Effects of Screen Time and Season on Cardiovascular System Indicators in Primary Schoolchildren.

Indicators of the cardiovascular system, including heart rate (HR) and blood pressure (BP) variability parameters, were analyzed in primary school students with different computer screen times. The study included 4084 students of grades 1-4 (age 7-12 years) from 66 Moscow schools. The screen time at school and out of school was assessed by teachers, based on the national Sanitary Rules and Regulations: 0, no screen time; 1, screen time matching hygienic standards; 2, screen time at least twice greater than recommended. Physiological examinations were carried out by spiroarteriocardiorhythmography with a face mask, the conditions corresponding to the functional stress test (mild hypercapnia/hypoxia). Testing took place in spring and autumn (independent samples). Statistical data processing was performed using nonparametric criteria. It was revealed that the introduction of computer technologies in school lessons within the limits of hygienic standards was accompanied by an increase, within the normal range, of systolic BP in girls at the end of grade 2 and 4 and in boys at the beginning and end of grade 4. Screen time at least twice higher than the hygienic standard did not have an additional effect on BP, but provoked shifts in the function of autonomic regulation. Boys were more sensitive to the influence of this environmental factor. Their pattern of seasonal variability in total power (TP) of the HR variability spectrum was reversed compared to that of children who did not use computers at school; i.e., higher TP values were observed in spring. In grade 4, the process was accompanied by an increase in spontaneous arterial baroreflex sensitivity and a decrease in the relative power of the LF range in the variability spectrum of systolic BP. The changes were assumed to reflect the adaptive response to changes in educational environment.

[Age-related changes of the latent period of simple sensorimotor reaction to the light stimuli in both men and women with different body mass index].

The study of the relationship of the latent period of simple sensorimotor reaction to the light stimulus and body mass index (BMI) in males and females aged 30-60 years (n = 507) was done. The boundary between the low (below Me - 1SD) and middle (from Me - 1SD to Me + 1SD) BMI was the value of 22.74 kg/m2, the boundary between the middle and high (above Me + 1SD) BMI - 33.16kg/m2. It is shown thatthere isan increase inthe proportion of people with high BMI with age (faster and more pronounced - in women). Sensorimotor reaction latency to the light stimuli does not change in men, and declines with agein women. However the data obtained indicate that developed with age alimentary obesity does not adversely affect neurophysiological parameters of the sensorimotor reactivity.

[Relationship between inertial features of the upper extremity and simple reaction time in boys and girls aged 17-18].

The latent period of visual sensor-motor reaction depends, in part, on the sensory and integrative processes in the brain, but is also influenced by the rate of the muscle contraction. There is no clear evidence in the literature whether the rotational inertia of segments of limbs has any direct effect on the reaction time. The aim of our study was to identify this relationship. The study involved 566 right handed students aged 16-17 of both genders beginning their post puberty period. Reaction time was measured during experimental adduction of the forearm and hand, using a special rotating handle and lever connected to a computer that recorded the reaction time (+/- 1 ms). Calculations of the rotational inertia were carried out using regression models by Zatsiorsky and other authors. Each gender group was divided into three subgroups: with high, medium and low values of rotational inertia. It was found that individuals with high values of rotational inertia of forearm and wrist demonstrated significantly longer reaction times. This pattern was apparent in both gender groups. Although males illustrated greater values of rotational inertia than females they demonstrated relatively shorter reaction times. This contradiction can be explained by greater muscle power of young men. We recommend taking into account the amount of rotational inertia of the responsive segment in all kinds of research which require measurement of reaction time.

[Functional tests for the assessment of the healthy people state using heart rate variabilIty].

An overview of current approaches to interpreting the results of spectral analysis of heart rate variability and blood pressure is demonstrated. The analysis of own obtained results were done using the method of assessment of heart rate variability and blood pressure in a variety of functional tests (mental load, moderate exercise, cold test, the restriction of pulmonary ventilation, controlled breathing at a frequency of 6 cycles per minute) in healthy adults. It was shown that all tests induced pronounced changes in the spectral indices of heart rate variability as well as the blood pressure, which were interpreted as changes in the state of autonomous regulation of subject's cardiovascular system. The direction and the degree of changes depend on the form of action.

[The features of cardio-respiratory system and autonomic regulation in parasportsmen with spinal injury].

A comprehensive study of the functional state of basketball athletes in wheelchairs with spinal cord injuries in the T6-T10 and paraplegia (n = 9, mean age 26.6 +/- 1.7 years) was held. As a control, we used disability groups with a similar injury, leading an active life (n = 13, mean age 44.5 +/- 2.6 years), athletes ( = 14, mean age 24.6 +/- 1.3 years) and healthy physically active men (n = 15, the average age of 24.9 +/- 0.6 years). In the athletes in wheelchairs it was revealed an increase in the length of the body in a sitting position, the increase in tidal volume and increasing in the effectiveness of the functional respiratory tests. These changes in the state of the musculoskeletal system and autonomic systems to ensure physical activity classified as adaptive and due to sports training. In the state of the cardiovascular system and its autonomic regulation parasportsmen showed a reduction in trauma-induced increase in diastolic blood pressure and increase in the magnitude of arterial baroreflex sensitivity, decreased due to spinal injury. These data indicate availability of compensatory processes aimed at optimizing the cardiovascular system through the mechanisms of baroreflex regulation.

[Functional characteristics of cardiovascular system in adolescents with prehypertension].

Based on the results of sanogenetic monitoring the health of schoolchildren found that among high school students to the proportion of adolescents with elevated blood pressure (hypertension + hypernormotension) increases from 15-20% in 8th class to 30-50% in 9-11th classes, while the proportion of adolescents with hypertension was 3.7% in all age groups. Comparison of blood pressure with parameters of neurovegetative regulation of the cardiovascular system revealed that the presence of high normal blood pressure in 13-14-year-olds and 17-18-year-olds correlated with an increase in the proportion of low frequencies in the spectrum of HRV and lower values of the sensitivity of arterial baroreflex. At the age of 15-16 years, high-normal blood pressure accompanied by a decrease in heart rate, increase the sensitivity of arterial baroreflex and correlates with reduced power high-frequency part of the spectrum of HRV. When performing a functional test (an increase of "dead" breathing space) in hypernormotension teenagers 15-16 years, unlike normotensive peers, there is a reduction of finger blood pressure, and relative power of low frequencies in the spectrum of HRV, which may be associated with maladaptive functional changes in the sympathetic unit of autonomic regulation.

[Dynamics of spectral parameters of the rat brain electrical activity in the model of depressive pain syndrome].

Changes in spectra of electrical activity of rat brain structures were studied during simulation of pain-depressive syndrome by the combination of deafferentation pain syndrome developed after the sciatic nerve section with subsequent induction of dopamine deficit-dependent depressive state formed in animals via systemic administration of neurotoxin MPTP. Changes in spectra of the electrical activity of the nucleus accumbens, frontal neocortex, amygdala, and caudate putamen during the development of pain-depressive syndrome pointed to the formation of a new functional state as compared to depressive state and pain syndrome simulated individually. Alterations in the state of hippocampus did not reach the level of statistical significance.

Changes in spectral measures of brain electrical activity in rats after transection of the sciatic nerve.

Electrophysiological measures of brain electrical activity were studied in rats during the development of neurogenic pain syndrome induced by transection of the sciatic nerve. At the peak of development of pain syndrome, three weeks after deafferentation, rearrangements in the spectra of electrical activity were seen in the limbic structures of the brain (hippocampus, amygdala, nucleus accumbens), in the frontal areas of the neocortex, and in the caudate-putamen complex: changes consisted of increases in the relative power of the delta and alpha ranges as compared with controls, along with a decrease in relative power in the beta-2 range. Changes in spectral measures of electrical activity in the limbic structures of the brain occurred independently of the clinical manifestations of neurogenic pain syndrome (autotomy). The increase in relative power in the alpha range of the spectrum of electrical activity in all the structures studied suggests that the reticular nucleus of the thalamus is involved in the pathogenetic mechanisms of neurogenic pain syndrome.

[Alterations of spectral parameters of rat brain electrical activity after sciatic nerve section].

Changes in electrophysiological brain characteristics accompanying the development of neurogenic pain syndrome induced by transsection of sciatic nerve were analyzed. At the maximum pain syndrome 3 weeks after the deafferentation, a reorganization of the brain electrical activity was observed in the limbic structures (hippocampus, amygdale, and nucleus accumbens), frontal cortex, and the caudate putamen. An increase in the relative spectral power of the delta and alpha bands and a decrease in the relative power of the beta2 band (as compared to baseline activity) took place. Alteration of the electrical activity in the limbic structures did not depend on manifestations of the neurogenic pain syndrome (autotomy). The increase in the relative spectral power of the alpha-band activity in all the structures under study suggests the involvement of the reticular thalamic nucleus in pathogenesis of neurogenic pain syndrome.

[Functional development of the vegetative regulation of the cardiovascular system in human ontogenesis].

Using the functional tests method, it was shown that the ontogenetic course of development of the cardiovascular system vegetative regulation after the age 6 years might be conditionally divided into some periods. About the age of 13-14 years, the spectral structure of heart rate variability reached the level of adult humans but is accompanied with features of functional strengthening in regulative systems. About the age of 15-16 years, maturation of indices received in quiet state (heart rate, stroke volume, spectral and statistical parameters of heart rate variability) is reached. At the same time, the functional maturation of heart rate regulating systems was complete thereby providing adaptive response of the organism during the implementation of functional tests. Functional maturation of peripheral blood pressure and the systems of its regulation completed after 16 years.

Involvement of brain dopaminergic systems in the development of an MPTP-induced depressive state in rats.

A depressive state was induced in Wistar rats by repeated i.p. injections of the proneurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which induces the death of dopaminergic neurons in the brain. Signs of the development of the experimental depressive state were a reduction in body weight and an increase in the proportion of REM sleep during daytime sleep. The rearrangement of the spectral characteristics of electrical activity during the development of experimental depressive syndrome in rats was shown to occur in target structures of the nigrostriatal, mesocortical, and mesolimbic dopaminergic systems of the brain, as well as in the amygdala and hippocampus. The most marked changes were seen in the terminal field of the nigrostriatal dopaminergic system and hippocampus. Spectral rearrangements of electrical activity in the theta-1 and theta-2 ranges in the hippocampus and dopaminergic structures suggest the involvement of the hippocampus in mediating changes in the emotional status of the experimental animals during the development of the MPTP-induced depressive state.

[Involvement of the brain dopaminergic systems in the development of the MPTP-induced depressive state in rats].

Depressive state was produced in Wistar rats by repeated intraperitoneal administration of proneurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) inducing death of brain dopaminergic neurons. Weight loss and increase in REM-sleep rate during diurnal sleep were considered to be signs of the development of an experimental depressive state. During the development of the depressive state of rats, the MPTP-induced reorganization of the spectral power of electrical activity was observed in the terminal fields of the nigrostriatal, mesocortical, and mesolimbic dopaminergic systems, amygdala, and hippocampus. The most pronounced changes were revealed in the terminal field of the nigrostriatal system and hippocampus. The reorganization of the spectral power in the thetal and theta2 bands in the hippocampus and dopaminergic structures suggests the involvement of the hippocampus in producing changes in the emotional state during development of the MPTP-induced depressive syndrome.

[Groups of passive and active control state in longitudinal experiments: an electrophysiological study].

Long-term electrophysiological experiments were carried out with rats with chronically implanted electrodes into dopaminergic brain structures. Within 4 weeks after surgery, the relative spectral power of electrical activity in the delta1 and delta2 frequency bands decreased, while the relative spectral power in the alpha, beta1 and beta2 bands increased. A delayed (to the 4-5th week after surgery) increase in the total amount of sleep and REM sleep percent was observed in the sleep architecture of these animals. Multiple (during 2 weeks daily) intraperitoneal saline injections altered the dynamic of electrophysiological indices on the 2nd-3rd postsurgery weeks. The total sleep amount being not increased, the total and mean REM sleep durations increased, and the dynamic of the relative spectral power of electrical activity in the dopaminergic brain structures in the delta1, alpha and beta2 bands was found to be changed.

Immunization of rats with conjugates of dopamine and serotonin with bovine serum albumin prevents the development of experimental MPTP-induced depressive syndrome (electrophysiological parameters).

Electrophysiological experiments on Wistar rats demonstrated that prior immunization of animals with conjugates of dopamine and serotonin with bovine serum albumin, as well as with bovine serum albumin alone, played a partial protective role in relation to the subsequent development in these animals of experimental MPTP-induced depressive syndrome: immunized animals showed no signs of the depressive state such as decreases in the latency of onset of REM sleep and the development of epileptiform activity in the caudate-putamen complex, though the increase in the proportion of REM sleep in the overall structure of sleep persisted. Changes in the spectral characteristics of brain electrical activity and sleep structure during the development of experimental MPTP-induced syndrome in animals immunized with conjugates of dopamine and serotonin with bovine serum albumin and with bovine serum albumin alone were antigen-specific and reflected functional shifts in the activity of those neurotransmitter systems targeted by immunization, as well as others sensitive to changes in the body's immunological status.

[Immunization of rats with bovine serum albumin conjugate with dopamine or 5-hydroxytryptamine prevents the development of experimental MPTP-induced depressive syndrome. An electrophysiological study]. / Immunizatsiia krys kon"iugatami dofamina i serotonina s bych'im syvorotochnym al'buminov predotvrashchaet razvitie éksperimental'nogo MFTP-indutsirovannogo depressivnogo sindroma (po élektrofiziologicheskim pokazateliam).

In electrophysiological experiments in Wistar rats it was shown that preventive immunization of animals with bovine serum albumin conjugated with dopamine or 5-hydroxytryptamine or with bovine serum albumin alone partly protects against the development of experimental MPTP-induced depressive syndrome. Signs of depressive-like state such as decrease in REM-sleep latency and the development of epileptiform activity in caudate putamen were not observed in immunized animals, whereas REM-sleep proportion in the total sleep structure was increased. Changes in the spectral characteristics of brain electric activity and sleep structure during development of experimental MPTP-induced syndrome in immunized rats are antigen-specific and reflect the functional shifts in neurotransmitter systems, both in those which are the target of the immune action and those sensitive to alterations in the immune state of a body.

Experimental depressive-pain syndrome in rats with initial various anxiety-phobic levels: a behavioral study.

Modeling of neurogenic pain syndrome by sciatic nerve transection in rats with pronounced dopamine-deficiency-dependent 1-methyl-4-phenyl-1,2,3,6,-tetrahydropyridine-induced experimental depressive syndrome forms a stable state of combined pain and depression, which can be considered as a model of the pain-depressive syndrome. The neurogenic pain syndrome prolongs the state of behavioral depression in rats irrespective of their initial anxiety level. The depressive symptoms can potentiate the severity of pain syndrome. By a number of indices, more pronounced behavioral changes during the development of pain-depressive syndrome occur in initially nonanxious rats.

[Alteration in the brain electrical activity, diurnal sleep structure, and the rat behavior after immunization with bovine serum albumin conjugated with dopamine]. / Izmeneniia élektricheskoi aktivnosti mozga, struktury dnevnogo sna i povedeniia krys posle immunizatsii zhivotnykh kon''iugatom dofamina s bych'im syvorotochnym al'buminom.

Male Wistar rats (380-430 g) were immunized with bovine serum albumin conjugated with dopamine (2 mg/kg, 0.25 ml) mixed with Freund's adjuvant complete (0.25 ml) or with bovine serum albumin mixed with Freund's adjuvant complete in the same doses. One week after the immunization with bovine serum albumin conjugated with dopamine, irregular spike activity and high-amplitude spindles associated with the state of awake immobility were recorded in the rat neocortex and caudate putamen, the relative power of the electrical activity in the caudate putamen was decreased in the alpha band, while the relative power of the beta 1 in the cortical EEG was increased. In the structure of 4-hour diurnal sleep, a decrease in the mean duration of sleep episodes and a reduction in the REM sleep content were observed. The parameters of the electrical activity and diurnal sleep structure returned to normal during the following 4 weeks. The open-field behavior 2 weeks after the second immunization (without Freund's adjuvant complete) did not differ from that of the control rats immunized only with bovine serum albumin. Titres of antibodies to dopamine after the second antigen injection were 1:32-1:64 in the electrophysiological series and 1:128-1:256 in behavioral experiments.