The effect of FF-MAS on porcine cumulus-oocyte complex maturation, fertilization and pronucleus formation in vitro.

Follicular fluid meiosis-activating sterol (FF-MAS) has been isolated from the follicular fluid (FF) of several species including man. FF-MAS increases the quality of in vitro oocyte maturation, and thus the developmental potential of oocytes exposed to FF-MAS during in vitro maturation is improved. The aim of the present study was to investigate the effects of FF-MAS on porcine oocyte maturation and pronucleus formation in vitro.

Effect of prematuration, meiosis activating sterol and enriched maturation medium on the nuclear maturation and competence to development of calf oocytes.

New strategies were proposed to improve the developmental competence of calf oocytes through in vitro technologies. Cumulus-oocyte complexes were first prematured for 24 h in the presence of meiosis inhibitors. Both Roscovitine alone (50 microM) or in combination with Butyrolactone-I (12.

Ultrastructural modifications in bovine oocytes maintained in meiotic arrest in vitro using roscovitine or butyrolactone.

Butyrolactone-I (BL-I) and roscovitine (ROSC) are selective inhibitors of the cyclin-dependent kinases, and both have been shown to reversibly inhibit meiotic resumption in cattle oocytes for 24 hr without having a negative affect on subsequent development to the blastocyst stage. The aim of the present study was to describe the morphological changes occurring in fully grown immature and in vitro matured bovine oocytes following exposure to either BL-I or ROSC for 24 hr at concentrations known to be consistent with normal development. Immature bovine cumulus oocyte complexes, recovered from the ovaries of slaughtered heifers, were incubated for 24 hr in the presence of one of the inhibitors.

Physiology of meiosis-activating sterol: endogenous formation and mode of action.

Background: In the context of mammalian oocyte maturation, it has been suggested that intermediates of cholesterol biosynthesis may represent the physiological signal that instructs the oocyte to reinitiate meiosis.

Methods: Endogenous levels of follicular fluid meiosis-activating sterol (FF-MAS) were monitored in rabbit ovarian tissue, and the influence of exogenous gonadotrophins on sterol formation was assessed. The involvement of cAMP in FF-MAS-induced versus spontaneous oocyte maturation in vitro in mice was also investigated, as was the direct microinjection of FF-MAS into mouse oocytes.

Resumption of meiosis induced by meiosis-activating sterol has a different signal transduction pathway than spontaneous resumption of meiosis in denuded mouse oocytes cultured in vitro.

The sterol 4,4-dimethyl-5-cholesta-8,14,24-trien-3-ol (follicular fluid meiosis-activating sterol [FF-MAS]) isolated from human follicular fluid induces resumption of meiosis in mouse oocytes cultured in vitro. The purpose of this study was to examine the hypothesis that differential signal transduction mechanisms exist for FF-MAS-induced and spontaneous in vitro resumption of meiosis in mouse oocytes. Mouse oocytes were dissected from ovaries originating from mice primed with FSH 48 h before oocyte collection.

Nuclear ultrastructure in bovine oocytes after inhibition of meiosis by chemical and biological inhibitors.

Various components of the ovarian follicle as well as different chemicals can suppress the resumption of meiosis in cumulus-oocyte complexes (COCs). In this study the nuclear ultrastructure of bovine COCs was assessed after 8 h of meiotic inhibition with 50 microM roscovitine (ROSC), 50 microM butyrolactone (BL-I), 2 mM 6-DMAP, 2 microM cycloheximide (CX), or a theca cell monolayer (TC). COCs were recovered according to standard in vitro methods, cultured in a simple and defined medium, and processed for transmission electron microscopy.

Autoradiographic localization of specific binding of meiosis-activating sterol to cumulus-oocyte complexes from marmoset, cow, and mouse.

The sterol, 4,4-dimethyl-5alpha-cholesta-8,14,24-trien-3beta-ol (FF-MAS), isolated from human follicular fluid, can induce resumption of meiosis in denuded and cumulus-enclosed mouse oocytes inhibited by hypoxanthine, IBMX, or dibutyric cyclic adenosine monophosphate. In this study the distribution of FF-MAS binding sites in denuded oocytes and in cumulus-oocyte complexes (COCs) was studied using light microscopic (LM) and transmission electron microscopic (TEM) autoradiography in marmoset, cow, and mouse oocytes. Denuded (n = 39) and cumulus-enclosed (n = 28) marmoset, cow, and mouse oocytes were cultured in the presence of [3H]FF-MAS with and without excess of unlabeled FF-MAS, respectively.

Meiosis-activating sterol-mediated resumption of meiosis in mouse oocytes in vitro is influenced by protein synthesis inhibition and cholera toxin.

To explore the possible signaling pathways of meiosis-activating sterol (MAS)-induced oocyte maturation and to elucidate whether the MAS pathway involves transcription or translation, arrested immature mouse oocytes were cultured with either the protein synthesis inhibitor cycloheximide or the heteronuclear RNA inhibitors alpha-amanitin or actinomycin D, respectively. Moreover, the possible involvement of a G protein-coupled receptor mechanism in MAS-mediated oocyte maturation was explored by influencing oocyte maturation with cholera toxin (CT). MAS-induced oocyte maturation was completely blocked by the addition of 50 microg/ml cycloheximide 4 h before the addition of MAS.