Osterix和核结合因子在成骨样细胞系分化过程中的表达

目的观察小鼠前成骨细胞MC3T3E1的诱导成骨过程中,Osterix(OSX)和核结合因子(Cbfa1)及其两种亚型Cbfa1/P56、Cbfa1/P57表达的变化,了解OSX和Cbfa1表达与成骨细胞分化的关系,探求与OSX变化趋势一致的Cbfa1亚型。方法在小鼠前成骨细胞MC3T3E1培养的不同时间(0、4、10、14、18、22 d),用半定量RT-PCR法检测OSX、Cbfa1、Cbfa1/P56、Cbfa1/P57 mRNA的表达;用Western-blot法检测Cbfa1蛋白的表达;Van Gie-Son苦味酸酸性复红染色法染色细胞Ⅰ型胶原;茜素红染色观察矿化结节形成。结果MC3T3E1在诱导成骨的培养条件下,从培养第18天开始出现矿化,第22天观察到明显的矿化结节形成。OSX mRNA、Cbfa1 mRNA和Cbfa1蛋白的表达量随MC3T3E1的成熟矿化逐渐增高,而Cbfa1/P56 mRNA表达量无变化,但Cbfa1/P57 mRNA在培养第18天和第22天的表达量明显增高。结论在MC3T3E1分化过程中,OSX和Cbfa1的表达量随成骨细胞的成熟逐渐增高。在Cb-fa1的亚型中,Cbfa1/P57的表达与OSX表达趋势一致。     

EPHA2在人骨髓间充质干细胞成骨分化中的作用

目的:研究EPHA2在人骨髓间充质干细胞(hBMSC)成骨分化过程中表达的动态变化及其在成骨分化中的作用.方法:hBMSC成骨分化诱导0、4、10和14 d后分别收集细胞提取RNA和蛋白,采用Real-timePCR和Western blot方法检测EPHA2mRNA及蛋白表达;使用EPHA2的si-RNA下调EPHA2表达后进行成骨分化诱导,检测下调EPHA2表达对早期成骨分化指标ALP活性及晚期成骨分化指标钙沉积、成骨分化标志物OSX、OCN和成骨分化关键转录因子RUNX2表达的影响.结果:EPHA2在hBMSC成骨分化过程中表达逐渐上升,下调EPHA2表达能抑制ALP活性和钙沉积,抑制OSX、OCN及关键转录因子RUNX2的表达.结论:EPHA2在hBMSC成骨分化过程中表达逐渐上升,EPHA2可能通过增强RUNX2的表达从而促进hBMSC成骨分化.     

成骨生长肽对大鼠骨髓基质细胞增殖分化的影响

目的 研究成骨生长肽(osteogenic growth peptide, OGP)在体外对骨髓基质细胞增殖和成骨向分化的影响.方法 在体外培养的大鼠骨髓基质细胞中加入不同浓度的OGP(10-11～10-7 mol/L),用MTT法检测细胞增殖,酶联免疫法检测细胞内碱性磷酸酶(ALP)的表达,RT-PCR法检测细胞内核心结合因子1(Cbfa1) mRNA的表达.结果 OGP对骨髓基质细胞增殖有促进作用(P《0.05),最大效应浓度为10-9 mol/L;能增加细胞内ALP活性(P《0.05),最大效应浓度为10-8 mol/L;可诱导Cbfa1 mRNA的表达(P《0.05).结论 OGP可促进骨髓基质细胞的增殖,并通过诱导其内Cbfa1 mRNA的表达促进其成骨向的分化.     

过氧化物酶体增殖物激活受体γ抑制高磷诱导血管平滑肌细胞钙化

目的 探讨过氧化物酶体增殖物激活受体γ(peroxisome proliferators activated receptor γ,PPARγ)对高磷诱导的小鼠血管平滑肌细胞(vascular smooth muscle cells,VSMCs)钙化的抑制作用.方法 体外培养小鼠血管平滑肌细胞,先分正常对照组、高磷组(HP,2.6 mmol/L),观察高磷对VSMCs的影响,再分为正常对照组、高磷组(HP,2.6 mmol/L)、罗格列酮组(RGL,10 μmol/L)、高磷(2.6 mmol/L)±罗格列酮(10 μmol/L)组(HP+RGL),观察PPARγ激动剂罗格列酮对高磷诱导的VSMCs钙化的抑制作用.茜素红S(alizarin red S)染色观察高磷对细胞钙盐沉积的影响.Western blot检测PPARγ、血管平滑肌22alpha蛋白标志物(SM22α)、骨形成蛋白2(BMP2)和成骨特异性转录因子2(Runx2)的表达变化.结果 与正常对照组相比,高磷处理后的VSMCs的钙盐沉积明显升高[(0.08 ±0.02)vs(0.19 ±0.03),P＜0.01],成骨细胞标志物BMP2[(0.26 ±0.02) vs (0.74±0.03),P＜0.01]及Runx2表达[(0.29 ±0.03) vs (0.91 ±0.04),P＜0.01)],明显升高.同时PPARγ[(0.93±0.04)vs(0.58±0.02),P＜0.05]及平滑肌细胞标志物SM22α表达减少[(1.02±0.09) vs(0.77±0.03),P＜0.05],而加入罗格列酮后,高磷状态下VSMCs的钙盐沉积明显降低[(0.19±0.02) vs(0.12±0.03),P＜0.05],PPARγ[(0.63 ±0.04)vs(0.85 ±0.03),P＜0.05]和SM22α[(0.69 ±0.02) vs(0.99±0.03),P＜0.01]表达明显上升,相反,BMP2[(1.02±0.04) vs (0.48±0.05),P＜0.01]及Runx2[(1.00 ±0.06) vs (0.67 ±0.03),P＜0.01]的表达则明显受抑.结论 高磷诱导VSMCs向成骨细胞分化和钙化可能与下调PPARγ的表达有关,而罗格列酮可通过激活PPARγ抑制高磷状态下VSMCs钙化的发生.     

R-spondin1在促进人骨髓间充质干细胞成骨分化中的作用

目的:研究Wnt信号通路激活剂R-spondin1在人骨髓间充质干细胞(hBMSC)成骨分化中的作用.方法:用0、5、10、20 μg/L R-spondin1处理hBMSC,利用荧光素酶实验检测R-spondin1对hBMSC中Wnt信号通路的作用,Western blot检测R-spondin1对Wnt信号通路下游靶基因β-catenin蛋白表达的影响;在成骨分化培养基中添加20 μg/L R-spondin1诱导hBMSC成骨分化,检测R-spondin1对早期成骨分化指标ALP活性及成骨分化晚期钙沉积、成骨分化标志物OSX、OCN和成骨分化关键转录因子RUNX2表达的影响.结果:R-spondin1增强hBMSC中Wnt信号通路,R-spondin1增强ALP活性和钙沉积,促进OSX、OCN及RUNX2的表达.结论:R-spondin1增强hBMSC中Wnt信号通路的作用,促进hBMSC成骨分化.     

骨关节炎软骨下骨的成骨细胞生物学表型研究

目的 培养骨关节炎患者软骨下骨成骨细胞,探讨硬化区和非硬化区软骨下骨成骨细胞的生物学特性.方法 收集本科2009年10月至2010年3月拟行全膝关节置换入院的骨关节炎患者7例,男性5例,女性2例,平均年龄68(55-79)岁,留取术后遗弃的胫骨平台骨组织.应用Ⅰ型胶原酶消化联合贴壁培养方法,培养软骨下骨的成骨细胞,光镜下观察细胞形态,免疫组化检测Ⅰ型胶原,NBT/BCIP染色法检测碱性磷酸酶,茜素红染色检测矿化结节,油红O染色检测脂质成分.应用实时定量RT-PCR技术检测并比较硬化区和非硬化区软骨下骨成骨细胞相关基因[碱性磷酸酶(ALP),骨钙蛋白(OCN),转化生长因子β1(TGF-β1),胰岛素样生长因子1(IGF-1),Ⅰ型胶原(COL1)A1/(COL1)A2,基质金属蛋白酶13(MMP-13),骨桥蛋白(OPN),肿瘤坏死因子(TNF-α),白介素(IL)-6和IL-8]的表达.应用茜素红染色比较两种细胞矿化能力.结果 光镜下观察到细胞渐从骨片中爬出的生长过程,免疫组化证实细胞表达Ⅰ型胶原,NBT/BCIP染色显示细胞表达碱性磷酸酶,茜素红染色显示细胞能形成矿化结节,油红O染色显示细胞内无脂质成分,证实Ⅰ型胶原酶消化联合贴壁培养方法能较好的培养出成骨细胞.茜素红染色显示软骨下骨硬化区成骨细胞矿化能力低于非硬化区[(0.92±0.06),(1.32±0.15),P＜0.01].RT-PCR显示,硬化区软骨下骨成骨细胞比非硬化区软骨下骨成骨细胞高表达基因OPN[(2.62±1.47)×10-2,(9.63±3.37)×10-4,P＜0.05]、OCN[(6.04 ±6.27)×10-6,(4.84±2.18)×10-6,P＜0.05]、ALP[(73.62±15.75)×10-4,(3.10±0.33)×10-4,P＜0.01]、IGF-1[(14.84±1.23)×10-4,(6.33±2.80)×10-4,P＜0.01]、IL-6[(8.24±1.05)×10-4,(2.64±0.37)×10-4,P＜0.01]、IL-8[(14.68 ±6.97)×10-6,(2.60±0.89)×10-6,P＜0.01]、MMP-13[(1.50±0.11)×10-3,(1.23±0.10)×10-3,P＜0.05]、TGF-β1[(4.41±0.42)×10-3,(2.96 ±0.36)×10-3,P＜0.01]、COL1A1[(55.44±21.61)×10-2,(9.17 ± 3.30)×10-2,P＜0.01];而TNF-α[(5.62±2.03)×10-6,(5.62±3.146)×10-6]和COL1A2[0.64±0.07,0.46±0.12]表达水平没有明显差异(P＞0.05).结论 硬化区软骨下骨成骨细胞的生物学表型变化是骨关节炎患者病变的重要特征之一.     

成骨生长肽对大鼠颅盖骨成骨细胞样细胞增殖和分化的影响

目的研究成骨生长肽(OGP)在体外对成骨细胞样细胞增殖分化的影响。方法在体外培养的新生大鼠颅盖骨成骨细胞样细胞中加入不同浓度的OGP(10-11mol/L~10-7mol/L),用MTT法检测细胞增殖,酶联免疫法检测细胞内碱性磷酸酶(ALP)的表达,RT-PCR法检测核心结合因子1(Cbfa1)mRNA的表达。结果OGP对成骨细胞样细胞增殖有促进作用(P<0.05),最大效应浓度为10-9mol/L;能增加细胞内ALP活性(P<0.05),最大效应浓度为10-8mol/L;可促进Cbfa1mRNA的表达(P<0.05),其最佳促进表达浓度为10-8mol/L,Cbfa1mRNA与β-actinmRNA像素值比值为0.89±0.02。结论OGP可促进成骨细胞样细胞增殖,增强Cbfa1mRNA的表达水平。     

阿司匹林对大鼠缺血心肌血管生成及内皮祖细胞动员的影响

目的观察阿司匹林对大鼠缺血心肌血管生成和内皮祖细胞(endothelial progenitor cells,EPCs)动员的影响和可能机制.方法实验大鼠分为正常对照组、假手术组、心肌缺血加大剂量阿司匹林组、心肌缺血加小剂量阿司匹林组和单纯心肌缺血组.心肌缺血组和假手术组于术后一周从心腔内取血测血管内皮生长因子(VEGF),外周血分离单个核细胞培养计数EPCs,28 d后取缺血区心肌免疫组化法测毛细血管密度.结果单纯心肌缺血组和假手术组与正常对照组相比,血浆VEGF显著增多[(101.51±16.97)、(94.67±11.78)vs(80.07±10.32),(P＜0.05)];心肌缺血加小剂量阿司匹林组与正常对照组相比,外周血EPCs显著增多[(42±7)vs(20±6),(P＜0.05)];单纯心肌缺血组与正常对照组相比,毛细血管密度显著增加[(600±104)vs(431±73),(P＜0.05)];大剂量阿司匹林抑制了因缺血导致的VEGF、EPCs和毛细血管密度的增加分别由缺血时的(101.51±16.97)、(46±9)、(600±104)降至(70.76±10.15)、(23±6)、(431±80),(P＜0.05).结论大剂量阿司匹林可通过抑制VEGF的表达,抑制大鼠缺血心肌的血管生成和因缺血和损伤导致的EPCs的动员.     

依普拉芬对新生大鼠颅盖骨成骨细胞增殖和分化的影响

目的 研究依普拉芬对体外培养的原代大鼠成骨细胞增殖和分化功能的影响.方法 体外分离培养新生大鼠颅盖骨成骨细胞,将不同浓度的依普拉芬加入培养液,测定细胞增殖情况、碱性磷酸酶(ALP)活性及钙化结节.结果 与阴性对照组相比, 各浓度组的依普拉芬均可增加成骨细胞数量(P＜0.01),提高细胞的ALP活性和促进钙化结节形成(P＜0.01),其中10-8～10-5 mol/L作用更为显著.结论 依普拉芬具有促进体外培养成骨细胞增殖、分化的作用.     

再障患者血清抑制物诱导骨髓基质细胞Fas表达与凋亡

目的:探讨再生障碍性贫血(再障)患者血清抑制物对骨髓基质细胞Fas表达与凋亡的诱导作用.方法:提纯的再障患者血清抑制蛋白组分加到培养7 d的骨髓基质细胞培养体系中48 h后,采用免疫组化法观察骨髓基质细胞的Fas表达,以形态学观察和TUNEL法测定骨髓基质细胞的凋亡,并设正常对照.结果:20例正常人骨髓基质细胞分别与0.1 μg/ml、1 μg/ml、10 μg/ml的再障血清抑制蛋白纽分共同培养后,Fas表达阳性率分别为(10.66±4.2)%(P＞0.05),(16.92±9.8)%(P＞0.05),(49.4±10.5)%(P＜0.01),而对照组为(14.4±7.8)%;凋亡细胞发生率分别为(5.6±1.6)%(P＞0.05),(24.82±8.2)%(P＜0.01),(43.3±9.8)%(P＜0.01),对照组为(4.6±1.5)%.结论:再障患者血清抑制蛋白组分与正常人骨髓基质细胞的凋亡有一定的量效关系.Fas-FasL系统可能是启动骨髓基质细胞凋亡的一条重要途径.     

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.     

APPLICATION OF LORNOXICAM TO PATIENT-CONTROLLED ANALGESIA IN PATIENTS UNDERGOING ABDOMINAL SURGERIES

FOR anesthesiologis s ,treatingpostoperativepainhas alwaysbeen a problem.Althoughopioidshave been provedtobe effective,theirsideeffectscouldnotbeignored.With thedevelopmentofscienceand pharmacology,many drugs with aspectsof satisfactoryanalgesicefficacyand couldbe welltoleratedby patientshave been developed.And lornoxicamisone of them, which isa non-steroidalanti-inflammatorydrug (NSAID ), with analgesic, anti-infl-ammatory,andantipyreticproperties.Itseliminationhalf-time(3 to 5 hours) isle…     

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.     

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.     

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.