54 



Colchicine 



undergo subsequently several cokhicinc-mitoses, animal cells either 

 remain arrested at j^rophase-metaphase or metaphase, or recover from 

 the action of the drug and, exceptionally, become polyploid. This is 

 true whether in protozoa, invertebrates, amphibians, or mammals; 

 tissue cultures show that colchicine is no more a chromatin poison in 

 animals than in plants. Nor does it appear to affect other nuclear 



mm 



Ot:.-"- • 



B 



D E 



Fig. 2.11 — Action of colchicine on the nuclei of developing eggs of Tubifex. A. After 

 44 hours, no nucleus is visible. Several cytoplasmic condensations (stippled) are notice- 

 able. Yolk platelets are block. B, C. Formation of "pseudonuclei" (black). These are 

 Feulgen-positive, apparently unstructured masses. D. Numerous pseudonuclei in an egg 

 treated for 70 hours with colchicine. E. Control egg at the same stage as D. Note that 

 colchicine has suppressed the cleavage clearly visible in E. (After Woker) 



Structures; there is no mention of any nucleolar changes apart from 

 their possible multiplication in relation to polyploidy. Changes in 

 the nuclear sap will be discussed later. 



2.6-2: Colchicine and X-ray combined. Neoplastic tissues have 

 been subjected to X-ray and colchicine, ^^ but small attention was 

 given to the relation between c-mitosis and the pretreatments that 

 influence the effect of X-ray in normal cells (cf. Chapter 10) . 



Allium root tips pretreated with 0.05 per cent colchicine and then 

 subjected to irradiation showed one-third as many chromatid aberra- 

 tions among colchicinized root tip cells as the controls. ^^ 



