Gef26对果蝇原代细胞F⁃actin的调控作用

目的：探讨Gef26对果蝇原代细胞发育的影响。方法：培养野生型、gef26突变体（gef266/+和gef263/+）以及gef266/+;Abl4/+双突变体果蝇胚胎的原代细胞,观察细胞形态。对细胞骨架F?actin进行荧光染色,观察细胞骨架的分布。结果：在果蝇胚胎的原代细胞中,野生型肌肉细胞形态正常,gef26突变体的肌肉细胞形态明显异常。gef266/+;Abl4/+双突变体肌肉细胞形态正常,即阿贝尔森酪氨酸激酶（Abelson tyrosine kinase,Abl）突变挽救gef26突变体肌肉细胞形态异常的表型。野生型肌肉细胞中的F?actin呈现规整的形态和连续排布,而两株gef26突变体肌肉细胞中的F?actin排布却呈现出不规整形态和不连续排布。gef266/+;Abl4/+双突变体细胞中的F?actin呈现出规整的形态和连续的排布,即Abl突变挽救gef26突变体F?actin组装紊乱的表型。结论：Gef26可能通过Abl信号通路调控肌动蛋白细胞骨架的组装。     

Calponin-1表达沉默对子宫平滑肌细胞生物学行为的影响

目的 研究抑制calponin-1表达对人子宫平滑肌细胞增殖、侵袭、凋亡和细胞骨架的影响,探讨妊娠时人子宫平滑肌细胞中calponin-1蛋白表达上调存分娩发动中的作用机制.方法 构建腺病毒siRNA-calponin-1质粒,转染原代培养的人子宫平滑肌细胞,分别用四甲基偶氮唑蓝(MTT)、Transwell侵袭实验和流式细胞术(AnnexinV/PI双染法)检测转染siRNA-calponin-1前后对子宫平滑肌细胞增殖、侵袭、凋亡的影响;同时用Rhodamine-Phailoidin标记子宫平滑肌细胞骨架蛋白(F-actin),荧光显微镜观察其变化并进行荧光定量检测.结果 实验组与空载体组、空白对照组比较,子官平滑肌细胞的运动能力明显下降(P<0.05),细胞增殖能力及凋亡率无明显差异(P>0.05);空载体组与空白对照组比较,差异无统计学意义P>0.05).实验组子宫平滑肌细胞中F-actin的含量减少,排列松散、不规则、微丝较细;空载体组、空白对照组子宫平滑肌细胞中F-actin微丝明显增多增粗、呈束状平行排列.结论 体外实验表明抑制calponin-1的表达可以抑制子宫平滑肌细胞的运动而不影响其增殖和凋亡,并可引起子宫平滑肌细胞F-actin的形态变化与重排.此结果提示:妊娠时子宫平滑肌细胞迁移能力的改变及F-actin的重排,可能是导致分娩发动的重要机制之一.     

MCF-7细胞他莫昔芬耐药过程中F-actin细胞骨架的重构促进细胞迁移

目的研究人乳腺癌细胞MCF-7获得他莫昔芬(tamoxifen,TAM)耐药过程中发生的肌动蛋白细胞骨架重构及其对细胞迁移能力的影响,并探讨相关分子机制。方法采用高浓度短时间4-羟基他莫昔芬(4-hydroxytamoxifen,OHT)冲击法诱导人乳腺癌MCF-7/TAM耐药细胞株(Tam-R)。运用FITC标记的鬼笔环肽染色观察纤维状肌动蛋白(F-actin)动态变化,免疫荧光分析E-钙粘蛋白在野生型MCF-7细胞(MCF-7W)及Tam-R细胞中的表达及分布,pull-down和Westernblot检测小GTP酶Rac1活性,Transwell细胞迁移实验评估F-actin骨架重构对Tam-R细胞迁移能力的影响。结果 MCF-7W细胞中F-actin富集于毗邻细胞膜周边,呈典型鹅卵石形态,E-钙粘蛋白分布与F-actin相似,可在毗邻细胞膜周边形成完整的黏附连接;而Tam-R细胞中F-actin纤维出现板状伪足和应力纤维两种异常形态,细胞外围不能通过E-cadherin与周围细胞形成完整的黏附连接。在Tam-R细胞中,PI3K抑制剂Wortmannin(WM)可抑制OHT引起的F-actin骨架重构、Rac1的活化和细胞迁移(P<0.05),而ERK1/2抑制剂U0126对OHT引起的F-actin骨架重构无明显影响。结论 OHT可能激活PI3K,促进Rac1活化,通过诱导F-actin骨架重构促进Tam-R细胞迁移。     

FABD结构域缺失削弱293T细胞BCR/ABL癌蛋白抗凋亡能力

目的 通过转染野生型pAd-Bcr/Abl及缺失突变型pAd-BCR/ABL-AFABD于293T细胞中,探讨FABD结构域对Bcr/Abl癌蛋白抗凋亡能力的影响及相关机制.方法 293T细胞分别转染野生型pAd-Bcr/Abl及缺失突变型pAd-Bcr/Abl-AFABD质粒,并设置Blank组和Adtrack组作为对照,分别培养24、48、72 h后,采用流式细胞术(FCM)检测转染荧光强度并筛选最佳转染条件,Western blot验证蛋白表达.采用WST-1(水溶性四唑盐)实验及FCM检测FABD结构域对BCR/ABL癌蛋白促增殖抗凋亡能力的影响;DAPI染色观察细胞核形态变化;Western blot分别检测p-bcr/abl、p-AKT、p-ERK表达及凋亡相关蛋白Caspase-3、PARP蛋白活化情况.结果 FCM检测结果显示质粒转染效率呈时间依赖性增加,并选择48 h为最佳转染时间.Western blot结果证实已经成功构建野生型pAd-Bcr/Abl及缺失突变型pAd-Ber/Abl-AFABD质粒.WST-1实验及FCM检测结果显示,FABD结构域缺失可显著抑制细胞增殖并促进凋亡,在处理48 h后细胞凋亡数达到29.0％ (P ＜0.05);在FABD结构域缺失后,p-AKT、p-ERK表达显著下调;凋亡相关蛋白Caspase-3、PARP均在48 h明显活化.结论 FABD结构域缺失可显著削弱BCR/ABL癌蛋白促增殖抗凋亡能力,其可能与下调AKT、ERK信号通路并激活线粒体凋亡途径有关.     

PDGF-BB诱导肺动脉平滑肌细胞表型转换时细胞骨架的变化

目的 研究血小板衍生生长因子（PDGF-BB）诱导大鼠肺动脉平滑肌细胞（PASMCs）表型转换时细胞骨架构象的改变，探讨PASMCs表型转换的机制。 方法 原代培养并鉴定SD大鼠PASMCs，将PASMCs分为对照组（细胞不加诱导剂培养24 h）、实验组（细胞用PDGF-BB 10 ng/mL诱导培养24 h）；实时荧光定量PCR（RT-qPCR）及Western blot检测细胞表型转化标志基因[α-肌动蛋白（α-SMA）、平滑肌22α蛋白（SM22α）]mRNA及相关蛋白的表达；免疫荧光法检测细胞骨架微丝F-actin及微管α-tubulin、β-tubulin的构象；CCK-8法检测细胞增殖能力及划痕实验观察细胞迁移能力。 结果 与对照组相比，PDGF-BB下调α-SMA及SM22α表达水平；细胞骨架荧光强度明显减弱，F-actin排列紊乱、边缘不规则、呈毛刺样，α-tubulin、β-tubulin形态模糊，表现为共定位；明显增强PASMCs增殖与迁移能力。 结论 PDGF-BB可能通过影响细胞骨架构象诱导PASMCs表型转换，进而改变细胞增殖及迁移能力。     

胶质细胞源性神经营养因子受体α1定点突变体制备及其稳定转染细胞株的构建及鉴定

目的:制备胶质细胞源性神经营养因子受体α1(GFRα1)的突变体质粒,并建立rGFRα1各突变体和RET基因双转染的稳定RCE细胞株.方法:通过Fugene6脂质体转染试剂,将PCR法快速制备的pcDNA3-rGFRα1突变体质粒分别与带潮霉素B抗性筛选标记的pcDNA3.1-RET质粒共转染野生型PC12细胞,建立rGFRα1各突变体和RET基因双转染的稳定PC12细胞株.经Western印迹和细胞免疫荧光化学方法对转染入PC12细胞中的各rGFRα1突变体基因和RET基因的表达进行鉴定.结果:Western印迹和细胞免疫荧光化学方法检测均证实了所构建的细胞株中有转入基因的正确表达.结论:成功构建了rGFRα1各突变体基因和RET基因同时转入表达的稳定细胞株,为研究rGFRα1中关键氨基酸的位点参与胶质细胞源性神经营养因子(GDNF)信号转导的作用奠定基础.     

α-突触核蛋白的突变体A53T对小胶质细胞激活的影响

目的：探究重组人的野生型α-突触核蛋白(wild type alpha-Synuclein, WT α-Syn)和重组人的α-突触核蛋白突变体A53T(α-Synuclein mutant A53T, α-Syn A53T) 对原代小胶质细胞的影响。方法：无菌培养原代小胶质细胞,细胞静息状态下加药处理,通过免疫荧光染色观察小胶质细胞的形态和Western Blot半定量分析CD11b的变化。结果：高浓度的WT α-Syn可以激活小胶质细胞;CD11b蛋白表达量明显升高;而2 μmol/L和5 μmol/L的α-Syn A53T均能激活小胶质细胞,CD11b蛋白表达量均升高。结论：相同浓度的WT α-Syn和α-Syn A53T,α-Syn A53T更容易激活小胶质细胞。     

负性共刺激分子B7-H4赋予肾癌细胞对化疗药物的耐药性研究

通过RT-PCR方法克隆出人野生型负性共刺激分子B7-H4基因,将目的片段双酶切(EcoR Ⅰ和BamH Ⅰ)后,与pIRES2-EGFP真核表达载体连接,构建重组真核表达载体pIRES2-EGFP-B7-H4-WT并进行鉴定;然后用定点突变法构建B7-H4核定位序列突变体基因,再构建重组真核表达载体pIRES2-EGFP-B7-H4-NLS-MT;脂质体转染法将重组载体导入786-O细胞,CCK8法研究转基因细胞株的增殖率及对化疗药物5-氟尿嘧啶、阿霉素和顺铂的耐药性。结果显示:B7-H4野生型转基因细胞株相较于空白质粒组,可有效促进786-O细胞增殖,并赋予786-O细胞对3种化疗药物的耐药性。与空白质粒组相比,对5-氟尿嘧啶的耐药倍数为2.06,对阿霉素的耐药倍数为1.81,对顺铂的耐药倍数为1.72。机制研究显示B7-H4野生型可赋予肿瘤细胞抗凋亡作用,1.25 μg/mL 5-氟尿嘧啶引起B7-H4 WT/786-O的细胞的凋亡率是20.2%,而Mock/786-O和B7-H4 NLS/MT/786-O细胞的凋亡率分别是41.1%和35.1%。说明B7-H4可能通过调控细胞凋亡赋予肿瘤细胞多药耐药性。当B7-H4核定位序列被突变后,这些功能都消失,说明B7-H4促肿瘤细胞增殖、赋予其多药耐药性的功能与其核定位序列密切相关。     

miR-26a靶向EZH2抑制涎腺腺样囊性癌ACC-M细胞的增殖活性

目的 探讨miR-26a对涎腺腺样囊性癌ACC-M细胞增殖能力的影响及其与EZH2的靶向关系. 方法 构建pcD-NATM6.2-pre-miR-26a、pmirGLO-EZH2野生型（pmirGLO-EZH2-WT）和突变型（pmirGLO-EZH2-MT）重组质粒,并采用荧光实时定量PCR（qRT-PCR）检测pre-miR-26a在ACC-M细胞中的转染效率,并与未处理组（control组）进行比较.同时采用MTT法分析miR-26a过表达对ACC-M细胞增殖活性的影响,并采用双荧光素酶报告基因系统、qRT-PCR和Western blot检测miR-26a与EZH2的靶向关系. 结果 将测序结果采用NCBI BLAST进行序列比对,结果显示pre-miR-26a、EZH2-WT和EZH2-MT重组质粒均构建成功,无碱基缺失或突变.qRT-PCR显示转染pre-miR-26a的ACC-M细胞其miR-26a的表达显著高于未处理组（P＜0.001）.MTT分析显示miR-26过表达可以明显抑制ACC-M细胞的增殖活性（P＜0.05）.此外,双荧光素酶报告基因系统（P=0.001）、qRT-PCR和Western blot均证实miR-26a能够显著下调EZH2的mRNA（P=0.001）和蛋白的表达（P=0.006）. 结论 miR-26a能够显著抑制涎腺腺样囊性癌ACC-M细胞的增殖活性,并且与EZH2之间存在良好的靶向关系.     

人脐静脉血内皮克隆形成细胞的分离培养与鉴定

目的体外建立一种简便的人脐静脉血内皮克隆形成细胞(ECFCs)分离培养方法,并对其进行鉴定。方法无菌条件下收集脐静脉血,以密度梯度离心法分离脐血单个核细胞(MNCs),诱导分化为ECFCs,倒置显微镜下观察其原代及传代培养细胞生长状况并通过流式细胞仪、免疫细胞化学、荧光双染色对ECFCs进行鉴定。结果 ECFCs培养过程可出现边界清楚的类圆形单层鹅卵石样细胞集落,细胞增殖能力强,连续传十几代细胞形态稳定,ECFCs高表达内皮系细胞表面抗原,而不表达造血系表面标记;可吞噬Dil-ac-LDL并结合FITC-UEA-1。结论通过简单、可靠的实验方法获得了ECFCs,为进一步探讨其生物学功能及临床应用提供了基础。     

Value of D-Dimers in patients with acute aortic dissection

Objective: To evaluatel the value of D-dimers in patients with acute aortic dissection (AAD). Methods: This study consisted of 16 patients with AAD and 27 non-AAD patients. Serum D-dimets were measured by Sta-Liatest D-DI immunoturbidimetric assay. Results: D-dimer level was higher (P ＜ 0.001) in patients with AAD(7.91 ± 5.52 μg/ml) than that in non- AAD group(1.57±1.24 μg/ml). D-dimer was positive (＞0.4 μg/ml) in all patients with AAD and in 10 control group patients (37%). Among patients with acute AAD, D-dimers tended to be higher in Stanford A than in Stanford B (8.67 ± 4.31 μg/ml vs. 3.24±1.27 μg/ml, P ＜0.01). D-dimer values tended to be higher in more extended disease(3.84 ± 1.65 μg/ml, 8.57 ± 3.58 μg/ml and 11.87 ± 5.69 μg/ml in thoracic aorta, thoracic and abdominal aorta, thoracic and abdominal aorta and iliacal arteries, respectively, P ＜ 0.05 for both 8.57 ± 3.58 and 11.87 ± 5.69 vs. 3.84 ± 1.65 ). Including the control group into the analysis, we found a sensitivity of 100%, a negative predictive value of 100%, and a specificity of 66% and a positive predictive value of 64% for D-dimer in diagnosis of AAD in our patients with suspected AAD. Conclusion: D-dimer was elevated in patients with AAD. A negative D-dimer test result could be useful in excluding AAD.     

Research of combined liver-kidney transplantation model in rats

Objective： To set up a simple and reliable rat model of combined liver-kidney transplantation. Methods： SD rats served as both donors and recipients. 4℃ sodium lactate Ringer＇s was infused from portal veins to donated livers,and from abdominal aorta to donated kidneys, respectively. Anastomosis of the portal vein and the inferior vena cava （IVC） inferior to the right kidney between the graft and the recipient was performed by a double cuff method, then the superior hepatic vena cava with suture. A patch of donated renal artery was anastomosed to the recipient abdominal aorta. The urethra and bile duct were reconstructed with a simple inside bracket. Results： Among 65 cases of combined liver-kidney transplantation, the success rate in the late 40 cases was 77.5%. The function of the grafted liver and kidney remained normal. Conclusion： This rat model of combined liver-kidney transplantation can be established in common laboratory conditions with high success rate and meet the needs of renal transplantation experiment.     

BLOOD PRESSURE CHANGE WITH AGE IN SALT-SENSITIVE TEENAGERS

Objective To observe blood pressure change with age in salt-sensitive teenagers whose salt sensitivity were determined by repeated testing.Methods Salt sensitivity was determined through intravenous infusion of normal saline combined with volume-depletion by oral diuretic furosemide in 55 teenagers. After five years, salt sensitivity was re-examined and subject blood pressure was followed up. Blood pressure changes in salt-sensitive teenagers were compared to that of non-salt sensitive teenagers over five years.Results After 5 years, the repetition rate of salt sensitivity determined by intravenous saline loading is 92.7%. In teenagers with salt sensitivity on the baseline, both the systolic blood pressure increments and increment rates were much higher than non-salt sensitive teenagers (12.7±12.1 mmHg vs. 2.8±5.2 mmHg, P＜ 0.01; 12.2%± 12.0% vs. 2.5% ±4.4%, P＜ 0.001,respectively). There was a similar trend for diastolic blood pressure (8.4 ± 6.4 mmHg vs. 3.7 ± 6.4 mmHg, P = 0.052; 13.2% ±10.6 % vs. 6.8%± 10.1%, P = 0.053, respectively).Conclusions Salt sensitivity determined by intravenous saline loading showed good reproducibility. Blood pressure increments with age were much higher in salt-sensitive teenagers than non-salt sensitive teenagers, especially in terms of systolic blood pressure.     

安心颗粒对急诊经皮冠状动脉介入术后生活质量影响的研究

目的：评价使用安心颗粒对急诊经皮冠状动脉介入术（PPCI）术后生活质量的影响.方法：将160例接受PPCI的急性ST段抬高型心肌梗死患者随机分为安心颗粒组（术前顿服安心颗粒8.8g,术后安心颗粒4.4 g/次,每日2次）和对照组（仅接受基础药物治疗）.所有患者均服用阿司匹林、氯吡格雷和阿托伐他汀.分别在入院时、出院前1d、出院后180 d时,应用心肌梗死多维度量表（MIDAS）、中文版SF-36评价量表对患者生活质量评分.并观察术后30 d以内的出血并发症、血小板减少症发生情况.结果：入院时和出院前1d,两组患者的心肌梗死MIDAS、SF-36量表评分比较无差异（P＞0.05）;出院后180 d时,与对照组比较,安心颗粒组MIDAS、SF-36评分明显减低（P＜0.05）;组内与入院时比较,两组出院前1d、出院后180 d时,MIDAS、SF-36评分均降低（P＜0.05）.两组患者在随访期间均无大量出血、少量出血、重度和极重度血小板减少症发生,安心颗粒组有4例、对照组有7例发生不明显出血（P＞0.05）.两组发生轻度血小板减少症的患者数比较无差异（P＞0.05）.结论：PPCI使用安心颗粒,能改善急性ST段抬高型心肌梗死患者的生活质量,且不增加出血风险.     

The comparative studies of the influences of Urapidil and Nicardipine on sino-atrial node function, atrio-ventricular node function and hemodynamics

Objective:To investigate the influences of urapidil and nicardipine on rabbit sinus function,atrio-ventricular node function and hemodynamics.Methods:Thirty-two Angora's rabbits were selected and randomly divided into four groups.U1 group:urapidil 0.25 mg/kg;U2 group:urapidil 0.5 mg/kg;N1 group:nicardipine 10 μg/kg;N2 group:nicardipine 20 μg/kg.All these medicine were administrated within 30 seconds.Measurements were taken before and after the administration of urapidil or nicardipine for the following data:mean blood pressure(MAP),heart rate(HR),sino-atrial conduction time(SACT),maximal sinoatrial recovery time(SNRTmax)corrected sinus node recovery time(CSNRT),index of sinus node recovery time(SNRTI),Wenckebach A-V conduction frequency (WB),and P-R interval.Results:Significant MAP and HR changes were identified in all of the four groups before and after administration of both urapidil and nicardipine.No significant changes could be found in the rest of the parameters.Intergroup analysis showed that SACT and CSNRT of N1 and N2 groups were shorter than those of the U2 group(P＜0.01);the MAP decreased(P＜0.01)and the HR increased drastically(P＜0.01).Conclusions:Neither urapidil(0.25 mg/kg,0.5 mg/kg)nor nicardipine(10μg/kg,20μg/kg)has any significant influence on rabbit sinus function or rabbit atrio-ventricular node function.Nicardipine could be a better choice than urapidil for parafunctional sinus node patients.     

Expression of OPGmRNA and ODFmRNA in the patients of hip fracture due to osteoporosis

Objective：To investigate the gene expression of osteoprotegerin（OPG） and osteoclast differentiation factor（ODF） in the bone tissue of patients with hip fracture due to osteoporosis. Methods：OPGmRNA and ODFmRNA in the bone tissue in 50 cases of osteoporosis sufferers（over 50 years old） with hip fracture（Observer Group） and 30 cases of hip facture sufferers with no osteoporosis（Control group） were analyzed with the Semi-Quantitative RT-PCR method. Results：The mRNA expressed of ODF, OPG were both high in the patients with hip fracture. In the control group, the expression of OPG mRNA was observed, while the expression of ODF mRNA was very slight. Conclusion：Aged patients contained all signals including OPG, ODF that are essential for inducing osteoclastogenesis and promoting bone resorption.     

The clinicopathological and immuohistochemical analysis of solid-pseudopapillary tumor of the pancreas： report of 9 cases

Objective：To investigate the clinical features, pathological characteristics and immunophenotype of solid-pseudopapillary tumor of the pancreas（SPTP）. Methods：Nine surgically treated cases of SPTP were retrospectively reviewed. Hematoxylin and Eosin（HE） staining and immunohistochemical staining were used to analyze all cases, and the general clinical data was collected. Results：Six patients were asymptomatic except for a palpable mass. Two patients complained of vague-epigastric pain. One patient appeared jaundice. The tumor was encapsulated and solid tissues alternately with cystic tissues. Histologically, the histological structure of solid portion was pseudopapillary with a fibrovascular core. Tumor cells were uniform and medium-sized which were arranged in sheets ets or nests or pseudopapillary patterns. Immunohistochemical studies demonstrated that SPTP proved positive in vimentin（9/9 cases）, AAT（9/9 cases）, NSE（9/9 cases）, ACT（7/9 cases）, CK20（2/9 cases）, CgA（1/9 cases）, S-100（3/gcases）, PR（4/gcases）, Syn（3/9 cases） and CD56（5/9cases）, negative in CEA and ER. Conclusion：SPTP is a tumor predominantly occurring in young women frequently without special symptoms. This tumor has various characteristical histological patterns with different immunophenotype.     

Dynamic Changes in Serum Estradiol and Progesterone levels in Patients of Premenstrual Syndrome with Adverse Flow of Liver-qi

Objective:To probe into the influence of changes of ovarian hormones on the pathogenesis of the specific sub-type premenstrual syndrome(PMS)and reveal partial microcosmic mechanisms of adverse flow of liver-qi.Methods:Estradiol(E2)and progesterone(P)levels in serum were determined at different phases of menstrual cycle by radioimmunoassay.Results:In the group of PMS with adverse flow of liver-qi.the secretive peak value Of E2 and P at the follicular phase significantly decreased,and the secretive peak value at the luteal phase did not come into being.Conclusions:Low E2 and P secretive peak at the follicular phase and absence of secretive peak at the luteal phase is one of the microcosmic mechanisms of PMS with adverse flow of liver-qi.One of the pathophysiologic mechanisms of specific sub-type PMS is probably the continuous low level of E2and P.     

Real-time Three-dimensional Echocardiography in Assessment of Left Ventricular and Right Ventricular Volumes

Real-time three-dimensional echocardiography (RT3DE)is a new ultrasound technique that enables dynamic threedimensional visualization and quantification of the heart in real time. Investigation of feasibility and methodology of RT3DE in determining left ventricular (LV) and right ventricular (RV) volumes, RT3DE was performed in 35 normal adults using Philips SONOS 7500 system with a 2-4 MHz matrix array transducer. The 60°×60° "pyramid" volume database was obtained and analyzed on a TomTec echo workstation. Both LV and RV volumes were calculated with four 3DE methods (i.e. apical 2, 4, 8, and 16-plane) through manually tracing ventricular endocardial borders in end diastole and end systole. Stroke volumes were then calculated. LV volume was also measured by 2DE Simpson's rule using GE VIVID 7 ultrasound machine.     

SCREENING FOR A 21-CHROMOSOME ABNORMALITY IN PREIMPLANTED EMBRYOS OF ELDERLY WOMEN

Increasing maternal age is the only etiological factor unequivocally linked to Down's syndrome in humans. The occurrence rate of newborns with Down's syndrome is about 1/220 in women over 35 years old. However, the occurrence rate in embryos fertilized in vitro, of the elder woman is unclear. Using FISH we screened the number of chromosome 21 in preimplanted embryos of 5 elderly women (average age, 38.4 years) to study the feasibility and necessity of screening trisomy 21 in embryos in patients over 35 years old at the in vitro fertilization (IVF) center.