52 Colchicine 



Tetraploid numbers would also develop in animals if colchicine 

 hit a cell in regular anaphase, because the two groups of chromosomes 

 intermingle, fuse, and form a restitution nucleus. ^^ This was demon- 

 strated in grasshopper neiuoblastic cells. This is basic to the develop- 

 ment of triploid animals by treating egg cells at second maturation 

 anaj^hase.*^'"* 



Pycnotic changes are very common ^vhen chromosomes revert to 

 the interphase. This is especially so in mammals where destruction 

 is the fate of most arrested metaphases.-^* ^■^' ^^ Toxic or strong con- 

 centration induces pycnosis. What structural changes occur are dif- 

 ficult to determine. Such changes are discussed imder the section of 

 chromosomal alteration. -'•> ^-^ 



2.6: Alterations of Chromosome Structure 



The most frequent change of the chromosomes in arrested animal 

 mitoses is an abnormal thickness and shortness."'' This is especially 

 evident in arrested and exploded metaphases of mammalian cells. 

 The shortening may be the consequence of an excessive coiling. Very 

 often these chromosomes degenerate, losing all visible structure; only 

 irregular clumps of basophilic material remain scattered in the cyto- 

 plasm, and these in turn fall to pieces.^s Agglutination and fusion 

 are also quite freqtient (Fig. 2.85. 2.8C) .29. ci. 12. 1.3, 24, 1.5 These have 

 been observed in cells where the colchicine action was incomplete and 

 where the spindle was apj^arent,!-^ a fact suggesting that the alkaloid 

 modifies the chromosomes themselves. 



In manmials, the colchicine-mitoses with short and clumped 

 chromosomes are more frequent when the dose of alkaloid is high.^i 

 Animals injected with colchicine show mitotic abnormalities that 

 vary from cell to cell. As an example, the tubules of the kidney con- 

 tain cells with exploded metaphases and shortened chromosomes, 

 while the cells of the renal pelvis show ball metaphases.'^- Short 

 chromosomes are seen in cells of regenerating liveri- when treated 

 with colchicine according to specific schedules of time and concentra- 

 tion. Similar shortening also appears following bile duct ligature,-'"* 

 and in carbon tetrachloride jjoisoning.i"* Such changes were also ob- 

 served in cells of human tissues poisoned with colchicine.^^ The 

 junior author had the luiique experience of following the successive 

 changes in cells of the human body in a clinical case. This occurred 

 when an individual suffering from an overdose of colchicine was 

 brought to the hospital in which the jiuiior author was a staff mem- 

 ber. These effects are described in detail in ChajKer 7. 



There is no clear evidence that their structure is damaeed. In 

 mammalian cells, pycnotic, ball, or star metaphases may often pro- 

 ceed to normal telophase, although many degenerate, the whole cell 

 being then rapidly destroyed. "i There is no clear indication that the 



