低分子肝素和尿激酶对老年大鼠肾小球内皮细胞损伤保护作用的比较

目的探讨炎症状态下增龄对肾小球内皮损伤的影响，比较低分子肝素和尿激酶对损伤的保护作用。方法3月龄及27月龄雌性Wistar大鼠各40只，随机分为正常对照组（NC组）、脂多糖（LPS）组（L组）、LPS＋氨甲环酸组（LT组）、LPS＋氨甲环酸＋低分子量肝素组（LTH组）及LPS＋氨甲环酸＋尿激酶组（LTUU组）。采用直接免疫荧光检测肾小球纤维蛋白沉积，Western印迹法检测血管内皮血栓调节蛋白（TM），纤溶酶原激活物抑制物1（PAI-1）蛋白质表达。结果（1）LPS刺激后纤维蛋白沉积增多（P〈0．05），TM几乎无表达（P〈0．01），PAI-1表达明显上调（P〈0．05）；（2）加用氨甲环酸后，PAI-1表达进一步上调（P〈0．05）；（3）应用低分子肝素和尿激酶后纤维蛋白沉积明显减轻（P〈0．05），PAI-1表达与LT组比较明显下调（P〈0．05），TM表达增多（P〈0．05），两组之间无统计学差异。（4）老年大鼠各组肾小球纤维蛋白沉积均比相同干预组的青年大鼠明显，PAI-1的表达均较青年大鼠相同干预组显著增多，TM表达则显著减少，差别均有统计学意义（P〈0．05）。结论增龄可加重LPS诱导的肾小球内皮损伤；低分子肝素与尿激酶均能有效保护老年大鼠肾小球血管内皮损伤，两者无明显差别，但增龄可减弱低分子肝素和尿激酶对血管内皮的保护作用。     

调控凝血活性对老年大鼠肺组织炎症反应的影响

目的 通过调控凝血活性,观察老年大鼠肺组织凝血酶受体(PAR-1)表达和纤维蛋白沉积变化与炎症反应之间的关系,探讨高凝状态对老年大鼠肺组织炎症反应的促进机制.方法 雌性Wistar大鼠3月龄(青年鼠)和27月龄(老年鼠)均随机分组,以脂多糖(LPS)腹腔注射诱导大鼠肺组织炎症反应,分别给予氨甲环酸、肝素或尿激酶调控凝血活性,检测PAR-1、细胞间黏附分子1(ICAM-1)表达及单核巨噬细胞浸润、纤维蛋白沉积水平的变化.结果 (1)氨甲环酸可使肺组织纤维蛋白沉积增加,而PAR-1表达无明显变化,浸润的炎细胞数目、ICAM-1的蛋白质表达水平较单独给予脂多糖显著上调(P＜0.05);(2)肝素和尿激酶均可使有炎症反应的肺组织纤维蛋白沉积显著减少,但仅有肝素能使PAR-1表达下调,肝素和尿激酶均可显著减少浸润的炎细胞数目及ICAM-1的蛋白质表达(P＜0.05),且两组下降程度差异无统计学意义(P＞0.05);(3)与相同处理的青年鼠比较,老年鼠肺组织纤维蛋白沉积、PAR-1表达显著增多(P＜0.05),浸润的炎细胞数目、ICAM-1的蛋白质表达水平亦显著增加(P＜0.05).结论 (1)凝血系统激活导致的纤维蛋白沉积和PAR-1表达上调,能够诱导黏附分子表达上调,促进炎症反应,增龄所导致的高凝状态能够促进肺组织纤维蛋白沉积及PAR-1表达,从而加重炎症反应;(2)纤维蛋白与PAR-1相比较,在凝血系统参与调节炎症反应的机制中,可能起着更主要的调节作用.     

调控纤维蛋白水平对不同鼠龄肾脏炎症反应的影响

目的　探讨调控纤维蛋白在不同鼠龄肾脏沉积水平对肾脏炎症反应的影响及其机制。　方法　青年及老年鼠均随机分4组,对照组予生理盐水腹腔注射;脂多糖组腹腔注射脂多糖,氨甲环酸组注射脂多糖加氨甲环酸,尿激酶组注射脂多糖及氨甲环酸加尿激酶。应用激光共聚焦显微镜分析纤维蛋白沉积,应用RT PCR、免疫组化及蛋白质印迹法分别检测肾组织细胞间黏附分子(ICAM 1)基因和蛋白质表达。　结果　(1)青年与老年鼠比较脂多糖、氨甲环酸、尿激酶组纤维蛋白、ICAM 1表达差别均有统计学意义(P<0 05);(2)氨甲环酸组与脂多糖、尿激酶组间比较纤维蛋白、ICAM 1基因及蛋白质表达差异均有统计学意义(P<0 05)。　结论　纤维蛋白可上调ICAM 1基因及蛋白质表达,促进肾脏炎症反应;增龄能促进肾脏纤维蛋白沉积及炎症反应。     

增龄对纤维蛋白急性肺损伤大鼠肺组织单核巨噬细胞趋化因子-1表达的影响

目的研究增龄对纤维蛋白诱导急性肺损伤大鼠肺组织单核巨噬细胞趋化因子-1 (MCP-1)表达的影响,探讨老年大鼠对炎性刺激易感的可能机制。方法青年及老年大鼠均根据腹腔注射不同的药物随机分为4组:对照组、脂多糖组、氨甲环酸组、肝素组。应用免疫组化分析纤维蛋白沉积;应用Western blot和Northern blot方法分别检测肺组织MCP-1蛋白质和基因表达。结果(1)青年和老年对照组大鼠肺组织内均无纤维蛋白沉积,老年大鼠脂多糖组、氨甲环酸组和肝素组均比青年大鼠相同干预组纤维蛋白沉积明显,差别均有统计学意义(18．5％±3．1％对12．3％±2．1％,32．5％±5．4％对24．1％±4．5％和20．8％±3．6％对12．6％±1．8％,均为P<0．05);(2)青年和老年对照组大鼠肺组织内几乎无MCP-1表达,老年大鼠脂多糖组、氨甲环酸组和肝素组的MCP-1表达均较青年大鼠相同干预组上调,差异有统计学意义(0．40±0．02对0．20±0．03,0．60±0．05对0．25±0．04和0．30±0．01对0．20±0．04,均为P<0．05);(3)经纤维蛋白沉积增加量校正后,老年氨甲环酸组大鼠肺组织MCP-1的表达量仍显著高于青年大鼠氨甲环酸组(P<0．05)。结论纤维蛋白可上调急性肺损伤肺组织MCP-1基因及蛋白质表达,促进肺组织炎症反应;增龄能够促进肺组织纤维蛋白沉积,增强其上调肺组织MCP-1表达的作用。     

雷公藤甲素对支气管哮喘小鼠STAT-1与ICAM-1表达的影响

目的 研究雷公藤甲素对支气管哮喘（简称哮喘）小鼠肺组织中信号转导和转录激活因子-1（STAT-1）与细胞间黏附分子-1（ICAM-1）表达的影响,探讨其治疗哮喘的机制.方法 40只雄性昆明小鼠随机分成4组：正常对照组、哮喘组、地塞米松治疗组及雷公藤甲素治疗组,以卵清蛋白致敏和激发方法建立哮喘小鼠动物模型并给予相应治疗.24 d后处死小鼠,检测BALF中白细胞总数及嗜酸粒细胞（EOS）计数;采用逆转录-聚合酶链反应（RT-PCR）方法检测肺组织中STAT-1、ICAM-1 mRNA表达水平;采用免疫组织化学法检测肺组织中STAT-1、ICAM-1蛋白表达水平.结果 哮喘组STAT-1、ICAM-1 mRNA及蛋白表达明显高于正常对照组（P＜0.01）,雷公藤甲素治疗组及地塞米松组明显低于哮喘组（P＜0.01）.肺组织STAT-1蛋白的表达与BALF中白细胞数、EOS计数及肺组织ICAM-1蛋白表达呈正相关（r分别为0.665,0.735,0.677,P＜0.01）.肺组织ICAM-1蛋白表达与白细胞总数、EOS计数呈正相关（r分别为0.792,0.776,P＜0.01）.结论 雷公藤甲素抑制哮喘气道炎症的机制可能与其抑制STAT-1与ICAM-1的表达活性有关.     

尿激酶型纤溶酶原激活物对糖尿病大鼠肾脏系膜基质的影响

目的 探讨尿激酶型纤溶酶原激活物（uPA）对糖尿病大鼠肾脏系膜基质表达的影响及机制.方法 8周龄健康雄性SD大鼠（体质量150～200 g）20只尾静脉注射链脲佐菌素,成功建立糖尿病大鼠模型后采用数字表法随机分为糖尿病组（n=10）和uPA组（n=10;尾静脉注射2500 U·kg^-1·d^-1 uPA,共4周）.另以10只正常大鼠为对照组.29d后处死大鼠,心脏取血检测血糖、血肌酐水平.过碘酸六胺银染色测定肾小球平均面积、肾小球平均容积和肾小球系膜区面积.免疫组织化学法检测肾脏尿激酶型纤溶酶原激活物受体（uPAR）、纤溶酶原激活物抑制剂-1（PAI-1）和Ⅳ型胶原表达水平.采用方差分析和q检验进行数据统计.结果 与正常对照组比较,糖尿病组大鼠明显出现尿蛋白[（25.4±4.3）mg/24 h vs（5.5±2.1）mg/24 h,q=4.27,P＜0.01],肾小球体积及系膜基质显著增加,肾小球系膜uPAR、PAI-1、Ⅳ型胶原表达显著增加（q值分别为3.63、3.97、4.21,均P＜0.05）.糖尿病大鼠注射uPA后,尿蛋白明显减少[（12.6±5.4）mg/24 h,q=3.45,P＜0.05],肾小球体积、系膜基质异常有所改善（q值分别为4.34、4.27,均P＜0.01）,肾小球系膜PAI-1、Ⅳ型胶原表达明显减少（q值分别为3.98、4.17,均P＜0.05）.结论注射uPA可明显降低糖尿病大鼠肾小球PAI-1蛋白表达,对uPAR表达的影响不大,提示uPA可能通过与uPAR结合、摄取PAI-1并加速其降解,从而调节肾小球系膜细胞及其基质表达,改善糖尿病系膜基质病变.     

Celecoxib对急性胰腺炎相关性肺损伤ICAM-1表达的影响

目的探讨Celecoxib对急性胰腺炎相关性肺损伤细胞间黏附分子1（ICAM-1）表达的影响。方法逆行胰胆管注射4%牛磺胆酸钠诱导SD大鼠急性出血坏死性胰腺炎模型（AHNP）。实验随机分为假手术组、AHNP组及Celecoxib预处理组,动态观察3、6和12 h肺组织中丙二醛（MDA）和髓过氧化物酶（MPO）含量,免疫组化检测ICAM-1蛋白表达。结果AHNP组肺组织MDA和MPO含量进行性增加,Celecoxib在各时间点均显著降低了AH-NP大鼠肺组织MPO活性及MDA水平（P〈0.05）;AHNP组ICAM-1表达上调,主要表达于血管内皮细胞,Celecoxib处理后表达显著下调（P〈0.05）。结论Celecoxib抑制ICAM-1的表达,可能是其减轻AHNP大鼠肺组织炎性损伤的重要环节之一。     

糖尿病大鼠PAI-1 mRNA的表达与心肌微血管改变的相关性研究

目的通过研究老龄和青年糖尿病（DM）大鼠心肌微血管数目与心肌组织PAI-1mRNA表达的改变,探讨高血糖和增龄对心肌微血管数目及心肌组织PAI—1mRNA表达的影响。方法老龄和青年SD大鼠分别随机分为DM组和对照组,STZ液腹腔注射建立DM大鼠模型,喂养8周后,处死大鼠,取部分左心室组织进行免疫组化;剩余部分留做心肌组织PAI-1mRNA检测。采用EnVision免疫组化法,CD34抗体检测心肌微血管内皮细胞特异性抗原CD34。利用医学图像分析软件计数心肌微血管数目。实时荧光定量PCR法检测各组心肌组织PAI—1mRNA的表达。结果各年龄段大鼠,DM组心肌微血管数目显著低于同龄段对照组（P〈0．01）,DM组心肌组织PAI-1mRNA的表达与同龄对照组相比则显著增多（P〈0．01）;老龄DM组心肌微血管数目明显低于青年DM组及青年对照组（P〈0．01）,老龄对照组心肌微血管数目与青年对照组无明显统计学差异（P〉0．05）,而老龄DM组心肌组织PAI-1mRNA表达显著高于青年DM组及青年对照组（P〈0．01）;并且老龄对照组心肌PAI-1mRNA的表达也高于青年对照组（P〈0．05）。结论增龄对DM大鼠心肌微血管数目有影响,而对非DM大鼠无明显影响。增龄使大鼠心肌组织PAI-1mRNA表达增强。各年龄段DM大鼠心肌微血管数目减少,心肌组织PAI-1mRNA表达增强。     

不同剂量氨甲环酸对全膝关节置换术后失血量的影响

目的 探讨不同剂量氨甲环酸对全膝关节置换术(TKA)围手术期失血量的影响.方法 选取2010年4月～2012年4月行单侧TKA的90例膝关节骨性关节炎和类风湿性关节炎患者,随机分为氨甲环酸10 mg/kg组、氨甲环酸15 mg/kg组、对照组三组各30例,分别将氨甲环酸分别按10、15 mg/kg的剂量(稀释于250 mL生理盐水后)静滴,3h后,以相同剂量再次给药;对照组予生理盐水250 mL静滴,3h后重复静滴1次.记录各组术后引流量、引流血液回输量、异体输血量、输血人数、输红细胞数,检测术前、术后6h、术后24 h、术后72 h血红蛋白量.结果 氨甲环酸10 mg/kg组、氨甲环酸15 mg/kg组术后引流血量均较对照组明显减少(P＜0.05、P＜0.01),术后6h的回输血量亦明显低于对照组(P ＜0.05、P＜0.01);氨甲环酸10 mg/kg组的术后异体输血量、输血人数较对照组和氨甲环酸15 mg/kg组明显减少(P均＜0.05);氨甲环酸15 mg/kg组有1例术后发生胸部疼痛,经螺旋CT检查发现有肺栓塞,但未危及生命,经抗血栓治疗后症状消失.结论 在TKA后早期使用氨甲环酸能明显降低患者术后失血量和异体输血量,剂量为10 mg/kg更为有效.     

TLR4基因表达及TNF-α在老年大鼠多器官功能障碍综合征中作用的研究

目的探讨Toll样受体4基因（TLR4）与TNF-α在老年大鼠多器官功能障碍综合征（MODSE）发病机制中的作用.方法20月龄和3月龄SD大鼠各40只,分别设为老年组及青年组,予油酸（OA）0.25ml/kg和脂多糖（LPS）3.5mg/kg分次静脉注射（间隔4h）,建立二次打击MODSE和青年多器官功能障碍综合征（MODSY）模型.观察对照组及伤后2、6、24h肺、心、肝、肾的病理改变及功能变化,检测肺、心、肝和肾组织中TLR4 mRNA表达及TNF-α含量.结果OA/LPS二次致伤能够导致青年及老年鼠MODS,其中肺脏损害出现最早最重,在同一时相点,老年鼠脏器损害重于青年鼠（P＜0.05～0.01）.致伤后肺、心、肝和肾组织中TLR4 mRNA表达均显著升高（P＜0.05～0.01）,以肺组织中表达最高,2h达峰值,心、肝、肾组织中于6h达峰值;各组织中TNF-α含量均显著升高（P＜0.05～0.01）,以肺组织中升幅最大.在相同时相点老年鼠各组织中TLR4 mRNA表达及TNF-α含量高于青年鼠（P＜0.05～0.01）.结论OA/LPS致伤后老年鼠肺组织中TLR4 mRNA表达及TNF-α水平迅速升高,在MODS发病机制中起重要作用,有可能是MODSE过程中肺损伤出现最早最重的重要原因.     

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.