Intracellular pathways of native iron in the maternal part of the porcine placenta

In the diffuse epitheliochorial porcine placenta iron is secreted as uteroferrin by the maternal epithelium of the areola-gland subunit of the placenta. To elucidate the intracellular pathways of physiological iron in uterine gland epithelium material from 10 sows at 15 to 111 days of gestation was processed for electron microscopy by different routine methods with or without postfixation in osmium tetroxide. Ferritin particles were identified by their size and shape and the content of iron was confirmed by X-ray energy dispersive microanalysis of accumulated ferritin particles. Distinct ferritin particles were not observed in the extracellular space either basal to or luminal to the epithelial cells. Intracellular ferritin was observed apparently free in the cytoplasm, but in variable amounts. Transfer tubules and dense bodies were located basally in the secretory cells. Both of these organelles contained ferritin particles, showed reaction sites for acid phosphatase and were stained by periodic acid-thiocarbohydrazide-silver proteinate. The ciliated cells differed by having apically located dense bodies containing numerous ferritin particles. Our finding of native ferritin in cells with hormonally regulated iron transport supports the concept that transfer tubules as part of the lysosomal complex are part of the endocytic pathway in secretory cells and indicate that ferritin here is an intracellular transport or storage intermediate.     

Effect of iron deficiency on placental cytokine expression and fetal growth in the pregnant rat.

Iron deficiency anemia is the most common nutritional disorder in the world. Anemia is especially serious during pregnancy, with deleterious consequences for both the mother and her developing fetus. We have developed a model to investigate the mechanisms whereby fetal growth and development are affected by maternal anemia. Weanling rats were fed a control or iron-deficient diet before and throughout pregnancy and were killed at Day 21. Dams on the deficient diet had lower hematocrits, serum iron concentrations, and liver iron levels. Similar results were recorded in the fetus, except that the degree of deficiency was markedly less, indicating compensation by the placenta. No effect was observed on maternal weight or the number and viability of fetuses. The fetuses from iron-deficient dams, however, were smaller than controls, with higher placental:fetal ratios and relatively smaller livers. Iron deficiency increased levels of tumor necrosis factor alpha (TNFalpha) only in the trophoblast giant cells of the placenta. In contrast, levels of type 1 TNFalpha receptor increased significantly in giant cells, labyrinth, cytotrophoblast, and fetal vessels. Leptin levels increased significantly in labyrinth and marginally (P = 0.054) in trophoblast giant cells. No change was observed in leptin receptor levels in any region of the placentas from iron-deficient dams. The data show that iron deficiency not only has direct effects on iron levels and metabolism but also on other regulators of growth and development, such as placental cytokines, and that these changes may, in part at least, explain the deleterious consequences of maternal iron deficiency during pregnancy.     

Distribution of Calcium, Iron, Copper, and Zinc in Two Portions of Placenta of Teenager and Adult Women

The placenta is fundamental for fetal development. The aim of this study was to determine Ca, Fe, Cu, and Zn content in the fetal and maternal portions of the placentas of teenage and adult women. Measurement of the minerals was conducted using Synchrotron radiation total reflection X-ray fluorescence. Forty samples from the fetal portion of teenagers and adults and 40 samples from the maternal portion of teenagers and adults were analyzed. There were significant differences in the Ca and Cu concentrations of the placenta's maternal portion when compared to the fetal portion, for both teenagers and adults. There were differences in Fe and Zn concentrations only when comparing the maternal portion of placenta with the fetal portion of the adults. These results suggest important differences in mineral content based on the placental portion. No significant difference was observed between the minerals studied of the maternal portion of teenagers and adults; however, in the fetal portion, mineral concentrations were greater in adults than in teenagers. Therefore, the mineral concentration of the fetal portion of the placenta is influenced by the mother's age. If there is mineral's competition between the mother and fetus during pregnancy in adolescence due to the importance of these minerals in growth and development, then the mechanism and reason for it should be elucidated in future research. In addition, we believe that further research should be carried out on transporters of these minerals in the same portions of the placentas analyzed by our group, in teenagers and adults.     

Studies on the mechanisms involved in iron transfer across the isolated guinea pig placenta by means of bolus experiments

Placental binding and uptake of diferric transferrin as well as transplacental iron transfer has been studied in isolated, perfused guinea pig placenta. The process of binding and uptake of transferrin was saturable only on the maternal side. On the fetal side no specific binding occurred. This indicates an asymmetric distribution of transferrin receptors. No receptors are present for albumin, neither on maternal, nor fetal side. Most of the 125I-59Fe transferrin, administered with a single bolus, enters the trophoblast. A small part remains attached to the plasma membranes, as shown by cell fractionation and in transferrin exchange experiments. The majority transferrin, which was internalized, is unlikely to be bound to plasma membranes and may be bound to receptors dissociated from plasma membranes. Based on kinetics of 59Fe appearance and washout at the fetal side of the perfused placenta as a model for trans-placental iron transfer has been postulated. A central feature is the role played by a small compartment (0.14 mumol) to which iron is supplied by a very rapid process at the trophoblast receptor, without internalisation of transferrin. A second un-identified pathway is supposed to regulate the magnitude of the iron transfer pool.     

Evolutionary implications of fetal and maternal microvillous surfaces in epitheliochorial placentae

According to the “parent-offspring conflict hypothesis” the rapid evolution and diversification of the mammalian placenta is driven by divergent optima of resource allocation between fetus and mother. The fetus has an interest to maximize its resource intake, while the mother has an interest to restrict the transfer of resources, and thus retain resources for subsequent pregnancies. In the epitheliochorial placenta, the contacting fetal and maternal surfaces at the feto-maternal interface are covered with microvilli, which leads to an increase of membrane surfaces available for transport processes. Because membranes are the site of active transport, the conflict hypothesis predicts that the fetal surfaces at the feto-maternal interfaces are larger than the maternal ones. We use transmission electron microscopy and a stereological method to estimate the factors by which the apical fetal and maternal membranes are enlarged by the microvilli. Ten species with an epitheliochorial placenta were studied. Focused ion beam—scanning electron microscopy (FIB-SEM) was used to create three-dimensional models of the interdigitating microvilli of the bovine and porcine placenta. In all species, the fetal surface was larger than the maternal. This was due to a higher number of fetal microvilli and to the presence of membrane folds at the base of the fetal, but not of maternal microvilli. Our results suggest that the ultrastructural morphology of the feto-maternal interface in the epitheliochorial placenta is shaped by conflicting interests between fetus and mother and thus represent a so far neglected arena of the parent-offspring conflict.     

Accumulation cyclique de fer et de quelques autres éléments dans le testicule de Littorina littorea (L.) (Gastéropode Prosobranche)

Iron, the presence of which can be revealed by histochemical techniques and microanalysis X, accumulates in the testis of Littorina littorea (L.). Its accumulation varies in relation to the annual cycle. The highest concentration occurs during the involution period (late summer) and is lowest during gametogenesis (early winter). Besides iron, S, P, Ca, Cl and sometimes Mg and F are found. These elements are contained in lysosomes of “epithelial cells” which develop in the testis following the reproductive stage.     

Role of transferrin in iron transport between maternal and fetal circulations of a perfused lobule of human placenta

The transfer of iron between the maternal and fetal circulations of an isolated perfused lobule of term human placenta was investigated using 125I-labelled or 59Fe-labelled diferric transferrin. There was negligible transplacental transfer of intact transferrin whereas nearly 4 per cent of the added 59Fe was transferred into the fetal circulation after 2 h, where it became associated with fetal transferrin. Over 20 per cent of the added 59Fe radioactivity was sequestered within the placental tissue during this period, associated with transferrin, ferritin and other uncharacterized molecules. This suggests an important role for an intracellular pool in regulating transfer. The presence of 10 mM chloroquine in the maternal circulation substantially reduced tissue accumulation of 59Fe and totally inhibited transfer to the fetus. It is concluded that the initial stages of iron transfer to the fetus involve the internalization of maternal iron-saturated transferrin bound to membrane receptors by receptor-mediated endocytosis, which can be inhibited by the drug chloroquine. Subsequently, the transplacental transfer of iron to the fetus does not involve the concomitant movement of transferrin.     

Localization of glycogen in the placenta and fetal and maternal livers of cadmium-exposed diabetic pregnant rats

This study was designed to investigate the effects of Cd exposure on the glycogen localization in the placenta and in fetal and maternal livers in streptozotocin (STZ)-induced-diabetic pregnant rats. Ninety-nine virgin female Wistar rats (200–220 g) were mated with 33 males for at least 12 h. From the onset of pregnancy, the rats were divided into four experimental groups (control, Cd treated, STZ treated, and Cd+STZ treated). The Cd-treated group was injected subcutaneously daily with CdCl₂ dissolved in isotonic NaCl, starting at the onset of pregnancy throughout the experiment. Diabetes was induced on d 13 of pregnancy by a single intraperitoneal injection of STZ in the STZ-treated group. In addition to the daily injection of Cd, a single intraperitoneal injection of STZ was also given on d 13 of pregnancy in the Cd+STZ-treated group. The rats received the last injection 24 h before being sacrificed and 10 randomly selected rats in each group were sacrificed on d 15 and d 20 of pregnancy. Blood samples were taken for determination of the serum glucose and insulin levels. Fetal and maternal livers of sacrificed rats in all groups were harvested on d 15 and d 20 of pregnancy, whereas placentas were harvested only on d 20 of pregnancy for histochemical examination. Although both Cd and STZ caused hyperglycemia and decreased insulin secretion, Cd-alone treatment increased the glycogen content only in the placental labyrinth, whereas STZ-alone treatment increased the glycogen content only in the maternal part of the placenta. Increased glycogen localization was observed in both the placental labyrinth and the maternal part of placenta when Cd and STZ were given together. Fetal and meternal livers of control and other treatment groups were not different regarding the glycogen content on d 15 or d 20 of pregnancy. It was concluded that Cd exposure during pregnancy might produce a glycogen localization in the placenta of diabetic rats. However, the function and the mechanisms of increased glycogen contents in the placenta of Cd-exposed pregnant diabetic rats remain unclear and further studies are needed.     

Morphological demonstration of non-heme iron and iron-binding proteins in placentas from cases of congenital nephrotic syndrome of Finnish type

Two placentas (gestational age 36 and 39 weeks respectively), obtained from Congenital Nephrotic Syndrome of Finnish type (CNF) cases, have been studied by histochemistry in relation to the presence of non-heme iron and iron-binding proteins (ferritin, transferrin and lactoferrin). Ten control placentas of gestational age ranging from 35 to 40 weeks have been also examined. Employing the Prussian Blue ferrocyanide method, an intense positive reaction of the trophoblastic basament membrane (TBM) was observed only in cases of CNF. By immunoperoxidase techniques, ferritin was demonstrated in the villous stroma whereas lactoferrin was identified only in the cytoplasm of polymorphonuclear neutrophils within fetal stem vessels; a clear positivity for transferrin was encountered on the apical site of the syncytial trophoblast. All these immunohistochemical findings were similar in CNF cases and in control placentas. Ultrastructural observations of terminal villi revealed the presence of osmiophilic granulo-filamentous hemosiderin-like bodies in TBM of placentas from CNF. Although the role of iron-binding proteins in the iron transport through the placenta seems to be unaltered in CNF, the presence of non-heme iron in TBM could represent a histochemical approach for placental diagnosis in this type of nephrotic syndrome.     

Physiological evidence consistent with the presence of a specific O2 carrier in the placenta.

In 30 experiments we perfused the fetal side of the sheep placenta with fluids which had different solubilities for argon, N2, and O2 (dextran, blood, and fluorocarbon emulsions). In some of the experiments we partially exchange-transfused the ewe with the fluorocarbon emulsion. By these procedures we were able to change the physical solubility of argon and N2 severalfold in the fetal perfusion fluid and maternal blood. We found that the diffusing capacity for argon and N2 did not increase with increases in physical solubility in the fetal perfusion medium or in maternal blood. This indicated that the rate-limiting step in the placental transfer of these gases is the small diffusing capacity of the placenta. In contrast, O2 diffusing capacity increased markedly with increased solubility in the fetal perfusion medium. Also the Po2 was frequently the same in the venous blood leaving both sides of the placenta. This indicates that O2 may reach equilibrium between maternal and fetal capillaries in one pass through the placenta. The results are compatible with the presence of specific O2 carrier in the placenta.     

Acidocalcisomes of trypanosomatids have species-specific elemental composition

The elemental composition and stoichiometric profile of elements present in acidocalcisomes of different genera of the Trypanosomatidae family (insect, plant, and mammalian parasites) submitted to parallel cultivation conditions were studied. X-ray microanalysis using transmission electron microscopy in conjunction with a morphometric approach was used to investigate the elemental content, number, distribution, and volumetric density of acidocalcisomes of different species. Microanalytical data showed that the different parasites possess the same elemental composition (oxygen, sodium, magnesium, phosphorus, calcium, iron, and zinc) in their acidocalcisomes. However, the relative concentrations of the elements varied among species, but not within acidocalcisomes of individual species. Iron was detected in acidocalcisomes of all species analyzed, characterizing this element as a constituent of these organelles. Taken together, the results strongly indicate a species-specific composition of acidocalcisomes in trypanosomatid parasites.     

Electron probe X-ray microanalysis of human muscle biopsies

Summary The elemental composition of human muscle fibres have been determined by electron probe microanalysis. In order to distinguish between different types of fibres, two approaches were used. In one approach individual fibres were isolated, portions of them used for a typing by histochemical methods and the main part used for X-ray microanalysis. In the other approach the muscle biopsy was serial-sectioned, some sections used for a histochemical typing and the others (16 m thick cryosections) used for X-ray microanalysis in the electron microscope.The comparison of the ratios between P, S and K in Study No. 1 and 2 indicates different concentrations of sulphur in the subsarcolemmal zone and in the interior of the fibre. Both routes give information on all elements (except the ten lightest ones) contained in the fibres or in sections of them, provided the concentration is high enough. In order to obtain quantitative data, expressed as mmol/kg_dw, the spectra of the specimens were compared to those of standards of known composition and the data subjected to a so called ZAF-correction (corrections for the atomic number effect, absorption of X-rays in the specimen and secondary fluorescence). Quantitative data concerning phosphorus, sulphur, chlorine and potassium were obtained in Study No. 2. A significantly higher sulphur concentration was found in type IIA muscle fibres as compared to those of type I.     

Polyamines and diamine oxidase activity in maternal, embryonal, and fetal tissues of rat after chronic ethanol consumption

The effects of maternal ethanol consumption for 4 weeks before and throughout gestation on polyamine content and diamine oxidase activity of maternal, embryonal and fetal tissues are reported. At the 12th day of pregnancy, a decrease of putrescine in the liver of the mother and marked increases in putrescine, cadaverine and spermidine in embryos were observed. At day 18, putrescine and cadaverine diminished in maternal liver and placenta, and no changes in amine content in fetal liver and brain were found. At day 12, diamine oxidase activity increased in maternal liver and placenta, whereas it greatly diminished in embryos. At day 18, enzyme activity decreased in maternal liver, placenta, fetal liver and brain. These results indicate that chronic ethanol ingestion induces alterations in polyamine concentrations and metabolism in growing and developing tissues during pregnancy that might contribute to the adverse effect of ethanol on conceptual development.     

Preliminary results of the placental decorin profile in bovine pregnancy and parturition

Decorin is a small leucine-rich proteoglycan which is involved in multiple biological functions mainly as a structural and signaling molecule. Due to its biological properties in connective tissue, decorin may participate in remodeling of ECM during attachment and detachment of placenta within the course of pregnancy and at parturition in cows. The aim of the study was to detect the presence of decorin protein in bovine placental tissues and to evaluate its profile during pregnancy and at parturition. Placental tissues from healthy pregnant cows (2–5 month) were collected in abattoir (n?=?10), while parturient tissues were obtained during caesarian section at physiological term (n?=?6). Maternal and fetal parts were separated manually and subjected to homogenization and to quantitative ELISA and verification by Western blotting with anti-decorin antibodies. ELISA test showed that the concentration of decorin during pregnancy was higher in the fetal part of placenta compared with the maternal part (p?<?0.001). Similar pattern was noted regarding to maternal and fetal samples derived from parturient cows. Our preliminary results demonstrate that the concentration of decorin is gestation time-dependent in healthy bovine placenta. Possible confirmation of the involvement of decorin in early pregnancy attachment and detachment of the placenta during parturition requires further research.     

Plasma placental RNA allelic ratio permits noninvasive prenatal chromosomal aneuploidy detection

Current methods for prenatal diagnosis of chromosomal aneuploidies involve the invasive sampling of fetal materials using procedures such as amniocentesis or chorionic villus sampling and constitute a finite risk to the fetus. Here, we outline a strategy for fetal chromosome dosage assessment that can be performed noninvasively through analysis of placental expressed mRNA in maternal plasma. We achieved noninvasive prenatal diagnosis of fetal trisomy 21 by determining the ratio between alleles of a single-nucleotide polymorphism (SNP) in PLAC4 mRNA, which is transcribed from chromosome 21 and expressed by the placenta, in maternal plasma. PLAC4 mRNA in maternal plasma was fetal derived and cleared after delivery. The allelic ratios in maternal plasma correlated with those in the placenta. Fetal trisomy 21 was detected noninvasively in 90% of cases and excluded in 96.5% of controls.     

Prenatal programing: At the intersection of maternal stress and immune activation

This article is part of a Special Issue "Neuroendocrine-Immune Axis in Health and Disease." Exposure to prenatal insults such as maternal stress and pathogenic infections has been associated with an increased risk for neurodevelopmental disorders. The mechanisms by which these programing events occur likely involve complex interactions between the maternal hormonal milieu, the placenta, and the developing fetus, in addition to compounding factors such as fetal sex and gestational stage of development. Despite the diverse biological processes involved, examination of common pathways in maternal stress and immune activation offers intriguing possibilities for elucidation of mechanistic insight. Further, the endocrine and sex-specific placenta is a tissue poised to be a key mediator in fetal programing, located at the intersection of the maternal and embryonic environments. In this review, we will discuss the potential shared mechanisms of maternal stress and immune pathway activation, with a particular focus on the important contribution and role of the placenta. This article is part of a Special Issue entitled (The Neuroendocrine-Immune).     

Maternal-Fetal Distribution of Calcium,Iron, Copper,and Zinc in Pregnant Teenagers and Adults

Adolescence is marked by intensive growth and development. When pregnancy occurs during this period of the mother’s growth, there is an increase in her nutritional needs. The aim of this study was to determine the levels of calcium, iron, copper, and zinc in maternal plasma, the placenta, and in the cord plasma of pregnant teenagers and adults. A total of 80 sets of maternal plasma, placentas, and cord plasma (40 from teenagers and 40 from adults) were analyzed using synchrotron radiation total reflection X-ray fluorescence. The levels of calcium, copper, and zinc in the maternal and cord plasma from teenagers were not significantly different than those from adults. Iron levels in the teenagers maternal and cord plasma were higher than in the adults. All of the minerals analyzed were present at higher levels in the placentas from adults than those from teenagers. However, the low quantities of placental calcium, iron, copper, and zinc in the teenagers do not compromise the levels of these minerals in the cord plasma. Future research regarding the placental transport of these minerals is recommended to investigate the efficiency of mechanisms of transfer of these minerals in pregnant teenagers.     

A theoretical analysis of the effect of placental metabolism on fetal oxygenation under conditions of limited oxygen availability.

The purpose of this theoretical paper is to examine the effects of placental metabolism on fetal oxygenation under conditions of limited oxygen availability. Features of the mathematical model used here include: (1) ordinary non-linear differential equations defining the oxygen partial pressure profiles in the maternal and fetal streams for a concurrent flow pattern; (2) the presence of maternal and fetal blood flow shunts; (3) consumption of oxygen by a metabolically active placenta; and (4) modification of the fetal input to the placenta by changing the rate of fetal oxygen consumption in response to changes in the rate of oxygen delivered to the fetus via the umbilical vein. Model parameters were chosen to be well within the range of values cited in the literature. Based on these calculations, we conclude that: (1) under normal conditions, approximately one-half of the fetal uterine-umbilical venous oxygen partial pressure difference can be attributed to placental oxygen consumption; (2) utilization of fetal oxygen to help maintain the metabolic activities of the placenta does not significantly impair fetal oxygenation under normal conditions; (3) consumption of oxygen by the placenta will have a significant detrimental effect on the rate of oxygen delivered to the fetus if oxygen availability is compromised; and (4) for the same rate of maternal oxygen delivered to the placenta, maternal hypoxemia has a significantly greater adverse effect on fetal oxygenation than does maternal anemia.     

Pregnancy and maternal iron deficiency stimulate hepatic CRBPII expression in rats

Iron deficiency impairs vitamin A (VA) metabolism in the rat but the mechanisms involved are unknown and the effect during development has not been investigated. We investigated the effect of pregnancy and maternal iron deficiency on VA metabolism in the mother and fetus. 54 rats were fed either a control or iron deficient diet for 2 weeks prior to mating and throughout pregnancy. Another 15 female rats followed the same diet and were used as non-pregnant controls. Maternal liver, placenta and fetal liver were collected at d21 for total VA, retinol and retinyl ester (RE) measurement and VA metabolic gene expression analysis. Iron deficiency increased maternal hepatic RE (P < .05) and total VA (P < .0001), fetal liver RE (P < .05), and decreased placenta total VA (P < .05). Pregnancy increased Cellular Retinol Binding Protein (CRBP)-II gene expression by 7 fold (P = .001), decreased VA levels (P = .0004) and VA metabolic gene expression (P < .0001) in the liver. Iron deficiency increased hepatic CRBPII expression by a further 2 fold (P = .044) and RBP4 by ~ 20% (P = .005), increased RBPR2 and decreased CRBPII, LRAT, and TTR in fetal liver, while it had no effect on VA metabolic gene expression in the placenta. Hepatic CRBPII expression is increased by pregnancy and further increased by iron deficiency, which may play an important role in VA metabolism and homeostasis. Maternal iron deficiency also alters VA metabolism in the fetus, which is likely to have consequences for development.