Immunosurgical studies on cytological and cytogenetic toxicity analysis of rat blastocysts after in vivo exposure to cyclophosphamide.
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AIM: To establish immunosurgery and indices of cytogenetic assessment for blastocyst and its inner cell mass (ICM), and to evaluate the toxic effects after in vivo exposure to cyclophosphamide. METHODS: Modified immunosurgery was established by preparation of rabbit-anti-rat spleen antiserum and induction of diluted rat mixed serum as complement. Pregnant rats on d 3 of gestation were injected i.p. cyclophosphamide (10, 20, and 40 mg.kg-1). On d 4, immunosurgery was performed on rat blastocysts. The cell number and the micronuclei of blastocyst and ICM were evaluated respectively. RESULTS: In the cyclophosphamide-treated rats, decreases of cell number (35 +/- 3, 32 +/- 1, 30 +/- 1, and 14 +/- 2, 11 +/- 1, 9 +/- 2) and increases of frequency of micronuclei (1.81%, 2.27%, 3.14%, and 2.53%, 2.98%, 4.75%) in blastocysts and ICM were observed in a dose-related manner. The changes of blastocyst were, however, not parallel to those of ICM which were more serious. CONCLUSION: Modified immunosurgery, an objective and elegant technique, was used on rat blastocysts. In vivo could cyclophosphamide injured ICM more than blastocysts. (+info)
Spatially regulated SpEts4 transcription factor activity along the sea urchin embryo animal-vegetal axis.
(10/4036)
Because the transcription of the SpHE gene is regulated cell-autonomously and asymmetrically along the maternally determined animal-vegetal axis of the very early sea urchin embryo, its regulators provide an excellent entry point for investigating the mechanism(s) that establishes this initial polarity. Previous studies support a model in which spatial regulation of SpHE transcription relies on multiple nonvegetal positive transcription factor activities (Wei, Z., Angerer, L. M. and Angerer, R. C. (1997) Dev. Biol. 187, 71-78) and a yeast one-hybrid screen has identified one, SpEts4, which binds with high specificity to a cis element in the SpHE regulatory region and confers positive activation of SpHE promoter transgenes (Wei, Z., Angerer, R. C. and Angerer, L. M. (1999) Mol. Cell. Biol. 19, 1271-1278). Here we demonstrate that SpEts4 can bind to the regulatory region of the endogenous SpHE gene because a dominant repressor, created by fusing SpEts4 DNA binding and Drosophila engrailed repression domains, suppresses its transcription. The pattern of expression of the SpEts4 gene is consistent with a role in regulating SpHE transcription in the nonvegetal region of the embryo during late cleavage/early blastula stages. Although maternal transcripts are uniformly distributed in the egg and early cleaving embryo, they rapidly turn over and are replaced by zygotic transcripts that accumulate in a pattern congruent with SpHE transcription. In addition, in vivo functional tests show that the SpEts4 cis element confers nonvegetal transcription of a beta-galactosidase reporter gene containing the SpHE basal promoter, and provide strong evidence that the activity of this transcription factor is an integral component of the nonvegetal transcriptional regulatory apparatus, which is proximal to, or part of, the mechanism that establishes the animal-vegetal axis of the sea urchin embryo. (+info)
Expression of inhibin/activin subunits and their receptors and binding proteins in human preimplantation embryos.
(11/4036)
PURPOSE: Our purpose was to study the role of inhibin/activin during embryogenesis. METHODS: Transcripts of inhibin/activin subunits (alpha, beta A, beta B), activin receptors (types I and II), and follistatin were detected by a reverse transcriptase-polymerase chain reaction in human reproductive cells and preembryos cultured alone or co-cultured with human endometrial cells. RESULTS: Transcripts of alpha, beta A, beta B subunits were all detected in granulosa luteal cells, but only beta A units were detected in endometrial stromal and decidualized cells. In human preimplantation embryos, none of these subunits were detected in embryos from the four-cell to the morula stage and only beta A subunits were detectable in blastocyst embryos. Activin receptors were detectable in all of the studied embryos and cells. Transcripts of beta A, activin receptors, and follistatin were differentially expressed in human preimplantation embryos cultured in vitro and their expressions were significantly enhanced with the presence of endometrial stromal cells. CONCLUSIONS: Our data suggest that there is a possible endometrium-embryo interaction via endometrial activins and preimplantation embryo receptors and that the embryonic expressions of these activins, their receptors, and binding proteins are dependent on embryonic stage. (+info)
Enhanced hatching rate of bovine IVM/IVF/IVC blastocysts using a 1.48-micron diode laser beam.
(12/4036)
PURPOSE: Our purpose was to test whether zona pellucida (ZP) drilling using a 1.48-micron diode laser beam on bovine IVM/IVF/IVC blastocysts is effective for embryo hatching. METHODS: Blastocysts produced in vitro at day 7 after IVF were divided into control and laser-drilled groups, respectively. RESULTS: When the rates of in vitro development of bovine embryos were examined, the average cleavage rate (> or = two-cell) was 82.3% and the blastocyst rate at day 7 after IVF was 32.5%. Using these blastocysts, when the laser drilling effect was investigated at 48 hr after treatment, the total hatching rate in the laser-drilled group (98.0%) was significantly higher than that in the control group (60.0%) (P < 0.001). Especially, the hatched rate of the laser-drilled group (68.0%) was significantly enhanced compared with that of the control group (30.0%) (P < 0.001). CONCLUSIONS: These results demonstrated that laser ZP drilling on bovine IVM/IVF/IVC blastocysts can significantly increase the hatching rate. (+info)
p70(S6K) controls selective mRNA translation during oocyte maturation and early embryogenesis in Xenopus laevis.
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In mammalian cells, p70(S6K) plays a key role in translational control of cell proliferation in response to growth factors. Because of the reliance on translational control in early vertebrate development, we cloned a Xenopus homolog of p70(S6K) and investigated the activity profile of p70(S6K) during Xenopus oocyte maturation and early embryogenesis. p70(S6K) activity is high in resting oocytes and decreases to background levels upon stimulation of maturation with progesterone. During embryonic development, three peaks of activity were observed: immediately after fertilization, shortly before the midblastula transition, and during gastrulation. Rapamycin, an inhibitor of p70(S6K) activation, caused oocytes to undergo germinal vesicle breakdown earlier than control oocytes, and sensitivity to progesterone was increased. Injection of a rapamycin-insensitive, constitutively active mutant of p70(S6K) reversed the effects of rapamycin. However, increases in S6 phosphorylation were not significantly affected by rapamycin during maturation. mos mRNA, which does not contain a 5'-terminal oligopyrimidine tract (5'-TOP), was translated earlier, and a larger amount of Mos protein was produced in rapamycin-treated oocytes. In fertilized eggs rapamycin treatment increased the translation of the Cdc25A phosphatase, which lacks a 5'-TOP. Translation assays in vivo using both DNA and RNA reporter constructs with the 5'-TOP from elongation factor 2 showed decreased translational activity with rapamycin, whereas constructs without a 5'-TOP or with an internal ribosome entry site were translated more efficiently upon rapamycin treatment. These results suggest that changes in p70(S6K) activity during oocyte maturation and early embryogenesis selectively alter the translational capacity available for mRNAs lacking a 5'-TOP region. (+info)
Development of nuclear transfer and parthenogenetic rabbit embryos activated with inositol 1,4,5-trisphosphate.
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The present study was carried out to evaluate the effects of different activation protocols, enucleation methods, and culture media on the development of parthenogenetic and nuclear transfer (NT) rabbit embryos. Electroporation of 25 mM inositol 1,4, 5-trisphosphate (IP3) in calcium- and magnesium-free PBS immediately induced a single intracellular calcium transient in 6 out of 14 metaphase II-stage rabbit oocytes evaluated during a 10-min recording period. The percentage of oocytes treated with IP3 followed by 6-dimethylaminopurine (IP3 + DMAP) that cleaved (83.9%) and reached the blastocyst stage (50%) was significantly higher (p < 0.05) than those activated with multiple pulses (61.6% and 30.1%, respectively) or treated with ionomycin + DMAP (52.9% and 5.7%, respectively). Development of IP3 + DMAP-activated rabbit oocytes and in vivo-fertilized zygotes in different culture media was studied. Development of activated oocytes to the blastocyst stage in Earle's balanced salt solution (EBSS) supplemented with MEM nonessential amino acids, basal medium Eagle amino acids, 1 mM L-glutamine, 0.4 mM sodium pyruvate, and 10% fetal bovine serum (FBS) (EBSS-complete) (40.6%) was significantly higher (p < 0.05) than those that developed in either Dulbecco's Modified Eagle's medium (DMEM)/RPMI + 10% FBS (15.5%) or CR1aa + 10% FBS (4%) medium. In addition, 100% of in vivo-fertilized rabbit zygotes developed to the blastocyst stage in EBSS-complete. A third set of experiments was carried out to study the efficiency of blind versus stained (Hoechst 33342) enucleation of oocytes. Twenty-nine of 48 blind enucleated and IP3 + DMAP-activated oocytes cleaved (60.4%), and 15 (31.2%) subsequently reached the blastocyst stage, whereas 9 of 52 oocytes enucleated using epifluorescence (17.3%) cleaved, and none of these reached the blastocyst stage. When the above parameters that yielded the highest blastocysts were combined in an NT experiment using adult rabbit fibroblast nuclei, 72.2% (39 of 54) of the fused nuclear transplant embryos cleaved and 29.6% (16 of 54) reached the blastocyst stage. (+info)
Stage-specific excitation of cannabinoid receptor exhibits differential effects on mouse embryonic development.
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Anandamide (N-arachidonoylethanolamine), an arachidonic acid derivative, is an endogenous ligand for both the brain-type (CB1-R) and spleen-type (CB2-R) cannabinoid receptors. We have previously demonstrated that preimplantation mouse embryos express mRNA for these receptors and that the periimplantation uterus contains the highest level of anandamide yet discovered in a mammalian tissue. We further demonstrated that 2-cell mouse embryos exposed to low levels of anandamide (7 nM) or other known cannabinoid agonists in culture exhibit markedly compromised embryonic development to blastocysts and that this effect is mediated by CB1-R. In contrast, the present study demonstrates that blastocysts exposed in culture to the same low levels of cannabinoid agonists exhibited accelerated trophoblast differentiation with respect to fibronectin-binding activity and trophoblast outgrowth. Again, these effects resulted from activation of embryonic CB1-R. There was a differential concentration-dependent effect of cannabinoids on the trophoblast, with an observed inhibition of differentiation at higher doses. These results provide evidence for the first time that cannabinoid effects are differentially executed depending on the embryonic stage and cannabinoid levels in the environment. Since uterine anandamide levels are lowest at the sites of implantation and highest at the interimplantation sites, the new findings imply that site-specific levels of anandamide and/or other endogenous ligands in the uterus may regulate implantation spatially by promoting trophoblast differentiation at the sites of blastocyst implantation. (+info)
Spatiotemporal expression of cyclooxygenase 1 and cyclooxygenase 2 during delayed implantation and the periimplantation period in the Western spotted skunk.
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Embryonic development in the western spotted skunk is arrested after blastocyst formation for about 200 days. This developmental arrest is believed to be due to insufficiency of uterine conditions to support continuous development. Implantation and decidualization are defective in cyclooxygenase 2 (Cox2)-, but not Cox1-, deficient mice. We therefore used Northern and in situ hybridization to investigate changes in uterine expression of Cox1 and Cox2 genes during various stages of pregnancy in the spotted skunk. Cox1 was constitutively expressed at all stages of pregnancy examined, but it did exhibit localized up-regulation in the trophoblast and necks of uterine glands at early implantation sites. Cox2 expression was highly regulated with little or no expression during delayed implantation. Cox2 expression was first detected in the uterus and trophoblast prior to blastocyst attachment and remained detectable for 5-6 days after blastocyst attachment. Cox2 expression was also localized in the luminal and glandular epithelia of uterine segments located between implantation chambers. Changes in Cox expression were not correlated with the abrupt increase in uterine weight that occurs simultaneously with renewed embryonic development but was correlated with an influx of serum proteins into the uterus observed in a previous study. (+info)