SEARCH · PubMed Health

Results for “ECTODERM”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1997

Dorso-ventral ectodermal compartments and origin of apical ectodermal ridge in developing chick limb.

We wish to understand how limbs are positioned with respect to the dorso-ventral axis of the body in vertebrate embryos, and how different regions of limb bud ectoderm, i.e. dorsal ectoderm, apical ridge and ventral ectoderm, originate. Signals from dorsal and ventral ectoderm control dorso-ventral patterning while the apical ectodermal ridge (AER) controls bud outgrowth and patterning along the proximo-distal axis. We show, using cell-fate tracers, the existence of two distinct ectodermal compartments, dorsal versus ventral, in both presumptive limb and flank of early chick embryos. This organisation of limb ectoderm is the first direct evidence, in vertebrates, of compartments in non-neural ectoderm. Since the apical ridge appears to be confined to this compartment boundary, this positions the limb. The mesoderm, unlike the ectoderm, does not contain two separate dorsal and ventral cell lineages, suggesting that dorsal and ventral ectoderm compartments may be important to ensure appropriate control of mesodermal cell fate. Surprisingly, we also show that cells which form the apical ridge are initially scattered in a wide region of early ectoderm and that both dorsal and ventral ectoderm cells contribute to the apical ridge, intermingling to some extent within it.

Animals↗

PubMed1989

Regionalisation of the mouse embryonic ectoderm: allocation of prospective ectodermal tissues during gastrulation.

The regionalisation of cell fate in the embryonic ectoderm was studied by analyzing the distribution of graft-derived cells in the chimaeric embryo following grafting of wheat germ agglutinin--gold-labelled cells and culturing primitive-streak-stage mouse embryos. Embryonic ectoderm in the anterior region of the egg cylinder contributes to the neuroectoderm of the prosencephalon and mesencephalon. Cells in the distal lateral region give rise to the neuroectoderm of the rhombencephalon and the spinal cord. Embryonic ectoderm at the archenteron and adjacent to the middle region of the primitive streak contributes to the neuroepithelium of the spinal cord. The proximal-lateral ectoderm and the ectodermal cells adjacent to the posterior region of the primitive streak produce the surface ectoderm, the epidermal placodes and the cranial neural crest cells. Some labelled cells grafted to the anterior midline are found in the oral ectodermal lining, whereas cells from the archenteron are found in the notochord. With respect to mesodermal tissues, ectoderm at the archenteron and the distal-lateral region of the egg cylinder gives rise to rhombencephalic somitomeres, and the embryonic ectoderm adjacent to the primitive streak contributes to the somitic mesoderm and the lateral mesoderm. Based upon results of this and other grafting studies, a map of prospective ectodermal tissues in the embryonic ectoderm of the full-streak-stage mouse embryo is constructed.

Animals↗

PubMed2003

Fate map of mouse ventral limb ectoderm and the apical ectodermal ridge.

The apical ectodermal ridge (AER) is a critical signaling center at the tip of the limb that promotes outgrowth. In mouse, formation of the AER involves a gradual restriction of AER gene expression from a broad ventral preAER domain to the tip of the limb, as well as progressive thickening of cells to form a multilayered epithelium. The AER is visible from embryonic day 10.5 to 13.5 (E10.5-E13.5) in the mouse forelimb. Previous short-term fate mapping studies indicated that, once a cell is incorporated into the AER, its descendents remain within the AER. In addition, some preAER cells appear to become incorporated into the ventral ectoderm. In the present study, we used an inducible CreER/loxP fate mapping approach in mouse to examine the long-term contribution of preAER cells to limb ventral ectoderm, as well as the ultimate fate of the mature AER cells. We used a CreER transgene that contains Msx2 regulatory sequences specific to the developing AER, and demonstrate by marking preAER cells that, at stage 2 of mouse limb bud development, the majority of the ventral ectoderm that protrudes from the body wall later covers only the paw. Furthermore, when Msx2-CreER-expressing preAER cells are marked after the onset of preAER gene expression, a similar domain of paw ventral ectoderm is marked at E16.5, in addition to the AER. Strikingly, mapping the long-term fate of cells that form the mature AER showed that, although this structure is indeed a distinct compartment, AER-derived cells are gradually lost after E12.5 and no cells remain by birth. A distinct dorsal/ventral border nevertheless is maintained in the ectoderm of the paw, with the distal-most border being located at the edge of the nail bed. These studies have uncovered new aspects of the cellular mechanisms involved in AER formation and in partitioning the ventral ectoderm in mouse limb.

Animals↗

PubMed1996

Hydra regeneration from recombined ectodermal and endodermal tissue. I. Epibolic ectodermal spreading is driven by cell intercalation.

Cell-cell interaction and cell rearrangement were examined in the process of epithelial sheet formation during regeneration from hydra cell aggregates. The ectodermal and endodermal epithelial cell layers of Hydra magnipapillata were separated by procaine treatment. Each of the separated layers was then dissociated into single cells and reaggregated to produce ectodermal or endodermal cell aggregates. When the two aggregate types were recombined, a firm adhesion was quickly established between them. This was followed by a vigorous spreading of the ectodermal epithelial cells as a thin layer over the endoderm in a manner similar to the 'epiboly' in some developing embryos. Cell movement in this spreading process was examined using fluorescent dyestaining. It revealed that cells initially located in the inside of the aggregate migrated to intercalate themselves among the cells originally present in the contact surface. This radial cell intercalation took place continuously in the contact surface of both the ectodermal and endodermal aggregates, and produced a rapid growth of the contact surface, eventually leading to complete envelopment of the entire endoderm by the ectoderm. The resulting structure was a small sphere having a two-layered epithelial organization as in normal hydra. This sphere regenerated into a complete hydra a few days later. A tryptic extract of hydra membrane fraction specifically inhibited the ectodermal spreading over the endoderm, but not the initial adhesion or the later regeneration processes. These observations suggest that radial cell intercalation at the contact surface plays a crucial role in producing ectodermal spreading and establishing epithelial sheet organization in the recombined aggregates. The intercalation is presumably activated by a signal exchange through the contact surface. The inhibitory effect of the membrane extract suggests that it contains a factor that is involved in some way in this signaling mechanism.

Animals↗

PubMed1995

Ventral ectodermal ridge and ventral ectodermal groove: two distinct morphological features in the developing rat embryo tail.

The ventral ectodermal ridge (VER) is a thickening of the surface ectoderm on the ventral side of the embryonic tail which resembles the apical ectodermal ridge of the limb bud. The morphological characteristics of the ventral part of the embryo tail were investigated in 10.5- to 14-day rat embryos by light microscopy of serial semithin sections and by scanning and transmission electron microscopy. In 10.5- to 11.5-day embryos the thickening of the ventral surface ectoderm includes the complete ventral midline of the tail and can be divided into two parts. The posterior part is elevated and represents the ventral ectodermal ridge. The anterior part is, in contrast to the ridge, concave, and we have termed it the ventral ectodermal groove (VEG). The cloacal membrane is located at its anterior end. Contacts between the VER and the mesenchymal cells are visible until an intact basal lamina is formed at 11.5 days. Similarly, the VEG is connected by elongated cell processes with the ventral part of the tail gut. Gap junctions are present between the apical parts of ridge and groove cells. The VEG flattens and disappears in 12-day embryos. At this stage the ridge is at its maximum height, simultaneously undergoing extensive cell death. The VER is no longer visible in 14-day rat embryos.

Animals↗

PubMed2000

Phenoloxidase, a marker enzyme for differentiation of the neural ectoderm and the epidermal ectoderm during embryonic development of amphioxus Branchiostoma belcheri tsingtaunese.

The development of phenoloxidase during amphioxus embryogenesis was spectrophotometrically and histochemically studied for the first time in the present study. It was found that (1) PO activity initially appeared in the general ectoderm including the neural ectoderm and the epidermal ectoderm at the early neurula stage but not in the mesoderm or the endoderm, and (2) PO activity disappeared in the neural plate cells but remained unchanged in the epidermal cells when the neural plate was morphologically quite distinct from the rest of the ectoderm. It is apparent that PO could serve as a marker enzyme for differentiation of the neural ectoderm from the epidermal ectoderm during embryonic development of amphioxus.

Animals↗

PubMed1997

Hydra regeneration from recombined ectodermal and endodermal tissue. II. Differential stability in the ectodermal and endodermal epithelial organization.

Hydra tissue consists of the ectodermal and the endodermal layers. When the two layers were separated by procaine treatment and then recombined, the ectodermal epithelial cells spread as a single cell layer over the endoderm as in epiboly in vertebrate embryogenesis, and the resultant spherical structure subsequently regenerated into a complete hydra. In this study, light and electron microscopy were used to examine the structural changes which took place in the cells and tissue during this epibolic ectodermal spreading process. Within a few hours after tissue recombination, the endoderm underwent dramatic changes; it lost its epithelial sheet organization, and turned into a mass of irregularly shaped cells without the apical-basal cell polarity initially present. In contrast, the ectoderm maintained its basic epithelial sheet organization as it spread over the endoderm. Later, the endodermal epithelial cells reorganized themselves into a single-layered epithelial sheet underneath the spreading ectodermal layer. The resultant spherical structure consisted of a single layer of ectodermal epithelial cells outside, a single layer of endodermal epithelial cells inside, and an empty cavity in the center as in normal hydra tissue. This structure regenerated into hydra in the following days. These and other observations demonstrate that the two-layered epithelial sheet organization is highly dynamic, and that its stability is maintained by strong interactions between the two layers in normal hydra. It is suggested that this dynamic nature of the hydra tissue, particularly the high plasticity of the endodermal epithelial sheet organization, may be an important element for the high regenerative capacity of this organism.

Animals↗

PubMed1997

Expression of Radical fringe in limb-bud ectoderm regulates apical ectodermal ridge formation.

The apical ectodermal ridge of the vertebrate limb bud lies at the junction of the dorsal and ventral ectoderm and directs patterning of the growing limb. Its formation is directed by the boundary between cells that do and cells that do not express the gene Radical fringe. This is similar to the establishment of the margin cells at the Drosophila wing dorsoventral border by fringe. Radical fringe expression in chick-limb dorsal ectoderm is established in part through repression by Engrailed-1 in the ventral ectoderm.

Animals↗

PubMed2003

Ectodermal Wnt3/beta-catenin signaling is required for the establishment and maintenance of the apical ectodermal ridge.

The formation of the apical ectodermal ridge (AER) is critical for the distal outgrowth and patterning of the vertebrate limb. Recent work in the chick has demonstrated that interplay between the Wnt and Fgf signaling pathways is essential in the limb mesenchyme and ectoderm in the establishment and perhaps the maintenance of the AER. In the mouse, whereas a role for Fgfs for AER establishment and function has been clearly demonstrated, the role of Wnt/beta-catenin signaling, although known to be important, is obscure. In this study, we demonstrate that Wnt3, which is expressed ubiquitously throughout the limb ectoderm, is essential for normal limb development and plays a critical role in the establishment of the AER. We also show that the conditional removal of beta-catenin in the ventral ectodermal cells is sufficient to elicit the mutant limb phenotype. In addition, removing beta-catenin after the induction of the ridge results in the disappearance of the AER, demonstrating the requirement for continued beta-catenin signaling for the maintenance of this structure. Finally, we demonstrate that Wnt/beta-catenin signaling lies upstream of the Bmp signaling pathway in establishment of the AER and regulation of the dorsoventral polarity of the limb.

Animals↗

PubMed1979

[Association of ectodermal dysplasia, cleft of the lip palate and "scrubbing-brush hair". Its situation in "D. E. F. syndromes" (ectodermal dysplasia, cleft of the lip and/or palate (author's transl)].

The "D. E. F.-syndromes" consist of ectodermal dysplasia, cleft of the lip and/or palate (fente labiale et/ou palatine). This group includes the A. E. C.- and the E. E. C.-syndromes. We are reporting two cases of D. E. F.-syndrome, in which there was a very particular hair dysplasia, which we named "scrubbing-brush hair". The first case was a boy. The disease was probably transmitted on the dominant autosomal mode. The ectodermal dysplasia was of hypohidrotic type. The second case was also observed in a boy. There was no similar genetic abnormality in the family. The ectodermal dysplasia was of hidrotic types. The embryological findings account for the association between the ectodermal dysplasia and the medial dysraphia of the face.

Abnormalities, Multiple↗

PubMed1996

Ectodermal dysplasia, Rapp-Hodgkin type in a mother and severe ectrodactyly-ectodermal dysplasia-clefting syndrome (EEC) in her child.

We describe a mother with manifestations most consistent with the Rapp-Hodgkin type of ectodermal dysplasia and her malformed newborn son with ectrodactyly, ectodermal dysplasia, cleft palate, and bilateral cystic and obstructive ureteroceles with hydroureters and cystic renal dysplasia as described in the EEC syndrome. This observation suggests that the Rapp-Hodgkin type of ectodermal dysplasia and EEC syndrome, both defined as autosomal dominant conditions with variable expression, may be manifestations of the same mutated gene. We also want to emphasize that urogenital anomaly is another hallmark of the EEC syndrome.

Abnormalities, Multiple↗

PubMed1998

Apical ectodermal ridge induction by the transplantation of En-1-overexpressing ectoderm in chick limb bud.

In the early chick embryo, the dorsal ventral (DV) boundary organizes the apical ectodermal ridge (AER) structure in the limb bud field. Here it is reported that Engrailed-1 (En-1), a homolog of the Drosophila segment polarity gene engrailed expressed in the ventral limb ectoderm, participates in AER formation at the DV boundary of the limb bud. Restricted ectopic expression of En-1 in the dorsal side of the limb bud by transplantation of En-1-overexpressing ectoderm induces ectopic AER at the boundary of En-1-positive and -negative cells. The results suggest that En-1 is involved in AER formation at the DV boundary of the limb bud.

Animals↗

PubMed1978

Lack of correlation between mesenchymal cell death and morphogenesis after different extents of apical ectodermal ridge/rim ectoderm removal in the chick embryo wing bud.

The removal of the apical ectodermal ridge (A.E.R.) subsequently causes distal deletion defects in the limb. There have been contradictory reports as to the appearance of cell death in the mesenchyme after A.E.R. removal, as well as to its morphogenetic significance. In our study the A.E.R./ rim ectoderm removal was varied to test whether different degrees of cell death would correlate with different degrees of distal deletions. From the right wing bud of stage 19 and 20 (HH) embryos the rim ectoderm was removed in four ways: all of the rim, the anterior third, the middle third (most of the A.E.R.), or its posterior third. The removal of all or of the anterior third caused a definite band of subwound mesenchymal cell death to appear. There was little or no cell death after removal of the middle or posterior thirds. Removal of the anterior third caused no distal deletion defects, and only a few were noted after removal of the posterior third. The proximo-distal level of the distal deletions, however, was the same after removal of all of the rim or only its middle third. As there was no difference in the degree of distal deletions after the removal of all or of the middle third of the rim but a definite difference in the mesenchymal cell death patterns we conclude that cell death is not part of the mechanisms of the distal deletion defect. Our findings also suggest that cell death does not play a role in the A.E.R.-mesenchyme reciprocal interaction that controls limb proximo-distal morphogenesis.

Animals↗

PubMed1989

Hypohidrotic ectodermal dysplasia: argument against an autosomal recessive form clinically indistinguishable from X-linked hypohidrotic ectodermal dysplasia (Christ-Siemens-Touraine syndrome)

Hypohidrotic ectodermal dysplasia (HED) is a well-described, X-linked recessive disorder characterized by hypohidrosis, hypodontia, and hypotrichosis in males. Reports of similarly affected females have suggested autosomal recessive inheritance in some families. The evidence for two clinically identical but genetically distinct disorders is not convincing, however. In two families with X-linked recessive inheritance of HED, the condition was severe in females. A critical review of previously reported cases of presumed autosomal recessive HED suggests that an autosomal recessive form of the condition identical to the X-linked HED may not exist. All sporadic instances of females with classic HED should be considered to be X-linked recessive, and counseling for X-linked recessive inheritance as well as autosomal recessive inheritance should be given.

Anodontia↗

PubMed1963