28 Colchicine 



larity exists between the separate desciiptions with animal cells-^ by 

 Professor Dustin and the plant work by Professor Levan. A colchicine- 

 mitosis was described by him as follows:^*' 



The effect of colchicine on the course of mitosis is entirely specific. . . . 

 Modification in mitotic behavior . . . will be abbreviated "c-mitosis." . . . 

 Prophase stages take place normally: the chromosomes divide, condense, and 

 assume metaphase appearance. . . . They are scattered over the cell. . . . This 

 condition (c-metaphase) lasts . . . long . . . after the disappearance of the 

 nuclear membrane. . . . Formation of "c-pairs" is peculiar to material treated 

 with colchicine. . . . Their origin is evidently due to a delay of the division 



of the centromere \fter a few hours . . . the two daughter chromosomes 



are straightened out . . . like "pairs of skis." . . . Centromeres are placed 

 opposite one another in each pair. . . . During the c-anaphase . . . division 

 of the centromeres does not take place quite simultaneously within <me cell. 



. . . Inactivation of the spindle ... is reversible \fter a period of 12-24 



hours in pure water the spindle begins to regenerate. ... In the course of 



the transition to normal spindle all kinds of aljnormalities are seen \fter 



36 hours the mitoses run their normal course. At a certain moment after 

 transfer from colchicine . . . frequent diploid mitoses are seen. . . . Highly 

 polyploid giant nuclei still linger in the prophase stages. . . . Numbers as 

 high as five hundred were not rare.* 



Simimarily. these are the interesting points covered thus far. An 

 untisual sight appears in a microscojiic field focused upon tissues 

 treated with colchicine; the nuclear mitoses are halted at metaphase, 

 and converted into c-mitoses.^"^- '^^' - This power to induce c-mitosis 

 belongs to select chemical and physical agents,'''^- ^^ of which the most 

 potent, in this respect, is colchicine. It acts upon mitosis with great 

 efficiency,'^" high specificity, and total selectivity. The obvious dif- 

 ference between normal nuclear mitosis and c-mitosis is the tremen- 

 dous accumulation of chromosomes within a given area (Fig. 2.2) 

 where ntmierous cells adjacent to each other are arrested in meta- 

 phase, a primary feature of c-mitosis activity. 



Now the total or partial reaction from this drug depends upon 



the interaction of (1) a specific concentration, (2) given exposure 



period, (3) particular mitotic stage when chemical contacts nucleus, 



(4) cellular type, and (5) environment favorable to mitosis. Under 



these conditions metaphases are arrested. Consequently metaphasic 



* A condensation of the concept of a cniitosis taken fioni I.cxaii. I'.):5S, Refer- 

 ence No. 26, Chap. 1. 



fig. 2.2 — Accumulation of arrested mitoses in animals injected with colchicine and sodium 

 cacodylate, both spindle poisons. A. Spleen of Siredon five days after a single injection 

 of colchicine. The organ has increased in size, and many arrested prophase-metaphases 

 can be observed. These belong mainly to young red blood cells. The longitudinal split- 

 ting of chromosomes can be noticed at some places. (From an unpublished photomi- 

 crograph by Delcourt) B. Accumulation of arrested metaphases of the "ball" type in 

 the intestinal crypts of the small intestine of a mouse. This condition follows injec- 

 tion of sodium cacodylate and is identical to that observed 6 hours after injection of 

 colchicine. Cf. Chapter 17. (From an unpublished photomicrograph from the work of 

 Piton and A. P. Dustin) 



