bluuebunny/crossref_metadata_2025 huggingface dataset:
VORTICAL FLOW OF INCOMPRESSIBLE VISCOUS FLUID IN FINITE CYLINDER
Authors: Kalis Harijs , Kangro Ilmārs
Published: September 2008

The effective use of vortex energy in production of strong velocity fields by different devices is one of the modern areas of applications, developed during the last decade. In this paper the distribution of velocity field for viscous incompressible fluid in a pipe with a system of finite number of circular vortex lines, positioned on the inner surface of the finite cylinder is calculated. The approximation of the corresponding boundary value problem for the Navier‐Stokes equations is based on the finite difference method. This procedure allows us to reduce the 2D problem decribed by the system of Navier‐ Stokes PDEs to the monotonous difference equations. Calculations are done using the computer program Matlab and the following regimes are calculated: a) the flow in a smooth pipe; b) the flow, poured inside a pipe through the circle; c) the flow, poured inside a pipe through the ring. The model is investigated for different values of parameters Re (Reynolds number), G(swirl number) and A (vortex intensity).
FINITE ELEMENT SOLUTION OF BOUNDARY VALUE PROBLEMS WITH NONLOCAL JUMP CONDITIONS
Authors: Koleva Miglena
Published: September 2008

We consider stationary linear problems on non‐connected layers with distinct material properties. Well posedness and the maximum principle (MP) for the differential problems are proved. A version of the finite element method (FEM) is used for discretization of the continuous problems. Also, the MP and convergence for the discrete solutions are established. An efficient algorithm for solution of the FEM algebraic equations is proposed. Numerical experiments for linear and nonlinear problems are discussed.
MATHEMATICAL ANALYSIS OF BLOOD FLOW THROUGH AN ARTERIAL SEGMENT WITH TIME‐DEPENDENT STENOSIS
Authors: Misra Jagadis Chandra , Adhikary Sudi D. , Shit Gopal Chandra
Published: September 2008

A mathematical model is developed here with an aim to study the pulsatile flow of blood through an arterial segment having a time‐dependent stenosis. Blood is considered to consist of a core layer where erythrocytes are concentrated and a peripheral plasma layer that is free from erythrocytes. The plasma layer is taken to behave as a Newtonian fluid, while the core layer is represented by as a Casson fluid (non‐Newtonian) model. The pulsatile flow is analyzed by considering a periodic pressure gradient, which is a function of time. A perturbation analysis is employed to solve the governing differential equations by taking the Womersley frequency parameter to be small (α < 1). This is a realistic assumption for physiological fluid flows, particularly for flow of blood in small vessels. Using appropriate boundary conditions, analytical expressions for the velocity profile, the volumetric flow rate, the wall shear stress and the flow resistance have been derived. These expressions are computed numerically and the computational results are presented graphically, in order to illustrate the variation of different quantities that are of particular interest in the study.
APPLICATIONS OF 3D PCA METHOD FOR EXTRACTION OF MEAN SHAPE AND GEOMETRICAL FEATURES OF BIOLOGICAL OBJECTS SET
Authors: Rychlik Michal , Stankiewicz Witold , Morzyński Marek
Published: September 2008

This article presents application of the Principal Component Analysis method for analysis of geometry of biological objects and computation of three dimensional anthropometric database. In this work as the biological objects the fifteen human femur bones were used. The geometry of each bone was obtained by using 3D structural light scanner. For PCA analysis all objects have to be described with the same FEM mesh. To achieve this, the modified fluid registration was used. PCA decomposes the set of 3D objects into mean geometry and individual features (empirical modes) describing deviations from mean value. In this paper the mean shape and features of real bones were presented and discussed.
GRID APPROXIMATION OF SINGULARLY PERTURBED PARABOLIC EQUATIONS WITH MOVING BOUNDARY LAYERS
Authors: Shishkin Grigorii
Published: September 2008

A grid approximation of a boundary value problem is considered for a singularly perturbed parabolic reaction‐diffusion equation in a domain with boundaries moving along the x‐axis in the positive direction. For small values of the parameter ϵ (that is the coefficient of the highest‐order derivative in the equation, ϵ ∈ (0,1]), a moving boundary layer appears in a neighbourhood of the left lateral boundary SL 1. It turns out that, in the class of difference schemes on rectangular grids condensing in a neighbourhood of SL 1 with respect to x and t, there do not exist schemes that converge even under the condition P 0 −1 Â ϵ1/2, where P 0 is the total number of nodes in the meshes used, that is, P 0 Â N N 0, where the values N and N 0 define the numbers of mesh points in x and t. On such meshes, convergence under the condition N −1 + N 0 −1 ≤ ϵ1/4 cannot be achieved. Examination of widths similar to Kolmogorov's widths allows us to establish necessary and sufficient conditions for the ϵ‐uniform convergence of approximations to the solution of the boundary value problem. Using these conditions, a scheme is constructed on a mesh being piece‐wise uniform in a coordinate system adapted to the moving boundary. This scheme converges ϵ‐uniformly at the rate O(N −1 ln N + N0 −1).
The spectrum of adult B‐lymphoid leukemias with BCR‐ABL: Molecular diagnostic, cytogenetic, and clinical laboratory perspectives
Authors: Klco Jeffery M. , Kreisel Friederike H. , Zehnbauer Barbara A. , Kulkarni Shashikant , Hassan Anjum , Frater John L.
Published: September 2008

The Philadelphia (Ph) chromosome is characteristic of chronic myelogenous leukemia (CML), but it is also the most frequent cytogenetic abnormality in precursor B‐lymphoblastic leukemia (ALL) of adults. The vast majority of CML patients have a BCR‐ABL translocation that yields a 210 kD (p210) oncoprotein, whereas adult Ph‐positive ALL cases can present with either a p190 or a p210 oncoprotein, or both. Considering that 30% of the patients with CML that progress to blast crisis will have a lymphoblastic presentation, adults presenting with a p210 ALL may have either a de novo ALL or CML presenting for the first time in lymphoblastic phase. To identify the distinguishing features, cases of p190‐ALL, p210‐ALL, and lymphoblastic CML were compared. In spite of significant overlap between the three entities, a number of features were found to aid in their differentiation. p210‐ALL patients present at a younger age with blasts that frequently show loss of expression of CD34, whereas p190‐ALL patients present with marked increase in peripheral blast percentage. Interestingly, bone marrow findings characteristic of a myeloproliferative disorder are specific, but are not sensitive for lymphoblastic CML. This study suggests that despite the similarities between these leukemias, p190‐ALL, p210‐ALL, and lymphoblastic phase CML likely represent three distinct diseases. Am. J. Hematol., 2008. © 2008 Wiley‐Liss, Inc.
Survival and disability in a cohort of neural tube defect births in Dublin, Ireland
Authors: Sutton Marie , Daly Leslie E. , Kirke Peadar N.
Published: September 2008

BACKGROUND:

Neural tube defects (NTDs) are a major cause of death and disability. Periconceptional folic acid prevents up to 70% of these malformations but public health campaigns to increase use of supplements have had disappointing results: The proposed mandatory fortification of bread products in Ireland has raised concerns about possible side effects. We examined data collected on a cohort of children born with NTDs in an era before fortification/supplementation to illustrate the serious consequences in terms of survival and disability.

METHODS:

All 623 infants born with NTDs in the Dublin area between 1976 and 1987 were included. Information was collected on mortality and length of survival for those who died, and for those who survived at least 5 years, interview‐based data were collected on age, place of residence, prevalence of hydrocephalus, degree of disability, schooling, and IQ.

RESULTS:

Seventy‐four births (12%) were stillborn. Of the livebirths only 41% were alive at 5 years. Factors associated with mortality were type of lesion, level of lesion, presence of other defects, hydrocephalus, year of birth, and gestation. Of the children who survived to 5 years or more, 75% had a disability and 56% were severely disabled. Type of lesion and level of lesion influenced disability risk.Of the survivors, 51% of children had mobility limitations, 59% were incontinent, 42% had hydrocephalus, and 17% had intellectual disability.

CONCLUSIONS:

These findings illustrate the devastating consequences of NTDs and underline the importance of effective intervention programs with folic acid for prevention. Birth Defects Research (Part A) 2008. © 2008 Wiley‐Liss, Inc.
Selective antibody precipitation using polyelectrolytes: A novel approach to the purification of monoclonal antibodies
Authors: McDonald Paul , Victa Corazon , Carter‐Franklin Jayme N. , Fahrner Robert
Published: September 2008

We evaluated the potential for polyelectrolyte induced precipitation of antibodies to replace traditional chromatography purification. We investigated the impact of solution pH, solution ionic strength and polyelectrolyte molecular weight on the degree of precipitation using the anionic polyelectrolytes polyvinylsulfonic acid (PVS), polyacrylic acid (PAA), and polystyrenesulfonic acid (PSS). As we approached the pI of the antibody, charge neutralization of the antibody reduced the antibody–polyelectrolyte interaction, reducing antibody precipitation. At a given pH, increasing solution ionic strength prevented the ionic interaction between the polyelectrolyte and the antibody, reducing antibody precipitation. With increasing pH of precipitation, there was an increase in impurity clearance. Increasing polyelectrolyte molecular weight allowed the precipitation to be performed under conditions of higher ionic strength. PVS was selected as the preferred polyelectrolyte based on step yield following resolubilization, purification performance, as well as the nature of the precipitate. We evaluated PVS precipitation as a replacement for the initial capture step, as well as an intermediate polishing step in the purification of a humanized monoclonal antibody. PVS precipitation separated the antibody from host cell impurities such as host cell proteins (HCP) and DNA, process impurities such as leached protein A, insulin and gentamicin, as well as antibody fragments and aggregates. PVS was subsequently removed from antibody pools to <1 µg/mg using anion exchange chromatography. PVS precipitation did not impact the biological activity of the resolubilized antibody. Biotechnol. Bioeng. 2009;102: 1141–1151. © 2008 Wiley Periodicals, Inc.
Non‐invasive self‐referencing electrochemical sensors for quantifying real‐time biofilm analyte flux
Authors: McLamore E.S. , Porterfield D.M. , Banks M.K.
Published: September 2008

Current techniques for characterizing biofilm physiology lack the signal filtering capability required for quantifying signals associated with real time biologically active transport. Though a great deal was learned from previous investigations, no results have been reported on the characterization of in vivo, real time biofilm flux using non‐invasive (non‐destructive) techniques. This article introduces the self‐referencing technique for applications in biofilm physiology. Self‐referencing is a non‐invasive sensing modality which is capable of sensing changes in biologically active analyte flux as small as 10 fmol cm−2 s−1. Studies directly characterizing flux, as opposed to concentration, have the advantage of quantifying real time changes in biologically active transport which are otherwise lost to background noise. The use of this modality for characterizing biofilm physiology is validated with a reversible enzyme inhibition study. The experiment used self‐referencing potentiometric sensors for quantifying real time ammonium and nitrite flux. Amperometric and optical sensing methods, though not presented herein, are also powerful sensing tools which benefit from operation in self‐referencing mode. Reversible ammonia monooxygenase inhibition by a copper chelator (thiourea), and subsequent relief by excess copper addition was successfully demonstrated using self‐referencing ion‐selective microelectrodes for a mature Nitrosomonas europaea biofilm. Biotechnol. Bioeng. 2009; 102: 791–799. © 2008 Wiley Periodicals, Inc.
Cross‐linking density alters early metabolic activities in chondrocytes encapsulated in poly(ethylene glycol) hydrogels and cultured in the rotating wall vessel
Authors: Villanueva Idalis , Klement Brenda J. , von Deutsch Daniel , Bryant Stephanie J.
Published: September 2008

In designing a tissue engineering strategy for cartilage repair, selection of both the bioreactor, and scaffold is important to the development of a mechanically functional tissue. The hydrodynamic environment associated with many bioreactors enhances nutrient transport, but also introduces fluid shear stress, which may influence cellular response. This study examined the combined effects of hydrogel cross‐linking and the hydrodynamic environment on early chondrocyte response. Specifically, chondrocytes were encapsulated in poly(ethylene glycol) (PEG) hydrogels having two different cross‐linked structures, corresponding to a low and high cross‐linking density. Both cross‐linked gels yielded high water contents (92% and 79%, respectively) and mesh sizes of 150 and 60 Å respectively. Cell‐laden PEG hydrogels were cultured in rotating wall vessels (RWV) or under static cultures for up to 5 days. Rotating cultures yielded low fluid shear stresses (≤0.11 Pa) at the hydrogel periphery indicating a laminar hydrodynamic environment. Chondrocyte response was measured through total DNA content, total nitric oxide (NO) production, and matrix deposition for glycosaminoglycans (GAG). In static cultures, gel cross‐linking had no effect on DNA content, NO production, or GAG production; although GAG production increased with culture time for both cross‐linked gels. In rotating cultures, DNA content increased, NO production decreased, and overall GAG production decreased when compared to static controls for the low cross‐linked gels. For the high cross‐linked gels, the hydrodynamic environment had no effect on DNA content, but exhibited similar results to the low cross‐linked gel for NO production, and matrix production. Our findings demonstrated that at early culture times, when there is limited matrix production, the hydrodynamic environment dramatically influences cell response in a manner dependent on the gel cross‐linking, which may impact long‐term tissue development. Biotechnol. Bioeng. 2009;102: 1242–1250. © 2008 Wiley Periodicals, Inc.
Engineering and expression of a chimeric transferrin receptor monoclonal antibody for blood–brain barrier delivery in the mouse
Authors: Boado Ruben J. , Zhang Yun , Wang Yuntao , Pardridge William M.
Published: September 2008

Protein therapeutics may be delivered across the blood–brain barrier (BBB) by genetic fusion to a BBB molecular Trojan horse. The latter is an endogenous peptide or a peptidomimetic monoclonal antibody (MAb) against a BBB receptor, such as the insulin receptor or the transferrin receptor (TfR). Fusion proteins have been engineered with the MAb against the human insulin receptor (HIR). However, the HIRMAb is not active against the rodent insulin receptor, and cannot be used for drug delivery across the mouse BBB. The rat 8D3 MAb against the mouse TfR is active as a drug delivery system in the mouse, and the present studies describe the cloning and sequencing of the variable region of the heavy chain (VH) and light chain (VL) of the rat 8D3 TfRMAb. The VH and VL were fused to the constant region of mouse IgG1 heavy chain and mouse kappa light chain, respectively, to produce a new chimeric TfRMAb. The chimeric TfRMAb was expressed in COS cells following dual transfection with the heavy and light chain expression plasmids, and was purified by protein G affinity chromatography. The affinity of the chimeric TfRMAb for the murine TfR was equal to the 8D3 MAb using a radio‐receptor assay and mouse fibroblasts. The chimeric TfRMAb was radio‐labeled and injected into mice for a pharmacokinetics study of the clearance of the chimeric TfRMAb. The chimeric TfRMAb was rapidly taken up by mouse brain in vivo at a level comparable to the rat 8D3 MAb. In summary, these studies describe the genetic engineering, expression, and validation of a chimeric TfRMAb with high activity for the mouse TfR, which can be used in future engineering of therapeutic fusion proteins for BBB drug delivery in the mouse. Biotechnol. Bioeng. 2009;102: 1251–1258. © 2008 Wiley Periodicals, Inc.
Molecular engineering of exocytic vesicle traffic enhances the productivity of Chinese hamster ovary cells
Authors: Peng Ren‐Wang , Fussenegger Martin
Published: September 2008

A complex vesicle trafficking system manages the precise and regulated distribution of proteins, membranes and other molecular cargo between cellular compartments as well as the secretion of (heterologous) proteins in mammalian cells. Sec1/Munc18 (SM) proteins are key components of the system by regulating membrane fusion. However, it is not clear how SM proteins contribute to the overall exocytosis. Here, functional analysis of the SM protein Sly1 and Munc18c suggested a united, positive impact upon SNARE‐based fusion of ER‐to‐Golgi‐ and Golgi‐to‐plasma membrane‐addressed exocytic vesicles and increased the secretory capacity of different therapeutic proteins in Chinese hamster ovary cells up to 40 pg/cell/day. Sly1‐ and Munc18c‐based vesicle traffic engineering cooperated with Xbp‐1‐mediated ER/Golgi organelle engineering. Our study supports a model for united function of SM proteins in stimulating vesicle trafficking machinery and provides a generic secretion engineering strategy to improve biopharmaceutical manufacturing of important protein therapeutics. Biotechnol. Bioeng. 2009;102: 1170‐1181. © 2008 Wiley Periodicals, Inc.
Redirecting the inactivation pathway of penicillin amidase and increasing amoxicillin production via a thermophilic molecular chaperone
Authors: Bergeron Lisa M. , Tokatlian Talar , Gomez Lizabeth , Clark Douglas S.
Published: September 2008

We have previously shown that a single‐subunit thermosome from Methanocaldococcus jannaschii (rTHS) can stabilize enzymes in semi‐aqueous media (Bergeron et al., 2008b). In the present study, rTHS was used to stabilize penicillin amidase (PGA) in methanol–water mixtures. Including methanol in the reaction medium for amoxicillin synthesis can suppress unwanted hydrolysis reactions but inactivate PGA. Inactivation and reactivation pathways proposed for PGA illustrate the predictability of enzyme stabilization by rTHS in co‐solvents. Calcium was necessary for reversible dissociation of the two PGA subunits in methanol–water and the presence of calcium resulted in an enhancement of chaperone‐assisted stabilization. rTHS also acted as a stabilizer in the enzymatic synthesis of the β‐lactam antibiotic amoxicillin. rTHS stabilized PGA, increasing its half‐life in 35% methanol by fivefold at 37°C. Stabilization by rTHS was enhanced but did not require the presence of ATP. Including rTHS in fed‐batch reactions performed in methanol–water resulted in nearly 4 times more amoxicillin than when the reaction was run without rTHS, and over threefold higher selectivity towards amoxicillin synthesis compared to aqueous conditions without rTHS. The thermosome and other thermophilic chaperones may thus be generally useful for stabilizing enzymes in their soluble form and expanding the range of conditions suitable for biocatalysis. Biotechnol. Bioeng. 2009;102: 417–424. © 2008 Wiley Periodicals, Inc.
Effect of sodium dodecylbenzene sulfonate on subtilisin Carlsberg proteolysis of an immobilized ovalbumin film
Authors: Foose Ladan L. , Blanch Harvey W. , Radke C.J.
Published: September 2008

Enzymatic degradation of immobilized ovalbumin multilayer films by subtilisin Carlsberg was investigated using in situ ellipsometry. Changes in the substrate cleavage rate in the presence of an anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), were assessed. Exposure of the protein film to SDBS prior to introduction of the enzyme increased the measured proteolysis rate threefold. Surfactant increased the measured film thickness, absorbing into the protein film and causing swelling. Surfactant‐induced film swelling was reversible upon aqueous rinsing. Nevertheless, exposure of enzyme to the surfactant‐rinsed film increased the proteolysis rate, most likely due to irreversible conformational changes induced in the substrate film by the surfactant. Simultaneous addition of SDBS with enzyme after the initial surfactant exposure did not produce additional protein‐removal benefit. Biotechnol. Bioeng. 2009;102: 1273–1277. © 2008 Wiley Periodicals, Inc.
Modeling electrostatic exclusion effects during ion exchange chromatography of monoclonal antibodies
Authors: Zydney Andrew L. , Harinarayan Chithkala , van Reis Robert
Published: September 2008

Recent experimental studies have shown a reduction in dynamic‐ binding capacity for both monoclonal antibodies and antigen‐binding fragments at very low conductivity, conditions that should generate the greatest electrostatic attraction. This behavior has been attributed to the steric and electrostatic exclusion of the charged protein from the entrance of the resin pores. This manuscript presents a quantitative mathematical description of this phenomenon. The protein partition coefficient was evaluated using models for the partitioning of a charged sphere into a charged cylindrical pore, with the pore size distribution evaluated by inverse size exclusion chromatography. The results were in very good agreement with experimental data for batch protein uptake and dynamic‐binding capacity over a range of pH and conductivity. This theoretical framework provides important insights into the behavior of ion exchange chromatography for protein purification. Biotechnol. Bioeng. 2009;102: 1131–1140. © 2008 Wiley Periodicals, Inc.
Attachment anxiety, intra‐group (dis)respect, actual efforts, and group donation
Authors: Erez Ayelet , Sleebos Ed , Mikulincer Mario , Van Ijzendoorn Marinus H. , Ellemers Naomi , Kroonenberg Pieter M.
Published: September 2008

The current study examines attachment‐style differences in responses to inductions of group respect and disrespect. Participants completed a scale assessing attachment anxiety and avoidance, performed group tasks, and received high, average, or low respect feedback from group members. Then we assessed commitment to this group, actual effort expenditure on behalf of the group, and money donation to the group. For participants scoring relatively high on attachment anxiety, high group respect heightened group commitment and effort expenditure on behalf of the group, whereas group disrespect led to lower group commitment but to more money donation to the group and higher effort expenditure. Participants who scored relatively low on attachment anxiety were not significantly affected by group respect or disrespect. The implications of attachment theory for group dynamics were discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Experimental and numerical characterization of the flowfield in the large‐scale UW live fire research facility
Authors: Devaud C. B. , Weisinger J. , Johnson D. A. , Weckman E. J.
Published: September 2008

Recently, a large‐scale (19.5m × 15.4m × 12.8m) live fire research facility (LFRF) has been built at the University of Waterloo with the capabilities of conducting controlled and systematic experimental studies to investigate the behaviour of large fuel spill fires in crosswinds. The present work is focused on characterizing the wind generated by banked fans and the flowfield in the LFRF using experimental techniques and large eddy simulation (LES). Two configurations are examined: the empty enclosure and the enclosure with a large blocking object (cylinder) aligned perpendicular to the flow direction.

Detailed velocity measurements are provided throughout the facility. The experimental results show that the flowfield inside the empty enclosure is consistent with the behaviour of a bluff wall jet.

Three‐dimensional LES are performed for the same two configurations. The experimental velocity profiles are used to set the inflow conditions in the calculations. The numerical predictions are all within the experimental uncertainty in the core region for the empty enclosure. For the case with the cylinder, the size of the wake is very well reproduced by the simulations and the shedding frequency corresponds to the value given in published experimental studies of a flow over free standing cylinders. The present LES model is also capable of predicting more detailed flow characteristics such as the stagnation and recirculation region, compared with what was achievable in the large‐scale experiments. In the wake the time‐averaged velocities from the LES results are overpredicted. Possible sources of discrepancy are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Identification of candidate tumor suppressor genes inactivated by promoter methylation in melanoma
Authors: Bonazzi Vanessa F. , Irwin Darryl , Hayward Nicholas K.
Published: September 2008

Tumor suppressor genes (TSGs) are sometimes inactivated by transcriptional silencing through promoter hypermethylation. To identify novel methylated TSGs in melanoma, we carried out global mRNA expression profiling on a panel of 12 melanoma cell lines treated with a combination of 5‐Aza‐2‐deoxycytidine (5AzadC) and an inhibitor of histone deacetylase, Trichostatin A. Reactivation of gene expression after drug treatment was assessed using Illumina whole‐genome microarrays. After qRT‐PCR confirmation, we followed up 8 genes (AKAP12, ARHGEF16, ARHGAP27, ENC1, PPP1R3C, PPP1R14C, RARRES1, and TP53INP1) by quantitative DNA methylation analysis using mass spectrometry of base‐specific cleaved amplification products in panels of melanoma cell lines and fresh tumors. PPP1R3C, ENC1, RARRES1, and TP53INP1, showed reduced mRNA expression in 35–59% of the melanoma cell lines compared to melanocytes and which was correlated with a high proportion of promoter methylation (>40–60%). The same genes also showed extensive promoter methylation in 6–25% of the tumor samples, thus confirming them as novel candidate TSGs in melanoma. © 2008 Wiley‐Liss, Inc.
Integration of genomic and gene expression data of childhood ALL without known aberrations identifies subgroups with specific genetic hallmarks
Authors: Bungaro Silvia , Dell'Orto Marta Campo , Zangrando Andrea , Basso Dario , Gorletta Tatiana , Lo Nigro Luca , Leszl Anna , Young Bryan D. , Basso Giuseppe , Bicciato Silvio , Biondi Andrea , te Kronnie Gertruy , Cazzaniga Giovanni
Published: September 2008

Pediatric acute lymphoblastic leukemia (ALL) comprises genetically distinct subtypes. However, 25% of cases still lack defined genetic hallmarks. To identify genomic aberrancies in childhood ALL patients nonclassifiable by conventional methods, we performed a single nucleotide polymorphisms (SNP) array‐based genomic analysis of leukemic cells from 29 cases. The vast majority of cases analyzed (19/24, 79%) showed genomic abnormalities; at least one of them affected either genes involved in cell cycle regulation or in B‐cell development. The most relevant abnormalities were CDKN2A/9p21 deletions (7/24, 29%), ETV6 (TEL)/12p13 deletions (3/24, 12%), and intrachromosomal amplifications of chromosome 21 (iAMP21) (3/24, 12%). To identify variation in expression of genes directly or indirectly affected by recurrent genomic alterations, we integrated genomic and gene expression data generated by microarray analyses of the same samples. SMAD1 emerged as a down‐regulated gene in CDKN2A homozygous deleted cases compared with nondeleted. The JAG1 gene, encoding the Jagged 1 ligand of the Notch receptor, was among a list of differentially expressed (up‐regulated) genes in ETV6‐deleted cases. Our findings demonstrate that integration of genomic analysis and gene expression profiling can identify genetic lesions undetected by routine methods and potential novel pathways involved in B‐progenitor ALL pathogenesis. © 2008 Wiley‐Liss, Inc.
Regulation of Schwann cell function by the extracellular matrix
Authors: Chernousov Michael A. , Yu Wei‐Ming , Chen Zu‐Lin , Carey David J. , Strickland Sidney
Published: September 2008

Laminins and collagens are extracellular matrix proteins that play essential roles in peripheral nervous system development. Laminin signals regulate Schwann cell proliferation and survival as well as actin cytoskeleton dynamics, which are essential steps for radial sorting and myelination of peripheral axons by Schwann cells. Collagen and their receptors promote Schwann cell adhesion, spreading, and myelination as well as neurite outgrowth. In this article, we will review the recent advances in the studies of laminin and collagen function in Schwann cell development. © 2008 Wiley‐Liss, Inc.
Molecular domains of myelinated axons in the peripheral nervous system
Authors: Salzer James L. , Brophy Peter J. , Peles Elior
Published: September 2008

Myelinated axons are organized into a series of specialized domains with distinct molecular compositions and functions. These domains, which include the node of Ranvier, the flanking paranodal junctions, the juxtaparanodes, and the internode, form as the result of interactions with myelinating Schwann cells. This domain organization is essential for action potential propagation by saltatory conduction and for the overall function and integrity of the axon. © 2008 Wiley‐Liss, Inc.
Molecular mechanisms of inherited demyelinating neuropathies
Authors: Scherer Steven S. , Wrabetz Lawrence
Published: September 2008

The past 15 years have witnessed the identification of more than 25 genes responsible for inherited neuropathies in humans, many associated with primary alterations of the myelin sheath. A remarkable body of work in patients, as well as animal and cellular models, has defined the clinical and molecular genetics of these illnesses and shed light on how mutations in associated genes produce the heterogeneity of dysmyelinating and demyelinating phenotypes. Here, we review selected recent developments from work on the molecular mechanisms of these disorders and their implications for treatment strategies. © 2008 Wiley‐Liss, Inc.
The function of RhoGTPases in axon ensheathment and myelination
Authors: Feltri M. Laura , Suter Ueli , Relvas João B.
Published: September 2008

RhoGTPases are molecular switches that integrate extracellular signals to perform diverse cellular responses. This ability relies on the network of proteins regulating RhoGTPases activity and localization, and on the interaction of RhoGTPases with many different cellular effectors. Myelination is an ideal place for RhoGTPases regulation, as it is the result of fine orchestration of many stimuli from at least two cell types. Recent work has revealed that RhoGTPases are required for Schwann cells to sort, ensheath, and myelinate axons. Here, we will review these recent advances showing the critical roles for RhoGTPases in various aspects of Schwann development and myelination, including the recent discovery of their involvement in Charcot‐Marie‐Tooth disease. Comparison with potential roles of RhoGTPases in central nervous system myelination will be drawn. © 2008 Wiley‐Liss, Inc.
Neuregulin‐1, a key axonal signal that drives Schwann cell growth and differentiation
Authors: Birchmeier Carmen , Nave Klaus‐Armin
Published: September 2008

Interactions between neuronal and glial cells are crucial for establishing a functional nervous system. Many aspects of Schwann cell development and physiology are regulated by neuronal signals; possibly the most spectacular is the elaboration of the myelin sheath. An extensive line of research has revealed that one neuronal factor, termed “neuregulin”, promotes Schwann cell growth and survival, migration along the extending axon, and myelination. The versatility of glial responses elicited by this factor is thus clearly astounding. © 2008 Wiley‐Liss, Inc.
Pituicyte modulation of neurohormone output
Authors: Rosso Lia , Mienville Jean‐Marc
Published: September 2008

Pituicytes have long been suspected to play a role in the regulation of neurohypophysial hormone output. This role has been mainly ascribed to morphological changes in these cells and subsequent modifications of their tight structural relationships with surrounding nerve terminals and capillaries. These entirely reversible changes are brought about by physiological states such as parturition, lactation, or dehydration, and it was inferred that they should facilitate neurohormone output, based on concerted analyses ofin vitro,in situ, andex vivoexperiments. Pituicyte stellation, thein vitrocounterpart of these morphological changes, can be induced by β‐adrenergic or A1‐adenosine receptor activation, and appears to result from inhibition of the small GTPase RhoA. Actin depolymerization is the key event allowing stellation. Vasopressin and oxytocin reverse stellation and return pituicytes to their basal shape by activating Cdc42, another small GTPase that reorganizes the actin cytoskeleton in a cortical position. Adenosine and neurohormones also have opposite actions on the efflux of taurine, a local messenger that is released by pituicytes in hypotonic conditions and accordingly inhibits vasopressin output from axon terminals. As adenosine is likely generated from endogenous ATP co‐released with neurohormones and broken down by local ectoATPases, these data suggest a subtle balance between a positive and a negative feedback on vasopressin output operated, respectively, by adenosine and vasopressin to maintain hydromineral homeostasis. A theoretical scenario is presented to account for the putative sequence of pituicyte‐related events following disturbance of the hydromineral system. © 2008 Wiley‐Liss, Inc.
Negative regulation of myelination: Relevance for development, injury, and demyelinating disease
Authors: Jessen Kristján R. , Mirsky Rhona
Published: September 2008

Dedifferentiation of myelinating Schwann cells is a key feature of nerve injury and demyelinating neuropathies. We review recent evidence that this dedifferentiation depends on activation of specific intracellular signaling molecules that drive the dedifferentiation program. In particular, we discuss the idea that Schwann cells contain negative transcriptional regulators of myelination that functionally complement positive regulators such as Krox‐20, and that myelination is therefore determined by a balance between two opposing transcriptional programs. Negative transcriptional regulators should be expressed prior to myelination, downregulated as myelination starts but reactivated as Schwann cells dedifferentiate following injury. The clearest evidence for a factor that works in this way relates to c‐Jun, while other factors may include Notch, Sox‐2, Pax‐3, Id2, Krox‐24, and Egr‐3. The role of cell–cell signals such as neuregulin‐1 and cytoplasmic signaling pathways such as the extracellular‐related kinase (ERK)1/2 pathway in promoting dedifferentiation of myelinating cells is also discussed. We also review evidence that neurotrophin 3 (NT3), purinergic signaling, and nitric oxide synthase are involved in suppressing myelination. The realization that myelination is subject to negative as well as positive controls contributes significantly to the understanding of Schwann cell plasticity. Negative regulators are likely to have a major role during injury, because they promote the transformation of damaged nerves to an environment that fosters neuronal survival and axonal regrowth. In neuropathies, however, activation of these pathways is likely to be harmful because they may be key contributors to demyelination, a situation which would open new routes for clinical intervention. © 2008 Wiley‐Liss, Inc.
Differential erbB signaling in astrocytes from the cerebral cortex and the hypothalamus of the human brain
Authors: Sharif Ariane , Duhem‐Tonnelle Véronique , Allet Cécile , Baroncini Marc , Loyens Anne , Kerr‐Conte Julie , Collier Francis , Blond Serge , Ojeda Sergio R. , Junier Marie‐Pierre , Prevot Vincent
Published: September 2008

Studies in rodents have shown that astroglial erbB tyrosine kinase receptors are key regulatory elements in neuron–glia communication. Although both astrocytes and deregulation of erbB functions have been implicated in the pathogenesis of many common human brain disorders, erbB signaling in native human brain astrocytes has never been explored. Taking advantage of our ability to perform primary cultures from the cortex and the hypothalamus of human fetuses, we conducted a thorough analysis of erbB signaling in human astrocytes. We showed that human cortical astrocytes express erbB1, erbB2, and erbB3, whereas human hypothalamic astrocytes express erbB1, erbB2, and erbB4 receptors. Ligand‐dependent activation of different erbB receptor heterodimeric complexes in these two populations of astrocytes translated into different morphological and proliferative responses. Although morphological plasticity was more pronounced in hypothalamic astrocytes than in cortical astrocytes, the former showed a lower mitogenic potential. Decreasing erbB4 expression via siRNA‐mediated gene knockdown revealed that erbB4 constitutively restrains basal proliferative activity in hypothalamic astrocytes. We further show that treatment of human astrocytes with a protein kinase C activator results in rapid tyrosine phosphorylation of erbB receptors that involves cleavage of endogenous membrane bound erbB ligands by metalloproteinases. Together, these results indicate that erbB signaling in primary human brain astrocytes is functional, region‐specific, and can be activated in a paracrine and/or autocrine manner. In addition, by revealing that some aspects of astroglial erbB signaling are different between human and rodents, our results provide a molecular framework to explore the potential involvement of astroglial erbB signaling deregulation in human brain disorders. © 2008 Wiley‐Liss, Inc.
Endogenous signals initiating inflammation in the injured nervous system
Authors: Pineau Isabelle , Lacroix Steve
Published: September 2008

Glial cells are known to respond to a variety of neural injuries and play an important role in tissue damage and repair in the injured nervous system. This glial response, which is initially characterized by the expression of proinflammatory cytokines and chemokines and the attraction of microglial cells toward sites of injury, literally occurs within seconds to minutes of the injury. This suggests that signals that are endogenous to the nervous system are responsible for initiating neuroinflammation. In this review, we summarize the most recent advances made in the identification of these endogenous signals and describe the receptors and signaling pathways by which these ligands stimulate the production of cytokines and chemokines. Among these endogenous damage signals are ligands for toll‐like receptors, including several heat shock proteins and extracellular matrix components, as well as self‐derived RNA and DNA and associated proteins. Growing evidence also suggests that nucleotides released upon injury and acting through P2 receptors, such as ATP and UTP or their analogues, could serve as endogenous signals for the rapid response of glial cells. © 2008 Wiley‐Liss, Inc.
Proteomic analysis of the retina: Removal of RPE alters outer segment assembly and retinal protein expression
Authors: Wang Xiaofei , Nookala Suba , Narayanan Chidambarathanu , Giorgianni Francesco , Beranova‐Giorgianni Sarka , Mccollum Gary , Gerling Ivan , Penn John S. , Jablonski Monica M.
Published: September 2008

The mechanisms that regulate the complex physiological task of photoreceptor outer segment assembly remain an enigma. One limiting factor in revealing the mechanism(s) by which this process is modulated is that not all of the role players who participate in this process are known. The purpose of this study was to determine some of the retinal proteins that likely play a critical role in regulating photoreceptor outer segment assembly. To do so, we analyzed and compared the proteome map of tadpole Xenopus laevis retinal pigment epithelium (RPE)‐supported retinas containing organized outer segments with that of RPE‐deprived retinas containing disorganized outer segments. Solubilized proteins were labeled with CyDye fluors followed by multiplexed two‐dimensional separation. The intensity of protein spots and comparison of proteome maps was performed using DeCyder software. Identification of differentially regulated proteins was determined using nanoLC‐ESI‐MS/MS analysis. We found a total of 27 protein spots, 21 of which were unique proteins, which were differentially expressed in retinas with disorganized outer segments. We predict that in the absence of the RPE, oxidative stress initiates an unfolded protein response. Subsequently, downregulation of several candidate Müller glial cell proteins may explain the inability of photoreceptors to properly fold their outer segment membranes. In this study, we have used identification and bioinformatics assessment of proteins that are differentially expressed in retinas with disorganized outer segments as a first step in determining probable key molecules involved in regulating photoreceptor outer segment assembly. © 2008 Wiley‐Liss, Inc.
Interactions between Schwann cells and macrophages in injury and inherited demyelinating disease
Authors: Martini Rudolf , Fischer Stefan , López‐Vales Rubèn , David Samuel
Published: September 2008

In this article we first discuss the factors that regulate macrophage recruitment, activation, and myelin phagocytosis during Wallerian degeneration and some of the factors involved in the termination of inflammation at the end of the period of Wallerian degeneration after peripheral nerve injuries. In particular, we deal with the early events that trigger chemokine and cytokine expression; the role of phospholipase A2 in initiating the breakdown of compact myelin, and chemokine, cytokine expression; and the role of MCP‐1, MIP‐1α, and IL‐1β in macrophage recruitment and myelin phagocytosis. We also discuss how inflammation may be switched off and the recently identified role of the Nogo receptor on activated macrophages in the clearance of these cells from the injured nerve. In the second half of the article we focus on the role of certain Schwann cell borne cytokines and chemokines, such as M‐CSF and MCP‐1 as well as intracellular signaling that regulate their expression in animal models of inherited demyelinating disease. Additionally, we present the preservation of sensory nerves fibers from macrophage attack in these animal models as a challenging paradigm for the development of putative treatment approaches. Finally, we also discuss the similarities and differences in these Schwann cell‐macrophage responses in injury‐induced Wallerian degeneration and inherited demyelinating diseases. Knowledge of the molecular mechanisms underlying Schwann cell‐macrophage interaction under pathological conditions is an important prerequisite to develop effective treatment strategies for various peripheral nerve disorders. © 2008 Wiley‐Liss, Inc.
The molecular machinery of myelin gene transcription in Schwann cells
Authors: Svaren John , Meijer Dies
Published: September 2008

During late fetal life, Schwann cells in the peripheral nerves singled out by the larger axons will transit through a promyelinating stage before exiting the cell cycle and initiating myelin formation. A network of extra‐ and intracellular signaling pathways, regulating a transcriptional program of cell differentiation, governs this progression of cellular changes, culminating in a highly differentiated cell. In this review, we focus on the roles of a number of transcription factors not only in myelination, during normal development, but also in demyelination, following nerve trauma. These factors include specification factors involved in early development of Schwann cells from neural crest (Sox10) as well as factors specifically required for transitions into the promyelinating and myelinating stages (Oct6/Scip and Krox20/Egr2). From this description, we can glean the first, still very incomplete, contours of a gene regulatory network that governs myelination and demyelination during development and regeneration. © 2008 Wiley‐Liss, Inc.
NOD2 plays an important role in the inflammatory responses of microglia and astrocytes to bacterial CNS pathogens
Authors: Chauhan Vinita S. , Sterka David G. , Furr Samantha R. , Young Amy B. , Marriott Ian
Published: September 2008

While glial cells are recognized for their roles in maintaining neuronal function, there is growing appreciation that resident central nervous system (CNS) cells initiate and/or augment inflammation following trauma or infection. We have recently demonstrated that microglia and astrocytes constitutively express nucleotide‐binding oligomerization domain‐2 (NOD2), a member of the novel nucleotide‐binding domain leucine‐rich repeat region containing a family of proteins (NLR) that functions as an intracellular receptor for a minimal motif present in all bacterial peptidoglycans. In this study, we have confirmed the functional nature of NOD2 expression in astrocytes and microglia and begun to determine the relative contribution that this NLR makes in inflammatory CNS responses to clinically relevant bacterial pathogens. We demonstrate the increased association of NOD2 with its downstream effector molecule, Rip2 kinase, in primary cultures of murine microglia and astrocytes following exposure to bacterial antigens. We show that this cytosolic receptor underlies the ability of muramyl dipeptide to augment the production of inflammatory cytokines by glia following exposure to specific ligands for disparate Toll‐like receptor homologues. In addition, we demonstrate that NOD2 is an important component in the in vitro inflammatory responses of resident glia to N. meningitidis and B. burgdorferi antigens. Finally, we have established that NOD2 is required, at least in part, for the astrogliosis, demyelination, behavioral changes, and elevated inflammatory cytokine levels observed following in vivo infection with these pathogens. As such, we have identified NOD2 as an important component in the generation of damaging CNS inflammation following bacterial infection. © 2008 Wiley‐Liss, Inc.