242 



Colchicine 



9.5-7; Regeneration in developing animals. The complex actions 

 of the Colchicum alkaloid in embryonic development and larval 

 groAvth have already been reviewed. It is not surprising that in some 

 conditions colchicine may actually inhibit regenerative growth; thus, 

 it could not properly be used as a tool. In AmbJystoma opacum and 

 A. punctatinu, 18 to 25 mm. long, limb regeneration was studied 



IIOOt mitoses 



1000 



900 



800 



700 



600- 



500- 



400 



300 



200 



100 



T- 



I \ A 



I \ / \ 



. Ligated kidney 



, Non- ligated kidney 



I i 



\l ^ 



\ 



\ 



\ 



\ 



\ 



\ 



\ 



\ 



\ 



_] I I L. 



_] I ] 1_ 



days: 2 4 



8 



12 14 16 IB 20 22 24 26 28 30 



Fig. 9.12 — Unilateral ligature of the ureter in a rat. Mitoses in ligated and non-ligated 

 kidney, detected by the colchicine-method. (After Herlanf^) 



when the larvae were placed in 1 : lOOO or 1:5000 solutions of colchi- 

 cine. If this was done at the moment of amputation, all regeneration 

 was suppressed. \^arious degrees of inhibition of the limb-blastema 

 formation and of further differentiation, according to the length of 

 the colchicine treatment, were described.®*^ 



The regenerating tail of tadpoles of Xenopus laevis reacts simi- 

 larly.*^'^ In very dilute solutions of colchicine, this material provided 

 some results which apjjeared to indicate not only that mitoses ^vere 

 arrested at metaphasc but that a true mitotic stimulation existed. 

 Figure 9.13 shows that in control animals the number of mitoses is 

 quite small. It colchicine is assumed to have only a metaphasic arrest- 

 ing action, it is possible to calculate the number of mitoses which 

 should be observed at various intervals, for the duration of mitosis 

 has been observed and calculated in Xenopus (Chapter 3; . Figure 

 9.13 indicates that many more mitoses are found than expected, and 



