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Color-coded computer graphics representations of the electrostatic potentials of trypsin, trypsin-inhibitor, prealbumin and its thyroxine complex, fragments of double-helical DNA, and a netropsin--DNA complex illustrate the electrostatic and topographic complementarity in macromolecule-ligand interactions. This approach is powerful in revealing intermolecular specificity and shows promise of having predictive value in drug design.
Can anesthesia simulation be used successfully in training to improve the abilities of anesthesiologists and so result in decreased morbidity and mortality due to human error? In this review, computer simulation is examined as a training technique to reduce human error during the administration of anesthesia and as a method for studying how anesthetic accidents occur. Simulation is used successfully in other fields, such as aviation pilot training. A discussion of what defines human error will enable understanding of how computer simulation may be used to reduce it. Simulation of the anesthesia environment has been only recently developed. At this time there are at least two simulators which have been developed for the anesthesia environment. The two simulations are different in that one is strictly computer based. One reproduces the anesthesia monitors using computer graphics. The other, the Comprehensive Anesthesia Simulation Environment (CASE) simulation, attempts to reproduce the entire operating room. These two available simulators are discussed. It is presently unknown whether or not the use of simulation in anesthesia training improves the quality of that training. However, simulators necessary to answer this question are either available now or will be in the near future.
The article refers to the development of several computer programs designed to fulfil the role of teaching aids in relation to the technological aspects of dentistry. The hardware used was a BBC Master computer, this being a deliberate choice, to demonstrate that it is not necessary to have state of the art computer technology in order to produce very satisfactory computer aided technical instruction packages. All the programs were written in BBC Basic. Computer graphics illustrate and simplify dynamic concepts involved in dental technology. The programs having been developed in house proved to be inexpensive, in addition the program structure allows for easy upgrading. An extract from one of the procedures that serves to make up the modules is included to demonstrate the simplicity of the programming and the modular concept of program development.
Insulin from an elasmobranch, the spiny dogfish (Squalus acanthias) has been purified to near homogeneity by means of acid-ethanol extraction and salt precipitation. The amino acid sequences of the performic-acid-oxidised A and B chains have been determined and exhibit some unusual features. The A chain contains a total of 22 amino acids; only the insulin from coypu (a member of the Rodentia suborder, Hystricomorpha), has previously been reported to contain an extension past the A21 asparagine. The B10 histidine, which is involved in the formation of the insulin hexamers in higher vertebrates through the co-ordination of zinc, is present in this elasmobranch insulin. Several substitutions relative to bovine insulin occur in the proposed receptor binding region (A5Gln leads to His, B21Glu leads to Pro, B22Arg leads to Lys, B25Phe leads to Tyr). In spite of these substitutions, the maximal response in the rat epididymal fat cell assay is the same for bovine and dogfish insulins; the concentration required to produce the half-maximal response is, however, approximately threefold greater for dogfish insulin than that of bovine insulin. The use of interactive computer graphics model-building predicts that the dogfish insulin can attain a three-dimensional structure very similar to that of bovine insulin; circular dichroic spectra are presented which support the model-building studies.
A method used to produce composite drawings of superimposed areas of brain infarction is described. The method uses a microcomputer interfaced to a digitising pad and linear plotter. Areas of brain damage are drawn on standardised maps, digitised, manipulated in computer memory, and summated using computer graphics facilities. The composites show the position of brain damage in groups of patients as a contour map of the extent of lesion overlap. The method can be used to study neurological and neuropsychological deficits using CT-scan, or other imaging techniques. Deep and superficial lesions may be displayed equally well.
In the models suggested recently for antigenic peptides binding in the alpha 1, alpha 2 groove of MHC class I molecules, the orientation of the peptide has been shown uniquely as: the N----C vector of the peptide being parallel to the N----C vector of the alpha 1 helix of MHC. Here, we demonstrate that the reverse orientation of the peptide is equally probable. This hypothesis is supported by molecular modelling calculations and computer graphic analyses on a murine class I MHC molecule H-2Kd and its complexes with a restricted peptide RYLENGKETLQ. Analysis of the complementary interactions between the peptide residues and the amino acid side chains lining the MHC groove shows that the binding orientation of the peptide may be allele-specific and could depend on the sequence and structure of the antigenic epitope.
Intensity modulated radiation therapy (IMRT) inverse planning is usually performed by pre-selecting parameters such as beam modality, beam configuration and importance factors and then optimizing the fluence profiles or beamlet weights. In reality, the IMRT dose optimization problem may be ill-conditioned and there may not be a physical solution to account for the chosen parameters and constraints. Planner intervention is often required to conduct a multiple trial-and-error process where several parameters are sequentially varied until an acceptable compromise is achieved. The resulting solution reflects a balance between the conflicting requirements of the target and the sensitive structures. A major problem of the conventional inverse planning formalism is that there exists no effective mechanism for a planner to fine-tune the dose distribution on a local level or to differentially modify the dose-volume histograms (DVHs) of the involved structures. In this paper we introduce a new inverse planning scheme with voxel-dependent importance factors and demonstrate that it provides us with an effective link between the system parameters and the dosimetric behaviour at a local level. The planning proceeds in two steps. After a conventional trial-and-error inverse planning procedure is completed, we identify the dose interval at which the fractional volume on the DVH curve needs to be changed. The voxels that receive dose in the selected range are then located and their voxel-dependent importance factors are adjusted accordingly. The fine-tuning of the DVHs is iterative in nature and, using widely available computer graphic software tools, the process can be made graphically interactive. The new IMRT planning scheme is applied to two test cases and the results indicate that our control over the differential shapes of the DVHs of the involved structures is,greatly enhanced. Thus the technique may have significant practical implications in facilitating the IMRT treatment planning process.
Imaging technology has been the pacesetter of stereotactic technique since its introduction in clinical practice. Quite recently, the extraordinary quality of diagnostic neuroimages and the growing availability of computing power has widened the field of applications of stereotaxy suggesting, at the same time, substantial evolution of its instrumentation. Fusion of multimodal digital images, integration of morphological and functional data, and dimensional rendering techniques have become powerful 'navigational aids' for tissue sampling, functional procedures and image-guided endoscopic surgery. Radiosurgical dose planning systems integrated with image processing and computer graphics routines allow efficient interactive evaluation of tissue-dose volumes superimposition in brachytherapy and external beam focused irradiation. Volumetric guided open surgery, assisted by intraoperative acquisition of stereotactic echographic and microscopic images, allows satisfactory treatment of deep-seated cerebral lesions. Further improvement is to be expected with the implementation of the ongoing development of localizing solutions totally integrated with the microsurgical instrumentation.
The small cytokine monocyte chemoattractant protein-1 has structural similarity to the neutrophil chemoattractant interleukin-8, but each protein is specific in attracting its own target cell. To investigate the structural basis of this cell type specificity, we have developed an Escherichia coli expression system for the monocyte chemoattractant and mutagenized selected amino acid residues to ones found at the corresponding positions of interleukin-8. We find that a double mutation of tyrosine 28 and arginine 30 to leucine and valine, respectively, causes a drastic decrease in chemotactic activity toward monocytes with the appearance of a novel (interleukin-8-like) neutrophil chemotactic activity. Computer graphic analysis predicts that, with the double substitution, a putative receptor binding groove of the monocyte chemoattractant protein would become topographically similar to that of interleukin-8. We therefore postulate that one or both of these amino acid residues are part of the binding contact of these small cytokines and their receptors.
PURPOSE: To evaluate and compare by high-magnification digital photography the lens epithelial cell (LEC) response and capsule dynamics in vivo after implantation of a square-edged and a round-edged silicone intraocular lens (IOL) in a fellow-eye study. SETTING: Private practice and Royal Victoria Hospital, Barrie, and Soldiers' Memorial Hospital, Orillia, Ontario, Canada. METHODS: After phacoemulsification, a single surgeon implanted a square-edged silicone IOL (SoFlex SE, Bausch & Lomb) in 25 patients who had previously had a conventional round-edged version of the same IOL (SoFlex Li61U, Bausch & Lomb) implanted in their contralateral eye within a 6-week period. SoFlex SE IOL recipients were selected sequentially from those scheduled for surgery within a 3-day period. The IOLs were sequentially photographed 1 week and 1, 3, 6, and 9 months after surgery using magnification of at least x64 through a biomicroscope and a high-resolution digital camera with adapter. Images were transferred to a graphics computer and compared over time. RESULTS: At 1 week, both designs had evidence of LEC migration along the posterior capsule, with the highest cell density around the 6 o'clock position. At 1 month, both IOL designs showed 360 degrees of anterior and posterior capsule adhesion to the edge of the optic. At 1 month, however, migrating LECs encountered a "damming" effect at the square posterior edge but not at the round edge. A thin fibrotic ring began to form around the SoFlex SE edge at 2 months and was complete for 360 degrees at 3 months. At 9 months, there was no evidence of LEC migration beyond this ring. With round-edged IOLs, the fibrotic ring never fully formed and LEC migration continued posterior to the optic. There was a tight capsule shrink-wrap effect with the square-edged IOLs with the fibrotic ring, allowing minimal IOL movement between 1 month and 9 months. The round-edged IOLs tended to decenter and rotate. Anterior capsulorhexis contraction was greater at every time point with the round-edged IOLs than with the square-edged IOLs. CONCLUSION: Early contact inhibition of LECs by a square-edged IOL design and its effects were demonstrated in vivo with sequential, high-resolution digital photography and commercially available graphics software.
The uropygial gland is one of the epidermal derivatives in birds. In the beginning of the morphogenesis of the uropygial gland of the quail embryo, placode formation occurs: Epidermal basal cells remain cuboidal until day 7 of incubation. At day 8 they begin to elongate, become columnar, and develop placode-like structure at day 9. To examine the proliferative activity of the epidermal basal cells, we recorded positions of [3H]-thymidine-labelled nuclei in serial sections by autoradiography (ARG) using a digitizer and a microcomputer. The distribution pattern of labelled nuclei was reconstituted and redisplayed on the cathode ray tube (CRT) as two-dimensional computer graphics. Three-dimensional reconstitution of the same serial sections revealed that cuboidal basal cells in the presumptive uropygial placode became columnar. Unlike the feather and scale placodes, the uropygial placode possessed no resting period of DNA synthesis. The labelling index of the uropygial placode increased considerably compared with that of nonplacode epidermis. No dermal condensation was observed beneath the uropygial placode.
A new system was developed for filing all the endoscopic images generated in our hospital. The system is composed of an on-line network for analog images supplied from the endoscopy stations and stored on 300 mm optical disks, on the one hand, and an off-line PACS for digital images recorded on a 130 mm magneto-optical disk (MOD) at each endoscopy station, on the other. For close examination of the images digital images are displayed from the MOD on a high-resolution computer graphic monitor, and for quick review of a large number of images, analog images are retrieved from the 300-mm optical disks. This system has been in clinical use at our university hospital for the past year and has proven useful for education of endoscopy, for the quality control of the endoscopy practice, and for the management of the patients.
The addition of zinc to insulin solution leads to a long-acting insulin preparation because the zinc stabilizes the less soluble hexameric form of the hormone. It is clear from the crystal structure of dizinc insulin that there is a space at the center of the hexamer, between the two zinc atoms, that could accommodate a small organic molecule. It should thus be possible to design a structure that could further stabilize the insulin hexamer by binding at this site. Computer graphic techniques have been used to design several molecules capable of forming multiple bonds to the six histidine residues surrounding the site. Synthesis and testing of one of these compounds, benzene-1,4-disulfonic acid, show a significant increase in weight-average molecular weight of insulin in solution, and control experiments with related structures suggest that this effect is due to the proposed binding mechanism.
The aim of this study is to establish with the help of a computer a new type of Class V cavity that would ensure minimal marginal gap of restoration work using restorative resins. Comparison of computer graphics has shown that the ideal Class V cavity for restorative resins is cone-like with the apex or smaller base pointing towards the pulp and the walls slightly convex towards the free surface of the cavity. To prepare this sort of cavity new specular-type burrs are required.
We describe a computer program system for finding, quantitating, and matching the protein spots resolved on a two-dimensional electropherogram. The programs that locate and quantitate the incorporation of radioactivity into individual spots are totally automatic, as are the programs for matching protein spots between two exposures of the same gel. A semi-automatic method is used to match protein spots between different gels. This procedure is quite fast with the use of a computer-graphic display, which is also helpful in the editing process. A data base is set up and programs have been written to correlate matched protein spots from multi-gel experiments and to efficiently plot out quantitative data from sequences of equivalent spots from many gels or even many multi-gel experiments. The practical use of this system is discussed.
Computer assisted operation planning systems are gaining increasing recognition in the field of surgery. These systems offer new possibilities for preparing an intervention, with the goal of reducing the amount of expensive operating-room time required for the intervention. The safest and most effective surgical approach should always be selected, but it is often difficult to transfer the output of the planning system to the intra-operative situation so that the planning results can be considered during the actual intervention. At the Fraunhofer Institute for Computer Graphics (IGD) in Darmstadt and the Centre for Advanced Media Technology (CAMTech) in Singapore methods are being developed to bridge the gap between the external planning session and the intra-operative case: Augmented Reality (AR) techniques are used to overlay preoperative scanned image data, as well as results of the planning session, on the operation field.
Dihydrofolate reductase (DHFR) is an important therapeutic target for treatment of cancer and microbial disease. Its species specificity has resulted in the sequencing of a number of vertebrate and bacterial DHFRs, and the three-dimensional structure of isozymes from Escherichia coli, Lactobacillus casei, and chicken liver has been elucidated, in the presence of the coenzyme NADPH and of a number of inhibitors. This information has enabled scientists to try to design improved and more selective inhibitors, based on the known coordinates of the enzyme features. Simple use of computer graphics or wire models has resulted in the design of inhibitors with 50 times the activity of trimethoprim, an antibacterial DHFR inhibitor, by making use of an unused ionic binding site. However, in a number of instances this approach was completely unsuccessful because hydrophobic sites of interaction were preferred. More sophisticated techniques involve energy minimization of the small molecule-macromolecule interactions to optimize the geometry. In this paper I describe the use of a molecular mechanics program, AMBER, for predicting the geometry and relative energetics of binding. Very encouraging results have been obtained for a closely related series of compounds. Where differing entropic and solvent effects are involved, predictions may be poor. The use of super computers and molecular dynamics methods should increase this capability in the near future.
Using X-ray and NMR data relating to the conformation of the antihypertensive, angiotensin-converting enzyme inhibitor, captopril, and structure--activity relationships of analogues, it has been possible to postulate with the aid of computer graphics, the orientation of the three functions, the thiol, the terminal carboxyl and the carbonyl group which are involved in binding to the enzyme. Bicyclic mimetics of captopril, with related arrays of these functions, have been designed and synthesized. Compounds with the closest approximation to the array in captopril are the most active inhibitors of angiotensin converting enzyme, in vitro.