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At least 19 recordsLinked to original sources
PubMed1976

The human yolk sac and yolk sac carcinoma. An ultrastructural study.

The ultrastructure of the yolk sac of a 39 day old human embryo was studied. The subcellular organization was suggestive of a highly specialized absorptive function proceeding in an exocelomic-viteline direction. These findings, compatible with intense metabolic activity, are at variance with the concept of rapid involution of the yolk sac following completion of its hemopoietic and angiogenetic functions. The speculation is advanced that a potential avenue exists in the yolk sac whereby maternally derived products encounter fetal endoderm. Ultrastructural features in the normal yolk sac were compared to those existing in a tumor showing the "endodermal sinus" pattern, and reviewed in the light of the pertinent literature. These findings support the concept that attributes an endomesoblastic derivation to such neoplasms.

Dysgerminoma↗
PubMed1985

Ultrastructure and hydrolase cytochemistry of the developing marmoset yolk sac.

Yolk sacs from Callithrix jacchus were investigated light and electron microscopically as well as by qualitative light microscopic enzyme histochemistry on days 35 to 126 of gestation. The thin yolk sac wall of the early stages (day 35-41) consists of the cuboid, endodermal epithelium, the mesothelium of the exocoelom and some interposed blood vessels. The inner endodermal surface is rather smooth. At later stages, the epithelium becomes highly prismatic and forms folds which are lined by a mesenchyme and blood vessels. Microvilli and a small number of endocytotic vesicles are observed at the apices of the epithelial cells, which are interconnected by gap junctions, desmosomes and interdigitations. The cytoplasm of the epithelial cells is characterized by a well-developed rough endoplasmic reticulum, a large Golgi apparatus and glycogen deposits. Four different membrane-bordered types of inclusions can be distinguished in the cytoplasm of the epithelial cells: The type I and II inclusions are considered as secretion granules. Their increase and their localization in the cavities of the endoplasmic reticulum at later stages are ascribed to an inhibition of the intracellular transport at the onset of involution. The type III and IV inclusions may represent lysosomes and related organelles. Bile capillary-like spaces exist between the epithelial cells. The basement membrane is incomplete below the epithelium and absent around the capillaries, the endothelium of which is porous in certain areas. Aminopeptidase M is highly active in the plasmalemma and the bile capillary-like structures of the epithelium, dipeptidylpeptidase IV in the mesothelium and alkaline phosphatase in the blood vessel endothelium. Other membrane hydrolases are absent. Acid proteases, glycosidases, non-specific phosphatases and non-specific esterases can be detected stage-dependently with moderate to high activities in the yolk sac epithelium. Compared with other organs, the yolk sac structure and hydrolase equipment are similar to those of the liver and may, therefore, have similar functions, e.g. synthesis and secretion of proteins. In addition, however, the yolk sac epithelium might also be involved in resorptive processes of material from the lumen followed by lysosomal digestion. The Callithrix jacchus yolk sac starts involution on day 80 of gestation by disintegration of the cells. On day 100, this process is completed. The stage of involution which is late in comparison with other primates, e.g. man and Rhesus monkey, is ascribed to the strongly delayed development of Callithrix jacchus.

Animals↗
PubMed1983

Ultrastructure of the placenta and fetal membranes of the dog: II. The yolk sac.

Yolk sacs from dogs at 40, 50, and 60 days of gestation were examined by electron microscopy. Free ribosomes, mitochondria, and rough endoplasmic reticulum (rER) are more prominent in both endoderm and mesothelium at 40 and 50 days than at 60 days, suggesting a greater synthetic capacity at the earlier stages. Smooth endoplasmic reticulum (sER) and glycogen are also present in greater amounts in the endoderm in the earlier stages. In the mesothelium, however, low amounts of sER and glycogen are consistently present. Certain possibilities relative to the nature of the synthetic activities in these two tissues are discussed. Large amounts of smooth-surfaced vesicles were observed along the basal edges of the 60-day mesothelium; they are indicative of transport processes occurring at this time. As gestation proceeds, in both endoderm and mesothelium, the Golgi complex remains well developed, there are more numerous lysosomelike bodies, and bundles of intermediate filaments either increase or become more diffused. In some endoderm cells at 60 days, large vacuoles and dense glycogen deposits were noted. These observations indicate that degenerative processes are gradually occurring in the endoderm and mesothelium as parturition draws near. Erythropoiesis occurs in the mesenchyme at 40 and 50 days. At 40 days also, segments of endothelium were seen within blood islands, indicating that the endothelial lining of some yolk sac vessels differentiates from cells located in the interior of such islands.

Animals↗
PubMed2003

Renal cell carcinoma antigen is expressed by yolk sac tumors and yolk sac elements of embryonal carcinomas.

Renal cell carcinoma antigen is a rather specific marker for normal and neoplastic renal tissue. We investigated the expression of this antigen in 34 gonadal and extragonadal germ cell tumors, including 8 pure yolk sac carcinomas and 26 embryonal carcinomas, 15 of which were combined with teratomas, seminomas, and dysgerminomas. Renal cell carcinoma antigen was demonstrated in all 8 yolk sac tumors and 21 of 26 embryonal carcinomas (81%). In yolk sac tumors, renal cell carcinoma antigen reactivity was diffusely present throughout the tumors. In embryonal carcinomas, this marker was identified only in yolk sac components. Both intracytoplasmic and membranous staining patterns were present. No reactivity was noticed in embryonal carcinoma cells, seminoma, dysgerminoma, and other components of teratomas. The study suggests an antigenic similarity between renal tubules and yolk sac tumors. Furthermore, the renal cell carcinoma antigen may be used as an addition to the panel of immunocytochemical markers for yolk sac carcinomas.

Adolescent↗
PubMed1977

An in vitro morphological study of the mouse visceral yolk sac and possible yolk sac immunocyte precursors.

Mouse visceral yolk sac has been organ cultured from 9 days of gestation, a time prior to the thymus being lymphoid, until 12 days of gestation, a time after which the thymus is lymphoid. During the culture period the endodermal epithelial cells survived well, erythropoiesis diminished, endothelial-lined cavities formed in the mesodermal mass, and cells developed which have been classified as large, medium and small immunocyte precursors. The cytoplasm of the immunocyte precursors contains polysomes, spherical mitochondria, a few profiles of rough endoplasmic reticulum, occasional granules and a large Golgi complex. This study offers morphological support for the yolk sac origin of immunocyte precursors in the mouse which may seed the thymus and liver.

Animals↗
PubMed2005

Chloride turnover and ion-transporting activities of yolk-sac preparations (yolk balls) separated from Mozambique tilapia embryos and incubated in freshwater and seawater.

We have recently established a unique in vitro experimental model for mitochondrion-rich cell (MRC) research, a ;yolk-ball' incubation system, in which the yolk sac is separated from the embryonic body of Mozambique tilapia embryos and subjected to in vitro incubation. To evaluate the ion-transporting property of the yolk balls, we examined Cl- content and turnover in yolk balls incubated in freshwater and seawater for 48 h, and distribution patterns of three ion transporters, Na+/K+-ATPase, Na+/K+/2Cl- cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR), in MRCs in the yolk-sac membrane. The Cl- turnover rate measured by whole-body influx of 36Cl- was about 60 times higher in yolk balls in seawater than in freshwater, while there was no essential difference in Cl- content between them. Na+/K+-ATPase-immunoreactive MRCs were larger in yolk balls from seawater than yolk balls from freshwater. Distribution patterns of ion-transporting proteins allowed us to classify MRCs in freshwater yolk balls into three types: cells showing only basolateral Na+/K+-ATPase, cells showing basolateral Na+/K+-ATPase and apical NKCC, and cells showing basolateral Na+/K+-ATPase and basolateral NKCC. The seawater yolk balls, on the other hand, were characterized by the appearance of MRCs possessing basolateral Na+/K+-ATPase, basolateral NKCC and apical CFTR. Those seawater-type MRCs were considered to secrete Cl- through the CFTR-positive apical opening to cope with diffusional Cl- influx. These findings indicate that the yolk balls preserve the Cl- transporting property of intact embryos, ensuring the propriety of the yolk ball as an in vitro experimental model for the yolk-sac membrane that contains MRCs.

Animals↗
PubMed1995

Expression of gamma-glutamyl transpeptidase in midgestation mouse yolk sac and mouse visceral yolk sac carcinoma cells.

gamma-Glutamyl transpeptidase (gamma GT) is a crucial enzyme for the metabolism of xenobiotics and endogenous mediators of biological functions (leukotrienes, prostaglandins, and hepoxillins). Yet little is known about its potential role during development. It is a single copy gene expressed from at least seven promoters. Using histochemistry and immunohistochemistry we demonstrate that gamma GT first appears in the midgestational yolk sacs of mouse embryos. Established cell lines with phenotypic features of yolk sac endoderm (JC-44) or embryonic stem cells were also assayed for the expression of gamma GT. Significant levels were detected in JC-44 cells and higher levels were found in JC-44-derived embryoid bodies. Because this cell line appears to be a good in vitro counterpart of yolk sac differentiation, we characterized the gamma GT mRNA types expressed in JC-44 cells. By ribonuclease protection analysis, gamma GT RNA types IV and VI represent about 80% of the total gamma GT RNA in JC-44 embryoid bodies. Reverse transcription-mediated polymerase chain reaction detected low amounts of gamma GT RNA types I, III, and V. Expression of gamma GT in yolk sac follows a pattern seen in many tissues in which one or two gamma GT RNA types dominate the expression profile; however, the reason for this tissue specificity is unknown.

Animals↗
PubMed1982

Erythropoiesis and lymphopoiesis in the chick yolk-sac-embryo chimeras: contribution of yolk sac and intraembryonic stem cells.

Lymphocyte development and ontogenetic changes in erythroid cells have been studied in chick-chick yolk-sac-embryo chimeras differing at the B locus antigens. Erythroid cells derived from the yolk sac or from the intraembryonic mesenchyme were demonstrated by indirect immunofluorescence in the peripheral blood of these allogenic chimeras. At 7 days of incubation, yolk-sac-derived red cells represent a majority in the peripheral blood. From 9 days of incubation onwards, embryo-derived erythrocytes appear in increasing proportions, making up approximately 90% of the peripheral blood cells at 17-18 days of development. After hatching, no yolk-sac-derived erythrocytes are found in the peripheral blood. Such a change from the yolk-sac-derived cells into embryo-derived cells was not observed in the lymphocytes, as analyzed using specific anti-B and anti-la antisera for detection of thymus and bursa cells, respectively. Ia-like antigens were detected on bursa cells using a triple layer immunofluorescence system. These results obtained from the allogeneic chimeras indicate that the early chicken yolk sac produces only transiently erythroid stem cells, while intraembryonic stem cells are involved in the production of definitive erythrocytes as well as of lymphocytes, both of T and B cells.

Animals↗
PubMed1987

Yolk sac tumors of the ovary and the human yolk sac.

In the present study a comparison was made between human yolk sacs and yolk sac tumors. Tubules surrounded by several to as many as 10 endodermal cells and intracellular tubules in one endodermal cell were frequently observed. The tubules were seen abundantly in the yolk sac of a 4-week pregnancy, and they resembled the reticular pattern of the yolk sac tumor. It was also observed that the papillary endoderm, which contained blood cells in the center and protruded into the endodermal tubules, resembled the Schiller-Duval body of yolk sac tumor. Ultrastructurally the tumor cells were similar to the yolk sac endoderm. alpha-Fetoprotein was positive in the yolk sac endoderm until approximately the seventh week of pregnancy. Yolk sac tumor was also alpha-fetoprotein-positive. In other words, our study of human yolk sacs of 4- to 11-week pregnancies presumes that the yolk sac tumor resembles the endoderm of 4- to 7-week pregnancies.

Endoderm↗
PubMed1992

Comparison of the metabolic activity of yolk sac tissue in the whole embryo and isolated yolk sac culture.

In rat visceral yolk sac tissue cultured from 10.5 to 12.5 days of prenatal age, metabolism of the lipoxygenase inhibitor N-hydroxy-N-methyl-7-propoxy-2-naphtalinethanamine (QA 208-199, QAB) and the accumulation of its metabolites have been shown previously. In this study, the metabolic activities of visceral yolk sac tissues cultured either alone or together with the embryo were compared. The metabolite patterns in medium and visceral yolk sac tissue generated by intact conceptuses or by isolated visceral yolk sac tissues were similar. After 24 as well as 48 h of culture, the major in vivo metabolite, 7-propoxy-naphthalene-2-ylacetic acid (QAA) and other, as yet unidentified metabolites, accumulated in embryo proper and visceral yolk sac tissues. QAB was not found in the embryo proper, and was only found in yolk sac tissues using the higher concentration. In particular the metabolites M5 and M6 exhibited a massive accumulation in the visceral yolk sac, whereas QAA, M3, and M4 accumulated to a much lesser degree. In isolated yolk sacs cultured for 48 h, tissue levels of QAA and M4 were similar to those in yolk sacs of cultured whole conceptuses, whereas M5 and M6 exhibited twofold higher levels in isolated yolk sacs. These findings were in agreement with the distinct increase of myeloid figures containing partly fragmented inclusion bodies in yolk sac tissues. These results suggest that the visceral yolk sac may be the major site of QAB metabolism in cultured rat conceptuses in vitro.

Animals↗
PubMed1995

CD34+ endothelial cell lines derived from murine yolk sac induce the proliferation and differentiation of yolk sac CD34+ hematopoietic progenitors.

Embryonic hematopoiesis is initiated in part in the blood islands of the yolk sac. Previous confocal microscopic analysis has shown that the CD34 antigen, a mucin-like cell surface glycoprotein that is expressed by hematopoietic progenitors and all endothelial cells of the adult and embryo, is also found on a subset of luminal hematopoietic-like cells in the yolk sac blood islands as well as on the vascular endothelium lining these early hematopoietic locations. We show here that, as in all other hematopoietic sites thus far examined, immunoaffinity-purified CD34+ nonadherent cells from murine yolk sacs contain the vast majority of erythroid and myeloid progenitor cell colony forming activity. To examine the developmental interactions between these CD34+ hematopoietic progenitor cells of the yolk sac and the CD34+ yolk sac endothelium, we have immunaffinity-purified adherent endothelial cells from day 10.5 yolk sacs using CD34 antiserum and produced cell lines by transformation with a retrovirus expressing the polyoma middle T antigen. Analysis of these cell lines for CD34, von Willebrand's factor, FLK 1 and FLT 1 expression, and capillary growth in Matrigel indicates that they appear to be endothelial cells, consistent with their original phenotype in vivo. Coculture of yolk sac CD34+ hematopoietic cells on these endothelial cell lines results in up to a 60-fold increase in total hematopoietic cell number after approximately 8 days. Analysis of these expanded hematopoietic cells showed that the majority were of the monocyte/macrophage lineage. In addition, examination of the cultures showed the rapid formation of numerous cobblestone areas, a previously described morphologic entity thought to be representative of early pluripotential stem cells. Scrutiny of the ability of these endothelial cell lines to expand committed progenitor cells showed up to a sixfold increase in erythroid and myeloid colony-forming cells after 3 to 6 days in culture, consistent with the notion that these embryonic endothelial cells mediate the expansion of these precursor cells. Polymerase chain reaction analyses showed that most of the cell lines produce FLK-2/FLT-3 ligand, stem cell factor, macrophage colony-stimulating factor, leukemia-inhibitory factor, and interleukin-6 (IL-6), whereas there is a generally low or not measurable production of granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, IL-1, IL-3, transforming growth factor beta-1, erythropoietin, or thrombopoietin. The output of mature hematopoietic cells from these cocultures can be modified to include an erythroid population by the addition of exogenous erythropoietin. These data suggest that endothelial cell lines derived form the yolk sac provide an appropriate hematopoietic environment for the expansion and differentiation of yolk sac progenitor cells into at least the myeloid and erythroid lineages.

Animals↗
PubMed1986

In vitro studies on the effect of yolk sac antisera on functions of the visceral yolk sac: I. Pinocytosis and transport of small molecules.

The production of congenital malformations by the administration of teratogenic antisera to pregnant animals has been reported from many laboratories. This work has focused our attention on the importance of the yolk sac placenta in supporting the rat embryo during early organogenesis and the significance of yolk sac dysfunction in rodent teratogenesis. The studies reported in this article deal with the effect of teratogenic antisera on the process of yolk sac transport; specifically pinocytosis (as measured by 14C-sucrose uptake) and small-molecule transport utilizing 14C-alpha-aminoisobutyric acid (AIB) and 3H-2-deoxyglucose (DOG). We sought to determine whether several different yolk sac localizing antibodies interfere with these transport processes, and, if so, which transport processes were most affected. The results of the experiments indicated that teratogenic antisera interfered with the process of pinocytosis in the yolk sac and that pinocytosis can be reduced as much as 40%. Nonteratogenic antisera, even when they localized in the yolk sac, did not interfere with the process of pinocytosis. Furthermore, the teratogenic antisera did not interfere with the transport of small molecules (either AIB or DOG) in the yolk sac. These results indicated that while fluorescent localization of an antiserum in the yolk sac did not invariably indicate the potential for teratogenicity, it is likely that the reduction in pinocytosis may directly correlate with the teratologic and embryopathic events. This work reaffirms the view that the yolk sac in important during rodent organogenesis and that yolk sac dysfunction can play an important role in the development of congenital malformations.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoisobutyric Acids↗
PubMed1986

Yolk sac sign: sonographic appearance of the fetal yolk sac in missed abortion.

With improving technology, the fetal yolk sac can be routinely visualized sonographically in all living gestations of six to ten weeks. The minimal growth of the yolk sac during this interval and its subsequent obscuration by the growing amniotic sac are verified in this study. An important new sign of missed abortion has been inferred by Bernard and Cooperberg (AJR 144:597, 1985), and is titled in this article the "yolk sac sign." A gestational sac of 25 mm or more in mean diameter and empty except for the yolk sac is highly suspicious for nonviable gestation. This one-year prospective study adds nine such cases. To enhance specificity of this sign, additional criteria specify a yolk sac measuring 4 mm, a free-floating position within the gestational sac, and evacuation of the yolk sac on follow-up scan. However, when a ring-like structure measures 3 mm or less and lies peripherally in the gestational sac, this must be presumed to be a potential fetal pole.

Abortion, Missed↗
PubMed1979

[Ligation of the yolk sac circulation and its effect on the yolk sac ultrastructure and development of the rat fetus].

The effect of an interruption of the yolk sac circulation on the rat visceral yolk sac and the development of the fetoplacental unit was examined in the last third of pregnancy. The yolk sac ischaemia was induced by ligating the blood vessels of the yolk sac stalk which connect the vitelline circulation with that of the fetus. A 3-hour ligature caused an extensive swelling of most cell organelles in the epithelial cells and in the capillary endothelia of the yolk sac. Other structural changes were indicative of a cessation of pinocytosis. A 6-hour ligature resulted in a common increase of cell swelling and in a beginning disintegration of the endothelial cells lining the vitelline capillaries. A 15-hour ligature caused severe ultrastructural cell lesions and macroscopical alterations suggestive of a progressive necrolar finding of a nearly complete loss of the amniotic fluid and the death of the fetus, although the maternal blood flow appeared to be still intact in the placenta.

Amniotic Fluid↗
PubMed1977

Yolk sac carcinoma (endodermal sinus tumor): ultrastructure and histogenesis of gonadal and extragonadal tumors in comparison with normal human yolk sac.

Human yolk sac carcinomas have been studied only twice with the electron microscope, and have never been compared at this level with normal human yolk sac. In the present study, the ultrastructural features of three primary ovarian yolk sac carcinomas, omental metastases from one of these, and a primary retroperitoneal yolk sac carcinoma in a male are reported, as are the ultrastructural findings in human yolk sac from normal 7- and 12-week gestations. The most prominent feature of the tumors is the presence of voluminous basement membrane material (the nature of which is confirmed by indirect enzyme-labeled antibody technique in one case) in both intra-and extracellular location, corresponding to the PAS-positive hyaline globules seen in these tumors by light microscopy. The tumor cells are also demonstrated to produce this material in tussue culture. Although basement membrane has not been described previously in normal human yolk sac at 8 and 10 weeks' gestation, it was present in the 7-week specimen which we studied, suggesting that its production may be a feature of only very young sac. Other ultrastructural findings are also similar in human yolk sac carcinoma, normal human yolk sac, and rodent yolk sac and yolk sac carcinomas. Thus, these studies confirm the suggested germ cell-derived yolk sac origin of the human tumor.

Adult↗
PubMed1994

In vitro differentiation of B cells and myeloid cells from the early mouse embryo and its extraembryonic yolk sac.

The yolk sac is the first site of hematopoiesis during ontogeny. However, the source of early embryonic hematopoietic stem cells remains unresolved. Early studies have shown that cells obtained from day-8 and -9 extraembryonic yolk sacs can give rise to T cells and myeloid cells, whereas the embryo itself appears to lack such cells. Controversy remains as to whether it is the embryo itself or the extraembryonic yolk sac that contains the initial precursors capable of differentiating into B cells. This study used the approach of enriching hematopoietic stem cells by immunocytoadherence and studying cells isolated from within the embryo itself or from the yolk sac obtained at days 8 and 9 of mouse embryonic development. We report that on day 9, both yolk sac-derived and embryo-derived cells can give rise to B cells and myeloid cells in vitro. On day 8, however, cells isolated from the yolk sac but not from the embryo produce myeloid colonies in vitro; neither source of stem cells generates B cells. Our study suggests that myeloid precursors migrate from yolk sac to embryo earlier than has previously been reported but that the origin for B cell precursors remains to be determined.

Animals↗