胰腺癌细胞株原钙黏附蛋白8基因的甲基化状态

目的 分析原钙黏附蛋白8(protocadherin 8,PCDH8)基因在胰腺癌细胞株的甲基化状态.方法 抽提6株胰腺癌细胞株PANC1、ASPC1、BxPC3、CFPAC、PaTu8988、SW1990和2例正常胰腺组织的总RNA,以甲基化特异性PCR(MSP)法检测PCDH8甲基化情况.应用DNA甲基化转移酶(DNMT)抑制剂5-氮杂2'-脱氧胞苷(5-Aza-dC)处理6株胰腺癌细胞株,采用实时定量PCR法检测处理前后细胞的PCDH8 mRNA表达.结果 2例正常胰腺组织PCDH8基因未发生甲基化,PANC1、BxPC3、CFPAC胰腺癌细胞株PCDH8基因部分甲基化,而PaTu8988、ASPC1、SW1990细胞完全甲基化.PCDH8mRNA在PANC1、SW1990、PaTu8988胰腺癌细胞株中有表达,表达的相对值(RQ)分别为1.576±0.648、0.013±0.008、0.002±0.001;BxPC3、CFPAC、ASPC1细胞株无PCDH8 mRNA表达.5-Aza-dC处理后,胰腺癌细胞株PANC1、ASPC1、BxPC3、CFPAC、PaTu8988、SW1990均有PCDH8 mRNA表达,表达量较处理前明显升高,相对表达量分别为7.463±2.628、10.696±1.539、7.852±2.762、421.815±1.493、118.595±4.089、6.690±1.884.结论 PCDH8基因启动子高甲基化是导致该基因在胰腺癌细胞株表达下降的主要原因之一.     

IRX1在胰腺癌中的表达及其启动子区甲基化状态

目的 检测胰腺癌的易洛魁族同源盒基因(IRX1)的表达及其启动子区的甲基化状态,探讨两者间的相关性.方法 采用实时PCR法检测12例胰腺癌组织及6株胰腺癌细胞株的IRX1 mRNA 表达.基因序列分析IRX1基因启动子区结构.应用甲基化抑制剂5-氮杂-2＇-脱氧胞苷(5-Aza-dC)处理胰腺癌细胞,采用甲基化特异性PCR(MSP)、非甲基化特异性PCR (USP)及实时PCR检测处理前后IRX1启动子甲基化状态和IRX1 mRNA表达.结果 胰腺癌组织IRX1 mRNA的表达量为0.31±0.11,显著低于癌旁正常胰腺组织的1.05±0.32(P ＜0.01).胰腺癌细胞AsPCl、BxPC3、Capan-2、PANC1、PaTu8988和SW1990的IRX1 mRNA表达量分别为0.36±0.08、0.34±0.16、0.37±0.11、0.25±0.06、0.31±0.04、0.36±0.02,均显著低于人肾上皮293细胞的1.03±0.28(P＜0.05或＜0.01).IRX1基因启动子区富含CpG岛.各胰腺癌细胞株IRX1基因启动子CpG岛对应位点均有甲基化,经5-Aza-dC处理后甲基化状态得以逆转,IRX mRNA的表达也得以恢复.结论 胰腺癌的IRX1 mRNA表达下降,与其IRX1基因启动子区CpG岛高甲基化状态相关.     

胰腺癌S100A4癌基因及ppENK抑癌基因的甲基化状态

目的 分析胰腺癌及胰腺癌细胞株ppENK、S100A4基因的甲基化状态.方法 收集31例胰腺癌及相应癌旁组织、5株胰腺癌细胞株及1例正常胰腺组织.采用MSP方法分析ppENK基因甲基化状态,采用COBRA方法分析S100A4基因甲基化状态,RT-PCR检测ppENK和S100A4 mRNA,免疫组化法检测S100A4蛋白表达,并与胰腺癌临床参数进行相关性分析.结果 正常胰腺组织ppENK基因无甲基化,S100A4基因高甲基化.31例胰腺癌组织中ppENK基因甲基化率为90.3%,与临床参数无相关性;S100A4基因低甲基化率为71.0%,仅与外周血CA19-9水平呈相关性(P=0.011,OR=0.05).S100A4蛋白在胰腺癌组织中表达率为87.1%,该表达与S100A4基因低甲基化相关(P=0.017),同时与肿瘤的分化程度有关,肿瘤分化程度越低,表达阳性率越高.S100A4基因低甲基化与ppENK基因甲基化相关(P=0.019).5株胰腺癌细胞株ppENK基因均甲基化,ppENK mRNA不表达;S100A4基因均低甲基化,S100A4 mRNA均高表达.结论 胰腺癌组织ppENK基因为高甲基化状态,而S100A4基因为低甲基化状态.     

RNA干扰DNMT1基因对胰腺癌细胞BxPC-3增殖的影响及相关机制

目的:探讨RNA干扰DNMT1基因对胰腺癌细胞BxPC-3增殖的影响及相关机制.方法:利用Lipofectamine TM2000转染DNMT1-siRNA至胰腺癌细胞BxPC-3.实验共分为3组:实验组(转染DNMT1-siRNA)、阴性对照组(转染negative-siRNA)和空白对照组(转染脂质体).转染48h后,应用荧光定量PCR法和Western blot法分别检测细胞中DNMT1 mRNA和蛋白的表达水平;MTT法检测细胞体外增殖活力;FCM法检测细胞凋亡;甲基化特异性PCR法(MSP)检测抑癌基因p16、RASSF1A和ppENK的启动子甲基化状态.结果:与空白对照组和阴性对照组相比,实验组的DNMT1 mRNA及蛋白表达量均显著降低(P<0.01);实验组细胞增殖明显受到抑制(P<0.05),细胞凋亡率明显增加(44.46%±5.98%vs3.74%±1.02%vs5.07%±1.16%,P<0.01).空白对照组与阴性对照组的p16、RASSF1A和ppENK基因甲基化阳性,而实验组的p16和ppENK基因甲基化阴性,RASSF1A基因部分甲基化.结论:DNMT1基因表达下调后,能抑制胰腺...     

5-氮杂-2’-脱氧胞苷对胰腺癌细胞PANC1的组织因子途径抑制物-2表达及CpG岛甲基化的影响

目的 探讨甲基化酶抑制剂5-氮杂-2'-脱氧胞苷(5-Aza-dC)对胰腺癌细胞系PANCI的抑癌基因组织因子途径抑制物2(tissue factor pathway inhibitor 2,TFPI-2)甲基化水平及基因表达的影响.方法 应用1×10-7、5 × 10-7、1×10-6mol/L的5-Aza-dC处理胰腺癌细胞系PANCI.用甲基化特异性PCR(MSP)、RT-PCR及蛋白质印迹法检测细胞TFPI-2基因的甲基化状态、mRNA及蛋白的表达.结果 未经5-Aza-dC处理的PANCI细胞的TFPI-2基因CpG岛为完全甲基化,无TFPI-2 mRNA及蛋白的表达.1×10-7、5×10-7、1×10-6mol/L的5-Aza-dC处理后,PANC1细胞的TFPI-2基因CpG岛甲基化逆转,从不完全甲基化到完全非甲基化;TFPI-2 mRNA相对表达量分别为0.211±0.087、0.327 ±0.068、0.609±0.017;TFPI-2蛋白相对表达量为0.429±0.121、0.675±0.044、1.132±O,124,呈剂量依赖性增加(P＜0.05).结论 胰腺癌细胞系PANC1的TFPI-2启动子高甲基化可能是导致该基因表达下调甚至失活的主要原因.5 -Aza-dC能够逆转其高甲基化状态,并诱导TFPI-2 mRNA及蛋白重新表达.     

胰腺癌细胞株中Elastase 3B基因启动子异常甲基化研究

目的 探讨Elastase 3B(ELA3B)基因在胰腺癌中低表达的分子机制.方法 应用RT-PCR方法检测2例正常胰腺组织和BxPC、CFPAC、PaTu8988、PANC1、SW1990 5株胰腺癌细胞株ELA3B基因表达.利用去甲基化试剂5-氮-2'-脱氧胞嘧啶(DAC)处理细胞株,再检测ELA3B基因表达,并用甲基化特异性PCR检测和测序进行验证.结果 ELA3B在正常胰腺组织中表达,而在BxPC、CFPAC、PaTu8988、PANC1和SW1990 5株胰腺癌细胞株中均无表达.DAC处理后,BxPC、PaTu8988、PANC1和SW1990 4株胰腺癌细胞株表达ELA3B,而CFPAC仍不表达.正常胰腺组织和PANC1 ELA3B基因部分甲基化,而其他4株胰腺癌细胞株则高甲基化.结论 ELA3B基因启动子的高甲基化是导致该基因在胰腺癌中表达下降的主要原因之一.     

胰腺癌细胞株PANC1异常甲基化miRNA的分析

目的 分析胰腺癌细胞株PANC1与正常胰腺组织表达有差异的启动子区甲基化miRNA,寻找与胰腺癌相关的高甲基化miRNA.方法 抽提PANC1与正常胰腺组织基因组DNA,超声断裂.应用抗5-甲基化嘧啶核苷抗体和免疫磁珠法获取甲基化DNA片段.通过DNA甲基化芯片筛选出PANC1与正常胰腺组织表达差异的高甲基化miRNA,采用重亚硫酸盐修饰的PCR (BSP)和TA克隆测序的方法进行验证.提取胰腺癌细胞株BxPC3、CFPAC1、PANC1、SW1990基因组DNA,采用结合重亚硫酸盐的限制性内切酶法(combined bisulfite restriction analysis,COBRA)验证芯片筛选出的差异表达的甲基化miRNA.结果 PANC1细胞与正常胰腺组织存在8个差异表达的甲基化miRNA,从中挑选出5个进行BSP+ TA克隆测序验证,其中miR-615、miR-663、miR-663b在PANC1细胞的甲基化率明显高于正常组织(60.6％比7.6％,88.8％比22.2％,94.4％比13.0％);miR-675的甲基化率与正常胰腺组织无明显差异(76.0％比100％);miR1826因测序结果误差较大而舍去.经COBRA验证,PANC1的上述4种miRNA均高甲基化;BxPC除miR-675外,其他3种均高甲基化;CFPAC1的miR-663、miR-663b高甲基化;SW1990的miR-615、miR-663高甲基化.结论 胰腺癌细胞株与正常胰腺组织间存在差异表达的高甲基化miRNA,其中miR-663高甲基化与胰腺癌可能相关.     

沉默ABCC4基因表达对人胰腺癌PANC1、BxPC-3细胞增殖的影响

目的 检测ABCC4基因沉默后对人胰腺癌PANC1、BxPC-3细胞增殖及细胞周期的影响.方法 构建插入靶向ABCC4的shRNA片段的重组慢病毒载体,感染人胰腺癌细胞株PANC1和BxPC-3.采用实时定量PCR法和蛋白质印迹法检测感染细胞的ABCC4 mRNA及蛋白表达,克隆形成实验测定感染细胞形成的克隆数,流式细胞仪检测感染细胞的细胞周期.结果 成功构建了插入靶向ABCC4的shRNA片段的重组慢病毒载体.重组慢病毒感染PANC1及BxPC-3细胞后,细胞ABCC4 mRNA表达被抑制(0.28 0.01比1.00±0.03,0.22 ±0.02比1.00 ±0.03,P值均＜0.05);ABCC4蛋白表达亦显著下调;感染的PANC1细胞克隆形成数量显著减少(4比65,P＜0.05);细胞周期阻滞在G1期[(54.98±1.78)％比(42.93±0.88)％,(68.55±0.75)％比(54.76 ±0.29)％].结论 沉默人胰腺癌PANC1和BxPC-3细胞的ABCC4基因表达可显著抑制癌细胞的增殖,使细胞阻滞于G1期.     

胰腺癌细胞株中Elastase 3B基因启动子异常甲基化研究

目的探讨Elastase 3B（ELA3B）基因在胰腺癌中低表达的分子机制。方法应用RT-PCR方法检测2例正常胰腺组织和BxPC、CFPAC、PaTu8988、PANC1、SW1990 5株胰腺癌细胞株ELA3B基因表达。利用去甲基化试剂5-氮-2′-脱氧胞嘧啶（DAC）处理细胞株,再检测ELA3B基因表达,并用甲基化特异性PCR检测和测序进行验证。结果ELA3B在正常胰腺组织中表达,而在BxPC、CFPAC、PaTu8988、PANC1和SW1990 5株胰腺癌细胞株中均无表达。DAC处理后,BxPC、PaTu8988、PANC1和SW1990 4株胰腺癌细胞株表达ELA3B,而CFPAC仍不表达。正常胰腺组织和PANC1 ELA3B基因部分甲基化,而其他4株胰腺癌细胞株则高甲基化。结论ELA3B基因启动子的高甲基化是导致该基因在胰腺癌中表达下降的主要原因之一。     

DNA甲基转移酶3b和microRNA-29b在胰腺癌细胞株中的表达及其相关性

目的 明确胰腺癌细胞株甲基转移酶( DNMT)3b和microRNA-29b(miR-29b)的表达,分析两者的相关性.方法 应用实时定量PCR法检测人胰腺癌细胞株PANC1、BxPC3、CFPAC、AsPC-1、Capan-2的DNMT3b mRNA和miR-29b表达.采用Pearson直线相关分析法分析两者表达量的相关性.结果 PANC1、BxPC3、CFPAC、AsPC-1、Capan-2的DNMT3b mRNA相对表达量分别为0.497±0.184、0.420±0.168、0.439±0.217、0.122 ±0.111和0.731±0.387;miR-29b的相对表达量分别为0.745±0.596、0.464±0.430、0.797±1.000、1.836±1.623和0.216 ±0.335,DNMT3b mRNA的表达量和miR-29b的表达量呈负相关关系(r=-0.922,P=0.026).结论 DNMT3b和miR-29b均参与了胰腺癌的发生发展,两者呈负相关关系.     

胰岛素瘤的解剖分布特点分析

目的胰岛素瘤是最常见的胰腺神经内分泌肿瘤，因其临床表现多样，导致诊断困难。影像学诊断尤其是超声内镜(EUS)在胰岛素瘤的诊断中起着重要作用，拥有较高的敏感性和特异性。本研究拟通过明确胰岛素瘤的解剖分布特点，以期有助于提高影像学的诊断准确率和降低漏诊率，尤其是在教育和培训实践中对于EUS的学习者更具有指导价值。 方法回顾性分析解放军总医院第一医学中心病案资料数据库1993年1月至2019年11月经外科手术、病理确诊为胰岛素瘤的患者的临床资料，检索方法采取搜索术后病理诊断为"胰岛素瘤"的病例，通过查阅病例的方法，提取出胰岛素瘤的大小和解剖分布等数据，进一步分析其特点。 结果共检索到确诊为胰岛素瘤的患者116例，其中，男45例、女71例，年龄13～76岁，平均年龄(44.4±14.85)岁。胰岛素瘤单发110例(94.8%)、多发6例(5.2%)。位置分布：头颈部46例(39.7%)，单发45例、多发1例；体尾部68例(58.6%)，单发65例、多发3例；全胰腺多发2例(1.7%)。病变大小特点：最大径0.4～3.4 cm，平均大小(1.53±0.58)cm。≤1 cm 29例、>1 cm而≤1.5 cm41例、>1.5 cm而≤2.0 cm28例，≤3 cm 15例，>3 cm 3例。年龄与肿瘤的大小相关，≤44岁患者肿瘤平均大小为(1.36±0.51)cm、>44岁患者肿瘤平均大小为(1.70±0.60)cm，P<0.05。头颈部的肿瘤大于体尾部的肿瘤，头颈部肿瘤平均大小(1.66±0.63)cm，体尾部(1.42±0.52)cm，P<0.05。 结论胰岛素瘤在胰腺体尾部较头颈部更好发；绝大多数单发，但可以全胰腺多发；多数小于1.5 cm，肿瘤的大小与患者年龄和肿瘤的解剖分布相关。     

Pathogenesis of carcinoma of the papilla of Vater

Most adenomas and carcinomas of the small intestine and extrahepatic bile ducts arise in the region of the papilla of Vater. In familial adenomatous polyposis (FAP) it is the main location for carcinomas after proctocolectomy. In many cases symptoms due to stenosis lead to diagnosis at an early tumor stage. In about 80%, curative intended resection is possible. Operability is the most relevant prognostic factor. Most ampullary carcinomas resp. carcinomas of the papilla of Vater develop from adenomatous or flat dysplastic precursor lesions. They can be sited in the ampulloduodenal part of the papilla of Vater, which is lined by intestinal mucosa. They also can develop in deeper parts of the ampulla, which are lined by pancreaticobiliary duct mucosa. Intestinal-type adenocarcinoma and pancreaticobiliary-type adenocarcinoma represent the main histological types of ampullary carcinoma. Furthermore, there exist unusual types and undifferentiated carcinomas. Many carcinomas of intestinal type express the immunohistochemical marker profile of intestinal mucosa (keratin 7?, keratin 20+, MUC2+). Carcinomas of pancreaticobiliary type usually show the immunohistochemical profile of pancreaticobiliary duct mucosa (keratin 7+, keratin 20?, MUC2?). Even poorly differentiated carcinomas, as well as unusual histological types, may conserve the marker profile of the mucosa they developed from. These findings underline the concept of histogenetically different carcinomas of the papilla of Vater which develop either from intestinal- or from pancreaticobiliary-type mucosa of the papilla of Vater. Molecular alterations in ampullary carcinomas are similar to those of colorectal as well as pancreatic carcinomas, although they appear at different frequencies. In future studies, molecular alterations in ampullary carcinomas should be correlated closely with the different histologic tumor types. Consequently, the histologic classification should reflect the histogenesis of ampullary tumors from the two different types of papillary mucosa.     

Demonstration of the mechanism of action of biguanides

Summary Palmitic acid oxidation in rat diaphragm homogenate is depressed by biguanide concentrations that are still incapable of inhibiting oxidative phosphorylation. Glucose oxidation is not directly effected by the same biguanide concentrations: however, the inhibitory effect of palmitic acid on glucose oxidation is partly removed by biguanides. Inhibition of fatty acid oxidation, which accounts for most of the metabolic effects caused by these drugs, can be regarded as the fundamental mechanism of action of biguanides. There is some evidence suggesting that these drugs might interact with carnitine, thus preventing long-chain fatty acids from being transported across the mitochondrial membrane to the site of oxidation. Traduzione a cura degli AA.     

Lack of correlation of degree of villous atrophy with severity of clinical presentation of coeliac disease

BACKGROUND AND AIM: Both the clinical presentation and the degree of mucosal damage in coeliac disease vary greatly. In view of conflicting information as to whether the mode of presentation correlates with the degree of villous atrophy, we reviewed a large cohort of patients with coeliac disease. PATIENTS AND METHODS: We correlated mode of presentation (classical, diarrhoea predominant or atypical/silent) with histology of duodenal biopsies and examined their trends over time. RESULTS: The cohort consisted of 499 adults, mean age 44.1 years, 68% females. The majority had silent coeliac disease (56%) and total villous atrophy (65%). There was no correlation of mode of presentation with the degree of villous atrophy (p=0.25). Sixty-eight percent of females and 58% of males had a severe villous atrophy (p=0.052). There was a significant trend over time for a greater proportion of patients presenting as atypical/silent coeliac disease and having partial villous atrophy, though the majority still had total villous atrophy. CONCLUSIONS: Among our patients the degree of villous atrophy in duodenal biopsies did not correlate with the mode of presentation, indicating that factors other than the degree of villous atrophy must account for diarrhoea in coeliac disease.     

血吸虫童虫生长发育及其机制的研究进展

血吸虫童虫是宿主免疫系统攻击的重要靶标,包括皮肤型、肺型和肝门型童虫。宿主分子对童虫生长发育具有重要作用。童虫生长发育机制包括免疫调节、信号转导、性别发育及凋亡等。肌动蛋白、组织蛋白酶、烯醇化酶和葡萄糖基转移酶等分子为血吸虫童虫生长发育的重要分子。本文对血吸虫童虫生长发育及其机制的研究进展做一综述。     

氯硝柳胺悬浮剂的毒性评价

目的评价氯硝柳胺悬浮剂的毒性，为现场大规模应用灭螺提供依据。方法按照中华人民共和国国家标准GB 15670-1995《农药登记毒理学试验方法》和鱼类毒性试验方法进行。结果经口、经皮肤的LDso雌、雄性大鼠均>5 000 mg/kg，经呼吸道的LCso雌、雄性大鼠均>5 000mg/m3，该药经口、经皮肤、经呼吸道毒性均属微毒类药物；兔眼用药后，观察期内无不良反应，对眼无刺激性；皮肤用药后对皮肤无刺激性。与氯硝柳胺原药、氯硝柳胺乙醇胺盐原药和氯硝柳胺乙醇胺盐可湿性粉剂相比，氯硝柳胺悬浮剂对鱼急性毒性最低。结论氯硝柳胺悬浮剂属微毒类药物，对鱼的毒性低于其乙醇胺盐可湿性粉剂，适合于现场应用。     

124例耐多药结核分枝杆菌基因突变特征分析

目的对临床分离的耐多药结核分枝杆菌相关基因的突变特征进行分析。方法对124例耐多药结核分枝杆菌以及50株敏感株的耐药相关基因(包括异烟肼inh A、kat G、oxyR-ahp C间隔区以及利福平rpo B)进行序列测定,分析其基因突变情况。结果异烟肼耐药inh A基因突变率为14.5%;kat G基因突变率为70.2%(87/124),主要位于315位;oxyR-ahp C间隔区突变率为15.3%;inh A、kat G两种基因同时突变率75.0%,三种基因同时突变率为89.5%。利福平rpo B基因突变的检出率高达95.2%,突变主要发生在531、526、516位点。结论我省耐多药菌异烟肼耐药相关基因最常见突变为kat G 315、inh A C-T(-15)、axyR-ahp C间隔区(-10)C-T,利福平为rpo B531、526、516。结合MDR-TB耐药相关基因的特征分析,可以建立一种快速、准确、特异的适合于我省的检测结核菌耐多药性的新方法。     

Assessment of quality of life of parents of children with juvenile chronic arthritis

The aim of the study was to assess the quality of life (QOL) and the psychological status of parents of children with juvenile chronic arthritis (JCA). The QOL, anxiety and depression of the parents of 28 children with JCA were evaluated and compared to those of the parents of 28 healthy children. Mothers of JCA children and mothers of healthy children reported similar QOL. The reported anxiety and depression levels were similar for mothers and fathers in both groups. The parents of children with pauciarticular-type JCA reported lower QOL and higher levels of anxiety and depression than the parents of children with other types, namely polyarticular and systemic JCA. These findings may be explained by the fact that the pauciarticular patients had shorter disease duration and were less frequently seen in the outpatient clinic. The QOL of mothers of children with JCA was found to be slightly impaired in the group of children with pauciarticular JCA. Future larger studies are needed to confirm these results, as the number of subjects in the three groups was rather low. Received: 26 September 2001 / Accepted: 8 February 2002     

Numerical Simulation of the Effect of Rate of Change of Glucose on Measurement Error of Continuous Glucose Monitors

Background

A 5-day in-patient study designed to assess the accuracy of the FreeStyle Navigator® Continuous Glucose Monitoring System revealed that the level of accuracy of the continuous sensor measurements was dependent on the rate of glucose change. When the absolute rate of change was less than 1 mg•dl⁻¹•min⁻¹ (75% of the time), the median absolute relative difference (ARD) was 8.5%, with 85% of all points falling within the A zone of the Clarke error grid. When the absolute rate of change was greater than 2 mg•dl⁻¹•min⁻¹ (8% of the time), the median ARD was 17.5%, with 59% of all points falling within the Clarke A zone.

Method

Numerical simulations were performed to investigate effects of the rate of change of glucose on sensor measurement error. This approach enabled physiologically relevant distributions of glucose values to be reordered to explore the effect of different glucose rate-of-change distributions on apparent sensor accuracy.

Results

The physiological lag between blood and interstitial fluid glucose levels is sufficient to account for the observed difference in sensor accuracy between periods of stable glucose and periods of rapidly changing glucose.

Conclusions

The role of physiological lag on the apparent decrease in sensor accuracy at high glucose rates of change has implications for clinical study design, regulatory review of continuous glucose sensors, and development of performance standards for this new technology. This work demonstrates the difficulty in comparing accuracy measures between different clinical studies and highlights the need for studies to include both relevant glucose distributions and relevant glucose rate-of-change distributions.     

Study of constancy of hydrogen-consuming flora of human colon

The constancy of the hydrogen consuming flora of the human colon was studied in 15 healthy subjects via two measurements obtained 18 to 36 months apart. Hydrogen disappearance rate and the major products of H₂-consuming bacteria, methane and sulfide, were measured during incubation of fecal homogenates with excess hydrogen and sulfate. In 11/15, the hydrogen consumption rate and the predominant hydrogen-consuming pathway (methanogenesis, sulfate reduction, or neither) remained constant. However, major shifts in these pathways were observed in four subjects, with two losing and two gaining the ability to produce methane. Methanogenesis was associated with the highest hydrogen consumption rate. This study demonstrates that clinically unrecognizable, major alterations of the colonic flora occur in healthy subjects. Understanding of the factors responsible for these alterations might allow for therapeutic manipulation of the colonic flora.Supported in part by the Department of Veterans Affairs and NIDDKD RO1 DK 13309-25.