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PubMed1977

[Selective contrast enhancement of microscopical specimen by optical procedures for automatized quantitative image analysis (author's transl)].

One of the most important problems in automatic image analysis is the discrimination of features by, a certain range of grey levels. To obtain as many as possible different grey levels sufficient contrast is achieved mainly by specific staining. Alternative and supplementary methods are some micrscopical methods, not routinely used. Interference microscopy, interference reflexion microscopy and microfluorimetry are discussed in detail. These optical procedures enhance the contrast of specimen specifically without the necessity for the application of specimen specifically without the necessity for the application of sophisticated staining methods. In interference contrast, tissues can be separately detected by grey level discrimination due to varying concentration of dry mass; this is shown for a cornifying part of fish skin (breeding tubercle of Rutilus rutilus L.). Furthermore, very small amounts of dry matter can be determined with high precision, as demonstrated for a single tissue culture cell (XTH-cell). Automatisation of image analysis provides a unique opportunity for routine application of interferometric measurements. The principles of the procedures are outlined. By interference reflexion microscopy cellular attachment areas to a glass surface are visualized, providing a powerful tool in cellular diagnosis based on grey level discrimination (darkest parts correspond to zones of closest contact to the substratum). A fast migrating lymphocyte and stationary endothelial cells have been chosen for demonstration. Various histochemical problems can be solved elegantly by fluorescence methods, e.g. mitochondria in living cells are specifically stained by a fluorochrome (DASPMI) and the distribution of fluorescence intensity can be followed within the mitochondrial population of a cell. Fluorescence was recorded from fotographic negatives taken with a fluorescence microscope. Additionally a short comment is given on the application of polarisation microscopy for feature detection.

Animals↗
PubMed1995

Cell-substrate interactions and locomotion of Dictyostelium wild-type and mutants defective in three cytoskeletal proteins: a study using quantitative reflection interference contrast microscopy.

Reflection interference contrast microscopy combined with digital image processing was applied to study the motion of Dictyostelium discoideum cells in their pre-aggregative state on substrata of different adhesiveness (glass, albumin-covered glass, and freshly cleaved mica). The temporal variations of the size and shape of the cell/substratum contact area and the time course of advancement of pseudopods protruding in contact with the substratum were analyzed. The major goal was to study differences between the locomotion of wild-type cells and strains of triple mutants deficient in two F-actin cross-linking proteins (alpha-actinin and the 120-kDa gelation factor) and one F-actin fragmenting protein (severin). The size of contact area, AC, of both wild-type and mutant cells fluctuates between minimum and maximum values on the order of minutes, pointing toward an intrinsic switching mechanism associated with the mechanochemical control system. The fluctuation amplitudes are much larger on freshly cleaved mica than on glass. Wild-type and mutant cells exhibit remarkable differences on mica but not on glass. These differences comprise the population median of AC and alterations in pseudopod protrusion. AC is smaller by a factor of two or more for all mutants. Pseudopods protrude slower and shorter in the mutants. It is concluded that cell shape and pseudopods are destabilized by defects in the actin-skeleton, which can be overcompensated by strongly adhesive substrata. Several features of amoeboid cell locomotion on substrata can be understood on the basis of the minimum bending energy concept of soft adhering shells and by assuming that adhesion induces local alterations of the composite membrane consisting of the protein/lipid bilayer on the cell surface and the underlying actin-cortex.

Animals↗
PubMed1995

Red blood cells, phase contrast, interference contrast microscopy and microspectrophotometry.

Following Teorell's (1) observation that the ghosts of hypotonically hemolysed erythrocytes reseal, it was shown that during the time they are permeable to hemoglobin, foreign macromolecules (dextran) can enter and that the hemolysed cell can achieve a final colloid-osmotic equilibrial state containing dextran and some residual Hb. In this way dextran reduces the hemoglobin loss in hypotonic hemolysis. Some hemoglobin loss is, however, inevitable, as it begins with a non-diffusive bulk outflow, sometimes observable as a jet, during which time a diffusive influx of the colloid-osmotic "balancer", dextran, is not possible. Finally, as expected from a process which is for the most part diffusive, transmembrane macromolecular transport is bidirectional; during hemolysis smaller molecules escape to a greater extent than larger ones.

Erythrocytes↗