scholarly journals Cyclic adenosine monophosphate modulator supplementation on in vitro maturation of bovine oocytes

Author(s):  
Minu Xaviour ◽  
Abhilash R.S. ◽  
Jayakumar C. ◽  
Amritha Aravind ◽  
Raji K.

Study evaluated the role of cAMP modulator (Forskolin and 3-isobutyl-1- methyl xanthine) supplementation on developmental competence of bovine oocytes. Cumulus oocyte complexes recovered from bovine ovaries of unknown reproductive status were used for the study. Oocytes retrieved by aspiration method were graded based on cumulus cell distribution and culture grade oocytes were selected for the study. A total of 414 culture grade oocytes were taken and divided into two groups. Group I constituted of 201 oocytes in which pre-maturation was carried out for a period of 2 h. In group II, 213 oocytes were selected in which normal maturation was carried out. Maturation was assessed after 24h of culture in CO2 incubator maintained at 38.5o C in 95 per cent humidified atmosphere of 5 per cent CO2 . Fertilisation was carried out using frozen thawed semen and the presumptive zygotes were then transferred to culture media and cleavage was assessed 48 h after insemination. A significantly higher maturation rate (p ?0.05) was observed in group I compared to group II (86.85 ± 1.19 vs 79.88 ± 2.67). There was a highly significant increase (p ?0.01) in cleavage rate in group I (65.92 ± 1.23) compared to group II (59.29 ± 1.50). A higher fertilisation rate was observed in group I (75.35 ± 1.19) than group II (71.88 ± 2.56). It could be concluded that pre-maturation with cAMP modulators improved the developmental competence of bovine oocytes.

2005 ◽  
Vol 17 (2) ◽  
pp. 277 ◽  
Author(s):  
A. Sathanawongs ◽  
S. Rojanasthien ◽  
A. Oranratnachai ◽  
J. Sumretprasong

This study was conducted to investigate the efficacy of FSH stimulation on the number of bovine oocytes retrieved by non-ultrasound-guided transvaginal ovum pickup and their developmental competence. In Experiment 1, to study the effect of FSH treatment on meiotic maturation, oocyte donors were divided into two groups (n = 5/group). Group I received no FSH treatment and aspiration was performed twice weekly, whereas Group II received 200 mg FSH (Folltropin-V) treatment twice daily for 3 days prior to aspiration, which was performed once every two weeks. Both groups were investigated for 8 weeks, after which crossover treatment continued for another 8 weeks. The retrieved oocytes were cultured for 24 h in vitro, and the chromosomal stages were evaluated by staining with 1% aceto-orcein. Experiment 2 was designed to determine the effect of FSH treatment on developmental competence of bovine oocytes. Oocytes were obtained from FSH-treated and untreated control cows (n = 3/group), and they were matured, fertilized, and cultured in vitro. The results showed that Group II females had a higher number of retrieved oocytes per cow per session than Group I females (7.05 ± 3.88 vs. 2.06 ± 0.99, respectively; P < 0.05). The FSH stimulation led to an increase in the proportion of matured oocytes (69.6% vs. 63.3%) and also increased the percentage of cleavage stage embryos (49.4% vs. 32.2%) compared with untreated control cows (P < 0.05). However, there was no difference between the two groups in percentage of morula and blastocyst formation (11.1%, 8.6% and 10.2%, 6.8%, respectively). In conclusion, the combination of non-ultrasound-guided transvaginal ovum pickup with FSH stimulation increased the number of retrieved oocytes per cow per session and tended to increase in vitro embryo production. The authors gratefully acknowledge the support by the Chiang Mai Artificial Insemination Center, Thailand.


2014 ◽  
Vol 26 (1) ◽  
pp. 198
Author(s):  
R. Urrego ◽  
E. Herrera ◽  
N. Chavarría ◽  
O. Camargo ◽  
N. Rodriguez-Osorio

The ability of bovine embryos to develop to the blastocyst stage, to implant, and to generate healthy offspring, depends greatly on the oocyte contribution. Oocyte competence is attributed to its close communication with the follicular environment and to its capacity to synthesise and store great amounts of mRNA. Higher developmental competence of bovine oocytes has been associated with the expression of certain genes and with the steroid concentration in the follicular fluid. Hence, the aim of this study was to establish the influence of OCT-4 and MATER mRNA abundance in the oocyte and the influence of progesterone and oestradiol follicular fluid concentration on the competence of bovine oocytes retrieved 30 min or 4 h after slaughter. Cumulus–oocyte complexes (COC) were left in postmortem ovaries for 30 min (Group I) or 4 h (Group II) at 30°C before aspiration. Progesterone and oestradiol concentrations were measured in the follicular fluid in both groups by immunoassay using an Immulite 2000 analyzer. Immature oocytes were evaluated for MATER and OCT-4 mRNA abundance by real-time PCR (total RNA isolated from pools of 100 oocytes per repeat) or were subjected to in vitro maturation (IVM), in vitro fertilization (IVF), and in vitro culture (IVC). For in vitro embryo production, 455 (Group I) and 470 (Group II) COC were used in three repeats. Progesterone concentration was lower (P ≤ 0.05) in Group II than in Group I. Conversely, oestradiol concentration did not vary between groups. Similarly, Group II oocytes exhibited the highest (P < 0.05) MATER and OCT-4 abundance. For embryo development, there were no significant differences between cleavage rates (72 h post-insemination) between both groups. However, blastocyst (168 h post-insemination) and hatching (216 h post-insemination) rates in Group II were greater (P < 0.05) with 21.3 compared with 30.7% and 54.2 compared with 75.3%, respectively. These results indicate that progesterone concentration in the follicle and the abundance of MATER and OCT-4 transcripts could be good predictors of embryo developmental competence and that retrieving COC 4 h after slaughter could increase blastocyst and hatching rates. This work was supported by COLCIENCIAS COD 122852128473 Colombia.


2011 ◽  
Vol 23 (1) ◽  
pp. 128
Author(s):  
J. Lee ◽  
J. Park ◽  
Y. Chun ◽  
W. Lee ◽  
K. Song

Study for equine somatic cell nuclear transfer (SCNT) is an attractive field for research, but it has not been a major field of study because it is hard to obtain a sufficient number of ovaries and it takes a lot of time and effort for the recovery of oocytes matured in vivo by ovum pickup. It was reported that the bovine cytoplast could support the remodelling of equine donor cells (Zhou et al. 2007 Reprod. Domest. Anim. 42, 243–247). The objectives of this study are 1) to monitor the early events of equine SCNT by interspecies SCNT (isSCNT) between bovine cytoplast and equine donor cell, and 2) to investigate the developmental competence of isSCNT embryos. Bovine oocytes were recovered from the follicles of slaughtered ovaries, and matured in TCM-199 supplemented with 10 mU mL–1 FSH, 50 ng mL–1 EGF, and 10% FBS at 39°C under 5% CO2 in air for 22 h. Fibroblasts derived from bovine or equine skin tissues were synchronized at G0/G1 stage by contact inhibition for 72 h. After IVM, oocytes with polar body were enucleated and electrically fused with equine or bovine skin fibroblasts (1.0 kV cm–1, 20 μs, 2 pulses). Fused couplets were activated with 5 μM ionomycin for 4 min followed by 5 h culture in 10 μg mL–1 cycloheximide (CHX) and/or 2 mM 6-DMAP, and cultured in modified synthetic oviduct fluid (mSOF) at 39°C under 5% CO2, 5% O2, and 90% N2 for 7 days. All analyses were performed using SAS (version 9.1; SAS Institute, Cary, NC, USA). The cleavage rate of isSCNT embryos derived from equine cell was not different (252/323, 78.7%; P = 0.94) from that of SCNT embryos derived from bovine cell (230/297, 79.2%). However, the rate of isSCNT embryos developed to over 8-cell stage was lower (3.3%; P < 0.0001) than that of bovine SCNT embryos (39.4%), and total cell number of isSCNT embryos developed to over 8-cell stage was lower (17.5, n = 12; P < 0.0001) than that (80.8, n = 110) of bovine SCNT embryos. Also, the rate of blastocyst formation of isSCNT embryos (0/323; 0.0%) was lower (P < 0.0001) than that of bovine SCNT embryos (83/297; 29.3%). Meanwhile, reconstructed oocytes for isSCNT were fixed at 8 h after activation to investigate the formation of pseudo-pronucleus (PPN) after post-activation treatment with CHX or CHX+6-DMAP. The ratio of oocytes with single PPN after treatment with CHX+6-DMAP (26/35; 74.3%) was not different (P = 0.63) from that of oocytes treated with CHX (24/36; 68.1%). Although isSCNT embryos derived from bovine cytoplast and equine donor cell could not develop to more than the 16-cell stage, it is believed that the results of this isSCNT study could be used for the preliminary data regarding the reprogramming of donor cell in equine SCNT.


2014 ◽  
Vol 26 (1) ◽  
pp. 197
Author(s):  
E. D. Souza ◽  
F. B. E. Paula ◽  
C. C. R. Quintao ◽  
J. H. M. Viana ◽  
L. T. Iguma ◽  
...  

The 90-kDa heat shock protein (HSP90) is a chaperone that is important for maintaing protein homeostasis under stress conditions. HSP90 seems also to be required for maturation of Xenopus oocytes (Fisher et al. 2000 EMBO J. 19, 1516) and first cleavage of mouse zygotes (Audouard et al. 2011 PloS One 6, e17109). This study aimed to evaluate the effect of inhibition of HSP90 by 17-(allylamino)-17-demethoxygeldanamycin (17AAG, Sigma St. Louis, MO, USA) during in vitro maturation (IVM) on bovine oocyte developmental competence. Immature cumulus–oocyte complexes (COC) were randomly allocated in 3 treatments during IVM: T0 (control; n = 240), no HSP90 inhibitor; T1: 2 μM HSP90 inhibitor (17AAG; n = 250) for the first 12 h of IVM; and T2: 2 μM HSP90 inhibitor (n = 188) for 24 h of IVM. In vitro maturation was performed in Nunc plates containing 400 μL of TCM-199 medium (Invitrogen, Carlsbad, CA, USA) supplemented with porcine FSH (Hertape Calier, Juatuba, Brazil) and 10% oestrus cow serum under 5% CO2, 95% humidity, and 38.5°C for 24 h. Oocytes were in vitro fertilized for 20 h and incubated under the same IVM conditions. Semen was processed by Percoll gradient (Nutricell, Campinas, Brazil) an IVF performed with 2 × 106 spermatozoa mL–1. Presumptive zygotes were completely denuded in a PBS solution with hyaluronidase and then cultured in wells with 500 μL of modified CR2aa medium supplemented with 2.5% fetal calf serum (Nutricell) in an incubator at 38.5°C under 5% CO2, 5% O2, 90% N2, and saturated humidity. Cleavage rate was evaluated 72 h post-fertilization and blastocyst rates were evaluated at Day 7 and Day 8. Data from 6 repetitions were analysed by generalized linear model procedure of SAS software (version 9.1; SAS Institute Inc., Cary, NC, USA), and means were compared by Student-Newman-Keuls test. Values are shown as mean ± s.e.m. There was a tendency (P = 0.08) for a lower cleavage rate in T2 (52.6 ± 5.8%) than in T0 (control; 74.2 ± 4.1%). Inhibition of HSP90 by 17AAG for 12 h and 24 h of IVM (T1 and T2, respectively) decreased blastocyst rates at Day 7 (20.4 ± 3.0% and 14.3 ± 2.6%, respectively; P < 0.01) and Day 8 (22.6 ± 4.1% and 16.9 ± 2.7%, respectively; P < 0.05) when compared with control (T0 = 31.8 ± 2.5% and 34.1 ± 2.9% for Day 7 and Day 8, respectively). In addition, the inhibition of HSP90 for 24 h decreased (P < 0.05) the proportion of hatched blastocysts at Day 8 (9.5 ± 5.0% for T2, respectively) when compared with control (T0 = 35.8 ± 3.9%), indicating a reduction on embryo quality. In conclusion, inhibition of HSP90 by 17AAG during IVM results in lower developmental competence, suggesting that this protein is also important for bovine oocytes. Further studies are required to investigate if the role of HSP90 on developmental competence of bovine oocyte is affected when under stress conditions. The authors acknowledge CNPq 473484/2011-0, FAPEMIG and FAPES for financial support.


2018 ◽  
Vol 30 (1) ◽  
pp. 206
Author(s):  
G. Singina ◽  
I. Lebedeva ◽  
T. Taradajnic ◽  
E. Shedova ◽  
A. Lopukhov ◽  
...  

Data on effects of progesterone (P4) during in vitro maturation of bovine oocytes on their capacity for embryonic development are contradictory. Our study was aimed at characterising effects of P4 and 2 luteotropic hormones, prolactin (PRL) and LH, on bovine oocyte developmental competence during the second step of two-step maturation (from metaphase (M)I to MII). Slaughterhouse-derived cumulus-enclosed oocytes (CEO) were matured for 12 or 24 h [one-step (OS) Control] in TCM-199 containing 10% fetal calf serum (FCS), 10 μg mL−1 porcine FSH, and 10 μg mL−1 ovine LH at 38.5°C and 5% CO2. The CEO cultured for 12 h were transferred to the following culture systems: (1) TCM-199 containing 10% FCS (Control 1) or (2) a monolayer of granulosa cells (GC) precultured for 12 h in TCM-199 containing 10% FCS (Control 2); then, the oocytes were matured for next 12 h. In both systems, the medium of experimental groups was supplemented with either P4 (50 ng mL−1) or bovine PRL (25 and 50 ng mL−1) or ovine LH (5 μg mL−1). All treatments were repeated 5 to 6 times using 138 to 196 oocytes per group. Following IVM, all oocytes underwent IVF as described previously (Singina et al. 2014 Reprod. Fertil. Dev. 26, 154). Embryos were cultured in CR1aa medium until Day 5 post-insemination and then transferred to the same medium supplemented with 5% FCS and cultured to Day 7. Embryo development was evaluated at Days 2 and 7 for cleavage and blastocyst formation. Apoptosis was detected by the TUNEL method using 26 to 47 blastocysts per group (from 4 to 5 separate experiments). For each system, arcsine-transformed data were analysed by one-way ANOVA. In OS Control, the cleavage and blastocyst rates were 68.9 ± 4.4% and 22.0 ± 2.4%, respectively. Regardless of the system or medium of two-step culture, the cleavage rate did not differ from that for OS Control, varying between 57.6 and 68.4%. In the absence of GC (System 1), the blastocyst yield in the P4 group (30.4 ± 0.8%) was greater (P < 0.05) than in OS Control and Control 1 (20.2 ± 2.7%) as well as in the groups treated with LH (19.1 ± 3.0%) and 25 ng mL−1 PRL (20.1 ± 2.7%). In the presence of GC, P4 raised the yield from 16.7 ± 2.3% (Control 2) to 27.7 ± 2.4% (P < 0.05). Furthermore, in System 2, the blastocyst rate in groups treated with P4 and 50 ng mL−1 PRL (25.0 ± 2.8%) was higher (P < 0.05) than in the LH group (13.9 ± 2.6%). Meanwhile, the proportion of apoptotic nuclei (2.3-6.9%) was not associated with the system of oocyte maturation or effects of hormones studied. Our data indicate that P4 (50 ng mL−1) can enhance the developmental competence of bovine oocytes during the second step of two-step maturation regardless of the presence of granulosa cells, whereas the similar effect of PRL (50 ng mL−1) is less pronounced and depends on the granulosa-conditioned environment. This research was supported by the Russian Science Foundation (project 16-16-10069).


Zygote ◽  
2014 ◽  
Vol 23 (3) ◽  
pp. 327-335 ◽  
Author(s):  
Hruda Nanda Malik ◽  
Dinesh Kumar Singhal ◽  
Shrabani Saugandhika ◽  
Amit Dubey ◽  
Ayan Mukherjee ◽  
...  

SummaryThe present study was carried out to investigate the effects of different activation methods and culture media on the in vitro development of parthenogenetic goat blastocysts. Calcium (Ca2+) ionophore, ethanol or a combination of the two, used as activating reagents, and embryo development medium (EDM), modified Charles Rosenkrans (mCR2a) medium and research vitro cleave (RVCL) medium were used to evaluate the developmental competence of goat blastocysts. Quantitative expression of apoptosis, stress and developmental competence-related genes were analysed in different stages of embryos. In RVCL medium, the cleavage rate of Ca2+ ionophore-treated oocytes (79.61 ± 0.86) was significantly (P < 0.05) higher than in ethanol (74.90 ± 1.51) or in the combination of both Ca2+ ionophore and ethanol. In mCR2a or EDM, hatched blastocyst production rate of Ca2+ ionophore-treated oocytes (8.33 ± 1.44) was significantly higher than in ethanol (6.46 ± 0.11) or in the combined treatment (6.70 ± 0.24). In ethanol, the cleavage, blastocyst and hatched blastocyst production rates in RVCL medium (74.90 ± 1.51, 18.30 ± 1.52 and 8.24 ± 0.15, respectively) were significantly higher than in EDM (67.81 ± 3.21, 14.59 ± 0.27 and 5.59 ± 0.42) or mCR2a medium (65.09 ± 1.57, 15.36 ± 0.52 and 6.46 ± 0.11). The expression of BAX, Oct-4 and GlUT1 transcripts increased gradually from 2-cell stage to blastocyst-stage embryos, whereas the transcript levels of Bcl-2 and MnSOD were significantly lower in blastocysts. In addition, different activation methods and culture media had little effect on the pattern of variation and relative abundance of the above genes in different stages of parthenogenetic activated goat embryos. In conclusion, Ca2+ ionophore as the activating agent, and RVCL as the culture medium are better than other tested options for development of parthenogenetic activated goat blastocysts.


Reproduction ◽  
2002 ◽  
pp. 455-465 ◽  
Author(s):  
YH Choi ◽  
CC Love ◽  
LB Love ◽  
DD Varner ◽  
S Brinsko ◽  
...  

This study was undertaken to evaluate the development of equine oocytes in vitro and in vivo after intracytoplasmic sperm injection (ICSI) with either fresh or frozen-thawed spermatozoa, without the use of additional activation treatments. Oocytes were collected from ovaries obtained from an abattoir and oocytes classified as having expanded cumulus cells were matured in M199 with 10% fetal bovine serum and 5 microU FSH ml(-1). After 24-26 h of in vitro maturation, oocytes with a first polar body were selected for manipulation. Fresh ejaculated stallion spermatozoa were used for the experiment after swim-up for 20 min in sperm-Tyrode's albumen lactate pyruvate. Frozen-thawed spermatozoa from the same stallion were treated in a similar way. Spermatozoa were immobilized and injected into the oocytes using a Piezo drill. Presumptive zygotes were cultured in G1.2 medium for 20 or 96 h after the injection was administered, or were transferred to the oviducts of recipient mares and recovered 96 h later. In addition, bovine oocytes with first polar bodies were injected with the two types of stallion spermatozoa and fixed 20 h after injection to examine pronuclear formation. Fertilization rate (pronucleus formation and cleavage) at 20 h after injection of spermatozoa was not significantly different between fresh and frozen-thawed sperm groups in either equine or bovine oocytes. Pronucleus formation after injection of spermatozoa into bovine oocytes was significantly higher than that for equine oocytes (P < 0.05). There were no significant differences in cleavage rate or average number of nuclei at 96 h between equine oocytes injected with fresh or frozen-thawed spermatozoa. However, embryos developed in vivo for 96 h had a significantly higher number of nuclei in both sperm treatments compared with those cultured in vitro. These results indicate that good activation rates may be obtained after injection of either fresh or frozen-thawed equine spermatozoa without additional activation treatment. Injection of frozen-thawed equine spermatozoa results in similar embryo development to that obtained with fresh equine spermatozoa. In vitro culture of equine zygotes in G1.2 medium results in a similar cleavage rate but reduced number of cells compared with in vivo culture within the oviduct. Bovine oocytes may be useful as models for assessing sperm function in horses.


2006 ◽  
Vol 18 (2) ◽  
pp. 272
Author(s):  
K. Kananen-Anttila ◽  
M. Eronen ◽  
J. Matilainen ◽  
M. Kallio ◽  
J. Peippo ◽  
...  

We have studied the effect of suppressed IVM on the developmental competence of bovine oocytes, aiming at elucidating the importance of cytoplasmic maturation in fertilization and embryo development. Six replicates of abattoir-derived oocytes were randomly divided into three IVM groups. Control (n = 950): TCM-199 with glutamax-I (Gibco, Grand Island, NY, USA), 0.25 mM Na-pyruvate, 100 IU mL−1 penicillin and 100 μg mL−1 streptomycin, 50 ng mL−1 FSH, and 10% fetal bovine serum (FBS) (Gibco); Serum+FSH-free (n = 944): same as control but without FSH and FBS; α-amanitin (n = 977): same as control but with 10 μg mL−1 α-amanitin. Nuclear maturation of oocytes was studied 24 h after the onset of IVM, the formation of sperm aster structure 10 hours post-insemination (hpi) and the formation of pronuclei 20 hpi. Sperm aster was visualized with β-tubulin antibody (modified from Navara et al. 1999 Dev. Biol. 162, 29–40). Presumptive zygotes were cultured until Day 7 in modified SOFaaci + 4 mg mL−1 fatty acid-free BSA in 5% O2. Cumulus cell expansion was seen only in the control group. The results of nuclear maturation, fertilization, and embryo development are summarized in Table 1. Serum and FSH deprivation did not have a statistically significant effect on the parameters studied (vs. control). α-amanitin exposure during IVM reduced nuclear maturation, fertilization, and Day 3 embryo cleavage vs. control, and resulted in total blockage of Day 7 blastocyst development. The treatment groups had significantly smaller mean diameters of male pronuclei (control: 14 ± 0.6 μ­m; serum+FSH-free: 12 ± 0.5 μ­m, P < 0.05; α-amanitin: 10 ± 0.6 μ­m, P < 0.001) and sperm asters (control: 86 ± 4 μ­m; serum+FSH-free: 82 ± 4 μ­m, P < 0.01; α-amanitin: 49 ± 7 μm, P < 0.001) (nonparametric Kruskall Wallis and Mann-Whitney U tests) vs. control group. Despite reduction in pronucleus and sperm aster diameter, serum and FSH deprivation during IVM did not affect in vitro developmental competence of bovine oocytes, suggesting a need for re-evaluation of the components of IVM. α-Amanitin exposure in IVM disturbed nuclear maturation, fertilization, and embryo development, indicating the essence of early transcription. Table 1. Average percentages ± (n) for nuclear maturation, fertilization (min two pronuclei), embryo cleavage, and blastocyst development


Author(s):  
Sonia B. Umdor ◽  
M. Karunakaran ◽  
D.K. Mandal ◽  
A. Santra ◽  
Subrata K. Das

Background: In vitro embryo production is a valuable tool for understanding early mammalian development, therapeutic applications, excellent source for research in the field of developmental biology and production of valuable animals. The purpose of this study is to improve the production of in vitro cattle embryos using fibroblast and platelet derived growth factor as media supplement. Methods: Ovaries were collected from local abattoir in 0.9% saline (30-35°C) supplemented with antibiotics. Cumulus oocyte complexes were aspirated, washed 5-6 times and placed in maturation media supplemented with growth factors and cultured in 5% CO2 incubator at 38.5°C with maximum humidity. After 24 h oocytes were co-incubated with in vitro capacitated sperms for fertilization for 15-18 h and then presumptive zygotes were cultured for embryo development. Cleavage was observed after 40-42 h and embryos were co-cultured with oviductal cells for 7-9 days. Result: The highest cleavage and blastocyst formation rates were 55.93 ± 4.75, 57.06 ± 4.78, 51.24 ± 4.12 and 3.26 ±1.53, 2.42 ± 1.02, 2.70 ± 1.17 in FGF (1ng ml-1), PDGF (10 ng ml-1) and in combination of FGF and PDGF (1ng ml-1 each) respectively. It can be concluded that PDGF (10 ng ml-1) enhanced cleavage rate and FGF (1ng ml-1) enhanced blastocyst formation rate.


Zygote ◽  
2014 ◽  
Vol 23 (4) ◽  
pp. 563-572 ◽  
Author(s):  
Gustavo Bruno Mota ◽  
Ingrid Oliveira e Silva ◽  
Danielle Kaiser de Souza ◽  
Flavia Tuany ◽  
Michele Munk Pereira ◽  
...  

SummaryThe aim of this study was to evaluate the dose–response effect of insulin, plus follicle-simulating hormone (FSH) at a fixed concentration, in a serum-free defined culture medium (DCM) on the in vitro maturation of bovine cumulus–oocyte complexes (COCs). For oocyte nuclear maturation, the expression levels of GDF9, GLUT1, PRDX1 and HSP70.1 transcripts related to oocyte and embryo developmental competence were analysed. For in vitro maturation (IVM), cumulus–oocyte complexes from slaughterhouse ovaries were distributed into four groups based on insulin concentration added to serum-free DCM, which was composed of alpha minimum essential medium (α-MEM), as basal medium: (1) DCM control: 0 ng/ml; (2) DCM1: 1 ng/ml; (3) DCM10: 10 ng/ml; and (4) DCM100: 100 ng/ml. After IVM, the nuclear status of a sample of oocytes was analysed and the other oocytes were submitted for in vitro fertilization (IVF) and in vitro culture (IVC). Different concentrations of insulin did not affect significantly the nuclear maturation and cleavage rate (72 h post-insemination) across all groups. Blastocyst rate (192 h post-insemination) did not differ in DCM control (24.3%), DCM1 (27.0%) and DCM10 (26.3%) groups, but the DCM100 (36.1%) group showed a greater blastocyst rate (P < 0.05) than the DCM control. Insulin concentrations of 1, 10, or 100 ng/ml decreased the relative levels of GDF9 and HSP70-1 transcripts in oocytes at the end of IVM (P < 0.05). The transcripts levels of PRDX1 decreased (P < 0.05) only when 10 or 100 ng/ml insulin was added to the DCM medium. No difference in levels of GLUT1 transcripts (P > 0.05) was observed at the different insulin concentrations. The results indicated that insulin added to DCM influenced levels of transcripts related to cellular stress (HSP70-1 and PRDX1) and oocyte competence (GDF9) in bovine oocytes and at higher concentrations enhanced blastocyst production.


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