小鼠髓源性半成熟树突状细胞致免疫耐受的实验研究

三组体外培养的小鼠骨髓细胞,分别采用低剂量粒细胞巨细胞集落刺激因子（GM-CSF）诱导、高剂量GM—CSF诱导及脂多糖（LPS）刺激、低剂量GM—CSF诱导及LPS刺激,使其分化为树突状细胞（DC）。流式细胞术检测DC表面CD11c、CD25、CD40、CD80和CD86、MHC-Ⅱ,ELISA法检测细胞培养上清液中IL-10、IL-12,初次和再次混合淋巴细胞实验检测DC刺激T细胞增殖能力,术前回输DC行同种异位心脏移植并观察术后移植心存活时间。结果显示,低剂量GM—CSF能诱导骨髓细胞分化为CD11c^＋、CD25^-、CD40^low、CD80^low和CD36^low、MHC-Ⅱ^low未成熟表型DC,经LPS刺激后分化为CD11c^＋、CD25^-、CD40^mid、CD80^low和CD86^low、MHC-Ⅱ^mid。半成熟表型DC;半成熟表型DC培养上清液中IL-10／IL-12明显升高,该DC可明显抑制同种异型T细胞增殖反应,较未成熟DC更能延长移植心存活时间。认为小鼠骨髓细胞经低剂量GM—CSF体外诱导可分化为未成熟DC,经LPS刺激可转化为半成熟DC,拥有更强的致耐受性。     

胞质转导肽-HBcAg18-27-Tapasin体外诱导小鼠髓源性树突状细胞成熟及在T淋巴细胞增殖中的作用

目的 观察融合蛋白胞质转导肽(CTP) -HBcAg18-27 -Tapasin诱导体外培养的小鼠髓源性树突状细胞(DC)成熟和对T淋巴细胞增殖的作用.方法 体外分离、培养近交系BALB/c小鼠髓源性DC,加入重组粒细胞-巨噬细胞集落刺激因子和IL-4培养5d,再加入脂多糖诱导成熟.10 μg/L CTP HBcAg18-27-Tapasin、50 μg/L CTP-HBcAg18-27-Tapasin、10 μg/L CTP-HBcAg18-27及RPMI-1640培养液加入培养介质.流式细胞术测定DC表面分子表达,ELISA法测定DC培养上清液中的IL-12p70的水平,细胞计数试剂盒检测T淋巴细胞增殖反应,流式细胞术检测增殖的T淋巴细胞内的细胞因子.多个样本均数间的比较采用单因素方差分析,组间两两比较采用LSD法.结果 成功体外诱导小鼠髓源性DC; CTP-HBcAg18-27Tapasin能明显上调DC表面分子CD80、CD86及主要组织相容性复合体Ⅰ分子的表达;50 μg/L CTP-HBcAg18-27-Tapasin组诱导DC分泌的IL 12p70水平为(61.12±10.25)pg/mL,依次高于10μg/LCTP-HBcAg18-27 -Tapasin组的(50.43±10.42) pg/mL、10μg/L CTD HBcAg18-27组的(40.17±8.54) pg/mL和空白组的(30.51±8.03) pg/mL(F=15.85,P=0.030和P=0.037);CTP HBcAg18-27-Tapasin诱导DC刺激T淋巴细胞增值能力明显高于对照组;流式细胞仪检测融合蛋白诱导的CTL水平50 μg/L CTP-HBcAg18-27-Tapasin组为(2.05±0.41)％、10 μg/L CTP-HBcAg18-27-Tapasin组为(1.06±0.10)％,高于10 μg/L CTP-HBcAg18-27组的(0.45±0.11)％和空白组的(0.09±0.02)％(F- 60.22,P=0.003).结论 CTP- HBcAg18-27-Tapasin可以促进DC的分化、成熟,增强DC刺激T淋巴细胞增殖能力并能增加CTL的表达.     

胞质转导肽-HBcAg18-27-Tapasin体外诱导HBV转基因小鼠髓源性树突状细胞成熟及在T淋巴细胞增殖中的作用

目的:观察融合蛋白胞质转导肽(cytoplasmic transduction peptide,CTP)-HBcAg18-27-Tapasin体外诱导HBV转基因小鼠髓源性树突状细胞(dendritic cell,DC)成熟和对T淋巴细胞增殖的作用.方法:体外分离、培养HBV转基因小鼠及近交系C57BL/6小鼠髓源性DC,加入重组粒细胞-巨噬细胞集落刺激因子和白介素(interleukin,IL)-4培养5d,再加入实验组10μg/mL CTP-HBcAg18-27-Tapasin、对照组10μg/mL CTP-HBcAg18-27、10μg/mL HBcAg18-27-Tapasin及空白组RPMI1640完全培养液.流式细胞术测定DC表面分子CD80、CD83、MHC-1的表达,ELISA法测定DC培养上清液中的IL-12p70的水平,细胞计数试剂盒(CCK-8)检测T淋巴细胞增殖反应,流式细胞仪检测增殖的T淋巴细胞内的细胞因子.结果:体外成功诱导小鼠髓源性DC;CTP-HBcAg18-27-Tapasin能明显上调DC表面分子CD80、CD83、MHC-1的表达;并且CTP-HBcAg18-27-Tapasin组诱导DC分泌的IL-12p70水平及诱导DC增殖T淋巴细胞增殖能力明显高于对照组及空白组[IL-12p70转基因小鼠(F=205.85,P=0.000);C57BL/6小鼠(F=406.20,P=0.000)];流式细胞仪检测实验组融合蛋白诱导的CTL水平也高于对照组[转基因小鼠(F=155.45,P=0.000);C57BL/6小鼠(F=392.90,P=0.000)],同时HBV转基因小鼠DC表面分子及在T淋巴细胞增殖中的作用要比C57BL/6小鼠低.结论:分子伴侣Tapasin修饰胞内化抗原肽能促进HBV转基因小鼠髓源性DC的分化、成熟,并能增强DC刺激T淋巴细胞增殖能力及诱导CTL的产生.     

结核杆菌Ag85A DNA疫苗在小鼠体内的免疫效应比较

目的探索增强结核杆菌DNA疫苗有效性的新方法，为研制并开发新一代高效结核杆菌DNA疫苗奠定基础。方法分别构建结核杆菌Ag85A抗原基因真核表达质粒及其与小鼠粒细胞-巨噬细胞集落刺激因子的真核嵌合表达质粒，体外转染COS7细胞检测两种重组质粒的表达活性后，将其分别用作DNA疫苗给BALB／c小鼠肌内注射，检测小鼠体内特异性体液免疫和细胞免疫应答相关指标，同时进行动物免疫保护性实验，比较分析两种DNA疫苗在小鼠体内的免疫效应。结果结核杆菌Ag85A抗原蛋白基因与小鼠粒细胞一巨噬细胞集落刺激因子的嵌合DNA疫苗在小鼠体内的免疫原性明显强于Ag85A抗原基因非嵌合DNA疫苗，但两种DNA疫苗的免疫保护性无明显差异。结论粒细胞-巨噬细胞集落刺激因子与结核杆菌免疫保护性抗原基因嵌合DNA疫苗能显著增强结核病DNA疫苗的免疫原性。     

PTD-HBcAg体外诱导小鼠髓源性树突状细胞成熟及在T淋巴细胞增殖中的作用

目的 观察融合蛋白PTD-HBcAg诱导体外培养的小鼠髓源性树突状细胞(DC)成熟及对T淋巴细胞增殖的作用.方法 体外分离培养近交系BALB/C小鼠髓源性DC加入重组粒细胞-巨噬细胞集落刺激因子(rgM-CSF)、重组IL-4培养5 d,再加人TNF-a、HBcAg和PTD-HBcAg诱导DC成熟.激光共聚焦显微镜观察免疫荧光在细胞中的分布及定位,流式细胞计数仪测定DC表面分子表达,ELISA法测定DC培养上清液中IL-12 p70的水平,CCK-8试剂盒检测T淋巴细胞增殖反应.组间数据比较采用t检验.结果 成功体外诱导培养小鼠髓源性DC,HBcAg主要定位于DC膜表面,而PTD-HBcAg能够穿透DC膜进入细胞质.PTD-HBcAg能明显上调DC表面分子CD80、CD86和主要组织相容性复合体(MHC)II类分子表达;50 mg/L和100 mg/L PTD-HBcAg诱导DC分泌IL-12 p70水半分别为(142.50±18.31)ng/L和(124.30±15.12)ng/L,明显高于HBcAg诱导组的(42.31±4.21)ng/L(t=9.234和9.045,均P＜0.05);PTD-HBcAg诱导DC刺激T淋巴细胞增殖能力明显高于HBcAg组及阳性对照TNF-a组.结论 PTD-HBcAg具有穿透DC膜能力,并能促进DC分化、成熟,明显上调表面共刺激分子表达,增强DC刺激T淋巴细胞增殖能力及分泌IL-12 p70的水平.     

小鼠骨髓源性树突状细胞的体外扩增、鉴定及生物学特性研究

目的 为树突状细胞(DC)的研究和应用奠定基础.方法 以重组小鼠粒细胞-巨噬细胞集落刺激因子(GM-CSF)、白细胞介素(IL-4)和脂多糖(LPS)体外诱导小鼠骨髓细胞分化为DC,倒置显微镜动态观察细胞形态学变化,流式细胞术分析细胞表面分子,混合淋巴细胞反应检测其刺激T细胞增殖能力.结果 经体外诱导培养第2～8天可见大量细胞集落形成;获得的DC具有典型树突状形态,同时DC可显著刺激同种异体混合淋巴细胞增殖.结论 体外诱导培养可获得小鼠骨髓来源DC,可广泛应用于临床及实验研究.     

多房棘球蚴分泌物抗原对脂多糖诱导小鼠骨髓来源的树突状细胞表型及功能的影响

目的 探究不同浓度多房棘球蚴分泌物抗原(Em-sAg)对脂多糖(LPS)诱导小鼠骨髓来源的树突状细胞(BMDC)表型和功能的影响。方法 小鼠骨髓腔中所分离的骨髓前体细胞,经小鼠重组粒细胞-巨噬细胞集落刺激因子(GM-CSF)刺激后形成BMDC,于正倒置显微镜下观察细胞形态。用流式细胞术鉴定BMDC纯度后,分为Control组、阳性对照组(LPS 1μg/mL)、LPS+3 mg/mL Em-sAg组、LPS+1.5 mg/mL Em-sAg组、LPS+0.75 mg/mL Em-sAg组、LPS+0.375 mg/mL Em-sAg组共6组。流式细胞术检测各组BMDC表面分子(CD80、CD86、MHC-Ⅱ分子)的表达情况,ELISA法检测各组细胞因子IL-12p70的表达水平。满足正态分布的计量资料多组间比较采用单因素方差分析,组间两两比较采用LSD-t检验表示。结果 在正倒置显微镜下观察到,培养8～10 d的细胞可见毛刺样突起,细胞呈完全悬浮状态。流式细胞术检测发现,CD11c的阳性率均在70%以上,据此鉴定所培养的细胞大部分为BMDC。流式细胞术的进一步结果表明,与Control...     

携带泛素-HBcAg融合基因的慢病毒表达载体构建及其体外诱导小鼠髓源性树突状细胞成熟

目的构建携带泛素-HBcAg融合基因的慢病毒表达载体,包装成重组慢病毒并观察其体外诱导小鼠髓源性树突状细胞（DC）成熟。方法 PCR扩增Ub-HBcAg融合基因,插入到慢病毒骨架质粒pWPXLd中,构建重组质粒pW-Ub-HBcAg。将构建的重组慢病毒质粒pW-Ub-HBcAg和包装质粒psPAX2、包膜质粒PMD2.G用脂质体共同转染293T细胞,获得携带Ub-HBcAg基因的重组慢病毒LV-Ub-HBcAg,并检测其在293T细胞中的表达。体外分离培养小鼠髓源性DC,加入重组慢病毒,流式细胞仪测定DC表面分子表达,ELISA测定DC培养上清中IL-12分泌水平。结果强制泛素化HBcAg融合基因的慢病毒表达载体经测序证实目的基因序列及插入方向均正确,W estern b lot能检测到目的蛋白在293T细胞中的表达。LV-Ub-HBcAg能上调DC表面分子的表达（CD86、CD80、MHC-Ⅱ类分子）,并且能促进DC分泌IL-12（139.2±10.75）pg/mL,明显高于LV-HBcAg组分泌的量（P〈0.01）。结论成功构建了携带强制泛素化HBcAg融合基因的慢病毒,转染293T细胞后能够稳定表达目的基因,并且能诱导DC分化、成熟,上调表面共刺激分子的表达,促进IL-12因子的分泌。     

HCV C-Fc融合基因修饰的树突状细胞疫苗抗HCV功能研究

目的　探讨丙型肝炎病毒 (HCV)C Fc基因修饰的树突状细胞 (DCs)能否诱导抗HCV细胞和体液免疫反应。方法　将pcDNA3 HCV Fc质粒用电穿孔法转染经过白介素 4 (IL 4 ) ,粒 巨噬细胞集落刺激因子 (GM CSF)刺激增殖的小鼠DCs前体细胞 ,观察HCV、Fc抗原表达 ;将制备的 5×10 5/ 10 0 μlDC疫苗皮下免疫Balb/c小鼠 ,两周后检测特异性抗体、脾脏CD4 、CD8 细胞增殖作用以及诱导的细胞毒性T淋巴细胞 (CTL)反应。结果　HCVC Fc基因电穿孔法转染细胞在上述细胞因子作用下发育成能有效表达HCVC Fc并具有典型形态学与表型特征的DCs。免疫小鼠后 ,HCVC Fc基因转染DCs能诱导产生抗HCV特异性抗体和较强的CTL反应。结论　HCVC Fc基因修饰的DCs能增强对HCV特异性CTL效应的诱导能力 ,提示它在抗病毒疫苗发展中的潜力     

树突状细胞来源胞外体转运丁型肝炎抗原诱导特异性细胞毒性T淋巴细胞反应的体外研究

目的探讨携带泛素化修饰丁型肝炎抗原(hepatitis D antigen, HDAg)的树突状细胞来源的胞外体(dendritic cell derived exosomes, Dexs)在诱导特异性细胞毒性T淋巴细胞(cytotoxic T lymphocyte, CTL)反应中的作用及其分子机制。方法提取并诱导C57BL/6小鼠髓源性树突状细胞(dendritic cell, DC)后与Ub-S-HDAg-Dexs共孵育48 h, 流式细胞仪检测表面分子[CD86、CD80、主要组织相容性复合体(major histocompatibility complex, MHC)Ⅱ]的表达水平。提取C57BL/6小鼠脾源性T淋巴细胞与经胞外体刺激的DC共孵育后共培养72 h, 分为Ub-S-HDAg-Dexs组(加入50 μg/mL Ub-S-HDAg-Dexs)、Blank-Dexs组(加入50 μg/mL无质粒转染的DC来源胞外体)、Con-Dexs组(加入50 μg/mL经空白慢病毒转染的DC来源胞外体)、PBS组[加入50 μL/mL磷酸盐缓冲液(phosphate-buffer...     

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.