bluuebunny/crossref_metadata_2025 huggingface dataset:
Feline Immunodeficiency Virus Xenoinfection: the Role of Chemokine Receptors and Envelope Diversity
Authors: Johnston J. B. , Power C.
Published: July 2002

The use of chemokine receptors as cell recognition signals is a property common to several lentiviruses, including feline, human, and simian immunodeficiency viruses. Previously, two feline immunodeficiency virus (FIV) isolates, V1CSF and Petaluma, were shown to use chemokine receptors in a strain-dependent manner to infect human peripheral blood mononuclear cells (PBMC) (J. Johnston and C. Power, J. Virol. 73:2491-2498, 1999). Since the sequences of these viruses differed primarily in regions of the FIV envelope gene implicated in receptor use and cell tropism, envelope chimeras of V1CSF and Petaluma were constructed to investigate the role of envelope diversity in the profiles of chemokine receptors used by FIV to infect primate cells. By use of a receptor-blocking assay, all viruses were found to infect human and macaque PBMC through a mechanism involving the CXCR4 receptor. However, infection by viruses encoding the V3-to-V5 region of the V1CSF surface unit was also inhibited by blockade of the CCR3 or CCR5 receptor. Similar results were obtained with GHOST cells, human osteosarcoma cells expressing specific combinations of chemokine receptors. CXCR4 was required for infection by all FIV strains, but viruses expressing the V3-to-V5 region of V1CSF required the concurrent presence of either CCR3 or CCR5. In contrast, CXCR4 alone was sufficient to allow infection of GHOST cells by FIV strains possessing the V3-to-V5 region of Petaluma. To assess the role of primate chemokine receptors in productive infection, Crandell feline kidney (CrFK) cells that expressed human CXCR4, CCR3, or CCR5 in addition to feline CXCR4 were generated. Sustained infection by viruses encoding the V3-to-V5 region of V1CSF was detected in CrFK cells expressing human CCR3 or CCR5 but not in cells expressing CXCR4 alone, while all CrFK cell lines were permissive to viruses encoding the V3-to-V5 region of Petaluma. These results indicate that FIV uses chemokine receptors to infect both human and nonhuman primate cells and that the profiles of these receptors are dependent on envelope sequence, and they provide insights into the mechanism by which xenoinfections may occur.
The Effect of Surfactants on the Acid-Base Behaviour of Methyl Red. Part II. A Spectrophotometric Comparison of the Effect of Triton X-100 and β-Cyclodextrin
Authors: Jirasová Jana , Bílý Jiří , Čermáková Ludmila
Published: July 2002

The effect of the non-ionogenic surfactant Triton X-100 (TX) and β-cyclodextrin (CD) on the absorption bands of methyl red was examined. The interactions of methyl red with the both substances were studied based on changes in the absorption curves after their resolution into Gaussian bands. The conditional dissociation constants of methyl red were determined at various concentrations of the additives (in the case of TX, both below and above its cmc value). At cTX = 0.06 mol l-1 the change in the conditional dissociation constant of methyl red was ∆pKa = -0.58 and at cCD = 6 mmol l-1 the ∆pKa value was identical.
Interpretation of Hydroxylic Solvent Effects Based on Correlations with Solvent Parameters. Reaction of Et3N with EtI
Authors: Calado António R. T. , Pinheiro Lídia M. V. , Albuquerque Lídia M. P. C. , Goncalves Raquel M. C. , Rosés Martí , Ràfols Clara , Bosch Elisabeth
Published: July 2002

Hydroxylic solvent effects on 20 rate constants, k, of the Menschutkin reaction of Et3N with EtI are unravelled and rationalized by means of multiple linear regression equations. To perform this analysis new k values in 2 mono- and 9 dialcohols are obtained. New values are also presented for the Kamlet and Taft solvatochromic parameters π*, α and β of 1-hexanol. The results show that the solvent dipolarity, polarizability and cohesive energy density are the main properties influencing the reactivity, for the set of studied solvents.
Physical Interpretation of Solubility Interaction Constants from the Series Expansion of the Relative Activity Coefficients
Authors: Nývlt Jaroslav , Eysseltová Jitka
Published: July 2002

Hydration analysis, which enables information on ionic processes in saturated solutions to be derived from solubility data in ternary systems, was applied to the interpretation of solubility interaction constants from the relative activity coefficient expansion. A close relationship was found between the hydration analysis parameters and the solubility interaction constants characterizing the relative activity of solute, which extends our insight into the ionic behaviour of the system studied by using the values of the interaction constants.
Coupling Kinetics of 4-Sulfobenzenediazonium Ion with 2,4-Thiazolidinedione, Its 3-Methyl Derivative and 3-Methyl-5-isoxazolone
Authors: Kaválek Jaromír , Macháček Vladimír , Štěrba Vojeslav
Published: July 2002

3- and 4-substituted 5-phenylazo derivatives of 2,4-thiazolidinedione were prepared as potential biologically active fungicides. The kinetics of coupling of 4-sulfobenzenediazonium salt with 2,4-thiazolidinedione and 3-methyl-2,4-thiazolidinedione have been studied and the results have been compared with kinetic data of coupling reaction of 3-methyl-5-isoxazolone.
Some 4-Substituted 1-(3-Pyridylmethyl)piperazines with Antihistamine Activity
Authors: Kmoníček Vojtěch , Valchář Martin , Polívka Zdeněk
Published: July 2002

Several compounds derived from nicotinic acid were prepared within a more extensive programme aiming at the synthesis of new substances with expected antihistamine and antidepressant activity. Some of these compounds display certain structural resemblance with the antidepressant agent piberaline (EGYT 475, Trelibet®, I) and its analogues. The products were used as intermediates for the synthesis of further compounds and most of them were subjected to pharmacological testing. Substituted nicotinic acid piperazides IIa - IId and IVa - IVe were obtained by reactions of nicotinoyl chloride (prepared in situ) with the correspondingly substituted piperazines. Reduction of the piperazides IIa - IId and IVa - IVd with diborane in situ in tetrahydrofuran afforded corresponding 1-substituted 4-(3-pyridylmethyl)piperazines IIIa - IIId and Va - Vd. Whereas the alkylation of 1-(2-pyrimidinyl)piperazine with 2-(chloromethyl)pyridine in ethanol in the presence of triethylamine resulted in compounds Ve, compound Vf was obtained by the addition reaction of 1-(3-pyridylmethyl)piperazine to acrylamide. The piperazides VIe and VIf were prepared by reactions of 2-(3-pyridyl)acetic acid with 1-(2-pyrimidinyl)piperazine or 3-(1-piperazinyl)propionamide in N,N-dimethylformamide in the presence 1,1'-carbonyldiimidazole. A similar procedure starting from nicotinic acid afforded the piperazide IVf. Compounds Vc and Vd showed significant affinity for the histamine H1-receptors (inhibition of binding of 2 nmol/l [3H]mepyramine in membranes from the rat brain: Vc, IC50 = 28 nmol/l; Vd, IC50 = 148 nmol/l). They also proved active in test of histamine aerosol in guinea pigs (PD50 = 4.1 mg/kg p.o. for compound Vc and 2.4 for compound Vd). Results of a more detailed pharmacological testing of these compounds will be published elsewhere.
Electrochemical Behaviour of Cobalt in NaOH Solutions
Authors: Abd El Rehim Sayed S. , El Basosi Ahmed A. , El Zein Salah M. , Osman Magda M.
Published: July 2002

The electrochemical behaviour of cobalt in 0.001 - 1 M NaOH was investigated by voltammetric techniques coupled with ESCA examination. The anodic polarization curve exhibits a well defined peak which corresponds to the formation of Co(OH)2 or CoO. Further peaks in the transpassive potential region correspond to the electrooxidation of Co(II) species to Co3O4 and CoOOH, respectively. The heights of the anodic peaks increase with the increase of NaOH concentration, temperature and scan rate. In cyclic voltammetry, the reverse scan consistently shows three cathodic peaks which are ascribed to the reduction of CoOOH, Co3O4 and CoO oxides, respectively. ESCA examination confirmed the presence of these oxides in the passive film.
Synthetic Analogues of 15,15-Acetals of Prostaglandin F2α and E2
Authors: Kozmík Václav , Paleček Jaroslav
Published: July 2002

Two series of 15,15-ethyleneacetals of PG F2α and PG E2 modified both in the α- and ω-chains were prepared with a view to find more stable and efficient analogues of this type. The synthesis of the analogues starting from the easily available (±)-[(3aα,4α,5β,6aα)]-5-(1,1'-biphenylyl-4-carbonyloxy)-4-formylhexahydro-2H-cyclopenta[b]furan-2-one, the so-called Corey aldehyde I, was based on conventional procedures, some of which were modified to achieve the optimum yields.
Preparation of Some N-Substituted 3-Amino-5-cyano-2-pyrazinecarboxamides
Authors: Doležal Martin , Hartl Jiří , Macháček Miloš
Published: July 2002

During the course of a search for new antimycotic agents a series of 3-amino-5-cyano-2-pyrazinecarboxamides I - XI have been synthesized. The prepared compounds were tested for their antimycotic activity. The MIC of these in the form of dimethyl sulfoxide solutions was measured against Candida albicans ATCC 44859, Candida tropicalis 156, Candida krusei E28, Candida glabrata 20/I, Trichosporon beigelii 1188, Trichophyton mentagrophytes 445, Aspergillus fumigatus 231, and Absidia corymbifera 272. None of the compounds studied was particularly effective.
Purification of Phenolic Waste Waters by Catalytic Oxidation
Authors: Tukač Vratislav , Hanika Jiří
Published: July 2002

Catalytic oxidation of phenolic substances in industrial waste waters is alternative for pollutants biodegradable with difficulty or toxic for activated sludge. The oxidation of an aqueous phenol solution by oxygen was carried out in the presence of industrial catalyst Cherox 46-11 (30% Cu, Chemopetrol Litvinov) in a stainless steel autoclave at 120 - 160 °C. Compared to the radical reaction, the rate of the catalytic oxidation was two times higher. The reaction order with respect to phenol was close to one. The presence of acids in high concentrations at low oxygen partial pressures speaks for the higher reaction order to oxygen.
The Paired Electrochemical Synthesis of Gluconic Acid and Sorbitol
Authors: Li Hongmei , Li Wei , Guo Zicheng , Gu Dengping , Cai Shengmin , Fujishima Akira
Published: July 2002

Gluconic acid and sorbitol are obtained simultaneously both with 90% yields by paired electrolysis of glucose, with a Pb sheet cathode and a dimension stable anode (DSA) in a press filtration diaphragm cell. The anolyte is composed from 66.7% glucose and 2% NaBr, and the catholyte from 66.7% glucose and 2.5% Na2SO4, respectively. The electrolysis was performed at the temperature of 60 C, at the current density of 50 mA cm-2, Qr is 110%. At this optimum conditions the current efficiencies for both gluconic acid and sorbitol are higher than 80%.
Side Reaction During the Deprotection of Cys(Acm)-Containing Peptides with Iodine. Synthesis of Disulfide Fragments from Cathepsin D Structure
Authors: Ježek Jan , Velková Vlasta , Kašička Václav , Prusík Zdeněk , Ubik Karel , Bartová Klaudie , Mareš Michael
Published: July 2002

Peptides H-TPPQC(Acm)FTV-NH2 (I) and H-VSVPC(Acm)QSASSAS-NH2 (III) were prepared by the solid phase method. Their oxidation with iodine afforded hexadecapeptide II, tetracosapeptide IV and eicosapeptide VI. The disulfide peptides II, IV and VI are designed according to the sequence of the processing loop in human cathepsin D. The purity of the peptides was determined by analytical HPLC and capillary zone electrophoresis. In addition to the expected [M + H]+ ion, FAB MS of HPLC-pure tetracosapeptide IV exhibited a molecular ion with the same relative molecular mass as the starting dodecapeptide III, in spite of clean HPLC separation of III and IV. Free-flow zone electrophoresis of IV separated peptide V, isomeric with III. Mass spectra, amino acid analysis and Edman sequencing revealed that the peptide V is a product of iodine-mediated S-->O shift of Acm group in the serine-rich peptide III. Daughter-ion spectra of protonated molecules, recorded after collision-induced dissociation, have shown that the Acm moiety is bonded to Ser 9 or Ser 10.
Template-Directed Syntheses of Rotaxanes
Authors: Bělohradský Martin , Raymo Françisco M. , Stoddart J. Fraser
Published: July 2002

Rotaxanes are molecules comprised of a dumbbell-shaped component encircled by one or more macrocyclic components. The early syntheses of rotaxanes were mainly based upon statistical threading or upon directed methodologies involving chemical conversion. However, with the advent of supramolecular chemistry, a series of host-guest and template-directed approaches to rotaxanes have been developed and employed successfully. We have devised a template-directed approach to rotaxanes incorporating π-electron deficient bipyridinium-based components and π-electron rich hydroquinone-based polyether components. The noncovalent bonding interactions responsible for the self-assembly of these molecular compounds are (i) π-π stacking interactions between the complementary aromatic units, (ii) hydrogen bonding interactions between the acidic hydrogen atoms in the α-positions with respect to the nitrogen atoms on the bipyridinium units and some of the polyether oxygen atoms, as well as, (iii) edge-to-face T-type interactions between some of the hydrogen atoms on the hydroquinone rings and the π-clouds of the aromatic spacers separating the bipyridinium units. By employing these methodologies, we have synthesised a range of [2]rotaxanes, [3]rotaxanes, and [4]rotaxanes. Furthermore, the dynamic processes involving the shuttling of the cyclic components along the dumbbell-shaped components associated with some of these rotaxanes have been investigated in some detail. The reversible control of the process via external stimuli - such as chemical and electrochemical - has been achieved in the case of a [2]rotaxane incorporating benzidine and biphenol recognition sites. These results suggest the possibility of generating, on the nanoscopic level, molecular devices in the shape of rotaxanes able to store and process informations, thus, affording molecular machines.
Effect of Halide Anions on Anodic Behaviour and Passivation of Copper in Alkaline Media
Authors: Abd El Rehim Sayed S. , Foad Essam E.
Published: July 2002

The effect of Cl- and Br- on the anodic behaviour and passivation of copper metal in NaOH solution has been investigated by a potentiodynamic technique complemented with XPS analysis. In halide free solutions, the anodic polarization curves involve three anodic peaks correlated to the electroformation of Cu2O, CuO and Cu(OH)2 on the anode surface. The presence of these species in the passive layer has been confirmed by XPS examination. An addition of the halide anions enhances the peak currents of anodic peaks and tends to rupture the passive layer inducing the pitting corrosion. The critical pitting potentials decrease with rising halide concentration while the alkali concentration has an opposite effect. The accelerating effect of Cl- to pitting corrosion is greater than that of Br-. The pitting corrosion was explained by an instantaneous nucleation and growth of anion salt nuclei. Three cathodic peaks on cyclic voltammetric curve were assigned to the electroreduction of pitting corrosion products, Cu(II) and Cu(I) oxides, respectively.
Microwave Activation of Homogeneous and Heterogeneous Catalytic Reactions
Authors: Hájek Milan
Published: July 2002

Microwave heating was applied in homogeneous and in heterogeneous reactions and the results were compared from the point of view of activation of chemical reactions. Reactions including the addition of halo compounds to alkenes catalyzed by copper and ruthenium complexes in different solvents and NaY zeolite catalyzed alkylation of secondary amine in the absence of solvent were studied as model reactions to compare possibilities of microwave activation of reactants and catalysts. Rate enhancement of over one order of magnitude in homogeneous reactions was caused mainly by thermal dielectric heating effect which resulted from the effective coupling of microwaves to polar solvents. Activation of reactants and catalysts was very low if any. In heterogeneously catalyzed alkylation reactions highly efficient activation of zeolite catalyst was recorded. The results indicated that the best reaction conditions were in experiments when both activation of catalyst and performance of reaction were carried out under microwave conditions. Rate enhancement was most probably caused by "hot spots" or by "selective heating" of active sites. In both homogeneous and heterogeneous reactions non-thermal activation (specific effect) was excluded.
An Effective Synthesis of 1,3-Oxathiolanes
Authors: Streinz Ludvík , Koutek Bohumír , Šaman David
Published: July 2002

2-Alkyl- or 2,2-dialkyl-1,3-oxathiolanes can be effectively prepared from aldehydes or ketones and 2-mercaptoethanol, with triisopropylsilyl triflate as a catalyst. The reaction is over within minutes and, despite the fact that water is nor removed during the reaction, the yields of products are high.
Regeneration Mechanism Studied by Potential-Time Response to Sinusoidal Current-Time Function
Authors: Alcaraz María-Luisa , Molina Ángela
Published: July 2002

A theoretical study of the potential-time response to sinusoidal current applied to static and dynamic electrodes for regeneration processes is presented. Methods for determination of the regeneration fraction, rate constant of the chemical reaction and heterogeneous kinetic parameters are proposed.
Comparison of Hydride Generator/Gas-Liquid Phase Separator Systems for Continuous Hydride Generation in Atomic Absorption Spectrometry
Authors: Krenželok Milan , Rychlovský Petr
Published: July 2002

A comparison of five kinds of hydride generator/gas-liquid phase separator systems used in the hydride generation in AAS is made. These systems are also compared with a newly designed type of separator. Optimum working conditions were tested and basic characteristics were measured for all the types of systems. The basic criteria for comparison of the systems were the measuring sensitivity, reproducibility and detection limit for the given system. Additional comparison criteria were the analysis frequency achieved, applicability of the given separator for flow-injection measurements and economic criteria.
Extraction of 133Ba with Bis[undecahydro-7,8-dicarbaundecaborato(2-)]cobaltate(1-) in the Presence of Dibenzo-18-crown-6
Authors: Vaňura Petr , Makrlík Emanuel
Published: July 2002

Extraction of barium with the nitrobenzene solution of bis[undecahydro-7,8-dicarbaundecaborato(2-)]cobaltate(1-) in the presence of dibenzo-18-crown-6 (DB18C6, L) has been investigated. The equilibrium data and typical maxima in the dependences of the Ba distribution ratios on the analytical concentration of DB18C6 in the system can be explained assuming that the species Ba2+, BaL2+, BaL22+, BaHL3+ and BaHL23+ to be extracted into the nitrobenzene phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.
Construction and Chemometric Analysis of Acidity Function in Perchloric Acid
Authors: Jirásková Eva , Kulhánek Jiří , Nevěčná Taťjana , Pytela Oldřich
Published: July 2002

Four 2,6-disubstituted anilines with CH3, Cl, and NO2 substituents have been synthesized and, together with four commercial substances of the same type, subjected to spectrophotometry to find the concentration ratios of the protonated and non-protonated forms in aqueous perchloric acid of 0.02-10.55 mol dm-3 concentration. By a procedure devised earlier, the acidity function has been constructed and the pKa values calculated. The Principal Component Analysis was applied to the acidity function obtained and on other eight acidity functions of perchloric acid were taken from literature. It was found that the first principal component explained 99.78% of variability, which indicated high degree of similarity of the said functions irrespective of the indicator type and solvent used. The regression dependences acidity function values on the first principle component are very close, the regression coefficient expressing the measure of sensitivity of the indicator to the acidifying medium. The pKa values obtained agree well with the literature data.
Glycosylation of 1-Aminoimidazole-2(3H)-thiones
Authors: Lagoja Irene M. , Van Aerschot Arthur , Hendrix Chris , Herdewijn Piet
Published: July 2002

The selectivity of the glycosylation of 1-aminoimidazole-2(3H)-thiones can be controlled. Depending on the chosen conditions, either the kinetically favored S-glycosides or the thermodynamically more stable N-glycosylated compounds are obtained in only one anomeric configuration (β-anomer).
Allopregnanolone Derivatives: Synthesis of 3α-Hydroxy-7a-homo-5α-pregnan-20-one
Authors: Chodounská Hana , Kasal Alexander
Published: July 2002

3α-Hydroxy-7a-homo-5α-pregnan-20-one and 3α-hydroxy-7a-homo-5α-pregnane-7,20-dione were prepared from (20R)-3α-(methoxymethoxy)-7-oxo-5α-pregnan-20-yl benzoate. Homo- logation of the B ring was carried out by the Demyanov rearrangement of the corresponding cyanohydrin. Alkaline hydrolysis of the protecting group and oxidation of the formed 20-hydroxy group and deprotection of the 3-hydroxy group were performed either with (20R)-3α-(methoxymethoxy)-7-oxo-7a-homo-5α-pregnan-20-ol derivative or with the product of the Huang Minlon deoxygenation at carbon 7.
Phase Equilibria in 4-Methylpentan-2-one-Water and 4-Methylpentan-2-one-4-Methylpentan-2-ol Systems and Their Thermodynamic Description
Authors: Řehák Karel , Matouš Jaroslav , Novák Josef P. , Heintz Andreas
Published: July 2002

Liquid-liquid equilibrium and excess enthalpies at 25, 40 and 60 °C were measured for the 4-methylpentan-2-one-water system. Vapour-liquid equilibrium at 115 °C and 99.96 kPa, and excess enthalpies at 25, 40 and 60 °C were determined for the 4-methylpentan-2-one- 4-methylpentan-2-ol system. The data obtained were correlated together with those given in literature using the superposition of the Wilson and Redlich-Kister equation. The correlation procedure utilised also the data on excess enthalpy measured in a heterogeneous region.
Simultaneous Determination of Dopamine, Serotonin and Their Metabolites in the Rat Brain by HPLC Method with Coulometric Detection
Authors: Bielavská Marcela , Kassa Jiří
Published: July 2002

A rapid and sensitive method for simultaneous determination of 3-hydroxytyramine (dopamine), 5-hydroxytryptamine (serotonin) and their metabolites - 3,4-dihydroxyphenylacetic acid, 3-methoxytyramine, 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid) and 5-hydroxyindole-3-acetic acid in the rat brain was developed. Brain samples with the internal standard and heparin were deproteinized by perchloric acid with ethylenediaminetetraacetic acid disodium salt and sodium sulfite. Following homogenization, centrifugation and filtration, the supernatant was directly injected into a reversed-phase HPLC system with coulometric detector. The response of the detected substances was linear in the range 12-700 ng/g of cerebellum homogenate (24-1 400 pg on column). Total recovery of the method was higher than 95%. The method was used for the determination of catecholamines and their metabolites in the chosen part of rat brain following the inhalation exposure to sarin (organophosphate).
Mitsunobu Transformations of 1,2-O-Isopropylidene-α-D-pentofuranoses Mediated by Zinc Salts
Authors: Moravcová Jitka , Špilová Lucie , Čapková Jindra , Chery Florence , Rollin Patrick
Published: July 2002

A one-pot regioselective heterofunctionalization of 1,2-O-isopropylidene-α-D-xylofuranose (1) and 1,2-O-isopropylidene-α-D-ribofuranose (2) with zinc azide, zinc thiocyanate or zinc N,N-dimethyldithiocarbamate via the Mitsunobu reaction has been performed. With 2, the reaction gave selectively the desired products substituted at C-5 in good isolated yields (60-65%). However, application of the same reaction conditions to 1 led to the predominant formation of a cyclic 3,5-anhydro derivative. In contrast, the reaction of hydrazoic acid with 1 afforded 5-azido-5-deoxy-1,2-O-isopropylidene-α-D-xylofuranose besides formerly unknown 5-azido-3,5-dideoxy-1,2-O-isopropylidene-α-D-glycero-pent-3-enofuranose and 3,5-diazido- 3,5-dideoxy-1,2-O-isopropylidene-α-D-ribofuranose; the yields depended on the reaction time and the molar ratio of reagents.
Alkylation of Partially Protected Xylofuranoses and Tetritols with (2,2,3,3,4,4,5,5,6,6,7,7,7-Tridecafluoroheptyl)oxirane and the Stability of Protecting Acetal Groups Towards Lewis Acid-Type Catalyst
Authors: Kefurt Karel , Moravcová Jitka , Bambasová Šárka , Buchalová Kateřina , Vymětalíková Barbora , Kefurtová Zdeňka , Staněk Jan , Paleta Oldřich
Published: July 2002

1,2-O-Isopropylidene-3-O-methyl-α-D-xylofuranose (2), 1,2-O-isopropylidene-α-D-xylofuranose (3), 2,4-O-ethylidene-D-erythritol (4) and 1,3-O-ethylidene-D-threitol (5) were alkylated with racemic (2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)oxirane (1) using boron trifluoride diethyl etherate as a catalyst. The desired mono- or disubstituted polyfluoroalkyl derivatives 6-11 were isolated only in low to medium yields. The fluoroalkylation was accompanied with disproportional distributions of the protecting acetal/ketal groups and polymerization of saccharides. Therefore the stability of 3, 4, 5, 5-O-acetyl-1,2-O-isopropylidene-α-D-xylofuranose (14) and 1,2-O-isopropylidene-α-D-glucofuranose (15) in the presence of a catalytic amount of boron trifluoride diethyl etherate was investigated in various solvents. A mechanism explaining the effect of the catalyst has been proposed.
Detection and Quantification of 7-Hydroxydehydroepiandrosterone Epimers in Three Body Fluids
Authors: Hampl Richard , Hill Martin , Stárka Luboslav
Published: July 2002

3β,7α-Dihydroxyandrost-5-en-17-one (1) (7α-OH-DHEA) and its 7β-hydroxy epimer2(7β-OH-DHEA) - 7α- and 7β-hydroxydehydroepiandrosterone - were detected and quantified in three human body fluids: in blood serum, saliva and ejaculate. Specific radioimmunoassay and gas chromatography-mass spectrometry have been used. For the first time the data on changes of these dehydroepiandrosterone metabolites are reported for a representative group of healthy subjects of both sexes (172 females and 217 males) during the life span. The serum levels of both 7-hydroxydehydroepiandrosterone epimers in serum and also in semen were in the low nanomolar range, while concentrations by one order of magnitude lower were found in saliva, but still within the detection limit. The results will serve as a basis for comparative studies of 7-hydroxydehydroepiandrosterone levels under various pathophysiological conditions, with a particular respect to autoimmune disorders.
3α-Fluoro Analogues of "Allopregnanolone" and Their Binding to GABAA Receptors
Authors: Slavíková Barbora , Kasal Alexander , Chodounská Hana , Krištofíková Zdena
Published: July 2002

(Diethylamino)sulfur trifluoride (DAST) was used for the preparation of 3α-fluorides (e.g., 3α-fluoro-5α-pregnane-12,20-dione, 3α-fluoro-16α-[(methoxycarbonyl)methyl]-5α-pregnan-20-one, methyl 3α-fluoro-5α-androstane-17β-carboxylate, 3α-fluoro-5β-pregnan-20-one) from the corresponding 3β-alcohols and for the preparation of 3,3-difluorides from 3-ketones (e.g., 3,3-difluoro-5α-pregnan-20-one). Boron trifluoride etherate was used for the conversion of an epoxide into 3α-fluoro-2β-hydroxy-5α-pregnan-20-one. Thein vitrobinding of the 3α-fluorides and the corresponding 3α-alcohols to the GABAAreceptor was established using [3H]muscimol and [35S]-tert-butylbicyclo[2.2.2]phosphorothionate as ligands.
Synthesis of Methoxynor Polyisoprenoid Alcohols by Alkylation of (3-Methoxyallyl)lithium Reagents
Authors: Jin Qingwu , Coates Robert M.
Published: July 2002

A series of six methyl enol ether analogs 8-13 of geraniol, (E,E)-farnesol, and (E,E,E)-geranylgeraniol was synthesized from a group of three allylic methyl ethers and three allylic chlorides. Lithiation of the 1-methyl-, or 1-alkenylvinyl ethers with sec-butyllithium at -78 °C followed by alkylations of the resulting (Z)-(3-methoxyallyl)lithium reagents afforded the six possible Z-configured(trans) methoxynor polyprenyl benzyl ethers bearing the methoxy substituent at the internal and terminal double bonds with high Z/E ratios (5 : 1-31 : 1) and 47-80% yields. Reductive cleavage of the benzyl groups with lithium in liquid ammonia gave the corresponding methoxynor polyprenols. 11-Methoxy-18-nor and 7-methoxy-19-nor geranylgeraniols (13 and 12) were converted to the corresponding diphosphates, 7 and 32, by the Poulter displacement method. The stability of the enol ether in 7 in aqueous solution at pH 8 was verified by NMR analyses. The diphosphates of the methoxynor polyprenols may prove useful as substrate analogs for terpene synthases to capture transient intermediates in cyclization reactions catalyzed by these enzymes.
Bioactive Flavanones from Luma chequen
Authors: Labbé Cecilia , Coll Josep , Connolly Joseph D. , Faini Francesca , Farrugia Louis J. , Rycroft David S.
Published: July 2002

A bioassay-guided chemical study of a methanolic extract of fresh leaves of Luma chequen led to the isolation of lumaflavanones A (1), B (2) and C (3) whose structures are proposed on the basis of NMR spectroscopic data. The structure of lumaflavanone A was confirmed by X-ray analysis. Antifeedant (Spodoptera littoralis), brine shrimp (Artemia salina) and fungistatic (Botrytis cinerea) bioassays showed that while 3 was the most active in the first two assays the mixture of 1 and 2 was more effective as a fungistatic.
Poly(2-bromoaniline) and Its Colloidal Dispersions
Authors: Stejskal Jaroslav , Trchová Miroslava , Prokeš Jan
Published: July 2002

Poly(2-bromoaniline) was prepared by oxidation of 2-bromoaniline with ammonium peroxydisulfate in the presence of hydrochloric acid. The conductivity of the poly(2-bromoaniline) hydrochloride so produced was 10-6 S cm-1, its density at 20 °C 1.78 g cm-3 and weight-average molar mass 18 500 g mol-1. The degree of protonation was estimated as being a half of that of polyaniline. The structure of poly(2-bromoaniline) is discussed on the basis of FTIR spectra. Colloidal dispersions were produced when the polymerization had been carried out in the presence of a particulate or polymeric stabilizer, viz. colloidal silica, poly(vinyl alcohol), poly(N-vinylpyrrolidone) or (hydroxypropyl)cellulose. The UV-VIS spectra of colloidal dispersions are used to discuss the transition between the protonated and base forms.
Principles of justice in health care rationing
Authors: Cookson Richard , Dolan Paul
Published: July 2002

This paper compares and contrasts three different substantive (as opposed to procedural) principles of justice for making health care priority-setting or “rationing” decisions: need principles, maximising principles and egalitarian principles. The principles are compared by tracing out their implications for a hypothetical rationing decision involving four identified patients. This decision has been the subject of an empirical study of public opinion based on small-group discussions, which found that the public seem to support a pluralistic combination of all three kinds of rationing principle. In conclusion, it is suggested that there is room for further work by philosophers and others on the development of a coherent and pluralistic theory of health care rationing which accords with public opinions.
Embryonic stem cell production through therapeutic cloning has fewer ethical problems than stem cell harvest from surplus IVF embryos
Authors: Hansen J-E S
Published: July 2002

Restrictions on research on therapeutic cloning are questionable as they inhibit the development of a technique which holds promise for succesful application of pluripotent stem cells in clinical treatment of severe diseases. It is argued in this article that the ethical concerns are less problematic using therapeutic cloning compared with using fertilised eggs as the source for stem cells. The moral status of an enucleated egg cell transplanted with a somatic cell nucleus is found to be more clearly not equivalent to that of a human being. Based on ethical considerations alone, research into therapeutic cloning should be encouraged in order to develop therapeutic applications of stem cells.
Medicine: the science and the art
Authors: Herman Joseph
Published: July 2002

Medicine has been said to be both a science and an art. Many practitioners regard this statement as containing an element of “either/or”. A brief look at what scientists and artists have written about their work and their world views, however, suggests that the two fields of endeavour form a complementary part of our attempts to understand ourselves and the world about us. Moreover, on occasion, each can perform some of the other's tasks. This paper quotes from the writings of physicians, scientists and people active in the humanities in order to demonstrate how frequently their thoughts converge. It also presents a case report from general practice illustrative of the idea that there is much common ground between the “hard” and the “soft” in medicine. Indeed, the profession's art and science may really be one.
Occupational exposure to carcinogens in the European Union
Authors: Kauppinen Timo , Toikkanen Jouni , Pedersen David , Young Randy , Ahrens Wolfgang , Boffetta Paolo , Hansen Johnni , Kromhout Hans , Blasco Jeronimo Maqueda , Mirabelli Dario , de la Orden-Rivera Victoria , Pannett Brian , Plato Nils , Savela Anja , Vincent Raymond , Kogevinas Manolis
Published: July 2002

OBJECTIVES

To construct a computer assisted information system for the estimation of the numbers of workers exposed to established and suspected human carcinogens in the member states of the European Union (EU).

METHODS

A database called CAREX (carcinogen exposure) was designed to provide selected exposure data and documented estimates of the number of workers exposed to carcinogens by country, carcinogen, and industry. CAREX includes data on agents evaluated by the International Agency for Research on Cancer (IARC) (all agents in groups 1 and 2A as of February 1995, and selected agents in group 2B) and on ionising radiation, displayed across the 55 industrial classes. The 1990–3 occupational exposure was estimated in two phases. Firstly, estimates were generated by the CAREX system on the basis of national labour force data and exposure prevalence estimates from two reference countries (Finland and the United States) which had the most comprehensive data available on exposures to these agents. For selected countries, these estimates were then refined by national experts in view of the perceived exposure patterns in their own countries compared with those of the reference countries.

RESULTS

About 32 million workers (23% of those employed) in the EU were exposed to agents covered by CAREX. At least 22 million workers were exposed to IARC group 1 carcinogens. The exposed workers had altogether 42 million exposures (1.3 mean exposures for each exposed worker). The most common exposures were solar radiation (9.1 million workers exposed at least 75% of working time), environmental tobacco smoke (7.5 million workers exposed at least 75% of working time), crystalline silica (3.2 million exposed), diesel exhaust (3.0 million), radon (2.7 million), and wood dust (2.6 million).

CONCLUSION

These preliminary estimates indicate that in the early 1990s, a substantial proportion of workers in the EU were exposed to carcinogens.
Hyperaldosteronism: recent concepts, diagnosis, and management
Authors: Foo R , O'Shaughnessy K M , Brown M J
Published: July 2002

As a cause for hypertension, aldosterone excess is now thought to be more prevalent than previously quoted in textbooks. Classical features of hypokalaemia and metabolic alkalosis can be absent even in the presence of marked hypertension. This implies the need for a high index of suspicion and possibly argues the case for routine screening, especially in patients with “difficult to treat” hypertension. Given multisystem target organ damage and increased cardiovascular risk associated with chronic uncontrolled hypertension, a readily treatable cause such as hyperaldosteronism is an important diagnosis to make. In addition, hyperaldosteronism related hypertension is now known to cover other recently identified monogenic disorders such as glucocorticoid remediable aldosteronism. These rarer monogenic hypertensive disorders provide clues to cracking the mystery behind polygenic “essential” hypertension. Apart from patients with hyperaldosteronism, a subset of the well recognised “low renin hypertension” patient group also appears to produce a dramatic and remarkable response when treated with spironolactone. We suggest that spironolactone sensitive hypertension may represent a wider spectrum of disorders where blood pressure is readily controlled by the addition of aldosterone receptor antagonist.
Chronic pericardial constriction linked to the antiparkinsonian dopamine agonist pergolide
Authors: Balachandran K P , Stewart D , Berg G A , Oldroyd K G
Published: July 2002

Constrictive pericarditis is present when a fibrotic, thickened, and adherent pericardium restricts diastolic filling of the heart. Several drugs can cause pericarditis, which can lead to chronic pericardial constriction. A case of constrictive pericarditis in a patient receiving the antiparkinsonian drug pergolide is reported.
Cutaneous leucocytoclastic vasculitis associated with omeprazole
Authors: Odeh M , Lurie M , Oliven A
Published: July 2002

Omeprazole is a potent proton pump inhibitor and usually is well tolerated. Adverse effects of this drug have been reported in up to 5% of patients, most of which are trivial and disappear rapidly on discontinuation of the drug. Skin adverse reactions attributed to omeprazole are uncommon and include rashes, urticaria, angio-oedema, acute disseminated epidermal necrolysis, lichen spinulosus, and contact dermatitis. Cutaneous leucocytoclastic vasculitis (CLV) has not been previously reported in association with omeprazole. The development of CLV in an elderly patient four weeks after starting treatment with omeprazole is described.
Ulcerative colitis after statin treatment
Authors: Rea W E , Durrant D C S , Boldy D A R
Published: July 2002

Statin treatment is widely used in both primary and secondary prevention of diseases in which hyperlipidaemia is a major risk factor, for example, ischaemic heart disease. The development of ulcerative colitis as an adverse reaction to simvastatin is reported, which, despite withdrawal of the drug, proved fatal. The adverse reaction profile of the statins is reviewed, which suggests that this is a class effect and not one limited to simvastatin.
C-banded karyotypes of twoSilenespecies with heteromorphic sex chromosomes
Authors: Grabowska-Joachimiak Aleksandra , Joachimiak Andrzej
Published: July 2002

Mitotic metaphase chromosomes of Silene latifolia (white campion) and Silene dioica (red campion) were studied and no substantial differences between the conventional karyotypes of these two species were detected. The classification of chromosomes into three distinct groups proposed for S. latifolia by Ciupercescu and colleagues was considered and discussed. Additionally, a new small satellite on the shorter arm of homobrachial chromosome 5 was found. Giemsa C-banded chromosomes of the two analysed species show many fixed and polymorphic heterochromatic bands, mainly distally and centromerically located. Our C-banding studies provided an opportunity to better characterize the sex chromosomes and some autosome types, and to detect differences between the two Silene karyotypes. It was shown that S. latifolia possesses a larger amount of polymorphic heterochromatin, especially of the centromeric type. The two Silene sex chromosomes are easily distinguishable not only by length or DNA amount differences but also by their Giemsa C-banding patterns. All Y chromosomes invariably show only one distally located band, and no other fixed or polymorphic bands on this chromosome were observed in either species. The X chromosomes possess two terminally located fixed bands, and some S. latifolia X chromosomes also have an extra-centric segment of variable length. The heterochromatin amount and distribution revealed by our Giemsa C-banding studies provide a clue to the problem of sex chromosome and karyotype evolution in these two closely related dioecious Silene species.Key words: dioecious plant, Silene dioica, Silene latifolia, karyotype, sex chromosomes, heterochromatin, C-banding.
Model testing of submerged vanes in strongly curved narrow channel bends
Authors: Voisin A , Townsend R D
Published: July 2002

This paper reports on a laboratory study that examines the effectiveness of submerged vanes for the control of erosion in strongly curved narrow channel bends. All previous researches on submerged vanes were performed in either straight or weakly curved channels that were hydraulically "wide". Submerged vanes are thin rectangular-shaped low-profile foils, typically set at small angles to the main current and arranged in either single or multiple parallel arrays in the longitudinal direction. When installed in a channel bend they induce a helicoidal vortex that interacts with and weakens the centrifugally induced secondary current. The latter effect leads to reduced local erosion near the bend's outer bank. Physical model testing was performed to determine the effects of several parameters affecting submerged vane performance, including submerged vane height H, length L, angle to main flow direction α, vane streamwise spacing δs, vane transverse spacing from outer bank δn, and bend angle φ. Submerged vanes effectively stabilize channel bend erosion by reducing the scour depth at the outer bank, generating positive transverse bed slope at the outer bank, and by reducing the net sediment loss through the channel. In general, an increase in vane height tends to shift the thalweg away from the outer bank; an increase in vane length tends to reduce the general erosion through the channel.Key words: submerged vanes, riverbank stabilization, bottom vanes, narrow channels, bank protection, bank stabilization, channel bends.
Lactoferrin and host defense
Authors: Ward Pauline P , Uribe-Luna Sonia , Conneely Orla M
Published: July 2002

Lactoferrin is a multifunctional member of the transferrin family of nonheme iron-binding glycoproteins. Lactoferrin is found at the mucosal surface where it functions as a prominent component of the first line of host defense against infection and inflammation. The protein is also an abundant component of the specific granules of neutrophils and can be released into the serum upon neutrophil degranulation. While the iron-binding properties were originally believed to be solely responsible for the host defense properties ascribed to lactoferrin, it is now known that other mechanisms contribute to the broad spectrum anti-infective and anti-inflammatory roles of this protein. In this article, current information on the functions and mechanism of action of lactoferrin are reviewed, with particular emphasis on the activities that contribute to this protein's role in host defense. In addition, studies demonstrating that lactoferrin inhibits allergen-induced skin inflammation in both mice and humans, most likely secondary to TNF-α (tumor necrosis factor α) production, are summarized. Collectively, these results suggest that lactoferrin functions as a key component of mammalian host defense at the mucosal surface.Key words: lactoferrin, host defense, anti-inflammatory activity, anti-allergic activity, antimicrobial.
Effect of saline drinking water on the size and water content of the gut and other organs of male and female mallards
Authors: Hughes M R , Bennett D C , Sullivan T M
Published: July 2002

Ducks absorb imbibed Na+and water in the anterior gut and reabsorb Na+and water from urine refluxed into the hind gut. In Mallards (Anas platyrhynchos) this process is sexually disparate: males reflux and reabsorb more water, mainly in the ceca. We examined the effect of saline acclimation on the size of Mallard organs, especially the gut and other osmoregulatory organs (kidneys, salt glands) in both sexes. We tested and accept two hypotheses: (1) saline increases the mass of the Mallard hind gut and other osmoregulatory organs and (2) saline has a greater effect on the organs of males. Drinking saline did not affect the mass of body, kidney, heart, or liver, but increased the mass of the salt glands, ileum, and ceca. Increases in organ mass were greater in males than in females. Saline acclimation increased the length of the jejunum only in males and decreased the length of the esophagus and the length and mass of the proventriculus only in females. Our data suggest that the upper and lower gut segments may play somewhat different roles in ion and water transport in the two sexes.
The maritime shrew, Sorex maritimensis (Insectivora: Soricidae): a newly recognized Canadian endemic
Authors: Stewart Donald T , Perry Neil D , Fumagalli Luca
Published: July 2002

Previous morphological and cytological analyses have suggested that the arctic shrew (Sorex arcticus) as currently recognized may be two distinct species. Specifically, those studies demonstrated considerable differentiation between the putative subspecies S. a. maritimensis and one or both of the other two subspecies, S. a. arcticus and S. a. laricorum. Phylogenetic analysis of 546 base pairs of cytochrome b sequence data from 10 arctic shrews from across Canada indicates that maritimensis is the sister-group to arcticus + laricorum. Furthermore, there is considerable genetic divergence between maritimensis and the other two putative subspecies (~89%; Kimura's two-parameter distance). Given that maritimensis and arcticus + laricorum appear to be reciprocally monophyletic clades with considerable genetic divergence (i.e., greater than that between other recognized pairs of sister-species within the S. araneusarcticus group), we propose that S. maritimensis be recognized as a distinct species. The proportion of third-position transversion substitutions between S. arcticus and S. maritimensis suggests that these two species shared a common ancestor approximately 2.4 million years ago.
Acoustic communication in the Palaearctic red cicada,Tibicina haematodes: chorus organisation, calling-song structure, and signal recognition
Authors: Sueur J , Aubin T
Published: July 2002

Males of the Palaearctic red cicada, Tibicina haematodes, produce calling songs that are attractive to both sexes. For the first time we (i) describe the organisation of the chorus formed by aggregating males, (ii) analysed the physical characteristics of the calling song, and (iii) used playback experiments of natural, modified, and allospecific signals to investigate the signal-recognition process. Males overlap each other's calling song and try to call first and last during a chorus, leading to what we term domino and last-word effects, respectively. The calling song consists of a two-part sequence made up of a succession of pulses. It is characterized by slow and fast amplitude modulations and three frequency bands. The structure of the signal varied among individuals in both temporal and frequency parameters. Our playback experiments showed that males make a rough analysis of frequency and duration features of the signal. They pay no attention to amplitude modulations. Because males are not capable of precise analysis, they reply to various allospecific calling songs. Females' analysis of the calling song being difficult to test, the role of this signal in sexual selection still needs to be documented.