Investigation on the origin of the definitive endoderm in the rat embryo

Development ◽  
1974 ◽  
Vol 32 (2) ◽  
pp. 445-459
Author(s):  
B. Levak-Švajger ◽  
A. Švajger
Keyword(s):  
Primitive Streak ◽  
Definitive Endoderm ◽  
Rat Embryo ◽  
Chick Blastoderm ◽  
Germ Layers ◽  
Kidney Capsule ◽  
Rat Embryos ◽  
Endodermal Cells ◽  
Derivatives Of

Single germ layers (or combinations of two of them) were isolated from the primitive streak and the head-fold stage rat embryos and grown for 15 days under the kidney capsule of syngeneic adult animals. The resulting teratomas were examined histologically for the presence of mature tissues, with special emphasis on derivatives of the primitive gut. Ectoderm isolated together with the initial mesodermal wings at the primitive streak stage gave rise to tissue derivatives of all three definitive germ layers. Derivatives of the primitive gut were regularly present in these grafts. At the head-fold stage, isolated ectoderm (including the region of the primitive streak) differentiated into ectodermal and mesodermal derivatives only. Endoderm isolated at the primitive streak stage did not develop when grafted and was always completely resorbed. At the head-fold stage, however, definitive endoderm differentiated into derivatives of the primitive gut if grafted together with adjacent mesoderm. These findings indirectly suggest the migration of prospective endodermal cells from the primitive ectoderm, and therefore a general analogy with the course of events during gastrulation in the chick blastoderm.

Regional developmental capacities of the rat embryonic endoderm at the head-fold stage

Development ◽  
1974 ◽  
Vol 32 (2) ◽  
pp. 461-467
Author(s):  
A. Švajger ◽  
B. Levak-Švajger
Keyword(s):  
Adult Male ◽  
Primitive Streak ◽  
Neural Plate ◽  
Male Rats ◽  
Germ Layers ◽  
Kidney Capsule ◽  
Gut Endoderm ◽  
Derivatives Of

Three areas, composed of all three germ layers, were isolated from Fischer strain rat embryonic shields at the head-fold stage, and grafted separately under the kidney capsule of adult male rats of the same strain. The areas were from the neural plate, Hensen's node and the primitive streak. The resulting teratomas were examined histologically for the presence of derivatives of the primitive gut. The grafts differed strikingly in their capacity to develop into different segments of the gut. Endoderm underlying the neural plate developed into derivatives of the foregut, while endoderm underlying the primitive streak developed mainly into derivatives of the mid- and hindgut. It was concluded that, at the head-fold stage, the capacities to develop into different segments of the definitive gut are already roughly limited to particular areas of the endoderm.

The histogenetic capacity of tissues in the caudal end of the embryonic axis of the mouse

Development ◽  
1984 ◽  
Vol 82 (1) ◽  
pp. 253-266
Author(s):  
P. P. L. Tam
Keyword(s):  
Developmental Stages ◽  
Primitive Streak ◽  
Mouse Embryos ◽  
Embryonic Axis ◽  
Tail Bud ◽  
Germ Layers ◽  
Kidney Capsule ◽  
Caudal Region ◽  
Caudal Portion ◽  
Adult Body

The caudal end of the embryonic axis consists of the primitive streak and the tail bud. Small fragments of this caudal tissue were transplanted from mouse embryos of various developmental stages to the kidney capsule in order to test their histogenetic capacity. The variety of mature tissues obtained from these small fragments was similar to that obtained by grafting a larger caudal portion of the embryo. Initially, the grafted tissue broke up into loose masses of embryonic mesenchyme and this was later re-organized into more compact tissues and into cysts that were lined with various types of epithelia. After 14 days in the ectopic site, grafted tissues coming from embryos of the primitive-streak, the early-somite and the forelimb-bud stages differentiated into structures that has presumably originated from the three embryonic germ layers. Many of these structures were related to the caudal region of the adult body, such as the mid- and hindgut segments and urogenital derivatives. The histogenetic capacity for endodermal tissues and urogenital organs was lost when the grafted tissue consisted entirely of the tail bud of the hindlimb-bud-stage embryos. The behaviour of the caudal tissues suggested that (1) the primordia for the various parts of embryonic body were derived from a small progenitor population in the primitive streak and the tail bud, and (2) the histogenetic capacity of this population changed during development.

Morphogenetic behaviour of the rat embryonic ectoderm as a renal homograft

Development ◽  
1981 ◽  
Vol 65 (Supplement) ◽  
pp. 243-267
Author(s):  
Anton Švajger ◽  
Božica Levak-Švajger ◽  
Ljiljana Kostović-Kneževic ◽  
Želimir Bradamante
Keyword(s):  
Neural Crest ◽  
Neural Crest Cells ◽  
Primitive Streak ◽  
Mesenchymal Cells ◽  
Epithelial Layer ◽  
Rat Embryo ◽  
Kidney Capsule ◽  
Embryonic Shield ◽  
Renal Homograft ◽  
Embryonic Ectoderm

Halves of transversely or longitudinally cut primary ectoderm of the pre-primitive streak and the early primitive streak rat embryonic shield developed after 15–30 days in renal homografts into benign teratomas composed of various adult tissues, often in perfect organspecific associations. No clear difference exists in histological composition of grafted halves of the same embryonic ectoderm. The primary ectoderm of the pre-primitive streak rat embryonic shield grafted under the kidney capsule for 2 days displayed an atypical morphogenetic behaviour, characterized by diffuse breaking up of the original epithelial layer into mesenchyme. Some of these cells associated into cystic or tubular epithelial structures. The definitive ectoderm of the head-fold-stage rat embryo grown as renal homograft for 1–3 days gave rise to groups of mesenchymal cells. These migrated from the basal side of the ectoderm in a manner which mimicked either the formation of the embryonic mesoderm or the initial migration of neural crest cells. This latter morphogenetic activity was retained in the entire nejjral epithelium of the early somite embryo but was only seen in the caudal open portion of the neural groove at the 10- to 12-somite stage. The efficient histogenesis in grafts of dissected primary ectoderm and the atypical morphogenetic behaviour of grafted primary and definitive rat embryonic ectoderm were discussed in the light of current concepts on mosaic and regulative development, interactive events during embryogenesis and positioning and patterning of cells by controlled morphogenetic cell displacement.

The marginal zone and its contribution to the hypoblast and primitive streak of the chick embryo

Development ◽  
1990 ◽  
Vol 109 (3) ◽  
pp. 667-682 ◽  
Author(s):  
C.D. Stern
Keyword(s):  
Chick Embryo ◽  
Marginal Zone ◽  
Primitive Streak ◽  
Time Lapse ◽  
Study Time ◽  
Fate Mapping ◽  
Deep Part ◽  
Germ Layers ◽  
Gut Endoderm ◽  
Transplantation Experiments

The marginal zone of the chick embryo has been shown to play an important role in the formation of the hypoblast and of the primitive streak. In this study, time-lapse filming, fate mapping, ablation and transplantation experiments were combined to study its contribution to these structures. 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. Within the deep part of the posterior marginal zone, a subpopulation of HNK-1-positive cells contributes to the hypoblast. Removal of the deep part of the marginal zone prevents regeneration of the hypoblast but not the formation of a primitive streak. Removal of both layers of the marginal zone leads to a primitive streak of abnormal morphology but mesendodermal cells nevertheless differentiate. 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. This conclusion does not support the idea that the influence of the posterior marginal zone on the development of axial structures is due to it being the source of secondary hypoblast cells.

De novo induction of the organizer and formation of the primitive streak in an experimental model of notochord reconstitution in avian embryos

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 201-213 ◽  
Author(s):  
S. Yuan ◽  
G.C. Schoenwolf
Keyword(s):  
Cell Fate ◽  
De Novo ◽  
Primitive Streak ◽  
Model System ◽  
Floor Plate ◽  
Avian Embryos ◽  
New Information ◽  
Derivatives Of ◽  
Novel Model ◽  
Neurula Stage

We have developed a model system for analyzing reconstitution of the notochord using cultured blastoderm isolates lacking Hensen's node and the primitive streak. Despite lacking normal notochordal precursor cells, the notochord still forms in these isolates during the 36 hours in culture. Reconstitution of the notochord involves an inducer, which acts upon a responder, thereby inducing a reconstituted notochord. To better understand the mechanism of notochord reconstitution, we asked whether formation of the notochord in the model system was preceded by reconstitution of Hensen's node, the organizer of the avian neuraxis. Our results show not only that a functional organizer is reconstituted, but that this organizer is induced from the responder. First, fate mapping reveals that the responder forms a density, morphologically similar to Hensen's node, during the first 10–12 hours in culture, and that this density expresses typical markers of Hensen's node. Second, the density, when fate mapped or when labeled and transplanted in place of Hensen's node, forms typical derivatives of Hensen's node such as endoderm, notochord and the floor plate of the neural tube. Third, the density, when transplanted to an ectopic site, induces a secondary neuraxis, identical to that induced by Hensen's node. And fourth, the density acts as a suppressor of notochord reconstitution, as does Hensen's node, when transplanted to other blastoderm isolates. Our results also reveal that the medial edge of the isolate forms a reconstituted primitive streak, which gives rise to the normal derivatives of the definitive primitive streak along its rostrocaudal extent and which expresses typical streak markers. Finally, our results demonstrate that the notochordal inducer also induces the reconstituted Hensen's node and, therefore, acts like a Nieuwkoop Center. These findings increase our understanding of the mechanism of notochord reconstitution, provide new information and a novel model system for studying the induction of the organizer and reveal the potential of the epiblast to regulate its cell fate and patterns of gene expression during late gastrula/early neurula stage in higher vertebrates.

Foregut endoderm is required at head process stages for anteriormost neural patterning in chick

Development ◽  
2001 ◽  
Vol 128 (3) ◽  
pp. 309-320 ◽  
Author(s):  
S. Withington ◽  
R. Beddington ◽  
J. Cooke
Keyword(s):  
Heart Development ◽  
Lower Layer ◽  
Early Stage ◽  
Cell Monolayer ◽  
Homeobox Gene ◽  
Primitive Streak ◽  
Definitive Endoderm ◽  
Gene Expressions ◽  
Specific System ◽  
Foregut Endoderm

Anterior definitive endoderm, the future pharynx and foregut lining, emerges from the anterior primitive streak and Hensen's node as a cell monolayer that replaces hypoblast during chick gastrulation. At early head process stages (4+ to 6; Hamburger and Hamilton) it lies beneath, lateral to and ahead of the ingressed axial mesoderm. Removal of the monolayer beneath and ahead of the node at stage 4 is followed by normal development, the removed cells being replaced by further ingressing cells from the node. However, similar removal during stages 4+ and 5 results in a permanent window denuded of definitive endoderm, beneath prechordal mesoderm and a variable sector of anterior notochord. The foregut tunnel then fails to form, heart development is confined to separated lateral regions, and the neural tube undergoes no ventral flexures at the normal positions in brain structure. Reduction in forebrain pattern is evident by the 12-somite stage, with most neuraxes lacking telencephalon and eyes, while forebrain expressions of the transcription factor genes GANF and BF1, and of FGF8, are absent or severely reduced. When the foregut endoderm removal is delayed until stage 6, later forebrain pattern appears once again complete, despite lack of foregut formation, of ventral flexure and of heart migration. Important gene expressions within axial mesoderm (chordin, Shh and BMP7) appear unaffected in all embryos, including those due to be pattern-deleted, during the hours following the operation when anterior brain pattern is believed to be determined. A specific system of neural anterior patterning signals, rather than an anterior sector of the initially neurally induced area, is lost following operation. Heterotopic lower layer replacement operations strongly suggest that these patterning signals are positionally specific to anteriormost presumptive foregut. The homeobox gene Hex and the chick Frizbee homologue Crescent are both expressed prominently within anterior definitive endoderm at the time when removal of this tissue results in forebrain defects, and the possible implications of this are discussed. The experiments also demonstrate how stomodeal ectoderm, the tissue that will, much later, form Rathke's pouch and the anterior pituitary, is independently specified by anteriormost lower layer signals at an early stage.

The differentiation of neural crest cells into visceral cartilages and odontoblasts in Amblystoma , and a re-examination of the germ-layer theory

1947 ◽  
Vol 134 (876) ◽  
pp. 377-398 ◽  
Keyword(s):  
Neural Crest ◽  
Normal Development ◽  
Neural Crest Cells ◽  
Early Embryo ◽  
Critical Study ◽  
Germ Layer ◽  
Germ Layers ◽  
Classical Form ◽  
Endodermal Cells ◽  
Dermal Bones

A critical study and demonstration of the distribution of yolk globules and of pigment granules in normal development of the axolotl shows that these cell inclusions can be regarded as infallible evidence of the origin of cells from endo-mesoderm or from ectoderm layers of the embryo respectively. It is demonstrated that ectodermal cells of the neural crest differentiate into the cartilages of the visceral arches, into odontoblasts, and it is more than probable that they differentiate into osteoblasts of dermal bones. It is further demonstrated that the enamel organs of the teeth can be formed from the ectodermal cells of the stomodaeal collar, from the endodermal cells of the gut wall, or from both. The germ-layer theory is examined as regards its theoretical implications in connexion with the homology of structures in the adult and the presumptive organ-forming regions of the early embryo. It is found that there is no invariable correlation between the germ layers and either the presumptive organ-forming regions or the formed structures. It follows that the germ layers are not determinants of differentiation in development, but embryonic structures which resemble one another closely in different forms although they may contain materials differing in origin and in fate. The germ -layer theory in its classical form must therefore be abandoned.

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