ABSTRACT
The effect of colcemide and puromycin on polarity and regulation in hydra has been investigated at the biological level using isolation and transplantation techniques.
Colcemide treatment of hydra from which the hypostome has been removed can bring about an alteration of polarity so that multiple distal structures (hypostome and tentacles) can form on a single animal. Such forms do not arise if the original hypostome is not removed. Treatment with puromycin is much less effective in altering polarity.
Transplantation experiments indicate that hypostome formation is inhibited by colcemide treatment but that this substance does not irreversibly affect the determined hypostome or the ‘adult’ hypostome which retain their organizing properties.
Puromycin treatment does not inhibit hypostome formation completely since some animals reconstitute tentacles while in puromycin. However, the hypostome which is formed does not possess the normal resistance to absorption following transplantation. This result may indicate that the factors responsible for the organizing properties of the hypostome (i.e. tentacle induction) are distinct from those which control resistance to absorption.
Both colcemide and puromycin change certain important properties of the subhypostomal region to those characteristic of more proximal regions. These properties are believed to ‘control’ polarity.
The effects of colcemide and puromycin on polarity and regulation are discussed in terms of their effects on a control system which has been previously postulated to account for polarised regulation in hydra. This system involves axial gradients in time for hypostome determination, inhibition of hypostome formation and threshold for inhibition. The experimental results can be explained as a consequence of the direct or indirect action of these substances on the axial gradients.
