二胚层胚

Tetraploid embryos could be produced by electrofusion at the stage of two-cell embryos, which could develop to blastocysts followed by fusion of cytoplasm and nucleus and cleavage in vitro. During the fusion of cytoplasm, the DNA methylation levels of the fused embryos are as high as these of two-cell diploid embryos in vivo Then the embryos are rapidly demethylated when the nucleus begin to fuse, resulting in the lowest DNA methylation levels when the nucleus are fused completely. After that, the DNA methylation levels of the fused embryos are gradually increased until the morula stage. However, whereas an asymmetric distribution of DNA methylation is established in vivo-derived blastocysts with a higher methylation level in the inner cell mass than that in the trophectoderm, we can not detect the asymmetric distribution in most in vitro-derived tetraploid blastocysts.

结果表明：利用电融合方法制备的小鼠四倍体胚胎在体外培养体系中经历细胞质融合、细胞核融合及细胞继续分裂发育直到囊胚期的过程，在细胞质融合的时候胚胎卵裂球同体内体外培养二倍体胚胎一样，呈现高度甲基化状态；在细胞核开始融合的时候，甲基化水平急速下降，在细胞核完全融合的时候甲基化水平达到最低点；随着胚胎继续分裂，胚胎甲基化水平逐渐增加，在桑葚胚期甲基化水平最高；但是囊胚期四倍体胚胎内细胞团同滋养层细胞甲基化荧光信号没有差别，这与体内体外培养二倍体囊胚内细胞团细胞甲基化荧光强度高于滋养层细胞甲基化荧光强度不同。

Tetraploid embryos could be produced by electrofusion at the stage of two-cell embryos, which could develop to blastocysts followed by fusion of cyto-plasm and nucleus and cleavage in vitro. During the fusion of cytoplasm, the DNA methylation levels of the fused embryos are as high as these of two-cell diploid embryos in vivo Then the embryos are rapidly demethylated when the nucleus begin to fuse, resulting in the lowest DNA methylation levels when the nucleus are fused completely. After that, the DNA methy-lation levels of the fused embryos are gradually increased until the morula stage. However, whereas an asymmetric distribu-tion of DNA methylation is established in vivo-derived blastocysts with a higher methylation level in the inner cell mass than that in the trophectoderm, we can not detect the asymmetric distribution in most in vitro-derived tetraploid blastocysts.

结果表明：利用电融合方法制备的小鼠四倍体胚胎在体外培养体系中经历细胞质融合、细胞核融合及细胞继续分裂发育直到囊胚期的过程，在细胞质融合的时候胚胎卵裂球同体内体外培养二倍体胚胎一样，呈现高度甲基化状态；在细胞核开始融合的时候，甲基化水平急速下降，在细胞核完全融合的时候甲基化水平达到最低点；随着胚胎继续分裂，胚胎甲基化水平逐渐增加，在桑葚胚期甲基化水平最高；但是囊胚期四倍体胚胎内细胞团同滋养层细胞甲基化荧光信号没有差别，这与体内体外培养二倍体囊胚内细胞团细胞甲基化荧光强度高于滋养层细胞甲基化荧光强度不同。

Tetraploid embryos could be produced by electrofusion at the stage of two-cell embryos, which could develop to blastcysts fellowed by fusion of cytoplasm and nucleus and cleavage in vitro.After fusion of cytoplasm, the DNA methylation levels of the fused embryos was very high as well as two-cell diploid embryos in vivo.Then the embryos was rapiddly demethylated when the nucleus begin to fuse, resulting the lowest DNA methylation levels when the nucleus fused completely.After that, the DNA methylation levels of fused embryos were gradually increased until the blastocysts stage.However, whereas an asymmetric distribution of DNA methylation was established in an vivo-derived blastocysts with a higher methylation level in the inner cell mass than in the trophectoderm, in most vitro-derived tetraploid blastocysts, we can not detect the asymmetric distribution.

结果表明：利用电融合方法制备的小鼠四倍体胚胎在体外培养体系中经历细胞质融合、细胞核融合及细胞继续分裂发育直到囊胚期的过程，在细胞质融合的时候胚胎卵裂球同体内体外培养二倍体胚胎一样，呈现高度甲基化状态；在细胞核开始融合的时候，甲基化水平急速下降，在细胞核完全融合的时候甲基化水平达到最低点；随着胚胎继续分裂，胚胎甲基化水平逐渐增加，在囊胚期甲基化水平最高；但是囊胚期四倍体胚胎内细胞团同滋养层细胞甲基化荧光信号没有差别，这与体内体外培养二倍体囊胚内细胞团细胞甲基化荧光强度高于滋养层细胞甲基化荧光强度不同。

Dogskin domestic pig scalp cow finished leather and raw materials for sale mainly in skin works mainly leather gloves years, specializing in the production of green leather, pigskin, sheepskin, mapiri, dogskin, gloves leather, shoe leather, garment leather, the second floor of leather, wet blue hides, leather and various grades of leather embryo.

国产猪皮狗皮牛头皮的成品皮销售及生料皮加工主要以手套革为主年，专业生产环保牛皮，猪皮，羊皮，马皮，狗皮，手套革，鞋里革，服装革，二层皮革，蓝湿皮，皮胚等各种档次皮革。

BACKGROUND: Embryonic stem cells develop from early blastular inner cell mass. Under proper condition, ESCs can maintain undifferentiated state in vitro, normal diploid nuclear type, and proliferative potential. In addition, ESCs possess multi-directional differentiation capacity and can differentiate into all sorts of cells of three germ layers.

背景：胚胎干细胞来源于发育早期囊胚的内细胞团，适当条件下能在体外维持未分化状态、正常二倍体核型及无限增殖能力，且具有多向分化潜能，能够发育分化成机体3个胚层的所有类型细胞。

The 28S rDNA molecular phylogenetic trees showed: 1 entoprocts and phylactolaemate ectoprocts constituted a sister group, strenghthening the opinion that entoprocts should be reunited into phylum Bryozoa; 2 the cheilostome gymnolaemates was obviously non-monophyletic; 3 bryozoans itself was polyphyletic beyond any doubt, its main lineages were scattered in different positions of the lophotrochozoan trees; 4 to our great interests, the phylogenetic position of cheilostomes was between the diploblastic and the triploblastic, indicating they may play an important role during the evolution route from the diplobastic to the triploblastic animals.

28S rDNA分子系统树显示，内肛动物和被唇类外肛动物聚在一起并互为姐妹群，支持将内肛动物重新归入苔藓动物门的结论；唇口目裸唇类外肛动物绝非单系发生；苔藓动物本身也不是单系发生的，其主要类群分别位于触手冠担轮动物系统树的不同位置，特别是，唇口目苔藓动物的系统地位介于二胚层动物和其它三胚层动物之间，可能是二胚层动物向三胚层动物演化过程中的一个关键类群。

Diploblastic cnidarians as the outgroups, the phylogenetic trees of bryozoans and lophotrochozoans were reconstructed by the 28S rDNA analyses of theirs and other related bilaterians obtained through GenBank with different methods, respectively. Meanwhile, the primary and predicted secondary structures of their partial divergent 28S rDNA domains were compared and analysed.

结合GenBank上其他三胚层动物的相关序列数据，以二胚层刺胞动物为外类群，运用遗传分析软件，以不同方法构建了苔藓动物以及触手冠担轮动物的分子系统树；同时绘制了各代表类群28S rDNA的部分多变区的二级结构，并对其形态学特征进行了比较分析。

As she looked at Warrington's manly face, and dark, melancholy eyes, she had settled in her mind that he must have been the victim of an unhappy attachment.

每逢看到沃林顿那刚毅的脸，那乌黑、忧郁的眼睛，她便会相信，他一定作过不幸的爱情的受害者。

Maybe they'll disappear into a pothole.

也许他们将在壶穴里消失