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.

Fetal thyroid function : diagnosis and management of fetal thyroid disorders

Abstract: The fetal hypothalamic-pituitary-thyroid axis develops independently of the maternal axis, but it is dependent on the maternal-placental system for adequate supply of iodide substrate. This iodide is supplied by direct transfer of maternal plasma iodide and by placental deiodination of T4. In addition, although placental transport of iodothyronines is limited, significant maternal-fetal transfer of T4 occurs, accounting for approximately 30% of the average 10 ug/dL serum-T4 concentration in fetal-cord blood at term. Current information suggests that this maternal contribution to the fetal-T4 levels is important for normal fetal maturation, particularly of the central nervous system. Combined maternal-fetal hypothyroxinemia can lead to irreversible fetal central nervous system damage. The timing of this fetal T4 dependency is not clear. It may be important in the first half of gestation, before the fetal thyroid gland is capable of T4 production, as well as the latter half of gestation when thyroid hormone effects on multiple organ systems are developing. Management of fetal thyroid dysfunction requires normalization of maternal serum T4 concentrations, avoidance or careful monitoring of potentially goitrogenic drug effects in the fetus, and in some instances, direct or indirect fetal therapy. In most cases fetal hypothyroidism is sporadic and undetected, and prognosis for normal growth and development is excellent if the mother is euthyroid and the hypothyroid state is detected and adequately treated at birth. Fetal treatment by intraamniotic thyroxine injection has been provided in cases of inadvertent maternal radioiodine treatment of Graves' disease between 10 and 20 weeks gestation and for fetal goiter detected by ultrasound. Effective treatment of fetal hyperthyroidism in pregnant women with high titers of thyroid stimulating autoantibody is possible by judicious administration of antithyroid drugs to the mother. Management of the hyperthyroid state in the neonate also is essential.

Adiponectin expression in human fetal tissues during mid- and late gestation.

Abstract: Adiponectin (ApN), an adipocytokine expressed in adipocytes with antidiabetic and antiatherogenic actions, has been detected in cord blood, suggesting a putative role in intrauterine fetal development. The aim of this study was to confirm the presence of ApN in the fetal circulation and directly investigate ApN expression in fetal tissues. The study showed high ApN levels in umbilical venous blood from fetuses [n = 44; 31.2 ± 14.1 (sd) mg/liter in umbilical vs. 8.4 ± 4.0 in maternal circulation (P < 0.0001)] that positively correlated with gestational age. By using RT-PCR, Western blotting, and immunohistochemistry, ApN was detected in several fetal tissues at mid- and late gestation (from 14 to 36 wk) but not in the placenta. ApN was expressed in tissues of mesodermic origin, i.e. brown and white adipocytes, skeletal muscle fibers of diaphragm and iliopsoas, smooth muscle cells of small intestine and arterial walls, perineurium and renal capsule, and tissues of ectodermal origin, i.e. epidermis and ocula...

Developmental expression of CYP2C and CYP2C-dependent activities in the human liver: in-vivo/in-vitro correlation and inducibility.

Abstract: Experiments were performed in vivo and in vitro to date the onset of hepatic CYP2C isoforms and CYP2C-dependent activities during the perinatal period in humans. Proteins were not detected by immunoblotting in fetal livers and developed in the first few weeks after birth, irrespective of the gestational age at birth. Similarly, the hydroxylation of tolbutamide, a marker for CYP2C9 was undetected in fetal liver microsomes and rose in the first month after birth. In adult liver preparations, the hydroxylation of diazepam correlated well with the CYP3 A content of microsomes (r = 0.858, p < 0.01) and with the 6 beta hydroxylation of testosterone (r = 0.830, p < 0.005), whereas demethylation was related to the bulk of CYP2C proteins (r = 0.865, p < 0.005). In fetal liver microsomes, hydroxylation and demethylation activities accounted for less than 5% of the adult activities and both increased immediately after birth to reach adult activities at 1 year of age. When diazepam was given for sedative purpose in neonates and infants, the in-vivo urinary excretion of desmethyl diazepam, temazepam and oxazepam was extremely low in 1-2 day newborns (less than 5 nmol metabolites excreted in 24 h per kg body weight) and developed in the first week after birth. In newborns, barbiturates and to a lesser extent steroids, acted as inducers of CYP2C isoforms and increased tolbutamide hydroxylation, diazepam demethylation and diazepam hydroxylation by 2 to 10-fold. The surge of CYP2C proteins was caused by an accumulation of RNAs occurring in the first week after birth. The hepatic content in CYP2C8, 2C9 and 2C18 RNA displayed the same profile of evolution, which suggested a coregulation of their synthesis during the neonatal period. Taken together, these biochemical and clinical data enable dating of the onset of CYP2C proteins to the first weeks after birth, which is of considerable clinical importance in pediatric pharmacology.

Developmental expression of genes for the stereoidogenic enzymes P450scc (20,22-desmolase), P450c17 (17 alpha-hydroxylase/17,20-lyase), and P450c21 (21-hydroxylase) in the human fetus

Abstract: Fetal adrenal steroidogenesis is required for the production of placental estrogen, and fetal testicular steroidogenesis is required for the development of male external genitalia. We studied the ontogeny and tissue specificity of expression of the genes for three steroidogenic enzymes: P450scc (the cholesterol side-chain cleavage enzyme), P450c17 (17 alpha-hydroxylase/17,20-lyase), and P450c21 (21-hydroxylase) in the human fetus. RNA from fetal tissues was probed with homologous human P450scc, P450c17, and P450c21 cDNAs cloned in our laboratory. At 20-21 weeks gestation, P450scc mRNA was most abundant in the adrenal, followed by testis, placenta, and ovary. P450c17 mRNA was also most abundant in the adrenal, followed by testis and ovary, but was undetectable in the placenta. P450c21 mRNA was detected only in the adrenal. None of these mRNAs was detected in kidney, liver, spleen, intestine, or muscle. Twenty-two fetal testis samples (13-25.8 weeks gestation) were studied. P450scc and P450c17 mRNAs were most abundant at 14-16 weeks and diminished to 35 and 19% of their peak values, respectively, by 20-25.8 weeks. Ovarian P450scc and P450c17 mRNAs were present, respectively, in only 6.2% and 1.8% of the maximum amount in the testis and did not vary detectably from 14.9 to 21.5 weeks gestation. The testicular and ovarian steroidogenic enzyme mRNA data correlate well with previously reported changes in gonadal steroidogenesis with gestational age. The presence of P450scc mRNA, but not P450c17 mRNA, in the placenta indicates that the placenta is able to initiate the synthesis of some steroid hormones, but is not able to synthesize estrogen de novo. Since P450c21 was found only in the adrenal, the extraadrenal 21-hydroxylation of progesterone to deoxycorticosterone, a common event in the fetus, is probably mediated by an enzyme(s) other than P450c21.

Placental 11-Beta Hydroxysteroid Dehydrogenase Methylation Is Associated with Newborn Growth and a Measure of Neurobehavioral Outcome

Abstract: Background There is growing evidence that the intrauterine environment can impact the neurodevelopment of the fetus through alterations in the functional epigenome of the placenta. In the placenta, the HSD11B2 gene encoding the 11-beta hydroxysteroid dehydrogenase enzyme, which is responsible for the inactivation of maternal cortisol, is regulated by DNA methylation, and has been shown to be susceptible to stressors from the maternal environment.