SEARCH · Search PubMed

Results for “mesoderm”

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.

SourceResearch connectionFrom yearThrough year

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

At least 577 records · Page 32Linked to original sources

PubMed1992

Mechanisms of early Drosophila mesoderm formation.

Several morphogenetic processes occur simultaneously during Drosophila gastrulation, including ventral furrow invagination to form the mesoderm, anterior and posterior midgut invagination to create the endoderm, and germ band extension. Mutations changing the behaviour of different parts of the embryo can be used to test the roles of different cell populations in gastrulation. Posterior midgut morphogenesis and germ band extension are partly independent, and neither depends on mesoderm formation, nor mesoderm formation on them. The invagination of the ventral furrow is caused by forces from within the prospective mesoderm (i.e. the invaginating cells) without any necessary contribution from other parts of the embryo. The events that lead to the cell shape changes mediating ventral furrow formation require the transcription of zygotic genes under the control of twist and snail. Such genes can be isolated by molecular and genetic screens.

Animals↗

PubMed2003

Origin and evolution of endoderm and mesoderm.

Germ layers are defined as cell layers that arise during early animal development, mostly during gastrulation, and that give rise to all tissues and organs in adults. The evolutionary origin of the inner germ layers, endoderm and mesoderm, and their relationship have been a matter of debate for decades. In this review we summarize the major modes of endoderm and mesoderm formation found in Metazoa and possible evolutionary scenarios to reconstruct the ancestral state. In the second part, we address the question whether endoderm as well as mesoderm are homologous among Bilateria. In this regard, we propose that the comparative analysis of some crucial transcription factors involved in the early specification and differentiation of these germ layers might provide cues for the level of homology. We focus on four classes of genes: the Zn-finger gene GATA 4-6, the bHLH gene twist, the Krüppel-like Zn-finger gene snail and the T-box gene brachyury. The role of each of these genes in mesendoderm formation is summarized and we propose that the specific function of each of these genes in endoderm and mesoderm formation evolved from the regulation of basic cellular features, such as cell adhesion, cell motility, cytoskeleton and cell cycle.

Animals↗

PubMed1991

Dose and time-dependent mesoderm induction and outgrowth formation by activin A in Xenopus laevis.

We examined the quality of mesoderm induced by the action of activin A on the Xenopus presumptive ectoderm when various concentrations and treatment times were employed. The minimum concentration of activin A to induce mesodermal tissues was inversely proportional to its treatment time. The explants differentiated into different types of mesodermal tissues, from ventral-type to dorsal-type depending on the concentration of activin A and its treatment time. To confirm whether activin A has a role in establishing axial organization, activin A was injected into the blastocoel of late blastulae. About 70% of the injected embryos formed secondary tail-shaped outgrowths in which muscle and neural tube differentiated. The amount of activin A to form secondary outgrowths was 0.5-2.5 pg, roughly consistent with the amount estimated from in vitro experiments. As we have detected almost the same amount of activin homologue in the early embryos (Asashima et al., 1991a), we speculate that activin A may be the natural mesodermal inducer, and that it is responsible for establishing axial organization in the Xenopus embryo.

Activins↗

PubMed1987

Scanning electron microscopy of the aggregation of head mesoderm cells from chick embryos.

Head mesoderm cells from chick embryos at different stages of development were dissociated and cultured on plastic coverslips. In all cultures several cellular aggregates were described by means of scanning electron microscopy. Isolated cells present filopodia and lamellipodia. However, when mesoderm cells make contact with one another the filopodial and lamellipodial activity in the contact cellular edge disappear. Thus, the cells into cellular clusters do not present projections. The clusters were circular and bidimensional in character. The scanning electron microscopic observations showed that it is the type 1 variant of "contact inhibition of locomotion" which occurs. By means of these mechanisms the bidimensional aggregates are formed and cellular overlapping is not present. Since the behaviour of the mesoderm cells "in vitro" in some way could be comparable to their behaviour "in situ", the results here observed are discussed in relation to the conduct of mesoderm cells "in vivo".

Animals↗

PubMed1986

A study of the pattern of prospective somites in the presomitic mesoderm of mouse embryos.

Consistently six to seven somites were formed in explants of presomitic mesoderm of 8.5-day to 11.5-day mouse embryos and this number correlated well with the number of somitomeres previously identified in the same tissue by stereo SEM (Tam, Meir & Jacobson, 1982). During this period of development, the size of the presomitic mesoderm varied up to two-fold but the number of prospective somites remained unchanged. This pattern in the presomitic mesoderm was stable with respect to the number and the position of somites that were formed, the craniocaudal sequence and the rate of segmentation. The prospective somite also went through an orderly sequence of expansion and cellular rearrangement prior to segmentation. During the differentiation of the presomitic mesoderm, somites were formed at the expense of somitomeres, suggesting that the somitomere was a morphological manifestation of the prospective somite.

Animals↗

PubMed1986

Changes in the transferrin requirement of cultured chick embryo mesoderm cells during early differentiation.

Mesodermal tissue from the chick embryo at various stages of early differentiation was cultured in hydrated gels of type I collagen in the presence and absence of transferrin. Primary mesoderm explants from primitive-streak-stage embryos responded to the presence of avian transferrin by significantly improved outgrowth which appeared to be related to the ability of the cells to attach to, and migrate in, the collagen. No evidence was obtained which suggested that this observation was dependent on increased cell proliferation. This outgrowth enhancement was not duplicated by transferrin of human origin. The avian transferrin did not produce this effect on cells cultured on plastic substrata, suggesting that the species-specific effect involves modulation by the extracellular matrix. Mesoderm explants from somite stages of development showed no increase in outgrowth in the presence of either avian or human transferrin as judged by counting the number of outwandering cells. Ultrastructural immunocytochemistry indicated surface binding of transferrin by cells in the gels, and the presence of endogenous transferrin on the surfaces of mesoderm cells in situ and in their extracellular environment. It is suggested that by binding to cell surface receptors, transferrin may be able to influence the strength of cellular adhesion to collagen and hence the capacity for cell locomotion.

Animals↗

PubMed1985

Morphological observations on the mesodermal cells in the 8 day opossum embryo.

Cells of the mesodermal layer of the 8 day opossum were examined by scanning and transmission electron microscopy after removal of the ectoderm. The mesodermal layer is formed by a multilayered network of large somewhat flattened, stellate-shaped cells, whose broad surfaces usually lie parallel to the external surface of the embryo. The mesodermal cells show numerous cytoplasmic processes which often appear as long delicate threads that may branch. The processes may course for considerable distances and establish contact with adjacent mesodermal cells. Contact points between processes, processes and cells, and between adjacent cell bodies showed junctional complexes. Most of the junctional complexes appeared morphologically similar to the nexus (communicating) type. Occasional desmosome-like junctions also were observed. Extracellular fibers were not observed.

Animals↗

PubMed1979

Role of the somitic mesoderm in the development of the thorax in bird embryos. II. Origin of thoracic and appendicular musculature.

The regional embryonic origin of trunk and limb musculature was determined through heterospecific homotopic or heterotopic transplantations of quail somitic or somiticsomatopleural mesoderm into chick hosts, and through localized X-irradiation of the somitic mesoderm. Experiments were performed on 2-day embryos. Results show that the myoblastic component of all truncal and appendicular muscles is of somitic origin. Intra- and perimuscular connective tissue as well as tendons are of somatopleural origin. X-ray destruction of the somitic mesoderm at and beyond the wing level resulted in the complete or almost complete absence of musculature in the wing and corresponding truncal region. The mapping of the cephalocaudal origin of the various muscles was found to be as follows: Intrinsic and extrinsic muscles of the wing and scapular girdle Somites 12-20 Grand pectoral muscle Somites 12-22 Intercostal muscles Somites 19-26 Abdominal muscles Somites 27-29 Intrinsic and extrinsic muscles of the leg and pelvic girdle Somites 26-32 Dorsal and intervertebral muscles Metameric level, specific origin In the heterotopic transplantations, the grafted somitic mesoderm gave rise to site-specific morphogenesis, irrespective of the cephalocaudal level of its origin. This result demonstrates that, at 2 days of incubation, the myogenic somitic cells are not regionalized.

Animals↗

PubMed1978

Limb-somite relationship: effect of removal of somitic mesoderm on the wing musculature.

The aim of this study is to test the ability of the intrinsic wing musculature to develop in the absence of somitic mesoderm. The experiments were performed on 2- to 2.5-day chick embryos either by replacing the somitic mesoderm adjacent to the wing field with a piece of 9-day chick embryonic midgut or by destroying, through local X-irradiation, not only the somitic mesoderm of the wing level, but also at least three somites (or presumptive somites) anterior and/or three presumptive somites posterior to the wing level. The replacemnt of somitic tissue scarcely affected the organogenesis of the forearm musculature, at least when both bones were present. In the other experiments, radio-destruction severely impaired the development of the forearm muscles, which were seldom all present and in most cases were entirely missing. The absence of a given muscle involves the simultaneous absence of the corresponding tendons. The possible origins of the muscles that formed despite the removal of the somitic mesoderm are discussed.

Animals↗

PubMed1983

[Experimental study of the effect of the ectoderm on the chondrogenic differentiation of the mesoderm of the mouse embryo limb in vitro. Results of a histological analysis].

The histological study of cultures of distal limb bud tips of 11 days old Mouse embryos and of dissociated mesoderm obtained from identical tips enabled us to demonstrate that distal bud mesoderm spontaneously differentiate into cartilage in vitro if its normal ectodermal covering is removed. If the ectoderm is present in situ or in close vicinity, the chondrogenic differentiation does not occur and mesodermal cells develop into a loose mesenchyme where numerous mitosis are observed. Experimental associations performed between limb bud mesoderm and epithelial sheets other than limb ectoderm demonstrated that the properties of this ectoderm are specific.

Animals↗

PubMed1993

[Regionalization of the expression of tenascin as a response to the inducers of mesoderm].

Tenascin (TN) is an extracellular matrix (ECM) glycoprotein which possesses antiadhesive properties and thus is able to modulate cell interactions with molecules of the ECM. In Xenopus embryos, TN is expressed dorsally in a very restricted pattern. We have studied the distribution of TN mRNA in tailbud-stage embryos by in situ hybridization. We show that TN transcripts are principally expressed in myotome cells. No TN mRNA could be detected in lateral plate mesoderm. This had led us to study TN expression in response to mesodermal inducers. Analysis of the distribution of TN after mesodermal induction of blastula animal caps with activin A and bFGF or after ectopic expression of XBra shows that TN expression is elicited when dorsal or posterior structures are formed. Our results show that TN regionalization in Xenopus embryos depends on mesoderm patterning.

Activins↗

PubMed1993

[Synchronous growth of a mixed mesodermal tumor and an adenocarcinoma of the urinary bladder].

The case of synchronous growth of a mesodermal mixed tumour and an adenocarcinoma in the bladder is presented. This is a rare phenomenon. Mesodermal mixed tumours are malignancies with both epithelial (carcinoma) and mesenchymal (sarcoma) differentiation. The term carcinosarcoma is frequently used in the literature. In most cases the prognosis of mesodermal mixed tumours, which depends mainly on the high rate of local recurrences, is poor. Therefore, cystectomy with suprapubic urinary diversion is the treatment of choice. However, results reported in the literature show that transurethral resection of the tumour may be adequate when there is only superficial growth of mesodermal mixed tumours. Short follow-up intervals are absolutely essential for patients treated this way.

Adenocarcinoma, Papillary↗

PubMed1977

[Contractility and epithelization in the chick embryo axial mesoderm].

The still unsegemented axial mesoderm was cross cut at different distances form the last somite under the normal physiological conditions, at the low temperature and under the effect of cytochalasin B. Under the normal conditions the inner cells of the axial mesoderm formed a lens-shaped cleft immediately after the operation; this movement was suppressed at the low temperature and absent under the effect of cytochalasin B. This suggests the active contractility of the mesodermal syncytium. The wound margin near the last somite acquired the epithelial structure already within several minutes after the cut, whereas in the more caudal regions it preserved the connective tissue character for a long time. The importance of the axial mesoderm contractility and its ability of epithelization for the somitogenesis is discussed.

Animals↗

PubMed1998

Involvement of NF-kappaB associated proteins in FGF-mediated mesoderm induction.

In this report, we have used mRNA injection to study the action of mutants of XrelA, a Xenopus homolog of the RelA (p65) component of NF-kappaB, on the induction of mesoderm in Xenopus embryos. A region of the rel homology domain of XrelA was deleted to create XrelA deltaSP, which retains the dimerization and activation domains, but no longer binds to DNA. We also made an analogous derivative of mammalian NF-kappaB1 (p50). We show that both constructs have dominant inhibitory activity. When message encoding either is injected into eggs or oocytes, DNA binding of rel family members is suppressed, as is transactivation of a kappaB-dependent promoter in embryos. Expression of XrelA deltaSP in animal caps blocks the induction of mesoderm by bFGF. In addition, this mutant prevents elongation movements generated by activin, but has little effect on posterior dorsal cytodifferentiation, which in marked contrast is blocked by inhibition of the FGF signal transduction pathway between the receptor and MAP kinase. The specificity of the XrelA deltaSP effect on FGF signaling is shown by rescue of mesodermal marker expression when XrelA deltaSP is co-expressed with a specific rel inhibitor. The target of these dominant negative constructs seems to be neither XrelA itself, nor p50, but rather some other molecule with which XrelA, rather than NF-kappaB1, heterodimerizes. We show that XrelA deltaSP blocks FGF induction of mesoderm downstream of MAP kinase and Xbra expression. Thus it prevents the maintenance of Xbra expression by inhibiting its autoregulation by embryonic FGF (eFGF). We suggest that XrelA deltaSP differs from other reported inhibitors of FGF signaling because it inhibits only gastrula stage FGF signaling and not the maternally programmed signaling at the blastula stage. Our results therefore suggest that zygotic FGF action is required for cell movements rather than dorsal differentiation.

Activins↗

PubMed1998

[Mixed uterine mesodermal sarcoma in the population of southern Israel in the years 1996-1971--clinical and pathological characteristics].

During 1971-1996, 17 patients with mixed mesodermal uterine tumors were treated. Average age at diagnosis was 67.3 years, 12/17 were of European and 5/17 of Afro-Asian extraction. The overall 5-year survival was 21%. 10/17 patients had mixed mesodermal tumors with a heterologous mesenchymal element, and 7/17 had a homologous mesenchymal element (carcinosarcoma). 6/17 had another primary malignancy, including breast cancer (3/17), bilateral metachronous breast tumor (2/17), and malignant lymphoma of the neck region (2/17). All 3 with breast cancer had previously been treated with tamoxifen. I had simultaneous mesodermal tumor and ovarian thecoma. Simultaneous autoimmune manifestations occurred in 2/17, including thrombocytopenic purpura in 1, and myasthenia gravis in another. Mesodermal tumor of the uterus is a relatively rare malignancy with aggressive behavior and poor prognosis. It also had unusual associations with other primary tumors, hormonal treatment, and autoimmune manifestations.

Aged↗

PubMed1998

FGF-2 alters the fate of mouse epiblast from ectoderm to mesoderm in vitro.

We have developed an in vitro differentiation assay to characterize the ability of peptide growth factors to induce differentiation in mouse epiblast. We report that culturing explants of mouse anterior epiblast, a tissue normally fated to give rise to neuroectoderm and surface ectoderm, in a serum-free, chemically defined medium with 10-50 ng/ml of FGF-2 induced gross changes in cell morphology. Treated cells adopted an elongated, flattened morphology but did not migrate from the explant. Instead, FGF-2-treated cells condensed into multicellular mounds or ridges. Immunocytochemistry showed that cells in treated explants expressed vimentin and in situ hybridization demonstrated that FGF-2 induced the expression of brachyury, goosecoid, and myo-D in regions of treated explants displaying morphological differentiation. Control explants cultured with platelet-derived growth factor AA (PDGF AA), transforming growth factor-beta 1 (TGF-beta 1), or in defined medium alone showed no morphological or biochemical differentiation. These results indicate that FGF-2 altered the fate of mouse anterior epiblast from ectoderm to mesoderm in vitro. Cell migration, which is characteristic of primitive streak mesoderm in vivo, was not induced by FGF-2 in these assays. However, the changes in morphology and the expression of mesodermal genes in vitro do support an early role for FGF signaling in the induction of mouse primitive streak mesoderm, as well as in later patterning events during embryogenesis.

Animals↗

PubMed1998

The Slug gene is not essential for mesoderm or neural crest development in mice.

The Slug gene encodes a zinc finger protein, homologous to the product of the Drosophila Snail gene, that is implicated in the generation and migration of both mesoderm and neural crest cells in several vertebrate species. We describe here the cloning and genetic analysis of the mouse Slug (Slugh) gene. Slugh encodes a 269-amino-acid protein the shares 92% amino acid identity with the product of the chicken Slug gene. We have characterized Slugh gene expression during early mouse embryogenesis by whole mount in situ hybridization of Slugh mRNA and through detection of beta-galactosidase expression from an in-frame SlughIacZ allele generated through homologous recombination. Slugh expression is first detected in extraembryonic mesoderm and is later detected in many mesodermal subsets, although it is not detected in the primitive streak. In contrast to many other vertebrates, the mouse Slug gene is not expressed in premigratory neural crest cells but is expressed in migratory neural crest cells. Analysis of a targeted null mutation that deleted all Slugh coding sequences revealed that Slugh is not required for mesoderm formation or for neural crest generation, migration, or development in mice. These results indicate that neither the expression pattern nor the biological function of the Slug gene is conserved among all vertebrates. These data also raise interesting questions about the regulation of neural crest generation, which is one of the distinguishing characteristics of the vertebrate subphylum.

Amino Acid Sequence↗

PubMed1976

Cytological and microspectrophotometric analysis of mesodermalized explants of Triturus gastrula ectoderm.

Using isolated presumptive ectoderm of the newt (Triturus pyrrhogaster) embryos as a reactor and extract of rat bone marrow as a mesodermal inductor, changes of cell number and mitotic index of the reactor cells were studied. In early stages of cultivation the increase in cell number in the mesodermalized ectodermal piece was slower than in the non-mesodermalized epidermal piece; but after 24 h it showed abrupt increase and reached a cell population equal to that of the control at 48 h of cultivation. In the experimental series, the mitotic index was 0 at 4 h after the application of the inducing stimulus, but increased precipitously in the next 8 h and reached a level of 4-4% at 12 h and thereafter decreased gradually. The cell cycle stopped at the S phase and stayed in it for several hours after the application of inductor. A sudden fall in cell number, observed in the mesodermalized epidermal piece between the 4th and the 8th h after the application of inducing stimulus, seems to be attributable to cell death which was brought about by the inducing stimulus. In the histogenetic process phases of repression on mitosis by an inducing stimulus, cell proliferation and nonproliferation seem to succeed each other.

Animals↗