Cellular Growth 125 



Plasticl changes are to be expected in the treated generation. 

 Whether or not changes are retained upon transfer to culture without 

 colchicine remains unconfirmed. Supposedly the elasticity of plastids 

 in S/)iyogyra changes inider the infkicnce of colchicine. ^-'^^ 



Inhibitions at higher concentrations were seciued ^\'ith Gonium 

 and Polystoma. Upon recovery the cells remained diploid as far as 

 the in\estigators were able to judge. Some action seems to have been 

 registered upon the /oospores and zygotes of the green alga Ulva.^'^ 



Studies dealing ^\ith the cell wall and colchicine are of interest 

 from the view of diflerentiation. Cell structure and composition of 

 the wall are modified by colchicine (Table 4.4) . 



4.^-^: Protozoa. A number of investigations^- ^i- -"• -^- ^^' ■''- ■'^- "^• 

 lis, 1.36, 144 oj^ various aspects of colchicine and the protozoa, as well 

 as regenerative studies^'"'" have been published since 1938. As long 

 ago as 1907, the action of colchicine on Payamecium was studied in 

 relation to toxicity and temperature changes.-'^'^ Increasing toxicity 

 -with raising the temperature was demonstrated by this early work. 

 No one has repeated these studies in the modern period, but most 

 have been concerned with cell division and problems of polyploidy. 

 Undoubtedlv the influence of cytology and genetics preconditioned 

 much of the experimentation since 1937. 



The species of protozoa tried for response to colchicine show tliat 

 strong solutions can be tolerated at 22° to 24°C. Fission occurs for 

 a number of species.'^ The microinjections of colchicine gi\e finther 

 information on the penetrability of the drug that may influence the 

 reaction. Failine of the drug to penetrate the cell may be one key 

 in explaining the resistance to colchicine of protozoa as a group. — - 



Some retardation in growth and changes in new cells developing 

 within a culture containing colchicine have been recorded. As a 

 general ride, the direct action of the chemical upon the cell or nucleus 

 has not been demonstrated. Some increases in "radio-sensitivity" ac- 

 companied the prctreatment by colchicine."'' In this case the cells 

 appearetl to be more sensitive to action of the X-ray after a treat- 

 ment.^" 



Table 4.7 may be used as a reference for a survey of work com- 

 pleted upon the j^rotozoa as a group. 



4.5: Differentiation Processes 



Alter a treatment with colchicine the new lea\e->. developing when 

 growth is resumed, ajjpear wrinkled and distorted. Apparently the 

 drug has directly or indirectly caused these new types. Some changes 

 are a residt of chimeras which are discussed in connection with poly- 

 ploidy. \e\. other very similar anomalies caimot l)e conclated directly 

 with an increase in the number of chromosomes. These celhilar and 



