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  • 1
    ISSN: 1432-041X
    Keywords: C-myc stability ; Development ; Amphibian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used the axolotl oocyte (Ambystoma mexicanum Shaw) to study the stability of exogenously injected Xenopus RNAs. Three different cellular developmental stages have been analysed: (1) the growing oocyte (stage III–IV of vitellogenesis), (2) the full-grown oocyte at the end of vitellogenesis (stage VI) and (3) the progesterone-matured stage VI oocyte. Three exogenous RNAs have been synthesized in vitro from a c-myc Xenopus cDNA clone. One transcript is 2.3 kb long (full length), the second is 1.5 kb long, with most of the 3′ untranslated region (3′UTR) removed, and the third corresponds to the 3′UTR (0.8 kb). After injection or coinjection of these exogenous Xenopus RNAs into axolotl oocytes, the stability of the molecules was studied after 5 min, 6 h and 21 h by extraction of total RNA and Northern blot analysis. Results show a difference in Xenopus RNA stability during axolotl oogenesis. In growing oocytes, the three synthetic transcripts are gradually degraded. The absence of the 3′UTR is not therefore sufficient to stabilize the transcript during early oogenesis. No degradation is observed in full-grown oocytes, suggesting the existence of stabilizing factors at the end of oogenesis. When stage VI oocytes are induced to mature by progesterone, only the 2.3 and 1.5 kb Xenopus RNAs disappear. This suggests a role for germinal vesicle breakdown in this degradation process as well as the existence of a factor present in the nucleus and involved in the specific destabilization of these RNAs after oocyte maturation. This degradation might implicate several destabilizing sequences localized in the coding or in the 3′UTR of the c-myc gene. In contrast, the 0.8 kb transcript (3′UTR) is not degraded during this period and remains very stable. Therefore, degradation appears distinct from one transcript to another and from one region to another within the same molecule. During maturation, the behaviour of the 2.3 and 1.5 kb transcripts is different when coinjected with the 3′UTR, suggesting a role in trans of this untranslated molecule in c-myc stability. Our approach allows us to analyse the role of the coding and 3′UTR regions of the c-myc RNA in the control of mRNA degradation in vivo.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 205 (1995), S. 192-197 
    ISSN: 1432-041X
    Keywords: mRNA stability ; c-myc ; mRNA ; Maturation ; Amphibian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have previously described an in vivo heterologous system which has allowed us to study the stability of different Xenopus c-myc RNA constructs injected into axolotl oocytes. In full-grown oocytes, degradation of c-myc RNA does not occur. In mature oocytes treated with progesterone, transcripts containing the coding sequence of the gene are degraded, whereas those corresponding to the 3'UTR (untranslated region) alone are stable. In order to study the role of nuclear or cytoplasmic components in this process, degradation of injected c-myc transcripts was analysed (i) after inhibition of germinal vesicle breakdown (GVBD) in progesterone treated oocytes (ii) after induced maturation of enucleated oocytes, (iii) injection of nuclear contents into immature oocytes and (iv) after direct injection into the germinal vesicle of full-grown oocytes. Our results demonstrate the role of a nuclear factor stockpiled in the germinal vesicle of full-grown oocytes and specifically involved in the degradation of c-myc transcripts containing the coding region. Further biochemical characterization of this new nuclear component should lead to a better understanding of the post-transcriptional control of c-myc expression during oogenesis and early development.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 195 (1986), S. 186-192 
    ISSN: 1432-041X
    Keywords: DNA ligase ; Gene activity ; Nuclear transplantation ; Ram spermatids ; Axolotl egg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary During animal development and gametogenesis two DNA ligases are found and successively expressed. In this study the two DNA ligases present in the axolotl egg and the two ligases present during ram sperm cell maturation were distinguished by biochemical and immunological methods. The expression of the genes for the heavy and light ram DNA ligases has been studied using transplantation of spermatid and sperm nuclei in axolotl eggs. We found that ram DNA ligases were expressed in axolotl egg cytoplasm. The exclusion phenomenon between the heavy and light form of DNA ligase is species-specific and involves a cytoplasmic mediator. In the transplanted ram germ cell nuclei the heavy ram DNA ligase expression was found to be sensitive to inhibitors of transcription while the light one was not. When mRNA was used, no exclusion process was observed and both the heavy and light enzyme expression were sensitive to cycloheximide and not to aamanitin. These results are discussed in terms of the possible stability of the gene-regulated state following nuclear transfer.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Chromosoma 17 (1965), S. 328-335 
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Summary A technique is described by which especially clear pictures of the chromosomes in blastulae of Ambystoma mexicanum can be obtained. An analysis of the karyotype is given. This study touches upon problems concerning the significance of heterochromatin and the relation between satellites and nucleoli.
    Notes: Résumé Une technique est décrite permettant d'obtenir des images chromosomiques particulièrement favorables fournies par des blastulas d'Axolotl. A partir de ce matériel le caryotype de cette espèce est analysé. Cette étude introduit des problèmes concernant la signification de l'hétérochromatine, ainsi que les rapports entre satellite et nucléoles.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of orthopaedic surgery & traumatology 8 (1998), S. 71-79 
    ISSN: 1432-1068
    Keywords: Leg fractures ; Non-union ; Infection ; Bone-grafting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The authors present a series of 22 cases of fistular non-unions of the leg treated by posterior intertibiofibular bone grafting (GITP), between 1982 and 1984. The average follow-up was 6 years (3–9 years). Healing occured in 16 cases within 326 days after GITP alone, 3 needed complementary grafting, and there were 2 failures (1 amputation). The authors emphasise the value of the early posterior retrofibular approach. This procedure should be done early where there is extensive bone loss, or in severe compound comminuted fractures.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Cell Differentiation and Development 27 (1989), S. 93 
    ISSN: 0922-3371
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Cell Differentiation and Development 27 (1989), S. 125 
    ISSN: 0922-3371
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Cell Differentiation and Development 27 (1989), S. 147 
    ISSN: 0922-3371
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Brain and Language 13 (1981), S. 191-196 
    ISSN: 0093-934X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Linguistics and Literary Studies , Medicine , Psychology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Brain and Language 22 (1984), S. 303-319 
    ISSN: 0093-934X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Linguistics and Literary Studies , Medicine , Psychology
    Type of Medium: Electronic Resource
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