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Ultrastructural changes during nuclear maturation in Bufo arenarum oocytes

Published online by Cambridge University Press:  01 August 1999

Inés Ramos
Affiliation:
Department of Developmental Biology, National Council for Scientific and Technical Research, National University of Tucumán, Tucumán, Argentina
Beatriz C. Winik
Affiliation:
Department of Developmental Biology, National Council for Scientific and Technical Research, National University of Tucumán, Tucumán, Argentina
Susana Cisint
Affiliation:
Department of Developmental Biology, National Council for Scientific and Technical Research, National University of Tucumán, Tucumán, Argentina
Claudia Crespo
Affiliation:
Department of Developmental Biology, National Council for Scientific and Technical Research, National University of Tucumán, Tucumán, Argentina
Marcela Medina
Affiliation:
Department of Developmental Biology, National Council for Scientific and Technical Research, National University of Tucumán, Tucumán, Argentina
Silvia Fernández
Affiliation:
Department of Developmental Biology, National Council for Scientific and Technical Research, National University of Tucumán, Tucumán, Argentina

Abstract

During progesterone-induced nuclear maturation the oocytes of Bufo arenarum undergo a series of nuclear and cytoplasmic changes. The breakdown of heterocellular communications between the follicular cell projections and the oocyte microvilli, and the consequent enlargement of the perivitelline space, were observed at the animal pole. The more evident cytoplasmic feature during nuclear maturation comprised the gathering of glycogen granules in clusters, some phagocytosed by empty vesicles. With respect to the location of these vesicles, some were observed in close proximity to the oolemma and others were freely suspended in the perivitelline space, extruded from the oocyte. Other visible events were the disruption of the annulate lamellae, the formation of an elaborate cortical endoplasmic reticulum and the rearrangement of the cortical granules in a monolayer immediately beneath the oolemma together with aggregates of endoplasmic reticulum cisternae. Our results show that during nuclear maturation the nuclear oocyte changes include a flattening of the spherical oocyte nucleus, its migration towards the surface of the animal pole, the disappearance of the nucleoli and the dissolution of the nuclear envelope.

Type
Research Article
Copyright
1999 Cambridge University Press

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