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  • Cladocera  (1)
  • Interspecies transfer  (1)
  • Springer  (2)
  • American Institute of Physics (AIP)
  • 1
    ISSN: 1432-0878
    Schlagwort(e): Implantation ; Embryo ; Vasculature ; Interspecies transfer ; Non-uterine implantation ; Rat (Sprague-Dawley) ; Guinea-pig (Dunkin Hartley) ; Mouse (Random Swiss;C57xCBAFl)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary Pre-implantation-stage embryos from rats, mice, and guinea-pigs were transferred to a non-uterine site — the anterior chamber of the eye — of female recipients. All 9 combinations of transfers were performed: 3 allogeneic (intraspecies) transfers as controls, and 6 xenogeneic (interspecies) transfers. Implantation, as judged by extravasation from blood vessels of the iris or ciliary body occurred with success rates of 90.4% per transfer in the control rat group, 76.9% in the control mouse group, and 81.8% in the control guinea-pig group. Significantly reduced implantation rates occurred in the rat to guinea-pig (0%), mouse to rat (46.9%), mouse to guinea-pig (6.7%), and guinea-pig to rat (0%) groups compared to controls. Reductions, although not significant, also occurred in the other 2 groups: rat to mouse (77.8%), and guinea-pig to mouse (44.4%). These results together with some ultrastructural and lightmicroscopical observations suggest a degree of species specificity involved in the vascular response to the implanting embryo. We propose that the peri-implantation embryo produces a signal(s) which is to some extent species specific and which in the normal allogeneic situation is responsible for the early vascular effects seen at implantation in most eutherian mammals.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 394 (1999), S. 29-39 
    ISSN: 1573-5117
    Schlagwort(e): endopolyploidy ; development ; ontogeny ; endomitosis ; ploidy ; modulation ; Cladocera
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Although the presence of polyploid cells in somatic tissues of the cladoceran Daphnia has been reported, the nature of ploidy level shifts through life has not been investigated. This study examined the effects of growth and age on ploidy level variation across 10 instars in Daphnia pulex. The transition from mitotic to endomitotic cycles occurred during embryogenesis in all tissues, but the timing of it appeared to be tissue-specific. Lower than expected DNA estimates for the 4C and 8C ploidy classes suggested an underreplication of the genome during the first two endomitotic cycles, while complete replication seemed to occur in subsequent cycles. Polyploid cells underwent from four to seven endomitotic cycles over the 13 postembryonic instars, with ploidy levels reaching a maximum of 2048C in the labrum. The number of polyploid cells in all tissues, except the digestive tract, remained uniform beyond the fourth instar. Three patterns of ploidy level increments were observed i n the various tissues. Polyploid cells in the epipodite and rostrum exhibited age-related shifts, reaching asymptotic levels, while those in the digestive tract similarly reached asymptotic levels but then re-entered the mitotic cycle to enable tissue growth. Finally, ploidy level shifts in both the labrum and the epidermis were affected by age and food levels.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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