姜黄素衍生物对激活的小胶质细胞诱导型一氧化氮合酶表达的抑制作用

目的 对比研究姜黄素(curcumin)及其衍生物对脂多糖(lipopolysacchar,LPS)激活的小胶质细胞-氧化氮(NO)的产生及诱导型-氧化氮合酶((inducible nitric oxide synthase,iNOS)表达的影响.方法 用LPS(1μg·mL-1)刺激原代培养的大鼠小胶质细胞,同时用不同浓度姜黄素及其衍生物F进行干预,应用免疫组化方法观察细胞活性;Western-blot方法检测iNOS蛋白的表达;用Cayman's Nitrate/Nitrite Colorimetric Assay Kit检测细胞上清液中NO的含量.结果 LPS作用4 h后,iNOS蛋白表达明显增强,NO释放量明显增加;使用姜黄素干预18 h后,浓度在5μg·mL-1 以上时可以显著抑制LPS激活的小胶质细胞iNOS蛋白的表达和NO的产生,但是姜黄素衍生物只有在浓度达到25μg·mL-1时才对iNOS蛋白的表达和NO的产生有明显的抑制效果.结论 姜黄素和它的衍生物都能够抑制LPS激活的小胶质细胞iNOS蛋白的表达以及NO的产生,但其衍生物的作用相对较弱.     

雷公藤内酯醇对Aβ_(1-42)激活的小胶质细胞一氧化氮释放和诱导型一氧化氮合酶表达的影响

目的研究雷公藤内酯醇(triptolide,T10)对β-淀粉样蛋白(β-amyloid,Aβ)1-42激活的小胶质细胞一氧化氮(nitrogenmonoxidum,NO)的产生及诱导型一氧化氮合酶(inducible nitric oxide synthase,iNOS)表达的影响。方法用不同浓度的T10(10-11、10-10、10-9、10-8mol/L)预孵育小胶质细胞12 h,然后加入10μmol/L Aβ1-42共孵育12 h;Griess反应检测上清NO的含量,Western blotting检测iNOS蛋白的表达。结果 Aβ组iNOS的表达和NO释放明显高于对照组(P<0.01)。T10可明显减少Aβ诱导的小胶质细胞iNOS的表达及NO的释放(P<0.05)。结论 T10可抑制Aβ1-42激活的小胶质细胞iNOS蛋白的表达及NO的释放。     

青蒿琥酯对脂多糖诱导的BV-2小胶质细胞激活的抑制作用

目的 观察青蒿琥酯对脂多糖（LPS）诱导的BV-2小胶质细胞炎症反应的抑制作用.方法 LPS诱导BV-2小胶质细胞活化建立炎症模型,观察青蒿琥酯（0.5、1.5、3.5 μmol/L）对细胞的作用.MTT检测细胞活性;Griess试剂法检测一氧化氮（NO）的释放;Western Blot检测核转录因子κB（NF-κB）的蛋白表达.结果 青蒿琥酯减少了活化的BV-2小胶质细胞NO的释放,降低了核内NF-κB的蛋白表达.结论 青蒿琥酯可能通过抑制LPS诱导的BV-2小胶质细胞NF-κB的激活从而抑制NO的产生,发挥抗炎作用。     

姜黄素抑制星形胶质细胞和小胶质细胞中脂多糖诱导的趋化因子的表达

目的：观察姜黄素对脂多糖诱导的星形胶质细胞和小胶质细胞中角质细胞源性趋化因子（CXCL1）和干扰素诱导蛋白10（CXCL10）表达的抑制作用。方法：（1）确定脂多糖刺激细胞的时间：将培养的C6星形胶质细胞株随机分为对照组、脂多糖1 h、3 h、6 h组。对照组未加入任何药物刺激;脂多糖1 h、3 h、6 h组应用1 μg/mL脂多糖分别刺激细胞1 h,3 h,6 h。采用real-time PCR方法检测细胞中趋化因子CXCL1和CXCL10 mRNA的表达,确定合适的脂多糖刺激时间。（2）姜黄素处理细胞实验：①C6细胞随机分成5组：对照组、脂多糖组、姜黄素2.5 μmol/L、10 μmol/L、25 μmol/L预处理组。对照组未加入任何药物刺激;脂多糖组用1 μg/mL脂多糖刺激细胞3 h;姜黄素预处理组分别用2.5 μmol/L、10 μmol/L、25 μmol/L姜黄素预孵育30 min后,再加入1 μg/mL脂多糖刺激细胞3 h。②原代培养的星形胶质细胞,分组方法和处理方法同①。③原代培养的小胶质细胞,随机分成对照组、脂多糖组、姜黄素25 μmol/L预处理组,方法同①。处理结束后,采用real-time PCR方法检测细胞中趋化因子CXCL1和CXCL10 mRNA的表达。结果：（1）与对照组比较,脂多糖刺激C6细胞3 h时,CXCL1（P<0.001）和CXCL10（P<0.05）表达最高,因此选择脂多糖刺激细胞时间为3 h。（2）在C6细胞中,与脂多糖组比较,姜黄素25 μmol/L预处理组CXCL1和CXCL10的表达均显著降低（P<0.001）。（3）在原代培养的星形胶质细胞中,与脂多糖组比较,姜黄素10 μmol/L预处理组（P<0.05）、姜黄素25 μmol/L预处理组（P<0.001）CXCL1的表达均显著降低,姜黄素25 μmol/L预处理组CXCL10的表达显著降低（P<0.001）。（4）在原代培养的小胶质细胞中,与脂多糖组比较,姜黄素25 μmol/L预处理组CXCL1和CXCL10的表达均显著降低（P<0.001）。结论：姜黄素能抑制星形胶质细胞和小胶质细胞中脂多糖诱导的趋化因子CXCL1和CXCL10的表达,具有抗炎作用。     

白藜芦醇对脂多糖诱导的星型胶质细胞炎症损伤的保护作用

目的研究白藜芦醇(RES)对脂多糖诱导的星型胶质细胞炎症因子释放的抑制作用,探索其对中枢神经系统保护作用的可能机制。方法 GFAP免疫组化法鉴定星型胶质细胞的纯度。采用不同浓度的RES与星型胶质细胞共同培养12 h,然后进行LPS损伤24 h,检测不同实验组乳酸脱氢酶(LDH)漏出量,cck-8法检测细胞存活率,Griess法检测NO释放量,Elisa法检测α-肿瘤坏死因子(TNF-α)表达量及Western blot法检测诱导型一氧化氮合酶(iNOS)蛋白的表达水平。结果离体培养的星形胶质细胞的阳性率为(95.49±1.86)%。LPS处理组细胞LDH漏出量升高,存活率降低,同时NO、TNF-α的释放量明显增加及iNOS蛋白的表达水平上调。测试浓度范围(5～50μmol/L)的RES能有效提高细胞存活率及降低LDH漏出量并呈现一定程度的剂量-反应关系。而在抑制NO、TNF-α释放及iNOS表达方面,只有25、50μmol/L的RES处理组有明显抑制作用,5μmol/L RES处理组与LPS处理组相比并无明显变化。结论较高浓度RES能明显抑制LPS诱导的星型胶质细胞炎症介质的释放,改善星型胶质细胞的炎症损伤,这种作用可能与抑制iNOS/NO的表达通路有关。     

汉黄芩素对脂多糖诱导的BV2细胞诱导型一氧化氮合酶表达的影响

[目的]探讨汉黄芩素对脂多糖(LPS)诱导的BV2细胞激活时所分泌的一氧化氮的产生以及诱导型一氧化氮合酶(iNOS)表达的影响.[方法]用10,100,500,1 000μg/L的LPS刺激小胶质细胞株BV2,并向LPS(100μg/L)中加入10,20,30μmol/L的汉黄芩素后再培养24h,采用Greiss法测定细胞外液所分泌的一氧化氮含量;应用Western-Blot及RT-PCR法分别检测iNOS蛋白和mRNA的表达.[结果]LPS高度激活BV2细胞,并且能使一氧化氮分泌增加,汉黄芩素呈剂量依赖性抑制一氧化氮的含量,同时抑制iNOS蛋白和mRNA的表达.[结论]汉黄芩素可有效抑制LPS激活的BV2细胞iNOS蛋白和mRNA的表达及一氧化氮的产生.     

美满霉素抑制脂多糖诱导的小胶质细胞诱导型一氧化氮合酶的表达及其相关机制

目的:探讨美满霉素(minocycline,MC)对脂多糖(lipopolysaccharide,LPS)诱导的小胶质细胞一氧化氮(NO)生成和诱导型一氧化氮合酶(iNOS)表达的影响及其相关分子机制?方法:LPS或联合MC刺激BV-2细胞,酶联免疫法检测培养上清中NO水平,免疫细胞化学观察iNOS的蛋白含量,RT-PCR技术评价iNOS的mRNA表达,免疫印迹研究p38丝裂原活化蛋白激酶(p38MAPK)的蛋白水平和磷酸化变化?结果:LPS(100 ng/ml)组NO含量显著升高(P < 0.05),且伴随iNOS蛋白和mRNA水平的明显上调,与对照组相比有显著性差异(P < 0.01)?MC(10 μmol/L)预处理(MC+LPS组)能明显抑制上述变化,NO含量?iNOS蛋白和mRNA水平较LPS组均显著下调(P均 < 0.01),但明显高于对照组(P均 < 0.05)?LPS也能诱导p38MAPK磷酸化,与对照组相比差异显著(P < 0.01),而MC预处理(MC+LPS组)能拮抗p38MAPK的磷酸化,较LPS组显著下调(P < 0.01),同时实验各组p38MAPK蛋白水平保持基本一致?结论:美满霉素能通过下调p38MAPK信号途径,抑制脂多糖刺激的小胶质细胞iNOS基因表达及NO生成,对脂多糖诱导的小胶细胞损伤有明显保护作用?     

姜黄素对胃癌MGC-803细胞磷酸化-丝氨酸/苏氨酸蛋白激酶表达的影响

目的 探讨姜黄素对胃癌MGC-803细胞磷酸化-丝氨酸/苏氨酸蛋白激酶(p-AKT)表达的影响.方法 将MGC-803细胞分为空白对照组和四个药物实验组,各组姜黄素浓度分别为5 μmol/L,10 μmol/L,20 μmol/L,40 μmol/L.经不同浓度的姜黄素作用24 h、48 h、72 h后,应用CCK8法检测姜黄素对MGC-803细胞增殖的影响;应用Annexin V-FITC/PI双染色法测定不同浓度的姜黄素作用24 h后胃癌MGC-803细胞凋亡情况;应用蛋白免疫印迹法检测不同浓度姜黄素作用24 h对MGC-803细胞内p-AKT蛋白表达水平的影响.结果 姜黄素对MGC-803细胞增殖有抑制作用,且呈剂量依赖性和时间依赖性.在5~40 μmol/L浓度范围内,姜黄素呈浓度依赖性地促进MGC-803细胞的凋亡,并下调MGC-803细胞中p-AKT的水平.结论 姜黄素可能是通过抑制p-AKT蛋白的表达和AKT信号通路促进MGC-803细胞凋亡并抑制其增殖.     

姜黄素对大鼠血管平滑肌细胞增殖和凋亡的影响

目的:观察姜黄素对大鼠血管平滑肌细胞(VSMCs)增殖和凋亡的影响及其机制.方法:采用组织块法体外培养大鼠VSMCs,MTT法测定姜黄素对VSMCs增殖的抑制作用.流式细胞术分析细胞凋亡,Western Blot印迹法检测VSMCsP21,P53,Bcl-2蛋白表达的变化.结果:MIT显示不同浓度姜黄素(7.5～120 μmol/L)在24～72 h范围内,浓度和时间依赖性抑制VSMCs增殖;流式细胞术显示30,60 μmoL/L姜黄素作用VSMCs 24 h后,凋亡率较对照组明显升高;30 μmol/L姜黄素在不同时间点可上调VSMCs P21蛋白表达,下调Bcl-2蛋白表达,对P53蛋白表达没有影响.结论:姜黄素具有明确的抑制VSMCs增殖,并能诱导血管平滑肌细胞凋亡,与上调VSMCa P21蛋白表达和下调Bcl-2蛋白表达有关.     

双氢青蒿素抑制LPS诱导的小胶质细胞炎症反应

目的 观察双氢青蒿素(dih ydroartemisinin,DHA)对脂多糖(lipopolysaccharide,LPS)诱导的BV-2小胶质细胞神经炎症反应的影响及其机制.方法 LPS诱导BV-2小胶质细胞活化建立炎症模型,用不同浓度DHA(0.5、1、2、4μmol/L)处理细胞,CCK-8检测细胞活性;选取lμmol/L DHA干预细胞,倒置相差显微镜下观察细胞形态的变化;RT-PCR检测iNOS、IL-1β、IL-6、TNF-α基因表达水平;ELISA检测培养基中IL-1β、IL-6、TNF-α的表达水平;Western blot检测NF-κB、IκBα及TLR4的蛋白表达.结果 低剂量的DHA(＜2μmol/L)对BV-2细胞活性无明显影响(P＞0.05),DHA可抑制LPS引起的BV-2细胞形态变化,DHA抑制活化的BV-2细胞iNOS、IL-1β、IL-6、TNF-α mRNA的表达(P＜0.01),减少IL-1β、IL-6、TNF-α炎症因子释放(P＜0.01),明显降低TLR4的蛋白表达,减少细胞质内IκBα的表达,并抑制NF-κB向核内移位(P＜0.01).结论 DHA可能通过作用于TLR4/NF-κB通路,抑制LPS诱导的BV-2小胶质细胞NF-κB的激活,从而抑制炎症因子的产生,发挥抗炎作用.     

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.