bluuebunny/crossref_metadata_2025 huggingface dataset:
RepFinder
Authors: Cheng Ming-Ming , Zhang Fang-Lue , Mitra Niloy J. , Huang Xiaolei , Hu Shi-Min
Published: July 2010

Repeated elements are ubiquitous and abundant in both manmade and natural scenes. Editing such images while preserving the repetitions and their relations is nontrivial due to overlap, missing parts, deformation across instances, illumination variation, etc. Manually enforcing such relations is laborious and error-prone. We propose a novel framework where user scribbles are used to guide detection and extraction of such repeated elements. Our detection process, which is based on a novel boundary band method, robustly extracts the repetitions along with their deformations. The algorithm only considers the shape of the elements, and ignores similarity based on color, texture, etc. We then use topological sorting to establish a partial depth ordering of overlapping repeated instances. Missing parts on occluded instances are completed using information from other instances. The extracted repeated instances can then be seamlessly edited and manipulated for a variety of high level tasks that are otherwise difficult to perform. We demonstrate the versatility of our framework on a large set of inputs of varying complexity, showing applications to image rearrangement, edit transfer, deformation propagation, and instance replacement.
Synthesizing structured image hybrids
Authors: Risser Eric , Han Charles , Dahyot Rozenn , Grinspun Eitan
Published: July 2010

Example-based texture synthesis algorithms generate novel texture images from example data. A popular hierarchical pixel-based approach uses spatial jitter to introduce diversity, at the risk of breaking coarse structure beyond repair. We propose a multiscale descriptor that enables appearance-space jitter, which retains structure. This idea enables repurposing of existing texture synthesis implementations for a qualitatively different problem statement and class of inputs: generating hybrids of structured images.
Vector solid textures
Authors: Wang Lvdi , Zhou Kun , Yu Yizhou , Guo Baining
Published: July 2010

In this paper, we introduce a compact random-access vector representation for solid textures made of intermixed regions with relatively smooth internal color variations. It is feature-preserving and resolution-independent. In this representation, a texture volume is divided into multiple regions. Region boundaries are implicitly defined using a signed distance function. Color variations within the regions are represented using compactly supported radial basis functions (RBFs). With a spatial indexing structure, such RBFs enable efficient color evaluation during real-time solid texture mapping. Effective techniques have been developed for generating such a vector representation from bitmap solid textures. Data structures and techniques have also been developed to compactly store region labels and distance values for efficient random access during boundary and color evaluation.
Unstructured video-based rendering
Authors: Ballan Luca , Brostow Gabriel J. , Puwein Jens , Pollefeys Marc
Published: July 2010

We present an algorithm designed for navigating around a performance that was filmed as a "casual" multi-view video collection: real-world footage captured on hand held cameras by a few audience members. The objective is to easily navigate in 3D, generating a video-based rendering (VBR) of a performance filmed with widely separated cameras. Casually filmed events are especially challenging because they yield footage with complicated backgrounds and camera motion. Such challenging conditions preclude the use of most algorithms that depend on correlation-based stereo or 3D shape-from-silhouettes.

Our algorithm builds on the concepts developed for the exploration of photo-collections of empty scenes. Interactive performer-specific view-interpolation is now possible through innovations in interactive rendering and offline-matting relating to i) modeling the foreground subject as video-sprites on billboards, ii) modeling the background geometry with adaptive view-dependent textures, and iii) view interpolation that follows a performer. The billboards are embedded in a simple but realistic reconstruction of the environment. The reconstructed environment provides very effective visual cues for spatial navigation as the user transitions between viewpoints. The prototype is tested on footage from several challenging events, and demonstrates the editorial utility of the whole system and the particular value of our new inter-billboard optimization.
Video tapestries with continuous temporal zoom
Authors: Barnes Connelly , Goldman Dan B. , Shechtman Eli , Finkelstein Adam
Published: July 2010

We present a novel approach for summarizing video in the form of a multiscale image that is continuous in both the spatial domain and across the scale dimension: There are no hard borders between discrete moments in time, and a user can zoom smoothly into the image to reveal additional temporal details. We call these artifacts
tapestries
because their continuous nature is akin to medieval tapestries and other narrative depictions predating the advent of motion pictures. We propose a set of criteria for such a summarization, and a series of optimizations motivated by these criteria. These can be performed as an entirely offline computation to produce high quality renderings, or by adjusting some optimization parameters the later stages can be solved in real time, enabling an interactive interface for video navigation. Our video tapestries combine the best aspects of two common visualizations, providing the visual clarity of DVD chapter menus with the information density and multiple scales of a video editing timeline representation. In addition, they provide continuous transitions between zoom levels. In a user study, participants preferred both the aesthetics and efficiency of tapestries over other interfaces for visual browsing.
Motion-based video retargeting with optimized crop-and-warp
Authors: Wang Yu-Shuen , Lin Hui-Chih , Sorkine Olga , Lee Tong-Yee
Published: July 2010

We introduce a video retargeting method that achieves high-quality resizing to arbitrary aspect ratios for complex videos containing diverse camera and dynamic motions. Previous content-aware retargeting methods mostly concentrated on spatial considerations, attempting to preserve the shape of salient objects in each frame by removing or distorting homogeneous background content. However, sacrificeable space is fundamentally limited in video, since object motion makes foreground and background regions correlated, causing waving and squeezing artifacts. We solve the retargeting problem by explicitly employing motion information and by distributing distortion in both spatial and temporal dimensions. We combine novel cropping and warping operators, where the cropping removes temporally-recurring contents and the warping utilizes available homogeneous regions to mask deformations while preserving motion. Variational optimization allows to find the best balance between the two operations, enabling retargeting of challenging videos with complex motions, numerous prominent objects and arbitrary depth variability. Our method compares favorably with state-of-the-art retargeting systems, as demonstrated in the examples and widely supported by the conducted user study.
Simulating virtual environments within virtual environments as the basis for a psychophysics of presence
Authors: Slater Mel , Spanlang Bernhard , Corominas David
Published: July 2010

A new definition of immersion with respect to virtual environment (VE) systems has been proposed in earlier work, based on the concept of simulation. One system (
A
) is said to be more immersive than another (
B
) if
A
can be used to simulate an application as if it were running on
B.
Here we show how this concept can be used as the basis for a psychophysics of presence in VEs, the sensation of being in the place depicted by the virtual environment displays (Place Illusion, PI), and also the illusion that events occurring in the virtual environment are real (Plausibility Illusion, Psi). The new methodology involves matching experiments akin to those in color science. Twenty participants first experienced PI or Psi in the initial highest level immersive system, and then in 5 different trials chose transitions from lower to higher order systems and declared a match whenever they felt the same level of PI or Psi as they had in the initial system. In each transition they could change the type of illumination model used, or the field-of-view, or the display type (powerwall or HMD) or the extent of self-representation by an avatar. The results showed that the 10 participants instructed to choose transitions to attain a level of PI corresponding to that in the initial system tended to first choose a wide field-of-view and head-mounted display, and then ensure that they had a virtual body that moved as they did. The other 10 in the Psi group concentrated far more on achieving a higher level of illumination realism, although having a virtual body representation was important for both groups. This methodology is offered as a way forward in the evaluation of the responses of people to immersive virtual environments, a unified theory and methodology for psychophysical measurement.
Smoothed local histogram filters
Authors: Kass Michael , Solomon Justin
Published: July 2010

Local image histograms contain a great deal of information useful for applications in computer graphics, computer vision and computational photography. Making use of that information has been challenging because of the expense of computing histogram properties over large neighborhoods. Efficient algorithms exist for some specific computations like the bilateral filter, but not others. Here, we present an efficient and practical method for computing accurate derivatives and integrals of locally-weighted histograms over large neighborhoods. The method allows us to compute the location, height, width and integral of all local histogram modes at interactive rates. Among other things, it enables the first constant-time isotropic median filter, robust isotropic image morphology operators, an efficient "dominant mode" filter and a non-iterative alternative to the mean shift. In addition, we present a method to combat the over-sharpening that is typical of histogram-based edge-preserving smoothing. This post-processing step should make histogram-based filters not only fast and efficient, but also suitable for a variety of new applications.
Efficient yarn-based cloth with adaptive contact linearization
Authors: Kaldor Jonathan M. , James Doug L. , Marschner Steve
Published: July 2010

Yarn-based cloth simulation can improve visual quality but at high computational costs due to the reliance on numerous persistent yarn-yarn contacts to generate material behavior. Finding so many contacts in densely interlinked geometry is a pathological case for traditional collision detection, and the sheer number of contact interactions makes contact processing the simulation bottleneck. In this paper, we propose a method for approximating penalty-based contact forces in yarn-yarn collisions by computing the exact contact response at one time step, then using a rotated linear force model to approximate forces in nearby deformed configurations. Because contacts internal to the cloth exhibit good temporal coherence, sufficient accuracy can be obtained with infrequent updates to the approximation, which are done adaptively in space and time. Furthermore, by tracking contact models we reduce the time to detect new contacts. The end result is a 7- to 9-fold speedup in contact processing and a 4- to 5-fold overall speedup, enabling simulation of character-scale garments.
Stable spaces for real-time clothing
Authors: de Aguiar Edilson , Sigal Leonid , Treuille Adrien , Hodgins Jessica K.
Published: July 2010

We present a technique for learning clothing models that enables the simultaneous animation of thousands of detailed garments in real-time. This surprisingly simple conditional model learns and preserves the key dynamic properties of a cloth motion along with folding details. Our approach requires no
a priori
physical model, but rather treats training data as a "black box." We show that the models learned with our method are stable over large time-steps and can approximately resolve cloth-body collisions. We also show that within a class of methods, no simpler model covers the full range of cloth dynamics captured by ours. Our method bridges the current gap between skinning and physical simulation, combining benefits of speed from the former with dynamic effects from the latter. We demonstrate our approach on a variety of apparel worn by male and female human characters performing a varied set of motions typically used in video games (
e.g.
, walking, running, jumping,
etc.
).
Example-based wrinkle synthesis for clothing animation
Authors: Wang Huamin , Hecht Florian , Ramamoorthi Ravi , O'Brien James F.
Published: July 2010

This paper describes a method for animating the appearance of clothing, such as pants or a shirt, that fits closely to a figure's body. Compared to flowing cloth, such as loose dresses or capes, these types of garments involve nearly continuous collision contact and small wrinkles, that can be troublesome for traditional cloth simulation methods. Based on the observation that the wrinkles in close-fitting clothing behave in a predominantly kinematic fashion, we have developed an example-based wrinkle synthesis technique. Our method drives wrinkle generation from the pose of the figure's kinematic skeleton. This approach allows high quality clothing wrinkles to be combined with a coarse cloth simulation that computes the global and dynamic aspects of the clothing motion. While the combined results do not exactly match a high-resolution reference simulation, they do capture many of the characteristic fine-scale features and wrinkles. Further, the combined system runs at interactive rates, making it suitable for applications where high-resolution offline simulations would not be a viable option. The wrinkle synthesis method uses a precomputed database built by simulating the high-resolution clothing as the articulated figure is moved over a range of poses. In principle, the space of poses is exponential in the total number of degrees of freedom; however clothing wrinkles are primarily affected by the nearest joints, allowing each joint to be processed independently. During synthesis, mesh interpolation is used to consider the influence of multiple joints, and combined with a coarse simulation to produce the final results at interactive rates.
A deformation transformer for real-time cloth animation
Authors: Feng Wei-Wen , Yu Yizhou , Kim Byung-Uck
Published: July 2010

Achieving interactive performance in cloth animation has significant implications in computer games and other interactive graphics applications. Although much progress has been made, it is still much desired to have real-time high-quality results that well preserve dynamic folds and wrinkles. In this paper, we introduce a hybrid method for real-time cloth animation. It relies on data-driven models to capture the relationship between cloth deformations at two resolutions. Such data-driven models are responsible for transforming low-quality simulated deformations at the low resolution into high-resolution cloth deformations with dynamically introduced fine details. Our data-driven transformation is trained using rotation invariant quantities extracted from the cloth models, and is independent of the simulation technique chosen for the lower resolution model. We have also developed a fast collision detection and handling scheme based on dynamically transformed bounding volumes. All the components in our algorithm can be efficiently implemented on programmable graphics hardware to achieve an overall real-time performance on high-resolution cloth models.
Popup
Authors: Li Xian-Ying , Shen Chao-Hui , Huang Shi-Sheng , Ju Tao , Hu Shi-Min
Published: July 2010

Paper architectures are 3D paper buildings created by folding and cutting. The creation process of paper architecture is often labor-intensive and highly skill-demanding, even with the aid of existing computer-aided design tools. We propose an automatic algorithm for generating paper architectures given a user-specified 3D model. The algorithm is grounded on geometric formulation of planar layout for paper architectures that can be popped-up in a rigid and stable manner, and sufficient conditions for a 3D surface to be popped-up from such a planar layout. Based on these conditions, our algorithm computes a class of paper architectures containing two sets of parallel patches that approximate the input geometry while guaranteed to be physically realizable. The method is demonstrated on a number of architectural examples, and physically engineered results are presented.
Effects of global illumination approximations on material appearance
Authors: Křivánek Jaroslav , Ferwerda James A. , Bala Kavita
Published: July 2010

Rendering applications in design, manufacturing, ecommerce and other fields are used to simulate the appearance of objects and scenes. Fidelity with respect to appearance is often critical, and calculating global illumination (GI) is an important contributor to image fidelity; but it is expensive to compute. GI approximation methods, such as virtual point light (VPL) algorithms, are efficient, but they can induce image artifacts and distortions of object appearance. In this paper we systematically study the perceptual effects on image quality and material appearance of global illumination approximations made by VPL algorithms. In a series of psychophysical experiments we investigate the relationships between rendering parameters, object properties and image fidelity in a VPL renderer. Using the results of these experiments we analyze how VPL counts and energy clamping levels affect the visibility of image artifacts and distortions of material appearance, and show how object geometry and material properties modulate these effects. We find the ranges of these parameters that produce VPL renderings that are visually equivalent to reference renderings. Further we identify classes of shapes and materials that cannot be accurately rendered using VPL methods with limited resources. Using these findings we propose simple heuristics to guide visually equivalent and efficient rendering, and present a method for correcting energy losses in VPL renderings. This work provides a strong perceptual foundation for a popular and efficient class of GI algorithms.
Filament-based smoke with vortex shedding and variational reconnection
Authors: Weißmann Steffen , Pinkall Ulrich
Published: July 2010

Simulating fluids based on vortex filaments is highly attractive for the creation of special effects because it gives artists full control over the simulation using familiar tools like curve editors or the scripted generation of new vortex filaments over time. Because filaments offer a very compact description of fluid flow, real time applications like games or virtual reality are also possible.

We present a complete model that includes moving obstacles with vortex shedding, all represented as filaments. Due to variational reconnection the long-time behavior of our method is excellent: Energy and momentum stay constant within reasonable bounds and computational complexity does not increase over time.
Discrete viscous threads
Authors: Bergou Miklós , Audoly Basile , Vouga Etienne , Wardetzky Max , Grinspun Eitan
Published: July 2010

We present a continuum-based discrete model for thin threads of viscous fluid by drawing upon the Rayleigh analogy to elastic rods, demonstrating canonical coiling, folding, and breakup in dynamic simulations. Our derivation emphasizes space-time symmetry, which sheds light on the role of time-parallel transport in eliminating---without approximation---all but an
O
(
n
) band of entries of the physical system's energy Hessian. The result is a fast, unified, implicit treatment of viscous threads and elastic rods that closely reproduces a variety of fascinating physical phenomena, including hysteretic transitions between coiling regimes, competition between surface tension and gravity, and the first numerical fluid-mechanical sewing machine. The novel implicit treatment also yields an order of magnitude speedup in our elastic rod dynamics.
Feature-aligned T-meshes
Authors: Myles Ashish , Pietroni Nico , Kovacs Denis , Zorin Denis
Published: July 2010

High-order and regularly sampled surface representations are more efficient and compact than general meshes and considerably simplify many geometric modeling and processing algorithms. A number of recent algorithms for conversion of arbitrary meshes to regularly sampled form (typically quadrangulation) aim to align the resulting mesh with feature lines of the geometry. While resulting in a substantial improvement in mesh quality, feature alignment makes it difficult to obtain coarse regular patch partitions of the mesh.

In this paper, we propose an approach to constructing patch layouts consisting of small numbers of quadrilateral patches while maintaining good feature alignment. To achieve this, we use quadrilateral T-meshes, for which the intersection of two faces may not be the whole edge or vertex, but a part of an edge. T-meshes offer more flexibility for reduction of the number of patches and vertices in a base domain while maintaining alignment with geometric features. At the same time, T-meshes retain many desirable features of quadrangulations, allowing construction of high-order representations, easy packing of regularly sampled geometric data into textures, as well as supporting different types of discretizations for physical simulation.
A wave-based anisotropic quadrangulation method
Authors: Zhang Muyang , Huang Jin , Liu Xinguo , Bao Hujun
Published: July 2010

This paper proposes a new method for remeshing a surface into anisotropically sized quads. The basic idea is to construct a special standing wave on the surface to generate the global quadrilateral structure. This wave based quadrangulation method is capable of controlling the quad size in two directions and precisely aligning the quads with feature lines. Similar to the previous methods, we augment the input surface with a vector field to guide the quad orientation. The anisotropic size control is achieved by using two size fields on the surface. In order to reduce singularity points, the size fields are optimized by a new curl minimization method. The experimental results show that the proposed method can successfully handle various quadrangulation requirements and complex shapes, which is difficult for the existing state-of-the-art methods.
Parameterizing subdivision surfaces
Authors: He Lei , Schaefer Scott , Hormann Kai
Published: July 2010

We present a method for parameterizing subdivision surfaces in an as-rigid-as-possible fashion. While much work has concentrated on parameterizing polygon meshes, little if any work has focused on subdivision surfaces despite their popularity. We show that polygon parameterization methods produce suboptimal results when applied to subdivision surfaces and describe how these methods may be modified to operate on subdivision surfaces. We also describe a method for creating extended charts to further reduce the distortion of the parameterization. Finally we demonstrate how to take advantage of the multi-resolution structure of subdivision surfaces to accelerate convergence of our optimization.
A multi-resolution approach to heat kernels on discrete surfaces
Authors: Vaxman Amir , Ben-Chen Mirela , Gotsman Craig
Published: July 2010

Studying the behavior of the heat diffusion process on a manifold is emerging as an important tool for analyzing the geometry of the manifold. Unfortunately, the high complexity of the computation of the heat kernel -- the key to the diffusion process - limits this type of analysis to 3D models of modest resolution. We show how to use the unique properties of the heat kernel of a discrete two dimensional manifold to overcome these limitations. Combining a multi-resolution approach with a novel approximation method for the heat kernel at short times results in an efficient and robust algorithm for computing the heat kernels of detailed models. We show experimentally that our method can achieve good approximations in a fraction of the time required by traditional algorithms. Finally, we demonstrate how these heat kernels can be used to improve a diffusion-based feature extraction algorithm.
Data-driven biped control
Authors: Lee Yoonsang , Kim Sungeun , Lee Jehee
Published: July 2010

We present a dynamic controller to physically simulate under-actuated three-dimensional full-body biped locomotion. Our data-driven controller takes motion capture reference data to reproduce realistic human locomotion through realtime physically based simulation. The key idea is modulating the reference trajectory continuously and seamlessly such that even a simple dynamic tracking controller can follow the reference trajectory while maintaining its balance. In our framework, biped control can be facilitated by a large array of existing data-driven animation techniques because our controller can take a stream of reference data generated on-the-fly at runtime. We demonstrate the effectiveness of our approach through examples that allow bipeds to turn, spin, and walk while steering its direction interactively.
Generalized biped walking control
Authors: Coros Stelian , Beaudoin Philippe , van de Panne Michiel
Published: July 2010

We present a control strategy for physically-simulated walking motions that generalizes well across gait parameters, motion styles, character proportions, and a variety of skills. The control is realtime, requires no character-specific or motion-specific tuning, is robust to disturbances, and is simple to compute. The method works by integrating tracking, using proportional-derivative control; foot placement, using an inverted pendulum model; and adjustments for gravity and velocity errors, using Jacobian transpose control. High-level gait parameters allow for forwards-and-backwards walking, various walking speeds, turns, walk-to-stop, idling, and stop-to-walk behaviors. Character proportions and motion styles can be authored interactively, with edits resulting in the instant realization of a suitable controller. The control is further shown to generalize across a variety of walking-related skills, including picking up objects placed at any height, lifting and walking with heavy crates, pushing and pulling crates, stepping over obstacles, ducking under obstacles, and climbing steps.
Nonuniform Boolean constraint satisfaction problems with cardinality constraint
Authors: Creignou Nadia , Schnoor Henning , Schnoor Ilka
Published: July 2010

We study the computational complexity of Boolean constraint satisfaction problems with cardinality constraint. A Galois connection between clones and coclones has received a lot of attention in the context of complexity considerations for constraint satisfaction problems. This connection does not seem to help when considering constraint satisfaction problems that support in addition a cardinality constraint. We prove that a similar Galois connection, involving a weaker closure operator and partial polymorphisms, can be applied to such problems. Thus, we establish dichotomies for the decision as well as for the counting problems in Schaefer's framework.
Superposition for fixed domains
Authors: Horbach Matthias , Weidenbach Christoph
Published: July 2010

Superposition is an established decision procedure for a variety of first-order logic theories represented by sets of clauses. A satisfiable theory, saturated by superposition, implicitly defines a minimal term-generated model for the theory. Proving universal properties with respect to a saturated theory directly leads to a modification of the minimal model's term-generated domain, as new Skolem functions are introduced. For many applications, this is not desired.

Therefore, we propose the first superposition calculus that can explicitly represent existentially quantified variables and can thus compute with respect to a given domain. This calculus is sound and refutationally complete in the limit for a first-order fixed domain semantics. For saturated Horn theories and classes of positive formulas, we can even employ the calculus to prove properties of the minimal model itself, going beyond the scope of known superposition-based approaches.
Typing streams in the Λμ-calculus
Authors: Saurin Alexis
Published: July 2010

Λμ-calculus is a Böhm-complete extension of Parigot's Λμ-calculus closely related with delimited control in functional programming. In this article, we investigate the meta-theory of untyped Λμ-calculus by proving confluence of the calculus and characterizing the basic observables for the Separation theorem,
canonical normal forms
. Then, we define Λ

s

, a new type system for Λμ-calculus that contains a special type construction for streams, and prove that strong normalization and type preservation hold. Thanks to the new typing discipline of Λ

s

, new computational behaviors can be observed, which were forbidden in previous type systems for λμ-calculi. Those new typed computational behaviors witness the stream interpretation of Λμ-calculus.
Targeting glutathione by dimethylfumarate protects against experimental malaria by enhancing erythrocyte cell membrane scrambling
Authors: Ghashghaeinia Mehrdad , Bobbala Diwakar , Wieder Thomas , Koka Saisudha , Brück Jürgen , Fehrenbacher Birgit , Röcken Martin , Schaller Martin , Lang Florian , Ghoreschi Kamran
Published: July 2010

The balance between GSH-levels and oxidative stress is critical for cell survival. The GSH-levels of erythrocytes are dramatically decreased during infection with Plasmodium spp. We therefore investigated the consequences of targeting GSH for erythrocyte and Plasmodium survival in vitro and in vivo using dimethylfumarate (DMF) at therapeutically established dosage. We first show that noninfected red blood cells (RBC) exposed to DMF undergo changes typical of apoptosis or eryptosis, such as cell shrinkage and cell membrane scrambling with subsequent phosphatidylserine (PS) exposure. DMF did not induce appreciable hemolysis. DMF-triggered PS exposure was mediated by intracellular GSH depletion and reversed by the antioxidative N-acetyl-l-cysteine. DMF treatment controlled intraerythrocyte DNA amplification and in vitro parasitemia of Plasmodium falciparum -infected RBC. In vivo, DMF treatment had no effect on RBC count or GSH levels in noninfected mice. Consistent with its effects on infected RBC, DMF treatment abrogated parasitemia and enhanced the survival of mice infected with Plasmodium berghei from 0% to 60%. In conclusion, DMF sensitizes the erythrocytes to the effect of Plasmodium infection on PS exposure, thus accelerating the clearance of infected erythrocytes. Accordingly, DMF treatment favorably influences the clinical course of malaria. As DMF targets mechanisms within the host cell, it is not likely to generate resistance of the pathogen.
Mitogenic factors promoting intestinal smooth muscle cell proliferation
Authors: Stanzel Roger D. P. , Lourenssen Sandra , Nair Dileep G. , Blennerhassett Michael G.
Published: July 2010

Intestinal smooth muscle cells are normally quiescent, but in the widely studied model of trinitrobenzene sulfonic acid (TNBS)-induced colitis in the rat, the onset of inflammation causes proliferation that leads to increased cell number and an altered phenotype. The factors that drive this are unclear and were studied in primary cultures of circular smooth muscle cells (CSMC) from the rat colon. While platelet-derived growth factor (PDGF)-AA, fibroblast growth factor (FGF), and epidermal growth factor (EGF) were ineffective, PDGF-BB and insulin-like growth factor-1 (IGF-1) caused significant increase in [3H]thymidine incorporation, bromodeoxyuridine uptake, and increased CSMC number, with PDGF-BB (≥0.2 nM) substantially more effective than IGF-1. Surprisingly, CSMC lacked expression of PDGF receptor-β (PDGF-Rβ) upon isolation but by 4 days in vitro, CSMC gained expression of PDGF-Rβ as shown by quantitative PCR, Western blot analysis, and immunocytochemistry; these CSMC responded to PDGF-BB but not IGF-1. PDGF-BB caused PDGF-Rβ phosphorylation and mobilization from the surface membrane, leading to activation of both Akt and ERK signaling pathways, which were essential for subsequent proliferation. In contrast, PDGF-AA, FGF, EGF, and IGF-1 were ineffective. In vivo, control CSMC lacked expression of PDGF-Rβ. However, this changed rapidly with TNBS-colitis, and by day 2 when CSMC proliferation in vivo is maximal, freshly isolated CSMC showed on-going PDGF-Rβ phosphorylation that was further increased by exogenous PDGF-BB. This suggests that the onset of PDGF-Rβ expression is a key factor in CSMC growth in vitro and in vivo, where inflammation may damage intrinsic inhibitory mechanisms and thus lead to hyperplasia.
SHP-2 phosphatase activity is required for PECAM-1-dependent cell motility
Authors: Zhu Jing-Xu , Cao Gaoyuan , Williams James T. , DeLisser Horace M.
Published: July 2010

Platelet endothelial cell adhesion molecule-1 (PECAM-1) has been implicated in endothelial cell motility during angiogenesis. Although there is evidence that SHP-2 plays a role in PECAM-1-dependent cell motility, the molecular basis of the activity of SHP-2 in this process has not been defined. To investigate the requirement of SHP-2 in PECAM-1-dependent cell motility, studies were done in which various constructs of SHP-2 were expressed in cell transfectants expressing PECAM-1. We observed that the levels of PECAM-1 tyrosine phosphorylation and SHP-2 association with PECAM-1 were significantly increased in cells expressing a phosphatase-inactive SHP-2 mutant, suggesting that the level of PECAM-1 tyrosine phosphorylation, and thus SHP-2 binding are regulated in part by bound, catalytically active SHP-2. We subsequently found that expression of PECAM-1 stimulated wound-induced migration and the formation of filopodia (a morphological feature of motile cells). These activities were associated with increased mitogen-activated protein kinase (MAPK) activation and the dephosphorylation of paxillin (an event implicated in the activation of MAPK). The phosphatase-inactive SHP-2 mutant, however, suppressed these PECAM-1-dependent phenomena, whereas the activity of PECAM-1 expressing cells was not altered by expression of wild-type SHP-2 or SHP-2 in which the scaffold/adaptor function had been disabled. Pharmacological inhibition of SHP-2 phosphatase activity also suppressed PECAM-1-dependent motility. Furthermore, PECAM-1 expression also stimulates tube formation, but none of the SHP-2 constructs affected this process. These findings therefore suggest a model for the involvement of SHP-2 in PECAM-1-dependent motility in which SHP-2, recruited by its interaction with PECAM-1, targets paxillin to ultimately activate the MAPK pathway and downstream events required for cell motility.
Dietary genistein and equol (4′, 7 isoflavandiol) reduce oxidative stress and protect rats against focal cerebral ischemia
Authors: Ma Yulin , Sullivan Jennifer C. , Schreihofer Derek A.
Published: July 2010

High soy diets reduce injury in rat models of focal cerebral ischemia and are proposed as alternatives to hormone replacement therapy for postmenopausal women. The present study tests the hypothesis that the major soy isoflavone genistein and the daidzein metabolite equol are neuroprotective in transient focal cerebral ischemia in male and ovariectomized (OVX) female rats by inhibiting oxidative stress. Genistein is the primary circulating soy isoflavone in humans, whereas equol is the primary circulating isoflavone in rats. Male and OVX female Sprague-Dawley rats were fed an isoflavone-reduced diet alone or supplemented with genistein (500 ppm) or equol (250 ppm) for 2 wk prior to 90-min transient middle cerebral artery occlusion followed by reperfusion under isoflurane anesthesia. Indices of oxidative stress were determined 24 h after reperfusion, and cerebral injury was evaluated 3 days after reperfusion. Genistein and equol significantly reduced infarct size in both sexes. Further studies in OVX female rats revealed that this neuroprotection was accompanied by a decrease in NAD(P)H oxidase activity and superoxide levels in the brain. In addition, equol reduced plasma thiobarbituric acid reactive substances, and neurological deficits up to 7 days after injury. There were no significant differences in cerebral blood flow among treatment groups. In conclusion, dietary soy isoflavones are neuroprotective in transient focal cerebral ischemia in male and OVX female rats. These isoflavones may protect the brain via increases in endogenous antioxidant mechanisms and reduced oxidative stress.
Maternal obesity and fetal metabolic programming: a fertile epigenetic soil
Authors: Heerwagen Margaret J. R. , Miller Melissa R. , Barbour Linda A. , Friedman Jacob E.
Published: July 2010

The incidence of obesity and overweight has reached epidemic levels in the United States and developed countries worldwide. Even more alarming is the increasing prevalence of metabolic diseases in younger children and adolescents. Infants born to obese, overweight, and diabetic mothers (even when normal weight) have increased adiposity and are at increased risk of later metabolic disease. In addition to maternal glucose, hyperlipidemia and inflammation may contribute to the childhood obesity epidemic through fetal metabolic programming, the mechanisms of which are not well understood. Pregravid obesity, when combined with normal changes in maternal metabolism, may magnify increases in inflammation and blood lipids, which can have profound effects on the developing embryo and the fetus in utero. Fetal exposure to excess blood lipids, particularly saturated fatty acids, can activate proinflammatory pathways, which could impact substrate metabolism and mitochondrial function, as well as stem cell fate, all of which affect organ development and the response to the postnatal environment. Fetal and neonatal life are characterized by tremendous plasticity and the ability to respond to environmental factors (nutrients, oxygen, hormones) by altering gene expression levels via epigenetic modifications. Given that lipids act as both transcriptional activators and signaling molecules, excess fetal lipid exposure may regulate genes involved in lipid sensing and metabolism through epigenetic mechanisms. Epigenetic regulation of gene expression is characterized by covalent modifications to DNA and chromatin that alter gene expression independent of gene sequence. Epigenetic modifications can be maintained through positive and negative feedback loops, thereby creating stable changes in the expression of metabolic genes and their main transcriptional regulators. The purpose of this article is to review current literature on maternal-fetal lipid metabolism and maternal obesity outcomes and to suggest some potential mechanisms for fetal metabolic programming in key organ systems that regulate postnatal energy balance, with an emphasis on epigenetics and the intrauterine environment.
Renal nitric oxide production in rat pregnancy: role of constitutive nitric oxide synthases
Authors: Smith Cheryl A. , Santymire Beth , Erdely Aaron , Venkat Vasuki , Losonczy György , Baylis Chris
Published: July 2010

Functional studies show that increased renal nitric oxide (NO) mediates the renal vasodilation and increased glomerular filtration rate that occur during normal pregnancy. We investigated whether changes in the constitutive NO synthases (NOS), endothelial (eNOS) and neuronal (nNOS), were associated with the increased renal NO production in normal midterm pregnancy in the rat. In kidneys from midterm pregnant (MP: 11–13 days gestation), late-term pregnant (LP: 18–20 days gestation), and similarly aged virgin (V) rats, transcript and protein abundance for eNOS and the nNOSα and nNOSβ splice variants, as well as the rate of l-arginine-to-l-citrulline conversion, were determined as a measure of NOS activity. At MP, renal cortical abundance of the total eNOS protein and phosphorylated (Ser1177) eNOS was reduced, and l-arginine-to-l-citrulline conversion in the cortical membrane fraction was decreased; these declines were also seen in LP. There were no changes in the eNOS transcript. In contrast, l-arginine-to-l-citrulline conversion in the soluble fraction of renal cortex increased at MP and then declined at LP. This MP increase was ablated by S-methylthiocitrulline, a nNOS inhibitor. Using Western blotting, we did not detect a change in the protein abundance or transcript of the 160-kDa nNOSα, but protein abundance and transcript of the nNOSβ were increased at MP in cortex. Collectively, these studies suggest that the soluble nNOSβ is responsible for the increased renal cortical NO production during pregnancy.
DC-specific ICAM-3-grabbing nonintegrin mediates internalization of HIV-1 into human podocytes
Authors: Mikulak J. , Teichberg S. , Arora S. , Kumar D. , Yadav A. , Salhan D. , Pullagura S. , Mathieson P. W. , Saleem M. A. , Singhal P. C.
Published: July 2010

Human immunodeficiency virus (HIV)-1 has been demonstrated to contribute to the pathogenesis of HIV-associated nephropathy. In renal biopsy studies, podocytes have been reported to be infected by HIV-1. However, the mechanism involved in HIV-1 internalization into podocytes is not clear. In the present study, we evaluated the occurrence of HIV-1 internalization into conditionally immortalized human podocytes and the mechanism involved. Human podocytes rapidly internalized R5 and X4 HIV-1 primary strains via an endocytosis-dependent pathway, without establishing a productive infection. The HIV-1 internalization was dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) receptor mediated. The role of DC-SIGN was confirmed by using specific blocking antibodies and transfection with small interfering (si) RNA/DC-SIGN. Since podocyte HIV-1 trafficking was not altered by pH-modulating agents, it appeared that HIV-1 routing occurred through nonacid vesicular compartments. Interestingly, transfection of podocytes with neither siRNA/caveolin-1 nor siRNA/clathrin heavy chain inhibited podocyte viral accumulation. Thus it appears that clathrin-coated vesicles and caveosomes may not be contributing to HIV-1-associated membrane traffic.
Daily physical activity enhances reactivity to insulin in skeletal muscle arterioles of hyperphagic Otsuka Long-Evans Tokushima Fatty rats
Authors: Mikus Catherine R. , Rector R. Scott , Arce-Esquivel Arturo A. , Libla Jessica L. , Booth Frank W. , Ibdah Jamal A. , Laughlin M. Harold , Thyfault John P.
Published: July 2010

Insulin-mediated glucose disposal is dependent on the vasodilator effects of insulin. In type 2 diabetes, insulin-stimulated vasodilation is impaired as a result of an imbalance in NO and ET-1 production. We tested the hypothesis that chronic voluntary wheel running (RUN) prevents impairments in insulin-stimulated vasodilation associated with obesity and type 2 diabetes independent of the effects of RUN on adiposity by randomizing Otsuka Long Evans Tokushima Fatty (OLETF) rats, a model of hyperphagia-induced obesity and type 2 diabetes, to 1) RUN, 2) caloric restriction (CR; diet adjusted to match body weights of RUN group), or 3) sedentary control (SED) groups ( n = 8/group) at 4 wk. At 40 wk, NO- and ET-1-mediated vasoreactivity to insulin (1–1,000 μIU/ml) was assessed in the presence of a nonselective ET-1 receptor blocker (tezosentan) or a NO synthase (NOS) inhibitor [ NG-nitro-l-arginine methyl ester (l-NAME)], respectively, in second-order arterioles isolated from the white portion of the gastrocnemius muscle. Body weight, fasting plasma glucose, and hemoglobin A1c were lower in RUN and CR than SED ( P < 0.05); however, the glucose area under the curve (AUC) following the intraperitoneal glucose tolerance test was lower only in the RUN group ( P < 0.05). Vasodilator responses to all doses of insulin were greater in RUN than SED or CR in the presence of a tezosentan ( P < 0.05), but group differences in vasoreactivity to insulin with coadministration of l-NAME were not observed. We conclude daily wheel running prevents obesity and type 2 diabetes-associated declines in insulin-stimulated vasodilation in skeletal muscle arterioles through mechanisms that appear to be NO mediated and independent of attenuating excess adiposity in hyperphagic rats.
Basing Perceptual Decisions on the Most Informative Sensory Neurons
Authors: Scolari Miranda , Serences John T.
Published: July 2010

Single unit recording studies show that perceptual decisions are often based on the output of sensory neurons that are maximally responsive (or “tuned”) to relevant stimulus features. However, when performing a difficult discrimination between two highly similar stimuli, perceptual decisions should instead be based on the activity of neurons tuned away from the relevant feature ( off-channel neurons) as these neurons undergo a larger firing rate change and are thus more informative. To test this hypothesis, we measured feature-selective responses in human primary visual cortex (V1) using functional magnetic resonance imaging and show that the degree of off-channel activation predicts performance on a difficult visual discrimination task. Moreover, this predictive relationship between off-channel activation and perceptual acuity is not simply the result of extensive practice with a specific stimulus feature (as in studies of perceptual learning). Instead, relying on the output of the most informative sensory neurons may represent a general, and optimal, strategy for efficiently computing perceptual decisions.
Isolating Event-related Neuronal Responses by Deconvolution
Authors: Ghazizadeh Ali , Fields Howard L. , Ambroggi Frederic
Published: July 2010

Although many studies in neuroscience are based on comparing neuronal responses to single, isolated sensory or motor events, multiple events frequently occur in close temporal proximity in freely moving animals. This often obscures the precise temporal correlation between each event and the relevant brain activity. By simulating neuronal responses in multi-event tasks, we show that perievent time histograms (PETHs) greatly distort the underlying true responses. We propose a multi-event deconvolution method that can separate the contribution of each event to the overall neuronal activity. The improvements over PETH in analyzing real data are demonstrated using simulated data and a sample electrophysiological recording obtained from rats in a task involving responses to a reward predictive cue.