低强度脉冲微波辐照对小鼠下丘脑SDH、MAO和G-6-Pase活性影响的研究

本文为观察低强度微波辐照对中枢神经系统的影响,选择下丘脑细胞线粒体标志酶琥珀酸脱氢酶(SDH)、单胺氧化酶(MAO)和内质网标志酶葡萄糖-6-磷酸酶(G-6-Pase)为指标,以显微分光光度术对上述酶进行组织化学定量分析。实验使用1mW/cm~2和5mW/cm~2脉冲微波急性辐照出生后15天及45天的小鼠。结果动物下丘脑部位的SDH、MAO和G-6-Pase活性均下降,提示低强度的微波辐照可影响神经细胞的能量代谢与介质代谢。     

微波免疫效应研究——低强度微波长期辐射对免疫功能的影响

本文以频率为3 GHz脉冲微波、功率密度为1和0.1mW/cm~2(SAR=0.32～0.2和0.032～0.02mW/g,大鼠),0.5和0.05mW/cm~2(SAR=0.6～0.45和0.06～0.045mW/g,小鼠)于微波暗室内对动物进行辐照,并设大鼠和小鼠两个假辐射组,每天5小时,每周6天,共11个月。结果发现:辐射组大鼠胸腺重量较轻、实质组织减少及胸腺细胞数减少,嗜中性粒细胞吞噬活性下降,血细胞凝集素效价(HAT)反应低落;但0.05mW/cm~2辐射组小鼠周血的淋巴细胞绝对值及HAT反应均较假辐射组为高。实验表明,低强度微波长期辐射,对机体免疫功能具有“亚临床损伤”的累积效应。强度较高时,免疫抑制反应较早出现;强度较低时,免疫抑制反应较迟出现,甚或仍呈免疫增强反应。     

毫米波辐照对小鼠植入后胚胎发育的影响：Ⅱ：生后精神生理学分析

本文用频率36.11GHz,功率密度为7.2mW/cm~2的毫米波,在小鼠怀孕6—15天时进行2小时/天的照射,用生后精神生理学指标进行分析。结果发现,未见导致胎仔生后耳廓张开、睁眼、睾丸下降、阴唇张开等生理指标的改变,也未使表面翻正、姿态纠正、听觉惊愕等早期反射指标发生变化,成熟仔鼠的游泳耐力亦未受明显影响。但可导致出生三天内的脍仔体重降低,一周后照射组胎仔体重与对照组无明显差别。毫米波辐射可导致成熟后仔鼠的学习及记忆能力降低,表现在Y型电迷宫条件反射实验中,需要较对照组鼠更多训练次数和错误次数才能达到规定标准。实验证明,低功率密度毫米波照射植入后期胚胎可引起仔鼠精细的精神生理学方面的改变。     

毫米波辐照对小鼠腺垂体,睾丸和肾上腺皮质超微结构的影响

本实验用频率36.11GHz,功率密度为5mW/cm~2的毫米波,每天30分钟,连续5天照射小鼠背部,于照后1、3、5、7天时处死,观察腺垂体、肾上腺和睾九的超微结构变化。结果发现照射后腺垂体部分促生长激素细胞、促性腺激素细胞出现一定程度的退行性变化,后期有分裂刺激现象。睾丸生精上皮细胞有一定程度的损伤性变化,少数细胞还见有凝固性坏死。睾丸支持细胞、间质细胞和肾上腺皮质细胞仅见轻微变化。上述结果证明低功率密度毫米波辐射对小鼠内分泌系统有一定程度的生物学效应。     

低强度微波辐射对人细胞非热生物效应的研究

选用频率2450MHz分别在1，3，5，7mW/cm^2的功率密度下使用新型宽带横电磁传输室辐照人外周淋巴细胞和红细胞以及Hela细胞。采用细胞遗传学实验技术，测定外周血淋巴细胞的微核发生率、染色体畸变率、SCE值及有丝分裂指数；通过聚丙烯酰胺凝胶电泳技术分析辐照后细胞膜骨架蛋白的变化；运用软琼脂细胞克隆形成法测定微波辐射对Hela细胞克隆形成能力的影响。结果表明在5mW/cm^2和7mW/cm^2的功率密度下能使淋巴细胞微核发生率、染色体畸变率、SCE值显著升高，使人红细胞膜骨架蛋白发航天部份解离，对Hela细胞克隆形成能力有明显的抑制作用。在7mW/cm^2功率密度下，辐射使人淋巴细胞有丝分裂指数显著降低，染色体发生明显的解螺旋现象，最后对细胞的非热效应进行了初步的探讨。     

微波免疫效应研究——微波对小鼠血细胞凝集素效价试验的影响

本文以7mW/cm~2（SAR=7.7mW/g）功率密度的3GHz脉冲波辐射青年昆明杂种小鼠（下同）（9～10周龄）60min/day，连续2天。辐射后第3天作绵羊红细胞（SRBC）免疫，第7天作血细胞凝集素效价（HAT）测定，有增加倾向，第8天达高峰（P＜0.01），第9天开始回降，第22天恢复到对照组水平，显示微波辐射对小鼠的免疫机能有短暂的增强作用。以1、5、7和12mW/cm~2不同功率密度（SAR分别为1.1、5.5、7.7和13.2mW/g）的微波辐射青年鼠，辐射与免疫条件同上，1mW/cm~2组小鼠的HAT无甚差异，5mW/cm~2组增加非常显著（P＜0.005），7mW/cm~2组增加最为显着（P＜0.001），12mW/cm~2组增加亦显著（P＜0.005），但比7mW/cm~2组为低。以5mW/cm~2相同功率密度的微波，辐射不同年龄小鼠（幼、青和成年鼠的SAR分别6、5.5和4.5mW/g），辐射与免疫条件同上，幼年鼠（4～5周龄）的HAT差异不显著，而青年与成年鼠（16周龄以上）明显增加（P＜0.005），尤以成年鼠增加为显著。     

耐辐射肺腺癌细胞模型的放射生物学鉴定

目的：体外构建耐辐射的肺腺癌细胞模型,研究与肿瘤细胞辐射抗性相关的生物学变化。方法：通过分次照射建立了耐辐射的肺腺癌细胞模型A549RR;将A549和A549RR细胞各随机分为两组,分别给予0和8Gy辐照,检测亲本细胞与耐辐射细胞的增殖能力和对放疗的敏感性;在A549、A549RR和辐射抗性部分消失的A549RR’三个细胞系中分别设置顺铂治疗组、顺铂联合放射治疗组和空白对照组,检测细胞对化疗及联合放化疗的敏感性;同时利用流式细胞术分别检测A549和A549RR细胞在接受0和8 Gy辐照后的细胞周期变化和凋亡情况,使用彗星试验检测DNA损伤情况,检测活性氧（ROS）和8-羟基脱氧鸟苷（8-OHdG）水平,并对细胞进行衰老相关β-半乳糖苷酶染色。结果：与亲本A549细胞相比,A549RR细胞的辐射抗性显著增强（P<0.01）,增殖能力显著下降（P<0.01）,化疗前后细胞活力无显著差异。相比亲本A549细胞,处于G2/M期的A549RR细胞显著减少（P<0.01）,处于S期的A549RR细胞显著增多（P<0.01）;高剂量辐照后,亲本A549细胞发生S期阻滞,而A5...     

2450MHz微波辐射对离体培养人肝癌细胞系(BEL—7402)的生物效应

本实验应用2450MHz微波进行了对体外培养人肝癌细胞系生物效应的研究。采用一循环液体散热装置控制介质温度,观察了在一定照射条件下对BEL-7402细胞系形态和增殖的影响。 在实验中观察到,50mW/cm~2～100mW/cm~2连续波一次照射30分钟对细胞的损伤程度与功率密度呈平行关系。其中75mW/cm~2照射30分钟,介质温度维持在43±0.57℃细胞生长抑制率为41％～65％,对细胞分裂和DNA合成均有明显的抑制作用,但这一作用在解除微波照射48小时后逐渐恢复。     

微波辐照诱导内质网应激致心肌微血管内皮细胞损伤

目的探讨微波辐照致心肌微血管内皮细胞损伤与内质网应激之间的关系。方法取培养3~4代心肌微血管内皮细胞随机分为对照组和辐照各组。1.分别采用10mW/cm2,30mW/cm2、50mW/cm2微波辐射心肌微血管内皮细胞,辐照时间均为6min。于照射后24h收集细胞。2.细胞被暴露于30mW/cm2微波6 min,继续培养1 h、3 h或24 h之后,内皮细胞被收集,对照组于24 h结束实验。以膜联蛋白V-碘化丙啶双染法检测细胞凋亡;鬼笔环肽染色法观察微血管内皮细胞骨架的变化,评价微血管内皮细胞的损伤情况;免疫印迹法检测内质网应激分子钙网蛋白(CRT)、葡萄糖调节蛋白78(GRP78)和CCAAT/增强子结合蛋白同源蛋白(CHOP)的蛋白表达,评价微波辐照是否引起微血管内皮细胞内质网应激。结果内皮细胞凋亡率的量效研究发现,微波辐照之后,10mW/cm2、30mW/cm2、50mW/cm2照射组的细胞凋亡率分别为(2.34±0.15)%、(2.72±0.96)%、(2.62±0.34)%,与对照组(0.88±0.32)%比较差异显著(P0.05)。时效研究则发现,30mW/cm2照射后1h、3h和24h细胞凋亡率分别为(1.12±0.15)%,(1.49±0.54)%和(1.85±0.45)%。与对照组(1.10%±0.28)%比较,照射后1h组差异不显著(P0.05),照射后3h组和24h组差异显著(P0.05);内质网应激分子的检测发现,30mW组CRT、GRP78、CHOP的蛋白表达分别较对照组升高124%,76%,256%。50mW组CHOP的蛋白表达分别较对照组升高52%,189%。与对照组相比,30mW组CRT、GRP78、CHOP GRP78、及50mW组GRP78、CHOP表达差异显著(P0.05)。10mW组CRT、GRP78、CHOP及50mW组CRT蛋白表达与对照组相比差异无显著性(P0.05)。对照组内皮细胞表现出很少的肌动蛋白纤维。内皮细胞暴露于微波引起的丝状肌动蛋白应力纤维数量的急剧增加。最大应力纤维的形成发生在内皮细胞受到照射后3h或照射功率为30mW。结论微波辐照可诱导严重内质网应激反应,造成大鼠心肌微血管内皮细胞损伤。     

微波辐照胚胎期小鼠及出生后的幼鼠对其发育的影响

本文以8mW/cm~2的3GHz脉冲微波对怀孕小鼠在整个孕期作每天5小时的辐射(R组)或假辐射(C组),观察对发育中小鼠的影响。母鼠受辐射的比吸收率(SAR)为3.0～3.5mW/g,辐射后未见体温升高。两组母鼠(R或C)的子代在3～20天龄时,各取一半继续辐射(相应为RR或CR组);另一半假辐射(RC或CC组)。结果在四组子鼠间的体重,翻正试验、听反应惊跳、开眼、前肢悬力测试,均未见差异。酸性磷酸酶(ACP)阳性的小鼠,其中性白细胞百分率,在出生后辐照时有增高现象。用显微分光光度计进行脑和肝的组织化学分析,发现脑内琥珀酸脱氢酶(SDH)下降,呈RR相似文献   

小鼠早期完整胚胎诱导子宫内膜白血病抑制因子和整合素β3表达并提高子宫容受性

目的: 探讨小鼠早期胚胎诱导子宫内膜容受性改变的空间结构,确定胚胎各个部分能否引起子宫内膜容受性中白血病抑制因子(LIF)和整合素β₃改变。方法: 选用6~8周昆明雌鼠,体外实验分为子宫内膜培养前组、子宫内膜单纯培养组、子宫内膜全胚胎共培养组、子宫内膜卵裂球共培养组、子宫内膜透明带共培养组,各组培养2 d后收集子宫内膜行下一步检测;体内实验分为胚胎移植前组、单纯培养液移植组、全胚胎移植组、卵裂球移植组、透明带移植组及正常妊娠未干预组,移植后2 d收集子宫内膜行下一步检测。荧光定量PCR检测整合素β₃和LIF mRNA表达;免疫组织化学及Western blotting检测整合素β₃和LIF的蛋白表达部位及表达水平。结果: 体外实验子宫内膜全胚胎共培养组中子宫内膜的整合素β₃ 和LIF表达显著高于其它组,体内实验正常妊娠未干预组的整合素β₃ 和LIF表达显著高于其它组。结论: 完整胚胎可显著提升小鼠孕早期子宫内膜容受性因子整合素β₃ 和LIF的表达,而单纯透明带或卵裂球则不能明显增加整合素β₃ 和LIF的表达。早期胚胎诱导子宫内膜容受性可能需要完整胚胎结构的存在。     

Computer-controlled, multilevel, morphometric analysis of blastomere size as biomarker of fragmentation and multinuclearity in human embryos

BACKGROUND: Little is known about blastomere size at different cleavage stages and its correlation with embryo quality in human embryos. Using a computer system for multilevel embryo morphology analysis we have analysed blastomeres of human embryos and correlated mean blastomere size with embryonic fragmentation and multinuclearity. METHODS: A consecutive cohort of 232 human 2-, 3- and 4-cell embryos from patients referred for ICSI treatment were included. Sequences of digital images were taken by focusing at 5- micro m intervals through the embryo. Blastomere sizes and number of nuclear structures were evaluated based on these sequences. The degree of embryonic fragmentation was evaluated by normal morphological assessment prior to transfer and correlated to the blastomere sizes. RESULTS: As a result of normal cell cleavage, mean blastomere size decreased significantly from a volume of 0.28 x 10(6) microm(3) at the 2-cell stage to 0.15 x 10(6) microm(3) at the 4-cell stage (P < 0.001). Mean blastomere size decreased significantly (P < 0.001) with increasing degree of embryonic fragmentation, where highly fragmented embryos showed a 43-67% reduction in blastomere volume compared with embryos with no fragmentation. Multinucleated blastomeres were significantly larger than non-multinucleated blastomeres (P < 0.001). On average, multinucleated blastomeres were 51.5, 67.8 and 73.1% larger than their non-multinucleated sibling blastomeres at the 2-, 3- and 4-cell stage, respectively. Furthermore, the average volume of non-multinucleated blastomeres originating from multinucleated embryos was significantly smaller than the average volume of the blastomeres from mononucleated embryos (P < 0.001). CONCLUSIONS: The results of this study show that the average blastomere size is significantly affected by degree of fragmentation and multinuclearity, and that computer-assisted, multilevel analysis of blastomere size may function as a biomarker for embryo quality.     

Construction of an evidence-based integrated morphology cleavage embryo score for implantation potential of embryos scored and transferred on day 2 after oocyte retrieval

BACKGROUND: Evidence-based morphological embryo scoring models for ranking of implantation potential are still scarce, and the need for a precise model increases when aiming for singleton pregnancies. METHODS: Prospectively, 2266 IVF/ICSI double-embryo, day 2 transfers were studied. The five variables scored in 3- to 5-step scales for the embryos transferred are blastomere number (BL), fragmentation, blastomere size variation ('equality', EQ), symmetry of the cleavage and mononuclearity in the blastomeres (NU). The scoring results of embryos with an individual traceability from scoring to implantation, i.e. treatments resulting in either no implantation (n=1385) or twin implantation (n=228), were studied for prognostic potential. RESULTS: Although all five variables correlated highly with implantation potential, only BL, NU and EQ remained independently significant after regression analysis. The equation thus derived formed the basis for a 10-point integrated morphology cleavage (IMC) embryo score. A table with the scoring point for each possible combination of the embryo variables is presented. The scoring model was statistically validated on the singleton pregnancy group (n=653). CONCLUSIONS: We suggest that this IMC embryo scoring, incorporating cleavage stage and information on the variation in blastomere size and the number of mononucleated blastomeres, may optimize embryo ranking and selection for day 2 transfers.     

Oxygen concentration during mouse oocyte in vitro maturation affects embryo and fetal development

BACKGROUND: Little is known of how the oxygen environment in the ovarian follicle affects oocyte and embryo development, but this has an important impact on the conditions used for in vitro maturation (IVM) of oocytes. We investigated the effect of varying oxygen concentrations during IVM on subsequent pre and post-implantation development. METHODS: IVM of mouse cumulus-oocyte complexes (COCs) was performed under 2, 5, 10 or 20% O(2) (6% CO(2), balance N(2)). In vivo-matured COCs were collected post ovulation. Embryos were generated by IVF and culture. Blastocyst development, cell number and apoptosis were assessed, and fetal and placental outcomes analysed following embryo transfer at day 18 of pregnancy. RESULTS: Oxygen concentration during IVM did not affect oocyte maturation or subsequent fertilization, cleavage and blastocyst development rates. Maturation of oocytes under 2% O(2) increased blastocyst trophectoderm cell number compared with all groups and numbers at 5% were higher than 20% (both P < 0.05). Percentage of apoptotic cells was increased in blastocysts developed from 2% O(2)-matured oocytes, compared with maturation at 5% O(2) or in vivo (P < 0.05). Rates of embryo implantation and development into a viable fetus were not altered by IVM oxygen. However, fetal weight was reduced following oocyte maturation at 5% O(2) compared wiht 20% O(2) and maturation at 5% O(2) also reduced placental weight, when compared with in vivo-matured oocytes (both P < 0.05). CONCLUSIONS: Level of O(2) exposure during oocyte maturation can alter the cellular composition of blastocysts, but these changes in cell number do not correlate with the altered fetal and placental outcomes after transfer.     

Morphological evaluation of human embryos and derivation of an embryo quality scoring system specific for day 3 embryos: a preliminary study

A scoring system specific for day 3 embryos has not been extensively explored. Most IVF laboratories continue to grade embryos solely on the basis of cell number and percentage fragmentation as was traditionally done for day 2 embryos. Additional morphological features, some unique to day 3 embryos, may be useful in selecting embryos most likely to blastulate and implant. The objective of this study was to derive an embryo scoring system for day 3 transfers which is predictive of positive pregnancy outcomes. A total of 316 transferred embryos from 93 patients was recorded on videotape and evaluated. The following parameters were used to grade the embryos: cell number, fragmentation pattern (FP), cytoplasmic pitting, compaction, equal sized blastomeres, blastomere expansion and absence of vacuoles. The clinical pregnancy rate was 41.9%, with an implantation rate of 18% per embryo transferred. The mean number of embryos transferred per patient was 3.4. Three formulae were derived to score embryo quality in each transfer based on the average score of individual embryos transferred. In the first scoring system, cell number alone was used to predict pregnancy outcome. The second scoring system was based on blastomere number and the observed FP. The third scoring system utilized both blastomere number and FP but also combined this with five morphological criteria to yield a final day 3 embryo quality (D3EQ) score. We found the D3EQ score to be prognostic of pregnancy outcome. This study suggests that although cell number and FP are certainly predictors of positive pregnancy outcomes, additional parameters specific to day 3 embryos should be used to stratify a cohort of embryos further.     

小鼠2-细胞胚胎卵裂球后代在囊胚中随机分布

目的 用异硫氰荧光素（FITC）-右旋糖苷和四甲基罗丹明（TMR）-右旋糖苷标记小鼠2-细胞胚胎的两个卵裂球,观察其发育,以探讨囊胚Em-Ab极性的形成。方法 向受精卵注射FITC-右旋糖苷确定标记物对胚胎的伤害性,向2-细胞胚胎两个卵裂球分别FITC-右旋糖苷分别和TMR-右旋糖苷,将标记后的胚胎体外培养发育至囊胚,观测两个卵裂球后代在囊胚中的分布情况。 结果 2-细胞胚胎两个卵裂球的后代在囊胚中分布并无规律。 结论 2-细胞胚胎卵裂球随机分布在囊胚的胚胎部分和胚外部分。     

Effect of culturing mouse embryos under different oxygen concentrations on subsequent fetal and placental development

The oxygen concentration used during embryo culture can influence embryo development and quality. Reducing the oxygen concentration in the atmosphere to 2% during post-compaction culture of mouse embryos perturbs embryonic gene expression. This study examined the effect of culturing mouse embryos under different oxygen concentrations on subsequent fetal and placental development. Embryos were cultured from the zygote to morula stage under 7% oxygen, followed by 20, 7 or 2% oxygen to the blastocyst stage. Cultured and in vivo developed blastocysts were transferred into pseudopregnant recipients. Fetal and placental outcomes were analysed at day 18 of pregnancy. Implantation rate was not influenced by embryo culture conditions, but resorption rates were increased in embryos cultured under 2% oxygen, compared with 7% oxygen. Day 18 fetal weights were reduced following culture under 2%, compared with 7 or 20% oxygen, or in vivo development. Placental weight was not influenced by culture conditions. No differences in the proportion of junctional or labyrinthine exchange regions within the placenta or the morphometry of the labyrinthine region were detected. Surface density (surface area/gram labyrinth) of trophoblast available for exchange was reduced in placentas developed from embryos cultured under 2% oxygen, compared with 7% oxygen. Placental gene expression of Slc2a1 , Slc2a3 , Igf2 , Igf2r and H19 was not influenced by oxygen conditions during embryo culture. Thus, exposure to 2% oxygen during post-compaction pre-implantation embryo development has adverse consequences for fetal development in the mouse. Oxygen is a significant component of the embryonic environment and reductions in oxygen availability can influence both embryonic gene expression and subsequent fetal development.     

Blastocyst formation and cell numbers in human frozen-thawed embryos following extended culture

BACKGROUND: Blastomere loss following human embryo cryopreservation has been shown to be associated with reduced implantation potential. In order to elucidate the underlying mechanism, the present study was designed to investigate the consequences of blastomere loss on subsequent preimplantation development in vitro. METHODS: Cryopreserved embryos destined for disposal were thawed and cultured for 96 h prior to determination of total cell numbers in resultant blastocysts. RESULTS: The proportion of embryos which formed blastocysts in vitro was significantly reduced when blastomere loss was evident in thawed embryos (25 versus 41% in fully intact thawed embryos). In addition, blastocysts from partially intact thawed embryos exhibited a significant reduction in total cell number (45.0 versus 58.4 in blastocysts from fully intact thawed embryos). Development to the blastocyst stage was significantly less frequent in fully intact thawed embryos which had been generated using ICSI (19%) compared with standard IVF (47%), although cell numbers in the resultant blastocysts were similar (57.1 and 58.6 respectively). CONCLUSIONS: Blastomere loss following cryopreservation impairs preimplantation development and results in reduced cell numbers at peri-implantation stages. ICSI is associated with reduced potential for post-thaw development of cryopreserved embryos in vitro.     

Parameters guiding selection of best embryos for transfer after cryopreservation: a reappraisal

BACKGROUND: The purpose of this study was to evaluate the respective influences of blastomere survival and resumption of mitosis on the outcome of frozen-thawed embryos. METHODS: A retrospective analysis was performed in our centre on 363 thawing cycles, involving 4-cell day 2 grade 1 embryos with <10% fragmentation. RESULTS: A higher implantation rate per transferred embryo was observed when all transferred embryos were characterized by fully intact blastomeres (100% blastomere survival) as compared with damaged embryos (50 or 75% blastomere survival) (22.0 versus 7.2%; P < 0.0001). Moreover, the implantation rate per transferred embryo was significantly higher for cleaved embryos compared with uncleaved embryos (19.7 versus 3%; P < 0.0001). Transfer of fully intact, cleaved embryos resulted in the highest implantation rates compared with transfer of damaged and uncleaved embryos (27.4 versus 0%; P < 0.0001). Intermediate implantation rates were observed when only one of the two criteria was fulfilled (13 versus 11% respectively; P > 0.05). Multivariate analysis showed that the clinical pregnancy rate was influenced by both criteria (odds ratio = 3.4 for transfer of embryos with six or more cells versus embryos with less than six cells. CONCLUSION: The results of our study suggest that the most important factor to predict further embryo development is the total number of blastomeres in transferred embryos, however they are obtained (good survival and/or resumption of mitosis).     

The frequency and developmental capability of human embryos containing multinucleated blastomeres

The frequency of multinucleated blastomeres (MNB) in 2- and 4-cell stage human embryos was recorded immediately before embryo transfer using a high-power inverted microscope. About 44% of patients (150/338) possessed embryos exhibiting MNB. The appearance of this nuclear abnormality was not correlated with maternal age. Overall, 15% of the otherwise good quality embryos (274/1885) that developed after monospermic fertilization contained several multinuclei (from two to seven) in at least one cell. Quite often MNB were found within all cells of the embryo (50% in 2-cell embryos). Blastomere multinucleation was significantly higher in 2-cell than 4-cell embryos (P <0.0001). This suggests that a considerable number of human embryos become abnormal during the first embryonic division. The embryos containing MNB were usually excluded for uterine transfers, with the exception of 19 cases when only such embryos could be replaced (6%; 19/338 patients). The results demonstrated that embryos with MNB may implant (4/19 cases; 21%) and they can lead to both spontaneous abortions and the successful birth of healthy infants (two cases). The fact that in the successful cases, 2-cell stage embryos with a mononucleated and a binucleated blastomere were transferred also suggests that due to the cell totipotency, development of a healthy baby is possible from one normal blastomere. Since multinucleation in early embryos may reflect gross chromosomal abnormalities or development of mosaic embryos, it is advisable not to replace embryos with MNB. Occasional transfers, however, can be considered because defective embryos may sometimes develop normally.