培哚普利改善糖尿病大鼠急性心肌梗死后内皮祖细胞动员

目的 观察培哚普利对糖尿病大鼠急性心肌梗死后骨髓内皮祖细胞动员和血管新生障碍的影响,并探讨其可能的分子机制.方法 高脂饮食联合小剂量链脲霉素诱导雄性SD大鼠糖尿病模型,成模4周后结扎冠状动脉左前降支造成急性心肌梗死模型.术后将大鼠随机分至培哚普利治疗组和模型组(各组n=15).流式细胞术检测术前及术后不同时间点(1、3、5、7、14和28天)外周血CD45-/low+CD133+ KDR+内皮祖细胞数量,ELISA法检测不同时间点血浆血管内皮生长因子水平.CD31免疫荧光染色法评估心肌梗死1个月后心肌梗死周围区血管新生情况.超声心动图评估心功能改变.免疫印迹法测定骨髓细胞中内皮祖细胞动员相关通路蛋白的表达.结果 培哚普利治疗可显著改善糖尿病时缺血诱导的内皮祖细胞动员障碍,使循环内皮祖细胞峰值明显升高(103±37个/106单核细胞比58±19个/106单核细胞,P＜0.05),同时伴有血浆血管内皮生长因子水平升高,骨髓内皮祖细胞动员通路的信号分子蛋白激酶B与内皮型一氧化氮合酶磷酸化增加以及基质金属蛋白酶9的表达升高(P＜0.05).与模型组相比,培哚普利治疗后糖尿病大鼠心肌梗死周围区新生毛细血管密度显著增加,射血分数及左心室短轴缩短率明显改善(所有P＜0.05).结论 培哚普利能改善糖尿病大鼠缺血诱导的骨髓内皮祖细胞动员障碍,增加缺血区血管新生,最终改善心功能.这种作用可能通过活化骨髓内皮祖细胞动员相关通路介导.     

基质细胞衍生因子1α促进大鼠骨髓源性内皮祖细胞血管样结构形成

目的观察基质细胞衍生因子1α对体外培养的大鼠骨髓源性内皮祖细胞血管样结构形成的影响。方法微孔法获取大鼠骨髓内皮祖细胞,采用免疫荧光鉴定内皮祖细胞特异性标记物VEGFR-2/CD133。1、10和100μg/L基质细胞衍生因子1α以及100μg/L基质细胞衍生因子1α+CXCR4拮抗剂AMD3100共处理内皮祖细胞,采用细胞培养、MTT等方法检测内皮祖细胞血管样结构形成和细胞增殖能力。结果体外培养的大鼠骨髓源性内皮祖细胞出现典型铺路石形状及血管样结构,与此同时内皮祖细胞分化成熟,表达内皮细胞特异性标记物vWF。MTT法检测发现,10和100μg/L基质细胞衍生因子1α处理组的OD值(分别为0.813±0.056和1.029±0.078)与对照组(0.591±0.054)比明显升高(P<0.01),而100μg/L基质细胞衍生因子1α+AMD3100组OD值(0.607±0.077)与对照组比差异无显著性,与100μg/L基质细胞衍生因子1α组比较明显降低(P<0.01)。100μg/L基质细胞衍生因子1α处理组血管样结构长度是对照组的近6倍(10.890±0.360比1.930±0.279,P<0.01),10...     

基质细胞衍生因子1α对大鼠骨髓源内皮祖细胞迁移的影响

目的观察基质细胞衍生因子1α对体外培养的大鼠骨髓源内皮祖细胞迁移的影响。方法微孔法从大鼠骨髓提取内皮祖细胞。免疫荧光鉴定血管内皮生长因子受体2和CD133,不同浓度基质细胞衍生因子1α处理内皮祖细胞后,采用Transwell迁移系统检测内皮祖细胞迁移能力。结果分离出的大鼠骨髓内皮祖细胞免疫荧光下血管内皮生长因子受体2 和CD133 双阳性,基质细胞衍生因子1α呈浓度依赖性促进内皮祖细胞迁移,对照组与基质细胞衍生因子1α各处理组比较差异均具显著性(P<0.05或P<0.01)。结论基质细胞衍生因子1α呈浓度依赖性促大鼠骨髓源内皮祖细胞迁移。     

静脉注射携带缺氧诱导因子的内皮祖细胞对裸鼠缺血下肢血管新生的作用

目的探讨静脉注射携带缺氧诱导因子1α的内皮祖细胞对裸鼠缺血下肢血管新生的作用及机制。方法在体外将腺病毒介导人缺氧诱导因子1α基因入人外周血内皮祖细胞,观察转染后的内皮祖细胞在裸鼠缺血下肢局部的促血管新生作用,并探讨其可能的作用机制。结果转染腺病毒—缺氧诱导因子1α后的内皮祖细胞在细胞内有效并持续表达;移植异种腺病毒—缺氧诱导因子1α内皮祖细胞至Balb/c鼠缺血下肢后可见外源性内皮祖细胞定向作用于缺血部位;移植腺病毒—缺氧诱导因子1α内皮祖细胞组较对照组明显促进体内毛细血管数目增加(P<0.05);mRNA检测提示过表达缺氧诱导因子1α基因可上调其下游的基质细胞衍生因子、CXCR4因子(P<0.05),增加内皮祖细胞招募,同时促血管内皮生长因子水平上调(P<0.05)。结论在体内,转染腺病毒—缺氧诱导因子1α的内皮祖细胞可促进缺血下肢的局部血管新生,这种内皮祖细胞数量的增加可能与基质细胞衍生因子、CXCR4的招募及血管内皮生长因子的分泌增加有关。     

胰岛素对糖尿病小鼠缺血诱导的血管新生障碍的影响

目的 观察糖尿病小鼠是否存在缺血诱导的血管新生障碍,以及胰岛素治疗对这种障碍的影响,并探讨其可能的分子机制.方法 链脲霉素诱导C57BL/6 雄鼠糖尿病,非糖尿病组给予等量缓冲液,糖尿病胰岛素治疗组术前及术后注射胰岛素控制血糖.左侧股动脉高位结扎离断造成单侧后肢缺血模型.ELISA法测定术前及术后(1、3、7及14天)血浆血管内皮生长因子(VEGF)及间充质衍生因子1α(SDF-1α)水平.CD31免疫组织化学染色法评估术前及术后(7、14天)双侧后肢血管新生情况.免疫印迹法测定腓肠肌组织血管内皮生长因子、内皮型一氧化氮合酶(eNOS)、蛋白激酶B(Akt)及其磷酸化产物的蛋白表达.结果 与非糖尿病组比较,糖尿病组小鼠缺血组织新生毛细血管密度显著减少(术后7天7.65±1.74比18.22±3.77, P<0.05),并伴随缺血诱导的血浆血管内皮生长因子及间充质衍生因子1α释放受抑(P<0.01),靶组织血管内皮生长因子蛋白表达上调受抑,蛋白激酶B及内皮型一氧化氮合酶磷酸化减弱(P<0.05),胰岛素治疗明显改善糖尿病动物组织缺血后血管新生程度(15.36±2.14比7.65±1.74,P<0.05),提高血浆血管内皮生长因子及间充质衍生因子1α释放水平(P<0.01),并增强缺血组织血管内皮生长因子及其下游信号分子的表达与活化(P<0.05).结论 胰岛素治疗有效改善糖尿病动物缺血诱导的血管新生障碍,其可能是通过恢复受损的SDF-1/VEGF/Akt/eNOS信号通路活化而介导.     

氨氯地平对糖尿病大鼠心肌梗死后骨髓内皮祖细胞动员及血管新生的改善作用

目的：观察氨氯地平对糖尿病大鼠心肌梗死（心梗）后骨髓内皮祖细胞(EPC)动员和血管新生障碍的改善作用以及对心功能的影响,并探讨其可能的分子机制。
　　方法：180~200g SPF级雄性Sprague-Dawley大鼠60只随机分为两部分：糖尿病大鼠（n=40）给予高脂饲料饲养四周后,腹腔注射30 mg/kg链脲佐菌素;非糖尿病大鼠(n=20)为正常饮食饲养。40只糖尿病大鼠结扎冠状动脉左前降支造成急性心梗模型。术后将大鼠随机分成对照组(n=20),每日予以0.5%羧甲基纤维素钠溶剂1ml灌胃,治疗组(n=20)每日予以氨氯地平2 mg/kg灌胃,继续高脂喂养四周。流式细胞术检测术前及术后不同时间点（第1、3、5、7、14和28 d）外周血CD45-/low+/CD133+/KDR+早期EPC数量,酶联免疫吸附法检测血浆血管内皮生长因子(VEGF)水平。CD31免疫荧光染色法评估心梗周围区血管新生情况。超声心动图评估心功能。免疫印迹法测定骨髓细胞中EPC动员相关信号通路蛋白的表达。
　　结果：外周血CD45-/low+/CD133+/KDR+ EPC水平术后峰值治疗组（第7 d,112±30/106单核细胞）较对照组（第5 d,55±10/106单核细胞）升高;血浆VEGF水平在心梗后峰值治疗组[第7 d ,（5.63±1.33）ng/L]较对照组[第5 d,(3.68±0.98) ng/L]升高;骨髓细胞蛋白激酶B与内皮型一氧化氮合酶的活化水平及基质金属蛋白酶-9的表达增加;心梗周围区新生毛细血管密度治疗组大鼠较对照组显著增加,左心室射血分数及左心室短轴缩短率明显提高。上述比较差异均有统计学意义（P<0.05~0.01）。
　　结论：氨氯地平治疗改善糖尿病大鼠缺血诱导的骨髓EPC动员障碍,缺血区血管新生以及心梗后心功能。这种作用可能通过改善VEGF/内皮型一氧化氮合酶信号通路活化而介导。     

胰岛素改善糖尿病小鼠骨髓内皮祖细胞动员障碍研究

目的:探讨胰岛素对糖尿病小鼠骨髓内皮祖细胞(EPC)动员的影响及其机制.方法:链脲霉素诱导C57BL/6雄鼠糖尿病,随机分为非糖尿病组、糖尿病组和糖尿病胰岛素治疗组(胰岛素组)3组(各组n=32).入组小鼠饲养2个月后行左侧股动脉高位结扎离断术造成急性单侧后肢缺血模型.胰岛素组皮下注射胰岛素控制血糖.流式细胞术检测术后(0,1,3,7天,n=6-10)外周血单个核细胞中干细胞因子受体/干细胞抗原-1/胎肝激酶-1阳性早期EPC比例.酶联免疫吸附法测定血浆及骨髓血管内皮生长因子(VEGF)及间充质衍生因子1α(SDF-1α)水平.免疫印迹法测定骨髓VEGF、蛋白激酶B、内皮一氧化氮合酶及基质金属蛋白酶-9的蛋白表达及磷酸化水平,酶谱法测定基质金属蛋白酶-9酶活性.结果:糖尿病组呈现缺血诱导的骨髓EPC动员障碍,动员高峰期其外周血早期EPC数量较非糖尿病组显著减少(P<0.01);并伴随血浆及骨髓VEGF及SDF-1α释放减少(P<0.01);骨髓VEGF蛋白表达受抑制、蛋白激酶B与内皮一氧化氮合酶磷酸化减弱及基质金属蛋白酶-9酶活性受损(P<0.05),差异均有统计学意义.胰岛素组缺血术后骨髓EPC动员能力、VEGF及SDF-1α释放水平及骨髓蛋白激酶B/内皮一氧化氮合酶/基质金属蛋白酶-9信号通路活化水平较糖尿病组均明显提高(P<0.05),差异均有统计学意义.结论:胰岛素改善糖尿病动物缺血诱导的骨髓EPC动员障碍,这种作用可能通过恢复受损的SDF-1α/VEGF信号通路活化而介导.     

血管内皮细胞生长因子与冠状动脉狭窄及侧支循环的关系

目的探讨急性心肌梗死患者血浆中血管内皮细胞生长因子的含量与冠状动脉狭窄程度及侧支循环形成的关系。方法对76例急性心肌梗死患者于入院后3~7天及6个月分别进行冠状动脉造影检查,确定冠状动脉狭窄的程度及有无侧支循环形成;于首次冠状动脉造影检查时采血5mL,采用酶联免疫吸附法检测血浆中血管内皮细胞生长因子含量。结果冠状动脉狭窄程度<50%、50%~75%和>75%的患者血浆血管内皮细胞生长因子含量分别为97.6±17.3ng/L、241.6±28.9ng/L和391.7±48.4ng/L,不同冠状动脉狭窄程度的血浆血管内皮细胞生长因子含量比较差异有统计学意义(P<0.01);24例有侧支循环形成的患者与52例无侧支循环形成的患者血浆中血管内皮细胞生长因子含量分别为410.3±42.9ng/L和220.9±105.2ng/L,两组比较差异有统计学意义(P<0.01)。结论急性心肌梗死患者血浆中血管内皮细胞生长因子的含量愈高,冠状动脉狭窄程度愈重,愈有利于侧支循环的形成。     

急性冠脉综合征患者内皮祖细胞及C反应蛋白的变化

目的:观察急性冠脉综合征(ACS)患者外周血中内皮祖细胞(EPCs)及C反应蛋白的变化。方法:入选40例ACS(不稳定型心绞痛18例、急性心肌梗死22例)患者与20例行冠状动脉造影术排除冠心病的正常人(正常对照组),取所有研究对象外周血100μl分别加入CD34-PE、AC133-异硫氰酸荧光素(FITC)荧光抗体使与EPCs表面CD34、AC133抗原结合,通过流式细胞仪检测PE、FITC阳性细胞的数量。同时检测高敏C反应蛋白(hsCRP)浓度。结果:与正常对照组比较,不稳定型心绞痛、急性心肌梗死患者外周血中EPCs数量显著增多[(0.48±0.04)%比(0.84±0.31)%比(1.57±0.62)%,P<0.001],hsCRP浓度明显升高[(0.63±011)mg/L比(7.8±0.59)mg/L比(11.2±0.46)mg/L,P<0.001],且上述指标在急性心肌梗死组明显高于不稳定心绞痛组(P<0.001),所有患者外周血中EPCs数量与hsCRP浓度正相关(r=0.82,P<0.001)。结论:急性冠脉综合征患者外周血中内皮祖细胞数量显著增多,可能与炎症因子激活骨髓干细胞分化为内皮祖细胞,参与血管修复有关。     

内皮抑素和血管内皮生长因子与2型糖尿病大血管病变的关系

目的探讨内皮抑素和血管内皮生长因子与2型糖尿病大血管病变发生的关系。方法用酶联免疫吸附测定法检测100例2型糖尿病患者(34例2型糖尿病无合并症、40例伴发一种大血管病变、26例伴发多种大血管病变)和30例正常对照者血清内皮抑素和血管内皮生长因子表达水平的变化。结果内皮抑素和血管内皮生长因子在2型糖尿病大血管病变各组(包括合并一种大血管病变组、合并两种以上大血管病变组)血清含量分别显著高于2型糖尿病无合并症和正常对照组(内皮抑素为32.4±15.6μg/L和35.1±20.2μg/L比11.2±8.6μg/L和9.9±6.7μg/L;血管内皮生长因子为133.5±36.8ng/L和302.1±52.4ng/L比90.2±42.4ng/L和81.3±33.5ng/L,P<0.01),两者在正常对照和2型糖尿病无合并症组间比较差异不显著;血管内皮生长因子在伴发一种大血管病变、多种大血管病变组间比较表达水平显著上调(133.5±36.8ng/L比302.1±52.4ng/L,P<0.01),而内皮抑素的表达差异不显著;在2型糖尿病伴发一种大血管病变组,内皮抑素和血管内皮生长因子成显著正相关(r=0.540,P<0.01)。结论血管内皮生长因子的表达水平与2型糖尿病大血管病变程度密切相关,内皮抑素和血管内皮生长因子可能以自稳态调节机制参与动脉粥样硬化的发生和发展。     

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.