Epidermal growth factor receptors in fetal and maternal rabbit lung

The pattern of morphologic and functional development of lung during intrauterine period is influenced by several endogenous compounds. Recently Epidermal Growth Factor (EGF), when administered in vivo, has been shown to accelerate pulmonary maturation in fetal rabbit and sheep. We sought evidence for EGF receptor occurrence in fetal and maternal rabbit lung plasma membranes. The percent specific binding (mean ± S.E.M.) (125-I) EGF to LPM in the mother (n=5) and the fetus at term (n=7) was 1.08 ± 0.08 and 2.25 ± 0.12 per 175 μg of LPM protein respectively. The number of receptor sites per mg of LPM protein in the mother were significantly less than that in the fetus (44 ± 11 and 250 ± 24 × 10^?10, p < 0.001) with no apparent differences in Kd (2.10 ± 0.39 and 2.47 ± 0.24 × 10⁹). Presence of high affinity receptors for EGF in fetal and maternal lung plasma membranes suggests a direct role of EGF in fetal lung maturation.     

Acute alcohol exposure, acidemia or glutamine administration impacts amino acid homeostasis in ovine maternal and fetal plasma

Fetal alcohol syndrome (FAS) is a significant problem in human reproductive medicine. Maternal alcohol administration alters maternal amino acid homeostasis and results in acidemia in both mother and fetus, causing fetal growth restriction. We hypothesized that administration of glutamine, which increases renal ammoniagenesis to regulate acid–base balance, may provide an intervention strategy. This hypothesis was tested using sheep as an animal model. On day 115 of gestation, ewes were anesthetized and aseptic surgery was performed to insert catheters into the fetal abdominal aorta as well as the maternal abdominal aorta and vena cava. On day 128 of gestation, ewes received intravenous administration of saline, alcohol [1.75 g/kg body weight (BW)/h], a bolus of 30 mg glutamine/kg BW, alcohol + a bolus of 30 mg glutamine/kg BW, a bolus of 100 mg glutamine/kg BW, alcohol + a bolus of 100 mg glutamine/kg BW, or received CO₂ administration to induce acidemia independent of alcohol. Blood samples were obtained simultaneously from the mother and the fetus at times 0 and 60 min (the time of peak blood alcohol concentration) of the study. Administration of alcohol to pregnant ewes led to a reduction in concentrations of glutamine and related amino acids in plasma by 21–30 %. An acute administration of glutamine to ewes, concurrent with alcohol administration, improved the profile of most amino acids (including citrulline and arginine) in maternal and fetal plasma. We suggest that glutamine may have a protective effect against alcohol-induced metabolic disorders and FAS in the ovine model.     

Placental Glucose Transfer: A Human In Vivo Study

ObjectivesThe placental transfer of nutrients is influenced by maternal metabolic state, placenta function and fetal demands. Human in vivo studies of this interplay are scarce and challenging. We aimed to establish a method to study placental nutrient transfer in humans. Focusing on glucose, we tested a hypothesis that maternal glucose concentrations and uteroplacental arterio-venous difference (reflecting maternal supply) determines the fetal venous-arterial glucose difference (reflecting fetal consumption).MethodsCross-sectional in vivo study of 40 healthy women with uncomplicated term pregnancies undergoing planned caesarean section. Glucose and insulin were measured in plasma from maternal and fetal sides of the placenta, at the incoming (radial artery and umbilical vein) and outgoing vessels (uterine vein and umbilical artery).ResultsThere were significant mean (SD) uteroplacental arterio-venous 0.29 (0.23) mmol/L and fetal venous-arterial 0.38 (0.31) mmol/L glucose differences. The transplacental maternal-fetal glucose gradient was 1.22 (0.42) mmol/L. The maternal arterial glucose concentration was correlated to the fetal venous glucose concentration (r = 0.86, p<0.001), but not to the fetal venous-arterial glucose difference. The uteroplacental arterio-venous glucose difference was neither correlated to the level of glucose in the umbilical vein, nor fetal venous-arterial glucose difference. The maternal-fetal gradient was correlated to fetal venous-arterial glucose difference (r = 0.8, p<0.001) and the glucose concentration in the umbilical artery (r = −0.45, p = 0.004). Glucose and insulin concentrations were correlated in the mother (r = 0.52, p = 0.001), but not significantly in the fetus. We found no significant correlation between maternal and fetal insulin values.ConclusionsWe did not find a relation between indicators of maternal glucose supply and the fetal venous-arterial glucose difference. Our findings indicate that the maternal-fetal glucose gradient is significantly influenced by the fetal venous-arterial difference and not merely dependent on maternal glucose concentration or the arterio-venous difference on the maternal side of the placenta.     

Feto-maternal production and transfer of cortisol in the rhesus (Macaca mulatta)

Four pregnant rhesus monkeys cnd their fetuses. were infused constantly with ¹⁴C-cortisol and ³H-cortisol. Steady state plasma specific activities for ¹⁴C and ³H-cortisol were obtained after 80 to 90 minutes in both mother and fetus. These data and the rates of infusion of radioactivity were used to calculate the following parameters for both mother and fetus: 1) metabolic clearance rates, 2) production rates, 3) mean adrenal secretory rates, 4) transfer rates from mother to fetus and fetus to mother cnd, 5) the fraction of cortisol in each vascular compartment derived from the maternal and fetal edrenals. Plasma cortisone concentrations, as well as the fraction of cortisone derived from fetal and maternal cortisol were determined. Tetrahydrocortisol and tetrahydrocortisone concentrations were calculated. Mean cortisol secretory rates for the maternal and fetal adrenals were 60.0±11.8 and 1.82±0.42 mg/day. Fifty-eight % of the cortisol in the fetal compartment was of maternal origin. During transfer across the placenta to the fetus, cortisol was largely converted to cortisone. In fetal plasma 76% of the cortisone was of maternal origin. Cortisone concentrations in fetal plasma were higher than those of cortisol.     

The relationship between maternal and fetal plasma protein binding of methadone in the ewe during the third trimester

The binding of methadone to maternal and fetal plasma proteins was determined throughout the third trimester in the pregnant ewe. Blood was sampled from chronic indwelling catheters placed in the maternal aorta and fetal aorta. Methadone binding was determined by use of equilibrium dialysis with (³H)-methadone. Maternal binding ranged from 50.4 to 89.5%, with a mean of 76.2 ±1.3 (SE)%. Fetal binding was initially significantly lower than maternal binding, but increased rapidly in the last two weeks before parturition. Prior to 130 days gestation, the ratio of fetal binding to maternal binding was 0.40 ± 0.03. This binding ratio increased to 0.82 ± 0.08 in the last few days of pregnancy. Preliminary results suggested that maternal binding was higher in the early post-partum period. These results demonstrate that the relationship between maternal and fetal plasma binding of methadone changes rapidly towards the end of pregnancy, and fetal binding approaches maternal binding at parturition.     

The placenta releases branched-chain keto acids into the umbilical and uterine circulations in the pregnant sheep

There was net uptake of branched-chain keto acids by the fetus from the umbilical circulation. Mean fetal uptake of the 3 keto acids 2-keto isovalerate, 2-keto isocaproate and 2-keto methylvalerate was 1.8 mumol/min per kg of fetus. The concentrations in the umbilical vein for these keto acids were 10.9 +/- 3.8 microM (mean +/- SD: 2-keto isovalerate), 19.7 +/- 6.1 microM (2-keto isocaproate) and 14.8 +/- 5.3 microM (2-keto methylvalerate) respectively. The coefficients of extraction for the same keto acids were 17.2%, 16.8% and 11.9% respectively. Fetal uptakes (both mumol/min and mumol/min per kg fetus) were positively correlated with umbilical supply. There were concentration gradients across the placenta, with fetal concentration: maternal concentration ratios of 3.3 +/- 1.5 for 2-keto isovalerate, 2.1 +/- 0.8 for 2-keto isocaproate and 1.3 +/- 0.6 for 2-keto methylvalerate. The net release of 2-keto acids into the umbilical circulation may conserve the carbon skeleton of branched-chain amino acids for fetal metabolism and growth. In the uterine circulation there was not a consistent pattern of release from or uptake by the uteroplacental tissues. It is suggested that branched-chain keto acids may contribute to fetal growth or energy metabolism.     

Acute cord occlusion increases blood ionized magnesium concentration in preterm fetal sheep during maternal magnesium sulfate exposure

This study tested the hypothesis that a pathophysiologic insult to the fetus that decreases pH (umbilical cord occlusion) produces an increase in physiologically active (i.e., ionized) magnesium concentration. Preterm pregnant sheep (n = 7) were instrumented with maternal and fetal catheters and an inflatable vascular occluder was placed around the umbilical cord. After a 2-day recovery period, each ewe received a 4-g loading dose, followed by continuous intravenous infusion of 1 g magnesium sulfate/h. After 48 h, an episode of acute fetal distress was produced by inflation of the umbilical occluder for 10 min. Maternal and fetal arterial blood samples were collected at regular intervals to quantitate ionized magnesium concentration and monitor physiologic status. Magnesium sulfate infusion increased maternal and fetal blood ionized magnesium concentration. In vitro blood analysis demonstrated that there was a linear inverse correlation (r2 = 0.99) between fetal sheep blood pH and ionized magnesium concentration. In vivo, 10 min of umbilical cord occlusion produced an increase in fetal blood ionized magnesium concentration in all animals (P = 0.02) that was temporally related to the decrease in fetal blood pH. Whether this increase in physiologically active magnesium concentration is beneficial (via neuroprotection) or deleterious (via suppression of stress response) to the distressed fetus remains to be determined.     

Placental transfer of synthetic and endogenous estrogen conjugates in the rhesus monkey (Macaca mulatta)

The placental transfer of conjugated and nonconjugated estrogens was compared in the pregnant rhesus monkey. Placement of catheters in the maternal and fetal circulation allowed for the sampling of blood after the administration of radiolabeled naturally occurring and synthetic estrogens to mother or fetus. In all cases, nonconjugated-estrogen placental transfer was greater than conjugated-estrogen transfer. Comparison of the conjugated estrogens suggested that diethylstilbestrol-monoglucuronide (DESG) was transferred less efficiently than the estrone-sulfate (E, S). High-performance liquid chromatog-raphy (HPLC) of selected plasma samples revealed that 50–90% of the E, S observed in the maternal circulation was cleaved after fetal administration. In contrast, HPLC of maternal or fetal plasma samples after DESG administration revealed only intact DESG. These results emphasize differences in the placental transfer of the synthetic and naturally occurring estrogen hormones.     

Concentrations of progesterone in arterial and venous plasma of fetal pigs and their dams in late gestation

Blood samples were drawn from uterine arteries and veins of pregnant gilts and from the umbilical artery and vein of each of their fetuses during laparotomy at Day 80. Concentrations of progesterone (P) were greater in fetal than maternal plasma. Uptake of P from the placenta by the fetal blood was evident but was not equivalent to the maternal uterine arterial-venous difference in P concentration. No correlation between plasma P and fetal weight was noted. Concentrations of P in both umbilical vessels of female fetuses were higher than in male fetuses. These data indicate that fetal sex affects the rate of transport and/or synthesis of P in the utero/placental compartment and/or the rate of metabolism of P in the fetus. The relative importance of de novo synthesis and transplacental transport of P in establishing concentrations of P in fetal blood remains to be elucidated.     

Effect of estrogen on the metabolism of cortisol and cortisone in the baboon fetus at midgestation

To determine whether the metabolism of cortisol (F) and cortisone (E) in the baboon fetus is regulated by estrogen, fetal interconversion of F/E was measured at midgestation after an experimental increase in placental estradiol (E2) production. Six baboons (Papio anubis) received increasing numbers of androstenedione implants (50 mg) inserted s.c. at 8-day intervals between Days 70 and 100 of gestation (term = Day 184) to elevate the production of estrogen; controls (N = 8) received no treatment. On Day 100 of gestation, each animal was anesthetized with ketamine:halothane/nitrous oxide, the fetus was exteriorized and [3H] F/[14C] E was infused via a fetal femoral vein for 70 min. Blood samples were then obtained from the contralateral fetal femoral vein, the umbilical vein/artery, and a maternal saphenous vein. After purification of F and E, the metabolic clearance rate (MCR), peripheral interconversion, and placental extraction of F and E were calculated. Maternal serum E2 concentrations (ng/ml; mean +/- SE) between Days 80 and 100 of gestation were greater (p less than 0.01) in androstenedione-treated baboons (2.2 +/- 0.2) than in untreated controls (1.2 +/- 0.1). Although the MCR of F was similar in control (5.2 +/- 0.3 1/day) and treated (7.7 +/- 1.0 1/day) animals, the MCR of E (13.5 +/- 2.0 1/day) was increased (25.8 +/- 2.5 1/day; p less than 0.05) by androstenedione treatment. Placental extraction of F (59 +/- 9%) was lower (p less than 0.01) than that of E (82 +/- 5%) in untreated baboons and was not affected by androstenedione treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

An in vivo study of ovine placental transport of essential amino acids

Under normal physiological conditions, essential amino acids (EA) are transported from mother to fetus at different rates. The mechanisms underlying these differences include the expression of several amino acid transport systems in the placenta and the regulation of EA concentrations in maternal and fetal plasma. To study the relation of EA transplacental flux to maternal plasma concentration, isotopes of EA were injected into the circulation of pregnant ewes. Measurements of concentration and molar enrichment in maternal and fetal plasma and of umbilical plasma flow were used to calculate the ratio of transplacental pulse flux to maternal concentration (clearance) for each EA. Five EA (Met, Phe, Leu, Ile, and Val) had relatively high and similar clearances and were followed, in order of decreasing clearance, by Trp, Thr, His, and Lys. The five high-clearance EA showed strong correlation (r(2) = 0.98) between the pulse flux and maternal concentration. The study suggests that five of the nine EA have similar affinity for a rate-limiting placental transport system that mediates rapid flux from mother to fetus, and that differences in transport rates within this group of EA are determined primarily by differences in maternal plasma concentration.     

Secretion of unconjugated estrone during pregnancy and around parturition in goats

The secretion of unconjugated estrone and its production site in pregnant goats were investigated in vivo. The mean estrone concentration (n = 15) in the peripheral plasma increased gradually, being 83 pg/ml on Day 40 and 483 pg/ml on Day 140 after mating. The estrone concentration increased rapidly after Day 2 before partum, reaching a peak at parturition (2370 pg/ml), and falling to 171 pg/ml at Day 1 post partum. The concentrations of estrone from the umbilical vein and umbilical artery did not differ from that found in the maternal jugular vein, suggesting that the fetus does not take part in estrogen production. The estrone concentration from the uterine vein after the fetus was removed was higher than the concentrations found in the maternal jugular vein and umbilical artery. In the placental tissue, a high concentration of estrone (18157 pg per gram of wet tissue) was detected. These findings suggest that the main production site of unconjugated estrone is the placenta.     

The Selenium Levels of Mothers and Their Neonates Using Hair,Breast Milk,Meconium, and Maternal and Umbilical Cord Blood in Van Basin

The objective of the present study is to calculate linear regressions between a mother and her child with respect to their selenium concentration (ng/g) in the following traits: maternal blood and umbilical cord blood, maternal and child hair, maternal milk and child umbilical cord blood, maternal milk and meconium, maternal blood plasma, and child meconium. The data were collected at Research Hospital of the University of Yüzüncü Yıl from 30 pairs of mothers and their newborn baby. The mean maternal serum Se level in 30 mothers was 68.52 ± 3.57 ng/g and cord plasma level was 119.90 ± 18.08 ng/g. The Se concentration in maternal and neonatal hair was 330.84 ± 39.03 and 1,124.76 ± 186.84 ng/g, respectively. The Se concentration of maternal milk at day 14 after delivery was determined as 68.63 ± 7.78 ng/g (n = 13) and the concentration of Se was 418.90 ± 45.49 ng/g (n = 22) for meconium of neonatal. There was no significant difference between maternal blood and milk Se levels. However, hair Se concentration was significantly higher than milk and maternal blood Se level. For each trait comparison, the average absolute difference in log₁₀-transformed Se concentration was calculated between a mother and her child. The observed average absolute difference was compared with a test distribution of 1,000 resampled bootstrap averages where the number of samples was maintained but the relationship between a mother and her child was randomized among samples (α = 0.05).     

Evaluation of bidirectional transfer of plasma DNA through placenta

To clarify the origin of cell-free fetal DNA in maternal plasma, we analyzed bidirectional transfer of plasma DNA between fetus and mother. We analyzed maternal and fetal plasma DNA obtained from 15 pregnant women at the time of Cesarean section. The subjects were five patients with preeclampsia and 10 gestational-age-matched normal controls. DNA was extracted from 1.5-ml plasma samples and the cellular fraction of maternal and umbilical blood. Seven polymorphic marker genes were analyzed. The relative concentration of fetal DNA in maternal plasma and maternal DNA in cord blood were evaluated. The relative concentration of maternal DNA in fetal circulation (median, 0.9%; range, 0.2–8.4%) was significantly lower than that of fetal DNA in maternal blood (14.3%, 2.3–64%), with P=0.007. The relative concentration of maternal DNA in fetal blood was not affected by preeclampsia. These findings indicate that cell-free DNA is unequally transferred through the placenta. The structural characteristics of the placenta suggest that the majority of cell-free fetal DNA in maternal plasma is derived from villous trophoblasts.     

Maternal plasma triglycerides as a source of fetal fatty acids.

The transfer of plasma triglyceride fatty acids from mother to fetus was studied in rats. Following i.v. injection of labelled chylomicron and very low density lipoprotein (VLDL) triglycerides into the mother, the time courses of the plasma triglycerides, free fatty acids, and fetal radioactivity were determined. The data were analysed using a mathematical model. From the results the following conclusions were drawn: To cover the need of fetal fatty acids, the placenta utilizes only VLDL triglycerides but not chylomicron triglycerides. Comparison of the amount of VLDL triglyceride fatty acids (0.04 micromoles/min/litter) and of maternal plasma free fatty acids (0.08 micronmoles/min/litter) transferred into the fetus indicates that the maternal plasma triglycerides are a source of fetal fatty acids, that cannot be neglected.     

Relationship between the appearance of preantral follicles in the fetal ovary of Antarctic minke whales (Balaenoptera bonaerensis) and hormone concentrations in the fetal heart, umbilical cord and maternal blood

The present study aimed to determine the relationship among changes in the number of preantral follicles and concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone (P4), androstenedione (A) and estradiol-17beta (E2) in the fetal heart, umbilical cord and maternal blood. Primordial follicles had already appeared in a 20 cm fetus and primary follicles were observed in a 50 cm fetus. In a 70 cm fetus, the number of primordial and primary follicles increased rapidly and secondary follicles were present. The concentrations of LH and FSH did not change between 20 cm and 160 cm in fetal length. When the fetal length became > 70 cm, serum levels in the fetus, umbilical cord and mothers, and E2 levels in umbilical cord increased synchronously (p < 0.05). These results showed increases in the number of preantral follicles in the Antarctic minke whale fetal ovary along with fetal growth during the early gestation period. These findings suggest that the change in preantral follicles was associated with changes in the concentration of steroids in early gestation periods. The changes in steroid concentrations in the fetal and umbilical cord blood and the increased number of preantral follicles were coincident at around 70 cm in fetal length, whereas the growth and differentiation of primordial and primary follicles appeared to be independent of FSH and LH.     

Placental transport of free palmitic and linoleic acids in the guinea pig

Radioisotopic tracers were used to measure the unidirectional transfer rates of free fatty acids across the placenta of fed and fasted pregnant guinea pigs. Free (14)C-labeled palmitic and linoleic acids (in serum) were injected simultaneously into a jugular vein of an anesthetized pregnant guinea pig. Serial samples of maternal blood were collected from a carotid artery; fetal blood was collected from the umbilical vein of an exposed fetus. Analysis of maternal and fetal plasma revealed that: (a) the half-lives of free palmitic and linoleic acid in maternal plasma are approximately 1.3 min and 0.7 min, both in fed animals with low plasma concentrations of these acids and in fasted animals with high concentrations; (b) free linoleic and palmitic acids cross the placenta from maternal to fetal plasma in a ratio of approximately 2.0, a value which appears not to change as the transfer rates of these acids from maternal to fetal plasma are increased by fasting the mother. It is suggested that the ratio in which free linoleic and palmitic acids cross the placenta from maternal to fetal plasma is determined by the ratio of the unbound free linoleic and palmitic acid concentrations in maternal plasma. A comparison of several species indicates that a much greater proportion of fetal fatty acids comes from the mother in the guinea pig and rabbit than in the rat, the sheep, or man.     

Plasma clearance of radiolabelled IGF-1 in the late gestation ovine fetus

We investigated the distribution of radiolabelled IGF-1 in the late gestation ovine fetus by exclusion gel chromatography following intravenous injection of 125I rh (recombinant human) met-IGF-1 into the chronically instrumented fetal lamb (120-130 days, n = 7). One minute after injection of 125I rh met-IGF-1 into the fetal femoral vein, 20.9 +/- 3.1% of the counts circulated in the 150K binding protein region, 55.0 +/- 3.7% in the 50K binding protein region and 18.7 +/- 0.6% in the free or 7K region. The chromatographic profiles obtained in the fetus were in general similar to those previously seen in the adult sheep. After an initial equilibration phase the half life of IGF-1 associated with the 150K binding fractions were 412.1 +/- 103.6 min. Two phases of clearance were observed for IGF-1 in association with the 50K binding fractions, an initial phase with a half life of 30.6 +/- 4.5 min followed by a second phase with a half life of 202.3 +/- 10.3 min. The 7K or 'free' form of IGF-1 had an initial half life of 12.6 +/- 5.1 min. Chromatography of samples of fetal tracheal fluid, fetal urine, amniotic fluid, maternal uterine venous plasma and maternal systemic plasma showed no movement of intact IGF-1 out of the fetal circulation into the fetal fluids or into the maternal circulation. However, when simultaneous samples were obtained from the fetal femoral artery and umbilical vein, higher radioactivity was consistently observed in the fetal femoral artery raising the possibility of placental uptake of IGF-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cortisol and cortisone levels in umbilical cord plasma and maternal plasma of normal pregnancies

A method for assaying cortisol and cortisone using chromatography on either paper or Sephadex LH-20 columns for isolation, followed by competitive protein binding, has been applied to umbilical cord and maternal plasma samples. In mixed cord plasma the mean cortisol concentration was 6.0 ± 0.8 μg/100 ml (n = 9) and the mean cortisone concentration was 13.5 ± 2.9 μg/100 ml (n = 9). In cord arterial plasma the mean cortisol concentration was 6.3 ± 2.9 μg/100 ml (n = 6) and the mean cortisone level was 10.1 ± 2.5 μg/100 ml (n = 6). For cord venous plasma, the mean level of cortisol was 5.6 ± 1.5 μg/100 ml (n = 6) and of cortisone was 13.5 ± 2.4 μg/100 ml (n = 6). Maternal plasma gave a mean value of cortisol of 42.3 ± 4.5 μg/100 ml (n = 6) and of cortisone of 6.2 ± 0.9 μg/100 ml. The results of this study suggest that the fetus at term-gestation produces cortisol. The significance of this production compared with placental transfer of maternal cortisol into the fetal circulation however is uncertain.