Bubbling of nuclei indicates the specimen is not optimally fixed.

• A. True
• B. False
• C. Only occurs in dehydrated tissues
• D. Indicates over-fixation

Answer: (A)

Nuclear bubbling is a sign that fixation was not sufficient or did not penetrate the tissue properly. Fixatives work by cross-linking proteins and stabilizing cellular structures, including the nuclear envelope and chromatin. When fixation is incomplete, cells begin to autolyze and fluids or gas can form within nuclear spaces, creating bubble-like voids. This artifact reflects suboptimal fixation rather than dehydration or over-fixation (which causes different issues like hardening or masking rather than bubbles). So observing bubbling indicates the specimen was not optimally fixed.