Miles J. Novy

An experimental model for intraamniotic infection and preterm labor in rhesus monkeys

OBJECTIVE Our purpose was to describe the temporal and quantitative relationship between intraamniotic infection and preterm labor in a nonhuman primate model. STUDY DESIGN On day 130 of gestation (term 167 days) four chronically instrumented rhesus monkeys (Macaca mulatta) were infected with an intraamniotic inoculation of 10(6) colony-forming units of group B streptococci. Four additional noninfected monkeys were followed up to spontaneous parturition as controls. Amniotic fluid was serially sampled in all monkeys both before and after inoculation for bacterial growth, tumor necrosis factor-alpha, interleukin-1 beta, interleukin-6, prostaglandin E2, and prostaglandin F2 alpha, and uterine activity was continuously recorded. RESULTS Increases in uterine contractility occurred 28 hours (range 14 to 40 hours) after inoculation and were preceded by increases in amniotic fluid cytokines and prostaglandins. Intraamniotic concentrations of tumor necrosis factor-alpha, interleukin-6, and interleukin-1 beta all rose dramatically 9, 15, and 18 hours after infection and 10 to 20 hours before increases in uterine contractility. In spontaneous parturition only interleukin-6 concentrations rose moderately (from 0.1 to 1.2 ng/ml). Increases in prostaglandin E2 and prostaglandin F2 alpha paralleled those of the cytokines. Peak prostaglandin concentrations in intraamniotic infection exceeded by severalfold concentrations seen in spontaneous parturition (16,046 pg/ml vs 2765 pg/ml for prostaglandin E2, p < 0.05; and 5547 pg/ml vs 708 pg/ml for prostaglandin F2 alpha, p < 0.05). In spite of intraamniotic none of the monkeys were febrile or had peripheral leukocytosis at the onset of labor. CONCLUSION In the rhesus monkey, after intraamniotic infection, there is a predictable and sequential increase in amniotic fluid tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6, followed by increases in prostaglandin E2 and prostaglandin F2 alpha. These increases all occur before an increase in uterine contractility and before clinical signs of infection. Our data provide evidence for a cause-and-effect relationship between intraamniotic infection and preterm labor and support the utility of measuring interleukin-6 or other cytokines in the diagnosis of intraamniotic infection.

Maternal cardiovascular dynamics: IV. The influence of gestational age on the maternal cardiovascular response to posture and exercise

Abstract Serial hemodynamic evaluations were carried out in 11 patients during pregnancy and the postpartum period. The patients were studied at rest in the supine, lateral, and sitting positions as well as during and after exercise on a bicycle ergometer. The cardiac output was found to be elevated to peak levels as early as 20 to 24 weeks of gestation and was maintained at this high level through the thirty-second week of gestation. At 38 to 40 weeks there was a decline in cardiac output in all positions. This fall was most pronounced in the supine position, in which the cardiac output was found to be lower than in the same position during the postpartum period. The heart rate increased only slightly during early gestation but continued to rise throughout pregnancy in the supine and lateral positions. Accordingly, The stroke volume showed a progressive decline from 20 to 24 weeks of gestation to term. The cardiovascular response to mild exercise was constant throughout pregnancy and similar to that encountered in nonpregnant individuals. However, moderate exercise indicated there is a progressive decline in circulatory reserve as pregnancy advances. This is not attributed to any change in cardiac function but rather to peripheral pooling of blood and obstruction to venous return by the large gravid uterus. Following exercise cardiovascular function returned to resting levels with equal rapidity during pregnancy and post partum.

Interleukin-Iβ Intra-Amniotic Infusion Induces TUmor Necrosis Factor-α, Prostaglandin Production, and Preterm COntractions in Pregnant Rhesus Monkeys

Objective: To describe the temporal and quantitative consequences of intra-amniotic interleukin-1β infusion in a nonhuman primate model. Methods: On days 128-138 of gestation (term 167 days), four chronically instrumented rhesus monkeys (Macaca mulatta) underwent serial intra-amniotic infusions of 2, 5, and 10-20 μg recombinant human interleukin-1β. Each infusion was for 2 hours, and subsequent infusions were at least 48 hours later. Amniotic fluid was sampled serially both before and after infusion for interleukin-1β, tumor necrosis factor-α (TFN-α), and prostaglandin (PG) E2 and F2α by specific assays, and uterine activity in each monkey was recorded continuously. Results: Intra-amniotic concentrations of interleukin-1β rose dramatically after infusion. This rise was rapidly followed by the appearance of TNF-α in the amniotic cavities of all animals, with maximal levels reached 5 hours after the initiation of the infusion. Both interleukin-1β and TNF-α were rapidly cleared from the amniotic fluid and returned to baseline levels by 24-48 hours. Increases in PGE2 and F2α paralleled those of the two cytokines but remained elevated for the duration of the experiments. The stimulation of uterine contractility from a pre-infusion level of 200 mmHg · seconds/hour to 6000 mmHg · seconds/hour occurred an average of 6-10 hours after interleukin-1β infusion. These stimulations were transient, usually abating by 22 hours after infusion, and did not result in frank labor. Conclusion: In the rhesus monkey, intra-amniotic infusion of interleukin-1β rapidly induces production of intra-amniotic TNF-α as well as PGE2 and F2α, followed by uterine contractility. Uterine activity diminishes as cytokine levels return to pre-infusion levels, even in the presence of elevated intra-amniotic PG levels. Tumor necrosis factor-α may act synergistically with interleukin-1β in the pathophysiology of cytokine-related preterm labor.

Dexamethasone and estradiol treatment in pregnant rhesus macaques: Effects on gestational length, maternal plasma hormones, and fetal growth

To determine the effects of suppressing fetal and maternal adrenal activity on parturition, we treated pregnant rhesus macaques with dexamethasone (0.25 to 4.0 mg, twice a day) from gestation day 130 until delivery (term = 167 days). Long-term dexamethasone treatment increased gestation length: 71% of fetuses were born postmaturely (after day 175 of gestation; X2 = 52.6; P less than 0.001). The dexamethasone decreased basal levels of maternal estradiol and cortisol, but not progesterone, and abolished the prepartum estrogen and prolactin surges; doses greater than 0.16 mg/kg per day resulted in fetal death but not premature delivery. That vaginal delivery was induced by estradiol benzoate in monkeys with prolonged pregnancy and dead fetuses, but not in those with live fetuses, suggests active fetal inhibition of prostaglandin synthesis. The dexamethasone retarded fetal growth (410 +/- 16 gm versus 501 +/- 5 gm for controls; P less than 0.001) and decreased thymus, spleen, and adrenal weights (P less than 0.01). A less significant decrease in brain weight was noted (P less than 0.1), as were decreases in biparietal diameter, occipitofrontal diameter, and head circumference (P less than 0.05). These results indicate that corticosteroids do not induce premature labor in primates. On the contrary, long-term dexamethasone administration is associated with prolonged pregnancy and suppression of estrogen biosynthesis.

Ureaplasma parvum or Mycoplasma hominis as Sole Pathogens Cause Chorioamnionitis, Preterm Delivery, and Fetal Pneumonia in Rhesus Macaques

The authors assess causal, cellular and inflammatory links between intraamniotic infection with Ureaplasma parvum or Mycoplasma hominis and preterm labor in a nonhuman primate model. Long-term catheterized rhesus monkeys received intraamniotic inoculations of clinical isolates of Ureaplasma parvum serovar 1, M hominis, media control or physiological saline. Genital mycoplasmas were quantified in amniotic fluid (AF) and documented in fetal tissues by culture and PCR. In association with elevated AF colony counts for U parvum or M hominis, there was a sequential upregulation of AF leukocytes, proinflammatory cytokines, prostaglandin E2 and F2a, metalloproteinase-9 and uterine activity ( P< .05). Fetal membranes and lung were uniformly positive for both microorganisms; fetal blood and cerebrospinal fluid cultures and PCR were more often positive for M hominis than U parvum. Histopathologic findings of chorioamnionitis, a systemic fetal inflammatory response and pneumonitis worsen with duration of in utero infection. U parvum or M hominis, as sole pathogens, elicit a robust proinflammatory response which contributes to preterm labor and fetal lung injury.

Transabdominal cervicoisthmic cerclage: A reappraisal 25 years after its introduction

Most cerclage operations for cervical insufficiency are performed transvaginally. The transabdominal route is beneficial in treating patients with cervices that are either extremely short, congenitally deformed, deeply lacerated, or markedly scarred because of previously failed transvaginal cerclage procedures. The average gestational age at surgery was 11.5 weeks and the operation was performed after early ultrasonographic verification of fetal viability. Patients with advanced cervical effacement or dilatation in the second trimester were excluded. A 5 mm wide Mersilene band was applied in an avascular space above the junction of the cervix and the uterine isthmus without dissection or tunneling among broad ligament vessels. This simplified surgical approach resulted in little operative blood loss (mean, 75 ml; range, 50 to 200 ml). After transabdominal cervicoisthmic cerclage, 21 pregnancies in 20 patients resulted in 18 term births, one premature birth with favorable outcome, and two early fetal deaths (90% salvage rate). A review of the world literature indicated 130 pregnancies with transabdominal cervicoisthmic cerclage during pregnancy and a cumulative success rate of 89%. Preconceptional transabdominal cervicoisthmic cerclage was reported in 30 pregnancies with an overall fetal survival rate of 81%. A survey of specialists in maternal-fetal medicine indicated an increasing interest and familiarity with transabdominal cervicoisthmic cerclage since its introduction more than two decades ago although this procedure is still not widely applied in obstetric practice.

Progesterone receptor localization and isoforms in myometrium, decidua, and fetal membranes from rhesus macaques: evidence for functional progesterone withdrawal at parturition.

Objective: It is not known whether withdrawal of progesterone (P) action is a prerequisite for parturition in women or in nonhuman primates because concentrations of circulating progesterone or progesterone receptors (PR) in myometrium and decidua do not decrease before delivery. To examine this potentially important regulatory mechanism, we determined PR isoforms, PR localization, and mRNA in myometrium, decidua, and fetal membranes from rhesus monkeys during pregnancy and in spontaneous labor at term. Methods: Gestational tissues were obtained midpregnancy (day 80-100), late pregnancy (day 130-145), and during spontaneous labor at term (day 161-167). Samples of rhesus monkey myometrium, decidua, chorion-decidua, and amnion were collected and analyzed for total nuclear and cytosolic PR by competitive binding assay. Progesterone receptor isoforms were identified and quantified by Western blot analysis, and PR mRNA was determined by a specific ribonuclease protection assay. Nuclear PR was localized by immunohistochemistry with monoclonal anti-PR (JZB39) after microwave stabilization. Results: Myometrium and decidua showed no change in total PR during pregnancy and labor. Nuclear PR was not detected in fetal membranes by binding assay but was localized in amnion epithelial and mesenchymal cells and in chorion laeve cytotrophoblasts by immunohistochemistry. Staining for PR was substantially less by serial antibody dilution in fetal membranes than in decidua. Message for PR was confirmed in all tissues analyzed. A significant (P < .05) shift in the ratio of PR isoforms (from PR-B dominance at midpregnancy to PR-A dominance in labor) was observed in myometrium but not in decidua. Both PR-A and PR-B isoforms and PR nuclear staining were nearly undetectable in amnion obtained during labor. Conclusion: A shift to PR-A dominance in myometrium at term together with a loss of PR in fetal membranes provides evidence for a functional progesterone withdrawal mechanism, which may facilitate the initiation of parturition in primates.

Improved oxygen release: an adaptation of mature red cells to hypoxia

Blood from patients with erythrocytosis secondary to arterial hypoxemia due either to congenital heart disease or to chronic obstructive pulmonary disease was shown to have a decreased affinity for oxygen; the average oxygen pressure required to produce 50% saturation of hemoglobin with oxygen was 29.8 mm Hg (average normal, 26.3 mm Hg). Such a displacement of the blood oxygen equilibrium curve promotes the release of oxygen from blood to the tissues. Studies were also performed upon blood from a man with complete erythrocyte aplasia who received all of his red cells by transfusion from presumably normal persons. With mild anemia (hematocrit, 28%), the affinity of his blood for oxygen was slightly diminished (an oxygen pressure of 27.0 mm Hg was required to produce 50% saturation of hemoglobin with oxygen). With severe anemia (hematocrit, 13.5%), however, his blood had a markedly decreased oxygen affinity (an oxygen pressure of 29.6 mm Hg was required to produce 50% saturation of hemoglobin with oxygen). We conclude that patients with various conditions characterized by an impairment in the oxygen supply system to tissues respond with a diminished affinity of their blood for oxygen. Although the mechanism which brings about this adaptation is not known, the displacement of the oxygen equilibrium curve is associated with an increase in heme-heme interaction. The decrease in blood oxygen affinity need not occur during erythropoiesis, but may be imposed upon mature circulating red cells.

Circadian hormonal interactions among the mother, fetus, and amniotic fluid☆☆☆★

Circadian rhythms and hormonal interactions among the maternal, fetal, and amniotic fluid compartments were studied in long-term catheterized rhesus macaque monkeys between days 127 and 138 of gestation (term = 167 days). Blood samples were collected at 3-hour intervals for 48 hours and analyzed by radioimmunoassay for estrone, estradiol, cortisol, progesterone, dehydroepiandrosterone sulfate, and prolactin. Distinct circadian rhythms were present for cortisol and progesterone in the maternal circulation and for progesterone and dehydroepiandrosterone sulfate in the fetal circulation (p less than 0.05). Although maternal and fetal estrogen levels were higher in AM samples than in PM samples, a statistically significant circadian rhythm was not present (p greater than 0.10). Fetal levels of progesterone and dehydroepiandrosterone sulfate and maternal levels of progesterone were highest between 9:00 PM and 3:00 AM and lowest between 9:00 AM and 3:00 PM. Maternal levels of cortisol were highest between 6:00 AM and 9:00 AM and lowest between 6:00 PM and 12 midnight. The circadian patterns of maternal cortisol and progesterone were inversely related to each other (r = -0.68; p less than 0.01). Amniotic fluid cortisol levels were highest between 9:00 AM and 12 noon and lowest between 6:00 PM and 3:00 AM (p less than 0.10). With the possible exception of cortisol, amniotic fluid steroid hormones did not demonstrate distinct diurnal fluctuations, nor did they correlate with steroid changes in maternal or fetal blood. Because the rhesus placenta is permeable to glucocorticoids it is likely that transplacental passage of maternal cortisol influences the activity of the fetal pituitary and adrenal so that the circadian rhythm in the fetal axis is 180 degrees out of phase with that of the maternal axis. The circadian rhythms in fetal dehydroepiandrosterone sulfate and progesterone in late gestation parallel the biorhythm in uterine contraction frequency and amplitude, with peaks during periods of darkness between 9:00 PM and 3:00 AM.

Direct effect of sex steroid-binding protein (SBP) of plasma on the metabolic clearance rate of testosterone in the rhesus macaque

We report direct evidence for the effect of the sex steroid-binding protein (SBP) on the metabolic clearance rate of testosterone (MCRT). Pure rhesus SBP or human SBP was infused intravenously into three different cycling female rhesus monkeys. MCRT was measured before and after SBP had reached 150-300% of basal levels. A decrease in MCRT was observed in all cases. The effect of SBP on MCRT was tested further in four additional cycling females by infusing immunoaffinity-purified monospecific human SBP antibodies known to cross-react with rhesus SBP. SBP dropped to 54, 40, 4 and 2% of basal levels with a concomitant increase of 118, 190, 320 and 640% of basal MCRT. In one of these animals, pure rabbit SBP was administered after the anti-human SBP infusion resulting in a decrease in MCRT. The magnitude of the SBP effect on MCRT is related to the distribution of testosterone (T) bound to SBP and albumin in the plasma. Calculations show that as long as the percent of T bound to SBP is equal or higher than the percent of T bound to albumin, the influence on MCRT is small. However, if SBP is reduced to the extent that T is bound mostly to albumin, the redistribution of T is associated with a dramatic increase in MCRT. We conclude that under normal conditions each animal has an optimum concentration of plasma SBP which binds a maximum amount of T. If SBP increases above this level, little effect on MCRT will result. However, a drop below the optimum level, as is the case in certain physiological or clinical conditions, will produce a large increase in the clearance of T.