bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Shock Cognate Protein 70 Is Involved in Rotavirus Cell Entry
Authors: Guerrero Carlos A. , Bouyssounade Daniela , Zárate Selene , Iša Pavel , López Tomás , Espinosa Rafaela , Romero Pedro , Méndez Ernesto , López Susana , Arias Carlos F.
Published: July 2002

In this work, we have identified the heat shock cognate protein (hsc70) as a receptor candidate for rotaviruses. hsc70 was shown to be present on the surface of MA104 cells, and antibodies to this protein blocked rotavirus infectivity, while not affecting the infectivity of reovirus and poliovirus. Preincubation of the hsc70 protein with the viruses also inhibited their infectivity. Triple-layered particles (mature virions), but not double-layered particles, bound hsc70 in a solid-phase assay, and this interaction was blocked by monoclonal antibodies to the virus surface proteins VP4 and VP7. Rotaviruses were shown to interact with hsc70 at a postattachment step, since antibodies to hsc70 and the protein itself did not inhibit the virus attachment to cells. We propose that the functional rotavirus receptor is a complex of several cell surface molecules that include, among others, hsc70.
Inter- and Intramolecular Recombinations in theCucumber Mosaic VirusGenome Related to Adaptation to Alstroemeria
Authors: Chen Yuh-Kun , Goldbach Rob , Prins Marcel
Published: July 2002

In four distinct alstroemeria-infecting cucumber mosaic virus (CMV) isolates, additional sequences of various lengths were present in the 3′ nontranslated regions of their RNAs 2 and 3, apparently the result of intra- and intermolecular recombination events. Competition experiments revealed that these recombined RNA 2 and 3 segments increased the biological fitness of CMV in alstroemeria.
Japanese Encephalitis Virus Infection Initiates Endoplasmic Reticulum Stress and an Unfolded Protein Response
Authors: Su Hong-Lin , Liao Ching-Len , Lin Yi-Ling
Published: July 2002

The malfunctioning of the endoplasmic reticulum (ER) of cells in hosts ranging from yeast to mammals can trigger an unfolded protein response (UPR). Such malfunctioning can result from a variety of ER stresses, including the inhibition of protein glycosylation and calcium imbalance. To cope with ER stresses, cells may rely on the UPR to send a signal(s) from the ER to the nucleus to stimulate appropriate cellular responses, including induction of chaperone expression. During
Japanese encephalitis virus
(JEV) infection, the lumen of the ER rapidly accumulates substantial amounts of viral proteins for virus progeny production. In the present study, we demonstrate that as evidenced by certain chaperone inductions, JEV infection triggers the UPR in fibroblast BHK-21 cells and in neuronal N18 and NT-2 cells, in which JEV results in apoptotic cell death. By contrast, no UPR was observed in apoptosis-resistant K562 cells infected by JEV. JEV infection also activates expression of CHOP/GADD153, a distinctive transcription factor often induced by the UPR, and appears to trigger activation of p38 mitogen-activated protein kinase, a posttranslational activator of CHOP. Ectopic enforcement of CHOP expression enhanced JEV-induced apoptosis, whereas treatment with a p38-specific inhibitor, SB203580, partially blocked JEV-induced apoptosis. Interestingly,
bcl-2
overexpression and treatment with a pancaspase inhibitor, z-VAD-fmk, inhibited CHOP induction and diminished JEV-induced apoptosis, suggesting that Bcl-2 and caspases could be the upstream regulators of CHOP. Our results thus suggest that virus-induced ER stress may participate, via p38-dependent and CHOP-mediated pathways, in the apoptotic process triggered by JEV infection.
The Common Retroviral Insertion LocusDsi1Maps 30 Kilobases Upstream of the P1 Promoter of the MurineRunx3/Cbfa3/Aml2Gene
Authors: Stewart Monica , MacKay Nancy , Cameron Ewan R. , Neil James C.
Published: July 2002

TheDsi1locus was identified as a common integration site for Moloney murine leukemia virus (MLV) in rat thymic lymphomas, but previous efforts to identify a gene affected by these insertions were unsuccessful. We considered theRunx3gene a potential candidate on the basis of genetic mapping which showed thatDsi1andRunx3are closely linked on mouse chromosome 4 and the precedent of the relatedRunx2gene, which emerged recently as aMyc-collaborating gene activated by retroviral insertion in thymic lymphomas of CD2-MYCmice. We now report the physical mapping of theDsi1locus to a site 30 kb upstream of the distal (P1) promoter of the murineRunx3gene. Comparison with the syntenic region of human chromosome 1 shows that the next gene is over 250 kb 5′ toRunx3, suggesting thatRunx3may be the primary target of retroviral insertions atDsi1. Screening of CD2-MYClymphomas for rearrangements atDsi1revealed a tumor cell line harboring an MLV provirus at this locus, in the orientation opposite that ofRunx3. Proviral insertion was associated with very high levels of expression ofRunx3, with a preponderance of transcripts arising at the P1 promoter. These results confirm thatRunx3is a target of retroviral insertions atDsi1and indicate thatRunx3can act as an alternative toRunx2as aMyc-collaborating gene in thymic lymphoma.
Compounds Interacting with the Neuroexcitatory Amino Acids: Synthesis of 2-(4-Aralkylpiperazine-1-yl)-1-arylethanols
Authors: Šilhánková Alexandra , Dobrovský Karel , Krejčí Ivan , Polívka Zdeněk
Published: July 2002

Amino ketones Ia - If and III were synthesized. Their reduction gave corresponding alcohols IIa - IIf, IVa and IVb. These were evaluated by methods of biochemical and behavioural pharmacology.
Synthesis of Some 2-(Substituted thio)pyridines and Thieno[2,3-b]pyridines
Authors: Abdel-Monem Maisa I.
Published: July 2002

Pyridine heterocycles occupy a unique position in medicinal chemistry. The naturally occurring B6 vitamine (pyridoxol, pyridoxal, pyridoxamine), some alkaloids and coenzymes contain pyridine nucleus. Many thienopyridine derivatives have been investigated because of the various biological activities such as against diabetes mellitus, as analgetics, anti-inflammatories, sedatives, and anticoagulants.
Synthesis of N-(3-Azido-2-hydroxypropyl), N-(3-Phthalimido-2-hydroxypropyl) and N-(3-Amino-2-hydroxypropyl) Derivatives of Heterocyclic Bases
Authors: Spassova Maria , Dvořáková Hana , Holý Antonín , Buděšínský Miloš , Masojídková Milena
Published: July 2002

Alkylation of heterocyclic bases with azidomethyloxirane (I) under basic catalysis with potassium or cesium carbonate afforded N-(3-azido-2-hydroxypropyl) derivatives II. Hydrogenation of these compounds over palladium on carbon gave the corresponding 3-amino-2-hydroxypropyl derivatives III. The same compounds III were prepared by alkylation of heterocyclic bases with phthalimidomethyloxirane (VII) in the presence of cesium carbonate and subsequent reaction of the formed N-(3-phthalimido-2-hydroxypropyl) derivatives VIII with hydrazine. The phthalimido derivatives VIII are easily hydrolyzed already in weakly alkaline aqueous medium to give 9-[3-(o-carboxybenzoylamino)-2-hydroxypropyl] derivatives IX and X.
Synthesis of (Z)-14-Heptadecen-4-olide and (Z)-11-Pentadecen-4-olide, Sex Pheromone Analogues of Ostrinia nubilalis and Cydia molesta
Authors: Hoskovec Michal , Šaman David , Koutek Bohumír
Published: July 2002

The key step in the preparation of racemic (Z)-14-heptadecen-4-olide (VIa) and (Z)-11-pentadecen-4-olide (VIb), sex pheromone analogues of Ostrinia nubilalis and Cydia molesta, was efficient cross-coupling reaction of 3-methoxycarbonylpropanoyl chloride with corresponding (Z)-alkenylmagnesium bromides. The methyl 4-oxo-(Z)-14-heptadecenoate (Va) and methyl 4-oxo-(Z)-11-pentadecenoate (Vb) prepared in this way were converted by one-pot reaction using sodium borohydride in an ethanolic solution to the required (Z)-alken-4-olides (VIa, VIb).
Biphase Reduction of Heptanal and Cyclohexanone by Sodium Formate Catalyzed by Ether-Phosphine Ruthenium(II) Complexes
Authors: Šabata Stanislav , Včelák Jaroslav , Hetflejš Jiří
Published: July 2002

RuCl2[P(C6H5)2OCH2CH2OCH3]2 has efficiently catalyzed the reduction of cyclohexanone and heptanal by sodium formate in chlorobenzene-water, using cetylpyridinium bromide as the phase transfer catalyst. In both cases, the reduction was first order both in the substrate and in the initial concentration of the catalyst. The catalyst activity in the aldehyde reduction could be increased by the addition of the free ligand while in the ketone reduction the ligand in excess decreased the reaction rate. Several other phosphines of the type P(C6H5)2L where L = C6H5, C4H9, C2H5OCH2CH2, C4H9OCH2CH2, 1,4-dioxanemethyl, tetrahydrofurfuryl, and P(i-C3H7)3) gave the less efficient catalysts. Kinetic and activation data for the reduction of both substrates are reported.
Experimental Study of Turbulent Macroinstabilities in an Agitated System with Axial High-Speed Impeller and with Radial Baffles
Authors: Brůha Oldřich , Fořt Ivan , Smolka Pavel , Jahoda Milan
Published: July 2002

The frequency of turbulent macroinstability occurrence was measured in liquids agitated in a cylindrical baffled vessel. As it has been proved by preceding experimental results of the authors, the stochastic quantity with frequency of occurrence of 10-1 to 100 s-1 is concerned. By suitable choosing the viscosity of liquids and frequency of impeller revolutins, the region of Reynolds mixing numbers was covered from the pure laminar up to fully developed turbulent regime. In addition to the equipment making it possible to record automatically the macroinstability occurrence, also the visualization method and videorecording were employed. It enabled us to describe in more detail the form of entire flow field in the agitated system and its behaviour in connection with the macroinstability occurrence. It follows from the experiments made that under turbulent regime of flow of agitated liquids the frequency of turbulent macroinstability occurrence is the same as the frequency of the primary circulation of agitated liquid.
Synthesis of New Chiral Ligands by Capping of Calix[4]arene Derivatives
Authors: Pinkhassik Evgueni , Stibor Ivan , Havlíček Vladimír
Published: July 2002

Calix[4]arene derivatives are used as a scaffold for the attachment of chiral substituents. Calix[4]arenes having either lower or upper rim capped with chiral binaphtholic species 5 and 6, as well as new biscalix[4]arenodiaza-18-crown-6 (8), have been synthesized.
Syntheses and Spectral Properties of Unsymmetrically 3,5-Disubstituted 2,6-Dimethyl-1,4-dihydropyridines
Authors: Ilavský Dušan , Milata Viktor
Published: July 2002

Unsymmetrically 3,5-disubstituted 4-(5-X-2-furyl)-2,6-dimethyl-1,4-dihydropyridines (where X = H, Br, NO2) have been synthesized and characterized by spectral methods (IR, UV, 1H NMR and MS). The modified Hantzsch method made it possible to prepare the title compounds as well as their N-alkylated derivatives. The paper also describes the N-alkylation of sodium salts of substituted 1,4-dihydropyridines using the phase-transfer catalysis.
Complexes of Tris(N-piperidinomethyl)phosphine Oxide with Zinc and Cadmium
Authors: Vojtíšek Pavel , Císařová Ivana
Published: July 2002

A number of compounds which can by their stoichiometry be classified into several groups have been prepared by reaction of tris(N-piperidinomethyl)phosphine oxide (tppo) with Zn(II) and Cd(II) salts. The structure of two Zn(II) complexes differing by their Zn : tppo ratio and of one Cd(II) complex has been determined by the X-ray diffraction technique. The results show that in all the cases tppo is bound as divalent chelate N,O-donor, but the geometry of coordination sphere of M(II) decisively affects the steric arrangement of the five-membered chelate ring. Structures of the compounds studied are entirely different from those of Zn(II) complexes of sterically less demanding P,P-dimethyl-P-aminomethylphosphine oxide (dmao). On the other hand, the way of coordination of tppo is the same as that found in the case of the Co(II) complex of tris(N,N-dimethylaminomethyl)phosphine oxide.
Study of Polycondensation of Tetraethoxysilane Catalyzed with Dibutylbis[1-oxo(dodecyl)oxy]stannane Using 1H NMR and 29Si NMR Spectrometry and Quasi Elastic Light Scattering
Authors: Brus Jiří , Kotlík Petr , Karhan Jiří
Published: July 2002

The polycondensation of tetraethoxysilane (TEOS) catalyzed with dibutylbis[1-oxo(dodecyl)oxy]stannane (dibutyltin dilaurate, DBTDL) has been investigated with the help of 1H and 29Si NMR spectrometry and quasi elastic light scattering (QELS). It has been found that in contrast to the acid catalyzed polycondensation the siloxane chain grows in linear and branched way, the proportion of cyclization reactions being slight. The rate of chain growth is relatively high, which is indicated by the impossibility to detect the presence of shorter oligomers in the reaction mixture by means of 29Si NMR. The found rate constant of polycondensation of TEOS catalyzed with DBTDL is k = 0.052 dm6 min-1 mol-1. From the determined condensation degree at the gelation point (0.20-0.35) and the ratio of consumed amount of ethoxysilane units to the consumed amount of monomer at the gelation point (0.49-0.69) it follows that the gel is predominantly formed by cross-linking of branched macromolecules, the reaction mixture containing no distinct proportions of polycyclic and highly condensed structural units. The density of network of the gel formed is relatively low, which was proved by 29Si CP/MAS NMR spectra of the solid gels. Investigation of QELS of the reaction mixture showed that the relatively large particles, microgels, were formed practically immediately after the reaction had started. The presence of such particles in the reaction mixture of acid catalyzed polycondensation of TEOS was not proved.
(-)-Armepavine: Gradient-Enhanced 2D NMR Study and X-Ray Crystal Structure Determination
Authors: Marek Radek , Marek Jaromír , Dostál Jiří , Slavík Jiří
Published: July 2002

(-)-Armepavine, a benzylisoquinoline alkaloid isolated from Papaver caucasicum, was examined by gradient-enhanced 2D NMR spectroscopy and X-ray diffraction analysis. Unambiguous 1H, 13C, and 15N NMR assignment of the title alkaloid is reported.
The Synthesis of A-Homo-B-norandrostanes: The Effect of a Hydroxyl on the Course of Hydrogenation of the ∆9-Double Bond
Authors: Kasal Alexander , Slavíková Barbora , Kohout Ladislav , Buděšínský Miloš
Published: July 2002

Acetolysis of 6β-mesyloxy-5-methyl-19-nor-5β-steroids (e.g. 10) was proved to yield 4a-homo-7,19-dinor compounds (e.g. 9) with a hydroxy group in the position 4aα. Hydrogenation of these compounds affords 9β,10β-dihydro derivatives (e.g. 12) predominantly, corresponding 9α,10α isomers (e.g. 13) are only formed in low yields. This sequence was used for the synthesis of analogues of androgen hormones 4aα-hydroxy-4aβ-methyl-4a-homo-7,19-dinor-5α,9β,10β- androstane-3,17-dione (27), 4aα,17β-dihydroxy-4aβ,17α-dimethyl-4a-homo-7,19-dinor-5α,9β,10β-androstan-3-one (28) and 4aα,17β-dihydroxy-4aβ-methyl-4a-homo-7,19-dinor-5α,9β,10β-androstan-3-one (29).
Gradient-Enhanced Inverse-Detected NMR Techniquesfor Determination of 1H-15N Coupling Constants in 2,2-Dimethylpenta-3,4-dienal Derivatives
Authors: Marek Radek
Published: July 2002

Determination of 15N chemical shifts and heteronuclear coupling constants of substituted 2,2-dimethylpenta-3,4-dienal hydrazones is presented. The chemical shifts were determined by gradient-enhanced inverse-detected NMR techniques and 1H-15N coupling constants were extracted from phase-sensitive gradient-enhanced single-quantum multiple bond correlation experiments. Stereospecific behaviour of the coupling constants 2J(1H,15N) and 1J(1H,13C) has been used to determine the configuration on a C=N double bond. The above-mentioned compounds exist predominantly as E isomers in deuteriochloroform.
An Influence of the Spatial Arrangement, Length of the Alkyl Chain and Temperature on Micellar Properties of N-Alkyl-N-{[2-(benzyloxy)cyclohexylmethyl]}-N,N-dimethylammonium Bromides in Aqueous Solutions
Authors: Oremusová Jarmila , Mislovičová Veronika
Published: July 2002

In this work we study influence of the length of the alkyl chain and temperature on critical micellar concentration (CMC) for cis and trans diastereoisomers of the N-alkyl-N-{[2-(benzyloxy)cyclohexylmethyl]}-N,N-dimethylammonium bromides in aqueous solutions using conductometric and spectrophotometric techniques. From the measured dependences, the degree of the counterion binding (β) and thermodynamic parameters of micellization (∆Gm0, ∆Hm0, ∆Sm0) were calculated and compared with the literature data on similar compounds. The results show that lengthening of the alkyl chain by one methylene group causes approximately a two-fold reduction in CMC. The β values decrease with temperature and with increasing length of the alkyl chain. While only a small decrease in the ∆Gm0 values (ca 1 kJ mol-1) due to increasing temperature was found, the decrease in ∆Hm0 is much more pronounced.
Peptide Inhibitors of Aspartic Proteinases with Hydroxyethylene Isostere Replacement of Peptide Bond. I. Preparation of Four Diastereoisomeric (2R or 2S,4R or 4S,5S)-2-Benzyl-5-[(tert-butoxycarbonyl)amino]-4-hydroxy-6-phenylhexanoic Acids
Authors: Litera Jaroslav , Buděšínský Miloš , Urban Ján , Souček Milan
Published: July 2002

By two separate routes were prepared four diastereoisomers of (2R or 2S,5R or 5S)-3-benzyl-5-{(1S)- [(tert-butoxycarbonyl)amino]-2-phenylethyl}tetrahydrofuran-2-ones (11, 12, 17 and 18). Since the furanones were derived from (S)-phenylalanine, absolute configurations of all chiral carbon atoms could be deduced from their 1H NMR spectra. The furanones were easily hydrolyzed to four (2R or 2S,4R or 4S,5S)-2-benzyl-5- [(tert-butoxycarbonyl)amino]-4-hydroxy-6-phenylbutanoic acids (20-23), hydroxyethylene isosteres of Phe-Phe peptide bond.
Cyclization of Phenacyl 2-{[2,2-Di(ethoxycarbonyl)vinyl]amino}benzoate
Authors: Hradil Pavel , Kvapil Lubomír , Hlaváč Jan , Lemr Karel , Ševčík Juraj
Published: July 2002

Reaction of phenacyl anthranilate (1) with diethyl (ethoxymethylidene)malonate afforded phenacyl 2-{[2,2-di(ethoxycarbonyl)vinyl]amino}benzoate (2) which on heating in polyphosphoric acid underwent degradation. Thermal cyclization of 2 in diphenyl ether gave phenacyl 3-(ethoxycarbonyl)-4-oxo-1,4-dihydroquinoline-8-carboxylate (4). The phenacyl group did not cyclize even on prolonged heating at 250 °C. Heating in sulfuric acid resulted in hydrolysis of the ethyl ester under formation of 4-oxo-8-[(phenacyloxy)carbonyl]-1,4-dihydroquinoline-3-carboxylic acid (6). The structure of 4 was confirmed by an independent synthesis.
New Effective Synthesis of (N-Acetyl- and N-Stearoyl-2-amino-2-deoxy-β-D-glucopyranosyl)-(1→4)-N-acetylnormuramoyl-L-2-aminobutanoyl-D-isoglutamine, Analogs of GMDP with Immunopotentiating Activity
Authors: Ledvina Miroslav , Zyka Daniel , Ježek Jan , Trnka Tomáš , Šaman David
Published: July 2002

Ethyl 3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside (5), prepared by benzylation of ethyl 2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside (4), was transformed by reaction with bromine into 3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide (6). Thioglycoside 5 in the presence of methyl triflate and glycosylbromide 6 in the presence of silver triflate were used as glycosyl donors for condensation with benzyl 2-acetamido-3-O-allyl-6-O-benzyl-2-deoxy-α-D-glucopyranoside (7), to give benzyl 2-acetamido-3-O-allyl-6-O-benzyl-4-O-(3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-2-deoxy-α-D-glucopyranoside (8). Its reductive dephthaloylation with NaBH4/AcOH afforded benzyl 2-acetamido-3-O-allyl-4-O-(2-amino-3,4,6-tri-O-benzyl-2-deoxy-β-D-glucopyranosyl)- 6-O-benzyl-2-deoxy-α-D-glucopyranoside (11). Compound 11 was N-acylated to give benzyl 2-acetamido-4-O-(2-acylamino-3,4,6-tri-O-benzyl-2-deoxy-β-D-glucopyranosyl)-3-O-allyl-6-O-benzyl-2-deoxy-α-D-glucopyranosides (12a) or (12b). These compounds were converted into corresponding benzyl 2-acetamido-4-O-(2-acylamino-3,4,6-tri-O-benzyl-2-deoxy-β-D-glucopyranosyl)-6-O-benzyl-3-O-carboxymethyl-2-deoxy-α-D-glucopyranosides which, by condensation with H-L-Abu-D-isoGln(OBzl) followed by hydrogenolysis of protective benzyl groups, furnished glycopeptides 16a and 16b. Intramolecular O→N migration of the allyl protecting group followed by its reduction to the propyl residue by reaction of compound 8 with hydrazine or hydrazinium acetate, to give benzyl 2-acetamido-4-O-(3,4,6-tri-O-benzyl-2-deoxy-2-propylamino-β-D-glucopyranosyl)-6-O-benzyl-2-deoxy-α-D-glucopyranoside (9), is also described.
N-Benzoyl-N-methylandrostan-17β-amines; 20-Aza Analogues of Brassinolide
Authors: Slavíková Barbora , Kasal Alexander , Kohout Ladislav
Published: July 2002

3β-Hydroxyandrost-5-en-17-one (1) was converted into 17β-(N-methylamino)androst-5-en-3β-ol (4). In the corresponding N-benzamide 5, structural features characteristic of brassinolide were produced in a standard way, i.e. via 3α,5α-cyclo derivatives 7 and 8, ∆2-olefin 9 and 2α,3α-diol 10. Baeyer-Villiger oxidation yielded two products: 2α,3α-dihydroxy-17β-N-(methylbenzamido)-7-oxa-7a-homo-5α-androstan-6-one (11) and 2α,3α-dihydroxy-17β-(N-methylbenzamido)-6-oxa-7a-homo-5α-androstan-7-one (12).
Azachalcone Derivatives and Their Bis Substituted Analogs as Novel Antimycobacterial Agents
Authors: Kozmík Václav , Lhoták Pavel , Odlerová Želmíra , Paleček Jaroslav
Published: July 2002

Fifteen novel substituted azachalcone derivatives and their bis substituted analogs were prepared from 3,5-diacetyl-2,6-dimethylpyridine by the Claisen-Schmidt condensation. The influence of the reaction conditions on the yield of mono- and bischalcones was studied to optimize the reaction. Spectral characteristics along with preliminary results of antimycobacterial activity of selected compounds are given.
Facile Synthesis of 1,2-Anhydro-5-O-tosyl-β-D-mannofuranurono-6,3-lactone
Authors: Vukojevic Nada , Dramicanin Tatjana , Peric Biljana , Popsavin Mirjana , Csanádi János , Miljković Dušan
Published: July 2002

A two-step synthesis of 1,2-anhydro-5-O-tosyl-β-D-mannofuranurono-6,3-lactone (1) has been achieved starting from D-glucofuranurono-6,3-lactone (2). Tosylation of 2 gave a mixture of 5-monotosylate 3 and 2,5-ditosylate 4 which were separated by crystallization followed by column chromatography. Acetylation of 3 gave 1,2-di-O-acetyl-5-O-tosyl-β-D-glucofuranurono-6,3-lactone (5) in the good yield. Treatment of ditosylate 4 with potassium carbonate in dry acetone afforded 1,2-anhydro-5-O-tosyl-β-D-mannofuranurono-6,3-lactone in 50% yield.
Theoretical Study of the Physisorption of CO on Metal Oxide Surfaces Using the KSCED-DFT Approach
Authors: Vulliermet Nathalie , Wesolowski Tomasz A. , Weber Jacques
Published: July 2002

Theoretical studies on structure and stretching frequency of the CO molecule physisorbed on the MgO(100) or ZnO(1010) surfaces are reported. The properties of the adsorbed molecule were investigated by means of the recently developed formalism of Kohn-Sham equations with constrained electron density (KSCED). The KSCED method makes it possible to divide a large system into two subsystems and to study one of them using Kohn-Sham-like equations with an effective potential which takes into account the interactions between subsystems. This method (KSCED) was shown to be adequate to study the properties of the CO molecule adsorbed on the MgO(100) surface as reported in a previous paper (Wesolowski et. al.: J. Mol. Struct., THEOCHEM, in press). The effect of the interactions with the surface on the CO stretching frequency and geometry was analyzed for vertically bound (C-down) CO at the Zn-site of the ZnO(1010) surface. The ZnO(1010) surface was represented using several cluster models: Zn2+, (ZnO3)4-, or Zn9O9 embedded in a matrix of point charges. The KSCED frequency shift of the CO stretching vibration is blue-shifted and in good agreement with experiment.
Photoassisted Production of O2-• and H2 in Aqueous Medium Stimulated by Polythiophene in ZSM-5 Zeolite Channels
Authors: Čík Gabriel , Šeršeň František , Bumbálová Alena
Published: July 2002

The formation of reactive oxygen species due to irradiation by a visible light of the polythiophene deposited in ZSM-5 zeolite channels in aqueous medium has been studied. Polymerization of thiophene was carried out in zeolite channels after the ion-exchange reaction of Na+ for Fe3+. By means of EPR spectroscopy, the temporarily generated 1O2 in irradiated aqueous medium was proved. The formation of O2-• was confirmed by the reduction of Fe3+-cytochrome c. Irradiation led to the water reduction to hydrogen.
Synthesis of Quaternary 1-[2-(Phosphonomethoxy)ethyl] Derivatives of 2,4-Diaminopyrimidine and Related Acyclic Nucleotide Analogs
Authors: Holý Antonín , Buděšínský Miloš , Podlaha Jaroslav , Císařová Ivana
Published: July 2002

Quaternization of 2,4-diaminopyrimidine (2) by diisopropyl 2-chloroethoxymethanephosphonate (3) followed by bromotrimethylsilane treatment and subsequent hydrolysis gave zwitterionic N1-[2-(phosphonomethoxy)ethyl] derivative, hydrogen {[2-(2,4-diaminopyrimidin-1-io)ethoxy]methyl}phosphonate (5). Its structure was confirmed by X-ray crystallography. The same product was obtained from 2-amino-4-[(dimethylaminomethylene)amino]pyrimidine (6) by an analogous reaction sequence followed by an aqueous ammonia treatment after the transsilylation reaction. Also the quaternizations of 4,6-diaminopyrimidine (7) and 2,4,6-triaminopyrimidine (8) with the halo derivative 3 afforded the zwitterionic N1-substituted compounds 9 and 10, respectively. In contrast to this regiospecific reaction, 2-aminopyrimidine (11) gave on treatment with compound 3 and following deprotection the exo-N2-isomer 13. This compound was also obtained by the reaction starting from 2-[(dimethylaminomethylene)amino]pyrimidine (12) which was prepared by treatment of compound 11 with dimethylformamide dineopentyl acetal. Also 2,3-diaminopyridine (14) gave by the above reaction a mixture of 2-amino-3-{[2-(phosphonomethoxy)ethyl]amino}pyridine (15) and quaternary N1-[2-(phosphonomethoxy)ethyl] derivative (16). None of these analogs of the antiviral PMEDAP exhibited any antiviral activity against DNA viruses or retroviruses, nor any cytostatic activity.
Synthesis of New Potential Bis-Intercalators Based on Chiral Pyridine-2,6-dicarboxamides
Authors: Amr Abd El-Galil , Abd El-Salam Osama I. , Attia Abd El-Hamid , Stibor Ivan
Published: July 2002

Potential bis-intercalating compounds N,N-dibenzylidene-N2,N2'-(pyridine-2,6-dicarbonyl)- di(aminoacidhydrazides) 4a-4j, N,N'-substituted pyridine-2,6-bis(carbohydrazides) 5a-5d and N,N'-substituted N2N2'-bis(pyridine-2,6-dicarbonyl)di(aminoacidhydrazides) 6a-6g, both racemic and optically active, can be easily synthesized from pyridine-2,6-bis(carbohydrazide), natural amino acids and aromatic aldehydes or anhydrides of aromatic ortho-dicarboxylic acids.
Diels-Alder Reactions of Vinyl Derivatives of [1]Benzothieno[3,2-b]furan
Authors: Pihera Pavel , Dvořáková Hana , Svoboda Jiří
Published: July 2002

2-Vinyl- (2) and 3-vinyl[1]benzothieno[3,2-b]furan (3) react with dimethyl acetylenedicarboxylate, methyl propiolate, maleic anhydride, or acrylonitrile endo-selectively as dienes to afford new [1]benzothieno[3,2-b][1]benzofuran derivatives 7-20. cis-Anhydrides 13 and 18 were transformed into dimethyl esters 21 and 22, respectively. It was shown that the base-catalyzed hydrolysis of 13 and 18 is accompanied by rearrangement of double bond in 13 and cis/trans isomerization of carboxylic group. Diesters 21 and 22, and nitriles 20 and 24 were aromatized by treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Selective monodecarboxylation of [1]benzothieno[3,2-b][1]benzofuran-8,9-dicarboxylic acid (26) and [1]benzothieno[3,2-b][1]benzofuran-6,7-dicarboxylic acid (27) afforded [1]benzothieno[3,2-b][1]benzofuran-8-carboxylic acid (28) and [1]benzothieno[3,2-b][1]benzofuran-7-carboxylic acid (29), respectively.
Peptide Maps of Porcine Pepsin Prepared Using Soluble and Immobilized α-Chymotrypsin
Authors: Vaňková Hana , Kučerová Zdenka , Tichá Marie
Published: July 2002

Reverse-phase high performance liquid chromatography (RP-HPLC) was used for characterization of peptide maps of porcine pepsin using soluble or immobilized α-chymotrypsin. The immobilized enzyme was prepared by its coupling to periodate-oxidized poly(acrylamide-co-allyl α-D-galactoside or allyl β-lactoside) copolymer (O-glycosylated acrylamide copolymer). After sodium cyanoborohydride reduction, a stable linkage was formed. Specific activity of α-chymotrypsin, linked to the copolymer containing bound α-D-galactosyl or β-lactosyl residues was 59.1 or 314.4% activity of soluble enzyme.
Synthesis of the New 2-Alkyl-nido-2,7,10-C3B8H11 Tricarbaborane by Protonation of [7-Alkyl-nido-7,8,10-C3B8H10]-: A Reversible Cage-Carbon Rearrangement
Authors: Shedlow Alexandra M. , Sneddon Larry G.
Published: July 2002

Protonation of the [7-R-nido-7,8,10-C3B8H10]- (where R = PhCH2 (1a) or R = Me (1b)) tricarbollide anion, with concentrated H2SO4 in a two-phase aqueous/CH2Cl2 system, yields the new neutral tricarbaborane: 2-R-nido-2,7,10-C3B8H11 (where R = PhCH2 (2a) or R = Me (2b)). The three cage-carbons of the [7-R-nido-7,8,10-C3B8H10]- anion are located on the open face, but spectroscopic and DFT/GIAO/NMR studies of 2a and 2b show that during the protonation reaction, isomerization of the cage framework occurs to produce the neutral tricarbaborane having a 2,7,10-structure in which only two of the carbons remain on the open face. The third (R-substituted) carbon adopts a five-coordinate vertex off of the open face, thus enabling the incoming proton to adopt a bridging position on the B-B edge of the new C2B3-open face. The skeletal rearrangement is reversible, since deprotonation of 2a or 2b regenerates the anions 1a and 1b, respectively, having the 7,8,10-configuration. In agreement with the experimentally observed structures of the anionic (7,8,10-structure) and neutral (2,7,10-structure) species, DFT calculations at the B3LYP/6-311G*-level show that the [7-Me-nido-7,8,10-C3B8H10]- anion (1b, structure 16) is 28.9 kcal/mol more stable than the [2-Me-nido-2,7,10-C3B8H10]- isomer (3b, structure 18), while for the neutral tricarbaborane, the 2-R-nido-2,7,10-C3B8H11 (2b, structure 14) structure is more stable than any 7,8,10-structure (structures 7-11) which has the added proton in an endo position on the open face. Transition state calculations at the HF/6-31G*-level yielded a simple, low-energy pathway (activation barrier of only 6.5 kcal/mol for the transition state TS18/16) for the rearrangement of [2-Me-nido-2,7,10-C3B8H10]- (3b, structure 18) to [7-Me-nido-7,8,10-C3B8H10]- (1b, structure 16) requiring the movement of only one cage atom, B11, from its original position in the C7-B8-B9-C10-B11 plane of 3b, to the C7-C8-B9-C10-B11 plane of 1b.
Application of 2-Substituted Ethyl Isothiocyanates and 2-Aminothiols in the Synthesis of the Analogs of Indole Phytoalexin Camalexin
Authors: Dzurilla Milan , Ružinský Martin , Kutschy Peter , Tewari Jalpa P. , Kováčik Vladimír
Published: July 2002

Treatment of (indol-1-yl)magnesium bromide or iodide with 2-bromoethyl isothiocyanate afforded 1-(4,5-dihydrothiazol-2-yl)indole (6). Analogous reaction with 2,2-dimethoxyethyl isothiocyanate led to corresponding 1-thiocarbamoylindole derivative (7), which was cyclized to 1-(5-methoxy-4,5-dihydrothiazol-2-yl)indole (8) by treatment with boron trifluoride etherate. New analogs of camalexin, namely 4',5'-dihydrocamalexin (12) and benzocamalexin (14) were prepared by cyclocondensation reaction of 1-(tert-butoxycarbonyl)indole-3-carbaldehyde with cysteamine and 2-aminobenzenethiol. Antifungal activity of the prepared compounds was studied, using the fungi Alternaria brassicae and Alternaria brassicicola.
Determination of the Nucleophilicity of Tricarbonyliron Coordinated Cyclohepta-1,3,5-triene
Authors: Mayr Herbert , Müller Karl-Heinz
Published: July 2002

The kinetics of the electrophilic additions of four diarylcarbenium ions (4a-4d) to tricarbonyl(η4-cyclohepta-1,3,5-triene)iron (1) have been studied photometrically. The second-order rate constants match the linear Gibbs energy relationship log k20 °C = s(E + N) and yield the nucleophilicity parameter N(1) = 3.69. It is concluded that electrophiles with E ≥ -9 will react with complex 1 at ambient temperature.
Reactions of a New Family of Amide Derivatives of Phenanthridinium Azomethine Ylides with Dipolarophiles
Authors: Trávníček Martin , Pospíšil Jiří , Potáček Milan
Published: July 2002

Reaction of a series of N-alkyl- and N,N-dialkylbromoacetamides 1a-1e with phenanthridine afforded quaternary phenanthridinium salts 2a-2e. These compounds treated with triethylamine form azomethine ylides which undergo a cycloaddition reaction with activated C=C bond, giving 3-(N-alkylcarbamoyl)-1,2,3,12b-tetrahydropyrrolo[1,2-f]phenanthridines 3a-3e, 4c, 5c, 6c or 3-(N-alkylcarbamoyl)-2,3-dihydropyrrolo[1,2-f]phenanthridine 7c. Their stereochemistry was studied by NMR spectroscopy. The best results were obtained with fumaronitrile as a dipolarophile. It has been found that the ylides react in syn conformations but if 1-adamantyl moiety is bound to the ylide, it reacts in anti conformation, too. The azomethine ylides show a very poor reactivity towards dimethyl fumarate or dimethyl maleate. Yet we could prepare products for ylide bearing 1-adamantyl group.
Effect of Lithium tert-Alkoxides on Anionic Polymerization of Butadiene Initiated with a Bifunctional Initiator
Authors: Toman Luděk , Vlček Petr , Sufčák Miloslav , Pleska Alexander , Spěváček Jiří , Holler Petr
Published: July 2002

Polymerization of buta-1,3-diene initiated by bifunctional dilithium initiator in tert-butyl methyl ether, hexane and hexane-toluene mixtures was studied in the presence of Li tert-butoxide, 2-methylpentan-2-olate, 3-methylpentan-3-olate or 2,3-dimethylbutan-2-olate. The alkoxides lower the overall polymerization rate and affect, to a certain extent, microstructure of formed polymers. When applied in a concentration equal to that of the initiating centres, they lower the content of vinyl structures in polybutadiene by 10-12%. Increasing concentration of the alkoxide has no perceptible effect and, if used in 12-fold excess over the initiator, the content of 1,2-structures even increases. Polymers prepared in the presence of an alkoxide mostly have unimodal and narrow MWDs.
Synthesis of Carbocyclic 4'-C-Hydroxymethyl Analogues of Azidodeoxythymidine, Deoxythymidine, Deoxydidehydrothymidine and Thymidine Carba Analogue with Fused Oxetane Ring
Authors: Hřebabecký Hubert , Holý Antonín
Published: July 2002

Tosylation of (±)-1-[trans-4-hydroxy-3,3-bis(hydroxymethyl)cyclopentyl]-5-methylpyrimidine-2(1H),4(3H)-dione (1) and (±)-1-[cis-4-hydroxy-3,3-bis(hydroxymethyl)cyclopentyl]-5-methylpyrimidine-2(1H),4(3H)-dione (2) and treatment of the obtained 1-{(1R*,3R*,4S*)- 4-hydroxy-3-(hydroxymethyl)-3-[(tosyloxy)methyl]cyclopentyl}-5-methylpyrimidine- 2(1H),4(3H)-dione (6) and 1-{(1R*,3S*,4R*)-4-hydroxy-3-(hydroxymethyl)-3-[(tosyloxy)- methyl]cyclopentyl}-5-methylpyrimidine-2(1H),4(3H)-dione (9) with methanolic sodium methoxide gave 1-[(1R*,4S*,6S*)-4-hydroxymethyl-2-oxabicyclo[3.2.0]hept-6-yl]-5-methylpyrimidine-2(1H),4(3H)-dione (7) and 1-[(1R*,4S*,6R*)-4-hydroxymethyl-2-oxabicyclo[3.2.0]hept-6-yl]-5-methylpyrimidine-2(1H),4(3H)-dione (10), respectively. Treatment of (±)-1-{cis-4-mesyloxy-3,3-bis[(trityloxy)methyl]cyclopentyl}-5-methylpyrimidine-2(1H),4(3H)-dione (11), which was prepared from 2 by tritylation and mesylation, with 1,8-diazabicyclo[5.4.0]undec-7-ene in dimethylformamide afforded after deprotection (±)-1-[4,4-bis(hydroxymethyl)cyclopent-2-en-1-yl]-5-methylpyrimidine-2(1H),4(3H)-dione (14). Hydrogen- ation of 14 led to (±)-1-[3,3-bis(hydroxymethyl)cyclopentyl]-5-methylpyrimidine-2(1H),4(3H)- dione (15). (±)-1-{trans-4-Mesyloxy-3,3-bis[(trityloxy)methyl]cyclopentyl}-5-methylpyrimidine- 2(1H),4(3H)-dione (17), which was prepared from 1, was converted to (1R*,9R*)-6-methyl-5-oxo-11,11-bis(trityloxymethyl)-2-oxa-4,8-diazatricyclo[7.2.1.03,8]dodec-3,6-diene (18). The compound 18 was deprotected and heated with lithium azide in dimethylformamide to give (±)-1-[trans-4-azido-3,3-bis(hydroxymethyl)cyclopentyl]-5-methylpyrimidine-2(1H),4(3H)-dione (21).
Bis(methylphosphonic Acid) Derivatives of 1,4,8,11-Tetraazacyclotetradecane (Cyclam). Synthesis, Crystal and Molecular Structures, and Solution Properties
Authors: Kotek Jan , Vojtíšek Pavel , Císařová Ivana , Hermann Petr , Jurečka Petr , Rohovec Jan , Lukeš Ivan
Published: July 2002

Cyclam derivatives with methylphosphonic acid arms in position 1,8 and substituent R = H, Me, CH2Ph in positions 4 and 11 are synthesised by Mannich reaction of an appropriate cyclam derivative, formaldehyde and phosphonic acid/diethyl phosphite followed by removal of protecting benzyl groups from nitrogen atoms. Mono(methylphosphonic acid) derivative of cyclam can be obtained by a similar route. Crystal structures of four phosphonic acid derivatives show the same ring conformation and orientation pendants due to strong intramolecular hydrogen bonds between phosphonate oxygen atoms and protonated nitrogen atoms adjacent over ethylene chains. The hydrogen bonds are stable even in aqueous solution. Activation parameters for destabilisation of the conformation are estimated from temperature-dependent NMR measurement. The protonation constants determined confirm the expected high basicity of the compounds and its dependence on the nitrogen atom substituents. The enhanced basicity of the nitrogen atoms non-bonded to methylenephosphonic acid moiety, is explained by the presence of the strong hydrogen bonds.
Symptomatic rickets in adolescence
Authors: Narchi H , El Jamil M , Kulaylat N
Published: July 2002

AIM

To describe 21 cases of symptomatic rickets in adolescents.

METHODS

The setting was a primary and secondary care hospital in Saudi Arabia providing medical care to Saudi Arab company employees and their families. Cases of symptomatic rickets diagnosed between January 1996 and December 1997 in adolescents aged 10 to 15 years were assessed with respect to clinical presentation, biochemical and radiological evaluation, dietary assessment, and estimation of sun exposure.

RESULTS

Symptomatic rickets developed in 21 adolescents (20 females), with a prevalence rate of 68 per 100 000 children years. Presentation included carpopedal spasms (n = 12), diffuse limb pains (n = 6), lower limbs deformities (n = 2), and generalised weakness (n = 1). Biochemical findings included hypocalcaemia (n = 19), hypophosphoraemia (n = 9), raised serum alkaline phosphatase (n = 21) and parathormone (n = 7), and reduced 25-hydroxyvitamin D concentrations (n = 7). Radiological studies were suggestive of rickets in only eight children. All children had an inadequate dietary calcium and vitamin D intake. All but one had less than 60 minutes sun exposure per day.

CONCLUSION

Even in sunny climates, adolescents, especially females, can be at risk of rickets. Hypocalcaemic tetany and limb pains were the most common presenting symptoms. Radiological evidence was not present in every case.
Diabetic ketoacidosis in Asian children
Authors: Alvi N S , Davies P , Kirk J M W , Shaw N J
Published: July 2002

Over the 10 year period 1987–1996, 328 children with type 1 diabetes mellitus presented in the city of Birmingham, England, of whom 27% had diabetic ketoacidosis. Asian children under the age of 5 had an eightfold increased risk of presenting in diabetic ketoacidosis compared with non-Asian children of the same age.
Effects of three different training modalities on the cross sectional area of the lumbar multifidus muscle in patients with chronic low back pain
Authors: Danneels L A , Vanderstraeten G G , Cambier D C , Witvrouw E E , Bourgois J , Dankaerts W , De Cuyper H J
Published: July 2002

Objectives—To determine the effect of different training schedules on the cross sectional area (CSA) of the lumbar multifidus muscle in patients with chronic low back pain.

Methods—Each of 59 nine patients was randomly assigned to one of three programmes: 10 weeks of stabilisation training (group 1; n = 19); 10 weeks of stabilisation training combined with dynamic resistance training (group 2; n = 20); 10 weeks of stabilisation training combined with dynamic-static resistance training (group 3; n = 20). Before and after 10 weeks of training, multifidus CSAs were measured from standard computed tomography images at three different levels (upper end plate of L3 and L4, and lower end plate of L4).

Results—The CSA of the multifidus muscle was significantly increased at all levels after training in group 3. In contrast, no significant differences were found in groups 1 and 2.

Conclusions—General stabilisation exercises and dynamic intensive lumbar resistance training have no significant effect on the CSA of the lumbar multifidus muscle in patients with chronic low back pain. The static holding component between the concentric and eccentric phase was found to be critical in inducing muscle hypertrophy during the first 10 weeks. Treatment consisting of stabilisation training combined with an intensive lumbar dynamic-static strengthening programme seems to be the most appropriate method of restoring the size of the multifidus muscle.
Neonatal thrombocytosis resulting from the maternal use of non-narcotic antischizophrenic drugs during pregnancy
Authors: Nako Y , Tachibana A , Fujiu T , Tomomasa T , Morikawa A
Published: July 2002

Neonatal thrombocytosis can result from maternal narcotic drug abuse. The case of a male infant is reported who was born to a woman with schizophrenia treated with non-narcotic psychotropic drugs during pregnancy; he developed severe prolonged thrombocytosis. The platelet count reached 1310 × 109/l on day 15. This thrombocytosis persisted for three months. The patient was treated with dipyridamole. A bone marrow aspirate showed normal myeloid and erythroid precursors with an increased number of megakaryocytes. Plasma concentrations of interleukin 6 and thrombopoietin were suppressed. No obvious complications from the thrombocytosis occurred, and the platelet count fell to within the upper limit of normal after 3 months of age. This case indicates that thrombocytosis may occur in infants born to mothers treated with non-narcotic psychopharmaceutical drugs during pregnancy. The thrombocytosis in this case may have been induced by factors other than interleukin 6 or thrombopoietin.
Microsatellite instability and the clinicopathological features of sporadic colorectal cancer
Authors: Ward R , Meagher A , Tomlinson I , O'Connor T , Norrie M , Wu R , Hawkins N
Published: July 2002

BACKGROUND AND AIMS

In this study, we prospectively examined the clinical significance of the microsatellite instability (MSI) phenotype in sporadic colorectal cancer, and investigated methods for effective identification of these tumours in routine pathology practice.

METHODS

DNA was extracted from 310 tumours collected from 302 consecutive individuals undergoing curative surgery for sporadic colorectal cancer. Microsatellite status was determined by polymerase chain reaction amplification using standard markers, while immunostaining was used to examine expression of MLH1, MSH2, and p53.

RESULTS

Eleven per cent of tumours showed high level instability (MSI-H), 6.8% had low level instability (MSI-L), and the remainder were stable. MSI-H tumours were significantly more likely to be of high histopathological grade, have a mucinous phenotype, and to harbour increased numbers of intraepithelial lymphocytes. They were also more likely to be right sided, occur in women, and be associated with improved overall survival. In total, 25 (8%) tumours showed loss of staining for MLH1 and a further three tumours showed absence of staining for MSH2. The positive and negative predictive value of immunohistochemistry in the detection of MSI-H tumours was greater than 95%.

CONCLUSIONS

We conclude that the MSI-H phenotype constitutes a pathologically and clinically distinct subtype of sporadic colorectal cancer. Immunohistochemical staining for MLH1 and MSH2 represents an inexpensive and accurate means of identifying such tumours.
Cannabinoids and the gastrointestinal tract
Authors: PERTWEE R G
Published: July 2002

The enteric nervous system of several species, including the mouse, rat, guinea pig and humans, contains cannabinoid CB1receptors that depress gastrointestinal motility, mainly by inhibiting ongoing contractile transmitter release. Signs of this depressant effect are, in the whole organism, delayed gastric emptying and inhibition of the transit of non-absorbable markers through the small intestine and, in isolated strips of ileal tissue, inhibition of evoked acetylcholine release, peristalsis, and cholinergic and non-adrenergic non-cholinergic (NANC) contractions of longitudinal or circular smooth muscle. These are contractions evoked electrically or by agents that are thought to stimulate contractile transmitter release either in tissue taken from morphine pretreated animals (naloxone) or in unpretreated tissue (γ-aminobutyric acid and 5-hydroxytryptamine). The inhibitory effects of cannabinoid receptor agonists on gastric emptying and intestinal transit are mediated to some extent by CB1receptors in the brain as well as by enteric CB1receptors. Gastric acid secretion is also inhibited in response to CB1receptor activation, although the detailed underlying mechanism has yet to be elucidated. Cannabinoid receptor agonists delay gastric emptying in humans as well as in rodents and probably also inhibit human gastric acid secretion. Cannabinoid pretreatment induces tolerance to the inhibitory effects of cannabinoid receptor agonists on gastrointestinal motility. Findings that the CB1selective antagonist/inverse agonist SR141716A produces in vivo and in vitro signs of increased motility of rodent small intestine probably reflect the presence in the enteric nervous system of a population of CB1receptors that are precoupled to their effector mechanisms. SR141716A has been reported not to behave in this manner in the myenteric plexus-longitudinal muscle preparation (MPLM) of human ileum unless this has first been rendered cannabinoid tolerant. Nor has it been found to induce “withdrawal” contractions in cannabinoid tolerant guinea pig ileal MPLM. Further research is required to investigate the role both of endogenous cannabinoid receptor agonists and of non-CB1cannabinoid receptors in the gastrointestinal tract. The extent to which the effects on gastrointestinal function of cannabinoid receptor agonists or antagonists/inverse agonists can be exploited therapeutically has yet to be investigated as has the extent to which these drugs can provoke unwanted effects in the gastrointestinal tract when used for other therapeutic purposes.
UK NEQAS in antibiotic assays
Authors: White L O
Published: July 2002

How providers of external quality assessment (EQA) programmes relate to and interact with the monitors and watchdog of clinical laboratory performance in the UK is described. With regard to the quality of antibiotic assays, the changes in methodologies and in performance quality between 1971 (when the UK NEQAS for Antibiotic Assays began) and 1999 is reviewed. How improvements in performance and changes of methodology are related is discussed. The findings and conclusions of two experimental pilot EQA distributions (the teicoplanin assay and serum bactericidal test) are also discussed.