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An analysis of transient changes in physiological parameters in response to the standardized tests could be used to evaluate the efficiency of the regulatory processes. Relationships between systolic time intervals and heart rate following the action of standing up from the supine position were investigated in 41 healthy men, aged 20 to 59 years, classified into three groups: (22 to 26 yrs, n=14), (33 to 49, yrs, n=13) and (51 to 59 yrs, n=14). The protocol consisted of the following sequence: laying down (20 minutes) - standing up (8 minutes). Ejection time, pre-ejection period, electromechanical systole, heart rate and the length of R-R intervals were continuously calculated using automatized impedance cardiography and electrocardiogram. The ratio of ejection time to pre-ejection period in young men was significantly higher in comparison with the other groups. The ratio of ejection time to the length of R-R interval increased with age in supine position and after standing up when R-R interval was maximal. It was suggested that changes of ejection time to pre-ejection period during the orthostatic manoeuvre are rather the result of balance between heart rate and hemodynamic factors, than solely related to heart rate.
Dynamics of the heart rate changes following standing up from the supine position was investigated in 41 healthy men aged 20 to 59 years, classified according to the age into three groups: (22 to 26 yrs, n=14), (33 to 49, yrs, n=13) and (51 to 59 yrs, n=14). The protocol consisted of twice repeated sequence: lying down - standing up - lying down. The subjects remained in each position for 8 minutes. The average and beat-to-beat heart rate (HR) were continuously calculated using the specialized computer program analysing ECG. The initial response was analysed using both the indices known from literature and newly introduced by the authors. The high reproducibility of the response was observed and the correlations between the indices were analysed. The relationship between the indices characterising the pattern of the response and age were analysed using the linear regression model. Most of these indices showed a tendency towards attenuation of the HR response with age. The closest correlation with age was found for the index characterising the initial increase of HR after standing up (r=-0.610, p<0.001). There were no correlations between the indices of HR response to standing up and the height or body mass of the healthy subjects.
Although lipopolysaccharide (LPS) is recognized to induce a biphasic cardiovascular response its mechanism is not fully elucidated. In this study we analysed the involvement of PAF, TXA2 and cysteinyl leukotrienes (cysLTs) in the acute cardiovascular effects of LPS in the isolated rat heart as well as in delayed phase of LPS response using a surrogate cellular model of the induction of NOS-2 by LPS in mouse macrophages. Perfusion of rat hearts with LPS resulted, in an immediate fall in heart contractility and coronary flow by 2.5 ± 0.59 ml min-1 and 560 ± 81 mmHg sec-1, respectively. This response was fully blocked by platelet activating factor (PAF) antagonist - WEB 2170 and partially inhibited, by inhibitor of cyclooxygenase (indomethacin) or by inhibitor of thromboxane synthase (camonagrel). The inhibition of leukotriene synthesis (BAY x1005) or cysLTs receptors (BAY x7195) was without effect. Administration of stable PAF analog (methylcarbamyl-PAF - MC-PAF) alone, mimicked heart response to LPS. In cultured mouse macrophages, MC-PAF did not induce NOS-2 expression and when given with LPS it slightly potentiated NOS-2 induction by LPS. However, in presence of WEB 2170 NOS-2 induction by LPS was inhibited in a dose-dependent manner. Inhibition of cyclooxygenase and leukotriene pathways had no effect on NOS-2 induced by LPS. These results indicate that PAF and TXA2 but not cysLTs mediate the instant heart response induced by LPS, while PAF alone mediates a delayed NOS-2 induction by LPS. Accordingly, PAF may constitute the mediator that links acute and delayed phases of LPS-induced cardiovascular response.
This study describes an experimental investigation where cardiovascular response was measured for a range of stimuli. The aim was to obtain relationships between stimuli and physiological variables that could be implemented in a general control system where the appropriate stimulus is selected for a desired test. Reaction time (Tr), blood pressure (BP) and heart rate (HR) were measured in 14 first-year aviation students (10 males, 4 females, age 19-23 years) during different types of computer-based tests : visual, auditory, mathematical. For all test responses across all subjects mean BP increased in 95%, HR increased in 66%. Both BP and HR increased concomitantly in 61% of responses. Average Tr was 583msec (visual), 477msec (auditory) and 10.3 sec (math). There was also a positive relation between BP, HR and Tr. A difference in these parameters was also seen between males and females. Findings of this study show that response to stress results in increased BP but not HR for all subjects studied. This indicates that short-term regulatory mechanisms of BP and HR are manifest only in some subjects some of the time for similar stimuli. These results can be used to implement an assessment procedures and test response criteria in an automated system for testing young student pilots.
Both intensive training and bed confinement impair orthostatic tolerance, however, moderate training may exert beneficial effect on cardiovascular adjustment to gravitational stimuli. It was hypothesized that moderate training attenuates effects of bed rest. To test this assumption 24 healthy male volunteers aged 20.8±0.9 yrs were subjected to 6° head down bed rest (HDBR) for 3 days before and after 6 weeks of moderate endurance training. Before and after HDBR graded LBNP tests (-15, -30, -50 mmHg) were performed. During these tests heart rate (HR), stroke volume (SV), blood pressure (BP), plasma catecholamines, ACTH, adrenomedullin, atrial natriuretic peptide, plasma renin activity (PRA) and hematocrit were determined. HDBR did not systematically influence LBNP tolerance up to -50 mmHg, but it enhanced rates of reduction of SV, cardiac output and systolic BP and increased elevations of HR and PRA. Training did not alter significantly effects of HDBR on LBNP-induced changes in HR, SV, CO and TPR but it attenuated decrease in systolic BP and diminished increases in plasma noradrenaline and PRA. In conclusion, training has negligible effect on the HDBR-induced changes in central hemodynamics during LBNP but may increase vascular sensitivity to some vasoconstricting factors.
Rats are social animals that use ultrasonic vocalizations (USV) to communicate. USV are usually divided into 50 kHz calls which accompany appetitive states, and 22 kHz vocalizations which are usually associated with aversive states. Both kinds of states are known to affect animals’ heart rate (HR). Also, the polyvagal theory claims that both cardiovascular parameters and USV emission is affected by the autonomous system, as they share a common signaling pathway. The aim of the study was to evaluate the changes in behavior, HR, and USV emission after playback of ultrasounds. Male Wistar rats were housed in pairs or separately for 4 weeks, and some of the animals underwent fear conditioning. Animals were implanted with DSI telemetry transmitters for acquisition of cardiovascular parameters. After recovery, rats were subjected to ultrasounds playback consisting of initial 10 min of static silence and five sets of 10 s sounds (50 or 22 kHz), either natural, collected from animals, or artificial tones, separated by 5 min silence intervals. Video, audio, and cardiovascular parameters were collected. Surprisingly, presentation of both 50 and 22 kHz sounds induced approach behavior. Both single- and pair-housed animals responded with a larger number of USV to both natural and artificial 50 kHz sounds playback rather than to 22 kHz sounds. The emitted USV were, almost exclusively, within the 50 kHz range. Animal HR levels decreased gradually during the experimental session. Single‑housed animals had, in general, higher HR than paired rats. There was an impact of every kind of ultrasonic presentation on HR levels; in general, 50 kHz ultrasonic playback caused a sudden increase in HR, whereas 22 kHz presentations evoked a HR drop. Surprisingly, USV and artificial tones had similar effects on HR and USV responses. Social context did not appear to alter rats’ USV emission. The results following fear conditioning are being analyzed. Also, in a separate set of experiments, rats ultrasonic responses were analyzed following presentation of a defined number of pre‑recorded USV.
The aim of the work is the study of the dependence of cardiovascular system reaction to the vestibular stimulation on the peculiarities of movements in the above-mentioned kinds of sports. Vestibular reactions of 108 males were studied, 93 of which were involved in cyclic (middle and long distance jogging, cross-country skiing, swimming), situational (sports game) and difficult to coordinate movements of stereotypical sports (gymnastics). The above facts indicate that sports contribute to the adaptation to vestibular load and, as a consequence, the development of less severe autonomic reactions to vestibular stimulation. It is essential that the vestibular resistance develops not only in those sports in which the motor activity abounds in a corner acceleration but also in those species sports where such similar accelerations are minimal. The influence of the specifics of the motor activity in some sports is reflected in the value of response in tests with a change of a head position.
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