bluuebunny/crossref_metadata_2025 huggingface dataset:
Raman spectroscopic study of effect of steam and carbon dioxide activation on microstructure of polyacrylonitrile‐based activated carbon fabrics
Authors: Ko Tse‐Hao , Kuo Wen‐Shyong , Hu Chung‐Hua
Published: August 2002

This work presents the different effects of steam and carbon dioxide activation on the microstructure of an oxidized polyacrylonitrile (PAN) fabric. An investigation was conducted on a series of carbonized fabrics and two series of activated carbon fabrics. The fabrics were activated by steam and carbon dioxide using heat‐treatment temperatures of 900–1100°C. Steam and carbon dioxide developed the microstructure initially present in the PAN‐based activated carbon fabrics, but with different effects. These fabrics in the form of fabric and powder were examined by X‐ray diffraction and Raman spectrometry. This study indicated that carbon dioxide only reacted with the crystalline edges or the irregular carbon on the fiber surface and that the inside structure of the fibers was not greatly affected. When the fabrics were activated using steam, water molecules reacted not only on the fiber surface but also with the carbon at the crystal edge and/or the nonregular carbon in the fibers, which led to communicating pore structures on the surface and in the inner portions of the fiber. This activation also promoted the denitrogenation reactions. Because of these structures and reactions, the activated carbon fabrics, which were activated by steam, had the highest stacking height for carbon layer planes (Lc), the highest number of layer planes (Lc/d002), the highest oxygen content, the largest crystal size (La), and the highest density over the other samples. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1090–1099, 2001
Preparation and properties of organosoluble, colorless, and high‐pretilt‐angle polyimides based on an alicyclic dianhydride and long‐main‐chain alkyl‐group‐containing diamines
Authors: Zhang Wei , Xu Hong‐Jie , Yin Jie , Guo Xiao‐Xia , Ye Yu‐Feng , Fang Jian‐Hua , Sui Yu , Zhu Zi‐Kang , Wang Zong‐Guang
Published: August 2002

Alicyclic polyimides (PIs) were prepared from 3‐carboxylmethyl‐cyclopentane‐1,2,4‐tricarboxylic acid dianhydride and α,ω‐di(4‐aminophenoxyl)alkanes. These PIs possessed good solubility in aprotic, strongly polar solvents such as N‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethyl formamide, and m‐cresol. They possessed high transparency in visible wavelengths and were almost colorless. The pretilt angle of a liquid‐crystal display with these PIs as the alignment layer increased linearly as the length of the alkyloxy groups increased; it was close to 5° for the PI samples PI‐10 and PI‐12. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2814–2820, 2001
Gas transport properties of 6FDA‐durene/1,3‐phenylenediamine (mPDA) copolyimides
Authors: Chung Tai‐Shung , Lin Wen‐Hui , Vora Rohit H.
Published: August 2002

The gas transport properties of He, H2, O2, N2, and CO2 for 6FDA‐durene, 6FDA‐mPDA, and their copolyimides have been investigated as a function of the composition, pressure, and temperature. The permeabilities, diffusion coefficients, and solubility coefficients follow the simple additional rules and Arrihenuis relationships for 6FDA‐durene/mPDA polyimides. The permeability decreases with an increase in pressure except He, and in the kinetic diameters of the penetrant molecules with the order of He, CO2, O2, and N2. The diffusion coefficients of O2, N2, and CO2 increase with increasing pressure and temperature. Interestingly, for these polyimides, the diffusion coefficient of O2 is larger than that of CO2. This may be caused by the strong quadrupole moment of the CO2 molecules or the difficulty in estimating the accurate diameter of CO2 molecules. The solubility coefficients decrease in the order of inherent condensability of the penetrant gases, namely CO2, O2, and N2. In addition, WAXD results show that 6FDA‐durene/mPDA polyimides are amorphous. The presence of a single glass transition temperature for these copolyimides indicates that these polyimides can be assumed to be random copolymers. They have excellent thermal stability exhibiting degradation temperature in a range of 493 to 548°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3552–3564, 2001
Tensile properties of Argiope trifasciata drag line silk obtained from the spider's web
Authors: Pérez‐Rigueiro J. , Elices M. , Llorca J. , Viney C.
Published: August 2002

The tensile properties of Argiope trifasciata (Argiopidae) drag line silk retrieved from mooring threads in the web were characterized. Scanning electron microscope images were used to determine the cross‐sectional area of the samples, allowing force‐displacement plots to be rescaled as stress–strain curves and to characterize fracture surfaces. Twenty‐eight samples were tested to obtain statistically significant values of the mechanical parameters (elastic modulus, stress and strain at the proportional limit, and tensile strength). The tensile strength of the material was subjected to a Weibull analysis—the first time that this has been attempted with a spider silk. A low value of the Weibull modulus, m = 3.4, was obtained, demonstrating that drag line monofilament does not have a sufficiently reliable tensile strength to function as an engineering material on its own. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2245–2251, 2001
Syntheses and characteristics of polyimides for the applications to alignment film for liquid crystal display
Authors: Lee Sang Jin , Ha Chang‐Sik , Lee Jin Kook
Published: August 2002

In this work, several polyimides (PIs) containing diphenyl ether group were synthesized and characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis. The relationship between the surface structures and the molecular chain conformations of the PIs, whether helical or zigzag, was discussed. The effects of the molecular chain conformations of the PIs on the pretilt angles of liquid crystal molecules were systematically investigated. The surface orientations of polyimides whose chains adopt zigzag and planar conformations were less improved by rubbing treatment than those of polyimides whose chains adopt helical and nonplanar conformations, because the polyimide chains of zigzag and planar conformation are easily packed. The polyimides, whose chains adopt helical and nonpolar conformations, gave larger pretilt angles than the polyimides whose chains adopt zigzag and planar conformations. The pretilt angles measured under the condition of rubbing depth of 0.5 mm were smaller than under the condition of rubbing depth of 0.3 mm. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2365–2371, 2001
Analysis of the crosslinking process of a phenolic resin by thermal scanning rheometry
Authors: Laza J. M. , Vilas J. L. , Rodríguez M. , Garay M. T. , Mijangos F. , León L. M.
Published: August 2002

The curing reaction of a phenolic resin (resole type) carried out in the absence of an initiator was studied by thermal scanning rheometry under isothermal conditions at temperatures from 70 to 105°C. The same curing reaction was studied in the presence of an acid as a catalyst in the temperature range of 50–80°C. The gel time, which was defined by several criteria, was found to be a good parameter to determine the apparent activation energy of this process. An empirical model was used to predict the change in complex viscosity with time until the gel time was reached. If first‐order kinetics were assumed, the apparent kinetic constant of the curing reaction could be obtained. Furthermore, the effect that the addition of water and free phenol had on the curing process of this type of resin was studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 57–65, 2002
Research anxiety and students' perceptions of research: An experiment. Part II. Content analysis of their writings on two experiences
Authors: Kracker Jacqueline , Wang Peiling
Published: August 2002

This is Part II of an experimental study investigating students' perceptions of research and research paper anxiety. The study integrates quantitative and qualitative designs to collect complimentary data. The participants were students in four sections of an upper division undergraduate course on technical and professional writing during the fall of 1999. A survey instrument used the Critical Incident Technique to solicit writings in students' own words about a memorable past research and writing experience at the beginning of the semester and the current research and writing at the end of the semester. The quantitative part of the survey measured students' perceptions about research using a questionnaire with five‐point Likert scale, and students' anxiety levels using a standard state anxiety test (STAI Y‐1). The first article, Part I, provides a detailed description of the experimental design and reports on quantitative results. This article reports on content analysis of students' writings about their experiences of the two research projects. Analysis of the data confirmed Kuhlthau's Information Search Process (ISP) model and revealed additional affective and cognitive aspects related to research and writing.
Taming the fierce roller: an “enhanced” understanding of cellular differentiation in Volvox
Authors: Miller Stephen M.
Published: August 2002

Few organisms offer a better opportunity to explore the mechanisms of cellular differentiation, and their origins, than Volvox. Volvox consists of just two cell types, germ and soma, and is the most complex member of a family of green algae that includes unicellular and multicellular relatives. At the heart of the cell‐fate determination program of Volvox carteri is the regA gene, which encodes a putative transcriptional repressor that prevents somatic cells from expressing reproductive functions. Stark et al.(1) have dissected the regA gene to determine how its expression is restricted to somatic cells. Their results suggest that regA expression is controlled by multiple enhancers, the most important of which prevents transcription in reproductive cells. While these findings shed light on Volvox development, they also raise a new set of questions about the mechanisms that control the germ–soma dichotomy in this organism. BioEssays 24:3–7, 2002. © 2002 John Wiley & Sons, Inc.
Surface‐enhanced Raman and steady fluorescence study of interaction between antitumoral drug 9‐aminoacridine and trypsin‐like protease related to metastasis processes, guanidinobenzoatase
Authors: Murza Adrian , Sánchez‐Cortés Santiago , García‐Ramos José V.
Published: August 2002

Fluorescence spectroscopy and surface‐enhanced Raman spectroscopy (SERS) were applied to study the interaction of the antitumoral drug 9‐aminoacridine (9AA) with a trypsin‐like protease guanidinobenzoatase (GB) extracted from a mouse Erlich tumor. As a consequence of this interaction, a strong 9AA exciplex emission was detected in the emission fluorescence spectra at certain drug and enzyme concentrations. A SERS study was accomplished on silver colloids at several excitation wavelengths in order to obtain more information about the interaction mechanism. The results derived from Raman spectroscopy indicated that 9AA in the amino monomeric form may interact with the enzyme by means of two different bonds: an ionic bond with a negatively charged amino acid and a ring stacking interaction with an aromatic residue placed in the catalytic site of GB. This interaction mechanism was responsible for a strong exciplex emission detected at a longer wavelength than the expected value of the normal fluorescence emission. Moreover, the GB concentration dependence of the interaction suggested that the drug was sensitive to the quaternary structure of the enzyme. © 2001 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 85–94, 2001
Dynamics and orientation of transmembrane peptide from bacteriorhodopsin incorporated into lipid bilayer as revealed by solid state 31P and 13C NMR spectroscopy
Authors: Kimura Shigeki , Naito Akira , Tuzi Satoru , Saitô Hazime
Published: August 2002

13C and 31P NMR spectra of a transmembrane peptide, [1‐13C]Ala14‐labeled A(6–34), of bacteriorhodopsin incorporated into dimyristoylphosphatidylcholine (DMPC) bilayer were recorded to clarify its dynamics and orientation in the lipid bilayer. This peptide is shown to take an α‐helical form both in liquid crystalline and gel phases, as viewed from the conformation dependent 13C chemical shifts. In addition, this peptide undergoes rapid rigid‐body rotation about the helical axis at ambient temperature as viewed from the axially symmetric 13C chemical shift anisotropy, whereas this symmetric anisotropy is changed to an asymmetric pattern at temperatures below 10°C. We further incorporated the peptide into the spontaneously aligned DMPC bilayer to applied magnetic field, induced by dynorphin (dynorphin:DMPC =1:10), a heptadeca‐opioid peptide with very high affinity to opioid receptor, in order to gain insight into its orientation in the bilayer. This magnetically aligned system turned out to be persistent even at 0°C as viewed from 31P NMR spectra of the lipid bilayer, after this peptide was incorporated into this system [A(6–34): dynorphin: DMPC = 4:10:100]. It was found from the 13C NMR spectra of [1‐13C]Ala14 A(6–34) that the helical axis of A(6–34) is oriented parallel to the bilayer normal irrespective of the presence or absence of reorientation motion about the helical axis at a temperature above the lowered gel to liquid crystalline phase transition. © 2002 John Wiley & Sons, Inc. Biopolymers 63: 122–131, 2002
A biosensor for the detection of triazine and phenylurea herbicides designed using Photosystem II coupled to a screen‐printed electrode
Authors: Koblížek Michal , Malý Jan , Masojídek Jiří , Komenda Josef , Kučera Tomáš , Giardi Maria T. , Mattoo Autar K. , Pilloton Roberto
Published: August 2002

A biosensor for the detection of triazine‐ and phenylurea‐type herbicides was constructed using isolated Photosystem II (PS II) complexes as a biosensing element. PSII isolated from the thermophilic cyanobacterium Synechococcus elongatus was immobilized on the surface of a screen‐printed sensor composed of a graphite working electrode and Ag/AgCl reference electrode deposited on a polymeric substrate. The biosensor was mounted in a flow microcell with illumination. The principle of the detection was based on the fact that herbicides selectively block PSII electron transport activity in a concentration‐dependent manner. Changes of the activity were registered amperometrically as the rate of photoreduction of an artificial electron acceptor. The setup resulted in a reusable herbicide biosensor with a good stability (half‐life of 24 h) and limit of detection of approximately 10−9 M for diuron, atrazine and simazine. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 110–116, 2002; DOI 10.1002/bit.10190
Efficiency of embryoid body formation and hematopoietic development from embryonic stem cells in different culture systems
Authors: Dang Stephen M. , Kyba Michael , Perlingeiro Rita , Daley George Q. , Zandstra Peter W.
Published: August 2002

Embryonic stem (ES) cells have tremendous potential as a cell source for cell‐based therapies. Realization of that potential will depend on our ability to understand and manipulate the factors that influence cell fate decisions and to develop scalable methods of cell production. We compared four standard ES cell differentiation culture systems by measuring aspects of embryoid body (EB) formation efficiency and cell proliferation, and by tracking development of a specific differentiated tissue type—blood—using functional (colony‐forming cell) and phenotypic (Flk‐1 and CD34 expression) assays. We report that individual murine ES cells form EBs with an efficiency of 42 ± 9%, but this value is rarely obtained because of EB aggregation—a process whereby two or more individual ES cells or EBs fuse to form a single, larger cell aggregate. Regardless of whether EBs were generated from a single ES cell in methylcellulose or liquid suspension culture, or aggregates of ES cells in hanging drop culture, they grew to a similar maximum cell number of 28,000 ± 9,000 cells per EB. Among the three methods for EB generation in suspension culture there were no differences in the kinetics or frequency of hematopoietic development. Thus, initiating EBs with a single ES cell and preventing EB aggregation should allow for maximum yield of differentiated cells in the EB system. EB differentiation cultures were also compared to attached differentiation culture using the same outputs. Attached colonies were not similarly limited in cell number; however, hematopoietic development in attached culture was impaired. The percentage of early Flk‐1 and CD34 expressing cells was dramatically lower than in EBs cultured in suspension, whereas hematopoietic colony formation was almost completely inhibited. These results provide a foundation for development of efficient, scalable bioprocesses for ES cell differentiation, and inform novel methods for the production of hematopoietic tissues. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 442–453, 2002.
A kinetic model for enzyme interfacial activity and stability: pa‐hydroxynitrile lyase at the diisopropyl ether/water interface
Authors: Cascão Pereira Luis G. , Hickel Andrea , Radke Clayton J. , Blanch Harvey W.
Published: August 2002

A kinetic framework is developed to describe enzyme activity and stability in two‐phase liquid–liquid systems. In particular, the model is applied to the enzymatic production of benzaldehyde from mandelonitrile by Prunus amygdalus hydroxynitrile lyase (pa‐Hnl) adsorbed at the diisopropyl ether (DIPE)/aqueous buffer interface (pH = 5.5). We quantitatively describe our previously obtained experimental kinetic results (Hickel et al., 1999; 2001), and we successfully account for the aqueous‐phase enzyme concentration dependence of product formation rates and the observed reaction rates at early times. Multilayer growth explains the early time reversibility of enzyme adsorption at the DIPE/buffer interface observed by both enzyme‐activity and dynamic‐interfacial‐tension washout experiments that replace the aqueous enzyme solution with a buffer solution. The postulated explanation for the unusual stability of pa‐Hnl adsorbed at the DIPE/buffer interface is attributed to a two‐layer adsorption mechanism. In the first layer, slow conformational change from the native state leads to irreversible attachment and partial loss of catalytic activity. In the second layer, pa‐Hnl is reversibly adsorbed without loss in catalytic activity. The measured catalytic activity is the combined effect of the deactivation kinetics of the first layer and of the adsorption kinetics of each layer. For the specific case of pa‐Hnl adsorbed at the DIPE/buffer interface, this combined effect is nearly constant for several hours resulting in no apparent loss of catalytic activity. Our proposed kinetic model can be extended to other interfacially active enzymes and other organic solvents. Finally, we indicate how interfacial‐tension lag times provide a powerful tool for rational solvent selection and enzyme engineering. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 595–605, 2002.
Neutral fat hydrolysis and long‐chain fatty acid oxidation during anaerobic digestion of slaughterhouse wastewater
Authors: Masse L. , Massé D. I. , Kennedy K. J. , Chou S. P.
Published: August 2002

Neutral fat hydrolysis and long‐chain fatty acid (LCFA) oxidation rates were determined during the digestion of slaughterhouse wastewater in anaerobic sequencing batch reactors operated at 25°C. The experimental substrate consisted of filtered slaughterhouse wastewater supplemented with pork fat particles at various average initial sizes (Din) ranging from 60 to 450 μm. At the Din tested, there was no significant particle size effect on the first‐order hydrolysis rate. The neutral fat hydrolysis rate averaged 0.63 ± 0.07 d−1. LCFA oxidation rate was modelled using a Monod‐type equation. The maximum substrate utilization rate (kmax) and the half‐saturation concentration (Ks) averaged 164 ± 37 mg LCFA/L/d and 35 ± 31 mg LCFA/L, respectively. Pork fat particle degradation was mainly controlled by LCFA oxidation rate and, to a lesser extent, by neutral fat hydrolysis rate. Hydrolysis pretreatment of fat‐containing wastewaters and sludges should not substantially accelerate their anaerobic treatment. At a Din of 450 μm, fat particles were found to inhibit methane production during the initial 20 h of digestion. Inhibition of methane production in the early phase of digestion was the only significant effect of fat particle size on anaerobic digestion of pork slaughterhouse wastewater. Soluble COD could not be used to determine the rate of lipid hydrolysis due to LCFA adsorption on the biomass. © 2002 Government of Canada. Exclusive worldwide publication rights in the article have been transferred to Wiley Periodicals, Inc. Biotechnol Bioeng 79: 43–52, 2002.
The metabolic burden of the PGK1 and ADH2 promoter systems for heterologous xylanase production by Saccharomyces cerevisiae in defined medium
Authors: Görgens Johann F. , van Zyl Willem H. , Knoetze Johannes H. , Hahn‐Hägerdal Bärbel
Published: August 2002

Five recombinant S. cerevisiae strains were cultivated under identical conditions to quantify the molecular basis of the metabolic burden of heterologous gene expression, and to evaluate mechanisms for the metabolic burden. Two recombinant S. cerevisiae strains, producing Trichoderma reesei xylanase II under control of either the PGK1 or ADH2 promoters, were compared quantitatively with three references strains, where either the heterologous xylanase II (XYN2) gene, or the heterologous gene and the promoter and terminator were omitted from the recombinant plasmid. Neither the replication of multiple copies of the 2‐μm‐based YEp352 plasmid nor the replication the foreign XYN2 gene represented a metabolic burden to the cell, as the growth of the host organism was not affected. The inclusion of a glycolytic promoter on the recombinant plasmid, however, reduced the maximum specific growth rate (12% to 15%), biomass yield on glucose (8% to 11%), and specific glucose consumption rate (6% to 10%) of the recombinant strains. The presence of the heterologous XYN2 gene on the recombinant plasmid caused a further reduction in the maximum specific growth rate (11% to 14%), biomass yield (4%), and specific glucose consumption rate (12%) of the host strain during active gene expression, which was dictated by the regulatory characteristics of the promoter utilized. The metabolic effect of foreign gene expression was disproportionally large, with respect to on the amount of heterologous protein produced. This was most likely due to an increased energetic demand for the expression of a foreign gene and/or a competition for limiting amounts of transcription or translation factors, biosynthetic precursors or metabolic energy. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 238–245, 2001.
A multivariate approach to combine univariate calibration information
Authors: Liao Jason J. Z.
Published: August 2002

It is common practice to calibrate a common value by combining information from different sources, e.g. days, instruments, laboratories, etc. Under each individual source a perfect univariate calibration can be used to calibrate the unknown. Then the common unknown can be estimated by combining the estimates from each source as a weighted mean (Johnson DJ, Krishnamoorthy K. J. Am. Statist. Assoc. 1996; 91: 1707–1715). However, this estimator can be obtained as a special solution directly from a multivariate calibration setting by combining information first and then estimating the common value. Two data sets were analyzed and they showed that the multivariate approach can possibly improve the univariate approach based on the closeness criterion. Copyright © 2001 John Wiley & Sons, Ltd.
Identification of membrane proteins in the hyperthermophilic archaeon Pyrococcus furiosus using proteomics and prediction programs
Authors: Holden James F. , Poole Farris L. , Tollaksen Sandra L. , Giometti Carol S. , Lim Hanjo , Yates John R. , Adams Michael W. W.
Published: August 2002

Cell‐free extracts from the hyperthermophilic archaeon Pyrococcus furiosus were separated into membrane and cytoplasmic fractions and each was analyzed by 2D‐gel electrophoresis. A total of 66 proteins were identified, 32 in the membrane fraction and 34 in the cytoplasmic fraction. Six prediction programs were used to predict the subcellular locations of these proteins. Three were based on signal‐peptides (SignalP, TargetP, and SOSUISignal) and three on transmembrane‐spanning α‐helices (TSEG, SOSUI, and PRED‐TMR2). A consensus of the six programs predicted that 23 of the 32 proteins (72%) from the membrane fraction should be in the membrane and that all of the proteins from the cytoplasmic fraction should be in the cytoplasm. Two membrane‐associated proteins predicted to be cytoplasmic by the programs are also predicted to consist primarily of transmembrane‐spanning β‐sheets using porin protein models, suggesting that they are, in fact, membrane components. An ATPase subunit homolog found in the membrane fraction, although predicted to be cytoplasmic, is most likely complexed with other ATPase subunits in the membrane fraction. An additional three proteins predicted to be cytoplasmic but found in the membrane fraction, may be cytoplasmic contaminants. These include a chaperone homolog that may have attached to denatured membrane proteins during cell fractionation. Omitting these three proteins would boost the membrane‐protein predictability of the models to near 80%. A consensus prediction using all six programs for all 2242 ORFs in the P. furiosus genome estimates that 24% of the ORF products are found in the membrane. However, this is likely to be a minimum value due to the programs' inability to recognize certain membrane‐related proteins, such as subunits associated with membrane complexes and porin‐type proteins. Copyright © 2001 John Wiley & Sons, Ltd.
A genomic approach for the identification and classification of genes involved in cell wall formation and its regulation in Saccharomyces cerevisiae
Authors: de Groot Piet W. J. , Ruiz Cristina , Vázquez de Aldana Carlos R. , Dueňas Encarnación , Cid Víctor J. , Del Rey Francisco , Rodríquez‐Peña José M. , Pérez Pilar , Andel Annemiek , Caubín Julio , Arroyo Javier , García Juan C. , Gil Concha , Molina María , García Luis J. , Nombela César , Klis Frans M.
Published: August 2002

Using a hierarchical approach, 620 non‐essential single‐gene yeast deletants generated by EUROFAN I were systematically screened for cell‐wall‐related phenotypes. By analyzing for altered sensitivity to the presence of Calcofluor white or SDS in the growth medium, altered sensitivity to sonication, or abnormal morphology, 145 (23%) mutants showing at least one cell wall‐related phenotype were selected. These were screened further to identify genes potentially involved in either the biosynthesis, remodeling or coupling of cell wall macromolecules or genes involved in the overall regulation of cell wall construction and to eliminate those genes with a more general, pleiotropic effect. Ninety percent of the mutants selected from the primary tests showed additional cell wall‐related phenotypes. When extrapolated to the entire yeast genome, these data indicate that over 1200 genes may directly or indirectly affect cell wall formation and its regulation. Twenty‐one mutants with altered levels of β1,3‐glucan synthase activity and five Calcofluor white‐resistant mutants with altered levels of chitin synthase activities were found, indicating that the corresponding genes affect β1,3‐glucan or chitin synthesis. By selecting for increased levels of specific cell wall components in the growth medium, we identified 13 genes that are possibly implicated in different steps of cell wall assembly. Furthermore, 14 mutants showed a constitutive activation of the cell wall integrity pathway, suggesting that they participate in the modulation of the pathway either directly acting as signaling components or by triggering the Slt2‐dependent compensatory mechanism. In conclusion, our screening approach represents a comprehensive functional analysis on a genomic scale of gene products involved in various aspects of fungal cell wall formation. Copyright © 2001 John Wiley & Sons, Ltd.
Synthesis, resolution, and investigation of the rotational interconversion process of atropisomeric 1,n‐diaza[n]paracyclophanes using cyclodextrin‐mediated capillary zone electrophoresis
Authors: Scharwächter Klaus P. , Hochmuth Detlev H. , Dittmann Helmutt , König Wilfried A.
Published: August 2002

A number of variously monosubstituted 1,n‐diaza[n]paracyclophanes (n = 10–12), which show planar chirality and atropisomerism due to hindered rotation about single bonds, were synthesized via a classical route to analyze their stereodynamic properties. Racemic analytes with 10‐ and 11‐membered bridges were resolved by capillary zone electrophoresis (CZE) in acidic phosphate buffers (pH 2.5–4.5) employing permethylated β‐ and γ‐cyclodextrin as chiral additives. Moreover, cyclodextrin mediated CZE was used in a discontinuously driven mode for investigations of the rotational interconversion process of conformationally labile homologues (n = 11). In stopped‐flow experiments, after baseline separation enantiomers were partially enantiomerized in situ inside the capillary by heating. The rate constants (kenan= ½krac) and rotational energy barriers (ΔG≠) were determined from the resulting enantiomeric ratios. Energy barriers between 113–126 kJ/mol were found depending on the substituent of the benzene ring and the degree of ionization of the amino groups in bridgehead positions. The energy barriers increased in order of the substituents: NO2>> CF3> Br > Cl > CH3≈ F. In addition, the rotational energy barriers were decreased by approximately 6–8 kJ/mol in the presence of the chiral selector. Chirality 13:679–690, 2001. © 2001 Wiley‐Liss, Inc.
Solvent‐dependent enantioselective interaction of some bis‐allylamide chiral selectors studied by NMR
Authors: Skogsberg Urban , Thunberg Linda , Allenmark Stig
Published: August 2002

A series of chiral selectors, all of them bis‐allylamides of C2‐symmetric dicarboxylic acids, were studied by NMR in different solvents in an attempt to affect the equilibria between free selector and the diastereomeric complexes formed by its interaction with the (+)‐ and (−)‐forms of O,O′‐dibenzoyltartaric acid (DBTA). The results show that by changing the polarity of the solvent the equilibria are displaced, as observed from changing chemical shift differences. Phase‐sensitive 1H{1H}‐NOESY experiments revealed different interactions between the chiral selector and the analyte enantiomers. The individual equilibrium constants were determined by separate studies of the equilibria between the selector and the respective enantiomers of the chiral DBTA probe. Chirality 13:272–278, 2001. © 2001 Wiley‐Liss, Inc.
Resolution, configurational assignment, and enantiopharmacology at glutamate receptors of 2‐amino‐3‐(3‐carboxy‐5‐methyl‐4‐isoxazolyl)propionic acid (ACPA) and demethyl‐ACPA
Authors: Johansen Tommy N. , Stensbøl Tine B. , Nielsen Birgitte , Vogensen Stine B. , Frydenvang Karla , Sløk Frank A. , Brünum;uner‐Osborne Hans , Madsen Ulf , Krogsgaard‐Larsen Povl
Published: August 2002

We have previously described (RS)‐2‐amino‐3‐(3‐carboxy‐5‐methyl‐4‐isoxazolyl)propionic acid (ACPA) as a potent agonist at the (RS)‐2‐amino‐3‐(3‐hydroxy‐5‐methyl‐4‐isoxazolyl)propionic acid (AMPA) receptor subtype of (S)‐glutamic acid (Glu) receptors. We now report the chromatographic resolution of ACPA and (RS)‐2‐amino‐3‐(3‐carboxy‐4‐isoxazolyl)propionic acid (demethyl‐ACPA) using a Sumichiral OA‐5000 column. The configuration of the enantiomers of both compounds have been assigned based on X‐ray crystallographic analyses, supported by circular dichroism spectra and elution orders on chiral HPLC columns. Furthermore, the enantiopharmacology of ACPA and demethyl‐ACPA was investigated using radioligand binding and cortical wedge electrophysiological assay systems and cloned metabotropic Glu receptors. (S)‐ACPA showed high affinity in AMPA binding (IC50 = 0.025 μM), low affinity in kainic acid binding (IC50 = 3.6 μM), and potent AMPA receptor agonist activity on cortical neurons (EC50 = 0.25 μM), whereas (R)‐ACPA was essentially inactive. Like (S)‐ACPA, (S)‐demethyl‐ACPA displayed high AMPA receptor affinity (IC50 = 0.039 μM), but was found to be a relatively weak AMPA receptor agonist (EC50 = 12 μM). The stereoselectivity observed for demethyl‐ACPA was high when based on AMPA receptor affinity (eudismic ratio = 250), but low when based on electrophysiological activity (eudismic ratio = 10). (R)‐Demethyl‐ACPA also possessed a weak NMDA receptor antagonist activity (IC50 = 220 μM). Among the enantiomers tested, only (S)‐demethyl‐ACPA showed activity at metabotropic receptors, being a weak antagonist at the mGlu2 receptor subtype (KB = 148 μM). Chirality 13:523–532, 2001. © 2001 Wiley‐Liss, Inc.
Lack of desmin results in abortive muscle regeneration and modifications in synaptic structure
Authors: Agbulut Onnik , Li Zhenlin , Périé Sophie , Ludosky Marie‐Aline , Paulin Denise , Cartaud Jean , Butler‐Browne Gillian
Published: August 2002

Desmin, a muscle‐specific intermediate filament protein, is expressed in all muscle tissues. Its absence leads to a multisystemic disorder involving cardiac, skeletal, and smooth muscles. In skeletal muscle, structural abnormalities include lack of alignment of myofibrils, Z disk streaming, and focal muscle degeneration. In this study, we have examined the consequences of an absence of desmin on the mechanisms of regeneration and the integrity of the neuromuscular junction. The muscles of desmin knock‐out and wild‐type mice were made to regenerate by injecting cardiotoxin and were examined 7 to 42 days following the injection. The absence of desmin resulted in a delayed and modified regeneration and an accumulation of adipocytes. This was associated with a persistence of small diameter muscle fibers containing both N‐CAM and developmental myosin isoforms. The amount of the slow myosin was increased, whereas there was a decrease in the fast isoform in the regenerated muscles of desmin knock‐out mice. Both regeneration and aging led to the appearance of elongated neuromuscular junctions with diffuse acetylcholinesterase staining and a decrease in the overall acetylcholinesterase activity in the muscles of these mice. The neuromuscular junctions were markedly disorganised and in some cases postjunctional folds were absent. We conclude that desmin is essential for terminal muscle regeneration, maturation of muscle fibers, and maintaining the complex folded structure of the postsynaptic apparatus of the neuromuscular junctions. Cell Motil. Cytoskeleton 49:51–66, 2001. © 2001 Wiley‐Liss, Inc.
Motional smearing of electrically recovered couplings measured from multipulse transients
Authors: Riley Scott A. , Vyas Shashi , Augustine Matthew P.
Published: August 2002

The measurement of residual dipolar and quadrupolar coupling constants in the liquid phase by using an electric field to destroy the isotropic nature of molecular tumbling is complicated by charge‐induced turbulent motion. In many cases this motion is due to charge injection at electrode surfaces, an effect that leads to an apparent removal of electrically recovered anisotropic spectral splittings when measured from a spin‐echo envelope modulation produced by a train of radio frequency (rf) pulses. To understand this averaging, the effect of quadrupolar couplings and enhanced molecular diffusion on free‐induction, spin‐echo, and Carr–Purcell signals is analytically determined in the special case of homogeneous rf pulses. Additional signal damping due to rf inhomogeneity and coupling constant heterogeneity is determined by numerically extending the kernel formalism introduced by Herzog and Hahn to understand spin diffusion in solids. Finally, the merit of the numerical approach is tested by comparison with analytical results for homogeneous rf pulses and experimental results for perdeuterated nitrobenzene involving inhomogeneous rf pulses and coupling heterogeneity. © 2001 John Wiley & Sons, Inc. Concepts Magn Reson 13: 171–189, 2001
Physical exercise and immune system function in cancer survivors
Authors: Fairey Adrian S. , Courneya Kerry S. , Field Catherine J. , Mackey John R.
Published: August 2002

BACKGROUND

There are a limited number of interventions for cancer survivors following completion of primary therapy that might reduce the risk of cancer recurrence and/or secondary malignancies and increase survival times. It has been proposed that physical exercise may be beneficial by enhancing the anticancer immune system response. The purpose of the current article is to: 1) briefly describe the immune system response to tumors, 2) discuss the impact of anticancer therapy on immune system function in cancer survivors, 3) provide a systematic and comprehensive review of the extant literature examining physical exercise and immune system function in cancer survivors, and 4) offer a critical analysis of this literature and outline directions for future research.

METHODS

A comprehensive literature search up to March 2001 identified empirical articles that examined the effects of physical exercise training on immune system function in cancer survivors from CD‐ROM database searches and manual searches.

RESULTS

To the authors' knowledge, six empirical studies published between 1994 and 2000 have examined physical exercise and immune system function in cancer survivors. Overall, four out of six studies reported statistically significant improvements in a number of cancer‐related immune system components as a result of exercise. However, there are several limitations that must be considered when interpreting the findings of these studies. These limitations involve the samples, designs, physical exercise interventions, physical fitness assessments, and immunologic assessments.

CONCLUSIONS

Additional research is needed to determine if physical exercise in cancer survivors may reduce the risk of cancer recurrence and secondary malignancies and increase survival times. Cancer 2002;94:539–51. © 2002 American Cancer Society.
A population‐based study of pediatric anaplastic large cell lymphoma
Authors: Alessandri Angela J. , Pritchard Sheila L. , Schultz Kirk R. , Massing Bonnie G.
Published: August 2002

BACKGROUND

Anaplastic large cell lymphoma (ALCL) is a relatively rare form of non‐Hodgkin lymphoma (NHL) in children constituting 10–15% of this entity. To the authors' knowledge, there are no population‐based pediatric studies in the literature, and incidence estimates have not been attempted.

METHODS

A population‐based study of all children in British Columbia, Canada, younger than 15 years of age presenting between January 1988 and December 1999 with an immunohistologically confirmed diagnosis of CD30+ ALCL was completed. Demographic, ethnic, clinical, treatment, and outcome details were collected on all patients. Population figures were obtained from census data through the BC STATS.

RESULTS

Ten patients were identified and confirmed to have ALCL on the basis of morphology and immunohistochemical stains. This equates to an annual incidence of 1.2 per million children younger than 15 years of age. The mean age at diagnosis was 8.23 years with a range of 1.4–13.0 years. There was an overrepresentation of East and Southeast Asian patients (40%) in the ALCL group compared with other subtypes of NHL and the pediatric population of British Columbia. Twenty percent of the patients had evidence of central nervous system (CNS) disease at diagnosis.

CONCLUSIONS

The annual incidence of ALCL in children younger than 15 years of age in British Columbia is 1.2 per million. The overrepresentation of East and Southeast Asian ethnic origin remains unexplained. The rate of CNS involvement is much higher than that previously reported in large non‐population‐based series (0–3%). Although the low numbers do not allow firm conclusions, it would seem prudent to continue to investigate all newly diagnosed patients for CNS involvement in British Columbia. Cancer 2002;94:1830–5. © 2002 American Cancer Society.

DOI 10.1002/cncr.10396
Early development of the retina and pineal complex in the sea lamprey: Comparative immunocytochemical study
Authors: Meléndez‐Ferro Miguel , Villar‐Cheda Begoña , Manoel Abalo Xesús , Pérez‐Costas Emma , Rodríguez‐Muñoz Rolando , Degrip Willem J. , Yáñez Julián , Rodicio María Celina , Anadón Ramón
Published: August 2002

Lampreys have a complex life cycle, with largely differentiated larval and adult periods. Despite the considerable interest of lampreys for understanding vertebrate evolution, knowledge of the early development of their eye and pineal complex is very scarce. Here, the early immunocytochemical organization of the pineal complex and retina of the sea lamprey was studied by use of antibodies against proliferating cell nuclear antigen (PCNA), opsin, serotonin, and γ‐aminobutyric acid (GABA). Cell differentiation in the retina, pineal organ, and habenula begins in prolarvae, as shown by the appearance of PCNA‐negative cells, whereas differentiation of the parapineal vesicle was delayed until the larval period. In medium‐sized to large larvae, PCNA‐immunoreactive (‐ir) cells were numerous in regions of the lateral retina near the differentiated part of the larval retina (central retina). A late‐proliferating region was observed in the right habenula. Opsin immunoreactivity appears in the pineal vesicle of early prolarvae and 3 or 4 days later in the retina. In the parapineal organ, opsin immunoreactivity was observed only in large larvae. In the pineal organ, serotonin immunoreactivity was first observed in late prolarvae in photoreceptive (photoneuroendocrine) cells, whereas only a few of these cells appeared in the parapineal organ of large larvae. No serotonin immunoreactivity was observed in the larval retina. GABA immunoreactivity appeared earlier in the retina than in the pineal complex. No GABA‐ir perikaryon was observed in the retina of larval lampreys, although a few GABA‐ir centrifugal fibers innervate the inner retina in late prolarvae. First GABA‐ir ganglion cells occur in the pineal organ of 15–17 mm larvae, and their number increases during the larval period. The only GABA‐ir structures observed in the parapineal ganglion of larvae were afferent fibers, which appeared rather late in development. The time sequence of development in these photoreceptive structures is rather different from that observed in teleosts and other vertebrates. This suggests that the unusual development of the three photoreceptive organs in lampreys reflects specialization for their different functions during the larval and adult periods. J. Comp. Neurol. 442:250–265, 2002. © 2001 Wiley‐Liss, Inc.
Intact sorting, targeting, and clustering of γ‐aminobutyric acid A receptor subtypes in hippocampal neurons in vitro
Authors: Brünig Ina , Scotti Eleonora , Sidler Corinne , Fritschy Jean‐Marc
Published: August 2002

The cellular and subcellular distribution of four GABAA receptor subtypes, identified by the presence of the α1, α2, α3, or α5 subunit, was investigated immunocytochemically in dissociated cultures of hippocampal neurons. We addressed the questions whether (1) cell‐type specific expression, (2) axonal/somatodendritic targeting, and (3) synaptic/extrasynaptic clustering of GABAA receptor subtypes was retained in vitro. For comparison, the in vivo distribution pattern was assessed in sections from adult rat brain. The differential expression of GABAA receptor subunits allowed to identify five morphologically distinct cell types in culture: the α1 subunit was observed in glutamic acid decarboxylase–positive interneurons, the α2 and α5 subunits marked pyramidal‐like cells, and the α3 subunit labeled three additional cell types, including presumptive hilar cells. All subunits were found in the somatodendritic compartment. In addition, appropriate axonal targeting was evidenced by the intense α2, and sometimes α3 subunit labeling of axon‐initial segments (AIS) of pyramidal cells and hilar cells, respectively. Accordingly, both receptor subtypes were targeted to AIS in vivo, as well. Synaptic receptors were identified by colocalization with gephyrin, a postsynaptic clustering protein, and apposition to presynaptic terminals labeled with synapsin I. In vitro and in vivo, α1‐ and α2‐receptor subtypes formed numerous synaptic clusters, α3‐GABAA receptors were located either synaptically or extrasynaptically depending on the cell type, whereas α5‐GABAA receptors were extrasynaptic. We conclude that receptor targeting to broad subcellular locations does not require specific GABAergic innervation patterns, which are disturbed in vitro, but depends on protein‐protein interactions in the postsynaptic cell that are both subunit‐ and neuron‐specific. J. Comp. Neurol. 443:43–55, 2002. © 2002 Wiley‐Liss, Inc.
Localization of P2X3 receptors and coexpression with P2X2 receptors during rat embryonic neurogenesis
Authors: Cheung Kwok‐Kuen , Burnstock Geoffrey
Published: August 2002

It is well known that extracellular ATP mediates rapid excitatory signaling by means of the ionotropic P2X receptors. One of its subunits, the P2X3 receptor, is well documented to be associated with sensory innervation in adult animals. It is speculated that the P2X3 receptor may have already been present in the early sensory system. The aim of this study was to investigate the distribution of the P2X3 receptor during neurogenesis by using immunohistochemistry on rat embryos from embryonic day (E)9.5–18.5. The P2X3 receptor was first identified in the hindbrain neural tube and the sensory ganglia in E11–11.5 embryos. At E14.5, the optic tract and retina, nucleus tractus solitarius, mesencephalic trigeminal nucleus, and sensory nerves in both respiratory and digestive tract showed positive staining. The facial nucleus, the prepositus hypoglossal nucleus, and the sympathetic ganglia also showed P2X3 immunoreactivity, even though these are not sensory associated. P2X3 immunoreactivity was detected in the vestibular nucleus, the nerves in mesentery, bladder, and kidney in E16.5 and in nerves in vibrissae in E18.5. P2X3 immunoreactivity in the facial nucleus, spinal trigeminal tract, the mesencephalic trigeminal nucleus, and the vestibular nucleus were undetectable in postnatal day 16 rat brainstem. The P2X3 receptor was coexpressed with the P2X2 receptor in nucleus tractus solitarius, dorsal root ganglion, nodose ganglion, and the taste bud in E16.5 embryo, which was 5 days later than the first appearance of the native P2X3 receptor. In summary, we present a detailed expression pattern of the P2X3 receptor during neurogenesis and report that P2X3 immunoreactivity is down‐regulated in early postnatal brainstems. J. Comp. Neurol. 443:368–382, 2002. © 2002 Wiley‐Liss, Inc.