Three-dimensional analysis of fibrillar centers and associated chromatin in the nucleolus of human oocytes in primordial follicles.

The intranucleolar localization of fibrillar centers and their relationships with nucleolus-associated chromatin were determined in stereopairs of human oocyte nucleoli obtained by computer reconstruction of serial sections. This study showed that there was no numerical relationship between the number of fibrillar centers and the number of chromosomal NORs. The three-dimensional reconstruction demonstrated that the majority of fibrillar centers was directly connected with the nucleolus-associated chromatin.

[Incidence of the morphological aspect on the rate of implantation of embryos obtained by fertilization in vitro]. / Incidence de l'aspect morphologique sur le taux d'implantation des embryons obtenus par fécondation in vitro.

1350 embryos obtained by In Vitro Fertilization (IVF) have been examined with the reverse microscope before their transfer in utero. Some embryos are "morphologically normal" (34.7%); some others are atypical. It is difficult to determinate the implantation rate by embryo according to morphological aspect because, most of the time we transfer several embryos to only one patient and we do not know, in case of pregnancy, which one or which ones have developed. Nevertheless, we have tried to appreciate, for 500 embryos transfers after IVF, the incidence of morphological aspect according to the presence or absence of "morphologically normal" embryos. The implantation rate is significantly higher in the groups in which you find "morphological normal" embryos than in the group where they are missing. (19.7% and 19.2% vs 10.2%). It seems that the aspect of the embryo when it is transferred, has an incidence on its future development.

Nucleolar changes in human embryo during the pre-implantation stage. Activation of ribosomal genes during the nucleologenesis.

We studied the structural and functional organization of human embryo nucleoli during the pre-implantation stage from spare embryos obtained by in vitro fertilization. In human embryo nucleoli, structural modifications occur during the first cleavages. They lead to the constitution of a reticulated nucleolus from an initial structure called primary nucleolus. They appear during the third cleavage and correspond to the nucleogenesis. Autoradiography shows no transcription in the primary nucleolus. Transcription of rDNA starts on the periphery of the initial structure after the 4-cell stage. It corresponds to the beginning of the embryonic gene expression. The entire nucleolus will be progressively concerned by this transcription during the reticulation. Silver staining at the ultrastructural level shows that Ag-NOR proteins are missing in the primary nucleolus. In the beginning of nucleogenesis, Ag-NOR proteins are first located on the nucleolar periphery. Their following distribution corresponds to the structures containing rDNA in the nucleolus. Nucleologenesis in the human embryo during the pre-implantation stage first requires an association of rDNA with a primary structure, then an activation of ribosomal genes.

[Estimation of the quality of embryos obtained during fertilization in vitro as a function of their morphology]. / Appréciation de la qualité des embryons obtenus lors de la fécondation in vitro en fonction de leur morphologie.

Embryo quality after IVF should allow provisions for their pregnancy potential. We have classified all the transferred embryos into 4 types according to morphological criteria and we have studied the implantation rate of the different types. The results show: That pregnancies have been obtained with the 4 types of embryos. That it has been impossible to demonstrate statistically significant differences between the different types of transferred embryos even if embryos morphologically normal seem to be more favourable than others to induce a pregnancy. That the average implantation rate for each transferred embryo is of 14.4%.

Pregnancies after ICSI using sperm with abnormal head-tail junction from two brothers: case report.

We report ICSI pregnancies in two couples with a history of long standing primary infertility in which the sperm of the male partner were either acephalic or had abnormal head-midpiece attachments. The two couples, in which the men are brothers, underwent ICSI. Sperm were analysed by transmission electron microscopy and immunocytochemistry with an anti-MPM2 monoclonal antibody. The first couple underwent two ICSI cycles, each consisting of the injection of two mature oocytes and the transfer of two embryos. A successful pregnancy occurred after the second transfer and led to the birth to a healthy girl. The second couple underwent three ICSI cycles, each consisting of the injection of 18 oocytes and the transfer of two embryos; the last of these led to a triple ongoing pregnancy which included two identical twins. Caesarean section led to the birth of three fetal-growth restricted children. This case report demonstrates that ongoing pregnancies can be achieved in cases of abnormal development of the head-neck attachment. The genetic origin of this syndrome is generally accepted, but the phenotypic heterogeneity observed by light and electron microscopy among published cases suggests that there are a variety of genetic causes of this syndrome.