Atrial fibrillation: a new explanation of the old phenomenon

We propose a new mechanism of atrial fibrillation basing on the results of 30 series of acute experiments on anesthetized cats. In brief, combination of two or more arrhythmogenic factors shortens the interval between the inward and outward ionic currents in cardiomyocytes to a critical value. Under these conditions repolarization of cardiomyocyte membrane reaches the excitation threshold before complete inactivation of the depolarizing currents. This inevitably results in autoexcitation of myocytes (or extrasystole), that in turn promotes repolarization. Once occurred, autoexcitation turns into self-triggering activity resembling tachyarrhythmia paroxysm.     

用于电刺激听神经方波刺激器的研制

本文主要介绍了用于电刺激听神经方波刺激器的基本设计原理 ,组成结构和三个主要性能指标 ,脉宽 相位 :2 5 μs phase、 5 0 μs phase、 10 0 μs phase ;电流强度 :5 0 μA～ 4 0 0 0 μA (每 5 0 μA一档上、下可调 ) ;频率 :30次 秒、 2 0 0次 秒、 4 0 0次 秒、 10 0 0次 秒、 12 0 0次 秒、 2 0 0 0次 秒 ,其特点有人机界面友好 ,性能稳定 ,安全性好 ,无需安装光电藕合器。为研究听神经兴奋性、优化电刺激听神经参数、以及评估电极的有效性和安全性提供实验仪器     

Ultrastructural Changes Associated with Peripheral Neuropathy in HIV/AIDS

Light and electron microscopic studies were performed on neuromuscular biopsy specimens from 12 neurologically affected seropositive patients, 7 with the acquired immune deficiency syndrome (AIDS), 2 with AIDS-related complex, and 3 with no symptoms except for neuropathy. All patients had an axonal injury associated or unassociated with demyelination and peripheral neurogenic atrophy. Capillary lesions were consistently present, which seems to be a new finding. Moreover, tubuloreticular inclusions (TRIs) were found in endomysial (9 of 12 cases) and endoneurial (7 of 12 cases) vessels. Statistical analysis showed that TRIs in more than 20% of endomysial vessels correlated with a survival time shorter than 12 months (P = 0.028). Thus the quantification of TRIs seems to be one of the vital prognostic elements in this patient population.     

The dendritic architecture of the medial terminal nucleus of the accessory optic system in the rat,rabbit, and cat

Summary The neurons of the medial terminal nucleus (MTN) of the accessory optic system (AOS) have been studied in the rat, rabbit and cat in Golgi-Cox and Golgi-Kopsch impregnated brain sections. The present anatomical findings permit a division of the MTN of these species into dorsal and ventral components (MTNd, MTNv), in agreement with other investigations. The MTNd contains predominantly linear-bipolar and linear-multipolar shaped neurons with cell bodies that measure in the range of 25–50 m. These neurons have 2 to 4 primary dendrites which, along with their smaller dendritic branches, are oriented in the plane of the long axis of the MTN (i.e. from ventromedial to dorsolateral). These linear-bipolar and linear-multipolar cells represent 70–80% of the neurons of the MTNd as seen in the Golgi impregnated sections. The remaining 20–30% of the MTNd neurons are nearly all multipolar in shape with somata measuring in the range of 15–25 m. An occasional multipolar neuron is larger, has a soma that measures around 30–60 m and has dendrites which extend outward from the cell body to cover large areas of the MTNd. There was considerable extension of the dendrites of MTNd neurons into the MTNv; however, the dendrites of MTNd neurons were not observed extending into the adjacent substantia nigra (SN) or ventral tegmental area (VTA) of Tsai (1925). Conversely, the dendrites of neurons in the neighboring SN and VTA course along the borders of the MTN but only occasionally extend into the MTN. The neuron population of the MTNv consists almost entirely of small-multipolar shaped cells with somata measuring from 15–25 m and dendritic trees resembling those described for multipolar cells of the MTNd. A small number of neurons of the ventral division are medium-multipolar in shape with cell bodies that measure approximately 30–60 m. Typically, these cells have several dendrites which extend ventrally within the MTNv and one or more dendrites that extend either across the MTNv or dorsally into the MTNd. Only a few linear-bipolar and linear-multipolar neurons were observed in the MTNv. The present findings are discussed in relation to anatomical, physiological, and histochemical studies on the MTN.Abbreviations to Figures CP Cerebral Peduncle - DTN Dorsal Terminal Nucleus - LG Lateral Geniculate Nucleus - LP Lateral Posterior Nucleus - MG Medial Geniculate Nucleus - ML Medial Lemniscus - MTNd Medial Terminal Nucleus, dorsal division - MTNv Medial Terminal Nucleus, ventral division - NTO Nucleus of the Optic Tract - PA Anterior Pretectal Nucleus - pn Nucleus Paranigralis - PP Posterior Pretectal Nucleus - Pul Pulvinar - PO Olivary Pretectal Nucleus - RN Red Nucleus - SGS Stratum Griseum Superficiale, Superior Colliculus - SN Substantia Nigra Supported by USPHS research grant EYO3642 from the National Eye Institute     

Apolipoprotein D is down-regulated during malignant transformation of neurofibromas

Apolipoprotein D (apoD) expression was studied in nonneoplastic peripheral nerve, neurofibromas (NFs), and malignant peripheral nerve sheath tumors (MPNSTs) by quantitative polymerase chain reaction, in situ hybridization, and immunohistochemistry. Multiplex quantitative polymerase chain reaction for messenger RNA was performed on a series of formalin-fixed and paraffin-embedded specimens that included 9 MPNSTs, 12 NFs, and 4 normal peripheral nerves. The average apoD expression was 108-fold decreased (DeltaCt = -7.3) in the MPNSTs compared with the NFs (P < .05). ApoD expression levels were 3.0-fold elevated (DeltaCt = 1.7) in the NFs compared with nonneoplastic peripheral nerve (P < .05). In situ hybridization for apoD RNA was performed on a separate series of 10 cases in which each microscopic section included both MPNST and the NF from which it arose. These studies confirmed elevated apoD expression in NFs compared with MPNSTs and demonstrated that this expression was variable among individual cells within the NFs. Differential expression by immunohistochemistry could only be demonstrated in selected areas, most likely because apoD protein is a small molecule that is secreted out of the cell into the extracellular space and plasma. ApoD expression initially increases a small amount with the formation of NFs from nonneoplastic peripheral nerve and subsequently decreases markedly as NFs transform into MPNSTs. This expression pattern may serve as a marker for cell cycle inhibition during peripheral nerve tumorigenesis.     

A comparative study of the somato-axonal flow of protein in the feline hypoglossal and vagus nerves

Summary After ³H-lysine was applied to the X^th and XII^th cranial nuclei, radioactive protein synthesized in the nerve cell bodies of the hypoglossal and vagus nerves moved down the axons of these fibers at maximal rates of 6.3±1.2 and 16±3 mm per day, respectively. The distribution of radiolabeled protein at various periods indicated that other proteinaceous components moved at slower velocities.     

A Novel Lymphocyte Signaling Defect: trk A Mutation in the Syndrome of Congenital Insensitivity to Pain and Anhidrosis (CIPA)

Congenital insensitivity to pain with anhidrosis is a syndrome characterized by loss of pain and sensation. The condition frequently evolves into deep wounds and prolonged healing times. Anhidrosis is another prominent component of the disorder. Often associated with recurrent episodes of unexplained fever, it can result in patient mortality. Recent investigations point to Trk A, the high affinity receptor for nerve growth factor (NGF), as a candidate for the site of the mutation that causes the disorder. Functional NGF receptors, such as Trk A and the Trk family of tyrosine kinases, are essential for NGF signaling of human lymphocytes. In this study, we demonstrated that the presence of a trk A mutation in patient B cells results in a novel lymphocyte signaling defect. In these B cells, NGF failed to induce Trk A phosphorylation, cytoskeleton assembly, or MAP kinase activation. These abnormalities may explain some of the clinical features of the disease.     

Wiping reflexes and nerve impulse patterns evoked by electrical stimulation of the skin in frogs.

Electric shocks applied to the skin evoke well aimed wiping reflexes in the frogs, Discoglossus pictus and Rana esculenta. In skin-grafted animals, moreover, wipes were misdirected from those areas which gave misdirected responses to tactile stimulation. Recordings from cutaneous sensory neurons revealed that only one action potential, with varying latency, was evoked per shock in any given unit. It is concluded that the capacity for sensory localization in anurans cannot depend upon specific patterns of afferent nerve impulses.     

人体神经定量电流感觉检测系统的研制

电流感觉阈值测试是人体神经感觉功能的定量感觉测试方法的一种．它采用特定频率的正弦恒电流刺激人体神经末梢感受器，检测人体对电流刺激的最小感受量，用于定量评估神经功能。本文回顾了国际上电流感觉阈值测试技术的发展与现状，介绍了我们开发的人体神经定量电流感觉检测系统。该系统采用生理心理统计算法过滤人体主观感受的影响，具有双盲全自动测量功能，测量结果具有很好的重复性。     

远端蒂腓肠神经营养血管皮瓣与肌皮瓣的临床应用与改进

目的:报道应用远端蒂腓肠神经营养血管皮瓣,肌皮瓣修复小腿下段及足踝部软组织缺损的可行性安全性和临床效果。方法:对42例以远端蒂腓肠神经营养血管(肌)皮瓣修复小腿下段及足踝部不同原因所致软组织缺损病例进行总结分析。本组男36例,女6例;年龄最大75岁、最小6岁;皮瓣最大面积17.0cm×15.0cm,最小6.0cm×5.0cm,其中12例皮瓣面积在10.0cm×10.0cm以上;6例设计为肌皮瓣(腓肠肌外侧头),肌瓣最大为10.0cm×7.0cm×2.0cm,最小为6.0cm×5.0cm×1.0cm。结果:所有病例术后皆出现不同程度的皮瓣肿胀,暗道较明道者明显。2例大皮瓣经行小隐静脉远端结扎仍出现肿胀、色暗,皮瓣近侧1/3坏死。皮瓣边缘坏死3例,换药治愈。部分坏死需行植皮者3例。36例术后伤口I期愈合,骨外露软件组织缺损覆盖修复满意,6例II期愈合,其中糖尿病,地中海贫血各一例。结论:(1)远端蒂腓肠神经营养血管皮瓣转位修复小腿下1/3及足踝部缺损创面,极有临床实用价值;(2)设计切取腓肠神经营养血管肌皮瓣修复小腿及足踝填充感染创腔是可行的;(3)但对其皮瓣及所携带的肌瓣究竟切取多大面积是安全的、肌瓣的血运机理以及远端蒂筋膜皮瓣中小隐静脉干是否结扎,何处结扎等问题仍有待进一步研究。