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.

Studies of insulin‐like growth factor ‐i and ‐ii by specific radioligand assays in umbilical cord blood

Abstract: SUMMARY Somatomedin concentrations in human umbilical sera (n= 206) were measured using a specific radioimmunoassay for insulin-like growth factor (IGF)-I and a specific radioreceptor assay for IGF-II following acid-ethanol extraction of the sera to remove the somatomedin binding proteins. IGF-I concentrations were lower (P< 0·001) than adult values and correlated with gestational age (P< 0·001) and birth weight (P< 0·0001). Multiple regression analysis demonstrated that both birth weight expressed independently of gestational age as the standard deviate score (P< 0·0001) and gestational age (P< 0·002) had effects on umbilical cord IGF-I concentrations. IGF-II concentrations were similar to adult values and did not correlate with gestational age, birth size or IGF-I values. IGF-II concentrations were higher (P< 0·005) in male than female fetuses. These data support a role for IGF-I in influencing fetal growth and suggest the independent regulation of the secretion of IGF-I and II in the perinatal period. These was no evidence to suggest a distinct perinatal form of somatomedin.

Studies of insulin, growth hormone and prolactin binding: ontogenesis, effects of sex and pregnancy.

Abstract: The ontogenesis of specific binding of 125I-labeled insulin, hGH and oPRL was measured in tissues from rat, rabbit and guinea pig. Binding of 125I-oPRL and 125I-hGH was very low in liver membranes from fetal and immature rats. A 9- fold (oPRL) and 3.5-fold (hGH) increase in binding occurred between 20 and 40 days of age with a greater increase in binding in mid and late pregnancy. Binding to male liver membranes was significantly lower at all stages of development. There were no significant changes in the binding of 125I-hGH from fetal through 30 day rabbit liver membranes. Between 30 and 60 days of age, a 6-fold increase in binding occurred, with a further increase in binding during pregnancy. A similar overall pattern was observed with I25I-bGH. The increase in specific binding of 125I-oPRL was more gradual and occurred earlier than for 125I-GH. In the guinea pig, three patterns of 125I-insulin binding with respect to development were observed. Fetal placenta and kidney showed marked increase in specifi...

Screening of Maternal Serum for Fetal Down's Syndrome in the First Trimester

Abstract: Background Screening of maternal serum to identify fetuses with Down's syndrome is now routinely offered during the second trimester of pregnancy. Prenatal screening by means of serum assays or ultrasonographic measurements, either alone or in combination, may also be possible in the first trimester. Methods We measured serum alpha-fetoprotein, unconjugated estriol, human chorionic gonadotropin (hCG), the free beta subunit of hCG, and pregnancy-associated protein A in 4412 women (82 percent of whom were 35 years of age or older) who came to 16 prenatal diagnostic centers for chorionic-villus sampling or early amniocentesis at 9 to 15 weeks of gestation. Ultrasound measurements of fetal nuchal translucency were also reported. Fetal chromosomal analysis was performed in all pregnancies. Altogether, there were 61 fetuses with Down's syndrome. Results A total of 48 pregnancies affected by Down's syndrome and 3169 unaffected pregnancies were identified before 14 weeks of gestation; the rates of detection of Do...

An interspecies comparison of placental antibody transfer: New insights into developmental toxicity testing of monoclonal antibodies

Abstract: There are profound differences in maternofetal transfer of immunoglobulins between species with extensive gestational transfer of maternal immunoglobulins in primates (including humans) via the chorioallantoic placenta as well as in rabbits and guinea pigs via the inverted yolk sac splanchnopleure. In contrast, other neonatal rodents (rats and mice) receive passive immunity predominantly postnatally. This transfer is mediated principally via FcRn receptors. Therapeutic monoclonal antibodies (mAbs) are most commonly of the IgG1 subclass, which is transported most efficiently to the fetus. In all animal species used for testing developmental toxicity, fetal exposure to IgG is very low during organogenesis, but this increases during the latter half of gestation such that the neonate is born with an IgG1 concentration similar to the mother (but not rats and mice). Review of mAb developmental toxicity studies of licensed products reveals Cynomolgus monkey as the species used in the majority of the cases (10 out of 15). Pregnancy outcome data from women gestationally exposed to mAb is limited. In general, the findings are consistent with the expected low exposure during organogenesis. Guinea-pigs and rabbits are potential candidates as "alternatives" to the use of nonhuman primates as the maternofetal transfer in the last part of gestation is at a level similar in humans. Based on the pattern of placental transfer of IgG in humans, study designs that allow detection of both the indirect effects in early gestation plus the effects of direct fetal exposure in mid and late gestation are recommended for developmental toxicity of mAbs.

Umbilical uptake of amino acids in the unstressed fetal lamb.

Abstract: The whole blood concentrations of 22 amino acids were measured in a chronic, unstressed fetal lamb preparations. Samples were taken daily from the umbilical artery, umbilical vein, and maternal artery over the latter quarter of gestation. 73 sets of samples (from the umbilical artery and vein and the maternal artery) from 13 animals were analyzed for amino acid levels. Oxygen contents were determined simultaneously in 48 sets (umbilical artery and vein) to relate fetal oxygen consumption to amino acid uptake via the umbilical circulation. The results indicate that there is no umbilical uptake of the acidic amino acids, glutamate and aspartate; there is, in fact, a net flux of glutamate out of the fetus into the placenta. As both of these amino acids are major constituents of body proteins, the data indicate that they are formed within the fetus. The umbilical uptake of some neutral and basic amino acids (e.g., valine, leucine, isoleucine, arginine, phenylalanine, and tyrosine) is in considerable excess of estimated growth requirements, suggesting that some amino acids undergo extensive transamination and oxidative degradation in the fetus. Finally, the net uptake of nitrogen, carbon, and calories by the growing ovine fetus in the form of amino acids, glucose, and lactate is compared to estimated requirements as determined in previous studies.