Infradian Rhythm in Proliferative Activity of a Culture of Embryonic Fibroblast-Like Cells from C57BL/6 Mice.

We studied daily dynamics of proliferative activity of embryonic fibroblast-like cells in culture during the logarithmic growth phase. Daily increase in cell count in the culture showed a 4-day rhythm that persisted over 3 weeks of culturing. In cultures from different animals, the phase of this rhythm was synchronous and did not depend on the moment of cell isolation. It can be hypothesized that the 4-day biorhythm of proliferative activity of embryonic fibroblast-like cells in culture is determined by external environmental factors, probably of electromagnetic nature.