环氧合酶-2在CCl4诱导大鼠肝纤维化形成中的作用

目的 探讨环氧合酶-2(cyclooxygenase-2, COX-2)在四氯化碳(CCl4)诱导大鼠肝纤维化形成过程中的作用.方法 用50% CCl4经腹腔注射,每周2次共8周诱导雄性S-D大鼠肝纤维化模型.将S-D大鼠随机分3组正常对照组给橄榄油腹腔注射;罗非昔布组在CCl4诱导肝纤维化模型的同时给予选择性COX-2抑制剂罗非昔布(按10 mg·d-1·kg-1体重溶于10 mL生理盐水中灌胃);模型对照组在CCl4诱导肝纤维化模型的同时给予同等体积的生理盐水灌胃.第8周末处死大鼠,病理组织学观察肝纤维化严重程度并评分,并通过Masson三色染色法将胶原染成蓝色,用图像分析仪自动分析胶原面积.用Western blot检测肝组织COX-2表达和Ⅳ型胶原.计数肝窦内α-SMA阳性的细胞数来观察肝星状细胞的活化.结果 与肝纤维化模型组相比,罗非昔布干预组肝组织纤维化严重程度明显减轻(平均积分分别为4.00±0.00 vs 2.89±0.60, P＜0.05)、胶原面积也减少(分别为30.7±8.9 vs 23.5±6.5, P＜0.05)、肝窦内平均α-SMA阳性细胞数明显减少(分别为12.5±1.3 vs 7.4±1.4, P＜0.01);Western blot分析提示与肝纤维化模型组相比,罗非昔布能降低Ⅳ型胶原表达、对COX-2表达无明显影响.结论 COX-2在肝纤维化的形成过程中发挥重要作用,选择性COX-2抑制剂罗非昔布具有减轻或阻止肝纤维生成的作用.     

结直肠肿瘤形成过程端粒酶表达的规律

目的　研究端粒酶在结直肠肿瘤形成、发展过程中的表达规律及其意义。　方法　应用 TRAP与PCR- EL ISA方法检测 30例结直肠腺瘤 ,4 0例配对癌组织和正常黏膜组织端粒酶活性。应用 SPSS1 0 .0统计软件结合临床资料进行分析。　结果　正常黏膜、腺瘤 <1 cm、1～ 2 cm、>2 cm及癌组织端粒酶阳性率分别为 0 ,1 3.3% ,2 5 .0 % ,71 .4 %及 95 .0 % ;端粒酶活性相对水平分别为 0 .0 1 3± 0 .0 0 6 ,0 .0 6 9± 0 .0 89,0 .1 0 2± 0 .0 96 ,0 .35 2± 0 .1 78及 0 .6 5 8± 0 .2 35。从正常黏膜→腺瘤→癌端粒酶阳性率及相对活性水平均逐渐增高 ,差异有显著性 (P<0 .0 5 )。端粒酶活性表达与腺瘤部位及组织学分型无关 (P>0 .0 5 ) ,与腺瘤的大小正相关 (P<0 .0 5 ) ;结直肠癌分化较差 ,Duke's分期较晚的肿瘤端粒酶活性水平较高 (P<0 .0 5 )。　结论　端粒酶激活可能发生于结直肠肿瘤发生的早期阶段 ,并随着腺瘤的增生扩大其表达水平逐步增高直至癌变。端粒酶活性水平可能影响结直肠肿瘤的生物学行为 ,是判断结直肠癌预后有意义的标记物     

罗非昔布对裸鼠人胃癌原位种植瘤组织中血管内皮生长因子和诱导型一氧化氮合酶表达的影响

目的 探讨罗非昔布对裸鼠人胃癌原位种植瘤组织中血管内皮生长因子(vascular endothelial growth factor, VEGF)、诱导型一氧化氮合酶(inducible nitric oxide synthase, iNOS)表达的影响.方法 建立裸鼠人胃癌原位种植转移模型,以罗非昔布给裸鼠灌胃,通过免疫组化Envision法检测罗非昔布对原位种植瘤胃癌组织中VEGF、iNOS蛋白的表达.结果 VEGF的表达:对照组VEGF阳性率为81.25%, 罗非昔布组为61.25%, 联合组为35.00%, 罗非昔布组与对照组相比,差异有显著性(P＜0.05), 联合组与罗非昔布组相比,差异有显著性(P＜0.05).iNOS的表达显示:对照组iNOS阳性率为73.75%,罗非昔布组为52.50%,联合组为26.67%,罗非昔布组与对照组相比,差异有显著性(P＜0.05).结论 环氧合酶-2抑制剂罗非昔布可能通过降低胃癌肿瘤组织中 VEGF、iNOS的表达,使肿瘤血管生成受抑,从而抑制胃癌细胞的生长和转移.     

叶绿酸对肠肿瘤模型鼠细胞增殖和凋亡的影响

目的 研究叶绿酸(Chlorophyllin CHL)对DMH (N,N' -Dimethylhydrazine dihydrochloride, 1,2-二甲基肼二盐酸盐) 诱导的结直肠肿瘤模型鼠的肠粘膜细胞增殖和凋亡的影响. 方法 以DMH诱导小鼠结直肠肿瘤,从诱导的不同阶段开始,施以相同剂量CHL干预,观察CHL对结直肠肿瘤的抑制作用;采取免疫组织化学方法染色,研究CHL对小鼠结直肠肿瘤PCNA, P21, Caspase-3 蛋白表达的影响.结果 (1)CHL各组小鼠结直肠癌发生率及平均肿瘤数均低于阳性对照组(P<0.05),腺癌百分率低于阳性对照组(P<0.01); (2)CHL各组小鼠肠肿瘤组织中PCNA及p21蛋白表达水平均显著低于阳性对照组 (P<0.001); Caspase-3 表达水平在DMH 和CHL组间无明显差异 (P>0.05) 结论 CHL能够抑制DMH诱导的小鼠结直肠肿瘤的PCNA,P21蛋白的表达,从而调控肿瘤细胞的增殖和凋亡.     

罗非昔布对裸鼠人胃癌原位种植瘤组织中微血管密度表达的影响

目的探讨罗非昔布对裸鼠人胃癌原位种植瘤组织中微血管密度(microvessel density,MVD)表达的影响。方法建立裸鼠人胃癌原位种植转移模型,随机分为生理盐水对照组、5-Fu化疗组、罗非昔布组及罗非昔布联合5-Fu化疗组(联合用药组),生理盐水、罗非昔布灌胃给药,5-Fu腹腔注射给药,采用免疫组织化学Envision法检测各组原位种植瘤组织中MVD的表达。结果MVD计数结果显示,生理盐水对照组为56.8±9.8,5-Fu化疗组为39.9±7.0,罗非昔布组为42.3±11.0,联合用药组为25.1±7.6。罗非昔布组与生理盐水对照组之间、罗非昔布组与联合用药组之间比较,差异均有统计学意义(P<0.05)。结论环氧合酶-2抑制剂罗非昔布可以通过降低胃癌肿瘤组织中MVD的表达,使胃肿瘤血管生成受到抑制;与化疗药物联合应用增加其抑制血管生成作用。     

选择性环氧合酶-2抑制剂对胃癌细胞生长的影响

目的　观察选择性环氧合酶 - 2 ( COX- 2 )抑制剂 (美洛昔康、塞来昔布、罗非昔布 )对人胃癌细胞株SGC790 1生长的影响以及罗非昔布对人胃癌裸鼠移植瘤生长的抑制效应。方法　采用 3H-胸腺嘧啶核苷 ( 3H- Td R)掺入法了解细胞的增殖 ;用免疫组化检测细胞增殖核抗原 ( PCNA)及细胞 COX- 2的表达 ;用 TUNEL 染色法检测细胞凋亡。建立人胃癌裸鼠原位移植瘤模型 ,给予罗非昔布 8周 ,观察肿瘤大小、COX- 2及 PCNA表达情况。结果三种选择性 COX- 2抑制剂均较阿司匹林更有效抑制体外培养的胃癌细胞 3H- Td R掺入 ,3H-胸腺嘧啶掺入值与药物浓度呈负相关。美洛昔康、塞来昔布、罗非昔布对胃癌细胞 3H-胸腺嘧啶掺入的 IC50 分别为 1.18× 10 - 7mol/ L、1.68× 10 - 8mol/ L、4.3 9× 10 - 9mol/ L。经 1× 10 - 5m ol/ L 的上述三种药物作用 2 4h,SGC790 1细胞凋亡指数分别为 19.8%± 1.8%、2 4.6%± 1.2 % 3 1.2 %± 2 .2 %。 COX- 2抑制剂的选择性越高 ,凋亡指数也显著升高 ( P<0 .0 1)。罗非昔布对裸鼠胃癌原位移植瘤的抑瘤率为 93 .9% ;肿瘤组织的 COX- 2、PCNA表达均较对照组明显下降。结论　COX- 2抑制剂的选择性越高 ,对胃癌生长抑制作用越强。罗非昔布可成为胃癌综合治疗的重要药物之一     

叶绿酸铜钠对结直肠肿瘤抑制作用的实验研究

目的：研究叶绿酸铜钠（CHL）对DMH（1,2-二甲基肼二盐酸盐）诱导的小鼠结直肠肿瘤的抑制作用。方法：80只幼鼠（4-5周）随机分为阴性对照组（NC组）、阳性对照组（DMH组）、CHLA组和CHLB组。DMH组和CHL组背部皮下注射DMH诱癌;NC组背部皮下注射生理盐水作对照。以CHL灌胃处理CHLA和CHLB组动物。处死小鼠后,解剖小鼠结直肠,固定,观察肿瘤发生情况,免疫组化染色示PCNA、Ras-p21及caspase-3等细胞增殖及凋亡相关因子的表达情况。结果：两CHL干预组小鼠结直肠肿瘤发生率与DMH组相比,差异无统计学意义（P〉0.05）;但其平均每鼠荷瘤数及结直肠癌百分率都显著低于DMH组（P〈0.05）;不同时间CHL干预对小鼠肿瘤的抑制作用差别不明显（P〉0.05）;两CHL干预组小鼠肠黏膜PCNA、Ras-p21蛋白表达水平均显著低于DMH组（P〈0.01）;caspase-3表达水平在DMH和CHL组间无明显差异（P〉0.05）。结论：CHL在诱癌起始阶段和始发后阶段给药均可抑制DMH诱导的小鼠结直肠肿瘤的发生,降低每鼠平均荷瘤数及肠癌百分率,这可能与其下调结直肠黏膜PCNA,Ras-p21水平,从而间接调控细胞增殖和凋亡平衡有关,CHL有望成为预防结直肠癌的理想化学制剂。     

结直肠肿瘤组织中β-catenin和c-myc的表达及其意义

目的 探讨β-catenin和c-myc在结直肠肿瘤中的意义.方法 用免疫组织化学技术检测非肿瘤结直肠组织、结直肠腺瘤组织和结直肠腺癌组织中β-catenin及c-myc.结果 β-catenin在非肿瘤结直肠组织、结直肠腺瘤组织和结直肠腺癌组织中异住异常表达率分别为8.0%、73.9%、96.2%,3组之间差异有统计学意义(P<0.05).非肿瘤结直肠组织、结直肠腺瘤组织和结直肠腺癌组织中c-myc表达的阳性率分别为4.0%、43.5%和76.9%,3组之间差异有统计学意义(P<0.05).结论 β-catenin异常表达及c-myc过度表达与结直肠肿瘤的发生有关,β-catenin异常表达可能与腺瘤的恶性转化易感性和结直肠腺癌的恶性行为有关,c-myc过度表达可能与结直肠肿瘤恶性化有关.     

散发性结直肠肿瘤β-catenin蛋白的表达及临床意义

目的　探讨 β- catenin在结直肠肿瘤发生、发展中的作用及临床意义。　方法　采用免疫组织化学方法检测 5 5例结直肠腺癌、33例结直肠腺瘤组织中 β- catenin基因蛋白产物的表达水平。　结果　 β- catenin在结直肠腺癌组织阳性表达率 4 5 / 5 5 (81.8% ) ,结直肠腺瘤组织阳性表达率 2 3/ 33(6 9.7% ) ,显著高于正常粘膜组织 (0 ) ,差异有显著性 (P<0 .0 5 )。低分化腺癌阳性表达率 (13/ 13)明显高于中、高分化结直肠腺癌 (19/ 2 3,13/ 19,P<0 .0 5 )。伴淋巴结转移阳性表达率 (2 5 / 2 7,92 .6 % )明显高于不伴淋巴结转移 (2 0 / 2 8,71.4 % ,P<0 .0 5 )。Dukes C、D期结直肠腺癌阳性表达率 (31/ 34,91.2 % )明显高于 A、B期 (14 / 2 1,6 6 .7% ,P<0 .0 5 )。β- catenin阳性表达与结直肠肿瘤的大小、部位、患者的年龄、性别无关。　结论　 β- catenin在散发性结直肠癌的发生发展过程中起重要作用。检测肿瘤组织 β- catenin基因蛋白产物的表达水平可作为临床判断其生物学行为的有效手段     

1,2-二甲肼对小鼠结直肠与卵巢的影响

目的探讨1,2-二甲肼(1,2-dimethylhydrazine,DMH)对小鼠结直肠与卵巢的影响。方法 60只雌性ICR小鼠随机平均分为A、B两组,A组给予腹腔注射DMH(20mg/kg,每周1次,连续24周),B组注射生理盐水作为对照,首次注射后12、16、20、24、28和32周分批处死小鼠,观察其结直肠与卵巢病理形态学改变。结果 A组小鼠结直肠发生显著病理改变,DMH注射12~16周后,小鼠结直肠上皮出现不同程度增生改变,20周后,2只小鼠发生结直肠肿瘤,并且随DMH作用时间的延长,肿瘤发生率逐渐增加,至32周共有7只小鼠发生结直肠腺瘤,5只结直肠腺癌,且肿瘤主要位于距肛门8cm内;值得注意的是,A组小鼠卵巢也发生明显病理改变,32周内共见21只A组小鼠发生卵巢血肿伴慢性炎症改变,而且,28和32周各发现1只A组小鼠卵巢出现绒毛膜癌病理学改变。实验过程中B组小鼠均未见异常。结论 DMH对小鼠结直肠与卵巢组织形态学变化具有显著影响,多次腹腔注射DMH能够导致小鼠结直肠与卵巢发生病理改变。     

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.     

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.