Which statement describes acetone as a fixative in this context?

• A. It is recommended for frozen brain sections to diagnose rabies and demonstration of cell surface antigens; it over-hardens tissue but preserves glycogen and some enzymes
• B. It is never used for fixation
• C. It is the primary fixative for Cajal staining of astrocytes
• D. It is identical to formalin

Answer: (A)

Acetone fixes tissue quickly by dehydration and coagulation, which helps preserve antigen sites and glycogen for studies on frozen sections. In the brain, this rapid fixation is advantageous for rabies diagnosis and for demonstrating cell surface antigens because it minimizes cross-linking that can mask epitopes, allowing antibodies to bind effectively. It also tends to over-hardening tissue if overused, explaining the note about brittleness. Acetone is not identical to formalin, which cross-links proteins and alters morphology more, and it is not the primary fixative for Cajal staining of astrocytes, which relies on different fixation methods. Therefore, this description correctly captures why acetone is used as a fixative in this context.