Françoise Urner

Localization of Tyrosine Phosphorylated Proteins in Human Sperm and Relation to Capacitation and Zona Pellucida Binding

Abstract Mammalian sperm must undergo a process known as capacitation before fertilization can take place. A key intracellular event that occurs during capacitation is protein tyrosine phosphorylation. The objective of this study was to investigate and visualize protein tyrosine phosphorylation patterns in human sperm during capacitation and interaction with the zona pellucida. The presence of specific patterns was also assessed in relation to the fertilizing capacity of the spermatozoa after in vitro fertilization. Protein tyrosine phosphorylation was investigated by immunofluorescence. Phosphorylation increased significantly with capacitation and was localized mainly to the principal piece of human sperm. Following binding to the zona pellucida, the percentage of sperm with phosphotyrosine residues localized to both the neck and the principal piece was significantly higher in bound sperm than in capacitated sperm in suspension. When the percentage of principal piece-positive sperm present after capacitation was <7%, fertilization rates after in vitro fertilization were reduced. Different compartments of human spermatozoa undergo a specific sequence of phosphorylation during both capacitation and upon binding to the zona pellucida. Tyrosine phosphorylation in the principal and neck piece may be considered a prerequisite for fertilization in humans.

Estradiol Receptors in the Urethra and the Bladder of the Female Rabbit

The presence of estradiol receptors was investigated in urethral and bladder tissue of mature pregnant and nonpregnant rabbits. Cytosolic fraction and nuclei were incubated with tritiated estradiol (3H-E2) at concentrations from 1 nM to 20 nM at 30 degrees C for 3 h with or without a 100-fold excess of diethylstilbestrol (DES). Incubation at 30 degrees C was selected so as to measure both occupied and unoccupied binding sites. The number of binding sites and their association constants were calculated by Scatchard analysis. Cytosolic binding sites for estradiol with high affinity (Ka = 0.31-0.58 X 10(9) M-1) were found in urethral tissue (785 fmol/mg DNA) and in bladder tissue (771 fmol/mg DNA). These results suggest that lower urinary tract of female rabbit could be a target organ for estradiol.

Number of transferred embryos: How to reduce multiple pregnancies

Abstract: Because the diagnostic tools for predicting whether an early cleavage stage embryo can lead to a viable pregnancy are still elusive, transfer of more than one embryo remains quite common. However, the only way to reduce multiple pregnancies, considered as the main adverse effect of assisted reproductive technology, is to transfer a single embryo. In countries such as Switzerland and Germany, the law allows cryopreservation only at the 2‐pronuclear stage. This restricts considerably the possibility of selecting the embryos to be transferred. Therefore, a good cryopreservation program at the 2‐pronuclear stage is an essential tool to optimize the efficiency of in vitro fertilization (IVF). We therefore recommend the Cumulated Singleton Delivery Rate (CUSIDERA) as a measure of standard IVF efficiency. This rate averages approximately 23.5% when calculated over the last 10 years in our unit and reaches a value above 35% for patients with more than 10 zygotes. Elective single‐embryo transfers and the decrease of iatrogenic multiple pregnancies in IVF remain dependent on better prognostic tools for the appropriate selection of patients, gametes, and zygotes.