The relation between conduction velocity and axonal length

Motor evoked potentials (MEPs) obtained by electrical root stimulation and F waves were used to examine the proximal nerve conduction velocity (CV) to tibialis anterior (TA), extensor digitorum brevis (EDB), flexor carpi radialis (FCR), and abductor pollicis brevis (APB) muscles in 40 humans. By subtracting motor latencies obtained by stimulating the peripheral nerve at the same point from the F-wave and MEP latencies, we could measure the CV over identical proximal segments. It was found that proximal CV to TA and FCR was significantly higher than to EDB and APB, respectively. Combining the data of the proximal CV to all four muscles in relation with axonal length resulted in a highly significant inverse relationship (r² = 0.77). Thus the axonal length explained to a large extent the higher CV of the arm nerves and also the inverse relation between body height and CV. The distal CV was always lower than proximal CV; however, there was no support for an additional effect of this gradient in explaining the relationship between CV and height since it was constant for all body heights. © John Wiley & Sons, Inc.     

Effects of trapidil-derivatives on calcium channel currents in isolated ventricular cells from mice

Summary A single glass micropipette voltage clamp technique with intracellular dialysis was used to study the effects of the trapidil derivatives AR 12–456 and AR 12–463 on Ca channel currents carried by Bat+ in isolated ventricular cells from mice hearts. Inspite of a more potent inhibition of the cAMP phosphodiesterase from heart (Bartel et al. 1985) a reversible Ca channel blocking action of both compounds could be observed. The concentration of half maximal block was calculated to about 50 mol/l for both derivatives tested. Neither a shift in the current-voltage relationships nor a significant change in the potential for half maximal activation was found. The maximal Ba²⁺ -conductance was reduced. The steady state inactivation was shifted towards more negative potentials by application of 100 mol/l AR 12–463. The decay of the Ba currents was accelerated in the range of the applied test potentials between –20 and +20 mV. It is concluded that the new trapidil derivatives with more potent inhibitory action on cardiac phosphodiesterase than trapidil can block myocardial Ca channels. Send offprint requests to B. Nilius     

前锯肌平面阻滞和胸椎旁神经阻滞在胸腔镜手术中的麻醉效果及对疼痛因子的影响

目的 研究前锯肌平面阻滞与胸椎旁神经阻滞对胸腔镜手术患者的麻醉效果及对疼痛因子的影响。方法 选取2020年11月—2021年9月安徽省池州市人民医院60例接受胸腔镜手术治疗的患者作为研究对象,按照随机数字表法分为A组和B组,每组30例。两组患者术中均接受气管插管全身麻醉,麻醉诱导前,A组选择前锯肌平面阻滞,B组选择胸椎旁神经阻滞。比较两组患者的麻醉效果、阻滞操作时间、阻滞起效时间、阻滞持续时间、生命体征、术后镇痛泵按压次数、术后舒芬太尼使用量、疼痛因子、术后疼痛评分及术后不良反应发生率。结果 A组的麻醉优良率为96.67%,B组的麻醉优良率为93.33%,两组比较,差异无统计学意义（P>0.05）。两组患者的麻醉平面、阻滞起效时间比较,差异无统计学意义（P>0.05）;A组较B组阻滞操作时间缩短,阻滞持续时间延长。两组患者切皮前后收缩压、舒张压、心率差值比较,差异无统计学意义（P>0.05）。A组的术后48 h内镇痛泵按压次数、术后舒芬太尼使用量较B组减少（P <0.05）。两组患者手术前后血清PGE2、IL-6差值比较,差异有统计学意义（P <0.05）...     

Frequency and Output-Dependent Change in Conduction Over Slow Pathways in a Patient with Sustained Ventricular Tachycardia Unrelated to Coronary Artery Disease

In a patient with sustained ventricular tachycardia, we obtained two different paced QRS morphologies from a single pacing site. In one QRS morphology the stimulus to the QRS complex was long, 150 msec, and in the other it was 100 msec. At the paced cycle length of 600 msec and the stimulus output of 4 V, one QRS morphology with the stimulus to the onset of QRS activation (St-QRS) interval of 150 msec was observed. At the paced cycle length of 400 msec, the other QRS morphology with a St-QRS interval of 100 msec was observed alternatively with the former. At the paced cycle length of 353 msec or 316 msec, the latter with a shorter St-QRS interval was exclusively observed. When the stimulus output was increased from 4 to 10 V, keeping with the paced cycle length at 400 msec, the St-QRS interval was shortened from 100 to 80 msec. For the two QRS morphologies with two St-QRS intervals, two slowly conducting pathways would be responsible. The site of the block in the faster pathway must be located at the proximity of the pacing site and the conduction at a shorter paced cycle length would be explained by "supernormal conduction."     

Influence of sinus impulses on the parasystolic cycle length

Recently, it has been shown that in most clinical cases of parasystole, the parasystolic rhythm is not completely independent of the sinus rhythm. In this study, to disclose the mechanism of such "irregular" parasystole, parasystolic cycles with an intervening sinus QRS complex (XSX) were compared with their immediately adjacent pure parasystolic cycles without any intervening nonparasystolic QRS complexes (XX) in 10 cases of ventricular parasystole. In eight cases, the XSX interval was equal to or nearly equal to the adjacent pure XX interval; in one, the XSX interval was shorter than the XX interval; and in only one, the XSX interval was longer than the XX interval. In six cases in which the XSX interval was almost equal to the XX interval, calculated XSX intervals with a later intervening sinus QRS complex were obtained from the differences between the XSSX interval (ie, interectopic interval with two intervening sinus QRS complexes) and its adjacent XX interval. In five of the six cases, the calculated XSX interval was shorter than the XX interval. These observations suggest that in most cases of parasystole, early intervening sinus impulses do not change the parasystolic cycle, whereas late intervening sinus impulses shorten the parasystolic cycle. This suggests the presence of type I second-degree entrance block as the mechanism of "irregular" parasystole.     

Computerized axial tomo-epidurographic and radiographic documentation of unilateral epidural analgesia

A 23-year-old primigravid patient who received epidural analgesia for pain of labour presented with persistent, apparently irremediable, unilateral analgesia. Computerized axial tomo-epidurography demonstrated absence of circumferential spread due to lateral placement of the catheter. Transforaminal escape of contrast medium into the paravertebral area had occurred and anterior and posterior midline partitioning of the epidural space was obvious. All the usual measures to promote contralateral analgesia, except re-insertion of the catheter, had been tried without success.     

星状神经节阻滞对急性心肌梗死患者应激激素水平的影响

目的 观察星状神经节阻滞对急性心肌梗死患者体内去甲肾上腺素（NE）、肾上腺素（adrenalin，ADR）、促肾上腺皮质激素（ACTH）、皮质醇（cortisol，ODR）等应激激素水平的影响。方法 选择已被确诊为急性心肌梗死患者68例，随机分为治疗组（34例）和对照组（34例）．治疗组患者采用星状神经节阻滞治疗，两周为一疗程；对照组常规内科治疗。于阻滞前及阻滞后24、48、72、144h抽取静脉血标本。测定各时段的NE、肾上腺素、ACTH、皮质醇应激激素的含量。结果 阻滞后治疗组患者的NE、ADR、ACTH、ODR应激激素的含量与阻滞前及同时段的对照组比较有明显的降低，P〈0．05。结论 星状神经节阻滞可快速有效地缓解由于冠状动脉供血不足引起的缺血性疼痛，抑制应激反应，降低患者体内NE、ADR、ACTH、00R应激激素的水平。     

Decrease of potassium permeability by intracellular application of sodium ions in snail neurons

In the identified neurons B1, B2 and B3 of Helix pomatia an intracellular injection of Na+ induced an outward current in 10% and an inward current in 90% of the experiments. The outward current was associated with an increase and the inward current with a decrease of the membrane conductance. Both currents reversed at membrane potentials of between -60 and -70 mV. Inward currents were also elicited by intracellular Li+ or tris-[hydroxymethyl]-aminomethane (Tris+) injection. All inward currents were reduced by extracellular administration of tetraethylammonium or quinine. It is suggested that the outward current represents a calcium-activated potassium current and that the inward current is due to a blockade of potassium channels from the intracellular side.     

Effects of local nerve cooling on conduction in vagal fibres shed light upon respiratory reflexes in the rabbit

In ten vagus nerves the effect of local cooling on the compound action potential was studied in the temperature range of 34 to 0 °C in spontaneously breathing, anaesthetized rabbits. The mean temperature at which the myelinated (A) fibres were completely blocked, was 10.2±2.4 °C (mean ± S.D.). In nine nerves, local vagus cooling to 0 °C failed to block all non-myelinated (C) fibres. In one nerve, total blocking occurred at 2.0 °C. We conclude that in the rabbit, the earlier found increase in tonic activity of the diaphragm following lung inflation or deflation during bilateral local vagus cooling to a temperature between 8 and 0 °C is due to afferent impulses in vagal C fibres.