Growth Factors 

 in the Tissues of Hydra 



Allison L. Burnett^ 



Universite libre de Bnixcllcs, Bnixelles, Belgium, and 

 The University of Virginia, Charlottesville, Virginia 



THE METABOLIC GRADIENT OF HYDRA 



The work of Child and Hyman (7) demonstrated that hydra 

 possesses body regions which show a striking difference in met- 

 abohc activity. This finding was corroborated by Hinrichs (9), 

 Weimer (20, 21, 22) and Child (5, 6). These investigations re- 

 vealed in general that hydra possesses a primary apico-basal 

 gradient with a secondary increase in metabolic activity in the 

 budding region. The areas of the tentacles and peduncle were 

 shown to have a low metabolic activity as compared to the hypo- 

 stome and budding region, and the basal disk, while less active 

 than the hypostome, was found to possess a metabolic activity 

 higher than that of the gastric region and much higher than that 

 of the tentacles and peduncle. Actually, it is unwise to state that 

 hydra possesses a gradient at all, for it isn't a gradient in the true 

 sense of the word. Hydra simply has three very active regions, 

 the hypostome, budding region, and basal disk; one fairly active 

 region, the gastric region; two regions of low metabolic activity, 

 the peduncle and tentacles. 



It is interesting to speculate on the factors which account for 

 these differences in metabolic activity along the length of the body 

 column. Burnett (3) has conducted a nutritional study on hydra 

 during periods of rich feeding and prolonged starvation. He found 



^Present address: Department of Biology, Western Reserve University, Cleveland, 

 Ohio. 



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