Cellular mechanisms of stimulation of bud production in Hydra by low levels of inorganic lead compounds.

Treatment of Hydra with subtoxic levels of inorganic lead compounds (lead nitrate and lead chloride) for perods ranging from 5 min to one hour causes a temporary increase in bud production as compared to untreated control animals. This effect can be inhibited by the addition of large amounts of calcium chloride to the culture medium. The increased rate of budding is preceded by a dramatic increase in the number of nerve cells per animal, which is first observed within six hours after lead treatment. This appears to be the result of an increased rate of mitosis in the undifferentiated interstitial cells and their subsequent differentiation into nerve cells. The total number of cells per animal also increases after exposure to lead compounds, suggesting that lead may act as a general mitotic stimulator of all dividing cell types in Hydra.