Biomedical subjects

J M Chassery

Publications and source records attributed to J M Chassery.

10 recordsLinked to original sources

PubMed2000

Nonrandom distribution of metaphase AgNOR staining patterns on human acrocentric chromosomes.

The metaphase nucleolar organizer regions (NORs) contain ribosomal genes associated with proteins such as upstream binding factor (UBF) and RNA polymerase I (RPI). These genes are clustered in 10 loci of the human acrocentric chromosomes (13, 14, 15, 21, and 22). Some NOR-associated proteins, termed AgNOR proteins, can be specifically stained by silver. In this study we took advantage of technical advances in digital imaging, image restoration techniques, and factorial correspondence analysis (FCA) to study the different AgNOR staining patterns of metaphase chromosomes in human lymphocytes. Three predominant patterns could be distinguished: pair (47%), stick-like (28%), and unstained (18%) structures. By studying the frequency of occurrence of each pattern on different chromosomes, two groups could be defined. Chromosomes 13, 14, and 21 carried predominantly pair or stick-like AgNOR structures, whereas chromosomes 15 and 22 mainly carried pair AgNOR structures or remained unstained. We suggest that the different AgNOR shapes reflect both the number of ribosomal genes carried by each chromosome and the differential recruitment of active ribosomal genes in each NOR cluster. This is the first study showing a nonrandom distribution of AgNOR shape among acrocentric chromosomes.

Chromosomes, Human↗

PubMed1999

3-D organization of ribosomal transcription units after DRB inhibition of RNA polymerase II transcription.

In each bead of the nucleolar necklace, using adenosine analog DRB-treated PtK1 cells, we investigated the three components of rDNA transcription, i.e. the gene, transcription factor UBF and transcripts. In situ hybridization revealed the unraveling and 3-D dispersion of most of the rDNA coding sequences within the nucleus. The signals were small, of similar intensity and tandemly organized in the necklace. This observation is compatible with the fact that they might correspond to single gene units. Active transcription was visualized in these units, demonstrating that they were active functional units. Transcript labeling was not similar for each unit, contrary to UBF labeling. UBF and rRNA transcripts were only partially colocalized, as demonstrated by 3-D image analysis and quantification. As visualized by electron microscopy, the necklace was composed of a small fibrillar center partially surrounded by a dense fibrillar component. The 3-D arrangement of this individual unit in the necklace, investigated both by confocal and electron microscopy in the same cells, showed that the individual beads were linked by a dense fibrillar component. The reversibility of this organization after removal of DRB indicated that the beads in the necklace are certainly the elementary functional domain of the nucleolus. In addition, these results lead us to suggest that the organization of a functional domain, presumably corresponding to a single gene, can be studied by in situ approaches.

Animals↗

PubMed1995

Application of confocal laser microscopy and three-dimensional Voronoi diagrams for volume and surface estimates of interphase chromosomes.

This study demonstrates the use of Voronoi tessellation procedures to obtain quantitative morphological data for chromosome territories in the cell nucleus. As a model system, chromosomes 7 and X were visualized in human female amniotic fluid cell nuclei by chromosomal in situ suppression hybridization with chromosome-specific composite probes. Light optical serial sections of 18 nuclei were obtained with a confocal scanning laser fluorescence microscope. A three-dimensional (3-D) tessellation of the image volumes defined by the stack of serial sections was then performed. For this purpose a Voronoi diagram, which consists of convex polyhedra structured in a graph environment, was built for each nucleus. The chromosome territories were extracted by applying the Delaunay graph, the dual of the Voronoi diagram, which describes the neighbourhood in the Voronoi diagram. The chromosome territories were then described by three morphological parameters, i.e. volume, surface area and a roundness factor (shape factor). The complete evaluation of a nucleus, including the calculation of the Voronoi diagram, 3-D visualization of extracted territories using computer graphic methods and parameterization was carried out on a Silicon Graphics workstation and was generally completed within 5 min. The geometric information obtained by this procedure revealed that both X- and 7-chromosome territories were similar in volume. Roundness factors indicated a pronounced variability in interphase shape for both pairs of chromosomes. Surface estimates showed a significant difference between the two X-territories but not between chromosome 7-territories.

Amniotic Fluid↗

PubMed1994

A new approach to man-machine communication for computerized microscopy.

HOME is a new computerized microscope designed to assist pathologists and cytotechnicians in routine examinations. The HOME workstation is composed of a standard light microscope fitted with objective and stage encoders, and a built-in high resolution computer display which superimposes dialog, drawing, and messages onto the optical microscope image. The software runs under Windows 3.x and provides interactive facilities such as accurate localization and relocation of zones of interest, morphometric measurements, patient data access, and quality control processes.

Cell Biology↗

PubMed1992

HOME: highly optimized microscope environment.

The Highly Optimized Microscope Environment (HOME) is a computerized microscope designed to assist pathologists and cytotechnicians in clinical routine tasks. The prototype system consists of a IBM-PC compatible computer and a light microscope in which a built-in high-resolution computer display image is superimposed on the optical image of the specimen. Also, a manually operated encoding stage and objective turret encoder are used to provide continuous monitoring of the stage coordinates and microscope magnification to the computer. This allows any position on a slide to be uniquely defined and makes it possible to measure interactively lengths and areas larger than the size of the microscope field. Software, written in the C language and operating under the MS-DOS/MS-Windows environment, is controlled by means of a mouse-driven cursor moving over menu light-buttons displayed on the microscope image. The HOME microscope workstation is potentially useful in a wide range of applications such as i) tagging information on particular cells and tissue structures that can thus be accurately located and relocated, ii) performing morphometric measurement, differential counting, and stereological assessment of biological specimens, and iii) training and educating laboratory personnel. Finally, HOME will offer in the near future a user-friendly interface for automatic image processing of cells and tissue entities in interactively selected specimen areas.

Animals↗

PubMed1986

An iterative region-growing process for cell image segmentation based on local color similarity and global shape criteria.

An image segmentation process was derived from an image model that assumed that cell images represent objects having characteristic relationships, limited shape properties and definite local color features. These assumptions allowed the design of a region-growing process in which the color features were used to iteratively aggregate image points in alternation with a test of the convexity of the aggregate obtained. The combination of both local and global criteria allowed the self-adaptation of the algorithm to segmentation difficulties and led to a self-assessment of the adequacy of the final segmentation result. The quality of the segmentation was evaluated by visual control of the match between cell images and the corresponding segmentation masks proposed by the algorithm. A comparison between this region-growing process and the conventional gray-level thresholding is illustrated. A field test involving 700 bone marrow cells, randomly selected from May-Grünwald-Giemsa-stained smears, allowed the evaluation of the efficiency, effectiveness and confidence of the algorithm: 96% of the cells were evaluated as correctly segmented by the algorithm's self-assessment of adequacy, with a 98% confidence. The principles of the other major segmentation algorithms are also reviewed.

Biometry↗

PubMed1979

[SAMBA : a cytophotometer coupled to a computer for the purpose of the automatic study of cell kinetics and the recognition of cell types].

The system SAMBA has been designed for automatic analysis of biological images, at the cellular or subcellular level. The examination is performed at the maximum resolution power of the microscope. It enables to discriminate by means of a pool of morphological and densitometrical parameters, between cells in the different phases of the cell cycle, or between cells belonging to various types in heterogeneous populations. Other recognition programs are at present beeing in progress, in order to promote the use of SAMBA in other fields of fundamental research and clinical application. Owing to the minicomputer now in use, SAMBA is an autonomous system, capable of beeing routinely used in diagnostic centers.

Bone Marrow Cells↗

PubMed1978

[Automatic recognition of different phases of the cell cycle and automatic count of the cells by means of a computer coupled to a cytophotometer].

Existing relationships between cell cycle phases and chromatin scattering within the nucleus led us to state more precisely our first alogrithm for cell cycle phases recognition. These refundments give evidence for the accuracy and the improving performance of the densitometric and morphologic analysis system used in this study: the "Samba".

Animals↗

PubMed1977

[A new image-processing system designed for densitometry and pattern analysis of microscopic specimen. Application to the automated recognition and counting of cells in the various phases of the mitotic cycle (author's transl)].

A new image analysing system, designed for microphotometric measurement and pattern recognition has been applied in the discrimination of cells from the various phases of the mitotic cycle. The data acquisition procedure is controlled by a programmable electronic unit and involves the combination of the shifting of the microscope moving stages and the scanning of the successive fields by a mechanical device. The data processing is achieved by a computer. The preliminary results we obtained have shown that such a system allows the automatic recognition and counting of the M, G1, S and G2 cells as also the G0 resting cells. The most useful parameters of the cell proliferation kinetics are thus obtained from a single specimen of a cell population.

Cell Count↗

PubMedDate not supplied

Segmentation and measurement based on 3D Voronoi diagram: application to confocal microscopy.

Computational geometry provides many solutions to imaging problems, especially for three-dimensional (3D) image compression, segmentation, and measurement. We present here a new method to partition volume data by Voronoi polyhedra structured in a graph environment. A dynamic construction of the 3D Voronoi diagram is proposed, using image information interactively. The process has been applied to segment and quantitate 3D biological data acquired with a confocal laser scanning microscope (CLSM). The discrete volume acquired represents a large mass of data and can be reduced with this particular method, before measurement (processing time) or archiving (memory space). Furthermore, the structure data is a powerful tool to rapidly compute parameters that are characteristic of the volume data.

Algorithms↗