Figure 14-20.

Gemistocytes (Gemistocytic Astrocytes), Cerebrum, Dog.

A, When astrocytes react to injury, initially by hypertrophy and later by the synthesis of increased glial filaments (astrogliosis), the nuclei enlarge and often the cell body, which is not normally visible in H&E-stained sections, will become visible. This type of reactive astrocyte is called a gemistocyte (plump astrocyte) (arrows). They occur in diseases in which there is alteration of intracellular and extracellular fluid balances or injury to the parenchyma, where healing will be by glial scarring (astrogliosis, e.g., to encapsulate a deep abscess or fill in a small area of dead space). H&E stain. B, Gemistocytes (arrows) are identified by immunohistochemical staining (brown color) with antibody to glial fibrillary acid protein. IHC DAB stain.

(A courtesy Dr. J.F. Zachary, College of Veterinary Medicine, University of Illinois. B courtesy Dr. A.D. Miller, College of Veterinary Medicine, Cornell University.)