified as being beneficial in our assay and shown to extend lifespan under normal laboratory conditions. We propose that this assay can be used to screen pharmacological as well as genetic interventions more rapidly for positive effects on lifespan.
Crystal structure of a Baeyer–Villiger monooxygenase
Authors: Malito Enrico , Alfieri Andrea , Fraaije Marco W. , Mattevi Andrea
Published: August 2004

Flavin-containing Baeyer–Villiger monooxygenases employ NADPH and molecular oxygen to catalyze the insertion of an oxygen atom into a carbon–carbon bond of a carbonylic substrate. These enzymes can potentially be exploited in a variety of biocatalytic applications given the wide use of Baeyer–Villiger reactions in synthetic organic chemistry. The catalytic activity of these enzymes involves the formation of two crucial intermediates: a flavin peroxide generated by the reaction of the reduced flavin with molecular oxygen and the “Criegee” intermediate resulting from the attack of the flavin peroxide onto the substrate that is being oxygenated. The crystal structure of phenylacetone monooxygenase, a Baeyer–Villiger monooxygenase from the thermophilic bacterium
Thermobifida fusca
, exhibits a two-domain architecture resembling that of the disulfide oxidoreductases. The active site is located in a cleft at the domain interface. An arginine residue lays above the flavin ring in a position suited to stabilize the negatively charged flavin-peroxide and Criegee intermediates. This amino acid residue is predicted to exist in two positions; the “IN” position found in the crystal structure and an “OUT” position that allows NADPH to approach the flavin to reduce the cofactor. Domain rotations are proposed to bring about the conformational changes involved in catalysis. The structural studies highlight the functional complexity of this class of flavoenzymes, which coordinate the binding of three substrates (molecular oxygen, NADPH, and phenylacetone) in proximity of the flavin cofactor with formation of two distinct catalytic intermediates.
Modulation of long-range neural synchrony reflects temporal limitations of visual attention in humans
Authors: Gross Joachim , Schmitz Frank , Schnitzler Irmtraud , Kessler Klaus , Shapiro Kimron , Hommel Bernhard , Schnitzler Alfons
Published: August 2004

Because of attentional limitations, the human visual system can process for awareness and response only a fraction of the input received. Lesion and functional imaging studies have identified frontal, temporal, and parietal areas as playing a major role in the attentional control of visual processing, but very little is known about how these areas interact to form a dynamic attentional network. We hypothesized that the network communicates by means of neural phase synchronization, and we used magnetoencephalography to study transient long-range interarea phase coupling in a well studied attentionally taxing dual-target task (attentional blink). Our results reveal that communication within the fronto-parieto-temporal attentional network proceeds via transient long-range phase synchronization in the beta band. Changes in synchronization reflect changes in the attentional demands of the task and are directly related to behavioral performance. Thus, we show how attentional limitations arise from the way in which the subsystems of the attentional network interact.
Proendocrine genes coordinate the pancreatic islet differentiation program
in vitro
Authors: Gasa Rosa , Mrejen Caroline , Leachman Nathaniel , Otten Marc , Barnes Michael , Wang Juehu , Chakrabarti Swarup , Mirmira Raghavendra , German Michael
Published: August 2004

In the developing pancreas, the basic helix–loop–helix (bHLH) protein Neurogenin3 (Ngn3) specifies which precursor cells ultimately will become endocrine cells and initiates the islet differentiation program. NeuroD1, a closely related bHLH protein and a downstream target of Ngn3, maintains the differentiation program initiated by Ngn3. We have developed an
in vitro
model of Ngn3-dependent differentiation by infecting pancreatic duct cell lines with an Ngn3-expressing adenovirus. We found that both Ngn3 and its downstream target NeuroD1 activated the islet differentiation program in these cells by inducing the expression of genes with early roles in the differentiation cascade, as well as genes characteristic of fully differentiated islet cells. Induction of these genes, as exemplified by the
insulin1
gene, involved alteration of the local chromatin structure. Interestingly, the subsets of genes activated by Ngn3 and NeuroD1 were not completely overlapping, indicating that these two bHLH proteins serve specific functions in the development of the endocrine pancreas. In addition, microarray gene expression analysis identified a previously uncharacterized group of Ngn3-induced genes with potentially important roles in islet development and function. These studies demonstrate how Ngn3 initiates islet differentiation and provide us with a model for testing methods for producing islet cells for people with diabetes.
The immunoglobulin family member dendrite arborization and synapse maturation 1 (Dasm1) controls excitatory synapse maturation
Authors: Shi Song-Hai , Cheng Tong , Jan Lily Yeh , Jan Yuh-Nung
Published: August 2004

In the developing mammalian brain, a large fraction of excitatory synapses initially contain only
N
-methyl-
d
-aspartate receptor and thus are “silent” at the resting membrane potential. As development progresses, synapses acquire α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPA-Rs). Although this maturation of excitatory synapses has been well characterized, the molecular basis for this developmental change is not known. Here, we report that dendrite arborization and synapse maturation 1 (Dasm1), an Ig superfamily member, controls excitatory synapse maturation. Dasm1 is localized at the excitatory synapses. Suppression of Dasm1 expression by using RNA interference or expression of dominant negative deletion mutants of Dasm1 in hippocampal neurons at late developmental stage specifically impairs AMPA-R-mediated, but not
N
-methyl-
d
-aspartate receptor-mediated, synaptic transmission. The ability of Dasm1 to regulate synaptic AMPA-Rs requires its intracellular C-terminal PDZ domain-binding motif, which interacts with two synaptic PDZ domain-containing proteins involved in spine/synapse maturation, Shank and S-SCAM. Moreover, expression of dominant negative deletion mutants of Dasm1 leads to more immature silent synapses. These results suggest that Dasm1, as a transmembrane molecule, likely provides a link to bridge extracellular signals and intracellular signaling complexes in controlling excitatory synapse maturation.
The Role of Business Networks in Market Development in Sub‐Saharan Africa
Authors: Fafchamps Marcel
Published: August 2004

This chapter examines the role of business networks in market development and community formation in Sub-Saharan Africa. It is shown that for firms above a minimum size, relational contracting is the rule in markets for agricultural products, and manufacturing inputs and outputs. The important roles of relationships in facilitating market exchange are documented. The role of community affiliation in the membership of business networks is then examined. It is argued that entry into existing networks is biased, and that referral by family and friends is the most likely cause of ethnic concetration.
Effects of Ondansetron in Early‐ Versus Late‐Onset Alcoholics: A Prospective, Open‐Label Study
Authors: Kranzler Henry R. , Pierucci‐Lagha Amira , Feinn Richard , Hernandez‐Avila Carlos
Published: August 2004

Background: Early‐onset alcoholics (EOAs) have a greater familial loading for alcoholism, more severe progression of the disorder, a greater severity of comorbid psychopathology, and a poorer response to treatment than late‐onset alcoholics (LOAs). Ondansetron, a 5‐hydroxytryptamine‐3 antagonist, was found to be superior to placebo in the treatment of EOAs, but not of LOAs. This study compared the tolerability and potential efficacy of an oral solution of ondansetron in EOAs versus LOAs.

Methods: Forty outpatients with alcohol dependence (67.5% male; 87.5% European American; 20 EOAs; 20 LOAs) received an oral solution of ondansetron at a dosage of 4 μg/kg twice daily for 8 weeks, together with weekly relapse‐prevention therapy.

Results: EOAs had a significantly greater decrease in drinks per day, drinks per drinking day, and alcohol‐related problems than LOAs. Changes in the level of carbohydrate‐deficient transferrin were consistent with changes in self‐reported drinking behavior.

Conclusions: An oral solution of ondansetron seems suitable for the treatment of alcohol dependence, yielding findings consistent with evidence from a placebo‐controlled trial that ondansetron, at a dosage of 4 μg/kg twice daily, is of value in the treatment of EOAs.
Effect of Acute Ethanol Exposure on the Dermal Inflammatory Response After Burn Injury
Authors: Faunce Douglas E. , Garner Jennifer L. , Llanas Julian N. , Patel Parag J. , Gregory Meredith S. , Duffner Lisa A. , Gamelli Richard L. , Kovacs Elizabeth J.
Published: August 2004

Background: More than 100,000 people each year are admitted to U.S. hospitals for severe burn injury. Strikingly, ethanol use prior to injury is apparent in nearly 50% of burn patients, rendering them six times more likely to die from infection than patients not exposed to ethanol. We previously reported that the kinetics and magnitude of neutrophil chemokine production and subsequent accumulation of neutrophils in the lung was dramatically altered when ethanol exposure preceded injury. Here, we tested whether burn injury and ethanol exposure combined, altered susceptibility to infection, neutrophil chemoattractant production, and neutrophil accumulation at the site of the burn wound.

Methods: Male B6D2F 1 mice were administered a dose of ethanol designed to achieve 90–100 mg/dl circulating levels and 30 min later subjected to a 15% total body surface area dorsal scald injury. Susceptibility to topically applied Pseudomonas aeruginosa was examined. At various times after injury, burn wound and normal tissues were collected for assessments of neutrophil counts, myeloperoxidase quantitation, and neutrophil chemoattractant (KC and MIP‐2) production.

Results: Ethanol exposure prior to burn injury enhanced susceptibility to infection after burn and was associated with significantly elevated production of KC, but not MIP‐2, at the wound site. Despite the enhanced elevation of KC, neutrophil accumulation in the wounds of ethanol exposed, burn injured mice did not differ from those that received burn injury alone. TNFα (a potent activator of neutrophils), however, was found to be significantly elevated in the wounds of mice that received only burn injury, but not in those that received injury in combination with prior ethanol exposure.

Conclusion: In the presence of ethanol, neutrophils are adequately recruited to the site of burn injury, but their host defense functions are impaired, perhaps due to the lack of proinflammatory cytokines such as TNFα.
Glutamatergic Neurotransmission and Neuronal Glucose Oxidation are Coupled during Intense Neuronal Activation
Authors: Patel Anant B. , de Graaf Robin A. , Mason Graeme F. , Kanamatsu Tomoyuki , Rothman Douglas L. , Shulman Robert G. , Behar Kevin L.
Published: August 2004

13C nuclear magnetic resonance (NMR) experiments have previously shown that glutamatergic neurotransmitter flux (Vcycle(Glu/Gln)) changes proportionately with neuronal glucose oxidation (CMRglc(ox)N) in the nonactivated cortex of anesthetized rats. Positron Emission Tomography measurements of glucose and oxygen uptake during sensory stimulation had shown that the incremental glucose utilization is greater than oxygen leading to the suggestion that the energy required for stimulated neuronal activity arises from nonoxidative glucose metabolism. In this study, the authors used spatially localized 1H-observed, 13C-edited NMR spectroscopy during an infusion of [1,6–13C2]glucose to assess the relationship between changes in Vcycle(Glu/Gln) and glucose utilization (CMRglc(ox)N and CMRglc(nonox)) during the intense cortical activity associated with bicuculline-induced seizures. Metabolic fluxes were determined by model-based analysis of the 13C-enrichment time courses of glutamate-C4 and glutamine-C4 (CMRglc(ox)N, Vcycle(Glu/Gln)) and lactate-C3 (CMRglc(nonox)). The exchange rate between α-ketoglutarate and glutamate was found to be significantly faster than TCA cycle flux both for control (41 μmol·g−1·min−1; 95% CI, 5 to 109 μmol·g−1·min−1) and during seizures (21 μmol·g−1·min−1; 95% CI, 4.4 to 51.8 μmol·g−1·min−1). During seizures, total glucose utilization (CMRglc(ox+nonox)) increased substantially (466% between 0 and 6 minutes; 277% between 6 and 55 minutes). Glucose oxidation (CMRglc(ox)N) also increased (214%; from 0.26 ± 0.02 to 0.57 ± 0.07 μmol·g−1·min−1) but to a lesser degree, resulting in a large increase in cortical lactate concentration. Vcycle(Glu/Gln) increased 233% (from 0.22 ± 0.04 to 0.52 ± 0.07 μmol·g−1·min−1), which was similar to the increase in glucose oxidation. The value of Vcycle(Glu/Gln) and CMRglc(ox)N obtained here lie on the line predicted in a previous study. These results indicate that neuronal glucose oxidation and not total glucose utilization is coupled to the glutamate/glutamine cycle during intense cortical activation.
PAR-1 Deficiency Protects against Neuronal Damage and Neurologic Deficits after Unilateral Cerebral Hypoxia/Ischemia
Authors: Olson Ellen E. , Lyuboslavsky Polina , Traynelis Stephen F. , McKeon Robert J.
Published: August 2004

Cardiovascular and neurologic surgeries often involve a temporary reduction in cerebral blood flow. In these conditions, as well as during cerebral ischemia and traumatic brain injury, the temporary loss of oxygen and glucose initiates a cascade of cellular events that culminate in neuronal death and damage. Understanding the mechanisms that contribute to neuronal death after hypoxia/ischemia is critically important for treatment of such brain injury. Here, we use a model of combined cerebral hypoxia/ischemia (H/I) to examine the role of protease-activated receptor-1 (PAR-1) in hypoxic/ischemic neuronal damage. Our data show that PAR-1-deficient mice have smaller lesion volumes than wild-type controls after 45 minutes of H/I. The results of the genetic block of PAR-1 were corroborated using a PAR-1 antagonist, which decreased infarct volume in wild-type C57Bl6 mice. Examination of cellular responses to H/I reveals that PAR-1 -/- animals have less cellular death and diminished glial fibrillary acidic protein expression. Additionally, PAR-1 -/- mice exhibit less motor behavior impairment in rotorod and inverted wire-hang tests. These data suggest that PAR-1 contributes to hypoxic/ischemic brain injury and are consistent with other studies that implicate serine proteases and their receptors in neuropathology after cerebral insults.
Relative Changes in Cerebral Blood Flow and Neuronal Activity in Local Microdomains during Generalized Seizures
Authors: Nersesyan Hrachya , Herman Peter , Erdogan Ersan , Hyder Fahmeed , Blumenfeld Hal
Published: August 2004

There is broad agreement that generalized tonic–clonic seizures (GTCS) and normal somatosensory stimulation are associated with increases in regional CBF. However, the data regarding CBF changes during absence seizures are controversial. Electrophysiologic studies in WAG/Rij rats, an established animal model of absence seizures, have shown spike-wave discharges (SWD) that are largest in the perioral somatosensory cortex while sparing the visual cortex. Recent functional magnetic resonance imaging (fMRI) studies in the same model have also shown localized increases in fMRI signals in the perioral somatosensory cortex during SWD. Because fMRI signals are only indirectly related to neuronal activity, the authors directly measured CBF and neuronal activity from specific microdomains of the WAG/Rij cortex using a specially designed probe combining laser-Doppler flowmetry and extracellular microelectrode recordings under fentanyl/haloperidol anesthesia. Using this approach, parallel increases in neuronal activity and CBF were observed during SWD in the whisker somatosensory (barrel) cortex, whereas the visual cortex showed no significant changes. For comparison, these measurements were repeated during somatosensory (whisker) stimulation, and bicuculline-induced GTCS in the same animals. Interestingly, whisker stimulation increased neuronal activity and CBF in the barrel cortex more than during SWD. During GTCS, much larger increases that included both the somatosensory and visual cortex were observed. Thus, SWD in this model produce parallel localized increases in neuronal activity and CBF with similar distribution to somatosensory stimulation, whereas GTCS produce larger and more widespread changes. The normal response to somatosensory stimulation appears to be poised between two abnormal responses produced by two physiologically different types of seizures.
Microbiological and observational analysis of cross contamination risks during domestic food preparation
Authors: Redmond Elizabeth C. , Griffith Christopher J. , Slader Jenny , Humphrey Tom J.
Published: August 2004

The use of an observational approach in conjunction with isolation techniques for campylobacter and salmonella detection has facilitated a detailed evaluation of the risk of cross contamination during food preparation. Identification of suspected exposure routes has linked naturally contaminated raw foods with important food‐handling malpractices, contaminated contact surfaces and ready‐to‐eat foods. In a model domestic kitchen, 29 per cent of food preparation sessions resulted in positive campylobacter isolations from prepared salads, cleaning materials and food‐contact surfaces. Typing results showed that specific campylobacter strains isolated from prepared chicken salads were the same as the strains isolated from the raw chicken pieces, indicating microbial transfer during food preparation. Data obtained from this study can be used for exposure assessment, risk management and in the development of consumer risk communication strategies.
“It will happen again”
Authors: Day Brennan , Burnice McKay Ruth , Ishman Michael , Chung Ed
Published: August 2004

Important lessons can be learnt from the recent SARS epidemic, which reminds us that despite technology and science, the world is not entirely secure from such outbreaks. In addition to health issues and the toll of human suffering, SARS caused much distress within the business community, especially those companies with operations in emerging economies. We look at what lessons can be and have been learnt from the epidemic, and offer a modified framework of crisis management planning to help businesses deal better with similar epidemics in the future. We are also disheartened that very little concrete action seems to have been implemented to foster contingency planning by businesses, despite the financial impact and crisis brought on by SARS.
Predicting openness and commitment to change
Authors: Chawla Anuradha , Kevin Kelloway E.
Published: August 2004

Developed and tested a model of the change management strategies that predict openness and commitment to a large‐scale organizational change. Based on a sample of 164 employees, a partially‐ and a fully‐mediated model were compared with the former providing the best fit to the data. Communication and job security predicted openness and trust both directly and indirectly, via procedural justice. Participation predicted trust directly and indirectly but predicted openness to change only indirectly (via procedural justice). Turnover intentions were negatively predicted by openness and trust. Finally, turnover intentions predicted neglect. These results highlight the role of procedural justice perceptions in understanding organizational change.
Recognition and development of hope for South African organizational leaders
Authors: Luthans Fred , Van Wyk René , Walumbwa Fred O.
Published: August 2004

The significant challenges faced by South Africa at present are well known. How to deal with the problems from a political and economic perspective abound, but taking a psychological approach has been neglected. This paper proposes a positive approach to South African organizational leadership based on the psychological capacity of hope. After giving a brief background on the context surrounding South African organizations, the theory, research, and application of hope relevant to organizational leadership in the “Rainbow Nation” are presented and analyzed. Such an overlooked positive approach represented by hopeful organizational leaders seems needed at this juncture of South Africa's present and future.