Genome sequencing in a genetically elusive multigenerational long QT syndrome pedigree identifies a novel LQT2-causative deeply intronic KCNH2 variant

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酸中毒时心脏克隆钾离子通道Kv1．4的动力学特性

目的：探讨心脏克隆钾离子通道Kv1．4的C型失活(Kv1．4△N)在非洲蟾蜍卵母细胞上表达后的动力学特性以及酸中毒时的改变。方法：将Kv1．4△N cRNA(最大体积为50 n1)注入非洲爪蟾的卵母细胞内,于18℃孵育16h以上。电极采用两步法拉制,微电极由1．5 mm口径的电极拉制。电极内充3M KCl,电阻0．5～1．0MΩ。采用双微电极电压钳制法(two electrode voltage clamp,TEV)在室温下(20～24℃)记录电流。结果：与正常pH时相比,酸性环境下,Kv1．4△N的峰电流减小,在pH7．4时通道在去极化至-40mv激活,而pH 6．8时为-30mv激活；通道在pH 7．4时最大失活为0．384±0．072,而在pH6．8时为0．197±0．013；在pH6．8时通道复活减慢(P＜0．05)。结论：酸中毒导致通道电流减小,并且使通道失活加快和恢复减慢。     

Beziehungen zwischen Kalium- und Kohlenhydratstoffwechselstörungen bei Diabetes Mellitus

Zusammenfassung Bei 84 Personen mit stabilem Kohlenhydratstoffwechsel wurde die Glucosetoleranz und ihre Beziehung zum Kaliumspiegel im Serum, Plasma und in Erythrocyten untersucht. Bei 43 Fettsüchtigen wurde mehrmals oral 2 mg eines Salureticums Polythiazid-Renese, Pfizer verabreicht. Die danach auftretende Hypokaliämie verursachte eine Verminderung der Glucosetoleranz, die bei 23 Kranken mit Diabetes mellitus am ausgeprägsten war. Bei 12 Kranken mit latentem Diabetes wurde eine mittelstarke und bei 8 Fettsüchtigen ohne Kohlenhydratstoffwechselstörungen nur eine schwache Verschlechterung der Glucosetoleranz gefunden. 36 Patienten mit Hypokaliämie erhielten eine Kaliumacetatund Bromkaliummischung bis zur Erlangung der Normokaliämie. Daraufhin normalisierte sich die Glucosetoleranz. Die gleichzeitige Verabreichung von Renese und der Kaliummischung in 15 Fällen führte zu einer unbedeutenden Erniedrigung des Kaliumspiegels ohne wesentliche Glykämieveränderungen. Beim Altersdiabetes erreichte man nach Anwendung der Kaliummischung allein bei 33 von 36 Behandelten eine deutliche Verbesserung der Glucosetoleranz und gleichzeitig einen geringgradigen Anstieg des Kaliumspiegels im Serum. Bei 5 Gesunden waren die Veränderungen unwesentlich. Sämtliche Ergebnisse sind statistisch gesichert. — Schlußfolgerung: Bei Beurteilung des latenten Diabetes und Diabetes mellitus sollte der mögliche Einfluß einer Störung des Kaliumstoffwechsels mit in Betracht gezogen werden.

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Relationships between disturbances in Potassium and carbohydrate metabolism in diabetes mellitus

Summary The glucose tolerance was measured in 84 patients examined under controlled conditions, and related to the potassium concentration of serum, or plasma and that in erythrocytes. Forty-three obese patients were given 2 mg of Polythiazid-Renese [Pfizer] by mouth for 7 days to promote elimination of salt. The resulting hypokaliaemia caused a reduction in glucose tolerance. This was greatest in 23 patients with diabetes mellitus, moderate in 12 patients with latent diabetes, and least in 8 obese patients with normal carbohydrate metabolism. Thirty-six hypokaliaemic patients were given a mixture of potassium acetate and potassium bromide for several days until serum potassium was normal. This brought about a return to normal of the values obtained in the glucose tolerance test. Simultaneous administration of Renese and the potassium mixture in 15 cases caused only an insignificant fall in serum potassium without any appreciable change in blood glucose. In 33 out of 36 patients with maturity-onset diabetes, the administration of the potassium mixture alone caused a noticable improvement in the glucose tolerance test and at the same time a small rise in serum potassium. In 5 normal subjects the changes were unimportant. The results obtained were statistically significant. — Conclusion: In the assessment of latent diabetes and of diabetes mellitus the role of disturbances in potassium metabolism should not be overlooked.

Nach einer Mitteilung auf der II. Tagung der Europäischen Gesellschaft für Diabetologie in Aarhus am 6. 7. 1966.     

On the mechanisms underlying diastolic voltage oscillations in the sinoatrial node

Aim

The study of the mechanisms underlying the oscillatory afterpotential (V_os) and prepotential (ThV_os).

Background

It has been recently shown that V_os and ThV_os play an obligatory role in the dominant sinoatrial node (SAN) discharge.

Methods

Guinea pig isolated SAN was studied in vitro by means of a microelectrode technique.

Results

High [K⁺]_o and premature stimuli unmask V_os superimposed on early diastolic depolarization and ThV_os within a less negative voltage range (“oscillatory zone”). Subthreshold stimuli elicit ThV_os in the oscillatory zone, but not at more negative values. Drive and caffeine shift the oscillatory zone in a negative direction. Low caffeine concentrations increase the size of V_os and of ThV_os, rate, and force. High caffeine concentrations suppress V_os but increase the size of ThV_os and shift them to more negative values until they eventually miss the threshold. In quiescent SAN in high caffeine, a fast drive enhances ThV_os size, thereby initiating a transient spontaneous rhythm (“overdrive excitation”). Adrenergic agonists potentiate caffeine-induced overdrive excitation through an increase in ThV_os. In high caffeine, the first twitch after quiescence is not larger, twitch relaxation is slower, V_os is abolished, and the prolonged nonoscillatory afterdepolarization V_ex is induced, consistent with an impairment of Ca²⁺ handling by the sarcoplasmic reticulum. The effects of caffeine in Tyrode's solution are accounted for by the caffeine-induced changes in the oscillatory potentials. Tetrodotoxin decreases force and size of both V_os and ThV_os.

Conclusions

The mechanism underlying V_os is related to a diastolic release of Ca²⁺ from a Ca²⁺-overloaded sarcoplasmic reticulum, whereas that of ThV_os appears to be related to ionic currents in the resting potential range that can initiate and sustain spontaneous discharge.     

Alterations in the brain-gut axis underlying visceral chemosensitivity in Nippostrongylus brasiliensis-infected mice

BACKGROUND & AIMS: Visceral hypersensitivity, a hallmark of irritable bowel syndrome, is generally considered to be mechanosensitive in nature and mediated via spinal afferents. Both stress and inflammation are implicated in visceral hypersensitivity, but the underlying molecular mechanisms of visceral hypersensitivity are unknown. METHODS: Mice were infected with Nippostrongylus brasiliensis (Nb) larvae, exposed to environmental stress and the following separate studies performed 3-4 weeks later. Mesenteric afferent nerve activity was recorded in response to either ramp balloon distention (60 mm Hg), or to an intraluminal perfusion of hydrochloric acid (50 mmol/L), or to octreotide administration (2 micromol/L). Intraperitoneal injection of cholera toxin B-488 identified neurons projecting to the abdominal viscera. Fluorescent neurons in dorsal root and nodose ganglia were isolated using laser-capture microdissection. RNA was hybridized to Affymetrix Mouse whole genome arrays for analysis to evaluate the effects of stress and infection. RESULTS: In mice previously infected with Nb, there was no change in intestinal afferent mechanosensitivity, but there was an increase in chemosensitive responses to intraluminal hydrochloric acid when compared with control animals. Gene expression profiles in vagal but not spinal visceral sensory neurons were significantly altered in stressed Nb-infected mice. Decreased afferent responses to somatostatin receptor 2 stimulation correlated with lower expression of vagal somatostatin receptor 2 in stressed Nb-infected mice, confirming a link between molecular data and functional sequelae. CONCLUSIONS: Alterations in the intestinal brain-gut axis, in chemosensitivity but not mechanosensitivity, and through vagal rather than spinal pathways, are implicated in stress-induced postinflammatory visceral hypersensitivity.     

血压盐敏感者一氧化氮系统与非对称性二甲基精氨酸和补钾的作用

目的通过观察慢性盐负荷及补钾后血浆非对称性二甲基精氨酸(ADMA)和血、尿一氧化氮(NO)水平的变化及其与血压的关系,探讨血压正常盐敏感者(SS)的血管内皮功能损伤及补钾的保护作用。方法选60例年龄在20～60岁的血压正常者参与为期3周的慢性盐负荷及补钾试验,包括基线调查3d,低盐(LS)饮食,高盐(HS)饮食,和高盐补钾(HS K)饮食各7d的研究。每个阶段均测量血压,并收集血、尿标本。血、尿NO用Griess法测量,血浆ADMA用高效液相色谱法测量。结果受试者60例中共检出SS13例,检出率为21.6%。盐负荷后,SS血浆ADMA的浓度明显升高[(0.89±0.09vs0.51±0.07)μmol/L,P<0.05],而血浆NO的水平则较LS饮食期显著降低[(41.8±7.6vs63.5±7.6)μmol/L,P<0.01]。在HS摄入的基础上大剂量口服补钾可以逆转单纯HS负荷对SS血浆ADMA浓度和血、尿NO水平的作用[(ADMA:0.52±0.09vs0.89±0.09)μmol/L;NO:(58.1±7.4vs41.8±7.6)μmol/L],血浆ADMA浓度和平均动脉压之间存在正相关关系。结论血压正常SS于HS负荷后伴随血压升高,血浆ADMA显著升高、NO降低,同时补充钾盐可以逆转前述作用,提示补钾可能通过抑制ADMA的升高降低血压。     

急性冠状动脉综合征患者的CD4+CD28null T淋巴细胞电压门控性Kv1.3钾通道数量增加

目的 运用膜片钳技术检测急性冠状动脉综合征(ACS)患者的CD4+CD28nullT淋巴细胞Kv1.3钾通道的数量是否增加,探讨CD4+CD28nullT淋巴细胞上Kv1.3钾通道的表达.方法 选择17例ACS患者,11例年龄、性别匹配的正常体检者作为对照.运用荧光染色标记及膜片钳技术检测单个T淋巴细胞(CD4+CD28nullT淋巴细胞和CD4+CD28+T淋巴细胞)上Kv1.3钾通道的数量,比较Kv1.3通道在两种细胞上的差别.结果 ACS患者的CD4+CD28nullT淋巴细胞比例为(6.97±2.05)%,明显高于对照组的(1.38±0.84)%(P<0.05).ACS患者的CD4+CD28nullT淋巴细胞数量与hsCRP浓度呈正相关(r=0.52,P<0.05).ACS患者CD4+CD28nullT淋巴细胞Kv1.3通道的电导、密度、数量明显高于对照组CD4+CD28+T淋巴细胞(P<0.01).而两组CD4+CD28+T淋巴细胞间Kv1.3通道的电导、密度、数量差异无统计学意义(P>0.05).结论 ACS患者CD4+CD28nullT淋巴细胞明显增多.ACS患者CD4+CD28nullT淋巴细胞上Kv1.3钾通道数量比自身和对照的CD4+CD28+T淋巴细胞明显增多,CD4+CD28nullT淋巴细胞的功能可能与Kv1.3钾通道增多相关.     

心房颤动患者心房肌钾电流的研究

目的:研究心房颤动患者心房肌内向整流钾电流和乙酰胆碱敏感钾电流的变化,探讨两种离子通道电流变化在心房颤动发生与维持中的作用。方法:应用膜片钳全细胞技术记录并比较19例风湿性心脏病心房颤动患者(心房颤动组)和18例风湿性心脏病窦性心律患者(窦性心律组)心房肌内向整流钾电流和乙酰胆碱敏感钾电流密度的大小。结果:在-60mV～-120mV时,与窦性心律组相比,心房颤动组内向整流钾电流密度绝对值增大,乙酰胆碱敏感钾电流密度绝对值降低。其中在-100mV时,内向整流钾电流密度从窦性心律组的(4.01±1.01)pA/pF(n=18)增大到心房颤动组的(8.94±1.26)pA/pF(n=19,P<0.001);乙酰胆碱敏感钾电流密度从窦性心律组的(24.57±0.77)pA/pF(n=18)降低为心房颤动组的(13.38±1.03)pA/pF(n=19,P<0.001)。结论:心房颤动时,内向整流钾电流密度绝对值增大,乙酰胆碱敏感钾电流密度绝对值降低,两种电流的改变可能与心房颤动的发生和维持有关。     

Anti-HERG activity and the risk of drug-induced arrhythmias and sudden death.

AIMS: Drug-induced QTc-prolongation, resulting from inhibition of HERG potassium channels may lead to serious ventricular arrhythmias and sudden death. We studied the quantitative anti-HERG activity of pro-arrhythmic drugs as a risk factor for this outcome in day-to-day practice. METHODS AND RESULTS: All 284,426 case reports of suspected adverse drug reactions of drugs with known anti-HERG activity received by the International Drug Monitoring Program of the World Health Organization (WHO-UMC) up to the first quarter of 2003, were used to calculate reporting odds ratios (RORs). Cases were defined as reports of cardiac arrest, sudden death, torsade de pointes, ventricular fibrillation, and ventricular tachycardia (n = 5591), and compared with non-cases regarding the anti-HERG activity, defined as the effective therapeutic plasma concentration (ETCPunbound) divided by the HERG IC50 value, of suspected drugs. We identified a significant association of 1.93 (95% CI: 1.89-1.98) between the anti-HERG activity of drugs, measured as log10 (ETCPunbound/IC50), and reporting of serious ventricular arrhythmias and sudden death to the WHO-UMC database. CONCLUSION: Anti-HERG activity is associated with the risk of reports of serious ventricular arrhythmias and sudden death in the WHO-UMC database. These findings are in support of the value of pre-clinical HERG testing to predict pro-arrhythmic effects of medicines.     

Controlling caries in exposed root surfaces with silver diamine fluoride: A systematic review with meta-analysis

Background

In this systematic review, the authors aim to assess the effect of silver diamine fluoride (SDF) in preventing and arresting caries in exposed root surfaces of adults.