We show that, within a meson-exchange dynamical model describing most of the existing pion electromagnetic production data up to the second resonance region, one is also able to obtain a good agreement with the π 0 photo-and electroproduction data near threshold. The potentials used in the model are derived from an effective chiral Lagrangian. The only sizable discrepancy between our results and the data is in the P −wave amplitude P 3 = 2M 1+ + M 1− where our prediction underestimate the data by about 20%. In the case of π 0 production, the effects of final state interaction in the threshold region are nearly saturated by single charge exchange rescattering. This indicates that in ChPT it might be sufficient to carry out the calculation just up to one-loop diagrams for threshold neutral pion production.Chiral perturbation theory (ChPT) provides us with a systematic scheme to describe the low energy interactions of Goldstone bosons among themselves and with other hadrons, because it is based on a low energy effective field theory respecting the symmetries of QCD, in particular chiral symmetry. There is generally good agreement between the ChPT pre-

p E 0 + multipole. The S 11 channel is of interest for several reasons. First of all, the first resonance S 11 (1535), which lies only 48 MeV above the ηN threshold, has a remarkably large ηN branching ratio. This necessitates the inclusion of the ηN channel into our MEX πN model. Secondly, the analyses based solely on pion photoproduction always underestimate the A p 1/2 helicity amplitude of S 11 (1535) with a value around 60 × 10 −3 GeV −1/2 , while extractions

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BackgroundThe use of oral progestin has been shown to effectively prevent luteining hormone (LH) surge during ovarian stimulation with daily human menopausal gonadotropin injections. This study was aimed to investigate the efficacy of long-acting follicle stimulating hormone (long-acting FSH; corifollitropin alfa, Elonva®) use in progestin-primed ovarian stimulation for normal and high responders undergoing IVF/ICSI.MethodsThis is a retrospective and proof-of-concept study. We developed an extremely patient-friendly protocol to be applied to forty-five normal or high responders, in which a single injection of corifollitropin alfa (Elonva®) was administered and medroxyprogesterone acetate (MPA) was taken orally every day from the day after Elonva injection to the day of trigger. Seven days after Elonva injection, folliculometry and hormone tests were performed, followed by short-acting daily FSH/LH injections, if needed, until the day before trigger. Duration of stimulation, number of injections and visits before trigger, incidence of premature LH surge, the number of oocytes retrieved, fertilization rate, cleavage rate, the rate of day 2 good embryos available, and cumulative ongoing pregnancy rate per retrieval were assessed.ResultsThe average age of the population was 34.7 years. Duration of stimulation was 9.4 days in average. Before trigger, only 3.6 injection shots and 1.4 visits were needed on average. There was no case of premature LH surge. Number of oocytes retrieved was 13.7, fertilization rate was 79.04%, cleavage rate was 91.11%, and day 2 good embryo rate was 64.34%, in average respectively. There was no case of ovarian hyperstimulation syndrome. The cumulative ongoing pregnancy rate per oocyte retrieval achieved a satisfactory level as 53.1%.ConclusionsOur protocol consisting of long-acting FSH injection and oral MPA preventing LH surge reduces the number of injections and visits to an extreme and achieves a satisfactory reproductive outcome, and, therefore, is a really patient-friendly and effective approach to ovarian stimulation.