bluuebunny/crossref_metadata_2025 huggingface dataset:
CCR5 and CXCR4 Usage by Non-Clade B Human Immunodeficiency Virus Type 1 Primary Isolates
Authors: Thompson Daniah A. D. , Cormier Emmanuel G. , Dragic Tatjana
Published: July 2002

CCR5 and CXCR4 usage has been studied extensively with a variety of clade B human immunodeficiency virus type 1 (HIV-1) isolates. The determinants of CCR5 coreceptor function are remarkably consistent, with a region critical for fusion and entry located in the CCR5 amino-terminal domain (Nt). In particular, negatively charged amino acids and sulfated tyrosines in the Nt are essential for gp120 binding to CCR5. The same types of residues are important for CXCR4-mediated viral fusion and entry, but they are dispersed throughout the extracellular domains of CXCR4, and their usage is isolate dependent. Here, we report on the determinants of CCR5 and CXCR4 coreceptor function for a panel of non-clade B isolates that are responsible for the majority of new HIV-1 infections worldwide. Consistent with clade B isolates, CXCR4 usage remains isolate dependent and is determined by the overall content of negatively charged and tyrosine residues. Residues in the Nt of CCR5 that are important for fusion and entry of clade B isolates are also important for the entry of all non-clade B HIV-1 isolates that we tested. Surprisingly, we found that in contrast to clade B isolates, a cluster of residues in the second extracellular loop of CCR5 significantly affects fusion and entry of all non-clade B isolates tested. This points to a different mechanism of CCR5 usage by these viruses and may have important implications for the development of HIV-1 inhibitors that target CCR5 coreceptor function.
Coding Sequences Upstream of the Human Immunodeficiency Virus Type 1 Reverse Transcriptase Domain in Gag-Pol Are Not Essential for Incorporation of the Pr160

gag-pol

into Virus Particles
Authors: Chiu Hsu-Chen , Yao Szu-Yung , Wang Chin-Tien
Published: July 2002

Incorporation of the human immunodeficiency virus type 1 (HIV-1) Gag-Pol into virions is thought to be mediated by the N-terminal Gag domain via interaction with the Gag precursor. However, one recent study has demonstrated that the murine leukemia virus Pol can be incorporated into virions independently of Gag-Pol expression, implying a possible interaction between the Pol and Gag precursor. To test whether the HIV-1 Pol can be incorporated into virions on removal of the N-terminal Gag domain and to define sequences required for the incorporation of Gag-Pol into virions in more detail, a series of HIV Gag-Pol expression plasmids with various extensive deletions in the region upstream of the reverse transcriptase (RT) domain was constructed, and viral incorporation of the Gag-Pol deletion mutants was examined by cotransfecting 293T cells with a plasmid expressing Pr55

gag

. Analysis indicated that deletion of the N-terminal two-thirds of the
gag
coding region did not significantly affect the incorporation of Gag-Pol into virions. In contrast, Gag-Pol proteins with deletions covering the capsid (CA) major homology regions and the adjacent C-terminal CA regions were impaired with respect to assembly into virions. However, Gag-Pol with sequences deleted upstream of the protease, or of the RT domain but retaining 15 N-terminal
gag
codons, could still be rescued into virions at a level about 20% of the wild-type level. When assayed in a nonmyristylated Gag-Pol context, all of the Gag-Pol deletion mutants were incorporated into virions at a level comparable to their myristylated counterparts, suggesting that the incorporation of the Gag-Pol deletion mutants into virions is independent of the N-terminal myristylation signal.
Expression of Exogenous Sam68, the 68-Kilodalton Src-Associated Protein in Mitosis, Is Able To Alleviate Impaired Rev Function in Astrocytes
Authors: Li Jinliang , Liu Ying , Park In-Woo , He Johnny J.
Published: July 2002

Human immunodeficiency virus type 1 (HIV-1) gene expression in astrocytes is restricted, resulting in a brief and limited synthesis of HIV-1 viral structural proteins. Impaired Rev function has been documented in these cells. However, the molecular mechanisms underlying the impaired Rev function are not fully understood. Using the astroglial cell line U87.MG as a model, we report here that HIV-1 gene expression down-regulated expression of Sam68, the 68-kDa Src-associated protein in mitosis, which was constitutively expressed at a lower level in astrocytes. Elevating the endogenous level of Sam68 expression considerably restored HIV-1 Rev function in astrocytes, as determined by a Rev-dependent reporter gene assay. However, elevation of Sam68 expression achieved only a modest increase in HIV-1 production, further supporting the notion that there are multiple cellular restrictions of HIV-1 gene expression in astrocytes. Mutagenesis analysis identified the region between amino acids 321 and 410 of Sam68 as being directly involved in the binding of Sam68 to Rev, while a double mutation in Rev, L78D and E79L, like those in the dominant-negative Rev mutant M10, eliminated Rev binding to Sam68. Moreover, subcellular fractionation and digital fluorescence microscopic imaging revealed that Sam68 expression promoted Rev nuclear export. Taken together, our studies demonstrate that a lower level of constitutive Sam68 expression, followed by further down-regulation by HIV-1 infection, contributes to impaired Rev function in astrocytes, and they suggest that Sam68 may play an important role in Rev nuclear export.
Molecular Transport in a Two-Dimensional Lattice of Sorption Sites
Authors: Kočiřík Milan , Zikánová Arlette , Dubský Josef , Kroček Petr
Published: July 2002

It is known from experimental study of the sorption of some aromatic compounds (such as p-xylene) in zeolites with the MFI lattice that the adsorption kinetics in such systems exhibits appreciable deviations from the 2nd Fick law. To account for those deviations, whose origin lies in the crystal bulk, the existence of two phases which are not in local chemical equilibrium is postulated: a mobile phase is assumed to occur in the straight zeolite channels whereas an immobile phase is assumed in the zig-zag channels. A microkinetic model is proposed assuming localization of the sorbed molecules on two kinds of centres arranged in a regular two-dimensional lattice, along which migration takes place in agreement with the Langmuir kinetics of exchange of molecules between the occupied and unoccupied centres. For an exact description of the time evolution of the considered physical system the model results in a set of ordinary differential equations which are transformed into a system of two partial differential equations providing a spatially continuous description of the physical system. This approach enables the phenomenological kinetic parameters to be interpreted in terms of the jump frequency of molecules between the various kinds of adsorption centres. For small perturbations in the concentration of the sorbing substance the mathematical model is linearized, and the behaviour of the system is illustrated using the numerical solution of the model equations. In dependence on changes in the model parameters, the transition from the case of pure diffusion along a one-dimensional lattice in the mobile phase, with the zig-zag channels inaccessible, via the case of a slowly establishing local equilibrium between the two sub-lattices, to the limiting case of instantaneously establishing local equilibrium between the sub-lattices is discussed.
Formation of Barrier Oxide Film on Lead in Borate Solutions
Authors: Abdel Aal Emad E. , Hefny Mohamed M.
Published: July 2002

Galvanostatic anodization of lead in borate solutions reveals that lead can form a barrier type oxide film. The rate of growth, R, fulfils the empirical relation, R = aib within the current density i range from 1.16 .10-4 to 3.19 .10-4 A cm-2. The magnitudes of the parameters a and b are 6.9 . 103 and 1.6, respectively, it has been found that the high field approximation is applicable for the oxide growth on lead. The coefficients of the dependence of R on solution temperature, T, pH and borate ion concentration, c, viz. (∂R/∂T), (∂R/∂pH) and (∂R/∂log c) are -18 . 10-4, -0.13 and 0.41, respectively.
Influence of the Formation of Aluminium Spinel, AlVO4, on the Catalytic Activity of V2O5 Supported on γ-Alumina
Authors: Abd El-Wahab Mohamed M. M. , Said Abd El-Aziz A.
Published: July 2002

Vanadium pentoxide catalysts supported on γ-alumina (1 - 50 mole %) were prepared by impregnation method and calcined at 400 and 680 °C for 4 h. The structure of the original and calcined samples was characterized by DTA and X-ray diffraction. The electrical conductivity measurements of the calcined samples reveal that the conductance increases while the Fermi potential decreases on increasing V2O5 content up to 50 mole %. The catalytic dehydration of isopropanol was carried out at 250 °C using a flow system. The results showed an observable increase in the extent of catalytic dehydration of the alcohol on increasing V2O5 content from 5 mole % to 50 mole % with the samples calcined at 400 °C. The catalysts calcined at 680 °C were found to exhibit maximum activity at the composition of 20 mole % V2O5. Above the maximum a sharp decrease in the conversion and the yield towards propylene was found due to formation of aluminium vanadate, i.e. AlVO4 spinel. The low activity associated with the existence of this spinel was correlated with the sharp decrease in the Fermi potential.
Study of Amino-Imino Tautomerism in Derivatives of 2-, 4- and 6-Aminonicotinic Acid
Authors: Smrčková Svatava , Juricová Kristina , Prutianov Viktor
Published: July 2002

13C NMR spectra of p-nitrobenzoyl 2-, 4-, and 6-aminopyridine-3-carboxylates, their hydrochlorides, trifluoroacetates and 1-benzyl derivatives were studied. As found from the chemical shifts of pyridine carbon atoms C-2, C-4 and C-6, the free bases exist in the amino form whereas hydrochlorides and 1-substituted pyridinium derivatives in the imino form. Trifluoroacetates of the 2- and 6-amino derivatives have structure similar to that of amidiniumcarboxylates (parallel hydrogen bonds and partially ionic character) whereas trifluoroacetate of the 4-amino derivative is structurally close to the corresponding hydrochloride. The found structures were confirmed by 1H NMR and IR spectroscopy.
Synthesis of 3-Amino- and 3-Acylamino-1-cyclopropylquinolin-4(1H)-ones
Authors: Rádl Stanislav
Published: July 2002

Antibacterial quinolones have attracted an increasing attention as a source of clinically useful drugs. During our research into antibacterial quinolones we were also interested in compounds having at the position 3 various groups that could mimic the carboxylic group present in these drugs. Having our own procedure for the preparation of 3-nitroquinolones, we decided to investigate the question of possible activity of 3-amino derivatives and 3-acylamino derivatives.
[3,3]- Versus [1,3]-Sigmatropic Rearrangement of O-Substituted Allyl N-Acylmonothiocarbamates
Authors: Ficeri Vlastimír , Kutschy Peter , Dzurilla Milan , Imrich Ján
Published: July 2002

Substituted allylic alcohols (2-buten-1-ol, 1-buten-3-ol, cinnamyl alcohol and 3-methyl-2-buten-1-ol) react with acyl isothiocyanates (4-chlorobenzoyl, 2,6-difluorobenzoyl, 3-phenylpropenoyl, 2-thienocarbonyl, 3-chloro-2-thienocarbonyl and 3-chloro-2-benzo[b]thienocarbonyl isothiocyanate) with the formation of highly reactive O-substituted allyl N-acylmonothiocarbamates, which either spontaneously or by heating in boiling benzene undergo [3,3]-sigmatropic rearrangement to S-substituted allyl N-acylmonothiocarbamates. The structure of S-esters with isomerized allylic group affords the unequivocal evidence of the [3,3]-sigmatropic route of studied rearrangement. Further heating of [3,3]-rearranged N-(4-chlorobenzoyl)monothiocarbamates results in the [1,3]-sigmatropic shift of monothiocarbamate group. Using arylalkyl alcohols with the allylic double bond inserted into an aromatic system the obtained O-esters either do not undergo any rearrangement (benzyl alcohol) or undergo [1,3]-sigmatropic rearrangement (2- and 3-furylmethanol and 1-(2-furyl)ethanol) to the corresponding S-esters. For explanation of this reaction the tandem of [3,3]- and [1,3]-sigmatropic rearrangements is suggested.
Synthesis of Some m-Substituted 1-Phenyl-6-azauracils
Authors: Slouka Jan , Bekárek Vojtěch , Hlaváč Jan
Published: July 2002

Many 1-aryl-6-azauracils derivatives were prepared so far, among them the representation of m-substituted 1-phenyl derivatives is relatively poor. In this communication we report on the synthesis of the starting material - dicarbamate I, which was used for the preparation of some new 1-phenyl-6-azauracil derivatives II, containing simple nitrogeneous group in m-position. We focused also on the compounds III having two 6-azauracil rings mutually bonded in m-position to the benzene ring. These compounds can form hydrogen bonds simultaneously with two bonding centres of fitted substrate and so they can serve as model compounds for the interaction studies. From this type of compounds the dinitrile IIIa is known so far.
The Potential-pH Diagrams Depicting the Hydrogen Chemisorption in the Pt-H2O, Ir-H2O, and Rh-H2O Systems at 25 °C
Authors: Loučka Tomáš
Published: July 2002

Thermodynamic data for the chemisorption of hydrogen on the Pt, Ir, and Rh electrodes were evaluated from data in the literature. On the basis of these data, the potential-pH diagrams were calculated for the Pt-H2O, Ir-H2O, and Rh-H2O systems describing the hydrogen chemisorption. For the hydrogen chemisorption, the surface was considered to be uniformly inhomogeneous.
Note to the Paper Entitled: TPD Study of Carbon Monoxide Interaction with Pd/Nb Bimetallic System
Authors: Jirsak Tomas , Nikolajenko Vladimír
Published: July 2002

New arrangement of temperature measurement by W-Ta thermocouple yields a slightly shifted temperature scale in comparison with that reported in the previous paper (Jirsak T., Nikolajenko V., Knor Z.: Collect. Czech. Chem. Commun. 59, 1709 (1994)). Temperatures resulting from the corrected thermoelectric voltages of the W-Ta thermocouple are given and figures with corrected temperature scales are presented.
Microporous Membranes from an Insoluble Polyimide
Authors: Schauer Jan , Marek Miroslav
Published: July 2002

Poly(amic acid) prepared from 3,3',4,4'-benzophenonetetracarboxylic dianhydride and bis(4-aminophenyl) ether was used for preparation of microporous membranes by the phase inversion process. Membranes coagulated in acetic anhydride were brittle but usable for ultrafiltration. Coagulation of the poly(amic acid) in water or lower alcohols and subsequent thermal cyclocondensation led to extremely brittle polyimides, which limits their use for ultrafiltration process.
Sterically Crowded Heterocycles. III. A General Approach to Imidazo[1,2-a]pyridines by Ferricyanide Oxidation of Quaternary Pyridinium Salts
Authors: Kubík Richard , Böhm Stanislav , Ruppertová Iveta , Kuthan Josef
Published: July 2002

Substituted 1-(pyridin-2-yl)-2,4,6-triphenylpyridinium perchlorates 1b-1e were converted with potassium ferricyanide and potassium hydroxide to sterically crowded 2-phenyl-3-[(Z)-1,3-diphenyl-3-oxopropenyl]imidazo[1,2-a]pyridines 2b-2e accompanied by minor isomeric 2-benzoyl-3,5-diphenyl-1-(pyridin-2-yl)pyrroles 3c-3e. 4-Phenyl-2,6-di(4-substituted phenyl)-1-(pyridin-2-yl)pyridinium salts 4a, 4b gave exclusively corresponding imidazo[1,2-a]pyridines 5a, 5b while the ferricyanide oxidation of 1-(5-iodo- and 5-cyanopyridin-2-yl)-2,4,6-triphenylpyridinium perchlorates 6a, 6b led to mixtures of major imidazo[1,2-a]pyridines 7a-7c and minor pyrroles 8a-8c. Some mechanistic aspects of the oxidation procedure are discussed in connection with a resistance of 2,6-diphenyl-1,3,5-trimethylpyridinium perchlorate (9c) towards the oxidizing agents.
Fusion Reactions of N-Heterocyclic Moieties to Thiopyrano[4',3':4,5]thieno[2,3-d]pyrimidines
Authors: Ahmed Essam K. , Fröhlich Johannes , Sauter Fritz
Published: July 2002

Derivatives of the novel heterocyclic parent systems imidazolo[1,2-a]thiopyrano[4',3':4,5]thieno[2,3-d]pyrimidine (B) and thiopyrano[4',3':4,5]thieno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine (C) have been synthesized by fusing pyrimidine moieties to 2-amino-4,7-dihydro-5H-thieno[2,3-c]thiopyran-3-carboxylic acid ethyl ester (1) and -3-carbonitrile (10), followed by cyclization reactions of the title intermediates A thus obtained.
Radiation Induced Graft Copolymerization of Vinyl Acetate and Isopropenyl Acetate Onto Isotactic Polypropylene
Authors: Misra Bhupendra N. , Chauhan G. S. , Kaur Inderjeet
Published: July 2002

Radiation-induced graft copolymerization of vinyl acetate (VAC) and isopropenyl acetate (PAC) onto isotactic polypropylene (IPP) has been studied. The percentage of grafting was calculated for various reaction parameters, and the optimum conditions for attaining the maximum percentage of grafting were determined. Maximal achieved extents of grafting are 39% and 29% for VAC and PAC, respectively. The reactivity of the two monomers with respect to grafting is discussed.
Synthesis of Novel n-Alkatrienyltrichlorosilane - Versatile Reagent and Precursor for Organic Monolayer Formation
Authors: Marković Rade , Holzschüh Eugen
Published: July 2002

Preparation of (Z,Z,Z)-9,12,15-octadecatrienyltrichlorosilane (2) by the reaction of the corresponding Grignard reagent with SiCl4 is described. The novel compound of the type RSiX3, useful for various organometallic applications and with the ability to form close-packed ordered monolayers chemically bonded to the surface, was thoroughly characterized by spectral analysis.
A New Electrophilic Rearrangement
Authors: Konečný Václav , Kováč Štefan
Published: July 2002

A new electrophilic rearrangement of 2-substituted 4-alkoxy-5-mercapto-2H-pyridazin-3-ones to 2-substituted 5-alkylthio-4-hydroxy-2H-pyridazin-3-ones is described.
Intramolecular Cyclization of Some Acyclic Nucleoside Analogs
Authors: Janeba Zlatko , Holý Antonín , Votavová Hana , Masojídková Milena
Published: July 2002

Reaction of stereoisomeric 8-bromo-9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines (8) with concentrated aqueous ammonia, sodium hydride, potassium tert-butoxide, or 1,8-diazabicyclo[5,4,0]undec-7-ene afforded 4e-O,8-anhydro-9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines 9 (derivatives of 1,3-oxazepino[2,3-e]adenine). The CD spectra of optically active stereoisomers of 9 have been studied and it was found that for threo isomers 9a and 9b their character corresponds to 5'-O,8-cycloadenosine. The compounds 9 were also prepared by oxidative cyclization of 9-(2,3-O-isopropylidene-2,3,4-trihydroxybutyl)adenines (7) with lead(IV) acetate in benzene. Reaction of 9-(4-hydroxybutyl)adenine (14) with lead(IV) acetate smoothly afforded the seven-membered ring derivative, 4'-O,8-anhydro-9-(4-hydroxybutyl)adenine (15); no anhydro products with five-, six-, and eight-membered ring were found. 2',3'-O-Isopropylideneinosine (16) reacted with lead(IV) acetate to give 5'-O,8-cyclo-2',3'-O-isopropylideneinosine (17) whereas 9-(4-hydroxybutyl)hypoxanthine (18) afforded no cyclic products.
Synthesis of Two-Armed Macrocycles via N,N'-Disubstituted ω,ω'-Diaminoether Precursors
Authors: Hosgören Halil , Karakaplan Mehmet , Togrul Mahmut
Published: July 2002

N,N'-Dialkyldiazacrowns and their precursors, bis(alkylamino) derivatives of tri- and tetraethylene glycols, are synthesized and characterized.
The Interfacial Behaviour of Mono-, Di-, and Triphosphate of Inosine at the Charged Interface
Authors: Ahmed Mohamed E.
Published: July 2002

The interfacial behaviour and adsorption equilibria of mono-, di-, and triphosphate of inosine (IMP, IDP, and ITP) were carried out in different buffer solutions by phase-sensitive ac voltammetry at HMDE. The characteristic properties and adsorption parameters of dilute and compact layers were evaluated from the obtained Frumkin isotherm at different pH values. The effect of some divalent metal ions on the adsorption stage and association of the investigated compounds has been studied.
Heterogeneous Physico-Chemical Interactions Following Electrode Reaction: Interaction of Folates with Thiols
Authors: Heyrovský Michael , Prokopová Barbora
Published: July 2002

Folates do not react chemically with thiols in solution, however, they cause shifts of voltammetric reversible reduction peaks of disulfides towards positive potentials. This is explained as due to the formation of adducts between folates and thiols at the electrode surface. Analogous shifts, but towards negative potentials, were observed with the voltammetric reversible oxidation peak of a reduced form of folic acid after addition of thiols, and were ascribed to the same cause. According to this interpretation the shifts would provide a measure of free enthalpy of the weak interaction between the two partners and the electrode. It is suggested that the observed effect could serve as a simplified model of processes which occur between folates and proteins in the microheterogeneous structure of the living matter.
Washing of Pulp Fibre Bed
Authors: Potůček František
Published: July 2002

The mechanism of the displacement washing of unbleached kraft pulp was investigated. The flow of the wash liquid through a pulp bed was described by the dispersion model using one dimensionless parameter known as the Peclet number. To characterize the displacement washing, the wash yield, dispersion coefficient, and bed efficiency, as well as time parameters such as the mean residence time of lignin, and space time were evaluated. Results obtained for kraft pulp were compared with those for static bed of glass spheres.
Production and Properties of Polypropylene Track Membranes
Authors: Kravets Lyubov I. , Dmitriev Sergei N. , Apel Pavel Yu.
Published: July 2002

This paper describes results of the method of manufacturing the polypropylene track membranes produced by physicochemical treatment under irradiation of accelerated heavy ions of polymer films. The developed method allows to produce membranes with pores of 0.1-0.2 μm in diameter and more, with an improved structural and physicochemical properties. Polypropylene track membranes of a novel sample are characterized by high homogeneity of pore sizes in magnitude, considerable mechanical strength, advanced thermal stability and resistance to oxidation in aggressive media. It opens new fields for their usage.
Hydrates of Quaternary Ammonium Aldehydes as Potential Reactivators of Sarin-Inhibited Acetylcholinesterase
Authors: Cabal Jiří , Hampl František , Liška František , Patočka Jiří , Riedl František , Ševčíková Kateřina
Published: July 2002

Synthesis of 2- (5a), 3- (5b) and 4-formyl-1-methylpyridinium iodides (5c) and (2,2-dihydroxyethyl)trimethylammonium chloride (6a) is described. In aqueous solution aldehydes 5 exist predominantly as hydrates - geminal diols 7. The ability of the geminal diols 6a and 7 to reactivate acetylcholinesterase inhibited by isopropyl methylfluorophosphonate (Sarin) was tested in vitro. Although compounds 6a and 7 exhibit an affinity towards the acetylcholinesterase bonding site comparable with that of the natural substrate acetylcholine, their reactivation ability was negligible. Second-order rate constants for cleavage of 4-nitrophenyl diphenyl phosphate (PNPDPP) with anions of the studied geminal diols were measured in order to determine their nucleophilicity.
Relative Shear Deformation of Non-Newtonian Liquidsin Impeller Induced Flow
Authors: Wichterle Kamil , Mitschka Pavel
Published: July 2002

Flow induced by rotating bodies is studied from the viewpoint of the shear of liquid particles. By solution of the boundary layer equations for Newtonian and power-law non-Newtonian liquids at a rotating disc, a typical velocity field was obtained. The shear distribution of particles leaving the disc edge shows that the most important deformation occurs in the boundary layer. Distribution of shear from the viewpoint of the volume flow rate is also presented. Application of the results to the prediction of particle-breakup dynamics at rotating impellers is discussed.
Ring-Opened Analogs of Indomethacin Affecting Human Neutrophil Functions
Authors: Andreani Aldo , Leoni Alberto , Locatelli Alessandra , Morigi Rita , Rambaldi Mirella , Gehret Jean-Claude , Traniello Serena , Cariani Alessio , Spisani Susanna
Published: July 2002

A series of ring-opened analogs of indomethacin was synthesized and tested in vitro (at concentrations ranging from 10-9 to 10-5 mol/l) on human neutrophil functions. Two compounds lacking the carboxylic group were subjected to the same tests and one of these showed unexpected activity. Among the acidic derivatives, compound 12 bearing the same substituents as indomethacin 10 (methoxy and 4-chlorobenzoyl groups) was the most active: it significantly lowered neutrophil responses in all five bioassays and at the three concentrations considered.
7-(1-Cyanobut-3-en-1-yl)-N6-[(N,N-dimethylamino)methylene]adenine as a Starting Compound for the Synthesis of α-Branched Acyclic Analogues of N7-Isomer of Adenosine
Authors: Hocková Dana , Masojídková Milena , Holý Antonín
Published: July 2002

7-(1-Cyanobut-3-en-1-yl)-N6-[(N,N-dimethylamino)methylene]adenine (2) was used as a multipurpose starting material for the synthesis of a series of α-branched acyclic analogues of N7-isomer of adenosine by further reactions on allyl (hydroxylation) and/or cyano group (hydrolysis, methanolysis or tetrazole formation).
Protonation of Some 5-Substituted Di(2-thienyl) Ketones in Sulfuric Acid. A Comparison with Other 2-Thienyl and Phenyl Ketones
Authors: Noto Renato , Gruttadauria Michelangelo , Lo Meo Paolo , Spinelli Domenico
Published: July 2002

Protonation equilibria of some 5-substituted di(2-thienyl) ketones have been investigated spectrophotometrically in aqueous solutions of sulfuric acid at 298 K. The experimental pKBH+ values have been analyzed by means of the Hammett equation. The calculated ρ as well as the pKBH+ and m* values have been compared with those for substituted 2-acetyl- thiophenes and phenyl 2-thienyl ketones.
Electrochemical Studies of the Complex (OC-6-22)-W(CO)3(dppm)2 at a Glassy Carbon Electrode in CH2Cl2
Authors: El-Hallag Ibrahim Shibl , Hassanien Amira Mahmoud
Published: July 2002

Electrochemical behaviour of tricarbonylbis[methylenebis(diphenylphosphine)] tungsten has been studied by convolution-deconvolution voltammetry and chronopotentiometry with glassy carbon electrode in dichloromethane solution. Electrochemical parameters of the investigated system have been determined and confirmed by theoretical treatment and by the proposed electrode mechanism.
Chlorofluoroacetic Acid as a Highly Versatile Derivatizing Agent: Assignment of Stereochemistry to Esters of Chiral Alcohols
Authors: Růžička Josef , Streinz Ludvík , Šaman David , Havlas Zdeněk , Wimmer Zdeněk , Zarevúcka Marie , Koutek Bohumír , Lešetický Ladislav
Published: July 2002

Stereochemistry of a series of diastereomeric esters obtained from chiral alcohols 1a-21a by derivatization with (S)- or (R)-chlorofluoroacetic acid was correlated with their LC and GC separation (∆tr) and NMR resolution (∆δ). Both the chromatographic and NMR spectral behavior of respective diastereomers was found to follow systematic rules reflecting their steric arrangement. Moreover, identical conformations of the esters seem to be preferred in solution as well as in the chromatographic processes. Reasons underlying this behavior are discussed.
Synthesis and 1H NMR Complexation Study of Thiacalix[4]arene Tetraacetates
Authors: Lhoták Pavel , Šťastný Václav , Zlatušková Petra , Stibor Ivan , Michlová Veronika , Tkadlecová Marcela , Havlíček Jaroslav , Sýkora Jan
Published: July 2002

Alkylation of thiacalix[4]arenes with ethyl bromoacetate led to high yields (≈60%) of corresponding tetraacetates in various conformations (cone, partial cone, 1,3-alternate) depending strictly on the carbonate (Na, K, Cs) used for the reaction. The complexation ability of new compounds was studied by 1H NMR.
A Review on Molecular Electrochemistry of Metallocene Dichloride and Dimethyl Complexes of Group 4 Metals: Redox Properties and Relation with Optical Ligand-to-Metal Charge Transfer Transitions
Authors: Loukova Galina V. , Strelets Vladimir V.
Published: July 2002

Emphasis is given to redox, photophysical, and photochemical properties of homologous bent metallocenes of group 4 transition metals. Comparative analysis of a variety of electron-transfer induced transformations and ligand-to-metal charge-transfer excited states is performed for bent metallocene complexes upon systematic variation of the identity of the metal ion (Ti, Zr or Hf), ancillary π- and monodentate σ- (Cl, Me) ligands. For such organometallic π-complexes, linear correlations exist between energies of optical and redox HOMO-to-LUMO electron transitions. It is suggested that combination of spectroscopic and electrochemical techniques provides important diagnostics to determine "ionisation potential" and "electron affinity" in solution (relative energies of frontier molecular orbitals obtained as redox potentials) and the energy gap in metallocene complexes. Some of earlier instructive cases of direct relationship between optical transition energies and differences in redox potentials revealed for inorganic and coordination compounds are discussed.
Square-Wave Voltammetry of Decamethylferrocene at the Three-Phase Junction Organic Liquid/Aqueous Solution/Graphite
Authors: Komorsky-Lovrić Šebojka , Lovrić Milivoj , Scholz Fritz
Published: July 2002

Drops of nitrobenzene and 1,2-dichloroethane with 0.1 M decamethylferrocene (dmfc) are attached to the surface of a paraffin-impregnated graphite electrode and immersed into various aqueous electrolytes. The oxidation of dmfc and the reduction of dmfc+ cation are enabled by simultaneous transfers of anions between the aqueous electrolyte and the organic solvents. Square-wave voltammetry of this reaction is reported. A linear relationship was observed between the peak potentials of dmfc and the standard Galvani potential differences of the anions. The influence of the anion concentration on this relation is explained.
Fully Automated Parallel Oligonucleotide Synthesizer
Authors: Lebl Michal , Burger Christine , Ellman Brett , Heiner David , Ibrahim Georges , Jones Aaron , Nibbe Mark , Thompson Jaylynn , Mudra Petr , Pokorný Vít , Poncar Pavel , Ženíšek Karel
Published: July 2002

Design and construction of automated synthesizers using the tilted plate centrifugation technology is described. Wash solutions and reagents common to all synthesized species are delivered automatically through a 96-channel distributor connected to a gear pump through two four-port selector valves. Building blocks and other specific reagents are delivered automatically through banks of solenoid valves, positioned over the individual wells of the microtiterplate. These instruments have the following capabilities: Parallel solid-phase oligonucleotide synthesis in the wells of polypropylene microtiter plates, which are slightly tilted down towards the center of rotation, thus generating a pocket in each well, in which the solid support is collected during centrifugation, while the liquid is expelled from the wells. Eight microtiterplates are processed simultaneously, providing thus a synthesizer with a capacity of 768 parallel syntheses. The instruments are capable of unattended continuous operation, providing thus a capacity of over two millions 20-mer oligonucleotides in a year.
Formation of Palladium Complex at Carbon Paste Surface in Chloride Solution as Studied by Cyclic Voltammetry
Authors: Lubert Karl-Heinz , Guttmann Markus , Beyer Lothar
Published: July 2002

The deposition and dissolution of palladium at non-modified carbon paste electrode (CPE) is studied by cyclic voltammetry in chloride solutions (c ≥ 0.5 M KCl and pH 3 to 6). The Pd0 is deposited from tetrachloropalladate solution by potential cycles from E ≥ 0 V (vs Ag/AgCl) or positive potentials up to -0.5 V or by potentiostatic treatment at E ≤ 0 V. Oxidation peaks appear during potential sweep to positive direction after the preceding deposition of Pd. The appearance of two anodic peaks depends mainly on the amount of Pd0 deposited. The peak at about +0.1 V is caused by the dissolution of a palladium mono- or submonolayer, whereas the oxidation peak at more positive potentials is attributed to the dissolution of Pd from a palladium multilayer. After palladium deposition and potential sweep to positive potentials E > +0.8 V (or potentiostatic treatment at E > +0.8 V), a cathodic peak appears at about 0 V and corresponding anodic peak at +0.1 V. It is concluded that these peaks are caused by reduction and oxidation of the chloropalladate surface complex formed during preceding application of anodic potentials. Reaction schemes of PdII/Pd0 and chloropalladate complex are discussed.
Analysis of Underivatized Brassinosteroids by HPLC/APCI-MS. Occurrence of 3-Epibrassinolide in Arabidopsis thaliana
Authors: Konstantinova Olga V. , Antonchick Andrey P. , Oldham Neil J. , Zhabinskii Vladimir N. , Khripach Vladimir A. , Schneider Bernd
Published: July 2002

In the course of investigations on brassinosteroid (BS) biosynthetic and metabolic pathways in plants, an approach using HPLC/APCI-MS analysis of underivatized BS for their identification in plant material has been developed. Its application to root-callus suspension cultures of Arabidopsis thaliana led to the first identification of 3-epibrassinolide as natural brassinosteroid.
Structure Types of Dihydroergotoxine Mesylates
Authors: Petříčková Hana , Čejka Jan , Hušák Michal , Kratochvíl Bohumil , Císařová Ivana , Jegorov Alexandr , Cvak Ladislav
Published: July 2002

Three new crystal structures of dihydroergopeptines: dihydro-α-ergokryptine mesylate monohydrate acetone solvate (1), dihydro-α-ergokryptine mesylate monohydrate nitromethane solvate (2), and dihydroergocornine mesylate monohydrate methanol solvate (3) have been determined by X-ray single crystal diffraction. These structures were compared with published structures of dihydro-α-ergokryptine mesylate monohydrate ethanol solvate (4), dihydro-β-ergokryptine mesylate monohydrate methanol solvate (5), and dihydroergocristine mesylate monohydrate (6).
Helicobacter pylori infection induced alteration of gene expression in human gastric cells
Authors: Chiou C-C , Chan C-C , Sheu D-L , Chen K-T , Li Y-S , Chan E-C
Published: July 2002

BACKGROUND

Helicobacter pylori, a human pathogen responsible for many digestive disorders, induces complex changes in patterns of gene expression in infected tissues. cDNA expression arrays provide a useful tool for studying these complex phenomena.

AIM

To identify genes that showed altered expression after H pylori infection of human gastric cells compared with uninfected controls.

METHODS

The gastric adenocarcinoma cell line AGS was cocultivated withH pylori. Growth of infected cells was determined by trypan blue exclusion assay. Complementary DNA probes derived from H pylori treated and untreated cells were hybridised to two identical Atlas human cDNA expression arrays, and those genes with altered expression levels were identified. A real time quantitative reverse transcription-polymerase chain reaction assay was used to better define expression patterns of these genes in endoscopically gastric mucosal biopsies with and withoutH pylori infection.

RESULTS

Over 24 hours, coincubation with H pylori inhibited AGS cell growth but did not cause a noticeable degree of cell death.H pylori treatment altered the pattern of gene expression in AGS cells. We identified 21 overexpressed genes and 17 suppressed genes from the cDNA expression arrays. The majority of genes were transcription factors such asc-jun, BTEB2, andETR101. Other genes were involved in signal transduction pathways, such as MAP kinase, interleukin 5, and insulin-like growth factor. Genes involved in cell cycle regulation and differentiation, such as CDC25B andNM23-H2, were also identified. In patients with H pylori infection (n=20), there was a significant difference forERCC3, Id-2, andNM23-H2 mRNA levels in infected gastric mucosa compared with uninfected gastric mucosa in patients without peptic diseases (n=20) (ERCC3 4.75 molecules/104 β-actin mRNA moleculesv 13.65, p<0.001;Id-2 16.1 v 23.4, p<0.05; NM23-H2 17.5v 45.5, p<0.001). There was no significant difference between mRNA levels of c-jun andCDC25B in H pylori colonised gastric mucosa and uninfected mucosa.

CONCLUSION

We demonstrated that H pylori infection caused alteration of gene expression in AGS cells. The differential hybridisation technique of Atlas human cDNA expression array is a useful method to identify host genes involved in pathogenic mechanisms in H pylori infection.
Wilson's disease with severe hepatic insufficiency: beneficial effects of early administration of D-penicillamine
Authors: Durand F , Bernuau J , Giostra E , Mentha G , Shouval D , Degott C , Benhamou J P , Valla D
Published: July 2002

BACKGROUND

Wilson's disease, heralded by severe hepatic insufficiency, is a rare disorder for which emergency liver transplantation is considered to be the only effective therapy.

AIMS

To report the features of Wilson's disease with severe hepatic insufficiency in a series of 17 patients and, during the second period of the study, to assess the efficacy of a policy consisting of early administration of D-penicillamine.

PATIENTS

Seventeen consecutive patients with Wilson's disease were studied. During the first period of the study (up to 1979), none of the patients received D-penicillamine. During the second period (after 1979), all patients without encephalopathy at admission received D-penicillamine.

RESULTS

The four patients observed during the first period who did not have encephalopathy at admission and did not receive D-penicillamine progressed to encephalopathy and died. Among the 13 consecutive patients observed during the second period, two patients with encephalopathy at admission did not receive D-penicillamine and were transplanted. The 11 remaining patients all received D-penicillamine. Ten of these patients survived without the need for transplantation and returned to compensated liver disease without liver insufficiency. In one patient, liver insufficiency progressed and transplantation had to be performed.

CONCLUSIONS

In most patients with Wilson's disease heralded by severe hepatic insufficiency and without encephalopathy at admission, early administration of D-penicillamine was associated with survival without transplantation. These results suggest the importance of early diagnosis of this form of Wilson's disease before the onset of encephalopathy, and favour early administration of D-penicillamine which could avoid the need for transplantation in most cases.
Paraovarian cystic endosalpingiosis in association with tamoxifen therapy: Figure 1
Authors: McCluggage W G , Weir P E
Published: July 2002

This report describes a case of macroscopically visible cystic endosalpingiosis involving the paraovarian region in a woman who had been taking tamoxifen for breast cancer. A 2.5 cm multicystic lesion was seen on the external surface of the right ovary and histological examination showed a mass of dilated glands lined by ciliated tubal-type epithelium and set in a fibrovascular stroma. Cystic endosalpingiosis resulting in a tumour-like mass is a rarely described entity which is probably not well recognised by histopathologists. Although unlikely to be mistaken for malignancy, the lesion may result in diagnostic confusion. The role of tamoxifen in the development of the lesion in the present case is not clear but the oestrogenic effects of this drug may have contributed to its formation.
Benign monoclonal expansion of CD8+ lymphocytes in HIV infection
Authors: Smith Penelope R , Cavenagh Jamie D , Milne Tim , Howe Denise , Wilkes Susanna J , Sinnott Paul , Forster Greta E , Helbert Matthew
Published: July 2002

Background—A transient expansion of the CD8+ T cell pool normally occurs in the early phase of HIV infection. Persistent expansion of this pool is observed in two related settings: diffuse infiltrative lymphocytosis syndrome (DILS) and HIV associated CD8+ lymphocytosis syndrome.

Aim—To investigate a group of HIV infected patients with CD8+ lymphocytosis syndrome with particular emphasis on whether monoclonality was present.

Methods—A group of 18 patients with HIV-1 infection and persistent circulating CD8+ lymphocytosis was compared with 21 HIV positive controls. Serum samples were tested for antinuclear antibodies, antibodies to extractable nuclear antigens, immunoglobulin levels, paraproteins, human T lymphotropic virus type 1 (HTLV-1), Epstein-Barr virus, and cytomegalovirus serology. Lymphocyte phenotyping and HLA-DR typing was performed, and T cell receptor (TCR) gene rearrangement studies used to identify monoclonal populations of T cells. CD4+ and CD8+ subsets of peripheral blood lymphocytes were purified to determine whether CD8+ populations inhibited HIV replication in autologous CD4+ cells.

Results—A subgroup of patients with HIV-1 infection was found to have expanded populations of CD8+ T cell large granular lymphocytes persisting for 6 to 30 months. The consensus immunophenotype was CD4− CD8+ DRhighCD11a+ CD11c+ CD16− CD28± CD56− CD57+, consistent with typical T cell large granular lymphocytes expressing cellular activation markers. Despite the finding of monoclonal TCR gene usage in five of 18 patients, there is evidence that the CD8+ expansions are reactive populations capable of mediating non-cytotoxic inhibition of HIV replication.

Conclusions—A subgroup of HIV positive patients has CD8+ lymphocytosis, but despite the frequent occurrence of monoclonal TCR gene usage there is evidence that this represents an immune response to viral infection rather than a malignant disorder.
Estimating antemortem drug concentrations from postmortem blood samples: the influence of postmortem redistribution: Table 1
Authors: Cook D S , Braithwaite R A , Hale K A
Published: July 2002

Aims—To compare blood drug concentrations during life with postmortem drug concentrations measured from a peripheral site and a central site.

Methods—Coroner's cases from October 1990 to July 1997 were reviewed. Six cases had data on both antemortem and postmortem blood drug concentrations. The postmortem to antemortem ratio was compared with the postmortem central to peripheral ratio, using cardiac blood as a central site and femoral blood as a peripheral site.

Results—Drugs that have a high postmortem central to peripheral ratio; that is, drugs that exhibit considerable postmortem redistribution, also have high postmortem to antemortem ratios.

Conclusions—A large degree of error can arise from attempting to estimate antemortem drug concentrations and the ingested dose from postmortem measurements. The chosen site and technique for postmortem blood sampling can greatly influence the concentration of drug measured.
Clinical ethics support services in the UK: an investigation of the current provision of ethics support to health professionals in the UK
Authors: Slowther Anne , Bunch Chris , Woolnough Brian , Hope Tony
Published: July 2002

Objective—To identify and describe the current state of clinical ethics support services in the UK.

Design—A series of questionnaire surveys of key individuals in National Health Service (NHS) trusts, health authorities, health boards, local research ethics committees and health professional organisations. Interviews with chairmen/women of clinical ethics committees identified in the surveys.

Setting—The UK National Health Service.

Results—Responses to the questionnaires were received from all but one NHS trust and all but one health authority/board. A variety of models of clinical ethics support were identified including twenty formal clinical ethics committees (CECs). A further twenty NHS trusts expressed an intention to establish a CEC within the next twelve months. Most CECs in the UK have been in existence less than five years and are still defining their role. The chairmen identified education of committee members and contact with other ethics committees as important requirements for committee development. Problems were identified around lack of support for the committee and with raising the profile of the committee within the institution. There has been little evaluation of clinical ethics support services either in the UK or in other countries with longer established services. What evaluation has occurred has focused on process rather than outcome measures.

Conclusions—Clinical ethics support services are developing in the UK. A number of issues have been identified that need to be addressed if such support services are to develop effectively.
Laryngeal and hypopharyngeal cancers and occupational exposure to formaldehyde and various dusts: a case-control study in France
Authors: Laforest Laurent , Luce Danièle , Goldberg Paquerette , Bégin Denis , Gérin Michel , Demers Paul A , Brugère Jacques , Leclerc Annette
Published: July 2002

OBJECTIVES

A case-control study was conducted in France to assess possible associations between occupational exposures and squamous cell carcinomas of the larynx and hypopharynx.

METHODS

The study was restricted to men, and included 201 hypopharyngeal cancers, 296 laryngeal cancers, and 296 controls (patients with other tumour sites). Detailed information on smoking, alcohol consumption, and lifetime occupational history was collected. Occupational exposure to seven substances (formaldehyde, leather dust, wood dust, flour dust, coal dust, silica dust, and textile dust) was assessed with a job exposure matrix. Exposure variables used in the analysis were probability, duration, and cumulative level of exposure. Odds ratios (ORs) with their 95% confidence intervals (95% CIs) were estimated by unconditional logistic regression, and were adjusted for major confounding factors (age, smoking, alcohol, and when relevant other occupational exposures).

RESULTS

Hypopharyngeal cancer was found to be associated with exposure to coal dust (OR 2.31, 95% CI 1.21 to 4.40), with a significant rise in risk with probability (p<0.005 for trend) and level (p<0.007 for trend) of exposure. Exposure to coal dust was also associated with an increased risk of laryngeal cancer (OR 1.67, 95% CI 0.92 to 3.02), but no dose-response pattern was found. A significant relation, limited to hypopharyngeal cancer, was found with the probability of exposure to formaldehyde (p<0.005 for trend), with a fourfold risk for the highest category (OR 3.78 , 95% CI 1.50 to 9.49). When subjects exposed to formaldehyde with a low probability were excluded, the risk also increased with duration (p<0.04) and cumulative level of exposure (p<0.14). No significant association was found for any other substance.

CONCLUSION

These results indicate that exposure to formaldehyde and coal dust may increase the risk of hypopharyngeal cancer.