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PubMed1988

Epithelial induction of stromal tenascin in the mouse mammary gland: from embryogenesis to carcinogenesis.

The distribution of the extracellular matrix glycoprotein tenascin was studied by immunofluorescence in the developmental history of the mouse mammary gland from embryogenesis to carcinogenesis. Tenascin appeared only in the mesenchyme immediately surrounding the epithelia just starting morphogenesis, that is, in embryonic mammary glands from 13th to 16th day of gestation, in mammary endbuds which are a characteristic structure starting development during maturation of the mammary gland, and in the stroma of malignant mammary tumors. However, tenascin was absent in the elongating ducts of embryonic, adult, proliferating, and involuting mammary glands and preneoplastic hyperplastic alveolar nodules. The transplantation of embryonic submandibular mesenchyme into adult mammary glands induces the development of duct-alveolus nodules, which morphologically resemble developing endbuds. Tenascin reappeared around those nodules during the initial stages of their development. Tenascin expression could be induced experimentally in several ways. First, tenascin was detected at the site where the first mammary tumor cells GMT-L metastasized. Second, tenascin was detected in the connective tissue in the tumors derived from the injected C3H mammary tumor cell line CMT315 into Balb/c nude mouse. Cross-strain marker anti-CSA antiserum clearly showed that the tenascin-positive fibroblasts were of Balb/c origin. Third, when embryonic mammary epithelium was explanted on to embryonic mammary fat pad cultures, the mesenchymal cells condensed immediately surrounding the epithelium. Tenascin was detected in these condensed cells. From these three observations we conclude that both embryonic and neoplastic epithelium induced tenascin synthesis in their surrounding mesenchyme.

Animals↗

PubMed1988

Multiple levels of regulation of tubulin gene expression during sea urchin embryogenesis.

The expression of the tubulin genes during embryogenesis of the sea urchin Lytechinus pictus has been analyzed. Single strand tracer excess titrations of alpha- and beta-tubulin mRNA and RNA gel blot hybridizations indicate that tubulin mRNA remains at a constant 1.3 X 10(5) transcripts per embryo during cleavage stages, increases during ciliogenesis shortly before hatching (12 hr PF), declines until midgastrula (30-35 hr PF), and then gradually increases 3-fold to about 6 X 10(5) per pluteus larva (72 hr PF). Tubulin synthesis changes in concert with its mRNA, except that during cleavage the relative rate of tubulin synthesis increases without a corresponding increase in tubulin mRNA abundance. The relative rates of tubulin gene transcription were assayed by a run-on assay in isolated nuclei. The synthesis of alpha- or beta-tubulin RNA results in little supplementation of maternal tubulin RNA during cleavage stages, but the rate increases at least 18-fold during ciliogenesis and then gradually decreases thereafter. The accumulation of tubulin mRNA after gastrulation can be accounted for by an ontogenetic increase in tubulin RNA stability, assayed by actinomycin D chase and RNA gel blot hybridization. The rates of synthesis, stabilities, and abundances of alpha- and beta-tubulin mRNAs were similar, suggesting coordinate regulation. These observations indicate the importance of translational regulation during cleavage, transcriptional regulation during ciliogenesis, and regulation of mRNA stability by the level of unpolymerized tubulin during later development.

Age Factors↗

PubMed1989

The determination of the adrenal medullary cell fate during embryogenesis.

One subset of neural crest cells, the sympathoadrenal precursors, undergoes a switch in phenotype expression, when they invade the adrenal anlagen and become associated with adrenocortical cells. To investigate the mechanisms responsible for the conversion of noradrenaline synthesizing precursors to adrenaline producing endocrine chromaffin cells we studied the role of glucocorticoids on the initial induction of adrenaline synthesis in embryonic adrenals and cultures of highly purified chromaffin precursor cells. We could show that in vivo differentiation of rat chromaffin precursors commences between 16.3 and 17.3 days of gestation. While adrenaline and the activity of the enzyme phenylethanolamine N-methyltransferase (PNMT), which converts noradrenaline to adrenaline, were present at Embryonic Day 17.3 (E17.3), they were not detectable in E16.3 adrenals. Small amounts of corticosterone were present in E16.3 adrenals and plasma, but in parallel with the initial induction of adrenaline biosynthesis, a sharp rise in organ and plasma glucocorticoid levels occurred until E17.3. Chromaffin precursor cells, isolated at E16.3 and cultured for 4 days, failed to express PNMT activity and adrenaline. However, 0.1 nM dexamethasone was already sufficient for the initial induction of adrenaline and its synthesizing enzyme. Specific glucocorticoid binding of freshly isolated chromaffin (precursor) cells revealed a developmental increase during embryogenesis, yet no glucocorticoid binding sites were detectable in chromaffin precursor cells at E16.3. They appeared at E17.3 in parallel with the initial induction of adrenaline biosynthesis and the enormous rise of adrenal and plasma corticosterone levels. We therefore conclude that glucocorticoids are essential and sufficient to trigger the differentiation of noradrenergic sympathoadrenal precursors to adrenergic chromaffin cells after a functional glucocorticoid receptor system has been established.

Adrenal Medulla↗

PubMed1990

U3 snRNPs and nucleolar development during oocyte maturation, fertilization and early embryogenesis in the mouse: U3 snRNA and snRNPs are not regulated coordinate with other snRNAs and snRNPs.

U3 small nuclear ribonucleic acids (snRNA) and U3 small nuclear ribonucleoprotein (snRNP), which are thought to be responsible for ribosomal RNA processing, are quantitated and localized during oocyte maturation, fertilization, and early embryogenesis in the mouse. On the basis of Northern blot and nuclease protection experiments, it is estimated that there are about 5 x 10(4) U3 snRNA molecules in an ovulated oocyte and in a two-cell embryo. This number then increases roughly 50-fold to 2.7 x 10(6) molecules per embryo by the blastocyst stage. At all stages of development U3 snRNP antigens colocalize with nucleoli, as defined by differential interference contrast microscopy and an antibody to a nucleolar epitope. The synthesis and distribution of U3 snRNA and U3 snRNP follow a pattern independent from other major U snRNPs and snRNAs.

Animals↗

PubMed1992

Position-specific expression of the annulin protein during grasshopper embryogenesis.

Annulin, named for its annular expression in developing limb buds, is a approximately 100 kDa membrane-associated protein that is expressed in a complex and changing pattern during grasshopper embryogenesis. Its expression is dynamic along the developing midline and in the mesoderm, transient in neuroepithelial sheath cells around mitotic neuroblasts, and position-specific in circumferential stripes in each limb bud segment. Annulin expression begins along the midline of the embryo at the onset of gastrulation. Mesoderm cells express the protein as they migrate away from the midline as do new cells that come to lie at the midline. During neurogenesis, annulin expression disappears from many midline cells until only a specific subset of midline glial cells expresses high levels of the protein. Starting at the beginning of neurogenesis, sheath cells express annulin in correlation with the mitotic activity of the neuroblasts they surround.

Animals↗

PubMed1992

Skeletal muscle satellite cells appear during late chicken embryogenesis.

The emergence of avian satellite cells during development has been studied using markers that distinguish adult from fetal cells. Previous studies by us have shown that myogenic cultures from fetal (Embryonic Day 10) and adult 12-16 weeks) chicken pectoralis muscle (PM) each regulate expression of the embryonic isoform of fast myosin heavy chain (MHC) differently. In fetal cultures, embryonic MHC is coexpressed with a ventricular MHC in both myocytes (differentiated myoblasts) and myotubes. In contrast, myocytes and newly formed myotubes in adult cultures express ventricular but not embryonic MHC. In the current study, the appearance of myocytes and myotubes which express ventricular but not embryonic MHC was used to determine when adult myoblasts first emerge during avian development. By examining patterns of MHC expression in mass and clonal cultures prepared from embryonic and posthatch chicken skeletal muscle using double-label immunofluorescence with isoform-specific monoclonal antibodies, we show that a significant number of myocytes and myotubes which stain for ventricular but not embryonic MHC are first seen in cultures derived from PM during fetal development (Embryonic Day 18) and comprise the majority, if not all, of the myoblasts present at hatching and beyond. These results suggest that adult type myoblasts become dominant in late embryogenesis. We also show that satellite cell cultures derived from adult slow muscle give results similar to those of cultures derived from adult fast muscle. Cultures derived from Embryonic Day 10 hindlimb form myocytes and myotubes that coexpress ventricular and embryonic MHCs in a manner similar to cells of the Embryonic Day 10 PM. Thus, adult and fetal expression patterns of ventricular and embryonic MHCs are correlated with developmental age but not muscle fiber type.

Animals↗

PubMed1992

Modulation of sea urchin actin mRNA prevalence during embryogenesis: nuclear synthesis and decay rate measurements of transcripts from five different genes.

The parameters determining the prevalence of the five actin gene transcripts that are differentially expressed during embryogenesis in the sea urchin Strongylocentrotus purpuratus were measured in vivo. These results and previous studies show that the developmental appearance of the cytoskeletal actin mRNA, CyI, CyIIa, CyIIb, and CyIIIa, and the muscle-specific actin message M, is transcriptionally regulated. The cytoskeletal actin genes are activated at the 64-cell stage or shortly thereafter. At this stage the specification of the early embryonic lineages has just completed. M gene transcription was detected only after muscle cells appear in the late embryo. The CyI, CyIIa, and CyIIb genes are transcribed at a moderate rate that does not vary significantly during development. In contrast, during late cleavage CyIIIa transcripts are produced at the maximum rate observed for structural genes in this embryo. In later stages, CyIIIa transcription is reduced at least 30-fold. The rate at which new actin transcripts enter the cytoplasm was also measured. The data show that essentially all primary actin gene transcripts are processed into mature messages. Actin message stability does not change during development. The mRNA half-life of the various messages was found to range from 4 hr to greater than 14 hr.

Actins↗

PubMed1992

Acquisition of a transcriptionally permissive state during the 1-cell stage of mouse embryogenesis.

Zygotic gene transcription initiates during the 2-cell stage of mouse embryogenesis. To learn more of the nature and timing of events leading up to transcriptional activation, we evaluated the ability of enucleated 1-cell-stage embryos to support transcription of the 2-cell-stage-specific gene(s) encoding the 70,000-Da transcription-requiring complex (TRC). Nuclei were transplanted from transcriptionally inhibited alpha-amanitin or N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide (H8)-treated 2-cell-stage embryos to either late or early enucleated 1-cell-stage recipients. Expression of the TRC gene(s) was much greater following transfer to late 1-cell than early 1-cell-stage recipients. In addition, treatment of early 1-cell-stage recipients with N6-monobutyryl cyclic AMP following transplantation of a nucleus from an H8-treated donor increased the rate of TRC synthesis to a value similar to that observed for late 1-cell-stage recipients. These results indicate that during the first cell cycle and prior to initiation of zygotic gene expression, the embryonic cytoplasm undergoes a transition from a transcriptionally nonpermissive to permissive state.

Amanitins↗

PubMed1984

dCMP-aminohydrolase activity during early sea urchin development. An example of negative enzyme control during embryogenesis.

In sea urchin, unfertilized eggs have a very high level of dCMP-aminohydrolase (dCMPase) activity, which decreases gradually and at the pluteus stage it is only about a quarter of that found in the unfertilized egg. But in abnormal embryos and in disaggregated cells from embryos, no decrease in the dCMPase activity takes place. To understand the control mechanism involved in this enzyme activity during development, we have analyzed the effect of various drugs which interfere with information transfer, such as actinomycin C, puromycin, 5-azacytidine, 2-thio-uracil and p-fluoro-DL-phenylalanine on dCMPase activity in embryos of Paracentrotus lividus and Sphaerechinus granularis. Among these drugs only actinomycin induces a remarkable increase of the dCMPase activity in embryos with respect to unfertilized eggs. Puromycin has a differential and dose-dependent effect. Other drugs, although they affect normal development and macromolecular synthesis, do not significantly alter the dCMPase activity. On the basis of these results we suggest the presence of a repressor mechanism in the control of dCMP-aminohydrolase level during early embryogenesis of sea urchin.

Animals↗

PubMed1994

The role of gravity in chick embryogenesis.

Thirty fertilized chick eggs preincubated for 0, 7 and 10 days on earth (10 eggs each) were flown in the space shuttle 'Endeavour' and further incubated for 7 days under microgravity. Twenty out of thirty eggs (9/10 ten-day-old; 10/10 seven-day-old; 1/10 zero-day-old) were recovered alive after landing. The only living embryo of the zero-day-old group died 24 days after launch, and was comparable to a 16-day-old embryo. The high mortality of the 0-day-old eggs appeared to be related to the specific inner structure of the egg. Simulation experiments performed on earth indicated that when yolk stayed in the albumen for more than 2 days, most of the embryos died. The subtle difference in specific gravity between the yolk (1.029) and albumen (1.040) plays a critical role in early chick embryogenesis.

Animals↗

PubMed1995

mRNA encoding the translation initiation factor eIF-4E is expressed early in Xenopus embryogenesis.

The translation initiation factor eIF-4E plays an important role in regulating the overall rate of translation in eukaryotic cells. To investigate the expression of eIF-4E itself, we characterized the eIF-4E mRNA expressed in Xenopus embryos. 5'-RACE was performed to determine the 5'-end of the mRNA and the result predicts isoforms differing at the amino-terminal end. Expression of the eIF-4E mRNA in Xenopus oocytes and embryos was examined by RT-PCR. Xenopus eIF-4E mRNA is produced during oogenesis and persists during the early stages of embryogenesis as a maternal mRNA.

Activin Receptors↗

PubMed1990

Ecdysteroid fluctuations during embryogenesis in the giant freshwater prawn, Macrobrachium rosenbergii.

Ecdysteroid levels during the embryogenesis of the giant freshwater prawn, Macrobrachium rosenbergii, were determined by radioimmunoassay and high-performance liquid chromatography. Ecdysteroids consisting of significant amounts of 20-hydroxyecdysone and high-polarity products (HPP) and lesser amounts of ecdysone and low-polarity products (LPP) were detected in mature ovaries and newly laid eggs. All ecdysteroid groups decreased gradually during the nauplius phase. With the formation of the compound eye and the appearance of the carapace and other body-like structures, marking morphogenesis to the zoeal stage, embryos showed the beginning of a continuous and dramatic increase in ecdysteroid concentrations sustained until larval hatchout. Ecdysteroid levels at hatchout were above 20-fold greater than ecdysteroid levels in newly laid eggs. More specifically, HPP and 20-hydroxyecdysone increased concomitantly, with a decrease in 20-hydroxyecdysone only at the end of the embryogenic period, while ecdysone and LPP levels remained low or undetectable. It may be postulated that the presence of ecdysteroids in ovaries and eggs represents a reserve of maternal ecdysteroids which are necessary at the commencement of embryonic development; with the differentiation of embryonic tissue capable of ecdysteroid synthesis, ecdysteroids increase rapidly to play a role in later embryonic development.

Animals↗

PubMed1986

Cell lineage-specific programs of expression of multiple actin genes during sea urchin embryogenesis.

We have determined spatial patterns of expression of individual actin genes in embryos of the sea urchin Strongylocentrotus purpuratus. Radioactively labeled probes specific for each of five cytoplasmic-type (Cy) and the single muscle-type (M) mRNAs were hybridized in situ to sections of fixed embryos. M actin mRNA appears only late in development and is confined to a few cells associated with the coelomic rudiments. The five Cy mRNAs fall into three sets, whose times and sites of expression during development are highly distinctive. Different cell lineages express messages of one or more of these sets, but never all three. Although all Cy actin mRNAs exhibit monophasic accumulation in the RNA of whole embryos during the course of development, such accumulation in many cases results from the summation of both increases and decreases in abundance within individual sets of cells. Within the genomic linkage group CyI-CyIIa-CyIIb, expression of CyI and CyIIb appears to be co-ordinate, and quite distinct from that of CyIIa. CyI and CyIIb are expressed in all lineages at some point in embryogenesis, but confined mainly to oral ectoderm and portions of the gut of the pluteus larva. CyIIa mRNAs are restricted to mesenchyme lineages throughout late gastrula stage, and subsequently accumulate in parts of the gut. The CyIIIa and CyIIIb genes, which form a separate linkage group, are expressed only in aboral ectoderm and its precursors. Furthermore, CyIII messages are the only detectable actin mRNAs in this cell lineage after late blastula stage.

Actins↗

PubMed1987

A Drosophila heat shock gene from locus 67B is expressed during embryogenesis and pupation.

We present a detailed characterization of the structure and expression of gene 3 from the 67B locus of Drosophila melanogaster. Northern blot analysis reveals a major poly(A)+ transcript during two stages of development: mid-embryogenesis and beginning of pupation. After heat shock, the abundance of this mRNA is increased and small amounts of larger RNAs representing alternate terminations of the major transcript appear. In Schneider 3 tissue culture cells, beside the major transcript, we also observe small amounts of the larger RNAs after a heat shock. The sequencing of cDNA and genomic clones shows an intronless transcription unit with one long open reading frame. The deduced polypeptide has 169 amino acids. It shares a strong homology with the four small heat shock proteins in the region also conserved in the mammalian alpha-crystalline B2 chain. In gene 3, this homology is restricted to the first 50 residues along the conserved 83 amino acid stretch. Two heat shock regulatory elements are localized upstream from the gene.

Animals↗

PubMed1988

An unusual split Drosophila heat shock gene expressed during embryogenesis, pupation and in testis.

Gene 2, one of the seven heat shock genes from locus 67B of Drosophila melanogaster, is transcribed into two polyadenylated RNAs having different developmental profiles of expression. The smaller transcript, of about 560 nucleotides, is expressed from mid-embryogenesis to the first two larval stages and again at the beginning of pupation. The larger transcript, 780 nucleotides, contains an additional 5' exon, accounting for its larger size. It is detected in pupae and adults, is male-specific and is localized in the testes. Heat shock does not affect the abundance of these two transcripts but induces the accumulation of a third RNA species of about 2000 nucleotides. This heat-shock RNA has the same cap site as the embryonic transcript, while its 3' portion entirely includes the neighbouring hsp22 gene. It appears, therefore, that in this case, heat shock alters the normal transcription termination process. By contrast to most heat shock genes, gene 2 contains several micro introns. One long open reading frame common to the three transcripts encodes a putative polypeptide of 111 amino acid residues. No homology was found with the other small heat shock genes of locus 67B.

Animals↗

PubMed1984

The role of Ca2+ in the regulation of embryogenesis in early amphibian and echinoderm embryos.

It is difficult to measure intracellular calcium concentrations in dividing embryos and, furthermore, these interact with pHi and with cyclic nucleotides. Nevertheless, the evidence currently suggests that changing [Ca2+]i levels probably do not have a major role in controlling normal cell-to-cell communication and so do not integrate cell division during programmed cleavage in amphibian embryos. However, treatments that are known or expected to raise artificially cytoplasmic calcium to relatively high levels cause abnormal embryogenesis, probably via the uncoupling of intercellular communication of the blastomeres, and also cortical contractions in early echinoderm and amphibian embryos.

Amphibians↗

PubMed1978

Expression of TEM-induced damage to postmeiotic stages of spermatogenesis of the mouse during early embryogenesis. II. Cytological investigations.

After treatment of postmeiotic stages of spermatogenesis of the mouse with TEM (0.2 or 0.4 mg/kg), dose- and stage-of-spermatogenesis-dependent frequencies of cytogenetic aberrations can be observed in early embryos. The frequencies of first-cleavage metaphases exhibiting structural aberrations (all of the chromosome type), the frequencies of 2 cell embryos and of 4--8 cell embryos containing nuclei accompanied by micronuclei or nuclei connected by bridges show a close correlation to frequencies of preimplantation loss of embryos recorded in a dominant lethal test. The frequencies of morulae/blastulae exhibiting blastomeres with micronuclei show a close correlation to the frequencies of total (pre- and post-implantation) loss of embryos. This indicates delayed expression of TEM-induced chromosomal damage which could persist undetected in very early stages of embryogenesis.

Animals↗

PubMed1983

Transforming ability of avian defective leukemia viruses in early embryogenesis.

The response to infection of chicken hemopoietic cells derived from the early stages of embryogenesis by avian myeloblastosis virus (AMV) and avian erythroblastosis virus (AEV) was investigated. It was found that erythroid progenitor cells were present in the blastoderm at a higher frequency than that of myeloid progenitor cells. These results correlate with the observation that target cells for AEV were found to be more numerous than those for AMV. Therefore, blastoderm cells are of potential value in understanding the mechanisms of oncogenesis at the level of the target cells.

Alpharetrovirus↗