Interests of pregnancy follow-up in cows after embryo transfer : special focusing on IVP & NT

(1996, September 13)

In this report, pregnancies were obtained after extreme in vitro conditions- IVM/F/C of the donor embryos, - IVM, enucleation and artificial activation of the recipient oocytes, - nuclear transfer and ... [more ▼]

In this report, pregnancies were obtained after extreme in vitro conditions- IVM/F/C of the donor embryos, - IVM, enucleation and artificial activation of the recipient oocytes, - nuclear transfer and - IVC of the reconstituted embryos. Even if the incidence of this syndrome is relatively low after embryo transfer, a possible increasing of its occurence cannot be excluded in correlation with an incomplete maturation of oocytes at the time of fertilization, smaller follicles giving non competent or partially competent oocytes. An other explanation of this syndrome resulting in the higher variation in newborn calves weight may be also partly explained by the in vitro conditions. The gametes and/or embryos may be submitted to media containing embryotoxic substances. In the other hand, gametes and/or embryos may not found embryotrophic substances in the media like growth factors... Owing to this phenomenon, strict recommendations should be followed concerning rigorous follow-up of pregnancies obtained after transfer of IVM/IVF/IVC or cloned embryos by pregnancy proteins (PSPB, PAG...) or hormone (placental lactogen, estrone sulfate) assay and, after birth, macroscopic examinations of newborn, cord and caroncules. [less ▲]

Assessment of nuclear totipotency of fetal bovine diploid germ cells by nuclear transfer.

in Theriogenology (1996), 46(5), 871-80

Nuclear transfer was used to study nuclear reprogramming of fetal diploid bovine germ cells collected at two stages of the fetal development. In the first case, germ cells of both sexes were collected ... [more ▼]

Nuclear transfer was used to study nuclear reprogramming of fetal diploid bovine germ cells collected at two stages of the fetal development. In the first case, germ cells of both sexes were collected during their period of intragonadal mitotic multiplication at 48 days post coitum (d.p.c.). In the second case, only male germ cells were collected after this period, between 105 and 185 d.p.c. Isolated germ cells were fused with enucleated oocytes. Reconstituted embryos were cultured in vitro and those reaching the compacted morula or blastocyst stage were transferred into synchronous recipient heifers. Of 511 reconstituted embryos with 48 d.p.c. germ cells (309 males and 202 females), 48% (247/511 ) cleaved; 2.7% (14/511 ) reached the compacted morula stage and 8 of them the blastocyst stage (1.6%). No difference was observed between sexes. All 14 compacted morulae/blastocysts were transferred into 6 recipients and one pregnancy was initiated. This recipient was slaughtered at Day 35 and an abnormal conceptus (extended trophectoderm and degenerated embryo) was collected. Its male sex, genetically determined, corresponded to that of donor fetus. Of 380 reconstituted embryos with male 105 to 185 d.p.c. germ cells, 72.1% (274/380 ) cleaved, 2.1% (8 380 ) reached the compact morula stage and 7 of these the blastocyst stage (1.8%). Three blastocysts and one morula were transferred into 4 recipients. Two became pregnant at Day 21 but only one at Day 35 which aborted around Day 40. Our results show that the nucleus of diploid bovine germ cells of both sexes can be reprogrammed. However, in the absence of further development of these reconstituted embryos, nuclear totipotency of bovine diploid germ cells remains to be evidenced. [less ▲]