IV. ISOLATION OF CHROMATIN THREADS 

 FROM CELL NUCLEI 



Claude and Potter ( 1943) succeeded in isolating chromatin threads 

 from the nuclei of spleen cells from leukemic mice and of liver cells 

 from normal guinea pigs and rats. Apparently these threads are 

 related to the chromosomes. On standing, especially in very dilute 

 salt solution, the filaments disintegrate and seem to be replaced by 

 free refractile granules. In distilled water the threads swell rapidly 

 and finally disappear. 



Claude and Potter Procedure 



Care should be taken to conduct all the operations in a cold room 

 at 0-5°. Grind gently batches of 20-30 g. of the cold tissue with an 

 equal weight of sand in a mortar for 3 min., and progressively add 

 six times the tissue weight of either distilled water or 0.9% sodium 

 chloride soln. having a pH of 7.4. Centrifuge the suspension for 1 

 min. at 1500 times gravity to throw down the sand and tissue debris. 

 Centrifuge the supernatant fluid for 10 min. at 1500 times gravity to 

 sediment the thread-like material, and discard the supernatant. Sus- 

 pend the material from 25 g. of tissue in 35 ml. of the saline soln. by 

 gentle shaking, and centrifuge by bringing to the speed correspond- 

 ing to a force of 1500 times gravity and then cutting off the current 

 in the centrifuge motor. This short "up-and-down run" throws down 

 any remaining sand and tissue debris. Subject the supernatant fluid 

 to another 10 min. centrifugation at 1500 times gravity and follow 

 by resuspension of the sediment in 35 ml. saline soln., another "up- 

 and-down run," and a final 10 min. centrifugation of the super- 

 natant fluid to bring down the white mass of chromatin threads. 



461 



