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May 26, 1945


JAMA. 1945;128(4):290-291. doi:10.1001/jama.1945.02860210046014

In 1943 Claude and Potter1 of the Rockefeller Institute isolated chromatin threads from the resting nuclei by purely mechanical means. The frozen spleens of leukemic rats were thawed and ground gently for three minutes with an equal weight of beach sand. With the temperature below 5 C. the resulting mixture was suspended in six times its weight of isotonic solution of sodium chloride, the suspension being maintained at pH 7.4 throughout the experiment. The suspension was then centrifuged for one minute in an ordinary laboratory centrifuge (1,500 × gravity) and the resulting sediment discarded. The supernatant fluid was then submitted to ten minutes' centrifugation at the same speed. This "long run" centrifugation brought down an abundant sediment of threadlike material. The threadlike precipitate was resuspended in slightly more than an equal volume of saline solution and the "long run" centrifuging repeated two times. The entire process was completed