SEARCH · Search PubMed

Results for “Computer Graphics”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources

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↗

PubMed2005

Interactive dynamic graphical techniques for the exploration of functional data.

INTRODUCTION: The use of interactive dynamic graphics has become a common practice for the exploration of multidimensional data sets. The availability of powerful and inexpensive hardware and software for graphical computing makes the use of such techniques feasible for the examination of complex forms of data. This paper describes some simple techniques, which were implemented in the LISP-STAT environment, for the visualization of functional data arising from studies of optical technologies used for the detection of cervical intraepithelial neoplasia or squamous intraepithelial lesions. MATERIALS AND METHODS: The methods demonstrated have been implemented in software coded in LISP-STAT, a free statistical computing package available for most computer systems. The data used in this paper are drawn from a previous study in which fluorescence spectroscopy was measured from cervical sites at 337 nm, 380 nm, and 460 nm excitation in cervical screening patients. The goal of the project is to explore biographical variables to better understand the biology of fluorescence. RESULTS: 199 measurements were taken in 55 women with normal Pap smears. The data are recorded as spectra showing the intensity of emission excitation versus emission in nanometers. Covariate variables available for analysis are current smoker vs. nonsmoker premenopausal vs. postmenopausal, tissue type (columnar, squamous, and transition zone), and age in years. Although the optical measurements show consistent changes between normal and abnormal tissue in individual patients, there is wide variation in the intensity of the measurements between patients, even for normal tissue. Patient age affects the fluorescent spectrum showing increasing intensity with increasing age. Menopausal status affects the fluorescent spectra coincidentally with age. Smoking and race do not appear to affect the spectra in this sample of patients. CONCLUSIONS: The use of interactive graphical techniques permits the data analyst to examine multidimensional data in intuitive ways. These explorations allow non-statisticians to explore the data in a perceptive manner that may lead to new approaches in algorithm development for optical technologies.

Analysis of Variance↗

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↗

PubMed1988

Enhancement and simplification of macromolecular images.

Computer graphics programs have been devised to display selected atomic features and to simplify images of complex macromolecular structures. By using boundary outlines, adjustment of size and shape of the molecular components, color coding, shading, and selective omission of obscuring detail, attention can be focused on specific interactions which determine higher levels of organization. A balanced color table has been constructed in which different hues have equal steps in brightness; this table has facilitated distinction of atom types and sequence coding together with representation of an optimum range of depth cueing and surface shading. The graphics system has been used with the atomic coordinates of the tobacco mosaic virus structure to simplify images of the protein subunit, to illustrate intermolecular interactions, and to relate subunit packing arrangements in different assemblies to the underlying atomic structure. The system has also been used to construct a schematic representation of the polyomavirus capsid, based on low resolution data. Application of artistic methods contributes to the effective presentation and interpretation of detailed scientific information about complex macromolecular structures.

Computer Graphics↗

PubMed1994

Effect of distamycin on chlorambucil-induced mutagenesis in pZ189: evidence of a role for minor groove alkylation at adenine N-3.

Previous work has shown that the bifunctional alkylating agent chlorambucil induces thermolabile adenine adducts and that the predominant chlorambucil-induced mutations in shuttle vector pZ189 are transversions at AT base pairs. In order to assess the role of thermolabile adducts in generating these transversions, pZ189 was treated with chlorambucil in the presence of distamycin, which specifically blocks formation of thermolabile adenine adducts. Analysis of the mutations resulting from replication of the damaged vector in human 293 cells showed that base substitutions at AT base pairs were specifically suppressed in concert with suppression of thermolabile adducts at specific sites in the supF target gene, strongly supporting a role for these adducts in mutagenesis. Since there is considerable evidence that these adducts are N-3 alkylations, a computer graphics model of such an adduct was constructed. Modeling studies indicated that the adduct could be formed with little distortion of the DNA helix. Analysis of the adduct using the HINT (Hydropathic INTeractions) program was consistent with the proposal that favorable hydrophobic interactions of the phenyl ring of chlorambucil with the wall of the minor groove may promote adenine N-3 alkylation by this drug.

Adenine↗

PubMed1988

Three-dimensional computerized reconstruction of histologic serial sections for orthopedic research.

New programs in image processing and computer graphics can now render three-dimensional images from serial tissue slices. Although neuroanatomists have used these techniques most intensively, there are exciting applications of this methodology in orthopedic research and investigative embryology. Three-dimensional reconstructions of histologic sections from newborn clubfeet have been used to determine the rotational alignment of the hindfoot bones. Similar studies could be undertaken to improve understanding of the normal and pathologic perinatal development of the spine, hip, and hand.

Computer Graphics↗