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.

Induction and Developmental Expression of Cytochrome P450IA1 Messenger RNA in Rat and Human Tissues: Detection by the Polymerase Chain Reaction

Abstract: The expression of cytochrome P450 genes directly within target cells is an important determinant of human susceptibility to cancers, birth defects, and other chemically initiated diseases. One pivotal gene, CYP1A1 , codes for an inducible cytochrome P450 isozyme (P450IA1) responsible for the bioactivation of numerous carcinogenic polycyclic hydrocarbons and aromatic amines. In this study, we used the polymerase chain reaction (PCR) to amplify endogenous P450IA1 mRNA transcripts in a variety of human and rat tissues from different stages of development. The PCR approach greatly enhanced detection sensitivities over those previously achieved and permitted characterization of constitutive as well as induced P450IA1 mRNA expression patterns in specific cell types and organs and during early gestational stages. P450IA1 mRNAs are expressed constitutively in the rat as early as day 15 of fetal liver development and increased in level with increasing developmental age. Transplacental treatment of fetal rats with 3-methylcholanthrene resulted in marked increases in P450IA1 mRNA levels, and responsiveness to the inducer also increased in concordance with developmental age. Comparatively lower constitutive and induced levels of the mRNA were detected in rat lung and kidney, but no P450IA1 mRNA was detected in the rat testis. PCR results obtained from experiments with human tissue samples demonstrated the presence of P450IA1 transcripts in whole organs, in purified cell fractions (lymphocytes, macrophages), and in fetuses as early as day 45 of human gestation. Data from cell culture studies indicated markedly higher levels of P450IA1 PCR product in human pulmonary alveolar macrophages following treatment with the inducing agent β-naphthoflavone. These results underscore the potential role of P450IA1 as a key determinant of individual susceptibility to tissuespecific and developmentally related cancers associated with certain environmental chemical exposures.

Impact of Maternal Undernutrition During the Periconceptional Period, Fetal Number, and Fetal Sex on the Development of the Hypothalamo-Pituitary Adrenal Axis in Sheep During Late Gestation

Abstract: Evidence from epidemiologic, clinical, and experimental studies has shown that a suboptimal intrauterine environment during early pregnancy can alter fetal growth and gestation length and is associated with an increased prevalence of adult hypertension and cardiovascular disease. It has been postulated that maternal nutrient restriction may act to reprogram the development of the pituitary-adrenal axis, resulting in excess glucocorticoid exposure and adverse health outcomes in later life. It is unknown, however, whether maternal nutrient restriction during the periconceptional period alters the development of the fetal pituitary-adrenal axis or whether the effects of periconceptional undernutrition can be reversed by the provision of an adequate level of maternal nutrition throughout the remainder of pregnancy. We have investigated the effect of restricted periconceptional nutrition (70% of control feed allowance) from 60 days before until 7 days after mating and the effect of restricted gestational nutrition from Day 8 to 147 of gestation on the development of the fetal hypothalamo-pituitary adrenal (HPA) axis in the sheep. In these studies, we have also investigated the effects of fetal number and sex on the pituitary-adrenal responses to periconceptional and gestational undernutrition. In ewes maintained on a control diet throughout the periconceptional and gestational periods, fetal plasma ACTH concentrations were higher and the prepartum surge in cortisol occurred earlier in singletons compared with twins. Plasma ACTH concentrations were also significantly higher in male compared with female singletons, and in twin fetuses, the prepartum surge in cortisol concentrations occurred earlier in males than in females. Periconceptional undernutrition resulted in higher fetal plasma concentrations of ACTH between 110 and 145 days of gestation and a significantly greater cortisol response to a bolus dose of corticotropin-releasing hormone in twin, but not singleton, fetuses in late gestation. We have therefore demonstrated that fetal number and sex each has an impact on the timing of the prepartum activation of the HPA axis in the sheep. Restriction of the level of maternal nutrition before and in the first week of a twin pregnancy results in stimulation of the fetal pituitary-adrenal axis in late gestation, and this effect is not reversed by the provision of a maintenance control diet from the second week of pregnancy.

Programming effects in sheep of prenatal growth restriction and glucocorticoid exposure

Abstract: Our aim was to determine the postnatal effects of single and repeated glucocorticoid injections during late gestation. Repeated (104, 111, 118, 125 days) or single (104 days) injections of betamethasone or saline were given to the ewe or by ultrasound guided injection to the fetus (term 150 days). Lambs were born spontaneously and studied at 3 and 6 mo and 1 yr of age. Arterial pressure was measured at each age, and we performed intravenous glucose tolerance tests at 6 mo and 1 yr. Repeated maternal, but not single maternal or fetal, betamethasone injections prolonged gestation, reduced weight at birth and 3 mo, and was associated with low arterial pressure at 3 mo but not at 6 mo and 1 yr. Glucose metabolism was altered in all betamethasone treatment groups, regardless of the number or route of injections. Our data demonstrate that glucocorticoid-induced fetal growth restriction is associated with a transient reduction in postnatal arterial pressure, but glucocorticoid exposure with or without growth restriction alters glucose metabolism.