Electrophysiologic mechanisms of ventricular arrhythmias

In this work the electrophysiologic mechanisms of ventricular arrhythmias have been briefly summarized. Ventricular arrhytmias can be caused either by pacemaker activity or by reentrant excitation. Enhancement of normal automaticy can generate a parasystolic rhythm in normal fibers. Abnormal automaticity may arise fom fibers in which maximum diastolic potential has been reduced by a variety of interventions. Triggered activity is caused by either an early (EAD) or delayed (DAD) afterdepolarization and requires a prior normal action potential for initiation. While there is growing evidence that EAD-induced triggered activity plays a significant role in the Long QTU syndrome and Torsade de Pointes, no clinical arrhythmias has definitely been ascribed to DADs, although DADs have been recorded in man after acute digoxin intoxication.Ventricular arrhytmias can be also caused by reentrant excitation, which can be subdivided into reflection or circus movement reentry (CMR). In the reflection model impulses in both directions are transmitted over the same pathway. In the CMR three models can be differentiated: the ring model, which requires a fixed anatomical obstacle; the figure-eight model and the leading circle model, where functional rather than fixed anatomical obstacles are involved.Abbreviations AV atrio-ventricular - CMR circus movement reentry - DAD delayed afterdepolarization - EAD early afterdepolarization - ECG electrocardiogram - LV left ventricle - MAP monophasic action potential - MF muscle fiber - PF Purkinje fiber - RV right ventricle - TdP Torsade de Pointes     

Acute actions of insulin-like growth factor II on glucose metabolism in adult rats

Summary The metabolic potency of recombinant human insulin-like growth factor II was studied in anaesthetized adult rats by obtaining dose-response curves for the hypoglycaemic action and for the stimulation of glucose metabolism during euglycaemic clamping. Compared to insulin, about 50 times higher doses of insulin-like growth factor II were required to result in identical in vivo responses, with half-maximally effective serum concentrations for the stimulation of glucose disposal during clamp studies of about 0.8 and 50 pmol/ml, respectively. A similar difference in potency was observed for the dose-dependent stimulatory actions on glucose metabolism in individual target tissues. Half-maximally effective serum concentrations in the range of 0.8 to 3.0 pmol/ml for insulin and of 40 to 70 pmol/ml for insulin-like growth factor II were seen to be required for 2-deoxyglucose uptake, glycogen formation in skeletal muscle and lipogenesis in epididymal fat. Maximal responses were identical with both peptides. These data suggest that in vivo acute metabolic actions of insulin-like growth factor II on carbohydrate metabolism occurred through insulin receptors.     

Dopamine antagonists reduce spontaneous electrical activity in cultured mammalian neurons from ventral mesencephalon

Mammalian neurons from ventral mesencephalon (VM) were grown in primary dissociated cell (PDC) culture. These neurons are predominantly non-dopaminergic. Many of these non-dopaminergic neurons have dopamine agonist and antagonist binding sites. Intracellular recordings were obtained from these neurons. When bathed in phosphate-buffered saline (PBS) solution they generated action potentials spontaneously. However, in the presence of haloperidol dissolved in PBS solution, the percentage of neurons which generated action potentials spontaneously was reduced in a dose-dependent manner (1–10 μM). This response was also obtained with (+) butaclamol (1 μM) but not with (−) butaclamol (1 μM). This neuroleptic inhibition of spontaneously generated action potentials was specific for neurons in PDC cultures of VM since neurons in PDC cultures of spinal cord did not demonstrate this phenomenon.     

原钒酸钠对Ⅱ型糖尿病的降糖作用研究

目的　观察原钒酸钠对Ⅱ型糖尿病大鼠的降糖作用。方法　用高脂饲料灌胃正常大鼠 ,引起肥胖 ,测定血中游离脂肪酸浓度。同时应用正糖钳技术检测胰岛素抗性 ,对产生胰岛素抵抗的大鼠腹腔注射小剂量链脲菌素 (5 5mg·kg-1) ,然后筛选空腹血糖值大于 11 1mmol·L-1大鼠为糖尿病模型组。连续灌胃原钒酸钠 7d后 ,测定空腹血糖值。结果　①大鼠喂食高脂饲料后 ,正糖钳实验中维持血糖稳态所需胰岛素量增多 ,为 (0 5 4± 0 0 2 )U·min-1,高于正常组 (P <0 0 1) ;同时血中游离脂肪酸浓度增加 ,从正常 (0 4 6 9±0 0 4 7)mmol·L-1至 (1 5 32± 0 2 91)mmol·L-1(P <0 0 1) ;②原钒酸钠对正常大鼠的血糖值无影响 ,而对Ⅱ型糖尿病大鼠的空腹血糖值及糖耐量曲线下面积有降低作用 (P <0 0 5 )。结论　实验结果证明了原钒酸钠可以明显降低Ⅱ型糖尿病大鼠的空腹血糖值 ,并且对糖耐量具有保护作用     

Control of feeding and sexual behaviors by neuropeptide Y: physiological implications

Recent evidence suggests that a variety of hypothalamic neuropeptides may mediate interneuronal communication to coordinate diverse neuroendocrine and behavioral functions. In this work, we describe the effects of neuropeptide Y (NPY) on feeding and sexual behaviors. We observed that central administration of bolus NPY stimulated a robust, dose-related feeding response in satiated male and female rats. Continuous NPY receptor activation also evoked dose-related, intermittent feeding in a manner normally observed during nocturnal feeding. It appears that the paraventricular nucleus in the hypothalamus may be the primary site of NPY action because the anticipated reciprocal changes in NPY concentrations, in response to food deprivation followed by ad libitum food intake, occurred only in this site. Additional findings revealed that NPY-induced feeding may follow either substantial reduction or complete restraint of an inhibitory influence on feeding mediated by alpha 2-adrenoreceptor systems in satiated rats. Further, NPY was found to suppress male and female sexual behaviors. The suppressive effects on sexual behavior were apparent prior to or at the time of the onset of feeding after NPY administration. These observations may provide a neurochemical basis for clinical and animal studies on disorders of feeding associated with diminished reproductive functions.     

青天葵抗甲、乙型流感病毒作用研究

目的研究青天葵在体外抗甲、乙型流感病毒株作用。方法选用狗肾细胞培养法考察青天葵不同极性部位对甲型(FM1)、乙型(昆40B)流感病毒的作用。结果青天葵水溶性部位对甲型流感病毒FM1有抑制作用。结论青天葵具有体外抗甲型流感病毒作用。     

复合动作电位传播速度的逐次提取法

本文在复时谱（ｃｅｐｓｔｒｕｍ）分析的基础上，提出了复会动作电位传播速度的逐次提取法，指出了这个方法在实际应用中遇到的各种问题，采用指教加权和参考曲线成功地解决了这些问题。这一方法的特点是速度分辨率高，并且不要求测量点到刺激点有很大的距离。仿真实验和动物实验均表明，这一方法准确，简便，可靠。     

单发室性早搏中RT间期规律的分析

目的探讨室性早搏前后RT间期变化的规律。方法选取单发、有完全代偿间期的室性早搏心电图,测量室早及其前后相邻波群(简称室早前、室早、室早后)的RT间期,进行对比。对室早前心室舒张时间与室早RT间期变化的关系进行分析。结果RT间期由短到长的顺序为:室早<室早前<室早后。室早前心室舒张时间与室早RT间期无线性相关关系。结论室早时RT间期最短,室早后RT间期最长,这一变化规律与心室舒张时间无关。     

氨乙基异硫脲对大鼠离体心脏冠脉结扎后再灌期心律失常与细胞动作电位的作用

用Langendorff方法与微电极技术研究自由基清除剂氨乙基异硫脲(AET)对离体大鼠心脏冠脉结扎后再灌期心律失常与细胞动作电位的作用。AET(0.001～1mmol/L)使室颤和室速发生率明显下降,使正常窦性心律时间增加。浓度为0.01～1mmol/L的AET可使不可逆室颤发生率下降为零。冠脉阻塞再灌损伤使缺血中心区心肌动作电位波形异常,APA,RP,V_(max)各参数下降。AET(0.1mmol/L)可使异常波形动作电位显著减少。     

Effects of dauricine,quinidine,and sotalol on action potential duration of papillary muscles in vitro

目的：观察蝙蝠葛碱对豚鼠乳头状肌的动作电位是否具有使用依赖性特征，并与奎尼丁、索他洛尔作平行比较．方法：利用细胞内微电极技术记录豚鼠乳头状肌跨膜动作电位．结果：蝙蝠葛碱２０μｍｏｌ·Ｌ－１能明显延长乳头状肌跨膜动作电位时程，在刺激周长为２００，３００，４００，６００，８００，１０００，２０００ｍｓ时，其延长动作电位时程的百分率分别为２２±８，１１±６，９±５，７±５，６±３，４３±２８，４５±２８，蝙蝠葛碱延长动作电位时程作用于刺激周期较短时作用明显，呈使用依赖性特征．而奎尼丁１μｍｏｌ·Ｌ－１和索他洛尔１０μｍｏｌ·Ｌ－１延长动作电位时程作用随刺激周期延长而增强，呈现逆向使用依赖性特征．结论：蝙蝠葛碱使用依赖性延长豚鼠乳头状肌动作电位时程．