A HUMAN EMBRYO OF TWO TO THREE PAIRS OF SOMITES

1945 ◽  
Vol 23e (6) ◽  
pp. 235-243 ◽  
Author(s):  
Ralph F. Shaner
Keyword(s):  
Neural Crest ◽  
Human Embryo ◽  
Primitive Streak ◽  
Yolk Sac ◽  
Human Embryos ◽  
Caudal Part ◽  
No Tail ◽  
Cloacal Membrane ◽  
Otic Placode ◽  
Umbilical Arteries

A description is given of a human embryo with two to three pairs of somites and about 25 days old. In general the embryo tallies with the few other human embryos of the same stage hitherto described. It has a well developed head fold, but no tail fold. Its neural groove is everywhere open. There is a minute neurenteric canal, a long primitive streak, and long cloacal membrane. The last is degenerate in its caudal part. The optic primordium is faint, but a clear otic placode is present. Between the two extends a neural crest, the earliest on record. A slight fore-gut is present, ending in an oral membrane. There is a long tubular allantois. The notochord is strap-like, issuing from a Henson's node and ending in a prechordal plate. Two well developed pairs of somites appear with the beginning of a third. The mesoderm is split to contain two body cavities, which join beneath the fore-gut. The yolk sac is partly covered with blood islands. There are two definite umbilical arteries and traces of umbilical veins. Solid strands of angioblastic tissue beneath the fore-gut are the only signs of a heart. Scattered indications of body vessels also occur.

Spinal cord-notochord relationship in normal human embryos and in a human embryo with double spinal cord

1993 ◽  
Vol 86 (5) ◽  
Author(s):  
Mirna Saraga-Babi� ◽  
Vedran Stefanovi� ◽  
Jorma Wartiovaara ◽  
Eero Lehtonen
Keyword(s):  
Spinal Cord ◽  
Human Embryo ◽  
Human Embryos ◽  
Normal Human

Study of yolk-sac endoderm organogenesis in the chick using a specific enzyme (cysteine lyase) as a marker of cell differentiation

Development ◽  
1973 ◽  
Vol 29 (1) ◽  
pp. 159-174
Author(s):  
Nelly Bennett
Keyword(s):  
Cell Differentiation ◽  
Blood Cells ◽  
Primitive Streak ◽  
Yolk Sac ◽  
Specific Enzyme ◽  
Cell Proliferation And Differentiation ◽  
Lyase Activity ◽  
Morphological Specialization

The detection of a specific enzyme (cysteine lyase) of the yolk-sac endoderm by a very sensitive method is employed to characterize cell differentiation during the early stages of endoderm organogenesis in the chick. The first cells to contain active cysteine lyase are found in the germ wall at the primitive streak stage. In vivo observations establish a relation between the morphological specialization and organization of endodermal cells, their loss of mitotic activity and the increase in cysteine lyase activity. They suggest an influence of the mesoderm on endoderm differentiation. In vitro experiments confirm the existence in the yolk-sac endoderm of an incompatibility between cell proliferation and differentiation, as well as the action of the mesoderm on both the structural organization of the endoblast and the appearance of cysteine lyase; this last action seems to be due mainly to blood cells; chicken and rabbit blood cells are equally active. The problems of the origin of the endoderm and of the interactions occurring during the organogenesis of the yolk-sac endoderm are discussed.

Human embryo research beyond the primitive streak

Science ◽  
2021 ◽  
Vol 371 (6533) ◽  
pp. 998-1000
Author(s):  
Insoo Hyun ◽  
Annelien L. Bredenoord ◽  
James Briscoe ◽  
Sigal Klipstein ◽  
Tao Tan
Keyword(s):  
Human Embryo ◽  
Primitive Streak ◽  
Embryo Research ◽  
Human Embryo Research

scholarly journals Protocol for controlled modeling of human epiblast and amnion development using stem cells

2019 ◽  
Author(s):  
Yi Zheng ◽  
Jianping Fu
Keyword(s):  
Stem Cells ◽  
Primordial Germ Cells ◽  
Primitive Streak ◽  
Human Embryos ◽  
Vitro Fertilization ◽  
Human Embryology ◽  
Post Implantation ◽  
Advance Knowledge ◽  
Early Human

Abstract Due to the inaccessibility of post-implantation human embryos and the restriction on in-vitro fertilization (IVF) embryos cultured beyond 14 days, the knowledge of early post-implantation human embryogenesis remains extremely limited. Recently, we have developed a microfluidic in-vitro platform, based on human pluripotent stem cells (hPSCs), which is capable of recapitulating several key developmental landmarks of early human post-implantation embryonic development, including lumenogenesis of the epiblast (EPI), amniogenesis, and specification of primordial germ cells (PGCs) and of primitive streak (PS) cells. Given its controllability and reproducibility, the microfluidic platform provides a powerful experimental platform to advance knowledge of human embryology and reproduction. This protocol describes the preparation of the microfluidic device and its implementation for modeling human post-implantation epiblast and amnion development using hPSCs.

Embryogenesis of fused umbilical arteries in human embryos

2005 ◽  
Vol 193 (5) ◽  
pp. 1709-1715 ◽  
Author(s):  
Shigehito Yamada ◽  
Junzo Hamanishi ◽  
Shozo Tanada ◽  
Mitsuhiro Tachibana ◽  
Rokuro Mimura ◽  
...  
Keyword(s):  
Human Embryos ◽  
Umbilical Arteries

Developmental expression of the alpha receptor for platelet-derived growth factor, which is deleted in the embryonic lethal Patch mutation

Development ◽  
1992 ◽  
Vol 115 (1) ◽  
pp. 289-303 ◽  
Author(s):  
A. Orr-Urtreger ◽  
M.T. Bedford ◽  
M.S. Do ◽  
L. Eisenbach ◽  
P. Lonai
Keyword(s):  
Primitive Streak ◽  
Yolk Sac ◽  
Developmental Expression ◽  
Wild Type ◽  
Neural Tubes ◽  
Pdgfra Gene ◽  
Branchial Arches ◽  
Early Organogenesis ◽  
Visceral Yolk Sac ◽  
Parietal Endoderm

The alpha receptor of PDGF (Pdgfra) is expressed in primitive endoderm and mesoderm derivatives throughout embryogenesis. In the early primitive streak stage the gene is transcribed in the visceral and parietal endoderm. Later it is expressed in the presomitic mesoderm, yolk sac and amnion. During somitogenesis its transcription localizes to the heart and the somites. Subsequently, it is transcribed in the dermatome, the sclerotome, the developing limb and in various mesenchymal tissues of visceral organs. Its wild-type expression pattern correlates well with the phenotype of homozygous mutant Patch (Ph) embryos, where the Pdgfra gene is deleted. The Ph phenotype is first detectable at the primitive streak stage with convoluted and hypertrophic visceral yolk sac, deformed neural plate and disorganized or missing mesoderm. Most Ph/Ph embryos die before the 11th day of gestation. Those that survive till early organogenesis are very small, have hypertrophic yolk sacs, small and undifferentiated somites, convoluted neural tubes, large heart and pericardium, rudimentary limb buds and branchial arches. Our observations together suggest that the alpha PDGF receptor may be required for the normal development of visceral endoderm and mesoderm derivatives.

The neural crest and the acoustic ganglion

Development ◽  
1967 ◽  
Vol 17 (3) ◽  
pp. 533-541
Author(s):  
M. S. Deol
Keyword(s):  
Neural Crest ◽  
Sole Source ◽  
New Approach ◽  
Present Purpose ◽  
Difference Of Opinion ◽  
Mammalian Embryos ◽  
The Subject ◽  
Otic Placode ◽  
The Difference ◽  
Mutant Genes

Although the origin of the acoustic ganglion has been the subject of numerous studies there is no unanimity of opinion about it. Most of the earlier investigators (Bartelmez, 1922; Adelman, 1925), using mammalian embryos, believed that it arose from the neural crest, but the experiments of Campenhout (1935) and Yntema (1937) on amphibian embryos led them to the view that it was largely, if not wholly, of placodal origin. This view was supported by Halley (1955), who worked on the cat, and later by Batten (1958), who worked on the sheep. In fact Batten stated categorically that the otic placode was the sole source of the acoustic ganglion. It was thought that an entirely new approach to the problem, namely the use of mutant genes, might help to resolve the difference of opinion. The most suitable mutant for the present purpose seemed to be piebald-lethal (symbol s1; Lane, 1966).

Ectodermal patterning in the avian embryo: epidermis versus neural plate

Development ◽  
1999 ◽  
Vol 126 (1) ◽  
pp. 63-73 ◽  
Author(s):  
E. Pera ◽  
S. Stein ◽  
M. Kessel
Keyword(s):  
Chick Embryo ◽  
Neural Crest ◽  
Plate Boundary ◽  
Homeobox Gene ◽  
Primitive Streak ◽  
Neural Plate ◽  
Avian Embryo ◽  
Neural Fate ◽  
Early Stages ◽  
Two Factors

Ectodermal patterning of the chick embryo begins in the uterus and continues during gastrulation, when cells with a neural fate become restricted to the neural plate around the primitive streak, and cells fated to become the epidermis to the periphery. The prospective epidermis at early stages is characterized by the expression of the homeobox gene DLX5, which remains an epidermal marker during gastrulation and neurulation. Later, some DLX5-expressing cells become internalized into the ventral forebrain and the neural crest at the hindbrain level. We studied the mechanism of ectodermal patterning by transplantation of Hensen's nodes and prechordal plates. The DLX5 marker indicates that not only a neural plate, but also a surrounding epidermis is induced in such operations. Similar effects can be obtained with neural plate grafts. These experiments demonstrate that the induction of a DLX5-positive epidermis is triggered by the midline, and the effect is transferred via the neural plate to the periphery. By repeated extirpations of the endoderm we suppressed the formation of an endoderm/mesoderm layer under the epiblast. This led to the generation of epidermis, and to the inhibition of neuroepithelium in the naked ectoderm. This suggests a signal necessary for neural, but inhibitory for epidermal development, normally coming from the lower layers. Finally, we demonstrate that BMP4, as well as BMP2, is capable of inducing epidermal fate by distorting the epidermis-neural plate boundary. This, however, does not happen independently within the neural plate or outside the normal DLX5 domain. In the area opaca, the co-transplantation of a BMP4 bead with a node graft leads to the induction of DLX5, thus indicating the cooperation of two factors. We conclude that ectodermal patterning is achieved by signalling both from the midline and from the periphery, within the upper but also from the lower layers.

La fine del concetto di “pre-embrione” nella Convenzione di Oviedo / The end of the concept of “pre-embryo” in the Oviedo Convention

2018 ◽  
Vol 66 (6) ◽  
pp. 735-745
Author(s):  
Carlo Casini ◽  
Marina Casini
Keyword(s):  
Human Embryo ◽  
Legal Status ◽  
Human Embryos ◽  
Specific Reference ◽  
Constitutional Court ◽  
The European Union ◽  
Council Of Europe ◽  
European Court ◽  
The Moment

Il contributo si sofferma sulla questione riguardante la ricerca scientifica sugli embrioni generati in vitro. L’articolo 18 della Convenzione riguarda specificamente la sperimentazione sull’embrione in vitro e per questo esso è sottoposto ad una riflessione particolarmente approfondita. L’obiettivo è quello di capire se dalla Convenzione emergono linee idonee a definire lo statuto giuridico dell’embrione umano. Gli Autori concludono nel senso che nonostante il concetto di pre-embrione (formulato proprio per teorizzare l’insignificanza dell’embrione umano nei primi 14 giorni dalla fecondazione) sia stato accolto in alcune leggi e abbia implicitamente guidato l’interpretazione di alcuni aspetti relativi alla valutazione del valore dell’embrione, la Convenzione di bioetica lo ha definitivamente respinto con il massimo di autorevolezza. La conclusione è raggiunta attraverso l’esame dell’art. 18 considerandone anche la precedente formulazione contenuta in una bozza; mediante una interpretazione sistematica della Convenzione che esige il riconoscimento del concepito, fin dalla fecondazione, come un “essere umano”; esaminando i contributi preparatori elaborati dalla Assemblea Parlamentare del Consiglio d’Europa e del Parlamento Europeo; prendendo in considerazione gli sviluppi della Convenzione di Oviedo con specifico riferimento al tema del pre-embrione. L’indagine si avvale poi anche di ampi riferimenti alla giurisprudenza della Corte europea dei diritti dell’uomo del Consiglio d’Europa, alla giurisprudenza della Corte di Giustizia dell’Unione Europea, ad alcune recenti decisioni della Corte Costituzionale italiana. ---------- The paper focuses on the question concerning scientific research on human embryos generated in vitro. Article 18 of the Oviedo Convention specifically concerns the experimentation on the in vitro embryos and for this reason it is subject to a particularly in-depth reflection. The goal is to understand if the Convention shows suitable lines to define the legal status of the human embryo. The authors conclude that despite the concept of pre-embryo (formulated to theorize the insignificance of the human embryo in the first 14 days of fertilization) has been accepted in some laws and has implicitly guided the interpretation of some aspects related to the evaluation of the value of the embryo, the Bioethics Convention definitively rejected it with the utmost authority. The conclusion is reached through the examination of the art. 18 also considering the previous formulation contained in a draft; through a systematic interpretation of the Convention which requires the recognition of the conceived, from the moment of fertilization, as a “human being”; examining the preparatory contributions prepared by the Parliamentary Assembly of the Council of Europe and the European Parliament; taking into consideration the developments of the Oviedo Convention with specific reference to the theme of the pre-embryo. The investigation also makes use of extensive references to the jurisprudence of the European Court of Human Rights of the Council of Europe, to the jurisprudence of the Court of Justice of the European Union, to some recent decisions of the Italian Constitutional Court.

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