Nissl substance

A Nissl body, also known as Nissl substance, is a large granular body found in neurons. These granules are of rough endoplasmic reticulum (RER) with rosettes of free ribosomes, and are the site of protein synthesis. It was named after Franz Nissl, a German neuropathologist who invented the Nissl staining method.

Nissl bodies can be demonstrated by a method of selective staining developed by Nissl (Nissl staining), using an aniline stain to label extranuclear RNA granules. This staining method is useful to localize the cell body, as it can be seen in the soma and dendrites of neurons, though not in the axon or axon hillock. Due to RNA's basophilic ("base-loving") properties it is stained blue by this method.

Nissl bodies show changes under various physiological conditions and in pathological conditions they may dissolve and disappear (chromatolysis).

The functions of Nissl bodies is thought to be the same as that of the rest of the ER and the golgi apparatus: the manufacture and release of proteins.

The ultrastructure of Nissl bodies suggests they are primarily concerned with the synthesis of proteins for intercellular use.

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