Some experiences with the preservation of tumour materials in liquid nitrogen

Abstract

Testing more than forty tumour strains from different kinds of animals and of different types, we found that equipment consisting of a BF- 3 freezer with additives and liquid nitrogen is useful for freezing down the tumour material at low rates. A supercooling effect has been observed which is deleterious for tumour viability when freezing is carried out automatically. It can be overcome by regulating the influx of liquid nitrogen into the deep freezer by hand during the critical times. The simple freezing medium used consisting of Hanks balanced salt solution with the addition of Glycerol ( 5%) or DMSO ( 7·5%) only is sufficient for most of the tumour strains tested, some of which however cannot be preserved with this preservation process. Studies are in progress to solve this problem.