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Results for “outer ectoderm”

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At least 19 recordsLinked to original sources

PubMed1990

Serotonin-immunoreactive neurons in the cnidarian Renilla koellikeri.

The cellular localization of 5-hydroxytryptamine (5-HT) was investigated in the pennatulid anthozoan Renilla koellikeri by means of peroxidase-antiperoxidase-immunohistochemistry with an antiserum against 5-HT-formaldehyde-protein conjugate. In many colonies, strong 5-HT-immunoreactivity was displayed by the cell bodies and beaded processes of relatively small neuronlike elements predominating in the outer ectoderm or scattered in the underlying mesoglea. The immunostained neurons of the mesoglea were generally bipolar and their relatively short processes extended toward myoepithelial cells. In the ectoderm, most immunostained neurons appeared pseudounipolar. These cell bodies were endowed with a small, superficially directed, conical appendage reaching the outer surface of the epithelium. Their neurites emerged from the inner pole of the perikarya and branched toward other immunopositive ectodermal and mesogleal nerve cells, or nematocytes in the tentacles. The networklike distribution of the presumed 5-HT ectodermal neurons varied between the different regions of colonies and along the autozooid column. In the context of earlier observations in cnidarians, these cytological features suggest a sensory as well as a modulatory function for 5-HT in Renilla koellikeri.

Animals↗

PubMed1978

An ultrastructural study of the dermal papulae of the starfish, Asterias rubens, with special reference to innervation of the muscles.

The ultrastructure of the dermal papulae of a starfish (Asterias rubens) is consistent with a respiratory function. The present study has shown no regions specialized for excretory mechanisms. The papulae consist of an outer ectodermal epithelium of sensory, support and gland cells and a small basiepithelial nerve plexus. A true basement membrane lies underneath the epithelium and regularly arranged longitudinal muscle bundles lie within the connective tissue. The coelomic cavity of the papulae is lined with ciliated endothelial cells, which overlie an irregular layer of circular muscles. A system of canals that are not lined by cells occurs at the base of the papulae with the circular muscles. The longitudinal and circular muscles show a different gross morphological arrangement and innervation. This paper proposes that there are "skeletal" and "visceral" types of smooth muscle in echinoderms and discusses this proposal at length.

Animals↗

PubMed1991

Gastrulation.

At gastrulation, a single layer of cells is converted into an outer ectodermal covering, an inner ectodermal tube, and in triploblastic phyla, a middle mesodermal layer. This morphogenesis is driven by motility and directed by cell interactions, some of which involve adhesion and others that involve information transfer.

Amino Acid Sequence↗

PubMed2025

Foxi2 and Sox3 are master regulators controlling ectoderm germ layer specification.

In vertebrates, germ layer specification represents a critical transition where pluripotent cells acquire lineage-specific identities. We identify the maternal transcription factors Foxi2 and Sox3 to be pivotal master regulators of ectodermal germ layer specification in Xenopus. Ectopic co-expression of Foxi2 and Sox3 in prospective endodermal tissue induces the expression of ectodermal markers while suppressing mesendodermal markers. Transcriptomics analyses reveal that Foxi2 and Sox3 jointly and independently regulate hundreds of ectodermal target genes. During early cleavage stages, Foxi2 and Sox3 pre-bind to key cis-regulatory modules (CRMs), marking sites that later recruit Ep300 and facilitate H3K27ac deposition, thereby shaping the epigenetic landscape of the ectodermal genome. These CRMs are highly enriched within ectoderm-specific super-enhancers (SEs). Our findings highlight the pivotal role of ectodermal SE-associated CRMs in precise and robust ectodermal gene activation, establishing Foxi2 and Sox3 as central architects of ectodermal lineage specification.

Ep300↗

PubMed1979

Fine structural differentiation of germ layers in the mouse at the time of mesoderm formation.

The morphology of early postimplantation mouse egg cylinders was studied using light and electron microscopy. Implantation sites at seven, seven and one-half and eight days of gestation were dissected from the myometrium and whole implants, including both decidua and egg cylinders were processed for electron microscopy. Pre-primitive streak egg cylinders were composed of two germ layers, a tall columnar ectoderm and an outer visceral endodermal layer. Ectodermal cells demonstrated large oval nuclei and an organelle sparse cytoplasm except for many free polyribosomes. The visceral endodermal layer was composed of two cell populations. One visceral endodermal cell type observed was tall columnar in shape and appeared absorptive as demonstrated by many microvilli, pinocytotic profiles and lysosomal granules. This population was confined to extraembryonic regions of the egg cylinder. The second visceral endodermal cell type, squamous in shape, evidenced only a few microvilli, pinocytotic profiles and lysosomal granules. This population was confined to the embryonic region of the egg cylinder. Concurrent with the formation of the primitive streak an increased number of cellular junctions and nuclear pores became evident in the ectoderm. Mesodermal cells were large and stellate-shaped exhibiting many filapodia which made contact with adjacent mesodermal elements. Later the cephalic region of the primitive streak proliferated resulting in the migration of wedge-shaped mass of cells, the head process. At the most ventral extremity of the post-primitive streak egg cylinder the cells of the head process became intimately associated with the ectoderm by areas of focal contact and gap junctions.

Animals↗

PubMedDate not supplied

[An immunohistochemical study of early embryogenesis in the clawed toad Xenopus laevis by using monoclonal antibodies to intermediate filament proteins].

Distribution of cytokeratin epitopes was studied in X. laevis embryos at stages 10-25 using 5 monoclonal antibodies against proteins of the human and rat keratin filaments. Specific staining was observed in chorda, outer layers of ectoderm and presumptive epidermis (late gastrula), and inner layer of presumptive epidermis. The cells of the stained zone (presumptive epidermis) were compressed while the cells of unstained zone (presumptive neuroectoderm) were extended tangentially.

Animals↗

PubMed1978

Surface topography of isolated gastrula ectoderm of Triturus vulgaris.

The surface topography of the outer cell layer of the two-layered gastrula ectoderm of Triturus vulgaris resembles that of the other amphibians: the cells are tightly packed and devoid of pseudopodia. The cells of the inner layer are spherical and interconnected with pseudopodia of various lengths. After excision of the ectoderm the peripheral cells of the outer layer elongate perpendicularly to the edge of the explant, while the number of pseudopodia on the inner layer greatly increases. The results show that the curling-up of the explant and formation of a sphere results from locomotor activity of the cells in both layers.

Animals↗

PubMed1979

Scanning electron microscopy (SEM) of cranial neural crest migration in chick embryos.

This study describes migrating cranial neural crest cells and the microenvironment through which they migrate in chick embryos. Just prior to and during cell migration, an extensive fibrillar meshwork is observed, particularly on the outer surface of the neural tube and the inner surface of the ectoderm. This meshwork in general had a random orientation. This suggested to us that the meshwork does not provide a directive vector for cell migration but rather a substratum to promote or enhance crest cell filopodial attachment as the cells migrate. Much remains to be done in characterizing the composition of this meshwork. Based on other studies in which a smiliar meshwork has been observed, it is not unreasonable to consider it to be partly collagenous. Another major component in the relatively cell-free space through which avian crest cells migrate is hyaluronic acid. The migrating crest cells are characteristically bipolar and are generally oriented in the direction of migration, although little is known about the actual mechanism of motility. Alterations in the migrating cell or in the environment through which it migrates may interfere with normal craniofacial morphogenesis, as discussed elsewhere in this volume by Johnston and Sulik.

Animals↗

PubMed1977

Artificial neural induction in amphibia. I. Sandwich explants.

1. Embryonic tissues (ectoderm, neural plate) of Ambystoma mexicanum and Tritus were killed with hot water and implanted into ectoderm sandwiches. They induced the ectoderm to form neural tissue, lentoids and unspecialized epidermis. Neural tissue always showed retina character. Egg pigment was eliminated and gathered at the outer retinal surface or in the centre of rosettes. Neural crest cells like mesenchyme or melanophores were completely lacking, retinal pigment did not develop. 2. The thus induced living retina tissue was reimplanted into fresh ectoderm after 2 days. It continued histogenetic and morphogenetic differentiation and formed ocular vesicles with numerous eye cups. It induced the enveloping ectoderm to again form retina, lentoids and unspecialized epidermis without neural crest derivatives or RPE. 3. This inductive process can be reproduced several times.

Ambystoma↗

PubMed1990

Immunocytochemical analysis of embryonic compartmentation with a monoclonal antibody against a cytokeratin-related antigen.

Mab 113F4, a monoclonal antibody recognizing an antigen in the outer synaptic layer of the chick neural retina, also recognizes an antigen appearing in all three germ layers of the gastrulating chick embryo. However, as neurulation proceeds, the antigen is down-regulated in three distinct patterns. First, the antigen is lost specifically from those trunk ectodermal cells destined to form the neural plate and, later, the neural tube. It remains absent from any neural derivative until day 13 when it appears in the outer synaptic layer of the neural retina, coincident with synaptogenesis in this region. Second, the entirety of the head ectoderm loses this antigen as the head lifts off the blastoderm. This down-regulation is followed later by a similar loss of antigen expression in the trunk ectoderm. Third, expression in the mesoderm becomes limited to the lateral plate and extraembryonic epithelia. Endodermal derivatives continue to express the antigen throughout development. Antigen 113F4 is localized within the cytoplasm and is organized in a fibrillar pattern. The intracellular localization of this antigen and its characteristic spatio-temporal tissue distribution are consistent with the antigen being a cytokeratin or cytokeratin-related antigen. The changes in tissue distribution suggest a possible role in tissue modelling in response to inductive interactions during development.

Animals↗

PubMed1976

[Ultrastructural aspects of the migration of somite cells to the posterior limb buds of mice].

Migrating cells originating selectively in the ventral lateral edge of the somites adjacent to the mouse hindlimb bud have been studied in transverse sections by transmission and scanning electron microscopy. Collected during the 10th and 11th gestational days, the embryos have been classified according to the number of metameres. As soon as the 28 somite stage, discrete cytological modifications occur in a limited caudal area of the ventro-lateral somitic edge. Loosing the typical epithelial arrangement characteristic of the dermatome cells, these ventral cells show large areas of close contact between their plasma membrane and a superficial microfilamentous material accumulates in the contact areas. At the 33 somite stage, the same groups of cells elongate and form long cellular trails invading the proximal area of the limb bud mesoderm. The migrating cells become polarized along the migrating axis and they retain large and smooth intercellular contacts with each other. Very selective ultrastructural features of the migrating somitic cells can be interpreted in relation to their cinetic activity or to their early myogenic differentiation. In addition to their mutual superficial relationships, the migrating cells are characterized by the presence of numerous oriented microtubules, of a high number of active mitochondria, of an abundant granular endoplasmic reticulum and of an hypertrophied Golgi apparatus regularly located near the nucleus in the "trailing" edge of the cells. Several dense granules with a diameter of 8 nm are present in the mitochondrial matrix. The extensive Golgi apparatus is associated to numerous thick walled vesicles, which increase from 60 to 150 nm in diameter as they become closer and closer to the plasma membrane. These vesicles are absent in the mesodermal cells of somatopleural origin; their presence in the migrating somitic cells is probably related to an early myogenic differentiation. The observation made near the distal end of the somitic cellular trails suggests that the more distal somitic cells rapidly loose their ultrastructural particularities as soon as they are dispersed in the limb bud mesoderm; this aspect of the processus, however, requires the study of later developmental stages. Other observations made in the same material bring some precisions to the ecto-mesodermal relationships which are established in the apical area of the limb bud. Scanning electron microscopic observations of thick sections reveal that the outer mesodermal cells of this area send numerous filopodia which make contact with the basement membrane underlying the apical ectodermal ridge.

Animals↗

PubMed1991

Abnormalities of ERG in congenital aniridia.

Congenital aniridia is generally associated with nystagmus, corneal pannus, cataract, ectopia lentis, glaucoma, macular hypoplasia, optic nerve hypoplasia and compromised visual function. Many theories have been proposed, including a failure in the development of the neural ectoderm and/or an aberrant development of mesoderm. We observed the ERG from 19 patients with congenital aniridia. Fourteen patients had abnormal ERG, including the reduced a wave trough under dark adapted red stimuli with dark adaptation; abnormal a or/and b waves in dark or/and light adapted ERG or abnormal oscillatory potentials. The ERG abnormalities reflected the disturbances either in the outer retina such as photoreceptors or in the structures of inner retina. The preserved visual function and several ocular abnormalities show that the aniridia may be a consequence of several pathogenetic mechanisms. This fact supported the opinion that congenital aniridia would be a concurrent failure of both ectoderm and mesoderm in embryonate development.

Adolescent↗

PubMed1977

Multiple fibrofolliculomas (Birt-Hogg-Dubé) associated with a large connective tissue nevus.

Multiple follicular tumors of the type recently described by Birt and colleagues as fibrofolliculomas were observed in the dorsal skin of a white man in association with a large connective tissue nevus. No signs of systemic disease or phakomatosis were present. This type of lesions represents benign neoplasia of the fibrous root sheath of the hair follicle in association with proliferations of the infundibular portion of the outer epithelial root sheath. Its existence supports the view that the mesodermal portions of the pilar apparatus can become neoplastic, and also provides another example of the close interactions existing between the ectodermal and mesodermal components of the hair follicle.

Hair↗

PubMed1979

In vitro development of core cells of the inner cell mass of the mouse blastocyst: effects of conditioned medium.

Blastocysts submitted to two rounds of immunosurgery give rise to cores of presumptive ectoderm cells, many of which do not survive for more than 48 hours when cultured individually. Precoating of the culture plates with conditioned medium (CM) from PYS-2 cells increases the incidence with which cores regenerate an outer layer. This procedure also improves the survival frequency of the cores, but only for a limited period of time. The small number of cores which survive for two weeks or more, either in uncoated or CM-coated plates, give rise to any array of cell types, including giant cells resembling trophoblast.

Animals↗

PubMed1977

Surface differentiation antigens of human mammary epithelial cells carried on the human milk fat globule.

Rabbit antibodies against components of the human milk fat globule bind specifically to normal human breast epithelial cells and cell lines derived from breast carcinomas, as well as to the outer surface of the human milk fat globule. Variation in indirect immunofluorescence staining in both intensity per cell and percentage of cells stained is observed for the different brest cell lines. Cells derived from other epithelial and other ectodermal tissues, fetal fibroblasts, cells of the blood buffy coat, and even fibroblasts of the breast itself do not bind the antibodies. This suggests that these antibodies are detecting cell-type-specific antigens. These normal breast epithelial cell antigens are on the cell surface and their expression is stable in long-term cultured cell lines, even after much chromosomal variation in a given line. By affinity chromatography, three distinct antigenic components can be isolated from the milk fat globule, one of which contains carbohydrate. These differentiation antigens of the human breast epithelial cell are not only useful as specific cell-type markers, but also can provide a tool to study the role of the cell surface in normal and neoplastic mammary development.

Animals↗

PubMed1991

Differential expression of two cadherins in Xenopus laevis.

Using a cadherin fraction from Xenopus tissue culture cells as an immunogen, two monoclonal antibodies were obtained that allowed the characterization of two distinct cadherins in the Xenopus embryo. The two cadherins differ in molecular weight, in their time of appearance during development and in their spatial pattern of expression. One of the antigens was identified as E-cadherin. It appears in the embryonic ectoderm during gastrulation when epidermal differentiation commences and it disappears from the neural plate area upon neural induction. The second antigen could not be allocated to any of the known cadherin subtypes and was termed U-cadherin. It is present in the egg and becomes deposited in newly formed inner cell membranes during cleavage, the outer apical membranes of the embryo remaining devoid of the cadherin throughout development. U-cadherin is found on membranes of all cells up to the late neurula stages. A conspicuous polarized expression of the antigen on the membranes of individual inner cells suggests its participation in the segregation of cell layers and organ anlagen. These findings are discussed in the context of current hypotheses on the role of cadherins in establishing the spatial structure of the embryo.

Animals↗

PubMed1990

Histochemical localization of transforming growth factor-beta 1 in developing rat molars using antibodies to different epitopes.

In this study transforming growth factor-beta 1 (TGF-beta 1) has been immunolocalized in developing rat molars using two well characterized polyclonal antibodies, Anti-CC and Anti-LC, that recognize extracellular and intracellular TGF-beta 1, respectively. With immunohistochemical methods and the ABC-peroxidase system of detection, the growth factor was immunolocalized within the ectodermally derived enamel organ and the neural crest-derived dental papilla at the early and advanced bell stages of development. With Anti-CC, widespread and abundant extracellular TGF-beta 1 was found associated with the stellate reticulum and within central and apical regions of dental papilla mesenchyme. In contrast, Anti-LC localized TGF-beta 1 intensely within the cells of the outer dental epithelium. Moderate immunostaining for TGF-beta 1 with Anti-LC was also evident within the apical cytoplasm of inner dental epithelial cells and odontoblasts. These findings support the hypothesis that TGF-beta 1 may play a paracrine role in tooth development by regulating the epithelial-mesenchymal interactions that influence growth and cytodifferentiation events.

Animals↗

PubMed1978

In vitro development of inner cell masses isolated immunosurgically from mouse blastocysts. I. Inner cell masses from 3.5-day p.c. blastocysts incubated for 24 h before immunosurgery.

This paper describes the in vitro development of inner cell masses isolated immunosurgically from mouse blastocysts which had been collected on 3.5 days p.c. and then incubated for 24 h. The inner cell masses continue to grow in culture and develop through a series of stages with increasing complexity of internal organization. By day 1 all of the cultured ICMs have an outer layer of endoderm, and by day 3 some of them have two distinct kinds of inside cells; a columnar epithelial layer and a thin hemisphere of elongated cells. Later, mesodermal cells appear to delaminate from a limited region of the columnar layer, close to where it forms a junction with the thinner cells. By day 5, about 25% of the cultured ICMs have a striking resemblance to normal 7.5-day p.c. C3H embryos, with embryonic ectoderm, extra-embryonic ectoderm and chorion, embryonic and extra-embryonic mesoderm, and visceral endoderm. When mechanically disrupted and grown as attached clumps of cells in a tissue dish, these embryo-like structures give rise to trophoblast-like giant cells. These results suggest that the inner cell mass of 4.5-day p.c. blastocysts contains cells which can give rise to trophoblast derivates in culture.

Animals↗