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At least 343 records · Page 19Linked to original sources

PubMed1987

Ecdysteroid levels during embryogenesis in the shrimp, Palaemon serratus (Crustacea Decapoda): quantitative and qualitative changes.

During the embryogenesis of Palaemon serratus profound changes in ecdysteroid concentrations were found. Ecdysteroid concentrations increase at the appearance of the Y-organ and a slight decrease is observed just before hatching. Two peaks of ecdysteroid concentration occur between these two events if Palaemon is reared at 19 degrees, but only one broad maximum is observed after rearing at 11-12 degrees. The pattern of ecdysteroids changes during embryogenesis; the ecdysone level decreases, while the 20-OH-ecdysone concentration and the amount of high polarity products increase. During the embryonic stage C the ratio of 20-OH-ecdysone to ecdysone was shown by HPLC analysis to steadily increase. After enzymatic hydrolysis of high-polarity products the main RIA-positive material elutes from reversed-phase HPLC columns as 20-OH-ecdysone.

Animals↗

PubMed1987

Unusual patterns of somatic embryogenesis in the domesticated carrot: developmental effects of exogenous auxins and auxin transport inhibitors.

The effects of various exogenous auxins and polar auxin transport inhibitors on somatic embryogenesis in carrot cultures were investigated. Indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid do not disrupt the sequence or the polarity of individual stages in embryo development, but tend to cause developing embryos to revert to undifferentiated callus, with increasing frequency in later embryo stages. The transport inhibitors, N-(1-naphthyl)phthalamic acid and 2,3,5-triiodobenzoic acid, block morphological transitions to the subsequent stage; for example, they cause the formation of enlarged globular and oblong embryos. Heart embryos in these treatments usually develop additional lateral growth axes. These results shed light on the role of auxin and its polar transport in somatic embryogenesis.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1982

Regulation of tubulin gene expression during embryogenesis in Drosophila melanogaster.

Four different tubulins have been identified that are expressed during embryogenesis in Drosophila melanogaster. Two alpha-tubulin subunits (alpha 1 and alpha 2) and one beta-tubulin subunit (beta 1) are expressed throughout embryonic development. A second beta-tubulin subunit (beta 3) is expressed only for a short period in mid-embryonic development. Synthesis of beta 3-tubulin in vitro in a rabbit reticulocyte translation system is directed by RNA extracted from embryos only at the stage when the protein is expressed. Thus we conclude that the mRNA encoding beta 3-tubulin is transcribed only during the brief period of beta 3-tubulin synthesis. The expression of beta 3-tubulin is accompanied by a coordinate transient increase in the level of synthesis of the embryonic alpha-tubulins, thereby maintaining an approximately equimolar synthesis of alpha- and beta-tubulin subunits throughout embryogenesis.

Animals↗

PubMed1984

Completion of mouse embryogenesis requires both the maternal and paternal genomes.

Transplantation of pronuclei between one-cell-stage embryos was used to construct diploid mouse embryos with two female pronuclei ( biparental gynogenones ) or two male pronuclei ( biparental androgenones ). The ability of these embryos to develop to term was compared with control nuclear-transplant embryos in which the male or the female pronucleus was replaced with an isoparental pronucleus from another embryo. The results show that diploid biparental gynogenetic and androgenetic embryos do not complete normal embryogenesis, whereas control nuclear transplant embryos do. We conclude that the maternal and paternal contributions to the embryonic genome in mammals are not equivalent and that a diploid genome derived from only one of the two parental sexes is incapable of supporting complete embryogenesis.

Animals↗

PubMed1985

Homeo box gene complex on mouse chromosome 11: molecular cloning, expression in embryogenesis, and homology to a human homeo box locus.

The homeo box is a 180 bp protein-coding domain found within homeotic genes of Drosophila and conserved in a variety of invertebrate and vertebrate species. It has been suggested that the mammalian homeo box sequences may play a role in controlling pattern formation during embryogenesis. We report findings that support this hypothesis. We have cloned three overlapping recombinant phage clones that cover a region of mouse chromosome 11 that contains a cluster of four homeo boxes (the Hox-2 locus). This locus encodes multiple transcripts that are expressed during embryogenesis. Forty kilobases of the Hox-2 region is devoid of repetitive elements and shows extensive homology with the human Hox-2 locus. These results provide direct evidence for genetic expression during embryonic development, a conserved organization in comparison to the cognate human locus, and a complexity of organization and transcript expression similar to that found in Drosophila.

Animals↗

PubMed1989

The function of PS integrins during Drosophila embryogenesis.

The Drosophila position-specific (PS) antigens are homologous to the vertebrate fibronectin receptor family, or integrins. A Drosophila gene required for embryonic morphogenesis, l(1)myospheroid, codes for a product homologous to the beta subunit of the vertebrate integrins. l(1)myospheroid mutants die during embryogenesis. We show here that they lack the beta subunit of the PS antigens. In the absence of the beta subunit in mutant embryos, the PS alpha subunits are not expressed on the cell surface. We conclude that the l(1)myospheroid phenotype represents the lack-of-function phenotype for these Drosophila integrins. In wild-type embryos, PS antigens are found at the interface between mesoderm and ectoderm, and later mainly at the attachment sites of muscles to the epidermis and gut. Together these results indicate that during embryogenesis, Drosophila integrins are used to attach mesoderm to ectoderm, and are required for the proper assembly of the extracellular matrix and for muscle attachment.

Animals↗

PubMed1991

Parental-specific methylation of an imprinted transgene is established during gametogenesis and progressively changes during embryogenesis.

Genomic imprinting is a regulatory process that requires a cell to recognize the parental origin of alleles. To understand how these alleles are distinguished, we have assessed changes in the DNA methylation of an imprinted transgene as it switches from one inheritance pattern to another while moving through gametogenesis and embryogenesis. We find that both maternally and paternally inherited methylation patterns are erased in primordial germ cells and that distinctive patterns emerge during germ cell maturation. In the case of the maternal allele, the methylation pattern is fully acquired during oogenesis. In the case of the paternal allele, the methylation pattern found in sperm undergoes further modification during embryogenesis. Thus, the distinction between "erased" maternal and paternal alleles is first established during their residence in different germ cells and then may be maintained by the recognition of the distinctive patterns that each allele displays in the zygote.

Alleles↗

PubMed1994

Different spatio-temporal expressions of three otx homeoprotein transcripts during zebrafish embryogenesis.

Three zebrafish otx homeoproteins containing a homeodomain homologous to that of the Drosophila orthodenticle head gap gene product have been identified by cloning and sequencing of cDNAs. The zebrafish otx2 homeoprotein shares high amino-acid sequence identity with the mouse Otx2 homeoprotein, whereas the zebrafish otx1 and otx3 homeoproteins exhibit moderate homology with the mouse Otx1 and Otx2 homeoproteins. Three otx homeoprotein mRNAs show different spatio-temporal expression patterns during zebrafish embryogenesis as revealed by Northern blot and whole mount in situ hybridization analyses. Large amounts of the otx1 homeoprotein mRNA are found in fertilized uncleaving eggs. The otx3 homeoprotein mRNA appears in the embryonic shield, the site of the organizer. In the developing brain, three zebrafish otx mRNAs are distributed in the diencephalon and the midbrain, but their fine expression patterns are different. These results suggest that three zebrafish otx homeoproteins, alone or in combination, may play roles in very early embryogenesis, gastrulation, and the development and subdivision of the diencephalon and the midbrain.

Amino Acid Sequence↗

PubMed1987

Transforming growth factor-beta: potential common mechanisms mediating its effects on embryogenesis, inflammation-repair, and carcinogenesis.

In conclusion, we have demonstrated that a single growth factor, TGF-beta, can act in either an autocrine or paracrine mode to bring about, either directly or indirectly, all of the complex events which together lead to the formation of granulation tissue and tumor stroma. All of the participating cell types, lymphocytes, macrophages, endothelial cells, and fibroblasts have receptors for TGF-beta and many of them secrete TGF-beta as well. Although other growth factors such as platelet-derived growth factor and fibroblast growth factor clearly also participate in these processes, we have shown that TGF-beta, alone, is sufficient to initiate the cascade of events, probably through its ability to chemoattract and to activate macrophages and fibroblasts. Without question, neovascularization and appropriately timed matrix synthesis and degradation are central to embryogenesis as well. Fibronectin, in particular, has been shown to promote cell adhesion and cell migration throughout embryogenesis (Hynes and Yamada, 1982; Rovasio et al., 1983). We propose that TGF-beta will be found to be an important mediator of embryonic development, not only by control of angiogenesis and matrix synthesis, but also by exerting direct local effects on cellular growth and differentiation (reviewed in Roberts and Sporn, 1987).

Animals↗

PubMed1988

Expression of the homeobox gene, Hox 2.1, during mouse embryogenesis.

This article reviews recent studies on the expression of the homeobox gene, Hox 2.1, during mouse embryogenesis, using the technique of in situ hybridization. Differential hybridization of radiolabelled antisense versus sense strand RNA is first clearly detected in sections of 8.5 day post coitum (p.c.) early somite embryos. At 12.5 days p.c., higher levels of Hox 2.1 expression are seen in the spinal cord, extending into the base of the hind brain. Hybridization of antisense Hox 2.1 RNA is also seen in the spinal ganglia, in the nodose ganglia of the Xth cranial nerve (which contains derivatives of the neural crest arising from the posterior hind brain), and in the myenteric plexus. Mesodermal cells of certain visceral organs also express Hox 2.1 RNA, in particular the mesoderm of the lung, stomach and meso- and meta-nephric kidney. Comparison of the spatial domains of expression of mouse homeobox genes reveals a pattern consistent with the idea that they play a role in anteroposterior positional specification during embryogenesis.

Embryonic and Fetal Development↗

PubMed1993

The c-ets-1 proto-oncogenes in Xenopus laevis: expression during oogenesis and embryogenesis.

We previously reported the cloning and sequencing of two cDNAs derived from the Xenopus laevis ets-1 gene (Stiegler et al., 1990). The Xl-ets-1a cDNA encodes a polypeptide highly homologous to known ets-1 proteins. The 3'-UTR contains two AATAAA polyadenylation signals together with three copies of the TTTTTAT sequence thought to confer a maturation-specific polyadenylation and implicated in the deadenylation of dormant mRNAs. Several transcripts with maternal characteristics were detected in oogenesis and early embryogenesis. A marked augmentation of the major transcript in the poly(A)+ fraction was detected at fertilization. Ets-1 transcripts were observed at constant levels during the cleavage stages but decreased abruptly at gastrulation, to reappear from neurulation to late embryogenesis. The possible contribution of 3'-UTR sequence elements to this behavior is discussed.

Adenosine↗

PubMed1995

Molecular cloning of Xenopus HGF cDNA and its expression studies in Xenopus early embryogenesis.

We isolated Xenopus HGF cDNA and examined its expression pattern in Xenopus early embryos and their dissected parts. Xenopus HGF consists of 710 amino acids and contains four kringle domains and serine protease-like structure just like mammalian HGF. Northern blot analysis showed that expression of Xenopus HGF mRNA starts at the late gastrula stage and its level increases during the period of later embryogenesis. Dissection experiments revealed that Xenopus HGF mRNA is expressed in the mesoderm region, especially in the ventral mesoderm, which for the most part gives rise to mesenchymal cells. Furthermore, HGF mRNA was expressed in response to activin A and basic FGF in blastula animal cap cells. Interestingly, a stronger activity was observed with bFGF than with activin and this finding corroborates the preferential expression of HGF mRNA in the ventral mesoderm. Based on these results, we conclude that the Xenopus homologue of HGF gene is transcribed during early embryogenesis preferentially in ventral mesodermal tissues, probably in response to the signals that induce ventral mesoderm.

Amino Acid Sequence↗

PubMed1994

Development of sibling inbred sea urchins: normal embryogenesis, but frequent postembryonic malformation, arrest and lethality.

Inbred lines of Strongylocentrotus purpuratus descended from a single pair of wild animals were constructed by sibling mating. We describe results from a systematic series of crosses in which eggs from F2 and from F3 females were fertilized respectively with sperm from their sibling males. Observations were also made on self-fertilized cultures derived from several naturally occurring hermaphrodites. Morphological development, survival efficiency, and expression of three territorial embryonic markers were assayed in the embryos developing from these crosses. Unexpectedly, out of > 90 controlled crosses, we observed no developmental failures whatsoever, up to the end of embryogenesis (i.e., onset of feeding) that could be attributed to homozygous, zygotically acting recessive genes. However, during postembryonic larval development, lethality, morphological malformation, and arrest are observed in inbred cultures at a high frequency. The incidence of these zygotic developmental failures is such that it appears that there is at least one recessive genetic defect affecting larval development per haploid parental genome. The relative imperviousness of the basic embryonic process to defects arising from homozygosity is consistent with other evidence implying that territorial specification in sea urchin embryogenesis is controlled by maternally rather than zygotically expressed gene products.

Animals↗

PubMed1995

The dosage compensation regulators MLE, MSL-1 and MSL-2 are interdependent since early embryogenesis in Drosophila.

We have analyzed the expression pattern and localization of MLE, MLS-1, MSL-2, and histone H4Ac16 during embryogenesis to determine when msl-dependent dosage compensation begins. Maternal MSL-1 and MLE are present in both sexes at fertilization. MSL-2 lacks a maternal component, and male-specific zygotic expression is detectable at the end of blastoderm. During germ band extension, MSL-1, MSL-2, MLE, and histone H4Ac16 display coincident sub-nuclear localization in male embryos. In embryos lacking one of the MSL proteins, the sub-nuclear localization of the other MSLs and of histone H4Ac16 is not detected. We conclude that the MSL proteins associate with the X chromosome and are interdependent since early embryogenesis.

Animals↗

PubMed2004

Esterase and lipase in camel tick Hyalomma dromedarii (Acari: Ixodidae) during embryogenesis.

Esterase and lipase activity showed significant changes during embryogenesis of camel tick Hyalomma dromedarii. From the elution profile of chromatography on DEAE-cellulose, six forms of H. dromedarii esterase (El to EVI) can be distinguished. Esterase EIII was purified to homogeneity after chromatography on Sepharose 6B. The molecular mass of esterase EIII was 45 kDa for the native enzyme and represented a monomer of 45 kDa by SDS-PAGE. Esterase EIII had an acidic pI at 5.3. Lipase activity was detected in the same DEAE-cellulose peaks (LI to LVI) of H. dromedarii esterases. The highest lipase activity was exhibited by lipase LIII. Esterase EIII and lipase LIII were compared with respect to Michaelis constant, substrate specificity, temperature optimum, heat stability, pH optimum, effect of metal ions and inhibitors. This study suggests that H. dromedarii lipolytic enzymes may play a central role in the interconversion of lipovitellins during embryogenesis.

Animals↗

PubMed2006

KDC2, a functional homomeric potassium channel expressed during carrot embryogenesis.

In Daucus carota, the model system for embryogenesis, it has been demonstrated that potassium and K(+) selective channels are involved in embryo development. Here, we report the isolation and cloning of a new carrot Shaker-like potassium channel, potassium D. carota channel 2 (KDC2), whose expression pattern during somatic embryogenesis proceeds along with the establishment of the polar axes and the settlement of the hypocotyl region. In plants, KDC2 transcript is localized at the shoot level, in the epidermis and guard cells, similarly to its Arabidopsis homolog KAT1. Electrophysiological assays indicated KDC2 as the first carrot subunit able to form homomeric functional channels in Xenopus oocytes, with properties similar to those of Arabidopsis KAT1.

Amino Acid Sequence↗

PubMed2004

The canonical Wnt pathway in early mammalian embryogenesis and stem cell maintenance/differentiation.

The Wnt signaling pathway plays essential roles in embryogenesis of higher eukaryotes from diploblastic, radially symmetrical cnidarians to mice and humans. Whereas studies in model organisms such as Drosophila and Xenopus continue to elucidate how the Wnt pathway is regulated, studies of mouse mutants and cultured mammalian cells start to reveal how the Wnt pathway controls development and differentiation in mammals. Here we review some of the recent progresses in our understanding of the Wnt pathway. We focus on how this pathway, through regulating transcription of its downstream target genes, specifies pattern formation during mammalian embryogenesis and functions in the differentiation and maintenance of stem cells both in vivo and in vitro.

Animals↗

PubMed2005

Identification and immunogold localization of a novel bromegrass (Bromus inermis Leyss) peroxisome channel protein induced by ABA, cold and drought stresses, and late embryogenesis.

A cDNA (BG-15) was isolated through differential screening of a cDNA library made from an ABA-treated bromegrass (Bromus inermis Leyss) suspension cell culture. The 819 bp pair cDNA encoded a 174 amino acid polypeptide with a calculated molecular mass of 18.08 kD and isolectric point of 7.50. The deduced amino acid sequences for the cDNA were 29.5% and 32.6% homologous to the known amino acid-selective channel proteins of the chloroplastic outer membrane in pea and barley, but were highly homologous (55.6% to 83.2%) to the putative membrane channel proteins from rice and Arabidopsis. Immunogold localization demonstrated that the channel protein encoded by this cDNA was present on the peroxisome membrane. High stringency southern analysis revealed that 1 to 2 copies of the peroxisomal channel protein (PCP) genes were present in the bromegrass genome. Northern and Western blots revealed that the PCP gene was responsive to both cold and drought stresses, and was rapidly induced by ABA (75 microM). The transcript of the PCP gene also accumulated during late embryogenesis, but declined rapidly during germination. Data taken together, responsiveness of the PCP to cold and drought stresses, and accumulation during late embryogenesis suggest this novel peroxisomal channel protein is associated with sugar and fatty acid metabolism through fatty acid import or succinate export from peroxisome during desiccation tolerance and energy metabolism.

Abscisic Acid↗