Role of cyclic AMP in the maturation of Ciona intestinalis oocytes.

Immature oocytes are arrested at prophase I of the meiotic process and maturation onset is indicated by oocyte nuclear disassembly (germinal vesicle breakdown or GVBD). Signaling pathways that elevate intracellular cyclic AMP (cAMP) may either prevent or induce oocyte maturation depending on the species. In some marine invertebrates and, in particular, in ascidian oocytes, cAMP triggers GVBD rather than blocking it.

Ion current activity and molecules modulating maturation and growth stages of ascidian (Ciona intestinalis) oocytes.

Electrophysiological techniques were used to study ion currents in the ascidian Ciona intestinalis oocyte plasma membranes during different stages of growth and meiosis. Three stages (A, B, C) of immature oocytes were discriminated in the ovary, with the germinal vesicle (GV) showing specific different features of growth and maturation. Stage A (pre-vitellogenic) oocytes exhibited the highest L-type Ca(2+)current activity, and were incompetent for meiosis resumption.

Ca2+ and Na+ current patterns during oocyte maturation, fertilization, and early developmental stages of Ciona intestinalis.

Using the whole-cell voltage clamp technique, the electrical changes in oocyte and embryo plasma membrane were followed during different meiotic and developmental stages in Ciona intestinalis. We show, for the first time, an electrophysiological characterization of the plasma membrane in oocytes at the germinal vesicle (GV) stage with high L-type calcium (Ca2+) current activity that decreased through meiosis. Moreover, the absence of Ca2+ reduced germinal vesicle breakdown (GVBD), which is consistent with a role of Ca2+ currents in the prophase/metaphase transition.

Calcium currents correlate with oocyte maturation during the reproductive cycle in Octopus vulgaris.

Using the whole-cell voltage clamp technique, we have studied the Ca2+ currents and the steady-state conductance during different oocyte growth stages and during the reproductive cycle of the female of Octopus vulgaris. Evidence is presented that L-type Ca2+ currents are high in small pre-vitellogenic oocytes (80-150 microm diameter) and significantly lower in early vitellogenic oocytes (180-300 microm diameter). Similarly, a significant decrease of the steady-state conductance occurred from the pre to early- vitellogenic oocytes.

Biochemical and functional characterization of protein kinase CK2 in ascidian Ciona intestinalis oocytes at fertilization. Cloning and sequence analysis of cDNA for alpha and beta subunits.

The ubiquitous and pleiotropic dual specificity protein kinase CK2 has been studied and characterized in many organisms, from yeast to mammals. Generally, the enzyme is composed of two catalytic (alpha and/or alpha') and two regulatory (beta) subunits, forming a differently assembled tetramer. Although prone to controversial interpretation, the function of CK2 has been associated with fundamental biological processes such as signal transduction, cell cycle progression, cell growth, apoptosis, and transcription.

Bioactive aldehydes from diatoms block the fertilization current in ascidian oocytes.

The effects of bioactive aldehydes from diatoms, unicellular algae at the base of the marine food web, were studied on fertilization and early development processes of the ascidian Ciona intestinalis. Using whole-cell voltage clamp techniques, we show that 2-trans-4-trans-decadienal (DD) and 2-trans-4-cis-7-cis-decatrienal (DT) inhibited the fertilization current which is generated in oocytes upon interaction with the spermatozoon. This inhibition was dose-dependent and was accompanied by inhibition of the voltage-gated calcium current activity of the plasma membrane.

Developmental potential in bovine oocytes is related to cumulus-oocyte complex grade, calcium current activity, and calcium stores.

A morphological classification of the immature cumulus-oocyte complex (COC), which grossly resembled the atresia grade of its follicle source, was used in bovine oocytes to determine 1) the developmental potential by either in vitro fertilization or parthenogenetic activation, 2) the calcium current activity by whole-cell voltage clamp technique, and 3) the intracytoplasmic calcium stores by microfluorimetric evaluation. The COC classification took into account some cumulus and ooplasm features, designated as follows: A) presence of a clear and compact cumulus and translucent ooplasm, B) dark and compact cumulus and dark ooplasm, and C) dark and expanded cumulus and dark ooplasm. We found no difference between in vitro fertilization and parthenogenetically activated oocytes in terms of cleavage rate and blastocyst production.