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Biomedical subjects

J J Capowski

Publications and source records attributed to J J Capowski.

13 recordsLinked to original sources
PubMed1995

A numeric index based on spatial frequency for the tortuosity of retinal vessels and its application to plus disease in retinopathy of prematurity.

BACKGROUND: In retinopathy of prematurity (ROP), tortuosity of vessels near the posterior pole of the fundus is an important clinical sign, yet clinicians have difficulty estimating how tortuous the vessels are. METHODS: The authors have devised an objective, numeric index of retinal blood vessel tortuosity that is especially sensitive to the structural changes in vessels that occur in ROP, but it is not particularly sensitive to non-ROP changes. Computer software is used to calculate the index from fundus images; the quality of these images is typical of photographs or video-cassette frames that the authors record in the premature nursery. RESULTS: The index reliably segregates tortuous vessels from nontortuous ones and separates eyes that reach ROP treatment threshold from eyes that do not. CONCLUSIONS: The index forms an objective measure of the ROP disease state. Its calculation requires only segments of vessels and thus, is potentially adaptable to imaging systems that automatically extract vessel portions from fundus images.

Fundus Oculi↗
PubMed1986

Morphology of HRP-injected spinocervical tract neurons: effect of dorsal rhizotomy.

Twenty-five physiologically identified spinocervical tract (SCT) neurons in the sixth lumbar segment of the cat were filled with HRP by intracellular injection. All were reconstructed from sagittal sections using the camera lucida, and a subset (n = 18) was also reconstructed using a computer reconstruction system. Thirteen cells were in intact preparations, nine were in spared root preparations (L5, L6, S1, S2 cut; L7 spared), and three were in preparations with L5 through S2 cut. Analysis of the dendritic tree of these neurons revealed little change in gross morphology after partial deafferentation despite increased proportions sensitive to nociceptive input (Sedivec et al., 1983). The dendrites still largely respected the lamina II-III border, and relatively few dendrites were directed ventrally from the cell body, although the ratio of ventral to dorsal dendrites was greater than normal. The major change was an increase in surface area and volume caused by changes in diameter (but not length) of the dendrites. Larger-than-usual maximum branch order of individual dendritic trees of some cells was also observed after chronic deafferentation. Thus, SCT cells in deafferented segments do not undergo atrophy, but show, rather, limited signs of growth and the possibility of dendritic reorganization. We have also computed correlations between different parameters of these cells (cell body size, number and size of primary dendrites, total area and length of individual dendrites) and have found that, as in motoneurons, diameter of the primary dendrite measured 30 micron from the soma is significantly correlated with total dendritic surface area and length. SCT neurons tend to have more dendrites than spinal alpha-motoneurons, but total surface area is smaller for a given diameter of a proximal dendrite.

Animals↗
PubMed1985

A simple motor controller for computer-assisted microscopy.

A very simple controller has been built which allows a laboratory computer to drive a stepping motor stage and focus axis motor of a research light microscope. Its cost is minimal; negligible in comparison to the controllers offered by the microscope manufactures. A subroutine has been written to enable the programmer to control the microscope easily. The controller has been installed in the UNC neuron reconstruction system and functions very well.

Computers↗
PubMed1985

A simple hidden line removal algorithm for serial section reconstruction.

A simple and efficient program for removing the hidden lines from the computer graphics display of a three-dimensional structure has been developed. The algorithm is optimized for serial section reconstruction, that is, for three-dimensional structures composed of a series of stacked planar outlines. Using the algorithm, an anatomist can generate a realistic static picture of a reasonably complex reconstruction in about 20 s on a small laboratory computer.

Anatomy↗
PubMed1984

Automated neuron tracing using the Marr-Hildreth zerocrossing technique.

Semiautomatic systems designed to trace neurons in three dimensions are slow and require many hours of work on the part of a human operator to trace even a single neuron completely. Attempts at constructing fully automatic systems have met with only limited success because of the dual problems of slow speed of travel down a fiber and time/space limitations on the intelligence of the program guiding the decision making. A novel approach to automatic tracing has been designed and initial implementation experiments have been carried out. Consideration of the five theoretical issues of edge detection, decision making, accuracy, robustness, and speed has led to the use of the Marr- Hildreth preprocessing filter and to a simple fiber-following algorithm that directly utilizes the output of that filter. Experimental results are encouraging and suggest that the approach is worthy of continued research.

Animals↗
PubMed1983

A system for the three-dimensional reconstruction of biological structures.

A system of programs for building three-dimensional models of biological structures was developed. Outlines of features such as cells, tissue edges, and neuron pathways are traced into a computer from tissue sections mounted on a light microscope or projected onto a data tablet. The three-dimensional models are built from a series of the two-dimensional outlines. The cathode ray tube displays of the three-dimensional models can be smoothly rotated for study, and a static display with hidden lines removed can be produced. Volume and surface area calculations for the models can be done. It is possible to obtain further anatomical data by counting and mapping silver grains in autoradiographs of tissue sections. The density of grains reveals pathways and boundaries in the structure. Displays of silver grain maps and counts can be superimposed on displays of the model of the structure.

Animals↗
PubMed1983

An automatic neuron reconstruction system.

Most contemporary neuron tracing systems are semi-automatic; that is, an operator follows neuron branches in a microscope or on a data tablet and instructs a computer when to record a spatial sample. A list of such samples is then used to generate a display of the neuron and to summarize statistically its structure. The tracing is tedious, and the operator must make subjective decisions about point types, thus biasing the results. A fully automatic system in which the computer views the image through a television digitizing system has been constructed. The computer follows the fibers and recognizes branchpoints and fiber endings. The coordinates, types of points, and fiber diameters are recorded in computer memory. An operator is required only to start the tracing of a fiber and to help the computer when it becomes "confused". The results are mixed. The computer can follow fibers quite successfully and can determine branches and endings with some success, but the procedure is an order of magnitude more slow than that of a skilled operator using a well-designed semi-automatic system.

Computers↗
PubMed1982

Neuron reconstruction using a Quantimet image analyzing computer system.

A PDP-11/34 laboratory computer, a Quantimet image analyzer, and a research light microscope with motorized X, Y stage and focus axis are used for "semi-automatic" neuron reconstruction. The operator examines each neuron tree through the microscope eyepieces, commands the Quantimet system to move the stage and focus the optics, and when a point along the neuron process is in focus under a cross-hairs, commands the PDP-11 computer to record the point's spatial coordinate. A list of such coordinates when stored in the PDP-11 forms a mathematical reconstruction of the neuron. Because the Quantimet system was not designed for this type of work, there may arise some problems when using it. Incremental microscope stage movements are difficult to produce; its display does not accurately depict neurons; its software does not facilitate the simple commands to the microscope motors required in neuron reconstruction. Despite these constraints, a neuron tracing system has been written which traces and statistically analyzes neurons.

Animals↗
PubMed1977

The terminal arborization pattern of primary afferent fibers in the substantia gelatinosa of the spinal cord in the cat.

The spinal cords of adult cats were impregnated using the Golgi-Kopsch technique and cut in the sagittal plane. Richly arborizing axon-trees were found in the substantia gelatinosa (lamina II of Rexed). Axon arborizations, characterized by a long rostro-caudal course, a single-stem fiber, multiple-arborizing side branches and large terminal and en passant boutons, were subjected to a semi-quantitative and later to a computer-aided analysis. These arborizations, presumably of primary afferent origin (Réthelyi, 1977), are arranged in narrow sheets. The sheets of the individual arborizations are tilted with respect to the sagittal plane (the dorsal edge of the sheet having a more lateral position than the ventral edge), and tilted with respect to each other's plane, but they are rigorously oriented in the rostro-caudal direction. The average thickness of the sheets encompassing the terminal and en passant bulbs of these arborizations is 16.65 micrometer (S.D. = 2.86; n = 10). Occasionally, the side branches and terminal bulbs of a single stem fiber arborize into two separate sheets. These anatomical results suggest that the activity of the peripheral fibers spreads in long and narrow neuropil fields in the substantia gelatinosa. This pattern suggests a fine scale somatotopic arrangement.

Afferent Pathways↗
PubMedDate not supplied

Observer sensitivity to retinal vessel diameter and tortuosity in retinopathy of prematurity: a model system.

BACKGROUND: Abnormally increased diameter and tortuosity of retinal blood vessels in the posterior pole, or "plus disease," is recognized as a powerful predictor of poor outcome in eyes with retinopathy of prematurity (ROP). Although the diagnosis of plus disease depends upon the examiner's ability to examine retinal blood vessels, the ability of the human observer to identify changes in retinal blood vessel diameter and tortuosity accurately has not been studied. METHODS: Using computer-aided analysis of fundus photographs from eyes with a wide range of ROP severity, we generated tracings of posterior pole blood vessels which varied by quintiles of mean vessel diameter and tortuosity. Subjects (23 naive and 12 expert observers) ranked groups of tracings in order of increasing mean vessel diameter and tortuosity. These ranking tests were performed on tracings derived from the same fundus and tracings derived from distinct fundi. In a similar fashion, subjects also compared one designated standard fundus tracing with 25 distinct fundus tracings. RESULTS: Vessel diameter was assessed correctly more often than vessel tortuosity, both among similar (> 99% vs 92% of the time, respectively, P < 0.001), or among distinct (88% vs 78% of the time, respectively, P < 0.001) fundus images. The mean vessel diameter and tortuosity of 25 distinct fundus images were correctly ranked versus a standard image in 89% of attempts. Assessments of increments in vessel diameter and tortuosity were independent. Naive and expert subjects performed indistinguishably on all tests. CONCLUSIONS: Intelligent human observers have considerable ability to discern clinically relevant increments in blood vessel diameter and tortuosity. This ability may facilitate standardization in the diagnosis of plus disease in ROP.

Computer Simulation↗