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PubMed1989

Crystallographic characterization and three-dimensional model of yeast Cu,Zn superoxide dismutase.

The Cu,Zn superoxide dismutase from yeast was crystallized in the orthorhombic space group P21212 with unit cell dimension a = 105.1 A,b = 142.2 A, c = 62.1 A. The crystals grow in 25 mM citrate, 10 mM phosphate buffer pH 6.5, and 6% (W/V) polyethylene glycol, with a Vm of 3,4 A3/dalton, for two dimers/asymmetric unit. The crystals were unstable in the mother liquor, but were stabilized by transfer to a 35% polyethylene glycol solution. This crystalline form diffracts at high resolution and is suitable for determination of the atomic structure. The three dimensional structure of the yeast enzyme could be model-built by computer graphics techniques using the bovine enzyme atomic coordinates as template. The proposed model requires removal of some salt bridges and non equivalence of the metal-binding sites in the subunits, in line with reported functional properties of the yeast enzyme.

Amino Acid Sequence↗

PubMedDate not supplied

Polished, professional presentation: unlocking the design elements.

Using available computer graphics software programs, a novice can develop a presentation. Going beyond the basics, however, requires knowledge of the use of the elements of design: fonts, colors, and graphics. This article describes how to select fonts and colors and provides guidelines for use of pictures and graphs. Guidelines for use of default settings and templates, and considerations related to the use of animation, sound, and projection are included. Examples are provided to demonstrate important points and creating a polished, professional product.

Audiovisual Aids↗

PubMed2000

Virtual tape measure for the operating microscope: system specifications and performance evaluation.

OBJECTIVE: The Virtual Tape Measure for the Operating Microscope (VTMOM) was created to assist surgeons in making accurate 3D measurements of anatomical structures seen in the surgical field under the operating microscope. The VTMOM employs augmented reality techniques by combining stereoscopic video images with stereoscopic computer graphics, and functions by relying on an operator's ability to align a 3D graphic pointer, which serves as the end-point of the virtual tape measure, with designated locations on the anatomical structure being measured. The VTMOM was evaluated for its baseline and application performances as well as its application efficacy. METHODS: Baseline performance was determined by measuring the mean error (bias) and standard deviation of error (imprecision) in measurements of non-anatomical objects. Application performance was determined by comparing the error in measuring the dimensions of aneurysm models with and without the VTMOM. Application efficacy was determined by comparing the error in selecting the appropriate aneurysm clip size with and without the VTMOM. RESULTS: Baseline performance indicated a bias of 0.3 mm and an imprecision of 0.6 mm. Application bias was 3.8 mm and imprecision was 2.8 mm for aneurysm diameter. The VTMOM did not improve aneurysm clip size selection accuracy. DISCUSSION AND CONCLUSION: The VTMOM is a potentially accurate tool for use under the operating microscope. However, its performance when measuring anatomical objects is highly dependent on complex visual features of the object surfaces.

Aneurysm↗

PubMed1991

Introduction to film recorders for computer-generated slide production.

The photographic method of recording computer graphics is now very much an automated procedure using film recorders, as compared with the old technique of photographing directly off the coloured video display. There are at present three types of film recorder available: terminal driven, direct drive and optical-font imager. Theoretical and practical information is given on each of these recorders based on the author's practical experience.

Computer Graphics↗

PubMed1989

Structural and biochemical comparison of the anti-mitotic agents colchicine, combretastatin A4 and amphethinile.

The novel agents amphethinile and combretastatin A4 are shown to be very similar to colchicine in their interactions with purified tubulin. All three agents can inhibit tubulin assembly at similar treatment levels and have comparable affinity constants for tubulin. Amphethinile and combretastatin A4 are capable of displacing colchicine but not vinblastine from tubulin. A comparison of the structures of these agents shows that whereas colchicine and combretastatin A4 contain a trimethoxybenzene group (a moiety also found in other colchicine-like agents such as podophyllotoxins and steganacin) no obvious similarity is seen for amphethinile. The three-dimensional structures of these agents, determined from either crystallographic data or by energy minimization procedures, show, however, that all three agents consist of two planar, or almost planar, ring systems which are tilted with respect to each other. Using computer graphic techniques it can be shown that their ring systems are superimposable and that the planar sections of each molecule are at an angle of 50-60 degrees to each other. It is proposed that the angular bicyclic structure of these agents is one determining factor for their efficient binding to tubulin.

Animals↗

PubMed1992

Three-dimensional CT scan reconstruction for the assessment of congenital aural atresia.

Major advances in medical computer graphics workstations have provided the capability to produce high quality three-dimensional image reconstructions from conventional thin-section computerized tomography (CT) scans with the ability to observe the imaged structure from any angle, with views and dimensions that are comparable to actual dissections. We have applied this technique to the temporal bone to assess congenital aural atresia in surgical planning for hearing reconstruction in six patients. The digital information produced by thin-section CT scanning allowed for the re-creation of multiplanar reformatted, shaded surface, and volumetric images. With this technique the surface landmarks of the temporal bone were readily visualized, the configuration of the atretic plate and middle ear in relation to the tegmen and glenoid fossa could be precisely assessed and the structure of the ossicular mass was easily analyzed. Most significantly, the facial nerve could be accurately and easily envisioned in its entire intratemporal course. Three-dimensional imaging is a highly desirable means for observing CT scan data to facilitate the surgical planning for correction of congenital aural atresia.

Adolescent↗

PubMed1996

Images, words, and questions: variables that influence beliefs about vision in children and adults.

In three studies we used animated computer graphics to examine beliefs among children and adults that vision involved input to the eyes (the intromission theory) or emissions from the eye (the extramission theory). Results supported previous findings which showed a decrease in extramission and an increase in intromission responses across age. The findings also indicated that there were more extramission interpretations when subjects were tested with graphic images, and more intromission interpretations when the questioning was purely verbal. However, the magnitude of the effect was highly dependent upon question format. The differences between graphic and verbal question presentations (A) are consistent with our theory on the origins of extramission beliefs, (B) suggest that beliefs can vary as a function of form of symbolization, and (C) are contrary to long-standing beliefs of educators and psychologists that emphasize the importance of concrete, pictorial representation.

Adolescent↗

PubMed1986

Three-dimensional CT reconstructions of tongue and airway in adult subjects with obstructive sleep apnea.

The interaction between airway and tongue structures in a sample of 25 adult men with obstructive sleep apnea was quantified on the basis of a series of preoperative CT slices obtained for each subject. Tracings were completed for tongue, and right and left nasal, nasopharynx, oropharynx, and hypopharynx structures; computer graphics were used to obtain superior and lateral three-dimensional reconstructions of all structures for each subject. In addition, cross-sectional areas of specific sites of airway constriction, surface area, volume, and ratio calculations were completed. The majority of the constrictions occurred in the oropharynx (0.52 +/- 0.18 cm2), but six subjects had two constrictions--one in the oropharynx and one in the hypopharynx. The airway had a mean volume of 13.89 +/- 5.33 cm3, whereas tongue volume ranged from 44.03 to 99.56 cm3 with a mean of 71.96 +/- 13.41 cm3. Subjects with more severe obstructive sleep apnea tended to have larger tongue and smaller airway volumes. The more obese subjects showed larger tongue surface areas and smaller airway surface areas. To determine the structural relationships between airway and tongue variables, a series of logarithmic plots was determined. An isometric relationship characterized tongue surface area and tongue volume. A logarithmic plot of oropharyngeal airway vs. tongue volume showed a negative allometric relationship. Tongue volume increased more rapidly than airway volume in subjects with obstructive sleep apnea. Subjects with large tongue volumes were observed to experience significant complications at the time of surgical treatment. Quantification of the volume of the oropharynx and its relationship to tongue volume provide an overview of the interaction between these structures.

Adult↗

PubMed1987

The hydration of protein secondary structures.

The hydration of the main-chain carbonyl (CO) groups in proteins have been studied using infra-red spectroscopy, and computer-graphics analysis of high resolution protein crystal structures. The IR measurements indicate that the strength of water binding to the CO groups is lower in beta-sheet proteins compared with alpha-helical ones. Analysis of the protein crystal structures shows that this is due primarily to differences in the geometry of water-CO group interactions in the two types of secondary structure.

Computer Graphics↗

PubMed1988

Prediction of the three-dimensional structure of the enzymatic domain of t-PA.

Tissue plasminogen activator (t-PA), an enzyme of the fibrinolytic system, is responsible for lysis of fibrin via activation of plasminogen, and therefore for degradation of blood clots. There are currently no X-ray crystal structure data of the t-PA molecule available either in whole or in part. We therefore predicted the three-dimensional structure of the protease domain by means of computer-graphical methods*. The model obtained forms a basis for understanding the binding of plasminogen to the active site of t-PA. In addition, the interactions of various inhibitors with t-PA were studied by modeling them into the active site. The model also yields an explanation for the observed amidolytic activity of t-PA in the single chain form.

Amino Acid Sequence↗

PubMed2000

Use of an ultrahigh-speed laser scanner for constructing three-dimensional shapes of dentition and occlusion.

STATEMENT OF PROBLEM: Acquisition of the 3-dimensional shape of dental casts is useful for quantitative evaluation of the diagnosis and treatment of occlusion. PURPOSE: This study demonstrated the acquisition of data through the use of an ultrahigh-speed laser scanner and an originally developed goniometer, the use of these tools to measure the entire 3-dimensional shape of the dental cast from multiple directions, and the connection of the data measurements to reconstruct the cast's occlusion with the use of a computer. MATERIAL AND METHODS: A commercially available apparatus that emits a line laser and completes 1 scan in only 0.6 seconds was used. To compensate for the unmeasured region, the cast was measured from 4 directions on the original goniometer, and the connection of data to obtain the entire image was carried out. Further, the reconstruction of the occlusion between the upper and lower casts was attempted by transferring the upper cast data to the lower cast. RESULTS: By the data connection, the entire shape of the upper and lower casts was constructed, and the characteristic structure was reproduced. The data connections were satisfactory for the flat surfaces but less accurate for the inclined surfaces. Reconstruction of the occlusion between the upper and lower casts was accomplished. It was then possible to visualize the occlusion from arbitrary directions and sections with computer graphics. CONCLUSION: The construction of the entire 3-dimensional shape of a dental cast and the reconstruction of the occlusion were accomplished using an ultrahigh-speed measurement system and original goniometer. These results will be useful for clinical applications such as computerized diagnoses and treatment of occlusion, and for the replacement of the stone casts in the dental office by computerized data.

Calibration↗

PubMed1991

Determination of the accuracy of three die systems.

This article reports the findings of two interrelated projects that measured the accuracy of electroplated, epoxy resin, and polyurethane die materials against a master tooth, using the Michigan Computer Graphics Coordinate Measuring System (MCGCMS). In the first phase, on occlusal die morphology, replications of a master tooth were used to validate the MCGCMS reliability. Eighteen total data sets derived from three silver-plated dies and three epoxy resin dies were then compared with a representative data set of the master tooth. The mean differences for all silver-plated die and epoxy die measurements against the master ranged from -42 to -49 and -46 to -230 microns/mm2, respectively. In the second phase, two epoxy die materials and a polyurethane system were compared with a master tooth in an identical manner. In paired comparisons to the master tooth, mean differences for Epoxydent material, epoxy resin, and polyurethane dies ranged from -147 to -153, -149 to -230, and -56 to -168 microns/mm2, respectively. A Student t test using a CLR ANOVA was performed between the master tooth and the five die systems. A significant difference was revealed between the enamel-silver difference and the enamel-Epoxydent difference data at the 95% confidence level. A significant difference also occurred between enamel-silver and enamel-epoxy resin. It was concluded that silver-plated dies are acceptable replicas of a master tooth. Epoxydent and epoxy resin dies did not provide reliable replications when compared with the silver-plated dies. Epoxy and polyurethane replications, although reported as accurate, were inconclusive.

Analysis of Variance↗

PubMed1987

High-pass resolution targets in peripheral vision.

Visual acuity was measured at 10 degree intervals on the horizontal meridian in two normal subjects, using high-pass spatial frequency filtered test targets in a computer graphics display. The close similarity between detection and recognition thresholds resulted in quick and reliable measurements. Peripheral acuity was proportional to local retinal ganglion cell separation. High-pass targets appear to be nearly ideal for clinical perimetry because of the easy test task and the possibility of interpreting results in terms of numbers of functional neuroretinal channels. The major limitation appears to be a somewhat fuzzy definition of small, circumscribed defects.

Adult↗

PubMed2001

A prior for global convexity in local shape-from-shading.

To solve the ill-posed problem of shape-from-shading, the visual system often relies on prior assumptions such as illumination from above or viewpoint from above. Here we demonstrate that a third prior assumption is used--namely that the surface is globally convex. We use complex surface shapes that are realistically rendered with computer graphics, and we find that performance in a local-shape-discrimination task is significantly higher when the shapes are globally convex than when they are globally concave. The results are surprising because the qualitative global shapes of the surfaces are perceptually unambiguous. The results generalise findings such as the hollow-potato illusion (Hill and Bruce 1994 Perception 23 1335-1337) which consider global shape perception only.

Analysis of Variance↗

PubMed1993

Three-dimensional reconstruction of the pig sheathed artery.

The structure of the sheathed artery and the number of branches of the sheathed capillary were investigated by three-dimensional reconstruction computer graphics in the pig spleen. The capillary branched 1 to 6 times in the capillary sheath in more than 90% of all samples examined. The sheathed artery varied in shape and size in accordance with the number of branches and direction of the capillary. The usual descriptions for the sheathed artery were suggested to be mostly in appropriate at least for that of the pig spleen.

Animals↗

PubMed1988

Integration of depth modules: stereo and shading.

We studied the integration of image disparities, edge information, and shading in the three-dimensional perception of complex yet well-controlled images generated with a computer-graphics system. The images showed end-on views of flat- and smooth-shaded ellipsoids, i.e., images with and without intensity discontinuities (edges). A map of perceived depth was measured by adjusting a small stereo depth probe interactively to the perceived surface. Our data show that disparate shading (even in the absence of disparate edges) yields a vivid stereoscopic depth perception. The perceived depth is significantly reduced if the disparities are completely removed (shape-from-shading). If edge information is available, it overrides both shape-from-shading and disparate shading. Degradations of depth perception corresponded to a reduced depth rather than to an increased scatter in the depth measurement. The results are compared with computer-vision algorithms for both single cues and their integration for three-dimensional vision.

Computer Graphics↗

PubMed1987

The effect of incubation time and temperature on growth of Escherichia coli on gradient plates containing sodium chloride and sodium nitrite.

Two-dimensional gradient plates are a convenient way of screening antimicrobial effects of preservative factors acting in combination across a broad range of physical and chemical conditions. We report the effects of sodium chloride, sodium nitrite and incubation temperature on the growth of Escherichia coli by staining, laser densitometry and computer graphics. Staining not only more easily distinguished the growth area but also gave an indication of the viability of cells present. 2-(p-iodophenyl)-3(p-nitrophenyl)-5-phenyl tetrazolium chloride was the more useful of the two stains used. Inhibitory concentrations of sodium chloride decreased with reduced incubation temperature. The response of E. coli to combinations of salt and nitrite on gradient plates was very similar to its response in liquid medium.

Computer Graphics↗

PubMed1992

Zero interaction response surfaces, interaction functions and difference response surfaces for combinations of biologically active agents.

In the field of combination experiments there is wide-spread confusion over definitions, terminology and methods for the evaluation of interaction between biologically active agents. According to our view the widely used isobole approach is the method of choice. In this contribution it is shown how the combination of the classical isobole approach with response surface modeling and computer graphics leads to powerful new methods for the assessment of interaction of biologically active agents. In particular, zero interaction response surfaces, difference response surfaces and interaction functions are proposed. Zero interaction response surfaces represent surfaces which display zero interaction in the whole dose range. Difference response surfaces display the difference between an actual response surface and the corresponding zero interaction response surface. Interaction functions are a generalization of the index of interaction, which describe the dose dependence of this quantity.

Computer Graphics↗