拉米夫定体外对慢性乙型肝炎患者树突状细胞功能的影响

目的:体外研究不同浓度拉米夫定(lamivu- dine,LAM)对慢性乙型肝炎(chronic hepatitis B,CHB)患者树突状细胞(dendritic cell,DC)功能影响．方法:分离慢乙肝患者外周血单核细胞,在含GM-CSF IL-4及不同浓度LAM(0,0．125, 0．25,0．5,1,2 mmol／L)培养条件下制备DC．观察DC形态学变化并用MTT法测定DC刺激同种异体淋巴细胞增殖能力,流式细胞仪(FCM) 测定其细胞表型分子CD1a,CD83,CD80及 HLA-DR的表达,ELISA法检测培养上清中 IL-12和IL-6含量．结果:在LAM 0．5 mmol／L组,DC表型分子 CD83,CD1a,HLA-DR的表达最高,CD80与 LAM未处理组相比无明显差异．与LAM未处理组相比,LAM 0．5 mmol／L处理组DC膜表面分子CD1a,CD83,HLA-DR表达增高(CD1a: 54．0±9．2 vs 33．6±10．1,P<0．05;CD83:20．3 ±6．1 vs 11．8±6．2,P<0．05;HLA-DR:74．5± 7．1 vs 52．9±7．7,P<0．05);其上清液中IL-12 分泌水平增高(810．0±91．5 ng／L vs 268．0± 34．3 ng／L,P<0．05),IL-6则显著降低(28．1± 2．6 ng／L vs 55．3±7．4 ng／L,P<0．05);刺激同种异体淋巴细胞增殖能力(SI)增强(1．9±0．6 vs 1．2±0．5,P<0．05)．结论:LAM体外可增强慢乙肝患者树突状细胞活性．     

rAAV／HCV核心抗原基因转染树突状细胞的免疫功能研究

目的 研究通过rAAV／HCV（hepatitis Cvirus,HCV）核心抗原基因（Coregene）转染树突状细胞（dendritic cell,DC）制备DC疫苗的免疫功能。方法分离外周血单个核细胞（DC前体细胞）,以rAAV／Core／Neo病毒转染DC前体细胞（基因转染组）,同时设293细胞裂解物刺激为对照组,转染12h后,均采用GM-CSF、IL-4、TNF-α诱导成熟。7天后收集细胞,流式细胞仪检测rAAV／Core／Neo病毒转染效率（即HCV核心抗原表达率）及DC表面标志CDl4、CD40、CD80、CD83、CD86的表达情况,混合淋巴细胞实验检测DC刺激自体T细胞增殖的能力,^51Cr释放法检测CTL对抗原阳性靶细胞的杀伤效率及特异性。结果rAAV／Core／Neo转染DC的效率超过90％,成熟DC高表达CD40、CD80、CD83、CD86,转染后的DC具有较强的刺激自体T细胞增殖能力,其CTL对HCV核心抗原阳性靶细胞具有很高的杀伤率及抗原特异性。结论rAAV／Core／Neo能够高效转染DC,转染后的DC能刺激自体T细胞增殖,使CTL对HCV核心抗原阳性靶细胞具有杀伤活性。     

HBV抗原基因修饰树突状细胞疫苗体外抗HBV的作用

目的：探讨腺病毒载体介导HBV抗原基因修饰的树突状细胞(DCs)诱导抗HBV特异性CTL反应方法：制备携带HBsAg、HBeAg和HBcAg基因的3种重组腺病毒Ad-HBs,Ad-HBe,Ad- HBc,分别转染自脐带血体外诱导培养的DCs,观察腺病毒转染DCs效率和DCs中HBV抗原的表达;混合淋巴细胞反应(MLR)测定HBV抗原基因修饰DCs刺激同种异体T淋巴细胞增殖能力;乳酸脱氢酶释放法检测特异性CTL细胞对HepG_222．1．5靶细胞的杀伤能力．结果：腺病毒载体能够高效介导HBV三个抗原基因在DCs中表达,90%以上DCs表达示踪基因EGFP,且DCs细胞形态完整：感染后72 h HBsAg和HBeAg含量分别为0．919和0．328(吸光度A值)．MLR实验显示,HBV抗原基因修饰DCs仍然具有刺激同种异体T细胞的增殖能力,Ad-HBs转染DCs组、Ad-HBe转染DCs组、Ad-HBc转染DCs组和未转染DCs组之间刺激T细胞的增殖水平无明显差异(F=1．194,P=0．389);在E：T比例为2：1,10：1和25：1时,Ad-HBs转染DC组、Ad-HBe转染DCs组和Ad-HBc转染DCs组对HepG_222．1．5细胞的杀伤率均明显高于未转染DCs组(P＜0．001);以Ad- HBc转染DC组对HepG_222．1．5细胞杀伤率最高．结论：HBV抗原基因修饰DCs疫苗具有刺激同种异体T细胞增殖能力,同时能增强抗HBV特异性CTL反应的能力,可能发展为一种新型抗病毒疫苗．     

胰腺癌细胞总RNA转染树突细胞与胰腺癌-树突融合细胞激发特异性细胞毒T淋巴细胞能力的比较研究

目的比较人胰腺癌MiaPaCa-2细胞总RNA电转染树突细胞(Dendritic Cell,DC)与DCMiaPaCa-2融合细胞体外激发抗原特异性细胞毒T淋巴细胞(Cytotoxic T Lymphocyte,CTL)能力的差异。方法自6例胰腺癌患者外周血单核细胞中分离、培养DC。使用电穿孔法将MiaPaCa-2细胞总RNA转染DC,使用细胞融合方法将胰腺癌MiaPaCa-2细胞抗原负载DC,以未负载抗原的DC为对照。使用流式细胞术(FCM)检测PE-MUC/FITC-CD86抗体双标细胞评估融合效率;四甲基偶氮唑盐(MTT)检测转染各组DC存活率;混合细胞培养法评价各组DC体外刺激自体T淋巴细胞增殖能力;ELISA法检测各组DC体外激发抗原特异性CTL因子释放量。结果采用PEG-DMSO诱导的DC与MiaPaCa-2的融合细胞同时表达DC表型和MUC1分子,CD86与MUC1双阳性表达率为(42.3±7.30)%;融合细胞组DC存活率呈时间依赖性下降,转染后96h的存活率降低至62.81%,而MiaPaCa-2总RNA转染组DC细胞存活率稳定在85%左右,两组间差异有统计学意义(P0.05);转染MiaPaCa-2总RNA DC刺激自体T细胞增殖指数(DC:T=1:10)为8432±611.25,显著高于DC-MiaPaCa-2融合细胞(DC:T=1:10)5672±107.51(P0.05);且MiaPaCa-2总RNA转染DC激发特异性CTL分泌IL-12p70、IL-10和IFN-γ细胞水平亦显著异于DC-MiaPaCa-2融合细胞(P0.05)。结论胰腺癌细胞总RNA转染DC较胰腺癌-树突融合细胞有更强的体外抗原特异性CTL激发能力。     

负载肝癌抗原树突细胞瘤苗对癌细胞免疫抑制作用

目的探讨人自体肝癌细胞裂解物致敏的树突细胞(DC)瘤苗对自体肝癌细胞免疫功能的影响。方法从肝癌患者外周血单个核细胞中诱导DC,用相关细胞因子及自体肝癌细胞刺激活化,制备DC瘤苗;应用流式细胞仪检测T淋巴细胞增殖情况,观察刺激术前及术后自体的T淋巴细胞以及产生的特异性的细胞毒性T淋巴细胞(CTL)对自身肿瘤细胞的抑制效果。结果肝癌DC瘤苗刺激术后自体T淋巴细胞增殖能力及抑制肿瘤细胞作用显著强于术前,T淋巴细胞增殖指数术后(1.86±0.15)较术前(1.18±0.13)显著增高、CD8+T细胞增殖指数术后(1.55±0.35)较术前(0.95±0.12)增加显著,术后与术前比较差异均有统计学意义(均P0.05)。肝癌DC瘤苗活化的术后自体CTL对自体肝癌细胞有较强杀伤作用,杀伤率由术前的(32.35±2.26)%增加到术后的(69.80±3.45)%。结论肝癌DC瘤苗活化的术后自体CTL对自体肝癌细胞杀伤作用比术前作用显著,DC瘤苗能有效地诱导抗肿瘤免疫反应,有望在肝癌术后的治疗中发挥作用。     

生存素siRNA表达质粒对MGC-803细胞增殖的影响

目的:应用siRNA表达载体介导的RNAi技术,观察 RNA干扰沉默生存素基因对胃癌MGC-803细胞增殖的影响．方法:用脂质体介导将生存素siRNA表达质粒转染 MGC-803细胞,通过倒置显微镜观察转染后细胞形态学的变化,四甲基偶氮唑蓝(MTT)法检测细胞增殖活性,流式细胞术分析细胞周期的变化,逆转录聚合酶链式反应(RT-PCR)方法检测生存素mRNA的表达水平．结果:生存素siRNA表达质粒转染组MGC-803细胞变圆、浮起,生存素siRNA表达质粒明显下调MGC-803 细胞内生存素mRNA的表达,与空白对照组相比降低了48．2％,阻断细胞周期在G1期(77．4％),显著抑制细胞增殖,siRNA转染组细胞吸光度比空白组显著降低 (24 h:0．272±0．048 vs 0．576±0．018;48 h:0．270±0．060 vs 0．809±0．027;72 h:0．143±0．046 vs 1．015±0．075;均 P<0．01)．转染24,48和72 h后的抑制率分别为53．4％, 66．7％和86.3％．结论:应用siRNA表达载体介导的RNAi技术,可有效下调生存素在MGC-803细胞中的表达,并在体外抑制细胞的增殖．     

胰腺癌细胞总RNA转染树突细胞诱导特异性CTL能力的体外研究

目的观察人胰腺癌Mia Pa Ca-2细胞总RNA电转染树突细胞(Dendritic Cell,DC)体外激发抗原特异性细胞毒T淋巴细胞(Cytotoxic T Lymphocyte,CTL)的能力。方法自6例胰腺癌患者外周血单核细胞中分离、培养DC。使用电穿孔法将Mia Pa Ca-2细胞总RNA体外转录和PCR扩增的MUC1m RNA转染DC,以未负载抗原的DC为对照。采用实时定量PCR技术检测各组DC中MUC1表达。四甲基偶氮唑盐(MTT)检测转染各组DC存活率变化;混合细胞培养法评价各组DC体外刺激自体T淋巴细胞增殖能力;ELISA法检测各组DC体外激发抗原特异性CTL细胞因子释放量。结果 Mia Pa Ca-2总RNA与MUC1 m RNA分别转染后48 h DC中目标抗原的相对表达量分别为37.24±3.17和34.53±2.02,两者比较无显著差异(P0.05)。电转染后96 h Mia Pa Ca-2总RNA转染组DC存活率降至60.81%,低于MUC1 m RNA单转染时DC的存活率(80%左右)(P0.05)。转染Mia Pa Ca-2总RNA DC刺激自体T细胞增殖指数为8 432±611.25,显著高于MUC1单独转染组3 664±305.17(P0.05);且转染Mia Pa Ca-2总RNA DC激发特异性CTL分泌IL-2、IL-10、Granzyme B、IFN-γ水平亦显著高于MUC1 m RNA单独转染组(P0.05)。结论胰腺癌肿瘤细胞总RNA转染的DC较单一胰腺癌相关抗原负载DC有更强的体外抗原特异性CTL激发能力。     

来氟米特对狼疮患者树突状细胞作用机制的初探

目的　探讨来氟米特(LEF)处理前后系统性红斑狼疮(SLE)患者树突状细胞(DC)表面标志及功能的改变,揭示LEF治疗SLE的作用机制,为开展“抑制性DCs”治疗SLE奠定实验基础。方法　(1)分离SLE患者外周血单核细胞,用细胞因子诱导DC成熟, LEF组再加入A7717262(来氟米特的活性代谢产物)培养。第9天收集DC细胞,流式细胞仪检测CD80、CD83、CD86和HLA DR的表达。(2)分别将A771726处理或不处理的第9天DC和T细胞进行培养, 72h后用MTT法检测DC刺激淋巴细胞增殖的能力,FACS检测T细胞亚群和ELISA检测培养上清中IL 10和IFNγ水平。结果A771726处理后虽DC形态无改变,但DC表达CD83、CD86和HLA DR百分数较对照组均明显降低(72 70±1 77vs 79 36±4 80, 63 50±14 06vs. 83 91±9 81, 80 44±12 56vs. 90 51±8 63,P值均<0 01)。A771726处理后的DC,其刺激T细胞增殖相应的吸光度值明显降低,混合培养的上清液中IL 10水平较无A771726处理的DC与T细胞的混合培养上清液明显降低,而IFNγ两者间无显著差异;但见CD 4 CD 25CTLA 4 T细胞百分比增高。结论　LEF在体外可抑制SLE患者外周血DC的成熟;未成熟DC能抑制T细胞增殖及T细胞向Th2 细胞转化,诱导CD 4 CD 25CTLA 4 T细胞产生,从而纠正SLE患者的部分免疫紊乱。     

自体DC体外增强结肠腺癌患者TDLN细胞的抗肿瘤活性

目的:探讨自体树突状细胞(DC)体外对结肠腺癌患者肿瘤引流区淋巴结(TDLN)细胞抗肿瘤活性的增强作用．方法:分离肿瘤患者的外周血单个核细胞 (PBMC)经IL-4,GM-CSF和TNF-α诱导其成熟,并以自体肿瘤冻融抗原预致敏,诱导其中的DC．另外,分离结肠癌患者的TDLN细胞, 在含有IL-2的培养体系中培养,并将TDLN 细胞分为3组:第1组为肿瘤抗原致敏的DC加 TDLN细胞(DC组);第2组冻融的肿瘤抗原加 TDLN细胞(Ag组);第3组不加DC及肿瘤抗原作为对照组(L组)．比较3组TDLN细胞对结肠腺癌细胞系LS174T和黑色素瘤细胞系A375的杀伤作用．结果:DC组对LS174T细胞系的杀伤作用明显优于Ag组与L组(效靶比为20:1时,56．13％±7．33％ vs 42．46％±7．68％,33．50％±7．00％, P<0．001:效靶比为10:1时,44．85％±6．50％ vs 30．50％±9．17％,26．75％±8．88％,P<0．001); 而对A375细胞,各组细胞的杀伤作用没有明显差异．结论:自体DC可明显增强结肠癌患者TDLN 细胞的杀伤作用．     

脐血树突状细胞介导的食管癌疫苗实验研究

目的　用杂交瘤技术制备脐血树突状细胞 (DC)和食管癌细胞融合疫苗 ,分析其生物学特征及体外诱导特异性免疫应答的能力。方法　 2 0 0 2 - 0 12 0 0 3- 0 3汕头大学医院第一附属医院分离脐血CD3 4 干细胞并诱导扩增为成熟DC ,并与EC10 9细胞融合 ,免疫磁珠法筛选EC10 9 DC ;流式细胞术鉴定疫苗表型 ;绘制疫苗生长曲线 ;MTT法测定瘤苗诱导淋巴细胞增殖能力及体外特异性免疫应答能力。结果　疫苗可体外生长 ,高表达CD80 、CD83 和CD86,并能有效刺激淋巴细胞增殖反应 ,体外诱导细胞毒T细胞 (CTL)对EC10 9的杀伤活性显著高于对照组 (P <0 0 5 )。结论　EC10 9 DC具备了刺激免疫细胞活化的分子表型 ,能在体外刺激淋巴细胞增殖和诱导特异性CTL杀伤作用     

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。     

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.