Comparison of Two Different Protocols for Induction of Parturition in Heifers with or without Estradiol Benzoate

Objectives of this study were to investigate the efficacy of dexamethasone in combination with estradiol benzoate in controlled induction of parturition in heifers, especially in the subjects of retained fetal membranes and dystocia caused by fetal oversize. A total number of 100 Holstein-Friesian heifers aged 24-25 months, mean weight 450 kg and body condition score of 3-4 from a dairy herd located in the suburb of Tabriz with similar nutrition and management systems were allocated at random into two groups. Group A （Control, n = 50） heifers, after passing the minimum 270 d of pregnancy were injected with 30 mg dexamethasone IM. Group B （Treatment, n = 50） heifers with the same period of pregnancy received 30 mg dexamethasone plus 20 mg estradiol benzoate IM on the same days of pregnancy. The overall durations of initial treatments to induction of parturition were （41.50 ~ 2.65） h in group A and （37.50 ：i： 1.27） h in group B. In group A, more dystocia cases were observed than in group B. After parturition, group A showed a higher percentage of retention of fetal membranes as well as the calf mortality and dystocia compared to group B. The differences between two groups were statistically significant （P 〈 0.05）. In conclusion, our results indicate that induction of parturition by estradiol benzoate and dexamethasone together will be more effective than dexamethasone alone because of the less retention of fetal membranes, easy calving and shorter time from induction to parturition.

Factors of Fetal Origin in the Regulation of Labor Initiation and Preterm Birth

Preterm birth is the leading cause of mortality and morbidity in newborns and children under 5 years-of-age.In order to improve the survival rate and quality of preterm infants,there is critical need to identify the specific mechanisms underlying the initiation of labor.Pregnancy represents a period of constant interactive dialog between mother and fetus.A disturbance in the pattern of maternal-fetal communication can induce physiological or pathological labor.Although a number of studies have investigated the contributions of maternal factors to the initiation of labor,the concept that fetal organ development and maternal adaptation are coordinated has emerged over recent years,thus emphasizing that factors of fetal origin may serve as hormonal signals for the initiation of labor.In this review,we summarize and discuss several specific mechanisms by which factors of fetal origin may influence parturition during term or preterm labor,including the specific regulation of fetal organs,including the lungs and accessory organs during pregnancy.Future research may focus on the specific pathways by which signals from the fetal lungs and other fetal organs interact with the maternal system to initiate eventual labor.

Characterization of urocortin in human pregnancy

Objective To examine whether urocortin is produced locally to regulate utero-placental vascular tone during pregnancy.Methods We examined the distribution of urocortin in human placenta, fetal membranes and uterine tissue at term in the presence and absence of labor using a urocortin antibody produced in our laboratory and the immunoperoxidase staining method. Subsequently, we tested urocortin secretion from chorio-decidual cells in vitro using an immunoblot technique. Then, we tested whether urocortin is present in maternal plasma throughout gestation using a radioimmunoassay. A Sephadex G-50 column was used to examine whether immunoreactive urocortin (IR-urocortin) in maternal plasma is the same as synthetic urocortin.Results IR-urocortin was observed in vascular smooth muscle of myometrium decidual stromal cells, syncytiotrophoblast and amnion epithelium. No differences in staining intensity for urocortin were detected between tissues obtained in the absence or presence of labor. Staining intensity for IR-urocortin was greatest in the decidua, suggesting this may be the main site of urocortin production. Positive staining for urocortin was observed in 40% of chorio-decidual cells with 34% of these cells secreting urocortin under basal conditions. Urocortin was detectable in maternal plasma from 16 weeks gestation and concentrations did not change as gestation progressed. IR-urocortin in the maternal plasma eluted from a Sephadex G-50 column at the same site as synthetic urocortin and had a calculated retention co-efficient of 0.44.Conclusion This study indicates that urocortin is produced by the decidua during human pregnancy and is detectable in maternal plasma. These data are consistent with the hypothesis that urocortin is produced locally by the decidua and may act to regulate utero-placental blood flow.