大鼠促红细胞生成素重组腺病毒载体的构建及其在大鼠SGNs中的表达

目的构建大鼠促红细胞生成素(erythropoietin,EPO)重组腺病毒载体,并转染于体外培养的大鼠螺旋神经元(spiral ganglion neurons,SGNs)。方法全基因合成大鼠EPO基因,亚克隆至穿梭质粒pAdTrack-CMV,构建重组穿梭质粒pAdTrack-CMV-EPO。经酶切、PCR及测序鉴定,再经PacⅠ酶切线性化后电转化感受态细胞,获得重组腺病毒载体pAdTrack-CMV-EPO,经PacⅠ酶切后转染至293细胞进行包装,制备重组腺病毒,扩增后进行病毒滴度测定及RT-PCR和Western blot鉴定。并转染至体外培养的螺旋神经元,免疫荧光检测及蛋白水平检测螺旋神经元中EPO表达。结果经KpnⅠ、HindⅢ酶切与测序鉴定显示,腺病毒载体pAdTrack-CMV-EPO构建成功,重组腺病毒AdEPO在293细胞中成功包装,扩增后病毒滴度为1.17×1011U/ml;经RT-PCR和Western blot检测EPO在293细胞中成功表达。重组腺病毒载体AdEPO经鉴定均构建正确;免疫荧光及Western blot检测转染腺病毒后螺旋神经元中EPO表达显著增强。结论成功构建了EPO重组腺病毒载体,并成功转染螺旋神经元,可显著增强螺旋神经元中EPO表达水平。     

人生长终止特异性同源盒基因重组腺病毒载体的构建及鉴定

目的 生长终止特异性同源盒(growth arrest-specific homeobox,Gax)基因表达产物是核转录因子,主要存在于心血管系统中,对胚胎发育、细胞生长、分化和迁移等起基因调控作用,其表达异常与多种疾病相关.为深入研究Gax基因在临床疾病中的作用,文中构建表达了人Gax基因的重组腺病毒载体.方法 根据pEGFP-N1-Gax质粒的多克隆位点,用NheⅠ和Hind Ⅲ双酶切获得人Gax基因片段,连接至穿梭质粒pDC18-mCMV上,构建穿梭质粒pDC318-mCMV-Gax,然后与骨架质粒pPE3共转染293包装细胞,同源重组产生复制缺陷型重组腺病毒载体Ad5-Gax,反复感染293细胞扩增病毒后,氯化铯梯度离心纯化病毒,并测定病毒滴度.结果 穿梭质粒pDC318-mCMV-Gax经双酶切和测序证实构建成功;PCR鉴定人Gax基因重组腺病毒载体构建成功,病毒滴度为4.5×1010pfu/ml.结论 该研究成功构建了重组腺病毒载体Ad5-Gax,为进一步在体内外研究Gax基因参与多种疾病的发生发展提供了材料.     

携带NR2B抗原表位的表达载体的构建与鉴定

目的构建携带N-甲基-D-天门冬氨酸受体(N-methyl-D-aspartate receptor,NMDAR)2B亚基抗原表位的表达载体并进行初步鉴定。方法在获得NMDAR2B(NR2B)抗原模拟表位碱基序列TCGCATCCGCCTGTGATGCCTTGGCC-TACTTCGACT的基础上,设计两条含起始密码子、终止密码子、双酶切位点的互补引物,应用PCR技术合成该表位,与表达载体pDC515重组为pDC515/nr2b,采用限制性内切酶酶切及DNA测序进行鉴定。结果经限制性酶切鉴定及DNA测序分析证实pDC515/nr2b含有NR2B抗原模拟表位片段。结论成功构建了含有NR2B模拟抗原表位的表达载体,为进一步研制NR2B抗原表位的DNA疫苗及其镇痛效应奠定了实验基础。     

重组腺病毒Ad5F35-SD-EGFP的构建及其对K562细胞增殖的影响

目的构建表达SH2-DED融合基因的新型重组腺病毒Ad5F35-SD-EGFP,观察其对K562细胞增殖的抑制作用。方法重叠PCR扩增SH2-DED融合基因并克隆至腺病毒穿梭载体pAdTrack-CMV中,构建成穿梭质粒pAdT-SD-EGFP并进行酶切和测序鉴定。穿梭质粒经Pme I酶切后转化pAd5F35-GFP的BJ5183感受态,通过细菌内同源重组产生重组腺病毒质粒pAd5F35-SD-EGFP及其突变体,Pac I酶切后转染AD293细胞进行包装。重组腺病毒Ad5F35-SD-EGFP经PCR和western blot鉴定后进行病毒扩增和滴度测定。体外感染K562细胞,通过MTT和流式周期检测实验观察Ad5F35-SD-EGFP对K562细胞增殖的影响。结果 PCR、酶切和测序结果均表明pAdT-SD-EGFP和pAd5F35-SD-EGFP构建成功;PCR、EGFP检测结果证明重组腺病毒Ad5F35-SD-EGFP包装扩增成功,滴度可达1.4×1012 pfu/ml。转染K562细胞后,Western blot可检测到目的蛋白的表达,MTT实验和流式周期检测结果证明其对K562细胞的增殖有明显的抑制作用。结论成功构建并鉴定了携带SH2-DED融合基因的重组腺病毒Ad5F35-SD-EGFP,其对BCR-ABL阳性K562细胞的增殖有明显的抑制作用。     

PTG重组腺病毒过表达载体的构建

目的 构建及鉴定携带小鼠PTG基因(NM＿016854)的过表达重组腺病毒载体,为深入研究PTG的功能奠定基础。方法 化学合成小鼠PTG基因的编码序列,经聚合酶链式反应(PCR)扩增、酶切,后插入GV314载体(CMV-MCS-3FLAG-SV40-EGFP),得到重组穿梭质粒pGV314-PTG;进一步BamHⅠ/AgeⅠ双酶切,产物交换入线性化表达载体pDC315,构建重组腺病毒Ad-PTG,将其转染HEK293T细胞包装成重组病毒颗粒,经在HEK293T细胞反复扩增数代后,进行纯化及滴度检测,最后利用PCR、Western blot及测序验证重组腺病毒。结果 经PCR、Western blot及测序后,结果显示成功构建pGV314-CMV-MCS-3FLAG-SV40-EGFP-PTG过表达腺病毒载体(Ad-PTG),终点稀释法测得病毒滴度为4×10¹⁰ PFU/ml, Western blot和荧光定量PCR显示PTG的蛋白和mRNA表达水平显著升高。结论 成功构建携带小鼠PTG基因的重组过表达腺病毒载体,且能有效上调肝细胞中PTG基因的表达。     

人白细胞介素21基因重组复制缺陷型腺病毒的制备与鉴定

目的 制备表达绿色荧光蛋白的含人白细胞介素21(IL-21)基因的重组复制缺陷型腺病毒,为IL-21基因治疗肿瘤的研究奠定基础.方法 从人外周血淋巴细胞提取总RNA,经RT-PCR扩增IL-21基因片段,PCR产物和pDC316-mCMV-EGFP载体分别经限制性内切酶Notl与HindⅢ双酶切,然后将酶切产物连接、转化,构建pDC316-IL21-EGFP重组质粒.重组质粒经酶切和测序鉴定后,与腺病毒骨架质粒pBHGlox_E1,3CreF35共转染293细胞,包装产生Ad5F35-IL21-EGFP重组腺病毒,并测定病毒滴度.观察Ad5F35-IL21-EGFP腺病毒转染后食管癌细胞EC-9706的生长曲线和细胞周期的变化.结果 pDC316-IL21-EGFP重组质粒经酶切和测序证实,IL-21基因片段正确插入pDC316-mCMV-EGFP栽体中且与GenBank中,IL-21基因序列一致.AdSF35-IL21-EGFP重组腺病毒栽体在293细胞中包装成功.获得成熟的病毒颗粒,经鉴定有IL-21基因和绿色荧光蛋白的表达.测得Ad5F35-IL-21-EGFP病毒颗粒滴度为9×1011VP/ml,感染性滴度为5×1010IU/ml.AdSF35-IL21-EGFP转染后,EC-9706细胞的生长缓慢(P＜0.05),G1期细胞增加,而G2期和S期细胞减少.结论 成功制备了表达绿色荧光蛋白的人IL-21基因的重组腺病毒,且病毒滴度较高.腺病毒介导的外源性IL-21基因可有效转染EC-9706细胞,并对其生长有抑制作用.     

Betatrophin重组腺病毒过表达载体的构建

［摘要］目的: 应用基因同源重组技术,构建及鉴定携带小鼠betatrophin基因Gm6484(NM_001080940)的复制缺陷型重组腺病毒载体,为进一步研究betatrophin的功能奠定基础。方法: 根据基因库中登录的小鼠betatrophin基因Gm6484(NM_001080940)序列,经化学合成得到含BamHⅠ/ AgeⅠ酶切位点的小鼠betatrophin基因全长cDNA质粒,将其酶切后插入到带有增强型绿色荧光蛋白（enhanced green fluorescent protein,EGFP）基因的GV314载体CMV MCS 3FLAG SV40 EGFP中,得到重组病毒穿梭质粒pGV314 betatrophin;经BamHⅠ/ AgeⅠ双酶切后,与线性化的pDC315病毒基因组质粒体外同源重组,构建含有目的基因的腺病毒载体Ad betatrophin,酶切线性化重组腺病毒质粒后转染HEK293T细胞包装成重组病毒颗粒,经在HEK293T细胞反复扩增数代后,利用聚合酶链式反应（PCR）、蛋白质印迹法及测序鉴定重组的腺病毒。结果： 阳性克隆质粒Ad betatrophin在HEK293T细胞中成功包装出重组病毒,经PCR、蛋白质印迹及测序检测表明重组腺病毒包装成功。结论： 成功构建了携带小鼠betatrophin基因的复制缺陷型重组腺病毒过表达载体。     

E型沙眼衣原体MOMP基因重组腺病毒的构建及免疫原性研究

目的:构建E型沙眼衣原体(Ct)主要外膜蛋白（MOMP）基因重组腺病毒,为沙眼衣原体腺病毒疫苗的研究奠定基础。方法: 根据Genebank中E型Ct MOMP基因序列设计引物,用高保真PCR方法从E型Ct基因组DNA中扩增得到MOMP基因片段,克隆至pcDNAII载体,测序后连接入腺病毒穿梭载体pDC316。穿梭载体pDC316 MOMP与含腺病毒基因组的辅助质粒PBHGlox△E1,3Cre共转染至HEK293细胞,在Cre loxP重组酶作用下进行重组,包装成重组腺病毒颗粒,用PCR和RT PCR方法进行鉴定。并用动物免疫试验检测重组腺病毒的免疫原性。结果:从E型Ct基因组DNA中扩增出约1.1?kb的特异MOMP基因片段,酶切鉴定及DNA序列测定证实穿梭载体pDC316 MOMP构建正确。穿梭载体pDC316 MOMP与含腺病毒基因组的辅助质粒PBHGlox△E1,3Cre共转染至293细胞,出现明显细胞病变效应。收集重组腺病毒,PCR法证实重组腺病毒含有MOMP基因,RT PCR证实重组腺病毒在293细胞能表达MOMP基因。重组腺病毒免疫小鼠可诱导特异性抗体产生,证明重组腺病毒具有良好免疫原性。结论:成功构建了E型沙眼衣原体MOMP基因重组腺病毒,该重组腺病毒可诱导小鼠产生特异性抗体。     

小鼠B7-H4重组腺病毒的构建及鉴定

目的:利用AdEasyTM XL system构建携带小鼠B 7-H4基因的重组腺病毒,并鉴定其生物学活性.方法:以RT-PCR方法从C5 7小鼠肺组织中扩增B7-H4全长基因并克隆到T载体,然后测序鉴定.经Xhol Ⅰ和EcoR Ⅴ双 酶切后接入pshuttle-CMV穿梭载体(简称PSC),构建重组腺病毒的穿梭质粒PSC-mB7-H4 ,并电转化至BJ5183-AD-1感受态细菌,经筛选获得携带mB7-H4的重组腺病毒的质粒pmB7 -H4/Ad.将此质粒转化人胚肾细胞(AD-293)产生复制缺陷的重组腺病毒mB7-H4/Ad .以RT-PCR及Western blot方法检测被mB7-H4/Ad感染的AD-293细胞中B7-H4 mRNA和蛋 白的表达,并观察重组腺病毒感染的小鼠成纤维细胞(L929)对T细胞增殖和细胞因子表达的影响. 结果:获得序列准确的mB7-H4基因并成功构建重组腺病毒表达质 粒,转化AD-293细胞获得重组腺病毒;细胞生物学实验证实,该重组腺病毒具有抑制CD3单抗诱导的T淋巴细胞的增殖和细胞因子的分泌. 结论:成功构建具有免疫抑制功能的mB7-H4重组腺病毒.     

小鼠NR4A1基因小分子干扰RNA重组腺病毒载体的构建与鉴定

目的:构建表达小鼠NR4A1基因的小分子干扰RNA(siRNA)重组腺病毒载体. 方法:根据siRNA靶序列设计并合成2条互补的64 bp寡核苷酸.pShuttle-H1穿梭质粒经BglⅡ、HindⅢ双酶切后,与退火的寡核苷酸进行连接,构建穿梭质粒pShuttle-H1-siRNA.PmeⅠ酶切pShuttle-H1-siRNA, 然后分别将腺病毒骨架质粒pAdEasy-1和穿梭质粒pShuttle-H1-siRNA转化至BJ-5183感受态细菌中进行同源重组.PacⅠ酶切线性化重组质粒pAdEasy-H1-siRNA后转染AD-293细胞进行病毒包装和扩增.Western blot检测NR4A1基因的表达. 结果:穿梭质粒pShuttle-H1-siRNA经双酶切和测序证实构建成功,进一步构建了表达小鼠NR4A1基因的siRNA重组腺病毒载体,重组腺病毒AdH1-siRNA/NR4A1感染小鼠睾丸间质细胞瘤细胞(MLTC-1)后显著抑制目的蛋白表达(抑制率为70%～90%). 结论:成功构建了表达小鼠NR4A1基因的siRNA重组腺病毒载体AdH1-siRNA/NR4A1,并在MLTC-1中验证其抑制NR4A1蛋白表达,为进一步研究NR4A1基因在多囊卵巢综合征(PCOS)中的作用奠定了基础.     

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.     

Scientific principles and rigorous processes should be followed in developing clinical guidelines for therapeutic interventions of integrative medicine

A clinical guideline for the therapeutic interventions of integrative medicine may be defined as a written document which states a series of recommendations on therapeutic interventions of integrative medicine for a special disease or condition. The guideline may provide assistance to medical professionals in making clinical decisions aimed at improving the clinical outcome of patients and reducing the costs of medical care（~＇4~. Recommendations issued by a guideline should be based on the best available evidence in both Western and Chinese medicine. For fulfilling this purpose, the development of clinical guidelines for therapeutic interventions in the field of integrative medicine should follow scientific principles and undergo a rigorous processes.     

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.