bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shape‐engineered fibroblasts: Cell elasticity and actin cytoskeletal features characterized by fluorescence and atomic force microscopy
Authors: Kidoaki Satoru , Matsuda Takehisa 
Published: January 2007

AbstractThe regulation of cell shape, which determines cell behaviors including adhesion, spreading, migration, and proliferation in an engineered artificial extracellular milieu, is an important task in tissue engineering and in development of functional biomaterials. To deepen the understandings of shape‐dependent cell mechanics, the cell elasticity and structural features of the actin cytoskeleton (CSK) were characterized for shape‐engineered fibroblasts; round and spindle‐shaped cells cultured on photolithographically microprocessed surfaces, employing the cellular microindentation tests and fluorescence observation of actin CSK by the combination of atomic force microscopy (AFM) and fluorescence microscopy (FM). The relationships among cell elasticity, the structural features of actin CSK, and engineered cell shape were analyzed and compared with those of control cells that had been cultured on nonprocessed surfaces (termed naturally extended cells). Results showed that the spindle‐shaped cells with sparse or no apical stress fibers (ASFs) exhibited similar stiffness to that of the naturally extended cells with dense ASFs. The elasticity of spindle‐shaped cells was affected only slightly by the stress fiber (SF) density, which is in marked contrast to the significant correlation shown between cell elasticity and SF density in naturally extended cells. This result implies that the elasticity of regionally restricted adhesion‐surface‐induced shape‐engineered cells, particularly of highly elongated cells, is affected predominantly by cell shape rather than by structural features of SFs. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Site specificity of α‐H abstraction reaction among secondary structure motif—Anab initiostudy
Authors: Lu Hsiu‐Feng , Li Feng‐Yin , Lin S. H. 
Published: January 2007

AbstractThe initial step of protein oxidation is studied through α‐H abstraction by an OH radical with various secondary structure motifs of proteins. It is found that there exist preferential α‐Hs in this kind of abstractions. The typical abstraction mechanism involves three steps: forming a pre‐reactive complex before abstraction, the abstraction reaction, and the H2O detachment from a post‐reactive complex to form the product, Cα‐center radical. Using the stability of the pre‐reactive complex and the reaction barrier, we provide some explanation for this site preference. The feasibility of α‐H abstraction by OH radical depends not only on the types of secondary structure, but also on the reaction condition, such as in aqueous or in gas phase. Moreover, the reactivity of the abstraction also depends on the location of α‐H in the secondary structure motifs. The preferential α‐Hs to be abstracted in β‐sheet are those immediate to the amide or carbonyl group, and without involving hydrogen bonding, whereas in reverse turns, the preferential α‐Hs are near the C‐terminal of type I and near the N‐terminal of type II. In general, the α‐Hs in α‐helix are more difficult to be abstracted than those in β‐sheet and polypeptide in linear form. It is consistent with the trend of their bond dissociation energies. Our theoretical rate constant ofN‐acetyldiglycin‐methylamide (Ac(Gly)2NHCH3) in aqueous solution (6.75 × 108M−1s−1) is close to the experimental observation ofN‐acetyldiglycinamide (Ac(Gly)2NH2) (8.6 × 108M−1s−1). © 2007 Wiley Periodicals, Inc. J Comput Chem 28: 783–794, 2007
The phosphodiesterase 5 inhibitor sildenafil stimulates angiogenesis through a protein kinase G/MAPK pathway
Authors: Pyriochou Anastasia , Zhou Zongmin , Koika Vasiliki , Petrou Christos , Cordopatis Paul , Sessa William C. , Papapetropoulos Andreas 
Published: January 2007

AbstractcGMP‐degrading pathways have received little attention in the context of angiogenesis. In the present study we set out to determine whether cGMP‐specific phosphodiesterase 5 (PDE5) inhibition affects new blood vessel growth. Incubation of chicken chorioallantoic membranes (CAMs) in vivo with sildenafil increased vascular length in a dose‐dependent manner. Moreover, incubation of cultured endothelial cells (ECs) with the PDE5 inhibitor promoted proliferation, migration, and organization into tube‐like structures. The effects of sildenafil on the angiogenesis‐related properties of EC could be blocked by pre‐treatment with the soluble guanylyl cyclase (sGC) inhibitor ODQ or the protein kinase G (PKG) I inhibitor DT‐3. In addition, over‐expression of sGC in EC led to an enhanced growth and migratory response to sildenafil. To study the signaling pathways implicated in the sildenafil‐stimulated angiogenic responses we determined the phosphorylation status of mitogen‐activated protein kinase (MAPK) members. Incubation of cells with sildenafil increased both extracellular signal regulated kinase 1/2 (ERK1/2) and p38 phosphorylation in a time‐dependent manner. Inhibition of MEK by PD98059 and p38 with SB203580 blocked sildenafil‐induced proliferation and migration, respectively, suggesting that these MAPK members are downstream of PDE5 and mediate the angiogenic effects of sildenafil. PDE5 inhibitors could, thus, be used in disease states where neo‐vessel growth is desired. J. Cell. Physiol. 211: 197–204, 2007. © 2007 Wiley‐Liss, Inc.
Accuracy of medicare claims data in identifying Parkinsonism cases: Comparison with the medicare current beneficiary survey
Authors: Noyes Katia , Liu Hangsheng , Holloway Robert , Dick Andrew W. 
Published: January 2007

AbstractStudy PurposeAdministrative databases are commonly used to examine use of healthcare service, with researchers relying on diagnostic codes to identify medical conditions. This study evaluates the accuracy of administrative claims in identifying Parkinsonism cases compared to the self‐reported Parkinson's disease (PD).MethodsThe reference cases were identified based on the self‐reported PD status and the use of PD drugs collected by the 1992–2000 Medicare Current Beneficiary Survey that contained 72,922 observations from 30,469 individuals. Using ICD‐9 CM, cases with PD were extracted from the corresponding Medicare claims. We compared prevalence of PD obtained using different types of claims.ResultsThe sensitivities were the highest when all claims were used (66%). All the specificities were greater than 99%. When drug use information was included in the gold standard, the sensitivities became lower, while the specificities and positive predictive values (PPVs) increased. Using more diagnostic codes improved the sensitivity of the identification process but reduced PPVs.ConclusionsAdministrative claims can provide fairly accurate and practical approach to “rule in” patients with PD. Depending on the purpose of evaluation, researchers may consider using more categories of claims to improve the sensitivity of the identification algorithm or use fewer diagnoses to minimize number of false positive cases. © 2006 Movement Disorder Society
Rat model of Parkinson's disease with bilateral motor abnormalities, reversible with levodopa, and dyskinesias
Authors: Paillé Vincent , Henry Vincent , Lescaudron Laurent , Brachet Philippe , Damier Philippe 
Published: January 2007

AbstractParkinson's disease (PD) is characterized by the bilateral degeneration of the midbrain dopamine‐containing neurons with the most severe lesion in the posterolateral part of the substantia nigra pars compacta (SNpc). In humans, such lesions lead to specific motor abnormalities (i.e., akinesia, rigidity, and tremor) that are greatly improved by levodopa treatment. After a few years, the beneficial effect of the treatment is frequently offset by the development of dyskinesias. To improve treatment strategies, an animal model showing most of the histological and clinical characteristics of the human disease is mandatory. Ten rats received a bilateral injection of small doses of 6‐OHDA in the medial forebrain bundle (MFB) and were compared with five sham‐lesioned rats. The 6‐OHDA‐lesioned rats progressively developed abnormal motor behavior (assessed by the stepping test) compared with the sham‐lesioned rats. The lesioned rats greatly improved under levodopa treatment, but developed concomitant dyskinesias. All 6‐OHDA‐lesioned animals had bilateral partial lesions of the SNpc, with the most severe lesion being in its posterolateral part. There was a significant correlation between the severity of the dopaminergic cell loss and the severity of the levodopa‐induced dyskinesias. These rats constitute an interesting model of PD, sharing some of the main characteristics of the human disease. © 2006 Movement Disorder Society
Vitamin D and Parkinson's disease—A hypothesis
Authors: Newmark Harold L. , Newmark Jonathan 
Published: January 2007

AbstractParkinson's disease (PD), a common disease of the elderly, is a movement disorder characterized by tremor, akinesia, and loss of postural reflexes, leading to immobility and frequent falls. It results from selective loss (death) of dopaminergic neurons in the substantia nigra region of the brain, largely developed prior to clinical diagnosis, and continuous after diagnosis, despite use of current therapeutic modalities. In PD in the United States the cause and mechanism of continued neuron cell death in the substantia nigra is currently unknown. We hypothesize, based upon several lines of evidence, that documented chronically inadequate vitamin D intake in the United States, particularly in the northern states and particularly in the elderly, is a significant factor in the pathogenesis of PD. This hypothesis implies that dietary aid for prevention and therapy for PD is possible. © 2006 Movement Disorder Society
Testosterone not associated with violent dreams or REM sleep behavior disorder in men with Parkinson's
Authors: Chou Kelvin L. , Moro‐De‐Casillas Maria L. , Amick Melissa M. , Borek Leora L. , Friedman Joseph H. 
Published: January 2007

AbstractWe examined the relationship between testosterone levels, violent dreams, and REM sleep behavior disorder (RBD) in 31 men with Parkinson's disease (PD): 12 with clinical RBD and 19 without. All PD patients with clinical RBD experienced violent dreams, but none of the 19 non‐RBD patients reported violent dreams. While dream content appears to be more aggressive in PD patients with clinical RBD, the presence of violent dreams or clinical RBD is not associated with testosterone levels in men with PD. © 2006 Movement Disorder Society
Midbrain sonography in patients with essential tremor
Authors: Stockner Heike , Sojer Martin , K Klaus Seppi , Mueller Joerg , Wenning Gregor K. , Schmidauer Christoph , Poewe Werner 
Published: January 2007

AbstractSeveral studies have reported an increased risk to develop Parkinson's disease (PD) in essential tremor (ET) populations. Hyperechogenicity of the substantia nigra (SN) is a common transcranial sonography (TCS) finding in PD and has been suggested as a PD risk‐marker in nonparkinsonian subjects. This study compared SN areas of 44 ET patients with 100 controls and 100 PD patients. Sixteen percent of ET patients had SN hyperechogenicity as compared with 3% of controls and 75% of PD patients. These findings might correspond to an increased risk of ET patients to develop PD. Long‐term follow‐up will show if those with hyperechogenic SN develop PD, while these without will not. © 2006 Movement Disorder Society
Impact of varying pulse frequency and duration on muscle torque production and fatigue
Authors: Gregory Chris M. , Dixon Warren , Bickel C. Scott 
Published: January 2007

AbstractNeuromuscular electrical stimulation (NMES) involves the use of electrical current to facilitate contraction of skeletal muscle. However, little is known concerning the effects of varying stimulation parameters on muscle function in humans. The purpose of this study was to determine the extent to which varying pulse duration and frequency altered torque production and fatigability of human skeletal muscle in vivo. Ten subjects underwent NMES‐elicited contractions of varying pulse frequencies and durations as well as fatigue tests using stimulation trains of equal total charge, yet differing parametric settings at a constant voltage. Total charge was a strong predictor of torque production, and pulse trains with equal total charge elicited identical torque output. Despite similar torque output, higher‐ frequency trains caused greater fatigue. These data demonstrate the ability to predictably control torque output by simultaneously controlling pulse frequency and duration and suggest the need to minimize stimulation frequency to control fatigue. Muscle Nerve, 2007
Severity, type, and distribution of myotonic discharges are different in type 1 and type 2 myotonic dystrophy
Authors: Logigian Eric L. , Ciafaloni Emma , Quinn L. Christine , Dilek Nuran , Pandya Shree , Moxley Richard T. , Thornton Charles A. 
Published: January 2007

AbstractTo characterize and compare electrical myotonia in myotonic dystrophy type 1 (DM1) and type 2 (DM2), 16 patients with genetically confirmed DM1 and 17 patients with DM2 underwent standardized concentric needle electromyography of deltoid, biceps, extensor digitorum communis, first dorsal interosseous, tensor fascia lata (TFL), vastus lateralis (VL), tibialis anterior, and thoracic paraspinal muscles. Eight needle insertions per muscle were made by electromyographers blinded to DM type who recorded the presence and type of myotonia (e.g., classic waxing–waning or less specific waning discharges). Manual muscle testing was performed by a physical therapist. Overall, myotonia was more elicitable in DM1 than DM2; only in VL and TFL was myotonia more elicitable in DM2 than DM1. The major type of myotonia was waxing–waning in DM1, and waning in DM2. Four DM2 (24%), but no DM1 patients had only waning myotonia. In the arms, myotonia was distally predominant in both DM1 and DM2. In the legs, it was distally predominant in DM1, but both proximal and distal in DM2. The severity of myotonia was positively correlated with muscle weakness and with the presence of waxing and waning discharges in DM1, but with neither in DM2. Thus, myotonia is qualitatively and quantitatively different in DM1 than DM2. Except for proximal leg muscles, myotonia is more evocable in DM1 than DM2. It tends to be waxing–waning in DM1 but waning in DM2, thus making electrodiagnosis of DM2 more challenging. Its severity correlates with muscle weakness and the presence of waxing–waning discharges in DM1 but not DM2. Muscle Nerve, 2007
Delamination Analysis of UD Composites Using Interface Elements
Authors: Balzani Claudio , Wagner Werner 
Published: January 2007

AbstractFor an accurate simulation of the mechanical behavior of laminated composites, several fracture modes should be considered. This work focuses on the numerical treatment of delamination within the framework of the finite element method. An interface element is presented which is written in terms of stress‐strain relationships. The constitutive law is mainly inspired by publications of De‐Andrés et al. [1] and Ortiz & Pandolfi [2]. A Smith‐Ferrante type cohesive free energy function is edited in a way that only tensile normal stresses trigger interlaminar damage. Furthermore, an additional penalty term avoids the interpenetration of the crack faces. The simulation of a DCB test shows the performance and the applicability of the model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The peridynamic model in non‐local elasticity theory
Authors: Emmrich Etienne , Weckner Olaf 
Published: January 2007

AbstractThe peridynamic model is described and an overview of some recent results concerning the analysis of the peridynamic equation of motion is given. Moreover, its numerical solution is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical analysis of an elastic contact problem with damage
Authors: Fernández José R. , Campo Marco 
Published: January 2007

AbstractIn this work, we consider a mathematical model for the quasistatic contact problem between an elastic body and a deformable obstacle, including the effect of the damage of the material, within the framework of the small deformation theory. The numerical analysis of the variational problem is provided using the finite element method to approximate the spatial variable and an Euler scheme to discretize the time derivatives. Finally, a two‐dimensional numerical problem is presented to show the performance of the method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust Algorithm for Brittle Fracture based on Energy Minimization
Authors: Gürses Ercan , Miehe Christian 
Published: January 2007

AbstractThe paper outlines a variational formulation of brittle fracture in solids and considers its numerical implementation by a distinct finite element method. The starting point is a variational setting of fracture mechanics that recasts a monotonic quasistatic fracture process into a sequence of incremental minimization problems. The proposed implementation introduces discretized crack patterns with material‐force‐driven incremental crack‐segment releases. These releases of crack segments constitute a sequence of positive definite subproblems with successively decreasing overall stiffness, providing an extremely robust algorithmic setting in the postcritical range. The formulation is embedded into accompanying r‐adaptive crack‐pattern reorientation procedures with material‐force‐based indicators, providing reorientations of elements at the crack‐tip. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On some relations between different interface crack models
Authors: Loboda Volodymyr , Herrmann Klaus 
Published: January 2007

AbstractExact analytical solutions for an interface crack with an artificial contact zone in isotropic, anisotropic and piezoelectric materials have been analyzed and their comparison with the correspondent classical results has been performed. This analysis showed the way of a presentation of the main results for an artificial contact zone model in the manner very similar to the classical model, and due to this phenomenon the essential simplification of the investigation of the contact zone model has been attained. The application of the obtained results to interface cracks in anisotropic and piezoelectric bimaterials can be demonstrated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical aspects of the XFEM — The XFEM p–Version
Authors: Peters Markus , Hackl Klaus 
Published: January 2007

AbstractThe XFEM is known to approximate the displacements and stresses around a crack tip in a very efficient way. But as we will present in this paper we have to deal with a phenomenon coming along with this method that compels us to use higher order shape functions for those elements that are enriched by the crack tip functions.For the computation of the stress–intensity–factors we are using a J–integral over a circular domain Ω. The accuracy of the results depend on• the radius of Ω• the number of elements used in the XFEM computation• the number of nodes which were enriched by the crack tip functions (number of layers) and• the shape functions which were used for the standard FE termFor more information about the XFEM we refer to [1]. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of Thermal Impact Welded Lightweight Structures
Authors: Utzinger Johannes , Menzel Andreas , Kuhl Ellen , Steinmann Paul 
Published: January 2007

AbstractIn the field of composites, welding of lightweight structures consisting of metal/fibre‐reinforced polymers is a very seminal issue, concerning for example the automotive industry. The theoretical and numerical modelling as well as the simulation of the mentioned composites is a crucial and integrating subarea. By using various material laws in a traction‐separation context, different experimental and analytical methods must be consulted to verify the mesomechanical models. In this contribution we discuss a characterisation of interfacial elasto‐plasticity with Lemaitre‐damage, which has been applied to model thermal impact welded single lap tensile specimens. Then, numerical and experimental results are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient crack growth analyzes by combining fast methods for BEM
Authors: Weber W. , Kolk K. , Kuhn G. 
Published: January 2007

AbstractThe combination of fast methods for the boundary element method (BEM) for efficient crack growth analyzes is presented. Due to the nonlinearity of fatigue crack growth an incremental procedure has to be applied. Within each increment a stress analysis is needed. Based on the asymptotic stress field the stress intensity factors (SIFs) are calculated by an extrapolation method. Then, a new crack front is determined by a reliable 3D crack growth criterion. Finally, the numerical model has to be updated for the next increment. The time dominant factor in each increment is the computation of the stress field. Due to the stress concentration problem the BEM is utilized. To speed‐up the calculation several independent fast methods are exploited. An algebraic technique is the adaptive cross approximation (ACA) method which is acting on the system matrix itself. The application of the substructure technique leads to a blockwise band matrix and therefore to reduced memory requirements. Further savings in memory and computation time are reached by modelling cracks with the dual discontinuity method (DDM) and using the ACA method in each substructure. The efficiency of the combined methods is shown by a complex industrial example. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic stability of a porous rectangular plate
Authors: Debowski Daniel , Magnucki Krzysztof 
Published: January 2007

AbstractThe study is devoted to a axial compressed porous‐cellular rectangular plate. Mechanical properties of the plate vary across is its thickness which is defined by the non‐linear function with dimensionless variable and coefficient of porosity. The material model used in the current paper is as described by Magnucki, Stasiewicz papers. The middle plane of the plate is the symmetry plane. First of all, a displacement field of any cross section of the plane was defined. The geometric and physical (according to Hook's law) relationships are linear. Afterwards, the components of strain and stress states in the plate were found. The Hamilton's principle to the problem of dynamic stability is used. This principle was allowed to formulate a system of five differential equations of dynamic stability of the plate satisfying boundary conditions. This basic system of differential equations was approximately solved with the use of Galerkin's method. The forms of unknown functions were assumed and the system of equations was reduced to a single ordinary differential equation of motion. The critical load determined used numerically processed was solved. Results of solution shown in the Figures for a family of isotropic porous‐cellular plates. The effect of porosity on the critical loads is presented. In the particular case of a rectangular plate made of an isotropic homogeneous material, the elasticity coefficients do not depend on the coordinate (thickness direction), giving a classical plate. The results obtained for porous plates are compared to a homogeneous isotropic rectangular plate. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupling of 3D Boundary Elements with Curved Finite Shell Elements
Authors: Helldörfer Bastian , Haas Michael , Kuhn Günther 
Published: January 2007

AbstractThe mixed‐dimensional coupling of finite shells and 3D boundary elements is presented. A stiffness formulation for the boundary element domain is generated by the Symmetric Galerkin Boundary Element Method and is assembled to the global finite element system. Multipoint constraints are derived in an integral sense by equating the work at the coupling interface. They are evaluated numerically during the analysis and avoid spurious stress concentrations also for curved interfaces. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)