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Maternal obesity in pregnancy has been linked to a spectrum of adverse developmental changes. Involvement of eCBs in obesity is well characterized. However, information regarding eCB physiology in obesity associated with pregnancy is sparse. This study evaluated fetomaternal hepatic, systemic, and placental eCB molecular changes in response to maternal consumption of a HFD. From ≥9 mo before conception, nonpregnant baboons ( Papio spp.) were fed a diet of either 45 (HFD; n = 11) or 12% fat or a control diet (CTR; n = 11), and dietary intervention continued through pregnancy. Maternal and fetal venous plasma samples were evaluated using liquid chromatography-mass spectrometry to quantify AEA and 2-AG. Placental, maternal and fetal hepatic tissues were analyzed using RT-PCR, Western blot, and immunohistochemistry. mRNA and protein expression of endocannabinoid receptors (CB1R and CB2R), FAAH, DAGL, MAGL, and COX-2 were determined. Statistical analyses were performed with the nonparametric Scheirer-Ray-Hare extension of the Kruskal-Wallis test to analyze the effects of diet (HFD vs. CTR), fetal sex (male vs. female), and the diet × sex interaction. Fetal weight was influenced by fetal sex but not by maternal diet. The increase in maternal weight in animals fed the HFD vs. the CTR diet approached significance ( P = 0.055). Maternal circulating 2-AG concentrations increased, and fetal circulating concentrations decreased in the HFD group, independently of fetal sex. CB1R receptor expression was detected in syncytiotrophoblasts (HFD) and the fetal endothelium (CTR and HFD). Placental CB2R protein expression was higher in males and lower in female fetuses in the HFD group. Fetal hepatic CB2R, FAAH, COX-2 (for both fetal sexes), and DAGLα (in male fetuses) protein expression decreased in the HFD group compared with the CTR group. We conclude that consumption of a HFD during pregnancy results in fetal systemic 2-AG and hepatic eCB deficiency.

Objective: We hypothesized that fetal folate serum concentrations are lower and placental folate transport is impaired in pregnancies of obese women., Study Design: Umbilical vein serum and placental tissue were collected from normal weight and obese pregnant women at term. Cellular localization (immunohistochemistry) of folate receptor-α (FR-α), proton coupled folate transporter (PCFT), and reduced folate carrier (RFC) was established. Protein expression (Western blot) and transporter activity (isotope labeled methyltetrahydrofolate) were determined in syncytiotrophoblast microvillus membranes (MVM)., Results: Fetal folate concentrations were similar in obese women as compared with normal weight women. Protein expression of FR-α in microvillus membranes was increased (+173%), in RFC was decreased (-41%), and in PCFT was unchanged. However, activity of FR-α, PCFT, and RFC was unaltered in obesity., Conclusion: Fetal serum folate concentrations and placental folate transport activity are not altered in obesity at term, which suggests that limited availability of folate does not contribute to abnormal gene methylation and developmental programming., (Copyright © 2011 Mosby, Inc. All rights reserved.)

Multiparous ewes received 100% (control, C, n = 13) or 50% (nutrient restricted, NR, n = 14) of NRC dietary requirements from d28-d78 of gestation. On d78, 5 C and 6 NR ewes were necropsied. The remaining 8 C and 8 NR ewes were fed to 100% of NRC from d78-d135 and necropsied. Maternal blood was collected at both necropsies and at weekly intervals for assay of glucose, insulin and leptin. Fetal blood was collected at d78 and d135 necropsies for assay of glucose and lipids. Cotyledonary (COT) tissue was evaluated for protein and mRNA expression [fatty acid transporter (FATP)1, FATP4, CD36, glucose transporter (GLUT)1 and GLUT3], mRNA expression only [placenta fatty acid binding protein (FABPpm) and lipoprotein lipase (LPL)], or expression of phosphorylated and total protein forms [AMP kinase (AMPK)α, acetyl-CoA carboxylase (ACC), extracellular signal-regulated kinase (Erk)1/2, mammalian target of rapamycin (mTOR) and protein kinase B (Akt)]. On d78, but not d135, placental and fetal weights were reduced (P < 0.05) in NR vs. C ewes. Maternal circulating glucose, insulin and leptin levels were decreased in NR vs. C ewes on d78 (P < 0.05) but similar at d135. Fetal blood glucose and triglyceride levels were lower in NR vs. C ewes (P < 0.05) on d78, but similar on d135. On d78, GLUT1, FATP4, CD36 mRNA and protein expression levels, FABPpm mRNA level, and leptin protein level were all increased (P < 0.05) in COT of NR vs. C ewes. AMPK, ACC, and Erk1/2 activities were also increased (P < 0.05) in NR vs. C COT on d78. In contrast, only FATP4 was increased (P < 0.05) at both the mRNA and protein levels in COT of NR realimented vs. C ewes on d135. These data demonstrate placental adaptation to maternal NR through increasing nutrient transporter production and growth signaling activity., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Objective: Our objective was to determine signaling molecules and apoptosis rate in the term placenta of a baboon model of maternal nutrient reduction (MNR)., Study Design: Female baboons were fed ad libitum for controls (n = 7) or 70% of control baboon diet (MNR; n = 6) from 30-165 days of gestation with necropsy at 165 days of gestation. Placental tissues were collected and fixed for immunohistochemistry or snap frozen to measure extracellular signal-regulated kinases, protein kinase B, JUN NH(2)-terminal kinase, X-linked inhibitor of apoptosis protein, and caspase 3. Placental villous apoptosis was determined by terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick-end labeling and cytokeratin 18 cleavage., Results: Compared with the control placentas, MNR placentas demonstrated reduced placental weight (P < .02), decreased phospho (p)-ERK (P < .04), increased placental villous apoptosis (P < .001), increased villous cytokeratin 18 cleavage, increased X-linked inhibitor of apoptosis protein (P < .007), and increased active caspase 3 (P < .02)., Conclusion: We conclude that placental apoptosis is increased in this baboon model of MNR at term and that the increase in X-linked inhibitor of apoptosis protein may be a protective mechanism against this apoptosis., (Published by Mosby, Inc.)

Unlabelled: HYPOTHESIS AND STUDY OBJECTIVES: We hypothesized that maternal obesity is associated with increased placental amino acid transport and hyperleptinemia. Our objectives were to study placental amino acid transport and the effect of leptin on placental amino acid transport in vitro in the setting of maternal obesity., Materials and Methods: Seven lean, BMI at entry 22.4, and seven obese, BMI at entry 31.5 (p < 0.001), pregnant women were studied at 39 weeks. We measured baseline and leptin-stimulated placental system A sodium-dependent neutral amino acid transporter (SNAT) activity, placental immunoreactive protein expression of SNAT, leptin and leptin receptor, and maternal and fetal plasma leptin concentrations, with significance set at p

Obesity in pregnant women is a growing public health concern. The placenta is a source of cytokines which can induce maternal gestational insulin resistance and alter nutrient transport to the fetus. Obesity induces placental inflammation at term, but the impact of obesity on placental inflammation earlier in pregnancy has not been defined. Using sheep as an experimental model, we hypothesized that maternal obesity (MO) would induce inflammation in the cotyledonary (COT) tissue of the placentome by mid-gestation. Nonpregnant ewes were randomly assigned to a control (C, 100% of NRC recommendations) or obese (OB, 150% of NRC) group from 60 days before conception to 75 day of gestation (dG), when ewes were necropsied and placental COT tissue collected for analyses. Free fatty acids content, triglyceride and cholesterol content were higher (P < 0.05) in the fetal plasma of OB compared to C ewes on day 75. MO increased mRNA levels of toll-like receptor (TLR) 2 (P < 0.05) and TLR4 (P = 0.06), macrophage markers cluster of differentiation (CD)11b (P = 0.06), CD14 and CD68 (P < 0.05), and proinflammatory cytokines tumor necrosis factor (TNF)alpha (P < 0.01), interleukin (IL)-6 (P < 0.05), IL-8(P < 0.01) and IL-18 (P = 0.06), in COT tissue. Inflammatory c-Jun N-terminal kinase (JNK)/c-Jun and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) signaling pathways were up-regulated (P < 0.05) in COT of OB ewes. In conclusion, MO enhanced the placental inflammatory response in OB ewes at mid-gestation, possibly as a result of increased TLR4 and free fatty acids., ((c) 2010. Published by Elsevier Ltd.)

Maternal obesity is present in 20-34% of pregnant women and has been associated with both intrauterine growth restriction and large-for-gestational age fetuses. While fetal and placental functions have been extensively studied in the baboon, no data are available on the effect of maternal obesity on placental structure and function in this species. We hypothesize that maternal obesity in the baboon is associated with a maternal inflammatory state and induces structural and functional changes in the placenta. The major findings of this study were: 1) decreased placental syncytiotrophoblast amplification factor, intact syncytiotrophoblast endoplasmic reticulum structure and decreased system A placental amino acid transport in obese animals; 2) fetal serum amino acid composition and mononuclear cells (PBMC) transcriptome were different in fetuses from obese compared with non-obese animals; and 3) maternal obesity in humans and baboons is similar in regard to increased placental and adipose tissue macrophage infiltration, increased CD14 expression in maternal PBMC and maternal hyperleptinemia. In summary, these data demonstrate that in obese baboons in the absence of increased fetal weight, placental and fetal phenotype are consistent with those described for large-for-gestational age human fetuses.

Fetal intrauterine growth restriction (IUGR) is known to negatively affect offspring health postnatally. This study evaluated the impacts of early gestational undernutrition followed by realimentation on bovine fetal and placental growth. Thirty multiparous beef cows bred to a single sire and gestating female fetuses were fed to meet NRC recommendations (control; n = 15) or fed below NRC recommendations (68.1% of NE(m) and 86.7% of MP recommendations; nutrient restricted, NR; n = 15) from d 30 to 125 of gestation. On d 125 of gestation, 10 control and 10 NR cows were necropsied. The remaining 5 NR cows were realimented to achieve similar BW and BCS with the remaining 5 control cows by d 190 of gestation; both groups were necropsied at d 245 of gestation. Fetal weight at d 125 of gestation was 948 +/- 14 g (n = 10) for control cows; however, fetal weights of NR cows fell into 2 distinct groups: NR non-IUGR cows had fetal weights similar to control cows (974 +/- 20 g, n = 6), whereas fetal weights of NR IUGR cows were reduced (773 +/- 23 g, n = 4; P < 0.01). Fetal brain weight as a percentage of fetal weight was increased (approximately 11%; P < 0.01) in the NR IUGR fetuses compared with fetuses from the other 2 groups, which were similar. Fetal heart weight as a percentage of fetal weight also tended to be increased (approximately 10%; P = 0.08) in NR IUGR fetuses compared with control fetuses. Nutrient-restricted IUGR cows exhibited reduced (P < 0.01) cotyledonary weights compared with NR non-IUGR and control cows, which were similar (192 +/- 27 vs. 309 +/- 22, and 337 +/- 17 g, respectively). Total placentome surface area also tended to be reduced (P = 0.07) in NR IUGR cows compared with NR non-IUGR and control cows, which again were similar (685.0 +/- 45.6 vs. 828.7 +/- 37.2 and 790.7 +/- 28.9 mm(2), respectively). On d 245 of gestation, fetal weights and caruncle weight were similar for NR and control cows; cotyledonary weights, however, were reduced in NR vs. control cows (1,430 +/- 133 vs. 2,137 +/- 133 g, P < 0.01). Decreased fetal growth in NR IUGR cows on d 125 of gestation was associated with decreased cotyledonary weights and reduced placentomal surface areas. The return of NR cows to a BW and BCS similar to that of control cows through realimentation beginning on d 126 resulted in similar fetal weights of NR and control cows by d 245 of gestation. Thus, a bout of fetal IUGR may go undetected if cows undernourished during early gestation receive feed supplementation in the second half of gestation to assure normal birth weight.

Both protein kinase B (Akt) and extracellular signal-regulated kinase 1/2 (ERK1/2) are down-stream components of the insulin/insulin like growth factor-1 (IGF-1) signaling pathway. AMP-activated protein kinase (AMPK) is known to sensitize cells to insulin/IGF-1 signaling. The objective of this study was to assess the activity of AMPK and its role in the observed down-regulation of insulin/IGF-1 signaling in cotyledonary (COT) arteries supplying the placental component of the ewe placentome. Nonpregnant ewes were randomly assigned to a control (C, 100% of NRC recommendations) or obesogenic (OB, 150% of NRC) diet from 60 days before conception until necropsy on day 75 of gestation (n=5/group) or until lambing (n=5/group). At necropsy on day 75 of gestation, the smallest terminal arteries that entered the COT tissues (0.5-1.0 mm in diameter) were collected for analyses. Fetal weights were approximately 20% greater (P<0.05) on OB than C ewes, but birth weights of lambs were similar across dietary groups. Fetal plasma concentrations of glucose, insulin and IGF-1 were higher (P<0.05) in the blood of fetuses from OB than C ewes. Total AMPK and phosphorylated AMPK at Thr 172 (the active form) were reduced (P<0.05) by 19.7+/-8.4% and 25.9+/-7.7%, respectively in the COT arterial tissues of OB ewes. Total acetyl-CoA carboxylase (ACC), a down-stream target of AMPK, and its phosphorylated form were also reduced (P<0.05) by 32.9+/-9.2% and 45.4+/-14.6%, respectively. The phosphorylation of IRS-1 at Ser 789, a site phosphorylated by AMPK, was 24.5+/-9.0% lower (P<0.05) in COT arteries of OB than C ewes. No alteration in total insulin receptor, total IGF-1 receptor or their phosphorylated forms was observed, down-stream insulin signaling was down-regulated in COT arteries of OB ewes, which may have resulted in the observed decrease in COT vascular development in OB ewes.

Adequate delivery of AA is essential for normal fetal growth and development. Recently, we reported that when ewes from the University of Wyoming flock (farm flock with adequate nutrition) were fed 50% (nutrient-restricted) or 100% (control-fed) of the NRC-recommended nutrient requirements between d 28 and 78 of gestation, fetal weights as well as concentrations of most AA in maternal and fetal blood were substantially reduced in nutrient-restricted vs. control-fed pregnancies. The current study utilized Baggs ewes, which were selected under a markedly different production system (range flock with limited nutrition), to test the hypothesis that adaptation of ewes to nutritional and environmental changes may alter placental efficiency and conceptus nutrient availability in the face of maternal nutrient restriction. Baggs ewes received 50 or 100% of the NRC nutrient requirements between d 28 and 78 of pregnancy. On d 78, maternal uterine arterial and fetal umbilical venous blood samples were obtained, and the ewes were euthanized. Amino acids and their metabolites (ammonia, urea, and polyamines) in plasma were analyzed using enzymatic and HPLC methods. The results showed that maternal plasma concentrations of 9 AA (Asp, Ile, Leu, Lys, Orn, Phe, Thr, Trp, and Val) as well as maternal and fetal plasma concentrations of ammonia and urea were reduced (P < 0.05) in nutrient-restricted compared with control-fed Baggs ewes. However, fetal plasma concentrations of all AA and polyamines did not differ (P = 0.842) between the 2 groups of ewes. Collectively, these findings suggest that Baggs ewes, by adapting to the harsh conditions and limited nutrition under which they were selected, were able to maintain fetal concentrations of AA in the face of a maternal nutrient restriction through augmenting placental efficiency.

This study evaluated the role of MAPK/ERK1/2 and/or PI3K/Akt signaling pathways in modulating ovine placentomal vascularity in response to periconceptional maternal nutrient restriction. Ewes were randomly assigned to be nutrient restricted (NR, 50% NRC recommendation, N=7) or control fed (CF, 100% NRC recommendation, N=7) from 60 +/- 2 days before to 30 days after conception (day 0). From day 31 of gestation, all ewes (CF and NR) were fed the control diet until necropsy on day 78. On day 78 of gestation, NR ewes exhibited greater vascularity in both caruncular (CAR) and cotyledon (COT) tissues than CF ewes. Akt or ERK1/2 content in CAR and COT arterial tissue did not differ across dietary treatment. The activated forms, phosphorylated Akt and phosphorylated ERK1/2, were significantly increased in COT but not CAR arterial tissues of NR ewes compared to those of CF ewes (P<0.05). For both CF and NR ewes, phosphorylated Akt and phosphorylated ERK1/2 content in COT are higher (P<0.05) than those in CAR arterial tissues. Immunohistochemical staining revealed cytoplasmic and nuclear localization of Akt, phosphorylated Akt, ERK1/2 and phosphorylated ERK1/2, with phosphorylated Akt and phosphorylated-ERK1/2 specifically localized in trophoblast cells, while binucleate cells remained unstained. In placentomal blood vessels, Akt, phosphorylated Akt, ERK1/2 and phosphorylated ERK1/2 were localized to both endothelium and smooth muscle cells. These findings demonstrate for the first time that periconceptional NR increases vascular density in both COT than CAR tissues of the ovine placentome, and that the MAPK/ERK1/2 and/or PI3K/Akt signaling pathways are increased in NR COT but not NR CAR arterial tissues.

Information on the influence of poor maternal nutrition on the regulation of responses to pregnancy, placental and fetal growth and development is critical to a better understanding of pregnancy physiology and pathophysiology. We determined normal changes and effects of controlled and monitored moderate nutrient restriction (NR) (global nutrient intake reduced to 70% of food consumed by mothers feeding ad libitum from 0.16 to 0.5 of gestation) in the baboon, on important hematological, biochemical, and hormonal indices of fetal growth and placental function. Serum IGF-I:IGFBP-3 ratio was lower in pregnant than control non-pregnant baboons feeding ad libitum. Serum concentrations of total and free IGF-I were decreased in NR mothers compared with controls (p<0.05). The decrease in fetal IGF-I did not reach significance (p=0.057). Serum IGF-I: IGFBP-3 ratio was decreased by NR in both mothers and fetuses. Maternal serum IGF-II was unchanged by NR. Placental IGF-I mRNA and protein abundance were similarly reduced whereas IGF-II mRNA increased in placental tissue of NR compared to control mothers. Systemic (maternal) and local (placental) IGFBP-1 and IGFBP-3 mRNA and protein abundance were unchanged by NR. Type 1 IGF receptor protein in the syncytiotrophoblast increased in NR. Type 2 IGF receptor protein was present in the stem villi core, and decreased after NR. We conclude that moderate NR in this important non-human primate model significantly disrupts the maternal and placental IGF-IGFBP axis and influences placental expression of this key system at the gene and protein level. Changes observed appear to be directed toward preserving placental growth.

The aims of the present study were to describe the ontogeny of spatial relationships between placental components in baboons and to investigate alterations in these indices following (1) moderate maternal nutrient restriction and (2) administration of glucocorticoids to pregnant baboons. We investigated the effects of glucocorticoids since they have been shown to play a role in the altered fetal growth that accompanies maternal nutrient restriction. Glucocorticoids are also given to pregnant women who threaten premature labor to accelerate fetal lung maturation. A third aim was to compare our findings to those in similar conditions in human pregnancy. Volumetric placental development in the baboon was similar to that in the human, although growth of fetal capillaries was slower over the second half of gestation in baboon than in human placentas. Intervillous space (IVS) and villous star volumes were halved at the end of gestation compared to the middle of gestation, as described in the human placenta. When mothers were fed 70% of feed eaten by controls fed ad libitum, placental volumetric structure was unchanged at mid-gestation but was altered by the end of gestation when placental weight, but not fetal weight or length, was decreased. At the end of gestation villous volume and surface area, capillary surface area, and the villous isomorphic coefficient were all decreased, In contrast, IVS hydraulic diameter was increased. All parameters were similar in pregnancies with male and female fetuses, with the exception of fetal capillary volume, which was unchanged in pooled samples and those from male fetuses, but decreased in pregnancies with female fetuses. Glucocorticoid administration during the second half of gestation did not produce any changes in the measured indices of placental composition. In summary, these changes in placental structure, associated with maternal nutrient restriction, would all act to decrease placental transport of nutrients. The influence of MNR on villous capillarization depends on fetal gender.

This study evaluated the role of MAPK/ERK1/2 and/or PI3-K/Akt signaling pathways in modulating bovine placentomal vascularity in response to maternal nutrient restriction. Beef cows were randomly assigned to control fed (Control, n=15, 100% of requirements) or nutrient restricted (NR, n=15, 50% requirements) diets from day 30 to day 125 of gestation. Ten cows from each dietary group were necropsied on day 125 (approximately 45% gestation), and the remaining cows in each diet group were then fed control diets and necropsied on day 250 (approximately 90% gestation). At day 125 of gestation, NR cows exhibited increased (P=0.06) COT vascularity, improved (P<0.05) placentome efficiency (fetal weight/placentomal weight), and increased (P<0.05) phosphorylated Akt and ERK1/2 in COT arteries compared to Control cows. By day 250, however, treatment differences in COT vascularity and phosphorylated Akt and ERK1/2 in COT arteries were lost. On both gestational days, no treatment difference was observed in the levels of phosphorylated Akt or ERK1/2 in CAR arteries. CAR vascularity was similar across treatment on day 125, but tended to be greater (P<0.10) in NR than Control cows on day 250. These data suggest that conceptuses react to an early gestational nutrient restriction by up-regulating COT growth signaling pathways associated with angiogenesis, and that these compensations do not persist to term.

Maternal nutrient restriction from early to midgestation can lead to fetal growth retardation, with long-term impacts on offspring growth, physiology, and metabolism. We hypothesized that ewes from flocks managed under markedly different environmental conditions and levels of nutrition might differ in their ability to protect their own fetus from a bout of maternal nutrient restriction. We utilized multiparous ewes of similar breeding, age, and parity from 2 flocks managed as 1) ewes adapted to a nomadic existence and year-long, limited nutrition near Baggs, WY (Baggs ewes), and 2) University of Wyoming ewes with a sedentary lifestyle and continuous provision of more than adequate nutrition (UW ewes). Groups of Baggs ewes and UW ewes were fed 50 (nutrient restricted) or 100% (control fed) of National Research Council recommendations from d 28 to 78 of gestation, then necropsied, and fetal and placental data were obtained. Although there was a marked decrease (P < 0.05) in fetal weight and blood glucose concentrations in nutrient-restricted vs. control fed UW ewes, there was no difference in these fetal measurements between nutrient-restricted and control-fed Baggs ewes. Nutrient-restricted and control-fed UW ewes exhibited predominantly type A placentomes on d 78, but there were fewer (P c0.05) type A and greater (P < 0.05) numbers of type B, C, and D placentomes in nutrient-restricted than control-fed Baggs ewes. Placental efficiency (fetal weight/placentomal weight) was reduced (P = 0.04) in d 78 nutrient-restricted UW ewes when compared with control-fed UW ewes. In contrast, nutrient-restricted and control-fed Baggs ewes exhibited similar placental efficiencies on d 78. This is the first report of different placental responses to a nutritional challenge during pregnancy when ewes were selected under different management systems. These data are consistent with the concept that Baggs ewes or their conceptuses, which were adapted to both harsh environments and limited nutrition, initiated conversion of type A placentomes to other placentomal types when subjected to an early to mid-gestational nutrient restriction, whereas this conversion failed to occur in UW ewes. This early placentomal conversion in the Baggs ewes may function to maintain normal nutrient delivery to their developing fetuses during maternal nutrient restriction.

Glucocorticoid administration to women in premature labor significantly decreases preterm infant morbidity and mortality. Fetal exposure to maternally administered glucocorticoids in late gestation causes fetal hypertension. We determined the effects of a single course (4 injections at 12-hr intervals) of dexamethasone (DM; 2 mg, a weight-adjusted dose equivalent to one-third the dose administered to pregnant women) or saline (S) in sheep at 103-104 days of gestation (dGA; term 149 dGA) on maternal and fetal blood pressure (BP). We also determined the BP and placental perfusion effects of acute maternal hypoxemia. Venous and arterial catheters were placed in 10 ewes and fetuses (DM = 6, S = 4) at 96 +/- 1 dGA. Maternal and fetal placental perfusion was determined with fluorescent microspheres. Dexamethasone increased fetal but not maternal BP; maternal and fetal placental blood flow and vascular resistance (VR) were unchanged. At 105 dGA, hypoxemia was induced for 1 hr by maternal nitrogen gas inhalation to decrease fetal PaO2 by 40%. Hypoxemia increased BP in DM but not S fetuses or mothers in either group. Hypoxemia decreased maternal placental blood flow by 39 +/- 7% and 51 +/- 9% and increased maternal placental VR by 65 +/- 7% and 69 +/- 6% in S and DM mothers, respectively. Hypoxemia did not alter fetal placental blood flow or VR in either treatment group. In summary, at 0.7 gestation, DM induces a hypertensive response to fetal hypoxemia that is characteristic of older fetuses but does not alter hypoxemia-induced reductions in maternal placental blood flow.

Despite National Institutes of Health recommendations to administer antenatal steroids as a single course to women threatening preterm delivery, repeated treatments are often given. We investigated effects of repeated dexamethasone (DM) administered to the ewe on small maternal and foetal placental arteries. We hypothesized that DM would increase responsiveness to endothelin-1 (ET-1) and norepinephrine (NE) and that foetal arteries would react differently to ET-1 and NE compared to maternal arteries. Ewes received three treatments beginning at 103, 110, and 117 days of gestation (dGA). Each treatment consisted of four IM injections of 2mg DM or saline at 12-h intervals. At 119 dGA, in vitro functional studies were performed using Mulvany wire myography and endothelin receptor (ETR) expression was quantified using real-time RTPCR and receptor ligand autoradiography. Foetal placental arteries demonstrated greater maximal contractility to ET-1 and lesser maximal contractility to NE compared to maternal arteries. DM increased the maximal contraction elicited by ET-1 and NE in foetal but not maternal placental arteries. DM also increased the abundance of type-A ETR but not type-B ETR mRNA in foetal but not maternal placental arteries. However, within the whole placentome, DM increased the abundance of type-B ETR and decreased type-A ETR mRNA, which was confirmed by similar changes in ETR binding specifically within the labyrinth region. In summary, repeated DM treatment results in agonist and vascular bed specific responses within the placenta.

Fetal glucocorticoid-induced premature labor in sheep is an established model of premature labor. However, the pathways by which fetal cortisol triggers subsequent maternal endocrine changes, including enhanced PG synthesis, leading to labor are unclear. The current study was undertaken to determine whether cortisol administration to adrenalectomized fetuses to clamp fetal cortisol at levels present early in the late gestation rise, which are inadequate to produce labor, can stimulate placental, myometrial, and endometrial prostaglandin G/H synthase 2 mRNA and protein expression. At 109--13 d gestation, fetal sheep adrenals were removed (n = 8), or sham surgery was performed (n = 4). From d 6 postadrenalectomy, maternal and fetal plasma cortisol were determined daily by RIA. From d 7 postadrenalectomy, cortisol (4 micro/min) was continuously infused iv to four adrenalectomized fetuses. Endometrium, myometrium, and placentome were collected from all three groups of ewes (n = 4 for each group), and total RNA and proteins were extracted from each intrauterine tissue and analyzed by Northern and Western for prostaglandin G/H synthase 2 mRNA and protein. P45017 alpha hydroxylase mRNA was analyzed in the placentome by Northern blot. Data were analyzed by ANOVA. Plasma cortisol levels remained low in sham-operated and adrenalectomized fetus, whereas during cortisol infusion to adrenalectomized and cortisol-treated fetuses, plasma cortisol increased to the late gestation level. After adrenalectomy, prostaglandin G/H synthase 2 did not change in any tissue studied. Fetal plasma cortisol replacement to late gestation levels increased prostaglandin G/H synthase 2 to levels similar to term levels in all three tissues. PGHS1 mRNA and protein did not change in any group studied. There was a minimal increase in P45017 alpha hydroxylase mRNA in the placentome in the adrenalectomized and cortisol-treated group. Cortisol- induced labor further increased P45017 alpha hydroxylase mRNA in the placentome compared with that in adrenalectomized and cortisol-treated animals. These data provide evidence for in vivo cortisol up-regulation of prostaglandin G/H synthase 2, but not PGHS1, in late gestation in the ovine placentome, myometrium, and endometrium. As stimulation of the estrogen biosynthetic pathway was minimal in the adrenalectomized and cortisol-treated group, these data provide support for the concept that cortisol has a direct effect on prostaglandin G/H synthase 2 expression in addition to its classical indirect pathway on prostaglandin G/H synthase 2 as a result of estrogen synthesis.

Objective: The purposes of this study were to determine (1) whether uterine tissues as well as the fetal placenta are involved in the development of prostaglandin-synthesizing capacity associated with impending labor in pregnant sheep and (2) whether the key enzyme of prostaglandin synthesis, prostaglandin H synthase 2, is differentially expressed in the different intrauterine tissues during late gestation and in association with labor., Study Design: Myometrium, endometrium, and fetal placenta were removed from ewes at 95 days' gestation, (n = 3), 101 to 110 days' gestation (n = 3), 111 to 120 days' gestation (n = 3), 121 to 130 days' gestation (n = 3), 131 to 140 days' gestation (n = 3), and 141 to 145 days' gestation (n = 4) and from ewes in spontaneous term labor at 143 to 147 days' gestation (n = 4). Expressions of prostaglandin H synthase 2 messenger ribonucleic acid and protein were determined by Northern blot and Western blot analyses. Prostaglandin H synthase 2 was localized in the fetal placenta by immunohistochemical means., Results: Levels of both prostaglandin H synthase 2 messenger ribonucleic acid and protein increased gradually from 115 days' gestation in the fetal placenta and from 131 days' gestation in the endometrium. A further and more significant increase in prostaglandin H synthase 2 concentration occurred in the placenta and endometrium during spontaneous term labor. In contrast, myometrial concentrations of prostaglandin H synthase 2 messenger ribonucleic acid and protein remained at steady basal levels during the course of pregnancy and increased only during labor. Prostaglandin H synthase 2 was localized in the trophoblast cells of the fetal placenta., Conclusions: Tissue-specific ontogenic expression of prostaglandin H synthase 2 was observed in myometrium, endometrium, and placenta during late ovine gestation and spontaneous term labor. Fetal placenta and endometrium showed increased expression of prostaglandin H synthase 2 messenger ribonucleic acid and protein during late ovine gestation, whereas myometrial prostaglandin H synthase 2 concentration remained low throughout late gestation. Prostaglandin H synthase 2 concentrations in the myometrium, endometrium, and placenta are all upwardly regulated during labor.

Objective: Our purpose was to determine differential effects of natural and synthetic glucocorticoids on cytochrome 17alpha-hydroxylase and cytochrome P-450 side-chain cleavage messenger ribonucleic acid in the sheep placenta and to determine whether feed-forward effects during labor are involved in further inducing placental cytochrome 17alpha-hydroxylase., Study Design: Sheep underwent placement of myometrial electromyogram electrodes while they were under general anesthesia at 117 days' gestation. At 125 days' gestation either saline solution (early control animals not in labor, n = 5), 0.48 mg betamethasone during 48 hours (n = 7), 0.48 mg dexamethasone during 48 hours (n = 7), or 55 mg cortisol during a maximum of 96 hours (n = 4) was directly administered intravenously to the fetus. Necropsies were performed at 127 to 129 days' gestation. We also studied 6 ewes in spontaneous term labor at 143-147 days' gestation, 6 term control animals not in labor at 140 to 147 days' gestation, and 6 sheep in which myometrial activity was inhibited by intravenous infusion to the ewe of the selective cyclooxygenase 2 inhibitor nimesulide 9 hours after the onset of labor beginning at 147 to 148 days' gestation. Total fetal placental ribonucleic acid was analyzed by Northern blot with complementary deoxyribonucleic acid probes for cytochrome 17alpha-hydroxylase, cytochrome P-450 side-chain cleavage, and 18S ribosomal ribonucleic acid to correct for loading., Results: Placental cytochrome 17alpha-hydroxylase messenger ribonucleic acid was detectable neither in term control animals not in labor nor in early control animals not in labor. Placental cytochrome 17alpha-hydroxylase messenger ribonucleic acid was induced in spontaneous term labor and all cortisol-infused sheep in labor with respect to term control animals not in labor and early control animals not in labor (P <.01). All betamethasone-infused sheep had myometrial contraction activity; however, only 4 of 7 had detectable placental cytochrome 17alpha-hydroxylase messenger ribonucleic acid. Placental cytochrome 17alpha-hydroxylase messenger ribonucleic acid was not detected in dexamethasone-infused sheep, even the 2 that had myometrial contractions. After reversal of the progression of spontaneous labor with nimesulide placental cytochrome 17alpha-hydroxylase messenger ribonucleic acid was significantly lower than the spontaneous term labor group (without nimesulide treatment). The placentas from all animals expressed cytochrome P-450 side-chain cleavage messenger ribonucleic acid, but no changes were associated with either gestational age studied (130 versus > 140 days' gestation) or glucocorticoid-induced premature labor and spontaneous term labor., Conclusions: (1) In sheep the expression of placental cytochrome 17alpha-hydroxylase is tightly associated with spontaneous term labor, and active synthesis of placental cytochrome 17alpha-hydroxylase is required during the progression of labor. (2) Cortisol is a more potent stimulator of placental cytochrome 17alpha-hydroxylase messenger ribonucleic acid in sheep than are synthetic glucocorticoids. (3) Betamethasone has a greater effect in inducing labor in sheep than does dexamethasone, possibly mediated through placental cytochrome 17alpha-hydroxylase.

Objective: Our purpose was to investigate, first, whether there were changes in the abundance of prostacyclin synthase protein in intrauterine tissues of pregnant ewes in association with spontaneous term labor. Second, we examined the effect of either estradiol or progesterone, or both, on regulation of prostacyclin synthase protein abundance in uterine tissues using an ovariectomized nonpregnant sheep model., Study Design: The abundance of prostacyclin synthase protein was quantified by Western blot analysis in the myometrium, endometrium, and placenta of pregnant ewes in spontaneous term labor (n = 6) and term control ewes not in labor (n = 6). The changes of prostacyclin synthase in the myometrium and endometrium of 20 ovariectomized nonpregnant sheep (n = 5 for each group) were evaluated after treatment with estradiol, progesterone, or both., Results: Prostacyclin synthase protein was present in pregnant and nonpregnant sheep myometrium, endometrium, and placenta at a molecular weight of about 55 kd. At spontaneous term labor the level of prostacyclin synthase decreased in endometrium (P <.05), increased in myometrium (P <.05), and remained unchanged in placenta. Estradiol and progesterone had no effect on prostacyclin synthase protein abundance in nonpregnant ovine endometrium and myometrium., Conclusions: The decrease in prostacyclin synthase in pregnant sheep endometrium during labor may indicate paracrine interactions between the endometrium, the myometrium, fetal membranes, or a combination of these. The significant increase of prostacyclin synthase in pregnant sheep myometrium at spontaneous term labor may contribute to the increased uterine sensitivity to oxytocin or stimulate vasodilatation during labor to increase myometrial blood flow. Neither estradiol nor progesterone at the dosages studied changed prostacyclin synthase expression in the nonpregnant myometrium and endometrium. The molecular mechanism or mechanisms that differentially regulate prostacyclin synthase expression in pregnant uterine tissues merit further study.

The oxytocin antagonist, atosiban (1-deamino-2-D-tyr(OET)-4-thr-8-orn-vasotocin/oxytocin), was infused i.v. to chronically instrumented pregnant baboons in the last third of pregnancy. Atosiban (6 microg/kg per min) inhibited myometrial electromyographic activity associated with spontaneous myometrial contractions that occurred around the onset of darkness between 134 and 162 days gestation (term 180 days gestation). The effect of atosiban on maternal heart rate was minimal. Maternal blood pressure remained unaltered during atosiban infusion. Fetal carotid arterial PO2 was unchanged during a 2-h infusion of atosiban. Transplacental passage of atosiban from mother to fetus was assessed at cesarean section under halothane anesthesia in four baboons and in two chronically instrumented fetuses in the absence of anesthesia. The maternal:fetal concentration gradient ranged from 9.2 to 22.8. Maternal atosiban clearance rates were 9.2-16.9 ml/kg per min. In conclusion, atosiban was very effective at inhibiting spontaneously occurring nocturnal myometrial contractions during the last third of gestation in the pregnant baboon. Although atosiban crosses the placenta relatively freely, there was no effect on fetal oxygenation.

To assess the interaction among androgens, placenta, and the hypothalamo-pituitary-adrenal axis we studied effects of androstenedione administered intravascularly to the pregnant monkey on maternal plasma CRH, ACTH, dehydroepiandrosterone sulfate (DHEAS), cortisol, and estradiol concentrations. Ten monkeys (128 +/- 3 days gestation; mean +/- SEM) were instrumented under general halothane anesthesia with maternal femoral artery and venous catheters and uterine electromyogram electrodes. At 137-144 days gestation, baseline maternal femoral artery samples for CRH, ACTH, DHEAS, cortisol, and estradiol measurements were taken at 1.5-h intervals for 7 h starting 2 h before darkness. On the following day, a continuous iv androstenedione infusion (0.3 mg/kg.min at 0.25 ml/h) in 10% intralipid was started at 0930 h in four monkeys; the other six animals received vehicle alone at the same rate starting at the same time. Maternal blood sampling was repeated 1 and 3 days after androstenedione or vehicle administration. Maternal plasma CRH, ACTH, DHEAS, cortisol, and estradiol levels were unaffected by intralipid. In contrast, androstenedione infusion produced a sustained increase in maternal plasma estradiol and a sustained fall in maternal plasma ACTH, but did not affect maternal plasma CRH, DHEAS, or cortisol concentrations. These results provide evidence for negative feedback regulation by androgens at the hypothalamo-pituitary-adrenal axis in the pregnant monkey. Lack of inhibition of maternal plasma CRH after androstenedione administration supports differential regulation of hypothalamic and placental CRH by androgens.

Maternal plasma corticotropin-Releasing Hormone (CRH) rises from midgestation to term and increases further during labor in pregnant women. The primate placenta contains both the CRH peptide and its gene and is the likely source of circulating CRH. In the present study, we examined CRH messenger RNA (mRNA) and peptide expression in fetal membranes and the placenta of 14 pregnant rhesus monkeys (140-161 days gestational age) using Northern blot analysis, in situ hybridization, and immunocytochemistry to define the cellular distribution of CRH during the last third of pregnancy and in relation to onset of both spontaneous term and androstenedione-induced preterm labor. To localize the target tissues for placental CRH, CRH receptor gene expression was also studied in the fetal membranes and placenta. CRH mRNA in the placenta was of similar molecular size to hypothalamic CRH. Placental CRH mRNA increased significantly during both spontaneous term and androstenedione-induced preterm labor (P < 0.05). Placental CRH peptide detected by CRH immunostaining also increased, matching the changes of CRH mRNA. In situ hybridization and immunocytochemistry demonstrated that syncytiotrophoblast cells are the major cell type expressing CRH mRNA and producing CRH protein. CRH mRNA was not detected in either amnion or chorion. CRH receptor complementary DNA and oligo probes that successfully hybridized CRH receptor mRNA in the fetal rhesus monkey hypothalamus failed to reveal the existence of CRH receptor mRNA in amnion, chorion, and placenta by Northern blot hybridization. In conclusion, placental but not fetal membrane syncytiotrophoblasts are the source of CRH production in the pregnant rhesus monkey. The significant increase in CRH peptide and mRNA content in both spontaneous term and androstenedione-induced preterm labor indicates a role for CRH in the process of parturition. The lack of CRH receptor mRNA in either the fetal membranes or the placenta suggests that placental CRH exerts its action at sites other than these tissues.

This study investigated whether the prostaglandin H synthase (PGHS) enzyme activity of sheep fetal placental cotyledon can be induced by cortisol at 128-131 days of gestation (dga) as compared to gestational age matched controls, before PGHS's normal gestational increase would occur (experiment 1). This study also investigated whether active PGHS is diminished following prostanoid synthesis in the labor process (experiment 2). A PGHS activity assay was employed in which PGE2 product was measured under initial velocity conditions. Labor was induced before term by continuous infusion of 10 mg of cortisol succinate per day (day 1) followed by 15 mg per day (days 2-4, or until delivery) of cortisol succinate administered through the fetal saphenous vein. Cotyledonary tissue was collected from sheep at term (142-145 dga), as judged by the absence of labor-type myometrial electromyogram (EMG) activity, and during cortisol induction at 128-131 dga. Tissue was also collected from term laboring animals immediately after fetal delivery while the fetus was still attached to the umbilicus and before placental delivery. At 128-131 dga, cortisol had no significant effect on PGHS activity as compared to gestational age matched saline-infused controls; thus, it is unlikely that cortisol directly induces PGHS. In experiment 2, normal progression of active spontaneous labor led to a significant diminution of PGHS activity (p < 0.05) that may be partially explained, based on thin-layer chromatography (TLC) results, as a significant decrease in PGE2 (p < 0.05) production coincident with a lesser compensatory increase in PGD2 (p = 0.06) output.

An activity assay is described quantification of prostaglandin synthase (PGHS) in sheep placental cotyledon under initial velocity conditions through measurement of the stable product prostaglandin E2 (PGE2). The effects of temperature, time, and substrate concentration on initial reaction velocity, and lipoxygenase and PGHS product formation in cotyledonary tissue, were examined in detail. We used this activity assay to determine whether or not an increase of active PGHS by placental location within the uterus might contribute selected prostaglandins (PG) for the directed initiation of parturition. Sheep cotyledon tissue was collected (n = 6 animals) from the ventral aspect of the uterine body, mid-horn, and horn tip at 122 days of gestation (dga), and from the same locations in the ventral body and horn tip at 142-145 dga (in animals at term but not in labor; n = 4). At 122 dga, there was no increase in active PGHS in cotyledonary tissue from the horn tip, mid-horn, or uterine body. By 142-145 dga, the horn showed significantly (p < 0.01) more enzyme activity than the body. At the same time, production of PGE2, expressed as a percentage of total eicosanoids, had not changed significantly. The development of an increase in PGHS toward the uterine tip implies that variations in regional PG production may contribute to the progression of labor.

The present study was designed to characterize the developmental pattern of specific prostaglandin endoperoxide synthase (PGS) isoform immunoreactivity and activity in tissues of fetal origin during the last half of gestation in sheep. Fetal amnion, allantochorion, and cotyledons were collected under halothane general anesthesia on days 79-80, 105-108, 120-122, 128-131, and 140-145 (term) of pregnancy. Solubilized extracts were prepared and analyzed by immunoblots using anti-PGS antibodies previously shown to recognize PGS isoform-1 and -2 (PGS-1 and PGS-2). PGS activity from cotyledon microsomes was assayed by the measurement of prostaglandin E2 (PGE2) production under initial velocity conditions. All fetal tissues contained PGS-1 at each of the stages of gestation examined, with minimal regulation of this isoform from 79-144 days gestation. In contrast, PGS-2 increased gradually in the cotyledons from 120-139 days gestation, with the most marked expression observed at term. PGS-2 was not detected in amnion or allantochorion. PGS activity in cotyledons increased (P < 0.01) in parallel with immunoreactive PGS-2 levels; indicating that PGS-2, rather than PGS-1, is associated with increased PG synthesis in this tissue. Both the activity (n = 5/group) and the amount of PGS-2 increased significantly from 105-108 days gestation to term (P < 0.01). We conclude that the increase in PGS that occurs at term in sheep is predominantly active PGS-2 localized to fetal cotyledons.

Objective: Our aim was to reassess the role of the fetus in the initiation of parturition in nonhuman primates. We tested the effect of the removal of the fetus at 121 to 130 days' gestation on the duration of gestation in pregnant rhesus monkeys., Study Design: Nine monkeys underwent fetectomy with the placenta in situ. Five monkeys underwent surgery without removal of the fetus., Results: In five control monkeys spontaneous vaginal delivery of live fetuses occurred at 163.8 +/- 4.6 days' gestation (mean +/- SD). In four of nine monkeys that underwent fetectomy the placenta delivered spontaneously at 185, 193, 201, and 207 days' gestation. The five remaining monkeys underwent cesarean section at 162, 189, 201, 202, and 219 days' gestation. Duration of placental retention in monkeys that underwent fetectomy (195 +/- 16.1 days' gestation) exceeded that in controls (p less than 0.05). Plasma progesterone and estradiol concentrations were normal for gestational age at fetectomy, indicating continued placental function., Conclusion: We conclude that the presence of a live fetus plays a significant role in the determination of the duration of normal pregnancy in the rhesus monkey.

To determine the capacity of the fetus to adapt to chronic O2 deficiency produced by decreased placental perfusion in the early development of growth retardation, we embolized the umbilical placental vascular bed of fetal sheep for a period of 9 days. Fetal umbilical placental embolization decreased arterial O2 content by 39%, decreased total placental blood flow by 33%, and produced a 20% reduction in mean fetal body weight. Neither the combined ventricular output nor the regional blood flow distribution was significantly different between the 8 growth-retarded and 7 normally grown fetuses despite the 39% decrease in fetal arterial O2 content. Thus a 33% reduction in total placental blood flow restricts normal fetal growth, but does not exceed the placental circulatory reserve capacity necessary to maintain normal basal metabolic oxygenation. Because the proportion of combined ventricular output to the placenta at rest is decreased in late IUGR fetuses but not in early IUGR fetuses, despite chronic oxygen deficiency, we conclude that the growth retarded fetus maintains a normal regional blood flow distribution until the placental circulatory reserve capacity is depleted.

The fine structural appearance of the placenta of the ewe has been examined following long-term infusion of CB154 into either the fetus or the pregnant ewe. Binucleate cells which usually contain aggregations of spherical membrane-bound electron-dense inclusions, are a characteristic component of the chorionic epithelium of the sheep. Following CB154 infusion into either the fetus or ewe at 111 to 137 days of gestation, binucleate cells were partially or completely depleted of the droplets which are present in binucleate cells of control animals at a similar gestational age. No obvious changes in the maternal epithelial syncytium were observed after CB154 administration. Infusion of CB154 into the fetus alone was also followed by degenerative changes in some binucleate cells which ranged from condensation of nuclei to complete cell fragmentation. Either a direct or an indirect action of CB154 on binucleate cells is suggested by these observations. Hypoprolactinaemia followed CB154 infusion in all treated animals; its possible influence on binucleate cell activity is discussed.

The alpaca is one of the four South American species of the family Camelidae. Its placenta, like that of other camelids, is diffuse and epitheliochorial in type. The chorionic epithelium is thrown into unbranched villi or folds which are closely apposed to corresponding undulations of the uterine epithelium, and the fetal-maternal interface consists of an intricate interdigitation of fetal and maternal microvilli. In late gestation both chorionic and uterine epithelia are deeply indented by placental capillaries, so that the minimum intercapillary distance across the diffusion pathway may be as little as 2 microns. This distance appears to be less than that found in the epitheliochorial placenta of any other species of domestic ungulate in late gestation: it may be one of several adaptations to pregnancy at high altitude. Delivery of the fetal membranes occurs some 45 minutes after the birth of the fetus. The placenta is non-deciduate.

Several clinical studies suggest that the Doppler indices (DI) derived from Doppler waveform analysis may be powerful predictors of perinatal compromise. In contrast, significant paucity exists in experimental verification of the central premise that the DI reliably reflect hemodynamic state downstream from the measurement point. This paper presents the results from two sets of acute animal experiments in which experimentally induced changes in the ovine fetoplacental circulation as reflected by the independently measured hemodynamic parameters were correlated with the corresponding variations in the DI. Doppler velocimetric measurements were performed under general anesthesia in ovine fetuses with gestational ages ranging from 100 to 110 days. A continuous wave Doppler instrument with a 4-MHz transducer was used. In three fetuses, variable vascular constriction was produced by a ligature placed approximately 10 cm from the probe location. In four fetuses, vasopressin was rapidly infused. The hemodynamic parameters measured included the peripheral resistance, volumetric flow, and pressure. The DI included the systolic-diastolic ratio, pulsatility index, and resistance index. The results indicate that, in hemodynamically stable and well-defined obstruction to downstream flow as achieved in the constriction experiments, the DI highly correlated with the hemodynamic state (p less than .005); however, during the more complex and unstable circulatory changes associated with vasopressin administration, these correlations were inconsistent and poor (p greater than .05). This study experimentally establishes in an in vivo animal system the hemodynamic validity of the DI within certain limits. However, the validity does not extend to hemodynamic changes associated with vasopressin administration. Further studies are required to address this issue.(ABSTRACT TRUNCATED AT 250 WORDS)

The MCR and placental permeability to oxytocin were determined in chronically catheterized pregnant sheep. Simultaneous maternal and fetal plasma oxytocin (OT) concentrations were measured by RIA before and during continuous infusion of synthetic OT to steady state conditions. Baseline fetal plasma OT concentrations were significantly higher than simultaneously collected maternal concentrations (1.6 +/- 0.13 vs. 1.1 +/- 0.13 muU/ml, respectively; P less than 0.01). Mean fetal OT MCRs were 12.0 +/- 1.35 and 12.1 +/- 1.09 ml/kg . min at OT infusion rates of 64 and 640 muU/kg . min. Mean maternal MCRs were 12.1 +/- 2.64 and 12.4 +/- 1.38 ml/kg . min at OT infusion rates of 80 and 800 muU/kg . min. Uterine contractions were induced by maternal OT infusion of 800 muU/kg . min but not by lower infusion rates; no uterine contractions were induced by fetal OT infusion. OT did not appear to cross the placenta in either direction under the present study conditions.

The placental changes which followed continuous infusion of cortisol into the sheep foetus in the later stages of gestation were, like the hormonal changes, broadly similar to those of spontaneous parturition. There was, however, a premature separation of foetal and maternal tissues in certain areas of the placental cotyledons, and this separation appeared to protect the foetal epithelium from the degenerative changes which normally take place in the short space of time between the birth of the lamb and the delivery of the foetal membranes. The results suggest that an experimental model in which premature labour is induced by the administration of cortisol to the foetus is probably incomplete, and that additional factors almost certainly contribute to the cascade phenomenon of spontaneous parturition.

Binucleate cells are a normal component of the ovine chorionic epithelium, but are usually separated from the fetal-maternal interface by a thin layer of cytoplasm derived from the principal or uni-nucleate cells of the trophoblast. They are distinguished not only by two distinct and separate nuclei, but also by conspicuous membrane-bound cytoplasmic inclusions in the form of haloed droplets. After fetal pituitary stalk section binucleate cells move up to and participate in the formation of the fetal-maternal interface; furthermore they extend clear blunt-ended pseudopodia into the maternal epithelial syncytium. These activities do not appear to be supppressed by fetal infusion of cortisol or ACTH. The apparent motility of binucleate cells, together with the presence of haloed droplets within the maternal epithelial syncytium, suggests that after fetal pituitary stalk section binucleate cells invade the uterine syncytium, lose their limiting membranes and discharge their contents into the syncytial cytoplasm. Large molecules such as ovine placental lactogen may be transported from fetal to maternal tissues by this mechanism.

Placental attachment and the ultrastructure of the decidua and placental labyrinth have been studied in rabbits during the final third of gestation. The placenta became progressively easier to separate from the uterine wall as gestation proceeded. This ease of separation was associated with degenerative changes in the decidual tissue, but disruption of the placental labyrinth was not observed until the last 24 hr of pregnancy. Two types of decidual cells were observed; smaller uninucleate glycogen-containing cells and larger multinucleate cells with lipid inclusions. The ageing placentae exhibited increasing decidual degeneration associated with deposition of extracellular fibrous materials. Glycogen became less widely distributed over the period of study and changed from the beta- to the alpha-configuration. In contrast to the observed disruption of the decidual tissue, the placental labyrinth maintained its integrity until the final stages of pregnancy. A dramatic increase in subcellular activity was observed in the syncytiotrophoblast after 28 days of gestation.

A variety of radioimmunoassays specifically characterized for use with fetal and maternal ovine plasma have been used to measure steroid hormone concentrations in small plasma samples drawn simultaneously from mother and fetus. By repeated sampling from the same animal preparation the changes over time of plasma concentrations of cortisol, pregnenolone and its sulphate, and oestrone and oestrone sulphate have been systematically studied. In animals delivering spontaneously at term the fetal plasma cortisol concentration rises between 120 and 130 days gestation and plays an important part in the maturation of several vital physiological systems, including the fetal thyroid axis. In normal term deliveries and premature deliveries induced by synthetic adrenocorticotropin (ACTH(1-24), 1 microgram h-1), the concentration of oestrone sulphate in maternal plasma increases before the fetal plasma concentration. Fetal and maternal oestrogens are probably important in the control of the low-grade tonic myometrial activity that occurs throughout gestation, in the initiation of labour and in the control of uterine blood flow. Low-grade tonic myometrial activity affects fetal oxygenation, fetal breathing and the fetal sleep state and may constitute a pathway through which the mother influences fetal development, with important physiological and possibly pathological consequences.

Maternal obesity (MO) causes maternal and fetal oxidative stress (OS) and metabolic dysfunction. We investigated whether supplementing obese mothers with resveratrol improves maternal metabolic alterations and reduces OS in the placenta and maternal and fetal liver. From weaning through pregnancy female Wistar rats ate chow (C) or a high-fat diet (MO). One month before mating until 19 days’ gestation (dG), half the rats received 20 mg resveratrol/kg/d orally (Cres and MOres). At 19dG, maternal body weight, retroperitoneal fat adipocyte size, metabolic parameters, and OS biomarkers in the placenta and liver were determined. MO mothers showed higher body weight, triglycerides and leptin serum concentrations, insulin resistance (IR), decreased small and increased large adipocytes, liver fat accumulation, and hepatic upregulation of genes related to IR and inflammatory processes. Placenta, maternal and fetal liver OS biomarkers were augmented in MO. MOres mothers showed more small and fewer large adipocytes, lower triglycerides serum concentrations, IR and liver fat accumulation, downregulation of genes related to IR and inflammatory processes, and lowered OS in mothers, placentas, and female fetal liver. Maternal resveratrol supplementation in obese rats improves maternal metabolism and reduces placental and liver OS of mothers and fetuses in a sex-dependent manner.

Objective: The purpose of this study was to examine glucocorticoid effects on umbilical placental perfusion. Study design: Pregnant sheep instrumented with uterine and umbilical ultrasound transit-time flow probes received 2 doses of 12 mg betamethasone (n = 6) or saline (n = 5) intramuscularly 24 hours apart. Results: Maternal blood pressure and uterine flow did not change during glucocorticoid exposure. Fetal blood pressure increased, and umbilical resistance showed a transient increase after each injection (P < .05), followed by an increase of umbilical flow (P < .05) that was closely correlated to an increase in fetal heart rate (r = 0.85, P < .001), which determines cardiac output of the developing heart. Umbilical waveform indices were decreased over the entire treatment period, indicating a decrease of resistance in the fetoplacental microcirculation (P < .05). Conclusion: Fetoplacental perfusion during glucocorticoid exposure is not limiting for nutrition exchange. Clinical interpretation of Doppler waveform indices needs to be interpreted with caution because they do not reflect dynamics of umbilical placental perfusion. [ABSTRACT FROM AUTHOR]

OBJECTIVE: We determined developmental and labor-related changes in 11β-hydroxysteroid (HSD) 1 and 2 expression in baboon placentas during the final third of gestation and labor. We examined whether maternal glucocorticoid administration alters placental 11β-HSD 2 expression. STUDY DESIGN: Maternal and fetal plasma cortisol concentrations were measured in five animals. Types 1 and 2 11β-HSD messenger RNA (mRNA) and protein in placentas obtained at 121 to 185 days' gestation (dGA, term approximately 185 dGA, n = 16), during labor between 141 and 193 dGA (n = 8), and after maternal administration of four doses of 87.5 µg/kg betamethasone (n = 5) at 12-hour intervals at 121 to 135 dGA were analyzed by Northern and Western blot. RESULTS: Cortisol levels were higher in maternal plasma than fetal (4-fold, P < .00001). Placental 11β-HSD 2 mRNA and protein decreased after 0.9 gestation (P < .001). 11β-HSD 1 mRNA remained unchanged. There was no effect of labor on placental 11β-HSD 1 and 2 mRNA and protein levels. Maternal betamethasone administration dramatically increased (P < .05) 11β-HSD 2 mRNA as well as protein without effect on 11β-HSD 1 mRNA and protein expression. CONCLUSIONS: The late-gestation baboon maternal plasma cortisol concentration is four times the fetal plasma concentration. Decreased placental 11β-HSD 2 may enhance maternal cortisol passage to the fetus at the end of gestation, thereby contributing to cortisol-mediated changes within the placenta and cortisol in fetal plasma at this stage of fetal development. The positive effect of betamethasone on placental 11β-HSD 2 induction further suggests an ability of the placenta to regulate glucocorticoid transfer in the presence of elevated maternal glucocorticoid. [ABSTRACT FROM AUTHOR]

Objective: We sought to evaluate whether in addition to cortisol, catecholamines also transfer psychosocial stress indirectly to the fetus by decreasing uterine blood flow (UBF) and increasing fetal anaerobic metabolism and stress hormones.Study Design: Seven pregnant sheep chronically instrumented with uterine ultrasound flow probes and catheters at 0.77 gestation underwent 2 hours of psychosocial stress by isolation. We used adrenergic blockade with labetalol to examine whether decreased UBF is catecholamine mediated and to determine to what extent stress transfer from mother to fetus is catecholamine dependent.Results: Stress induced transient increases in maternal cortisol and norepinephrine (NE). Maximum fetal plasma cortisol concentrations were 8.1 ± 2.1% of those in the mother suggesting its maternal origin. In parallel to the maternal NE increase, UBF decreased by maximum 22% for 30 minutes (P < .05). Fetal NE remained elevated for >2 hours accompanied by a prolonged blood pressure increase (P < .05). Fetuses developed a delayed and prolonged shift toward anaerobic metabolism in the presence of an unaltered oxygen supply. Adrenergic blockade prevented the stress-induced UBF decrease and, consequently, the fetal NE and blood pressure increase and the shift toward anaerobic metabolism.Conclusion: We conclude that catecholamine-induced decrease of UBF is a mechanism of maternal-fetal stress transfer. It may explain the influence of maternal stress on fetal development and on programming of adverse health outcomes in later life especially during early pregnancy when fetal glucocorticoid receptor expression is limited. [ABSTRACT FROM AUTHOR]