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Studies on maturation and differentiation without cleavage in Chaetopterus variopedatus: Effects of ions, ionophores, sulfhydril reagents, colchicine and cytochalasin B

par Brachet, Jean ;Denis-Donini, S
Référence Differentiation, 11, 1-3, page (19-37)
Publication Publié, 1978

Article révisé par les pairs

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Résumé :

Differentiation without cleavage in Chaetopterus eggs has been reexamined cytologically with particular emphasis on RNA distribution. The induction of differentiation without cleavage by KCl treatment requires the presence of Ca2+ in the medium. Once activation has been induced by KCl, external Ca2+ is no longer required for differentiation without cleavage until the swimming larvae stage. The Ca2+ ionophore A23187 induces maturation and activation in Chaetopterus eggs in the presence of Ca2+; if the activated eggs are transfered to normal medium, differentiation without cleavage and occasional parthenogenesis follow. The K+ ionophore valinomycin slowly induces germinal vesicle breakdown, but maturation is abortive and there is no further development. The ionophore stops cleavage in fertilized eggs. After a few hours, valinomycin‐treated oocytes develop large, transparent, RNA‐rich blebs. Maturation can be induced, in Cheatopterus eggs, by organomercurials but not by dithiothreitol. DNA replication and amoeboid movements take place in organomercurial treated eggs but neither hatching nor ciliation occurs. Colchicine is more effective than cytochalasin B for the inhibition of differentiation without cleavage, however the reverse is true for the inhibition of valinomycin‐induced blebbing. Copyright © 1978, Wiley Blackwell. All rights reserved