Low concentrations of MEM vitamins during in vitro maturation of porcine oocytes improves subsequent parthenogenetic development

To investigate the effects of water-soluble vitamin supplementation for IVM/IVC of porcine oocytes and evaluate maturation and developmental capacity in vitro, porcine cumulus oocyte complexes (COCs) was matured in NCSU-23-based medium with water-soluble vitamins for 44 h and then cultured in PZM-3 for 7 days following activation. The COCs were allocated into five treatment groups and matured in various concentrations of MEM vitamins (control, 0.05, 0.1, 0.2, 0.4, and 1x). Metaphase II plates of the cumulus-free oocytes were observed following Hoechest 33258 staining. The COCs were allocated into four treatment groups, matured in various concentrations of MEM vitamins (control, 0.05, 0.1, 0.2, and 0.4x) and cultured in PZM-3 following activation. Also, COCS were matured without MEM vitamins and cultured in PZM-3 with various concentrations (control, 0.1, 0.4, 1.0, and 2.0 x) of MEM vitamins. Furthermore, 2 x 2 factorial (IVM/IVC) experiments were performed in IVM medium with or without 0.05 x MEM vitamins and IVC medium with or without 0.4x MEM vitamins to examine the in vitro development of parthenogenetic embryos. Maturation rates of COCs treated with MEM vitamins did not differ significantly among groups. However, compared to the control group, oocytes matured with the addition of 0.05 x MEM vitamins developed to blastocysts at a higher percentage (P<0.05) following activation and culture in PZM-3 without MEM vitamins. Total cell number of blastocysts was significantly higher in the 0.05 x group. Addition of 0.4x MEM vitamins decreased (P<0.05) cleavage and blastocyst developmental rates compared with 0.05 x MEM vitamins-treated group. In contrast, addition of vitamins to PZM-3 medium for in vitro culture of activated porcine oocytes did not affect development. In conclusion, addition of a low concentration of MEM vitamins to IVM medium for porcine oocytes enhanced subsequent development and improved embryo quality.     

Effects of epidermal growth factor on early embryonic development after in vitro fertilization of oocytes collected from ewes treated with follicle stimulating hormone

Epidermal growth factor (EGF) has been shown to enhance the in vitro rate of blastocyst formation in several species. Follicular development was induced in ewes (n=15) by twice daily administration of FSH-P on Days 13 and 14 of the estrous cycle. Cumulus oocyte complexes (COCs) were collected from all visible follicles (n=25+/-2.4/ewe) on Day 15. COCs from each ewe were cultured separately for 24h in maturation medium (containing 10% serum, LH, FSH and estradiol) with (8.2+/-0.9 per ewe) or without (7.8+/-0.8 per ewe) EGF (10 ng/ml). Oocytes were then denuded by hyaluronidase treatment, and healthy oocytes were cultured in the presence of frozen-thawed semen in synthetic oviductal fluid (SOF) medium containing 2% sheep serum. After 18-20 h, zygotes were transferred to SOF medium without glucose and cultured for about 36 h until they reached the 4-8 cell stage. Embryos were transferred to SOF medium with glucose for further development. Medium was changed every other day until blastocyst formation on Day 8 of culture (Day 1=day of fertilization). The rate of embryonic development was evaluated throughout the culture period. After maturation, cumulus cells were more expanded in the presence than in the absence of EGF. The rates of fertilization (overall 75.7+/-3.9%) and morula formation (overall 40.6+/-7.1%) were similar (P>0.05) for COCs cultured with or without EGF. However, EGF increased (P<0.01) the number of blastocysts (1.4+/-0.1 versus 0.6+/-0.2 per ewe) and tended to increase (P<0.1) the rate of blastocyst formation (21.0+/-6.6% versus 13.4+/-4.3% per ewe). These data demonstrate that EGF increases blastocyst formation in FSH-treated ewes. Therefore, EGF is recommended as a supplement to maturation medium to enhance embryonic development in vitro in FSH-treated sheep.     

Supplements to in vitro maturation media affect the production of bovine blastocysts and their apoptotic index but not the proportions of matured and apoptotic oocytes

The objective of this study was to compare the effect of different supplements to the basic IVM medium (TCM199) on the efficiency of cattle oocyte maturation and blastocyst production, and the incidence of apoptosis in both oocytes and blastocysts. Two protein supplements (FBS and fafBSA) and a macromolecule (PVP40) were compared in a 3 treatmentsx9 replicates design. Cumulus-oocyte complexes (COCs) aspirated from slaughterhouse ovaries were matured for 24h in TCM199 medium supplemented with 10% FBS, 6% fafBSA or 4% PVP40 (50-70 COCs in each treatment/replicate), then inseminated and cultured in vitro for 8 days. Immature and mature oocytes as well as Day 8 blastocysts were subjected to TUNEL analysis. Cleavage rate was monitored on Day 2 post-insemination (pi), whereas blastocyst yield on Day 8 pi. The composition of maturation media did not affect zygotic cleavage rate on Day 2 (on average 71.0%), however the blastocyst rate on Day 8 pi was significantly lower (P<0.001) for embryos derived from oocytes matured with PVP40 (16.0%) than for those matured with FBS (22.4%) or fafBSA (22.1%). The rate of TUNEL positive oocytes differed significantly between immature (1.4%) and mature (11.2%) oocytes (P<0.01). Supplements to maturation medium were not related to the incidence of apoptosis in mature oocytes (11.2%) and the rate of oocytes at the second metaphase stage (71.5%). Cumulus cell expansion was reduced by maturation in medium supplemented with PVP40. This macromolecule was also correlated with higher apoptotic index in blastocysts (5.8%) when compared to FBS (3.2%) and fafBSA (3.1%; P<0.001). In conclusion, lower blastocyst rate and elevated apoptotic index in embryos derived from oocytes matured with PVP40 may suggest that synthetic macromolecule provides less balanced environment for oocyte maturation and therefore should be treated with caution.     

Development of goat embryos after in vitro fertilization and parthenogenetic activation by different methods.

Effective activation protocols that can be used during nuclear transfer investigations in goats need to be developed. We compared the development of IVF goat embryos with those of nonfertilized parthogenetically developing oocytes activated by treatment with either ionomycin or ethanol, both followed by immediate exposure to 6-diethylaminopurine (6-DMAP). Cumulus oocyte complexes (COCs) recovered from abattoir goat ovaries were either matured in a conventional laboratory incubator or placed in pre-equilibrated maturation medium and shipped overnight in a battery-operated dry incubator to another laboratory. Mature COCs were allocated randomly to one of three treatment groups. Group 1 oocytes (n=169 shipped, n=253 not shipped) were fertilized in vitro at 24 h postmaturation (hpm). The remaining COCs were activated at 28 hpm in either ionomycin (Group 2: n=362 shipped, n=202 not shipped), or ethanol (Group 3: n=263 shipped, n=249 not shipped). Activated oocytes were immediately incubated in 6-DMAP for 4 h. Blastocyst development was evaluated on Day 8 post-insemination/activation. Percent cleavage was comparable in shipped and nonshipped oocytes and in all treatment groups. In both shipped and nonshipped oocytes, parthenotes developing from ionomycin- and ethanol-activated oocytes had significantly greater blastocyst development (P<0.01) compared to IVF embryos (28.5 +/- 3.0, 27.4 +/- 2.8, 10.3 +/- 3.0, respectively for the nonshipped oocytes and 9.9 +/- 2.1, 10.3 +/- 2.4, 3.7 +/- 4.7 respectively for the shipped oocytes). Shipped oocytes had lower blastocyst development compared to nonshipped oocytes in the three treatment groups. The mean blastocyst cell number was not statistically different between shipped and nonshipped oocytes or among treatment groups, suggesting that all were equally viable.     

Sphingosine 1-phosphate protects bovine oocytes from heat shock during maturation

Sphingosine 1-phosphate (S1P) is a sphingolipid metabolite that can block apoptosis by counteracting the proapoptotic effects of ceramide. Experiments were performed to evaluate whether S1P blocks the disruption in oocyte developmental competence caused by heat shock. Cumulus-oocyte complexes (COCs) were placed in maturation medium and cultured at 38.5 or 41 degrees C for the first 12 h of maturation. Incubation during the last 10 h of maturation, fertilization, and embryonic development were performed at 38.5 degrees C. Heat shock during the first 12 h of maturation reduced cleavage rate, the number of oocytes developing to the blastocyst stage, and the percentage of cleaved embryo that subsequently developed to blastocysts. Addition of 50 nM S1P to maturation medium had no effect on oocytes matured at 38.5 degrees C but blocked effects of thermal stress on cleavage and subsequent development. The blastocysts formed at Day 8 did not differ between S1P and control groups in caspase activity, total cell number, or percentage of cells that were apoptotic. Blocking endogenous generation of S1P by addition of 50 nM N1N-dimethylsphingosine, a sphingosine kinase inhibitor, reduced or tended to reduce cleavage rate and blastocyst development regardless of whether maturation of COCs was at 38.5 or 41 degrees C. Results demonstrate that S1P protects oocytes from a physiologically relevant heat shock and affects oocyte maturation even in the absence of heat shock. The S1P-treated oocytes that survived heat shock and became blastocysts had a normal developmental potential as determined by caspase activity, total cell number, and percentage of apoptotic cells. Thus, modulation of developmental competence of oocytes using S1P may be a useful approach for enhancing fertility in situations where developmental competence of oocytes is compromised.     

Effect of MEM vitamins and forskolin on embryo development and vitrification tolerance of in vitro-produced pig embryos

The aims of this study were (1) to determine the effect of in vitro maturation (IVM) medium supplementation with MEM vitamins on in vitro embryo development and sensitivity to vitrification of Day 6 blastocysts and (2) to evaluate whether the addition of forskolin to in vitro culture (IVC) medium enhances blastocyst survival following Super Open Pulled Straw (SOPS) vitrification. Cumulus–oocyte complexes (COCs; n = 4000) were matured with 0.0% or 0.05% (v/v) MEM vitamins. After 44 h of IVM, the oocytes were in vitro fertilized, and presumptive zygotes were cultured. At Day 5 of IVC, embryos from both experimental groups were cultured for 24 h with 0 or 10 μM forskolin, achieving a 2 × 2 factorial design. The blastocyst formation rate was assessed on Day 6, and subsets of samples from the four experimental groups were vitrified (n = 469) or kept fresh (n = 546). Fresh and vitrified-warmed blastocysts were cultured for 24 h prior to embryo survival and total blastocyst cell number assessment. The MEM vitamins increased (P < 0.001) the blastocyst formation rate at Day 6, but they did not affect embryo survival after vitrification. In contrast, the addition of forskolin to the culture medium enhanced (P < 0.05) the blastocyst vitrification tolerance. The total blastocyst cell number was similar among the groups. In conclusion, supplementation with 0.05% MEM vitamins improved the blastocyst formation rate, and the addition of 10 μM forskolin to the culture medium increased survival in Day 6 in vitro-produced blastocysts after SOPS vitrification.     

Effect of cysteamine supplementation of in vitro matured bovine oocytes on chilling sensitivity and development of embryos

In vitro techniques for production of bovine embryos including in vitro oocyte maturation (IVM), fertilization (IVF) and culture (IVC) are becoming increasingly employed for a variety of research purposes. However, decreased viability following cryopreservation by conventional methods has limited commercial applications of these technologies. A practical alternative to facilitate transport would be to arrest development by chilling without freezing. The present research was undertaken to evaluate chilling sensitivity of IVM-IVF embryos at different stages of development, and to determine possible beneficial effects of cysteamine treatment during IVM, previously shown to enhance embryo development in culture, on survival following chilling at different stages. Embryos produced by standard IVM-IVF-IVC methods were chilled to 0 degrees C for 30 min at 2-cell (30-34 h post-insemination, hpi), 8-cell (48-52 hpi) or blastocyst (166-170 hpi) stages. Viability after chilling was assessed by IVC with development to expanded blastocyst stage determined on days 7 and 8 post-insemination (pi) and hatching blastocyst stage determined on days 9 and 10 pi. Control embryos at the same stages were handled similarly, but without chilling, and development during culture similarly assessed. The effect of cysteamine supplementation (100 microM) of the IVM medium was determined for both chilled and non-chilled (control) embryos. Cysteamine supplementation during IVM had no significant effect on oocyte maturation or fertilization, but increased the proportions of oocytes developing to blastocyst stage by day 7 (13.7+/-0.9% versus 7.2+/-0.9%; P<0.05), total blastocysts (20.5+/-0.9% versus 15.3+/-1.3%; P<0.05), and hatching blastocysts (16.8+/-1.6% versus 12.0+/-1.5%; P<0.05). The greater survival in terms of hatching (78.6+/-7.0) following chilling of blastocysts produced by IVM-IVF of oocytes matured in media supplemented with cysteamine offers promise for applications requiring short-term storage to facilitate transport of in vitro produced bovine embryos.     

Bovine parthenogenetic blastocysts following in vitro maturation and oocyte activation with ethanol

The appropriate in vitro bovine oocyte maturation and ethanol activation conditions for preimplantation bovine embryo parthenogenetic development to the blastocyst stage were investigated. A 7% ethanol concentration significantly enhanced (P<0.05) the proportion of activated, in vitro-matured bovine oocytes (7% ethanol, 83.4 +/- 3.2% versus 0% ethanol, 63.9 +/- 2.0%). The proportion of activated oocytes was significantly higher (P<0.05) by treatment with 7% ethanol for a minimum of 2 minutes (2 minutes, 89.8 +/- 4.0% versus 0.5 minutes 63.4 +/- 4.9%). Oocyte maturation for periods ranging from 30, 34, 38 and 44 hours resulted in a significant increase (P<0.05) in the proportion of activated oocytes, and in oocytes displaying 2 or 3 pronuclei versus oocytes matured for 26 hours. The proportion of cleaved, activated oocytes (2-cell stage), 4 -cell stage and parthenogenetic morula/blastocysts was significantly higher (P<0.05) within the 34-hour oocyte maturation treatment group. Although the 44-hour oocyte maturation treatment group displayed the highest proportion of activated oocytes with 2 pronuclei, it did not display the highest cleavage frequency, possibly due to the effects of postovulatory aging. Several morphologically normal parthenogenetic bovine blastocysts developed from oocytes that were in vitro matured for 34 hours. The ability to produce such parthenogenetic embryos will eventually facilitate investigation into the role(s) of the maternal and paternal genomes during bovine early development.     

Culture media for mouse oocyte maturation affect subsequent embryonic development

These experiments were done to determine whether the culture medium used for the spontaneous maturation of mouse oocytes can affect the subsequent capacity of the ova to become fertilized and complete preimplantation development in vitro and development to live young. Oocytes obtained from antral follicles of gonadotropin-primed immature mice underwent spontaneous maturation in control medium, i.e. Eagle's Minimum Essential Medium (MEM) supplemented with 5% fetal bovine serum, or in one of eight different media which were also supplemented with serum. All of the ova were fertilized in Whitten's medium and were assessed for cleavage to the 2-cell stage and for further preimplantation development to blastocysts during culture in Whitten's medium. Three of the eight media used for oocyte maturation improved the capacity of the ova to develop to the blastocyst stage when compared with the control: Waymouth MB 752/1, MEM with non-essential amino acids, and MEM Alpha; Waymouth medium promoted the highest frequency of development of ova to the blastocyst stage. Moreover, the blastocysts derived from oocytes that matured in Waymouth medium contained more cells than blastocysts derived from oocytes that matured in control medium. Although BGJb medium promoted the cleavage of eggs to the 2-cell stage when present during oocyte maturation, it had a detrimental effect on their subsequent preimplantation developmental capacity. Following transfer to foster mothers, more 2-cell stage embryos developed to live young after oocyte maturation in Waymouth medium (21%) than in control medium (13%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of oocyte quality, semen donor and embryo co-culture system on the efficiency of blastocyst production in goats

The aim of the study was to determine whether the selection of immature oocytes by a combination of cumulus-oocyte-complexes (COCs) morphology and staining with brilliant cresyl blue (BCB) would be helpful in selecting developmentally competent oocytes, and thereby increase the efficiency of blastocyst production from ovarian oocytes of FSH-primed, adult goats. In a second experiment the interaction between oocyte quality and semen donor was assessed. In a third experiment the usefulness of Vero cells for co-culture with goat embryos was investigated. In the pool of morphologically normal COCs recovered from ovaries following slicing (21.9+/-11.0), the mean rate of COCs classified as BCB+ was 85.6%, and the BCB- was approximately 11%. Oocytes classified as grade 1 and BCB+ exhibited the highest developmental competence (P<0.001) after in vitro maturation and fertilization compared with oocytes of grade 1 BCB- and grade 2 BCB+ or BCB-. There were no significant differences in developmental competence in grade 2 oocytes, regardless of BCB coloration. No significant differences in embryo cleavage and blastocyst formation rates among three bucks were observed when morphologically normal, BCB+ oocytes were used. For all tested bucks, differences in embryo production efficiency were related only to the oocyte quality. Similar blastocyst rates were developed from embryos co-cultured with goat oviduct epithelial cells (34.3%) and with Vero cells (33.3%). These results show that the most important criterion for selection of COCs before maturation is the visual assessment of morphological features. Staining with BCB of COCs recovered from adult goats does not enhance efficiency of selection of developmentally competent oocytes for IVF.     

Effect of the absence or presence of various protein supplements on further development of bovine oocytes during in vitro maturation

The evaluation of culture medium for bovine oocytes has progressed toward more defined conditions during the last few years. The main objective of this study was to evaluate different sources of albumin as a protein supplement during in vitro maturation (IVM) of bovine oocytes in synthetic oviduct fluid medium (SOF). The replacement of protein with polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA) was also evaluated. The effect of recombinant human FSH on cumulus expansion and nuclear maturation in SOF containing BSA (BSA-V) or PVP-40 was also studied. Addition of BSA-V during IVM retarded nuclear maturation when compared with addition of PVP-40 or use of SOF alone. The inclusion of different concentrations of BSA-V, fetal calf serum (FCS), or PVA during IVM had no positive effect on the developmental capacity of the oocytes compared with the use of SOF alone with no supplement but significantly decreased the percentage of embryos reaching the morula and blastocyst stages. However, when BSA-V was replaced with purified BSA, BSA that was essentially free of fatty acids, or chicken egg albumin, embryonic development rates were restored. The presence of PVP-40 but not PVP-360 during IVM significantly increased morula and blastocyst production. These results indicate that although SOF alone can support bovine oocyte maturation, a high proportion of morulae and blastocysts can be produced from IVM oocytes cultured in medium containing PVP-40. These studies are the first to show that the effect of FSH on nuclear maturation and cumulus expansion is dependent on substrates present in IVM medium.     

Follicle size-dependent effects of sow follicular fluid on in vitro cumulus expansion, nuclear maturation and blastocyst formation of sow cumulus oocytes complexes

Follicular fluid from 2 to 4 and 5 to 8 mm diameter non-atretic follicles (SFF and LFF, respectively) of sows was added during IVM of cumulus oocytes complexes (COCs) to study its effects on cumulus expansion, nuclear maturation, and subsequent fertilization and embryo development in presence or absence of recombinant human FSH. COCs aspirated from 2 to 5 mm follicles of sow ovaries, were cultured for the first 22 h in TCM-199 and 100 microM cysteamine, with or without 10% pFF and/or 0.05 IU/ml recombinant hFSH. For the next 22 h, the COCs were cultured in the same medium, but without pFF and FSH. After culture, cumulus cells were removed and the oocytes were either fixed and stained to evaluate nuclear stages or co-incubated with fresh sperm. Twenty-four hours after fertilization, presumptive zygotes were fixed to examine fertilization or cultured for 6 days to allow blastocyst formation. Subsequently, embryos were evaluated and the blastocysts were fixed and stained to determine cell numbers. When LFF was added to maturation medium, cumulus expansion and percentage of nuclear maturation (277 +/- 61 microm and 72%, respectively) of COCs were significantly higher (P < 0.05) than those in SFF (238 +/- 33 microm and 55%, respectively). However, in the presence of FSH both FF stimulated cumulus expansion and nuclear maturation to a similar degree. No differences were observed with regards to sperm penetration, male pronucleus formation, and to polyspermia between fertilized oocytes matured either in SFF or LFF. Fertilized oocytes matured in the presence of LFF without or with FSH showed a higher cleavage (45 +/- 7% and 51 +/- 7%, respectively) and blastocyst (14 +/- 4% and 22 +/- 6%, respectively) formation rate compared to SFF (cleavage, 35 +/- 8% and 41 +/- 4%, blastocyst: 8 +/- 3 and 13 +/-3, respectively; P < 0.05). The mean number of cells per blastocyst did not differ significantly between treatments. These findings indicate that factor(s) within follicles at later stages of development play an important role during oocyte maturation and thereby enhance developmental competence to occur.     

In vitro thermal stress induces apoptosis and reduces development of porcine parthenotes

The precise physiological causes that result in reduced development of oocytes after heat shock (HS) are not clear. In this study, apoptosis, heat shock protein70 (hsp70), and in vitro development of porcine oocytes were evaluated after HS. Porcine cumulus-oocyte complexes (COCs) were subjected to in vitro maturation for 42 h. The matured oocytes were then heated at 41.5 degrees C for 0 h (control, C0h), 1 h (HS1h), 2 h (HS2h), or 4 h (HS4h). An additional group of oocytes was cultured for 4 h without HS (control, C4h). In Experiment 1, expression of hsp70 was detected by Western-blotting and no difference between controls and HS groups was observed. In Experiment 2, apoptosis of matured oocytes after HS was examined by Annexin V-FITC and TUNEL. No significant TUNEL-positive signals were detected in the heated oocytes compared to the controls, but the intensity of Annexin V-FITC labeling among different groups increased with length of HS and in vitro culture (P<0.05). Oocytes were parthenogenetically activated by an electric pulse plus 6-DMAP (Experiment 3). Mean (+/-S.E.M.) embryonic development in HS2h (cleavage: 42+/-29%; blastocyst: 11+/-10%) and HS4h (cleavage: 36+/-28%; blastocyst: 11+/-8%) were decreased when compared to those in C0h (cleavage: 63+/-12%; blastocyst: 24+/-14%) and C4h (cleavage: 66+/-8%; blastocyst: 21+/-11%). Numbers of blastocysts with TUNEL-positive signals were similar among groups, but the signals increased before the eight-cell stage in HS groups (P<0.05). In conclusion, developmental competence of matured pig oocytes was compromised after heat shock, but it was not closely associated with the expression of oocyte hsp70. However, there may be a link between apoptosis and developmental competence of porcine oocytes.     

Preincubation of cumulus-oocyte complexes before exposure to gonadotropins improves the developmental competence of porcine embryos matured and fertilized in vitro

The objectives of the present study were to examine whether delayed exposure of porcine cumulus-oocyte complexes (COCs) to gonadotropins affects the diameter of oocytes, the nuclear morphology of the germinal vesicle, the rate of germinal vesicle breakdown (GVBD), and the embryonic developmental rate of inseminated oocytes following maturation and fertilization in vitro (IVM/IVF). After preincubation (experimental) or no preincubation (control) in BSA-free NCSU23 medium containing 1096 porcine follicular fluid for 12 h, COCs were cultured for maturation in the same medium supplemented with gonadotropins for 20 h and then without those gonadotropins for 20 h. During the preincubation period, the nuclear morphology of the germinal vesicles became more homogeneous. Incidence of GVBD after 20 h of maturation culture was not different between the control and experimental group. When cultured in NCSU23 medium for 7 d following IVF, the incidence of embryos that developed to the blastocyst stage (23.1 +/- 3.1%) was higher in the experimental group than in the control group (8.7 +/- 1.2%). Blastocysts in the experimental group had a larger number of cells than control blastocysts. Following embryo transfer into the oviduct of recipient gilts, IVM/IVF embryos had elongated by Day 12 of gestation. These results indicate that preincubation of porcine COCs, before exposure to gonadotropins to induce the resumption of meiosis, increases the rate of development of IVM/IVF embryos to the blastocyst stage.     

Preimplantation embryonic development of spontaneous mouse parthenotes after oocyte meiotic maturation in vitro

Of eggs ovulated in LT/Sv mice, 10–20% undergo spontaneous parthenogenetic activation, and 40–50% of the parthenotes develop to blastocysts when cultured in simple defined medium from the one-cell stage. Similar percentages of oocytes isolated from Graafian follicles undergo parthenogenetic activation after spontaneous maturation in simple defined medium, but embryonic development proceeds no further than the two-cell stage. The simple defined medium that supported preimplantation development of ovulated eggs and spontaneous maturation of extrafollicular oocytes contained no serum, free amino acids, or vitamins. The present experiments were conducted to determine what conditions during spontaneous maturation of extrafollicular oocytes could promote the ability of oocytes to develop to blastocysts after parthenogenetic activation and mimic the environment of preovulatory follicles. Cumulus-enclosed oocytes that were matured in simple medium supplemented with fetal bovine serum (FBS) developed to blastocysts after spontaneous parthenogenetic activation. Furthermore, minimum essential medium (MEM), a complex medium containing free amino acids and vitamins, could substitute completely for FBS for maturing oocytes from (C57BL/6J × LT/Sv)F₁ mice, and to a lesser extent for maturing LT/Sv oocytes. Therefore, even though germinal vesicle breakdown in mouse oocytes and preimplantation development of mouse eggs can occur in the absence of an exogenous supply of free amino acids and vitamins, a complete, or normal, mouse oocyte maturation cannot. These results also demonstrated that gonadotropins are not necessary during oocyte meiotic maturation for parthenogenetically activated eggs to develop through the preimplantation stages. Luteinizing hormone or 17β-estradiol in MEM during oocyte maturation had no effect on the subsequent development of parthenotes. In contrast, follicle stimulating hormone (FSH) and progesterone in the maturation medium decreased the number of ova that subsequently cleaved, and FSH decreased the number of cleaved eggs that developed to blastocysts.     

Effect of follicular size on in vitro developmental competence of oocytes and viability of embryos after transfer in the dromedary (Camelus dromedarius)

The aim of this work was to determine the effect of follicle size on camel oocyte quality as measured by developmental competence in vitro and in vivo. Ovaries from a local slaughterhouse were dissected to obtain two classes of follicle size: small (3-6 mm) and large (>6 mm) follicles. Quality of the oocytes was assessed after in vitro maturation (IVM), in vitro fertilization (IVF) and in vitro culture (IVC) of cumulus oocyte complexes (COCs). All cultures were done in four replicates at 38.5 degrees C, under 5% CO(2) and high humidity (>95%). Only COCs with cumulus and homogenous (dark) cytoplasm were used. The COCs were matured for 28 h in TCM-199 medium supplemented with 10% heat-treated fetal calf serum (FCS), 10 ng/mL EGF, and 250 microM cysteamine. Nuclear maturation rate for each class of follicle size was determined by contrast phase microscopy in a sample of COCs (n=30) denuded, fixed and stained with aceto-orcein. In vitro fertilization was performed using fresh semen (0.5 x 10(6)spermatozoa/mL in modified TALP-solution). Fertilized oocytes were cultured in mKSOMaa, under 5% O(2) and 90% N(2). The percentage of COCs reaching metaphase II (MII) after 28 h of maturation was 87% (26/30) and 73% (22/30) for oocytes originating from large and small follicles, respectively (P>0.1). The rate of total cleavage (two cells to blastocyst stage) was greater (P<0.05) for oocytes originating from large follicles (72%; 116/162) than for those derived from small follicles (59%; 140/237). The percentage of fertilized oocytes reaching the blastocyst stage was 35% (57/162) and 20% (48/237) for oocytes collected from large and small follicles, respectively (P<0.05). The viability of in vitro-produced hatched blastocyst from the two groups (15 from 3 to 6mm follicle size and 22 from follicles >6 mm) was assessed by transfer to synchronized recipients. None of the hatched blastocysts from small follicles resulted in a pregnancy whereas 68% (15/22) of the transferred hatched embryos from large follicles developed into a 25-day pregnancy. Of the resulting 15 pregnancies, 53% (n=8) aborted (five between 2 and 4 months and three between 5 and 7 months of pregnancy). The remaining seven pregnant females gave birth to normal healthy offsprings (four females and three males). The present study shows that dromedary oocytes developmental competence is acquired late during the final phase of follicular development and this developmental ability translates into greater pregnancy rates after transfer of in vitro produced hatched blastocysts.     

Simulation of intrafollicular conditions prevents GVBD in bovine oocytes: a better alternative to affect their developmental capacity after two-step culture

To increase the developmental competence of bovine oocytes isolated from small, medium, and large follicles (2-3, 3-4, and 4-6 mm in diameter, respectively), we tried to modify the conditions for their in vitro culture. The first step involved conditions maintaining at least for 48 hr a reversible inhibition of the germinal vesicle breakdown (GVBD) and the second step stimulated the resumption of meiosis and completion of nuclear and cytoplasmic maturation during the subsequent 20-22 hr of culture. The effectiveness of this model depended mainly on the medium composition (reduced NaHCO3, substitution of serum with serum albumin, addition of antioxidants (curcumin), increased viscosity by agar, the reduction of oxygen concentration (within 6%-8%), the reduction of the proportion between the number of cumulus-oocyte complexes (COCs), and the reduction of the amount of a medium (within 6-7 mul per COC) to amplify the GVBD-inhibitory effect of oocyte surrounding granulosa cells. The COCs were incubated in clumps of 6-7 COCs. The effectiveness and reversibility of GVBD inhibition depended also on the duration of COCs isolation. The full reversibility of the GV block was controlled morphologically and also by measuring histone H1 and MAP kinase activities. The two-step versus one-step (24 hr) maturation technique was evaluated by the percentage of total and hatched blastocysts at day 9. When compared with one-step maturation, the two-step culture showed a slightly increased proportion of total and hatched blastocysts developed from growing follicles, mainly from the smallest category (13.9% vs. 7.1% and 9.2% vs. 3.3% for total blastocysts and hatched, respectively). However, the two-step culture of oocytes from large regressing follicles substantially reduced the blastocyst yield (9.7% vs. 39.1% and 4.9% vs. 26.7% for total blastocysts and hatched, respectively). The transfer of ten blastocysts (developed after two-step culture) to ten recipients resulted in seven pregnancies.     

Developmental competence of porcine oocytes selected by brilliant cresyl blue and matured individually in a chemically defined culture medium

The objective of this study was to investigate the effects of oocyte selection using brilliant cresyl blue (BCB) and culture density during individual in vitro maturation (IVM) on porcine oocyte maturity and subsequent embryo development using a chemically defined medium. Cumulus-oocyte complexes (COCs) were classified as BCB-positive or BCB-negative after exposure to a BCB solution for 90 min. The classified COCs were matured in a group (15 COCs per 100-μL droplet) or individually (1 COC per 1-, 2.5-, 5-, or 10-μL droplet). Meiotic competence, intraoocyte glutathione concentration, and developmental competence after intracytoplasmic sperm injection were monitored. The BCB selected oocytes competent for nuclear and cytoplasmic maturation. Furthermore, meiotic competence for oocytes matured individually in a 5-μL droplet was superior (P < 0.05) to that of oocytes matured in a 1-μL droplet. Also, the culture density in a 5-μL droplet during IVM resulted in a higher (P < 0.05) rate of cleaved embryos than that in a 1-μL droplet and produced a similar rate of blastocysts compared with that of a group culture system. Conversely, BCB selection did not improve cleavage and blastocyst formation. In conclusion, it was possible to predict porcine oocytes competent for maturation using oocyte selection with BCB. Moreover, a 5-μL droplet during the individual IVM culture was most suitable for oocyte maturation and subsequent embryo development, although every culture density used in this study supported development up to the blastocyst stage.     

Storage of bovine isolated follicles: a new alternative way to improve the recovery rate of viable embryos from ovarian follicles of slaughtered cows

The vitality of bovine oocytes stored in isolated follicles was examined. The aim of this work was to prolong the time of in vitro manipulation of oocytes before their maturation and develop a new alternative of oocyte "capacitation" to improve the quality of in vitro produced embryos. Follicles were dissected from the ovaries of slaughtered cows; subsequently, follicles were divided according to their diameter into three categories (2-3, 3-4 and 4-6 mm), and stored at 17-18 degrees C for 24 or 48 h in a modified tissue culture medium-199 (TCM-199) with reduced pH. After that time, the cumulus-oocyte complexes (COCs) were isolated, matured, fertilized, and embryos cultured in vitro for a total of 9 days. The percentage of total blastocysts, and hatched blastocysts developed from oocytes, initially kept ("capacitated") for 24h at 17-18 degrees C, within follicles of 3-6mm size categories, were significantly higher than that oocytes of the control [of control oocytes] (44.9 and 30.3% versus 36.2 and 20.4%, respectively). The oocytes of follicles stored for 48 h at 17-18 degrees C already had decreased developmental capacity. Interesting data were obtained when COCs of the 3-4 and 4-6 categories were additionally divided into two subgroups according to their presumed developmental history (originating from the supposed growing "fit" in contrast to the supposed regressing "unfit" follicles). The higher improvement in the rate of hatched blastocysts from 24h stored oocytes was observed only in the subgroup originated from "fit" COCs (15.3 versus 25.0%, and 20.0 versus 34.4%, in the 3-4 and 4-6mm categories, respectively). The transfer of 26 blastocysts (developed of follicles kept for 24h at 17-18 degrees C) to 26 recipient heifers resulted in 18 pregnancies. Storage of follicles at 17-18 degrees C in vitro resulted not only in recovery of higher numbers of blastocysts of better quality but also facilitated the safe transport of follicles for a long distance. The extended, time of follicle storage before the proper oocyte maturation allowed also the synchronization of an appropriate number of recipient animals according to the number of isolated follicles.