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Nicotinamide alters the calcium release pattern and the degradation of MPF activity after fertilisation in ascidian oocytes

Published online by Cambridge University Press:  01 August 1999

Martin Wilding
Affiliation:
Stazione Zoologia ‘Anton Dohrn’, Villa Comunale, 80121 Naples, Italy.
Marcella Marino
Affiliation:
Stazione Zoologia ‘Anton Dohrn’, Villa Comunale, 80121 Naples, Italy.
Daniela Dale
Affiliation:
Stazione Zoologia ‘Anton Dohrn’, Villa Comunale, 80121 Naples, Italy.

Abstract

Fertilisation in ascidian oocytes triggers a plasma membrane current, the release of intracellular calcium and the degradation of Maturation Promoting Factor (MPF) activity leading to the completion of meiosis and the initiation of embryo development. We have previously shown that the fertilisation current in ascidians is produced through the metabolism of nicotinamide nucleotide (NN) metabolites to ADP ribose. In this study we have used nicotinamide to test whether NN metabolism plays additional roles in fertilisation in ascidians. Nicotinamide treatment blocked calcium-induced calcium release (CICR) and arrested the cell cycle prior to the completion of meiosis I. Nicotinamide further prevented the abolition of MPF activity after fertilisation. Interestingly, nicotinamide treatment caused ascidian oocytes to form interphase-like pronuclei after fertilisation, despite the high MPF activity. The data demonstrate that NN metabolism is involved in calcium signalling through CICR and further suggest that a NN metabolite acts as a messenger connecting MPF activity to the formation of the meiotic apparatus.

Type
Research Article
Copyright
1999 Cambridge University Press

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