C. Arnoult et al., CELL CYCLE-RELATED FLUCTUATIONS IN OOCYTE SURFACE-AREA OF THE ASCIDIAN CIONA-INTESTINALIS AFTER MEIOSIS RESUMPTION, Developmental biology, 166(1), 1994, pp. 1-10
Variations in capacitance or cell surface area were recorded on patch-
clamped eggs of the ascidian Ciona intestinalis between the resumption
of meiosis and the first mitotic cleavages. The membrane surface area
increased within the first minutes after fertilization and then oscil
lated in phase with the cell cycles of the two meiotic divisions and f
irst mitotic cleavage. With drugs, we generated two opposite situation
s (removal and insertion) of artificial variation in capacitance. In u
nfertilized eggs, cytochalasin induced a drop in capacitance linked to
a decrease in calcium current intensity and specifically disturbed me
mbrane removal linked to the first meiotic division cycle. It left una
ffected the following cycles, in agreement with previous results that
only the first meiosis cycle is microfilament dependent. In fertilized
eggs, membrane removal at each cycle was hindered by emetine, an inhi
bitor of protein synthesis. The resulting membrane extrusion was obser
ved in sections by electron microscopy and was linked to an increase i
n calcium current intensity. These fluctuations in surface area never
involved the microtubule network, since nocodazole had no effect on an
y cycle. The fluctuations of membrane surface area after meiosis resum
ption in phase with cell cycles in Ciorna oocytes paralleled the patte
rn previously described in the ascidian Boltenia villosa. This may ref
lect the mechanism by which the oocyte regulates, with possibly differ
ent mediators at each cycle, the connection between cell surface and i
nternal membrane networks. This interrelation includes the insertion a
nd removal of ion channels necessary to developmental control. (C) 199
4 Academic Press, Inc.