The yolk sac of the fetal rat and the proximal small intestine of the neonatal rat selectively transport maternal IgG. IgG-Fc receptors are thought to mediate transport across the epithelium of both tissues. We used a mouse mAb (MC-39) against the 45-54-kD component of the Fc receptor of the neonatal intestine to find an antigenically related protein that might function as an Fc receptor in fet...

Progenitor cells capable of giving rise to functional macrophages in in vitro culture were first detectable in the fetal yolk sac of the mouse between day 7 and 8 of gestation. Macrophage progenitors were not detectable outside the yolk sac until day 11. Although the early yolk sac contained macrophage precursors, no cells with the morphologic or functional characteristics of mouse promonocytes...

Background: The bovine yolk sac derives from visceral endoderm and its development occurs between days 18-23 of gestation. The study of this membrane is important for comparative data and has already been performed in rodents, sheep and in cattle, especially Bos taurus. In species Bos indicus the yolk sac has not quite been studied and is believed that there are morphological differences betwee...

Thyroid hormones (THs) are essential for the correct development of nearly every structure in the body from the very early stages of development, yet the embryonic thyroid gland is not functional at these stages. To clarify the roles of the egg yolk as a source of THs, the TH content in the yolk and the expression of TH regulator genes in the yolk sac membrane were evaluated throughout the 21-d...

Conceptuses from 9.5-day pregnant rats were cultured for 48 h in heat-inactivated homologous serum to which leupeptin, a specific inhibitor of the lysosomal cysteine-proteinases, was added for the final or the penultimate 6 h. The presence of leupeptin (25 micrograms/ml or above) increased the protein content of yolk sacs at harvesting to approximately twice the control value. The protein conte...

The yolk sac of the 12-day chicken embryo retains the blast stage progenitors to cells of the myeloid lineages with a very low level of contamination by more mature myeloid cells which have begun to express the characteristic myeloid cell markers. Both in vivo and in vitro experiments have supported the hypothesis that target cells for the BAI-A strain of avian myeloblastosis virus are containe...

Gastric adenocarcinoma with yolk sac tumor (YST) differentiation has rarely been reported. We report a case of primary gastric adenocarcinoma with yolk sac tumor differentiation and liver metastases of the YST component in a 50-years-old patient. This was suspected due to high serum level of alpha fetoprotein in the presence of a gastric fundal tumor. Gastric carcinoma with yolk sac tumor compo...

Yolk sac tumor rarely involves the pericardium. A 17-year-old boy had a mediastinal mass leading to total obstruction of the superior vena cava with cardiac tamponade and pleural effusion. Further imaging studies and biopsy showed that the origin was a yolk sac tumor. After surgery and adjuvant chemotherapy, no recurrence was noted during a follow-up of 20 months. This report describes the magn...

malignant germ-cell tumors (mgct) are rare tumors of childhood accounting for less than 3% of pediatric malignancies. endodermal sinus tumor (est) forms the most common histologic subtype of mgct. the vagina is an extremely rare site for gcts. an 8-month-old female was admitted with a short history of vaginal bleeding, and a mass protruding from the vagina. she was pale and a mass was palpable ...