幽门螺杆菌VacA N端真核表达载体的构建、鉴定及其诱导巨噬细胞空泡化和凋亡的观察

目的构建幽门螺杆菌(Helicobacter pylori,HP)空泡毒素(Vacuolating cytotoxin,VacA)基因的真核表达载体pDsRed-Monomer-C1/vacA,并在THP-1巨噬细胞中表达,为研究VacA单一毒力决定簇的致病性奠定实验基础。方法用Primer 5.0软件设计引物,以HP基因组为模板,PCR扩增vacA目的基因片段,克隆入真核表达载体pDsRed-Monomer-C1中,经酶切、PCR鉴定及测序鉴定后,转染THP-1巨噬细胞中,荧光显微镜和Western-blot检测VacA蛋白在细胞中的表达;电镜观察巨噬细胞(MΦ)的空泡样变和凋亡;流式细胞仪检测细胞的凋亡率。结果PCR扩增得到了大小约为1 428bp的目的片段,双酶切及测序鉴定证明成功构建了HP真核表达重组载体;转染后24h,重组质粒组部分细胞中有聚集的荧光颗粒,部分细胞发生空泡样变和凋亡改变;细胞凋亡率明显高于空质粒组和阴性对照组(P<0.001),细胞核因子-κB(nuclear factorkappaB,NF-κB)的抑制剂二硫代氨基甲酸吡咯烷(pyrrolidine dithiocarbamate,PDTC)抑制细胞的凋亡。结论VacA蛋白瞬时高表达促进THP-1巨噬细胞空泡样变和凋亡。NF-κB可能参与调节VacA诱导的巨噬细胞凋亡。     

pEGFP-restin重组质粒的构建及其在BGC-803胃癌细胞中的表达

目的:构建一种含人肿瘤休眠蛋白基因(restin)的质粒,以绿色荧光蛋白作为报告基因,观察其在胃癌细胞中的表达,为探讨其抗肿瘤作用的分子机制打下基础.方法:从人胚肾组织中,以RT-PCR方法扩增restin基因片段,将restin片段和增强型绿色荧光表达质粒pEGFP-C1酶切、纯化、连接、转化、筛选,构建pEGFP-restin重组质粒,转染胃癌细胞,荧光显微镜下观测绿色荧光蛋白的表达,并对表达产物进行Western blot鉴定.结果:RT-PCR产物经琼脂糖电泳,在预期位置(600 bp)处阳性条带表达;重组载体经酶切分析,插入片段表达restin基因;pEGFP-restin重组质粒成功转染胃癌细胞,在荧光显微镜下强绿色荧光蛋白表达,Western blot鉴定结果显示pEGFP-restin上的restin基因在BGC-803细胞中正确表达.结论:成功构建了pEGFP-restin重组质粒,为进一步研究restin的功能提供了重要的实验材料.     

幽门螺杆菌空泡形成细胞毒素A亚单位的克隆表达和P37抗体的制备

背景:空泡形成细胞毒素A(VacA)是幽门螺杆菌(H.pylori)的重要致病因子,研究VacA的致病机制有助于进一步明确H.pylori的致病机制。目的:原核表达H.pyloriVacA亚单位P37和P58,制备P37多克隆抗体并分析其活性。方法:以聚合酶链反应(PCR)扩增H.pylorivacA基因的p37和p58片段,克隆入原核表达载体pQE31,构建重组质粒pQE31-p37和pQE31-p58,转化大肠杆菌(E.coli)M15,诱导蛋白表达。以镍-次氮基三乙酸(Ni-NTA)亲和层析纯化融合蛋白,以纯化P37蛋白免疫家兔,获取抗P37血清,以酶联免疫吸附测定(ELISA)检测抗体效价。以蛋白质印迹法(Westernblot)分析P37抗体与VacA的结合能力,观察P37抗体对VacA致胃癌细胞空泡化的抑制作用。结果:十二烷基硫酸钠聚丙烯酰胺凝胶电泳(SDS-PAGE)显示,E.coliM15经诱导后表达相对分子质量分别为37kDa(1Da=0.9921u)和58kDa的P37和P58融合蛋白,经纯化后为单一蛋白。纯化P37蛋白免疫家兔后获得的抗P37血清抗体效价为1×106。P37抗体能中和VacA阳性H.pylori分泌的VacA,抑制VacA对胃癌细胞的空泡化作用。结论:本实验成功构建了原核表达载体pQE31-p37和pQE31-p58,获得了高纯度单一蛋白和高效价P37抗体,该抗体具有中和VacA毒性的作用。     

人端粒酶反义寡核苷酸抑制三种不同分化程度胃癌细胞生长及作用机制研究

目的 研究特定序列人端粒酶反义寡核苷酸(AS-0DN)抑制三种分化程度不同的胃癌细胞(MKN-45、SGC-7901、MKN-28)生长的可能性，并阐述其抑制胃癌细胞生长的作用与胃癌细胞分化程度的相关性。方法 在指定的作用时问和浓度等条件下，以AS-0DN作用于不同分化程度的三种胃癌细胞，用改良端粒酶活性定量检测法测定AS-0DN片段作用前后胃癌细胞的端粒酶活性；用锥虫蓝染色法观察细胞活力；用倒置显微镜、电镜、流式细胞仪和原位末端标记(TUNEL)法观察细胞凋亡情况。结果以指定浓度的AS-ODN作用后，MKN-45和SGC-7901细胞出现明显的端粒酶活性和细胞生长抑制(P＜0．05)，但在同样浓度条件下，MKN-28胃癌细胞只出现端粒酶活性抑制。错义序列对照组则无明显变化。以10 μmol／L的AS-ODN连续作用三种胃癌细胞96h后，光镜、电镜和TUNEL法检测均发现MKN-45和SGC-7901细胞表现出特有的凋亡征象，流式细胞仪检测证实MKN-45和SGG-7901细胞的平均凋亡率在44．75％和33．56％，错义序列对照组则无明显变化(P＜0．05)。结论 AS-0DN能有效抑制胃癌细胞生长，其作用机制主要是抑制端粒酶活性和诱导细胞凋亡。AS-0DN对中分化胃癌细胞的生长抑制最显著，对低分化胃癌细胞的抑制作用略强于高分化胃癌细胞，提示端粒酶反义核酸的抑制作用不依赖于胃癌细胞的分化程度。     

基因沉默血管内皮生长因子受体3对胃癌细胞增殖的抑制作用

目的: 探讨靶向血管内皮生长受体-3(vascularendothelial growth factor receptor-3, VEGFR-3)小干扰RNA重组载体对胃癌细胞增殖的作用.方法: 构建pSUPER-shRNA/VEGFR3重组载体, 将其转染入胃癌细胞SGC-7901, 采用MTT法观察细胞的生长曲线, RT-PCR检测重组载体在转染前后VEGFR-3 mRNA表达水平的变化, Western blot检测VEGFR-3的蛋白表达.结果: pSUPER-shRNA/VEGFR3重组载体可显著抑制SGC-7901细胞中VEGFR-3基因的表达( P<0.05); 转染pSUPER-shRNA/VEGFR3的SGC-7901细胞生长明显受抑制( P<0.05),VEGFR-3基因蛋白表达明显降低( P<0.05).结论: pSUPER-shRNA/VEGFR3重组载体能够对胃癌细胞SGC-7901中VEGFR-3形成基因沉默, 并抑制胃癌细胞的增殖.     

奥曲肽联合5-FU对人胃癌细胞株SGC-7901生长的影响

用不同浓度的奥曲肽联合5-FU作用SGC-7901细胞后，用MTT法测定细胞生长抑制率，流式细胞仪检测细胞中的Bel和Bax蛋白。结果奥曲肽作用于SGC-7901细胞24h后，可显著抑制胃癌细胞的生长，相同浓度奥曲肽加入80μg/ml 5-FU，细胞抑制率明显增强，与单用奥曲肽相比，P〈0.05；经奥曲肽及5-Fu处理的胃癌细胞，其Bcl蛋白表达显著减少，而Bax蛋白表达显著增加，二药联合与单药应用相比，P〈0.05。认为奥曲肽可显著抑制胃癌细胞的生长，奥曲肽联合5-FU对胃癌细胞的生长抑制作用增强；其作用机制是下调SGC-7901的Bel蛋白表达，而上调Bax蛋白表达。     

蛋白酪氨酸磷酸酶抑制剂对VacA空泡活性的影响

目的　幽门螺杆菌 (Hp)的空泡毒素 (VacA)受体属于与细胞信号转导密切相关的受体蛋白酪氨酸磷酸酶家族 (RPTP) ,但VacA导致空泡形成的具体机制尚不清楚。研究干扰信号转导后空泡形成的变化 ,可为临床治疗有毒Hp菌株感染提供新思路。 方法　采用Hp液体培养上清浓缩液作为粗制VacA毒素 ,将蛋白酪氨酸磷酸酶抑制剂 (PTPI)及蛋白酪氨酸激酶抑制剂 (PTKI)木黄酮倍比稀释后 ,与VacA共同作用于胃癌细胞 ,观察VacA空泡毒性的变化。结果　PTPI浓度达到 2 .7μmol/L时 ,即产生对VacA空泡活性显著的抑制作用 (A550 =0 .46± 0 .0 6比 0 .5 9± 0 .0 4,P <0 .0 5 ) ,至 2 1.5 μmol/L时抑制作用可达 10 0 % (A550 =0 .0 9± 0 .0 2 )。PTPI浓度高于 2 1.5 μmol/L时可见部分细胞死亡。将PTPI作用于已产生空泡的细胞 ,采用能引起空泡抑制作用的 4个浓度梯度 2 1.5、10 .8、5 .4及 2 .7μmol/L ,2 4h后PTPI组与空白对照相比 ,A550 无显著差异。 16～ 5 0 0 μmol/L浓度木黄酮均未对空泡活性产生明显的影响。结论　PTPI对VacA空泡活性具有显著的抑制作用 ,间接证实VacA受体的属性为受体RPTP ,VacA毒素的作用可能与干扰细胞内的信号转导过程有关     

幽门螺旋杆菌ureB、vacA基因的原核表达产物及其与感染病人血清的免疫反应性

目的 在大肠杆菌中重组表达幽门螺旋杆菌UreB、VacA蛋白,并对目的产物与感染病人血清的反应性进行验证.方法 PCR扩增获得ureB、vacA基因,分子生物学方法将基因片段克隆人pET22b( )表达载体并在大肠杆菌中诱导表达,表达产物经Ni离子亲和层析进行纯化,纯化产物采用Western Blot方法鉴定其与感染病人血清的免疫反应性.结果 构建的重组大肠杆菌高效表达UreB、VacA蛋白,Ni离子亲和层析后获得90%以上纯度的目的蛋白,与感染病人血清具有良好的免疫反应性.结论 重组UreB、VacA蛋白可作为幽门螺旋杆菌感染检测的候选分子.     

重组人p53腺病毒感染对携带不同p53状态胃癌细胞增殖和凋亡的影响

目的研究重组人p53腺病毒感染不同p53状态胃癌细胞对其p53蛋白表达、生长抑制率、细胞周期与凋亡率的影响。方法不同浓度重组人p53腺病毒感染3种不同p53状态胃癌细胞,即含野生型p53基因的细胞(wild-type)、含突变型p53基因的细胞(mutant-type)、含空载质粒即p53基因缺失的细胞(vector-cell)。48 h后,用Western blotting法检测p53蛋白在3种胃癌细胞中的表达;用MTT法测定重组人p53腺病毒感染3种胃癌细胞的生长抑制率,用流式细胞仪检测细胞周期分布和凋亡率。结果rAd-p53感染3种胃癌细胞48 h后p53蛋白表达阳性,对照组p53基因缺失的胃癌细胞无表达,对照组含野生型p53基因的细胞和含突变型p53基因的细胞弱表达。rAd-p53对3种胃癌细胞的生长抑制效应在一定的浓度范围内呈剂量依赖性,而与细胞内在的p53状态无关。含野生型p53基因的细胞、含突变型p53基因的细胞和p53基因缺失的细胞感染rAd-p53后诱导G2/M期阻滞与细胞凋亡率分别增加2.5、3.6、3.2倍。结论腺病毒介导p53基因感染3种不同p53状态胃癌细胞改变细胞内在的p53状态,p53蛋白表达、生长抑制率、细胞周期分布、凋亡率均与细胞内在的p53状态无关。     

restin基因转染对裸鼠胃癌移植瘤生长的影响

目的:探讨restin基因转染对胃癌细胞BGC803裸鼠移植瘤生长抑制作用及对肿瘤血管生成的影响.方法:将重组质粒pEGFP-restin转染BGC-803细胞,以绿色荧光蛋白示踪其对胃癌细胞BGC-803生长的影响:RT-PCR鉴定目的基因的表达:通过裸鼠移植瘤实验比较restin对裸鼠移植瘤的生长抑制作用,免疫组织化学染色方法观察微血管密度(MVD)和血管内皮生长因子(VEGF)的表达.结果:重组质粒经RT-PCR扩增后在600bp处稳定表达:将pEGFP-restin重质粒转染胃癌细胞BGC-803,荧光显微镜下见转染组细胞发出绿色荧光,肿瘤细胞形态不一;裸鼠移植瘤实验显示,与对照组(空载体组和未转染组)比较,转染组胃癌细胞生长速度缓慢,肿瘤体积小(P＜0.01);空载体组与转染组的抑瘤率分别为3.60%、29.02%:免疫组化显示,转染组肿瘤微血管密度减少(4.25±0.29 vs 9.79±0.94,10.34±1.22,均P＜0.05),转染组VEGF表达降低(12.24 3.45 vs 44.52±9.70,39.76±6.38,均P＜0.05).结论:restin基因转染可抑制裸鼠移植瘤生长,影响肿瘤新生血管形成可能是其抗肿瘤作用之一.     

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.     

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.     

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.     

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。     

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     

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。     

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.