A boussinesq model of natural convection in the human eye and the formation of Krukenberg's spindle

The cornea of the human eye is cooled by the surrounding air and by evaporation of the tear film. The temperature difference between the cornea and the iris (at core body temperature) causes circulation of the aqueous humor in the anterior chamber of the eye. Others have suggested that the circulation pattern governs the shape of the Krukenberg spindle, a distinctive vertical band of pigment on the posterior cornea surface in some pathologies. We modeled aqueous humor flow the human eye, treating the humor as a Boussinesq fluid and setting the corneal temperature based on infrared surface temperature measurements. The model predicts convection currents in the anterior chamber with velocities comparable to those resulting from forced flow through the gap between the iris and lens. When paths of pigment particles are calculated based on the predicted flow field, the particles circulate throughout the anterior chamber but tend to be near the vertical centerline of the eye for a greatest period of time. Further, the particles are usually in close proximity to the cornea only when they are near the vertical centerline. We conclude that the convective flow pattern of aqueous humor is consistent with a vertical pigment spindle. © 2002 Biomedical Engineering Society. PAC2002: 4266Ew, 8710+e, 8719Pp     

2型糖尿病视网膜病变患者外周血单个核细胞中PEDF与TNF-α水平的变化

 目的:色素上皮衍生因子（PEDF）是影响糖尿病视网膜病变（DR）发生发展的重要因子,本研究观察2型糖尿病视网膜病变患者外周血单个核细胞（PBMCs）中PEDF、磷酸化NF-κB p65及TNF-α的表达,探讨DR的发病机制。方法:选取2011年10月~2013年4月在我院内分泌科住院确诊为2型糖尿病的患者(DM组)108例,并根据眼底造影结果将患者分为无糖尿病视网膜病变组（NDR组）52例和糖尿病视网膜病变组（DR组）56例,同期糖耐量实验正常者52例作为对照组（NC组）。密度梯度离心法收集患者 PBMCs,提取总蛋白,Western blotting检测3组患者PBMCs中PEDF、磷酸化NF-κB p65和TNF-α蛋白表达水平,ELISA测定血浆PEDF与TNF-α水平,收集患者体检指标并测量患者生化指标。结果:Western blotting检测结果显示NDR组和DR组PEDF、磷酸化NF-κB p65和TNF-α蛋白水平明显高于NC组（P<0.05）;DR组TNF-α蛋白水平明显高于NDR组（P<0.05）,DR组PEDF及磷酸化NF-κB p65蛋白水平略高于NDR组,差异无统计学意义（P>0.05）;NDR组和DR组血浆PEDF与TNF-α水平均明显高于NC组（P<0.05）,DR组明显高于NDR组（P<0.05）。在糖尿病组,血浆PEDF水平与TNF-α及血尿酸水平呈正相关（r=0.39,r=0.25,P<0.05）。结论:本研究首次证实PBMCs中可表达PEDF;2型糖尿病患者PBMCs中PEDF表达水平增加,TNF-α及血浆PEDF的表达水平上调,PEDF可能通过与炎症因子TNF-α相互作用影响DR发生发展。     

豚鼠胆囊胆固醇结石形成过程中肠道传输功能下降的细胞及分子机制探讨

目的探讨豚鼠胆囊胆固醇结石形成过程中肠道传输功能下降的细胞和分子机制及其与胆石形成的关系。方法健康雄性豚鼠40只,4周龄,体质量120～125g。将其随机分为实验组与对照组,每组20只。实验组给予致石饲料（胆固醇含量2%）,对照组给予正常颗粒饲料。8周造模结束后,用逆转录聚合酶链反应（RT-PCR）检测小肠组织中c-kit及scf的mRNA的表达情况,利用末端回肠全层铺片免疫荧光化学染色及激光共聚焦显微镜观察各组Cajal样间质细胞（ICCs）数量的变化。结果 RT-PCR结果显示,与对照组相比,实验组豚鼠小肠c-kit（0.316±0.056vs0.912±0.103;t=6.582,P〈0.01）和scf（0.499±0.012 vs 0.899±0.124;t=6.163,P〈0.01）的mRNA水平的表达量下降;对照组豚鼠回肠ICCs平均阳性面积为（56.24±2.68）%,实验组为（22.26±1.14）%,较对照组明显降低（t=15.256,P〈0.01）。结论饮食诱导的豚鼠胆囊胆固醇结石形成过程中,小肠c-kit和scf基因mRNA表达水平下降,ICCs数量明显减少。c-kit/scf通路抑制可能参与胆囊胆固醇结石的形成过程中肠道传输功能下降的发生。     

Bile acid composition in brown pigment stones

The bile acids in brown pigment stones and gallbladder bile were fractionated into free acids, glycine and taurine conjugates, and sulfates using diethylaminohydroxypropyl Sephadex LH-20 (DEAP-LH-20) column chromatography and were quantitated by gas chromatography. Twenty-eight cases of brown pigment stones were studied and divided into two groups: those with and those without bacteria possessing bile acid-deconjugating activity. In the former, free bile acid amounted to 62±34% of the total bile acid, while in the latter, only 0.1% of total bile acid was free bile acid. The fraction of total bile acid made up of free bile acids was found to be consistently higher in brown pigment stones than in the corresponding bile, irrespective of the presence or absence of biliary infection. Free bile acid is present in negligible amounts in normal bile. Total bile acid concentration in the bile of patients with brown pigment stones was significantly less than that of controls (13 vs 50 mg/ml). Biliary infection is almost always present in cases with brown pigment stones. These findings suggest that bacterial infection is present at the initiation of brown pigment stone formation as well as during the period of ensuing stone growth.     

缺氧对体外培养的大鼠肾成纤维细胞PEDF和VEGF表达的影响

目的：探讨缺氧对不同浓度葡萄糖培养的大鼠肾成纤维细胞（NRK细胞）血管内皮生长因子（VEGF）与色素上皮衍生因子（PEDF）表达和变化情况。方法：将NRK细胞分为：正常组、甘露醇组、缺氧对照组、高糖A、B组、缺氧A、B组。用四唑盐比色实验法检测各组NRK细胞的数目,用ELISA法测定NRK细胞VEGF与PEDF蛋白的表达情况。结果：与正常对照组相比,高糖组和缺氧组的NRK细胞数目显著减少（P〈0．01）。在缺氧条件下NRK细胞VEGF蛋白含量明显升高（P〈0．01,P〈0．05）,PEDF蛋白含量明显下降（P〈0．01）,并呈剂量依赖性;随着时间的延长,各组NRK细胞的VEGF蛋白含量呈上升趋势（P〈0．01）,PEDF蛋白含量呈下降趋势（P〈0．01）。结论：缺氧使不同浓度的高糖诱导的肾成纤维细胞VEGF与PEDF的表达失衡,这可能是糖尿病肾病发生的重要机制。     

着色剂氧化铈及氧化铒对牙科氧化锆陶瓷颜色及性能的影响

背景：有研究提出在氧化锆中添加稀土氧化物,可以在一定程度上改变氧化锆自身颜色,以期满足口腔临床要求,达到美观。 目的：对添加稀土氧化物氧化锆的色度值和机械性能进行评价。 方法：用ShadeEye电脑比色仪测试件的L*a*b*值,用X射线衍射仪(D/max-RB)分析材料的晶相结构,在EZ-100万能实验机上测试其三点弯曲强度。使用扫描电镜观察试样弯曲断口显微形态。 结果与结论：①烧结后所形成的氧化锆试件材料主晶相结构为四方相氧化锆,未见第2种晶相结构。②氧化铈与氧化锆混合呈淡黄色;氧化铒与氧化锆混合呈浅粉红色,并随着剂量的增加,颜色随之加深;二者混合试件使氧化锆呈浅桔黄色,并随着剂量的增加,颜色随之加深。③单独添加二氧化铈后,材料的抗弯强度呈下降趋势,单独添加氧化铒后,材料的抗弯强度呈下降趋势,二氧化铈和氧化铒混合试件抗弯强度随二氧化铈和氧化铒含量的增加而降低,单独添加二氧化铈仅少量降低了抗弯强度,当加入氧化铒后对材料强度降低的影响更加明显。表明,稀土氧化物与氧化锆混合可以改变氧化锆自身颜色,并且具有一定的抗弯性。     

Upper gastrointestinal emergencies

Upper gastrointestinal emergencies form the majority (in some centres 60–70%) of an unselected general surgical emergency take and non-specialist general surgeons need to have a thorough knowledge of the presentation and initial management of these conditions. Recent developments in the management of gallstone disease, pancreatitis and liver trauma in particular are covered in this article.     

氩激光光凝诱导兔视网膜色素上皮变性后其功能与形态的变化

目的通过氩离子激光诱导建立兔视网膜色素上皮(retinal pigment epithelium,RPE)局部变性模型,观察光凝前、后视网膜功能及形态特征。方法青紫蓝兔10只,其中7只兔左眼行氩离子眼底激光光凝,分别检测激光光凝前及光凝后不同时间点的闪光视网膜电图(flash-electroretinography,F-ERG),分析视功能改变情况。另3只实验兔按同样方法建模后7d摘除眼球做病理切片,HE染色后光镜下观察其组织病理学改变。结果激光光凝后1 d F-ERG中视杆细胞反应b波波幅降至最低,3d后有小幅回升并趋于平稳,但仍低于光凝前水平,峰潜时无显著变化;光凝后4h最大混合反应a、b波波幅降至最低,1d后略有回升,7d后呈平稳状态低于光凝前水平,峰潜时无显著变化;光凝后1d振荡电位OPs的∑O值降至最低,3d后逐步回升,但仍低于光凝前水平。光凝后7dRPE细胞变性破坏,深层脉络膜及节细胞层无明显影响。结论激光光凝可以破坏RPE细胞及邻近光感受器细胞,建立RPE局部变性模型,其功能与形态均有改变。     

激光损伤致猪视网膜色素上皮细胞中游离钙变化的实验研究

目的探讨激光照射后视网膜色素上皮（ＲＰＥ）细胞中游离钙的变化规律。方法用不同输出功率的氩离子激光照射培养的猪ＲＰＥ细胞（光斑直径２００μｍ,照射时间０２ｓ）,用激光扫描共聚焦显微镜测量光凝斑周围ＲＰＥ细胞中游离钙的浓度。结果用０．９、１．８及２．７Ｗ的激光照射后,ＲＰＥ细胞中游离钙浓度（ｎｍｏｌ／Ｌ）分别为４１５±１４８、５２５±２４７、９９４±２０３,而空白对照组为２２２±６４,各组之间差异均有非常显著意义（均为Ｐ＜００１）。结论激光损伤可使ＲＰＥ细胞中游离钙浓度明显升高,升高程度与激光能量的大小呈正相关。