169 Nuclear Maturation Kinetics and In Vitro Fecundation of Immature Bovine Oocytes Injected into Preovulatory Follicles

2018 ◽  
Vol 30 (1) ◽  
pp. 224
Author(s):  
L. M. S. Simoes ◽  
A. P. C. Santos ◽  
E. A. Lima ◽  
R. E. Orlandi ◽  
M. P. Bottino ◽  
...  
Keyword(s):  
Oocyte Maturation ◽  
Germinal Vesicle ◽  
Causative Factor ◽  
Nuclear Maturation ◽  
Preovulatory Follicles ◽  
Fertilization Capacity ◽  
Bovine Oocytes ◽  
Metaphase I

The objective was to evaluate in vitro nuclear maturation and fecundation kinetics of oocytes injected into preovulatory follicles of synchronized cows using the intra-follicular oocyte injection (IFOI) technique. In experiment 1, 438 immature abattoir-bovine cumulus–oocyte complexes (COC) of grades I, II, and III were randomly allocated to 1 of 3 groups: Matvitro (n = 111), COC matured in vitro for 22 h; Matvivo20 (n = 172) and Matvivo30 (n = 155), 30 oocytes were injected into each preovulatory follicle of pre-synchronized recipients. In Matvivo20, oocytes were matured for 19.8 ± 0.1 h and in Matvivo30, for 28.3 ± 0.1 h. All cows received 12.5 mg of LH (Lutropin, Bioniche, Canada) at IFOI (Matvivo20) or 10 h after IFOI (Matvivo30). Oocytes from Matvivo20 and Matvivo30 were aspirated 20 h after LH injection for assessment of oocyte maturation and recovery rates. Oocytes were evaluated according to maturation kinetics as germinal vesicle, metaphase I, anaphase I, telophase I, metaphase II, parthenogenetically activated, and degenerated (chromosomal aberrations, presence of diffuse or indefinite chromatin). In experiment 2, immature abattoir-bovine COC (n = 202) of grades I, II, and III were randomly distributed into 2 groups: Matvitro (n = 103), COC were matured and fertilized in vitro; Matvivo (n = 99), same as Matvivo20 protocol, and COC fertilized in vitro. Presumptive zygotes were evaluated as fertilized, unfertilized, or polyspermic. Statistical analyses were performed by the GLIMMIX procedure of SAS (SAS Institute Inc., Cary, NC, USA). Recovery rate was lower (P < 0.001) in Matvivo20 (52.9%, 91/172) compared with Matvivo30 (72.9%, 113/155). Germinal vesicle (P = 0.94), metaphase I (P = 0.98), anaphase I (P = 0.99), and telophase I (P = 0.20) rates were similar. However, there were differences in metaphase II [Matvitro: 81.0% (90/111)a, Matvivo20: 74.5% (35/47)a, and Matvivo30: 41.6% (32/77)b; P = 0.001], degenerate [Matvitro: 5.4% (6/111)c, Matvivo20: 21.3% (10/47)b and Matvivo30: 48.1% (37/77); P = 0.001] and parthenogenetically activated [Matvitro: 0.0% (0/111)b, Matvivo20: 0.0% (0/47)b and Matvivo30: 9.1% (7/77)a; P = 0.001]. Polyspermic (P = 0.18) and abnormal (P = 0.98) rates were similar. However, there was a higher rate (P = 0.05) of fertilized oocytes in Matvivo (60.6%, 60/99) than in Matvitro (46.6%, 48/103). In conclusion, oocyte maturation in vivo after IFOI for 20 h does not alter maturation kinetics and increases in vitro oocyte fertilization capacity. However, the 10-h increase in intra-follicular oocyte permanence decreased the proportion of viable oocytes. Thus, the oocyte maturation phase is not the limiting causative factor for the low IFOI-embryo production rates.

Octylphenol, an environmental oestrogen, affects oocyte maturation in cattle

2001 ◽  
Vol 2001 ◽  
pp. 64-64 ◽  
Author(s):  
P Pocar ◽  
R Augustin ◽  
F Gandolfi ◽  
B Fischer
Keyword(s):  
Oocyte Maturation ◽  
Nonionic Surfactants ◽  
Cumulus Cells ◽  
Model System ◽  
Animal Cells ◽  
Nuclear Maturation ◽  
Maturation In Vitro ◽  
Bovine Oocytes

4-tert-octylphenol (OP) is an alkylphenolic compound formed as metabolite of some nonionic surfactants that are widely used in industrial detergents, as plastic additives, dispersant for insecticides, etc. (Naylor et al., 1992). OP accumulates in adipose tissue. Micromolar concentrations of these compounds may constitute health hazards to animal cells. Furthermore, it has previously been shown to exert oestrogenic activity in vivo and in vitro (White et al., 1994). A growing concern about “endocrine disruptors” and their impact on oestrogen-dependent phenomena led us investigate the effects of OP on oocyte maturation. For variuos reasons bovine oocytes were chosen as the model system. We examined the effects of OP exposure on oocyte nuclear maturation in vitro and on the expression of oestrogen receptors in cumulus cells.

scholarly journals Effect of Hyaluronan on Developmental Competence and Quality of Oocytes and Obtained Blastocysts fromIn VitroMaturation of Bovine Oocytes

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Jolanta Opiela ◽  
Joanna Romanek ◽  
Daniel Lipiński ◽  
Zdzisław Smorąg
Keyword(s):  
Dna Fragmentation ◽  
Oocyte Maturation ◽  
Developmental Competence ◽  
Meiotic Maturation ◽  
Nuclear Maturation ◽  
Significant Difference ◽  
The Mean ◽  
Bovine Oocytes

The objective of the present study was to evaluate the effect of hyaluronan (HA) during IVM on meiotic maturation, embryonic development, and the quality of oocytes, granulosa cells (GC), and obtained blastocysts. COCs were maturedin vitroin control medium and medium with additional 0.035% or 0.07% of exogenous HA. The meiotic maturity did not differ between the analysed groups. The best rate and the highest quality of obtained blastocysts were observed when 0.07% HA was used. A highly significant difference (P<0.001) was noted in the mean number of apoptotic nuclei per blastocyst and in the DCI between the 0.07% HA and the control blastocysts (P<0.01). Our results suggest that addition of 0.035% HA and 0.07% HA to oocyte maturation media does not affect oocyte nuclear maturation and DNA fragmentation. However, the addition of 0.07% HA during IVM decreases the level of blastocysts DNA fragmentation. Finally, our results suggest that it may be risky to increase the HA concentration during IVM above 0.07% as we found significantly higherBaxmRNA expression levels in GC cultured with 0.07% HA. The final concentration of HA being supplemented to oocyte maturation media is critical for the success of the IVP procedure.

scholarly journals Effects of gonadotrophin in vivo and 2-hydroxyoestradiol-17β in vitro on follicular steroid hormone profile associated with oocyte maturation in the catfish Heteropneustes fossilis

2006 ◽  
Vol 189 (2) ◽  
pp. 341-353 ◽  
Author(s):  
A Mishra ◽  
K P Joy
Keyword(s):  
Oocyte Maturation ◽  
Germinal Vesicle ◽  
Hplc Method ◽  
Heteropneustes Fossilis ◽  
Germinal Vesicle Breakdown ◽  
Steroid Profile ◽  
17 Hydroxyprogesterone ◽  
Envelope Layer

An HPLC method was used to tentatively identify progesterone (P4) and its metabolites (17-hydroxyprogesterone (17-P4) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P)), corticosteroids (cortisol and corticosterone) and testosterone in ovary/follicular preparations of the catfish Heteropneustes fossilis associated with in vivo or in vitro oocyte maturation/ovulation. A single i.p. injection of human chorionic gonadotrophin (100 IU/fish, sampled at 0, 8 and 16 h) induced oocyte maturation and ovulation, which coincided with significant and progressive increases in 17,20β-P, and P4 and 17-P4, the precursors of the former. Both cortisol and corticosterone also increased significantly. Conversely, testosterone decreased significantly and progressively over time. Under in vitro conditions, incubation of post-vitellogenic (intact) follicles or follicular envelope (layer) with 2-hydroxyoestradiol (2-OHE2, 5 μM for 0, 6 and 24 h) elicited a sharp significant increase in 17,20β-P, the increase being higher in the follicular envelope incubate. P4 and 17-P4 also registered significant increases over the time with the peak values at 24 h. Cortisol and corticosterone increased significantly in the intact follicle, but not in the follicular envelope incubate. Testosterone decreased significantly in the intact follicle, but increased significantly (24 h) in the follicular envelope incubate. Coincident with these changes, the percentage of germinal vesicle breakdown (GVBD) increased over the time in the intact follicle incubate (48.9% at 6 h and 79.8% at 24 h). Denuded oocytes on incubation with 2-OHE2 (5 μM) did not produce any significant change in the percentage of GVBD or in the steroid profile. While corticosterone and 17,20β-P were undetected, P4, 17-P4, cortisol and testosterone were detected in low amounts. The results show that the 2-OHE2-induced GVBD response seems to be mediated through the production of 17,20β-P and corticosteroids. It is suggested that hydroxyoestrogens seem to be a component in the gonadotrophin cascade of regulation of oocyte maturation/ovulation in the catfish.

Effect of administering a crude equine gonadotrophin preparation to mares on follicular development, oocyte recovery rate and oocyte maturation in vivo

Reproduction ◽  
2000 ◽  
pp. 351-360 ◽  
Author(s):  
I Bruck ◽  
J Bezard ◽  
M Baltsen ◽  
B Synnestvedt ◽  
I Couty ◽  
...  
Keyword(s):  
Oocyte Maturation ◽  
Recovery Rate ◽  
In Vitro Maturation ◽  
Follicular Development ◽  
Vitro Fertilization ◽  
Nuclear Maturation ◽  
Oocyte Yield ◽  
Oocyte Recovery

In mares, the shortage of oocytes and the variability in nuclear maturation at a certain time of the oestrous cycle hinders the optimization of methods for in vitro maturation and in vitro fertilization. Increasing the number of small-to-medium-sized follicles available for aspiration in vivo may increase the overall oocyte yield. The aims of the present study were to investigate whether administration of crude equine gonadotrophins affects follicular development, oocyte recovery rate, in vivo oocyte maturation and follicular concentrations of meiosis-activating sterols. During oestrus, all follicles >/= 4 mm were aspirated from 19 pony mares (first aspiration: A1). Over the next 8 days, the mares were treated daily with either 25 mg crude equine gonadotrophins (n = 10) or physiological saline (n = 9). Between day 1 and day 8, follicular growth was monitored by ultrasonography. On day 8, all follicles >/= 4 mm were evacuated (second aspiration: A2) and nuclear maturation of the recovered oocytes was assessed after orcein staining. Follicular growth between A1 and A2, as well as the number and size of follicles at A2 were similar for control mares and mares treated with crude equine gonadotrophins. The oocyte recovery rates at A1 and A2 were similar. At A2, the oocyte recovery rate and oocyte maturation in vivo were not affected by treatment with crude equine gonadotrophins. The number of expanded cumulus oophorus complexes recovered from follicles </= 29 mm was significantly higher at A1 than at A2. The number of oocytes at the germinal vesicle stage was significantly higher at A2 (41.5%) than at A1 (17.8%). Meiosis-activating sterols (FF-MAS and T-MAS) were identified in follicular fluid recovered at A2. Follicular concentrations of FF-MAS and T-MAS were unaffected by treatment with crude equine gonadotrophins. The present study demonstrates that follicular aspiration during oestrus allowed a new follicular population to develop and resulted in a higher degree of synchronization of oocyte development with respect to cumulus expansion and nuclear maturation. The availability of a more homogeneous population of oocytes might facilitate a better optimization of in vitro maturation and in vitro fertilization techniques in mares. Administration of crude equine gonadotrophins during early dioestrus did not affect the growth of small follicles, the oocyte yield after aspiration or oocyte maturation in vivo.

Effect of butafosfan supplementation during oocyte maturation on bovine embryo development

Zygote ◽  
2019 ◽  
Vol 27 (05) ◽  
pp. 321-328
Author(s):  
Lucas Teixeira Hax ◽  
Joao Alveiro Alvarado Rincón ◽  
Augusto Schneider ◽  
Lígia Margareth Cantarelli Pegoraro ◽  
Letícia Franco Collares ◽  
...  
Keyword(s):  
Gene Expression ◽  
Embryo Development ◽  
Oocyte Maturation ◽  
Cumulus Cells ◽  
Oocyte Quality ◽  
Bovine Embryo ◽  
Cleavage Rate ◽  
Nuclear Maturation

SummaryAround 60–80% of oocytes maturated in vivo reached competence, while the proportion of maturation in vitro is rarely higher than 40%. In this sense, butafosfan has been used in vivo to improve metabolic condition of postpartum cows, and can represent an alternative to increase reproductive efficiency in cows. The aim of this study was to evaluate the addition of increasing doses of butafosfan during oocyte maturation in vitro on the initial embryo development in cattle. In total, 1400 cumulus–oocyte complexes (COCs) were distributed in four groups and maturated according to supplementation with increasing concentrations of butafosfan (0 mg/ml, 0.05 mg/ml, 0.1 mg/ml and 0.2 mg/ml). Then, 20 oocytes per group were collected to evaluate nuclear maturation and gene expression on cumulus cells and oocytes and the remaining oocytes were inseminated and cultured until day 7, when blastocysts were collected for gene expression analysis. A dose-dependent effect of butafosfan was observed, with decrease of cleavage rate and embryo development with higher doses. No difference between groups was observed in maturation rate and expression of genes related to oocyte quality. Our results suggest that butafosfan is prejudicial for oocytes, compromising cleavage and embryo development.

Effects of ghrelin on activation of Akt1 and ERK1/2 pathways during in vitro maturation of bovine oocytes

Zygote ◽  
2017 ◽  
Vol 25 (2) ◽  
pp. 183-189 ◽  
Author(s):  
Thomas-Markos Chouzouris ◽  
Eleni Dovolou ◽  
Fotini Krania ◽  
Ioannis S. Pappas ◽  
Konstantinos Dafopoulos ◽  
...  
Keyword(s):  
Oocyte Maturation ◽  
Cumulus Cells ◽  
Treated Group ◽  
Control Group ◽  
Dependent Manner ◽  
Nuclear Maturation ◽  
Bovine Oocytes ◽  
Phosphorylation Rate ◽  
Matured Oocyte

SummaryThe purpose of this study was to investigate the possible molecular pathways through which ghrelin accelerates in vitro oocyte maturation. Bovine cumulus–oocyte complexes (COCs), after 18 or 24 h maturation in the absence or the presence of 800 pg ml–1 of acylated ghrelin were either assessed for nuclear maturation or underwent in vitro fertilization in standard media and putative zygotes were cultured in vitro for 8 days. In a subset of COCs the levels of phosphorylated Akt1 and ERK1/2 (MAPK1/3) were assessed at the 0th, 6th, 10th, 18th and 24th hours of in vitro maturation (IVM). At 18 and 24 h no difference existed in the proportion of matured oocytes in the ghrelin-treated group, while in the control group more (P < 0.05) matured oocyte were found at 24 h. Oocyte maturation for 24 h in the presence of ghrelin resulted in substantially reduced (P < 0.05) blastocyst yield(16.3%) in comparison with that obtained after 18 h (30.0%) or to both control groups (29.3% and 26.9%, for 18 and 24 h in maturation, respectively). Ghrelin-treated oocytes expressed lower Akt1 phosphorylation rate at the 10th hour of IVM, and higher ERK1/2 at the 6th and 10th hours of IVM compared with controls. In cumulus cells, at the 18th and 24th hours of IVM Akt1 phosphorylation rate was higher in ghrelin-treated oocytes. Our results imply that ghrelin acts in a different time-dependent manner on bovine oocytes and cumulus cells modulating Akt1 and ERK1/2 phosphorylation, which brings about acceleration of the oocyte maturation process.

scholarly journals Embryonic poly(A)-binding protein (EPAB) is required for oocyte maturation and female fertility in mice

2012 ◽  
Vol 446 (1) ◽  
pp. 47-58 ◽  
Author(s):  
Ozlem Guzeloglu-Kayisli ◽  
Maria D. Lalioti ◽  
Fulya Aydiner ◽  
Isaac Sasson ◽  
Orkan Ilbay ◽  
...  
Keyword(s):  
Oocyte Maturation ◽  
Binding Protein ◽  
Germinal Vesicle ◽  
Cyclin B1 ◽  
Female Fertility ◽  
Prostaglandin Synthase ◽  
Translational Activation ◽  
Factor Α

Gene expression during oocyte maturation and early embryogenesis up to zygotic genome activation requires translational activation of maternally-derived mRNAs. EPAB [embryonic poly(A)-binding protein] is the predominant poly(A)-binding protein during this period in Xenopus, mouse and human. In Xenopus oocytes, ePAB stabilizes maternal mRNAs and promotes their translation. To assess the role of EPAB in mammalian reproduction, we generated Epab-knockout mice. Although Epab−/− males and Epab+/− of both sexes were fertile, Epab−/− female mice were infertile, and could not generate embryos or mature oocytes in vivo or in vitro. Epab−/− oocytes failed to achieve translational activation of maternally-stored mRNAs upon stimulation of oocyte maturation, including Ccnb1 (cyclin B1) and Dazl (deleted in azoospermia-like) mRNAs. Microinjection of Epab mRNA into Epab−/− germinal vesicle stage oocytes did not rescue maturation, suggesting that EPAB is also required for earlier stages of oogenesis. In addition, late antral follicles in the ovaries of Epab−/− mice exhibited impaired cumulus expansion, and a 8-fold decrease in ovulation, associated with a significant down-regulation of mRNAs encoding the EGF (epidermal growth factor)-like growth factors Areg (amphiregulin), Ereg (epiregulin) and Btc (betacellulin), and their downstream regulators, Ptgs2 (prostaglandin synthase 2), Has2 (hyaluronan synthase 2) and Tnfaip6 (tumour necrosis factor α-induced protein 6). The findings from the present study indicate that EPAB is necessary for oogenesis, folliculogenesis and female fertility in mice.

171 IN VIVO AND IN VITRO MATURATION OF WOOD BISON (BISON BISON ATHABASCAE) CUMULUS–OOCYTE COMPLEXES DURING THE OVULATORY SEASON

2014 ◽  
Vol 26 (1) ◽  
pp. 199
Author(s):  
M. P. Cervantes ◽  
M. Anzar ◽  
R. J. Mapletoft ◽  
J. M. Palomino ◽  
G. P. Adams
Keyword(s):  
In Vitro Maturation ◽  
Calf Serum ◽  
Germinal Vesicle ◽  
Bison Bison ◽  
Germinal Vesicle Breakdown ◽  
Cumulus Expansion ◽  
Nuclear Maturation ◽  
Wood Bison

Technologies are being developed to conserve the genetic diversity of wood bison. Knowledge of the characteristics of in vivo and in vitro maturation of the cumulus–oocyte complex (COC) are needed in wood bison to design efficient in vitro embryo production protocols. The objectives were to (1) determine the optimal interval after hCG treatment for in vivo maturation of COC in superstimulated wood bison, and (2) compare the characteristics of COC after in vitro and in vivo maturation. Ovarian synchronization was induced in 25 bison during October and November by giving a luteolytic dose of prostaglandin followed 8 days later by follicular ablation (Day –1). Ovarian superstimulation was induced with FSH (Folltropin-V) given i.m. on Day 0 (300 mg) and Day 2 (100 mg). A second luteolytic dose of prostaglandin was given on Day 3. Bison were assigned randomly to 5 groups (n = 5/group). The COC were collected by transvaginal follicle aspiration on Day 4 and were either assessed immediately (0 h, control), or matured in vitro for 24 or 30 h (in vitro maturation), or collected on Day 5 (in vivo maturation), 24 or 30 h after bison were given 2000 IU of hCG i.m. on Day 4. In vitro maturation was done in TCM-199 with 5% calf serum, 5 μg mL–1 LH, 0.5 μg mL–1 FSH, and 0.05 μg mL–1 gentamicin, at 38.5°C and in a 5% CO2 humidified atmosphere. Nuclear maturation was classified as germinal vesicle (GV), germinal vesicle breakdown (GVBD), metaphase I (MI), or metaphase II (MII) with anti-lamin AC/DAPI staining. Groups were compared by analysis of variance and Fisher's exact test (Table 1). A mean (±s.e.m.) of 7.3 ± 1.7 COC were collected per bison, with no difference among groups. The COC in the control (0 h) group were at the nonexpanded GV stage. Cumulus cells were more expanded after in vivo than in vitro maturation, and the percentage of fully expanded COC was the highest in the 30-h in vivo maturation group (87%; P < 0.05). The greatest number of oocytes reached MII stage after 24 h of in vitro maturation, and 30 h of in vivo maturation. In conclusion, nuclear maturation occurred more quickly in vitro compared with in vivo, but the degree and incidence of cumulus expansion was greater after in vivo maturation. The competence of oocytes to undergo fertilization and develop into embryos remains to be investigated. Table 1.Cumulus expansion and nuclear maturation of wood bison oocytes

180 LONG-TERM TRANSPORTATION OF BOVINE OOCYTES WITH MEIOTIC BLOCKERS: EFFECTS ON NUCLEAR MATURATION

2017 ◽  
Vol 29 (1) ◽  
pp. 198
Author(s):  
P. C. Dall'Acqua ◽  
B. C. S. Leao ◽  
N. A. S. Rocha-Frigoni ◽  
G. B. Nunes ◽  
M. Ambrogi ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Growth Factor Receptor ◽  
Germinal Vesicle ◽  
Inhibitory Effect ◽  
Study Data ◽  
Receptor Protein ◽  
Nuclear Maturation ◽  
Meiotic Inhibitors ◽  
Bovine Oocytes

The aim of this study was to assess the blockade and the reversal of meiosis block in bovine oocytes treated with a cyclin-dependent kinase inhibitor (butyrolactone-I; BL) combined or not with a selective inhibitor of epidermal growth factor receptor protein (tyrphostin AG 1478; AG) in a prematuration (PM) culture during oocyte transport. Cumulus-oocyte complexes (n = 4107) were transported in PM medium (TCM-199 with bicarbonate and 0.3% BSA) supplemented with one of the following inhibitors: 50 µM BL; 100 µM BL; 1 µM AG; 50 µM BL + 1 µM AG; or 100 µM BL + 1µM AG. Cumulus-oocyte complexes were transported in well-sealed polystyrene tubes (30 oocytes/tube) containing 200 μL of PM medium covered with mineral oil and gassed with 5% O2, 5% CO2, and 90% N2. The tubes were packed in a portable incubator (Thawing Unit MT 35/42, Minitub, Tiefenbach, Germany) at 38.5°C for 22 h. Afterward, treated oocytes were removed from meiotic inhibitors, transferred to in vitro maturation (IVM) medium (TCM-199 with bicarbonate, 0.5 mg mL−1 of FSH, 100 IU mL−1 of hCG, and 10% FCS), and cultured in a bench-top incubator (Thermo Fisher Scientific, Waltham, MA, USA) under 38.5°C and 5% CO2 in air for 20, 22, 24, or 26 h. The control groups were IVM for 20, 22, 24, or 26 h in IVM medium in the bench-top incubator at 38.5°C and 5% CO2 in air (Control; C) or in the portable incubator under the same conditions used for the treated groups (Transport Control; TC). For meiosis evaluation, oocytes were stained with 1% Hoescht immediately after follicle removal (0 h), at 6 and 22 h of PM, and after 20, 22, 24, and 26 h of IVM, and were classified as immature (germinal vesicle; GV) or mature (metaphase II; MII); intermediate phases of meiosis (GV breakdown, metaphase I, anaphase I, or telophase I) were not demonstrated in this study. Data were analysed by ANOVA followed by Tukey’s test (P < 0.05) and are presented as mean ± standard error of the mean. The GV rates after 6 h of transport did not differ (P > 0.05) between 0-h oocytes (88.6 ± 2.3%) and the treated groups (70.3 ± 1.9% to 79.3 ± 2.2%); although GV rates of C (49.5 ± 2.4%) and TC (49.5 ± 2.4%) groups differed (P < 0.05) from 0-h oocytes, they did not differ from treated oocytes with the exception of the 1 µM AG group (79.3 ± 2.2%), which differed from TC (P < 0.05). After 22 h of transport, the GV rates of treated oocytes (50.3 ± 5.5 to 70.3 ± 6.6%) did not differ (P > 0.05) from 0-h oocytes (88.6 ± 2.3%) and were higher (P < 0.05) than C (4.6 ± 2.8%) and TC (8.3 ± 4.5%) that had the highest MII rates (68.4 ± 5.3 and 75.5 ± 2.0%, respectively, for C and TC) compared with the other groups (0 to 13.2 ± 10.2%). After meiotic inhibitors removal and IVM, meiosis block was fully reversed and there were no differences (P > 0.05) in the rates of MII between treated oocytes and C and TC groups after 20 (56.6%, averaged), 22 (57.7%, averaged), 24 (66.2%, averaged), or 26 h of IVM (57.0%, averaged). In conclusion, the meiotic inhibitors were effective in maintaining the majority of treated oocytes in GV stage after 22 h of transport and the inhibitory effect was fully reverted after its removal. Research was supported by FAPESP and CAPES.

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