CYTOCHEMICAL OBSERVATIONS 5 



correlation between RNA content and protein synthesis has been 

 found. The same is also true for plant cells. For instance, in roots of 

 Vicia faba (Jensen, 1955) and in the alga Acetabularia, the RNA 

 content of the nucleolus decreases when the organism stops growing 

 after it has been left in the dark for some weeks (Stich, 1951). Of 

 interest, in the same respect, is a report of Turian (1956), who con- 

 cludes that heteroauxin awakens the activity of the RNA system 

 for protein synthesis. 



This series of examples clearly shows that we are dealing with a 

 very general phenomenon, which occurs in all living organisms, 

 even when they are submitted to abnormal experimental conditions. 

 One objection could, however, be made. Although cytochemical 

 methods can give an idea of the RNA content of the cell, they yield 

 no information about the rate of protein synthesis. It was logical 

 for Caspersson (1941) and Brachet (1942) to think that gland cells 

 or rapidly dividing cells are the site of extensive protein synthesis, 

 but it must be admitted that no proof of that contention was given 

 at that time. 



It is for this reason that, in collaboration with Dr. Ficq, we tried 

 to establish a correlation between basophilia and incorporation of 

 labeled phenylalanine in the various organs of the mouse (Ficq and 

 Brachet, 1956). By combining Unna staining with a track auto- 

 radiography method, it was possible to show that, in short-time 

 experiments, there is an excellent correlation between the intensity 

 of pyronine staining and the incorporation of the labeled amino 

 acid into the proteins. As shown in Fig. 5 (p. 13), the strongly 

 basophilic exocrine pancreas shows much greater incorporation of 

 the labeled phenylalanine into its proteins than the islets of Langer- 

 hans which are poorer in RNA. Heart muscle, as one might expect 

 from its low basophilia, shows very little radioactivity (Fig. 6, 

 p. 14). Similar observations with the same method were made on 

 reticulocytes by Gavosto and Rechenmann (1954). They found that 

 RNA content and incorporation of glycine into proteins decrease 

 simultaneously during red blood cell formation. 



Results almost identical to those of Ficq and Brachet (1956) have 

 been independently reported by Niklas and Oehlert (1956), who 



References, p. 50154 



