156 EIGSTI 



viewed by Loudon (chapter 6, Colchicine) and by Eigsti and Dustin (1955). 

 The compound is described as methyl ether of an enolone containing three 

 additional methoxyl groups, an acetylated primary amino group, and three 

 nonbenzenoid double bonds. The structure is novel chiefly in respect to the 

 two fused 7-membered ring of its tricyclic system (Loudon, 1955). Com- 

 plete synthesis offers no needed economic replacement since the natural 

 product is abundant and completely effective. However, more complete esti- 

 mate of the pattern of atoms and specific action upon mitotic processes offers 

 promise of discovering new ways to control cellular activities. For improved 

 chemotherapy more knowledge of atomic specificity in relation to biological 

 processes would be valuable. Here is an excellent field for future research. 



When colchicine comes in contact with dividing cells the spindle fibers are 

 at once reduced, as well as structurally changed. Other cells are uniformly 

 arrested at the metaphasic stage. Such action leads to a restitution nucleus 

 with double the number of chromosomes. Metaphasic arrest by spindle in- 

 hibition is the central feature of the "C-mitosis" as described by Levan (1938), 

 a process familiar to many biologists (Eigsti and Dustin, 1955). 



The chemical acts specifically upon the spindle and has not been demon- 

 strated conclusively to alter chromosomal structure. Its selective reaction is 

 total for all cells in mitosis. No serious consequences occur in cells after the 

 drug has been dissipated from the cell, except that more chromosomes are 

 present than before contact with the substance. 



As the cell recovers from a treatment, a new spindle is formed and the 

 restitutional nucleus undergoes a regular mitosis, now as a polyploid cell. If 

 sufficient numbers of cells in a given area are simultaneously changed from 

 diploid to tetraploid, the new tissue will be tetraploid. However, experimental 

 conditions may allow only a few tetraploid cells, the majority remaining 

 diploid. A more rapid growth by diploid cells causes presumable tetraploids 

 to revert back to diploids. Success can be obtained only when specific condi- 

 tions are well understood and entirely accounted for in the procedures de- 

 signed to create tetraploids. 



Five interacting factors must be considered for successful experiments de- 

 signed to induce polyploids (Eigsti and Dustin, 1955). These are (1) con- 

 centration of the solution, (2) exposure schedule, (3) number of chromosomes 

 of species treated, (4) specific stages of mitosis, and (5) general conditions 

 for growth. More experimenters use the 0.2 per cent aqueous solution than 

 any other concentration. This strength can be recommended generally for 

 inducing polyploidy. A direct contact between the chemical and nucleus must 

 be maintained for not less than 48 hours. Even longer exposures are used. 

 Schedules providing an intermittency for the treatment are applicable where 

 roots may be treated by alternate immersion in colchicine 12 hours and water 

 12 hours, extending the total treatment to 3, 4, 5, or 6 days. A drop of the 

 0.2 per cent solution may be applied to very young seedlings each morning 



