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PubMed1976

On the yolk sac of the cat. Endoderm and mesothelium.

The ultrastructure of feline yolk sacs from 11 stages between the 14th and the 66th day is described with reference to the endoderm and the mesothelium; supplementary histochemical and cytochemical studies are included. Despite the absence of yolk, the endodermal epithelium shows a high degree of differentiation and activity, especially in the period between the 25th and the 38th day. Large stacks of RER, abundant SER, mitochondria enveloped by RER cisternae, and a peculiar type of lysosome are the most prominent organelles. Acid phosphatase, succinic dehydrogenase and NAD- and NADP-diaphorases are found with high activity, whereas the 17beta-hydroxysteroid dehydrogenase assay stains the endothelium only moderately. Indications of reabsorption are less marked. In view of the apparent immaturity of the liver parenchymal cells at this stage, the yolk sac endoderm of cat is suggested to act as an important extraembryonic site of biosynthesis. As preliminary results of a chemical analysis show that the yolk sac fluid has nearly no nutritional value, the substances synthesized are believed to be transported directly to the fetus. The mesothelium shows relatively few alterations over the period studied, is less rich in organelles and is obviously far less active than the endoderm.

Animals↗
PubMed1979

Freeze-fracture observations on the visceral yolk sac placenta of rats, mice and hamsters. With special reference to endodermal cell tight junctions.

Freeze-fracture replicas of visceral yolk sac from rats, mice and hamsters in late stages of gestation were studied by electron microscopy. Special attention was directed toward determining the types of junctional specializations that exist between the columnar endoderm cells of this placental membrane. In all three species, well-developed, zonular tight (occluding) junctions were found on the contiguous lateral surfaces of the endoderm cells. The tight junctional network, located in an immediate subluminal position, was from 0.2--0.5 micrometers in depth and consisted at any point of 2--5, interconnecting, approximately 9 eta wide, strands (P-face) or shallow furrows (E-face). Patch-like aggregations of irregular intramembrane particles, characteristic of desmosomes (maculae adherentes), also were observed at scattered sites below the tight junctions. However, no evidence of gap (communicating) junctions was encountered. The endoderm cells of the rodent visceral yolk sac have been shown to play a central role in the selective transport of macromolecular substances from the maternal to the fetal system. Tight junctions may be vital to this endodermal cell function by preventing random paracellular fluxes of macromolecules.

Animals↗
PubMed1984

Evolution of Xenopus endodermal cells cultured on different extracellular matrix components. Identification of primordial germ cells.

Plated on untreated glass substrate, Xenopus endodermal cells are unable to undergo any morphological or cytological differentiation. Culture on artificial substrates prepared with components of the extracellular matrix, the endodermal cell behavior is entirely different. To identify the primordial germ cells (PGC), we use three coated substrate types: fibronectin, collagen and collagen plus fibronectin. These substrates allow us to distinguish three cell types shortly after explantation. Using fibronectin-coated substrate, most of the cells, after attachment and spreading, form cellular islets which tend to fuse, leading to the formation of a polyhedric cell monolayer. Such fusing is notably reduced on composite substrate (Coll + FN) or on collagen substrate only. Thus it is possible to distinguish the special morphological features exhibited by the rest of the cells. Some of them retain the aspect of endodermal gastrula cells in vitro. Others, elongated or spindle-shaped, possess the characteristics of PGC. Nevertheless, the identification and sampling of the presumed germ cells is easier on COLL + FN-coated substrate. The morphological and cytological characteristics of the elongated cells are similar to those observed during PGC migration through the endodermal mass. According to these results, there is little doubt that these elongated cells are primordial germ cells.

Animals↗
PubMed1985

Study on membrane recycling in the rat visceral yolk-sac endoderm using concanavalin-A conjugates.

The internalization and intracellular movements of apical-cell-membrane material were investigated in the endodermal cells of cultured visceral yolk-sacs of rats (whole-embryo culture; explanted at 10.5 days of gestation and cultured for 24 h) using horseradish peroxidase- and ferritin-labelled concanavalin A (Con-A HRP, Con-A Fer). When visceral yolk-sac endoderm was exposed to Con-A HRP or Con-A Fer for 5 min at 4 degrees C, the apical cell membranes containing a well-developed fuzzy coat were heavily labelled, whereas apical vacuoles, lysosomes and apical canaliculi were not. Incubation of Con-A-labelled endoderm for 5-60 min at 20 degrees and 37 degrees C in Con-A-free serum resulted in a temperature-dependent internalization of membrane-bound lectin into coated vesicles, apical vacuoles and lysosomes, and the apical cell membranes were cleared of the heavy labelling. With increasing incubation time, the number of labelled vacuolar structures and the intensity of their labelling decreased gradually, whereas the number of labelled apical canaliculi increased. Thus, after 30 and 60 min at 37 degrees C, most of the apical canaliculi contained high concentrations of the markers. It was possible to observe labelled apical canaliculi that were in continuity with labelled apical vacuoles and lysosomes as well as with the apical cell membrane. These findings in rat endodermal cells indicate that constituents of the apical cell membrane are internalized in apical vacuoles and lysosomes, and are then brought back to the apical cell membrane by the apical canaliculi, which concentrate and store this membrane material.

Animals↗
PubMed1986

Endoderm-secreted factor stimulates growth of embryonal carcinoma stem cells.

Stem cells of the embryonal carcinoma cell line called H6 can be induced to differentiate to endoderm-like cells by retinoic acid (3 X 10(-6) M). We have detected a diffusible and stable factor which is secreted by H6 endoderm-like cells and stimulates the growth of H6 stem cells. The stimulation by the endoderm-like cells is considerably greater than that by mouse fibroblasts or H6 stem cells themselves. No reciprocal stimulation of endoderm-like cells by stem cells occurs. Part but not all of the stimulation might be due to extracellular matrix proteins or to insulin-like growth factor type 2, each of which also stimulates the growth of H6 stem cells. Insulin causes no such stimulation.

Animals↗
PubMed2004

Endodermal sinus tumour of the omentum in a child.

Endodermal sinus tumour usually arises in a gonad; extragonadal endodermal sinus tumours are rare. We report a 3-year-old boy with an endodermal sinus tumour arising in the greater omentum, which may be the second reported case in the English literature. He presented with a solid mass in the upper abdomen and a markedly raised serum alpha-fetoprotein (AFP) level. Following percutaneous needle biopsy and omentectomy, histological examination revealed classic morphological features of an endodermal sinus tumour. This rare diagnosis is possible from the imaging features in association with a raised serum level of AFP.

Biomarkers, Tumor↗
PubMed2000

Anterior endoderm and head induction in early vertebrate embryos.

Early work on the formation of the vertebrate body axis indicated the existence of separate head- and trunk-inducing regions in Spemann's organizer of the amphibian gastrula. In mammals some head-organizing activity may be located in anterior visceral (extraembryonic) endoderm (AVE). By analogy, the equivalent structure in the Xenopus laevis gastrula, the anterior endoderm, has been proposed to be the amphibian head organizer. Here we review recent data that challenge this notion and indicate that the involvement of AVE in head induction seems to be an exclusively mammalian characteristic. In X. laevis and chick, it is the prechordal endomesoderm that is the dominant source of head-inducing signals during early gastrulation. Furthermore, head induction in mammals needs a combination of signals from anterior primitive endoderm, prechordal plate, and anterior ectoderm. Thus, despite the homology of vertebrate anterior primitive endoderm, a role in head induction seems not to be conserved.

Animals↗
PubMed2002

Global gene expression patterns during differentiation of F9 embryonal carcinoma cells into parietal endoderm.

Expression levels of over 8,900 murine genes were examined, using cDNA microarrays, during the differentiation of F9 cells into parietal endoderm following exposure to retinoic acid/dibutyryl cAMP. Gene induction and repression over the time course exhibited a biphasic pattern consistent with a transition from undifferentiated F9 cells to primitive endoderm and finally parietal endoderm. A 6-h induction with retinoic acid/cAMP/cycloheximide resulted in 109 candidate immediate response genes. During a 9-day time course 516 genes were selected as being significantly induced/repressed. Several of these genes had been previously identified as having altered expression patterns in F9 cells undergoing differentiation by retinoic acid/cAMP. Functional characterization of these genes demonstrated that the majority were transcription factors while others included surface antigens and genes involved in intracellular transport. Cluster analysis, utilizing both a hierarchical algorithm and self-organizing map, resulted in very similar gene clusters. Our studies revealed an extremely complex set of interacting signals that decide between cell death, differentiation, cell cycle withdrawal, and ultimately the traits associated with the terminal differentiated parietal endoderm cell type. The sets of genes identified here can now be modulated in a rational way to try to understand their role in differentiation.

Animals↗
PubMed1984

Stage-specific embryonic antigen 3 as a marker of visceral extraembryonic endoderm.

The distribution of the stage-specific embryonic antigen SSEA-3 was studied immunohistochemically on postimplantation mouse embryos. This carbohydrate antigen, identified as an epitope of a globo-series ganglioside isolated from human teratocarcinoma cells (Kannagi et al., 1983, J. Biol. Chem. 258, 8934-8942) was originally detected on the zygote and mouse early cleavage-stage embryos. It disappears on the early blastocyst and reappears on the primitive endoderm of the implanting blastocyst (Shevinsky et al., 1982, Cell 30, 697-705). We now show in the early egg cylinder (on the sixth day of pregnancy) SSEA-3 is present in the entire visceral endoderm but not in any other part of the conceptus. From Day 7 of pregnancy onward, SSEA-3 is restricted to the extraembryonic visceral endoderm and the visceral yolk sac cells. Therefore, SSEA-3 is a useful marker for this endodermal cell lineage in midgestational mouse embryos.

Animals↗
PubMed1985

Abnormal embryonic development induced by antibodies to rat visceral yolk-sac endoderm: isolation of the antigen and localization to microvillar membrane.

An antigenic substance was isolated from rat visceral yolk-sac endoderm of the 18th-20th days of gestation by extraction with the nonionic detergent Nonidet P-40, Sephacryl S-300 gel filtration, and Ricinus communis agglutinin affinity chromatography. The rabbit antiserum directed against this antigenic substance when injected into pregnant rats during the period of organogenesis caused abnormal embryonic development, fetal growth retardation, and embryonic death. Ouchterlony gel diffusion analysis demonstrated that the antiserum formed one immunoprecipitin band against the crude detergent extract and a complete identity between the present visceral yolk-sac antigen and the renal glycoprotein antigen previously isolated (C. C. K. Leung, (1982) J. Exp. Med. 156, 372-384). The antigen eluted from the antibody affinity column appeared to consist of two major peptides of 60 and 30 kDa when analyzed by SDS-polyacrylamide gel electrophoresis. Indirect immunofluorescent and immunoperoxidase localization studies at the light microscopic level demonstrated that both rat renal proximal tubule and embryonic visceral yolk-sac endoderm at various gestational stages (including the organogenetic period) shared the same antigen. Indirect immunoperoxidase localization studies at the electron microscopic level demonstrated that the antigen was a part of (or associated with) the microvillar membrane and membrane invaginations at the base of the microvilli of the renal proximal tubule and visceral yolk-sac endoderm. In vivo immunoperoxidase localization studies demonstrated that the teratogenic antibodies localized within the large phagolysosomes and the apical vesicles of the visceral yolk-sac endoderm. It is postulated that visceral yolk-sac pathology was induced by the antibodies.

Animals↗
PubMed1988

The role of cell interactions in the differentiation of teratocarcinoma-derived parietal and visceral endoderm.

Cell interactions have been implicated in the differentiation of visceral and parietal endoderm in the developing mouse embryo. Embryoid bodies formed from F9 embryonal carcinoma cells have been useful in characterizing the events which lead to endoderm formation. As part of our effort to specify the interactions which may be involved in this process we have isolated visceral endoderm-like cells (VE) from F9 embryoid bodies and cultured them under various conditions. Using a combination of immunoprecipitation and enzyme-linked immunosorbent assay, we demonstrate that monolayer culture of these cells on a number of different substrates leads to a dramatic decrease in the level of alphafetoprotein (AFP), a VE-specific marker. Northern blot analysis of AFP mRNA indicates very low levels of this message are present after 48 hr in monolayer culture. Coincident with the drop in AFP levels is an increase in the levels of the cytokeratin Endo C and tissue plasminogen activator, both markers for parietal endoderm (PE). Morphological evidence at the ultrastructural level supports a transition from VE to PE. In contrast, the VE phenotype can be maintained in vitro by interaction with aggregates, but not monolayers, of stem cells. In addition, culturing the cells on the curved surface of gelatin-coated dextran beads, but not on a flat gelatin surface facilitates AFP expression and the cells are morphologically intermediate between VE and PE cells. The potential role of junctional complexes and cell shape are discussed.

Animals↗
PubMed1987

Importance of a fibroblastic support for in vitro differentiation of intestinal endodermal cells and for their response to glucocorticoids.

Microexplants of 14- or 15-day-old fetal rat intestinal endoderm, separated from mesenchyme by collagenase, were placed on culture dishes coated with different extracellular matrix components or on confluent monolayers of intestinal mesenchymal cells or of fetal skin fibroblasts. Only small variations in the attachment or spreading of the endodermal cells could be observed when they were cultured on the different acellular substrata, and their survival never exceeded one week. When cocultured with intestinal or skin fibroblasts, endodermal cells proliferated and the survival time was prolonged to 2 or 3 weeks. Furthermore, differentiation, as assessed by the polarization of the cells, occurred and was characterized by the maturation of apical brush borders and by the synthesis of microvillar digestive enzymes visualized immunocytochemically with monoclonal antibodies. Glucocorticoids accelerated structural differentiation and stimulated or induced brush border enzymes only in the coculture conditions. These experiments emphasize the role of a fibroblastic support without tissue specificity on the cytodifferentiation of intestinal endodermal cells. They also suggest a mesenchymal dependence on the hormonal response.

Animals↗
PubMed1992

Ectopic somatic endoderm in secondary human yolk sac.

Three secondary human yolk sacs (SHYSs) showing heterotopic endodermal tubular structures of the gut-forming type were analyzed from a series of 180 SHYSs. These structures were similar to the early somatic endoderm involved in the formation of gut and lung. They may have arisen either as sequestrations in growth-disorganized embryos or as a phenomenon of differentiation from extraembryonal endoderm, which would indicate that extraembryonal tissues such as the SHYSs retain the capacity to differentiate somatic endoderm in developmentally altered embryos. It is possible that these structures may be the precursors of placental hepatic tissue and teratomas. Their morphologic resemblance to similar structures found in glandular, polyvesicular, and intestinal human yolk sac tumors provides yet another example of the similarity between SHYSs and yolk sac tumors.

Abortion, Spontaneous↗
PubMedDate not supplied

Effect of delayed implantation on differentiation of the extra-embryonic endoderm in the mouse blastocyst.

Delayed implanting blastocysts recovered from both ovariectomized and lactating pregnant mice were examined for the presence of primitive endoderm. One or more of three different criteria were used to identify this tissue which was found to be present in nearly all such blastocysts, regardless of the length of time for which their implantation had been delayed. Furthermore, the tissue appeared to differentiate in blastocysts from ovariectomized females at approximately the same postcoital stage as in those from sham-operated controls. Formation of the parietal endoderm layer was not observed in a single instance during delay, but began approximately 10 h after it had been terminated by injecting ovariectomized females with oestradiol benzoate. Cells in mitosis were found both at longer intervals after the onset of implantation delay and at shorter intervals after its termination than reported previously. It is concluded that, contrary to what might have been anticipated from certain earlier studies, there seem to be no obvious advantages in using delayed implanting rather than nondelayed blastocysts for investigating initial steps in differentiation of the primitive endoderm. Delayed blastocysts may, nevertheless, be of value in elucidating factors controlling the differentiation or onset of migration of parietal endoderm cells.

Animals↗
PubMed2004

Involvement of Ras in extraembryonic endoderm differentiation of embryonic stem cells.

Embryonic stem (ES) cells, derived from the inner cell mass of blastocyst can differentiate into multiple cell lineages. In this study, we examined the possible involvement of Ras in ES cell differentiation. We found that Ras was activated upon formation of embryoid bodies (EBs), an initial step in ES cell differentiation. When expressed during EB differentiation, a dominant-negative mutant of Ras suppressed induction of marker genes for extraembryonic endoderm differentiation, including GATA-4, GATA-6, alpha-fetoprotein, and hepatocyte nuclear factor 3beta, while an activated mutant promoted their induction. Expression of a Ras mutant that selectively activates the Raf/MEK/Erk pathway also enhanced induction of extraembryonic endoderm markers, and treatment with a MEK inhibitor resulted in their decreased expression. In addition, Ras stimulated downregulation of Nanog, a suppressor of endoderm differentiation in ES cells. These data suggest that Ras activation during EB differentiation plays a crucial role in initiation of extraembryonic endoderm differentiation.

Animals↗
PubMed2004

Ku80 is required but not sufficient for Galpha13-mediated endodermal differentiation in P19 embryonic carcinoma cells.

We have shown that a constitutively active Galpha13 (Galpha13Q226L) induces differentiation in P19 embryonic carcinoma cells to an endodermal phenotype. In this report, we demonstrate that Ku, a heterodimer of p80 (Ku80) and p70 (Ku70), is upregulated in P19 cells overexpressing Galpha13Q226L. Ku is the regulatory subunit of the DNA-dependent protein kinase and is primarily involved in DNA repair and recombination. Ku80 also is a somatostatin receptor. We show that while overexpression of Ku80 drastically reduced P19 cell proliferation, it was not sufficient to induce endodermal differentiation. However, coexpression of Galpha13Q226L and an antisense Ku80 abrogated the retarded growth rate and endodermal differentiation observed in cells expressing only Galpha13Q226L. Overexpression of Galpha13Q226L or Ku80 downregulated RNA polymerase I-mediated transcriptional activity and overexpression of antisense Ku80 restored the activity to control level. These results suggest that Ku80 is required for Galpha13-mediated endodermal differentiation in P19 cells.

Animals↗
PubMed2005

Eomesodermin is a localized maternal determinant required for endoderm induction in zebrafish.

In zebrafish, endoderm induction occurs in marginal blastomeres and requires Casanova (Cas), the first endoderm-specific factor expressed in the embryo. Whereas the transcription factors Gata5 and Bon are necessary and sufficient for cas expression in marginal blastomeres, Bon and Gata5 are unable to induce cas in animal pole cells, suggesting that cas expression requires an additional, unidentified factor(s). Here, we show that cas expression depends upon the T box transcription factor Eomesodermin (Eomes), a maternal determinant that is localized to marginal blastomeres. Eomes synergizes potently with Bon and Gata5 to induce cas, even in animal pole blastomeres. We show that Eomes is required for endogenous endoderm induction, acting via an essential binding site in the cas promoter. Direct physical interactions between Eomes, Bon, and Gata5 suggest that Eomes promotes endoderm induction in marginal blastomeres by facilitating the assembly of a transcriptional activating complex on the cas promoter.

Animals↗
PubMed2004

Establishment and characterization of a parietal endoderm-like cell line derived from Engelbreth-Holm-Swarm tumor (EHSPEL), a possible resource for an engineered basement membrane matrix.

Engelbreth-Holm-Swarm (EHS) tumor produces large amounts of basement membrane (BM) components, which are widely used as cell culture substrates mimicking BM functions. EHS tumor arose spontaneously in an ST/Eh strain mouse and has been propagated by transplantation. In the present study, we established a cell line, EHSPEL (EHS Parietal Endoderm-Like), which can be cultured ex vivo and preserves the capacity to form tumors in vivo. EHSPEL cells secreted large amounts of laminin-1 into the medium and deposited BM components onto dishes. To further characterize EHSPEL cells, their gene expression profile was compared to those of parietal endoderm cells from Reichert's membrane at embryonic day 13.5, differentiated F9 embryonal carcinoma cells, and PYS-2 parietal endoderm cells. These analyses outlined not only common features of parietal endoderm-like cells that underlie the efficient production of BM components, but also germline cell-like features of EHSPEL cells, at least some of which may play crucial roles in their capacity to form tumors that accumulate abundant BM components in vivo. Karyotyping of EHSPEL cells using chromosome painting probes showed a large number of interchromosomal rearrangements and partial chromosome hyperploidy. Exogenous introduction of a human laminin-alpha(4)-EGFP fusion protein into EHSPEL cells resulted in the production and deposition of human-mouse-hybrid laminin-8. This strategy should be applicable for creating efficient systems to produce chimeric laminins as well as BM-like gels with modified biological activity.

Animals↗