Involvement of catecholamines in the regulation of oocyte maturation in frogs

Zygote ◽  
2002 ◽  
Vol 10 (3) ◽  
pp. 271-281 ◽  
Author(s):  
Inés Ramos ◽  
Susana Cisint ◽  
Claudia A. Crespo ◽  
Marcela F. Medina ◽  
Silvia N. Fernández
Keyword(s):  
Oocyte Maturation ◽  
Germinal Vesicle ◽  
Significant Inhibition ◽  
Follicle Cells ◽  
Germinal Vesicle Breakdown ◽  
Nuclear Maturation ◽  
Dose Dependent ◽  
Metabolic Behaviour

The present study investigates the role of catecholamines in the regulation of Bufo arenarum oocyte maturation. The metabolic changes in the oxidation of carbohydrates and the meiotic resumption evinced by the germinal vesicle breakdown were used as indicators of cytoplasmic and nuclear maturation, respectively. The results obtained suggest that noradrenaline (norepinephrine) could be one of the factors responsible for the metabolic behaviour that characterises cytoplasmically immature oocytes. The use of adrenaline (epinephrine), on the other hand, induced a metabolic change which made oocytes cytoplasmically mature. The effect of both catecholamines, which was dose-dependent, was observed in ovarian oocytes (surrounded by follicle cells) as well as in coelomic oocytes (free from follicle cells), suggesting the presence of adrenergic receptors in the gamete. The results obtained using adrenergic agonists and antagonists suggest that the effect of adrenaline would be due to an interaction with β2-receptors. Although catecholamines have an influence on the determination of the stage of cytoplasmic maturation of the oocytes, they do not affect nuclear maturation by themselves. Nevertheless, pretreatment of follicles with adrenaline caused a significant inhibition in progesterone-induced nuclear maturation even though this effect was markedly weaker when using noradrenaline.

Role of prolactin in nuclear maturation and ovulation in amphibian oocytes

Zygote ◽  
2005 ◽  
Vol 13 (3) ◽  
pp. 265-268
Author(s):  
Inés Ramos ◽  
Susana Cisint ◽  
Marcela F. Medina ◽  
Claudia A. Crespo ◽  
Silvia N. Fernández
Keyword(s):  
Oocyte Maturation ◽  
Incubation Medium ◽  
Germinal Vesicle ◽  
Sexual Cycle ◽  
Breeding Period ◽  
Germinal Vesicle Breakdown ◽  
Nuclear Maturation ◽  
Bufo Arenarum

The present study was undertaken to determine the effect of prolactin (Prl) on Bufo arenarum oocyte maturation and ovulation, two characteristic events of the breeding period, the stage of the sexual cycle in which gamete growth is complete. We observed that Prl, at the doses assayed, did not affect nuclear maturation per se. In addition, when follicles were pretreated with Prl and progesterone was later added to the medium as a physiological nuclear maturation inducer, the percentage of germinal vesicle breakdown obtained with the steroid was unaffected by Prl. The analysis of the in vitro ovulation process demonstrated that pituitary homologous homogenate (PHH) produced a dose- and month-dependent stimulating effect. The maximum percentage of ovulated oocytes was obtained from the end of July to October, the period in which oviposition naturally occurs. Prl by itself did not affect the ovulation process, but when both the hormone and PHH were present in the incubation medium, a significant increase in ovulated oocytes was observed. The results suggest that Prl does not participate in oocyte maturation; however, its presence in the incubation medium would increase oocyte sensitivity to the action of the physiological ovulation inducers.

scholarly journals Requirement of mosXe protein kinase for meiotic maturation of Xenopus oocytes induced by a cdc2 mutant lacking regulatory phosphorylation sites.

1992 ◽  
Vol 12 (7) ◽  
pp. 3192-3203 ◽  
Author(s):  
K M Pickham ◽  
A N Meyer ◽  
J Li ◽  
D J Donoghue
Keyword(s):  
Protein Kinase ◽  
Oocyte Maturation ◽  
Xenopus Oocytes ◽  
Germinal Vesicle ◽  
Cyclin B1 ◽  
Phosphorylation Sites ◽  
Germinal Vesicle Breakdown ◽  
Regulatory Phosphorylation

The p34cdc2 protein kinase is a component of maturation-promoting factor, the master regulator of the cell cycle in all eukaryotes. The activity of p34cdc2 is itself tightly regulated by phosphorylation and dephosphorylation. Predicted regulatory phosphorylation sites of Xenopus p34cdc2 were mutated in vitro, and in vitro-transcribed RNAs were injected into Xenopus oocytes. The cdc2 single mutants Thr-14----Ala and Tyr-15----Phe did not induce germinal vesicle breakdown (BVBD) upon microinjection into oocytes. In contrast, the cdc2 double mutant Ala-14/Phe-15 did induce GVBD. Both the Ala-14 and Ala-14/Phe-15p34cdc2 mutants were shown to coimmunoprecipitate cyclin B1 and to phosphorylate histone H1 in immune complex kinase assays. Microinjection of antisense oligonucleotides to c-mosXe was used to demonstrate the role of mos protein synthesis in the induction of GVBD by the Ala-14/Phe-15 cdc2 mutant. Thr-161 was also mutated. p34cdc2 single mutants Ala-161 and Glu-161 and triple mutants Ala-14/Phe-15/Ala-161 and Ala-14/Phe-15/Glu-161 failed to induce GVBD in oocytes and showed a decreased binding to cyclin B1 in coimmunoprecipitations. Each of the cdc2 mutants was also assayed by coinjection with cyclin B1 or c-mosXe RNA into oocytes. Several of the cdc2 mutants were found to affect the kinetics of cyclin B1 and/or mos-induced GVBD upon coinjection, although none affected the rate of progesterone-induced maturation. We demonstrate here the significance of Thr-14, Tyr-15, and Thr-161 of p34cdc2 in Xenopus oocyte maturation. In addition, these results suggest a regulatory role for mosXe in induction of oocyte maturation by the cdc2 mutant Ala-14/Phe-15.

Antioxidants Stimulate Germinal Vesicle Breakdown, But Inhibit Chromosome Formation And Spindle Assembly In Porcine Oocytes

2000 ◽  
Vol 6 (S2) ◽  
pp. 964-965
Author(s):  
Qing-Yuan Sun ◽  
Randall S. Prather ◽  
Heide Schatten
Keyword(s):  
Oocyte Maturation ◽  
Germinal Vesicle ◽  
Spindle Assembly ◽  
Mouse Oocyte ◽  
Germinal Vesicle Breakdown ◽  
Oocyte Meiosis ◽  
First Polar Body ◽  
Porcine Oocyte ◽  
Chromosome Formation

Mammalian oocytes are arrested at the diplotene stage of the first meiotic division. Release of oocytes from their follicles induces meiotic resumption characterized by germinal vesicle breakdown (GVBD), followed by the chromosome formation and metaphase I spindle organization and finally the extrusion the first polar body. Recently it was shown that cellpermeant antioxidants significantly inhibit spontaneous resumption of meiosis in mouse oocytes, which may indicate a role of oxygen radicals in oocyte maturation. The regulation of mouse oocyte meiosis resumption is different from that of large domestic animals in that GVBD is independent of Ca2+ and protein synthesis. The present study investigated the influence of two cell-permeant antioxidants, 2(3)-ter-butyl-4-hydroxyanisole (BHA) and nordihydroguaiaretic acid (NDGA), on porcine oocyte meiosis resumption, chromatin behavior and spindle assembly. Our findings revealed a different role of antioxidants in porcine oocyte meiosis resumption than in mouse oocyte maturation.

The role of calcium in the nuclear maturation of Bufo arenarum oocytes

Zygote ◽  
2004 ◽  
Vol 12 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Liliana I. Zelarayán ◽  
Graciela Sánchez Toranzo ◽  
Julia M. Oterino ◽  
Marta I. Bühler
Keyword(s):  
Intracellular Calcium ◽  
Germinal Vesicle ◽  
Reproductive Period ◽  
Protein Kinase Activity ◽  
Channel Blockers ◽  
Germinal Vesicle Breakdown ◽  
Nuclear Maturation ◽  
Bufo Arenarum ◽  
Hormonal Stimulus

In Bufo arenarum, progesterone is the physiological maturation inducer. However, in this species, oocytes reinitiate meiosis with no need of an exogenous hormonal stimulus when deprived of their enveloping cell, a phenomenon called spontaneous maturation. We demonstrated that in Bufo arenarum spontaneous maturation occurs only in oocytes obtained during the reproductive period, which can be considered competent to mature spontaneously, in contrast to those in the non-reproductive period, which are incompetent. Interestingly, full-grown Bufo arenarum oocytes always respond to progesterone regardless of the season in which they are obtained. There is a general consensus that both a transient increase in intracellular calcium and a decrease in cAMP-dependent protein kinase activity are the first steps in the mechanisms by which progesterone induces maturation in amphibians. In the present work we analysed the role of calcium in the spontaneous and progesterone-induced maturation of Bufo arenarum oocytes. Results demonstrated that the absence of calcium in the incubation medium or the prevention of Ca2+ influx by channel blockers such as CdCl2 or NiCl2 did not prevent meiosis reinitiation in either type of maturation. The inhibition of the Ca2+-calmodulin complex in no case affected the maturation of the treated oocytes. However, when the oocytes were deprived of calcium by incubation in Ca2+-free AR + A23187, meiosis resumption was inhibited. In brief, we demonstrated that in Bufo arenarum the reinitiation of meiosis is a process independent of extracellular calcium at any period of the year and that oocytes require adequate levels of intracellular calcium for germinal vesicle breakdown to occur.

Behavior of γ-tubulin during spindle formation in Xenopus oocytes: requirement of cytoplasmic dynein-dependent translocation

Zygote ◽  
2005 ◽  
Vol 13 (3) ◽  
pp. 219-226 ◽  
Author(s):  
Tomoya Kotani ◽  
Masakane Yamashita
Keyword(s):  
Oocyte Maturation ◽  
Late Stage ◽  
Xenopus Oocytes ◽  
Germinal Vesicle ◽  
Cytoplasmic Dynein ◽  
Microtubule Organization ◽  
Germinal Vesicle Breakdown ◽  
Spindle Formation ◽  
Bipolar Spindle

Vertebrate oocytes do not contain centrosomes and therefore form an acentrosomal spindle during oocyte maturation. γ-Tubulin is known to be essential for nucleation of microtubules at centrosomes, but little is known about the behaviour and role of γ-tubulin during spindle formation in oocytes. We first observed sequential localization of γ-tubulin during spindle formation in Xenopus oocytes. γ-Tubulin assembled in the basal regions of the germinal vesicle (GV) at the onset of germinal vesicle breakdown (GVBD) and remained on the microtubule-organizing centre (MTOC) until a complex of the MTOC and transient-microtubule array (TMA) reached the oocyte surface. Prior to bipolar spindle formation, oocytes formed an aggregation of microtubules and γ-tubulin was concentrated at the centre of the aggregation. At the late stage of bipolar spindle formation, γ-tubulin accumulated at each pole. Anti-dynein antibody disrupted the localization of γ-tubulin, indicating that the translocation described above is dependent on dynein activity. We finally revealed that XMAP215, a microtubule-associated protein cooperating with γ-tubulin for the assembly of microtubules, but not γ-tubulin, was phosphorylated during oocyte maturation. These results suggest that γ-tubulin is translocated by dynein to regulate microtubule organization leading to spindle formation and that modification of the molecules that cooperate with γ-tubulin, but not γ-tubulin itself, is important for microtubule reorganization.

scholarly journals Antioxidants reversibly inhibit the spontaneous resumption of meiosis

1999 ◽  
Vol 276 (4) ◽  
pp. E684-E688 ◽  
Author(s):  
M. Takami ◽  
S. L. Preston ◽  
V. A. Toyloy ◽  
Harold R. Behrman
Keyword(s):  
Oocyte Maturation ◽  
Oxygen Radicals ◽  
Germinal Vesicle ◽  
Nordihydroguaiaretic Acid ◽  
Butylated Hydroxytoluene ◽  
Germinal Vesicle Breakdown ◽  
Tert Butyl ◽  
Tert Butyl Hydroperoxide ◽  
Lauryl Gallate

We previously showed that the cell-permeant antioxidant 2(3)- tert-butyl-4-hydroxyanisole (BHA) inhibited germinal vesicle breakdown (GVBD) in oocyte-cumulus complexes (OCC) of the rat. The objective of the present studies was to assess other antioxidants and whether such inhibition was reversible. Spontaneous GVBD in OCC incubated for 2 h was significantly inhibited ( P < 0.005) by nordihydroguaiaretic acid (NDGA; GVBD = 19.4%), BHA (GVBD = 25.7%), octyl gallate (OG; GVBD = 52.2%), ethoxyquin (EQ; GVBD = 58.8%), 2,6-di- tert-butyl-hydroxymethyl phenol (TBHMP; GVBD = 59%), butylated hydroxytoluene (BHT; GVBD = 59.5%), and tert-butyl hydroperoxide (TBHP; GVBD = 60.0%). Other antioxidants that produced lower but significant ( P < 0.05) inhibition of oocyte maturation included propyl gallate (PG; GVBD = 70.3%), 2,4,5-trihydroxybutrophenone (THBP; GVBD = 71.4%), and lauryl gallate (LG; GVBD = 71.4%). Antioxidants that had no effect on oocyte maturation at the same concentration (100 μM) included ascorbic acid, vitamin E, and Trolox. Inhibition of GVBD was evident for up to 8 h of incubation of OCC and denuded oocytes (DO) with BHA or NDGA and was reversed by washing. NDGA was less potent than BHA for inhibition of GVBD in DO, unlike that seen with OCC. Oocyte maturation was induced by incubation of follicles for 3 h with human chorionic gonadotropin (hCG), and this response was inhibited by BHA or NDGA. These findings support the conclusion that cell-permeant antioxidants inhibit spontaneous resumption of meiosis, which may implicate a role of oxygen radicals in oocyte maturation.

scholarly journals Ca2+cyt negatively regulates the initiation of oocyte maturation

2004 ◽  
Vol 165 (1) ◽  
pp. 63-75 ◽  
Author(s):  
Lu Sun ◽  
Khaled Machaca
Keyword(s):  
Cell Cycle ◽  
Oocyte Maturation ◽  
Cell Cycle Progression ◽  
Germinal Vesicle ◽  
Germinal Vesicle Breakdown ◽  
Cycle Progression ◽  
Nuclear Maturation ◽  
Oocyte Meiosis ◽  
Kinase Cascade ◽  
Cell Cycle Machinery

Ca2+ is a ubiquitous intracellular messenger that is important for cell cycle progression. Genetic and biochemical evidence support a role for Ca2+ in mitosis. In contrast, there has been a long-standing debate as to whether Ca2+ signals are required for oocyte meiosis. Here, we show that cytoplasmic Ca2+ (Ca2+cyt) plays a dual role during Xenopus oocyte maturation. Ca2+ signals are dispensable for meiosis entry (germinal vesicle breakdown and chromosome condensation), but are required for the completion of meiosis I. Interestingly, in the absence of Ca2+cyt signals oocytes enter meiosis more rapidly due to faster activation of the MAPK-maturation promoting factor (MPF) kinase cascade. This Ca2+-dependent negative regulation of the cell cycle machinery (MAPK-MPF cascade) is due to Ca2+cyt acting downstream of protein kinase A but upstream of Mos (a MAPK kinase kinase). Therefore, high Ca2+cyt delays meiosis entry by negatively regulating the initiation of the MAPK-MPF cascade. These results show that Ca2+ modulates both the cell cycle machinery and nuclear maturation during meiosis.

Requirement of mosXe protein kinase for meiotic maturation of Xenopus oocytes induced by a cdc2 mutant lacking regulatory phosphorylation sites

1992 ◽  
Vol 12 (7) ◽  
pp. 3192-3203
Author(s):  
K M Pickham ◽  
A N Meyer ◽  
J Li ◽  
D J Donoghue
Keyword(s):  
Protein Kinase ◽  
Oocyte Maturation ◽  
Xenopus Oocytes ◽  
Germinal Vesicle ◽  
Cyclin B1 ◽  
Phosphorylation Sites ◽  
Germinal Vesicle Breakdown ◽  
Regulatory Phosphorylation

The p34cdc2 protein kinase is a component of maturation-promoting factor, the master regulator of the cell cycle in all eukaryotes. The activity of p34cdc2 is itself tightly regulated by phosphorylation and dephosphorylation. Predicted regulatory phosphorylation sites of Xenopus p34cdc2 were mutated in vitro, and in vitro-transcribed RNAs were injected into Xenopus oocytes. The cdc2 single mutants Thr-14----Ala and Tyr-15----Phe did not induce germinal vesicle breakdown (BVBD) upon microinjection into oocytes. In contrast, the cdc2 double mutant Ala-14/Phe-15 did induce GVBD. Both the Ala-14 and Ala-14/Phe-15p34cdc2 mutants were shown to coimmunoprecipitate cyclin B1 and to phosphorylate histone H1 in immune complex kinase assays. Microinjection of antisense oligonucleotides to c-mosXe was used to demonstrate the role of mos protein synthesis in the induction of GVBD by the Ala-14/Phe-15 cdc2 mutant. Thr-161 was also mutated. p34cdc2 single mutants Ala-161 and Glu-161 and triple mutants Ala-14/Phe-15/Ala-161 and Ala-14/Phe-15/Glu-161 failed to induce GVBD in oocytes and showed a decreased binding to cyclin B1 in coimmunoprecipitations. Each of the cdc2 mutants was also assayed by coinjection with cyclin B1 or c-mosXe RNA into oocytes. Several of the cdc2 mutants were found to affect the kinetics of cyclin B1 and/or mos-induced GVBD upon coinjection, although none affected the rate of progesterone-induced maturation. We demonstrate here the significance of Thr-14, Tyr-15, and Thr-161 of p34cdc2 in Xenopus oocyte maturation. In addition, these results suggest a regulatory role for mosXe in induction of oocyte maturation by the cdc2 mutant Ala-14/Phe-15.

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