Expression of Cu/Zn and Mn superoxide dismutases during bovine embryo development: influence of in vitro culture.

peer reviewedTemporal pattern of expression of Cu/Zn and Mn superoxide dismutases (SODs) was investigated in bovine oocytes and embryos produced in vitro in two different culture conditions and in vivo after superovulation. SODs were examined at a transcriptional level in single oocytes and embryos by reverse transcriptase-polymerase chain reaction (RT-PCR) and, at a protein level, by Western blotting on pools of embryos. mRNA encoding Cu/Zn SOD were detected in in vitro bovine embryos throughout preattachment development as well as in in vivo derived morulae and blastocysts. Transcripts for Mn SOD gene were detected in most immature and in vitro matured oocytes as well as in some zygotes and 5- to 8-cell embryos while no transcript was found at the 9-to 16-cell stage in both culture conditions. In vitro embryonic expression of Mn SOD was detected earlier in the presence of serum. Half of the morulae showed the transcript if cultured with 5% serum while none without serum. At the blastocyst stage Mn SOD could be detected independently of culture conditions. For in vivo-derived embryos Mn SOD transcripts were detected both in morulae and blastocysts. Immunoblotting analyses revealed that Cu/Zn SOD and Mn SOD were also present at a protein level in in vitro-derived zygotes and blastocysts. Together these data demonstrate, for the first time, that Mn SOD is transcribed and that Cu/Zn and Mn SOD proteins are expressed in preimplantation bovine embryos. Finally, they suggest that Mn SOD transcription is altered by in vitro culture conditions

Peroxiredoxins in gametogenesis and embryo development.

Reactive oxygen species have been implicated in gametogenesis and embryo development in animals. As peroxiredoxins are now recognized as important protective antioxidant enzymes as well as modulators of hydrogen peroxide-mediated signaling, we addressed here the putative role of this novel family of peroxidases in gamete maturation and during embryogenesis in mammals and insects

La gestion du changement par la « traduction » : regard critique

Depuis plusieurs années, l’administration publique s’efforce d’améliorer la qualité de ses services en recourant de manière accrue aux TIC. C’est dans ce contexte de déploiement de l’e-gouvernement, que nous sommes intervenus en tant que soutien méthodologique lors de la mise en oeuvre d’un e-projet au sein d’un service public fédéral. Contestant l’idée que la technologie se diffuse, créant à elle seule les usages, nous avons mobilisé pendant deux ans les préceptes et principes de la « sociologie de la traduction » afin d’accompagner le développement du e-projet dans une perspective constructiviste et dynamique. Cependant, ce modèle de gestion du changement ne nous a pas toujours permis de dépasser les réticences et les blocages dus à l’intégration des TIC. Cette contribution apporte un regard critique sur l’approche adoptée, en mettant en lumière les conditions d’utilisation du modèle de la traduction pour qu’il puisse servir de manière efficace en tant que méthode de gestion du changement

Apoptosis at the time of embryo implantation in mouse and rat.

The aim of this review is to summarize the information currently available regarding the occurrence of apoptosis in the developing embryo and in the receptive uterus during the peri-implantation period of gestation. Cell death is detected in the inner cell mass of late pre-implantation embryos as the result of an eliminative process that helps trim the embryonic cell lineages of surplus or dysfunctional stem cells. Cell death is also detected in the epiblastic core of early post-implantation embryos, where the process is implicated in the formation of the pro-amniotic cavity. On the maternal side, uterine epithelial cells situated around the attachment site undergo cell death during the initial phase of implantation in order to facilitate embryo anchorage and access to maternal blood supply. Uterine stromal cells closest to the implantation chamber first transform into decidual cells and then commit suicide to make room for the rapidly growing embryo. Although apoptosis is well recognized as a crucial determinant of successful peri-implantation development, our understanding of the cellular and molecular mechanisms regulating this process clearly lags behind the comprehension of cell death control in other systems

Poly(A) RNA is reduced by half during bovine oocyte maturation but increases when meiotic arrest is maintained with CDK inhibitors.

Variations in the amount of different RNA species were investigated during in vitro maturation of bovine oocytes. Total RNA content was estimated to be 2 ng before meiosis, and after meiosis resumption, no decrease was observed. Ribosomal RNA did not appear to be degraded either, whereas poly(A) RNA was reduced by half after meiosis resumption, from 53 pg to 25 pg per oocyte. Real-time polymerase chain reaction was performed on growth and differentiation factor-9 (GDF-9), on cyclin B1, and on two genes implicated in the resistance to oxidative stress, glucose-6-phosphate-dehydrogenase (G6PD) and peroxiredoxin-6 (PRDX6). When these transcripts were reverse-transcribed with hexamers, the amplification results were not different before or after in vitro maturation. But when reverse transcription was performed with oligo(dT), amplification was dramatically reduced after maturation, except for cyclin B1 mRNA, implying deadenylation without degradation of three transcripts. Although calf oocytes have a lower developmental competence, their poly(A) RNA contents were not different from that of cow oocytes, nor were they differently affected during maturation. When bovine oocytes were maintained in vitro under meiotic arrest with CDK inhibitors, their poly(A) RNA amount increased, but this rise did not change the poly(A) RNA level once maturation was achieved. The increase could not be observed under transcription inhibition and, when impeding transcription and adenylation, the poly(A) RNA decreased to a level normally observed after maturation, in spite of the maintenance of meiotic arrest. These results demonstrate the importance of adenylation and deadenylation processes during in vitro maturation of bovine oocytes

Cell cycle duration at the time of maternal zygotic transition for in vitro produced bovine embryos: effect of oxygen tension and transcription inhibition.

Early embryonic cleavages are mostly regulated by maternal components then control of development progressively depends on newly synthesized zygotic products. The timing of the first cleavages is a way to assess embryo quality. The goal of this study was to evaluate the duration of the fourth cell cycle, at the time of maternal-to-zygotic transition (MZT) in in vitro-produced bovine embryos by means of cinematographic analysis. We found that 75% of the embryos displayed a long fourth cycle (43.5 +/- 5.4 h) whereas the remaining embryos had a very short fourth cell cycle (8.9 +/- 2.9 h). Both groups did not differ in cleavage rhythm up to the eight-cell stage and timing of cavitation and blastocyst expansion was identical. However, embryos with a short fourth cell cycle had a better blastocyst rate than embryos with a long cycle (59% versus 38%, P < 0.01). Total cell number, inner cell mass (ICM):total cell ratio, and hatching rate were identical for blastocysts produced from embryos with either a long or a short fourth cell cycle. In a second experiment, we showed that increasing the oxygen tension, from 5% to 20%, decreased the percentage of embryos with a short fourth cell cycle, from 25% to 11% (P < 0.01), indicating that suboptimal culture conditions can influence the length of this cycle. Finally, we investigated whether fourth cell cycle duration could be influenced by transcription inhibition. With alpha-amanitin added at 18 h postinsemination (HPI), cleavage was reduced (66% versus 79%) and, at 70 HPI, the 9- to 16-cell rate increased (50% versus 25%) concomitantly with a 5- to 8-cell rate decrease (16% versus 47%). A similar pattern was observed when the drug was added at 6 HPI or 42 HPI but not at 0 HPI. Cinematographic analysis revealed that alpha-amanitin increased the first cell cycle duration whereas the second and third cell cycles were not affected. With the drug, one third of the embryos could develop up to the 9- to 16-cell stage and they all had a short fourth cell cycle (11.2 +/- 3.7 h) with a good synchrony of cleavage between blastomeres. These results suggest that duration of the fourth cell cycle of bovine embryo, during the MZT, is under a zygotic transcriptional control that can be affected by oxidative conditions