-8- 



SYNCHRONIZED GROWTH 

 IN TETRAHYMENA CELLS* 



Erik Zeiithen 



CAKLSBERG FOUNDATION 



For the study of the chemical events by which the cell prepares for 

 division and which take the cell through division, the synchronous sys- 

 tems are exceedingly useful. First, because enough material is available 

 for chemical analysis, and second, because one sample of a population 

 serves as a control for other samples in which division is interfered 

 with experimentally. Finally, a synchronous mass population can be 

 considered a tremendously amplified model of a single cell, a model 

 which— unlike the single cell— can be sampled at intervals without in- 

 terfering with the cyclical changes of the cell. Nature has supplied us 

 with only a few naturally synchronized cell systems. The fertilized 

 marine eggs and the anthers of lily flowers are among the best known. 



The system 



Mass population of Tctrahymena pyriformis, strain GL, can be 

 brought into division synchrony by a series of temperature shocks 

 ( Scherbaum and Zeuthen, 1954; Zeuthen and Scherbaum, 1954; Scher- 

 baum and Zeuthen, 1955). At some point of logarithmic growth at 28° 

 C. (optimum), when the population density has not yet exceeded 

 50,000 cells/ml, a series of shifts of the temperature between 28° C. 

 (30 minutes) and 34° C. (30 minutes) is initiated. This "standard pro- 

 cedure" blocks division but permits continued growth to oversized cells. 



* Resttlts not yet published will be fully reported in the Compt. Rend. Lab. 

 Carlsberg by the author alone and in association with Magister Leif Rasmussen 

 and {for the data on glycogen) with Miss Birgit Hegner. 



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