The effect of bacterial endotoxin of phagocytosis of Tetrahymena and serotonin induced imprinting.

Endotoxin inhibited the phagocytosis of Tetrahymena pyriformis after a short exposure and, to a lesser degree, after repeated treatments during one week (about 35 generations). Endotoxin also prevented the development of serotonin imprinting. Detoxified endotoxin (Tolerin) affected the phagocytosis of Tetrahymena much less, indicating that the lipid-A part of the molecule may account for the membrane-toxic effect.