RATE OF SYNTHESIS AND QUANTITATIVE 



VARIATIONS OF THE RIBONUCLEIC ACID 



DURING THE GROWTH OF A CULTURE OF 



POLYTOMELLA COECA* 



R. JEENER 



The cytoplasm of the cells of a colourless flagellate, Polyto- 

 mella coeca, has 50 to 80 per cent of its total proteins bound to 

 ribonucleoprotein particles, resembling those of mammalian 

 liver cells in their speed of sedimentation, their ribonucleic 

 acid (RNA), phospholipid and enzyme content and their 

 extreme heterogeneity (Claude, 1946; Brachet and Jeener, 

 1944; Chantrenne, 1947). 



The study, by means of labelled phosphate, of the RNA 

 increase in a culture oiPolytomella showed apparently that the 

 quantity of RNA synthesized at any instant is proportional 

 to the quantity of RNA present. The only interpretation 

 of this fact which we believe to be pertinent is that the cyto- 

 plasmic particles, to which all the RNA is bound, multiply 

 by autoduplication, as Brachet (1944, 1949a, 1949&, 1951) 

 suggested several times. 



We present here a short survey of some results, which, we 

 believe, bring arguments in favour of this assumption and 

 which will be published with more details elsewhere. 



We study a culture of Polytomella, the growth of which is 

 limited by the complete utilization of the phosphate of the 

 medium, labelled with ^^P at the moment of seeding; to this 

 culture we add a large excess of non-labelled phosphate. The 

 growth of the culture resumes and a particularly rapid protein 

 synthesis begins. The evolution of the RNA (per cell or per 

 unit volume of culture) shows three characteristic phases: a 

 phase of decrease for 2 to 5 hours, followed by a return to the 



♦Part of the communication presented by D. Szafarz. 



184 



