scholarly journals The Relationship between Nuclear Maturation and Cortical Granule Distribution in Cultured Porcine Oocytes

2002 ◽  
Vol 19 (1) ◽  
pp. 21-25 ◽  
Author(s):  
Hiroko Takano ◽  
Chika Kanda ◽  
Sueo Niimura
Keyword(s):  
Cortical Granule ◽  
Nuclear Maturation ◽  
The Relationship

scholarly journals Cytoplasmic activation of starfish oocytes by sperm and divalent ionophore A-23187.

1975 ◽  
Vol 66 (1) ◽  
pp. 86-94 ◽  
Author(s):  
A W Schuetz
Keyword(s):  
Membrane Separation ◽  
Germinal Vesicle ◽  
Vitelline Membrane ◽  
Cortical Granule ◽  
Oocyte Activation ◽  
Surf Clam ◽  
Nuclear Maturation ◽  
A 23187 ◽  
Parthenogenetic Development ◽  
The Relationship

The relationship between onset of the early cytoplasmic stages of oocyte activation (vitelline membrane separation and elevation) and nuclear meiotic maturation was investigated in starfish oocytes after their exposure to divalent ionophore (A-23187) or sperm. Meiotically mature oocytes, isolated in calcium-free seawater, underwent activation in response to sperm or ionophore as previously reported. Large, immature starfish oocytes, arrested in prophase I of meiosis (germinal vesicle stage), underwent vitelline membrane elevation when treated with divalent ionophore A-23187 or starfish sperm. Histological studies demonstrated that cortical granule breakdown in the oocyte cortex was associated with vitelline membrane elevation after these treatments. Activation of oocytes by sperm occurred only in response to starfish sperm. Sea urchin, sand dollar, surf clam, or marine worm sperm did not induce vitelline membrane elevation of either immature or mature starfish oocytes. Sperm- or ionophore-activated immature oocytes underwent nuclear maturation after addition of the meiosis-inducing hormone, l-methyladenine; however, parthenogenetic development did not occur and embryonic development was markedly inhibited. In contrast to previous studies, the present results indicate that cytoplasmic activation can be initiated before and without hormone induction of the nuclear maturation process. Differentiation of the oocyte cell surface or cortex reactivity therefore appears to occur during oogenesis rather than as a consequence of maturation. The data further support the view that divalent ions mediate certain of the early activation responses initiated by sperm at the time of fertilization and that synchronization of fertilization to the meiotic process in the oocyte is important for the occurrence of normal development.

scholarly journals STEROID INHIBITION OF PROTEIN INCORPORATION BY ISOLATED AMPHIBIAN OOCYTES

1974 ◽  
Vol 61 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Allen W. Schuetz ◽  
Robin A. Wallace ◽  
James N. Dumont
Keyword(s):  
Rana Pipiens ◽  
Follicle Cells ◽  
Blood Protein ◽  
Short Treatment ◽  
Nuclear Maturation ◽  
Desoxycorticosterone Acetate ◽  
Protein Incorporation ◽  
The Relationship ◽  
Stimulation Of

The relationship between blood protein (vitellogenin) incorporation and nuclear maturation was studied in individual amphibian oocytes after in vitro exposure to desoxycorticosterone acetate (DOCA). Isolated Rana pipiens oocytes were incubated in vitro with radioactively labeled oocyte yolk precursor ([3H]vitellogenin) obtained from estrogenized Xenopus laevis. Incorporation of labeled vitellogenin into the oocytes continued over a 24-h period. Oocytes simultaneously exposed to DOCA and to labeled vitellogenin exhibited both inhibition of vitellogenin incorporation and stimulation of nuclear maturation and cortical changes. Inhibition of vitellogenin incorporation was observed after approximately 9 h of incubation and was correlated with the time of nuclear breakdown. Preincubation of oocytes in steroid for 9 h essentially terminated vitellogenin incorporation. Incorporation of vitellogenin occurred after removal of follicle cells from the oocyte by a short treatment with EDTA. These results demonstrate the macromolecular vitellogenin transport system remains operative in oocytes which can undergo nuclear maturation and that the steroid DOCA can affect its function. Evidence suggests that the mechanism of steroid inhibition is in part the result of inhibition of the micropinocytotic process in the oocyte cortex.

scholarly journals Prediction of maturational competence of feline oocytes using supravital staining of cumulus cells by propidium iodide

Zygote ◽  
2011 ◽  
Vol 20 (4) ◽  
pp. 333-337 ◽  
Author(s):  
Kenzo Uchikura ◽  
Masashi Nagano ◽  
Mitsugu Hishinuma
Keyword(s):  
Propidium Iodide ◽  
Cumulus Cell ◽  
Membrane Integrity ◽  
Cumulus Cells ◽  
Nuclear Maturation ◽  
Non Invasive ◽  
Maturation Rate ◽  
Cell Layers ◽  
The Relationship

SummaryWe examined the relationship between integrity of cumulus cells and nuclear maturation rate after in vitro culture to determine a non-invasive prediction of the maturational competence of feline oocytes. Feline cumulus–oocyte complexes (COCs) were collected from either small (400–800 μm) or large (≥800 μm) follicles. Immediately after collection, cumulus cells were evaluated morphologically (thickness of cumulus cell layers) and stained with propidium iodide (PI), which penetrates only non-viable cells. Cumulus cells without PI staining were judged as having good membrane integrity. After evaluation, COCs were cultured for 30 h and their nuclear maturation rate was determined. The nuclear maturation rate of oocytes derived from large follicles (89.8%) was higher (p < 0.05) than that from small follicles (60.8%). There was no difference in the maturation rate of oocytes from follicles with the same size regardless of cumulus morphology. In contrast, oocytes that had cumulus cells with good membrane integrity showed a higher maturation rate (93.8%) than oocytes with poor cumulus integrity (76.9%) in large follicles (p < 0.05). We conclude that evaluation of membrane integrity of cumulus cells by propidium iodide staining can be used to predict the maturational competence of oocytes.

Retinol improves in vitro oocyte nuclear maturation under heat stress in heifers

Zygote ◽  
2012 ◽  
Vol 21 (4) ◽  
pp. 377-384 ◽  
Author(s):  
M.J. Maya-Soriano ◽  
E. Taberner ◽  
M. López-Béjar
Keyword(s):  
Heat Stress ◽  
Oleic Acid ◽  
Ovarian Follicle ◽  
Premature Aging ◽  
Cortical Granule ◽  
Protective Effects ◽  
Oocyte Competence ◽  
Nuclear Maturation ◽  
Antioxidant Agents

SummaryHeat stress (HS) is especially harmful for bovine ovarian follicle development and oocyte competence. Furthermore, HS causes premature aging in oocytes due to high levels of reactive oxygen species (ROS), involved in the harmful effects over the oocyte maturation and the steroidogenic activity of follicular cells. In this study, the presumptive protective effects of antioxidant agents on heat-stressed oocytes were evaluated. Heifer oocytes were matured for 22 h under control (38°C) and HS conditions (41.5°C at 18–21 h of maturation). For each oocyte, nuclear stage and cortical granule (CG) distribution were evaluated. Steroidogenic activity of cumulus cells was also recorded. The antioxidant agents used in the study were: retinol (1.43 μg/ml), retinyl (0.28 μg/ml) and oleic acid (0.05 mg/ml). Based on a chi-squared test (P < 0.05), HS affected negatively the metaphase II (MII) progression and produced a premature CG exocytosis. Retinol improved the oocyte MII progression. However, retinyl and oleic acid, at the concentrations used in this study, could not counteract adverse effects of HS. A decrease in progesterone and increase in estradiol availability were observed when retinyl and oleic acid were supplemented to the maturation medium, respectively. In conclusion, retinol proved to be valuable in heat-stressed oocytes protecting nuclear maturation.

250 EFFECT OF LOW OXYGEN TENSION ATMOSPHERE AND MATURATION MEDIA ON IN VITRO-MATURED SWINE OOCYTES

2009 ◽  
Vol 21 (1) ◽  
pp. 223
Author(s):  
M. G. Marques ◽  
F. R. O. de Barros ◽  
M. D. Goissis ◽  
P. V. Cavalcanti ◽  
A. C. Nicacio ◽  
...  
Keyword(s):  
Oxygen Tension ◽  
Cortical Granule ◽  
Low Oxygen ◽  
Cortical Granules ◽  
Significance Level ◽  
Migration Rates ◽  
Nuclear Maturation ◽  
Low Oxygen Tension ◽  
Maturation Rate

The aim of this study was to evaluate the efficiency of a low oxygen tension atmosphere (5% CO2, 5% O2, and 90% N2) on swine oocyte maturation in chemically defined media or when supplemented with porcine follicular fluid (PFF). Briefly, oocytes were in vitro matured for 44 h in TCM-199 with 10% PFF or 0.1% PVA added, under a low oxygen tension atmosphere or a normal oxygen tension atmosphere (5% CO2 in air, approximate 20% O2). At 0 and 44 h of maturation, cumulus oophorus cells were removed. To evaluate the migration of cortical granules, oocytes were fixed, permeabilized, and incubated in 100 μg of FITC-PNA mL–1 for 30 min. Oocytes were then incubated in 10 μg mL–1 of Rnase for 30 min and in 10 μg mL–1 of propidium iodide for 10 min to verify nuclear maturation by confocal microscopy (Zeiss LSM 510 Meta). Heat shock protein 70 (HSP70) content was assessed as described in Kawarsky and King (2001 Zygote 9(3), 39–50) to verify oxidative stress. Data were analyzed by the SAS System for Windows (2000). The nonparametric ANOVA NPAR1WAY procedure was applied to evaluate nuclear maturation rate by comparing groups in pairs. Migration of cortical granules and HSP70 content were analyzed using PROC GLM (LSD test of means). The effects of treatment and manipulation were verified in all analyses. The significance level was 5%, and data were presented as means ± SEM. Results indicated that the percentage of metaphase II oocytes did not differ among groups after 44 h of maturation [PFF 5% O2 (89.16 ± 3.73a), PFF 20% O2 (86.59 ± 6a), PVA 5% O2 (79.62 ± 8.22a), and PVA 20% O2 (93 ± 5.17a)]. However, these groups were different from the 0-h group (0 ± 0b). Results for the percentage of cortical granule migration showed that 0-h oocytes (38.92 ± 2.75a) had lower migration rates compared with other groups. After 44 h of maturation, migration of the cortical granule rate of the PFF-supplemented group under a 5% O2 atmosphere (61.66 ± 3.21b) was different when compared with the PVA 20% O2 group (50.97 ± 3.48c). The other groups showed intermediate results, but without statistical differences [PFF 20% O2 (58.51 ± 2.5bc) and PVA 5% O2 (53.75 ± 3.14bc)] for the migration of cortical granules. Moreover, no difference at pixel quantification of HSP70 was observed among groups after 44 h of maturation [PFF 5% O2 (116.45 ± 40.94a), PFF 20% O2 (44.44 ± 12.66a), PVA 5% O2 (29.95 ± 7.95a), and PVA 20% O2 (58.49 ± 22.2a)], although these groups were different from the 0-h group (247.41 ± 38.59b). Although the HSP content decreased throughout in vitro maturation of swine oocytes under the low and high oxygen tension atmospheres, it can be concluded that a low oxygen tension atmosphere did not affect nuclear maturation and rates of cortical granule migration regardless of maturation media supplementation. Financial support: FAPESP (grant no. 05/01420-7).

Cumulus cell features and nuclear chromatin configuration of in vitro matured canine COCs and the influence of in vivo serum progesterone concentrations of ovary donors

Zygote ◽  
2009 ◽  
Vol 17 (1) ◽  
pp. 79-91 ◽  
Author(s):  
B. A. Rodrigues ◽  
A. E. F. Silva ◽  
P. Rodriguez ◽  
L. F. Cavalcante ◽  
J. L. Rodrigues
Keyword(s):  
Cumulus Cell ◽  
Nuclear Chromatin ◽  
Serum Progesterone ◽  
Nuclear Maturation ◽  
Cumulus Oocyte Complex ◽  
Chromatin Configuration ◽  
The Relationship

SummaryPhenotype integrity is viewed as an indicator of cumulus–oocyte complex (COC) viability. The objectives of this study were: (a) to observe the influence of cumulus investment expansion on the nuclear chromatin configuration of canine oocytes matured in vitro; (b) to examine the relationship between cumulus cell (CC) expansion and its morphology after in vitro maturation (IVM); (c) to ascertain the influence of in vivo serum progesterone (SP) concentrations of ovary donors on oocyte nuclear maturation, CC phenotypes and degrees of CC expansion of in vitro matured COCs. After 48 h of IVM in modified TCM 199, CCs from grade 1 and 2 COCs were stained with propidium iodide. Oocyte chromatin configuration was visualized by Hoechst 33342 stain. Results showed that oocyte IVM was not influenced by degree of CC expansion (D1, D2 and D3) in COCs. From the CC types (C1, C2 and C3), number of C1 types was higher at D1 expansion and differed from those observed at D2 and D3 expansions. Additionally, rates of apoptosis in D1 CCs were lower than those observed in D2 CCs (p < 0.05). Oocyte nuclear maturation was not influenced by in vivo SP concentrations of ovary donors. On the other hand, D3 expansion prevailed in COCs from bitches at SP > 2.5 ng/ml (p < 0.001). Moreover, in vitro CC apoptosis was associated both with low (0–1 ng/ml) and with high (>5 ng/ml) in vivo SP levels. These findings indicate that morphology of CCs from in vitro matured dog oocytes gives valuable information on viability of COCs and could possibly be used as a parameter in predicting the quality of oocytes destined for in vitro fertilization (IVF) and their outcomes.

155 EFFECTS OF CULTURE WITH OVALBUMIN IN ABSENCE OF FETAL BOVINE SERUM AND BOVINE SERUM ALBUMIN ON IN VITRO PRODUCTION OF CATTLE EMBRYOS

2010 ◽  
Vol 22 (1) ◽  
pp. 236
Author(s):  
T. A. D. Tetzner ◽  
N. Z. Saraiva ◽  
C. S. Oliveira ◽  
S. C. Méo ◽  
M. M. Souza ◽  
...  
Keyword(s):  
Bovine Serum ◽  
Cell Number ◽  
Differential Staining ◽  
Control Group ◽  
Cortical Granule ◽  
In Vitro Production ◽  
Nuclear Maturation ◽  
Fetal Bovine ◽  
Vitro Production

Embryo quality is influenced by culture conditions, which affect IVM, IVF, and IVC rates. One of the most efficient ways to evaluate the embryonic quality of IVP blastocysts is by differential staining of inner cell mass (ICM) and trophoblast (TF). Bovine embryos of superior quality should present the total number of cells close to the number of cell cycles (Neuber et al. 2002 Theriogenology 57, 2193-2202). In this study, we analyzed the effects of fetal bovine serum (F) and bovine serum albumin (B) replacement for ovalbumin (O) on nuclear maturation, cortical granule migration, pronuclear development, blastocyst rates, and differential staining of ICM and TF in Day 7 blastocysts. The treatment groups were named as follows: the first letter is the protein source used for IVM, the second for IVF, and the third for IVC. When 2 protein sources were used in the same step, the plus symbol (+) was used. The oocytes were IVM in TCM-199, supplemented with the following: 10% F, or 4 mg mL-1 B, or 4 mg mL-1 O, and 1.0 Âμg mL-1 of FSH, 50 Âμg mL-1 of hCG, 1.0 Âμg mL-1 of estradiol, 0.2 mM sodium pyruvate, and 83.4 Âμg mL-1 of amikacin. IVF was accomplished in TALP-IVF medium, with 0.2 mM pyruvate, 83.4 Âμg mL-1 of amikacin, and 6 mg mL-1 B or O. IVC was in SOF, with F, B, or O. The control group (CONT) consisted of the treatment FBF + B. Pronuclear development was compared by the chi-square test, whereas the other results were analyzed by ANOVA followed by the Tukey test, using SAS at 5% significance level (SAS Institute Inc., Cary, NC, USA). For IVM, the treatments F, B, O, and B + O did not affect (P > 0.05) nuclear maturation (73.92 to 78.78%) and cortical granule migration rates (58.89 to 66.76%). Regarding pronuclear development, the treatment FO (76.67%) was similar (P > 0.05) to the control group (82.95%), which was superior (P < 0.05) to the treatments BB (56.98%), BO (39.02%), OB (37.36%), and OO (39.24%). Blastocyst rates in FBF (42.8%) and control (45.0%) groups were superior (P < 0.05) to treatment OOO (26.0%) but similar (P > 0.05) to FOF, BBB, BOB, and OBO (32.0 to 35.8%). The average of blastocyst ICM cells of the group OOO (16.79) was inferior (P < 0.05) to the other groups. However, the average of TF cells on blastocysts of the group OOO (38.25) was similar (P > 0.05) to the groups BBB (45.74) and BOB (45.60) and inferior (P < 0.05) to the groups CONT (57.59), FBF (54.41), FOF (56.74), and OBO (47.35). The total average cells in the blastocysts of the group OOO (56.04) was inferior (P < 0.05) to the groups CONT (84.86), FBF (78.96), FOF (81.32), BBB (68.11), BOB (69.55), and OBO (69.82). The total cell number in the treatments, with several sources of protein supplementation, varied from 56.04 to 84.86. Considering the evaluation interval, this average cell number was discreetly inferior to that expected for the chronological age of the blastocysts. We concluded that it is possible to produce bovine embryos in the absence of F and/or B, with the protein source O, although it reduced blastocyst rates when used in all 3 steps of embryo in vitro production and resulted in blastocysts of inferior quality. Financial support: FAPESP 05/60389-2 and CNPq.

Insulin–transferrin–selenium (ITS) improves maturation of porcine oocytes in vitro

Zygote ◽  
2011 ◽  
Vol 19 (3) ◽  
pp. 191-197 ◽  
Author(s):  
Junhe Hu ◽  
Xiaoling Ma ◽  
Jian Chang Bao ◽  
Wei Li ◽  
De Cheng ◽  
...  
Keyword(s):  
Hormone Treatment ◽  
Treated Group ◽  
Control Group ◽  
Cortical Granule ◽  
Type I ◽  
Nuclear Maturation ◽  
Porcine Oocyte ◽  
Epidermal Growth ◽  
Cytoplasmic Maturation

SummaryThe objective of this study was to determine if insulin–transferrin–selenium (ITS) promoted a nuclear and cytoplasmic maturation of porcine oocytes that better supports subsequent embryonic development. The rate of oocyte in vitro maturation (IVM) in an experimental group treated with hormones for 42 h was significantly increased compared with that in a control group without hormone treatment (47.8% vs. 11.7%, respectively, p < 0.05). Following reduction of the hormone treatment period from 42 h to 21 h, which included both the first 21 h period of hormones treatment (45.4%) and the second 21 h period of hormone treatment (44.8%), the rate of oocyte IVM was still higher than that of the control group (p < 0.05). To improve porcine oocyte nuclear maturation, 1% ITS was added to medium supplemented with hormones. The rate of nuclear maturation in the ITS-treated group was significantly higher than in the ITS-untreated group (78.6% vs. 54.4%, respectively, p < 0.05). ITS treatment also significantly reduced the per cent of oocytes with type I and type III cortical granule (CG) distribution, respectively, and significantly increased the per cent of oocytes with type II CG distribution (85.3%). These observations indicated that the synchronization rates of nuclear and ooplasmic maturation reached 67.04% (78.56 × 85.33%). In conclusion, the combination of modified Tissue Culture Medium-199 (mM199) + 10 ng/ml epidermal growth factor (EGF) + 10 IU/ml pregnant mare serum gonadotrophin (PMSG) + 10 IU/ml human chorion gonadotrophin (hCG) + 2.5 IU/ml follicle stimulating hormone (FSH) + 1% ITS is suitable for culturing porcine oocytes in vitro, and effectively enhances porcine oocyte nuclear and cytoplasmic maturation.

Regulation of development in the fully grown mouse oocyte: chromosome-mediated temporal and spatial differentiation of the cytoplasm and plasma membrane

Development ◽  
1986 ◽  
Vol 93 (1) ◽  
pp. 213-238
Author(s):  
Jonathan Van Blerkom ◽  
Hobart Bell
Keyword(s):  
Plasma Membrane ◽  
Spatial Differentiation ◽  
Nuclear Maturation ◽  
Random Fashion ◽  
Mitochondria Transfer ◽  
Temporal And Spatial ◽  
Membrane Changes ◽  
Specific Association ◽  
And Migration ◽  
The Relationship

The relationship between nuclear maturation and the differentiation of the cytoplasm and plasma membrane during resumption of arrested meiosis was investigated by culture of GV- and MII-stagemouse oocytes in the presence and absence of nocodazole. Culture in the presence of nocodazole was associated with dispersal of MI and MII chromosomes throughout the subplasmalemmal cytoplasm. A progression of cortical (thickening of actin filaments) and plasma membrane changes (denudation of microvilli, reduction in cell surface glycoproteins, formation of chromosome-containing evaginations) that normally occurs in proximity to chromosomes associated with intact MI or MII spindles tookplace only in those regions of the cortical cytoplasm containing the dispersed subplasmalemmal chromosomes. The dispersion and migration of the chromosomes occurred in an apparently random fashion. Fluorescent probe analysis of normal and treated oocytes indicated a stage-specific association between the spatial distribution of chromosomes and mitochondria. Transfer of individual bivalent chromosomes to untreated oocytes at different stages of maturation and to cytoplasts derived from oocytes anucleated prior to GVB demonstrated (1) the necessity of chromosomes for cytoplasmic and plasma membrane differentiation, and (2) that the capacity of the cytoplasm and plasma membrane to differentiate in response to the presence of a chromosome is acquired prior to GVB.

286 ASSESSMENT OF NUCLEAR AND CYTOPLASMATIC MATURATION IN VITRO OF OOCYTES COLLECTED AT DIFFERENT STAGES OF FOLLICULAR WAVE FROM NELORE COWS (BOS TAURUS INDICUS)

2010 ◽  
Vol 22 (1) ◽  
pp. 300
Author(s):  
D. S. Melo ◽  
T. A. D. Tetzner ◽  
E. C. Gazotto ◽  
R. Vantini ◽  
N. Z. Saraiva ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Cortical Granule ◽  
Limiting Factor ◽  
Cleavage Rate ◽  
Significance Level ◽  
Oocyte Competence ◽  
Nuclear Maturation ◽  
Follicular Wave ◽  
The Moment

The objective of experiment 1 was to evaluate the influence of follicular wave moment on the quality and number of recovered oocytes through ovum pick-up (OPU), as well as blastocyst rate, in Nelore cows. Two hypotheses were tested: (1) the number of recovered viable COC would be higher at Days 3 and 5 than at Days 7 and 9; (2) the COC aspirated at the beginning of the follicular wave (Day 3 or Day 5) would be more competent and would produce more blastocysts than COC obtained at the end of the wave (Day 7 and Day 9), because these would be in a certain degree of advanced atresia. Cows (n = 10) received 2 mL of estradiol benzoate (Estrogin®), an auricular progestagen implant (Crestar®) for 7 days, and 2 mL of PGF2 analog (Preloban®) at the moment of implant retrieval. After 24 h animals were submitted to aspiration of the dominant follicle (ADF), this moment being considered Day 0. After ADF the donors were submitted to OPU on Days 3, 5, 7, and 9 (groups D3, D5, D7, and D9, respectively) of the new follicular wave. Each animal was submitted to all treatments. In each phase the protocol began with a 2-day interval from the group D9, D7, D5, and D3. Recovered COC went to IVM, IVF, and IVC in the same session of IVP. Statistical analysis were performed with SAS software (SAS Institute, Cary, NC, USA), using ANOVA at a 5% level of significance. There was no difference in the total number of follicles visualized at the moment of OPU among groups (D3:195, D5:189, D7:161, D9:151) or in the recovery rate (77.94; 78.30; 72.04; 73.50) and number of recovered total structures (152, 148, 116, 111). There was no difference in the total number of viable COC (133, 137, 103, 97) or in cleavage rate of COC in the 4 groups (79.69; 83.45; 71.84; 76.28). The total number and the blastocyst rates were higher in groups D3 and D5 (66, 49%, and 62, 45.25%) than in groups D7 and D9 (34, 33%, and 35, 36.08%). Statistical analysis was performed with the chi-square test, with a significance level of 5%. In experiment 2 nuclear and cytoplasmatic maturation were evaluated in COC recovered at Days 4 and 8 regarding nuclear maturation (progression to metaphase II stage) and cortical granule migration, respectively. The hypothesis tested was that COCs recovered at the beginning of the follicular wave would have a higher competence and therefore higher maturation rate compared with those the aspirated at the end. There was no difference in the number of viable COC (78 v. 97), percentages of nuclear maturation (74.35 v. 53.6), and cytoplasmatic maturation (48.71 v. 30.92). The results of the 2 experiments demonstrated that the beginning wave (Days 3 to 5) is the most appropriate moment for obtaining oocytes destined for IVP because of the greater oocyte competence and consequently, larger number and increased blastocyst production rates. Moreover, the results obtained in experiment 2 indicate that the low rate of cytoplasmic maturation can be a major limiting factor of IVP in Nelore cows. FAPESP.

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