The visceral yolk sac plays a critical role in normal embryogenesis, yet little is known about the specific molecules that regulate its development. We show here that four winged-helix genes (HNF-3alpha, HNF-3beta, HNF-3gamma and HFH-4) are restricted to visceral endoderm. In the absence of HNF-3beta, visceral endoderm forms but the morphogenetic movements by which the embryo becomes enclosed w...

Background: During the past 20 years a lot of information is achieved about the first trimester of pregnancy through ultrasound and intrauterine fertilization. Many researchers tried to use the symptoms of ultrasound in early pregnancy like measuring the gestational sac and yolk sac of the pregnancy to predict the continuation of pregnancy. Aim of the recent study is to predict the risk of spon...

A xenograft line, HX 53, has been established in immune-suppressed mice from a specimen of a lymph node metastasis in a patient with a histological diagnosis of seminoma but with markedly raised circulating levels of alpha-fetoprotein. Histological, immunocytochemical, and ultrastructural studies of this xenograft line have suggested that a solid variant of yolk sac carcinoma may exist, which m...

T H E placentation of Erinaceus europea has been described by Hubrecht (1889). An account of the development and structure of the avascular and vascular yolksac placentae which are formed in this species has been presented (Morris, 1953). Reichert's membrane is formed in the wall of the yolk-sac and it persists to term. A further study of the yolk-sac placentae, Reichert's membrane, the decidua...

The dominant hemoglobin of the adult hamster was detected in yolk-sac erythroid cells, and its identity was confirmed by peptide mapping and by analysis of relevant peptides. Both the presence and active synthesis of two embryonic hemoglobins presumed to exist only in yolk-sac erythroid cells were detected in neonatal liver and spleen. Thus the time span of expression of both embryonic and adul...

The possible relationship among malignancy, differentiation, and chro mosomal constitution of primary embryo-derived tumors was studied. Tumors were induced by transplanting 7-day-oId mouse embryos under the kidney capsule of syngeneic BALB/c recipients. Transplantation of 101 embryos resulted in 81 tumor-bearing mice: 36 teratocarcinomas; 18 teratomas; and 27 yolk sac tumors. Some of the yolk ...

Yolk sac tumour is the most common germ cell tumour in infants and children, with a majority of them arising in the gonads. Rare cases of extra - gonadal germ cell tumours have been described in the literature. We are presenting here, a case of a yolk sac tumour of the cryptorchid testis in a 2 year old child, who initially presented with a mass in the left lobe of the liver, with huge ascites ...

Two distinct patterns of chimaerism were found in conceptuses produced by injecting dissociated 4.5-day inner cell mass cells into genetically dissimilar blastocysts. Pattern 1: donor cells were found in the endoderm layer of the visceral yolk sac, but not in the adjacent mesoderm layer of this organ or in the foetus itself. Pattern 2: donor cells were found in the mesoderm layer of the viscera...

A polyvalent antigen composed of heat-killed agar-grown Legionella pneumophila serogroups 1-4 suspended in a suspension of yolk-sac from embryonated hens' eggs has been examined for use in the indirect fluorescent antibody test for Legionella infection. The serological response detected by monovalent antigen correlated well with that detected by polyvalent antigen. The use of polyvalent antigen...

A critical role for the endothelium of yolk sac and dorsal aorta has been shown in embryonic hematopoiesis. A stromal cell line derived from yolk sac, YSCL-72, has been chosen to search for a novel molecule associated with embryonic hematopoiesis. Analysis between YSCL-72 and an adult aorta-derived endothelial cell line, EOMA, demonstrated that activated leukocyte cell adhesion molecule (ALCAM,...