bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of retention on traditional alkyl, polar endcapped, and polar embedded group stationary phases
Authors: Coym Jason W.
Published: May 2008

The development of new RP stationary phases containing polar groups has provided the chromatographer with a variety of stationary phase choices with differing selectivities. Polar endcapped and polar embedded group stationary phases have found use in solving a wide variety of separation problems, especially for the efficient separation of organic bases as well as separations necessitating the use of highly aqueous mobile phases. In this report, the retention thermodynamics of small, nonpolar solutes on traditional alkyl, polar endcapped, and polar embedded group stationary phases are compared. It is found that the nonpolar (methylene) transfer enthalpy is less favorable when polar embedded group phases are used, when compared to traditional or polar endcapped phases. In contrast, the transfer enthalpy of a phenyl group is found to be more favorable when a polar endcapped phase is used. In addition, the retention characteristics of these phases are compared using a set of solutes with differing solvatochromic parameters. Hydrogen‐bond acids appear to have enhanced retention on polar embedded group phases, while hydrogen‐bond bases have enhanced retention on polar endcapped phases.
Optimisation of the GC‐MS conditions for the determination of the 15 EU foodstuff priority polycyclic aromatic hydrocarbons
Authors: Bordajandi Luisa R. , Dabrio Marta , Ulberth Franz , Emons Hendrik
Published: May 2008

European legislation has recently established a list of 15 priority polycyclic aromatic hydrocarbons (PAHs) to be monitored in foodstuff. Thus, the accurate determination of these compounds has become a highly relevant issue. The fact that some of these European Union (EU) PAHs differ from those typically analysed, requires the re‐evaluation of the instrumental conditions for the proper determination of the new target compounds. In this study, the influence of the stationary phase and dimensions of the GC capillary column on the chromatographic resolution of the 15 EU PAHs has been investigated. Apolar (DB‐5 type) and medium polar (DB‐17 type) stationary phases with different lengths and film thickness have been evaluated for the separation of the target compounds, with special emphasis on those coelutions involving isomers such as the three benzofluoranthenes included in the EU PAHs. In addition, the influence of the injection technique and the column dimensions on the recovery of the high molecular mass PAHs has been studied. A programmable temperature vaporising (PTV) injector has been used in three different operational modes and the results were compared to those obtained using on‐column injection. The experimental parameters involved in the injection step were optimised by using experimental design.
A simple HPLC‐MS method for the quantitative determination of the composition of bacterial medium chain‐length polyhydroxyalkanoates
Authors: Grubelnik Andreas , Wiesli Luzia , Furrer Patrick , Rentsch Daniel , Hany Roland , Meyer Veronika R.
Published: May 2008

Bacterial poly(hydroxyalkanoates) (PHAs) vary in the composition of their monomeric units. Besides saturated side‐chains, unsaturated ones can also be found. The latter leads to unwanted by‐products (THF ester, secondary alcohols) during acidic cleavage of the polymer backbone in the conventional analytical assays. To prevent these problems, we developed a new method for the reductive depolymerization of medium chain‐length PHAs, leading to monomeric diols that can be separated and quantified by HPLC/MS. Reduction is performed at room temperature with lithium aluminum hydride within 5–15 min. The new method is faster and simpler than the previous ones and is quantitative. The results are consistent with the ones obtained by quantitative 1H NMR.
On building better construct measures: Implications of a general hierarchical model
Authors: Mowen John C. , Voss Kevin E.
Published: May 2008

Four problems occur in the scale development process: (a) defining the construct, (b) drawing items from multiple domains, (c) identifying dimensions, and (d) showing nomological validity. In order to minimize these problems, the authors propose a general hierarchical model (GHM) that provides an organizational structure for placing many of the individual difference constructs used in marketing and consumer behavior. Three principles, which were derived from the GHM, add to the current scale development paradigm: (a) Define and test the construct within a hierarchical network that includes antecedents and consequences, (b) define and test the construct's dimensionality, and (c) match the construct's items to its level in the hierarchical system. By using these steps in scale development, researchers can build more precise measures possessing higher levels of validity and reliability. © 2008 Wiley Periodicals, Inc.
Understanding the role of retail store service in light of self‐image–store image congruence
Authors: O'Cass Aron , Grace Debra
Published: May 2008

The relationships among a consumer's service experience, the servicescape, and perceived value for the money spent on the service are important theoretical as well as practical issues. Little effort has, however, been devoted to understanding these in the context of the effects of consumer image–store image congruency. Image congruency has not only been shown to be valuable in relation to product choices, but has also been shown to contribute to our understanding of retail store choice and preferences. This study examines the effect of retailer service provision and the retail store environment (servicescape) on the customers' perception of value for money. The study also examines the role of self–store image congruence in the above relationships. The findings confirm the hypothesized relationships in the conceptual model (except for servicescape effects). The findings also indicate that the effects are stronger for those individuals experiencing high self–store image congruence. © 2008 Wiley Periodicals, Inc.
α‐Melanocyte stimulating hormone and adrenocorticotropic hormone: An alternative approach when thinking about restless legs syndrome?
Authors: Koo Brian B. , Feng Pingfu , Dostal Jesse , Strohl Kingman P.
Published: May 2008

α‐Melanocyte stimulating hormone (α‐MSH) and adrenocorticotropic hormone (ACTH) possess properties suggesting that they may be involved in the pathogenesis of restless legs syndrome (RLS). We sought to determine if α‐MSH and ACTH when administered centrally in rat recapitulate features reminiscent of RLS: increased activity, sleep fragmentation, and periodic movements during sleep. Rats were instrumented with electroencephalography, electromyography, and intracerebral cannulae and recorded for the measurement of sleep, periodic movements, and behavior following intracerebroventricular administration of α‐MSH, ACTH, or saline. Studied behavior included grooming, locomotion, and rearing during wake and limb movements during sleep. Vigilance states included active wake (AW), quiet wake (QW), slow wave sleep I (SWSI), slow wave sleep II (SWSII), and paradoxical sleep (PS). All rats received normal saline acting as their own controls. Different rats received α‐MSH in doses of 0.05, 0.5, 1.0, 2.0, and 6.0 μg or ACTH in doses of 0.5, 1.0, and 2.0 μg. Administered α‐MSH caused an increase in waking behavior and prolongation of sleep latency, while ACTH stimulated waking behavior and fragmented sleep, yielding more AW and less SWSII and PS. Both hormones increased periodic movements during sleep. When administered centrally in rat, α‐MSH and ACTH stimulate motor activity in wake, cause changes in sleep architecture, and increase periodic movements in sleep. These melanocortin hormones may play a role in the pathogenesis of RLS. © 2008 Movement Disorder Society
Treadmill walking in Parkinson's disease patients: Adaptation and generalization effect
Authors: Bello Olalla , Sanchez Jose Andres , Fernandez‐del‐Olmo Miguel
Published: May 2008

We examined the adaptation and generalization effect of one familiarization treadmill walking session on gait in patients with Parkinson's disease (PD) with different degrees of disease severity. Eight moderate PD patients (Hoehn and Yahr stage 2–2.5), eight advanced PD patients (Hoehn and Yahr 3), and eight matched control subjects participated in this study. Subjects first walked overground on a 10‐m walkway at a self‐selected speed (pretreadmill). They then performed a 20‐min treadmill training session, followed by three trials of overground walking (Post1, Post2, Post3). Cadence, step length, speed, and coefficient of variation of stride time (CV) were recorded. During the treadmill session the advanced PD patients significantly decreased their cadence (t = 3.9, P ≤ 0.01) and increased their step length (t = 4.27, P ≤ 0.01) compared with pretreadmill walking. After the treadmill, all subjects walked overground significantly faster (F = 16.51 P ≤ 0.001) and with a larger step length (F = 13.03 P ≤ 0.01) than pretreadmill walking. The present study shows a specific adaptation to walk over the treadmill for the advanced PD patients. Moreover, this confirms the potential therapeutic use of the treadmill for PD gait rehabilitation since a single familiarization session lead to an increase in the step length and thus to the improvement of the main gait impairment in PD. © 2008 Movement Disorder Society
Numerical solution of Fokker‐Planck equation using the cubic B‐spline scaling functions
Authors: Lakestani Mehrdad , Dehghan Mehdi
Published: May 2008

In this article a numerical technique is presented for the solution of Fokker‐Planck equation. This method uses the cubic B‐spline scaling functions. The method consists of expanding the required approximate solution as the elements of cubic B‐spline scaling function. Using the operational matrix of derivative, the problem will be reduced to a set of algebraic equations. Some numerical examples are included to demonstrate the validity and applicability of the technique. The method is easy to implement and produces very accurate results. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Radiation risks from imaging studies in children with cancer
Authors: Robbins Elizabeth
Published: May 2008

Individuals exposed to high doses of ionizing radiation are known to be at risk of developing cancer. Recent reviews about the late effects of ionizing radiation indicate that even low doses of radiation can cause cancer. Significant radiation exposure occurs with commonly used imaging studies including CT scans, PET scans, and bone scans. Children with cancer, particularly those children with solid tumors, are exposed to frequent low doses of ionizing radiation from multiple imaging studies performed at initial diagnosis, throughout treatment, and during the follow‐up period. This review provides estimates of cumulative radiation doses from imaging studies in children undergoing chemotherapy and/or surgery for various malignancies. Current risk estimates indicate that the radiation exposure from these imaging studies may be sufficient to increase the lifetime risk of cancer. Pediatr Blood Cancer 2008;51:453–457. © 2008 Wiley‐Liss, Inc.
A facile route to hollow superparamagnetic magnetite/polystyrene nanocomposite microspheres via inverse miniemulsion polymerization
Authors: Yang Song , Liu Huarong , Zhang Zhicheng
Published: May 2008

In this article, we report a facile route to the preparation of hollow superparamagnetic magnetite/polystyrene nanocomposite microspheres via inverse miniemulsion polymerization at room temperature and under ambient pressure. Water droplets act as a soft template for the formation of hollow structure. Meanwhile, the existence of amphipathic magnetite nanoparticles (MPs) which can assemble at the interface of W/O is favorable to the interfacial polymerization of styrene, ensuring the formation of hollow nanocomposite microspheres. The final products were thoroughly characterized by X‐ray powder diffraction (XRD), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field‐emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and X‐ray photoelectron spectroscopy (XPS), which showed the formation of hollow magnetite/polystyrene nanocomposite microspheres. Magnetic hysteresis loop measurements revealed that both MPs and hollow nanocomposite microspheres displayed superparamagnetism. The effects of the content of H2O, sorbitan monooleate (Span 80) and styrene and the dose rate on the morphology of nanocomposite microspheres were studied. Furthermore, the mechanism of the formation of the hollow magnetic microspheres was also discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3900–3910, 2008
Study on the shear viscosity behavior of keratin/PEO blends for nanofibre electrospinning
Authors: Varesano Alessio , Aluigi Annalisa , Vineis Claudia , Tonin Claudio
Published: May 2008

Graessley's theory has been applied to keratin/PEO concentrated aqueous solutions giving qualitative insight to the rheology of these polymer blends in electrospinning. The shear rate dependent viscosity of different blends was compared with that of pure polymer solutions. The characteristic time τη was calculated by the minimum value of $ \dot \gamma $ at the beginning of the non‐Newtonian viscosity behavior. Flow curves of PEO (at concentration from 1.0 to 7.0 wt %) reduce to a single curve by plotting η/η0 against $ \dot \gamma{\tau_\eta} $. Moreover, PEO solutions exhibit a linear proportionality between zero‐shear viscosity and the characteristic time η0 ∝ τη. Keratin/PEO blend solutions follow the same proportionality at very high and low keratin content, whereas linearity drops when the keratin content range from 50 to 70%. The departure from the theory has been interpreted as a sign of some interaction between the macromolecules of keratin and PEO. It was supposed that keratin displaces solvent molecules and expands the PEO chain coils increasing the relaxation time of the polymer solution. This behavior was correlated with changes in the morphology of the nanofibres produced by electrospinning from these polymer blends. Finally, additive rules to zero‐shear viscosity were applied to keratin and PEO solutions, indicating that the experimental η0 values were higher than the theoretical ones for all the proportions of the blends, especially for high keratin amount. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1193–1201, 2008
Preparation and characterization of vinylidene chloride‐co‐vinyl chloride copolymer/fluorinated synthetic mica nanocomposites I thermal and mechanical properties studies
Authors: Hsieh Tar‐Hwa , Huang Jan‐Kuan , Ho Ko‐Shan , Bi Xiaotao , Ho Tsung‐Han , Yang Shin‐Shiao , Chang Yu‐Chen
Published: May 2008

Poly(vinylidene chloride‐co‐vinylchloride)/organically modified fluorinated synthetic mica (MEE) (VDC‐VC/MEE) nanocomposites were prepared by melt blending of VDC‐VC copolymer with MEE, in the presence of dioctyl phthalate (DOP) which acted as a plasticizer and a cointercalating agent. The nanostructure, thermal, and dynamic mechanical properties of the VDC‐VC/MEE nanocomposites were studied by wide angle X‐ray diffractometer (WAXD), scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and dynamic mechanical analyzer (DMA). It was found that partially intercalated and partially exfoliated structures coexisted in VDC‐VC/MEE nanocomposities. Below 8 wt % MEE content, the intercalation effect of nanocomposites decreased with increasing the MEE content. Under a nitrogen atmosphere, VDC‐VC/MEE nanocomposites exhibited a single step thermal degradation behavior. The nanostructure of VDC‐VC/MEE can effectively prevent volatile gases from being released, and thus enhances its thermal stability. The thermal stability of VDC‐VC/MEE nanocomposites is strongly related to the morphology of nanocomposites and the degraded composites structure. DMA revealed a significant improvement in the storage modulus within the testing temperature range. The increase in storage modulus depends on the MEE content, which is attributed to the dispersed phase morphology. The glass transition temperature of VDC‐VC/MEE nanocomposites is affected by the chain mobility in the nanocomposites rather than the aggregative morphology. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1214–1225, 2008
Morphology and properties of cyanate ester/liquid polyurethane/silica nanocomposites
Authors: Zhang Qi‐Lu , Ma Xiao‐Yan , Liang Guo‐Zheng , Qu Xiao‐Hong , Huang Yun , Wang Shu‐Hui , Kou Kai‐Chang
Published: May 2008

The high‐speed homogeneous shearing method was applied to prepare nanocomposites of cyanate ester (CE) with liquid polyurethane elastomer (PUR) and silica. To investigate the influence of various components on the morphology and properties of the ternary composites, the binary composites of CE/PUR and CE/silica were also involved in this article. The morphology of the cured materials of binary and ternary systems was investigated by transmission electron microscopy (TEM), and the results show that silica nanoparticles were uniformly distributed in the ternary and binary matrix. Phase separation of elastomer in composites was not observed by TEM. FTIR test and dynamic mechanical analysis (DMA) proved that chemical linking was existent between PUR and CE. Scanning electron microscopy examinations and mechanical properties tests were carried out. The results show that ternary composites displayed higher fracture toughness and impact strength compared with most of the binary systems. This suggests that the addition of PUR and nanosilica can synergistically improve the toughness of CE. DMA studies confirmed that the incorporation of silica can increase the storage modulus and Tg for CE and CE/PUR system, since there are a good adhesion and a strong hydrogen bonding between silica and polymers. The thermal property of ternary composites increases with the increase of silica nanoparticle loading. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1243–1251, 2008
Layer‐by‐layer assembly of gelatin
Authors: Lin Yuan , Su Zhaohui
Published: May 2008

Electrostatic assembly of one species can be realized using gelatin as a polyampholyte. Under suitable conditions where the electrostatic attraction and repulsion were both significant and in balance, linear growth of multilayers driven by electrostatic interactions was sustained over many successive assembly steps, and the maximum amount of adsorption of each layer was reached when the solution pH was around the isoelectric point. The rearrangement of the adsorbed chains after drying was confirmed by contact angle analysis. In addition with only one species involved, the assembled thin films should be chemically uniform rather than layered. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1252–1257, 2008
Amyotrophic lateral sclerosis: Protein chaperone dysfunction revealed by proteomic studies of animal models
Authors: Jain Mohit Raja , Ge Wei‐wen , Elkabes Stella , Li Hong
Published: May 2008

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects motor neurons and causes progressive muscle weakness and atrophy. The etiology and pathogenesis of ALS are largely unknown and no effective treatment is presently available. About 10% of patients have the familial or inherited form of the disease (fALS), among which 20% is linked to mutations with Cu2+/Zn2+ superoxide dismutase (mSOD1). Transgenic animals expressing human mSOD1 are excellent models for understanding not only fALS but sporadic ALS as well. Pathological features in both ALS patients and mSOD1 transgenic animals' spinal cords share commonalties including the accumulation of misfolded protein inclusions. Recent proteomic investigations on ALS animal models have discovered alterations in protein expression, protein‐protein interactions and post‐translational modifications. These efforts have revealed aspects of potential pathogenic mechanisms and identified probable therapeutic targets. The present review summarizes the major findings of proteomics studies performed on the mSOD1 mice with particular emphasis on the spinal cord proteome. These results are compared with those reported using cell cultures or specimens obtained from ALS patients. The convergence of pathogenic processes on protein chaperone function, and its relationship to protein degradation, metabolic dysfunction and oxidative signaling events is discussed.
Proteomics‐based investigations of animal models of disease
Authors: Bousette Nicolas , Gramolini Anthony O. , Kislinger Thomas
Published: May 2008

Cells contain a large yet, constant genome, which contains all the coding information necessary to sustain cellular physiology. However, proteins are the end products of genes, and hence dictate the phenotype of cells and tissues. Therefore, proteomics can provide key information for the elucidation of physiological and pathophysiological mechanisms by identifying the protein profile from cells and tissues. The relatively novel techniques used for the study of proteomics thus have the potential to improve diagnostic, prognostic, as well as therapeutic avenues. In this review, we first discuss the benefits of animal models over the use of human samples for the proteomic analysis of human disease. Next, we aim to demonstrate the potential of proteomics in the elucidation of disease mechanisms that may not be possible by other conventional technologies. Following this, we describe the use of proteomics for the analysis of PTM and protein interactions in animal models and their relevance to the study of human disease. Finally, we discuss the development of clinical biomarkers for the early diagnosis of disease via proteomic analysis of animal models. We also discuss the development of standard proteomes and relate how this data will benefit future proteomic research. A comprehensive review of all animal models used in conjunction with proteomics is beyond the scope of this manuscript. Therefore, we aimed to cover a large breadth of topics, which together, demonstrate the potential of proteomics as a powerful tool in biomedical research.
Study of environmental degradation of silver surface
Authors: Águas H. , Silva R. J. C. , Viegas M. , Pereira L. , Fortunato E. , Martins R.
Published: May 2008

To evaluate the evolution of a dark film formation on silver surface objects, several coupons were catalogued and place inside a museum, located in an urban area. The changes on these samples were measured by spectroscopic ellipsometry, in periods of months. This technique allows the reduction of the coupons exposure time, in several months, due to its high sensitivity to surface modifications, with acceptable results for the evaluation of its degradation. The thicknesses of the degradation layers and the optical properties of silver oxide, chloride and sulphide reference samples were determined using a mixture of Tauc‐Lorentz and Drude models. The composition of the silver corrosion layer was determined by fitting the layer using a Bruggeman Effective Medium Approximation (BEMA) of the three products plus voids. It was found that the thickness of the layer depends in the placement of the coupons, namely, inside or outside displayers. The average film thickness after 6 months was of 180 Å and 280 Å, inside and outside the displayers, respectively. The main compounds found in the layers were the silver chlorides and sulphides, which composition changed with the thickness of the layer, and the exposition time. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A numerical procedure for combined many‐body‐QED calculations
Authors: Lindgren Ingvar , Salomonson Sten , Hedendahl Daniel
Published: May 2008

A procedure for relativistically covariant many‐body perturbation theory (MBPT) has been developed, and some numerical implementation has been started. The procedure is based upon the previously introduced covariant evolution operator, which is a field‐theoretical concept, closely related to MBPT. The procedure leads to all kinds of relativistic and quantum‐electrodynamical effects, and can be shown for two‐particle systems to lead to the Bethe‐Salpeter equation. In the implementation an extension to the photonic Fock space is made, where the number of photons no longer is constant. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
How to diagnose hantavirus infections and detect them in rodents and insectivores
Authors: Vaheri Antti , Vapalahti Olli , Plyusnin Alexander
Published: May 2008

Hantaviruses are carried by rodents and insectivores in which they cause persistent and generally asymptomatic infections. Several hantaviruses can infect humans and many of them cause either haemorrhagic fever with renal syndrome (HFRS) in Eurasia or hantavirus cardiopulmonary syndrome (HCPS) in the Americas. In humans hantavirus infections are diagnosed using IgM‐capture tests but also by RT‐PCR detection of viral RNA. For detection of hantavirus infections in rodents and insectivores, serology followed by immunoblotting of, for example, lung tissue, and RT‐PCR detection of viral RNA may be used, and if of interest followed by sequencing and virus isolation. For sero/genotyping of hantavirus infections in humans and carrier animals neutralisation tests/RNA sequencing are required. Hantaviruses are prime examples of emerging and re‐emerging infections and it seems likely that many new hantaviruses will be detected in the near future. Copyright © 2008 John Wiley & Sons, Ltd.
Characterizing the capacity gain of stream control scheduling in MIMO wireless mesh networks
Authors: Wang Yue , Chiu Dah‐Ming , Lui John C. S.
Published: May 2008

Stream control (SC) has recently attracted attentions in the research of multiple input multiple output (MIMO) wireless networks as a potential way to improve network capacity. However, inappropriate use of SC may significantly degrade network capacity as well. In this paper, we provide the first formal study on SC scheduling in MIMO wireless mesh networks (WMNs). We derive the theoretical upper bound on network capacity gain of SC scheduling. We also provide an efficient scheduling algorithm and show that its achieved network capacity gain is close to its theoretical upper bound. Moreover, we point out the poor performance of a previous SC scheduling algorithm SCMA under the general settings of WMNs. This formal characterization provides a deeper understanding of steam control scheduling in MIMO WMNs. Copyright © 2008 John Wiley & Sons, Ltd.
WKB analysis for the Gross–Pitaevskii equation with non-trivial boundary conditions at infinity
Authors: Alazard Thomas , Carles Rémi
Published: May 2008

We consider the semi-classical limit for the Gross–Pitaevskii equation. In order to consider non-trivial boundary conditions at infinity, we work in Zhidkov spaces rather than in Sobolev spaces. For the usual cubic nonlinearity, we obtain a point-wise description of the wave function as the Planck constant goes to zero, so long as no singularity appears in the limit system. For a cubic-quintic nonlinearity, we show that working with analytic data may be necessary and sufficient to obtain a similar result.
Well-posedness and scattering for the KP-II equation in a critical space
Authors: Hadac Martin , Herr Sebastian , Koch Herbert
Published: May 2008

The Cauchy problem for the Kadomtsev–Petviashvili-II equation

(u_{t} + u_{xxx} + uu_{x})_{x} + u_{yy} = 0

is considered. A small data global well-posedness and scattering result in the scale invariant, non-isotropic, homogeneous Sobolev space

\dot H^{−\frac{1}{2},0}(\mathbb{R}^{2})

is derived. Additionally, it is proved that for arbitrarily large initial data the Cauchy problem is locally well-posed in the homogeneous space

\dot H^{−\frac{1}{2},0}(\mathbb{R}^{2})

and in the inhomogeneous space

H^{−\frac{1}{2},0}(\mathbb{R}^{2})

, respectively.
Acyclic retinoid inhibits functional interaction of transcription factors Krüppel‐like factor 5 and retinoic acid receptor‐alpha
Authors: Kada Nanae , Suzuki Toru , Aizawa Kenichi , Munemasa Yoshiko , Matsumura Takayoshi , Sawaki Daigo , Nagai Ryozo
Published: May 2008

We show that transcription factor Krüppel‐like factor 5 (KLF5), which is important in cardiovascular remodeling, interacts with retinoic acid receptor‐alpha (RARα) to regulate downstream gene expression. Here, we investigated whether acyclic retinoid (ACR) regulates KLF5 and inhibits vascular remodeling. Co‐immunoprecipitation and pull‐down binding assay showed that ACR attenuates functional interaction of KLF5 and RARα. ACR affects KLF5 functions by regulating transactivation of platelet‐derived growth factor A (PDGF‐A) chain. ACR may be a new vascular therapy to target KLF5 in cardiovascular pathology.
Implementing CompacT SelecT Automated Cell Culture in Support of Alzheimer's Disease-Targeted Drug Discovery
Authors: Lou Zhuangwei , Wang Yiqun , Nawoschik Stan , Riddell David , Martone Robert , Dunlop John
Published: May 2008

The CompacT SelecT is the latest generation automated cell culture system in the SelecT product line allowing incubation of up to 90 T-175 flasks and preparation of 210 assay-ready plates. We have successfully implemented the CompacT SelecT in support of a number of cell-based assays used in our Alzheimer's disease (AD) lead optimization programs. One of the distinguishing features of AD pathology is deposition of two neurotoxic forms of the beta-amyloid peptide (Aβ40 and Aβ42) in the brains of patients. It is thought that specifically lowering Aβ40 and Aβ42 in the brains of patients will halt the progression of the disease. The generation of Aβ requires sequential cleavage of the type-I integral membrane amyloid precursor protein (APP) by two proteases, β-secretase (BACE) then γ-secretase. In the specific examples presented here, we have transitioned two cell lines supporting drug discovery efforts for identifying β- and γ-secretase inhibitors (GSIs) from manual cell culture protocols to fully automation using CompacT SelecT. In Chinese hamster ovary (CHO) cells which over express wild-type APP (CHOAPP cells), robust secretion of Aβ40 was observed from cells cultured manually and with CompacT SelecT with signal:background ratios of 54–99 and 23–47, respectively. Despite the reduced signal:background observed with the CompacT SelecT cultured cells, the rank order of potency for a series of 18 BACE inhibitors in reducing Aβ40 secretion was identical when manually cultured cells were compared with CompacT SelecT cultured cells. The correlation coefficient when comparing the two sets of EC50 values was r2 = 0.99. Similarly, CHO cells that over express a reporter construct for the Swedish mutant APP that generates high levels of Aβ peptide (CHOAPP-NL cells) cultured with CompacT SelecT exhibited a reduced secretion of Aβ40 and Aβ42 when compared with manually cultured cells; signal:background ratios for secretion of Aβ40 from CHOAPP-NL cells were 57–71 and 16–31, and for Aβ42 secretion 8–18 and 4–11 comparing manual and automated cell culture, respectively. Similar to the observations in CHOAPP cells, an identical rank order of potency for a series of GSIs was observed when CHOAPP-NL cells cultured manually and in CompacT SelecT were compared; r2 = 0.99 and 0.98, respectively, for EC50 values for inhibition of Aβ40 and Aβ42 secretion. Taken together, the robust signal:background and identical pharmacological profile of inhibitors provide validation for the implementation of automated cell culture for CHOAPP and CHOAPP-NL cells in support of β- and γ-secretase-targeted drug discovery.
Cell Culture Automation and Quality Engineering: A Necessary Partnership to Develop Optimized Manufacturing Processes for Cell-Based Therapies
Authors: Thomas R.J. , Chandra A. , Hourd P.C. , Williams D.J.
Published: May 2008

The translation of experimental cell-based therapies to volume produced commercially successful clinical products that satisfy the regulator requires the development of automated manufacturing processes to achieve capable and scaleable processes that are both economic and able to meet the unpredictable demands of the market place. The Healthcare Engineering group at Loughborough has conducted novel demonstrators of the transfer of manual human cell culture processes to the CompacT SelecT (The Automation Partnership) automated cell culture platform, including an osteoblast cell line, embryonic carcinoma cell line, primary bone marrow-derived mesenchymal stem cells, primary umbilical cord-derived progenitor cells, and human embryonic stem cells. The work aims to develop and optimize automated cell culture processes for manufacturing cell-based therapies in a quality system and current good manufacturing practice (cGMP) compliant manner and is underpinned by the application of a six-sigma inspired quality engineering approach.

In this technical brief, we outline the need for automated cell culture systems and automated process engineering for the manufacture of cell populations for therapeutic applications. We review the transfer of a manual cell culture process to an automated process and the subsequent methodology for process improvement using examples from our laboratory of the application of these principles to an important regenerative medicine cell type, the human mesenchymal stem cell. We believe that systematic process improvement methodologies combined with the process stability provided by automation are essential to engineer optimized cGMP compliant manufacturing processes that will be required to realize the promise of cell-based therapies.
Automated Application of a Novel High Yield, High Performance Tissue Culture Flask
Authors: Szymanski Stacey L. , Huff Kevin W. , Patel Amita D. , Murray Justin R. , Feasby James , Sharma Bethel V. , Young Denise K. , Strulovici Berta , Peltier Richard R. , Johnson Eric N. , Rush Alison
Published: May 2008

As the drug discovery process evolves and demands more challenging and relevant assays, we have experienced a recent and significant escalation in the number of cell-based high-throughput assays for both small molecule and target identification screens. This has resulted in an increased need for the reproducible production of high quality cells in large quantities. Historically, manual cell culture was the only option available for providing cells in sufficient numbers for small molecule ultra-high-throughput screens (uHTSs), representing a technology gap in our automated cell culture process.

Recently, we have applied an automated solution in the form of a novel 10-layer tissue culture flask, the HYPERFlask (Corning, Lowell, MA). This technology, when introduced as an upgrade to the SelecT (an automated cell culture system manufactured by The Automation Partnership, Ltd., Royston, England), provides a new approach to automating production of the high number of cells required for uHTS and consequently a highly desirable alternative to manual cell culture.

The HYPERFlask has a surface area of 1720 cm2 and can yield up to 3 × 108 cells after 3 days in culture. This can be compared to a typical yield of 2 × 107 cells from a T175 flask (with a surface area of 175 cm2), the current standard flask type for automated cell culture on the SelecT. Cells grown in both flask types are of comparable quality, as demonstrated by equivalent cell viability, yield per cm2, functional response, and pharmacology.
Living with Irresolute Cell Lines in an Automated World
Authors: Hogan Christopher , Simons Sarah , Zhang Haiyan , Burdick Debra
Published: May 2008

An automated cell-culture platform becomes the nucleus of an organization performing cell-based research. However, every cell-based project placed on the system brings unique challenges. With each cell line comes millions of years of evolutionary encumbrance and a genetic inclination driving unique phenotypic peculiarities. In vivo, diverse eukaryotic cells rely on their “mammalian host” for survival. An automated system must perform in vitro, the myriad actions needed to sustain multiple cell lines as well, hence becoming an “automated host.” Cells invariably, will endeavor to do as they please. Molding these cells into the operational bounds of a man-made system requires insight into the relationship between cell and machine.

Citing our own experiences, we will describe herein the use of the SelecT automated cell-culture platform (The Automation Partnership, Hertfordshire, England) in our discovery and preclinical profiling programs at Novartis. Achieving the balance between cells and the automated environment, and accommodating variable cell dynamics are discussed.
Adapting Cell-Based Assays to the High-Throughput Screening Platform: Problems Encountered and Lessons Learned
Authors: Maddox Clinton B. , Rasmussen Lynn , White E. Lucile
Published: May 2008

In recent years, cell-based phenotypic assays have emerged as an effective and robust addition to the array of assay technologies available for drug discovery in the high-throughput screening (HTS) arena. Previously, biochemical target-based assays have been the technology of choice. With the emergence of stem cells as a basis for a new screening technology, it is important to keep in mind the lessons that have been learned from the adaptation of existing stable cell lines onto the HTS drug discovery platform, with special consideration being given to assay miniaturization, liquid-handling complications, and instrument-introduced artifacts. We present an overview of the problems encountered with the implementation of multiple cell-based assays at the High Throughput Screening Center at Southern Research Institute as well as empirically defined effective solutions to these problems. These include examples of artifacts induced by temperature differences throughout the screening campaign, cell-plating conditions including the effect of room temperature incubation on assay consistency, DMSO carry over, and incubator-induced artifacts.
“What Does Heaven Ever Say?” A Methods-centered Approach to Cross-cultural Engagement
Authors: JENCO LEIGH KATHRYN
Published: May 2008

How can we conduct cross-cultural inquiry without reproducing the ethnocentric categories that prompt critique in the first place? Postcolonial and comparative political theorists have called into question the “universal” applicability of Western liberal political norms, but their critiques are drawn most often from competing Western discourses (e.g., poststructuralism) rather than from the culturally diverse traditions of scholarship whose ideas they examine. In contrast, I suggest attending to these culturally situated traditions of scholarship, especially their methods of inquiry, in addition to their substantive ideas. This method-centered approach reinterprets cross-cultural engagement, not as a tool for modifying existing parochial debates on the basis of “non-Western” cases, but as an opportunity to ask new questions through alternative frames of reference. Examining the interpretive methodologies of two Chinese classicists, I show how their methods offer not only new ideas but also new methods for the practice of political and cross-cultural theory.
Pax Asiatica versus Bella Levantina: The Foundations of War and Peace in East Asia and the Middle East
Authors: SOLINGEN ETEL
Published: May 2008

Although turmoil characterized both the Middle East and East Asia in the two decades following World War II, the two regions looked dramatically different at the dawn of the twenty-first century. Since 1965 the incidence of interstate wars and militarized conflicts has been nearly five times higher in the Middle East, as was their severity, including the use of ballistic missiles and chemical weapons. By contrast, declining militarized conflict and rising intraregional cooperation has replaced earlier patterns in East Asia. There are no systematic efforts explaining this contrast betweenBella Levantinaand an evolvingPax Asiatica. This article traces these diverging paths to competing domestic models of political survival. East Asian leaders pivoted their political control on economic performance and integration in the global economy, whereas Middle East leaders relied on inward-looking self-sufficiency, state and military entrepreneurship, and a related brand of nationalism. I examine permissive and catalytic conditions explaining the models' emergence; their respective intended and unintended effects on states, military, and authoritarian institutions; and their implications for regional conflict. The final section distills conceptual and methodological conclusions.
Can Institutions Build Unity in Multiethnic States?
Authors: ELKINS ZACHARY , SIDES JOHN
Published: May 2008

We investigate whether political institutions can promote attachment to the state in multiethnic societies. Building on literatures on nationalism, democratization, and conflict resolution, we discuss the importance of attachment, understood as a psychological identification with, and pride in, the state. We construct a model of state attachment, specifying the individual-, group-, and state-level conditions that foster it. Then, using cross-national survey data from 51 multiethnic states, we show that, in general, ethnic minorities manifest less attachment to the states in which they reside than do majorities. Combining the survey data with minority group attributes and country-level attributes, we show that the attachment of minorities varies importantly across groups and countries. Our central finding is that federalism and proportional electoral systems—two highly touted solutions to ethnic divisions—have at best mixed effects. These results have implications for state-building and democratic consolidation in ethnically heterogeneous states.
Allocating Defensive Resources with Private Information about Vulnerability
Authors: POWELL ROBERT
Published: May 2008

In many resources-allocation problems, strategic adversaries move sequentially and are likely to have private information about the effectiveness of their spending. A defender, for example, often has to allocate its defensive resources before an attacker (e.g., a terrorist group) decides where to strike. Defenders are also likely to have private information about the vulnerability of the things they are trying to protect. Sequential decisions and private information about effectiveness creates a dilemma for a defender. Allocating more to a highly vulnerable site reduces the expected losses should that site be attacked but may also signal that that site is more vulnerable and thereby increase the probability of an attack. Modeling this tradeoff as a signaling game, the analysis shows that secrecy concerns generally swamp vulnerability concerns when more vulnerable sites are weakly harder to protect on the margin. The defender pools in equilibrium, that is, allocates its resources in the same way, regardless of the level of vulnerability. If more vulnerable sites are easier to protect on the margin, vulnerability concerns may swamp secrecy concerns.
Institutions and Equilibrium in the United States Supreme Court
Authors: ANDERSON IV ROBERT , TAHK ALEXANDER M.
Published: May 2008

Over the last decade the scholarship on judicial politics has increasingly emphasized the strategic aspects of decision making in the United States Supreme Court. This scholarship, however, has struggled with two significant limitations—the restriction to unidimensional policy spaces and the assumption of binary comparisons of alternatives. These two assumptions have the advantage of implying stable, predictable outcomes, but lack a sound theoretical foundation and assume away potentially important aspects of strategic behavior on the Court. In this article, we identify institutional features of the Court that, under certain conditions, allow us to relax these two assumptions without sacrificing stable, predictable policy outcomes. In particular, we formalize the “part-by-part” opinion voting used by the justices, a feature that, together with separable preferences over policy issues, implies stable policy outcomes around the issue-by-issue median of the justices.
A Bayesian method for jointly estimating allele age and selection intensity
Authors: SLATKIN MONTGOMERY
Published: May 2008

The problem of jointly estimating the intensity of past selection affecting an allele and the allele's age is formulated in a Bayesian framework. The prior distribution of allele age given its frequency is obtained from existing population genetics theory. The prior distribution of selection intensity is assumed to reflect the fact that positive selection on a new mutant is more likely to be weak than strong. The general approach is illustrated by the development of an importance sampling method applicable to low-frequency alleles. This method can be used either when the haplotypes of closely linked marker loci are known or when the lengths of linked ancestral chromosomal segments can be inferred. The method is illustrated with an application to the A− allele of G6PD in Africa. Because changes in allele frequency and recombination are both intrinsically stochastic, there are limits to the accuracy achievable with any method.
Asymmetrical mating patterns and the evolution of biased style-morph ratios in a tristylous daffodil
Authors: HODGINS KATHRYN A. , BARRETT SPENCER C. H.
Published: May 2008

Non-random mating in plant populations can be influenced by numerous reproductive and demographic factors, including floral morphology and inter-plant distance. Here, we investigate patterns of outcrossed mating through male function inNarcissus triandrus, a tristylous, bee-pollinated wild daffodil from the Iberian Peninsula, to test pollen transfer models which predict that floral morphology promotes asymmetrical mating and biased morph ratios. Unlike other tristylous species,N. triandrushas an incompatibility system that permits intra-morph mating and long-level rather than mid-level stamens in the L-morph. Incomplete sex-organ reciprocity should result in significant intra-morph mating in the L-morph. We measured mating patterns in two L-biased populations – dimorphic (two style morphs) and trimorphic (three style morphs) – using multilocus genotyping and maximum-likelihood-based paternity analysis. We also examined the spatial distribution of style morphs and neutral markers to investigate the potential consequence of spatially restricted mating on morph ratios. As predicted, we detected significant amounts of intra-morph mating in the L-morph in both populations. Pollen transfer coefficients generally supported predictions based on the Darwinian hypothesis that anthers and stigmas of equivalent level promote pollinator-mediated cross-pollination in heterostylous populations. There was evidence of significant spatial aggregation of both style morphs and neutral markers in populations ofN. triandrus, probably as a result of restricted pollen and seed dispersal. Our results provide empirical support for theoretical models of pollen transfer, which indicate that the commonly observed L-biased morph ratios inNarcissusspecies result from significant intra-morph mating in the L-morph because of its atypical floral morphology.