ABSTRACT
Much of the information we know today about solution effects during controlled-rate freezing comes from previously published works. Specifi cally, those papers published between 1950 and 1980. Therefore, the topic of solution effects is not new, but actually very old, especially if one considers the works of Luyet, (1,2), for example. These early works have laid the foundation for modern cryobiology, at least as it applies to the storage of mammalian cells, including oocytes and embryos. The information in the collective works of Lovelock, Meryman, Mazur, Polge, Smith, Levitt, Farrant, Willadsen, Luyet and company provide us an invaluable resource from which we can continue to learn about the effects of cryopreservation on cells. It is therefore benefi cial to review some of these manuscripts in order to comment on the principles of controlledrate cooling. The idea of solution effects or how the intracellular environment as well as the extracellular environment will impact the cells during cooling comes into play. These effects can also be described, if only in part, due to our incomplete understanding of exactly what happens during any form of cellular cooling and/or freezing. The importance of having a general understanding of solution effects, and for that matter, of controlled-rate cooling, is so that we are better able to understand how to freeze cells in such a way that they can remain viable upon rewarming. This chapter will therefore discuss the principles and the practical applications of controlled-rate cooling and solution effects. For the purposes of this book, I will focus on mammalian oocytes. What is confusing, or can be, is that the principles or theoretical ideas about solution effects and cooling, and how to cool to obtain viability, sometimes do not work when applied to a dynamic and complex system such as a living cell. Discussions of this type may best serve as a starting point for evaluating the complexities of cellular cryopreservation. Practical application of principles and/or theories leads to interesting and often unexpected results. The unexpected results we obtain then have us thinking of ways to explain them in a scientifi cally sound manner.
