bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of 2‐chloropyrazine oxidation products and several derivatives by multinuclear magnetic resonance
Authors: Cmoch Piotr 
Published: August 2003

Abstract1H, 13C, 14N and 15N NMR chemical shifts were used to prove the structures of the products of 2‐chloropyrazine oxidation. It was shown that oxidation by hydrogen peroxide in acetic acid or m‐chloroperbenzoic acid leads to the N4‐oxide, whereas potassium persulfate in sulfuric acid gives the N1‐oxide as the main product. Additionally, the results of NMR measurements of products from the nucleophilic substitution of the chlorine atom by azide anion, yielding the respective azides, and ethylation reactions of both 2‐chloropyrazine N‐oxides leading to the N‐ethyl salts confirm the structures of both isomeric N‐oxides. Protonation studies of the compounds obtained are also reported. The favoured protonation site is found to be the N atom that is not hindered by any substituents, and in some cases probably the oxygen atom of the N‐oxide function. Copyright © 2003 John Wiley & Sons, Ltd.
Characterization of reduced iso‐α‐acids derived from hops (Humulus lupulus) by NMR
Authors: Nord Lars I. , Sørensen Steen Bech , Duus Jens Ø. 
Published: August 2003

AbstractReduced forms of iso‐α‐acids (isohumulones), used in modern beer brewing were separated and characterized by 1H and 13C NMR spectroscopy. Components from mixtures of rho‐iso‐α‐acids, tetrahydro‐iso‐α‐acids, and hexahydro‐iso‐α‐acids were isolated using high‐performance liquid chromatography (HPLC) and analyzed by use of one‐ and two‐dimensional NMR experiments. The data presented assign the identities of the main peaks in the HPLC traces for the reduced iso‐α‐acids. Previous tentative assignments regarding the cis and trans configurations and the structures of the acyl residues of the reduced iso‐α‐acids were confirmed and extensive NMR assignments were made. Furthermore, the previously unknown stereochemistry in the C‐4 side‐chain of the rho‐ and hexahydro‐iso‐α‐acids was assigned. Copyright © 2003 John Wiley & Sons, Ltd.
A study of NMR parameters of cyclobutenones and benzocyclobutenones
Authors: Frimer Aryeh A. , Sharon Ofer , Gottlieb Hugo E. 
Published: August 2003

AbstractAn NMR study of ketones 5–12 was undertaken to gain insight into the low electrophilicity of the carbonyl moiety of butenones 9–11. Initial IR studies on compounds 9–12 indicated that there is relatively strong double bond character (and hence low electrophilicity) in the carbonyl of saturated and unsaturated cyclobutyl ketones. The 13C chemical shifts confirm that the carbonyl moiety is highly conjugated with the fused benzene ring in 9, and with the olefinic linkage in 10 and 11. Partial positive charge is distributed away from the carbonyl carbon, which is also expected to lower the electrophilicity of the carbonyl carbon atoms of 9–11. One‐bond carbon–proton coupling constants (1JCH) depend directly on carbon hybridization. In the four‐membered ring ketones 9–12 the experimental values are larger than in cyclobutane, probably as a result of the additional strain of the extra trigonal centers in the ring. A similar trend is seen in the case of the olefinic CH in 10 and 11 (ca 175 Hz), for which the coupling constant is larger than for the corresponding carbon in cyclobutene. 1JCC values between the ring carbon atoms of the cyclobutenones are some 20% lower than in the models—a bigger difference than in cyclobutanes, again indicative of the increased ring strain. The very low 42.4 Hz coupling between C‐1 and C‐2 in 9 might well indicate a measure of bond localization. 2JCC and 3JCC values are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Validity of esophageal pressure measurements with positive end‐expiratory pressure in preterm infants
Authors: Seddon Paul C. , Davis G. Michael 
Published: August 2003

AbstractPrevious research suggested that esophageal pressure changes (ΔPes) may not reflect pleural pressure changes (ΔPpl) in the presence of positive end‐expiratory pressure (PEEP), making assessments of dynamic lung mechanics invalid in these circumstances. To test this hypothesis, we measured ΔPes using a water‐filled catheter in 18 preterm infants with lung disease (9 intubated), and adjusted the catheter position to achieve a valid occlusion test. End‐expiratory occlusions were then carried out at PEEP (cm H2O) of 0, 4, and 8, and plots of ΔPes against ΔPao during airway occlusion were examined to derive the ratio ΔPes/ΔPao and the r value (as a measure of linearity). There was no significant change in ΔPes/ΔPao, which remained close to 1.0 as PEEP was increased from 0 to 8 cm H2O, and r also remained close to unity, indicating no appreciable hysteresis or alinearity of the plots. Our results show that ΔPes, when measured with an appropriately placed water‐filled catheter, continues to reflect ΔPpl accurately when lung volume is raised by applying PEEP up to 8 cm H2O. Pediatr Pulmonol. 2003; 36:216–222. © 2003 Wiley‐Liss, Inc.
Assessing bronchodilator responsiveness in infants using partial expiratory flow‐volume curves
Authors: Sheikh Shahid , Castile Robert , Hayes John , McCoy Karen , Eid Nemr 
Published: August 2003

AbstractOur objective was to compare the effectiveness of maximum forced expiratory flow measured at functional residual capacity (V′maxFRC) and the ratio of flow at 75% of the forced expiratory volume to peak forced expiratory flow (FEF75/FEFpeak) for detecting bronchodilator‐related changes in wheezy infants. In 55 infants (mean age, 7.8 ± 3.1 months) with a history of recurrent wheezing, V′maxFRC and FEF75/FEFpeak were measured at baseline and 15 min following nebulized albuterol. Mean results from 4 baseline and 4 postalbuterol partial expiratory flow‐volume curves were compared at baseline and following bronchodilator challenge. The strength (relative effect size) of each measure for assessing change was quantified by dividing the mean of the pre‐ to postdifferences by the standard deviation of the differences. Mean percent predicted V′maxFRC was 41.3 ± 34.3% at baseline and 44.4 ± 34.0% following albuterol. Mean FEF75/FEFpeak was 26.7 ± 13.4% at baseline and 35.8 ± 14.3% following albuterol. The mean percent change from baseline [(post‐pre)/pre] in percent predicted V′maxFRC was 18.3 ± 39.3, and for FEF75/FEFpeak, it was 44.1 ± 36.8. The change in FEF75/FEFpeak following albuterol was significantly greater than the change in V′maxFRC (P < 0.0001). The relative effect size for mean percent change from baseline in V′maxFRC was 0.47, and for FEF75/FEFpeak, 1.20. Changes in FEF75/FEFpeak appear to differentiate changes in airway function following administration of a bronchodilator better than do changes in V′maxFRC. Pediatr Pulmonol. 2003; 36:196–201. © 2003 Wiley‐Liss, Inc.
Investigation of the induced‐fit mechanism and catalytic activity of the human cytomegalovirus protease homodimer via molecular dynamics simulations
Authors: de Oliveira César Augusto Fernandes , Guimarães Cristiano Ruch Werneck , Barreiro Gabriela , de Alencastro Ricardo Bicca 
Published: August 2003

AbstractHuman cytomegalovirus (HCMV) is a highly species‐specific DNA virus infecting up to 80% of the general population. The viral genome contains the open reading frame UL80, which encodes the full‐length 80 kDa HCMV serine protease and its substrate. Full‐length HCMV protease is composed of an N‐terminal 256‐amino‐acid proteolytic domain, called assemblin, a linker region, and a C‐terminal structural domain, the assembly protein precursor. Biochemical studies have shown that dimerization activates assemblin because of an induced stabilization of the oxyanion hole (Arg166). Thus, we performed here molecular dynamics (MD) simulations on HCMV protease models to study the induced‐fit mechanism of the enzyme upon the binding of substrates and peptidyl inhibitors, and structural and energetic factors that are responsible for the catalytic activity of the enzyme dimer. Long and stable trajectories were obtained for the models of the monomeric and dimeric states, free in solution and bound to a peptidyl‐activated carbonyl inhibitor, with very good agreement between theoretical and experimental results. Our results suggest that HCMV protease is indeed a novel example of serine protease that operates by an induced‐fit mechanism. Also, in agreement with mutagenesis studies, our MD simulations suggest that the dimeric form is necessary to activate the enzyme because of an induced stabilization of the oxyanion hole. Proteins 2003;52:483–491. © 2003 Wiley‐Liss, Inc.
A left‐handed α‐helix containing both L‐ and D‐amino acids: The solution structure of the antimicrobial lipodepsipeptide tolaasin
Authors: Jourdan Fabrice , Lazzaroni Silvia , Méndez Blanca López , Lo Cantore Pietro , de Julio Marianna , Amodeo Pietro , Iacobellis Nicola S. , Evidente Antonio , Motta Andrea 
Published: August 2003

AbstractThe 18‐amino acid cytolytic lipodepsipeptide tolaasin, produced in culture by virulent strains of Pseudomonas tolaasii, is the causal agent of the brown blotch disease of the cultivated mushroom. Tolaasin has a sequence of D‐amino acids in its N‐terminal region, then alternates L‐ and D‐amino acids, and bears a C‐terminal lactone macrocycle composed of 5‐residues. The solution structure of tolaasin in sodium dodecyl sulfate was studied by 2D‐NMR spectroscopy and molecular dynamics simulated annealing calculations. Tolaasin forms an amphipathic left‐handed α‐helix in the regionDPro2‐DalloThr14 comprising the sequence of seven D‐amino acids and the adjacent L‐D‐L‐D‐D‐region. To the best of our knowledge, this is the first recognized example of a left‐handed α‐helix including both D‐ and L‐amino acids. The lactone macrocycle adopts a “boat‐like” conformation and is shifted from the helical axis as to form a “golf‐club” overall conformation. These structural features will be of importance in understanding, and preventing, tolaasin's role in the bacterial colonization of the host plant, and its toxic action on cells. Furthermore, the observed antimicrobial activity together with the potential resistance to enzymatic degradation and the increased antigenicity (both due to the presence of L‐ and D‐amino acids) strongly suggests for tolaasin a potential role as a template model for the design of new therapeutic antibacterial molecules. Proteins 2003;52:534–543. © 2003 Wiley‐Liss, Inc.
Evidence that SNF1‐related kinase and hexokinase are involved in separate sugar‐signalling pathways modulating post‐translational redox activation of ADP‐glucose pyrophosphorylase in potato tubers
Authors: Tiessen Axel , Prescha Katrin , Branscheid Anja , Palacios Natalia , McKibbin Rowan , Halford Nigel G. , Geigenberger Peter 
Published: August 2003

SummaryWe recently discovered that post‐translational redox modulation of ADP‐glucose pyrophosphorylase (AGPase) is a powerful new mechanism to adjust the rate of starch synthesis to the availability of sucrose in growing potato tubers. A strong correlation was observed between the endogenous levels of sucrose and the redox‐activation state of AGPase. To identify candidate components linking AGPase redox modulation to sugar supply, we used potato tuber discs as a model system. When the discs were cut from growing wild‐type potato tubers and incubated for 2 h in the absence of sugars, redox activation of AGPase decreased because of a decrease in internal sugar levels. The decrease in AGPase redox activation could be prevented when glucose or sucrose was supplied to the discs. Both sucrose uptake and redox activation of AGPase were increased when EDTA was used to prepare the tuber discs. However, EDTA treatment of discs had no effect on glucose uptake. Feeding of different glucose analogues revealed that the phosphorylation of hexoses by hexokinase is an essential component in the glucose‐dependent redox activation of AGPase. In contrast to this, feeding of the non‐metabolisable sucrose analogue, palatinose, leads to a similar activation as with sucrose, indicating that metabolism of sucrose is not necessary in the sucrose‐dependent AGPase activation. The influence of sucrose and glucose on redox activation of AGPase was also investigated in discs cut from tubers of antisense plants with reduced SNF1‐related protein kinase activity (SnRK1). Feeding of sucrose to tuber discs prevented AGPase redox inactivation in the wild type but not in SnRK1 antisense lines. However, feeding of glucose leads to a similar activation of AGPase in the wild type and in SnRK1 transformants. AGPase redox activation was also increased in transgenic tubers with ectopic overexpression of invertase, containing high levels of glucose and low sucrose levels. Expression of a bacterial glucokinase in the invertase‐expressing background led to a decrease in AGPase activation state and tuber starch content. These results show that both sucrose and glucose lead to post‐translational redox activation of AGPase, and that they do this by two different pathways involving SnRK1 and an endogenous hexokinase, respectively.
Layout modeling and construction procedure for the arrangement of exhibition spaces in a fair
Authors: Schneuwly P. , Widmer M. 
Published: August 2003

AbstractThis paper tackles a subset of layout problems that is not a subject of the scientific research to date: the arrangement of the exhibition spaces in a fair. A fair is a large‐scale exhibition for goods and services; for example a trade fair or a regional fair. The layout problem of fairs consists in finding an acceptable layout for both the exhibitors, the visitors, and the organizer of the fair. A model for representing the layout of fairs is presented: the adjacency model. Based on the adjacency model, a construction procedure is developed that leads to the generation of alternative layout solutions. Numerical results for the layout of a real fair are reported.
Genotyping and Phenotyping of Beta2-Toxigenic
Clostridium perfringens
Fecal Isolates Associated with Gastrointestinal Diseases in Piglets
Authors: Waters Michael , Savoie Amanda , Garmory Helen S. , Bueschel Dawn , Popoff Michel R. , Songer J. Glenn , Titball Richard W. , McClane Bruce A. , Sarker Mahfuzur R. 
Published: August 2003

ABSTRACT

Although
Clostridium perfringens
is recognized as an important cause of clostridial enteric diseases, only limited knowledge exists concerning the association of particular
C. perfringens
toxinotypes (type A to E) with gastrointestinal (GI) diseases in domestic animals. Some
C. perfringens
isolates also produce the newly discovered beta2-toxin (CPB2). Recent epidemiological studies suggested that
C. perfringens
isolates carrying the gene encoding CPB2 (
cpb2
) are strongly associated with clostridial GI diseases in domestic animals, including necrotic enteritis in piglets and typhlocolitis in horses. These putative relationships, obtained by PCR genotyping, were tested in the present study by further genotyping and phenotyping of 29
cpb2
-positive
C. perfringens
isolates from pigs with GI disease (pig GI disease isolates). PCR and restriction fragment length polymorphism analysis reconfirmed the presence of
cpb2
gene sequences in all the disease isolates included in the study. Furthermore, genotyping by pulsed-field gel electrophoresis analyses showed that the pig GI disease isolates included in this study all carry a plasmid
cpb2
gene, yet no clonal relationships were detected between the
cpb2
-positive pig GI disease isolates surveyed. Finally, CPB2-specific Western blotting demonstrated CPB2 expression by all of the
cpb2
-positive isolates surveyed. The CPB2 proteins made by five of these pig GI disease isolates were shown to have the same deduced amino acid sequences as the biologically active CPB2 protein made by the original type C isolate, CWC245. Collectively, our present results support a significant association between CPB2-positive
C. perfringens
isolates and diarrhea in piglets.
Identification of Swine Hepatitis E Virus (HEV) and Prevalence of Anti-HEV Antibodies in Swine and Human Populations in Korea
Authors: Choi In-Soo , Kwon Hyuk-Joon , Shin Na-Ri , Yoo Han Sang 
Published: August 2003

ABSTRACT
The swine hepatitis E virus (HEV) is considered to be a new zoonotic agent due to its close genomic resemblance to the human HEV and its ability to infect nonhuman primates. Hepatitis caused by HEV infection has been a serious public health problem in developing countries. However, recent seroprevalence studies indicate that the HEV also circulates in industrialized countries. In this study, a nested reverse transcription (RT)-PCR was developed to detect a part of the swine HEV open reading frame 2. Three Korean isolates of swine HEV were identified in 128 swine sera (2.3% prevalence) by the nested RT-PCR method. They were isolated from 2- to 3-month old pigs showing an age-specific prevalence of the HEV viremia. A phylogenetic tree analysis with a number of swine and human HEV isolates indicated that all Korean isolates of the swine HEV belong to genotype III. They were closely related to the swine and human HEV isolates that were identified in the United States and Japan. In addition, they formed a distinct branch in genotype III, showing a 92.7 to 99.8% identity at their nucleotide sequences. The overall prevalence of anti-swine HEV antibodies in swine was 15%. Antibodies to the swine HEV were not detected in 1-month-old pigs. However, the anti-swine HEV antibodies appeared in pigs older than 1 month and also showed an age-specific prevalence. The antibody prevalence rates to the swine HEV were 6.0, 10.0, 36.0, and 25.0%, in 2-, 3-, 4-, and 5-to-7-month-old pigs, respectively. In addition, the seroprevalence in sows to the swine HEV was 8.8%. On the other hand, 18% of blood donors in Korea were found to be positive for anti-HEV antibodies. Overall, this study indicates that subclinical HEV infections may prevail in swine and human populations in Korea.
VIM-1 Metallo-β-Lactamase-Producing
Klebsiella pneumoniae
Strains in Greek Hospitals
Authors: Giakkoupi P. , Xanthaki A. , Kanelopoulou M. , Vlahaki A. , Miriagou V. , Kontou S. , Papafraggas E. , Malamou-Lada H. , Tzouvelekis L. S. , Legakis N. J. , Vatopoulos A. C. 
Published: August 2003

ABSTRACT

Seventeen
Klebsiella pneumoniae
clinical isolates carrying the
bla
VIM-1
metallo-β-lactamase gene were collected in the intensive care units of three hospitals in Athens, Greece, in 2002. They exhibited various carbapenem resistance levels (Etest MICs of imipenem ranged from 4 to 32 μg/ml). All isolates gave positive results by the imipenem-EDTA synergy Etest. The isolates were classified into four main types by pulsed-field gel electrophoresis; the majority of the isolates (5 and 10 isolates) belonged to two types. The
bla
VIM-1
gene cassette was part of the variable region of a class 1 integron that also included
aac6
,
dhfrI
, and
aadA
. This structure was carried by transferable plasmids.
Comparison of Real-Time PCR, Conventional PCR, and Galactomannan Antigen Detection by Enzyme-Linked Immunosorbent Assay Using Bronchoalveolar Lavage Fluid Samples from Hematology Patients for Diagnosis of Invasive Pulmonary Aspergillosis
Authors: Sanguinetti Maurizio , Posteraro Brunella , Pagano Livio , Pagliari Gabriella , Fianchi Luana , Mele Luca , La Sorda Marilena , Franco Angelica , Fadda Giovanni 
Published: August 2003

ABSTRACT

An iCycler iQ real-time PCR assay targeting 18S rRNA
Aspergillus
-specific sequences was developed for the diagnosis of invasive pulmonary aspergillosis (IPA). Positive findings were obtained for 18 of 20 (90%) bronchoalveolar lavage (BAL) fluid specimens from patients with probable or confirmed IPA and were obtained for none of the 24 BAL samples from patients with no clinical evidence of aspergillosis. These results were concordant with those of a nested PCR assay, which detected 90% of the patients with IPA, while galactomannan ELISA revealed positivity for 100% of these patients, suggesting that combined use of methods might improve the diagnosis of IPA.
Novel Nosocomial Infections by
Stenotrophomonas maltophilia
: First Reported Case from Lucknow, North India
Authors: Mukhopadhyay Chiranjoy , Bhargava Anudita , Ayyagari Archana 
Published: August 2003

ABSTRACT

We describe a case of empyema with infected ascites caused by
Stenotrophomonas maltophilia
, which has rarely been reported as pathogenic. The source was determined to a disinfectant solution. The isolate was sensitive to a newer carbapenem-meropenem, and the patient was treated successfully. This case represents a novel dual presentation of a nosocomial infection by the isolate in question.
Chromosome banding in Amphibia
Authors: Schmid M. , Feichtinger W. , Steinlein C. , Haaf T. , Schartl M. , Visbal García R. , Manzanilla Pupo J. , Fernández Badillo A. 
Published: August 2003

A 15-year cytogenetic survey on one population of the leaf litter frog <i>Eleutherodactylus maussi</i> in northern Venezuela confirmed the existence of multiple XXAA♂/XAA<sup>Y</sup>♀ sex chromosomes which originated by a centric (Robertsonian) fusion between the original Y chromosome and an autosome. 95% of the male individuals in this population are carriers of this Y-autosome fusion. In male meiosis the XAA<sup>Y</sup> sex chromosomes pair in the expected trivalent configuration. In the same population, 5% of the male animals still possess the original, free XY sex chromosomes. In a second population of <i>E. maussi</i> analyzed, all male specimens are characterized by these ancestral XY chromosomes which form normal bivalents in meiosis. <i>E. maussi</i> apparently represents the first vertebrate species discovered in which a derived Y-autosome fusion still coexists with the ancestral free XY sex chromosomes. The free XY sex chromosomes, as well as the multiple XA<sup>Y</sup> sex chromosomes are still in a very primitive (homomorphic) stage of differentiation. With no banding technique applied it is possible to distinguish the Y from the X. DNA flow cytometric measurements show that the genome of <i>E. maussi</i> is among the largest in the anuran family Leptodactylidae. The present study also supplies further data on differential chromosome banding and fluorescence in situ hybridization experiments in this amphibian species.