Cell-to-substrate adhesions during spreading and locomotion of carcinoma cells : A study by microcinematography and reflection contrast microscopy

Motility and patterns of adhesion were determined by time-lapse cinematography and reflection contrast microscopy for two types of carcinoma cells, selected for their different motile behavior and not for their malignancy. Cells from the V2 rabbit carcinoma become locomotory soon after having established the necessary contact to the substratum. In contrast, cells from a human epidermoid carcinoma (LICR-OC-1) first attain a fully spread configuration before some cells slightly round up again for a slow locomotory activity of short range and duration. Reflection contrast showed that during spreading and locomotion, the cells from both carcinomas displayed a predominance of grey, the color associated with close contacts. Fully spread cells, on the other hand, presented a multitude of focal contacts in individually different arrangements of black streaks and dots, randomly distributed over the entire cell area. The functional meaning of this heterogeneity in the arrangement of focal contacts in fully spread cells is not yet understood. The importance of close contacts for spreading and locomotion, however, seems to be established and is in agreement with findings reported for other cell types engaged in the same activities. It is therefore suggested that the formation of substrate contacts depends on cellular activity rather than on the cell type.     

Automated analysis of living cells through the quantitative use of automated phase contrast microscopy

A simplified theory of image formation in phase contrast microscopy is presented. It is shown that the phase shift induced in light (related to the refractive index) by the observed object can be reconstructed, point by point, from the phase-contrast digitally sampled image through an appropriate algorithm. This allows one to make quantitative observations on unstained, living cells.     

Automated analysis of living cells through the quantitative use of automated phase contrast microscopy

A simplified theory of image formation in phase contrast microscopy is presented. It is shown that the phase shift induced in light (related to the refractive index) by the observed object can be reconstructed, point by point, from the phase-contrast digitally sampled image through an appropriate algorithm. This allows one to make quantitative observations on unstained, living cells.     

Probing the biophysical properties of tumor cells during mitosis by atomic force microscopy

Mitosis is an important physiological event accompanying with dramatic changes of cellar biophysical properties. Failure of mitosis results in cell death or chromosome aneuploidy. In this study, we used atomic force microscopy to probe and compare the biophysical properties of tumor cells at different stages during mitosis. The rounding forces of MCF-7 cells oscillated during mitosis. At anaphase, the average elasticity of cells was higher than that at other phases. Cholesterol depletion with M\(\upbeta \)CD led to an increase in the average elasticity, whereas the average roughness of membrane surface decreased at the absence of cholesterol. Our study indicated that the distribution of actin filaments could affect the biophysical properties of tumor cells and cellular morphology during mitosis. Furthermore, the biophysical properties of tumor cells were also regulated by membrane cholesterol during mitosis. This work provides a new detection approach for monitoring tumor cell development at single cell level.     

Ribonucleic acid transfer from nucleus to cytoplasm during interphase and mitosis in mouse somatic cells cultured in vitro

Summary Kidney cells from primary cultures of 15-day old mouse embryos were incubated for 2, 5 or 10 min with H³-uridine, then either fixed immediately or incubated again for various periods in a chase medium containing an excess of unlabeled uridine and cytidine. The number of grains over the non-nucleolar part of the nucleus (chromatin), the nucleolus and the cytoplasm were counted on the autoradiograms.The grain count showed that both chromatin and nucleolus incorporate very rapidly H³-uridine from the medium, whereas a time lag elapses before any H³-radioactivity above background is detected in the cytoplasm. Incorporation of H³-uridine into the RNA of the nucleus and the nucleolus is not immediately blocked after chase, suggesting that the labeled precursor pool is not completely washed out from the living cell, or diluted by the excess of unlabeled uridine present in the medium. The grain count over the nucleus and the nucleolus rises for a certain time after chase and then gradually declines; H³-radioactivity appears in the cytoplasm 10 min after chase and keeps rising through a 110-min interval. The experiment, then — even though it suggests that the bulk of cellular RNA is synthesized in the chromatin and the nucleolus and then continuously released into the cytoplasm — does not rule out the possibility that some RNA fraction, characterized by a low turnover rate, is synthesized independently in the cytoplasm.Synthesis of RNA is a continuous process throughout the cell cycle, except during metaphase and anaphase. It ceases at prometaphase after the disappearance of the nucleolus and disintegration of the nuclear membrane, and resumes in early telophase. Part of the chromosomal RNA does not remain associated with the chromosomes through division, but is suddenly released into the cytoplasm when the cell enters metaphase.