牛卵母细胞冷冻保存研究进展

通过随时随地提供具有发育能力的卵母细胞,卵母细胞冷冻保存赋予体外受精、核移植、转基因等胚胎工程技术的极大灵活性,还可为珍稀濒危野生动物的保种提供技术参考.综述了牛卵母细胞冷冻保存方法及冷冻保存对牛卵母细胞结构和发育能力的影响.     

牛卵母细胞冷冻保存研究进展

通过随时随地提供具有发育能力的卵母细胞，卵母细胞冷冻保存赋予体外受精，核移植，转基因等胚胎工程技术的极大灵活性，还可为珍稀濒危野生动物的保种提供技术参考。综述了牛卵母细胞冷冻保存方法及冷冻保存对牛卵母细胞结构和发育能力的影响。     

牛羊卵母细胞玻璃化冷冻保存的研究进展

卵母细胞玻璃化冷冻保存对于胚胎生物技术的发展具有重要意义,因其简便、快速、廉价等优点而广泛应用于人类辅助生殖、体外胚胎生产、转基因、克隆等方面.由于受到低温和抗冻保护剂的影响,卵母细胞在冷冻过程中都会造成形态和功能上的损伤,并且存活率和发育能力随之降低.本文以牛、羊卵母细胞玻璃化冷冻保存为例,对卵母细胞玻璃化冷冻保存的...     

猪卵母细胞冷冻保存效果的评判

建立快速、准确、有效的猪卵母细胞冷冻保存效果的判定方法,将有助于促进猪卵母细胞冷冻保存的研究,从而提高猪卵母细胞冷冻保存效果,为哺乳动物配子和胚胎工程方面的研究提供大量优质卵母细胞。作者主要介绍通过形态学观察结果和发育潜力来判定猪卵母细胞冷冻保存效果的一些方法,如检查冷冻解冻后猪卵母细胞形态和超微结构正常情况,或进行体外成熟、体外受精、孤雌激活、显微受精,然后据此对猪的卵母细胞冷冻保存效果进行评判。     

猪卵母细胞玻璃化冷冻保存的研究进展

卵母细胞冷冻保存对于畜牧业生产和人类辅助生殖具有重要意义。随着玻璃化冷冻技术日趋成熟，其现已广泛应用于牛、羊等大家畜的卵母细胞冷冻保存。然而，猪卵母细胞的冷冻保存至今仍处于试验研究阶段，由于猪卵母细胞脂质含量高，对低温敏感，在玻璃化冷冻保存过程中极易受到冷冻保护剂毒性以及渗透胁迫、氧化应激等损伤，造成细胞骨架以及亚细胞器受损，最终导致细胞发育能力降低甚至死亡。近年来，人们在提高猪卵母细胞冷冻保存效率的研究中取得了突破性进展。本文简要介绍了卵母细胞冷冻保存的常见方法及作用机理，总结了猪卵母细胞在玻璃化冷冻过程中造成的细胞损伤类型及影响，概述了人们针对不同类型的冷冻损伤提出的解决方法和取得的成就，并对其应用前景进行展望，为今后提高猪卵母细胞的玻璃化冷冻效率提供新思路。     

哺乳动物卵母细胞低温存活的影响因素

哺乳动物卵母细胞的有效冷冻保存,会大大提高众多繁殖技术的实用性。那些最初用于哺乳动物卵裂期胚胎的平衡和非平衡冷冻保存方法,已经用于卵母细胞,但受精率和发育率显著低于没有冷冻的卵母细胞。在家畜上还未曾有过从冷冻卵母细胞发育到幼畜的研究报导。细胞骨架元素、减数分裂纺锤体和其它卵皮质组分,对遇冷和防冻剂的敏感性,不利于卵母细胞冷冻保存。降温过程中其它物理因素也会影响卵母细胞的存活。那些影响卵母细胞渗透反应和冷冻生物学反应的生物物理参数的估计将日益重要,有助于创造新的冷冻方法。     

超低温冷冻引发卵母细胞氧化应激及抗氧化剂的应用

卵母细胞超低温冷冻保存在人工辅助生殖和畜牧业上已有广泛应用。然而，超低温冷冻保存造成卵母细胞活性氧大量累积，引发一系列氧化应激，最终导致卵母细胞体内外发育潜力下降。卵母细胞内源的抗氧化酶无法彻底对抗氧化应激，因此在冷冻过程中常添加外源抗氧化剂来减少氧化损伤。文章着重分析了冷冻诱导卵母细胞产生的各种氧化应激、抗氧化剂对抗氧化损伤的效果及其作用机制，为提高卵母细胞冷冻保存效率提供参考。     

绵羊卵母细胞冷冻保存方法的研究

实验探讨了两种绵羊卵母细胞冷冻保存方法效果的差异。解冻的绵羊卵母细胞，挑选出形态完好的进行体外受精，然后进一步培养，比较发育情况。实验结果表明，79.7％与94.3％的卵母细胞形态正常，受精率分别为21.06％与31.87％。玻璃化冷冻保存后形态正常率较高（P＜0.01）。     

冷冻保存对猪卵母细胞超微结构及发育潜力的影响

随着辅助生殖技术的发展,配子与胚胎的超低温冷冻保存已成为动物种质资源保存的新热点,有可能在相当程度上替代活畜保种。但由于猪卵母细胞中含有大量脂滴,对低温敏感,耐受性差,给猪卵母细胞的冷冻保存带来很大的困难。目前还没有关于猪卵母细胞冷冻-解冻后经体外受精,然后移植产仔的成功报道,其原因可能是冷冻破坏了细胞骨架的结构。因此本文主要分析了冷冻保存对猪卵母细胞细胞骨架及其冻融后发育潜力的影响。     

家畜卵母细胞冷冻保存研究进展

自Whittingham(1977)首次成功的报道冷冻-解冻的小鼠卵母细胞活仔以来，国内外诸多学者对家畜及人的卵母细胞冷冻保存进行了研究。目前，已有小鼠、家兔、牛等动物以及人的卵母细胞冷冻成功，并得到了后代。在国内，山羊、绵羊、猪等家畜的卵母细胞冷冻保存也已有报道。随着胚胎工程技术的不断发展，卵母细胞的冷冻保存越来越受到重视，这将推动卵母细胞的冷冻保存取得更大进展。     

A phenotypic study of murine oocyte death in vivo

Most studies of oocyte apoptosis have been performed in vitro and have employed the method of artificial induction of apoptosis by an anti-cancer agent. However, the process of oocyte death in vivo has not been clearly identified. To investigate the death process in unfertilized oocytes in vivo, we examined the cytochemical change of oocytes collected by oviduct flushing at various intervals after hCG injection. At each collection time, the collected oocytes were phenotypically classified under the microscope into four groups: single-cell oocytes (non-activated and without a nucleus and cytokinesis), activated oocytes (single-, 2- or 4-cell with a nucleus), fragmented oocytes, and dead oocytes. The number of single oocytes decreased and dead oocytes increased with the lapse of time, but the number of activated oocytes or fragmented oocytes did not. Also, most of the dead oocytes observed were single cell. At each time point, single oocytes were stained with anti-tubulin antibody to examine their spindle status. At 24 h after hCG injection, all ovulated oocytes had a normal bipolar spindle, while at 64 h all single-cell oocytes had no spindle. From these observations, we concluded that most oocyte deaths in vivo occur in the single oocyte stage, not in activated or fragmented oocytes.     

Activation and penetration in vitro of pig oocytes treated with calcium ionophore

The present study examined the effects of pre-treatment of pig oocytes with different concentrations (0-50 microM) of calcium ionophore A23187 (CaA) on their activation, development and penetration in vitro. Although untreated oocytes were not activated and did not cleave in culture, high proportions of treated oocytes did so and 20% of oocytes developed to the blastocyst stage when treated with 6.25 microM CaA for 2 min. However, these proportions were reduced in a concentration-dependent manner. When inseminated in vitro with 1 x 10(6) spermatozoa/ml, the penetration rate of oocytes treated with 6.25 microM CaA was similar to that of untreated oocytes. However, fewer oocytes treated with 12.5 and 50 microM CaA were penetrated than untreated oocytes. On the other hand, the proportion of monospermy of oocytes treated with 6.25 microM CaA was higher than the values in oocytes not treated or treated with 50 microM CaA. The time required for zona dissolution of oocytes treated with 6.25 and 12.5 microM CaA was not different from that in untreated oocytes, but oocytes treated with 50 microM CaA required a longer time than untreated oocytes, indicating that zona solubility by protease does not reflect penetrability of oocytes in vitro. When oocytes were inseminated with different concentrations (1-10 x 10(6) cells/ml) of spermatozoa, the highest penetration rate was observed at 1 x 10(6) cells/ml in untreated oocytes and a similar result was obtained in oocytes treated with 6.25 microM CaA. There was no difference in the rate of monospermy in untreated oocytes among different concentrations of spermatozoa, but in treated oocytes, higher proportions of monospermy were observed at 0.5-5 x 10(6) than 10 x 10(6) cells/ml. At 1 x 10(6) cells/ml, the proportion of monospermy was higher in treated than untreated oocytes. These results suggest that pre-treatment of pig oocytes with 6.25 microM CaA, an appropriate concentration, inhibits polyspermic penetration in vitro when insemination occurs with spermatozoa at a concentration of 1 x 10(6) cells/ml.     

兔·卵·母·细·胞·孤·雌·激·活·的·研·究

本研究探讨了兔卵母细胞孤雌激活的方法。兔卵母细胞经7%乙醇单独激活处理5min的卵裂率(13.0%),显著低于乙醇处理后在2mmol/LDMAP继续处理3h(48.1%)和5μmol/L离子霉素处理后在DMAP继续处理3h的卵母细胞(92.2%);离子霉素+DMAP处理组的囊胚发育率(27.1%)亦显著(P<0.05)高于乙醇+DMAP处理组(15.4%)和乙醇单独处理组(0%)。当用离子霉素和DMAP激活处理时,注射hCG后18h卵母细胞的卵裂率(92.1%)和囊胚率(35.3%)最高2,4h后卵母细胞的卵裂率(19.0%)和囊胚发育率(4.2%)均显著(P<0.05)下降。卵母细胞经离子霉素激活处理后,在DMAP继续处理1、35、h的卵裂率差异显著(P<0.05);而囊胚发育率无显著(P>0.05)差异。离子霉素和DMAP处理后再电激1次对卵母细胞的卵裂率(83.3%、80.0%)和囊胚率(30.0%、27.0%)无显著(P>0.05)影响。以上研究表明:离子霉素+DMAP是兔卵母细胞最有效的激活方法,注射hCG后18h的卵母细胞可取得较好的激活效果。     

共培养体系对哺乳动物卵母细胞体外成熟影响的研究进展

卵母细胞体外成熟是进行体外胚胎生产的关键环节,但目前哺乳动物卵母细胞体外成熟培养存在成熟率低、受精率低和胚胎质量差等问题。卵母细胞体外成熟培养体系是制约卵母细胞体外成熟效果的重要因素,共培养体系可提高哺乳动物卵母细胞体外成熟效率。本文主要从卵母细胞成熟与卵泡细胞共培养、与裸卵共培养和与间充质干细胞共培养3个方面综述共培养体系对哺乳动物卵母细胞体外成熟的影响,为共培养体系应用于卵母细胞体外成熟提供理论依据和研究借鉴。     

Alterations of spindle and microfilament assembly in aged cat oocytes

To obtain insights into the cytoplasmic maturation status of cat oocytes recovered from cat ovaries following hormone treatment, we first examined microtubule and microfilament assembly in cat oocytes recovered from hormone-treated ovaries at various stages of maturation. Additionally, we determined the alteration of spindle and microfilament assembly, as well as mitogen-activated protein kinase (MAPK) activity, in cat oocytes at 0, 6, 12 and 18 h of further maturation in vitro. We then looked at pronuclear formation and cleavage of these oocytes following parthenogenetic activation. Similar to other species, microtubules are present in germinal vesicle (GV) stage cat oocytes, and following GV breakdown, microtubules encompassed condensed chromatin particles to form the meiotic metaphase spindle. Microfilaments were located in the cortex and around the GV. A microfilament-rich area, in which the chromatin is located, was observed in the oocytes during meiotic maturation. Maturation rates in aged oocytes (cultured for 18 h) were increased when compared with that in relatively fresh oocytes (<12 h culture), and the number of oocytes with abnormal spindle shapes was also increased in aged oocytes. Furthermore, in aged oocytes, the incidence of the metaphase plate observed outside the thick microfilament domain was higher compared with that of young oocytes, and this seemed to result in an increase in the number of oocytes with two pronuclei and one polar body following activation. Western blot analysis revealed a decrease in MAPK activity in aged cat oocytes. Taken collectively, these results suggest that the optimum time for improved cytoplasmic maturation is <12 h in cat oocytes recovered from hormone-treated ovaries.     

牛体外成熟卵母细胞染色体形态学研究

[目的]为了给牛体细胞克隆和转基因克隆工作提供基础性材料.[方法]在显微镜下,从卵液中捡出卵丘-卵母细胞复合体,置入成熟培养液中进行成熟培养,处理培养不同时期的卵母细胞,所得的去掉卵丘的卵母细胞固定在载玻片上,染色、冲洗、晾干,在显微镜下观察.[结果]表明:成熟培养0 h到4 h大多数卵母细胞处于GV期(97.5%～87.8%),培养6 h以后GVBD发生了卵母细胞数量明显增多(51.6%),成熟培养8 h～12 h处于Pre-MI的卵母细胞逐渐减少(76.7%～43.2%),MI期卵母细胞逐渐增多(13.3%～50.0%).成熟培养16 h有17.8%的卵母细胞处于MII期,大部分细胞仍处于MI期(40.0%)和AI/TI期(42.2%).从16 h～24 h,MII期卵逐渐增多,培养24 h后大多数卵母细胞排出第一极体到达MII期(86.5%).[结论]在减数分裂过程中,染色体也发生了显著的形态变化.第一次减数分裂中期时的染色体清晰可数,进入后期时,分开的两团染色体各自凝集成染色质团,并且一直持续到末期,到达第二次减数分裂中期时又成为清晰可数的染色体状态.     

Sucrose assists selection of high‐quality oocytes in pigs

We investigated whether high‐quality in vitro matured (IVM) oocytes can be distinguished from poor ones based on the morphological changes after treatment with hyperosmotic medium containing 0.2 mol/L sucrose in pigs. We hypothesize that IVM oocytes maintaining round shape have higher quality than mis‐shapened oocytes following dehydration. Oocyte quality was verified by determining embryonic developmental competence using in vitro fertilization, nuclear transfer and parthenogenetic activation. In all cases, the round oocytes had greater (p < .05) developmental competence than that of mis‐shapened oocytes in terms of blastocyst rate and total cell number in blastocysts obtained after 6 days of in vitro culture. We also confirm that round aged oocytes are higher in quality than mis‐shapened aged oocytes. In an attempt to find out why high‐quality oocytes maintain a round shape whereas poorer oocytes become mis‐shapened following sucrose treatment, we examined the arrangement of actin microfilaments and microtubules. Abnormal organization of these cytoskeletal components was higher (p < .05) in mis‐shapened oocytes compared to round oocytes after 52 hr of IVM. In conclusion, sucrose treatment helps selection of high‐quality oocytes, including aged oocytes, in pigs. Abnormal cytoskeleton arrangements partly explain for low developmental competence of mis‐shapened oocytes.     

Meiotic resumption of porcine immature oocytes is prevented by ooplasmic Gsalpha functions

A high cyclic adenosine monophosphate (cAMP) level in fully-grown immature oocytes prevents meiotic resumption. In Xenopus, inhibitory cAMP is synthesized within oocytes depending on a stimulatory alpha-subunit of G-protein (Gsalpha). In the present study, we examined whether ooplasmic Gsalpha is involved in meiotic arrest of porcine oocytes. First, we studied the presence of Gsalpha molecules in porcine oocytes by immunoblotting, and this suggested the presence of reported isoforms (45 and 48 kDa) not only in cumulus cells but also in porcine oocytes. Then we injected an anti-Gsalpha antibody into porcine immature oocytes and found that inhibition of ooplasmic Gsalpha functions significantly promoted germinal vesicle breakdown of the oocytes, whose spontaneous meiotic resumption was prevented by 3-isobutyl-l-methylxanthine (IBMX) treatment. Although cyclin B synthesis and M-phase promoting factor (MPF) activation were largely prevented until 30 h of culture in IBMX-treated oocytes, injection of anti-Gsalpha antibody into these oocytes partially recovered cyclin B synthesis and activated MPF activity at 30 h. These results suggest that meiotic resumption of porcine oocytes is prevented by ooplasmic Gsalpha, which may stimulate cAMP synthesis within porcine oocytes, and that synthesized cAMP prevents meiotic resumption of oocytes through the signaling pathways involved in MPF activation.     

Growth of primordial oocytes in neonatal and adult mammals

Mammalian ovaries are endowed with a huge number of small oocytes (primordial oocytes) in primordial follicles. A small number of primordial oocytes start to grow, while others remain quiescent. Little is known about the mechanism regulating the activation of primordial oocytes. Recently, we found that primordial follicles in mature cows and prepubertal pigs took longer to initiate growth in xenografts compared with those in neonatal animals. We think that primordial oocytes in adult mammals are different from those in neonatal mammals. In this review, we summarize the results regarding the activation of primordial oocytes in neonatal and adult ovaries of different species and propose a model in which ovaries of neonatal mammals contain a mixed population of both quiescent and activated primordial oocytes, while almost all primordial oocytes are quiescent in adult females. The dormancy of primordial oocytes may be required to reserve the non-growing oocyte pool for the long reproductive life in mammals. FOXO3 is considered one of the molecules responsible for the dormancy of primordial oocytes in adult ovaries. These quiescent primordial oocytes are activated, perhaps by certain mechanisms involving the interaction between stimulatory and inhibitory factors, to enter the growth phase.