siRNA干扰galectin-3表达对人胃癌细胞株SGC-7901增殖、凋亡和化疗敏感性的影响

Galectin-3属于半乳凝素家族成员,参与细胞生长和凋亡、细胞黏附、新生血管形成、肿瘤浸润和转移等多种生理和病理过程,在多种恶性肿瘤细胞中呈高表达。目的:研究siRNA干扰galectin-3表达对人胃癌细胞株SGC-7901增殖、凋亡和化疗敏感性的影响。方法:合成靶向galectin-3的siRNA并转染SGC-7901细胞,以real time PCR和蛋白质印迹法检测干扰效果。CCK-8实验检测细胞增殖,流式细胞术检测细胞凋亡。结果:Galectin-3siRNA转染24 h后转染效率为83.8%,转染后SGC-7901细胞的galectin-3表达显著受抑,mRNA和蛋白表达量分别较空白对照组降低87.8%和90.4%(P0.01)。转染后24 h、48 h和72 h,galectin-3 siRNA组SGC-7901细胞增殖抑制率分别为15.57%±1.45%、32.90%±0.76%和57.35%±1.05%,转染后72 h该组细胞凋亡率为46.17%±2.39%,均显著高于同时间点空白对照组、空脂质体组和阴性对照siRNA组(P0.01)。Galectin-3 siRNA组SGC-7901细胞由化疗药物奥沙利铂诱导的增殖抑制亦较其余三组显著增加(P0.01)。结论:以siRNA干扰galectin-3表达后,SGC-7901细胞增殖减少、凋亡增加,对化疗药物的敏感性增强,表明galectin-3有望成为胃癌基因治疗的有效靶点。     

VEGF基因表达抑制对胃腺癌细胞SGC-7901增殖的影响

目的:研究siRNA(small interfering RNA)对人胃腺癌细胞SGC-7901的VEGF基因表达的影响．方法:选择血管内皮生长因子(VEGF)基因为靶基因,设计两组针对VEGF mRNA的小干扰RNA,合成DNA寡核苷酸链,体外转录合成siRNA．以人胃腺癌细胞系SGC-7901为靶细胞,应用脂质体转染的方法,将siRNA导入细胞．采用Hoechst33258染色观察siRNA作用于SGC-7901细胞中出现凋亡小体的情况．流式细胞仪检测细胞周期的改变,RT-PCR法比较转染前后VEGF mRNA表达水平的变化, ELISA法检测细胞培养液中VEGF蛋白分泌量的变化．结果:两组siRNA转染后均能有效地抑制 SGC-7901细胞的生长,诱导细胞凋亡产生凋亡小体．siRNA作用于SGC-7901细胞．其细胞周期均发生了明显的变化,主要表现为G0／G1 期细胞增多,S期细胞减少,并使细胞周期阻滞于G0／G1期(siRNA1组,siRNA2组G0／G1期VS 对照组G0／G1期:75．04％,76．52％ vs 58．37％, P<0．01;siRNA1组,siRNA2组S期vs对照组S 期:17．82％,16．73％ vs 39．52％,P<0．01),而其他组则无明显变化．VEGF mRNA的表达量大幅度减少(siRNA1组,siRNA2组vs对照组: 0．638±0．078,0．656±0．085 vs 0．941±0．046, P<0．01),相对应的VEGF蛋白水平也显著降低(164．7±22．7,166．3±26．6 vs 414．0±61．5, P<0．01),而其他组siRNA转染后则无上述作用．结论:应用靶向VEGF基因RNA干扰技术可以有效抑制胃癌细胞SGC-7901的增殖．     

GRP78在胃癌中表达水平及沉默表达后对人胃癌SGC-7901/DDP细胞增殖和凋亡的影响

目的研究内质网分子伴侣葡萄糖调节蛋白78(glucose regulated protein 78,GRP78)在人不同胃组织(正常胃组织和胃癌组织)和细胞(正常胃上皮GES1细胞、胃癌SGC-7901细胞、多耐药性胃癌SGC-7901/DDP细胞)中的表达水平;揭示GRP78沉默表达对SGC-7901/DDP细胞增殖和凋亡的影响。方法利用实时荧光定量PCR(Real-time PCR)和免疫印迹(Western blotting)方法分别检测人正常胃组织、胃癌组织、人正常胃上皮GES1细胞、胃癌SGC-7901细胞、多耐药性胃癌SGC-7901/DDP细胞中GRP78 mRNA和蛋白表达水平。利用LipfectamineTM2000将GRP78 siRNA转染至SGC-7901/DDP细胞中,同时设置未转染Control组和无义转染Control siRNA组。Real-time PCR和Western blotting方法检测各组SGC-7901/DDP细胞转染效率;MTT方法检测各组SGC-7901细胞的生长活力变化和不同浓度顺铂DDP作用下细胞增殖抑制率;流式细胞术检测各组SGC-7901细胞凋亡情况。结果胃癌组织中GRP78 mRNA和蛋白表达水平显著高于正常胃组织(P0.05);多耐药性胃癌SGC-7901/DDP细胞中GRP78 mRNA和蛋白表达水平显著高于胃癌SGC-7901细胞和正常胃上皮GES1细胞(P0.05);GRP78 siRNA转染SGC-7901/DDP细胞后GRP78 mRNA和蛋白表达水平显著下降(P0.05);与Control组和Control siRNA组相比,GRP78 siRNA转染组SGC-7901/DDP细胞生长活力显著下降,DDP作用下细胞增殖抑制率和细胞凋亡率显著增加(P0.05)。结论 GRP78 mRNA和蛋白在胃癌组织中高表达,在多耐药性胃癌SGC-7901/DDP细胞中也高表达,证实GRP78在胃癌中发挥促癌基因的作用。而GRP78 siRNA转染能够沉默SGC-7901/DDP细胞中GRP78基因表达,抑制SGC-7901/DDP细胞增殖并促进细胞凋亡。     

siRNA沉默Livin基因对胃癌细胞生长、凋亡的影响

目的:观察小分子干扰RNA(siRNA)沉默Livin基因在胃癌BGC-823细胞中的表达, 并探讨Livin基因对胃癌细胞生长、凋亡的影响.方法:自行设计两条针对Livin基因的siRNA:Livin-sh-1和Livin-sh-2, 以此构建相应的表达载体并分别转染至对数生长期胃癌BGC-823细胞, 经G418筛选后分别采用半定量RTPCR检测不同siRNA实验分组细胞BGC-823mRNA水平变化, 四氮唑盐比色法(MTT)检测细胞增殖、流式细胞仪检测胃癌细胞的凋亡.结果:siRNA对照组与空siRNA载体组Livinα/β mRNA表达差别无显著性; 但转染siRNA组Livin α/β mRNA表达显著低于空白对照组和空siRNA载体组(Livin α:0.11±0.07 vs 0.37±0.10, 0.34±0.08; Livin β:0.13±0.04 vs 0.43±0.09, 0.45±0.11, 均P<0.05). 空白对照组与空siRNA载体组相比, 24、48、96 h和1 wk时细胞生长未受影响; 而siRNA组在转染后24 h和48 h细胞生长未受影响, 但在96 h和1 wk时则被明显抑制( P<0.01). 转染siRNA组的细胞的凋亡率与空白对照组和转染空siRNA载体组相比显著增加(14.85%±1.35% vs 4.51%±0.36%, 6.13%±0.71%, 均P<0.05).结论:siRNA沉默Livin基因能抑制胃癌细胞的生长, 促进胃癌细胞的凋亡, Livin基因有可能成为胃癌治疗的新靶点.     

Livin基因沉默对大肠癌细胞凋亡和化疗敏感性的影响

目的 观察沉默Livin基因对大肠癌HT-29细胞凋亡和化疗敏感性的影响.方法 采用脂质体转染技术将化学合成的Livin siRNA转入HT-29细胞,RT-PCR和Western印迹法检测转染效果.选用5-氟尿嘧啶(5-FU)作用于转染和未转染的细胞,MTT检测各组细胞的增殖、流式细胞仪检测细胞的凋亡.结果 si-Livin1转染组Livinα mRNA、Livinβ mRNA和Livin蛋白表达水平较其余干扰组和对照组显著降低(P<0.01).5-FU对HT-29细胞的生长抑制作用强于si-Livin1转染组(P<0.01),而si-Livin1+5-FU组对细胞的生长抑制率显著高于单独si-Livin1转染组和单独5-FU作用组(P<0.01).与空白对照组比较,si-Livin1转染可使细胞出现明显凋亡现象(P<0.01),5-FU对细胞的促凋亡作用强于si-Livin1转染组(P<0.01),si-Livin1+5-FU组的凋亡率显著高于单独si-Livin1转染组和单独5-FU作用组(P<0.01).结论 siRNA沉默Livin基因能够抑制HT-29细胞的生长,促其凋亡,提高5-FU的化疗敏感性.Livin基因有望成为大肠癌治疗的新靶点.     

TGIF对胃癌细胞株SGC-7901的维甲酸信号通路的影响

目的:探讨TG-相互作用因子(TGIF)对胃癌SGC-7901 细胞株中维甲酸信号通路的影响．方法:在TGIF表达质粒稳定转染SGC-7901细胞后,用 Western blot鉴定高表达TGIF的阳性克隆．在TGIF反义寡核苷酸瞬时转染SGC-7901细胞株后,用RT-PCR检测转染效率．再用1 μmol／L ATRA分别处理稳定转染组或瞬时转染组及其对照组细胞,MTT观察细胞增殖速度的变化,流式细胞术观察细胞凋亡率的变化．结果:稳定转染TGIF表达质粒和瞬时转染TGIF反义寡核苷酸对SGC-7901细胞的增殖和凋亡没有明显影响．但在ATRA作用后,TGIF表达质粒转染组细胞的增殖速度比未转染组和空白质粒转染组细胞快(0．434± 0．035 vs 0．386±0．020,0．360±0．014,P<0．05),而细胞的凋亡率的变化比未转染组和空白质粒转染组细胞小,仅由1．14％增加至1．39％．TGIF反义寡核苷酸转染组细胞的增殖速度比未转染组和突变寡核苷酸转染组细胞慢(0．320±0．044 vs 0．388±0．024,0．409±0．041, P<0．05)．而细胞凋亡率的变化比后两组大,由3．09％上升至10．2％．结论:TGIF能拮抗ATRA抑制SGC-7901细胞增殖和诱导其凋亡的作用,TGIF可能参与了对SGC-7901细胞的维甲酸信号通路的抑制．     

Ad-p27mt转染重组腺病毒治疗裸鼠内人胃癌的分子机制

目的:研究Ad-p27mt转染重组腺病毒对人胃癌细胞凋亡的作用及机制.方法:Ad-p27mt转染重组腺病毒导入胃癌细胞株SGC-7901内;流式细胞仪检测凋亡染色体亚二倍体峰值,了解Ad-p27mt对人胃癌组织凋亡的作用;TUNEL法检测DNA片断,在Ad-p27mt组和Ad-LacZ组中分析细胞的凋亡.结果:Ad-p27mt成功转入人胃癌细胞SGC-7901内,转化率达100%.流式细胞仪检测发现在感染后18h出现G1-S相前出现凋亡染色体亚二倍体峰值,并且DNA电泳出现凋亡特征性的条带;TUNEL法检测Ad-p27治疗组与对照组的凋亡率分别是92.3%±3.76%和2.01%±0.15%,两组的差异有显著性(P<0.01).结论:重组腺病毒转染的人p27突变基因能诱导裸鼠体内人胃癌细胞SGC-7901的凋亡.     

核糖核酸干扰沉默生长抑制因子1基因表达对胃腺癌AGS细胞凋亡的影响

目的 探讨RNA干扰沉默生长抑制因子1(ING1)基因表达对胃腺癌AGS细胞凋亡的影响。方法人胃腺癌细胞株AGS经常规培养后分为空白对照组、阴性对照组[转染阴性对照小干扰RNA(siRNA)序列]、siRNA组（转染特异性ING1 siRNA序列）。应用免疫荧光、定量PCR和免疫印迹方法检测转染后不同时间的ING1基因表达沉默效果。应用流式细胞技术检测ING1基因表达沉默对AGS细胞凋亡的影响。结果ING1主要在AGS细胞胞质中表达。在荧光定量PCR技术检测中将空白对照组的ING1基因表达量设为1,则转染后24和40 h阴性对照组的ING1基因相对表达量分别为0.88±0.16和0.92±0.13,siRNA组ING1基因相对表达量分别为0.38±0.09和0.17±0.06。空白对照组和阴性对照组比较,P值分别=0.78和0.82。空白对照组和siRNA组比较,P值均=0.01。阴性对照组和siRNA组比较,P值分别=0.02和0.01。免疫印迹技术检测结果显示,转染后40 h AGS细胞中ING1蛋白表达水平明显下调。空白对照组AGS细胞凋亡率为11.06％±0.97％,阴性对照组、siRNA组转染40 h后AGS细胞凋亡率为11.82％±0.69％和 6.70％±0.41％。空白对照组与siRNA组比较P=0.024。空白对照组与阴性对照组比较P=0.76。阴性对照组与siRNA组比较P=0.019。结论ING1在人胃癌细胞凋亡过程中发挥重要作用,可能成为胃癌基因治疗的新靶点。     

siRNA干扰GADD45联合顺铂对人卵巢癌细胞增殖及凋亡的影响

目的研究siRNA沉默GADD45联合顺铂对人卵巢癌细胞SKOV-3增殖和凋亡的影响及相关作用机制。方法将化学合成的GADD45基因siRNA序列转染至SKOV-3细胞中,将SKOV-3细胞分为5组:空白对照组、阴性对照组、干扰组、顺铂组、联合组(干扰+顺铂)。通过MTT比色法、流式细胞术和分光光度法分别检测SKOV-3细胞增殖率、细胞凋亡率、细胞周期各时相分布、Caspase-3和Caspase-9的活力变化以及胞质中Cytochrome C水平变化。结果 GADD45 siRNA转染后,相对于顺铂处理组,联合组细胞凋亡率明显增加(P<0.01);细胞周期各时相重新分布,G0/G1期细胞显著减少(P<0.01),S期和G2/M期细胞则显著增多(P<0.01);Caspase-3和Caspase-9活力显著升高,胞质中细胞Cytochrome C水平明显增加(P<0.01)。结论 GADD45靶向siRNA沉默联合顺铂处理通过调节细胞周期进程阻碍DNA损伤修复进而促进了线粒体依赖性的细胞凋亡,GADD45可作为人卵巢癌基因治疗的后选靶点。     

siRNA对生长抑素基因表达的抑制作用

目的:研究siRNA对生长抑素(SOM)基因表达的抑制作用．方法:根据生长抑素基因序列设计和合成 RNA干扰的靶序列,应用RiboMAXT7体外转录试剂盒合成siRNA并转染胃癌细胞系 SGC-7901,经RT-PCR,免疫组化法检测生长抑素在mRNA和蛋白质水平的抑制效应．结果:成功合成了siRNA(21 bp)．胃癌细胞系 SGC-7901中SOM基因的表达呈强阳性,分布在胞质中,siRNA作用48 h后SOM基因的表达明显抑制,与空转染和空白对照组相比有显著性差异(49．71％±0．056％vs 10．49％±0．021％, 0％,P<0．01)．结论:siRNA可特异性抑制生长抑素基因的表达．     

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。     

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。     

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.