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At least 847 records · Page 47Linked to original sources
PubMed2004

Comparison of c-Fos immunoreactivity in pancreatic beta cells and cells with neural crest, endoderm and mesoderm origin in rats.

AIMS: Pancreatic beta cells are known to share many similarities with neuronal cells, but their origin remains controversial. It has been hypothesized that pancreatic beta cells are derived from neural crest cells. The aim of this study was to investigate the similarities between pancreatic beta cells and cells with neural crest, endoderm and mesoderm origin with respect to c-Fos immunoreactivity (c-Fos-ir), which has a role in important cellular processes including cellular proliferation, growth, differentiation and apoptosis. METHODS: c-Fos-ir was analyzed by immunohistochemical methods in formaline-fixed, paraffin-embedded sections of rat pancreatic beta cells (BCs), in adrenal medullary chromaffin cells (CCs) that are derived from neural crest, in exocrine pancreatic acinar cells (ACs) that are derived from endoderm, and in adrenal cortex zona reticularis cells (RCs) that are derived from mesoderm. RESULTS: The statistical comparisons revealed no significant differences between BCs and CCs with respect to c-Fos-ir (p>0.05). However, a highly significant difference (p<0.001) with respect to c-Fos-ir both between ACs and RCs, and between these two cell types and each of the two other cell types was noted. CONCLUSIONS: As opposed to findings in cells without neural crest origin, the observed similarity between BCs and CCs with respect to c-Fos-ir, provides additional evidence for the similarity of these cells with cells derived from neural crest.

Adrenal Cortex↗
PubMed1997

Short historical survey of pattern formation in the endo-mesoderm and the neural anlage in the vertebrates: the role of vertical and planar inductive actions.

After some introductory remarks about vertical versus horizontal inductive interactions and about planar versus homoiogenetic induction, the author discusses: a) the historical development of the more recently studied endo-mesoderm induction in the Urodeles and in the anuran Xenopus laevis, b) the possible causal relationship between endo-mesoderm induction and the initiation of the gastrulation process, and c) the older history of the regional neural induction as initially studied in the Urodeles and only recently analysed in the anuran Xenopus laevis. The essential vertical interaction in the neural induction process both in urodelian and in anuran amphibians is emphasized.

Amphibians↗
PubMed1997

Mesoderm-derived cells proliferate in the embryonic central nervous system: confocal microscopy and three-dimensional visualization.

In the chick and quail embryo, two cell populations migrate into the neural tube from the surrounding mesodermal tissues during the fourth day of incubation: individual cells which represent macrophages, and endothelial cells which remain continuous with the extraneural vessels. We report here on the proliferative capacity of these mesoderm-derived cells. A double-immunofluorescence protocol for two monoclonal antibodies of subtype IgG1, the endothelial cell/macrophage marker QH1, and the S-phase marker bromodeoxyuridine, was developed. With confocal laser scanning microscopy of thick microtome sections, labeling indices of intraneural individual QH1-positive cells (12%) and of endothelial cells (10%) were determined. In contrast, the labeling index of extraneural endothelial cells was 25%. With three-dimensional visualization of confocal data, the variable morphology of macrophages was shown. Our results indicate that: (1) proliferative activity of intraneural capillary endothelial cells is less than expected and that it is absent from sprouts; (2) both spheroidal and ramified macrophages proliferate inside the neural tissues; and (3) ramified macrophages frequently make contact with capillary endothelial cells. We conclude that most embryonic microglia may be derived from the early invasive QH1+ macrophages.

Animals↗
PubMed2001

Homologues of c-hairy1 (her9) and lunatic fringe in zebrafish are expressed in the developing central nervous system, but not in the presomitic mesoderm.

A number of genes that are involved in somitogenesis in vertebrates are cyclically expressed in the presomitic mesoderm. These include homologues of the Drosophila genes fringe and hairy. We have analysed here two genes that belong to these classes in the zebrafish, namely the apparent orthologues of lunatic fringe (l-fng) and of c-hairy1 (called her9). However, unlike the respective mouse and chicken genes, they are not expressed cyclically in the presomitic mesoderm. Instead, both genes are mainly expressed in the central nervous system. her9 is predominantly expressed in the fore- and midbrain, and transiently in the hindbrain. Thus, the previously identified and only very distantly related her1 gene of zebrafish has more similarities to the expression of the c-hairy1 gene than its apparent orthologue her9, indicating that sequence similarity and similarity of function are not necessarily linked in this case. l-fng expression is found in alternating pre-rhombomeres, comparable to the equivalent mouse gene expression and in the anterior compartments of the mature somites, which was also shown for the chicken l-fng gene. The latter expression indicates that it might be involved in boundary definition and cell fate decision processes, rather than in pre-patterning of the somites. Interestingly, a similar role has previously been inferred for the grasshopper homologue of l-fng. This suggests that the function of l-fng in boundary definition of the somites might be ancestral, while its recruitment to the pre-patterning process of the somites might be a derived feature in higher vertebrates.

Amino Acid Sequence↗
PubMed2003

Characterization and expression of a presomitic mesoderm-specific mespo gene in zebrafish.

A complete zebrafish mespo cDNA encoding a protein of 131 amino acids with a bHLH domain in the C-terminal has been isolated. The bHLH domain of zebrafish Mespo is highly similar to those in the mouse, chick and Xenopus, sharing 82.4%, 80.4% and 74.5% amino acid identity, respectively. At 50% epiboly, the zebrafish mespo is first detected in the marginal zone of the blastoderm but excluding the prospective shield. Subsequently, mespo expression is intensified in the involuting mesoderm at 60% epiboly, and then restricted to the presomitic mesoderm (PSM) at 95% epiboly. At the 1-somite stage, mespo expression becomes reduced in the most rostral PSM. During segmentation, mespo expression is gradually downregulated at the most rostral segmental plate where cells are being coalesced to form somites. In spadetail mutant embryos, most of mespo-expressing cells were missing.

Amino Acid Sequence↗
PubMed2005

Tribolium mae expression suggests roles in terminal and midline patterning and in the specification of mesoderm.

In Drosophila, the Mae protein ("modulator of the activity of Ets") regulates receptor tyrosine kinase (RTK)-dependent mitogen-activated protein kinase (MAPK) signaling. Mae has been shown to bind the Yan and Pointed-P2 transcription factors, thereby changing their ability to activate or repress target genes. In this work we show that the mae ortholog of the red flour beetle Tribolium castaneum (Tc'mae) is active at the posterior, but not the anterior pole of the blastoderm. Since MAPK signaling is known to be active at both poles, Tc'Mae could function to modulate terminal MAPK signaling to differentiate the developmental programs at the anterior and posterior poles of the Tribolium blastoderm embryo. Tc'mae is also expressed along the midline of the germband, similar as in Drosophila, where it is involved in the patterning of midline cells. Before gastrulation and in the growth zone, Tc'mae is active in mesoderm precursor cells. This suggests that in short germ embryos MAPK signaling may also be involved in the specification of mesoderm.

Amino Acid Sequence↗
PubMed1999

Regulation by members of the transforming growth factor beta superfamily of the digital and interdigital fates of the autopodial limb mesoderm.

Embryonic limb outgrowth is accomplished by the proliferation of mesodermal cells in the progress zone. In this region, mesodermal cells are maintained in an undifferentiated and proliferating state by the action of the apical ectodermal ridge (AER). Differentiation of these cells into individual skeletal elements occurs when the cells are displaced proximally and leave the influence of the AER as a consequence of the accumulation of cells in that region. Here we review the evidence obtained in the last few years showing that members of the transforming growth factor beta (TGFbeta) subfamily and bone morphogenetic proteins (BMPs) act as proximal signals in the autopod regulating the fate of the progress zone cells towards chondrogenesis or apoptosis. Our findings show that apoptosis is regulated by BMPs while chondrogenesis requires the interaction of TGFbetas and BMPs. Fibroblast growth factors (FGFs) produced by the AER exert an opposite function to both TGFbetas and BMPs, maintaining the progress zone cells in an undifferentiated state.

Animals↗
PubMedDate not supplied

Case report of a 22-week fetus with 47,XXX karyotype and multiple lower mesodermal defects.

A 22-week stillborn fetus with 47,XXX karyotype had lower mesodermal defects consisting of irregular fusion of the sacral vertebrae, anal agenesis, multicystic dysplasia of a horseshoe kidney, a single umbilical artery, dysplastic ovaries, and uterine hypoplasia. This case provides additional evidence for an association between trisomy X and genitourinary defects including lower mesodermal defects sequence.

Abnormalities, Multiple↗
PubMed2000

Effects of Polycomb group mutations on the expression of Ultrabithorax in the Drosophila visceral mesoderm.

The Polycomb group (PcG) genes encode repressors of many developmental regulatory genes including homeotic genes and are known to act by modifying chromatin structure through complex formation. We describe how Ultrabithorax (Ubx) expression is affected by the PcG mutants in the visceral mesoderm. Mutant embryos of the genes extra sex combs (esc), Polycomb (Pc), additional sex combs (Asx) and pleiohomeotic (pho) were examined. In each mutation, Ubx was ectopically expressed outside of their normal domains along the anterior-posterior axis in the visceral mesoderm, which is consistent with the effect of PcG proteins repressing the homeotic genes in other tissues. All of these four PcG mutations exhibit complete or partial lack of midgut constriction. However, two thirds of esc mutant embryos did not show Ubx expression in parasegment 7 (PS7). Even in the embryos showing ectopic Ubx expression, the level of Ubx expression in the PcG mutations was weaker than that in normal embryos. We suggest that in PcG mutations the ectopic Ubx expression is caused by lack of PcG repressor proteins, while the weaker or lack of Ubx expression is due to the repression of Ubx by Abd-B protein which is ectopically expressed in PcG mutations as well.

Animals↗
PubMed1983

The origin of the mesoderm in an anuran, Xenopus laevis, and a urodele, Ambystoma mexicanum.

We have investigated whether superficial cells of the blastula contribute to mesodermal structures in the anuran Xenopus laevis and the urodele Ambystoma mexicanum. The superficial cells alone of late blastulae of both embryos were labelled with Bolton-Hunter reagent and the embryos were allowed to develop. The progeny of the labelled cells were identified at later stages and the results demonstrate that superficial cells of Xenopus blastulae make no significant contribution to the mesoderm, whereas those of the axolotl Ambystoma always contribute.

Ambystoma↗
PubMed1987

Pathfinding by pioneer neurons in isolated, opened and mesoderm-free limb buds of embryonic grasshoppers.

The Ti1 afferent neurons are the first neurons to undergo axonogenesis in limb buds of embryonic grasshoppers. Their growth cones pioneer a stereotyped pathway through the limb which becomes the route of one of the major leg nerve trunks. The growth cones appear to be oriented by several kinds of guidance cues, including guidepost neurons, a developing limb segment boundary, and an additional proximally orienting cue(s). In the experiments reported here, we have investigated the possible nature and source of proximally orienting and segment boundary cues by surgical manipulations of the limb. Before the onset of pioneer axonogenesis, limbs were isolated from the body, opened longitudinally and pinned out flat, or stripped of mesoderm. Pioneer axon routes in cultured, surgically manipulated limb buds were compared to routes in cultured control limbs. The results indicate that proximal extension of pioneer growth cones along the limb axis does not require (during the period of growth) tissue extrinsic to the limb, contact guidance by the limb contour, an axial electrical field, a diffusion gradient generated by a localized source, mesodermal cells, or guidepost neurons; adequate guidance information for proximal growth apparently can be provided by the limb epidermal epithelium (including the basal lamina) and/or by internal polarity of the pioneer neurons. Adequate guidance information for the segment boundary portion of the pioneer route apparently can be provided by the limb epithelium.

Animals↗
PubMed1990

Temporal changes in the response of chick limb bud mesodermal cells to transforming growth factor beta-type 1.

Transforming growth factor beta (TGF beta) has been found in adult and developing bone in vivo and has varied effects on chondrocytes and osteoblasts in culture. We investigated the effects of TGF beta-type 1 on embryonic chick endochondral bone precursors in culture. Stage 24 chick limb bud mesoderm cells were cultured at high density. Under these conditions a dense mat containing nodules of cartilage surrounded by alkaline phosphatase-positive cells formed. Exposure of mesodermal cells to TGF beta-type 1 over the course of 4-7 days or during Days 3 and 4 caused a reduction in alkaline phosphatase activity and [35S]sulfate incorporation into proteoglycans. When the TGF beta-type 1 was applied during Days 1-2, it caused an increase in both parameters: these increases were observed in the absence of a corresponding change in [3H]thymidine incorporation. The specificity of the effects of TGF beta-type 1 was confirmed by neutralizing antibodies. These studies show that TGF beta-type 1 modulates the phenotype of embryonic endochondral bone precursors. The influence may depend on the window of exposure to the growth factor and, therefore, on the state of differentiation of the cells.

Alkaline Phosphatase↗
PubMed1991

Stimulation of chondrogenesis in limb bud mesoderm cells by recombinant human bone morphogenetic protein 2B (BMP-2B) and modulation by transforming growth factor beta 1 and beta 2.

Bone morphogenetic protein 2B (BMP-2B) also called BMP-4 is one of a family of cartilage and bone-inductive proteins derived from bone matrix and belongs to the transforming growth factor beta (TGF-beta) superfamily. These bone-inductive proteins isolated from adult bone may be involved in bone repair. However, they may also play a role in cartilage and bone formation during embryonic development. To test whether BMP-2B influences cartilage formation by embryonic cells, recombinant human BMP-2B was applied to cultured limb bud mesoderm plated at three different densities. BMP-2B stimulated cartilage formation as assessed by Alcian blue staining and incorporation of radioactive sulfate into sulfated proteoglycans. Cells cultured at all three densities in the presence of 10 ng/ml BMP-2B formed a nearly continuous sheet of cartilage with abundant extracellular matrix and type II collagen. In addition, when cells were cultured in 0.5% serum in the presence of 10 ng/ml of BMP-2B for 5 days there was an increase in alkaline phosphatase as detected by histochemical and biochemical methods. Transforming growth factor beta isoforms (TGF-beta 1 and TGF-beta 2) inhibited sulfate incorporation into proteoglycans in a dose-dependent manner. This inhibition by TGF beta was overcome by recombinant BMP-2B. This study demonstrates that recombinant BMP-2B stimulates cartilage formation by chick limb bud mesoderm in vitro and is further modulated by TGF-beta isoforms.

Alkaline Phosphatase↗
PubMed1988

Induction of mesodermal tissues by acidic and basic heparin binding growth factors.

The inducing activity of two heparin binding growth factors HBGF-1 (prostate epithelial cell growth factor; acidic pI) and HBGF-2 (fibroblast growth factor; basic pI) from bovine brain has been tested on totipotent ectoderm from early amphibian (Xenopus laevis, Ambystoma mexicanum) embryos. Both factors induced, at high concentrations, mostly compact spheres surrounded by a non-epidermal epithelium. When the concentration or time of incubation was reduced, large muscle inductions frequently organized as somites were formed besides endothelial vesicles, mesenchyme and smaller areas of intestine-like epithelium. Further reduction of the concentrations or the time of incubation led to an increase in size and number of endothelium-lined vesicles and of mesenchyme, whereas the induction of muscle decreased. At still lower concentrations the overall rate of inductions decreased. The relationship of the growth factors to the vegetalizing factor from chicken embryos, dilution of which shows a similar shift in induced organs, is discussed. The present and previous experiments suggest that different mesodermal and endodermal tissues are induced by secondary interactions in which additional factors are involved. The induced organs derive from dorsal as well as from ventral mesoderm.

Animals↗
PubMed1990

Activins are expressed early in Xenopus embryogenesis and can induce axial mesoderm and anterior structures.

We show that mammalian and Xenopus activins induce dorsal axial mesoderm and anterior structures in explants of Xenopus blastula cells that would otherwise form epidermis. The induced explants of animal cap cells can form notochord, muscle, neural tissue, and eyes all arranged in a rudimentary axial pattern. Activin A shares inductive properties and antigenic determinants with PIF, an inducing factor recently isolated from mouse macrophage culture supernatants. Genes encoding Xenopus activin beta A and beta B chains were cloned. Activin beta B transcripts are first detected in Xenopus blastula, whereas activin beta A transcripts do not appear until the late gastrula stage. Recombinant Xenopus activin beta B protein induces mesodermal and neural tissues similar to those induced by mammalian activin A and PIF. Furthermore, ectopic expression of Xenopus activin beta B produces a second body axis in embryos injected with synthetic mRNA. Our results suggest that early induction and axial patterning are accomplished by endogenous activin B, not activin A, in Xenopus.

Activins↗
PubMed1991

Ubiquitous MyoD transcription at the midblastula transition precedes induction-dependent MyoD expression in presumptive mesoderm of X. laevis.

We have used a quantitative reverse transcription-polymerase chain reaction assay to detect MyoD mRNA during early embryonic development of Xenopus laevis. We find that during a short period of time following the midblastula transition MyoD becomes transcriptionally activated at a low level ubiquitously throughout the embryo. Restriction of MyoD expression to muscle precursor cells appears as a subsequent event, in which the process of mesoderm induction stabilizes transcription only in the marginal zone of the embryo, the presumptive mesoderm.

Animals↗
PubMed1993

Processed Vg1 protein is an axial mesoderm inducer in Xenopus.

Vg1 is a TGF beta-related growth factor encoded by a maternal mRNA localized to vegetal blastomeres in Xenopus embryos. Vg1 precursor protein is abundant in vegetal cells, but the processed mature form has not been readily detected and no activity has been demonstrated for the putative Vg1 mature protein. We have engineered a BMP2-Vg1 fusion (BVg1) that promotes formation of mature Vg1 protein in vivo. Injection of BVg1 mRNA induces dorsal mesoderm in animal cap cells, and BVg1 expression in ultraviolet-ventralized embryos fully restores a normal dorsal axis. Blastomeres expressing BVg1 act as a Nieuwkoop center, the region that induces the Spemann organizer. our results lead us to suggest that localized posttranslational processing of Vg1 precursor protein on the future dorsal side of the embryo is a key step in generating dorsal mesoderm and the body axis in Xenopus.

Amino Acid Sequence↗
PubMed1983

Peritoneal exudate in larval Rana pipiens contains cells that are embryologically derived from dorsal lateral plate mesoderm.

The embryonic origin of cells functioning in a peritoneal exudate response of larval Rana pipiens was investigated. Normal larva received injections of sodium caseinate on day 0 and cells in the peritoneal cavity were assayed on days 3, 5, 7, 9, 11, 13 and 16. Experimental animals that received cytogenetically labeled transplants of dorsal mesoderm at 67-72 hours of development were injected with sodium caseinate on day 0 and assayed on days 5, 7 and 9. Feulgen-DNA microdensitometric analysis showed that the peritoneal exudate from days 5, 7, 9 contained hemopoietic cells that were derived from the embryonic transplant. Therefore, dorsal mesoderm gave rise to cells capable of functioning in a peritoneal exudate response to injections of sodium caseinate.

Animals↗