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  • Artificial heart  (1)
  • Egg evolution  (1)
  • 2000-2004  (2)
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  • 1
    ISSN: 1432-041X
    Schlagwort(e): Key words Noggin ; Direct development ; Egg evolution ; Head development ; Body axis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  We tested the effects of noggin RNA from Xenopus laevis on axis induction in embryos of a direct developing frog, Eleutherodactylus coqui. We microinjected noggin RNA into one blastomere of 4-cell embryos at the site close to the animal pole, and found that overexpression of noggin RNA is not only sufficient to induce additional axes but also induces heads with eyes. We also injected noggin RNA into 8-cell or 16-cell embryos in various sites, including the marginal zone, above the marginal zone, and the vegetal pole, and found the formation of a complete secondary axis in all three types of injection. These effects of X. laevis noggin RNA on the E. coqui embryo are remarkably different from those found in the X. laevis embryo itself. It has been shown previously that overexpression of noggin RNA on the ventral side of the normal X. laevis embryo induces only a partial axis, with no head structures. We show here that the failure of noggin induction of a complete axis when overexpressed on the ventral side of the X. laevis embryos is not due to an insufficient amount of RNA injected. Also, the failure is unlikely due to inhibition from the primary axis since noggin RNA can induce duplicated head structures on opposite sides of UV-irradiated X. laevis embryos. There appear to be fundamental differences in the responses of E. coqui and X. laevis embryos to exogenous noggin RNA. We propose that these differences stem from an alteration in cytoplasmic arrangements that occurred during evolution of this large egg.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1619-0904
    Schlagwort(e): Artificial heart ; Undulation pump ; Animal experiment ; Implantable total artificial heart
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract In the University of Tokyo, various types of total artificial heart (TAH) have been studied. Based on the experiences of TAH research, the development of the undulation pump total artifical heart (UPTAH) started in 1994. The undulation pump is a small-size, continuous-flow, displacement-type blood pump, and the UPTAH is a unique implantable total artificial heart that uses the undulation pump. To date, three models of UPTAH have been developed. The first model, UPTAH1, was developed to investigate the possibility of reducing the size of the device so it could be implanted in small adults, such as Japanese patients, in 1994. The second model, UPTAH2, which was the prototype of the animal experimental model, was developed in 1996 to investigate the possibility of survival with the UPTAH. The third model, UPTAH3, which is the present model, was developed in 1998 to enable long-term survival in animal experiments and to investigate the pathophysiology of the UPTAH. From July 1996 to October 1999, 22 implantations of UPTAH2 or UPTAH3 were performed in goats. In spite of the limitation of their small chest cavity, the UPTAH could be implanted into the chest of all goats. Using UPTAH3, survival of 31 days could be obtained. The research and development of UPTAH are ongoing.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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