The functional state of the sympathoadrenal system and the autonomic regulation of the cardiac rhythm in younger schoolchildren

A comparative analysis of functional states of the sympathoadrenal system (SAS) and its reactions to isometric muscular effort was performed in seven-year-old schoolchildren of both sexes with different types of cardiac regulation. Children with a predominance of sympathetic influences displayed a higher excretion of noradrenaline and a lower excretion of dopamine than their counterparts with normal or vagal tone. A graded isometric exercise changed the functional state of the SAS in a manner dependent on the initial autonomic tone, baseline excretion of catecholamines, and sex. Boys displayed more strained reactions of the SAS than girls did, which was associated with a decrease in its reserve potential, especially pronounced in the states of vagal and normal tones. This suggests imperfect mechanisms of adaptation to static loads.     

Functional state of the cardiovascular system in 13-year-old adolescents with different types of autonomic nervous regulation

The features of the functional state of cardiovascular system in 13-year-old children with different types of autonomic nervous regulation were studied. Children with normotonic and parasympathetic types of autonomic regulation were found to have the highest adaptation capacities. The autonomic nervous system influences the bioelectrical processes in myocardium, the duration of cardiac cycle phases, and cerebral blood flow. Schoolchildren aged 13 years with higher sympathetic activity have shorter duration of the cardiac cycle, the phase of isometric contraction, and diastole. They have a lower pulse blood flow rate and a higher tone of large and medium cerebral vessels. No relationship was revealed between the initial autonomic nervous regulation of heart rate and the type of adaptation of myocardium to physical dynamic loads, as well as the type of adaptation of cerebral circulation to mental stress.     

Effect of hyperbaric oxygenation on several functional and morphologic properties of the heart and catecholamine metabolism in the presence of compensatory myocardial hypertrophy]

Rabbits subjected to hyperbaric oxygenation (HBO) for one month following ascending aorta stenosis developed less distinct hypertrophy and signs of myocardial dystrophy with a more distinct enhancement of the left ventricular contractility than animals with aortic stenosis kept under normal pressure. In rabbits with heart hypertrophy developing under HBO the increasing adaptive capacity of the myocardium was accompanied by an elevation in functional reserve of the sympathetic regulation apparatus. Apparently HBO aided the development of the optimum cardiac adaptation to a high afterload.     

Influence of the initial autonomic tone on the state of hemodynamics of primary schoolchildren

The functional state of the cardiovascular system and its reaction to local isometric exercise in seven- and eight-year-old children was studied with consideration for the initial tone of the autonomic nervous system. Using the methods of variational pulsometry and tetrapolar thoracic rheography, it was established that children with predominant sympathetic influences on the heart rate (67?56.55% of the total number of those examined) had increased stroke and minute blood volumes against the background of relative tachycardia, compared with normo- and vagotonics. In sympathotonic boys, the leading component in the mechanism of urgent adaptation of the cardiovascular system to static exercise is spastic reactions of the vascular bed, which allow this contingent of schoolchildren to be identified as a group of children at high risk of autonomic dystonia with the hypertensive vascular syndrome.     

Cardiovascular alterations and autonomic imbalance in an experimental model of depression

Depressed patients with and without a history of cardiovascular pathology display signs, such as elevated heart rate, decreased heart rate variability, and increased physiological reactivity to environmental stressors, which may indicate a predisposition to cardiovascular disease. The specific physiological mechanisms associating depression with such altered cardiovascular parameters are presently unclear. The current study investigated cardiovascular regulation in the chronic mild stress rodent model of depression and examined the specific autonomic nervous system mechanisms underlying the responses. Sprague-Dawley rats exposed to a series of mild, unpredictable stressors over 4 wk displayed anhedonia (an essential feature of human depression), along with elevated resting heart rate, decreased heart rate variability, and exaggerated pressor and heart rate responses to air jet stress. Results obtained from experiments studying autonomic blockade suggest that cardiovascular alterations in the chronic mild stress model are mediated by elevated sympathetic tone to the heart. The present findings have implications for the study of pathophysiological links between affective disorders and cardiovascular disease.     

Adaptation in Sport: Present State, Problems, Prospects

The current state of the problem of adaptation in sport, its theoretical and practical aspects, and also prospects of its development are considered. Specific features of the mechanisms and regularities of adaptation to exercise were studied in athletes over 15 years. Four stages of adaptive rearrangements are proposed: physiological tension of the organism, adaptation, dysadaptation, and readaptation. Each stage is characterized by specific functional changes and regulatory and energy provision. The concept of a special functional system of adaptation in athletes is based theoretically and confirmed experimentally. Knowledge of the regularities of the development of this system allows us to efficiently and variously influence its links to accelerate adaptation to exercise and to increase training, i.e., to control the adaptation process.     

Ontogenic changes in cardiac rhythm during acute hypoxia in dogs and rabbits]

Newborn dogs and rabbits exhibit unequal reactivity of cardiac activity to acute hypoxia as compared to adult ones, being lesser in the newborn. In dogs, during postnatal life as well as during adaptation to hypoxia, tachycardic effect of atropine increases indicating the increase in vagal tone. In growing rabbits, cardiac rhythm decreases, the decrease being presumably due to changes in the tone of the sympathetic nervous system, since no significant changes were observed in cardiac activity during atropine administration.     

The influence of the sympathetic innervation on the skin microvascular tone and blood flow oscillations

The influence of the sympathetic innervation on the tone of resistive vessels and blood flow oscillations was studied using laser Doppler flowmetry and skin thermography in 18 healthy subjects (before and after reflex cold and heat tests and local thermal testing), 42 patients with denervation syndromes caused by median nerve damage, and 10 patients with an acute stage of aseptic inflammation after radius fracture. The blood flow oscillations in the range of neurogenic sympathetic influences (0.02–0.052 Hz) supported by low-frequency sympathetic rhythms are an essential component of neurovascular interrelations. The importance of these oscillations is determined by their contribution to an increase in tissue perfusion owing to a decrease in the peripheral resistance and also by the leveling of drastic changes in blood flow and stabilization of microhemodynamics upon pronounced changes in the stationary tone. The high-and low-frequency (tonic and oscillatory, respectively) sympathetic rhythmic activities are expressed in two ways: (1) a synchronous increase or decrease in their amplitudes and (2) frequency dominance. The reactivity of the vessel smooth muscles is an important factor in maintaining the blood flow oscillations. Denervation decreases the oscillation amplitude in the neurogenic range. Under the conditions of local “inflammatory sympatholysis,” reflex tonic effects, rather than oscillatory ones, of the sympathetic impulses are mainly suppressed. An isolated evaluation of the blood flow oscillations in the neurogenic sympathetic range cannot be a measure of sympathetic activity. In studies on its functional state and evaluation of the neurogenic tone (NT) of resistive vessels, it is necessary to take into account the parameters of both stationary and oscillatory components of the NT.     

Ovarian changes in the progeny of females subjected to prolonged cooling

The ovaries of immature offspring of the females, subjected to cooling (+5 degrees-+7 degrees C) for 80 days (including pregnancy period) have been investigated. As a control the ovaries of immature offspring of the females, living in the vivarium have been studied. By means of the light optic, electron microscopic, fluorescent-histochemical and morphometric methods, analysis of the generative structures and activity of the sympathetic innervation of the ovaries of performed. Ultramicroscopic organization of ovocytes with early signs of destruction is examined. In the animals of the test group total number of follicles and indices of sympathetic mediation of the ovaries decrease, while more than two-fold increase of ovocytes with signs of destruction is noted, predominantly in the primordial follicles. Thus, a prolonged adaptation of the female to cooling results in certain changes of the ovarian reproductive function in the offspring.     

Characteristics of the formation of compensatory and adaptive responses of sailors to chronic stress

Rhythmography and omegametry have been used to study the physiological functions in 45 sailors during a 157-day sea voyage in the northern and northwestern Atlantic. The characteristics of the formation of compensatory and adaptive responses of sailors to long-term, chronic stress caused by work at sea are analyzed. Patterns of the variation in autonomic tone in different months of the long voyage and the dependence of the constant potential of the brain on the autonomic balance are described. Markov chain models are used to simulate the adaptation outcome for different states of the autonomic balance. The specific features of the functional physiological characteristics of sailors at different levels of functional reactivity are analyzed. It is found that humoral mechanisms serve as a link between the factors ensuring structural and functional rearrangement of the mechanisms of constant potential formation in chronic fatigue. A reciprocal mechanism is shown to underlie the formation of functional states during the second half of the voyage.     

Measuring intracardiac impedance for the determination of sympathetic nerve activity in frequency-adapted electrostimulation--Part 2: Clinical results]

The results of a multicenter clinical study involving patients receiving the first ANS controlled rate adaptive pacemaker are presented. In the patients with primary or secondary chronotropic insufficiency, it is possible to reestablish the closed loop control system that includes the baroreceptors, the medulla oblongata, the cardiac output and the mean arterial blood pressure. This system serves to keep the blood pressure constant in the face of changing demands on the circulation. Utilizing intracardiac impedance measurements, the myocardial contractility can be determined, which contains information about the current sympathetic tone, and thus represents an excellent physiological input for a rate adaptive mechanism. The results presented are taken from a study population of over 200 patients. The objective evaluation of this new approach was performed echocardiographically, by ergometry and 24-hour Holter monitoring.     

Effect of the early postnatal administration of cortisol on development of the nervous control of cardiac function in albino rats

When infant rats were treated with cortisol, in daily s.c. doses of 20 mg X kg-1, between the ages of 2 and 15 days, the noradrenaline content of their heart and spleen, between the ages of 23 and 65 days, was lower than in the controls. The decrease in the noradrenaline content did not diminish with advancing age; on the contrary, it was the most pronounced at 65 days. Cortisol treatment did not affect the noradrenaline content of skeletal muscles. The functional significance of the decrease in the noradrenaline content was studied in nervous control of the sinoatrial node of the heart. In agreement with the drop in noradrenaline concentration, transmural stimulation of the sinoatrial node region of isolated atria led to a mild, but statistically significant reduction of the function of sympathetic nerve endings, whereas parasympathetic innervation of the node showed no signs of impairment. This peripheral functional deficiency of sympathetic innervation of the node is not seen in the intact organism, where it is masked by central nervous mechanisms. Rats given cortisol postnatally had a significantly higher heart rate at 23, 33 and 44 days, because, in the presence of normal sympathetic influence, the tone of the parasympathetic nerves was reduced. The heart rate was highest at 23 days; with advancing age the difference diminished and at 65 days it was statistically nonsignificant.     

Interrelations between the sympathoadrenal system,adrenal cortex,and autonomic tone in seven- to nine-year-old children

Comprehensive study of the functional state of the sympathoadrenal system (SAS) and adrenal cortex (AC) and the specific features of the autonomic regulation of the cardiac rhythm revealed close correlations between the excretion of catecholamines (CAs) and androgens, on the one hand, and the initial autonomic tone (IAT) of the cardiovascular system of children, on the other hand. Most schoolchildren of both sexes with a predominant dependence of their cardiac rhythm on sympathetic influences were shown to excrete more noradrenaline (NA), 17-hydroxycorticosteroids, and 17-ketosteroids and less dopamine than their normotonic and vagotonic counterparts, which was accompanied by an increase in the NA-to-adrenaline ratio. In contrast, eight-and nine-year-old girls exhibited a relatively decreased activity of glucocorticoid functions of the AC associated with sympathicotonia. A local static effort performed as a functional test caused similarly directed changes in the functional states of the SAS and AC in a manner dependent on the child’s IAT, age, and sex. In the states of sympathicotonia or normotonia, nine-year-old girls exhibited a decrease in the excretion of CAs and DOPA or their insignificant increase accompanied by strengthening of the functional activity of the AC, especially of its androgen function. This may be interpreted as a manifestation of specific neuroendocrine interrelations in the adaptive mechanisms of nine-year-old girls and a higher stability of the pituitary-adrenal system, which controls metabolic processes in the growing body. In contrast, in normotonic and vagotonic seven-year-old boys (as well as in sympathicotonic eight-year-old boys), the local static effort revealed simultaneous decreases in the reserve potentials of the SAS and AC, probably caused by fatigue and asthenization of these children during their schoolwork.     

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.     

Adaptive changes in temperature sensitivity in humans under the conditions of cold, heat, and prolonged exercise

In humans adapted for a long time to various conditions—cold, heat, and physical exercise—differently directed changes in temperature sensitivity are observed. During long-term adaptation of humans to cold, a decrease in cold sensitivity is observed. Vice versa, in humans adapted to a hot climate, sensitivity to heat is decreased. Prolonged physical exercise does not change the sensitivity to heat but considerably increases the sensitivity to cold. Some mechanisms and the role of noradrenaline, the postganglionic neurotransmitter of the sympathetic nervous system, in the adaptive processes of a change in temperature sensitivity are considered.     

Physical working capacity and factors responsible for it after exposure to 120-day antiorthostatic hypokinesia

The effect of 120-day antiorthostatic hypokinesia on human physical working capacity and functional state was studied. The study revealed two adaptation phases: the first phase is characterized by a significant decrease in working capacity and the second by relative readaptation. However, the unfavorable effect of 120-day antiorthostatic hypokinesia was evident as a decrease in the effectiveness of function of the cardiorespiratory system that increased the physiological cost of physical work.     

Comprehensive Approach to Functional State Evaluation in Humans: Report I. Methodology of Diagnosis of the Functional State

By means of a complex of cost-effective, rapid, and, whenever possible, computerized screening procedures, a systematic two-week study period of the functional states of subjects in a small group of healthy adults was performed. The daily variations of 125 parameters and periodic changes in 51 parameters of somatic and mental health were investigated at increasing doses of an adaptive drug. In the initial state of the subjects, various deviations of the somatic parameters from the normal level were found, presumably of a nutritional origin. The adaptive drug was found to normalize the changed parameters of somatic health within a week due to a strain in the regulatory systems and a decline in the functional reserves of adaptation. At the end of the examination, excessive doses of the adaptive drug returned the majority of the somatic parameters to the initial levels. At the same time, the work capacity of the subjects decreased and the strain on the autonomic nervous system and the level of stress increased. Discomfort and fatigue developed, which restricted the abilities of the examined subjects to choose behavioral tactics.     

Raised tone reveals ATP as a sympathetic neurotransmitter in the porcine mesenteric arterial bed

The relative importance of ATP as a functional sympathetic neurotransmitter in blood vessels has been shown to be increased when the level of preexisting vascular tone or pressure is increased, in studies carried out in rat mesenteric arteries. The aim of the present study was to determine whether tone influences the involvement of ATP as a sympathetic cotransmitter with noradrenaline in another species. We used the porcine perfused mesenteric arterial bed and porcine mesenteric large, medium and small arteries mounted for isometric tension recording, because purinergic cotransmission can vary depending on the size of the blood vessel. In the perfused mesenteric bed at basal tone, sympathetic neurogenic vasocontractile responses were abolished by prazosin, an α₁-adrenoceptor antagonist, but there was no significant effect of α,β-methylene ATP, a P2X receptor-desensitizing agent. Submaximal precontraction of the mesenteric arterial bed with U46619, a thromboxane A₂ mimetic, augmented the sympathetic neurogenic vasocontractile responses; under these conditions, both α,β-methylene ATP and prazosin attenuated the neurogenic responses. In the mesenteric large, medium and small arteries, prazosin attenuated the sympathetic neurogenic contractile responses under conditions of both basal and U46619-raised tone. α,β-Methylene ATP was effective in all of these arteries only under conditions of U46619-induced tone, causing a similar inhibition in all arteries, but had no significant effect on sympathetic neurogenic contractions at basal tone. These data show that ATP is a cotransmitter with noradrenaline in porcine mesenteric arteries; the purinergic component was revealed under conditions of partial precontraction, which is more relevant to physiological conditions.     

Effect of antihypertensive therapy on sympathetic nervous system activity in patients with essential hypertension

The sympathetic nervous system (SNS) plays a major role in blood pressure regulation. Although the exact relationship of the SNS to the etiology of hypertension remains undetermined, many of the agents used to treat hypertension interfere with this system. Clonidine, methyldopa, guanethidine, and reserpine decrease SNS tone whereas hydralazine, minoxidil, and hydrochlorothiazide increase it. Most evidence suggests that beta-adrenergic blocking agents decrease SNS activity. The effect of prazosin and captopril on the SNS requires further study. The appropriate use of these antihypertensive agents requires a knowledge of their sites of action and the physiological reflexes they induce. Efficacy, toxicity, and effective drug combinations can be predicted based on their mechanism of action and effect on SNS activity.     

The morphogenetic patterns of the higher autonomic centers in a pathological pregnancy]

Neurosecretory, parasympathetic and sympathetic centers of 49 mature fetuses subjected to toxicity were studied using light and electron microscopy. These centers were characterized by similar regularities of neurocytes development. Higher degree of maturity was typical for neurosecretory, while minimal for sympathetic centers. A higher degree of maturity and functional performance of vegetative regulatory system predominated in large fetuses. A general rule was a relative independence of forming truncal and spinal morphosystems and their nuclei on body and brain masses. Dyschronia of vegetative centers development reduces an adaptive potential of the fetus and causes fatal outcome in intranatal period.