肝星状细胞活化在大鼠肝硬化门脉高压形成中的作用

[目的]探讨肝星状细胞(HSC)活化在大鼠肝硬化门脉高压形成中的作用.[方法]采用二甲基亚硝胺(DMN)4周12次腹腔注射制作大鼠肝硬化模型,分别于造模后1 d、2 d、3 d、1周、2周、4周、6周、8周作为动态观察时相点,免疫组化染色观察肝组织α-平滑肌肌动蛋白(α-SMA)、Ⅳ型胶原(ColⅣ)、层黏连蛋白(LN)表达,电镜观察肝组织超微结构,肠系膜前静脉分支插管法测门脉压力(Ppv).[结果]造模2、3 d后肝窦壁α-SMA染色逐渐增强,4周时阳性表达最为明显;模型大鼠肝窦壁ColⅣ阳性染色呈现先弱后强,LN的沉积随造模时间的延长而进行性增加,4周时表达最为明显,电镜下可见肝窦内皮失窗孔和基底膜形成;DMN大鼠HSC中α-SMA表达量与Ppv高低呈显著正相关(P＜0.05).[结论]活化的HSC通过分泌大量的ColⅣ和LN形成肝窦内皮下基底膜以及因表达α-SMA而收缩力增强,是肝硬化肝窦阻力增加和门脉高压形成的重要病理细胞学基础.     

大鼠肝纤维化形成中基质金属蛋白酶2、9活性变化的病理意义

目的探讨大鼠肝纤维化形成中基质金属蛋白酶2、9(MMP 2、MMP 9)活性变化及其病理意义.方法采用二甲基亚硝胺4周1 2次腹腔注射制作大鼠肝纤维化模型,分别于造模后1、2、3 d、1、2、4、6、8周作为动态观察时相点;MMP-2和MM P-9活性测定采用酶谱法,透射电镜观察肝组织超微结构,免疫组织化学观察肝窦壁Ⅳ型胶原(CⅣ)、层黏连蛋白(LN)和Ⅰ型胶原(C I)表达,weste rn blot方法测定肝组织金属组织蛋白酶抑制剂2(TIMP 2)含量.结果造模后第2、3天,MMP 2、MMP 9活性(灰度值)显著增加(2 dMMP-2正常对照组为54.72±4.56,模型组为70.76±7.63,F=16.27,P＜0.05;MMP-9分别为25.72±4.29和51.76±15.33,F=13.38,P＜0.05).肝窦壁CⅣ(阳性面积比%)在造模第2、3天直至1周显著减少(2 d正常对照组为6.06±1.35,模型组为2.86±0.63,F=69.12,P＜0.05),4周末则显著增加(正常对照组为6.06±1.35,模型组为8.04±1.50,F=14.42,P＜0.05).MMP-9活性与肝窦壁CⅣ表达量呈显著负相关(r=-0.729,P＜0.05);肝窦壁LN沉积4周末达峰值;正常肝窦壁无C I表达,造模4周后肝窦壁C I呈阳性染色; 4周模型大鼠可见完整的基底膜形成;肝纤维化后期TIM P 2表达异常增加.结论早期MMP 9(主要的)、MMP 2活性升高,降解肝窦内皮细胞下正常分布的CⅣ,是肝窦毛细血管化形成的重要因素;后期T I M P-2表达增加,可能是该模型肝纤维化不易自行消退的原因之一.     

胆管上皮细胞增生在胆管结扎大鼠胆汁性肝纤维化形成中的作用

目的 研究胆管上皮细胞(biliary epithelia cells,BECs)增生在胆管结扎(bile duct ligation,BDL)大鼠胆汁性肝纤维化形成中的作用.方法 BDL的方法制作大鼠胆汁性肝纤维化模型,5周后杀鼠取材,观察内容包括大鼠血清总胆红素(TBlL)、总胆汁酸(TBA),肝组织羟脯氨酸(Hyp)含量,组织病理学,免疫组织化学观测Ⅰ型胶原(Col Ⅰ)、Ⅳ型胶原(Col Ⅳ)、层粘蛋白(LN)、纤连蛋白(FN)和α-平滑肌肌动蛋白(α-SMA);肝组织片激光显微切割(LCM)获取BECs,实时荧光定量PCR检测BECs表达Procollagen α1(Ⅳ)、血小板衍生生长因子B(PDGF-B)、结缔组织生长因子(CTGF)及转化生长因子β1(TGF-β1)mRNA.结果 1、胆管结扎模型大鼠血清TBiL和TBA含量均值分别为假手术组大鼠的22倍和3倍(P＜0.01);模型组大鼠肝组织Hyp含量是假手术组的4倍(P＜0.01);2、模型组大鼠BECs增生非常显著,肝实质细胞比例显著减少;3、模型组大鼠在增生胆管周围的LM表达显著增加;FN不但在肝窦内有阳性染色,还强烈地表达于增生的胆管周围;肝窦壁的Col Ⅰ阳性染色增强,增殖的BECs周围未见明显阳性染色;肝窦壁ColⅣ表达未见明显变化,但强烈表达于增殖的BECs周围的基底膜上;α-SMA阳性染色见于汇管区周围的肌成纤维细胞上,且这些肌成纤维细胞常常围绕在增生的胆管上皮细胞周围.4、模型组大鼠BECs的Procol α1(Ⅳ)、PDGF-B、TGF-β1及CTGF的mRNA表达量均显著增加(与假手术组比较,均为P＜0.001).结论 BECs增生是BDL大鼠胆汁性肝纤维化的启动因素和中心病理环节,抑制胆管上皮细胞的异常增生及其细胞生物学病理变化应是抗胆汁性肝纤维化治疗学研究的主要目标.     

氯沙坦抗大鼠肝纤维化的研究

目的 :研究血管紧张素Ⅱ 1型受体拮抗剂氯沙坦对二甲基亚硝胺 (DMN)诱导的肝纤维化大鼠模型的疗效及可能的机制。方法 :制备DMN诱导的大鼠肝纤维化模型 ,同时应用氯沙坦灌胃 ,共 8周。肝组织进行常规HE及Masson三色染色。测定血清肝功能及透明质酸 (HA)。大鼠肝组织Ⅰ型胶原 (ColⅠ )、Ⅲ型胶原 (ColⅢ )及转化生长因子 βl(TGF β1)mRNA的水平用RT PCR方法检测。结果 :氯沙坦可明显改善肝纤维化的程度 ,降低血清ALT及HA的水平 (P <0 .0 1)。同时模型组ColⅠ、ColⅢ及TGF β1mRNA的水平明显高于正常对照组 ,氯沙坦治疗组明显低于模型组 (P <0 .0 0 1)。结论 :氯沙坦具有良好的抗肝纤维化作用 ,且能够抑制肝组织ColⅠ、ColⅢ及TGF β1mRNA的水平 ,从而发挥其抗肝纤维化的作用。     

γ-干扰素抑制肝纤维化大鼠Ⅰ、Ⅲ型胶原和基质金属蛋白酶组织抑制因子基因表达

目的观察γ干扰素(γIFN)对二甲基亚硝胺(DMN)诱导肝纤维化大鼠肝脏Ⅰ型胶原(ColⅠ)、Ⅲ型胶原(ColⅢ)和基质金属蛋白酶组织抑制因子1(TIMP1)基因表达的作用。方法45只Wistar大鼠随机分为正常对照组(15只)、模型组(15只)和γIFN预防组(15只)。模型组用0.5%DMN10mgkg体重腹腔内注射,共6周,第1周连续3次,其后每周2次;γIFN预防组大鼠则在用DMN腹腔注射同时,每天皮下注射γIFN105Ukg体重,停止DMN注射后再用药2周,共8周。正常对照组以生理盐水腹腔内注射。于第8周处死大鼠,进行病理组织学检查、羟脯氨酸含量测定;以RTPCR法检测肝组织中ColⅠ、ColⅢ和TIMP1mRNA水平,BioRad凝胶成像系统对电泳结果进行半定量分析。结果肝组织病理检查显示,模型组大鼠在第6周停用DMN时,多数大鼠肝纤维化达2～3级,有的大鼠甚至出现腹水,停用DMN后,肝纤维化程度仍持续加重,至8周末所有大鼠肝纤维化达3～4级,且大多数伴有腹水。γIFN预防组病变较轻,最严重肝纤维化只有3级。RTPCR结果显示,正常对照组ColⅠ、ColⅢ、TIMP1mRNA表达水平分别为0.66±0.05、0.59±0.05、0.56±0.04,而模型组则分别为0.92±0.06、0.75±0.07、0.91±0.07,与对照组相比均明显升高,差异有统计学意义,γIFN预防组分别为0.73±0.06、0.66±0.07、0.66±0.05     

消黄方对二甲基亚硝胺大鼠肝纤维化氧化应激的影响

目的探讨消黄方对二甲基亚硝胺(dimethylnitrosamine,DMN)肝纤维化大鼠肝组织氧化应激的影响。方法雄性Wistar大鼠30只,随机分为正常组及DMN模型组,DMN模型组大鼠DMN(10 mg/kg)每周前3天连续腹腔注射共4周制备大鼠肝纤维化模型,造模第3周,DMN大鼠随机分为模型对照组和消黄方组(例数10),消黄方组每天造模的同时给予方剂煎出液灌胃2周。造模4周末,处死全部大鼠,获取肝组织,检测肝组织羟脯氨酸(hydroxy prone,Hyp)含量,检测肝组织超氧化物歧化酶活性(superoxidedismutase,SOD)、谷胱甘肽转移酶(glutathione-S-transfcrase,GST)活性、谷胱甘肽(glutathione,GSH)及丙二醛含量(malondialdehyd,MDA)等氧化应激指标,实时定量PCR检测肝脏Ⅰ型胶原mRNA表达。结果与正常组相比,DMN模型组大鼠肝组织MDA含量及GST活性显著升高(P<0.01),分别为正常组的2.37倍和2.04倍,而GSH含量和SOD活性则显著降低(P<0.01),分别是正常组的0.37和0.47倍。与模型对照组相比,消黄方组显著降低肝组织MDA含量(P<0.05),增高GSH含量和SOD活性(P<0.01),实时定量PCR结果显示Ⅰ型胶原造模后达到正常组的34倍,消黄方组显著降低(P<0.01)。结论氧化应激是肝纤维化形成的重要病理因素之一,消黄方能显著改善DMN纤维化大鼠肝组织氧化应激。     

肝窦毛细血管化在二甲基亚硝胺大鼠肝纤维化门静脉高压形成中的作用

目的 研究肝窦毛细血管化在二甲基亚硝胺(DMN)大鼠肝纤维化门静脉高压形成中的作用。方法经4周12次腹腔注射DMN制备火鼠肝纤维化模型,应用电镜技术、免疫组织化学方法结合大鼠门静脉压力测定,24周动态分析肝纤维化形成过程中肝窦毛细血管化与门静脉压力变化的相关性。结果 大鼠门静脉压力随着造模的进行不断升高,造模4周时达(1.10 ±0.18)kPa,明显高于对照组(0.52±0.04)kPa(t=6.41.P<0.0 1)。造模停止后,大鼠门静脉压力逐渐恢复正常。其动态变化与电镜下肝窦毛细血管化的变化规律一致;与反映肝窦内皮表型改变的第Ⅷ因子相关抗原的动态变化成正相关(r=0.833,P<0.01);与反映肝窦内皮下基底膜形成的层黏连蛋白的动态变化成正相关(r=0.953,P<0.01);与反映肝窦壁星状细胞活化收缩的α-平滑肌肌动蛋白的动态变化成正相关(r=0.919,P<0.01)。结论 肝窦毛细血管化是DMN肝纤维化模型门静脉高压产生的主要原因。     

氯沙坦抗大鼠肝纤维化的研究

目的：研究血管紧张素Ⅱ1型受体拮抗剂氯沙坦对二甲基亚硝胺(DMN)诱导的肝纤维化大鼠模型的疗效及可能的机制。方法：制备DMN诱导的大鼠肝纤维化模型，同时应用氯沙坦灌胃，共8周。肝组织进行常规HE及Masson三色染色。测定血清肝功能及透明质酸(HA)。大鼠肝组织I型胶原(ColⅠ)、Ⅲ型胶原(ColⅢ)及转化生长因子-β1(TGF-β1)mRNA的水平用RT-PCR方法检测。结果：氯沙坦可明显改善肝纤维化的程度，降低血清ALT及HA的水平(P＜0．01)。同时模型组Col I、ColⅢ及TGF-β1 mRNA的水平明显高于正常对照组，氯沙坦治疗组明显低于模型组(P＜0．001)。结论：氯沙坦具有良好的抗肝纤维化作用，且能够抑制肝组织ColⅠ、ColⅢ及TGF-β1 mRNA的水平，从而发挥其抗肝纤维化的作用。     

肝窦内皮细胞损伤在大鼠肝纤维化形成中的作用

目的 研究肝窦内皮细胞损伤在二甲基亚硝胺大鼠肝纤维化形成中的作用。方法 采用二甲基亚硝胺(dimethylnitrosamine,DMN)4周12次腹腔注射制备大鼠肝纤维化模型,应用电镜技术、免疫组织化学及图像分析方法结合血清生化测定,24周动态观察肝纤维化形成过程中肝窦内皮细胞损伤及其表型的改变。结果 造模2d后肝结构未见明显改变,肝窦内皮细胞(sinusoidal endothelial cell,SEC)远侧胞浆窗孔数减少、造模1周SEC失窗孔更明显,肝组织内未见明显变性坏死及纤维间隔形成,造模4周时见肝组织内大片出血坏死,有大量假小叶形成,内皮下出现SEC窗孔减少。SEC失窗孔早于肝细胞发生较为严重的坏死、肝纤维化的形成以及肝窦内皮下基底膜的形成。造模4周HA(ng/ml)和肝羟脯氨酸(ug/g)平均含量分别为231.30±143.80和223.04±37.09,对照组分别为56.50±18.10和61.55±20.85,t值在3.14～8.28,P<0.05。结论 DMN引起大鼠肝窦内皮细胞损伤及其表型改变可能是其诱导肝纤维化重要的始动机制之一。     

银杏叶提取物对肝纤维化大鼠转化生长因子β1及Ⅰ型胶原蛋白的影响

[目的]研究银杏叶提取物(EGb)对肝纤维化大鼠的保护作用及其可能机制.[方法]36只Wistar大鼠随机分为空白对照组、模型组、EGb预防4、8周组.用CCl4腹腔注射诱导大鼠肝纤维化模型,采用免疫组化半定量法观察EGb干预4、8周后肝组织转化生长因子β1(TGF-β1)、Ⅰ型胶原(Col Ⅰ)蛋白的表达,苏木精-伊红及苦味酸酸性品红胶原染色法观察肝组织病理形态学的改变,并检测肝功能、脂质过氧化指标等.[结果]与模型组相比,EGb干预治疗4、8周后,大鼠肝组织TGFβ1、Col Ⅰ蛋白的表达显著降低(P＜0.05),并显著改善肝纤维化分级(P＜0.05),使血清丙氨酸氨基转移酶、天冬氨酸转氨酶降低,清蛋白升高(P＜0.01),并使肝组织丙二醛明显降低(P＜0.01),8周较4周更明显.[结论]EGb具有抗脂质过氧化,降低TGF-β1的表达、抑制Col Ⅰ合成的作用.     

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.