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The quantitative parameters of the balanced influence of the sympathetic and parasympathetic divisions of the autonomic nervous system, including the variation range of the histogram of differences between successive electrocardiogram RR intervals, the number of zero differences, and the sum of differences between successive RR intervals, are suggested. 相似文献
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A technique has been developed for the analysis of differences between successive RR intervals in the long-term records of the cardiac rhythm. The differences corresponded to certain patterns of changes in the heart rate, such as deceleration and acceleration. The patterns of differences characterized the state of the heart and the body as a whole. 相似文献
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The goal of our study was to determine whether evidence for chaos in heart rate variability (HRV) can be observed when the respiratory input to the autonomic controller of heart rate is forced by the deterministic pattern associated with periodic breathing. We simultaneously recorded, in supine healthy volunteers, RR intervals and breathing volumes for 20 to 30 min (1024 data point series) during three protocols: rest (control), fixed breathing (15 breath/min) and voluntary periodic breathing (3 breaths with 2 s inspiration and 2 s expiration followed by an 8 s breath hold). On both the RR interval and breathing volume series we applied the non-linear prediction method (Sugihara and May algorithm) to the original time series and to distribution-conserved isospectral surrogate data. Our results showed that, in contrast to the control test, during both fixed and voluntary periodic breathing the variability of breathing volumes was clearly deterministic non-chaotic. During all the three protocols, the RR-interval series’ non-linear predictability was consistent with one of a chaotic series. However, at rest, no clear difference was observed between the RR-interval series and their surrogates, which means that no clear chaos was observed. During fixed breathing a difference appeared, and this difference seemed clearer during voluntary periodic breathing. We concluded that HRV dynamics were chaotic when respiration was forced with a deterministic non-chaotic pattern and that normal spontaneous respiratory influences might mask the normally chaotic pattern in HRV. Received: 7 August 1995 / Accepted in revised form: 20 March 1997 相似文献
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A. A. Dzizinskii S. G. Kuklin I. M. Mikhalevich N. Yu. Rozhkova 《Human physiology》2005,31(2):195-198
An attempt was made to classify the heart rate (HR) regulation states observed during 24-h monitoring of HR variability parameters in patients with essential hypertension and coronary heart disease. A continuous chain of nonoverlapping 5-min intervals was studied, and the cardiointerval mode, the spectral powers in the ranges of respiratory and first-order slow waves, their ratio, and the total spectral power were determined for each interval. Combinations of HR characteristics obtained for 5-min intervals were classified using nonparametric clustering methods. The standard clustering always revealed a limited number (8–13) of classes of HR regulation states. For every patient, the classes of states were numbered and their chronological sequence was studied with a mathematical apparatus for analyzing Markov chains. A set of state-to-state transitions significantly differing in frequency from random transitions was revealed for every patient.Translated from Fiziologiya Cheloveka, Vol. 31, No. 2, 2005, pp. 85–89.Original Russian Text Copyright © 2005 by Dzizinskii, Kuklin, Mikhalevich, Rozhkova. 相似文献
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G Connors S Gillis C Hunse R Gagnon B Richardson 《Journal of developmental physiology》1991,15(6):331-336
The association and possible interactions of fetal behavioural state, fetal heart rate and vascular resistance was studied in 23 healthy pregnant women between 36 and 40 weeks' gestation. Doppler flow velocity waveforms were obtained from fetal cerebral (anterior cerebral, internal carotid and basilar), descending aorta and umbilical arteries during fetal behavioural state 1F and repeated during 2F. The Resistance Index (RI) was used as a measure of vascular resistance. Decreased vascular resistance was observed in all vessels except the umbilical artery during fetal behavioural state 2F compared to 1F (P less than 0.001). A significant interaction was observed between fetal heart rate and fetal behavioural state on the RI of the vessels studied, with a greater negative slope for RI plotted against fetal heart rate in fetal behavioural state 2F (-0.00139) compared to 1F (0.00005) (P less than 0.001). We conclude that the transition from fetal behavioural state 1F to 2F is associated with a significant reduction in cerebral and systemic vascular resistance, with no apparent change in placental resistance. Furthermore, fetal behavioural state and fetal heart rate interact, demonstrating a stronger association of fetal heart rate and RI in fetal behavioural state 2F in keeping with an increase in baroreflex sensitivity at this time. 相似文献
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Heartbeat fluctuations in mammals display a robust temporal structure characterized by scale-invariant/fractal patterns. These scale-invariant patterns likely confer physiological advantage because they change with cardiovascular disease and these changes are associated with reduced survival. Models of physical systems imply that to produce scale-invariant patterns, factors influencing the system at different time scales must be coupled via a network of feedback interactions. A similar cardiac control network is hypothesized to be responsible for the scale-invariant pattern in heartbeat dynamics, although the essential network components have not been determined. Here is shown that scale-invariant cardiac control occurs across time scales from minutes to approximately 24 h, and that lesioning the mammalian circadian pacemaker (suprachiasmatic nucleus; SCN) completely abolishes the scale-invariant pattern at time scales>or approximately 4 h. At time scales相似文献
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Intrachromosomal asymmetry, one of the two aspects of karyotype asymmetry, increases because of shifts of the centromere position from the median/submedian to terminal or subterminal. Conventional measures of asymmetry use comparisons with the most symmetrical karyotype and thus are an absolute measure of variation in the centromeric index. Conversely, the CVCI index, the coefficient of variation for the centromeric index, only evaluates the relative variation in the centromeric index. We performed a detailed analysis of the capability of the CVCI index and conventional measures of karyotype asymmetry to accurately characterize differences in intrachromosomal asymmetry. Our results show that the CVCI index is unable to accurately evaluate intrachromosomal asymmetry. In fact, the CVCI index evaluates a different measure than other conventional measures of karyotype asymmetry. Therefore, to avoid confusion, we propose that the variation evaluated by the CVCI index should be named heterogeneity of the centromeric index. 相似文献
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L. V. Mezentseva 《Biophysics》2011,56(2):281-285
A computer model of excitation conduction in the heart has been employed to study the nonlinear heart rate dynamics under
stress loads. The modeling was aimed to test the hypothesis explaining changes in the heart rate dynamics during nociceptive
stress loads by the occurrence of train extracardial impulsation arriving at the sinoatrial node. The computer simulation
shows that, with a particular set of parameters, the model imitates the dynamics of RR intervals observed in experiments.
The present model provides a unified theoretical basis for further simulation of various types of ventricular disturbances
under external extreme loads. 相似文献
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V. A. Mashin 《Biophysics》2006,51(3):471-479
The relationship of the slope of the heart rate graph regression curve (b 1) with periodic (linear) and nonlinear heart rate dynamics has been studied in stationary short-time series (256 points). For estimating nonlinear dynamics, a parameter derived from correlation dimension has been used, which has made it possible to estimate chaotic processes in short-time series. According to the results of the study, the heart rate dynamics in short-time series may be represented as a sum of linear (periodic) and nonlinear (stochastic) processes. The relationships of b 1 with both the linear and the nonlinear heart rate dynamics have been demonstrated. Equations for calculating the absolute and relative (to the periodic oscillation amplitude) noises in the heart rate dynamics in short-time series are proposed. Stochastic nonlinear dynamics in different physiological states of humans have been compared. It has been found that the increase in the relative noise intensity in the heart rate dynamics with an increase in respiration rate is determined not only by the decrease in the amplitude of respiratory waves, but also by an increase in the amplitude of the noise itself. The absolute noise intensity is decreased in the states of neurotic excitement, fatigue, and, especially, mental stress. In the state of rest, nonlinear (stochastic) processes dominate over linear (periodic) ones. 相似文献
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Dinitrophenol influences the rate and yield of Acetobacter methanolicus during the growth on glucose
Acetobacter methanolicuswas grown on glucose in the presence of dinitrophenol (DNP) under carbon/energy-limited conditions. DNP affected both the growth yield and the growth rate (Dsh) at which the energy generation was shifted from a complete to an incomplete substrate oxidation by using the PQQ-linked glucose dehydrogenase. The more the growth yield was decreased, the higher both the DNP concentration and the growth rate became. At about 0.53 mM DNP, growth was completely stopped. Dsh decreased from 0.21h?1in the absence of DNP to 0.175 h?1and 0.075 h?1in the presence of 0.2 mM and 0.4 mM DNP, respectively. The experimental data are discussed in terms of the limitations in the generation of energy and some stress situations which are exerted by the presence of the uncoupler. 相似文献
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The in vitro folding of rhodanese involves a competition between formation of properly folded enzyme and off-pathway inactive species. Co-solvents like glycerol or low temperature, e.g. refolding at 10 degrees C, successfully retard the off-pathway formation of large inactive aggregates, but the process does not yield 100% active enzyme. These data suggest that mis-folded species are formed from early folding intermediates. GroEL can capture early folding intermediates, and it loses the ability to capture and reactivate rhodanese if the enzyme is allowed first to spontaneously fold for longer times before it is presented to GroEL, a process that leads to the formation of unproductive intermediates. In addition, GroEL cannot reverse large aggregates once they are formed, but it could capture some folding intermediates and activate them, even though they are not capable of forming active enzyme if left to spontaneous refolding. The interaction between GroEL and rhodanese substantially but not completely inhibits intra-protein inactivation, which is responsible for incomplete activation during unassisted refolding. Thus, GroEL not only decreases aggregation, but it gives the highest reactivation of any method of assistance. The results are interpreted using a previously suggested model based on studies of the spontaneous folding of rhodanese (Gorovits, B. M., McGee, W. A., and Horowitz, P. M. (1998) Biochim. Biophys. Acta 1382, 120--128 and Panda, M., Gorovits, B. M., and Horowitz, P. M. (2000) J. Biol. Chem. 275, 63--70). 相似文献
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Viola AU Simon C Ehrhart J Geny B Piquard F Muzet A Brandenberger G 《Journal of biological rhythms》2002,17(6):539-547
Adverse cardiovascular events are known to exhibit 24-h variations with a peak incidence in the morning hours and a nonuniform distribution during the night. The authors examined whether these 24-h variations could be related to circadian or sleep-related changes in heart rate (HR) and in HR variability (HRV). To differentiate the effect of circadian and sleep-related influences, independent of posture and of meal ingestion, seven normal subjects were studied over 24 h, once with nocturnal sleep from 2300 to 0700 h and once after a night of sleep deprivation followed by 8 h of daytime sleep from 0700 to 1500 h. The subjects were submitted to constant conditions (continuous enteral nutrition and bed rest). HRV was calculated every 5 min using two indexes: the standard deviation of normal R-R intervals (SDNN) and the ratio of low-frequency to low-frequency plus high-frequency power. Sleep processes exerted a predominant influence on the 24-h profiles of HR and HRV, with lowest HRV levels during slow wave sleep, high levels during REM sleep and intrasleep awakenings, and abrupt increases in HR at each transition from deeper sleep to lighter sleep or awakenings. The circadian influence was smaller, except for SDNN, which displayed a nocturnal increase of 140% whether the subjects slept or not. This study demonstrates that 24-h variations in HR and HRV are little influenced by the circadian clock andare mainly sleep-stage dependent. The results suggest an important role for exogenous factors in the morning increase in cardiovascular events. During sleep, the sudden rises in HR at each transition from deeper sleep to lighter sleep or awakenings might precipitate the adverse cardiac events. 相似文献
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B I Laptev I B Bardamova S A Afanas'ev E Iu Talaeva 《Biulleten' eksperimental'no? biologii i meditsiny》1990,110(11):455-457
The influence of finoptin and Ca2+ concentration decrease on cAMP dynamic during cardiac cycle in guinea pig isolated heart, activated by isadrin (3 x 10(-8) M), has been studied. In isadrin activation of adrenoceptors cAMP concentration increased by 50% during contraction and decreased during relaxation. Hypocalcium solution (0.15 mM) and finoptin decreased cAMP concentration and influenced its dynamic during cardiac cycle. 相似文献
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A one-dimensional model is used to study the dynamics of the hydrodynamic parameters of the lightning channel in the return stroke and after the pulse current is damped. The effect of the continuous residual electric current during pauses between the successive strokes on the plasma cooling in the channel is analyzed. It is shown that a continuous electric current, which is several orders of magnitude lower than the peak current in the return stroke, is capable of maintaining the channel conductivity. This effect cannot be explained merely by Joule heating but is largely governed by the fact that the turbulent heat transport is substantially suppressed. In this case, even a continuous current as low as 50–100 A is capable of maintaining the conductivity of the lightning channel at a level at which only M-components can develop in the channel rather than the dart leader of the subsequent stroke. 相似文献