Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “germ layer specification”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 595 records · Page 33Linked to original sources
PubMed2006

Endo16 is required for gastrulation in the sea urchin Lytechinus variegatus.

The Endo16 gene encodes a large extracellular protein with several functional domains that provide some insight into the role of this protein during embryonic development. We isolated the full-length cDNA sequence from Lytechinus variegatus and utilized morpholinos to further investigate the role of Endo16 during embryonic development in this species. Endo16-deficient embryos failed to undergo gastrulation and the blastocoele became filled with dissociated cells after 24 h of incubation. Moreover, there was a delay in endoderm differentiation as assayed by staining with an antibody that recognizes Endo1. The differentiation of other cell types including oral ectoderm, primary mesenchymal cells (PMC) and secondary mesenchymal cells (SMC) appeared to be normal, although the patterns of protein expression did not resemble control embryos due to the gross morphological abnormalities elicited by the LvEndo16 morpholino. Microinjection of full-length EGFP mRNA with the LvEndo16 morpholino-targeted sequence confirmed that this phenotype can be attributed specifically to the loss of Endo16 protein. Taken together, our data suggest that Endo16 may be required for the cell-extracellular matrix (ECM) interactions that are required for endoderm differentiation in the sea urchin embryo.

Amino Acid Sequence↗
PubMed1979

Models for study of the specificity by which indigenous lactobacilli adhere to murine gastric epithelia.

A Lactobacillus strain isolated from a mouse (indigenous) and another strain isolated from swine feces (nonindigenous) were compared in two model systems for their ability to adhere in vitro and in vivo to keratinizing squamous and columnar epithelia of mouse stomachs. In one model, stomachs dissected from specific-pathogen-free or germfree mice were injected with suspensions of lactobacilli labeled with [(3)H]thymidine and incubated at 37 degrees C. Thereafter, the non-secreting and secreting tissues were separated and washed vigorously. The radioactivity remaining with each tissue was counted by liquid scintillation spectrometry. When the radioactivity remaining with these tissues ranged between 500 and 100,000 cpm, the calculated radioactivity (disintegrations per minute) was related linearly to the number of lactobacilli adhering to the tissue. The estimate of the number of bacteria adherent to the tissue was not influenced significantly by artifacts in the techniques used. In this model, both Lactobacillus strains adhered in equally high numbers to both types of epithelial surfaces from stomachs from germfree mice. In contrast, in the second model, in which germfree mice were monoassociated with one or the other of the Lactobacillus strains, only the strain indigenous to the mouse formed dense layers on the epithelia of the nonsecreting portions of the stomachs, although both strains maintained high population levels throughout the gastrointestinal tracts of the animals. The capacity to adhere to the mucosal surface is undoubtedly necessary for lactobacilli to colonize gastric epithelia in mice. Our findings suggest, however, that nutritional or environmental conditions dictate whether particular Lactobacillus strains can colonize particular surfaces in the stomachs of living animals.

Animals↗
PubMed2004

The promise of human embryonic stem cells.

Pluripotency refers to the ability of a cell to give rise to cells that originate from all three germ layers. Among the available human pluripotent cells, human embryonic stem cells (hESCs) are considered to have the greatest probability for practical clinical application because of their simple propagation and stability in culture. Since their first derivation, issues concerning hESC maintenance and self-renewal have been widely addressed. The first part of this review presents the accumulated knowledge concerning the self-renewal of hESCs and discusses recent genetic profile data, which seem to shed light on hESC self-renewal and pluripotency mechanism. The second part deals with the regenerative potential of hESCs. Available lineage-specific differentiations of hESCs are presented, with detailed data on the ability of hESCs to differentiate into trophoblast cells, an observation that might broaden the definition of their developmental potential. Specific focus is given to vascular cell differentiation, including endothelial and smooth muscle cells. Transplantation limitations as well as current steps taken toward resolution conclude the review.

Blastocyst↗
PubMed2005

[Derivation of germ cells from mouse embryonic stem cells in culture].

Mouse embryonic stem cells derive from the inner cell mass of the blastocyst and give rise to the three primitive embryonic layers, which later will form all the different tissue types of an adult. Embryonic stem cells are thus defined as totipotent cells. In vitro, these cells can give rise to all the somatic cells. Different laboratories have now shown that cultured embryonic stem cells can also differentiate into germline cells. By using the transcription factor Oct-4 as a tool for the visualization of germ cells, it has been shown the derivation of oocytes from mouse embryonic stem cells. These works should contribute to various areas, including therapeutic cloning which associates nuclear transfer and selective production of a specific cell type.

Animals↗
PubMed2006

Zebrafish Staufen1 and Staufen2 are required for the survival and migration of primordial germ cells.

In sexually reproducing organisms, primordial germ cells (PGCs) give rise to the cells of the germ line, the gametes. In many animals, PGCs are set apart from somatic cells early during embryogenesis. Work in Drosophila, C. elegans, Xenopus, and zebrafish has shown that maternally provided localized cytoplasmic determinants specify the germ line in these organisms (Raz, E., 2003. Primordial germ-cell development: the zebrafish perspective. Nat. Rev., Genet. 4, 690--700; Santos, A.C., Lehmann, R., 2004. Germ cell specification and migration in Drosophila and beyond. Curr. Biol. 14, R578-R589). The Drosophila RNA-binding protein, Staufen is required for germ cell formation, and mutations in stau result in a maternal effect grandchild-less phenotype (Schupbach,T., Weischaus, E., 1989. Female sterile mutations on the second chromosome of Drosophila melanogaster:1. Maternal effect mutations. Genetics 121, 101-17). Here we describe the functions of two zebrafish Staufen-related proteins, Stau1 and Stau2. When Stau1 or Stau2 functions are compromised in embryos by injecting antisense morpholino modified oligonucleotides or dominant-negative Stau peptides, germ layer patterning is not affected. However, expression of the PGC marker vasa is not maintained. Furthermore, expression of a green fluorescent protein (GFP):nanos 3'UTR fusion protein in germ cells shows that PGC migration is aberrant, and the mis-migrating PGCs do not survive in Stau-compromised embryos. Stau2 is also required for survival of neurons in the central nervous system (CNS). These phenotypes are rescued by co-injection of Drosophila stau mRNA. Thus, staufen has an evolutionarily conserved function in germ cells. In addition, we have identified a function for Stau proteins in PGC migration.

Amino Acid Sequence↗
PubMed1992

Presence of GABA-immunoreactive neurons within intracortical patches in area 18 of the cat.

In cat visual cortex, horizontal, intracortical connections spread laterally to link together specific columnar sites. When visualized by retrograde tracers, these intracortical connections appear as periodic, columnar patches of dense cellular labeling interspersed with areas of much less dense labeling. We looked for anatomical evidence for direct inhibition among the patchy, horizontal connections in area 18, by combining retrograde labeling using wheat germ agglutinin (WGA) conjugated to horseradish peroxidase (HRP) with immunohistochemistry using an antiserum against the inhibitory neurotransmitter gamma-amino butyric acid (GABA). We found numerous double-labeled cells associated with some, but not all, of the local patches nearest to the injection site. In the superficial layers, the GABA-immunoreactive cells also labeled with WGA-HRP were confined to a zone approximately 1.0 mm from the center of the injection, while the double-labeled cells in the deeper layers spanned greater distances, up to 3.0 mm from the injection center. These more distant, double-labeled cells in the deeper layers were located on the edges or outside of the patches of dense labeling. Thus, all of the more distant intracortical patches, as well as some of the more proximal patches were devoid of double-labeled cells--a finding which suggests that direct inhibition may occur among only a selected group of the 'short range' intracortical patches and among none of the long-range patches.

Animals↗
PubMed2005

Antero-posterior patterning of the vertebrate digestive tract: 40 years after Nicole Le Douarin's PhD thesis.

This review is dedicated to the work on chick digestive tract organogenesis that Nicole Le Douarin performed as a PhD student under the direction of Etienne Wolf. I discuss how she laid the grounds for future work by establishing fate maps at somitic stages, by describing morphogenetic movements between germ layers and by pointing to signaling events between endoderm and mesoderm. Her inspiring work was extended by others, in particular at the molecular level, leading to a better understanding of antero-posterior patterning in the digestive tract. Antero-posterior patterning of endoderm is initiated at gastrulation when future anterior and posterior endoderm ingress at different times and accordingly express different genes. Plasticity is however maintained at somite stages and even later, when organ primordia can be delineated. There is a cross-talk between endoderm and mesoderm and the two layers exchange instructive signals that induce specific antero-posterior identities as well as permissive signals required for organogenesis from previously patterned fields. Recent experiments suggest that several signaling molecules involved in neural tube antero-posterior patterning are also instrumental in the digestive tract including retinoic acid and FGF4.

Animals↗
PubMed1985

Hemopoiesis in cellulose ester membrane: characterization of the epilayer responsible for recognition and lodgement of hemopoietic cells.

Following intraperitoneal (i.p.) insertion of cellulose ester membranes in the mouse, the membranes develop a cellular coat that after sublethal irradiation and i.p. infusion of marrow cells supports the growth of hemopoietic colonies. The uppermost layer of this cellular coat (the epilayer) becomes extremely attenuated and develops numerous microvilli that interact with infused cells to trap and lodge them. This phenomenon is analogous to specific lodging of hemopoietic stem cells in the marrow after bone marrow transplantation. The mechanism of this interaction is not clear, but attention has recently focused on specific interaction of sugar residues of membrane glycoproteins. We have characterized the free surface of this epilayer with various lectins, glycosylated ferritins, and antifactor VIII antibody. There is strong binding of the three lectins Ricinis communis agglutinin (RCA II), phytohemagglutinin (PHA), and wheat germ agglutinin (WGA), but not Ulex europeaus agglutinin, concanavalin A, the tested glycosylated ferritins, or antifactor VIII antibody. The highest density of binding is on microvilli. Since marrow sinus endothelium also strongly binds RCA II, PHA, and WGA, it is possible that the sugar residues of membrane glycoproteins specifically binding these lectins are responsible for cellular and molecular recognition and transport across the epilayer.

Animals↗
PubMed1981

[V. M. Shimkevich's principle of methorisis and its relation to the evolutionary dynamics of the esophageal epithelium of fish].

In 31 species of Teleostei and Chondrostei a possibility to apply the principle of methorisis (displacement of borders between embryonic germs and, respectively, between their tissue derivatives) to the epithelial layer of the esophagus in these vertebrates has been considered. Appearance of the esophageal capillary networks is connected with the phenomenon of displacement. It is noted that food does not evidently affect directly the esophageal epithelium. Simultaneously, peculiarities in the structure of the esophageal epithelium of some Teleostei and Chondrostei are observed.

Animals↗
PubMed1996

A role for nitric oxide in the development of the ferret retinogeniculate projection.

The ferret retinogeniculate projection segregates into eye-specific layers during the first postnatal week and into ON/OFF sublaminae, which receive inputs from either on-center or off-center retinal ganglion cells, during the third and fourth postnatal weeks. The restriction of retinogeniculate axon arbors into eye-specific layers appears to depend on action potential activity () but does not require activation of NMDA receptors (). The formation of ON/OFF sublaminae is also activity-dependent and is disrupted by in vivo blockade of NMDA receptors (). To investigate a possible mechanism whereby blockade of postsynaptic NMDA receptors in the lateral geniculate nucleus (LGN) results in changes in the size and position of presynaptic axon arbors, we tested the role of the diffusible messenger nitric oxide (NO) in the development of the retinogeniculate pathway. We found previously that NO synthase (NOS) is transiently expressed in LGN cells during the refinement of retinogeniculate projections (). In this study, treatment with NG-nitro-L-arginine (L-NoArg), an arginine analog that inhibits NOS, during the third and fourth postnatal weeks resulted in an overall pattern of sublamination that was significantly reduced compared with normal and control animals. Single retinogeniculate axon arbors were located in the middle of eye-specific layers rather than toward the inner or outer half as in normal or control animals. The effect of NOS inhibition was not a consequence of the hypertensive effect of L-NoArg. In contrast to the effect of L-NoArg on the formation of ON/OFF sublaminae, treatment with L-NoArg during the first postnatal week did not disrupt the formation of eye-specific layers. Biochemical assays indicated significant inhibition of NOS during both treatment periods. These data suggest that NO acts together with NMDA receptors in activity-dependent refinement of connections during a specific phase of retinogeniculate development.

Animals↗
PubMed1998

Synaptic and neurochemical characterization of parallel pathways to the cytochrome oxidase blobs of primate visual cortex.

The primary visual cortex (V1) of primates is unique in that it is both the recipient of visual signals, arriving via parallel pathways (magnocellular [M], parvocellular [P], and koniocellular [K]) from the thalamus, and the source of several output streams to higher order visual areas. Within this scheme, output compartments of V1, such as the cytochrome oxidase (CO) rich blobs in cortical layer III, synthesize new output pathways appropriate for the next steps in visual analysis. Our chief aim in this study was to examine and compare the synaptic arrangements and neurochemistry of elements involving direct lateral geniculate nucleus (LGN) input from the K pathway with those involving indirect LGN input from the M and P pathways arriving from cortical layer IV. Geniculocortical K axons were labeled via iontophoretic injections of wheat germ agglutinin-horseradish peroxidase into the LGN and intracortical layer IV axons (indirect P and M pathways to the CO-blobs) were labeled by iontophoretic injections of Phaseolus vulgaris leucoagglutinin into layer IV. The neurochemical content of both pre- and postsynaptic profiles was identified by postembedding immunocytochemistry for gamma-amino butyric acid (GABA) and glutamate. Sizes of pre- and postsynaptic elements were quantified by using an image analysis system, BioQuant IV. Our chief finding is that K LGN axons and layer IV axons (indirect input from M and P pathways) exhibit different synaptic relationships to CO blob cells. Specifically, our results show that within the CO blobs: 1) all K cell axons contain glutamate, and the vast majority of layer IV axons contain glutamate with only 5% containing GABA; 2) K axons terminate mainly on dendritic spines of glutamatergic cells, while layer IV axons terminate mainly on dendritic shafts of glutamatergic cells; 3) K axons have larger boutons and contact larger postsynaptic dendrites, which suggests that they synapse closer to the cell body within the CO blobs than do layer IV axons. Taken together, these results suggest that each input pathway to the CO blobs uses a different strategy to contribute to the processing of visual information within these compartments.

Animals↗
PubMed2007

The role of histone acetylation in regulating early gene expression patterns during early embryonic stem cell differentiation.

We have examined the role of histone acetylation in the very earliest steps of differentiation of mouse embryonic stem cells in response to withdrawal of leukemia inhibitory factor (LIF) as a differentiation signal. The cells undergo dramatic changes in morphology and an ordered program of gene expression changes representing differentiation to all three germ layers over the first 3-5 days of LIF withdrawal. We observed a global increase in acetylation on histone H4 and to a lesser extent on histone H3 over this time period. Treatment of the cells with trichostatin A (TSA), a histone deacetylase inhibitor, induced changes in morphology, gene expression, and histone acetylation that mimicked differentiation induced by withdrawal of LIF. We examined localized histone acetylation in the regulatory regions of genes that were transcriptionally either active in undifferentiated cells, induced during differentiation, or inactive under all treatments. There was striking concordance in the histone acetylation patterns of specific genes induced by both TSA and LIF withdrawal. Increased histone acetylation in local regions correlated best with induction of gene expression. Finally, TSA treatment did not support the maintenance or progression of differentiation. Upon removal of TSA, the cells reverted to the undifferentiated phenotype. We concluded that increased histone acetylation at specific genes played a role in their expression, but additional events are required for maintenance of differentiated gene expression and loss of the pluripotent state.

Acetylation↗
PubMed2006

RBP-Jkappa-dependent notch signaling is dispensable for mouse early embryonic development.

The Notch signaling pathway is an evolutionarily conserved signaling system which has been shown to be essential in cell fate specification and in numerous aspects of embryonic development in all metazoans thus far studied. We recently demonstrated that several components of the Notch signaling pathway, including the four Notch receptors and their five ligands known in mammals, are expressed in mouse oocytes, in mouse preimplantation embryos, or both. This suggested a possible implication of the Notch pathway in the first cell fate specification of the dividing mouse embryo, which results in the formation of the blastocyst. To address this issue directly, we generated zygotes in which both the maternal and the zygotic expression of Rbpsuh, a key element of the core Notch signaling pathway, were abrogated. We find that such zygotes give rise to blastocysts which implant and develop normally. Nevertheless, after gastrulation, these embryos die around midgestation, similarly to Rbpsuh-null mutants. This demonstrates that the RBP-Jkappa-dependent pathway, otherwise called the canonical Notch pathway, is dispensable for blastocyst morphogenesis and the establishment of the three germ layers, ectoderm, endoderm, and mesoderm. These results are discussed in the light of recent observations which have challenged this conclusion.

Animals↗
PubMed1993

Analysis of the gooseberry locus in Drosophila embryos: gooseberry determines the cuticular pattern and activates gooseberry neuro.

The segment-polarity class of segmentation genes in Drosophila are primarily involved in the specification of sub-segmental units. In addition, some of the segment-polarity genes have been shown to specify cell fates within the central nervous system. One of these loci, gooseberry, consists of two divergently transcribed genes, gooseberry and gooseberry neuro, which share a paired box as well as a paired-type homebox. Here, the expression patterns of the two gooseberry gene products are described in detail. The gooseberry protein appears in a characteristic segment-polarity pattern of stripes at gastrulation and persists until head involution. It is initially restricted to the ectodermal and neuroectodermal germ layer, but is later detected in mesodermal and neuronal cells as well. The gooseberry neuro protein first appears during germ band extension in cells of the central nervous system and also, much later, in epidermal stripes and in a small number of muscle cells. P-element-mediated transformation with the gooseberry gene has been used to demonstrate that gooseberry transactivates gooseberry neuro and is sufficient to rescue the gooseberry cuticular phenotype in the absence of gooseberry neuro.

Animals↗
PubMed1987

The histone H1(0)/H5 variant and terminal differentiation of cells during development of Xenopus laevis.

The maintenance of the differentiated condition is supposed to be associated with the presence of a histone of the H1(0)/H5 subclass. If the H1(0)/H5 variant has an important role in differentiation distinct from that of H1, it should display differential expression in time and position during development. Here we report that this prediction is verified during Xenopus laevis development, in which tadpoles exhibit a very characteristic, developmentally regulated pattern of histone H1(0)/H5 expression that is different for the derivatives of each embryonic germ layer. However, the pattern of appearance of this variant during development does not reflect a simple correlation between its presence and the state of differentiation. Therefore, these results are pertinent to current ideas on differentiation and the involvement of lysine-rich histones in the repression of eukaryotic genes.

Aging↗
PubMed1985

[Occurrence of molds in airborne dusts in poultry farms].

To reach conclusions in terms of industrial hygiene, mycological samples were taken in modern poultry farms between 1979 and 1981. Sedimentation plates, the Krotow slit collector and the SPG-10 airborne dust sampler were used to determine the mould content of the air. The lowest germ counts were made in cage systems, while somewhat higher numbers were recorded among adult bids kept in the floor systems. Unexpectedly high numbers of mould germs were found in the air of large poultry houses where chickens were reared on relatively fresh litter. The fungus genera Penicillium and Cladosporium and, in one case, the species Scopulariopsis brevicaulis were predominant on old litter in both the floor and the cage system, whereas moulds of the Aspergillus group (Aspergillus candidus and A. versicolor) were additionally existent on fresh straw layers.

Agriculture↗
PubMed2001

Translational control in vertebrate development.

Translational control plays a large role in vertebrate oocyte maturation and contributes to the induction of the germ layers. Translational regulation is also observed in the regulation of cell proliferation and differentiation. The features of an mRNA that mediate translational control are found both in the 5' and in the 3' untranslated regions (UTRs). In the 5' UTR, secondary structure, the binding of proteins, and the presence of upstream open reading frames can interfere with the association of initiation factors with the cap, or with scanning of the initiation complex. The 3' UTR can mediate translational activation by directing cytoplasmic polyadenylation and can confer translational repression by interference with the assembly of initiation complexes. Besides mRNA-specific translational control elements, the nonspecific RNA-binding proteins contribute to the modulation of translation in development. This review discusses examples of translational control and their relevance for developmental regulation.

Animals↗
PubMed1996

Interaction of human immunodeficiency virus type 1 envelope glycoprotein gp120 with a galactoglycerolipid associated with human sperm.

The expression of a molecule recognized by anti-galactosyl ceramide antibodies (MAb) O1 on the surface membrane of human spermatozoa was investigated by biochemical and immunochemical methods. Indirect immunofluorescence shows that this molecule is preferentially localized on the middle piece of the sperm tail. Immuno-thin-layer chromatography has identified it as a glycolipid related but not identical to galactosylceramide. Consistent with a structure similar to galactosylceramide, the sperm glycolipid is capable of binding gp120. An improved ELISA has been utilized to demonstrate the specificity of binding of the antibodies and gp120 to the isolated lipid fraction. Identity of the binding site of the two ligands to the glycolipid is suggested by competition assays. On the basis of preliminary biochemical analysis this glycolipid was tentatively classified as a galactosylalkylacylglycerolipid (GalAAG), the nonsulfated form of the seminolipid, a glycolipid known to be present in the testis and germ cells of mammals. These data indicate that human sperm express a glycolipid similar in structure to the receptor for HIV described on the CD4- neural and colonic epithelial cell lines, and moreover suggest that this glycolipid could also function as HIV receptor and possibly be implicated in its transmission.

Antibodies, Monoclonal↗