Comparative structural analysis of human Nav1.1 and Nav1.5 reveals mutational hotspots for sodium channelopathies

Among the nine subtypes of human voltage-gated sodium (Na_v) channels, the brain and cardiac isoforms, Na_v1.1 and Na_v1.5, each carry more than 400 missense mutations respectively associated with epilepsy and cardiac disorders. High-resolution structures are required for structure–function relationship dissection of the disease variants. We report the cryo-EM structures of the full-length human Na_v1.1–β4 complex at 3.3 Å resolution here and the Na_v1.5-E1784K variant in the accompanying paper. Up to 341 and 261 disease-related missense mutations in Na_v1.1 and Na_v1.5, respectively, are resolved. Comparative structural analysis reveals several clusters of disease mutations that are common to both Na_v1.1 and Na_v1.5. Among these, the majority of mutations on the extracellular loops above the pore domain and the supporting segments for the selectivity filter may impair structural integrity, while those on the pore domain and the voltage-sensing domains mostly interfere with electromechanical coupling and fast inactivation. Our systematic structural delineation of these mutations provides important insight into their pathogenic mechanism, which will facilitate the development of precise therapeutic interventions against various sodium channelopathies.

The nine subtypes of human voltage-gated sodium (Na_v) channels are responsible for the initiation and transmission of electrical impulses in different tissues: Na_v1.1 to Na_v1.3 and Na_v1.6 mainly function in the central nervous system, Na_v1.7 to Na_v1.9 are mostly distributed in the peripheral nervous system, Na_v1.4 is specialized in skeletal muscle, and Na_v1.5 is the primary cardiac isoform (1–4). Abnormalities of these channels, hinging on their tissue specificity, are associated with a broad spectrum of channelopathies. To date, more than 1,000 disease mutations have been identified in the primary sequence of Na_v channels, among which Na_v1.1 and Na_v1.5 each host more than 400 missense mutations (5–8).Na_v1.1 is encoded by SCN1A, which may have the largest number of epilepsy-related mutations. Up to 900 SCN1A mutations, more than half of which result in truncations (9), have been identified in epilepsy syndromes with different severities. Nonsense and hundreds of missense mutations of SCN1A are found in 70 to 80% of patients with Dravet syndrome, which is also known as the severe myoclonic epilepsy of infancy (10–13) (SI Appendix, Table S1). Several dozen missense mutations are associated with generalized epilepsy with febrile seizures plus and intractable childhood epilepsy with generalized tonic-clonic seizures (10) (SI Appendix, Table S2). Although most of the Na_v1.1 disease mutations lead to loss of function to different degrees, some represent gain of function. In most cases, the pathogenic mechanism remains elusive.A brief summary of Na_v1.5 pathophysiology is presented in the companion paper (14). Mechanistic understanding of the sodium channelopathies entails high-resolution structures of human Na_v channels. In the past 4 y, we have reported the cryoelectron microscopy (cryo-EM) structures, at resolutions ranging between 2.6 and 4.0 Å, of Na_v channels from insect (Na_vPaS), electric eel (EeNa_v1.4), and finally human, including Na_v1.2, Na_v1.4, Na_v1.5, and Na_v1.7, in the presence of multiple modulators, such as β1 and β2 subunits, peptide toxins, and small-molecule toxins tetrodotoxin and saxitoxin (15–21). Structures of a truncated rat Na_v1.5 were recently reported (22). All structurally resolved eukaryotic Na_v channels except for Na_vPaS exhibit similar conformations of potentially inactivated state.Notwithstanding these advances, high-resolution structures of human Na_v1.1 and Na_v1.5 wild-type and representative disease variants are necessary to provide accurate templates to directly map the disease mutations and to facilitate drug discovery. Furthermore, as these two channels harbor 80% of all identified mutations related to sodium channelopathies, a comparative analysis of their structures may reveal potential mutational hotspots, offering invaluable insight into the function and disease mechanism of Na_v channels.Here we present the cryo-EM structure of human Na_v1.1 associated with a modulating auxiliary subunit β4. In the accompanying paper, we report the structure of human Na_v1.5 that carries a common disease variant E1784K. Comparative structural analyses have revealed several clusters of disease mutations that are common to both Na_v1.1 and Na_v1.5.     

Differential Effect of Adenosine on Anterograde and Retrograde Fast Pathway Conduction in Patients with Atrioventricular Nodal Reentrant Tachycardia

Adenosine and Retrograde Fast Pathway Conduction . Introduction : Several studies have shown that the fast pathway is more responsive to adenosine than the slow pathway in patients with AV nodal reentrant tachycardia. Little information is available regarding the effect of adenosine on anterograde and retrograde fast pathway conduction.
Methods and Results : The effects of adenosine on anterograde and retrograde fast pathway conduction were evaluated in 116 patients (mean age 47 ± 16 years) with typical AV nodal reentrant tachycardia. Each patient received 12 mg of adenosine during ventricular pacing at a cycle length 20 msec longer than the fast pathway VA block cycle length and during sinus rhythm or atrial pacing at 20 msec longer than the fast pathway AV block cycle length. Anterograde block occurred in 98% of patients compared with retrograde fast pathway block in 62% of patients ( P < 0.001). Unresponsiveness of the retrograde fast pathway to adenosine was associated with a shorter AV block cycle length (374 ± 78 vs 333 ± 74 msec, P < 0.01), a shorter VA block cycle length (383 ± 121 vs 307 ± 49 msec, P < 0.001), and a shorter VA interval during tachycardia (53 ± 23 vs 41 ± 17 msec, P < 0.01).
Conclusion : Although anterograde fast pathway conduction is almost always blocked by 12 mg of adenosine, retrograde fast pathway conduction is not blocked by adenosine in 38% of patients with typical AV nodal reentrant tachycardia. This indicates that the anterograde and retrograde fast pathways may be anatomically and/or functionally distinct. Unresponsiveness of VA conduction to adenosine is not a reliable indicator of an accessory pathway.     

Role of fine‐needle aspiration cytology and fluid cytology in extra‐pulmonary tuberculosis

Extra‐pulmonary tuberculosis is the presence of disease in an organ without obvious involvement of the lungs (World Health Organization, Tuberculosis Fact sheet, 2006). The present article focuses on the incidence of extra‐pulmonary tuberculosis as an emerging and clinically significant disease to be reckoned with in the present era. It also highlights fine‐needle aspiration cytology (FNAC) as an inexpensive, less invasive procedure for early diagnosis of such tuberculosis and timely initiation of specific therapy. All cases of proved tuberculosis presenting to the M.V.J. Medical College and Research Hospital were recorded over a period of two years (2008–2010); and categorized as pulmonary and extra‐pulmonary cases. A total of 96 cases of tuberculosis were observed; extra‐pulmonary tuberculosis was seen in 64 cases. Of these 56 cases were from lymphnodes and 8 from extra‐nodal sites which included tuberculous dactylitis (two cases), tuberculous mastitis (two cases), tuberculous synovial effusion (one case), pericardial effusion (one case), epididymo‐orchitis (one case), and cold abscess (one case). The cytology patterns observed included granulomatous inflammation and necrosis with or without acid fast bacilli. Diagn. Cytopathol. 2013. © 2012 Wiley Periodicals, Inc.     

Change of Mechanical Properties of Repair Mortars after Frost Resistance Rests

The use of repair mortars for concrete structures repair with no or limited resistance to the impact caused by freeze and thaw cycles is often the primary repair failure cause. This is particularly important in Poland. Due to the geographical location of the country, there is a large temperature difference between summer and winter. The number of passes through the threshold temperature of 0 °C throughout the year in the winter season exceeds 100. The article presents a comparison of the frost resistance results of tests of repair mortars. The first method was performed according to the Polish Guidelines (without the use of de-icing salts) and the second method according to PN-EN 1504-3 (with the use of de-icing salts). The results obtained were inconsistent in many areas. In particular, significant differences in the results for the change in compressive strength and the change in bending strength were observed. In the case of the frost resistance testing without the use of de-icing salts, a decrease in compressive strength was usually accompanied by a decrease in bending strength. In the case of frost resistance tests with the use of de-icing salts, an increase in the bending strength of mortars was observed (even by a dozen or so percent) with a decrease in the compressive strength of mortars (even by several dozen percent).     

施行负压吸引快速羊水减量术孕妇的围术期护理

目的探讨负压吸引快速羊水减量术治疗羊水过多孕妇的围术期护理方法。方法回顾性分析并总结2010年5月至2012年12月在同济大学附属第一妇婴保健院施行快速负压吸引羊水减量术的57例孕妇的临床资料。结果 57例孕妇行羊水减量术75次,平均抽取羊水量为(2640±1208)ml,手术过程均顺利;1例孕妇当日发生胎膜早破流产,无胎盘早剥及宫腔感染发生。结论精心细致的围术期护理有利于缓解负压吸引快速羊水减量术孕妇的紧张心理,减少术后并发症的发生,改善妊娠结局。     

快通道心脏外科技术应用于非体外循环冠脉搭桥术的护理研究

目的探讨快通道心脏外科技术行非体外循环冠状动脉旁路移植术(OPCABG)患者的护理特点。方法 32例OPCABG患者,其中16例术后手术室内即刻拔除气管内插管,16例术后常规机械辅助通气,比较两组患者围手术期资料,探讨护理的特点。结果两组一般临床资料除高血压、左室射血分数因素外其他因素构成比相同,无统计学差异。两组无手术死亡。与对照组相比,快通道组ICU时间缩短、术后住院时间缩短。结论快通道心脏外科技术应用于OPCABG是安全有效,呼吸系统管理和术后镇痛是术后护理的重点。     

快速康复外科在经鼻蝶入路垂体瘤切除术围术期护理中的应用

目的 探讨快速康复外科理念在经鼻蝶入路垂体瘤切除术患者围术期护理中应用的效果.方法 回顾分析本科490例经鼻蝶入路垂体瘤切除术患者的临床资料,其中93例运用快速康复理念进行围术期护理,总结护理经验.结果 快速康复外科理念的应用,减少了患者心理和生理的应激反应.结论 应用快速康复外科理念对经鼻蝶入路垂体瘤切除术患者进行围术期护理,有利于减少患者的应激反应、缩短住院日、降低住院费用、促进患者康复.     

Frequency analysis of first heart sound for the elderly

Frequency analysis of first heart sound in elderly and expired cases was performed to reveal changes of the cardiovascular system accompanying aging. The vibration was analyzed for isometric contraction phase or 0.06 seconds following the main vibration of first sound by means of fast Fourier transform technique, and main frequency was compared. Mean main frequencies were 43.0 +/- 15.4 cps (mean +/- SD) in 21 cases from 54 years to 69 years, 41.4 +/- 12.6 cps in 34 cases from 70 years to 79 years, 40.0 +/- 14.4 cps in 19 cases from 80 years to 89 years, and 44.2 +/- 4.5 cps in 4 cases from 90 years to 94 years. It was 44.4 +/- 8.0 cps in 6 cases with left ventricular hypertrophy (LVH) on ECG, and 37.2 +/- 7.5 cps in 18 cases without LVH. It was 35.7 +/- 6.5 cps in 9 cases who expired and 32.6 +/- 5.8 cps in cases of those who died within a year. Though mean main frequencies were almost equal in these groups, it is higher than that of younger subjects, which suggests stiffness of the cardiovascular system of the aged. It was suggested that the stiffness of the cardiovascular system is greater than the increase in cardiac weight of elderly subjects with LVH. Mean main frequency was low in subjects who dies within a year, which may be due to cardiomegaly.     

Properties and substrate of slow pathway exposed with a compact node targeted fast pathway ablation in rabbit atrioventricular node

INTRODUCTION: The properties and substrates of slow and fast AV nodal pathway remain unclear. This applies particularly to the slow pathway (SP), which is largely concealed by fast pathway (FP) conduction. We designed a new FP ablation approach that exposes the SP over the entire cycle length range and allows for its independent characterization and ablation. METHODS AND RESULTS: Premature stimulation was performed before and after FP ablation with 5.4 +/- 1.9 lesions (300-microm diameter each; overall lesion size 1.4 +/- 0.5 mm) targeting the junction between perinodal and compact node tissues in seven rabbit heart preparations. The resulting SP recovery curve and control curve had the same maximum nodal conduction time (165 +/- 22 msec vs 164 +/- 24 msec; P = NS) and effective refractory period (101 +/- 10 msec vs 100 +/- 9 msec; P = NS). The two curves covered the same cycle length range. However, the SP curve was shifted up with respect to control one at intermediate and long cycle lengths and thus showed a longer minimum nodal conduction time (81 +/- 15 msec vs 66 +/- 10 msec; P < 0.01) and functional refractory period (180 +/- 11 msec vs 170 +/- 12 msec; P < 0.05). The SP curve was continuous and closely fitted by a single exponential function. Small local lesions (2 +/- 1) applied to the posterior nodal extension resulted in third-degree nodal block in all preparations. CONCLUSION: The posterior nodal extension can sustain effective atrial-His conduction at all cycle lengths and account for both the manifest and concealed portion of SP. Slow and FP conduction primarily arise from the posterior extension and compact node, respectively.