Factors contributing to denucleation of cerebral mast cells

When mast cells, identified by metachromatic color in cresyl-echt-violet-stained paraffin sections, aggregate in large numbers, the intensity of cytoplasmic granulation varies. The intensely stained cytoplasmic granules of heavily granulated cells may be pushed over the microscopic section by the microntome blade either in the direction of cutting or against it. In the pale mast cells, in which a progressive pyknosis and atrophy of the nuclei by compaction of DNA particles take place, dislodgment and displacement of the pyknotic nuclei may occur in 1.1-2.3% of these cells. The pyknotic nuclei are expelled, usually in the direction of cutting, and deposited on top of the mi-roscopic section at various distances from their original site. While this expulsion is regarded as artifactitious, caused by the mechanical actioh of the microtome blade, the nuclear pyknosis, which is a prerequisite, is associated with intravital alterations.