A Substance Secreted from Tetrahymena and Mammalian Sera Act as Mitogens on Paramecium tetraurelia

Abstract

We previously isolated and purified Paramecium growth factor (ParGF) from a cell-free fluid of an early stationary mass culture of Paramecium tetraurelia (Tanabe et al., 1990). The mitogenic activity of the purified ParGF and of the crude sample (ca. a 100-fold concentrate obtained by ultrafiltration of cell-free fluid) has been assessed based on restoration of the fission rate of the jumyo mutant of P. tetraurelia in daily reisolation cultures. With this assay system, we found that crude samples of Tetrahymena pyriformis and T. thermophila showed mitogenic activity. This suggests that Tetrahymena cells secrete a mitogenic factor(s) like ParGF. To some extent, fetal bovine serum (FBS) and calf serum (CS) also acted as mitogens on the jumyo mutant. Of nine mammalian growth factors assayed for their mitogenic effects on the jumyo mutant, epidermal growth factor (EGF) and transforming growth factor α (TGFα) were slightly and occasionally effective. These results support the idea of actual use of similar kind of growth factors to control cell divisions from protozoa to mammals.