阿魏酸钠对TNF-α致血管内皮细胞凋亡的作用

目的 探讨阿魏酸钠（sodium femlate，SF）对TNF-α引起的血管内皮细胞（VEC）凋亡的作用及机制。方法 以培养的人脐静脉内皮细胞（HUVEC）为实验模型，采用电镜、TUNEL法观察凋亡细胞，用免疫组化技术检测bcl-2和bax的表达。结果 电镜观察TNF-α组可见VEC凋亡典型特征；TUNEL法检测TNF-α组VEC凋亡率为35．2％，显著高于对照组，SF组和TNF-d＋SF组（JD〈0．01）；TNF-α组bcl-2表达聪显减少，同时加入SF后bcl-2表达明显上升，而TNF-α可诱导bax表达增加，加入SF后明显降低。结论 TNF-d能诱导VEC凋亡，SF可抑制细胞凋亡，同时SF可使TNF-α诱导的VEC中bcl-2表达明显恢复，而对bax表达明显降低。     

游离脂肪酸对人脐静脉内皮细胞eNOSmRNA及ET-1mRNA表达水平的影响

目的研究游离脂肪酸（FFA）对离体培养人血管内皮细胞（HUVEC）eNOS mRNA和ET-1mRNA表达水平的影响。方法用不同的FFA培养HUVEC，分为C16：0、C18：0、C18：1、C18：2、C24：0及对照组，每组选用4个浓度，孵育24h，用RT—PCR方法，半定量测定eNOS mRNA和ET-1mRNA的表达。结果①C18：1、C18：2组（t≥200μmol／L）eNOS mRNA表达值低于对照组（P〈0．05）且呈浓度依赖性，而C18：2组eNOS mRNA表达值比C18：1组低（P〈0．05）。②C18：1组以及C18：2组ET-1mRNA表达值低于对照组（P〈0．05），呈浓度依赖性。③C16：0、C18：0、C24：0组（≥200μmol／L），ET-1mRNA表达值增高（P〈0．05），呈浓度依赖性。④C18：0、C18：1、C18：2各组相同FFA水平相比较，ET-1mRNA表达水平依次降低（P〈0．05）。⑤C18：1、C18：2组eNOS mRNA与ET-1mRNA表达值之比高于对照组（P〈0．05）。C16：0、C18：0、C24：0各组此比值低于对照组（P〈0．05）。C18：0、C18：1、C18：2各组同浓度FFA条件下此比值依次升高（P〈0．05）。C16：0、C18：0、C24：0各组同浓度FFA条件下此比值无显著差异（P〉0．05）。结论①FFA对内皮细胞eNOS mRNA表达水平的影响与链长无关，而与FFA饱和程度有一定关系。②不饱和脂肪酸（UFA）降低eNOS mRNA以及ET-1mRNA表达；提示UFA倾向于维护血管舒张功能。③饱和脂肪酸（SFA）呈浓度依赖性促进ET-1mRNA表达可能是导致内皮功能障碍的部分原因。     

5-氮胞苷诱导对骨髓间充质千细胞凋亡影响的实验研究

目的：研究5-胞苷（5-azacytidine，5-aza）对体外培养的兔骨髓问充质于细胞（mensenchymal stemcell，MSC）凋亡的影响。方法：体外分离培养兔MSC，用不同浓度5-aza诱导不同时间．观察MSC凋亡情况。结果：正常培养兔MSC有轻度细胞捌亡；5-aza诱导浓度达15μmol／L时凋亡率明显增加（P〈0．01）．当浓度达10μmol／L，诱导时间延长则细胞洲亡率明显增加（P〈0．05），超过15μmol／l。时出现成片细胞死亡。结论：5-aza诱导对体外培养兔骨髓间质干细胞有诱导细胞凋亡作用，其作用程度与诱导时间及浓度有关。     

不同浓度脂多糖对支气管哮喘大鼠模型建立的影响及调节机制

目的 观察不同浓度大肠埃希菌脂多糖（E．coli LPS）对年幼期哮喘大鼠模型建立的影响及其调控机制。方法 清洁级SD大鼠45只，随机分为对照组（A组）、哮喘组（B组）、LPS组（C组），FC组又分为C1组（LPS0．1μg／m1）、C2组（LPS10μg／m1）、C3组（LPS100μg／m1）]，每组9只。用卵白蛋白（OVA）致敏与激发建立大鼠哮喘模型。光镜、电镜观察肺组织病理及超微结构的变化；支气管肺泡灌洗液（BALF）中嗜酸粒细胞（EOS）及其它炎症细胞计数；酶联免疫吸附试验（ELISA）法测定血清OVA-sIgE与BALF中TGF-β1含量；TUNEL法检测肺组织EOS凋亡。结果①光镜电镜观察：光镜下B组见支气管及血管周围、肺间质及肺泡腔内炎性细胞浸润，支气管黏膜下水肿，黏液腺增生，黏膜皱折增多，部分黏膜上皮细胞脱落，可见气道黏液栓；C1组、C3组上述改变无明显减轻；C2组上述现象明显减轻。电镜下B组见EOS数量增多，周围有大量浆细胞聚集；C1组无明显改变；C2组凋亡的EOS增多；C3组中性粒细胞和凋亡的EOS均增多。②BALF中炎症细胞计数：B组BALF中细胞总数、EOS绝对计数和EOS占细胞总数的百分比（EOS％）均高于A组（均P〈0．01）；C2组均低于B组（均P〈0．01）。③血清OVA-sIgE和BALF中TGF-β1含量：血清OVA-sIgE检测，B组高于A组（P〈0．01）；C2组、C3组明显低于B组（均P〈O．01）；但C1组与B组比较无统计学意义（P〉0．05）。BALF中TGF-β1。含量测定，B组与A组比较，两组有显著性差异（P〈0．05）；C2组、C3组明显高于B组（均P〈0．01）。④肺组织EOS凋亡率检测结果，B组与A组比较，两组有显著性差异（P〈0．05）；C2组、C3组与B组比较EOS凋亡率均明显增高（均P〈0．01）；但C1组与B组比较无统计学意义（P〉0．05）。相关分析结果，BALF中TGF-β1。水平与EOS数呈显著性负相关（r=-0．483，P〈0．01）；EOS绝对计数与血清OVA-sIgE水平呈显著性正相关（r=0．634，P〈0．01）。结论E．coliLPS（〉10μg／m1）通过降低OVA—sIgE水平，增加TGF-β1分泌，诱导EOS凋亡，从而可能减轻变态反应症状，但过高浓度E．coliLPS（100μg／m1）可能会促使中性粒细胞增高。     

IGF-1对MC3T3-E1细胞凋亡及凋亡调控蛋白Bax、Bcl-2表达的影响

目的 探讨胰岛素样生长因子-1（IGF-1）对小鼠前成骨样MC3T3-E1细胞凋亡基因相关蛋白Bax／Bcl-2表达的影响。方法 MC3T3-E1细胞分组培养，应用4个浓度的IGF-1（1ng／mL、10ng／mL、30ng／mL、50ng／mL）干预24h。观察MC3T3-E1细胞动态生长状况：流式细胞技术检测细胞凋亡率；免疫组织化学法检测凋亡蛋白Pax／Bcl-2的表达水平。结果 与正常血清对照组相比，无血清对照组MC3T3-E1细胞凋亡率增加（P〈0．05）；与无血清组相比，IGF-1组MC3T3-E1细胞凋亡率降低（P〈0．05），Bax表达减弱（P〈0．05），Bcl-2表达增强（P〈0．05）；各浓度组间比较，（1～50）ng／mL浓度范围内MC3T3-E1细胞凋亡率随IGF-1浓度加大而逐渐降低（P〈0．05），Bax表达逐渐减弱（P〈0．05），50ng／mL浓度组Bcl-2表达明显增强（P〈0．01），Bcl-2／Bax灰度比与细胞凋亡率呈显著正相关（r=0.917，P〈0．01）。结论 一定浓度的IGF-1同时调节Bax和Bcl-2表达，抑制无血清培养诱导的细胞凋亡。并存在剂量依赖性效应。     

MRL/lpr鼠骨髓间充质干细胞对T淋巴细胞作用的研究

目的 探讨狼疮鼠（MRL／lpr）及正常鼠（C57BL／6）骨髓间充质干细胞（MSCs）体外生物学特性、对T淋巴细胞作用的影响。方法 采用直接贴壁筛选法分离培养扩增两种鼠系骨髓MSCs，流式细胞术鉴定MSCs表面标记物，观察MSCs生长状况并绘制生长曲线；取C57BL／6鼠脾脏细胞，经尼龙毛柱分选CD3T淋巴细胞．经刀豆蛋白A（ConA）刺激，取正常及狼疮鼠MSCs或MSCs培养上清与T细胞共培养72h，然后羧基荧光素二醋酸盐琥珀酰亚胺酯（CFSE）染色测定T细胞增殖，流式细胞术检测共培养前后T细胞活化及T细胞的凋亡率。结果 第2代（P2）后狼疮鼠MSCs生长增殖快于正常鼠MSCs；正常及狼疮鼠MSCs共培养均可抑制正常鼠T细胞的增殖（P〈0．05），与MSCs上清共培养对正常鼠T细胞增殖无抑制作用（P〉0．05）；与两种MSCs或上清共培养均可降低正常T细胞的活化（P〈0．05）及凋亡率（P〈0．05）。对正常T细胞增殖、活化、凋亡的影响，狼疮鼠MSCs与正常鼠MSCs间差异无统计学意义（P〉0．05）。结论 狼疮鼠MSCs在体外生长上存在异常．但对T细胞增殖、活化、凋亡免疫调节无异常。     

复原胶囊对气虚血瘀证冠心病血液TXB2、6-Keto-PGF1a、NO、ROS的干预作用及相关机制研究

目的 研究气虚血瘀证冠心病血液血栓素B2（TXB2）、6-酮-前列环素F1a（6-Keto-PGF1a）、一氧化氮（NO）、活性氧（ROS）的变化及复原胶囊对其作用机制。方法 气虚血瘀证冠心病患者共42例随机抽取24例作为治疗组、18例作为对照组，另设14例健康人为青年对照组。采用化学比色法及放射免疫法（RAI）检测治疗组服复原胶囊2月前后血液NO、ROS、TXB2、6-Keto-PGF1a水平；并与对照组及健康对照组进行比较。结果 治疗组、对照组血液TXB2、ROS显著高于健康对照组（P〈0．01）；而6-Keto-PGF1a、NO显著低于健康对照组（P〈0．01）。治疗组服药2月后，血浆TXB2、ROS显著降低（P〈0．01）；但仍高于健康对照组（P〉0．05）；6-Keto-PGF1a、NO显著升高（P〈0．01）。但仍低于健康对照组（P〉0．05）。结论 中药复原胶囊升高血液6-Keto-PGF1a、NO水平，降低TXB2、ROS水平，这可能与复原胶囊改善血管内皮细胞（vessel endothelial cell，VEC）功能、恢复VEC的正常结构和功能有关。     

别嘌呤醇对高糖诱导损伤的人脐静脉血管内皮细胞的保护作用

目的探讨别嘌呤醇对高糖损伤后的人脐静脉血管内皮细胞（HUVEC）的保护作用及其机制。方法以HUVEC为研究对象,体外培养至第三代,分为：①20mmol／L高糖损伤对照组;②别嘌呤醇保护组（浓度分别为0．1mmol／L、0．2mmol／L、0．3mmol／L）;③维生素C阳性对照组（浓度为100mg／L）。不同浓度别嘌呤醇及维生素C先与HUVEC孵育24h,再加入20mmol／L高糖诱导损伤48h,测定各组细胞上清液中一氧化氮（NO）、丙二醛（MDA）、超氧化物歧化酶（SOD）、细胞间黏附分子-1（ICAM-1）含量及细胞凋亡率。结果别嘌呤醇（0．1mmol／L、0．2mmol／L、0．3mmol／L）药物保护组的细胞凋亡率低于20mmol／L高糖组,其中以0．3mmol／L更为明显（P〈0．01）;细胞培养液中SOD、NO的量均较20mmol／L高糖组增高,其中以0．3mmd／L别嘌呤醇组更为明显（P〈0．01）。药物保护组细胞培养液中合成MDA、ICAM-1较波动性高糖组降低,且在一定浓度范围内（0．05-49．30mmol／L）呈浓度依赖性（P〈0．05）。结论①别嘌呤醇对高糖体外诱导的HUVEC损伤有保护作用,呈浓度依赖性。②别嘌呤醇对高糖体外诱导HUVEC损伤保护作用的机制包括抑制氧化应激、炎症反应及细胞凋亡。     

维生素C诱导人胃癌细胞株MKN45凋亡的实验研究

目的 探讨维生素C对胃癌细胞株MKN45增殖、凋亡的影响及其相关机制。方法在体外培养的胃癌细胞株MKN45中加入不同浓度（0．05、0．1、0．5、1mg／m1）的维生素C,通过MTT比色法检测维生素C对细胞生长活力的影响;应用荧光显微镜、流式细胞术、DNALadder分析法检测细胞凋亡情况;应用分光光度法检测Caspase-3活性;应用化学显色法测定维生素C作用MKN4524h后细胞内超氧化物歧化酶（SOD）活性、丙二醛（MDA）含量。结果维生素C对胃癌细胞株MKN45有显著的生长抑制作用;与对照组比较,1mg／ml维生素C处理后,细胞凋亡率升高（P〈0．01）,并呈现凋亡的形态学改变,DNALadder分析呈典型“梯状”条带;Caspase-3活性升高（P〈0．05）。与对照组相比,维生素c处理组细胞内的SOD活性下降,MDA含量增加（P〈0．05）。结论1mg／ml浓度的维生素c作用24h后,可诱导胃癌细胞MKN45凋亡,其机制可能是通过提高Caspase-3的活性以及通过自身自氧化的氧化应激效应而诱导肿瘤细胞凋亡。     

彩色多普勒超声辐照对人脐静脉内皮细胞ECV304生物学特征的影响

目的探讨不同辐照时间的彩色多普勒超声（CDtJS）对人脐静脉内皮细胞ECV304（ECV304）生物学特性的影响。方法收集对数生长期ECV304细胞，分别给予CDUS辐照1、5、10、20、30min。未辐照细胞作为对照。MTr法观察细胞生长，流式细胞术测定细胞生长周期及凋亡率，Matrix试剂检测细胞管形形成能力，transwell法检测细胞迁移率。结果CDUS辐照5、10min时能促进ECV304细胞生长，辐照20、30min时抑制ECV304细胞生长，抑制率明显高于辐照1min时（P均〈0．05）。CDUS辐照30min时，ECV304细胞G2／M期比例和凋亡率（分别为22．14％和11．91％）均明显高于对照组（16．32％、0．11％），P均〈0．05；细胞管状结构形成明显低于对照组，小管间距离减小；迁移率亦显著低于对照组（P均〈0．05）。结论CDUS辐照可能影响脐静脉内皮细胞ECV304周期分布、增殖、凋亡、迁移和管状结构的形成；对胎儿行彩色多普勒超声检查应严格控制在10min内，最长不超过20min。     

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.