A single-fibre EMG study of neuromuscular transmission in migraine patients

It is known that mutations of CACNA1A, which encodes a neuronal P/Q Ca(2+) channel, are present in patients with familial hemiplegic migraine, and possibly in other types of migraine as well. This calcium channel is also involved in neuromuscular transmission. To assess if the single-fibre EMG (SFEMG) method can demonstrate a neuromuscular transmission deficit in migraine, a group of 26 patients with different types of migraine and 20 healthy control subjects were studied. The migraine patients were divided into three groups: 8 patients with migraine without aura (MoA), 12 with migraine with aura excluding visual aura (MA) and 6 with visual aura (VA). A SFEMG of the voluntarily activated extensor digitorum communis muscle was performed. The SFEMG results were normal in the healthy controls and the MoA group (migraine without aura). Slight neuromuscular transmission disturbances were present in 6/12 (50%) of patients with MA and in 1/6 (17%) of patients with VA. We suggest that abnormal neuromuscular transmission detectable by SFEMG may reflect a genetically determined dysfunction of the P/Q Ca(2+) channels in a subgroup of migraineurs with aura.     

Abnormal neuromuscular transmission in cluster headache

OBJECTIVE: To identify and investigate any dysfunction of neuromuscular transmission in episodic cluster headache. BACKGROUND: Abnormal neuromuscular transmission has been shown in migraine with aura and in migraine without aura by using single fiber electromyography. Especially for migraine with aura, a genetic cause has been postulated. Episodic cluster headache is a primary headache disorder in which genetic factors may, at times, play a strong role. METHODS: Single fiber electromyography during voluntary contraction of the extensor digitorum communis muscle, nerve conduction studies of upper and lower extremities, and concentric needle electromyography of the extensor digitorum communis were performed on 6 patients with episodic cluster headache and 6 age-matched normal controls. Twenty potential pairs were recorded from each subject. Twenty individual jitter values and a mean jitter value were calculated for each subject. Both mean individual jitter values and numbers of abnormal individual jitter values were compared in patients with cluster headache versus normal controls. RESULTS: Three of 6 patients with episodic cluster headache showed pronounced neuromuscular transmission abnormalities by single fiber electromyography. None of the controls had any neuromuscular transmission abnormality. Another patient with episodic cluster headache had borderline dysfunction of neuromuscular transmission. Transmission was clearly normal in only 2 of 6 patients with cluster headache. CONCLUSION: These results suggest that episodic cluster headache may share the same abnormality of neuromuscular transmission observed in migraine.     

Subclinical neuromuscular transmission abnormality detected by single-fibre EMG is more pronounced in cluster headache than in migraine with aura

The aim was to investigate neuromuscular transmission (NMT) by single-fibre EMG (SFEMG) in a large series of patients having migraine with aura (MA) or cluster headache (CH). Recent studies using SFEMG have shown subclinical dysfunction of NMT in MA and CH. Forty-three patients having MA, 51 with CH and 38 healthy control subjects underwent nerve conduction studies, EMG and SFEMG during voluntary contraction of the extensor digitorum communis muscle. Twenty different potential pairs were recorded and individual, mean and total abnormal individual jitter values were calculated. The results obtained from MA patients were compared with those from CH patients. In MA patients, 32 of 860 jitters were abnormally high, whereas 73 of 1020 of the jitters showed this abnormality in CH patients. None of the control subjects, five MA patients (11.6%) and 11 CH patients (21.6%) were designated as having subclinical NMT abnormality. Thus, patients having junction dysfunction were significantly more common in the CH group. The subclinical NMT abnormality shown by SFEMG is more common in CH than in MA. These two primary headache syndromes may have some shared functional abnormality of NMT constituents which is more evident in CH.     

Comparative effects of mibefradil and other calcium antagonists on resistance arteries of different end organs

The biphasic contractile responses of rat isolated mesenteric, renal, coronary and basilar small arteries to potassium-induced depolarization were investigated. The tonic phase is assumed to be exclusively the result of L-type calcium channel (LCC) activation, whereas in the generation of the phasic phase T-type calcium channels (TCC) may be involved. In order to evaluate whether TCC blockade has any influence on depolarization-induced contractions the effects of the LCC antagonists nifedipine, diltiazem and verapamil were compared with those of the combined L- and TCC antagonist mibefradil. Small arteries (size 393.6 +/- 4.8 microns, n = 104) were dissected from the respective organs of male Wistar rats (300-350 g) and studied in an isometric wire myograph. The effects of increasing concentrations of the calcium antagonists on repetitive potassium-induced contractions were quantified by means of cumulative concentration-response curves. A comparison was made with mesenteric vessels of SHR and WKY for nifedipine and mibefradil. Nifedipine was the most potent compound in blocking both the phasic phase (reduction 66-77%) and the tonic phase (IC50 = 1.1-5.4 nM). The effect of mibefradil on the phasic response was comparable to that of verapamil and diltiazem. With respect to the tonic response mibefradil was comparable to verapamil (IC50 = 19.6-178.9 nM). These findings indicate that the TCC blockade does not contribute to the vasodilator effect of mibefradil under the conditions investigated.     

钙在嗜铬细胞瘤细胞缺氧性脑损伤中的作用研究

目的观察缺氧后大鼠肾上腺嗜铬细胞瘤(PC12)细胞内游离钙的浓度(犤Ca2+犦i)、环磷酸腺苷(cAMP)、钙调蛋白(CaM)和钙调蛋白激酶II(Ca2+/CaM-PKII)的变化。方法采用放免技术,从细胞水平进一步观察缺氧对PC12细胞的毒性、细胞内犤Ca2+犦i变化,cAMP、CaM和Ca2+/CaM-PKII的变化。结果缺氧组PC12细胞cAMP、CaM含量在缺氧后24h明显高于正常对照组;Ca2+/CaM-PKII活性明显低于正常对照组。结论犤Ca2+犦i、cAMP、CaM和Ca2+/CaM-PKII在缺氧PC12细胞损伤机制中起了重要的作用。     

Inhibitory effects of tacrine and physostigmine on catecholamine secretion and membrane currents in guinea-pig adrenal chromaffin cells

Summary— The effects of tacrine and physostigmine on catecholamine secretion induced by veratridine and high K⁺, and on voltage-dependent Na⁺ and Ca²⁺ currents, were investigated in guinea-pig adrenal chromaffin cells. In perfused adrenal glands, tacrine (100 μM) caused an inhibition of veratridine-induced catecholamine secretion, but physostigmine (100 μM) did not. In dispersed cells, both tacrine (1 μM-1 mM) and physostigmine (1 μM-1 mM) decreased catecholamine secretion induced by veratridine in a dose-dependent manner. The inhibitory effect of tacrine was much greater than that of physostigmine. Tacrine alone at a high concentration (such as 1 mM) caused a substantial increase in catecholamine secretion by itself and completely abolished the veratridine-induced secretory response in dispersed cells. High-concentration physostigmine showed a similar effect, but to a much lesser extent. The high K⁺ (46.2 mM)-evoked catecholamine secretion from dispersed cells was not affected by tacrine (1–100 μM) or physostigmine (1 μM-1 mM). In fura-2 loaded cells, tacrine (100 μM) almost abolished [Ca²⁺]i rise induced by veratridine, but only slightly reduced that evoked by high K⁺. In voltage-clamped cells, tacrine (300 μM) depressed the voltage-dependent Na⁺ and Ca²⁺ currents by about 93% and 69%, and physostigmine (300 μM) depressed them by about 30% and 17%, respectively. These results suggest that tacrine decreases the veratridine-induced catecholamine secretion primarily by inhibiting the voltage-dependent Na⁺ channels rather than the Ca²⁺ channels. Physostigmine acts in a manner similar to tacrine, but its potency is much lower than that of tacrine.     

Diabetes mellitus and subjects' ageing: a study on the ATP content and ATP-related enzyme activities in human erythrocytes

Na⁺/K⁺- and Ca²⁺-ATPase are the major ATP-dependent membrane-bound enzymes that regulate the cation transmembrane gradient which is altered both in red blood cell (RBC) senescence and in RBCs of diabetic patients. In an attempt to clarify the possible connection between diabetes mellitus and ageing, we investigated the relationship between RBC ATP content, Na⁺/K⁺-ATPase, Ca²⁺-ATPase activities and ageing in healthy, insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) subjects. A significant correlation was found (r = ?0.82; P < 0.001) between RBC ATP content and subject's age only in the control group. A significant reduction in Na⁺/K⁺-ATPase activity was observed in the older group (C₂) of control subjects, in comparison with the younger (C₁) one. In both IDDM and NIDDM subjects, the enzymatic activity was significantly decreased when compared with healthy subjects of similar age (P < 0.001). A significant negative correlation was found between age and enzymatic activity in healthy subjects (r = ?0.60; P < 0.001). No difference was observed in the RBC membrane Ca²⁺-ATPase activity between younger (C₁) and older (C₂) healthy subjects. Ca²⁺-ATPase activity was significantly increased both in IDDM patients compared with C₁ (P < 0.001) and in NIDDM patients compared with C₂ (P < 0.001). The present data indicate that ageing causes a reduction in the erythrocyte ATP content in both healthy and diabetic subjects. In diabetic patients Na⁺/K⁺-ATPase activity decreases independently of age.     

Effects of homocysteine on l-arginine transport and nitric oxide formation in human platelets

BACKGROUND: Recent evidence indicates that hyperhomocysteinaemia is an independent risk factor for atherosclerosis, thrombosis and other cardiovascular diseases. This may be secondary to impaired fibrinolysis or increased platelet reactivity. Nitric oxide (NO), a product from l-arginine by NOS and potent antiaggregating agent, plays an important role in the regulation of platelet function. DESIGN: The present study aimed to define the effect of homocysteine on the l-arginine/NO pathway in human platelets. l-Arginine uptake, NO formation and Ca2+ levels were measured. Moreover the homocysteine effect on platelet activation induced by thrombin was tested. RESULTS: Homocysteine causes a concentration-dependent inhibition of l-arginine transport. Results show that homocysteine does not modify the Km parameter, but it significantly decreases the Vmax value. The nitrite and nitrate formation, strictly correlated with the l-arginine transport, also significantly decreased. In contrast, cNOS activity remained unchanged upon homocysteine treatment. In addition homocysteine in a dose dependent manner increased the intracellular Ca2+ concentration and platelet response to thrombin. CONCLUSIONS: Results indicate that the l-arginine/NO pathway is one of the various targets of homocysteine in human platelets. The increased Ca2+ levels associated with reduced NO formation may generate hyperactivation and may contribute to the thrombogenic processes.     

超早期推拿对骨骼肌急性钝挫伤模型大鼠肌细胞膜修复相关蛋白dysferlin表达的影响

目的:观察超早期推拿对骨骼肌急性钝挫伤模型大鼠肌细胞膜修复相关蛋白dysferlin表达的影响,探寻dysferlin在骨骼肌钝挫伤肌细胞膜修复中的作用机制。方法:SD大鼠55只,随机分为正常对照组(n=5)、自然恢复组(n=25)、推拿组(n=25)。根据推拿治疗的天数计时,自然恢复组和推拿组分别在1d、2d、3d、5d、7d五个时间点处死,每亚组每个时间点5只,在腓肠肌标记的区域内取肌肉组织,HE观察组织的形态变化,运用Western blot检测蛋白dysferlin的表达情况,并进行统计学分析。结果:HE结果显示,与正常对照组相比,骨骼肌钝挫伤后,1d和2d肌纤维出现肿胀;3d出现炎性细胞浸润且自然恢复组比推拿组更加严重;5d炎性细胞浸润更加明显;7d推拿组炎性细胞较5d明显减少,结缔组织形成较少,7d自然恢复组有大量的结缔组织填充在肌纤维之间。WB结果显示:dysferlin在模型组中比在正常对照组中的表达明显增多;各个相应时间点推拿组较自然恢复组表达量明显增多(P0.05),且随着时间的推移dysferlin在推拿组各亚组、自然恢复组各亚组中的表达量呈逐渐上升趋势。结论:在骨骼肌急性钝挫伤模型大鼠腓肠肌修复过程中,超早期推拿可增加膜修复蛋白dysferlin的表达,促进破裂的肌细胞膜及时修复,可能有利于损伤肌细胞的修复,从而帮助受损的骨骼肌修复。     

Regional differences in the vasorelaxant effects of nicorandil and amlodipine on isolated porcine coronary arteries

Summary— The vasorelaxant effects of nicorandil, a K⁺-channel opener, and amlodipine, a dihydropyridine-type Ca²⁺-channel blocker, were investigated on partially and maximally K⁺-depolarized ring preparations from the porcine left anterior descending coronary artery. By comparing vascular responses in the proximal and distal parts of the epicardial segment, the scope of the study was to evaluate regional differences in the action of nicorandil and amlodipine. Nicorandil (10 ⁷- 10^-4 M) shifted the K⁺ concentration-response curves to the right and depressed the maximal contractile responses in a concentration-dependent manner, consistent with K⁺-channel opening and secondary non-K⁺-channel opening mechanisms of action. Nicorandil had a significantly more potent relaxant effect in the proximal compared to the distal arterial rings contracted with 85 mM K⁺. Pretreatment with methylene blue (10^-5 M) did not significantly influence the regional difference in the action of nicorandil. Amlodipine (10⁹- 10^-6 M) had a significantly more potent and effective inhibitory and relaxant effect than nicorandil under the same conditions. In contrast to nicorandil, the effect of amlodipine was more prominent in the distal compared to the proximal vessel rings. The cumulative addition of extracellular Ca²⁺ exhibited a more potent contractile response in the distal rather than in the proximal rings. Nicorandil totally and amlodipine partly eliminated the contractile responses to the lowest concentration of Ca²⁺. The inhibitory effect of amlodipine on the contractile responses to higher Ca²⁺ concentrations was more pronounced than that of nicorandil. The results show that there are regional differences in the responsiveness of porcine coronary arteries to Ca²⁺, nicorandil and amlodipine. Our findings indicate that the regional difference in nicorandil-induced vasodilation was caused neither by the K⁺-channel opening nor by the nitrate-like mechanism of action, but could be due to a direct Ca²⁺-influx blocking effect of the drug.     

针刺对大鼠局部筋膜和脊髓细胞外信号调节凝酶1/2和P38丝裂原活化蛋白激酶信号通路的影响

目的:观察针刺捻转拉伸大鼠皮下筋膜对局部筋膜和脊髓背角细胞外信号调节激酶1/2（extracellular signal-regulated kinase, ERK1/2）和丝裂原活化蛋白激酶P38(P38 MAPK)信号通路的影响及筋膜结缔组织的形态学变化。方法：20只SD大鼠通过随机分组,每组5只,针刺后三里组和针刺非穴位组进行手针捻转,拉伸刺激组进行拉伸刺激,采用免疫组化技术观察筋膜和脊髓组织中细胞信号蛋白的变化;利用相差显微镜观察拉伸刺激组局部皮下筋膜形态学变化。结果：组织学改变：拉伸刺激组皮下筋膜的纤维以拉伸点为中心呈向心性分布,单位面积内细胞密度增大,细胞骨架和胞核重构成“扁梭形”。 细胞信号蛋白变化：针刺组筋膜结缔组织ERK1/2和P38MAPK表达与对照组相比均有增加,但以非穴组增加显著;ERK1/2与P38MAPK在脊髓中的表达位置由胞质转向胞核,ERK1/2与空白对照组相比差异没有显著性意义;P38MAPK的表达有所增加。结论：针刺对局部浅筋膜的ERK1/2和P38有上调作用,但与脊髓中的信号蛋白增加幅度并不完全一致,说明针刺对机体除了神经调节外,筋膜结缔组织支架可能在微观的信号转导层面对局部细胞分化与增殖具有促进作用。