NISSL BODIES: STRUCTURE, FUNCTIONS AND ALTERATIONS - GEOGRAFÍA - 2025

The bodies of Nissl, also called Nissl substance is a structure found inside neurons. Specifically, it is observed in the nucleus of the cell (called the soma) and in the dendrites.

The axons or nerve processes that neuronal signals travel through are never devoid of Nissl bodies. They consist of clusters of rough endoplasmic reticulum. This structure only exists in cells that have a nucleus, such as neurons.

Nissl bodies near the nucleus of the neuron

Nissl bodies serve primarily to synthesize and release proteins. These are essential for neuronal growth and axon regeneration in the peripheral nervous system.

Nissl bodies are defined as basophilic accumulations found in the cytoplasm of neurons, composed of rough endoplasmic reticulum and ribosomes. Its name comes from the German psychiatrist and neurologist Franz Nissl (1860-1919).

It is important to know that, in some physiological conditions and in certain pathologies, Nissl bodies can change and even dissolve and disappear. An example is chromatolysis, which will be described later.

Nissl bodies can be seen very easily under the light microscope as they selectively stain for their RNA content.

Discovery of Nissl's bodies

A few years ago, researchers were trying to find a way to detect the location of brain damage. To do this, they realized that a good way to find out was to stain the somas (nuclei) of brain cells post-mortem.

At the end of the last century, Franz Nissl discovered a dye called methylene blue. It was originally used to dye fabrics, but it was found to have the ability to stain the cell somas of brain tissue.

Nissl noticed that there were specific elements in neurons that took up the dye, which became known as "Nissl bodies" or "Nissl substance." It is also called "chromophilic substance" due to its high affinity to be dyed by basic dyes.

He observed that they were composed of RNA, DNA, and related proteins in the nucleus of the cell. In addition, they were also dispersed in the form of granules throughout the cytoplasm. The latter is an essential component of cells that is located within the plasma membrane but outside the cell nucleus.

In addition to methylene blue, many other dyes are used to observe cell bodies. The most used is cresyl violet. This has made it possible to identify masses of cellular bodies, in addition to the location of Nissl bodies.

Structure and composition of Nissl bodies

Nissl bodies are accumulations of rough endoplasmic reticulum (RER). These are organelles that synthesize and transfer proteins.

They are located next to the envelope of the neuronal soma, attached to it in order to capture the information necessary for proper protein synthesis.

Its structure is a set of stacked membranes. It is called "rough" because of its appearance, since it also has a large number of ribosomes arranged in a spiral on its surface. Ribosomes are groupings of proteins and ribonucleic acid (RNA) that synthesize proteins from the genetic information they receive from DNA through messenger RNA.

Structurally, Nissl bodies are made up of a series of cisternae that are distributed throughout the cell cytoplasm.

These organelles, having a large number of ribosomes, contain ribosomal ribonucleic acid (rRNA) and messenger ribonucleic acid (mRNA):

RRNA

It is a type of ribonucleic acid that comes from ribosomes, and is essential for the synthesis of proteins in all living beings. It is the most abundant component of ribosomes, being found in 60%. RRNA is one of the only genetic materials found in all cells.

On the other hand, antibiotics such as chloramphenicol, ricin or paromomycin act by affecting rRNA.

MRNA

Messenger RNA is the type of ribonucleic acid that transmits genetic information from the DNA of the neuronal soma to a ribosome of the substance of Nissl.

In this way, it defines the order in which the amino acids of a protein are to be joined. It works by dictating a template or pattern so that that protein is synthesized in the correct way.

Messenger RNA usually transforms before performing its function. For example, fragments are removed, non-coding ones are added, or certain nitrogenous bases are modified.

Alterations in these processes can be possible causes of diseases of genetic origin, mutations, and premature aging syndrome (Hutchinson-Gilford Progeria).

Features

Nissl bodies appear to have the same function as the endoplasmic reticulum and Golgi apparatus of any cell: to create and secrete proteins.

These structures synthesize protein molecules that are essential for the transmission of nerve impulses between neurons.

They also serve to maintain and regenerate nerve fibers. The synthesized proteins travel along the dendrites and axons and replace the proteins that are destroyed in cellular activity.

Subsequently, the excess proteins produced by the Nissl bodies are transmitted to the Golgi apparatus. They are temporarily stored there, and some have carbohydrates added.

In addition, when there is some damage to the neuron or problems in its functioning, the Nissl bodies mobilize and gather in the periphery of the cytoplasm to try to alleviate the damage.

On the other hand, Nissl bodies can store proteins to prevent them from being released into the cell's cytoplasm. Thus, it ensures that they do not interfere with the functioning of the neuron, releasing only when needed.

For example, if it were to uncontrollably release enzymatic proteins that break down other substances, they would eliminate vital elements essential for the neuron.

Alterations

The main alteration associated with Nissl bodies is chromatolysis. It is defined as the disappearance of the substance of Nissl from the cytoplasm after brain injury and is a form of axonal regeneration.

Damage to axons will produce structural and biochemical changes in neurons. One of these changes consists of the mobilization towards the periphery and the destruction of the bodies of Nissl.

Once these disappear, the cytoskeleton is restructured and repaired, accumulating intermediate fibers in the cytoplasm. Nissl bodies can also disappear in extreme neuronal fatigue.

References

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3. Neuron Engine: Nissl Bodies. (sf). Retrieved on April 28, 2017, from Yale University: medcell.med.yale.edu.
4. Nissl bodies. (sf). Retrieved on April 28, 2017, from Merriam- Webster: merriam-webster.com.
5. Nissl body. (sf). Retrieved on April 28, 2017, from Wikipedia: en.wikipedia.org.
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