Fetus

About: Fetus is a research topic. Over the lifetime, 21567 publications have been published within this topic receiving 646380 citations. The topic is also known as: foetus & fœtus.

Adaptation of nutrient supply to fetal demand in the mouse involves interaction between the Igf2 gene and placental transporter systems

Abstract: The mammalian fetus is unique in its dependence during gestation on the supply of maternal nutrients through the placenta. Maternal supply and fetal demand for nutrients need to be fine tuned for healthy growth and development of the fetus along its genetic trajectory. An altered balance between supply and demand can lead to deviations from this trajectory with long-term consequences for health. We have previously shown that in a knockout lacking the imprinted placental-specific Igf2 transcript (P0), growth of the placenta is compromised from early gestation but fetal growth is normal until late gestation, suggesting functional adaptation of the placenta to meet the fetal demands. Here, we show that placental transport of glucose and amino acids are increased in the Igf2 P0+/- null and that this up-regulation of transport occurs, at least in part, through increased expression of the transporter genes Slc2a3 and Slc38a4, the imprinted member of the System A amino acid transporter gene family. Decreasing fetal demand genetically by removal of fetal Igf2 abolished up-regulation of both transport systems and reduced placental System A amino acid transport activity and expression of Slc38a2 in late gestation. Our results provide direct evidence that the placenta can respond to fetal demand signals through regulation of expression of specific placental transport systems. Thus, crosstalk between an imprinted growth demand gene (Igf2) and placental supply transporter genes (Slc38a4, Slc38a2, and Slc2a3) may be a component of the genetic control of nutrient supply and demand during mammalian development.

Prenatal glucocorticoid exposure leads to offspring hyperglycaemia in the rat: studies with the 11 b -hydroxysteroid dehydrogenase inhibitor carbenoxolone

Abstract: Recent human epidemiological studies have linked low birth weight with a substantially increased risk of non-insulin-dependent diabetes mellitus in later life. These data suggest that the intrauterine environment plays a crucial role in determining later glucose homeostasis, but the mechanism is unknown. We have proposed that exposure of the fetus to excess maternal glucocorticoids may underpin the epidemiological findings. Normally placental 11 β -hydroxysteroid dehydrogenase type 2 (11 β -HSD-2) protects the fetus from the normally higher maternal levels of glucocorticoids by inactivating corticosterone and cortisol to inert 11-keto products. Here we show that administration of carbenoxolone, an inhibitor of placental 11 β -HSD 2, to pregnant rats, leads to a significant reduction in average birth weight (20 % fall). At 6 months of age, the male offspring of carbenoxolone-treated pregnancies had similar weights to controls, but showed significantly higher fasting plasma glucose (6.0 ± 0.3 vs 4.8 ± 0.2 mmol/l; p < 0.01) and exhibited significantly greater plasma glucose (10 % higher) and insulin (38 % higher) responses to an oral glucose load. These effects of carbenoxolone require intact maternal adrenal glands suggesting that inhibition of feto-placental 11 β -HSD 2 is key. These data support the notion that defiency of placental 11 β -HSD, by exposing the fetus to excess maternal glucocorticoids, reduces growth and predisposes to hyperglycaemia in later life. [Diabetologia (1996) 39: 1299–1305]

Placental defects and embryonic lethality in mice lacking suppressor of cytokine signaling 3

Abstract: Mice lacking suppressor of cytokine signaling 3 (SOCS3) exhibited embryonic lethality with death occurring between days 11 and 13 of gestation. At this stage, SOCS3−/− embryos were slightly smaller than wild type but appeared otherwise normal, and histological analysis failed to detect any anatomical abnormalities responsible for the lethal phenotype. Rather, in all SOCS3−/− embryos examined, defects were evident in placental development that would account for their developmental arrest and death. The placental spongiotrophoblast layer was significantly reduced and accompanied by increased numbers of giant trophoblast cells. Delayed branching of the chorioallantois was evident, and, although embryonic blood vessels were present in the labyrinthine layer of SOCS3−/− placentas, the network of embryonic vessels and maternal sinuses was poorly developed. Yolk sac erythropoiesis was normal, and, although the SOCS3−/− fetal liver was small at day 12.5 of gestation (E12.5), normal frequencies of erythroblasts and hematopoietic progenitor cells, including blast forming unit-erythroid (BFU-E) and, colony forming unit-erythroid (CFU-E) were present at both E11.5 and E12.5. Colony formation for both BFU-E and CFU-E from SOCS3−/− mice displayed wild-type quantitative responsiveness to erythropoietin (EPO), in the presence or absence of IL-3 or stem cell factor (SCF). These data suggest that SOCS3 is required for placental development but dispensable for normal hematopoiesis in the mouse embryo.

Prenatal nicotine increases pulmonary α7 nicotinic receptor expression and alters fetal lung development in monkeys

Abstract: It is well established that maternal smoking during pregnancy is a leading preventable cause of low birth weight and prematurity. Less appreciated is that maternal smoking during pregnancy is also associated with alterations in pulmonary function at birth and greater incidence of respiratory illnesses after birth. To determine if this is the direct result of nicotine interacting with nicotinic cholinergic receptors (nAChRs) during lung development, rhesus monkeys were treated with 1 mg/kg/day of nicotine from days 26 to 134 of pregnancy. Nicotine administration caused lung hypoplasia and reduced surface complexity of developing alveoli. Immunohistochemistry and in situ α-bungarotoxin (αBGT) binding showed that α7 nAChRs are present in the developing lung in airway epithelial cells, cells surrounding large airways and blood vessels, alveolar type II cells, free alveolar macrophages, and pulmonary neuroendocrine cells (PNEC). As detected both by immunohistochemistry and by αBGT binding, nicotine administration markedly increased α7 receptor subunit expression and binding in the fetal lung. Correlating with areas of increased α7 expression, collagen expression surrounding large airways and vessels was significantly increased. Nicotine also significantly increased numbers of type II cells and neuroendocrine cells in neuroepithelial bodies. These findings demonstrate that nicotine can alter fetal monkey lung development by crossing the placenta to interact directly with nicotinic receptors on non-neuronal cells in the developing lung, and that similar effects likely occur in human infants whose mothers smoke during pregnancy. J. Clin. Invest. 103:637–647 (1999)