The anti-protozoal drug pentamidine blocks KIR2.x-mediated inward rectifier current by entering the cytoplasmic pore region of the channel

Background and purpose:

Pentamidine is a drug used in treatment of protozoal infections. Pentamidine treatment may cause sudden cardiac death by provoking cardiac arrhythmias associated with QTc prolongation and U-wave alterations. This proarrhythmic effect was linked to inhibition of hERG trafficking, but not to acute block of ion channels contributing to the action potential. Because the U-wave has been linked to the cardiac inward rectifier current (I_K1), we examined the action and mechanism of pentamidine-mediated I_K1 block.

Experimental approach:

Patch clamp measurements of I_K1 were made on cultured adult canine ventricular cardiomyocytes, K_IR2.1-HEK293 cells and K_IR2.x inside-out patches. Pentamidine binding to cytoplasmic amino acid residues of K_IR2.1 channels was studied by molecular modelling.

Key results:

Pentamidine application (24 h) decreased I_K1 in cultured canine cardiomyocytes and K_IR2.1-HEK293 cells under whole cell clamp conditions. Pentamidine inhibited I_K1 in K_IR2.1-HEK293 cells 10 min after application. When applied to the cytoplasmic side under inside-out patch clamp conditions, pentamidine block of I_K1 was acute (IC₅₀= 0.17 µM). Molecular modelling predicted pentamidine-channel interactions in the cytoplasmic pore region of K_IR2.1 at amino acids E224, D259 and E299. Mutation of these conserved residues to alanine reduced pentamidine block of I_K1. Block was independent of the presence of spermine. K_IR2.2, and K_IR2.3 based I_K1 was also sensitive to pentamidine blockade.

Conclusions and implications:

Pentamidine inhibits cardiac I_K1 by interacting with three negatively charged amino acids in the cytoplasmic pore region. Our findings may provide new insights for development of specific I_K1 blocking compounds.     

卵胞质移植、克隆与逆向克隆

目的:最近人类卵细胞间的胞质移植被作为人类辅助生殖生物技术的手段并成为研究热点。本文回顾了该领域的研究进展和存在的问题,并以此为基础提出“逆向克隆技术”这一新概念。资料来源:应用计算机检索PUBMED 1998-01/2006-12期间的相关文章,检索词为“ooplasmic transfer,mitochondria heteroplasmy,animal cloning”,并限定文章语言种类为English。同时计算机检索万方数据库1998-01/2006-12期间的相关文章,检索词为“胞质转移,线粒体异质性,动物克隆”,并限定文章语言种类为中文。资料选择:对资料进行初审,并查看每篇文献后的引文。纳入标准:文章所述内容应与卵胞质移植、克隆或逆向克隆研究相关。排除标准:重复研究或Meta分析类文章。资料提炼:共收集到126篇相关文献,31篇文献符合纳入标准,排除的95篇文献为内容陈旧或重复。符合纳入标准的31篇文献中,17篇涉及卵胞质移植,13篇涉及动物克隆,1篇涉及逆克隆。资料综合:人类的生殖技术领域发展迅速,卵胞质移植技术得到广泛应用。研究表明,卵胞质对受精和胚胎发育具有重要作用,其中线粒体与受精和胚胎发育关系最为密切。大量实验对细胞质与细胞核的相互作用、基因组的重编程机制上进一步研究,同时也在技术上不断改进。克隆技术有广阔的应用前景,同时也存在着不少问题,基于此提出以胞质转移为基础的“逆向克隆技术”。结论:线粒体对卵母细胞的受精和胚胎发育有显著影响,但卵胞质移植可能导致线粒体的异质性及其潜在的问题还需要进一步研究。以卵胞质转移为基础的“逆向克隆技术”是否能达到克隆动物的结果前景喜人。     

Plunging ranula: CT diagnosis

A plunging ranula is a cystic mass in the submandibular area arising from an occluded sublingual gland. Fluid from the obstructed gland dissects between the fascial planes and muscle of the base of the tongue to the submandibular triangle. A plunging ranula can be readily identified preoperatively with computed tomography as a cystic mass in the suprahyoid anterior neck. Three case reports are presented.     

Two-dimensional iodopeptide mapping demonstrates that erythrocyte Rh D, c, and E polypeptides are structurally homologous but nonidentical

The 32,000 molecular weight (mol wt) erythrocyte Rh D, c, and E polypeptides were separately purified from cDE/cDE erythrocytes by monoclonal immunoprecipitations and compared by two-dimensional iodopeptide mapping. Digestions of the isolated Rh polypeptides with alpha-chymotrypsin revealed a high degree of structural homology between c and E (13/14 iodopeptides were identical) and less striking homology between D and c or E (8/19 identical). The iodopeptide maps of Rh proteins purified by a nonimmunologic protocol from cDE/cDE erythrocytes were virtually identical to the composite pattern (D + c + E) deduced from the individual maps of Rh D, c, and E iodopeptides. Digestions of the isolated Rh polypeptides with trypsin revealed an overall homology of approximately 50% between iodopeptides derived from D, c, and E. These data indicate that the erythrocyte Rh D, c, and E antigens are carried by homologous but distinct molecular species; c and E appear more closely related to each other than to D.     

South African hypertension practice guideline 2014

This is the sixth hypertension guideline published by the Southern African Hypertension Society (SAHS). Currently 30.4% of the adult population have hypertension (HTN),1 necessitating a simplified approach to assessment and treatment, which reflects realistic objectives that can be implemented by medical practitioners, nurse practitioners and pharmacists to diminish the impact of HTN and related cardiovascular disease (CVD) risk in this country. For full details on management not contained in this document please refer to the more detailed hypertension guideline 2011.2     

Differential expression of p53, p21waf1/cip1 and hdm2 dependent on DNA damage in Bloom's syndrome fibroblasts

The Bloom's syndrome gene, BLM, encodes a protein which bears homology to the RecQ helicases. It is believed to be involved in DNA replication and has been implicated in the maintenance of genomic stability. To investigate whether BLM was involved in cellular responses to DNA damage Bloom's syndrome fibroblasts were treated with either UV or ionizing radiation and the levels of p53 and two of its down stream effectors, p21waf1/cip1 and hdm2, were determined by western blot analysis. Following 20 J/m2 UVC-radiation we observed that the maximal accumulation of p21waf1/cip1 and hdm2 proteins preceded that of p53 in both a normal diploid fibroblast cell strain (GM0038) and in two Bloom's syndrome cell strains. Furthermore, the Bloom's syndrome cells demonstrated a delayed and prolonged accumulation of all three proteins and a delayed recovery of the protein levels back to pre-damage levels compared with the normal cell strain. Conversely, normal and Bloom's syndrome cell response following 2.5 Gy of ionizing radiation was quite similar for p21waf1/cip1 and hdm2, but differed significantly for p53. Maximum accumulation of p53 occurred within 2 h of damage and preceded that of p21waf1/cip1 and hdm2. These results suggest that the BLM protein may play a role in the detection of certain types of DNA damage and in the cellular response to that damage.      

The effect of diabetes mellitus on the association between measures of glycaemic control and ICU mortality: a retrospective cohort study

Introduction

In critical illness, four measures of glycaemic control are associated with ICU mortality: mean glucose concentration, glucose variability, the incidence of hypoglycaemia (≤ 2.2 mmol/l) or low glucose (2.3 to 4.7 mmol/l). Underlying diabetes mellitus (DM) might affect these associations. Our objective was to study whether the association between these measures of glycaemic control and ICU mortality differs between patients without and with DM and to explore the cutoff value for detrimental low glucose in both cohorts.

Methods

This retrospective database cohort study included patients admitted between January 2004 and June 2011 to a 24-bed medical/surgical ICU in a teaching hospital. We analysed glucose and outcome data from 10,320 patients: 8,682 without DM and 1,638 with DM. The cohorts were subdivided into quintiles of mean glucose and quartiles of glucose variability. Multivariable regression models were used to examine the independent association between the four measures of glycaemic control and ICU mortality, and for defining the cutoff value for detrimental low glucose.

Results

Regarding mean glucose, a U-shaped relation was observed in the non-DM cohort with an increased ICU mortality in the lowest and highest glucose quintiles (odds ratio = 1.4 and 1.8, P < 0.001). No clear pattern was found in the DM cohort. Glucose variability was related to ICU mortality only in the non-DM cohort, with highest ICU mortality in the upper variability quartile (odds ratio = 1.7, P < 0.001). Hypoglycaemia was associated with ICU mortality in both cohorts (odds ratio non-DM = 2.5, P < 0.001; odds ratio DM = 4.2, P = 0.001), while low-glucose concentrations up to 4.9 mmol/l were associated with an increased risk of ICU mortality in the non-DM cohort and up to 3.5 mmol/l in the DM cohort.

Conclusion

Mean glucose and high glucose variability are related to ICU mortality in the non-DM cohort but not in the DM cohort. Hypoglycaemia (≤ 2.2 mmol/l) was associated with ICU mortality in both. The cutoff value for detrimental low glucose is higher in the non-DM cohort (4.9 mmol/l) than in the DM cohort (3.5 mmol/l). While hypoglycaemia (≤ 2.2 mmol/l) should be avoided in both groups, DM patients seem to tolerate a wider glucose range than non-DM patients.     

藏药薰倒牛的活性物质研究

从植物藏药薰倒牛(BiebersteiniaheterostemonMaxim.)中首次分离得7个化合物,经化学方法和光谱解析鉴定为:β-谷甾醇(Ⅰ)、胡萝卜甙(Ⅱ)、伞形花内酯(Ⅲ)、5,7,3′-三羟基-8,4′,5′-三甲氧基黄酮(Ⅳ)、木犀草素-7-葡萄糖甙(Ⅴ)、槲皮素-7-葡萄糖甙(Ⅵ)和N-3-甲基-2-丁烯基脲(Ⅶ)。其中Ⅳ和Ⅶ是二个新的天然产物。药理实验表明化合物Ⅶ有镇痛、降压等活性。     

颅内血管支架成形术：介入前后CTA的可行性和局限性

目的：CTA对于评估颅内动脉狭窄程度和颅内支架随访是一种无创性检查。我们通过分析一组病例来评估CTA关于颅内血管支架成形术前后的动脉狭窄程度及支架随访的可行性。方法：颅内放置支架前后的8例患者接受CTA检查,一共有9个动脉狭窄并有临床症状。用CTA与传统血管造影对观察血管狭窄程度和植入支架的大小进行比较。结果：对于支架植入前的血管狭窄程度,CTA与传统血管造影比较,相差约为-15％～12％。     

利用T_1加权DCE-MRI技术对脑胶质瘤分级

应用T1加权动态对比度增强磁共振成像(DCE-MRI)技术对脑胶质瘤进行术前分级,验证其用于脑胶质瘤分级的准确性和可重复性。对26例脑胶质瘤患者团注Gd-DTPA对比剂后,以1.5TSiemens Syngo MRI扫描仪采集DCE T1加权图像。首先基于改进的Tofts两室药物动力学模型,从采集到的动态组图像建立病灶区感兴趣区内的平均信号强度-时间曲线,然后应用非线性最小二乘拟合方法对该曲线进行拟合,获取定量参数。这些参数包括:初始增强率ER、回流速率常数Kep、排泄速率常数Kel、曲线下面积AUC、峰值高度PH、到达峰值的时间TTP,最后与临床组织病理学结果进行比较,建立这些定量参数与脑胶质瘤分级之间的定量关系。采用独立样本t检验比较任意两个分级之间各定量参数的统计学差异,P0.05作为统计学差异标准。ER、AUC和PH随着脑胶质瘤的病理分级由低到高地增加;低级别脑胶质瘤中的Ⅰ与Ⅱ级之间以及高级别中的Ⅲ与Ⅳ级之间的比较结果显示,ER、AUC和PH的值均无明显统计学差异(P0.05);低级别与高级别级之间的比较结果显示,仅参数ER的差异具有统计学意义(P0.05)。ER是术前准确界定脑胶质瘤低级别与高级别的最具敏感性和特异性的参数,其界定阈值约为0.68。