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The role of fetal cortisol in cardiovascular maturation in late gestation in the chronically instrumented sheep fetus has been studied. The fetal arterial blood pressure (FABP) and fetal heart rate (FHR) of five animals have been recorded continuously from 120 days of gestation to spontaneous term labor. The peak times and amplitudes of cosinor analysis were then compared at 120-126, 127-133 and 134-140 days of gestation. Results showed an increase in FABP but a decrease in FHR which are maintained consistently from 120 to 140 days of gestation. The higher FABP is controlled by the fetal adrenal but do not prevent cortisol from sustaining a higher FABP.

The effect of repeated compression of the umbilical cord of late-gestation sheep fetus in the hemodynamics cardiovascular responses was investigated through Sham experiments conducted on pregnant ewes carrying fetuses at 130 days of gestation. Results have shown that repeated cord compression abolished the primary fetal cardiovascular responses. It was indicated that the magnitude and gain of fetal cardiovascular responses may be altered by repeated preexposure to a stress.

Nonhuman primate (NHP) studies are crucial to biomedical research. NHPs are the species most similar to humans in lifespan, body size, and hormonal profiles. Planning research requires statistical power evaluation, which is difficult to perform when lacking directly relevant preliminary data. This is especially true for NHP developmental programming studies, which are scarce. We review the sample sizes reported, challenges, areas needing further work, and goals of NHP maternal nutritional programming studies. The literature search included 27 keywords, for example, maternal obesity, intrauterine growth restriction, maternal high-fat diet, and maternal nutrient reduction. Only fetal and postnatal offspring studies involving tissue collection or imaging were included. Twenty-eight studies investigated maternal over-nutrition and 33 under-nutrition; 23 involved macaques and 38 baboons. Analysis by sex was performed in 19; minimum group size ranged from 1 to 8 (mean 4.7 ± 0.52, median 4, mode 3) and maximum group size from 3 to 16 (8.3 ± 0.93, 8, 8). Sexes were pooled in 42 studies; minimum group size ranged from 2 to 16 (mean 5.3 ± 0.35, median 6, mode 6) and maximum group size from 4 to 26 (10.2 ± 0.92, 8, 8). A typical study with sex-based analyses had group size minimum 4 and maximum 8 per sex. Among studies with sexes pooled, minimum group size averaged 6 and maximum 8. All studies reported some significant differences between groups. Therefore, studies with group sizes 3–8 can detect significance between groups. To address deficiencies in the literature, goals include increasing age range, more frequently considering sex as a biological variable, expanding topics, replicating studies, exploring intergenerational effects, and examining interventions. [ABSTRACT FROM AUTHOR]

Mechanisms linking maternal nutrient restriction (MNR) to intra-uterine growth restriction (IUGR) and programming of adult disease remain to be established. The impact of controlled MNR on maternal and fetal amino acid metabolism has not been studied in non-human primates. We hypothesised that MNR in pregnant baboons decreases fetal amino acid availability by mid-gestation. We determined maternal and fetal circulating amino acid concentrations at 90 d gestation (90dG, term 184dG) in control baboons fed ad libitum (C, n 8) or 70 % of C (MNR, n 6). Before pregnancy, C and MNR body weights and circulating amino acids were similar. At 90dG, MNR mothers had lower body weight than C mothers (P< 0·05). Fetal and placental weights were similar between the groups. MNR reduced maternal blood urea N (BUN), fetal BUN and fetal BUN:creatinine. Except for histidine and lysine in the C and MNR groups and glutamine in the MNR group, circulating concentrations of all amino acids were lower at 90dG compared with pre-pregnancy. Maternal circulating amino acids at 90dG were similar in the MNR and C groups. In contrast, MNR fetal β-alanine, glycine and taurine all increased. In conclusion, maternal circulating amino acids were maintained at normal levels and fetal amino acid availability was not impaired in response to 30 % global MNR in pregnant baboons. However, MNR weight gain was reduced, suggesting adaptation in maternal–fetal resource allocation in an attempt to maintain normal fetal growth. We speculate that these adaptive mechanisms may fail later in gestation when fetal nutrient demands increase rapidly, resulting in IUGR. [ABSTRACT FROM PUBLISHER]

Objectives: Pregnant baboons were studied to determine the precise time of the switch from myometrial contractures to contractions in relation to photoperiod after laparotomy and at parturition. We compared the patterns recorded in baboons to those we have previously reported in pregnant rhesus monkeys to determine fundamental primate characteristics.Methods: Seven pregnant baboons (126–160 days’ gestation) were instrumented with femoral arterial and venous catheters and electrodes for myometrial electromyogram. All animals were subjected to a 14-hour light:10-hour dark photoperiod. Myometrial activity was monitored using a computer-based data acquisition system. Onset time for all switches was noted and standardized against time of lights off. Animals were studied at three stages of pregnancy (stage 1, first 10 days after laparotomy; stage 2, more than 10 days after laparotomy and more than 10 days before cesarean; and stage 3, 10 days before cesarean section or vaginal delivery).Results: All baboons demonstrated myometrial switches for a variable number of days preceding parturition. Onset of darkness was 0 hours. Average time of stage 1 switch onset was 2.17 ± 0.60 hours and was not different from stage 3 switch onset, which was −1.00 ± 0.27 hours.Conclusions: Myometrial contractile patterns showed clear photoperiodicity in the switch from contractures to contractions in late pregnancy in the baboon. The relationship of the switch from contractures to contractions was not altered by surgical laparotomy. There was a significant difference in the time of switch in relation to photoperiod between pregnant rhesus monkeys and baboons. However, the fact that a significant photoperiod exists in both species indicates a fundamental similarity in the switch from contractures to contractions in primate pregnancy. [Copyright &y& Elsevier]

Objective:We tested the hypothesis that betamethasone is more potent than dexamethasone in inducing the essential mechanisms of parturition in sheep.Methods:Twenty-one sheep were instrumented under general anesthesia with maternal and fetal arterial and venous catheters and myometrial electromyogram electrodes at 117 days' gestation (dGA). At 125 dGA at 12:00 PM, after 2 days of baseline recording, either saline (n = 7, control group), betamethasone (n = 7), or dexamethasone (n = 7) was administered into the fetal jugular vein at a rate of 10 μg/hour. A total dose of 0.48 mg was given over the next 48 hours. The animals underwent autopsy 3 days after the end of the infusion period (130 dGA), or earlier if labor resulted from the glucocorticoid administration. Daily maternal and fetal arterial blood samples (4 mL) for hormone measurement were taken at 10:00 AM throughout the study period. Additional arterial blood samples were taken if the animal developed labor. Maternal plasma progesterone and fetal ACTH and cortisol concentrations were measured by radioimmunoassay, and corticosteroid-binding globulin (CBG) binding capacity was determined by saturation analysis. Myometrial activity was monitored continuously throughout the experimental protocol.Results:All seven betamethasone-treated animals developed labor after the glucocorticoid infusion regimen. In contrast, only two of seven dexamethasone-treated animals developed labor. Fetal treatment with betamethasone produced a greater and earlier fall in maternal plasma progesterone than fetal treatment with dexamethasone. Both betamethasone and dexamethasone treatments elevated fetal plasma CBG to similar binding capacities. Elevated fetal plasma ACTH and cortisol concentrations at the end of the infusion period in both betamethasone- and dexamethasone-treated animals were not related to the development of labor-type contractions.Conclusion:These data support the hypothesis that betamethasone is more potent than dexamethasone in inducing the essential mechanisms of parturition in sheep. [ABSTRACT FROM PUBLISHER]

Objective:Our purposes were to asses the effects of prostaglandin (PG) E2 and PGF2α on myometrial contractility in pregnant sheep and baboons in an in vitro superfusion study, and to characterize further the PGE-sensitive (EP) receptor subtype involved in the myometrial response to PGE2 by using the selective prostanoid EP2 agonist AH 13205.Methods:Strip preparations of uterine muscle from 15 sheep (107-145 days' gestational age) and ten baboons (158-185 days' gestation) were studied. Cumulative concentration-response curves (CRC) were constructed to oxytocin (4.2 pmol/L to 0.42 μmol/L, PGE2 (0.1 nmol/L to 1 μmol/L), and PGF2α (1 nmol/L to 100 μmol/L), and 50% effective concentration (EC50) values (mean and 95% confidence interval) were calculated. We also tested the hypothesis that PGE2-induced myometrial relaxation in pregnant baboons could be mediated by EP2-prostanoid receptors. Myometrial strips were stimulated by oxytocin (0.42 nmol/L), and CRCs to the EP2-agonist AH 13205 (0.1 nmol/L to 10 μmol/L) were constructed.Results:Prostaglandin F2α stimulated myometrial activity in a concentration-related fashion in all preparations from both sheep and baboons. The EC50 in the sheep myometrium for PGF2α (52 nmol/L, 95% confidence interval [CI] 25-110) was significantly (P < .05) lower than that in baboon myometrium (183 nmol/L, 95% CI 93-355). Oxytocin stimulated myometrial activity in preparations of both sheep (EC50 = 0.29 nmol/L, 95% CI 0.11-0.71) and baboon (EC50 = 0.31 nmol/L, 95% CI 0.18-0.52). In contrast, responses to PGE2 were species-related: PGE2 caused concentration-related stimulation of myometrial activity in sheep tissue (EC50 = 3.2 nmol/L, 95% CI 2.0-5.0), but induced concentration-related inhibition of activity in baboon myometrium (50% inhibitory concentration [IC50] = 21 nmol/L, 95% CI 2.2-203). A concentration-related inhibitory response to AH 13205 (IC50 = 3.56 nmol/L, 95% CI 1.28-5.99) was obtained in the baboon. In contrast, AH 13205 failed to inhibit comparable myometrial strip preparations from pregnant sheep.Conclusions:The present studies suggest that both sheep and baboon myometrium contain prostanoid receptors that mediate stimulation. In addition, baboon myometrium, like that from the human, contains AH 13205-sensitive EP receptors (EP2 receptors), which mediate inhibition. The pregnant baboon may therefore represent a suitable animal model for investigations into the use of EP2 agonists for the prevention of premature labor in humans. [ABSTRACT FROM PUBLISHER]