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At least 127 records · Page 7Linked to original sources
PubMed1998

Neuronavigation using an articulated arm with a bayonet probe on a computer graphic composite of magnetic resonance and computerized tomography images.

This report describes a neurosurgical navigational system using a newly-designed articulated arm with an interchangeable probe shaped like a bayonet, which can be used in deep structures through narrow openings. This system enables three-dimensional integration of magnetic resonance and computed tomographical images, and thereby yields computer graphic composites of the scalp, brain, skull, and vessels. The arm was used in 15 patients during open brain surgery, including 5 skull base procedures. This system was useful for comprehension of skull base anatomy and could conveniently be used in microscopic neurosurgical procedures without limiting the operative field.

Adult↗
PubMed1987

Computer-graphics interpretations of residue exchanges between the alpha, beta and gamma subunits of human-liver alcohol dehydrogenase class I isozymes.

Three-dimensional models of human alcohol dehydrogenase subunits have been constructed, based on the homologous horse enzyme, with computer graphics. All types of class I subunits (alpha, beta, and gamma) and the major allelic variants (beta 1/beta 2 and gamma 1/gamma 2) have been studied. Residue differences between the E-type subunit of the horse enzyme and any of the subunits of the human isozymes occur at 64 positions, about half of which are isozyme-specific. About two thirds of the substitutions are at the surface and all differences can be accommodated in highly conserved three-dimensional structures. The model of the gamma isozyme is most similar to the crystallographically analyzed horse liver E-type alcohol dehydrogenase, and has all the functional residues identical to those of the E subunit except for one which is slightly smaller: Val-141 in the substrate pocket. The residues involved in coenzyme binding are generally conserved between the horse enzyme and the alpha, beta, and gamma types of the human enzyme. In contrast, single exchanges of these residues are the ones involved in the major allelic differences (beta 1 versus beta 2 and gamma 1 versus gamma 2), which affects the overall rate of alcohol oxidation since NADH dissociation is the rate-determining step. Residue 47 is His in beta 2 and Arg in the beta 1, gamma 1, and gamma 2 subunits, and in horse liver alcohol dehydrogenase. Both His and Arg can make a hydrogen bond to a phosphate oxygen atom of NAD; hence the lower turnover rate of beta 1 apparently derives from a charge effect. The substitution to Gly in the alpha subunit results in one less hydrogen bond in NAD binding, and consequently in rapid dissociation. This may explain why the overall rate is an order of magnitude faster than that of beta 1. The important difference between gamma 1 and gamma 2 is an exchange at position 271 from Arg to Gln which can give a hydrogen bond from Gln in gamma 2 to the adenine of NAD. The tighter binding to gamma 2 can account for the slower overall catalytic rate in this isozyme. The kinetics and interactions of cyclohexanol and benzyl alcohol with the isozymes were judged by docking experiments using an interactive fitting program.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohol Dehydrogenase↗
PubMed1984

An interactive computer graphics study of thermolysin-catalyzed peptide cleavage and inhibition by N-carboxymethyl dipeptides.

Interactive computer graphics was used as a tool in studying the cleavage mechanism of the model substrate Z-Phe-Phe-Leu-Trp by the zinc endopeptidase thermolysin. Two Michaelis complexes and three binding orientations of the tetrahedral intermediate to the crystal structure of thermolysin were investigated. Our results indicate that a Michaelis complex, which does not involve coordination of the scissile peptide to the zinc, is consistent with available experimental data and the most plausible of the two complexes. A tetrahedral intermediate complex wherein the two oxygens of the hydrated scissile peptide straddle the zinc in a bidentate fashion results in the most favorable interactions with the active site. The preferred tetrahedral intermediate and Michaelis complex provide a rationalization for the published substrate data. A trajectory for proceeding from the Michaelis complex to the tetrahedral intermediate is proposed. This trajectory involves a simultaneous activation of the zinc-bound water molecule concurrent with attack on the scissile peptide. A detailed ordered product release mechanism is also presented. These studies suggest some modifications and a number of extensions to the mechanism proposed earlier [Kester, W. R., & Matthews, B. W. (1977) Biochemistry 16, 2506; Holmes, M. A., & Matthews, B. W. (1981) Biochemistry 20, 6912]. The binding mode of the thermolysin inhibitor N-(1-carboxy-3-phenylpropyl)-L-leucyl-L-tryptophan [Monzingo, A. F., & Matthews, B. W. (1984) Biochemistry (preceding paper in this issue)] is compared with that of the preferred tetrahedral intermediate, providing insight into this inhibitor design.

Binding Sites↗
PubMed1989

Adverse reactions of imidazole antifungal agents: computer graphic studies of cytochrome P-450 interactions.

The imidazole antifungal agents give rise to adverse reactions and clinically relevant drug interactions. This is due to lack of specificity of the antifungal agents that interact avidly not only with the fungal but also with mammalian cytochrome P-450 proteins. A computer graphic technique capable of predicting the interaction of these structurally-related imidazoles with fungal and mammalian cytochrome P-450 proteins is described. This prediction is achieved by comparing the molecular conformation of these drugs with lanosterol, the substrate of the fungal cytochrome P-450, and with phenobarbitone, an inducing agent of a family of mammalian cytochrome P-450, toward which the antifungal agents show highest inhibitory activity.

Animals↗
PubMed1995

Antibody humanization predicted by computer graphic analysis.

Humanized antibodies continue to be evaluated in clinical trials, and each trial will yield valuable information for the design of the next generation of humanized antibodies. More attention will be given to the use of antibody fragments and the selection of human antibody specificities from phage libraries for human antibody therapeutics. Computer graphic analysis and molecular modeling of antibody structures will continue to be invaluable for predicting structural modifications for humanization of antibodies and for extracting structural information from antigen binding sites that can ultimately lead to small molecule therapeutics.

Animals↗
PubMed1983

Measuring creativity through computer graphics of hearing-impaired children.

The purpose of this study was to investigate variables affecting visual creativity of 31 hearing-impaired children through the medium of computer graphics. These children ranged in age from 8.0 to 15.9 yr. 16 subjects attended total-communication educational programs and 15 subjects attended aural/oral classes. Each subject worked independently at a computer terminal equipped with a graphics menu developed for a subject's use. Hardcopy printouts of four images per subject were evaluated for creativity, aesthetics, and imagery. Analysis suggested that creativity among hearing-impaired children is influenced by age and communication mode used in the educational setting.

Adolescent↗
PubMed1975

Computer graphics--three dimensional reconstruction of thalamic anatomy from serial sections.

This paper describes an interactive program which uses computer graphics techniques to reconstruct a three dimensional representation of thalamic anatomy from two dimensional serial secretion. Figures traced on a Rand tablet, connected to a DEC-340 display, are digitized and scaled. The three dimensional display capabilities of the Adage AGT-30 are used to present the reconstructed structures. Two dimensional cross sections of an arbitrary plane may also be displayed. The program has applications in stereotaxic surgery, teaching neuroanatomy, and may be used to reconstruct other anatomic structures from serial sections.

Computers↗
PubMed1994

Use of computer graphic filters for the nuclear grading of hematoxylin and eosin-stained specimens from prostatic lesions.

An inexpensive workstation is being developed to assist pathologists in diagnosing routine hematoxylin and eosin-stained slides. A linear discriminant model was applied to karyometric features of prostate lesions, and a grade according to Mostofi was determined from the discriminant values. Twenty cases, five of hyperplasia and five each of carcinoma Mostofi grades I, II and III, for a total of 600 nuclei, were selected to train the model. Computer graphic filters were constructed from the discriminant values. Each segmented nucleus has a colored frame (the graphic filter) displayed around it. The color, determined from discriminant values and correlated with the grades, ranges from green for hyperplasia, yellow for low grade, orange for medium grade and red for high grade. An additional 20 cases, 5 of hyperplasia and 5 each of the Mostofi grades, for a total of 538 nuclei, were selected to test the graphic filter. Ninety-six percent of the hyperplasia nuclei were framed in green, 84% of low grade nuclei were framed in yellow, 90% of medium grade nuclei were framed in orange, and 89% of high grade nuclei were framed in red. These results indicate the potential of the color graphic filter to show the pathologist immediate and accurate visual information about the grade of a nucleus. This method may help with the difficult diagnosis of borderline lesions and may help in making the diagnosis from scanty biopsy material.

Cell Nucleus↗
PubMedDate not supplied

The intercondylar notch in acute tears of the anterior cruciate ligament: a computer graphics study.

Although the intercondylar notch becomes narrowed with a failed repair of the ACL or with chronic instability of the knee, narrowed intercondylar notches have frequently been observed during arthrotomy for an acute ACL tear in previously uninjured knees. In order to determine whether the structure of the intercondylar notch predisposes a knee to anterior cruciate tears, a computer graphics study was designed. Notch view roentgenograms of 50 patients with an acute ACL injury and 50 "normal" patients without history of significant knee injury were compared. An interactive graphics design station was used to obtain the area of the anterior opening (ANT) and posterior arch (POST) of the intercondylar notch. A "total" (TOTAL) area was obtained by tracing the distal 7.5 cm of the femur. Only the ratios of areas obtained from each roentgenogram were used for comparison because of varying femur sizes among patients and possible slightly varying techniques of taking the notch view roentgenogram itself. The following ratios were developed: ANT/POST, POST/TOTAL, and (POST-ANT)/TOTAL. The difference between the means of the ratio POST/TOTAL for knees with acute ACL tears and those for normal knees was statistically significant (P less than 0.005). This study suggests that a narrowed posterior arch of the intercondylar notch may predispose a knee to ACL tear.

Adolescent↗
PubMed1995

Intraductal extension of primary invasive breast carcinoma treated by breast-conservative surgery. Computer graphic three-dimensional reconstruction of the mammary duct-lobular systems.

BACKGROUND: Intraductal tumor extension is a characteristic feature of primary breast carcinoma, and is an important consideration in patients undergoing breast conservative surgery. However, there have been no reports of studies of intraductal extension within the mammary ductal tree. METHODS: Quadrantectomy specimens from 20 patients with primary invasive breast carcinoma were examined by subgross and stereomicroscopic technique to visualize intraductal tumor extension. Serial 2 mm-thick sections were subjected to two-dimensional (2-D) tumor mapping, measuring the distances and angles of extension, and to three-dimensional (3-D) reconstruction of the mammary duct-lobular systems by means of computer graphics. RESULTS: Intraductal tumor extension was found in 16 of 20 specimens (80.0%), extending continuously from the primary invasive carcinoma through the mammary ductal tree. The distances and angles of extension were larger in tumors with microcalcifications, papillotubular invasive ductal carcinoma, 30% or more of intraductal component, and comedo-type intraductal tumor extension. The 3-D reconstructions demonstrated three types of extension; central (11 cases), peripheral (3 cases), and mixed (2 cases). Further, there were some ductal branches anastomosing with different mammary duct-lobular systems at various sites. In one specimen, intraductal tumor extended widely from the primary invasive carcinoma through a branch connecting adjacent mammary duct-lobular systems. CONCLUSIONS: Three-dimensional reconstruction images of intraductal extension of invasive breast carcinomas are presented for the first time to the authors' knowledge. Examples of ductal anastomoses were observed, and should be considered as a risk factor for possible widespread intraductal extension through multiple mammary duct-lobular systems.

Adult↗
PubMed1995

Development of the conduction system in the rat heart as determined by Leu-7 (HNK-1) immunohistochemistry and computer graphics reconstruction.

BACKGROUND: The development of the heart conduction system is controversial. Our previous study demonstrated anti-Leu-7 antibody to cross-react with the cells of the conduction system in the embryonic rat heart. Thus, detailed analysis of the development of the conduction system was performed by immunohistochemical reaction with the use of the antibody. DESIGN: Horizontal serial sections of hearts obtained from embryonic and neonatal rats were treated for immunohistochemical reaction with anti-Leu-7 antibody, and three-dimensional images were reconstructed by computer graphics. Images were analyzed by superimposing the results on scanning electron micrographs. RESULTS: The development of the rat heart conduction system starts at 10 days and is completed by 18 days of gestation. The presence of three internodal tracts (INT1, -2, and -3) and two primordia of the atrioventricular node were confirmed in this process. INT1 and -3 pass through the septum spurium. INT2 follows the same route as the posterior internodal tract of James, but the other two INTs showed no correlation to previously described tracts. The sinuatrial node and INTs were found to be derivatives of the so-called S-A ring, and the bundle of His and bundle branches were found to be derived from the B-V ring. In this study, no immunoreactivity was observed in cells of the truncobulbar portion. CONCLUSIONS: Three internodal tracts and two atrioventricular node primordia were observed in the developing heart. The paths of the three internodal tracts showed intimate relationships with the internal structures of the heart. The developmental significance of the septum spurium, sinus septum, and venous valve was discussed.

Animals↗
PubMed1998

Three-dimensional computer-graphic demonstration of facial soft tissue changes in mandibular prognathic patients after mandibular sagittal ramus osteotomy.

The purpose of this study is to demonstrate the three-dimensional changes in facial soft tissues in prognathic patients after orthognathic surgery. The soft tissue and skeletal tissue changes were analyzed with a noncontact three-dimensional digitizing system and roentgenographic cephalometry, respectively. Forty prognathic patients with or without asymmetry, who received only mandibular sagittal ramus osteotomy, were included in the study. The preoperative and 3-month postoperative digitized soft tissue images were superimposed from the nose to the forehead. Changes in the facial soft tissue were illustrated using a computer graphic image with tomographic cross sections at 1-cm intervals. Sagittal soft tissue dislocations of 75 facial measurement points were also calculated. Examination of patients with minimum transverse movement of the mandible revealed significant correlation between soft tissue and related hard tissue dislocation in the sagittal dimension in most landmarks at and below the upper lip. This noncontact three-dimensional digitizing system is very useful in analyzing facial soft tissue changes caused by orthognathic surgery.

Adult↗
PubMed1984

Computer graphics modelling of human renin. Specificity, catalytic activity and intron-exon junctions.

A model has been constructed using computer graphics for human renin based on the sequence derived from that of the gene and the 3-dimensional structure defined at high resolution for other homologous aspartic proteinases. Human renin can adopt a 3-dimensional structure close to that of other aspartic proteinases, in which amino acids corresponding to intron-exon junctions in the gene are at surface regions in the 3-dimensional structure. As expected, the essential catalytic residues are retained and the nearby residue 304 is alanine as in the mouse sequence, supporting the idea that Asp 304 of other aspartic proteinases may contribute to the low pH of their optimal activity. There are interesting differences at subsite S3' which may contribute to the specificity of human renin. Certain residues at the surface of the enzyme adjacent to the active site cleft are unique to renins and may play a role in recognition and binding of angiotensinogen.

Amino Acid Sequence↗
PubMed1995

Rotational and translational components of motion parallax: observers' sensitivity and implications for three-dimensional computer graphics.

The motion of objects during motion parallax can be decomposed into 2 observer-relative components: translation and rotation. The depth ratio of objects in the visual field is specified by the inverse ratio of their angular displacement (from translation) or equivalently by the inverse ratio of their rotations. Despite the equal mathematical status of these 2 information sources, it was predicted that observers would be far more sensitive to the translational than rotational component. Such a differential sensitivity is implicitly assumed by the computer graphics technique billboarding, in which 3-dimensional (3-D) objects are drawn as planar forms (i.e., billboards) maintained normal to the line of sight. In 3 experiments, observers were found to be consistently less sensitive to rotational anomalies. The implications of these findings for kinetic depth effect displays and billboarding techniques are discussed.

Adolescent↗
PubMed1989

Mapping the N6-region of the adenosine A1 receptor with computer graphics.

N6-substituted adenosine derivatives can be very potent and selective agonists at A1 receptors. The N6-region is usually described by a general model introduced by Kusachi et al. (J. Med. Chem. 1985, 28, 1636). Structure-activity relationships for this region have recently been reported from a detailed study by Daly et al. (Biochem. Pharmacol. 1986, 35, 2467). The N6-region of the A1 receptor was now investigated in further detail with the aid of computer graphics. A map of the N6-region was constructed on the basis of a selected set of data from Daly et al. This map allows Kusachi's model to be extended with two new subregions: a C subregion, accommodating cycloalkyl substituents and a B subregion, which is filled by bulky substituents, such as a norbornanyl moiety. Furthermore, three regions can be distinguished, where occupation leads to diminished receptor affinity, so-called forbidden areas. The extended model permits the contribution of each subregion to be determined quantitatively, allowing accurate prediction of affinities of compounds that were not used to construct the map.

Adenosine↗
PubMed1989

Chemical and computer graphics studies on the topography of the ribonuclease A active site cleft. A model of the enzyme-pentanucleotide substrate complex.

The affinity labelling of bovine pancreatic ribonuclease A with 6-chloropurine 5' ribonucleotide allowed us to postulate the existence of a new phosphate-binding subsite, P2, adjacent to the main purine-binding subsite. The study of this reaction in greater detail together with the study of a complex of the enzyme with the pentanucleotide pApUpApApG by means of model building and computer graphics indicate that at least five phosphate groups of the RNA molecule can interact with five positive regions of the enzyme. In each one a lysine residue is present: Lys-104, -66, -41, -7 and -37 appear sequentially in the 5'----3' direction. The distance between each lysine is 0.7-0.8 nm, the same distance as that found between the phosphate groups on the RNA molecule. The study also enabled many amino acid residues of the enzyme to be described as forming part of, or being near, the different binding subsites.

Binding Sites↗
PubMed1986

Gabexate mesylate inhibition of serine proteases: thermodynamic and computer-graphics analysis.

The inhibitory effect of gabexate mesylate, which is used therapeutically in the treatment of pancreatitis and disseminated intravascular coagulation, and as a regional anticoagulant agent for hemodialysis, has been measured on bovine factor Xa, bovine alpha-thrombin, human Lys77-plasmin, human urinary kallikrein, human urokinase, porcine pancreatic beta-kallikrein-B, and bovine beta-trypsin catalyzed hydrolysis of p-nitrophenyl esters of N-alpha-carbobenzoxy-L-arginine and N-alpha-carbobenzoxy-L-lysine. On the basis of enzyme:gabexate mesylate affinities, the serine proteases can be arranged as follows: human urinary kallikrein approximately porcine pancreatic beta-kallikrein-B much less than bovine beta-trypsin approximately bovine factor Xa approximately human Lys77-plasmin approximately human urokinase approximately bovine alpha-thrombin. The mode of binding of gabexate mesylate to the serine proteases conforms to the active-reactive site geometries observed in their complexes with natural and synthetic inhibitors. Differences in gabexate mesylate affinities for these proteases reflect structural differences at their primary specificity subsite, which have been investigated by comparative analysis of amino acid sequences and by computer-graphics techniques.

Animals↗