To preserve morphology of fixed tissue that is to be frozen, infiltrate with what concentration?

• A. 30% sucrose
• B. 70% ethanol
• C. Distilled water
• D. Plain saline

Answer: (A)

Preserving tissue architecture during freezing requires a cryoprotectant to prevent ice crystal damage. Infiltrating fixed tissue with 30% sucrose provides an osmotic, water-replacing environment that reduces ice crystal formation as the tissue freezes. This helps maintain morphology for cryosectioning. Ethanol would dehydrate and disrupt structure, distilled water would freeze into damaging crystals, and plain saline offers no protection against freezing. Thus, 30% sucrose is the appropriate choice.