Which stain is used to demonstrate cross striations in muscle fibers?

• A. Phosphotungstic acid-hematoxylin
• B. Masson Trichrome
• C. Verhoeff-van Gieson
• D. Oil Red O

Answer: (A)

Cross striations reflect the repeating sarcomere units within skeletal muscle fibers, so the staining method that best highlights these alternating dark and light bands is designed to bind to the myofibrillar components in the sarcomere. Phosphotungstic acid-hematoxylin penetrates and differentially stains the contractile proteins in muscle, producing distinct dark transverse bands along each fiber that reveal the cross-striated pattern. This makes the sarcomere architecture clearly visible under the light microscope.

Other stains serve different purposes: Masson Trichrome emphasizes connective tissue and muscle fibers with contrasting colors but does not reveal the fine sarcomere striations; Verhoeff-van Gieson highlights elastic fibers and general tissue contrasts; Oil Red O stains lipids in frozen sections. None of these show the characteristic cross-striations as PTAH does.