bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of Linoleic Acid on pH Inside Sodium bis(2–ethylhexyl)sulfosuccinate Reverse Micelles in Isooctane and on the Enzymic Activity of Soybean Lipoxygenase
Authors: Rodakiewicz‐Nowak Janina , Maślakiewicz Pawel , Haber Jerzy 
Published: August 2004

The effective pH of sodium bis(2‐ethylhexyl)sulfosuccinate (AOT) reverse micelles (pHrm), containing buffers of different pH (pHst) and various amounts of linoleic acid, was studied within the range of compositions used to study the activity of soybean lipoxygenase in reverse micelles. Significant shifts of pHrm versus pHst were observed for the solutions of relatively higher pHst, dependent on linoleic acid and buffer concentrations. The effect diminished as pHst became closer to 7. When low‐ionic‐strength buffers were added to AOT solutions in isooctane, a significant buffering effect of linoleic acid in reverse micelles was observed. Solubilization of > 3 mM linoleic acid in micellar solutions containing 25 mM buffers gave the observed pHrm values almost independent of pHst. This effect diminished with the ionic strength of the buffering solution, but did not vanish even at 200 mM buffer. The observed effects result from the balance between ionization of linoleic acid and its partition between the water pool and the micellar interface.The enzymic activity of soybean lipoxygenase in the AOT reverse micellar solutions of the determined pHrm values was also studied. A significant reduction of the kinetics of the enzymic activity was observed, for all studied reverse micellar solutions. Changes of pHrm, caused by the presence of acidic substrate (linoleic acid) do not explain the observed reduction of activity directly through the effect on the enzyme. Due to unfavourable partition of the substrate between the microphases present in the systems, enhanced by reduction of pH at higher total concentrations of linoleic acid, the saturation of the enzyme with the substrate was not observed in the system and is difficult to attain experimentally in reverse micelles.A shift of the lipoxygenase activity/pHrm profile but negligible shift of the activity/pHst profile, with respect to aqueous buffer solutions, were observed. This indicates that either the information given by pH indicators used does not reveal the true pH of the enzyme in these reverse micelles, or that the sample of the enzyme is pH‐insensitive over a broader pH range than results from the relationship observed for linoleic acid in aqueous solutions. The latter conclusion is consistent with the data on lipoxygenase activity towards linoleyl sulfate in aqueous solutions [Bild, G. S., Ramadoss, C. S. & Axelrod, B. (1977) Lipids 12, 732–735]. Conditions for measuring pH‐independent lipoxygenase activity in reverse micelles are discussed.
Cloning of the maoA Gene that Encodes Aromatic Amine Oxidase of Escherichia coli W3350 and Characterization of the Overexpressed Enzyme
Authors: Steinebach Vincent , Benen Jac A. E. , Bader Rechien , Postma Pieter W. , De Vries Simon , Duine Johannis A. 
Published: August 2004

The mao operon of Escherichia coli W3350, which comprises the genes maoC and maoA, was cloned and appeared to be similar to that of Klebsiella aerogenes [Sugino, H., Sasaki, M., Azakami, H., Yamashita, M. & Murooka, Y. (1992) J. Bacteriol. 174, 2485–2492]. The gene that encodes aromatic amine oxidase (maoA) was isolated, sequenced, and expressed in E. coli TG2.The purified enzyme exhibited properties characteristic of a copper/topaquinone(TPQ)‐containing amine oxidase with respect to the optical absorption and EPR spectra, the size of the subunits, and the optical absorption spectra obtained upon derivatization with hydrazines. However, high‐resolution anion‐exchange chromatography revealed that the preparation was heterogeneous. The enzyme preparation appeared to consist of at least four enzyme species with different specific activities, A474m/A340nm ratios and TPQ/subunit ratios. Since the overall properties of the overexpressed enzyme and the authentic enzyme were similar and the separated enzyme species had identical N‐terminal amino acid sequences, the heterogeneity does not seem to be caused by improper expression of the gene in the recombinant strain but by factors that interfere with the processing of the specific tyrosine in the precursor enzyme to functional TPQ. Although other causes cannot be excluded, the spectral data and TPQ/subunit ratios reported in the literature for other amine oxidases suggest that suboptimal synthesis of functional TPQ also occurs in other organisms.
Flavin Motion in p‐Hydroxybenzoate Hydroxylase
Authors: Van Der Bolt Frank J. T. , Vervoort Jacques , Van Berkel Willem J. H. 
Published: August 2004

The side chain of Tyr222 in p ‐hydroxybenzoate hydroxylase interacts with the carboxy moiety of the substrate. Studies on the Tyr222→Phe mutant, [F222]p ‐hydroxybenzoate hydroxylase, have shown that disruption of this interaction hampers the hydroxylation of 4‐hydroxybenzoate. Tyr222 is possibly involved in flavin motion, which may facilitate the exchange of substrate and product during catalysis. To elucidate the function of Tyr222 in more detail, in the present study the substrate and effector specificity of the Tyr222→Ala mutant, [A222]p ‐hydroxybenzoate hydroxylase, was investigated.Replacement of Tyr→222 by Ala impairs the binding of the physiological substrate 4‐hydroxybenzoate and the substrate analog 4‐aminobenzoate. With these compounds, [A222]p ‐hydroxybenzoate hydroxylase mainly acts as a NADPH oxidase. [A222]p ‐hydroxybenzoate hydroxylase tightly interacts with 2,4‐dihydroxybenzoate and 2‐hydroxy‐4‐aminobenzoate. Crystallographic data [Schreuder, H. A., Mattevi, A., Oblomova, G., Kalk, K. H., Hoi, W. G. J., van der Bolt, F. J. T. & van Berkel, W. J. H (1994) Biochemistry 33, 10161–10170] suggest that this is due to motion of the flavin ring out of the active site, allowing hydrogen‐bond interaction between the 2‐hydroxy group of the substrate analogs and N3 of the flavin. [A222]p ‐Hydroxybenzoate hydroxylase produces about 0.6 mol 2,3,4‐trihydroxybenzoate from 2,4‐dihy‐droxybenzoate/mol NADPH oxidized. This indicates that reduction of the Tyr222→Ala mutant shifts the equilibrium of flavin conformers towards the productive ‘in’ position.[A222]p ‐Hydroxybenzoate hydroxylase converts 2‐fluoro‐4‐hydroxybenzoate to 2‐fluoro‐3,4‐dihydroxybenzoate. The regioselectivity of hydroxylation suggests that [A222]p ‐hydroxybenzoate hydroxylase binds the fluorinated substrate in the same orientation as wild‐type. Spectral studies suggest that wild‐type and [A222]p ‐hydroxybenzoate hydroxylase bind 2‐fluoro‐4‐hydroxybenzoate in the phenolate form with the flavin ring preferring the ‘out’ conformation. Despite activation of the fluorinated substrate and in contrast to the wild‐type enzyme, [A222]p ‐hydroxybenzoate hydroxylase largely produces hydrogen peroxide.The effector specificity of p ‐hydroxybenzoate hydroxylase is not changed by the Tyr222→‐Ala replacement. This supports the idea that the effector specificity is mainly dictated by the protein‐substrate interactions at the re ‐side of the flavin ring.
Formation of a Novel Enzymatic Metabolite of Leukotriene A4 in Tissues of Xenopus laevis
Authors: Strömberg Filippa , Hamberg Mats , Rosenqvist Urban , Dahlén Sven‐Erik , Haeggström Jesper Z. 
Published: August 2004

Leukotriene‐A4 hydrolase catalyzes the final step in the biosynthesis of the potent proinflammatory mediator leukotriene B4. Previously, leukotriene‐A4 hydrolase has been characterized from human, mouse and rat sources, i.e. only from mammalian species. In the present investigation, expression of leukotriene‐A4 hydrolase was studied in organs of Xenopus laevis. Enzyme activity was found in all nine organs tested with the highest levels in the intestine and the reproductive organs, i.e. oocytes and testes, previously unrecognized rich sources of the enzyme. No immunoreactive leukotriene‐A4 hydrolase was detected in Western blots of 10 000×g supernatants of X. laevis organ homogenates, using a polyclonal antiserum raised against human leukotriene‐A4 hydrolase. Likewise, Northern blot analysis of liver total RNA did not detect Xenopus leukotriene‐A4 hydrolase mRNA using a human cDNA probe. These results indicate significant structural differences between the human and toad enzymes.Incubations of 10 000×g supernatants of organ homogenates with leukotriene A4 revealed the formation of a novel metabolite, denoted compound X. Conversion of leukotriene A4 into compound X was due to an enzymatic activity as judged by its protein dependence, heat sensitivity, and resistance to ultrafiltration, and this activity appeared to be linked, directly or indirectly, to leukotriene‐A4 hydrolase.From data obtained by ultraviolet spectrophotometry, gas chromatography coupled to mass spectrometry, ultraviolet‐induced isomerization, and comparison with a synthetic standard, compound X was assigned the structure 5S,12R‐dihydroxy‐6,10‐trans 8,14‐cis‐eicosatetraenoic acid. Finally, compound X was found to exhibit contractile activity in guinea‐pig lung parenchyma, apparently elicited via a leukotriene B receptor.
The Anticoagulant Effect of the Human Secretory Phospholipase A2 on Blood Plasma and on a Cell‐Free System is Due to a Phospholipid‐Independent Mechanism of Action Involving the Inhibition of Factor Va
Authors: Mounier Carine , Franken Peet A. , Verheij Hubertus M. , Bon Cassian 
Published: August 2004

Blood platelets play a central role in haemostasis by leading to plug formation and by increasing the efficiency of blood coagulation. We have previously shown that blood platelets contain a group II secretory phospholipase A2 (sPLA2 grII) which is released into the extracellular medium upon activation but is unable to stimulate blood platelets. We presently reported an investigation of the putative involvement of the human sPLA2 grII (hsPLA2 grII) in the coagulation process, both in the absence and in the presence of activated platelets. We show that this enzyme prolongs the recalcification time of blood plasma even in the presence of activated platelets.The positive action of blood platelets on coagulation is correlated, at least in part, with the appearence at the cellular surface of procoagulant phospholipids which constitute a potential target for hsPLA2 grII. We therefore investigated the involvement of its enzymatic activity in the anticoagulant effect of this enzyme. We observed that the replacement of CaCl2 by SrCl2 to initiate the coagulation cascade did not suppress, but rather increased, the inhibitory action of hsPLA2 grII. Moreover, hsPLA2 grII hydrolyzed only a minor proportion of platelet phospholipids, and it did not affect plasma phospholipids. Taken together, these observations strongly suggest that the major action of hsPLA2 grII on blood coagulation does not involve the hydrolysis of phospholipids, in contrast with the strong anticoagulant effect of the group II venom phospholipase A2 from Crotalus durrissus terrificus.We next studied which step of the coagulation cascade was affected by hsPLA2 grII. Using purified coagulation factors, we demonstrated that hsPLA2 grII strongly inhibited the prothrombinase activity. This inhibitory effect was independent of the presence of phospholipids but required factor Va, leading to the hypothesis that hsPLA2 grII inhibited this factor. Further, the anticoagulant effect of hsPLA2 grII was observed on normal and factor‐X‐deficient plasma, but not on factor‐V‐deficient plasma.In conclusion, the anticoagulant action of hsPLA2 grII is based on a nonenzymatic mechanism of action involving the inhibition of factor Va.
A Klebsiella pneumoniae Strain that Shares a Type‐Specific Antigen with Shigella flexneri Serotype 6
Authors: Ansaruzzaman Mohammed , Albert M. John , Holme Tord , Jansson Per‐Erik , Rahman M. Mahbubur , Widmalm Göran 
Published: August 2004

A strain of Klebsiella pneumoniae was found as the only isolate with pathogenic potential from the stool of a two‐year old patient with diarrhoea. A strong serological cross‐reactivity with Shigella flexneri serotype 6 was demonstrated. The cross‐reacting antigens were shown to reside in the cell wall lipopolysaccharide. Studies of the pathogenic potential of the Klebsiella strain showed low level of invasion of HEp‐2 cells. However, tests for adherence to HEp‐2 cells as well as tests for toxin production were negative. The strain had several small plasmids and was multidrug resistant. These data do not form a sufficient basis for estimating the pathogenic potential of the organism. No K antigen was detected. The structure of the O‐antigenic polysaccharide from the K. pneumoniae strain was investigated using methylation analysis, NMR spectroscopy, and Smith degradation as the principal methods. The O‐antigenic polysaccharide has the following pentasaccharide repeating unit:
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This structure is not identical to any of the previously described O‐antigens of K. pneumoniae. The strong serological cross‐reactivity with the Shigella flexneri serotype 6 O‐antigen can most likely be attributed to the structural element α‐l‐Rhap ‐(1→)‐α‐l‐Rhap present in the O‐polysaccharide repeating unit of this serotype. Antiserum raised against the K. pneumoniae strain also agglutinated S. dysenteriae serotype 1 and strains of all different serotypes of S. flexneri. The Shigella strains contain the structural element α‐l‐Rhap ‐(1→3)‐α‐l‐Rhap in their O‐antigen polysaccharides which may be responsible for the observed cross‐reactivity.
Sphingomyelin‐Derived Lipids Differentially Regulate the Extracellular Signal‐Regulated Kinase 2 (ERK‐2) and c‐Jun N‐Terminal Kinase (JNK) Signal Cascades in Airway Smooth Muscle
Authors: Pyne Susan , Chapman Joanna , Steele Leslie , Pyne Nigel J. 
Published: August 2004

In ASM cells platelet‐derived growth factor stimulates rapid transient sphingosine phosphate formation, the activation of extracellular signal‐regulated kinase 2 (ERK‐2), the phosphorylation of p70S6K, and a ninefold increase in DNA synthesis. In contrast, this growth factor fails to activate c‐Jun N‐terminal kinase (JNK). Based upon these findings, we have tested whether the sphingomyelin‐derived sphingolipids play a role in growth factor signalling by assessing their effect on ERK‐2, JNK, and p70S6K.We demonstrate that sphingosine phosphate induces the activation of ERK‐2, is ineffective against JNK, and fails to induce the phosphorylation of p70S6K. The latter may explain why it is a poor mitogen when added directly to ASM cells. In contrast, sphingosine and cell‐permeable ceramides elicit the prominent tyrosyl phosphorylation and activation of JNK, are poor stimulators of ERK‐2, and do not induce the phosphorylation of p70S6K. Therefore, the specificity of signalling through either ERK‐2 or JNK cascades may be determined by the rapid agonist‐dependent interconversion of these sphingomyelin‐derived lipids. This may also provide a dynamic mechanism that enables growth factors and cytokines to elicit pleiotropic cell responses, such as proliferation and cell survival. For instance, both ceramide and sphingosine will elicit growth arrest via activation of JNK, whereas sphingosine phosphate will potentiate growth‐factor‐stimulated DNA synthesis, a consequence of the activation of ERK‐2. Furthermore, under certain conditions, sphingosine and ceramide stimulate cAMP formation, a negative modulator of cell growth, whereas sphingosine phosphate depresses cAMP, thereby enhancing its own growth‐promoting properties.From these studies, it is evident that sphingosine phosphate displays a signalling profile that is consistent with it mediating part of the action of platelet‐derived growth factor.
Dissection of the Basic Subdomain of the c‐Jun Oncoprotein
Authors: Krebs Daniel , Dahmani Benamar , Monnot Monique , Mauffret Olivier , Troalen Frédéric , Fermandjian Serge 
Published: August 2004

In a previous paper, we reported on the structural properties of a 35‐residue peptide corresponding to a modified basic subdomain (bSD) of the basic zipper protein c‐Jun (residues 252–281) as determined by combined use of 1H‐NMR, circular dichroism (CD) and Fourier transform infrared (FT‐IR) spectroscopies [Krebs, D., Dahmani, B., El Antri, S., Monnot, M., Convert, O., Mauffret, O., Troalen, F. & Fermandjian, S. (1995) Eur: J. Biochem. 231, 370–380]. The fragments NP and CP (the N‐terminal residues 1–19 and C‐terminal residues 16–35 of bSD, respectively) proved to be particularly useful for the assignment of the 1H‐NMR spectra of the full‐length bSD, which has been achieved completely in aqueous solution and partially in trifluoroethanol. Here, we report on The structural properties of NP and CP in aqueous solution and under varying H2O/trifluoroethanol conditions, again using 1H‐NMR, CD and FT‐IR experiments. Both CD and FT‐TR results established that the fragments are weakly structured in aqueous solution. Addition of trifluoroethanol to aqueous solutions of the peptides produced their stabilization into helix, following a profile sigmoidal for NP and nearly linear for CP. Quantitative NOES, secondary Ha chemical shifts, NH temperature coefficients and 3JαN coupling constants for the peptides in aqueous solutions provided indications for weak helix features (nascent helices) manifested within two sites (continuous dNN NOEs) in both NP and CP. For each peptide, an excellent agreement was observed between experiments and predictions with the AGADIR program fur the location of these nascent helices in the sequences. Trifluoroethanol provoked both the a‐helix stabilization within these sites and the α‐helix propagation to adjacent and no acid residues.Finally, our results reflected the high flexibility and helix potential of the NP and CP fragments, these two properties seeming crucial for the accomodation of c‐Jun to its specific DNA targets. The results demonstrated also the fragmentation's benefits in dissecting a protein or a complex peptide into smaller fragments and analyzing their structure individually.
Social services provided for physically abused children in Sweden: background factors and interventions
Authors: Lindell Charlotta , Svedin Carl Göran 
Published: August 2004

This study aims at describing and analysing what kinds of social services are provided for physically abused children in Sweden. The social services files were examined for 113 children under 15 years of age (67 boys and 46 girls) who had been reported to the police as having been physically abused by a parent or equivalent caretaker in a particular police district. The children's social services files indicated an increased risk of a parental abusive behaviour prior to the abuse incident. There had been former interventions in 81 per cent of the families and previous reports on neglect or abuse in 44 per cent of the 113 families. After the abuse incident, investiga‐tions were opened in 80 per cent of the cases. The three most common interventions were placement in foster care, referrals to Child and Adolescent Psychiatric Service and Social Services support contacts. The study shows that there was a tendency towards more proactive work with injured children, children of immigrant parents and children of mentally ill parents.
Prices, Devices, People, or Rules: The Relative Effectiveness of Policy Instruments in Water Conservation1
Authors: Campbell Heather E. , Johnson Ryan M. , Larson Elizabeth Hunt 
Published: August 2004

AbstractWater conservation policy is a natural laboratory for addressing general issues of relevance to policy analysis and public administration, particularly the relative effectiveness of policies in changing human behavior. Using multivariate regression analysis of a dataset comprised of more than 200,000 monthly observations of more than 19,000 household accounts over six years, this paper makes three main contributions. First, it contributes to the substantive area of water conservation policy by analyzing what works. Second, it contributes to our understanding of generic policy instruments. Third, it raises an important issue regarding standard assumptions about selection bias. The results support earlier work warning that offsetting behavior can negate engineering solutions to policy problems, but further indicate that adding communication to engineering solutions can create cooperation that overcomes offsetting behavior. They also provide evidence that appropriate regulation can be effective, and that pricing can be effective even when price elasticities of demand are low.
The Impact of Low Trust on Economic Development: The Case of Latin America
Authors: Neace M. B. 
Published: August 2004

AbstractDeficiencies of trust in many Latin American countries significantly impede efforts to attain sufficient levels of sustainable, long‐term economic growth. This paper discusses the role of trust as seen through the eyes of small entrepreneurs in Latin America. Three tables are discussed that specifically portray the role of trust in society, how entrepreneurs use trust to sustain their enterprises and socioeconomic networks, and the impacts of low trust in economic development in Latin America. This paper confirms what many leading scholars have claimed over the past two decades, that a cultural legacy of fractious civil societies accompanied with disruptive and often‐corrupt polities does matter when measuring human progress and economic development.
The Policy Sciences and the Unmasking Turn of Mind1
Authors: Ryan Philip 
Published: August 2004

AbstractTo unmask an idea is to disarm it by claiming that it has been advanced in the service of unacknowledged motives, bypassing the question of whether the idea is true or false. Most of us engage in the occasional unmasking of policy arguments. But unmasking becomes problematic when it is a “turn of mind,” a standard tool applied to a wide range of arguments, as in the work of policy writers Deborah Stone and William Riker. This article argues that the unmasking turn of mind misunderstands the world of policy and politics, and poses risks to a society's practice of deliberation on policy matters. Guidelines for responsible unmasking are proposed.
Community Capacity Building: A Critical Evaluation of the Third Sector Approach
Authors: Williams Colin C. 
Published: August 2004

AbstractThroughout the advanced economies, public policy has become ever more deeply involved in developing the capacities of communities to help themselves. Until now, this has been pursued through facilitating the development of community‐based groups. The aim of this paper, however, is to critically evaluate the implications and legitimacy of this public policy approach that views developing community‐based groups and community capacity building as synonymous. Drawing upon empirical evidence from the United Kingdom, it is here revealed that this third sector approach of developing community‐based groups privileges a culture of community involvement that relatively few engage in and is more characteristic of affluent populations, while disregarding informal acts of one‐to‐one engagement that are both a more popular form of community involvement and also more characteristic of the participatory culture of less affluent populations. The paper concludes by exploring how public policy might respond, especially with regard to the finding that less affluent populations have relatively informal cultures of engagement.
PARALLEL COPYING GARBAGE COLLECTION USING DELAYED ALLOCATION
Authors: PETRANK EREZ , KOLODNER ELLIOT K. 
Published: August 2004

We present a new approach to parallel copying garbage collection on symmetric multiprocessor (SMP) machines appropriate for Java and other object-oriented languages. Parallel, in this setting, means that the collector runs in several parallel threads. Our collector is based on a new idea called delayed allocation, which completely eliminates the fragmentation problem of previous parallel copying collectors while still keeping low synchronization, high efficiency, and simplicity of collection. In addition to this main idea, we also discuss several other ideas such as termination detection, balancing the distribution of work, and dealing with contention during work distribution.