Effects of melatonin treatment on follicular development and oocyte quality in Chios ewes - short communication.

Follicular development and oocyte quality were assessed by laparoscopic observation and in vitro 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 in vitro 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 in vitro . These results indicate that melatonin is a potent regulator of follicular development and oocyte competence during the anoestrous period of the ewe.

Effect of plasmin, plasminogen activators and a plasmin inhibitor on bovine in vitro embryo production.

In the present study, four experiments were conducted to investigate the possible effects of plasminogen activators (urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator (t-PA)), plasmin, and a plasmin inhibitor (epsilon-aminocaproic acid (epsilon-ACA)) on different stages of bovine in vitro embryo production (IVP). The concentrations of these modifiers in IVP media were conditioned according to the plasminogen activator activity of bovine preovulatory follicular fluid. Media were modified in a single phase of IVP with an 18 h or 24 h incubation for in vitro maturation (IVM) and a 24 h or 48 h incubation for the IVF or in vitro culture (IVC), respectively. After IVM the oocytes were either fixed and stained or underwent IVF and IVC. The main findings were: (1) plasmin added to the 18 h IVM medium increased maturation rate without affecting fertilisation or embryo development rates; (2) t-PA added to the IVF medium significantly increased cleavage; (3) u-PA added to the IVC medium significantly increased embryo development rates; (4) the efficiency of all phases of IVP was reduced after the addition of epsilon-ACA; and (5) plasminogen addition had no effect in any IVP phase tested. We conclude that the members of the plasminogen activator-plasmin system contribute in different ways to bovine IVM, IVF and IVC.