Frequency Of Cardiac Contractions Research Articles

Методология ингаляционной анестезии при ортопедических оперативных вмешательствах у собак

The article presents the results of a study on the effect of inhaled anesthetics on the state of the animal body during orthopedic surgical interventions to identify possible intra- and postoperative complications associated with anesthetic care. The studies were carried out on a group of clinically ill dogs with joint pathologies selected by the method of analogues without regard to gender and age. According to the results of the conducted studies, it was revealed that when using Isoflurane, unlike Sevoflurane, there is a significant decrease in blood pressure; an increase in the frequency of cardiac contractions; nephrotoxic and hepatotoxic effects, however, these indicators have a negligible effect on the general condition of the animal. The priority of choosing an anesthetic was not revealed in our study, since all the studied groups of animals underwent anesthesia well during surgical interventions.

Canagliflozin Reduces the Contractile Response of Isolated Heart of Normal Adult Rats

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) represent a unique class of glucose-declining renal-targeted drugs. The SGLT2i Canagliflozin (CANA) is an anti-hyperglycemic drug that reduces various cardiovascular and renal outcomes in patients with type 2 diabetes mellitus. This study aimed to explore the potential effects of CANA on the isolated healthy adult rat hearts to show if CANA has positive inotropic or cardiac depressant effects via analyzing the amplitude and frequency of cardiac contractions. In isolated normal adult rat hearts, the effects of CANA on cardiac contractility were examined. In a dose-response curve, CANA led to a significant cardiac depressant effect in a dose-dependent manner. This cardiac depressant effect of CANA (10-6 M) was not prevented by atropine. However, this cardiac depressant effect was partially antagonized by both Isoproterenol (10-5 M) and Calcium chloride (10-6 M), suggesting beta-adrenoceptor and calcium channel blocking actions. In addition, the cardiac depressant effect of CANA (10-6 M) was mitigated in part by Nitric oxide synthase inhibitor, L-NAME, suggesting that its action probably depends to some extent on the accumulation of nitric oxide, which decreases the rise of intracellular Calcium. Data from this study demonstrate that CANA has a significant cardiac relaxant effect in isolated hearts of healthy adult rats by different possible mechanisms. This inhibitory effect on cardiac contractility may help improve the diastolic ventricular filling providing a therapeutic potential to help the other cardioprotective mechanisms of CANA in the prevention and treatment of heart failure.

EXPERIMENTAL VERIFICATION OF EFFECTIVENESS OF TAKING PART IN ADDITIONAL MOTOR ACTIVITIES IN CONNECTION WITH FEMALE ABILITY

Achieving a health effect in sports activities within the Higher school is possible by applying a variety of targeted means and methods. The relevance of the study: Obtaining data on the impact of additional cyclic activity and gradual inclusion of exercises for general strength and resistance to the working capacity of students within the training process. Purpose of the study: Study of the reaction of the cardiovascular system and the achievements of female students after application of additional complexes of exercises in the syllabus of callanetics. At the beginning and at the end of the summer semester of 2018/2019 the female students were subjected to a 5-minute stepwise load of the cross trainer with a measurement of the frequency of cardiac contractions of the first, third and fifth minutes and the distance travelled distance of each of the three loading steps. For the realization of the research project a series of exercises with cyclic aerobic focus as well as static and dynamic strength exercises without and with aggravated. The applied exercises enhance the functional capabilities of the cardiovascular system and the level of total endurance and performance.

Соціально-біологічні аспекти фізичної культури

The article deals with the main socio-biological aspects of physical culture and sport as the principles of interaction of social and biological laws in the process of mastering human values of physical culture. An integral part of the methodology of training physical education is a system of knowledge of exercises with consideration of medical and biological aspects. Without knowledge of the method of exercises physical training exercises can not be clearly and correctly performed, and therefore the effect of these exercises will decrease and will not give the desired effect. And in this direction classes should have a clear methodological focus on increasing the level of physical preparedness and functional state of the applicants. Developing a method of physical activity should follow a clear theoretical and methodological provision of educational programs and be developed by professional specialists in the field of physical culture, since the lack of a precise method of exercising can lead to more serious consequences, even to injuries. The article examined the socio-biological aspects of the physical culture of higher education graduates, as well as considered the solutions to some of the problems students encounter most often. To improve the efficiency of physical education of student youth, the following provisions need to be implemented: rational methods and organization of classes; adequacy of the content of physical training for future professional activity; optimization of physical training by using non-traditional means and modern methods, especially when working with women's contingents; regular medical and biological control: determining the level of functional status of applicants; curve design due to changes in the frequency of cardiac contractions; definition of general motor activity, etc. Formation of the consciousness of the needy and stable habit of the carers about their health and the level of physical preparedness. Consequently, the acute issues related to this problem will be considered in the further direction of the medical and biological foundations of physical culture and sports of higher education graduates.

Features of lesion of the cardiovascular system in patients with acute brucellosis

Heart damage in acute brucellosis can determine the severity of the disease, affect the quality of life of the patient and the prognosis of the disease as a whole. The purpose of the study is the integrated assessment of the cardiovascular system (CCS) in patients with acute brucellosis on the basis of clinical and instrumental examination results. 120 patients with acute brucellosis were examined, the average age of patients was 35.9±2.8 years. In order to assess the state of the CCS, all patients were registered with the electrocardiogram in 12 standard leads, blood pressure (BP), and echocardiography. Statistical processing of the results was carried out using “STATISTICA 6.0” using parametric and non-parametric methods for evaluating the obtained results. During the study, it was found that 77.50% of patients with acute brucellosis had certain signs of abnormalities in the work of the CCS. Among clinical manifestations cardialgia is dominated by a non-ischemic nature, a marked increase in the frequency of cardiac contractions and a decrease in the level of predominantly diastolic blood pressure. Electrocardiographic changes are characterized by a predominant disruption of the function of automatism. The tendency to rhythm disturbances is confirmed by the detection of ventricular arrhythmias in them, prolongation of QT interval in some patients. Diagnosed disturbances of ventricular repolarization process, along with other changes, can be evidence of myocardial damage and its structural transformations. There was also a tendency to increase the size of the left heart, reducing the contractile capacity of the left ventricle and formation of one third of patients with diastolic dysfunction, which may be evidence of changes in the myocardium due to systemic inflammation inherent in brucellosis. Consequently, in the vast majority of patients with acute brucellosis, there are signs of lesion of the CCS that can be detected already during the routine clinical examination.

Мodern views on the pathogenetic and prognostic aspects of prolonged and postterm pregnancy.

The etiology and pathogenesis of post-term pregnancy to date have not been studied sufficiently, despite the considerable arsenal of scientific publications devoted to this problem.Post-term pregnancy should be considered as a pathological problem, which depends on both the mother's condition and the condition of the fetus. The scientific literature highlights a number of reasons for pregnancy overcoming: a change in the hormonal state (high levels of progestins and low estrogen), changes in myometrium, dysfunction of the pituitary-adrenal system of the fetus, changes in the central nervous system. With the onset of pregnancy, its course, development and the nature of generic activity are associated with corticosteroids, chorionic gonadotrophin, placental lactogen, oxytocin, catecholamines, acetylcholine, serotonin, histamine and prostaglandins, as well as psychological traumas, toxicosis of the second half of pregnancy. The role of metabolic processes such as acidosis, change of pH-cord blood, deficiency of vitamins D, C, B, P, E, as well as reduction of trace elements such as copper, zinc, magnesium in blood, myometrium and placenta are also shown. The role of the immune factor in the etiology of post-term pregnancy is shown. Changing the equilibrium in the ratio of transplacental immunity and immunological tolerance. When post-term pregnancy occurs in the blood of pregnant women, there are no T-killers against fetal cells, high T-supressor pregnancy products are preserved. One of the factors in post-term pregnancy is the reduction of nitric oxide secretion by the endothelium of the cervical vessels. The leading role belongs to neurohumoral factors of regulation of the state of the uterus. When post-term pregnancy is occurs declared and sclerotic processes in the vessels of the placenta and placental place, the thin of the hematochorial barrier, apoptosis placental cells, changes in the morphology of vessels of the umbilical cord, microcirculation disorders. As a result, the fetus is stretching the cavity of the right ventricle and changing the frequency of cardiac contractions, decreasing its motor activity. Ultrasound examination for pregnancy dates reduces the mistake of the diagnosis. Consequently, in the scientific literature, there are many conceptions of post-term pregnancy, each of which has the right to exist and all of them are important prognostic tests, therefore, a thorough examination of pregnant women is necessary taking into account all possible risk factors for post-term pregnancy.

Modeling Biotechnical Systems in Sports

The objective is to describe biotechnical systems, to specify their functioning and to determine the conditions to decrease the uncertainty of the systems; to search and interprete the hidden periodic behavior of the numerical series occurring in training and competitive activities.Materials and methods. The functioning of biotechnical systems was studied. To characterize the functional state of the system, the study used analysis of the cardiovascular system functioning, which was quantitatively characterized by the frequency of cardiac contractions taken in the dynamic mode with a pulsimeter with per-second discretization of time and analyzed using a software package.Results. The article proposes to use a certain approach to handle numerical series when studying biological and natural processes. The hidden periodic behavior of the numerical series occurring in training and competitive activities of athletes were sought out and interpreted. The paper presents some biotechnical systems.Conclusions. The paper proposes an approach to studying biotechnical systems. The human heart rate changes throughout the day depending on the time and is of fluctuating nature with certain periods, whereas the heart rate periods depend on the person’s activity and the time of day. At the same time, when in rest, the heart rate tends to decrease the amplitude. Moreover, the heart rate reading significantly depends on the load of the person. All this confirms the need to conduct a sufficiently detailed study of the human heart rate and its exposue to external and internal factors as well as the correlation between the latter. The uncertainty of the system decreases with the introduction of additional information.

Hypotensive, cardiodepressant, and vasorelaxant activities of black currant (Ribes nigrum 'Ben Sarek') juice.

The aim of this study was to evaluate the effects of black currant (Ribes nigrum L. 'Ben Sarek') juice on the blood pressure and frequency of cardiac contractions, as well as vasomotor responses of rat aortic rings. Arterial blood pressure was measured directly from the carotid artery in the anaesthetized rabbits. The aortic rings were pre-contracted with KCl (80 mmol·L-1), after which black currant juice was added. An intravenous injection of black currant juice (0.33-166.5 mg·kg-1) induced a significant and dose-dependent decrease of rabbit arterial blood pressure and heart rate. The black currant juice decreased arterial blood pressure of rabbit by 22.33% ± 3.76% (p < 0.05) and heart rate by 17.18% ± 2.93% (p < 0.05). Cumulative addition of the black currant juice (0.01-3 mg·mL-1) inhibited concentration-dependent KCl induced contractions of the isolated rat aorta. The black currant juice, at the concentration of 3 mg·mL-1, caused a maximum relaxation of 21.75% ± 3.15% (p < 0.05). These results demonstrate that black currant juice can induce hypotension. The hypotensive effect of the black currant may occur as the consequence of its inhibitory activity on the rate of heart contraction and vasorelaxant effects.

3D cardiac μtissues within a microfluidic device with real-time contractile stress readout.

We present the development of three-dimensional (3D) cardiac microtissues within a microfluidic device with the ability to quantify real-time contractile stress measurements in situ. Using a 3D patterning technology that allows for the precise spatial distribution of cells within the device, we created an array of 3D cardiac microtissues from neonatal mouse cardiomyocytes. We integrated the 3D micropatterning technology with microfluidics to achieve perfused cell-laden structures. The cells were encapsulated within a degradable gelatin methacrylate hydrogel, which was sandwiched between two polyacrylamide hydrogels. The polyacrylamide hydrogels were used as "stress sensors" to acquire the contractile stresses generated by the beating cardiac cells. The cardiac-specific response of the engineered 3D system was examined by exposing it to epinephrine, an adrenergic neurotransmitter known to increase the magnitude and frequency of cardiac contractions. In response to exogenous epinephrine the engineered cardiac tissues exhibited an increased beating frequency and stress magnitude. Such cost-effective and easy-to-adapt 3D cardiac systems with real-time functional readout could be an attractive technological platform for drug discovery and development.

Gaba-ergic mechanisms in the caudal ventrolateral region of the cat medulla regulating vascular tonus and cardiac activity

In acute experiments on anesthetized cats data are obtained attesting to the fact that injections of GABA (0.5–50 µmoles/liter) into neuronal structures of the caudal ventrolateral medulla (CVLM) are accompanied by the development of hypertensive reactions caused by an increase in spontaneous activity in the sympathetic fibers of the renal and inferior cardiac nerves. An asymmetry is discovered in the realization of the inhibitory chrono- and inotropic influences on the heart emanating from the region investigated. Blocking of the GABA receptors with bicuculline (0.2–5.0 µmoles/liter) causes a sharp drop in the level of the systemic arterial pressure, a decrease in the strength and frequency of cardiac contractions, and a falling-off of the background activity in the peripheral symphathetic nerves. The findings suggest that the sympathoinhibitory CVLM neurons are under the constant inhibitory control of the GABA-ergic neurons.

Dependence of the electrical activity of the hippocampus on the probability of reinforcement of an alimentary conditional stimulus

The dynamics of the changes in the number of instrumental motor reactions and in the frequency of cardiac contractions and of the theta rhythm of the hippocampus during the replacement of constant reinforcement by various schedules of probabilistic reinforcement of an alimentary conditional stimulus were investigated in three dogs. At the 70 and 50% level of reinforcement, the instrumental reflex appeared in response to all of the presentations of the signal stimulus. The greatest decrease in the number of respondent reactions was observed at 5% probability. The pulse rate both in the intersignal period and during the receipt of an empty feeder depended on the probability of reinforcement employed and on the individual characteristics of the animals. The frequency of the theta rhythm in all of the dogs was highest at the 30% level; the lowest values were observed at the 5% level of reinforcement. The data obtained again attest to the complex genesis of emotional excitation, the magnitude of which depends both on the informational (indeterminacy) and on the motivational (the significance of the reinforcement) factors.

Electrophysiological correlates of slow periodicity of cardiac rhythm.

Regular changes in frequency of cardiac contractions with a period of more than 10 sec were investigated in acute experimentation on immobilized cats. Possible conditions for the origination of decasecond periodicity of cardiac rhythm are examined. Quantitative characteristics are presented. It is shown that spontaneous galvanic skin surges can be grouped in relation to phases of slow oscillations in cardiac rhythm. In some experiments synchronous decasecond oscillations were registered in the frequency of cardiac contractions with change in amplitudes of electrical responses of the hippocampus to stimulation of the amygdaloid complex. The possible functional significance of slow modulation in the frequency of cardiac contractions and the mechanisms responsible for determining the association of observed phenomena are discussed.

Effect of stimulation of the hypothalamus on the activity of the cardiovascular system in long-term experiments

In chronic experiments on waking unanesthetized dogs a study was made of the effect produced by stimulating various portions of the hypothalamus on the blood pressure and the frequency of cardiac contractions. Blood pressure was recorded in the coronary artery or in the subcutaneous artery of the knee joint. As demonstrated, stimulation of the posterior hypothalamus (caudal portion of the tuber cinereum and of the mamillary body) increased the blood pressure by 20–40 mm Hg, whereas stimulation of the anterior hypothalamus (the area of the supraoptic and paraventricular nuclei) decreased the pressure in a number of cases by 10–20 mm Hg. The frequency of cardiac contraction usually increased by 10–14 (at times by 60 beats) per minute; the rise in response to stimulation of the anterior hypothalamus was less pronounced. In individual cases there was an insignificant deceleration of the cardiac rhythm by 4–8 contractions per minute. Other autonomic and somatic reactions often accompanied the blood pressure and pulse changes, i.e., the pupil size changes, those of respiration, of the smelling reaction, licking, urination, defecation, general motor excitation, etc.

The electrocardiogram of healthy rabbits in standard and chest leads and methods of recording it

Two hundred twenty-two electrocardiograms were recorded in 36 rabbits during a period of 20 months. Three standard and four chest leads were used. Needle electrodes were introduced subcutaneously into the right, left anterior and left posterior extremity; the chest electrodes were introduced at the following points: points I (CR) and IV (CR5) at the intersection of the vertical line (corresponding to the anterior axillary, line) with the horizontal line at the level of the heart; points II and III (CR1 and CR4) at the crossing of the parasternal lines with the horizontal. Electrocardiograms recorded with the animal on its back did not substantially differ from those recorded with the animal in the normal position. Five different positions of cardiac electrical axis were observed: normal, left, right, vertical and mixed. These may be spontaneously converted into borderline types. The number of cardiac contractions ranged from 180 to 330 per minute, averaging 250. The duration of the waves and intervals was between 0.01 and 0.02 seconds, depending on the number of cardiac contractions. The value of electric systole depended on the frequency of cardiac contractions. The ECG of the rabbit possesses specific features which should be taken into account in evaluating the cardiac function.

The inotropic and chronotropic components of the cardiac activity of dogs at rest

The values of the final maximal intra-arterial blood pressure and the average frequency of cardiac contractions were studied in 4 dogs which lay at rest. In experiments of up to 50 minutes there occurred a gradual reduction of these values depending on the duration of the rest period. This regularity was observed both in dogs intact and in animals whose vessels were not subject to the cerebral neural tonic effect at the site of examination.

Temperature Characteristics for Heart Rate in Embryos of Limulus.

For a number of Limulus embryos the relationship has been determined between temperature and the frequency of cardiac contractions, during stages of development when the (myogenic) heart is still devoid of a nervous system. A thermostat maintaining any desired temperature between 0.05° and 45° to within ±0.01° or better, and quickly adjustable, was devised to facilitate this work. The temperature characteristics obtained are not the same in all individuals. The values μ= 11,500 and 16,400 are usual; but μ = 20,000 and μ = 25,100 also occur. These are well recognized values in numerous other vital processes, but differ from the magnitude (μ = 12,200) which seems typical for the thermal control of frequency of contraction in the heart of the adult (the temperature of the ganglion being altered). This need not be interpreted as corresponding to an essential difference between myogenic and neurogenic rhythm. The critical temperatures for heart rhythm also differ among individuals; the following are of definite occurrence, in different cases: 9°, 20°, 27°, 31°, 41°, 45°. The results are chiefly important as indicating relatively greater metabolic lability in embryonic than in adult tissues. It is concluded that the apparent inconstancy of μ for contraction rate in explants of chick myocardium (H. Murray) is due to the presence of several functional pacemakers having different temperature characteristics, corresponding to the finding of different μ's for the hearts of similar Limulus embryos. This is proved by the fact that in cases giving atypical μ's, the latitude of variation is not a constant fraction of the mean; the marginal heart-beat frequencies yield typical μ's.