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Nature of the 1‐Methyladenine‐Requiring Phase in Maturation of Starfish Oocytes
Author(s) -
NEMOTO SHINICHI
Publication year - 1982
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1111/j.1440-169x.1982.00429.x
Subject(s) - germinal vesicle , starfish , dithiothreitol , oocyte , cytoplasm , microbiology and biotechnology , biology , maturation promoting factor , intracellular , ionophore , chemistry , biophysics , biochemistry , endocrinology , andrology , embryo , cell , medicine , ecology , cyclin dependent kinase 1 , membrane , cell cycle , enzyme
Reinitiation of meiosis in starfish oocytes requires the continuous presence of 1‐methyladenine (1‐MeAde) in the surrounding medium for a definite period. The length of the ‘hormone‐dependent phase’ (HDP) in Asterina pectinifera , which was defined as the time necessary for induction of 50% germinal vesicle breakdown (GVBD), was found to be about 11 min at 17°C, and 8 min at 20°C. Repeated treatments for shorter periods with 1‐MeAde revealed that the action of this agent was cumulative, and that stable intermediate states between the unstimulated and fully stimulated levels existed during the HDP. Measurement of the stiffness of oocytes also demonstrated this stable intermediate state. Thus, there may be a factor(s) in the cytoplasm that accumulates continuously during the HDP and triggers GVBD when it reaches a critical level(s). When dithiothreitol (DTT) was used as an artificial maturation‐inducing agent, the intermediate state was far less stable, suggesting a difference in the modes of action of 1‐MeAde and DTT. Isotonic CaCl 2 , the Ca 2+ ionophore (A 23187) and methylxanthines, which are known to cause increase in intracellular Ca 2+ , had additive effects with 1‐MeAde. These results suggest that part of the action of 1‐MeAde is to release Ca 2+ in the oocyte cytoplasm.