Which stain is known to stain glial fibers blue?

• A. Phosphotungstic acid-hematoxylin
• B. Luxol fast blue
• C. Bodian
• D. Holmes

Answer: (A)

Phosphotungstic acid-hematoxylin selectively stains glial filaments blue, making the delicate astrocytic processes stand out in CNS tissue. This stain highlights the fibrillar components of glial cells, which is why you see blue glial fibers where astrocytic processes are present. Luxol fast blue, by contrast, targets myelin lipids and stains myelin blue but not glial filaments. Bodian and Holmes are silver stains used to visualize nerve fibers and reticular elements, typically producing dark or black markings rather than blue glial filaments. So the blue staining of glial fibers is a hallmark of PTAH.