There is a way to inoculate a culture of media with just a few dozen cells of Tetrahymena and get it to grow into a flourishing population. Consider the figure below (from ). In panel A, you see the phenomenon I spoke of in the last entry, where a culture that starts with less than 500 cells/ml dies, but flourishes when started with 5000 cells/ml. Yet in panel B, you can see this density-dependence is gone.
What happened? Something was added to the cultures shown in panel B.
Mammalian insulin. Insulin can substitute for the Tetrahymena growth factor and induce growth and division in the cells. Reminds me of something like this.
Of course, most people are familiar with insulin:
Insulin is a hormone that is central to regulating the energy and glucose metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle.
But did you know that insulin stimulates the glucose uptake of Tetrahymena pyriformis?
Now you do. Front-loading is a craaazy idea, eh?
 Christensen ST. 1993. Insulin rescues the unicellular eukaryote Tetrahymena from dying in a complete, synthetic nutrient medium. Cell Biol Int. 17:833-7.