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MII Oocytes (mii + oocyte)
Selected AbstractsMechanism of malsegregations at meiosis: premature centromere separation and precocious division in female Chinese hamsters stimulated with gonadotropic hormonesCONGENITAL ANOMALIES, Issue 3 2000Shin-ichi Sonta ABSTRACT, Using female Chinese hamsters stimulated with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG), we investigated the influence of hormonal stimulation upon meiotic segregation in oocytes. In 1,576 oocytes ovulated spontaneously from 197 non-treated mature females, the number (percentage) of hyperhaploid oocytes with more than 12 (12,14) chromosomes was 16 (1.0%). These cells had no extra single chromatids, but all had extra chromosomes. Single chromatids were seen in 7 (0.4%) cells with a haploid chromosome set. On the other hand, a total of 1,329 and 1,198 second meiotic (MII) oocytes from 64 mature females and 61 immature females stimulated with PMSG and hCG, respectively, were subjected to chromosomal analysis. Single chromatids were seen in 34 (2.6%) and 62 (5.2%) of these oocytes, respectively. Since these chromatids were mostly paired and the sister chromatids existed near each other in many cells, they may have separated from some chromosomes of haploid cells. Compared with the non-treated females, the frequency of cells with single chromatids was significantly greater in oocytes from both mature and immature females stimulated with PMSG and hCG. The number (percentage) of hyperhaploid cells from mature and immature PMSG-hCG-stimulated females, respectively, was 15 (1.1%) and 14 (1.2%), which was not significantly greater than that in non-treated females. Most of these cells had extra whole chromosomes but one oocyte from mature females and one from immature females had an extra single chromatid. These findings indicate that such hormonal stimulation induces premature centromere separation in MII oocytes and precocious division at anaphase I, which can be assumed by the presence of MII cells with extra single chromatids. Considering that no or less hyperhaploid MII oocytes with an extra single chromatid were seen in oocytes from spontaneous ovulation and from artificial ovulation on hormonal stimulation, these findings suggest that the major mechanism of malsegregations at first meiotic (MI) division is not a precocious division but rather, errors such as nondisjunction of homologous chromosomes (dyads). [source] Molecular characterization and polyadenylation-regulated expression of cyclin B1 and Cdc2 in porcine oocytes and early parthenotesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 1 2010Ding-Xiao Zhang Meiotic maturation of mammalian oocytes is controlled by the maturation/M-phase promotion factor (MPF), a complex of Cdc2 kinase and cyclin B protein. To better understand the molecular mechanism of oocyte maturation, we characterized porcine cyclin B1 and Cdc2 genes, both of which are widely expressed in pig tissues. We further analyzed their expression profiles during in vitro maturation of pig oocyte and early embryonic development at both the mRNA and protein level. Two isoforms of cyclin B1, comprising the same open reading frame but differing in 3,-UTR length, were identified. Cyclin B1 transcripts was up-regulated after 30,hr of maturation, while Cdc2 mRNA levels were unchanged during maturation except for a sharp decline at 44,hr. Cyclin B1 protein synthesis increased with oocyte maturation. Cdc2 protein expression was relatively low during 0,18,hr, followed by a higher level of expression up to 44,hr of maturation. Poly(A)-test PCR clearly revealed that both cyclin B1 isoforms underwent cytoplasmic polyadenylation starting around 18,24,hr during maturation, while a substantial de-adenylation and degradation of Cdc2 isoforms were observed in metaphase II oocytes and during embryo development after parthenogenetic activation. Porcine MII oocytes derived from small follicles (,3,mm) and bad quality 2-cell parthenotes showed lower developmental competence and lower levels of cyclin B1 protein, and Cdc2 mRNA or both gene mRNAs, respectively, compared to their control counterparts. These results suggested that cyclin B1 was regulated posttranscriptionally by cytoplasmic polyadenylation during porcine oocyte maturation. Further, the decreased expression of maternal cyclin B1 and Cdc2 at the mRNA or protein level in developmentally incompetent oocytes and embryos was responsible for, at least in part, a profound defect in further embryonic development. Mol. Reprod. Dev. 77: 38,50, 2010. © 2009 Wiley-Liss, Inc. [source] Changes in global histone acetylation pattern in somatic cell nuclei after their transfer into oocytes at different stages of maturationMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 3 2008Helena Fulka Abstract In our study, we have examined the pattern of global histone modification changes in somatic cell nuclei after their transfer into mouse oocytes at different stages of maturation or after their parthenogenetic activation. While germinal vesicle (GV) staged immature oocytes are strongly labeled with anti-acetylated histone H3 and H4 antibodies, the signal is absent in both metaphase I and metaphase II oocytes (MI, MII). In contrast, the oocytes of all maturation stages show a presence of trimethylated H3/K4 in their chromatin. When somatic cells were fused to intact or enucleated GV oocytes, both the GV and the somatic cell nucleus showed a very strong signal for all the antibodies used. On the other hand, when somatic cells nuclei that are AcH3 and AcH4 positive before fusion are introduced into either intact or enucleated MI or MII oocytes, their acetylation signal decreased rapidly and was totally absent after a prolonged culture. This was not the case when anti-trimethyl H3/K4 antibody was used. The somatic cell chromatin showed only a slight decrease in the intensity of labeling after its transfer into MI or MII oocytes. This decrease was, however, evident only after a prolonged culture. These results suggest not only a relatively higher stability of the methylation modification but also some difference between the oocyte and somatic chromatin. The ability to deacetylate the chromatin of transferred somatic nuclei disappears rapidly after the oocyte activation. Our results indicate that at least some reprogramming activity appears in the oocyte cytoplasm almost immediately after GV breakdown (GVBD), and that this activity rapidly disappears after the oocyte activation. Mol. Reprod. Dev. 75: 556,564, 2008. © 2007 Wiley-Liss, Inc. [source] Effect of maturation stage at cryopreservation on post-thaw cytoskeleton quality and fertilizability of equine oocytesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 5 2006T. Tharasanit Abstract Oocyte cryopreservation is a potentially valuable technique for salvaging the germ-line when a valuable mare dies, but facilities for in vitro embryo production or oocyte transfer are not immediately available. This study examined the influence of maturation stage and freezing technique on the cryopreservability of equine oocytes. Cumulus oocyte complexes were frozen at the immature stage (GV) or after maturation in vitro for 30 hr (MII), using either conventional slow freezing (CF) or open pulled straw vitrification (OPS); cryoprotectant-exposed and untreated nonfrozen oocytes served as controls. After thawing, GV oocytes were matured in vitro, and MII oocytes were incubated for 0 or 6 hr, before staining to examine meiotic spindle quality by confocal microscopy. To assess fertilizability, CF MII oocytes were subjected to intracytoplasmic sperm injection (ICSI) and cultured in vitro. At 12, 24, and 48 hr after ICSI, injected oocytes were fixed to examine their progression through fertilization. Both maturation stage and freezing technique affected oocyte survival. The meiosis resumption rate was higher for OPS than CF for GV oocytes (28% vs. 1.2%; P,<,0.05), but still much lower than for controls (66%). Cryopreserving oocytes at either stage induced meiotic spindle disruption (37%,67% normal spindles vs. 99% in controls; P,<,0.05). Among frozen oocytes, however, spindle quality was best for oocytes frozen by CF at the MII stage and incubated for 6 hr post-thaw (67% normal); since this combination of cryopreservation/IVM yielded the highest proportion of oocytes reaching MII with a normal spindle (35% compared to <20% for other groups), it was used when examining the effects of cryopreservation on fertilizability. In this respect, the rate of normal fertilization for CF MII oocytes after ICSI was much lower than for controls (total oocyte activation rate, 26% vs. 56%; cleavage rate at 48 hr, 8% vs. 42%: P,<,0.05). Thus, although IVM followed by CF yields a respectable percentage of normal-looking MII oocytes (35%), their ability to support fertilization is severely compromised. Mol. Reprod. Dev. © 2006 Wiley-Liss, Inc. [source] Elevated Histone H1 (MPF) and Mitogen-activated Protein Kinase Activities in Pig Oocytes Following In Vitro Maturation do not Indicate Cytoplasmic MaturationREPRODUCTION IN DOMESTIC ANIMALS, Issue 2 2009MA Setiadi Contents Effects of different media (TCM 199 + BSA, TCM 199 + FCS, TCM 199 + NBCS, Whitten's medium + BSA) supplemented with estradiol-17, and two isolated and everted follicle shells on MPF and MAP kinase activities and the sensitivity to parthenogenetic activation of pig oocytes were examined at the end of culture (48 h). Elevated (P < 0.05) activities of MAP kinase were recorded in metaphase II oocytes following culture in Whitten's medium, whereas MPF levels were lowest (P < 0.05) in MII oocytes matured in TCM 199 supplemented with BSA. Oocytes matured in TCM 199 based media showed higher (P < 0.05) activation rates when compared to oocytes incubated in Whitten's medium. Whitten's medium supplemented with different protein sources (amino acids, FCS, BSA) was used to study the effects of different exposure periods to eCG/hCG stimulation on MPF and MAP kinase activities and in vivo fertilisability following culture for 48 h. MPF and MAP kinase activities were significantly increased by eCG/hCG stimulation of COCs during maturation. Further, the continuous presence of eCG/hCG during culture (48 h) significantly increased the levels of both kinases in comparison to stimulation by gonadotrophins alone during the first 24 h of incubation. In vivo fertilisation of oocytes matured in Whitten's medium supplemented with eCG/hCG for 24 or 48 h led to a significant retardation of early embryonic development compared to ovulated oocytes. In conclusion, media composition and gonadotrophin stimulation affect MPF/MAP kinase activities and the susceptibility to parthenogenetic activation of IVM oocytes. However, elevated kinase levels in pig oocytes following culture do not indicate complete cytoplasmic maturation. [source] Effects of PKC , on early genome transcription activation in mouse 1-cell stage fertilized eggsCELL BIOCHEMISTRY AND FUNCTION, Issue 6 2007Bing-zhi Yu Abstract Effects of PKC , on the activation of embryonic transcription in 1-cell stage fertilized mouse eggs were explored. The effects of PKC antagonist calphostin C and PKC , specific inhibitor on the activation of embryonic early transcription were observed by Western blotting and cell immunofluorescence. PKC activity increased gradually from G1 phase to late G2 phase in mouse 1-cell stage fertilized eggs, and reached a maximum in G2 stage. Calphostin C inhibited PKC activity by about 47% in 1-cell stage fertilized eggs. Calphostin C inhibited early transcription in 1-cell stage fertilized eggs (p,<,0.01). PKC ,-Thr410 in G2 were about 27% and 110% higher than those in G1 phase of 1-cell stage fertilized eggs and MII oocytes, respectively. PKC , specific inhibitor can also inhibit early transcription in 1-cell stage fertilized eggs (p,<,0.05). The results suggest that PKC , participates in early transcription activation in mouse 1-cell stage fertilized eggs. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||