38 



Colchicine 



mitotic stage on hand when colchicine reaches the nucleus may de- 

 termine the metaphasic type. 



Since the action is reversible/^'^ cells may recover from the action 

 of the drug. Arrested types appearing during the recovery sequence"'' 

 on the way to complete bipolar mitosis are as significant as those 

 showing up ^vhen the drug is acting upon the mitosis. ^ 



STAR 



DISTORTED STAR 



EXPLODED 



BALL 



Fig. 2.5 — Schematic representations of the main types of arrested metaphases. (After 



Barber and Callan) 



Length of exposine and concentration are directly related to the 

 pattern that will develop.'^ A given situation must be noted with 

 reference to these two factors. 



Then, as was mentioned before, concentration, cxposmc, mitotic 

 stage, kind of cell, recovery, active treatment, and general growth 

 conditions become critical to the formation of an arrested metaphasic 

 pattern whether oriented or imoriented.^ Even though the interact- 

 ing factors are several, the number of metaphasic types is surprisingly 



