抄録
It was more than 20 years ago that Breedis et al. (1938) and Mider et al. (1939) reported on the effect of freezing on some transplantable mammalian tumors and the normal skin. Since then many investigations have been made to preserve mammalian tumor cells at a low temperature by Snell et al. (1949), Craigie (1949), Blumenthal et al. (1950), and Warner et al. (1950) . Especially mouse leukemic cells (Gabrielson et al., 1952) and ascites tumor cells (Morgan et al., 1956) made themselves suitable materials to searching for the optimal conditions for storage of animal tumor cells. Recently several mammalian cell lines cultivated in vitro have also been stored successfully for a long term by workers in the fields of tissue culture, virology, cell biology and so on such as Scherer and his colleagues (1954, 1960), Westwood et al. (1957), Swim et al. (1958), van der Veen et al. (1958), Hauschka et al. (1959), Stulberg et al. (1959), and Craven (1960) . The longest case so far reported was of HeLa and L strains (Scherer, 1960) which proved to be viable after 4 to 5 years' storage. In almost all cases, the important condition for successful storage seemed to be the concentration of glycerol mixed with serum or growth medium containing serum as well as the temperature for keeping cells. The optimal concentration of glycerol for many types of cells was revealed to be 5 to 20%, and the temperature to be around -70°C, ranging from -60°C to -80°C.
For the purpose of maintaining cell lines including altered sublines without further changes to give feasible materials to the study on variability of mammalian cells in vitro, several experimental series have been made in this laboratory. The present paper deals with the storage of 15 mammalian cell strains (13 human, a rat and a mouse cell line) . Among them was the strain HeLa which could be kept viable as long as 19 months, showing the capacity of multiplication after thawing. The other lines of the human, rat or mouse origin showed viability and multiplicability after 5 to 12 months' storage. For the strain L derived from the mouse and JTC-6 from the rat, the optimal concentration of glycerol was proved to be less than that for human cell lines.
