Robert S. Ledley’s research while affiliated with Georgetown University and other places

First Page of the Article

It is pointed out that even though the red-green-blue (RGB) color system is used by TV cameras and monitors, the perceptions of human observers are better described by other color systems which correspond more directly to the subjective human sensation of color. One of the simplest and most widely used of these alternative systems is the hue, saturation, intensity (HSI) color system. The authors describe the detailed derivation of the HSI system in terms of the RGB system and discuss how pattern recognition techniques and concepts originally developed for black-and-white images can be applied to color images in the HSI system

A tomographic scanner for scanning an area of interest is described, comprising: a source of penetrating radiation; means for moving the source of penetrating radiation in an arc, a detector array comprising an endless chain of detectors; and means for moving the detector array in a second arc, the first and second arcs being sized and shaped and the first and second means being adapted to cause the source and the detector array to move at velocities such that a plurality of parallel beam paths may be propagated from the source through the area to the detector array in each of a plurality of angular positions of the source and the detector array.

V/SCAN™ is a computerized video scanning instrument incorporating new concepts in the analysis of microscopic images, having applications to the detailed analysis and construction of chromosome karyotypes. Its primary use is for research applications in the areas of automating hybrid cell karyotyping where 150 or more chromosomes may appear, of automating prometaphase banding pattern analysis where complex banding patterns occur, and of automating fluorescence stains of chromosomal probes which appear on interphase cells. The instrument also includes the capability of very high-speed locating of chromosome spreads and other objects, and of large-scale image archiving and retrieval.

An abstract is not available.

We have designed and constructed a computer-controlled, fully automated system for Southern-type nucleic acid hybridization analysis. Restriction enzyme digests of DNA are placed into sample wells of the gel contained on a nine-fingered plastic frame. The 32-labeled probe is loaded into the hybridization chamber. Instructions for all the subsequent steps in the fully automated process are specified by the operator's answers to questions which appear on the computer screen at the start of the experiment. The system performs horizontal submarine electrophoresis. An adjustable endpoint detector concludes electrophoresis. Automatic voltage/temperature feedback control maintains maximum allowable voltage while keeping the temperature constant. Following electrophoresis a robot arm moves the gel frame from station to station. The system then affixes the separated fragments to a solid phase matrix, denatures, neutralizes, hybridizes, washes, dries and detects the 32 P according to the specifications preprogrammed by the operator. The results, printed out by the computer, give a plot of radioactivity versus distance from the origin for each of the nine simultaneous hybridizations.

Development of techniques for silver staining of proteins separated by polyacrylamide gel electrophoresis has increased experimental detection limits. However, the precise basis for the reaction between silver and polypeptides is still unclear and, depending upon the choice of silver reagent, may even differ. We compared protein stain intensity with silver diamine (ammoniacal silver) and silver nitrate reagents based on amino acid composition by determining the protein amount required to generate an arbitrary staining intensity and then calculating moles of each amino acid present in some representative proteins. We compared these values for each amino acid, taken singly, as well as for combinations of two and more. In no case could staining be attributed entirely to specific or classes of amino acids, thus supporting the argument that an inherent difference exists between primary reactive centers for the two staining reagents.

We have devised methodology which allows for the rapid mechanical fixation of proteins in polyacrylamide slab gels. Proteins so fixed remain in the gel even after four days of soaking. The potential utility of this approach is discussed.

We have developed a computerized system for electroretinographic (ERG) testing and analysis. This system is designed both for routine clinical use and for research applications, and has been incorporated into an extant mini-computer controlled device, the CENOG (Computerized Electro Neuro Ophthalmograph), previously developed by our lab for the automated neuro-ophthalmological testing and analysis of eye movements and visual evoked responses. A brief description of this ERG system will be given, and some preliminary results presented.