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The objective was to compare effects of three metabolic regulators on development of post-compaction bovine embryos. In-vitro-produced 8- to 16-cell embryos were allocated to treatments for 72 h in G2.2 medium as follows: 0.3 microm phenazine ethosulfate (PES); 27 microm sodium azide (NaN3); 30 microm 2,4-dinitrophenol (DNP); and control, no regulator. Treatments responded similarly for blastocyst rates and embryo quality responses (P > 0.1). The PES treatment resulted in higher glucose metabolism than the NaN3 treatment (18.5 v. 14.5 pmol per embryo per h, P < 0.05), and both did not differ from DNP or the control. The PES treatment tended to result in more flux of glucose through the pentose phosphate pathway (PPP) than the control (50.5 v. 21.5%, P < 0.11). The NaN3 treatment caused more glucose uptake than the PES treatment (38.9 v. 13.1 pmol per embryo per h, P < 0.01), but neither differed from the control or DNP treatment (P > 0.1). Glycolysis for the PES treatment was 187%, which was higher than any of the other groups (88-94%; P < 0.01). There were fewer medium + large lipid granules in the cytoplasm of PES-treated embryos than any other group, including the in vitro control (P < 0.01). However, in vivo control embryos had still fewer large and medium-sized lipid granules (P < 0.01) than the PES treatment. Developmental competence to Day 14 after embryo transfer was similar among treatments. The PES treatment increased glucose metabolism, tended to increase the PPP flux of glucose and clearly reduced accumulation of lipids in embryos produced in the chemically defined media used. Use of PES in culture media may be a promising approach to improving in vitro production of embryos.

The toxic and/or beneficial effects of four metabolic regulators on embryo development were evaluated. In-vitro-produced compact morulae were cultured for 3 days in a chemically defined medium + bovine serum albumin (BSA; CDM-2) plus regulators (4991 total embryos). Phenazine ethosulfate (PES), phloretin (PL), pyrroline-5-carboxylate (P5C), and sodium azide (NaN3) were evaluated at four doses each in factorial combinations with four concentrations of glucose: 0, 0.5, 2, and 8 mm. Phenazine ethosulfate at 0.9 microm resulted in poorer development than lower or no PES. Phloretin was, in general, detrimental for embryo development, but most markedly at the highest dose (270 microm). Pyrroline-5-carboxylate had little effect on post-compaction embryos at the doses studied, 9 to 81 microm. Sodium azide at the concentrations used (3, 9, and 27 microm) had little effect on embryo development compared with controls. Concentrations of glucose had little effect on development of embryos. A fifth metabolic regulator, 2,4-dinitrophenol (DNP), was studied at various doses at pre-morula or morula-blastocyst stages cultured in 2 mm glucose. Embryos (2189 total) cultured in 90 microm DNP developed more slowly and were darker than embryos cultured at lower doses. Embryos cultured in 30 microm DNP had a higher blastocyst rate (48.3%) than controls (34.9%). In the last experiment using G1.2/G2.2 media, DNP (30 microm) resulted in a marked decrease in embryonic development when embryos were exposed at the zygote to 8- to 16-cell stages but had little effect when morulae were exposed for 2 days. The dose-response information for these metabolic regulators is crucial for designing future experiments.

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Chitosan is a partially deacetylated polymer obtained from the alkaline deacetylation of chitin, which is a glucose-based unbranched polysaccharide widely distributed in nature as the main component of exoskeletons of crustaceans and insects. Chitosan has a variety of physicochemical and biological properties resulting in numerous applications. In addition to its lack of toxicity and allergenicity, its biocompatibility, biodegradability, and bioactivity make it a very attractive substance for diverse applications as a biomaterial in pharmaceutical and medical fields. Chitosan stimulates cell growth and it has been used in fibroblast culture, increasing cell proliferation. For these reasons, it is important to evaluate if this polymer has a positive effect on embryo production. The aim of this study was to evaluate porcine oocyte maturation and embryo development, comparing the effect of supplementing different concentrations of chitosan to the maturation (MM) and development media (DM). Cumulus-oocyte complexes (COC) were aspirated from ovarian follicles of slaughtered sows. The COC were matured in supplemented TCM-199 (MM) and incubated for 44 h. All incubations were performed at 38.5°C, with 5% CO2 in air and humidity at saturation. After maturation IVF was performed, frozen-thawed semen from the same boar was used and gametes were co-incubated in MTBM for 7 h. Then, putative zygotes were cultured in NCSU-23 (DM) for 144 h. The following experiments were performed: 1) addition of 0 (control), 35, 50, 100, and 150 ppm chitosan to the MM (n = 1353), 2) addition of 0, 50, 100, and 150 ppm chitosan to the DM (n = 739), 3) addition of 0, 50, 100, and 150 ppm of chitosan to the MM first and then the same concentrations to the DM (n = 702). When chitosan was added to the MM, the highest percentage of matured oocytes (metaphase II) was obtained in the 50 ppm treatment (87%, P < 0.05) when compared with the control, 100, and 150 ppm groups (78, 78, and 82%, respectively). Regarding the percentage of blastocysts, there were no differences when comparing the treatment and the control groups (ranging from 12 to 13%). After addition of chitosan to the putative zygotes in the DM, the percentage of morulae in the 150 ppm treatment was significantly increased with regard to the other groups (54 v. 46%, respectively, P < 0.05). When adding chitosan to both MM and DM, there was no effect on embryo development. It is concluded that the addition of chitosan to the MM at a concentration of 50 ppm significantly improved oocyte maturation and a concentration of 150 ppm in the DM increased the percentage of morulae. Chitosan had a positive effect on oocyte maturation and embryo development. These results justify further investigations to find out if chitosan can be useful as a supplement for chemically defined media.

The pterostilbene (PT) molecule is a phytoalexin with a reducing effect on reactive oxygen species (ROS) and with a capacity to block lipogenesis. However, the potential reducing effects of PT on equatorial lipid accumulation and ROS have not yet been elucidated for in vitro-derived bovine embryos. The present study evaluated the effects of concentrations of 3, 1, 0.33, 0.11 μM PT, and a vehicle group on the percentage of cleaved embryos, embryos with more than 6 cells, percentage of blastocyst on Day 7 and 8, percentage of transferable embryos on Day 7, the cell count and relative concentration of lipids. In the second experiment, the effects of 0.33 μM PT and a vehicle group within two different O 2 environments (5% and 20%) were evaluated for ROS generation and the percentage of Day 8 blastocysts. In the first experiment, no significant differences were found between the treatments with PT and the vehicle group (p > .05) concerning the percentage of cleaved embryos and embryos with more than 6 cells. Lipid reduction was observed in the groups treated with PT versus the vehicle group (p < .05). The vehicle group showed a higher rate of blastocyst production on Days 7 and 8 (p < .05) and an increase in the percentage of transferable embryos on Day 7 compared to the PT treatment groups (p < .05). Cell counts were not significantly different between treatments with PT and the vehicle group (p > .05). In the second experiment, the O 2 concentration did not significantly affect ROS generation (p > .05); however, the groups treated with PT (0.33 μM) had a reduction in ROS (p < .05). The O 2 concentration also did not significantly affect the rate of blastocyst production on Day 8 (p = .7696). Future research should be conducted to ascertain whether the reduction of lipids could enhance the cryopreservation and post-thaw viability of PT-treated embryos.

Vitrification of bovine immature oocytes has been reported using an open pulled straw, but with limited success. In a previous report, we developed an alternative material (nylon mesh) for vitrification of large quantities of oocytes and embryos. This study was conducted to demonstrate effects of components of a cryoprotectant and a protocol of exposure for bovine immature oocytes on their subsequent in vitro maturation, fertilization and development after cryopreservation by vitrification using a nylon mesh. Bovine oocytes at the germinal vesicle stage were collected from 2-5 mm follicles in ovaries, and cumulus-oocytes complexes (COCs) were randomly assigned to treatment groups. Before vitrification, COCs were exposed to the cryoprotectant, which was composed of 40% ethylene glycol, 18% ficoll and 0.3 M sucrose (EFS40) or 0.3 M trehalose (EFT40) by single step or stepwise exposure. Forty COCs were transferred onto a nylon mesh (0.5 cm 2 ), which was then plunged directly into liquid nitrogen. After thawing in warm medium, vitrified COCs were in vitro-matured, fertilized and cultured. After culture for in vitro maturation, the rates in the oocytes reaching to metaphase II were 64.1% and 63.1% in the stepwise exposure to EFS40 or EFT40, respectively, which was significantly higher (P < 0.05) than the corresponding rates after a single step (22.6% and 10.0%, respectively). There was no significant effect of the two sugars on in vitro maturation after single or step-wise equilibration. Transmission electron microscopy revealed that the cytoplasm of oocytes equilibrated in a single step had many vacuoles and broken mitochondria, while oocytes equilibrated in a step-wise manner had significantly fewer abnormalities and were similar to untreated controls. Cleavage rate of thawed oocytes after IVMFC was significantly higher after stepwise exposure to EFS40 or EFT40 than that after single step exposure (37.7% and 22.2% v. 20.8% and 0%, respectively, P < 0.05).Step-wise equilibration of oocytes in EFT40 was dramatically detrimental: no cleaved embryos developed to blastocysts after a single step exposure to either vitrification solution, or stepwise exposure to EFT40. However, blastocysts were obtained following stepwise exposure to EFS40 (8%). These results suggest that stepwise equilibration and vitrification on a nylon mesh minimizes structural damage to the organelles of immature oocytes and facilitates successful cryopreservation.