The Effect of Cooling Regimens on the Transplantation Potential of Marrow

These experiments were designed to identify those portions of the cooling curve, variations in which most affect the repopulating potential of thawed marrow. Murine bone marrow was suspended in Hanks' solution containing 12% glycerol and 4% calf serum. One ml samples of this suspension were frozen at controlled cooling rates and after thawing the transplantation potential of each sample was bioassayed. The bioassay was based on the colony producing potential of hematopoietic tissue injected into lethally irradiated mice. The cooling curve was divided into five separate phases each of which was studied independently at several levels. At the levels studied, the rate of cooling to freezing, the duration of the pre‐freezing plateau and the temperature at which freezing was initiated did not affect the repopulating potential of marrow. However, the repopulating potential of marrow decreased in a linear fashion as: (1) the post‐freezing plateau was lengthened or (2) as the rate of cooling from freezing to —100 C was increased.