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At least 271 records · Page 15Linked to original sources
PubMed1976

Morphological correlates of synaptic transmission in lamprey spinal cord.

The dye Procion brown was used to identify in the light and electron microscope, synaptic contacts made between monosynaptically coupled neurons in the lamprey spinal cord whose synaptic interaction had been recorded. Synaptic contacts were made on different dendrites of the postsynaptic cell at different distances from the soma. Some of the contacts were made on dentritic spines and some on the smooth shaft of the dentrites. Serial sections through synaptic contacts made on dendritic processess of the postsynaptic cells were used for three-dimensional reconstruction of the synapses using computer graphics techniques. The computer reconstructions and detailed examination of the serial EM micrographs revealed the large proliferation of membrane involved in making these en passant synapses as well as the morphological changes due to stimulation of the presynaptic axon. These changes include depletion of synaptic vesicles and formation of complex vesicles and synaptic cisternae. Besides chemical synaptic contacts, four electrotonic contacts were located, confirming the mixed electrochemical synaptic response recorded from the postsynaptic cell. The mean quantum content was estimated and compared with the estimate of the available transmitter pool, assuming the quantal release hypothesis applies at these synapses. The total transmitter pool was estimated by counting all synaptic vesicles in all synaptic contacts. It was estimated that about 6% of the total transmitter pool is available for release at these synapses. This compares with less than 1% at the neuromuscular junction and about 20% at sympathetic synapses. These results support the hypothesis that synaptic vesicles may be recycled as described by Heuser and Reese (22) at the neuromuscular junction. Ongoing studies are investigating the effect on a variety of synaptic junctions to stimulation for different periods of time of presynaptic axons. The methods described in this study can also be used to test the models of synaptic interaction on dendritic trees described by Rall (39) and Jack and Redman (24).

Action Potentials↗
PubMed1989

[Development of a system for ultrasonic three-dimensional reconstruction of fetus].

We have developed a system for ultrasonic three-dimensional (3-D) fetus reconstruction using computers. Either a real-time linear array probe or a convex array probe of an ultrasonic scanner was mounted on a position sensor arm of a manual compound scanner in order to detect the position of the probe. A microcomputer was used to convert the position information to what could be recorded on a video tape as an image. This image was superimposed on the ultrasonic tomographic image simultaneously with a superimposer and recorded on a video tape. Fetuses in utero were scanned in seven cases. More than forty ultrasonic section image on the video tape were fed into a minicomputer. The shape of the fetus was displayed three-dimensionally by means of computer graphics. The computer-generated display produced a 3-D image of the fetus and showed the usefulness and accuracy of this system. Since it took only a few seconds for data collection by ultrasonic inspection, fetal movement did not adversely affect the results. Data input took about ten minutes for 40 slices, and 3-D reconstruction and display took about two minutes. The system made it possible to observe and record the 3-D image of the fetus in utero non-invasively and therefore is expected to make it much easier to obtain a 3-D picture of the fetus in utero.

Computer Systems↗
PubMed1985

Electrostatic interactions during electron transfer reactions between c-type cytochromes and flavodoxin.

The interaction of three different c-type cytochromes with flavodoxin has been studied by computer graphics modelling and computational methods. Flavodoxin and each cytochrome can make similar hypothetical electron transfer complexes that are characterized by nearly coplanar arrangement of the prosthetic groups, close intermolecular contacts at the protein-protein interface, and complementary intermolecular salt linkages. Computation of the electrostatic free energy of each complex showed that all were electrostatically stable. However, both the magnitude and behavior of the electrostatic stabilization as a function of solution ionic strength differed for the three cytochrome c-flavodoxin complexes. Variation in the computed electrostatic stabilization appears to reflect differences in the surface distribution of all charged groups in the complex, rather than differences localized at the site of intermolecular contact. The computed electrostatic association constants for the complexes and the measured kinetic rates of electron transfer in solution show a remarkable similarity in their ionic strength dependence. This correlation suggests electrostatic interactions influence electron transfer rates between protein molecules at the intermolecular association step. Comparative calculations for the three cytochrome c-flavodoxin complexes show that these ionic strength effects also involve all charged groups in both redox partners.

Clostridium↗
PubMed1986

The high-tech hand surgery interface.

We have reviewed a potpourri of high-tech advances of interest to the hand surgeon: electronically controlled prostheses, functional neuromuscular stimulation, computer graphics, data base computer programs, 3-D imaging, magnetic resonance imaging, and lasers--fields that point toward new directions in medicine, in general, and in our specialty, in particular, as we enter the twenty-first century. With clearer understanding of the basics, we can overcome the natural tendencies of negativism fostered by the complexities of the new ideas and proceed with optimism and curiosity.

Animals↗
PubMed1988

Photographic assessment of the antiplaque properties of sanguinarine and chlorhexidine.

The purpose of this study was to assess the effect of rinsing and topical application of sanguinarine on labial surface plaque accumulation, compared with topically applied water, and compared with rinsing with chlorhexidine, while refraining from all oral hygiene measures for 5 days. Color photographs of the disclosed plaque were taken at the end of each phase of treatment and blindly traced using an Apple II micro-computer graphic tablet digitizer. The plaque score for each tooth was calculated by dividing the computer reading of the labial plaque surface area by the total labial surface area of the tooth. Topically applied sanguinarine showed better plaque reduction than mouthrinsing with sanguinarine. There was a significant reduction in plaque accumulation after rinsing with chlorhexidine compared with topically applied sanguinarine, water, and mouthrinsing with sanguinarine. The results of this study indicate that chlorhexidine is a more superior antiplaque agent than sanguinarine. The use of an Apple II micro-computer graphic tablet digitizer provided a valuable method for accurate plaque assessments.

Administration, Topical↗
PubMed1989

Painting with pixels.

Two decades ago the subject of computer graphics was regarded as pure science fiction, more within the realms of Star Trek fantasy than of everyday use, but today it is difficult to avoid its influence. Television programmes abound with slick moving, twisting, distorting images, the printing media throws colourful shapes and forms off the page at you, and computer games explode noisily into our living rooms. In a very short space of time computer graphics have risen from being a toy of the affluent minority to a working tool of the cost-conscious majority. Even the most purist of artists have realized that in order to survive in an increasingly competitive world they must inevitably take the plunge into the world of electronic imagery.

Computer Graphics↗
PubMed1988

Solid perception mechanism by a shading pattern: spatial frequency components in a corrugated wave pattern.

Illumination allows solid object perception to be obtained and depicted by a shading pattern produced by lighting. The shading cue, as one of solid perception cues (Gibson 1979), was investigated in regard to a white corrugated wave shape, using computer graphic device: Tospix-2. The reason the corrugated wave was chosen, is that an alternately bright and dark pattern, produced by shading, can be conveniently analyzed into contained spatial frequencies. This paper reports spatial frequency properties contained in the shading pattern. The shading patterns, input into the computer graphic device, are analyzed by Fourier Transformation by the same device. After the filtration by various spatial frequency low and high pass filters, Inverse Fourier Transformation is carried out for the residual components. The result of the analysis indicates that the third through higher harmonics components are important in regard to presenting a solid reality feeling in solid perception. Sakata (1983) also reported that an edged pattern, superimposed onto a lower sinusoidal pattern, was important in solid perception. The third through higher harmonics components express the changing position of luminance on the pattern, and a slanted plane relating to the light direction. Detection of a solid shape, constructed with flat planes, is assumed to be on the bottom of the perfect curved solid perception mechanism. Apparent evidence for this assumption, in difficult visual conditions, is that a flat paneled solid is seen before the curved solid. This mechanism is explained by two spatial frequency neural network systems, assumed as having correspondence with higher spatial frequency detection and lower spatial frequency detection.

Computer Graphics↗
PubMed1988

Metabolic activation of carcinogens and toxic chemicals.

1. The spatial parameters and electronic structures of 100 exogenous and endogenous chemicals have been determined by computer graphics, from which their oxidative metabolism by the cytochrome P-448 (activation) or the other families of cytochromes P-450 (generally detoxication) have been predicted. 2. The spatial parameters of these chemicals primarily determine the family of cytochrome P-450 by which the chemicals are metabolized and the electronic structures primarily determine their ease of oxidative metabolism. 3. The role of oxidative metabolism of xenobiotics by the cytochromes P-448, and their binding to the cytosolic Ah receptor, are considered in relationship to the mechanisms of chemical toxicity, mutagenicity, carcinogenicity, and co-carcinogenicity. 4. The mechanisms of chemical toxicity and carcinogenesis are considered in respect of activation through cytochrome P-448-mediated, conformationally-hindered oxygenation to reactive intermediates which, unlike most cytochrome P-450-oxygenated metabolites, are not acceptable substrates for conjugation and detoxication and therefore react with essential intracellular macromolecules. 5. The computer graphic method of determining the molecular conformations and electronic structures of molecules is a rapid, scientifically-based procedure for evaluation of the potential toxicity, mutagenicity and carcinogenicity of chemicals.

Biotransformation↗
PubMed1988

Corneal modeling.

The Corneal Modeling System is presented as an integrated instrument system designed to give the corneal surgeon the capability of measuring and designing alterations of corneal shape that are comparable to the computer-aided design (CAD) capability used in aerospace design and other industries. The system provides realtime digital video image acquisition using a high-resolution, cylindrical photokeratoscope and scanning laser slit lamp. From these digitized images, the system's computer derives topographic and pachymetric information in sufficient density to produce a continuous mathematical function that represents both the front and the back surface of the cornea. The mathematical model may then be sampled in as many points as the clinical application requires, in the form of either computer graphics or a numerical data stream to control precision machinery to make contact lenses or tissue lenses. Representative computer graphics of normal and pathologic corneal conditions are presented.

Cornea↗
PubMed1992

Stereolithographic models for surgical planning: preliminary report.

Recent application of computer graphics, using standardized cephalometric analyses, have allowed the surgeon to visualize the predicted surgical outcome on the computer video monitor. Stereolithographic models constructed from digital image data (computed tomography and magnetic resonance) will allow the surgeon to view the external and internal anatomy prior to surgery. This article describes the development of such technology and reports its use in one case.

Adult↗
PubMed1989

Computer-assisted resonance assignments.

Investigation of NMR spectra by automatic procedures began only a few years ago. Many projects are still in progress and results have not been published; completed projects, with published results, have not yet found their final form. Other approaches might be incorporated. One example is the simulation of cross-peaks. These calculations explicitly take into account spectral parameters set for data acquisition and processing. They thus allow realistic simulations of expected peak patterns. Comparison of experimentally obtained peaks with a collection of simulated peaks helps characterize the spin system and determine coupling constants, especially in strongly coupled systems. Whereas automatic assignment procedures will require improvement for quite some time, it seems that useful and time-saving software tools complementing pure computer graphics will be available in the very near future.

Algorithms↗
PubMedDate not supplied

A medical workstation for the evaluation of alternative 3D radiotherapy treatment plans.

A medical workstation for the evaluation of alternative 3D radiotherapy plans is described. Our system can simultaneously apply qualitative as well as quantitative evaluation methods to as many as three 3D dose distributions. The user interface of the workstation has been designed with the demands of radiation oncologists in mind. The handling of the large amounts of 3D data (CT data, up to three 3D dose distributions, volumes of interest) is assisted by computer graphics.

Computer Graphics↗
PubMed1978

Computer-generated graphic models of the N2-substituted deoxyguanosine adducts of 2-acetylaminofluorene and benzo[a]pyrene and the O6-substituted deoxyguanosine adduct of 1-naphthylamine in the DNA double helix.

Computer models of three deoxyguanosine-carcinogen adducts in double-helical DNA are presented. The carcinogen moiety is rotated and the best fit within the double helix is evaluated. The 2-acetylaminofluorene (AAF) derivative, 3-(deoxyguanosin-N2-yl)-AAF, is found to be situated within the minor groove, has very little freedom of rotation and causes little helical distortion. The (+)-anti-benzo[a]-pyrene (BP)-diol epoxide-N2 adduct, 10beta-(deoxyguanosin-N2-yl)-7beta, 8alpha,9alpha-trihydroxy-7,8,9,10-tetrahydro-BP, has a similar fit with a greater degree of steric interaction, suggesting that this adduct could cause some local destabilization. The 1-naphthylamine (NA) derivative, N1-(deoxyguanosine-O6-yl)-1-NA, resides within the major groove, does not perturb the helix and has considerable freedom of movement.

1-Naphthylamine↗
PubMed1983

The image-combining computer microscope--an interactive instrument for morphometry of the nervous system.

The image-combining computer microscope is a new configuration of light microscope and computer graphics instrumentation which provides remarkable morphometric capabilities over a wide range of applications. The key component is the well known camera lucida, an image-combining device that is used to superimpose the computer graphics image upon the microscope's image of the object under study. Illumination need not be limited to the bright-field variety. The image superposition permits the investigator to study the object and acquire data from it while always looking through the microscope oculars. A computer controlled stepping motor driven stage is integrated with translations of the graphics image to permit image superposition and data acquisition at maximum visual magnification over the full expanse of a 25 X 25 mm tissue section. The investigator controls the system by means of a graphics tablet and a "Menu" area visible to him in the microscope's field of view. Spatial data in all 3 dimensions can be acquired easily since the z-axis is also stepping motor controlled. EM micrograph transparencies can be studied similarly. Stereological applications are possible by superimposing test grids upon the image. The system is self-contained and carries out data analysis programs written in C or Basic. Simplicity of operation has been emphasized throughout.

Animals↗
PubMed1983

Three-dimensional surface descriptions from sensed data.

Computer graphics are being employed in several fields to display images of objects that have never been seen by human eyes. The information collected by CAT scanners, ultrasound sensing systems, and other automatic measuring devices is typically not in a displayable form. This paper surveys several techniques for constructing three-dimensional descriptions of these sensed objects in forms suitable for manipulation by computer graphics display programs.

Computers↗