bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive mesh generation for global diffuse illumination
Authors: Campbell A. T. , Fussell Donald S.
Published: November 2005

Rapid developments in the design of algorithms for rendering globally illuminated scenes have taken place in the past five years. Net energy methods such as the hemicube and other radiosity algorithms have become very effective at computing the energy balance for scenes containing diffusely reflecting objects. Such methods first break up a scene description into a relatively large number of elements, or possibly several levels of elements. Energy transfers among these elements are then determined using a variety of means. While much progress has been made in the design of energy transfer algorithms, little or no attention has been paid to the proper generation of the mesh of surface elements. This paper presents a technique for adaptively creating a mesh of surface elements as the energy transfers are computed. The method allows large numbers of small elements to be placed at parts of the scene where the most active energy transfers occur without requiring that other parts of the scene be needlessly subdivided to the same degree. As a result, the computational effort in the energy transfer computations can be concentrated where it has the most effect.
Artificial reality with force-feedback: development of desktop virtual space with compact master manipulator
Authors: Iwata Hiroo
Published: November 2005

A new configuration of Human Interface for "artificial reality" is discussed. This paper describes a method of implementing force-feedback in a virtual space manipulation system. The system is composed of two subsystems, a real-time graphic display system and a tactile input device with reaction force generator. A specialized graphics computer (Stardent TITAN) provides a realtime image of the virtual space. A 9 degree-of-freedom manipulator has been developed as a tactile input device. The manipulator applies reaction forces to the fingers and palm of the operator. The generated forces are calculated from a solid model of the virtual space. The performance of the system is exemplified in manipulation of virtual solid objects such as a mockup for industrial design and a 3D animated character.
Paint by numbers: abstract image representations
Authors: Haeberli Paul
Published: November 2005

Computer graphics research has concentrated on creating photo-realistic images of synthetic objects. These images communicate surface shading and curvature, as well as the depth relationships of objects in a scene. These renderings are traditionally represented by a rectangular array of pixels that tile the image plane.As an alternative to photo-realism, it is possible to create abstract images using an ordered collection of brush strokes. These abstract images filter and refine visual information before it is presented to the viewer. By controlling the color, shape, size, and orientation of individual brush strokes, impressionistic paintings of computer generated or photographic images can easily be created.
Direct WYSIWYG painting and texturing on 3D shapes
Authors: Hanrahan Pat , Haeberli Paul
Published: November 2005

This paper describes a 3D object-space paint program. This program allows the user to directly manipulate the parameters used to shade the surface of the 3D shape by applying pigment to its surface. The pigment has all the properties normally associated with material shading models. This includes, but is not limited to, the diffuse color, the specular color, and the surface roughness. The pigment also can have thickness, which is modeled by simultaneously creating a bump map attached to the shape. The output of the paint program is a 3D model with associated texture maps. This information can be used with any rendering program with texture mapping capabilities. Almost all traditional techniques of 2D computer image painting have analogues in 3D object painting, but there are also many new techniques unique to 3D. One example is the use of solid textures to pattern the surface.
Performance-driven facial animation
Authors: Williams Lance
Published: November 2005

As computer graphics technique rises to the challenge of rendering lifelike performers, more lifelike performance is required. The techniques used to animate robots, arthropods, and suits of armor, have been extended to flexible surfaces of fur and flesh. Physical models of muscle and skin have been devised. But more complex databases and sophisticated physical modeling do not directly address the performance problem. The gestures and expressions of a human actor are not the solution to a dynamic system. This paper describes a means of acquiring the expressions of real faces, and applying them to computer-generated faces. Such an "electronic mask" offers a means for the traditional talents of actors to be flexibly incorporated in digital animations. Efforts in a similar spirit have resulted in servo-controlled "animatrons," high-technology puppets, and CG puppetry [1]. The manner in which the skills of actors and puppetteers as well as animators are accommodated in such systems may point the way for a more general incorporation of human nuance into our emerging computer media.The ensuing description is divided into two major subjects: the construction of a highly-resoved human head model with photographic texture mapping, and the concept demonstration of a system to animate this model by tracking and applying the expressions of a human performer.
A model for anisotropic reflection
Authors: Poulin Pierre , Fournier Alain
Published: November 2005

A reflection and refraction model for anisotropic surfaces is introduced. The anisotropy is simulated by small cylinders (added or subtracted) distributed on the anisotropic surface. Different levels of anisotropy are achieved by varying the distance between each cylinder and/or rising the cylinders more or less from the surface. Multidirectional anisotropy is modelled by orienting groups of cylinders in different direction. The intensity of the reflected light is computed by determining the visible and illuminated portion of the cylinders, taking self-blocking into account. We present two techniques to compute this in practice. In one the intensity is computed by sampling the surface of the cylinders. The other is an analytic solution. In the case of the diffuse component, the solution is exact. In the case of the specular component, an approximation is developed using a Chebyshev polynomial approximation of the specular term, and integrating the polynomial.This model can be implemented easily within most rendering system, given a suitable mechanism to define and alter surface tangents. The effectiveness of the model and the visual importance of anisotropy are illustrated with some pictures.
The accumulation buffer: hardware support for high-quality rendering
Authors: Haeberli Paul , Akeley Kurt
Published: November 2005

This paper describes a system architecture that supports realtime generation of complex images, efficient generation of extremely high-quality images, and a smooth trade-off between the two.Based on the paradigm of integration, the architecture extends a state-of-the-art rendering system with an additional high-precision image buffer. This additional buffer, called the Accumulation Buffer, is used to integrate images that are rendered into the framebuffer. While originally conceived as a solution to the problem of aliasing, the Accumulation Buffer provides a general solution to the problems of motion blur and depth-of-field as well.Because the architecture is a direct extension of current workstation rendering technology, we begin by discussing the performance and quality characteristics of that technology. The problem of spatial aliasing is then discussed, and the Accumulation Buffer is shown to be a desirable solution. Finally the generality of the Accumulation Buffer is explored, concentrating on its application to the problems of motion blur, depth-of-field, and soft shadows.
Real-time robot motion planning using rasterizing computer graphics hardware
Authors: Lengyel Jed , Reichert Mark , Donald Bruce R. , Greenberg Donald P.
Published: November 2005

We present a real-time robot motion planner that is fast and complete to a resolution. The technique is guaranteed to find a path if one exists at the resolution, and all paths returned are safe. The planner can handle
any
polyhedral geometry of robot and obstacles, including disjoint and highly concave unions of polyhedra.The planner uses standard graphics hardware to rasterize configuration space obstacles into a series of bitmap slices, and then uses dynamic programming to create a navigation function (a discrete vector-valued function) and to calculate paths in this rasterized space. The motion paths which the planner produces are minimal with respect to an
L
1
(Manhattan) distance metric that includes rotation as well as translation.Several examples are shown illustrating the competence of the planner at generating planar rotational and translational plans for complex two and three dimensional robots. Dynamic motion sequences, including complicated and non-obvious backtracking solutions, can be executed in real time.
Generalized B-spline surfaces of arbitrary topology
Authors: Loop Charles , DeRose T. D.
Published: November 2005

B-spline surfaces, although widely used, are incapable of describing surfaces of arbitrary topology. It is not possible to model a general closed surface or a surface with handles as a single non-degenerate B-spline. In practice such surfaces are often needed. In this paper, we present generalizations of biquadratic and bicubic B-spline surfaces that are capable of capturing surfaces of arbitrary topology (although restrictions are placed on the connectivity of the control mesh). These results are obtained by relaxing the sufficient but not necessary smoothness constraints imposed by B-splines and through the use of an n-sided generalization of Bézier surfaces called S-patches.
Rendering and animation of gaseous phenomena by combining fast volume and scanline A-buffer techniques
Authors: Ebert D. S. , Parent Richard E.
Published: November 2005

This paper describes a new technique that efficiently combines volume rendering and scanline a-buffer techniques. This technique is useful for combining all types of volume-rendered objects with scanline rendered objects and is especially useful for rendering scenes containing gaseous phenomena such as clouds, fog, and smoke. The rendering and animation of these phenomena has been a difficult problem in computer graphics.A new algorithm for realistically modeling and animating gaseous phenomena is presented, providing true three-dimensional volumes of gas. The gases are modeled using turbulent flow based solid texturing to define their geometry and are animated based on turbulent flow simulations. A low albedo illumination model is used that takes into consideration self-shadowing of the volumes.
Footprint evaluation for volume rendering
Authors: Westover Lee
Published: November 2005

This paper presents a forward mapping rendering algorithm to display regular volumetric grids that may not have the same spacings in the three grid directions. It takes advantage of the fact that convolution can be thought of as distributing energy from input samples into space. The renderer calculates an image plane footprint for each data sample and uses the footprint to spread the sample's energy onto the image plane. A result of the technique is that the forward mapping algorithm can support perspective without excessive cost, and support adaptive resampling of the three-dimensional data set during image generation.
SIGCHR
Authors: Wright Thomas
Published: November 2005

SIGCHR is a portable, device-independent character generator for computer-driven, line-drawing plotters. The meaning of "portable" in this context is described, and the methods used for attaining portability in this algorithm are outlined. A test program for SIGCHR is presented, and the results of executing that program are shown.
An algorithm to shade a plot
Authors: Ison N. T.
Published: November 2005

An algorithm to shade a plot with straight lines, broken lines in the form of dashes, or symbols is described.
An approach to graphics system design
Authors: Newman W. M. , Sproull R. F.
Published: November 2005

A discussion of some of the problems that arise in the design of high-level general-purpose device-independent graphics systems is presented. These problems are shown to be most easily solved by avoiding the use of complex display data structures prior to the picture transformation process. The use of a display file containing the transformed picture is proposed instead. This approach restricts the range of display equipment suitable for use as output devices but does not prevent the use of high-performance equipment. The use of a small set of high-level graphic input functions is also suggested and it is shown why this appears to be the best solution to the problem of programming graphic input devices. Included, too, is an outline description of a graphics system designed along the proposed lines.
A polyhedron clipping and capping algorithm and a display system for three dimensional finite element models
Authors: Stephenson Michael B. , Christiansen Henry N.
Published: November 2005

This paper describes an algorithm for clipping and capping polyhedrons and a display system for three-dimensional finite element math models to facilitate viewing internal surfaces in the form of continuous tone computer generated color images. A plane is passed through the model with the result that the elements (or portions thereof) on one side of the plane may be eliminated. A new grid is generated for the cutting plane to include the prediction of such quantities as displacements, stresses, and temperatures. The Cutting plane is colored and/or warped to indicate the variation of selected scalar functions.
Surface definition for branching, contour-defined objects
Authors: Shantz Michael
Published: November 2005

Recent work on mapping polygonal surface mosaics onto contour defined objects has resulted in minimum flow algorithms which do a good job of mapping a surface between two single contours. This report extends these algorithms to handle contour defined objects which are highly branched and have holes.For branching contours where n contours in section I are connected to m contours in section i+1, the surfaces are mapped by first concatenating the section I contours into a single large contour using a minimum number of minimum distance links, similarly concatenating the section I+1 contours, then performing the one to one mapping between the resulting composite contours.Capping off a single arbitrarily shaped contour may be done by computing the medial axis transform of the contour, constructing the medial axis contour and mapping a surface from the contour to the medial axis contour.Medial axis transforms of the section I+1 contours may also be projected onto section I and concatenated with the section I contours to handle the mapping of convoluted, highly branched objects. These algorithms have applications to three-dimensional CAT scanner data, topographical map data and object representation for knowledge guided vision systems.
A scan line algorithm for displaying parametrically defined surfaces
Authors: Blinn James F.
Published: November 2005

This paper presents a scan line algorithm for drawing pictures of parametrically defined surfaces. A scan line algorithm is characterized by the order in which it generates the picture elements of the image. These are generated left to right, top to bottom in much the same way as a picture is scanned out on a TV screen. Parametrically defined surfaces are those generated by a set of bivariate functions defining the X,Y, and Z position of points on the surface. The primary driving mechanism behind such an algorithm is the inversion of the functions used to define the surface. To keep the algorithm general enough to apply to a wide variety of functional forms, this inversion is done numerically. It is only required to provide a mechanism for evaluating the function and its derivatives at any parametric location.The algorithm proceeds in two phases. First, a numerical search is made to find the local maxima of the Y definition function within the desired parameter ranges. These determine when portions of the surface first become visible as the scan plane progresses down the screen. Secondly, the actual scan conversion process is performed, maintaining a list of segments of the surface intersecting the current scan plane. As the scan plane passes local maxima of the Y function, new segments are added to the list. In additon, any existing segments are updated to reflect their intersection with the updated scan plane. All intersection calculations are performed by a bivariate Newton-Raphson solution of the defining equations. If the solution does not converge, it is due to the scan plane passing a local minimum, causing segments to be deleted from the active list. Finally, within one scan line, an X scan must be performed to generate the Z information about the surface for each picture element. This is also performed by a bivariate Newton-Raphson iteration with a different set of defining functions.
A scan line algorithm for computer display of curved surfaces
Authors: Whitted Turner
Published: November 2005

The conventional procedure for generating shaded images of curved surfaces is to approximate each surface element by a mosaic of polygons and to then apply one of several established polygon display algorithms. The method described here produces an excellent approximation of bi-cubic parametric surfaces in scan line order. Each surface patch is described in terms of edge curves which are intersected by successive scanning planes to form endpoints of scan line segments. Visibility is calculated for each segment by a hybrid priority/z-buffer scheme. Shading is computed using Phong's illumination model with interpolated surface normal values.
Stochastic modeling in computer graphics
Authors: Fournier Alain , Fussell Don
Published: November 2005

A recurrent problem in generating realistic pictures by computers is to represent natural irregular objects and phenomena without undue time or space overhead. We develop a new and powerful solution to this problem by modeling objects as sample paths of stochastic processes. Of particular interest are those stochastic processes which previously have been found to be useful models of the natural phenomena to be represented. One such model applicable to the representation of terrains, known as "fractional Brownian motion", has been proposed by B. Mandelbrot.The value of a new approach to object modeling in Computer Graphics depends largely on the efficiency of the techniques used to implement the model. We introduce here a new, efficient algorithm for rendering realistic surfaces defined using the stochastic process mentioned above. A major advantage of this technique is that it allows us to compute the surface to arbitrary levels of detail without increasing the database. Thus objects with complex appearance can be displayed from a very small database. The character of the surface can be controlled by merely modifying a few parameters. A similar change allows complex motion to be created inexpensively.As examples of applications of the method, we show an artificial planet viewed at various levels of detail, and a piece of paper being uncrumpled.
Core System implementations
Authors: Chappell Gary , Bono Peter
Published: November 2005

The number of facilities across the country "implementing" some "flavor" of the SIGGRAPH/GSPC Core System "strawman standard" ["Status Report of the Graphic Standards Planning Committee of ACM/SIGGRAPH", Computer Graphics, Vol. II, Number 3, Fall 1977] has reached approximately fifteen. To keep the graphics community informed about the reception and usage of the Core System, we have collected descriptions of the status of each facility, as reproduced here. An Implementor's Forum will occur in November '78, which we hope will provide both significant interfacility communication and some concensus among implementors on such topics as FORTRAN '77 compatible calling sequences for Core System routines, the structure of intermediate (neutral, pseudo-, etc.) display files, and techniques and algorithms for viewing, clipping, picking, and echoing.
Fast digital vector- and circle generator with binary rate
Authors: Möller Gerd
Published: November 2005

Digital graphic generators can be used as interfaces to different graphic output devices such as plotters, vector and raster-scan displays. The principle of digital vector and circle generation with binary rate multipliers (BRM) is represented. There is given a formula which describes the discrete approximation of the ideal BRM function.
Coherent global motion percepts from stochastic local motions (abstract only)
Authors: Williams D. W. , Sekuler R.
Published: November 2005

A percept of global, coherent motion results when many different localized motion vectors are combined. We studied the percept with dynamic random dot kinematograms in which each element took an independent, random walk of constant step size. Directions of displacement from frame to frame were chosen from a uniform distribution. The tendency to see coherent, global flow along the mean of the uniform distribution varied with the range of the distribution.Psychometric functions were obtained with kinematograms having various step sizes (0.1 to 1.4 degrees) and element densities (0.2 to 1.6 dots per square degree). Results fall into two categories, depending on whether the step size is larger or smaller than 1.0 degree. For step sizes greater than 1.0 degree changes in dot density altered the psychometric function. No change was found if the step size was less than one degree. These changes in the psychometric function with step size and density are consistent with Ullman's "minimal map theory" of motion correspondence.For the smaller step sizes, the constancy of the results over a large range of dot densities suggests that spurious directions of displacement due to the interference of random walks for different dots are not important. That is, only the directions of local motion determined by the predefined distribution of directions significantly contribute to the percept. We also found that although temporal summation occurred in a nonlinear manner over frames, it depended only on the set of directions present from frame to frame, not on the spatial relationships between local motion vectors over time. Taken together, these two results suggest that directions of the individual steps are independently detected and that these responses are pooled over time and space to generate the perception of coherent motion.
Computing the velocity field along contours (abstract only)
Authors: Hildreth Ellen C.
Published: November 2005

In this paper, we present a computational study of the measurement of motion. Similar to other visual processes, the motion of elements is not determined uniquely by information in the changing image; additional constraint is required to compute a unique velocity field. Given this global ambiguity of motion, local measurements from the changing image cannot possibly specify a unique local velocity vector, and in fact, may only specify one component of velocity. Computation of the full two-dimensional velocity field generally requires the integration of local motion measurements, either over an area, or along contours in the image. We examine the integration of local motion measurements along contours, using an additional constraint of smoothness of the velocity field. The predictions of an algorithm based on this constraint are compared with human motion perception on a few demonstrations.
On the estimation of dense displacement vector fields from image sequences (abstract only)
Authors: Nagel H. H.
Published: November 2005

Based on recent experimental as well as theoretical investigations, a generalization of previously published approaches towards the estimation of displacement vector fields is formulated. The calculus of variation allows to transform this approach into a set of two partial differential equations for the two components of the displacement vector field. Some simplifying assumptions facilitate the derivation of an iterative solution approach which can be studied in closed form.
Determining 3-D motion parameters of a rigid body
Authors: Yen B. L. , Huang T. S.
Published: November 2005

A vector-geometrical approach is given for the determination of 3-D motion parameters of a rigid body from point correspondences over 2 time sequential images. The resulting algorithms are similar to existing methods. However, the geometrical interpretations provide much valuable insight into the nature of the problem and the uniqueness question.
Multicomputer architectures for real-time perception (abstract only)
Authors: Uhr Leonard
Published: November 2005

This paper examines the computing demands that must be met by a system capable of scene description and perception of real-world moving objects. A brief survey is made of the major different kinds of computer systems that have been built, or designed, and of the different sources of potential speed-up of processing that have been exploited. Finally, a number of alternative possible hardware architectures that might be capable of handling real-time perception of moving objects are suggested, and examined.
Selective attention to aspects of motion configurations
Authors: Pomerantz James R. , Toth Nelson
Published: November 2005

The motion of a dot configuration may be described as the sum of its relative (part) and common (whole) motion components. Is either of these two component dimensions extracted before the other in human perception? Reaction time data from selective attention experiments show that neither dimension can be responded to without interference from the other, implying that neither is processed more quickly than or ahead of the other. Following Garner's nomenclature, common and relative motions appear to act as either symmetrically
integral
or
configural
dimensions, depending on the particular motion configurations tested.
Graphics programming independent of interaction techniques and styles
Authors: Kamran Abid , Feldman Michael B.
Published: November 2005

The Information Display Systems project is seeking, among other goals, to apply the principles of top-down design and functional abstraction to the design of interactive systems, particularly those involving interactive computer graphics. An important part of this effort is to develop a methodology and a programming environment to facilitate the functional separation of program modules handling a set of application semantics from program modules handling user interaction.We have developed a model for such an environment, and implemented a prototype version with a number of components:• an interaction language (IL) adapted from augmented transition networks, in which the syntax of interactive dialogs can be written;• an interpreter for the IL;• a set of "style modules" to handle such interaction style-dependent attributes as level of prompting and amount of information to be input in a "transaction";• a library of user profiles to carry information on users' preferred styles of interaction;• a logical-screen handler to handle distribution of different types of output onto logical viewing surfaces;• a library of interaction techniques.Graphics support is provided by a standard device-independent graphics package, in our case the ACM/SIGGRAPH/GSPC Core System. We have called this environment the Abstract Interaction Handler (AIH).This paper provides an overview of our system model, and descriptions of the various components of the current implementation. A number of interesting open questions are raised; proposals for improvements to the system are offered.
A personal view of progress in computer aided design
Authors: Bézier Pierre E.
Published: November 2005

An earlier version of this paper was presented by Dr. Bézier at the SIGGRAPH '85 Conference, in accepting the 1985 Steven A. Coons Award for Outstanding Creative Contributions to Computer Graphics.
A real time three-dimensional color animation system
Authors: Tripp Edwin R.
Published: November 2005

A system is described for the generation of real time quasi three-dimensional animated television images. The technique utilized is a composite of the "multi-plane" cartoon animation technique and three-dimensional object projection techniques using polygonal patch representations of objects. The hardware environment consists of a hierarchical memory structure utilizing shift register "background" planes and a fast random access main image "foreground" plane. The foreground plane has a variable "depth" with respect to the background planes. Perspective relations in the image structure are maintained in real time with only infrequent updating of the background data.
Improving interaction with a raster display
Authors: Tanimoto Steven L.
Published: November 2005

Interacting with a raster display can be frustratingly slow if images must be transmitted over slow data links such as standard telephone lines. When interaction with a graphics terminal is based on the system displaying detailed pictures and then a response by the user, the slow row-by-row painting method should be replaced by a hierarchical refining scheme discussed here. The small overhead in the refining scheme is a small price to pay for increased convenience to the human.
Interactive SIGGRAPH proceedings
Authors: Phillips Dick
Published: November 2005

The following article accompanied a demonstration of the SIGGRAPH interactive proceedings prototype at EDUCOM '89 in Ann Arbor, Michigan on October 15-18, 1989. It speaks to an educational audience and motivates the SIGGRAPH participation in this innovative multimedia project.
Area and volume coherence for efficient visualization of 3D scalar functions
Authors: Max Nelson , Hanrahan Pat , Crawfis Roger
Published: November 2005

We present an algorithm for compositing a combination of density clouds and contour surfaces used to represent a scalar function on a 3-D volume subdivided into convex polyhedra. The scalar function is interpolated between values defined at the vertices, and the polyhedra are sorted in depth before compositing. For
n
tetrahedra comprising a Delaunay triangulation, this sorting can always be done in O(
n
) time. Since a Delaunay triangulation can be efficiently computed for scattered data points, this provides a method for visualizing such data sets. The integrals for opacity and visible intensity along a ray through a convex polyhedron are computed analytically, and this computation is coherent across the polyhedron's projected area.
Direct volume rendering of curvilinear volumes
Authors: Wihelms Jane , Challinger Judy , Alper Naim , Ramamoorthy Shankar , Vaziri Arsi
Published: November 2005

Direct volume rendering can visualize sampled 3D scalar data as a continuous medium or extract features. However, it is generally slow. Furthermore, most algorithms for direct volume rendering have assumed rectilinear gridded data. This paper discusses methods for using direct volume rendering when the original volume is curvilinear, i.e., is divided into six-sided cells which are not necessarily equilateral hexahedra. One approach is to ray-cast such volumes directly. An alternative approach is to ray-cast such volumes directly. An alternative approach is to interpolate the sample volumes to a rectilinear grid, and use this regular volume for rendering. Advantages and disadvantages of the two approaches in terms of speed and image quality are explored.
Rendering volumetric data using STICKS representation scheme
Authors: Montani Claudio , Scopigno Roberto
Published: November 2005

An increasing need to efficiently represent and render 3D volumetric data is being experienced in many application fields ranging from scientific and medical visualization to CAD. A technique of representing this kind of data, the Sticks representation scheme, is proposed here with the aim of allowing an efficient representation and rendering of voxel data on low-capability workstations. This data model is based on a 3D extension of the well-known run-length encoding methods. It requires O(kn
2
) memory cells to represent O(n
3
) volumetric data and produces a degree of data compression greater than that of the Octree model. Rendering a frontal orthographic projection of a Sticks-represented volume is a very simple task and requires only a partial scan of the data. A Ray Tracing algorithm is presented for the synthesis of gradient-shaded parallel projections; the proposed algorithm exploits the data compression to drastically reduce the complexity of rendering.
Microsomal triglyceride transfer protein −493T variant reduces IDL plus LDL apoB production and the plasma concentration of large LDL particles
Authors: Lundahl Björn , Skoglund-Andersson Camilla , Caslake Muriel , Bedford Dorothy , Stewart Philip , Hamsten Anders , Packard Christopher J. , Karpe Fredrik
Published: November 2005

The microsomal triglyceride transfer protein (MTP) is essential for the synthesis and secretion of apolipoprotein B (apoB)-containing lipoproteins. We investigated the role the MTP −493G/T gene polymorphism in determining the apoB-100 secretion pattern and LDL heterogeneity in healthy human subjects. Groups of carriers of the T and the G variants ( n = 6 each) were recruited from a cohort of healthy 50-yr-old men. Kinetic studies were performed by endogenous [2H3]leucine labeling of apoB and subsequent quantification of the stable isotope incorporation. apoB production rates, metabolic conversions, and eliminations were calculated by multicompartmental modeling (SAAM-II). LDL subfraction distribution was analyzed in the entire cohort ( n = 377). Carriers of the MTP −493T allele had lower plasma LDL apoB and lower concentration of large LDL particles [LDL-I: 136 ± 57 (TT) vs. 175 ± 55 (GG) mg/l, P < 0.01]. Kinetic modeling suggested that MTP −493T homozygotes had a 60% lower direct production rate of intermediate-density lipoprotein (IDL) plus LDL compared with homozygotes for the G allele ( P < 0.05). No differences were seen in production rates of large and small VLDL, nor were there any differences in metabolic conversion or elimination rates of apoB between the genotype groups. This study shows that a polymorphism in the MTP gene affects the spectrum of endogenous apoB-containing lipoprotein particles produced in humans. Reduced direct production of LDL plus IDL appears to be related to lower plasma concentrations of large LDL particles.
Involvement of Dorsal Column Nucleus Neurons in Nociceptive Transmission in Aged Rats
Authors: Kitagawa Junichi , Tsuboi Yoshiyuki , Ogawa Akiko , Ren Ke , Hitomi Suzuro , Saitoh Kimiko , Takahashi Osamu , Masuda Yuji , Harada Toshiyuki , Hanzawa Naoki , Kanda Kenro , Iwata Koichi
Published: November 2005

To clarify the functional role of the dorsal column nucleus (DCN) in nociception in rats with advancing age, single neuronal activity and substance P–like immunoreactivity (SP-LI) of the gracile nucleus (GN) were studied in aged rats (29 to 34 mo old) and adult rats (9 to 12 mo old). A total of 122 neurons [aged: 34 wide-dynamic-range (WDR), two nociceptive-specific (NS), and 32 low-threshold mechanical (LTM) neurons; adult: 22 WDR and 32 LTM neurons] were recorded from GN. For WDR neurons, the latency to antidromic activation of the ventral posterior lateral nucleus of the thalamus showed no difference between the aged and adult rats. Sciatic nerve stimulation with C-fiber intensity induced responses of GN with significantly longer latency in aged rats than in adults, whereas there was no difference in the response latency to A-fiber intensity stimulation. Background activity and afterdischarges were significantly higher in the aged rats than those in the adult rats. Responses to noxious mechanical and thermal stimuli were significantly greater in the aged rats during application of graded stimuli. There were no significant differences in responses to nonnoxious mechanical stimulus, mechanical response threshold, and the size of the receptive fields between neurons in the aged and adult rats. The area occupied by SP-LI fibers in the GN and the size of SP-LI dorsal root ganglia neurons were significantly larger in aged rats than in adults. The present findings suggest that the hyperexcitability of GN neurons could be involved in abnormal noxious pain sensations with advancing age.
Transient Voltage-Dependent Potassium Currents Are Reduced in NTS Neurons Isolated From Renal Wrap Hypertensive Rats
Authors: Belugin Sergei , Mifflin Steve
Published: November 2005

Whole cell patch-clamp measurements were made in neurons enzymatically dispersed from the nucleus of the solitary tract (NTS) to determine if alterations occur in voltage-dependent potassium channels from rats made hypertensive (HT) by unilateral nephrectomy/renal wrap for 4 wk. Some rats had the fluorescent tracer DiA applied to the aortic nerve before the experiment to identify NTS neurons receiving monosynaptic baroreceptor afferent inputs. Mean arterial pressure (MAP) was greater in 4-wk HT (165 ± 5 mmHg, n = 26, P < 0.001) rats compared with normotensive (NT) rats (109 ± 3 mmHg measured in 10 of 69 rats). Transient outward currents (TOCs) were observed in 67–82% of NTS neurons from NT and HT rats. At activation voltages from −10 to +10 mV, TOCs were significantly less in HT neurons compared with those observed in NT neurons ( P < 0.001). There were no differences in the voltage-dependent activation kinetics, the voltage dependence of steady-state inactivation, and the rise and decay time constants of the TOCs comparing neurons isolated from NT and HT rats. The 4-aminopyridine–sensitive component of the TOC was significantly less in neurons from HT compared with NT rats ( P < 0.001), whereas steady-state outward currents, whether or not sensitive to 4-aminopyridine or tetraethylammonium, were not different. Delayed excitation, studied under current clamp, was observed in 60–80% of NTS neurons from NT and HT rats and was not different comparing neurons from NT and HT rats. However, examination of the subset of NTS neurons exhibiting somatic DiA fluorescence revealed that DiA-labeled neurons from HT rats had a significantly shorter duration delayed excitation ( n = 8 cells, P = 0.022) than DiA-labeled neurons from NT rats ( n = 7 cells). Neurons with delayed excitation from HT rats had a significantly broader first action potential (AP) and a slower maximal downstroke velocity of repolarization compared with NT neurons with delayed excitation ( P = 0.016 and P = 0.014, respectively). The number of APs in the first 200 ms of a sustained depolarization was greater in HT than NT neurons ( P = 0.012). These results suggest that HT of 4-wk duration reduces TOCs in NTS neurons, and this contributes to reduced delayed excitation and increased AP responses to depolarizing inputs. Such changes could alter baroreflex function in hypertension.
Calcium From Internal Stores Triggers GABA Release From Retinal Amacrine Cells
Authors: Warrier Ajithkumar , Borges Salvador , Dalcino David , Walters Cameron , Wilson Martin
Published: November 2005

The Ca2+ that promotes transmitter release is generally thought to enter presynaptic terminals through voltage-gated Ca2+channels. Using electrophysiology and Ca2+ imaging, we show that, in amacrine cell dendrites, at least some of the Ca2+ that triggers transmitter release comes from endoplasmic reticulum Ca2+ stores. We show that both inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs) are present in these dendrites and both participate in the elevation of cytoplasmic [Ca2+] during the brief depolarization of a dendrite. Only the Ca2+ released through IP3Rs, however, seems to promote the release of transmitter. Antagonists for the IP3R reduced transmitter release, whereas RyR blockers had no effect. Application of an agonist for metabotropic glutamate receptor, known to liberate Ca2+ from internal stores, enhanced both spontaneous and evoked transmitter release.
Directional Selectivity of BOLD Activity in Human Posterior Parietal Cortex for Memory-Guided Double-Step Saccades
Authors: Medendorp W. Pieter , Goltz Herbert C. , Vilis Tutis
Published: November 2005

We used functional magnetic resonance imaging (fMRI) to investigate the role of the human posterior parietal cortex (PPC) in storing target locations for delayed double-step saccades. To do so, we exploited the laterality of a subregion of PPC that preferentially responds to the memory of a target location presented in the contralateral visual field. Using an event-related design, we tracked fMRI signal changes in this region while subjects remembered the locations of two sequentially flashed targets, presented in either the same or different visual hemifields, and then saccaded to them in sequence. After presentation of the first target, the fMRI signal was always related to the side of the visual field in which it had been presented. When the second target was added, the cortical activity depended on the respective locations of both targets but was still significantly selective for the target of the first saccade. We conclude that this region within the human posterior parietal cortex not only acts as spatial storage center by retaining target locations for subsequent saccades but is also involved in selecting the target for the first intended saccade.
Distinctive morphological and gene/protein expression signatures during myogenesis in novel cell lines from extraocular and hindlimb muscle
Authors: Porter John D. , Israel Sheri , Gong Bendi , Merriam Anita P. , Feuerman Jason , Khanna Sangeeta , Kaminski Henry J.
Published: November 2005

Skeletal muscles are not created equal. The underutilized concept of muscle allotypes defines distinct muscle groups that differ in their intrinsic capacity to express novel traits when exposed to a facilitating extrinsic environment. Allotype-specific traits may have significance as determinants of the preferential involvement or sparing of muscle groups that is observed in a variety of neuromuscular diseases. Little is known, however, of the developmental mechanisms underlying the distinctive skeletal muscle allotypes. The lack of appropriate in vitro models, to dissociate the cell-autonomous and non-cell-autonomous mechanisms behind allotype diversity, has been a barrier to such studies. Here, we derived novel cell lines from the extraocular and hindlimb muscle allotypes and assessed their similarities and differences during early myogenesis using morphological and gene/protein expression profiling tools. Our data establish that there are fundamental differences in the transcriptional and cellular signaling pathways used by the two myoblast lineages. Taken together, these data show that myoblast lineage plays a significant role in the divergence of the distinctive muscle groups or allotypes.
Early Dural Reaction to Polylactide in Cranial Defects in Rabbits
Authors: Mueller Andreas A. , Rahn Berton A. , Gogolewski Sylwester , Leiggener Christoph S.
Published: November 2005

Restoring the bone integrity to injured calvariae remains a challenge to surgeons. In this study, the dural biocompatibility of biodegradable poly-L/DL-lactide 80/20 and 70/30 defect covers, designed for guided bone regeneration, was assessed. In each of the 16 test rabbits, bilateral (8.3 mm) cranial defects were created. The different covers were applied to one defect each in every rabbit and consisted of three parts: an epicranial cover, a spacer, and a dural cover. All defects had closed after 8 weeks due to new bone formation. A few giant cells were found at the cover-to-dura interface in equal numbers for both covers. Dural bone formation was present in 15 of 16 rabbits and progressed unhindered by the defect cover or its early degradation products.
Shunt Revisions in Children – Can They Be Avoided?
Authors: Enger Per Ø. , Svendsen Frode , Sommerfelt Kristian , Wester Knut
Published: November 2005

Background: Shunt failure is by far the most frequent problem in children with shunts, and most of them will experience this condition at some point in their lives. In order to identify causes of shunt failure, and to compare multi-component and one-piece shunt systems, we analyzed retrospectively all pediatric shunt procedures in our Department during an 11-year period. The study does not deal with shunt infections. Methods: We reviewed the records of all pediatric shunting procedures between January 1986 and December 1996. Results: The study included 161 children operated for hydrocephalus with a total of 431 procedures. The procedures included 124 (29%) primary insertions, 10 (2%) reinsertions and 297 (69%) revisions; 206 (69%) of the revisions were due to shunt failures, of which 74 (36%) were caused by the failure of the surgical technique (misplaced ventricular catheters, disconnected shunts, or misplaced peritoneal catheters). Conclusions: Improvement of the surgical technique may reduce the incidence of shunt failures and revisions. The results obtained in a small department like ours do not seem to differ substantially from those obtained in more specialized departments with a larger patient group. Practical measures that may reduce the risk of shunt failures are suggested.
Primary Endovascular Therapy with Clot Retrieval and Balloon Angioplasty for Acute Basilar Artery Occlusion
Authors: Zaidat Osama O. , Tolbert Marshall , Smith Tony P. , Alexander Michael J.
Published: November 2005

This case report demonstrates that mechanical clot disruption and retrieval may be performed safely and successfully in a child with basilar artery (BA) thrombosis. A 16-year-old boy presented to our institution with locked-in syndrome 20 h after symptom onset. Brain MRI and cerebral angiography findings were consistent with BA occlusion. The child underwent endovascular therapy with clot retrieval followed by balloon angioplasty achieving immediate recanalization and clinical recovery on 3-month follow-up. This case highlights the use of primary neurointerventional devices in children with BA occlusion presenting beyond the conventional therapeutic window for other interventions.
Mutational Analysis of Amino Acid Positions Crucial for IgE-Binding Epitopes of the Major Apple (Malus domestica) Allergen, Mal d 1
Authors: Ma Yan , Gadermaier Gabriele , Bohle Barbara , Bolhaar Suzanne , Knulst Andre , Markovic-Housley Zora , Breiteneder Heimo , Briza Peter , Hoffmann-Sommergruber Karin , Ferreira Fatima
Published: November 2005

Background: Individual amino acid residues of the major birch pollen allergen, Bet v 1, have been identified to be crucial for IgE recognition. The objective of the present study was to evaluate whether this concept was applicable for the Bet v 1-homologous apple allergen, Mal d 1. Methods: A Mal d 1 five-point mutant was produced by PCR techniques, cloned into pMW 172 and expressed in Escherichia coli BL21(DE3) cells. To evaluate the allergenic properties of the engineered protein compared to Mal d 1 wild-type IgE immunoblotting, ELISA, peripheral blood monocytes proliferation assays, and skin prick tests were performed. Results: The Mal d 1 mutant showed reduced capacity to bind specific IgE as compared to wild-ype Mal d 1 in in vitro assays in the majority of the sera tested. In ELISA, 10 out of 14 serum samples displayed an 88–30% decrease in IgE binding to Mal d 1 mutant compared to wild-type Mal d 1. Skin prick tests in apple-allergic patients (n = 2) confirmed the markedly decreased ability of the Mal d 1 mutant to induce allergic reactions in vivo. However, the relevant T cell epitopes were present in the mutated molecule according to peripheral blood mononuclear cell proliferation assays. Conclusions: Our findings suggest that it is possible to modulate the IgE-binding properties of allergens by single amino acid substitutions at crucial positions which might be useful for future immunotherapy of birch-pollen-associated food allergies which are not ameliorated by birch pollen immunotherapy.