Quantitative phase imaging of living cells: application of the phase volume and area functions to the analysis of "nucleolar stress".

We applied coherent phase microscopy to develop a method of quantitative evaluation of functional state of eukaryotic cells using the coordinates of characteristic points (CP) in the functions of the phase volume W and area S. In a fragment of a single cell image (HCT116 human colon carcinoma cell line) with detectable nucleolus, the values of the phase thickness, area, and volume were calculated. These values dramatically changed within the initial minutes of cell exposure to the transcriptional inhibitor actinomycin D.

Quantitative real-time analysis of nucleolar stress by coherent phase microscopy.

We develop a method of coherent phase microscopy (CPM) for direct visualization of nonfixed, nonstained mammalian cells (both cultured cells and freshly isolated tumor biopsies) followed by computer-assisted data analysis. The major purpose of CPM is to evaluate the refractive properties of optically dense intracellular structures such as the nucleus and the nucleoli. In particular, we focus on quantitative real-time analysis of the nucleolar dynamics using phase thickness as an equivalent of optical path difference for optically nonhomogenous biological objects.

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.

Study of optical parameters of the nucleoli under the effect of transcription inhibitors by coherent phase microscopy.

The use of coherent phase microscopy for online quantitative registration of nucleolar reaction to transcription inhibition is validated. Reduction of phase thickness of the nucleoli was detected during the first minutes of the experiment; 30 min after addition of the drug rarefaction zones predominated and areas of condensation were seen. These changes reflect the dynamics of disorders in the nucleolar ultrastructure during transcription inhibition.