, whereas the TE forms chorionic membrane and later becomes a major part of the conceptus placenta. Because fertilized eggs in most mammalian species lack yolk sac development, the conceptus must form the placenta to receive nutrients and gases from the
Kazuhiko Imakawa, Rulan Bai, Hiroshi Fujiwara, Atsushi Ideta, Yoshito Aoyagi and Kazuya Kusama
Agnieszka Waclawik and Adam J Ziecik
Introduction Maternal recognition of pregnancy requires reciprocal communication between the pre-implantation conceptus (embryo and associated membranes) and maternal system: uterine endometrium and corpus luteum (CL). In the pig
P. V. HOLMES and A. D. DICKSON
Post-coital unilateral ovariectomy in rabbits (Little, Haynes & Lamming, 1970), rats (Lamming & Little, 1968) and mice (Bruce, Renwick & Finn, 1968) impairs embryonic survival in the ipsilateral uterine horn. These findings suggest that each ovary controls conceptus survival in its adjacent uterine horn. The existence of such a mechanism has been disputed in the rat (Wu & Dickmann, 1971) and mouse (McLaren, 1970), and conflicts with the premises involved in induction of bilateral blastocyst implantation after ovariectomy using exogenous hormones. McLaren (1970) worked with the Q strain, and Bruce et al. (1968) demonstrated a variation of the local effect between the P and TO strains. Our aim was to uncover any local effect in a fourth strain of mice.
Swiss Webster albino mice were maintained and anaesthetized as described previously (Holmes & Dickson, 1971). Bilaterally ovariectomized, sham bilaterally ovariectomized, left unilaterally ovariectomized and right unilaterally ovariectomized groups were studied.
J. L. Vallet, F. W. Bazer, C.J. Ashworth, H. M. Johnson and C. H. Pontzer
A radioimmunoassay has been developed for quantitation of ovine trophoblast protein-1 (oTP-1), a sheep conceptus secretory protein which allows for maintenance of the corpus luteum during early pregnancy. The assay was validated for dialysed and undialysed culture medium and pregnant uterine flushings ranging from no dilution (neat) to dilutions of 1:2500 for dialysed media, 1:100-1:1000 for undialysed media and 1:50-1:1000 for pregnant uterine flushings. The assay accurately measured oTP-1 added to undiluted and diluted dialysed and undialysed culture media and pregnant uterine flushings. No cross-reaction was detectable for bovine α or γ interferon, bovine calmodulin, feline conceptus secretory proteins, equine conceptus secretory proteins, porcine conceptus secretory proteins, bovine conceptus secretory proteins and proteins in a uterine flushing collected from a non-pregnant ewe. Immunoreactivity in the assay matched that for oTP-1 throughout oTP-1 purification. This assay is the first validated assay which may be used to quantitate production of oTP-1 in culture or content of oTP-1 in uterine flushings.
R. M. MOOR, L. E. A. ROWSON, MARY F. HAY and B. V. CALDWELL
Interruption of pregnancy occurred in 25 out of 57 unilaterally pregnant sheep after gonadotrophins (pregnant mare serum and human chorionic gonadotrophin) had been injected at various times, ranging from day 17 to 70, in order to induce additional corpora lutea. The conceptus became moribund before luteal regression occurred. The same gonadotrophins administered on day 50 to hysterectomized sheep did not affect the corpora lutea. It would therefore appear that the primary action of the gonadotrophins is on the conceptus and that luteal regression is a secondary response.
F. Miyauchi, H. Kato, H. Yamashita, K. Ueda, H. Tamura, T. Mano and T. Torigoe
The effects of a conceptus-derived substance on the activity of 3β-hydroxysteroid dehydrogenase (3β-HSD) and 20α-HSD in the ovary were studied in the rat. On day 7 of pregnancy (day 1 = insemination), rats were laparotomized and the desired number of conceptuses was aspirated from the uterus; thus, rats carrying one, two, three, four, five to seven or eight to ten conceptuses were prepared. They were autopsied on day 15 and 3β-HSD and 20α-HSD activity in the corpus luteum (CL) or non-luteal ovarian tissue (NLO) was determined. Conceptus number was directly related to 3β-HSD and inversely related to 20α-HSD activity in the CL. The serum progesterone level and CL weight were also directly related to conceptus number. Neither 3β-HSD nor 20α-HSD activity in the NLO was affected by conceptus number. These results indicated that 3β-HSD and 20α-HSD in the CL are probably regulated by placental hormone secreted in proportion to the number of conceptuses; in the NLO these enzymes may be controlled by a different mechanism.
J. Endocr. (1984) 101, 285–288
M.C. Lacroix, G. Charpigny and P. Reinaud
This study describes the presence in and production by the ovine conceptus of an oxytocin-like peptide during the early stages of development. Oxycotin was measured by radioimmunoassay in ovine conceptuses from days 14 to 30 of pregnancy. Tissue concentrations of oxytocin increased from day 14 (24.8 ± 5 pg/100 mg) until day 19 (122.9 ± 52 pg/100 mg) and then decreased (3 ± 1 pg /100 mg). Oxytocin was released into culture medium by day-15 ovine conceptuses at a rate of 262 ± 55 pg/24 h. Reverse-phase high-performance liquid chromatography (HPLC) analysis of peptides extracted from a pool of ovine conceptuses was conducted using chromatographic conditions developed to separate oxytocin from other nonapeptides. Radioimmunoassay of HPLC fractions for oxytocin revealed an immunoactive conceptus peptide in a single fraction at the same retention time as chromatographed authentic oxytocin. Radioimmunoassay and chromatographic data therefore suggest that this oxytocin-like peptide is similar, if not identical, to authentic oxytocin. Concentrations of oxytocin in conceptus tissue were maximal during the period of inhibition of luteal regression (days 14-19). It is proposed that conceptus oxytocin is involved in the maintenance of luteal function in early pregnancy.
S C Riley, J K Findlay and L A Salamonsen
Previous studies have demonstrated that endothelin is present in the ovine endometrium and increases at around the expected time of implantation. To characterize further uterine endothelin at the time of establishment of pregnancy in sheep, endothelin was measured by radioimmunoassay in uterine flushings obtained during the oestrous cycle and in pregnant ewes up to the time of implantation (day 16). During the oestrous cycle, the highest amounts of endothelin were present in uterine flushings on day 14 (1·1 ±0·2 ng endothelin/uterus). During early pregnancy, basal levels of endothelin (0·5–0·6 ng endothelin/uterus) were present in uterine flushings for the first 10 days and then increased on day 14 to levels similar to those found at the equivalent stage of the oestrous cycle. On days 15 and 16 of pregnancy, endothelin content in the uterine lumen increased to significantly (P<0·05) higher concentrations (2·9±0·4 ng endothelin/uterus) when compared with the non-fertile cycle. The principal isoform present in flushings at the time of implantation was endothelin-1, as determined by reverse-phase HPLC. Endothelin was released principally by purified endometrial epithelial cells in culture, with barely detectable amounts released by endometrial stromal cells or conceptus tissue, which is consistent with the epithelium being the principal source of endothelin in the uterine lumen. Endothelin binding sites were present in endometrium and myometrium, as demonstrated by specific binding of 125I-labelled endothelin-1, which was saturable and displaced by endothelin-1. Both endothelinA and B sub-types of receptors were present as demonstrated by the biphasic displacement of 125I-labelled endothelin-1 binding by the specific endothelinB agonist BQ3020. These were localised principally on luminal and glandular epithelium and in the vasculature of the endometrium and myometrium as shown by autoradiography. Endothelin receptors were also present on the conceptus obtained at the time of implantation. In the day 20 conceptus, endothelin immunostaining was localised principally in the heart, in trophoblast in uninucleate but not in binucleate cells, and in fetal membranes. This immunostaining of the conceptus may represent binding to receptor sites. It is concluded that endothelin-1 is present in the uterine lumen and may play an important role in the paracrine regulation of the conceptus and endometrium at the time of rapid embryo development, implantation and early placentation.
Journal of Endocrinology (1995) 147, 235–244
G E Mann, J H Payne and G E Lamming
In intact cyclic ewes intrauterine infusion of conceptus secretory proteins results in the suppression of both endometrial oxytocin receptor concentrations and oxytocin-induced prostaglandin F2α release. However, similar infusion in progesterone-treated ovariectomized ewes, while suppressing endometrial oxytocin receptors, does not fully inhibit oxytocin-induced prostaglandin F2α release. To examine whether this anomaly resulted from an inadequate simulation of the luteal phase in the ovariectomized ewe treated with progesterone alone, the effects of additional treatment with two other ovarian hormones, oestradiol-17β and oxytocin, was investigated. Rather than permitting conceptus secretory protein to successfully inhibit oxytocin-induced prostaglandin F2α release, treatment with oestradiol-17β in addition to progesterone actually resulted in an advancement in the timing of release. However, treatment with oxytocin, alone or in combination with oestradiol, permitted the full inhibition of oxytocin-induced prostaglandin F2α release. To confirm that this effect did not result from the action of oxytocin alone, independently of the action of conceptus secretory protein, a second experiment was undertaken using a similar protocol but without the infusion of conceptus secretory protein. In this situation, oxytocin-induced prostaglandin F2α release was only partially inhibited suggesting that both luteal oxytocin and conceptus secretory proteins are necessary to facilitate the full inhibition of luteolysis during early pregnancy in the ewe.
Journal of Endocrinology (1996) 150, 473–478
Jacqueline M Wallace
throughout gestation (maintenance). This facilitates a small degree of maternal growth ensuring that the nutrient requirements for optimum conceptus growth are met: this is achieved by modest step-wise increases in maternal dietary intake during the final