Role of cumulus cells on in vitro maturation of canine oocytes.

The objectives of the present study were to investigate the relationship between the morphological status of cumulus cells surrounding canine oocytes after maturation culture and the meiotic stage of the oocytes. In addition, the effect of the removal of cumulus cells from canine cumulus-oocyte complexes (COCs) during maturation culture on their meiotic competence was examined. Canine COCs were collected from bitches at the anoestrous and dioestrous stages and only COCs with >110 microm in vitelline diameter were cultured in medium 199 with 10% canine serum for 72 h. In the first experiment, the relation between the morphological status of cumulus cells surrounding oocytes cultured for 72 h and their meiotic stages was examined. At the end of maturation culture, the proportions of intact, partially nude and completely nude oocytes were 65.2%, 22.9% and 11.9%, respectively. The proportion of maturation to metaphase II of completely nude oocytes was highest among the oocytes with different morphological status of cumulus cells. In the second experiment, the cumulus cells were partially or completely removed from COCs at 48 h after the start of maturation culture and the oocytes were cultured for a further 24 h. The proportion of oocytes reaching metaphase II in the completely denuded oocytes was significantly higher than that in the control oocytes without the removal treatment of cumulus cells. The results indicate that morphological status of cumulus cells surrounding oocytes may be related to the nuclear maturation of canine oocytes, and the removal of cumulus cells from COCs during maturation culture can promote the completion of oocyte meiotic maturation.

Reproduction in Domestic Animals = Zuchthygiene


Developmental competence of cat oocytes from ovaries stored at various temperature for 24 h.

We conducted two experiments to investigate the effects of storage temperature and period for cat ovaries on the meiotic and developmental competence of oocytes collected from the ovaries. In Experiment 1, ovaries were stored in physiological saline for 24 h at 4 C, 23-25 C, or 38 C (cold, room, and incubator temperature groups, respectively), and then oocytes were collected from the ovaries in each group. Morphologically intact oocytes were then selected and cultured in maturation medium for 24 h. Significantly more oocytes reached metaphase II (MII) in the cold temperature group (53.4%) than in the room and incubator temperature groups (20.0 and 2.4%, respectively). In Experiment 2, ovaries were stored in physiological saline at room temperature for 0, 6, 12 or 18 h, and then they were stored at 4 C (cold storage) until reaching a total storage period of 24 h. After storage of the ovaries, morphologically intact oocytes were matured, fertilized with frozen-thawed spermatozoa, and cultured in vitro. The rates of morphologically intact oocytes obtained from the ovaries stored at room temperature for 0, 6, 12 or 18 h were 35.3, 30.0, 26.4 and 14.7%, respectively, and the rates of intact oocytes that reached MII were 63.2, 36.4, 26.5 and 11.9%, respectively. The results suggested that the numbers of morphologically intact oocytes and intact oocytes that reached MII after in vitro maturation decrease gradually as the period of storage at room temperature before cold storage increases. Only oocytes from ovaries stored for 6 h developed to the blastocyst stage after in vitro maturation and fertilization when ovaries were stored at room temperature before cold storage. These results indicate that 24 h storage of ovaries at high temperatures (>23 C) decreases the meiotic competence of oocytes. The quality and developmental competence of oocytes are influenced by the length of storage at room temperature before cold storage.

The Journal of Reproduction and Development


Ovarian follicular and corpus luteum changes, progesterone concentrations, estrus and ovulation following estradiol benzoate/progesterone based treatment protocol in cross-bred cows.

The objectives of the present study were to investigate the effects of the stage of the estrous cycle at the start of an estradiol benzoate (EB) and progesterone (P) based treatment protocol on new follicular wave emergence, subsequent estrus and ovulation. The experiment was conducted using a crossover design with each cow (five cross-bred cows) being assigned to one of three groups at 3-month intervals within a 1-year period. Estrous cycle stage in individual cows was initially synchronized with prostaglandin F(2)alpha. After detection of estrus, each cow was injected intramuscularly (i.m.) with 2 mg EB and 200 mg P (EB/P) on day 5, 12 or 17 of the estrous cycle (estrus=day 0), followed by 1 mg EB i.m. 12 days after the EB/P treatment. Ovarian ultrasonographic examinations showed that the emergence of a new follicular wave occurred after EB/P treatment in all groups and the mean interval from EB/P treatment to wave emergence did not differ among the groups (3.2-3.8 days). All cows in each group exhibited behavioral estrus and ovulated the newly formed dominant follicle. However, cows in the day-17 group exhibited estrus 1-3 days before the second EB injection. The concentrations of progesterone showed faster reduction, during the treatment period, in the day-12 and -17 groups compared to the day-5 group. These results indicate that the EB/P treatment induces an emergence of a new follicular wave, irrespective of the estrous cycle stage at the start of treatment, but the effect of EB/P protocol on estrous/ovulation synchronization is influenced by the stage of the estrous cycle.


Effects of electric field strengths on fusion and in vitro development of domestic cat embryos derived by somatic cell nuclear transfer.

The present study was conducted to determine the effect of electric field strength on the rate of membrane fusion between the somatic cell and cytoplast and on subsequent in vitro development of reconstructed embryos. Additionally, the in vitro developmental competence of cat oocytes artificially activated after 44 h of maturation culture was examined. An efficient fusion rate (64.2%) was obtained by applying a single pulse of 1.5 kV/cm for 50 micros, and the fusion rate remained almost constant at the higher field intensity (59.8 and 54.9% at 1.7 and 2.0 kV/cm, respectively). Although the cleavage rate of fused embryos increased with an increase of the electric field strength, there were no differences among the groups with respect to the proportion of development to the morula and blastocyst stages. In the additional experiment, oocytes at the metaphase II stage after culture for 44 h were activated by the combination of calcium ionophore (CaI) with cycloheximide (CHX). Some (11.8%) of activated oocytes developed to the blastocyst stage. Results from this study indicated that electric field strength affects the rates of fusion and cleavage but has no significant effects on the development to the blastocyst stage of reconstructed embryos. Prolonged maturation culture of cat oocytes (up to 44 h) decreased their ability to develop to the blastocyst stage.


Meiotic competence of canine oocytes embedded in collagen gel.

The present study was conducted to examine the meiotic competence of canine oocytes embedded in collagen gel, and to investigate the effects of timed exposure of the oocytes embedded in collagen gel to gonadotrophins during maturation culture, on their nuclear maturation. Cumulus-oocyte complexes (COCs) were collected from bitches at the anoestrous and dioestrous stages of the reproductive cycle. In the first experiment, half of the COCs were embedded in collagen gels. The COCs with or without collagen-gel embedding were cultured in a TCM-199 medium supplemented with 0.1 IU/ml human menopausal gonadotropin (hMG) and 10 IU/ml human chorionic gonadotropin (hCG) for 72 h. In the second experiment, the COCs embedded in collagen gels were cultured in TCM-199 medium with gonadotrophins (hMG and hCG) for various periods (0, 24, 48 and 72 h) and then cultured in the medium without gonadotrophins until reaching total culture period (72 h). The percentage of the oocytes reaching metaphase I and metaphase II (MI/MII) was significantly higher (p < 0.05) in COCs with collagen-gel embedding than in COCs without collagen-gel embedding. The percentage of oocytes that were arrested at the germinal vesicle stage was significantly lower (p < 0.05) in oocytes cultured with gonadotrophins than in oocytes cultured without gonadotrophins. However, there were no significant differences in the percentages of oocytes that reached each stage of meiosis among the groups, irrespective of the duration of exposure to gonadotrophins. These observations indicate that embedding of COCs by collagen gel enhances the meiotic competence of canine oocytes, but removal of hormone supplement from maturation medium does not improve the ability of the oocytes to reach MII stage.


Effects of single and double exposure to brilliant cresyl blue on the selection of porcine oocytes for in vitro production of embryos.

The aim of this study was to evaluate the effectiveness and toxicity of single and double application of the brilliant cresyl blue (BCB) test on the selection of porcine oocytes as an indirect measure of oocyte growth for in vitro fertilization (IVF) and nuclear transfer. In the first experiment, oocytes were exposed to BCB before and after maturation culture and classified according to their cytoplasmic coloration: blue coloration and colorless. The classified oocytes were fertilized with spermatozoa and then cultured for 7 days. The percentages of maturation to metaphase II in blue oocytes at the start of maturation culture were higher than those of colorless oocytes (68.7-70.1% versus 0.8-3.6%, P < 0.05). However, double application of BCB test before and after maturation culture had a toxic effect on fertilization and embryonic development. No significant differences in the blastocyst formation were found between blue oocytes without double application of BCB test and control oocytes without any application of BCB test, whereas the total cell number per blastocyst from the blue oocytes was higher than that from the control oocytes (48.0 versus 34.2, P < 0.05). In the second experiment, oocytes were exposed to the BCB test before or after maturation culture, and then the matured oocytes were activated to evaluate the ability of parthenogenetic development. The proportion of blastocyst formation of blue oocytes classified after maturation culture was lower than that of blue oocytes classified before maturation culture (10.0% versus 27.0%, P < 0.05). Therefore, double application of the BCB test before and after maturation culture impaired fertilization and embryonic development, whereas a single application before maturation culture was efficient to select oocytes for IVF and nuclear transfer.


Development of cat embryos produced by intracytoplasmic injection of spermatozoa stored in alcohol.

This study was conducted to examine whether cat spermatozoa stored in ethanol for 1 month was capable of developing into pronuclei and of supporting normal embryonic development. In vitro matured oocytes were injected with frozen-thawed spermatozoa and ethanol-stored spermatozoa. The status of oocytes and sperm nuclei was examined at 4 and 18 h after injection of spermatozoa, and the presumptive zygotes were cultured for 7 days to assess the development of oocytes injected with each storage sperm. The percentage of enlarged sperm head at 4 h after injection was higher in ethanol-stored spermatozoa than in frozen-thawed spermatozoa, but there was no significant difference in the development of oocytes and sperm nuclei at 18 h after injection between the two groups. The development of oocytes to the blastocyst stage after injection of spermatozoa was observed only in oocytes with frozen-thawed spermatozoa. Of oocytes injected with ethanol-stored spermatozoa, two (2.8%) oocytes developed to the 16-cell stage. These results indicate that cat spermatozoa stored in ethanol can decondense and form male pronuclei after intracytoplasmic injection. However, the oocytes injected with ethanol-stored spermatozoa did not have the ability to develop to the blastocyst stage.


Effect of maturation culture period of oocytes on the sex ratio of in vitro fertilized bovine embryos.

It has been suggested that the maturational stage of oocytes at time of insemination influences the sex ratio of resulting embryos. However, there are very few reports concerning the relationship between the maturation culture period of oocytes and the sex ratio of resulting embryos. The objective of this study was to investigate the effects of in vitro maturation culture period for bovine oocytes on the sex ratio of in vitro produced blastocysts using a novel technique of loop-mediated isothermal amplification (LAMP). Cumulus-oocyte complexes were collected from the ovaries of slaughtered cows, and then matured in vitro for various periods (16, 22, 28, and 34 h). After maturation culture for each period, the oocytes were inseminated with frozen-thawed spermatozoa, and then cultured in vitro. Blastocysts were harvested on Day 7 after insemination, and the sex of the embryos was examined using the LAMP method. The rates of oocytes matured to the metaphase II stage were significantly lower (P < 0.05) in the 16-h maturation group than in the other groups. The proportion of blastocyst formation after insemination was significantly higher (P < 0.05) in the 22-h maturation group than in the other groups. The proportion of male blastocysts increased with the increase in maturation culture period. The proportion of male blastocysts derived from oocytes matured for 34 h was significantly higher (P < 0.05) than from oocytes matured for 16 and 22 h. These results indicate that the sex ratio of in vitro fertilized embryos is apparently influenced by the maturation culture period of the oocytes.


Effect of cycloheximide on in vitro development of electrically activated feline oocytes.

This study was conducted to improve parthenogenetic development in vitro of feline oocytes following a combined activation treatment of electrical stimulation and cycloheximide. In vitro matured (IVM) oocytes were stimulated electrically by a DC electrical pulse of 2 kV/cm for 50 micros. The stimulated oocytes were then incubated in MK-1 medium with or without cycloheximide and subsequently cultured in vitro for 6 days. No significant differences were observed between the two groups with respect to the proportions of cleavage, development to the morula stage, and the cell number of blastocysts. However, exposure of electrically stimulated oocytes to cycloheximide significantly increased the rate of development of the stimulated oocytes into the blastocyst stage compared with oocytes stimulated by electrical stimulation alone (31.0% vs 6.7%). The results from the present study suggested that a single electrical stimulation was insufficient to activate the IVM cat oocytes at 24 h of maturation and that exposure to cycloheximide following electrical stimulation improved the efficacy of the parthenogenetic development of domestic cat oocytes.


Analysis of DNA fragmentation of porcine embryos exposed to cryoprotectants.

The chemical toxicity of cryoprotectants to porcine embryos was examined by the evaluation of survival and DNA damage after exposure to cryoprotectants. Porcine blastocysts were exposed to 10% of ethylene glycol (EG), 1,2-propanediol (PD) or glycerol (GLY) for 1 h at room temperature (23-25 degrees C) and then cultured in vitro for 24 h. The survival rates of blastocysts exposed to PD and GLY were significantly lower than those of control blastocysts in which the embryos were exposed to carrier solution without cryoprotectants. Significantly more DNA-fragmented nuclei occurred in the cryoprotectant-exposed blastocysts, compared with the control blastocysts. Moreover, the indices of DNA-fragmented nuclei in the blastocysts without blastocoele re-formation after culture were significantly higher than those with blastocoele re-formation, irrespective of the exposure treatment. These results indicate that the exposure of porcine blastocysts to cryoprotectant decreases the survival rates and increases the DNA-fragmented nuclei in embryos.

Reproduction in Domestic Animals = Zuchthygiene


Effects of beta-mercaptoethanol and cycloheximide on survival and DNA damage of bovine embryos stored at 4 degrees C for 72 h.

The objectives of this study were to determine the effects of cycloheximide (CHX) and beta-mercaptoethanol (beta-ME) during storage of in vitro-produced (IVP) bovine blastocysts for 72 h at 4 degrees C on their survival, hatching capacity and DNA damage. In Experiment 1, when blastocysts were stored in a medium supplemented with 25, 50 or 100 microg/mL of CHX, or 25, 50 or 100 microM of beta-ME, the blastocysts stored with 25 microg/mL of CHX had a significantly higher survival rate than that of the blastocysts stored without CHX (79.5% versus 54.2%). In contrast, beta-ME had no apparent effects on the survival and hatching capacity of stored embryos. In Experiment 2, to investigate synergistic effects of CHX and beta-ME during storage of blastocysts on their developmental parameters and DNA damage, they were stored in the medium with CHX (25 microg/mL) and beta-ME (50 microM). The combination of CHX and beta-ME had no significant effects on the survival of blastocysts. The proportion (6.8%) of DNA-fragmented cells in the blastocysts stored with CHX was similar to that (5.4%) in the non-stored blastocysts (positive control) and significantly lower than that (9.7%) in the blastocysts stored without CHX and beta-ME (negative control). However, there were no significant differences among the proportions of dead cells of blastocysts in the storage groups. Therefore, the supplementation of CHX in the storage medium had a beneficial effect on the proportions of survival and DNA-fragmented cells in the stored embryos, whereas the beta-ME alone or in combination with CHX had no positive effects on either of these proportions.


In vitro development and post-thaw survival of blastocysts derived from delipidated zygotes from domestic cats.

The ability to cryopreserve in vitro-produced feline embryos was investigated. To improve the survival rate of cryopreserved embryos, first the developmental ability of in vitro fertilized feline zygotes (after removal of intracellular lipids) was determined, followed by the post-thaw survival of cryopreserved blastocysts derived from delipidated zygotes. More than 67% of the delipidated zygotes cleaved and 36% of them developed to the morula stage. The developmental ability of delipidated zygotes to the blastocyst stage (26%) was similar to that of sham-operated (30.5%) or control embryos (31.3%). Although the survival rate of delipidated blastocysts (81.8%) after freezing and thawing tended to be higher than that of control embryos without delipidation (60.6%), rates were not significantly different between the both groups. In conclusion, in vitro-produced feline blastocysts were successfully frozen, removal of the cytoplasmic lipid content in feline zygotes did not impair their in vitro developmental competence (up to the blastocyst stage), and reduction of cytoplasmic lipids by aspiration had no apparent effects on the survival of in vitro-derived blastocysts after cryopreservation.


Effects of hexoses on in vitro oocyte maturation and embryo development in pigs.

The objective was to determine the effects of supplementing hexoses in oocyte maturation and embryo culture medium on in vitro maturation (IVM) and in vitro fertilization (IVF) of porcine oocytes and in vitro development of in vitro produced (IVP) porcine embryos. In the first experiment, oocytes were matured in vitro in modified North Carolina State University (NCSU)-37 medium, supplemented with hexoses (glucose, fructose or galactose) at various concentrations: 0 (control), 2.5, 5.5 and 10 mM. Supplementing the maturation medium with either glucose or fructose (5.5 mM) increased the percentages of oocytes that matured to metaphase II (79.4 and 70.2%, respectively), as compared with the control group (P < 0.05). However, supplementing galactose had no effects on meiotic maturation and fertilization. In the second experiment, cleaved embryos were collected 3 days after IVF of oocytes matured in the maturation medium supplemented with 5.5 mM of glucose; they were cultured for an additional 4 days in modified NCSU-37 medium, supplemented with 5.5mM of glucose, fructose or galactose. The incidence of blastocyst formation was higher (P < 0.05) in the glucose and fructose groups (18.6 and 18.2%, respectively) than in the galactose group and non-supplemented control group (12.9 and 9.2%). Moreover, fructose supplementation increased the total cell number/blastocyst (48.0 versus 37.6) and reduced the index of DNA-fragmented nucleus in the blastocysts (7.6% versus 11.8%), as compared with glucose supplementation (P < 0.05). In conclusion, fructose was a practical alternative to glucose for supporting IVM of porcine oocytes and fructose was superior to glucose for producing high-quality porcine embryos in vitro.


Effect of the removal of cumulus cells on the nuclear maturation, fertilization and development of porcine oocytes.

The present study was conducted to investigate the effects of attachment of cumulus cells to porcine oocytes during the process of maturation and fertilization on the nuclear maturation, fertilization and subsequent development after in vitro fertilization (IVF). In the first experiment, the cumulus cells were removed from cumulus-oocyte complexes (COCs) at 0, 24 and 42 h after the onset of maturation culture and were then cultured until reaching 42 h of cultivation. In the second experiment, COCs were denuded as described in the first experiment, then fertilized and cultured for 7 days. As a control, cumulus cells were allowed to maintain attachment to the oocytes until the end of IVF. The proportion of oocytes reaching metaphase II significantly increased with the delay in the removal treatment of cumulus cells. The proportion of normal fertilization gradually increased with delay in the removal treatment of cumulus cells from COCs until the end of IVF. However, no significant difference in the proportion of normal fertilization was found between the 42-h and control groups. The removal treatment of cumulus cells in the 0- and 24-h group significantly (p < 0.05) decreased the proportion of cleaved embryos when compared with the control, and none of them developed to the blastocyst stage. The proportion of development to the blastocyst stage was significantly higher (p < 0.05) in the control group than in the 42-h group (18.1% vs 12.4%; p < 0.05). The present study indicates that the attachment of cumulus cells to the oocyte during maturation and fertilization is important to support oocyte nuclear maturation, fertilization and subsequent embryo development. Particularly, the attachment of cumulus cells to the oocyte during IVF promotes embryonic development.


Relationship between oxygen consumption and sex of bovine in vitro fertilized embryos.

The present study was conducted to examine the relationship between the oxygen consumption rate and sex ratio of bovine in vitro fertilized embryos on each day of blastocyst formation. The quality of blastocysts collected on day 7, 8, and 9 after in vitro fertilization (IVF) were categorized as ranks A and B (excellent and good, respectively) based on microscopic observation of the morphology. The oxygen consumption rate and sex of individual blastocysts were evaluated using two novel techniques: scanning electrochemical microscopy (SECM) and loop-mediated isothermal amplification (LAMP), respectively. The oxygen consumption rates of embryos of rank A were significantly higher (p < 0.05) than those of rank B, irrespective of the day of blastocyst appearance after IVF. Neither did the proportion of male embryos of ranks A and B differ significantly from each other at any of the days examined, nor from the average proportion (53%). The oxygen consumption rate of embryos of rank B collected on day 8 was significantly higher (p < 0.05) in female embryos than in male embryos collected on the same day. However, there were no apparent differences of oxygen consumption rates at each day of blastocyst appearance between male and female embryos of rank A. These results indicate that the oxygen consumption rate of individual embryos reflects their quality but does not correlate with the sex ratio of embryos of excellent quality.


Effects of ovary storage time and temperature on DNA fragmentation and development of porcine oocytes.

The present study was conducted to investigate the effects of storage time and temperature of porcine ovaries on the quality and nuclear maturation in vitro of oocytes obtained from stored ovaries and their subsequent development after in vitro fertilization. The ovaries were stored in physiological saline for 0, 3, 6, 9 and 12 h at various temperatures (4, 15, 25 and 35 C). The pH of follicular fluid obtained from the ovaries, DNA fragmentation of the oocyte nucleus and meiotic competence of oocytes were examined. Some oocytes from ovaries stored at 15, 25 and 35 C for 6 h were fertilized in vitro, and then cultured for 7 days to examine the ability of embryos to develop to the blastocyst stage. When the ovaries were stored at 35 C, the pH of follicular fluid decreased and the proportions of oocytes with DNA fragmented nuclei increased as the storage time was prolonged, and the storage of ovaries for 6, 9 and 12 h resulted in lower maturation rates of oocytes. When the ovaries were stored at 4, 15, 25 and 35 C for 6 h, the storage at higher temperatures (> or =15 C) decreased the pH of follicular fluid and induced nucleic DNA fragmentation in higher proportions of oocytes. None of the oocytes from ovaries stored at 4 C reached metaphase II. The storage of ovaries at 15 C reduced the rates of in vitro fertilized oocytes and subsequent embryo development, but there were no significant differences in the rates of fertilization and blastocyst formation between oocytes from ovaries stored at 25 C and 35 C. Our findings indicate that the storage of ovaries at 25-35 C for 6 h is effective for maintaining the developmental competence of porcine oocytes even though the development rates were lower than those of ovaries stored at 35 C for 3 h.

The Journal of Reproduction and Development


Development of interspecies cloned embryos in yak and dog.

Interspecies nuclear transfer (NT) could be an alternative to replicate animals when supply of recipient oocytes is limited or in vitro embryo production systems are incomplete. In the present study, embryonic development was assessed following interspecies NT of donor cumulus cells derived from yak and dog into the recipient ooplasm of domestic cow. The percentages of fusion and subsequent embryo development to the eight-cell stage of interspecies NT embryos were comparable to those of intraspecies NT embryos (cow-cow NT embryos). The percentage of development to blastocysts was significantly lower (p < 0.05) in yak-cow NT embryos than that in cow-cow NT embryos (10.9% vs. 39.8%). In dog-cow NT embryos, only one embryo (0.4%) developed to the blastocyst stage. These results indicate that interspecies NT embryos possess equally developmental competence to the eight-cell stage as intraspecies NT embryos, but the development to blastocysts is very low when dog somatic cells are used as the donor nuclei.


Effects of oxygen tension on the development and quality of porcine in vitro fertilized embryos.

The present study was conducted to examine the effect of oxygen tension during in vitro culture (IVC) of porcine oocytes/embryos on their development and quality using two different culture systems. Porcine cumulus oocyte complexes (COCs) were matured (IVM) and fertilized (IVF) in vitro, and subsequently cultured for 6 days in a simple and economical portable incubator or a standard CO(2) incubator. While the same temperature (38.5 degrees C) and CO(2) concentration (5%) were used in the both systems, the portable incubator was operated in a negative air pressure (- 300 mmHg) to create an O(2) level at 8-10% (low O(2) concentration), or in a positive air pressure (high O(2) concentration). To compare the two culture systems, IVM and IVF of COCs and subsequent IVC of in vitro produced (IVP) embryos were carried out in the portable incubator with a low O(2) concentration (Group I) or in the standard incubator with a high O(2) concentration (Group II). To assess the effect of O(2) concentration on IVC of IVP embryos, some oocytes that had been cultured in the standard incubator for IVM and IVF were subsequently cultured in the portable incubator with a low O(2) concentration (Group III) or a high O(2) concentration (Group IV). The occurrence of DNA fragmentation in the blastocysts produced under different culture conditions was examined by TUNEL staining to assess embryo quality. The rates of oocytes that reached MII and were penetrated by spermatozoa following IVF did not differ between the two incubation systems. In contrast, the proportions of development to blastocysts and the mean cell number of blastocysts in Group I were higher than those in Group II and Group IV. The index of DNA-fragmented nucleus in the blastocysts of Group I was significantly lower than that in the blastocysts of Group II. Therefore, low oxygen tension during IVM, IVF and IVC enhanced the subsequent development of IVP embryos to the blastocyst stage and improved their quality.


Effect of replacement of pyruvate/lactate in culture medium with glucose on preimplantation development of porcine embryos in vitro.

The effect of glucose supplementation at different times in in vitro culture on the developmental competence of in vitro produced (IVP) porcine embryos was examined. In Experiment 1, when IVP embryos were cultured in modified NCSU-37 supplemented with pyruvate and lactate (IVC-pyr/lac) for 0 h, 24 h, 48 h, 72 h, 96 h, or 118 h and subsequently in modified NCSU-37 supplemented with glucose (IVC-glu) until Day 6 (Day 0=day of in vitro fertilization), the rates of blastocyst formation were significantly higher in embryos cultured in IVC-pyr/lac for 24 or 48 h (24.4% and 23.0%, respectively) than in embryos cultured in IVC-pyr/lac for the whole culture period (14.5%). However, there were no significant differences between embryos obtained after the energy source replacement and embryos cultured in IVC-glu for the whole culture period on the rates (15.2%-24.4%, and 16.8% respectively). Replacement of pyruvate/lactate with glucose at 58 h of culture in Experiment 2 significantly enhanced the rate (31.3%) compared to those after replacement at 48 h, 53 h and 63 h of culture (20.6%, 20.8%, and 21.1%, respectively). In conclusion, replacement of pyruvate/lactate with glucose as the energy substrate was optimal at 58 h of culture for the development of porcine embryos to the blastocyst stage.


Blastocysts derived from in vitro-fertilized cat oocytes after vitrification and dilution with sucrose.

Experiments were conducted to find an optimal incubation period in a sucrose solution during dilution of cryoprotectants for obtaining a higher level of survival and development of cat oocytes cryopreserved by vitrification method. In the first experiment, in vitro-matured fresh oocytes were exposed to 0.5M sucrose solution for 1 or 5 min before in vitro fertilization (IVF). The percentage of development to the blastocyst stage significantly decreased in oocytes exposed for 5 min, compared with oocytes exposed for 1 min and control oocytes without exposure to sucrose (P<0.05). In the second experiment, oocytes that had been vitrified in 40% ethylene glycol and 0.3M sucrose were liquefied and then incubated in 0.5M sucrose for 0.5, 1 or 5 min to dilute the cryoprotectant. The percentage of cleavage (>or=2-cell stage) of vitrified-liquefied oocytes incubated for 0.5 min was significantly higher (P<0.05) than that of other groups. Development of vitrified-liquefied oocytes to the morula and blastocyst stages after IVF was observed only in oocytes incubated in sucrose for 0.5 min. The present study indicates that the oocytes have sensitivity to the toxic effect of sucrose and that the incubation period during dilution of the cryoprotectant is of critical importance for developmental competence of vitrified-liquefied cat oocytes.


Influence of recipient dams of different breeds on performance of Japanese Black calves produced by embryo transfer.


Production of cloned calves by the transfer of somatic cells derived from frozen tissues using simple portable CO2 incubator.

Asian-Australasian Journal of Animal Sciences


Relationship between DNA fragmentation and nuclear status of in vitro-matured porcine oocytes: role of cumulus cells.

The present study was conducted to investigate the effects of the attachment of cumulus cells to oocytes and coculture with cumulus cells during maturation culture on the nuclear status and DNA fragmentation of porcine denuded oocytes (DOs). In the first experiment, cumulus cells were removed from cumulus-oocyte complexes (COCs) at 0, 8, 16, 24 or 32 h after the onset of maturation culture and the DOs were then cultured in their original droplets until 42 h of culture was reached. In the second experiment, all COCs were denuded before the onset of culture and the DOs were cocultured with their removed cumulus cells. The DOs were transferred into fresh medium at 0, 8, 16, 24 or 32 h after the onset of coculture with cumulus cells and then cultured until 42 h of culture was reached. After culture, DNA fragmentation and the nuclear status of oocytes were examined using the terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) method. When the DOs were returned to the same droplets after removal of the cumulus cells, the removal of the cumulus cells after 16 h of culture significantly decreased the proportion of oocytes remaining at the germinal vesicle (GV) stage. However, coculture treatment of DOs in the presence of their removed cumulus cells had no significant effects on the GV breakdown (GVBD) of oocytes. There were no significant differences in the proportion maturing to MII oocytes among the groups following removal of cumulus cells after the onset of maturation culture; however, DOs cocultured with cumulus cells until the end of maturation culture exhibited an increased maturation rate compared with DOs cocultured for 8 and 16 h. The total proportion of TUNEL-positive oocytes of oocytes remaining at the GV stage was higher than that of oocytes reaching other stages, irrespective of the removal of cumulus cells and coculture treatments. However, coculture for more than 16 h decreased the total proportion of TUNEL-positive oocytes. Our results indicate that the attachment of cumulus cells to oocytes may have a critical role for oocytes undergoing GVBD and that coculture with cumulus cells promotes the ability of oocytes to complete maturation. Moreover, coculture with cumulus cells may assist the oocyte to avoid undergoing DNA fragmentation.

Reproduction, Fertility, and Development


Influence of maturation culture period on the development of canine oocytes after in vitro maturation and fertilization.

The objective of this study was to determine an optimum maturation period of canine oocytes for the development in vitro after in vitro fertilization (IVF). Canine oocytes larger than 110 micrometers in diameter, which were collected from ovaries at the follicular phase of the reproductive cycle, were cultured for each time (48, 72 and 96 h) in TCM 199 medium supplemented with 10% canine serum, fertilized, and then cultured in vitro for 8 days. Significantly more oocytes reached metaphase II (MII) in the 72-h culture group than in the 48-h culture group (25.6% vs. 41.0%). The percentages of oocytes that reached MII or beyond after maturation culture did not differ significantly between the 72- and 96-h culture groups, but the percentage of parthenogenetically activated oocytes in the 96-h culture group was significantly higher than that in the 72-h culture group. The percentages of cleaved embryos after IVF were significantly higher in the 48- and 72-h culture groups than in the 96-h culture group. In the 48-h culture group, 3.9% of fertilized oocytes developed to the 16-cell stage or beyond, but none of the cleaved embryos in the 72- and 96-h culture groups developed to the same stage. These results indicate that full nuclear maturation of oocytes collected from ovaries at the follicular phase occurs after 72 h of in vitro culture. However, an optimum maturation period (48 h) for the in vitro development of canine oocytes after IVF may be different from the period necessary to reach the maximal oocyte maturation rate, when based on the developmental stage of the cleaved embryos.


Effects of cooling ovaries before oocyte aspiration on meiotic competence of porcine oocytes and of exposing in vitro matured oocytes to ambient temperature on in vitro fertilization and development of the oocytes.

Experiments were conducted to evaluate the effects of cooling porcine ovaries to low temperature (4 degrees C, 15 degrees C, 20 degrees C, 25 degrees C or 30 degrees C) for 1 h on the meiotic competence of their oocytes. Moreover, it was determined whether or not the exposure of in vitro matured oocytes to ambient temperature (20 degrees C, 25 degrees C or 30 degrees C) for 1 h affects the fertilization and developmental competence of the oocytes. There was no difference between the proportions of oocytes that underwent maturation to metaphase II when isolated from control ovaries held at 35 degrees C and ovaries exposed to 30 degrees C. However, the percentages of oocytes from ovaries exposed to 25 degrees C or less were significantly lower than those of oocytes from ovaries exposed to 30 degrees C and control ovaries. The proportions of total and normal fertilization of oocytes that had been exposed to 20 degrees C before in vitro fertilization (IVF) were significantly lower than those of control oocytes maintained at 38.5 degrees C. However, cooling in vitro matured oocytes had no effects on their cleavage and development to blastocysts after IVF. These data suggest that exposing porcine ovaries to a low temperature of 25 degrees C or less before aspiration of oocytes may adversely affect their subsequent in vitro maturation. It may be necessary to maintain the oocytes at a temperature of more than 25 degrees C during manipulation of oocytes for retaining the fertilizability of the oocytes.


Influence of the DNA amount per microinjection on the development and EGFP expression in bovine embryos.


Effects of serum-free culture media on in vitro development of domestic cat embryos following in vitro maturation and fertilization.

This study was conducted to determine the adequate medium for a serum-free culture system of domestic cat embryos produced by in vitro maturation (IVM) and fertilization (IVF). Cumulusoocyte complexes recovered from cat ovaries were matured in vitro for 24 h, and then inseminated in vitro for 12 h. After insemination, the oocytes were cultured in five media [Ham's F10, Waymouth 752/1 (Waymouth), TCM199, modified Earle's balanced salt solution (MK-1) and CR1aa], each of which contained 0.4% bovine serum albumin. There were no significant differences among the rates of fertilization of oocytes cultured in five media following IVF. The rate of oocytes/embryos developed to at least the morula stage was significantly lower (p < 0.05) in Waymouth than in MK-1, TCM199 and CR1aa. Moreover, none of the embryos cultured in Ham's F10 and Waymouth developed to the blastocyst stage. There were no differences among the rates of development to the blastocyst stage of oocytes/embryos cultured in MK-1, TCM199 and CR1aa. These results indicate that the type of serum-free medium has a major impact on in vitro development of domestic cat embryos derived from IVM/IVF, and MK-1, TCM199 and CR1aa media are suitable for in vitro culture of cat embryos in a serum-free culture system.

Reproduction in Domestic Animals = Zuchthygiene


Effects of oocyte culture density on meiotic competence of canine oocytes.

This study was conducted to determine a suitable ratio of oocytes to medium for in vitro maturation (IVM) of cumulus-oocyte complexes (COCs) collected from bitches at anoestrus and dioestrus and to examine the meiotic competence of COCs cultured singly or in different group sizes. In the first experiment, different numbers of COCs (5, 10, 15 and 20 per drop) were cultured for 72 h in 100 microl drops of maturation medium. The meiotic competence of oocytes from ovaries at anoestrus was affected by the number of COCs incubated, whereas at dioestrus, the incubation number of COCs had no effect. In the second experiment, COCs were cultured singly or in different group sizes for 72 h by suitable oocyte density according to the reproductive cycle of the donor. In the anoestrous group, 1, 5 and 10 COCs were cultured in 10, 50 and 100 microl drops of the medium (10 microl per COC), respectively. In the dioestrous group, 1, 5 and 15 COCs were cultured in 7, 35 and 105 microl drops of the medium (7 microl per COC), respectively. There were no differences in the proportions of oocytes reaching metaphase II among the different group sizes in each stage of the reproductive cycle of the donor. The results indicate that the influence of oocyte density on the meiotic competence of oocytes differs according to the stage of the reproductive cycle of the donor. Moreover, the group sizes have no effect on the meiotic competence of oocytes cultured at suitable oocyte density according to the reproductive cycle of the donor.


Analysis of DNA fragmentation in bovine somatic nuclear transfer embryos using TUNEL.

The production of cloned animals is an inefficient process because of early or late embryonic losses. This study focused on the DNA fragmentation that occurs during embryonic development. The occurrence of DNA fragmentation was examined in bovine embryos produced by in vitro fertilization (IVF) and somatic cell nuclear transfer (NT) using the terminal deoxynucleotidyl transferase (TdT) nick-end labelling (TUNEL). IVF and NT embryos at the two-cell to blastocyst stage were stained by TUNEL for the analysis of DNA-fragmented nuclei and with propidium iodide for determination of the total number of cells. DNA fragmentation was first detected in NT embryos at the four-cell stage, but in IVF embryos at the six- to eight-cell stage. The percentage of embryos with at least one DNA-fragmented nucleus increased with the advance of the developmental stage of embryos in both IVF and NT groups. The DNA-fragmented nucleus index in NT embryos that developed beyond the four-cell stage was significantly higher (P<0.01) than that of IVF embryos at the same stage. In the both IVF and NT groups, TUNEL-labelled cells were detected in almost all blastocysts and were mainly observed in presumptive inner cell mass (ICM) cells of embryos. The DNA-fragmented nucleus index was negatively correlated with the total number of cells in NT blastocysts, but this relationship was not observed in IVF blastocysts. These results suggest that the high occurrence of DNA fragmentation observed in NT embryos may be related to early embryonic loss after transfer.


Correlation between the cell number and diameter in bovine embryos produced in vitro.

This study was designed to examine the effects of age and developmental stage of in vitro-produced bovine embryos on the cell number of the embryos and to investigate the correlation between the cell number and diameter in the embryos. The diameter and cell number in blastocysts and expanded blastocysts collected on days 7-9 after in vitro fertilization (IVF) were examined. Although the diameters of the blastocysts collected on days 7 and 8 after IVF were smaller than those of the expanded blastocysts collected on day 9, the cell number in both types of embryos was similar. The cell numbers of the blastocysts and expanded blastocysts decreased with increasing embryo age. There were positive correlations between the cell number and diameter in bovine embryos at each stage collected on each day after IVF. However, the value of the correlation coefficient in the day-9 expanded blastocyst group tended to be higher than that in the other groups. These results indicate that the cell number of in vitro-produced embryos is affected by the embryonic stage and age. The diameter of the embryo may be potentially used for the viability testing of the expanded blastocysts collected on day 9 after IVF.


In vitro maturation, fertilization and development of domestic cat oocytes recovered from ovaries collected at three stages of the reproductive cycle.

This study was conducted to examine the effect of the donor cat's reproductive cycle stage on in vitro maturation (IVM), in vitro fertilization (IVF), and in vitro development of oocytes recovered from ovaries that were collected and stored at 35 degrees C for a short period (1-6 h). Based on the presence or absence of follicles and corpora lutea, the ovarian pairs collected were classified into inactive, follicular, or luteal stages. Nuclear status of 161 cumulus-oocyte complexes (COCs) were examined immediately after recovery; 91.3% of the oocytes were found to be at the immature germinal vesicle (GV) stage, and 3.7% of the oocytes were at metaphase II (MII) stage. The percentage of the oocytes at the GV stage was significantly lower in the follicular stage than in the inactive stage (P < 0.01). Of the oocytes from the follicular stage, 9.1% were at MII stage. After culture for 24 h, however, the proportions of oocytes that reached metaphase I and MII were not different among the reproductive cycle stages of the ovaries collected (P > 0.05). After co-incubation with sperm, 63.1% of oocytes were fertilized, but there were no significant differences among the reproductive cycle stages of the ovaries with respect to the proportions of normal and polyspermic fertilization. However, the number of oocytes reaching cleavage stage and development to the morula and blastocyst stages from follicular stage ovaries were significantly lower (P < 0.05) than those obtained from inactive and luteal stage ovaries. These results indicate that the reproductive cycle stage of donor cat ovaries, stored at 35 degrees C, has no apparent effects on the frequencies of maturation and fertilization of oocytes, but influences developmental competence of the oocytes following IVM or IVF.


Effect of protein supplementation on development to the hatching and hatched blastocyst stages of cat IVF embryos.

The effects of protein supplementation in culture medium on development to the hatching and hatched blastocyst stages of cat in vitro-fertilized embryos were investigated. In the first experiment, presumptive zygotes derived from in vitro maturation and in vitro fertilization (IVF) were cultured in modified Earle's balanced salt solution (MK-1) supplemented with 0.4% bovine serum albumin (BSA) or 5% fetal bovine serum (FBS) for 9 days. There were no significant differences between the BSA and FBS groups with respect to the proportion of cleavage and development to the morula and blastocyst stages of zygotes. However, the presence of FBS in the medium enhanced development to the hatching blastocyst stage of zygotes compared with the BSA group (31.4% v. 7.8%). Moreover, 2.9% of zygotes cultured with FBS developed to the hatched blastocyst stage. The mean cell number of blastocysts derived from zygotes cultured with FBS was significantly higher (P<0.01) than that from zygotes cultured with BSA (136.6 v.101.5). In the second experiment, embryos at the morula orblastocyst stage, which were produced by culturing in MK-1 supplemented with 0.4% BSA after IVF, were subsequently cultured in MK-1 with 0.4% BSA or 5% FBS. Significantly more morulae developed to the blastocyst (P<0.05) and hatching blastocyst stages (P<0.01) in the FBS group than in the BSA group (71.5% and 53.6% v. 44.9% and 6.0%, respectively). Although none of the morulae cultured with BSA developed to the hatched blastocyst stage, 11.5% of morulae cultured with FBS developed to the hatched blastocyst stage. Moreover, the proportion of development to the hatching blastocyst stage of blastocysts was significantly higher (P<0.01) in the FBS group than in the BSA group (68.7% v. 9.8%). None of the blastocysts cultured with BSA developed to the hatched blastocyst stage, whereas 7.3% of blastocysts cultured with FBS developed to the hatched blastocyst stage. The results of the present study indicate that supplementation with FBS at different stages of early embryo development promotes development to the hatching and hatched blastocyst stages of cat IVF embryos.

Reproduction, Fertility, and Development


Improvement of the culture conditions for in vitro production of cattle embryos in a portable CO2 incubator.

The effects of different concentrations of growth hormone (GH) on in vitro maturation (IVM), fertilization (IVF) and culture (IVC) of bovine oocyte/embryos in CR1aa or CR2aa media using a simple CO2 incubator were investigated. The IVM/IVF/IVC of oocytes were carried out in the presence of 0, 50, 100 and 200 ng/ml GH in the medium. The proportion of metaphase II oocytes was significantly higher (p < 0.05) in 200 ng/ml compared with 0 ng/ml GH in CR1aa medium (59 versus 85%, respectively), but this effect was not observed under CR2aa. Higher concentrations of GH yielded lower rates of unfertilized ova and thus superior cleavage rates (36.5 +/- 0.2 and 63.5 +/- 2.0% versus 17.5 +/- 0.2 and 82.5 +/- 1.5% or 40.4 +/- 0.6 and 59.6 +/- 1.4% versus 16.6 +/- 1.2 and 83.4 +/- 6.2% for 0 and 200 ng/ml GH in portable or ordinary incubator, respectively) in CR1aa. This dose-dependent effect was also observed in the percentages of transferable embryos, although not statistically different (17.2 +/- 1.7 versus 27.3 +/- 1.8% and 16.6 +/- 3.1 versus 26.0 +/- 1.4%, for 0 versus 200 ng/ml GH in portable and ordinary incubator, respectively). In contrast to the CR1aa, different concentrations of GH in CR2aa medium did not increase either fertilization or cleavage rates. In fact, higher concentrations of GH in this medium negatively affected the rate of transferable embryos. Hence, percentages of transferable embryos obtained in the portable incubator under 0 or 50 ng/ml GH were higher (p < 0.05) compared with those obtained in 100 or 200 ng/ml GH (35.4 +/- 5.7 or 40.5 +/- 5.4% versus 22.4 +/- 2.4 or 15.5 +/- 2.1%, respectively). There was however, no significant difference in the rate of transferable embryos in an ordinary incubator employing CR2aa medium, but the trend was more or less similar to that observed in the portable incubator. Despite the fact that relatively fewer oocytes were employed for the culture in the ordinary incubator, overall results observed employing the simple portable CO2 incubator were within the range of those obtained in an ordinary incubator: implying that the simple portable incubator can effectively be employed for the in vitro production of bovine embryos under field conditions.


Developmental competence of bovine embryos reconstructed by the transfer of somatic cells derived from frozen tissues.

The ability of frozen-thawed fetal skin was examined to generate viable cell lines for nuclear transfer. Fetal skin frozen at -35 degrees C or -80 degrees C in the presence of 5% DMSO were used as tissue explants to generate somatic cells. The resultant confluent cells were then used as donors for nuclear transfer (NT). Of the bovine NT embryos reconstructed from the somatic cells, 78% to 81% showed cleavage, 43% to 48% reached the stage of morula formation and 34% to 35% reached blastocyst formation. There were no significant differences in development (P>0.05) when the NT embryos were compared with those reconstructed from fresh somatic-cell-derived skin tissues (75%, 45%, and 38%, for cleavage, and development to morula and blastocyst stages, respectively). The results indicated that cell lines derived from bovine fetal skin cryopreserved by a simple method could be used as donors in nuclear transfer. The resulting embryos showed similar development in vitro to those reconstructed from unfrozen fetal-skin-derived somatic cells.

The Journal of Veterinary Medical Science


Influence of oocyte quality, culture media and gonadotropins on cleavage rate and development of in vitro fertilized buffalo embryos.

The present study was designed to examine the influence of oocyte quality, culture media and gonadotropins on cleavage rate and development of in vitro fertilized buffalo embryos. Three experiments were conducted. In experiment 1, oocytes were classified by number of cumulus cell layers and morphology of the ooplasm as good, fair or poor. Oocytes were cultured for IVM, IVF and IVC in CR1aa medium. In experiment 2, good quality oocytes were cultured for maturation in: (1) CR1aa; (2) CR2aa; (3) TCM-199; (4) MEM or (5) RPMI-1640, and then fertilized using frozen thawed buffalo spermatozoa in CR1aa. The oocytes were cultured in the same medium used for maturation after fertilization. In experiment 3, oocytes were classified into three groups: group (1) was without gonadotropin and serve as a control; group (2) in which IVM medium was supplemented with 10microg/ml FSH and group (3) in which IVM medium was supplemented with 10IUml(-1) eCG. In all experiments, oocytes were kept at 38.5 degrees C under 5% CO(2) for IVM, IVF, IVC and examined for cleavage and embryo development rates on days 3 and 8, respectively. Good and fair quality oocytes produced a higher cleavage rate (P<0.01) than poor quality oocytes. Morula production rate was also higher (P<0.01) for good as compared with fair quality oocytes. Embryo development with poor quality oocytes was arrested at the two to sixteen cell stage. In experiment 2, the cleavage rate was higher (P<0.05) in CR1aa than CR2aa, and higher (P<0.01) than TCM-199, MEM and RPMI-1640. The numbers of morulae and blastocysts were higher (P<0.01) for oocytes cultured in CR1aa and CR2aa media than TCM-199 or MEM. In experiment 3, the addition of FSH or eCG to the maturation medium increased (P<0.01) cleavage and developmental rates of buffalo embryo compared with control medium. In conclusion, the IVM of good quality buffalo oocytes in CR1aa or CR2aa medium and the addition of FSH or eCG in maturation medium produced higher cleavage and developmental rates of IVF buffalo embryos.


The effect of prefreezing the diluent portion of the straw in a step-wise vitrification process using ethylene glycol and polyvinylpyrrolidone to preserve bovine blastocysts.

A total of 678 bovine blastocysts, which had been produced by in vitro maturation, fertilization, and culture, were placed into plastic straws and were vitrified in various solutions of ethylene glycol (EG) + polyvinylpyrrolidone (PVP). Part of the straw was loaded with TCM199 medium + 0.3 M trehalose as a diluent; the diluent portions of the straw were prefrozen to either -30 or -196 degrees C. Then, the embryos suspended in the vitrification solution were pipetted into the balance of the straw and vitrified by direct immersion into liquid nitrogen. For thawing, the straws were warmed for 3 s in air and 20 s in a water bath at 39 degrees C and then agitated to mix the diluent and cryoprotectant solution for 5 min followed by culture in TCM199 + 10% FCS + 5 + microg/ml insulin + 50 microg/ml gentamycin sulfate for 72 h. Variables that were examined were the time of exposure to EG prior to vitrification, the PVP concentration, and the temperature of exposure to EG + PVP prior to vitrification. Survival and hatching rates of the blastocysts exposed to 40% EG in four steps at 4 degrees C were higher than those of embryos exposed in two steps (81.3 +/- 4.3% and 80.2 +/- 3.4% vs 67.6 +/- 4.5% and 71.5 +/- 4.7%, respectively; P < 0.05). The same indices were superior following vitrification-thawing of the blastocysts in 40% EG + 20% PVP than it was in 40% EG + 10% PVP (76.1 +/- 5.5% vs 63.7 +/- 1.8%; P < 0.05; and 61.6 +/- 6.0% vs 70.5 +/- 4.7%; P < 0.01, respectively). Exposure to the vitrification solution (40% EG + 20% PVP) at higher temperatures (37.5 degrees C vs 4 degrees C) reduced both survival and hatching rates (45.8 +/- 6.9% vs 83.9 +/- 4.4% and 41.5 +/- 1.8% vs 64.0 +/- 4.7%, respectively; P < 0.001). These results indicate that blastocysts vitrified after prefreezing the diluent portions of the straws do favor developmental competence of in vitro produced embryos.


Effects of size and storage temperature on meiotic competence of domestic cat oocytes.


The effects of donor cell type and culture medium on in vitro development of domestic cat embryos reconstructed by nuclear transplantation.

Asian-Australasian Journal of Animal Sciences


Size distribution and meiotic competence of oocytes obtained from bitch ovaries at various stages of the oestrous cycle.

The present study was conducted to examine the effects of the stage of the oestrous cycle on the meiotic competence of canine oocytes and also to investigate the relationship between the stage of the oestrous cycle and the relative size distribution of oocytes obtained from bitches at three stages of the cycle (anoestrus, follicular phase and dioestrus). Only healthy-looking cumulus-oocyte complexes were used for in vitro maturation and these were divided into three groups based on diameter (< 110, 110 to < 120 and > or = 120 microm). The mean diameter of oocytes from ovaries at anoestrus, the follicular phase and dioestrus was 103.6, 119.2 and 107.7 microm, respectively. The percentage of large oocytes (> or = 120 microm) collected at the follicular phase was higher (P<0.01) than that collected at dioestrus and the percentage of oocytes > or = 120 microm collected from ovaries at dioestrus was higher (P<0.01) than that collected at anoestrus. After culture for 72 h, significantly more oocytes reached metaphase II (MII) in the follicular phase than in the other stages (P<0.01), and more oocytes reached MII in dioestrus than in anoestrus (P<0.05). In the > or = 120 microm group, the frequency of oocytes that resumed meiosis in the follicular phase was higher (P<0.05) than in the other stages. However, in the smaller diameter (< 120 microm) groups, there were no significant differences between ovaries at different stages of the oestrous cycle with respect to the proportion of oocytes reaching each stage of meiosis. Thus, the oestrous cycle stage influences maturation frequency. Moreover, oocytes demonstrated a size-related ability to undergo meiotic maturation, irrespective of the stage of the oestrous cycle. These results suggest that the effects of the stage of the oestrous cycle may result from differences in the distribution of large oocytes.


Canine oocyte diameter in relation to meiotic competence and sperm penetration

This study was conducted to determine the diameter of canine oocytes that are able to attain full meiotic competence and sperm penetration. Oocytes were collected from ovaries of bitches at various stages of the estrous cycle. Only healthy-looking cumulus-oocyte complexes were used for in vitro maturation, and were divided into four groups based on diameter: <100, 100 to <110, 110 to <120 and >120 microm. Following in vitro maturation or fertilization, oocytes were stained to assess nuclear maturation and penetration rates. The mean oocyte diameter was 108.5 +/- 0.4 microm. The oocytes displayed size-related ability to undergo meiotic maturation. After culture for 72 h, the rates of oocytes that remained at the germinal vesicle stage in the <110 microm groups were significantly higher (P<0.01) than in the > or = 110 microm groups. None of the oocytes <110 microm reached metaphase II (MU), but 4.9 and 21.5% of the oocytes that were greater than 110 and 120 microm, respectively, progressed to MII. After in vitro fertilization for 20 h, 10 to 25% of oocytes were penetrated by spermatozoa, but there were no clear relationships between oocyte diameter and penetration rates of the oocyte by sperm. In the <120 microm groups, sperm penetration was mostly found in oocytes arrested at the germinal vesicle stage. However, a total of eight oocytes > or = 120 microm in diameter were penetrated by spermatozoa, of which five oocytes reached MII. These results suggest that there is a clear relationship between oocyte diameter and meiotic competence, but no relationship between oocyte diameter and sperm penetration. Canine oocytes may have acquired meiotic competence once they reach at a diameter of 120 microm, but the oocytes may allow the entry of spermatozoa into the ooplasm irrespective of oocyte diameter.


Developmental competence of frozen-thawed blastocysts from fair-quality bovine embryos cultured with beta-mercaptoethanol.

Two-hundred-and-thirty-one fair-quality embryos at the compacted morula stage collected from 89 superovulated cows were cultured in TCM199 or Brinster's BMOC-3 medium with or without 100 microM beta-mercaptoethanol (beta-ME). After 24 h culture, a total of 142 fair-quality embryos developed to the blastocyst stage, of which 106 were subsequently frozen with 1.8 M ethylene glycol. The mean cell number and development rates of frozen-thawed blastocysts from the fair-quality embryos cultured in TCM199 containing beta-ME were higher than those of the fair-quality embryos directly frozen without culture. The pregnancy rates obtained with frozen blastocysts from fair-quality embryos tended to be lower than those of non-cultured fresh fair-quality embryos and cultured fresh blastocysts. These results indicate that the inclusion of beta-ME in pre-freezing culture media improve the development of frozen-thawed blastocysts from fair-quality embryos, but not the pregnancy rate.


The quality and maturation of bitch oocytes recovered from ovaries by the slicing method.

Oocytes were recovered from bitch ovaries at various stages of the estrous cycle by the slicing method. The proportion of Grade A oocytes (darkly pigmented and surrounded in part, or whole, by dense layers of cumulus cells) were counted. Only Grade A oocytes were cultured in TCM199 supplemented with 5% fetal calf serum for evaluation of meiotic competence. There were no significant differences in the total number of oocytes or the proportion of Grade A oocytes that were recovered from bitches at various stages of the estrous cycle. Only 11% of the oocytes reached metaphase II (MII) at 72 hr after initiation of maturation culture. However, the proportions of oocytes reaching MII did not increase with culturing for up to 120 hr.


Development of canine oocytes matured and fertilised in vitro.


Effect of removal of large follicles after artificial insemination on embryo yield of superovulated beef cows.


Assessment of developmental competence of nuclei from bovine parthenogenetic embryos.

The Journal of Reproduction and Development


Pellet freezing of in vitro produced bovine embryos using dry ice.

In vitro produced bovine embryos were frozen by pellet freezing or vitrification method. In the pellet freezing method, the embryos were cooled on the dry ice and then frozen as pellets. At warming, the pellets were immersed directly into 0.5 M sucrose. The survival rates of blastocysts frozen by the pellet freezing method were higher (P<0.01) in 40% ethylene glycol (EG) than those in the lower concentrations (20 and 30% EG). Higher survival rates of blastocysts frozen by the pellet freezing method were obtained but the development rates did not differ, as compared with those by the vitrification method. There were no significant differences between the pellet freezing and vitrification method in the frequencies of post-thaw survival of hatched blastocysts. These results demonstrate that the pellet freezing method using dry ice can be used successfully for the cryopreservation of blastocysts.


Relationship between dead cells and DNA fragmentation in bovine embryos produced in vitro and stored at 4 degrees C.

DNA fragmentation and its relationship with dead cells were examined in bovine blastocysts produced in vitro and stored at 4 degrees C for 1-5 days. Survival and development to the hatching and hatched blastocyst stage decreased with increasing storage time. Both were significantly lower at 72 hr than at 48 hr. None of the embryos stored for 120 hr developed to the hatching or hatched blastocyst stage. The proportion of dead cells per embryo increased progressively as the time of storage increased, until 69% of embryonic cells were dead after 120 hr of storage. There was no significant difference between the proportions of DNA fragmentation per embryo stored for 0 and 24 hr (12% vs 16%). However, the proportion of DNA fragmentation in embryos stored for longer than 48 hr was significantly greater than that in embryos stored for less than 24 hr. There were no significant differences among those stored for longer than 48 hr (28-33%). These results suggest that the reduced developmental competence of bovine embryos stored at 4 degrees C is characterized by necrotic change rather than apoptotic change.


Development to live young from bovine small oocytes after growth, maturation and fertilization in vitro.

Bovine oocytes (90 to 99 microns in diameter) were isolated from early antral follicles (0.5 to 0.7 mm in diameter). Cumulus-oocyte complexes (COC) with pieces of parietal granulosa were embedded in collagen gels and cultured for 14 d. After in vitro growth culture, oocytes recovered from the collagen gels were further matured, fertilized and cultured in vitro, and then were transferred to recipient cows. After 14 d of growth culture, 37% of the oocytes (203/556) showed normal morphology in the collagen gels. The mean diameter of the oocytes was 110.1 +/- 6.0 microns, significantly larger (P < 0.01) than before growth culture (94.8 +/- 2.7 microns), and 77% were at the germinal vesicle stage while 23% had undergone germinal vesicle breakdown. After 24 h of maturation culture followed by insemination, 27% of in vitro-grown oocytes reached the second metaphase, and 42% of the oocytes were normally fertilized. After insemination, 18.2% of in vitro-grown oocytes cleaved and 3.7% developed to the blastocyst stage. Three blastocysts obtained from in vitro-produced 90- to 99-micron oocytes were transferred to 3 recipients. One recipient subsequently became pregnant and delivered a live calf on Day 277. These results demonstrated for the first time that 90 to 99-micron oocytes from early antral follicles can complete growth and acquire full developmental competence in vitro so that live young can be produced after maturation, fertilization, subsequent culture in vitro, and transfer to recipient cows.


Fine structure of bovine morulae and blastocysts in vivo and in vitro.

The ultrastructure of bovine morulae and blastocysts developed from in vitro-matured and -fertilized oocytes in a serum-supplemented medium was compared with that of morulae and blastocysts collected non-surgically from superovulated cows. In the in vivo-derived morulae, two characteristic cells types could be identified by the electron-density of their cytoplasm and by their ultrastructural features. One type appeared light in color with low electron-dense cytoplasm. These cells were located in the peripheral layer of the cluster of blastomeres, possessed numerous cellular organelles such as mitochondria and Golgi apparatus and had microvilli projecting into the perivitelline space. The other cell type was distinguished by cytoplasm that stained more densely than that of the lighter-appearing cells. The darker-appearing cells generally possessed fewer organelles than the lighter cells, but many lysosome-like structures were present in the cytoplasm. The in vitro-developed morulae also contained two types of cells similar to those observed in the in vivo morulae. However, most of the in vitro-developed cells possessed numerous lipid droplets and contained fewer lysosome-like structures than the cells of the in vivo-derived morulae. The blastocysts, both in vivo and in vitro, showed a clear differentiation of trophoblast cells and inner cell mass (ICM)-cells. In the in vivo-derived blastocyst, the apical membrane of trophoblast cells was covered with large, numerous microvilli and well-developed junctional complexes were observed. Lipid droplets were present in the cytoplasm of trophoblast and ICM-cells but were not abundant. In vitro-developed blastocysts showed less well-developed junctional complexes between trophoblast cells, less well-developed apical microvilli on the trophoblast cells, and contained large numbers of lipid droplets. This accumulation of lipid droplets was higher in the trophoblast cells than in the ICM-cells. The zonae pellucidae of in vitro-developed embryos were thinner than that of the in vivo-derived embryos. This study demonstrates conspicuous differences in the ultrastructural features between the in vivo-derived and in vitro-developed embryos, suggesting that the ultrastructure may reflect the various physiological anomalies observed in previous studies.


New technique, using a portable CO2 incubator, for the production of in vitro fertilized Egyptian buffalo embryos.


Effect of serum on the in vitro maturation of canine oocytes.

The meiotic competence of canine oocytes cultured for 72 h in medium supplemented with three different concentrations (5, 10 and 20%) of anoestrous, oestrous or metoestrous bitch serum, or with 0.3% bovine serum albumin (BSA), was examined. The oestrous serum supplement had a positive effect on the resumption of meiosis, compared with the other supplements (P<0.05). The number of oocytes that reached metaphase I (MI) and metaphase II (MII) was significantly higher (P<0.05) with the oestrous serum supplement than with the anoestrous serum supplement. There were no significant differences among the three different concentrations in each serum type with respect to the proportion of oocytes that completed meiosis (MI to MII). The number of oocytes that resumed meiosis in the 10% oestrous serum supplement was significantly higher (P<0.05) than those of each concentration of the anoestrous and metoestrous serum supplements, and of the 0.3% BSA supplement. Moreover, a higher number of oocytes reached MII in the presence of the 10% oestrous serum supplement than with the 10% anoestrous serum supplement. These results suggest that supplementation of the culture medium with 10% oestrous serum is the optimal treatment for in vitro maturation of canine oocytes.

Reproduction, Fertility, and Development


Cryopreservation of mature bovine oocytes by vitrification in straws.

Experiments were conducted to determine optimal conditions for vitrification of in vitro matured bovine oocytes in straws. In the first series of experiments, the effects of stepwise addition before exposure of oocytes to vitrification solution consisting of 30% (v/v) ethylene glycol (EG) with 0.35 M sucrose was tested. The rates of morphological survival and cleavage of oocytes vitrified by the three-step addition procedure were higher than those vitrified by the one-step addition procedure. In the second series, the effect of the concentration of the vitrification solution was tested (20, 30, 40, and 50% EG, all with 0.35 M sucrose). The survival rates of oocytes vitrified in 20 and 30% EG were lower than those in 40 and 50% EG. The rates of cleavage and development to blastocysts of oocytes vitrified in 40% EG were the highest among the four groups. In the third series, the effect of duration of exposure of oocytes to 0.5 M sucrose (1, 5, and 10 min) at the first step during the three-step dilution was tested. Although there were no significant differences among the groups with respect to developmental competence of oocytes vitrified in 40% EG, the highest development rate (10%) to blastocysts was observed when oocytes were exposed to sucrose for 5 min. These data demonstrate that improvements to the concentration of cryoprotectant and addition procedures have critical effects on the developmental competence of oocytes vitrified in straws.


Superovulatory responses in Japanese black beef cows following largest follicle aspiration or human chorionic gonadotrophin (hCG) treatment.

The effect of largest follicle aspiration or hCG administration before induction of superovulation on the ovarian response of Japanese Black beef cows was investigated using a crossover design in which induction of superovulation was attempted in every cow. The superovulatory response of cows whose largest follicle had been aspirated from the ovaries by ultrasound-guided follicular aspiration 1 day before induction of superovulation, did not differ from the response in non-treated control cows. In contrast, in cows given 5,000 IU of hCG 3 days before induction of superovulation, the proportions of fertilized ova and transferable embryos significantly decreased compared with the other groups.

The Journal of Veterinary Medical Science


Effects of centrifugation and lipid removal on the cryopreservation of in vitro produced bovine embryos at the eight-cell stage.

The effects of intracellular lipid polarization and lipid removal treatments on the postthawed in vitro development of frozen bovine embryos at the 8-cell stage were studied. As the first step, bovine presumptive zygotes were centrifuged at 16,000 g for 20 min for the cytoplasmic lipid polarization and their lipid layers were removed by micromanipulation in order to examine the influence of these treatments on the developmental capacity of bovine zygotes. As the second step, bovine embryos developed to the 8-cell stage following centrifugation treatment at various forces (8000, 12,000, and 16,000 g) or lipid removal treatment at the 1-cell stage were frozen in 1.8 M ethylene glycol + 0.05 M trehalose supplemented with 5% polyvinylpyrrolidone in a one-step procedure. There were no significant differences among the control (nontreatment), lipid-polarized, and lipid-removed groups with respect to the developmental capacity of fresh nonfrozen zygotes (experiment 1). The rates of survival and development to the blastocyst of frozen-thawed 8-cell embryos increased slightly with increasing force of centrifugation (experiment 2). The rate of development into blastocysts of the frozen-thawed 8-cell embryos was significantly higher in the groups that underwent centrifugation (at 16,000 g for 20 min; P < 0.05) or lipid removal (P < 0.01) treatments than the control (intact) group. However, there were no significant differences among the groups with respect to the rate of development to the expanded/hatched blastocyst stage. In addition, the mean cell numbers of embryos developed into blastocysts (day 8) derived from frozen-thawed 8-cell embryos tended to be low in the centrifugation and lipid removal groups compared to the controls (experiment 3). These results suggest that although the centrifugation with or without lipid removal treatments has no detrimental effects on the developmental capacity of bovine zygotes, the freezing tolerance of bovine 8-cell embryos was not improved by these treatments.


Superovulatory response in beef cows following removal of the largest ovarian follicle.


Bovine oocyte diameter in relation to developmental competence.

This study was conducted to determine the diameter of bovine oocytes that were able to attain their full developmental competence to blastocysts. Oocytes were recovered by aspiration of surface-visible follicles (1 to 7 mm in diameter) from slaughterhouse ovaries. Only healthy-looking cumulus-oocyte complexes were used for in vitro maturation, and they were divided into six groups based on diameter: < 110 microm, 110 to < 115 microm, 115 to < 120 microm, 120 to < 125 microm, 125 to < 130 microm and >/= 130 microm. Oocytes were processed through standard procedures for in vitro maturation, fertilization and culture. Following in vitro maturation or fertilization, some oocytes were stained to assess nuclear maturation and penetration rates. The numbers of embryos that cleaved at 42 h post insemination and developed to blastocysts and hatched blastocysts after 8 days of culture were recorded. The mean oocyte diameters were 114.0 +/- 4.8 microm. The oocytes displayed size-related ability to undergo meiotic maturation. The rates of nuclear maturation of oocytes in the greater than 115-microm size range were significantly higher than those of oocytes with diameters < 115 microm. In the < 120 microm diameter groups, the polyspermic fertilization rates of oocytes < 115 microm were significantly higher than those of oocytes 115 to < 120 microm in diameter. The rates of cleavage and development to blastocysts and hatched blastocysts rose as oocyte diameter increased. Among oocytes with a diameter >110 microm, oocytes < 120 microm were found to have significantly lower developmental competence than oocytes 120 to < 130 microm in diameter. These results suggest that bovine oocytes have acquired full meiotic competence at a diameter of 115 microm but not yet attained full developmental competence to blastocysts, and that oocytes have acquired full developmental competence at a diameter of 120 microm.


Cryopreservation of mature bovine oocytes following centrifugation treatment.

In vitro matured bovine oocytes were frozen slowly in 1.6 M 1,2-propanediol following centrifugation treatment for polarization of lipid droplets in the cytoplasm. After thawing, the survival of the oocytes was assessed morphologically and also by in vitro fertilization and culture. The polarization of cytoplasmic lipid droplets had a negative effect on the survival of frozen-thawed oocytes. Thus, this treatment did not improve the frequency of normal fertilization and development to blastocysts, compared with that of frozen control oocytes. However, the frequency of polyspermy and activation of lipid-polarized oocytes that survived after freezing-thawing and subsequent in vitro fertilization tended to be less than those of surviving control oocytes. In addition, the effect of centrifugation treatment was to produce a small but significant increase in the cleavage rate of oocytes that survived after freezing-thawing and the development rates to blastocysts of surviving lipid-polarized oocytes tended to increase, compared with those of surviving control oocytes. These results suggest that the freezing tolerance of the spindle and other organelles of in vitro matured bovine oocytes is associated with lipid droplets and may be improved by the polarization of cytoplasmic lipid droplets before cryopreservation.


Effects of exposure to room temperature, chilling and freezing of bovine one-cell embryos with centrifugation treatment in the presence of various cryoprotectants on their development to blastocysts.


Development of oocytes derived from the first dominant follicles of beef cows.


A frozen-thawed in vitro-matured bovine oocyte derived calf with normal growth and fertility.

The growth and fertility of a female calf obtained from a frozen-thawed bovine oocyte was assessed. The birth weight of the calf was lower than the mean birth weight of calves from in vitro fertilized embryos (IVF-controls) and calves obtained by artificial insemination (AI-controls). The growth rate of the calf up to 6 months was slower than that of the IVF-controls, but similar to that of the AI-controls. When the calf developed into a heifer (200 kg), she was inseminated with frozen semen and 280 days later delivered a male calf. The chromosoms of this cow were normal. These findings suggest that the growth and fertility of the calf derived from the frozen oocyte are normal.


Normal calves obtained after direct transfer of vitrified bovine embryos using ethylene glycol, trehalose, and polyvinylpyrrolidone.

In the present study, IVF bovine embryos were vitrified using as the cryoprotectants, ethylene glycol plus trehalose plus the polymer, polyvinylpyrrolidone (PVP). In Experiment I, toxicity of the vitrification solution (VS) containing 20% PVP was tested in relation to temperature and exposure time. One hundred percent embryo development was observed with treatment at 5 degrees C for 5 min, whereas only 55.5% embryos were developed when the treatment was carried out at 20 degrees C for 5 min. In Experiment II, embryos were vitrified using one of the three treatments (Treatment A, 40% ethylene glycol (EG); treatment B, 40% EG + 11.3% trehalose; and treatment C, 40% EG + 11.3% trehalose + 20% PVP and rehydrations) was performed directly in mPBS. Highest development (84.1%) and hatching rate (68.2%) were obtained when embryos were vitrified with the vitrification solution used in treatment C. In Experiment III, embryos were vitrified as in Experiment II (treatment C). The development and hatching rates were compared after rehydration in different rehydration solutions. No significant difference was observed among the development and hatching rates when rehydration was carried out in different concentrations of trehalose. Five vitrified-warmed bovine embryos were transferred directly to five recipients and three recipients gave birth to three normal calves.


Development of in vitro matured bovine oocytes activated with low temperature.


The efficiency of ethylene glycol, trehalose and polyvinylpyrrolidone for successful vitrification of IVF bovine embryos.

The Journal of Reproduction and Development


In vitro fertilization and development of immature and mature bovine oocytes cryopreserved by ethylene glycol with sucrose.

Immature and mature bovine oocytes were frozen slowly in 1.8 M ethylene glycol (EG) with different concentrations of sucrose (0, 0.1, and 0.2 M). After thawing and dilution of the cryoprotectant by a one-step procedure, the survival of the oocytes was assessed morphologically and also by in vitro fertilization and culture. Sucrose had no effect on the survival and fertilization rates of frozen-thawed oocytes. However, higher cleavage rates of frozen-thawed immature oocytes were obtained with 0.2 M sucrose used in combination with EG. Moreover, none of the immature oocytes frozen in EG without sucrose developed into blastocysts, but about 1% of immature oocytes frozen with sucrose developed into blastocysts. The cleavage rates of mature oocytes frozen in EG were significantly lower with sucrose than without sucrose. However, no significant difference was observed in the development to blastocysts. Transfer of four blastocysts derived from frozen-thawed immature oocytes into two recipient heifers resulted in one pregnancy.


Developmental capacity of bovine follicular oocytes collected from ovaries of pubertal heifers obtained through a spay device.


The development of immature bovine oocytes cryopreserved by 1,2-propanediol.


Developmental competence of bovine oocytes frozen at different cooling rates.

Experiments were conducted to determine the optimal cooling conditions for improving the developmental competence of in vitro-matured bovine oocytes when frozen in 1.6 M 1,2-propanediol. Bovine oocytes were cooled from 0 degree to -5.5 degrees C at 1 degree C/min, seeded, and then cooled to -30 degrees C at different cooling rates (0.3 degree, 0.6 degree or 0.9 degree C/min) and then plunged into LN2. When frozen-thawed oocytes were fertilized in vitro, the proportions of fertilization and developmental competence did not differ among the three groups frozen at different cooling rates. The findings indicated that a cooling rate of less than 1.0 degree C/min in the freezing procedure did not affect the developmental competence of postthaw in vitro-matured bovine oocytes.


Postthaw viability of the inner cell mass of in vitro-matured/in vitro-fertilized bovine embryos frozen in various cryoprotectants.

A study was conducted to examine the viability of inner cell mass (ICM) cells of frozen-thawed in vitro-matured (IVM)/in vitro-fertilized (IVF)-derived embryos using various cryoprotectants. Expanded blastocysts were frozen and thawed in 1.4 M glycerol with 0.25 M sucrose (GL), 1.6 M propylene glycol (PG), 1.8 M ethylene glycol (EG), or 1.3 M ethylene glycol monomethyl ether (EME) as cryoprotectants using a one-step method. After thawing, the embryos were cocultured for 24 h with cumulus cells in TCM199. Embryos which were viable after thawing and developed beyond the blastocyst stage were treated by immunosurgery and differential fluorochrome staining for ICM cell counts. Overall, there were no significant differences in the development to blastocyst stage after 24 h culture in each cryoprotectant (P < 0.05, chi 2 analysis). The viability of ICM cells of frozen-thawed embryos with each cryoprotectant was lower (GL, 72.7%; PG, 67.8%; EG, 77.5%; EME, 74.7%) than that of unfrozen embryos (84.4%). In the case of PG as a cryoprotectant, viability of ICM cells was significantly lower than that of unfrozen embryos (P < 0.05, ANOVA analysis). Our results suggest that the viability of ICM cells of frozen-thawed bovine embryos tend to be lower than that of unfrozen embryos irrespective of the cryoprotectants used. PG was significantly more toxic to the ICM cells compared with the other cryoprotectants.


Viability of frozen-thawed bovine IVM/IVF embryos in relation to aging using various cryoprotectants.

Bovine IVF embryos developed on Days 7, 8 and 9 were equilibrated with 1.6 M propylene glycol (PG), 1.8 M ethylene glycol (EG), 1.1 M diethylene glycol (DEG) or 1.3 M ethylene glycol monomethyl ether (EME) for 10 to 20 min in modified phosphate buffered saline. (mPBS) supplemented with 10% superovulated cow serum. The embryos were loaded into 0.25-ml plastic straws and were placed directly into a 0 degrees C alcohol bath chamber and held for 2 min. They were cooled from 0 degrees C to -5.5 degrees C at 1 degrees C/min and then seeded, followed by a 10-min holding period at -5.5 degrees C. The straws were then cooled to -30 degrees C at 0.3 degrees C/min before plunging into liquid nitrogen. Embryos were thawed and placed directly into the culture medium and washed 3 times. The survival rates of the Day-9 embryos based on reappearance of blastocoele, expansion, and hatching after 48 h of post-thaw culture were significantly lower (P<0.01) than those of the Day-7 and 8 embryos, in all of the cryoprotectants tested. On the other hand, while the reappearance of blastocoele and expansion of blastocysts after 48 h of post-thaw culture were not significantly different among each cryoprotectant, the percentage of hatching blastocysts were significantly different between DEG and EME (P<0.05), between DEG and EG (P<0.01) and between PG and EG (P<0.05). These findings demonstrate that the age of the embryo (Day 7 and 8) is very important for the successful freezing of IVF bovine embryos. Also, as to the hatching rates, EME and EG are superior as cryoprotectants than the other 2 cryoprotectants tested.


Effect of washing, antibiotics and trypsin treatment of bovine embryos on the removal of adhering K99+ Escherichia coli.

Bovine embryos with the intact zona pellucida were exposed in vitro to K99+ Escherichia coli (K99 E. coli). The recommended procedures for washing and treating embryos were then evaluated for their effectiveness in removing or killing the adherent bacteria. After 10-step washing, bacteria were recovered not only from the embryos exposed to E. coli suspensions but also from those treated with trypsin during washing. On the other hand, no bacteria were recovered from any embryos treated with antibiotics (gentamicin; 50 micrograms/ml) in culture medium before washing, indicating that the recommended washing procedures with appropriate antibiotics assure that zona pellucida-intact bovine embryos are free from E. coli.

The Journal of Veterinary Medical Science


Survival rate of frozen-thawed bovine IVM/IVF embryos in relation to post-thaw exposure time in two cryoprotectants.

The relationship between post-thaw exposure time in cryoprotectants and the viability of in vitro fertilized (IVF)-derived bovine embryos after culture was examined. Good- and excellent-quality Day 7 to Day 8 blastocysts and expanded blastocysts were frozen by the nonstepwise method using 1.6 M propylene glycol (PG) or ethylene glycol (EG) as the cryoprotectant. After the straws were thawed, the embryos were kept in the cryoprotectants for 1, 10, or 30 min. Then the embryos were placed directly into culture medium and washed three times, followed by coculture with cumulus cells. After 48 h of culture, there were no significant differences in survival rate among the various exposure times in PG (79-81%) and EG (71-75%). After 72 h of culture, there were no significant differences among the various exposure times in the fully expanded (PG 76-81%; EG 71-72%), hatching (PG 69-74%; EG 58-71%), and hatched blastocyst rates (PG 60-71%; EG 47-65%). Our findings suggest that different post-thaw exposure times up to 30 min using PG or EG as the cryoprotectant are not harmful to IVF bovine embryos.


Developmental capacity of bovine oocytes frozen in different cryoprotectants.

Iso-osmolar concentrations of 1.6 M of 1,2-propanediol, glycerol and dimethylsulfoxide were compared for their effectiveness as cryoprotectants for in vitro-matured bovine oocytes. Survival, defined as the number of morphologically normal oocytes, after freeze-thawing in 1,2-propanediol (49.8%) was significantly higher (P<0.01) than in glycerol (28.6%) or dimethylsulfoxide (32.6%). After insemination, the fertilization rate of morphologically normal oocytes frozen-thawed in 1,2-propanediol (57.9%) was higher (P<0.05) than that of those frozen in dimethylsulfoxide (38.3%). However, the proportion of surviving oocytes developing to blastocysts was not different among the 3 groups.


Effect of trypsin treatment of in vitro fertilized bovine embryos on their subsequent survival and development.

The object of this study was to determine whether several washings with trypsin affected the survival and development of in vitro fertilized (IVF) bovine embryos. The embryos developed to blastocysts 7-8 days after insemination, were washed 12 times in washing medium (modified Dulbecco's phosphate-buffered saline (mPBS) containing 20% fetal bovine serum (FBS): 25 mM Hepes TCM199 with Earle's salts = 1:1), or in a series of three washes in the washing medium, two in mPBS containing 0.3% bovine serum albumin (BSA), two in 0.25% trypsin in Hank's solution (without Ca++ and Mg++) for a total time in the trypsin of 60 to 90 sec and five in the washing medium. After washing, the embryos were either cultured in vitro or cryopreserved. The fresh and frozen-thawed embryos were either cultured for 72 hr in vitro for evaluating development or transferred nonsurgically to recipient cows. Development of fresh and frozen-thawed embryos in vitro in control-washed and trypsin-washed embryos did not differ. Pregnancy rates did not differ (P > 0.05) among recipient cows receiving control-washed or trypsin-washed embryos, and transferring fresh or frozen-thawed embryos. These results indicate that the treatment of bovine IVF embryos with trypsin during washing did not have a positive effect on embryonic development.


Successful vitrification of bovine blastocysts, derived by in vitro maturation and fertilization.

Bovine blastocysts were produced through maturation, fertilization, and development in vitro. For vitrification, solutions designated EFS, GFS, and PFS were prepared; these were 40% ethylene glycol, 40% glycerol, and 40% propylene glycol, respectively, diluted in modified phosphate-buffered saline (PBS) containing 30% Ficoll + 0.5 M sucrose. The embryos were exposed to the solutions in one step at room temperature, kept in the solutions for various times, vitrified in liquid nitrogen, and warmed rapidly. When the embryos were vitrified in EFS solution after 1 or 2 min exposure, the postwarming survival rate, assessed by the reexpansion of the blastocoel, was 74-77%. However, when the exposure time was extended to 3 min or longer, this rate dropped to 7-0%. This reduction was attributed to the toxicity of ethylene glycol. Of the embryos vitrified in GFS solution, 53% survived when they were cooled after 1 min exposure; as the duration of the exposure increased, the survival rate increased, reaching a peak (72%) at 4 min. The rate then decreased gradually with exposure time. In PFS solution, embryos surviving after vitrification were recovered only with 1 min exposure (33%), reflecting the high toxicity of propylene glycol. After vitrification in EFS or GFS solution, two embryos were nonsurgically transferred into each of 14 recipient animals. Of the 14 recipients, ten (71%) became pregnant; two resulted in early stillbirths, four recipients delivered twins (four alive and four stillborn), and two delivered single live calves, demonstrating the effectiveness of this simple vitrification method for the cryopreservation of in-vitro-produced bovine blastocysts.


Effects of different lots of semen from the same bull on in vitro development of bovine oocytes fertilized in vitro.

The effectiveness of 8 different lots of semen from the same bull on the in vitro development of bovine oocytes fertilized in vitro was evaluated. Cleavage and development rates to the blastocyst stage were not significantly different among the 8 lots of semen. However, the cleavage and development rates varied no more than +/-11 and +/-6%, respectively, in overall rates. A maximum of 35.2 and 27.9% difference in cleavage and development rates to the blastocyst stage, respectively, was observed using a single straw from the same semen lot for insemination in 4 trials. This variation tended to be higher than that observed for the cleavage and development rates of oocytes after insemination with double straws from a single lot. These results indicate that the developmental capacity of embryos after insemination are affected by factors associated with a different semen lot from the same bull and with different straws from a single lot.


Developmental capacity of bovine oocytes cryopreserved after maturation in vitro and of frozen-thawed bovine embryos derived from frozen mature oocytes.

The present study was conducted 1) to investigate the post-thaw developmental capacity of in vitro mature bovine oocytes (Metaphase II) frozen by 1.6 M of 1,2-propanediol and 2) to confirm the viability of frozen bovine embryos derived from frozen mature oocytes. The cleavage and developmental rates to the blastocyst stage of frozen-thawed mature oocytes were significantly lower (P<0.01) than that of nonfrozen oocytes. When mature oocytes were treated with hyaluronidase, trypsin, or base solution (solution control) before processing to remove the cumulus cells, the developmental rates to the blastocyst stage of frozen-thawed oocytes were 2.8% (5/180), 3.1% (9/295) and 1.1% (1/89), respectively. The viability and developmental capacity of frozen-thawed bovine embryos derived from frozen mature oocytes were not different from those of frozen-thawed bovine embryos derived from nonfrozen mature oocytes (control). Furthermore, nonfrozen and frozen-thawed embryos derived from frozen-thawed mature oocytes were nonsurgically transferred to recipient cows. One of the four and one of the two recipient cows became pregnant, respectively. The results of this study demonstrated the viability of embryos obtained from frozen-thawed bovine oocytes at Metaphase II followed by in vitro fertilization and culture to the blastocyst stage in vitro.


Effect of antibiotics treatment of in vitro fertilized bovine embryos to remove adhering bacteria.