缬沙坦与硝苯地平对自发性高血压大鼠左心室肥厚心肌细胞G 蛋白偶联受体激酶2的表达及亚细胞分布的影响

目的 观察缬沙坦及硝苯地平对自发性高血压大鼠(SHR)左心室肥厚心肌细胞G 蛋白偶联受体激酶2(GRK2)的表达及亚细胞分布的影响.方法 选择自发性高血压大鼠(SHR)为研究对象(n=30),随机分为对照组(n=6),低剂量缬沙坦组[L 缬沙坦,10 mg /(kg·d),n=6],高剂量缬沙坦组[H缬沙坦,30 mg /(kg·d),n=6],低剂量硝苯地平组[L 硝苯地平,10 mg /kg,2 次/ d,n=6],高剂量硝苯地平组[H 硝苯地平,30mg /(kg·次),2 次/d,n=6],由6 月龄喂养至8月龄,处死后分离心脏,通过免疫荧光标记、激光共聚焦显微镜及Werstern Blot 等方法,观察左心室心肌细胞GRK2的表达及亚细胞分布的变化.结果 与对照组比较,两药物干预的SHR 左心室心肌细胞膜蛋白GRK2表达及分布减少,高剂量较低剂量又有进一步减少,差异均有统计学意义(均P＜0.05).缬沙坦组左心室心肌细胞膜蛋白GRK2表达及左心室重量较硝苯地平组减少,差异有统计学意义(P＜0.05).相关性分析结果示两药物干预组大鼠左心室心肌细胞膜蛋白GRK2透光密度与左心室重量呈正相关(缬沙坦组r＝0.837,硝苯地平组r＝0.829,均P＜0.01).结论 缬沙坦与硝苯地平改善左心室肥厚可能与抑制SHR 左心室心肌细胞膜蛋白GRK2表达有关,缬沙坦较硝苯地平能更好地改善心肌肥厚可能与其抑制GRK2表达使其进一步减少有关.     

卡托普利对高血压左心室肥大心肌细胞中GRK_2表达和亚细胞分布的影响

目的:研究G蛋白偶联受体激酶2(GRK2)在高血压心肌肥大发生发展机制中的作用和卡托普利对心肌中GRK2表达水平、活性及亚细胞分布的影响,探讨卡托普利抑制心肌肥大的机制.方法:通过免疫荧光标记、共聚焦显微镜及Western blot等方法,检测6月龄的WKY(WKY组)、自发性高血压(SHR,SHRA组)大鼠,8月龄SHR(SHRB组)和卡托普利干预SHR(SHRC组)大鼠左心室心肌细胞中GRK2的表达及其分布.结果:各组大鼠左室心肌组织总蛋白中GRK2表达无明显变化(P>0.05).细胞质中GRK2表达SHRA组比WKY组表达减少(P<0.01);SHRB组比SHRC组GRK2表达进一步减少(P<0.01);而SHRC组比SHRB组GRK2表达增加( P<0.05).细胞膜蛋白中GRK2在SHRA组比WKY组表达增加(P<0.01);SHRB组比SHRA组GRK2表达进一步增加(P<0.05);而SHRC组比SHRB组GRK2表达减少(P<0.01).细胞核蛋白中无GRK2表达.共聚焦显微镜观察发现GRK2在SHR大鼠细胞膜特别是心肌细胞两端的闰盘聚集明显,卡托普利能减少GRK2在细胞膜分布.结论:GRK2与心肌细胞肥大发生发展关系密切,参与心肌肥大细胞信号转导的调控,卡托普利能通过调节GRK2亚细胞分布而发挥抑制心肌肥大作用.     

自发性高血压大鼠心肌细胞蛋白激酶C活性的变化及其与心肌细胞凋亡的关系

目的 :研究自发性高血压大鼠 (SHR)心肌细胞蛋白激酶 C(PKC)活性的动态变化及其与心肌细胞调亡的关系。　　方法 :将 17只 SHR分为 3组 :1月龄 SHR组 (n=6 )、10月龄 SHR组 (n=6 )和 18～ 2 0月龄 SHR组 (n=5 )。每组均等数按鼠龄、体重及雌雄配对配予 WKY大鼠做对照。采用同位素法、电镜技术和末端脱氧核糖核苷酸转移酶介导的脱氧三磷酸尿苷缺口末端标记法检测 SHR左心室心肌细胞 PKC活性和心肌细胞凋亡的变化。采用直线回归分析确定PKC活性与心肌细胞凋亡的关系。　　结果 :11月龄 SHR组和 18～ 2 0月龄 SHR组心肌细胞膜 PKC活性显著低于同龄 WKY大鼠组 ,而心肌细胞凋亡却显著高于同龄 WKY大鼠组 (P均 <0 .0 1) ;但 10月龄 SHR组心肌细胞膜 PKC活性显著高于同龄 WKY大鼠组、1月龄 SHR组和 18～ 2 0月龄 SHR组而心肌细胞凋亡却显著低于同龄 WKY大鼠组 (P均 <0 .0 1) ;各组间心肌细胞浆 PKC活性无显著性差异 (P均 >0 .0 5 )。 2 SHR心肌细胞膜 PKC活性与心肌细胞凋亡指数呈显著负相关 (P<0 .0 5 ) ,但心肌细胞浆 PKC活性与心肌细胞凋亡指数不相关 (P>0 .0 5 )。　　结论 :心肌细胞膜 PKC活性降低可能与 SHR心肌细胞凋亡增加和充血性心力衰竭相关 ,而心肌细胞膜 PKC活性增加可能与 SHR心肌细胞凋亡减少和     

不同降压药物对自发性高血压大鼠模型左室心肌细胞中TRPC3及TRPC6表达的影响

目的:探讨缬沙坦、雷米普利及氨氯地平对自发性高血压大鼠（SHR）左室心肌中瞬时受体通道蛋白C亚族3及6(TRPC3及TRPC6)表达的影响。方法: 将24只12周龄SHR大鼠随机分为4组,即SHR组、缬沙坦组、雷米普利组及氨氯地平组,每组6只。另以6只同龄的Wistar Kyoto大鼠(WKY)为正常对照组。给药4周后,检测各组大鼠的血压、左室质量指数、左室心肌细胞横径;RT-PCR及Western Blot检测TRPC3及TRPC6 mRNA 及其蛋白的表达。结果: SHR组血压、左室质量指数及左室心肌细胞横径均明显高于对照组（P<0.05）,3个药物组上述指标均较SHR组降低（P<0.05）;5个组均有TRPC3及TRPC6的表达,SHR组TRPC3及TRPC6 mRNA及其蛋白的表达显著高于对照组（P<0.05）,3个药物组TRPC3 mRNA及TRPC6 mRNA及其蛋白的表达均显著低于SHR组（P<0.05）,缬沙坦组TRPC3 mRNA及其蛋白表达的减少最显著（P<0.05）;3个药物组TRPC6 mRNA及其蛋白的表达有所下降,但组间比较差异无显著性。结论: SHR组及对照组大鼠均有TRPC3及TRPC6的表达,TRPC3及TRPC6可能共同参与调节心肌肥厚的病理生理过程;缬沙坦可能通过抑制TRPC3蛋白的表达参与逆转左室肥厚的过程。     

缬沙坦治疗对自发性高血压大鼠心肌纤维化的影响

目的观察缬沙坦对自发性高血压大鼠(SHR)心肌纤维化的影响.方法 30只12周龄雄性SHR大鼠,随机分成3组(1)大剂量缬沙坦组(n=10 缬沙坦30 mg/kg*d);(2)小剂量缬沙坦组(n=10 缬沙坦10 mg/kg*d); (3)SHR空白对照组(n=10);(4) 同龄雄性正常血压WKY 大鼠对照组(n=10).给药4周; 天狼星红染色法使胶原特殊染色,计算机图象分析测量心肌切片的胶原容积分数和心肌小动脉周围胶原面积与小动脉面积比表示心肌纤维化程度.结果与SHR组相比大小剂量缬沙坦组,均能有效降低SHR血压(P<0.05).并能改善SHR大鼠左心室肥厚(P<0.05)并使心室内、外膜及心肌小动脉周围的胶原减少,其中大剂量组各指标均较SHR有显著差异(P<0.05).结论缬沙坦对SHR大鼠的心肌纤维有显著的抑制作用.     

缬沙坦对自发性高血压大鼠心肌凋亡及bcl-2、bax蛋白的表达的影响

目的探讨自发性高血压大鼠(SHR),左心室肥厚过程中,心肌组织凋亡情况及凋亡调节蛋白bcl-2、bax表达的变化,AT1受体拮抗剂缬沙坦对心肌细胞凋亡的影响.方法实验动物为8周龄分为缬沙坦治疗组和非治疗组(SHR无药组),以Wistar鼠作为正常血压对照组,观察期限为8周.采用TdT介导的dUTP缺口末端标记技术(TUNEL)判定心肌细胞凋亡,并行免疫组化、Western印迹等方法检测实验动物心肌组织凋亡调节蛋白bcl-2、bax的表达情况.结果 SHR心肌组织中存在细胞凋亡现象,并有bax高表达.缬沙坦治疗8周后,SHR心肌组织bax蛋白表达显著降低至接近Wistar组.Bcl-2蛋白在SHR治疗组及Wistar组表达较SHR非治疗组有增高趋势(P>0.05).前两组bax/bcl-2比值较后者显著降低(P<0.05).结论心肌细胞凋亡是代偿性心肌肥厚可能机制之一.高血压病早期缬沙坦在降压同时可有效抑制心肌细胞凋亡,具有积极的抗心室重建作用.     

缬沙坦对自发性高血压大鼠心肌凋亡及bcl-2、bax蛋白的表达的影响

目的　探讨自发性高血压大鼠 (SHR) ,左心室肥厚过程中 ,心肌组织凋亡情况及凋亡调节蛋白bcl 2、bax表达的变化 ,AT1受体拮抗剂缬沙坦对心肌细胞凋亡的影响。方法　实验动物为 8周龄分为缬沙坦治疗组和非治疗组(SHR无药组 ) ,以Wistar鼠作为正常血压对照组 ,观察期限为 8周。采用TdT介导的dUTP缺口末端标记技术(TUNEL)判定心肌细胞凋亡 ,并行免疫组化、Western印迹等方法检测实验动物心肌组织凋亡调节蛋白bcl- 2、bax的表达情况。结果　SHR心肌组织中存在细胞凋亡现象 ,并有bax高表达。缬沙坦治疗 8周后 ,SHR心肌组织bax蛋白表达显著降低至接近Wistar组。Bcl 2蛋白在SHR治疗组及Wistar组表达较SHR非治疗组有增高趋势 (P >0 0 5 )。前两组bax/bcl 2比值较后者显著降低 (P <0 0 5 )。结论　心肌细胞凋亡是代偿性心肌肥厚可能机制之一。高血压病早期缬沙坦在降压同时可有效抑制心肌细胞凋亡 ,具有积极的抗心室重建作用。     

缬沙坦通过下调X-盒结合蛋白1表达抑制糖尿病心肌病大鼠心肌细胞凋亡

目的：研究糖尿病心肌病（DCM）模型大鼠心肌组织中X-盒结合蛋白1（XBP1）与心肌细胞凋亡之间的联系，以及明确缬沙坦抑制心肌细胞凋亡的作用机制。方法：将清洁级雄性8周龄Wistar大鼠50只随机分为两部分：腹腔注射65 mg/kg的柠檬酸盐缓冲液的大鼠为对照组（n=10）；腹腔注射链脲佐菌素65 mg/kg大鼠（n=40）注射7天后，收集大鼠尾静脉血测空腹血糖，其中37只连续2次空腹血糖≥16.7mmol/L（300mg/dl）为DCM大鼠建模成功并将其随机分为2组：给予以生理盐水灌胃的为DCM组（n=20）,以30mg/kg·d灌胃缬沙坦给药的为DCM+缬沙坦组（n=17）。三组大鼠饲养过程中检测体重、血糖、血压、心功能等指标变化。大鼠16周后处死观察心肌组织结构、细胞形态、胶原分布情况，TUNEL染色观察心肌细胞凋亡，并通过免疫荧光、蛋白印迹法（Western blot）、实时定量逆转录-聚合酶链反应（RT-PCR）及半定量RT-PCR检测各组大鼠心肌组织中cytochrome c、cleaved caspase 3、葡萄糖调节蛋白78（GPR78）和剪接型XBP1（XBP1-s）表达水平。结果：DCM组大鼠与对照组相比，心肌结构紊乱，胶原含量明显增加，心肌细胞凋亡增加（P<0.05），GRP78、XBP1-s、cleaved caspase 3和cytochrome c蛋白及核糖核酸（RNA）表达水平明显升高（P<0.05），DCM+缬沙坦组与DCM组相比，心肌细胞排列较整齐，心肌间质内和小动脉周围胶原纤维显著减少，心肌细胞凋亡明显减少（P<0.05），GRP78、XBP1-s、cleaved caspase 3和cytochrome c蛋白及RNA表达水平明显下降（P<0.05）。结论：DCM大鼠心肌组织中存在着调节内质网应激的关键因子-XBP1的活化，DCM病程中存在着XBP1调控的内质网应激相关凋亡途径的激活，心肌细胞凋亡增加，而缬沙坦能够抑制DCM大鼠心肌细胞XBP1的激活，减少心肌细胞凋亡。     

不同降压药物对自发性高血压大鼠模型左室心肌细胞中TRPC3及TRPC6表达的影响

目的探讨缬沙坦、雷米普利及氨氯地平对自发性高血压大鼠(SHR)左室心肌中瞬时受体通道蛋白C亚族3及6(TRPC3及TRPC6)表达的影响。方法将24只12周龄SHR大鼠随机分为4组,即SHR组、缬沙坦组、雷米普利组及氨氯地平组,每组6只。另以6只同龄的Wistar Kyoto大鼠(WKY)为正常对照组。给药4周后,检测各组大鼠的血压、左室质量指数、左室心肌细胞横径;RTPCR及Western Blot检测TRPC3及TRPC6 mRNA及其蛋白的表达。结果 SHR组血压、左室质量指数及左室心肌细胞横径均明显高于对照组(P<0.05),3个药物组上述指标均较SHR组降低。结论 SHR组及对照组大鼠均有TRPC3及TRPC6的表达,TRPC3及TRPC6可能共同参与调节心肌肥厚的病理生理过程;缬沙坦可能通过抑制TRPC3蛋白的表达参与逆转左室肥厚的过程。     

不同降压药物对自发性高血压大鼠模型左室心肌细胞中TRPC3及TRPC6表达的影响

目的探讨缬沙坦、雷米普利及氨氯地平对自发性高血压大鼠(SHR)左室心肌中瞬时受体通道蛋白C亚族3及6(TRPC3及TRPC6)表达的影响。方法将24只12周龄SHR大鼠随机分为4组,即SHR组、缬沙坦组、雷米普利组及氨氯地平组,每组6只。另以6只同龄的Wistar Kyoto大鼠(WKY)为正常对照组。给药4周后,检测各组大鼠的血压、左室质量指数、左室心肌细胞横径;RTPCR及Western Blot检测TRPC3及TRPC6 mRNA及其蛋白的表达。结果 SHR组血压、左室质量指数及左室心肌细胞横径均明显高于对照组(P<0.05),3个药物组上述指标均较SHR组降低。结论 SHR组及对照组大鼠均有TRPC3及TRPC6的表达,TRPC3及TRPC6可能共同参与调节心肌肥厚的病理生理过程;缬沙坦可能通过抑制TRPC3蛋白的表达参与逆转左室肥厚的过程。     

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.