二甲双胍对人胰腺癌细胞迁移的抑制作用

目的:研究二甲双胍对胰腺癌细胞迁移的影响,并初步探讨可能机制.方法:体外培养人胰腺癌细胞株Bxpc-3,予二甲双胍进行干预作为实验组(M组),无药物组作为对照组(C组).MTT检测二甲双胍对Bxpc-3细胞存活率的影响,细胞划痕实验检测划痕愈合率,RT-PCR检测MMP-2、MMP-9 mRNA的表达,Elisa检测细胞培养上清液MMP-2、MMP-9蛋白的分泌量.结果:与对照组相比,MTT结果示二甲双胍可以抑制人胰腺癌细胞株Bxpc-3的增殖,并呈时间-浓度依赖性(F=8.991,124,114.61,P<0.01);划痕实验示二甲双胍干预组12、24、48h与对照组相比划痕愈合率显著下降(t=7.683,9.013,10.471,P<0.01);RT-PCR示二甲双胍干预组MMP-2、MMP-9mRNA的表达显著降低(t=16.563,28.494,P<0.01);Elisa示二甲双胍干预组MMP-2、MMP-9蛋白分泌明显下降(t=9.428,13.542,P<0.01).结论:二甲双胍能显著抑制人胰腺癌细胞株Bxpc-3的增殖及迁移,其主要机制可能与抑制MMP-2、MMP-9活性有关.     

二甲双胍联合顺铂对人肺癌裸鼠移植瘤治疗作用的研究

目的 研究二甲双胍联合常用的化疗药物顺铂对于人肺癌裸鼠移植瘤的抑瘤作用及对生存素(Survivin)、基质金属蛋白酶2(MMP-2)和Ki67分子表达的影响,致力于探索治疗肺癌的新的有效药物.方法 建立肺癌裸鼠移植瘤模型,将裸鼠随机分为二甲双胍组、顺铂组、二甲双胍联合顺铂组及对照组,给药42 d后,处死动物,留取肿瘤组织,免疫组织化学法及实时荧光定量PCR法检测肿瘤组织中Survivin、MMP-2和Ki67蛋白及mRNA的表达.结果 二甲双胍组、顺铂组和二甲双胍联合顺铂组抑瘤率分别为28.97％、35.34％和54.65％.与对照组比较,顺铂组及二甲双胍联合顺铂组Survivin、MMP-2和Ki67蛋白及mRNA表达水平均降低(P值均＜0.05),二甲双胍组MMP-2蛋白及mRNA表达水平降低(P值均＜0.05);与二甲双胍组、顺铂组比较,二甲双胍联合顺铂组Survivin、MMP-2和Ki67蛋白及mRNA表达水平均降低(P值均＜0.05).结论 二甲双胍组可抑制MMP-2的表达,顺铂组及二甲双胍联合顺铂组均可抑制Survivin、MMP-2和Ki67的表达,二甲双胍和顺铂联合应用可以增强抗肿瘤的疗效.     

二甲双胍抑制人胰腺癌细胞株Patu8988的增殖

二甲双胍孵育胰腺癌细胞株Patu8988 72 h后应用CCK-8(Cell counting Kit-8)检测细胞增殖,流式细胞仪分析细胞周期,RT-PCR检测相关基因表达.干预后细胞增殖呈浓度依赖性抑制(r=0.994.,P＜0.05),细胞周期G0/G1期所占比例显著增加,G2/M期显著减少(均P＜0.05),相关基因MMP-3、CyclinD1、p53表达下调,Bax表达上调.结果表明二甲双胍抑制Patu8988细胞增殖,主要机制可能与阻滞细胞周期、影响相关基因表达有关.     

高铁环境对成骨细胞生物活性的影响

目的探讨高铁环境对人成骨细胞(hFOB1.19)活性指标的影响。方法采用细胞贴壁法培养成骨细胞(hFOB1.19)后,将不同浓度枸橼酸铁铵(50、100、200μmol/L)加入细胞培养基,用MTT法检测成骨细胞增生活性;碱性磷酸酶活性试剂盒检测碱性磷酸酶活性;流式细胞仪检测成骨细胞凋亡情况;Vonkossa染色法行钙结节染色;用RT-PCR和Western blotting分别检测Ⅰ型胶原(COL1)的基因及蛋白表达变化。结果用不同浓度枸橼酸铁铵干预成骨细胞后,与对照组相比,48 h与72 h组成骨细胞增生活性呈剂量依赖性降低,差异有统计学意义(P0.05);48 h组成骨细胞凋亡率呈浓度依赖性升高,与对照组比较差异有统计学意义(P0.05);不同浓度枸橼酸铁铵干预10 d和14 d时各组成骨细胞碱性磷酸酶活性均随枸橼酸铁铵浓度增高而降低,差异有统计学意义(P0.05);与对照组相比,枸橼酸铁铵干预17 d后钙结节染色结果显示,矿化面积和钙结节形成随铁离子浓度增加而减少;枸橼酸铁铵干预3 d后呈剂量依赖性下调Ⅰ型胶原基因和蛋白的表达。结论高铁环境使成骨细胞成骨活性指标均受到抑制。     

重组人结缔组织生长因子对人成骨细胞增殖、分化及凋亡的影响

目的 研究重组人结缔组织生长因子(rCTGF)对人成骨细胞增殖、分化及凋亡的影响.方法 用rCTGF干预体外培养的人成骨细胞,采用[3H]-TdR掺入法检测人成骨细胞增殖率,α-磷酸萘酚法测定细胞内碱性磷酸酶活性变化,放射免疫法测定骨钙素含量的变化,Western印迹法检测Ⅰ型胶原表达的变化,应用流式细胞仪检测rCTGF埘成骨细胞凋亡的影响.结果 rCTGF呈剂量依赖性促进人成骨细胞增殖,200 ng/ml rCTGF达最大效应;rCrrGF干预显著促进人成骨细胞分化,rCTGF旱剂量依赖性增加Ⅰ型胶原、骨钙素表达及碱件磷酸酶活性;rCTGF干预可显著减少成骨细胞凋亡.结论 rCTGF可显著促进人成骨细胞增殖、分化,并抑制人成骨细胞凋亡.     

糖尿病大鼠肾脏组织TGF-β1和MMP-2的表达及丹红注射液的干预作用

目的探讨糖尿病大鼠肾脏组织中转化生长因子(TGF)-β1和基质金属蛋白酶(MMP)-2的表达及丹红注射液的干预作用。方法 48只8周龄雄性SD大鼠中随机抽取12只为正常对照组,剩余为造模组。用腹腔注射链脲佐菌素(55 mg/kg)的方法造模,正常对照组按等量腹腔注射枸橼酸缓冲液,造模成功后分为糖尿病对照组、丹红注射液干预组以及二甲双胍治疗组,每组12只,药物干预共持续8 w,在8 w后测定大鼠体重,其中正常对照组以及糖尿病对照组在实验过程中每日腹腔注射蒸馏水2 ml/kg,丹红注射液干预组每日腹腔注射丹红注射液2 ml/kg,二甲双胍治疗组用蒸馏水配制的(300 mg/kg)灌胃;大鼠麻醉后从腹主动脉采集血液标本检测空腹血糖(FPG)、总胆固醇(TC)、甘油三酯(TG)、尿素氮(BUN)、血肌酐(SCr)水平;用代谢笼收集大鼠24 h尿量,用全自动生化分析仪检测大鼠尿蛋白,采用HE染色观察肾组织的病理变化;实时定量PCR检测肾组织中TGF-β1和MMP-2 mRNA表达;免疫组化检测肾组织中TGF-β1和MMP-2的蛋白表达。结果实验至第8周末,三组造模组大鼠的体重均低于正常对照组,而造模组之间体重差异无统计学意义(P>0.05)。造模组大鼠的FPG较正常对照组明显升高(P<0.05);造模组大鼠的TC、TG、BUN、SCr水平较正常对照组明显升高,其中丹红注射液干预组及二甲双胍治疗组大鼠的TC、TG较糖尿病对照组明显降低(P<0.05);HE染色发现造模组大鼠的肾小球肥大增生,肾小囊的囊腔缩小,其中丹红注射液干预组和二甲双胍治疗组大鼠肾组织病变的程度较糖尿病对照组有改善;造模组大鼠24 h尿量明显高于正常对照组,但是造模组之间差异无统计学意义(P>0.05);尿蛋白较正常对照组明显升高(P<0.05),其中丹红注射液干预组和二甲双胍治疗组大鼠较糖尿病对照组明显下降;造模组大鼠肾组织中TGF-β1 mRNA及蛋白水平较正常对照组明显增高,而丹红注射液干预组及二甲双胍治疗组中TGF-β1的表达量相对糖尿病对照组减少(P<0.05);造模组大鼠肾组织中的MMP-2 mRNA及蛋白水平较正常对照组明显降低,而丹红注射液干预组及二甲双胍治疗组中MMP-2相对糖尿病对照组增加(P<0.05)。结论 DN的发生发展可能与TGF-β1的过度表达和MMP-2低表达有关,丹红注射液可以通过抑制TGF-β1和促进MMP-2的表达改善糖尿病大鼠肾功能。     

铁离子对人成骨细胞(hFOB1.19)生物活性影响

目的探讨铁离子对成骨细胞株(hFOB1.19)生物活性,包括碱性磷酸酶活性(alkaline phosphatase activity,APA)、细胞凋亡、钙结节、Ⅰ型胶原(type 1 collagen,COL 1)和骨钙素(osteocalcin,OC)的影响。方法成骨细胞(hFOB1.19)于5%CO234℃培养箱内培养,将不同浓度枸橼酸铁铵(ferric ammonium citrate,FAC)50、100、200μmol/L和去铁胺(deferoxamine,DFO)5、10、20μmol/L分别加入细胞培养基中,MTT法检测成骨细胞增生活性;碱性磷酸酶活性试剂盒检测碱性磷酸酶活性;流式细胞仪检测细胞凋亡;Von kossa染色法行钙结节染色;RT-PCR和Western blotting法分别检测COL1和骨钙素(bone gla protein,BGP)的基因及蛋白表达。结果 (1)48 h后增生活性:FAC组细胞增生活性随FAC干预浓度的增加呈剂量依赖性降低(P0.05),DFO组在5μmol/L浓度组时促进成骨细胞增生,在10、20μmol/L浓度组时抑制成骨细胞增生。(2)10 d时碱性磷酸酶活性:FAC组碱性磷酸酶活性随FAC干预浓度的增加而降低,DFO组碱性磷酸酶活性随DFO干预浓度的增加而升高(P0.05);(3)48 h时凋亡:FAC组细胞凋亡率呈剂量依赖性升高(P0.05),DFO组在5、10μmol/L浓度时抑制细胞凋亡(P0.05),在20μmol/L则促进成骨细胞凋亡(P0.05);(4)21 d时钙结节染色:FAC组随铁离子干预浓度增加,成骨细胞矿化面积、钙结节形成数量均减少,DFO组在5、10μmol/L浓度时促进成骨细胞矿化功能,而20μmol/L浓度时对成骨细胞矿化有抑制效应;(5)3 d时基因及蛋白表达:FAC组COL1、BGP基因和蛋白的表达呈剂量依赖性下调(P0.05);DFO组COLⅠ、BGP基因的表达呈剂量依赖性上调(P0.05),DFO在5、10μmol/L浓度时促进COL1、BGP蛋白表达,在20μmol/L浓度时抑制COL1、BGP蛋白表达。结论不同浓度枸橼酸铁铵均抑制成骨细胞功能活性,提示高铁环境不利于成骨细胞的成骨功能。低铁环境对成骨细胞有双重效应,低剂量去铁胺对成骨细胞活性有促进作用,而高剂量去铁胺则对成骨细胞活性有抑制效应。     

高胆固醇对成骨细胞MG63增殖的影响

目的探讨胆固醇对成骨细胞MG63增殖的影响及其可能机制。方法体外培养人骨肉瘤细胞(MG63),分别加入0、12.5、25.0、50.0μg/mL的胆固醇,培养24、48、72h,采用MTT方法检测细胞增殖情况;收集细胞裂解液测定细胞碱性磷酸酶(ALP)、超氧化物歧化酶(SOD)、丙二醛(MDA)水平;采用qRT-PCR方法测定MG63细胞骨碱性磷酸酶(BALP)、Ⅰ型胶原(ColA1)、骨形态发生蛋白-2(BMP2)和核结合因子α1(Cbfα1)的基因表达水平。结果培养于含不同浓度胆固醇溶液培养基中的MG63细胞增殖在各时段均被抑制;胆固醇可致成骨细胞ALP、SOD活性降低,MDA水平增加,增加MG63细胞氧化损伤;胆固醇抑制MG63细胞内BALP、Ⅰ型胶原、BMP2和Cbfα1的基因表达。结论高胆固醇血症增加骨质疏松症发病风险可能与游离胆固醇抑制成骨细胞增殖有关。     

铁过载对成骨细胞铁稳态及生物活性的影响

目的了解铁过载对成骨细胞铁稳态及生物活性的影响。方法 34℃条件下体外培养人成骨细胞(hFOB1.19),以不同浓度(50、100、200μmol/L)枸橼酸铁铵(FAC)干预,用RT-PCR检测成骨细胞铁调节基因膜转铁蛋白(FPN1)、转铁蛋白受体(TfR)和二价金属转运蛋白1(DMT1)表达的变化;用激光共聚焦扫描显微镜(CLSM)观察成骨细胞铁离子荧光强度;流式细胞仪检测成骨细胞活性氧(ROS)水平;碱性磷酸酶活性试剂盒检测碱性磷酸酶活性;Vonkossa染色法行钙结节染色。结果与对照组相比,FAC干预48h后FPN1mRNA的表达随FAC干预浓度增加呈剂量依赖性上调,TfR、DMT1mRNA的表达呈剂量依赖性下调(P0.05);FAC干预48h后成骨细胞铁离子荧光强度剂量依赖性减弱,与对照组相比差异有统计学意义(P0.05);48h后成骨细胞ROS水平随FAC干预浓度增加呈剂量依赖性升高(P0.05);FAC干预10d后各组成骨细胞碱性磷酸酶活性均随FAC浓度增高而降低,差异有统计学意义(P0.05);与对照组相比,FAC干预17d后成骨细胞钙结节染色显示矿化面积和钙结节形成随FAC浓度增加而减少。结论铁过载对成骨细胞生物活性有明显抑制作用,其机制可能与细胞内铁离子浓度增加及活性氧水平升高有关。     

二甲双胍通过基质金属蛋白酶抑制血管内皮损伤后的内膜增生

目的 观察二甲双胍对血管内皮损伤后内膜增生的影响,并探讨其可能机制。方法 选用300～350 g的健康雄性SD大鼠45只,随机分为对照组、颈动脉球囊损伤组、颈动脉球囊损伤＋二甲双胍组,3周后HE染色观察内膜增生情况,real-time PCR、Western blot和免疫组织化学染色检测颈动脉组织中基质金属蛋白酶2（MMP-2）、基质金属蛋白酶9（MMP-9）的表达情况。结果 球囊损伤后,颈动脉出现明显的内膜增生,颈动脉组织中MMP-2、MMP-9的mRNA和蛋白表达显著上调（P<0.01）;二甲双胍削弱血管内皮损伤所致MMP-2和MMP-9的表达上调（P<0.05）,并抑制血管内皮损伤后的内膜增生（P<0.01）。结论 二甲双胍可能通过抑制MMP-2和MMP-9的表达防止血管损伤后内膜增生。     

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.     

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。     

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。     

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.