应用抑制性消减杂交技术克隆乙型肝炎病毒全S蛋白反式激活基因

目的应用抑制性消减杂交(SSH)技术构建乙型肝炎病毒(HBV)全S蛋白反式激活基因差异表达的cDNA消减文库,克隆HBV全S蛋白反式激活相关基因.方法以HBV全S表达质粒pcDNA3.1(-)-全S转染HepG2细胞,以空载体pcDNA3.1(-)为对照;制备转染后的细胞裂解液,从中提取mRNA并逆转录为cDNA,经RsaI酶切后将实验组cDNA分成两组,分别与两种不同的接头衔接,再与对照组cDNA进行两次消减杂交及两次抑制性PCR,将产物与T/A载体连接,构建cDNA消减文库,并转染大肠杆菌进行文库扩增,随机挑选克隆PCR扩增后进行测序及同源性分析.结果成功构建人HBV全S蛋白反式激活基因差异表达的cD-NA消减文库.文库扩增后得到86个白色克隆,进行菌落PCR分析,均得到100-1000 bp插入片段.挑取35个含有插入片段的阳性克隆测序分析,获得33个已知基因序列,和2个未知基因,通过生物信息学分析获得其全长序列,其中之一命名为全S蛋白反式激活基因1(CSTP1),已在GenBank中注册,注册号:AY553877.未知基因的功能还正在研究中.结论应用SSH技术成功构建了HBV全S反式激活基因差异表达的cDNA消减文库.该文库的建立为进一步阐明HBV全S反式调节的靶基因及致肝病发生的分子生物学机制提供理论依据.     

应用抑制性消减杂交技术筛选丙型肝炎病毒E1蛋白反式激活基因

目的　应用抑制性消减杂交 (SSH)技术构建丙型肝炎病毒 (HCV)E1蛋白反式激活基因差异表达的cDNA消减文库 ,克隆HCVE1蛋白反式激活相关基因。方法　以HCVE1表达质粒pcDNA3 .1( -) E1转染肝母细胞瘤细胞系HepG2细胞 ,以空载体pcDNA3 .1( -)为对照 ;制备转染后的细胞裂解液 ,从中提取mRNA并逆转录为cDNA ,经RsaI酶切后将实验组cDNA分成 2组 ,分别与 2种不同的接头衔接 ,再与对照组cDNA进行 2次消减杂交及 2次抑制性PCR ,将产物与T/A载体连接 ,构建cDNA消减文库 ,并转染大肠杆菌进行文库扩增 ,随机挑选克隆PCR扩增后进行测序及同源性分析。结果　成功构建人HCVE1蛋白反式激活基因差异表达的cDNA消减文库。文库扩增后得到 89个阳性克隆 ,进行菌落PCR分析 ,均得到 10 0 10 0 0bp插入片段。挑取 46个含有插入片段的阳性克隆测序分析 ,获得 44个已知基因序列和 2个未知基因。通过生物信息学分析获得其全长序列 ,已被GenBank收录。结论　应用SSH技术成功构建了HCVE1反式激活基因差异表达的cDNA消减文库。该文库的建立为进一步阐明HCVE1反式调节的靶基因及致肝脏疾病发生的分子生物学机制提供理论依据     

应用抑制性消减杂交技术筛选乙型肝炎病毒DNA聚合酶末端蛋白的反式激活基因

目的 应用抑制性消减杂交(SSH)技术构建乙型肝炎病毒(HBV)DNA聚合酶末端蛋白(TP)反式激活基因的差异表达的cDNA消减文库，克隆TP反式激活相关基因。方法 以TP表达质粒pcDNA3．1(-)-TP转染HepG2细胞，以空载休peDNA3，1(-)为对照；制备转染后的细胞裂解液，提取mRNA并逆转录为cDNA，经Rsal酶切后，将实验组cDNA分成两组，分别与两种不同的接头衔接，再与对照组cDNA进行两次消减杂交及两次抑制性PCR，将产物与T／A载体连接，构建cDNA消减文库，并转染大肠杆菌进行文库扩增，随机挑选克隆PCR扩增后进行测序及同源性分析。结果 文库扩增后得到35个阳性克隆，经菌落聚合酶链反应(PCR)分析，得到34个200-1000bp插入片段。对所得片段测序，并进行同源性分析，显示14种己知基因编码蛋白和1种未加功能基因序列，可能是TP反式激活靶基因。结论 成功构建乙型肝炎病毒TP反式激活基因差异发达的cDNA消减文库，为今后进一步分析、研究病毒蛋白的致病机制奠定基础。     

丙型肝炎病毒非结构蛋白NS4B反式激活基因的克隆化研究

目的应用抑制性消减杂交(suppression subtractive hybridization,SSH)技术构建丙型肝炎病毒(HCV)非结构蛋白4B(NS4B)转染细胞差异表达cDNA消减文库,克隆HCV NS4B蛋白反式激活相关基因.方法以HCV NS4B表达质粒pcDNA3.1(-)-NS4B转染HepG2细胞,以空载体pcDNA3.1(-)为对照,制备转染后的细胞裂解液,提取mRNA并逆转录为cDNA,进行抑制性消减杂交分析.将富集的二次PCR产物与T/A载体连接,并转染大肠杆菌进行文库扩增,随机挑取克隆聚合酶链反应(PCR)扩增后进行测序及同源性分析.结果文库扩增后得到33个阳性克隆,经菌落PCR分析显示其中28个克隆含有大小不等的200～1000 bp插入片段.测序及同源性分析显示,12种已知基因编码蛋白,包括一些与细胞周期、信号传导及肿瘤发生等细胞生长调节密切相关的蛋白编码基因,可能是NS4B反式激活靶基因.结论成功构建了HCV NS4B反式激活基因差异表达的cDNA消减文库,为进一步阐明HCV NS4B反式调节的靶基因在肝炎、肝纤维化和肝细胞癌发生的分子生物学机制提供理论依据.     

截短型HBsAg中蛋白反式激活基因的克隆

目的：应用抑制性消减杂交技术构建乙型肝炎病毒（HBV）截短型中蛋白（MHBs^t)反式 激活基因差异表达的cDNA消减文库，克隆HBV截短型中蛋白反式激活相关基因。方法：以HBV截短型中蛋白表面质粒pcDNA3.1(-)-Tt167转染HepG2细胞，以空载体pcDNA3.1(-）为对照；制备转染后的细胞裂解液，提取mRNA并逆转录为cDNA，经Rsa I酶切后，将实验组cDNA分成两组，分别与两种不同的接头衔接，再与对照组cDNA进行两次消减杂交及两次抑制性聚合酶链反应（PCR），将产物与T／A载体连接，构建cDNA消减文库，并转染大肠杆菌进行文库扩增，随机挑选克隆PCR扩增后进行测序及同源性分析。结果：成功构建人HBV截短型中蛋白反式激活基因差异表达的cDNA消减文库。文库扩增后得到94个白色克隆，进行菌落PCR分析，均得到200－800bp插入片段。挑取50个插入片段测序，并通过生物学信息学分析获得其全长基因序列，结果共获得23种编码基因，包括19种已知基因的4种未知基因。结论：筛选到的cDNA全长序列，包括一些与细胞生长调节、免疫应答及肿瘤发生密切相关的蛋白编码基因，因此可能是HBV截短型中蛋白反式激活靶基因。     

应用抑制性消减杂交技术克隆和筛选PS1TP5反式激活相关基因

目的构建乙型肝炎病毒前-S1蛋白反式激活基因5(PS1TP5)的反式激活相关基因差异表达的cDNA,克隆PS1TP5蛋白反式激活相关基因。方法以PS1TP5表达质粒pcDNA3.1(-)-myc-his(A)-PS1TP5转染HepG2细胞,以空载体pcDNA3.1(-)-myc-his(A)为对照,制备转染后的细胞裂解液,提取mRNA并合成cDNA,经RsaⅠ酶切后将实验组cDNA分成两组,分别衔接两种不同接头,再与对照组cDNA进行两次消减杂交及两次PCR反应,产物与T/A克隆载体连接,构建cDNA消减文库,并转染大肠杆菌进行文库扩增,随机挑选克隆经PCR鉴定后进行测序及同源性分析。结果成功构建人PS1TP5蛋白反式激活相关基因差异表达的cDNA。扩增后得到70个200～1 000 bp插入片段的克隆,随机挑选其中30个插入片段测序,并通过生物信息学分析获得其全长基因序列,结果共获得24种编码基因,其中1个为未知功能的新基因,电子拼接后命名为HBV PS1TP5TP1(乙型肝炎病毒前-S1蛋白反式激活蛋白5反式激活蛋白1),GenBank注册号DQ487761。结论筛选到的cDNA全长序列,包括一些与细胞...     

乙型肝炎病毒X蛋白反式激活基因克隆化的研究

目的 应用抑制性消减杂交（SSH）技术构建乙型肝炎病毒X蛋白（HBX）反式激活基因差异表达的cDNA消减文库，克隆HBX反式激活相关基因。方法 以HBX表达质粒pcDNA3.1(-)-X转染HepG2细胞，以空载体pcDNA3.1(-)转染的HepG2细胞为对照。制备转染后的细胞裂解液，提取mRNA并逆转录为cDNA，经RsaⅠ酶切后，将实验组cDNA分成两组。分别与两组不同的接头衔接，再对照组cDNA进行两次消减杂交及两次抑制聚合酶链反应（PCR），将产物与T/A载体连接，构建cDNA消减文库，并转染大肠杆菌进行文库扩增，随机挑选克隆PCR扩增后进行测序及同源性分析。结果 成功构建人HBX反式激活基因差异表达的cDNA消减文库；文库扩增后得到85个白色克隆，进行菌落PCR分析。均得以200-1000bp插入片段，挑取含有插入片段的65个克隆进行测序，并通过生物信息学分析获得19种已知基因序列。和15个未知基因。结论 应用SSH技术成功构建了HBX反式激活基因差异表达的cDNA消减文库，该文库的建立为进一步阐明HBX反式调节的靶基因及致肝细胞癌发生的分子生物学机制提供理论依据。     

乙型肝炎病毒前-S1蛋白反式激活蛋白3基因的克隆化研究

目的应用抑制性消减杂交技术(SSH)及生物信息学技术(bioinformatics)筛选并克隆乙型肝炎病毒(HBV)前-S1蛋白(Pre-S1)反式激活新型靶基因，进一步阐明HBV感染相关疾病的发病机制。方法以HBV前-S1蛋白表达质粒pcDNA3．1(-)-PreS1转染HepG2细胞，以空载体pcDNA3．1(-)为平行对照，提取mRNA并进行抑制性消减杂交分析。并应用分子生物学技术，结合生物信息学技术，克隆HBV前-S1反式激活作用的新的靶基因。结果对于所获基因片段序列分析表明，其中之一为新型基因片段。从HepG2细胞提取总RNA，以逆转录多聚酶链反应(RT—PCR)技术扩增获得该新基因的全长序列，并测序证实，因其可以被前-S1蛋白反式激活，故命名为前-S1反式激活蛋白3(PSITP3)，已在GenBank中注册，注册号：AY446274。PSITP3基因的编码序列全长为1173个核苷酸(nt)，编码产物由390个氨基酸残基(aa)组成。结论HBV前-S1蛋白在HBV进入宿主细胞的过程中起着重要的作用，最近的研究表明前-S1蛋白还具有反式激活的作用，上调宿主细胞某些基因的表达，从而改变宿主正常的免疫应答水平，引起病变。HBV前-S1反式激活新靶基因的发现，为进一步研究HBV前-S1蛋白的分子生物学机制和探索新型治疗技术奠定基础。     

应用抑制性消减杂交技术克隆乙型肝炎病毒DNAPTP1的反式调节基因

目的:应用抑制性消减杂交技术及生物信息学技术筛选并克隆乙型肝炎病毒DNAPTP1反式激活的新型靶基因．方法:以HBV DNAPTP1表达质粒pcDNA3．1(-)- DNAPTP1 转染HepG2细胞,以空载体pcDNA3．1(-)为对照;制备转染后的细胞裂解液,提取mRNA并逆转录为cDNA,经Rsa Ⅰ酶切后,将实验组cDNA分成两组,分别与两种不同的接头衔接,再与对照组cDNA进行两次消减杂交及两次抑制性聚合酶链反应(PCR),将产物与pGEM-Teasy载体连接,构建 cDNA消减文库,并转染大肠杆菌进行文库扩增,随机挑选克隆PCR扩增后进行测序及同源性分析．结果:成功构建DNAPTP1反式激活基因差异表达的cDNA 消减文库．文库扩增后得到60个白色克隆,经菌落PCR分析,得到32个200-1 000 bp插入片段．对所得片段测序,并进行同源性分析,获得3个差异表达的已知蛋白基因和4个未知功能的染色体序列．结论:筛选到的cDNA全长序列,包括一些与细胞生长调节、物质代谢、免疫及细胞凋亡密切相关的蛋白编码基因,推测了DNAPTP1可能存在的调控机制的线索．     

乙型肝炎病毒DNA聚合酶中核糖核酸酶RNase H反式调节基因DNAPTP4的克隆化研究

目的应用抑制性消减杂交(SSH)技术筛选乙型肝炎病毒(HBV)核糖核酸酶RNaseH蛋白反式激活基因差异表达的cDNA,克隆RNaseH反式激活相关靶基因。方法以RNaseH表达质粒pcDNA31(-)RNaseH转染HepG2细胞,以空载体pcDNA31(-)为对照;制备转染后的细胞裂解液,提取mRNA并逆转录为cDNA,经RsaⅠ酶切后,将实验组cDNA分成两组,分别与两种不同的接头衔接,再与对照组cDNA进行两次消减杂交及两次抑制性PCR,将产物与T/A载体连接,构建cDNA消减文库,并转染大肠杆菌进行文库扩增,随机挑选克隆PCR扩增后进行测序及同源性分析,其未知基因片段通过Kozak规则和多聚腺苷酸信号序列,初步确定。以逆转录聚合酶链反应(RTPCR)技术扩增获得该新基因的全长序列,并测序加以证实。结果该新基因被命名为DNAPTP4,在GenBank中注册,注册号为AY450392。DNAPTP4基因的编码序列全长为828个核苷酸(nt),编码产物由276个氨基酸残基(aa)组成。结论应用SSH技术成功筛选与克隆RNaseH反式激活新型靶基因DNAPTP4,为进一步阐明RNaseH反式调节作用及其在HBV感染中的分子生物学机制提供理论依据和研究方法。     

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。     

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。     

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。     

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.