Observation of cultivated cells by scanning electron microscopy and differential interference microscopy.

HeLa S3 cells and primary cultured cells of mouse kidney have been studied using scanning electron microscopy and differential interference microscopy. After photomicrographs were taken with the differential interference microscope, the cells were fixed with either 1% osmium tetroxide or 2.5% glutaraldehyde, and then the same fields as the differential interference photomicrographs were photographed again in the scanning electron microscope. The results of differential interference microscopy revealed that most of the nuclei of HeLa cells and mouse kidney cells appeared thinner than the surrouding cytoplasm. On the other hand, the observations of scanning electron microscopy revealed that nuclei thinner than the surrounding cytoplasm tend to increase in HeLa cells, while the thicker nuclei have a tendency to increase in primary cultured mouse kidney cells. The fixation method did not affect these results. These results indicate that the observations by differential interference and scanning electron microscopy agreed well in established cell lines, but did not in primary cultured cells. Transmission electron microscopy of sections revealed that there were both types of nuclei, concave and convex, which supports the results obtained from the scanning electron microscopy. That nuclei appear either concave or convex in the surrounding cytoplasm is not an artifact but considered to be a physiological phenomenon related either to the cell cycle or cell establishment in vitro.