bluuebunny/crossref_metadata_2025 huggingface dataset:
Panel of
Bacillus subtilis
Reporter Strains Indicative of Various Modes of Action
Authors: Hutter Bernd , Fischer Christina , Jacobi Alexander , Schaab Christoph , Loferer Hannes
Published: June 2004

In a recent project, we collected the transcriptional profiles of
Bacillus subtilis
168 after treatment with a large set of diverse antibacterial agents. One result of the data analysis was the identification of marker genes that are indicative of certain compounds or compound classes. We cloned these promoter regions in front of a luciferase reporter gene and reintroduced the constructs individually into the
B. subtilis
chromosome. Strains were analyzed for their responsiveness after treatment with a set of 37 antibacterials. Twelve functional reporter strains were generated that were selectively and significantly upregulated by the compounds. The selectivity of the reporter strains ranged from generic pathways like protein biosynthesis, cell wall biosynthesis, and fatty acid biosynthesis to compound classes (quinolones and glycopeptides) and individual compounds (rifampin, cycloserine, and clindamycin). Five of the strains are amenable for high-throughput applications, e.g., pathway-specific screening. In summary, we successfully generated
B. subtilis
reporter strains that are indicative of the mechanisms of action of various classes of antibacterials. The set of reporter strains presented herein can be used for mode-of-action analyses and for whole-cell screening of compound libraries in a mode-of-action-specific manner.
Antibacterial Effects of Amoxicillin-Clavulanate against
Streptococcus pneumoniae
and
Haemophilus influenzae
Strains for Which MICs Are High, in an In Vitro Pharmacokinetic Model
Authors: MacGowan Alasdair P. , Noel Alan R. , Rogers Chris A. , Bowker Karen E.
Published: June 2004

The antibacterial effect of amoxicillin-clavulanate in two formulations, pharmacokinetically enhanced 16:1 amoxicillin-clavulanate twice a day (b.i.d.) and standard 7:1 amoxicillin-clavulanate b.i.d., were studied in an in vitro pharmacokinetic model of infection. Five strains of
Streptococcus pneumoniae
and two of
Haemophilus influenzae
, all associated with raised MICs (2 to 8 mg/liter), were used. The antibacterial effect was measured over 24 h by the area under the bacterial kill curve (AUBKC) and the log change in viable count at 24 h (Δ24). A high 10
8
CFU/ml and low 10
6
CFU/ml initial inocula were used. Employing the Δ24 effect measure, the time above MIC (T>MIC) 50% maximum effect (EC
50
) for
S. pneumoniae
was in the range 21 to 28% with an 80% maximal response of 41 to 51%, for the AUBKC measure, the value was 26 to 39%, irrespective of inoculum. For
H. influenzae
, the T>MIC EC
50
was 28 to 37%, and the 80% maximum response was 32 to 48% for the Δ24 measure and 20 to 48% for AUBKC. The maximum response occurred at a T>MIC of 50 to 60% for both species and inocula. The
S. pneumoniae
data were analyzed by analysis of variance to assess the effect of inoculum, formulation, and MIC on antibacterial effect. Standard and enhanced formulations had different effects depending on MIC, with the standard formulation less effective at higher amoxicillin-clavulanate MICs. This is explained by the greater T>MICs of the enhanced formulation. Although resistant to amoxicillin-clavulanate by conventional breakpoints,
S. pneumoniae
and
H. influenzae
strains for which MICs are 2 or 4 mg/liter may well respond to therapy with pharmacokinetically enhanced formulation amoxicillin-clavulanate.
The Antimalarial Potential of 4-Quinolinecarbinolamines May Be Limited due to Neurotoxicity and Cross-Resistance in Mefloquine-ResistantPlasmodium falciparumStrains
Authors: Dow Geoffrey S. , Koenig Michael L. , Wolf Lesley , Gerena Lucia , Lopez-Sanchez Miriam , Hudson Thomas H. , Bhattacharjee Apurba K.
Published: June 2004

The clinical potential of mefloquine has been compromised by reports of adverse neurological effects. A series of 4-quinolinecarbinolamines were compared in terms of neurotoxicity and antimalarial activity in an attempt to identify replacement drugs. Neurotoxicity (MTT [thiazolyl blue reduction] assay) was assessed by exposure of cultured embryonic rat neurons to graded concentrations of the drugs for 20 min. The 50% inhibitory concentration (IC50) of mefloquine was 25 μM, while those of the analogs were 19 to 200 μM. The relative (to mefloquine) therapeutic indices of the analogs were determined after using the tritiated hypoxanthine assay for assessment of the antimalarial activity of the analogs against mefloquine-sensitive (W2) and -resistant (D6 and TM91C235)Plasmodium falciparumstrains. Five analogs, WR157801, WR073892, WR007930, WR007333, and WR226253, were less neurotoxic than mefloquine and exhibited higher relative therapeutic indices (RTIs) against TM91C235 (2.9 to 12.2). Conventional quinoline antimalarials were generally less neurotoxic (IC50s of 400, 600, and 900 for amodiaquine, chloroquine, and quinine) or had higher RTIs (e.g., 30 for halofantrine against TM91C235). The neurotoxicity data for the 4-quinolinecarbinolamines were used to develop a three-dimensional (3D), function-based pharmacophore. The crucial molecular features correlated with neurotoxicity were a hydrogen bond acceptor (lipid) function, an aliphatic hydrophobic function, and a ring aromatic function specifically distributed in the 3D surface of the molecule. Mapping of the 3D structures of a series of structurally diverse quinolines to the pharmacophore allowed accurate qualitative predictions of neurotoxicity (or not) to be made. Extension of this in silico screening approach may aid in the identification of less-neurotoxic quinoline analogs.
Effect of a Combination of Clevudine and Emtricitabine with Adenovirus-Mediated Delivery of Gamma Interferon in the Woodchuck Model of Hepatitis B Virus Infection
Authors: Jacquard A. C. , Nassal M. , Pichoud C. , Ren S. , Schultz U. , Guerret S. , Chevallier M. , Werle B. , Peyrol S. , Jamard C. , Rimsky L. T. , Trepo C. , Zoulim F.
Published: June 2004

Our aim was to evaluate the antiviral effect of a combination of two nucleoside reverse transcriptase inhibitors, emtricitabine (FTC) and clevudine (L-FMAU), with the addition of an adenovirus-driven delivery of recombinant gamma interferon (IFN-γ) in the woodchuck model of hepatitis B virus infection. Six woodchuck hepatitis virus (WHV)-infected woodchucks received L-FMAU (10 mg/kg) plus FTC (30 mg/kg) intraperitoneally for 8 weeks; six other animals received in addition an intravenous injection of a recombinant adenovirus vector expressing woodchuck IFN-γ (Ad-IFN) at weeks 4 and 8. In the control group, two animals received Ad-IFN alone, two received adenovirus vector expressing the green fluorescent protein reporter gene, and one remained untreated. In less than 2 weeks, all woodchucks that received L-FMAU plus FTC showed a rapid and marked inhibition of viral replication, with a 4-log
10
drop in serum WHV DNA. In two animals, viremia remained suppressed for several months after the end of treatment. Similarly, a dramatic decrease in intrahepatic replicative intermediates of viral DNA was observed in the L-FMAU/FTC-treated groups. The additional administration of Ad-IFN led to increased inflammation in the liver but did not enhance the antiviral effect of the L-FMAU/FTC combination. In conclusion, therapies combining L-FMAU and FTC in WHV-infected woodchucks resulted in a potent and sustained antihepadnaviral effect both in the liver and in the blood circulation. However, no extra benefit of adding IFN-γ gene transduction to the L-FMAU/FTC combination could be detected.
Incidence of the Recently Described Sulfonamide Resistance Gene
sul3
among German
Salmonella enterica
Strains Isolated from Livestock and Food
Authors: Guerra Beatriz , Junker Ernst , Helmuth Reiner
Published: June 2004

The
sul3
gene recently described in
Escherichia coli
was found in 22 of 512 (4.3%) German
Salmonella
isolates from different regions and sources and of different serotypes, antimicrobial resistance phenotypes, and genomic groups. This is the first report on the prevalence of
sul3
among
Salmonella
strains, and the findings support the strong potential of this determinant to spread within bacterial populations.
Antimicrobial Susceptibility Patterns and Macrolide Resistance Genes of β-Hemolytic Streptococci in Korea
Authors: Uh Young , Jang In Ho , Hwang Gyu Yel , Lee Mi Kyung , Yoon Kap Jun , Kim Hyo Youl
Published: June 2004

In 540 beta-hemolytic streptococci, the rates of resistance to tetracycline, chloramphenicol, erythromycin, and clindamycin were 80.0, 22.8, 20.2, and 19.1%, respectively. Of the erythromycin-resistant isolates, 63.3% had the constitutive macrolide-lincosamide-streptogramin B (MLS
B
) resistance phenotype, 23.9% had the M phenotype, and 12.8% had the inducible MLS
B
resistance phenotype. The constitutive MLS
B
resistance phenotype with the
erm
(B) gene was dominant in Korea.
Micafungin Enhances Neutrophil Fungicidal Functions against
Candida
Pseudohyphae
Authors: Gil-Lamaignere Cristina , Salvenmoser Stefanie , Hess Regina , Müller Frank-Michael C.
Published: June 2004

We evaluated the effect of the combination of micafungin and polymorphonuclear leukocytes (PMN) against hyphae of
Candida albicans
and
Candida dubliniensis
. Micafungin enhanced the PMN oxidative burst dose dependently. The combination was synergistic (
C. albicans
) or additive (
C. dubliniensis
); when PMN were pretreated with granulocyte-macrophage colony-stimulating factor, the combination was more effective.
Proteomic Analysis of Azole Resistance in
Candida albicans
Clinical Isolates
Authors: Hooshdaran Massoumeh Z. , Barker Katherine S. , Hilliard George M. , Kusch Harald , Morschhäuser Joachim , Rogers P. David
Published: June 2004

Changes in protein expression within a matched set of
Candida albicans
isolates representing the acquisition of azole resistance were examined by two-dimensional polyacrylamide gel electrophoresis and peptide mass fingerprinting. Proteins differentially expressed in association with azole resistance included Grp2p, Ifd1p, Ifd4p, Ifd5p, and Erg10p, a protein involved in the ergosterol biosynthesis pathway.
pncA
Mutations in Pyrazinamide-Resistant
Mycobacterium tuberculosis
Isolates in Portugal
Authors: Portugal Isabel , Barreiro Luís , Moniz-Pereira José , Brum Laura
Published: June 2004

The nucleotide sequences of the
pncA
genes within 55 multidrug-resistant pyrazinamide-resistant
Mycobacterium tuberculosis
clinical isolates were determined. Fifty-three out of the 55 isolates were pyrazinamidase (PZase) negative. Four strains contained a wild-type
pncA
gene, and PZase activity was undetectable in two of these strains. Seven of the 18 identified
pncA
mutations found have not been described in previous studies.
Substitutions at Methionine 220 in the 14α-Sterol Demethylase (Cyp51A) of
Aspergillus fumigatus
Are Responsible for Resistance In Vitro to Azole Antifungal Drugs
Authors: Mellado E. , Garcia-Effron G. , Alcazar-Fuoli L. , Cuenca-Estrella M. , Rodriguez-Tudela J. L.
Published: June 2004

Five clinical isolates of
Aspergillus fumigatus
that exhibited similar patterns of reduced susceptibility to itraconazole and other triazole drugs were analyzed. Sequence analysis of genes (
cyp51A
and
cyp51B
) encoding the 14α-sterol demethylases revealed that all five strains harbored mutations in
cyp51A
resulting in the replacement of methionine at residue 220 by valine, lysine, or threonine. When the mutated
cyp51A
genes were introduced into an
A. fumigatus
wild-type strain, the transformants exhibited reduced susceptibility to all triazole agents, confirming that the mutations were responsible for the resistance phenotype.
In Vitro and Bactericidal Activities of ABT-492, a Novel Fluoroquinolone, against Gram-Positive and Gram-Negative Organisms
Authors: Almer Laurel S. , Hoffrage Jennifer B. , Keller Erika L. , Flamm Robert K. , Shortridge Virginia D.
Published: June 2004

In vitro activities of ABT-492, ciprofloxacin, levofloxacin, trovafloxacin, moxifloxacin, gatifloxacin, and gemifloxacin were compared. ABT-492 was more potent against quinolone-susceptible and -resistant gram-positive organisms, had activity similar to that of ciprofloxacin against certain members of the familyEnterobacteriaceae, and had comparable activity against quinolone-susceptible, nonfermentative, gram-negative organisms. Bactericidal activity of ABT-492 was also evaluated.
Ternary Corrections in the Liquid-Liquid Equilibria for Four-Component System Heptane-Toluene-N-Methylpyrrolidone-Ethylene Glycol
Authors: Graczová Elena , Surový Július
Published: June 2004

Prediction for four-component liquid-liquid equilibrium is based on binary a ternary equilibrium data. Three-parameter equations for the excess Gibbs energy (NRTL equation, Redlich-Kister 4th order expansion and Wilson equation in Novák modification) extended by universal ternary contribution were employed for a thermodynamic description of the four-component system. The computation method was applied for a model four-component system heptane-toluene-N-methylpyrrolidone-ethylene glycol, t = 50 °C. The computed equilibrium data were compared with experimental ones measured for the weight ratio of the mixture N-methylpyrrolidone per ethylene glycol 20/80, 40/60 and 60/40.
Interactions of the SiHxCly Silicon Species with the Si4H9 Cluster
Authors: Burda Jaroslav , Bureš Michal , Černý Čestmír
Published: June 2004

The CNDO/2 method was applied to the investigation of the surface reaction occurring during the epitaxial growth of silicon single crystals. The aim of the work was to find silicon species from which the crystal growth is possible under the reaction conditions chosen to comply with the application of the CVD technological method. Calculations suggest that the SiH2, SiHCl and SiH3 species are feasible for the further growth.
Empirical Size-Dependent Growth Rate Models
Authors: Mydlarz Jerzy
Published: June 2004

A comparison of well known size-dependent crystal growth rate models has been presented. The models have been verified for crystal size distributions which have been recently presented in the literature. It is shown that for large crystal size range both the Abegg-Stevenson-Larson (ASL) model and the Canning-Randolph (C-R) model can be reduced to the simplest Bransom model. Two another kinetics size-dependent growth rate models have been presented and tested for size distributions which were recently presented by Mydlarz and Jones. Application of the proposed size-dependent growth models gives much better estimation of growth rate than other size-dependent models tested as well as Sikdar and White-Bendig-Larson methods.
Synthesis and Cyclization of Some 5-Aminobenzimidazole and 5-Aminobenzotriazole Derivatives
Authors: Bobošík Vladimír , Milata Viktor , Ilavský Dušan , Goljer Igor
Published: June 2004

Alkoxymethylene derivatives I of 2,4-pentanedione, 3-oxobutanenitrile, and methyl and ethyl 3-oxobutanoates with substituted 1-phenyl-5-aminobenzimidazoles and -benzotriazoles II give the products of nucleophilic substitution III and IV which, bearing ester groups, undergo thermal cyclizations to the corresponding 8-acetyl-3-phenyl-6,9-dihydroazolo[4,5-f]quinolin-9(3H)-ones V and VI. IR, UV, 1H and 13C NMR data are given.
Long-Range Proton-Carbon Shift Correlations. Comparison of One-Dimensional with Two-Dimensional Techniques
Authors: Uhrín Dušan
Published: June 2004

Effectiveness of two 13C-detected NMR methods - two dimensional heterocorrelated experiment and one-dimensional semiselective INEPT specified for mapping the long-range spin-spin interactions nJ(C,H) was investigated with dehydroaltenusin (I), a secondary metabolite of Alternaria tenuis and Talaromyces flavus moulds.
Side Reactions in Bromination of α-Ergocryptine
Authors: Cvak Ladislav , Stuchlík Josef , Schreiberová Magdalena , Sedmera Petr , Flieger Miroslav
Published: June 2004

2,3-Dihydro-2-oxo-α-ergocryptine (III) and 2,3-dihydro-2-oxo-3-hydroxy-α-ergocryptine (IV) were found as the side reaction products in bromination of α-ergocryptine (I) with bromine in the presence of water. 2,3-Dihydro-2-oxo-3-ethoxy-α-ergocryptine (V) was formed in the presence of ethanol.
Time-Dependent Non-Steady-State Diffusivities of C6 Paraffins in Silicalite by Zero-Length Column Method
Authors: Shavit Daniel , Voogd Patrick , Kouwenhoven Herman W.
Published: June 2004

Long-time diffusion experiments of n-hexane, 2-methylpentane and 2,3-dimethylbutane in silicalite according to the zero-length column method showed a significant decrease of the diffusion coefficients for longer times. A new and simple model of "uncoupled dual diffusion" is proposed to fit the experimental data. The calculated fast-diffusion coefficients as well as the calculated mean activation energies of diffusion of n-hexane and 2-methylpentane were almost equal and in reasonable agreement with literature data. A decrease of the adsorption partial pressure from 5.5 to 0.6 Torr did not have any influence on the fast-diffusion coefficient of n-hexane, which implies that the decrease of the diffusion coefficient in this range is not simply due to a non-linear isotherm. The proposed dual diffusion model may represent effects such as the presence of multiple energy states available for adsorbed molecules in the zeolite lattice, and/or diffusion anisotropy due to differences in the channel configurations in the three crystallografic directions.
Application of 23Na Nutation NMR to Characterize the Cation Effect in Ion-Exchanged NaY Zeolites
Authors: Chao Kuei-Jung , Lin Chiung-Fang
Published: June 2004

The two-dimensional sodium-23 nutation NMR was used to monitor the behavior of sodium ions in the partially alkali, alkali-earth or rare-earth ion exchanged NaY zeolites. The sodium-23 nutation spectra of the hydrated and rehydrated Y zeolites consist of two peaks at 1 and 2ωrf in F1 axis with chemical shifts of 0-10 ppm. For the degree of IA, IIA or RE cation exchange <45%, only one peak at 1ωrf was found. For the degree of cation exchange >45%, the second peak at 2ωrf might be observed. The correlation between the relative intensities and lineshapes of two peaks and the nature and distribution of cations in the supercages and sodalite cages with degree of exchange and heating treatment was studied.
NMR Studies of Benzene Adsorbed on Synthetic Faujasite-Type Zeolites
Authors: Liu Shang-Bin , Wu Jin-Fu , Ma Long-Ja , Lin May-Whei , Chen Tun-Li
Published: June 2004

The sorption and transport properties of benzene on dehydrated NaX and NaY zeolites have been investigated directly by 1H and 13C NMR measurements of the adsorbed benzene and probed indirectly by 129Xe NMR of the coadsorbed xenon. Dehydrated NaX and NaY zeolite adsorbate samples containing various adsorbate concentrations and having various sample bed configurations, which were subjected to different preparatory and experimental conditions, have been examined. Thermal treatment at a temperature (>250 °C) much greater than the boiling point of bulk benzene (80 °C) for an extended period of several hours is indispensable to ensure a homogeneous benzene distribution within the supercages of the faujasite-type zeolites.
Study of Coke Distribution in HZSM-5 by 129-Xe NMR
Authors: Bonardet Jean L. , Barrage M. C. , Fraissard Jack P. , Kubelková Ludmila , Nováková Jana , Ernst Horst , Freude Dieter
Published: June 2004

The location of coke formed during conversion of methanol or acetone on HZSM-5 zeolites has been examined using 129-Xe NMR spectroscopy. The results show that the type of reaction and the method of regeneration have great importance for the location of carbonaceous residues inside or outside the zeolite framework.
Comparison of HZSM-5 Zeolite and SAPO-5 Molecular Sieve in 1-Hexanol Conversion
Authors: Kalvachev Yuri A. , Bezouhanova Cvetana P. , Lechert Hans
Published: June 2004

The IR spectra of 1-hexanol adsorbed on SAPO-5 molecular sieves and on HZSM-5 zeolite were compared. It has been found, that both types of catalysts activate at 423 K the dehydration of 1-hexanol. In the IR spectra bands at 670 cm-1 (Z-isomer), 889 cm-1 (CH2=C< fragment), 911 cm-1 (CH2=CH-) and 965 cm-1 (E-isomer) have been observed, indicating that the skeletal and positional isomerization took place. A carbonyl compound (1730 cm-1) was formed at room temperature on all the investigated catalysts and disappeared upon heating. The activity of HZSM-5 in olefin isomerization and in dehydrogenation was greater than that of SAPO-5.
AlPO4 Molecular Sieves Modified with Metal Chelate Complexes
Authors: Kowalak Stanisłav , Balkus Kenneth J.
Published: June 2004

A new method for modification AlPO4 molecular sieves has been presented. Lack of ion-exchange properties makes the modification of aluminium phosphates for catalytic applications difficult. We have developed a method that involves the crystallization of AlPO4 molecular sieves around metal complexes. This results in encapsulation of the complexes within the intracrystalline pore system. Several metallophthalocyanines have been successfully encapsulated into AlPO4-5 and subsequently tested as catalysts for cyclohexene oxidation. Significant differences in activity result from the presence of different metallophthalocyanines.
Synthesis of Copper Containing Zeolites: New, Simple and Efficient Method for Quantitative Exchange
Authors: Gubelmann Michel H. , Guisnet Michel , Perot Guy , Pouilloux Yannick
Published: June 2004

A new technique is described which allows the quantitative exchange of copper(II) into ZSM-5 zeolites. The sequence consists of two steps: (i) impregnation of the zeolite with copper(II) in amounts higher than the exchange capacity; (ii) leaching of the copper in excess with respect to the exchange capacity with a chlorobenzene-water mixture at high temperature. The performances of the new materials in the hydrolysis of chlorobenzene, as well as preliminary informations on the nature of the catalyst and the type of mechanism are presented.
Fries Rearrangement of Phenyl Acetate over ZSM-5 Based Catalysts
Authors: Vogt Andreas H. G. , Kouwenhoven Herman W.
Published: June 2004

Catalysts based on samples of ZSM-5, differing in Si/Al ratio were applied in the Fries rearrangement of phenyl acetate. Experiments were carried out in batch reactors at 180 °C and continuously at various temperatures both in liquid phase and gas phase. A reaction scheme is proposed.
Semilocal and Nonlocal Semiempirical Model Potentials for Group IV Compounds
Authors: Walther Peter , Gruendler Wolfgang
Published: June 2004

Semilocal and nonlocal FSGO model potentials are given for group IV atomic cores, together with a theoretical justification. The parameters were calibrated on experimental molecular data. The model potentials are applied to the molecules CH4, SiH4, GeH4, CH3SiH3, CH3GeH3 and SiH3GeH3. Bond lengths and bond angles are in good agreement with the experimental results.
N-Phenyl-N,N"-Guanidinedicarboxylic Acid Esters. Synthesis, Anthelmintic and Pesticidal Effects
Authors: Palát Karel , Čeladník Milan , Daněk Jaroslav , Varkonda Štefan
Published: June 2004

Substituted phenylammonium chlorides react with cyanamide to give the corresponding phenylguanidines which on treatment with chloroformate esters give N-subst.phenyl-N,N"-guanidinedicarboxylic acid esters. All substances prepared have been tested for their anthelmintic activity against the model helminths Nippostrongylus brasilienses and Hymenolepis nana var. fraterna. The most significant activity has been found with diethyl N-(4-nitrophenyl)-N,N"-guanidinedicarboxylate. In pesticidal screening the compounds have shown fungicidal activity and particularly ovicidal activity against Tetranychus urticae which activity is increased with the compounds having a nitro group in the benzene ring.
Synthesis of the 4A-Type Zeolite from Pretreated Red Opalite
Authors: Cekova Blaga , Zlatanović V. , Stamboliev H.
Published: June 2004

Synthetic 4A-type zeolite was obtained from a natural raw material of volcanic origin which was thermally and chemically pretreated. The procedures are described together with the characteristics of the zeolite. The 4A-type zeolite prepared in the described way exhibits about 70% of crystallinity when compared with the commercial products and a somewhat lower surface area.
Study of the Mixed Coordinated Systems Cu(II)-Valinate Ion-Glycinate Ion and Cu(II)-Valinate Ion-Leucinate Ion
Authors: Sanz Alaejos María Teresa , Rodríguez Placeres Jesús César , García Montelongo Francisco J.
Published: June 2004

The mixed ligand ternary systems Cu(II)-valinate ion-glycinate ion and Cu(II)-valinate ion-leucinate ion have been studied polarographically at 25 ± 0.1 °C and at ionic strength 1.0 mol l-1, adjusted with sodium perchlorate. The formation of the mixed complexes [Cu(Val-)(Gly-)] and [Cu(Val-)(Leu-)] have been verified, with stability constants β11 = (4.6 ± 0.2).1015 and β11 = (7.2 ± 0.3).1015, respectively.
Absolute Stereochemistry of (-)-Wieland-Miescher Ketone as Established by the X-ray Crystallographic and CD Exciton Chirality Methods
Authors: Harada Nobuyuki , Sugioka Tatsuo , Uda Hisashi , Kuriki Takeo
Published: June 2004

The 8aR absolute stereochemistry of Wieland-Miescher ketone (-)-I was established by the X-ray structure analysis of its bis(4-bromobenzoate) derivatives (1R,6R,8aR)-(+)-IV and (1R,6S,8aR)-(-)-V. The absolute configuration of (-)-I was corroborated further by the application of the CD exciton chirality method to bis(4-bromobenzoates) (+)-IV and (-)-V.
Bromonitriles in Heterocyclic Synthesis. Synthesis and Reactions of Thiazolo[3,2-a]pyrimidines (III)
Authors: Geies Ahmed A.
Published: June 2004

As a continuation of our previous work about the synthesis and properties of thiazolopyrimidines, which are expected to be of biological and medicinal importance, the present work is aimed to synthesize new polyfunctional substituted thiazolo[3,2-a]pyrimidines. Pyrimidine derivatives I were reacted with bromomalononitrile or ethyl bromocyanoacetate at room temperature in ethanol in presence of potassium hydroxide as a basic catalyst followed by refluxing the reaction mixture to give thiazolo[3,2-a]pyrimidines IIa-IId.
Efficiency of Tetraphenylimido Diphosphate as an Extractant
Authors: Navrátil Oldřich , Herrmann Eckhard
Published: June 2004

Tetraphenylimido diphosphate (HA) and five other bidentate reagents containing PO and CO groups in a close vicinity to phenyl or phenoxy groups were examined as reagent for solvent extraction of some metals. Hafnium, scandium and rare earth compounds were found to easily pass from weakly acid aqueous solutions into benzene solutions of HA, whereas the other reagents investigated mostly lack this extracting power. The causes of this effect are discussed.
Oxidative and Basic Transformations of Some 1-Heteroaryloligophenylpyridinium Salts. Limitations to the Applicability of Ferricyanide Oxidation
Authors: Böhm Stanislav , Kubík Richard , Němeček Jan , Kuthan Josef
Published: June 2004

Ferricyanide oxidation of 2,3,4,6-tetraphenyl-1-(2'-pyridyl)pyridinium perchlorate (III) gave, in addition to the biheterocyclic product Ib, two pyrrole derivatives IIb and IIc and in some conditions also the diketone IV. Additional pyrrole derivatives, VII and IX, were obtained analogously from the thiazole 2,4,6-triphenylpyridinium salts V and VIb. Alkalysis of the thiazole salts V and VIb and of the imidazole salts VIc and VId using alcoholic KOH afforded the biheterocyclic products XI-XIV. The mechanisms of the conversions involved are discussed.
Syntheses Starting from 2,6-Dialkylphenylhydrazines
Authors: Krutošíková Alžbeta , Dandárová Miloslava , Konečný Václav
Published: June 2004

1,4-Disubstituted semicarbazides I, dithiocarbazates II, III and diesters of N-(2,6-dialkylphenylamino)imidodithiocarbonic acid IV, V were prepared from 2,6-dialkylphenylhydrazines. The products were tested for pesticide activity.
Metastable Region of Aqueous Solutions of Potassium Chloride Containing Lead(II) Ions
Authors: Nývlt Jaroslav , Sittová Zdeňka
Published: June 2004

The method of cooling at a constant rate was applied to determine the width of the metastable region of aqueous solutions of potassium chloride saturated at approximately 40 °C and containing 0 to 0.1 wt.% Pb(NO3)2. Lead(II) ions widen the metastable region up to a Pb(NO3)2 concentration of about 0.01% at which solution is apparently saturated with the addition. Additional increase in the Pb(NO3)2 concentration rather makes the metastable region narrower. The experimental data are compared with published values and discussed in terms of theories. A plausible explanation of the observed dependences is based on Glasner's theory of nucleation of KCl in the presence of Pb2+ ions.
Kinetics and Mechanism of Oxidation of Formic Acid by Chromium(VI). Inhibition by Manganese(II) Ion
Authors: Arias Conchita , Perez-Benito Joaquin F.
Published: June 2004

Experiments have been done to clarify the mechanism of the chromium(VI)-formic acid reaction in aqueous perchloric acid media, both in the absence and in the presence of manganese(II) ion. Two mechanisms are proposed, one for slightly acid solutions (I) and the other for strongly acid ones (II). Both mechanisms are first order in both oxidant and reductant, but they differ in the order to hydrogen ion (1 for mechanism I and 3 for mechanism II). The activation energy for mechanism I (60.4 ± 0.9 kJ mol-1) is considerably higher than that for mechanism II (41.2 ± 0.4 kJ mol-1). The rate-controlling steps proposed for mechanisms I and II are the H2CrO4-HCOOH and HCrO3+-HCOOH2+ reactions, respectively. Mechanism I is inhibited by manganese(II) ion, but mechanism II is not, which suggests that mechanism I involves Cr(IV) as an intermediate, whereas mechanism II does not.
Reactions of 4-Aroyl-3-chloro-6-phenylpyridazines with Some Nucleophilic Reagents, Synthesis of Some Fused Pyridazine Derivatives
Authors: Ismail M. F. , Elkhamry A. A. , Sayed F. S. , Emara S. A. , Shindy A. A.
Published: June 2004

As a part of our programme directed towards the synthesis of some fused pyridazine derivatives, we reported recently a novel method for the synthesis of some 4-aroyl-6-phenylpyridazin-3(2H)-ones and 4-aroyl-3-chloro-6-phenylpyridazines as readily available starting materials for this purpose. In the present investigation the reaction of 4-aroyl-3-chloro-6-phenylpyridazines (Ia-Ic) with some nucleophiles is studied.
Dehydrogenation of Substituted Alcohols to Aldehydes on Zinc Oxide-Chromium Oxide Catalysts
Authors: Gulková Daniela , Kraus Miloš
Published: June 2004

Sixteen primary alcohols of the structure RCH2OH (R = CH3, C2H5, (CH3)2CH, (CH3)3CCH2, HOCH2, CH3OCH2, C6H5, C6H5CH2, C6H5OCH2, ClCH2, BrCH2, F3C, CNCH2, (CH3)2NCH2, (C2H5)2NCH2 and tetrahydrofurfuryl) were explored for the possibility of obtaining the corresponding aldehydes by dehydrogenation on solid catalysts. Various catalysts were tested and two zinc oxide-chromium oxide catalysts were selected for further work because their activity and selectivity was satisfactory; moreover, the selectivity could be improved by addition of sodium into the catalysts and of water into the feed. The reaction was performed in the temperature range 250-450 °C and at atmospheric pressure. 2-Chloroethanol, 2-bromoethanol, ethylene glycol, 2-cyanoethanol and 2-(N,N-diethylamino)ethanol decomposed and deactivated the catalyst. The other alcohols were studied from the point of kinetics of dehydrogenation, which was described by a Langmuir-Hinshelwood type rate equation (3), and of substituent effects on rate, which were correlated by Taft equation (1) with the slope ρ = -1.46. The preparative value of catalytic dehydrogenation for obtaining substituted aldehydes was confirmed by prolonged runs and isolation of the aldehydic product by distillation using as the feeds 2-methoxyethanol and 2-(N,N-dimethylamino)ethanol, respectively.
Preparation and Utilization of a Biosensor Based on Galactose Oxidase
Authors: Vrbová Eva , Pecková Jitka , Marek Miroslav
Published: June 2004

An enzyme electrode for D-galactose determination was prepared by fixation of a carrier with immobilized galactose oxidase (E.C. 1.1.3.9) or coimmobilized galactose oxidase and catalase (E.C. 1.11.1.6) to a Clark-type oxygen sensor. The enzymes were immobilized either on a partially hydrolyzed nylon mesh or on a native collagen membrane using the Ugi reaction with cyclohexyl isocyanide and glutaraldehyde. The biosensors were characterized by the specific activity of the immobilized galactose oxidase, the apparent Michaelis constant KM(app.), and the stability expressed by time and a number of the performed analyses. The substrate specificity of the biosensor and the effect of pH and temperature of the reaction mixture on the response magnitude were also tested. The prepared biosensor was used for the determination of D-galactose content in samples of blood plasma and serum of patients with suspected galactosemia.
Oxidation of α-Amino Acids by Permanganate: Isokinetic Relation
Authors: Insausti Maria J. , Alvarez-Macho Maria P. , Mata-Pérez Fernando
Published: June 2004

The oxidation of three α-amino acids by permanganate under neutral conditions has been studied at various temperatures. The use of Exner's statistical method shows no existence of an isokinetic relation in the heterogeneous process but for the homogeneous process such a relation has been found. Moreover, the existence of linear free energy relations was confirmed for the homogeneous process.
Mn-Mo-O Catalysts for Methanol Oxidation. I. Preparation and Characterization of the Catalysts
Authors: Ivanov Krasimir , Litcheva Penka , Klissurski Dimitar
Published: June 2004

Mn-Mo-O catalysts with a different Mo/Mn ratio have been prepared by precipitation. The precipitate composition as a function of solution concentration and pH was studied by X-ray, IR, thermal and chemical methods. Formation of manganese molybdates with MnMoO4.1.5H2O, Mn3Mo3O12.2.5H2O, and Mn3Mo4O15.4H2O composition has been supposed. It is concluded that pure MnMoO4 may be obtained in both acid and alkaline media, the pH values depending on the concentration of the initial solutions. The maximum Mo/Mn ratio in the precipitates is 1.33. The formation of pure Mn3Mo4O15.4H2O is possible in weakly acidic media. This process is favoured by increasing the concentration of initial solutions.
Doubly Bridged Calix[8]crowns
Authors: Geraci Corrada , Consoli Grazia M. L. , Piattelli Mario , Neri Placido
Published: June 2004

Biscrowned calix[8]arenes were obtained by alkylation of p-tert-butylcalix[8]arene or calix[8]monocrowns with triethylene glycol ditosylate, in the presence of various bases. Of the 22 possible isomers, 1,4:2,5-, 1,3:2,5-, 1,4:2,3-, 1,4:5,8-, and 1,2:3,4-calix[8]biscrown-4 (3-7) were isolated in 7-30% yields. The presence of two crown bridges in 1,3:2,5- and 1,4:2,5-biscrown-4 (4, 5) leads to a significant rigidness of the calix[8]arene macrocycle and implies inherent chirality. The increased preorganization of calix[8]biscrowns, with respect to monocrowns, leads to significant complexing abilities for alkali cations with a marked preference for Cs+ over Na+.
Nodular symbionts ofShepherdia,Alnus, andMyricafrom a sand dune ecosystem: trends in occurrence of soilborneFrankiagenotypes
Authors: Huguet V , Batzli J M , Zimpfer J F , Gourbière F , Dawson J O , Fernandez M P
Published: June 2004

A successional sand dune system along the Lake Michigan shoreline was chosen to study the impact of edaphic factors, vegetation cover, and topographic position on Frankia strain distribution and infectivity. On this site, three actinorhizal species, Myrica gale L., Alnus incana (L.) Moench subsp. rugosa (Du Roi) Clausen, and Shepherdia canadensis (L.) Nutt., grew in different communities. Soil samples were collected on plots devoid of actinorhizal plants and serially diluted to inoculate the three native host plants in a greenhouse study. Strains present in the nodules formed were then genetically characterized using PCR-RFLP of the 16S23S intergenic spacer (IGS). An additional study site was included to estimate the impact of the sympatric presence of the three host species on soil infectivity and strain diversity. On this second site, soils used as inocula were collected in the rhizosphere of M. gale and S. canadensis. The M. gale and A. incana nodular strains belonged to an homogeneous cluster, whereas the S. cana densis nodular strains were separated into two distinct genetic clusters, irrespective of edaphic conditions and proximity to the host's root systems. A χ2analysis conducted on Shepherdia-infective strains showed the dominance of two distinct genotypes, with one of them being specific to newly formed dunes lacking plant cover and the other specific to older, stable dunes with dense vegetative cover.Key words: Frankia, Myrica, Shepherdia, Alnus, IGS 16S23S, sand dunes.
A SPLITTING CRITERION FOR RANK 2 BUNDLES ON A GENERAL SEXTIC THREEFOLD
Authors: CHIANTINI LUCA , MADONNA CARLO
Published: June 2004

In this paper we show that on a general sextic hypersurface X⊂ℙ4, a rank 2 vector bundle ℰ splits if and only if h1(ℰ(n))=0 for any n∈ℤ. We get thus a characterization of complete intersection curves in X.
ON THE CONE OF CURVES AND OF LINE BUNDLES OF A RATIONAL SURFACE
Authors: GALINDO C. , MONSERRAT F.
Published: June 2004

Let Z be a smooth projective rational surface. A condition that implies the polyhedrality of the cone of curves of Z is given. This one depends only on the configuration of infinitely near points associated with the morphism which provides Z from a relatively minimal model X and it holds for a wide range of surfaces whose anticanonical bundle is not ample. When the above configuration is a chain, the condition consists uniquely on deciding whether certain datum is positive. Furthermore, we study polyhedrality and regularity of the characteristic cone and of the cone of curves of Z for some particular cases.
THE CURVATURE OF A HESSIAN METRIC
Authors: TOTARO BURT
Published: June 2004

Inspired by Wilson's paper on sectional curvatures of Kähler moduli, we consider a natural Riemannian metric on a hypersurface {f=1} in a real vector space, defined using the Hessian of a homogeneous polynomial f. We give examples to answer a question posed by Wilson about when this metric has nonpositive curvature. Also, we exhibit a large class of polynomials f on R3 such that the associated metric has constant negative curvature. We ask if our examples, together with one example by Dubrovin, are the only ones with constant negative curvature. This question can be rephrased as an appealing question in classical invariant theory, involving the "Clebsch covariant". We give a positive answer for polynomials of degree at most 4, as well as a partial result in any degree.
NARROW WIDTH PENTAQUARKS
Authors: BUCCELLA F. , SORBA P.
Published: June 2004

A general study of pentaquarks built with four quarks in a L=1 state and an antiquark in S-wave shows that several of such states are forbidden by a selection rule, which holds in the limit of flavor symmetry, to decay into a baryon and a meson final state. We identify the most promising [Formula: see text] multiplet for the classification of the Θ+ and Ξ-- particles recently discovered with the prediction of a narrow width for both of them.
SUBLATTICES OF LATTICES OF ORDER-CONVEX SETS, III: THE CASE OF TOTALLY ORDERED SETS
Authors: SEMENOVA MARINA , WEHRUNG FRIEDRICH
Published: June 2004

For a partially ordered set P, let Co(P) denote the lattice of all order-convex subsets of P. For a positive integer n, we denote by [Formula: see text] (resp., SUB(n)) the class of all lattices that can be embedded into a lattice of the form [Formula: see text] where  is a family of chains (resp., chains with at most n elements). We prove the following results:

(1) Both classes [Formula: see text] and SUB(n), for any positive integer n, are locally finite, finitely based varieties of lattices, and we find finite equational bases of these varieties.

(2) The variety [Formula: see text] is the quasivariety join of all the varieties SUB(n), for 1≤n<ω, and it has only countably many subvarieties. We classify these varieties, together with all the finite subdirectly irreducible members of [Formula: see text].

(3) Every finite subdirectly irreducible member of [Formula: see text] is projective within [Formula: see text], and every subquasivariety of [Formula: see text] is a variety.
Nitric oxide's role in the heart: control of beating or breathing?
Authors: Paulus Walter J. , Bronzwaer Jean G. F.
Published: June 2004

Beneficial actions of nitric oxide (NO) in failing myocardium have frequently been overshadowed by poorly documented negative inotropic effects mainly derived from in vitro cardiac preparations. NO's beneficial actions include control of myocardial energetics and improvement of left ventricular (LV) diastolic distensibility. In isolated cardiomyocytes, administration of NO increases their diastolic cell length consistent with a rightward shift of the passive length-tension relation. This shift is explained by cGMP-induced phosphorylation of troponin I, which prevents calcium-independent diastolic cross-bridge cycling and concomitant diastolic stiffening of the myocardium. Similar improvements in diastolic stiffness have been observed in isolated guinea pig hearts, in pacing-induced heart failure dogs, and in patients with dilated cardiomyopathy or aortic stenosis and have been shown to result in higher LV preload reserve and stroke work. NO also controls myocardial energetics through its effects on mitochondrial respiration, oxygen consumption, and substrate utilization. The effects of NO on diastolic LV performance appear to be synergistic with its effects on myocardial energetics through prevention of myocardial energy wastage induced by LV contraction against late-systolic reflected arterial pressure waves and through prevention of diastolic LV stiffening, which is essential for the maintenance of adequate subendocardial coronary perfusion. A drop in these concerted actions of NO on diastolic LV distensibility and on myocardial energetics could well be instrumental for the relentless deterioration of failing myocardium.
Endocardial endothelium in the avascular frog heart: role for diffusion of NO in control of cardiac O2 consumption
Authors: Adler Alexandra , Huang Harer , Wang Zipping , Conetta Joseph , Levee Ellen , Zhang Xiaoping , Hintze Thomas H.
Published: June 2004

We investigated the role of nitric oxide (NO) in the control of myocardial O2 consumption in the hearts of female Xenopus frogs, which lack a coronary vascular endothelium and in which the endocardial endothelium is the only source of NO to regulate cardiac myocyte function. Hence, frogs are an ideal model in which to explore the role of diffusion of NO from the endocardial endothelium (EE) without vascular endothelial or cardiac cell NO production. In Xenopus hearts we examined the regulation of cardiac O2 consumption in vitro at 25°C and 37°C. The NO-mediated control of O2 consumption by bradykinin or carbachol was significantly ( P < 0.05) lower at 25°C (79 ± 13 or 73 ± 11 nmol/min) than at 37°C (159 ± 26 or 201 ± 13 nmol/min). The response to the NO donor S-nitroso- N-acetyl penicillamine was also markedly lower at 25°C (90 ± 8 nmol/min) compared with 37°C (218 ± 15 nmol/min). When Triton X-100 was perfused into hearts, the inhibition of myocardial O2 consumption by bradykinin (18 ± 2 nmol/min) or carbachol (29 ± 4 nmol/min) was abolished. Hematoxylin and eosin slides of Triton X-100-perfused heart tissue confirmed the absence of the EE. Although endothelial NO synthase protein levels were decreased to a variable degree in the Triton X-100-perfused heart, NO2 production (indicating eNOS activity) decreased by >80%. It appears that the EE of the frog heart is the sole source of NO to regulate myocyte O2 consumption. When these cells are removed, the ability of NO to regulate O2 consumption is severely limited. Thus our results suggest that the EE produces enough NO, which diffuses from the EE to cardiac myocytes, to regulate myocardial O2 consumption. Because of the close proximity of the EE to underlying myocytes, NO can diffuse over a distance and act as a messenger between the EE and the rest of the heart to control mitochondrial function and O2 consumption.
Requirement of the epidermal growth factor receptor in renal epithelial cell proliferation and migration
Authors: Zhuang Shougang , Dang Yujing , Schnellmann Rick G.
Published: June 2004

We showed that renal proximal tubular cells (RPTC) can proliferate and migrate following plating and oxidant or mechanical injury in the absence of exogenous growth factors; however, the mechanisms of this response remain unclear. We examined whether epidermal growth factor receptor (EGFR) signaling is activated following plating and mechanical injury and mediates RPTC proliferation and migration. EGFR, Akt [a target of phosphoinositide-3-kinase (PI3K)], and ERK1/2 were activated after plating and mechanical injury, and their phosphorylation was further enhanced by addition of exogenous EGF. Inactivation of the EGFR with the selective inhibitor AG-1478 completely blocked phosphorylation of EGFR, Akt, and ERK1/2 and blocked cell proliferation and migration after plating and injury. Inhibition of PI3K with LY-294002 blocked Akt phosphorylation and proliferation, whereas U-0126 blocked ERK1/2 phosphorylation but had no effect on proliferation. Furthermore, p38 was phosphorylated following mechanical injury and the p38 inhibitor SB-203580 blocked p38 phosphorylation and cell migration. In contrast, neither PI3K nor ERK1/2 inhibition blocked cell migration. These results show that EGFR activation is required for RPTC proliferation and migration and that proliferation is mediated by PI3K, whereas migration is mediated by p38.
Early diabetes as a model for testing the regulation of juxtaglomerular NOS I
Authors: Thomson Scott C. , Deng Aihua , Komine Norikuni , Hammes John S. , Blantz Roland C. , Gabbai Francis B.
Published: June 2004

Dysregulation of kidney nitric oxide synthase (NOS) I may alter renal hemodynamics in diabetes. Four types of studies were performed in anesthetized 1- to 2-wk-streptozotocin diabetic rats. 1) Glomerular filtration rate (GFR) was measured before and during NOS I blockade. Subsequent addition of nonspecific NOS blocker tested for residual NO from other isoforms. Acute systemic NOS I blockade reduced GFR only in diabetics. Nonspecific NOS blockade had no additional effect on NOS I-blocked diabetics. 2) Renal blood flow (RBF) was monitored for evidence that tubuloglomerular feedback (TGF) resets during 1 h of continuous activation with benzolamide. NOS I blockade was added to test for the role of NOS I in TGF resetting. During 1 h of TGF activation in controls, RBF initially declined and then returned to baseline. In diabetic and NOS I-blocked rats, RBF declined and remained low. 3) The ability of NOS I blockade to increase the homeostatic efficiency of TGF in diabetes was tested by micropuncture in free-flowing nephrons. The addition of NOS I blocker to the tubular fluid increased TGF efficiency in control and diabetic rats. 4) The influence of distal salt delivery on local NOS I activity was tested by micropuncture. Henle's loop was perfused at varying rates with NOS I blocker while single-nephron GFR (SNGFR) from the late proximal tubule was measured. In controls, NOS I blockade mainly reduced SNGFR when flow through Henle's loop was high. In diabetics, NOS I blockade reduced SNGFR independently of flow through Henle's loop. In conclusion, normally, salt delivered to the macula densa (MD) exerts immediate control over MD NOS I activity. In diabetes, there is ongoing overactivity of NOS I that is not regulated by MD salt.