Nucleolus

This neuron shows a euchromatic nucleus with a well-defined nucleolus.  The nucleolus is the site of ribosomal RNA transcription and the initial assembly of ribosomes.  Nuclei generally have one nucleolus; however, multiple nucleoli are common in highly active cells, such as liver cells.  1000x

This neuron shows a euchromatic nucleus with a well-defined nucleolus.  The nucleolus is the site of ribosomal RNA transcription and the initial assembly of ribosomes.  Nuclei generally have one nucleolus; however, multiple nucleoli are common in highly active cells, such as liver cells.  1000x

Nissl substance is a unique aggregation of rough endoplasmic reticulum and polysomes in neurons.

During fixation, tissue shrinkage occurs; however, different components of the tissue shrink at different rates.  This results in the formation of artifactual spaces which are not present in living tissue.