Single blastomeres as a source of mouse embryonic stem cells: effect of genetic background, medium supplements, and signaling modulators on derivation efficiency

PURPOSE

To assess the role of the genetic background, the culture medium supplements, and the presence of modulators of signaling pathways on mouse embryonic stem cell derivation from single blastomeres from 8-cell embryos.

METHODS

Mice from permissive and non-permissive genetic backgrounds, different culture media supplements, knockout serum replacement (KSR) and N2B27, and the presence or absence of 2i treatment were used to derive mouse embryonic stem cells (mESC) from single blastomeres isolated from 8-cell embryos and from control embryos at the blastocyst stage. After the sixth passage, the putative mESC were analyzed by immunofluorescence to assess their pluripotency and, after in vitro differentiation induction, their ability to differentiate into derivatives of the three primary germ layers. Selected mESC lines derived from single blastomeres in the most efficient culture conditions were further characterized to validate their stemness.

RESULTS

In control embryos, high mESC derivation efficiencies (70-96.9%) were obtained from permissive backgrounds or when embryos were cultured in medium complemented with 2i regardless of their genetic background. By contrast, only blastomeres isolated from embryos from permissive background cultured in KSR-containing medium complemented with 2i were moderately successful in the derivation of mESC lines (22.9-24.5%). Moreover, we report for the first time that B6CBAF2 embryos behave as permissive in terms of mESC derivation.

CONCLUSIONS

Single blastomeres have higher requirements than whole blastocysts for pluripotency maintenance and mESC derivation. The need for 2i suggests that modulation of signaling pathways to recreate a commitment towards inner cell mass could be essential to efficiently derive mESC from single blastomeres.

Resveratrol enhances the clearance of mitochondrial damage by vitrification and improves the development of vitrified-warmed bovine embryos

The present study investigated the vitrification-induced deterioration of mitochondrial functions that may reduce the developmental ability of post-warming bovine embryos. In addition, the effect of supplementation of the culture medium with resveratrol on the mitochondrial functions and post-warming embryonic development was examined. Two days after in vitro fertilization, embryos with 8–12 cells (referred to hereafter as 8-cell embryos) were vitrified and warmed, followed by in vitro incubation for 5 days in a culture medium containing either the vehicle or 0.5 μM resveratrol. Vitrification reduced embryonic development until the blastocyst stage, reduced the ATP content of embryos, and impaired the mitochondrial genome integrity, as determined by real-time polymerase chain reaction. Although the total cell number and mitochondrial DNA copy number (Mt-number) of blastocysts were low in the vitrified embryos, the Mt-number per blastomere was similar among the blastocysts derived from fresh (non-vitrified) and vitrified-warmed embryos. Supplementation of the culture medium with resveratrol enhanced the post-warming embryonic development and reduced the Mt-number and reactive oxygen species level in blastocysts and blastomeres without affecting the ATP content. An increase in the content of cell-free mitochondrial DNA in the spent culture medium was observed following cultivation of embryos with resveratrol. These results suggested that vitrification induces mitochondrial damages and that resveratrol may enhance the development of post-warming embryos and activates the degeneration of damaged mitochondria, as indicated by the increase in the cell-free mitochondrial DNA content in the spent culture medium and the decrease in the Mt-number of blastocysts and blastomeres.

Natrium fluoride influences methylation modifications and induces apoptosis in mouse early embryos

This study epigenetically examined the effect of fluoride on early embryos of Kunming mice administered with 0, 20 (low), 60 (medium), and 120 mg/L (high) sodium fluoride (NaF). The results showed that NaF repressed oocyte maturation, fertilization and blastocyst formation in all NaF-treated groups. Meanwhile, TUNEL assay showed that embryo apoptosis was induced dramatically in blastocyst stage at either low or medium doses, and in 8-cell stage at high dose, compared to the control, suggesting a dose-dependent effect. Furthermore, the immunostaining displayed global increases of DNA methylation, H3K9m2 and H3K4m2 with increasing dose, which were consistent with gene expression results, exhibiting general increases of DNMT1, DNMT3a, G9a, LSD1, and MLL1 and a reduction of JHDM2a in transcription and protein levels. More closely, the differential methylation domain in parentally imprinted gene H19 showed low methylation, while materanlly imprinted gene IGF2 showed high methylaiton in NaF-treated groups compared to the control group, which corresponded with high expression of H19 and low expression of IGF2 confirmed by qPCR. Collectively, we demonstrated that fluoride epigenetically impaired mouse oocyte maturation and embryonic development, supplying a better knowledge of fluoride in toxicology and a deeper evaluation of its potential influence in physiological and clinical implications.

Cyclosporine A improves adhesion and invasion of mouse preimplantation embryos via upregulating integrin β3 and matrix metalloproteinase-9

Our previous study has demonstrated cyclosporin A (CsA) promotes the migration and invasiveness of human first-trimester trophoblast cells in vitro. Here, we further investigated the effect of CsA on the early implantation in vitro of mouse embryo. Female C57 mice were superovulated and mated, and then two-cell embryos were harvested from the oviducts and sequentially cultured in vitro in G1 and G2 media with 0, 0.1, 1.0 or 10 μM of CsA. Blastocyte formation, blastocyte cell number and apoptosis, embryo hatching were assessed in 4-6 dpc. The adhesion and stretching growth of hatched embryos in laminin coated dishes were evaluated from 5 dpc to 8 dpc, and the expressions of implantation serine proteinase 1 (ISP1), integrin (itg) β3 and matrix metalloproteinase (MMP)-9 were determined by real time PCR and immunofluorescence, respectively. We showed there was no significant difference in blastocyst formation rates, hatching rates, number of whole embryonic cells, apoptotic cells, and distribution of inner cell masses (ICMs) and trophoblasts (TB) between the CsA- and control-treated groups. Expression of ISP1 mRNA was unaffected on 5 dpc. After hatching, adhesion rate of 7 dpc significantly increased in 0.1 and 1.0 μM of CsA treatment, and embryo area of 8 dpc stretch growing on laminin were increased in 1.0 μM of CsA. The mRNA and protein expression of itgβ3 and MMP-9 on 7 dpc blastocyst were up-regulated. In conclusion, CsA in low dosage up-regulates itgβ3 and MMP-9 expression, and enhances embryonic adhesion and invasion, which is beneficial to the embryo implantation.

Serotonin has early, cilia-independent roles in Xenopus left-right patterning

Consistent left-right (LR) patterning of the heart and viscera is a crucial part of normal embryogenesis. Because errors of laterality form a common class of birth defects, it is important to understand the molecular mechanisms and stage at which LR asymmetry is initiated. Frog embryos are a system uniquely suited to analysis of the mechanisms involved in orientation of the LR axis because of the many genetic and pharmacological tools available for use and the fate-map and accessibility of early blastomeres. Two major models exist for the origin of LR asymmetry and both implicate pre-nervous serotonergic signaling. In the first, the charged serotonin molecule is instructive for LR patterning; it is redistributed asymmetrically along the LR axis and signals intracellularly on the right side at cleavage stages. A second model suggests that serotonin is a permissive factor required to specify the dorsal region of the embryo containing chiral cilia that generate asymmetric fluid flow during neurulation, a much later process. We performed theory-neutral experiments designed to distinguish between these models. The results uniformly support a role for serotonin in the cleavage-stage embryo, long before the appearance of cilia, in ventral right blastomeres that do not contribute to the ciliated organ.

[Cyto B dependent and ouabain insensitive regulatory volume decrease in bicellular mouse embryo]

Mouse single-cell embryos exhibit robust Regulatory Volume Decrease (RVD). In what manner the very early mammalian embryo following zygote stage is appreciably altered by the anisotonic extracellular solution is, as yet, totally unclear. Little attention was paid to this direction since there was no way to determine the blastomere volume. This work has served to quantitatively investigate the osmotic response of bicellular mouse embryos employing Laser Scanning Microtomography (LSM) followed with three-dimensional reconstruction (3 DR). We have shown that bicellular mouse embryos in hypotonic Dulbecco's experience RVD. Embryonic cells subjected to hyposmolar exhibit rapid osmotic swelling followed by gradual shrinking back toward their original volume. The van't Hoff law defines swelling phase with the effective hydraulic conductivity of 0.3 micron x min(-1) x atm(-1). Water release during RVD in bicellular mouse embryos is abolished by Cytochalasin B (Cyto B) and the volume recovery is insensitive to ouabain treatment.

Simple and efficient derivation of mouse embryonic stem cell lines using differentiation inhibitors or proliferation stimulators

The inhibition of endogenous differentiation-inducing signaling or the enhancement of growth capacity and viability of preimplantation embryos, via 2i (PD0325901 and CHIR99021), dramatically improves the establishment of mouse embryonic stem cells (mESCs). Using adrenocorticotropic hormone fragments 1-24 (ACTH 1-24), which enhances survival and/or proliferation of mESCs, also increases the derivation of mESCs from single blastomeres significantly. The CHIR99021 pathway and the proposed ACTH pathway are likely different. Therefore, this study aimed to assess the synergetic effects of 2i and ACTH 1-24 on derivation of mESCs. Results in the present study demonstrate that germline-transmitted mESCs could be efficiently derived from ICR and C57BL/6J at 0.5-4.5 days postcoitum denuded zygotes to blastocysts or isolated blastomeres of 2-8-cell embryos and cultured in 10 μL droplets with human foreskin fibroblast (Hs68) or STO (a mouse embryonic fibroblast line) feeders and in knockout serum replacement (KSR) ESC medium containing 2i or ACTH 1-24. The overall success rates for C57BL/6J and ICR were 56.2% when cultured in 2i+ACTH 1-24, 26.6% in 2i, 6.7% in ACTH 1-24, and 4.8% in KSR ESC medium. These results imply that CHIR99021 and ACTH 1-24 are synergistically enhancing the establishment of mESCs. The proposed protocol also demonstrates a highly efficient and reproducible method, has a simple layout, is easy to apply, and could be used as an alternative method for routinely establishing mESC lines.

Manipulating and imaging the early Xenopus laevis embryo

Over the past half century, the Xenopus laevis embryo has become a popular model system for studying vertebrate early development at molecular, cellular, and multicellular levels. The year-round availability of easily fertilized eggs, the embryo's large size and rapid development, and the hardiness of both adults and offspring against a wide range of laboratory conditions provide unmatched advantages for a variety of approaches, particularly "cutting and pasting" experiments, to explore embryogenesis. There is, however, a common perception that the Xenopus embryo is intractable for microscope work, due to its store of large, refractile yolk platelets and abundant cortical pigmentation. This chapter presents easily adapted protocols to surmount, and in some cases take advantage of, these optical properties to facilitate live-cell microscopic analysis of commonly used experimental manipulations of early Xenopus embryos.

[A "micromere model" of cellular interactions in sea urchin embryos]

It has been shown that the isolation of sea urchin blastomeres before "pos-division adhesion" leads mainly to the formation of similar blastomeres at the stage of the 4th cleavage division, whereas after adhesion it results in the formation of micromeres simultaneously with intact embryos. Similar results were obtained in five sea urchin species. It has been concluded that there exists a critical point in the cleavage process, when blastomeres exchange information that determines further pattern of cleavage. It has been shown on this "micromere model" that serotonin and its analogues influence the cleavage pattern of half embryos. These data served as a basis for the hypothesis of "protosynapse", a double-sided symmetric structure in which both blastomeres are not only source and a target of the signal but also a passive obstacle for the leakage of the signal substance from the interblastomere cleft to the milieu. Such a structure is also able to provide the primary asymmetry of blastomeres. The micromere model may be useful in specific pharmacological screening.

Distinct embryotoxic effects of lithium appeared in a new assessment model of the sea urchin: the whole embryo assay and the blastomere culture assay

Early embryogenesis is one of the most sensitive and critical stages in animal development. Here we propose a new assessment model on the effect of pollutant to multicellular organism development. That is a comparison between the whole embryo assay and the blastomere culture assay. We examined the LiCl effect on the sea urchin early development in both of whole embryos and the culture of isolated blastomeres. The mesoderm and endoderm region were capable to differentiate into skeletogenic cells when they were isolated at 60-cell stage and cultured in vitro. The embryo developed to exogastrula by the vegetalizing effect of the same LiCl condition where ectodermal region changed their fate to endoderm, while the isolated blastomeres from the presumptive ectoderm region differentiated into skeletogenic cells in the culture with LiCl. The effect of LiCl to the sea urchin embryo and to the dissociated blastomere is a unique example where same cells response distinctly to the same agent depend on the condition around them. Present results show the importance of examining the process in cellular and tissue levels for the exact understanding on the morphological effect of chemicals and metals.

Differential cytotoxic effects of mono-(2-ethylhexyl) phthalate on blastomere-derived embryonic stem cells and differentiating neurons

Potential applications of embryonic stem (ES) cells are not limited to regenerative medicine but can also include in vitro screening of various toxicants. In this study, we established mouse ES cell lines from isolated blastomeres of two-cell stage embryos and examined their potential use as an in vitro system for the study of developmental toxicity. Two ES cell lines were established from 69 blastomere-derived blastocysts (2.9%). The blastomere-derived ES (bm-ES) cells were treated with mono-(2-ethylhexyl) phthalate (MEHP) in an undifferentiated state or after directed differentiation into early neural cell types. We observed significantly decreased cell viability when undifferentiated bm-ES cells were exposed to a high dose of MEHP (1000 microM). The cytotoxic effects of MEHP were accompanied by increased DNA fragmentation, nuclear condensation, and activation of Caspase-3, which are biochemical and morphological features of apoptosis. Compared to undifferentiated bm-ES cells, considerably lower doses of MEHP (50 and 100 microM) were sufficient to induce cell death in early neurons differentiated from bm-ES cells. At the lower doses, the number of neural cells positive for the active form of Caspase-3 was greater than that for undifferentiated bm-ES cells. Thus, our data indicate that differentiating neurons are more sensitive to MEHP than undifferentiated ES cells, and that undifferentiated ES cells may have more efficient defense systems against cytotoxic stresses. These findings might contribute to the development of a new predictive screening method for assessment of hazards for developmental toxicity.

Cryopreservation of zebrafish (Danio rerio) blastomeres by controlled slow cooling

Cryopreservation is now a common practice in the fields of aquaculture, conservation and biomedicine. One approach for maintaining the genetic diversity of both nuclear genome and mitochondrial DNA is cryopreservation of the blastomere. This study sets out to determine an optimum cryopreservation protocol for blastomeres isolated from 50% epiboly zebrafish embryos. Freezing was performed in 0.25 ml straws in a programmable freezer. The optimum slow cooling protocol is identified as 5 degree C per min, from 22 to -6 degree C, holding for 15 min, 0.3 degree C per min from -6 to -40 degree C, 2 degree C per min from -40 to -80 degree C, cells were held for 10 min at -80 degree C before plunging into the liquid nitrogen. Thawing was performed in a water bath at 28 degrees C for 15 s followed by four step-wise removal of the cryoprotectant. Blastomeres had the highest survival level (70.2 +/- 3.2%) when a mixture of 1.5 M dimethyl sulfoxide (DMSO) and 0.1 M sucrose were used as cryoprotectants. This was higher than that achieved with either of the sugar alternatives, trehalose (60.6 +/- 3.1%) or glucose (43.1 +/- 4.9%). In the present study, cryopreservation of 50 percent epiboly zebrafish blastomeres was studied for the first time using controlled slow cooling method.

Comparison of toxicity of smoke from traditional and harm-reduction cigarettes using mouse embryonic stem cells as a novel model for preimplantation development

BACKGROUND

Embryonic stem cells (ESC), which originate from the inner cell mass of blastocysts, are valuable models for testing the effects of toxicants on preimplantation development. In this study, mouse ESC (mESC) were used to compare the toxicity of mainstream (MS) and sidestream (SS) cigarette smoke on cell attachment, survival and proliferation. In addition, smoke from a traditional commercial cigarette was compared with smoke from three harm-reduction brands.

METHODS

MS and SS smoke solutions were made using an analytical smoking machine and tested at three doses using D3 mESC plated on 0.2% gelatin. At 6 and 24 h, images were taken and the number of attached cells was evaluated.

RESULTS

Both MS and SS smoke from traditional and harm-reduction cigarettes inhibited cell attachment, survival and proliferation dose dependently. For all brands, SS smoke was more potent than MS smoke. However, removal of the cigarette filter increased the toxicity of MS smoke to that of SS smoke. Both MS and SS smoke from harm-reduction cigarettes were as inhibitory, or more inhibitory, than their counterparts from the traditional brand. When preimplantation mouse embryos were cultured for 1 h in MS or SS smoke solutions from a harm-reduction brand, blastomeres became apoptotic, in agreement with the data obtained using mESC.

CONCLUSIONS

mESC provide a valuable model for toxicological studies on the preimplantation stage of development and were used to show that MS and SS smoke from traditional and harm-reduction cigarettes are detrimental to embryonic cells prior to implantation.

Chemical enhancement in embryo development and stem cell derivation from single blastomeres

Several chemicals targeting the mitogen-activated protein (MAP) kinase signaling pathway, which play an important role in regulating cell growth and differentiation, have shown enhancing effects on the development of the inner cell mass (ICM) and the derivation of ES cells. However, investigation of such chemicals on early embryonic development and the establishment of ES cell lines has not been elucidated. This study was aimed to determine if ACTH, MAP2K1 inhibitor [MAP2K1 (I)], and MAPK14 inhibitor [MAPK14 (I)] could enhance the development of the ICM in preimplantation mouse embryos and blastocyst outgrowths, and the establishment of ES cell lines from blastomeres of early embryos. We have demonstrated that both MAP2K1 (I) and MAPK14 (I) delay early embryo development and inhibit the development of embryos from early blastomeres. On the other hand, ACTH had a positive effect on embryos derived from early blastomeres. As a result, 17 ES cell lines were established. Among these ES cell lines, nine and five ES cell lines were established from single blastomeres of two-cell embryos with and without the supplement of ACTH, respectively. In addition to two-cell isolated blastomeres, three ES cell lines were established from blastomeres of four-cell embryos only with the supplement of ACTH. Our results suggest that ACTH can enhance the derivation of ES cells from single blastomere-derived embryos.

Peroxisome proliferator-activated receptor-gamma agonist rosiglitazone reverses the adverse effects of diet-induced obesity on oocyte quality

Obesity and its physiological consequences are increasingly prevalent among women of reproductive age and are associated with infertility. To investigate, female mice were fed a high-fat diet until the onset of insulin resistance, followed by assessments of ovarian gene expression, ovulation, fertilization, and oocyte developmental competence. We report defects to ovarian function associated with diet-induced obesity (DIO) that result in poor oocyte quality, subsequently reduced blastocyst survival rates, and abnormal embryonic cellular differentiation. To identify critical cellular mediators of ovarian responses to obesity induced insulin resistance, DIO females were treated for 4 d before mating with an insulin-sensitizing pharmaceutical: glucose and lipid-lowering AMP kinase activator, 5-aminoimidazole 4-carboxamide-riboside, 30 mg/kg.d; sodium salicylate, IkappaK inhibitor that reverses insulin resistance, 50 mg/kg.d; or peroxisome proliferator activated receptor-gamma agonist rosiglitazone, 10 mg/kg.d. 5-aminoimidazole 4-carboxamide-riboside or sodium salicylate treatment did not have significant effects on the reproductive parameters examined. However, embryonic development to the blastocyst stage was significantly improved when DIO mice were treated with rosiglitazone, effectively repairing development rates. Rosiglitazone also normalized DIO-associated abnormal blastomere allocation to the inner cell mass. Such improvements to oocyte quality were coupled with weight loss, improved glucose metabolism, and changes in ovarian mRNA expression of peroxisome proliferator activated receptor-regulated genes, Cd36, Scarb1, and Fabp4 cholesterol transporters. These studies demonstrate that peri-conception treatment with select insulin-sensitizing pharmaceuticals can directly influence ovarian functions and ultimately exert positive effects on oocyte developmental competence. Improved blastocyst quality in obese females treated with rosiglitazone before mating indicates that peroxisome proliferator activated receptor-gamma is a key target for metabolic regulation of ovarian function and oocyte quality.

Mesenchymal cell fusion in the sea urchin embryo

Mesenchymal cells of the sea urchin embryo provide a valuable experimental model for the analysis of cell-cell fusion in vivo. The unsurpassed optical transparency of the sea urchin embryo facilitates analysis of cell fusion in vivo using fluorescent markers and time-lapse three-dimensional imaging. Two populations of mesodermal cells engage in homotypic cell-cell fusion during gastrulation: primary mesenchyme cells and blastocoelar cells. In this chapter, we describe methods for studying the dynamics of cell fusion in living embryos. These methods have been used to analyze the fusion of primary mesenchyme cells and are also applicable to blastocoelar cell fusion. Although the molecular basis of cell fusion in the sea urchin has not been investigated, tools have recently become available that highlight the potential of this experimental model for integrating dynamic morphogenetic behaviors with underlying molecular mechanisms.

Derivation of human embryonic stem cells from single blastomeres

This protocol details a method to derive human embryonic stem (hES) cells from single blastomeres. Blastomeres are removed from morula (eight-cell)-stage embryos and cultured until they form multicell aggregates. These blastomere-derived cell aggregates are plated into microdrops seeded with mitotically inactivated feeder cells, and then connected with neighboring microdrops seeded with green fluorescent protein-positive hES cells. The resulting blastomere-derived outgrowths are cultured in the same manner as blastocyst-derived hES cells. The whole process takes about 3-4 months.

Diets enriched in unsaturated fatty acids enhance early embryonic development in lactating Holstein cows

We hypothesized that a diet enriched in alpha-linolenic acid would enhance embryonic development relative to diets enriched in linoleic or saturated fatty acids. Twenty-four lactating Holstein cows (86+/-22 d postpartum) were assigned to one of three diets containing saturated fatty acids (SAT; high in palmitic and stearic acids), whole flaxseed (FLX; high in alpha-linolenic acid) or sunflower seed (SUN; high in linoleic acid). Rations were formulated to provide 750 g supplemental fat/cow/d in all dietary groups. Ovulation (Day 0) was synchronized approximately 20 d after diets began. Ultrasound-guided follicular ablation of all follicles >8 mm was performed 5 d after ovulation; super stimulatory treatments began 2 d after follicular ablation, and embryos were collected non-surgically 7 d after AI. Fertilization rate, numbers of follicles and ovulations, and total and transferable embryos did not differ (P>0.05) among dietary groups. Sixty-one transferable embryos were stained and total blastomere number determined. Blastomere number was affected by diet (P<0.01); without regard to stage of development, embryos collected from cows fed SAT had lower (P<0.01) blastomere numbers (mean+/-S.E.M.; 77.1+/-3.9) than those from cows fed FLX (93.4+/-3.3) or SUN (97.2+/-3.5). Differences were most evident in the expanded blastocyst stage; at this stage, embryos of cows fed FLX and SUN diets had more blastomeres (P<0.02) than those of cows fed SAT (115.4+/-6.3, 132.3+/-8.3, and 89.3+/-9.6 cells, respectively). Although our hypothesis was only partially supported, embryonic development was enhanced in Holstein cows fed unsaturated fatty acids compared to those fed saturated fatty acids.

Vitrification of zebrafish embryo blastomeres in microvolumes

Cryopreservation of fish embryos may play an important role in biodiversity preservation and in aquaculture, but it is very difficult. In addition, the cryopreservation of fish embryo blastomeres makes conservation strategies feasible when they are used in germ-line chimaerism, including interspecific chimaerism. Fish embryo blastomere cryopreservation has been achieved by equilibrium procedures, but to our knowledge, no data on vitrification procedures are available. In the present work, zebrafish embryo blastomeres were successfully vitrified in microvolumes: a number of 0.25 microl drops, sufficient to contain all the blastomeres of an embryo at blastula stage (from 1000-cell stage to oblong stage), were placed over a 2.5 cm loop of nylon filament. In this procedure, where intracellular cryoprotectant permeation is not required, blastomeres were exposed to cryoprotectants for a maximum of 25 sec prior vitrification. The assayed cryoprotectants (ethylene glycol, propylene glycol, dimethyl sulphoxide, glycerol and methanol) are all frequently used in fish embryo and blastomere cryopreservation. Methanol was finally rejected because of the excessive concentration required for the vitrification (15M). All other cryoprotectants were prepared (individually) at 5 M in Hanks' buffered salt solution (sigma) plus 20% FBS (vitrification solutions: vs). After direct thawing in Hanks' buffered salt solution plus 20% FBS, acceptable survival rates were obtained with ethylene glycol: 82.8%, propylene glycol: 87.7%, dimethyl sulphoxide: 93.4%, and glycerol: 73.9% (p < 0.05). Dimethyl sulphoxide showed the highest blastomere survival rate and allowed the rescue of as much as 20% of the total blastomeres from each zebrafish blastula embryo.

[Effect of local microapplication of serotoninergic drugs on membrane currents of Paracentrotus lividus early embryos]

It was shown that local application of agonists of the 3rd type receptors SR57277A and quipazine into the interblastomere cleft of Paracentrotus lividus embryos evoked specific membrane currents. At the same time, ligands of 5-HT3-receptors specifically affected the cleavage patterns of half-embryos, i.e., imitated or avoided the interblastomere signal. In the view of the data obtained, we discuss a more precise concept of protosynapse, where the distribution of membrane serotonin receptors is restricted to the period of blastomere formation during cleavage and localized in the area of interblastomere contact.

Focal adhesion kinase signaling at sites of integrin-mediated adhesion controls axon pathfinding

Extracellular matrix (ECM) components regulate neurite outgrowth in tissue culture and in vivo. Live imaging of phosphotyrosine (PY) signals revealed that Xenopus laevis growth cones extending on permissive ECM substrata assemble adhesive point contacts containing enriched levels of tyrosine-phosphorylated proteins. Whereas focal adhesion kinase (FAK) signaling is dispensable for the assembly of focal adhesions in non-neuronal cells, FAK activity is required for the formation of growth cone point contacts. FAK-dependent point contacts promote rapid neurite outgrowth by stabilizing lamellipodial protrusions on permissive ECM substrata. Moreover, local FAK activity is required for ECM-dependent growth cone turning in vitro, suggesting that FAK may control axon pathfinding in vivo. Consistent with this possibility, proper growth and guidance of Rohon-Beard sensory neurons and spinal commissural interneurons requires FAK activity. These findings identify FAK as a key regulator of axon growth and guidance downstream of growth cone-ECM interactions.

Production of porcine cloned transgenic embryos expressing green fluorescent protein by somatic cell nuclear transfer

In the present study, nuclear transferred embryos (NTEs) were reconstructed by using pig fetal fibroblasts as donors and in vitro matured oocytes as recipients. The effects of G418 selection on donor cells, duration of IVM of prepubertal gilt oocytes and oxygen tension in IVM of oocytes were investigated. The results were as follows: (i) When G418 selected cells expressing GFP were used as donors, the cleavage rate of NTEs decreased drastically in comparison to NTEs derived from donors without antibiotic selection (47.5% vs. 71.6%, p < 0.05). For the blastocyst rate, no significant difference was observed between two groups (10% vs. 10.4%, p > 0.05). (ii) The rate of nuclear maturation of oocytes increased significantly when IVM duration time was extended from 36 to 42 h (83.6% vs. 96.7%, p < 0.05). However, no statistical difference was observed between NTEs derived from oocytes of 36 h IVM group and NTEs from oocytes of 42 h IVM group in the rates of cleavage (59.3% vs. 73.6%, p > 0.05) and blastocyst formation (9.3% vs. 13.2%, p > 0.05); (iii) no significant difference was observed between NTEs reconstructed from oocytes matured under lower oxygen (7% O2) tension and NTEs derived from oocytes matured under higher oxygen tension (20% O2) in cleavage rate (70.6% vs. 67.1%, p > 0.05) and blastocyst rate (11.8% vs. 12.3%, p > 0.05). These results suggest that: (i) G418 selection does not have a significant effect on cleavage rate of NTEs expressing GFP. (ii) Nuclear maturation is greatly improved by prolonging IVM duration from 36 to 42 h, while no significant differences were observed for developmental potential of transgenic embryos. Thus IVM 42 h is the better choice in order to obtain maximum number of M II oocytes as recipients. (iii) Lower oxygen tension and higher oxygen tension in IVM have no significant effect on development of cloned embryos.

Meiotic arrest in vitro by phosphodiesterase 3-inhibitor enhances maturation capacity of human oocytes and allows subsequent embryonic development

Controlling nuclear maturation during oocyte culture might improve nuclear-cytoplasmic maturation synchrony. We aimed to evaluate the quality of in vitro-matured, germinal vesicle (GV)-stage human oocytes following a prematuration culture (PMC) with a meiotic arrester, phosphodiesterase 3-inhibitor (PDE3-I). Follicles (diameter, 6-12 mm) were retrieved 34-36 h post-hCG administration from informed, consenting patients who had undergone controlled ovarian stimulation. Cumulus-enclosed oocytes (CEOs) presenting moderate expansion or full compaction were placed in PMC with the PDE3-I, Org9935, for 24 or 48 h. Subsequently, oocytes were removed from PMC, denuded of cumulus cells, matured in vitro, and fertilized, and the resulting embryos were cultured. In the presence of PDE3-I, approximately 98% of the oocytes were arrested at the GV stage. Following PDE3-I removal, oocytes acquired a higher maturation rate than oocytes that were immediately denuded of cumulus cells after retrieval and in vitro matured (67% vs. 46%, P = 0.01). In controls, immature CEOs retrieved with moderate expansion reached higher maturation rates compared to fully compacted CEOs, but in PMC groups, high values of maturation were achieved for both morphological classes of CEOs. No effect of PMC on fertilization was observed. A 24-h PMC period proved to be the most effective in preserving embryonic integrity. Similar proportions of nuclear abnormalities were observed in embryos of all in vitro groups. In summary, PMC with the specific PDE3-I had a beneficial effect on human CEOs by enhancing maturation, benefiting mainly the fully compacted CEOs. This resulted in an increased yield of mature oocytes available for insemination without compromising embryonic development. These results suggest that applying an inhibitor to control the rate of nuclear maturity by regulating intraoocyte PDE3 activity may allow the synchronization of nuclear and ooplasmic maturation.

Impact of follicular-fluid meiosis-activating sterol in an albumin-based formulation on the incidence of human pre-embryos with chromosome abnormalities

OBJECTIVE

To evaluate the effect of adding follicular-fluid meiosis-activating sterol (FF-MAS) in a novel 0.2% recombinant human albumin-based formulation to cumulus-enclosed oocytes on chromosomal status and development of pre-embryos.

DESIGN

Multicenter, prospective, randomized, open (double-blind for vehicle and FF-MAS groups), four parallel groups, controlled trial.

SETTING

Four public IVF clinics in Denmark.

PATIENT(S)

Two hundred eighteen women undergoing IVF donated 483 oocytes.

INTERVENTION(S)

Follicle-stimulating hormone/hCG-primed cumulus-enclosed oocytes randomized to 4 hours of exposure to medium with 1 or 10 micromol/L of FF-MAS dissolved in 0.2% recombinant human albumin, medium with 0.2% recombinant human albumin (vehicle control), or medium alone (control) before insemination.

MAIN OUTCOME MEASURE(S)

Primary endpoint: incidence of human pre-embryos with chromosomal abnormalities. Secondary endpoint: fertilization rate, cleavage rate, and pre-embryo quality assessed after 68 hours of culture.

RESULT(S)

At pre-embryo level, the overall abnormality rates in the control, vehicle control, and 1- and 10-micromol/L FF-MAS groups were 53%, 39%, 42%, 53%, respectively, and at blastomere level 49%, 44%, 44%, and 48%, respectively. After 20 and 26 hours, the fertilization rates were between 67% and 71% in all groups. No differences in the cleavage rates were observed.

CONCLUSION(S)

The concentrations of FF-MAS in a novel 0.2% recombinant human albumin-based formulation of FF-MAS did not increase the risk of chromosomal abnormalities in pre-embryos or blastomeres. No statistically significant differences in fertilization rate, cleavage rate, or number of good quality pre-embryos were found among the four groups.

Gonadotropin-releasing hormone I analog acts as an antiapoptotic factor in mouse blastocysts

Both GnRH-I and its receptor (GnRHR)-I have been shown to be expressed in the mammalian preimplantation embryo. In this study, we investigated the molecular mechanisms of GnRH-I in the regulation of early embryonic development in mouse. We found that GnRH-I and GnRHR-I mRNAs were detectable throughout early embryonic stages and that expression levels of both increased significantly after the early blastocyst stage. In blastocysts, GnRH-I and GnRHR-I expression was detected in both inner cell mass and trophectoderm cells. The pregnant uterus also expressed both genes, suggesting that preimplantation embryos could be affected by GnRH through both paracrine and autocrine signaling. Treatment with GnRH-I agonist, buserelin, promoted development of two-cell-stage embryos to the expanded and hatched blastocyst stages and inhibited apoptosis in a dose-dependent manner. In contrast, treatment with GnRH-I antagonist, ganirelix acetate, inhibited development of preimplantation embryos beyond the expanded blastocyst stage and induced apoptosis; both effects could be reversed by cotreatment with GnRH-I agonist. GnRH-I antagonist-induced cell death was mediated by disruption of mitochondrial function, release of cytochrome c, and activation of caspase-3. Furthermore, treatment with GnRH-I antagonist decreased expression of two antiapoptotic growth factors, epidermal growth factor and IGF-II, in blastocysts. These results indicate that GnRH-I, acting as an antiapoptotic factor, is an important growth factor in development of mouse blastocysts.

Permeability of mouse oocytes and embryos at various developmental stages to five cryoprotectants

To assess the permeability of mouse oocytes and embryos, matured oocytes and embryos at various stages of development were placed in five cryoprotectant solutions at 25 C for 25 min. From the cross-sectional areas of the oocytes/embryos, the relative change in volume was analyzed. In oocytes, shrinkage was least extensive and recovery was quickest in the propylene glycol solution, showing that propylene glycol permeates the oocytes most rapidly. Dimethyl sulfoxide, acetamide, and ethylene glycol permeated the oocytes slightly more slowly than propylene glycol. The oocytes in glycerol shrunk extensively and then expanded marginally, indicating slow permeation. The volume changes of 1-cell and 2-cell embryos were similar to those of oocytes, showing little change in permeability. In 8-cell embryos, the volume recovered much faster than in the earlier stages especially in glycerol and acetamide. In morulae, the volume recovery was much faster in glycerol and in ethylene glycol; in ethylene glycol, the extent of shrinkage was small and the recovery was fast, indicating an extremely rapid permeation. Although the permeability of oocytes/embryos generally increased as embryo development proceeded, the degree of increase varied greatly among the cryoprotectants. Interestingly, the volume change in propylene glycol was virtually unaffected by the stage of development. Such information will be valuable for determining a suitable protocol for the cryopreservation of oocytes/embryos at different stages of development.

Synthesis, structural investigations on organotin(IV) chlorin-e6 complexes, their effect on sea urchin embryonic development and induced apoptosis

Four new organotin(IV) chlorin derivatives, [chlorin=chlorin-e(6)=21H,23H-porphine-2-propanoic acid, 18-carboxy-20-(carboxymethyl)-8-ethenyl-13-ethyl-2,3-di-hydro-3,7,12,17-tetramethyl-(2S-trans)-], with formula (R(2)Sn)(3)(chlorin)(2).2H(2)O (R=Me, n-Bu) and (R(3)Sn)(3)chlorin.2H(2)O (R=Me, Ph) have been synthesized. The solid state and solution phase structures have been investigated by FT-IR, (119)Sn Mössbauer, (1)H and (13)C NMR spectroscopy. In the solid state, (R(2)Sn)(3)(chlorin)(2).2H(2)O complexes contain six coordinated Sn(IV), in a skew trapezoidal environment by forming trans-R(2)SnO(4) polymeric units. As far as (R(3)Sn)(3)chlorin.2H(2)O complexes are concerned, Sn(IV) is five coordinated in a polymeric (oligomeric) trigonal bipyramidal environment and eq-R(3)SnO(2) units, in the solid state. In saturated solutions, a polymeric structure comparable to the solid phase, with carboxylate groups of the ligand behaving in monoanionic bidentate fashion bridging Sn(IV) atoms, was detected for the (Me(3)Sn)(3)chlorin.2H(2)O complex, while in more diluted ones a tetrahedral configuration for the trimethyltin(IV) moieties was observed. Cytotoxic activity of the novel organotin(IV) chlorin was investigated in order to assay the effect on sea urchin embryonic development. The results obtained demonstrated that (n-Bu(2)Sn)(3)(chlorin)(2).2H(2)O and (Ph(3)Sn)(3)chlorin.2H(2)O exerted the antimitotic effect on the early stages of sea urchin development. In addition, the cytotoxic effect exerted by (n-Bu(2)Sn)(3)(chlorin)(2).2H(2)O appeared with necrosis of the blastomeres, which were clearly destroyed. After treatment with (Ph(3)Sn)(3)chlorin.2H(2)O, a programmed cell death was triggered, as shown by light microscope observations through morphological assays. The apoptotic events in 2-cell stage embryos revealed: (i) DNA fragmentation, with the TUNEL reaction (terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling); (ii) phosphatidylserine translocation in the membrane, with Annexin-V assay and (iii) cytoplasm blebbing, with the TUNEL reaction. The results demonstrated that the novel compound (Ph(3)Sn)(3)chlorin.2H(2)O was the most toxic derivative, by exerting antimitotic effect very early and by triggering apoptosis in the 2-cell stage of sea urchin embryonic development.

[Variance analysis of Cd2+, Zn2+, and Mn2+ effect on membrane Na+,K(+)-ATPase activity of loach embryos]

The evaluation of influences Cd2+, Zn2+, Mn2+ in concentrations 10(-6), 10(-5), 10(-4) M (factor of dose) on the Na+, K(+)-ATP-ase activity in the early period of development (60-330 min.) of loach embryos (time factor) using one- and two-factor analysis of variance has been performed. It has been detected, that the changes of enzyme activity are mainly caused by action of the explored cations and do not depend on time of embryos development. The most influence on activity in the indicated period of embryos development of loach renders Cd2+ in concentration 10(-4) M, relative value of its influence being 95.7% (p = 0.01). Substantial concentration dependence of the Na+, K(+)-ATP-ase activity is exposed to the action of each of cations. The values of the influence of their concentration changes during the studied period of development differ insignificantly for all cations and make 76.2-77.5% (p < 0.01).

The first cleavage of the mouse zygote predicts the blastocyst axis

One of the unanswered questions in mammalian development is how the embryonic-abembryonic axis of the blastocyst is first established. It is possible that the first cleavage division contributes to this process, because in most mouse embryos the progeny of one two-cell blastomere primarily populate the embryonic part of the blastocyst and the progeny of its sister populate the abembryonic part. However, it is not known whether the embryonic-abembryonic axis is set up by the first cleavage itself, by polarity in the oocyte that then sets the first cleavage plane with respect to the animal pole, or indeed whether it can be divorced entirely from the first cleavage and established in relation to the animal pole. Here we test the importance of the orientation of the first cleavage by imposing an elongated shape on the zygote so that the division no longer passes close to the animal pole, marked by the second polar body. Non-invasive lineage tracing shows that even when the first cleavage occurs along the short axis imposed by this experimental treatment, the progeny of the resulting two-cell blastomeres tend to populate the respective embryonic and abembryonic parts of the blastocyst. Thus, the first cleavage contributes to breaking the symmetry of the embryo, generating blastomeres with different developmental characteristics.

Heparanase improves mouse embryo implantation

OBJECTIVE

To improve mouse embryonic implantation by recombinant heparanase supplementation. Heparanase, an endoglycosidase-degrading heparan sulfate proteoglycan, may have a role in embryonic implantation because of its enzymatic, angiogenic, and adhesive properties. Increasing endometrial receptivity could improve one of the most difficult pathologies in human fertility.

DESIGN

Comparison between mouse blastocysts obtained after 24-hour incubation of morulae with or without heparanase.

SETTING

Experimental laboratory in a medical center.

ANIMAL(S)

Mice.

INTERVENTION(S)

Morulae were flushed from CB6F1 female mice and incubated for 24 hours at 37 degrees C in M16 medium supplemented with 0.1 mg/mL heparanase (n = 203), with albumin (n = 60), or with medium alone (n = 258).

MAIN OUTCOME MEASURE(S)

Blastocysts were evaluated by heparanase immunostaining (n = 10), activity assay (n = 283), and transfer to foster mice uterine horns (n = 228). The number of implantation sites was compared.

RESULT(S)

Immunostaining demonstrated that heparanase is constitutively expressed in mouse morulae and blastocyts. Heparanase supplementation resulted in increased staining and enzymatic activity in blastocyts. Implantation rates for the heparanase, M16 medium, and albumin groups, were 36.9%, 17.8%, and 20%, respectively (P<.01).

CONCLUSION(S)

Heparanase was found to be constitutively expressed by blastocyst-stage embryos. Moreover, the amount of heparanase was markedly increased by incubation of morulae with recombinant heparanase, evaluated by immunostaining and enzymatic activity. Heparanase supplementation resulted in approximately a twofold increase in embryo implantation rate in vivo. Taken together, these data suggest that heparanase is actively involved in embryo implantation.

Mifepristone (Ru486) antagonizes monocyte chemotactic protein-3 down-regulation at early mouse pregnancy revealing immunomodulatory events in Ru486 induced abortion

PROBLEM

The survival of an embryo bearing the paternal antigens within the immunocompetent environment of the maternal uterus renders 'pregnancy' to be a state of immunological paradox. The ratio of Th1/Th2 responses is crucial for pregnancy maintenance. Monocyte Chemotactic Protein-3 (MCP3) is a pro-inflammatory, CC chemokine and a Th1 effector which is capable of eliciting significant anti-tumoral immune responses.

METHOD OF STUDY

MCP3 expression was investigated in the murine uterine tissue at different days of initial pregnancy and the effect of RU 486 in immature and delayed implantation model studied using Western blotting and Immunocytochemical techniques.

RESULTS AND CONCLUSION

Our results show very high uterine MCP3 expression during pre-implantation followed by a significant MCP3 down-regulation at peri-implantation and low levels of MCP3 during post-implantation period. At the peri-implantation stage, embryos exhibited lowered MCP3 expression when compared with the pre-implantation stage. Ru486, a progesterone antagonist when given in a competitive mode with progesterone resulted in a massive surge in MCP3 expression in both immature mice and delayed implantation models. We hypothesize that it is imperative for MCP3 expression to be down-regulated for the success of pregnancy. The cross-talk between Ru486 and amplified MCP3 expression may be one of the mechanisms by way of which RU486 performs its abortificient and anti tumor role.

Inhibition of embryonic development by microcystin-LR in zebrafish, Danio rerio

Microcystin-LR (MC-LR), a cyanobacterial toxin, is a potent inhibitor of protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A). PP1 and PP2A are critical regulators in embryonic development. However, the effects of MC-LR in embryonic development have been controversial. MC-LR has been demonstrated to be highly toxic in medaka, but not in zebrafish or rabbit embryos. The causes of difference may be due to membrane impermeability that impaired the delivery of MC-LR into cytoplasm of zebrafish and rabbit embryos. Therefore, we microinjected MC-LR directly into developing zebrafish embryos and investigated the effects of MC-LR on embryonic development. We demonstrated that MC-LR induced the lethality of zebrafish embryos in a dose- and time-dependent manner. MC-LR also induced the loss of blastomere coherence via the interference of beta-catenin and cadherins distributions. Furthermore, the MC-LR treated fry revealed various developmental defects. These results suggested that MC-LR might affect the phosphorylation equilibrium of signaling molecules, including beta-catenin and cadherins, required early in zebrafish embryonic development.

[Ultrastructural changes in loach (Misgurnus fossilis L.) embryos under borocin treatment]

The ultrastructure of embryo cells of the loach (Misgurnus fossilis L.) at the stage of first division of blastomers in control and under the conditions of fluoroquinole borocin treatment has been investigated. The influence of this antibiotic at concentrations 5 and 25 mkg/ml has resulted in significant ultrastructural changes of embryo cells, such as hypertrophy of channels of the smoth and rough endoplasmic reticulum, disorganization of Golgy complex and mitochondrias, destruction of cytoplasm and mitochondrial membranes, rarefaction of cytoplasm and cell oedema. Such changes confirm the toxic influence of borocin on the embryo during early development.

Potassium assay in blastomere of two-cell mouse embryo after equilibration and washing from cryoprotector

The need for effective methods of cryopreservation of early mammalian embryos necessitates the study of the mechanisms of blastomere adaptation to the equilibration procedure and subsequent washing from the cryoprotector. The osmotic effects during these procedures can cause electrolyte imbalance in embryonic cells. Intracellular potassium concentrations at the stage of two-blastomere mouse embryo were studied by electron probe microanalysis.

[GnRH antagonists and embryo implantation potential]

In several trials, the GnRH antagonists regimens have been associated with a slightly lower pregnancy and implantation rate than the established GnRH agonist protocols. Several embryo classification systems have been developed to grade embryo quality, and a cumulative embryo score has been proposed to predict pregnancy. The cumulative embryo score is based on a 4-point embryo score in which all cleaved embryos were assigned 1 point and 1 additional point was added for each of the following features: absence of fragmentation (or fragmentation involving <20% of the embryonic surface), absence of irregularities in blastomere size or shape, and four-cell stage (regardless of cell morphology). This cumulative embryo score is highly correlated with embryo implantation rates. In a non prospective study concerning 641 IVF cycles with oocyte retrieval, pregnancy and implantation rates were statistically lower in the group of patients treated with GnRH antagonist. The explanation of this difference is the indication in IVF cycles: the women with tubal infertility and/or endometriosis had lower pregnancy and implantation rates in IVF cycles if an antagonist was administrated. There was no difference between the 2 groups in ICSI cycles. Subsequently, in IVF cycles, antagonist should not be administrated to women with tubal infertility and/or endometriosis.

Effect of glutamine on preimplantation mouse embryo development in vitro

OBJECTIVES

The purpose of this research was to study the independent effect of the amino acid glutamine on preimplantation mouse embryo development in vitro.

STUDY DESIGN

Two-cell stage mouse embryos were cultured in human tubal fluid medium in the presence and absence of 1 mmol/L of glutamine. Outcomes for morphology and cleavage rates were compared with Fisher's and Mann-Whitney's tests, respectively.

RESULTS

Glutamine increased the proportion of embryos that developed to the blastocyst stage (86.4%) compared with those cultured without glutamine (59.1%) (P =.052). The percentages of embryos developing to the morula or hatching blastocyst stages were comparable in the 2 groups. Blastocyst total cell numbers were significantly higher in the glutamine group (34+/-1.7 vs 18.5+/-3.5, respectively; values are mean+/-SEM, P =.044).

CONCLUSION

The amino acid glutamine independently improves preimplantation mouse embryo development in vitro. Further studies are needed to examine the applicability of these results to humans.

[Effect of heavy metal cations on the activity of membrane Na+, K+ -ATPase in embryos of loach (Misgurnus fossilis L.)]

The activity of membrane Na+, K+ -ATPase of embryos of loach (Misgurnus fossilis L.) at early stages of development in the normal conditions and under the influence of heavy metal cations has been investigated. It was established, that the influence of such heavy metal cations as Ni2+, Co2+, Sn2+, Zn2+, Mn2+ and Cd2+ in concentrations 10(-6) - 10(-4) M results in reduction of activity of membrane Na+, K+ -ATPase of loach embryos. It was shown, that the inhibition effect is more expressed with the increase of concentrations of heavy metal cations in the incubation medium. The definition of inhibition constants Io.5 has allowed to analyze the sensitivity of Na+, K+ -ATPase to influence of various cations of heavy metals at different stages of blastomer division. Possible mechanisms of influence of heavy metal cations on the activity of membrane Na+, K+ -ATPase of loach embryos have been considered.

Effects of Fatty Acid-Free Bovine Serum Albumin and Fetal Calf Serum Supplementing Repair Cultures on Pre- and Post-Warm Viability of Biopsied Bovine Embryos Produced In Vitro

The objective of this study was to investigate the influence of fatty acid-free bovine serum albumin (BSA) or fetal calf serum (FCS) on the re-expansion of biopsied blastocysts and post-warm viability of subsequently vitrified embryos. Firstly, blastocysts produced in vitro were biopsied at Day 7 and cultured to allow repair in TCM199 with 0.3% BSA or 5% FCS for 24 h. The re-expansion rates and mean total numbers of cells of the re-expanded embryos after the repair culture with BSA were almost the same as that with FCS. Secondly, after biopsied embryos were similarly cultured for repair with BSA or FCS, re-expanded embryos were selected for vitrification. After warming and exposure to 0.5 M sucrose with 20% FCS in mPBS, the embryos were cultured in TCM199 with 5% FCS for 24 h. The re-expansion rate and mean total number of cells in re-expanded blastocysts in the BSA treatment group (97.4 +/- 2.9% and 106 +/- 42) was significantly higher than that in the FCS treatment group (51.6 +/- 9.1% and 61 +/- 38), respectively (P<0.05 and P<0.01). In conclusion, both FCS and BSA supplementation can be useful for repairing cultures of bovine biopsied blastocysts; but, compared with BSA supplementation, FCS supplementation during repair culture reduces the post-warm viability of biopsied and subsequently vitrified embryos.

Advanced In Vitro Production of Pig Blastocysts Obtained through Determining the Time for Glucose Supplementation

The objective was to determine the effect of glucose supplementation on development (to the blastocyst stage) of in vitro matured (IVM) porcine oocytes that were either in vitro fertilized (IVF) or electrically activated (EA). Embryos were incubated for 46 or 58 h post insemination (hpi) in an NCSU37-based medium containing 0.17 mM sodium pyruvate and 2.73 mM sodium lactate (IVC-PyrLac), and then transferred to an NCSU37-based medium containing 5.55 mM glucose (IVC-Glu) and cultured until Days 6 (Day 0 = day of EA or IVF). The proportions of oocytes that had formed full blastocysts by Day 6 following transfer to IVC-glu at 46 hpi was 23.5 and 41.2% in the IVF and EA groups respectively; these were lower (P<0.001) than the proportions of oocytes that formed full blastocysts after transfer at 58 hpi (60.3 and 78.7%). However, there was no significant difference in total cell number (at Day 6) between embryos transferred at 46 vs 58 hpi. We inferred that in vitro-derived pig embryos can efficiently use glucose as an energy source starting at approximately 58 hpi; exposure to glucose at that time enhanced development to the blastocyst stage as well as blastocyst quality.

[Effect of antibiotics on Na(+),K(+)-ATP-ase activity of the membranes in the Misgurnus fossilis L. embryos]

The influence of some antibiotics of the fluoroquinolone classes on the Na+, K(+)-ATP-ase activity of loach embryo (Misqurnus fossilis L.) was investigated at different stages of blastomer divisions. It was determined that norofloxacin and borocin induce a dose-dependent decrease in Na+, K(+)-ATP-ase activity. Addition of norofloxacin (5.25 mcg/ml) into the incubation media caused pronounced oscillations in Na+, K(+)-ATP-ase activity, following borocin addition (5,15.25 mcg/ml) this effect was less pronounced. A conclusion was drawn about the influence of the fluoroquinolone on the membrane level.

Differential growth, cell proliferation, and apoptosis of mouse embryo in various culture media and in coculture

Sequential culture and coculture are two methods of improving the development of preimplantation embryos in vitro. Direct comparison of the efficiency of these methods is limited. Proliferation and apoptosis determine the total number of blastomere in preimplantation embryo, which is a sensitive parameter for evaluation of the development of embryo in vitro. In this study, we compared the proliferation and apoptosis of mouse embryo in different culture media, including CZB, KSOM, MTF, G1.2/G2.2 sequential culture media, and in human oviductal cell coculture. Sequential culture using G1.2/G2.2 was superior to KSOM, MTF, and CZB/CZB + G with respect to the formation of 3-4 cell embryos, morula, and blastocyst. G1.2/G2.2 cultured blastocyst had significantly more proliferating blastomeres and higher total cell number per blastocyst than those cultured in KSOM or CZB/CZB + G. Compared to embryos cultured in G1.2/G2.2, embryos cocultured in G1.2/G2.2 hatched more frequently. Cocultured blastocysts also had significantly higher percentage of proliferating cell and lower percentage of apoptotic cell per blastocyst than those cultured in G1.2/G2.2. It was concluded that G1.2/G2.2 facilitated the proliferation of blastomere whilst human oviductal cell coculture suppressed apoptosis in addition to stimulating proliferation of blastomere.

Administration of increasing amounts of gonadotrophin compromises preimplantation development of parthenogenetic mouse embryos

The aim of the present study was to examine the effect of ovarian stimulation with increasing amounts of pregnant mare's serum gonadotrophin (PMSG) on preimplantation development of diploid parthenogenetic embryos in vitro. Administration of 5, 10 and 20 IU PMSG significantly increased the number of oocytes obtained per mouse in a dose-dependent manner. The amount of PMSG administered did not alter the proportion of degenerate oocytes. However, there was a significant decrease in the proportion of 8-cell/compacted embryos after 53 h of culture with the administration of increasing amounts of PMSG. Proportion of embryos reaching at the blastocyst stage after 79 h of culture was reduced significantly in both the 10 and 20 IU PMSG groups. Reduced blastocyst development after 96 h of culture, however, was significant only in the 20 IU PMSG group. Total blastocyst, trophectoderm and inner cell mass numbers were also reduced significantly with the administration of 20 IU PMSG. It is concluded on the basis of these observations that preimplantation development of diploid parthenogenetic oocytes, which depends virtually entirely on maternal molecules accumulated during oogenesis along with gene products derived from the maternal genome, is compromised with the administration of increasing amounts of PMSG.

Actions of Tumor Necrosis Factor-α on Oocyte Maturation and Embryonic Development in Cattle1

PROBLEM

Infertility can accompany mastitis in cattle. Involvement of tumor necrosis factor-alpha (TNF-alpha) in this phenomenon is suggested by observations that circulating concentrations of TNF-alpha are elevated after intramammary infection or infusion of endotoxin. It was hypothesized that (1) TNF-alpha acts on the oocyte during maturation to decrease the percent of oocytes that cleave and develop following fertilization; (2) exposure of embryos to TNF-alpha after fertilization reduces development to the blastocyst stage; and (3) TNF-alpha increases the proportion of blastomeres that undergo apoptosis in a stage-of-development dependent manner.

METHOD OF STUDY

In one experiment, oocytes were matured with various concentrations of TNF-alpha and then fertilized and cultured without TNF-alpha. In another study, embryos were cultured with TNF-alpha for 8 days beginning after fertilization. Finally, embryos were collected at the two or four-cell stage (at 28-30 hr after insemination) or when > or = 9-cells (at day 4 after insemination) and cultured +/- TNF-alpha for 24 hr. The proportion of blastomeres undergoing apoptosis was then determined by the TUNEL procedure.

RESULTS

Addition of TNF-alpha to maturation medium did not affect the proportion of oocytes that cleaved. However, the percent of oocytes that developed to the blastocyst stage at day 8 after insemination was reduced (P = 0.05) at all TNF-alpha concentrations tested (0.1-100 ng/mL). When added during embryo culture, there was no significant effect of TNF-alpha on the proportion of oocytes that became blastocysts. In addition, TNF-alpha did not induce apoptosis in two and four-cell embryos. For embryos > or = 9-cells, however, 10 and 100 ng/mL TNF-alpha increased (P < 0.05) the percent of blastomeres labeling as TUNEL-positive.

CONCLUSION

TNF-alpha can have deleterious actions on oocyte maturation that compromise development of the resultant embryo. While exposure of fertilized embryos to TNF-alpha did not inhibit development to the blastocyst stage, TNF-alpha increased the percentage of blastomeres undergoing apoptosis when exposure occurred for embryos > or = 9-cells. Increased blastomere apoptosis could conceivably compromise subsequent embryo survival.

Comparison of the results of human embryo biopsy and outcome of PGD after zona drilling using acid Tyrode medium or a laser

BACKGROUND

Zona pellucida opening for blastomere removal can be done by mechanical or chemical means, or by laser. So far, only limited data on the use of laser systems for zona drilling in cases of PGD are available.

METHODS

Results of embryo biopsy and outcome of PGD in two periods were compared. In the first period, acid Tyrode medium was used for zona drilling. In the second period, zona drilling was performed by a 1.48 micro m infrared laser.

RESULTS

In the first period, 59 cycles resulted in 53 biopsy procedures with 356 biopsied embryos. In the second period, these numbers were 69 cycles, 69 biopsy procedures and 402 biopsied embryos. Fewer blastomeres were intact (95.2%) after zona drilling with acid Tyrode than after laser zona drilling (98.3%, P = 0.02). Rates of positive HCG (37.5% versus 35.5%), ongoing pregnancy rates (31.3% versus 25.0%) and ongoing implantation rates (18.9% versus 14.9%) did not differ.

CONCLUSIONS

The use of a laser for zona drilling in cases of PGD is an easier procedure and results in more intact blastomeres. Since similar pregnancy rates are obtained, it is advantageous to use a laser for zona drilling. Further follow-up is necessary to prove the safety of this procedure.

Frequency of sex chromosomal mosaicism in bovine embryos and its effects on sexing using a single blastomere by PCR

Assessment of nuclear status is important when a biopsied single blastomere is used for embryo sexing. In this study we investigated the nuclear status of blastomeres derived from 8- to 16-cell stage in vitro fertilised bovine embryos to determine the representativeness of a single blastomere for embryo sexing. In 24 embryos analysed, the agreement in sex determination between a biopsied single blastomere and a matched blastocyst by polymerase chain reaction (PCR) was 83.3%. To clarify the discrepancies, karyotypes of blastomeres in 8- to 16-cell stage bovine embryos were analysed. We applied vinblastine sulfate at various concentrations and for different exposure times for metaphase plate induction in 8- to 16-cell stage bovine embryos. The 1.0 mg/ml vinblastine sulfate treatment for 15 h was selected as the most effective condition for induction of a metaphase plate (> 45%). Among 22 embryos under these conditions, only 8 of 10 that had a normal diploid chromosome complement showed a sex chromosomal composition of XX or XY (36.4%) and 2 diploid embryos showed mosaicism of the opposite sex of XX and XY in blastomeres of the embryo (9.1%). One haploid embryo contained only one X-chromosome (4.5%). Four of another 11 embryos with a mixoploid chromosomal complement contained a haploid blastomere with a wrong sex chromosome (18.2%). In conclusion, assessment of nuclear status of 8- to 16-cell stage bovine embryos revealed that morphologically normal embryos had a considerable proportion of mixoploid blastomeres and sex chromosomal mosaicism; these could be the cause of discrepancies in the sex between biopsied single blastomeres and matched blastocysts by PCR.

Improved embryo development with decreased apoptosis in blastomeres after the treatment of cloned bovine embryos with ?-mercaptoethanol and hemoglobin

In preliminary experiments, the treatment of donor somatic cells with beta-mercaptoethanol (ME) or hemoglobin (Hb) improved in vitro-development of bovine cloned embryos. This study was subsequently evaluated whether the exposure to Hb and/or ME during in vitro-maturation or embryo culture could further promote the development of embryos cloned with ME-treated donor cells. A prospective, randomized study was conducted and, embryo development, cell number, and apoptosis in blastocysts were monitored. A significant (P < 0.05) effect was found after the combined treatment of cloned embryos with Hb (1 microg/ml) and ME (10 microM); the development of morulae (53 vs. 35%) was greatly improved, which resulted in enhanced blastocyst formation (38%). However, cell number and apoptosis in blastocysts were predominantly affected by ME rather than Hb; a significant increase in total cell number of blastomeres (142-154 vs. 123 cells/embryo), inner cell mass (ICM) (39-41 vs. 27), and trophectoderm (TE) (103-114 vs. 98), and the ratio of ICM to TE cell number (0.26-0.27 vs. 0.22) was found. Also, the apoptosis index indicating the ratio of apoptotic cell to normal blastomere number was greatly reduced after ME treatments (0.85 vs. 0.056-0.069). When embryos cloned with ME-treated cells were cultured in Hb + ME-containing medium, any of the treatments to recipient oocytes before enucleation did not further promote the development. In conclusion, combined treatment of cloned embryos with Hb + ME not only improved in vitro-development but also decreased blastomere apoptosis. The use of ME-treated donor cells and the culture of cloned embryos in Hb + ME-containing medium yielded the optimal results for promoting the production of blastocysts with improved quality.