CELL DIVISION AND PROTEIN SYNTHESIS 547 



place after the termination of the last temperature shock and up to a time 

 when two synchronous divisions have displayed themsehes. This is 

 perhaps not so strange since Telrahyuuua is highly polyploid and probably 

 becomes even more so when it is synchronized. 



According to our interpretations Tetrahyuufia cells }iiiist produce 

 "di\ision proteins" before e\ery di\ision. This is so whether the cells are 

 in the logarithmic growth phase, whether they are synchronized and grow 

 in proteose-peptone, or, most importantly, whether they perform syn- 

 chronous divisions without growth. During the period of cycling tempera- 

 ture used for the synchronization Tctnihymeiia grows large and produces 

 a lot of proteins. However, it fails to produce "division proteins" to the 

 level required for a single di\ision. In tact we consider that the synchrony 

 is induced because at EH all cells are equally low in "division proteins" 

 which later, at constant 28' C, are produced synchronously to give rise 

 to the first synchronous di\"ision in standard time. 



For the synchronized cells in proteose-peptone increases in respiration, 

 in dry matter, and in protein synthesis are discontinuous (review by 

 Zeuthen [13]). In all these measures synthesis is slowed around division. 

 The synthesis of " di\ision proteins" is likely to be a small traction of the 

 total since it is obser\ed also in starving cells. It may or it may not follow 

 total synthesis and it mav or may not be continuous through a series of 

 divisions. Howex er, that part of the synthesis which conditions a division 

 seems to be sharply delimited and goes from 40-50 min. before one to 

 40- :;o min. before the next synchronous tission. The way we interpret our 

 results is that firstly the cell charges itself to a threshold level with 

 "division protein". Then, around 40 50 min. before synchronous tission 

 all "division protein" changes from a state in which it will decay in the 

 presence of /)-FPhe, to a state when it will not. So we think that stabiliza- 

 tion has suddenly taken place. And this stabilization would be a condition 

 for all the kinetic phases of the di\ ision process later to take place. 



The drop before division i from maximum to no capacity to become 

 set-back bv /)-FPhe occurs at the time when the anarchic tield [3, 9] is 

 just beginning to organize into the definiti\e oral membranelles of the 

 second mouth. This is personal information from Dr. Joseph Frankel 

 obtained under identical conditions in our laboratory. 



This new orientation in space of previously synthesized kinetosomes 

 may be one of the earliest manifestations of the action of the stabilized 

 " division protein ". 



The work reported will be published in the C. R. Lab. Carhherg by 

 Rose E. Cerroni, Leif Rasmussen and the author. 



References 



1. Christensson, E., Acta pJiysifd. scaml. 45, 339 (1959). 



2. Hamburger, K., and Zeuthen, E., C. R. Lab. Carhhci-i:; 32, i ('i960'). 



