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There are several popular techniques for visualizing various components of a cell.
Hematoxylin and eosin (H & E) are common substances used to stain cells for examination under a light microscope. Hematoxylin is a blue, basic dye that binds acidic cellular components and stains blue. Since the nucleus has a high concentration of nucleic acids, it appears dark blue after staining. This is generally the most visible and identifiable portion of the cell. Eosin is a red, acidic dye that stains basic compounds.
Another cytochemical technique is PAS (periodic acid Schiff), which binds carbohydrates and gives a magenta color under the light microscope. This method is useful for detecting glycoproteins (e.g., glycocalyx on cell surface), glycogen, and the Golgi apparatus.
Immunohistochemistry permits the detection of specific proteins in a histological section. Antibodies that target the desired protein are generally labeled in one of the following ways: 1) fluorescent dye (for light microscopy); 2) enzyme (for light or electron microscopy); or 3) colloidal gold (for electron microscopy).
Autoradiography involves the introduction of a radioactive isotope into the cell. The cell is later "sectioned" and placed under a photographic emulsion of silver bromide crystals. Beta particles emitted from the tissue section react with the film to form silver grains. Unreacted crystals are eventually washed away, leaving a pattern of grains. This method is useful for determining the migration of certain elements within the cell.
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Histology is the anatomical study of cells and tissues, as observed at the microscopic level.
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Light microscopy (LM) involves the standard lab microscope that includes a light source, a stage for the observed speciment, and a mono- or binocular eyepiece for viewing. In histological studies, this method frequently requires the cells to be stained to provide contrast.
Confocal microscopy uses a laser beam to visualize the contours of different planes, which are combined to create a three dimensional image of the observed specimen.
Compared to light microscopy, electron microscopy (EM) can provide a much higher magnification of up to nearly 200,000 times the original size. The tissue sections are stained with heavy metals, which affect the flow of electrons from the electromagnetic source to the electron detector. Transmission electron microscopy (TEM) visualizes a thin section, while scanning electron microscopy (SEM) provides a three dimensional image.
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