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CHAPTER 3
Comparison and optimisation of porcine oocyte
maturation following synchronisation by CHX or
cAMP
3.1 INTRODUCTION
The developmental competence of mammalian oocytes is dependent upon successful
maturation in vivo or in vitro. Oocyte maturation is the final step of oogenesis and
results in the formation of oocytes capable of being fertilised. It is carried out by
meiosis and involves development of the capacity for nuclear membrane breakdown
and for meiotic progression from the diplotene stage of the first meiotic prophase (PI)
to MII stage (Picton and Gosden, 1998).
In vitro maturation (IVM) is the technique of culturing immature oocytes obtained
from antral follicles to allow them to resume meiosis and complete maturation in
vitro. IVM has been developed in many species including rabbits (Pincus and
Enzmann, 1935), mice (Moricard and Fonbrune, 1937), human (Pincus and Saunders,
1939; Edwards, 1965), rats (Edwards, 1962), hamsters (Edwards, 1962), monkeys
(Edwards, 1962; Edwards, 1965), cows (Edwards, 1965) and sheep (Edwards, 1965).
In pigs, IVM was first reported by Edwards (1965), however, compared to other farm
animal species the maturation period is prolonged and characterised by a high level of
asynchrony between oocytes. On reaching MII, oocytes begin ageing which is
characterised by an increase in spontaneous oocyte activation and a
drop in MPF
activities as is discussed in Chapter 1. This asynchrony between porcine oocytes
during maturation may have significant effects on subsequent development following
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