The capacity of the yolk sac to generate multilineage, adult-type hematopoiesis was investigated in vivo using vascular endothelial-cadherin deficient embryos. In these mutants, the yolk sac is not connected to the vasculature of the embryo and therefore all hematopoietic activity detected therein is intrinsic to the yolk sac and not derived from intraembryonic sources. At embryonic days 9.5 an...

The potential absorptive role of the yolk sac membrane was evaluated by examining protein and enzyme patterns in embryonic fluids and by comparing the synthetic capacity of the secondary yolk sac, fetal liver and placenta for human chorionic gonadotrophin (HCG) and alpha-fetoprotein (alphaFP). In yolk sac fluid samples, protein electrophoresis showed two main electrophoretic bands with mobiliti...

In the chicken, maternal IgG is deposited in the oocyte yolk and subsequently transported intact by the foetal chick yolk sac into the chick circulation. Such transport appears to require a specific membrane-localized IgG receptor. Using the assay of 125I-yolk IgG binding, we have investigated the existence and properties of such receptors in yolk sac tissue disks. We find that: (1) There are s...

•Yolk sac germ cell tumours are rare in post-menopausal patients.•Most involve mixed yolk sac tumours•Consider diagnosis in patients with a pelvic-abdominal mass and raised AFP.

A primary intracranial yolk sac tumor (YST) is a type of germ cell tumor (GCT) and usually involves the pineal or suprasellar regions, as do other GCTs. Primary YST in the basal ganglia is not common, and bilateral basal ganglia involvement is even rarer. Early diagnosis is often difficult because of minimal or subtle findings without space-occupying lesions shown on neuroimaging during the ear...

The extra-embryonic coelom (EEC) and secondary yolk sac are prominent structures in the gestational sac during the first trimester of human pregnancy, at a time before the definitive placental circulation becomes established. We propose that the EEC and yolk sac play a critical role in the nutrition of early pregnancy, fulfilling exchange functions which are assumed by the placenta at a later s...

Studies were conducted to explore the synthesis of retinol-binding protein and transthyretin by embryonic and extraembryonic tissues during fetal development in the rat. The levels of retinol-binding protein mRNA and transthyretin mRNA were measured in fetal liver and in extraembryonic tissues by RNA gel blot analysis and hybridization with specific cDNA probes. Retinol-binding protein mRNA and...

Studies of receptor-mediated lipoprotein metabolic pathways in avian species have revealed that physiological intricacies of specific cell types are highly analogous to those in mammals. A prime example for the power of comparative studies across different animal kingdoms, elucidated in the chicken, is that the expression of different lipoprotein receptors in somatic cells and oocytes are the k...

It has been previously suggested that abnormal yolk sac characteristics and slow embryonic foetal heart rate are associated with poor gestational outcome and these parameters can be used to assess foetal viability in first trimester of pregnancies. However there is paucity of evidence in Indian medical literature. The purpose of present study was to examine the role of yolk sac characteristics ...