Browsing by Author "Merchán Vargas, Shirley Lissette"

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    Efecto del cuerpo lúteo sobre la producción in vitro de embriones bovinos y su posterior tolerancia a la criopreservación
    (2019-05-13) Tenemaza Cumbe, Milton Alejandro; Merchán Vargas, Shirley Lissette; Soria Parra, Manuel Elías
    This research was conducted to determine the effect of the corpus luteum on the rate of cleavage of bovine oocytes and the subsequent competence to develop to blastocysts and to tolerate the cryopreservation. The ovaries selected for this study were recovered from the municipal slaughterhouse of Cuenca, from non-pregnant cows with a corpus luteum (CCL) in one ovary (ipsilateral, group 1, CCL) and without CL in the contralateral ovary (group 2; SCL), and of cows without CL in both ovarys (control, group 3; C). The cumulus-oocyte complexes (COCs) were categorized and only those with apt (A and B) quality were included for maturation for 18-24 hours. The COCs were fertilized in vitro and the blastocysts obtained were cryopreserved by vitrification or freezing. From 348 ovaries, 2532 oocytes were obtained in 13 replicates, which, according to quality, 63.8% corresponded to categories (A and B) apt and 36.2% to (C and D) not apt. The proportion of AB oocytes was grater (P <0.05) in CCL (66.6%) than in SCL (61.9%) and C (62.7%). A greater proportion of oocytes from the CCL group cleaved in comparison to the SCL and C (68.3 versus 43.8 and 46.6% respectively; P<0.01). Likewise, a greater proportion of total embryos was obtained in CCL (39.0%) than in SCL (29.2%) and C (29.8%) (P <0.05). From the total of clivated embryos, a greater percentage (P <0.01) of embryos attained the blastocyst stage on day 7 and were cryopreserved, in the CCL group (68.2%) than in SCL (39.8%) and C (38.7%). Embryonic survival after vitrification or freezing determined at 2, 24 and 48 hours was statistically similar among the three study groups. General, the presence of a corpus luteum in the ovary at the time of recovering the oocytes affected the percentage of cleavage and embryo production on day 7, but did not influence the cryotolerance of the blastocysts. In addition, according to these results it is presumed that the effect of the corpus luteum occurred trough local mechanisms.