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Biomedical subjects

N Bonnet

Publications and source records attributed to N Bonnet.

At least 19 recordsLinked to original sources
PubMed1992

Semiautomatic quantification of silver-stained nucleolar organizer regions in tissue sections and cellular smears.

Silver staining of nucleoli reveals argyrophilic proteins associated with nucleolar organizer region (Ag-NOR) proteins. Argyrophilic components appear as dots about 1 micron in diameter dispersed throughout the nucleolus (Ag-NOR dots). The count of Ag-NOR dots is a useful index for improving the cancer diagnosis and determination of prognosis. Here we describe software developed on a medium-cost image analyzer in order to evaluate the mean area of NORs and their number relative to an internal reference, the number and areas of clusters of NORs and the area of the nucleus. Statistical analysis of the data was performed during counting. The first application concerned counting NOR dots during mitosis in cell imprints; those counts were 2.3, 15.3 and 55.56 for the metaphase, telophase and interphase, respectively (relative to unitary dots of metaphase cells). In the second application we demonstrated a significant difference in NOR numbers between two groups of prostatic cancers with good and poor prognoses (6.05 +/- 2.79 SD and 7.96 +/- 3.01, respectively; with Student's t test, = 1.999; P = .05).

Animals↗
PubMed1991

Semi-automatic quantitation of dense markers in cytochemistry.

The quantitation of electron dense labelling is very tedious when it is done "by hand". Accordingly we developed software allowing, at electron microscopic level, a semi-automatic counting of dense markers in biological specimens. It includes the digitization of images and extraction of dense particles from the grey level of the background. The definition of the areas of interest was carried out by the observer but all quantitative calculations were done automatically. This method was applied to different biological materials (phospholipid and lysozyme labelling in secretory granules of human submucosal bronchial gland cells). The results obtained by this semi-automatic procedure were in good agreement with those obtained by manual counting of colloidal gold labelling (r = 0.97).

Automation↗
PubMed1991

Quantitative immunolocalization of four immunodominant antigens of Toxoplasma gondii.

Ultrastructural localization of four immunodominant antigens of Toxoplasma gondii was investigated quantitatively on thin sections and replicas by an immunogold technique using four monoclonal antibodies (Mab). On immunoblot Mab IV47, GII9, II38 and IE10 identified proteins of 28, 30, 45 and 66-70 kDa, respectively. Use of digital image analyzer and a semi-automatic procedure developed by us, the patterns of label distribution were compared in three cell structures: cell surface, submembrane area and rhoptries. On the whole cell surface, protein P28 and P30 were 2.5 and 4 times more abundant than P66-70 respectively. The protein P28 was essentially concentrated in the submembrane area with a labeling of 195.4 +/- 46.7 gold particles/microns 2 that follows a decreasing gradient from this area to the cell centre. In the rhoptries, all four antigens were detected, P45 and P66-70 being major with a labeling of 97.1 +/- 31.1 gold particles/microns 2 and 155.1 +/- 39.3 gold particles/microns 2 respectively. The results support the hypothesis that rhoptries are the essential site for antigen storage.

Animals↗
PubMed1991

Digital three-dimensional visualization of cellular organelles studied by medium- and high-voltage electron microscopy.

Tilted thick sections (one-half to several micrometers) of biological specimens observed with medium- to high-voltage electron microscopes are extremely useful for the study of the three-dimensional (3-D) structure of organelles. If high resolution in 3-D visualization and 3-D reconstruction is needed, many images corresponding to various angles of rotation and tilt must be recorded. This necessitates very time-consuming work--including eventual photographic processing--before good positioning of the object is defined. We have developed software which permits very rapid and precise determination of the tilt-axis, the registration of tilted views, 3-D measurements and 3-D visualization. Images are digitized either from negative films or directly with a camera fitted to the microscope. The application of the software is performed in minutes and allows for a rapid check of the quality of the tilt-series and of the features of interest of the object. Application of the software to the study of the 3-D structure of active components of the nucleolus stained with silver is shown.

Cell Nucleolus↗
PubMed1991

Identification of phospholipids in secretory granules of human submucosal gland respiratory cells.

Although it has been shown that tracheal epithelial cells in culture synthesize and secrete phospholipids, no direct evidence for in situ phospholipid storage in human respiratory secretory epithelial cells has been demonstrated. We used a high-resolution cytochemical enzyme-gold technique to identify and precisely localize phospholipids in human submucosal gland secretory cells. In addition, lysozyme, a specific serous cell marker, was identified using the biotinstreptavidin gold technique with lysozyme antiserum. This double labeling of phospholipids and lysozyme was performed using gold particles of diameters 15 nm and 5 nm, respectively. Quantitation of phospholipid labeling was performed on an image analyzer. Phospholipids were identified in serous granules (8.87 +/- 2.21 gold particles/microns 2) in a significantly (p less than 0.05) higher density than in mucous granules (5.57 +/- 3.07 gold particles/microns 2). These results support the hypothesis that submucosal human airway serous and mucous secretory cells produce phospholipids which may be secreted in the airway lumen.

Bronchoalveolar Lavage Fluid↗
PubMed1990

EELS elemental mapping with unconventional methods. I. Theoretical basis: image analysis with multivariate statistics and entropy concepts.

Electron energy loss filtered images recorded within a transmission analytical electron microscope are now widely used for the mapping of the elemental distribution of a given atomic species in a specimen prepared as a thin film. Such an image processing may produce both valuable results and artifacts if a careful inspection of all the hypotheses needed by the calculation is not carried out. This paper presents some general statistical methods for a contrast information analysis of a noisy image data set. After a brief introduction of different concepts such as contrast, variance, information and entropy, two unconventional approaches for image analysis are explained: the relative entropy computed with respect to a pure random and signal-free image and the factorial analysis of correspondence (a branch of multivariate statistics). In the companion article (part II), these concepts are applied to real experiments and the results compared with those obtained with a conventional method. Although electron energy loss spectroscopy is the only technique considered here, these methods for image analysis can be applied to a wide variety of noisy data sets (spectra, images, ...) recorded from various sources (electrons, photons, ...).

Algorithms↗
PubMed1990

Stress at work and mental health status among female hospital workers.

Relations between working conditions and mental health status of female hospital workers were studied in a sample of 1505 women: 43% were nurses, 32% auxiliaries, and 7% ancillary staff; 13% were other qualified health care staff, mainly head nurses; 5% had occupations other than direct health care; 63% worked on the morning, 20% on the afternoon, and 17% on the night shift. Data were collected at the annual routine medical visit by the occupational health practitioner, using self administered questionnaires and clinical assessments. Five health indicators were considered: a high score to the general health questionnaire (GHQ); fatigue; sleep impairment; use of antidepressants, sleeping pills, or sedatives; and diagnosis of psychiatric morbidity at clinical assessment. Four indices of stress at work were defined: job stress, mental load, insufficiency in internal training and discussion, and strain caused by schedule. The analysis was conducted by multiple logistic regression, controlling for type of occupation, shift, number of years of work in hospital, daily travel time to work, age, marital status, number of children, and wish to move house. Sleep impairment was mostly linked to shift and strain due to schedule. For all other indicators of mental health impairment and especially high GHQ scores, the adjusted odds ratios increased significantly with the levels of job stress, mental load, and strain due to schedule. This evidence of association between work involving an excessive cumulation of stress factors and mental wellbeing should be considered in interventions aimed at improving the working conditions of hospital workers.

Adult↗
PubMed1989

Which image parameter(s) for the automation of the electron microscope?

Experiments on automating the transmission electron microscope rely on the search for minimum variance. This image parameter gives satisfactory results for automatic focusing, astigmatism correction, and beam alignment. We investigate here the different image descriptors that might also be used; we conclude that texture parameters, which are directional, would be better candidates correcting astigmatism and beam tilt.

Image Enhancement↗
PubMed1989

[Evolution of the primary successes of percutaneous aortic valvuloplasty].

Between November 1985 and August 1988, we performed 89 percutaneous aortic valvuloplasties. Sixty-two of these were considered a primary success on the basis of two main criteria: stage I or II on discharge and greater than 50 p. 100 increase in aortic valve area. The mean age of these patients was 78.4 +/- 6.1 years. On actuarial analysis, after 5 months 98 p. 100 of the patients with primary success were alive and 89 p. 100 were in stage I or II and had not been operated upon or redilated. At 15 months 79 p. 100 of the patients with primary success were alive, but only 48 p. 100 were in stage I or II and neither operated upon or redilated. Ultrasonic data obtained one and twelve months after dilatation were compared in 8 patients who had kept the full functional benefit of angioplasty for 14.6 +/- 4.3 months (group 1) and 9 patients who had lost this initial benefit (group 2). In group 1 patients the aortic valve area had moderately and non significantly diminished from 0.92 to 0.72 cm2. In group 2 patients the aortic valve area had gone down from 0.89 to 0.63 cm2 (p less than 0.01), indicating restenosis. We conclude that after the 4th post-valvuloplasty month the medium-term success of the procedure undergoes some degradation, and in these patients the echocardiographic signs of stenosis are clear-cut.

Aged↗
PubMed1988

Image registration in electron microscopy: application of a robust method.

The geometric registration of two electron microscopic images generally is performed by maximizing the cross-correlation coefficient between them. We show that a new similarity measure (the number of sign changes) is useful for performing simultaneously geometric and gray-level registration. This method is robust, which means that it provides a good estimation of the parameters even in the presence of outliers that cannot be described by the registration model.

Computer Simulation↗
PubMed1988

Evaluation and optimization of the performance of elastic and inelastic scanning transmission electron microscope imaging by correlation analysis.

Scanning Transmission Electron Microscopes (STEM) offer specific characters, such as multidetector configuration, energy loss spectroscopy, external control of the probe raster, which make them quite suited to digital image acquisition and innovative data processing. Considering pixel intensities as random variables, one can apply cross-correlation techniques to pairs of duplicated images. Such methods are used to investigate imaging properties of the instrument, such as the point resolution and the signal to noise ratio, in its different working modes. Concerning the annular dark field, one shows that there exist optimum values for defocus and angle of illumination which minimize the probe size at a value of about 0.5 nm. The same techniques are also used to evaluate the characteristics of energy filtered images recorded in a specific energy window loss around an ionization edge: the degradation in edge resolution with respect to the accompanying ADF images is only of the order of 0.2 to 0.3 nm, which sets the delocalization parameter for an energy loss of 100 eV (i.e. for U-O4-5) well below 1 nm in agreement with theoretical predictions.

DNA↗
PubMed1988

Developments in processing image sequences for elemental mapping.

Elemental mapping consists in searching the distribution of a given chemical species over an extended specimen area, with relation to topographical or structural features. It can be done with EELS core signals from a combination of several energy filtered images. One major problem encountered in the processing of such sequences of images lies in the extrapolation errors due to a difficult estimate of the background below the characteristic signal. The chosen method must be sufficiently reliable to avoid the risk of both "false positive" and "false negative" values: the first category may stem from spurious signals or from a non-satisfactory fit of the background. The second category is mainly due to a limited sensitivity. The EELS signal is often much weaker than the background intensity; an extrapolation error can therefore transform a negative value into a positive one, or vice versa. The purpose of the present contribution is to check the validity of the processing at different levels: i) different mathematical models of background; ii) different types of fitting procedures (one-parameter and two-parameters fits); iii) different fitting methods and several associated manipulations, such as a quasi local estimation of the involved fitting parameters. The statistical validity of those techniques is discussed through several tests on real images obtained from different specimens (Co/CeO2 catalysts, ferritin molecules, U and Tb staining clusters). Progress is made on the way of quantitative elemental mapping at a given confidence level, and towards the identification of single atoms.

Electron Probe Microanalysis↗
PubMed1987

Crystallographic study of the ferritin molecule: new results obtained from natural crystals in situ (mollusc oocyte) and from isolated molecules (horse spleen).

The aim of the present work is to gather new information on the ferritin molecule. Natural crystals of ferritin occurring in the yolk platelets of a mollusc oocyte were studied. Their crystallographic structure was found to be equivalent to one of the structures obtained by artificial crystallization (fcc; a = 15 nm). Individual ferritin particles isolated from horse spleen were studied by microdiffraction techniques, using field emission gun transmission electron microscopy. The iron core crystals display a hexagonal structure; our results confirm the value of the unit cell parameter a (0.51 nm) and, for the first time, we have been able to extract the value of the unit cell parameter c (0.95 nm). Thus, among the three models described in the literature for the crystalline structure of the iron complex, our results corroborate that of Towe and Bradley (J. Colloid. Interf. Sci., 1967, 25, 384-392).

Animals↗
PubMed1986

[Hodgkin's disease].

Explore the source record for details and available documents.

Combined Modality Therapy↗
PubMed1985

Subunit arrangement of Escherichia coli F1-ATPase studied by scanning transmission electron microscopy.

The shape and the arrangement of subunits in Escherichia coli F1-ATPase (ECF1) lacking the delta subunit have been explored with a high performance scanning transmission electron microscope. In tilting experiments, the ECF1 molecule appeared as a flat cylinder whose width (approx. 120 A) was about twice its height. The symmetry of front view projections of ECF1 has been investigated by computer analysis. In a population taken at random from the data bank, one third of the particles showed five-fold radial symmetry components, one third six-fold radial symmetry components and the last third no typical symmetry. The six-fold radial symmetry was consistent with a hexagonal arrangement of six large peripheric masses, which probably correspond to the three alpha and the three beta subunits of ECF1. The five-fold radial symmetry was tentatively explained by a fusion of two juxtaposed peripheric subunits. Lateral projections showed a zig-zag organization of the large masses, suggesting that the large alpha and beta subunits are located on two levels, with some degree of intercalation between the subunits of the two levels.

Cell Membrane↗
PubMed1985

Three-dimensional graphical reconstruction from HVEM stereoviews of biological specimens by means of a microcomputer.

A microcomputer reconstruction technique has been developed in order to permit a larger exploitation of stereomicroscopy. The microcomputer facility consists of a digitizing tablet, a microcomputer, a graphics terminal, a graphics plotter and a printer. The technique has been applied to the study of HVEM stereopairs, performed by recording two images of the same area of a specimen (thick section of araldite-embedded leech ganglion neurons), tilted relative to the beam axis through an angle 0/20 degrees. Coordinates of N conjugate points of interest, expressed in a common reference system were obtained with the help of a digitizing tablet and the misorientation between the two images was determined by a method based on a least square technique. New projections of the object on different planes are provided by the microcomputer facility. Also the microcomputer method permits to obtain new stereopairs drawings, in various orientations and slices from a three-dimensional reconstruction of the object oriented in any direction in space. The method permits to obtain computed anaglyph drawings, printed here, which are stereoviews of the same object.

Animals↗