罗格列酮对血管紧张素Ⅱ诱导血管平滑肌细胞增殖的影响

目的 探讨罗格列酮对血管紧张素Ⅱ诱导血管平滑肌细胞增殖的影响及可能的机制.方法 原代培养大鼠血管平滑肌细胞,取第4～8代细胞进行实验.用终浓度为1 μmol/L血管紧张素Ⅱ诱导6 h,随机分成对照组(含10% FBS的DMEM培养基)、1 μmol/L血管紧张素Ⅱ组、不同浓度罗格列酮(20、30、40及50μmol/L) 干预组,30 μmol/L罗格列酮干预不同时间组 (6、12、18及24 h).分别采用MTT和流式细胞术观察血管平滑肌细胞增殖和增殖周期的变化;逆转录聚合酶链反应和免疫印迹法测定不同干预条件下血管平滑肌细胞血管紧张素Ⅱ2型受体mRNA和蛋白的表达水平.结果 血管紧张素Ⅱ组吸光值明显高于对照组(P<0.01),20、30、40及50μmol/L罗格列酮干预12 h及30μmol/L 罗格列酮干预6、12、18及24 h后,吸光值明显降低(P<0.05或P<0.01);血管紧张素Ⅱ组增殖指数和S期细胞分数明显高于对照组(P<0.01).随着罗格列酮干预浓度的增加或干预时间的延长,增殖指数、S期细胞分数及处于S期分数均明显下降(P<0.05或P<0.01).与血管紧张素Ⅱ组相比,不同浓度(20、30及50μmol/L)罗格列酮干预12 h及同一浓度(30μmol/L)干预不同时间(6、12及24 h)显著升高血管紧张素Ⅱ2型受体mRNA和蛋白的表达(P<0.05或P<0.01).结论 罗格列酮至少部分通过上调血管紧张素Ⅱ2型受体表达,阻止血管平滑肌细胞从G0/G1期向S期、G2/M期转化,从而抑制血管紧张素Ⅱ诱导血管平滑肌细胞的增殖、迁移,发挥血管保护作用.     

阿司匹林对血管平滑肌细胞增殖及增殖细胞核抗原表达的影响

目的探讨阿司匹林对大鼠血管平滑肌细胞增殖的影响及相关机制。方法体外培养大鼠主动脉平滑肌细胞,用不同浓度的阿司匹林处理,并且设置对照组,采用MTT法检测阿司匹林对血管平滑肌细胞增殖活性的影响,用免疫细胞化学和逆转录聚合酶链反应检测阿司匹林作用后血管平滑肌细胞中增殖细胞核抗原的表达。结果较高浓度(5×10-3mol/L)的阿司匹林对血管平滑肌细胞的增殖有明显抑制作用(P<0.05),相对抑制率为31.5%。与对照组相比,该浓度组血管平滑肌细胞中增殖细胞核抗原的蛋白和mRNA表达量均显著降低(P<0.05)。结论阿司匹林可能通过降低增殖细胞核抗原的表达来抑制血管平滑肌的增殖,对心血管系统具有抗血小板聚集之外的保护作用。     

同型半胱氨酸干扰胰岛素样生长因子2和H19的印迹表达及其与血管平滑肌细胞增殖的关系

目的采用动脉粥样硬化的独立危险因子同型半胱氨酸刺激脐静脉血管平滑肌细胞,观察同型半胱氨酸对血管平滑肌细胞胰岛素样生长因子2和H19表达的干扰作用,分析二者与血管平滑肌细胞增殖的关系及其在动脉粥样硬化发病中的可能作用。方法将培养的脐静脉血管平滑肌细胞分为0、50、100、200、500及1000μmol/L同型半胱氨酸组,以0μmol/L同型半胱氨酸组为空白对照组。用不同浓度的同型半胱氨酸刺激血管平滑肌细胞48 h后,MTT法检测血管平滑肌细胞的增殖水平;半定量逆转录聚合酶链反应法检测血管平滑肌细胞胰岛素样生长因子2和H19的mRNA表达水平,Western Blotting法检测血管平滑肌细胞胰岛素样生长因子2的蛋白表达水平。结果与空白对照组相比较,同型半胱氨酸各浓度组血管平滑肌细胞的增殖活力明显增加,以高浓度(500及1 000μmol/L)组为著(P0.05)。同时,同型半胱氨酸组血管平滑肌细胞H19的mRNA表达水平增加,500及1000μmol/L浓度组(0.548 6±0.063 3及0.733 3±0.049 6)明显高于空白对照组(0.202 2±0.012 4)(P0.05);胰岛素样生长因子2的mRNA和蛋白表达均下降,尤以高浓度组为著,500及1 000μmol/L浓度组的mRNA(0.258 8±0.024 8及0.168 9±0.069 6)和蛋白(0.116 7±0.015 5及0.083 7±0.018 0)表达水平均明显低于空白对照组(0.515 8±0.018 9和0.244 3±0.042 3)(P0.05)。结论同型半胱氨酸能干扰胰岛素样生长因子2和H19的表达,并可能进一步促进血管平滑肌细胞的增殖。     

罗格列酮抑制体外培养大鼠血管平滑肌细胞的增殖和迁移作用

目的 探讨罗格列酮对大鼠主动脉平滑肌细胞增殖及迁移行为的影响.方法 组织贴块法原代培养大鼠主动脉平滑肌细胞,胞浆内免疫组织化学染色鉴定细胞.取第5代纯化细胞无血清培养使细胞同步,用血小板源性生长因子BB或碱性纤维细胞生长因子诱导细胞增殖和迁移,之前不加或加入罗格列酮(1、5和10μmol/L)进行预处理.应用免疫组织化学染色法检测细胞核内增殖细胞核抗原的表达,流式细胞仪分析细胞周期分布,Boyden趋化小室观测细胞迁移能力.结果 罗格列酮能够显著抑制血小板源性生长因子BB或碱性纤维细胞生长因子诱导的平滑肌细胞核内增殖细胞核抗原的表达,抑制细胞由G0/G1期向S期的转变,抑制细胞在Boyden室间的迁徙,且呈明显的荆量依赖关系(P<0.0001).结论 罗格列酮能够抑制血小板源性生长因子BB或碱性纤维细胞生长因子诱导的血管平滑肌细胞的增殖和迁移.     

血管紧张素转化酶2在香烟提取物诱导的大鼠肺动脉平滑肌细胞增殖中的作用

目的探讨血管紧张素转化酶2(angiotensin-converting enzyme2,ACE2)在香烟提取物(cigarette smoke extract,CSE)诱导的大鼠肺动脉平滑肌细胞(pulmonary artery smooth muscle cells,PASMCs)增殖中的作用。方法分离大鼠PASMCs并培养,加入1μmol/L或10μmol/L氯沙坦(一种特异性的血管紧张素II受体拮抗剂)预处理30min,加入2%CSE处理24h,用CCK-8检测试剂盒检测细胞增殖,Western blotting法检测细胞ACE2蛋白含量。结果 2%CSE能显著诱导大鼠PASMCs增殖,2%CSE处理后细胞表达ACE2水平较对照组明显降低;经过10μmol/L氯沙坦预处理的大鼠PASMCs增殖较单纯用2%CSE处理的细胞增殖减慢,但细胞ACE2表达水平相对升高。结论 CSE能诱导大鼠PASMCs增殖,这可能与CSE降低细胞ACE2表达水平有关,因此ACE2在吸烟引起的肺血管重构中可能具有保护作用。     

辣椒素通过抑制肾小管间质纤维化改善高盐诱导肾脏损害的作用

目的探讨辣椒素对高盐诱导肾小管间质纤维化(RIF)的作用和机制。方法雄性Wistar大鼠36只,随机分为普食组(n=12,0.5%正常盐饲料)、高盐组(n=12,4%高盐饲料)、辣椒素组(n=12,4%高盐+0.02%辣椒素饲料)。每4周用智能无创鼠尾动脉血压仪测大鼠尾动脉收缩压;24周测定血肌酐、24h尿蛋白、尿视黄醇结合蛋白和尿TH-糖蛋白;HE、Masson染色观察肾髓质形态及纤维化;免疫组化法及Western-blot法检测肾髓质区瞬时受体电位通道香草醛亚型1(TRPV1)、转化生长因子β_1(TGF-β_1)、p-Smad2/3、α平滑肌肌动蛋白(α-SMA)、波形蛋白、Ⅰ型胶原、Ⅲ型胶原蛋白表达。结果与普食组相比,高盐组大鼠血压升高[(138.9±6.8)比(107.8±7.6)mm Hg,P0.05],RIF指数明显增高(23.55±2.23比11.30±1.26,P0.05),24h尿蛋白、视黄醇结合蛋白明显增高,TH-糖蛋白降低;肾脏髓质区TRPV1表达降低,TGF-β_1、α-SMA、p-Smad2/3、波形蛋白、Ⅰ型胶原、Ⅲ型胶原蛋白表达增高。辣椒素干预后,大鼠尾动脉收缩压较高盐组明显降低[(119.5±8.3)比(138.9±6.8)mm Hg,P0.05],RIF指数明显降低(15.65±1.72比23.55±2.23,P0.05),24h尿蛋白、视黄醇结合蛋白降低,TH-糖蛋白排泄增高,肾髓质TRPV1表达明显增加,TGF-β_1、α-SMA、p-Smad2/3、波形蛋白、Ⅰ型胶原、Ⅲ型胶原蛋白表达显著降低(均P0.05)。结论长期高盐摄入可诱导Wistar大鼠RIF,辣椒素可能通过激活TRPV1,抑制RIF,改善高盐诱导的高血压肾脏损伤。     

萘哌地尔衍生物YMⅢ对血管紧张素Ⅱ诱导大鼠胸主动脉平滑肌细胞增殖的抑制作用

目的 研究萘哌地尔衍生物YMⅢ对血管紧张素Ⅱ诱导Wistar大鼠和自发性高血压大鼠胸主动脉平滑肌细胞增殖的抑制作用及机制.方法 将Wistar大鼠和自发性高血压大鼠胸主动脉平滑肌细胞进行体外培养,采用四甲基偶氮唑盐比色法检测YMⅢ对胸主动脉平滑肌细胞和血管紧张素Ⅱ诱导胸主动脉平滑肌细胞增殖的影响;用实时逆转录聚合酶链反应技术检测血管紧张素原、c-myc mRNA表达.结果 未经血管紧张素Ⅱ处理的胸主动脉平滑肌细胞.0.1 μmol/L YMⅢ能抑制Wistar大鼠和自发性高血压大鼠胸主动脉平滑肌细胞增殖;YMⅢ(0.01、0.05、0.1 μmol/L)能呈浓度依赖性抑制血管紧张素Ⅱ所致Wistar大鼠和自发性高血压大鼠胸主动脉平滑肌细胞的增殖;YMⅢ(0.05～0.1 μmol/L)作用能使血管紧张素Ⅱ所致Wistar大鼠血管紧张素原、c-myc mRNA表达水平下调,而各浓度YMⅢ均能下调血管紧张素Ⅱ所致自发性高血压大鼠胸主动脉平滑肌细胞的血管紧张素原、c-myc mRNA表达.结论 YMⅢ明显抑制血管紧张素Ⅱ诱导大鼠胸主动脉平滑肌细胞的增殖,且抑制增殖作用在自发性高血压大鼠比在Wistar大鼠明显,其作用机制可能与下调血管紧张素原、c-myc mRNA的表达有关.     

碱性成纤维细胞生长因子在烟草烟雾诱导大鼠血管平滑肌细胞增殖中的作用

目的探讨烟草烟雾提取物对大鼠血管平滑肌细胞增殖的影响及碱性成纤维细胞生长因子在其中的作用。方法按不同浓度烟草烟雾提取物(0、2.5%、5%、10%和20%)分为对照组、低浓度、中等浓度、高浓度和过高浓度烟草烟雾提取物组刺激血管平滑肌细胞,采用MTT法观察细胞增殖变化,免疫细胞化学法测定碱性成纤维细胞生长因子和增殖细胞核抗原蛋白的表达,同时用逆转录-聚合酶链反应法检测碱性成纤维细胞生长因子mRNA表达。用筛选出的最适烟草烟雾提取物浓度处理大鼠血管平滑肌细胞不同时间(0、4、8、12 h和24 h)后,检测碱性成纤维细胞生长因子mRNA及碱性成纤维细胞生长因子和增殖细胞核抗原蛋白的变化。用碱性成纤维细胞生长因子抗体和最适浓度烟草烟雾提取物干预血管平滑肌细胞24 h后检测细胞增殖及碱性成纤维细胞生长因子和增殖细胞核抗原蛋白表达的变化。结果 (1)与对照组相比,低浓度烟草烟雾提取物组(P0.05)和中浓度组血管平滑肌细胞增加明显(P0.01),而高浓度组和过高浓度组与对照组比较差异无显著性(P0.05)。碱性成纤维细胞生长因子mRNA、蛋白和增殖细胞核抗原蛋白在对照组中有少量表达,低浓度烟草烟雾提取物组表达增加(P0.01),中浓度烟草烟雾提取物组达到高峰,高浓度和过高浓度烟草烟雾提取物组仍高于对照组(P0.01)。(2)对照组(不加烟草烟雾提取物组即0 h组)血管平滑肌细胞中有少量碱性成纤维细胞生长因子mRNA、蛋白和增殖细胞核抗原蛋白表达。低浓度烟草烟雾提取物刺激4 h后细胞内碱性成纤维细胞生长因子mRNA、蛋白和增殖细胞核抗原蛋白表达增加(P0.01),碱性成纤维细胞生长因子mRNA于8 h达高峰;碱性成纤维细胞生长因子和增殖细胞核抗原蛋白于12 h达高峰。(3)碱性成纤维细胞生长因子抗体可显著抑制5%烟草烟雾提取物诱导的血管平滑肌细胞增殖和碱性成纤维细胞生长因子、增殖细胞核抗原蛋白表达增加。结论低浓度和中浓度烟草烟雾提取物对大鼠血管平滑肌细胞的促增殖作用逐渐增加;高浓度和过高浓度组时促增殖作用反而减弱。烟草烟雾提取物可能是通过增加碱性成纤维细胞生长因子的表达促进大鼠血管平滑肌细胞的增殖。     

利拉鲁肽经AMPK途径对平滑肌细胞KCa3.1蛋白表达的影响

目的探讨利拉鲁肽经激活腺苷酸活化的蛋白激酶(AMPK)途径对平滑肌细胞KCa3.1蛋白表达的影响。方法制备SD大鼠血管平滑肌细胞模型,大鼠主动脉平滑肌细胞采用利拉鲁肽进行干预,测定未加入利拉鲁肽及加入利拉鲁肽15 min后磷酸化AMPK(PAMPK)/AMPK比值。将平滑肌细胞分为4组培养:A组为正常组,B组采用血管紧张素Ⅱ100 nmol/L,C组采用利拉鲁肽1μmol/L+血管紧张素Ⅱ100 nmol/L,D组采用利拉鲁肽1μmol/L+AMPK阻滞剂4μmol/L+血管紧张素Ⅱ100 nmol/L。培养72 h后使用Western-Blotting检测KCa3.1蛋白表达。结果显微镜下可见细胞呈长梭状、三角状,α-actin细胞免疫荧光染色后,胞浆着色为红色,确认为血管平滑肌细胞。利拉鲁肽与大鼠血管平滑肌作用15 min后,与基线比较PAMPK水平明显上升,PAMPK与AMPK比值明显上调,差异有统计学意义(P0.05)。C组平滑肌细胞KCa3.1蛋白表达较B组下降(P0.05)。结论利拉鲁肽可激活AMPK细胞通路,抑制平滑肌细胞上KCa3.1蛋白表达。     

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.