Interferometric studies of endothelial cells in primary culture.

A population of endothelial cells grown from Xenopus laevis tadpole hearts was investigated by microinterferometry. The resulting interferograms were evaluated by an automatic image analyzer. The mean values of dry mass were 778 +/- 340 pg (10(-15) g) for whole cells, 648 +/- 309 pg for cytoplasm, 116 +/- 45 pg for nuclei, and 19 +/- 10 pg for nucleoli. Two subpopulations of cells were identified, an actively growing one and a less active one. The density (dry mass per microm2) of the nuclei and nucleoli of less active cells was greater than that of the nuclei and nucleoli of actively growing cells. In addition, the inactive cells were always large and possessed a considerable amount of cytoplasm. The entrance of cells into S-phase could not be detected by microinterferometry; and no differences were apparent between cells possessing one nucleolus and those containing two nucleoli. The values obtained in these amphibian cells were compared with those derived from mammalian cells.