Characteristics of the myocardium functional state and cerebral circulation of seven- to ten-year-old children with different variants of autonomic nervous regulation of the heart rate

A complex study of the functional state of the cardiovascular system of seven- to ten-year-old children with different types of autonomic nervous regulation of the heart rate was performed. It was found that the autonomic nervous system strongly affects the adaptive capacity of the body, bioelectrical processes in the myocardium, the duration of cardiac-cycle phases, the pulse volume, and the tone of large and small cerebral vessels.     

Quick adaptation of the myocardium and autonomic nervous regulation of the cardiac rhythm in 10- to 11-year-old children operating a computer

A study of quick adaptation of the myocardium of subjects operating a computer, depending on the adaptive capacities of the body, was conducted in 100 children with ages varying between 10 and 11 years using the electrocardiography method for the analysis of heart rate variability. Significant differences in the bioelectrical processes in the myocardium and autonomic nervous regulation of the cardiac rhythm (CR) were found in children with different adaptive capacities of the body. Quick adaptation to the operator activity in children with a good adaptive capacity is characterized by intensification of atrial activity and metabolic processes in the myocardium, as well as by a shortened duration of the cardiac cycle due to a shorter diastolic time, determined by increased sympathetic influences on the CR. In children with a decreased adaptive capacity, a decrease in the atrial excitability and myocardial metabolism, an increase in the systolic time, a decrease in the diastolic time, and an increase in parasympathetic influences on the CR are observed.     

Changes in cardiohemodynamic parameters,cardiointervalography, and microcirculation observed in local cold test in young men born in northern regions

The cardiohemodynamic and blood microcirculation parameters at rest and under local cold exposure in young male subjects have been estimated. It has been found that the subjects with the initially low velocity of erythrocytes (blood flow) in their nail bed capillaries have higher blood pressure, stroke volume, cardiac output, and cardiac index, which proves that these subjects have the hyperkinetic type of blood flow with the pronounced hypertensive reaction. At the same time, the shift of heart rate variability values under the cold exposure indicates that the activation of the sympathetic autonomic nervous system is more statistically significant than that in those subjects who originally had a higher velocity of erythrocytes. In the subjects of this group, no changes were observed in either heart rate autonomic regulation or index of tension under the local cold exposure, which proved that these subjects had the enhanced functional reserves of the cardiovascular system and autonomic regulation. They also had a fairly pronounced reactivity of the parameters of systemic hemodynamics, which manifested itself in changes in their blood filling parameters against the background of decrease in total peripheral vascular resistance and coefficient of integral tonicity.     

Blood pressure and blood flow variation during postural change from sitting to standing: model development and validation.

Short-term cardiovascular responses to postural change from sitting to standing involve complex interactions between the autonomic nervous system, which regulates blood pressure, and cerebral autoregulation, which maintains cerebral perfusion. We present a mathematical model that can predict dynamic changes in beat-to-beat arterial blood pressure and middle cerebral artery blood flow velocity during postural change from sitting to standing. Our cardiovascular model utilizes 11 compartments to describe blood pressure, blood flow, compliance, and resistance in the heart and systemic circulation. To include dynamics due to the pulsatile nature of blood pressure and blood flow, resistances in the large systemic arteries are modeled using nonlinear functions of pressure. A physiologically based submodel is used to describe effects of gravity on venous blood pooling during postural change. Two types of control mechanisms are included: 1) autonomic regulation mediated by sympathetic and parasympathetic responses, which affect heart rate, cardiac contractility, resistance, and compliance, and 2) autoregulation mediated by responses to local changes in myogenic tone, metabolic demand, and CO(2) concentration, which affect cerebrovascular resistance. Finally, we formulate an inverse least-squares problem to estimate parameters and demonstrate that our mathematical model is in agreement with physiological data from a young subject during postural change from sitting to standing.     

迷走神经功能调节与心肌缺血保护

心血管系统的生理活动受自主神经系统(autonomic nervous system,ANS)调节.已有研究表明,自主神经功能紊乱,尤其是迷走神经功能低下,与心血管疾病(cardiovascular disease,CVD)的发生、发展及预后密切相关.本文结合国内外研究现状,就本研究室在迷走神经对心脏不同部位的调控及其对心肌的保护作用机制方面的研究成果进行阐述.通过收缩功能检测及标准玻璃微电极细胞内记录技术,发现迷走神经递质--乙酰胆碱对哺乳动物心室肌有直接作用,可抑制细胞收缩力及动作电位时程;通过组织化学染色及分子生物学方法进一步证明心室有毒蕈碱受体分布;通过膜片钳技术显示在部分动物心室肌上存在乙酰胆碱激活的内向整流钾通道(acetylcholine-activated potassium channel,KACh),并且其电流(IK·ACh)和心房肌一样具有衰减现象.前期研究证明心房肌IK·ACh的衰减与毒蕈碱受体、G蛋白或钾通道磷酸化有关;而心室肌的IK·ACh还有待于进一步研究.我们建立了相关动物模型,结合心率变异性分析等自主神经评价方法,探讨ANS在健康和疾病状态下的变化情况,证明了迷走神经对心脏调节的增龄性改变及代偿效应.通过提高迷走张力(乙酰胆碱缺血预/后适应、有氧运动、β受体阻断剂),研究改善自主神经平衡对缺血心肌的保护作用以及胆碱能抗炎通路防御缺血,再灌注诱导的炎症损伤机制.综合评价心脏自主神经调节,改善交感和迷走张力平衡,将为CVD防治的基础研究提供重要的理论依据.     

A view of the cardiac rhythm control: Intrinsic regulation

Regulation of the cardiac rhythm is intricate and occurs at least at two major levels, intrinsic and extrinsic. In turn, each of these levels can be divided into several sublevels. The factors regulating the cardiac activity eventually affect the duration of spontaneous diastolic depolarization of pacemaker myocytes of the sinoatrial node and, to a far lesser extent, the conduction velocity in the conduction system of the heart. Intrinsic regulation of the heart rate (HR) includes the myogenic sublevel and the sublevels of cell-to-cell communication, the cardiac nervous system, and humoral factors produced within the heart. Myogenic regulation is considered to be the first sublevel in control of the cardiac function. The available data suggest myogenic regulation only for the contractility of the myocardium. The cell-to-cell regulation sublevel involves two principal mechanisms. One depends on the heterogeneous structure of the sinoatrial node and within-node shifts of the dominant pacemaker, which is a group of cells that determine the HR and govern all other cells of the sinoatrial node. The other mechanism is based on the effects of peptides produced by cardiomyocytes and endothelial cells on pacemaker cells of the sinoatrial node. Regulatory peptides are also produced by the cardiac nervous system, which includes sensory and effector autonomic fibers, represents the cardiac part of the metasympathetic system, and forms intramural ganglia. In addition to modulating the HR, these peptides affect the contractility, microcirculation, coronary blood flow, preload, and afterload. Currently available data demonstrate that the autonomic nervous system is far more intricate than believed earlier. Using various neuropeptides, this system provides for fine adjustment of the cell functions, subject to its immediate control.Translated from Fiziologiya Cheloveka, Vol. 31, No. 2, 2005, pp. 116–129.Original Russian Text Copyright © 2005 by Nozdrachev, Kotelnikov, Mazhara, Naumov.Deceased.     

Thermal effects of mobile phone RF fields on children: a provocation study

The aim of this study was to examine thermal and local blood flow responses in the head area of the preadolescent boys during exposure to radiofrequency (RF) electromagnetic fields produced by a GSM mobile phone. The design was a double-blinded sham-controlled study of 26 boys, aged 14-15 years. The SAR distribution was calculated and modelled in detail. The duration of the sham periods and exposures with GSM 900 phone was 15 min each, and the tests were carried out in a climatic chamber in controlled thermoneutral conditions. The ear canal temperatures were registered from both ear canals, and the skin temperatures at several sites of the head, trunk and extremities. The local cerebral blood flow was monitored by a near-infrared spectroscopy (NIRS), and the autonomic nervous system function by recordings of ECG and continuous blood pressure. During the short-term RF exposure, local cerebral blood flow did not change, the ear canal temperature did not increase significantly and autonomic nervous system was not interfered. The strengths of this study were the age of the population, multifactorial physiological monitoring and strictly controlled thermal environment. The limitations of the study were large inter-individual variation in the physiological responses, and short duration of the exposure. Longer provocation protocols, however, might cause in children distress related confounding physiological responses.     

Use of a Physiological Monitoring Model for Comprehensive Evaluation of Adaptive Capacities in Schoolchildren during Learning: I. Influence of Various Motor Activity Regimens on Cardiac Rhythm Indices in Junior Schoolchildren

The dynamics of changes in the indices of the autonomic regulation of cardiac rhythm was studied in junior schoolchildren during adaptation to physical exercise. An analysis of variation pulsometry parameters throughout the school year showed the role of the sympathetic and parasympathetic parts of the autonomic nervous system in the formation of body adaptive reactions to various motor activity regimens.     

Causal interactions between the cerebral cortex and the autonomic nervous system

Mental states such as stress and anxiety can cause heart disease.On the other hand,meditation can improve cardiac performance.In this study,the heart rate variability,directed transfer function and corrected conditional entropy were used to investigate the effects of mental tasks on cardiac performance,and the functional coupling between the cerebral cortex and the heart.When subjects tried to decrease their heart rate by volition,the sympathetic nervous system was inhibited and the heart rate decreased.When subjects tried to increase their heart rate by volition,the parasympathetic nervous system was inhibited and the sympathetic nervous system was stimulated,and the heart rate increased.When autonomic nervous system activity was regulated by mental tasks,the information flow from the post-central areas to the pre-central areas of the cerebral cortex increased,and there was greater coupling between the brain and the heart.Use of directed transfer function and corrected conditional entropy techniques enabled analysis of electroencephalographic recordings,and of the information flow causing functional coupling between the brain and the heart.     

Blood pressure regulation and cardiac autonomic control in mice overexpressing alpha- and gamma-melanocyte stimulating hormone

Melanocyte stimulating hormones (MSH) derived from pro-opiomelanocortin have been demonstrated to participate in the central regulation of cardiovascular functions. The aim of the present study was to elucidate the chronic effects of increased melanocortin activation on blood pressure regulation and autonomic nervous system function. We adapted telemetry to transgenic mice overexpressing alpha- and gamma-MSH and measured blood pressure, heart rate and locomotor activity, and analyzed heart rate variability (HRV) in the frequency-domain as well as baroreflex function by the sequence technique. Transgenic (MSH-OE) mice had increased systolic blood pressure but their heart rate was similar to wild-type (WT) controls. The 24-h mean of systolic blood pressure was 132+/-7mmHg in MSH-OE and 113+/-4mmHg in WT mice. Locomotor activity was decreased in the MSH-OE mice. Furthermore, MSH-OE mice showed slower adaptation to mild environmental stress in terms of blood pressure changes. The low frequency (LF) power of HRV tended to be higher in MSH-OE mice compared to WT mice, without a difference in overall variability. The assessment of baroreflex function indicated enhanced baroreflex effectiveness and more frequent baroreflex operations in MSH-OE mice. Baseline heart rate, increased LF power of HRV and increased baroreflex activity may all reflect maintenance of baroreflex integrity and an increase in cardiac vagal activity to counteract the increased blood pressure. These results provide new evidence that long-term activation of the melanocortin system elevates blood pressure without increasing heart rate.     

Reaction of Cardiac Activity of Senior Pupils of Schools Providing Differentiated Education upon Examination Stress

Effects of examination stress on psychological characteristics and indices of the autonomic nervous system were studied in pupils of the eighth and tenth grades of high schools providing differential (test group, Neuron gymnasium) and general education (control group). General health state and levels of activity and mood (feeling, activity, mood; FAM) and neuroticism (according to Eysenck) were determined in both groups. Main hemodynamic indices (heart rate and blood pressure) were measured, and mathematical analysis of the heart rate by was performed according to Baevskii. Comparative analysis of psychophysiological tests and heart rate changes in the control and test groups points to a high tension in the cardiac rhythm regulation mechanisms and strong anxiety in schoolchildren in the differential education school. The character and depth of preexamination stress depended on the type of autonomic control of cardiac activity. Schoolchildren with sympathicotonic cardiac rhythm regulation showed the strongest emotional tension. Schoolchildren with the normotonic type of regulation were the most calm.     

Localized real time blood flow measurements

A novel method for real time, localized, flow measurements is applied to blood flow in human fingers. Results for arterial and venous flow in normal subjects and patients with abnormal blood circulation are presented. Effects of blood flow regulation by the autonomic nervous system have been observed. Stricture of the digital arteries could be clearly demonstrated in a patient with Raynaud's phenomenon. Experimental signals due to pulsatile flow in a model system can be simulated in a quantitative way. The calibration, however, depends on the actual spin-spin relaxation time and the shape of the pulsatile flow vs. time curve. Due to these limitations, the volume flow rate can be measured with a relative error of approximately +/- 25%.     

Alternating lateralization of plasma catecholamines and nasal patency in humans

The nose receives both sympathetic and parasympathetic innervation that is manifested by the alternating dominance of sympathetic activity on one side with concurrent parasympathetic dominance on the other. This ultradian rhythm of autonomic function, known as the nasal cycle, averages 2-3 hours in length. Previous experiments have shown that the nasal cycle is correlated in an inversely coupled fashion to the alternating dominance of activity in the two cerebral hemispheres, suggesting a common mechanism of regulation. Here we show that there is an alternation in catecholamine levels of blood drawn from anticubital veins that may also correlate with the nasal cycle. Radioenzymatic measurement of norepinephrine, epinephrine, and dopamine in blood sampled simultaneously from both arms every 7.5 minutes for periods of 3-6 hours demonstrated alternating high levels of catecholamine in one of the two arms. This alternating lateralization of neurotransmitters was observed in 7 out of 7 experiments using resting human male subjects. The ratio of norepinephrine in the two arms also parallels the pattern of airflow in the nasal cycle. This study suggests that the autonomic nervous system may alternate in activity through paired structures.     

Autonomic nervous control of postprandial hemodynamic changes at rest and upright exercise

Postprandial hemodynamic changes were studied in healthy subjects at rest and during exercise in the upright position with and without autonomic blockade of the heart. At rest cardiac output increased 61% mostly because of a stroke volume increase accomplished by left ventricular end-diastolic dilation. These changes seemed to be dependent on the autonomic nervous system, whereas the postprandial heart rate increase did not. During exercise cardiac output was 23% higher after food intake due to a rise in both stroke volume and heart rate. These changes were apparently under influence of the autonomic nervous system, whereas left ventricular dilation was not. The present findings indicate that most of the postprandial changes in the central circulation are under control of the autonomic nervous system.     

Involvement of the sympatho-vagal balance in the formation of respiration-dependent oscillations in the human cardiovascular system

The effect of deep breathing controlled in both rate and amplitude on the heart rate variability (HRV) and respiration-dependent blood flow oscillations was studied in the forearm and finger-pad skin of healthy 18- to 25-year-old volunteers. In order to reveal the effects of the divisions of the autonomic nervous system on the amplitudes of respiratory sinus arrhythmia (RSA) and skin blood flow oscillations, we studied the indices of the cardiovascular system in two groups of subjects with respectively lower and higher values of the sympatho-vagal balance. This index was calculated as a ratio of low frequency and high frequency HRV spectral power (LF/HF) under the conditions of spontaneous breathing. It was found that, in subjects with a predominant parasympathetic tone, the amplitudes of RSA and the rate of blood flow in the finger-pad skin were higher compared to subjects with a predominant sympathetic tone during respiration with the frequency lower than 4 cycle/min. In the forearm skin, where sympathetic innervation is weaker compared to the finger-pad skin, there were no significant differences in respiration-dependent oscillations of the rate of blood flow in two groups of subjects.     

Role of autonomic nervous system on heart rate in experimental hypertension

Heart rate and the role of the autonomic nervous system in hypertensive conscious rats by subtotal nephrectomy were studied. Heart rate is significantly higher in the hypertensive rats. Sympathetic blockade with an intravenous injection of propranolol produces a higher decrease in heart rate of hypertensive rats than in control rats. Intravenous injection of atropine produces an increase in heart rate in both groups of animals. It is significantly higher in the control rats than in hypertensive animals. When the autonomic nervous system is blocked with atropine and propranolol, intrinsic heart rate is similar in both groups of animals. Similar results are obtained after blocking ganglionic transmission with hexamethonium. No significative differences are observed in heart rate after intracerebroventricular injection of hemicholinium-3 between both groups of rats. Results show an increased cardiac sympathetic tone, reduced parasympathetic activities, no alterations in the pacemaker activity and implications of central acetylcholine. These alterations in the autonomic nervous system have an important role in the maintenance of elevated heart rate in this experimental model of arterial hypertension.     

Music Attenuated a Decrease in Parasympathetic Nervous System Activity after Exercise

Music and exercise can both affect autonomic nervous system activity. However, the effects of the combination of music and exercise on autonomic activity are poorly understood. Additionally, it remains unknown whether music affects post-exercise orthostatic tolerance. The aim of this study was to evaluate the effects of music on autonomic nervous system activity in orthostatic tolerance after exercise. Twenty-six healthy graduate students participated in four sessions in a random order on four separate days: a sedentary session, a music session, a bicycling session, and a bicycling with music session. Participants were asked to listen to their favorite music and to exercise on a cycle ergometer. We evaluated autonomic nervous system activity before and after each session using frequency analysis of heart rate variability. High frequency power, an index of parasympathetic nervous system activity, was significantly increased in the music session. Heart rate was increased, and high frequency power was decreased, in the bicycling session. There was no significant difference in high frequency power before and after the bicycling with music session, although heart rate was significantly increased. Additionally, both music and exercise did not significantly affect heart rate, systolic blood pressure or also heart rate variability indices in the orthostatic test. These data suggest that music increased parasympathetic activity and attenuated the exercise-induced decrease in parasympathetic activity without altering the orthostatic tolerance after exercise. Therefore, music may be an effective approach for improving post-exercise parasympathetic reactivation, resulting in a faster recovery and a reduction in cardiac stress after exercise.     

Intracoronary gastrin 17 increases cardiac perfusion and function through autonomic nervous system, CCK receptors, and nitric oxide in anesthetized pigs

The release of gastrointestinal hormones has been reported to modulate reflex cardiovascular responses caused by gastric distension, although the role played by gastrin 17 is as yet unknown. The present study was therefore planned to determine the primary in vivo effect of gastrin 17 on coronary blood flow and cardiac function and the involvement of autonomic nervous system, CCK1/2 receptors, and nitric oxide (NO). In 40 anesthetized pigs, gastrin 17 was infused into the left anterior descending coronary artery at constant heart rate and arterial blood pressure. In 35 of the 40 pigs, the mechanisms of the observed hemodynamic responses were analyzed by repeating gastrin 17 infusion after autonomic nervous system and NO blockade, and after specific CCK receptors agonists/antagonists administration. Intracoronary gastrin 17 administration caused dose-related increases of both coronary blood flow and cardiac function. The intracoronary co-administration of CCK33/pentagastrin and gastrin 17 potentiated the coronary effects observed when the above agents were given alone (P <0.05). The potentiation of the cardiac response was observed only with the co-administration of pentagastrin and gastrin 17 (P <0.05). Moreover, blockade of muscarinic cholinoceptors (intravenous atropine) and of α-adrenoceptors (intravenous phentolamine) did not abolish the hemodynamic responses to gastrin 17. The cardiac and vascular effects of the hormone were prevented by blockade of β-adrenoceptors (intravenous atenolol and butoxamine), CCK1/2 receptors (intracoronary lorglumide and CAM-1028), and NO synthase (intracoronary Nω-nitro-l-arginine methyl ester). In conclusion, gastrin 17 primarily increased coronary blood flow and cardiac function through the involvement of CCK receptors, β-adrenoceptors, and NO release.     

Activity of key redox enzymes in rabbits with different typologic features

It has been found that the activity of LDG, PDG, IDG, SDG, NADN-DG, NADFN-DG, CO, G-6-FDG and 6-FGDG in the cerebral cortex, liver and kidneys of rabbits with a strong type of nervous activity, as a rule, is higher than in the animals with a weak type of the nervous system. Between the animals with different types of the nervous system distinctions are also revealed in the character of regulation of a number of metabolic cycles. It is suggested that typological features of the nervous system are determined by the character of metabolic processes.     

Lateral Preferences as Possible Phenotypic Predictors of the Reserves of the Cardiovascular System and the Features of Sensorimotor Integration in Climbers

The lateral preferences of the hands, the reserves of the cardiovascular system and the features of sensorimotor integration in mountain climbers as possible predictors of adaptation to extreme factors of the external environment have been investigated. The subjects were 15 climbers of high class (men aged 25.5–62.8 years). We used the following methods: reflexometric technique ReBFB (complex sensorimotor reaction in the model of go/no-go, computer simulation according to Chernikov); the assessment of lateral preferences using the standard samples; the orthostatic test (with the recording of the heart rate and evaluation of adaptive reserves based on the indices of mathematical analysis of the cardiac rhythm in the transition period according to a technique by Riftin). Sensorimotor integration was performed under normal conditions and under normobaric hypoxia. All indicators were correlated with the age and proficiency of the climbers. We observed no statistically significant correlations between age and the reserves of the cardiovascular system in the group of climbers. Reflexometry in normoxic conditions showed an improvement in the orientation of subjects in the sensory flow as compared with the initial level. The sensorimotor integration (as a response of sensorimotor responses) was more stable during hypoxia as compared with the same indices in normoxia. Noticeable correlation was observed between the results of the humeral test and the reserves of the cardiovascular system defined by orthostatic hypotension: the reserves were higher in the subjects with a higher level of left-hand preference. The regulation of the autonomic nervous system is correlated with left-handedness, which results in more effective adaptation to the high altitude in left-handers. The parameter of handedness can be used as a phenotypic predictor of the level of the cardiovascular system reserves in climbers. It is suggested that the factor of hypoxia with small exposure has a stimulating effect on sensorimotor integration in climbers.