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N Bonnet

Publications and source records attributed to N Bonnet.

79 records · Page 5Linked to original sources
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↗
PubMed1982

Observation and simulation of unstained DNA images in bright field TEM.

Images of unstained, unshadowed DNA prepared by the Kleinschmidt method have been obtained in bright field TEM with a usable contrast. Operating conditions include a strong defocus and a highly coherent illuminating beam. Observations suggest that a specific interaction exists between the nucleic acid and the carrier protein: cytochrome C. Computer simulations of beam-specimen interaction and of image formation were performed. The calculated dependence of contrast on defocus agrees qualitatively with the experimental results. We conclude that experiments with unstained biological specimens are feasible and are necessary (in spite of difficulties) to corroborate results obtained with stained material.

Chemical Phenomena↗
PubMedDate not supplied

Peripheral extracorporeal membrane oxygenation (ECMO) in patients with posttransplant cardiac graft failure.

INTRODUCTION: We sought to report the usefulness of extracorporeal membrane oxygenation (ECMO) in heart transplant patients. PATIENTS: Between March 2002 and August 2004, 14 heart transplant patients (11 men and three women, 36 +/- 15 years old, range = 12 to 50) with primary graft failure underwent peripheral ECMO implantation. Three patients had pulmonary hypertension and three had been transplanted with hearts from marginal donors. At the time of implantation, all were in severe cardiogenic shock despite maximal inotropic support. In six patients, the ECMO was implanted in the operating room since cardiopulmonary bypass could not be weaned. In the eight remaining patients, ECMO was implanted in the intensive care unit, during the first 48 hours in seven cases. In one patient, implantation was performed during external resuscitation. In all cases, femoral vessels were canulated using the Seldinger technique after anterior wall exposure. Distal arterial perfusion of the lower limb was systematically used. RESULTS: Pump outflow was high enough in all the cases (mean: 2.6 +/- 0.2 L/min/m(2)). Three patients died on circulatory support. One patient was implanted with a total artificial heart after a few hours and another one underwent unsuccessful emergent retransplantation. Nine patients were weaned from ECMO after a mean duration of 5 +/- 2.5 days. Among them, one died of infection at 10 days after weaning and seven others were discharged to rehabilitation centers. CONCLUSION: Fast operating room or bedside implantation of a peripheral ECMO allows the physician to stabilize the hemodynamic status of patients with cardiac graft failure, potentially leading toward myocardial recovery.

Adolescent↗