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B. Vigier, Dien Tran, F. du Mesnil du Buisson, Y. Heyman and Nathalie Josso

Summary. Monoclonal antibodies against bovine anti-Müllerian hormone (AMH) were used to study the hormone in cattle. Anti-Müllerian activity of testicular tissue, immunoreactive testicular AMH, serum AMH concentration and AMH production by incubated testicular tissue were detectable from 42 days, i.e. at the time of seminiferous tubule differentiation, and peaked between 50 and 80 days, when the Müllerian ducts regress in the male fetus. All the values stabilized at a lower level until 30 days after birth and then slowly decreased. At 18 months, only traces of AMH immunoreactivity were detectable in testicular tissue and serum concentration and AMH production by incubated testicular tissue were negligible; the main source of AMH in the adult animal was the rete testis fluid. Study of the disappearance rate of AMH from the serum of castrated calves gave a half-life of approximately 2 days for bovine AMH.

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Y Du, C S Pribenszky, M Molnár, X Zhang, H Yang, M Kuwayama, A M Pedersen, K Villemoes, L Bolund and G Vajta

The purpose of the present study was to improve cryotolerance using high hydrostatic pressure (HHP) pretreatment of porcine in vitro matured (IVM) oocytes, to facilitate their further developmental competence after parthenogenetic activation. A total of 1668 porcine IVM oocytes were used in our present study. The pressure tolerance and optimal duration of recovery after HHP treatment were determined. Oocytes were treated with either 20 or 40 MPa (200 and 400 times greater than atmospheric pressure) for 60 min, with an interval of 10, 70, and 130 min between pressure treatment and subsequent vitrification under each pressure parameter. Oocytes from all vitrification groups had much lower developmental competence than fresh oocytes (P<0.01) measured as cleavage and blastocyst rates. However, significantly higher blastocyst rates (P<0.01) were obtained in the groups of 20 MPa pressure, with either 70 (11.4±2.4%) or 130 (13.1±3.2%) min recovery, when compared with the vitrification control group without HHP treatment where no blastocysts were obtained. The influence of temperature at HHP treatment on further embryo development was also investigated. Treatments of 20 MPa with 70 min recovery were performed at 37 °C or 25 °C. Oocytes pressurized at 37 °C had a significantly higher blastocyst (14.1±1.4%) rate than those treated at 25 °C (5.3±1.1%; P<0.01). Our results demonstrate that HHP pretreatment could considerably improve the developmental competence of vitrified pig in vitro matured (IVM) oocytes. The HHP pretreatment will be tested as a means to improve survival and developmental competence at different developmental stages in different species including humans.