Action-blindsight in healthy subjects after transcranial magnetic stimulation

Clinical cases of blindsight have shown that visually guided movements can be accomplished without conscious visual perception. Here, we show that blindsight can be induced in healthy subjects by using transcranial magnetic stimulation over the visual cortex. Transcranial magnetic stimulation blocked the conscious perception of a visual stimulus, but subjects still corrected an ongoing reaching movement in response to the stimulus. The data show that correction of reaching movements does not require conscious perception of a visual target stimulus, even in healthy people. Our results support previous results suggesting that an efference copy is involved in movement correction, and this mechanism seems to be consistent even for movement correction without perception.     

低强度神经节丛刺激对正常心室电生理性质和急性心肌缺血室性心律失常发生的影响

目的 研究低强度神经节丛(GP)刺激对正常心室电生理性质和急性心肌缺血室性心律失常发生的影响.方法 体重18～25kg的正常成年杂种犬39只随机分为正常心脏组(n=12)和急性心肌缺血组(n=27,其中对照组12只,低强度GP刺激组15只),以2根多极电生理导管记录左、右心室局部电图,以自制Ag-AgC1电极记录左、右心室单相动作电位.在正常犬,分别在6h低强度GP刺激前和刺激后测量心室各部位有效不应期(ERP)、动作电位时限(APD),APD回复性质和APD交替以及血清乙酰胆碱和去甲肾上腺素浓度;在急性心肌缺血犬,比较室性心律失常的发生情况.结果 在正常犬,6h低强度GP刺激显著延长心室各部位ERP及APD(P＜0.05),但未改变其空间离散度;6h低强度GP刺激促进APD交替发生但不改变APD回复曲线斜率及其空间离散度;6h低强度GP刺激后血清去甲肾上腺素和乙酰胆碱水平均显著增加(P＜0.05).在急性心肌缺血犬,低强度GP刺激组室性心律失常的发生率显著低于对照组(P＜0.05).结论 低强度GP刺激不增加正常心脏室性心律失常的风险且有助于抑制急性心肌缺血心脏室性心律失常的发生.     

Effects of cocaine on heart rate variability in healthy subjects

In this study, we found that cocaine decreased the high-frequency power of heart rate variability in normal volunteers, implicating a decrease in vagal tone. However, the results of our autonomic blocking studies indicated the opposite, suggesting a major influence of cardiac sympathetic drive on the high-frequency power of heart rate variability.     

健康人心率震荡的昼夜节律及其与心率变异性的相关性分析

心率震荡（heart rate turbulence，HRT）的病理生理机制至今仍未完全阐明，一些资料表明其与压力反射敏感性高度相关，且与心率变异性（heart rate variability，HRV）之间也存在显著的相关关系。本组资料观察健康人HRT的昼夜变化并通过与HRV的相关性分析，进一步探讨HRT与自主神经的关系。     

Circadian rhythm of spectral indices of heart rate variability in healthy subjects

Circadian pattern of heart rate variability spectral indices, including hourly, 24-hour, night, day, morning, and sex-adjusted measures of low frequency (LF), high frequency (HF), and LF/HF, was evaluated in healthy persons in 24-hour 3-lead electrocardiogram. HF showed circadian pattern with the greatest night values and LF/HF with the smallest night values. Peaks of hourly LF were found between 5 and 9 am and between 4 and 6 pm. The smallest LF was between 11 pm and 3 am. Hourly HF peaked between 11 pm and 5 am. The smallest HF was observed between midday and 2 pm. LF/HF peaked between 6 and 9 am as well as between 4 and 6 pm with the smallest values between midnight and 5 am. Sex adjustment was of no significance. In healthy subjects, HF and LF/HF have circadian pattern. Evaluation of all 5-minute intervals of 24-hour period seems to be a precise method of heart rate variability analysis.     

Effects of hypercholesterolaemia without ischemia on some electrophysiological and ultrastructural properties of the rabbit heart

The electrophysiological and ultrastructural alterations that occur in chronic hypercholesterolaemia were studied in isolated atria including sinoatrial (SA) and atrioventricular (AV) nodes that were obtained from rabbits subjected in 1% cholesterol diet for 18 weeks. Transmembrane action potentials were recorded simultaneously with the His bundle electrogram. The results were compared with corresponding values obtained in normal control atria. During sinus rhythm or constant atrial stimulation, the electrophysiological studies demonstrated no significant alterations of the electrical activity of the SA node, crista terminalis and AV node in preparations obtained from cholesterol-fed rabbits. Premature atrial stimulation at a critical range of coupling intervals initiated supraventricular tachycardias in $\text{7}\text{12}$ of the high cholesterol preparations but in none of the controls. Premature atrial impulses within this critical range were characterized by slow conduction through the AV node. Ultrastructural analysis of hearts obtained from cholesterol-fed rabbits revealed highly selective degenerative changes of the AV nodal cells and diffuse degeneration processes of the cardiac nerves but no obstructive coronary lesions. It was concluded that hypercholesterolaemia per se without myocardial ischemia may result in electrophysiological and ultrastructural abnormalities of the AV node and the cardiac neural tissue.     

Diurnal change in heart rate variability in healthy and diabetic subjects.

We assessed the hourly coefficient of variance of RR intervals (CVRR) in 29 subjects with non-insulin-dependent diabetes mellitus and 19 age-matched healthy subjects using an ambulatory 24-hour ECG monitoring system. We also evaluated CVRR during 100 beats in both groups in the supine posture at 07:00 and 10:00 in the morning. Hourly CVRR showed an overt diurnal variation in both groups especially in the daytime and at midnight, but was significantly lower (p less than 0.05) in diabetic patients. CVRR during resting 100 beats at 07:00 was significantly higher (p less than 0.05) than that at 10:00 in both groups. These findings indicate that HRV shows an obvious diurnal variation in both groups. As a steep and marked change occurs in the morning, careful consideration is necessary to assess the test performed for a short time span at random times throughout the day, particularly in the morning.     

Caffeine slows heart rate autonomic recovery following strength exercise in healthy subjects

Introduction and objectivesStudies assessing the effects of caffeine (CAF) on the cardiovascular system have demonstrated that CAF can delay cardiac recovery following exercise. This study intended to assess the impact of CAF intake before physical exercise on heart rate variability (HRV) and cardiovascular parameters.MethodsThis is a prospective, crossover, controlled clinical trial conducted at the University of Pernambuco, Petrolina, PE, Brazil. The experimental protocol was split into three stages with a minimum of 48 hours between them. Exercises intensity was standardized based on the one repetition maximum test (1RM), obtaining the load of each volunteer for the intensity of 75% of 1RM. In the second and third phases, the control protocols were applied and 300 mg caffeine was given 45 minutes before training. HRV indices were determined at the subsequent times: 0 to 5 minutes of rest (before) and during 30 minutes of recovery (Rec) (after exercise), divided into six intervals, each of 5 minutes.ResultsThe final sample involved 30 volunteers. CAF delayed HRV recovery after resistance exercise. In general, CAF impaired recovery of HRV after resistance exercise. Significant changes were observed in the RMSSD, SDNN, TINN, SD1, low frequency and high frequency indices between the control and CAF group.ConclusionCAF protocol delayed parasympathetic regulation of heart rhythm following exercise, slowing recovery of HR, blood pressure and HRV indices after exercise.     

Reaction of cyclic plasma nucleotides of healthy subjects and essential hypertension patients to insulin stimulation

A total of 112 patients with borderline arterial hypertension and essential hypertension of the labile and stable forms were examined. The plasma levels of cyclic AMP and cyclic GMP as well as the renin activity of the blood were determined in all those studied both at rest and following insulin administration. The findings obtained point to a certain role of cyclic nucleotides in the development and stabilization of arterial hypertension.     

Cholinesterase activity of blood monocytes in healthy subjects and ischemic heart disease patients

Cholesterolesterase activity was assayed in monocytes of coronary patients and normal controls matched for age and showing no evidence of coronary disease. Cholesterolesterase level of coronary patients was significantly lower than that of the controls this two-fold difference in activity being particularly significant in patients with stable angina of effort, functional class 3-4, and progressive angina pectoris. Control subjects tended to have higher cholesterolesterase values than would appear normal for their age.     

Measuring gastric PGE2 release in healthy and alcoholic subjects after ethanol stimulation.

The aim of this work was to study the effect of 20% and 40% ethanol, administered acutely, on gastric PGE2 release in normal subjects and alcoholics. Ethanol 20% did not modify the release of PGE2 into the gastric juice, whereas 40% ethanol increased PGE2 release only in healthy subjects. The basal PGE2 levels were higher in alcoholic patients.     

An analysis of the circadian rhythm of the heart rate and arrhythmias in healthy elderly subjects]

The incidence of asymptomatic arrhythmia detected by Holter monitor in the normal aged population is high. Nevertheless, there are few studies in the literature about the existence and characteristics of their circadian rhythm (CR). The aim of this study, is to determine the presence of CR of the heart rate (HR), supraventricular and ventricular extrasystoles (SVE, VE), atrial tachycardias (AT) and ventricular complex tachycardias (VCT) in the normal aged population. We studied 120 subjects, older than 70 years of age, belonging to a pensioner club, without apparent cardiovascular disease by history, physical, ECG, Chest X-Ray and echocardiography. All the patients had a 24 hours Holter monitor. 42 patients whose recording showed more than 50 SVE and/or more than 50 VE were included in the study. To study the CR the cosinor method was used. In the simple analysis, the HR had significant CR in 40 subjects (95.2%), the SVE in 18 out of 29 (62.1%) and the VE in 16 out of 26 (61.5%). The global analysis showed significant CR for the HR, with an acrophase at 15:47 hours (confidence limits at 95% between 14:45 and 15:42 hours) and for the VE, (acrophase: 15:35 hours, confidence limits between 11:53 and 19:05 hours). There was not significant CR for the SVE because the wide dispersion of the acrophases between the subjects. The AT had significant CR but no the VCT. We conclude that the majority of the aged normal subjects with frequent ectopy had significant CR for the HR and extrasystoles. The VE follow a CR similar to the frequency, suggesting a common modulation of the autonomic nervous system. The SVE variation follow a different CR.