(n.) The outer layer of the blastoderm; the ectoderm. See Blastoderm, Delamination.
Example Sentences:
(1) Expansion of the cell sheet following attachment, and the fusion of epiblasts advancing toward each other, does not require the presence of mineralocorticoid.
(2) At the midgastrula stage the epiblast cells have the highest dry weight due to the highest protein concentration in the cytoplasm and the biggest cell volume.
(3) Proliferation occurs throughout the extra-embryonic epiblast during the expansion period.
(4) These observations are consistent with an epiblast origin for the avian germ line, and are strikingly similar to those reported for the early mouse embryo using the same antibody (Hahnel & Eddy, 1986).
(5) IGFBP-2 mRNA was detected throughout the epiblast of the egg cylinder as early as e7, when IGF-II expression was restricted to trophectoderm and other extraembryonic cells.
(6) It is also noted that the inadequate differentiation of the epiblast and endoderm would not have been apparent without microscopic examination.
(7) Both X chromosomes continued to replicate synchronously in the embryonic ectoderm or epiblast at this stage.
(8) The resulting space is not homologous with the primordial amniotic cavity; instead, it is a transitory tropho-epiblastic cavity.
(9) After the yolk has been covered, the epiblast continues to grow, with proliferation restricted largely to band just distal to the advancing edge of the area vasculosa.
(10) Primordial germ cells in the mouse are known to be derived from the epiblast.
(11) In general, the dorsoventral orientation of the previously induced epiblast was retained, but the orientation of the competent epiblast cells was more flexible and could be influenced by the neighbouring neuralised cells.
(12) The results of this study show that the epiblast cells of chick blastoderm at Hamburger-Hamilton stage 1 contain macrobodies which themselves contain particles resembling the 'lining bodies' described by Bellairs.
(13) At one time presumed to be derived from a common "neural" ancestor, all are now deemed to be "neuroendocrine-programmed," arising either in the embryonic epiblast itself or in one of its principal descendants.
(14) Epiblastic cells never gave rise to skeletal myotubes.
(15) The definitive amniotic epithelium forms by the upfolding and mitotic proliferation of the margins of the epiblastic disc; this process is completed in 11-day rhesus, and 9-day human, blastocysts.
(16) At 108 h and 120 h pc the polar trophoblast (Rauber's layer) is an intact epithelium overlying the epiblast of the inner cell mass.
(17) The epiblast cells of the optic bud do not migrate into the brain and the lamina is formed by the proliferation of the central imaginal disc.
(18) By the time of primitive streak formation (stage 4-5) the dorsal surface of the epiblast displayed increased binding sites, while the frequency of sites on the ventral surface of the endoblast was reduced.
(19) A microinjection technique is described for fate mapping the epiblast of avian embryos.
(20) Injection in situ of a short-term lineage label (horse radish peroxidase) into single epiblast cells at 6.7 days p.c.
Hypoblast
Definition:
(n.) The inner or lower layer of the blastoderm; -- called also endoderm, entoderm, and sometimes hypoderm. See Illust. of Blastoderm, Delamination, and Ectoderm.
Example Sentences:
(1) Gastrulation is accompanied by a sharp increase in the AChE activity which was most pronounced in anterior hypoblast.
(2) (1) Removal of both the area opaca and the marginal zone of the area pellucida from a blastoderm stripped of its hypoblast (type-IV operation) prevents the regeneration of a normally functioning primary hypoblast.
(3) These results show that the two main properties of the posterior marginal zone (contributing to the hypoblast and controlling the site of primitive streak formation) are separable, and reside in different germ layers.
(4) The 36 hour stage was represented by bulky growth of mesodermal-like cells and changes in hypoblast layer where some of the cells degenerated and some were transformed to mesenchymal spindle-like cells.
(5) Tritiated quail hypoblast (after incubation of the embryo in the presence of 3H-glucosamine) was transplanted onto unlabelled chicken blastoderm deprived of its hypoblast.
(6) In the area pellucida, the fibronectin was (1) associated with the basal lamina of the epiblast, (2) present between epiblastic and hypoblastic cells and (3) occasionally internalized in hypoblastic cells.
(7) It was found that the deep (endodermal) portion of the posterior marginal zone contributes to the hypoblast and to the junctional endoblast, while the epiblast portion of the same region contributes to the epiblast of the primitive streak and to the definitive (gut) endoderm derived from it.
(8) TGF-beta 1 precursor was seen in both the epiblast and the hypoblast.
(9) Removal of the deep part of the marginal zone prevents regeneration of the hypoblast but not the formation of a primitive streak.
(10) Chick embryos treated with tunicamycin (TN), a specific inhibitor of N-linked glycosylation of proteins, show little or no ECM, diminished cell adhesion and a dramatic alteration in the architecture of the epiblast and of the hypoblast.
(11) A chemical basis for the transmission of signals during gastrulation has been investigated by using chimaeric embryos resulting from the combination of 3H-glucosamine-labelled and unlabelled hypoblast with epiblast taken from chicken and quail embryos at stage 3 of Vakaet (1970).
(12) The roof of the vesicle is constructed to rather large columnar cells which are in continuity wiht hypoblast cells.
(13) By contrast, alpha-amanitin resulted in a decrease in synthesis of several polypeptides, which are either undetectable or weakly present in the hypoblast.
(14) It was found that the first cells that appeared between the primitive endoderm (hypoblast) and trophoblast were separated from the latter by a basal lamina but appeared to be either loosely attached to the endoderm or to have been detached from it.
(15) The hypoblast explant tended to fragment into smaller groups of cells, many of which migrated around the definitive endoblast, thus mimicking the situation in vivo.
(16) Transfer of label may occur to mesoblast cells, but not between chicken and quail hypoblast cells.
(17) The morphology of the chimaeric embryos, as studied by scanning electron microscopy, suggests a direct deposition of these macromolecules by filopodia of the dorsal surface of the hypoblast.
(18) The labeled hypoblast was recombined with its denuded unlabeled epiblast.
(19) In comparison with the definitive endoblast, the hypoblast cells attached more readily to the glass, produced larger ruffle membranes, moved more rapidly, showed poorer contact-inhibition of locomotion and showed a greater tendency to break away from the main explant.
(20) The hypoblast, mesoderm and epiblast of gastrulating chick embryos have some HNK-1-related proteins in common, while others are unique to specific tissues.