Atomic force microscopy imaging of dried or living bacteria.

Atomic force microscopy (AFM) was used to obtain micrographs of dried bacteria in air, and of living ones in their culture medium. Images of dried bacteria were very similar to images obtained elsewhere by the much more complicated cryoetching preparation technique for transmission electron microscopy. Living bacteria were immobilized on a poly-L-lysine film, and directly observed in their culture medium at a resolution unattainable by any other technique applicable to living material. The images were similar to those obtained in scanning electron microscopy where the specimen must be fixed, dried and coated with conductive material, and as a result, no longer viable.

Intracellular localization of drugs in cultured tumor cells by ion microscopy and image processing.

Several drugs, containing a halogen atom, F or Br, that are being used in antiviral or anticancer therapy, were studied for their localization in cultured cells by ion microanalysis. The association allows to reduce the exposure time to define the intracellular localization of the studied element. The topography of the cells is given by the image of the polyatomic ion 26CN-. The image of the distribution of 81Br- or 19F-, coded in another color scale, can be superimposed, giving a polychromic image of the cell, thus showing the intracellular localization of the compound. MCF-7 tumor cells were cultured in the presence of pyrimidine derivatives. 5-Bromo-2'-deoxyuridine (BUdR) and 5-trifluorothymidine (F3TdR) were localized in the nucleus, 5-fluoro-2'-deoxyuridine (FUdR) in the nucleus and only in some nucleoli. The method is simple and rapid, as compared with techniques using radiolabeled compounds, or with immunocytochemical techniques. It is possible to observe two different compounds in the same cell. It could be applied to other compounds containing a halogen atom.

Processing of secondary ion microscope images: an example of application to the thyroid.

Ion microscopy is a microanalytical method by which one can obtain distribution images of any chemical element with isotope discrimination even at very low local concentrations, in successive slices of the specimen. These images are obtained at the price of progressive erosion of the specimen, so that the analysis may not be replayed and it is necessary to record the maximum amount of information during specimen erosion. We present an improvement of this method using a highly sensitive camera connected to a video analog-digital converter. The images are acquired and digitized on line and may be processed by an image computer. We illustrate the technique described with an application of ion microscopy that is made possible by digital recording and processing of images. This application concerns the precise comparison of iodine isotopes and phosphorus distributions in sections of the thyroid gland of rats which were submitted to an iodine-deficient diet followed by an injection of 129I.

Cathodoluminescence applied to the study of human glomerulonephritis.

The cathodoluminescence (CL) emission of fluorescent species submitted to electron beam irradiation in a scanning electron microscope may be used to reveal the localisation of the emitter at microscopic level. This technique has been applied to the study of human renal biopsies with membraneous glomerulonephritis. Cryosections of biopsies were stained with specific antibody, labelled either by fluorescein or by rhodamine. Rhodamine exhibited a stronger luminescence and a greater resistance to the 'beam effect' than fluorescein. We obtained CL panchromatic pictures of sections labelled with rhodamine at enlargements up to X15 000, without noticeable quenching of emission.

Computation of ventilation-perfusion ratio with Kr-81m in pulmonary embolism.

Diagnostic difficulties occur in pulmonary embolism (PE) during visual analysis of ventilation-perfusion images in matched defects or in chronic obstructive lung disease (COPD). In 44 patients with angiographically confirmed PE and in 40 patients with COPD, the regional ventilation-perfusion ratios (V/Q) were therefore computed using krypton-81m for each perfusion defect, and were displayed in a functional image. In patients with PE and mismatched defects, a high V/Q (1.96) was observed. A V/Q greater than 1.25 was also found in nine of 11 patients having PE and indeterminate studies (studies with perfusion abnormalities matched by radiographic abnormalities). COPD was characterized by matched defects and low V/Q. The percentage of patients correctly classified as having PE or COPD increased from 56% when considering the match or mismatched character to 88% when based on a V/Q of 1.25 in the region of the perfusion defect. This quantitative analysis, therefore, seems useful in classifying patients with scintigraphic suspicion of PE.

[Hydration of the animal cornea: spectrometric study using proton nuclear magnetic resonance]. / Hydratation de la cornée animale: étude spectrométrique par résonance magnétique nucléaire (R.M.N.) du proton.

The concentration of water in isolated corneas was studied using a Nuclear Magnetic Resonance Protonic (P N M R) technique. The corneas were maintained in moist chambers or in different aqueous fluids in order to compare the results obtained by. P N M R with those provided by classical techniques. The magnetization ratio, associated to water component measured as a function of corneal conservation time has permitted to establish the corneal water content variation. The corneas preserved in moist chamber exhibited a slow dehydration of about 15% in the first day. On the contrary, hydration was evident in liquid media, the strongest in pure water. No significant differences were found between saline, T C Earle medium and Neomycin ophthalmic suspension. P N M R technique give an index of corneal hydration in these conditions and it seems possible to use a P N M R apparatus for the evaluation of a corneal graft before surgery.

Cathodoluminescence applied to immunofluorenscence: present state and improved technical prospects by prism spectrometer light selection.

For studies on cathodoluminescence, we equipped a scanning electron microscope with a prism spectrometer and sensitive photomultiplier. The apparatus is described and our initial results are presented on the analyse of cathodoluminescence. The material observed promarily involved studies of immunofluorescent specimens. Humal lymphocytes were labelled with a fluorescent antibody and cryosections of rat kidney with Masugi nephritis were labelled with a fluorescent specific antibody. Our apparatus permitted monochromatic imaging of cathodoluminescence emissions and resulted in much improved micrographs. Some possible improvements of the technique are discussed.

Ultrastructural study of spontaneous bone marrow rosette-forming cells.

Mouse bone marrow contains spontaneous rosette-forming cells (RFC) which include more than 70% T-cell precursors, as assessed by their transformation into theta-positive cells after incubation with thymic hormone. Such spontaneous RFC, examined in C57B1/6 mouse bone marrow by electron and scanning electron microscopy, have consistently been shown to be small, inactive mouse lymphocytes when macrophages have been eliminated by cell preincubation. These data suggest that thymic hormone target cells include small quiescent lymphocytes.