Reduction of phase thickness is a characteristic reaction of the nucleoli to toxicity as shown by coherent phase microscopy.

Optical parameters of human cell nucleoli (HCT116 colorectal cancer cells) in depolymerization of microtubules and depletion of intracellular ATP pool were studied by coherent phase microscopy. These influences were associated with a rapid (recorded within the first minutes) reduction of the phase thickness of the nucleoli. These changes are similar to the nucleolar response to direct inhibitors of transcription. Hence, quantitative parameters of coherent phase microscopy describe common reaction of the nucleolus to stress; reduction of optical thickness of the nucleolus is a component of this reaction.