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(also called tigroid body), a condensed portion of the cytoplasm of a nerve cell. Nissl bodies were first described at the end of the 19th century by the German scientist F. Nissl.
Nissl bodies can be viewed under a light microscope after staining with methylene blue or other basic stains. They appear as rounded masses that occupy the entire body of the cell as well as the bases of the outgrowths. Electron microscopy reveals that the Nissl bodies contain aggregates of ribosomes and cisternae of the endoplasmic reticulum. Nissl substance, which forms the Nissl bodies, consists of ribonucleic acid (RNA), proteins, acid polysaccharides, and lipids; it participates actively in the synthesis of cell proteins.
Changes in the chemical composition, shape, and staining characteristics of Nissl bodies occur as a result of trauma to the nervous system, inflammatory or infectious diseases, poisoning, oxygen deprivation, or shifts in the function of the neurons.