Transverse versus longitudinal electrical propagation within the atrioventricular node during dual pathway conduction: Basis of dual pathway electrophysiology and His electrogram alternans (Zhang's phenomenon)

Background

We have discovered and validated that AV node dual pathway conduction results in a new phenomenon termed His electrogram alternans (HEA), which indicates dual inputs rather than a final common pathway from the AV node into the His bundle. However, the electrophysiological basis for AV node dual pathway conduction and HEA has not been clarified. This study was designed to elucidate the electrophysiological basis for dual pathway conduction and HEA.

Methods

By using HEA as an index of dual pathway electrophysiology, action potentials from multiple locations in the superior and inferior AV nodal domains were obtained to monitor electrical propagation during dual pathway conduction in 8 isolated rabbit hearts.

Results

Fibers inside the AV node were generally aligned along the AV conduction axis. During fast pathway (FP) conduction, electrical excitation in the AV node was propagated in a superior to inferior direction across the major fiber orientation. In contrast, slow pathway (SP) conduction occurred when the superior–inferior propagation failed within the superior nodal domain, permitting electrical propagation to proceed in the inferior nodal domain along the fiber orientation in a posterior to anterior direction. In effect, FP activated first the superior distal node, while SP activated first the inferior distal node. This functional dissociation of superior-fast and inferior-slow domains in distal node produced dual inputs into the His bundle.

Conclusions

Transverse versus longitudinal electrical propagation within the AV node produces functional dissociation in the distal node, resulting in superior-fast and inferior-slow inputs into the His bundle and HEA during dual pathway conduction.     

Possible ways of reducing dental erosive potential of acidic beverages

Frequent consumption of acidic beverages is related to excessive tooth wear, namely dental erosion. Preventive measures may involve reduction or elimination of acidic drink consumption. However, the success of this approach is difficult to achieve as it is highly dependent on patient compliance. Therefore, a practical way of minimizing the erosive potential of popular acidic drinks may be their chemical modification. The aim of this article was to review the different methods of modification and their shortcomings. The available literature demonstrates that the erosive potential of most acidic beverages could be reduced. To date, the effectiveness of soluble calcium salts supplementation is the best established. However, modification can reduce the sensorial quality of the drink and shorten its shelf‐life. There is also a need to evaluate the lowest effective and safe dose of the additive.     

Conservative surgical and microsurgical techniques for the management of dental implants that impinge on the inferior alveolar nerve

Loss of sensation in the lip after insertion of an implant is annoying. The aim of this paper was to describe two techniques for management of osseointegrated dental implants that impinge on the mandibular nerve, the purpose of which is to improve sensation without unscrewing the dental implant.     

Spinal transient receptor potential ankyrin 1 channel contributes to central pain hypersensitivity in various pathophysiological conditions in the rat

The transient receptor potential ankyrin 1 (TRPA1) ion channel is expressed on nociceptive primary afferent neurons. On the proximal nerve ending within the spinal dorsal horn, TRPA1 regulates transmission to spinal interneurons, and thereby pain hypersensitivity. Here we assessed whether the contribution of the spinal TRPA1 channel to pain hypersensitivity varies with the experimental pain model, properties of test stimulation or the behavioral pain response. The antihypersensitivity effect of intrathecally (i.t.) administered Chembridge-5861528 (CHEM; a selective TRPA1 channel antagonist; 5-10 μg) was determined in various experimental models of pain hypersensitivity in the rat. In spinal nerve ligation and rapid eye movement (REM) sleep deprivation models, i.t. CHEM attenuated mechanical hypersensitivity. Capsaicin-induced secondary (central) but not primary (peripheral) mechanical hypersensitivity was also reduced by i.t. administration of CHEM or A-967079, another TRPA1 channel antagonist. Formalin-induced secondary mechanical hypersensitivity, but not spontaneous pain, was suppressed by i.t. CHEM. Moreover, mechanical hypersensitivity induced by cholekystokinin in the rostroventromedial medulla was attenuated by i.t. pretreatment with CHEM. Independent of the model, the antihypersensitivity effect induced by i.t. CHEM was predominant on responses evoked by low-intensity stimuli (?6 g). CHEM (10 μg i.t.) failed to attenuate pain behavior in healthy controls or mechanical hypersensitivities induced by i.t. administrations of a GABA_A receptor antagonist, or NMDA or 5-HT₃ receptor agonists. Conversely, i.t. administration of a TRPA1 channel agonist, cinnamon aldehyde, induced mechanical hypersensitivity. The results indicate that the spinal TRPA1 channel exerts an important role in secondary (central) pain hypersensitivity to low-intensity mechanical stimulation in various pain hypersensitivity conditions.     

五子衍宗丸对少弱精子症模型大鼠精子线粒体膜电位及超微结构影响

目的:研究五子衍宗丸对少弱精子症模型大鼠精子线粒体膜电位(MMP)水平及线粒体超微结构的影响。方法:取体重为200～220 g雄性SD大鼠60只,随机分成正常组,模型组,对照组(黄精赞育胶囊组),五子衍宗丸低、中、高剂量组,除正常组外,其他各组大鼠灌服雷公藤多苷[30 mg/(kg.d)],连续8周,制备少弱精子症模型。造模结束后,正常组、模型组给予等容量蒸馏水[10 ml/(kg.d)],对照组给予黄精赞育胶囊溶液[3.01 g/(kg.d)],五子衍宗丸各组分别给予水提液,低剂量组[2.30 g生药/(kg.d)],中剂量组[4.60 g生药/(kg.d)],高剂量组[9.20 g生药/(kg.d)],连续30 d。末次给药后30 min,采用荧光流式细胞技术(JC-1染色)测定精子MMP水平(JC-1+%),并通过透射电镜观察精子线粒体超微结构的改变。结果:①MMP:JC-1+%和强度分别为:正常组70.80±4.92、4 360±945;模型组33.77±6.19、1 4685±496;对照组56.34±10.35、3 277±895;五子衍宗丸低剂量组40.80±10.40、2 016±767;中剂量组59.40±6.51、3 897±643;高剂量组60.71±7.81、3 371±6467。造模各组大鼠精子线粒体JC-1+%及强度均明显下降,与正常组比较差异有显著性意义(P均<0.05);连续给药30 d后,给药各组均能明显提高精子MMP,增加JC-1+%,除低剂量组外,其他用药各组与模型组比较差异有显著性意义(P均<0.05)。②精子线粒体超微结构:雷公藤造模后,精子外膜松散、变性,线粒体肿胀、大小不一、线粒体膜不完整,轴丝结构不清或出现断裂。给予五子衍宗丸30 d后,精子外膜及线粒体膜结构完整,减少线粒体肿胀,轴丝及微管结构基本正常。结论:雷公藤多苷能降低精子MMP水平,破坏线粒体的结构。五子衍宗丸能明显提高少弱精子症模型大鼠精子MMP水平,减轻精子线粒体结构损伤。保护精子线粒体结构与功能的完整是五子衍宗丸治疗少弱精子症的机制之一。     

Global repolarization sequence of the right atrium: monphasic action potential mapping in health pigs

The aim of the study was to explore the global sequence of atrial repolarization and its correlation to that of activation. Endocardial monophasic action potentials (MAPs) were sequentially recorded from 51 +/- 14 sites in the right atrium of ten healthy pigs using the CARTO electroanatomic mapping system. Local activation time (AT), MAP duration, and 90% repolarization time (RT) were obtained, and from these data, color coded three-dimensional maps of AT and RT sequences and spatial distribution of MAP duration were reconstructed. The results of the study were: (1) An activation sequence was recognizable in all maps, starting from the posterosuperior wall and ending in the posteroinferior wall near the tricuspid annulus. (2) The repolarization sequence was also recognizable in all maps, and mainly followed the sequence of activation. (3) A significant positive correlation between the RT and AT was observed in all maps with an average r value being 0.571 +/- 0.159 (P < 0.01 - 0.0001), suggesting that progressively later AT associates with progressively longer RT. (4) No consistent correlation between the MAP duration and AT was found. In conclusion, repolarization gradients exist over the atrial endocardium in healthy pigs. The repolarization sequence follows the same sequence as the activation, suggesting that the spatiotemporal pattern of activation is an important determinant of the characteristics of the repolarization sequence.     

慢性非细菌性前列腺炎大鼠前列腺平滑肌细胞BKCa通道对膜电位的影响

目的:探讨慢性非细菌性前列腺炎(CAP)SD大鼠前列腺平滑肌细胞(PSMCs)BKCa通道对细胞膜电位的影响及其在CAP中的意义。方法:将40只雄性SD大鼠随机分为CAP模型组和正常对照组,去势加雌激素注射方法诱导CAP模型,体外组织块贴壁法培养并纯化PSMCs,细胞经膜电位敏感的荧光染料DiBAC4孵育后在激光共聚焦显微镜(LSCM)下动态定量观察激活BKCa通道所引起的膜电位变化。结果:细胞外钙离子浓度升高,激活BKCa通道使CAP组与正常对照组PSMCs细胞膜均发生超极化,两组效应均能被BKCa通道特异性阻滞剂Iberiotoxin(IbTX)阻断而减弱。但CAP组超极化幅度明显减低,两组细胞超极化效应引起的DiBAC4荧光强度变化值分别为18.78±2.92、38.85±7.10(P<0.05,n=20),经IbTX作用后两组细胞DiBAC4荧光强度变化值分别为1.61±0.46、6.12±1.32(P<0.05,n=20),差异有显著性。结论:CAP组SD大鼠PSMCs细胞膜BKCa通道介导的超极化效应明显减弱,可能导致其对膜电位的调节能力及抑制平滑肌细胞过度收缩能力降低,从而引起CAP盆腔疼痛综合征及下尿路症状。