家兔早期胚胎细胞发育能力的研究

本文利用胚泡注射法制作嵌合体对家兔交配后96,120和144小时的ICM细胞的发育能力进行了研究。供体胚胎取自青紫兰灰免,受体胚胎取自新西兰白兔,结果表明96和120小时供胚的ICM细胞与96小时受胚胚泡组合后均能参与发育,形成嵌合兔,144小时者未获得嵌合体。由于120小时的ICM细胞发育的2只表型为雄性的嵌合兔,其中1只不育,其性腺和外周血核型表明不育兔为xx/xy性嵌合,性腺中有处于不同发育程度的卵巢和精细管,外周血含xx和xy两种核型。本实验结果首次证明家兔交配后120小时胚泡的ICM细胞仍具有参与嵌合体发育的能力。它不仅能参与体细胞的分化,并具有形成生殖细胞的能力。交配后144小时胚泡的ICM细胞其发育能力似乎已发生了局限。     

胚胎小肠Cajal细胞的发育研究

目的研究人胚胎小肠cajal细胞的发育变化规律。方法采用全层铺片结合切片的免疫细胞化学技术。结果Cajal细胞呈酪氨酸激酶受体(Kit)和波形蛋白(vinlentin)免疫反应阳性。在胚胎发育早期,cajal细胞较少,为单层,稀疏分布于肌间神经丛周围,细胞为梭形,可见两个短而小的突起,未见分支;随着胎龄的增加,Cajal细胞数量增多,胞体增大,突起伸长,并出现分支。此时,肌间神经丛周围的Cajal细胞出现两层,其长轴彼此垂直,分别平行于环行肌和纵行肌。与此同时环行肌层内亦可见少许Cajal细胞;出生前,肌间神经丛部位的Cajal细胞接近成熟,两层细胞的突起进一步增多、伸长,彼此间形成与成人相似的完整的细胞网络。此时深肌丛附近亦可见少量Cajal细胞。结论人的小肠Cajal细胞发育有一定的时间顺序,即肌间神经丛周围最先出现,肌内次之,深肌丛较晚,出生前肌间神经丛周围的Cajal细胞已经接近成熟。这种发育演变若发生异常,可能导致某些胃肠动力障碍性疾病。     

家兔胚胎细胞核移植的研究

本研究以兔为实验材料,对细胞核过程中显微操作、电融合、电活化以及移核胚的培养等基本问题进行了研究。对兔进行PMSG－hCG超数排卵,收集成熟母细胞和16－细胞胚;后者经胰蛋白酶消化,去除胶膜和透明带,在不含Ca62 、Mg^2 的分离中分成单个卵裂球;然后,分别对两者做CB预处理;首次尝试采用WQilladsen法,去除卵母细胞核、并将单个卵裂球注入透明带,同时、与McGrath-Solter法进行比较;通过电融合使供体核进入去核的卵母细胞内;将所得移核胚在体外或在中间内体内培养并观察。结果表明：一、Willadsen法与McGrath-Solter法比较,核移植操作的成功率及以后的电融合率均无明显差异（Tab.1)。相对于后者,Willadsen法更简便、易于掌握并提高去核率。二、hCG超排注射后13－15h,观察卵母细胞发现：其中,67．8％保留有第一极体。此时的卵子若去除1／3胞质量,去核率可以达到58．3％。若推迟去核时间,第一极体退化,失去去核标志。三、比较不同电脉冲条件,发现强度为0．63kv/cm,持续160μs的一次电脉冲可获较高移核胚的融合率（70．8％）（Tab.2）;并可使61．1％的成熟卵母细胞活化。四、比较移核胚在体外和在中间有体内两种培养条件,前者只有34．6％能发育到6－8细胞期,而后者有23．0％能发育到桑椹胚或囊胚（Tab.3)。说明：需进一步优化家兔胚体外培养条件。     

金鱼胚胎细胞超低温保存及其发育能力的研究

将金鱼囊胚期的细胞分离后,保存于-196℃液氮中,并对保存后化冻的细胞用细胞核移植的方法检测了其细胞核发育的能力。本文首次证明了经冷冻后的细胞核被移至去核卵中能发育成正常的个体。并证明在冷冻液中加入胶原蛋白可以提高化冻后细胞的存活率。本实验的结果为长期保存端黄卵的各种鱼类的基因库提供了新的途径。     

小鼠电融合四倍体胚胎早期发育的研究

多倍体发育现象在低等动物,尤其是在无脊椎动物中比较普遍,在哺乳动物中多倍体往往发育到胚胎早期就死亡,因而在自然界中不能存活。探讨哺乳类四倍体不能存活的原因是当今生物学研究的热点问题之一。目前,电融合技术是大量获得四倍体胚胎的主要手段。本以8－12周龄昆明小白鼠为实验对象,取其2－细胞胚胎于Whitten氏液中进行电融合,再移入CZB液中培养。电刺激的条件分别为：1．0kv/cm,40μs,和0．8kv/cm,80μs。对融合胚发育的状态、细胞数目及染色体组成等进行观察的结果表明,融合胚培养24小时后发育到4－细胞期,并发生致密化（Tab.1)。融合胚的囊胚形成时间与体内发育的同期胚胎及体外培养的同期二倍体胚胎基本一致（Tab,2;Fig.1)。融合囊胚的细胞数平均为13．0±4．95,显（P＜0．01）少于体外发育囊胚（37．0±5．92）和体内发育囊胚（41．6±2．4）的细胞数（Tab.3)。融合胚各个分裂相的染色体数目分布情况见Fig.2,其四倍体（4n＝80）率为42．86％,非整倍体率达57．14％。而对照组的体内发育囊胚的非整倍体率仅为11．54％;（Tab.4),与Kaufman的结果（12．4％）很接近,说明本实验中的染色体制备技术和分析方法是可行的。融合囊胚的细胞数目减少和高发的非整倍体率可能是四倍体胚胎发育能力差的原因。     

两栖类胚胎表皮细胞的传导能力

两栖类胚胎表皮细胞在胚胎发育的一定时期具有传导能力。叙述了胚胎表皮细胞传导的性质、胚胎表皮细胞间兴奋传导的结构基础以及胚胎早期兴奋传导的通路，并提出了有待进一步探索的问题。     

鼠兔核质杂交胚胎早期发育的研究

细胞核移植技术已被证明是研究发育中核质相互关系的非常重要的手段之一,电融合技术也是近十年发展起来的新型细胞融合技术也是近十年发展起来的新型细胞融合技术,本实验运用这两项技术,进行了鼠、兔目间核质杂交实验,小鼠８－细胞核在激活的兔去核卵母细胞中,发五了染色体超前凝聚及核膨胀,融合卵移植到小鼠输卵管４．５天后,冲洗出,有５．４％的重构卵发育到囊胚期,通过染色体检查,囊胚细胞中均为小鼠染色体,其中一个囊     

小鼠电激活孤雌胚胎早期体内外发育能力的比较

目的探讨小鼠电激活孤雌胚胎的早期体内、外发育能力。方法 利用不同电脉冲参数和激活液对小鼠卵母细胞进行活化,观察激活后的小鼠孤雌胚体外发育状况和移植后的发育能力。结果非电解质激活液优于电解质液,脉冲强度、脉冲宽度和脉冲次数3个参数各自处于某一范围内时,他们之间存在某种相关性,降低其中1个参数可通过升高另外2个参数得到补偿,经筛选较适宜的电脉冲参数为：1.0 kV/cm、40μs、2 p,或者1.5kV/cm、30/μs、2 p,分别为74.65%和71.19%,体外囊胚发育率分别为43.40%和47.62%。电激活孤雌胚体外发育时序比正常胚胎慢,但囊胚细胞数与对照组差异不显著。它们经胚胎移植后,其中的一部分能够着床,但着床率仅为3.6%,极显著低于对照组（67%,P〈0.01）。结论电刺激能够较好地模拟正常受精过程激活小鼠卵母细胞,但激活后的多数小鼠孤雌胚胎着床能力较低,不能够顺利着床。     

动物胚胎发育讲座（一）：动物胚胎早期发育概况

动物胚胎发育讲座（一）──动物胚胎早期发育概况张天荫（山东大学生物学系济南２５０１００）１生殖细胞与受精生殖细胞的发生在后生动物大致相似,都要经过增殖期、生长期和成熟期。增殖期乃是精（卵）原细胞经过多次有丝分裂使数量不断增加;生长期是部分精（卵）原细...     

Epigenetic stability of embryonic stem cells and developmental potential

Recent studies highlight the tremendous potential of human embryonic stem (ES) cells and their derivatives as therapeutic tools for degenerative diseases. However, derivation and culture of ES cells can induce epigenetic alterations, which can have long lasting effects on gene expression and phenotype. Research on human and mouse stem cells indicates that developmental, cancer-related genes, and genes regulated by genomic imprinting are particularly susceptible to changes in DNA methylation. Together with the occurrence of genetic alterations, epigenetic instability needs to be monitored when considering human stem cells for therapeutic and technological purposes. Here, we discuss the maintenance of epigenetic information in cultured stem cells and embryos and how this influences their developmental potential.     

An assessment of the developmental potential of embryonic stem cells in the midgestation mouse embryo

Embryonic stem cells (ES) cells were injected into host blastocysts either in groups of 10-15 cells or as single cells in order to test their developmental potential in the developing embryo. The analysis of midgestation chimaeras, by electrophoretic separation of glucose phosphate isomerase (GPI) isozymes, showed that ES cells were capable of colonizing trophectoderm and primitive endoderm derivatives at a low frequency, as well as producing a high rate of chimaerism in tissues of the fetus and extraembryonic mesoderm.     

The participation of the embryonic genome during early cleavage in the rabbit

Actinomycin D and the mushroom toxin α-amanitin similarly inhibit ribonucleic acid synthesis in the rabbit zygote. Actinomycin D also causes an immediate arrest of cleavage, whereas α-amanitin allows limited further development. The decreasing rate of amino acid incorporation caused by continuous exposure of cleaving rabbit embryos to α-amanitin suggests that a relatively homogeneous embryonic RNA is involved in the support of early protein synthesis and is turning over with a half-life of approximately 24 hr, or three cell generation times.     

Epigenetic integrity of paternal imprints enhances the developmental potential of androgenetic haploid embryonic stem cells

The use of two inhibitors of Mek1/2 and Gsk3β(2i)promotes the generation of mouse diploid and haploid embryonic stem cells(ESCs)from the inner cell mass of biparental and uniparental blastocysts,respectively.However,a system enabling long-term maintenance of imprints in ESCs has proven challenging.Here,we report that the use of a two-step a2i(alternative two inhibitors of Src and Gsk3β,TSa2i)derivation/culture protocol results in the establishment of androgenetic haploid ESCs(AG-haESCs)with stable DNA methylation at paternal DMRs(differentially DNA methylated regions)up to passage 60 that can efficiently support generating mice upon oocyte injection.We also show coexistence of H3K9me3 marks and ZFP57 bindings with intact DMR methylations.Furthermore,we demonstrate that TSa2itreated AG-haESCs are a heterogeneous cell population regarding paternal DMR methylation.Strikingly,AGhaESCs with late passages display increased paternal-DMR methylations and improved developmental potential compared to early-passage cells,in part through the enhanced proliferation of H19-DMR hypermethylated cells.Together,we establish AG-haESCs that can longterm maintain paternal imprints.     

The differentiation of early embryonic stem cells into adipocytes-like cells

An early embryonic stem cell line, EES-6 cells, was established from 2-cell stage embryos of ddY mice. The cells were maintained in an undifferentiated state with D-MEM/F12 medium supplemented with 10% fetal bovine serum (FBS) (GM) and 1 ng of leukemia inhibitory factor (LIF) without any feeder cells. In this study, EES cells were cultured with a medium containing embryotrophic factors (ETFs) which promoted the differentiation of EES cells into white and brown adipocytes-like cells for a period of 5 days. Lipid droplets in brown adipocyte-like cells were stained with Sudan III; however, large lipid-like droplets in white or brown adipocyte-like cells were unstained with either Sudan III or alcian blue. These findings have numerous possibilities for therapeutic use such as regeneration of skin and wound healing.     

Testing potential developmental toxicants with a cytotoxicity assay based on human embryonic stem cells

Since the differentiation of embryonic stem cells mimics early development, these cells could potentially permit the detection of embryotoxicants which interfere with this process. Although reliable tests based on murine embryonic stem cells exist, no such methods are available for human embryonic stem (hES) cells. Nonetheless, to avoid the false classification of substances due to inter-species differences, human-relevant toxicity tests are needed. We therefore developed an assay based on three human cell types, representing different degrees of developmental maturation, namely, human foreskin fibroblasts, hES cell-derived progenitor cells, and pluripotent hES cells. A set of embryotoxicants for which existing in vivo data were available, namely, all-trans retinoic acid (ATRA), 13-cis retinoic acid (13CRA), valproic acid (VPA) and dimethyl sulphoxide (DMSO), were tested. 5-fluorouracil (5-FU) was used as a positive control, and saccharin as a negative control. Two methods were compared for the assessment of cell viability -- the determination of intracellular ATP content and of resazurin reduction. In addition, the protective capacity of basic fibroblast growth factor (bFGF) against retinoid-induced toxicity was investigated. This novel assay system reliably detected the embryotoxic potentials of the test substances, 5-FU, ATRA, 13-CRA (a substance that displays inter-species differences in its effects) and VPA. This was possible due to the apparent differences in the sensitivities of the human cell types used in the assay system. Thus, our results clearly indicate the advantages and relevance of using hES cells in in vitro developmental toxicity testing.     

Restriction of cloning potential in agarose of early chick embryonic cells as development progresses

Early chick embryonic cells, prior to the formation of the primitive streak, form colonies when cultured in soft agarose [Mitrani, E.: Exp. Cell Res. 152, 148-153 (1984)]. The present work is an attempt to determine at which stages of development this ability is expressed and which areas of the chick embryo harbour the colony-forming cells. We found that the capacity to form colonies decreases as development progresses and cells enter alternative differentiation pathways. At pre-primitive streak stages, the capacity is concentrated to the peripheral areas of the embryo and decreases towards the centre. With the onset of hypoblast formation only cells from Area Opaca and, to a lesser degree, the Marginal Zone, can form colonies in agarose. At post-primitive streak stages only extra-embryonic cells can form colonies in agarose. By 48 h of incubation all cells of the chick blastoderm seem to have lost the capacity to form colonies in agarose.