244 



Colchicine 



that instead of a gradual rise, there is a steep increase on the fifth 

 day. However, the experimental conditions are complex and stimuli 

 from other growth-promoting substances cannot be exclnded. These 

 data with those given in Section 9.2 comprise the best evidence to 

 date of possible mitotic stimulation of animal cells by colchicine. 



In Xenopus, a short treatment, one hour in a 1:2000 solution, may 

 comj)letelv inhibit growth. However, regeneration often proceeds 

 normally during the first three days after this "colchicine shock" be- 

 cause cellular migration is not disturbed. On the fifth day, on the 

 contrary, when divisions should be taking place, regeneration was 

 completely inhibited (Fig. 9.14). Some pharmacological conclusions 

 are important to mention; they are the results of an extensive series 

 of experiments on this favorable material. Colchicine was demon- 



TABLE9.10 

 Influence of Alloxan Diabetes on Pancreatic, Pituitary, ancI Suprarenal 

 Mitoses; Inhibition by Insulin; Stimulation by Pituitary Extracts 

 I: rats injected with 150 mg/kg alloxan 

 II: ?W. -f 10 to 20 units insulin per day 

 III: id. + pituitary extract (about 32 mg. dry powder per day) 

 (After Cavallero'^) 



strated to act locally, for no inhibition was observed when only the 

 anterior part of the larva was immersed in the solution. This is also 

 evidenced by the absence of inhibition if colchicine is applied to 

 another wound close to the amputation. Experiments in which the 

 tail blastema was amputated and growth resumed, demonstrated that 

 colchicine did not penetrate more than 2 mm. from the wound. These 

 also showed that colchicine was fixed in the tissues of the wound for 



