The effect of pregnancy on the expression of uterine oxytocin, oestrogen and progesterone receptors during early pregnancy in the cow

Quantitative analysis of changes in endometrial gland morphology during the bovine oestrous cycle and their association with progesterone levels

This study describes a digital technique for uterine morphometry and its application to endometrial structure during the bovine oestrous cycle. Neither the number nor the size of uterine gland ducts changed during the cycle but a reduction in total endometrial area from days 0 to 8 after oestrus led to an increase in the proportion of the endometrium occupied by gland ducts (gland duct density). This effect on day 8 was maintained to day 16. When endometrial morphology was related to circulating progesterone concentrations on days 5 and 8 of the luteal phase, no relationships were found on day 5, but on day 8, a high progesterone concentration was associated with an increased number of gland ducts. Furthermore, in animals slaughtered on day 8, a high progesterone concentration on day 5 was associated with decreased gland duct size, though a simultaneous decrease in endometrial area led to an increase in gland duct density. The results suggest that contrary to expectation, endometrial glands do not grow and regress during the oestrous cycle, although cyclic changes in endometrial area controlled by progesterone lead to changes in gland duct density.

Relative transcript abundance of oxytocin receptor gene in porcine uterus during luteolysis and early pregnancy

The aim of the present study was to investigate transcript localization of the oxytocin receptor (OTR) gene in different cells of the porcine uterus during luteolysis and early pregnancy (days 14-16) using in situ hybridization (ISH). OTR mRNA was localized in the uterine luminal epithelium (LEC), glandular epithelium (GEC), stromal cells (SC) of the endometrium, in the longitudinal muscle layer (LM) and circular muscle layer (CM) of the myometrium. The OTR transcript was quantified by optical density units of silver grains. The OTR transcript levels in the endometrium and myometrium were statistically higher during luteolysis than during early pregnancy (P<0.05). Besides, during luteolysis, the mRNA level was higher in the LEC, GEC of the endometrium and LM of the myometrium compared to that observed in the SC of endometrium and CM of the myometrium, respectively (P<0.05). In summary: 1) the level of OTR mRNA in uterine tissues is higher during luteolysis compared to early pregnancy, 2) the OTR transcript level in endometrial cells did not correspond to the sensitivity of these cells to oxytocin (OT), 3) the myometrial expression of the OTR gene is appropriate to control contractile activity and secretion of PG during luteolysis.

Evaluation of the effect of muscular injection of progesterone on days 2-5 following insemination on pregnancy rate in dairy cows

It was hypothesized that suboptimal progesterone concentrations during the late embryo and early fetal period may act to compromise conceptus development in dairy cattle. The importance of progesterone during early pregnancy in cows is well established. Adequate secretion of progesterone is clearly the major requirement for success of early pregnancy. The aim of this study was to evaluate the efficacy of exogenous progesterone injection from day 2 to 5 following AI on conception rate in dairy cattle. At 48 h after the AI the cows were alternately assigned to treatment group (n = 40), received 4 consecutive day, from Day 2 to 5, i.m. injection of 100 mg progesterone (Vetagesterone, Aburaihan, Iran, Each mL contains: 2.5 mg progesterone) and control group (n = 68), received no treatment. The study population was stratified by parity, milk yield production, number of AI and days in milk. Pregnancy proportion in treatment and control groups were 30.88 and 35%, respectively. The results demonstrated that there was no significant differences between two groups (p < 0.05).

Pregnancy, Bovine Somatotropin, and Dietary n-3 Fatty Acids in Lactating Dairy Cows: II. Endometrial Gene Expression Related to Maintenance of Pregnancy

The objectives were to examine the effects of bovine somatotropin (bST), pregnancy, and dietary fatty acids on expression of key endometrial genes and proteins regulating prostaglandin synthesis in lactating dairy cows. Two diets were fed, at about 17 d in milk (DIM), in which oil of whole cottonseed (control diet) was compared with calcium salts of fish oil-enriched lipid (FO). Ovulation was synchronized in cows with a presynchronization plus Ovsynch protocol and cows were inseminated artificially or not inseminated on d 0 (d 0 = time of synchronized ovulation; 77 +/- 12 DIM). On d 0 and 11, cows received bST (500 mg) or no bST, and were slaughtered on d 17 to recover uterine secretions and endometrial tissue. Number of cows in the control diet: 5 bST-treated cyclic (bST-C), 5 non-bST-treated cyclic (no bST-C), 4 bST-treated pregnant (bST-P), and 5 non-bST-treated pregnant (no bST-P) cows and in the FO diet: 4 bST-treated FO-cyclic (bST-FO-C) and 5 non-bST-treated cyclic (no bST-FO-C) cows. The FO diet increased progesterone receptor (PR) mRNA, and treatment with bST increased PR mRNA concentration in endometrium of no bST-C, but not in no bST-FO-C or no bST-P cows. Concentrations of estrogen receptor-alpha (ERalpha) mRNA and protein, and oxytocin receptor (OTR) mRNA were decreased in no bST-P cows compared with no bST-C cows. Treatment with bST tended to increase OTR and ERalpha mRNA concentrations in cyclic cows fed control or FO diets. Immunohistochemistry demonstrated effects of bST, FO, and pregnancy on distributions of ERalpha and PR proteins in endometrium. Pregnancy and FO feeding decreased ERalpha abundance in luminal epithelium. Prostaglandin H synthase-2 (PGHS-2) protein was elevated in pregnant cows and localized to the luminal epithelium. Both FO and bST treatments reduced staining intensity of PGHS-2 protein. Concentrations of prostaglandin E synthase mRNA were elevated in either cyclic or pregnant cows in response to bST, whereas bST decreased prostaglandin F synthase mRNA in pregnant cows. Uterine lumen fluids had more PGF2alpha and prostaglandin E2 in pregnant than cyclic cows. Uterine lumen fluids of bST-P cows contained more prostaglandin E2 than those from no bST-P cows. In summary, both pregnancy and bST altered endometrial gene expression, and cyclic cows responded differently to bST than pregnant cows. Feeding FO modulated PR, ERalpha, and PGHS-2 expression and distribution among endometrial cell types in a manner that may favor establishment and maintenance of pregnancy.

Timing of prostaglandin F(2alpha) release episodes and oxytocin receptor development during luteolysis in the cow

The timing of PGF(2alpha) release and the timing and extent of the rise in endometrial oxytocin receptors was determined in relation to the timing of the progesterone fall during luteolysis in cycling cows. In cows undergoing luteolysis (n = 6), measurement of PGF(2alpha) metabolite in hourly plasma samples collected during daily 10 h sampling periods identified a total of 2.2+/-0.5 PGF(2alpha) release episodes per animal, each of 4.0+/-0.4 h duration. In cows in which luteolysis was not observed (n = 4) no PGF(2alpha) release episodes were identified. In a further three cows in which additional repeated uterine biopsies were collected on days 15, 17, 19, 21 and 23, endometrial oxytocin receptors were initially undetectable (<15 fmol/mg protein) but had increased to 120+/-19 fmol/mg protein prior to the initiation of PGF(2alpha) release episodes. Receptor concentrations then continued to increase reaching peak concentrations of 651+/-142 after luteolysis had been completed.

Pregnancy effects on distribution of progesterone receptors, oestrogen receptor α, glucocorticoid receptors, Ki-67 antigen and apoptosis in the bovine interplacentomal uterine wall and foetal membranes

Until recently, studies dealing with the uterus of the pregnant cow focus primarily on the placentome or on early and late pregnancy. Thus, there is a paucity of information about many aspects of the interplacentomal uterine wall including adherent foetal membranes. Corresponding tissue specimens were collected at the slaughterhouse and in animals undergoing premature caesarean section. Two specimens per month of pregnancy were assessed immunohistochemically for progesterone receptors, oestrogen receptor alpha and glucocorticoid receptors, Ki-67 protein and TUNEL procedure was performed. The latter two methods were employed in three animals each per months 1 and 2, 3 and 4, 7 and 8 and in six animals undergoing caesarean section at days 274 and 275 post insemination or during spontaneous labour. Results indicate that proliferation and apoptosis are of minor importance for tissue homeostasis since both can histochemically be detected only sporadically. Thus, at the sites investigated here, cellular hypertrophy plays an important role for tissue growth during pregnancy. Progesterone receptors, oestrogen receptor alpha and glucocorticoid receptors, however, exhibit cell type and pregnancy stage specific distribution patterns within the tissues assessed. Progesterone receptor immunoreactive scores remained fairly unchanged during pregnancy. Oestrogen receptor alpha scores, however, generally decreased and glucocorticoid receptors increased with ongoing gestation. Progesterone receptors and oestrogen receptor alpha were present in endometrial stroma and in myometrial smooth muscle cells during whole pregnancy. Oestrogen receptor alpha was detectable during whole pregnancy also in uterine glands. Progesterone receptors were, however, present at a very low level at the latter site only during months 1-3 and 6-9. Oestrogen receptor alpha and glucocorticoid receptors may also mediate uterine blood flow since they were present in the tunica media of uterine blood vessels. Results of the present study indicate, that progesterone and its receptor play an important role during whole gestation, mainly for uterine quiescence. Glucocorticoids and their receptors - possibly in cooperation with oestrogens and decreasing amounts of the oestrogen receptor alpha - should trigger processes initiating parturition, such as endometrial prostaglandin production. Further studies - including the periparturient period - should help to understand the exact role of the extraplacental compartment of the uterine wall for the initiation and progress of parturition.

A comparison of the anti-luteolytic activities of recombinant ovine interferon-alpha and -tau in sheep

Interferon tau (IFNT) is secreted by the trophectoderm of ruminant conceptuses during the peri-implantation period and serves an anti-luteolytic function. The question as to whether IFNT is superior as an anti-luteolytic agent to closely related Type I IFNs, such as IFN alpha (IFNA), which have a different function, remains unanswered. Thus, the aim of this study was to determine whether equivalent antiviral (AV) units of ovIFNA and ovIFNT are equipotent in extending estrous cycle length. Four distinct ovIFNA mRNA (ovIFNA1-4) were cloned from ovine lymphocytes. Recombinant ovine IFNs (ovIFNT4 and ovIFNA1) were prepared in the yeast Pichia pastoris. The AV activity of the purified IFNs was determined on a bovine cell line (MDBK) and on transformed ovine luminal uterine epithelial cells. Indwelling uterine catheters were fitted into crossbred ewes on Day 3 postestrus (Day 0 = estrus). Between Days 10 and 18 postestrus, ewes received twice-daily infusions of 0.7 x 10(7) IU of either ovIFNA1 or T4, plus serum albumin. Control ewes received serum albumin only. Daily blood samples were collected for progesterone determination, and ewes were monitored twice daily for estrus. Both ovIFNA (P = 0.04) and ovIFNT (P = 0.01) caused estrous cycle extension in nonpregnant ewes compared to controls when administered at equivalent AV doses. In conclusion, the uniqueness of IFNT as an anti-luteolytic agent most likely resides in its unique expression pattern rather than its special biopotency.

Sexual dimorphism in interferon-tau production by in vivo-derived bovine embryos

Interferon-tau (IFN-tau) is an anti-luteolytic factor responsible for preventing regression of the maternal corpus luteum (CL) during early pregnancy of cattle. In vitro-produced (IVP) bovine embryos first produce IFN-tau as blastocysts. In the present study, we have examined whether sexually dimorphic production of IFN-tau, which is observed among IVP blastocysts, also occurs among in vivo-produced blastocysts, and whether this difference between the sexes persists to day 14 when silencing of one of the X-chromosomes in the trophectoderm is complete. Embryos were flushed from cattle that had been superovulated and bred by AI. Blastocysts (63 male, 62 female) recovered between days 8.5 and 9.5 of pregnancy, were cultured individually. No differences were observed between males and females in either their developmental stage or quality at the beginning, during, and at the end of culture. Female embryos produced more IFN-tau than males by 24 hr (mean values, males: 16.6 +/- 3.7, females: 49.4 +/- 9.0 pg per embryo; P < 0.05) and 48 hr (male: 189.8 +/- 37.1, female: 410.9 +/- 66.6 pg per embryo; P < 0.05). However, the variability in IFN-tau production between individual blastocysts was so great that IFN-tau secretion is unlikely to be of value as a non-invasive means to predict embryo sex. When conceptuses were recovered at day 14, elongating males (n = 25) and females (n = 24) were similar in dimension and did not differ in their IFN-tau production after 4.5 hr (male: 2,550 +/- 607, female: 2,376 +/- 772 ng per conceptus) and 24 hr (male: 12,056 +/- 2,438, female: 8,447 +/- 1,630 ng per conceptus) of culture. Thus, sexual dimorphism in IFN-tau production is observed in both IVP and in vivo-produced expanded blastocysts, but is lost by day 14 of in vivo development.

Pregnancy and Bovine Somatotropin in Nonlactating Dairy Cows: II. Endometrial Gene Expression Related to Maintenance of Pregnancy

The objective was to evaluate the effects of pregnancy and bovine somatotropin (bST) on endometrial gene and protein expression related to maintenance of pregnancy in nonlactating dairy cows at d 17. In endometrial tissues, treatment with bST increased the steady state concentration of oxytocin receptor (OTR) mRNA; bST-treated cyclic (bST-C) cows had greater OTR mRNA than bST-treated pregnant (bST-P) cows. Estradiol receptor alpha (ERalpha) mRNA was reduced in bST-P cows compared with control P and C (no bST) cows. Western blotting revealed that pregnancy decreased the abundance of ERalpha protein, and bST stimulated an increase in ERalpha protein in C and P cows. Treatment with bST increased steady state concentrations of progesterone receptor (PR) mRNA. No differences were detected in steady state mRNA concentrations of prostaglandin H synthase-2 (PGHS-2), prostaglandin E synthase, and prostaglandin F synthase due to pregnancy or bST treatment. However, PGHS-2 protein was increased in response to pregnancy and bST treatment. Immunostaining indicated that P decreased ERalpha protein in luminal epithelium and increased PR protein in epithelial cells of the uterine glands. The PR protein response in the glands was less in bST-P cows than in P cows. In the stromal layer of the endometrium, bST decreased PR protein abundance in C and P cows. The PGHS-2 protein was localized exclusively in the luminal epithelium cells of endometrium and was increased in P cows. In conclusion, distinctly different mRNA and protein responses were detected between C and P cows related to prostaglandin biosynthesis, and bST-induced changes may potentially impact mechanisms associated with maintenance of pregnancy in nonlactating cows.

Tocolysis with atosiban: experience in the management of premature labor before 24 weeks of pregnancy

OBJECTIVE

Atosiban has been shown to be an effective tocolytic agent with a low rate of side effects during 24 to 33 weeks of gestation. Atosiban acts through selective, competitive inhibition of both oxytocin and vasopressin, so that there are reasons to assume that a tocolytic effect can also be achieved earlier in the pregnancy.

STUDY DESIGN

In this prospective, randomized pilot study, 20 women in the 18th through 24th week of gestation who presented at our hospital with preterm labor were treated with atosiban. In the control group 20 women received saline infusions. All patients received antibiotic therapy. A cervical cerclage was performed when indicated as was correction of the vaginal pH.

RESULTS

The tocolytic effect began after 3-10 min (median: 6.5 min). Treatment time until the complete absence of contractions was 3-12 h (median: 7.5 h). Pregnancies were prolonged between 11.1 and 21.7 weeks (median: 15.6 weeks) in the atosiban group vs. 10.5-19.1 weeks in the control group. If well tolerated, atosiban was continued. There were no significant alterations in the routine laboratory parameters, circulation parameters, and fluid balance.

CONCLUSION

In summary, atosiban showed itself to be effective for tocolytic treatment for premature labor, even during 18 and 24 weeks of pregnancy, while exhibiting its known, favorable profile of side effects.

Interferon-τ Induces Degradation of Prostaglandin H Synthase-2 Messenger RNA in Bovine Endometrial Cells Through a Transcription-Dependent Mechanism1

A series of experiments were undertaken to examine the effects of interferon (IFN)-tau on regulation of prostaglandin H synthase (PGHS)-2 mRNA in bovine endometrial (BEND) cells as a means to elucidate the actions of IFN-tau to maintain pregnancy. The objective was to determine if IFN-tau mediates posttranscriptional regulation of PGHS-2 mRNA. Cells were treated with phorbol 12,13-dibutyrate (PdBu) for 3 h to induce PGHS-2 mRNA expression. Actinomycin D (0 or 1 microg/ml) or the p38 mitogen-activated protein kinase (MAPK) inhibitor, SB203580 (1 microM), were added at 3 h, followed by addition of IFN-tau (0 or 50 ng/ml) at 3.5 h and extraction of RNA at 4.5 h. The concentrations of PGHS-2 mRNA were stable between 3 and 4.5 h regardless of actinomycin D. Simultaneous treatment of PdBu-treated cells with actinomycin D and SB203580 (1 microM) decreased PGHS-2 mRNA. Addition of IFN-tau (50 ng/ml) reduced PGHS-2 mRNA, which was not observed when actinomycin D was present. Concurrent treatments of cells with SB203580 and IFN-tau (5 ng/ml) decreased concentrations of PGHS-2 mRNA in an additive manner. Although IFN-tau reduced PGHS-2 mRNA concentrations, phosphorylation of p38 MAPK was induced by IFN-tau, PdBu, and PdBu combined with IFN-tau after 10 min of treatment. Both the p38 MAPK inhibitor and IFN-tau decreased prostaglandin F(2alpha) secretion, and decreases were additive when the two were given together. In summary, activation of p38 MAPK by PdBu is required for continued presence of PGHS-2 mRNA and secretion of prostaglandin F(2alpha) in BEND cells. Interferon-tau mediates a transcription-dependent mechanism, which induces degradation of PGHS-2 mRNA. However, the consequences of an IFN-tau-induced activation of p38 MAPK warrant further investigation, because inhibition of p38 MAPK caused a degradation of PGHS-2 mRNA.

Identification of interferon-tau isoforms expressed by the peri-implantation goat (Capra hircus) conceptus

Interferon-tau (IFN-tau) is the maternal recognition of pregnancy factor in pecoran ruminants. The aims of this study were to identify the various IFN-tau transcripts in the peri-implantation caprine (ca) conceptus and to compare these nucleotide sequences phylogenetically with established mRNA sequences from the goat. Conceptuses (n = 5) were collected from Boer crossbred and Angora female goats by laparotomy at days 17 and 18 of pregnancy. Total cellular RNA was extracted and RT-PCR was performed by standard procedures using a DNA polymerase with proofreading activity and gene-specific primers complimentary to non-coding regions of the published caIFN-tau sequence. Nine distinct nucleotide sequences were isolated that encode five distinct caIFN-tau proteins. These caIFN-tau have greater sequence homology with ovine IFN-tau (94-96% nucleotide identity; 90-93% amino acid identity) than with bovine IFN-tau (<92% nucleotide identity; <85% amino acid identity). The novel caIFN-tau isoforms contained pronounced nucleotide and amino acid sequence identity with one another (97-99% nucleotide identity; 94-99% amino acid identity) but only moderate sequence identity with the previously identified caIFN-tau (94-96% nucleotide identity; 87-90% amino acid identity). In conclusion, multiple caIFN-tau mRNA species are expressed during peri-implantation conceptus development and distinct clusters of caIFN-tau genes appear to have evolved in this species.

Identification of bovine and novel interferon-? alleles in the American plains bison (bison bison) by analysis of hybrid cattle x bison blastocysts

The objective of this study was to generate bison x cattle hybrid embryos by in vitro fertilization, to assess their developmental potential, to determine the pattern of secretion of the embryonic signaling molecule interferon-tau (IFN-tau), and to identify novel IFN-tau mRNA polymorphism in the American plains bison. A total of 600 bovine oocytes were inseminated with frozen-thawed bison semen. Of these, 40.7% cleaved and 14.8% proceeded to the blastocyst stage. Individual blastocysts were cultured on a basement membrane (Matrigel) and their ability to attach and form outgrowths was monitored. A total of 36 blastocysts were cultured of which 22 formed outgrowths. During individual culture, medium samples were collected and their IFN-tau concentration was measured. On day 6 after onset of individual culture, attached outgrowths produced significantly more IFN-tau than unattached viable or degenerate blastocysts. At this time, female conceptuses also produced significantly more IFN-tau than their male cohorts. However, by day 12 this difference had disappeared. Total mRNA was extracted from three individual outgrowths and analyzed by RT-PCR. Subsequent sequencing of 28 clones showed several known bovine IFN-tau sequences as well as two novel sequences termed bisIFN-tau1 and 2. To determine the origin of these, DNA was extracted from bison semen and analyzed by PCR. One bovine IFN-tau sequence (bovIFN-tau1d) as well as bisIFN-tau2 and a third novel sequence bisIFN-tau3 were detected. This study demonstrates the feasibility of using hybrid embryos for the analysis of developmentally regulated gene expression in species where embryos may not be available.

The role of sex steroid receptors in sheep female reproductive physiology

Cell responsiveness to steroid hormones is related to the number and affinity of its receptors, thus factors affecting steroid expression will influence tissue sensitivity and functionality. The present review discusses the role of oestrogen and progesterone receptors in sheep female reproductive physiology. The mechanism of steroid hormone action in the target cell is introduced first; the tissue distribution, physiological functions and regulation of oestrogen receptor subtypes and progesterone receptor isoforms in ruminants are reported. The role of steroid receptors in target tissues (with emphasis on the uterus and pituitary gland) during different physiological events is addressed in an attempt to clarify oestrogen and progesterone actions in different developmental and reproductive stages: prepubertal period, oestrous cycle, pregnancy, post-partum period and seasonal anoestrus. The present review shows how the distinct reproductive stages are accompanied by dramatic changes in uterine receptor expression. The role of oestrogen and progesterone receptors in the molecular mechanism responsible for premature luteolysis that results in subnormal luteal function is discussed. Finally, the effect of nutrition on sex steroid receptor expression and the involvement on reproductive performance is reported.

The effects of estrogen, its antagonist ICI 182, 780, and interferon-tau on the expression of estrogen receptors and integrin alphaV beta 3 on cycle day 16 in bovine endometrium

We have shown previously that downregulation of intercaruncular stromal integrin alphavbeta3 in bovine endometrium on day 16 of the estrous cycle coincided with the antibody recognition of estrogen receptors (ER) in the luminal epithelium. In pregnancy, these changes were not observed. Our hypothesis was that on day 16 of the estrous cycle, estrogen from the dominant follicle causes a reduction in integrin alphavbeta3 and affects ERalpha in the luminal epithelium. The pregnancy recognition protein, interferon-tau (IFN-tau), may prevent downregulation of integrin alphavbeta3 and suppress ERalpha expression in the luminal epithelium. On days 14 to 16, heifers received uterine infusions of the anti-estrogen ICI 182, 780, estradiol 17beta, IFN-tau or the saline control. On day 16, reproductive tracts were collected for analysis of integrin alphavbeta3 and ERalpha. Estrogen receptor alpha immunoreactivity was largely restricted to the luminal epithelium in control animals. Using anti-ERalpha recognizing the amino terminus, estrogen-treated animals showed reactivity in the stroma, shallow and deep glands and myometrium as is typical of estrus, whereas ICI 182, 870 treated heifers showed little or no reactivity. In contrast, carboxyl terminus-directed antibodies showed a widespread distribution of ERalpha with reactivity detected in the uterine epithelium, stroma and myometrium of both estrogen and ICI 182, 780 treated animals. Heifers treated with IFN-tau had low ERalpha reactivity overall. Control and IFN-tau treated heifers had lower intercaruncular stromal expression of integrin alphavbeta3 in comparison to estrogen and ICI 182, 780 treatments. Overall, the results suggest that on day 16 of the estrous cycle, estrogen effects on integrin alphavbeta3 are indirect and do not directly involve ERalpha in the luminal epithelium. During pregnancy, interferon-tau may block ERalpha in the luminal epithelium but likely does not rescue integrin alphavbeta3 expression.

Interferon-tau in bovine blastocysts following parthenogenetic activation of oocytes: pattern of secretion and polymorphism in expressed mRNA sequences

A series of experiments were conducted to examine the pattern of production and secretion of interferon-tau (IFN-tau) by blastocysts following parthenogenetic activation of bovine oocytes. In the first experiment, 36.8, 24.1, and 33.2% of IVF-derived and parthenogenetically activated oocytes cultured in the presence or absence of a monolayer of buffalo rat liver cells, respectively, reached the blastocyst stage. Following individual culture of blastocysts, IFN-tau concentration in medium droplets was similar among the three groups, although IVF-derived blastocysts contained significantly more cells. In the second experiment, 156 IVF-derived blastocysts were sexed by PCR with 75 and 81, respectively, being male and female. IFN-tau secretion of these was compared to that of 70 parthenogenetic blastocysts. Female and parthenogenetic blastocysts produced significantly more IFN-tau than their male counterparts. In the third experiment, the ability of hatched blastocysts to form outgrowths and the pattern of their IFN-tau secretion were examined. Of the 48 IVF-derived blastocysts, 44 formed outgrowths compared to 41 of the 42 hatched parthenotes. Parthenogenetic outgrowths were significantly larger after 7 days, but this difference had disappeared after 14 days. IFN-tau secretion did not differ between the two groups. Lastly, sequence analyses of expressed mRNA from individual parthenogenetic blastocyst outgrowths showed four different transcript types which, based on their predicted amino acid sequence, belong to two subgroups, IFN-tau1 and IFN-tau3. In addition, one new transcript sequence was identified, encoding a new protein isoform.

Embryonic signals and survival

The objective of this review is to give an overview of the signaling mechanisms between the conceptus and the mother before implantation. The interactions between the embryo and uterus are complex and essential for normal embryo development and implantation. Problems in the signaling mechanisms are thought to play a significant role in early embryonic mortality since a high rate of embryonic morality occurs during this period. This review will focus on the mechanisms involved in the development of the conceptus and the prevention of luteolysis. It is based primarily on what is known in ruminants but also refers to work in other species such as the mouse and primates.

The role of arginine vasopressin in human labour: functional studies, fetal production and localisation of V1a receptor mRNA

OBJECTIVE

To investigate labour-associated changes in: 1. the myometrial contractile response to arginine vasopressin compared with oxytocin in vitro 2. fetal production of arginine vasopressin and 3. myometrial vasopressin V1a receptor mRNA.

DESIGN

The contractile response to vasopressin (compared with oxytocin) was investigated in paired myometrial strips in vitro. Blood was taken from the umbilical artery and vein at delivery and arginine vasopressin measured by radio-immunoassay. V1a receptor mRNA was determined by in situ hybridisation.

RESULTS

Myometrium was more sensitive to arginine vasopressin than oxytocin (P<0.05 for frequency, amplitude and activity integral in paired strips) after, but not before labour. There was a marked umbilical arteriovenous difference in arginine vasopressin concentration at delivery suggesting fetal production which was not influenced by labour. Myometrial vasopressin V1a receptor mRNA was not increased after the onset of labour.

CONCLUSIONS

The human uterus is extremely sensitive to arginine vasopressin in vitro. Arginine vasopressin is produced by the fetus but fetal formation is not increased during labour.

Uterine-conceptus interactions and reproductive failure in cattle

The dialogue between trophectoderm cells of the conceptus and epithelial cells of the endometrium is critical to CL maintenance and embryo survival. The signal transduction mechanisms by which bovine interferon (IFN)-tau regulates cyclooxygenase (COX)-2 expression and secretion of prostaglandin F2alpha (PGF2alpha) in bovine endometrial (BEND) cells is examined. Stimulation of Protein Kinase C with a phorbol ester (phorbol 12, 13 dibutyrate [PDBu]) activates COX-2 gene expression and PGF2alpha secretion via the mitogen-activated protein kinase (MAPK) pathway. Interferon-tau attenuates PDBu activation of PGF2alpha secretion, but this inhibitory effect appears to be independent of the MAPK pathway. Embryonic IFN-tau, acting through a Type I IFN receptor, activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway resulting in activation or repression of interferon-stimulated genes. Experimental evidence is provided that IFN-tau regulation of STATs regulates gene expression of COX-2 in a manner that decreases secretion of PGF2alpha. Maternal regulation of the antiluteolytic pathway is discussed relative to the ability of the polyunsaturated fatty acid, eicosapentaenoic (EPA), to decrease endometrial secretion of PGF2alpha and progesterone to increase both conceptus development and IFN-tau secretion.

Oestrous cycle and pregnancy effects on the distribution of oestrogen and progesterone receptors in bovine endometrium

Reproductive cyclicity and pregnancy require cell and tissue specific expression of oestrogen (OR) and progesterone receptors (PR). To determine the effects of cycle day and early pregnancy (days 16-30) on the distribution of OR and PR, uteri were collected from cycling (n=39), pregnant (n=14), and steroid-treated ovariectomized cattle (n=10). Immunohistochemistry was used to localize OR and PR, and staining intensity was scored. Moderate staining for the PR was detected in the stroma at proestrus (days 17-20). Expression increased through oestrous, reaching maximal levels by metestrus (days 1-6) (P< 0.05). During diestrus (days 7-16), PR expression was downregulated (P< 0.05). Progesterone receptor expression was detected in the luminal epithelium in one of three animals each at days 3 and 6 of the oestrous cycle. In pregnant animals only, caruncular stroma showed reduced PR staining compared to intercaruncular stroma (P< 0.05). Reactivity to the OR antibody in cycling animals was detected in the stroma and glandular epithelium. Levels increased through proestrus and oestrous, were maximal during metestrus (P< 0.05), and decreased during diestrus (P< 0.05). Interestingly, there was transient upregulation in the luminal epithelium on day 16 or day 14 (P< 0.05). This was not evident at day 16 of pregnancy, although some OR reactivity was present in stroma and glands. By day 18 of pregnancy OR were undetectable (P< 0.05). Oestrogen-treated ovariectomized animals had increased OR and PR expression in comparison to progesterone treated cows (P< 0.05). Untreated ovariectomized cows showed constitutive steroid receptor expression. These results support the widely accepted role for sex steroids in the regulation of their receptors and indicate that there is paracrine regulation of steroid receptor expression in the bovine uterus.

Hormonal regulation of oxytocin-induced prostaglandin F(2alpha) secretion by the bovine and ovine uterus in vivo

In long-term ovariectomized ewes and cows, endometrial oxytocin receptors rest at relatively high levels but oxytocin is unable to induce prostaglandin F(2alpha) release. A series of studies were carried out to investigate the roles of physiological levels of progesterone and estradiol in "activating" these receptors in terms of permitting oxytocin-induced prostaglandin F(2alpha) release. In long-term ovariectomized cows, treatment with progesterone, but not estradiol, resulted in the induction of responsiveness to oxytocin. This responsiveness appeared within 2 d of progesterone treatment, reached a maximum by 6 d and was maintained to Day 18. In ovariectomized ewes, while estradiol treatment did induce temporary responsiveness to oxytocin after 3 d of treatment, treatment with progesterone was required to induce sustained responsiveness that appeared by Day 9 of treatment and was maintained to Day 12. Measurement of endometrial receptors for oxytocin revealed a significant decline in oxytocin receptors by Day 6 of progesterone treatment when responsiveness to oxytocin was maximal, demonstrating that receptor concentrations were not a limiting factor. The most likely mechanism by which progesterone treatment induces responsiveness to oxytocin may be through the up regulation of post receptor signaling pathways and/or enzymes involved in prostaglandin synthesis.

Polymorphic forms of expressed bovine interferon-tau genes: relative transcript abundance during early placental development, promoter sequences of genes and biological activity of protein products

Multiple interferon (IFN)-tau genes exist in cattle, but it has remained unclear how many are expressed, the extent of their variation, and whether different genes exhibit similar patterns of expression and code for proteins with similar biological activities. A total of 118 complementary DNA (cDNA) were bi-directionally sequenced from reverse-transcribed bovine (bo) conceptus RNA over the period from blastocyst formation until day 25 of pregnancy. Fourteen different cDNAs, encoding eight different IFN-tau, were confirmed unique. All showed high sequence conservation (>98% nucleotide identity; >96% amino acid identity). The cDNA fell into three, recently evolved, phylogenetic groups (tau1, 2, and 3). Mean concentrations of IFN-tau messenger RNA were greater at day 17 and day 19 than at day 14 and day 25, with different genes showing comparable expression patterns, although there appeared to be a major bias in expression of two genes (for boIFN-tau1c and tau3a) in blastocysts. Genes representing members of the three boIFN-tau groups were cloned. Their promoter regions were conserved over regions considered important for transcriptional activation. Recombinant protein generated in Escherichia coli from representative genes in the three groups had similar but not identical antiviral activities. In summary, many IFN-tau genes, which are probably under similar transcriptional control, are expressed in bovine trophoblast during the peri-implantation period of development.

Control of interferon-tau secretion by in vitro-derived bovine blastocysts during extended culture and outgrowth formation

A series of experiments was conducted to examine the pattern of interferon-tau (IFN-tau) secretion by bovine blastocysts during extended culture in vitro. In the first experiment, blastocysts were cultured individually for three 48-hour periods. The day of blastocyst formation affected how much IFN-tau was produced during the first two culture periods, but not during the third period. The overall secretion of IFN-tau during the 6-day period increased significantly and well beyond what could be accounted for by the concomitant increase in cell numbers. In the second experiment, blastocysts were initially cultured in individual droplets for 48 hr, then plated into 48-well plates. Medium concentrations of IFN-tau were determined after 48 hr and again after 6 and 12 days of culture. Initial IFN-tau secretion did not affect the ability to form outgrowths or their final size, and initial differences in secretion between groups of blastocysts had disappeared by the second and third analyses. In the third experiment, blastocysts were cultured individually for 48 hr in droplets containing the medium that had been flushed through the uteri of non-pregnant sheep on days 10, 12, and 15 of the estrous cycle. Culture in the medium obtained from the Day 15 flush significantly increased the number of cells that blastocysts contained, as well as IFN-tau secretion.

Interferon-tau suppresses prostaglandin F2alpha secretion independently of the mitogen-activated protein kinase and nuclear factor kappa B pathways

Pregnancy is established in ruminants through inhibitory actions of interferon (IFN)-tau on the release of prostaglandin F2alpha (PGF), which allows the corpus luteum to survive and continue to produce progesterone. Experiments were designed to 1) delineate the signal transduction pathway coordinating the synthesis of PGF, 2) determine how rapidly recombinant bovine (rb) IFN-tau attenuated phorbol ester (PDBu)-induced secretion of PGF, and 3) establish the site at which rbIFN-tau attenuates the secretion of PGF in cultured bovine endometrial (BEND) cells. BEND cells were untreated (control) or treated for 5, 10, 60, 180, or 300 min with PDBu (100 ng/ml), rbIFN-tau (50 or 500 ng/ml), PDBu + rbIFN-tau, or PDBu + PD98059 (MEK-1 inhibitor; 50 microM). Secretion of PGF was induced (P < 0.0001) by PDBu within 180 min, but induction was inhibited 74% by the addition of rbIFN-tau (P < 0.0001) and was ablated completely by PD98059. Parallel results were obtained for cyclooxygenase (COX)-2 protein expression. PDBu induced (P < 0.05) activation of the Raf-1/MEK-1/ERK-1/2 pathway, which was obligatory for the expression of COX-2 and secretion of PGF but was not altered by cotreatment with rbIFN-tau. PDBu induced (P < 0.05) transcription of c-jun and c-fos mRNAs within 30 min; induction was inhibited (P < 0.05) by cotreatment with PD98059 but not by cotreatment with rbIFN-tau. Treatment of BEND cells with rbIFN-tau also did not attenuate PDBu-induced degradation of IkappaBalpha, suggesting that the IkappaBalpha/NFkappaB pathway is not a site of IFN-tau inhibition of PGF. However, rbIFN-tau did block transcription of the COX-2 gene induced by PDBu within 30 min. In conclusion, COX-2 expression and PGF secretion induced by PDBu is mediated through the Raf-1/MEK-1/ERK-1/2 pathway, but this pathway is not disrupted by rbIFN-tau. Because rbIFN-tau inhibits COX-2 mRNA within 30 min, we hypothesized that transcription factors activated by rbIFN-tau rapidly and directly attenuate COX-2 gene expression, thereby suppressing secretion of PGF.

Identification of the expressed forms of ovine interferon-tau in the periimplantation conceptus: sequence relationships and comparative biological activities

Interferon-tau (IFN-tau) is secreted from trophectoderm of periimplantation ruminant conceptuses and is a critical component of pregnancy recognition. Multiple genes encode IFN-tau. The objectives of this study were to identify expressed forms of ovine IFN-tau and to compare their biological activities. Sequences analyzed after cloning 36 reverse transcription-polymerase chain reaction products of ovine conceptus RNA provided seven new cDNA that were similar in sequence to previously cloned forms (p3, p6, and p8 cDNA). Phylogenetic analysis of amino acid sequence for all new and previously reported forms showed that ovine IFN-tau forms can be divided into three main groups. Equivalent amounts of mRNA for p3, p6, and p8 forms were detected in conceptuses following RNase protection. Recombinant p3 and p8 protein had similar antiviral activity on ovine and bovine cells whereas p6 protein was less active. The p3 form was the most potent of the three in its ability to extend estrous cycle length in nonpregnant ewes. In summary, there appeared to be three main groups of ovine IFN-tau, each containing several variant forms. Antiviral activity was not particularly well correlated with ability to prevent luteolysis, suggesting that distinct intracellular mechanisms are used to exert the various actions of IFN-tau.