Deficiency In Serum Ionized Magnesium But Not Total Magnesium In Patients With Migraines. Possible Role Of Ica2+/IMg2+ Ratio

SYNOPSIS
It has been suggested that magnesium (Mg) may play a role in the pathogenesis of headaches. Serum and intracellular measurements of Mg in headache patients have produced inconsistent results. The recent development of an ion-selective electrode for Mg²⁺ allowed precise measurement of serum ionized magnesium (IMg²⁺) in patients with various headache syndromes. Low serum Img²⁺ and a high ICa²⁺/IMg²⁺ ratio were found in 42% of patients having an attack of migraine, but only in 23% of patients with e severe continuous headache. Total serum Mg was normal in both groups of patients. However, in patients with low serum IMg²⁺ total serum Mg was lower than in patients with normal serum IMg²⁺. These results are compatible with the serotonin and vascular concepts of migraine pathogenesis. Low IMg²⁺ and a high ICa²⁺/Img²⁺ would result in cerebral vasospasm and reduced blood flow in the brain. The activity of serotonin receptors can also be affected by changes in IMg²⁺ levels. The finding of a difference in IMg²⁺ levels in two different headache types suggests a possible novel classification of headaches and that migraine patients with a low serum IMg²⁺ or a high ICa²⁺/IMg²⁺ ratio may benefit from Mg supplementation.     

CACNA1A Nonsense Mutation is Associated With Basilar-Type Migraine and Episodic Ataxia Type 2

Mutations in the CACNA1A gene on chromosome 19 have been associated with a variety of clinical disorders, including familial hemiplegic migraine type 1 and episodic ataxia type 2 (EA2). We report a patient with 2 distinct attack types, one representing EA2 and the other, basilar-type migraine. Genetic testing revealed a novel nonsense mutation in the CACNA1A gene at codon position 583. Treatment with acetazolamide relieved both types of attacks. We hypothesize that the CACNA1A gene mutation may contribute to both typical EA2 and typical basilar-type migraine, extending the spectrum of clinical manifestations associated with CACNA1A mutations.     

Levcromakalim decreases vascular tone, cytoplasmic Ca2+ and Ca2+ sensitivity in canine basilar artery

Summary— The involvement of large conductance Ca²⁺-activated K⁺ channels (BK) and ATP-sensitive K⁺ (K_ATP) channels in the regulation of canine basilar arterial tone was estimated in the presence of the agonist and blockers of these channels, by simultaneously measuring the changes in intracellular Ca²⁺ concentration ([Ca²⁺]_i) with the fura-2 microfluorimetric method. In the resting condition, levcromakalim reduced [Ca²⁺]_i and vascular tone. Levcromakalim suppressed the serotonin-induced increases in [Ca²⁺]_i and force of contraction, the maximum effects of which were much greater than those of nicardipine. The inhibitory effects of levcromakalim were blocked by glibenclamide but not by tetraethylammonium (TEA) or iberiotoxin (IbTX). In the presence of levcromakalim, the curve relating [Ca²⁺]_i with force in the presence of serotonin at different extracellular Ca²⁺ concentration ([Ca²⁺]_o) was shifted down- and right-ward compared with that in the absence of levcromakalim, suggesting that levcromakalim may reduce the Ca²⁺-sensitivity of the contractile proteins. Thus, levcromakalim may be a good candidate to suppress delayed cerebral vasospasm after subarachnoid hemorrhage.     

PAR-1-dependent pp60src activation is dependent on protein kinase C and increased [Ca2+]i: evidence that pp60src does not regulate PAR-1-dependent Ca2+ entry in human platelets

Summary. Background: The role of the tyrosine kinase pp60^src in PAR‐1‐dependent Ca²⁺ entry was investigated in human platelets. pp60^src plays a role in thapsigargin (TG)‐evoked store‐operated Ca²⁺ entry (SOCE), which is thought to be a major component of thrombin‐evoked Ca²⁺ entry. Methods: pp60^src tyr⁴¹⁶ phosphorylation was used to assess pp60^src activation. Fura‐2‐loaded platelets were used to monitor intracellular Ca²⁺ concentration ([Ca²⁺]_i). Results: Activation of PAR‐1 with the specific agonist SFLLRN increased pp60^src activation within 10 s. This required phospholipase C (PLC) activity, Ca²⁺ release and a rise in intracellular Ca²⁺. PP2, an inhibitor of Src‐family tyrosine kinases, inhibited SFLLRN‐evoked Ca²⁺ entry, but also inhibited Ca²⁺ release and the extrusion of Ca²⁺ by the plasma membrane Ca²⁺ ATPase. Actin polymerization and conventional protein kinase C (cPKC) activity were required for TG‐ and SFLLRN‐evoked pp60^src activation. Although Gö6976, an inhibitor of cPKCs, inhibited TG‐evoked SOCE, it had little effect on SFLLRN‐ or thrombin‐evoked Ca²⁺ entry. Conclusions: These data indicate that stimulation of PAR‐1 leads to activation of pp60^src in human platelets, through PLC and cPKC activation, Ca²⁺ release and actin polymerization. However, as PKC and actin polymerization are not needed for SFLLRN‐evoked Ca²⁺ entry, we suggest that pp60^src is also not required. The apparent inhibition of SFLLRN‐evoked Ca²⁺ entry by PP2 is likely to be secondary to reduced Ca²⁺ release. These data argue against a contribution of this SOCE pathway to PAR‐1‐dependent Ca²⁺ entry.     

No involvement of the calcium channel gene (CACNA1A) in a family with cluster headache

It is very likely that genetic factors play a role in the pathophysiology of cluster headache (CH). As CH shares its paroxysmal character with migraine, and migraine has been described in coexistence with CH in some families, we hypothesized that both diseases might share a genetic aetiology. In this study, we tested whether the migraine CACNA1A gene on chromosome 19 is involved in CH in an extended pedigree. Haplotype analysis did not reveal an obvious disease haplotype, and SSCP analysis of all 47 exons of the CACNA1A gene did not reveal a causative mutation. CH in this family is not caused by mutations in the CACNA1A gene.     

Comparative Absorption of Ferri-Haemoglobin-59Fe/Ferro-Haemoglobin-59Fe and 59Fe3+/59Fe2+ in Humans with Normal and Depleted Iron Stores*

Abstract. The intestinal ⁵⁹Fe absorption from ferri- and ferro-haemogIobin-⁵⁹Fe and ⁵⁹Fe³⁺ and ⁵⁹Fe⁺ was calculated from whole body-⁵⁹Fe-retention measurements in subjects with normal and depleted iron stores. A ferri-haemoglobin-⁵⁹Fe/ferro-haemoglobin-⁵⁹Fe absorption ratio of 1.03 ±0.11 was observed for the absorption of ferri-haemoglobin-⁵⁹Fe (8.6± 0.77%) and ferro-haemogIobin-⁵⁹Fe (8.7±0.94%) in persons with normal iron stores. Depletion of iron stores caused a slight but significant higher rise of ferri-haemoglobin-⁵⁹Fe absorption (22 ± 1.7%) than the increase of ferro-haemoglobin-⁵⁹Fe absorption (18 ±0.9%) so that the absorption ratio was 1.24±0.073.—This remarkable iron valence independence of haemoglobin iron absorption is in considerable contrast to the well-established valence dependence of inorganic iron absorption which favours ferrous iron absorption especially with rising iron doses. The ⁵⁹Fe³⁺/⁵⁹Fe²⁺ absorption ratio for a diagnostic 0.56 mg Fe dose increased from 0.43 in subjects with normal iron stores to 0.74 in persons with depleted iron stores, whereas this absorption ratio was augmented only from 0.21 to 0.28 for the therapeutic 50 mg Fe-dose.—The different influence of iron valence on iron absorption from inorganic and haemoglobin iron supports other evidence for the existence of two separate mechanisms for ferrous iron and haem iron absorption in humans.     

Abnormal Na+K+ cotransport function in a group of patients with essential hypertension

In 50 normotensive controls, the increase in erythrocyte Na+ concentration up to 12.4 +/- 2.0 mmol/l cells (mean +/- SD) ensures half-maximal stimulation of outward Na+,K+ cotransport fluxes. Forty-six out of sixty-five patients with essential hypertension required more than 16 mmol/l cells of internal Na+ concentration to obtain a similar effect, strongly suggesting an abnormal cotransport function. Seven out of fourteen hypertensive patients with normal Na,K cotransport function showed Na+,Li+ countertransport fluxes higher than the normal upper limit of 220 mumol (1 cells h)-1. Conversely, countertransport fluxes were normal in fourteen hypertensives with abnormal cotransport function. The above results indicate that the total population of patients with essential hypertension is heterogeneous and includes one subgroup of subjects with abnormal Na+,K+ cotransport function, and another with increased Na+,Li+ countertransport fluxes.     

The 13C-mixed triglyceride breath test in healthy adults: determinants of the 13CO2 response

Defects in lipolysis due to pancreatic insufficiency can be diagnosed by the mixed triglyceride (MTG) ¹³CO₂ breath test. However, the effects of various test conditions on the ¹³CO₂ response have only been partially elucidated. In healthy adults, we performed the ¹³CO₂ mixed triglyceride breath test and we compared (a) the inter- and intra-individual variation in the ¹³CO₂ response; (b) the effect of two different test meals; (c) the effect of an additional meal during the test; and (d) the effect of physical exercise during the test. Upon repeating the test in the same individual (test meal cream), repeatability coefficients were large, with respect to either time to maximum ¹³C excretion rate (3.8 h), maximum ¹³C excretion rate (4.9% ¹³C dose h^?1) or cumulative recovery of ¹³C over the 9-h study period (22.7% ¹³C dose). The cumulative ¹³C expiration over 9 h obtained with the test meal composed of cream was quantitatively similar to that obtained with bread and butter: 42.2 ± 8.4% and 47.7 ± 6.3% respectively. Fasting for 9 h during the test resulted in similar ¹³C expiration rates and cumulative ¹³C expiration (43.4% ± 7.2%) when compared with consumption of an additional meal 3 h after the start of the test (38.3 ± 5.3%). The ¹³CO₂ response increased in five out of seven subjects, but decreased in the other two, when moderate exercise was performed (bicycle ergometer, 50 W for 5 h). We conclude that the repeatability of the MTG test in healthy adults is low. The present results indicate that a solid and a liquid test meal, containing a similar amount of fats, give similar cumulative ¹³CO₂ responses, and that stringent prolonged fasting during the test is unnecessary. Standardization of physical activity seems preferable, since the unequivocal effects of moderate exercise on the ¹³CO₂ response were observed in the individuals studied.     

Alpha1-Adrenergic Blockers: Do They Have a Place in the Prophylaxis of Migraine?

On the basis of the author's personal experience with migraine, and occasional reports in the literature suggesting that alpha₁-adrenergic blocking drugs may have a beneficial effect in the prophylaxis of migraine, 10 patients with migraine in a general neurology practice were placed on either terazosin or doxazosin. A decrease in migraine frequency or severity or both was seen in all but I patient, but 5 patients discontinued the drug due to side effects. No serious adverse reactions were reported. This anecdotal experience with the alpha 1 -adrenergic blockers warrants a controlled, double-blind study of this class of drugs for the prophylaxis of migraine.     

Screen for CACNA1A and ATP1A2 mutations in sporadic hemiplegic migraine patients

The aim of this study was to investigate the involvement of the CACNA1A and ATP1A2 gene in a population-based sample of sporadic hemiplegic migraine (SHM). Patients with SHM ( n  = 105) were identified in a nationwide search in the Danish population. We sequenced all exons and promoter regions of the CACNA1A and ATP1A2 genes in 100 patients with SHM to search for possible SHM mutations. Novel DNA variants were discovered in eight SHM patients, four in exons of the CACNA1A gene and four in exons of the ATP1A2 gene. Six of the variants were considered non-pathogenic. The causal role of the two remaining DNA variants is unknown until functional studies have been made or independent genetic evidence is discovered. Only very few DNA variants were identified in 100 SHM patients, and regardless of whether the identified variants are causal the CACNA1A and ATP1A2 genes are not major genes in SHM.     

Primary and secondary agonists can use P2X1 receptors as a major pathway to increase intracellular Ca2+ in the human platelet

In the platelet, it is well established that many G-protein- and tyrosine kinase-coupled receptors stimulate phospholipase-C-dependent Ca(2+) mobilization; however, the extent to which secondary activation of adenosine 5'-triphosphate (ATP)-gated P2X(1) receptors contributes to intracellular Ca(2+) responses remains unclear. We now show that selective inhibition of P2X(1) receptors substantially reduces the [Ca(2+)](i) increase evoked by several important agonists in human platelets; for collagen, thromboxane A(2), thrombin, and adenosine 5'-diphoshate (ADP) the maximal effect was a reduction to 18%, 34%, 52%, and 69% of control, respectively. The direct contribution of P2X(1) to the secondary Ca(2+) response was far greater than that of either P2Y receptors activated by co-released ADP, or via synergistic P2X(1):P2Y interactions. The relative contribution of P2X(1) to the peak Ca(2+) increase varied with the strength of the initial stimulus, being greater at low compared to high levels of stimulation for both glycoprotein VI and PAR-1, whereas P2X(1) contributed equally at both low and high levels of stimulation of thromboxane A(2) receptors. In contrast, only strong stimulation of P2Y receptors resulted in significant P2X(1) receptor activation. ATP release was detected by soluble luciferin:luciferase in response to all agonists that stimulated secondary P2X(1) receptor activation. However, P2X(1) receptors were stimulated earlier and to a greater extent than predicted from the average ATP release, which can be accounted for by a predominantly autocrine mechanism of activation. Given the central role of [Ca(2+)](i) increases in platelet activation, these studies indicate that ATP should be considered alongside ADP and thromboxane A(2) as a significant secondary platelet agonist.     

A Double-Blind Comparison of OnabotulinumtoxinA (BOTOX®) and Topiramate (TOPAMAX®) for the Prophylactic Treatment of Chronic Migraine: A Pilot Study

Background.— There is a need for effective prophylactic therapy for chronic migraine (CM) that has minimal side effects. Objective.— To compare the efficacy and safety of onabotulinumtoxinA (BOTOX^®, Allergan, Inc., Irvine, CA) and topiramate (TOPAMAX^®, Ortho‐McNeil, Titusville, NJ) prophylactic treatment in patients with CM. Methods.— In this single‐center, double‐blind trial, patients with CM received either onabotulinumtoxinA, maximum 200 units (U) at baseline and month 3 (100 U fixed‐site and 100 U follow‐the‐pain), plus an oral placebo, or topiramate, 4‐week titration to 100 mg/day with option for additional 4‐week titration to 200 mg/day, plus placebo saline injections. OnabotulinumtoxinA or placebo saline injection was administered at baseline and month 3 only, while topiramate oral treatment or oral placebo was continued through the end of the study. The primary endpoint was treatment responder rate assessed using Physician Global Assessment 9‐point scale (+4 = clearance of signs and symptoms and ?4 = very marked worsening [about 100% worse]). Secondary endpoints included the change from baseline in the number of headache (HA)/migraine days per month (HA diary), and HA disability measured using Headache Impact Test (HIT‐6), HA diary, Migraine Disability Assessment (MIDAS) questionnaire, and Migraine Impact Questionnaire (MIQ). The overall study duration was approximately 10.5 months, which included a 4‐week screening period and a 2‐week optional final safety visit. Follow‐up visits for assessments occurred at months 1, 3, 6, and 9. Adverse events (AEs) were documented. Results.— Of 60 patients randomized to treatment (mean age, 36.8 ± 10.3 years; 90% female), 36 completed the study at the end of the 9 months of active treatment (onabotulinumtoxinA, 19/30 [63.3%]; topiramate, 17/30 [56.7%]). In the topiramate group, 7/29 (24.1%) discontinued study because of treatment‐related AEs vs 2/26 (7.7%) in the onabotulinumtoxinA group. Between 68% and 83% of patients for both onabotulinumtoxinA and topiramate groups reported at least a slight (25%) improvement in migraine; response to treatment was assessed using Physician Global Assessment at months 1, 3, 6, and 9. Most patients in both groups reported moderate to marked improvements at all time points. No significant between‐group differences were observed, except for marked improvement at month 9 (onabotulinumtoxinA, 27.3% vs topiramate, 60.9%, P = .0234, chi‐square). In both groups, HA/migraine days decreased and MIDAS and HIT‐6 scores improved. Patient‐reported quality of life measures assessed using MIQ after treatment with onabotulinumtoxinA paralleled those seen after treatment with topiramate in most respects. At month 9, 40.9% and 42.9% of patients in the onabotulinumtoxinA and topiramate groups, respectively, reported ≥50% reduction in HA/migraine days. Forty‐one treatment‐related AEs were reported in 18 onabotulinumtoxinA‐treated patients vs 87 in 25 topiramate‐treated patients, and 2.7% of patients in the onabotulinumtoxinA group and 24.1% of patients in the topiramate group reported AEs that required permanent discontinuation of study treatment. Conclusions.— OnabotulinumtoxinA and topiramate demonstrated similar efficacy in the prophylactic treatment of CM. Patients receiving onabotulinumtoxinA had fewer AEs and discontinuations.     

甲状腺激素T3对心肌细胞钠钾泵及钙泵功能的影响

目的观察甲状腺激素T3(三碘甲腺原氨酸)对鼠缺血再灌注(I/R)心肌细胞钠钾泵及钙泵功能的影响,探讨T3在心肌保护中的作用.方法将实验大鼠分为甲状腺功能正常(A组)和甲状腺功能减退(甲减,B组)两组,每组又分别随机分成对照组、缺血组、单纯灌注液组、T3灌注液组;测定左室心肌与体重的比值;测定各组心肌细胞Na+-K+-ATPase、Ca2+-ATPase活性.结果甲减状态大鼠心肌细胞Na+-K+-ATPase、Ca2+-ATPase活性分别下降10.8%、43.2%(P＜0.01).缺血30min,A、B两组的Na+-K+-ATPase、Ca2+-ATPase活性均明显降低,并随着复灌进一步下降.然而,在复灌20min时,T3灌注液组的酶活性较单纯灌注液组显著提高,A组Na+-K+-ATPase活性(14.93±0.87)μmol/(mg*h)比较(12.17±0.91)μmol/(mg*h),P＜0.05,Ca2+-ATPase活性(11.20±1.07)μmol/(mg*h)比较(7.33±0.56)μmol/(mg*h),P＜0.01;B组Na+-K+-ATPase(14.10±0.51)μmol/(mg*h)比较(10.89±0.76)μmol/(mg*h),P＜0.01,Ca2+-ATPase活性(6.89±0.52)μmol/(mg*h)比较(5.23±0.71)μmol/(mg*h),P＜0.05.结论甲减状态及I/R过程心肌细胞钠钾泵及钙泵功能受到严重损害,T3可显著提高钠钾泵及钙泵功能,可部分逆转I/R过程中泵功能的损害,降低胞浆中Ca2+浓度,减轻心肌细胞的损伤,对心肌保护有益.