p-CREB在小鼠植入前胚的表达及其与2-细胞阻滞的关系

目的观察p-CREB在小鼠植入前胚以及阻滞品系(昆明小鼠)与非阻滞品系(B6C3F1小鼠)2-细胞胚的分布与表达,初步探讨p-CREB在小鼠植入前胚中的作用以及与小鼠2-细胞阻滞的关系。方法利用激光扫描共聚焦显微镜检测p-CREB在B6C3F1小鼠植入前胚中的定位,比较不同品系小鼠体外培养以及B6C3F1小鼠体外培养与体内发育2-细胞胚内p-CREB的表达变化。结果 p-CREB的免疫阳性反应在小鼠1-细胞胚中主要分布于细胞质中;2-细胞胚及其后期植入前胚主要定位于细胞核内;昆明小鼠体外培养2-细胞胚核内荧光强度显著低于同一条件发育的B6C3F1小鼠,B6C3F1小鼠体外培养2-细胞胚核内荧光强度显著高于体内发育。结论 p-CREB在小鼠植入前胚发育中起重要作用,p-CREB在昆明小鼠2-细胞胚核内表达较低可能与小鼠2-细胞阻滞有关。     

小鼠四倍体早期胚胎基因组甲基化模式

利用小鼠抗5-甲基胞嘧啶(5MeC)单克隆抗体检测了体外培养小鼠四倍体早期胚胎的基因组甲基化模式。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。因此, 小鼠体外培养四倍体胚胎的甲基化模式是不正常的, 这可能是四倍体小鼠难以发育到妊娠足月的原因之一。这是对小鼠四倍体早期胚胎基因组甲基化模式的首次报道。     

哺乳动物早期胚胎体外发育阻滞的研究进展

哺乳动物胚胎在体外培养中普遍存在早期发育阻滞的现象。对此,人们用形态学、生物化学、分子生物学、显微操作等手段开展了磷酸、葡萄糖、次黄嘌呤和细胞质因素对早期胚胎发育阻滞的影响的研究。本综合分析了共培养系统的优缺点。说明了采用完全成分已知的培养液对进行有关研究的必要性。列出了有效运用于克服小鼠、大鼠、仓鼠、兔、猪、羊、牛、猴等动物早期胚胎阻滞的成分知的培养液的名称。     

昆明小鼠卵子的体外受精及发育的研究

ICR等品系小鼠的体外受精研究已获得了产仔的结果,但昆明(KM)小鼠(Mus musculus)这方面的研究则不多见。尤其是其早期胚胎体外培养中存在的“2细胞阻滞”现象,仍未能克服。本研究的目的是建立一套稳定有效的昆明小鼠体外受精及体外培养系     

克服昆明小鼠体外受精卵发育阻滞方法的研究

本研究应用CZB和WM培养液进行昆明小鼠体外受精胚胎的发育培养,建立了一个可行的胚胎体外培养的新方法,并通过改变培养液的成分及其含量,对胚胎发育的阻滞机理和突破方法进行了初步的探索。培养于WM中的受精卵发生阻滞,有48％停留于2细胞阶段;而CZB中的胚胎有81％发育为桑椹胚和囊胚。在WM中添加EDTA和谷氨酰胺得到了66％的囊胚;加大WM中乳酸钠和丙酮酸钠的比值未能克服发育的阻滞现象。实验结果表明,EDTA和谷氨酰胺在克服阻滞时具有协同作用。     

葡萄糖对小鼠胚胎体外发育的影响

通过在CZB培养液中添加不同浓度葡萄糖及在胚胎发育的不同阶段加入葡萄糖,对小鼠胚胎进行体外培养,以探讨葡萄糖在小鼠早期胚胎体外发育中的作用。其结果表明,小鼠胚胎在含糖CZB与在无糖CZB中培养比较,4-细胞发育率无差异;各浓度葡萄糖组囊胚率显著高于无糖组,其中3.0mmol/L浓度组囊胚细胞数显著高于其余组;实验二：2-细胞至4-细胞、4-细胞至桑椹胚前添加葡萄糖囊胚率显著提高。上述结果证明,在小鼠胚胎体外培养中加入葡萄糖不会导致2-细胞阻滞;葡萄糖浓度增加至10mmol/L对小鼠胚胎无毒性作用,其最适浓度为3.0mmol/L;2-细胞至4-细胞、4-细胞至桑椹胚前添加葡萄糖是必要的。关键词 葡萄糖;小鼠;2-细胞阻滞;胚胎;体外发育     

Fundulus heteroclitus卵子的发育能力的研究

以实验的方法来研究 Fundulus heteroclitus 卵子分裂球的发育能力,最早的工作是 Morgan 1893和1895年的报告。他在2细胞时期,用针穿破卵膜,刺死一个分裂球。针抽出后,轻轻的抑压卵膜,挤出刺死的分裂球的细胞质,但不损伤下面的卵黄。经过这样手术以后,遗留在膜内的分裂球能继续发育。68个卵子中,20个左右在胚胎形成前死亡,其余都能继续发育,成为正常的胚胎。胚胎的身体一般比正常的小,比正常的二分之一来得大。Morgan 在他1893年的论文中,认为去掉一半分裂球的卵子,发育成为大于二分之一胚胎的原因,是留存的细胞质多于二分之一的结果。因在2细胞时期,     

M16添加硫氧还蛋白过氧化物酶Ⅱ无法克服昆明小鼠早胚体外发育2-细胞阻滞

目的观察硫氧还蛋白过氧化物酶Ⅱ(Peroxiredoxin Ⅱ,PrxII)是否可以克服昆明(Kunming)小鼠早胚体外发育2-细胞阻滞。方法取昆明小鼠1-细胞胚置于含PrxII蛋白的M16培养液中培养,观察PrxII对昆明小鼠早胚发育潜能和2-细胞胚内活性氧自由基(reactive oxygen species,ROS)水平的影响;同时比较昆明和B6C3F1小鼠1-细胞胚在M16中各自的发育情况;激光扫描共聚焦显微镜分别检测比较昆明与B6C3F1小鼠体外培养2-细胞胚内ROS水平以及昆明小鼠体外培养与体内发育2-细胞胚内ROS水平。结果M16培养液中添加PrxII蛋白(1nmol/L和100nMol/L)可以明显降低昆明小鼠体外培养2-细胞胚内ROS水平(P<0.05),但不能克服昆明小鼠体外发育2-细胞阻滞;昆明小鼠1-细胞胚在M16中培养存在2-细胞阻滞现象,而B6C3F1小鼠无2-细胞阻滞现象;昆明小鼠体外培养2-细胞胚内ROS水平显著低于体内发育2-细胞胚(P<0.05),亦略低于B6C3F1小鼠体外培养2-细胞胚内ROS水平(P>0.05)。结论M16培养液中添加PrxII可以明显降低2-细胞胚...     

几种克服昆明小鼠2一细胞胚胎发育阻滞的培养液研究

比较了几种培养液对克服昆明小鼠胚胎２－细胞发育阻滞的效果。实验１的结果表明，在Ｍ１６及ＣＺＢ培养液基础上，加减几种成分得到的改进Ｍ１６培养液（用ｍＭ１６表示）和改进的ＣＺＢ培养液（用ｍＣＺＢ表示）均能有效克服２－细胞阻滞现象。除去Ｍ１６和ＣＺＢ培养液中的葡萄糖和磷酸盐后添加５．５５ｍｍｏｌ／Ｌ牛磺酸、１００或１１０μｍｏｌ／Ｌ ＥＤＴＡ、２ｍｍｏｌ／Ｌ谷氨酰胺和２％必需氨基酸（ＥＡＡ）及１％非必需     

兔核移植胚胎起始发育的超微结构研究

对兔核移植胚胎起始发育的超微结构变化进行电镜观察,并与供体桑椹胚细胞,受体卵母细胞及同期正常受精胚胎的超微结构进行比较,“原核”期兔核移植胚胎的超微结构明显不同于供体桑椹胚细胞及受体卵母细胞的超微结构,而与同期正常受精胚胎相似,但有些核移植胚胎中皮质反应,及核仁和线粒体中出电子致密的网眼结构,与正常受精卵存在差别,分裂至２－细胞期时,与正常２－细胞胚超微结构更相似,结果提示,兔胚胎细胞核移植后,供     

多能性转录因子OCT4和SOX2在体外发育的小鼠2-细胞胚胎的表达与定位

为探讨多能性转录因子OCT4和SOX2在昆明小鼠(Mus musculus)2-细胞胚胎发育过程中与2-细胞胚胎阻滞发生的相关性,本研究应用实时荧光定量PCR技术检测了小鼠卵母细胞及在M16培养液中培养的不同发育阶段体外受精胚Oct4和Sox2基因的表达,并利用实时荧光定量PCR和免疫荧光技术比较了2-细胞胚、2-细胞阻滞胚和4-细胞胚的OCT4和SOX2的表达与定位。采用ANOVA对实验所得的数据进行分析,P0.05被认为是具有显著性差异。研究结果显示,2-细胞胚只有24.8%发育成4-细胞胚,75.2%的2-细胞胚发生了阻滞。Sox2和Oct4的m RNA在MⅡ期卵母细胞、原核胚、2-细胞胚、4-细胞胚、桑椹胚和囊胚中都有表达。Oct4 m RNA的表达水平在4-细胞胚显著高于2-细胞胚和2-细胞阻滞胚(P0.05),Sox2 m RNA的表达水平在2-细胞胚显著高于2-细胞阻滞胚和4-细胞胚(P0.05),而后两者之间没有差异(P0.05)。OCT4蛋白在2-细胞胚和4-细胞胚中与核共定位,但在2-细胞阻滞胚中弥散存在于胞质中。SOX2蛋白在以上3类胚胎中始终定位于细胞核。上述结果提示,转录因子OCT4和SOX2的表达和定位与小鼠2-细胞胚胎发育阻滞相关,母源性SOX2表达的维持对胚胎合子基因组激活(ZGA)的发生具有重要作用,母源性OCT4的异常定位可能影响了合子基因组激活相关基因的激活,而合子中Oct4的表达影响合子基因组激活后胚胎的发育。     

Delay of ZGA initiation occurred in 2-cell blocked mouse embryos

One-cell mouse embryos from KM strain and B6C3F1 strain were cultured in M16 medium, in which2-cell block generally occurs. Embryos of KM strain exhibited 2-cell block, whereas B6C3F1 embryos,which are regarded as a nonblocking strain, proceeded to the 4-cell stage in our culture condition. It is oftenassumed that the block of early development is due to the failure of zygotic gene activation (ZGA) in culturedembryos. In this study we examined protein synthesis patterns by two-dimensional gel electrophoresis of[35^S] methionine radiolabeled 2-cell embryos. Embryos from the blocking strain and the nonblocking strainwere compared in their development both in vitro and in vivo. The detection of TRC expression, a markerof ZGA, at 42 h post hCG in KM embryos developed in vitro suggested that ZGA was also initiated even inthe 2-cell arrested embryos. Nevertheless, a significant delay of ZGA was observed in KM strain as comparedwith normally developed B6C3F1 embryos. At the very beginning of major ZGA as early as 36 h post hCG,TRC has already been expressed in B6C3F1 embryos developed in vitro and KM embryos developed in vivo.But for 2-cell blocked KM embryos, TRC was still not detectable even at 38 h post hCG. These evidences suggest that 2-cell-blocked embryos do initiate ZGA, and that 2-cell block phenomenon is due not to the disability in initiating ZGA, but to a delay of ZGA.     

Mouse embryos stressed by physiological levels of osmolarity become arrested in the late 2-cell stage before entry into M phase

Preimplantation mouse embryos of many strains become arrested at the 2-cell stage if the osmolarity of culture medium that normally supports development to blastocysts is raised to approximately that of their normal physiological environment in the oviduct. Arrest can be prevented if molecules that serve as "organic osmolytes" are present in the medium, because organic osmolytes, principally glycine, are accumulated by embryos to provide intracellular osmotic support and regulate cell volume. Medium with an osmolarity of 310 mOsM induced arrest of approximately 80% of CF1 mouse embryos at the 2-cell stage, in contrast to the approximately 100% that progressed beyond the 2-cell stage at 250 or 301 mOsM with glycine. The nature of this arrest induced by physiological levels of osmolarity is unknown. Arrest was reversible by transfer to lower-osmolarity medium at any point during the 2-cell stage, but not after embryos would normally have progressed to the 4-cell stage. Cessation of development likely was not due to apoptosis, as shown by lack of external annexin V binding, detectable cytochrome c release from mitochondria, or nuclear DNA fragmentation. Two-cell embryos cultured at 310 mOsM progressed through the S phase, and zygotic genome activation markers were expressed. However, most embryos failed to initiate the M phase, as evidenced by intact nuclei with decondensed chromosomes, low M-phase promoting factor activity, and an inactive form of CDK1, although a few blastomeres were arrested in metaphase. Thus, embryos become arrested late in the G(2) stage of the second embryonic cell cycle when stressed by physiological osmolarity in the absence of organic osmolytes.     

Cyclin B1 levels in the porcine 4-cell stage embryo

The relative quantity of cyclin B1 was determined during the development of in vitro and in vivo derived porcine 4-cell embryos by western blotting and immunolocalised during the 4-cell stage. After cleavage to the 4-cell stage cyclin B1 localised to the cytoplasm at the 5, 10, 18 and 25 time points and localised to the nucleus 33 h post 4-cell cleavage (P4CC). The relative abundance of cyclin B1 was not significantly different in in vivo or in vitro derived 4-cell stage embryos cultured in the absence of the RNA polymerase inhibitor alpha-amanitin. Cyclin B1 protein was not detectable in embryos cultured in medium without alpha-amanitin for 5, 10, 18 or 25 h P4CC followed by culture in medium with alpha-amanitin to 33 P4CC. These results suggest that the maternal to zygotic transition of mRNA production that occurs at the 4-cell stage of the pig embryo does not result in an increase in cyclin B1 production. In addition, cyclin B1 protein levels remained constant in the absence of embryonic genome activation at the 4-cell stage.     

Analysis of cytoplasmic factors in developmental cleavage of mouse embryo

One-cell embryos from certain mouse strains were found incapable of developing beyond the 2-cell stage in vitro (2-cell block), but a microinjection of EDTA effectively overcame this block. When 2-cell arrested embryos were fused with embryos that had developed to the late 2-cell stage in vivo, the fusants developed beyond the 2-cell stage. Microinjection of cytoplasm of in vivo 2-cell embryos into 1-cell embryos also obviated the 2-cell block. Analyses of 35S-labeled embryos by 2-dimensional polyacrylamide gel electrophoresis indicated changes in synthetic protein patterns possibly related to this block.     

Changes of lipid composition in non-cultured and cultured porcine embryos

The objective of the present study was to evaluate the lipid composition of cultured and non-cultured pig embryos during cleavage using histochemical methods. The authors studied pig zygotes as well as 2-to 4-cell embryos, morulae, and blastocysts that were either non-cultured or cultured in NCSU-23 medium. To detect different types of lipids, the authors used the Churukian method with Oil red O, the Sudan black B method, the Cain method with Nile blue sulfate, and the modified osmium tetroxide-ethanol treatment. In the zygotic lipid droplets, diverse classes of unsaturated and saturated lipids were found, with particularly high levels of unsaturated hydrophobic lipids, mainly triglycerides and other esters, free fatty acids, and phospholipids. In the zygotic cytoplasm, the authors observed high levels of fatty acids and phospholipids. The total lipid content remained constant up to the morula stage, decreasing later at the blastocyst stage, but the overall amount of unsaturated lipids declined earlier, at the 2-to 4-cell stage. The amount of free fatty acids and phospholipids decreased during cleavage in both non-cultured and cultured porcine embryos. The main differences between the non-cultured and cultured embryos were the more pronounced reduction in the amount of unsaturated hydrophobic lipids in droplets and the cytoplasmic free fatty acids observed in the cultured morula and the lower content of phospholipids in the cytoplasm of the cultured 2-to 4-cell embryos relative to the non-cultured embryos. The decrease in the unsaturated lipid, free fatty acid, and phospholipid content during in vivo development and the differences in the amount of these types of lipids between developmentally matched cultured and non-cultured pig embryos correlate well with modifications of lipid and carbohydrate metabolism.