bluuebunny/crossref_metadata_2025 huggingface dataset:
A rapid and sensitive CE method with field‐enhanced sample injection and in‐capillary derivatization for selenomethionine metabolism catalyzed by flavin‐containing monooxygenases
Authors: Hai Xin , Nauwelaers Thomas , Busson Roger , Adams Erwin , Hoogmartens Jos , Van Schepdael Ann
Published: September 2010

A rapid and sensitive electrophoretically mediated microanalysis method with field‐enhanced sample injection (FESI) for in‐capillary derivatization was developed to determine selenomethionine (SeMet) and selenomethionine selenoxide (SeOMet). Phthalic anhydride (PA) was selected as the derivatization reagent due to the fast reaction at room temperature and the stability of derivatives. The in‐capillary derivatization was accomplished by electrophoretically mixing PA and sample plugs. PA reagent was introduced hydrodynamically into the capillary, whereas the sample solution was injected electrokinetically, thus allowing a selective preconcentration of the analytes by FESI. For FESI, the optimum sample solvent was 2 mM borate solution. The borate buffer was suitable for both in‐capillary derivatization and separation of the derivatives. The combination of electrophoretically mediated microanalysis with FESI for in‐capillary derivatization was successfully achieved with about 800‐fold concentration sensitivity enhancement compared to direct CE‐UV detection in the same setup. The present method is miniaturized and fully automated, which ensures the on‐line derivatization, stacking, separation and detection in 10 min. Finally, the developed method was successfully applied to measure enzyme activities by analyzing the reaction mixtures of SeMet with human flavin‐containing monooxygenases (FMO). The results showed that both FMO1 and FMO3, but not FMO5 could catalyze the Se‐oxygenation of SeMet.
Comparative enantioseparations of pharmaceuticals in capillary electrochromatography on polysaccharide‐based chiral stationary phases containing selectors with or without chlorinated derivatives
Authors: Hendrickx Ans , Mangelings Debby , Chankvetadze Bezhan , Vander Heyden Yvan
Published: September 2010

The screening conditions of an existing chiral strategy in CEC were tested for their applicability on four chlorine‐containing polysaccharide‐based stationary phases. The selectors of these phases are cellulose tris(3‐chloro‐4‐methylphenylcarbamate), amylose tris(5‐chloro‐2‐methylphenylcarbamate), cellulose tris(4‐chloro‐3‐methylphenylcarbamate) and cellulose tris(3,5‐dichlorophenylcarbamate). The enantioselectivity of these phases was compared with those of the four phases without chlorine (Chiralpak® AD‐RH, Chiralcel® OD‐RH, Chiralpak® AS‐RH and Chiralcel® OJ‐RH) used in the earlier defined strategy. A test set of 48 structurally diverse drug compounds was analyzed using the screening conditions of the strategy. These results led to possibilities to upgrade the current screening strategy so that improved success rates are obtained. The chlorine‐containing chiral stationary phases demonstrated an added value to the screening process since they showed enantioresolution for compounds not resolved by the chiral stationary phases not containing chlorine in their structure.
A novel 18O inverse labeling‐based workflow for accurate bottom‐up mass spectrometry quantification of proteins separated by gel electrophoresis
Authors: Santos Hugo M. , Glez‐Peña Daniel , Reboiro‐Jato Miguel , Fdez‐Riverola Florentino , Diniz Mário S. , Lodeiro Carlos , Capelo‐Martínez José‐Luis
Published: September 2010

In the present work we report on a novel and fast protocol for accurate bottom‐up protein quantification that overcomes the drawbacks of in‐gel digestion and MALDI analysis, while maintaining their benefits. It relies on the following steps: (i) gel electrophoresis separation of proteins, (ii) fast in‐gel protein digestion with trypsin, (iii) 18O‐labeling through the decoupled method, (iv) quantification through selected peptides previously chosen using the 18O inverse labeling approach and that, finally, (v) it takes advantage of software specifically developed to select the peptides that will drive the quantification of the protein in an automated mode. We have accurately quantified the following six proteins: glycogen phosphorylase, BSA, ovalbumin, carbonic anhydrase, trypsin inhibitor, and α‐lactalbumin. As a case study we have quantified the protein vitellogenin in plasma of Cyprinus carpio exposed to high levels of estrogens. The proposed new protocol was validated against the traditional ELISA method; both were found to provide comparable results (non‐parametric Mann–Whitney U‐test).
Simultaneous sizing and electrophoretic mobility measurement of sub‐micron particles using Brownian motion
Authors: Palanisami Akilan , Miller John H.
Published: September 2010

The size and surface chemistry of micron scale particles are of fundamental importance in studies of biology and air particulate pollution. However, typical electrophoretic measurements of these and other sub‐micron scale particles (300 nm–1 μm) cannot resolve size information within heterogeneous mixtures unambiguously. Using optical microscopy, we monitor electrophoretic motion together with the Brownian velocity fluctuations – using the latter to measure size by either the Green–Kubo relation or by calibration from known size standards. Particle diameters are resolved to ±12% with 95% confidence. Strikingly, the size resolution improves as the particle size decreases due to the increased Brownian motion. The sizing ability of the Brownian assessed electrophoresis method described here complements the electrophoretic mobility resolution of the traditional CE.
Highly sensitive trivalent copper chelate‐H2O2 system for CE‐chemiluminescent detection of luminol‐type compounds
Authors: Fu Zhifeng , Li Zongyun , Xie Haoyue , Li Tao , Li Cuifang
Published: September 2010

Luminol‐type compounds can be used as chemiluminescent (CL) derivatization reagents for amines, carboxylic acids and protein. Copper chelate diperiodatocuprate(III) (K5[Cu(HIO6)2], DPC) was synthesized by complexation of copper at trivalent oxidation state and periodate in a strong basic medium. It was found that DPC can greatly enhance the reaction between luminol‐type compounds and H2O2 to produce very strong CL emission. Based on this fact, a rapid CE method combined with high‐sensitive end‐column CL detection was established to simultaneously analyze luminol and N‐(4‐aminobutyl)‐N‐ethylisoluminol (ABEI) with wide concentration range of 3.0–300 nmol/L in 5 min. The RSDs of the signal intensity and the migration time were less than 3.9 and 7.0% for a standard sample containing 100 nmol/L luminol and ABEI (n=5), respectively. The investigation implies that DPC is a promising sensitizer for CE‐CL detection of a great variety of biomolecules and drugs in biological samples after derivatization using luminol derivatives.
Stressin' Sestrins take an aging fight
Authors: Budanov Andrei V. , Lee Jun Hee , Karin Michael
Published: September 2010

Sestrins (Sesns) are a family of highly conserved stress‐responsive proteins, transcriptionally regulated by p53 and forkhead transcription factor that exhibit oxidoreductase activity in vitro and can protect cells from oxidative stress. However, their major biochemical and physiological function does not appear to depend on their redox (reduction and oxidation) activity. Sesns promote activation of adenosine‐5′‐monophosphate (AMP)‐dependent protein kinase in both mammals and flies. Stress‐induced Sesn expression results in inhibition of the target of rapamycin complex 1 (TORC1) and the physiological and pathological implications of disrupting the Sesns‐TORC1 crosstalk are now being unravelled. Detailing their mechanism of action and exploring their roles in human physiology point to exciting new insights to topics as diverse as stress, cancer, metabolism and aging.
Channel and floodplain sediment dynamics in a reach of the tropical meandering Rio Beni (Bolivian Amazonia)
Authors: Gautier Emmanuèle , Brunstein Daniel , Vauchel Philippe , Jouanneau Jean‐Marie , Roulet Marc , Garcia Coral , Guyot Jean‐Loup , Castro Marcello
Published: September 2010

The study investigates interactions, water and sediment exchanges, between a rapidly migrating meander and its associated floodplain at fine temporal and spatial scales. The Beni River, an Amazonian free meandering river, makes the transition between Andean ranges and Amazonian lowlands. For the period 2002–2006, an assemblage of tools and methods (water and sediment discharges, topometric and bathymetric surveys, sedimentation rate estimations from unsupported 210Pb and sediment trapping system) was used to jointly analyse the influence on the sediment budget of external factors (mainly water and sediment discharge) and the inherent behaviour of the system. The main issue addressed is the investigation of the complex relationship between ‘morphological conditioning’ of fluvial landform and process. The first part of the study was undertaken with the aim of linking erosion–deposition in an active meander with water and sediment fluxes. The three inter‐annual evolutions are characterized by very unequal sediment budgets; the first two intervals underwent predominant erosion, and the latter slight accumulation. Digital elevation models, evaluated for the active meander, demonstrate that sedimentation on the point bar depends more on external factors than erosion of the concave bank, which fluctuates slightly. The second part of the study, focusing on water and sediment exchanges between active bend and floodplain, examines the respective parts played by overbank flow and by an abandoned channel on the diffusion and sequestration of sediment. The association of short‐ and long‐term estimation of sedimentation rates suggests that floodplain construction is associated with two different processes and rhythms of sediment transportation. Finally, a sediment budget is proposed for the Beni River in the upper part of the Amazonian lowlands. Copyright © 2010 John Wiley & Sons, Ltd.
Formative conditions and sedimentary structures of sandy 3D antidunes: an application of the gravel step‐pool model to fine‐grained sand in an experimental flume
Authors: Yokokawa Miwa , Hasegawa Kazuyoshi , Kanbayashi Satoru , Endo Noritaka
Published: September 2010

Antidunes and their sedimentary structures can be useful in reconstructing paleo‐hydraulic conditions, especially for large discharge events. However, three‐dimensional (3D) antidunes in sand‐sized sediments have not yet been studied extensively, as compared to either two‐dimensional (2D) antidunes or antidunes in gravel‐sized sediments. In this study, we estimated formative conditions of gravel step‐pool morphologies and applied them to the formation of 3D antidunes over a sand bed. Formative conditions are expressed in terms of a relationship between the water discharge per unit width and the bed slope. Flume experiments demonstrated that 3D mound‐like antidune configurations and their associated internal sedimentary structures could be preserved. Internal sedimentary structures were characterized by shallow lens‐like structures whose bases were erosional. Although gently‐dipping concave‐upward lamination was dominant, convex‐upward lamination was occasionally observed. The dimensions of lenticular lamina‐sets can be used to estimate antidune geometry. Thus if 3D antidunes can be interpreted in the stratigraphic record, it is possible to estimate the paleo‐hydraulic parameters such as water discharge and bed slope more precisely than previously. Copyright © 2010 John Wiley & Sons, Ltd.
The nature and transport of the fine‐grained component of Swift Creek Landslide, Northwest Washington
Authors: Bayer Tovah M. , Linneman Scott
Published: September 2010

Extreme sedimentation in Swift Creek, located in the Cascades foothills in NW Washington (48°55′N, 122°16′W), results from erosion of the oversteepened, unvegetated toe of a large (55 hectares) active landslide. Deposition of landslide‐derived sediment has necessitated costly mitigation projects in the channel including annual dredging and temporary sediment traps in an attempt to reduce the risk of flooding and damage to man‐made structures downstream. This study attempts to understand the process of sediment production along with the corresponding erosion rates of the sediment source to help with the development of mitigation plans and construction of optimal sediment reservoirs.

The bedload and suspended sediment in the creek are a direct result of the weathering process of the serpentinitic bedrock underlying the landslide. The serpentinite does not weather to smectite clay, as previously thought. Instead, it weathers to asbestiform chrysotile with minor amounts of chlorite, illite and hydrotalcite, all of which occur in clay seeps on the unvegetated surface of the landslide. The chrysotile fibers average 2 µm in length and make up at least 50%, by volume, of the suspended load transported in Swift Creek. This study does not address the environmental or health implications of the asbestiform chrysotile transport or deposition.

During the sampled time between February 2005 and February 2006, 127 discrete suspended sediment samples were collected and discharge was measured 66 times. The suspended sediment concentrations ranged from 0·02 g L−1 to 41·6 g L−1 and the discharge ranged from 0·0 m3 s−1 to 0·5 m3 s−1. A nonlinear functional model estimated the total suspended sediment flux from detailed precipitation records and discrete suspended sediment concentration and discharge measurements to be 910 t km−2 yr−1. When the suspended sediment flux is coupled with estimates of downstream deposition of coarse sediment, the estimated erosion rate for the entire Swift Creek landslide is 158 mm yr−1. The majority of the material entering Swift Creek is presumed to originate on the unvegetated toe of the landslide, for which the erosion rate is thus approximately 1 m yr−1. Copyright © 2010 John Wiley & Sons, Ltd.
Nonlinearity and unsteadiness in river meandering: a review of progress in theory and modelling
Authors: Pittaluga Michele Bolla , Seminara Giovanni
Published: September 2010

River meandering has been extensively investigated. Two fundamental features to be explored in order to make further progress are nonlinearity and unsteadiness. Linear steady models have played an important role in the development of the subject but suffer from a number of limits. Moreover, rivers are not steady systems; rather their states respond to hydrologic forcing subject to seasonal oscillations, punctuated by the occurrence of flood events. We first derive a classification of river bends based on a systematic assessment of the various physical mechanisms affecting their morphodynamic equilibrium and their evolution in response to variations of hydrodynamic forcing. Using the database by Lagasse et al. (2004) we also show that natural meanders are typically mildly curved and long, i.e. such that both the centrifugal and the topographic secondary flows are weak, but they are almost invariably nonlinear. We then review some recent developments which allow us to treat analytically the flow and bed topography of mildly curved and long nonlinear bends subject to steady forcing, taking advantage of the fact that flow and bed topography in mildly curved long bends are slowly varying. Results show that nonlinearity has a number of consequences: most notably damping of the morphodynamic response and upstream shifting of the location of the nonlinear peak of the flow speed. Next we extend the latter model to the case of unsteady forcing. Results are found to depend crucially on the ratio between the flood duration and a morphodynamic timescale. It turns out that, in a channel subject to a repeated sequence of floods, the system reaches a dynamic equilibrium. We conclude the paper discussing how the present assessment relates to the debate on meander modelling of the late 1980s and suggesting what we see as promising lines of future developments.
Novelty preference in patients with developmental amnesia
Authors: Munoz M. , Chadwick M. , Perez‐Hernandez E. , Vargha‐Khadem F. , Mishkin M.
Published: September 2010

To re‐examine whether or not selective hippocampal damage reduces novelty preference in visual paired comparison (VPC), we presented two different versions of the task to a group of patients with developmental amnesia (DA), each of whom sustained this form of pathology early in life. Compared with normal control participants, the DA group showed a delay‐dependent reduction in novelty preference on one version of the task and an overall reduction on both versions combined. Because VPC is widely considered to be a measure of incidental recognition, the results appear to support the view that the hippocampus contributes to recognition memory. A difficulty for this conclusion, however, is that according to one current view the hippocampal contribution to recognition is limited to task conditions that encourage recollection of an item in some associated context, and according to another current view, to recognition of an item with the high confidence judgment that reflects a strong memory. By contrast, VPC, throughout which the participant remains entirely uninstructed other than to view the stimuli, would seem to lack such task conditions and so would likely lead to recognition based on familiarity rather than recollection or, alternatively, weak memories rather than strong. However, before concluding that the VPC impairment therefore contradicts both current views regarding the role of the hippocampus in recognition memory, two possibilities that would resolve this issue need to be investigated. One is that some variable in VPC, such as the extended period of stimulus encoding during familiarization, overrides its incidental nature, and, because this condition promotes either recollection‐ or strength‐based recognition, renders the task hippocampal‐dependent. The other possibility is that VPC, rather than providing a measure of incidental recognition, actually assesses an implicit, information‐gathering process modulated by habituation, for which the hippocampus is also partly responsible, independent of its role in recognition. © 2010 Wiley Periodicals, Inc.
Bridging divergent neural models of recognition memory: Introduction to the special issue and commentary on key issues
Authors: Voss Joel L. , Paller Ken A.
Published: September 2010

This special issue reviews progress that has been made in recent years in understanding neural processing relevant for recognition memory. Here we describe how the nine reviews that comprise this issue weigh in on some of the most pressing and hotly debated issues in the study of recognition memory, including: (1) the number of processes that support recognition, (2) the nature of these processes, and (3) how these processes map onto neural processing events and brain structures. We then discuss the challenges inherent in attempting to incorporate the fundamentally different types of information that result from various cognitive neuroscience methods (e.g., electrophysiological recordings of neurons, lesion‐deficit studies, analyses of brain potentials and activations, modeling of behavioral responses, and phenomenological reports), and make suggestions for how to better integrate these disparate data types when making inferences about recognition memory. As the articles in this special issue make clear, great strides have been made in understanding how organisms are able to appreciate repetition. And yet, several controversies in this area have still not been resolved, but these articles clarify the core disagreements as well as the tests that must be conducted to seek resolution. This special issue as a whole should thus facilitate advancements in the future study of the neural mechanisms of recognition. © 2010 Wiley‐Liss, Inc.
Effects of adult‐generated granule cells on coordinated network activity in the dentate gyrus
Authors: Lacefield Clay O. , Itskov Vladimir , Reardon Thomas , Hen René , Gordon Joshua A.
Published: September 2010

Throughout the adult life of most mammals, new neurons are continuously generated in the dentate gyrus of the hippocampal formation. Recent work has documented specific cognitive deficits after elimination of adult hippocampal neurogenesis in rodents, suggesting that these neurons may contribute to information processing in hippocampal circuits. Young adult‐born neurons exhibit enhanced excitability and have altered capacity for synaptic plasticity in hippocampal slice preparations in vitro. Still, little is known about the effect of adult‐born granule cells on hippocampal activity in vivo. To assess the impact of these new neurons on neural circuits in the dentate, we recorded perforant‐path evoked responses and spontaneous network activity from the dentate gyrus of urethane‐anesthetized mice whose hippocampus had been focally X‐irradiated to eliminate the population of young adult‐born granule cells. After X‐irradiation, perforant‐path responses were reduced in magnitude. In contrast, there was a marked increase in the amplitude of spontaneous γ‐frequency bursts in the dentate gyrus and hilus, as well as increased synchronization of dentate neuron firing to these bursts. A similar increase in gamma burst amplitude was also found in animals in which adult neurogenesis was eliminated using the GFAP:TK pharmacogenetic ablation technique. These data suggest that young neurons may inhibit or destabilize recurrent network activity in the dentate and hilus. This unexpected result yields a new perspective on how a modest number of young adult‐generated granule cells may modulate activity in the larger population of mature granule cells, rather than acting solely as independent encoding units. © 2010 Wiley Periodicals, Inc., Inc.
Hippocampal volumetrics in treatment‐resistant depression and schizophrenia: The devil's in De‐Tail
Authors: Maller Jerome J. , Daskalakis Zafiris J. , Thomson Richard H.S. , Daigle Melissa , Barr Mera S. , Fitzgerald Paul B.
Published: September 2010

Studies of patients with major depressive disorder (MDD) and schizophrenia (SCH) have revealed reduced hippocampal volumes, but findings have been inconsistent due to sample and measurement differences. The current study sought to measure this structure in a large sample of MDD, SCH, and healthy subjects, using a strict measurement protocol, to elucidate morphological‐specific volumetric differences. Patients with treatment‐resistant MDD (N = 182) and treatment‐resistant SCH with auditory‐verbal hallucinations (N = 52), and healthy controls (N = 76) underwent psychiatric assessments and brain MRI. The findings indicate that (1) MDD and SCH patients have reduced total hippocampal volume which was marked in the tails (more so in patients with MDD), (2) region of interest estimation protocols and sample characteristics may help explain volumetric differences between previous SCH studies. © 2010 Wiley Periodicals, Inc., Inc.
The ECM protein LTBP‐2 is a suppressor of esophageal squamous cell carcinoma tumor formation but higher tumor expression associates with poor patient outcome
Authors: Chan Stephen Ho Kin , Yee Ko Josephine Mun , Chan Kwok Wah , Chan Yuen Piu , Tao Qian , Hyytiainen Marko , Keski‐Oja Jorma , Law Simon , Srivastava Gopesh , Tang Johnny , Tsao Sai Wah , Chen Han , Stanbridge Eric J. , Lung Maria Li
Published: September 2010

Our previous studies of chromosome 14 transfer into tumorigenic esophageal squamous cell carcinoma (ESCC) cell line, SLMT, suggested the existence of tumor suppressor genes on chromosome 14. Gene expression profiling of microcell hybrids and the tumor segregants identified an interesting gene, LTBP‐2 (latent transforming growth factor β binding protein 2), which has been analyzed here for its role in ESCC. LTBP‐2 maps to 14q24 and encodes a secreted protein, which is a component of the extracellular matrix microfibrils. LTBP‐2 expression was downregulated in ESCC cell lines and tumor tissues. Promoter hypermethylation was found to be involved in LTBP‐2 inactivation. Functional studies indicated its tumor‐suppressive roles in ESCC. In the in vitro colony formation and Matrigel three‐dimensional culture assays, LTBP‐2 decreased the colony‐forming abilities of ESCC cell lines. LTBP‐2 expression was associated with reduction of cell migrating and invasive abilities. LTBP‐2 could also reduce the tube‐forming ability of endothelial cells. Moreover, LTBP‐2 induced tumor suppression in in vivo nude mouse assays. Tissue microarray immunohistochemical staining analysis indicated that LTBP‐2 expression is reduced in tumor tissues when compared to normal tissues, and LTBP‐2 expression correlated significantly with the survival of ESCC patients. Thus, LTBP‐2 appears to play an important role in ESCC.
Biomimetic matrices for myocardial stabilization and stem cell transplantation
Authors: Wall Samuel T. , Yeh Che‐Chung , Tu Richard Y. K. , Mann Michael J. , Healy Kevin E.
Published: September 2010

Although natural biological matrices have demonstrated modest improvement in the survival of cells transplanted into the infarcted myocardium, these materials have not been amenable to systematic optimization and therefore have limited potential to treat postinfarct cardiac injuries. Here we have developed tunable bioactive semi‐interpenetrating polymer network (sIPN) hydrogels with matrix metalloproteinase (MMP) labile crosslinkers to be used as an assistive microenvironment for transplantation of bone marrow‐derived mesenchymal stem cells (BMSCs) into the infarcted myocardium. Injectable sIPN hydrogels were designed with a range of mechanical and biological properties that yielded material‐dependent BMSC proliferation in vitro. Five groups were evaluated to treat myocardial infarction (MI) in adult mice: saline injection; green fluorescent protein (GFP)(+)‐BMSCs delivered in saline; a sIPN matrix; a sIPN + GFP(+)‐BMSCs; and Matrigel™ + GFP(+)‐BMSCs. Injection of cells alone created a transient improvement in LV function that declined over time, and the synthetic hydrogel without cells resulted in the highest LV function at 6 weeks. Donor GFP‐positive cells were detected after matrix‐enhanced transplantation, but not without matrix support. Biomimetic sIPN hydrogel matrices succeeded both in mechanically supporting the injured myocardium and modestly enhancing donor cell survival. These matrices provide a foundation for systematic development of “pro‐survival” microenvironments, and improvement in the long‐term results of cardiac stem cell transplantation therapies. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.
Keratin–hydroxyapatite composites: Biocompatibility, osseointegration, and physical properties in an ovine model
Authors: Dias George J. , Mahoney Patricia , Swain Michael , Kelly Robert J. , Smith Robert A. , Ali Mohammad A.
Published: September 2010

Reconstituted keratin has shown promise as an orthopaedic biomaterial. Thisin vivostudy investigates the biological response of composite materials prepared from reconstituted keratin containing a high content of hydroxyapatite (HA) (40 wt % HA), implanted for up to 18 weeks in the long bones of sheep. Keratin–HA composites were compared with a commercially available polylactic acid (PLA) HA composite (BIO RCI HA®, Smith and Nephew). Porous keratin–HA materials displayed excellent biocompatibility and osseointegration, with full integration into bone by 12 weeks. Dense keratin–HA materials also showed excellent biocompatibility, with a more limited osseointegration, involving the penetration of new bone into the periphery of the implant after eight weeks. In contrast, the PLA–HA implant did not integrate with surrounding tissue. Microindentation showed that porous keratin–HA implants were initially soft, but became stiffer as new bone penetrated the implant from four weeks onwards. In contrast, although the initial rigidity of dense keratin–HA composites was maintained for at least two weeks, the implant material weakened after four weeks. The PLA–HA implant maintained its physical properties throughout the course of the trial. This study demonstrates the increased osseointegration/osteoconduction capacity of keratin–HA composites and provides further evidence supporting the suitability of keratin‐based materials, such as bone graft substitutes and soft tissue fixation devices. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.
Toward biomimetic materials in bone regeneration: Functional behavior of mesenchymal stem cells on a broad spectrum of extracellular matrix components
Authors: Ode Andrea , Duda Georg N. , Glaeser Juliane D. , Matziolis Georg , Frauenschuh Simone , Perka Carsten , Wilson Cameron J. , Kasper Grit
Published: September 2010

Bone defect treatments can be augmented by mesenchymal stem cell (MSC) based therapies. MSC interaction with the extracellular matrix (ECM) of the surrounding tissue regulates their functional behavior. Understanding of these specific regulatory mechanisms is essential for the therapeutic stimulation of MSC in vivo. However, these interactions are presently only partially understood. This study examined in parallel, for the first time, the effects on the functional behavior of MSCs of 13 ECM components from bone, cartilage and hematoma compared to a control protein, and hence draws conclusions for rational biomaterial design. ECM components specifically modulated MSC adhesion, migration, proliferation, and osteogenic differentiation, for example, fibronectin facilitated migration, adhesion, and proliferation, but not osteogenic differentiation, whereas fibrinogen enhanced adhesion and proliferation, but not migration. Subsequently, the integrin expression pattern of MSCs was determined and related to the cell behavior on specific ECM components. Finally, on this basis, peptide sequences are reported for the potential stimulation of MSC functions. Based on the results of this study, ECM component coatings could be designed to specifically guide cell functions. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.
Biocompatibility and bioactivity of designer self‐assembling nanofiber scaffold containing FGL motif for rat dorsal root ganglion neurons
Authors: Zou Zhenwei , Zheng Qixin , Wu Yongchao , Guo Xiaodong , Yang Shuhua , Li Jingfeng , Pan Haitao
Published: September 2010

We report here a designer self‐assembling peptide nanofiber scaffold developed specifically for nerve tissue engineering. We synthesized a peptide FGL‐RADA containing FGL (EVYVVAENQQGKSKA), the motif of neural cell adhesion molecule (NCAM), and then attended to make a FGL nanofiber scaffold (FGL‐NS) by assembling FGL‐RADA with the peptide RADA‐16 (AcN‐RADARADARADARADA‐CONH2). The microstructures of the scaffolds were tested using atomic force microscopy (AFM), and rheological properties of materials were accessed. Then we demonstrated the biocompatibility and bioactivity of FGL‐NS for rat dorsal root ganglion neurons (DRGn). We found that the designer self‐assembling peptide scaffold was noncytotoxic to neurons and able to promote adhesion and neurite sprouting of neurons. Our results indicate that the designer peptide scaffold containing FGL had excellent biocompatibility and bioactivity with adult sensory neurons and could be used for neuronal regeneration. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.
Augmentation of postswelling surgical sealant potential of adhesive hydrogels
Authors: Shazly Tarek M. , Baker Aaron B. , Naber John R. , Bon Adriana , Van Vliet Krystyn J. , Edelman Elazer R.
Published: September 2010

Two‐component hydrogels formed with star polyethylene glycol amine and linear dextran aldehyde polymers (PEG:dextran) show promise as tissue‐specific surgical sealants. However, there is a significant loss of adhesion strength to soft tissues following PEG:dextran swelling, which may limit material ability to appose disjoined tissues and prevent leakage from surgical sites. We covalently incorporated the modified amino acid L‐3,4‐dihydroxyphenylalanine (L‐DOPA) into PEG:dextran to enhance postswelling sealant performance. L‐DOPA is an essential component of marine animal adhesive plaques and has been used to confer wet adhesion in synthetic materials. As both PEG:dextran cohesion and adhesion are mediated by aldehyde‐amine interactions, L‐DOPA side‐groups make it a potent network modulator with potential to affect multiple material properties. Following 1‐h submersion in aqueous media, PEG:dextran doped with 3 mM
L‐DOPA/M aldehyde on average swelled 50.3% less, had 287.4% greater stiffness, and had 53.6% greater functional adhesion strength compared to the neat hydrogel. Increased concentrations of L‐DOPA up to 11 mM
L‐DOPA/M aldehyde similarly curtailed swelling and mitigated property loss with hydration, but sacrificed initial functional adhesion strength, material modulus, and biocompatibility. Taken together, these data support tailored L‐DOPA conjugation as a promising approach to enhance the clinical performance of PEG:dextran sealants. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.
Modulation of mesenchymal stem cells behaviors by chitosan/gelatin/pectin network films
Authors: Li Junjie , Sun Hong , Zhang Rui , Li Ruyue , Yin Yuji , Wang Hui , Liu Yuxi , Yao Fanglian , Yao Kangde
Published: September 2010

In this article, the chitosan/gelatin/pectin (CGP) network films were prepared to build appropriate physicochemical and mechanical microenvironment for attachment, proliferation, and differentiation of mesenchymal stem cells (MSCs). Results suggested that the hydrophilicity and mechanical character of CGP composites films could be modulated via adjusting the pectin content in the composites. The investigations of attachment and proliferation behaviors of mesenchymal stem cells (MSCs) on the CGP films were carried out. The morphology of cells was observed with hematoxylin/eosin staining (HE) and scanning electron microscope (SEM). The osteogenic differentiation of MSCs was investigated via ALP and polymerase chain reaction (PCR). Results suggested that the CGP films have excellent biocompatibility. MSCs seeded on CGP (0.1) film show higher proliferation capacity compared with other samples. Moreover, osteogenic differentiation of MSCs also depends on the properties of the substrate. The MSCs seeded on CGP (0.5) expressed the highest ALP activity, osteogenic gene expression and mineral formation capacity. These results suggest that the composition of the CGP network films could effectively modulate their physicochemical and mechanical properties and further regulate the cell behaviors of MSCs. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010.
Comparison of MTT assay, flow cytometry, and RT‐PCR in the evaluation of cytotoxicity of five prosthodontic materials
Authors: Wang Xue , Xia Yang , Liu Laikui , Liu Mei , Gu Ning , Guang Hanbing , Zhang Feimin
Published: September 2010

In the present study, the cytotoxic effects of five prosthodontic materials on the L929 cell line were assessed by flow cytometry (FCM), reverse transcription PCR (RT‐PCR), and MTT (3‐(4,5‐dimethylthiazole‐2‐yl)‐2,5‐diphenyltetrazoli‐umbromide) assay. The cells were treated with eluates resin (RE), pressable ceramics (PC), Co‐Cr alloy‐porcelain (CC), Ni‐Cr alloy‐porcelain (NC), and diatomite ceramics (DC). The cytotoxicity of all the materials tested by the MTT assay was grade 1. By FCM analysis, apoptosis rates of DC and PC were low, with no significant difference from the control (p > 0.05). The rest of the groups induced much higher apoptosis rates (p < 0.05), with the highest in the RE group. The necrotic cell levels of RE was also significantly increased (p < 0.05). Bcl‐2 and Bax mRNA expression were determined by RT‐PCR, and the Bax/Bcl‐2 ratio in the DC and PC groups were not significantly different from the control (p > 0.05), whereas CC, NC, and RE groups showed significant differences (p < 0.05). Taken together, the results suggest that FCM and RT‐PCR analyses can supplement the traditional MTT assay in evaluating the cytotoxicity of prosthodontic materials for selecting highly biocompatible materials. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010.
In vitro evaluation of cytotoxicity of silver‐containing borate bioactive glass
Authors: Luo Shi‐Hua , Xiao Wei , Wei Xiao‐Juan , Jia Wei‐Tao , Zhang Chang‐Qing , Huang Wen‐Hai , Jin Dong‐Xu , Rahaman Mohamed N. , Day Delbert E.
Published: September 2010

The cytotoxicity of silver‐containing borate bioactive glass was evaluated in vitro from the response of osteoblastic and fibroblastic cells in media containing the dissolution products of the glass. Glass frits containing 0−2 weight percent (wt %) Ag were prepared by a conventional melting and quenching process. The amount of Ag dissolved from the glass into a simulated body fluid (SBF), measured using atomic emission spectroscopy, increased rapidly within the first 48 h, but slowed considerably at longer times. Structural and microchemical analysis showed that the formation of a hydroxyapatite‐like layer on the glass surface within 14 days of immersion in the SBF. The response of MC3T3‐E1 and L929 cells to the dissolution products of the glass was evaluated using SEM observation of cell morphology, and assays of MTT hydrolysis, lactate dehydrogenase release, and alkaline phosphatase activity after incubation for up to 48 h. Cytotoxic effects were found for the borate glass containing 2 wt % Ag, but not for 0.75 and 1 wt % Ag. This borate glass containing up to ∼1 wt % Ag could provide a coating material for bacterial inhibition and enhanced bioactivity of orthopaedic implant materials such as titanium. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010.
Correction to: Complete enumeration of pure‐level and mixed‐level orthogonal arrays
Authors: Schoen Eric D. , Eendebak Pieter T. , Nguyen Man V. M.
Published: September 2010

We correct an error found in Schoen, Endebak, Nguyen, J Combin Designs 18 (2010), 123–140. © 2010 Wiley Periodicals, Inc. J Combin Designs 18: 488, 2010
THE EFFICACY OF CENTRAL BANK INTERVENTION ON THE FOREIGN EXCHANGE MARKET: UGANDA'S EXPERIENCE
Authors: Hisali Eria
Published: September 2010

This paper employs conditional probabilities generated from a homogenous two‐state Markov chain to obtain maximum likelihood estimates of the efficacy of central bank intervention on the foreign exchange market in Uganda. This enables us to explicitly model the fact that intervention actions usually do not target the exchange rate itself but rather its orderly movement. The results suggest that seasonal pressures are largely responsible for moving the short‐term exchange rate process between the different state spaces. Intervention reduces the probability of the exchange rate process staying in a regime characterised by sharp and disruptive tendencies. Copyright © 2010 John Wiley & Sons, Ltd.
Frequency response of multipoint chemical shift‐based spectral decomposition
Authors: Brodsky Ethan K. , Chebrolu Venkata V. , Block Walter F. , Reeder Scott B.
Published: September 2010

Purpose

To provide a framework for characterizing the frequency response of multipoint chemical shift based species separation techniques.

Materials and Methods

Multipoint chemical shift based species separation techniques acquire complex images at multiple echo times and perform maximum likelihood estimation to decompose signal from different species into separate images. In general, after a nonlinear process of estimating and demodulating the field map, these decomposition methods are linear transforms from the echo‐time domain to the chemical‐shift‐frequency domain, analogous to the discrete Fourier transform (DFT). In this work we describe a technique for finding the magnitude and phase of chemical shift decomposition for input signals over a range of frequencies using numerical and experimental modeling and examine several important cases of species separation.

Results

Simple expressions can be derived to describe the response to a wide variety of input signals. Agreement between numerical modeling and experimental results is very good.

Conclusion

Chemical shift‐based species separation is linear, and therefore can be fully described by the magnitude and phase curves of the frequency response. The periodic nature of the frequency response has important implications for the robustness of various techniques for resolving ambiguities in field inhomogeneity. J. Magn. Reson. Imaging 2010;32:943–952. © 2010 Wiley‐Liss, Inc.
Toward local arterial input functions in dynamic contrast‐enhanced MRI
Authors: Fluckiger Jacob U. , Schabel Matthias C. , DiBella Edward V.R.
Published: September 2010

Purpose

To present a method for estimating the local arterial input function (AIF) within a dynamic contrast‐enhanced MRI scan, based on the alternating minimization with model (AMM) method.

Materials and Methods

This method clusters a subset of data into representative curves, which are then input to the AMM algorithm to return a parameterized AIF and pharmacokinetic parameters. Computer simulations are used to investigate the accuracy with which the AMM is able to estimate the true AIF as a function of the input tissue curves.

Results

Simulations show that a power law relates uncertainty in kinetic parameters and SNR and heterogeneity of the input. Kinetic parameters calculated with the measured AIF are significantly different from those calculated with either a global (P < 0.005) or a local input function (P = 0.0). The use of local AIFs instead of measured AIFs yield mean lesion‐averaged parameter changes: Ktrans: +24% [+15%, +70%], kep: +13% [−36%, +300%]. Globally estimated input functions yield mean lesion‐averaged changes: Ktrans: +9% [−38%, +65%], kep: +13% [−100%, +400%]. The observed improvement in fit quality with local AIFs was found to be significant when additional free parameters were accounted for using the Akaike information criterion.

Conclusion

Local AIFs result in significantly different kinetic parameter values. The statistically significant improvement in fit quality suggests that changes in parameter estimates using local AIFs reflect differences in underlying tissue physiology. J. Magn. Reson. Imaging 2010;32:924–934. © 2010 Wiley‐Liss, Inc.
Sp1 phosphorylation is involved in myelin basic protein gene transcription
Authors: Guo Lili , Eviatar‐Ribak Tamar , Miskimins Robin
Published: September 2010

Myelin basic protein (MBP), which helps form compact myelin sheets, is a major protein expressed during oligodendrocyte (OL) differentiation. Myelin basic protein expression is regulated mainly at the transcriptional level. Previous studies showed that the transcription factor Sp1 can activate the MBP promoter. Data from the laboratory also indicate that Sp1 is expressed highly in both growing and differentiated cells. Because this is true, we wanted to understand how Sp1 activity is regulated such that it increases MBP gene transcription only in differentiating cells. Phosphorylation is one major way to regulate transcription factor activity. Our results show that there is more Sp1 binding to the MBP promoter in differentiating OLs. Sp1 is also more phosphorylated in differentiating OLs than in precursor cells. Using inhibitors of different pathways, we found that the protein kinase C (PKC) modulator phorbol 12‐myristate 13‐acetate (PMA) can increase Sp1 phosphorylation when the cells are treated for 1 hr and can decrease Sp1 phosphorylation with long treatment (12 hr). The increased phosphorylation of Sp1 induced by PMA in short treatments could be abolished by the extracellular signal‐regulated kinases (ERK) pathway inhibitor PD98059. This indicates that PKC phosphorylates Sp1 through the ERK pathway. Mutation of Sp1 threonines 453 and 739, which are phosphorylated by ERK, decreased MBP transcriptional activity. Furthermore, we found that PKC regulates Sp1 phosphorylation only in differentiating OLs. In conclusion, our results indicate that, in OLs, Sp1 phosphorylation can be regulated by PKC‐ERK pathways. This phosphorylation is important for MBP transcription and oligodendrocyte differentiation. © 2010 Wiley‐Liss, Inc.
Neural stem cells secrete factors that promote auditory cell proliferation via a leukemia inhibitory factor signaling pathway
Authors: Chen Hsin‐Chien , Ma Hsin‐I , Sytwu Huey‐Kang , Wang Hsing‐Won , Chen Chia‐Chi V. , Liu Shu‐Chen , Chen Chi‐Huang , Chen Hang‐Kang , Wang Chih‐Hung
Published: September 2010

The capacity for perpetual self‐renewal is one of the main characteristics of stem cells. Little is known about the effect of embryonic neural stem cell (NSC)‐secreted factors on auditory cell proliferation in vitro. In the present work, two auditory cell types were cultured in the presence of NSC‐secreted molecules and were evaluated in vitro. Our results demonstrated that both cell viability and cell proliferation were significantly enhanced upon treatment with NSC conditioned medium, which contains significantly elevated levels of leukemia inhibitory factor (LIF) secreted by NSCs. The NSC conditioned medium not only activated the expression of leukemia inhibitory factor receptor in House Ear Institute‐organ of Corti 1 cells but also up‐regulated the LIF downstream signal transducers and activators of transcription (STAT) 1 and STAT3. Blocking either the LIF signaling pathway with neutralizing antibodies or the downstream Janus kinase (JAK)/STAT pathway with JAK2 inhibitor AG490 resulted in a dose‐dependent inhibition of cell proliferation, suggesting that NSC‐secreted molecules promote auditory cell survival via the regulatory LIF/JAK/STAT signaling pathway. © 2010 Wiley‐Liss, Inc.
Potential changes in outdoor thermal comfort conditions in Gothenburg, Sweden due to climate change: the influence of urban geometry
Authors: Thorsson Sofia , Lindberg Fredrik , Björklund Jesper , Holmer Björn , Rayner David
Published: September 2010

Quantitative information about outdoor thermal comfort, on various temporal and spatial scales, is required to design better cities and mitigate heat problems not only in warm but also in temperate climates. The overall objective of this study is to explore the augmentation of global/regional climate changes by urban features such as geometry in a compact mid‐rise high‐latitude city (Gothenburg). The magnitude of spatial and temporal variations of intra‐urban mean radiant temperatures (Tmrt) is quantified using the SOLWEIG (SOlar and LongWave Environmental Irradiance Geometry) model. Hourly time resolution, statistically downscaled meteorological data, based on the ECHAM5‐GCM under the A1B emission scenario is used to simulate changes in Tmrt and physiologically equivalent temperature (PET) at the 2080–2099 time horizon.

Results show that urban geometry causes large intra‐urban differences in Tmrt, on hourly, daytime and yearly time scales. In general, open areas are warmer than adjacent narrow street canyons in summer, but cooler in winter. According to the ECHAM5‐based scenario, the daytime Tmrt will increase by 3.2 °C by the end of this century. This is 0.4° more than simulated increase in air temperature (2.8 °C) and is mainly a result of decreases in summer cloudiness. Occasions of strong/extreme heat stress are expected to triple. This equates to 20–100 h a year, depending on geometry. Conversely, the number of hours with strong/extreme cold stress decreases by 400–450 h. Furthermore, the number of hours with no thermal stress increases by 40–200 h a year.

The study confirms the potential for using geometry to mitigate daytime thermal stress. A densely built structure mitigates extreme swings in Tmrt and PET, improving outdoor comfort conditions both in summer and in winter. Furthermore, it highlights the importance of including information on either Tmrt or thermal comfort in climate scenarios to describe the combined effects of changes in multiple climate variables and to more realistically measure the impact on humans. Copyright © 2010 Royal Meteorological Society