Follicular development and oocyte quality were assessed by laparoscopic observation and
fertilisation, respectively, in melatonin-treated (Group M) and control (Group C) anoestrous Chios ewes (n = 10 in each group). Fourteen days after melatonin insertion, all ewes had laparoscopic evaluation of the follicular population followed by oocyte pick-up (OPU); on day 22 intravaginal progestagen sponges were inserted for 14 days. Two days after sponge removal the follicular population was re-evaluated and a second follicular aspiration was performed. Collected oocytes from the second OPU underwent
maturation, fertilisation and culture. The number of large follicles was higher in Group M than in the control ewes during the first OPU and tended to be so (P = 0.06) at the second. Morphologically, oocytes collected from controls were of better quality than those from Group M; however, more oocytes collected from melatonintreated animals fertilised and developed
. These results indicate that melatonin is a potent regulator of follicular development and oocyte competence during the anoestrous period of the ewe.
The effects of modification of the in vitro embryo culture media (IVC) with the addition of urokinase-type plasminogen activator (u-PA) on the yield and/or quality of bovine embryos were examined in two experiments. In Experiment 1, denuded embryos were cultured in semi-defined synthetic oviductal fluid (SOF) for seven days, while in Experiment 2 embryos were co-cultured with cumulus cell monolayer in a serum-containing SOF medium. Plasminogen activator activity (PAA) and plasminogen activator inhibition (PAI) were determined in all spent IVC media. At the activity used (5 IU/ml), u-PA had no effect either on in vitro embryo production rates or on embryo quality as revealed by gene expression analysis of 10 important mRNA transcripts related to apoptosis, oxidation, implantation and metabolism. PAA and PAI analysis indicated the need for wellbalanced plasminogen activators and inhibitors as a culture environment for embryo development. However, more research is needed to unveil the mechanism by which u-PA is involved in in vitro embryo production systems.