维甲酸诱导大鼠产生肛门直肠畸形及其伴发畸形

目的利用维甲酸诱导大鼠肛门直肠畸形并探讨维生素A类物与肛门直肠畸形发生之间的关系.方法利用成熟未孕的Wistar大鼠,在妊娠10d时经胃管注入维甲酸,诱导产生肛门直肠畸形动物模型,分别在妊娠16、18、20d时剖宫取出胎鼠,进行实体观察、畸形率统计,同时行病理形态学研究.对照组仅给予橄榄油,剖宫时间及观察项目同致畸组.结果维甲酸致畸组共获得胎鼠96只,其中肛门直肠畸形发生率81.3%(78/96),显性脊柱裂46.9%(45/96),无尾畸形70.8%(68/96),足畸形37.5%(36/96).对照组剖出74只胎鼠,均未见上述畸形.致畸组与对照组在妊娠16d、18d、20d时身长及体重相应各组数据经t检验统计差异显著(P<0.01),致畸组均较对照组为差.结论维甲酸是一种良好的诱导肛门直肠畸形动物模型的致畸剂,其发生机制可能是过量维甲酸通过干扰维生素A酸信号系统影响正常胚胎发生所致.     

全反式维甲酸诱导骨骼畸形大鼠血清及羊水内碱性成纤维细胞生长因子的表达

目的探究应用全反式维甲酸诱导骨骼畸形大鼠血清及羊水内碱性成纤维细胞生长因子(FGF2)的表达。方法选择孕10d的Wistar大鼠50只,体质量250~300g。分实验组和对照组,每组各25只。实验组予溶有全反式维甲酸的大豆油(40 mg/mL),按照135 mg/kg以灌胃方式给药制作骨骼畸形胎鼠模型;对照组给予等体积的大豆油。孕20 d时处死母鼠,采集母鼠血液,实验组每窝选择骨骼畸形胎鼠4只,对照组每窝随机选取胎鼠4只,抽取胎鼠羊水标本,应用酶联免疫吸附分析测定血液及羊水内FGF2浓度;利用游标卡尺测量胎鼠头臀长,双前肢各段及双后肢的长度。结果实验组胎鼠出现四肢发育不良、脊柱裂、下颌裂等畸形。实验组胎鼠头臀长、双前肢各段及双后肢长度与对照组相比,差异具有统计学意义(P0.05)。实验组母鼠血液及胎鼠羊水内FGF2的浓度与对照组相比[(24.124±1.271)pg/mL vs(27.451±2.026)pg/mL,(23.918±0.369)pg/mL vs(27.305±2.125)pg/mL],差异具有统计学意义(P0.05)。结论全反式维甲酸诱导骨骼畸形大鼠FGF2表达情况低于骨骼发育正常的大鼠。     

全反式维甲酸诱导骨骼畸形大鼠血清及羊水内碱性成纤维细胞生长因子的表达简

目的探究应用全反式维甲酸诱导骨骼畸形大鼠血清及羊水内碱性成纤维细胞生长因子（FGF2）的表达。方法选择孕10d的Wistar大鼠50只,体质量250～300g。分实验组和对照组.每组各25只。实验组予溶有全反式维甲酸的大豆油（40mg／mL）,按照135mg/hg以灌胃方式给药制作骨骼畸形胎鼠模型;对照组给予等体积的大豆油。孕20d时处死母鼠,采集母鼠血液,实验组每窝选择骨骼畸形胎鼠4只,对照组每窝随机选取胎鼠4只,抽取胎鼠羊水标本,应用酶联免疫吸附分析测定血液及羊水内FGF2浓度：利用游标卡尺测量胎鼠头臀长,双前肢各段及双后肢的长度。结果实验组胎鼠出现四肢发育不良、脊柱裂、下颌裂等畸形。实验组胎鼠头臀长、双前肢各段及双后肢长度与对照组相比.差异具有统计学意义（P〈0.05）。实验组母鼠血液及胎鼠羊水内FGF2的浓度与对照组相比[（24.124±1.271）pg／mL vs（27.451±2.026）pg／mL,（23.918±0.369）pg／mL vs（27.305±2.125）pg／mL],差异具有统计学意义（P〈0.05）。结论全反式维甲酸诱导骨骼畸形大隐.FGF2表茯情况低干骨骼发育正常的大鼠。     

灵芝孢子在预防维甲酸诱导胚胎小鼠发生神经管畸形过程中对Cdk4表达的影响

目的探讨预先服用灵芝孢子在降低维甲酸诱导胚胎小鼠发生神经管畸形过程中对依赖细胞周期蛋白激酶4(cyclindependentproteinkinase4,Cdk4)表达的影响。方法于孕期小鼠E0d时给予灵芝孢子组的孕鼠胃饲灵芝孢子溶液,8g·kg-1·d-1。实验对照组的孕鼠胃饲等量溶剂。于E7.75d时,两组孕鼠一次性胃饲维甲酸,剂量为50mg/kg体重。正常对照组孕鼠胃饲等量灵芝孢子溶剂,但是在E7.75d时,仅给予维甲酸溶剂。空白对照组孕鼠常规饲养不作任何处理。在孕期E10.5d时取出4组孕鼠的胚胎,应用免疫荧光组织化学染色和Westernblot检测胚胎神经管神经上皮Cdk4表达情况。结果实验对照组孕鼠胚胎神经管神经上皮细胞Cdk4的表达明显降低,而灵芝孢子组胚胎表达Cdk4的强度明显高于实验对照组。正常对照组与空白对照组相比Cdk4的表达无统计学意义(P>0.05)。结论灵芝孢子可能是通过增强神经管神经上皮细胞表达Cdk4降低维甲酸诱导胚胎小鼠神经管畸形的发生。     

桉叶油对维甲酸干扰大鼠胚胎植入及生长发育的影响

目的探讨桉叶油对维甲酸干扰大鼠胚胎植入及生长发育的影响。方法 SD孕鼠42只,随机分为6组,FA组正常对照组、溶剂组(花生油+RA)、3个实验组(桉叶油高、中、低剂量+RA)及RA组。溶剂组用花生油2ml/只于孕第7~14天灌胃,每天1次,孕第10天维甲酸40mg/kg灌胃1次。桉叶油3个剂量组分别用300mg/kg、200mg/kg、100mg/kg的桉叶油于孕第7~14天灌胃,每天1次,孕第10天维甲酸40mg/kg灌胃1次。RA组用40mg/kg的维甲酸于孕第10天灌胃1次。正常对照组给予自由摄食饮水。各组于孕21d早上处死孕鼠,取胚胎,记录孕鼠体重,子宫重,胎盘重。计胚胎植入总数,吸收胎数、活胎数、死胎数。观察胚胎外形,并测量胎鼠体重、身长、尾长。结果正常对照组、桉叶油+RA和溶剂+RA组孕鼠增重、子宫重、胎盘重与RA组比较均无差异;溶剂+RA组的孕鼠的胎盘重较其他各组低,与RA和桉叶油+RA各组比较差异无显著性,与正常对照组比较有差异(P0.05)。正常对照组的活胎率[(97.3±4.6)%]较灌胃维甲酸各组的活胎率高(P0.05),吸收胎率[(2.6±4.6)%]和畸形率(0)较灌胃维甲酸各组低(P0.05),死胎率为0;在灌胃维甲酸各组中,桉叶油高[(79.6±14.5)%]、中[(67.6±30.8)%]剂量组的活胎率较RA[(58.6±26.6)%]组高,但比较无差异;畸胎率[(44.5±41.6)%;(57.5±35.1)%]较RA[(68.1±43.6)%]组低,但差异无统计学意义。灌胃维甲酸各组的吸收胎率比较无差异。正常对照组的胎鼠体重、身长、尾长均值明显高于灌胃维甲酸各组胎鼠的体重、身长、尾长均值(P0.05);在灌胃维甲酸各组中,桉叶油各组胎鼠体重、身长的均值明显高于RA组和溶剂对照组(P0.05);溶剂对照组胎鼠体重、身长、尾长与RA组比较无差异;桉叶油各组胎鼠尾长的均值均高于RA组,但比较无差异。结论维甲酸干扰了大鼠胚胎的植入和发育,桉叶油对RA干扰大鼠胚胎植入有一定的拮抗作用,对RA引起的胎鼠生长发育迟缓有一定的抑制作用。     

GATA-4在HCY诱导鼠胚心脏畸形中的表达及意义

目的探讨锌指转录因子GATA-4在同型半胱氨酸（Homocysteine,HCY）诱导的大鼠胚胎发育畸形心脏的表达水平及相关意义。方法SD成年健康清洁级雌、雄大鼠各16只,常规方法交配获取孕鼠后,随机分为2组：1正常对照组,2HCY组。各组孕鼠分别于妊娠第13、15、17、19天剖腹取出胚胎,通过切片进行胎鼠心脏组织学观察以确定心脏畸形情况,并通过RT-PCR法半定量测定胎心GATA-4因子mRNA表达。结果HCY组不良胚胎率及胚胎心脏畸形率与对照组相比均显著增高（P〈0.001）;HCY组各妊娠天数胎鼠心脏GATA-4因子mRNA表达均较对照组减少,但无统计学意义（P〉0.05）;而心脏发育畸形胎鼠的心脏GATA-4因子mRNA表达比心脏发育正常胎鼠明显降低（P〈0.001）。结论HCY诱导的孕鼠不良胚胎率及胚胎心脏畸形率均明显增高,且胎鼠畸形心脏组织中GATA-4表达下调,表明锌指转录因子GATA-4的心脏表达抑制与HCY对大鼠胚胎心脏的毒性作用之间存在重要关系。     

灵芝孢子降低维甲酸诱导的孕鼠胚胎神经管畸形的发生

目的 探讨灵芝孢子能否促进受维甲酸诱导,而停滞在G0/G1期的胚胎神经管神经上皮细胞重新进入细胞周期循环,继续增殖和分化,减少神经管畸形的发生.方法 于实验对照组和灵芝孢子组小鼠孕期胚胎E17.75d时一次性胃饲全反式维甲酸,造成这两组孕鼠的胚胎出现神经管畸形.然后,给予灵芝孢子组孕鼠胃饲灵芝孢子溶液.在孕期E10.5d时取出两组孕鼠的胚胎,分别计数胚胎的神经管畸形发生率.应用免疫荧光组织化学染色和流式细胞仪检测胚胎神经管神经上皮的巢蛋白(nestin)表达情况.应用DNA定量荧光染色和RT-PCR技术检测胚胎神经管依赖细胞周期蛋白激酶2(Cdk2) mRNA和Cdk4 mRNA的转录.结果 灵芝孢子组孕鼠胚胎的神经管畸形发生率显著低于实验对照组.神经管神经上皮细胞表达nestin的百分率也明显大于实验对照组.实验对照组孕鼠胚胎的神经管细胞在G0/G1期的比例则显著高于灵芝孢子组,但是实验对照组神经管细胞S期的比例低,低于灵芝孢子组形态正常的胚胎神经管细胞.RT-PCR检测发现,灵芝孢子组孕鼠胚胎神经管细胞能够正常转录Cdk4 mRNA,而实验对照组则低转录Cdk4 mRNA.结论 灵芝孢子能够减少维甲酸诱导的妊娠小鼠孕期E10.5d胚胎神经管畸形的发生.     

灵芝孢子在降低维甲酸诱导胚胎小鼠发生神经管畸形过程中对Cdk4表达的影响

目的 探讨灵芝孢子在降低维甲酸诱导胚胎小鼠发生神经管畸形过程中对依赖细胞周期蛋白激酶4(CDk4)表达的影响.方法 给予实验对照组和灵芝孢子组妊娠E7.75d的小鼠一次性胃饲维甲酸,造成这2组孕鼠的胚胎出现神经管畸形.然后,给予灵芝孢子组孕鼠胃饲灵芝孢子溶液.在孕期E10.5d时取出2组孕鼠的胚胎,应用免疫荧光组织化学染色和Western blotting检测胚胎神经管神经上皮依赖细胞周期蛋白激酶4(Cdk4)的表达情况.结果 在灵芝孢子组可以观察到形态正常的胚胎中,神经管的神经上皮细胞有Cdk4的表达,其表达水平与空白对照组及正常对照组相比较没有明显差异.在灵芝孢子组形态异常的胚胎中,其神经管的神经上皮细胞也有cdk4的表达,但其表达水平与空白对照组及正常对照组相比较是低的.结论 灵芝孢子可能是通过促进神经管神经上皮细胞上调Cdk4的表达来减轻维甲酸诱导的胚胎小鼠神经管畸形.     

CO_2气腹对胎鼠脑超微结构和Caspase-3表达的影响

目的探讨CO2气腹对胎鼠脑组织结构及脑组织Caspase-3表达的影响。方法选择不同CO2气腹压力,建立孕鼠的CO2气腹模型,于鼠孕17 d的24 h内取胎鼠脑组织分别进行HE染色、免疫组化、电镜制片,观察胎鼠脑组织结构变化和胎鼠脑组织Caspase-3表达。结果透射电镜观察显示随气腹压力的增加,胎鼠脑组织可见细胞轻微可逆性损害。Caspase-3在实验组与对照组间胎鼠脑组织表达无明显变化（P〉0.05）,同时组间Caspase-3的表达也无显著性差异（P〉0.05）。结论 CO2气腹压力升高对胎鼠大脑细胞产生可逆性轻度损伤。     

维甲酸诱导的小鼠神经管畸形模型中神经系统相关基因的表达情况分析

 摘要: 目的: 研究在全反式维甲酸诱导小鼠神经管畸形模型中神经系统相关基因（ASH2L,HDAC4,NSPC1与DOK5）的表达变化。方法: 取8只E8.5的C57/BL6孕鼠随机分为两组：对照组（4只），模型组（4只）。对照组腹腔注射橄榄油，模型组腹腔注射全反式维甲酸；E13.5取胚胎。采用Real-time PCR检测两组小鼠脑和脊髓中ASH2L,HDAC4,NSPC1与DOK5的mRNA表达；采用Western Blotting技术检测两组小鼠脑和脊髓中ASH2L,HDAC4,NSPC1与DOK5的蛋白表达情况。结果：全反式维甲酸可诱导小鼠出现典型神经管畸形；与对照组相比，全反式维甲酸处理组的致畸胚胎脑和脊髓中,ASH2L HDAC4, NSPC1和DOK5的mRNA表达有所下降（P<0.05）；同时这些基因的蛋白水平也显著下降 (P<0.05)。结论：ASH2L,HDAC4,NSPC1和DOK5可能是抑制全反式维甲酸致神经管畸形的潜在基因。     

双胎妊娠-胎宫内死亡20例临床分析

目的探讨双胎妊娠-胎宫内死亡的原因、临床处理及预后。方法回顾性分析1994年3月至2008年2月北京大学第三医院双胎妊娠-胎宫内死亡的病例共20例。结果双胎-胎宫内死亡的发生率为3．2％,其中双卵双胎17例,单卵双胎3例。28w前发现-胎宫内死亡者6例,平均期待治疗95．8天,平均分娩孕周为34．4w（32^＋4-39w）;28w后发现-胎宫内死亡者14例,平均期待治疗10．1天,平均分娩孕周为34．6w（29^＋4-39^＋2w）;仅2例新生儿发生轻度窒息。无一例孕妇发生凝血功能障碍。追踪新生儿6月至14年,1例新生儿因合并隐性脊柱裂及早产原因早期死亡,1例患儿3岁时发生运动障碍性脑瘫（分娩孕周为29^＋6w）,4例失访,其余均健康存活。结论双胎妊娠-胎宫内死亡后可采取期待治疗,严密监测存活胎儿宫内状况,尽量延长孕周,可提高存活胎儿的生存质量。     

Suppression by cyclohexanetriones of retinoic acid-induced cartilage degradation in vitro and teratogenicity in vivo

In cultured fetal rat bones, cyclohexanetriones that stimulate prostaglandin synthesis inhibited retinoic acid-induced cartilage degradation in a dose-dependent manner. The inhibition by the cyclohexanetrione Ro 31-0521 was reversible, indicating that the effect was not due to cytotoxicity. Excess retinoic acid is teratogenic in rats and adversely affects the normal differentiation of various morphogenetic systems, depending on the time of administration. The following retinoic acid-induced malformations were suppressed by Ro 31-0521: malformations of long bones and of apical phalanges induced on days 13 and 15 of gestation, respectively; spina bifida and tail malformations induced on day 11 of gestation and cleft palate induced on day 15 of gestation. However, cleft palate and other head malformations including exencephaly induced by retinoic acid on day 11 of gestation were not suppressed but even increased by Ro 31-0521. At a high dose, Ro 31-0521 given alone on day 11 of gestation was embryolethal and teratogenic but was not on the tested other days, indicating that the cyclohexanetrione at specific stages and doses also interfered with normal morphogenesis like retinoic acid. Assuming that stimulation of prostaglandin synthesis is the main biological effect of the cyclohexanetriones, our findings suggest that prostaglandins may be involved in mediating retinoid action.     

Influencing clinical practice regarding the use of antiepileptic medications during pregnancy: Modeling the potential impact on the prevalences of spina bifida and cleft palate in the United States

Selected antiepileptic drugs (AEDs) increase the risk of birth defects. To assess the impact of influencing AED prescribing practices on spina bifida and cleft palate we searched the literature for estimates of the association between valproic acid or carbamazepine use during pregnancy and these defects and summarized the associations using meta-analyses. We estimated distributions of the prevalence of valproic acid and carbamazepine use among women of childbearing age based on analyses of four data sets. We estimated the attributable fractions and the number of children born with each defect that could be prevented annually in the United States if valproic acid and carbamazepine were not used during pregnancy. The summary odds ratio estimate for the association between valproic acid and spina bifida was 11.9 (95% uncertainty interval (UI): 4.0–21.2); for valproic acid and cleft palate 5.8 (95% UI: 3.3–9.5); for carbamazepine and spina bifida 3.6 (95% UI: 1.3–7.8); and for carbamazepine and cleft palate 2.4 (95% UI: 1.1–4.5) in the United States. Approximately 40 infants (95% UI: 10–100) with spina bifida and 35 infants (95% UI: 10–70) with cleft palate could be born without these defects each year if valproic acid were not used during pregnancy; 5 infants (95% UI: 0–15) with spina bifida and 5 infants (95% UI: 0–15) with cleft palate could be born without these defects each year if carbamazepine were not used during pregnancy. This modeling approach could be extended to other medications to estimate the impact of translating pharmacoepidemiologic data to evidence-based prenatal care practice. Published 2011 Wiley-Liss, Inc.     

桉叶油联合维甲酸对SD胎鼠脑组织Pax3和缝隙连接蛋白43表达的影响

目的探讨桉叶油联合维甲酸(RA)对SD胎鼠脑组织转录因子Pax3、缝隙连接蛋白43(Cx43)表达的影响。方法 SD孕鼠42只,随机分为6组,每组7只,正常对照组,RA组,溶剂对照组(花生油+RA),3个实验组(桉叶油高、中、低剂量+RA)。正常对照组自由摄食饮水,溶剂对照组于孕第7~14天每只花生油2ml灌胃,每天1次,孕第10天40mg/kg RA灌胃1次。桉叶油3个剂量组于孕第7~14天分别桉叶油300、200和100mg/kg灌胃,每天1次,孕第10天40mg/kg RA灌胃1次。RA组于孕第10天40mg/kg RA灌胃1次。各组于孕21天处死孕鼠取胚胎,Western blotting、免疫组织化学技术检测胎鼠脑组织的Pax3、Cx43蛋白的表达。Real-time PCR检测脑组织Pax3、Cx43 mRNA表达。阿利新蓝和茜素红进行骨骼染色,体视显微镜下观测椎骨发育,脊柱间隙。结果维甲酸灌胃各组胎鼠椎骨数量异常的胎鼠数与正常对照组比较差异无显著性,但在维甲酸灌胃各组中,胎鼠椎骨形态异常的异常率和胎鼠椎骨分裂的百分率最低值分别为55%(桉叶油高剂量+RA组)和45.8%(桉叶油低剂量+RA组),较正常对照组高(0)(P0.05)。在维甲酸灌胃各组中,桉叶油各组胎鼠椎骨形态异常的异常率和胎鼠椎骨分裂的百分率最高值分别为62.5%(桉叶油低剂量+RA组)和55.0%(桉叶油高剂量+RA组),较维甲酸组(73.7%,73.7%)和溶剂对照组低(68.2%,63.6%,P0.05)。与正常组胎鼠比较,维甲酸灌胃各组大脑组织的Pax3、Cx43蛋白及其mRNA的表达较正常组高(P0.05),在维甲酸灌胃各组中,桉叶油灌胃各组胎鼠脑组织Pax3、Cx43蛋白及其mRNA的表达较单纯RA灌胃组低,其差异有统计学意义(P0.05)。结论桉叶油对维甲酸引起胎鼠神经管缺陷有一定的拮抗作用。其机制可能与桉叶油拮抗维甲酸上调胎鼠神经组织的Pax3、Cx43蛋白过度表达有关     

Brain tissue fragments in the amniotic fluid of rats with neural tube defect

AIMS: Brain tissue nodules are occasionally seen in the lungs of neural tube defect (NTD) cases. We looked for brain tissue fragments in amniotic fluid of rats with NTD as it is the basis for the aspiration hypothesis. METHODS: Eighty-seven pregnant rats were randomly divided into experimental (n=58) and control (n=29) groups. Experimental rats received 100,000 U of vitamin A in 1 mL of corn oil on gestational days 8, 9 and 10, while control rats received corn oil. On gestational days 15, 18, 19, 20 and 21, amniotic fluid was drawn from three control animals and five experimental animals and analysed. RESULTS: NTD was found in 22.75% of experimental fetuses and in no control fetuses. Brain tissue fragment number and volume fraction increased between gestational days 18 and 20, falling on day 21. CONCLUSIONS: Excessive doses of vitamin A induce a high rate of early fetal death and development of NTD. Brain tissue fragments in the amniotic fluid reflect the evolution from exencephaly to anencephaly and could support the aspiration hypothesis. However, as it is a late event in the rat, this model may not reproduce the brain tissue nodules in the lung.     

D-chiro-inositol is more effective than myo-inositol in preventing folate-resistant mouse neural tube defects

BACKGROUND: Among mouse genetic mutants that develop neural tube defects (NTDs), some respond to folic acid administration during early pregnancy, whereas NTDs in other mutants are not prevented. This parallels human NTDs, in which up to 30% of cases may be resistant to folic acid. Most spina bifida cases in the folic acid-resistant 'curly tail' mouse can be prevented by treatment with inositol early in embryonic development. Here, the effectiveness and safety during pregnancy of two isomers, myo- and D-chiro-inositol, in preventing mouse NTDs was compared. METHODS AND RESULTS: Inositol was administered either directly to embryos in vitro, or to pregnant females by s.c. or oral routes. Although D-chiro- and myo-inositol both reduced the frequency of spina bifida in curly tail mice by all routes of administration, D-chiro-inositol consistently exhibited the more potent effect, reducing spina bifida by 73-86% in utero compared with a 53-56% reduction with myo-inositol. Pathological analysis revealed no association of either myo- or D-chiro-inositol with reduced litter size or fetal malformation. CONCLUSIONS: D-chiro-inositol offers a safe and effective method for preventing folic acid-resistant NTDs in the curly tail mouse. This raises the possibility of using inositol as an adjunct therapy to folic acid for prevention of NTDs in humans.     

Questioning the rationale and conduct of the management of myelomeningocele study

Surgical intervention in fetal spina bifida developed from the belief that amniotic fluid damages the spinal cord in utero and low spinal pressure from failure of neural tube closure causes hindbrain herniation leading to hydrocephalus after birth for many infants with open spinal lesions. Intrauterine intervention is undergoing a randomised human trial known by the acronym MOMS. It is hoped that randomisation and long-term follow up will demonstrate whether benefits to the infant may result from closure of the vertebral defect before birth. It is argued here that the premise upon which the pathogenesis of neural injury in human spina bifida used to launch this study is mistaken. This has implications for the conduct and conclusions of the trial.It is proposed that fetal surgery improves central nervous system outcome by improving cerebrospinal fluid flow at the foramen magnum. Successful intervention results in a more normal development of both neural and skeletal components of the neuraxis. Closure of the defect is required before signs of hindbrain herniation and ventriculomegaly are evident on ultrasound imaging as these are indicators of the presence of fetal hydrocephalus.     

Morphology of experimental spina bifida in the chick embryo.

Open malformations of the central nervous system may involve the brain or spinal cord, or both. Preliminary experiments in which a window was cut in the shell overlying early chick embryos (with removal of 2 ml of albumen) produced a range of neural and non-neural malformations. Exposure of Stage 5--10 embryos at 26 hours of incubation produced open brain and cord defects. Embryos were recovered at 11--12 days for gross examination. Open cord defects in 12 day experimental embryos could be divided morphologically into 2 types. One group showed an everted symmetrical plaque of neural tissue. In the other group the cord defect was more irregular, partly covered by skin, and often combined with rump and trunk defects. Skeletal staining showed that vertebral lesions increased in severity in a cranio-caudal sequence. Spina bifida occulta was found in the cervical and upper thoracic regions; spina bifida manifesta, associated with open cord defects, occurred from the lower thoracic to the sacral regions; vertebral deletions were almost confined to the caudal region. Spina bifida manifesta at the site of open cord defects also showed 2 distinct patterns. Regular cord defects were associated with regular spinal defects, showing loss of spinous processes, reduction of laminae and eversion of the pedicles. Irregular cord defects were associated with more irregular spinal defects showing vertebral deletions or fusions, rumplessness, and pelvic reduction. Neither group, however, showed local kyphosis or scoliosis. Early neurogenesis in the avian and human embryos is very similar with development of the spinal cord from neural plate and tail bud materials which fuse in an overlap zone. These experimental defects in the chick embryo, separable into regular and irregular types thus provide a useful model for investigation of the embryogenesis of spina bifida.