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At least 595 records · Page 33Linked to original sources
PubMed1994

MAP kinase is activated during mesoderm induction in Xenopus laevis.

MAP kinase (MAPK) is activated in animal cap explants from Xenopus embryos in response to mesoderm induction by FGF. This activation is rapid, appearing within 1 min of treatment with FGF, and prolonged, lasting for at least 2 hr. By immunoblot analysis, this activation of MAPK is coupled with an electrophoretic shift to the slowly migrating, phosphorylated form of MAPK. Activin-stimulated mesoderm induction also results in the activation of MAPK, but only upon prolonged exposure. However, activin can potentiate the activation of MAPK by FGF as early as 1 min after administration. These findings suggest that MAPK is involved in the early signaling events of FGF-mediated mesoderm induction, and this involvement is modulated by other mesoderm inducers such as activin.

Amino Acid Sequence↗
PubMed1987

Heterotransplantation of mixed mesodermal tumor cells in nude mouse--histology of metastatic foci.

The mixed mesodermal tumor has an admixture of carcinoma and sarcoma. The HIRS-BM tumor cell line, derived from the mixed mesodermal tumor, was transplanted into the peritoneal cavity of BALB/c nude mice, and the metastatic foci were examined histologically and karyologically. The HIRS-BM cells produced mixed mesodermal tumors (admixture of adenocarcinoma and rhabdomyosarcoma) resembling the original tumor. The normal interstitial tissue was not present on the boundary of the sarcoma and carcinoma. These results support the combination theory as the cause of mixed mesodermal tumor.

Adenocarcinoma↗
PubMed1983

Muscle pioneers: large mesodermal cells that erect a scaffold for developing muscles and motoneurones in grasshopper embryos.

During embryonic development, muscles differentiate in the appropriate places and motoneurone growth cones find the appropriate muscles; both events occur concurrently and with remarkable specificity. What are the cellular interactions that orchestrate this coordinated development of nerve and muscle? In the development of vertebrate skeletal muscles, motoneurone growth cones arrive in the periphery along stereotyped routes and enter the appropriately located masses of mesodermal cells usually before differentiated muscle fibres appear and before the masses cleave into separate muscles. We find that a similar sequence of events occurs in the grasshopper embryo. We are interested in how mesodermal cells become organized into the appropriate muscles and what guides motoneurone growth cones to their appropriate targets. Fortunately, in the grasshopper embryo the mesodermal cells in the periphery and motoneurones in the central nervous system (CNS) are large, accessible and in many cases individually identifiable from early in their development. We report here the discovery of a class of large mesodermal cells, which we call muscle pioneers, that arise early in development when the embryonic environment is relatively simple and distances short. By their growth and association with particular sites along the ectoderm, the muscle pioneers appear to erect a scaffold for later developing muscles and motoneurone growth cones.

Animals↗
PubMed1975

Interrelationship between poly (ADP-Rib) synthesis, intracellular NAD levels, and muscle or cartilage differentiation from mesodermal cells of embryonic chick limb.

Mesodermal cells of embryonic chick limbs have the capacity to differentiate into either muscle or cartilage. Previous reports from this laboratory show a correlation between pyridine nucleotide levels and this differentiation, and thus suggest that fluctuations in the cellular NAD levels play a role in the control of muscle versus cartilage development. Poly(ADP-Rib) is chromatin-associated and forms from the polymerization of NAD with the excision of nicotinamide. The studies reported here show that: (A) the rate of net synthesis of poly(ADP-Rib) is correlated with the differentiation of chondrogenic cells from stage 24 limb mesodermal cells grown in vitro; (B) inhibition of chondrogenic expression caused by exposure to nicotinamide or BrdUrd is correlated with maintenance of basal levels of poly(ADP-Rib) synthesis, and this inhibition is dependent on the concentration of nicotinamide or BrdUrd exogenously supplied; (C) potentiation of chondrogenic expression caused by exposure of limb mesodermal cells in vitro to 3-acetylpyridine is correlated with stimulation of the rate of poly(ADP-Rib) synthesis if corrected for the specific activity of the ATP pool or compared to untreated cultures on a per cell basis; (D) isolated chromatin from mesodermal cells has the enzymatic machinery for synthesizing poly(ADP-Rib); (E) this machinery is inhibited by nicotinamide, thymidine, and 3-acetylpyridine; and (F) newly synthesized poly(ADP-Rib) is either associated with a discrete fraction of chromatin or is completely extracted from chromatin by the high column salts, which result in an aggregation with eventual elution at the exclusion volume position of the agarose column. Taken together, these observations provide a possible explanation for how fluctuations in cellular NAD levels can communicate with or be "sensed" by genomic related machinery and eventually result in differtial phenotypic expression.

Adenine↗
PubMed1995

Dorsal-ventral patterning and differentiation of noggin-induced neural tissue in the absence of mesoderm.

In Xenopus development, dorsal mesoderm is thought to play a key role in both induction and patterning of the nervous system. Previously, we identified a secreted factor, noggin, which is expressed in dorsal mesoderm and which can mimic that tissue's neural-inducing activity, without inducing mesoderm. Here the neural tissue induced in ectodermal explants by noggin is further characterized using four neural-specific genes: two putative RNA-binding proteins, nrp-1 and etr-1; the synaptobrevin sybII; and the lipocalin cpl-1. First we determine the expression domain of each gene during embryogenesis. Then we analyze expression of these genes in noggin-treated explants. All markers, including the differentiated marker sybII, are expressed in noggin-induced neural tissue. Furthermore, cpl-1, a marker of dorsal brain, and etr-1, a marker absent in much of the dorsal forebrain, are expressed in non-overlapping territories within these explants. We conclude that the despite the absence of mesoderm, noggin-induced neural tissue shows considerable differentiation and organization, which may represent dorsal-ventral patterning of the forebrain.

Amino Acid Sequence↗
PubMed1975

[A heterologous mesodermal tumor of the uterus of the pleomorphic rhabdomyosarcoma type].

In the available literature mesodermal tumours of the uterus are described under various names (botryoid sarcoma, carcinocarcoma, chondrosarcoma, rabdomyosarcoma, etc.). For the sake of unification of terminology of these tumours, Kehrer suggested the term "mesodermal mixed tumours", thereby reflecting their origin from cellular elements of the mesoderma. Histologically, benign and malignant variants of tumours are identified; these tumours are characterized by multi-component composition of tissues forming integral parts thereof, the latter may be homologous or heterologous. Clinically, the said tumours are diagnosed in rare cases. Diagnosis is made on the basis of a microscopical investigation of a scrape from the uterine cavity, or investigation of the operation material. Heterologic tumours of the uterus of the type of rabdomyosarcoma have been described by a number of authors. As to their microscopical structure, they may be divided into embryonal, alveolar and pleomorphous. A case of heterologic mesodermal tumour, verified as a pleomorphous rabdomyosarcoma, which could develop in a long existed mesodermal tumour of the uterus in a woman 67 years of age, is described.

Aged↗
PubMed2000

p68, a DEAD-box RNA helicase, is expressed in chordate embryo neural and mesodermal tissues.

The p68 DEAD-box RNA helicases have been identified in diverse organisms, including yeast, invertebrates, and mammals. DEAD-box RNA helicases are thought to unwind duplexed RNAs, and the p68 family may participate in initiating nucleolar assembly. Recent evidence also suggests that they are developmentally regulated in chordate embryos. bobcat, a newly described member of this gene family, has been found in eggs and developing embryos of the ascidian urochordate, Molgula oculata. Antisense RNA experiments have implicated this gene in establishing basic chordate features, including the notochord and neural tube in ascidians (Swalla et al. 1999). We have isolated p68 homologs from chick and Xenopus in order to investigate their possible role in vertebrate development. We show that embryonic expression of p68 in chick, frog, and ascidian embryos is high in the developing brain and spinal cord as well as in the sensory vesicles. In frog embryos, p68 expression also marks the streams of migrating cranial neural crest cells throughout neural tube development and in tailbud stages, but neural crest expression is faint in chick embryos. Ascidian embryos also show mesodermal p68 expression during gastrulation and neurulation, and we document some p68 mesodermal expression in both chick and frog. Thus, as shown in these studies, p68 is expressed in early neural development and in various mesodermal tissues in a variety of chordate embryos, including chick, frog, and ascidian. Further functional experiments will be necessary to understand the role(s) p68 may play in vertebrate development.

Animals↗
PubMed2000

Nodal and bone morphogenetic protein 5 interact in murine mesoderm formation and implantation.

Mice mutant for the TGF-beta family member, nodal, lack mesoderm and die between E8.5 and E9.5. The short ear-lethal (se(l) ) mutation, a deletion that eliminates Bmp-5, causes a strikingly similar gastrulation defect. Here we analyze se(l);nodal compound mutants and find a dosage effect. Embryos homozygous for one mutation show distinct gastrulation stage defects that depend on whether they are heterozygous or homozygous for the other mutation. Embryos mutant for nodal or se(l);nodal compound mutants fail to execute an antigenic shift indicative of mesoderm differentiation and ectoderm cells are shunted into an apoptotic pathway. Furthermore, we find a novel phenotype in se(l);nodal double mutant litters, in which two to four genetically different embryos are contained within the same deciduum. Both the gastrulation and implantation phenotypes can also arise in short ear-viable (se(v) ) and se(v); nodal mutant mice. These data indicate that loss of Bmp-5 may underlie the se(l) gastrulation phenotype and suggest that nodal and Bmp-5 interact during murine mesoderm formation. Our data also reveal an unsuspected role for Bmp-5 in implantation and the decidual response in the mouse.

Animals↗
PubMed1978

Origin and differentiation of the yolk sac and extraembryonic mesoderm in presomite human and rhesus monkey embryos.

Reexamination of presomite human and rhesus monkey embryos in the Carnegie Collection provides no evidence to corroborate the hypothesis that the trophoblast is the source of all extraembryonic tissues in these embryos. Instead, the present study indicates that the developmental pattern of the yolk sac and extraembryonic mesoderm is homologous to that in other eutharian mammals. The primary yolk sac of 10- to 11-day human blastocysts is partially filled with a meshwork of extraembryonic endoderm, whereas such a meshwork is absent in the rhesus monkey. It is suggested that this endodermal meshwork develops as the result of interstitial implantation in the human embryo. A small secondary yolk sac develops in 12- to 13-day human and macaque embryos as the result of pinching off of a portion of the larger primary yolk sac. Development of a secondary yolk sac in higher primates appears to be related causally to differential rates of expansion of the blastocyst and primary yolk sac within the simplex uterus. The caudal margin of the primitive streak develops precociously in 12- to 14-day human and macaque embryos, and this appears to be the source of all the extraembryonic mesoderm of the chorion, chorionic villi, and body stalk. It is suggested that the peripheral spread of extraembryonic mesoderm plays in inductive role in the development of chorionic villi, similar to other types of epithelial-mesenchymal inductive interactions. In contrast to previous hypotheses, the human and macaque trophoblasts appear to give rise only to additional trophoblast.

Amnion↗
PubMed1993

Origin of extraembryonic mesoderm in experimental animals: relevance to chorionic mosaicism in humans.

Confined chorionic mosaicism, a discordance in the karyotype between the fetus and placenta, occurs in 1% of chorionic villus sampling (CVS) cases. While the cytogenetic discrepancies occurring between different fetal tissues may pose clinical dilemmas, they can also be viewed as a natural experiment to determine early cell lineage relationships in the human. We reviewed extensive data in experimental animals to define the origin of the human extraembryonic mesoderm. The extraembryonic mesoderm in humans is an important component of the CVS culture preparation. Previously, the extraembryonic mesoderm was thought to originate in the cytotrophoblast or primitive streak. More recent evidence supports its origin from the yolk sac, which does not always correlate with the fetal karyotype. We formulated a model of early human cell lineage and employed it to clarify clinical cases of chorionic mosaicism in two large published studies.

Animals↗
PubMed1992

Mesoderm induction and axis determination in Xenopus laevis.

In Xenopus, as in all amphibians and possibly in vertebrate embryos in general, mesoderm formation and the establishment of the dorsoventral axis depend on inductive cell interactions. Molecules involved in mesoderm induction include FGF which acts predominantly as a ventrolateral inducer, the TGF-beta homolog activin which can induce all types of mesoderm, and members of the Wnt family which have powerful dorsalizing effects. Early effects of inducer action include the activation of regulatory genes. Among such genes, particular interest is focused on three genes encoding putative transcription factors that are expressed specifically in the Spemann organizer region of the gastrula. Expression of one of these genes, goosecoid, has been shown to be sufficient to elicit the formation of a dorsal axis including head and notochord in the embryo.

Animals↗
PubMed1989

An essential role of even-skipped for homeotic gene expression in the Drosophila visceral mesoderm.

We have analysed homeotic gene expression in the embryonic visceral mesoderm of segmentation mutants by antibody staining against Ultrabithorax, Antennapedia and Sex combs reduced protein. We found that even-skipped (eve) function is crucially required for homeotic gene expression, whereas most other segmentation mutations have only minor effects on position and/or width of the homeotic expression domains in this germ layer. Analysis of pair-rule double mutants indicates that complete loss of homeotic gene activity in the visceral mesoderm, as observed in amorphic eve mutants, correlates with loss of engrailed (en) expression in the epidermis and loss of segmentation. We suggest that the establishment of parasegment borders, a consequence of eve expression and witnessed by subsequent en expression, is a necessary precondition for homeotic gene expression in the visceral mesoderm.

Animals↗
PubMed1989

Proenkephalin A is expressed in mesodermal lineages during organogenesis.

Proenkephalin A (PEA) encodes several neuropeptides with an opioid activity, as well as other peptides with as yet unknown functions. As an initial step toward finding possible roles for PEA gene products in non-neuronal tissues, we have determined sites of PEA expression during mouse embryonic development, employing in situ hybridization. We report here the unexpected observation that in addition to its abundance in brain, PEA RNA is expressed in non-differentiated mesodermal cells of diverse lineages in the process of their development into several adult tissues and organs; it drops to undetectable levels upon terminal differentiation of these tissues. In a particular example of differentiating mesoderm, the developing kidney, the transient expression of PEA mRNA and of its encoded peptide Met-enkephalin was demonstrated by both in situ and Northern blot hybridizations, as well as by a radioimmunoassay. These findings suggest a novel role for PEA-derived peptide(s) in mesoderm growth or differentiation during organogenesis.

Animals↗
PubMed1989

MyoD expression in the forming somites is an early response to mesoderm induction in Xenopus embryos.

We describe the cloning, cDNA sequence and embryonic expression of a Xenopus homologue of MyoD, a mouse gene encoding a DNA-binding protein that can activate muscle gene expression in cultured cells. The predicted Xenopus MyoD protein sequence is remarkably similar to mouse MyoD. Zygotic expression of MyoD begins in early gastrulae, but there is a low level of unlocalized maternal message. Northern blot analysis of dissected embryos and in situ hybridization show that MyoD RNA is restricted to the gastrula mesoderm and to the somites of neurulae and tailbud embryos. The time and place of MyoD expression are consistent with a role for MyoD in the activation of other muscle genes in the somites of the frog embryo. However, MyoD is skeletal muscle-specific and is not expressed even in the early embryonic heart, which co-expresses cardiac and skeletal actin isoforms. Striated muscle genes can therefore be activated in some embryonic tissues in the absence of MyoD. The concentration of MyoD in the somites falls once they have formed, suggesting that MyoD may act there transiently to establish muscle gene expression. MyoD transcription is activated following mesoderm induction, and is the earliest muscle-specific response to mesoderm-inducing factors so far described.

Amino Acid Sequence↗
PubMed1989

Coordinate action of a proximal homeoprotein binding site and a distal sequence confers the Ultrabithorax expression pattern in the visceral mesoderm.

Spatially regulated expression of the homeotic gene Ultrabithorax (Ubx) in the visceral mesoderm can be mimicked in transformed Drosophila embryos by expression of a Ubx--beta-galactosidase fusion gene. Here we show that a proximal homeoprotien binding sequence downstream of the Ubx transcription start site, the B element, is required for this pattern. A distal upstream Ubx sequence, but not the B element, is sufficient to confer the pattern if linked to an hsp70 TATA box in a heterologous construct. The pattern in this case requires Ubx function, like endogenous Ubx expression in the visceral mesoderm, suggesting that the distal upstream sequence contains an important target sequence for autoregulation. We propose that the B element, in the context of the Ubx promoter, functions to mediate enhancer function of the distal sequence. Thus, the visceral mesoderm pattern requires coordinate action of a proximal and a distal regulatory element.

Animals↗
PubMed1979

Cyclic AMP derivatives stimulate the chondrogenic differentiation of the mesoderm subjacent to the apical ectodermal ridge of the chick limb bud.

Recent studies indicate that one of the major functions of the apical ectodermal ridge (AER) of the embryonic chick limb bud is to maintain mesenchymal cells directly subjacent to it (i.e., cells extending 0.4-0.5 mm from the AER) in a labile, undifferentiated condition. Furthermore, when mesenchymal cells are freed from the AER's influence, either artifically or as a result of normal polarized proximal-to-distal limb outgrowth, they are freed to commence cytodifferentiation. In a preliminary attempt to investigate at a molecular level the mechanism by which the AER exerts its "negative" effect on the cytodifferentiation of subridge mesenchymal cells, we have examined the effect of a variety of agents that elevate cyclic AMP levels on the chondrogenic differentiation of the unspecialized subridge mesoderm of the limb bud in an organ culture system. Dibutyryl- and 8-hydroxy-cyclic AMP elicit a dose-dependent increase in the rate and amount of cartilage matrix formation and a corresponding dose-dependent increase in sulfated glycosaminoglycan accumulation by subridge mesoderm explants. The stimulatory effect of suboptimal concentrations of cyclic AMP derivatives is potentiated by the addition of theophylline. The stimulatory effect is limited to cyclic AMP derivatives, since dibutyryl-cyclic GMP and 5'-AMP have no effect. Thus agents that elevate intracellular cyclic AMP levels stimulate the chondrogenic differentiation of the unspecialized subridge mesoderm of the embryonic chick limb bud.

Animals↗
PubMed1983

Ectodermal control of the avascular zone of the peripheral mesoderm in the chick embryo.

Prospective skin ectoderm is underlaid by a relatively thick (100 +/- 20 micrometer) avascular zone of mesoderm in most regions of the early embryo. To determine whether or not the ectoderm exercises a role in the establishment and maintenance of the avascular zone, trypsin-isolated pieces of backskin ectoderm from chick or quail embryos were implanted as a sheet into a slit cut deep into the capillary bed of the wing bud of host chick embryos of stages 19-23. In sham operations, slits were cut at various anteroposterior levels, and the wing was allowed to heal. At intervals of 3-48 hr after these operations, embryos were injected with India ink, fixed, and cleared. Implants formed flattened vesicles, usually in continuity with host ectoderm, but sometimes completely internalized. Periderm cells from each side of the vesicle faced each other, and the cells of the cuboidal layer faced an avascular mesodermal layer at least 100 micrometer thick at all points. The implantation of prospective skin ectoderm resulted in the formation of an avascular zone in normally vascularized mesoderm of the wing bud. In contrast, the vascular bed of the limb bud abutted directly on implants of Millipore filters or of Silastic silicone (Dow Corning). Likewise, the capillary bed came in direct contact with implants of retinal pigment epithelium, an ectodermal derivative normally in close contact with the vascular choroid coat of the eye. These results, taken in conjunction with earlier experiments that show the necessity of the apical ectodermal ridge for the formation of the marginal veins of the limb bud, suggest that epithelial-mesenchymal interactions are involved in important aspects of vasculogenesis in early embryos.

Animals↗
PubMed1991

Fibroblast growth factor and culture in monolayer rescue mesoderm cells destined to die in the developing avian wing.

In an effort to elucidate control mechanisms for developmentally programmed cell death, conditions were sought that rescue the cells destined to die. Three areas of mesodermal cell death in the chick wing were examined: the posterior necrotic zone (PNZ), the opaque patch (OP), and apical mesoderm. The PNZ and OP are areas of normally programmed cell death, whereas the apical mesoderm undergoes cell death only after the overlying apical ectodermal ridge is excised. Cell death in vitro was quantitated using the chromium-release assay. While these tissues undergo apparently normal cell death in organ culture, in monolayer culture almost all are rescued. In addition, the cells are rescued by the addition of fibroblast growth factor to organ cultures. Since fibroblast growth factor is present in decreasing amounts in the limb at this stage of development, normal cell death may occur upon withdrawal of growth factor.

Animals↗