Placental and fetal growth and development in late rat gestation is dependent on adrenomedullin

Adrenomedullin is a potent, endogenous vasodilator peptide synthesized and secreted by diverse locations such as adrenal glands, lungs, kidneys, vascular smooth muscle, and endothelium. Homozygous deletion of the adrenomedullin gene is embryonic lethal. We hypothesized that adrenomedullin has an important role in placental and fetal growth and development in rat pregnancy. The current study evaluated maternal systolic blood pressure, litter size, placental and pup weight, pup mortality, and placental pathology in pregnant rats following continuous in utero exposure to an adrenomedullin antagonist. Osmotic minipumps were inserted on Gestational Day 14 to continuously deliver either adrenomedullin, adrenomedullin antagonist, or vehicle control. Systolic blood pressure was recorded daily. Pregnant rats were killed on Gestational Day 15-18, 20, and/or 22 to evaluate placental development and fetal growth. The placentas were graded for the presence of necrosis in the decidua and fetal labyrinth as well as fetal vessel development in the labyrinth. A trend toward increased systolic blood pressure was noted between Gestational Days 17 and 20 in mothers treated with adrenomedullin antagonist, but the difference was not statistically significant. Antagonism of adrenomedullin function during rat pregnancy caused fetal growth restriction, decreased placental size, gross necrosis of placental margins and amniotic membranes, histologically deficient fetal vessel development in the labyrinth, and fetal edema. Adrenomedullin contributes to angiogenesis, functions as a growth factor, and helps regulate vascular tone during rat gestation.     

Hepatic metabolite profiles in mice with a suboptimal selenium status

Selenium is an essential trace element and mediates its functions via various selenoproteins such as glutathione peroxidases or thioredoxin reductases. A suboptimal selenium supply causes metabolic disturbances and is associated with an increased risk to develop different disorders, including cancer or cardiovascular diseases. This study aimed to assess the impact of a suboptimal selenium status on the hepatic metabolome of male mice analyzed by a targeted liquid chromatography/tandem mass spectrometry and a method based on non-targeted gas chromatography hyphenated with mass spectrometry. Feeding animals a diet with about half of the recommended selenium content supplied as selenomethionine caused liver glutathione peroxidase and thioredoxin reductase activities to decline and lipid peroxidation to increase. Serum T₃ thyroid hormone concentration also declined via a reduced hepatic deiodinase activity. Metabolite profiling revealed predominantly changes in cysteine and carbon-1 metabolism as well as in selected lipid subclasses. In particular the concentrations of palmitoylcarnitines and oleoylcarnitines (C18:1 and C16:1) and various phosphatidylcholine species containing saturated fatty acids were elevated. Increased taurine levels suggested an enhanced cysteine flux through the salvage pathway whereas increased homocysteine levels appeared to be a consequence of a massive down-regulation of cystathionine β lyase (cystathionine β synthase) and a reduced flux through the transsulfuration pathway. The findings demonstrate that a suboptimal selenium status causes alterations in lipid and carbon-1 metabolism in mouse liver. These changes may contribute to the development of diseases associated with a suboptimal selenium status.     

Expansion of the fetoplacental vasculature in late gestation is strain dependent in mice

How the fetoplacental arterial tree grows and expands during late gestational development is largely unknown. In this study, we quantified changes in arterial branching in the fetal exchange region of the mouse placenta during late gestation, when capillarization increases rapidly. We studied two commonly used mouse strains, CD1 and C57Bl/6 (B6), at embryonic days (E)13.5, 15.5, and 17.5. B6 mice differ from CD1 mice by exhibiting a blunted fetal weight gain in late gestation. We found that B6 capillarization and interhemal membrane thinning were reduced and placental hypoxia-inducible factor-1α and VEGF-A expression were higher than CD1 near term. Automated vascular segmentation of microcomputed tomography data sets revealed that the number of arterial vessels ≥50 μm remained constant during late gestation in both strains, despite large increases in downstream capillary volume quantified by stereology (+65% in B6 mice and +200% in CD1 mice). Arterial diameters expanded in both strains from E13.5 to E15.5; however, diameters continued to expand to E17.5 in B6 mice only. The diameter scaling coefficient at branch sites was near optimal (-3.0) and remained constant in CD1 mice, whereas it decreased, becoming abnormal, in B6 mice at term (-3.5 ± 0.2). Based on arterial tree geometry, resistance remained constant throughout late gestation (～0.45 mmHg·s·μl(-1)) in CD1 mice, whereas it decreased by 50% in late gestation in B6 mice. Quantification of the fetoplacental vasculature revealed significant strain-dependent differences in arterial and capillary expansion in late gestation. In both strains, enlargement of the fetoplacental arterial tree occurred primarily by increased arterial diameters with no change in segment numbers in late gestation.     

Placental blood flow in rats fed alcohol before and during gestation

Female Sprague-Dawley rats were either given 20% alcohol in drinking water and solid diet $\text{ad libitum}$ (alcohol group) or were pair-fed to the alcohol group (pair-fed group) or were given water and solid diet $\text{ad libitum (ad libitum}$ group) for four weeks. They were then mated and the alcohol group was changed to 30% alcohol in water. On day 20 of gestation each rat was injected with ⁵⁷Co-labeled microspheres into the left ventricle and radioactivity was determined in the placentas and kidneys. Cardiac output and blood flow to the placentas and kidneys was calculated. Fetuses and placentas were weighed, and the osmolality of the maternal plasma and water content of the muscle was determined. Cardiac output and blood flow to the kidneys did not differ among the three groups. Blood flow to the placenta, whether expressed as m1/min/g placenta or m1/min/placenta, or as % of cardiac output was significantly reduced in the alcohol group compared with the pair-fed and $\text{ad libitum}$ groups, which did not differ from one another. Fetuses were significantly lighter and placentas were significantly heavier in the alcohol group than in the other two groups. Plasma osmolality was increased and muscle water was decreased about 7% in the alcohol group, indicating a moderate degree of dehydration. It is concluded that chronic alcohol consumption leads to a redistribution of blood, with less blood supplying the placentas. This may contribute to the growth retardation seen in fetal alcohol syndrome.     

Placental restriction of fetal growth decreases IGF1 and leptin mRNA expression in the perirenal adipose tissue of late gestation fetal sheep

Placental restriction (PR) of fetal growth results in a low birth weight and an increased visceral fat mass in postnatal life. We investigated whether PR alters expression of genes that regulate adipogenesis [IGF1, IGF1 receptor (IGF1R), IGF2, IGF2R, proliferator-activated receptor-gamma, retinoid-X-receptor-alpha], adipocyte metabolism (lipoprotein lipase, G3PDH, GAPDH) and adipokine signaling (leptin, adiponectin) in visceral adipose tissue before birth. PR was induced by removal of the majority of endometrial caruncles in nonpregnant ewes before mating. Fetal blood samples were collected from 116 days gestation, and perirenal visceral adipose tissue (PAT) was collected from PR and control fetuses at 145 days. PAT gene expression was measured by quantitative RT-PCR. PR fetuses had a lower weight (PR 2.90 +/- 0.32 kg; control, 5.12 +/- 0.24 kg; P < 0.0001), mean gestational arterial Po(2) (P < 0.0001), plasma glucose (P < 0.01), and insulin concentrations (P < 0.02), than controls. The expression of IGF1 mRNA in PAT was lower in the PR fetuses (PR, 0.332 +/- 0.063; control, 0.741 +/- 0.083; P < 0.01). Leptin mRNA expression in PAT was also lower in PR fetuses (PR, 0.077 +/- 0.009; control, 0.115 +/- 0.013; P < 0.05), although there was no difference in the expression of other adipokine or adipogenic genes in PAT between PR and control fetuses. Thus, restriction of placental and hence, fetal substrate supply results in decreased IGF1 and leptin expression in fetal visceral adipose tissue, which may alter the functional development of the perirenal fat depot and contribute to altered leptin signaling in the growth-restricted newborn and the subsequent emergence of an increased visceral adiposity.     

Effects of late gestation shearing on BW,feed intake and plasma metabolite concentrations in Rambouillet ewes managed outdoors during winter

The majority of lambs in the United States are born from late winter to early spring and pregnant ewes are generally sheared in the last third of pregnancy. Although there are benefits to shearing before parturition, shorn animals may be more vulnerable to the cold, highly variable climatic conditions associated with these seasons. The objective of this study was to determine if late gestation shearing induces differences in individual BW, dry matter intake (DMI) and plasma metabolite concentration of finewool ewes managed outdoors during winter. Thirty-six mature, pregnant Rambouillet ewes (3.8±0.45 years; 76.8±11.4 kg) were managed in a drylot with ad libitum access to pelleted alfalfa in bunks capable of measuring individual daily DMI. The treatment group consisted of ewes sheared at ~5 weeks before the estimated parturition date (shorn; n=18). Unshorn ewes (n=18) remained in full fleece throughout the experiment and were shorn on the last day of the experiment ~2 weeks before the estimated parturition date. Blood was collected on days 0 (before shearing shorn group), 7, 14 and 21 (before shearing unshorn group) of the trial, and plasma was isolated and analyzed for non-esterified fatty acid (NEFA), β-hydroxybutyrate (BHB) and glucose (GLU) concentrations. There was no effect of shearing on ewe DMI or BW during the trial (P⩾0.35). Plasma NEFA and GLU concentrations were similar (P⩾0.36) between shearing groups, though plasma BHB concentration was 103.7 μmol/l greater (24.1%; P<0.01) in unshorn ewes. Lamb BW at birth was not affected (P=0.30) by ewe shearing treatment. Under conditions of this study, no differences in economically important aspects of sheep production were observed between shorn and unshorn pregnant ewes.     

MathDAMP: a package for differential analysis of metabolite profiles

Background  

With the advent of metabolomics as a powerful tool for both functional and biomarker discovery, the identification of specific differences between complex metabolite profiles is becoming a major challenge in the data analysis pipeline. The task remains difficult, given the datasets' size, complexity, and common shifts in migration (elution/retention) times between samples analyzed by hyphenated mass spectrometry methods.     

Acid-base regulation after maximal exercise testing in late gestation

Kemp, Justin G., Felicia A. Greer, and Larry A. Wolfe.Acid-base regulation after maximal exercise testing in late gestation. J. Appl. Physiol. 83(2):644-651, 1997.This study employed Stewart's physicochemicalapproach to quantify the effects of pregnancy and strenuous exercise onthe independent determinants of plasmaH⁺ concentration([H⁺]). Subjects werenine physically active pregnant women [mean gestational age = 33 ± 1 (SE) wk] and 14 age-matched nonpregnant controls. Venousblood samples and respiratory data were obtained at rest and during 15 min of recovery from a maximal cycle ergometer test that involved 20 W/min increases in work rate to exhaustion. Mean values for[H⁺],PCO₂, and total protein increased,whereas those for bicarbonate concentration([HCO₃]) and the strong ion difference ([SID]) decreased in the transition fromrest to maximal exercise within both groups. At rest and throughoutpostexercise recovery, the pregnant group exhibited significantly lowermean values for PCO₂,[HCO₃], and total protein,whereas [SID] was significantly lower at rest and early recovery from exercise.[H⁺] was also lower atall sampling times in the pregnant group, but this effect wassignificant only at rest. Our results support the hypothesis thatreduced PCO₂ and weak acidconcentration are important mechanisms to regulate plasma[H⁺] and to maintain aless acidic plasma environment at rest and after exercise in lategestation compared with the nonpregnant state. These effects areestablished in the resting state and appear to be maintained aftermaximal exertion.

     

Placental, renal, and ileal sulfate transporter gene expression in mouse gestation

Sulfate is important for mammalian growth and development. During pregnancy, maternal circulating sulfate levels increase by 2-fold, enhancing sulfate availability to the fetus. We used quantitative real-time PCR to determine sulfate transporter mRNA levels during mouse gestation in three tissues: kidney and ileum, to identify transporters involved in sulfate absorption and maintaining high maternal circulating sulfate level; and placenta, to build a model of directional sulfate transport from mother to fetus. In the kidney, Slc13a1 and Slc26a1 were the most abundant sulfate transporter mRNAs, which increased by ≈2-fold at E4.5 or E6.5, whereas lower levels of Slc26a2, Slc26a6, and Slc26a7 mRNA increased by ≈3- to 6-fold from E4.5. Ileal sulfate transporter mRNA levels were not increased in gestation, but slight decreases (by ≈30-40%) were found for Slc26a3 and Slc26a6. In placentae, Slc13a4 and Slc26a2 mRNAs were most abundant, with levels increasing from E10.5 and peaking (≈8-fold) from E14.5 to E18.5, whereas Slc26a1 increased by ≈3-fold at E18.5. The spatial expression of placental mRNAs was determined by in situ hybridization showing Slc13a4 and Slc26a6 in yolk sac, Slc26a1 in spongiotrophoblasts, and Slc13a4, Slc26a2, Slc26a3, and Slc26a7 in the labyrinthine layer. Within the labyrinth, cell-specific staining revealed Slc13a4 expression in syncytiotrophoblast-II (SynT-II) and Slc26a2 in SynT-I. Together, these data show kidney Slc13a1 and Slc26a1 and placental Slc13a4 and Slc26a2 to be the most abundant sulfate transporter mRNAs in mouse gestation, which likely play important physiological roles in maintaining high maternal serum sulfate levels during pregnancy and mediating sulfate supply to the fetus.     

Placental transfer of nutrients during gestation in the viviparous lizard, Pseudemoia spenceri

Energy, ionic, protein and lipid contents and fatty acid profiles for the major lipid classes of freshly ovulated eggs and neonates of the viviparous lizard, Pseudemoia spenceri, were measured. Litter size is 1.7 ± 0.1, with larger females producing larger neonates. Placentotrophy results in approximately 23% more dry matter in the neonates than in the fresh egg. The increase in the quantity of protein and lipid during development is not significant and is reflected in the similarity of energy densities of eggs and neonates. As a percentage of dry matter, neonates have slightly lower proportions of lipid and protein than eggs because of significant uptake of ash, calcium, potassium and sodium, but not of magnesium, across the placenta. The amounts of triacylglycerol and phospholipid are not significantly different between the egg and the neonate, but neonates contain significantly more cholesterol and cholesteryl ester. The amounts of the major fatty acids, palmitic and oleic acids, recovered from the total lipids of the neonate do not differ significantly from the amounts present in the egg lipids, but the neonates contain significantly less linoleic and α-linolenic acids and more palmitoleic, stearic and arachidonic acids than the eggs. The amount of docosahexaenoic acid recovered from the lipids of the neonate is 2.6-times greater than the amount initially present in the egg. P. spenceri has a relatively larger egg and a smaller reliance on placentotrophy than other species in the same genus, all of which have a similar placental morphology. Nevertheless, the pattern of embryonic nutrition includes both obligative and facultative placentotrophy. All the major components of yolk of oviparous species are present in eggs of P. spenceri, but most are augmented during development by placental transfer. Accepted: 8 April 1999     

GABA-mediated inhibition of breathing in the late gestation sheep fetus

The effects of the GABA antagonist picrotoxin, and the GABA agonist muscimol, have been studied in chronically instrumented unanaesthetized fetal sheep of 115-132 days gestation. Picrotoxin (300-400 micrograms/kg intravenous bolus injection) induced a period of stimulated breathing (40-112 min) which was associated with high voltage electrocortical activity, but inhibited by hypoxia. Muscimol (4 mg infused) had the opposite effect and caused a prolonged period of apnoea (85-418 mins) which was followed by a rebound period of increased breathing. These observations suggest that the GABA-ergic system may be involved in the apnoea of high voltage sleep states in the late gestation fetal sheep, but not in the apnoea associated with hypoxaemia in the fetus.     

Carbohydrate metabolism in the fetal pig during late gestation.

In acute experiments on pregnant sows under sodium pentobarbitone anaesthesia, acid base balance, oxygenation and plasma metabolite concentrations were well maintained in the dam and all fetuses which remained undisturbed in utero, irrespective of the duration of the experiment. Fetal liver glycogen concentrations were also unaffected by the time of removal of the fetus. By contrast, intravascular catheterization and withdrawal of blood led to fetal hyperglycaemia and depletion of hepatic glycogen although blood gas and pH values were not changed by these procedures. In the 1 1/2--2 h sampling period following catheterization the normal positive umbilical venous-arterial differences in plasma glucose and lactate generally became reversed. These changes were prevented by the administration of hexamethonium (10--15 mg . kg-1 i.v.) but the drug did not block the fall in hepatic glycogen in catheterized fetuses. Both adrenaline and noradrenaline, which were each infused intravenously at 2.7--3.9 or 0.6--0.9 microgram . kg-1 . min-1, resulted in fetal hyperglycaemia and lacticacidemia together with a fall in arterial blood pH; hepatic glycogen concentrations in these fetuses were also reduced. The apparent sensitivity of the glycogenolytic mechanism to surgical trauma and haemorrhage in the fetal piglet is discussed in relation to findings in other species.     

Steroid profiles of healthy individuals

Urine steroid profiles of healthy individuals can be divided into two groups according to greatly different excretion rates of dehydroepiandrosterone (DHEA). About 80% of the population show an excretion of DHEA in urine of just above the detection limit or less of the main androgens androsterone (A) and etiocholanolone (E). This excretion is only enhanced in psychological stress situations. The remaining 20% excrete DHEA in roughly equal amounts as A and E.While the relation of excreted steroids is rather constant, the absolute amounts may vary greatly. In contrast to the behaviour of all other steroids DHEA excretion is not in relation to other steroids. The group of “high DHEA” producing individuals in particular shows drastic changes in the excretion during a day: the DHEA excretion rapidly rises from morning until afternoon and then drops to rather low values in the resting period during the night. A recognizable DHEA production seems to be closely related to the waking period.     

Production of prostaglandin f2alpha and its metabolite by endometrium and yolk sac placenta in late gestation in the tammar wallaby, Macropus Eugenii

In this study, we investigated production of prostaglandin (PG) F2alpha and its metabolite, PGFM, by uterine tissues from tammar wallabies in late pregnancy. Endometrial explants were prepared from gravid and nongravid uteri of tammars between Day 18 of gestation (primitive streak) and Day 26.5 (term) and were incubated in Ham's F-10 medium supplemented with glutamine and antibiotics for 20 h. PGF2alpha and PGFM in the medium were assayed by specific, validated RIAs. Control tissues (leg muscle) did not produce detectable amounts of either PG. Both gravid and nongravid endometria secreted PGF2alpha, and production increased significantly in both gravid and nongravid uteri towards term. PGFM was produced in small amounts by both gravid and nongravid uteri, and the rate of production did not increase. Neither oxytocin nor dexamethasone stimulated PG production in vitro in any tissue at any stage. Thus, the surge in peripheral plasma PGFM levels seen at parturition may arise from increased uterine PG production, but further study is needed to define what triggers this release.