-210 Nottingham - Nottingham eTheses - The University of Nottingham

In addition to the listed benefits of cAMP treatment for porcine SCNT, cAMP
treatment was also preferred in terms of cost and timing of experiments. Hormones
(PMSG and hCG) are required to be added in the maturation media throughout IVM
for CHX treatment even after oocytes were released from CHX. This needed extra
hormones to wash oocytes when released from CHX treatment. In contrast, hormones
were only needed for cAMP treated oocytes during the first 22 h of culture, as was
cheaper than CHX treatment. For the experimental timing, it is a better timing to
change media after 22 h than 12 h avoiding working in the night or dawn shift.
Furthermore, cAMP inhibition in meiotic resumption has been reported in mouse, rat,
porcine, bovine, rabbit and even human oocytes (Cho et al., 1974; Magnusson and
Hillensjö, 1977; Rice and McGaughey, 1981; Sirard and First, 1988; Hosoi et al., 1989;
T hell
and Hillensjö, 1993). However, protein synthesis plays an important role in the
maturation of mammalian oocytes but there are species differences in the requirement
of protein synthesis for GVBD. CHX can block GVBD in porcine, ovine and bovine
oocytes but not murine oocytes (Fulka et al., 1986; Moor and Crosby, 1986; Hunter
and Moor, 1987). GVBD in mouse oocytes occurs independently of protein synthesis
(Fulka et al., 1986). In addition, CHX reduced the developmental competence of
bovine oocytes (Lonergan et al., 1998).
For SCNT, timing for enucleation is also important. In the second experiment, I
determined the changes of the meiotic progression of cAMP treated oocytes between
38 hpm and 44 hpm mainly for the timing of TI enucleation. However, in experiments
in Chapter 3, the percentage of MII oocytes among total cAMP treated oocytes
increased rapidly after 36 hpm. Data obtained combined with former experiment in
Chapter 3 (section 3.3.3) suggested that the majority of cAMP treated oocytes
progressed to MII stage between 36 hpm and 44 hpm whilst the proportion of MI and
AI/TI oocytes reduced significantly at 38 hpm, indicating 36 -38 hpm could be a
suitable time window in which to enucleate porcine oocytes. Both TI and AI/TI
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