Digestion of an exogenous protein by rat yolk-sac cultured in vitro.
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ABSTRACT:
SUBMITTER: Williams KE
PROVIDER: S-EPMC1178054 | biostudies-other | 1971 Nov
REPOSITORIES: biostudies-other
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Project description:The rates of uptake of 125I-labelled poly(vinylpyrrolidone), [14C]sucrose and colloidal [198Au]gold by 17.5-day rat yolk sac cultured in vitro were studied. Over a 6.5h period each substrate was accumulated at a constant and reproducible rate of approx. 2microliter/h per mg of protein. After accumulation in vitro, the three substances were released from the tissue into substrate-free medium at low rates. Sucrose present in the medium at concentrations up to 10 mg/ml was without effect on the accumulation of either [14C]sucrose or 125I-labelled poly(vinylpyrrolidone), but at higher concentrations inhibited the uptake of both substrates. Some batches of colloidal [198Au]gold had a significantly higher Endocytic Index (up to 5 microliter/h per mg of protein). The Endocytic Index of such a batch decreased with increasing substrate concentration, but colloidal gold did not decrease the Endocytic Index of 125I-labelled poly(vinylpyrrolidone). It is concluded that the three substrates enter the yolk sac by pinocytosis in the liquid phase. Those batches of colloidal [198Au]gold with higher Endocytic Indices are considered to enter also by adsorption on membrane binding-sites.
| S-EPMC1183757 | biostudies-other
Project description:RNASeq reveals conservation of function among the yolk sacs of human, mouse and chicken
| PRJEB18767 | ENA
Project description:The yolk sac is the first site of blood-cell production during embryonic development in both murine and human. Heat shock proteins (HSPs), including HSP70 and HSP27, have been shown to play regulatory roles during erythropoiesis. However, it remains unknown whether HSP60, a molecular chaperone that resides mainly in mitochondria, could also regulate early erythropoiesis. In this study, we used Tie2-Cre to deactivate the Hspd1 gene in both hematopoietic and vascular endothelial cells, and found that Tie2-Cre+Hspd1f/f (HSP60CKO) mice were embryonic lethal between the embryonic day 10.5 (E10.5) and E11.5, exhibiting growth retardation, anemia, and vascular defects. Of these, anemia was observed first, independently of vascular and growth phenotypes. Reduced numbers of erythrocytes, as well as an increase in cell apoptosis, were found in the HSP60CKO yolk sac as early as E9.0, indicating that deletion of HSP60 led to abnormality in yolk sac erythropoiesis. Deletion of HSP60 was also able to reduce mitochondrial membrane potential and the expression of the voltage-dependent anion channel (VDAC) in yolk sac erythrocytes. Furthermore, cyclosporine A (CsA), which is a well-recognized modulator in regulating the opening of the mitochondrial permeability transition pore (mPTP) by interacting with Cyclophilin D (CypD), could significantly decrease cell apoptosis and partially restore VDAC expression in mutant yolk sac erythrocytes. Taken together, we demonstrated an essential role of HSP60 in regulating yolk sac cell survival partially via a mPTP-dependent mechanism.
| S-EPMC6786998 | biostudies-literature
Project description:Human embryogenesis entails complex signalling interactions between embryonic and extra-embryonic cells. However, how extra-embryonic cells direct morphogenesis within the human embryo remains largely unknown due to a lack of relevant stem cell models. Here, we have established conditions to differentiate human pluripotent stem cells (hPSCs) into yolk sac-like cells (YSLCs) that resemble the post-implantation human hypoblast molecularly and functionally. YSLCs induce the expression of pluripotency and anterior ectoderm markers in human embryonic stem cells (hESCs) at the expense of mesoderm and endoderm markers. This activity is mediated by the release of BMP and WNT signalling pathway inhibitors, and, therefore, resembles the functioning of the anterior visceral endoderm signalling centre of the mouse embryo, which establishes the anterior-posterior axis. Our results implicate the yolk sac in epiblast cell fate specification in the human embryo and propose YSLCs as a tool for studying post-implantation human embryo development in vitro.
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Project description:Portions of a 125I-iodinated bovine serum albumin preparation were exposed to freezing, acetic acid (pH 3.5, 3.0 or 2.5), urea or formaldehyde, and the effect of these treatments on the rates of pinocytic uptake by yolk sacs from 17.5-day-pregnant rats cultured in vitro and of clearance from the rat bloodstream were studied. Uptake of albumin by the yolk sac was followed by rapid release of [125I]iodo-L-tyrosine into the culture medium. Similarly clearance of albumin in vivo was accompanied by the appearance of trichloroacetic acid-soluble radioactivity in the bloodstream. In both systems the rates of uptake of modified albumin preparations formed a series: formaldehyde or urea greater than acetic acid greater than freezing. The increased rates of uptake of modified albumin preparations could not be ascribed to the formation of aggregates nor, in the yolk-sac system, to an increase in the rate of pinosome formation. It is concluded that the various treatments to which the albumin was subjected increase to varying degrees the affinity of the albumin molecule for binding sites on that region of the plasma membrane from which pinocytic vesicles are formed. Some comparable experiments with native and desialylated human orosomucoid indicate that the rat yolk-sac epithelial cells do not possess the recognition system for uptake of asialoglycoproteins that exists on the surface of hepatic parenchymal cells.
| S-EPMC1164838 | biostudies-other
Project description:The yolk sac is an extraembryonic membrane, of saccular form, connected to the ventral region of the embryo. It is the main source of nutrition for the embryo during the period when the placenta is not fully formed. The aim of this study was to generate tubular structures using mesenchymal stem cells from the bovine yolk sac (bYS-MSCs) and determine if these structures can be a model for in vitro vasculogenesis. The evaluation of this tissue by histochemistry revealed a strong marking of collagen fibers and PAS technique negativity. In transmission electron microscopy, cytoplasmic organelles with large nuclei were observed. The vessel formation assay on a Matrigel substrate showed that the mesenchymal cells of the yolk sac without growth factors (VEGF) are capable of forming branches, sprouting cells, and tubular structures similar to capillary blood. These tubular structures were xenotransplanted subcutaneously into the mesentery of BALB/c/nude mice; after 45 days, vascularized tissue and extensions of blood vessels around the tubular structures could be observed. Real-time PCR (qPCR) demonstrated an expression of the VEGF gene in different gestational age groups. No difference in distribution or expression was detected among groups. Our results suggest that the spontaneous formation of tubules from the yolk sac can be an experimental model to elucidate initial organogenesis and the possible formation of blood capillaries from in vitro mesenchymal cells and possible route of organoid production.
| S-EPMC6431375 | biostudies-literature
Project description:BackgroundThe yolk sac (YS) is an extra-embryonic tissue that surrounds the yolk and absorbs, digests and transports nutrients during incubation of the avian embryo as well as during early term mammalian embryonic development. Understanding YS functions and development may enhance the efficient transfer of nutrients and optimize embryo development. To identify temporal large-scale patterns of gene expression and gain insights into processes and mechanisms in the YS, we performed a transcriptome study of the YS of chick embryos on embryonic days (E) E13, E15, E17, E19, and E21 (hatch).Results3547 genes exhibited a significantly changed expression across days. Clustering and functional annotation of these genes as well as histological sectioning of the YS revealed that we monitored two cell types: the epithelial cells and the erythropoietic cells of the YS. We observed a significant up-regulation of epithelial genes involved in lipid transport and metabolism between E13 and E19. YS epithelial cells expressed a vast array of lipoprotein receptors and fatty acid transporters. Several lysosomal genes (CTSA, PSAP, NPC2) and apolipoproteins genes (apoA1, A2, B, C3) were among the highest expressed, reflecting the intensive digestion and re-synthesis of lipoproteins in YS epithelial cells. Genes associated with cytoskeletal structure were down-regulated between E17 and E21 supporting histological evidence of a degradation of YS epithelial cells towards hatch. Expression patterns of hemoglobin synthesis genes indicated a high erythropoietic capacity of the YS between E13 and E15, which decreased towards hatch. YS histological sections confirmed these results. We also observed that YS epithelial cells expressed high levels of genes coding for plasma carrier proteins (ALB, AFP, LTF, TTR), normally produced by the liver.ConclusionsHere we expand current knowledge on developmental, nutritional and molecular processes in the YS. We demonstrate that in the final week of chick embryonic development, the YS plays different roles to support or replace the functions of several organs that have not yet reached their full functional capacity. The YS has a similar functional role as the intestine in digestion and transport of nutrients, the liver in producing plasma carrier proteins and coagulation factors, and the bone marrow in synthesis of blood cells.
| S-EPMC4246430 | biostudies-literature
Project description:The yolk sac tissue (YST) is a multifunctional metabolic organ supporting chicken embryonic development. This study examined whether incubation temperatures (ITs) affect YST functions. For this purpose, 300 eggs were assigned to 3 groups and incubated at control IT of 37.8°C, at 1.5°C below, 36.3°C (cold IT), and at 1.5°C above, 39.3°C (hot IT). For each group, 6 embryos' whole body mass and residual yolk (RSY) weights were recorded during incubation, and YST was sampled for both histology and gene expression analysis. YST functionality during incubation was examined by regression analysis, comparing changes in expression patterns of genes involved in lipid uptake and metabolism (LRP2, ApoA1), oligopeptides uptake (PepT1), gluconeogenesis (FBP1), glycogenesis (GYS2), and thyroid hormones regulation (TTR, DIO1, DIO2). Results show that hot and cold ITs affected YST gene expression and yolk utilization. PepT1 expression decreased towards hatch, in both hot and cold ITs, while in the Control IT, it reached a plateau. ApoA1 and DIO2 expression showed a moderate linear fit compared to polynomial fit in the control. GYS2 expression had no change along incubation, while in the control IT, it showed a polynomial fit. Expression of LRP2, FBP1, and DIO1 genes was affected by either cold or hot IT's. TTR expression patterns were similar in all IT groups. The variations in gene expression patterns observed in the 3 ITs can explain the changes in yolk utilization, an important parameter for hatchling quality. While the control IT showed optimal utilization, with an RSY value of 11.12% at the day of hatch, the cold and hot IT groups exhibited lower utilization with an RSY value of 18.18 and 29.99%, respectively. These findings are the first to show that ITs change the expression of key YST genes, leading to variations in yolk utilization by the embryo.
| S-EPMC7647798 | biostudies-literature
Project description:The embryonic heart and vessels are dynamic and form and remodel while functional. Much has been learned about the genetic mechanisms underlying the development of the cardiovascular system, but we are just beginning to understand how changes in heart and vessel structure are influenced by hemodynamic forces such as shear stress. Recent work has shown that vessel remodeling in the mouse yolk sac is secondarily effected when cardiac function is reduced or absent. These findings indicate that proper circulation is required for vessel remodeling, but have not defined whether the role of circulation is to provide mechanical cues, to deliver oxygen or to circulate signaling molecules. Here, we used time-lapse confocal microscopy to determine the role of fluid-derived forces in vessel remodeling in the developing murine yolk sac. Novel methods were used to characterize flows in normal embryos and in embryos with impaired contractility (Mlc2a(-/-)). We found abnormal plasma and erythroblast circulation in these embryos, which led us to hypothesize that the entry of erythroblasts into circulation is a key event in triggering vessel remodeling. We tested this by sequestering erythroblasts in the blood islands, thereby lowering the hematocrit and reducing shear stress, and found that vessel remodeling and the expression of eNOS (Nos3) depends on erythroblast flow. Further, we rescued remodeling defects and eNOS expression in low-hematocrit embryos by restoring the viscosity of the blood. These data show that hemodynamic force is necessary and sufficient to induce vessel remodeling in the mammalian yolk sac.
| S-EPMC4260474 | biostudies-literature
Project description:Organogenesis of the testis is initiated when expression of Sry in pre-Sertoli cells directs the gonad toward a male-specific fate. The cells in the early bipotential gonad undergo de novo organization to form testis cords that enclose germ cells inside tubules lined by epithelial Sertoli cells. Although Sertoli cells are a driving force in the de novo formation of testis cords, recent studies in mouse showed that reorganization of the vasculature and of interstitial cells also play critical roles in testis cord morphogenesis. However, the mechanism driving reorganization of the vasculature during fetal organogenesis remained unclear. Here we demonstrate that fetal macrophages are associated with nascent gonadal and mesonephric vasculature during the initial phases of testis morphogenesis. Macrophages mediate vascular reorganization and prune errant germ cells and somatic cells after testis architecture is established. We show that gonadal macrophages are derived from primitive yolk-sac hematopoietic progenitors and exhibit hallmarks of M2 activation status, suggestive of angiogenic and tissue remodeling functions. Depletion of macrophages resulted in impaired vascular reorganization and abnormal cord formation. These findings reveal a previously unappreciated role for macrophages in testis morphogenesis and suggest that macrophages are an intermediary between neovascularization and organ architecture during fetal organogenesis.
| S-EPMC4060703 | biostudies-literature