Action du mercaptoéthanol et de l'acide lipoïque sur la morphogénèse de l'embryon de poulet

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Recherches sur les acides désoxyribonucléiques d'Acetabularia mediterranea

The density of the DNA present in the cytoplasm of Acetabularia mediterranea has been determined by centrifugation in a CsCl gradient. Electron microscope examination has demonstrated that a unique DNA having a density of 1.704 g/cm3 is extracted from a pure fraction of chloro‐plasts. The method elaborated by Suyama and Bonner for the isolation of the mitochondria has enabled us to isolate a sub‐cellular fraction with cytochrome oxidase activity, from which we were able to extract a small amount of pure DNA which is probably mitochondrial DNA, having only one density peak at 1.715 g/cm3; unlike mitochondrial DNA, chloroplast DNA is sensitive to prolonged maintenance of the algae in the dark, as well as to treatment of a suspension of chloroplasts and mitochondria with deoxyribonuclease. Under our experimental conditions, centrifugation of cytoplasmic DNA in CsCl to which ethidium bromide is added seems to exclude the possibility that circular molecules of DNA occur whether of chloroplastic or of mitochondrial origin. Both cytoplasmic DNA readily undergo thermal denaturation. Renaturation of chloroplast DNA is incomplete, whereas mitochondrial DNA renatures readily completely. During the process of cyst formation and nuclear multiplication, it is possible to extract newly formed DNA which is probably nuclear: it has a density of 1.696 g/cm3. All three DNA, with a boyant density of 1.696, 1.704, 1.715 g/cm3, respectively, disappear after treatment with deoxyribonuclease, but remain intact after treatment with a mixture of α‐ and β‐amylases. We would like to suggest that following many years of laboratory culture, Acetabularia mediterranea may have given rise to new genetically distinct species. Such an hypothesis would explain the apparent lack of agreement between our own findings and those of Gibor and of Schweiger. Copyright © 1971, Wiley Blackwell. All rights reservedSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Study of the role of sulfhydryl groups in the morphogenesis of the chick embryo.

Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Net DNA synthesis in anucleate fragments of Acetabularia mediterranea

Journal ArticleSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Guide des travaux pratiques d'histologie

Laboratoire d'Histologie, Neuroanatomie et Neuropathologie2e candidature médecine, 2e candidature sciences biomédicales - MEDC 117info:eu-repo/semantics/published

Etude du rôle des groupes sulfhydriles dans la morphogénèse de l'embryon de poulet

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Effets de l'hydroxyurée sur Acet abularia mediterranea

Effects of hydroxyurea on Acetabularia mediterranea. The effects of hydroxyurea, an inhibitor of DNA synthesis, on the morphogenesis, the synthesis of nucleic acids and the density of the cytoplasmic DNA's have been studied in nucleate and anucleate fragments of the unicellular alga Acetabularia mediterranea. It was found that: (1) the morphostatic effect of hydroxyurea is most marked at the beginning of cap formation; (2) in the presence of hydroxyurea, the synthesis of nucleic acids in the cytoplasm is inhibited in the whole algae as well as in anucleate fragments; (3) on the other hand, nuclear DNA synthesis which accompanies the formation of cysts, does not seem to be influenced by the presence of hydroxyurea in the culture medium; (4) no modifications of the density of the various cytoplasmic DNA's, as a result of treatment with hydroxyurea, have ever been observed. The significance of these results is discussed in the light of previous hypotheses concerning the mode of action of hydroxyurea. © 1969.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Free RNA polymerase activities in isolated nuclei from Xenopus laevis embryos. Stimulation of endogenous template-bound RNA polymerase II activity by poly d(A-T)

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Effets de l'acide α-lipoïque sur le métabolisme des acides nucléiques chez les embryons de Batraciens et de Poulet

Both the oxidized and the reduced forms of lipoic acid inhibit neural tube closure in pleurodeles and in chicken embryos. Oxidized lipoic acid inhibits the incorporation of H3-uridine and H3-cytidine into DNA; it inhibits the stage which involves the reduction of the ribonucleosides to the deoxyribonucleosides: in fact, the incorporation of H3-deoxyuridine is little or not at all affected by this substance. The action of reduced lipoic acid and reduced triphosphopyridine nucleotide on the reduction of ribose to deoxyribose is just the opposite of that exerted by oxidized lipoic acid. The addition of TPNH to oxidized lipoic acid prevents the inhibition of the incorporation of the ribonucleosides normally observed with oxidized lipoic acid. The degree of incorporation of H3-thymidine in the presence of these components appears to be "complementary" to the incorporation of H3-uridine and H3-cytidine into DNA. RNA metabolism is also deeply disturbed in embryos treated with oxidized or reduced lipoic acid. The effect of lipoic acid, whether oxidized or reduced, seems to be specific, since neither dithiodiglycol nor mercaptoethanol have the same effects on the incorporation of ribonucleosides into DNA. The significance of these autoradiographic findings is discussed; it is finally suggested that the arrest of morphogenesis might result from a disturbance of nucleic acid metabolism. © 1964.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effets de l'acide lipoïque oxydé sur la synthèse de l'acide désoxyribonucléique chez les embryons de batraciens et de poulet

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