早产儿喂养不耐受肠道菌群多样性研究

目的：采用变性梯度凝胶电泳聚合酶链反应（ PCR－DGGE）技术从微生物生态学的角度分析比较喂养不耐受（ FI）与健康早产儿肠道细菌群落结构的多样性及相似性。方法以2013年11月至2014年9月在第四军医大学附属唐都医院儿科新生儿病房诊断为FI的早产儿为FI组。选择与FI组胎龄、日龄、出生体重相匹配的非FI早产儿作为对照组。采集出现FI时和同时间段对照组的粪便标本,进行16SrDNAV3区扩增和变性梯度凝胶电泳（DGGE）,从而分析比较两组间肠道菌群多样性指数及相似性。结果细菌多样性检测显示FI组的肠道菌群多样性指数香农－维纳指数（H）、丰度（S）、均衡度指数（E）和辛普森多样性指数（D）均低于对照组（均P＜0．05）;相似性矩阵图及聚类分析结果显示组内菌群相似性较组间高（P＜0．05）;PCA结果同聚类分析一致。结论肠道微生物群落多样性的改变及群落结构紊乱可能是引起早产儿FI的重要因素。     

Mathematical Modeling of Crystallization Elution Fractionation of Ethylene/1‐Octene Copolymers

Crystallization elution fractionation (CEF) is a relatively new polyolefin characterization technique used to estimate the chemical composition distribution (CCD) of semicrystalline copolymers. CEF is developed to enhance the resolution and reduce the analysis time of temperature rising elution fractionation (TREF) by separating polymer samples in both the crystallization and elution steps. A model based on the concept of population balance, crystallization/dissolution kinetics, and dispersion model is developed to understand the CEF fractionation mechanisms. The proposed CEF model is found to describe well the experimental CEF profiles of a series of ethylene/1‐octene copolymers with different comonomer contents.

     

On the Homogeneity of Metallocene Ethylene–Propylene Copolymers as Investigated by Multiple Fractionation Techniques

The chemical heterogeneity of ethylene–propylene copolymers by multiple fractionation techniques is addressed. Three metallocene copolymer samples with different ethylene contents, ranging from 30 to 50 mol% are analyzed using bulk methods to confirm their molecular heterogeneity. In a second step, the samples are fractionated by temperature rising elution fractionation (TREF) to obtain fractions at 30, 60, 90, and 130 °C. These fractions are subsequently analyzed regarding their thermal and molecular properties. Differential scanning calorimetry, crystallization analysis fractionation, and high‐temperature high performance liquid chromatography (HT‐HPLC) results reveal that the TREF fractions collected at 130 °C are mainly due to polypropylene homopolymer, which is rather unexpected considering the high ethylene contents of the bulk samples. Most importantly, HT‐HPLC reveals a remarkably high chemical heterogeneity of the fractions and thus the bulk samples. Solution ¹³C NMR provides the comonomer contents and sequence distributions of the fractions. These indicate that the same TREF fractions from different samples have distinctively different chemical compositions.

     

Journey of a patient with chronic thromboembolic pulmonary hypertension

Right ventricle (RV) dysfunction is a key outcome determinant and a leading cause of death for patients with chronic thromboembolic pulmonary hypertension (CTEPH). In this report, we followed the 5-year clinical journey of a patient with CTEPH. The tricuspid pressure gradient was significantly increased in the early phase of CTEPH and “normalized” at the late phase of this patient’s clinical journey, but this “normalized” gradient is not a positive treatment response but rather an ominous sign of advancing right heart failure owing to an exhaustion of RV contractile function. Thus, appropriate interpretation of the tricuspid pressure gradient change is of importance for assessing RV dysfunction and treatment outcome during follow-up in patients with CTEPH. Besides systolic pulmonary artery pressure (SPAP), other RV functional parameters such as tricuspid annular plane systolic excursion, RV fractional area change, and RV longitudinal strain, together with clinical markers, may provide additional guidance regarding functional improvement or progression in patients with CTEPH.     

High systemic HCO 3 − and topical 16,16-dimethyl-PGE2 protect gastric mucosa against luminal acid by enhancing its preepithelial buffer capacity

Systemic metabolic alkalosis and topical prostaglandins protect the gastric mucosa against luminal acid. This study investigates whether this protection is mediated by increased epithelial HCO ₃ ^– secretion with resultant alkalization of the preepithelial mucus-HCO ₃ ^– buffer layer. Surface pH of chamberedex vivo rat gastric epithelium was measured with liquid sensor pH microelectrodes during luminal perfusion of increasing acidities (0, 10, 30, 50, 100 mM HCl). The experimental groups were: (1) control, (2) topical 16,16-dimethyl-PGE₂ treatment, (3) high-HCO ₃ ^– metabolic alkalosis, and (4) low-HCO ₃ ^– respiratory alkalosis. The gastric mucosa of PGE₂-treated and high-HCO ₃ ^– alkalotic rats tolerated significantly better luminal acid than that of controls, but the tolerance of low-HCO ₃ ^– alkalotic rats was significantly impaired. There was a significant correlation between arterial HCO ₃ ^– concentration (but not arterial pH) and surface pH (r=0.81,P<0.01). This suggests that the protective actions of systemic high-HCO ₃ ^– alkalosis and topical-PGE₂ treatment in the gastric mucosa against luminal acid are, at least in part, mediated by enhanced buffer capacity of the preepithelial mucus-HCO ₃ ^– layer.This study is supported by grants from the Medical Research Council of the Academy of Finland and Sigrid Juselius Foundation, Helsinki, Finland and Orion Research Council, Espoo, Finland.     

Clinical events after transjugular intrahepatic portosystemic shunt: Correlation with hemodynamic findings

Background & Aims: Transjugular intrahepatic portosystemic shunt (TIPS) procedures are increasingly being used, but the relationship between the hemodynamic effects of TIPS and the clinical events on follow-up remains undefined. Hence, we have investigated the hemodynamic correlations of portal hypertension–related events after a TIPS procedure. Methods: Prospective follow-up of 122 cirrhotic patients who had a TIPS procedure performed because of variceal hemorrhage was conducted. Results: The portacaval pressure gradient (PPG) significantly decreased after the TIPS procedure (from 19.7 ± 4.6 to 8.6 ± 2.7 mm Hg; P > 0.001), but increased thereafter and at rebleeding (n = 25) was >12 mm Hg in all patients (18.4 ± 4.6 mm Hg). Twenty-six patients developed ascites; the PPG (measured in 19) was always >12 mm Hg. Increasing the PPG to >12 mm Hg occurred very frequently (83% at 1 year). Within 1 year, 77% of patients underwent balloon angioplasty or restenting. However, 80% had again a PPG of >12 mm Hg 1 year after reintervention. Hepatic encephalopathy developed in 31% of patients at 1 year; 21 of 23 patients had a PPG of <12 mm Hg. Conclusions: Total protection from the risk of recurrent complications of portal hypertension after a TIPS procedure requires that the PPG be decreased and maintained <12 mm Hg. However, reintervention will be required in most patients within 1 year and again the second year. On the other hand, such portal decompression is associated with an increased risk of hepatic encephalopathy.GASTROENTEROLOGY 1998;114:1296-1303     

Acoustic analysis for a split MRI system using FE method

In some MRI‐LINAC (Magnetic Resonance Imaging and Linear Accelerator) hybrid systems, the MRI scanner is split into two parts to form a central gap for the accommodation of the patient or a LINAC. Little is known about the acoustic characteristics of the split gradient coil structure needed for this system; however, it is believed to be very different from its typical configurations. It is important to develop dedicated numerical methods for the characterization of the unique acoustic properties, to provide engineering solutions for the noise attenuation for such a new system. In this article, we modeled the acoustic fields of a split MRI system and traditional gradient structures using the finite element method. The models were validated against acoustic experimental results obtained from a conventional MRI scanner. The acoustic field distribution analysis showed that the average sound pressure levels in the central gap were lower than those in the cylindrical tunnels of the split MRI system at most frequencies. This was also true when both the x coils or z coils were energized independently. Thus, if the patient bed is placed perpendicular to the axis of the main magnet of the split MRI system, the patient will be subjected to relatively lower acoustic intensities compared with that if the patient bed is placed parallel to the axis of the main magnet. Further work is planned to reduce the sound level in the central gap where the patient bed may be placed for this split system. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 45B: 85–96, 2015     

奥曲肽治疗对食管胃底静脉曲张出血的肝静脉压力梯度及血流速度的影响观察

目的:观察奥曲肽治疗肝硬化门静脉高压食管胃底静脉曲张出血肝静脉压力梯度(HVPG)等的变化,探讨奥曲肽止血机制.方法:采用随机对照的方法,病例分为低剂量奥曲肽治疗组(A组,n=18);高剂量奥曲肽治疗组(B组,n=18)和对照组(C组,n =18).治疗肝硬化食管胃底静脉曲张出血,在基础治疗(禁食、输液、输血、对症处理)的基础上,全部病例予以奥美拉唑注射液40 mg,每12h1次静脉滴注抑酸.治疗组A、B组分别以奥曲肽注射液25、50 μg/h的速度微泵静脉维持治疗.观察治疗前后HVPG,门静脉内径,血流速度及呕血、黑便等的改变情况.结果:治疗前与治疗后24、72 h,两治疗组HVPG比较对照组显著降低,有统计学差异(P =0.00,P=0.00).而治疗组A、B治疗后24 h HVPG有统计学差异(P=0.00),治疗后72 h HVPG无统计学差异(P=0.14).治疗组比较对照组门静脉内径减小有统计学差异(P＜0.05);治疗组A、B与对照组在治疗24、72 h呕血,黑便量相比较明显减少,有统计学差异(P＜0.05).结论:奥曲肽能显著降低HVPG,减少门静脉内径,较高浓度奥曲肽在24 h内疗效更快,奥曲肽联合奥美拉唑比较单独奥美拉唑止血疗效更显著.     

HPLC-DAD法测定“武当三号金银花”不同部位中芦丁和木犀草苷的含量

目的：建立HPLC－DAD法测定“武当三号金银花”不同部位中芦丁和木犀草苷的含量。方法采用Fortis Xi Phenyl柱（250 mm ×4．6 mm,5μm）;流动相为乙腈（A）—0．5％冰醋酸溶液（B）进行线性梯度洗脱;检测波长为354 nm;柱温：30℃。结果芦丁和木犀草苷在各自测定的范围内均呈良好的线性关系（r≥0．9994）,平均回收率分别为99．4％、99．3％。结论该法操作简单,灵敏度高,重现性好,为控制“武当三号金银花”不同部位芦丁和木犀草苷的质量提供了一种可靠的方法。