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.     

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.     

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。     

Renal nerve stimulation restores tubuloglomerular feedback after acute renal denervation

Renal nerves play an important role in the setting of the sensitivity of the tubuloglomerular feedback (TGF) mechanism. We recently reported a time-dependent resetting of TGF to a lower sensitivity 3–4 h after acute unilateral renal denervation (aDNX). This effect persisted after 1 week, but was then less pronounced. To determine whether normal TGF sensitivity could be restored in aDNX kidneys by low-frequency renal nerve stimulation (RNS), the following experiments were performed. Rats with aDNX were prepared for micropuncture. In one experimental group proximal tubular free flow (P_t) and stop flow pressures (P_sf) were measured during RNS at frequencies of 2, 4 and 6 Hz. In another series of experiments the TGF sensitivity was evaluated from the P_sf responses at different loop perfusion rates after 20 min of RNS at a frequency of 2 Hz. The maximal drop in P_sf (ΔP_sf) and the tubular flow rate at which half the maximal response in ΔP_sf was observed (turning point, TP), were recorded. At RNS frequencies of 2, 4 and 6 Hz, P_t decreased from the control level of 14.1 ± 0.8–13.1 ± 1.0, 12.4 ± 1.1 and 11.2 ± 0.8 mmHg (decrease 21%, P < 0.05), respectively, while at zero perfusion and during RNS at 2 and 4 Hz P_sf decreased from 42.5 ± 1.6 to 38.2 ± 1.4 and 32.8 ± 4.3 mmHg (decrease 23%, P < 0.05), respectively. The TGF characteristics were found to be reset from the normal sensitivity with TP of 19.0 ± 1.1 nL min^–1 and ΔP_sf of 8.7 ± 0.9 mmHg to TP of 28.3 ± 2.4 nL min^–1 (increase 49%, P < 0.05) and ΔP_sf of 5.8 ± 1.2 mmHg (decrease 33%) after aDNX. After 20 min of RNS at 2 Hz TP was normalized and ΔP_sf was 33% higher. Thus the present findings indicate that the resetting of the TGF sensitivity that occurred 2–3 h after aDNX could be partially restored by 20 min of RNS at a frequency of 2 Hz. These results imply that renal nerves have an important impact on the setting of the sensitivity of the TGF mechanism.