title: Increased free Ca2+ levels delay the onset of mitosis in fertilized and artificially activated eggs of the sea urchin.
abstract: Increasing free Ca2+ in the cytoplasm of fertilized and NH4OH- or A23187-activated eggs of Strongylocentrotus purpuratus and Lytechinus variegatus resulted in significant delays in the onset of mitosis. The increased Ca2+ levels were induced by addition of the calcium ionophore A23187 to suspensions of fertilized and activated eggs, or by fertilizing NH4OH-activated eggs. The delays may represent a temporary inhibition of the activation and activities of the mitotic proteins. It is postulated that relatively high free Ca2+ levels in the cytoplasm prevents activation of the mitotic proteins. Active Ca2+ sequestration is therefore suggested as an essential factor in the onset and progression of early mitosis.
mesh_terms: D064753:Ammonium Hydroxide; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D005260:Female; D006096:Gramicidin / Q000494:pharmacology; D006878:Hydroxides / Q000494:pharmacology; D008938:Mitosis / Q000187:drug effects; D010063:Ovum / Q000166:cytology*; D012617:Sea Urchins; D013997:Time Factors; D015053:Zygote / Q000166:cytology*
chemical_list: D006878:Hydroxides; D006096:Gramicidin; D000001:Calcimycin; D064753:Ammonium Hydroxide; D002118:Calcium